Abstract:
An image formation device, such as a printer, forms an image in a transfer format. The image formation device is configured to execute a predetermined down sequence to prepare the device for the next image formation operation after completion of an image formation operation. Alternatively, when a predetermined condition is satisfied, the device is configured to execute a blank rotation sequence instead of executing the down sequence after completion of an image formation operation. The device may have the ability to form an image from different image generation sources. A determination of whether an image formation operation switches from one image generation source to using another image generation source may be based on whether the predetermined condition is satisfied. The predetermined condition may be that the sizes of the images formed using each image generation source are equal. The down sequence may include a density control for stabilizing a cleaning operation inside the device and an output density of the device. The blank rotation sequence may not include the density control. The device may also be configured to restart an image formation operation after the blank rotation sequence.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image formation device having an image formation mechanism which requires cleaning operation and density control operation after the end of image formation operation, an image formation method, an image formation system and a storage medium which implements the image formation method. 
     2. Related Background Art 
     Up to this time, in a color copying machine which has a transfer drum and an intermediate transfer body and forms a color image by an electrophotographic method, cleaning operation has been performed after the end of image formation operation. This operation is necessary for preventing dirt from being generated in the output image of the next image formation operation because each color toner of Y, M, C or K remains behind in a photosensitive drum and a transfer belt. Further, to increase the stability of an output image, density control which stabilizes the density of the output image is also performed at the end of image formation operation. 
     Conversely, even in such color copying machine, many composite machines in which printer and FAX (facsimile) system functions are integrated have been proposed in recent years, and in this type of color copying machine, how the productivity as a composite machine is to be improved becomes an issue. 
     However, the above conventional color copying machine has the following problems. 
     In the cleaning operation and density control operation after the end of the above image formation operation, the operation time may also take several ten seconds. For example, if an attempt is made to output an image as a printer after the end of copy operation, the switching time is required much and the capability of a switching continuous output to which importance is attached as the productivity of a composite machine cannot help being deteriorated greatly. 
     SUMMARY OF THE INVENTION 
     In consideration of the problems in the prior art described above, an object of the present invention is to provide an image formation device which can minimize the time required before the execution of new image formation operation such as the time required for operation switching and improve productivity, an image formation method, an image formation system and a storage medium which implements the image formation method. 
     To attain this object, an image formation device of the present invention provides an image forming means which forms an image in a transfer format, a down sequence executing means which executes a predetermined down sequence ready for the ready image formation by the image forming means at the end of image formation operation and a blank rotation executing means which executes blank rotation that is a sequence not including the down sequence after the end of image formation operation, and executes the blank rotation instead of executing the down sequence under a predetermined condition. 
     Further, in an image formation device of the present invention, the image forming means can form an image from different image generation sources, and it is subject to the above predetermined condition that image formation is switched from one image generation source to the image formation based on an image from the other image generation source. 
     Furthermore, in an image formation device of the present invention, in case the image formation is switched from the one image generation source to the image formation based on the image from the other image generation source, it is subject to the predetermined condition that the sizes of both formation images before and after they are switched are equal. 
     Besides, in an image formation device of the present invention, the down sequence includes the density control for stabilizing the cleaning operation inside the device or the output density of the device. 
     Further, in an image formation device of the present invention, the blank rotation is a sequence not including the density control for stabilizing the cleaning operation inside the device and the output density of the device. 
     Furthermore, an image formation device of the present invention comprises an image formation operation restarting means which restarts the image formation operation after the blank operation. 
     Besides, an image formation method of the present invention, wherein the image formation processing which forms an image in a transfer format and the down sequence execution processing which executes a predetermined down sequence ready for the next image formation by the image forming means after the end of image formation operation, provides the blank rotation execution processing which executes blank rotation that is a sequence not including the down sequence after the end of image formation operation, and performs the blank rotation instead of executing the down sequence under a predetermined condition. 
     Further, an image formation system of the present invention comprises a data sender which sends image data and an image formation device having an image forming means which forms an image of the image data sent from the data sender in a transfer format and having a down sequence executing means which executes a predetermined down sequence ready for the next image formation by the image forming means after the end of image formation operation. The image formation system provides a blank rotation executing means which executes blank rotation that is a sequence not including the down sequence after the end of image formation operation and executes the blank rotation instead of executing the down sequence under a predetermined condition. 
     Furthermore, a storage medium of the present invention stores the program which can be read by a computer and which implements an image formation method that performs the image formation processing which forms an image in a transfer format and the down sequence execution processing which executes a predetermined down sequence ready for the next image formation by the image forming means at the end of image formation operation, and the image formation method comprises a step of executing blank rotation that is a sequence not including the down sequence under the predetermined condition after the end of the image formation operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the entire configuration of a color formation device according to one embodiment of the present invention; 
     FIGS. 2A and 2B are block diagrams showing the main configuration of a color image formation device in which a reader controller is not installed; 
     FIG. 3 is a diagram of the principal part showing the details of a video I/F  61 ; 
     FIG. 4 is a detailed diagram of a video I/F  61 ; 
     FIG. 5 is a diagram of the sheet carrying for a printer  62 ; 
     FIG. 6 is a timing diagram for signals exchanged between video I/F  61 ; 
     FIG. 7 is a timing diagram of the communication between a printer controller  25  and an engine control unit  23 ; 
     FIG. 8 is a sequence diagram showing the serial communication at print operation; 
     FIG. 9 is a configuration diagram of the principal part of a color image formation device according to an embodiment; 
     FIG. 10 is the entire configuration diagram in which an option controller is connected; 
     FIG. 11 is a diagram showing main signals exchanged between a printer controller  25  and an option controller  26 ; 
     FIG. 12 is a timing diagram of the serial communication between printer controller  25  and an option controller  26 ; 
     FIG. 13 is a diagram showing the data storage format of the shared memory inside an option controller  26 ; 
     FIG. 14 is a timing diagram of the sheet feed operation in an embodiment; 
     FIG. 15 is a sectional view showing the configuration of a color image formation device according to an embodiment; 
     FIG. 16 is a configuration diagram showing an electrical connection in which a reader controller for reading an original image is installed; 
     FIG. 17 is a block diagram showing an electrical configuration in which a reader controller  24  is installed; 
     FIG. 18 is a block diagram showing the configuration inside a reader controller  24 ; 
     FIG. 19 is a diagram showing a timing difference at copy operation and print operation; 
     FIG. 20 is a flow chart showing the copy/print mode switching operation; and 
     FIG. 21 is a flow chart showing the switching operation of a copy job. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiments of the present invention are described below with reference to the drawings. 
     [Entire Configuration] 
     FIG. 1 is a block diagram showing the entire configuration of a color image formation device according to one embodiment of the present invention. 
     In FIG. 1,  11  is a reader unit, and an original stand  12 , a light source  13 , a photoelectric converting means  14  and an analog-to-digital converting means  15  are installed in this reader unit  11 . 
     Further,  21  is a printer main unit, and an image formation unit  22 , a DC controller  23  which controls the printer sheet carrying and image formation, a reader controller  24 , a printer controller  25  and an option controller  26  are built in this printer main unit  11 . 
       31  is a sheet feed cassette deck which can be added as an option and  32  is a sorter which can be added as an option. These sheet feed cassette deck  31  and sorter  32  are controlled by the option controller  26 . 
     Besides,  40  is a host computer connected to the printer controller  25  in one-to-one correspondence or via a network. 
     The reader controller  24  has the functions of controlling the processing of a digital image output from the analog-to-digital converting means  15 , controlling a motor not illustrated for reading an original and controlling the communication between the DC controller  23  and the printer controller  25 . 
     In this embodiment, the reader controller  24  is arranged in the printer main unit  21  so that an external cable for controlling the communication between the DC controller  23  and the printer controller  25  will not be provided. 
     [Configuration between Printer Controller and Printer] 
     In this embodiment, a reader controller is connected between a printer controller and a printer engine and processing is performed between the printer controller and the printer engine. First, the configuration of the printer controller and the printer engine which becomes the prerequisite is described here showing the configuration in which a reader controller is not installed. 
     FIGS. 2A and 2B are block diagrams showing the main configuration of a color image formation device in which a reader controller is not installed. 
       61  of FIGS. 2A and 2B is a video I/F and performs the communication between a printer engine  62  described later and the printer controller  25 . The details about each signal of this video I/F  61  are described later. 
       62  is a printer engine and forms an electric image signal received via the I/F  61  so as to be observed by the eye. After the result is transferred and fused on a sheet of recording paper, it is output. To attain these image formation sequences, the printer engine  62  detects the condition of the printer and reports it to the printer controller  25  in addition to controlling various loads. 
       25  is a printer controller and receives the data sent via the host computer  40  or a network  71 . This data is sent in various formats such as bit map data and data written in a PDL (Page Description Language). This data is expanded on a memory and transfers data to the engine printer  62  as raster format data. Thus the data created by the host computer  40  or the data sent via the network  71  can be output to the printer. 
     Next, the details about the video I/F  61  which connects the printer controller  25  and the printer engine  62  are described using FIGS. 3 and 4. 
       25  of FIG. 3 shows a printer controller.  23  is an engine control unit (DC controller) which controls the engine inside the printer engine  62 . Signals shown in FIG. 3 are exchanged between the printer controller  25  and the engine control unit  23 . Besides, FIG. 4 shows a list of signals of this video I/F  61 . In particular, only typical signals shown in FIG. 3 are described here. 
     First, /PPRDY is a signal indicating that the communication with the printer controller  25  is enabled after the power is supplied to the printer engine  25  and processing such as setup is completed. /CPRDY is a signal indicating that the communication with the engine control unit  23  is enabled after the power is supplied to the printer engine  25  and processing such as setup is completed. 
     The /RDY signal is a signal indicating that print operation is enabled after the engine control unit  23  receives a print start instruction (/PRNT signal described later) from the printer controller  25 . The conditions under this signal becomes true only when each unit of the printer engine  62  is normally operating, such as (1) the temperature inside a fixing unit reaches a predetermined temperature, (2) no recording paper remains behind in the printer and (3) a polygonal mirror is rotating at a predetermined speed. 
     The /PRNT signal is a signal through which the printer controller  25  instructs the engine control unit  23  to start or continue print operation. The /TOP signal is a synchronous signal which is transferred from the engine control unit  23  to the printer controller  25  and becomes the vertical scanning standard of an image. This /TOP signal is output in a predetermined time after the /PRNT signal is output from the printer controller  25 . 
     The /LSYNC signal is a synchronous signal the printer controller  25  uses as the horizontal scanning standard and is output to the printer controller  25  in a predetermined time after the /PRNT signal is output from the printer controller  25  in the same manner as the /TOP signal. The /VCLK signal is a synchronous clock for the /VDOEN and /VDO signals described later and generates a frequency clock which corresponds to an image signal from the printer controller  25 . 
     The /VDOEN signal is a signal which controls entering of an image signal the printer controller  25  outputs to the engine control unit  23 . The engine control unit  23  detects that this /VDOEN signal is True or False synchronizing with the /VCLK signal. In case of True, the image signal is entered and in case of False, it is not entered. 
     The /VDO signal is image data. The printer controller  25  outputs this /VDO signal based on the /TOP signal in the vertical direction and the /LSYNC signal in the horizontal direction synchronizing with the /VCLK signal. The /CCLK signal is a synchronous clock used when the printer controller  25  sends a serial command to the engine control unit  23  and when the engine control unit  23  returns a serial status to the printer controller  25 , and is output from the printer controller  25 . 
     The /CBSY signal is a signal indicating to the engine control unit  23  that the printer controller  25  is sending a serial command using the /CMD signal described later. The /CMD signal is a signal used when the printer controller  25  sends serial information to the engine control unit  23 , and this serial information is called a command. The /SBSY signal is a signal indicating to the printer controller  25  that the engine control unit  23  is returning a serial status using the /STS signal. 
     The /STS signal is a signal used when the engine control unit  23  returns serial information to the printer controller  25 , and this serial information is called a status. The /CCRT signal is a signal for reporting a printer status to the printer controller  25  when it is changed. When the printer controller  25  receives this report signal, it issues a command to inquire about how the condition on the side of the engine is changed using the /CMD signal and the engine control unit  23  reports the condition to the engine using the /STS signal. 
     Next, the printer engine the engine control unit  23  controls is described using FIG.  5 . FIG. 5 is a diagram in which the internal configuration of the printer is shown laying stress on sheet carrying. 
       81  of FIG. 5 is a scanner. After the scanner receives the image signal /VDO sent from the printer controller  25  and converts it to laser beam, a photosensitive drum  82  is irradiated with it and an image is formed on the photosensitive drum  82 . While the photosensitive drum  82  is rotating counterclockwise, it reaches a developing unit  83  and a black developing unit  84 . 
     The developing units  83  and  84  load (develop) toner on the photosensitive drum  82  in accordance with an electric charge charged on the photosensitive drum. When an image is black and white, only the black developing unit  84  is operated, and when it consists of colors, both the developing units  83  and  84  are used. Then the image generated on the photosensitive drum  82  is transferred to an intermediate transfer body  85  which is rotating clockwise. This intermediate transfer body  85  rotates once to develop black toner in the black and white mode and rotates four times to develop yellow, magenta, cyan and black in the color mode. 
     Conversely, the recording paper fed by a pickup roller  91  or  92  from a upper cassette  88  or a lower cassette  89  is carried in accordance with a sheet feed roller  93  or  94  and further carried to the front of a registration roller  99  by a carrying roller  95 . Then, after the image formation on the intermediate transfer body  85  is completed, the recording paper is carried between the intermediate transfer body  85  and a transfer belt  86  by the registration roller  99 . As soon as the recording paper is reached here, the transfer belt  86  touches the intermediate transfer body  85  and toner is transferred to the recording paper. An image transferred to the recording paper is fused on the recording paper due to heat and pressurization by a fusing roller  87 . 
     The recording paper on which an image is fused is carried to either a face-up sheet discharge port  97  or a face-down sheet discharge port  98  previously designated by the printer controller  25  and is discharged. 
     By the above image formation operation, a black and white image or a color image is recorded on a sheet of recording paper. In a color printer having the above configuration, the operation which is independent of the image formation operation called a down sequence including cleaning operation and density control is executed. It is described below. 
     The cleaning operation after the image formation in a down sequence traces the following procedure, for example. 
     In other words, when the transfer to the final recording paper in the image recording of a plurality of pages is completed, the operation which cleans each color toner remaining behind on the photosensitive drum  82 , the intermediate transfer body  85  and the transfer belt  86  is started. At normal image formation, toner is transferred from the developing units  83 ,  84  to the photosensitive drum  82  and from the photosensitive  82  to the intermediate transfer body  85 , then from the intermediate transfer body  85  to the recording paper on the transfer belt  86 . For cleaning, to collect the toner left in each unit in a discharge toner tray not illustrated, reverse potential is applied at image formation. If such operation is performed every colors, almost the same time as the color image formation becomes necessary. 
     Such cleaning operation can also be omitted if an image with the same size is continuously output in a plurality of pages. However, if an attempt is made to switch an image size during output, the portion beyond the image area after switching may be stained and a fault such as scattering of hard-to-clean toner may be caused. Accordingly, in a color image formation device, when the image size is switched, cleaning may be inhibited from being executed or the switching of the image size be inhibited during the same sequence. 
     Further, in a down sequence, density control forms a specific image pattern on the intermediate transfer body  85  or the photosensitive drum  82  and changes various process parameters such as charging, exposure, development and transfer based on a value read by a density sensor not illustrated, then sets image formation conditions for appropriate density. For the operation which forms and reads the pattern, the photosensitive drum  82  and the intermediate transfer body  85  need be rotated without forming an image and moreover the operation must be executed independently of the above cleaning operation. 
     To perform these down sequences, it takes some time until a device is stopped after an image is formed. For example, assume that the circumferential length of the intermediate transfer body  85  is 500 mm and the process speed inside the device is 100 mm per second. If cleaning is performed for four colors of Y. M, C and K and density control is performed, the down sequence of at least 5×4+5=25 seconds is excessively required because it takes 500/100=5 seconds for one circumference of the intermediate transfer body  85 . 
     Consequently, the image information sent from the printer controller  25  can be output including the down sequence. 
     Next, timing of signals exchanged between the video I/F  61  is shown in FIG.  6 . This shows the signal explanation of the video I/F  61  described previously in accordance with a lapse of time. 
     First, when the preparation for the image information of the printer controller  25  is completed, the /PRNT signal is set Low (True) and is transmitted to the engine control unit  23 . Simultaneously with this, the image synchronous signal /VCLK signal used for the transfer of an image signal is also generated. In response to it, when the engine control unit  23  performs various settings inside the printer to enable acceptance of an image, the /TOP signal and the /LSYNC signal are output to the printer controller  25 . Together with the vertical synchronous signal /TOP and horizontal synchronous signal /LSYNC, the printer controller  25  transfers the image signal /VDO and the image enable signal /VDEON to the engine control unit  23 . 
     Next, how commands and status are being exchanged during these print operations in the serial communication is described using FIG.  7 . FIG. 7 is a diagram showing timing of the communication between the printer controller  25  and the engine control unit  23 . 
     First, the case where the lowest /CCRT signal is not used is described. When the printer controller  25  should like to issue a command to the engine control unit  23 , the /CBSY signal is set Low (True) and command data is sent to the /CMD signal synchronizing with the clock signal /CCLK. After the engine control unit  23  which receives it checks that the /CBSY signal is High (False), /SBSY is set Low (True) and the status data on the side of the engine which corresponds to the command is sent to /STS synchronizing with the /CCLK signal generated from the printer controller  25 . The printer controller  25  receives this status data and continues or interrupts print control according to the state. 
     Next, the /CCRT signal is described. This signal goes Low (True) if a change occurs in the condition on the side of the engine the printer controller  25  designates previously. For example, assume that the printer controller  25  is preset with /CMD so as to validate the /CCRT signal if no paper is generated. Then assume that there is a sheet of remaining recording paper and the printer controller  25  issues a printout request for two sheet of recording paper. 
     For the first recording paper, print sequence operation is normally processed without causing any problem. However, because the second recording paper cannot be found, the printer engine side detects the change of the condition and changes the /CCRT signal from High to Low when the image formation of the second recording paper is started. This signal is transmitted to the printer controller  25 . When the printer controller  25  detects this, it immediately issues a command which requests the sheet feed unit paper existence status to the engine control unit  23  to know that no paper occurs in which sheet feed cassette. Accordingly, the engine control unit  23  returns no paper cassette status to the controller  25 . The /CCRT signal is cleared to High at the timing at which the /SBSY signal to which the status is returned goes Low. 
     The print operation is described here showing exchange of the commands/status of the printer controller  25  and the engine control unit  23  in FIG. 8 more specifically. This assumes an color output. 
     When a print start request is generated, the printer controller  25  performs image data conversion processing and checks the printer ready condition for the engine control unit  23 . Then a command which designates the sheet feed stage of recording paper is issued. Further, a command which requests a size of recording paper in the designated cassette is issued. The engine control unit  23  returns the corresponding status to a series of these commands. 
     Subsequently, a sheet discharge port is decided with a command which designates the sheet discharge port and a page mode designation command which designates how many pages of images are to be formed is issued. Finally, by issuing a command which designates the monochrome or color mode, all settings on the side of the printer are completed. 
     Then, the printer controller  25  generates the print request /PRNT signal for the engine control unit  23 . In response to this, the /TOP signal is returned from the engine control unit  23  for a predetermined time. By making the vertical scanning direction synchronize with this /TOP signal and the horizontal scanning direction synchronize with the /LSYNC signal then matching the /VDO signal with /VCLK, an image is transferred to the engine control unit  23 . In this case, because the color mode is set, the /TOP signal is generated four times and an image for four colors C, M, Y and K will be formed. 
     Further, after the final /TOP signal is generated, the /PRNT signal restores High (False). Accordingly, the engine control unit  23  detects that a print request is completed and moves to postprocessing such as the cleaning operation of the intermediate transfer body. Further, after the transferred recording paper passes through the fusing roller  87 , it is discharged to the designated sheet discharge port. Finally, after the printer controller  25  checks no recording paper carrying state (sheet discharge end) for the engine control unit  23 , it causes a print end and waits in the ready condition until the next print request is generated. 
     If an illegal condition such as a recording paper jam, no recording paper described above, or door opening by a user is generated during the above operation, a printer error is immediately transmitted from the engine control unit  23  to the printer controller  25  using the above /CCRT signal. The printer controller  25  will perform counteraction processing which corresponds to the error. 
     The above is the processing performed between the printer controller  25  and the printer engine (engine control unit  23 ). 
     FIG. 9 is a configuration diagram of the principal part of a color image formation device in which a reader controller is not installed, and the same code is assigned to elements common to FIG.  1 . 
     In FIG. 9,  21  is a printer main unit.  23  is a DC controller which controls the sheet carrying and image formation of the printer and  22  is an image formation unit.  25  is a printer controller and is built in the printer main unit  21 . Further,  40  is a host computer connected in one-to-one correspondence or via a network.  31  is a sheet feed cassette deck which can be added as an option and  32  is a sorter which can be added as an option.  26  is an option controller which controls the option cassette deck  23  and the option stesorter  32 . 
     [Configuration of Printer Controller and Option Controller] 
     Next, as shown in FIG. 9, the entire overview when an option controller and an option device are connected is described using FIG.  10 . FIG. 10 is the entire configuration diagram when the option controller is connected. 
       111  is an option I/F and performs the communication between the printer controller  25  and the option controller  26 . The printer controller  25  can control an option device  120  such as the sheet feed cassette deck  31  and the sorter  32  which can be added as an option by controlling the option controller  26 . 
       112  is a paper handling I/F and performs the communication between the option controller  26  and the option device  120 . Because the printer controller  25  can control the option device  120  by the option I/F  111 , a detailed description about the paper handling I/F  112  is omitted in this embodiment. 
     Next, signals used in the option I/F  111  are described using FIG.  11 . FIG. 11 is a diagram showing main signals exchanged between the printer controller  25  and the option controller  26 . 
     The CLK signal of FIG. 11 is a synchronous clock for communication control and is a signal transferred from the option controller  26  to the printer controller  25 . The /TX signal is a data signal for communication control and is a signal transferred from the printer controller  25  to the option controller  26 . This /TX signal indicates addressing of the shared memory inside the option controller  26  and write data to the shared memory. 
     The /RX signal is a data signal for communication control and is a signal transferred from the option controller  26  to the printer controller  25 . This /RX signal indicates the read data from the shared memory inside the option controller  26  and data such as parity information and access completion information. 
     The /STROBE signal is a communication enable signal for communication control and is a signal transferred from the printer controller  25  to the option controller  26 . This signal performs communication between True and True. The /CKEN signal is a clock enable signal for communication control and is a signal transferred from the printer controller  25  to the option controller  26 . This /CKEN signal indicates to the option controller  26  that the printer controller  25  can receive the /CLK signal and controls 8 bits as a unit. 
     The /PRNT signal is a signal defined on the video I/F  61 . The /PRNT signal is a signal through which the printer controller  25  instruct the engine control unit  23  to start or continue print operation and is also supplied to the option controller  26 . The /TOP signal is a signal which is defined on the video I/F  16  and transferred from the engine control unit  23  to the printer controller  25 , then passes through the option controller  26 . This signal shows timing at which the print sheet waiting at a registration roller is recarried. 
     The /PDLY signal is a signal which is defined on the video I/F  61  and transferred from the engine control unit  23  to the printer controller  25 , then passes through the option controller  26 . This /PDLY signal shows timing at which a print sheet is discharged from the printer engine  62 . The /PFED signal is a signal which is defined on the video I/F  61  and transferred from the engine control unit  23  to the printer controller  26 . This /PFED signal passes through the option controller  26  and is output only when the sheet feed unit is designated for an option input device. The signal indicates timing at which the print sheet is fed from the option input device to the printer. 
     FIG. 12 is a timing diagram of the serial communication between the printer controller  25  and the option controller  26 . 
     The printer controller  25  sets the /STROBE signal True while it is performing communication. When the printer controller  25  sets the /CKEN signal True, the /CLK signal is supplied from the option controller  26  and data is sent from the printer controller  25  to the option controller  26  using the /TX signal. Simultaneously with this, the printer controller  25  receives data from the option controller  26  using the RX signal. Send and receive data is used to read and write the shared memory inside the option controller  26 . 
     The printer controller  25  controls the option controller  26  by writing and reading data to and from the shared memory inside of the option controller  26 . The inside of the shared memory is divided into a carrying condition management area  141 , a command and status management area  142  and a startup area  143 . 
     The carrying condition management area  141  is an area representing the information required for sheet carrying every print image and contains  40  images. The data for one print image contains the data showing a sheet feed port, a sheet discharge port, a sheet size, a sheet discharge mode and the sheet carrying condition of the option device  120 . The printer controller  25  writes the sheet feed port, sheet discharge port, sheet size and sheet discharge mode in the carrying condition management area  141  which corresponds to every print image. The option controller  26  judges the condition of the option device  120  and writes the condition of the sheet carrying in the carrying condition management area  141  which corresponds to every print image. By using the area for these  40  images in a ring shape, the latest information about the  40  images can always be shared by the printer controller  25  and the option controller  26 . Further, the area to which the status of each option device  120  is reported also exists in the carrying condition management area. According to this status, the printer controller  25  can identify a state such as no paper, a jam, and a fault while the option device  120  is waiting and sleeping. 
     The command and status control area  142  controls the command and status between the printer controller  25  and the option controller  26 . Command data is written from the printer controller  25  to the option controller  26  and the option controller  26  writes the status data which corresponds to commands. Some commands include a command which inquires about the condition of the option device and instructs the operation for the option device  120 . 
     The startup area  143  is used to initialize the communication between the printer controller  25  and the option controller  126 . 
     FIG. 14 is a timing diagram of the sheet feed operation in this embodiment. Using this diagram, the timing of the signal among the printer controller  25 , the engine control unit  23  and the option controller  26  at operation is described. 
     First, the printer controller  25  writes sheet feed information in the carrying condition management area  141  and instructs a sheet feed preparation. When the printer controller  26  instructs the option device  120  to prepare for sheet feed and the sheet feed preparation is completed, the option controller  26  allows a print permission flag in the carrying condition management area  141 . 
     The printer controller  25  detects that the print permission flag is allowed in the carrying condition management area  141  and sets the /PRNT signal True for the engine control unit  23 . 
     The engine control unit  23  returns the /TOP signal to the printer controller  25  after a predetermined period and an image is transferred to the control unit  23  synchronizing with this /TOP signal as described previously. The engine control unit  23  outputs the /PFED signal to the printer controller  25  in a predetermined period after it issues the /TOP signal and the print controller  25  instructs the option controller  26  to carry a sheet to the engine. 
     The option controller  26  instructs the option sheet feed device  31  (FIG. 1) to start the sheet carrying in the printer engine. When the carried sheet forms a loop by a registration roller and waits, the engine control unit  23  sets the /PFED signal False. Meanwhile, an image is formed on the intermediate transfer body  85 . In a predetermined period after the /TOP signal is output, the engine control unit  23  refeeds the sheet which is waiting by the registration roller and outputs the /TOPR signal to the printer controller  25 . In a predetermined period after the TOPR signal is output, the engine control unit  23  outputs the /PDLV signal. This signal indicates that a sheet is discharged outward. 
     If an illegal condition such as a jam of a recording sheet and door opening by a user is generated in the option device  120  during above operation, an error inside the option device  120  is immediately transmitted from the option controller  26  to the printer controller  25  using the option device status of the carrying condition management area  141  described previously. Accordingly, the printer  25  performs counteraction processing which corresponds to the error. 
     Further, if an illegal condition such as a jam of a recording sheet in the engine control unit  23  and door opening by a user, the printer controller  25  receives a notice from the engine control unit  23  and performs the processing which corresponds to the notice, then at the same time, instructs a command which stops the operation to the option controller  26 . The option controller  26  stops the operation of the option device  120  with the command which starts the operation. 
     [Configuration in Which a Reader Controller is Installed] 
     Next, the case (configuration example of FIG. 1) where a reader controller which optically reads not only the image data output from the printer controller  25  but also an original image on a sheet and converts them to digital signals and then outputs them is installed based on the data transferred from the host computer  40 , is described. 
     FIG. 15 is a cross-sectional diagram showing the configuration of a color image formation device according to this embodiment, and a specific configuration example of the color image formation device shown in FIG.  1 . However, the sorter  32  is omitted. 
     In FIG. 15,  160  is an original feed device for carrying an original including that which is to be optically read. This original feed device  160  is driven synchronizing with the optical reading device (reader unit)  11  and an original image is shifted on the original stand glass  12  by the feed device  160 . Then the optical reading device  11  scans the image moving in the horizontal direction of the diagram and sends the reflected light to which appropriate optical processing applies to the photoelectric conversion unit  14 . 
     FIG. 16 is a configuration diagram showing an electrical connection when a reader controller for reading an original image in the configuration in which the printer controller  25  and the engine control unit  23  shown in FIG. 3 are provided. 
     In FIG. 16,  24  is a reader controller and is arranged between the electrical middle between the printer controller  25  and the engine control unit  23  shown in FIG.  3 . Signal lines between the printer controller  25  and the reader controller  24  and between the engine control unit  23  and the reader controller  24  have the same functions as the signal lines shown in FIG. 3 described previously. However, because the signals on the side of the printer controller  25  physically differ from those on the side of the engine control unit  23 , the names of the signals are distinguished by assigning C to the former and P to the latter. 
     Further,  161  is an image signal proc unit inside the reader controller  24  and  162  is an original scanning optical system control unit which controls the optical reading unit  11 .  163  is an original feed control unit which controls the original feed device  160 .  164  is a console unit.  165  is an image input unit. The image signal converted by the photoelectric conversion unit  14  is input from the image input unit  165  and transferred to the image signal proc unit  161  inside the reader controller  24 . 
     FIG. 17 is a block diagram showing an electrical connection in which the reader controller  24  is installed in the configuration between the printer controller  25  and the option controller  26  shown in FIG. 11 shown above. 
     The reader controller  24  is arranged in the electrical middle between the printer controller  25  and the engine control unit  26 . The signal lines between the printer controller  25  and the reader controller and between the reader controller  24  and the option controller  26  have the same functions as those shown in FIG. 11 described previously. However, because the signals on the side of the printer controller  25  physically differ from those on the side of the option controller  26 , the names of the signals are distinguished by assigning C to the former and P to the latter. 
     Next, the configuration inside the reader controller  24  is shown in FIG.  18 . 
     In FIG. 18,  181  is a selector. The selector selects either an output of the image signal proc unit  161  or a signal sent from the printer controller  25  and outputs it to the engine control unit  23 . The signal system switched by the selector  181  consists of the following three signals video clock (/VCLK), video enable (/VDOEN) and video data (/VDO). 
       182  is a serial communication controller which performs the communication between the engine control unit  23  and the option controller  26 .  183  is an I/O port which exchanges a signal to compensate the communication in the communication controller  182 .  184  is an interruption controller. The image top request signal (/PTOP) and the printer condition change signal (/PCCRT) are input to the interruption controller  184 .  185  is a serial communication controller which performs the communication with the printer controller  25 . 
       186  is an I/O port which exchanges a signal to compensate the communication in the communication controller  185 .  187   a ,  187   b  are gates and control whether to send the signal sent from the printer to the printer controller  25 . The gates  187   a ,  187   b  control the image top request signal (/TOP) and the line synchronous signal (/LSYNC). 
       188  is a signal control circuit having a gate function and a flag set function and controls the printer condition change signal (/CCRT). By opening and closing a gate, whether to transmit the printer condition change signal (/PCCRT) the engine control unit  23  issues to the printer controller  25  or by setting a flag, the printer condition change signal (/CCRT) can be issued from the reader controller  24  to the printer controller  25 . Besides,  189  is a CPU which controls the entire. 
     [Copy Operation] 
     The method for reading a full color original image and outputting it from a color image formation device using these is described. 
     When the copy start key not illustrated on the console unit  164  is input after various copy conditions including a size of recording paper and the number of sheets of recording paper are set by the operation of various keys, the reader controller  24  closes the gate units  187   a ,  187   b  and the signal control circuit  188  or sets the selector  181  so that an output of the image signal proc unit  161  can be selected for the purpose of the copy mode. Subsequently, the printer ready condition signal (/PRDY) is checked for the engine control unit  23  using the I/O port  186 . 
     Next, various settings are performed using the serial communication controller  182 . First, a command which designates the sheet feed step for recording paper is issued. Further, a command which requests a size of the recording paper on a designated cassette is issued. The engine control unit  23  returns the corresponding status to a series of these commands. 
     Subsequently, a sheet discharge port is decided with a command which designates the sheet discharge port and a page mode designation command which designates how many pages of images are formed is issued. Finally, by issuing a command which designates the monochrome or color mode, all settings on the side of the printer are completed. 
     If the option device  120  is connected, data such as a sheet feed port, a sheet discharge port and a sheet size which correspond to one print page is further written in the carrying condition management area  141  described previously using the serial communication controller  182 . 
     After an original is fed onto an original stand by the original feed device  160 , the reader controller  24  generates the print request (/PPRNT signal) to the engine control unit  23 . In response to this, the /PTOP signal is returned from the engine control unit  23  after a predetermined time. This is processed by the interruption controller  184  and the optical reading device  11  is operated so as to synchronize with the /PTOP signal. By making the vertical scanning direction synchronize with this /PTOP signal and the horizontal direction synchronizing with the /PLSYNC signal, then the /PVDO signal synchronize with /PVCLK, the signal input from the photoelectric conversion device  14  to the image signal proc unit  161  is transferred to the engine control unit  23 . In this case, because the color mode is set, the optical reading device  11  is operated for four times and an image consisting of four colors C, M, Y and K is formed for the /PTOP signal which is generated for four times. 
     If the option device  120  is connected, in a predetermined period after the final /PTOP signal is generated, the /PFED signal is received from the engine control unit  23  and the reader controller  24  passes this signal through the option controller  26  as the /OPFED signal. When the reader controller detects the /PFED signal, it instructs the option controller  26  to carry a sheet to the engine control unit  23  using the serial communication controller  182 . In response to this, the option controller  26  instructs the option sheet feed device  31  (FIG. 1) to carry a sheet. 
     Further, after the final /PTOP signal is generated, the /PPRNT signal restores High (False). Accordingly, the engine control unit  23  detects that a print request is completed and moves to postprocessing such as the cleaning operation of the intermediate transfer body . Furthermore, after the transferred recording paper passes through the fusing roller, it is discharged to the specified sheet discharge port. 
     If the option sorter  32  (FIG. 1) is connected, the option controller  26  controls the option sorter  32  so as to discharge a sheet to the specified bin of the option sorter  32  according to the data of the discharge port set by the carrying condition management area described previously. 
     Finally, after the reader controller  24  checks no recording paper carrying condition (sheet discharge end) for the engine control unit  23 , a print end occurs. After the reader controller executes the down sequence described previously, it waits in the ready condition until the next print request is generated. 
     [Print Operation] 
     Next, the method for outputting an image of the above printer controller  25  from a color image formation device is described. 
     When copy operation is completed, the reader controller  24  enters the ready condition. At this time, the reader controller releases the above gate units  187   a ,  187   b  and the signal control circuit  188  for the purpose of print operation. The reader controller  24  checks the printer ready state signal (/PRDY) for the engine control unit  23  using the I/O port  186 . If the signal is acceptable (OK), the reader controller sets the printer ready signal (/CRDY) for the printer controller  25  using the I/O port  186 . 
     Subsequently, the printer controller  25  communicates with a host computer to perform various settings including designation of a size of recording paper. The reader controller  24  receives them using the serial communication controller  185  and a CPU  189  interprets them. According to the contents, the reader controller  24  performs various settings using the serial communication controller  182  at this time. For a series of commands, the engine control unit  23  returns the corresponding status to the reader controller  24  and the reader controller  24  receives it using the serial communication controller  182 . The CPU  189  interprets the received contents and the reader controller performs communication to the printer controller  25  using the serial communication controller  185  at this time. 
     If the option controller  26  is connected, the reader controller  24  receives the command from the printer  25  and the data set in the carrying condition management area  141  using the serial communication controller  185  and the CPU  189  interprets them. According to the contents, the reader controller  24  performs various settings using the serial communication controller  182  at this time. For a series of commands and the carrying condition management data, the option controller  26  returns the corresponding status and data to the reader controller  24  and the reader controller  24  receives them using the serial communication controller  182 . The CPU  189  interprets the received contents and the reader controller performs communication to the printer controller  25  using the serial communication controller  185  at this time. 
     Subsequently, the printer controller  25  generates the printer request (/CPRNT signal) for the reader controller  24 . The reader controller  24  receives it and generates the print request (/PPRNT signal) for the engine control unit  23 . In response to this, the /PTOP signal is returned from the engine control unit  23  after a predetermined time. This passes through the signal control circuit  188  and is returned to the reader controller  24  as the /CTOP signal. 
     The reader controller  24  makes the vertical scanning direction synchronize with the /CTOP signal. Further, the /PLSYNC signal makes the horizontal direction synchronize with the /CLSYNC signal which passes through the gate  187   a  and the /CVDO signal synchronize with /CVCLK and transfers them to the reader controller  24 . In the reader controller  24 , the selector  181  is set so as to select a signal sent from the printer controller  25  and the signal sent from the printer controller  25  is sent to the engine control unit  23  as /PVCLK, /PVDOEN or /PVDO. 
     If the option controller  26  is connected, when the reader controller  24  receives the /PFED signal from the engine control unit  23 , it passes through the printer controller  25  as the /CPFED signal. The reader controller  24  receives an instruction which carries a sheet from the option sheet feed device  31  to the engine control unit  23  from the printer controller  25  using the serial communication controller  185 . The CPU  189  interprets the instruction and transfers it to the option controller  26  using the serial communication controller  182 . 
     [Difference between Print Operation and Copy Operation] 
     The difference between print operation and copy operation about the image sending timing is described here. 
     Although a detailed description about the configuration of the print controller  25  is omitted, it is internally provided with an image memory and the image data to be printed is previously provided there. Accordingly, for the image top request signal (/TOP signal) sent from the engine control unit  23 , the time required until print data (/VDO) is output is only an electrical delay time. 
     Conversely, in the copy mode, an original is read moving the optical reading device  11  and image data is output. As shown in FIG. 19, an acceleration time is required from the condition in which the optical reading device  11  to the condition in which it moves at a high speed at which the original is read, and it takes about several 100 ms, for example. Accordingly, if the engine control unit  23  issues the image top request signal (/TOP signal) in the copy mode at the same timing as the signal in the print mode, the time the print image data (/VDO) reaches the engine will be delayed by several 100 ms in the copy mode. Therefore, /TOP is issued at copy earlier than at print. 
     [Copy and Print Switching Output] 
     Next, the characteristic part of the present invention is described. 
     A color image formation device for which the present invention is executed can designate a print priority according to a function on the console unit  164  and for example, it can be set to any one of copy priority, printer priority and the same precedence between copy and printer priority. 
     The case where the same precedence is set to the output of copy and printer is described. If a notice of an image output is reported from the printer controller  25  through the serial communication controller  185  while copy is being executed in the color mode, the reader controller  24  judges that it enters the down sequence as is after copy is completed or such control that can continue the image formation sequence is performed to execute the output from the printer controller  25  without any delay. 
     A flow of this judgment is shown in FIG.  20 . 
     In FIG. 20, first, a print output notice is issued from the printer controller  25  through the serial communication controller  85  (Step S 11 ). The reader controller  24  which receives a command judges whether it is time density control is necessary immediately before the image formation of a copy output is completed (Step S 12 ). 
     Usually, for density control, the necessity of its execution is judged based on the total number of images formed and a humidity or temperature value, and the density control is executed at the end of copy as much as possible in consideration of the convenience of a user. Because the timing the user receives a product is not delayed by executing the density control at the end of copy, the productivity as a function need not be reduced. However, if image formation operation is kept long, the density control is not executed for a long period of time and the quality of an output image may be deteriorated. Therefore, if such judgment is passed, the density control must be executed even if the output request from the printer controller  25  is awaited. In this example device, the cumulative number of printouts is subject to the execution of density control. In other words, (1) when 50 sheets of printouts are executed after the power is started up regardless of black and white prints and color prints and (2) when 395 sheets of printouts for black and white prints and 95 sheets of printouts for color prints are executed after the density control is executed according to item (1), it is time the density control is necessary. 
     Accordingly, if the time a new output is issued is the time the execution of density control is necessary, processing is on standby until the copy being executed currently is completed (Step S 13 ). Before the print operation which conforms to the next output notice, processing enters the down sequence and continuously performs density control and cleaning operation (Step S 14 ). 
     If the time density control is to be executed is not reached, whether the size of an image being output at copy and that for which the output is requested from the printer controller  25  are the same is judged (Step S 15 ). When the printer controller  25  issues an output notice in the above Step  11 , it also transmits an output image and an output mode to the reader controller  24  via the communication at the same time. If an output image size differs, because the image formation area on the photosensitive drum  82  and the intermediate transfer body  85  (FIG. 5) differs, cleaning must be performed according to the image size at copy. 
     For the same size, after processing is on standby until the copy output being executed currently is completed (Step S 16 ), it switches from the copy output to the printer output without executing the down sequence (Step S 19 ) if an image is ready for being output from the printer (Step S 19 ). Conversely, if the image is not ready for being immediately output from the printer (Step S 17 ), processing is on standby by once inserting the blank rotation in which the photosensitive drum  82  and the intermediate transfer body  85  are simply rotated without forming an image for them without executing the down sequence (Step  18 ). Then, the blank rotation is inserted until the preparation for an image output from the printer is arranged and subsequently processing switches from the copy output to the printer output if the preparation for the image output is arranged (Step  19 ). Thus, as compared with the case where the down sequence is executed, the copy and printer output can be switched for a short time. In other words, as compared with the case where the photosensitive drum  82  stops rotating, by executing the blank rotation, the photosensitive drum  82  and the intermediate transfer body  85  can immediately be brought to the normal rotation for forming an image. 
     The number of blank rotations to be inserted at switching can be calculated if it is known how long an output is enabled later after a printer notice is reached. In such case, the down sequence time and the blank rotation are compared, and the control in which no down sequence is executed only when the blank rotation time is shorter is also enabled and this can improve productivity more efficiently. 
     By storing the program which conforms to the flow chart shown in FIG. 20 in a storage inside the CPU  189  and operating it, the control method described above can be implemented. 
     Thus, according to this embodiment, if it is known before the end of image output operation that there is an output according to another image configuration function, so long as the down sequence such as cleaning operation and density control need not be inserted comparing the conditions of both output images, an attempt is made to insert the image formation operation or the blank rotation operation not including the cleaning and density control. Consequently, the operation switching time can be minimized and the productivity as a composite machine can be improved. 
     In the above description, the present invention is described using the switching from copy operation to print operation as an example. Conversely, this description can also apply to the switching of print operation to copy operation, and in another mode, for example, to the switching of an image generation source such as the switching from FAX receive operation to another print or copy operation. 
     In the example described above, an example in which the present invention applies at the switching between different jobs such as copy, print and FAX is detailed. 
     Then, an example in which the present invention applies to the copy operation which is the same job is described. In the copy operation, the time until the copy operation of the next job after the final sheet for the copy operation of one job is discharged is started is important. This time is called SCOT (Second Copy Time) as a standard value representing the copy productivity of the second job and is highly valued from the aspect of easiness of use by a user. In particular, for a color copy, because the processing such as the cleaning after print operation must be performed more than a blank and white copy, there is a problem the SCOT is also prolonged for a black and white copying machine. This SCOT is shortened as follows: 
     The control operation of the reader controller  24  is described using the flow chart of FIG.  21 . 
     The reader controller  24  at the end of copy operation first checks whether the execution time of density control which is the condition always requiring the down sequence is reached (Step S 21 ). This judgment is performed as to whether the cumulative number of printouts reaches a predetermined number in the same manner as described above. For Yes, because density control processing need be performed at job end, the down sequence cannot be skipped. Accordingly, processing is on standby until the final output sheet is discharged outward (Step S 22 ) and subsequently processing enters the down sequence and performs the density control and cleaning operation (Step S 23 ). As described previously, the execution of this down sequence requires time, and this processing is required for maintaining image quality satisfactorily. After the end of the down sequence, the start of the next copy enters the acceptance enable condition (Step S 24 ), then the printer is stopped. 
     Next, if the execution time of density control is not reached, that is to say, if No occurs in the above Step S 21 , the printer is instructed to insert blank rotation (Step S 26 ). Then, processing is on standby until the final output sheet is discharged outward (Step S 27 ) and depressing of the copy start key in the console unit  164  is judged (Step S 28 ). At this time, although the printer is performing the blank rotation, the start of the next copy enters acceptance enable condition on the console unit  164 . At this time, if the start of the next copy is not instructed (a user does not perform the operation of the copy start key), processing goes to Step S 29 . In Step S 29 , the number of blank rotations is counted and whether a predetermined number is reached is checked. If the predetermined number is not reached, processing returns to Step S 28  described previously and the same check is repeated. Conversely, when the number of blank rotations reaches the predetermined number, processing enters the down sequence, density control and cleaning operation are performed and the printer is stopped. In the condition before the number of blank rotations reaches the predetermined number, only the operator panel can accept a copy and practically the printer is in the blank rotation condition. After the number of blank rotations reaches the predetermined number, the operator panel can accept a copy and moreover the printer itself stops the blank rotation and enters the standby condition. Besides, in the processing of Step S 29 , the number of insertions for the blank rotation until processing enters the down sequence is restricted, and for example, according to the condition of the frequency of device use, a user can set and change the number of insertions. 
     Conversely, in Step S 28  described previously, if the printer is in the condition of blank rotation and the operator panel enables a copy start, when a user depresses the copy start key, the reader unit  11  sets up an optical motor for performing lamp lighting and document scan and at the same time checks whether the processing is completed, then judges whether the preparation for the next copy is completed (OK) (Step S 31 ). If the preparation is not OK (completed), processing returns to Step S 28  described previously without starting copy operation. Conversely, if the preparation for the next copy is OK (completed), to release the blank rotation condition the printer continues, an instruction of blank rotation release is issued to the printer (Step S 32 ). Then, as soon as a synchronous signal is reached from the printer, processing enters the normal print condition and the next copy operation is started (Step S 33 ). Thus, the operation of the next copy can be started so as to skip the down sequence. 
     The operation of FIG. 21 is described assuming that the check as to whether the size being output in Step S 15  of FIG.  20  and the size of the next job are equal is omitted and the printer can skip the down sequence even if the output size is not equal. Needless to say, in the same manner as FIG. 20, control may also be executed by including the match and mismatch of the size in the judgment of the execution of down sequence. 
     The present invention is not restricted to a device according to the embodiment described above and may also apply a system comprising a plurality of units and a device consisting of one unit. Needless to say, the storage medium storing the program code of software which implements the function of the embodiment described previously is also supplied to a system or device and the system or device can also be completed when the computer (or CPU  189  or MPU) reads and executes the program code stored in the storage medium. 
     In this case, the program code itself read from a storage medium implements the function of the embodiment described previously and the storage medium storing the program code comprises the present invention. As storage media for supplying the program code, for example, a floppy disc, hard disc, optical disc, magneto-optical disc, CD-ROM, CD-R, magnetic tape, nonvolatile memory card and ROM can be used. Further, by executing the read program code a computer reads, the function of the embodiment described previously is not only implemented, but also based on the instruction of the program code, the OS running on the computer performs part or all of practical processing. Needless to say, the case where the function of the embodiment described previously is implemented by the processing is also included. 
     Further, after the program code read from a storage medium is written in the memory installed in a function extended board inserted in a computer and a function extended unit connected to the computer, the CPU which installs the extended function in the function extended board and the function extended unit performs part or all of practical processing on the basis of the instruction of the next program code. Needless to say, the case where the function of the embodiment described previously is implemented by the processing is also included. 
     The present invention is described above using the desirable example configuration, but needless to say, the present invention is not restricted to this and enables various modifications and changes within the claims.