JP2001356647A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which solves the problem, such as defective fixing and paper wrinkle, caused when performing a print job of a large size recording sheet continuously, after performing paper feeding of many small size recording sheets continuously, without causing cost increase of a device and deterioration in processing efficiency of the whole print job. SOLUTION: The image forming device judges whether or not the continuation print number A of the recording sheet of small size is larger than the prescribed value K for every completion of the print job for which the paper feeding of the small size recording sheet is performed (step S106), when the continuation print number A is larger than K, next, the device judges whether or not the print job for which the paper feeding of the large size recording sheet is performed, is in the reservation print job (step S107), and when it exists, next, the print job is performed (step S108). Thereby, before the difference of temperature of a fixing roll exceeds a prescribed range, the paper feeding of the large size recording sheet can be performed, the difference of temperature is relaxed and neither the defective fixing nor the paper winkle is caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a fixing device of a fixing roller type, and more particularly to a technique for preventing an excessive temperature difference in the axial direction of the fixing roller.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus,
The toner image formed on the recording sheet is fixed by applying pressure while heating at a predetermined temperature by a fixing roller. The fixing roller is provided with heat almost uniformly in the axial direction of the roller by an internal heater, but passes a recording sheet having a width smaller than the maximum sheet passing width of the fixing roller (hereinafter, referred to as “small size recording sheet”). When paper is used, only the paper passing portion is deprived of heat by the recording sheet. Therefore, when such a small-sized recording sheet is continuously passed in a large amount, the non-sheet passing portion of the fixing roller is heated with almost no loss of heat, so that the temperature becomes high, and the temperature difference in the roller axis direction is increased. Becomes extremely large.

[0003] When the temperature difference in the axial direction of the fixing roller becomes remarkable in this way, when an image forming process for a wider recording sheet (hereinafter, referred to as a “large-sized recording sheet”) is performed, Since a portion of the large-size recording sheet contacts the high-temperature portion of the fixing roller, which was a non-sheet-passing portion of the small-size recording sheet, toner on the recording sheet in that portion may adhere to the roller surface and cause defective fixing. ,
Alternatively, there is a problem that a difference in the amount of water evaporation in the recording sheet due to a temperature difference in the roller axis direction causes paper wrinkles and the like.

As a method for solving such a problem, for example, Japanese Patent Application Laid-Open No. Hei 8-234620 discloses a method in which small-size paper is continuously passed, and then large-size dummy paper or a special-purpose sheet is passed. There is disclosed a technique for removing heat from a non-sheet passing portion of a fixing roller and preventing overheating of this portion (first conventional technology). Also, JP-A-8-27872
In Japanese Patent Application Laid-Open No. 11-109781 and Japanese Patent Application Laid-Open No. 11-109781, when the temperature difference in the fixing roller becomes remarkable, the image forming process is temporarily stopped and waits for a predetermined time so that the temperature difference falls within a certain range. A technique for resuming image formation after a delay has been disclosed (second prior art).

[0005]

However, in the first prior art, it is necessary to newly provide a mechanism for feeding a dummy sheet or a special-purpose sheet, thereby avoiding an increase in the cost of the image forming apparatus. Absent. In addition, the second
In the related art, a predetermined time has to be waited for eliminating the temperature difference in the fixing roller, and the efficiency of the entire image forming process is reduced.

The present invention has been made in view of the above problems, and can prevent the occurrence of defective fixing and paper wrinkles without increasing the cost of the apparatus or reducing the efficiency of image forming processing. It is an object to provide an image forming apparatus.

[0007]

According to the present invention, there is provided a first image forming apparatus for forming an image on a recording sheet having a first width in a direction perpendicular to a sheet passing direction in an image forming section. And the second image formation for forming an image on a recording sheet having a second width larger than the first width in the direction orthogonal to the sheet passing direction can be selectively executed, An image forming apparatus including a fixing roller for thermally fixing a recording sheet on which the image is formed, wherein a temperature difference in an axial direction of the fixing roller is determined at a predetermined timing by a receiving unit that receives a plurality of print jobs. Determining means for determining whether or not the temperature exceeds the range; determining that the temperature difference in the axial direction of the fixing roller exceeds a predetermined range; Control means for selecting at least one of the print jobs when there is a print job for performing the second image formation among the print jobs, and then controlling the image forming unit to execute the print job. It is characterized by having.

The present invention further comprises a counting means for counting the number of continuous executions of the first image formation, wherein the determination means determines that the number of continuous executions of the first image formation exceeds a predetermined number. Preferably, it is determined that the temperature difference in the axial direction of the fixing roller exceeds a predetermined range. Further, the present invention further includes a detecting unit that detects a temperature of a portion of the fixing roller surface where the recording sheet having the first width does not pass, wherein the determining unit determines that the temperature detected by the detecting unit is a predetermined value. When it exceeds, it is determined that the temperature difference in the axial direction of the fixing roller exceeds a predetermined range.

Further, the present invention is characterized in that the predetermined timing in the determination means is each time a print job for executing the first image formation ends. Still further, according to the present invention, the predetermined timing in the determination unit is each time the first image formation is performed once, and the control unit determines the temperature difference in the axial direction of the fixing roller by the determination unit. Is determined to exceed a predetermined range, and if there is a print job for forming a second image among the print jobs received by the receiving unit, the print job currently being processed is temporarily interrupted and the second At least one of the image forming print jobs is executed, and after the print job is completed, the image forming unit is controlled to continuously execute the interrupted print job.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below using a digital copying machine (hereinafter simply referred to as "copier") as an example. Embodiment 1 (Overall Configuration of Copying Machine) FIG. 1 is a diagram showing an overall configuration of a copying machine 1 according to Embodiment 1 of the present invention.

As shown in FIG. 1, the copying machine 1 includes an automatic document feeder 10, an image reader 20, a controller 30, a printer 40, a fixing unit 50, a paper feeding unit 60, and a paper re-feeding unit 7.
Consists of zero. The automatic document feeder 10 includes the document feed tray 1
1, a separation roller 12, a conveyance belt 13, a document discharge tray 14, and the like. Documents stacked on the document supply tray 11 are separated one by one by the separation roller 12, the conveyance belt 13, and the like to form a platen glass. Scanner 2 of image reader unit 20 is sent to a predetermined reading position on
2, the document is discharged to the document discharge tray 14.

The image reader unit 20 includes the scanner 2
2, a CCD image sensor 23 and other optical systems are provided, and a document image on the platen glass 21 is read and photoelectrically converted by the CCD image sensor 23 to obtain an image signal. This image signal is A / D-converted by the control unit 30 and subjected to a known correction process to become image data, which is stored in a memory inside the control unit 30.

The printer section 40 includes a laser diode 4
1, photosensitive drum 42, charging charger 43, developing unit 4
4 and a transfer charger 45. The laser diode 41 is driven based on the image data, and scans the photosensitive drum 42 with the laser beam. The photosensitive drum 42 has a charging charger 43 before exposure.
The electrostatic latent image is formed by the above exposure scanning, and the electrostatic latent image is visualized by supplying the toner from the developing device 44.

On the other hand, the paper supply section 60 includes two paper cassettes 61a and 61b, each of which stores recording sheets of different sizes. Photoconductor drum 42
The recording sheet fed from one of the paper cassettes 61a and 61b at the same timing as the image forming operation described above, the toner image on the photosensitive drum 42 is transferred onto the recording sheet by the electrostatic force of the transfer charger 45. The image is transferred and conveyed to the fixing unit 50.

The fixing roller 51 in the fixing section 50 includes
A heater is built in, and a fixing roller 51 is provided as described later.
Is controlled. The transferred recording sheet is heated and pressed by the fixing roller 51 to fix the toner image. The fixed recording sheet is discharged onto a discharge tray 71 via a re-feed unit 70. On the other hand, when printing is also performed on the back side of the recording sheet (so-called double-sided copy), the re-feeding unit 70 reverses the front and back of the recording sheet.
By sending it to the transfer position below the photosensitive drum 42 again, printing on the back surface of the recording sheet is realized.

An operation panel 80 (FIG. 2) is installed at a position on the front surface of the image reader section 20 where it can be easily operated. The operation panel 80 is provided with a numeric keypad for inputting the number of copies and a copy magnification, a start key for starting a copy operation, a display unit for displaying a set print mode, and the like. The user can make a desired input.

In the fixing section 50, a fixing roller 51 is provided.
Sensor S that detects the surface temperature at the substantially central portion in the axial direction of
E1 (see FIG. 2) is provided, and the fixing temperature is controlled based on the detection result of this sensor. (Configuration of Control Unit 30) FIG. 2 is a block diagram showing the configuration of the control unit 30 in the copying machine 1.

As shown in FIG. 1, the control unit 30 includes a main control unit 31, a signal processing unit 32, a memory control unit 33, a packet memory 34, a page memory 35, a print control unit 36, an external interface 37, and the like. .
The main control unit 31 sends instructions to the other units to execute a print mode accepted by the operation panel 80 to execute a smooth print operation.

The signal processing section 32 includes the image reader section 20.
The A / D conversion is performed to convert the image signal obtained as described above into a digital multi-valued signal. After performing known corrections such as density conversion, shading correction, and edge enhancement processing, the image signal is sent to the memory control unit 33. Further, it receives transmission data from an external terminal on the network via the external interface 37. The transmission data is data to be printed out, such as image data and character code strings (hereinafter, referred to as “data”).
It is called "print target data". ) And data including control information such as a print request, a print mode, a page signal and an identification signal indicating the type of data (hereinafter, referred to as “control data”). The signal processing unit 32 Upon receipt, first, the type of data is determined. If the data to be printed is bitmap-developed image data, it is sent to the memory control unit 33 as it is, and if it is character code data, it is transmitted to the font memory 321. The data is bit-mapped based on the font table in the table and sent to the memory control unit 33.

The memory control unit 33 compresses the image data sent from the signal processing unit 32 and stores it in the packet memory 34 for each page. Then, the main control unit 31
, The image data of the corresponding page is sequentially read out, decompressed, and written in the page memory 35. The print control unit 36 reads the image data from the page memory 35 according to the instruction from the main control unit 31, sends the image data to the print head 401, and also prints the printer unit 40, the fixing unit 50, the paper feeding unit 60, and The image forming system composed of the paper feed unit 70 is controlled in a unified manner, an image forming process is executed, and a print count signal is transmitted to the main control unit 31 each time one image formation is completed. Further, the print controller 36 controls the temperature of the fixing roller 51 based on the detection result from the sensor SE1 provided on the fixing roller 51.

The main control unit 31 causes the counter 38 to count the number of continuous prints of the small-size recording sheet based on the print count signal. Through an operation from the operation panel 80, a job for forming an image based on image data read from the image reader unit 20 and a job for forming an image based on a print request received from an external terminal via the external interface 37 (hereinafter, any one of the following) A job is also called a “print job.”
Are assigned a job number in the order in which they are received, and in association with this, print mode information such as the print size, the number of prints, and the number of copies of the print job are registered in a job management table in a memory inside the main control unit 31. You.

The print mode information is included in the control data for a print job received from an external terminal, and when the image is read by the image reader unit 20 in accordance with an instruction from the operation panel 80. The print size is obtained from an instruction from the operation panel 80 or obtained by a size detection sensor (not shown) provided below the platen glass 21. The number of prints is obtained from a microswitch ( (Not shown), and is obtained by counting the number of passing documents detected by the method. Further, the number of copies depends on the setting from the operation panel 80.

Then, the main control unit 31 selects a next print job to be executed under predetermined conditions while referring to the job management table. Details will be described later. FIG. 3 is a diagram showing an example of the configuration of the job management table in the main control unit 31. When a print job is received from the operation panel 80 or via the external interface 37 as described above, a job number is assigned, and print mode information such as the print size, the number of prints, and the number of prints of the print job is given. It is registered in the corresponding column of the job management table in association with the job number.

(Control Operation by Control Unit 30) FIG. 4 is a flowchart showing a main routine of a control operation of the entire copying machine 1 by the control unit 30. First, in step S1, it is determined whether or not a print start instruction has been issued by the main control unit 31. This is determined based on whether a copy start instruction has been received from the operation panel 80 or whether a print request has been received from an external terminal. When there is a print start instruction from the operation panel 80, the main control unit 31
Is controlled to read a document image, and when a print request is made, the transmission data is accepted, the respective image data is stored in the packet memory 34, and registered as a print job in the job management table.

Then, in the next step S2, of the unprocessed print jobs registered in the job management table, image formation is executed for the print job with the smallest job number (step S2). In this case,
A print job instructed to start copying may be executed with the highest priority. In step S3, a process of selecting a print job to be executed next from the job management table is executed. Thereafter, in step S4, other processes such as temperature control of the fixing roller are performed. In step S5,
In step S3, it is determined whether or not the next print job to be executed is selected. If the next print job is selected (YES in step S5), the process returns to step S2 to return to the image of the selected print job. Perform shaping. If it is determined in step S5 that the next print job has not been selected, no unprocessed print job remains, and the process returns to step S1 and waits for an instruction to start the next print job.

FIG. 5 is a flowchart showing a subroutine of the next job selection control in step S3. First, it is determined whether or not the currently selected print job has been started (step S101). If the print job has been started, the print job is referred to a small-size recording sheet (see FIG. 3) by referring to the job management table. Then B5
It is determined whether or not the print job is a print job (hereinafter, referred to as a “small size job”) for passing a sheet of a size (step S).
102), if the job is a small-size job, the counter 38 counts the number A of prints executed until the end of the print job (step S103).

When the print job is completed (YES in step S104), it is determined whether an unprocessed print job (reserved print job) is registered with reference to the job management table (step S105).
If registered, it is determined whether or not the number of executed prints A counted by the counter 38 is larger than a predetermined value K (step S106).

As the value of K, the temperature difference between the sheet passing portion and the non-sheet passing portion in the axial direction on the surface of the fixing roller 51 generated when the small size recording sheet is continuously passed is the next large size recording sheet. The threshold value is set with reference to a limit value within a range in which toner does not adhere and paper wrinkles do not occur even if the sheet passes, and is set in advance in consideration of a predetermined safety factor through experiments or the like. If the safety factor is A <K at the end of one small-size job and the next execution of another small-size job, the temperature difference at the end of the print job exceeds the above limit value. It is set so that there is no. At this time, the average number of prints in one print job will be referred to.

In the present embodiment, the value of K is
The number is set to about 30 to 100 sheets. And
If it is determined that the number A of prints to be executed is larger than the predetermined value K, a large-size recording sheet (A4 size in FIG. 3) is set on the fixing roller 51 in the registered reserved print job with reference to the job management table. ) Is determined (step S107), and if so, the print job with the smallest job number is selected from the print jobs (step S108). , The count value of the counter 38 is reset.

On the other hand, if it is determined in step S102 that the print job being executed is not a small-size job, or if the number A of small-size jobs is less than or equal to a predetermined value K in step S106, or if it is determined in step S107. If there is no large-size job among the reserved print jobs registered in the job management table, the next small-size job is selected in each case according to the job number in the job management table.

Thereafter, the process returns to the main routine for controlling the operation of the entire printer, and executes the print job selected as described above. As described above, in the first embodiment, when the number of prints A to be executed exceeds the predetermined value K after the execution of the small-size job is completed, the large-size job is selected from the job management table and is executed, whereby the small-size job is executed. The heat of the non-sheet passing portion of the fixing roller in the size job is absorbed by the recording sheet, and the temperature difference in the axial direction of the fixing roller is kept within a predetermined range without lowering the efficiency of the entire print job.

Although the number of prints A has become larger than the predetermined value K as described above (step S1).
If it is determined that there is no large-sized job in step S107, the next print job (in this case, a small-sized job) is selected and executed. As long as a small-size job is being executed, there is no problem of fixing failure or paper wrinkling on the small-sized recording sheet.However, when a large-size job is accepted and then executed, the same as in the past. Problems can arise.

However, as described above, the predetermined value K is a value in consideration of the safety factor, and it is assumed that the copying machine is frequently used by a large number of people via a LAN or the like as an operating environment. Therefore, it is considered that a large-size job is accepted before the temperature difference of the fixing roller exceeds the true allowable range after the determination is made that A> K, and there is no practical problem in this respect.

(Embodiment 2) In the first embodiment, in the next job selection control, the number of continuous prints A of small-size recording sheets is compared with a predetermined value K every time a small-size job is completed, and the next job is selected. However, in the second embodiment, the above comparison is performed each time printing is performed once during execution of a small-size job. Therefore, the configuration of the entire copying machine and the control unit 30 are the same as those of the first embodiment, and only the control operation unique to the present embodiment will be described below.

FIG. 6 is a flowchart showing a subroutine of the next job selection control (step S3 in FIG. 4) in the second embodiment. The currently selected print job is started, and if it is a small size job (YES in step S201, Y in step S202)
ES), every time printing is performed once, 1 is added to the number of prints A executed so far in the counter 38 (steps S203 and S204), and it is determined whether the value of A after the addition exceeds a predetermined value K. Judge (Step S20)
5).

If it is determined in step S205 that the number A of prints to be executed has exceeded the predetermined value K, it is determined whether a large-size job among unprocessed print jobs is reserved by referring to the job management table (step S205).
206). If the large-size job is reserved, the current print job is temporarily interrupted (step S207), and the unexecuted image data of the interrupted print job is saved in the packet memory 34 (step S208).
Next, a print job having the smallest job number is selected from the reserved large-size jobs (step S20).
9) After executing this print job (step S
210), the unexecuted image data saved in step S208 is read out again from the packet memory 34 and restored (step S211), and the interrupted execution of the small size job is resumed (step S212). Thereafter, it is determined whether the small size job has been completed (step S213), and steps S203 to S2 are performed until the small size job is completed.
Step 13 is repeated.

Note that K in the determination in step S205
May be the same value as in the first embodiment, but in the present embodiment, the comparison between A and K is performed each time printing is performed, and a large-size job is immediately determined from the result. Since it can be executed, the value of K may be slightly increased by estimating the safety factor smaller than in the case of the first embodiment.

If it is determined in step S202 that the print job to be executed is not a small size job, or if a large size job has not been reserved in the job management table in step S206, the current print job is The process is continued until the process ends (step S214). If it is determined in step S205 that the number of prints A to be executed does not exceed the predetermined value K, the process returns to step S203 and repeats the above operation until it is determined in step S213 that the current small-size job has been completed.

If it is determined in step S213 that the current print job has been completed, it is determined whether an unprocessed reserved print job has been registered in the job management table (step S215). Selects the next print job in the order of registration (step S216), and if not, returns to the main routine for controlling the operation of the entire printer as it is.

As described above, in the second embodiment,
If the number A of prints to be executed exceeds the predetermined value K while the small-size job is being executed and there is a reserved print job for the large-size job, the small-size job is immediately interrupted and the large-size job is stopped. Is performed, it is possible to maintain the temperature difference in the axial direction of the fixing roller within a predetermined range without lowering the efficiency of the entire print job, and there is no problem of defective fixing and occurrence of paper wrinkles. .

Third Embodiment In both the first and second embodiments, in the next job selection control, the number A of continuous prints of small-sized recording sheets is compared with a predetermined value K to determine the axis of the fixing roller. In the third embodiment, the temperature difference in the axial direction of the fixing roller 51 is directly detected, and the next job is determined based on the detection result. I have to choose. That is, in addition to the sensor SE1 for controlling the temperature of the fixing roller 51, a temperature sensor for detecting the surface temperature of the non-sheet passing portion (particularly, preferably the axial end portion) of the small-sized recording sheet of the fixing roller 51. SE2 is separately provided, and when this detected temperature exceeds a predetermined value, it is determined that the temperature difference has become larger than the predetermined value, and the next print job is selected. As described above, since the temperature of the paper passing portion of the fixing roller 51 is controlled to a predetermined fixing temperature as described above, the temperature difference can be determined only by detecting the temperature of the non-paper passing portion. .

Therefore, the entire configuration of the copying machine is the same as that of the first and second embodiments except that the sensor SE2 is added, so that the description thereof will be omitted, and the following explanation will be omitted hereafter. Only the control will be described. FIG.
13 is a flowchart illustrating a subroutine of next job selection control according to the third embodiment.

The currently selected print job is started, and if it is a small size job (YES in step S301, YES in step S302), each time printing is performed, the print job is detected by the sensor SE2. It is determined whether or not the temperature T (hereinafter, referred to as “non-sheet passing portion temperature T”) exceeds a predetermined value H (step S304). As the value of H, the upper limit of the allowable range is set so that the temperature difference between the sheet passing portion and the non-sheet passing portion in the axial direction on the surface of the fixing roller 51 does not cause the above-described fixing failure or paper wrinkling. For example, the normal fixing temperature is about 20 to 30
The value obtained by adding ° C is set.

If it is determined in step S304 that the non-sheet passing portion temperature T has exceeded the predetermined value H, it is next determined whether or not a large-size job has been reserved by referring to the job management table (step S305). . If the large-size job is reserved, the current print job is temporarily interrupted (step S306), and the unexecuted image data of the print job is saved in the packet memory 34 (step S307). Next, a print job having the smallest job number is selected from the reserved large size jobs (step S308), and after executing this print job (step S309), the unexecuted portion saved as described above is saved. Is read out again from the packet memory 34 and restored (step S310), and the print job is restarted (step S311). afterwards,
It is determined whether the print job has been completed (step S312), and if not, step S303.
And the above operation is repeated.

On the other hand, if it is determined in step S302 that the print job to be executed is not a small-size job, or if a large-size job has not been reserved in the job management table in step S305, the current job is not changed in any case. The process is continued until the print job is completed (step S313). If it is determined in step S304 that the non-sheet passing portion temperature T has not exceeded the predetermined value H, the process skips to step S312, and the process proceeds to step S303 until it is determined that the current print job has been completed.
Repeat the following steps.

If it is determined in step S312 that the current print job has been completed, it is determined whether an unprocessed reserved print job has been registered in the job management table (step S314). And the next print job in the order of reservation (step S31)
5) If not registered, the process returns to the main routine for controlling the operation of the entire printer.

As described above, in the third embodiment,
If the fixing roller end temperature T exceeds a predetermined value H during the execution of the small-size job, the small-size job is temporarily interrupted, and the large-size job is selected and executed, thereby improving the efficiency of the entire print job. The temperature difference in the axial direction of the fixing roller can be kept within a predetermined range without lowering the fixing roller, and it is possible to prevent the occurrence of defective fixing and paper wrinkles when a large-size job is executed.

(Modification) The copying machine according to the present invention has been described based on the embodiment.
It is needless to say that the present invention is not limited to the above-described embodiment, and the following modified examples can be implemented. (1) In the above-described embodiment, the small-size recording sheet is “B5” and the large-size recording sheet is “A4”. However, the size of the recording sheet is not limited to this, and the recording sheet is not limited to “B5”. It is sufficient that the recording sheet to be printed has a relatively large width in the axial direction and a relatively small width.

(2) In the above embodiment, the determination of the small size and the large size of the recording sheet is made only based on the size of the recording sheet. Is also good. In this case,
Even in the same size, in an image forming apparatus capable of switching between vertical paper passing and horizontal paper passing, regardless of the size of the recording sheet, small-sized recording sheets are used for large-size sheets and large-size sheets are used for large-size sheets. It is determined to be a size recording sheet.

In the case of the digital image forming apparatus as in the present embodiment, since the rotation of the image data can be easily performed, for example, in step S107 in FIG. However, if there is no large-size job, the image data of the next print job is intentionally rotated by 90 degrees so as to be printed on a laterally passing recording sheet. It is also possible not to exceed the predetermined range.

(3) In the above-described embodiment, it is needless to say that it is desirable that a large-sized recording sheet be passed through the full width of the fixing roller. In the reserved print job, the recording sheet having the largest width orthogonal to the recording sheet passing direction may be selected as the large-sized recording sheet.

(4) In the above embodiment, the digital copying machine has been described. However, the present invention has a fixing roller, such as another laser printer or a plain paper facsimile, and accepts reservations for a plurality of print jobs. The present invention can be applied to all the image forming apparatuses capable of performing the above operations.

[0053]

As described above, in the image forming apparatus according to the present invention, it is determined that the temperature difference in the axial direction of the fixing roller exceeds a predetermined range, and the received print job is orthogonal to the sheet passing direction. If there is a print job in which the width of the recording sheet in the direction is wider than that of the current print job, the image forming unit selects at least one of the print jobs and then executes the print job. Control, it is possible to prevent the temperature difference in the axial direction of the fixing roller from being exceeded by a large amount of small-sized recording sheets passing through a predetermined range. No defects or wrinkles occur.

Further, in performing the above control, it is not necessary to add a new mechanism to the image forming apparatus or to provide a waiting time for a print job for adjusting the temperature of the fixing roller. There is no increase in cost or reduction in the efficiency of the entire print job.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a copying machine according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a control unit in the copying machine.

FIG. 3 is a diagram showing an example of a job management table stored in a memory in a control unit of the copying machine.

FIG. 4 is a flowchart showing a control operation of the entire copying machine.

FIG. 5 is a flowchart illustrating a subroutine of next job selection control according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating a subroutine of next job selection control according to the second embodiment of the present invention.

FIG. 7 is a flowchart illustrating a subroutine of next job selection control according to the third embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Copier 10 Automatic document transport section 20 Image reader section 30 Control section 30 40 Printer section 50 Fixing section 51 Fixing roller 31 Main control section 32 Signal processing section 34 Packet memory 36 Print control section 38 Counter

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H027 DA12 DA38 DA46 DC19 EA12 EC02 EC20 ED16 ED25 EE02 EE07 EF06 EF09 FA05 FA35 FB07 FB13 2H033 AA02 AA09 BA30 BA32 BB01 BB28 CA04 CA07 CA17 CA27 CA35 CA37

Claims (5)

[Claims] In the image forming section, a first image formation for forming an image on a recording sheet having a first width in a direction orthogonal to the paper passing direction is provided, and a width in a direction perpendicular to the paper passing direction is provided. A second image forming operation for forming an image on a recording sheet having a second width larger than the first width can be selectively executed, and a fixing roller for thermally fixing the recording sheet on which the image is formed is provided. An image forming apparatus comprising: a receiving unit that receives a plurality of print jobs; a determining unit that determines, at a predetermined timing, whether a temperature difference in an axial direction of the fixing roller exceeds a predetermined range; Means for determining that the temperature difference in the axial direction of the fixing roller exceeds a predetermined range, and executing a second image formation among print jobs received by the receiving means. An image forming apparatus that selects at least one of the print jobs and then controls the image forming unit to execute the print job. 2. The image forming apparatus according to claim 1, further comprising a counting unit that counts the number of continuous executions of the first image formation, wherein the determination unit determines that the number of continuous executions of the first image formation exceeds a predetermined number. 2. The image forming apparatus according to claim 1, wherein it is determined that the temperature difference in the axial direction of the roller exceeds a predetermined range. 3. A detecting means for detecting a temperature of a portion on the surface of the fixing roller through which the recording sheet of the first width does not pass, wherein the determining means detects that the temperature detected by the detecting means exceeds a predetermined value. The image forming apparatus according to claim 1, wherein when determining that the temperature difference in the axial direction of the fixing roller exceeds a predetermined range. 4. The image forming apparatus according to claim 1, wherein the predetermined timing in the determination unit is each time a print job for executing the first image formation ends. 5. The predetermined timing in the determination unit is each time the first image formation is performed once, and the control unit determines that the temperature difference in the axial direction of the fixing roller is within a predetermined range by the determination unit. And if there is a print job for forming the second image among the print jobs received by the receiving unit, the print job currently being processed is temporarily interrupted to perform the second image formation. 4. The image forming unit according to claim 1, wherein at least one of the print jobs is executed, and after the print job is completed, the image forming unit is controlled to continuously execute the interrupted print job. An image forming apparatus according to any one of the above.