JP3079852B2 - Image forming device - Google Patents

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, and more particularly to an image forming apparatus including fixing means for fixing a toner image by heating while nipping and conveying a recording sheet onto which a toner image has been transferred.

[0002]

2. Description of the Related Art Conventionally, in a copying machine, a printer and other image forming apparatuses, a roller fixing device is most commonly used as a fixing means for heating and fixing a toner image while nipping and transporting a recording sheet onto which a toner image has been transferred. Has been adopted.

This roller fixing device is composed of a heat roller (fixing roller) and a pressure roller that presses against the heat roller. By passing a recording paper having an unfixed toner image on the surface between the pair of rollers, heat is applied. Is added to fuse and fix the toner.

A recording paper conveyed in a paper conveyance path of an image forming apparatus is charged by a discharge device when a toner image is transferred from a photosensitive drum, or comes into contact with another member in the conveyance path. In some cases, the sheet may be charged with static electricity or may be humid depending on environmental conditions. In such a case, the transfer condition changes, and the sheet is caught and a jam occurs.

Due to the occurrence of the jam, the image forming operation is interrupted, and the rollers of the fixing device also stop rotating. In such a case, in the heating section of the fixing device, the pressure roller may be deformed, and if the heat roller and the pressure roller are stopped while the sheet is sandwiched, the sheet may be ignited. In general, when such a jam or the like is stopped, the heat roller and the pressure roller are separated from each other, and the rollers are brought into contact again when the image forming operation is resumed after the jammed paper is removed. .

However, the unfixed toner on the recording paper adheres to the heat roller when the heat roller and the pressure roller are separated from each other when the jam occurs, and the heat roller and the pressure roller are reconnected when the image forming operation is resumed after the jam is removed. The surface of both rollers becomes dirty due to contact and rotation, and the recording paper passes between the rollers to which the unfixed toner has adhered for fixing during the subsequent image formation, and eventually stains the recording paper. There was an inconvenience of letting them do it.

In order to solve such a problem, recently, when a fixing jam has occurred, a predetermined number of sheets to be fed are passed through the sheet without writing an image and discharged to a discharge tray. A fixing jam sheet passing control device has been proposed which clears the count of the number of sheets passed when a fixing jam further occurs during the passing of the blank sheet (Japanese Patent Laid-Open No. 3-48271). Reference).

[0008]

However, in the fixing jam sheet passing control device described in Japanese Patent Application Laid-Open No. 3-48271, a blank sheet is passed with the fixing jam specified. However, it is not possible to cope with all the abnormalities that cause excessive contamination.

Further, in this fixing jam sheet passing control device,
It is characterized by clearing the count of the number of sheets fed when further fixing jam occurs while passing blank paper, but this may cause unfixed toner to adhere to blank paper and stain the rollers. However, if there is a blank sheet that has passed through the fixing device before the occurrence of a fixing jam during blank sheet passing, the count of the number of fed sheets will be cleared, and a predetermined number of sheets will be passed again. There is an inconvenience that the same number of blank sheets as the number of sheets passing through the fixing device before the occurrence of the fixing jam during blank sheet passing are passed in duplicate, and wasteful sheets are fed by that amount.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned disadvantages of the prior art, and has as its object to solve the problem of unfixed toner that has adhered to the fixing means after a device abnormality such as a paper jam or an abnormal image forming operation has been resolved. An object of the present invention is to provide an image forming apparatus capable of efficiently preventing recording paper from being stained due to toner.

[0011]

According to the first aspect of the present invention, there is provided an image forming apparatus, comprising: a sheet feeding unit for feeding a recording sheet; and a toner image on an image carrier on the recording sheet fed by the sheet feeding unit. Transfer means for transferring, fixing means for heating and fixing the toner image while nipping and conveying the recording paper after the toner image transfer,
Conveyance means for conveying the recording paper from the paper supply means to the fixing means via the transfer means; first detection means for detecting an abnormality of the apparatus; and detection of whether or not recording paper is present in the fixing means. Second detecting means, a counting means for counting the number of remaining sheets in the apparatus passing through the fixing means, an abnormality detecting means for the first detecting means, and a second detecting means for detecting the recording paper. If the detection is detected, the fixing unit is cleaned by the residual paper in the apparatus being nipped and conveyed by the fixing unit.
Both when controlling the conveying means such that, on the basis of the count value of said counting means, when the number of remaining sheets in the device passes through the fixing unit is insufficient to predetermined specified number, the lack number recording paper Is supplied by the paper supply unit and nipped and conveyed to the fixing unit, thereby cleaning the fixing unit.
And a control means for controlling said feeding means and said conveying means so as to.

Here, the counting of the number of remaining papers in the apparatus passing through the fixing means is performed such that the counting means counts the number of residual papers actually passing through the fixing means based on the output of the second detecting means. Alternatively, any configuration may be used in which the counting means counts the number of remaining sheets present on the upstream side of the fixing device in the recording sheet conveying path.

According to a second aspect of the present invention, there is provided an image forming apparatus, comprising: paper feeding means for feeding recording paper; transfer means for transferring a toner image on an image carrier onto the recording paper fed by the paper feeding means; A fixing unit that heat-fixes the toner image while nipping and conveying the recording paper after the transfer of the toner image, a conveying unit that conveys the recording paper from the paper feeding unit to the fixing unit via the transfer unit, First detecting means for detecting an abnormality, second detecting means for detecting whether or not recording paper is present in the fixing means, and measuring means for measuring a passage time of the residual paper passing through the fixing means. , when the first detection means detects the abnormality and the second detection means detects the recording sheet, this residual sheet within the apparatus is held and conveyed to the fixing unit
Wherein the fixing means controls said conveying means so as to be cleaned together when the time obtained by adding the passing time measured by said measuring means does not reach a predetermined specified time, the size equivalent to the lack of time and at a The number of recording papers is
By being pinched and conveyed to the fixing unit is fed by
Control means for controlling the sheet feeding means and the transport means so that the fixing means is cleaned .

According to a third aspect of the present invention, there is provided an image forming apparatus according to the first aspect.
3. The image forming apparatus according to claim 2, wherein the residual paper is untransferred residual paper.

[0015]

The operation of the image forming apparatus according to the first aspect will now be described with reference to FIG.

During the image forming operation, an error occurs in the apparatus (paper jam,
When an abnormality in the image forming operation occurs, the first detecting unit 2
8 detects this. Thus, the operation of the device is stopped. At this time, if the recording paper 12 on which the toner image has not been fixed remains in the fixing unit 22, the portion where the recording paper 12 constituting the fixing unit 22 is nipped and conveyed is stained. The detecting means 30 detects the remaining unfixed recording paper 12. For this reason, after the paper jam or the abnormality of the apparatus is resolved, the control section 34 nips and conveys the residual paper in the apparatus to the fixing section 22 so that the fixing section 22
When controlling the transport unit 24 so as to be cleaned , the fixing unit 2 is controlled based on the count value of the counting unit 32 that counts the number of remaining sheets in the apparatus that passes through the fixing unit 22.
If the residual number of sheets in the apparatus passing through the 2 if insufficient to predetermined specified number, this recording sheet 12 of the insufficient number is held and conveyed to the fixing unit 22 is fed by paper feed unit 14
Controls the sheet feeding unit 14 and the conveying unit 24 so that the fixing unit 22 is cleaned . On the other hand, such control is not performed unless the number of remaining sheets in the apparatus that passes through the fixing unit 22 is not smaller than a predetermined specified number.

When the number of remaining papers in the apparatus is insufficient to a predetermined number, the remaining paper and the newly fed recording paper 12 are added up to add a predetermined number of recording papers 12.
Fixing means 22 cleaned but Rukoto is fed to the fixing section 22
Is, when the remaining sheet in the apparatus has reached a predetermined specified number of sheets, in Rukoto only remaining sheet is fed to the fixing section 22
Fixing means 22 is Rukoto cleaned.

Further, according to the image forming apparatus of the second aspect, similarly to the image forming apparatus of the first aspect, the fixing unit 2 is provided.
If the portion where the recording paper 12 constituting the second recording paper 12 is nipped and contaminated is generated, the second detection means 30 detects the remaining unfixed recording paper 12. Therefore, the constant in the control means 34, after the abnormality has been eliminated in jams or device, the remaining sheet in the apparatus is held and conveyed to the fixing section 22
When controlling the transporting means 24 so that the attaching means 22 is cleaned, when the total time of the passing time of the residual paper passing through the fixing means 22 measured by the measuring means does not reach a predetermined specified time, the size and number of the recording sheets 12 corresponding to the insufficient time is fed by a sheet feeding means 12 fixing means 2
The sheet feeding unit 14 and the conveying unit 24 are controlled so that the fixing unit 22 is cleaned by being nipped and conveyed by the sheet feeding unit 2. On the other hand, when the total time of the passing times of the residual paper passing through the fixing unit 22 has reached a predetermined specified time, such control is not performed.

When the total time of the remaining paper passing through the fixing means 22 does not reach the predetermined time, the recording paper 12 having the size and the number of sheets corresponding to the shortage is fixed. 22 is fed to the fixing in the Rukoto
Means 22 is cleaned, when the time which is the sum of the transit time of the remaining sheet passing through the fixing unit 22 has reached the predetermined specified time, only the remaining sheet is fed to the fixing section 22 Rukoto
In fixing unit 22 is Rukoto cleaned.

Furthermore, according to the image forming apparatus of the present invention, only the untransferred residual paper to which the toner is not adhered, that is, only the white paper is treated as the residual paper. It is not counted when counting the number of remaining papers in the apparatus that passes through the fixing unit 22, and is not a time measurement that is the sum of the passing times of the remaining papers that pass through the fixing unit 22. Accordingly, a predetermined number of blank sheets or a number of blank sheets whose size and total passing time correspond to the predetermined specified time are passed through the fixing unit 22, and the cleaning effect of the fixing unit 22 is improved.

In the image forming apparatus according to any one of the first to third aspects, if the recording paper of a plurality of sizes can be fed from the paper feeding means, the recording paper is transported in a direction perpendicular to the recording paper transport direction. It is preferable that the recording paper having the widest dimension be passed through the fixing unit as a recording paper of a shortage from the viewpoint of enhancing the cleaning effect of the fixing unit.

[0022]

【Example】

<< First Embodiment >> A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 schematically shows the appearance of the image forming apparatus 10 according to the first embodiment.

The image forming apparatus 10 includes a paper feeding unit 14 for feeding a recording paper 12 and a recording paper 12 based on image data.
(See FIG. 4) An image forming section 40 for recording an image thereon, and a discharge section 42 for discharging the recording paper 12 after the image recording,
These components are arranged in order from right to left in FIG.

In the paper supply section 14, drawer-type first to third paper supply trays 14A, 14B and 14C are vertically arranged in three stages so as to be able to supply three types of papers of different sizes. ing. Corresponding to this, the drawer-type first to third discharge trays 42A and 42 are similarly provided in the discharge section 42.
B and 42C are prepared. Of these, the first and second discharge trays 42A and 42 disposed in the upper and middle stages, respectively.
B is a tray for discharging the recording paper 12 on which an image is recorded during a normal image forming operation, and a lower discharge tray 42C is a recording paper on which image quality failure has occurred due to some abnormality of the image forming apparatus 10. An image defective paper discharge tray for discharging the recording paper 12 that has passed through at the time of paper feed control for cleaning the fixing unit 12 or a cleaning unit to be described later.

An operation panel 44 is provided on the upper surface of the main body case 46 of the image forming section 40. The operation panel 44 includes keys for inputting various instructions and a liquid crystal display for display (neither is shown). Are displayed, and when an abnormality occurs, the contents of instructions to the operator are displayed on this display.

FIG. 3 schematically shows the internal structure of the image forming section 40. In the main body case 46 of the image forming unit 40, the photosensitive drum 16 as an image carrier is disposed at a position slightly closer to the sheet feeding unit 14 than the center and slightly above the center in the height direction. I have.

A charge corotron 48 for charging the photosensitive drum 16 is provided around the photosensitive drum 16.
And an exposure device 50 for irradiating the charged photosensitive drum 16 surface with a laser beam corresponding to an image image.
And a developing unit 52 for visualizing (developing) the electrostatic latent image formed on the photosensitive drum 16 by the irradiation of the laser beam with toner, and transferring the toner image visualized by the developing unit 52 to the recording paper 12. Transfer corotron 18 as transfer means, and photosensitive drum 1 after transfer
6 and a cleaner 54 for cleaning and removing the toner remaining on the surface are sequentially arranged clockwise. The transfer corotron is disposed above the recording paper transport path 56 except for the transfer corotron 18, and the transfer corotron is disposed below the recording paper transport path 56 directly below the photosensitive drum 16.

On the downstream side of the photosensitive drum 16 in the recording paper transport path 56, a transport belt 58 is arranged along the recording paper transport path 56, and further downstream of this, the roller fixing device 22 as fixing means is provided. Are located.

The roller fixing device 22 includes a main body case 46.
3 includes a heat roller 60 disposed with the direction perpendicular to the paper surface of FIG. 3 as a longitudinal direction, and a pressure roller 62 that can contact and separate from the heat roller 60.

The heat roller 60 is, as shown in FIG.
Both ends are supported by a pair of stays 64A and 64B projecting downward from the upper surface of the main body case 46, and are driven by driving means (not shown) to rotate counterclockwise as viewed from the right side in FIG. The heat roller 60 is integrally provided with a heater 66 for heating at a support shaft portion, and the heat roller 60 is heated by the heater 66.

The pressure roller 62 is disposed opposite to the heat roller 60, and is a pair of rollers composed of a substantially L-shaped plate member supported by the main body case 46 so as to be able to move up and down about a support shaft 69. The holding members 68A and 68B are pivotally supported between one ends (upper ends in FIG. 4). The shaft of the pressure roller 62 is constantly urged in the direction of the heat roller 60 (direction of arrow A) by urging means (not shown). The roller holding members 68A and 68B have a pair of cams 72 whose other ends rotate counterclockwise in FIG.
The cams 72A, 72B are always in contact with the upper surfaces of the shafts A, 72B, respectively. When the cams 72A, 72B rotate by the operation of the solenoid 70, the roller holding members 68A, 68B rotate clockwise about the support shaft 69, As a result, the pressure roller 62 is pressed against the heat roller 6 against the urging force of the urging means (not shown).
0, the operation of the solenoid 70 is stopped, and the urging force of the urging means (not shown) and the solenoid 7 are stopped.
Cams 72A, 72A by the action of the return spring
B rotates clockwise in FIG. 4, and the pressure roller 62 is configured to press against the heat roller 60. In this way, the pressure roller 62 reciprocates in the direction of arrow A or B according to the operation / non-operation of the solenoid 70, and the heat roller 6
It is designed to be pressed against and separated from zero. In this case, the nip pressure between the heat roller 60 and the pressure roller 62 is changed by changing the mounting angle of the cams 72A, 72B.
Easy to adjust.

At the downstream side of the recording paper conveyance path 56 near the heat roller 60, a fixing device paper sensor 30 as first detecting means for detecting whether or not the recording paper 12 exists in the roller fixing device 22 is provided. Have been. This fixing device paper sensor 30
In the present embodiment, also functions as a sensor that detects that the residual paper has passed through the roller fixing device 22 during the paper passing control described later.

Here, the operation of the image forming apparatus 10 configured as described above during normal image formation will be briefly described.

When the recording paper 12 is fed from the paper feed tray (one of the first to third paper feed trays 14A, 14B, 14C) selected by the paper feed tray selection switch on the operation panel 44, The recording paper 12 is transported by a pair of conveying rollers 7.
4 and 76 are fed between the photosensitive drum 16 and the transfer corotron 18. At this time, the photoreceptor layer on the surface of the rotating photosensitive drum 16 is charged corotron 48.
The exposure device 50 irradiates a laser beam on the charged photoreceptor layer to form an electrostatic latent image. The electrostatic latent image is developed by a developing device 52, and the electrostatic latent image is visualized. The formed toner image is formed on the photosensitive layer on the surface of the photosensitive drum 16.

For this reason, the toner image is transferred by the transfer corotron 18 onto the recording paper 12 sent between the photosensitive drum 16 and the transfer corotron 18. It is sent to the fixing device 22.

At this time, the heat roller 60 and the pressure roller 62 constituting the roller fixing device 22 are in pressure contact with each other, and when the recording paper 12 is conveyed by these rollers 60 and 62 when the recording paper 12 is nipped. The toner image is heated and fixed, and the recording paper 12 on which the toner image has been fixed passes through a conveyance roller 78, and a discharge tray (one of the first and second discharge trays 42A and 42B) determined corresponding to the paper feed tray selected. ).

In FIG. 3, reference numerals 80, 82, 84, 8
Reference numeral 6 denotes a pair of transport rollers arranged along a transport path through which the recording paper 12 passes during double-sided printing. In double-sided printing, the recording paper 12 after passing through the roller fixing unit 22 is used for switching a paper passing path (not shown). Once sent to the roller pair 78 side by the branch claw,
After stopping at a position where the roller pair 78 sandwiches the predetermined position of the recording sheet, the roller pair 78 is reversed and passed through a conveyance path for double-sided printing with the rear end of the recording sheet 12 leading, and the conveyance roller pairs 80, 82, 8.
The recording paper 12 is conveyed by the conveying rollers 4, 86 and the conveying roller pair 76, and printing (image formation) on the other side of the recording paper 12 on which no printing is performed is performed.

FIG. 5 shows a configuration of a control system for controlling a series of operations from feeding to discharging of the image forming apparatus 10.

The control system includes a microcomputer (hereinafter referred to as “microcomputer”) 34 as control means, a paper feed control circuit 90 in which the flow of each job is controlled by a CPU 88 in the microcomputer 34, a transport control A circuit 92, an image forming control circuit 94, and a fixing device control circuit 9;
6 is included.

The microcomputer 34 has a CPU (central processing unit).
88, a ROM 34A, a RAM 34B and an input / output interface (I / O) 34C connected to the CPU 88 via a system bus. The control circuits 90 to 96 are connected to the CPU 88 via the input / output interface 34C. Have been. In the ROM 34A, a control algorithm or the like corresponding to a flowchart described later is stored in advance. The RAM 34B is used as a work area.

The paper feed control circuit 90 controls the paper feed unit 14, and feeds the image from the paper feed tray (14A, 14B, 14C) selected mainly according to a command from the microcomputer 34 into the image forming unit 40. A drive motor for feeding the recording paper 12 is controlled.

The transport control circuit 92 mainly includes a pair of transport rollers 74 and 7 arranged along the recording paper transport path 56.
6, 78 and the like and the conveyor belt 58 are controlled.

The image forming control circuit 94 controls the image forming section 40, and is configured so that the above-described normal image forming operation is performed mainly in accordance with a command from the microcomputer 34 (the photosensitive drum 16, the photosensitive drum 16, and the like). Charge corotron 48,
The exposure device 50, the transfer corotron 52, the cleaner 54, and the like are controlled.

The fixing device control circuit 96 includes the roller fixing device 22.
And controls mainly the rotation of the drive motor of the heat roller 60, the heating of the heater 66, the on / off of the solenoid 70, and the like.

Although not shown in FIG. 3, a plurality of paper detection sensors for detecting the presence / absence of recording paper are arranged at predetermined intervals along the recording paper transport path 56. .

Next, the operation of this embodiment including the abnormal state will be described with reference to the flowchart of FIG. 6 showing the control algorithm of the CPU 88 in the microcomputer 34.

The control algorithm starts when the operator operates the instruction input keys on the operation panel 44 to set the printing conditions and then turns on the start button.

In step 100, initial settings are made. In step 102, the fixing device cleaning flag is cleared. Then, in step 104, the above-described image forming operation is performed.

In the next step 106, it is determined whether or not a paper jam has been detected. The determination of this paper jam is, for example,
The number of rotations of the motor driving the pair of conveying rollers 74 and 76 or the motor driving the heat roller 60 is monitored to reduce the number of rotations suddenly, or the current flowing to these motors is monitored to monitor the overload current. Is performed by determining that a paper jam has occurred. The recording paper 12 is detected by the upstream sensor using a pair of conveying rollers for which a paper jam is to be determined or a paper detection sensor (including the paper sensor 30 for the fixing device) provided above and downstream of the roller fixing device 22. If the downstream sensor does not detect the recording paper 12 after a lapse of a predetermined time from, a paper jam may be determined.

If the determination in step 106 is affirmative, the process proceeds to step 108, where the image forming operation is stopped (including the stop of the motor of the transport system). Pressure roller 6
After separating the two, at step 112, a paper jam is displayed on the liquid crystal display on the operation panel. Then, in the next step 114, it is determined whether or not the recording paper 12 is present in the roller fixing device 22 by checking the output of the fixing device paper sensor 30.
If the recording paper 12 does not exist, the flow shifts to step 118 to determine whether or not the jam removal has been completed (whether or not the jammed recording paper 12 has been removed). If the jam removal has not been completed, the process proceeds to a paper feed control subroutine (to be described later) of step 136 after waiting for the jam removal to be completed.

On the other hand, if the recording paper 12 is present in step 114, the unfixed toner may be placed on the heat roller 60 to cause image contamination as described in the section of the prior art. After the container cleaning flag is set, the flow proceeds to step 118 to wait for the completion of the jam removal, and then proceeds to the paper feed control subroutine of step 136.

On the other hand, if the determination in step 106 is negative, the process proceeds to step 120, where it is determined whether there is an abnormality in the image forming operation. Here, the abnormality of the image forming operation refers to, for example, abnormal rotation of the motor, abnormal image quality, and the like. The abnormal rotation of the motor can be detected in the same manner as described above. The density can be detected by the output of a density sensor (not shown) that constantly monitors the density.

If the determination in step 120 is negative, that is, if there is no paper jam and there is no abnormality in the image forming operation, the flow advances to step 122 to complete all the processes instructed by the operator before the start of the image forming control. It is determined whether or not the processing has been performed, and if all processing has not been completed, the process returns to step 104. Then, when there is no abnormality in both the paper jam and the image forming operation, when all the instructed processes are completed, the determination in step 122 is affirmed, and the control operation ends.

On the other hand, if the determination in step 120 is affirmative, the same processing and determination as in steps 108 to 118 described above are performed in steps 124 to 134, and then the flow proceeds to step 136, where the subroutine of the paper feed control is performed. Transition. However, in this case, in step 128, the details of the abnormality detected in step 120 are displayed on the liquid crystal display.

Next, a control operation of a subroutine of a sheet passing control for the roller fixing unit 22 will be described with reference to a flowchart of FIG.

In this subroutine, first, step 2
At 00, it is determined whether there is any remaining paper (indicating the recording paper 12 remaining in the apparatus) in the image forming unit 40. Here, it is most simple and reliable to detect the presence or absence of the residual paper based on, for example, the output of a paper detection sensor (not shown) disposed in each section of the recording paper transport path 56. The method is adopted, but the image forming unit 40
It can also be estimated from the difference between the number of recording papers 12 fed into the printer and the number of recording papers 12 discharged to the discharge unit.

If there is no remaining paper in step 200, the process returns to the main routine of FIG. 6. If there is any remaining paper, the flow advances to step 202 to determine whether or not the fixing device cleaning flag is set. Judge. If the fixing device cleaning flag is not set,
Since it is not necessary to clean the roller fixing device, the process proceeds to step 204 to control the pair of transport rollers and the like so as to discharge the residual paper to the third discharge tray 42C (hereinafter, appropriately referred to as “discharge control”).
Is started, and the process proceeds to step 224. Step 2
At 24, the process waits until there is no remaining paper in the image forming unit 40, and when there is no remaining paper, the discharge control is stopped at step 226, and the process returns to the main routine of FIG.

On the other hand, if the fixing device cleaning flag is set in step 202, it is necessary to clean the roller fixing device. Therefore, the flow advances to step 206 to discharge the residual sheet to the third discharge tray 42C. After the control of the conveying rollers and the like, the process proceeds to step 208. In this step 208, after clearing the count value of a fixing device paper passage counter (which is constituted by a software counter in the microcomputer) as a not-shown counting means, the process proceeds to step 210
Waits for the output of the fixing unit paper sensor 30 to change from off to on, and then in the next step 212, waits for the output of the fixing unit paper sensor 30 to change from on to off.
This is because when the residual paper passes between the heat roller 60 and the pressure roller 62, the output of the fixing device paper sensor 30 changes from OFF → ON → OFF, and the roller fixing device 22 This is to detect that the vehicle has passed.

If the output of the fixing device paper sensor 30 changes from ON to OFF at step 212, the process proceeds to step 214, where the fixing device paper passage counter is counted up.
In step 216, it is determined whether or not there is any remaining paper in the image forming unit 40. If the determination in step 216 is denied, the process returns to step 210 because there is still residual paper in the image forming unit 40, and repeats the processing and determination in steps 210 to 216 until the determination in step 216 is affirmed. .

If the determination in step 216 is affirmative, the process proceeds to step 218, where the count value N _ALL of the fixing device paper passage counter is set to a predetermined specified number N _TH (this is because the pressure roller 62 and the heat roller 60 are in the pressed state). By passing the recording paper 12 between them, the untransferred toner adhered to the rollers 60 and 62 is fixed to the recording paper 12 and the number of recording papers is sufficient to clean the rollers. If the determination is negative, the remaining sheets of the specified number N _TH or more pass through the roller fixing device 22 and
Since the cleaning of 0 and the pressure roller 62 has been sufficiently performed, the process proceeds to step 226 to stop the above-described discharge control, and then returns to the main routine of FIG.

On the other hand, if the determination at step 218 is affirmative, the routine proceeds to step 220, where the difference N (= N) between the specified number N _TH and the count value N _ALL of the fixing device paper passage counter is set.
After calculating ( _TH− N _ALL ), the paper feed tray (first to third paper feed trays 14) selected first in step 222
A to 14C), the N recording papers 12 are fed and passed through the roller fixing device 22. And step 2
At 24, the fed recording paper 12 passes through the roller fixing device 22, is discharged to the third discharge tray 42C, and waits for the remaining paper to disappear in the image forming section 40. After stopping the discharge control by proceeding to FIG.
Returns to the main routine.

After returning to the main routine, since the cleaning of the roller fixing device 22 has been completed, the process returns to step 102 to clear (reset) the fixing device cleaning flag, and thereafter, the above-described processing judgment is repeated.

As described above, according to the first embodiment, an abnormality (paper jam, abnormal image forming operation) occurs in the apparatus during the image forming operation, and the image forming operation (operation of the apparatus) is stopped. If the recording paper 12 on which the toner image has not been fixed remains in the roller fixing device 22, the fixing device paper sensor 30 detects the remaining unfixed recording paper 12. As a result, an abnormality of the device in which the heat roller 60 constituting the roller fixing device 22 (and thus the pressure roller 62) is easily stained is detected. If the recording paper 12 on which the toner image remaining on the roller fixing unit 22 is not fixed is detected, the microcomputer 34 removes the paper remaining in the apparatus after the paper jam or the abnormality of the apparatus is resolved. When controlling the pair of conveying rollers so as to be conveyed to the device 22, when the remaining paper in the apparatus passing through the roller fixing device 22 is insufficient to a predetermined specified number _NTH , the remaining paper is newly added. When a predetermined specified number _NTH of the recording papers 12 are fed through the roller fixing device 22 by summing the fed recording papers 12 and the remaining paper in the apparatus has reached the predetermined specified number _NTH. Controls the paper feed unit 14 and the pair of transport rollers so that only the residual paper passes through the roller fixing device 22.

Therefore, when an abnormality occurs in the apparatus in which the roller fixing device 22 is liable to be contaminated, the abnormality is reliably detected, and
The roller fixing unit 22 can be cleaned by efficiently using the remaining paper in the apparatus. When the number of remaining papers in the apparatus reaches a predetermined specified number, a new recording is performed from the paper feeding unit 14. The paper 12 is not supplied wastefully.

Although the above embodiment does not particularly describe a case where a fixing jam has occurred during the control of the sheet feeding to the roller fixing unit 22, in this case, the operation of the apparatus is detected by detecting the fixing jam. Is stopped, and after that, the recording paper 12 which has become a fixing jam is removed, and then the paper passing control is continued. At this time, since the paper feed control is performed so that the total number of recording papers 12 to be passed becomes the predetermined specified number N _TH , the fixing jam occurs during the passing of the white paper that does not possibly stain the roller fixing device 22. In the case where a paper jam occurs, the blank paper that has passed before the occurrence of the fixing jam does not overlap and be wastefully passed.

In the above-described embodiment, when an abnormality occurs in the apparatus that causes the roller fixing unit 22 to become dirty during the image forming operation, the paper passing for cleaning the roller fixing unit 22 is continued. Although the case where the control algorithm for performing the control is employed is exemplified, when the control algorithm of the endless cycle is employed, the sheet passing control for cleaning the roller fixing device 22 may be performed immediately after the control is started. .

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIGS.

The second embodiment has the same hardware configuration as the first embodiment described above.
The only difference is that the control program of No. 8 is different and that a passage time measuring timer (not shown) in the microcomputer 34 is used as a measuring means instead of the paper passage counter of the fixing device. Therefore, in the following, description will be made focusing on this difference, and description of overlapping parts will be omitted.

FIG. 9 is a flowchart showing a subroutine of the sheet passing control in the control algorithm of the CPU 88 in this embodiment. The main routine is the first routine.
This is the same as the embodiment.

In this subroutine, first, step 3
At 00, it is determined whether or not a residual sheet exists in the image forming unit 40. Here, the presence / absence detection of the remaining paper is determined by the first
This is performed in the same manner as in the embodiment.

If there is no remaining paper in step 300, the process returns to the main routine of FIG. 6. If there is remaining paper, the flow advances to step 302 to determine whether or not the fixing device cleaning flag is set. Judge. If the fixing device cleaning flag is not set,
Since it is not necessary to clean the roller fixing device, the flow proceeds to step 304 to control the pair of conveying rollers so as to discharge the residual paper to the third discharge tray 42C, and then proceeds to step 328. In step 328, the process waits until there is no remaining paper in the image forming unit 40.
Then, the control returns to the main routine of FIG.

On the other hand, if the fixing device cleaning flag is set in step 302, it is necessary to clean the roller fixing device. Therefore, the flow advances to step 306 to discharge the residual sheet to the third discharge tray 42C. After the control of the conveying rollers and the like, the process proceeds to step 308. In step 308, the time measured by the transit time measuring timer (not shown) T _{AL L}
Is cleared, in step 310, the fixing device paper sensor 3
Wait for the output of 0 to change from off to on. When the output of the fixing device paper sensor 30 changes to ON, step 31
2, the time measurement by the passage time measurement timer is started.
Wait for the output of the switch to change from on to off.

When the output of the fixing device paper sensor 30 changes from ON to OFF, the process proceeds to step 316, and the time measurement by the passage time measurement timer is stopped. As a result, the time T _PASS during which one sheet of residual paper passes through the roller fixing device is measured.

In the next step 318, replaces the value obtained by adding the current passing time measurements T _PASS the transit time sum T _ALL up last time (T _ALL + T _PASS) in transit time sum T _{AL L} up to the previous time After updating the total transit time value T _ALL , it is determined in step 320 whether or not there is any remaining paper in the image forming unit 40. If the determination at step 320 is denied, the process returns to step 310 because there is still residual paper in the image forming unit 40, and returns to step 32.
The processing / determination of steps 310 to 320 is repeated until the determination of 0 is affirmed.

If the determination at step 320 is affirmative, the routine proceeds to step 322, where the total passing time T _ALL is set to the predetermined specified time T _TH (this is because the recording paper is located between the pressure roller 62 and the heat roller 60 in the pressed state). 12 is sufficient to fix the untransferred toner adhered to the rollers 60 and 62 onto the recording paper 12 and clean the rollers). In this case, the number of remaining sheets equal to or greater than the specified time T _TH has passed through the roller fixing device 22 and the heat roller 60 and the pressure roller 62 have been sufficiently cleaned. 33
After returning to 0 and stopping the discharge control, the process returns to the main routine of FIG.

[0077] On the other hand, when the determination in step 322 is affirmative, after calculating the difference T (= T _TH -T _ALL) of willing the prescribed time T _TH and transit time sum T _ALL in step 324, In step 326, the process proceeds to a subroutine in which NMIN sheets of recording paper 12 corresponding to the minimum value of the number of sheets equal to or greater than the difference T are fed from the sheet feeding tray and passed to the roller fixing device 22.

In this subroutine, as shown in FIG. 9, a preselected paper feed tray (any of the first to third paper feed trays 14A to 14C: in this embodiment, this paper feed The size information is read from the recording paper that has been conveyed at the time of occurrence of an abnormality in the apparatus (which matches the paper feeding tray), and paper feeding is started from that tray (step 400), and the count value of a soft counter (not shown) is counted. Up (step 402).
This counting is performed when the recording paper 12 (white paper) fed from the paper feed tray (any one of the first to third paper feed trays 14A to 14C) passes through the roller fixing device 22. Although not shown here, the detection of the passing time is actually performed by detecting that the output of the fixing device paper sensor 30 changes from off to on to off.

In the next step 404, the paper length in the transport direction is set to L, and the paper feed speed of the roller fixing unit 22 is set to V.
It is determined whether or not T (= T _TH −T _ALL ) ≦ N × (L / V) holds. If the determination in step 404 is negative, step 40 is repeated until the determination is positive.
2. The processing / determination in step 404 is repeated, and if the determination in step 404 is affirmative, the routine returns to the calling routine.

That is, in this manner, NMIN recording sheets 1
2 is fed from the paper feed tray, passed through the roller fixing device 22, and then discharged to the third discharge tray 42C.

In step 328, the process proceeds to step 330 after the residual paper in the image forming unit 40 has been exhausted, stops the discharge control, and returns to the main routine of FIG.

After returning to the main routine, since the cleaning of the roller fixing device 22 has been completed, the process returns to step 102 to clear (reset) the fixing device cleaning flag, and thereafter, the above-described processing judgment is repeated. As described above, this second
According to the embodiment, similarly to the first embodiment, the roller fixing device 2
The fixing device paper sensor 30 detects the unfixed recording paper 12 remaining in the fixing roller 2, whereby the heat roller 60 constituting the roller fixing device 22 (and the pressure roller 62) is liable to be stained. An abnormal state of the device is detected. And
If it is detected that the recording paper 12 on which the toner image of the roller fixing device 22 has not been fixed remains, the microcomputer 34
However, after the paper jam or the abnormality of the apparatus is resolved, when controlling the pair of conveying rollers so that the residual paper in the apparatus is conveyed to the roller fixing unit 22, the roller fixing unit measured by the passage time measurement timer is used. When the total time T _ALL of the passing times of the remaining papers passing through the predetermined time T _TH does not reach the predetermined time T _TH , the recording paper 12 having the size and the number of sheets corresponding to the shortage time is supplied from the paper feeding unit 14 to the roller fixing device 22. when the controls paper feed unit 14 and the conveying roller equally be conveyed, total time T _ALL transit time remaining sheet passing through the roller fixing device 22 has reached a predetermined specified time T _TH is ,
The paper supply unit 14 and the pair of transport rollers are controlled so that only the residual paper is passed through the roller fixing device 22.

Therefore, the second embodiment can provide the same effect as that of the first embodiment.

Note that the sheet passing time of the roller fixing unit 22, that is, the fixing unit cleaning time varies depending on the size of the recording sheet.
The number of sheets may be set according to the size, but the standard size is specified in advance, and if the length is twice as long as the ratio of the standard size in the paper passing direction, one sheet is counted as two when counting the number of sheets. Is also good.

<< Third Embodiment >> Next, a third embodiment of the present invention will be described with reference to FIGS.

In the third embodiment, the configuration of the hardware is the same as that of the first embodiment. Therefore, the same reference numerals are used for the same portions in the description, and the detailed description of the configuration is omitted.

In this embodiment, n paper detection sensors (not shown) and a paper sensor 30 (not shown) arranged at predetermined intervals on the paper transport path 56 upstream of the roller fixing device 22. An information management table as shown in FIG. 10 is prepared, which is made up of table data corresponding to each of the above. The information management table is stored in the RAM 34B in the microcomputer 34. The rewriting management of the table data of the information management table is performed by the CPU 88. Here, in order to simplify the description, between the sensors adjacent to each other,
It is assumed that these sensors are arranged so that only one recording sheet 12 physically exists.

This will be described in more detail.
The presence or absence of the recording paper 12 at the sensor position is determined based on the outputs of the n sensors and the fixing device paper detection sensor 30. If the recording paper 12 is present, "1" is given as the paper presence / absence data. Records "0", obtains information on the size of the recording paper 12 fed from the selected paper feed tray, records the size information, and transfers the transfer point of the photosensitive drum 16 during the image forming operation. (Position where the transfer corotron is provided) When the output of the sensor k (the k-th sensor) arranged closest to the downstream side changes from off to on, the transfer presence / absence data of the sensor k is set to “0”. From "1" to "1". However, if an image is not being formed, even if the output of the sensor k changes from off to on, the transfer presence / absence data of the sensor is not rewritten and remains at "0".

Further, the CPU 88 moves the table data of the immediately preceding sensor to the table of the sensor when the output of the sensor changes from OFF to ON. However, at the first sensor position, there is no previous data, so when the output of the sensor changes from off to on, the paper presence / absence data is set to “1” and the size information of the recording paper 12 is changed. It is to be recorded. Note that all data in this information management table is initially “0”.

Next, the roller fixing device 2 in the third embodiment
The control operation of the subroutine of the sheet passing control for No. 2 will be described with reference to the flowchart of FIG. The main routine is the same as in the first embodiment.

In this subroutine, first, step 5
At 00, it is determined whether or not a residual sheet exists in the image forming unit 40. Here, the detection of the presence or absence of the residual paper is performed based on the outputs of the sensors arranged in each part of the recording paper transport path 56.

If no residual paper exists in step 500, the process returns to the main routine of FIG. 6. If residual paper exists, the flow advances to step 502 to determine whether or not the fixing device cleaning flag is set. Judge. If the fixing device cleaning flag is not set,
Since cleaning of the roller fixing device 22 is not necessary, step 508 is performed.
Then, after controlling the pair of conveying rollers so as to discharge the residual paper to the residual paper discharge tray, the flow proceeds to step 516. In step 516, the process waits until there is no remaining paper in the image forming unit 40.
After the above-described discharge control is stopped, the process returns to the main routine of FIG.

On the other hand, if the fixing device cleaning flag is set in step 502, it is necessary to clean the roller fixing device 22, so the process proceeds to step 504, where the number of sheets remaining on the upstream side of the roller fixing device 22 is reduced. It is determined based on the data of the information management table described above.

In the next step 506, the roller fixing device 2
(2) It is determined whether or not the number of remaining sheets N _ALL on the upstream side is smaller than a predetermined specified number of sheets N _TH . If this determination is denied, the process proceeds to step 508, but if the determination is affirmed, the process proceeds to step 508. Then, the process proceeds to step 510, where the difference N = N _TH −N between the specified number N _TH and the number N _ALL of the remaining sheets upstream of the roller fixing device 22.
Calculate _ALL .

In the next step 512, the conveying rollers and the like are controlled so as to discharge the residual paper to the residual paper discharge tray, and the N recording papers 12 are fed from the paper feed tray first selected in step 514. It passes through a roller fixing device 22.

In the next step 516, the process waits until the residual paper no longer exists in the image forming section 40. If all the residual paper has not been discharged, the flow advances to step 518 to stop the above discharge control. Return to the main routine.

After returning to the main routine, since the cleaning of the roller fixing device 22 has been completed, the process returns to step 102 to clear (reset) the fixing device cleaning flag, and thereafter, the above-described processing judgment is repeated.

As described above, according to the third embodiment, the same operation and effect as those of the first embodiment can be obtained. In addition, the specified number _NTH and the upstream side of the roller fixing device 22 can be obtained by using the data of the information management table. difference N = N _TH with number N _ALL remaining sheet of the -
Since N _ALL can be calculated before the start of the residual paper discharge control, N recording papers 12 (white paper) can be fed from the paper feed tray immediately after the start of the residual paper discharge control.
As a result, the recording paper 12 fed after the remaining paper is discharged, and the cleaning time of the fixing unit can be reduced as compared with the first and second embodiments.

<< Fourth Embodiment >> Next, a fourth embodiment of the present invention will be described.

In the fourth embodiment, the configuration of the hardware section is the first.
CP which is the same as that of the embodiment, and is similar to that of the third embodiment.
U performs information writing management of the information management table.

Next, the roller fixing device 2 in the fourth embodiment is described.
The control operation of the subroutine of the sheet passing control for No. 2 will be described with reference to the flowchart of FIG. The main routine is the same as in the first embodiment.

FIG. 7 is a flowchart of this subroutine.
When compared with the subroutine of the sheet passing control in the first embodiment, step 214 and step 613 to step 61 are performed.
4 is different from that of FIG.
Step 614 will be described, and the description of the other parts will be omitted.

At step 613, the fixing device paper sensor 3
It is determined from the table data corresponding to 0 whether or not the transfer presence / absence data is “0”. Here, the fact that the transfer presence / absence data is “0” means that the toner image has not been transferred to the remaining paper (at the upstream side of the transfer point when the image forming operation is stopped due to a paper jam or an abnormal image forming operation). (Remaining paper) that has passed through the roller fixing device 22.
If the data indicating the presence or absence of transfer is not “0”, that is, “1”, the remaining paper on which the toner image has been transferred is
Means that the paper was passed.

If the determination in step 613 is denied, the process proceeds to step 616. If the determination is affirmed, the process proceeds to step 614 to count up the fixing device paper passage counter, and then proceeds to step 616.

In other respects, the same processing / judgment is performed as the corresponding step number of the subroutine in the first embodiment (for example, step numbers corresponding to step 600 and step 200).

As described above, in the fourth embodiment, only the remaining paper before the transfer is counted by the paper passage counter of the fixing device, and as a result, only the recording paper 12 on which the toner image has not been transferred is conveyed to the roller fixing device. It is passed through for cleaning of 22,
As a result, the roller fixing device 22, specifically, the heat roller 60
The cleaning effect between the pressure roller 62 and the pressure roller 62 can be improved.

<< Fifth Embodiment >> Next, a fifth embodiment of the present invention will be described.

In the fifth embodiment, the configuration of the hardware is the same as that of the first embodiment.
The information writing management of the information management table is performed by 88.

Here, the control operation of the subroutine of the sheet passing control for the roller fixing device 22 in the fifth embodiment will be described with reference to the flowchart of FIG.

FIG. 1 is a flowchart of this subroutine.
As compared with the subroutine of the sheet passing control in the first embodiment, only the step 504 and the step 704 are different. Therefore, only the step 704 will be described here, and the description of the other steps will be omitted.

In step 704, the process proceeds to a subroutine for calculating the untransferred residual sheet on the upstream side of the roller fixing device 22.

In this subroutine, as shown in the flow chart of FIG. 14, in step 800, the count value N of a counter (software counter in the microcomputer) for counting the number of untransferred residual sheets on the upstream side of the roller fixing device 22.
After setting _ALL to "0" and setting the count value I of the counter for counting the sensor number to "1", the table data of the information management table is checked.

That is, in the next step 802, it is determined from the table data corresponding to the sensor number I whether or not the paper presence / absence data is "1".
The process moves to step 808 to determine whether or not I = n. Since the determination in step 808 is not affirmative until the table data of all the sensors arranged on the upstream side of the fixing device has been checked, the determination in step 808 is denied in the first cycle, and step 810 is performed.
Then, the counter for counting the sensor number is counted up, and the process returns to step 802.

On the other hand, if the determination in step 802 is affirmative, the flow advances to step 804 to determine from the table data corresponding to the sensor number I whether or not the data indicating the presence or absence of transfer is "0". If it is not "0", the process proceeds to step 808, and if it is "0", the counter for counting the number of untransferred residual sheets on the upstream side of the fixing device is counted up, and then the process proceeds to step 808.

At the n-th cycle, the table data of all the sensors arranged on the upstream side of the fixing device is checked, and the judgment in step 808 is affirmed, and the routine returns to the calling routine.

In this way, in this embodiment, the number of untransferred residual sheets on the upstream side of the fixing device is calculated.

In other respects, the same processes and judgments as those of the corresponding step numbers of the subroutine in the third embodiment (for example, step numbers corresponding to step 500 and step 700) are performed.

According to the fifth embodiment described above, the third
The same effect as in the embodiment can be obtained, and only the residual paper before transfer
Is the specified number N_THAnd the sheet of residual paper upstream of the roller fixing device 22
Number N _ALLDifference N = N_TH-N_ALLIs subject to calculation
As a result, only the recording paper 12 on which the toner image has not been transferred is
The paper is passed through for cleaning the fixing device 22, thereby
Roller fixing device 22, specifically, heat roller 60 and pressure roller
62 and the cleaning effect can be improved.

In the second embodiment described above, steps similar to step 613 of the fourth embodiment are inserted after step 314 or after step 316.
The cleaning effect of the fixing device can be improved by using only the remaining paper before transfer as the object of calculating the total transit time T _ALL .

Further, in any of the first to fifth embodiments, it is necessary to convey the recording paper 12 having the widest width in the conveying direction for cleaning by passing through the roller fixing device 22 for cleaning. 60 and the pressure roller 62 can be cleaned in the longitudinal direction, so that when the recording paper is fed again from the paper feeding unit 14 after the paper jam or the abnormality of the apparatus is cleared, the three paper feeding trays are used. It is also possible to select a paper feed tray containing the recording paper having the widest width in the inner transport direction and feed paper from this tray.

[0121]

As described above, according to the present invention, the contamination of the recording paper caused by the unfixed toner adhered to the fixing means after the abnormality of the apparatus such as a paper jam or abnormality of the image forming operation is eliminated. There is an unprecedented excellent effect that it can be efficiently prevented.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a perspective view schematically showing an appearance of the image forming apparatus according to the first embodiment.

FIG. 3 is a schematic configuration diagram illustrating an image forming unit of FIG. 2;

FIG. 4 is a perspective view schematically showing a configuration of a roller fixing device.

FIG. 5 is a block diagram illustrating a configuration of a control system according to the first embodiment.

FIG. 6 is a flowchart of a main routine corresponding to a control algorithm of a CPU according to the first embodiment.

FIG. 7 is a flowchart illustrating a subroutine of sheet passing control in FIG. 6;

FIG. 8 is a flowchart illustrating a subroutine of sheet passing control according to a second embodiment.

FIG. 9 is a flowchart showing a subroutine for feeding N _MIN sheets in FIG. 8;

FIG. 10 is a configuration diagram of an information management table according to a third embodiment.

FIG. 11 is a flowchart illustrating a paper feed control subroutine according to a third embodiment.

FIG. 12 is a flowchart illustrating a subroutine of sheet passing control according to a fourth embodiment.

FIG. 13 is a flowchart illustrating a subroutine of sheet passing control according to a fifth embodiment.

FIG. 14 is a flowchart showing a subroutine for calculating untransferred residual paper in FIG. 13;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Recording paper 12 14 Paper supply means 16 Image carrier 18 Transfer means 22 Fixing means 24 Conveying means 28 First detecting means 30 Second detecting means 32 Counting means 34 Control means

Continuation of front page (56) References JP-A-1-122855 (JP, A) JP-A-3-48271 (JP, A) JP-A-63-135982 (JP, A) JP-A-5-158295 (JP) JP-A-63-274980 (JP, A) JP-A-4-1622073 (JP, A) JP-A-57-191661 (JP, A) JP-A-3-18540 (JP, A) 60-172050 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 21/00 370-500 G03G 15/20 102-107

Claims (3)

(57) [Claims] A sheet feeding unit for feeding a recording sheet; a transferring unit for transferring a toner image on an image carrier onto the recording sheet fed by the sheet feeding unit; and a recording sheet after the toner image is transferred. A fixing unit that heats and fixes the toner image while nipping and conveying the sheet; a conveying unit that conveys a recording sheet from the paper supply unit to the fixing unit via a transfer unit; and a first detection that detects an abnormality of the apparatus. Means for detecting whether recording paper is present in the fixing means.
Detecting means, counting means for counting the number of residual sheets in the apparatus passing through the fixing means, and when the first detecting means detects an abnormality and the second detecting means detects recording paper Then, the fixing unit is cleaned by the residual paper in the apparatus being nipped and conveyed by the fixing unit.
By controlling the conveying means such that together, when on the basis of the count value of said counting means, the number of remaining sheets in the device passes through the fixing unit is insufficient to predetermined specified number,
The insufficient number of recording papers are fed by the paper feeding means and nipped and conveyed by the fixing means to clean the fixing means.
An image forming apparatus comprising: a control unit configured to control the sheet feeding unit and the conveyance unit so as to be swept . 2. A paper feeding means for feeding recording paper, a transfer means for transferring a toner image on an image carrier onto the recording paper fed by the paper feeding means, and a recording paper after the toner image is transferred A fixing unit that heats and fixes the toner image while nipping and conveying the sheet; a conveying unit that conveys a recording sheet from the paper supply unit to the fixing unit via a transfer unit; and a first detection that detects an abnormality of the apparatus. Means for detecting whether recording paper is present in the fixing means.
Detecting means, measuring means for measuring the passage time of the residual paper passing through the fixing means, and when the first detecting means detects an abnormality and the second detecting means detects the recording paper, The fixing unit is cleaned by the residual paper in the apparatus being nipped and conveyed by the fixing unit.
By controlling the conveying means such that together, when the time obtained by adding the passing time measured by said measuring means does not reach a predetermined specified time, the size and number of recording sheets is the feed corresponding to that lack of time An image forming apparatus comprising: a control unit that controls the sheet feeding unit and the conveying unit so that the fixing unit is cleaned by being fed by the unit and nipped and conveyed by the fixing unit . 3. The image forming apparatus according to claim 1, wherein the residual paper is untransferred residual paper.