JP2002318512A - Electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device constituted so that a pair of rollers for a fixation device, specially fixing rollers can be more effectively cleaned. SOLUTION: In the image forming device provided with a thermal fixation system fixing device 17, a recording material carrying device, an image storage device for storing an image of a prescribed pattern and an optical writing device for forming the image on an image carrier, and for cleaning the fixing device 17 while making the recording material with the recorded image pass through the fixing device 17 again, in the case of forming the image of the prescribed pattern, at least one of a developing bias, a writing light quantity, the rotating speed of a developing roller, a transfer current and the current of the image carrier is changed, and then, the weight per unit area of toner transferred to the recording material is controlled so as to be increased more than the toner weight in the case of forming a normal image.

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 such as a facsimile, a laser printer, a copying machine, etc., and more particularly to a method in which a transfer material on which unfixed toner is loaded is passed through a pair of rollers and heated and pressed. The present invention relates to an image forming apparatus including a fixing device for fixing the toner.

[0002]

2. Description of the Related Art A fixing device used for fixing image information placed as a toner image on a transfer material to the transfer material includes a heating roller having a built-in heater and a pressure roller. Are well-known.

In such an apparatus, toner or paper dust adheres to the surface of the heating roller or the surface of the pressure roller due to long-term use, so that the toner on the roller contaminates the image on the transfer material, There have been problems such as the occurrence of back contamination of the transfer material, and in some cases, the transfer material wrapping around the rollers and causing paper jams.

Therefore, various methods and configurations have been proposed for removing toner and the like adhering to the surface of the heating roller or the surface of the pressure roller.

For example, in Japanese Patent Application Laid-Open No. 5-158375, in order to clean a pair of fixing rotators having a controlled surface temperature, a cleaning layer exhibiting adhesiveness is formed on a cleaning sheet, and the sheet is formed. It describes that the surface temperature of the rotating body is maintained at a cleaning temperature higher than the fixing temperature for the transfer material when passing through the nip portion of the rotating body.

[0006]

However, in such a method, a special cleaning sheet must be prepared for cleaning the fixing rotary member, and the cleaning sheet is manually supplied by an operator. It must be supplied from the paper unit every time cleaning is performed. Therefore, the following problems exist.

[0007] Separate cost is required for preparing the cleaning sheet, it is troublesome to prepare and store the cleaning sheet in advance for cleaning a predetermined number of sheets, and the cleaning sheet is supplied from the manual sheet feeding unit. In order to do so, the operator must accompany the device body, and depending on the installation location, it may cause a large amount of time loss,
And the operation of manual paper feeding itself is rather cumbersome from the viewpoint of operation.

Further, by utilizing the property that the toner or paper powder attached to the surface of the pressure roller easily adheres to the solid-coated image printed on the transfer material, the transfer surface on which the solid-coated image is printed can be used as a printing surface. A method of cleaning by re-passing the paper so as to be in contact with the pressure roller has been proposed. For example, JP-A-3-39
In Japanese Patent Application Laid-Open No. 771, the cleaning image previously stored in the image data storage unit is output by the image output unit at the stage when a predetermined number of prints have been performed, whereby a cleaning transfer material is prepared. It is disclosed to perform cleaning of the pressure roller. This eliminates the need to store a transfer material for cleaning having a solid image.

Further, even if cleaning is performed periodically, a temperature detecting element for detecting the surface temperature of the roller, and a safety device for shutting off energization to the heating source when the surface temperature of the heating roller reaches a temperature higher than a set temperature. Toner accumulates between the polyimide tape covering the device and the roller, and the accumulated toner cannot be removed by the transfer material for cleaning, and as the number of sheets of the transfer material on which the unfixed toner image is formed increases, the The amount of toner accumulated between the tape and the heating roller increases, and a part of the accumulated toner slips from between the polyimide tape and the heating roller, causing stains on a transfer material to be fixed later, or under pressure. There is also a problem that the cleaning transfer material is wound around the pressure roller when the roller is excessively soiled. In order to solve these problems, Japanese Patent Application Laid-Open No. 4-134
No. 477, the surface temperature of the fixing roller is set higher than the fixing temperature, the toner attached to the roller is heated from the time of fixing, and a part of the toner is sufficiently melted.
It has been proposed that a cleaning image stored in a ROM is formed on a transfer material and cleaning is performed using the transfer material.

As described above, in the system in which the specific pattern is printed out on the transfer material and fed to the fixing device to clean the pressure roller, the above-mentioned problems (1) to (4) do not occur. In addition, by switching the transport path, cleaning can be performed not only on the pressure roller but also on the fixing roller.

[0011] The present invention, in light of such prior art,
It is an object of the present invention to provide an image forming apparatus capable of cleaning a roller pair of a fixing device more effectively, particularly a fixing roller.

[0012]

According to the present invention, in order to solve the above-mentioned problem, a recording material on which an image formed on an image carrier is transferred is passed through a recording material, and the toner image is fixed by heat. A fixing device that feeds a recording material, an image storage device that stores an image of a predetermined pattern, and an optical writing device that forms the image of the predetermined pattern on an image carrier. When an image of a predetermined pattern is formed in an image forming apparatus that cleans a fixing device by passing a recording material on which an image is recorded again through a fixing device, a developing bias, a writing light amount, a rotation speed of a developing roller, and a transfer current. By changing at least one of the drum currents, the toner weight per unit area transferred to the recording material is controlled so as to be larger than that during normal image formation.

A recording material size detecting device is provided to detect the size of the recording material on which the image is to be formed when an image of a predetermined pattern is formed, and to control the feeding of the recording material according to the result. Is preferred.

When a recording material on which an image of a predetermined pattern is recorded is passed through the fixing device, at least the speed of lowering the paper passing speed than during normal fixing and the setting of the fixing device at a temperature higher than the fixing temperature are required. It is still more suitable to do one.

When a recording material on which an image of a predetermined pattern is recorded is passed through a fixing device, it is convenient if the transport direction is configured to be reversible.

It is more preferable that the image forming apparatus is provided with a reversing section in the conveying device and is capable of forming an image on both sides of the recording material so that the recording material on which a predetermined pattern of images is recorded can be selected to be reversible or not. .

When an image of a predetermined pattern is recorded on one side of the recording material, the recording material is reversed at the reversing section, and when the image of the predetermined pattern is also recorded on the other surface, cleaning is performed using the previously recorded image. Next, it is preferable to clean the fixing device again without reversing.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an embodiment shown in the drawings.

The basic configuration of the image forming apparatus and the operation in the normal image forming mode are basically the same as those of the conventional one, and are as follows.

In the double-sided recording laser printer shown in FIG. 1 in which the apparatus main body 10 is mounted on a sheet unit 11, the apparatus main body 10 includes an upper structure 10a and a lower structure 1
0b, and the upper structure 10a is attached to the lower structure 10b using a shaft 10c so as to be freely opened and closed. Device body 10
A belt-shaped photoconductor 12 is provided substantially at the center of the inside. Around the photosensitive member 12, in the order of the driving directions indicated by arrows,
The charging device 13, the developing device 14, the transfer device 15, and the cleaning device 16 are arranged. In the publication of the photoconductor 12, a fixing device 17 is provided, and an optical writing device 18 is disposed above the charging device 13 and the cleaning device 16. The static eliminator 9 is disposed downstream of the cleaning device 16.

In the bottom wall 10d of the apparatus main body 10, a paper feed port 19 is provided on the operation side on the right side in the figure.
A paper feed roller 20 is provided. A transport path 21 that passes under the photoconductor 12 is provided between the paper feed roller 20 and the fixing device 17.
A pair of transport rollers 22 and a registration roller 23 are provided between the paper feed roller 20 and the photoconductor 12 in the transport path 21.

At the exit side of the fixing device 17, the upper structure 1
A paper discharge guide 25 for guiding a sheet to the upper stack portion 24 on the upper surface of the paper discharge guide 0a is provided, and two pairs of paper discharge rollers 26 and 27 are provided below the paper discharge guide 25. The lower stack unit 2 is provided on the sheet discharge side of the discharge roller pair.
8 and a second switching claw 29 for switching the sheet conveying direction between the upper stack 24 and the lower stack 28 between the lower stack 28 and the sheet discharge roller pair 27. Further, the discharge roller pair 26 and the discharge roller pair 2
7, a switchable first switching claw 30 is provided. A discharge port 31 for refeeding paper is provided on the bottom wall 11d below the first switching claw 30. A guide 32 for guiding a sheet to the discharge port 31 is provided between the first switching claw 30 and the discharge port 31. Is provided integrally with the lower frame 17 a of the fixing device 17. The guide 32 is formed of, for example, a resin material having high heat resistance.

On the operation side of the lower structure 10b, a manual feed device 33 is provided so that sheets can be manually fed one by one without using automatic feeding. The receiving portion 33a that receives the rear end of the manually fed sheet and the hanging sheet is attached to the operation side surface of the sheet unit 11 so that the position can be freely changed in three steps, upper, middle and lower, according to the length of the sheet. Can be.

On the other hand, the sheet unit 11 is detachably attached to the sheet cassette 40 in a plurality of stages vertically from the operation side. On the lower side of the paper feed cassette 40, a push-up lever 34 whose one end is urged upward by a spring or the like is provided. The apparatus main body 1 is provided on the sheet feeding side of the lower cassette 40.
A paper feed roller 20 similar to that of the paper feed roller 0 is provided.

The paper feed cassette 40 is box-shaped, with guide plates 41 and 42 standing up and down, a bottom plate 43 rotatable upward from the center, and a separation pad at the front end. A separating member 44 is provided. At the front side, a sheet conveying path 45 is vertically penetrated, and a pulling handle 46 is provided at the front end of the sheet cassette.

When recording is performed by automatic paper feeding, one of the paper feeding rollers 20 is selectively driven to separate sheets one by one from the uppermost one by the separating member 44 and the paper feeding roller 20. To feed into the transport path 21 or into the transport path 21 via the upper sheet transport path 45. When performing manual paper feeding instead of automatic paper feeding,
From 3, sheets are manually fed one by one and sent out into the transport path 21.

Then, the paper feed cassette 40 or the manual feed device 3
The sheet fed from 3 into the conveyance path 21 is conveyed to the registration roller pair 23 via the conveyance roller pair 22, and is conveyed to the lower side of the photoconductor 12 at a timing by the registration roller pair 23.

The photosensitive member 12 is driven in a clockwise direction as indicated by an arrow. At this time, the surface is uniformly charged by a charger 13 and irradiated with a laser beam from an optical writer 18 so that the photosensitive member 12 To form an electrostatic latent image. This latent image is developed
, Is visualized by the toner.

This visible image is transferred by the transfer device 15 onto the upper surface of the sheet conveyed below the photoreceptor 12. The transferred sheet is conveyed to the fixing device 17 to fix the transferred image, and the sheet is sent from the fixing device 17 to the sheet discharge roller pair 26 and sent to the sheet discharge roller pair 27 side by the first switching claw 30. The two switching claws 29 are used to switch to the stack portion 24 or the lower stack portion 28 on the upper surface, and discharge to either of them.

In this laser printer, a sheet feeding cassette 40 can be mounted in the sheet unit 11 instead of the sheet feeding unit 50, and the sheet feeding cassette 5
Reference numeral 0 indicates that the sheet transport path 51 is vertically penetrated on the front side in the same manner as in the above-described paper feed cassette 40, and the pulling handle 5 is provided on the front end.
2 is provided. And re-feed unit 5
0, there is a lower reversing path 53 extending from left to right in the figure.
A transport path 53 following a is provided.

In the transport path 53, a transport roller pair 54,
55 and 56 are provided, and a forward / reverse rotation roller pair 57 is provided at a position past the reversing portion at the right end of the transport path 53 in the drawing. Further, at the front side inside the re-feeding unit 50, when the re-feeding unit 50 is attached to the apparatus main body 10, a paper feeding roller 58 that comes into pressure contact with the paper feeding roller 20 of the apparatus main body 10 is provided. A third switching claw 59 for guiding the sheet is switchably attached to the reversing unit. By switching the first switching claw 30,
The sheet after image transfer is transferred from the discharge roller pair 26 to the discharge port 31.
, And guided by the guide 32 to the transport path 53.

Then, the fixed sheet is conveyed in the conveying path 53 of the sheet re-feed unit 50 by the conveying roller pairs 54, 55, 56, and is forward-reversely driven by the third switching claw 59.
To the reversing path 5 by the forward rotation of the forward / reverse rotation roller pair 57.
Enter 3a. Then, it is further fed and the rear end is the third switching claw 5
9, the forward / reverse roller 57 rotates in the reverse direction, the sheet is reversed, and the sheet feeding roller 20 and the sheet feeding roller 58
Is fed to the nip portion, and is fed again into the apparatus main body 10. Then, the toner image is transferred to the back surface of the sheet, and is discharged onto the stack unit 24 or 28 via the fixing device 17.
That is, images are formed on both sides of the sheet.

The third switching claw 59 is, as shown in FIG.
When at the position indicated by the solid line, the pair of transport rollers 54, 55, 5
The sheet (image-formed) conveyed in step 6 does not enter the reversing path 53a, but is re-fed into the apparatus main body 10 by the feed roller pair 20, 58, and additional information is added to the already formed image surface. Can be written.

The above-described image forming process, sheet conveyance control, and temperature control in the fixing device are performed by a CPU (not shown).
Is controlled by The control unit including the CPU is also provided with a ROM (not shown) for storing an image signal of a test pattern, which is a cleaning image, and is output from the ROM by pressing a test print switch (not shown), for example. The laser beam is modulated by the image signal to form a fixed pattern image on the sheet.

In FIG. 2, which shows a schematic configuration of the fixing device, the fixing device 17 is composed of a lower frame 17a and an upper frame 17b indicated by two-dot chain lines, and a heater 172 is provided inside the hollow fixing roller 170. Fixed.
The surface of the fixing roller 170 is processed to improve the releasability of the toner, and a temperature detecting element and a device for ensuring safety are arranged around the fixing roller 170 although not shown. . Further, both ends of the fixing roller 170 are rotatably supported by bearings (not shown).
71 is coaxially mounted and rotated by a drive gear (not shown). On the other hand, the pressing roller 173 has a shaft 173.
The outer peripheral portion a is formed of a material such as rubber, and both ends thereof are rotatably supported by bearings 174 and are pressed against the fixing roller 170 by a compression spring 175. When the recording sheet passes through the nip formed at the press-contact portion, the toner on the sheet is fixed by heat and the pressure generated by press-contact of both rollers.

As the number of sheets passing therethrough increases, the fixing roller 17
0 and the surface of the pressure roller 173 gradually adheres to the surface of the pressure roller 173, which is transferred to a recording sheet and causes image defects. Therefore, after printing a predetermined number of sheets or when a dirty image is generated, the fixing roller Alternatively, it is necessary to remove dirt from the pressure roller. Therefore, when the number of printed sheets is counted and a predetermined value is reached, a signal is given to the CPU from a counter unit (not shown), or a signal is given to the CPU when an operator presses a test print switch. A sheet to be a cleaning sheet is sent out from the sheet feed roller 20 from 40-1 or 40-2. On the other hand, a pattern as shown in FIG. 3, for example, is formed on the photoconductor 12 by the optical writing unit 18 according to the image signal output from the ROM. The pattern is formed on a sheet by development and transfer processing. At this time, at least one control value of the developing bias, the writing light amount, the rotation speed of the developing roller, the transfer current and the drum current is changed according to a command of the control system, and the toner amount per unit area (M / M A) is adjusted so as to be larger than that in normal image formation. The adjustment improves the adhesiveness of the cleaning sheet when the toner is dissolved.

The sheet on which the cleaning pattern has been transferred is fixed by the fixing device 17, and is re-fed to the fixing device via the conveyance path by the switching adjustment of the switching claw so that the pattern comes into contact with the roller to be cleaned. . Refeeding can also be performed manually. The pattern on the sheet re-fed to the fixing device 17 is partially melted by the heat in the fixing device, develops viscosity, and cleans the roller. At this time, in order to further improve the adhesiveness of the toner and enhance the cleaning effect, it is preferable to increase the control temperature of the fixing device or reduce the paper passing speed when passing through the cleaning pattern.

The cleaning sheet used for cleaning the fixing device may be a sheet used for ordinary printing. However, the size of the cleaning sheet is set in the longitudinal direction of the roller so that no cleaning remains on the roller, particularly in the end area. That is, it is necessary in principle that the sheet has a maximum sheet passing width in the sheet width direction. As in the apparatus shown in FIG. 1, an apparatus having a plurality of sheet cassettes and forming an image on sheets of a plurality of sizes is often provided with a mechanism capable of arbitrarily selecting a sheet size. In the case of a simple apparatus, it is preferable that the apparatus automatically selects the size of the maximum sheet passing width during the cleaning process and uses it for cleaning. Such an apparatus is generally provided with a means for detecting the sheet size. Therefore, the size of the cleaning sheet is also detected during the cleaning process to determine whether or not the sheet is the maximum width sheet. It is more appropriate if it is configured as follows. This control flow is illustrated in FIG. That is, when a roller cleaning instruction is issued from the CPU, the size of the set sheet is detected by the size detection means, and the set sheet is determined based on whether or not the information matches that of the sheet having the maximum width. Is determined. If the sheet has the maximum width, a roller cleaning mode is started. If the set sheet is not of the maximum width, a message that an appropriate size for cleaning is not set is displayed on an operation unit (not shown). Since the width requiring cleaning at that time may be narrow, the roller cleaning mode is started when cleaning with the small size sheet is permitted. If cleaning should not be performed forcibly, set the correct size paper and start again.

In order to more reliably clean the rollers, as shown in FIG. 5, the conveyance direction is reversed a plurality of times while the cleaning sheet is held by the fixing device, so that the tacky toner area is formed. The driving may be controlled so as to contact the roller to be cleaned plural times.

As shown in FIG. 1, when automatic printing can be performed on both sides of the recording sheet, it is possible to determine and select which one of the fixing roller and the pressure roller to clean, thereby forming an image for cleaning. The process from cleaning to cleaning of the designated roller can be automated. This judgment / selection
For example, the apparatus may be automatically selected according to conditions such as the number of sheets passed by the apparatus, or a message may be issued to the operator to select cleaning based on stains on a printed image. The operation of each of the fixing roller and the pressure roller will be described below with reference to the example of FIG.

When cleaning the fixing roller, the recording sheet on which the pattern shown in FIG.
When the third switching claw 59 is switched to the solid line position in FIG. As a result, the toner adhering as dirt on the fixing roller is removed by the cleaning pattern portion.

When cleaning the pressure roller, the recording sheet on which the pattern shown in FIG.
When the third switching claw 59 is switched to the position shown by the broken line in FIG. 1 and is sent to the reversing path 53a, the roller pair 57 is again rotated through the image forming unit and passed through the fixing unit 17, and the cleaning pattern is changed to the pressure roller. The toner adhering as dirt on the pressure roller is removed by the cleaning pattern portion.

The operation for cleaning the fixing roller and the pressure roller at the same time will be described with reference to FIG.

First, the recording sheet on which the cleaning pattern shown in FIG.
To the reversing path 53a by the third switching claw 59. Next, the roller pair 57 is reversed to be sent to the image forming unit, where the cleaning pattern is formed on the back surface of the recording sheet in the forming unit (image forming unit). The recording sheet is conveyed to the fixing device 17 and the back surface is fixed. At the same time, the pressure roller is cleaned by the cleaning pattern formed on the back surface. After passing through the fixing device 17, the recording sheet is again sent to the sheet re-feeding unit 50, and is then sent to the image forming unit without being inverted by the third switching claw 59.
The sheet is conveyed to the fixing device 17 without forming an image in the forming section. In the fixing device 17, the cleaning pattern formed on the back surface of the sheet comes into contact with the fixing roller,
The fixing roller is cleaned. In this case, since the cleaning pattern on the surface is in contact with the pressure roller side,
At the same time, the pressure roller is cleaned again. Thereafter, the sheet is discharged without being guided again to the sheet re-feeding unit 50, but may be sent to the sheet re-feeding unit again in order to repeat the above-described steps in order to ensure reliable cleaning.

In the above-described embodiment, the fixing device is constituted by a fixing roller and a pressure roller. However, an endless belt is arranged around the heat source, and the pressure roller is installed facing the heat source. Naturally, the present invention is also applied to a fixing device configured to pass a sheet between the pressure roller and the endless belt.

[0046]

According to the first aspect of the present invention, at the time of forming an image of a predetermined pattern, at least one of a developing bias, a writing light amount, a developing roller rotation speed, a transfer current, and a drum current is changed. Since the toner weight per unit area transferred to the recording material is controlled to be larger than that in normal image formation, the adhesiveness for cleaning when the fixing device is cleaned is improved, and better cleaning is performed. Can be.

According to the apparatus of the second aspect, the size of the recording material is detected, and the feeding control of the recording material is performed according to the result, so that the optimum size is selected and the cleaning is performed.

According to the apparatus of the third aspect, when a recording material on which an image of a predetermined pattern is recorded is passed through a fixing device,
Since the sheet passing speed is slower than that during normal fixing or the fixing device is set at a temperature higher than the fixing temperature, it is possible to clean using a toner having higher viscosity.

According to the apparatus of the fourth aspect, when a recording material on which an image of a predetermined pattern is recorded is passed through a fixing device,
Since the transport direction is configured to be reversible, the fixing device can be more reliably cleaned.

According to the apparatus of the fifth aspect, since the recording material on which the image of the predetermined pattern is recorded can be selected whether or not it can be reversed, the necessary surface of the fixing device is cleaned.

According to the apparatus of the sixth aspect, when an image of a predetermined pattern is recorded on one side of a recording material, and the recording material is inverted by an inverting section to record an image of the same predetermined pattern on the other side. Since the cleaning is performed on the previously recorded image, and then the cleaning of the fixing device is performed again without reversing, both sides of the fixing device are cleaned at one time with one recording material.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an image forming apparatus according to the present invention.

FIG. 2 is a schematic diagram of a fixing device in the image forming apparatus of FIG.

FIG. 3 is a schematic diagram illustrating an example of a recording sheet provided with an image of a cleaning pattern.

FIG. 4 is a diagram showing a cleaning flow when detecting the size of a recording sheet.

FIG. 5 is a conceptual diagram showing how the fixing device performs normal / reverse rotation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Apparatus main body 11 Sheet unit 12 Photoreceptor 13 Charging device 14 Developing device 15 Transfer device 16 Cleaning device 17 Fixing device 18 Optical writing device 19 Paper feed port 20 Paper feed roller 21 Transport path 22 Transport roller pair 23 Registration roller pair 24 Upper stack Unit 25 Discharge guide 26, 27 Discharge roller pair 28 Lower stack unit 29 Second switching claw 30 First switching claw 31 Discharge port 32 Guide 33 Manual feeder 33a Receiving unit 34 Push-up lever 40 Paper cassette 41, 42 Guide plate 43 Bottom plate 44 Separation member 45 Sheet transport path 46 Handle 50 Re-feed unit 51 Sheet transport path 52 Handle 53 Transport path 53a Reverse path 54, 55, 56 Transport roller pair 57 Forward / reverse roller pair 58 Feed roller 59 Third switching claw

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[Procedure amendment]

[Submission date] March 4, 2002 (2002.3.4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Electrophotographic image forming apparatus

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a facsimile, a laser printer, and a copying machine, and more particularly to an image forming apparatus capable of recording images on both sides of a recording material. is there.

[0002]

2. Description of the Related Art An image forming apparatus capable of recording image information on both sides of a recording material is known. In such an apparatus, it is common that image information is once recorded and fixed on one side of the recording material, and then the recording material is turned over so that the front and back are reversed, and then the image information is recorded and fixed on the back side.

A reversing mechanism is used for reversing the recording material. The reversing mechanism reverses the recording material by switching back the recording material traveling on the conveyance path. Therefore, the possibility of jamming the recording material in the reversing mechanism is likely to be higher than in other conveyance paths. Nevertheless, conventionally, such a reversing mechanism is fixedly attached to the image forming apparatus, and it is difficult to perform the jam processing.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and when a jam occurs on a reversal path,
It is an object of the present invention to provide an image forming apparatus in which the jam processing is easy.

[0005]

In order to solve this problem, according to the present invention, a sheet feeding cassette for storing unrecorded recording material and a recording sheet on one side are provided at the lower side inside the apparatus main body of the image forming apparatus. The re-feeding unit that temporarily stores the made recording material and feeds it again for recording on the other side can be interchanged and installed.When the above-mentioned re-feeding unit is installed, In order to convey the recording paper from the sheet unit provided below to the inside of the apparatus main body, a sheet conveying path is provided in a substantially vertical direction on the front side as viewed from the mounting direction of the re-feeding unit. An image forming apparatus is configured.

It is preferable that a handle for attaching and detaching the refeed unit to and from the apparatus main body is provided on the further side of the refeed unit with respect to the sheet conveying path. Also, a first switching claw is disposed immediately downstream of the fixing device in the transport direction of the recording material transport path, and the recording material is guided toward the re-feeding unit by switching the first switching claw.
When the first switching claw is switched to guide the recording material to the stack portion, the recording material is switched to be guided to the upper stack portion or the lower stack portion. It is also preferable that a possible second switching claw is provided downstream of the first switching claw in the transport direction of the recording material transport path.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an embodiment shown in the drawings. The basic configuration of the image forming apparatus and the operation in the normal image forming mode are basically the same as those of the related art, and are as follows.

In the double-sided recording laser printer shown in FIG. 1 in which the apparatus main body 10 is mounted on a sheet unit 11, the apparatus main body 10 has an upper structure 10a and a lower structure 1
0b, and the upper structure 10a is attached to the lower structure 10b using a shaft 10c so as to be freely opened and closed. Device body 10
A belt-shaped photoconductor 12 is provided substantially at the center of the inside. Around the photosensitive member 12, in the order of the driving directions indicated by arrows,
The charging device 13, the developing device 14, the transfer device 15, and the cleaning device 16 are arranged. A fixing device 17 is provided behind the photoconductor 12, and an optical writing device 18 is disposed above the charging device 13 and the cleaning device 16. The static eliminator 9 is disposed downstream of the cleaning device 16.

In the bottom wall 10d of the apparatus main body 10, a paper feed port 19 is provided on the operation side on the right side in the figure.
A paper feed roller 20 is provided. A transport path 21 passing below the photoconductor 12 is provided between the paper feed roller 20 and the fixing device 17.
A pair of transport rollers 22 and a registration roller 23 are provided between the paper feed roller 20 and the photoconductor 12 in the transport path 21.

On the exit side of the fixing device 17, an upper structure 1 is provided.
A paper discharge guide 25 for guiding a sheet to the upper stack portion 24 on the upper surface of the paper discharge guide 0a is provided, and two pairs of paper discharge rollers 26 and 27 are provided below the paper discharge guide 25. The lower stack unit 2 is provided on the sheet discharge side of the discharge roller pair.
8 and a second switching claw 29 for switching the sheet conveying direction between the upper stack 24 and the lower stack 28 between the lower stack 28 and the sheet discharge roller pair 27. Further, the discharge roller pair 26 and the discharge roller pair 2
7, a switchable first switching claw 30 is provided. Below the first switching claw 30, an outlet 31 for refeeding paper is provided on the bottom wall 11d. Between the first switching claw 30 and the outlet 31, a guide 32 for guiding the sheet to the outlet 31 is provided. It is provided integrally with the lower frame 17a of the fixing device 17. The guide 32 is formed of, for example, a resin material having high heat resistance.

A manual feed device 33 is provided on the operation side of the lower structure 10b so that sheets can be manually fed one by one without using automatic feeding. The receiving portion 33a that receives the rear end of the manually fed sheet and the hanging sheet is attached to the operation side surface of the sheet unit 11 so that the position can be freely changed in three steps, upper, middle and lower, according to the length of the sheet. Can be.

On the other hand, the sheet unit 11 has a plurality of paper cassettes 40 detachably mounted vertically from the operation side. On the lower side of the paper feed cassette 40, a push-up lever 34 whose one end is urged upward by a spring or the like is provided. Further, the apparatus main body 1 is provided on the sheet feeding side of the lower cassette 40.
A paper feed roller 20 similar to that of the paper feed roller 0 is provided.

The paper feed cassette 40 is box-shaped, with guide plates 41 and 42 standing up and down, a bottom plate 43 which is rotatable upward from the center, and a separation pad at the front end. A separating member 44 is provided. At the front side, a sheet conveying path 45 is vertically penetrated, and a pulling handle 46 is provided at the front end of the sheet cassette.

When recording is performed by automatic paper feeding, one of the paper feeding rollers 20 is selectively driven to separate sheets one by one from the uppermost one by the separating member 44 and the paper feeding roller 20. To feed into the transport path 21 or into the transport path 21 via the upper sheet transport path 45. When performing manual paper feeding instead of automatic paper feeding,
From 3, sheets are manually fed one by one and sent out into the transport path 21.

The paper feed cassette 40 or the manual feed device 3
The sheet fed from 3 into the conveyance path 21 is conveyed to the registration roller pair 23 via the conveyance roller pair 22, and is conveyed below the photoreceptor 12 at a timing by the registration roller pair 23.

The photosensitive member 12 is driven clockwise as indicated by an arrow. At this time, the surface of the photosensitive member 12 is uniformly charged by the charger 13 and is irradiated with laser light from the optical writer 18 so that the surface of the photosensitive member 12 is electrostatically charged. Form a latent image. This latent image is visualized by toner when passing through the developing device 14.

This visible image is transferred by the transfer unit 15 onto the upper surface of the sheet conveyed below the photoreceptor 12.
The transferred sheet is conveyed to the fixing device 17 to fix the transferred image, and the sheet is transferred from the fixing device 17 to the discharge roller pair 26.
To the discharge roller pair 27 side by the first switching claw 30,
Further, the stack is switched to the stack portion 24 or the lower stack portion 28 on the upper surface by the second switching claw 29 and discharged to either of them.

In this laser printer, the portion of the sheet re-feeding unit 50 in the sheet unit 11 can be replaced with the sheet feeding cassette 40. As in the case of 40, the sheet conveying path 51 is vertically penetrated on the front side, and has a box shape provided with a handle 52 for drawing out at the front end. In the refeed unit 50, there is provided a transport path 53 extending from the left to the right in the figure and connected to the lower reversing path 53a.

In the transport path 53, a transport roller pair 54,
55 and 56 are provided, and a forward / reverse rotation roller pair 57 is provided at a position past the reversing portion at the right end of the transport path 53 in the drawing. Further, at the front side inside the re-feeding unit 50, when the re-feeding unit 50 is attached to the apparatus main body 10, a paper feeding roller 58 that comes into pressure contact with the paper feeding roller 20 of the apparatus main body 10 is provided. A third switching claw 59 for guiding the sheet is switchably attached to the reversing unit. By switching the first switching claw 30,
The sheet after image transfer is transferred from the discharge roller pair 26 to the discharge port 31.
, And guided by the guide 32 to the transport path 53.

Then, the sheet after fixing is conveyed in the conveying path 53 of the re-feed unit 50 by the conveying roller pairs 54, 55 and 56, and by the third switching claw 59, the forward / reverse roller pair 57
To the reversing path 5 by the forward rotation of the forward / reverse rotation roller pair 57.
Enter 3a. Then, it is further fed and the rear end is the third switching claw 5
9, the forward / reverse roller 57 rotates in the reverse direction, the sheet is reversed, and the sheet feeding roller 20 and the sheet feeding roller 58
Is fed to the nip portion, and is fed again into the apparatus main body 10. Then, the toner image is transferred to the back surface of the sheet, and is discharged onto the stack unit 24 or 28 via the fixing device 17.
That is, images are formed on both sides of the sheet.

The third switching claw 59 is, as shown in FIG.
When at the position indicated by the solid line, the pair of transport rollers 54, 55, 5
The sheet (image-formed) conveyed in step 6 does not enter the reversing path 53a, but is re-fed into the apparatus main body 10 by the feed roller pair 20, 58, and additional information is added to the already formed image surface. Can be written.

The above-described image forming process, sheet conveyance control, and temperature control in the fixing device are performed by a CPU (not shown).
Is controlled by The control unit including the CPU is also provided with a ROM (not shown) for storing an image signal of a test pattern, which is a cleaning image, and is output from the ROM by pressing a test print switch (not shown), for example. The laser beam is modulated by the image signal to form a fixed pattern image on the sheet.

In FIG. 2, which shows a schematic configuration of the fixing device, the fixing device 17 includes a lower frame 17a and an upper frame 17b indicated by two-dot chain lines, and a heater 172 is provided inside the hollow fixing roller 170. Fixed.
The surface of the fixing roller 170 is processed to improve the releasability of the toner, and a temperature detecting element and a device for ensuring safety are arranged around the fixing roller 170 although not shown. . Further, both ends of the fixing roller 170 are rotatably supported by bearings (not shown).
71 is coaxially mounted and rotated by a drive gear (not shown). On the other hand, the pressure roller 173 is
73a is formed on the outer periphery of a material such as rubber, and both ends thereof are rotatably supported by bearings 174,
5 is pressed against the fixing roller 170. When the recording sheet passes through the nip portion formed at the pressed portion, the toner on the sheet is fixed by heat and the pressure caused by the pressing of the two rollers.

As the number of sheets passing therethrough increases, the fixing roller 17
0 and the surface of the pressure roller 173 gradually adheres to the surface of the pressure roller 173, which is transferred to a recording sheet and causes image defects. Therefore, after printing a predetermined number of sheets or when a dirty image is generated, the fixing roller Alternatively, it is necessary to remove dirt from the pressure roller. Therefore, when the number of printed sheets is counted and a predetermined value is reached, a signal is given to the CPU from a counter unit (not shown), or a signal is given to the CPU when an operator presses a test print switch. A sheet to be a cleaning sheet is sent out from the sheet feed roller 20 from 40-1 or 40-2. On the other hand, a pattern as shown in FIG. 3, for example, is formed on the photoconductor 12 by the optical writing unit 18 according to the image signal output from the ROM. The pattern is formed on a sheet by development and transfer processing. At this time, at least one control value of the developing bias, the writing light amount, the rotation speed of the developing roller, the transfer current and the drum current is changed according to a command of the control system, and the toner amount per unit area (M / M A) is adjusted so as to be larger than that in normal image formation. The adjustment improves the adhesiveness of the cleaning sheet when the toner is dissolved.

The sheet on which the cleaning pattern has been transferred is fixed by the fixing device 17, and is re-fed to the fixing device via the conveyance path by the switching adjustment of the switching claw so that the pattern comes into contact with the roller to be cleaned. . Refeeding can also be performed manually. The pattern on the sheet re-fed to the fixing device 17 is partially melted by the heat in the fixing device, develops viscosity, and cleans the roller. At this time, in order to further improve the adhesiveness of the toner and enhance the cleaning effect, it is preferable to increase the control temperature of the fixing device or reduce the paper passing speed when passing through the cleaning pattern.

The cleaning sheet used for cleaning the fixing device may be a sheet used for ordinary printing. However, the size of the cleaning sheet is set in the longitudinal direction of the roller so that no cleaning remains on the roller, particularly in the end area. That is, it is necessary in principle that the sheet has a maximum sheet passing width in the sheet width direction. As in the apparatus shown in FIG. 1, an apparatus having a plurality of sheet cassettes and forming an image on sheets of a plurality of sizes is often provided with a mechanism capable of arbitrarily selecting a sheet size. In the case of a simple apparatus, it is preferable that the apparatus automatically selects the size of the maximum sheet passing width during the cleaning process and uses it for cleaning. Since such an apparatus generally includes a means for detecting the sheet size, the size of the cleaning sheet is also detected during the cleaning process to determine whether or not the sheet has the maximum width. It is more appropriate if configured. This control flow is illustrated in FIG. That is, when a roller cleaning instruction is issued from the CPU, the size of the set sheet is detected by the size detection means, and the set sheet is determined based on whether or not the information matches that of the sheet having the maximum width. Is determined. If the sheet has the maximum width, a roller cleaning mode is started. If the set sheet is not of the maximum width, a message that an appropriate size for cleaning is not set is displayed on an operation unit (not shown). Since the width requiring cleaning at that time may be narrow, the roller cleaning mode is started when cleaning with the small size sheet is permitted. If cleaning should not be performed forcibly, set the correct size paper and start again.

In order to more reliably clean the rollers, as shown in FIG. 5, while the cleaning sheet is being held by the fixing device, the conveying direction is reversed a plurality of times so that the tacky toner area is formed. The driving may be controlled so as to contact the roller to be cleaned plural times.

As shown in FIG. 1, when automatic printing is possible on both sides of the recording sheet, it is possible to determine and select which of the fixing roller and the pressure roller to clean, thereby forming a cleaning image. The process from cleaning to cleaning of the designated roller can be automated. This judgment / selection
For example, the apparatus may be automatically selected according to conditions such as the number of sheets passed by the apparatus, or a message may be issued to the operator to select cleaning based on stains on a printed image. The operation of each of the fixing roller and the pressure roller will be described below with reference to the example of FIG.

When cleaning the fixing roller, the recording sheet on which the pattern shown in FIG.
When the third switching claw 59 is switched to the solid line position in FIG. 1 and is not directed to the reversing path, but is directly sent to the paper feeding main body of the roller 20 and passed through the fixing device 17, the cleaning pattern comes into contact with the surface of the fixing roller. Accordingly, the toner adhering as dirt on the fixing roller is removed by the cleaning pattern portion.

When cleaning the pressure roller, the recording sheet on which the pattern shown in FIG.
When the third switching claw 59 is switched to the position shown by the broken line in FIG. 1 and is sent to the reversing path 53a, the roller pair 57 is again rotated through the image forming unit and passed through the fixing unit 17, and the cleaning pattern is changed to the pressure roller. The toner adhering as dirt on the pressure roller is removed by the cleaning pattern portion.

The operation for cleaning the fixing roller and the pressure roller at the same time will be described with reference to FIG. First, the recording sheet on which the cleaning pattern shown in FIG. 3 is formed and fixed on one side is sent to the sheet re-feed unit 50, and sent to the reversing path 53a by the third switching claw 59. Next, the roller pair 57 is reversed to be sent to the image forming unit, where the cleaning pattern is formed on the back surface of the recording sheet in the forming unit (image forming unit). The recording sheet is conveyed to the fixing device 17 and the back surface is fixed. At the same time, the pressure roller is cleaned by the cleaning pattern formed on the back surface. After passing through the fixing device 17, the recording sheet is again sent to the sheet re-feeding unit 50.
The sheet is sent to the image forming section without being inverted at 9, and is conveyed to the fixing device 17 without forming an image at the forming section. In the fixing device 17, the cleaning pattern formed on the back surface of the sheet comes into contact with the fixing roller, and the fixing roller is cleaned. Further, in this case, since the cleaning pattern on the surface is in contact with the pressure roller side, the pressure roller is simultaneously cleaned again. Thereafter, the sheet is discharged without being guided again to the sheet re-feeding unit 50, but may be sent to the sheet re-feeding unit again in order to repeat the above-described steps in order to ensure reliable cleaning.

In the above embodiment, the fixing device is constituted by the fixing roller and the pressure roller. However, an endless belt is arranged around the heat source, and the pressure roller is installed facing the heat source. Naturally, the present invention is also applied to a fixing device configured to pass a sheet between the pressure roller and the endless belt.

[0033]

According to the present invention, at the lower side inside the apparatus main body of the image forming apparatus, a sheet feeding cassette for storing unrecorded recording material, and a recording material temporarily recorded on one side and temporarily stored on the other side. A re-feed unit for feeding paper again for recording can be interchanged and mounted. When the above-described re-feed unit is mounted, a sheet unit provided below the re-feed unit is moved from the apparatus to the above-described apparatus. In order to convey the recording paper into the main body, a sheet conveyance path is provided in a substantially vertical direction on the front side as viewed from the mounting direction of the refeed unit, so that a jam occurs in the refeed unit (reversing path). If a unit occurs, it can be easily processed by pulling out the unit, and when double-sided recording is not required, a normal paper cassette can be used instead. Body feeder Additional Tsu steal can be suppressed. Further, when such a separate paper feed cassette is added, the recording material transport path can be shared.

A first switching claw is disposed immediately downstream of the fixing device in the transport direction of the recording material transport path, and by switching the first switching claw, the recording material is guided toward the re-feeding unit. The recording material is guided to the stack portion or branched, and the first material is guided to the stack portion.
A second switching claw is provided downstream of the first switching claw in the conveyance direction of the recording material conveyance path so that the recording material can be guided to the upper stack portion or the lower stack portion when the switching claw is switched. As a result, a path to the sheet re-feeding unit is taken immediately after the fixing unit, so that a so-called first print time in the case of double-sided image recording can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an image forming apparatus according to the present invention.

FIG. 2 is a schematic diagram of a fixing device in the image forming apparatus of FIG.

FIG. 3 is a schematic diagram illustrating an example of a recording sheet provided with an image of a cleaning pattern.

FIG. 4 is a diagram showing a cleaning flow when detecting the size of a recording sheet.

FIG. 5 is a conceptual diagram showing how the fixing device performs normal / reverse rotation.

DESCRIPTION OF SYMBOLS 10 Device body 11 Sheet unit 12 Photoconductor 13 Charger 14 Developing device 15 Transfer device 16 Cleaning device 17 Fixing device 18 Optical writing device 19 Paper feed port 20 Paper feed roller 21 Transport path 22 Transport roller pair 23 Resist Roller pair 24 Upper stack portion 25 Discharge guide 26, 27 Discharge roller pair 28 Lower stack portion 29 Second switching claw 30 First switching claw 31 Discharge port 32 Guide 33 Manual feeder 33a Receiving portion 34 Push-up lever 40 Paper feed cassette 41 , 42 Guide plate 43 Bottom plate 44 Separation member 45 Sheet transport path 46 Handle 50 Refeed unit 51 Sheet transport path 52 Handle 53 Transport path 53a Reverse path 54, 55, 56 Transport roller pair 57 Forward / reverse roller pair 58 Feed roller 59 Third switching claw

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 G03G 15/20 105 3K058 15/20 105 H05B 3/00 310C H05B 3/00 310 G03G 15 / 08 507H (72) Inventor Tadashi Ishikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Seiji Saito 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company F Terms (Reference) 2H027 DA12 DA50 DC10 EA01 EA02 EA03 EA04 EA05 EA12 EC03 EC20 EF06 FA11 2H028 BA09 BA16 BB00 BB04 2H033 AA08 AA46 BA11 BA30 BB37 CA07 CA27 CA36 CA40 CA48 2H077 AD02 AD16 BA01 DB20 DB12 DB12 DB12 HB12 JA02 JB10 JB49 PA02 PA11 PA15 PA17 3K058 AA82 BA18 CA12 GA06

Claims (6)

[Claims] 1. A fixing device for fixing a toner image by a thermal action by passing a recording material onto which a toner image formed on an image carrier is transferred, a conveying device for feeding the recording material,
An image storage device that stores an image of a predetermined pattern, and an optical writing device that forms the image of the predetermined pattern on an image carrier, and a recording material on which the image of the predetermined pattern is recorded is again passed through a fixing device. In the image forming apparatus for cleaning the fixing device, when forming the image of the predetermined pattern, at least one of a developing bias, a writing light amount, a rotation speed of a developing roller, a transfer current, and a drum current is changed, and a recording material is changed. An image forming apparatus which controls so that the weight of toner per unit area transferred to the image forming unit becomes larger than that during normal image formation. 2. A recording material size detecting device, comprising: when forming an image of the predetermined pattern, detecting the size of the recording material on which the image is to be formed, and controlling the feeding of the recording material according to the result. The image forming apparatus according to claim 1, wherein: 3. When the recording material on which the image of the predetermined pattern is recorded is passed through a fixing device, the sheet passing speed is set lower than at the time of normal fixing, and the fixing device is set at a temperature higher than a fixing temperature. The image forming apparatus according to claim 1, wherein the image forming apparatus performs at least one of the following. 4. The image forming apparatus according to claim 1, wherein when the recording material on which the image of the predetermined pattern is recorded passes through a fixing device, the conveying direction is configured to be reversible. The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 1, further comprising a reversing section provided in said conveying device, wherein an image forming apparatus capable of forming an image on both sides of the recording material can select whether or not the recording material on which the image of the predetermined pattern is recorded can be reversed. The image forming apparatus according to claim 1. 6. An image of a predetermined pattern is recorded on one surface of a recording material, and when the recording material is reversed at a reversing unit to record an image of the same pattern on the other surface, cleaning is performed with the previously recorded image. 6. The image forming apparatus according to claim 5, wherein the fixing device is cleaned again without reversing.