JP2003098890A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To smoothly transfer a sheet carrying an unfixed toner image on both sides to a fixing area, and to make the image quality of both sides of the sheet the same. SOLUTION: This photoconductor has a photoreceptor 1 and an intermediate transfer belt 10,
The first visible image once transferred from the photoconductor to the intermediate transfer belt is
In an image forming apparatus capable of transferring a visible image to both sides of a sheet by transferring a second visible image from a photoconductor to the other surface of the sheet while transferring the second visible image from the photoconductor to the one side of the sheet P from the intermediate transfer belt, Is provided, and the elastic force applied to the sheet at the fixing nip portion is set to be the same for the first visible image and the second visible image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image on both sides of a recording medium.

[0002]

2. Description of the Related Art There is known an image forming apparatus such as a copying machine, a printer or a facsimile, which is configured to form an image on both sides of a recording medium (hereinafter also referred to as "paper"). In the conventional image forming apparatus capable of double-sided recording, the image (visual image) formed on the image carrier is transferred and fixed on a sheet, the sheet is inverted by an inversion path or the like, and the sheet is fed again to be fed. It is a general method to transfer and fix another image (visual image) on the back side.

In the case of double-sided recording by this method, there are many problems in securing the reliability of the sheet conveyance, such as switching the sheet conveyance direction and curling the sheet by fixing a single-sided image. On the other hand, in JP-A-1-209470 and JP-A-11-327335, after a toner image is transferred to both sides of a sheet using a first image carrier and a second image carrier, A system in which fixing is performed once is disclosed.

In the one disclosed in JP-A-1-209470, a first image formed on a photoconductor is transferred onto a transfer belt by a first transfer means, and then a second image formed on the photoconductor is transferred.
The image is transferred onto one surface of the sheet by the first transfer unit. After that, the first image on the transfer belt is transferred to the other surface of the paper by the second transfer means, so that the images are transferred to both surfaces of the paper and the paper is conveyed to the fixing device to be fixed.

The one disclosed in Japanese Patent Laid-Open No. 11-327335 is a type provided with two transfer means.
Transfer the color image to both sides of the paper and convey it to the fixing device.
It is a one-time fix. In this apparatus, a spur having a plurality of protrusions on its peripheral surface is provided as a member for guiding the conveyance of a sheet having unfixed toner images on both sides.

[0006]

In each of the above-mentioned publications, an unfixed toner image is carried on both sides of the paper.
Since the fixing process is performed every time, the images may be different on the front and back of the paper (for example, image density).

In view of the above-mentioned drawbacks, the present invention solves this problem and smoothly conveys a sheet carrying an unfixed toner image on both sides to a fixing area, thereby making it possible to obtain an image having the same image quality on both sides of the sheet. An object is to provide a forming apparatus.

[0008]

According to the present invention, the above-mentioned problems include a first image carrier and a second image carrier, and from the first image carrier to the second image carrier. Transferring the first developed image once transferred from the second image carrier to one surface of the recording medium, and transferring the second developed image from the first image carrier to the other surface of the recording medium. In an image forming apparatus capable of transferring a visible image to both sides of a recording medium by means of a fixing device for fixing the transferred visible image to both sides of the recording medium, the elastic force applied to the recording medium at the fixing nip portion is It is solved by setting the first and second visible images to be the same.

A first image carrier and a second image carrier,
In an image forming apparatus capable of transferring a visible image to both surfaces of a recording medium, a visible image is transferred from the first image bearing member to a second image bearing member, and another visible image is transferred from the first image bearing member. It is adapted to be transferred onto one surface of a recording medium, and when the first visible image on the second image carrier is thermally transferred and fixed on the other surface of the second image carrier. At the same time, a fixing device for fixing the second different visible image transferred to one surface of the recording medium is provided, and the elastic force applied to the recording medium at the fixing nip portion causes the first visible image and the second visible image. The above problem can also be solved by setting the same for the image.

Further, the first image carrier having the first image bearing member and the second image bearing member, and the first visible image once transferred from the first image bearing member to the second image bearing member is converted into the second image bearing member. Transfer from the carrier to one side of the recording medium, and transfer from the first image carrier to the second image carrier.
In an image forming apparatus capable of transferring a visible image to both surfaces of a recording medium by transferring the visible image to the other surface of the recording medium, a fixing device for fixing the transferred visible image to both surfaces of the recording medium is provided. The above problem can also be solved by setting the temperature of the recording medium at the nip portion to be the same on both sides.

Further, in an image forming apparatus having a first image carrier and a second image carrier and capable of transferring a visible image to both sides of a recording medium, the first image carrier and the second image are transferred. A visible image is transferred to a carrier, and another visible image is transferred from the first image carrier to one surface of the recording medium, and the second image is transferred onto the second image carrier. A fixing device for thermally transferring and fixing the first visible image on the image carrier to the other surface of the recording medium, and at the same time fixing the second different visible image transferred to the one surface of the recording medium, The above problem can be solved even if the temperature of the recording medium at the fixing nip portion is set to be the same on both sides.

It is preferable that the second image carrier has an endless belt shape. As means for applying an elastic force from the second image carrier to the recording medium, a roller provided at a position opposite to the means for fixing the second visible image and within the range of the second image carrier is used. Is preferable.

As means for applying heat to the recording medium from the endless belt-shaped second image carrier, it is located at the position opposite to the roller for fixing the second visible image and inside the belt of the second image carrier. It is also preferable to use the provided heat source built-in roller. It is more preferable to have respective temperature detecting means for fixing each of the first visible image and the second visible image, and to control these individually. Each of the temperature detecting means is preferably provided on the belt surface as the first visible image side and on the roller surface as the second visible image side.

It is more preferable that the roller having a built-in heat source also has means for pressing the recording medium from the second image carrier. From the structure of the second visible image fixing roller, the heater,
It is convenient that the core metal, the elastic layer, and the surface layer are the heater, the core metal, and the elastic layer from the center of the configuration of the first heat roller with a built-in heat source for fixing the visible image.

The hardness and thickness of the elastic layer and the surface layer of the second visible image fixing roller, the hardness and thickness of the elastic layer of the first heat roller with a built-in visible image fixing heat source, and the tension of the belt of the second image carrier are controlled. It is even more effective to make the elastic forces applied to both sides of the recording medium the same. Each of the elastic layer of the second visible image fixing roller and the elastic layer of the first visible image fixing heat source built-in roller has a thickness of 0.1 mm or less, or the surface layer of the second visible image fixing roller, It is convenient if each thickness of the belt of the image carrier is 100 μm or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional configuration diagram of a printer that is an example of an image forming apparatus to which the present invention is applied.

In the printer shown in this figure, a photosensitive drum 1 which is a first image bearing member is arranged substantially in the center of the apparatus. Around the photosensitive drum 1, a cleaning device 2,
A charge eliminating lamp L, a charging device 3, a developing device 5 and the like are provided. An exposure device 4 is provided above the photosensitive drum 1, and the laser beam 4A emitted from the exposure device 4 is
The photoconductor 1 is irradiated with light at a writing position between the charging device 3 and the developing device 5.

In this embodiment, the photosensitive drum 1, the cleaning device 2, the charge eliminating lamp L, the charging device 3, the developing device 5 and the like are integrally incorporated into a unit, and the process cartridge can be replaced at the end of its life. .

A belt unit BU is arranged below the photosensitive drum 1. The belt unit BU is centered on the intermediate transfer belt 10 as the second image carrier,
The photosensitive member 1 is provided so that a part thereof contacts the intermediate transfer belt 10. The intermediate transfer belt 10 is a roller 11,
It is stretched around 12 and 13 and is supported so as to be able to travel counterclockwise in the figure. The intermediate transfer belt 10 has heat resistance and has a resistance value that allows toner to be transferred.

Inside the loop of the intermediate transfer belt 10,
Backing rollers 14, 15, cooling means 16, 16, fixing auxiliary means (fixing roller) 18, first transfer means 20, etc. are arranged. The first transfer unit 20 is provided at a position facing the photoconductor 1 with the belt 10 interposed therebetween, and transfers the toner image formed on the photoconductor 1 to the intermediate transfer belt 10 or a sheet (belt 1).
(The surface facing 0).

A second transfer means 21, a heating device 30, and a belt cleaning device 25 are arranged on the outer peripheral portion of the intermediate transfer belt 10. The heating device 30 is rotatable about a fulcrum 30A as shown by an arrow G, and this rotating operation is realized by a mechanism (not shown) to move the fixing roller 30B up and down to sandwich the intermediate transfer belt 10 (and a sheet). Fixing auxiliary means 1
8 can be pressed and separated. Heating device 3
On the upper left side of 0, a fan F1 for exhausting the air inside the machine to prevent the temperature inside the machine from rising excessively is provided.

The cleaning device 25 for the intermediate transfer belt 10 includes a cleaning roller 25A and a blade 2 inside.
5B, toner conveying means 25C, etc., and has a function of wiping off unnecessary toner remaining on the surface of the intermediate transfer belt 10. The toner accumulated in the cleaning device 25 is
The toner is transferred to a collection container (not shown) by the toner transfer unit 25C. The cleaning device 25 is configured to be rotatable about a rotation fulcrum D as indicated by an arrow H. By rotating the entire cleaning device 25 by a mechanism (not shown), the cleaning roller 25A moves to the intermediate transfer belt 10
Can be approached and separated from.

A paper feed cassette 26 is provided at the bottom of the apparatus body. The paper feed cassette 26 is constructed so that it can be pulled out toward the front in the drawing. A transfer paper P as a recording material is stored in the cassette 26. A paper feed roller 27 is provided at an upper position on the front end side (right side in the drawing) of the cassette 26 in the paper feed direction.
Is provided. A registration roller pair 28 is provided on the right side of the photosensitive drum 1, and a guide member 29 for guiding the paper is provided on the right side of the registration roller pair 28. Above the cassette 26, the electrical component E1 and the control device E2 are arranged. Further, a manual paper feeding device (paper feeding tray) 35 is provided on the right side surface of the device, and a second paper feeding roller 36 for feeding the paper P set on the bottom plate 37.
Is provided. The sheet fed from the manual sheet feeder 35 is guided by the guide member 29 to the registration roller 28.

Fixing means (heating device 30, fixing auxiliary means 1
A switching guide 42 is provided at the left side of 8). The switching guide 42 is configured so as to be swingable around a support shaft 43, and the sheet stack sent out from the belt unit BU is conveyed in the sheet discharge stack section 40 provided on the upper surface of the apparatus body.
Alternatively, the discharge tray 44 on the side of the apparatus is switched. The switching guide 42 is operated by an actuator (not shown) (for example, a solenoid). When the switching guide 42 is at the position shown in the figure, the paper is sent to the paper discharge stack section 40, and when the switching guide 42 is switched in the direction of the arrow J, the paper is sent to the paper discharge tray 44.

Above the switching guide 42, a pair of conveying rollers 32A for conveying the sheet is arranged. Further, a paper discharge roller pair 32B for discharging the paper to the paper discharge stack section 40 is arranged further above. Between the transport roller pair 32A and the paper discharge roller pair 32b are guide members 31A and B.
Guided by. On the other hand, on the left side of the switching guide 42, a paper discharge roller pair 32 for discharging the paper to the paper discharge tray 44 is arranged.

The structure of the fixing means will be described with reference to FIG.
The fixing roller 30B housed in the heating device is composed of a heat source A, a core metal A, an elastic layer A, and a Teflon layer A from the center. The fixing assisting means 18 is also composed of a heat source B, a core metal B, and an elastic layer B from the center. An intermediate transfer belt 10, which is a second image carrier, is set on the outer side of the belt, and the belt is made of Teflon (trade name). The hardness, thickness, and belt tension of the elastic layer are adjusted so that the elastic force applied from the fixing roller 30B to the sheet (recording medium) is the same as the elastic force applied from the intermediate transfer belt 10 to the sheet. By setting the thickness of each elastic layer at this time to 0.1 mm or less and the thickness of the Teflon to 100 μm or less, it is possible to secure a certain degree of heat conduction. Further, it is more preferable that the thermistors 38 and 39 are installed near the surfaces of the fixing roller 30B and the fixing auxiliary means 18 to detect the temperature and individually control the temperature. Further, the fixing roller 30B is not in contact with the intermediate transfer belt 10 except when the paper is passed through the fixing roller 30B.
The fixing assisting means 18 does not perform the heating operation except when the paper is passed.

An image forming operation in the printer configured as described above will be described. First, the operation when images are obtained on both sides of the paper will be described. When images are to be obtained on both sides of the sheet, the image formed first is called the first side image, the image formed later is called the second side image, and the side of the sheet to which the first side image is transferred is the first side of the sheet. The surface of the paper on which the second surface image is transferred will be referred to as the second surface of the paper.

The image forming apparatus of this embodiment is a so-called printer, and a signal for writing is sent from a host machine (not shown) such as a PC. The exposure device 4 is driven based on the received image signal, and light from a laser light source (not shown) of the exposure device is scanned by a polygon mirror 4B which is rotationally driven by a motor, and a normal mirror,
The photosensitive drum 1 uniformly charged by the charging device 3 is irradiated through the fθ lens 4C and the like, and a latent image corresponding to the writing information is formed on the photosensitive body 1.

The electrostatic latent image on the photoconductor 1 is developed by the developing device 5, and a visible image with toner is formed and held on the surface of the photoconductor. The toner image on the photoconductor 1 is transferred to the first transfer unit 20 on the back side of the intermediate transfer belt 10, which is the second image carrier.
The image is transferred onto the surface of the intermediate transfer belt 10 that runs in synchronization with the photoconductor 1 by the (transfer roller). The surface of the photoconductor 1 is cleaned of the remaining toner by the cleaning device 2 and discharged by the discharge lamp L to prepare for the next image forming cycle.

The intermediate transfer belt 10 carries the toner image transferred onto the surface (the image to be transferred onto the first surface of the paper) and runs counterclockwise in the figure. At this time, the second transfer unit (transfer charger) 21, the heating device 30, and the intermediate transfer belt cleaning device 25 are arranged so that the toner image is not disturbed.
Is controlled to maintain a non-operating state (electrical input interruption or separation from the intermediate transfer belt 10).

When the intermediate transfer belt 10 travels to a predetermined position, a toner image to be formed on the other surface (second surface) of the paper starts to be formed on the photoconductor 1 by the above-described process, and the paper is fed. Is started. Paper feed roller 27 or 36
When is rotated in the direction of the arrow, the paper P in the paper feed cassette 26 or at the top of the manual feed tray 35 is pulled out and conveyed to the registration roller pair 28.

The intermediate transfer belt 10 travels in synchronism with the photosensitive member 1, and the toner image (first surface image) previously transferred onto the intermediate transfer belt 10 is rotated once and the intermediate transfer belt 10 and the photosensitive member 1 are rotated. It is conveyed toward the position where 1 contacts.

First, the toner on the surface of the photoconductor 1 is transferred by the first transfer means 20 onto the sheet (second surface) fed between the intermediate transfer belt 10 and the photoconductor 1 via the pair of registration rollers 28. At the time of this transfer, the paper and the image (second side image)
Registration roller pair 28 so that the position of
With the timing, the sheet is conveyed at a timing. Needless to say, the positions of the paper and the first surface image are also regular.

Toner on the paper from the photoconductor 1 (second surface image)
While the image is being transferred, the other side of the paper is
Moves with the toner on the first surface (the first surface of the paper is in close contact with the first surface image transferred onto the belt 10). When the paper passes through the action area of the second transfer means 21, a voltage is applied to the transfer means 21, and the toner (first surface image) on the intermediate transfer belt 10 is transferred to the paper.

By the action of the first transfer means 20 and the second transfer means 21, the paper having the toner images transferred on both sides thereof is sent to the fixing area by the running of the intermediate transfer belt 10. Here, the heating device 30 is lowered so that the fixing roller 30B is pressed against the fixing assisting means 18 with the intermediate transfer belt 10 interposed therebetween, and the heating device 30 and the fixing assisting means 18 cooperate with each other to form a toner image on the paper ( Both sides are fixed at once. After the toner image is transferred, the paper is fixed in a state where the paper and the intermediate transfer belt 10 are overlapped without being separated from the intermediate transfer belt 10, so that the toner image is not disturbed and the occurrence of image blur is prevented.
Further, the elastic force and temperature applied from the fixing roller 30B to the front surface of the paper and the elastic force and temperature applied to the rear surface of the paper from the intermediate transfer belt 10 having the fixing auxiliary means 18 inside are adjusted in the same manner. There is no difference in the image characteristics on the front and back of the paper. Fixing roller 30B and intermediate transfer belt 1
Each surface of No. 0 is made of Teflon and has the same surface characteristics (for example, surface roughness and hardness).

The sheet of paper after fixing is separated from the intermediate transfer belt 10 by the roller 11 by the curvature, the conveying direction is switched by the switching guide 42, and the sheet stacking unit 4 on the upper surface of the apparatus.
0 or discharged to the discharge tray 44 on the side of the apparatus.

When the paper is discharged to the paper discharge stack 40 on the upper surface of the apparatus, the second surface of the double-sided image, that is, the surface directly transferred from the photoconductor to the paper becomes the lower surface, and the paper discharge stack 40 is formed. In order to align the pages, the image of the second page is created first, the toner image is held on the intermediate transfer belt 10, and the image of the first page is created later. The surface of the body 1 may be directly transferred to the paper. Therefore, when the sheets are discharged to the discharge stack unit 40 in page order (face-down sheet discharge), the first side image is the second page image and the second side image is the first page image. The same applies to the images on the third and subsequent pages. If there is an image on an even page, the image on the even page is first formed, transferred and held on the intermediate transfer belt 10, and the image immediately before the even page is formed. Odd pages are created later and transferred directly from the surface of the photoconductor 1 to paper. The image formation order in this case is 2 → 1 → 4
→ 3 → 6 → 5 ...

On the other hand, when the paper is discharged to the paper discharge tray 44 on the side surface of the apparatus, the second surface of the double-sided image, that is, the surface directly transferred from the photoconductor to the paper becomes the upper surface and is discharged to the paper discharge tray 44. Placed. Therefore, the discharge stack unit 4
When the pages are aligned when the sheets are discharged to 0 (face-down sheet discharge), the first side image is the first page image and the second side image is the second page image. The same applies to the images on the third and subsequent pages. If there is an image on an odd page, the image on the odd page is first formed and transferred onto the intermediate transfer belt 10.
Hold and create one even page after the odd page,
The surface of the photoconductor 1 is directly transferred to the paper. In this case, the image forming order is shown by the number of pages, 1 → 2 → 3 → 4 → 5 → 6 ...
Becomes

In this example, the user can specify the tray (stack section) for ejecting the sheets from the operation panel (not shown) or the host computer. That is, the user can specify which of a plurality of paper discharge units (the paper discharge stack unit 40 and the paper discharge tray 44) to discharge the paper. Then, whichever paper discharge unit is designated, the paper is discharged to each paper discharge unit in page order.
The image forming order is automatically controlled. The control of the image forming order is performed by a control unit (not shown) of the image forming apparatus.

Therefore, no matter which discharge unit is specified, the user does not have to worry about the image forming order (image transfer surface on the paper) or the like, and simply specifies (selects) the discharge unit. The pages are ejected in the order of pages, and proper ejection at the time of double-sided recording can be obtained by a simple operation. The change of the image forming order for page alignment can be realized by a known technique of storing image data in a memory.

In this example, when the paper is fed from the manual feed tray 35 and discharged to the paper discharge tray 44, the paper transport path from the paper feed unit to the paper discharge unit is substantially linear. Therefore,
When recording on stiff paper, such as thick paper or OHP film, use the manual feed tray 35 to discharge the paper to the paper output tray 4.
By specifying 4, even in the case of a thick and high-rigidity recording medium, page aligned double-sided printing can be obtained without impairing transportability.

When normal paper is used, the paper can be fed from either the paper feed cassette 26 or the manual feed tray 35, and the paper ejection section can be designated by either the stack section 40 or the paper ejection tray 44. it can. Of course, also in that case, page-aligned double-sided printing can be obtained. An operation of feeding the paper from the paper feed cassette 26 and discharging the paper to the stack unit 40 may be provided as a default setting for normal paper that is frequently used.

By the way, normally, when a reverse image (mirror image) is formed on the photosensitive member 1 and directly transferred to a sheet, a normal image can be obtained. However, the image transferred on the intermediate transfer belt 10 is printed on the sheet. When the image is transferred onto the sheet, when it is formed as a mirror image on the photoconductor 1, the image becomes a mirror image when the sheet is transferred. Therefore, in this example, the image (first surface image) transferred from the intermediate transfer belt 10 to the sheet is formed into a normal image on the surface of the photoconductor 1 and the toner image (second image) directly transferred from the photoconductor 1 to the paper is formed. (Surface image)
Is exposed so that it becomes a mirror image on the surface of the photoreceptor. The exposure for switching between the normal image and the reverse image can be realized by a known image processing technique.

The cleaning device 25 separated from the intermediate transfer belt 10 rotates the cleaning device 25 so that the cleaning roller 25A contacts the belt 10 after the image is transferred from the intermediate transfer belt 10 to the sheet.
The residual toner after being transferred to the paper is cleaned by the cleaning roller 2
It is transferred to the surface of 5A and scraped by the blade 25B. The scraped toner is collected in a storage unit (not shown) by the toner conveying unit 25C. Since the residual toner heated by the fixing means 30 and 18 is more likely to transfer to the cleaning roller 25A before being cooled, it is cleaned on the upstream side of the cooling means 16.

The intermediate transfer belt 10 that has passed through the cleaning area is cooled by the operation of the cooling means 16.
As the cooling means 16, various heat dissipation methods can be adopted. In the method of circulating air, it is convenient to circulate the air after transferring it to a recording medium (paper) so as not to disturb the toner image held on the surface of the intermediate transfer belt 10.
A cooling means using a heat pipe, which takes heat by directly contacting the inner surface of the loop of the intermediate transfer belt 10, can be adopted.

Next, the operation for obtaining an image on one side of a sheet will be described. The operation during single-sided recording will be described separately for the case of discharging to the discharge stack section 40 on the upper surface of the apparatus and the case of discharging to the discharge tray 44 on the side surface of the apparatus.

First, the one-sided recording operation when paper is discharged to the paper discharge stack section 40 on the upper surface of the apparatus will be described. In this case, the step of transferring the toner to the intermediate transfer belt 10 can be omitted, and the toner image formed on the surface of the photoconductor 1 is directly transferred to the paper. In the case of a one-sided image, the toner image on the photoconductor 1 is a mirror image, and becomes a normal image when transferred onto a sheet.

In FIG. 1, the paper P is sent between the photoconductor 1 and the intermediate transfer belt 10 in synchronism with the toner image formed on the photoconductor 1, and the first transfer means 20 is moved. Thus, the toner image is transferred from the photoconductor 1 onto the paper (the top surface of the paper: the surface on the photoconductor 1 side).

The second transfer means 21 does not operate, the sheet moves together with the intermediate transfer belt 10, and the toner is fixed. At this time, the heating device 30 is lowered and the fixing roller 30B is pressed against the fixing assisting means 18 with the belt 10 interposed therebetween. After that, the paper is separated from the intermediate transfer belt 10, discharged through the guide members 31A and B, and the paper discharge roller pair 32B, and placed on the paper discharge stack unit 40 with the image surface facing down (face down). It With such a configuration, even if the originals over several pages are processed in order from the first page, the printed matter is in the page order when taken out from the paper discharge stack section 40. The order of image formation at this time is 1 → 2 → 3
→ 4 → 5 → 6 ...

Next, the one-sided recording operation when the paper is discharged to the paper discharge tray 44 on the side surface of the apparatus will be described. In this case, the toner image formed on the photoconductor 1 is temporarily transferred to the intermediate transfer belt 10 (operation of the first transfer unit 20). The intermediate transfer belt 10 carries one rotation while carrying the toner image (at this time,
The heating device 30 is lifted and separated from the intermediate transfer belt 10), and the paper P is placed between the photoconductor 1 and the intermediate transfer belt 10 in synchronization with the toner image on the intermediate transfer belt 10. The toner image is transferred from the intermediate transfer belt 10 onto the paper (the lower surface of the paper: the surface on the side of the belt 10) by the second transfer means 21, and is lowered.
Then, the fixing auxiliary means 18 fixes the toner image on the sheet. With such a configuration, even if several pages of originals are processed in order from one page, the printed matter is in page order when taken out from the paper discharge tray 44. The image forming order at this time is 1 → 2 → 3 → 4 → 5 → 6 ....

In the case of single-sided printing, even when the sheets are discharged to the sheet discharge stack section 40 on the upper surface of the apparatus, the sheet discharge tray 44 on the side surface of the apparatus.
When the sheet is discharged to the sheet, the image forming order is the same as 1 → 2 → 3 → 4 →, but the surface of the sheet on which the image is transferred is different. That is, in the former case, the toner image is transferred from the photoconductor 1 to the upper surface of the paper = the surface on the photoconductor 1 side, whereas in the latter case, the lower surface of the paper =
The toner image is transferred from the intermediate transfer belt 10 to the surface on the belt 10 side.

The present invention has been described above with reference to the illustrated example, but the present invention is not limited to this, and various modifications can be made. For example, during double-sided recording, the intermediate transfer belt 10 to which the first-side image is transferred is not rotated once but the belt may be reversed to convey the first-side image to a predetermined position. In this case, the first
The image carrier (photoreceptor 1) and the second image carrier (intermediate transfer belt 10) need to be separated from each other. The same applies to the case where the second transfer unit 21 is not provided and the intermediate transfer belt 10 is conveyed to the heating unit without being transferred to the sheet and is thermally transferred and fixed by the heating unit. Similarly to the above, when fixing paper with toner transferred on both sides,
The elastic force and temperature applied from the fixing roller 30B to the front surface of the paper are adjusted to be the same as the elastic force and temperature applied to the back surface of the paper from the intermediate transfer belt 10 in which the fixing auxiliary means 18 is installed. Further, in the present example, the first image carrier is the photosensitive drum, but it may be a belt type image carrier.

Further, although the above-mentioned example is a monochromatic image forming process, the present invention can be applied to an image forming apparatus which adopts a color image forming process using multicolor toners. This will be described. A charge eliminating lamp L, a cleaning device 2, a charging device 3, and a developing device 5 are arranged on the outer peripheral portion of the photoconductor 1 serving as the first image carrier, which is rotatably supported and rotates in the arrow direction. A space is provided between the charging device 3 and the developing device 5 for receiving the optical information emitted from the lower exposure device 4. There are four photoconductors 1 (a, b, c,
d) Yes, but the surrounding parts configuration is the same. The color of the color material (toner) handled by the developing device 5 is different. Part of the plurality of photoconductors 1 is in contact with the intermediate transfer belt 10, which is the second image carrier. The intermediate transfer belt 10 is a roller 1 that is long in the lateral direction and is rotatable in the direction of the arrow so that it can rotate.
It is supported and stretched between 1 and 12, and a first transfer unit 20 is arranged near the photoconductor 1 on the back side (inside of the loop). In addition, a backing roller 14 is arranged.
The backing roller 14 and the first transfer means 20 ensure that the transfer portion nip is properly secured. An intermediate transfer belt cleaning device 25 is arranged outside the belt loop.

The exposure device 4 is a well-known laser system and irradiates light information corresponding to the color of the toner to be color-separated and developed as a latent image on the surface of the uniformly charged photoreceptor. An exposure device including an LED array and an image forming means can also be adopted. The photoconductor 1 has a structure in which an organic semiconductor layer which is a photoconductive substance is provided on the surface of an aluminum cylinder having a diameter of about 30 to 100 mm. A belt-shaped photoconductor can also be adopted. The intermediate transfer belt 10 is a belt having a resistance value that allows toner to be transferred from the photoconductor 1. Substrate thickness is 50-50
A belt based on a 0 μm resin film or rubber, the surface layer of which has a low surface energy coating, and the volume resistance value of the entire belt is 10 ⁶ to 10 ¹² Ωcm, and the surface resistivity (Ω / □) is 10 ⁵ It is in the range of 10 to ¹² .

An intermediate transfer member 100, which is a belt-shaped third image carrier, is arranged on the right side of the drawing. Intermediate transfer member 10
0 is movable in the direction of arrow B,
6 and 117 are supported and stretched, and the second transfer means 120 is provided on the back side (inside the loop) of the intermediate transfer belt 1.
It is arranged in the vicinity of the roller 11 supporting 0. In addition, a heating roller 130, backing rollers 114 and 115, and a backing plate BP are arranged. The rotating roller 116 also serves as a cooling unit. A third image carrier cleaning device 250, a charger CH, and the like are arranged outside the belt loop. The cleaning device 250 includes a roller 250A, a blade 250B, and a toner conveying unit 250 inside.
After the toner is transferred to the paper by using C or the like, unnecessary toner and paper dust remaining on the surface of the third image carrier are wiped off. In the figure, the roller 250A is in a state of being separated from the surface of the third image carrier. It can rotate around the fulcrum 250D,
The structure is such that it can be brought into contact with and separated from the surface of the image carrier. Before the transfer onto the paper, the third image carrier is released when carrying the toner image, and when cleaning is required, the third image carrier rotates in the counterclockwise direction in the figure and contacts.

The transfer means 120 and the backing roller 11
5, by the roller 11 supporting the second image carrier 10,
The second image carrier 10 and the third image carrier 100 are in contact with each other,
Form a predetermined transfer nip. The members (rollers, backing members) inside the second and third image carriers are grounded except for the transfer means (rollers) 20 and 120.
This is to ensure transfer efficiency and prevent the occurrence of abnormal images.

The third image carrier (intermediate transfer member) 100 is heat-resistant and allows toner to be transferred from the second image carrier 10, and also carries an image while the carried toner image is transferred onto a sheet. A belt having a resistance value suitable for. The substrate has a thickness of 50 to 500 μm of polyimide or polyamide-imide, and the surface layer is coated with a low surface energy such as fluorine, and the volume resistance value of the entire belt is 10 ⁶ to 10 ^6.
12 Ωcm, surface resistivity (Ω / □) 10 ⁵ to 10
It is in the range of ¹² .

The sheets P are stored in sheet feeding devices (sheet feeding cassettes) 26-1 and 26-2 in the lower part of the figure, and the uppermost sheet is fed by the sheet feeding roller 27 one by one and through a plurality of guides 29. It is conveyed to the registration roller pair 28.

A heating device 30 for the fixing unit, discharge guides 31A and 31B, a pair of discharge rollers 32, and a discharge stack unit 40 are arranged above the drawing. As described above, the heating device 30 has a roller having a heater built in a surface layer material such as silicone rubber, but may be provided as a belt fixing device having a heating element housed in a belt loop. The heating roller 130 also has the same configuration as the fixing roller 30B and the fixing auxiliary means 18 described above. The toner on the surface of the second image bearing member is contacted with the paper to thermally fuse the toner,
In the step of transferring to the third image carrier, the heating device 30 is separated from the surface of the third image carrier 100 by using a mechanism (not shown).

The first image carrier 1, the cleaning device 2,
The charging device 3, the developing device 5 and the like may be integrally incorporated and configured as a process cartridge so that they can be replaced at the end of their life. Above the second image carrier 10 and below the paper discharge stack portion 40, there is provided a storage portion TS that can store the toner TC for replenishment. The toner colors are four colors of magenta, cyan, yellow, and black (a,
b, c, d) and is in the form of a cartridge.
It is replenished to the developing device of the corresponding color by the powder pump. The toner cartridge can be handled by opening the cover 40A that is a part of the paper discharge stack unit 40. Cover 4
OA 0A is configured to be openable about a rotation fulcrum 40B at one end. Since this fulcrum is on the side of the paper discharge roller 32, even if the cover 40A is opened when there is a recorded paper in the paper discharge stack section 40, the recorded paper falls and the page order is out of order. Such a problem does not occur.

Toner storage unit TS and heating device (fixing means)
A heat insulating member W is interposed between the heat insulating member W and the heat insulating member 30. Therefore, it is possible to prevent the replenishment toner TC from melting and sticking due to repeated heating and cooling. As the heat insulating method, resin, flocked resin, or a laminate of these materials having an air layer can be employed. It is also effective to provide an air flow passage communicating with the fan F1 to take in outside air.

Further, charging means for the first image carrier,
The configuration of the developing device, the first and second transfer means, or the fixing device is not limited to the configuration of the above example, and an appropriate method can be adopted. Needless to say, the image forming apparatus is not limited to the printer and may be a copying machine or a facsimile. The same applies to the configuration of the fixing device, and for example, an induction heating system or a thermal heater can be adopted.

[0063]

As described above, according to the image forming apparatus of the present invention, the fixing device for fixing the visible images transferred on both sides of the recording medium is provided, and the elastic force applied to the paper at the fixing nip portion is provided. Alternatively, since the temperature is set to be the same on both sides of the sheet, the sheet holding the unfixed image can be smoothly conveyed to the fixing area, and the image quality on both sides of the sheet can be the same.

Further, a visible image is transferred from the first image carrier to the second image carrier, and another visible image is transferred from the first image carrier to one surface of the sheet. On the second image carrier, the first visible image on the second image carrier is thermally transferred and fixed on the other side of the paper, and at the same time, the second another visible image transferred on one side of the paper is transferred. By providing a fixing device for fixing and setting the elastic force or the temperature applied to the paper at the fixing nip portion to be the same for the first visible image and the second visible image, even in a process including thermal transfer. It is possible to make the recorded images have the same quality on both sides.

If the second image carrier is an endless belt,
It is possible to secure a stable transportability of the sheet and easily obtain a stable pressure or temperature. As a means for applying an elastic force to the paper from the second image carrier, if a roller provided at a position facing the means for fixing the second visible image and within the range of the second image carrier is used, The elastic force urging means is present on the side of the second image carrier that does not face the visible image. As a means for applying heat to the paper from the endless belt-shaped second image carrier, a heat source is provided at the position opposite to the roller for fixing the second visible image and inside the belt of the second image carrier. If a built-in roller is used, stable temperature supply is easy.
If each temperature detecting unit is provided for fixing the first visible image and the second visible image, and these are individually controlled, it is easy to ensure the same temperature control on both sides of the paper.

If the roller having a built-in heat source also has a means for pressing the recording medium from the second image carrier, heating and pressing can be performed at the same time, and the same quality can be achieved on both sides of the paper more efficiently and stably. The image can be realized.

The elastic layers of the second visible image fixing roller and the elastic layer of the first visible image fixing heat source built-in roller each have a thickness of 0.1 mm.
Or less than the surface layer of the second image fixing roller and the second
When the thickness of the belt of the image carrier is 100 μm or less, heat conduction to the fixing surface can be improved, the waiting time can be shortened, and energy can be saved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a monochrome printer which is an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a partial schematic diagram illustrating the configuration of a fixing device.

FIG. 3 is a schematic configuration diagram of a multicolor printer showing another example.

[Explanation of symbols]

1 photoconductor drum (first image carrier) 10 Intermediate transfer belt (second image carrier) 18,30B fixing roller 30 heating device

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H028 BA16 BC00 BD00                 2H033 BA32 BB14 BB15 BB18 BB33                       BB34 CA02 CA07 CA30                 2H200 GA23 GB22 GB25 JC03 JC07                       JC09 JC13 JC15 JC16 MA04                       MA20 MB04 MB05

Claims (14)

[Claims] 1. A first image bearing member having a first image bearing member and a second image bearing member, wherein the first visible image once transferred from the first image bearing member to the second image bearing member is converted into the second image bearing member. An image in which a visible image can be transferred to both surfaces of a recording medium by transferring the second visible image from the first image carrier to the other surface of the recording medium while being transferred from the carrier to one surface of the recording medium. In the forming apparatus, a fixing device for fixing the visible images transferred to both surfaces of the recording medium is provided, and the elastic force applied to the recording medium at the fixing nip portion is the same for the first visible image and the second visible image. The image forming apparatus is set to. 2. An image forming apparatus having a first image carrier and a second image carrier, capable of transferring a visible image to both surfaces of a recording medium, the first image carrier to the second image. A visible image is transferred to a carrier, and another visible image is transferred from the first image carrier to one surface of a recording medium, and the second image is transferred onto the second image carrier. First on the image carrier
A fixing device is provided for thermally transferring and fixing the visible image to the other surface of the recording medium, and at the same time, fixing the second different visible image transferred to the one surface of the recording medium, and the recording medium at the fixing nip portion. The image forming apparatus is characterized in that the elastic force applied to is set to be the same for the first and second visible images. 3. A first image bearing member having a first image bearing member and a second image bearing member, wherein the first visible image once transferred from the first image bearing member to the second image bearing member is converted into the second image bearing member. An image in which a visible image can be transferred to both surfaces of a recording medium by transferring the second visible image from the first image carrier to the other surface of the recording medium while being transferred from the carrier to one surface of the recording medium. The forming device is provided with a fixing device for fixing the transferred images on both sides of the recording medium, and the temperature of the recording medium at the fixing nip portion is set to be the same on both sides. Image forming apparatus. 4. An image forming apparatus having a first image carrier and a second image carrier, capable of transferring a visible image to both surfaces of a recording medium, the first image carrier to the second image. A visible image is transferred to a carrier, and another visible image is transferred from the first image carrier to one surface of a recording medium, and the second image is transferred onto the second image carrier. First on the image carrier
A fixing device is provided for thermally transferring and fixing the visible image to the other surface of the recording medium, and at the same time, fixing the second different visible image transferred to the one surface of the recording medium, and the recording medium at the fixing nip portion. The image forming apparatus is characterized in that the temperature is set to be the same on both sides. 5. The image forming apparatus according to claim 1, wherein the second image carrier has an endless belt shape. 6. The means for applying an elastic force from the second image carrier to the recording medium is provided at a position opposite to the means for fixing the second visible image and within the range of the second image carrier. The image forming apparatus according to claim 1, further comprising a roller. 7. A belt of the second image carrier, which is at a position facing a roller for fixing the second visible image, as a means for applying heat to the recording medium from the second image carrier having an endless belt shape. The image forming apparatus according to claim 3, wherein a roller with a built-in heat source provided inside is used. 8. The image forming apparatus according to claim 7, wherein each of the first and second visible images has a temperature detecting unit for fixing the image, and these temperature detecting units are individually controlled. 9. The image forming apparatus according to claim 8, wherein each of the temperature detecting means is provided on a belt surface as a first visible image side and on a roller surface as a second visible image side. . 10. The image forming apparatus according to claim 7, wherein the heat source built-in roller also has a unit for pressing the recording medium from the second image carrier. 11. A heater, a core metal, an elastic layer, and a surface layer from the center of the configuration of the second visible image fixing roller, and a heater, a core metal, from the configuration of the first heat roller with a built-in heat source for fixing the visible image. The image forming apparatus according to claim 10, wherein the image forming apparatus is an elastic layer. 12. The hardness and thickness of the elastic layer and the surface layer of the second visible image fixing roller, the hardness and thickness of the elastic layer of the first heat roller with a built-in heat source for visual image fixing, and the tension of the belt of the second image carrier. The image forming apparatus according to claim 11, wherein the elastic forces applied to both sides of the recording medium are controlled to be the same. 13. The elastic layer of the second visible image fixing roller and the elastic layer of the first heat roller with built-in visible image fixing roller each have a thickness of 0.1.
The image forming apparatus according to claim 12, wherein the image forming apparatus has a size of not more than mm. 14. A surface layer of a second visible image fixing roller;
13. The image forming apparatus according to claim 12, wherein each thickness of the belt of the image carrier is 100 μm or less.