JPH11212382A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wrinkling even in the case of using an envelope as recording material even if a paper feeding path is the one by which the recording material is bent by arranging a pressure roller and a heating roller so that an advancing angle formed by the advancing direction of the recording material with a direction from the center of the pressure roller to the center of the heating roller may be within a specified range. SOLUTION: A fixing device 26 is provided with the heating roller 241 and the pressure roller 242. By making transfer paper pass between the rollers 241 and 242, toner is melted by heating and pressuring by the rollers 241 and 242. In this device, the rollers 241 and 242 and a guiding member 31 are arranged so that the advancing angle formed by the advancing direction where the envelope guided by the member 31 advances to the rollers 241 and 242 with the direction from the center of the roller 242 to the center of the roller 241 may be >=80 deg. and <=120 deg..

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 copying machine and a printer, and more particularly, to an image forming apparatus that forms an image by fixing a toner image formed on a recording material.

[0002]

2. Description of the Related Art As an image forming apparatus, an apparatus using an electrophotographic method is widely used. FIG. 3 shows a schematic sectional view of the image forming apparatus. In this image forming apparatus, when an image is formed, the photosensitive drum 1 rotating in the direction of the arrow is uniformly charged by the charging means 2. The charged photosensitive drum 1 is subjected to image exposure based on an image by the exposure unit 3 to form an electrostatic latent image on the photosensitive drum 1. Then, the latent image is developed by the developing device. In this development, the toner carried on the developing sleeve 4 is
By applying a bias to the developing sleeve 4, the toner is transferred to the photosensitive drum 1, and a toner image is formed on the photosensitive drum 1. After that, the transfer unit 5 transfers the toner image formed on the photosensitive drum 1 onto a separately transported recording material P, and a toner image is formed on the recording material P. The recording material P on which the toner image has been formed (transferred) is separated from the photosensitive drum 1 and further conveyed to the fixing unit 7. Then, the toner image is fixed on the recording material P by passing between the heating roller 7A and the pressure roller 7B of the fixing unit 7. The fixed recording material P is a pair of rollers 8
And further discharged out of the machine. In addition,
The photoreceptor drum 1 after the transfer is cleaned by the cleaning unit 6 and is prepared for the next image formation.

[0003]

In such an image forming apparatus, demands for space saving and miniaturization have become strict, and various restrictions have been imposed on the arrangement in the image forming apparatus. As one of them, the conveyance path of the recording material P from the transfer means 5 to the fixing means 7 should not be a straight line but a conveyance path which bends the recording material as shown by a dashed line in FIG. You may have to.
This is because the cleaning device 6 is disposed and the recording material P
In order to improve the separability of the image forming apparatus, there is a restriction for various reasons, such as a paper feed cassette (not shown) arranged below in the image forming apparatus.

In the case of such a bent conveyance path, when an envelope is passed as a recording material P between the heating roller 7A and the pressure roller 7B, the envelope is formed of double paper. Therefore, wrinkles are generated on the concave side of the bent envelope.

In the image forming apparatus described in the section of the related art, an OHT (Overhead) is used as a recording material P.
d Projector Transparency)
When an image is formed on a light-transmissive recording material P, a higher amount of heat is applied to improve the light-transmitting performance of toner and OHT. In order to increase the amount of heat to improve the light transmission performance, the transport speed of the OHT is reduced, and the temperature of the heating roller 7A is also increased. In particular, when the image forming apparatus forms a color image, this light transmission performance is one of the most important performances required, and it is necessary to increase the amount of heat applied.

However, the OHT provided with a high calorific value is
May deform into a wavy shape. For this reason, even if the OHT has once passed between the heating roller 7A and the pressure roller 7B, the deformed portion (particularly, the portion that is deformed in a wavy shape and protrudes toward the heating roller 7A). When the sheet comes into contact with the heating roller 7A again, an offset occurs, and the toner in that portion peels off, which causes an image defect.

Therefore, the first aspect of the present invention is to provide a recording material feeding path from an image forming position (transfer means) to a fixing means, wherein the feeding path is such that the recording material is bent. A first object is to prevent wrinkles from occurring even when an envelope is used as a recording material.

It is a second object of the present invention to prevent offset and prevent image defects due to peeling of toner even when the light transmitting recording material used as the recording material is deformed. And

[0009]

A first object of the present invention is to provide an image forming means for forming a toner image on a recording material, and a recording material on which the toner image has been formed by the image forming means. And a fixing unit for fixing the toner image on the recording material by passing between the fixing unit and the fixing unit from the position where the toner image is formed on the recording material by the image forming unit. And guide means for guiding the recording material in a deflected state, and an entry direction in which the recording material guided by the guide means enters the heating roller and the pressure roller; and The heating roller, the pressure roller, and the guide means are arranged such that an entry angle formed by a direction from a center of the heating roller to a center of the heating roller is 80 ° or more and 120 ° or less. The problem can be solved by an image forming apparatus characterized in that it is placed.

The second object is to provide an image forming means for forming a toner image on a recording material, and to pass the recording material on which the toner image is formed by the image forming means between a heating roller and a pressure roller. Accordingly, in an image forming apparatus having a fixing unit for fixing a toner image on a recording material, when the recording material is a light-transmitting recording material, the surface temperature of the heating roller is set to T (° C.) The transport speed of the light transmitting recording material nipped and transported by the roller and the pressure roller is set to L.
When S (mm / sec), the condition of T / LS ≧ 15.9 is satisfied, and the conveying direction of the recording material from the nip portion between the heating roller and the pressure roller to the heating roller and the pressure roller The discharge direction to the regulating member that regulates the conveyance of the recording material adjacent to the downstream side, and the discharge angle formed by the direction from the center of the pressure roller to the center of the heating roller is 70 degrees or more, The problem can be solved by an image forming apparatus in which the heating roller, the pressure roller, and the regulating member are arranged.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a color printer, and FIG. 2 is an enlarged view of a fixing device and its vicinity.

First, prior to the description of an embodiment of the present invention, an image forming process and each mechanism of a color printer which is an example of the image forming apparatus of the present invention will be described. This color printer superimposes each color toner image sequentially formed on an image carrier, and then superimposes the superimposed color toner image formed on the image carrier once on a transfer paper as a recording material at a transfer unit. To form a color image, and then separating the recording paper from the surface of the image carrier by the separating means, and passing the toner image on the recording material by passing between the heating roller and the pressure roller of the fixing means. This is a color image forming apparatus of a fixing type.

The photosensitive drum 10, which is an image carrier, has an OP
A C photoconductor (organic photoconductor) is formed by coating on a drum substrate, and is grounded and driven to rotate clockwise as shown.
A charging means scorotron charger 11, a grid (not numbered) that are potential held at grid potential V _G uniform charging of the high voltage V _H to the photosensitive drum 10 peripheral surface with corona discharge wire (unsigned) By corona discharge. Prior to charging by the scorotron charger 11, a pre-charging static eliminator (PC) using a light emitting diode or the like to eliminate the history of the photosensitive drum 10 up to the previous print.
L) Exposure by 12 is performed to eliminate static electricity on the peripheral surface of the photosensitive drum 10.

After the photosensitive drum 10 is uniformly charged, image exposure based on an image signal is performed by an exposure optical system 13 as image exposure means. The optical path of the exposure optical system 13 is bent by a reflecting mirror (no sign) through a rotating polygon mirror (no sign), an fθ lens (no sign), and a cylindrical lens (no sign) using a laser diode (not shown) as a light emitting source, and main scanning is performed. The latent image is formed by the rotation of the photosensitive drum 10 (sub-scan).
In the present embodiment performs exposure on a character portion, towards the exposed portion potential V _L to form an inverted latent image as a lower potential than the charge potential V _H.

Around the periphery of the photosensitive drum 10, Y and Y each containing a two-component developer composed of a toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a magnetic carrier. A developing device 14, which is an M, C, and K developing device, is provided. The developing device 14 for each color has a built-in magnet roll 142 serving as a magnetic field generating means, and a developing sleeve 14 serving as a developer transport body that holds and rotates the developer.
1 is provided.

First, yellow development by the Y developing device 14 for the first color is performed by the developing sleeve 141 which rotates while holding the Y developer. The developer is a magnetic carrier having an average particle diameter of 20 to 50 μm around which magnetite is coated with an insulating resin around a core, and a pigment and a charge control agent according to the color with a polyester as a main material, silica,
The toner is made up of a toner having an average particle diameter of 4 to 10 μm to which titanium oxide or the like is added. The developer is placed on the developing sleeve 141 by a layer thickness regulating member 143 which is a layer thickness regulating means described later and a developer receiving member 144. The developer is conveyed to the development area while being regulated to a developer layer thickness of 100 to 400 μm.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is larger than the developer layer thickness.
5 to 1.0 mm, during which the AC bias V _AC and D
C bias _VDC is applied in a superimposed manner. DC bias V
_DC and the photosensitive member charge potential V _H, for charging the toner are the same polarity, AC bias toner given the opportunity to leave from the magnetic carrier by V _AC, during positive charging DC
Not adhere to a portion of the bias V _DC from a high potential photoconductor charge potential V _H, attached to a lower exposed portion potential V _L portion of potential than the DC bias V _DC, the photosensitive drum 10 above by non-contact reversal development Is developed (developed), and a Y toner image is formed on the photosensitive drum 10.

After the visualization of the first color is completed, the magenta image forming process of the second color is started, and the scorotron charger 1 is again turned on.
1 is performed, and a latent image based on image data of the second color is formed by the exposure optical system 13. At this time 1
The charge elimination by the PCL 12 performed in the color image forming process is not performed because the Y toner image attached to the image portion of the first color scatters due to a sharp drop in the surrounding potential.

[0019] Again among the photoreceptor drum 10 peripheral surface of the entire surface is charged to the photosensitive drum charge potential V _H across the photosensitive member, get the same latent image and a color for the portion having no first color image Then, an M toner image is formed by development in the M developing unit 14, but in a portion where the first color image is developed again, the light shielding by the toner attached to the first color and the toner itself are performed. the influence of the charge with a latent image of a slightly higher potential V _M than the first color of the exposed portion potential V _L is formed, D
Development according to the potential difference between C bias V _DC and the potential V _M is performed.

For the third color cyan and the fourth color black, the same image forming process as that for the second color magenta is performed, and the Y, M, C and K toner images are formed on the peripheral surface of the photosensitive drum 10. A color superimposed color toner image is formed.

A toner supply device for controlling and replenishing each of the Y, M, C, and K developing units 14 with a new color toner includes a detachable Y, M, C, and K toner cartridge 15,
A toner storage unit 16 for Y, M, C, and K, and a toner conveying unit 161 for Y, M, C, and K. When a decrease in toner density is detected for each color, toner storage from the toner cartridge 15 is performed. Means 16, toner conveying means 16
After 1, unused toner is supplied and supplied into the developing device 14 for each color from a toner supply port (not shown) formed in the top plate 140 </ b> A.

On the other hand, the half-moon roller 2
One recording material (transfer paper, etc.) P carried out through 1
The sheet is temporarily stopped near the registration sensor position via the intermediate sheet feeding roller pairs 22A and 22B, and is fed to the transfer area by the rotation operation of the registration roller pair 23 of the sheet feeding unit when the transfer timing is adjusted.

In the transfer area, a transfer roller 17 as transfer means for applying a voltage for transferring a color toner image on the peripheral surface of the photosensitive drum 10 to the transfer material P in synchronization with the transfer timing is pressed against the transfer area. The color toner image on the peripheral surface of the photosensitive drum 10 is transferred onto the transfer paper P at a time while sandwiching the fed transfer material P.

Next, the transfer paper P is neutralized by the sawtooth electrode 18 as a separating means, separated from the peripheral surface of the photosensitive drum 10, and conveyed to a fixing device 24 as a fixing means. Then, the color toner image on the transfer paper P is fixed by the fixing device 24. That is, the fixing device 24 includes a heating roller (upper roller) 241 and a pressing roller (lower roller) 2.
And transfer paper P to these heating rollers 2
41 and the pressing roller 242, the heating by the heating roller 241 and the pressing roller 242,
The toner is welded by pressing.

The transfer paper P on which the color toner image is fixed is
The sheet is discharged onto a sheet discharge tray 26 outside the apparatus via a pair of sheet discharge rollers 25A, 25B, and 25C. The transfer roller 17
After the transfer paper P has passed, it is retracted from the peripheral surface of the photosensitive drum 10 to prepare for the formation of the next toner image.

On the other hand, the photosensitive drum 1 from which the transfer paper P is separated
In the case of No. 0, the residual toner is removed and cleaned by the pressure contact of the blade 191 of the cleaning device 19, and the charge is removed by the PCL 12 and charged by the scorotron charger 11 again to start the next image forming process. The blade 191
Moves immediately after the cleaning of the surface of the photosensitive drum, and retracts from the peripheral surface of the photosensitive drum 10. The waste toner scraped into the cleaning device 19 by the blade 191 is discharged by a screw 192 and then stored in a waste toner collecting container (not shown).

By the way, in such a color printer, demands for space saving and miniaturization are becoming severe, and various restrictions are placed on the arrangement in the color printer. For example, in order to arrange the cleaning device 19, to improve the separability of the transfer paper P, and to arrange the paper feed cassette 20 below the inside of the color printer, in the present embodiment, the transfer roller 17 and the transfer roller 17 are used. A guide member 31 for guiding the transfer of the transfer paper P from the sawtooth electrode 18 to the fixing device 24 has a downwardly convex shape.

Therefore, the transfer paper P (the transfer paper P on which the color toner image is formed) that has left the transfer area is transferred to the photosensitive drum 1
The transfer member 17 is conveyed along with the rotation of the transfer roller 17 and the transfer roller 17, and the lower surface thereof is guided (guided) by the guide member 31. The transfer paper P at this time is not straight, but is conveyed in a bent state that is convex downward. In other words, the conveyance path from the position (transfer area) where the color toner image is transferred (formed) on the transfer paper P to the fixing unit 24 is such that the transfer path is once directed downward from the transfer area and then upward. During this time, the transfer paper P is bent. Then, the transfer paper P guided by the guide member 31 enters between the heating roller 241 and the pressure roller 242 of the fixing device 24.

The heating roller 241 has a halogen lamp (not shown) as a heat source inside.
The pressure roller 242 is urged toward the heating roller 241 by an elastic member (not shown) such as a spring. And
Since the roller hardness of the heating roller 241 and the pressure roller 242 is set to a relatively close value of 3 (HV: Vickers hardness) or less, the heating roller 241
The nip formed by the pressure roller 242 is substantially planar (flat state). The hardness was measured by using a rubber hardness tester (spring type) hardness tester “Asuka C” (Polymer Instruments Co., Ltd.) with rollers 241 and 24
2 itself was set and measured.

In the case of such a bent transport path,
When an envelope is passed as a recording material between the heating roller 7A and the pressure roller 7B, a linear velocity difference occurs between the front and back of the envelope because the envelope is made of double paper, and the concave side (upper side) Wrinkles occur on the paper.

Therefore, the present inventors have developed a color printer which is restricted by such a transport route,
In a color printer in which the feeding path is forced to be deflected by the guide member 31, the inventor has studied earnestly how to prevent the envelope from being wrinkled due to the feeding path.

As a result of various studies, the present inventors have found that, even in such a feeding path, the envelope guided by the guide member 31 enters the heating roller 241 and the pressure roller 242. The wrinkles generated in the envelope are suppressed depending on the approach angle (see FIG. 2) between the direction (see FIG. 2) and the direction from the center of the pressure roller 242 to the center of the heating roller 241 (a direction in FIG. 2). I realized that I can do it.

The experiment and the results will be described. 1 and 2 in which the approach angle is variously changed by changing the arrangement of the heating roller 241 and the pressure roller 242.
(A guide member 3)
1 was provided in a convex shape below). The envelope (transfer paper) used is CLCRAVONBRILLI
ANT COM-10 24lb and GilbertPa
per COM-1024 lb.

Table 1 shows the results of the experiment. Table 1
The wrinkle occurrence rate in the table is represented by (wrinkle occurrence number) / (total number of paper passing envelopes). In addition, wrinkle level “0” indicates that no wrinkles are generated, and “1” indicates that wrinkles having a length of less than 10 mm are slightly generated but have no practical problem.
"3" indicates that wrinkles having a length of 20 mm or more are conspicuous and not practically endurable.

[0035]

[Table 1]

As can be seen from Table 1, the approach angle is 80 °.
By setting the angle to 120 ° or less, the generation of wrinkles in the envelope can be suppressed. In particular, it is preferable to set the angle to 90 ° or more and less than 110 °.

In the above description, the solution of the problem in the case of using an envelope as the recording material has been described.
(Overhead Projector Trans
It has been found that a different problem occurs when a light-transmissive recording material such as a non-transparent recording material is used. That is,
When an image is formed on an OHT, it is necessary to apply a higher amount of heat in order to improve the light transmission performance of the toner or the OHT. Therefore, the transport speed of the OHT (heating roller 24
1 and the pressure roller 242), and the surface temperature of the heating roller 241 is also increased. In particular, in the case of a color printer that forms a color image as in the present embodiment, this light transmission performance is one of the most important performances required, and the amount of heat applied needs to be increased as compared with a monochrome printer. There is.

However, the OHT provided with a high calorific value is
May deform into a wavy shape. In particular, according to the study of the present inventors, the surface temperature of the heating roller 241 was set to T (° C.),
Assuming that the transport speed of the OHT nipped and transported by the heating roller, the front 241 and the pressure roller 242 is LS (mm / sec), this phenomenon appears remarkably when T / LS ≧ 15.9. When this phenomenon occurs, the OHT that has once passed between the heating roller 241 and the pressure roller 242
However, when the deformed portion (particularly, the portion of the wavy deformed portion that is convex toward the heating roller 241) comes into contact with the heating roller 241 again, an offset occurs, and the toner in the portion is removed. Peeling causes image defects.

Therefore, the present inventors have found that even under the condition of T / LS ≧ 15.9 at which the OHT is deformed in a wavy shape, the color toner fixed on the OHT is peeled off, which causes image defects. We studied how to prevent it.

As a result of various investigations, the present inventors have found that even under such conditions, the heating roller 241 and the pressure roller 242 can be removed from the nip portion.
The discharge direction (see FIG. 2) to the regulating member that regulates the conveyance of the transfer paper P adjacent to the downstream side of the transfer paper P in the conveyance direction of the transfer roller P from the center of the pressure roller 242 and the center of the heating roller 241 It was found that depending on the discharge angle (see FIG. 2) between the direction (see FIG. 2) and the color toner image, the color toner image did not peel off and no image defects occurred. The discharge direction is defined as a nip between the heating roller 241 and the pressure roller 242 and a discharge roller pair 25A positioned adjacent to the heating roller 241 and the pressure roller on the downstream side in the transport direction. In a state where P is nipped, the direction is from the nip portion between the heating roller 241 and the pressure roller 242 toward the leading end side of the transfer paper P.

The experiment and the results will be described. An experiment was conducted using a color printer as shown in FIGS. 1 and 2 in which the discharge angle was variously changed by changing the arrangement of the discharge roller pair 25A with respect to the heating roller 241 and the pressure roller 242. The OHT used was CG37
00 (manufactured by 3M). The experiment was performed on the heating roller 2
The surface temperature T of the OHT 41 is 210 ° C., and the transport speed LS of the OHT nipped and transported by the heating roller 241 and the pressure roller 242 is 12.125 mm / sec (the transport speed L of plain paper).
S (about 1/8 of S). The determination is made at the start of the first sheet immediately after the power is turned on (a state in which the surface of the heating roller 241 has reached a predetermined temperature but the periphery of the fixing device 24 is not sufficiently warmed) and the 50th print (the fixing device 24 has not been heated). It was visually determined whether or not the color toner image on the OHT surface in a state where the periphery was sufficiently warmed was peeled off.

Table 2 shows the results of the experiment. Table 2
The occurrence rate in the medium is represented by (the number of occurrences of peeling in a part of the color toner image) / (the total number of paper passing OHTs).

[0043]

[Table 2]

As can be seen from Table 2, the discharge angle is 70 °.
By doing so, the color toner image on the OHT does not peel off, and image defects can be suppressed.
It is understood that it is preferable to set the angle to 90 ° or more. Also,
Although not shown in Table 2, when the discharge angle is larger than 135 °, a curl-like thermal deformation generated in the OHT itself causes a problem in the subsequent use of the OHT. Therefore, the discharge angle is preferably 135 ° or less.

In this embodiment, the heating roller 241
The guide member 32 for guiding the transfer sheet P provided between the pressure roller 242 and the discharge roller pair 25A includes a heating roller 241 and a pressure roller 242, and the discharge roller pair 2A.
In the state where the transfer paper P is nipped with the transfer roller 5A, the adjacent regulating member is the discharge roller pair 25A. When the guide member 32 contacts the transfer paper P while nipping the paper P and regulates the transfer of the transfer paper P, the guide member 32 becomes a regulating member.

[0046]

As described above in detail, according to the first aspect of the present invention, when the recording material feeding path from the transfer means to the fixing means is a paper feeding path which deflects the recording material. However, even if an envelope is used as a recording material, wrinkles can be prevented.

According to the second aspect of the present invention, even if the light transmitting recording material used as the recording material is deformed,
Offset can be prevented, and image defects due to toner peeling can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color printer.

FIG. 2 is an enlarged view of a fixing device and its vicinity.

FIG. 3 is a schematic sectional view of an image forming apparatus using an electrophotographic method.

[Explanation of symbols]

 24 Fixing Device (Fixing Means) 25A Discharge Roller Pair (Regulating Member) 31 Guide Member (Guide Means) 241 Heating Roller 242 Pressure Roller

Claims (4)

[Claims] An image forming means for forming a toner image on the recording material; and a recording material on which the toner image has been formed by the image forming means is passed between a heating roller and a pressure roller to record the image. Fixing means for fixing a toner image on a material, wherein the recording material is bent from a position where the toner image is formed on the recording material by the image forming means to the fixing means. And a guide means for guiding the recording material guided by the guide means, and an entry direction in which the recording material guided by the guide means enters the heating roller and the pressure roller, and a direction from the center of the pressure roller to the center of the heating roller. The image forming apparatus, wherein the heating roller, the pressure roller, and the guide unit are arranged so that an approach angle formed by the direction is 80 ° or more and 120 ° or less. Apparatus. 2. An image forming means for forming a toner image on a recording material, and a recording material on which the toner image has been formed by the image forming means is passed between a heating roller and a pressure roller to perform recording. A fixing unit for fixing a toner image on a recording material, wherein when the recording material is a light transmitting recording material, the surface temperature of the heating roller is set to T (° C.); When the transport speed of the light-transmissive recording material nipped and transported by the pressure roller is LS (mm / sec), the condition of T / LS ≧ 15.9 is satisfied, and the nip portion of the heating roller and the pressure roller is satisfied. From the discharge direction to the regulating member that regulates the conveyance of the recording material adjacent to the heating roller and the pressure roller on the downstream side in the conveyance direction of the recording material, and from the center of the pressure roller to the center of the heating roller Discharge angle between the direction, so that 70 degrees or more, the heating roller, the pressure roller, and an image forming apparatus characterized in that a regulating member. 3. The image forming apparatus according to claim 2, wherein the discharge angle is 135 degrees or less. 4. The image forming apparatus according to claim 1, wherein a nip formed by the heating roller and the pressure roller has a substantially planar shape.