JPH0398946A - Electrophotography device - Google Patents

Abstract

PURPOSE:To curtail the difference in expansion between the front side and rear side of a paper sheet, so as to compensate for face curl or back curl by making the carrying speed of a carrier roller faster than that of a fixed roller. CONSTITUTION:An image on a photosensitive matter is copied on a paper sheet, and the copied image on the sheet is sandwiched by a fixed roller 51, and after it is thus carried and thermally set, it is carried through carrier rollers 61, 62. The carrying speed of the carrier rollers 61, 62 is made faster than that of the fixed roller 51. When the edge of the recorded sheet enters between the respective carrier rollers 61, 62, the paper sheet between the carrier rollers 61, 62 and the fixed roller 51 is forcefully stretched by the carrier rollers 61, 62 of faster carrying speed, whereby face curl or back curl of the recorded paper sheet can be compensated.

Description

[Detailed Description of the Invention] Industrial Field of Application This invention is applicable to printers, copiers, facsimiles, etc. that use lasers. *Related to electrophotographic equipment that records on paper using the electrophotographic method of electrophotography, exposure, development, transfer, and fixing. Conventionally, in this type of electrophotographic apparatus, for example, as shown in FIG. 11, a toner image on a photoreceptor 3 is transferred to a sheet 2 fed from a paper cassette 1, and the transferred image on the sheet is fixed. After being heated and fixed by the rollers 4, even if the paper 2 is curled like a face curl or a back curl, the paper 2 is ejected as it is by the conveying roller 5 without correcting the curl.
It was stuck on paper output tray 6.

In addition, in a recording system that records on both sides of a sheet of paper 2 as shown in FIG. and return to the device body 7.
Paper was being fed to.

Conventionally, in the former method, the recorded paper 2 is ejected in a curled state, resulting in uneven paper on the paper ejection tray 6 as shown in FIG. 7, or as shown in FIG. However, there was a problem in that the stacking accuracy was poor due to pages falling off the paper output tray 6.

In addition, in the latter case, since the paper is re-fed while curled, the leading edge of the paper collides with various parts of the conveyance path and cannot be conveyed smoothly, resulting in black streaks on the printing surface 2a as shown in FIG. There was a problem in that poor adhesion caused transfer defects, leading to deterioration in image quality.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to correct face curl or back curl of recorded paper to improve stacking accuracy and to prevent deterioration of image quality.

In order to achieve the above object, claim 1. In this invention described in , an electrophotographic apparatus in which an image on a photoreceptor is transferred to paper, the transferred image on the paper is held and conveyed by fixing rollers, heat-fixed, and then conveyed through a discharge roller. It is characterized in that the conveying speed of the conveying roller is faster than the conveying speed of the fixing roller.

Also, claim 2. In the present invention described in , in an electrophotographic apparatus that transfers an image on a photoreceptor to a sheet of paper, heats and fixes the transferred image on the sheet while holding and conveying the image between fixing rollers, and then conveys the image through the conveying roller. A curl detection means for detecting the curl direction of the paper passing through the conveyance roller is provided near the roller, and a curl detection means is provided in the paper conveyance path between the conveyance roller and the fixing roller based on the detection signal of the curl detection means. , characterized in that a paper guide is provided for squeezing the paper in the paper transport path in a direction opposite to the direction in which the paper curls.

Fuki 211 history and claim 1. In the invention described in , when the leading edge of the recorded paper enters between the conveyance rollers, the paper between the conveyance roller and the fixing roller is strongly pulled by the conveyance rollers having a high conveyance speed.

Also, claim 2. In the invention described in , when the paper passes the conveyance roller, the detection means detects the curl direction of the paper, and the paper guide is actuated based on the detection signal,
The paper between the conveyance roller and the fixing roller is squeezed to the opposite side to the curl direction of the paper.

One embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 shows a schematic configuration of a laser printer which is an embodiment of the present invention. Reference numeral 10 in the figure is the main body of the device,
It is placed on an optional dedicated table 11.

A drum-shaped photoreceptor 12 is provided in the center of the apparatus main body 10 and rotates clockwise in the figure. And the photoreceptor 12
A charging means 13, an optical writing means 14, a developing means 15, a transfer means 16, and a cleaning means 17 are arranged around the rotation direction in this order. Of these, the developing means 15.
The cleaning means 17 and the like are housed within the image forming case 18.

On the other hand, a first paper feed cassette 19 and a second paper feed cassette 20 are vertically and removably loaded on the right side of the apparatus main body 10 in the drawing. And those paper feed cassettes l9・
The mounting portion 20 is provided with a paper feeding means 24 having paper feeding rollers 21, 2l, a registration sensor 22, a pair of registration rollers 23, 23, and the like. On the other hand, on the opposite side of the paper feeding means 24 across the aforementioned transfer means 16, a conveying means 25, a fixing means 26, a switching means 27, an ejection conveying means 28, etc. are arranged in this order.

The paper discharge conveying means 28 includes a face-down paper discharge path 29, a face-up paper discharge path 30, and a double-sided print paper discharge path 31. The face-down sheet discharge path 29 leads to a sheet discharge stack section 33 on the apparatus main body LO through a discharge means 32 provided on the apparatus main body IO.Face-up sheet discharge path 3
0 leads to a face-up tray 34 provided on the side of the main body 1o so as to be openable and closable. Double-sided print paper output path 31
leads to the dedicated table 11.

In addition, in the apparatus main body 10, for example, a main motor 35 is disposed below the transfer means 16, and a power supply unit 36 is disposed below the conveyance means 25 and the fixing means 26. On the other hand, a control means 37 is provided in the upper part of the apparatus main body 1o.
It becomes by arranging. In this control means 37, the device main body 10
In addition to controlling the engine itself, it also controls interaction with the host machine.

By the way, the dedicated table 1 is provided with a paper reversing means 38 in communication with the above-mentioned double-sided print wandering paper path 31, and a reversing means 38 connected from the paper reversing means 38 to the paper feeding means 24 of the apparatus main body 10 described above. A paper feeding means 39 is provided. Further, a large-volume paper feed cassette 40 is removably loaded on the right side of the dedicated table 1 in the drawing. A large amount of paper feeding means 42 having a paper feeding roller 41 and the like is provided at the mounting portion of the large amount of paper feeding cassette 40.

However, when operating the laser printer now,
The paper feed roller 2-r7 or the paper feed roller 41 is appropriately selected and driven to sequentially feed out the paper 45 from the cassettes 19 and 40. Then, the registration sensor 22 detects the leading edge of the paper 45, and the sheet 45 stops when it hits the registration rollers 23, thereby preventing the occurrence of skew.

On the other hand, the surface of the photoreceptor 12 is sequentially charged by the charging means 13 while rotating clockwise in the figure, and the surface of the photoreceptor 12 is charged by the next optical writing means l.
In step 4, a laser beam is irradiated to form an electrostatic latent image on the surface, and then as it passes through a developing means 5, the electrostatic latent image is sequentially turned into a visible image. Then, the above-mentioned registration rollers 23, 23 are driven by aligning the image with the resist, and the above-mentioned paper 45, which was in contact with the registration rollers 23, 23, is sent out toward the photoreceptor l2. The image on the photoreceptor 12 is then transferred onto the paper 45 by the transfer means 6.
After the transfer, the surface of the photoreceptor 12 is cleaned by a cleaning means 17.

On the other hand, the paper 45 is transferred to the fixing means 26 by the conveying means 25.
The image transferred thereto is fixed by the fixing means 26 thereof. When a large amount of paper 45 is to be discharged, or when it is desired to stack the paper 45 in page order, the sheet is passed through the face-down paper discharge path 29 of the paper discharge conveyance means 28 to the conveyance rollers 46 and 4.
6, the paper is conveyed via the discharge means 32 to the discharge stack section 33.
send it off to When the paper 45 is thick paper such as a postcard, the switching means 27 switches the ejection direction, and the sheet is sent out through the face-up paper ejection path 30 of the wandering paper transport means 28 at the ejection port 47, as shown by the chain line. It is stacked face-up on the face-up tray 34 which is opened as it is. Furthermore, if you want to record on the back side, the switching means 27 similarly switches the ejection direction, the paper is transported by the transport rollers 48 through the double-sided printing wandering paper path 31 of the wandering paper transporting means 28, and the paper is transferred to the paper reversing means of the dedicated table 1l. Leads to 38. Then, it is turned over and the paper re-feeding means 3
9 and is again conveyed to the paper feeding means 24 of the apparatus main body 10, and again abutted against the registration rollers 23 and stopped. Then, it is recorded on the back side as well and is discharged onto the discharge stack section 33 or the face-up tray 34.

Now, M-term l. In the present invention described in , the above-described laser printer is specifically constructed as shown in FIGS. 1 and 2.

That is, in the fixing means 26, a fixing roller 50 that has a built-in heater (not shown) to heat the fixing roller 50 and a pressure roller 51 that presses against the fixing roller 50 are arranged in an upper and lower pair. The fixing roller 50 and the pressure roller 51 are connected to respective roller shafts 53 and 53 on opposing side plates 54 and 5 of the apparatus main body 10.
It is rotatably supported by bearings 55 and 55 of No. 4, respectively. The fixing roller 51 has one end 53a of its roller shaft 53.
protrudes outward from one side plate 54. One end portion 53a is integrally provided with an inner belt gear 56 and an outer belt gear 57 in order toward the end.

The outer belt gear 57 has an outer diameter smaller than that of the inner belt gear 56, and a belt 58 is passed around a main motor (not shown). Another belt 59 is attached to the inner belt gear 56.
Spread it around.

On the other hand, in the discharged paper conveying means 28, a pair of upper and lower conveying rollers 6l and 62 are arranged near the entrance of the wandering paper path. The conveying rollers 6l and 62 are arranged parallel to the fixing roller 5 and the pressure roller 52, with respective conveying roller shafts 63 and 64 rotatably supported by bearings 65 and 65 of the side plates 54 and 54, respectively. .

The outer diameter of the conveying rollers 61 and 62 is the same as that of the fixing roller 5.
The outer diameter is approximately the same as that of 1. The conveyance rollers 61 and 62
One end 63a of the conveyance roller shaft 63 of the upper conveyance roller 6l projects from the side plate 54 to the same side as the outer belt gear 57 and the like.

A driven disk 66, a felt 67, a drive disk 68, etc. are provided at one end 63a in this order toward the end. The driven disk 66 is
A cylindrical portion 66a is fitted into the one end portion 63a, and a pin 69 is passed through and fixed in the radial direction. The felt 67 has an annular shape, and its center is inserted into the one end 63a,
The circumference is held between the driven disk 66 and the drive disk 68. The drive disk 68 is provided with a belt gear 68b on the outer periphery of the cylindrical portion 68a, the number of teeth of which is smaller than the number of teeth of the inner belt gear 56. Furthermore, a slit 68c is provided in the inner circumference of the cylindrical portion 68a of the drive disk 68 in the axial direction.

Then, the cylindrical portion 68a is inserted into the one end portion 63a, and the guide pin 70 is protruded into the slit 68c to allow the drive disk 68 to move in the thrust direction with respect to the one end portion 63a, while preventing movement in the radial direction. regulate. The guide pin 70 passes through the one end portion 63a in the radial direction. Further, one end of the compression spring 7 is pressed against the drive disk 68, and the felt 67 is pressed against the drive disk 68.
and urges toward the driven disk 66 side. The other end of the compression spring 71 is pressed against a fixed part 72 such as a nut. The fixing component 72 is detachably attached to one end portion 63a. Then, the drive disk 68 wraps around the belt gear 68b and the pelt 59 that is wrapped around the inner belt gear 56 of the fixing roller 51. Note that the reference numeral 73 in the figure is a paper guide.

When the main motor (not shown) is driven, the fixing roller 51 is rotated via the belt 58, and the pressure roller 5
2 go around. At the same time, the upper conveyance roller 61 is rotated in the same direction as the fixing roller 5 via another belt 59, and the lower conveyance roller 62 rotates along with it. At this time, as described above, since the number of teeth of the inner belt gear 56 of the fixing roller 51 is greater than that of the belt gear 68b of the drive disk 68, and the outer diameters of the fixing roller 5l and the conveying roller 6l are almost the same, The conveyance speed of the conveyance roller 61 becomes higher than the conveyance speed of the fixing roller 5.

Therefore, the recorded paper 45 fixed by the fixing means 26
When the tip of the paper 45 enters between the transport rollers 6 and 62 as shown in Figure 2, the paper 45 is strongly pulled by the transport rollers 61 and 62, eliminating the difference in elongation between the front and back sides of the paper, resulting in face curl or pack. Correct curls.

Next, claim 2. The invention described in 1. specifically has a structure as shown in FIG. That is, the fixing means 26
A paper guide 79 is disposed in the paper transport path between the pair of upper and lower fixing rollers 75 and pressure rollers 76 of the paper transport means 28 and the pair of upper and lower transport rollers 77 and 78 of the paper discharge transport means 28. The paper guide 79 has a flat box shape with a hollow interior, and has a paper inlet 79a on the side of the conveyance roller 75 and pressure roller 76, and a paper outlet 79b on the side of the conveyance rollers 77 and 78.

Then, on the paper entrance 79a side, the paper guide 79
is rotatably supported on a bracket 81 by a shaft 80. Further, a cam shaft 8 of a cam 82 is provided below the paper guide 79.
3 is extended perpendicularly to the paper conveyance direction, and its both ends are rotatably supported by the brackets 8. Note that the camshaft 83 is connected to a drive mechanism (not shown). A tension spring 84 is provided on the paper outlet 79b side of the paper guide 79.
The tension spring 84 urges the paper guide 79 to press it against the cam 82.

The other end of the tension spring 84 is hooked to the bracket 81. On the opposite side of the paper guide 79 across the transport rollers 77 and 78, paper curl detection means 85 and 86 are disposed vertically across the paper transport path. These curl detection means 85 and 86 are composed of fillers 87 and 88 and optical sensors 89 and 90. Each of the fillers 87
- 88 is rotatably supported approximately in the middle of its length by a shaft 9l, and maintains equilibrium in a vertical state in its natural state.

One end 87a, 88a of each filler 87, 88
are opposed to each other across the paper conveyance path. On the other hand, filler 8
The other ends 87b and 88b of 7 and 88 are connected to the respective optical sensors 89.
・It enters between the light emitting part and the light receiving part of 90 and blocks the light. Each of the optical sensors 89 and 90 is connected to a control section (not shown), and the control section and the drive mechanism of the cam 82 are connected.

After the transferred image on the paper 45 is fixed by the fixing means 26, the paper is passed through a paper guide 79 and transport rollers 77 and 78. At this time, as shown in FIG.
If the paper a is not curled, it moves straight along the paper conveyance path without touching the fillers 87 and 88. However, when the paper 45 is face curled, the leading edge 45a of the paper touches and pushes one end 87a of the upper filler 87, as shown in the drawing. Then, the filler 87 rotates in the direction of arrow A about the shaft 9l, and the other end 87b of the filler 87 retreats from between the light emitting section and the light receiving section of the optical sensor 89. As a result, the optical sensor 89 is brought into a bright (transmissive) state and the face curl of the paper 45 is detected.

Then, a detection signal is sent to the control section (not shown), and the cam 82 is rotated in the direction of arrow B about the shaft 83 via the drive mechanism (not shown) connected to the control section. Then, the paper guide 79 rotates in the direction of arrow C using the shaft 8o as a fulcrum against the tension spring 84, and the paper guide 79 rotates in the direction of arrow C against the tension spring 84.
Pull up the paper 45 on the side and squeeze the paper 45 in the opposite direction to the curl direction. As a result, the difference in elongation between the front and back sides of the paper 45 is eliminated, and the face curl is corrected.

Note that claim 2. In the embodiment of the present invention described in , the case where the paper is face-curled has been explained. For example, when the paper is back-curled as in a top conveyance bottom writing type printer, as shown in FIG. paper 4
5 comes into contact with one end 88a of the filler 88 on the lower side. In that case, the cam 82 moves eight times in the direction of arrow D, and the tension spring 84 pulls down the paper guide 79 in the direction of arrow E. Then, push down the paper 45 on the paper outlet 79 side,
Straighten the curl by squeezing the paper in the opposite direction to the curl.

From the above, it follows that claim l. According to the invention described in , since the paper is held between the fixing section and strongly pulled by the transport rollers having a high transport speed, the difference in elongation between the front and back sides of the paper can be reduced and face curl or back curl can be corrected.

Also, claim 2. According to the present invention described in , since the paper guide squeezes the paper in the opposite direction to the curl direction, the difference in elongation between the front and back sides of the paper can be reduced, and face curl or back curl can be corrected.

Therefore, it is possible to improve stacking accuracy and prevent deterioration in image quality.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 2 is a plan view of the vicinity of a fixing roller and a conveyance roller of a laser printer according to an embodiment of the present invention described in 1. FIG. 2 is a side view thereof. Figure 3 is claim 2
．． FIG. 4 is an explanatory diagram of correcting the face curl of the paper, and FIG. 5 is a side view of the vicinity of the fixing roller and conveyance roller of a laser printer according to an embodiment of the present invention described in FIG. FIG. 6th
The figure is in claim l. and claim 2. 1 is an overall schematic configuration diagram of the internal mechanism of a laser printer which is an embodiment of the present invention described in FIG. Figures 7 to 11 show examples of conventional electrophotographic devices, Figures 7 and 8 are explanatory diagrams when the stacking accuracy of the paper becomes poor, and Figure 9 shows the image quality of the paper. Explanatory diagram of the case of decrease, Fig. 10, 1st
FIG. 1 is an explanatory diagram illustrating a paper conveyance path in a conventional apparatus. 10... Apparatus main body 12... Photoreceptor 26... Fixing means 28... Paper discharge conveying means 5... Paper 1... Fixing roller 2... Pressure roller, 62... Conveyance roller 9・・・・・・
... Paper guide 5, 86 ... Curl detection means Patent applicant Patent attorney Nakao Co., Ltd. Figure 3 Figure 4 Figure 2 Figure 7 Figure 8 Figure 6 Figure 33 Figure 9 Figure 10 Figure 8 Figure

Claims (1)

[Scope of Claims] 1. An electrophotographic apparatus in which an image on a photoreceptor is transferred to a sheet of paper, the transferred image on the sheet is held and conveyed by fixing rollers, heat-fixed, and then conveyed through the conveying roller. An electrophotographic apparatus, wherein the conveyance speed of the conveyance roller is faster than the conveyance speed of the fixing roller. 2. In an electrophotographic apparatus that transfers an image on a photoreceptor to a sheet of paper, heats and fixes the transferred image on the sheet while holding and transporting the image between fixing rollers, and then transports the image through the transport roller, near the transport roller, Curl detection means for detecting the curl direction of the paper passing through the conveyance roller is provided, and the paper conveyance path between the conveyance roller and the fixing roller is detected based on the detection signal of the curl detection means. An electrophotographic device comprising a paper guide for squeezing the paper in a direction opposite to the curl direction of the paper.