JPS631670A - Sheet curl correcting device - Google Patents

Abstract

PURPOSE:To make it possible to correct a curl entirely over sheet, in a copying machine, by arranging a pair of correcting rollers for correcting a curl of a sheet so that the straight line connecting between the center lines of rotary shafts thereof is inclined with respect to the sheet guide direction. CONSTITUTION:A sheet is subjected, by a fixing roller 21, to such a trend that it is curled toward a heat roller 210, and is guided to correcting rollers 230 by means of guide plates 231, 232. These curl correcting rollers 230 are composed of a drive roller 230a and a driven roller 230b making press-contact with the former, and the straight line (a) connecting between the centers of the rotary shafts of both rollers 230a, 230b is inclined at an angle which is greater than 90 deg., such as, for example, 120 deg. with respect to the straight line (b) passing through the press-contact point between the rollers 230a, 230b so that a curl may be effectively removed from a sheet entirely thereover. Accordingly, the sheet is conveyed to a sheet treating device after the curl of the sheet is completely corrected. Thus, it is possible to correct a curl, not only at the leading or trailing end of a sheet but also entirely over the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a paper curl correction device for correcting curls when the paper is conveyed between rollers.

<Prior Art> According to an image forming apparatus such as an electrophotographic copying machine, an image formed on a recording medium is transferred to a sheet of paper, and the image is fixed by passing the sheet through a fixed M section and then ejected from the main body of the apparatus. are doing. In this case, the paper is transferred from the paper feed section through a feed roller, a conveyance roller, etc. The paper is transported to a transfer position facing the medium, and from this transfer position, it is guided throughout the transport path, passing through the entire fixing section, passing through a paper ejection roller, and being ejected.

As mentioned above, paper tends to get wrapped around the conveyance rollers and the like and curl while being conveyed.

For example, in an automatic duplex copying machine, in order to copy the entire back side of a sheet that has been copied on one side, the paper that has been copied on one side is stocked in the -H duplex copying unit, and then the paper is fed again from the unit for back side copying. There is something. In this case, the paper that has been copied on one side tends to curl due to the heat and pressure applied when it passes through the fixing section, especially the fixing roller. However, due to the influence of this curl, the paper may warp or become cylindrical, resulting in uneven paper when stocking. Please be aware that this may cause problems such as not being able to feed paper correctly for backside copying.

In order to solve the above-mentioned problem, all stages of curl correction devices are installed in the paper conveyance path. For example, this correcting device is disclosed in Japanese Utility Model Application Publication No. 61-49362 titled ``Paper Fixing Curl Correction Mechanism in Copying Machine''. This mechanism is shown in Figure 6 (
This is an example. As shown in the figure, the curl correction mechanism is used to straighten the paper that passes through the fixing roller and guides it to the two pairs of transport rollers.
The guide J has a guide f and a guide 2 provided opposite to the guide l. The conveying roller 3 and the tension roller 5 are conveying means after fixing, and the conveying roller 5 and the tension roller 6 are conveying means for conveying the toner to the intermediate tray. The peripheral speed of the transport roller 5 is set to be faster than the peripheral speed of the transport roller 3.

In the configuration as described above, when the sheet passes through the fixing roller and is used for double-sided or composite copying, for example, the sheet is guided between the conveyance roller 3 and the tension roller 4 by the guide 1.21. The leading edge of the paper that has completely passed through the transport roller 3 is guided between the paper guides 1 and 2, and is sent between the transport roller 3 and the tension roller 6. The paper held between the two pairs of transport rollers is conveyed in a stretched state because the peripheral speed of the transport roller 5 is faster than that of the transport roller 3.

As a result, the lower tip of the edge body 1a of the guide I, which is set above the paper nipping points, contacts and presses the back surface of the paper which is under tension. By pressing the tip of this edge body la against the back side of the paper and conveying the paper in that state,
It exerts an effect on the paper that causes it to curl in the opposite direction to the fixing curl. Therefore, when the paper passes the edge body 1a, the curl of the paper is stretched out and disappears.

However, with the curl correction device having the structure shown in FIG. 1, there is a distance between the edge body +a of the guide 1 and the conveyance roller 51. It becomes impossible to correct the curl at the leading edge of the paper.

Purpose of the Invention The present invention is to provide an apparatus for correcting curls of paper throughout the paper transport path, and capable of correcting the entire roll of paper.

In particular, it is an object of the present invention to make it possible to completely correct curls on the entire sheet including the leading edge of the sheet.

<Embodiment> FIG. 1 is a sectional view showing an example of a paper curl correction device according to the present invention, and FIG. 2 is a schematic diagram of a copying machine to which the device shown in FIG. 1 is applied.

FIG. 2 (In this case, the photoconductor !0 is formed on the drum face down and rotated in the direction of the arrow.The photoconductor IO is charged to a specific polarity with the corona discharger IN, and the optical system +2i trowel is placed on the document table. By projecting reflected light from the original, an electrostatic latent image corresponding to the original is formed on its surface.The electrostatic latent image formed on the photoreceptor 10 is then transferred to the developing device 13 (visible The toner image is converted into a toner image and moved to a transfer position where the transfer paper is transported appropriately.A corona discharger 14 is placed at the transfer position to electrostatically transfer the toner image onto the paper. After this transfer, the paper is electrostatically separated from the photoreceptor 10 by an AC corona discharger installed in parallel with the transfer corona discharger 14.

After the toner image is transferred, the photoreceptor 10 moves away from this transfer position and moves to a cleaning position. The toner image is not entirely transferred onto the paper at the transfer position, but a negative portion remains. This residual toner? A cleaning device 15 is provided at a cleaning position to remove the particles from the surface of the photoreceptor 10.

The cleaning device 15 scrapes off residual toner by bringing one elastic rubber blade into pressure contact with the surface of the photoreceptor 10, for example. After this cleaning, the photosensitive member 10 is ready for the next image formation.

On the other hand, the paper conveyed to the transfer position is transported to the paper feed section 16.
The sheets are then fed one by one via a feed roller 17, a conveyance roller 18, and a synchronous roller 19.

The synchronous roller 19 temporarily stops (standby) the paper fed from the paper feed section 16 and controls the paper conveyance in conjunction with the photoreceptor 100 rotations l. This makes it possible to match the leading edge of the paper and the leading edge of the copy formed image, or to transfer the copied image to the center of the paper.

After the toner image is transferred, the sheet of paper sent to the transfer position is electrostatically peeled off from the photoreceptor 10 by the action of an AC corona discharger, and is conveyed on a conveyor belt 20 and sent to a fixing roller 21 . The conveyor belt '20 is stretched between rollers at both ends, and the back surface of the sheet is attracted to the surface of the belt by the air suction action of the suction means 22, and the sheet is conveyed. Please note that the fixing roller 21 consists of a heat roller 210 whose surface is coated with Teflon, and a heat roller 210 whose surface is coated with Teflon.
The roller A is made up of a pressure roller 211 whose surface is coated with silicone rubber or the like.

When the paper passes through the fixing roller 21, the toner image is heated and fixed onto the paper. At this time, since the paper is heated by the fixing roller 21, the paper tends to curl particularly toward the heat roller 210 side.

In order to correct this curl, a curl correction device 2.3 is provided after the fixing roller 21.

The paper passing through the curl correction device 23 has its curl corrected, and is delivered to the paper processing device 24. The paper processing device 24 transfers the unloaded paper to each bin of the sorter (
A transport section 2 is used to guide the transport to the intermediate tray 27 inside the copying machine main body when sending to the shelf) 25 and when performing compositing or double-sided copying.
It has a gate 28 that switches between sending the data to 6 and 6.

When sending paper to each bin 25, this gate 28 is located at the position shown in FIG. 26. The conveying section 26 has a gate 29 for switching between duplex copying and composite copying, and a reversing conveyance section 30 for double-sided copying.For composite copying, the paper is transferred to the intermediate tray at the gate 29. Conveyance path 31 conveying to 27
You will be guided to.

Further, in the case of single-sided copying, the paper is guided to the conveyance path 31 via the reversing conveyance section 30 at the gate 29, and then to the intermediate tray 2.
Sent to 7. In this case, the composite copy is stocked on the intermediate tray 27 so that the copied image on the paper is on the lower side and, in the case of single-sided copying, the copied image on the paper is on the upper side. The paper stocked in this intermediate tray 27 is conveyed to the synchronous roller 19 described above via each conveyance roller,
Duplex or composite copies will be made.

As explained above, by correcting the curl of the paper passing through the fixing roller 21 by the correction device 23, the paper is not caught in each conveyance path, and the paper is conveyed smoothly. The details of this curl correction @23 are as shown in Figure 1.
A guide plate 23+ that guides the paper sent from the fixing roller 21 to the curl correction roller 230 and the roller 230.
and 232. Curl correction roller 230
are arranged so as to be inclined with respect to the paper conveyance (guidance) direction as shown in the figure.

In particular, the curl correction roller 230 is a driving roller 230a.
and a driven roller 230 that is in pressure contact with and follows the roller 230a.
It is composed of b. A straight line a connecting the centers of the rotational axes of the rollers 230a and 230b is the guide plate 231 and 232.
The curl correction roller 230 is arranged so that the angle α of the straight line BL passing through all the contact points of the rollers 280a and 230b that guide the paper is 90° or more (an obtuse angle).

A suitable angle α is, for example, 120°.

In the above configuration, as shown in FIG. 3, the paper passes through the fixing roller 21, is guided by guide plates 231 and 232, and is led to the correction roller 230. The paper is 35
The second fixing roller tends to curl toward the heat roller 210 side. However, the paper 35 is conveyed by the correction roller 2301 in a direction opposite to the curl direction. Therefore, since the correction roller 230 acts to bend the paper in the opposite direction to the curl direction, the curl of the paper is corrected and the paper is delivered to the paper processing device 24 . In this case, since the correction roller 230 corrects the curl by conveying the paper in the opposite direction to the curl direction, the curl can be corrected not only at the leading edge but also at the trailing edge of the paper. Therefore, it is possible to effectively remove curls all over the body.

An example of the curl correction roller 230 is shown in FIG. Figure 4 (all ice, drive roller 2
30a has a convex portion slightly larger than the roller diameter at both ends, and a driven roller 230b is provided so as to press against this convex portion. In addition, in FIG. 4 [bl, the drive roller 2
A convex portion slightly larger than the roller diameter is provided at the center of the roller 30a, and a concave portion is provided in the driven roller 230b corresponding to the convex portion, forming a shape G so that the rollers 230b are pressed against each other. The curl correction roller 2301 having such a shape holds the paper and corrects the curl of the paper more effectively.

Here, if the circumferential speed of the curl correction roller 230 is faster than the paper conveyance speed of most copying machines, the curl correction of the paper (
This is more effective. In other words, when the paper is transported by the copying machine, that is, by the fixing roller 21, the speed depends on the transport speed of the fixing roller 21, regardless of the circumferential speed of the curl correction roller 230. Therefore, since the paper is conveyed under tension by the curl correction roller 230i, strong pressure is applied in the direction opposite to the curl direction of the paper, thereby increasing the curl correction effect. Then, when the trailing edge of the paper passes the fixing roller 21t, the paper is transported depending on the transport speed of the curl correction roller 230. In this case, the sheet of paper after passing through the curl correction roller 230 is bent too much and wrinkles are likely to occur. Therefore, the conveyance roller 24 of the paper processing device 24 after the curl correction roller 230
This can be prevented by setting the conveyance speed of 0 faster than the fixing roller 21 and slower than the conveyance speed of the correction roller 230.

On the other hand, FIG. 5 is a characteristic diagram showing the dirt on the peeling claw for completely peeling off the paper from the photoreceptor 10 when the uninvented curl correction device 23 is used. In order to separate the paper from the photoreceptor, an AC corona discharger is used to eliminate static electricity from the paper and electrostatically separate the paper. In this case, as an auxiliary means for peeling, a peeling claw (not shown) lightly contacts the surface of the photoreceptor 10 to assist in paper peeling.Here, if the paper can be peeled off without receiving assistance from the peeling claw, the paper is peeled off. will not be contaminated by toner images on the paper.For this purpose, a voltage that is a combination of high AC voltage and DC voltage is applied to the AC corona discharger.By increasing the total DC voltage, the electrostatic This improves the peelability and prevents the peeling claw from becoming stained with toner.If the pressure is increased, the reverse transfer of the toner image on the paper causes white spots, making it impossible to obtain a normal image.

On the other hand, white spots can be prevented by keeping the DC voltage low. However, the paper comes into close contact with the photoreceptor lO, and the peeling claw becomes more contaminated with toner.

This is because the paper adheres closely to the photoreceptor IO and is peeled off by the peeling claw. Conventionally, when performing 1 composite copying, when the paper is passed through the fixing roller 21' with its leading edge curled and then conveyed again to the transfer position, the paper is curled in the direction in which it wraps around the photoreceptor 10.

Therefore, the paper wraps around the photoreceptor 10 and is peeled off by peeling, increasing the probability that the peeling becomes dirty as shown in the figure.

This also applies to the curl correction mechanism shown in FIG. However, according to the uninvented invention, even if the curl is corrected, including the leading edge of the paper after fixing, and the paper is conveyed to the transfer position again, the dirt on the peeling claw is significantly reduced compared to conventional methods. are doing.

In addition, in the case of double-sided copying, when the paper that has not been curled is conveyed again for transfer, it curls in the opposite direction (not wrapping around the photoreceptor lO), which increases the paper's peelability and prevents stains on the peeling claw. It seems that it will disappear. However, the close contact between the paper and the photoreceptor 10 at the transfer position is poor, and the toner image transfer efficiency is extremely poor. This point has not yet been invented; according to this, the curl of the paper can be corrected.
The transfer efficiency of toner images is not reduced. Furthermore, as shown in Figure 5, the stains on the peeled nails are also significant (as in the case of composite copies).
Reduce this.

According to the uninvented paper curl correction device, the curl of the paper after fixing can be effectively corrected by transporting the paper in the direction opposite to the curl direction (including the leading edge of the paper). In this case, the curl is corrected not only at the leading edge or trailing edge of the sheet but also on the entire sheet.

[Brief explanation of the drawing]

FIG. 3 is a diagram showing the curl correcting action of paper according to the present invention, FIG. 4 (aXb) is a front view showing a curl correcting roller according to the present invention, and FIG. FIG. 6 is a characteristic diagram for comparison with a conventional example showing stains caused by paper peeling, and FIG. 6 is a sectional view showing a conventional curl correction mechanism. 21. Fixing roller 23: Curl correction device 230: Curl correction roller 231.232. Guide board 35; Paper agent Patent attorney Kiritsugu Sugiyama (and 1 other person) No. ! figure

Claims (1)

[Claims] 1. A device for correcting the curl of paper that occurs when it passes through a fixing roller, etc., including a guide means for guiding the paper after passing the fixing roller, and a guide means for correcting the curl of the paper guided by the guide means. Curling of paper, comprising a correction roller for correction, and the correction roller is arranged so as to be inclined so that the center lines of the rotational axes of the rollers form an obtuse angle with respect to the guiding direction by the guide means. Correction device. 2. The paper curl correction device according to claim 1, wherein the paper conveyance speed of the correction roller is set faster than the conveyance speed of the fixing roller.