JPH059026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a paper feed control device for an electrophotographic apparatus, and in particular to an electrophotographic apparatus suitable for preventing paper perforations from being soiled by toner images on the surface of a photosensitive drum. The present invention relates to a paper feed control device of the device.

[Background of the invention]

FIG. 5 is a configuration explanatory diagram showing an example of the principle of an electrophotographic apparatus. The outline of the principle will be explained below using FIG. Laser light generated by laser 1 enters optical modulator 2 . The laser light entering the optical modulator 2 is modulated according to dot data obtained by decomposing the character image. The modulated laser light is
The light passes through the reflecting mirror 3 and reaches the rotating polygon mirror 4, and scans the surface of the photosensitive drum 5. Since the surface of the photosensitive drum 5 is uniformly charged in advance by the charger 6, the surface of the photosensitive drum 5 is charged every time the laser beam scans.
An electrostatic latent image is formed on the surface. Photosensitive drum 5
is rotating at a constant circumferential speed, and its electrostatic latent image is carried onto the developing device 7 and developed. The developed surface of the photosensitive drum 5 is conveyed to a transfer device 8.

The paper 9 is fed by a paper feed truck 10, runs at a constant speed in front of the transfer device 8, and is pressed against the surface of the photosensitive drum 5 by a retractor 11. The toner image on the surface of the photosensitive drum 5 carried before the transfer device 8 is transferred onto a sheet of paper 9 by the transfer device 8 . After the paper 9 on which the toner image has been transferred passes through a buffer 12 , it is preheated by a preheater 13 . Thereafter, it passes between the heat roll 14 and the backup roll 15, which are heated to a high temperature, and is fixed by heat and pressure. The fixed paper 9 is transferred to a paper folding device 18 by a skirting roll 16 and a puller 17.
are sent sequentially into the

Based on the principle of the electrophotographic apparatus described above, in order to correctly transfer the toner image on the surface of the photosensitive drum 5 onto the paper 9, it is necessary that there is no speed difference between the circumferential speed of the photosensitive drum 5 and the paper feeding speed at the transfer position. It is. If there is a speed difference between the circumferential speed of the photosensitive drum 5 and the paper feeding speed, the character image transferred to the paper 9 will be blurred. As the paper feeds faster, the character image shrinks and
If the paper feed is slow, the character image will be elongated.
Therefore, a method is adopted in which the paper feed is started from a position where the paper perforations are set back from the center of the transfer position, the paper feed speed is increased to the circumferential speed of the photosensitive drum 5, and the control is performed so that the difference in speed between the two is eliminated at the transfer position. There is.

Below, the paper perforation is 0.35 from the center of the transfer position.
Paper feed starts from the position moved back by an inch, printing is performed at a paper feed speed of 35 inches/second, and at the end of printing, the paper perforation passes the paper feed start position, paper feed stops, and then the paper continues until the paper feed starts at the paper feed start position. An example of an electrophotographic apparatus having a paper feed control mechanism for retracting the paper will be described.

FIG. 6 is a configuration explanatory diagram showing the paper feeding operation from the start of paper feeding until the paper reaches a constant speed.
A is a diagram showing the relationship between the elapsed time of the paper feed operation and the paper feed speed; Paper perforation 19
starts paper feeding from point a, which is 0.35 inch backward from the center of the transfer position, and after 20 cmsec, the paper feeding speed becomes 35 inches/sec, and the paper perforation 19 is
The center of the transfer position reaches point b. The buffer 12 rises by 0.35 inches from the start of paper feeding, absorbs the difference in paper feeding speed between the paper feeding tractor 10 and the heat roll 14 during printing, and moves to prevent paper breakage.

Next, the paper feeding operation at the end of printing will be explained using FIGS. 7 to 9.

FIG. 7 is a configuration explanatory diagram showing the conventional paper retreat operation after printing is completed, where A, B, and C are the paper perforations 19 at points c, d, and e, respectively, and D is the elapsed time of the paper feed operation. FIG. 3 is a diagram showing the relationship between the paper feed speed and the paper feed speed.

Fig. 8 is a circuit diagram for performing a conventional paper retraction operation, Fig. 9 is a time chart for explaining the operation of Fig. 8, and a is a paper feed signal of Fig. 8.
PFEED-N, b is paper feed stop signal BRK-N,
C is a POS SEARCH-N signal, d is a paper retraction signal P REVERSE-P, and e is a diagram showing the relationship between the paper feed operation elapsed time and the paper feed speed.

Transfer of the toner image on the photosensitive drum 5 to the paper 9 is completed, and the paper perforation 19 is at the center of the transfer position (7th
When reaching point C in figure a), the paper feed signal PFEED
-N turns off. When the PFEED-N signal changes from a low level to a high level, the one shot 20 in Fig. 8 oscillates, and the paper feed stop signal BRK is output for 20 msec.
- Generates N. The paper 9 travels 0.35 inch beyond point C and stops at point d, as shown in FIG. 7B.
Since the heat roll 14 has stopped before the paper feed signal PFEED-N is turned off, the buffer 12 is raised 0.35 inches from the level during printing.

When the one shot 20 stops oscillating, the output of the AND gate 21 becomes high level. POS−
The SEARCH-N signal becomes low level when a paper position detector (not shown) detects that the paper perforation 19 is at the paper feed start position. output becomes high level,
A paper retraction signal P REVERSE-P is generated.

P REVERSE-When the P signal goes high,
A paper feed control circuit (not shown) moves the paper 9 backward at a low speed of 3.5 inches/second for 200 msec.
Later, the paper perforation 19 reaches a point e (see FIG. 7C) which is 0.35 inch backward from the center of the transfer position.

When a paper position detector (not shown) detects that the paper perforation 19 has returned to the paper feed start position, the POS-SEARCH-N signal becomes low level, the P REVERSE-P signal also becomes low level, and the paper 9 stops. At this time, buffer 1
2 is 0.7 inches below point d.

As explained above, the paper retreating operation is always performed at the end of printing.

Next, a problem that occurs when printing stops while a toner image remains on the surface of the photosensitive drum 5 will be explained using FIG. 7. When detecting an abnormality in the printing device such as an abnormality in the paper feeding system, detecting the end of the paper 9, and needing to replace the paper 9, etc., after all toner images on the surface of the photosensitive drum 5 have been transferred to the paper 9. If stopping printing makes the printed data unusable or hindering the continuation of the next printing, stop scanning the laser beam to the photosensitive drum 5 and create a toner image on the surface of the photosensitive drum 5. Printing is stopped with the remaining . Such a case occurs at least once when printing one box of paper due to paper replacement.

The following is an example of an electrophotographic apparatus in which the scanning position of the laser beam on the photosensitive drum 5 and the transfer position of the toner image on the surface of the photosensitive drum 5 to the paper 9 are in a positional relationship of 180 degrees on the surface of the photosensitive drum 5. I will explain about it. When the paper feed stop signal BRK-N is generated while a toner image remains on the surface of the photosensitive drum 5, the maximum amount of paper on the surface of the photosensitive drum 5 is
Print data for half a rotation (16.2 inches) has been written, and a toner image has been formed. The photosensitive drum 5 rotates at a circumferential speed of 35 inches/second, and the toner images on the surface of the photosensitive drum are sequentially transported to a transfer position.
By the time all toner images pass the transfer position
It takes 16.2 inches ÷ 35 inches/second = 463 msec. On the other hand, the paper 9 temporarily stops at a position 0.35 inches beyond the center of the transfer position (point d), and then retreats to a position 0.35 inch backward from the center of the transfer position (point e).

When printing paper with a large paper weight, for example, 135Kg paper, the paper perforation 19 will close to the photosensitive drum 5 due to the rigidity of the paper, even though the retractor 11 is completely retracted during the paper retraction operation.
At that time, since a toner image remains on the surface of the photosensitive drum, a problem arises in that the paper perforation 19 becomes stained with the toner image.
When the paper ream is large, when the paper perforation 19 is a mountain perforation, or when a large amount of toner image remains on the surface of the photosensitive drum 5, the toner image on the paper perforation 19 may become dirty. It gets so bad that the final printed page becomes unusable.

Therefore, for paper with a large paper ream, by adjusting the paper tension at the transfer position to be strong, it is possible to reduce the staining caused by the toner image at paper perforation 19. When printing on small paper, for example 55 kg paper, the tension on the paper becomes too strong and the paper 9.
This results in the problem that the hole portion of the material may peel off. In other words, the tension of the paper at the transfer position must be adjusted depending on the amount of paper to be printed, which is very inconvenient.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to prevent the perforations of paper from becoming dirty due to toner images on the surface of a photosensitive drum, and to provide an electrophotographic method capable of maintaining good print quality. An object of the present invention is to provide a paper feed control device for an apparatus.

[Summary of the invention]

In the present invention, when the laser beam is turned off and printing is stopped with a toner image remaining on the photosensitive drum surface, the toner image remaining on the photosensitive drum surface is transferred to the photosensitive drum from the laser beam scanning position to the transfer position. As the drum rotates, the toner image passes through all the transfer positions, and the toner image in the area that has passed is erased by the photosensitive drum cleaning mechanism, so even if the photosensitive drum and the paper come into contact after that, the toner image will not remain on the paper. This method was developed with an eye to the fact that paper perforations are located at a position retreating from the transfer position, and the paper feed is started from this position in order to equalize the paper feed speed and the circumferential speed of the photosensitive drum at the transfer position. At the end of printing, the paper feed control mechanism stops the paper feed after the paper perforation passes the paper feed start position, and further moves the paper back so that the paper perforation reaches the paper feed start position. If printing is to be stopped with a toner image remaining on the paper, the paper stop timing is delayed, paper feeding is stopped at a position where the paper perforation is past the transfer position, and
The present invention is characterized in that it includes means for moving the paper backward after all the toner images on the surface of the photosensitive drum have passed through the transfer position.

[Embodiments of the invention]

The present invention will be explained in detail below with reference to the embodiment shown in FIGS. 1 and 2, and FIGS. 3 and 4.

The first is a configuration explanatory diagram showing an embodiment for explaining the paper feed operation of the paper feed control device of the electrophotographic apparatus of the present invention, and A to D are diagrams showing the configuration of paper perforations 19 at points f, g, and h, respectively. , E is a diagram showing the relationship between the elapsed time of the paper feed operation and the paper feed speed. The principle structure of the electrophotographic apparatus is the same as that shown in FIG. FIG. 2 is a circuit diagram showing an embodiment of the paper feed control device of the present invention. In FIG. 2, the DATA ON-N signal is a low level signal when the toner image remains on the surface of the photosensitive drum 5, and becomes a high level signal when all toner images are transferred to the paper 9, and the 1/2INCHCLK signal is a signal that is at a low level when the toner image remains on the surface of the photosensitive drum 5. /2
This signal is generated every time inch paper is fed, and other signals PFEED-N, BRK-N, POS SEARCG-
N, POS SEARCH-N is the same as in Figure 8,
The explanation will be omitted here. Figures 3 and 4 show cases where a toner image remains on the surface of the photosensitive drum 5 in Figure 2 (DATA ON-N signal is low level) and cases where no toner image remains on the surface of the photosensitive drum 5, respectively. This is a time chart of each signal in FIG. 2 (DATA ON-N signal is high level).

First, the paper feeding operation when a toner image remains on the surface of the photosensitive drum 5 will be described with reference to FIGS. 1 to 3. When the paper perforation 19 reaches the transfer position center point f, PEEED is reached as shown in Figure 3b.
-N signal becomes high level, and 1/2INCH in a of the same figure
In response to the CLK signal, the first side outputs of the D flip-flops 23 and 24 shown in FIG. 2 become high level in sequence as shown in FIG. The output of the OR gate 26 becomes a high level, and the output of the AND gate 27 in FIG. 2 changes from a low level to a high level as shown in FIG. 3e. Note that 25 in FIG. 2 is an inverter. At point g, one shot 20 in Figure 2 is the third
The paper 9 oscillates as shown in FIG. At the same timing when the one shot 20 starts oscillating, the one shot 28 in FIG.
Oscillation begins as shown in Figure g. DATA ON−
Since the N signal is at a low level and the output of the AND gate 29 in FIG. 2 remains at a low level, after the one shot 28 stops oscillating, the output of the OR gate 30 in FIG. 2 changes as shown in FIG. 3h. The PR EVERSE-P signal becomes high as shown in FIG. 3j, and the paper 9 begins to move backward. During the oscillation time of the one shot 28 of 200 msec, the paper 9 remains stopped at point h. Since the point h is located 1.35 inches beyond the transfer position center point f, the paper perforation 19 does not come into contact with the photosensitive drum 5, and therefore the paper perforation 19 is not soiled with the toner image. After 250 msec has elapsed from point f, the paper 9 begins to move backward from point h at a low speed of 3.5 inches/second, and stops at point i, which is 1.7 inches backward from point h.

Paper perforation 19 is the transfer position (transfer position center f
±0.35 inches from point h) is 1 inch ÷ 3.5 inches/second = 290 msec from point h, f
It is 250msec + 290msec = 540msec after the point,
The time required for the photosensitive drum 5 to rotate from the laser beam scanning position to the transfer position (half a revolution of the photosensitive drum) is longer than 463 msec. Therefore, by the time the paper perforation 19 passes the transfer position, there is no longer a toner image on the surface of the photosensitive drum 5, and even if the paper perforation 19 and the photosensitive drum 5 come into contact, the paper perforation 19 has no toner image. It won't get dirty.

Note that i in Figure 3 is the POS SEARCH-N signal,
k is a diagram showing the relationship between elapsed time of paper feeding operation and paper feeding speed.

Next, the paper feeding operation when no toner image remains on the surface of the photosensitive drum 5 is shown in FIGS. 2 and 4.
This will be explained using figures. As shown in Figure 4b,
Since the DATA ON-N signal is at a high level and the output of the OR gate 26 remains at a high level as shown in Figure 4c, the PFEED
-N signal becomes high level, AND gate 27
The output of BRK- is at a high level as shown in Fig. 4d, and the one shot 20 oscillates as shown in Fig. 4e.
An N signal is generated, and the paper 9 is 0.35 from the center of the transfer position.
Stops after an inch of advance. DATA ON-N
Since the signal is at a high level, when the one shot 20 stops oscillating, the output of the AND gate 29 becomes a high level, and the output of the OR gate 30 becomes as shown in Fig. 4g.
The P REVERSE-P signal becomes high level as shown in FIG. 4i, and the paper 9 begins to move backward. In addition, f in Fig. 4 is the 0 side output of the one shot 28, h is the POS SEARCH-N signal,
j is a diagram showing the relationship between the elapsed time of the paper feeding operation and the paper feeding speed.

As explained above, when no toner image remains on the surface of the photosensitive drum 5, the same paper feeding operation as before is performed, so that printing efficiency does not decrease even if intermittent printing is performed.

As described above, according to the embodiment of the present invention, when printing is to be stopped while a toner image remains on the surface of the photosensitive drum 5, the timing of stopping the paper 9 is delayed, and the paper perforation 19 is Since it is designed to prevent staining with images, good print quality can be maintained and printing efficiency can be prevented from decreasing.

In the above embodiment, the half circumference of the photosensitive drum is 16.2 inches, and the laser beam scanning position and the transfer position on the surface of the photosensitive drum 5 are in a 180 degree positional relationship. Regardless of the positional relationship between the laser beam scanning position and the transfer position, the period from when the paper perforation 19 passes the transfer position after printing is completed until the paper perforation 19 retreats to the transfer position during paper retraction operation is The time may be set to be longer than "the time required for the photosensitive drum 5 to rotate from the laser beam scanning position to the transfer position".

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent the perforations of the paper from being contaminated by the toner image on the surface of the photosensitive drum, maintain good printing quality, and prevent the printing efficiency from decreasing. The effect is that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the paper feeding operation of a paper feeding control device of an electrophotographic apparatus according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the paper feeding control device of the present invention. 3 and 4 are time charts of each signal in FIG. 2 when a toner image is left on the surface of the photosensitive drum and when no toner image is left on the photosensitive drum surface in FIG. 2, respectively, and FIG. 5 is a time chart of each signal of the electrophotographic apparatus. Configuration explanatory diagram showing an example of the principle, No. 6
The figure is a structural explanatory diagram showing the paper feeding operation from the start of paper feeding until the paper reaches a constant speed. Figure 7 is a structural explanatory diagram showing the paper retracting operation after conventional printing is completed. Figure 8 is the conventional paper retracting operation. FIG. 9 is a time chart for explaining the operation of FIG. 8. 1... Laser, 2... Optical modulator, 4... Rotating polygon mirror, 5... Photosensitive drum, 6... Charger, 7...
...Developer, 8...Transfer device, 9...Paper, 10...
Paper feed track, 11... Retrack, 12...
...Buffer, 13...Play heater, 19...Paper perforation, 20...One shot, 21,2
2, 27, 29... Ondo Gate, 23, 24...
...D flip-flop, 25...Inverter, 2
6, 30...or gate, 28...one shot.

Claims (1)

[Claims] 1. A photosensitive drum that rotates at a constant circumferential speed, a transfer device that copies the toner image on the surface of the photosensitive drum onto paper,
In order to equalize the paper feed speed and the circumferential speed of the photosensitive drum at the transfer position, a paper perforation is located at a position retreating from the transfer position, and paper feed is started from this position, and when printing is completed, the paper perforation is the paper feed start position. In the electrophotographic apparatus, the electrophotographic apparatus includes a paper feed control mechanism that stops the paper feed after passing the paper, and further moves the paper back so that the paper perforations are at the paper feed start position. If printing is to be stopped in a state where the paper has been transferred, the paper stop timing is delayed, paper feeding is stopped at the device where the paper perforation has gone beyond the transfer position, and the toner image on the surface of the photosensitive drum is completely removed from the transfer position. A paper feed control device for an electrophotographic apparatus, characterized in that the paper feed control mechanism includes means for moving the paper backward after passing the paper.