JPH03211575A - Transfer charging device - Google Patents

Abstract

PURPOSE:To make it possible to drive a transfer corotron with a constant current without hindrance, to sufficiently restore a photosensitive sheet and to improve image quality by providing a switching and control means for switching the set value of the current supplied from a constant-current source so that it may be a nearly constant impressed voltage regardless of the size of a paper to be transferred. CONSTITUTION:The 1st set value of the constant-current source 100 is made such a current value that becomes the impressed voltage with which the photosensitive sheet is sufficiently restored, and the 2nd set value is made such a current value that becomes the specified impressed voltage in the case of processing the paper of A3 size at the time of transferring. Then, the set value is made such a current value that becomes the nearly constant impressed voltage every paper size, and the n-th set value is for a minimum size. The value is set such a current value that becomes the specified impressed voltage in the case of processing a postcard, and a switch 101 is properly switched by the switching and control means 102 in accordance with cycle information 103 and paper size information 104. Thus, the transfer corotron 67 is driven with the constant current without hindrance and the deterioration of a photosensitive means caused by flash fixing is sufficiently restored, then the image quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic printing device that applies the principles of electrophotography, and in particular, it flash-fixes a toner image electrostatically attracted to a photosensitive means, and the fixed toner image The unfixed toner adsorbed on the paper is transferred to the paper by corona discharge of a transfer corotron, and the photosensitive means deteriorated by flash fixing is restored (refreshed) by corona discharge of the transfer corotron and/or charging corotron. The present invention relates to an electrostatic printing device.

BACKGROUND OF THE INVENTION Printing by electrophotography has been known for a long time. For example, the zero printing method disclosed in US Pat. No. 2,576,047, or the electrophotographic apparatus disclosed in Japanese Patent Publication No. 1554/1984 can be cited. An electrostatic printing device that applies the principles of such electrophotography produces non-photosensitive insulating images by fixing a toner image formed on a photoconductive sheet (g-optical sheet) by electrophotography. That is, by forming a printing mask on a photosensitive sheet, then uniformly charging this printing mask with a charging corotron, uniformly irradiating light to discharge the photosensitive area, and developing the toner. This is a device that attaches powder only on a non-photosensitive fixed toner image to form a new toner image, and transfers this onto a suitable transfer material such as paper by corona discharge by a transfer corotron, and is used as a printing cycle. The steps below the mask charging step are repeated.

Such an electrostatic printing device generally houses a feed roll and a take-up roll of a photosensitive sheet made of zinc oxide or the like in a photosensitive sheet holding drum with a part of its periphery cut out. The structure is such that the photosensitive sheet unwound from the photosensitive sheet is wound around the outer peripheral surface of the photosensitive sheet holding drum, and the cutout portion of the holding drum is closed, leaving a gap for the photosensitive sheet to pass through. With this kind of drum structure,
A printing mask is created by the above steps on the photosensitive sheet wound around the photosensitive sheet holding drum, and when a predetermined number of sheets have been printed using this printing mask, a predetermined length of the photosensitive sheet is wound up by a take-up roll. Then, a new photosensitive sheet is wound onto the holding drum and used for the next printing mask production.

By the way, in the electrostatic printing apparatus as described above, toner images are fixed on the photosensitive sheet for producing a printing mask by a flash fixing device disposed opposite to the photosensitive sheet holding drum. However, since oxygen is released from the zinc oxide surface during flash fixing, the potential characteristics of the photosensitive sheet are deteriorated, the image reproduction density is low, and the background area is easily fogged. This deterioration of characteristics can be improved by re-adsorbing the released oxygen by charging the corotron after fixing the mask. Therefore, after fixing the toner image, while rotating the drum, the charged corotron installed for uniform exposure and the toner One or both of the transfer corotrons for transferring an image to a transfer paper or the like is discharged, and the air flow around the drum is stopped to make the area around the mask rich in ozone and restore the deteriorated charging property. Hereinafter, this will be referred to as a reflexo cycle.

Problems to be Solved by the Invention A transfer corotron for transferring an unfixed toner image carried on a photosensitive sheet onto a sheet of paper, etc. is generally driven at a constant voltage. If voltage drive is used, leakage may occur and white spots may appear in the image. The occurrence of leaks is particularly noticeable during multiple copies.

Therefore, in order to prevent the occurrence of leakage, it may be possible to deal with this by driving the transfer corotron with a constant current. However, depending on the presence or absence of paper or its size, the load on the drive circuit of the transfer corotron changes, causing the applied voltage to change, resulting in poor image quality such as image density varying depending on the paper size. In addition, when the transfer corotron is driven with a constant current, the current value is set to the applied voltage necessary to transfer the toner image to the paper, so the voltage drops during the refresh cycle and the photosensitive sheet is sufficiently The problem was that it could not be recovered.

The present invention has been made in consideration of these points, and its purpose is to enable the transfer corotron to be driven at a constant current without any hindrance, and to sufficiently recover the photosensitive sheet to improve the image quality. It is to be.

Means for Solving the Problems The toner image electrostatically attracted to a drum-shaped photosensitive means is flash-fixed, and the unfixed toner adsorbed onto the fixed toner image is transferred to a transfer means arranged opposite to the photosensitive means. In an electrostatic printing device that transfers images onto paper using corona discharge, a constant current source is provided that can switch the set value of the current supplied to the transfer means in a plurality of stages. A means for switching and controlling the set value of the current supplied from the constant current source is provided, and when transferring unfixed toner, the deteriorated photosensitive means is restored to the current value set according to the size of the transfer paper. When this happens, the current value is appropriately switched to the one set accordingly. The set current value of the constant current source is, for example, a current value that is measured in advance so that an approximately constant applied voltage is obtained for each size of paper that can be used in the electrostatic printing apparatus to which the present invention is applied, The constant current source is set based on these current values. In addition, a current value that provides a desired applied voltage during a refresh cycle, that is, when there is no paper, is also measured and set in the same manner.

In addition, when the transfer means and/or the charging means are driven with constant current, if the photosensitive sheet is not sufficiently recovered from deterioration due to a drop in applied voltage during the refresh cycle, etc.
The following configuration can be adopted. That is, a means for controlling the rotational speed of the photosensitive means is provided so that the photosensitive means is rotated at a lower speed when the deteriorated photosensitive means is restored than when an unfixed toner image on the photosensitive means is transferred to paper. Since the rotational speed of the photosensitive means is low, even if the voltage applied to the transfer means and/or the charging means drops, oxidation due to corona discharge can be sufficiently performed.

Function: In general constant current drive, the load resistance of the current supply circuit of the transfer means changes when the paper size differs.
The voltage applied to the transfer means changes, causing image quality deterioration. However, according to the present invention, the current value supplied to the transfer means is changed appropriately for each paper size, so that the applied voltage is almost constant even if the paper size differs, so the above-mentioned image quality deterioration is avoided. do not have. In addition, during the refresh cycle, since there is no paper on the photosensitive means, the load resistance of the circuit is low, and with general constant current drive, the applied voltage is significantly reduced, which is sufficient to prevent deterioration of the surface of the photosensitive means due to flash fixation. However, in the present invention, such a problem does not occur because current is supplied at a set current value that provides the applied voltage necessary to restore the surface of the photosensitive means.

Note that the present invention can be similarly applied to driving the charging means in an electrostatic printing apparatus in which corona discharge is performed by the charging means alone or simultaneously with the transfer means during the refresh cycle. In this case, it may be possible to perform two-step switching between a current value that provides the applied voltage necessary for uniformly charging the photosensitive means and a current value that provides the applied voltage necessary for refreshing.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In describing the embodiments, first the overall configuration of an electrostatic printing apparatus suitable for applying the present invention will be described, and then specific application examples of the present invention will be described.

(1) Overall structure of electrostatic printing device First, referring to FIGS. 1 and 2, l is the main body of the electrostatic printing device, and a platen glass 3 on which a document 2 to be copied or printed is placed is provided on the top. It is being platen glass 3
is attached to the upper surface of a top cover 4 provided to cover the upper part of the main body l, and a platen cover 6 attached to the platen glass 3 via a hinge 5 on the top cover 4 side can be opened and closed. It is set in.

One end of the top cover 4 is pivotally attached to the main body 1 by a support shaft 7, and the other end can be opened upward about the support shaft 7. On the back side of the top cover 4, there is a light source 8 that scans and exposes the original 2 placed on the platen glass 3, and an optical system 9 that guides the reflected light from the original 2 to a photosensitive sheet (sheet-like photoreceptor) 27, which will be described later. It is provided.

The light source 8 is, for example, an annular halogen lamp, which reflects the light emitted from the light source 8 toward the original 2, and is mounted on a lamp carriage 10 together with a flapper 8a, and scans the copy surface of the original 2 as the lamp carriage IO moves. It is designed to be exposed to light.

The reflected light from the original 2 is guided toward the lens carriage 15 by a first mirror 12 mounted on the lamp carriage 10 and second and third mirrors 13 and 14 mounted on the first mirror carriage 11. It has become. The lens carriage 15 is movably attached to a guide rail 16 laid below and parallel to the platen glass 3, and the lens carriage 15 is provided with a lens 17 for condensing light.

A second mirror carriage 18 is provided behind the lens 17 and guided by a guide rail 16. A fourth mirror 19 is attached to the second mirror carriage 18 and guides the reflected light from the original 2 that is focused by the lens IT to the photosensitive sheet 27 side through the dustproof glass 20. .

On the other hand, the lamp carriage 10.11 on which the light source 8 is mounted
Mirror carriage 11, lens carriage 15 and second
The mirror carriage γ is driven by the drive system 21 as follows. That is, the drive system 21 has a drive source composed of a DC servo motor (not shown), and this drive source drives each of the carriages 10.11 and 15.18 via a power transmission means 22 such as a wire. It looks like this. Lens carriage 17 and second mirror carriage 1
8 is moved only when changing the magnification, and is fixed during scanning exposure. When forming a same-size image of the original on the photosensitive sheet 27, the lamp carriage 10 is moved at the same speed as the circumferential speed of the photosensitive sheet 27, and the first mirror carriage 11 is moved at 1/2 the speed. be done.

In FIG. 1, reference numeral 25 denotes a photoreceptor unit, which has a scroll drum 26 that is rotated in forward and reverse directions by a main motor (not shown) at a speed of, for example, three steps in the forward direction shown by the arrow and one step in the reverse direction. There is. The photoreceptor unit 25 is configured to be pulled out from inside the apparatus when replacing the photosensitive sheet 27 or replenishing developer.

As shown in FIG. 3, a slot 7) 26a is provided on the outer periphery of the scroll drum 26 in the axial direction, and a pair of guide rolls 30, 31 rotate at both ends of the slot 7l-26a in the circumferential direction. Possibly supported. Photosensitive sheet 2
7 is a feeding shaft 2 housed in a scroll drum 26
8 and is set in a roll-like manner, and is fed out to the outside of the scroll drum 26 through the slit 26a. Also, scroll drum 2
The rotating scroll drum 26 is inserted into the slit 26H of No.6.
Mask plate 29 that prevents toner from entering
is provided.

As shown in FIG. 4, this mask plate 29 has an outer circumferential surface 29a having the same curvature as the scroll drum 26, and is attached so that the outer circumferential surface 29a is slightly recessed into the outer circumferential surface of the scroll drum 26. ing. Also, on the inner circumferential side, inclined surfaces 29b and 29c having different angles, respectively.
is formed. A notch 29d is provided in the outer circumferential surface 29H that is continuous with the inclined surface 29b located in the normal rotation direction of the scroll drum 26. When the mask plate 29 passes through a developing device 45, which will be described later, the developer is transferred to the scroll drum 26. In addition, one of the inclined surfaces 29b and 29c is formed at a steep angle, so that even if a part of the developer enters the scroll drum 26, it will not flow into the inclined surface 29c. By dropping the developer along the scroll drum 26, the developer can be discharged to the outside of the scroll drum 26.

One end of the rolled photosensitive sheet set on the feeding shaft 28 is inserted into the slit 26H of the scroll drum 26.
It is taken out of the scroll drum 26 through a narrow gap between the guide roll 30 and the mask plate 29 provided in the scroll drum 26 . The photosensitive sheet 27 taken out of the scroll drum 26 goes around the outer peripheral surface of the scroll drum 26 almost once, reaches the slit 26a, and is inserted between the guide roll 31 and the mask plate 29 provided on the opposite side of the gap m. It is taken into the scroll drum 26 again through the narrow gap, and is wound up on a winding shaft 32 arranged parallel to the feeding shaft 28.

Note that the winding operation of the photosensitive sheet 270 and the rotational drive of the scroll drum 26 will be described later.

On the other hand, the following parts are arranged around the scroll drum 26 along the normal rotation direction of the scroll drum 26.

Reference numeral 35 denotes a charging corotron (charger) that uniformly charges the photosensitive sheet 27 wound around the outer circumference of the scroll drum 26.
A static eliminating corotron (static eliminating device) 36 is provided on the upstream side of the photosensitive sheet 27 to eliminate charges on the photosensitive sheet 27.

Reference numeral 37 denotes an image area adjustment lamp for erasing the non-image area between the image areas on the photosensitive sheet 27 and the non-image areas on both sides of the image area, and is constructed as follows.

That is, the lamp case 37a has a slit-shaped opening on the side of the photosensitive sheet 27, and the interior of the lamp case 37a is divided into a plurality of lamp chambers, each of which accommodates a miniature light bulb-shaped tungsten lamp. , each tungsten lamp is selectively blinked according to the document size to erase the electric charge on the non-image area on the photosensitive sheet 27.

A light shielding plate 38 formed of a black Mylar sheet or the like is provided at the lower edge of the slit-shaped opening 37b of the lamp case 37a.
is attached diagonally along the surface of the photosensitive sheet 27 to prevent a part of the light from leaking to the uniform exposure/static charge removal chamber 40 side. - The exposure/static charge removal chamber 40 is installed below the image area adjustment lamp 37, and uniformly exposes the mask image formed on the surface of the photosensitive sheet in the print mode to generate an electrostatic latent image for printing. is formed on the mask, and also lights up during cleaning to protect the photosensitive sheet 27.
It also has the function of making cleaning easier by uniformly exposing the surface.

- A flash fixing device 41 is installed below the exposure/static charge removal chamber 40, and the flash fixing device 41 has an opening on the side of the photosensitive sheet 27, and a flash lamp 41b is housed in a reflector 41a. . This flash lamp 41b blinks in synchronization with the rotation of the scroll drum 26 in the print mode, and
It has a function of fixing the toner image formed on the photosensitive sheet 27 by a certain width and creating a printing mask on the photosensitive sheet 27, and it is detected by the photosensitive member temperature sensor 42 installed upstream of the charging corotron 35. According to the surface temperature of the photosensitive sheet 27, the voltage applied from the flash fixing power source 43 to the seven-flash fixing device 41 is controlled.

Further, a developing device 45 is installed below the scroll drum 26, and this developing device 45 is composed of a developing unit 46 having a housing 46a with an open top, and a toner supply section 47. Guide rails 48 are laid on both sides of the lower part of the developing unit 46, and these guide rails 48 are placed on guide rolls 49 provided on the main body 1 side, so that the entire developing unit 46 is placed on the front side of the apparatus main body. It can be pulled out. Housing 46
In the opening a, two mutually parallel developing rolls 50a and 50b are horizontally provided adjacent to the photosensitive sheet 27. These developing rolls 50a and 50b are magnetic brush developing rolls, and are rotated in the same direction (clockwise in the figure) as the scroll drum 26 during development, and the magnetic brush of the developer formed on the outer circumferential surface of the scroll drum 26 is rotated. The electrostatic latent image on the photosensitive sheet 27 wrapped around the outer peripheral surface is developed. Each developing roll 50a.

Below 50b is a stirring roll 5 that supplies the developer to the developing roll and also stirs the developer in the housing 46a.
1 is provided. A large number of buckets) 51a are provided on the outer periphery of the stirring roll 51 at equal intervals in the circumferential direction, and as the stirring roll 510 rotates, these buckets) 5
1a scoops up the developer at the bottom of the housing 46a and supplies it to developing rolls 50a and 50b.

Further, the developer supplied to the developing roll 50a by the stirring roll 51 is scraped off by a trimmer 52 installed near the developing roll 50a, and is formed on the outer peripheral surface of the developing roll 50a. The height of the magnetic brush is regulated to be constant. The developer on the developing roll 50a is transferred to a developing roll 50b provided adjacent to the developing roll 50a, and the two developing rolls 50a are formed.

The electrostatic latent image on the photosensitive sheet 27 is developed by the magnetic brush of the developer attached to the photosensitive sheet 50b. The developer that has completed the development of the electrostatic latent image on the photosensitive sheet 27 is scraped off from the outer peripheral surface of the developing roll 50b by a scraping blade 53 provided in contact with the developing roll 50b, and the scraped developer is The agent is uniformly mixed by a cross mixer 54 provided below the scraping blade 53. Below the cross mixer 54 is an auger 57 that mixes the toner supplied from the toner supply section 47 and the developer dropped by the cross mixer 54 with the developer in the housing 46a.
is provided.

The toner supply section 47 includes a toner housing 47 whose bottom portion is pivotally connected to the side of the developing unit 46 by a pin (not shown).
It has a. The upper part of the toner housing 47a is a semi-cylindrical cartridge guide 47b, and the upper toner cartridge can be inserted and removed from the end of the cartridge guide 47b. Further, an agitator 55 is provided below the cartridge guide 47b, and a toner supply roll 56 is provided at the lower opening of the toner housing 47a. The agitator 55 is formed of, for example, a wire, and rotates clockwise at a speed of, for example, about 7.3 rpm, so that the toner supplied from the toner cartridge reaches the toner supply roll 56 without causing a blocking phenomenon. Stirring.

The toner supply roll 56 provided at the lower opening of the toner housing 47a is made of a foam such as polyurethane resin, and a portion of the toner enters into numerous holes provided on the surface. There is. The toner supply roll 56 is rotated at a speed of 4 rpm, so that approximately 0.5 g of toner can be supplied into the housing 46a per second.

This developing device 45 is also used as a magnetic brush cleaning device for scraping off toner adhering to the photosensitive sheet 27 wound on the scroll drum 26.

When used as a cleaning device, the charge on the photosensitive sheet 27 is neutralized by the charge eliminating corotron 36, and the charge on the photosensitive sheet 27 is completely eliminated by lighting the charge eliminating lamp 40. As a result, the developing rolls 50a, 50
The magnetic brush on b rubs against the residual toner on the photosensitive sheet 27 and scrapes it off. In this case, the rotation of the stirring roll 51 is stopped to stop supplying the developer to the developing roll 50a.

Further, 60 indicates a paper feeding device, which has multiple stages, for example, two
It is provided with paper cassettes 61 in stages. These paper cassettes 61 can be freely pulled out toward the front side of the main body 10 along guide rails 62, and a cassette holder is detachably mounted in a stand 63. 60a.

Reference numeral 60b is a feed roll that sends out the paper from inside the paper roller 61. The paper sent out from the feed roll 60a or 60b is sent to a paper transport mechanism 64 that includes a transport roller 65 and a registration roll 66. The registration roll 66 is timed to align with the toner image formed on the photosensitive sheet 27 and sent to the transfer position. Reference numeral 67 denotes a transfer corotron (transfer device), which serves to bring the paper into close contact with the photosensitive sheet 27 and to transfer the toner image on the photosensitive sheet 27 onto the paper by performing corona discharge with a polarity opposite to that of the toner. . The paper adsorbed to the photosensitive sheet 27 is peeled off by a peeling belt 68 formed of a thin metal plate made of stainless steel or the like provided at one end (rear side) of the scroll drum 26, and the direction of conveyance of the paper is changed by a turning means 99. and is sent to a vacuum suction conveyance device 69.

The paper onto which the toner image has been transferred by the transfer corotron 67 is sent to a fixing device 70 by a vacuum suction conveyance device 69. The fixing device 70 includes a heat roll 71 with a built-in heat source.
and a pressure roll 72 that presses the paper to be fixed onto the heat roll 71. The paper on which the toner image has been fixed by the fixing device 70 is ejected to a paper ejection tray 74 by an ejection roll 73. The general structure of the electrostatic printing apparatus has been explained above, and next, the photoreceptor unit 2
5 and the winding operation of the photosensitive sheet 27 will be explained.

Referring to FIG. 5, a sectional view of the drive mechanism of the photoreceptor unit 25 and the photosensitive sheet winding mechanism is shown. Also,
Figure 6 is a sectional view taken along the line ■-■ in Figure 5, and Figure 7 is a cross-sectional view taken along the line ■ in Figure 5.
It is a sectional view taken along the line -■.

First, the drive system for the scroll drum 26 will be explained.

The feeding shaft 28 is provided with a feeding roll 75 for winding the photosensitive sheet 27 into a roll, and the winding shaft 32 is provided with a winding roll 7 for winding the photosensitive sheet 27.
6 is provided. The scroll drum 26, which rotatably accommodates the feed roll 75 and take-up roll 76 of the photosensitive sheet 27, is rotatably attached to a pair of side plates 77 provided on the main body of the apparatus. A part of a hollow shaft 79 made of a sintered oil-impregnated member that also serves as a bearing is fixed to a flange 78 provided on a part of the scroll drum 26, and a dog clutch 80 is installed in the middle part of this hollow shaft 79. are connected.

The dog clutch 80 is connected within a bearing support member 81 fixed to the outside of the side plate 77 to one end side of a hollow outer relay shaft 82 made of a sintered oil-impregnated member that also serves as a bearing. The outer relay shaft 82 is supported within the bearing support member 81 so as to be prevented from reversing by arranging a one-way clutch 83 for preventing reversal at a suitable position on its outer periphery.
The other end of the outer relay shaft 82 is connected to the inner periphery of an input gear 85 via a one-way clutch 84 for normal rotation.

The above is the drive system for the scroll drum 26, and next, the photosensitive sheet winding system will be explained.

A feed roll 75 arranged inside the scroll drum 26
A ratchet 86 for preventing rotation of the feed roll 75 is provided on one end of the shaft 28 of the scroll drum 2.
6 is rotated, the ratchet 86 is rotated by the spring 86a.
is engaged to hold the feed roll 75 so as not to rotate, and this ratchet 86 is disengaged by a release means such as a solenoid (not shown), and at this time, the feed roll 75 is allowed to rotate. There is.

In addition, a take-up roll 76 is
A planet gear 87 is attached to one end side of the shaft 32 of the roll.
A ratchet wheel 89 is provided integrally with the rotor, and a reversal prevention ratchet 88 biased by a spring 88a is engaged with the ratchet wheel 89.

Thereby, the winding shaft 32 is held so as not to rotate in the direction opposite to the winding direction of the photosensitive sheet 27. The planet gear 87 meshes with a sun gear 90 whose shaft portion is rotatably inserted into the hollow shaft 79, and the shaft end of the sun gear 90 is connected to a dog clutch 91 inside the outer relay shaft 82, and this dog clutch 91 is connected to one end side of an inner relay shaft 92 rotatably provided within the outer relay shaft 82. A human power hub 93 and a clutch 94 are provided on the outer periphery of the other end of the inner relay shaft 92, and a one-way clutch 95 for reverse rotation is arranged in series on the outside of the forward rotation direction clutch 84 in the axial direction. It is connected to the inner periphery of the input gear 85.

The operation of the scroll drum drive mechanism configured as described above will be described below. External drive power is transmitted from a motor (not shown) to the input gear 8 via a sprocket 97 provided at one end of the relay shaft 96 and by a gear 98 provided at the other end.
5. When the scroll drum 26 is rotated steadily, the human power is used to rotate it in the normal direction. In response to this,
The driving force is transmitted to the outer relay shaft 82 by the forward rotation one-way clutch 84 in the input gear 85, and further transmitted to the hollow shaft 79 via the dog clutch 80, and the driving force is transmitted to the hollow shaft 79 via the dog clutch 80.
scroll drum 26 via a flange 78 fixed to
Rotate steadily at the desired rotation speed. At this time, the one-way clutch 83 for preventing reverse rotation in the bearing support member 81 does not engage because the outer relay shaft 82 rotates in the normal direction, so that the reverse rotation prevention function does not work. At this time, since the rotation stopper ratchet 86 provided on the shaft 28 of the feed roll 75 in the scroll drum 26 is locked by the action of the spring 86a, the photosensitive sheet 27 on the take-up roll 76 side is also locked.
The planet gear 87 provided on the shaft 32 of the take-up roll 76 is prevented from rotating. Therefore, the sun gear 90 is the scroll drum 2.
6, the scroll drum 26 rotates at the same speed in the rotation direction of the scroll drum 26. This 900 rotations of the sun gear is transmitted from its shaft to the input hub 93 via the dog clutch 91, and the input hub 93 is Just rotate it.
It has no effect on the one-way reverse clutch 95.

Next, a case will be described in which the photosensitive sheet 27 wound around the outer peripheral surface of the scroll drum 26 is rolled up.

In the case of winding up the photosensitive sheet, the external drive force is reversed to rotate the input gear 85 in the opposite direction to that in the case of scroll drum drive. In response to this, the reverse direction clutch 95 provided on the inner periphery of the input gear 85 operates to transmit the driving force to the inner relay shaft 92.
The sun gear 90 is rotated via the dog clutch 91, and the planet gear 87 is rotated by the sun gear 900 rotations, and the rotation of the planet gear 87 rotates the shaft 32.
The winding roll 76 is rotated through the winding roll 76 to wind up the photosensitive sheet 27 onto the winding roll 76 .

At this time, the one-way clutch 84 for forward rotation provided in the manual gear 85 does not operate for reverse rotation, so the scroll drum 26 does not rotate, but the ratchet 86 provided on the shaft 28 of the feed roll 75 releases the solenoid, etc. Since the locked state is released by the operation of the means, the photosensitive sheet 27 can be easily rolled up.

Then, the winding state of the photosensitive sheet 270 is detected by the photosensitive sheet feed amount detection device, and when it is detected that feeding of the desired segment has been completed, the signal is sent to the control device, and the control device rotates the feeding roll 75. A command is given to a release means such as a solenoid (not shown) of the stop ratchet 86 to lock the rotation stop ratchet 86 again and stop the rotation of the feed roll 75. At this time, the rotation on the take-up roll 76 side continues;
Therefore, tension is gradually applied to the photosensitive sheet 27 as the take-up roll 76 rotates, and when the torque reaches the limit torque set in advance in the clutch 94, the external input is cut off by the clutch 94, and the take-up roll 76 stops rotating. At the same time as it is stopped, the ratchet 88 for preventing reverse rotation is activated and becomes locked.

As a result, the photosensitive sheet 27 is uniformly adhered to the outer peripheral surface of the scroll drum 26 under a constant tension, and this state is maintained thereafter.

At this time, the limit torque value of the clutch 94 is higher than the pulling load of the photosensitive sheet 27 in order to wrap the photosensitive sheet 27 evenly and sufficiently around the outer peripheral surface of the scroll drum 26, and the breaking tension of the photosensitive sheet 27 is It goes without saying that it should be set to a lower value than . Additionally, in this process, by locking the feed roll 75 with the rotation stop ratchet 86, a brake is applied to the take-up port-luer 6 side via the photosensitive sheet 27, and the rotation of the planet gear 87 on the take-up roll 76 side is stopped. In order to stop the scroll drum 26, a reversing force is applied to the scroll drum 26 by the rotational force of the sun gear 90 which has been engaged with the planet gear 87, but this reversing force causes the reverse rotation prevention-direction clutch 83 to engage with the housing of the bearing support member 81. This prevents the scroll drum 26 from rotating.

Next, the winding operation of the photosensitive sheet 270 is completed by cutting off the external drive input. The external drive input may be cut off by setting a delay time in advance and immediately after this time has elapsed.

Next, the operation of the electrostatic printing apparatus configured as above will be briefly described.

First, when the copy mode is selected and the start button is pressed, the scroll drum 26 begins to rotate at a medium speed, the photosensitive sheet 27 is uniformly charged by the charging corotron 35, and scanning exposure synchronized with the rotation of the scroll drum 26 is performed. An electrostatic latent image corresponding to the original is formed on the photosensitive sheet 27.

After this electrostatic latent image is developed by a developing device 45, it is transferred onto a sheet of paper by a transfer corotron 67, and the toner image on this sheet is fixed by a fixing device 70 to obtain a copy. After transferring the toner image to the paper by transfer corotron 67, scroll drum 26 is rotated one more revolution for a cleaning cycle. During this cleaning cycle, the potential on the photosensitive sheet 27 is reduced to approximately O volts by the static eliminating corotron 36 and the static eliminating lamp 40, and the residual toner on the photosensitive sheet 27 is cleaned by the magnetic brush of the developing device 45. . The above is the basic operation of the copy mode, and one copy can be made in two rotations. The photosensitive sheet 27 wound on the scroll drum 26 can be reused after cleaning.

Next, the print mode will be explained. The print mode consists of a plate-making step and a printing step. When automatic printing mode is selected, both modes operate continuously. When the start button is pressed, the scroll drum 26 begins to rotate at a medium speed, and the charged corotron 35 charges the photosensitive sheet 27.
is uniformly charged, an electrostatic latent image corresponding to the document is formed on the photosensitive sheet 27 by scanning exposure synchronized with the rotational speed of the scroll drum 26, and this latent image is developed by the developer [45 to form the photosensitive sheet 27. A toner image is formed thereon. Next, the scroll drum 26 is rotated at a low speed, and the photosensitive sheet 27 is
The toner image formed thereon is fixed by a flash fixing device 41 to create a printing mask. If left in this state, the electrical characteristics of the printing mask will be poor, so the scroll drum 26
While rotating the master, the electrical characteristics of the master are adjusted using the charging corotron 35U and the transfer corotron 67. That is, a low potential phenomenon of the mask appears, which is thought to be due to oxygen being released from the zinc oxide surface of the photosensitive sheet 27 during flash fixing.
On the other hand, after fixing the mask, while rotating the scroll drum 26, the charging corotron 35 and the transfer corotron 6 are
7 is discharged, and the air flow around the scroll drum is stopped to make the area around the mask rich in ozone, thereby speeding up recovery of the charging characteristics of the mask.

This completes the plate-making step, and the printing step continues. In the printing step, the scroll drum 26 is rotated at a high speed while the printing mask is uniformly charged with the charging corotron 35, and then the entire surface of the mask is exposed with the uniform exposure lamp 40 to charge only the toner image area. leave. This is developed into a toner image by a developing device 45, transferred onto paper by a transfer corotron 67, and then fixed by a fixing device 70 to obtain a print image. Since the image exposure step is omitted in the print mode, the scroll drum 26 can be rotated at high speed.
For A4 size paper, it is possible to achieve a printing speed of 100 sheets per minute with two prints per revolution. After printing is completed, the mask is rolled up into the scroll drum 26 by the above-mentioned winding mechanism, and the unused surface of the photosensitive sheet 27 is rolled up into the scroll drum 26.
is set on the outer circumferential surface of the

(2) Specific Application Examples Hereinafter, specific application examples of the present invention will be explained with reference to FIG.

Since the surface of the photosensitive sheet 27 made of zinc oxide or the like has deteriorated due to flash fixing for fixing toner images, the surface is rotated by corona discharge from a corotron before the next charging and exposure process. (I need to refresh). However, as described above, around the photoconductor unit 25, in which the photoconductor sheet 27 is wound around the scroll drum 26, there are a charging corotron 35, a flash fixing device 411, a developing unit 46, a paper transport mechanism 64, a transfer corotron 67, and a turntable. Since various devices such as means 99 are provided, it is not preferable to provide a separate corotron for refreshing from the viewpoint of device miniaturization. I am dealing with it by discharging it.

The transfer corotron 67, which is disposed facing the photoreceptor unit 25, is constructed by surrounding a single stretched corotron wire 67a made of tungsten or the like with a shield 67b. During the transfer cycle, the transfer corotron 67 transfers the toner image carried on the photosensitive sheet of the rotating photoreceptor unit 25 to the photoreceptor unit 25.
The image is transferred to the paper by corona discharge from the back side of the paper that is being fed in synchronization with the process. Further, in the refresh cycle, after the toner image carried on the photosensitive sheet to form a printing mask is fixed by a flash fixing device, corona discharge is performed so that the photosensitive sheet 27
refresh the surface.

Reference numeral 100 denotes a constant current source that supplies current to the transfer corotron, and this constant current source 100 has a first setting value to an nth setting value (n
is 2,3.4. . . , the number of paper sizes plus 1) can be driven at a constant current with a preset current value. Reference numeral 101 denotes a switch for switching the current value supplied from a constant current source, and this switch 101 is switched and controlled by a switching and controlling means 102. The switching/control means 102 receives cycle information (information on whether the processing by the transfer corotron is a toner image transfer cycle or a photosensitive sheet refresh cycle) 103;
and transfer cycle, size information of paper to be processed (A3.A4.B4゜postcard,...) 104
The switch 101 is changed according to the following. That is, the first set value of the constant current source 100 is set to a current value that provides an applied voltage that can sufficiently recover the photosensitive sheet 27, and the second set value is set to a predetermined applied voltage when processing A3 size paper during transfer. The current value is set so that the applied voltage is approximately constant for each paper size, and the nth set value is the current value that provides a predetermined applied voltage when processing a postcard of the minimum size. The switching/control means 102 appropriately switches the switch 101 according to the cycle information 103 and the paper size information 104.

The above description is for the case where the present invention is applied to the transfer corotron 67, but it can be similarly applied to the charging corotron 35. In this case, two current values that provide desired applied voltages in each of the charging cycle and the refresh cycle may be set and changed as appropriate.

Further, the driving means for rotating the photosensitive unit 25 is controlled by the speed control means 105, and the rotational speed of the refresh cycle is set to be lower than the rotational speed of the transfer cycle, so that deterioration of the photosensitive sheet 27 can be more effectively recovered. This is what you can do.

According to this embodiment, the transfer corotron 67 has one wire (67a) for running thick paper such as postcards (to downsize the transfer corotron), and if one wire is driven at a constant voltage, leaks will occur more frequently. However, since the transfer corotron 67 is driven with a constant current, leaks are less likely to occur and good image quality without unevenness can be obtained. Then, since the current value to be supplied is changed according to the paper size during refreshing and transfer, and constant current driving is performed at a current value that provides a predetermined applied voltage, the photosensitive sheet 27 can be sufficiently recovered. In addition, the applied voltage does not vary depending on the paper size, and deterioration of image quality can be prevented.

4. Effects of the Invention By applying the present invention, it is possible to drive the transfer means and/or charging means at a constant current with an approximately constant applied voltage even if the paper size differs, so leaks can be prevented and image quality can be improved. In addition, the deterioration of the photosensitive means caused by flash fixing can be sufficiently recovered, and thus the image quality can also be improved.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an electrostatic printing device suitable for applying the present invention, Fig. 2 is an external perspective view of the electrostatic printing device, Fig. 3 is a side view of the photoreceptor unit, and Fig. 4 is 5 is a sectional view of the scroll drum drive mechanism and photosensitive sheet winding mechanism; FIG. 6 is a sectional view taken along line Vl-VI in FIG. 5; and FIG. A line sectional view and FIG. 8 are diagrams for explaining a specific application example of the present invention. 25... Photosensitive unit, 27... Photosensitive unit, 35... Charging corotron, 41... Flash fixing device, 67... Transfer corotron, 100... Constant current source, 102... Switching Control means, 105... Speed control means.

Claims (1)

[Scope of Claims] 1. A toner image electrostatically attracted to a drum-shaped photosensitive means is flash-fixed, and the unfixed toner adsorbed on the fixed toner image is transferred to a device placed opposite to the photosensitive means. In an electrostatic printing device configured to transfer onto paper by means of corona discharge of a means, a constant current source capable of switching a setting value of the current supplied to the transfer means in a plurality of stages is provided, and the current supplied from the constant current source is 1. A transfer charging device characterized by being provided with a switching/control means for switching the set value of , so that the applied voltage is approximately constant regardless of the size of the transfer paper. 2. The toner image electrostatically attracted to a drum-shaped photosensitive means is flash-fixed, and the unfixed toner adsorbed on the fixed toner image is transferred by corona discharge of a transfer means arranged opposite to the photosensitive means. In an electrostatic printing device, the photosensitive means deteriorated by the flash fixing is restored by the corona discharge of the transfer means while transferring onto the paper, and the current supplied to the transfer means is set to first and second set values. A constant current source that can be switched between two stages is provided, and the current is switched to be supplied to the transfer means at the first set value when transferring unfixed toner and at the second set value when recovering the deteriorated photosensitive means. A transfer charging device characterized by being provided with a switching/control means. 3. Uniformly charging the drum-shaped photosensitive means with a charging means,
After exposure and development, the toner image electrostatically attracted to the photosensitive means is flash-fixed, and the unfixed toner adsorbed on the fixed toner image is transferred to the paper by the corona discharge of the transfer means, and the charging means In an electrostatic printing device in which the photosensitive means deteriorated by the flash fixing is recovered by corona discharge, the current supplied to the charging means can be switched to two stages, a first setting value and a second setting value. and a switching/control means for switching to supply current to the charging means at the first set value when uniformly charging the photosensitive means and at the second set value when recovering the deteriorated photosensitive means. Characteristic transfer charging device. 4. Uniformly charging the drum-shaped photosensitive means with a charging means,
After exposure and development, the toner image electrostatically attracted to the photosensitive means is flash-fixed, and the unfixed toner adsorbed on the fixed toner image is transferred to the paper by corona discharge of the transfer means, and the transfer means and In an electrostatic printing device in which the photosensitive means deteriorated by the flash fixing is recovered by corona discharge of the charging means, means is provided for controlling the rotational speed of the photosensitive means, and an unfixed toner image on the photosensitive means is fixed. An electrostatic printing device characterized in that the photosensitive means is rotated at a lower speed during recovery of the deteriorated photosensitive means than during transfer to paper.