JPH0375665A - Electrostatic printer - Google Patents

Abstract

PURPOSE:To allow the use of a photosensitive sheet consisting of a base paper formed as a thin layer without generating hygroscopic wrinkling by providing a heating means below a photosensitive sheet holding drum, feeding electricity to the heating means when the power source of the device is off and breaking the power feed to the heating means when the power source is on. CONSTITUTION:A heater 105 for heating the photosensitive sheet 27 wound on a scroll drum 26 is provided at the lower side of a developing device 45. The drum heater 105 is so controlled as to be turned on when the power source of the device is off and to be turned off when the power source of the device is on so that the photosensitive sheet 27 on the scroll drum 26 is warmed and dehumidified at all times even during the operation and stop of the device. The drum heater 105 is constituted by providing a heating wire 107 onto a base plate 106 made of aluminum and pressing and fixing the heating wire 107 from above the same by means of a holder 108 likewise formed of aluminum. The generation of the hygroscopic wrinkling of the photosensitive sheet is effectively prevented in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic printing device applying the principles of electrophotography.

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 electronic printing apparatus disclosed in Japanese Patent Publication No. 1554/1984 can be cited. An electrostatic printing device that applies the principles of electrophotography produces non-photosensitive insulating images by fixing a toner image formed on a photoconductive sheet (photosensitive sheet) using electrophotography. That is, a printing master is formed on a photosensitive sheet, and then the printing master is uniformly charged and then uniformly irradiated with light to discharge the photosensitive area, and then developed, thereby removing the toner powder. This is a device that forms a new toner image by depositing it only on the photosensitive fixed toner image, and transfers it onto a suitable transfer material such as transfer paper. It is repetitive.

The image quality of printed matter obtained by this electrostatic printing device is
Since both the electrophotographic characteristics up to the creation of the printing master and the electrostatic printing characteristics during printing appear, the image quality of the printed matter is much more difficult to control than the conventional copy image quality. Furthermore, when using this electrostatic printing device to immediately obtain prints from originals, if the desired image quality is not obtained, the print master created during the electrostatic printing process will be wasted, which is time-consuming and economical. It will be a big loss.

Such an electrostatic printing device houses a photosensitive sheet feeding roll and take-up roll made of zinc oxide or the like in a photosensitive sheet holding drum with a part of its periphery cut out in a membrane, and the photosensitive sheet is fed out. The structure is such that the photosensitive sheet unwound from the roll is wound around the outer circumferential 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 (for example, Japanese Patent Laid-Open No. 136471/1983). No. and Utility Model Application Publication No. 63-21977>.

With the drum structure of the electrostatic printing device configured in this way, a print master is created by the above steps on the photosensitive sheet wound around the photosensitive sheet holding drum, and printing of a predetermined number of sheets is completed using this print master. Then, a predetermined length of the photosensitive sheet is wound up by a take-up roll, and a new photosensitive sheet is wound onto the holding drum to be used for creating the next printing master.

Problems to be Solved by the Invention The photosensitive sheets used in conventional electrostatic printing devices have conductive layers on both sides of a base paper, and a Zn○ photosensitive layer is laminated on one of the conductive layers with a blocking layer interposed therebetween. The base paper used was relatively thick paper weighing 80g and 5m. However, since photosensitive sheets using such cardboard as the base paper are expensive, this has a significant impact on product development costs.

As a means to reduce the cost of photosensitive sheets, it is possible to thin the base paper to a weight of 62 g S"1% 55 g sm. By making the base paper thin in this way, it is possible to It is possible to increase the number of segments per winding (one segment is just wound on the outer circumferential surface of the photosensitive sheet holding drum), and it is possible to achieve a significant cost reduction. It has been found that when the base paper of the sheet is thinned, the photosensitive sheet absorbs moisture under high temperature and high humidity conditions, causing wrinkles and image quality defects such as white spots.

The present invention has been made in view of these points, and its purpose is to prevent the occurrence of moisture absorption wrinkles under high temperature and high humidity when using a photosensitive sheet made of thin base paper. It is an object of the present invention to provide an electrostatic printing device having the following features.

Means and operation for solving the problem As a first solution, a photosensitive sheet feeding roller and a take-up roll are housed in a photosensitive sheet holding drum with a part of its periphery cut out, and the photosensitive sheet is fed out from the feeding roll. In an electrostatic printing apparatus, a printing master is formed on the photosensitive sheet by winding a photosensitive sheet on the outer peripheral surface of the photosensitive sheet holding drum, and a heating means is provided below the photosensitive sheet holding drum. supplying power to the heating means when the power is off (with the plug in the outlet),
A control means is provided to cut off power supply to the heating means when the device is powered on.

By operating the heating means at all times when the power of the apparatus is turned off in this manner, the heating means can warm and dehumidify the photosensitive sheet wound around the photosensitive sheet holding drum, thereby preventing the occurrence of wrinkles due to moisture absorption. be able to. Furthermore, when the power of the apparatus is turned on, the entire apparatus is warmed by the heat of the fixing device, etc., so active measures to dehumidify the photosensitive sheet are not required, and the power supply to the heating means is controlled to be cut off.

The second solution is that a predetermined tension is normally applied when winding a photosensitive sheet onto a photosensitive sheet holding drum, but a means is provided to release this tension when the device is not in use. . That is, a lock means for selectively locking the rotation of the feed roll is provided on the feed roll side, and a drive means for driving the take-up roll, a torque control means for controlling the torque of this drive means, and a take-up roller are provided on the take-up roll side. A reversal prevention means is provided to prevent the roll from reversing. Further, the locking means is unlocked when the device is powered off, and the locking means is activated when the device is powered on to lock the feeding roll,
A control means is provided for driving the driving means to apply a predetermined tension to the photosensitive sheet.

In this manner, by releasing the tension of the photosensitive sheet wound on the photosensitive sheet holding drum when the apparatus is not in use, it is possible to prevent wrinkles in the photosensitive sheet due to moisture absorption.

As a third solution, instead of releasing the tension, a means is provided to uniformly apply the tension to prevent moisture absorption wrinkles. That is, in the drum structure of the conventional electrostatic printing device, the photosensitive sheet fed out from the feeding roll is guided by a pair of guide rolls provided on both sides of the notch in the circumferential direction of the drum, while being guided by the photosensitive sheet on the outer peripheral surface of the photosensitive sheet holding drum. The guide roll is wound with a predetermined tension, but by forming the guide roll in such a shape that the diameter is largest at the center in the axial direction and gradually decreases toward both ends, the occurrence of moisture absorption wrinkles is prevented.

If the diameter of the guide roll is uniform in the axial direction, play between the photosensitive sheet and the guide roll is likely to occur in the center, which increases the amount of displacement of the photosensitive sheet in the center, causing moisture absorption wrinkles in the center of the photosensitive sheet. It's easy to do. Therefore, by configuring the shape of the guide roll as described above, play between the photosensitive sheet and the guide roll can be eliminated, and the amount of displacement of the photosensitive sheet during winding can be made approximately uniform in the axial direction. This makes it possible to eliminate variations in tension when winding up the photosensitive sheet, and prevent moisture absorption wrinkles from occurring due to uneven tension.

In addition to the above-mentioned configuration, the photosensitive sheet holding drum is provided with a plurality of axial slits spaced apart in the circumferential direction that are slightly smaller than the width of the photosensitive sheet and slightly larger than the maximum image width of the photosensitive sheet. absorbs tension variations in both the process direction and the drum circumferential direction.
The tension applied to the photosensitive sheet during winding can be made more uniform.

Example Embodiments of the present invention will be described in detail below based on the drawings.

In explaining the embodiments, first, the overall structure of an electrostatic printing apparatus suitable for applying the present invention will be explained, then moisture absorption wrinkles in a photosensitive sheet will be analyzed, and finally, a solution to moisture absorption wrinkles will be explained.

(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 connected to the main body 1 by a support shaft 7, and the top cover 4 can be opened upward from the other end around 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 document 2, and is mounted on a lamp carriage 10 together with a flapper 8a, and scans the copy surface of the document 2 as the lamp carriage 10 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. ing. 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 a fourth mirror 19 is attached to the second mirror carriage 18 to collect light onto the lens 17. The reflected light from the original document 2 is guided to the photosensitive sheet 27 side via the dustproof glass 20.

On the other hand, the lamp carriage 10 on which the light source 8 is mounted, the first
Mirror carriage IL Lens carriage 15 and 2nd
The mirror carriage 18 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 '
Tsuji 11 is moved at a speed of 172.

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 slit 26a is provided in the outer circumference of the scroll drum 26 in the axial direction, and a pair of idle rolls 3 are provided at both ends of the slit 26a in the circumferential direction.
0.31 is rotatably supported. Photosensitive sheet 27
is a feeding shaft 28 housed within the scroll drum 26.
The scroll drum 26 is wound into a roll and set, and is fed out to the outside of the scroll drum 26 through the slit 26a. In addition, the scroll drum 26
A master plate 29 is provided in the slit 26H to prevent toner from entering the scroll drum 26 during rotation.

As shown in FIG. 4, this master 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 being punished. 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 master 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.
The scroll drum 26 is taken out from a narrow gap between the guide roll 30 and the master 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 placed between the guide roll 31 provided on the opposite side of the slit and the master plate 29. 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 27 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.
On the upstream side thereof, a static eliminating corotron 36 for eliminating charges on the photosensitive sheet 27 is provided. 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 electrostatic latent image for printing is mastered by uniformly exposing the master image formed on the surface of the photosensitive sheet during printing mode. In addition to being formed on the photosensitive sheet 27, it also has the function of making cleaning easier by lighting up during cleaning to uniformly expose the surface of the photosensitive sheet 27.

- 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 the function of fixing the toner image formed on the photosensitive sheet 27 in a fixed width to create a printing master on the photosensitive sheet 27, and it is detected by the photosensitive body temperature sensor 42 installed upstream of the charging corotron 35. The voltage applied from the flash fixing power source 43 to the flash fixing device 41 is controlled according to the surface temperature of the photosensitive sheet 27.

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 4'8 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 in front of the main body of the apparatus. It can be pulled out to the side. housing 4
Two mutually parallel developing rolls 50a and 50b are horizontally provided adjacent to the photosensitive sheet 27 in the opening 6a. These developing rolls 5Qa and 50b are magnetic brush developing rolls, and during development, they are rotated in the same direction as the scroll drum 26 (clockwise in the figure), and the magnetic brushes of the developer formed on the outer peripheral surface cause the outer periphery of the scroll drum 26 to be The electrostatic latent image on the photosensitive sheet 27 wrapped around the 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 are provided on the outer periphery of the stirring roll 51) 51. packets a are provided at equal intervals in the circumferential direction, and as the stirring roll 51 rotates, these packets 51a scoop up the developer at the bottom of the housing 46a and supply it to the 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 applied to 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. An auger 57 is provided below the cross mixer 54 to mix 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.

The toner supply unit 47 includes a toner housing 47 whose bottom portion is pivotally attached to the side of the developing unit 46 by a bottle (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 fixed, for example, by a wire, and rotates clockwise at a speed of, for example, about 7.3 rpm, so that the toner replenished from the toner cartridge reaches the toner supply roll 56 without causing a blocking phenomenon. Stirring.

A toner supply roll 56 provided at the lower opening of the toner housing 47a is provided with a foam material such as polyurethane resin, so that a portion of the toner enters into numerous holes provided on the surface. . The toner supply roll 56 is rotated at a speed of 4 rpm, which causes the toner supply roll 56 to rotate at a speed of about 0
．． 5 g of toner can be supplied into the housing 46a.

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
61 is provided. These paper cassettes 61 can be freely pulled out toward the front side of the main body 1 along guide rails 62, and a cassette holder is detachably mounted in a stand 63. 60a.

60b is a feed roll that sends out the paper from inside the paper cassette 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 roller 66. The registration roller 66 is timed to match the toner image formed on the photosensitive sheet 27, and the toner image is 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 separated by a peeling belt 68 which is fixed by a thin metal plate made of stainless steel or the like provided on one end side (rear side) of the scroll drum 26, and is sent to a vacuum suction conveyance device 69. It has become.

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 has a heat roll 7 with a built-in heat source.
1, and a pressure roll 72 that presses the paper to be fixed onto the heat roll 71. The sheet of paper on which the toner image has been fixed by the fixing device 70 is discharged onto a paper discharge tray 74 by a discharge roll 73 . The general structure of the electrostatic printing apparatus has been described above, and next, the driving of the photosensitive unit 25 and the winding operation of the photosensitive sheet 27 will be described.

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,
6 is a sectional view taken along the line VI-VI in FIG. 5, and FIG. 7 is a sectional view taken along the line ■-■ in FIG.

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. One end 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 of the hollow shaft 79. 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 a human-powered 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 at 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 manual gear 85.

The operation of the scroll drum drive mechanism configured as described above will be described below. External drive input is from a motor (not shown) via a sprocket 97 provided at one end of the relay shaft 96, and a manual gear 8 by a gear 98 provided at the other end.
5. When the scroll drum 26 is to be rotated steadily, the input is normally rotated. 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 rotates at the same speed in the rotational direction of the scroll drum 26, and the rotation of the sun gear 90 is transmitted from its shaft to the input shaft 93 via the dog clutch 91, and Just by rotating 93,
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 driving force is reversed to rotate the input gear 85 in the opposite direction to that in the case of scroll drum driving. 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 rotation of the sun gear 90, 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 input 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.

The winding state of the photosensitive sheet 27 is detected by the photosensitive sheet feeding 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 from this control device the feeding roll 75 is controlled. A command is given to a release means such as a solenoid (not shown) of the rotation 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 human power 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 roll 76 side via the photosensitive sheet 27, and the rotation of the planet gear 87 on the take-up roll 76 side is stopped. Therefore, a reversing force acts on the scroll drum 26 due to the rotational force of the sun gear 90 that is meshed with the planet gear 87, but this reversing force is caused by the reversal prevention-direction clutch 83 meshing 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 27 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 described above will be briefly explained.

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. In this cleaning cycle, the potential on the photosensitive sheet 27 is reduced to approximately 0 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 developing device 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 master. If left in this state, the electrical characteristics of the printing master will be poor, so the scroll drum 26
The electrical characteristics of the master are adjusted by the charging corotron 35 and the transfer corotron 67 while rotating at high speed. That is,
During flash fixing, a low potential phenomenon appears on the master, which is thought to be due to oxygen being released from the zinc oxide surface of the photosensitive sheet 27. In contrast, after fixing the master, the charging corotron 35 and the transfer corotron are rotated at high speed while the scroll drum 26 is being rotated at high speed. 67 and stop the air flow around the scroll drum to make the area around the master rich in ozone, thereby speeding up the recovery of the charging characteristics of the master.

This completes the plate making step and continues the printing step. In the printing step, the scroll drum 2
The printing master is uniformly charged with a charging corotron 35 while rotating the printer 6 at high speed, and then the entire surface of the master is exposed with a uniform exposure lamp 40 to leave charges only in the toner image area. 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, and A
The 4th edition can achieve a printing speed of 100 sheets per minute with 2 prints per revolution.

After printing is completed, the master is wound into the scroll drum 26 by the above-mentioned winding mechanism, and the unused surface of the photosensitive sheet 27 is set on the outer peripheral surface of the scroll drum 26.

The overall configuration and basic operation of the electrostatic printing device are as described above. Conventionally, the base paper of the photosensitive sheet 27 has a basis weight of 80
Relatively thick paper of g5m was used. Therefore, moisture absorption wrinkles hardly occurred on the photosensitive sheet 27 under high temperature and high humidity conditions, and good copy images and print images could be obtained. However, if the photosensitive sheet 27 is made thinner to reduce costs as described above, a problem arises in that moisture absorption wrinkles occur in the photosensitive sheet under high temperature and high humidity conditions, which causes image defects. The present invention aims to provide an electrostatic printing device with good copy quality and print quality by using a photosensitive sheet that prevents the occurrence of moisture absorption wrinkles that occur when the photosensitive sheet is made thin and reduces costs. be.

Hereinafter, the results of analyzing moisture absorption wrinkles that occur when the photosensitive sheet is thinned will be explained, and then a solution to the moisture absorption wrinkles will be explained.

(2) Analysis of moisture absorption wrinkles on photosensitive sheet The photosensitive sheet 27 is constructed as shown in FIG.

That is, conductive layers 101 are provided on both sides of a base paper 100, and Zn○ is deposited on one conductive layer 101 via a blocking layer 102.
It is constructed by laminating photosensitive layers 103. Electrostatic printing device XP- manufactured by Fuji Xerox Co., Ltd. currently on the market
The photosensitive sheet 27 used in the ``loo'' uses a relatively thick paper of 80 g and 5 m as the base paper 100, but the photosensitive sheet 27 used in the electrostatic printing device of the present invention uses 5 m as the base paper 100.
It is intended to use thin paper of 2 g and 5 m. Below, X
The photosensitive sheet used for P-100 is called the current master, and the thinner photosensitive sheet is called the cost reduction master (C/
(abbreviated as D master).

(a) Check the occurrence of moisture absorption wrinkles at the beginning and end of winding of the current master and C/D master. According to this, wrinkles are more likely to occur on the unwinding side than on the winding side and the unwinding side (feeding side). It was confirmed that there are many In addition, more wrinkles occur at the beginning and end of winding of the photosensitive sheet than at the end of winding, and when the photosensitive sheet is set inside the device and when it is left outside the device, moisture absorption wrinkles are more likely to occur inside the device. It was confirmed that there are many The degree of wrinkle progression is 28℃/85℃.
It was confirmed that the product almost stopped after about 8 hours after being left in the A zone of 10%.

(b) Confirmation of the relationship between moisture absorption wrinkles and winding tension It was confirmed that the occurrence of moisture absorption wrinkles cannot be completely prevented in the C/D master even if the winding tension is changed. However, after winding up the film by 100 degrees, releasing the tension, and leaving it in the A zone for about 10 hours, it was found that the occurrence of moisture absorption wrinkles was very slight and did not adversely affect the image quality.

(C) Measurement of the amount of displacement of the guide roll during winding It was found that the amount of displacement of the guide roll on the winding side was larger than that of the guide roll on the unwinding side. Than this,
It was found that the tension applied to the photosensitive sheet on the unwinding side was small at the guide roll portion, and moisture absorption wrinkles were more likely to occur on the unwinding side.

Furthermore, it was confirmed that the amount of displacement near the center of the guide roll was large on both the winding side and the unwinding side, and play between the photosensitive sheet (master) and the guide roll was likely to occur. The results of this experiment revealed that in the current idle rolls, which have a uniform diameter in the axial direction, the tension applied to the photosensitive sheet at the guide roll portion fluctuates greatly in the axial direction.

(d) Measurement of Master Shrinkage Rate and Elongation Rate It was found that between the current master and the C/D master, the C/D master is generally larger in terms of shrinkage rate and elongation rate. This is thought to be due to the fact that the base paper is made thinner in the C/D master.

(e) Checking whether water is absorbed from the back side (conductive layer side) of the photosensitive sheet. Using a normal scroll drum and a scroll drum with multiple axial slits in the circumferential direction of the drum, each A photosensitive sheet wound around a scroll drum was left in the A zone, and the state of moisture absorption wrinkles was compared. From this experimental result, it could not be determined whether water was mainly absorbed from the back side of the photosensitive sheet. However, it was confirmed that no wrinkles were generated at the slit portion. From this, it is thought that in the slit portion where the tension is considered to be uniform, even if water is absorbed, wrinkles do not form because there is an escape route for the wrinkles.

(3) Solution to Moisture Absorption Wrinkles First Embodiment As shown in FIG. ) 105,
By controlling the drum heater 105 so that it is turned on when the device is powered off (in this case, the plug is always inserted into an AC 100V outlet) and turned off when the device is powered on, it is possible to control the drum heater 105 while the device is operating or stopped. By always warming and dehumidifying the photosensitive sheet 27 on the scroll drum 26, the occurrence of wrinkles due to moisture absorption in the photosensitive sheet is prevented. The reason why the power supply to the drum heater 105 is turned off when the apparatus is powered on is that when the apparatus is powered on, the entire apparatus is warmed by the heat of the fixing device 70, etc., so active measures to dehumidify the photosensitive sheet are necessary. This is to prevent this from happening. Furthermore, if power is continued to be supplied to the drum heater 105 while the apparatus is in operation, the photosensitive sheet 27
It is thought that the surface becomes too hot, causing problems such as deterioration of the photosensitive sheet.

The drum heater 105 is constructed as shown in FIGS. 9 and 10. That is, the heating wire 107 is provided on a base plate 106 made of aluminum as shown in FIG. 9, and the heating wire 107 is fixed by being held down from above by a holder 108 also made of aluminum.

In FIG. 9, 109 is a lead wire, and 110
is a connector. The drum heater 105 configured in this way is fixed to the main body of the apparatus with screws in an upright position as shown in FIG.

Although the drum heater 105 is always on when the apparatus is stopped (power is off), it was confirmed that the surface temperature of the drum heater 105 remains constant at about 113°C. At this time, the surface of the scroll drum 26 will be heated to about 37°C. Furthermore, when the device is turned on and placed in a ready state, the power to the drum heater 105 is turned off, but the temperature of the surface of the drum heater 105 at this time is approximately 30°C. , scroll drum 2
It was confirmed that the temperature of the 6 surface was approximately 36°C. From this, it can be seen that by using the drum heater when the device is powered off, the surface of the scroll drum can be heated to the same extent as when the device is in operation. It has been confirmed that the use of the drum heater 105 can effectively prevent the occurrence of moisture absorption wrinkles on the photosensitive sheet without causing any adverse effects.

Second Example From the above-mentioned analysis of moisture absorption wrinkles on the photosensitive sheet, it was found that when the winding tension was released after winding up the photosensitive sheet, the occurrence of moisture absorption wrinkles became slight. Control as follows.

That is, in FIG. 6, the ratchet 86 for stopping the rotation of the feed roll 75 is released by a release means such as a solenoid (not shown) when the power of the apparatus is turned off, and the photosensitive sheet 27 wound on the scroll drum 26 is released while the apparatus is stopped. Control to release tension. Then, by turning off the release means in conjunction with turning on the power of the apparatus, the rotation stopping ratchet 86 locks the feed roll 75, and the input gear 85 is reversed in FIG. 5 by a driving means (not shown). As a result, the one-way reverse clutch 95, the inner relay shaft 92, the dog clutch 9
1. Hollow shaft 79, sun gear 90 and planet gear 87
The take-up roll 76 is rotated via the. Therefore, tension is gradually applied to the photosensitive sheet 27 by the rotation of the take-up roll 76, 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 rotation of the take-up roll 76 is stopped. 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.

As explained above, in this embodiment, the tension on the photosensitive sheet is temporarily released while the apparatus is stopped, and the tension is applied again to the photosensitive sheet on the scroll drum when the apparatus is turned on, so that moisture absorption It is possible to prevent the occurrence of wrinkles in the photosensitive sheet due to

Third Example From the analysis of moisture absorption wrinkles in the photosensitive sheet described above, it has been found that moisture absorption wrinkles can be prevented by keeping the winding tension of the photosensitive sheet uniform. Therefore, in this embodiment, the 11th
A scroll drum 126 as shown in the figure is employed. That is, while conventional guide rolls have a uniform diameter in the axial direction, the guide roll 127 of this embodiment has a shape that has a maximum diameter at the center in the axial direction and gradually decreases in diameter toward both ends. ing. By making the guide roll 127 into such a shape, the photosensitive sheet and the guide roll 1
27 play can be eliminated.

This makes it possible to eliminate variations in tension during winding up of the photosensitive sheet, and prevent the occurrence of moisture absorption wrinkles due to uneven tension.

Furthermore, the scroll drum 126 of this embodiment is provided with a plurality of slits 128 that extend in the axial direction and are spaced apart in the circumferential direction of the scroll drum. Thereby, variations in tension in the process direction and the drum circumferential direction can be absorbed by these slits 1281i, and the tension applied to the photosensitive sheet during winding can be made more uniform.

Effects of the Invention Since the electrostatic printing apparatus of the present invention is constructed as described in detail above, it has the effect that it is possible to use a photosensitive sheet made of a thin layer of base paper without causing moisture absorption wrinkles. By making the base paper thinner, it is possible to significantly reduce the cost of photosensitive sheets.

[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 Figure 5 is a cross-sectional view of the scroll drum drive mechanism and photosensitive sheet winding mechanism; Figure 6 is a cross-sectional view taken along the line ■-■ in Figure 5; Figure 7 is a cross-sectional view taken along the line ■-■ in Figure 5. 8 is a configuration diagram of a photosensitive sheet, FIG. 9 is a plan view of a drum heater, FIG. 10 is a sectional view taken along line X-X in FIG. 9, and FIG. 11 is a scroll drum according to an embodiment of the present invention. FIG. 5... Photoconductor unit, 6... Scroll drum, 7... Photosensitive sheet, 8... Feeding shaft, 2... Winding shaft, 5... Feeding roll, 6... Winding up Roll, 6... Ratchet for rotation stop, 8... Ratchet for preventing reverse rotation, 05... Drum heater, 26... Scroll drum, 27... Guide roll, 28... Slit. Figure 4

Claims (1)

[Scope of Claims] (1) A photosensitive sheet feeding roll and a take-up roll are housed in a photosensitive sheet holding drum with a part of its periphery cut out, and the photosensitive sheet fed out from the feeding roll is held therein. In an electrostatic printing device in which a printing master is formed on the photosensitive sheet by winding it around the outer peripheral surface of a drum, a heating means is provided below the photosensitive sheet holding drum, and the heating means is provided when the power of the device is turned off. 1. An electrostatic printing device comprising a control means for supplying power to the heating means and cutting off power supply to the heating means when the power of the device is turned on. (2) A photosensitive sheet feeding roll and a take-up roll are housed in a photosensitive sheet holding drum with a part of its periphery cut out, and the photosensitive sheet fed out from the feeding roll is placed on the outer peripheral surface of the photosensitive sheet holding drum. As well as winding
A lock means for selectively locking the rotation of the feed roll is provided on the feed roll side, and a drive means for driving the take-up roll, a torque control means for controlling the torque of the drive means, and a wind-up roll are provided on the take-up roll side. In an electrostatic printing device provided with a reversal prevention means for preventing a roll from reversing, the locking means is unlocked when the device is powered off, and the locking device is activated when the device is powered on. 1. An electrostatic printing apparatus comprising: a control means for locking the feed roll and driving the driving means to apply a predetermined tension to the photosensitive sheet. (3) A photosensitive sheet feeding roll and a take-up roll for the photosensitive sheet are housed in a photosensitive sheet holding drum with a part cut out around the drum, and the photosensitive sheet fed out from the feeding roll is placed on both sides of the notch in the drum circumferential direction. In an electrostatic printing device, the photosensitive sheet is wound around the outer circumferential surface of the photosensitive sheet holding drum to form a print master on the photosensitive sheet while being guided by a pair of guide rolls. Largest at the center of the direction,
An electrostatic printing device characterized in that it is formed in a shape that gradually becomes smaller toward both sides. (4) A plurality of slits in the axial direction, which are slightly smaller than the width of the photosensitive sheet and slightly larger than the maximum image width of the photosensitive sheet, are provided in the photosensitive sheet holding drum at intervals in the circumferential direction. 4. The electrostatic printing device according to 4.