JP2677376B2 - Copier shading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shading device for a copying machine, and more particularly to a shading device for a copier with full exposure.

(Prior Art) Conventionally, there has been widely known a so-called full-exposure type copying machine in which a photoreceptor is formed into an endless belt or an annular belt by a seam, and a flat portion is entirely exposed to form an image.

In this type of copying machine, the original area of the maximum original size is always exposed on the photosensitive surface.Therefore, when copying a smaller size, the trailing edge of the image moves and an extra exposure area is created. Therefore, the image is filled in an extra area on the rear end side of the image and exposed to increase the copy speed, thereby increasing the copy efficiency.

However, if an attempt is made to increase the copying speed in this way, as described above, the image area spacing on the photoconductor surface becomes several tens.
mm, and double exposure will occur, so
There is a problem that a good image is not formed.

Therefore, conventionally, the above-mentioned problem has been dealt with by providing a light blocking member that is movable only on the trailing edge side of the image and blocking the area on the trailing edge side of the image where the original image is not projected.

However, in many copying machines of the above type, the copying magnification can be changed by moving the imaging lens in the direction of contact with and separation from the photoconductor. In this type of copier, changing the copy magnification causes not only the trailing edge of the image but also the leading edge of the image to move. Therefore, in order to always fix the leading edge of the image, move the imaging lens of the photoconductor. I was also moving in the direction.

That is, in the conventional copying machine of the type in which the copying magnification can be changed as well, the imaging lens must be moved not only in the contacting / separating direction with respect to the photoconductor but also in the moving direction of the photoconductor. There is a problem that the mechanism of the image optical system becomes very complicated.

Further, in the conventional copying machine in which the copying magnification can be changed, the light shielding member is moved every time the copying magnification and the transfer paper size are input from the operation panel of the copying machine. There was also a problem that the operability and operability when changing the paper size were extremely poor.

Further, in the conventional copying machine in which the copying magnification can be changed, the light-shielding member moves in parallel with the moving direction of the photoconductor, so that there is a problem that the size of the apparatus cannot be relatively reduced.

In addition, there is a problem that the system of light-shielding control in the area where the original image is not projected is relatively poor.

Further, when the incident angle of the image light beam is large, there is a problem that the diffracted light wraps around the photoconductor by the light shielding member to a large extent, and a high quality image cannot be obtained.

Furthermore, there is a problem that when the device is miniaturized and the light shielding member is brought extremely close to the photoconductor in order to minimize the wraparound of the diffracted light, the photoconductor is damaged.

(Object) An object of the first invention is to increase the copying speed by increasing the copying speed by simplifying the mechanism of the imaging optical system of the copying machine in which the imaging position on the photoconductor changes depending on the copying magnification. It is to provide a light-shielding device to obtain.

A second object of the present invention is to provide a light-shielding device for a copying machine, which can improve the operability and operability at the time of changing the magnification and the size of the transfer paper, while increasing the copying speed and the copying efficiency.

A third object of the present invention is to provide a light-shielding device for a copying machine, which is capable of downsizing the device, is excellent in precision of light-shielding control, can obtain a high-quality image, and has no fear of damaging a photoconductor. To provide.

(Structure) In order to achieve the above-mentioned object, the light-shielding device of the copying machine according to the first aspect of the invention can expose the endless photoconductor by reducing the exposure area from the maximum original size by the whole-surface exposure method. In the optical system of the copying machine in which the image is exposed on the trailing end side of the reduced and exposed image area, a light blocking member that regulates the leading edge and the trailing edge of the image, and the respective light blocking members are provided. Driving means for moving the members according to the copy magnification, the front light-shielding member to a position determined by the copy magnification, and the rear-end light-shielding member moved to a position determined by the copy magnification and the transfer paper size. And a control unit for shielding the non-projected area of the original image from light.

Further, in order to achieve the above object, the light shielding device of the copying machine according to the second aspect of the present invention can expose the endless photoconductor by reducing the exposure area from the maximum original size by the whole surface exposure method. In the optical system of the copying machine in which the image is exposed on the trailing end side of the reduced and exposed image area, a light blocking member that regulates the leading edge and the trailing edge of the image, and the respective light blocking members are provided. Driving means for moving in accordance with the copy magnification, the front light-shielding member to a position determined by the copy magnification, and the rear-end light-shielding member moved to a position determined by the copy magnification and the transfer paper size. And a control unit for blocking the area where the original image is not projected from light, and each of the light blocking members is configured to move after the start of the copying operation.

Furthermore, in order to achieve the above object, the light shielding device of the copying machine according to the third aspect of the invention is a movement that restricts at least one end in the traveling direction of the image forming position on the photoconductor according to the copy magnification and the transfer paper size. In a possible light-shielding device, an L-shaped angle having a substantially photoconductor width, a rotatable winding roll, a light-shielding sheet having one end fixed to the L-shaped angle and the other end wound on the winding roll, A driving means for moving the L-shaped angle, the bending curve of the L-shaped angle forms a forward end of the L-shaped angle moved by the driving means, and the bent portion of the L-shaped angle is It is characterized in that it is bent toward the photosensitive member side and forms an acute angle with the light shielding sheet fixing side.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a full-exposure copying machine to which a shading device according to an embodiment of the present invention is applied.

In the figure, a contact glass 2 is arranged above the copying machine 1, and an original placed on the contact glass 2 is uniformly illuminated by a lighting device 19. The light reflected from the document is reflected by the imaging lens 3 as shown by the solid line.
An image is formed on the surface of the belt-shaped photoconductor 8 via. A light-shielding device 100 including a front-side light-shielding device 35 and a rear-end light-shielding device 36 is disposed between the lens 3 and the photoconductor 8 to prevent an area where a document image is not projected in the moving direction of the photoconductor 8. The light is shielded from the front end and the rear end. The belt-shaped photoconductor 8 is rotated counterclockwise by a belt support roller 15 rotated by a driving device (not shown), and its surface is preliminarily uniformly charged by a charging device 14. This charged surface is exposed by the image light beam to form an electrostatic latent image on the surface of the photoconductor 8. This electrostatic latent image has the potential outside the latent image area lowered by the eraser 7,
It is visualized by the developing device 9 and sent to the transfer device 10. The transfer paper is unwound by the paper feeding device 16 and is conveyed by the conveying path 17
The visible image is transferred by being conveyed to the transfer device 10 through. The recorded transfer paper is separated from the photoconductor 8 by the separating device 11, and guided into the fixing device 12 by being guided by the guide. Then, the toner image is fixed by the heat of a heater (not shown), and then discharged to the paper discharge tray 18. The surface of the photoconductor 8 after the transfer is cleaned by the cleaning device 13 to remove the residual toner.

Here, when the copying magnification is changed, the contact glass 2 and the lens 3 are moved in the vertical direction in the figure by a driving device (not shown) in accordance with the magnification to form an image on the photoconductor 8. The position changes. That is, the leading end position 20 and the trailing end position 21 of the latent image indicated by the solid line move to the position indicated by the alternate long and short dash line. Then, the above-mentioned light shielding device 10
0, that is, the front-side light-shielding device 35 and the rear-end light-shielding device 36 respectively move in the moving direction of the photoconductor 8 (left-right direction in the drawing), and shade the area in the moving direction of the photoconductor 8 where the original image is not projected. To do. That is, even when the magnification is changed, the light blocking device 100 blocks the area where the document image is not projected, as indicated by the imaginary line.

As shown in FIG. 1, the shading device 100 has a tip-side shading device 35 that regulates the latent image tip position, and the same shape as the tip-side shading device 35. It is composed of an end side light shielding device 36. FIG. 2 shows the shading device 100 in more detail.

As shown in the figure, the front-side light-shielding device 35 and the rear-end light-shielding device 36 include an L-shaped angle 4 as a light-shielding member, and the L-shaped angle 4.
Light-weight shading sheet 5 with one end fixed to the mold angle 4
And respectively. The width P of the L-shaped angle 4 is substantially the same as the width of the photosensitive member 8, and the folding curve 4A is the tip of the L-shaped angle 4 when the L-shaped angle 4 is advanced, as shown in FIG. Will be placed. That is, the tip-side light-shielding device 35 is arranged so as to be the tip when advancing to the right side in the drawing, and the rear-end-side light-shielding device 36 is arranged so as to be the tip when advancing leftward in the drawing. As shown in FIG. 3, the bent portion 4B of the L-shaped angle 4 is bent toward the photoconductor 8 side (downward in the drawing).
4B is configured to form an acute angle with the fixing portion 4C that fixes the light shielding sheet 5. That is, the bent portion 4B and the fixed portion
The angle θ with 4C is not a right angle, but an acute angle. The other end of the light shielding sheet 5 whose one end is fixed to this fixing portion 4C is
It is fixed to the light-shielding sheet winding roll 6. As shown in FIG. 4, the light-shielding sheet take-up roll 6 is in the form of a hollow cylinder, and the roll shaft 22 is rotatably accommodated therein via resin bearings 39, 39 arranged at both ends. . Roll axis
Both ends of 22 respectively project from the light-shielding sheet take-up roll 6, and the projecting portions are rotatably supported by bearings 37, 37 that are tightly fitted to the frame 38. The protruding portion of the roll shaft 22 and the light-shielding sheet take-up roll 6 are connected (coupled) by torsion coil springs 23, 23 so that a predetermined rotational torque is generated in the torsion coil springs 23, 23. ing. That is, the light-shielding sheet take-up roll 6
The back tension is always applied to the roll shaft 22 by the rotation torque of the torsion coil springs 23. Pulleys 31 and 32 are fixed to both ends of the roll shaft 22, respectively. Here, the pitch circle diameters of the pulleys 31 and 32 are substantially the same as the diameter of the light-shielding sheet take-up roll 6. As shown in FIG. 2, a drive belt 25 is wound around the pulley 31, and a drive belt 34 is wound around the pulley 32. The drive belt 25 is a rotatable pulley fixed to a frame (not shown). 24, the drive belt 34 is a rotatable pulley 33 fixed to a frame (not shown).
Have been passed over to each. Where the drive belt 25,3
4 is stretched so that a certain amount of tension is applied. Then, a gear 30b is fixed coaxially with the pulley 24, and the gear 30b is rotated by the drive motor 26.
Are engaged. The drive motor 26 is a well-known pulse motor, and is rotated by an angle corresponding to the number of pulses from a CPU in a controller (not shown). Both ends of the fixed portion 4C of the L-shaped angle 4 extend outward,
Intermediate portions of both ends thereof are fixed to the drive belts 25 and 34 by belt stoppers 27 and 27. This belt stop 27,27
The fixed position for the drive belts 25, 34 is a position where a predetermined torque is applied to the torsion coil springs 23, 23. That is, by fixing at this position, the light shielding sheet 5
A certain tension to prevent the light-shielding sheet 5 from loosening, and the mechanical backlash of the drive system to be coil springs 23, 23.
I am trying to absorb it. The end portion of the fixing portion 4C on the drive belt 25 side further extends outward, and the filler portion 28
Is formed. An optical HP sensor 29 fixed to a frame (not shown) is arranged at the passage position of the filler portion 28, and the filler portion 28 is formed together with the L-shaped angle 4 above.
When moving to the HP sensor 29, the HP sensor 29 is turned on. Further, the paper feed unit 16 shown in FIG. 1 is provided with a size detecting means for detecting the size of the set transfer paper, and the set transfer paper size is displayed on a panel (not shown). It is like this.

Therefore, when the drive motor 26 is driven, as shown in FIG. 5, the rotational force thereof is coaxially fixed to the gear 30a.
Is transmitted to the drive belt 25 via the gear 30b and the pulley 24.
It is transmitted to. When the drive belt 25 is driven, its driving force is transmitted to the roll shaft 22 via the pulley 31, and is transmitted to the pulley 32 fixed to the opposite end of the roll shaft 22. Then, when the pulley 32 is rotated, the rotational force is transmitted to the drive belt 34, and the pulley 33 is rotated. On the other hand, the driving force of the drive belts 25, 34 is transmitted to both ends of the L-shaped angle 4 via the belt stoppers 27, 27 and moves the light shielding sheet 5. When the light-shielding sheet 5 moves, the light-shielding sheet winding roll 6 having one end fixed to the light-shielding sheet 5 rotates, and the rotational force is transmitted to the torsion coil springs 23, 23. In addition, the pulley 31
Thus, when the roll shaft 22 rotates, the rotational force is transmitted to the torsion coil springs 23, 23. Thus, the torsion coil springs 23, 23 are rotated by the light-shielding sheet take-up roll 6 and by the roll shaft 22, but as described above, the pitch circle diameters of the pulleys 31, 32 are Since the diameter of the light-shielding sheet take-up roll 6 is substantially the same and the spring constant and the fixed position are set in advance so that a predetermined tension is applied to the light-shielding sheet 5, the light-shielding sheet 5 is always substantially constant. Back tension will be applied.

FIG. 6 is a block diagram of a control unit included in the light shielding device of FIG. As shown in the figure, the hydrophilicity input to the operation unit 51, the transfer paper size detection signal of the paper feed unit 16, the HP sensor
The ON signal from 29 is input to the CPU 50. This CPU50
It is connected to ROM52, and its output pulse signal is the drive motor 26
Is output to

The ROM 52 stores a program for operating the apparatus, and also stores movement amount data of the light shielding sheet 5 which is predetermined by the copying magnification and the transfer paper size.

FIG. 7 is a flowchart showing the programs stored in the ROM 52.

 The operation of this apparatus will be described below according to the program.

First, in step 1, when the power is turned on, in step 2, the light shielding sheet 5 of the tip side light shielding device 35 is
Then, homing of the light shielding sheet 5 of the rear end side light shielding device 36, that is, the movement of the light shielding sheets 5, 5 to the reference position is performed.
Here, in this embodiment, the home position (reference position for position control) of the light shielding sheets 5, 5 (L-shaped angles 4, 4) is set to the copy mode with the highest frequency. That is, when the transfer paper size is A4 and the magnification is the same size, the home position is a position where the L-shaped angles 4, 4 and the light shielding sheets 5, 5 shield the area where the document image is not projected. Then, the HP sensors 29, 29 are positioned so as to detect the filler portions 28, 28 at this home position and send an ON signal. In this way, when the shading sheets 5, 5 are homed in step 2, the process proceeds to step 3, and in step 3, it is determined whether or not the print button (copy start button) is turned on, and it is turned on. If not, the same determination is repeated until the print button is turned on, and if it is turned on, the process proceeds to step 4. In step 4, the movement amount (movement amount data) based on the copy magnification of the light shielding sheet 5 of the front side light shielding device 35 is read from the ROM 52. Here, as described above, the ROM 52 stores the movement amount data of the light shielding sheet 5 which is predetermined by the copy magnification and the transfer paper size. This movement amount data is such that when the copy magnification and the transfer paper size are the same size, and the size is changed from A4, if the light shielding sheet 5 is moved from the home position by this amount, the area where the original image is not projected can be completely shielded. Is the amount. That is, in step 4, the amount of movement required to shield the area of the light-shielding sheet 5 of the front-side light-shielding device 35 where the original image is not projected is read according to the copy magnification.
Then proceed to step 5, and in step 5,
Proceed to step 5, and in step 5, the rear end side light shielding device 36
The movement amount (movement amount data) based on the copy magnification and the transfer paper size of the light shielding sheet 5 is read from the ROM 52. That is, in step 5, according to the copy magnification input from the operation unit 51 and the transfer paper size input from the paper feeding unit 16, the area of the light shielding sheet 5 of the rear end side light shielding device 36 where the original image is not projected is selected. The amount of movement required to shield the light is read. Then, the process proceeds to step 6, and in step 6, the light shielding sheets 5, 5 on the front end side and the rear end side are respectively moved. That is, a pulse signal is sent from the CPU 50 to each of the drive motors 26, 26, and the gears 30a, 30a rotate by an amount corresponding to the amount of movement to move the light shielding sheets 5, 5 on the front end side and the rear end side, respectively. Done. That is, as described with reference to FIG. 5, the driving force is transmitted, and the light shielding sheets 5, 5 on the front end side and the rear end side are moved. Then, in step 7, it is determined whether or not the copying is completed. If the copying is not completed, the same determination is repeated until the copying is completed, and when the copying is completed, it is determined in step 8 whether or not the power is turned off. It Here, if it is determined that it is still on, the process returns to step 3 in preparation for the next copy, and if it is determined to be off, the program ends.

According to the light-shielding device of the copying machine of the embodiment having such a configuration, the following effects can be obtained.

That is, the front side light blocking device 35 and the rear side light blocking device 36 are provided respectively, and the imaging lens 3 is moved in the moving direction of the photoconductor 8 (first
Since the front and rear ends of the image are shielded by the light-shielding members without moving in the left-right direction in the figure, the mechanism of the imaging optical system can be extremely simplified.

In addition, the light shielding sheets 5 and 5 of the front side and rear side light shielding devices are
Instead of moving each time the copy magnification and transfer paper size are input, it is configured to move immediately after all conditions such as copy magnification and transfer paper size are correctly input and the print button is turned on. It is possible to improve operability and operability when changing the magnification and changing the size of the transfer paper.

Further, according to this light-shielding device of the copying machine, since the light-shielding devices 35 and 36 on the front end side and the rear-end side are composed of the lightweight sheets 5 and 5, the weight of the device can be reduced.

Further, according to the shading device of this copying machine, the shading sheet 5,
Since 5 is wound up by the light-shielding sheet winding rolls 6, 6, the space in the longitudinal direction of the light-shielding device (the left-right direction in FIG. 1) is small, and the device can be downsized.

In addition, according to the shading device of this copying machine, the L-shaped angle
Since the bent portions 4B and 4B of 4 and 4 make an acute angle with the fixed portions 4C and 4C, the angle θ formed between the bent portion 4B and the fixed portion 4C is
Compared with an L-shaped angle having a right angle, the amount of movement can be shortened and the device can be downsized. FIG. 8 compares these. As shown in the figure, when the input angle of the image light beam to the photoconductor 8 is large (on the left side in the drawing), the L-shaped angle 4 of this embodiment causes the image light beam to pass through the tip 4D of the bent portion 4B. When the angle of incidence is small and the incident angle is small (on the right side in the figure), the image light beam can be restricted by the bending line 4A, so the movement of the L-shaped angle 104 with the angle θ between the bent portion 4B and the fixed portion 4C as a right angle. The movement amount A can be shortened as compared with the amount B. Also,
Compared with the L-shaped angle 104, the L-shaped angle 4 does not have to be convex outward, that is, the L-shaped angle 4 can be recessed inward by the maximum outer movement difference C, thus further reducing the size of the device. To be

Further, according to the shading device of this copying machine, the shading sheet 5,
Since the front end of the forward side of 5 is fixed to the L-shaped angle 4, 4 having high rigidity, the wobbling of the forward end of the light shielding sheet 5, 5 is prevented, and the light shielding boundary is L-shaped angle 4, 4. As a result, a straight line is formed, so that light-shielding control of an area where the original image is not projected is accurately performed.

Further, according to the shading device of this copying machine, the bent portions 4B, 4B
Since the L-shaped angle 4, 4 with
Minimizing the wraparound of the diffracted light to the photoconductor 8 regardless of the size of the incident angle of the image light beam to the photoconductor 8 as compared with a device in which a flat plate having no bent portion is used as a light shielding member. Is possible. That is, when the incident angle of the image light beam on the photoconductor 8 is small, as shown in FIG. 9, the diffracted light by the L-shaped angle 4 and the diffracted light by the flat plate light-shielding member shown in black are also the same. When the length X is small but the incident angle is large, as shown in FIG. 10, the length Z of the diffracted light by the L-shaped angle 4 is the length of the diffracted light by the flat light shielding member shown in black. It is considerably smaller than Y. That is, if the L-shaped angle 4 is used, wraparound of the diffracted light to the photoconductor 8 can be minimized and a high quality image can be obtained regardless of the size of the incident angle of the image light beam on the photoconductor 8.

Incidentally, even if a flat plate light shielding member is used, if the member is brought as close as possible to the photoconductor 8, the wraparound of the diffracted light can be minimized.
However, if the light-shielding member is brought too close to the photoconductor 8, the photoconductor 8 may come into contact with the light-shielding member when the photoconductor 8 is detached, and the photoconductor 8 may be damaged. Further, if the light blocking member is moved too far away from the photoconductor 8 in order to avoid it, the diffracted light will more easily wrap around and the device will become larger. However, in this embodiment, since the L-shaped angle 4 is used, it is possible to move the light-shielding sheet 5 away from the photoconductor 8 to some extent, and even if the light-shielding sheet 5 is moved away, the diffracted light is prevented from wrapping around to a minimum, and the device is compact. It can be achieved to some extent.

Further, according to the light-shielding device of this copying machine, since the L-shaped angle 4 and the light-shielding sheet 5 are moved by driving the belts on both sides, the leading end of the light-shielding sheet 5 is biased to one side, and one-sided belt drive that easily causes a light-shielding defect. Compared with, the light blocking accuracy can be improved.

Further, according to the shading device of this copying machine, the drive motor 26
Since the single drive belt 25 and the drive belts 34 are driven, the drive system is simplified and the manufacturing cost is reduced.

Further, according to the shading device of this copying machine, the transmission force by the belt is transmitted to the L-shaped angle 4 and the roll shaft 22 at the same time, and the shading sheet take-up roll 6 that moves integrally with the L-shaped angle 4 is used. Since the roll shaft 22 and the roll shaft 22 are connected by the torsion coil springs 23, 23, the L-shaped angle 4
No matter where the (shading sheet 5) is, the shading sheet 5
The same tension always acts on the light shielding sheet 5 to prevent the light shielding sheet 5 from bending.

Furthermore, according to the shading device of this copying machine, the other ends of the torsion coil springs 23, 23, one end of which is fixed to the shading sheet winding roll 6, are free from the shading sheet winding roll 6, Since it is fixed to the roll shaft 22 that is rotated by the belt, the back tension of the light shielding sheet 5 can always be made constant regardless of the position of the L-shaped angle 4 (light shielding sheet 5), and a drive motor with a small output can be used. The light shielding sheet 5 can be moved. Incidentally, the torsion coil springs 23,23
If a general method of fixing the other end of the light shielding sheet to a non-moving portion is used, the back tension becomes stronger as the light shielding sheet 5 advances and extends, and the light shielding sheet 5 is moved by a drive motor having a large output. There must be.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the invention.

(Effects) As described above, according to the light shielding device of the copying machine of the first invention, it is possible to expose the endless photoconductor by reducing the exposure area from the maximum original size by the whole surface exposure method. , In the optical system of the copying machine, which is configured so that the image is exposed on the trailing end side of the reduced and exposed image area,
Light-shielding members that regulate the front and rear ends of the image, drive units that move the respective light-shielding members according to the copy magnification, and the rear-end light-shielding members at the positions determined by the copy magnification. Since the members are respectively moved to the positions determined by the copy magnification and the transfer paper size, and the control means for shielding the non-projected area of the original image is provided, the mechanism of the imaging optical system is simplified. At the same time, it is possible to increase the copy speed and increase the copy efficiency.

Further, according to the light shielding device of the copying machine of the second invention, it is possible to expose the endless photoconductor by reducing the exposure area from the maximum original size by the whole surface exposure method. In the optical system of the copying machine so that the image is exposed on the trailing end side of the exposed image area, in the optical system of the copying machine, a light blocking member that regulates the leading edge and the trailing edge of the image, and the respective light blocking members Driving means for moving in accordance with the copy magnification, the front light-shielding member to a position determined by the copy magnification, and the rear-end light-shielding member moved to a position determined by the copy magnification and the transfer paper size. And a control means for shielding the non-projected area of the original image, and the light shielding members are moved after the copying operation is started. Therefore, the operability and the operability when the magnification is changed or when the transfer paper size is changed. Direction Expedited copy speed while reducing, it is possible to increase the copy efficiency.

Furthermore, according to the light-shielding device of the copying machine of the third invention, in the movable light-shielding device that regulates at least one end in the traveling direction of the image forming position on the photoconductor in accordance with the copy magnification and the transfer paper size, An L-shaped angle having a substantially photoconductor width, a rotatable winding roll, a light-shielding sheet whose one end is fixed to the L-shaped angle and the other end is wound by the winding roll, and the L-shaped angle is moved. And a bending means of the L-shaped angle that forms the tip of the L-shaped angle that is moved by the driving means when the L-shaped angle moves forward, and the bent portion of the L-shaped angle is bent toward the photoconductor. In addition, since it is configured to form an acute angle with respect to the fixed side of the light-shielding sheet, the copying apparatus can be downsized, and
The shading device of the copying machine is excellent in the accuracy of shading control and can obtain a high-quality image without fear of damaging the photoreceptor.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a copier for overall exposure to which a light shielding device according to an embodiment of the present invention is applied, FIG. 2 is a perspective view of the same light shielding device, and FIG. 3 is an L-shaped angle and a light shielding sheet side. Sectional view, FIG. 4 is a side sectional view of a light-shielding sheet take-up roll and a roll shaft, FIG. 5 is a block diagram showing a torque transmission path of the same light-shielding device, and FIG. 6 is a block diagram of a control unit of the same light-shielding device. FIG. 7 is a flow chart of a program stored in the ROM in FIG. 6, FIG. 8 is a diagram explaining that the movement amount of the L-shaped angle changes depending on the shape of the L-shaped angle, and FIG. FIG. 10 is a diagram showing a state of diffracted light by an L-shaped angle when an incident angle of an image light ray on a body is small,
The figure shows L when the incident angle of the image beam on the photoconductor is large.
It is a figure which shows the state of the diffracted light by a mold angle. 1 ... Copying machine, 3 ... Imaging lens, 4 ... L-shaped angle, 4A ... L-shaped angled bending curve, 4B ... L-shaped angled bending portion, 4C ... L-shaped angled light shielding sheet Fixed part of
5 ... Shading sheet, 6 ... Shading sheet winding roll, 8
…… Photoconductor, 16 …… Paper feed section, 20 …… Image front end, 21 …… Image rear end, 22 …… Roll axis, 23 …… Torsion coil spring, 2
4,31,32,33 …… Pulley, 25,34 …… Drive belt, 26 ……
Drive motor, 28 ... Filler part, 29 ... HP sensor, 30a,
30b …… Gear, 35 …… Front side light blocking device, 36 …… Rear end side light blocking device, 50 …… CPU, 51 …… Operating section, 52 …… ROM, 100…
... Shading device, P ... Photoconductor width (L-shaped angle, shading sheet width) θ: Angle formed by the bent portion and the fixed portion.

Continuation of the front page (56) Reference JP-A-55-159466 (JP, A) JP-A-51-6732 (JP, A) JP-A-47-4483 (JP, A) JP-A-54-149621 (JP , A) JP 56-132358 (JP, A) JP 61-6632 (JP, A) JP 61-282869 (JP, A) JP 62-89033 (JP, A) JP 1-303423 (JP, A) JP-A-56-143467 (JP, A) JP-A-60-138526 (JP, A) JP-A-60-138527 (JP, A) Actual development-Sho 52-155552 (JP, U)

Claims (3)

(57) [Claims] 1. An endless photoconductor can be exposed by reducing the exposure area to a size smaller than the maximum original size by an overall exposure method, and an image is formed on the rear end side of the reduced and exposed image area. In an optical system of a copying machine configured to perform exposure by closing the light, a light-shielding member that regulates the front and rear edges of an image, drive units that move each light-shielding member according to the copy magnification, and the light-shielding at the front edge are provided. Place the member at the position determined by the copy magnification,
A shading device for a copying machine, comprising: a control unit that moves the rear-end shading member to a position determined by a copying magnification and a transfer paper size to shade a non-projected area of a document image. 2. An endless photoconductor can be exposed by reducing the exposure area to a size smaller than the maximum original size by an overall exposure method, and an image is formed on the rear end side of the reduced and exposed image area. In an optical system of a copying machine configured to perform exposure by closing the light, a light-shielding member that regulates the front and rear edges of an image, drive units that move each light-shielding member according to the copy magnification, and the light-shielding at the front edge are provided. Place the member at the position determined by the copy magnification,
And a control unit configured to move the trailing edge light-shielding member to a position determined by the copy magnification and the transfer paper size so as to shield the non-projected area of the original image. Each of the light-shielding members moves after the copying operation is started. A shading device for a copying machine, which is configured to: 3. A movable light-shielding device that regulates at least one end in the traveling direction of an image-forming position on a photoconductor in accordance with a copy magnification and a transfer paper size, and an L-shaped angle having a substantially photoconductor width and rotation. A free-winding roll, a light-shielding sheet having one end fixed to the L-shaped angle and the other end being wound by the winding-roll, and a drive means for moving the L-shaped angle are provided. The folding curve forms the tip of the L-shaped angle that is moved by the driving means when the L-shaped angle is advanced, and the bent portion of the L-shaped angle is bent toward the photoconductor and is at an acute angle with respect to the light-shielding sheet fixed side. A shading device for a copying machine, characterized in that