JPH041344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an unnecessary charge removing device for removing unnecessary charges from among the charges applied to the surface of a photoreceptor in a copying machine.

"Prior Art" A copying machine uses a drum-shaped or belt-shaped photoreceptor to create an image through the steps of charging, forming an electrostatic latent image by exposure, developing, transferring, and fixing.

By the way, in such a copying machine, a charge is uniformly applied to the entire surface of the photoreceptor during the charging process, so in order to avoid unnecessary development, a lamp for removing the charge is placed on the copy paper after charging is completed. It lights up according to its size and removes the charge from unnecessary parts.

However, when using such a copying machine to copy, for example, a B5 size original onto A4 size copy paper,
The size of the copy paper becomes larger than the image area (the area where an electrostatic latent image is formed corresponding to the image of the original). For this reason, there was a problem in that stains on the document cover around the document were copied at the same time, resulting in inferior quality of the copy paper.

In order to solve this problem, an unnecessary charge removal device was previously proposed in which a charge removal lamp is lit according to the size of the document (see Japanese Patent Laid-Open No. 59-94770). .

In the unnecessary charge removal device according to this proposal, the 11th
As shown in the figure, there are 8
Two lamps 2 are arranged in series in the axial direction of the photoreceptor 1, and their lighting is controlled according to the size of the document.

However, with the unnecessary charge removing device proposed by this proposal, there is no problem when the document size is a predetermined size such as A4 size, but there is a problem when it is not. That is, when copying a document smaller than A4 size and larger than B5 size, for example, the lighting control of lamp 2 will be performed for either A4 size or B5 size. When controlling the lighting of the lamp 2 for an A4 size document, the area where the charge remains is larger than the image area, so dirt and the like around the document will be copied at the same time. On the other hand, when controlling the lighting of the lamp 2 in B5 size, the area where the charge remains is smaller than the image area, so the image will be missing.

Recently, copying machines equipped with a reduction/enlargement function have been commercialized. In such a copying machine, if the lighting of the lamp for charge removal is controlled according to the size of the document, the area where the charge remains will be smaller than the image area in the case of enlarged copying, while the area where charge remains will be smaller than the image area in the case of reduced copying. It gets bigger.

``Means for solving the problem'' As described above, with the unnecessary charge removal device proposed earlier, when the original size is other than the specified size such as A4 size, or when reducing or enlarging the copy, There were problems such as the copy paper being inferior in quality and the image being missing.

SUMMARY OF THE INVENTION In view of these circumstances, an object of the present invention is to provide an unnecessary charge removal device that can always match an area where charges remain to an image area.

"Means for Solving the Problems" In the present invention, electric charges are uniformly applied to the surface of the photoreceptor, and two sides of the document are aligned with two sides forming a predetermined corner of the platen glass. Scanning exposure is performed to form an electrostatic latent image on the surface of the photoreceptor so that one of the two sides in the scanning direction of the document is projected near one end of the photoreceptor in a direction perpendicular to the direction of movement of the photoreceptor. In a copying machine that creates an image through the steps of development, transfer, and fixing after forming a photoreceptor, () a plurality of light-emitting elements that can selectively emit light are placed on the surface of a photoreceptor at predetermined positions. The photoreceptors are arranged in series from one end of the photoreceptor to the other end on the opposite side in a direction perpendicular to the direction of movement of the photoreceptor while maintaining a distance of (a) a first charge removing means which is movable in a direction perpendicular to the direction of movement of the photoreceptor; a second charge removing means capable of removing charges within a range that covers at least one end of the photoreceptor and an end of the first charge removing means on the one end side; and (1) moving the first charge removing means. () copying magnification input means for inputting a copying magnification; () original size setting means; and () original size given by the original size setting means and copying magnification inputted by the copying magnification input means. a calculation means for calculating the position of one side of the area located on the other end side of the photoreceptor in the image area on the photoreceptor obtained by multiplying the value;
Based on the calculation result of the calculation means, when some of the light emitting elements of the first charge removing means are turned on, the boundary between the light emitting elements that are turned on and the light emitting elements that are turned off is located on one side of the above-mentioned area. and control means for controlling the moving means and controlling the lighting of the first and second charge removing means.

According to the present invention, the boundary between the light-emitting elements of the charge removal means that are lit and those that are off is always located on a predetermined side of the image area, so that the area where charges remain is It will always match the image area.

"Example" The present invention will be explained in detail with reference to Examples below.

FIG. 1 shows the main parts of the unnecessary charge removing device of this embodiment. In this device, first and second charge removing members 6 and 7 are respectively disposed facing the surface of a drum-shaped photoreceptor 5. Among these, the first charge removing member 6 includes a lamp, a light emitting diode, etc., and is fixed to a frame (not shown). As shown in FIG. 2, the second charge removing member 7 has a structure in which a plurality of light emitting elements 8 made of light emitting diodes or the like are arranged at intervals on a rod-shaped base 9. This second charge removal member 7 has its light emitting element 8 facing the surface of the photoreceptor 5 and is arranged parallel to its axis, and is movable in the coaxial direction as shown by arrows A and B. ing.

When an electrostatic latent image corresponding to the image of the document is formed on the surface of the photoreceptor 5 by this unnecessary charge removing device, for example, as shown by diagonal lines in FIG.
The charge removing member 6 removes the charges in the area on the left side of the image area 10 where this electrostatic latent image is formed. The second charge removal member 7 removes the charge in the area on the right side of the image area 10 when a predetermined part of the light emitting element 8 turns on.

When this unnecessary charge removing device removes charges in an area other than the image area 10 in the circumferential direction of the photoreceptor 5, all of the light emitted by not only the first charge removing member 6 but also the second charge removing member 7 is removed. This will cause element 8 to light up. At this time, the lighting control of the second charge removing member 7 may be performed based on the detection result by detecting the amount by which the photoreceptor 5 has rotated in the direction of the arrow in FIG. 1 from the home position. Whether or not the photoreceptor 5 has reached the home position can be detected by detecting the permanent magnet 11 provided on one side thereof by a magnetic sensor (not shown). How much the photoconductor 5 has rotated from the home position in the direction of arrow C can be determined by
A number of slits formed around a disk 12 provided at the other end constitute a transmission type rotation amount detection sensor 1.
It can be detected by being detected by 3.

By the way, in this unnecessary charge removing device, the second charge removing member 7 is movable in the directions of arrows A and B. In addition, this unnecessary charge removal device needs to detect the size of the document. Therefore, these devices will be explained next.

FIG. 4 shows a device for moving the second charge removing member 7. The second charge removing member 7 is attached to the slide plate 16. The slide plate 16 is guided by a guide (not shown) and is movable in the directions of arrows A and B. A rack 17 is installed at a predetermined location on the slide plate 16.
is provided. The rack 17 has a pinion 19 attached to the output shaft of the step motor 18.
It is intertwined with. Therefore, when the stepping motor 18 rotates forward or backward, the slide plate 16
At the same time, the second charge removing member 7 is moved in the direction of arrow A or B. A light shielding plate 20 for detecting the home position of the second charge removing member 7 is provided at another predetermined location on the slide plate 16. The light shielding plate 20 is configured to pass between the light emitting element and the light receiving element of the transmission type position detection sensor 21 as the slide plate 16 moves. The position detection sensor 21 is fixed to the frame.

FIG. 5 shows a document size detection device. In this apparatus, document detection sensors 33 and 34 in the X and Y directions are provided on two predetermined sides of the platen glass 31 to detect the size of the document 32 in the X and Y directions, respectively. These sensors 33 and 34 each have a structure in which a large number of pairs of light emitting elements and light receiving elements are arranged in series in close contact with each other.

In the X-direction document detection sensor 33, among the light rays emitted from the respective light emitting elements, those reflected by the surface of the document 32 that is in close contact with the platen glass 31 are detected by the corresponding light receiving elements (X ₁ , X _n
etc.). Here, X ₁ refers to the light- _receiving element located at the leftmost end in FIG. say. As the X _n light receiving elements of the X-direction original detection sensor 33 receive light in this manner, the size of the original 32 in the X-direction that is in close contact with the platen glass 2 is detected.

On the other hand, in the document detection sensor 34 in the Y direction, among the light rays emitted from the light emitting elements, those reflected by the surface of the document 32 that is in close contact with the platen glass 31 are detected by the corresponding light receiving elements (Y ₁ ,
Y _o, etc.). Here, Y ₁ refers to the light-receiving element located closest to you in FIG. 4, and Y _o refers to the light-receiving element located on the surface of the document 32 that is in close contact with the platen glass 31 at a position opposite to the rear edge in the same figure. Refers to elements. Like this
When the Y _o light receiving element of the direction original detection sensor 34 receives light, the size of the original 32 in the Y direction which is in close contact with the platen glass 31 is detected.

Next, a case will be described in which the unnecessary charge removing device controls lighting and movement of the second charge removing member 7 based on the size of the original 32, the copying reduction ratio, and the size of the copy paper. At this time, it is assumed that the second charge removing member 7 is initially located at the home position. In addition, the size of the copy paper in the axial direction of the photoreceptor 5 is L ₁ mm, the size of the original 32 is L ₂ mm,
Let Rmm be the amount of movement of the second charge removing member 7 per step by the stepping motor 18, Pmm be the pitch of the light emitting elements 8 of the second charge removing member 7, and M be the copying magnification.

In this unnecessary charge removing device, lighting and movement control of the second charge removing member 7 is performed based on the smaller of the range of the image area 10 in the axial direction of the photoreceptor 5 and the size of the copy paper. .
The range of the image area 10 is a value (L ₂ ×M) obtained by multiplying the size L ₂ of the original 31 by the reduction ratio M.

When (L ₂ × M)≧L ₁ , that is, when the range of the image area 10 is equal to or larger than the size of the copy paper, the size L ₁ of the copy paper is divided by the pitch of the light emitting elements 8. An integer N is determined from among the values, and a value Q is determined by dividing the remainder S at that time by the amount R of movement of the second charge removing member 7 per one step by the stepping motor 18.

L ₁ /P=N remainder S, S/R=Q ₁ (L ₂ ×M) <L ₁
In other words, if the range of the image area 10 is smaller than the size of the copy paper, calculate the integer N among the values obtained by dividing the range of the image area 10 (L ₂ × M) by the pitch P of the light emitting element 8. , and the value Q obtained by dividing the remainder S by the amount of movement R of the second charge removing member 7 per one step by the stepping motor 18 is determined.

(L ₂ ×M)/P=N...Remainder S, S/R=Q And in either case, based on the integer N, the Nth light emitting element 8 of the second charge removal member 7 from the left in FIG. The lights above will be turned off, and the others will be turned on. At this time, when the value Q is 0, as shown in FIG.
Of these, the midpoint between the N-th and N+1-th corresponds to the left side 10A of the image area 10. Therefore, in this case, the second charge removing member 7
will remain at the home position. On the other hand, when the value Q ₁ is greater than or equal to 1, the N+1-th light emitting element 8 faces the left side of the image area 10, as shown in FIG. 7, for example. Therefore, in this case, a Q pulse is applied to the stepping motor 18 to move the second charge removing member 7 by Q×R in the direction of arrow B.
Then, as shown in FIG.
The middle point between the th one and the N+1 th one coincides with the left side 10A of the image area 10.

Next, a specific example will be described in which the unnecessary charge removing device controls lighting and movement of the second charge removing member 7 based on the size of the document. At this time, it is assumed that the second charge removing member 7 is initially located at the home position. Further, the pitch P of the light emitting elements 8 of the second charge removing member 7 is 20 mm, the gap D is 1 mm, and the amount of movement R of the second charge removing member 7 per one step by the stepping motor 18 is 0.25 mm. shall be.

Under these conditions, for example, a full-size copy of an A4-sized original is A4
Suppose that this is done on a 1-size copy paper. In this case,
The sizes L ₁ and L ₂ of the copy paper and the original in the axial direction of the photoreceptor 5 are both 210 mm, and the copy reduction magnification M is 1. Therefore, the range of the image area 10 (L ₂
×M) is 210 mm, which is equal to the size of copy paper. Dividing the copy paper size L ₁ (210 mm) by the pitch P (20 mm) of the light emitting element 8 gives an integer N of 10.
is obtained, and by dividing the remainder S (10 mm) by the amount of movement R (0.25 mm) of the second charge removing member 7 per step by the stepping motor 18, a value Q of 40 is obtained.

Therefore, in this case, among the light emitting elements 8 of the second charge removing member 7, the tenth ones from the left in FIG. 3 are turned off, and the others are turned on. Also, the stepping motor 18 has 40
By applying a pulse, the second charge removing member 7 is moved in the direction of arrow B by 40×0.25=10 mm. Even if the document is of a size other than the predetermined size, such as A4 size, the lighting and movement of the second charge removing member 7 will be controlled in the same way.

Next, movement control of the second charge removing member 7 will be specifically explained.

FIG. 9 schematically shows the circuit configuration of this unnecessary charge removing device. This device is equipped with a CPU (central processing unit) 41, and is connected to various parts through a bus line 42 such as a data bus.
Of these, ROM (read only memory) 43
is a memory in which a program for controlling the circuit is written. A RAM (random access memory) 44 not only stores copy condition data of copy reduction ratios set on an operation panel (not shown), but also temporarily stores other processing data. A RAM 45 backed up by a battery stores data regarding the current position of the second charge removal member 7. The position of the second charge removal member 7 can be expressed by the number of pulses applied to the stepping motor 18 to determine how far it has moved in the direction of arrow B in FIG. 3 from the home position. Therefore, the data stored in the RAM 45 is data containing the number of pulses applied to the stepping motor 18.

The operation panel input section 46 is a data input section for inputting various data on the operation panel. The sensor input port 47 is a circuit portion that inputs data output from the position detection sensor 21 and data output from the document detection sensors 33 and 34, processes them, and sends them onto the bus line 42. The motor driver 48 is a circuit that controls the driving of the stepping motor 18. The light emitting element driver 49 is a circuit that controls lighting of the light emitting element 8 of the second charge removing member 7 and the lamp of the first charge removing member 6.

Next, the operation of this unnecessary charge removing device will be explained with reference to a flowchart (FIG. 10). The CPU 41 first monitors whether the original 32 is set on the platen glass 31 (step). This is a document detection sensor 33, 34 that detects the presence or absence of a document 32 in the X and Y directions.
This is done by checking whether the detection is detected by each part of the detection output using the data as the detection output. When the original 32 is set on the platen glass 31 (Y), its size is detected by the original sensors 33 and 34 in the X direction and the Y direction.
The CPU 41 reads the document 32 based on the detected data.
Determine the size of (step). As a result, the size of the document 32 is determined not only when it is a predetermined size such as A4 size, but also when it is not.

Next, the CPU 41 calculates the position of the left side 10A of the image area 10 on the surface of the photoreceptor 11 based on the size data in the Y direction of the original 32, the size data in the same direction of the copy paper, and the copying magnification (step). As described above, this calculation is performed by calculating the number of pulses to be applied to the stepping motor 18 while the second charge removing member 7 is located at the home position.

Next, the CPU 41 reads the previous applied pulse number data written in the RAM 45, and determines whether the number of pulses corresponding to this data is the same as the number of pulses to be applied to the stepping motor 18 this time ( step). If they are the same (Y), it means that the current position of the second charge removing member 7 is the same as the previous position. Such a situation may occur when copying an original of the same size as the previous original under the same copying conditions as the previous copy. If they are not the same (N), the CPU 41 next determines whether the position detection sensor 21 is in an off state (step). Here, when the position detection sensor 21 is in an off state, it means that the light shielding plate 20 is located to the left of the position detection sensor 21, as shown in FIG. On the other hand, when the position detection sensor 21 is in an on state, it means that the light shielding plate 20 is shielding the position detection sensor 21 from light.

When the position detection sensor 21 is on (step; N), the motor driver 48 is driven in the reverse direction, and the stepping motor 18 starts to rotate in the reverse direction (step). Then the slide plate 16
At the same time, the light shielding plate 20 is moved in the direction of arrow B. At this time, the CPU 41 monitors whether the position detection sensor 21 is turned off (step). If it is turned off (Y), the stepping motor 18 is stopped. As a result, the light shielding plate 20 is positioned to the left of the position detection sensor 21 in FIG. 4. The subsequent operation is the same as when the position detection sensor 21 is in the OFF state (Y) in step.

If the position detection sensor 21 is in the off state in the step (Y), the motor driver 4
8 is driven to rotate in the normal direction, and normal rotation of the stepping motor 18 is started (step). Then, the light shielding plate 20 is moved in the direction of arrow A together with the slide plate 16. At this time, the CPU 41 monitors whether the position detection sensor 21 is turned on (step). If it is turned on (Y), the stepping motor 18 is stopped (step). As a result, the second charge removing member 7 is located at the home position together with the light shielding plate 20 and the like.

Next, the CPU 41 determines whether the number of pulses to be applied to the stepping motor 18 this time is 1 or more (step). If it is 1 or more (Y), the CPU 41 sets the number of pulses to be applied this time in a built-in counter (step). next
The CPU 41 causes the motor driver 48 to rotate forward by one pulse, causes the stepping motor 18 to rotate forward by one step (step), and decreases the counter by one (step). Next, the CPU 41 determines whether the set number of the counter is 0 or not (step). If it is not 0 (N), the stepping motor 18 is further rotated forward by one step, and the counter is decreased by one (step,
). When the set number of the counter becomes 0 (step; Y), the CPU 41 writes data containing the current number of applied pulses to the RAM 45 (step).

If the number of pulses to be applied this time in step is not 1 or more, that is, 0 (N), there is no need to move the second charge removing member 7, so the CPU 41 sets the number of pulses to be applied this time, that is, 0, as the content. The data will be written to the RAM 45 (step).

"Effects of the Invention" As explained above, according to the present invention, the area where the charge remains can always be made to match the image area, so the copy paper will not look inferior or the image will not be missing, and the image will be clean. Able to make accurate copies. Further, since the developer does not adhere to unnecessary portions during the developing process, cleaning failures do not occur in these portions, and the subsequent copying is not adversely affected. Furthermore, the developing device and the developer are not subjected to unnecessary abuse, the durability is improved, and it is economical.

[Brief explanation of drawings]

Figures 1 to 10 are for explaining embodiments of the present invention, of which Figure 1 is a perspective view showing the main parts of the unnecessary charge removal device, and Figure 2 is a perspective view of the second charge removal member. FIG. 3 is a plan view showing an example of removing unnecessary charges on a photoreceptor; FIG. 4 is a perspective view showing main parts of the second charge removal member moving device; FIG. 5 is a perspective view showing the main parts of the document size detection device, FIGS. 6 to 8 are diagrams shown for explaining lighting and movement control of the second charge removing member,
FIG. 9 is a block diagram showing the main parts of the electric circuit of the unnecessary charge removing device, FIG. 10 is a flowchart showing the operation of the device in controlling the movement of the second charge removing member, and FIG.
FIG. 1 is a perspective view showing an example of a conventional unnecessary charge removing device. 5...Photoreceptor, 6...Fixed charge removal member,
7...Movable charge removal member, 8...Light emitting element,
10... Image area, 10A... Left side (predetermined side), 18... Step pig motor, 20... Light shielding plate, 21... Position detection sensor, 31... Platen glass, 32... Original, 33, 34... Original detection sensor, 41...CPU, 43...ROM, 44,
45...RAM, 46...Operation panel input section, 4
7...Sensor input port, 48...Motor driver, 49...Light emitting element driver.

Claims (1)

[Claims] 1. Charge is uniformly applied to the surface of the photoconductor, and scanning exposure is performed with the two sides of the document aligned with the two sides forming the predetermined corners of the platen glass, and the document is exposed. After forming an electrostatic latent image on the surface of the photoreceptor so that one of the two sides in the scanning direction is projected near one end of the photoreceptor in a direction perpendicular to the direction of movement of the photoreceptor, In a copying machine that creates an image through each process of development, transfer, and fixing, a plurality of light-emitting elements that can selectively emit light are kept at a predetermined distance from the surface of the photoreceptor while the photoreceptor is moved. The light emitting elements are arranged in series from one end of the photoreceptor and the other end on the opposite side in a direction perpendicular to the direction of movement of the photoreceptor, and are movable in the direction perpendicular to the direction of movement of the photoreceptor by at least the arrangement interval of these light emitting elements. a first charge removing means fixedly disposed at a predetermined distance from the surface of the photoreceptor, and arranged between one end of the photoreceptor in a direction perpendicular to the moving direction of the photoreceptor and a first charge removing means on the one end side; 1
a second charge removing means capable of removing charges within a range that covers at least an end of the charge removing means; a moving means for moving the first charge removing means; and a copying magnification for inputting a copying magnification. an input means, an original size setting means, and a photosensitive area in an image area on the photoreceptor obtained by multiplying the original size given by the original size setting means and the copy magnification value inputted from the copy magnification input means; a calculating means for calculating the position of one side of the region located on the other end side of the body; and a calculating means for calculating the position of one side of the region located on the other end side of the body; control means for controlling the moving means so that a boundary between a light emitting element and a light emitting element that is turned off is located on one side of the area, and controlling lighting of the first and second charge removing means; An unnecessary charge removing device characterized by: