JP2732992B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine for forming a latent image formed on a photoreceptor into a visible image and transferring the developed image to transfer paper to form an image. The present invention relates to an image forming apparatus that appropriately balances the density of an image transferred on paper in a main scanning direction.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine which forms a latent image formed on a photosensitive member and forms the image by transferring the latent image to transfer paper, the difference in the charging ability of the photosensitive drum is different. In addition, the surface potential of the photosensitive drum in the main scanning direction becomes non-uniform due to contamination of the charge wire and the shield case constituting the charger, and the density of the image transferred to the transfer paper may become non-uniform. For example, fog may occur on a part of the front side or the rear side of the transfer paper in the main scanning direction.

Conventionally, in order to solve the above-mentioned problem, for example, the surface potential of the photosensitive drum is detected, and the inclination angle of the charge wire in the axial direction with respect to the surface of the photosensitive drum is adjusted based on the detection result to thereby adjust the photosensitive drum. A technique for making the surface potential uniform has been proposed (JP-A-61-1516).
No. 69).

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the method disclosed in Japanese Patent No. 1669, the inclination angle of the charge wire is adjusted by detecting the surface potential of the photoreceptor drum. It is difficult to reduce the non-uniformity of the density of the image on the transfer paper when it is caused by the moisture absorption state of the paper.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an image forming apparatus capable of forming a suitable image by reducing fogging of a transfer sheet after transfer in a main scanning direction. And

[0006]

According to the first aspect of the present invention,
An image forming apparatus that forms a latent image of an image of a document read by an optical system on a photoconductor and then visualizes the latent image to form an image on transfer paper is separated from the photoconductor surface by a predetermined distance. Charging means having a charging wire which is stretched and whose tilt angle in a vertical plane with respect to the axial direction of the photoreceptor surface can be changed; and a transfer paper on which an image of a preset reference document is formed is transported on a transport path. Once at a predetermined position,
Density detecting means for detecting the image density distribution of the transfer paper in the main scanning direction; storage means for storing an appropriate density for the image of the reference document; detection data from the density detecting means and appropriate density from the storage means A calculating means for calculating the tilt angle of the charge wire from the data; and a control means for controlling the tilt angle of the charge wire based on the tilt angle calculated by the calculating means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the optical system is capable of reciprocating, and sub-scans the surface of the original placing plate disposed within the reciprocating range. Is set as a range, while the reference manuscript is
It is arranged at a position within the reciprocating range and outside the sub-scanning range, and the lower surface is formed on the lower surface of a member flush with the original placing surface.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, a re-feeding means for feeding the transfer paper on which the image is formed to the photosensitive member again, and a tilt angle of the charge wire. When the adjustment is performed, the transfer paper on which the image of the reference original is formed is re-fed to the photoconductor, and after the image of the reference original is formed on the transfer paper, the image density is detected. And a density detection control means.

[0009]

According to the first aspect of the present invention, the transfer paper on which the image of the reference document is formed is fed to a predetermined position provided on the feeding path, and is temporarily stopped and stopped in the main scanning direction. An image density distribution is detected. Then, the inclination angle of the charge wire for charging the photoconductor is calculated from the detection result and data of an appropriate density for the image of the reference document set in advance, and the inclination angle of the charge wire in the charging unit is calculated based on the calculation result. Controlled.

According to the second aspect of the present invention, the optical system is moved to a position below the member on which the reference original is formed,
The image of the reference document is read with the optical system stopped at the position.

According to the third aspect of the present invention, when the inclination angle of the charge wire is adjusted based on the image density of the transfer sheet on which the image of the reference document is formed, the transfer sheet is further transferred to the photosensitive member. After re-feeding and transferring the image of the reference document again to the back surface of the transfer sheet under the adjusted charging conditions, the image density of the transfer sheet after the transfer is detected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus (copier) according to the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram showing an example of a copying machine to which the present invention is applied.

In FIG. 1, a copying machine 1 includes a contact glass 2 as a document placing plate on an upper surface thereof, and an automatic document feeder 3 for automatically transporting and discharging a copy document onto the contact glass 2. The optical system includes an optical mechanism L, an image forming means P, a reversing device K, a paper re-feeding mechanism R, and a paper transport mechanism for feeding and transporting the transfer paper.

The optical mechanism L comprises a first optical system 11 comprising a halogen lamp 4, reflecting mirrors 5 and 6, a second optical system 12 comprising reflecting mirrors 7 and 8, a reflecting mirror 9 and an imaging lens 10
It is composed of At the approximate center of the optical mechanism L,
An optical system drive motor 13 is provided, and the first optical system 1 is driven by the optical system drive motor 13.
The first and second optical systems 12 are reciprocated at required intervals to irradiate the image forming means P with a document image. Especially,
The first optical system 11 is reciprocally movable to a position on the lower surface of the contact glass 2 and on both sides of the sub-scanning range (the position of the home position switch 14 and the like). To ensure stability.

A home position switch 14 is provided at an initial set position of the first and second optical systems 11 and 12, and a timing switch 15 is provided near the home position switch 14, whereby the optical systems 11 and 12 are initialized. It is detected that the copying machine has been set at the set position, and an operation reference of each mechanism in the copying machine 1 is instructed. Further, between the position where the first optical system is detected by the timing switch 15 and the contact glass 2 and on the lower surface of the indication plate 16 for indicating the leading end of the original placing position, the exposure amount adjustment of the halogen lamp 4 is performed. The reference document 17 is arranged and formed. The reference document 17 is flush with the contact glass 2 to ensure detection accuracy. Note that a white original is applied to the reference original 17 so that image fog detection can be performed.

The image forming means P includes a photosensitive drum 18 on which an electrostatic latent image is formed by irradiating the original image from the optical mechanism L, and an upstream side along the peripheral surface of the photosensitive drum 18. , A charging device 19 for charging the surface of the photosensitive drum 18 to a predetermined potential, a developing device 20 for visualizing an electrostatic latent image, and a transfer device for transferring an original image on the photosensitive drum 18 to transfer paper. 21, a separation device 22 for separating transfer paper after transfer from the photosensitive drum 18 and a cleaning device 23 for removing residual toner on the photosensitive drum 18.

In this copying machine, the charging potential of the photosensitive drum 18 can be inclined in the axial direction based on the detection result of the density detecting device G as described later.
That is, the tilt angle of the charge wire of the charging device 19 can be changed in a plane perpendicular to the axial direction of the surface of the photosensitive drum 18.

FIG. 2 is a partially cutaway perspective view showing the structure of the charging device 19. In the drawing, reference numeral 191 denotes a shield case having a substantially U-shaped cross section made of a conductive member such as metal, 192 denotes a charge wire, and 193 denotes a front end of the charge wire (an end on the near side of the copying machine). The end block 194 is the charge wire 192.
195 is a slider for changing the distance of the front end of the charge wire 192 from the surface of the photosensitive drum 18, and 196 is a motor for driving the slider 195. The base 195a of the slider 195 is screwed to the rotation shaft of the motor 196, and moves the slider 195 up and down according to the forward and reverse rotation of the motor 196.

Although not shown, the slider 195 is not provided on the end block for fixing the rear end of the charge wire 192, and the end block between the rear end of the charge wire 192 and the photosensitive drum 18 is not shown. The distance is fixed.

The shield case 191 has an opening facing the photosensitive drum 18 and is provided in parallel with the axis of the photosensitive drum 18 at a predetermined interval. By moving the slider 195 up and down, the front end of the charge wire 192 approaches or separates from the photosensitive drum 18, and the inclination angle of the charge wire 192 in the plane perpendicular to the axial direction of the surface of the photosensitive drum 18 changes. It is supposed to. As is well known, the charge wire 19
2 is brought closer to the photosensitive drum 18, the surface potential of the photosensitive drum 18 increases. Therefore, the charge wire 1
By changing the tilt angle of 92, the charged potential of the photosensitive drum 18 is tilted in the axial direction, thereby correcting uneven density of the image formed on the transfer paper in the main scanning direction and reducing fog. You can do it. The correction of the image density in the main scanning direction of the transfer paper will be described later.

FIG. 3 is a sectional view of a main part showing the structure of a second embodiment of the charging device 19. As shown in FIG. The figure shows a slider 195 'having a rod-shaped base 195a' at the upper end,
95a 'is passed through a hole 193b provided in the top plate 193a of the end block 193, and is attached to the end block 193. On the other hand, the contact member 197 having a tapered lower side 197a is attached to the upper end of the base 195a' of the slider 195 '. , So as to be movable in the front-rear direction. The base 195 'is urged upward by a charge wire 192, and the end block 193 is provided by a collar 195b'.
Is prevented from slipping out. The contact member 197 is driven by a motor (not shown). The base member 19 of the slider 195 'is moved by moving the contact member 197 back and forth.
5 'moves relative to the taper 197a,
5 'moves up and down.

Returning to FIG. 1, as a sheet transport mechanism, a sheet feed cassette 24, a sheet feed roller 25, and a pair of registration rollers 26 are arranged in this order from the upstream side in the feeding direction. The paper is fed to the drum 18 and the transfer is performed. As a paper transport mechanism for the transfer paper after the transfer, a transport belt 27, a fixing device 28, a discharge roller pair 29, a paper discharge tray 30, and the like are provided.

The reversing device K is a device disposed between the fixing device 28 and the discharge roller pair 29.
1, a configuration including a reverse running roller 32 and a reversing passage 33. The path switching plate 31 is switched to each position shown by the solid line and the broken line in FIG. 1 to linearly guide the transfer paper from the conveying roller pair 34 to the discharge roller pair 29, and to transfer the transfer paper after fixing. Once carried into the reversing passage 33,
A path for carrying out the sheet to the sheet re-feeding mechanism R in the inverted state is formed. When the reverse running roller 32 is carried out to the sheet re-feeding mechanism R, the position thereof is displaced so as to contact the roller above the discharge roller pair 29.

The re-feed mechanism R forms a return path from the reversing device K to the paper feed side, and includes an intermediate tray 35 for temporarily storing transfer paper, and an intermediate tray 35.
Communication path 36 for transferring the transfer paper to the intermediate tray 35
And a re-feeding path 37 for feeding the transfer sheet again to the image forming means P. On the upstream side of the intermediate tray 35,
Conveying roller pairs 38, 3 constituting the above-mentioned reversing communication path 36
9 and 40, and between them, transport path switching plates 41 and 42 for switching the transport distance to the intermediate tray 35 according to the size of the transfer paper are provided.
The re-feeding end of the printer is provided with a feed roller 43 for feeding stored transfer paper and a density detecting device G to be described later.

In the copying machine 1 having the above-described structure, the light of the halogen lamp 4 is reflected by the original, and the reflected image is transmitted through the reflecting mirrors 6, 7, 8, an imaging lens 10, and a reflecting mirror 9 to the photosensitive member. It is led to the drum 18. The photosensitive drum 18 is shown in FIG.
After being charged to a predetermined voltage by the charging device 19 while rotating in the direction of the arrow, the original image is irradiated and exposed to form an electrostatic latent image. After the electrostatic latent image on the surface of the photosensitive drum 18 is developed by the developing device 20, the electrostatic latent image is transferred by the transfer device 21 onto the transfer paper fed from the paper feed cassette 24. The transfer paper after the transfer is separated from the photosensitive drum 18 by the separation device 22, and is discharged from the discharge tray 3 via the conveyance belt 27, the fixing device 28 and the discharge roller pair 29.
0 is discharged.

On the other hand, when double-sided copying is performed, the path switching plate 31 is switched to the solid line position shown in FIG. Via the communication path 36, the intermediate tray 35
It is stored and stopped with its transfer surface up. Then, at a predetermined timing, the intermediate roller 35 is sent out by the sending roller 43.
The original is transferred to the image forming unit P via the re-feeding path 37, and the original image is again transferred to the back surface of the transfer sheet by the above-described process, and then discharged onto the discharge tray 30.

Here, the above-mentioned concentration detecting device will be described with reference to the drawings. FIG. 4 is a diagram viewed from an arrow A in FIG. 1 showing an example of a density detecting device applied to the copying machine of the present invention.

The density detecting device G includes a density sensor 49 for detecting the image density of the transfer paper 44 stored on the intermediate tray 35, and the density sensor 49 detects the density of the transfer paper 44 in the main scanning direction of the transfer paper 44 (before and after the copying machine 1). (The direction; the direction of the arrow in FIG. 4).

The driving unit 52 includes a front pulley 45 and a rear pulley 46 disposed on both front and rear ends of the intermediate tray 35.
And an endless timing belt 47 mounted between the pulleys 45 and 46, and a stepping motor 48 for driving the front pulley 45 to rotate. The timing belt 48 47 is configured to be rotated forward and backward. The density sensor 49 is connected to the timing belt 4.
7, and is integrally moved back and forth in conjunction with the forward and reverse rotation of the timing belt 47.

The density sensor 49 is, for example, a light emitting element 49
The light emitting element 491 and the light receiving element 492 are positioned on the lower side so that the image density of the transfer paper 44 stored on the intermediate tray 35 can be detected by a reflection type photo sensor or the like including the light receiving element 1 and the light receiving element 492. It is arranged toward. Also,
A detection piece 50 is provided on the timing belt 47, and a position detection sensor 51 for detecting the detection piece 50 is provided near the front pulley 45. Thereby, the movement base point of the density sensor 49 is designated.

In the normal mode, the intermediate tray 3
5 and the density sensor 49
Each of the pulleys 45 and 46 is disposed so as to have a predetermined height from the upper surface of the intermediate tray 35 so that the pulleys 45 and 46 do not interfere with each other.

When the stepping motor 48 is driven by a control device (not shown) in the density detecting device G having the above structure, the timing belt 47 is driven through the front pulley 45.
Is driven to rotate, and the density sensor 49 moves forward to capture the image density of the transfer paper 44 on the intermediate tray 35 in the main scanning direction. Has become.

Next, a block configuration showing a control system for performing image density adjustment in the copying machine will be described with reference to FIG.

In FIG. 3, reference numeral 53 denotes a central control unit (hereinafter, referred to as CPU) for controlling the operation of the copying machine 1.
In addition to controlling a normal image forming operation (hereinafter, referred to as a normal copying mode), an adjusting operation (hereinafter, referred to as an “adjusting operation”) for appropriately and uniformly adjusting the image density of the transferred transfer paper in the main scanning direction.
Image density adjustment mode). In the image density adjustment mode, the CPU 53 adjusts the image density of the transfer paper after transfer in the main scanning direction by adjusting the inclination angle of the charge wire 192 of the charging device 18. 54
Is a mode changeover switch for switching between the normal copy mode and the image density adjustment mode, and is disposed, for example, at an appropriate position on the upper surface of the copying machine main body. Reference numeral 55 denotes a timer for controlling the movement of the first optical system 11 to a predetermined position in order to read the image of the reference document 17 in the image density adjustment mode. Reference numeral 56 denotes a memory in which an appropriate value of the image density of the transfer paper on which the image of the reference document 17 is formed is stored. 57
Is a charging voltage adjusting device that adjusts a charging voltage applied to the charging wire 192 of the charging device 19. For example, an output value of a high-voltage transformer for generating a charging voltage is controlled by the CPU.
The adjustment is performed based on the 53 control signals.

Here, the image density adjustment mode will be briefly described with reference to FIGS.

FIG. 6 shows an example of the image density in the main scanning direction of the transfer paper on which the image of the reference document 17 is formed. The photoconductor drum 18 is charged in a state where the charge wire 192 of the charging device 19 is stretched in parallel with the photoconductor drum 18 in the axial direction. The vertical axis indicates the image density, and the horizontal axis indicates the position of the transfer paper in the main scanning direction. Point A on the horizontal axis indicates the front end position of the transfer paper,
Point B indicates the rear end position of the transfer sheet.

FIG. 3 shows a case where the image density is uniform and proper. Indicates that the image density is high at the front end of the transfer paper and is at the proper density at the rear end position B, and indicates that the image density is high at the rear end of the transfer paper and the appropriate density is at the front end position A. Is shown. Similarly, FIG. 4 shows a case where the image density is dark on the rear end side of the transfer paper, where the image density is lighter than the appropriate density at the front end position A and higher than the appropriate density at the rear end position B.

In the above case, since the image density is uniform and appropriate in the main scanning direction, no fog occurs on the transfer paper, and the image density is not adjusted. on the other hand,
In the case of (2), the image density becomes higher than the appropriate density as it approaches the front end position A, so that the fog easily occurs at the front end of the transfer paper. Therefore, fogging is likely to occur at the rear end of the transfer paper. Therefore, in the cases (1) and (2), the image density is adjusted so that the charging potential of the photosensitive drum 18 is appropriately inclined in the main scanning direction in accordance with the image density inclination, so that the state (1) is obtained.

In the case of (1), fogging is likely to occur at the rear end of the transfer sheet, as in the case of (2), and the image density near the front end position A becomes lower than the appropriate density, making the image hard to see. In this case, the charging potential of the photosensitive drum 18 is appropriately tilted in the main scanning direction in accordance with the tilt of the image density, and the charging density is changed as a whole to adjust the image density. You.

FIG. 7 is a diagram showing a state where the inclination angle of the charge wire 192 for adjusting the image density is adjusted. The vertical axis indicates the distance between the charge wire 192 and the surface of the photosensitive drum 18, and the horizontal axis indicates the distance between the charge wire 192 and the photosensitive drum 18.
2 in the main scanning direction. Point A on the horizontal axis indicates a position corresponding to the front end position of the transfer sheet, and point B indicates a position corresponding to the rear end position of the transfer sheet.

In the same figure, each represents a charge wire 19 for correcting the image density shown in FIG.
2 illustrates an adjustment state.

As described above, when the charge wire 192 is brought close to the photosensitive drum 18, the surface potential of the photosensitive drum 18 increases. Therefore, by inclining the charge wire 192 so that the distance D between the charge wire 192 and the surface of the photoconductor drum 18 increases as the image density becomes higher than the appropriate density, the surface potential of the photoconductor drum 18 becomes main. It can be made uniform in the scanning direction. 7 shows the result of adjusting the inclination of the charge wire 192 according to the change in the image density shown in FIG. In this case, since the image density at the rear end position B of the transfer paper is an appropriate density, the charging voltage applied to the charge wire 192 is not changed, and the front end position A of the charge wire 192 is not changed.
The image density is adjusted simply by moving the image upward.

On the other hand, the inclination of the charge wire 192 is adjusted according to the change in the image density shown in FIG. In this case, the front end position A of the charge wire 192
8, the surface potential at the rear end position A of the photosensitive drum 18 becomes higher than the standard potential Vo, and the image density at the front end position A of the transfer paper becomes the proper density, as indicated by the solid line in FIG. As the density further increases, the surface potential at the rear end position B of the photosensitive drum 18 becomes the standard potential Vo, and the image density at the front end position B of the transfer paper is also higher than the appropriate density.

Therefore, in this case, the charge wire 19
2 changes the charging voltage applied to the charging wire 192, the surface potential of the photosensitive drum 18 changes as a whole according to the amount of the change, so that the voltage applied to the charging wire 192 is set to a value lower than the standard value. As shown by the broken line in FIG. 8, the surface potential of the photosensitive drum 18 is reduced as a whole. As a result, the surface potential at the rear end position A of the photosensitive drum 18 becomes the standard potential V
At the same time, the surface potential at the rear end position B is set to a predetermined value lower than the standard potential Vo, and the image density of the transfer paper can be uniformly and appropriately adjusted in the main scanning direction.

The charging voltage applied to the charge wire 192 may be adjusted in the same manner as described above.

As described above, in the image density adjustment mode,
By adjusting the inclination angle of the charging wire 192 of the charging device 19 and the charging voltage applied to the charging wire 192 according to the image density distribution in the main scanning direction of the transfer paper on which the image of the reference document 17 is formed. The image density of the transfer paper in the main scanning direction is uniformly adjusted.

In this embodiment, the charge wire 19
2 was moved up and down to change the tilt angle of the charge wire 192 in the positive and negative directions.
92 can be moved up and down.
92 may be vertically movable as a whole, and its tilt angle may be changed in both positive and negative directions. In this way, the image density can be adjusted only by adjusting the charge wire 192.

When the charging voltage applied to the charge wire 192 is changed, the surface potential of the photosensitive drum 18 changes as a whole according to the amount of change.

Next, the operation in the image density adjustment mode will be described with reference to the flowchart of FIG.

First, when the image density adjusting mode is selected by the mode changeover switch 54 (step S1), the first mode is selected.
Then, the second optical systems 11 and 12 start going forward (step S2). Subsequently, when the first optical system 11 is detected by the timing switch 15 due to the forward movement of the optical system (Step S).
3) In response, the timer 55 starts counting down for a preset time (step 4), and when the count value becomes 0 (YES in step S5),
The forward movement of the second optical systems 11 and 12 is stopped (Step S)
6). Thus, the first optical system 12 is set at a position below the reference document 17.

Subsequently, transfer paper is fed from the paper supply cassette 24 (step S7), and the image of the reference original 17 is transferred and formed on the transfer paper. The CPU 53 causes the image of the reference document 17 to be exposed at a predetermined timing with respect to the feeding of the transfer paper, and a predetermined range of the leading end of the transfer paper, that is,
The image of the reference document 17 is formed in a range where the density can be detected by the image density detecting device D (step S8). The transfer direction of the transfer paper on which the image is formed is reversed by the reversing device K, and the intermediate tray 35 is reversed by the reversing communication path 36.
Is stored in. Then, when the transfer paper is stored in the intermediate tray 35, the density detecting device G operates, the image density is detected in the main scanning direction of the transfer paper, and this density data is output to the CPU 53 (step S1). S9).

Subsequently, the CPU 53 compares the input density data with the reference density data read from the memory 59, and determines whether or not the density data is within a preset allowable range (step S6). ). If it is within the allowable range, it is determined that image fogging has not occurred, and the process proceeds to step S16 without adjusting the image density, returning the first and second optical systems 11 and 12 to the initial set position and (Step S16) The transfer paper in the intermediate tray 35 is discharged onto the discharge tray 30 (Step S1).
7), the image density adjustment operation ends.

On the other hand, if the image density is out of the allowable range in step S10, that is, if image fogging has occurred (YES in S10), the inclination angle of the charge wire 192 is adjusted based on the detected density data. At the same time (step S11), the charging voltage applied to the charge wire 192 is adjusted (step S12). The adjustment of the inclination of the charge wire 192 and the applied voltage is performed by storing adjustment data in advance in a memory in the CPU 53 as a conversion table, and using the conversion table to set an adjustment value based on the detected density data. Alternatively, the adjustment value may be calculated from error data between the detected density data and the reference density data. Then, the inclination angle of the charge wire 192 is adjusted by driving the motor 196 based on the set or calculated adjustment data, and the output value of the high voltage transformer is adjusted based on the adjustment data to adjust the voltage applied to the charge wire 192. Is done.

Subsequently, it is determined whether or not double-sided copying of the transfer sheet has been completed (step 13). If the double-sided copy of the transfer sheet has not been completed, the photosensitive drum 1 of the transfer sheet is determined.
8 is started (step S14), and step S14 is started.
8, the image of the reference document 17 is formed again on the back surface of the transfer paper in steps S8 to S10, and the image density after the adjustment is confirmed. If the adjusted image density is appropriate (YES in step S10), the process proceeds to step S16, and the image density adjustment operation ends.

On the other hand, if the adjusted image density is not appropriate (NO in step 10), steps S11 and S12 are performed again.
The adjustment of the above-described charge wire 192 is performed.

If the double-sided copying of the transfer sheet has been completed in step 13, the transfer sheet stored in the intermediate tray 35 is discharged to the discharge tray 30 (step 15), and the process returns to step S 7 to return to the sheet cassette 24. , And the above-described adjustment operation is repeated.

In the above embodiment, the reference original 17 is provided in the copying machine 1. However, in the copying machine 1 having no reference source 17, the reference original is placed on the original placing plate. By reading the image of the reference document, the same adjustment operation of the image density can be performed.

A pair of the light emitting element 491 and the light receiving element 4
92, the image density is detected by scanning in the main scanning direction of the transfer paper.
A line sensor for reading an image in the main scanning direction of the transfer paper may be provided downstream of 2, and the image density may be determined by reading the image of the transfer paper on which the image has been formed. In this way, the image density can be detected quickly during the transfer of the transfer paper and the density can be quickly adjusted, and the image density can be adjusted even in a copying machine having no duplex copying function as in the present embodiment. Can be.

In the above embodiment, the image density adjustment mode is selected by the mode changeover switch 54. However, for example, when the main power is turned on or after a predetermined number of images are formed, the image density adjustment mode is automatically set. The mode may be shifted to.

[0060]

As described above, according to the present invention,
The transfer paper on which the image of the reference document is formed is fed to a predetermined position on the transport path, temporarily stopped, the image density of the transfer paper in the main scanning direction is detected, and the charging device is charged based on the detection result. The charging potential of the photoconductor in the main scanning direction is inclined by adjusting the inclination angle of the wire, so even if the image density distribution in the main scanning direction of the transfer paper after transfer becomes uneven, it can be easily performed. Density correction is possible,
Suitable image formation can be performed. In particular, since the image density is adjusted based on the detection data obtained by detecting the image density of the transfer paper after image formation, the image density can be adjusted even when the image density distribution becomes uneven due to a combination of various factors. Correction can be suitably made.

Further, since the reference original is provided in the image forming apparatus, it is not necessary to separately prepare a reference original when adjusting the image density, and the adjustment operation is facilitated.

Further, a re-feeding means for feeding the transfer paper on which the image has been formed to the photoreceptor again is provided. After the image density is adjusted, the transfer paper is fed again, and the image of the reference original is adjusted under the adjusted conditions. Since the image density of the formed transfer paper is checked, the accuracy of the image density adjustment is further improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating an example of a copying machine (image forming apparatus) to which the present invention is applied.

FIG. 2 is a partially cutaway perspective view showing the structure of the charging device.

FIG. 3 is a sectional view of a main part showing a structure of a second embodiment of the charging device.

FIG. 4 is a view as viewed from the direction indicated by the arrow A in FIG. 1 showing an example of a density detecting device applied to the copying machine of the present invention.

FIG. 5 is a block diagram of a control system for performing image density adjustment in the copying machine according to the present invention.

FIG. 6 is a diagram illustrating an example of an image density in a main scanning direction of a transfer sheet on which an image of a reference document is formed.

FIG. 7 is a diagram illustrating a state in which a tilt angle of a charge wire is adjusted in order to correct a tilt of an image density.

FIG. 8 is a diagram showing the surface potential of the photosensitive drum when the inclination angle of the charge wire and the applied voltage are adjusted.

FIG. 9 is a flowchart illustrating an operation in an image density adjustment mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier (image forming apparatus) L Optical mechanism P Image forming means K Reversing device R Refeeding mechanism G Density detecting device 14 Home position switch 15 Timing switch 19 Charging device 191 Shield case 192 Charge wire 193 End block 194 Tension spring 195 , 195 'slider 196 motor 197 contact member 35 intermediate tray 53 CPU 54 mode changeover switch 55 timer 56 memory 57 charging voltage adjusting device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor: Seiichi Kitagawa 1-2-2, Tamazo, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor: Hideki Ishida 1-2-28, Tamazo, Chuo-ku, Osaka Mita (56) References JP-A-3-101767 (JP, A) JP-A-63-173068 (JP, A) JP-A-2-34873 (JP, A)

Claims (3)

(57) [Claims] An image forming apparatus that forms a latent image of an image of a document read by an optical system on a photosensitive member, and then visualizes the latent image to form an image on transfer paper; A charging means having a charging wire stretched at a distance and having a tilt angle in a vertical plane with respect to the axial direction of the photoreceptor surface which can be changed; and a transfer on which an image of a preset reference document is formed Remove the paper at a predetermined position on theconveyance path.
A stop means for detecting the image density distribution of the transfer paper in the main scanning direction; a storage means for storing an appropriate density for the image of the reference document; a detection data from the density detection means; Calculation means for calculating the inclination angle of the charge wire from the appropriate concentration data from the means, and control means for controlling the inclination angle of the charge wire based on the inclination angle calculated by the calculation means. an image forming apparatus comprising. 2. The image forming apparatus according to claim 1, wherein
The optical system is capable of reciprocating , the document mounting plate surface arranged in the reciprocating range is set as a sub-scanning range, while the reference document is in the reciprocating range,
And an image forming apparatus which is provided at a position outside the sub-scanning range and whose lower surface is formed on the lower surface of a member flush with the original placing surface. 3. The image forming apparatus according to claim 1, wherein
Re-feeding means for feeding the transfer paper on which the image has been formed to the photoconductor again, and when the tilt angle of the charge wire is adjusted, the transfer paper on which the image of the reference document is formed is An image forming apparatus comprising: a density detection control unit that re-feeds the image to the photosensitive member, forms an image of the reference document on the transfer sheet, and detects the image density.