JPH1078706A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing needless transfer to a transfer belt and the grinding of a photoreceptor drum. SOLUTION: This image forming device is provided with a detection means detecting recording paper by observing a transfer control coefficient, a control means controlling the carrying of the recording paper and the recording of an image, and a means(a blade turning-on solenoid 104 and a blade turning-off solenoid 105) for changing a distance between a transfer blade(transfer electrifier) 323 and the photoreceptor drum 342. In this case, the carrying of the recording paper and the recording of the image are controlled and the distance between the blade 323 and the drum 342 is changed in accordance with the detected result by the detection means. By detecting the change of the transfer control coefficient to the blade 323 in the case the recording paper is carried and separating the blade 323 from the drum 342 when abnormality is detected, the needless transfer to the transfer belt 333 and the grinding of the drum 342 are prevented.

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 adopting an electrophotographic system for obtaining an image by transferring toner adhered to a photoreceptor onto recording paper.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, when a recording sheet is conveyed by a motor, a roller, or the like, the recording sheet is detected at various positions to control various sheet feeding operations and is necessary for a copying process. Power supply is controlled.

Here, an example of an image forming apparatus that forms a color image using four photosensitive drums by exposing with LEDs will be described.

FIG. 12 is a block diagram showing a configuration of an LED driving circuit. In the LED driving circuit, a CMYK image signal from an image processing unit (not shown) is converted to a binary conversion unit 20.
1 and sent to the delay units 206 to 209 via the buffer units 202 to 205, respectively. By adjusting the difference in the distance between the leading edge position of the paper and each image forming unit, printing at a predetermined position of four colors is possible. Becomes Note that the LED drive unit 2
10 to 312 generate signals for driving the LED units 214 to 217.

FIG. 13 is a cross-sectional view of an image forming apparatus employing an electrophotographic system. In FIG. 13, 317 is an M image forming section, 318 is a C image forming section, 319 is a Y image forming section,
Reference numeral 320 denotes a K image forming unit, which has the same configuration. Therefore, here, only the M image forming unit 317 will be described, and description of the other image forming units 318 to 320 will be omitted.

In the M image forming unit 317, reference numeral 342 denotes a photosensitive drum, and a latent image is formed on the photosensitive drum 342 by light from the LED unit 214 shown in FIG. 321 is a primary charger, and the primary charger 3
21 prepares a latent image by charging the surface of the photosensitive drum 342 to a predetermined potential.

A developing unit 322 develops a latent image on the photosensitive drum 342 and visualizes it as a toner image. Note that the developing device 322 includes a developing sleeve 345 for applying a developing bias to perform development.

Reference numeral 323 denotes a blade-shaped contact transfer charger, which discharges from the back of the transfer belt 333 and transfers the toner image on the photosensitive drum 342 to recording paper on the transfer belt 333. In the present embodiment, the cleaner is not provided because the transfer efficiency is high, but it goes without saying that there is no problem even if the cleaner is mounted.

In FIG. 13, reference numerals 343 to 345 denote photosensitive drums, 324, 327 and 330 denote primary chargers,
5, 328 and 331 are developing devices, 346 to 348 are developing sleeves, and 326, 329 and 332 are contact transfer chargers.

Next, a procedure for forming an image on a recording sheet will be described.

The recording paper stored in the cassettes 340 and 341 is supplied one by one to the transfer belt 333 by the pickup rollers 339 and 338 by the paper feed rollers 336 and 337. The fed recording paper is charged by an adsorption charger 346.

Reference numeral 348 denotes a transfer belt roller, which drives the transfer belt 333 and, in combination with the attraction charger 346, charges the recording paper and causes the transfer belt 333 to attract the recording paper. Reference numeral 347 denotes a paper edge sensor constituted by a conventional reflection type photosensor, which detects the edge of the recording paper on the transfer belt 333.

The recording paper conveyed by the transfer belt 333 is transferred to the image forming units 317 to 320 by the MC.
A toner image is formed on the surface in the order of YK. The recording paper that has passed through the K image forming unit 320 at the last stage is
After the charge is removed by the charge removing charger 349 to facilitate separation from the transfer belt 333, the toner is separated from the transfer belt 333. Reference numeral 350 denotes a peeling charger, which prevents image disturbance due to peeling discharge when the recording paper is separated from the transfer belt 333.

The separated recording paper is supplied to pre-fixing chargers 351 and 3 in order to supplement the toner attraction force and prevent image disturbance.
After the charging process is performed at 52 and the toner image is heat-fixed at the fixing device 334, the toner image is discharged to a discharge tray 335.

At this time, the detection of the recording paper has been performed by detecting optical interruption or reflection using an optical element such as a photo interrupter.

[0016]

However, when arranging a photo-interrupter or the like in the apparatus, there are places where the installation position is limited spatially or where there is an optically undetectable place.

Further, when transferring the toner to the recording paper, for example, when a transfer voltage is applied by using a blade-shaped contact transfer charger (hereinafter referred to as a transfer blade), the transfer blade is in contact with the photosensitive drum. Then, drum deterioration such as scraping of the photosensitive drum occurs, which affects the life of the photosensitive drum.

Further, when recording paper of an irregular size is used, the recording paper protrudes and is printed on the transfer belt.
The transfer belt becomes contaminated, and the back surface of the recording paper, transfer efficiency deterioration, and the like cause image deterioration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an image forming apparatus capable of preventing unnecessary transfer to a transfer belt and scraping of a photosensitive drum.

[0020]

In order to achieve the above object, the invention according to claim 1 comprises a detecting means for detecting a recording paper by observing a transfer control coefficient, and a control for controlling conveyance of the recording paper and image recording. Means, in an image forming apparatus including means for changing the distance between the transfer charger and the photosensitive drum,
It is characterized in that the control of the conveyance of the recording paper and the image recording and the distance between the transfer charger and the photosensitive drum are changed according to the detection result by the detection means.

According to a second aspect of the present invention, in the first aspect of the present invention, the transfer charger is moved by on / off control of a solenoid to change a distance between the transfer charger and the photosensitive drum. And

According to a third aspect of the present invention, in the first aspect of the present invention, the transfer belt is rotated about one point by a cam to displace the transfer belt with respect to the photosensitive drum, and the distance between the transfer charger and the photosensitive drum is reduced. It is characterized by changing.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the cam rotates the photosensitive drum about one point to displace the photosensitive drum with respect to the transfer belt, thereby reducing the distance between the transfer charger and the photosensitive drum. It is characterized by changing.

Therefore, according to the present invention, a change in the transfer control coefficient to the transfer charger when the recording paper is conveyed is detected, and when an abnormality is detected, the transfer charger is moved away from the photosensitive drum. For example, unnecessary transfer to the transfer belt and scraping of the photosensitive drum can be prevented.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a block diagram showing a configuration of a drive control system of a transfer blade of an image forming apparatus according to Embodiment 1 of the present invention. It is configured to be movable with respect to the belt.
The CPU 101 shown in FIG.
And drives the solenoid 104 for blade-on and the solenoid 105 for blade-off in accordance with the input from the transfer voltage detecting AD converter 410.

FIG. 2 is a circuit diagram of a drive control system of the transfer blade. In FIG. 2, reference numeral 401 denotes a flyback transformer for generating a transfer voltage, L1 denotes a power supply side winding, L2 denotes a load side winding, and L3 denotes a voltage. It is an auxiliary winding for monitoring. Also, 402
Is a transistor for switching the current from the DC power supply VDD to the flyback transformer 401, 403 is a transfer current control circuit, and the transfer current control circuit 403 adjusts the detection value of the transfer current detection resistor R1 so that the transfer current becomes constant. The transistor 402 is PWM-controlled based on the above.

The flyback generated in the power supply side winding L1 is transmitted to the load side winding L2, and the rectifier diode 404
And smoothed by the smoothing capacitor 405 and supplied to the transfer blade 323. The R2 smoothing capacitor 40
A discharge resistor 5 and a leak protection resistor R3.

Reference numeral 410 denotes a transfer voltage detecting AD converter. The CPU 101 monitors the transfer voltage based on a digital output of the transfer voltage detecting AD converter 410.

The transfer blade 323 is controlled by a constant current, and a change in impedance due to the recording paper reaching the transfer blade 323 appears as a change in transfer voltage. This change is shown in FIG. In the present embodiment,
The impedance of the transfer blade 323 is about 1000M
Ω, the transfer current is 1 μA, and a transfer voltage of about 1000 V is generated. The change in impedance due to the recording paper reaching the transfer blade 323 is about 10% in absolute value, and in this embodiment, the point at which the recording paper changes by 5% is defined as the recording paper arrival point. Although only the transfer blade 323 is described here, the transfer blades 326 and 32 shown in FIG.
The same applies to 9,332.

FIG. 4 is a configuration diagram of a drive mechanism of the transfer blade 323.

When the blade-on solenoid 104 is turned on, the transfer blade 323 moves in the direction in contact with the transfer belt 333, and when the blade-off solenoid 105 is turned on, the transfer blade 323 moves in the direction away from the transfer belt 333.

FIG. 5 is a flowchart showing a control operation in the image forming apparatus according to the present embodiment. Hereinafter, the operation will be described with reference to the flowchart shown in FIG.

When the image forming operation starts (S1),
This routine is started with the start of the printing operation (S
2). Since the time required for the recording paper to reach the transfer position can be determined from the transport speed and the apparatus configuration, the time is waited (S3), and the blade-on solenoid 104 is turned on to bring the transfer blade 323 into contact with the transfer belt 333 (S4). .

After a lapse of a predetermined time, by detecting a change in the transfer voltage, it is determined that the recording paper has reached the transfer position (S5). At this time, if the recording sheet has not reached the transfer position, it is determined that a jam has occurred, and a jam processing routine is performed. For example, the motor is stopped to stop the printing operation (S6).

If the recording paper has normally reached the transfer position, printing is started (S7).

It is determined that the recording paper has passed the transfer position by detecting a change in the transfer voltage after the start of printing (S8).

When the passage of the recording paper is detected, it is determined whether the printing is completed at this time (S9). For example, the determination can be made from the recording paper size and the conveyance speed using a soft timer means.

If the size of the recording paper is as set, the printing should have been completed, and the process ends normally (S10).

On the other hand, if the recording paper is irregular or a conveyance error occurs, printing may not be completed even if the recording paper passes. At this time, the blade-off solenoid 105 is turned on, the transfer blade 323 is turned off (separated from the transfer belt 333), and the image forming operation is interrupted (S11).

As described above, the change in the transfer voltage when the recording paper is conveyed is detected, and the transfer blade 323 is detected.
Is turned off, it is possible to prevent unnecessary image formation on the transfer belt 333. Further, by preventing the transfer blade 323 from contacting the photosensitive drum 342 more than necessary, the deterioration of the photosensitive drum 342 can be prevented.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7 are configuration diagrams of a main part of the image forming apparatus according to the second embodiment.
FIG. 8 is a flowchart showing a control operation in the image forming apparatus.

In this embodiment, the transfer belt 333 is configured to be movable with respect to the photosensitive drums 342 to 345. That is, the transfer belt 333 is moved up and down by the belt up / down fulcrum 701 by the belt up / down cam 702.
FIG. 6 shows a state in which the transfer belt 333 is raised. At this time, the transfer belt 333 is
Is in contact with FIG. 7 shows a state where the transfer belt 333 is lowered. At this time, the transfer belt 333 is separated from the photosensitive drums 342 to 345.

The operation will now be described with reference to the flowchart shown in FIG.

S1 to S9 shown in FIG.
Is the same as If the printing is not completed even after the recording paper passes, the transfer belt 333 is lowered as shown in FIG. 7 to interrupt the image forming operation (S13). Thus, the transfer belt 3
By lowering 33, it is possible to prevent unnecessary image formation on transfer belt 333.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. 9 and 10 are configuration diagrams of a main part of the image forming apparatus according to Embodiment 3, and FIG. 11 is a flowchart illustrating a control operation in the image forming apparatus.

In this embodiment, the photosensitive drums 342-3
45 is configured to be movable. That is, the photosensitive drum 342
345 move up and down by a drum up / down fulcrum 703 by a drum up / down cam 704. FIG. 9 shows the photosensitive drum 3
42 to 345 are in a lowered state. At this time, the transfer belt 333 is in contact with the photosensitive drums 342 to 345. FIG. 10 shows a state in which the photosensitive drums 342 to 345 are raised. At this time, the transfer belt 333 is separated from the photosensitive drums 342 to 345.

The operation will now be described with reference to the flowchart shown in FIG.

Steps S1 to S9 shown in FIG. 11 are the same as those in the first embodiment. If the printing is not completed even after the recording paper has passed, as shown in FIG.
5, the image forming operation is interrupted (S14). By raising the photosensitive drums 342 to 345 in this way, it is possible to prevent unnecessary image formation on the transfer belt 333.

[0050]

As apparent from the above description, according to the present invention, detecting means for detecting recording paper by observing a transfer control coefficient, control means for controlling conveyance of recording paper and image recording, and In an image forming apparatus including a unit that changes a distance between a charging unit and a photosensitive drum, control of conveyance of a recording sheet and image recording according to a detection result by the detection unit and a distance between the transfer charging unit and the photosensitive drum Is changed, it is possible to obtain an effect that unnecessary transfer to the transfer belt and scraping of the photosensitive drum can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a drive control system of a transfer blade of an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram of a transfer blade drive control system of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a change in a transfer voltage when a recording paper reaches a transfer blade and when the recording paper passes.

FIG. 4 is a configuration diagram of a transfer blade driving mechanism of the image forming apparatus according to Embodiment 1 of the present invention;

FIG. 5 is a flowchart showing a control operation in the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 6 is a configuration diagram of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing a control operation in the image forming apparatus according to Embodiment 2 of the present invention.

FIG. 9 is a configuration diagram of a main part of an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 10 is a configuration diagram of a main part of an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 11 is a flowchart illustrating a control operation in the image forming apparatus according to Embodiment 3 of the present invention.

FIG. 12 is a block diagram illustrating a configuration of an LED driving circuit of a conventional image forming apparatus.

FIG. 13 is a sectional view of a conventional image forming apparatus.

[Explanation of symbols]

101 CPU (Control Means) 104 Blade-On Solenoid 105 Blade-Off Solenoid 323, 326, 329, 332 Transfer Blade (Transfer Charger) 333 Transfer Belt 342-345 Photosensitive Drum 410 Transfer Voltage Detection AD Converter (Detection Means) 702 Belt vertical cam 704 Drum vertical cam

Claims (4)

[Claims] 1. An image comprising: a detection unit for detecting a recording sheet by observing a transfer control coefficient; a control unit for controlling recording sheet conveyance and image recording; and a unit for changing a distance between a transfer charger and a photosensitive drum. In the image forming apparatus, the control of the conveyance of the recording sheet and the image recording and the change of the distance between the transfer charger and the photosensitive drum are changed according to the detection result by the detection unit. 2. The image forming apparatus according to claim 1, wherein the transfer charger is moved by on / off control of a solenoid to change a distance between the transfer charger and the photosensitive drum. 3. The image forming apparatus according to claim 1, wherein a cam rotates the transfer belt about one point to displace the transfer belt with respect to the photosensitive drum, thereby changing a distance between the transfer charger and the photosensitive drum. apparatus. 4. The image forming apparatus according to claim 1, wherein the cam rotates the photosensitive drum about one point to displace the photosensitive drum with respect to the transfer belt, thereby changing a distance between the transfer charger and the photosensitive drum. apparatus.