JPH03153263A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To suppress deterioration caused by the fatigue of a whole photosensitive body by operating a main electrifier and a transfer electrifier only for a printing part which is the minimum necessary part of the photosensitive body. CONSTITUTION:A control part 7 detects the printing part on the surface of the photosensitive body corresponding to the image part of a printing pattern from the printing pattern stored in a storage part 8. Then, when it detects the facing state of the printing part and the main electrostatic charger 2 based on the position of the printing part and the output of a moving position detection means 9, it turns on the charger 2, and turns on the transfer electrifier 4 when it detects the facing state of the printing part and the charger 4. Besides, the control part 7 turns off the electrifier 2 when it detects the facing state of a nonprinting part and the electrifier 2 and turns off the electrifier 4 when it detects the facing state of the nonprinting part and the electrifier 4. Therefore, the electrifier 2 and the charger 4 are operated only for the printing part of the photosensitive body by the control action of the control part 7 with respect to the electrifier 2 and the electrifier 4. Thus, the deterioration caused by the fatigue of the whole photosensitive body is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic apparatus such as a laser printer that prints based on a print pattern stored in a storage unit.

[Conventional technology]

Conventionally, electrophotographic laser printers irradiate the surface of the photoreceptor, which has been charged to a predetermined potential with a main charger, with laser light in accordance with a printing pattern stored in a storage section. forming an electrostatic latent image;
This electrostatic latent image is developed with toner, and the resulting toner image is transferred onto transfer paper using a transfer charger. The toner image on the transfer paper is then fixed on the transfer paper to obtain a desired image on the transfer paper.

[Means to solve the problem]

However, in the above-mentioned conventional laser printer, regardless of the printed portion in the image area of the photoreceptor surface corresponding to the image portion of the printed pattern stored in the storage section, and the non-printed portion that is a portion other than the printed portion, The main charger and transfer charger are turned off during or near the rotation of the photoreceptor.
It is in the N state. For this reason, since both chargers are turned on even in a non-printing area where turning on of the main charger and transfer charger is unnecessary, deterioration due to fatigue of the photoreceptor is accelerated. That is, as shown in FIG. 4, for example, the dark area surface potential a1 and the bright area surface potential a when the transfer charger is used are different between the case where the transfer charger is not used and the case where the transfer charger is used.

In contrast, as the amount of copies increases, the dark area surface potential b decreases when a transfer charger is used, and the bright area surface potential b decreases.
2 rises. This indicates that even when the photoreceptor is charged by the main charger, the surface potential of the dark area does not increase sufficiently, and the surface potential of the bright area does not decrease sufficiently when exposed to light. If the photoreceptor deteriorates in this way, the density of the resulting image will decrease and lines will become thinner.

In particular, in the case of the reversal development method, the charge applied from the transfer charger to the photoreceptor has a reverse property with respect to the surface potential of the photoreceptor, which has the problem of further accelerating deterioration of the photoreceptor. There is.

[Means to solve the problem]

In order to solve the above-mentioned problems, an electrophotographic apparatus of the present invention has the surface of a photoreceptor charged to a predetermined potential by a main charger, and emitted from an exposure device according to a print pattern stored in a storage section. By being exposed to light, an electrostatic latent image is formed on the surface of the photoconductor, and this electrostatic TrL latent image is developed by a developing device to form a toner image, and this toner image is transferred to a transfer paper by a transfer charger. The following measures have been taken in the electrophotographic device that transfers images.

That is, a moving position detection means of the photoreceptor detects a printed part on the surface of the photoreceptor corresponding to an image part of the printed pattern from the printed pattern stored in the storage section, and detects the position of this printed part and the moving position detection means. Based on the output of The main charger is turned off when it detects that the non-printing area, which is a part other than the printing area on the surface of the photoconductor, faces the main charger, and when it detects that the non-printing area and the transfer charger face each other, and a control section that turns off the transfer charger.

[For production]

According to the above configuration, the control unit detects, from the print pattern stored in the storage unit, a printed portion on the surface of the photoreceptor that corresponds to an image portion of the print pattern. Then, when the position of the printing section and the output of the movement position detecting means detect the facing state of the printing section and the main charger, the main charger is turned on, and the facing state of the printing section and the transfer charger is detected. When detected, the transfer charger is turned on. Further, the control unit turns off the main charger when it detects that the non-printing area, which is a part other than the printing area on the surface of the photoconductor, faces the main charger, and turns off the main charger, so that the non-printing area and the transfer charger face each other. When the state is detected, the transfer charger is turned off.

As mentioned above, in an electrophotographic device such as a laser printer that forms an electrostatic latent image by exposing the surface of a photoconductor with light emitted from an exposure device based on a print pattern stored in a storage section, reflection from a document is Unlike a copying machine that exposes a photoreceptor to light, it is possible to identify printed areas and non-printed areas on the surface of the photoreceptor in advance before an image forming operation. Therefore, the main charger and the transfer charger can be operated only when facing the printed portion on the surface of the photoreceptor.

Due to the control operation of the control unit for the main charger and transfer charger as described above, the main charger and transfer charger act only on the printed area of the photoreceptor, and the entire photoreceptor is Deterioration due to fatigue is suppressed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

A laser printer is an electrophotographic device using a reversal development method.
As shown in FIG. 2, a photoreceptor drum 1 having an organic photoreceptor is provided. Around the photoreceptor drum 1, there is a main charger 2 that charges the surface of the photoreceptor drum 1 to a predetermined potential;
A developing device 3 having a developing magnet roller 3a, which develops the electrostatic latent image formed on the surface of the photoreceptor drum 1 into a toner image, and transfers the toner image on the surface of the photoreceptor drum 1 onto a transfer paper (not shown). It is equipped with a transfer charger 4 and a cleaning device ra, 5 for removing residual toner on the surface of the photoreceptor. The main charger 2 and the transfer charger 4 are corona chargers, and have charger wires 2a and 4a, respectively.

A laser beam for exposing the surface of the photoreceptor drum 1 to form an electrostatic latent image is applied to the surface of the photoreceptor drum 1 between the main charger 2 and the developing device 3 as shown in FIG. The laser beam is irradiated from a laser beam irradiation device 6. This laser beam irradiation device 6 is connected to a control section 7, and this control section 7
Further connected are a storage section 8 for storing print patterns, a timer 9 as a movement position detecting means for measuring a predetermined time, and the main charger 2 and transfer charger 4 described above.

The control section 7, storage section 8, and timer 9 described above are constituted by a microcomputer.

The control section 7 controls the operation of the main charger 2 and the transfer charger 4 based on the print pattern stored in the storage section 8 and the timing operation of the timer 9. That is,
By reading the print pattern stored in the storage unit 8, the control unit 7 controls the print area B and the photoreceptor drum 1 on the surface of the photoreceptor drum 1, as shown in FIG.
It is possible to identify the non-printed portion, which is a portion other than the printed portion on the surface. In Fig. 3, this non-printing area corresponds to, for example, the area A between the first transfer paper and the corresponding printing area B, and the area A between the first transfer paper and the corresponding printing area B and the second transfer paper. Furthermore, the control section 7 can detect the timing at which the printing section B and the main charger 2 or the transfer charger 4 face each other by the timing operation of the timer 9. can. Therefore, at the timing when the printing area B on the surface of the photosensitive drum 1 and the main charger 2 or the transfer charger 4 face each other, the control unit 7 controls the main charger 2 and the transfer charger 4 to ONL and non-printing, respectively. At the timing when the main charger 2 or the transfer charger 4 faces each other, control is performed to turn off the main charger 2 and the transfer charger 4, respectively. Furthermore, the control unit 7 controls the laser beam irradiation device 6 so that the laser beam is irradiated to the printed portion B on the surface of the photoreceptor drum 1 according to the print pattern stored in the storage unit 8. It has become.

In the above configuration, when the laser printer operates and the photosensitive drum 1 starts rotating, the timer 9 starts timing operation. The control unit 7 controls the photosensitive drum 1 based on the print pattern stored in the storage unit 8 and the timing operation of the timer 9.
The main charger 2 is turned on only at the timing when the print part B and the main charger 2 face each other. As a result, only the printed portion B on the surface of the photoreceptor drum 1 is charged by the main charger 2 to a predetermined dark area potential.

Next, the printed portion B on the surface of the photoreceptor drum 1 is irradiated with laser light from the laser light irradiation device 6 controlled by the control section 7 . As a result, the potential of the laser beam irradiated portion in the printing portion B decreases, and an electrostatic latent image is formed.

Next, the electrostatic latent image on the printed portion B is developed by the developing device 3 and becomes a toner image. At this time, the toner is a negatively charged toner and adheres to a portion of the electrostatic latent image whose potential has decreased due to exposure.

Next, the control unit 7 detects the facing state of the print portion B on the surface of the photosensitive drum 1 and the transfer charger 4, and turns on the transfer charger 4 only in the tamping when both face each other. As a result, the toner image on the printing section B is transferred to the transfer paper supplied from the paper feeding section (not shown). The toner image transferred to the transfer paper is then fixed to the transfer paper by a fixing device (not shown).

As described above, since the main charger 2 and the transfer charger 4 are controlled to operate only at the timing when they face the printed portion B on the surface of the photoreceptor drum 1, deterioration of the photoreceptor drum 1 due to fatigue is suppressed. Furthermore, since the operating time of the main charger 2 and the transfer charger 4 is reduced, the lifespan of both charger wires 2a and 4a can be extended.

In this embodiment, the moving position detection means of the photoreceptor is a timer 9.
Consisting of, but not limited to,
For example, it is possible to use something that can detect the rotational position of the photosensitive drum 1, such as a low-resolution encoder.

〔Effect of the invention〕

As described above, the electrophotographic apparatus of the present invention detects the printed portion on the surface of the photoreceptor corresponding to the image portion of the print pattern from the photoreceptor movement position detection means and the print pattern stored in the storage section. , from the position of the printing section and the output of the movement position detection means, when the facing state of the printing section and the main charger is detected, the main charger is turned on, and the facing state of the printing section and the transfer charger is detected. When the transfer charger is turned on, the transfer charger is turned on, and when it is detected that the main charger faces the non-printed area on the surface of the photoconductor other than the printed area, the main charger is turned off, and the transfer charger is turned off to separate the non-printed area and the transfer charger. The transfer charger is configured to include a control unit that turns off the transfer charger when a state in which it faces the charger is detected.

Therefore, since the main charger and transfer charger act only on the printing area, which is the minimum necessary part of the photoreceptor, deterioration due to fatigue of the photoreceptor as a whole is suppressed, and good images can be maintained over a long period of time. This has the effect of being able to obtain the following.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of the main parts of an electrophotographic apparatus. FIG. 2 is an explanatory diagram showing the structure around the photoreceptor drum. FIG. 3 is an explanatory diagram showing the operation timing of the main charger and the transfer charger. FIG. 4 shows a conventional example, and is a graph showing changes in bright area surface potential and dark area surface potential with respect to copy amount when a transfer charger is used and when a transfer charger is not used. 1 is a photosensitive drum, 2 is a main charger, 3 is a developing device, 4 is a transfer charger, 5 is a cleaning device, 6 is a laser beam irradiation device, 7 is a control section, 8 is a storage section, 9 is a timer (moving position detection means).

Claims (1)

[Scope of Claims] 1. The surface of the photoreceptor is charged to a predetermined potential by a main charger and exposed to light emitted from an exposure device in accordance with a print pattern stored in a storage unit, In an electrophotographic apparatus, an electrostatic latent image is formed on the surface of a photoreceptor, this electrostatic latent image is developed by a developing device to form a toner image, and this toner image is transferred to transfer paper by a transfer charger. detecting a printed portion on the surface of the photoreceptor that corresponds to an image portion of the print pattern from the photoreceptor movement position detection means and the print pattern stored in the storage unit;
Based on the position of the printing section and the output of the movement position detection means, when the facing state of the printing section and the main charger was detected, the main charger was turned on, and the facing state of the printing section and the transfer charger was detected. At times, the transfer charger is turned on, but when it is detected that the main charger faces a non-printing area on the surface of the photoconductor other than the print area, the main charger is turned off, and the transfer charger is turned off. Turn the transfer charger to O when it detects that it is facing the device.
An electrophotographic apparatus comprising: a control unit for FF.