JPS6197669A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To maintain the surface potential of a photosensitive body at good level so as to perform excellent printing in which the brightness is uniform, by constituting an electrophotographic device in such a way that, when the surface potential of the photosensitive body immediately after a charging section is charged is too high, the high pressure level is lowered and, when the surface potential is too low, the high pressure level is raised. CONSTITUTION:The surface potential of a photosensitive body 2 is measured by means of a measuring instrument 32 and the high-pressure level of a high- pressure generator 29 which supplies high pressure to an electrostatic charger 3 is adjusted in accordance with the output of the instrument 32. By measuring the surface potential of the photosensitive body 2 immediately after the body 2 is charged by the charging section 3, the charged level of the photosensitive body 2 at the first time of using is lowered even when the sensitivity is too high and the surface potential is controlled at an almost fixed level, and thus, excellent printing i which the brightness is kept uniform, can be performed always.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention includes at least a charging section, an exposure section, and a developing section that are sequentially arranged along the moving direction of the photoconductor, and the photoconductor charged in the charging section. The present invention relates to an improvement in an electrophotographic apparatus that forms an image on a photosensitive surface in an exposure section and further develops it in a development section to obtain a photographic image.

[Prior Art] Conventionally, in this type of electrophotographic apparatus, exposure and development were performed sequentially without taking any measures to prevent the surface potential of the photoreceptor from becoming abnormally high due to charging by the charging section. It was used to obtain electronic photographs.

[Problems to be Solved by the Invention] By the way, in this type of device, when the photoconductor is in a new state, and when it is used for the first time or after not being used for a while, the photoconductor is The sensitivity may become too good and the surface potential due to charging may become abnormally high. However, since the above-mentioned conventional apparatus does not have any countermeasures, in such a case, the image formation by exposure becomes insufficient, resulting in the resulting electrophotograph being too dark, resulting in the problem of not being able to obtain a high-quality electrophotograph. Ta.

This invention was made to solve such problems.When the surface potential of the photoreceptor due to charging becomes abnormally high, the charging on the photoreceptor is weakened, and the surface potential of the photoreceptor due to charging is reduced. When the electrostatic charge becomes too high, the electrostatic charge on the photoreceptor is strengthened, so that the surface potential of the photoreceptor can always be kept at a good potential, and the electrophotographic device can always obtain high-quality electrophotographs with approximately constant brightness. The purpose is to provide.

[Means for Solving the Problems] The present invention includes at least a charging section, an exposing section, and a developing section that are sequentially arranged along the moving direction of the photoconductor, and the photosensitive surface of the photoconductor charged by the charging section is In an electrophotographic apparatus that forms an image in an exposure section and further develops it in a development section to obtain a photographic image, a surface potential measuring device is installed between the charging section and the exposure section and measures the surface potential of the photoreceptor; A high voltage generator that supplies a high voltage to the charging section, and a level adjustment circuit that adjusts the level of the high voltage supplied from the high voltage generator to the charging section according to the level of the surface potential measured by a surface potential measuring device, The level adjustment circuit adjusts the high voltage level supplied to the charging section to be low when the surface potential level is high, and adjusts the high voltage level supplied to the charging section to be high when the surface potential level is low. It is.

[Function] In the present invention having such a configuration, the surface potential of the photoreceptor immediately after being charged by the charging section is measured with a measuring device, and when the surface potential is too high, the high voltage level supplied to the charging section is lowered. When the surface potential becomes too low, the high voltage level supplied to the charging section is increased to strengthen the charging, thereby keeping the surface potential of the photoreceptor substantially constant.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the present invention will be described as applied to an electrophotographic printer using a laser.

FIG. 1 shows the overall configuration, and 1 is a casing. A photosensitive drum 2 as a photosensitive member having a photosensitive surface formed along the outer periphery is installed in the center of the housing 1, and the photosensitive drum 2 is rotated at a constant speed by a motor (not shown). Along the circumference of the photosensitive drum 2,
A charger 3 forming a charging section, a generator 5 for scanning laser beam 4 forming an exposure section, a developing section 6, a transfer section 7 having a transfer charger, a static elimination lamp 8 forming a static elimination section, and a wiping roller 9 are provided. has been done.

An insertion slot 1 for a paper feed cassette 10 is provided at the lower side of the housing 1.
1 is formed between the insertion opening 11 and the transfer section 7, and a paper feed roller 13 and a paper feed guide 1 for guiding the paper 12 stored in the paper feed cassette 10 to the transfer section 7.
4 is provided.

Note that a paper insertion section 15 for manually feeding paper is also provided on the side surface of the housing 1.

On the opposite side of the transfer section 7 to the paper feed guide 14, a conveyor 16 and two fixing rollers 17a, 17 are provided.
A fixing section 18 consisting of b is provided.

As shown in FIG. 2, the laser beam generating device 5 includes a laser light emitting element 51 that is turned on and off according to information;
A rotating polygon mirror 52 and an fθ lens 53 that horizontally scan the laser light from the light emitting element 51, a scan start position sensor 54, a scan end position sensor 55, and each sensor 54, 55 are irradiated with laser light, respectively. Reflecting mirrors 56 and 57 direct the laser beam to the photosensitive drum 2.
and a mirror 58 for directing the light to the photosensitive surface.

FIG. 3 is a block diagram showing the circuit configuration, and 21 is a CPU (central processing unit) constituting the control section, and 22 is a CPU 21.
23 is a character generator, and 24 is a RAM (random access memory) in which the program data for controlling each part is stored. ), 25 is an interface for taking in information from the outside, 26 is various sensors 27 such as the scan start sensor 54 and scan end sensor 55, various lamps 28 such as the static elimination lamp 8, and high voltage is applied to the charger 3. It performs input/output control for various motors 30 such as the high-pressure generator 29 that supplies the photosensitive drum 2 and the motor that rotationally drives the rotating polygon mirror 52, and also transmits information to the laser beam generator M5. This is an I10 boat that controls the output of Said cpu21 and ROM2
2. Character generator 23, RAM 24, interface 25, I10 port 26 and pass line 31
connected by. The CPU 21 receives information input from the outside via the interface 25.
When storing the information in the AM 24 and subsequently printing the information, the character generator 23 converts the information into character pattern information and then outputs the information to the laser beam generator 5 via the I10 boat 26.

Further, the CPU 21 sends information to various sensors 27 via the I10 boat 26 based on the program data in the ROM 22.
, various lamps 28, high pressure generator 29 and various motors 3o
selectively 1liIII. The high voltage generator 29 is also controlled by a level adjustment circuit 33 which adjusts the high voltage level in response to the measured output of the surface potential meter 32.

That is, as shown in FIG.
is provided between the electrostatic charger 3 and the laser irradiation part R from the laser beam generator 5, and the surface potential measuring device 32
The surface potential of the photosensitive surface of the photosensitive drum 2 is measured, and a voltage signal proportional to the magnitude of the surface potential is output. The output from the surface potential measuring device 32 is connected to the level adjustment circuit 3.
3. The level adjustment circuit 33 includes a resistor 34
．． 35 connected in series, and an operational amplifier 36 having one input terminal (+) connected to the voltage dividing point output of this voltage dividing circuit. The other input terminal (-) of the operational amplifier 36 is grounded via a resistor 37 and connected to an output terminal via a resistor 38. In the level adjustment circuit 33, the output of the surface potential measuring device 32 is applied to the voltage dividing circuit, and the output of the operational amplifier 36 is supplied to the high voltage generator 29. The operational amplifier 3
The output vO of 6 is given by (Re + RF)/R8XV8. Note that R8 is the resistance value of the resistor 37, and Rp is the resistance value of the resistor 3.
The resistance value of 8, Vs is the output of the voltage dividing point of the voltage dividing circuit.

The two high voltage generators set the high voltage level supplied to the charger 3 to be low when the input level from the operational amplifier 36 increases, and conversely, when the input level from the operational amplifier 36 decreases, the high voltage level is supplied to the charger 3. The high pressure level to be used is set at a high level.

In the apparatus of the present invention having such a configuration, the surface potential of the photosensitive drum 2 is always measured by the surface potential measuring device 32 immediately after charging, and if the surface potential is abnormally high, the calculation is performed. As the output level of the amplifier 36 increases, the level of the high voltage supplied from the high voltage generator 29 to the charger 3 is lowered, and the charging of the photosensitive surface of the photosensitive drum 2 is weakened. As a result, the surface potential of the photosensitive surface decreases, and even if the photosensitive surface is too sensitive, such as when using it for the first time or after not using it for a while, the charge is weakened and the exposure Image formation by the laser is performed well in the area, and the brightness is approximately constant from the first use, making it possible to perform high-quality printing.

Furthermore, when the surface potential of the photosensitive surface becomes too low, the output level of the operational amplifier 36 is lowered, so that the level of high voltage supplied from the high voltage generator 29 to the charger 3 is increased, and the photosensitive surface of the photosensitive drum 2 is charged. strengthen. As a result, the surface potential of the photosensitive surface increases, and in this case as well, image formation by the laser at the exposed area is performed well.
Brightness is approximately constant and high-quality printing can be performed.

Therefore, no matter what the sensitivity of the photosensitive surface of the photosensitive drum 2 is, by varying the charging state, the surface potential of the photosensitive surface can be kept approximately constant, and as a result, the brightness is always constant. You can obtain high-quality electronic photographs.

In the above embodiments, the present invention was applied to a laser electrophotographic printer, but the present invention is not necessarily limited to this, and can also be applied to a normal copying machine.

[Effects of the Invention] As detailed above, according to the present invention, the degree of charging is changed according to the state of the surface potential of the photoreceptor, and the surface potential is controlled to be approximately constant before exposure and development are performed. By performing this operation, it is possible to provide an electrophotographic apparatus that can always obtain high-quality electrophotographs with substantially constant brightness.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which FIG. 1 is a diagram showing the overall configuration, FIG. 2 is a perspective view showing the configuration of the laser beam generator, FIG. 3 is a block diagram showing the circuit configuration, and FIG. 4
The figure is a diagram showing the circuit configuration of the main part. 2... Photosensitive drum (photosensitive member), 3... Charger (charging section), 5... Laser beam generator (exposure section), 6... Developing section, 21... CPU (central processing unit) ), 22...ROM (read-only memory), 29...High voltage generator, 32...Surface potential measuring device, 33...Level adjustment circuit. Applicant's representative: Rishiki I, Takehiko Suzue No. 1 Figure 3

Claims (1)

[Claims] At least a charging section, an exposing section, and a developing section are sequentially disposed along the moving direction of the photoconductor, and the exposing section forms an image on the photosensitive surface of the photoconductor charged by the charging section, and An electrophotographic apparatus that obtains a photographic image by developing in a developing section includes a surface potential measuring device that is installed between the charging section and the exposure section and measures the surface potential of the photoreceptor, and a high voltage is applied to the charging section. A high-voltage generator for supplying the voltage, and a level adjustment circuit for adjusting the level of the high voltage supplied from the high-voltage generator to the charging section according to the level of the surface potential measured by the surface potential measuring device, and the level adjustment circuit is characterized in that when the surface potential level is high, the high voltage level supplied to the charging section is adjusted to be low, and when the surface potential level is low, the high voltage level supplied to the charging section is adjusted to be high. electrophotographic equipment.