JPH11327259A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which improves image quality on recording paper. SOLUTION: A specific voltage (for example, -1.2 'kV') is applied to an auxiliary electrification brush 41 from a high-voltage power source part 15a. Then, before a photoconductive film 31 of a photoreceptor drum 30 is uniformly electrified by an electrifier 40, the photoconductive film 31 is made to electrify in auxiliary by the auxiliary electrification brush 41. Therefore, the photoconductive film 31 is more uniformly electrified by the synergistic effect of the electrification by the auxiliary electrification brush 41 and the electrification by the electrifier 40. Therefore, irregularity in the electrification does not occur on the photoconductive film 31 and a decrease in electrification efficiency does also not occur. Accordingly, a sharp image can be recorded on the recording paper. The image quality on the recording paper can thus be improved.

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 for forming an image using an electrophotographic method.

[0002]

2. Description of the Related Art In recent years, in an image forming apparatus, a method of recording an image on a recording sheet by using an electrophotographic method has been frequently used. The electrophotographic image forming apparatus generally includes a charger for uniformly charging the surface of a photoconductor, an exposure device for irradiating light to the surface of the photoconductor to form an electrostatic latent image, A developing device for forming a toner image by attaching toner supplied from a toner case, a transfer device for transferring the toner image to recording paper, and a heat fixing device for fixing the transferred toner image to recording paper are provided. .

[0003]

In such an electrophotographic image forming apparatus, a conductive brush roller is frequently used as a charger. Then, the conductive brush roller is brought into uniform contact with the photoconductive film on the photosensitive drum to charge the photoconductive film. However,
If the conductive brush roller is used for a long period of time, a portion where the conductive brush roller does not uniformly contact the photoconductive film occurs due to aging or the like. As a result, charging unevenness occurs on the photoconductive film on the photosensitive drum, and charging efficiency is reduced. In this state, when the electrostatic latent image is formed on the photoconductive film by the exposure device, the potential difference between the portion where the electrostatic latent image is formed and the surrounding portion is reduced. For this reason, the amount of toner adhered on the electrostatic latent image by the developing device becomes insufficient, or the toner adheres to the entire photoconductor. as a result,
The resolution of the image transferred to the recording paper is reduced, or the entire image is darkened. In other words, the image quality on the recording paper decreases.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an image forming apparatus capable of improving image quality on recording paper.

[0005]

According to the first aspect of the present invention, there is provided a charging brush roller for charging a photoconductor to a predetermined voltage, and a charging brush roller for charging the photoconductor by the charging brush roller. And an auxiliary charging means for auxiliary charging of the photoreceptor.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the auxiliary charging means is a brush made of a conductive fiber. In the invention according to claim 3,
In the image forming apparatus according to the first or second aspect, the auxiliary charging unit is applied with substantially the same voltage as the voltage applied to the charging brush roller.

In the embodiments of the invention described below, the "image forming apparatus" described in claims or means for solving the problems corresponds to the facsimile apparatus 1, and the "auxiliary charging means" similarly It corresponds to the auxiliary charging brush 41.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an image forming apparatus according to the present invention is embodied in a facsimile machine will be described below with reference to the drawings.

As shown in FIG. 1, a facsimile machine 1
Are MPU 11, ROM 12, RAM 13, reading unit 1
4, a recording unit 15, an operation unit 16, a display unit 17, an image memory 18, a codec 19, a modem 20, and an NCU 21. Each of the units 11 to 21 is connected via a bus 22.

The MPU 11 controls each unit constituting the facsimile machine 1. The ROM 12 stores a program for controlling the facsimile machine 1. RAM 13
Temporarily stores various information on the facsimile machine 1.

The reading section 14 reads image data on a document and outputs black and white binary image data. The recording unit 15 is composed of an electrophotographic printer, and records received image data or image data of a document read by the reading unit 14 on recording paper in a recording operation or a copying operation of received image data. Further, the recording unit 15 includes a high-voltage power supply unit 1 for operating each device constituting the recording process.
5a. In addition, including the high voltage power supply unit 15a,
Details of the recording unit 15 will be described later.

An operation unit 16 is a numeric keypad (including * and # keys) for inputting a telephone number and the like, a registration of abbreviated numbers, abbreviated keys for transmitting from the abbreviated numbers, and an operation for starting an original reading operation. Start key, "Communication (FA
X) Communication for setting "operation" or "copy" operation /
A copy key and various operation keys such as an image quality setting key for setting image quality at reading to “standard”, “high image quality”, and “ultra high image quality” are provided. Display unit 1 such as LCD
Reference numeral 7 displays various information indicating the operation state of the facsimile machine 1 and the like.

An image memory 18 temporarily stores received image data and image data read by the reading unit 14, binarized, and compression-encoded by the codec 19. The codec 19 encodes the image data read by the reading unit 14 for transmission according to the MH, MR, MMR method, or the like. The codec 19 decodes the received image data.

The modem 20 conforms to ITU-T Recommendation T.30. 30 based on a facsimile transmission control procedure according to V.30. 1
7, V. 27ter, V.A. Modulation and demodulation of transmission / reception data in accordance with any one of E.29 and the like. The NCU 21 has a function of controlling connection with the telephone line L and detecting transmission and reception of a dial signal corresponding to the telephone number of the other party.

Next, a specific configuration of the recording section 15 will be described in detail according to a recording process. As shown in FIG. 2, a photoconductor drum 30 as a photoconductor is rotatably supported on a shaft, and a photoconductive film 31 is formed on an outer peripheral surface thereof.

The charger 40 is constituted by a brush roller (charging brush roller) in which a conductive brush is implanted. A predetermined voltage (for example, -1.2 [kV]) is applied to the charger 40 from the high-voltage power supply unit 15a. Charger 40
Charges the photoconductive film 31 of the photosensitive drum 30 uniformly to a predetermined potential (for example, -750 [V]) by the predetermined voltage.

The auxiliary charging brush 41 is formed of a conductive fiber brush. The auxiliary charging brush 41 is provided before the charger 40 in the rotation direction of the photosensitive drum 30. The auxiliary charging brush 41 also has a high-voltage power supply 15
A predetermined voltage (for example, -1.2 [kV]) is applied from a. The auxiliary charging brush 41 auxiliary charges the photoconductive film 31 of the photosensitive drum 30 by the predetermined voltage. That is, the auxiliary charging brush 41 auxiliary-charges the photoconductive film 31 of the photosensitive drum 30 to a predetermined potential (for example, -750 [V]) prior to the uniform charging by the charger 40.

The exposing device 50 includes an LED array 51, and irradiates the photoconductive film 31 of the photosensitive drum 30 with light to form an electrostatic latent image. The developing unit 60 includes a toner case 61 for storing toner, a supply roller 62 disposed below the toner case 61 to which a predetermined voltage (for example, −500 [V]) is applied, and a supply roller 62. The toner case 6 is located between the toner case 6 and the photosensitive drum 30.
1 and a predetermined voltage (for example, -300)
[V]) is applied thereto.
The toner conveyed from the toner case 61 by the supply roller 62 and the developing roller 63 and provided with a negative polarity changes the applied polarity and the potential of the electrostatic latent image formed on the photosensitive drum 30. Thus, the electrostatic latent image is selectively attached to the electrostatic latent image. A toner image is formed on the photosensitive drum 30 by the toner attached to the electrostatic latent image.

A stirring body 64 is rotatably supported in the toner case 61. By the rotation of the stirring body 64, the toner in the toner case 61 is constantly stirred, and the toner is maintained at a uniform density.

The transfer device 90 is provided below the photosensitive drum 30. A predetermined voltage (for example, 600 [V] to 3.5 [kV]) is applied to the transfer unit 90 from the high voltage unit 15a. Then, based on the difference between the predetermined potential and the potential of the toner image, the transfer device 90
The upper toner image is transferred onto recording paper.

The heat fixing device 100 includes a heating roller 101 and a pressure roller 102, and is disposed on the recording paper feed side of the photosensitive drum 30. Then, the heat fixing device 100 is configured such that the recording paper is
02, the toner image on the recording paper is heated and fixed.

In the present embodiment, the auxiliary charging, charging, exposure, development,
A series of processes such as transfer to recording paper and heat fixing are one unit of recording process.

As described above, according to the present embodiment, the following operations and effects can be obtained. (1) Before the photoconductive film 31 of the photosensitive drum 30 is uniformly charged by the charger 40, the photoconductive film 31 is
1 is auxiliary charging. Therefore, the photoconductive film 31 can be more uniformly charged by the synergistic effect of the charging by the auxiliary charging brush 41 and the charging by the charger 40. Therefore, no charging unevenness occurs on the photoconductive film 31 and the charging efficiency does not decrease. As a result, a clear image can be recorded on the recording paper. Therefore, the image quality on the recording paper can be improved.

(2) The auxiliary charging brush 41 is formed of a conductive fiber brush. For this reason, the photosensitive drum 3
The 0 photoconductive film 31 can be auxiliary-charged with a simple configuration.

(3) In addition, the auxiliary charging brush 41 can also serve as a memory removing brush for uniformly dispersing the toner remaining on the photoconductive film 31 of the photosensitive drum 30. Therefore, the memory removal brush can be omitted.

(4) By pre-charging by the auxiliary charging brush 41, the photoconductive film 31 of the photosensitive drum 30 is auxiliary-charged to substantially the same potential as the charging potential by the charger 40. Therefore, a sufficient potential difference between the portion where the electrostatic latent image is formed and the surrounding portion is also ensured. As a result, a sufficient amount of toner attached to the toner image is also ensured. Therefore, clear image quality can be obtained without lowering the resolution.

(5) Charger 40 and auxiliary charging brush 41
Are the same. For this reason, the charger 40
A predetermined voltage (for example, -1.2 [kV]) applied to the auxiliary charging brush 41 can be used as it is. Therefore, there is no need to newly design the high-voltage power supply unit 15a for newly installing the auxiliary charging brush 41.

The present embodiment can be embodied with the following modifications. As shown by a two-dot chain line in FIG. 2, a memory removing brush 91 composed of a conductive brush is disposed between the auxiliary charging brush 41 and the transfer unit 90, and the photoconductor drum 30 after the transfer is transferred.
A configuration may be adopted in which the toner remaining on the upper surface is disturbed to be uniformly dispersed on the photosensitive drum 30.

There is a high possibility that the toner remaining on the photoconductive film 31 of the photosensitive drum 30 after the transfer will adhere to the charger 40 and the auxiliary charging brush 41. Therefore, a so-called cleaning sequence (charging off, development on, transfer on) may be executed before the start of exposure or after the end of transfer. With this configuration, the charger 4
The toner remaining on the zero and auxiliary charging brush 41 can be collected by the developing roller 63 and supplied again from the developing roller 63.

The voltage applied to the auxiliary charging brush 41 is
The voltage may be slightly higher than the voltage applied to the charger 40 (for example, -1.1 [kV]). That is, if the charging potential of the photoconductive film 31 by the charger 40 is -750 [V], the charging potential of the photoconductive film 31 by the auxiliary charging brush 41 may be about -700 [V].

Further, technical ideas other than the claims grasped from the above embodiment will be described below together with their effects. [1] In the image forming apparatus according to any one of claims 1 to 3, control for executing a cleaning sequence for collecting toner adhered to the charging brush roller and the auxiliary charging unit at a predetermined timing. Image forming apparatus provided with means.

In the above embodiment, [1]
The "control means" described in (1) corresponds to the MPU 11, the ROM 12, and the RAM 13. With this configuration, the toner attached to the charging brush roller and the auxiliary charging unit can be collected during the recording process. Therefore, the amount of toner remaining on the photoconductor is reduced. Therefore,
The image quality on the recording paper can be further improved.

[2] The image forming apparatus according to any one of [1] to [3] and [1], wherein the removing means for uniformly dispersing the toner remaining on the photoreceptor after transfer is provided. An image forming apparatus provided before the auxiliary charging unit.

In the above embodiment, the above [2]
The "removal means" described in (1) corresponds to the memory removal brush 91. With this configuration, in addition to the effect of the above [1], the toner remaining on the photoconductor after transfer can be uniformly disturbed and uniformly dispersed on the photoconductor. Therefore, the image quality on the recording paper can be further improved.

[3] A charging brush roller for charging the photoreceptor to a predetermined potential, an exposure device for exposing the charged photoreceptor to form an electrostatic latent image, and attaching toner to the formed electrostatic latent image A developing device for transferring the developed toner image to recording paper, a heat fixing device for heating and fixing the transferred toner image, and a photoconductor between the transfer device and the charging brush roller. An image forming apparatus comprising: an auxiliary charging unit that performs auxiliary charging.

With this configuration, the image quality on the recording paper can be improved.

[0037]

Since the present invention is configured as described above, it has the following effects. According to the invention described in any one of claims 1 to 3, the image quality on the recording paper can be improved.

In particular, according to the second aspect of the invention, in addition to the effect of the first aspect, the photosensitive member can be auxiliary-charged with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a facsimile apparatus according to an embodiment.

FIG. 2 is a partial sectional view showing a recording unit of the facsimile apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Facsimile apparatus as an image forming apparatus, 40 ... Charging brush roller as a charger, 41 ... Auxiliary charging brush as auxiliary charging means.

Claims (3)

[Claims] 1. An image forming apparatus comprising: a charging brush roller for charging a photoconductor to a predetermined voltage; and an auxiliary charging unit for auxiliary charging of the photoconductor before charging the photoconductor by the charging brush roller. 2. The image forming apparatus according to claim 1, wherein the auxiliary charging unit is a brush made of a conductive fiber. 3. The image forming apparatus according to claim 1, wherein the auxiliary charging unit applies substantially the same voltage as the voltage applied to the charging brush roller.