JPH05216301A - Process cartridge for image forming device - Google Patents

Abstract

PURPOSE:To facilitate the replacement of a constant voltage element which determines a grid voltage of an electrification electrode fixed in a process cartridge together with a photosensitive drum. CONSTITUTION:The process cartridge 20 attached to an image forming device is composed of the photosensitive drum 3, the electrification electrode 4, a cleaner 10, a housing 21 for holding them, and a unit cover 22 attached to the housing 21. A contact piece 26 for connection is attached to the unit cover 22 together with the Zener diode 25 which determines a grid voltage of the electrification electrode 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the arrangement of constant voltage elements that determine the grid voltage of a grid provided on a strip electrode.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus such as a copying machine or an image scanner comprises a platen on which a document is placed, a document irradiation lamp which reciprocates below the platen, a reflection mirror, and a fixed projection lens and a reflection mirror. A photosensitive drum that is endlessly rotated by a scanning optical system and a band electrode that are charged with a predetermined potential, and toner is applied to the electrostatic latent image formed on the surface of the photosensitive drum by the scanning optical system. A developing device for developing the toner image, a transfer electrode for transferring a toner image onto a recording paper surface which is a transfer material conveyed below the surface of the photosensitive drum, a separation electrode and a removing electrode, and the recording paper surface. The fixing device fixes the toner image transferred onto the surface of the photosensitive member, and the cleaning device removes the toner and paper dust remaining on the surface of the photosensitive member after the transfer. In recent popular copying machines and the like, for example, a process cartridge in which a band electrode, a photosensitive drum, a cleaning device, and the like are unitized is detachably attached to an image forming apparatus, thereby making it considerably compact.

Then, desired toner images are successively recorded on the surface of the recording paper which is intermittently conveyed along a predetermined conveying path. Conventionally, the grid voltage applied to the grid of the strip electrode unit is determined by a constant voltage element such as a varistor or a zener diode arranged in the electrode block portion of the strip electrode.

[0004]

Since the charging performance of a photosensitive drum usually varies depending on the manufacturing process and manufacturing lot, it is necessary to adjust or change the charging condition according to the charging performance.

As a countermeasure against this, a technical means disclosed in Japanese Patent Application Laid-Open No. 59-147376 is disclosed. This means for adjusting the charging potential of the photosensitive member uses a constant voltage element such as a varistor or a zener diode in combination with a variable resistor. I am trying to adjust it. Therefore, since the variable resistor is used, not only is it costly, but its adjustment is very troublesome. It is also already known that a constant voltage element is selected without using a variable resistor so as to correspond to the charging performance of a photosensitive drum incorporated in a cartridge. In general, both ends of the strip electrode in the longitudinal direction are provided with electrode blocks which are connected to a high-voltage power supply by tensioning the electrode wires, and the electrode block openings which are opened to attach the electrode wires are stretched. After installation, a lightning strike prevention plate is attached in a hermetically sealed state. Conventionally, a varistor and a zener diode are attached to the electrode block side, and if they are to be replaced, the lightning protection plate must be removed and rewiring must be carried out, which requires a lot of labor and time.

It is an object of the present invention to provide a process cartridge of an image forming apparatus which solves the above problems and can easily replace a constant voltage element that determines a grid voltage of a strip electrode.

[0007]

To this end, in a process cartridge in which at least an image carrier and a charging unit are unitized and detachably mounted in an image forming apparatus, a grid voltage of a grid provided in the charging unit is determined. The present invention is achieved by a process cartridge of an image forming apparatus characterized in that a constant voltage element is provided on a unit cover of the process cartridge.

[0008]

1 is a side sectional view showing the structure of a process cartridge of FIG. 1, a top view showing the structure of a band electrode of FIG. 2, and a side sectional view showing the structure of an image forming apparatus of FIG. Explained by. However, the present invention is not limited to this embodiment.

As shown in FIG. 3, an electrophotographic image forming apparatus 18 is provided.
A platen glass P for placing a document M is provided on the upper surface of the main body 1, and a scanning optical system 2 is provided below the platen glass P in the main body 1. The scanning optical system 2 includes a reciprocating document irradiation lamp 2a, a first mirror 2b, second and third mirrors 2c forming a V shape, and a fixed lens 2.
d and the fourth mirror 2e. A photosensitive drum 3 is rotatably provided in the direction of the arrow at the center of the inside of the main body 1, and a belt electrode 4 for uniformly charging the photosensitive body 3a along the rotation direction is provided around the photosensitive drum 3, and a toner replenishing device. Developing device 6 that is replenished with toner by 5 and has a developing sleeve 6a built-in;
A transfer electrode 7, a separation electrode 8, a charge eliminating electrode 9, and a cleaning device 10 are sequentially arranged. Paper cassette 11,
Two types of recording papers of different sizes are housed in 11 'and set in the main body 1. 12 is a paper cassette 11
Is a first paper feed roller that feeds the recording paper stored in to a standby position before the second supply roller 13, and is a roller 12a that is rotated via a belt to prevent double feeding of the recording paper.
12a and a stop roller (also referred to as a separating roller) 12b. Reference numeral 13 is an appropriate timing so that the recording paper fed by the first paper feed roller 12 is temporarily stopped at the standby position, and then the front end of the visible image on the photoconductor 3a and the front end of the recording paper are aligned at the transfer position. The second paper feed roller 14 that feeds paper again toward the transfer position at 14 is a guide plate for guiding the recording paper fed by the first paper feed roller 12 to the position of the second paper feed roller 13, It is opened and closed by operating a lever (not shown) so that the jammed paper can be taken out by inserting a hand. Reference numeral 15 is a conveying device that conveys the recording paper after transfer to a fixing position, and the fixing device 16 is a heating roller.
16a and pressure roller 16b. Reference numeral 17 denotes a paper discharge roller that discharges the recording paper after fixing to the outside of the main body. The belt electrode 4, the photosensitive drum 3, and the cleaning device 10 are unitized as a process cartridge 20 surrounded by a solid line and are detachably attached to the image forming device 18. The process cartridge 20 may include the developing device 6 and the transfer electrode 7 in addition to the above-described structure, or may include only the photosensitive drum 3 and the band electrode 4.

When the copy button is operated in the above apparatus, the original M on the platen glass P is exposed and scanned by the scanning optical system 2, and an electrostatic latent image of the original M is formed on the photoconductor 3a of the photoconductor drum 3. It This electrostatic latent image is developed by the developing device 6.
To form a visible image, and this visible image is transferred by the transfer electrode 7 to the recording paper fed from one of the paper feed cassettes 11 and 11 'of the main body 1. After the transfer, the recording paper is separated from the photoconductor 3a by the separation electrode 8 and is fixed by the conveying device 15
The sheet is conveyed to 16, fixed there, and ejected by the ejection roller 17.

In this way, desired toner images are successively recorded on the recording paper surface. In the present invention, a constant voltage element for applying a constant voltage to the grid of the strip electrode 4 mounted in the process cartridge mounted in the image forming apparatus 18 is arranged as follows.

As shown in FIG. 1, the process cartridge 20 mounted on the image forming apparatus 18 includes a photosensitive drum 3 rotating in the direction of the arrow, a belt electrode 4 located above the photosensitive drum 3, and a cleaning located on the left side of the photosensitive drum 3. Consisting of device 10 and
The photoconductor drum 3 is rotatably supported on both side walls of the cartridge housing 21 in the width direction (perpendicular to the paper surface), and the belt electrode 4 and the cleaning device 10 are parallel to the shaft center of the photoconductor drum 3 as described above. It is attached to the housing 21 at a predetermined position. Then, the unit cover 22 is fitted to a predetermined position of the cartridge housing 21 and screwed to form the process cartridge 20. The widthwise dimension of the process cartridge 20 is, for example, such a length that the photosensitive drum 3, the belt electrode 4, and the cleaning device 10 capable of recording a toner image in the widthwise direction of B4 size recording paper are mounted. . As shown in FIGS. 1 and 2, the strip electrode 4 detachably mounted in the process cartridge 20 has a rectangular box-shaped left electrode block having an opening 4f whose upper surface is open. Side plates 4c are attached to both side surfaces in the longitudinal direction of 4a and the right electrode block 4b with an opening 4f interposed therebetween to set a predetermined length. Then, the left and right electrode blocks 4a, 4b
Terminal 4e to which electrode wire 4d is attached almost in the center
The electrode wire 4d is inserted from above each opening 4f, and both ends of the electrode wire 4d are locked and stretched to each terminal 4e. A lightning strike prevention plate 23 is attached to the upper surface of the opening 4f. A grid 24 is stretched on the surface opposite to the opening 4f in parallel with the electrode wire 4d.

The width dimension A shown by the chain line in FIG. 2 is the dimension in the width direction of the B4 size recording paper. Therefore, the length of the electrode wire 4d and the grid 24 (FIG. 1) capable of charging the photosensitive drum 3 of the strip electrode 4 is set to be slightly longer than the width A for both sides. Then, as shown in FIG. 1, the grid 24 of the strip electrode 4 and the peripheral surface of the photosensitive drum 3 are attached to the housing 21 so that they face each other with a predetermined gap and their longitudinal directions are parallel to each other.

On the other hand, the unit cover 22 is a molded member made of a synthetic resin material and is attached to a predetermined mounting surface (not shown) of the housing 21. The belt electrode 4, the photosensitive drum 3, and the cleaning device 10 are attached.
It is designed to cover each. As shown in FIG. 1, a zener diode 25, which is a constant voltage element, is integrally attached to a predetermined position on the inner surface of the unit cover 22 in the upper left direction of the strip electrode 4 together with the bent end of the contact piece 26. Grounded by an appropriate method. And the contact piece
The other end of 26 is bent in an inverted V shape so as to have elasticity. The Zener diode 25 attached to the unit cover 22 is selected and attached in advance so as to have a grid voltage corresponding to the charging performance of the photosensitive drum 3 incorporated in the process cartridge 20. Therefore, a good electrostatic latent image is always formed on the photosensitive drum 3 in the process cartridge 20. In this way, the unit cover 22 to which the zener diode 25 and the contact piece 26 are attached is attached at a predetermined position from above the housing 21 in which the band electrode 4, the photosensitive drum 3, and the cleaning device 10 are attached. The elastic part 26a of the contact piece 26 is
Connected to the grid of, for example, the left electrode block 4a
A circuit including the grid 24 and the Zener diode 25 is formed by pressing the left side surface (which may be the right electrode block 4b) (FIG. 1). It should be noted that the varistor is not limited to the zener diode 25 of the constant voltage element and may be a varistor.

With this structure, if the zener diode 25 is to be replaced in order to change the grid voltage, the unit cover 22 to which the zener diode 25 can be applied so that a required constant voltage can be applied in advance. It was easy to work because it could be replaced with.

Further, the grid voltage can be known without removing the strip electrode 4 from the cartridge, which is very convenient for the work.

[0017]

As described above, according to the present invention, since the constant voltage element for determining the grid voltage of the strip electrode is provided on the unit cover of the process cartridge, the replacement work of the constant voltage element becomes extremely easy, and the strip electrode can be changed one by one. It is very convenient because you can know the grid voltage without removing it from the cartridge.

[Brief description of drawings]

FIG. 1 is a side sectional view showing the structure of a process cartridge according to an embodiment of the present invention.

FIG. 2 is a top view showing the configuration of a band electrode.

FIG. 3 is a side sectional view showing the configuration of the image forming apparatus.

[Explanation of symbols]

 2 Scanning optical system 3 Photoreceptor drum 4 Band electrode 4a Left electrode block 4b Right electrode block 4d Electrode wire 10 Cleaning device 18 Image forming device 20 Process cartridge 21 Case 22 Unit cover 24 Grid 25 Zener diode (constant voltage element) 26 Contact Piece

Claims (1)

[Claims] 1. A process cartridge in which at least an image carrier and a charging unit are unitized and detachably mounted in an image forming apparatus, and a constant voltage element for determining a grid voltage of a grid provided in the charging unit is provided in the process cartridge. A process cartridge for an image forming apparatus, which is provided on a unit cover.