JPS589229Y2 - Photosensitive drum of electrophotographic copying machine - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a photosensitive drum for a transfer type electrophotographic copying machine.

In transfer-type electrophotographic copying machines, S is used as a photoreceptor.
E, ZnO, OPC, etc. are used, and toner is attracted to the electrostatic latent image formed thereon to form a developed image, and this developed image is transferred to copy paper.

The photoreceptor is then repeatedly used after being cleaned and neutralized.

By the way, among the photoreceptors, ZnO. Since the OPC has a relatively short lifespan, it is necessary to make it easy to replace it.

For example, in the case of an OPC photoreceptor, it is made into a long sheet and rolled into a photoreceptor drum, and then used by wrapping it around the circumferential surface of the photoreceptor drum. The structure is such that the body extends out so that it appears on the circumferential surface of the photoreceptor drum.

FIG. 1 shows an electrophotographic copying machine equipped with a photosensitive drum having the above structure.

Reference numeral 1 denotes a photoreceptor drum, inside which a winding roll 2 is installed.
and a feed roll 3 are provided.

The long sheet-shaped OPC photoreceptor 4 wound around the feeding roll 3 comes out of the drum through the slit 5 of the photoreceptor drum 1, is wound around the circumferential surface of the photoreceptor drum 1, and then exits from the slit 5 again. It enters the drum and is wound onto the winding roll 2.

The slit 5 is closed by a drum seal 6 to prevent developer from entering the drum through the slit 5.

The drum seal 6 is made of metal and is normally grounded.

The OPC photoconductor 4 wound around the circumferential surface of the photoconductor drum 1 is charged with a charging section 7 by rotation of the photoconductor drum 1 in the direction of arrow A.
Exposure section 8, development section 9, transfer section 10, static elimination section 11. It passes through the learning section 12 in sequence.

By the way, various problems arise due to the drum seal 6 being grounded.

First, when it reaches the developing section 9, a large potential difference occurs between it and the drum seal 6, which is grounded and has zero potential, since the developing bias 8 is applied to the developing section 9. .

This potential difference is caused by the OPC photoreceptor 4 carrying the electrostatic latent image.
Since the potential difference between the part and the developing section 9 is of opposite polarity,
The developer carrier is attracted to the drum seal 5.

Then, this carrier scatters as the photoreceptor drum 1 rotates.

In order to overcome this problem, conventionally, the developing bias 8 was grounded in synchronization with the timing when the drum seal 6 reached the developing section 9.

However, the developing bias #8 is usually several hundred volts,
A complex configuration is required to turn this on and off at the right time.

The effect of grounding the drum seal 6 is on the developing section 9.
This occurs not only in the charging section 7, but also in the charging section 7 and the like.

That is, the charged potential of the portion of the OPC photoreceptor 4 adjacent to the drum seal 6 is lower than that of other portions.

This is because when the drum seal 6 passes through the charging section 7, as shown in FIG.
There is a period when the photoconductor 4 faces the photoconductor 4, and during this period, the discharge current from the charger 1a flows in a concentrated manner to the grounded drum seal 6, and the OPC photoconductor 4
This is thought to be due to the decrease in the current flowing towards the .

The present invention aims to solve the above problem, and is characterized in that the drum seal is grounded via a constant voltage element.

As an example of a constant voltage element that grounds the drum seal 6, a bidirectional constant voltage element (commonly known as a varistor) D can be used.

The rating of the element is preferably selected to be approximately the same voltage as the developing bias (8).

The drum seal 6, which is grounded through the bidirectional constant voltage element, is raised to the same potential as the rated voltage of the constant voltage element by the corona discharge current when it passes through the charging section 7, so the drum seal 6 is grounded via the two-way constant voltage element. The discharge current from 7a is prevented from concentrating on the drum seal 6, and the charging state of the OPC photoreceptor 4 is improved.

Further, in the developing section 9, the potential of the drum seal 6 also increases due to the current generated by the developing bias.

Since this potential is selected to be approximately the same as the developing bias (18), carrier adhesion does not occur.

In the apparatus shown in FIG. 1, the surface potential of the OPC photoreceptor 4 after charging is approximately -800V, the surface potential of the white background portion after exposure is approximately -200V, and the developing bias VB is -300V.
By using a bidirectional constant voltage element with a rating of 300 V, the problem of carrier adhesion in the developing section 9 was solved, and the potential distribution on the circumferential surface of the photosensitive drum 1 was improved as shown in FIG. Ta.

In this graph, the horizontal axis shows the position on the circumferential surface of the photoreceptor drum 1, the vertical axis shows the potential on the same circumferential surface, and the range of a is O
This is the area around which the PC photoreceptor 4 is wound, and the area b is the area where the drum seal 6 is provided.

The solid line shows the potential distribution when the drum seal 6 is grounded via a bidirectional constant voltage element, and the chain line shows the potential distribution when the drum seal 6 is directly grounded.

As is clear from this graph, the OPC photoreceptor 4 is more uniformly charged up to the end of the photoreceptor 4 according to the present invention.

In the embodiment described above, a bidirectional constant voltage element was used in order to deal with the problem in the static eliminator 11, but this problem is usually caused by the influence of the developing part 9 and the charging part 7. A unidirectional constant voltage element (commonly known as a Zener diode) may also be used.

In addition, in the above embodiment, the OPC photoreceptor 4 was drawn out from within the photoreceptor drum 1; however,
In the case of using a ZnO photoreceptor 13 as shown in FIG. , which causes the same problem as the drum seal 6, is grounded via a constant voltage element.

In addition, in the above example, in a developing bias voltage variable device, a one-way constant voltage element with an appropriate rated voltage and a capacitor are connected in parallel, the capacitor is charged to the rated voltage in the charging section, and this potential is applied to the developing bias voltage. It may also be used by the department.

As described above, the present invention has a simple structure in which the metal fitting provided at the joint of the photoreceptor is grounded via a constant voltage element.
Problems caused by directly grounding it can be solved at once.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the present invention, FIG. 2 is a side view showing the relationship between the charger and the drum seal, and FIG. 3 is a graph showing the potential distribution on the circumferential surface of the photoreceptor drum. FIG. 4 is a side view showing another embodiment. 1...
・Photoconductor drum, 4...OPC photoconductor, 6...
...Drum seal, 13...ZnO photoreceptor, 14...Press metal fitting, D...Bidirectional constant voltage element.

Claims (1)

[Scope of utility model registration request] 1. A photoreceptor drum for an electrophotographic copying machine, characterized in that the photoreceptor drum has a metal fitting at a joint portion of a photoreceptor wound around the circumferential surface of the drum, and the metal fitting is grounded via a constant voltage element.