JPS6380278A - Copying machine - Google Patents

Abstract

PURPOSE:To contrive the reduction of the number of parts, and a cost by using a developing bias power source as a voltage supply source to the grid of a scorotron electrifying device, as well. CONSTITUTION:A developing bias power source is used as a voltage supply source to the grid of a scorotron electrifying device, as well. When a copying start is commanded, a corona current is discharged to a photosensitive drum 1 through a grid 2 from a scorotron electrifying device 3 and the surface of the photosensitive drum 1 is electrified. A part of the corona current is conducted to the grid 2, and the current conducted to the grid 2 increases as the surface potential of the photosensitive drum 1 becomes high. at the time point when the surface potential of the photosensitive drum 1 reaches a prescribed value, the corona current are wholly conducted to the grid 2 and the discharge to the photosensitive drum 1 is stopped. On the other hand, when an exposure is executed from an exposing device to an original set to a prescribed position and a reflected light from the original is radiated to the photosensitive drum 1 through an optical system, a latent image is formed on the surface of the photosensitive drum 1. Subsequently, by a magnet roller 4, a toner is supplied to the photosensitive drum 1 and the latent image is developed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a copying machine.

[Prior art]

As shown in FIG. 2, a scorotron charging device 3 equipped with a grid 2 for stabilizing the surface potential of the photosensitive drum 1 is known as a charging device for charging a photosensitive drum 1 in a copying machine. By the way, in order to stabilize the surface potential of the photosensitive drum 1 with the grid 2, it is necessary to maintain the voltage of the grid 2 constant.
As a method for controlling this grid voltage, a method has been proposed in which a variable resistor 7 is interposed between the grid 2 and the ground GND. However, in the above structure, grid 2
The performance is affected by the temperature characteristics of the variable resistor 7, and in a fixed environment, that is, if the temperature of the variable resistor 7 is constant, the grid voltage will be held constant, but if the environment changes, the grid voltage will fluctuate. However, in reality, there is a drawback that it is difficult to sufficiently stabilize the surface potential of the photosensitive drum 1.

Therefore, as shown in FIG. 3, a copying machine has been proposed in which a predetermined voltage is supplied to the grid 2 from a high-voltage power supply 8 provided for exclusive use. However, with such a copying machine,
Although the grid voltage is made constant, and thereby the surface potential of the photosensitive drum 1 can be stabilized, a dedicated power source 8 for the grid 2 is required, resulting in a problem that the price of the copying machine becomes high. In particular, there is a strong demand for lower prices in home-use copying machines, which have become popular in recent years, so it is difficult to install a dedicated power supply 8 for the grid 2 in terms of cost.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and it is necessary to apply a developing bias voltage to a developing means to adjust the density of a non-image area of copy paper. The purpose of the present invention is to provide a copying machine in which the grid voltage can be kept constant by using the equipped developing bias power supply as a voltage supply source to the grid of a scorotron charging device, and the price does not increase. It is something.

[Structure of the invention]

In order to achieve the above object, the copying machine of the present invention includes a scorotron charging device equipped with a grid for controlling the surface potential of a photoreceptor, and a developing means. and a single power source that supplies a predetermined bias voltage to the developing means,
In other words, the conventional development bias power supply can also be used as a voltage supply source for the grid of the scorotron charging device, thereby reducing the number of parts without requiring a dedicated power supply for the grid. The present invention is characterized in that it is constructed so that the grid voltage can be kept constant and the surface potential of the photoreceptor can be stabilized, in addition to aiming at reductions in power consumption and cost.

〔Example〕

An embodiment of the present invention will be described below based on FIG.

Inside the copying machine, a photosensitive drum 1 as a photosensitive member having a photosensitive layer formed on its surface is rotatably supported, and around this photosensitive drum 1 are a scorotron charging device 3 equipped with a grid 2 and a developing means. A magnet roller 4, a transfer device (not shown), a peeling device (not shown), a cleaning device (not shown), and the like are arranged.

5 is a power supply, and the negative terminal of this power supply 5 is electrically connected to the ground GND.

On the other hand, the positive terminal of the power source 5 is electrically connected to the grid 2 and also to the magnet roller 4 via a resistor 6. - Generally, the voltage supplied from the power supply 5 to the grid 2, that is, the grid voltage, is higher than the developing bias voltage applied from the power supply 5 to the magnet roller 4, so the terminal voltage of the power supply 5 is set in correspondence with the grid voltage, The developing bias voltage is adjusted by iA using a resistor 6 or the like so that it has a value lower than the grid voltage. The grid voltage is usually about 400 to 800 V (-400 to 800 V in the case of (-) charging). In addition, the developing bias voltage is usually 100 to 400 v ((-)
In the case of charging, the voltage is about -100 to -400V). Although not shown, the copying machine is equipped with an exposure device, an optical system, a feeding device, a fixing device, a printing device, etc., as is well known.

In the above configuration, when a command to start copying is given, a corona current is discharged from the scorotron charging device 3 to the photosensitive drum l via the grid 2, and the surface of the photosensitive drum l is charged. A part of the corona current flows through the grid 2, and the current flowing through the grid 2 increases as the surface potential of the photosensitive drum 1 becomes higher. When the surface potential of the photosensitive drum 1 reaches a certain value, all of the corona current flows to the grid 2, and the discharge to the photosensitive drum 1 is stopped. In this case, since the grid voltage is maintained constant by the power source 5, the surface potential of the photosensitive drum 1 also becomes constant at the time when the discharge of the corona current stops.

On the other hand, a document placed at a predetermined position is exposed to light from the exposure device, and reflected light from the document is irradiated onto the photosensitive drum 1 via the optical system, thereby forming a latent image on the surface of the photosensitive drum 1. It is formed.

Subsequently, toner is supplied to the photosensitive drum 1 by the magnet roller 4, and the latent image is developed.

Subsequently, a copy sheet is sent to the photosensitive drum 1 by the paper feeding device, and a toner image is transferred onto the fed copy sheet by the transfer device. Next, remove the transferred copy paper from above. After the toner image is peeled off from the photosensitive drum 1 by the pXIJ device and the toner image is fixed on the copy paper by the fixing device, the copy paper is discharged by the paper discharge device. Furthermore, the toner remaining on the photosensitive drum 1 is removed by the cleaning device. The density of the non-image area on the copy paper is adjusted by the developing bias voltage applied to the magnet roller 4.

In the above embodiment, the developing bias voltage is adjusted by the resistor 6, but it goes without saying that the developing bias voltage may be adjusted by other methods.

〔Effect of the invention〕

As described above, the copying machine of the present invention includes a scorotron charging device equipped with a grid for controlling the surface potential of a photoreceptor, and a developing means, while supplying a predetermined voltage to the grid. , a single power source is provided for supplying a predetermined bias voltage to the developing means. In other words, the conventional developing bias power source is also used as a voltage supply source to the grid of the scorotron charging device. As a result, it is not necessary to install a dedicated power supply for the grid, and the number of parts and costs can be reduced, and the voltage of the grid can be maintained constant to increase the voltage of the photoreceptor. This has the effect of stabilizing the surface potential.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are schematic explanatory diagrams showing conventional examples, respectively. 1 is a photosensitive drum (photosensitive member), 2 is a grid, 3 is a scorotron charging device, 4 is a magnet roller (developing means),
5 is a power source.

Claims (1)

[Claims] 1. In a copying machine having a scorotron charging device equipped with a grid for controlling the surface potential of the photoreceptor and a developing means, a predetermined voltage is supplied to the grid, and a predetermined bias voltage is applied to the developing means. A copying machine characterized by being equipped with a single power supply.