JPS6388576A - Developing device for electronic recorder - Google Patents

Abstract

PURPOSE:To reduce the supply amount of toner to a photosensitive drum by adjusting a developing bias voltage value so that the absolute value of the developing bias voltage applied to a developing means except during image exposure is larger than the absolute value during the image exposure. CONSTITUTION:Toner required for development is supplied from a magnet roller 5 to the photosensitive drum 1 during the image exposure and a control unit 9 applies a high developing bias voltage of 450V from a high voltage source 8 to a metallic sleeve 5b through a relay 6 except during the image exposure to light a blank lamp 2. In this case, the value of the developing bias voltage is larger than during the image exposure, so the holding force for the toner by the magnet roller 5 becomes larger than during the image exposure and charges on the photosensitive drum 1 are removed to a certain extent through the projection of light by the blank lamp 2. Consequently, the supply amount of toner from the magnet roller 5 to the photosensitive drum 1 is made smaller than before except during the image exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device in an electronic recording machine such as a copying machine.

[Prior art]

Generally, in an electronic recording machine such as a copying machine, a predetermined developing bias voltage having a polarity opposite to that of the toner is applied to a magnet roller that supplies toner as a colored substance charged with positive or negative polarity to a photosensitive drum. By applying , the density of the non-image area on the copy paper on which the original image has been copied is adjusted. By the way, conventionally,
The value of the developing bias voltage described above was always set to a constant value regardless of whether or not image exposure was in progress during which toner should be supplied to the photosensitive drum. Since the toner is sent from the magnet roller to the photosensitive drum even when the image exposure amount is outside the medium amount, there is a drawback that the toner is wasted. Conventionally, a blank lamp is installed facing the photosensitive drum, and when the image exposure is outside the medium amount, the blank lamp irradiates the photosensitive drum with light to remove static electricity, and when the image exposure is outside the medium amount, the photosensitive drum is charged with light. However, even with this method, it has been difficult to sufficiently reduce the amount of toner supplied to the photosensitive drum at times other than image exposure.

[Purpose of the invention]

The present invention has been made in consideration of the problems of the prior art described in section 2.The present invention has been made in view of the problems of the prior art described in section 2. The purpose is to provide a developing device for a recording machine.

[Structure of the invention]

In order to achieve the above object, a developing device for an electronic recording machine according to the present invention is a developing device for an electronic recording machine that applies a developing bias voltage to a developing means such as a magnetic roller that supplies toner to a photoreceptor. In the apparatus, the absolute value of the developing bias voltage applied to the developing means when a non-image area of the photoreceptor that has not been subjected to image exposure passes through the developing means, that is, when the image exposure is outside the medium amount, is: A developing device that adjusts the value of the developing bias voltage so that when the image area of the photoreceptor that has undergone imagewise exposure passes through the developing device, the absolute value of the developing bias voltage is greater than the absolute value of the developing bias voltage that is applied to the developing device during the imagewise exposure. A bias voltage adjustment means is provided, which increases the toner retention force of the developing means when the image exposure is outside the medium amount compared to during the image exposure, and when the toner is not originally required to be sent to the photoconductor when the image exposure is outside the medium amount. The present invention is characterized in that it is configured to reduce the amount of toner supplied from the developing means to the photoreceptor at a time, thereby minimizing wasteful consumption of toner.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 and 2.

As shown in FIG. 1, a photosensitive drum 1 as a photosensitive member is rotatably supported in a copying machine, which is an example of an electronic recording machine. 2. A developing device 3, a transfer charger (not shown), a peeling device (not shown), a cleaning device (not shown), etc. are sequentially arranged along the circumferential direction.

Although not shown, inside the copying machine there are, as is well known, the following:
It has a built-in light source, optical system, fixing device, paper feeding/ejecting device, etc.

2. The developing device 3 includes a magnetic roller 5 as a developing means built in a developing tank 4 containing a mixture of toner as a colored substance (not shown) and a carrier such as iron powder as a conveying substance. Become. This magnet roller 5 has a structure in which a metal sleeve 5b is rotatably arranged around the outer periphery of a cylindrical magnetic body 5a that magnetically attracts the carrier. In the developer tank 4, the toner is charged to a polarity opposite to that of the photosensitive drum 1 due to frictional charging. with this,
The carrier is configured to be charged to the opposite polarity to the toner, that is, to the same polarity as the photosensitive drum 1. In this embodiment, since the photosensitive drum 1 is charged to a positive polarity, the toner is charged to a negative polarity and the carrier is charged to a positive polarity.

The metal sleeve 5b of the magnet roller 5 is supplied with a low-voltage or high-voltage positive developing bias from either a low-voltage power source 7 with a terminal voltage of 250V or a high-voltage power source 8 with a terminal voltage of 450V via a relay 6. A voltage is applied. The polarity of this developing bias voltage is the same as the charge on the photosensitive drum 1, that is, the polarity opposite to that of the toner, and is positive in this embodiment. Further, the value of the developing bias voltage by the low voltage power source 7 is set lower than the surface potential of the photosensitive drum 1. The control unit 9, which functions as a developing bias voltage adjusting means, operates the relay 6 through the driver 10, and electrically connects either the power source 7 or 8 to the metal sleeve. At the same time, the lighting timing of the blank lamp 2 is controlled.

In the above configuration, when copying is performed, the surface of the photosensitive drum 1 is charged to a predetermined positive potential by the charging charger. Subsequently, in this charged state, an original (not shown) set at a predetermined position is irradiated with the light source, and reflected light from the original is guided to the photosensitive drum 1 via the optical system to perform image exposure. As a result, an electrical latent image corresponding to the image of the document is formed on the photosensitive drum 1. Next, toner is supplied from the developing tank 4 to the photosensitive drum 1 by the metal sleeve 5b of the magnetic roller 5, and after developing the latent image and forming an image of the toner on the photosensitive drum 1, the paper feeding device The toner image is transferred onto the copy paper fed to the photosensitive drum 1 by the transfer device. Subsequently, after the transferred toner image is fixed on the copy paper by the above-mentioned fixing device,
The fixed copy paper is discharged from the copying machine by the 1- paper discharge device. Note that the toner remaining on the photosensitive drum 1 is recovered by the cleaning device.

During image exposure on the photosensitive drum 1, that is, when an image area on the photosensitive drum 1 passes through the magnet roller 5, the control unit 9 connects the metal sleeve 5b of the magnet roller 5 with a low-voltage power source via a relay 6. A low developing bias voltage of 7 to 250 V is applied, and the blank lamp 2 is extinguished. Thereby, during image exposure, the toner necessary for development is supplied from the magnet roller 5 to the photosensitive drum 1. On the other hand, when the non-image area of the photosensitive drum 1 passes through the magnet roller 5, the control unit 9 controls the high-voltage power supply 8 to be connected to the metal sleeve 5b via the relay 6.
A high developing bias voltage of 0 V is applied, and the blank lamp 2 is turned on. In this case, since the value of the developing bias voltage becomes larger than during image exposure, the toner retention angle by the magnet roller 5 increases compared to during image exposure, and the charge on the photosensitive drum 1 due to the irradiation of light from the blank lamp 2 increases. is removed to some extent, the number of times the toner is supplied from the magnet roller 5 to the photosensitive drum 1 at times other than during image exposure when there is no need to send toner to the photosensitive drum 1 is reduced compared to the conventional method, and as a result, wasted [toner] is removed. consumption can be reduced.

FIG. 2 shows the switching timing of the high and low developing bias voltages by the control unit 9. In Fig. 2, (a) shows the connection between the high voltage power supply 8 and the metal sleeve 5 of the magnet roller 5.
Indicates the timing of application of high developing bias voltage to b, (1
)) indicates the timing of applying a low developing bias voltage from the low voltage power source 7 to the metal sleeve 5b, and (C) indicates the timing of turning on the blank lamp 2. As is clear from Figure 2,
In this embodiment, a high developing bias voltage is applied based on the lighting timing of the blank lamp 2. More specifically, for example, in section A in which copying is performed continuously at predetermined time intervals, the application of the high developing bias voltage to the metal sleeve 5b starts slightly later than when the blank lamp 2 starts lighting. At the same time, the smoke extinguishing of the blank lamp 2 is completed slightly earlier than the time when the smoke extinguishing is completed.

Table 1 shows the results of measuring the amounts of toner and carrier recovered from the photosensitive drum 1 by the cleaning device 1 when the developing bias voltage was varied.

[Margin below]

Table 1 As is clear from Table 1 above, when the developing bias voltage is in the range of 450 V or less, the amount of toner recovered from the photosensitive drum 1 decreases as the developing bias voltage increases, and the amount of carrier recovered decreases. It was “0”. However,
When the developing bias voltage exceeds 450V, the photosensitive drum 1
As the developing bias voltage increased, the amount of carrier and toner recovered increased. From this result, it was determined that the optimum value for the developing bias voltage at times other than during image exposure was 450 V, and the terminal voltage of the high voltage power supply 8 was set accordingly. However, the values of the high and low developing bias voltages are not fixed, but can be changed depending on the surface potential of the photosensitive drum 1, that is, how much the photosensitive drum 1 is charged by the charger described in 2. It is.

In the above embodiment, the polarity of the charge charged on the photosensitive drum 1 and the metal sleeve 5b of the magnet roller 5 are
The polarity of the developing bias voltage applied to the photosensitive drum 1 was set to be positive, and the toner was charged negatively; You can let me. However, also in this case, the absolute value of the developing bias voltage at times other than during image exposure is set to be larger than the absolute value of the developing bias voltage during image exposure. It goes without saying that the present invention can also be applied to developing devices of electronic recording machines other than copying machines, such as laser printers.

〔Effect of the invention〕

As described above, the developing device for an electronic recording machine according to the present invention has the following features:
A developing device ζ of an electronic recording machine is configured to apply a developing bias voltage to a developing means for supplying toner to a photoreceptor. The absolute value of the developing bias voltage is
The structure includes a developing bias voltage adjusting means for adjusting the value of the developing bias voltage so that the value of the developing bias voltage is greater than the absolute value of the developing bias voltage applied to the developing means when the image area of the photoreceptor passes through the developing means. . As a result, the toner retention force of the developing means at times other than during image exposure is increased compared to during image exposure, and the toner retention force from the developing means to the photoreceptor is increased at times other than during image exposure, which originally does not require sending toner to the photoreceptor. This has the effect of reducing the amount of toner supplied and reducing wasteful toner consumption.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is an explanatory diagram of a copying machine equipped with the developing device of the present invention, and FIG. 2 shows the switching timing of the developing bias voltage. FIG. 1 is a photosensitive drum (photosensitive member), 3 is a developing device, 5 is a magnet roller (developing means), and 9 is a control unit (developing bias voltage adjusting means).

Claims (1)

[Claims] 1. In a developing device of an electronic recording machine, in which a developing bias voltage is applied to a developing means that supplies toner to a photoreceptor, a developing bias voltage is applied to the developing means when a non-image area of the photoreceptor passes through the developing means. A developing bias voltage that adjusts the value of the developing bias voltage so that the absolute value of the developing bias voltage is greater than the absolute value of the developing bias voltage applied to the developing means when the image area of the photoreceptor passes through the developing means. A developing device for an electronic recording machine, characterized in that it is equipped with an adjusting means.