JPS6026363A - Power feeding system of electrostatic charger - Google Patents

Abstract

PURPOSE:To make an electrostatic charging current constant by connecting the shield of a specific charger whose current is desired to be constant to the housing ground through a resistance, and detecting a shield current by the resistance and controlling a primary side so that the current becomes constant. CONSTITUTION:Chargers 2 and 5 are insulated from a housing, and the shields of the chargers are grounded to the housing by resistances R1 and R2 for current detection. The load current of the charger 2 detected by the resistance R1 is compared with a reference value by an error amplifier 9 and inputted to an inverter driving circuit 8 to control the primary-side applied power of an inverter transformer 7. The load current flowing from a high-voltage output to the chargers is distributed from the charging wires of the chargers to the charger shields and a photosensitive drum 1 in approximate 3:1 proportion. Thus, the charging current has the constant ratio to the current flowing from the charging wires of the charger to the charger shields. Consequently, the current flowing to the shield of the charger 2 is detected by the resistor R1 to perform control, and variation in charger impedance is corrected sufficiently to hold the charging current of the charger 2 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply system for a plurality of chargers in an image forming apparatus that utilizes charging, such as an electrophotographic copying machine, and particularly relates to a power supply system that achieves constant charging current. .

For example, in an electrophotographic copying machine, a charger for charging a photoreceptor, a transfer charger for transferring a developed image,
Furthermore, a plurality of chargers are used, such as a charger for removing residual charges.

In the past, various supply methods have been tried to make the current constant. In addition to the general power supply system in which a front voltage transformer is individually provided for each charger, a plurality of high voltage secondary right brains are provided in - high voltage transformers, and each output is rectified and then supplied to each charger. Among them, a power supply system that detects the load current of a predetermined charger and controls the power applied to the primary side of the high-voltage transformer has already been put into practical use. However, the former requires a high-voltage transformer and its peripheral circuits for each charger, and the latter also requires multiple secondary windings and rectifier circuits, so power is supplied from the -winding to multiple chargers. Compared to conventional constant-voltage power supply systems, this has led to larger equipment and higher costs.

The present invention eliminates the above-mentioned drawbacks and reduces the cost increase of the device.
It is intended to make the charging current of a predetermined charger among a plurality of chargers a constant current without any work that would lead to an increase in size.

A feature of the present invention is that high-voltage power is supplied to a plurality of chargers from one common secondary winding of a high-voltage transformer, and a shield resistance of a particular charger for which constant current is particularly desired among the plurality of chargers is provided. The shield current of the specific charger is detected by this resistor, and the primary side of the high voltage transformer is controlled so as to keep the shield current constant based on the detection output. It's about doing. Since the charge current of the charger has a property that it is in a constant ratio with the shield current, by doing the above, the charging current of the charger is made constant.

The present invention will be explained in detail below.

Fig. 1 shows an example of an electrophotographic copying machine, in which 1 is a photosensitive drum that rotates in the direction of the arrow, and has a structure in which a photosensitive layer is formed on an aluminum conductor plate. Grounded to the frame. Reference numeral 2 denotes a charger for charging the photosensitive drum, which charges the surface of the photosensitive drum with a negative charge.

Reference numeral 3 represents light reflected from the original document, and the resistance value of the portion of the photosensitive drum that is hit by this reflected light decreases, thereby discharging negative charges and forming a latent image on the photosensitive drum. 4 is a developing device that brings toner particles containing positive charges close to the photosensitive drum, and causes the toner to adhere to the portions of the photosensitive drum where negative charges remain, R11, which corresponds to the dark portions of the original, to form a toner image. . Reference numeral 5 denotes a transfer charger which attracts and attaches the toner image on the sensitive drum 9 to the transfer paper 6.

The chargers 2 and 5 are insulated from the rod as shown in the figure, and the shields of these chargers are connected to current detection resistors R1 and R2, respectively.
is grounded to the frame by. The load current of the charger 2 detected by the resistor R is compared with a reference value by an error amplifier 9 and input to an inverter drive circuit 8 to control the power applied to the primary side of the inverter transformer 7. Charger 2
, 5 are respectively supplied with power from a common secondary winding of the transformer 7 through a circuit consisting of a rectifier diode D1, a bleeder resistor R3, a smoothing capacitor C1, and a spark prevention resistor R4+Rsk.

The load current flowing from the high voltage output to the charger is distributed from the charging wire of each charger to the charger shield and the photosensitive drum 1 at a constant ratio of approximately 3:1.

What essentially contributes to the charging of the photosensitive drum by the charger 2 and the transfer charging by the transfer charger 5 is the BLQ flowing from the charging wire of the charger to the photosensitive drum.
As mentioned above, this charging current is in a constant ratio with the current flowing from the charging wire of the box or container to the charging device shield.
By detecting the current flowing through the shield of the paper bag 2 with the resistor R and performing the control as described above, fluctuations in the electrical impedance due to environmental changes can be sufficiently compensated for. This allows the current in the weapon 2 belt to be kept at a constant value. In this case, the transfer charger 5 is not subjected to constant flow control, but this is due to the constant flow control of the charger 2.
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In the above embodiment, the shield current of the charger 2 is detected by the resistor R1 to make the current of the charger 2 a constant current. By detecting the shield current, it is also possible to make the charging current of the charger 5, that is, the transfer current, constant m in the same manner as described above.

The embodiment shown in FIG. 1 is a case where the chargers 2 and 5 have the same polarity, but if they are chargers of opposite polarity, as shown in FIG. By adding a rectifier circuit called smoothing capacitor C2, charger 2
It is possible to make the charging current hill constant. Also in this case, instead of the charger 20, the transfer charger 5 can be made to have a constant current as described above. In the embodiment shown in FIG. 2, the light 3 is scanned (background scanned) using a laser beam instead of the original reflected light, and the toner having a negative charge is ejected to the EJt (&
This is an embodiment for a laser beam printer or the like.

As explained above, according to the present invention, it is possible to measure the load's current permeation of a desired charger using a simpler circuit configuration with fewer parts than the conventional constant current power supply method described above. It is possible to supply power to multiple chargers while controlling the current flow, and it is possible to avoid increasing the size and cost of the device.

[Brief explanation of drawings]

FIG. 1 shows a circuit configuration of an embodiment of the present invention, and FIG. 2 shows an example of application to a laser beam printer, and a circuit showing an embodiment of the present invention in the case of supplying positive high voltage to a transfer charger. FIG. 1... Photosensitive drum 2... Photosensitive drum charger 3... Original reflected light 4... Developing device 5... Transfer fluorescent device 6... Transfer paper 7... Inverter transformer 8... Inverter drive circuit 9...Error amplifiers Dl, Dl...Rectifier diodes Kl, R2...Current detection resistor R3...Zorida resistor R4+ R5...Spark prevention resistors C1, C2... Smoothing capacitor diagram 1

Claims (1)

[Claims] In an electronic image forming apparatus that uses charging, high voltage power is supplied to multiple chargers from a common secondary winding of a high voltage transformer, and the shield of a predetermined charger among these chargers is connected to the image forming apparatus. The shield current of the predetermined charger is detected by a resistor that is insulated from the frame ground and inserted between the shield of the predetermined charger and the frame ground, and the shield current is kept constant by this detection output. A charger power feeding system characterized in that the primary side of the high voltage transformer is controlled so as to adjust the voltage.