JPS5816266A - Powder source for development bias - Google Patents

Abstract

PURPOSE:To obtain a bias power source of simple constitution for development by providing a switching part for controlling the charging voltage of a CR charging circuit, and switching clock pulses for controlling it and thus controlling a set voltage output. CONSTITUTION:When a clock signal is applied from a clock generation part 1 to the base of a transistor TR1, a capacitor C is charged to a prescribed voltage with a time constant CR, and development is carried out by a development bias which corresponds to the clock. After the development, a signal is sent from the clock generation part 1 to a TR2, which turns on to discharge the charged capacitor C with a time constant CR'. Thus, a bias power source of simple constitution for development is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a developing bias power source applied to a developing section of an electrostatic copying machine.

The electrostatic latent image formed on the electrophotographic photoreceptor is developed in the developing section. At this time, in order to prevent fogging, that is, background smearing, etc., the conductive support member of the photoreceptor and the developing sleeve are A bias voltage is applied between the two.

Conventionally, as a method for applying this bias voltage, the first
The method shown in FIG. 2 or FIG. 2 is adopted. The method shown in Figure 1 requires a high-voltage element to set the output voltage, and high-voltage switching elements (QA, QB,
QC...) to the number of switching stages (A, B.

C...) has the disadvantage of being separated. Also the second
The system having a feedback loop as shown in the figure has the disadvantage that it is difficult to stably switch the output voltage and obtain variable operation over a wide range, and the circuit is complicated and expensive.

A current of 10 μA flows, and from the above facts, it is clear that a constant voltage power supply that supplies a load with very little load fluctuation is sufficient as the power supply.

The present invention is aimed at solving the drawbacks of the prior art and configuring the subject system using a simple circuit system. To provide a power source for cultivation bias, characterized in that a switching section is provided to control the charging voltage of a charging circuit, and a set voltage output is controlled by driving the switching section or switching the number of p-sink pulses. It is.

That is, the present invention is a system in which a voltage corresponding to the number of pulses is charged to a capacitor I-1 and the load is supplied as a power source for developing bias, and the following effects can be obtained.

(1) The above-described power source for developing bias can be achieved with an extremely simple circuit configuration.

(2) The output voltage can be set by the number of pulses,
Direct digital control is performed by signals from a computer or the like.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 3 shows a circuit diagram of an embodiment of the present invention.
2 is a clock generation section, 2 is a CR charging circuit, 3 is a stabilized voltage supply section, and a diode D in the CR charging circuit 2 is provided to prevent backflow of current.

Then, a clock signal is applied to the CR charging circuit 2, which is configured so that a predetermined voltage is charged to the capacitor C with the time constant of CR by applying one clock signal (negative pulse) to the base of the transistor Tr1. A pulse group with a set number of clocks and a clock period is applied from the generator 1 to the base of the transistor Tr1, and a voltage corresponding to the number of clocks is shown in the timing chart of the output voltage.

The purpose of the transistor Trg is to short-circuit the capacitor C, and when the base of the transistor Tr2 is in the Low state, the transistor Tr2 is OFI? ' state, and an output voltage corresponding to the number of eyes that is input to the base of the transistor Tr1 is obtained, but after reaching a predetermined developing bias, development is performed, and after the development is completed, the transistor T
As shown in FIG. 4, when a High signal is input to the base of r2 from the clock generator l,
is turned on, and the charge stored in the capacitor C is discharged according to the time constant of the capacitor C and the resistor R'.

At the time of the next developing process, charging is performed again from both ends of the capacitor C.

Next, in the circuit diagram of FIG. 3, a constant current source can be created using the stabilized voltage supply section 3 instead of the resistor hole, and the circuit can be configured so that the capacitor C is charged with this constant current l. As shown in FIG.
If the time of ``high'' (transistor Try is 0FF) is t, the voltage E0 obtained with one input pulse is 5-Eo2-・jet, and the voltage En obtained with n input pulses is theoretically becomes Bn=-threat i・ten.

Here, the capacitor C must have sufficient voltage resistance to handle the above voltage, and if C, t, and t are set constant in the above equation, En=*n, (k: constant) The output voltage is determined as a linear function of the number n of input pulses from the clock generator 1. The bias voltage formed in this way decreases while the bias current is being supplied, but it is necessary to maintain the voltage across capacitor C so as not to affect the image density during development. It is necessary to set it large enough that there is no problem. Also, the rise time of the bias voltage depends not only on the capacitance of capacitor C, but also on the duty ratio and frequency of the clock pulse.
6- Therefore, it is necessary to set an appropriate duty ratio and frequency in advance so as to satisfy the setting accuracy and the time required to reach the set voltage.

Of course, if the duty ratio and frequency are controlled with a variable number of 12, the output voltage will be variable even if the number of pulses is constant, but considering that it will be controlled with a microcomputer etc., it is possible to control with the number of pulses of the present invention. is most preferred.

In the present invention, the charging pressure is set only by the number of pulses from OV without providing a feedback loop or base pressure, so it is necessary to provide a discharge path and short-circuit the discharge after the development process is completed. In the embodiment shown in FIG. 3, discharge is performed by the transistor Tr2 at the end of the development process.

Since the clock pulse control for bias voltage application according to the present invention is an extremely simple method when controlled by digital control, it can be used as shown in the following embodiment.

(1) When the overall process control of copying is performed by a microcomputer, the clock generating section 1 shown in FIG. 3 is replaced with the aforementioned microcomputer, and the output voltage is controlled by clock pulses generated by the microcomputer. Here, the number of clock pulses is calculated by a microcomputer from the set voltage of the developing bias. Further, when the developing process is completed, a discharge short circuit is similarly performed by a signal from the microcomputer to the transistor Trg after a predetermined period of time has elapsed. That is, according to the present invention, the developing bias source can be easily controlled by a microcomputer.

(2) A clock pulse generating section 1 is provided inside the developing bias source, and the number of clock pulses corresponding to each set voltage output is set in advance in each clock pulse generating section, and the required developing bias voltage is set. You can select and output. At the end of the development process, a discharge instruction is given by a signal from the control section of the copying machine or by a signal generated after a certain period of time has elapsed, and the short circuit is made.

As described above in the embodiments of the present invention, the present invention has a configuration particularly preferable for control by a microcomputer, so that changes in the amount of lamp light, deterioration of the photoreceptor, and toner in the case of two-component development can be avoided. It is also possible to stabilize the image by detecting the factors that change the image density and feeding them back to the number of clock pulses, ie, the bias voltage.

[Brief explanation of drawings]

1 and 2 schematically show an output system used as a conventional developing bias power source, FIG. 3 shows a circuit diagram of an embodiment of the present invention, and FIG. 4 shows the circuit diagram shown in FIG. shows a time chart of clock pulses and output voltage in the circuit.
FIG. 5 shows the relationship between the clock pulse and the output voltage and part of the circuit for an embodiment in which a constant power source is used to charge the capacitor as a modification of the embodiment shown in FIG. ■・・・Clock generation unit 2・Group CI”L charging circuit 3・・・Stabilization military pressure supply department agent Yoshimi Kuwahara 9- 11th η Figure 2

Claims (4)

[Claims] (1) In a development bias power supply having a stabilized voltage supply section and a C-type charging circuit, a switching section for controlling the charging voltage of the C-type charging circuit is provided, and the number of clock pulses for driving the switching section is switched. By this,
A developing bias power supply characterized in that the constant voltage output is controlled. (2) The developing bias power source according to claim 1, further comprising a discharge path that short-circuits the charge charged in the CR charging circuit at the end of the developing timing. (3) The developing bias power supply according to claim 1 or 2, wherein the clock pulse is generated by an external microcomputer for controlling the copying process. (4) The clock pulse generating section is provided inside the power supply for the development process, and a number of clock pulses corresponding to a set voltage output is set in advance in the clock pulse generating section. A developing bias power source according to claim 1 or 2.