JPH0739352Y2 - High voltage power supply for copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a high-voltage power supply device for a copying machine, and more particularly to a high-voltage power supply device for supplying a constant current to a discharger such as a charging discharger of the copying machine. It is a thing.

(Prior Art) Conventionally, electrophotographic copying machines based on electrophotography have been widely put into practical use. In this electrophotographic copying machine, a discharge device such as a corona discharger is used for uniform charging of the electrophotographic photosensitive member, toner image transfer, sheet peeling, charge removal from the photosensitive member, and the like.
In many cases, a common high voltage transformer supplies a high voltage current of direct current or alternating current to a rectifier circuit. As is well known, the charging potential of the electrophotographic photosensitive member is closely related to the image density of the copy. Therefore, in the high voltage power supply device using the common high voltage transformer as described above, conventionally, the charging process for uniformly charging the photosensitive member is performed. A desired constant voltage is applied to the charging discharger by controlling the voltage of the DC output supplied to the discharger (hereinafter referred to as the charging discharger) or the secondary winding voltage of the high voltage transformer. Was there.

(Problems to be solved by the invention) However, as described above, even if the DC output supplied to the charging discharger is controlled to a constant voltage and a constant voltage is applied to the charging discharger, The stability of the charging potential of the photographic photoreceptor depends on the discharge characteristics of the discharger and the environmental characteristics of the photoreceptor such as temperature and humidity, atmospheric pressure, etc., and the potential of the photoreceptor cannot be stabilized.

Therefore, an object of the present invention is to provide a high-voltage power supply device for a copying machine which can stably control the potential of the photoconductor.

(Means and Actions for Solving Problems) The high-voltage power supply device for a copying machine according to the present invention extracts one output from a single high-voltage transformer and a secondary winding of the high-voltage transformer, and uniformizes the photosensitive member. A multi-output circuit for supplying electric power to a plurality of dischargers including a charging discharger for charging, a current detection circuit for detecting a direct current supplied to the charging discharger, and the direct current detected by the current detection circuit And a control circuit for controlling the primary winding voltage of the high-voltage transformer so that the voltage becomes a predetermined value, the output of the multi-output circuit other than the charging discharger is controlled in conjunction with the output to the discharger. It is characterized by doing so.

In the above configuration, the direct current output supplied to the charging discharger is controlled to be constant current, so that the direct current output supplied to the charging discharger is controlled to constant voltage,
The charging potential of the photoconductor is not influenced by the discharge characteristics of the discharger and the environmental characteristics of the photoconductor such as temperature and humidity and atmospheric pressure, and the potential of the photoconductor can be controlled in a stable state.

Further, the high-voltage power supply device of the present invention controls the primary winding voltage of the high-voltage transformer as described above, while supplying power from the secondary winding to the discharging process discharger and other dischargers. , The output to other than the charging discharger can be controlled in conjunction with the output to the discharging discharger, so that the discharge characteristics of the charging discharger and the photoreceptor Considering environmental characteristics such as temperature and humidity, atmospheric pressure,
Since the optimum electric potential is applied to the electric potential of the photoconductor, the steps other than uniform charging such as transfer and sheet peeling can be performed extremely stably.

To prevent the charging potential of the photoconductor from being affected by the discharge characteristics of the discharge device and the environmental characteristics of the photoconductor such as temperature and humidity, atmospheric pressure, etc., a direct current supplied to the transfer discharge device among the plurality of discharge devices. It is also possible to make constant. However, in the case of the transfer discharger, the discharge characteristics of the paper used for copying change significantly further, which adversely affects the output of the high-voltage transformer to other dischargers. Therefore, as in the device of the present invention, it is extremely effective to control the output of the entire high voltage transformer so that the direct current supplied to the charging discharger becomes a constant current.

Further, in the above configuration, it is particularly preferable that the current detection circuit is configured to detect the current flowing in the rectifier circuit that supplies the direct current to the charging discharger.

By doing so, as compared with the case of detecting the shield current of the charging discharger, for example, a means for insulating the discharger shield from the main body of the copying machine and a wire for connecting the shield current detection circuit and the power supply main body And the like are unnecessary, and the cost can be reduced.

(Embodiment) Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 shows a high voltage power supply device for a copying machine according to an embodiment of the present invention. The electrophotographic photosensitive member 1 of the copying machine is adapted to be rotated in the direction of arrow A by a driving device (not shown). Around the photosensitive member 1, a charging corotron (which charges the surface of the photosensitive member 1 uniformly). Corona discharger 2), a transfer corotron 3 that transfers the toner image formed on the surface of the photoconductor 1 to a copy sheet (not shown), a peeling corotron 4 that peels the copy sheet from the surface of the photoconductor 1, and toner. A destaticizing corotron 5 for destaticizing the surface of the photoconductor 1 after the image transfer is provided. The charging corotron 2, the transfer corotron 3, the peeling corotron 4, and the discharging corotron 5 are supplied with electric power from an AC power supply 8 via a common high-voltage transformer 7 of a high-voltage power supply device 6. In this embodiment, all the lines connected to the secondary winding 7b of the high voltage transformer 7 form a multi-output circuit.

The charging corotron 2 has a secondary winding of the high-voltage transformer 7.
A direct current I ₀ is supplied from 7b through a rectifying circuit composed of diodes 9 and 10 and capacitors 11 and 12. A resistor 14 as an impedance element is inserted between the first-stage diode 9 and the common ground 13, and this resistor 14
A capacitor 15 for ripple removal is arranged in parallel with. The voltage V applied to the resistor 14 is compared with a reference voltage V ₀ by a comparator 16, which compares the voltage V with the reference voltage V _0.
The control signal S is output according to the magnitude of. The AC power supply 8 for supplying an AC current to the primary winding 7a of the high voltage transformer 7 is
The voltage variable circuit 17 is formed to have a variable voltage value, and the voltage variable circuit 17 is controlled according to the control signal S.

The direct current I ₀ supplied to the charging corotron 2 is an average value of the current i flowing through the diode 9 (that is, , T is a cycle), the resistance value of the resistor 14 is R (known), and the capacitance of the capacitor 15 is large, V = I _0.
Since it is R, the DC current I ₀ can be obtained by measuring the voltage V (average voltage) applied to the resistor 14. The reference voltage V ₀ is set to the value of the voltage V when the direct current I ₀ is a desired value, that is, V = I ₀ · R, and the comparator 16 determines that the voltage V exceeds the reference voltage V ₀ (that is, When the direct current I ₀ exceeds a desired value), for example, an “H” signal is used as the control signal S,
When the voltage V is equal to or lower than the reference voltage V ₀ , the “L” signal is output. When the voltage variable circuit 17 receives the above-mentioned "H" signal, it lowers the primary winding voltage of the high-voltage transformer 7, while when it receives the above-mentioned "L" signal, it raises the primary winding voltage of the AC power supply 8. Manipulate. As a result, the magnitude of the direct current I ₀ supplied to the charging corotron 2 is controlled to the desired value. The reference voltage V ₀ may be manipulated by an external signal to control the charging potential of the photoconductor.

As described above, in this high-voltage power supply device, the direct current I ₀ supplied to the charging corotron 2 is detected by measuring the current i (directly the voltage V) flowing through the diode 9 of the rectifier circuit. , The DC current I _{0 accordingly}
As compared with the case where the shield current of the charging corotron 2 is measured, the shield insulation means, the wire connecting the shield current measuring circuit and the power supply unit, etc. are unnecessary. The structure becomes simple.

As shown in FIG. 2, diodes 21, 22, 23, 24, 25
... and a capacitor 26, 27, 28, 29, 30, 31, ... even when a multi-stage rectifier circuit is used, a resistor 14 is inserted between the first-stage diode 21 and the common ground 13 and added to the resistor 14. When the voltage V is measured, the direct current I ₀ supplied to the charging discharger via the rectifying circuit is detected. Further, in the circuits of FIGS. 1 and 2, the diode may be reversed in direction to provide a negative output.

(Effect of the Invention) As is apparent from the embodiments described above, the high-voltage power supply device for a copying machine of the present invention controls the output of the entire high-voltage transformer so that the direct current supplied to the charging discharger becomes a constant current. By doing so, extremely stable potential control of the photoconductor is realized, and therefore, an effect of stabilizing the image density of the copy is produced.

Further, in the high-voltage power supply device for a copying machine according to the present invention, all the DC outputs to the plurality of dischargers can be controlled as described above, but only one control circuit is required. The cost of the copying machine can be reduced as compared with the case where a control circuit is provided for each discharger to control the potential of the photoconductor.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing another example of a power supply apparatus to which the present invention can be applied. 2 ... Charging corotron, 6 ... High-voltage power supply device 7 ... High-voltage transformer, 8 ... AC power supply 9, 10, 21, 22, 23, 24, 25 ... Diodes 11, 12, 15, 26, 27, 28, 29, 30, 31 ... Capacitor 13 ... Common ground, 14 ... Resistor 16 ... Comparator, 17 ... Voltage variable circuit

Claims (3)

[Scope of utility model registration request] 1. A high voltage transformer and a plurality of outputs from a secondary winding of the high voltage transformer are supplied to supply power to a plurality of dischargers including a discharger for a charging step for uniformly charging a photosensitive member. A multi-output circuit, a current detection circuit for detecting a DC current supplied to the charging process discharger, and a primary winding of the high-voltage transformer so that the DC current detected by the current detection circuit has a predetermined value. And a control circuit for controlling the voltage, and the output of the multi-output circuit other than the discharging device for the charging process is controlled in conjunction with the output to the discharging device. apparatus. 2. The utility model registration according to claim 1, wherein the current detection circuit detects a current flowing in a rectifying circuit which supplies a direct current to the discharger for the charging step. High voltage power supply for copiers. 3. The rectifier circuit comprises a diode and a capacitor, and the current detection circuit measures a voltage applied to an impedance element provided between the diode and a common ground. The high voltage power supply device for a copying machine according to claim 2 of the utility model registration claim.