JP2865169B2 - High voltage discharge current supply device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage discharge for reducing a control error caused by a leakage current of a power supply line for supplying a high-voltage discharge current by performing a constant current control in an electrophotographic copying machine. The present invention relates to a current supply device. [Prior Art] FIG. 4 is a diagram showing a schematic configuration of an electrophotographic copying machine, and FIG. 5 is a diagram showing a schematic configuration of a power supply line of the electrophotographic copying machine. In the figure, 21 is a document, 22 is a platen, 23 is an exposure lamp,
24 is a mirror group, 25 is a lens group, 26 is a head drive device, 27
Is a charger, 28 is a paper feed tray, 29 is a developing device, 30 is a transfer device, 31 is a cleaner, 32 is a photosensitive drum, 33 is a fixing device,
Reference numeral 34 denotes a discharge tray, 41 denotes a low-voltage power supply unit, and 42 and 43 denote load-side units. In the electrophotographic copying machine, as shown in FIG. 4, a drum-shaped photosensitive drum 32 serving as an image carrier is rotatably provided in the center of the main body, and a light is provided on a lower surface of a platen 22 on which the original 21 is placed. Lamp 23 that irradiates the document
A reflecting mirror group 24 and a lens group 25 are provided for transmitting the reflected light from 21 to the exposed portion on the photosensitive drum 32. In the vicinity of the upper portion of the photosensitive drum 32, a charger 27 facing the photosensitive drum 32 is provided, and further, a developing device 29, a transfer device 30, a cleaner 31, and the like are provided along the rotation direction. In addition, a paper feed tray 28, a fixing device 33, a paper discharge tray 34, and the like are arranged corresponding to such an electronic copying system. Such an electrophotographic copying machine generally has a low-voltage power supply unit 41 as shown in FIG. 5, for example, 24 V as a power supply from the low-voltage power supply unit 41, and as a control power supply for driving an OP amplifier and other logic. 15V or 5V is supplied to the load side units 42 and 43. The low-voltage power supply unit 41 is generally provided with a transformer for each power supply of each voltage, a rectifier on the secondary side thereof, a smoothing circuit, and is configured to supply a predetermined voltage.
Needless to say, a power supply stabilizing circuit, an overload protection circuit, and the like are also provided. The load-side units 42 and 43 include, for example, a high-voltage power supply unit and a scanning servo of an optical system necessary for driving the photosensitive drum 32, driving the optical scanning type, and controlling each component. Optical system servo unit to drive,
There are a main control servo unit and a main control unit. 6 and 7 are diagrams showing a configuration example of a transfer discharge current supply circuit of the transfer device. The high-voltage power supply for supplying the high-voltage discharge current for transfer is, for example, as shown in FIG. 6, a current monitor detection inserted between the low-voltage side of the high-voltage power supply (that is, the low-voltage side of the secondary winding of the transformer) and the ground. The supply current is detected by the circuit 7, and a value corresponding to the detected current (for example, a voltage drop of the current detection resistor) is compared with a reference value (reference voltage) by an error amplifier, and the switching transistor is switched based on the error amplification signal. The booster circuit having the known switching converter 6 is controlled to obtain a high voltage. This high-voltage output is provided with a rectifying / smoothing circuit 5 composed of a diode, a capacitor, and the like connected in series between the high-voltage side and the low-voltage side of the secondary winding of the transformer. The discharge current is supplied to the discharge wire 2 covered with the shield case 3 of FIG. The shield case 3 is connected to the low voltage side of the secondary winding of the transformer, and the shield case 3
Is returned to the low voltage side of the high voltage output. The transfer device is provided with a chute 4 for guiding the sheet to the wire 2 so that the sheet can be tacked at an appropriate point. This chute 4 is connected to the frame ground via a high resistance. On the other hand, in the AC system, as shown in FIG. 7, in order to improve the accuracy of the discharge current monitor of the AC output, the outer periphery of the high voltage wire is shielded, and the leakage current from the shield is forcibly monitored by the current monitor in the high voltage power supply. It is configured to return to a stage subsequent to the detection circuit 7, that is, to the low voltage side of the high voltage output. [Problems to be Solved by the Invention] However, in the transfer device, since the chute 4 is grounded to the frame ground via the high resistance as described above, the current I _M detected by the current monitor detection circuit 7 is
Is a plus leakage current I _C of the chute 4 to the transfer discharge current I _D flowing into as illustrated photoreceptor. Therefore, the shoot current I _C causes an error. For example, even if the value of the component of the shoot current I _C is added to the value corresponding to the transfer discharge current _ID as a reference value of the error amplifier circuit, the shoot current I _C
Is a relatively large value, because the moisture content of the sheet such as paper is changed in response to environmental changes such as humidity, chute current I _C by the change varies greatly, monitor suitable for transfer discharge current control There is a problem that can not be. In the AC system, the outer periphery of the high-voltage electric wire is shielded, and the leakage current from the shield is forcibly returned to the subsequent stage of the transfer discharge current monitor detection circuit in the high-voltage power supply, that is, to the low-voltage side of the high-voltage output. However, shielded high-voltage electric wires are not only expensive, but also greatly reduce the efficiency of the high-voltage power supply due to leakage from the shield. In addition, shielded high-voltage electric wires tend to generate a concentrated electric field at the end of the shield, and it is necessary to secure the distance between the charged part of the high-voltage electric wire and the shield. have. SUMMARY OF THE INVENTION The present invention solves the above-described problems, and can eliminate various leakage currents from a discharge current monitor, and can realize a stable supply of a high-voltage power supply without using a shielded wire. It is an object to provide a current supply device. [Means for Solving the Problems] For this purpose, the present invention provides a chute for guiding a sheet to a transfer position for transferring a developed image on a photosensitive member connected to a ground, and a sheet guided by the chute. For a transfer device including a wire for discharging on the photoreceptor and a corona discharger including a shield case covering the wire, a high voltage is applied between the wire and the ground by a high voltage output of a high voltage power supply. Current detection means is inserted into the high-voltage output return line to detect a current flowing between the low-voltage side of the high-voltage output and the ground, and to control a discharge current supplied from the wire to the photoconductor based on the detection result. In the high-voltage discharge current supply device, a high-voltage electric wire connecting the high-voltage output of the high-voltage power supply to the wire has a distance from the ground frame along the high-voltage electric wire. A holding means is provided for holding at a constant interval so as to be constant, and the chute is connected to the shield case via a resistor, and a leak current flowing through the chute via the resistor and a current flowing in the shield case are provided. Are fed back to the low voltage side of the high voltage output. The holding means preferably comprises a cylindrical pipe portion through which the high-voltage electric wire passes, and an elongated spacer portion having a predetermined height with respect to a ground frame adjacent to the pipe portion and along the pipe portion. It is a pipe. [Operation] In the high-voltage discharge current supply device of the present invention, errors caused by these leak currents can be eliminated by returning the current flowing through the shield and the chute of the transfer device to the low-voltage side of the high-voltage output. In the case of an AC system or a system containing an AC component, the distance between the high-voltage electric wire and the ground frame is maintained at a constant interval along the wiring of the high-voltage electric wire by the holding means, thereby maintaining the distance from the frame. The stray capacitance between the wires can be kept constant, and the component of the leak current flowing from the high-voltage wire to the ground included in the value detected by the current detection means is constant and smaller than the leak current flowing through the shielded wire. Become. Therefore, for the constant current control, the error can be corrected more accurately without complicating the control circuit, for example, only by adding the value corresponding to the leak current to the reference value given to the error amplifier. Therefore,
Even if a shielded wire is not used, a stable supply of a high voltage power supply can be realized, and moreover, a more efficient supply can be achieved than when a shielded wire is used. When a support pipe is used as the holding means,
Since the support pipe can be directly held with respect to the wiring of the high-voltage electric wire, the space can be efficiently designed and can be easily applied to the wiring of the high-voltage electric wire with flexibility. Embodiment An embodiment will be described below with reference to the drawings. FIG. 1 is a view showing one embodiment of a high-voltage discharge current supply device according to the present invention. In the figure, 1 is a photosensitive drum, 2 is a corotron wire, 3 is a corotron shield case, 4
Denotes a shoot, 5 denotes a rectifying and smoothing circuit, 6 denotes a switching converter, and 5 denotes a discharge current monitor detection circuit. In FIG. 1, a transfer device includes a chute 4 for guiding a sheet to a transfer position for transferring a developed image on a photoconductor 1 connected to a ground, and a photoconductor 1 on the photoconductor 1 via the sheet guided by the chute 4. Discharge wire 2 and its wire 2
A corona discharger including a shield case 3 that covers the
The chute 4 is connected to the subsequent stage of the discharge current monitor detection circuit 7 via a high resistance. In this case, the chute 4 is connected to the shield case 3 via a high resistance as shown by the solid line in FIG.
Or the chute 4 may be connected to the latter stage of the discharge current monitor detection circuit 7 via a high resistance separately from the shield case 3 as shown by the dotted line in the drawing, that is, to the lower voltage side of the high voltage output. . With the above connection configuration, the chute 4
The leakage current flowing in the same way as the current flowing in the shield case 3 flows downstream of the discharge current monitor detection circuit 7, that is, on the low voltage side of the high voltage output, and these leakage currents are removed from the detected current. And discharge current control. 2 and 3 are views showing another embodiment of the high-voltage discharge current supply device according to the present invention, in which 11 is a case, 12 is a substrate, 13 is a high-voltage transformer, 14 is a support pipe, and 15 is a high-voltage electric wire. , 16 indicate a cable tie. In the example shown in FIG.
The shielded high-voltage electric wires 15 are supported on the upper part, and the distance between the high-voltage electric wires 15 and the ground frame (grounded frame) is fixed so as to be constant. For this purpose, in the example shown in FIG. 2, the supporting pipe 14 is connected to the case 11 as a ground frame so that the high-voltage wires 15 are supported at a predetermined interval as shown in FIG. Cylindrical pipe part through which the pipe part and the case
11 and an elongated spacer having a certain height. In the example shown in FIG. 3, the cable tie 16 fixes and supports the high-voltage wires 15 on the board 12 of the high-voltage power supply. Are supported by a support member so as to be at a constant interval along. With the above configuration, the stray capacitance between the high-voltage electric wire and the ground frame of the copying machine can be kept constant, and the high-voltage electric wire can be used as a shield dress.
Moreover, the leakage current can be kept constant,
Moreover, the size can be reduced as compared with the case where a shielded wire is used. Therefore, for the constant current control, for example, a value corresponding to the leakage current may be added to the reference value of the error amplifier of the known switching converter 6, so that the error correction for the leakage current of the high-voltage wire can be performed without complicating the control. The control accuracy of the discharge current flowing to the photoconductor can be improved. It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the description has been given by applying to the transfer device of the electrophotographic copying machine.
It goes without saying that the present invention may be applied to a discharge current supply circuit other than the transfer device. [Effects of the Invention] As is apparent from the above description, according to the present invention, since the shield current and the leakage current can be excluded from the detection signal of the discharge current monitor detection circuit, the detection accuracy of the transfer discharge current is improved. Control accuracy can be improved. In addition, in the AC system, shielded high-voltage wires can be used, so the cost can be reduced without lowering the efficiency of the high-voltage power supply, and this was performed when shielded high-voltage wires were used. Work such as terminal treatment of the shield becomes unnecessary. When a support pipe is used as the holding means,
Since the support pipe can be directly held with respect to the wiring of the high-voltage electric wire, the space can be efficiently designed and can be easily applied to the wiring of the high-voltage electric wire with flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing one embodiment of a high-voltage discharge current supply device according to the present invention, and FIGS. 2 and 3 are other embodiments of the high-voltage discharge current supply device according to the present invention. , FIG. 4 is a diagram showing a schematic configuration of an electrophotographic copying machine, FIG. 5 is a diagram showing a schematic configuration of a power supply line of the electrophotographic copying machine, and FIG. 6 and FIG. FIG. 3 is a diagram illustrating a configuration example of a discharge current supply circuit. 1 ... Photoconductor drum, 2 ... Corotron wire, 3 ...
... Corotron shield case, 4 ... Shoot, 5 ...
... Rectifier smoothing circuit, 6 ... Switching converter, 5 ...
... discharge current monitor detection circuit, 11 ... case, 12 ... board, 13 ... high voltage transformer, 14 ... support pipe, 15 ... high voltage electric wire, 16 ... cable tie.

Claims (1)

(57) [Claims] A chute that guides the sheet to a transfer position for transferring a developed image on the photoconductor connected to the ground, a wire that discharges onto the photoconductor through the sheet guided by the chute, and a shield case that covers the wire And a corona discharger including a high voltage output of a high voltage power supply, and a high voltage is applied between the wire and the ground, and a current detection unit is inserted into a return line of the high voltage output. A high-voltage discharge current supply device that detects a current flowing between the low-voltage side of the high-voltage output and the ground and controls a constant current of a discharge current supplied from the wire to the photoconductor based on the detection result. Holding means for holding the high-voltage wires connected to the wires at a constant interval so that the distance to the ground frame is constant along the wiring of the high-voltage wires; And connecting the chute with the shield case via a resistor to return a leak current flowing through the chute via the resistor and a current flowing in the shield case to the low voltage side of the high voltage output. High voltage discharge current supply device. 2. The holding means is a support pipe comprising a cylindrical pipe portion through which the high-voltage electric wire passes, and an elongated spacer portion having a predetermined height with respect to a ground frame adjacent to the pipe portion and along the pipe portion. The high-voltage discharge current supply device according to claim 1.