JPH09204126A - Cleaning equipment - Google Patents

Abstract

(57) Abstract: By averaging the potential of a cleaning member, even if the cleaning potential or the potential difference between the cleaning potential and the photoconductor belt becomes large, reverse adhesion of toner is less likely to occur and cleaning performance also deteriorates. Not provide a cleaning device. SOLUTION: A cleaning roller 11 for removing residual toner on a photosensitive belt 1, and a cleaning roller 11
A constant current power supply 17 for supplying a constant current and a potential averaging means for averaging the potential of the cleaning roller 11 are provided. As this potential averaging means, a capacitive reactance element (capacitor 19) connected between the cleaning roller 11 and the ground can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device for an image forming apparatus such as a copying machine, a facsimile machine or a printer, and more specifically, it remains on the surface of an image carrier after transferring a toner image onto a transfer material. The present invention relates to a cleaning device for an image forming apparatus that removes and cleans residual toner.

[0002]

2. Description of the Related Art Conventionally, as a cleaning device for an image forming apparatus of this type, a toner collecting member for collecting toner on a cleaning roller between a magnetic brush cleaning roller and an image carrier, and the cleaning roller and the cleaning member. It is known that a constant current power source is connected between the roller and the roller (see Japanese Patent Laid-Open No. 1-259393). According to this cleaning device, a constant current value can always be ensured even if the cleaning agent changes with time and the electric resistance increases, so that good cleaning performance can be maintained.

[0003]

However, in the cleaning device having the above structure, since a constant current is supplied to the cleaning member, the cleaning potential may increase when the electric resistance of the cleaning agent used for the cleaning member increases. There is. If this cleaning potential rises excessively, the electric field near the surface of the cleaning member becomes large, and the electric charge is injected into the cleaned toner, and the electric charge-injected toner returns to the image carrier, a so-called toner. Reverse adhesion occurs. Further, the phenomenon that the cleaning potential rises excessively may occur not only when the cleaning agent deteriorates with time, but also when the cleaning agent starts to be used. For example, when a pre-cleaning charger is provided for uniformly charging the toner remaining on the image carrier after transfer with a potential having a polarity opposite to the cleaning potential before cleaning with the cleaning member, the If the absolute value of the surface potential (potential of the opposite polarity to the cleaning potential) of the image carrier after being charged by the cleaning charger is small, the absolute value of the cleaning potential becomes large. This facilitates the injection of charges from the cleaning member into the toner. More specifically, for example, in the case of a negatively charged image carrier, when the absolute value of the surface potential (positive polarity) of the image carrier after being charged by the pre-cleaning charger is small, the absolute value of the negatively charged cleaning potential. Becomes large, and negative charges are easily injected into the toner. Further, it is considered that the toner reverse adhesion is likely to occur even when the electric field near the surface of the cleaning member becomes large due to the large potential difference between the cleaning potential and the image carrier.

The inventor of the present invention has carried out detailed observations and experiments relating to the reverse toner adhesion, and in addition to the absolute value of the cleaning potential and the absolute value of the potential difference between the cleaning potential and the surface potential of the image carrier, It has been found that the degree of change in these potentials or the potential difference tends to greatly contribute to the above-mentioned toner reverse adhesion. Specifically, they have found that the greater the degree of change in the potential or the potential difference, the more likely toner reverse adhesion tends to occur. For example, it was confirmed by experiments that toner reverse adhesion is likely to occur on the downstream side in the moving direction of the surface of the image carrier at the joint between the image carriers such as the photoconductor belt. As described above, toner reverse adhesion is likely to occur at the joint of the image carrier because the electrostatic potential is different from that of the periphery thereof, and thus the surface potential of the joint is significantly different from the surface potential of the periphery thereof and the image carrier of the joint is It is considered that this is because the potential difference between the cleaning potential and the surface potential of the image carrier greatly changes on the downstream side in the surface moving direction.

In order to prevent the reverse adhesion of the toner, it is known that a potential limiting means (zener diode or the like) is provided between the cleaning member and the ground to limit the cleaning potential within a certain limit. (See Japanese Patent Laid-Open No. 5-35159). However, in this cleaning device, when the deterioration of the cleaning agent progresses over time and the electric resistance increases, the cleaning potential that should originally increase in accordance with the increase in the electric resistance does not rise, so that the cleaning member and the image carrier There is a problem that the magnitude of the current flowing through the body is reduced and the cleaning performance is deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to prevent reverse toner adhesion even if the cleaning potential or the potential difference between the cleaning potential and the image carrier is large. Moreover, it is an object of the present invention to provide a cleaning device in which cleaning performance is not deteriorated.

[0007]

In order to achieve the above object, the invention of claim 1 removes the residual toner remaining on the surface of the image carrier after transferring the toner image onto the transfer material. In a cleaning device of an image forming apparatus for cleaning, a cleaning member that removes residual toner on the image carrier, a constant current power supply that supplies a constant current to the cleaning member, and a potential average that averages the potential of the cleaning member. It is characterized in that a conversion means is provided.

According to a second aspect of the present invention, in the cleaning device according to the first aspect, a capacitive reactance element connected between the cleaning member and the ground is used as the potential averaging means. is there.

According to the first aspect of the invention, when the cleaning member removes the residual toner on the image bearing member for cleaning, a constant current is supplied from the constant current power source to the cleaning member. The performance can be obtained. Further, the potential of the cleaning member is averaged by the potential averaging means so that the potential does not change suddenly.

According to the second aspect of the present invention, the capacitive reactance element is connected between the cleaning member and the ground, and the potential of the cleaning member is averaged so that the potential does not change abruptly. To

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a cleaning device of an electrophotographic copying machine (hereinafter referred to as "copying machine") which is an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a cleaning device according to this embodiment. In this cleaning device, a negative polarity OPC belt (hereinafter, referred to as “photoconductor belt”) 1 as an image carrier is a driving roller and a driven roller 2, which are not shown.
It is stretched around 3 and 4, and a predetermined tension is given by a biasing means such as a spring (not shown). This photoconductor belt 1
Is about 430 mm / in the direction of arrow A when the driving roller is rotated by a motor during the copying operation of the copying machine.
It moves with s and has a predetermined polarity (negative polarity) with a charger not shown.
After being uniformly charged to an electrostatic latent image, an electrostatic latent image is formed by image exposure by an exposing unit (not shown). This electrostatic latent image is developed into a toner image by a developing device (not shown), and is transferred to a transfer paper 5 as a transfer material fed from a paper feeding device (not shown) by a transfer charger 6 to which a negative voltage is applied. It After the transfer of the toner image, the transfer paper 5 is separated by a separation charger 7 to which an AC voltage is applied, the toner image is fixed by a fixing device (not shown), and then the transfer paper 5 is ejected to the outside of the machine. In addition, the residual toner remaining on the photosensitive belt 1 after the transfer has different polarities and holding charge amounts, so that the pre-cleaning charger 8 is used.
After the positive charge is given by the cleaning device 9
Is removed by

In the cleaning device 9 according to this embodiment, the cleaning facing roller 10 is arranged on the back side of the photosensitive belt 1, and the cleaning roller 11 as a cleaning member including the cleaning sleeve 11a and the built-in magnet roller 11b is cleaned. It is arranged so as to face the opposing roller 10 with the photoconductor belt 1 interposed therebetween. The cleaning sleeve 11a is rotationally driven in the direction of arrow B (counterclockwise) by a drive mechanism (not shown), and the cleaning agent 12 containing toner and carrier is carried on the outer peripheral surface thereof by the magnetic force of the magnet roller 11b, so that the magnetic brush is retained. Form. The photoconductor belt 1 is guided by the cleaning opposing roller 10 and has a predetermined gap between the photoconductor belt 1 and the cleaning sleeve 11a.

A bias voltage having a polarity (negative polarity) opposite to the charge polarity of the residual toner on the photosensitive belt 1 is applied to the cleaning sleeve 11a from the constant current power source 17, whereby the cleaning agent 12 contains The carrier is negatively charged. Also, the cleaning sleeve 11a
The carrier is negatively charged by frictional charging between the toner of the cleaning agent 12 and the carrier accompanying the rotation of the carrier.
In this embodiment, the output current value of the constant current power supply 17 is set to -2.
It is set to 0 μA. With the bias voltage thus applied, the magnetic brush made of the cleaning agent 12 carried on the cleaning sleeve 11a removes (cleans) the residual toner on the photosensitive belt 1 while electrically attracting it.

Further, a toner collecting roller 13 as a toner collecting member is arranged so as to come into contact with the magnetic brush of the cleaning agent carried on the cleaning sleeve 11a at a predetermined gap. A bias voltage having a polarity opposite to the charging polarity of the toner is applied from the constant current power source 18 to the core of the toner collecting roller 13, whereby a part of the toner in the cleaning agent 12 is electrically transferred to the toner collecting roller 13. Is sucked in. In this embodiment, the output current value of the constant current power source 18 is set to -10 μA.
With the bias voltage thus applied, the toner collecting roller 13 rotates in the direction of arrow C (clockwise) to collect the toner from the magnetic brush on the cleaning sleeve 11a. The toner collected by the toner collecting roller 13 is
It is scraped off by the blade 14 and the toner carrying coil 15
Is dropped onto the toner receiving case 16 to which is attached, is conveyed by the toner conveying coil 15, and is collected in a waste toner bottle (not shown).

FIG. 2 is an equivalent circuit diagram of the cleaning device of this embodiment. In FIG. 2, resistances R1 and R2 are the resistance of the cleaning agent 12 present between the cleaning sleeve 11a and the toner collecting roller 13 and the resistance of the cleaning agent 12 present between the cleaning sleeve 11a and the photosensitive belt 1, respectively. Indicates resistance. Further, the photosensitive belt 1 is one in which a conductive layer and an organic photosensitive layer are laminated on a base material and conductive paint layers are provided at both ends of the conductive layer, and the conductive paint layer is grounded. The resistance 3 indicates the resistance of the photosensitive drum 1 (the resistance of the conductive layer, the organic photosensitive layer, and the conductive coating layer). The constant current power supply 17 is connected between the cleaning sleeve 11a and the ground, and applies a bias voltage to the cleaning sleeve 11a. Further, the constant current power source 18 is connected between the core metal portion of the toner collecting roller 13 and the cleaning sleeve 11a and insulated from the ground, and applies a bias voltage to the toner collecting roller 13. In the figure, I1 is a current supplied from the constant current power supply 18, and I2 is a current supplied from the constant current power supply 17.

A capacitive reactance element (capacitor) 19 is connected between the cleaning sleeve 11a and the ground as a potential averaging means for averaging the potential of the cleaning sleeve 11a (cleaning potential). The current I1 supplied from the constant current power source 17 is divided into a current I3 flowing through the resistance R2 of the cleaning agent 12 and a resistance R3 of the photosensitive belt 1 and a current I4 flowing through the capacitor 19.

3 (a) and 3 (b) respectively show capacitances C = 780 pF and 123 as the capacitor 19.
The measurement result of the time change of the cleaning potential Vcl when an electrolytic capacitor of 0 pF is connected is shown. As shown in FIG. 3, the cleaning potential Vcl is integrated and averaged by the capacitor 19, and a sharp time-varying AC component of about Vp-p = 30 to 40 V (FIG. Comparative Example of No.) disappeared, and the reverse adhesion of toner to the photosensitive belt 1 did not occur. FIG.
From the measurement result of C = 1230 pF in (b), it can be seen that the gradual time-varying component also tends to disappear.

Here, the capacitance C of the capacitor 19 is
It is desirable to select the cleaning potential Vcl within a range that follows the surface potential of the photoconductor belt 1.
It is also possible to prevent deterioration of cleaning performance. Under the process conditions of this embodiment, 30 pF to 1500 pF was optimal.

As described above, according to the cleaning device of the present embodiment, by connecting the condenser 19 described above,
Since the AC component that sharply changes with time can be eliminated from the cleaning potential Vcl, the cleaning potential (Vcl)
Of the surface of the photosensitive belt 1 (V
pcc) and cleaning potential (Vcl) difference Vpcc
Even if −Vcl becomes large, the reverse adhesion of toner to the photosensitive belt 1 does not occur. Furthermore, since a constant current can be supplied to the cleaning sleeve 11a by the constant current power supply 17, the cleaning performance does not decrease even if the electric resistance of the cleaning agent 1 increases.

[0020]

According to the first or second aspect of the present invention, a constant current can be supplied from the constant current power source to the cleaning member at the time of cleaning to obtain a constant cleaning performance, and the cleaning member can be provided by the potential averaging means. By averaging the potentials of No. 3, since the potentials do not change abruptly, even if the cleaning potential or the potential difference between the cleaning potential and the image carrier becomes large, the reverse adhesion of toner hardly occurs and the cleaning performance is also improved. It has the effect of not decreasing.

In particular, according to the second aspect of the present invention, the potential of the cleaning member is averaged by a simple structure in which the capacitive reactance element is connected between the cleaning member and the ground to rapidly increase the potential. There is an effect that it is possible to prevent the toner from being reversely adhered to the image carrier by keeping the same.

[Brief description of drawings]

FIG. 1 is a front view showing a schematic configuration of a cleaning device according to an embodiment.

FIG. 2 is an equivalent circuit diagram of the cleaning device.

FIG. 3A and FIG. 3B are graphs showing a change over time of a cleaning potential of the cleaning device.

FIG. 4 is a graph showing a change over time of a cleaning potential of a cleaning device according to a comparative example.

[Explanation of symbols]

 1 Photoconductor Belt 11 Cleaning Roller 11a Cleaning Sleeve 11b Magnet Roller 12 Cleaning Agent 13 Toner Collection Roller 14 Blade 15 Toner Conveying Coil 16 Toner Receiving Case 17 Constant Current Power Supply for Cleaning Sleeve 18 Constant Current Power Supply 19 for Toner Recovery Roller 19 Capacitor

Claims (2)

[Claims] 1. A cleaning device of an image forming apparatus for removing and cleaning residual toner remaining on the surface of an image carrier after transferring a toner image onto a transfer material, A cleaning device comprising: a cleaning member to be removed; a constant current power supply for supplying a constant current to the cleaning member; and a potential averaging means for averaging the potential of the cleaning member. 2. The cleaning device according to claim 1, wherein a capacitive reactance element connected between the cleaning member and a ground is used as the potential averaging means.