JPS60170879A - Electrostatic brush cleaning device - Google Patents

Abstract

PURPOSE:To perform cleaning operation excellently by rubbing two conductive brush rolls against an image carrier at an interval in its moving direction, and impressing those conductive brush rolls with a DC voltage which is opposite in polarity and lower than a corona discharging start voltage. CONSTITUTION:A photosensitive body 13 is a P type photosensitive body formed by providing a photosensitive layer 13b on the surface of a conductive layer 13a, and (+) toner particles and (-) toner particles are present on the surface of the photosensitive layer 13b, so that residual toner having a both positive and negative polarity electrostatic charge distribution is present and moves toward a housing 10. The 1st conductive brush roll 11 is impressed with a 400-500V (+) charge and a brush 11a consisting of 10<0>-10<4>OMEGAcm contacts the photosensitive body 13 and is rubbed against the surface of the photosensitive body with (+) toner particles and (-) toner particles while generating fine plus corona atop. Almost no corona particles are charged electrostatically with the fine corona from brush tips and only the photosensitive body 13 is destaticized principally.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic brush cleaning device that removes residual toner on an image carrier by rubbing a conductive push roller against the image carrier.

Prior Art As shown in FIG. 1, a conductive brush roll 2 is provided in a housing 1 so as to rub against an image bearing member (hereinafter referred to as a photoreceptor) 3, and a detoning roll 4 is attached to the conductive brush roll 2. At the same time, the detoning roll 4
A low voltage is applied to the four-electric brush roll 2, a voltage of the same polarity is applied to the detoning roll 4, and a cleaning corotron 6 and a lamp 7 are placed in front of the housing 1. The remaining toner image (hereinafter referred to as residual toner) transferred from the photoreceptor 3 to the paper is
First, the cleaning corotron 6 to which a DC voltage is applied is charged to a single polarity. One side is charged to 1-+.

Next, the conductive brush roll 2 to which a DC voltage of the opposite polarity to that of the cleaning corotron 6 is applied is rubbed against the photoreceptor 3 to clean the residual toner on the photoreceptor 3 using Coulomb force.

The cleaned residual toner is transferred to a conductive roller 2 Kmm, transferred to a dining roll 4, removed by a scraper 5, falls onto a hopper 8, and is conveyed to the outside of the housing 1 by a screw conveyor 9. Electrostatic brush cleaning devices are known.

In such an electrostatic brush cleaning device, the efficiency of cleaning residual toner depends in principle on the amount of charge on the residual toner.

FIG. 2 is a table showing the relationship between the amount of charge of residual toner and the cleaning efficiency. If the amount of charge is in the range of α and b, the cleaning efficiency is excellent;
On the 1 side, the cleaning efficiency deteriorates rapidly.

Brush, α side (-2 side, conductive brush roll 2
The Coulomb force that attracts the residual toner to the conductive brush roll side also becomes larger than the mirror image force generated between the residual toner and the photoreceptor, making cleaning impossible. Insufficient cleaning results in poor cleaning, resulting in a sharp decline in cleaning efficiency.

Note that the values of α and b are generally as follows.

a * I 10μ'/yl + b medium + 301tC
/PI On the other hand, the charge distribution of the residual toner is in a state spanning both positive and negative polarities, as shown in FIG.

The reasons for this are: (1) During the development process, toner of opposite polarity adheres to the portion of the image that overlaps with the background portion.

■ Because reverse ionization occurs in the normal transfer process,
A polarity reversal occurs in a portion of the toner.

etc. are being considered.

Therefore, the cleaning corotron 6 applies an electric charge to the residual toner to correct the band distribution of the residual toner to 1, for example, l-1 side, as shown in FIG. It is not possible to cause absorption between 'tα and b.

The reason for this is that the above-mentioned reverse polarity toner in the background area is very coarsely distributed, and in order to reverse the polarity of toner particles in such a state with the cleaning corotron, the ion current of the cleaning corotron must be simplified.

However, it must be set several times higher than when reversing the polarity of densely distributed toner image particles.

If an ionic current density that can reverse the polarity of the opposite polarity toner in the background area is given, the toner particles in the image area will become even more (-) than α.
) is thought to be due to the appearance of electrically charged objects.

Therefore, since the charging distribution of the residual toner cannot be set between α and b by the cleaning corotron, for example, the residual toner in the shaded area in FIG. 4 cannot be cleaned, resulting in a cleaning failure.

FIG. 5 is a schematic diagram showing the parameters (wind run) of the cleaning device that exhibits a good cleaning performance when toner having a substantially uniform band distribution between 0 and 6 enters the cleaning device. be.

If the pressure (brush bias) at the mark 210' on the conductive brush roll is less than the line A-B, the electrostatic cleaner/glue will be insufficient and a cleaning failure will occur, and the line C--
At D or higher, corona discharge occurs from the tip of the brush at the rubbing area between the photoreceptor and the conductive brush roll, and the polarity of the toner on the photoreceptor is reversed or the amount of charge is reduced, resulting in poor cleaning. If the circumferential speed of the conductive brush roll (brush circumferential speed) is less than straight line A-C, cleaning failure will occur due to insufficient mechanical cleaning action and excessive toner adhesion to the brush. At a brush circumferential speed above (approximately 500 W x pc), toner particles separated from the photoreceptor scatter and form a cloud, causing the toner to leak outside the brush.

That is, the area surrounded by A-E-E'-C is the cleaning window of the conventional electrostatic brush cleaning device t shown in FIG.

OBJECTS OF THE INVENTION It is an object of the invention to enable cleaning to be performed satisfactorily regardless of the charge amount and charge distribution of residual toner.

Structure of the invention 1. A second conductive brush roll is rubbed against the image carrier, and a DC voltage of 0 is applied to the first conductive brush roll to generate a corona discharge at the rubbing portion with the image carrier. A DC-rt pressure having a polarity opposite to the above-mentioned DC voltage and lower than the corona discharge starting voltage was applied to the roll.

Embodiment FIG. 6 is an explanatory diagram of an electrostatic brush cleaning device. The second conductive brush rolls I+ and +2 are provided in sliding contact with the photoreceptor 13 serving as an image bearing member, and the first conductive brush rolls I+ and +2 are provided in sliding contact with the photoreceptor 13 serving as an image bearing member. Second conductive brush rolls 11, 12
The first thing is. 2nd day toning roll 14. +5 is in contact and the 1st. 2nd day toning roll 14°1
5 has the 1st. A second scraper 16,17 is in contact.

Reference numeral 18 is an auger provided in the hopper 19, and a first auger on the back surface of the photoreceptor 13. 24th electric brush roll I+
, 12 is in pressure contact with a backup roll 20, and a cleaning lamp 21 is provided facing the first conductive brush roll 11.

A positive voltage is applied to the first conductive brush roll 11 and the first daytoning roll 14, and a negative voltage is applied to the second conductive brush roll 12 and the second daytoning roll 15. There is.

Next, we will explain the operation along with the details of each part.

The photoreceptor 13 is a P-type photoreceptor with a photoreceptor layer 135 provided on the surface of a conductive layer 13α, as shown in FIG.

On the surface of the photosensitive layer 136, the (1) toner particles and the (0) toner particles remain, and residual toner exists having a charge distribution of both positive and negative polarities as shown in FIG.

Move toward the housing 10.

The first torme-conducting brush roll 11 has a voltage of 400 to 500V (
+) A charge is applied, and the brush 11α made of conductive fibers of 1♂ to 1049 m comes into contact with the photoreceptor 13.

The tip rubs the toner particles and the photoreceptor surface without generating minute positive corona.

On the other hand, in the minute corona from the tip of the brush, almost no toner particles are removed or charged, and only the photoreceptor 13 is mainly charged. Further, the toner particles are mechanically slipped over the photoreceptor surface by the brush 11α, and the -1 charge (negative charge) on the photoreceptor surface that was in contact with the positively charged toner λ becomes a positive corona. The static electricity is removed and the light is extinguished.

Further, since the back surface of the photoreceptor 13 is irradiated with light by the cleaning lamp 21, the surface of the photoreceptor is not positively charged, and the toner particles in the state shown in FIG.
(2) The toner particles are in the state shown in Figure S.

In other words, before the brush 11α rubs against the brush 11α, as shown in FIG.
1α゛, as shown in the 8th factor, the O toner particles and their mirror image charge (+I) separate from the thickness of the photosensitive layer 13b and are attracted, so the attraction force decreases. This is because it is a P-type photoreceptor. The positive charge (+1) cannot pass through the interface between the photosensitive layer +3h and the conductive layer 13α and therefore exists in the conductive layer 13a.

For this purpose, the +-+ toner particles are transferred to the first conductive brush roll 11 to which the +1 voltage is applied.

The first conductive brush roll 11 has the same polarity as the first conductive brush roll 11 after rubbing against the photoreceptor 13, and has a polarity of approximately 30
The toner is rubbed against the Ml detoning roll 14 to which a high 0'' voltage is applied, and the captured toner is adsorbed and transferred to the first daytoning roll 14.

At this time, the potential difference between the first conductive brush roll 11 and the photoreceptor 13 is 400 to 500 V, and the 12th thickness 1-column brush roll 11 and f! The potential difference with the Jl detoning roll 14 is about 300 mm, which is smaller than the above-mentioned potential difference. This is to prevent corona discharge from occurring in the area.

Then, the small amount of toner particles that were not captured by the first conductive brush roll 11 and the small amount of toner whose polarity was changed (■→■λ) by the first conductive brush roll 11 are subjected to a heavy pressure of about -300■ (
The toner particles are captured by the second conductive brush roll 12 to which a voltage equal to or lower than the corona discharge starting voltage is applied, and the captured toner particles are transferred to the second daytoning roll 15 by absorption of N.

1st. The toner transferred to the second detoning roll 14.15 is transferred to the first detoning roll 14.15. It is scraped off by the second scrape 16° 17 and falls into the hopper 19, and is carried out of the housing 10 by the auger 18.

As described above, the residual toner on the photoreceptor 13 can be efficiently cleaned, and the cleaning performance is improved.

In the above embodiment, a low voltage was applied to the first conductive brush roll 11 to generate a minute corona.
A strong corona may be generated by fully applying a high pressure of +500 to ++ooov to the conductive brush roll 11.

In this case, the ■toner particles and ■toner particles on the photoreceptor 13 are affected by the strong positive corona, and ■toner particles (negatively charged toner are changed to ■one particle (negatively charged toner 2) and all of them are lost). The toner becomes ■.

Therefore, the first conductive brush roll 11 only serves to charge the toner particles and disturb the toner on the photoreceptor, and has no ability to capture the C toner.
The daytoning roll 14 becomes unnecessary.

As a result, the positive polarity toner enters and is captured by the second conductive plan roll 12, so that it is possible to exhibit good leaning performance as described above.

The brush of the fourteenth electric brush roll 11 can cover the entire surface of the toner particles by increasing the applied voltage.

On the other hand, in the case of charging by the cleaning corotron 6 shown in FIG. 1, as shown in FIG. 9, only the upper side of the toner particles can be charged, and most of the surface of the photoreceptor that is in the shadow of the toner particles is charged. Since this does not work, the toner particles are insufficiently charged, resulting in poor cleaning efficiency.

Effect of the Invention No. 14 Corona discharge is generated at the rubbing portion between the conductive brush roll 11 and the image bearing member 13 to charge or eliminate static electricity on the residual toner and the image bearing member 13, and then the second conductive brush roll 1
Since residual toner is captured by the cleaning method 2, cleaning can be performed satisfactorily regardless of the charge amount and charge distribution of the residual toner.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional example, and FIG. 2 is a table showing the relationship between toner charge amount and cleaning efficiency. Figure 3 is a table showing the amount of charge of residual toner, Figure 4 is a table showing the amount of charge of residual toner after processing with a cleaning corotron, and the fifth factor is a cleaning device that exhibits good cleaning performance. FIG. 6 is an overall explanatory diagram showing an example of the present invention. FIG. 7 is an explanatory diagram showing the state of adhesion of residual toner to the photoreceptor. v and gm are the first conductivity. Explanatory diagram of the state of being rubbed with a sex brush roll, No. 9
The figure is an explanatory diagram of the charging state by the cleaning corotron. 11 is a first conductive brush roll, 12 is a second conductive brush roll, and 13 is an image carrier. Representative: Fuji Xerox Co., Ltd. Patent attorney: Masaaki Yonehara Patent attorney: Tadashi Hamamoto Figure 1 Figure 2 No'a'l Figure 3 Figure 4

Claims (1)

[Claims] 1st image carrier 13. a second conductive brush roll I+;
12 at intervals in the moving direction of the image carrier 13, and a first
The conductive brush roll 11 has a distance of 11 m from the image carrier 13.
A DC voltage is applied to the second conductive brush roll 12 at which a corona discharge occurs from the tip of the brush 11α, and the polarity is opposite to that of the voltage applied to the second conductive brush roll 11, and the voltage is applied to start corona discharge. An electrostatic brush cleaning device characterized by applying a DC voltage below the voltage.