JPH09204129A - Image forming device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To shorten the cleaning time and prevent rubbing on the surface of an image carrier as much as possible by performing an appropriate amount of cleaning according to the adhered state of foreign matter adhering to the surface of the image carrier. Extend the life of the image carrier. A marker 13 (marking means) for detecting the adhered state of foreign matter on the surface of a photoreceptor 1 (image carrier) and a CCD sensor 12 (marking detection means) for reading a mark made by the marker 13 are provided. The time when it is confirmed that the mark made by the CCD sensor 12 has been removed is regarded as the state in which the foreign matter is removed, and the pre-driving of the cleaning device 7 (cleaning means) is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printing machine, a printer, etc., which is provided with a cleaning device for removing foreign matters adhering to the surface of an image carrier.

[0002]

2. Description of the Related Art Conventionally, various forms of image forming apparatuses utilizing so-called electrophotography have been proposed.
In this type of image forming apparatus, a plurality of corona chargers are provided for the purpose of charging a photoreceptor as an image carrier and transferring a toner image to a transfer member.
In this way, it is generally practiced to charge the surface of the photoconductor, the recording material, etc. to a desired state and achieve the purpose.

Therefore, the molecules in the air may change due to the corona discharge of the corona charger, and a slight amount of substances such as nitrogen oxides may be produced. Then, such a corona product adheres to the surface of the photoconductor to reduce the surface resistance, blur the electrostatic latent image formed on the surface of the photoconductor, and deteriorate the quality of the formed image. May affect In addition, this phenomenon changes its degree depending on the environmental conditions.
Especially, the problem was remarkable in a high humidity environment.

Conventionally, in order to solve the above-mentioned problems, a method of heating and drying the surface of the photosensitive member or an elastic roller made of silicon rubber or the like is pressed against the surface of the photosensitive member and rotated to rotate the surface of the photosensitive member. There has been proposed a method of removing corona products by rubbing the surface.

In the former method of drying, the surface of the photosensitive member is heated by a heater, but this method has a problem that the corona product and the toner are fixed to the surface protective layer of the photosensitive member. In addition, heating the photosensitive member with the heater significantly increases the power consumption of the electrophotographic apparatus and further extends the waiting time before the apparatus can be used from a cold state.

The latter method of rubbing has a stable effect even when the photoconductor is used for a long period of time, and a substance existing in the transfer portion area such as paper or paper dust adheres to the photoconductor surface. It is an excellent method because it has an effect of removing the toner when it is fixed and fused.

FIG. 7 shows a configuration of a conventional technique for explaining the latter rubbing method. In the figure, reference numeral 1 denotes a cylindrical photoconductor, which rotates in the direction of arrow A101 in the figure. This photoreceptor 10
After being uniformly charged by the corona discharger 102, image exposure 103 is irradiated with image exposure 103, and an electrostatic latent image corresponding to the original is formed and visualized by the developing unit 104.

The visualized toner image is transferred to the transfer member 10.
The image is transferred onto the surface of the transfer member S ′ supplied from No. 5. At this time, if necessary, the transfer corona discharger 10 may be transferred from the back side.
A charge having a polarity opposite to that of the toner is given by 6. After that, the transfer member S ′ is conveyed after separation, and is fixed if necessary.

The photosensitive member 101 is then cleaned by the cleaning device 1.
The cleaning blade 10 is rubbed by a rubbing roller 107a formed of an elastic material having a fixed bearing to remove a substance that becomes an image blur on the surface, and then the cleaning blade 10
The residual toner is removed by 7b and the residual charge is removed by pre-exposure 108, and the process proceeds to the next cycle. At this time, the rotation direction and speed of the rubbing roller 107a are set to the photoconductor 101.
Relative speed difference is given to the rotation direction and speed. In the figure, 107c is a scraper for removing toner and the like adhering to the surface of the rubbing roller 107a. 1
Reference numeral 07d is a feed screw for discharging the residual toner, paper dust, etc. accumulated in the cleaning device to the outside. Also, 1
Reference numeral 10 is a separation charger, and 111 is a separation roller.

[0010]

However, in the above-mentioned conventional example, since the rubbing roller 107a is made of an elastic material and is pressed against the surface of the photosensitive member to rotate, the rubbing roller 107a is used for a long period of time. The diameter and the surface condition of the toner change, and the ability to rub the surface of the photoreceptor 101 at the beginning is reduced, so that foreign substances such as corona products cannot be effectively removed.

In addition, if the rubbing ability is designed in consideration of an ultra-high humidity environment, it is necessary to increase the contact force of the rubbing roller. As a result, scratches may occur, and streaks and uneven density may occur on the image.

Further, conventionally, regardless of the amount of foreign matter adhering to the surface of the photoconductor, the photoconductor is pre-rotated for a certain period of time when the apparatus is started, and the cleaning device 1
07 was working. Therefore, even when the amount of foreign matter adhered is small, the waiting time of the user is the same and the surface of the photoconductor is rubbed more than necessary and worn. On the other hand, when the amount of foreign matter adhered is large, the surface of the photoconductor is not completely cleaned, which may lead to deterioration of image quality.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to perform an appropriate amount of cleaning in accordance with the adhered state of foreign matter adhering to the surface of the image carrier. The purpose is to shorten the cleaning time and prevent the surface of the image carrier from rubbing as much as possible to extend the life of the image carrier.

Further, irrespective of the environmental condition in which the image forming apparatus is used and the change in the surface condition depending on the number of images formed on the image carrier, the rubbing force within a predetermined range is maintained and a stable foreign substance removing ability is exhibited. Is to let.

[0015]

SUMMARY OF THE INVENTION To achieve the above object, the present invention comprises a cleaning device having a contact member that abuts the surface of a moving image carrier of an image forming unit, and at least starts up the device. In the image forming apparatus, the contact member of the cleaning device rubs the surface of the image carrier to remove foreign matter adhering to the image carrier by pre-driving the image carrier without performing image formation. The foreign matter detection means for detecting the adhered state of the foreign matter is provided, and when the foreign matter detection means confirms that the foreign matter is removed, the front drive is stopped.

Therefore, the adhering state of the foreign matter adhering to the image carrier is detected, and an appropriate amount of removal is carried out accordingly.

It is also preferable that the foreign matter detecting means includes marking means for marking ink on the surface of the image bearing member and marking detecting means for detecting the marking.

According to this means, the foreign matter marking adhered to the surface of the image carrier is regarded as the foreign matter adhered to the surface of the image carrier, and the time required for removing the foreign matter due to the change of the surface of the image carrier is taken as the time for removing the marking. Can be set.

Further, the foreign matter detecting means changes the surface potential by charging the image bearing member provided in the image forming section and exposing the surface of the image bearing member charged by the charging means. The exposure means, and a surface potential measuring means for measuring the surface potential of the position of the image carrier surface exposed by the exposing means, the predetermined exposure pattern formed by the exposing means, and the surface potential measuring means. It is also preferable to compare the surface potential pattern changed according to the exposure pattern to be measured and detect the adhesion state of the foreign matter based on the deviation of the inclination angle of the rising portion of the exposure pattern and the surface potential pattern.

Also by this means, the adhered state of the foreign matter on the surface of the image carrier is detected as a deviation of the surface potential pattern.

Load torque measuring means for measuring a load torque applied to the image carrier by the contact member and contact force adjusting means for changing the contact force of the contact member for contacting the surface of the image carrier. It is also preferable that the abutment member is controlled so as to keep the load torque applied to the image carrier within a certain range.

Therefore, with this configuration, the relationship between the contact member and the surface of the image carrier is always set to a constant rubbing state.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

(Embodiment 1) FIG. 1 illustrates the present invention in which a rotating cylindrical amorphous silicon photoconductor 1 as an image carrier is used.
1 shows an embodiment in the case of being applied to an electrophotographic image forming apparatus provided with (hereinafter, referred to as a photosensitive member unless particularly necessary).

In this image forming apparatus, a charger 2 is disposed in the vicinity of a surface photoconductive layer of a photosensitive member 1 formed in a rotating cylindrical shape.
The surface of the photoconductive layer is uniformly charged to become a charging surface, and an unillustrated original to be copied is scanned on this charging surface, and image exposure 3 with light and darkness according to image information is projected in the direction of the arrow. An electrostatic latent image is formed on the charged surface.

This electrostatic latent image becomes a transfer toner image by the toner supplied by the developing device 4, and this transfer toner image is transferred to the transfer surface of the sheet-shaped transfer material S which is transferred through the transfer path 5 and is supplied to the transfer portion. , And is transferred by the transfer charger 6.

Further, the transfer material S is separated from the surface of the photoconductor 1 by the separation electrode 10 and the separation roller 11 and is fed to a fixing device (not shown) arranged downstream.

On the other hand, during transfer, the residual toner remaining on the surface of the photoconductor 1 without being transferred to the transfer material S reaches the cleaning device 7 as the photoconductor 1 rotates in the direction of arrow A1.

A cleaning blade 7b is attached to the cleaning device 7, and the free end of the cleaning blade 7b is pressed against the surface of the photoconductor 1 to remove residual toner carried by the rotation of the photoconductor 1 after transfer. It is like this.

A cleaning roller 7a as an abutting member is arranged on the upstream side of the blade 7b so as to come into pressure contact with the surface of the photoconductor 1 with respect to the traveling direction of the photoconductor 1, and the cleaning roller 7a is exposed to light. It is configured to remove foreign matter such as paper powder, deposits from transfer paper, corona products, and the like by pressing and rubbing the body 1.

The cleaning roller 7a in the present embodiment is formed by forming an elastic layer made of urethane rubber sponge on a stainless steel shaft, and the elastic layer has a thickness of 3.5 mm. The material used for the elastic layer is 2
A relatively low hardness of 0 ° to 40 ° (load of Asker C 500 g) is desirable. In addition to the urethane rubber sponge used in the present embodiment, silicone rubber sponge, EPDM
(Ethylene-propylene-diene rubber) sponge and the like are suitable.

The cleaning roller 7a is rotated in a direction indicated by an arrow A1 or in a direction opposite thereto so as to have a relative speed with respect to the photoconductor 1, and a nip width of 1 to 6 mm in pressure contact with the surface of the photoconductor 1 and the cleaning roller 7a. It has been found that a good foreign matter removing action can be obtained by setting the peripheral speed to 50 to 300% of that of the photoconductor 1. Further, the cleaning roller 7a may be provided with a surface layer made of solid urethane rubber or the like on the outer side of its elastic layer.

Reference numeral 7c in the figure denotes a scraper for removing toner and the like adhering to the surface of the cleaning roller 7a, which is made of resin or thin sheet metal. Further, 7d is a feed screw for discharging the residual toner, paper dust and the like accumulated in the cleaning device 7 to the outside of the cleaner.

The present embodiment will be specifically described below. Image blurring (hereinafter referred to as image deletion) caused by the corona product adhering to the surface of the photoconductor 1 in a high humidity environment is the worst when the main body is started up. This is because the corona product generated by the previous image formation adhered and accumulated on the surface of the photoconductor 1 over time. After that, several copies were made and the surface of the photoconductor 1 was rubbed and polished by the cleaning roller 7a. As a result, the adhering substances are gradually removed and the image deletion disappears. However, in order to prevent the image deletion from occurring in the first copy, it is necessary to perform the pre-multi-rotation as the pre-driving before the image formation.

If the pre-multi-rotation time is equal to or longer than a predetermined length, the corona product is completely removed. However, if the length is longer than necessary, deterioration of the surface layer of the photoconductor 1 is promoted, resulting in streaks and image unevenness. Etc. occur. The time for performing multiple pre-rotations varies depending on the usage of the photoconductor, the environment in which the copier is used, etc.
Even if the sequential timer is used to set a fixed time as in the past, the image deletion may not be completely removed. Therefore, an index showing that the removal of the corona-generating substance is completed is needed.

Therefore, in the present invention, in order to develop a substitute characteristic indicating that the corona-generating substance has been removed as foreign matter detecting means, after marking the surface of the amorphous silicon photoconductor 1 with an oil-based ink, The characteristic that the corona generating substance is completely removed and the image deletion does not occur when the mark of the oil-based ink is rubbed against the cleaning roller and disappears when the pre-multi-rotation is performed is used. It is considered that this is because the adhesion of the oil-based ink to the surface of the amorphous silicon photoconductor and the adhesion of the corona product to the surface of the amorphous silicon photoconductor are almost the same.

In the figure, numeral 13 is a marker as a marking means, which is prepared by dissolving an oil-soluble dye or pigment together with an oil-soluble resin and an additive in a quick-drying organic solvent such as ethyl acetate and soaking it in felt or the like. A commercially available oily marker can be used instead. Suitable organic solvents are ketones such as acetone, alcohols such as ethanol and isopropyl alcohol, petroleum ethers, aliphatic hydrocarbons such as toluene and hexane, and aromatic hydrocarbons such as benzene. Further, the marker 13 can be brought into or out of contact with the surface of the photoconductor 1 by turning on or off a solenoid (not shown).

Next, the sequence operation of this embodiment will be described with reference to the flow chart of FIG.
When the main switch is turned on (S001) in the image forming apparatus as shown in the figure, the marker 13 is turned on and comes into contact with the surface of the photoconductor 1 (S002), an oil-based ink mark is formed, and a CCD sensor as a marking detection unit is formed. 1
It is confirmed that the mark is made by 2 (S00
3). In the present embodiment, three oil-based markers 13 are provided in the longitudinal direction of the photoconductor 1, and approximately 5 m are provided on the surface of the photoconductor 1.
A circular mark of m diameter is formed.

Next, the heater (not shown) of the fixing device is turned on, the temperature of the fixing roller begins to rise, and the photosensitive member 1 rotates (S004, S005), and the cleaning roller 7a.
When the surface of the photoconductor 1 is rubbed and polished, the mark disappears in a few minutes.

This is confirmed by the CCD sensor 12 (S006), and when the temperature of the fixing roller reaches a predetermined temperature, the pre-multi-rotation is terminated (S007) and the copy waiting state is entered (S008).

In order to verify the effect when the cleaning device according to the present invention is operated for a long period of time, an example of comparison with a system in which the pre-multi-rotation time is controlled to 3 to 11 minutes by a timer is shown in FIG. 3 (a). Shown in. In this verification experiment, in each of the samples SP1 to SP4, 10K sheet materials were passed per day, and the number of operating sheets was 10
Streaks due to image deletion and photoconductor scraping at start-up after 0 days for 0K sheets (50 days for 500K sheets)
This is a comparative evaluation of the occurrence of unevenness.

From the results shown in FIG. 3 (a), the rubbing ability is insufficient and the image deletion deteriorates due to long-term operation in the pre-multi-rotation of the sample SP2 for 3 minutes. Sample SP
In the pre-multi-rotation of 7 minutes of 3, there is no problem in image deletion and photoconductor scraping in the initial stage, but both deteriorate with long-term operation. Further, in the system in which the sample SP4 was pre-multi-rotated for 11 minutes, there was no problem in image deletion even during a long-term operation, but the photoconductor was poorly scraped.

On the other hand, by carrying out the present embodiment of the sample SP1, good results are obtained over a long period of time in terms of image deletion and photoconductor abrasion. Further, in the present embodiment, the time actually spent for the pre-multi-rotation gradually increases as the number of operating sheets increases as shown in FIG. 3B, and thus an appropriate polishing ability is obtained. It is considered to be a thing.

(Second Embodiment) FIG. 4 is a schematic configuration diagram of a copying machine according to a second embodiment of the present invention, in which the same components as those in the first embodiment are designated by the same reference numerals. The same as that of the first embodiment, and detailed description thereof will be omitted.

Reference numeral 14 in the drawing is a torque measuring device as a load torque measuring means for measuring the load torque of the cleaning roller 7b. Further, reference numeral 16 is a pressure device as a contact force adjusting means for changing the contact force of the cleaning roller 7b with the surface of the photosensitive drum 1, and the pressing force can be changed by the pressure control device 15.

When the surface of the cleaning roller 7a is worn due to long-term operation of the apparatus, the surface roughness is changed, and the frictional force is reduced, the ability of rubbing and polishing the photosensitive drum 1 is reduced,
The occurrence of image deletion cannot be suppressed. In the present embodiment, the reduction of the frictional force is detected by measuring the torque of the cleaning roller 7a, and when the frictional force falls below a certain value, the pressurizing controller 15 controls to increase the pressing force.

By carrying out the present embodiment, the apparatus can be operated for a long period of time without causing a great damage to the photosensitive member 1 and the cleaning roller 7a.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention, and is a schematic structural diagram of a digital copying machine which performs laser exposure.

In the figure, 20 is a minute surface electrometer as a surface potential measuring means for measuring the surface potential of the photoconductor 1 which is arranged on the downstream side of the exposure area, and is constituted so as to be movable in the longitudinal direction of the drum.

After the surface of the photoconductor 1 is uniformly charged by the primary charger 2, a predetermined exposure pattern stored in the memory is automatically exposed by the exposing means. In this embodiment, the pattern is a binary rectangular pattern with one wavelength of 160 μm formed only by turning on and off the laser.

Therefore, the drum surface potential of the photoconductor 1 obtained by scanning the pattern with a fine surface electrometer has a shape as shown in FIG. 6 (a). 6 is generated due to corona products and the like, the surface electrons on the surface of the drum on which the exposure pattern has been formed are reduced in resistance when image sticking occurs and the image deletion occurs.
The shape is as shown in (b).

In the present embodiment, the image deletion is not recognized when the inclination α changing from the dark portion potential Vd to the bright portion potential Vl in FIG. 6B becomes a predetermined value or more, and at this time, the image deletion is not recognized. The front multi-rotation of the cleaning roller 7a is completed.

As a result, regardless of environmental changes, the state of adhesion of foreign matter adhering to the surface of the photoconductor 1 can be grasped and proper pre-multi-rotation can be performed. In this embodiment, Vd
= 400 V, Vl = 50 V, and α = 4 [V / μm]
Was the perceived branch of the image stream.

[0054]

As described above, according to the present invention, the adhering condition of the foreign matter on the surface of the image bearing member is detected by the foreign matter detecting means, and the pre-driving of the cleaning device is performed according to the amount of the foreign matter. Only the foreign matter is removed, and the quality of the formed image is kept good. In addition, since the pre-driving of the removal cleaning device is not performed more than necessary, the pre-driving time is short, and deterioration of the surface of the image bearing member is suppressed, so that good quality image formation can be performed for a long time. Is possible.

Since the foreign matter detecting means is provided with the marking means and the marking detecting means, the ink marking marked on the surface of the image bearing member is regarded as the foreign matter adhering to the surface of the image bearing member, so that the surface of the image bearing member changes with time. It is possible to set the time for removing the ink marking as the foreign matter removal required time regardless of the change in the foreign matter removal required time due to.

The foreign matter detecting means can also detect the adhered state of foreign matter on the surface of the image carrier as a deviation of the surface potential pattern by measuring the surface potential of the surface of the image carrier exposed to a specific pattern. Becomes

Further, since the relationship between the contact member and the surface of the image carrier is always set to a constant sliding condition by the load torque measuring means and the contact force adjusting means, the foreign matter removing ability of the cleaning device is within a certain range. Stabilizes at.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram illustrating a characteristic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart of the first embodiment of the present invention.

FIG. 3A is a diagram showing a verification result of the first embodiment of the present invention. FIG. 3B is a diagram showing the relationship between the number of operating sheets and the previous multi-rotation time.

FIG. 4 is a sectional configuration diagram illustrating a characteristic configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a sectional configuration diagram illustrating a characteristic configuration of an image forming apparatus according to a third embodiment of the present invention.

FIG. 6 is a comparison diagram of an exposure pattern and a surface potential pattern in the third embodiment of the present invention.

FIG. 7 is a cross-sectional configuration diagram illustrating an image forming apparatus according to a conventional technique.

[Explanation of symbols]

 1 Photoreceptor 2 Charging Device 3 Image Exposure 4 Developing Device 5 Conveyance Path 6 Transfer Charging Device 7 Cleaning Device 7a Cleaning Roller (Abutting Member) 7b Cleaning Blade 7c Scraper 7d Screw 10 Separation Charger 11 Separation Roller 12 CCD Sensor (Marking Detection) Means) 13 marker (marking means) A1 arrow S transfer material

Claims (4)

[Claims] 1. A cleaning device having a contact member that comes into contact with the surface of a moving image carrier of an image forming unit, wherein the image carrier is pre-driven without image formation at the time of starting the device. In the image forming apparatus, in which the contact member of the cleaning device rubs the surface of the image carrier to remove the adhered foreign matter, the foreign matter detection unit for detecting the adhered state of the foreign matter on the surface of the image carrier is provided. The image forming apparatus is controlled so as to stop the pre-driving when it is confirmed that the adherence has been removed. 2. The image forming apparatus according to claim 1, wherein the foreign matter detecting means includes marking means for marking ink on the surface of the image carrier and marking detecting means for detecting the marking. apparatus. 3. The foreign matter detecting means changes the surface potential of the image forming body by exposing the surface of the image bearing body charged by the charging means and the charging means for charging the image bearing body provided in the image forming section. And an exposure unit for allowing the exposure unit to measure the surface potential of the position of the image carrier surface exposed by the exposure unit, a predetermined exposure pattern formed by the exposure unit,
Comparing the surface potential pattern changed according to the exposure pattern measured by the surface potential measuring means, and detecting the adhered state of the foreign matter by the deviation of the inclination angle of the rising portion of the exposure pattern and the surface potential pattern. The image forming apparatus according to claim 1. 4. A load torque measuring means for measuring a load torque applied to the image carrier by the contact member, and a contact force adjusting means for changing a contact force of the contact member contacting the surface of the image carrier. 4. The image forming apparatus according to claim 1, wherein the contact member controls the load torque applied to the image carrier within a predetermined range.