JPH0460660A - Contact electrifier and image forming device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the variance in electrification due to pollution of an electrifying member for contact electrification by providing a means which cleans the face of the electrifying member contreting the surface of a body to be electrified. CONSTITUTION:A contact electrifier which brings an electrifying member 12 into contact with the surface of a body 1 to be electrified to electrify this surface is provided with a means 11 which cleans the face of the electrifying member 2 contreting the surface of the body 1 to be electrified. As a result, foreign matters stuck to the surface of the electrifying member 2 are removed by the cleaning means 11 even if foreign matters are transferred from the surface of the body 1 to be electrified to the contact electrifying member 2 or foreign matters are directly stuck by sprinkling. Thus, the occurrence of the variance in electrification due to pollution of the electrifying member 2 or sticking and solidification of pollutive matters is prevented to keep a satisfactory uniform electrifying property, and a picture of good quality is stably outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a contact-type charging device that charges (including neutralizes) the surface of a charged object by bringing a charging member into contact with the surface to be charged. The present invention also relates to an image forming apparatus using the contact charging device.

(Prior art) For example, in image forming apparatuses such as electrophotographic devices (copying machines, printers, image display devices, etc.) and electrostatic recording devices, the surface of an image carrier as a charged body such as a photoreceptor or dielectric is subjected to charging treatment. Corona chargers have been widely used as devices for this purpose.

A corona charger charges the surface of an object to be charged, such as an image carrier, with a predetermined polarity.
It is effective as a device for uniformly charging the potential.

However, there are problems such as the need for an expensive high-voltage transformer (approximately 6 to 8 KV) to obtain a predetermined charging potential, and the fact that undesirable ozone is generated due to corona discharge, so it is necessary to devise a countermeasure structure. have.

In contrast to such corona chargers, there is a contact charging device that charges the surface of the object by bringing a charging member to which a DC voltage or a superimposed voltage of DC and AC is applied to the surface of the object to be charged. Because it has the advantages of being able to achieve low pressure and generating only a small amount of ozone, it is used, for example, in corona, which is used to charge the surface of image carriers such as photoreceptors and dielectrics, and other objects to be charged in image forming apparatuses. It has attracted attention as an alternative to chargers and is gradually being used.

For example, when a conductive roller (charging roller) as a charging member is brought into contact with the surface of a photoreceptor as an object to be charged, and a positive or negative DC voltage of several 100V to 2KV or a DC voltage is applied to the roller. Oscillating voltage that has a peak-to-peak voltage that is more than twice the charging start voltage of the photoreceptor (voltage whose voltage value changes periodically over time, such as alternating voltage and two-ac voltage)
The surface of the photoreceptor is charged to several hundreds of volts to 1.5 kilovolts by applying a superimposed voltage of the voltage and the direct current voltage.

In addition to roller type charging members, plate type, brush type,
It can be of any suitable shape, such as a rod type, oblong block type, heald type, or bat type.

(Problems to be Solved by the Invention) Since the charging member for contact charging performs charging by bringing it into contact with the surface of the object to be charged with a predetermined pressing force, it tends to collect various foreign matters on the surface of the object to be charged and become dirty.

For example, in a transfer-type image forming apparatus, residual developer (toner) remaining after transfer on the surface of the image carrier that is cleaned and removed by the cleaning means, silica particles of submicron order (1 μm or less) added externally to the toner, fine resin powder When some of the paper powder, talc, or other foreign matter on the transfer paper passes through the cleaning means, it is transferred to the position of the charging member that is in contact with the surface of the image carrier as a charging means for the image carrier. As a result, it adheres to the charging member and stains the surface of the charging member.

When a cleaning means or a cleaning plate is used for cleaning the surface of the image carrier, so-called plate turning may sometimes occur when the apparatus is started, and when such plate turning occurs, there may be a large amount of foreign matter or the position of the charging member. As a result, the surface of the charging member becomes dirty (contaminated).

The plate turning phenomenon is particularly likely to occur when the image carrier and cleaning plate are new and the frictional force acting between them is very large when the device is started.
Is the edge of a new blade coated with a lubricant such as polynylidene fluoride resin (P, V, D, F) powder? In the case of an apparatus configured with a process cartridge that is made into an integrated unit and can be detached and replaced from the image forming apparatus main body, the blade may be coated due to the shock when the process cartridge is attached or removed from the apparatus main body. If some of the lubricant falls off and adheres to the surface of the image carrier and reaches the position of the contact charging member, or if the plate is located above the contact charging member, the lubricant may fall off. may fall directly onto the contact charging member, and the surface of the charging member may become contaminated with fallen lubricant.

If the contact surface of the contact charging member with respect to the object to be charged is contaminated as described above, this will result in uneven charging in the charging process of the surface of the object to be charged.

Further, a part of the contaminants that adhere to the contact charging may adhere firmly to the surface of the object to be charged, resulting in uneven charging. If the apparatus is an image forming apparatus, such charging unevenness may result in deterioration of the image quality of the output image.

The present invention does not solve the above problems caused by contamination of the charging member in contact charging (means for solving the problems).The present invention provides a contact charging device and a contact charging device characterized by the following configuration. This is the image forming apparatus used.

(1) A contact type charging device that charges the surface of the charged object by bringing the charging member into contact with the surface of the charged object is characterized in that the charging device is equipped with a means for cleaning the contact surface of the charging member with respect to the surface of the charged object. Contact charging device.

(2) The charging member is a rotating body (1)
The contact charging device described in .

(3) The cleaning member of the cleaning means is in contact with the charging member, and due to the charging sequence with the charging member, the cleaning member has frictional charging property that is opposite in polarity to the polarity of the foreign matter adhering to the charging member. The contact charging device according to feature (1) or (2).

(4) The contact charging device according to item (3), wherein the cleaning member is a rotating body.

(5) Cleaning foreign matter that has migrated from the charging member to the cleaning member when in contact with the cleaning member. Therefore, the surface of the charging member that comes into contact with the charged object has triboelectric charging properties that are opposite in polarity to the polarity of the foreign matter adhering to the cleaning member. The contact charging device according to item (3) or item (4), characterized in that:

(6) An image forming apparatus in which at least an image bearing member and a contact type charging device for charging the image bearing member are configured as a process cartridge that can be freely attached to and detached from the main body of the apparatus, and a means for cleaning the charging member is provided. An image forming apparatus characterized in that a scraper in contact with a cleaning member is provided on the process cartridge side, and the scraper also serves as a shutter for an exposure opening of the process cartridge.

(Function) Even if foreign matter transfers from the surface of the object to be charged to the contact charging member, or even if the foreign matter is directly attached to the contact charging member by being sprinkled, the foreign matter adhering to the surface of the charging member will be removed by the presence of the cleaning means. This prevents the surface of the charging member from being contaminated by foreign matter.

The occurrence of charging unevenness due to contamination of the member and the solid adhesion of contaminants to the surface of the charged object are prevented, and stable and uniform charging performance is maintained over a long period of time.

In an image forming apparatus using a contact charging device, it is possible to maintain high image quality.

The cleaning means brings a cleaning member into contact with the surface of the charging member, and in this case, the cleaning member has a triboelectric charging property that is opposite in polarity to the polarity of the foreign matter adhering to the charging member due to the charging sequence with the charging member. The foreign matter adhering to the charging member is electrostatically and efficiently adhered to the cleaning member side and removed, thereby improving the cleaning efficiency of the charging member by the cleaning member.

In addition, a scraper is provided in contact with the cleaning member to remove foreign matter that has migrated to the cleaning member. By having triboelectric properties, foreign matter adhering to the cleaning member is electrostatically and efficiently adhered to the scraper side and removed, the cleaning member has good glue cleaning efficiency, and the efficiency of cleaning the charged member by the cleaning member is improved. Stable and well maintained over a long period of time.

The scraper doubles as the shutter of the exposure opening of the process cartridge in an image forming apparatus in which the process cartridge including an image carrier and a contact charging member is detachably attached to the apparatus main body. The process cartridge can be simplified.

(Example) <Example Work> FIG. 1 is a schematic configuration diagram of an image forming apparatus as an example.

The image forming apparatus of this example is a laser beam printer using an electrophotographic process.

1 is an image carrier as an object to be charged, and in this example, a tram-shaped OPC photoreceptor (organic semiconductor ,
(hereinafter referred to as a photosensitive drum).

Reference numeral 2 denotes a charging roller serving as a contact charging member for uniformly primary charging the surface of the photosensitive drum.

The charging roller 2 of this example includes a core metal 2a, a conductive rubber roller portion 2b formed concentrically around the core metal 2a and containing carbon dispersed therein, a high-resistance coating layer formed sequentially on the outer periphery, and a nylon conductive rubber roller portion 2b formed concentrically around the core metal 2a. It consists of a multilayer structure with the outermost layer of the coating. In the high-resistance coating layer, when a defect such as a hole occurs on the surface of the photosensitive drum 1 in contact with the charging roller 2, an electrostatic latent image corresponding to that from the charging roller 2 is sequentially formed.

The outermost layer serves to prevent residual solvent from seeping out from the rubber roller portion 2b, and is formed to have a thickness of 1 to 20 μm.

This charging roller is arranged almost parallel to the photosensitive tram 1 with both ends of a core metal 2a rotatably supported by bearings (not shown), and is pressed against the surface of the photosensitive drum 1 by a pressing means 2c such as a spring. The photosensitive drum 1 is constantly pressed against the photosensitive drum 1 and rotates as the photosensitive drum 1 is rotated.

By applying a bias voltage to this charging roller 2 from a bias applying power source (not shown), the circumferential surface of the rotating photosensitive drum 1 is uniformly primary charged to a predetermined polarity (negative in this example) and potential using a contact charging method. Charged.

By scanning and exposing one surface of the photosensitive drum that has been subjected to the primary charging process using a laser beam that is modulated in accordance with the time-series electric digital pixel signal of the target image information output from the laser scanner 3. Then, the electrostatic latent image formed on the surface of the photosensitive drum is reversely developed by the developing device 4. 4a is a developer box, 4b is a developer sleeve,
t indicates a contained developer, and 4C indicates a developer stirring plate. The developer t in this example is a one-component negative magnetic toner mainly composed of styrene-acrylic, and 0.8 weight of transferred Neka Silica is added to this for the purpose of improving fluidity and increasing and stabilizing the amount of charged charge. It is attached externally.

The reverse developed toner image is transferred onto the surface of the transfer material P fed at appropriate timing from a paper feeding means (not shown) to the transfer portion between the photosensitive tram 1 and the transfer roller 5 as a transfer means. To go.

The transfer material P to which the toner image has been transferred is separated from one surface of the photosensitive drum and introduced into a fixing device (not shown), where the image is fixed.
It is output as an image formation (print).

After the image transfer, the photosensitive drum surface is cleaned by a cleaning device 6 to remove residual developer remaining on the surface of the photosensitive drum and other contaminants attached to the drum surface, and then subjected to primary charging processing by the charging roller 2 again. After undergoing the following image forming process, the edges are turned over and used for image forming.

The cleaning device 6 of this example is of a plate type, and 6a is a cleaning device box, 6b is a cleaning blade having rubber elasticity, and 6C is a scoop sheet. The cleaning blade is oriented counter to the direction of surface movement of the photosensitive tram 1, and its leading edge is brought into pressure contact with the surface of the photosensitive drum 1, and contaminants on the surface of the photosensitive drum 1 are removed by the leading edge of the cleaning blade 6b. It is wiped and scraped off the drum surface and stored in the cleaner box 6a.

When the photosensitive drum 1 and the cleaning blade 6b are both new, as described above, both 1 and 6 are connected to each other when the apparatus is started.
Since the frictional force acting between the cleaning blades 6b and 6b is very large and the plate is likely to turn over, a lubricant such as P-V-D-F powder is usually applied to the edge of the cleaning blade 6b.

The image forming apparatus of this example includes a photosensitive tram 1 and a charging roller 2.
Four process devices, namely, a developing device 4 and a cleaning device 6, are assembled into a common housing in a predetermined mutual arrangement to form a process cartridge 10 that can be freely attached to and removed from an image forming apparatus.

The process cartridge 10 of this example has a photosensitive drum 1 inside, a developing device 4 on the lower side, and a cleaning device 6 on the upper side.
are arranged, and a laser beam introduction passage 8 (exposure opening) is formed between the lower developer box 4a and the upper cleaner box 6a.

Further, the charging roller 2 is arranged in the recessed space by recessing the bottom surface of the upper cleaning device box 6a upward toward the photosensitive drum 1, and the cleaning plate 6b is located almost above the charging roller 2. ing.

In the case of this example device, the transfer roller 5, the transfer material guide plate 7,
By opening and operating the movable front panel of the device (not shown) that supports the assembly of the fixing device (not shown), etc., the inside of the device main body can be brought into an open state (shown by a two-dot chain line). The process cartridge 10 can be attached to and detached from the main body of the apparatus in the direction of arrows a-b. Process cartridge 1
0 into the receiver 1989 on the device main body side and close the front panel of the device, the device main body and the process cartridge 10 side are mechanically and electrically linked, and the device is ready for operation. become.

Reference numeral 11 denotes a rotating brush roller as a cleaning means for cleaning the surface of the charging roller 2 as a contact charging member.

In the apparatus of this example, the brush roller 11 is disposed on the apparatus main body side, and when the process cartridge 10 is properly installed in the apparatus main body side, it comes into contact with the outer surface of the charging roller 2 on the process cartridge 10 side. It is located in.

During the process of attaching and detaching the process cartridge 10, the brush roller 11
Corresponding to the system introduction passage section 8, interference with the cartridge 1o is prevented.

In this example, the brush roller 11 is made of flocked glass fibers, and the diameter of the fibers is approximately 20 μm, the length is 3 mm, and the flocking density is 90.
It was set to 0 pieces/cm.

The brush roller 11 is synchronized with the rotation of the photosensitive drum 1 and driven to rotate in the same direction as the charging roller 2, which rotates as the photosensitive drum 1 rotates, at 1/4 of the rotation speed of the charging roller 2. , the surface of the charging roller 2 is rubbed by the brush roller 11 due to the difference in circumferential speed between the two rollers 11 and 2.

Therefore, it passes through the cleaning blade 6b or reaches the position of the charging roller 2 due to the plate turning over.
Toner, Nekasilica, resin fine powder, etc. adhering to the roller surface
Paper powder, talc, etc., as well as P, ■, and D-F that have fallen off the surface of the cleaning plate 6b and adhered to the charging roller 2.
Contaminants such as powder adhering to the charging roller are scraped off or collected and removed from the surface of the charging roller 2 by a brush roller that is in contact with and rubbing against the charging roller 2, and the charging roller 2 is removed from the surface of the charging roller 2 when it comes into contact with the photosensitive drum 1. The contact surface is always maintained in a clean state over a long period of time, and uneven charging due to contamination on the surface of the charging roller 2 and solid adhesion of contaminants on the surface of the photosensitive drum 1 are prevented, and the surface is stable over a long period of time. Maintaining uniform charging properties,
It becomes possible to maintain high image quality.

Further, in this embodiment, the P-V-D-F powder applied to the edge portion of the cleaning plate 6b is a highly negatively chargeable substance, and this powder is applied to polycarbonate, which is the surface material of the photosensitive drum, and the charging roller 2. The brush of the brush roller 11 is made of glass fiber, which is charged to a positive polarity by rubbing against the outermost nylon coating of the charging roller 2. The negatively charged P-V-D-F powder and negative silica adhering to the surface of the charging roller 2 are effectively trapped on the positively charged glass fiber brush roller 11.

When the surface of the photosensitive drum continues to be charged by the charging roller 2 contaminated with toner fine powder, silica particles, etc., dots with silica particles as cores are likely to be attracted to the drum surface on the surface of the photosensitive member. This greatly depends on the amount of externally added silica to the toner, the surface material of the photosensitive drum, and the usage environment, but according to experiments, the amount of externally added silica was 0.8 parts by weight, the drum surface was polycarbonate, and the environment was 32.5°C. At -15% RH, drum fusion occurred after 1,000 to 3,000 prints.

On the other hand, in the apparatus of this embodiment, since the charging roller 2 is equipped with the cleaning stage 11, not only does the drum fusion not occur even when printing more than 10,000 sheets, but also when the process cartridge is initially used. It is also possible to prevent the charging roller from being contaminated easily by P-V-D-F powder (Example 2) This example (Fig. 2) differs from that of Example 1 (Fig. 1) in that the brush roller 11 is The brush roller 11 is configured to scrape silica particles, toner fine powder, etc. trapped from the charging roller 2 surface with a scraper 12.

The souffle bar 12 is a pair of parallelogram link mechanisms provided on both the front and back end plates of the cleaning device box 6a of the process cartridge 10! 3 is supported so that it can move vertically and parallelly within the laser beam introduction passage 8.

Then, the parallelogram link mechanism 13 is constantly urged to rotate clockwise in the drawing by the screw spring 13a, and the cartridge is moved to the right! 0 is removed from the main body of the apparatus, the scraper 12 is pressed against the lower surface of the bottom plate of the cleaning device box 6a by the above-mentioned rotation biasing force of the parallelogram link mechanism 13 as shown by the two-dot chain line. The laser beam is moved upward in parallel in the laser beam introduction passage section 8 until the laser beam introduction passage 8 is reached, and is maintained in a retracted state.

When the process cartridge 10 is inserted into the main body of the apparatus, the protrusion 13b on the side of the parallelogram link mechanism 13 comes into contact with the stopper 14 on the main body of the apparatus a little before the insertion end point, and the receiver is stopped, and in this state, the process cartridge 10 is inserted. When it is inserted to the end point, the parallelogram link mechanism 13 rotates counterclockwise against the torsion spring 13a, and the scraper 12 moves parallel downward in the laser beam introduction passage 8 to remove the scraper 12. A relatively stiff contact piece 12 made of polyethylene tereft film (sheet) or polyethylene film (sheet) provided along the edge of the tip of the
A is brought into contact with the brush roller 11, and this state is maintained as long as the process cartridge 10 is attached to the apparatus main body.

The brush roller 11 is scraped by the contact piece 12a of the scraper 12 during rotation. In this embodiment, the direction of rotation of the brush roller 11 is set so that the silica particles, toner fine powder, etc. on the surface of the charging roller 2 that are trapped by the brush roller 11 are retained on the top #j of the scraper 12 and scattering inside the machine is minimized. The direction is opposite to 2.

Contact piece 12a for the brush roller of the scraper 12
As described above, the contact piece 12a is a film made of polyethylene terephthalate, polyethylene, or the like, and the contact piece 12a is positively charged due to the frictional charging series in relation to the glass fiber of the brush roller 11. Therefore, the negative polarity P-V-D trapped from the charging roller 2 surface to the brush roller 11
The -F powder and negative silica are electrostatically and efficiently transferred to the contact piece 12a side of the scraper, so that the brush roller 11, which serves as a cleaning member for the charging roller 2, is efficiently refined.

As described above, the scraper 12 is configured to move between the action position and the retracted position relative to the brush roller 11 in conjunction with the attachment and detachment of the process cartridge 10 to and from the main body of the apparatus. There is no interference between the roller 11 and the roller 11, which interferes with the attachment and detachment of the cartridge.

<Embodiment 3> In this embodiment (FIG. 3), the scraper 12 for the brush roller 11 is moved to the laser beam introduction passage 8 when the process cartridge 10 is removed from the apparatus main body.
It is designed to also serve as a shirt flap plate that holds the opening in the closed state.

That is, the scraper 12 is freely rotatable about the shaft 12b, and when the cartridge 10 is removed from the main body of the apparatus, it is moved downward by its own weight or by the biasing force of the closing spring as shown by the two-dot chain line, and the shirt strip is removed. Cartridge 1 as a plate
The opening of the laser beam introduction passage section 8 of No. 0 is closed.

When this cartridge 10 is inserted into the main body of the apparatus, during the insertion process, the scraper 12 as a shutter plate moves inward of the passage part 8 like a solid line water against its own weight or against the closing spring. When the process cartridge is flipped up almost horizontally to open the opening of the laser beam introduction passage 8 and the process cartridge is inserted at the end of insertion, the tip edge of the scraper 12 or the brush that has come into contact with the charging roller 2 It comes into contact with the roller 11, and this state is maintained as long as the cartridge 10 is attached to the main body of the apparatus.

The scraper 12 may be manually flipped up and locked in the open state when the cartridge 10 is inserted into the apparatus main body.

This embodiment can provide the same effects as the second embodiment at low cost.

In Examples 1 to 3, the contact charging member is not limited to a roller type, but may be a rotating belt type, a web type, a blade type, a pad type, a block type, a rod type, or the like. In the case of a stationary charging member such as a blade type, the cleaning means has the function of scraping or wiping foreign matter accumulated at the edge of the contact nip between the cleaning means and the surface of the object to be charged. Bye.

In addition, the brush roller 11 as a cleaning means,
It can also be in the form of a rotating belt body, a blade body, a web body, a bat body, etc.

If the charging member 2 is disposed on the side of the process cartridge 10 that is attached to and detached from the main body of the apparatus as in the first to third embodiments, the cleaning means 11 is also attached to the process cartridge 10.
Equipment may also be provided on the side.

(Effects of the Invention) As described above, according to the present invention, a contact-type charging device can prevent charging unevenness caused by contamination of a charging member and the adhesion and hardening of contaminants to the surface of a charged object, thereby achieving good results. Uniform charging properties can be maintained over a long period of time, and image forming apparatuses using this charging device can stably output images of good quality by preventing deterioration in the quality of output images caused by uneven charging. becomes possible.

[Brief explanation of drawings]

1 to 3 are schematic configuration diagrams of apparatuses of first to third embodiments, respectively. 1 is a photosensitive drum as an object to be charged, 2 is a charging roller as a charging member, 11 is a brush roller as a cleaning member for the charging member, and 12 and 12a are scraper agent Riyuki Dou.

Claims (6)

[Claims] (1) A contact charging device that charges the surface of the object to be charged by bringing the charging member into contact with the surface of the object to be charged, characterized in that it is equipped with means for cleaning the contact surface of the charging member with respect to the surface of the object to be charged. Device. (2) The contact charging device according to claim 1, wherein the charging member is a rotating body. (3) The cleaning member of the cleaning means is in contact with the charging member, and the cleaning member has a triboelectric charging property that is opposite in polarity to the polarity of the foreign matter adhering to the charging member due to the charging sequence with the charging member. The contact charging device according to claim 1 or 2, characterized in that: (4) The contact charging device according to claim 3, wherein the cleaning member is a rotating body. (5) A scraper is provided in contact with the cleaning member to remove foreign matter transferred from the charging member to the cleaning member, and the scraper has a polarity of the foreign matter adhering to the cleaning member due to the charging sequence with the cleaning member. 5. The contact charging device according to claim 3, wherein the contact charging device has reverse polarity triboelectrification. (6) An image forming apparatus in which at least an image bearing member and a contact type charging device for charging the image bearing member are configured as a process cartridge that can be freely attached to and detached from the main body of the apparatus, and a means for cleaning the charging member is provided. An image forming apparatus comprising: a scraper in contact with a cleaning member on the process cartridge side; the scraper also serving as a shutter for an exposure opening of the process cartridge.