JPH05197276A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device in which an image carrier is reproduced without adding hard particulates, etc., having a grinding action in developer and by which high image quality is maintained over a long term. CONSTITUTION:Toner T is prevented from being supplied to a developing roller 33 by controlling bias by a bias impressing means 50 in timing when a non image forming area corresponding to an interval between consecutively passing papers on a photosensitive drum 3 is opposed to the roller 33. Thus, a toner feeding amount to the roller 33 is drastically reduced and the roller 33 directly comes in contact with the non image forming area on the photosensitive drum 3 without interposing the toner T. In such a case, the surface of the photosensitive drum 3 is ground by the roller 33, thereby reproducing the photosensitive drum 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing an electrostatic latent image in an electrophotographic device or an electrostatic recording device,
In particular, the present invention relates to a developing device capable of obtaining a high-quality image by using a one-component developer.

[0002]

2. Description of the Related Art Currently, an image forming apparatus has an electrophotographic system,
The electrostatic recording method is widely applied. Among them, as a developing method for visualizing an electrostatic latent image, colored particles called toner and magnetic particles called carrier are mixed, and an electric charge is given to this toner to convey a developer which is a mixture of toner and carrier by magnetic force. The two-component developing method, in which an electrostatic latent image is developed by electrostatic force, has become mainstream.

However, the two-component developing method has disadvantages such as an increase in size and complexity of the developing device and the need to control the mixing ratio of the toner and the carrier. Products that employ a one-component development method that does not require are being commercialized. Among them, the non-magnetic one-component developing method which does not have a magnet in the developing device has advantages such as reduction in size and weight of the developing device, cost reduction, and colorization, and many research reports have been recently made.

As a conventional developing device of this type,
The toner (developer) stored in the hopper is conveyed to the developing roller by a toner supply roller which is in contact with a developing roller as a developer conveying means and rotates in the same direction as the developing roller. Then, a thin toner layer is formed on the developing roller by a thin layer forming member that is in line contact with the developing roller at a uniform pressure, and the thin toner layer is brought close to or in contact with the image carrier to form an electrophotographic photoreceptor. A developing device for visualizing an electrostatic latent image on an image carrier is known.

However, in the developing device of this type, when the electrostatic latent image is repeatedly developed, the colorant and the surface treatment agent contained in the toner particles as the developer are formed on the image carrier. However, there is a problem in that the additives such as the above adhere and accumulate and the sensitivity decreases, which adversely affects image blurring and the like.

[0006]

Therefore, a method is known in which hard fine particles having an abrasive action are added to a developer and the surface of the image bearing member is abraded at the time of development to regenerate the image bearing member.

However, the added abrasive particles are separated from the toner by the continuous use of the toner, and are electrically attached to the image carrier to damage the surface and shorten the life of the image carrier, resulting in high quality. There was a problem that the image quality of could not be maintained for a long period of time.

The present invention has been made in view of the above circumstances. It is possible to reproduce an image bearing member without adding hard fine particles having an abrasive effect to a developer, and to obtain a high quality image for a long time. An object of the present invention is to provide a developing device that can be maintained for the entire time.

[0009]

In order to solve the above problems, the present invention provides a developing device for visualizing a latent image on an image carrier by bringing a thin layer of a one-component developer into contact with the image carrier. And a developing device main body having a developer accommodating portion for accommodating the one-component developer, and a developer disposed in the developing device main body and in a state of being in contact with the developed portion of the image carrier. And a developer layer forming means for forming a thin layer of the one-component developer on the surface of the developer conveying means, and a developer conveying means inside the developing device main body. A developer supplying unit that is rotatably provided while being pressed and supplies the developer in the developer accommodating portion to the developer conveying unit, and the developer conveying unit that conveys the developer during the developing operation with respect to the developer supplying unit. Bias voltage to supply And a bias applying unit that controls the applied bias so as not to supply the developer to the developer transporting unit at a timing when the non-image forming regions corresponding to the sheet interval of continuous sheet passing of the image carrier face each other. It is configured as follows.

[0010]

According to the developing device of the present invention, the developer is not supplied to the developer conveying means by controlling the bias at the timing at which the non-image forming areas corresponding to the paper intervals of the continuous paper passing of the image carrier face each other. To do so. As a result, the amount of developer carried to the developer carrying means is significantly reduced, and the developer carrying means is brought into direct contact with the non-image forming area of the image carrier without the intermediary of the developer. The surface of the carrier is abraded by the developer carrying means to regenerate the image carrier. In this way, the image bearing member can be regenerated without adding hard fine particles having an abrasive effect to the developer, and high-quality image quality can be maintained for a long period of time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, with reference to FIG. 2, the configuration of a cleanerless process type image forming apparatus 1 employing the developing device of the present invention is shown.

In FIG. 2, a photosensitive drum 3 as an image bearing member having a diameter such that the peripheral surface length is smaller than the length of an image to be recorded is indicated by an arrow A at a substantially central portion of the image forming apparatus main body 2. It is provided so that it can rotate in any direction. The photoconductor drum 3 is made of an organic photoconductor (OPC) photoconductive material.

Around the photosensitive drum 3, a red LED 4 as a charge eliminating means, which acts as described later, and a depatterning device 5 as a depatterning means for the transfer residual toner are sequentially provided along the rotation direction of the photosensitive drum 3. A scorotron charger 6 as a charging means, a laser device 7 as an electrostatic latent image forming means,
A developing device 8 as a cleaning and developing means and a transfer roller 9 as a transfer means are provided. Then, an image forming means 10 for forming a toner image TI as a developer image on the peripheral surface of the photosensitive drum 3 is configured.

In the apparatus main body 2, a sheet of paper P as a material to be transferred, which is taken out from a paper feed cassette 11 mounted on one side of the apparatus main body 2, and the photosensitive drum 3 of the image forming means 10 and the aforesaid A sheet conveyance path 14 is formed as a transfer material conveyance path that leads to a sheet discharge tray 13 disposed on the other side of the apparatus main body 2 via an image transfer section 12 between the transfer roller 9 and the transfer roller 9.

The image transfer section 1 of the sheet conveying path 14
On the upstream side of 2, the aligning roller pair 16 which feeds the paper P taken out from the paper feeding cassette 11 via the paper feeding roller 15 and then feeds it to the image transfer unit 12 at a timing is provided. Are arranged.

Further, on the downstream side of the image transfer section 12,
A fixing device 1 for fixing the toner image TI transferred onto the paper P
A paper discharge roller pair 18 for discharging the paper 7 and the fixed paper P to the paper discharge tray 13 is provided. Further, a gate 20 for guiding the sheet P fixed by the fixing device 17 to the reversal conveying path 19 is provided between the fixing device 17 and the paper discharge roller pair 18.

The sheet P guided to the reversing conveyance path 19 has an image forming surface facing downward through a sheet discharge roller pair 21 and a sheet discharge section 22 formed of a recess formed on the upper surface side of the apparatus main body 2. It will be ejected in this condition. Next, the image forming operation of the image forming apparatus 1 configured as described above will be described.

While rotating the photoconductor drum 3, the peripheral surface of the photoconductor drum 3 is negatively charged substantially uniformly by the scorotron charger 6. Then, a laser beam 7A is irradiated to the charged area from the laser device 7 in accordance with image information to be recorded and exposed to form an electrostatic latent image on the surface of the photosensitive drum 3. Then, the electrostatic latent image faces the developing device 8 as the photosensitive drum 3 rotates.

Here, the developing roller 33 on which a toner T layer as a so-called one-component developer having a triboelectric charging property is formed.
Starts to rotate and adheres the toner T to the electrostatic latent image on the photosensitive drum 3 to form the toner image TI shown in FIG. In this case, the toner T adheres to the light irradiation area and undergoes so-called reversal development. The toner image TI after development is then conveyed to a transfer area facing the transfer roller 9.

On the other hand, in the transfer area, the paper P is taken out from the paper feeding cassette 11 by the rotation of the paper feeding roller 15 and is sent via the conveying means 16 in synchronization with the rotation of the photosensitive drum 3.

The back side of the sheet P conveyed here is charged to a positive polarity by the transfer roller 9. Therefore, the toner image TI on the surface of the photoconductor drum 3 is electrostatically attracted to the paper P and transferred.

Since such a contact type transfer means exhibits stable transfer characteristics even under high humidity, it has the effect of reducing the amount of residual developer remaining on the transfer sheet and lightening the burden of cleaning. The paper dust is also removed to prevent the toner T from mixing. Further, the sheet P after transfer is sent to the fixing device 17, where the toner T is melted and fixed on the sheet P by heat and pressure, and then discharged.

By the way, on the surface of the photosensitive drum 3 after the transfer, a small amount of the toner T left untransferred and the positive and negative electrostatic latent images left after the transfer of the toner T remain. There is.

The toner T or the electrostatic latent image is first conveyed to the non-patterning device 5 after the negative latent image is erased by the red LED 4, disturbed and unpatterned, and returns to the charging step. After charging, it is exposed by the laser device 7 to form an electrostatic latent image, and again reaches the developing cleaning position facing the developing device 8 (second time).

In this case, in the electrostatic latent image formed for the second time, even in the exposed portion (image portion to which toner should be attached) and the non-exposed portion (non-image portion), the roller transfer greatly reduces. In addition, since the residual toner is substantially evenly and sufficiently thinly scattered in advance, exposure unevenness does not occur.
Therefore, even in the second development, the residual potential after exposure becomes uniform, so that a uniform toner image can be obtained.

Here, the developing roller 33 is in contact with the photosensitive drum 3 in order to enhance the cleaning ability (nip).
And the developing bias having a value between the residual potential of the exposed portion and the potential of the non-exposed portion is applied. As a result, new toner T is attached from the developing roller 33 to the exposed portion, and at the same time, in the non-exposed portion, the toner T attached because the attraction force by the developing bias exceeds that of the photosensitive drum 3 one after another. It is attracted to the developing device 8 and collected.

In this way, the photosensitive drum 3 is rotated in an overlapping manner and used in duplicate, and one recorded image is obtained. Then, after development and cleaning, the toner image TI is transferred to the paper P at a position facing the transfer roller 9. Hereinafter, similar steps are repeated. Next, the configuration of the developing device 8 of the present invention will be described in detail with reference to FIGS. 1 and 3 to 7. FIG. 1 is a sectional view of the developing device 8. The developing device 8 has a developing device main body 32 integrally formed with a toner hopper 31 whose inside serves as a toner accommodating portion 30 as a developer accommodating portion.

The developing device main body 32 is in a state in which a portion facing the photosensitive drum 3 is opened, and the nip width is elastically and deformed with respect to the photosensitive drum 3 in the vicinity of the opening. And a developing roller (also referred to as a developing roller) 33 which also functions as a cleaning roller and rotates in a state of being in the width direction (arrow B direction) with respect to the rotation direction of the photosensitive drum 3. ing.

A toner T is attached to the developing roller 33 at a portion corresponding to the bottom of the toner accommodating portion 30 on the rear side of the developing roller 33.
Toner supply roller 3 as a developer supply means for supplying toner
4 are provided. The toner supply roller 34 also serves as a recovery roller for recovering the undeveloped toner T'on the development roller 33.

A developing roller 33 is provided in the developing device main body 32.
Located above the roller 35, which regulates the toner conveyance amount by the developing roller 33 and forms a thin layer of the toner T on the surface of the developing roller 33 as a developer layer forming means. Is provided. A recovery blade 37 is provided in contact with the lower surface side of the developing roller 33. A mixer 38 as a stirring means is provided in the toner container 30 to stir the toner T.

In the developing system used in the developing device 8 of the present invention, the first characteristic required for the developing roller 33 is that it has "conductivity and elasticity", and the simplest constitution is satisfied. Is a combination of a metal shaft and a conductive rubber roller. Therefore, in the present invention, the toner T is conveyed while being in pressure contact with the developing roller 33, so that the surface smoothness can be satisfied.

That is, the developing roller 33, as shown in FIGS. 1 and 3, has an elastic layer 33B and a surface conductive layer 33C sequentially formed around a metal shaft 33A so as to have a resilient roller as a whole. Is composed of.

In the embodiment, the elastic layer 33B has a rubber hardness of 25 degrees, an elongation of about 425%, and a resistance value of 5 × 10 ^3. Ωcm
The surface conductive layer 33C is made of a conductive polyurethane paint (manufactured by Nippon Miractolan Co., Ltd.).
Spalex) Resistance value 5 × 10 ³ Ωcm, elongation 353
%, And the layer thickness was about 70 μm. As a result, the rubber hardness of the formed developing roller 109 is about 3
0 degree, the resistance of the shaft 109a and the surface is about 100 KΩ,
The surface roughness became about 3 μm.

Further, a predetermined developing bias voltage is applied from the developing bias power source V ₁ to the metal shaft 33A as a support of the developing roller 33 through a protective resistor R.

The toner transfer roller 34 is a developing roller 33.
The toner transfer roller 34 has two roles of supplying the toner T to the developing roller 33 and scraping the toner T on the developing roller 33 after development.
On the outer circumference of 10 ⁶ It has a layer 34B of flexible polyurethane foam having a conductivity of Ωcm or less. The contact depth with respect to the developing roller 33 is about 0.2 to 1.0 mm, the contact width is 0.5 to 4.0 mm, and the rotation speed is the developing roller 33.
The peripheral speed is 90mm in the against direction (arrow C direction)
It was set to rotate at / sec.

Further, the toner transfer roller 34 is connected to the bias applying means 50, and the toner transfer roller 34 is connected to the toner during the developing operation.
A bias voltage for supplying T to the developing roller 33 is applied, and the toner is applied at a timing when the non-image forming areas corresponding to the sheet interval (print-to-print interval) of continuous passage of the photosensitive drum 3 face each other. A reverse bias voltage that does not supply T to the developing roller 33 is applied.

That is, the toner supply bias power source V ₂ and the toner peeling bias power source V ₃ can be connected and switched via the switch S to the metal shaft 34A of the toner transfer roller 34.

As shown in FIG. 1, the blade 35 includes a first blade holder 40, a spacer 41 and a second blade holder 40.
It is held by the blade holder 42. The first blade holder 40 is rotatably supported via a shaft 43, and is constantly biased by a plurality of compression springs 44 for pressurization so as to rotate in a predetermined direction. The urging force of the compression spring 44 presses the developing roller 35 against the developing roller 33.

A foam material 45 made of maltoprene or the like is attached to the back surface of the blade 35.
Touches the baffle plate 46 attached to the first blade holder 40. As a result, the vibration of the blade 35 can be suppressed and a favorable toner T layer can be formed.

As shown in FIGS. 4 and 5, the blade 35 has, for example, silicone rubber or urethane at the tip of a thin leaf spring material 35A having a thickness of 2 mm and a length of 20 mm made of urethane resin as a supporting member. 1. A chip 35B made of a rubber elastic body or a resin having a radius of 1.5 mm is provided in at least a region larger than the image forming width in the longitudinal direction.
B is pressed against the developing roller 33 with a predetermined weight.

The urethane resin of the chip 33B is a thin leaf spring 3.
Compared to the urethane resin of 3A, one having a JIS-A standard rubber hardness is used, and the elasticity of the thin leaf spring 33A is not impaired. In this embodiment, as described above, the thin leaf spring 33A uses the JIS-A standard 75 ° urethane resin and the chip 33B uses the JIS-A standard 50 ° urethane resin.

At this time, in the blade 35, as shown in FIG. 5, the length L in the longitudinal direction is shorter than the length L ₁ in the longitudinal direction of the developing roller 33 by d1 + d2, and the width L of the image forming region. It is set longer than ₂ .

Since the plurality of compression springs 44 have a lower spring constant than the thin leaf spring material 35A of the blade 35, even if the abutting portion of the blade 35 is worn, the pressing force hardly changes, and a good toner thin layer is formed. It can be maintained. The toner T passing therethrough is negatively triboelectrically charged with the same polarity as the photosensitive drum 3, and forms one to three layers of toner T on the surface of the developing roller 33.

Image formation was performed under the following conditions using the developing device 8 of the present invention in which the main constituent members described in detail above are mounted. The surface potential of the photosensitive drum 3 is −550V and the developing bias is −220V. Development bias is 100K-5
Power is supplied to the metal shaft 33A of the developing roller 33 via a protective resistance R of 0 MΩ. The peripheral speed of the photosensitive drum 3 is 70 mm / sec, and the peripheral speed of the developing roller 33 is 180 mm / sec.
The toner supply roller 34 rotates at a peripheral speed of 90 mm / sec in the directions of the arrows in the figure. The developing roller 33 and the photosensitive drum 3 are in contact with each other with a contact width of about 0.5 mm to 4 mm.

In such a state, at the time of the developing operation, the switch S of the bias applying means 50 is connected to the toner supply bias power source V ₂ side (the position indicated by the chain double-dashed line in FIG. 1) so that the toner supply roller is turned on. A negative bias voltage is supplied to the laser 34. As a result, a sufficient amount of toner T is supplied to the developing roller 33 side to form a reliable layer, and a good developing operation can be maintained.

Further, at the timing when the non-image forming areas corresponding to the paper interval of the continuous passage of the photosensitive drum 3 face each other,
A positive bias voltage is supplied to the toner supply roller 34 by connecting the switch S of the bias applying means 50 to the toner peeling bias power source V ₃ side (solid line position in FIG. 1). As a result, the transport amount of the toner T to the developing roller 33 is greatly reduced, and the toner T on the developing roller 33 is sucked and removed.

As a result, the developing roller 33 is brought into direct contact with the non-image forming area of the photosensitive drum 3 without passing through the toner T. At this time, the surface of the photosensitive drum 3 is abraded by the developing roller 33. Reproduction of the photosensitive drum 3 is performed. As described above, the photosensitive drum 3 can be regenerated without adding hard fine particles having a polishing action to the toner T, and high-quality image can be maintained for a long period of time. ..

FIG. 6 is a comparison of image quality by passing a sheet when a reverse bias of +100 V is applied to the toner supply roller 34 between sheets, when the reverse bias is set to the ground potential, and when the reverse bias is not applied. 500 without reverse bias
While the image quality deteriorates sharply after 0 sheets, the life could be extended to about 100 million sheets when a reverse bias was applied.

In the blade 35 as the developer layer forming means, since the chip 35B is mounted on the thin leaf spring material 35A, the elasticity of the chip 35B facilitates the operation.
Moreover, it is possible to reliably form a toner layer having no unevenness. However, the accuracy in the tangential direction between the developing roller 33 and the chip 35B is important because it causes pressure unevenness and affects the toner layer and the image.

Therefore, in this embodiment, as described above with reference to FIG. 5, in the blade 35, the tip 33B is mounted at a position separated by d1 from the end of the thin leaf spring 33A. To improve the accuracy of the mounting structure in the lateral direction of the thin leaf spring, that is, the tangential direction with respect to the developing roller 33 described above, by being used as a retainer and a positioning when mounted by molding or adhesion. You can If d ₁ is too large, the layer forming state will be poor due to the pressure due to the flow of the toner. Therefore, the thickness may be about 0.5 mm to 5 mm, preferably about 0.5 mm to 2 mm. In this embodiment, d ₁ is 0.5 mm.

The length L of the blade 35 in the longitudinal direction is shorter than the length of the developing roller 33 in the longitudinal direction by d ₁ + d ₂ . It is necessary that the length of d ₁ + d ₂ is at least about 1 mm on one side, and if it is too long, the developing device itself becomes large, so it is desirable to set it to about 2 to 20 mm. At this time, the length L of the blade 35 is set to be larger than the effective developing width.

In FIG. 7, the length of d ₁ + d ₂ is -2 mm (the blade is longer than the developing roller), 0 mm (the same length),
The image density and the fog on the image in the case of 2 mm and 4 mm are shown. When d ₁ + d ₂ was 0 or less, the image density was decreased and the fog was increased.

Therefore, in the present invention, the bias is controlled at the timing at which the non-image forming area corresponding to the sheet interval between the continuous sheet P of the photosensitive drum 3 and the succeeding sheet P faces each other. Therefore, the toner T is not supplied to the developing roller 33. As a result, the amount of developer conveyed to the developing roller 33 is greatly reduced, and the developing roller 33 moves to the toner T
It comes into direct contact with the non-image forming area of the photoconductor drum 3 without passing through, and at this time, the surface of the photoconductor drum 3 is abraded by the developing roller 33, and the photoconductor drum 3 is regenerated. In this way, the photosensitive drum 3 can be regenerated without adding hard fine particles having a polishing effect to the developer, and high-quality image quality can be maintained for a long period of time.

In the above embodiment, the toner T
As a means for not supplying the developing roller 33 to the developing roller 33, the switch S of the bias applying means 50 is set to the toner peeling bias power source V ₃
Although the positive bias voltage is supplied to the toner supply roller 34 by connecting to the side (solid line position in FIG. 1), as shown in FIG. 8, the switch S is connected to ground. You may do it. Of course, the present invention can be variously modified without departing from the scope of the invention.

[0055]

As described above, according to the present invention, the image bearing member can be regenerated without adding hard fine particles having an abrasive effect to the developer, and a high quality image can be obtained. It is possible to provide a developing device that can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a positive-side potential application of a developing device of the present invention.

FIG. 2 is a sectional view of an image forming apparatus that employs the developing device shown in FIG.

FIG. 3 is a partial sectional view of a developing roller of the developing device shown in FIG.

FIG. 4 is a perspective view of a blade of the developing device shown in FIG.

FIG. 5 is an explanatory diagram showing a dimensional relationship of blades.

FIG. 6 is an explanatory diagram showing a comparison of image quality at the time of ground with and without applying a reverse bias.

FIG. 7 is an explanatory diagram showing the relationship between the length of a blade and the image quality.

FIG. 8 is a cross-sectional view showing an example of applying a ground potential of the developing device of the present invention.

[Explanation of symbols]

3 ... Photosensitive drum (image carrier), 8 ... Developing device, 30 ...
Toner container (developer container), 32 ... Developing device main body,
33 ... Developing roller (developer conveying means), 34 ... toner supply roller (developer supplying means), 35 ... blade (developer layer forming means), 50 ... bias applying means, P ... paper (cover) Transfer material), T ... Non-magnetic toner (developer).

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigenobu Osawa 70 Yanagicho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Yanagimachi factory

Claims (2)

[Claims] 1. A developing device for visualizing a latent image on the image carrier by bringing a thin layer of the one-component developer into contact with the image carrier, the developer container containing the one-component developer. A developing device main body including: a developing device main body; and a developer transporting unit that is arranged in the developing device main body and in contact with the developed portion of the image carrier to supply the developer to the developed portion; A developer layer forming means for forming a thin layer of the one-component developer on the surface of the developer carrying means; and a developing device in the developer accommodating portion rotatably provided in the developing device main body while being pressed against the developer carrying means. A developer supplying means for supplying the developer to the developer carrying means, and a bias voltage for supplying the developer to the developer carrying means during a developing operation to the developer supplying means, and an image carrier. For paper spacing of continuous paper Developing apparatus is characterized in that the non-image forming region to respond is by comprising: a bias applying means for controlling the bias applied to not supplied to the developer conveying means a developer at a timing opposite, the. 2. A developing device for visualizing a latent image on the image carrier by bringing a thin layer of the one-component developer into contact with the image carrier, the developer container containing the one-component developer. A developing device main body including: a developing device main body; and a developer transporting unit that is arranged in the developing device main body and in contact with the developed portion of the image carrier to supply the developer to the developed portion; A developer layer forming means which is shorter than the developer conveying means and which is longer than the width of the image forming region and which forms a thin layer of the one-component developer on the surface of the developer conveying means by contacting the developer conveying means in the longitudinal direction. And a developer supplying means that is rotatably provided in the developing device main body while being in pressure contact with the developer conveying means and supplies the developer in the developer accommodating portion to the developer conveying means, and to the developer supplying means. On the other hand, during development A bias voltage is applied so as to supply the image developer to the developer carrying means, and the developer is carried to the developer carrying means at the timing when the non-image forming regions corresponding to the paper intervals of the continuous paper passing of the image carrier face each other. And a bias applying unit that controls an applied bias so as not to supply the developing device.