JPH1184839A - Method and device two component development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure high density followability even if an image is formed at a high speed or black-white ratio by preliminarily stirring a two-component developer, to charge toner, besides the fact that the charged toner is used for development by using the same two component developer, separating the charged toner band supplying it to the two component developer thereby performing development. SOLUTION: Besides the fact that the charged toner is used for the development by a developing mechanism A, through the use of the two-component developer, the same two-component developer is preliminarily stirred by a preliminary stirring mechanism B to charge the toner, and this toner is separated by a supplying mechanism C, as necessary and supplied to the two-component developer used for the development. In such a case, in the preliminary stirring by the preliminary stirring mechanism B, the toner can be charged to obtain the same charge quantity, on the same electrifying condition as that when the charged toner is used for the development by the developing mechanism A using the two-component developer. Therefore, the toner charged by this charging is separated by the supplying mechanism C and supplied to the two-component developer differently used for the development by the developing mechanism A, so that even if the charged toner is used for the development as it is, a deficiency in a charge quantity is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method and a developing apparatus used for an image forming apparatus such as a copying machine and a printer, and more particularly to a two-component developing method using a two-component developer mainly composed of a toner and a carrier. It concerns the device.

[0002]

2. Description of the Related Art In developing with a two-component developer, the degree of charge of the toner affects the image quality. Therefore, conventionally, aside from supplying the charged toner to the development while agitating the two-component developer by the developing mechanism to frictionally charge the toner, a replenishing mechanism for replenishing the toner to the developing mechanism is provided with the replenishing mechanism. After the toner is frictionally charged with a rubber blade or a brush member provided on a stirring bucket roller or the like,
There has been proposed a technique for preventing the occurrence of image troubles such as fogging due to defective charging of toner by supplying the toner to a developing mechanism.

[0003]

However, in the above-described developing method and apparatus, the charging member for frictionally charging the toner in the replenishing mechanism is different from the carrier in the developing mechanism. Since the charge amount of the toner does not reach the charge amount of the toner required by the developing mechanism, the developing mechanism needs to be recharged so as to compensate for the insufficient charge amount. For this reason, in a high-speed image forming apparatus or an image forming apparatus that forms an image having a high black / white ratio, the developing mechanism does not easily compensate for the insufficient charging of the toner, and secures the followability to a high density while obtaining a good image. There is a problem that it is difficult to do.

An object of the present invention is to provide a high-density follow-up property while obtaining a good image even when forming an image at a high speed or a high black / white ratio. And a device therefor.

[0005]

In order to achieve the above-mentioned object, the two-component developing method of the present invention is different from the method of using a two-component developer for developing a charged toner.
The component developer is preliminarily stirred to charge the toner, the charged toner is separated as necessary, and replenished to the two-component developer used for the development to perform the development. Things.

In such a configuration, by the preliminary stirring of the two-component developer, the same amount of charge can be charged under the same charging conditions as when the two-component developer is used for development. Even if the two-component developer is replenished and used for development as it is, the amount of charge does not become insufficient, so that special time for recharging is not required at the time of development, and high-speed or high Even in image formation with a white ratio, high density followability can be ensured while obtaining a good image. Further, since the preliminary stirring only needs to stir the two-component developer, there is no need for a special charging member such as a rubber blade conventionally provided in a bucket roller or the like,
There is also an advantage that can be realized by a simple, small and inexpensive device.

The two-component developing device of the present invention includes a developing mechanism for developing charged toner using a two-component developer, a pre-stirring mechanism for pre-stirring the same two-component developer separately from the developing mechanism, A replenishing mechanism for separating the charged toner charged by the preliminary stirring by the preliminary stirring mechanism and supplying the charged toner to the developing mechanism;
The main feature is to have.

In such a configuration, the charging of the toner by the preliminary stirring of the two-component developer, the timely separation of the charged toner and the timely separation of the toner by the preparatory stirring of the two-component developer are performed in accordance with the timely operation of each mechanism and the developing operation by the developing mechanism. Supply to the developing mechanism can be stably achieved.

[0009] The two-component developing apparatus of the present invention is also characterized in that the replenishing mechanism electrostatically captures the charged toner by a member to which a bias is applied, separates the toner, and transfers the separated toner to the developing mechanism.

In such a configuration, the separation of the charged toner from the two-component developer and transfer to the developing mechanism can be reliably achieved by the forcible charging of the biased member and its polarity.

The two-component developing apparatus of the present invention is also characterized in that the replenishing mechanism controls the toner replenishing amount by changing the applied bias value.

In such a configuration, the amount of charge of the member changes depending on the applied bias value, and the amount of electrostatic capture of the charged toner in the two-component developer to be transferred to the developing mechanism changes. The supply amount to the mechanism can be freely controlled, and it is easy to cope with differences in various image forming conditions.

The two-component developing device of the present invention is also characterized in that the replenishing mechanism controls the amount of toner replenishment by changing the time for applying the bias.

In such a configuration, even when the bias value to be applied is constant, by changing the application time, the time during which the member to which the bias is applied is charged and functions for toner replenishment changes. Therefore, the amount of charged toner to be captured and transferred changes, so that the amount of charged toner supplied to the developing mechanism can be freely controlled.

The two-component developing device of the present invention is also characterized in that the replenishing mechanism controls the replenishing amount of the toner by changing the transfer speed of carrying the separated charged toner and transferring it to the developing mechanism.

In such a configuration, when the charged toner separated from the two-component developer is carried and transferred to the developing mechanism for replenishment, the charged toner is transferred even if the amount of captured, separated and carried charged toner is constant. By changing the speed at which
The replenishment amount of the charged toner to the developing mechanism can be freely controlled.

Further objects and features of the present invention will be apparent from the following detailed description and drawings.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below in detail with reference to the accompanying drawings together with examples.

(Embodiment 1) The embodiment 1 is shown in FIG.
As shown in (1), developing an electrostatic latent image formed by an electrophotographic method on a photoreceptor 1 made of various materials and formed in various forms such as a drum and a belt using a two-component developer 1 is an example of a method and an apparatus thereof.

Basically, apart from subjecting the charged toner to the development by the developing mechanism A using a two-component developer,
The same two-component developer is preliminarily stirred by the pre-stirring mechanism B to charge the toner, and the charged toner is separated as necessary by the replenishing mechanism C, and is used for the development. Replenish.

In this case, in the preliminary stirring by the preliminary stirring mechanism B, the same charge amount can be charged under the same charging condition as when the charged toner is subjected to development by the developing mechanism A using the two-component developer. Therefore, the toner charged by the charge is separated by the replenishing mechanism C, and replenished to the two-component developer used for development by the developing mechanism A separately. There is no. For this reason, the developing mechanism A does not require a special time for recharging the replenished toner, and achieves high density follow-up while obtaining a good image even when forming an image at a high speed or a high black / white ratio. Can be secured.

The preliminary stirring by the preliminary stirring mechanism B is as follows.
Since it is only necessary to stir the two-component developer similarly to the developing mechanism A, a special charging member such as a rubber blade or a brush member conventionally provided on a bucket roller or the like is unnecessary, and a simple, small, and inexpensive device is used. There are also benefits that can be realized. In addition, by the timely operation of the developing mechanism A, the preliminary stirring mechanism B, and the replenishing mechanism C, the toner is charged by the preliminary stirring of the two-component developer of the preliminary stirring mechanism B, Separation of toner charged by the toner by the supply mechanism C and its developing mechanism A
Supply can be stably achieved.

The developing mechanism A, the pre-stirring mechanism B, and the replenishing mechanism C are compactly constructed by using a developing tank 5a and a pre-stirring tank 5b arranged in two stages below and above the casing 5. . As an example, the developing mechanism A is a developing tank 5
a, a developing roller 2, a bucket roller 3, and a spiral roller 4 are provided, a preliminary stirring mechanism B is provided with a stirring roller 8 in a preliminary stirring tank 5b, and a replenishing mechanism C is provided in a preliminary stirring tank 5b. Following the stirring roller 8, a magnet roller 7 and a donor roller 6 are provided.
At the position facing the bucket roller 3 at the bottom of the developing tank 5a,
An ATDC sensor 11 for detecting the toner concentration of the two-component developer and used for controlling the toner concentration is provided.

The developing roller 2, the bucket roller 3, the spiral roller 4, the magnet roller 7, and the stirring roller 8 are rotationally driven synchronously by a drive mechanism (not shown) operated by a motor M1, and the donor roller 6 is operated by a motor M2. It is independently driven to rotate by another driving mechanism (not shown). The driving of the motors M1 and M2 is controlled by the control device 21 via the drivers 22 and 23. The control device 21 preferably uses a microcomputer or the like that controls the operation of an image forming apparatus such as a copying machine equipped with the developing device of the first embodiment. However, it is not so limited.

By rotating and rotating the bucket roller 3, the two-component developer stored in the developing tank 5a is mixed and stirred to charge the toner to a negative polarity and to charge the carrier to a positive polarity, and to a desired charge amount. The charged two-component developer is supplied to the developing roller 2, and in addition, the two-component developer is transported in a fixed direction along the axis, and the two-component developer is conveyed in the opposite axial direction. In cooperation with the spiral roller 4 to be conveyed, the two-component developer is circulated as viewed from above, and the distribution of the ratio of the toner and the carrier of the two-component developer in the developing tank 5a is kept uniform.

The two-component developer supplied from the bucket roller 3 to the developing roller 2 is conveyed and supplied to a developing area in a portion facing the adjacent photosensitive member 1 by the rotation of the developing roller 2, where the negative electrode is charged. An electric field generated between the developing bias V1 applied to the developing roller 2 through the charging circuit 24 by the control device 21 and the electric charge V0 forming the electrostatic latent image on the photoreceptor 1 is generated only by the toner charged to the developing roller 2. Is supplied to the photoreceptor 1 to develop the electrostatic latent image into a visible image with toner. In this embodiment, the developing bias V1 is -400V.

The pre-stirring tank 5b contains a two-component developer composed of the same kind of toner and carrier as the two-component developer used in the developing tank 5a. The toner replenishes the toner consumed in the developing mechanism A. The two-component developer in the preliminary stirring tank 5b is mixed and stirred by the rotation of the stirring roller 8, and the toner is charged to a negative polarity and the carrier is charged to a positive polarity.

At the same time, the charged two-component developer is conveyed by the rotation of the stirring roller 8 to a portion facing the adjacent magnet roller 7, and the charged toner is electrostatically attracted to the carrier magnetically attracted by the developer. It is held and moves to the magnet roller 7. The excess of the two-component developer transferred onto the magnet roller 7 is scraped off by the scraper 12 at the position where the scraper 12 is in sliding contact with the magnet roller 7, and is recovered again in the preliminary stirring tank 5b.

When the toner is not replenished, the biases V2 and V3 applied to the donor roller 6 and the magnet roller 7 via the charging circuit 24 by the control device 21 are set to have the same potential. At the same time, the rotation of the donor roller 6 is stopped.

As a result, even if the appropriate amount of the two-component developer remaining on the magnet roller 7 is further transferred and opposed to the stopped donor roller 6, the two-component developer is mechanically removed from the donor roller 6. And the charged toner in the two-component developer is not transferred to the side of the donor roller 6 because no electric field is generated between the magnet roller 7 and the donor roller 6. Accordingly, the two-component developer on the magnet roller 7 passes through the portion facing the donor roller 6 as it is, and the scraper 13
Are scraped off and collected by the scraper 13 at the position where they are in sliding contact.

During toner replenishment, a potential difference between the donor roller 6 and the magnet roller 7 at which the donor roller 6 becomes positive is applied, and the donor roller 6 is driven to rotate. At this time, only the negatively charged toner is charged by the electric field generated by the potential difference between the donor roller 6 and the magnet roller 7.
The toner is separated from the two-component developer and supplied from the magnet roller 7 to the donor roller 6. Further, the charged toner on the rotating donor roller 6 is transferred to a position on the side of the developing mechanism A where the scraper 14 is in sliding contact with the donor roller 6, is scraped off by the scraper 14, and is transferred to the bucket roller 3 of the developing mechanism A. Is supplied.

The ATDC sensor 11 is located below the bucket roller 3, and its output voltage changes in accordance with the toner concentration in the two-component developer in the developing tank 5a.
1 is input. From the viewpoint of securing the toner concentration during development and stabilizing the image such as fog prevention, it is desirable that the toner concentration is constant, and the sensor output monitored by the control device 21 falls below the preset toner concentration lower limit value. If the corresponding output value deviates to the low density side, a potential difference for supplying the toner is provided between the donor roller 6 and the magnet roller 7 described above, and the donor roller 6 is driven to rotate to supply the toner. To do.

At the same time, the amount of change in the output voltage of the ATDC sensor 11 per unit time is also monitored by the control device 21. When the amount of change per unit time is smaller than a predetermined value, that is, when the output voltage changes, When the black / white ratio of the image to be developed is low and the consumption of toner in the development is small, a potential of 0 V is applied to the magnet roller 7 and a potential of +300 V is applied to the donor roller 6. As a result, the potential difference between the two is reduced, the transfer amount of the charged toner from the magnet roller 7 to the donor roller 6 is reduced, and the toner supply amount is suppressed. When the output voltage change is larger than a preset value, that is, when the black / white ratio of the image to be formed is high,
When the toner consumption in the development is large, 0 V is applied to the magnet roller 7 and +500 V is applied to the donor roller 6. As a result, the potential difference between the two is increased, the transfer amount of the charged toner from the magnet roller 7 to the donor roller 6 is increased, and the toner supply amount is increased.

As described above, by changing the bias value so as to change the potential difference between the donor roller 6 and the magnet roller 7 in accordance with the amount of toner consumption in the developing mechanism A, the toner supply amount can be freely changed. Can be changed.

The specific operation of the bias value varies depending on the mechanism of separation of the charged toner by the bias value and the transfer mechanism to the developing mechanism A. A shutter 10 is provided in a communication port 5c at the bottom of the pre-stirring tank 5b with the developing tank 5a. By opening this shutter, the two-component developer in the developing tank 5a can be supplied or supplied from the pre-stirring tank 5b side. I have to.

(Embodiment 2) Embodiment 2 is different from Embodiment 1 in the control mode of the toner replenishment amount, and the other basic configuration is not particularly different from that of Embodiment 1. 1 will be described below with reference to FIG.

When the output of the ATDC sensor 11 deviates from the output value corresponding to the preset toner density lower limit value to the low density side, that is, the black / white ratio of the image to be formed is low, and the toner consumption in the development Is small, the donor roller 6 rotates at a rate of, for example, 0.6 seconds per second so that the toner replenishing capacity becomes 60%. When the output voltage change amount is larger than a preset value, that is, the toner is formed. When the black / white ratio of the image is high and the toner consumption in the development is large, the donor roller 6 is rotated, for example, for one second per second, and therefore, continuously, so that the toner replenishing ability becomes 100%. To

As described above, by changing the rotation time of the donor roller 6 in accordance with the amount of toner consumption in the developing mechanism A, the toner supply amount can be freely changed.

The same operation and effect can be obtained by changing the bias application time for giving a potential difference for toner replenishment between the donor roller 6 and the magnet roller 7 instead of changing the rotation time of the donor roller 6. Is obtained.

(Embodiment 3) Embodiment 3 is different from Embodiment 1 in the control mode of the toner replenishment amount, and the other basic configuration is not particularly different from that of Embodiment 1. 1 will be described below with reference to FIG.

The motor M2 of the donor roller 6 is connected to the controller 2
The number of revolutions changes from 1 in accordance with the control voltage applied via the driver 23. When the output of the ATDC sensor 11 deviates from the output value corresponding to the preset toner density lower limit to the low density side, a potential of +500 V is applied to the donor roller 6, a potential of 0 V is applied to the magnet roller 7, and The donor roller 6 is rotated to supply toner into the developing tank 5a.

At this time, the monitored ATDC sensor 1
1 when the amount of change per unit time is smaller than a preset value, that is, the black / white ratio of an image to be formed is low, and the amount of toner consumed during development is small. When the amount is small, the donor roller 6 is continuously rotated at 12 rpm to reduce the transfer speed of the charged toner to the developing mechanism A, to suppress the toner supply amount, and when the output change amount is larger than a preset value. That is, when the black / white ratio of the image to be formed is high and the toner consumption in the development is large, the donor roller 6 rotates continuously at 20 rpm to increase the transfer speed of the charged toner to the developing mechanism A, and Increase supply.

As described above, by changing the toner transfer speed by the donor roller 6 in accordance with the amount of toner consumption in the developing mechanism A, the toner supply amount can be freely changed.

The specific operation of the transfer speed varies depending on the transfer mechanism of the charged toner to the developing mechanism A.

[0045]

According to the two-component developing method of the present invention, the charged toner obtained by the preliminary stirring can be separated and supplied to the two-component developer used separately for the development, and then used for the development as it is. The charge amount is not insufficient, no special time is required for recharging at the time of development, and high density followability can be secured while obtaining a good image even when forming an image at a high speed or a high black / white ratio. Can be. Further, there is an advantage that a special charging member such as a rubber blade conventionally provided on a bucket roller or the like is not required for the preliminary stirring, and the device can be realized by a simple, small, and inexpensive device.

According to the main features of the two-component developing device of the present invention, in accordance with the developing operation, the toner is charged by the pre-stirring of the two-component developer, the toner charged by the toner is separated in a timely manner, and the toner is transferred to the developing mechanism. Supply can be stably achieved.

In another feature of the two-component developing device of the present invention,
Separation of the charged toner from the two-component developer and transfer to the developing mechanism can be reliably achieved by forced charging of the biased member and its polarity.

According to another feature of the two-component developing device of the present invention, the amount of charge of the member changes depending on the applied bias value, and the amount of electrostatically captured charged toner in the two-component developer transferred to the developing mechanism. Therefore, the replenishment amount of the charged toner to the developing mechanism can be freely controlled, and it is easy to cope with the difference in various image forming conditions.

According to still another feature of the two-component developing apparatus of the present invention, even when the applied bias value is constant, the member to which the bias is applied is charged by changing the application time, so that the function for supplying toner is provided. Time, and the amount of capturing and transferring the charged toner changes accordingly,
The replenishment amount of the charged toner to the developing mechanism can be freely controlled.

According to another feature of the two-component developing device of the present invention, the amount of the charged toner captured, separated and carried when carrying the charged toner separated from the two-component developer and transferring it to the developing mechanism for replenishment. Is constant, the amount of charged toner supplied to the developing mechanism can be freely controlled by changing the speed at which the charged toner is transferred.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a two-component developing device according to a first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List A developing mechanism B pre-stirring mechanism C replenishing mechanism 1 photoreceptor 2 developing roller 3 bucket roller 5a developing tank 5b pre-stirring tank 6 donor roller 7 magnet roller 8 stir roller 11 ATDC sensor 21 control device 22, 23 driver 24 charging circuit M1, M2 motor

Claims (6)

[Claims] 1. Separately from charging a charged toner for development using a two-component developer, the same two-component developer is preliminarily stirred to charge the toner, and the charged toner is separated as required. Then, the two-component developer used in the development is replenished and the development is performed. 2. A developing mechanism for subjecting a charged toner to development using a two-component developer, a pre-stirring mechanism for separately stirring the same two-component developer separately from the developing mechanism, and a pre-stirring by the pre-stirring mechanism. A replenishing mechanism for separating charged charged toner and replenishing it to a developing mechanism. 3. The two-component developing device according to claim 2, wherein the replenishing mechanism electrostatically captures and separates the charged toner by a member to which a bias is applied, and transfers the charged toner to the developing mechanism. 4. The two-component developing device according to claim 3, wherein the replenishing mechanism controls a toner replenishing amount by changing an applied bias value. 5. The two-component developing device according to claim 3, wherein the replenishing mechanism controls a toner replenishing amount by changing a bias applying time. 6. The two-component developing apparatus according to claim 2, wherein the replenishing mechanism controls a toner replenishing amount by changing a transfer speed at which the separated charged toner is carried and transferred to the developing mechanism.