JPH1195536A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten an aging means capable of stabilizing fluctuated electrifiability and to prevent the splashing of toner caused by a sudden increase of the electric charge quantity of a developer by setting the concn. of the toner of a fresh developer when exchanging developers, lower than the stable concn. of the toner in a developing device. SOLUTION: A deterioration in a two-component developer used in the developing device 5, due to aging is inevitable and it is necessary that the deteriorated developer is exchanged. After the exchange, the electric charge quantity of an initial developer is decreased and easily made inhomogeneous as well, so that the aging for stirring/circulating the developer in a developing unit 10 for a specified time is executed. But, when the aging is executed, a phenomenon where the electrification of the developer transiently and excessively rises, drops when the rising exceeds a certain peak and converges at a certain point is generated. At this time, the concn. of the toner of the developer is previously adjusted to be rather lower than a control target value. The developer adjusted to be rather lower than the control target value is used as the fresh developer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a developing device for developing a latent image formed on an image bearing member using a two-component developer including a toner and a carrier.

[0002]

2. Description of the Related Art Many electrophotographic image forming apparatuses such as copiers, facsimiles and printers use a two-component developer composed of a toner and a carrier. This two-component developer is unavoidable to deteriorate over time,
The deteriorated developer needs to be replaced when its life is reached.
At the time of this replacement, even if the replacement new developer has been packaged sufficiently after production and shipped, it is inevitable that the charge amount of the toner in the developer due to leaving for a long time is reduced. For this reason, in the apparatus after the replacement of the developer, the toner adhesion amount is not stable in copying several tens of sheets, and the image density often fluctuates. In addition, when a developer is set and shipped in a factory in order to shorten the loading operation of the device, the charge amount is significantly reduced and uneven compared to the developer which is packaged and shipped. Cheap.

[0003] As means for solving such a problem,
This is to stir and circulate the inside of the developing device for a predetermined time at the time of replacement of the developer, and this operation increases and stabilizes the charge amount of the developer. This technique is the basic operation of what is commonly called aging, inching and the like. In addition, other means have been proposed, but at an idea level, and at present, the above-described stirring and circulation is mostly performed. This is because the above means is a simple and reliable technique that does not require special equipment.

[0004] The problem of unstable developing ability of the initial developer is not limited to the above-described decrease in the toner charge amount. After the above-mentioned aging operation, the charge of the developer temporarily rises excessively, and this rise tends to decrease after passing a certain peak and converge at a certain point. The reason for this is that the charge amount of the carrier is changed in Japanese Patent Application Laid-Open No. Hei 5-249832. In view of this, in setting the density after aging, the charge amount of the carrier is set lower in anticipation of a stable level. You are dealing with it.

In Japanese Patent Application Laid-Open Nos. 5-323667 and 1-222561, the reason for this is that the condition of the agent such as the particle size distribution and charge amount distribution of the agent produced in the manufacturing process is formed in the developing unit. This is because it is not the same as the condition. Then, the method for producing the agent is given a characteristic so as to approach the state after the initial aging.

[0006]

However, the technique for imparting a characteristic to the method of manufacturing the agent is not perfect, and it has nothing to do with the above-mentioned solution for the reduction of the toner leaving, so that the aging means must be implemented after all. At present it is necessary to do it. Therefore, an aging operation for converging the developer to a charged state that stabilizes the developing ability by repeating the toner supply and the stirring operation in the developing device after the initial agent is mounted is dealt with.

Further, in order to control the replaced initial developer to a predetermined toner concentration target range, the amount of toner adhered to the photoreceptor is generally detected by a reflection type optical sensor, and based on the detected amount. The mainstream is a case in which the toner supply control is performed first, and a case in which the developer in the developing device is detected by a sensor of magnetic permeability or bulk density and the toner supply control is performed based on the detected magnetic permeability or bulk density. However, neither control method can cope with the rapid increase in developer charge that occurs during aging of the developer, and the former reflective optical sensor method temporarily reduces the amount of adhesion due to a sudden increase in charge. As a result, the toner concentration is temporarily controlled to be excessively increased, and there is a concern that toner scattering may occur.

In the latter method of detecting the magnetic permeability or bulk density by a sensor, the magnetic permeability rises and the bulk density decreases due to a temporary increase in the charge amount, and as a result, the toner concentration is temporarily and excessively increased. As a result, there is also a concern that toner scattering may occur.

In view of the above circumstances, the present invention reduces the aging means capable of stabilizing the charging property of the exchanged developer and prevents toner scattering due to a rapid increase in the developer charge. It is an object of the present invention to provide an image forming apparatus capable of performing the following.

[0010]

To achieve the above object, the present invention provides a developing apparatus for developing a latent image formed on an image bearing member using a two-component developer comprising a toner and a carrier. In the image forming apparatus having the configuration described above, the replacement developer used when the developer of the development device is replaced has a toner concentration set lower than a toner concentration stable in the development device.

It is to be noted that the present invention is advantageous in that, before the normal image forming operation, the replaced developer is supplied to the developing device to correct the toner concentration to be stable and to stabilize the charging ability of the developer. It is a target.

In order to further achieve the above object, the present invention provides an image forming apparatus having a developing device for developing a latent image formed on an image bearing member using a two-component developer comprising a toner and a carrier. Wherein the developer filled in the developing device in the image forming apparatus main body shipped from the factory has a toner concentration set lower than a toner concentration stabilized in the developing device.

The present invention is effective when the developer is supplied to the developing device to correct the toner concentration and stabilize the charging ability of the developer prior to the normal image forming operation. is there.

Further, according to the present invention, the replacement developer is set to be lower than the control target value of the toner concentration, and while the developer is supplied into the developing device and is stabilized, the replacement developer is insufficient. It is effective to supply toner for a minute.

Further, the present invention is effective when the toner replenishment that is insufficient for the control target value is a replenishment without using sensor control.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram illustrating a printer unit of the image forming apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image bearing member. When the photosensitive drum 1 is driven to rotate in the direction of the arrow, a laser is applied to a portion uniformly charged by the charging device 2. Image exposure indicated by the exposure means 3 is performed,
An electrostatic latent image is formed on the photosensitive drum 1. When the latent image reaches a position facing the developing device 5, the latent image is visualized as a toner image. On the other hand, the transfer material is transported from a paper feed unit (not shown) to the image forming unit via a registration roller, and the transfer device 5 transfers the toner image on the photosensitive drum 1. The transfer material after the transfer is sent to a fixing device (not shown), and the toner image is fixed on the transfer material.

After the transfer, toner remains on the photosensitive drum 1, and the residual toner is cleaned by the cleaning device 6. Then, the photosensitive drum 1 after cleaning is cleaned of residual charges by the charge removing device 7 and is ready for image formation.

The developing device 5 uses a two-component developer, and includes a developing roller 1 facing the photosensitive drum 1.
And a hopper 11 serving as a toner replenishing section for replenishing toner stored in the developing device 10.
And The developing device 10 includes a stirring member 14 such as a stirring roller and a paddle, and a doctor (not shown) for controlling a layer thickness on the developing roller 12. The developing roller 1
2, a developing bias 13 is applied. The toner is
The replenished toner and developer are replenished from the popper 11 to the developing chamber 10, and the replenished toner and developer are agitated by the agitating member 14 in the developing chamber 10. The developing roller 12 transfers the developer from the developing device 10 to the developing area facing the photoconductor 1. Carried and transported In order to create an appropriate potential difference between a developing sleeve (not shown) and the photoconductor 1 in the developing area, a developing bias 13 is applied, and a toner image is formed in accordance with a potential difference from an electrostatic latent image formed on the photoconductor 1. Is formed.

In this two-component developing apparatus, it is inevitable that the two-component developer deteriorates with use over time, and the deteriorated developer needs to be replaced over its life. After this replacement, the initial developer tends to have a reduced charge amount and become non-uniform, so it is necessary to perform aging by stirring and circulating the developer in the developing device 10 for a predetermined time.

However, when aging is performed, the charge of the developer temporarily rises excessively, and this rise goes down after a certain peak and then converges at a certain point. FIG. 2 shows this phenomenon graphically.

At this time, the toner density of the conventional replacement developer is adjusted to the control target value. The charge of this developer temporarily rises rapidly during aging, as indicated by the symbol B in the graph of FIG. The developing device performs toner density control using a sensor, and this rapid rise in charge causes the toner to be controlled, as indicated by the symbol A in the graph of FIG.
An excessive supply of toner occurs, and there is a concern that toner is scattered.

Therefore, in the present invention, the toner concentration of the replacement developer is previously adjusted to be lower than the control target value. By using the developer whose toner concentration is adjusted to be lower than the control target value as the replacement developer, as shown in the graph of FIG. The time until stabilization by increasing the amount is shortened.
Then, for the developer whose toner concentration has been adjusted to a lower value in advance, the amount of insufficient toner for the toner concentration to be the control target value is also known, so if the insufficient amount is replenished over a predetermined time instead of sensor control, The control value can be substantially set, and in this case, as shown in the graph of FIG. 2C, the toner density does not need to be increased.

After replenishing the developer whose toner concentration is adjusted to be lower than the control target value, the developing unit 1 performs an aging operation prior to the first image forming operation.
Agitating and circulating the developer within 0 and supplying toner are performed. That is, since the initial developer capacity and toner concentration and the target control concentration are known in advance, a predetermined amount of toner given in advance during stirring and circulation of the developer can be used for a predetermined time without using sensor control. Replenish over time. For example, the initial capacity of the replacement developer is 400 g and the toner density is 3
If the target control density is 5 wt%, about 8 g of toner is supplied into the developing device during aging. It is more effective to perform this aging operation at the same time as the start-up work of another unit, for example, the work of adjusting the temperature of the fixing device, etc., because the initial adjustment time of the image forming apparatus is shortened.

By lowering the toner concentration in advance, the probability of contact between the carrier and the toner is increased, and the time required to increase the charge amount and stabilize is shortened. In addition, since it is known that the toner is replenished to achieve the target toner concentration, there is no need to worry about excessive toner concentration, background contamination, and toner scattering.

That is, according to the present invention, the time required for stabilizing the charge amount (aging time) can be shortened as compared with the case where the toner concentration of the replacement developer is equal to or higher than the control target value in weight%. In addition, it is possible to avoid problems such as excessive toner concentration / toner scattering due to a sudden increase in the amount of charge during the aging operation.

According to the present invention, the toner concentration of the replacement developer is adjusted to be lower than the control target value in advance even when the developer is set and shipped in a factory in order to shorten the loading operation of the apparatus. By doing so, the above effect can be obtained.

[0028]

According to the present invention, it is possible to shorten the aging means capable of stabilizing the charging property of the exchanged developer and prevent toner scattering caused by a rapid increase in the developer charge. it can. In addition, it is possible to shorten the time until the charge amount is increased and stabilized. Therefore,
According to the present invention, the initial adjustment including aging at the time of replacing the developer can be performed cleanly and smoothly.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a printer unit of an image forming apparatus according to the present invention.

FIG. 2 is a graph showing a relationship between toner density and developer charge amount after replacement of a developer, wherein (1) is a conventional toner density, and (2)
Is the conventional developer charge amount, (3) is the toner concentration of the present invention,
(4) shows the charge amount of the developer of the present invention.

[Explanation of symbols]

 Reference Signs List 1 photoconductor 4 developing device 10 developing device

Claims (6)

[Claims] 1. An image forming apparatus having a developing device for developing a latent image formed on an image bearing member using a two-component developer including a toner and a carrier, wherein the developer of the developing device is replaced. The image forming apparatus according to claim 1, wherein the toner concentration of the replacement developer is set lower than the toner concentration stabilized in the developing device. 2. The image forming apparatus according to claim 1, wherein prior to a normal image forming operation, the replaced developer is supplied into the developing device to correct the toner concentration to be stable and to adjust the charging ability of the developer. An image forming apparatus for performing stabilization. 3. An image forming apparatus having a developing device for developing a latent image formed on an image bearing member using a two-component developer comprising a toner and a carrier. Wherein the toner concentration of the developer filled in the developing device is set lower than the toner concentration stabilized in the developing device. 4. The image forming apparatus according to claim 3, wherein prior to a normal image forming operation, the developer is replenished into the developing device to correct the toner concentration and stabilize the charging ability of the developer. And an image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the replacement developer is set lower than a control target value of the toner density, and the developer is supplied into the development device. An image forming apparatus which supplies a shortage of toner with respect to a control target value during a stable operation. 6. An image forming apparatus according to claim 5, wherein the toner replenishment for a shortage of the control target value is a replenishment without using sensor control.