JPS63113571A - Image forming device - Google Patents

Abstract

PURPOSE:To form a stable image extending over a long period by using the toner of other constitution than that of a toner contained in advance in a developing device, as the replenishing toner of a toner replenishing device. CONSTITUTION:The toner concentration of a developer D in a developer containing part 11 is detected by a toner concentration detector 14, and when the toner concentration reaches a prescribed level, a replenishing signal is sent to a toner replenishing device 20, and the toner t2 of the quantity corresponding to the consumption is replenished automatically. As for this replenishing toner t2, that of other constitution than that of an initial toner t1 contained in advance in the developer containing part 11 is used. In such a way, the initial distribution is held by suppressing the extension of the electrification quantity distribution of the toner in the developer D, and a stable image can be formed extending over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Field of Application) The present invention relates to image forming apparatuses such as copying machines and electronic printers, and particularly relates to an image forming apparatus using a two-component developer consisting of a toner and a carrier. The present invention relates to an improvement in a forming apparatus including a developing device for visualizing an electrostatic latent image and a toner replenishing device for replenishing toner into the developing device.

<Prior Art> Usually, in an image forming apparatus, such as a copying machine, which is equipped with a developing device that visualizes an electrostatic latent image using a two-component developer consisting of toner and carrier, the developing device is equipped with a toner replenishing device. It has a structure that allows it to be attached and replenish toner as needed.

However, conventionally, the toner replenishing device is supplied with toner having the same structure as the toner stored in advance in the developing device.

(Problems to be Solved by the Invention) However, according to such a conventional replenishment method, as the number of copies increases, the image density gradually increases, as shown by the line graph of white circles in FIG. In Figure 2, as shown by the line graph with white circles, the amount of charge decreased as the number of copies increased, resulting in an unstable state.

This is due to the formation of a toner film on the carrier due to the stress caused by the rotation of the developing roller and stirring member or the leveler (doctor blade) during the copy cycle, or due to the adhesion of highly charged toner particles to the carrier.
The original effect of retaining a predetermined charge on the toner due to friction between the carrier and the toner has diminished, and it has become impossible to obtain the original amount of charge as the copy cycle progresses.

For this reason, there are disadvantages such as the image 11 degrees being higher than necessary, fogging development and toner scattering causing internal contamination, and toner consumption increasing due to the increase in toner of opposite polarity that does not contribute to development. Measures have been taken to shorten the lifespan of the developer and replace it regularly, or to increase the amount of developer used.

The above matters will be supplemented with reference to FIGS. 3 and 7. FIG. 3 is an explanatory diagram showing the initial toner charge amount distribution, and FIG. 7 is a diagram showing the transition of the toner charge amount distribution when the same toner is replenished.

Not all individual charged particles contribute to development, at least toner that has been exposed to charges of opposite polarity cannot contribute to development, and toner with a charge amount of around 0 has almost no charge and is therefore retained. Otherwise, it may cause scattering, etc.

As can be seen by comparing FIGS. 3 and 7, this tendency gradually changes as the copy cycle progresses even when toner of the same material is used. This is thought to be due to the gradual change in the way friction is applied to obtain charge on the supplied toner.

In this way, in the past, countermeasures were taken by shortening the lifespan of the developer and replacing it periodically, or by increasing the amount of developer, which caused problems such as being extremely uneconomical and increasing the size of the equipment. was there.

The present invention has been made based on the above-mentioned circumstances, and its purpose is to suppress the spread of the toner charge amount distribution and maintain the initial distribution without changing the basic configuration, and to maintain the initial distribution over a long period of time. An object of the present invention is to provide an image forming apparatus that can perform stable image formation.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention visualizes an electrostatic latent image using a two-component developer consisting of a toner and a carrier. In an image forming apparatus comprising a developing device and a toner replenishing device that replenishes toner within the developing device, toner replenishing toner for the toner replenishing device is separate from toner stored in advance in the developing device. It is designed to use toner of the following composition.

(Function) That is, the present invention forcibly maintains good distribution characteristics by gradually replenishing the frictional electrification of the toner and carrier that constitute the developer stored in the developer Q device in advance. The life of the developer can be extended, thereby making it possible to form images stably over a long period of time without changing the basic structure.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 6.

First, the image forming process will be explained with reference to FIG.

In the figure, reference numeral 1 denotes a drum-shaped photoreceptor as a recording medium, and charging means 2. Latent image forming means 3. Developing means 4. Transfer means 5. Peeling means 6. Cleaning means 7. The static eliminating means 8 are arranged in sequence.

Then, after the photoreceptor 1 is uniformly charged by the charging means 2, an electrostatic latent image is formed by exposure by the latent image forming means 3,
Is it possible to develop this using developing means 4? Become JF.

Next, the image is transferred onto the paper P by the transfer means 5, and the image is peeled off from the photoreceptor 1 by the peeling means 6 and guided to the fixing means (not shown) side. On the other hand, the photoreceptor 1 after the transfer is cleaned by the 'r74 cleaning means 7, and then the latent image is erased by the static eliminating means 8 to complete one process.

The developing means 4 is a two-component developing device that performs development using a two-component developer, and has the following construction. That is, 10 in the figure is the main body of the developing device, and the inside of this main body 10 of the developing device is 3 to 3 with negative polarity and the carrier C.
It serves as a developer accommodating portion 11 that accommodates a two-component developer consisting of toner t1 mixed with 5% by weight, and
Developing roller 12. tj! Stirring member 13. A toner concentration detector 14, leveler (doctor blade) 15, etc. are arranged.

Further, a chamber 18 is formed in the rear portion of the developing device main body 10, and is partitioned by a partition wall 16 and communicates with the developer storage section 11 through a lower opening 17. The replenishment toner t2 is appropriately supplied from there.

At the upper part of the chamber 18, a toner conveying and supplying mechanism 21 is disposed that evenly and evenly conveys the replenishment toner t2 supplied from the toner replenishing device 20, and below this, a stirring member 2'2 is disposed. The situation is as follows.

The toner replenishing device 20 has a removable toner hopper 23 having a toner replenishing port corresponding to a toner receiving port formed in the developing device main body 10. The stored toner t1
In this state, toner t2 having a different configuration from that in the first embodiment is accommodated.

On the other hand, on the circumferential surface of the developing roller 12, developer particles adhere in the form of a brush due to lines of magnetic force emitted from the developing roller 12, forming a developer magnetic brush D'.
The developer magnetic brush D' is caused to continuously rub against the surface of the photoreceptor 1 by the rotation of the roller 12.

Then, the toner t1 (also t2 after toner replenishment) in the developer magnetic brush D' is electrostatically transferred to the electrostatic m image formed on the surface of the photoreceptor 1, and the electrostatic latent image is visualized. I will do it.

On the other hand, the toner concentration of the developer in the developer storage section 11 is detected by the toner concentration detector 14, and when the toner concentration reaches a predetermined level, a replenishment signal is sent to the toner replenishment device 20, and a Toner t2 will be automatically replenished.

In the present invention, by using as the replenishment toner t2 a toner having a different configuration from the initial toner t1 previously stored in the developer storage section 11, the charge distribution of the toner in the developer can be improved. This suppresses the spread and maintains the initial distribution, allowing stable image formation over a long period of time.

Next, the developer stored in the developer storage section 11 in advance will be explained.

First, as the carrier C, a Ca-Zn-based ferrite oxide with an average particle size peaking at 70 to 100μ and a bulk specific gravity of 2.5 is used.
~2.8 g/ctx3. Use dark red, silver-gray, spherical particles with a mesh pattern on the surface. Further, toner t1 is a black toner in which the resin is styrene acrylic and the pigment is carbon black as a main component, the average particle size is around 10 to 11 μ, the bulk specific gravity is 0.3 to 0.35, and the glass transition point is 60. Use one with a temperature of ~75°C. (Hereinafter, this toner will be referred to as type a).

On the other hand, as the replenishment toner t2, (a) type a toner tl with additives of 0.3 to 0.
A mixture of 5% by weight. (Hereafter, this toner is type b.
).

(b) Type A toner t1 mixed with 1% by weight of additives. (Hereinafter, this toner will be referred to as type C).

02 types were prepared and experiments were conducted on each.

The above additive is an external additive for a magnetic component toner, which is a styrene acrylic toner with carbon black as its main component mixed with magnetic powder, and its average particle size is 10 to 11 μm.
It was before and after.

When the amount of charge (ΔQ) was measured for replenishment toners of both type A and C with different amounts of additives, as shown in Figure 5, the initial type A toner t
It was found that the amount of charge could be increased compared to the case where No. 1 was used.

Although not shown here, these types B are used.

When an attempt was made to produce an image using the replenishment toner t2 of C to constitute an initial developer, the image density could not be maintained from the initial first sheet.

Therefore, type a toner t1 was used to form the initial developer layer, and type b and c toners were used as replenishment toner t2. ) and black triangle graph (type C
As shown in case 2), a stable state with little variation was obtained regardless of the copy cycle, and moreover, the initial target lifespan was fully exceeded and good images were obtained.

As a verification, the toner charge amount distribution was measured after 40 minutes, and the results shown in FIG. 6 were obtained, and it was found that the distribution form was hardly different from the initial one shown in FIG. 3.

The mechanism and theoretical analysis of frictional electrification have not been fully elucidated, so it is not clear why such good results were obtained, but it has been fully proven from the experimental results.

My guess is that toner with a different charge distribution as shown in Figure 3 is present in the developing device in a gradually changing ratio as the copy cycle progresses, so the way the friction is applied constantly changes. From a macroscopic perspective, it can be thought that the charge balance is maintained exactly.

In the above embodiment, an external additive made of magnetic component toner was used as an additive for replenishment toner, but internal additives may also be mixed in. Of course, the amount is not limited to the above example, and the point is that the toner contained in the initial developer and the replenishment toner are different and the band I'll can be corrected. Also good.

In addition, it goes without saying that the present invention can be modified in various ways without departing from the gist of the invention.

"Effects of the Invention" Since the present invention has been explained above, the FJ of toner and carrier constituting the developer stored in the developing device in advance is achieved.
By gradually replenishing the triboelectric charge with another toner, it is possible to forcibly maintain the distribution characteristics and extend the life of the developer. This allows for stable image formation over a long period of time without any changes to the basic structure. This has the advantage that it is possible to provide an image forming apparatus that is capable of.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the relationship between the number of copies and image density, Figure 2 is an explanatory diagram showing the relationship between the number of copies and charge amount, and Figure 3 is an explanatory diagram showing the distribution of toner charge amount of the initial toner. , Figure 4 is a diagram showing the image forming process, Figure 5 is an explanatory diagram showing how the toner charge amount increases when additives are added, and Figure 6 is the toner charge amount distribution when another toner is replenished. FIG. 7 is a diagram showing the transition of the toner charge amount distribution when the same toner is replenished. tl...Initial toner, t2...Replenishment toner, C...
- Carrier, D... Developer, 4... Developing means (two-component developing device), 20... Toner replenishing device. Applicant's agent Patent attorney Takehiko Suzue Translated by Coffee Co., Ltd. (xlooo) Figure 1 Copy LL (xlooo) Figure 2 Figure 7 Attachment 11 Figure 5

Claims (4)

[Claims] (1) Image formation comprising a developing device that visualizes an electrostatic latent image using a two-component developer consisting of toner and carrier, and a toner replenishing device that replenishes toner within the developing device. An image forming apparatus characterized in that the toner supplying device uses toner of a different composition from the toner stored in advance in the developing device as replenishing toner. (2) The image forming apparatus according to claim 1, wherein the replenishment toner has a function of controlling the amount of charge for the image forming cycle. (3) The image forming apparatus according to claim 1, wherein the replenishment toner is constructed by adding an additive to an initial toner stored in advance in the developing device. (4) The image forming apparatus according to claim 3, wherein the additive material is an external additive material made of a magnetic component type toner.