JPS63103280A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To miniaturize the whole of a device and to improve the handlability and the durability by supplying a charged toner at speed higher than the carrying speed of a magnetic brush to transport it to the magnetic brush side and supplying the proper quantity of the toner with a simple structure. CONSTITUTION:A toner supply roll 24 is pressed to a sponge roll 27 assisting in toner supply, and a toner 25 stored in a toner tank 23 is sent to a magnetic brush 14 by the rotation of the toner supply roll 24. In this case, the rotational speed of the toner supply roll 24 is increased to supply the toner at the speed higher than the carrying speed of the magnetic brush 14 for the purpose of compensating the degradation in use efficiency of the supply toner due to toner dispersion. Thus, a sufficient picture density is obtained. The whole of the device is considerably miniaturized and is made easy to handle.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an electrostatic latent image developing device, and in particular to a hybrid electrostatic latent image developing device that allows a dry two-component developer to be used in the same way as a component developer. The present invention relates to a latent image developing device.

(Prior Art) Generally, in a developing device using a dry two-component developer, as shown in FIG. It is provided.

By the stirring mechanism such as the stirring roller 2, the toner replenished from the toner hopper 5 side is sufficiently mixed with the carrier.
After being stirred, it is supplied to the developing roller 6.
The material is attached in layers to a magnetic brush formed on the surface of the material. The thickness of this adhered developer layer is regulated by a doctor blade 7.

The developing roller 6 includes a plurality of magnets 9 inside a sleeve 8, and by rotating at least one of the sleeve 8 and the magnets 9 in a certain direction, the magnetic brush formed on the surface of the sleeve 8 is rotated in a certain direction. will be moved to. When this magnetic brush comes into contact with the photoreceptor 10, the electrostatic latent image formed on the photoreceptor 10 is developed and visualized. After this development, the magnetic brush is scraped into the developing tank 1, and mixing and stirring are performed again by the stirring mechanism.

As described above, the two-component developer requires sufficient stirring and mixing in order to ensure uniformity of toner concentration or to charge the toner well. Therefore, above 2
Conventional developing devices using component developers have the advantage of being able to stabilize image quality, but as mentioned above, the developer must be sufficiently stirred, and various stirring mechanisms are required for this purpose. In addition, sufficient space is required to form the stirring channel. Further, the carrier is required to have good fluidity in order to obtain good stirring properties. In particular, carriers that exhibit cohesive properties even after the magnetic field is removed due to residual magnetism cannot be used in the developing device that does not have the above-mentioned stirring mechanism. Furthermore, if stirring is carried out frequently, the carrier will become fatigued quickly, resulting in poor durability.

On the other hand, in order to overcome the drawbacks of such developing devices using two-component developers, various developing devices have been developed in which mixing and stirring of the developer can be omitted. Such developing devices include those in which the toner is adhered to the surface of the charging roller and the toner is supplied by bringing the charging roller into contact with a magnetic brush, and those in which the toner is supplied using a magnetic brush. Some devices supply +-toner to the roller and form a thin layer of toner on the developing roller.

However, the former method has the disadvantage that the toner concentration on the developing roller L tends to be uneven, and the latter method has the problem that the developer still needs to be sufficiently mixed and stirred.

(Purpose) An object of the present invention is to reduce the overall size of the device, improve its handling properties, and improve its durability, while also maintaining good image stability. It is an object of the present invention to provide a developing device that can be handled in the same way as a component developer.

(Structure) The developing device according to the present invention transports the charged 1-toner in the toner supply area to the magnetic brush side at a speed faster than the transport speed of the magnetic brush, and also transports the charged 1-toner in the toner collection area to the magnetic brush side. The present invention is characterized in that toner remaining on the magnetic brush is collected from the magnetic brush.

Hereinafter, the configuration of a developing device of the present invention will be explained based on the illustrated embodiment.

As shown in FIG. 1, a photosensitive drum 1 as a latent image carrier is rotated in the direction of arrow A by a drive mechanism (not shown).
A non-magnetic cylindrical sleeve 12 made of aluminum or the like is arranged near the sleeve 1 .

Inside the cylindrical sleeve 12, magnets 13 each having a plurality of different magnetic poles arranged alternately are arranged inside the cylindrical sleeve 12.
The magnetic brushes 14 are arranged at a constant distance from the inner peripheral surface of the cylindrical sleeve 12, and are configured so that the magnetic force of these magnets 13 forms a magnetic brush 14 on the surface of the cylindrical sleeve 12. This magnetic brush 14 is activated by rotating at least one of the cylindrical sleeve 1 and the magnet 13.
It is moved in the direction of arrow B in the figure.

Further, a developing bias voltage of the same polarity is applied to the cylindrical sleeve 12 and the photosensitive drum 11 by a power supply circuit 15. Then, the magnetic brush 14 on the cylindrical sleeve 12 contacts the photoreceptor drum 11 on which the electrostatic latent image 16 is formed while moving, and applies toner to the electrostatic latent image 16.
A visible image 17 is formed.

In this embodiment, one cylindrical sleeve 12 has an outer diameter of 20 mm, for example, and the cylindrical sleeve 12 is used as the magnet 13.
By employing a magnetic brush having a surface magnetic force of approximately 900 Gauss, the height of the magnetic brush 14 can be set to 0.3 to 5 mm (preferably 0.7 to 2 mm).

On the other hand, the above-mentioned development bias voltage is applied to prevent background smearing and adjust image density. For example, when the latent image potential is 1800V and regular development is performed, it is O to -500V.
In the case of reversal development, it is preferable to apply a voltage of -200V to -8V while using a negatively charged toner.
It is appropriate to apply a bias voltage of about 00V. Here, the final developing bias value is determined depending on the original density or the user's request.

A toner collection roller 18 is installed on the lower side of the cylindrical sleeve 12 as a toner collection means for collecting residual toner from the magnetic brush 14 after development. This toner collection roller I8 has a magnetic brush 14.
A predetermined bias voltage for toner collection is applied by a toner collection power supply circuit 19 . The bias voltage for toner collection is
It is used to collect the toner remaining on the magnetic brush 14, and is set at the same level as the development potential, that is, at a level that allows full-surface development when the toner collection roller 18 is used as a latent image carrier. For example, if the latent image potential is -go
ov, when the developing bias voltage is 1200 V, the bias voltage for toner collection may be set to -600 V m degrees.

Here, it is not necessary to collect all the toner contained in the magnetic brush 14, and it is sufficient to selectively collect the toner near the surface of the magnetic brush 14. In other words, the purpose of this recovery is to eliminate the difference in the distribution of the magnetic brushes 14'' caused by development.

Therefore, for example, toner may be collected evenly when there is a difference in toner consumption in black areas, halftone areas, and background areas.

Generally, the toner adhesion amount of a two-component developer is 0.8 to 1.0 II 1 g per unit area, and
1 and the magnetic brush 14 are supplied with toner to the latent image 16 while being given a relative speed of approximately 1:3. That is, the magnetic brush 14 has a density of 0.27 to 0.27 per unit area.
This results in a toner supply capacity of only 0.33 mg. Therefore, if toner is collected in an amount exceeding this toner supply capacity, the toner concentration distribution on the magnetic brush 14 will be made uniform, and the influence of development will be completely eliminated.

To explain this point in more detail, due to the characteristics of a very common two-component developer with a bulk specific gravity of 2 and a toner concentration of 3%, a height of 1
The weight of a mm magnetic brush is 0.2 g per unit area, and the toner contained therein is 6 mg, so the toner that actually contributes to development is only about 5% of the magnetic brush. Therefore, if you collect toner equivalent to this 5%,
Differences in toner concentration distribution on the magnetic brush 14 can be eliminated. In the magnetic brush of the present invention, about 0.3 mg
/cm2 of toner is unevenly distributed near the surface of the magnetic brush by a toner supply roller, which will be described later, so that the difference in toner consumption can be effectively eliminated.

In FIG. 1, the collection rollers 1 to 18 are rotationally driven in the direction of arrow C. This is because the toner once collected by the 1-toner collection roller 18 is transferred to the magnetic brush 14.
This is to prevent it from re-adhering to the surface.

A scraping blade 21 is attached to the toner collecting roller 18 , and the scraping blade 21 scrapes off the collected toner, and the scraped toner is returned to the toner tank 23 .

Further, a toner supply roller 24 serving as a toner supply means is placed vj in a lower side portion of the cylindrical sleeve 12, that is, a downstream portion of the magnetic brush 14 so as to be in contact with the magnetic brush 14. The toner supply roller 24 is provided in pressure contact with a sponge roller 27 for assisting the toner supply, and is rotationally driven in the direction indicated by the arrow by a rotational drive mechanism (not shown). As the toner supply roller 24 rotates, the toner 25 stored in the toner tank 23 is sent to the magnetic brush 14.

Further, the toner supply roller 24 has a function of uniformly regulating the height of the ears of the magnetic brush 14, and contributes to eliminating uneven image density.

Further, a toner regulation blade 26 is attached to the toner supply roller 24 . This toner layer regulation blade 26 is provided so as to be in pressure contact with the toner supply roller 24, and thereby the toner 25 is deposited on the toner supply roller 24 in a uniform thin layer, and the toner 25 is evenly deposited on the toner supply roller 24.
5 frictional charging is performed. here,
In order to make better use of the function of uniformly regulating the height of the ears of the magnetic brush 14, a regulating member such as a blade or roller is installed between the sleeve 12 and the developing area and the position where the sleeve 12 contacts the supply roller 24. It may be placed close to.

On the other hand, a predetermined bias voltage for supplying toner is applied to the toner supply roller 24 by a power supply circuit 28, and the toner 25 is transferred to the magnetic brush 14 well by this bias voltage for supplying 1 hener. It turns out.

The bias voltage for toner supply has the same polarity as the charged toner, and is set to approximately 0 to 600 V. By setting the bias voltage for toner supply to a polarity opposite to that of the charged toner, the 1-toner can be reliably held on the toner supply roller 24. In this case, it is preferable that the bias voltage is lower than the developing bias. here,
When the voltages applied to the sleeve 12, toner collection roller 18, and toner supply roller 24 are VB, VR, and VD, which have the opposite polarity to the toner, IVRI>IVB.
It is preferable to set the relationship I>IVBI from the viewpoint of the toner balance of the sleeve 12J-. Furthermore, in order to keep the toner concentration on the sleeve 12 more uniform, it is preferable to set the relationship IVBI-1vol>1vnl-1vl.

The toner collecting roller 18 and the toner supplying roller 24 may be made of any material that can provide an electrical bias effect between them and the cylindrical sleeve 12, and may be made of metal, conductive rubber, or the like. In addition, these rollers 18, 24
are arranged so as to be in contact with the magnetic brush 14 at a ratio of 50% to 100% of the height thereof. However, if the absolute value of the air gap is 1 mm or less, 100%
It can also be installed beyond. However, in this case, it is essential to use electrical bias means. Further, the outer diameter of each roller 18° 24 can be arbitrarily selected, but due to the demand for miniaturization, for example, it is 80% or less of the outer diameter of the cylindrical sleeve 12, or an absolute value of 5 to 60 mm (preferably 8 to 60 mm). 40 mm).

Incidentally, the amount of toner supplied to the magnetic brush 14 changes depending on the relative speed between the magnetic brush 14 and the supply roller 24.

That is, in the above embodiment, the outer diameter of the cylindrical sleeve 12 is 20 ylnl and is rotated at a rotation speed of 344 rpm, while the outer diameter of the toner supply roller 24 is 16 m.
m, and when this is rotated at a rotational speed of 43 rpm, the surface speeds (360n+m/5ee) of both of them become equal to each other. Under this condition, a positively charged toner of about 0.3 mg/cm2 is deposited on the toner supply roller 24 in a uniform thin layer, and the power supply circuit 28 applies a +20
When 0V was applied, almost all the toner was transferred to the magnetic brush 14. On the other hand, when the photoreceptor 11 holding a latent image of -aoov was moved at a speed of 120 mI+I/sac and the latent image was developed under a developing bias of -200V by the power supply circuit 15, toner adhered to the photoreceptor IL. The amount was 0.4 mg/cm''. The toner recovery bias at this time was -600.

Next, the rotation speed of only the toner supply roller 24 is set to 859 rpm.
As a result of conducting the same experiment as above, the photoreceptor 1
The toner adhesion amount on No. 1 was 0.8 mg/cm''.

As is clear from this, not all of the toner transferred to the magnetic brush 14 contributes to development;
It can be seen that the amount of toner adhering to the photoreceptor 11, that is, the sharpness of the image, differs depending on the speed at which the toner is transferred to the photoreceptor 11. One possible reason for this is that the toner transferred from the toner supply roller 24 to the magnetic brush 14 diffuses into the magnetic brush 14.

Therefore, in order to compensate for the decrease in the utilization efficiency of the supplied toner due to the diffusion of the toner, it is sufficient to increase the rotation speed of the toner supply roller 24 so that the toner supply speed is faster than the conveyance speed of the magnetic brush 14. It is possible to obtain a high image density. As a means for increasing the toner supply speed, as described above, the number of revolutions of the toner supply roller 24 may be increased by changing the specifications of the well-known rotation transmission mechanism (not shown);
The outer diameter of the toner supply roller 24 may be increased.

In such a hybrid type developing device, first, the toner 25 in the toner tank 23 is held by the toner supply roller 24 by rotation of the toner supply roller 24 . This retained toner is further removed by the toner regulating blade 2.
6, the layer is triboelectrically charged while being uniformly thinned. Then, toner is uniformly supplied and transferred to the magnetic brush 14 in a thin layer at a speed that is at least faster than the transport speed of the magnetic brush 14 and under a predetermined toner supply bias voltage. Next, the magnetic brush 14 supplied with toner is transferred to the photoreceptor drum 11 side, and the electrostatic latent image 16 formed on the photoreceptor drum 11 is developed. After this development is completed, the magnetic brush 14 has a toner density difference (
However, the residual toner on the magnetic brush 14 is transferred to and collected by the toner collecting roller 18 by the action of the toner collecting bias voltage. As a result, the difference in toner density between the magnetic brushes 14 is eliminated and the toner density becomes uniform. That is, after collecting the toner, the magnetic brush 14 leaves the toner collecting roller 18 in a state where only the carrier is present or in a state where the toner concentration is uniformly distributed, and moves toward the toner supply side again.

Incidentally, if an agitator 35 is provided in the toner tank 33 as in the above-mentioned developing device shown in FIG.

Toner blocking that occurs when a large amount of toner is stored can be prevented, and image stability can be improved. At this time, the mixing efficiency of the collected toner and the new toner can be increased by transferring the 1 hener peeled off from the toner collection roller 38 as close as possible to the agitator 35 by the 1 to 1 peeling member 31.

The developing device shown in FIG. 3 is an example in which two toner collection rollers 48 are installed on the upstream side of the magnetic brush 14, and two toner supply rollers 44 are installed on the downstream side. If a plurality of toner collection rollers and a plurality of toner supply rollers are provided as in this developing device, toner can be supplied and collected with sufficient margin, and the rotational speed of the magnetic brush 14 can be increased to perform high-speed copying and high-speed Even when printing is performed, stable developing conditions without a decrease in toner density or image deterioration can be maintained.

In each of the above-described embodiments, a cylindrical sleeve is used, but a belt-shaped sleeve may also be used.

(Effects) As described above, the hybrid type developing device according to the present invention supplies toner charged in the toner supply area faster than the conveyance speed of the magnetic brush and transfers it to the magnetic brush side. Since the magnetic brush is provided with the means, toner can be supplied properly using a magnetic brush with a simple structure and without excess or deficiency. Therefore, there is no need to stir the two-component developer as in the past, and it is possible to omit the various stirring mechanisms and stirring spaces of the developing device that uses the two-component developer, making it possible to significantly downsize the entire device. , and the handling can be facilitated in the same manner as the one-component development method. Further, by omitting the stirring mechanism, early fatigue of the carrier can be prevented, and the stability and flexibility of images obtained by the two-component development method can be maintained. Furthermore, even when toner consumption is high in color copying, printing, etc., a large amount of toner can be supplied without stirring, and stable images with little density change and image deterioration can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a developing device showing one embodiment of the present invention;
2 and 3 are longitudinal sectional views of a developing device showing other embodiments of the present invention, and FIG. 4 is a longitudinal sectional view of a conventional developing device. 12... Cylindrical sleeve, 14... Magnetic brush, 1
5゜19.27...Power supply circuit, 18,38.48...
- Toner collection roller, 24, 34. 44... Toner supply roller, 25... Toner. Procedure fFF,) Lil Giant Book April 15, 1985 1, Display of the case Patent Application No. 249299 of 1988 2, Name of the invention Electrostatic latent image developing device 3, Person making the amendment Relationship to the case Patent Applicant name (674) Ricoh Co., Ltd. 4, Agent
Person 5, "Detailed Description of the Invention" column of the specification subject to amendment (1) From "formed" in line 9 of page 2 of the specification to "became" in line 10 of the same page is corrected to "forms a layered magnetic brush." (2) In the same page, page 3, line 15, ``Motainai'' is corrected to ``Assumed''. (3) "Vise" in line 16 of page 6 of the same document is "bias"
Correct. (4) "Downward" in line 20 of page 6 is corrected to "upward." (5) Correct "toner collection" in line 19 of page 11 to "toner collection". (6) "Totoshita" in line 10 of page 13 is corrected to "tojita". (7) Correct "noudo" in line 20 of page 13 to "density".

Claims (1)

[Claims] An electrostatic latent image is developed to visualize an electrostatic latent image formed on a latent image carrier by toner adhered to a magnetic brush that is sequentially conveyed between a toner supply area, a development area, and a toner collection area. In the image developing device, a toner supply means for transporting the charged toner in the toner supply area to the magnetic brush side at a speed faster than the conveyance speed of the magnetic brush;
An electrostatic latent image developing device comprising: toner collection means for collecting toner remaining on the magnetic brush from the magnetic brush in the toner collection area.