JPH06295123A - Method for adjusting grain size of toner in developing device - Google Patents

Abstract

PURPOSE:To provide the grain size adjusting method of toner in a developing device by which the toner whose grain size is small is prevented from being stored in the developing device because the toner whose grain size is large is selectively consumed at a developing time. CONSTITUTION:Every time that the fixed quantity of developing is executed, a grain size adjustment process including a first process where the toner is transferred to a developing roll 3 from a magnetic roll 4 under a bias voltage and a toner layer is formed on the roll 3, a second process where the toner whose grain size is large and which is easily transferred is returned to the roll 4 from the toner layer on the roll 3 under a bias voltage whose direction is reverse to the first process, and a third process where the toner whose grain size is small and which is left on the roll 3 is transferred on an electrostatic latent image holding body 1 under a bias voltage between the roll 3 and the holding body 1 is executed in addition to a developing process. Thus, the toner whose grain size is small is eliminated by a cleaning device and the grain size distribution of the toner in the developing device can be kept constant.

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 forming a thin layer of non-magnetic toner on a developing roll, and transferring and adhering the toner to the electrostatic latent image on the electrostatic latent image carrier to visualize it. , A toner particle size adjusting method for adjusting a particle size distribution of a non-magnetic toner in a two-component developer.

[0002]

2. Description of the Related Art Conventionally, various types of developing devices for developing an electrostatic latent image on a photoconductor to form a visible image have been proposed according to the type of developer used. Of these, a developing device using a non-magnetic one-component developer in which a pigment or the like is dispersed in a thermoplastic resin in the form of powder and a charge control agent is externally added is used as a toner by forming a toner layer on a developer carrier. It is known to fly an electrostatic latent image to visualize it. In such a developing device, since the photosensitive member and the developer carrying member are not in contact with each other, a visible image is less disturbed and a high quality image can be obtained. It has an advantage that images can be formed in a superimposed manner. However, in such a one-component developing device, the charge amount of the toner is unstable and there is a problem in the long-term maintainability of the image quality, and the toner transport amount of the developer carrier fluctuates due to a slight change in the toner characteristics. There is a problem.

On the other hand, in a two-component developing device using a two-component developer containing a non-magnetic toner and a magnetic carrier, the charge amount of the toner is stabilized by frictional charging with the magnetic carrier, and the above problems are solved. . However, forming a magnetic brush in which magnetic carriers are connected in a spike shape on the developer carrier,
Since development is performed by bringing the magnetic brush into contact with the electrostatic latent image in the development area, there is a problem that the visible image is disturbed and the image sharpness is lowered.

As described above, the one-component developing device and the two-component developing device have their respective characteristics, and the advantages of the developing device using the one-component developer and the advantages of the developing device using the two-component developer are well understood. In combination, developing devices have been proposed which have the desired characteristics of both. FIG. 4 shows JP-A-3-113.
FIG. 3 is a schematic configuration diagram showing a developing device described in Japanese Patent No. 474. This developing device 120 is a developing roll 101 that conveys a non-magnetic toner on the surface thereof, which is opposed to the electrostatic latent image holding member 105, in a housing 115 that houses a two-component developer.
And a magnetic roll 102 which is arranged close to the developing roll 101 and conveys the two-component developer while adsorbing the two-component developer on the surface.
The developer is stirred and conveyed, and the magnetic roll 10
2 has a developer stirring member 113 for supplying the developer.

The developing roll 101 has a cylindrical shape and is supported so as to be rotatable about its axis.
By rotating the developing roll 101, a thin layer of toner formed on the surface is conveyed to a developing area facing the electrostatic latent image holding member 105. The electrostatic latent image holding member 105 is a belt-shaped photosensitive member capable of forming an electrostatic latent image on the surface by the irradiation of image light after uniform charging, and the electrostatic latent image holding member. In the gap between the body 105 and the developing roll 101, a control electrode 111 formed by stretching a plurality of wires in the axial direction of the developing roll 101 substantially in parallel is arranged near the developing roll 101 at a distance. The magnetic roll 102 has a plurality of magnetic poles arranged at fixed positions inside thereof, and can form a magnetic brush on the surface of which magnetic carriers accompanied by non-magnetic toner are connected in a spike shape.

In such a developing device, the magnetic brush of the developer formed on the magnetic roll 102 is conveyed by the rotation of the surface of the magnetic roll and rubs against the surface of the developing roll 101. An electrostatic field is formed between the magnetic roll 102 and the developing roll 101 by the DC power supplies 106 and 107, and the toner attached to the magnetic carrier is transferred to the surface of the developing roll 101 to form a thin layer of toner. To do. On the other hand, the magnetic carrier remains magnetically adsorbed on the developer carrier. The thin layer of toner formed on the developing roll 101 is transported to the developing area, and the toner is clouded by the alternating electric field formed between the developing roll 101 and the control electrode 111 and adheres to the electrostatic latent image to develop. Is performed.

Such a developing device can be mainly used in a multicolor image forming apparatus using a plurality of developing devices containing toners of different colors. In particular, an image forming method in which the electrostatic latent image carrier is rotated once to repeat the charging, exposing, and developing processes a plurality of times to form toner images of a plurality of colors on the electrostatic latent image carrier. In the apparatus, there is an advantage that the toner layer and the electrostatic latent image carrier can be developed without contacting each other without disturbing the toner image formed in the previous step.

[0008]

However, in the developing device as described above, when the toner is transferred to the surface of the electrostatic latent image holding member under the bias voltage between the developing roll and the electrostatic latent image holding member. In addition, in the toner layer formed on the developing roll, a phenomenon that the toner having a large particle size is selectively consumed occurs. Therefore, although good development could be achieved in the initial stage, the toner of a small particle size was accumulated in the developing device due to long-term use, and the initial performance could not be maintained. Therefore, there is a problem that the image quality is deteriorated. The present invention has been made in view of the above problems, and an object thereof is to prevent toner having a small particle diameter from accumulating in a developing device and obtain a good image without deterioration in image quality. It is to provide a method for adjusting the particle size of toner in a developing device.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is arranged to face an electrostatic latent image holding member on which an electrostatic latent image is formed due to a difference in charging potential, A developing roll for adhering and conveying non-magnetic toner, and a two-component developer provided opposite to the developing roll, which magnetically adsorbs and conveys a non-magnetic toner. A method for adjusting the particle size of toner in a developing device having a magnetic roll for supplying a non-magnetic toner from the magnetic roll to the developing roll under a bias voltage between the magnetic roll and the developing roll. And a first step of forming a toner layer on the developing roll,
A second step of returning a large particle size toner that is easily transferred from the toner layer on the developing roll to the magnetic roll under a bias voltage in the reverse direction of the first step, the developing roll and the electrostatic latent image. And a third step of transferring the toner having a small particle size remaining on the developing roll to the electrostatic latent image carrier under a bias voltage between the image carrier and the electrostatic latent image carrier.

[0010]

In the method of adjusting the toner particle size in the developing device having the above-described structure, the first step of transferring the non-magnetic toner from the magnetic roll to the developing roll under a bias voltage to form a toner layer on the developing roll, The first step includes a second step of returning to the magnetic roll a toner having a large particle size that is easily transferred from the toner layer on the developing roll under a bias voltage in the reverse direction, so that the toner layer on the developing roll is included. The toner having a large particle size is removed from the toner to form a toner layer composed of only a toner having a relatively small particle size on the surface of the developing roll.

Furthermore, the method further includes a third step of transferring the small particle size toner remaining on the developing roll to the electrostatic latent image holding member under a bias voltage between the developing roll and the electrostatic latent image holding member. The toner having a small particle size is removed from the electrostatic latent image carrier through the cleaning device. Therefore, when the large-sized toner is selectively consumed by the development and the proportion of the small-sized toner increases, the small-sized toner is removed by the above process, and the small-sized toner is stored in the developing device. It is possible to prevent the accumulation. Therefore, the particle size distribution of the toner in the developing device can be maintained substantially uniform, and the initial developing performance can be maintained and the deterioration of image quality can be prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of a developing device capable of implementing the toner particle size adjusting method in the developing device according to the present invention, and FIG. 2 is an enlarged view showing a developing roll and a magnetic roll of this developing device. Is. This developing device is provided so as to face the electrostatic latent image holder 1 capable of holding an electrostatic latent image due to a difference in charging potential, and is a two-component developer including a non-magnetic toner 20 and a magnetic carrier 21. A magnetic roll 4 that magnetically adsorbs a two-component developer to form a magnetic brush on the surface in a housing 14 that accommodates the developer, and a developer regulating member 1 that regulates the amount of the developer adsorbed on the magnetic roll 4.
5 and a cylindrical developing roll 3 which is disposed so as to be close to the magnetic roll 4 and the electrostatic latent image carrier 1 at different positions, and which rotates by adhering the non-magnetic toner 20 thereto. A control electrode 5 for controlling the flight of the non-magnetic toner 20 is provided at a position where the developing roller 3 and the electrostatic latent image carrier 1 face each other. Further, a first developer stirring chamber 6 is provided in a position adjacent to the magnetic roll 4 in the housing 14, and a second developer stirring chamber partitioned by the first developer stirring chamber 6 and the partition wall 8 is provided. A room 7 is provided.

The first developer stirring chamber 6 and the second developer stirring chamber 7 communicate with each other at both ends in the axial direction of the magnetic roll 4, and the stirring of the developer and the axial direction of the developer are communicated with each other. A first screw auger 9 and a second screw auger 10 that carry the developer are provided. These two screw augers 9 and 10 are set in the rotation directions so as to convey the developer in mutually opposite directions, and the developer moves between the first developer stirring chamber 6 and the second developer stirring chamber 7. It circulates.

The magnetic roll 4 has a rotatable cylindrical sleeve arranged on the outer periphery of a magnet supported so that its position is immovable. As shown in FIG. 2, the surface of the sleeve is nonmagnetic. Magnetic carrier 21 with toner 20
Is magnetically attracted to form a magnetic brush of a two-component developer, and the sleeve is rotated to convey the developer. A DC superimposed AC voltage (DC component voltage is -300 V) can be applied to the magnetic roll 4 from the magnetic roll bias power supply 11. The developing roll 3 is a cylinder of aluminum whose surface is alumite treated or a cylinder of phenolic resin.
Alternatively, an aluminum cylinder having a resin layer formed on its surface is used, and a DC voltage of -200 V can be applied from the DC power supply 12.

The developing roll 3 and the electrostatic latent image carrier 1
Are arranged so as to face each other with a gap of 200 to 500 μm held therebetween, and the rotation direction is such that the movement of both surfaces is opposite at the position where the developing roll 3 and the electrostatic latent image holding member 1 face each other. Is set. Further, even at the position where the developing roll 3 and the magnetic roll 4 face each other, the rotation direction is set so that the facing surfaces of both of them move in opposite directions. The rotation directions of the developing roller 3 and the electrostatic latent image carrier 1 are set so that the surfaces of the developing roller 3 and the magnetic roller 4 are in the same direction at the positions facing each other. It may be changed depending on the developer used, the position where the developer regulating member 15 is installed, and the like.

The control electrode 5 is composed of four tungsten wires having a diameter of 30 to 200 μm stretched substantially parallel to each other in the axial direction of the developing roll, and is arranged near the developing roll 3 at a distance. The control electrode 5 has a developing bias power source 13 and a direct current electrode 12 for direct current superimposed alternating voltage (alternating current peak-to-peak voltage is 800 V, frequency 5 k
Hz) can be applied, and between the control electrode 5 and the developing roll 3, between the control electrode 5 and the electrostatic latent image carrier 1, and between the developing roll 3 and the electrostatic latent image carrier 1. Creates an electric field,
These opposing portions are development areas.

In the developing device, the non-magnetic toner 20 and the magnetic carrier 21 are conveyed and stirred in the first developer stirring chamber 6 and the second developer stirring chamber 7. As a result, the distribution of the non-magnetic toner in the developer is maintained uniform, and a predetermined negative charge is imparted to the non-magnetic toner by frictional charging between the non-magnetic toner and the magnetic carrier. The agitated developer is supplied to the magnetic roll 4 by the first screw auger 9. The magnetic roll 4 magnetically adsorbs the developer to form a magnetic brush of the developer composed of the non-magnetic toner 20 and the magnetic carrier 21, and conveys the magnetic brush to a position facing the developing roll 3 by rotation.

The developing roll 3 has a DC power source 12 of -2.
A DC voltage of 00 V is applied, and a DC superimposed AC voltage of a DC component of −300 V is applied to the magnetic roll 4 from the magnetic roll bias power supply 11. Due to these applied voltages, an electric field is formed between the developing roll 3 and the magnetic roll 4, the charged toner is transferred to the developing roll 3, and a toner layer is formed on the surface of the developing roll 3. On the other hand, the magnetic carrier 21 remains magnetically attracted to the magnetic roll 4 without being transferred.

The toner layer formed on the developing roll 3 is
The developing roller 3 is rotated to be conveyed to a developing area, and is clouded by an alternating electric field formed between the control electrode 5 and the developing roller 3. The clouded toner flies in the electrostatic field between the electrostatic latent image carrier 1 and the developing roller 3,
The electrostatic latent image carrier 1 is attached to the surface of the electrostatic latent image carrier 1 and developed.
At this time, the toner having a large particle size is more likely to be peeled off from the developing roll and is more likely to be transferred to the electrostatic latent image holding member than that having a small particle size. Therefore, the amount of the toner remaining on the developing roll that does not contribute to the development and is returned to the portion facing the magnetic roll again has a small particle size.

Next, a method of adjusting the particle size of the toner in the developing device in the developing device will be described. FIG. 3 is a timing chart showing a method of adjusting the toner particle size in the developing device according to the embodiment of the present invention. This toner particle size adjusting method is performed separately from the developing step every time a certain period of use of the developing device is used or every time a certain number of images are developed, and the toner is stored in the developing device by the steps described below. Only the toner having a small particle size is removed from the developer.

In the step for adjusting the particle size, the two-component developer is supplied to the magnetic roll 4 as in the developing step, and only the toner is transferred from the magnetic roll 4 to the developing roll 3. At this time, the magnetic roll 4 has a DC component potential of −30.
At 0 V, the potential of the developing roll 3 is maintained at -200 V, and toner is transferred and a toner layer is formed on the developing roll while the developing roll 3 rotates 5 times.

After that, the voltage applied to the magnetic roll 4 is turned off while the rotations of the developing roll 3 and the magnetic roll 4 are being driven, and the potential becomes approximately 0V. Then developing roll 3
In the electric field formed between the magnetic roll 4 and the magnetic roll 4, a force of attracting the negatively charged toner on the roll 3 to the magnetic roll 4 side works, and the toner on the developing roll 3 is gradually returned to the magnetic roll 4. The toner layer gradually becomes thinner as the developing roll 3 rotates. At this time, the larger the particle size of the toner on the developing roller 3 is, the more easily it is affected by the electric field.

After the applied voltage to the magnetic roll 4 is turned off,
Some time (in this embodiment, the developing roll is rotated twice)
After that, the DC superimposed voltage is applied to the control electrode 4. At this time, the electrostatic latent image carrier 1 is destaticized and the surface potential is about 50V. The toner layer on the developing roller 3 is pulled back from the toner having a large particle diameter to the magnetic roller 4 side, so that the toner having a small particle diameter remains, and this toner is generated between the control electrode 4 and the developing roller 3 in the developing area. It is peeled off from the developing roll 3 due to the electric field between them and becomes a cloud. The clouded toner is transferred onto the electrostatic latent image carrier by the electric field between the developing roll 3 and the electrostatic latent image carrier 1. In this embodiment, this process is continued while the developing roll rotates three times. The toner transferred onto the electrostatic latent image carrier 1 is removed by a cleaning device. By the operation of such a developing device,
The small particle size toner in the toner is selectively removed.

As described above, the toner having a small particle size is removed by carrying out the above-mentioned step for adjusting the particle size every time the developing step is carried out for a certain period. Therefore, a large amount of toner with a large particle size is consumed in the developing process, but only the toner with a small particle size is not accumulated in the developing device, and the particle size distribution of the toner is adjusted. Therefore, it is possible to obtain a good image without deterioration in image quality even after long-term use.

[0025]

As described above, according to the method of adjusting the particle size of the toner in the developing device of the present invention, the toner layer consisting of only the toner having a small particle size in the developer in the developing device is formed on the surface of the developing roll. Since the toner is transferred to and removed from the electrostatic latent image holding member, the particle size can be adjusted so that the toner having a small particle size is not accumulated in the developing device.
As a result, it is possible to maintain the initial developing performance and prevent the image quality from deteriorating, and it is possible to always perform development with good image quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a developing device capable of implementing a toner particle size adjusting method in a developing device according to the present invention.

FIG. 2 is an enlarged view showing a developing roll and a magnetic roll of the developing device shown in FIG.

FIG. 3 is a timing chart showing a method of adjusting the particle size of toner in the developing device, which is an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional developing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrostatic latent image holder 2 Developing device 3 Developing roll 4 Magnetic roll 5 Control electrode 6 First developer stirring chamber 7 Second developer stirring chamber 8 Partition 9 First screw auger 10 Second screw auger 11 Bias power supply for magnetic roll 12 DC power supply 13 AC power supply 14 Housing 15 Developer regulating member 20 Non-magnetic toner 21 Magnetic carrier

Claims (1)

[Claims] 1. A developing roll, which is arranged so as to face an electrostatic latent image holding member on which an electrostatic latent image is formed due to a difference in charging potential, and which conveys non-magnetic toner by adhering it to a surface thereof, and the developing roll. Adjusting the particle size of toner in a developing device having a magnetic roll that is provided facing each other and that magnetically attracts and conveys a two-component developer containing a magnetic carrier and a non-magnetic toner to supply the non-magnetic toner to a developing roll. A first step of transferring a non-magnetic toner from the magnetic roll to the developing roll under a bias voltage between the magnetic roll and the developing roll to form a toner layer on the developing roll; A second step of returning a large particle size toner, which is easily transferred, from the toner layer on the developing roller to the magnetic roller under a bias voltage in the reverse direction of the first step; the developing roller and the electrostatic latent image. Between holding body Third step and the particle size adjustment method of the developing device toner which comprises a to transfer the toner having a small particle size remaining on the developing roll under a bias voltage to the electrostatic latent image holding member.