JPH0833688B2 - Development device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in a recording device such as an electrophotographic method or an electrostatic recording method.

2. Description of the Related Art In the electrophotographic method and electrostatic recording method, an electrostatic latent image is formed on a photoconductor or a recording body, a developer is brought close to the electrostatic latent image, and toner in the developer is attached to the electrostatic latent image. Visualize the image, transfer it to paper, fix it, and record.

The developer and the developing method which have been put into practical use in this recording method are a one-component developing method using a developer consisting only of magnetic toner, iron powder, resin particles in which a magnetic material is dispersed, and resin-coated ferrite sintering. There is a two-component developing method using a developer in which a magnetic carrier such as body particles and a toner composed of resin particles in which a pigment is dispersed are mixed. The one-component developing method has an advantage that the toner density control is unnecessary and the structure of the developing device can be simplified. However, it is difficult to perform the developing operation such as the stabilization of the charge of the toner is complicated and the image quality is disadvantageous. As a color image recording toner, a magnetic toner in which a magnetic material is dispersed cannot be used in terms of color tone and saturation, and a non-magnetic toner is used. There is a problem that it cannot be applied.

On the other hand, the two-component developing method has been widely put into practical use because it has advantages such as easy developing operation, relatively good image quality formed, and less restriction on the toner material used. However, the two-component developing method has a large influence on the image quality due to the toner density, and when the toner density is low, the image density is lowered, and when the toner density is high, the fogging to the non-image area is likely to occur. The toner scatters from the agent magnetic brush and causes problems such as contamination of the inside of the apparatus. For this reason,
Toner density control is required in the two-component developing method, and this toner density control is performed by a device that detects a change in image density or developer inductance and automatically replenishes toner based on this detection signal. However, there is a drawback that the device becomes expensive.

Therefore, as a method for easily adjusting the toner concentration in the two-component developing method, the magnetic brush of the two-component developer is rubbed against the mesh and the screen, and the electrostatic force to the magnetic brush side or the sending side is passed through the openings of the mesh screen. Method for adjusting the toner concentration in a two-component developer by moving the conductive toner (Japanese Patent Laid-Open No. 59-55463) or extending in the axial direction of the developing sleeve within the area of the magnetic field of the magnetic roller. Then, the empty space provided on the upstream side of the developing area and the toner supply slit for conducting the toner supply tank, and the toner contained in the toner supply tank are passed through the toner supply slit to enter the empty space. A method using a developing device equipped with a toner supplying means for supplying (Japanese Patent Laid-Open No. 61-53677) has been proposed.

However, as a result of various studies by the present inventors, the former two types of methods for easily adjusting the toner concentration maintain a relatively stable toner concentration during development with a small toner consumption amount. When developing with a high blackening rate and consuming a large amount of toner, there was a problem that the chance of rubbing between the magnetic brush and the electroscopic toner was insufficient and the toner supply was insufficient, resulting in a low toner density. . Also,
The amount of toner in the toner tank and the fluidity of the toner material have a great influence on the toner concentration, and there are many points in which control is difficult due to the configuration of the developing device. In the latter method, when non-magnetic toner is used, the toner is non-magnetic, so there is no toner supply force due to the rotation of the toner due to the rotation of the magnetic roller, so pressure is applied to other supply slits. However, it is difficult to uniformly apply pressure to the entire supply slit, and high toner concentration is obtained in a portion where the pressure is strong and low toner concentration is obtained in a portion where the pressure is weak. There is a problem in that a stable image cannot be obtained due to a large variation in density.

In order to solve the above problems, the inventors of the present invention regulate a developing sleeve having a magnet roll inside for supporting and conveying a developer composed of a magnetic carrier and toner, and a height of the developer. And a mesh member having a plurality of openings having an opening diameter larger than the particle diameters of the magnetic carrier particles and the toner particles, which are provided so as to be embedded in the developer, in a region where the magnetic field of the magnet roll extends. A developing device equipped with is proposed.

This developing device includes a developing sleeve,
The developer composed of the magnetic carrier and the toner in the portion enclosed by the blade and the mesh member is subjected to a constant pressure and stirring force by the magnetic force of the magnet roll and the conveying force of the developing sleeve, and is sufficiently rubbed and stirred to be sufficiently charged. To form a developer having an appropriate toner concentration. At this time, if the amount of the magnetic carrier is large, the pressure becomes large, and the surplus magnetic carrier overcomes the attraction force by the magnetic force of the magnet roll and passes through the opening of the mesh member and moves to the toner chamber side. The magnetic carrier that has moved to the toner chamber side is mixed and stirred with the toner, and a developer having a high toner concentration is formed in the vicinity of the mesh member.

When the toner on the developing sleeve is consumed by the development of the electrostatic latent image, the pressure applied to the developer in the portion enclosed by the developing sleeve, the blade, and the mesh member decreases according to the amount of toner consumption, and the mesh member The magnetic carrier in the high-toner-concentration developer in the vicinity is supplied to the developing sleeve side through the opening of the mesh member by the attraction force by the magnetic force of the magnet roll inside the developing sleeve while the toner is charged and absorbed. In this way, the net-like member is provided at a position where it is embedded in the developer within the magnetic field and the region of the magnet roll, and the pressure applied to the developer on the developing sleeve is kept constant, so that the movement of the magnetic carrier can be prevented. The toner is supplied according to the amount of toner consumed, and the proper toner density is maintained. Even if the toner is a non-magnetic toner, the toner is supplied with the magnetic carrier in a state of being charged and adsorbed to the magnetic carrier together with the magnetic carrier, so that a special supplying device is not required, and the fluidity of the toner is high. The influence of material characteristics such as

Problems to be Solved by the Invention However, as a result of further studies on the developing device proposed by the present inventors, the following problems occurred. The developing agent on the developing sleeve is regulated by the blade so that the developer is continuously supplied onto the developing sleeve. However, since the developer on the developing sleeve forms a layer, it is difficult to smoothly replace the developer contained in the developing sleeve, the blade and the mesh member with the developer. Therefore, when an electrostatic latent image having a distribution of the blackening rate and a toner amount required for development that greatly varies in the sleeve axial direction is continuously developed, the blackening rate is high and a large amount of toner consumption is required. In the portion, the toner concentration of the developer on the developing sleeve gradually decreases, and the developer on the developing sleeve is changed in the axial direction of the developing sleeve so as to correspond to the distribution of the blackening rate of the electrostatic latent image. Distribution will occur. Therefore, it is difficult to obtain a stable image when continuously developing an electrostatic latent image having a distribution of blackening rate.

The present invention has been made in order to solve the above problems, when the electrostatic latent image having a distribution in the blackening ratio is continuously developed, the blackening ratio of the electrostatic latent image has a small effect, Another object of the present invention is to provide a developing device which has little influence of material properties such as magnetism of the toner material and fluidity and which can adjust the toner density without requiring a special device.

Means for Solving the Problems In order to solve the above problems, the developing device of the present invention includes an independently rotatable magnet roll for supporting and conveying a developer including a magnetic carrier and toner. Particles of magnetic carrier particles and toner particles provided so as to be embedded in the developing sleeve, a blade for restricting the rising of the developer, and a region of the magnetic roll of the magnetic roll. A mesh member having a plurality of openings having an opening diameter larger than the diameter, and the magnet roll and the developing sleeve are both rotating during an operation not required for recording, the same mode as during operation required for recording And a mode in which the magnet roll is rotated and the developing sleeve is stopped.

Effect of the Invention With the above-described structure, the present invention causes the developing sleeve and the magnet roll to rotate together during an operation required for recording, and the time during which the developing sleeve and the magnet roll rotate together during an operation not required for recording, and the developing sleeve stops. Then, it takes time for the magnet roll to rotate. When the developing sleeve stops and the magnet roll rotates, the carrying force of the developing sleeve disappears, so that the developer easily rolls due to the rotation of the magnet roll. Therefore, the spike of the developer formed on the developing sleeve is higher than that when the developing sleeve and the magnet roll are both rotating, and a large amount of the developer flows out from the blade. As a result, the pressure applied to the developer in the portion enclosed by the developing sleeve, the blade, and the mesh member is lowered, and the developing sleeve is stopped, so that the rolling of the developer is easily performed by the rotation of the magnet roll. . As a result, the developer in which the layer of the magnetic brush is formed on the developing sleeve is easily re-mixed with the developer mixed and stirred in the portion covered by the developing sleeve, the blade and the mesh member. Homogenize. After passing through such a state, when the developing sleeve and the magnet roll are rotated together, the spike of the developer on the developing sleeve, the pressure exerted by the developer on the portion covered by the developing sleeve, the blade, and the mesh member is the original pressure. Returned to, on the developing sleeve, compared to the case where the above state is not passed,
A more uniformized developer is supplied. Therefore, even when the electrostatic latent image having the distribution of the blackening rate is continuously developed, the influence of the distribution of the blackening rate of the electrostatic latent image can be reduced.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are cross-sectional views of the developing device in the embodiment of the present invention, and FIG. 1 shows a mode in which the developing sleeve and the magnet roll are both rotating. FIG. 2 shows a mode in which the developing sleeve is stopped and the magnet roll is rotating. In FIGS. 1 and 2, 1 is a developing device housing, 2 is a developing sleeve,
3 is a magnet roll, 4 is a blade, 5 is a mesh member having a plurality of openings, 6 is a toner chamber, 7 is a protective cover, 8 is a toner stirring blade, 9 is a developer, and 9 is a magnetic carrier. It consists of 91 and toner 92. A developer chamber 10 is formed by the developing sleeve 2, the blade 4, and the mesh member 5. Reference numeral 11 denotes a photoconductor drum on which an electrostatic latent image is formed, which is formed by forming a photoconductive layer 13 on the surface of a conductive holding body 12.

Details of the configuration and operation of the developing device configured as described above will be described below.

The developing sleeve 2 is made of a cylindrical conductive non-magnetic material, and has a magnet roll 3 inside of which the N and S poles are alternately magnetized. The developing sleeve 2 and the magnet roll 3 are
It is possible to rotate each independently. When developing the electrostatic latent image formed on the photoconductor drum 11, as shown in FIG. 1, the developing sleeve 2 rotates in the direction of arrow a and the magnet roll 3 rotates in the direction of arrow b to develop the latent image. The agent 9 is conveyed in the direction of arrow a to form a layer of a magnetic brush, and the electrostatic latent image is rubbed to develop. The blade 4 is the developing sleeve 2
And is installed upstream of the developing area in the developer transport direction. The blade 4 regulates the height of the brush of the developer magnetic brush, and the distance between the blade 4 and the developing sleeve 2 is precisely set. Either a magnetic material or a non-magnetic material can be used as the blade 4. The mesh member 5 extends parallel to the axial direction of the developing sleeve 2, and is provided so as to be embedded in the developer 9 in the region where the magnetic field of the magnet roll 3 reaches. As the mesh member 5, non-magnetic metal materials such as stainless steel, copper and brass, magnetic metal materials such as steel and nickel, silk,
It may be a woven fiber or wire made of an organic polymer material such as nylon or polyester, or may be formed, punched or etched, as long as it has a plurality of openings. The opening diameter of the opening of the mesh member 5 is determined by the developer, that is, the magnetic carrier,
Sufficient dimensions are required for the toner and the magnetic carrier charged with the toner to pass therethrough. A commonly used two-component developer has a particle size of 3 to 20 μm and a particle size of 3 to 20 μm.
It consists of a magnetic carrier of 20 μm to 150 μm. Therefore, from the function of holding the pressure of the developer on the developing sleeve with an opening diameter of 150 μm or more, that is, 100 mesh or less.
It is desirable that the mesh size is 9.2 mesh or more (opening diameter 2 mm or less), and a mesh member having a porosity of 30% to 70% can be used. The toner stirring blade 8 has a function of rotating and stirring the toner 92 existing in the toner chamber 6 to increase the fluidity of the toner and send the toner to the vicinity of the developer 9. The protective cover 7 has the functions of preventing the toner from scattering from the developer magnetic brush on the developing sleeve and preventing foreign matter from entering the developer. The developing device housing 1 is made of an organic polymer material, a metal material, or the like, and holds and fixes the developing sleeve 2, the magnet roll 3, the blade 4, the mesh member 5, the protective cover 7 and the toner stirring blade 8 as described above. The chamber 6 is configured. Developer 9
Is a mixture of the magnetic carrier 91 and the toner 92, the amount of which is required to be sufficient for the mesh member to be embedded in the developer and necessary for forming the layer of the magnetic brush on the developing sleeve 2. And a sufficient amount to fill the volume of the developer chamber 10, which is included in the developing sleeve 2, the blade 4, the mesh member 5 and a part of the developing device housing 1, is larger than the total amount.

By operating the developing device in a mode in which the developing sleeve 2 and the magnet roll 3 both rotate as shown in FIG. 1, it is possible to keep the toner concentration of the developer within an appropriate range. It is not always enough. Therefore, during the operation of developing the electrostatic latent image required for recording, the developing device is operated in the mode in which the developing sleeve 2 and the magnet roll 3 shown in FIG. The developing device is operated, the rotation of the developing sleeve 2 is controlled during the operation, and the developing sleeve 2 and the magnet roll 3 rotate together, as shown in FIG. Is operated in the mode shown in FIG. When the rotation of the developing sleeve 2 is stopped, the developer conveying force by the developing sleeve 2 is lost, and the developer easily rolls due to the rotation of the magnet roll 3. Get higher That is, since the amount of developer flowing out from the blade 4 onto the developing sleeve 2 increases, the amount of developer in the developer chamber 10 correspondingly decreases, and the pressure received by the developer in the developer chamber 10 decreases. For this reason, the developer in the developer chamber 10 easily rolls due to the rotation of the magnet roll 3, and the developer forming the magnetic brush layer on the developing sleeve 2 reaches the developer chamber 10 when it reaches the developer chamber 10. Developer room
The developer that had been stirred at 10 is mixed again with stirring and homogenized. After such a state, when the mode is switched again to the mode in which the developing sleeve and the magnet roll are both rotating, the toner concentration of the developer on the developing sleeve is the mode in which the developing sleeve is stopped and the magnet roll is rotating. It will be uniform compared to the case where it does not pass. The longer the time for operating the developing device in the mode in which the developing sleeve is stopped and the magnet roll is rotating, the greater the effect, but if it is too long, the amount of developer flowing out onto the driving sleeve increases,
Since the developer is compressed between the photoconductor drum and the developing sleeve, and the compressed developer has a harmful effect such as damaging the photoconductor drum, the developer should be appropriately selected according to the combination with the device in which the developing device is incorporated. You have to choose.

Next, the results of an experiment conducted by incorporating this developing device into an electrophotographic copying machine will be specifically described.

The copying machine uses a Se type photosensitive drum with a drum diameter of 60 mm, the drum peripheral speed is 105 mm / scc, and the charging potential is +750 V.
With A4 size, it has a copying speed of 15 sheets / minute. The developing condition of the developing device is that the developing sleeve has a diameter of 24.5 mm and the rotation speed is 60.
rpm, magnet roll has 8 poles, magnetic flux density 800 gauss rotation speed 400r
pm, the distance between the photosensitive drum and the developing sleeve is 0.44 mm, the blade is made of 4 mm thick magnetic stainless steel, the distance between the blade and the developing sleeve is 0.3 mm, and the rotation of the toner stirring blade is linked with the rotation of the developing sleeve. The rotation speed of the cage
It was 45 rpm.

Magnetic carrier is 75% by weight in styrene acrylic resin
A magnetic substance-dispersed resin carrier in which the magnetite was dispersed was used, which has a particle size distribution of an average particle size of 60 μm, a particle size of 20 μm or less and a particle size of 100 μm or more and 5% or less. The toner is a non-magnetic red image negatively charged toner in which 5% by weight of a pigment and other inorganic material components are dispersed in styrene acrylic resin, and the average particle diameter is 12 μm, the particle diameter is 5 μm or less, and 20 μm.
A particle size distribution in which m or more was 5% or less was used. The developer initially charged is 90 wt% of magnetic resin carrier and 10 wt% of toner.
% Mixture (greater than the sum of the amount required to form a magnetic brush on the developing sleeve and the amount sufficient to fill the developer chamber) and 150 g of toner was charged to the toner chamber.

A 32 mesh (opening size 0.50 mm) wire mesh made of non-magnetic stainless steel was used as the mesh member.

In the copying machine, in continuous copying, the time required for one copying is 4 seconds, 2 seconds of which is the time required for developing an electrostatic latent image for image copying, and the remaining 2 seconds is required for image copying. There is no charge, and the surface of the photoconductor drum has been discharged.

Under such conditions, continuous copying is performed, during which both the developing sleeve and the magnet roll are rotated at a predetermined number of revolutions, and the drive of only the developing sleeve is controlled to reduce the time required for image copying. The developing device was operated so that the rotation was stopped for 0.5 seconds. In this respect, blackening rate 0%, 6%, 15%,
20% of four kinds of originals were aligned vertically to the developing sleeve axis and simultaneously copied. The toner concentration of the developer on the developing sleeve corresponding to each original was measured for every 500 copies, and 3000 copies were made. The toner concentration was measured by collecting 0.1 g of each developer from the developing sleeve and measuring the weight change before and after combustion. (Experiment 1) Next, the same experiment as described above was performed by controlling the developing sleeve so that the rotation of the developing sleeve was stopped for 0.8 sec during the time not required for image copying. (Experiment 2) For comparison, the same experiment was performed by continuously rotating the developing sleeve and the magnet roll without stopping the developing sleeve halfway. (Experiment 3) Table 1 shows variations in toner concentration in the above three experiments.

As is clear from the results shown in Table 1, in Experiments 1 and 2, variations in toner density due to the blackening rate of the original are smaller than in Experiment 3. That is, the blackening rate is distributed by operating the developing device in a mode in which the developing sleeve and the magnet roll are both rotating and in a mode in which the developing sleeve is stopped and the magnet roll is rotating for a time not necessary for image copying. Even if a manuscript having a mark is continuously copied, it is less affected by the blackening rate of the manuscript.

It should be noted that the present invention is not limited to the conditions of the above embodiment, but may be appropriately determined depending on the situation. Needless to say, the present invention is effective even if continuous copying is not used.

EFFECTS OF THE INVENTION As described above, according to the present invention, there is provided a developing sleeve having an independently rotatable magnet roll therein for supporting and conveying a developer including a magnetic carrier and a toner, and the ears of the developer. A blade for regulating the magnetic roll, and a plurality of opening diameters larger than the particle diameters of the magnetic carrier particles and the toner particles, which are provided so as to be embedded in the developer in a region where the magnetic field of the magnet roll extends. A net-like member having an opening, and the magnet roll and the developing sleeve rotate together during an operation not required for recording, the same mode as the operation required for recording, and the developing roller rotates when the magnet roll rotates. This is a developing device that operates in the stopped mode. According to this, when an electrostatic latent image having a distribution of blackening ratio is continuously developed, it is affected by the blackening ratio of the electrostatic latent image. Is less Further, the presence or absence of magnetism in the toner material and the influence of material properties such as fluidity are small, and the toner density on the developing sleeve can be adjusted without requiring a special device.

[Brief description of drawings]

1 and 2 show a developing device in an embodiment of the present invention. FIG. 1 is a sectional view of an operating state in a mode in which the developing sleeve and the magnet roll are both rotating, and FIG. 2 is the developing sleeve stopped. It is sectional drawing of the operating state in the mode in which the magnet roll is rotating. 2 ... development sleeve, 3 ... magnet roll, 4 ... blade, 5 ... mesh member, 9 ... developer.

Claims (1)

[Claims] 1. A developing sleeve having a independently rotatable magnet roll for supporting and conveying a developer composed of a magnetic carrier and toner, and a blade for restricting the rising of the developer. A net-like member having a plurality of openings having an opening diameter larger than the particle diameters of the magnetic carrier particles and the toner particles, the mesh member being provided so as to be embedded in the developer in a region where the magnetic field of the magnet roll extends. The magnet roll and the developing sleeve both rotate during an operation not required for recording, the same mode as the operation time required for recording, and the mode in which the magnet roll rotates and the developing sleeve stops. A developing device.