JPS63247777A - Developing device - Google Patents

Abstract

PURPOSE:To stabilize the characteristic of a developing device, and also, to relax the working accuracy of a carrying body by allowing a rotatable cylindrical toner carrying means to carry a one-component toner, and specifying a relation of roughness of the surface and an average grain size of the toner, at the time of developing an electrostatic latent image on a charge holding body. CONSTITUTION:On the outer periphery of a photosensitive drum 16 having a photoconductive body 18 of zinc oxide, etc., an electrifier 19 and a toner carrying body 23 consisting of a developing roller 24 and a fur brush 25 are provided, and a one-component toner 22 contained in a storage part 29 is fed to the carrying body 23. Subsequently, by a blade 43 for slide-contacting with the roller 24, layer thickness of the toner 22 accumulated on the roller 24 is controlled, and by using it, an electrostatic latent image formed on the photoconductive body 18 is developed. In this constitution, roughness of the surface of the roller 24 being a toner carrying body is held within a range of 1.5D-8D, when an average grain size of the toner 22 is denoted as D. In such a way, the blade 43 does not hit directly against the surface of the roller 24, and damage of the blade 43 and the toner 22 is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to a developing device of an image forming apparatus such as a copying machine or a printer to which electrophotography is applied.

BACKGROUND OF THE INVENTION Conventionally, developing methods using a dry developer are broadly divided into two types: methods using a two-component developer and methods using a one-component developer.

The method using a two-component developer uses a mixed developer of toner and carrier, so it requires a toner concentration control device to maintain a constant mixing ratio of toner and carrier, and has disadvantages such as periodic replacement due to carrier deterioration. have. Therefore, recently, in order to eliminate the above-mentioned drawbacks, a developing method using only a one-component developer without using a carrier has been proposed.

This developing method is disclosed, for example, in Japanese Unexamined Patent Publication No. 60-33578, and its construction is shown in FIGS. 8 and 9.

The details of the conventional example shown in FIGS. 8 and 9 will be explained below. FIG. 8 is a schematic perspective view of a conventional developing device. This developing device 1 uses a non-magnetic developer, and a side frame 4.5 is attached to both sides of a pack frame 2 and a front frame 3 which are spaced apart to form a developing device 6. The top opening 6A is provided with a lid 7 that can be opened and closed for replenishing the developer, and the bottom opening 8 is provided with a developer carrier, such as aluminum, that supports and transports the developer on its surface. Alternatively, a developing roller 9 made of stainless steel or the like is rotatably supported on both side frames 4.5. Further, between the front frame 3 and the developing roller 9, there is an elastic material such as silicone butadiene rubber or urethane rubber that is in pressure contact with the developing roller 9 and applies the developer T that has entered under pressure onto the surface of the developing roller 9. An elastic blade 10 made of stainless steel, phosphor bronze, urethane sheet, or the like is attached to the front frame 3 via a blade holder 11.

The developing device 1 is arranged at a position where the developer applied to the developing roller 9 is not in contact with the photoreceptor 14. This non-contact arrangement requires a distance of 10 to 300μ between the two.
A gap of m is maintained. In order to maintain this gap dimension, for example, a gap regulation roller 12 is rotatably attached to the shaft of the developing roller 9, and this gap regulation roller 12 is connected to the photoreceptor 14.
The center-to-center distance between the photoreceptor 14 and the developing roller 9 is maintained constant by abutting against peripheral surfaces at both ends of the photoreceptor 14 or receiving rollers (not shown) attached to the shaft of the photoreceptor 14 .

Further, a power source 13 is provided that applies a voltage to the developing roller 9 to form an electric field between the photoreceptor 14 and the developing roller 9 .

Next, the operation and effects of the developing device 1 will be explained. The developing device 1 is filled with developer T, and the developing roller 9
When the developer T is rotated in the direction of the arrow W1 shown in the figure, the developer T is conveyed in the direction of the arrow W1 by the conveying force of the developing roller 9, and is frictionally charged with the elastic blade 10. At this time, since the first uneven rough surface 15 is formed on the surface of the developing roller 9, the conveyance force of the developer in contact with the developing roller 9 and the developer T in the vicinity is increased, and the developer in the vicinity of the developing roller T is reliably conveyed in the direction of arrow W1 and undergoes fluid dislocation.

It is said that the unevenness provided on the developing roller 9 has a value of 0.07D to 1.5D, where D is the developer particle diameter.For example, if the developer particle diameter is 10 μm,
It is said that a value of 0.7 μm to 15 μm is good.

Problems to be Solved by the Invention However, in the conventional developing device, there is no developer (toner). There were problems with the stability of charge amount and charging performance, making stable image reproduction difficult.

That is, in the conventional developing device, the density of the developed image decreases as the operating time thereof accumulates.

Figures 10 and 11 show variations in the thickness and charge amount of a single layer of toner on the toner carrier when a conventional developing device is operated continuously.The zero layer thickness remains approximately constant. However, the amount of charge gradually increases until it exceeds the allowable value, and as a result, the image density gradually decreases and falls below the allowable value.
(Fig. 12) The number of sheets that can be developed while maintaining the image density at an acceptable value is approximately 1,500 sheets for a toner capacity equivalent to 3,000 sheets (6% original), which is not sufficient for actual use. I can not say.

We have experimentally found that the main cause of this property deterioration is the detachment of silica added to the toner surface.

A means for solving the problems and a technical means of the present invention for solving the above problems is to set the surface roughness of the surface of the toner carrier within a certain range, and the present invention is a device for developing an electrostatic latent image on a charge carrier by carrying a single-component toner on a rotatably supported cylindrical toner carrying means, in which the surface roughness of the toner carrying means is , where D is the average particle diameter of the toner used, the developing device is within the range of 1.5D to 8D.

We have experimentally discovered this technical means.At present, the effect of this technical means is unknown, but it has dramatically improved the stability of the characteristics of the developing device, and has improved the toner. Since the processing precision of the carrier can be relaxed, the yield can be improved and the cost can also be reduced.

Example Examples of the present invention will be described below.

1 to 4 are sectional views of essential parts of an embodiment of the present invention,
This is an example of use in an electrophotographic copying machine. In Figure 1,
Reference numeral 16 denotes a charge carrier, such as electrostatic recording paper or a photosensitive drum.

In this embodiment, the charge carrier 16 is a photosensitive drum having a photoconductor 18 such as zinc oxide, selenium, or an organic photoconductive material supported on the surface of an aluminum base 17. (Thus, the charge holding body 16 is hereinafter referred to as the photosensitive drum 16.) Reference numeral 19 is a charger that uses a first DC high voltage power source 20 to charge the photoconductor 18 on the photosensitive drum 16, for example, in the case of zinc oxide. In the case of negative or selenium, a positive corona is applied to charge the entire surface of the photoconductor 18.

Reference numeral 21 denotes an optical section that projects a patterned optical image onto the photosensitive drum 16 to form an electrostatic latent image. A developer 22 is a normal one-component insulating toner. Note that the developer 22 may be a magnetic toner or a non-magnetic toner.

Reference numeral 23 denotes toner carrying means, which is composed of a developing roller 24 and a cylindrical elastic body 25 which is a second supplying means.

Further, the developing roller 24 is a metal roller made of stainless steel, aluminum, etc., a roller whose surface is coated with resin, etc., and its structure is as shown in FIG. , 2
4b is a smooth surface, and the center surface 24c is formed with a rough surface with fine irregularities, and is placed at a constant distance from the photosensitive drum 16, for example, in a counterclockwise direction as shown in FIG. It is rotating. The cylindrical elastic body 25 is a fur brush, a roller made of sponge, or the like, and a layer of elastic material 27 is formed on the outer peripheral surface of the core metal 26. In this embodiment, the cylindrical elastic body 25 is a fur brush, and the elastic material 27 is made of conductive fur using carbon-containing rayon fibers. Also fur brush 25
is in sliding contact with the surface of the developing roller 24 and rotated, for example, in a clockwise direction and at a circumferential speed higher than the circumferential speed of the developing roller 24 .

Furthermore, as shown in FIG. 3, the fibers of the fur brush 25 form a spiral in the direction in which the developer 22 moves from the outer periphery of both ends of the fur brush 25 to the center during rotation. Reference numeral 28 denotes a toner storage means, which is composed of a storage section 29 that stores the developer 22 and a first toner supply means 30 that supplies toner to the toner carrying means 23. In addition, storage section 2
Reference numeral 9 has an opening 31 for replenishing the developer 22 at one end and is formed of a part of the housing 32 . Further, the toner supply means 3
0 fixes one end of a sheet-like elastic member 34 made of, for example, polyethylene terephthalate with a thickness of about 30 μm to the outer peripheral surface of the mandrel 33, and rotates or swings the mandrel 33 to transfer the developer 22 to the toner carrying means 23. It is what we supply.

In this embodiment, the mandrel 33 rotates clockwise. 3
Reference numeral 5 denotes a partition plate provided between the first toner supply means 3° and the toner carrying means 23, and an opening 36 through which the developer 22 flows in and out between the first toner supply means 30 and the toner carrying means 23. It has. 37 is a scraping board today's holiday 32
It is formed of a part of the fur brush 25 and makes sliding contact with the fur brush 25 to equalize the amount of developer 22 in the fur brush 25 and scrape off overcharged developer 22 in the fur brush 25. 38 is a lid of the replenishment opening 31. As shown in FIG. 2, 39 is a bearing for the developing roller 24, and 40 is a bearing for the fur brush 25.

Reference numeral 41 denotes a second DC high-voltage power source serving as a voltage applying means, which applies a voltage between the developing roller 24 and the fur brush 25. 42 is a detection means for detecting the current value of the second DC high voltage power supply 41 and detecting the presence or absence of the developer 22.

A blade 43 is a layer thickness regulating means for regulating the layer thickness of the developer 22. In this embodiment, a rubber blade made of an elastic material such as urethane rubber is used, but the blade material may be other rubber materials, It may be made of an elastic synthetic resin such as polyethylene terephthalate, an elastic metal such as phosphor bronze or spring steel, or an elastic metal or synthetic resin coated with a fluororesin. Further, the blade 43 is provided in pressure contact with the surface of the developing roller 24 on the downstream side of the storage section 29 with respect to the rotating direction of the developing roller 24 and on the upstream side of the portion facing the photosensitive drum 16 . Furthermore, the width of the blade 43 is set to such a length that it comes into contact with the outer circumferential surfaces 24a and 24b at both ends of the developing roller 24, as shown in FIG. 44 and 45 are sealing materials for preventing the developer 22 from leaking, and are made of an elastic material such as felt, sponge, or rubber.

Further, the sealing materials 44 and 45 are in contact with the outer circumferential surfaces 24a and 24b at both ends of the developing roller 24 and both end surfaces of the blade 43. Note that the fur brush 25 is made of a conductive material so that the developer 22 that is frictionally charged on the developing roller 24 is
It has the function of preventing overcharging and making the potential uniform. Therefore, the specific resistance of the fur brush 25 is 10 ΩCm.
below, preferably 103Ωcm to 107Ωcm
It is better to use conductive materials.

The fur brush 25 may be made of not only conductive rayon fiber as in this embodiment, but also other conductive fibers, or a fur brush made by electrostatic flocking to make the coating uniform. It is also effective to use

Furthermore, it goes without saying that the above-described effects of frictional charging, coating, etc. can be effectively performed even if a conductive sponge, conductive cloth, or soft wire brush is used as the elastic material 27 of the cylindrical elastic body 25. In addition, when the developer 22 is a one-component magnetic toner, a magnetic roller is used as the mandrel 36, a magnetic brush is formed on the outer periphery, and the cylindrical elastic body 2
It is also effective to set it to 5.

Next, specific numerical values will be described for the developing device of the above embodiment configured as described above.

The photoconductor 18 on the photosensitive drum 16 is made of zinc oxide, and the cylindrical elastic body 25 is made of an elastic material 27 on an aluminum core 26.
A fur brush in which about 3,600 rayon fibers containing carbon and having a specific resistance of about 105 Ωam are flocked per cm2, the linear pressure of the blade 43 that presses against the developing roller 24 is 25 g/cm2, the I'6 optical drum 16 and the developing roller 24
The gap was 0.15 mm, and the developer 22 was an ordinary positively charged non-magnetic one-component toner.

The average particle size of the toner is about 10 μm.

As the developing roller 24 rotates, the charged developer 22 on the surface of the developing roller 24 passes through the blade 43, where part of it is scraped off to a predetermined layer thickness of approximately 40 μm (the layer thickness at this time is 10 μm). ~70μm
(preferably).

Now, in a developing device with a conventional configuration, the surface of the toner carrier is usually polished by sandblasting or other means.
As mentioned above, it has a matte finish with a surface roughness of ~20 μm.

However, this value was not taken into consideration from the viewpoint of detachment of silica from the toner surface. Therefore, we conducted an experiment to determine the appropriate value for this surface roughness within the above range from the viewpoint of silica removal. In other words, the stability of the developing unit itself during continuous operation (
thickness of the toner layer on the toner carrier and stability of its charge amount)
An experiment was conducted to find an appropriate value for the above-mentioned surface roughness from the viewpoints of , stability of the image density of the developed image, and stability of the image density of the developed image. As a result, it was unexpectedly found that the appropriate values tended to exist outside the above range. In Figures 5, 6, and 7,
Using the above surface roughness as a parameter, toner layer thickness, toner charge amount 1. Indicates the temporal stability of image density,
As is clear from these figures, the surface roughness is 15 μm.
Above, the characteristics are extremely stable. Note that the surface of the developing roller 24 is roughened by sandblasting as in the past.

At present, it is unclear why the properties suddenly become stable when the surface roughness becomes 15 μm or more.

However, at present, as mentioned above, these properties become unstable when the silica added to the toner surface detaches, and the detachment of silica is closely related to the surface roughness of the toner carrier. It is highly likely that this will be the case.

Now, as shown in Figures S5 to 7, the characteristics can be stabilized by roughening the surface roughness of the toner carrier, but in that case,
There is a concern that the toner thickness regulating member may be damaged. However, in reality, once a single layer of toner is formed on the carrier, the rough surface of the toner carrier no longer comes into direct contact with the regulating member, so damage to the layer thickness regulating member is less likely to occur than in the past. Similarly, there are hardly any.

In addition, damage to the toner itself is considered to be practically non-existent, based on experimental data showing stable characteristics.

As is clear from FIG. 7, in this example,
3 for toner capacity equivalent to 3500 sheets (6% original)
Even after developing more than 1,000 sheets, the image density sufficiently maintains the required value.

Next, another significant advantage of the present invention is that the processing accuracy of the toner carrier can be made loose. That is, in the case of a conventional toner carrier having a rough surface, it was necessary to process the cylindricity of the cylindrical surface of the carrier with an accuracy of 10 to 20 μm @ degree before performing sandblasting, but in the present invention, the cylindricity of the cylindrical surface of the carrier has to be processed to an accuracy of 40 μm. It has been experimentally confirmed that machining with a certain degree of accuracy is sufficient. Regarding this point, a surface roughness of about 15 μm is equivalent to 30 to 40 μm in terms of cylindricity, so it is not unthinkable to think that it is not necessary to make the machining accuracy of the cylindrical surface smaller than 40 μm. However, the exact reason for this is currently unknown.

Further, in the above embodiments, the layer thickness regulating member is made of an elastic material, but it goes without saying that the same effect can be obtained even if a rigid blade is used.

As described in detail, in the present invention, the stability of the characteristics of the developing device is dramatically improved, and the processing precision of the toner carrier can be relaxed, so the yield is improved and the cost is reduced. can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an image forming apparatus having a developing device according to an embodiment of the present invention, FIGS. 2 and 3 are perspective views of various parts of the image forming apparatus shown in FIG. 1, and FIG. Another sectional view of the image forming apparatus shown in FIG. 1, FIGS. 5, 6, and 7 are characteristic diagrams for explaining the same apparatus, and FIG. 8 is a perspective view of an image forming apparatus having a conventional developing device. , FIG. 9 is a sectional side view of the device, and FIGS. 10, 11, and 12 are characteristic diagrams for explaining the device. DESCRIPTION OF SYMBOLS 16... Charge holding body, 22... Developer (one component toner), 23... Toner carrying means, 28... Toner storage means, 35... Partition plate, 36... Opening agent Person Name Patent Attorney Toshio Nakao 1 Idiot Figure 2 Figure 5 Figure 6 Ko

Claims (1)

[Claims] An apparatus for developing an electrostatic latent image on a charge carrier by carrying a single-component toner on a rotatably supported cylindrical toner carrying means, the surface roughness of the surface of the toner carrying means being When the average particle size of the toner used is D, 1.5
A developing device within the range of D to 8D.