JPS6289975A - developing device - Google Patents

Abstract

PURPOSE:To obtain a developing device of high image quality where density variance does not occur, by providing a means which coats an electrostatically charged developer on a developer carrier and a layer thickness control means which controls the layer thickness of this developer. CONSTITUTION:The layer thickness of a coated developer 19 on the surface of a developing roller 22 is 50-150mum and is thicker than a prescribed value and is somewhat uneven. When the electrostatically charged developer 19 on the surface of the developing roller 22 passes a blade 27 consisting of urethane rubber in accordance with rotation of the developing roll 22, the developer 19 is charged positively more uniformly and is scraped partially to be controlled to prescribed layer thickness. At this time, 10-50mum layer thickness is preferable. Thus, the developer 19 on the developing roller 22 is formed in a uniform thin layer the prescribed layer thickness to obtain good images without development density variance.

Description

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

2. Description of the Related Art Conventionally, developing methods using dry toner are roughly 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 carrier and toner, so it requires a toner concentration control device to keep the mixture ratio of toner and carrier constant, and has drawbacks such as regular 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 includes, for example, those disclosed in Japanese Patent Laid-Open No. 54-43038 and Japanese Patent Laid-Open No. 58-152260, the construction of which is shown in FIGS. 4 and 5.

In Fig. 4 (Japanese Unexamined Patent Publication No. 54-43038), 1
2 is a developing roller, 2 is a toner, 3 is a hopper, 4 is a blade, and 5 is a photoreceptor. The developing row 21 is made of a metal material with an uneven surface, and the toner 2 is supplied from the hopper 3 . Next, when the developing roller 1 rotates in the direction of the arrow, the toner 2 is charged to a predetermined polarity by the blade 4 in sliding contact with the surface of the developing roller 1 and coated on the surface of the developing roller 1. Next, the charged toner 2B,
When it faces the electrostatic latent image on the photoreceptor 6, it flies and develops it.

In Figure 5 (Japanese Unexamined Patent Publication No. 58-152280),
6 is a photoconductor, 7 is a developing roller made of a conductive urethane material that is in sliding contact with the photoconductor e, 8 is a conductive fur brush that is in rolling contact with the developing roller 7, and 9 is a circuit for applying a voltage to the conductive fur brush 8 and the developing roller 7. It is comprised of a power supply for applying, 10 a voltage divider for adjusting the voltage of the power supply 9, and 11 a hopper containing toner 12. The toner 12 supplied from the hopper 11 to the fur brush 8 is frictionally charged by the fur brush 8, and then coated from the fur brush 8 onto the developing roller 7 by the voltage of the power source 9. It attaches to the image and develops it. Further, when a predetermined developed density is not obtained as a result of development, adjustment is made using the voltage divider 1o.

Problems to be Solved by the Invention However, with this type of system, there are problems with the charging properties of the developer (toner) and the formation of a uniform layer thickness on the developing roller, making it difficult to reproduce high-quality images. I was doing it.

In other words, in the case shown in Fig. 4, the toner in the surface layer on the developing roller contacts the blade, the toner in the lower layer contacts the developing roller and is charged by friction, but the toner in the middle layer contacts each other and is charged by friction. Not charged. If toner is thrown onto the photoreceptor from the developing roller in this state, problems such as the uncharged toner in the intermediate layer scattering inside the device and fogging occur. Furthermore, since only a portion of the surface of the toner in the surface layer and the lower layer is contact-charged, there is a problem in that the developer density changes greatly depending on the humidity.

In the case shown in FIG. 5, the charged toner on the fur brush is coated on the developing roller by an electric field between the fur brush and the developing roller. Therefore, if the toner density on the fur brush is not constant, uneven toner coating will occur on the developing roller, so a means for uniformly supplying the toner from the hopper to the fur brush is required.

However, even if there is a means to uniformly supply toner to the fur brush, there is a problem in that uneven toner coating occurs on the developing roller due to the specific resistance of the fur brush and variations in brush density, resulting in uneven density during development. was occurring.

The present invention solves the conventional problems and provides a developing device with high image quality.

Means for solving the problems and technical means of the present invention for solving the above problems include means for coating a developer carrier with a charged developer, and regulating the layer thickness of the developer. A layer thickness regulating means is provided.

For production The effect of this technical means is as follows.

That is, the charged developer is transferred onto the developer carrier by at least an electric field and coated to a thickness greater than a predetermined developer layer thickness. Next, excess developer is scraped off by the layer thickness regulating means to form a predetermined developer layer thickness on the developer carrier. Next, development is carried out by ejecting the developer using an electric field or the like between the latent image holding member and the developer carrying member. Therefore, the developer on the developer carrier in the developing section is uniformly charged and uniformly coated. Therefore, it is possible to develop high-quality images without toner scattering, fogging, or uneven development density.

Embodiment FIG. 1 shows a developing device according to a first embodiment of the present invention, and is an example used in a developing process of a copying machine.

In FIG. 1, reference numeral 13 denotes a photosensitive drum which is a latent image holder, and is coated with zinc oxide on the surface of a base 14 made of aluminum, for example.
It supports a photosensitive material 16 such as selenium or an organic photoconductive material.

1θ is a charger which charges the latent image holder 1 using a high-voltage DC power supply 17.
Depending on the photosensitive material 15 on the latent image carrier 13, for example, a negative corona is applied in the case of zinc oxide, and a positive corona is applied in the case of selenium.
3) is charged over the entire surface. Reference numeral 18 denotes an optical section that projects a patterned optical image onto the photosensitive drum 13 to form an electrostatic latent image. A developer 19 is a commercially available one-component insulating toner. Note that the toner may be magnetic or non-magnetic. Reference numeral 20 denotes a housing having an outlet portion 21 at one end and housing the developer 19. Reference numeral 22 denotes a developer carrier (hereinafter referred to as a developing roller), such as a metal roller made of stainless steel or aluminum, a roller whose surface is coated with a resin, or a resin roller with a resin layer formed on a metal core. Preferably, fine irregularities are formed on the surface. Further, the developing roller 22 is located at the exit portion 21 and the photosensitive drum 13
For example, the first
Rotate counterclockwise as shown in the figure. Reference numeral 23 is a cylindrical elastic body, and a layer of elastic material 25 is formed on the outer peripheral surface of the metal core 24. The cylindrical elastic body 23 is in sliding contact with the surface of the reed developing roller 22 within the developer 19 of the housing 2o, and is rotated clockwise, for example, as shown in FIG. In this embodiment, a fur brush in which carbon-containing rayon fiber is used as the elastic material 26 is used as the cylindrical elastic body 23. Reference numeral 28 denotes a scraping plate which makes sliding contact with the elastic material 25 of the cylindrical elastic body 23 to make the amount of developer 19 in the elastic material 25 uniform. Furthermore, the cylindrical elastic body 23 agitates the developer 19 and performs frictional charging due to friction between the cylindrical elastic body 23 and the developer 19, and also comes into close or sliding contact with the surface of the casing 20 and with the scraping plate 28. This helps triboelectrically charge the developer 19. Further, the circumferential speed of the cylindrical elastic body 23 is made faster than the circumferential speed of the developing roller 222, and serves to scrape off excess developer 19 adhering to the surface of the developing roller 22 after development. Reference numeral 26 is a DC power source serving as a voltage applying means, which connects the developing roller 2.
A voltage is applied between the cylindrical elastic body 2 and the cylindrical elastic body 23. The elastic material 26 may be insulating or conductive, but if an insulating material is used, the voltage applied to the developing roller 22 and the cylindrical elastic body 23 by the DC power source 26 needs to be high, making the device expensive. Since this is dangerous, it is preferable to use a conductive material with a specific resistance of about 10 Ωα or less.

In addition, as the elastic material 26, other conductive fibers may be used in addition to the conductive rayon fiber as in this embodiment, and an electrostatic flocking type fur brush may be used to make the coating uniform. It is also effective. Furthermore, even if the cylindrical elastic body 23 is formed using a conductive sponge, conductive cloth, soft wire brush, etc. as the elastic material 25, the above-mentioned effects of frictional charging, coating, etc. will of course be effectively performed. be. Note that when the developer 19 is a one-component magnetic toner, a magnetic roller is used as the mandrel 24, and a magnetic brush is formed on the outer periphery of the mandrel 24.
It is also effective to do so.

A blade 27 is a layer thickness regulating means for regulating the layer thickness of the developer (therefore, in this embodiment, it is hereinafter referred to as blade 27). In this embodiment, it is made of an elastic material such as urethane rubber. Other rubber materials may be used, elastic resins such as polyethylene terephthalate resin, elastic metals such as phosphor bronze or spring steel, materials coated with fluororesin, or combinations of these may also be used. Of course.

This blade 27 is located downstream of the developer section of the housing 20 with respect to the rotational direction of the developing roller 22, and is connected to the photosensitive drum 13.
It is provided in sliding contact with the developing row 222 on the upstream side of the portion facing the developing roller 222 .

The operation of the developing device of the first embodiment configured as described above will be explained. Here, in order to make the operation easier to understand, the photosensitive material 16 on the latent image holder 13 is made of zinc oxide, and the cylindrical elastic body 23 is made of zinc oxide. contains carbon as an elastic material 25 on an aluminum core 24 and has a specific resistance of approximately 105 Ωm.
A case will be described in which a fur brush having about 3,600 rayon fibers/day is used (therefore, in this embodiment, the cylindrical elastic body 23 will be hereinafter referred to as a fur brush). As the developer 19, a commercially available positively charged non-magnetic component toner was used.

In FIG. 1, a high voltage of about -eKV is applied to a charger 16 by a high voltage DC power supply 17, and the entire surface of the photosensitive drum 13 is negatively charged to about -6ooV by a negative corona. Next, the reflected image (
If a pattern light image) is projected, the portion corresponding to the non-image area of the document on the photosensitive drum 13 will be almost completely covered by reflected light. The static electricity is removed to a residual potential close to (2), forming a positive electrostatic latent image.

During this time, the developer 19 in the housing 20 is supplied into the elastic material 26 by the rotation of the fur brush 23, and is positively charged by friction with the elastic material 25. Next, the excess developer 19 in the elastic material 26 is scraped off by a scraping plate 28 and an appropriate amount is supplied.
By rubbing against 0, it becomes more positively charged. Furthermore, the developer 1S is transferred to the developing roller 22 by the rotation of the fur brush 23.
The object is transported to a position facing the object. The developer 19 supplied in an appropriate amount is further uniformly charged positively as it rubs against the surface of the developing roller 22. Next, a DC power supply 26 applies a voltage between the developing roller 22 and the fur brush 23 with the fur brush 23 side being positive, and the charged developer is transferred and coated on the surface of the developing roller 22. The voltage applied by the DC power supply 26 is preferably about 30V to 250V, and in this embodiment, 100V is applied.

Note that when the developer 19 is transferred from the cylindrical elastic body 23 to the developing roller 22 by the electric field generated by the DC power source 26, uncharged developer and developer charged with the opposite sign are difficult to transfer, and there is a developer sorting effect. Therefore, more uniform charging is possible and a good image can be obtained.

The layer thickness of the developer 19 on the coated surface of the developing roller 22 is approximately 60 to 160 μm, which is greater than a predetermined layer thickness, and there is some variation. Subsequently, as the developing roller 22 rotates, the developing roller 22
The developer 19 charged on the surface passes through a blade 27 made of urethane rubber, and at this time it is further uniformly charged positively by the blade 27 and is partially scraped off to regulate the layer thickness to a predetermined thickness. Note that the layer thickness at this time is 1
The thickness is preferably about 0 to 50 μm.

Therefore, the developer 19 on the developing row 222 forms a uniform thin layer with a predetermined thickness, and it is possible to obtain a good image without unevenness in development density.

In addition, according to this configuration, stirring of the developer 19, frictional charging,
Since the coating on the developing row 222 by voltage application and the uniform thinning by the blade 27 are reliably performed,
Since the start-up is fast and a predetermined amount of charge can be reached within one cycle, no extra waiting time is required.

The photosensitive drum 13 and the developing roller 22 are provided at opposing positions with a gap of about 0.1 mm maintained between them.
When the negatively charged electrostatic latent image on the top faces the positively charged developer 19 on the developing roller 22, the developer 19 flies to the electrostatic latent image on the photosensitive drum 13 by electrostatic force and can be developed. .

After development, the extra developer 19 remaining on the surface of the developing roller 22 is scraped off by the fur brush 23, erasing the history of the previous process, so that a high-quality image without ghosts can be obtained.

Next, a second embodiment of the present invention will be described.

FIG. 2 shows a second embodiment of the invention, in which parts having the same functions as in the first embodiment are given the same numbers. In FIG. 2, a conductive sponge is used as the elastic material 26, and this is attached to the aluminum core 24.
A roller formed in a cylindrical shape around the cylindrical elastic body 23 is used. The layer thickness regulating means 27 is a rigid body made of metal such as stainless steel, hard resin, ceramics, etc., and is mounted so as to be accurately spaced from the surface of the developing roller 22 by a predetermined layer thickness of the developer 19. .

Reference numeral 29 denotes a partition plate for preventing uncharged developer 19 from reaching the vicinity of developing roller 22 and cylindrical elastic body 23 and for preventing excess developer from remaining. It is easy to understand that even if a conductive sponge roller is used as the cylindrical elastic body 23, the effects of frictional charging, coating, etc. described in the first embodiment can be effectively performed.

In this embodiment, the developing roller 22 and the cylindrical elastic body 23 are
are facing each other in close proximity with a constant gap between them. In addition,
This gap is preferably 0.1 to Oe 5 m.

This gap has the effect of more reliably performing the sorting action of the uncharged developer or the developer charged with the opposite sign as described in the first embodiment. When the cylindrical elastic body 23 rotates and comes to a position facing the developing roller 22, the developer 19 is released as in the first embodiment.
The developing roller 22 is coated with a predetermined layer thickness by the electric field from the DC power source 2e, and the layer thickness regulating means 27 is coated.
The thickness of the layer is regulated to a predetermined value, and when the layer faces the electrostatic latent image on the photosensitive drum 13, development is performed by electrostatic force.

Reference numeral 31 denotes a bias voltage applying means that applies a DC bias voltage between the photosensitive drum 13 and the developing roller 22. By applying a direct current bias voltage, the developer 19 flies due to the synergistic effect of the electrostatic force caused by the electrostatic latent image and the electric field caused by the direct current bias, so that more effective development can be achieved. It should be noted that the developing device having this configuration can cope well even when the bias voltage is alternating current or when alternating current is superimposed on direct current, and it is also possible to not use the bias voltage applying means 31.

Next, a third embodiment of the present invention will be described.

FIG. 3 shows a third embodiment of the invention, in which parts having the same functions as in the first and second embodiments are given the same numbers. In FIG. 3, the layer thickness regulating means 27 is a rigid body made of metal such as stainless steel, coated with fluororesin, or hard resin.
It is made of ceramics or the like and is brought into contact with the developing roller 22 by the force of a pressing spring 3o. The rest of the configuration is the same as the first embodiment, and the operation is also the same as described in the first embodiment.

As in this embodiment, the layer pressure regulating means 27 is a rigid body (
For example, by making the surface of metal (for example, metal), it is possible to obtain a smoother surface than that of rubber, etc., and by bringing this into contact with the developing roller, uniform developer 1 without streaks or unevenness can be obtained.
Since 9 thin layers are formed, a higher quality image can be obtained.

The present invention can be used not only in the three embodiments described above, but also in the case of negative-positive reversal development in laser printers, etc., and can also be used for charging the developer, coating the developer carrier, and applying the developer to the developer. Needless to say, even more configurations are possible by controlling the layer thickness and combining each element.

In addition, the present invention is well suited to non-magnetic component developers, and has a non-contact structure with the latent image carrier, making it suitable for the formation of color images in which developers of multiple colors are layered and developed on the latent image carrier. is also advantageous.

Effects of the Invention In the present invention, since the developer in the developing section is uniformly charged and formed in a uniform layer thickness, it is possible not only to develop high-quality images without toner scattering, fogging, or uneven development density. It has great effects, such as enabling non-contact flying development of non-magnetic component developers using a DC electric field and being advantageous in forming color images in which developers of a plurality of colors are layered on a latent image carrier.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a developing device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a developing device according to a second embodiment of the present invention, and FIG. 3 is a cross-sectional view of a developing device according to a second embodiment of the present invention. FIGS. 4 and 6 are sectional views of main parts of conventional developing apparatuses, respectively. 20... Housing, 22... Developer carrier, 23... Cylindrical elastic body, 26... DC power supply, 27... Layer thickness regulation means, 28...
- Scraping plate, 29... Partition -J, 30... Pressing spring, 31... Bias voltage impression 2, most applying means.

Claims (14)

[Claims] (1) A developing device for visualizing an electrostatic latent image formed on a latent image holder, which includes a developer carrier, means for charging the developer, and transporting the charged developer using at least an electric field. A developing device comprising: means for coating the developer on the developer carrier; and layer thickness regulating means for regulating the developer on the developer carrier to a predetermined layer thickness. (2) The means for charging the developer rotates a cylindrical elastic body to cause relative movement between the developer and the components of the developing device, and the friction between the developer and the components of the developing device causes development. The developing device according to claim 1, wherein the developing device triboelectrically charges the agent. (3) The developing device according to claim 1 or 2, further comprising a partition plate that comes into contact with the cylindrical elastic body upstream of the opposing portion of the cylindrical elastic body and the developer carrier. (4) The developing device according to claim 1 or 2, further comprising a scraping plate that comes into sliding contact with the cylindrical elastic body. (5) The developing device according to claim 2, 3, or 4, wherein the cylindrical elastic body is a fur brush. (6) The developing device according to claim 2, 3, or 4, wherein the cylindrical elastic body is a roller made of sponge. (7) Claim 5 in which the fur brush is conductive
Developing device described in Section 1. (8) The developing device according to claim 6, wherein the roller made of sponge is electrically conductive. (9) The developing device according to claim 1, wherein the electric field serving as the means for transporting the charged developer is based on a voltage applied between the developer carrier and the cylindrical elastic body. (10) The developing device according to claim 9, wherein the developer carrier and the cylindrical elastic body are opposed to each other with a gap provided therebetween. (11) The developing device according to claim 1, wherein the layer thickness regulating means is an elastic blade. (12) The developing device according to claim 1, wherein the layer pressure regulating means is a rigid blade. (13) The developing device according to claim 1, wherein the developer on the developer carrier and the latent image carrier are not in contact with each other. (14) The developing device according to claim 1, further comprising means for applying a DC electric field between the developer carrier and the latent image carrier.