JPH03204665A - Developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention regulates the layer thickness of toner carried on a toner carrying member by a toner regulating means, and forms a latent image on a latent image carrier with the toner after regulation. The present invention relates to a developing device that visualizes a developed electrostatic latent image.

[Conventional technology]

It has been well known that the above type of developing device is used in image forming devices that form an electrostatic latent image on a latent image carrier and make it visible using toner, such as electronic copying machines, printers, facsimile machines, etc. It is.

This type of developing device regulates the layer thickness of the toner carried on the toner carrying member by a toner regulating means to make the thickness almost constant, and visualizes the electrostatic latent image with an appropriate amount of toner. It is configured as follows.

As a conventional toner regulating means, a regulating blade that is pressed against a toner carrying member is widely used, and the layer thickness of the toner on the toner carrying member is regulated by the pressure received from the regulating blade.

[Problem to be solved by the invention]

However, when the toner layer thickness is increased solely by the pressure of the regulating blade, the toner is strongly pressed against the toner carrying member, which not only applies excessive stress to the toner but also causes the toner to be deposited on the toner carrying member. There is a possibility that a filming may be formed. Furthermore, it is difficult to level and control the toner layer thickness uniformly over the entire surface using only pressure. If an electrostatic latent image is visualized using toner having a non-uniform layer thickness, the image quality inevitably deteriorates.

An object of the present invention is to provide a developing device that eliminates the above-mentioned conventional drawbacks.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a developing device of the type described at the beginning, in which a toner regulating means includes a regulating roller positioned facing a toner carrying member while rotating, and a regulating roller that is in contact with the regulating roller. The present invention proposes a developing device characterized by comprising a charging/scraping member that frictionally charges the toner to a polarity opposite to that of the toner and scrapes off the toner adhering to the regulating row.

[Effect]

The negative portion of the toner carried on the toner carrying member is electrostatically transferred to the regulation roller, and its layer thickness is regulated. The charging/scraping member frictionally charges the regulating roller to a polarity opposite to that of the toner, and scrapes off the toner adhering to the regulating roller.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a drum-shaped photoreceptor, which is an example of the configuration of a latent image carrier, and is driven to rotate in the direction of the arrow in the figure. This photoreceptor 1 has a photosensitive layer 1B formed around a drum-shaped conductive support IA that is grounded.

A developing device 10 according to an embodiment of the present invention is disposed close to and facing the photoreceptor 1, and a two-component developer containing, for example, non-magnetic insulating toner and a magnetic carrier is contained in the developing chamber 2 of the developing device 10. is housed therein, and toner is replenished from the toner replenishment chamber 3 in response to a decrease in image density.

Auxiliary agents may be added to the toner as necessary.

The developer in the developing chamber 2 is mixed and stirred by the rotation of the stirring member 4, the toner and the carrier are frictionally charged to have different polarities, and the toner is electrostatically held around the carrier. A developer carrying member 5 made of a non-magnetic and conductive cylindrical body is provided adjacent to the stirring member 4, and the developer drawn up by the stirring member 4 is supplied to the peripheral surface of the developer carrying member 5.

A magnet 7 in which a plurality of magnetic poles are arranged in the circumferential direction is provided in the developer carrying member 5, and as the developer carrying member 5, the magnet 7, or both rotate, the supplied developer is transferred to the magnet 7. The developer is conveyed around the developer carrying member 5 in the direction of the arrow while being supported on the circumferential surface of the developer carrying member by magnetic force. That is, the developer around the developer carrying member is conveyed as a magnetic brush.

A toner carrying member 6 is disposed in close proximity to the developer carrying member 5, and is made of a cylindrical member whose entire body is a conductor or whose outer periphery is a conductor. The toner carrying member 6 is also disposed facing the photoreceptor 1 so as to be close to it, and is driven to rotate in the direction of the arrow in the figure.

The developer conveyed around the developer carrying member 5 is transferred to the cutting plate 8.
At this point, the ears are cut to a specified thickness, and then
It comes into contact with the surface of the toner carrying member 6. Normally, the magnetic brush of the developer carried on the developer carrying member 5 is attached to the cutting plate 8.
As a result, the toner is cut to a thickness thinner than the gap between the developer carrying member 5 and the toner carrying member 6, and the toner receiver between both the developer carrying members 5 and 6 is conveyed to the transfer area. 8a is a separator that separates the developer on the developer carrying member 5.

Between the developer carrying member 5 and the toner carrying member 6, only the toner charged to a predetermined amount or more out of the toner and carrier of the developer carried on the developer carrying member is transferred from the developer carrying member 5 to the toner. A bias voltage is applied by power sources E1 and E2 such that the toner is electrostatically attracted towards the carrier member 6 and held on the surface of the toner carrier member. By applying such a bias voltage, the charged toner that has electrostatically adhered around the carrier moves away from the carrier and toward the toner carrying member 6, where it gathers and forms toner around the toner carrying member. A layer is formed.

The toner carried on the toner carrying member 6 in this manner is conveyed together with the toner carrying member 6 in the rotational direction thereof, and its layer thickness is regulated by the toner regulating means 9. The toner layer with a regulated layer thickness is further carried on a toner carrying member 6 and conveyed, and in the development area between the photoconductor 1 and the toner carrying member 6, it is applied to the electrostatic latent image formed on the photoconductor 1. The toner is electrostatically transferred and the latent image becomes visible. In the example shown in the figure, the photoreceptor 1 and the toner carrying member 6 face each other with a predetermined spacing, and the toner on the toner carrying member 6 is flown onto the electrostatic latent image on the photoreceptor 1 in the developing area without contact. Although the configuration is such that development is performed, the toner carrying member 6 may be brought into contact with the photoreceptor 1 via the toner to perform contact development.

Next, details of the toner regulating means 9 according to the present invention will be explained.

The toner regulating means 9 has a regulating roller 11 provided close to the toner carrying member 6, and this roller 1 is located upstream of the developing area in the rotational direction of the toner carrying member 6 and is arranged to carry the developer. It is located on the downstream side of member 5. Further, the regulating roller 11 is rotationally driven in the counterclockwise direction in FIG. 1, and in the area where the roller 11 and the toner carrying member 6 face each other, both rotate in opposite directions.

The toner regulating means 9 further frictionally charges the regulating roller 11 to a polarity opposite to that of the toner, and the regulating roller 1
In the example shown in FIG. 1, this member is constituted by an elastic blade 12 made of rubber.

The elastic blade 12 is held at its proximal end by a holder 13 and fixed to the developing case of the developing device, and its distal end is pressed against the circumferential surface of the regulating roller 11 by its own elasticity, thereby controlling the rotating regulating roller 11 to a predetermined position. Triboelectrically charges the polarity. For example, when the toner is triboelectrically charged to a negative polarity due to friction with the carrier, the regulating roller 11 is triboelectrically charged to the opposite polarity to a positive polarity by the elastic blade 12 .

As described above, the toner transferred from the developer carrying member 5 to the toner carrying member 6 is carried by the carrying member 6 and conveyed, and reaches the closest portion between the regulating roller 11 and the toner carrying member 6. At this time, the toner is subjected to a scraping action and a leveling action by the regulating roller 11, and excess toner is scraped off.
And the layer thickness is leveled to be constant. at the same time,
The regulating roller 11 is charged with the opposite polarity to the toner.

The excess toner is electrostatically adhered to the regulation roller 11 due to the electric field formed between the regulation roller 11 and the toner carrying member 6 .

In this way, the toner on the toner carrying member 6 is subjected to the scraping or leveling action by the regulating roller 11 and the action of the electric field, so that the layer thickness is evened out, and a toner layer with a constant thickness is always obtained. It will be done. Since development is performed using toner having such a uniform thickness, the quality of the visible image can be improved.

In the example shown in FIG. 1, since non-contact development is performed in the development area, the toner layer is thinner than the distance between the toner carrying member 6 and the photoreceptor 1, and its layer thickness is regulated. It flies onto the electrostatic latent image in the developing area.

The toner adhering to the regulating roller 11 is removed by the elastic blade 12.
It is scraped off and falls downward.

In this way, the blade 12 serves to frictionally charge the regulating roller 11 and scrape off toner adhering to its surface.

According to the above configuration, the layer thickness of the toner is regulated not only by pressure from the regulating roller 11 but also by electrostatic force, so the toner layer thickness can be more reliably uniform compared to a case where the toner layer is regulated only by pressure. Moreover, even if the pressure applied by the regulating roller 11 to the toner is small, the toner can be reliably made into a thin layer. Therefore, the stress applied to the toner can be reduced, and the problem of toner filming being formed on the surface of the toner carrying member 6 can be eliminated.

Further, the regulating roller 11 is constantly cleaned by the elastic blade 12, and the cleaned peripheral surface of the regulating roller regulates the layer thickness of the toner, so that the uniform layer thickness regulating effect is enhanced. Moreover, since the elastic blade 12 performs two functions: frictional charging of the regulating roller 11 and cleaning, the structure can be simplified and costs can be reduced compared to the case where separate members are provided to perform each function.

The regulating roller 11 may be supported immovably with a predetermined gap between the regulating roller 11 and the toner carrying member 6, or the regulating roller 11 may be movably supported in a direction toward and away from the toner carrying member 6. , regulating roller 1 by its own weight or weak spring force.
1 may be biased against the toner carrying member 6. In either case, the pressing force applied to the toner by the regulating roller 11 is weaker than in the past.

Alternatively, the regulating roller 11 is supported in an immovable position with a predetermined gap from the toner carrying member 6 so that the regulating roller 11 does not apply substantial pressure to the toner, and the toner is removed substantially only by the action of an electric field. It is also possible to regulate the layer thickness. In this way, the stress applied to the negative layer toner can be reduced, and the occurrence of toner filming can be reliably prevented.

In the embodiment shown in FIG. 2, the charging/scraping member that frictionally charges the regulating roller 11 and removes the toner attached thereto is constituted by a brush 15 provided on a holder 14 fixed immovably. ing.

FIG. 3 shows an example in which the charging and scraping member is constituted by a brush roller 16 that is stationary or rotationally driven in an appropriate direction. In the embodiments shown in FIGS. 2 and 3, the brush rubs against the rotating regulation roller 11, frictionally charges the roller 11 to a polarity opposite to that of the toner, and scrapes off the adhered toner. .

Note that the toner carrying member 6 is slightly spaced apart from the toner carrying member 6.
Even if the above-mentioned regulating roller 11, which rotates in a non-contact state, is configured so as not to be charged by friction, the toner layer thickness can be more uniformly regulated than the conventional toner regulating means using a blade, and the toner can be carried more easily. Although the occurrence of toner filming on the member 6 can be suppressed, the layer thickness regulation effect and toner filming prevention effect are better than the structure in which the roller 11 is frictionally charged and a portion of the toner is electrostatically attached to the regulation roller 11. is inferior.

By the way, in a developing device such as the developing device shown in FIG. 1, in which a two-component developer is supported on the developer carrying member 5 and only the toner is transferred to the toner carrying member 6 for development. controls the amount of toner transferred to the toner carrying member 6 at the time of transfer, and controls the amount of toner transferred to the toner carrying member 6.
By applying a toner layer as uniform as possible to the surface of the toner layer, the toner layer thickness regulation by the toner regulating means 9 can be made more reliable.

Therefore, in the embodiment shown in FIG. 1, the rotation of at least one of the developer carrying member 5 and the roller-shaped magnet (magnet roll) 7 installed therein is controlled by a control device (not shown). It is configured to That is,
The developer carrying member 5 is applied so that the toner in the developer carried by the developer carrying member 5 is evenly applied to the surface of the toner carrying member 6, and the thickness is as constant as possible, and the amount is not too much or too little. The rotational speed of at least one of the magnets 7 is controlled. In this way, a uniform toner layer can be formed on the toner carrying member 6, and the quality of the visible image can be improved.

In conventional developing devices of this type, the above-mentioned idea is not adopted, and a DC voltage or an AC voltage is simply applied between the developer carrying member 5 and the toner carrying member 6 to remove the toner in the developer. Since the toner was simply applied onto the toner carrying member 6, there was a risk that the applied toner layer would be non-uniform or that the amount would be too much or too little. Although it is possible to regulate the amount of toner applied by controlling the applied bias voltage, it is not easy to control the bias in practice.

Furthermore, if the rotation speed of at least one of the developer carrying member 5 and the magnet 7 is controlled, it becomes possible to adjust the image density.

That is, by controlling this rotation, the toner carrying member 6
The amount of transferred toner is adjusted to increase the amount of transferred toner when obtaining a high-density image, and decrease the amount of transferred toner when lowering the image density. In this way, the copy density can be adjusted without adjusting the amount of light or the developing bias.

By the way, in the developing device shown in FIG. 1, which performs development by causing toner to fly onto the electrostatic latent image in the developing area,
Normally, a voltage of alternating current or a voltage in which alternating current and direct current are superimposed is applied to the toner carrying member 6 by a power source E□.

On the other hand, a plurality of developing devices as shown in FIG. A color development method is also known in which a color image is obtained by overlapping toner images of different colors.

However, when carrying out such overlapping development, if an alternating current electric field is applied to the development area of the downstream development device to perform development,
In the developing area, toner moves back and forth between the photoreceptor 1 and the toner carrying member 6, so that the toner formed on the photoreceptor 1 by the upstream developing device is transferred to the downstream developing device. There is a risk that the toner particles may be drawn toward the toner carrying member 6 and cause color mixing or muddying of the color image on the photoreceptor.

Therefore, in the developing device shown in FIG. 1, a DC power source is used as the power source E, and a DC voltage is applied to the conductive toner carrying member 6, and an AC voltage is not applied. That is, in order to prevent toner from adhering to the background portion of the photoreceptor 1, a DC voltage is applied between the conductive support IA of the photoreceptor 1 and the toner carrying member 6, but an AC voltage is not applied. . Therefore, in the developing area, toner is transferred to the photoreceptor 1.
There is no reciprocating movement between the toner carrying member 6 and the toner carrying member 6.

With such a configuration, the developing device 10 shown in FIG. 1 is arranged downstream of another developing device (not shown), and a toner image of a color formed by the upstream developing device is formed on the photoreceptor 1. After that, when a toner image of another color is superimposed on the photoreceptor 1 using the developing device 10 shown in FIG. It is possible to prevent problems caused by toners of different colors being mixed in.

Note that a DC power source can be used as the other power source E2 shown in FIG. Naturally, it is possible to form an electric field such that the toner therein electrostatically moves toward the toner carrying member 6.

As described above, the developing device is capable of forming high-quality images by transferring only the charged toner in the one-component developer on the developer carrying member 5 onto the toner carrying member 6 and performing development with the sufficiently charged toner. Although a specific example in which the present invention is applied is shown, the present invention is a type of development in which toner containing no carrier is stored in a developing chamber, and the toner is directly carried on a toner carrying member and conveyed for development. It is clear that it can also be applied to devices.

〔Effect of the invention〕

According to the present invention, the thickness of the toner layer on the toner carrying member is regulated by the regulation roller which is frictionally charged with the opposite polarity. It is possible to suppress the defects that cause the formation of scratches. Furthermore, since the charging roller is used to frictionally charge the regulation roller and remove toner attached to the roller, the structure can be simplified and an increase in cost can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a developing device according to one embodiment of the present invention, and FIG.
3 and 3 are diagrams showing other examples of the toner regulating means, respectively. 6... Toner carrying member 9... Toner regulating means 1
0...Developing device

Claims (1)

[Claims] The layer thickness of the toner carried on the toner carrying member is regulated by a toner regulating means, and the electrostatic latent image formed on the latent image carrying member is visualized by the regulated toner. In the developing device, the toner regulating means includes a regulating roller positioned facing the toner carrying member while rotating, and contacting the regulating roller to frictionally charge the roller to a polarity opposite to the charging polarity of the toner; A developing device comprising a charging and scraping member that scrapes off toner adhering to a regulating roller.