JPH04324469A - Method and device for developing - Google Patents

Abstract

PURPOSE:To always keep a printing density constant even if a printing rate is fluctuated, in a developing method and device forming the uniform thin layer of a developer on a developer carrier by a layer thickness regulating member and supplying the developer to a latent image carrier via the developer carrier. CONSTITUTION:In an electrophotographic recorder carrying out development by the developing device having the developer carrier 4 supplying the developer to the latent image carrier 1, a means 9 regulating the thickness of the layer of the developer on the developer carrier 4, and a developer replenishing means 10 replenishing the developer to the developer carrier 4, the developer replenishing means 10 is composed of a rotary member and has a configuration so as to change a circumferential speed. In other words, the constitution that the printing rate is detected from printing information and the rotational and circumferential speed of the developer replenishing means 10 is changed according to the detected printing rate, is adopted.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a developing method and a developing device in an electrophotographic recording apparatus such as an electrophotographic copying machine or an electrophotographic printer, and more particularly, to a developing method and a developing device for use in an electrophotographic recording apparatus such as an electrophotographic copying machine or an electrophotographic printer. The present invention relates to a developing method and a developing device in which a thin layer is formed and a developer is supplied to a latent image carrier via a developer carrier.

0002

2. Description of the Related Art FIG. 6 is a partial cross-sectional/side view of an electrophotographic recording apparatus equipped with a conventional developing device. Reference numeral 1 denotes a drum-shaped latent image carrier, and a uniform charger 2, an exposure device 3, a developer carrier 4, a transfer roller 5, and a cleaning device 6 are arranged in this order around the outer periphery of the drum-shaped latent image carrier.

The latent image carrier 1 conveys the latent image formed on its surface to a developing section, and then transfers the developed toner image onto a recording sheet 7.
The image is transported to the transfer position. This latent image carrier 1
Depending on the latent image forming method, a photoconductive material such as a photoconductor (organic photoconductor, selenium photoconductor, amorphous silicon photoconductor, etc.) or an insulator can be used.

After the surface of the latent image carrier 1 is uniformly charged by a uniform charger 2 consisting of a rotating brush or the like, an electrostatic latent image is formed by a latent image writing means (exposure means) 3 such as a laser optical unit. Then, a toner image is formed by the next developer carrier 4.

The developer carrier 4 transports/supplies developer to the developing section of the latent image carrier 1 by rotating around a rotating shaft 8 . Developer carrier 4 and latent image carrier 1
A voltage is applied to the developer carrier 4, which is a conductive member, via the rotating shaft 8 so that electric fields in opposite directions are generated between the image area and the background area of the latent image.

For example, when an organic photoreceptor is used as the latent image carrier 1, the potential of the image area is about -100V, and the potential of the background area is about -100V.
Since the voltage is about 600V, -300V is applied to the developer carrier 4.
Apply a voltage of V. The material used for the developer carrier 4 is a porous urethane sponge imparted with electrical conductivity.

A blade-shaped layer thickness regulating member 9 is pressed against the developer carrier 4 to regulate the layer thickness of the developer on the developer carrier 4 to be constant. Further, a voltage of -400 V is applied to the layer thickness regulating member 9 in order to triboelectrically charge the developer and increase the amount of charge by charge injection charging.

Reference numeral 10 denotes a developer replenishing means, which collects the developer remaining on the developer carrier 4 after developing the latent image and supplies the developer to the developer carrier 4 to perform the development. It has a function of making the layer thickness of the developer on the agent carrier 4 uniform. Reference numeral 11 denotes a rotation shaft of the developer replenishing means 10, which applies a voltage to the developer replenishing means 10, which is a conductive member, and rotates the developer replenishing means 10.

The voltage applied to the developer replenishing means 10 is lower than the voltage applied to the developer carrier 4 so that the negatively charged developer can be mechanically and electrically supplied to the developer carrier 4. Approximately -400V is suitable. The developer replenishing means 10 may be a sponge, a brush, or the like. In addition, 1
Reference numeral 2 denotes a developer reservoir section, which stores developer to be supplied to the developer carrier 4.

When toner is attached to the electrostatic latent image on the latent image carrier 1 from the developer carrier 4 and development is performed, the latent image carrier 1 moves to the transfer section, and the toner image is transferred to the transfer roller 5, etc. The image is transferred onto the recording paper 7 by a transfer device. At this time, the developer remaining on the latent image carrier 1 without being transferred is removed by the blade-shaped cleaning means 6, and the state returns to the initial state. on the other hand,
The toner image transferred to the recording paper 7 is thermally fixed by the fixing means 13.

By the way, in this way, the layer thickness regulating member 9 comes into contact with the developer carrier 4 to form a uniform thin layer of developer,
In the developing device that supplies developer to the latent image carrier 1,
Many developers are known that use one-component developers, that is, developers that are composed only of toner and do not contain carrier particles.

In this developing device, the toner is charged by being injected with a charge by the voltage applied to the layer thickness regulating member 9, is conveyed to the developing section by the rotation of the developer carrier 4, and is applied to the developer carrier 4. By setting the voltage so that electric fields are generated in opposite directions in the image area and the background area of the latent image carrier 1, toner is adhered to the latent image carrier 1.

In a developing device employing such a developing method, in order to obtain good printing, the layer of developer formed on the developer carrier 4 must be uniformly thin and uniformly charged. It is important to be present. For this purpose, the developer supplied to the developer carrier 4 by the developer replenishing means 10 is made into a thin layer on the developer carrier 4 by layer thickness regulating means 9 of various shapes and materials, and is charged. .

[0014]

By making the thin layer of developer on the surface of the developer carrier 4 uniform in this way, a constant amount of developer is always supplied to the latent image carrier 1, and the recording paper 7 Printing is performed at a constant density. However, since the developer supply amount is set so that printing with the optimum density is performed when the printing rate on the recording paper 7 is normal, when the printing rate on the recording paper 7 is high, the latent image carrier Since the amount of developer consumed on one surface increases, the developer gradually becomes insufficient and the print density becomes thinner.

That is, even when printing on the same sheet, the amount of developer consumed is completely different between printing with a high coverage rate and printing with a low coverage rate. For example, printing with a coverage rate of 80% consumes 80 times as much developer as printing with a coverage rate of 1%. However, in the conventional device, the developer replenishing means 10, which supplements the excess or deficiency of developer in the developer carrier 4, rotates at a constant circumferential speed, and in any case, the developer replenishing means 10, which replenishes the excess or deficiency of developer in the developer carrier 4, rotates at a constant circumferential speed. The agent is always in a fixed amount.

Therefore, in the case of printing with a high printing rate, the amount of developer refilled by the developer replenishing means 10 is limited to the amount
The developer cannot keep up with the amount consumed by development, resulting in a situation where the developer on the developer carrier 4 becomes insufficient. As a result, the printing density is insufficient, and the printing density changes between the beginning and the end of printing, especially within a single page, causing the problem that the printing density is dark at the beginning and becomes lighter towards the end.

The technical problem of the present invention is to address such problems and to ensure that the print density remains constant even if the print rate varies.

[0018]

[Means for Solving the Problems] Claim 1 is the basic principle of the present invention, and includes a developer carrier 4 that supplies developer to the latent image carrier 1, and a developer carrier 4 that supplies developer to the latent image carrier 1; In an electrophotographic recording apparatus in which development is performed by a developing device having a layer thickness regulating means 9 and a developer replenishing means 10 for replenishing the developer carrier 4, the developer replenishing means 10 rotates. It is made up of several members and is configured to be able to change the circumferential speed. In this apparatus, a printing rate is detected from printing information, and the rotational peripheral speed of the developer replenishing means 10 is changed in accordance with the printing rate.

The invention of claim 2 is an apparatus for carrying out this method, which comprises: a developer carrier 4 that supplies developer to the latent image carrier 1; and a developer layer on the developer carrier 4. In an electrophotographic recording apparatus in which development is performed using a developing device having a thickness regulating means 9 and a developer replenishing means 10 for replenishing developer to the developer carrier 4, at least the surface of the developer carrier 4 is It consists of a porous sponge-like material.

The developer layer thickness regulating means 9 is pressed against the outer periphery of the developer carrier 4 by spring pressure, and the developer replenishing means 10 is composed of a rotating member and is rotated by a motor control circuit 14. Speed can be controlled. Reference numeral 15 denotes a circuit for detecting a printing rate from printing information, and the motor control circuit 14 is controlled by a printing rate signal inputted from this printing rate detection circuit 15.

[0021]

According to the method of claim 1, by detecting the printing rate from the printing information and changing the rotational peripheral speed of the developer replenishing means 10 according to the printing rate, the latent image carrier 1
The amount of developer supplied to the machine can be controlled.

That is, when the printing rate increases, the circumferential speed of the developer replenishing means 10 increases, and when the printing rate decreases,
The circumferential speed of the developer replenishing means 10 is controlled to be low. As a result, when the printing rate increases, a large amount of developer is supplied commensurate with the printing rate, and when the printing rate decreases, the amount of developer supplied decreases, so when the printing rate on the recording paper is high, the print density increases. This eliminates the problem of a decrease in print density, and regardless of whether the printing rate is high or low, the density is always constant, and good print quality that is easy to read is obtained.

Claim 2 is an invention of an apparatus for carrying out this method, which includes a developer carrier 4 that supplies developer to the latent image carrier 1, and a layer thickness of the developer on the developer carrier 4. In an electrophotographic recording apparatus in which development is performed by a developing device having a means 9 for regulating the amount of developer and a developer replenishing means 10 for replenishing the developer into the developer carrier 4, at least the surface of the developer carrier 4 is porous. It consists of a spongy body. Further, the developer layer thickness regulating means 9 is pressed against the outer periphery of the developer carrier 4 by spring pressure.

Therefore, when the circumferential speed of the developer replenishing means 10 increases and the amount of developer supplied to the developer carrier 4 increases, the layer of developer on the surface of the developer carrier 4 becomes elastic. It pushes aside the rich developer carrier surface and the layer thickness regulating means 9 and passes under the layer thickness regulating means 9. In this way, the layer thickness can be obtained in accordance with the amount of developer supplied to the developer carrier 4 by the developer replenishing means 10, and the amount of developer supplied to the latent image carrier 1 can be controlled.

Further, the developer replenishing means 10 can be rotationally driven by a motor M, and the circumferential speed of the developer replenishing means 10 is controlled by a motor control circuit 14 according to a printing rate signal inputted from a printing rate detecting circuit 15. Therefore, the circumferential speed of the developer replenishing means 10 can be faithfully controlled according to the printing rate in the printing information, and the amount of developer replenishment can be controlled according to the printing rate.

[0026]

EXAMPLES Next, how the developing method and developing device according to the present invention are actually implemented will be explained using examples. 2 and 3 are block diagrams showing an embodiment of a method for detecting a printing rate in printing information.

In the embodiment shown in FIG. 2, the data for one sheet of paper sent from the CPU 16 is taken into the buffer memory 17, and then the print information is sent to the page interpretation section 18, and the data is sent to the exposure means line by line for output. A print signal is simultaneously sent to the detection unit 15 for the pixel 3 and the black pixel. The black pixel detection unit 15 calculates the printing rate relative to the total number of pixels by detecting the number of black pixels in the input print signal for one line, and notifies the motor control circuit 14 of the calculated printing rate.

Furthermore, by inputting a print signal for one line to the exposure means 3, a latent image is written on the latent image carrier line by line. As shown in FIG. 1, when the portion P1 on which the latent image has been written by the exposure means 3 on the latent image carrier 1 reaches the developing section P2, the printing rate is determined according to the black pixel detection of the same row. Synchronization is maintained so that the position on the developer carrier 4 where the amount of developer supplied is controlled reaches the developing section P2. For example, the dimensions between the developing section P2 and the latent image writing section P1 of the latent image carrier 1, the developer replenishing means 10 of the developer carrier 4, etc.
Synchronization is possible by setting the dimensions between the contact portion P2 with the latent image carrier 1 and the contact portion P2 with the latent image carrier 1.

In this way, the printing rate is detected for each line for one page, and when printing is completed while controlling the circumferential speed of the developer replenishing means 10, the printing information for the next page is stored in the buffer memory 17. By repeating the same operations as described above, printing is performed while controlling the amount of developer replenishment.

In the embodiment shown in FIG. 3, print information sent one line at a time from the CPU 16 is sent to the exposure means 3 via the buffer memory 17, and a latent image is written on the latent image carrier 1. At the same time, the counter 15 counts the black pixels in the print signal for one line.
The printing rate is calculated by counting with c, and the motor control circuit 14
Notify the printing rate.

In this way, the printing rate is detected line by line, the peripheral speed of the developer replenishing means 10 is controlled according to the printing rate, and the latent image is written while controlling the amount of developer replenishment. .

FIG. 4 is a partial cross-sectional/side view showing an embodiment of the developing device according to the present invention. A developer carrier 4 that supplies developer to the latent image carrier drum 1 rotates around a rotating shaft 8, and one-component developer is transported/supplied to the developing section P2 of the latent image carrier 1. The material of the one-component developer carrier 4 has a pore size of 10
μm, number of cells approximately 200 cells/inch, volume resistivity 1
Porous urethane sponge (manufactured by Toyo Polymer) with a hardness of 04 to 107 Ω・cm and a hardness of 23 degrees (Asker C hardness tester)
(Product name: Rubicel) was used.

The one-component developer replenishing means 10 is for replenishing the one-component developer carrier 4 with the one-component developer, and uses a urethane sponge with a cell count of approximately 40 cells/inch and a volume resistivity of 104 Ω·cm. there was.

The layer thickness regulating means 9 for regulating the amount of developer adhering to the developer carrier 4 is made of a plate spring made of stainless steel (SUS304) with a rounded end treated with a round edge, and a coil spring 19. was used so that the pressing pressure on the developer carrier 4 was 35 gf/cm.

In this way, the developer carrier 4 is made of a porous urethane sponge, the layer thickness regulating means 9 is a leaf spring, and the layer thickness regulating means 9 is pressed against the developer carrier 4 by the coil spring 19. With this structure, the thickness of the developer layer can be formed in accordance with the amount of developer whose supply amount is controlled by the developer replenishing means 10.

Note that 20 is a casing, 21 is a developer,
22 is a developer stirring means, and 23 is a developer conveying means.

FIG. 5 shows the results of measuring the print density difference when the circumferential speed of the developer replenishing means 10 was changed based on the circumferential speed of the developer carrier 4 in the apparatus of this embodiment. . Printing is performed at a printing rate of 50%, and the density difference between pages (
When examining the change in the difference between the start and end of printing, it was found that even if the pressure of the layer thickness regulating means 9 was the same, the circumferential speed ratio of the developer replenishing means 10 was 1.4 to 1.5. When the speed is lower, the difference in print density becomes larger, indicating that there is a shortage of developer. On the other hand, the circumferential speed ratio is 1.6
At higher speeds, the difference in print density is reduced to such an extent that it cannot be discerned visually, and the print has a uniform density at the beginning and end.

[0038]

[Table 1]

Table 1 shows an example in which the ratio of the circumferential speed of the monocomponent developer replenishing means 10 to the monocomponent developer carrier 4 is changed in accordance with the printing rate. According to this example, when the circumferential speed ratio of the developer replenishing means 10 to the developer carrier 4 was set and development, transfer, and heat fixing were performed, a decrease in density and a print history occurred for any printing rate. was also not recognized.

In a normal electrophotographic recording apparatus, the developer replenishing means 10 is connected to the developer carrier 4 through a gear, and the circumferential speed ratio is set constant; however, in the case of the present invention, the developer replenishing means 10 is The agent replenishment means 10 is connected to a single drive motor,
The rotation speed of the drive motor is changed according to the printing rate.

[0041]

As described above, according to the present invention, since a method is adopted in which when the printing rate changes, an amount of developer corresponding to the printing rate is supplied to the developing section of the latent image carrier 1. The amount can be supplied according to the amount of agent consumed, and the printing density remains constant even if the printing rate changes.

Further, the developer carrier 4 may be made of a porous urethane sponge, and the layer thickness regulating means 9 may be composed of a leaf spring, or the layer thickness regulating means 9 may be attached to the developer carrier 4 with a coil spring 19. Due to the pressing structure, by changing the circumferential speed of the developer replenishing means 10, the developer carrier 4
The amount of developer replenished to the latent image carrier 1 can be easily controlled, and the amount of developer supplied to the latent image carrier 1 can be controlled in accordance with the printing rate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the basic principle of a developing method and a developing device according to the present invention.

FIG. 2 is a block diagram showing a first embodiment of a method for detecting a printing rate of printed information.

FIG. 3 is a block diagram showing a second embodiment of a method for detecting a printing rate of printed information.

FIG. 4 is a partial cross-sectional/side view showing an embodiment of a developing device according to the present invention.

FIG. 5 shows the results of measuring print density differences when changing the circumferential speed ratio of the developer replenishing means to the developer carrier in the developing device of the example.

FIG. 6 is a partial cross-sectional/side view of an electrophotographic recording apparatus equipped with a conventional developing device.

[Explanation of symbols]

1 Latent image carrier (latent image carrier drum) P1 Latent image writing section P2 Developing section 2 Uniform charger 3 Exposure means 4 Developer carrier 5 Transfer means (transfer roller) 6 Cleaning means 7 Recording paper 9 Layer thickness regulating means (Layer thickness regulating member) 10 Developer replenishment means 12 Developer reservoir 13 Fixing means M Developer replenishment means drive motor 14 Motor control circuit 15 Print rate detection circuit (black pixel detection section) 15c Black pixel counter 19 Coil Spring 21 Developer

Claims (2)

[Claims] 1. A developer carrier (4) for supplying developer to the latent image carrier (1), a means (9) for regulating the layer thickness of the developer on the developer carrier (4), and , a developer replenishing means (10) for replenishing the developer carrier (4) with developer;
In an electrophotographic recording device in which development is performed with a developing device having A developing method characterized in that the rotation peripheral speed of the developer replenishing means (10) is changed according to the printing rate. 2. A developer carrier (4) for supplying developer to the latent image carrier (1), a means (9) for regulating the layer thickness of the developer on the developer carrier (4), and , a developer replenishing means (10) for replenishing the developer carrier (4) with developer;
In an electrophotographic recording device in which development is performed with a developing device having The developer replenishing means (10) is composed of a rotating member, and the circumferential speed can be controlled by a motor control circuit (14). It has a circuit (15) that detects a printing rate from printing information, and controls the motor control circuit (1) according to a printing rate signal inputted from the printing rate detection circuit (15).
4) A developing device characterized in that: