JPH07295322A - Color image forming device - Google Patents

Abstract

PURPOSE:To sufficiently secure the stirring time of developer and to obtain a high-quality image even when a developing device is miniaturized by separately arranging the developing device and a toner replenishment means by using a toner carrying means and making the toner carrying means from a metallic pipe. CONSTITUTION:The developer for developing an electrostatic latent image is housed in a developer container 1, uniformly carried inside the container by the rotation of a carrying screw 2 and supplied to a developing roll 3. When toner is consumed and the concentration thereof becomes thin, it is detected by a toner concentration detector 4 and transmitted to the toner cartridge driving means of a toner cartridge 5 as an electric signal. Then, a stirring blade 6 is actuated. By the rotation of the blade 6, the toner housed in the cartridge 5 is stirred and sent to a toner carrying pipe 7. Since the pipe 7 is a metallic pipe, the desired electrostatic charge quantity of the toner is obtained while the toner is carried toward the container 1 by the triboelectrification of the toner and the pipe 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art A color electrophotographic apparatus such as a color laser printer utilizing an electrophotographic process is a mixture of an image carrier on which an electrostatic latent image is formed according to different print data, for example, a toner and a carrier. A developing container containing a two-component developer, a stirring means for stirring and mixing the developer, a toner replenishing means for replenishing the developing container with toner, and a toner concentration detecting means for detecting the toner concentration in the developer inside the developing container are provided. A plurality of developing devices that are means for visualizing the electrostatic latent image provided, a developing device selecting means that operates the developing devices according to the developing color, and a control device that controls these are provided. The toner is supplied to the developing container from the toner supplying means.

Various means have been proposed for developing devices used for the purpose of downsizing and cost reduction of color electrophotographic devices. For example, as disclosed in Japanese Unexamined Patent Publication No. 63-202769, a plurality of developing devices are provided, each developing device is mounted on a rotating body, and each developing device carries an image by rotational movement of the rotating body. There has been proposed a movable developing device that moves to a predetermined developing position facing the body and performs development at the developing position. In such a rotary-moving type developing device, a toner replenishing means is provided outside the developing device, and the toner is replenished to each developing device through the toner conveying means. However, since the developer is agitated after the developing device is moved to the developing position, the agitation time is determined by the development time, so that the agitation is not sufficiently performed and there is a problem in the image quality immediately after the toner replenishment. It was

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to secure a sufficient stirring time of the developer even if the developing device is downsized,
An object of the present invention is to provide an image forming apparatus capable of obtaining a high quality image.

[0005]

SUMMARY OF THE INVENTION The present invention comprises an image carrier on which an electrostatic latent image is formed according to different print data, a developing container containing a developer, and a stirring means for stirring the developer. A plurality of developing devices that are means for visualizing the electrostatic latent image, a toner replenishing device that replenishes the developing device with toner, and a toner that conveys the toner in the toner replenishing device to the developing device. In a color image forming apparatus,
It is made of metal pipe and has a length of 300
It is characterized in that it has a toner conveying means exceeding mm.
The toner conveying unit can set the charge amount of the toner to a desired toner charge amount while conveying the toner. Preferably, a stirring unit for stirring the developer is added below the toner replenishing unit, and the charge amount of the developer is quickly stabilized by the stirring unit, and then the developer is conveyed to the developing device. Further, the developer in the developing device is also conveyed to the stirring means. Thereby, the characteristics of the developer can always be kept stable.

[0006]

According to the present invention, the developing device and the toner replenishing means are separately arranged by using the toner conveying means. As a result, the configuration of the conventional image forming apparatus can be further downsized. Further, since the toner can be sufficiently charged in advance by the toner conveying means and the stirring means, a high quality image can be obtained.

[0007]

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

FIG. 1 shows an embodiment of a developing device to which the present invention is applied. The developer for developing the electrostatic latent image is contained in the developing container 1, and the developer is uniformly fed into the developing device by the rotation of the feeding screw 2 and supplied to the developing roll 3. The toner is contained in the toner cartridge 5. When the electrostatic latent image on the image carrier is developed by the developing roller 3, the toner is consumed and the toner density becomes low.
This is detected by the toner concentration detector 4 and sent as an electric signal to a toner cartridge driving means (not shown) to operate the stirring blade 6. The toner stirred by the rotation of the stirring blade 6 is sent to the toner transport pipe 7. Since the toner carrying pipe 7 is made of metal, a desired toner charge amount is obtained by frictional charging between the toner and the toner carrying pipe 7 while the toner is carried toward the developing container 1.

2 and 3 show examples of changes in the toner charge amount measured by the toner carrying pipe 7 of the present invention. Figure 2
Indicates the toner charge amount with respect to the stirring time when the toner is introduced into the conveying means by using the toner conveying means of different materials. When the metallic pipe is used, the toner charge amount becomes stable in a short time as compared with the non-metallic pipe according to the conventional invention.

FIG. 3 is an example showing a change in the toner charge amount with respect to the length of the pipe. When using the non-metallic pipe according to the conventional invention, in order to obtain a stable toner charge amount,
It is necessary to lengthen the pipe to secure the time required for charging. On the other hand, when the metallic pipe of the present invention is used, stable characteristics are exhibited regardless of the length of the pipe. Therefore, by using a metallic pipe and lengthening it, the developing device and the toner conveying means can be arranged separately from each other. The toner transport pipe 7 may be rotatable. This makes it possible to charge the toner faster. The toner carried to the developing container 1 by the toner carrying pipe 7 falls onto the carrying screw 2. afterwards,
The toner and the developer are mixed and agitated by the rotation of the conveying screw 2, and are uniformly conveyed into the developing device and supplied to the developing roll 3.

FIG. 4 shows an embodiment of a developing device to which the present invention is applied. A developer stirring chamber 8 is provided below the toner cartridge 5, and is composed of a stirring screw 9 and a toner concentration detector 4. The developing container 1 is provided in the stirring chamber 8.
The same developer as the developer inside is contained. The developer in which the electrostatic latent image on the image carrier is developed by the developing roll 3 is conveyed to the upper part of the developing roll 3 by rotation, and is taken into the developer carrying pipe 7b attached to the side plate of the developing container 1 to be stirred. 8 is transported. On the other hand, the toner concentration detected by the toner concentration detector 4 in the developing container 1 is, for example,
When it is lower than 3 wt%, the stirring blade 6 is operated to supply the toner to the stirring chamber 8. The replenishment toner and the developer sent by the developer carrying pipe 7b are fed by the stirring screw 9 to
Mix and stir until the toner concentration reaches 3 wt%. The developer of 3 wt% is supplied into the developing container 1 through the developer transport pipe 7a. As a result, the developer in the developing container 1 always maintains new characteristics, and the image obtained by printing can also maintain the initial quality.

[0012]

According to the present invention, the developing device and the toner replenishing means are separately arranged by using the toner conveying means. As a result, the configuration of the conventional image forming apparatus can be further downsized. Further, since the toner can be sufficiently charged in advance, a high quality image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of a developing device showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a change in charge amount depending on a stirring time, using the toner conveying pipe according to the present invention.

FIG. 3 is a characteristic diagram of a change in charge amount depending on the length of a toner conveying pipe according to the present invention.

FIG. 4 is an explanatory view of a developing device showing an embodiment of the present invention.

[Explanation of symbols]

1 ... Developing container, 2 ... Conveying screw, 3 ... Developing roll,
4 ... Toner density detector, 5 ... Toner cartridge, 6 ...
Stirrer blade, 7 ... Transport pipe.

Claims (2)

[Claims] 1. An electrostatic latent image provided with an image carrier on which an electrostatic latent image is formed according to different print data, a developing container for containing a developer, and a stirring means for stirring the developer. In a color image forming apparatus including a plurality of developing devices that are means for visualizing, a toner replenishing device that replenishes toner to the developing device, and a toner conveying device that conveys the toner in the toner replenishing device to the developing device, A color image forming apparatus comprising a metal pipe and having a toner conveying means having a length of more than 300 mm. 2. The agitating means for agitating the developer located below the toner replenishing means, the developer in the agitating means, and the developer for conveying the developer in the developing device. The color image forming apparatus having a conveying unit.