JPH03282488A - Developing device - Google Patents

Abstract

PURPOSE:To realize this developing device having reduced density fluctuations by setting the carrying power of the starting part of a developer stirring/ carrying means greater than that of the other parts. CONSTITUTION:Screws 8 and 9 as the developer stirring/carrying means where spiral members 6 and 7 are provided on shafts 4 and 5 arranged at a prescribed interval in a direction orthogonal to the shafts 4 and 5, in the rear of a developing sleeve 2. Carrying directions are reversely disposed each other. On the other hand, a terminal part 8b in the carrying direction of the screw 8 and the starting part 9a of the screw 9, and the terminal part 9b of the screw 9 and the starting part 8a of the screw 8 are communicated, respectively, and the circulating path of a developer is formed. Further, on the terminal parts 8b and 9b, the directions of the screw are reversed, and the developer is delivered to the starting parts 9a and 8a, respectively. Then the screws of the starting parts 9a and 8a are double wound, and set so as to obtain great carrying power. Thus, the developer and replenished toner are effectively stirred, and the fluctuations of the toner concentration of the developer are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device for developing a latent image formed by electrostatic recording, electrophotography, or the like.

[Prior Art] As a developer for developing the latent image, a two-component developer consisting of a mixture of non-magnetic toner particles and magnetic particles is mainly used. (mixing ratio of magnetic particles and magnetic particles) has a great influence on the quality of the image formed. For example, when the toner density is high, the density of one image also increases, and at the same time, so-called blurring occurs. On the other hand, when the toner density is low, image transfer is more likely to occur as the image density decreases. In particular, now that full-color images are being produced, the desired color image is usually formed by overlapping multiple colors using three or more color developing devices, or even slight changes in the density of each color. Since this affects the overall image tone, stricter toner density control is required.

Concentration control methods conventionally implemented under such circumstances include the following. That is, the toner density for obtaining the optimum image quality is set in advance, and then the toner density within the developing device is actually detected using a density detection sensor. If the density detected by the density detection sensor is lower than the set density, a replenishing means in a toner replenishing device (hereinafter referred to as a hopper) is driven to replenish toner into the developing device. is transported through the developing device by a developer stirring and transporting means such as a screw, mixed with and stirred with the developer therein, and then transported to the concentration detection section where its concentration is detected again.The above steps are repeated. By doing so, the toner density is always maintained near the set density.

In such a developing device, it is necessary to mix the toner supplied from the hopper with the developer in the developing device and stir the toner to a uniform density.

[Problem to be Solved by the Invention 1] However, as devices have become smaller in recent years, developing devices have become smaller and the amount of developer held by the developing devices has also become smaller. Therefore, there is a problem in that the ratio of replenishment toner to the developer held by the developing device becomes low, making it difficult to efficiently stir the developer. Particularly in the developing device of a color image device that produces many solid images, it is desired to have a large amount of toner to be replenished and more efficient agitation.

The present invention has been made in view of the above problems, and enables stable image formation by efficiently stirring the developer and replenishment toner in the developing device and suppressing fluctuations in the toner concentration of the developer in the developing device. The purpose is to provide a developing device. It is an object of the present invention to provide a developing device that suppresses fluctuations in image density and tone, particularly in a color developing device that produces many solid images, and is effective for high-speed image forming devices.

[Means for Solving the Problems] According to the present invention, the above object is achieved by: In a developing device including a plurality of developer stirring and conveying means each having a spiral member provided on a shaft within a developer storage container, the above-mentioned developer The agitating and conveying means are arranged in parallel at a predetermined interval in a direction perpendicular to the axis, and the conveying directions of adjacent developer agitating and conveying means are opposite to each other, and the conveying direction of one developer agitating and conveying means is A partition member is provided between each developer agitation and conveyance means so that the terminal end of the developer agitation and conveyance means communicates with the start end in the conveyance direction of the other developer agitation and conveyance means to form a developer circulation path. This is achieved in that the conveying force at the starting end of the means in the conveying direction is set to be greater than the conveying force at other parts in the conveying direction.

[Function] According to the present invention, the developer existing at the starting end in the conveyance direction of the first developer agitation conveyance means is not stirred by the spiral member provided on the shaft, and is therefore subjected to a predetermined conveyance force in the axial direction. and is conveyed to reach the terminal end in one conveyance direction. The developer that has reached the end of the net is blocked by the twill member or the inner wall of the developer storage container, and moves toward the communication portion formed between the inner wall of the developer storage container and the partition member. The developer that has passed through the communication portion is sent to a starting end in the transporting direction of the second developer agitation and transport means, or the transporting force at the starting end is set to be greater than other parts. , to compensate for the temporarily weakened conveying force in the communication portion and to send out the developer without any delay. The delivered developer is not stirred by the spiral member and is transported in the axial direction with a predetermined transporting force, and reaches the terminal end of the second developer stirring and transporting means in the transporting direction. If the developer agitation and conveyance means is disposed on the tool, then the developer agitation and conveyance is carried out via another developer agitation and conveyance means, and if there are two developer agitation and conveyance means, the second developer agitation and conveyance is carried out. The developer is returned from the means to the starting end of the first developer stirring and conveying means. At this time, the conveyance force may be temporarily weakened because the developer passes through the communication section as described above, or the conveyance force may be set to be large at the starting end of the first developer agitation conveyance means. Sends out developer without a hitch. In this way, the circulation of the developer becomes smooth and without any lag, and sufficient agitation is performed.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 1 to 5 of the accompanying drawings.

In FIG. 1, l is a developer storage container.

An opening is formed in the front (upper side in FIG. 1) of the developer storage container, and in the opening, a developing sleeve 2 serving as a developer carrier has a fixed magnet 3 therein so as to be rotatable. It is arranged. Behind the developing sleeve 2 is a shaft 4. S
Screws 8°9, which are developer agitation and conveyance means and have spiral members 6 and 7 on top, are lined up at a predetermined interval in a direction perpendicular to the shafts 4 and 5, and are arranged so that the conveyance directions are opposite to each other. has been done. A partition wall IO serving as a partition member is provided between the screws 8 and 9, and divides the inside of the developer storage container into a developing chamber at the front and a supply chamber at the rear. Further, communication portions A and B are provided between both ends of the partition wall 10 and the side wall of the developer storage container, and the terminal end portion 8b of the screw 8 in the conveyance direction (indicated by arrow C in FIG. 1) , a starting end 9a of the screw 9 in the conveying direction (indicated by an arrow in FIG. 1), and a terminal end 9b of the screw 9.
and the starting end 8a of the screw 8, respectively, to form a developer circulation path. At the terminal ends 8b and 9b, the direction of the screw is reversed,
The developer is delivered to the starting end portions 9a and 8a, respectively. On the other hand, the screws at the starting ends 9a and 8a have two threads, and are set to have a large conveying force.

Next, the overall configuration of the apparatus of this embodiment will be explained using FIG. 2.

In FIG. 2, reference numeral 3 denotes a photosensitive drum 11 as a latent image carrier which is rotated at a constant speed in the direction of arrow E, and an electrostatic latent image is formed on the surface of the photosensitive drum II by electrophotography. After this electrostatic latent image is developed by the developing bag M12 of this embodiment, it is transferred to a transfer medium (not shown).

The developing device 12 includes a developing sleeve 2 for holding the developer 13, a fixed magnet 3 in the developing sleeve 2, screws 8 and 9 for transporting and stirring the developer I3, and a regulating plate 1.
The F developer 13 contained in the developer storage container 1 of the developing device 12 is a two-component developer consisting of toner and carrier.

A portion of the developer 13 in the developer storage container 1 is held on the developing sleeve 2 by the magnetic force of the fixed magnet 3, and the developer 13 is held on the developing sleeve 2 by rotation of the developing sleeve 2 in the direction of arrow F. As the developing sleeve 2 rotates, it is transported upward and reaches the regulation plate 14 mentioned above. A part of the developer 13 passes through the regulation plate 14 and reaches the developing area G where the developing sleeve 2 and the photosensitive tram 11 face each other. Then, at that position, electric @tS
Due to the superimposed alternating voltages of DC and AC applied to the developing sleeper 2, some of the toner particles are transferred to the photosensitive tram 11, and the remaining toner and carrier are further conveyed on the developing sleeper 2 and stored again as developer. Collected in container l. Note that the method of transferring the toner onto the photosensitive tram 11 is as follows:
The method is not limited to the above method.

On the other hand, the developer 9 regulated by the regulation plate 14 is pushed by the developer 13 from behind and rises along the regulation plate 14, and when it reaches the earthen wall of the developer storage container L, it reverses and follows the path of arrow H. It then descends and reaches the lower part of the developer storage container l again. In this way, the developer 13 continues to circulate within the developer storage container 1, or the toner is consumed for development, so that the toner concentration within the developer storage container 1 gradually decreases.

This change in toner concentration is detected by a concentration detection device 16 provided at the upper part of the developing device 12, and based on the detection signal, a developer replenishment screw I8 in a hopper 17, which is a toner replenishment device, and a screw 9 on the replenishment chamber side are , the rotation of the screw 8 on the developing chamber side is controlled.

Incidentally, replenishment toner 19 is stored in the hopper 17, and 1 g of replenishment toner is conveyed through the lower part of the hopper 17 as the replenishment screw 18 rotates.
The hopper 17 is guided through a replenishment port 2a that opens at the end thereof. Then, this replenishment toner 19 falls from the supply port zO, is conveyed by the screw 9 installed in the developer storage container I, and is mixed with the developer 13 in the developer storage container 1.

Next, stirring and circulation of the developer by the screw 9 on the supply chamber side and the screw 8 on the development chamber side will be explained using FIG. 1.

The developer in the replenishment chamber is conveyed in the D direction by the rotation of the screw 9, and at the terminal end 9b in the conveyance direction, the developer is transferred to the communication portion A.
is delivered to the developing chamber side, is conveyed in the C direction by the screw 8 on the developing chamber side, and is connected to the communication section B at the terminal end 8b.
It passes through and is delivered to the supply room.

In this way, the developer is circulated back and forth with the partition wall IO as a boundary by the two screws. During this time, in the developing chamber side, even though the toner is not conveyed to the screw 8, the developing sleeper is rotated as described above to circulate along the arrows F and H shown in FIG. 2 along with the developing sleeper. Further, on the supply chamber side, the toner is circulated without being supplied from the hopper 17.

A return screw is provided at the end of each screw in the conveyance direction, and the return screw blocks further conveyance force and delivers the developer to the opposite screw side in each communication portion. Generally, the developer tends to stay in this delivery section, and by reducing this stagnation, the efficiency of circulation can be improved. In order to increase the transport efficiency of this delivery section, the spiral member of each screw is provided in two turns at the starting end in the transport direction of each screw. Therefore, the circulation of the developer in the delivery section becomes smooth, and even when a large amount of replenishment toner is used, sufficient agitation can be achieved.

Next, the toner degree control method will be explained in detail with reference to FIGS. 2 to 5.

The L-1 degree detection device 16 is arranged to detect the flow of the developer 13 inside through a transparent window 21 provided in the regulation plate 14 . In this concentration detection device 16, as shown in FIG. 3, the irradiated light from one of the two-way light emitting elements 22 is incident on the light receiving element 23. Then, the other irradiated light is focused through the slit 24 and then enters the light receiving element 25. The output signal t from the light-receiving element 23 changes according to the toner concentration, while the output signal ``t'' from the light-receiving element 25 is adjusted so that it becomes the same output as the light-receiving element signal t at the specified toner concentration. Both signals t and r enter the differential circuit 26 in FIG. 2, from which a signal S corresponding to the difference between r and t is output.

The signal S is input to the heptad driver 27, and the value of the signal S is used to control the rotation time of the motor 28, which is the drive source for the screw I8. In other words, a preset drive time data table (hereinafter referred to as replenishment data table)
The driving time of the motor 28 is determined by selecting the one corresponding to the value of 5 from among them.

In order to drive the motor 28 in this way, the amount of toner supplied from the hopper 17 corresponding to the toner consumption of the developer is t=J.
Becomes Noh. In addition, the Oki signal S is manually operated by another motor driver 29. Therefore, by selecting the one corresponding to the value of S from the preset data fills (hereinafter referred to as stirring data fills), the motor 3
0 drive time is determined and the drying time 30 is driven. Here, the motor 30 is.

This is the motor that drives the screw 8.9. -F The stirring time for the stirring cheetah full is set so that the amount of toner to be replenished is sufficiently stirred for the value of S, so that the stirring time corresponds to the amount of toner to be replenished. In other words, it is possible to perform optimal stirring according to the amount of toner consumed.

FIG. 4 shows the relationship between the signal S and the rotation time of the motor 28.
The figure shows a club showing the relationship between the signal S and the rotation time of the motor 3D. The data shown in FIGS. 4 and 5 are written in the replenishment data file and the stirring data file, respectively. Therefore, even outside the limited development process time for developing the latent image on the photosensitive drum 11 from the developing sleeve 2, toner is replenished from the hopper at a speed suitable for the amount of toner consumed. The developer in the developing device can be stirred according to the amount of toner supplied.

In this embodiment, a developing sleeve driving means (not shown),
Although the drive motor 30 that drives the screws 8 and 9 for stirring the developer has been described independently, it is also possible to adopt a configuration in which the drive motor 30 rotates the developing sleeve 2, the screws 8, and the screws 9 synchronously. . In that case, the surface potential of the photosensitive drum and the output of the developing bias 15 may be adjusted so that the toner from the developing sleeve does not transfer to the photosensitive drum during the non-developing process. In addition to the optical method shown in FIG. 3, any known method such as magnetic change detection or sunblink detection may be used as a toner concentration detection method.

Additionally, the relationship between toner concentration and replenishment amount (replenishment time) is also the fourth factor.
The relationship is not limited to a linear relationship as shown in the figure, but any correspondence relationship such as an exponential function or a multi-stage relationship may be used as long as the relationship is optimal for the system of the apparatus to which the present invention is applied. Similarly, the relationship between toner concentration and stirring time is not limited to that shown in FIG. In addition, as a means for improving the delivery efficiency at one end of the screw, in addition to winding the starting end of each screw with two threads, it is also possible to provide a spiral member with two or more threads, and the pitch of the spiral member It is also possible to make the area larger than other parts.

[Effects of the Invention] As explained above, according to the present invention, since the conveyance force at the starting end of the developer agitation and conveyance means is set to be larger than that at other parts, the developer agitation and conveyance is The efficiency of developer delivery between means is improved. As a result, it becomes possible to provide a developing device in which uniformity of the developer per toner replenishment is accelerated and density fluctuations are reduced.

Further, it is possible to reduce the load on the sealing member provided at the end of the shaft and provide a durable developing device.

Furthermore, since there is no local pressure on the developer, deterioration of the developer can be prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration around the developer stirring and conveying means of an apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of the entire apparatus according to an embodiment of the present invention, including the apparatus shown in FIG. 1. FIG. 3 is a vertical cross-sectional view of the density detection device of the device shown in FIG. 2, and FIG. 4 shows the output signal of the differential circuit of the device shown in FIG. 2 and the developer stirring and conveying means in the toner supply device. FIG. 5 shows the relationship between the output signal of the differential circuit of the device shown in FIG. 2 and the rotation time of the drive source of the developer stirring and conveying means in the developer storage container. It is a diagram. l...Developer storage container 2...Developer carrier (developing sleeve) 4, S-
-...Shaft 6.7...Spiral member 8.9...Developer stirring and conveying means (screw)
10...--Partition member (partition wall)

Claims (3)

[Claims] (1) In a developing device having a plurality of developer agitation and conveyance means each having a spiral member on its axis within a developer storage container, the developer agitation and conveyance means are arranged in parallel at a predetermined interval in a direction perpendicular to the axis; Adjacent developer agitation and conveyance means are arranged so that the conveyance directions are opposite to each other, and the terminal end in the conveyance direction of one developer agitation and conveyance means and the start end in the conveyance direction of the other developer agitation and conveyance means. A partition member is provided between each of the developer agitation and conveyance means so as to communicate with each other to form a developer circulation path, and the conveyance force at the starting end of each developer agitation and conveyance means in the conveyance direction is equal to that of the other developer agitation and conveyance means in the conveyance direction. A developing device characterized in that the developing device is set to be larger than the conveying force in the portion. (2) The conveying force at the starting end in the conveying direction of the developer agitation conveying means is made larger than the conveying force at other parts in the conveying direction by winding the spiral member in multiple threads at the starting end. The developing device according to claim 1, wherein the developing device is set. (3) The conveying force at the starting end in the conveying direction of the developer agitation conveying means can be increased by making the pitch of the spiral member at the starting end larger than the pitch at other parts in the conveying direction. 2. The developing device according to claim 1, wherein the developing device is set to be larger than .