JP2843643B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for developing an electrostatic latent image on an image carrier in an image forming apparatus such as an electrophotographic copying machine or a printer. The present invention relates to a developing device for developing an electrostatic latent image with a one-component toner.

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine and a printer, an electrostatic latent image formed on an image carrier by charging and exposure is developed by a developing device and visualized as a toner image. .

In the above development, the insulating toner composed of insulating colored particles is mainly composed of a synthetic resin such as styrene acryl or polyester, which is mixed with a carrier such as iron powder and glass beads, stirred, and charged by frictional charging. Applying a developing bias voltage to the developing sleeve, or using a material that contains a magnetic material in the main component of synthetic resin and has a charge by being transported on a metal cylindrical developing sleeve. In general, the toner is caused to fly and adhere to the electrostatic latent image on the image carrier, developed, and the electrostatic latent image is visualized as a toner image.

The development characteristics of these insulating toners are greatly affected by the amount of charge (hereinafter referred to as tribo) of the toner, and in order to obtain a good image by development, the toner on the development sleeve is, on average, within a predetermined range. It is desirable to maintain the amount of tribo.

That is, when the toner has a low triboelectricity, the force of transferring from the developing sleeve to the electrostatic latent image on the image carrier is weak, and the density of an image obtained by development is low. On the other hand, when the tribo becomes extremely high (generally, the toner, which is a small particle, has a large surface area per volume, so the tribo tends to be high). Conversely, the toner itself strongly adheres to the developing sleeve due to the reflection power of the toner itself,
The lowermost layer of the toner layer on the sleeve is difficult to separate. In such a case, the tribo does not rise because the other toner is less likely to be triboelectrically charged with the sleeve surface, and the density of the image obtained by the development is similarly reduced. Further, since the number of times of frictional electrification between toners increases, so-called inverted toner charged to a polarity opposite to a desired polarity easily occurs.

Such a phenomenon is likely to occur particularly when new toner having a small amount of tribo is mixed with old toner having a relatively small amount of tribo just after replenishing the toner in the developing device.

As can be seen from FIGS. 4 (a) to 4 (c), which show changes in the toner particle size distribution during a large number of continuous developments, the newly replenished toner having a small amount of tribo (the newly replenished toner particle In FIG. 4 (a)), a relatively large amount of toner having a small particle diameter, which tends to have a triboelectricity, is relatively large on the sleeve (the particle size distribution of the toner on the sleeve is shown in FIG. 4 (b)). Shown), toner having a small particle size,
In particular, the toner having a particle size of 8 to 12 μm, which most contributes to development, requires a rising time until it has a tribo, so that the image density temporarily decreases. The old toner having a large particle size not consumed in the development (the particle size distribution of the old toner not consumed in the development is shown in FIG. 4 (c)). This is also due to the fact that the so-called reversal fog resulting from this is temporarily increased.

Conventionally, as a means for avoiding the phenomenon of low image density as described above, as shown in FIG. 5, a developing container 12 of a developing device is separated by a partition wall 10 into a small volume developing device in which a developing sleeve 2 is installed. C and a large-volume hopper D containing the toner 3, and a toner cut-out roller 9 provided at the opening of the partition wall 10 separates the hopper D from the developing unit C.
The toner 3 is replenished little by little, or conversely, the toner 3 is replenished little by little while sufficient toner 3 still exists in the developing section C. Further, countermeasures such as supplying the toner 3 to the developing unit C after stirring the toner 3 to some extent in the hopper unit D are taken.

In FIG. 5, reference numeral 1 denotes a photosensitive drum serving as an image carrier facing the developing sleeve 2, reference numeral 7 denotes a developing magnet that is immovably provided in the developing sleeve 2, and reference numeral 8 denotes a developing sleeve 2.
A magnetic blade 11 provided on the top of the toner cartridge 11 is a capacitance detecting type toner remaining amount detecting means provided in the developing section C in the vicinity of the developing sleeve 2.

However, in order to take the above measures,
In any case, the hopper section D needs to have a considerably large toner storage volume (for example, at least 400 cc or more), and in particular, a small electrophotographic apparatus having a copy speed of about 4 to 16 sheets / minute, and a disposable developing apparatus is a disposable type. In an electrophotographic apparatus employing a so-called process cartridge system,
It is a big problem. In order to take the above measures,
A replenishing device for replenishing the toner 3 from the hopper portion D to the developing portion C and various means such as a separately driven motor for appropriately driving the replenishing device for preventing excessive toner replenishment are also required. There is a disadvantage that it becomes high.

Therefore, an object of the present invention is a relatively simple and inexpensive configuration,
It is possible to obtain good images with little density fluctuation such as reverse fog and low density from the beginning to the end of printing during many consecutive printings, and it is also possible to detect in advance and run out of toner with high accuracy in advance. The purpose of the present invention is to provide a developed developing device.

Means for Solving the Problems The above object is achieved by a developing device according to the present invention. In summary, the present invention provides a large-volume toner container containing a one-component magnetic toner in a developing container and a small-volume developing unit provided with a developer carrier, and the toner container and the developing unit With the slit-shaped toner intake port,
The toner accommodating portion is provided with a toner agitating / transferring portion that is constantly rotating during a developing operation, a toner intake magnetic pole of a developing magnet installed in the developer carrier is directed toward the toner intake port, and the developing device is further placed in the developing unit. The developing device further includes a capacitance detection type toner remaining amount detection unit provided in proximity to the developer carrier.

Examples Hereinafter, examples of the present invention will be described in detail.

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention. This embodiment shows a disposable developing device applied to a process cartridge type image forming apparatus.

As shown in FIG. 1, the present developing apparatus includes a large-volume hopper section A and a small-volume developing section B in a cartridge developing container 21 which can be fitted into an image forming apparatus. In the hopper section A, two stirring blades 5 are provided as stirring and transfer means for stirring and transporting the one-component magnetic toner 3 accommodated therein to the developing section B, and fed into the developing section B. A developing sleeve 2 that carries the toner 3 and conveys it to a developing position facing the photosensitive drum 1 is rotatably provided. The developing sleeve 2 has an outer diameter of 20 mm, and the photosensitive drum 1 has an outer diameter of 30 mm. This photosensitive drum 1 is made of an organic photoreceptor.

The toner 3 has styrene acrylic as a main component,
This is a one-component magnetic toner containing 60 parts by weight of magnetite. The stirring blade 5 receives the drive from the photosensitive drum 1 and rotates at half the rotation speed of the photosensitive drum 1, thereby stirring the toner 3 in the hopper A and sending the toner 3 into the developing unit B. The stirring blade 5 is always operated during development and is not stopped. The stirring blade 5 has a bone structure as shown in FIG. 2 in order to prevent the toner 3 in the hopper A from being excessively stirred. A rubber sheet 5a is provided at the tip of the developing unit 3 so that the developing unit 3 can be efficiently fed into the developing unit B.

The toner 3 sent by the stirring blade 5 passes through a slit-like toner intake port 4a of the film 4 provided at the opening of the partition wall 22 of the developing container 21 that separates the hopper section A and the developing section B from the developing section. It is sent into B. When a new developing device 1 is used for the first time, the above-mentioned toner intake port 4a is formed by a service person or a user tearing the film 4 when the new developing device 1 is used for the first time. Are prevented from moving into the developing section B. The film 4 is made of a polyethylene film.

The toner 3 sent into the developing section B is attracted by a magnetic force of a developing magnet 7 installed in the developing sleeve 2 and is carried on the developing sleeve 2. 2 is applied to the developing sleeve 2 to a predetermined thickness by a urethane rubber blade 6 provided so as to come into contact with the upper half peripheral surface of the developing sleeve 2. In the developing section B, an electrostatic capacity detection type toner remaining amount detecting means 18 made of a stainless steel plate is provided at a partition wall 22.

S ₁ pole of the developing pole of the developing magnet 7 has a magnetic flux density of about 850 Gauss on the surface of the developing sleeve 2, also N ₁ pole incorporation pole of toner 3, about on the surface of the developing sleeve 2 It has a magnetic flux density of 850 gauss.

Now, in the present invention, the toner inlet 4a of the film 4 to contact with the hopper A of the developing container 21 and the developing unit B, and toward the peak of the magnetic flux density of the toner uptake pole N ₁ of the developing magnet 7, the uptake The toner 3 in the vicinity of the opening 4a is magnetically restrained, and the lump of the restrained toner 3 is taken in the opening 4a.
Is almost closed. In this case, even if the stirring blade 5 is always operated in the hopper A, excessive toner 3 is not sent to the space near the sleeve 2,
No clogging of the toner 3 occurs. In addition, the hopper portion A depends on the amount of the toner 3 carried by the sleeve 2.
Since the toner 3 is replenished from the inside, the change in the image due to the toner replenishment as described above is extremely reduced.

In this embodiment therefore, the width along the axial direction of the developing sleeve 2 of the slit-shaped toner inlet 4a of the above mentioned film 4 and 4 mm, on the developing sleeve 2 surface of the magnetic flux density by the magnetic poles N ₁ of the magnet 7 The distance between the peak position and the toner intake port 4a is about 8 mm.

If the width of the toner intake port 4a and the distance between the peak position of the magnetic flux density on the surface of the sleeve 2 and the toner intake port 4a are too large, the object of the present invention cannot be achieved, and the size of the developing device can be reduced. I can't do it. Conversely, if it is too small, replenishment and flow of the toner 3 into the developing section B are hindered,
During the development of a solid black image, uneven density and white spots occur. For example, if the outer diameter of the developing sleeve is 20 mm, the magnetic flux density of the toner uptake pole N ₁ of 800 gauss and outside, in the width of the toner inlet 4a is 3mm or less, replenishment occurs failure of the toner 3 to the developing unit B, the toner uptake If the width of the mouth 4a is 20 mm or more, the effect of the present invention was not sufficient.

The width of the toner intake port 4a is preferably 5 to 10 mm.
Was effective. Further, the distance between the toner inlet 4a and the surface of the developing sleeve 2 is 5 to 10 mm, so that the amount of the toner 3 taken in can be stabilized and a space for the flow of the taken toner 3 can be provided. I liked it in that respect. Still angle facing the peak of the magnetic flux density of the toner uptake pole N ₁ is 15 degrees ± toward the center of the toner inlet 4a, when preferably in 5 ° ±,
A stable image could be obtained with respect to changes in conditions such as environmental changes, print pattern changes, and print intervals.

In the present invention, a small-volume developing section B in which the developing sleeve 2 is provided is provided to reduce the space near the developing sleeve 2, and the toner 3 is filled in the developing section B while closing the toner intake port 4 a of the film 4 with the toner 3. Therefore, the shape of the lump of the toner 3 in the space near the developing sleeve 2 becomes substantially constant. When the new toner 3 is replenished from the hopper A, the mass of the toner 3 rapidly breaks down and changes. Therefore, the amount of toner 3 detected by the electrostatic capacity detection type toner remaining amount detecting unit 18 installed in the developing unit B is low. It is possible to detect the running out of toner with high accuracy at a high cost.

According to the configuration of the present embodiment, it is possible to notify that the toner has run out before printing 100 to 200 sheets where white spots occur on an A4 size print image with a print rate of 4%.

FIG. 3 is a sectional view showing another embodiment of the developing device of the present invention.

The developing device according to the present embodiment includes a hopper section A in the developing container 21.
1, a 185 mm-thick mylar sheet 23 is provided in place of the stirring blade 5 in the developing device of the first embodiment described with reference to FIG. 1, thereby stirring and transferring the toner 3 in the hopper A. It is characteristic. Other configurations of the developing device of the present embodiment are the same as those of the developing device of FIG. 1, and the same reference numerals as those shown in FIG. 1 in FIG. 3 denote the same members.

When the toner 3 in the hopper A is solidified by leaving for a long time, tapping, or the like, the stirring blade 5 of the developing device of the first embodiment requires a large driving torque to stir and transport the solidified toner 3. For this reason, the tooth of the drive gear of the stirring blade 5 jumps, or the metal stirring blade 5 itself is bent and deformed, so that the toner 3 cannot easily be stirred and transferred.

Since this is flexible according to the mylar sheet 23, the toner 3 around the mylar sheet 23 can be agitated and transferred while gradually disintegrating. There is no gear tooth jump. According to Mylar sheet 23, the configuration is simple,
There is also an advantage that the price is easy.

When the flexible Mylar sheet 23 is used, the feed amount of the toner 3 may fluctuate depending on the amount of the toner 3 remaining in the hopper portion A. However, in the present invention, as described above, the toner intake port of the film 4 Since the toner 3 is taken in while closing 4a with the toner 3, the amount of the toner 3 taken into the developing section B is relatively stable from the initial use of the developing device to just before the toner 3 runs out, and there is no problem. .

Effect of the Invention As described above, the developing device of the present invention is provided with a large-volume toner storage section containing a one-component magnetic toner in a developing container and a small-volume developing section provided with a developer carrier. The toner accommodating section and the developing section are communicated with each other through a slit-shaped toner intake port, and the toner accommodating section is provided with a toner agitating / transporting means which is constantly rotated during the developing operation, and the developing means installed in the developer carrier. The magnet's toner intake magnet is oriented toward the toner intake, making it a relatively simple and inexpensive configuration, and good images with little density fluctuations such as reverse fog and low density from the beginning to the end of printing during multiple continuous printing. Can be obtained. Furthermore, since a toner amount detection unit of a capacitance detection type is installed in the image developing unit in proximity to the developer carrier,
It is now possible to detect and run out of toner with high accuracy in advance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention. FIG. 2 is a perspective view showing a stirring blade installed in a hopper of the developing device of FIG. FIG. 3 is a sectional view showing another embodiment of the developing device of the present invention. FIGS. 4 (a), (b) and (c) are graphs showing a change in toner particle size distribution during a large number of continuous developments in a conventional developing device. FIG. 5 is a sectional view showing an example of a conventional developing device provided with a developing section and a hopper section. 2: Developing sleeve 3: One-component magnetic toner 4a: Toner intake port 5: Stirring blade 7: Developing magnet 18: Toner remaining amount detection means 23: Mylar sheet A: Hopper section B: Development section N ₁ : Toner intake pole

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-96978 (JP, A) JP-A-3-55577 (JP, A) JP-A-2-285374 (JP, A) JP-A-2- JP-A-64-18168 (JP, A) JP-A-62-75479 (JP, A) JP-A-61-262765 (JP, A) JP-A-61-57967 (JP, A) Japanese Utility Model Showa 63-94451 (JP, U) Japanese Utility Model Showa 62-120762 (JP, U) Japanese Utility Model Showa 62-84062 (JP, U) Japanese Utility Model Showa 61-119163 (JP, U) Japanese Patent Publication No. 5-67233 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08-15/095

Claims (2)

(57) [Claims] A large-volume toner storage section containing a one-component magnetic toner in a development container and a small-volume development section provided with a developer carrier are provided, and the toner storage section and the development section are slit. A toner agitator that constantly rotates during the developing operation in the toner container,
A transfer means is provided, and a toner intake magnetic pole of a developing magnet installed in the developer carrier is directed toward the toner intake port, and further, a capacitance detection type toner remaining in the developing section is brought close to the developer carrier. A developing device provided with an amount detecting means. 2. The developing device according to claim 1, wherein the width of the slit-shaped toner intake port is 3 to 20 mm.