JPH033229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device employed in, for example, an electrophotographic copying machine.

Currently, in electrophotographic copying machines and the like, many developing devices are in practical use that develop an electrostatic latent image formed on a photoreceptor using a powder developer consisting of two components, toner and carrier.

In the development process of electrophotography, etc., which uses a powder developer consisting of two components, toner and carrier, the toner component in the developer electrostatically adheres to the electrostatic latent image formed on the photoreceptor. So-called development is performed. Therefore, unless new toner is replenished to correspond to the amount of toner removed from the developer during development, the toner specific density of the developer will gradually decrease and the density distribution of the copied image will change. Correspondingly, unevenness occurs in the density distribution within the developer. Therefore, in addition to the original developing function, a developing device that uses a two-component powder developer receives fresh toner from a toner replenisher corresponding to the amount of toner consumed during development. It is necessary to have a stirring function to sufficiently stir the toner with the developer to charge the toner to a predetermined amount and at the same time to even out the density unevenness that occurs.

Incidentally, the space occupied by the developing device in the copying machine is limited, and the circulation cycle of development, stirring, and development naturally takes a short time. One of the conditions for a developing device with good performance is how quickly and uniformly the replenished toner can be dispersed within the developing device within this short period of time, that is, how well it can be stirred. However, in general, this type of developer is a special powder extremely lacking in self-flowing properties, and often tends to be insufficiently stirred (stirred insufficiently). Although agitation is carried out in the circulation flow that is the original development process, the most effective method is to provide a large movement of the developer in the width direction of the developing device, that is, in the direction perpendicular to the circulation flow. That is, when the amount of movement in the perpendicular direction in the stirring section is small, the unevenness in the distribution of the falling amount of toner replenished from the toner replenisher is directly reflected in the unevenness of the developer concentration in the developer device. In addition, since the toner replenisher normally replenishes toner in a width range corresponding to the width of the developing device, even if there are parts with a large amount of toner and parts with a small amount of toner within the replenishment range, there is little movement in the width direction. Since it is not possible to equalize slight variations in the amount of toner within the developing device, it is necessary to make the distribution of the amount of toner falling from the toner replenisher uniform, making the design, assembly, and adjustment of the toner replenisher itself difficult.

Furthermore, if copying is performed continuously in which toner consumption is concentrated in only a portion of the development width, and an imbalance occurs in the specific toner density between areas where toner consumption occurred and areas where toner consumption did not occur, this problem may occur. A problem arises in that uniformity cannot be achieved.

Therefore, in recent years, two screw-like stirring shafts that move the developer in opposite directions in the developer collection and stirring section have been installed in parallel, allowing the developer to rotate around the shaft and move the developer in the axial direction. As a result, a developer circulation loop covering the entire development width is formed while being stirred, and a system with improved agitation efficiency compared to the conventional rotary blade type, deflection plate type, or a combination of the two has been developed and put into practical use. has been made into

When using these multiple screw-shaped stirring shafts,
If we focus only on the stirring section, we can form a near-ideal developer circulation loop.

However, in actual development conditions, the same developer does not always stay in the stirring section, and most of the developer circulates in a loop of stirring section -> developing section -> stirring section. For minute parts, stirring using a screw-like stirring shaft is only temporary. Therefore, in the case of this stirring method, the stirring efficiency is considerably better than that of the conventional rotary blade type, deflection plate type, or combination of both types, but it takes time to balance the specific toner concentration within the device.

In addition, when toner is replenished from one end of the developing device, toner is supplied to the developer entering the toner replenishing section by the action of two screw-like agitating shafts, resulting in a highly concentrated developer. Agent is delivered into the developer device. The high-density developer is gradually stirred and mixed with the developer forming a development loop, and is intended to eventually reach a predetermined specific toner density. In this case, although the developer has a considerably high concentration after toner is replenished, no means is taken to regulate the mixing ratio of the developer forming a development loop. Therefore, in reality, most of the high-concentration developer after toner replenishment is mixed in the near chamber where it enters the developing device from the toner replenishing section, and very little reaches the opposite end of the toner replenishing section. The distribution of the specific toner concentration within the toner supply section is disequilibrium, increasing closer to the toner replenishing section, and the advantage of screw shaft agitation is not utilized.

As described above, there are several methods of agitation within the developing device, but the current technology depends largely on the characteristics of the toner replenisher (i.e., the distribution of the amount of toner falling), and does not affect the entire device. In terms of design, manufacturing, assembly, and adjustment, there is a need for a developing device with good agitation performance that is not affected by the performance of the toner replenisher.

The present invention has been made based on the above circumstances, and its purpose is to efficiently stir and circulate the developer without causing it to partially stagnate, even if there is a large deviation in the toner supply amount distribution. It is an object of the present invention to provide a developing device that can perform uniform and good development even when there is an imbalance in toner specific density due to copying.

Hereinafter, the present invention will be explained with reference to an illustrated embodiment. Reference numeral 1 in FIG. 1 is a case forming the main body of the developing device, and the inside of this case 1 is divided by a partition plate 2 into a developing section 3 and a collecting and agitating section 4 for developer a. Inside the developing section 3, a developing magnetic roll 5 serving as a developing means is arranged in the upper part, and a conveying magnetic roll 6 for transporting the developer a in the stirring area to the magnetic roll 5 is arranged in the lower part. These magnetic rollers 5 and 6 each have a structure in which a magnet body 8 is fixedly arranged inside a rotating sleeve 7 made of a non-magnetic material.

Further, the partition plate 2 has a scraper 9 integrally formed at its upper end portion as a developer collecting means for scraping off the developer a adsorbed on the developing magnetic roll 5 and guiding it to the collecting and agitating section 4. At the same time, a doctor blade 10 is integrally molded at the lower end portion of the developer blade 10 to limit the thickness of the developer a that is attracted to the conveying magnetic roll 6 and is conveyed to the developing magnetic roll 5 side. Further, a magnetic shielding plate 20 for shielding leakage magnetic flux from the conveying magnetic roll 6 is integrally provided on the surface of the partition plate 2 facing the collecting and stirring section 4 side.

Further, a doctor blade 12 is attached to the lower edge of the opening of the developing magnetic roll exposure window of the case 1 to regulate the thickness of the developer a guided toward the drum-shaped photoreceptor 11 side.

Furthermore, two screw-shaped stirring shafts 13 and 14 are rotatably arranged in parallel in the collecting and stirring section 4 . As shown in FIG. 2, these stirring shafts 13, 14 have long threaded portions 13a, 14a wound in the same direction, and long threaded portions 13a, 14a wound in the opposite ends.
A short threaded portion 13b, 1 whose winding direction is opposite to that of a.
4b, and a guide 15 having a substantially J-shaped cross section is provided below one of the stirring shafts 14 along the outer peripheral surface of the stirring shaft 14.

Further, the height of the rising wall portion 15a located between the stirring shafts 13 and 14 of the guide 15 is formed so as to gradually become lower in the direction in which the developer a is transferred due to the rotation of the stirring shaft 14, as shown in FIG. has been done.

Furthermore, as shown in FIG. 3, one end of the collecting and stirring section 4 protrudes from the main body of the developing device, and serves as a toner replenishing section 16 that receives toner from a toner replenishing device (not shown). This toner supply section 1
6 has a toner receiving port 17 at a position opposite to the ends of the stirring shafts 13 and 14, and the stirring shaft 1
A partition plate 18 is provided between the toner receiving port 3 and 14, with one end continuous with the rising wall portion 15a of the guide and the other end extending to the vicinity of the opening edge of the toner receiving port 17. It is being

Note that 19 shown in FIG. 1 is a cover that releasably closes the upper end opening of the case 1. next,
The operation of the above embodiment will be explained.

First, in the developing state, the developing magnetic roll 5
is rotating simultaneously in the direction of arrow A, the conveying magnetic roll 6 in the direction of arrow B, the first stirring shaft 13 in the direction of arrow C, and the second stirring shaft 14 in the direction of arrow D. In this state, the developer a in the collecting and agitating section 4 is first drawn out from the collecting and agitating section 4 by the magnetic roll 6 and travels on the magnetic roll 6 in the direction of arrow B. The developer a on the magnetic roll 6 is delivered to the magnetic roll 5 in a region close to the magnetic roll 6 and the magnetic roll 5 . The developer a transferred to the magnetic roll 5 is regulated to a predetermined thickness by scraping off excess thickness of the developer a by a doctor blade 12. That is, the doctor blade 12 separates the flow in the directions of arrows A and E. The developer a in the flow E falls as it is to the lower part of the case 1 forming the main body of the developing device, is again attracted to the magnetic roll 6, and merges with the developer a drawn out from the collecting and agitating section 4. The developer a on the magnetic roll 5 that has passed through the doctor blade 12 forms a so-called magnetic brush shape due to the action of the magnet 8 in the vicinity of the photoreceptor 11 and the magnetic roll 5, and slides into contact with the photoreceptor 11 for development. Do this.

Development is accomplished by electrostatically transferring toner components in the developer a to the photoreceptor 11. Therefore, the developer a on the magnetic roll 5 after passing through this area has a low toner specific density. When the developer moves further in the direction of arrow A, the developer a on the magnetic roll 5 is forcibly peeled off from the magnetic roll 5 by the scraper 9 and falls into the collection agitation section 4 .

Two stirring shafts 13 and 14 in the collecting and stirring section 4
are rotating in the directions of arrows C and D, respectively, and the rotation of these stirring shafts 13 and 14 causes the developer a to circulate in the directions of arrows F ₁ and F ₂ in FIG. 2. Therefore, in the collecting and stirring section 4, the developer a is transferred to the magnetic roll 5.
→Collection stirring section 4 →Flow G of magnetic roll 6 and arrow
Two loop circulation flows of F ₁ and F ₂ are formed at the same time.

A part of the developer a collected from the magnetic roll 5 is guided to the toner replenishing section 16 by the flow of arrow _F1 . The partition plate 18 of the toner supply section 16 is connected to the stirring shaft 1.
3, it has the effect of ensuring that the developer a entering the developer is transferred to the side of the agitation shaft 14 that is sent into the developing device. Toner replenishment is performed while the developer a is being transferred from the stirring shaft 13 to the stirring shaft 14. The timing of replenishment is appropriate depending on the amount of toner consumed during development.

On the other hand, the amount of developer a in the area receiving toner replenishment is a part of the developer a in the device, and the developer a immediately after toner replenishment locally has a much higher concentration than the predetermined toner specific concentration. There is. To smooth out the local density unevenness created by such toner replenishment and the density unevenness that gradually occurs due to development into a uniform density without unevenness in a short time in the stirring and development loop. is necessary.
When examining the axial movement of the developer a by the stirring shafts 13 and 14, as mentioned above, the stirring shaft 14
On the other hand, if there is no appropriate guide in the moving direction, it is rare for the developer a in the same portion to move completely from the starting point to the ending point. The developer a repeats an inflow→movement→discrete→inflow process with respect to the stirring shaft 14, gradually replacing it with another developer a, and moving as a whole in the axial direction.

Therefore, if there is no appropriate conveyance guide for the screw shaft 14, the high-concentration developer after toner replenishment will quickly separate from the screw shaft 14. Furthermore, the flow F ₁ to the toner replenishing section 16 is close to each other, and as a result, a high concentration area is formed in this vicinity, making it impossible to achieve good diffusion throughout the entire developing device.

The guide 15 solves the above-mentioned problems all at once.

As shown in FIG. 3, the height of the rising wall portion 15 of the guide 15 decreases as it moves away from the toner supply section 16, and the length of the guide 15 is made slightly shorter than the length of the developing device. Therefore, the high concentration developer a after toner replenishment is transferred to the stirring shaft 14.
By the action of the guide 15, the toner is supplied and sent out (arrow F ₂ ). As the rising wall portion 15a of the guide 15 gradually becomes lower, the high-concentration developer a sequentially overflows into the collecting and agitating portion 4 in fixed amounts, and is distributed in the length direction of the developing device, and at the same time, the high-concentration developer a flows into the scraper. The developer a falling and collected from the developer 9 is appropriately stirred and mixed during the rotation of the stirring shaft 13 and flowing in the direction of the magnetic roller 6 .

As a result of experiments, it was found that when the falling point of the developer a collected from the scraper 9 is centered approximately at the center of the two stirring shafts 13 and 14, the best stirring can be performed and no concentration imbalance occurs. I understand. If the distribution of the falling amount is extremely biased toward one of the stirring shafts 13, 14, the conveyance amount of that stirring shaft 13, 14 will increase, and the developer a will be biased in that direction, causing the other stirring shaft 14, 13 Near the end of the area, the amount of developer a decreases, and problems such as uneven concentration of developer a in that area tend to occur.

As described above, the guide 15 has a rising wall portion 15a that is gradually lowered in the direction of movement.
An even better agitation condition was obtained by setting the wall surface height to such a level that the developer a inside the guide 15 and the other developer a are completely separated from each other for a certain length L from the outlet part of the guide 15. . Although the high-concentration developer a is not directly supplied into the collecting and stirring section 4 in this region of length L, the developer a whose concentration has been increased by being stirred and mixed in a portion farther than the region L is already present. Stirring shaft 13
Since the toner is appropriately moved toward the toner replenishing section 16, the toner specific density increases similarly to other parts, and the density within the developing device is made uniform.

On the other hand, the developer a filled in the developing device is
Must be utilized 100% effectively. Developer a stagnates in a part of the device and does not contribute to development agitation
If there is, a burden is placed on the remaining developer a, which shortens the life of the developer a. Increasing the utilization rate and agitation efficiency of the developer a in the developing device is effective for extending the life of the developer a. However, even in the limited space of the developing device, there are often areas where the developer a does not flow due to the inappropriate cross-sectional shape of the developing device due to the behavioral characteristics of the special powder called developer a. Generally, when there is leakage magnetic flux from the magnetic roller, the developer a is restrained by the magnetic force on the surface of the fixed member installed close to the magnetic roller on the opposite side of the magnetic roller, and the flow of the entire developer is interrupted. Adversely affects stirring. That is, the collecting and stirring section 4 side of the partition plate 2 is mainly affected by the leakage magnetic flux from the magnetic roll 6. The developer a having a certain thickness on the partition plate 2 is fixed as if on the partition plate 2 by the magnetic force from the magnetic roll 6. Such developer a does not contribute to the stirring or development of other developers a.

The magnetic shielding plate 20 protects against such leakage magnetic flux area.
By providing this, the above-mentioned problems can be solved. In this embodiment, a 0.4 mm thick mild steel plate is provided integrally with the partition plate 2 over the entire width of the developing device as a magnetic shielding plate at the position shown in FIG. As a result, the developer a in the collecting and stirring section 4 does not accumulate anywhere.

As described above, the collecting and stirring section 4 includes a plurality of screw-shaped stirring shafts 13 and 14 provided so that the developer a moves in mutually opposite directions, and these stirring shafts 1.
The developer a is provided along the rotating circumferential surface of the agitation shaft 14 such that a rising wall 15a is interposed between the developer a and the agitation shaft 14.
a guide 15 that transports the developer only in the axial direction; and a guide 15 that collects the developer a after passing through the development position from the magnetic developing roll 5, and collects the developer a such that the center of the flow path thereof is the stirring shaft 13, 14. Developing section 3 shown by arrow G
→ Collection and agitation section 4 → 2 of developer a between the development section 3 and the loop in the collection and agitation section 4 indicated by arrows F ₁ and F ₂
Two circulation systems can be clearly formed at the same time, and by blocking the leakage magnetic flux to the collecting and agitating section 4, there is no accumulation of developer a in the developing device, and all the developer a is developed and agitated. Moreover, the toner flow becomes smooth, and the specific toner density within the developing device is always uniform. Therefore, even if the copy size is uneven, density unevenness in the developing device will not be unbalanced.

Note that the present invention is not limited to the above embodiment.

That is, in the embodiment, the guide 15 is provided only on the delivery stirring shaft 14, but a similar guide may be used on the other stirring shaft 13 as well. In the structure of the embodiment, the toner replenishing part 16 has been described as having a shape that protrudes from one end of the apparatus main body, but the shape is not limited to this, and the toner replenishing part 16 is provided in a part of the inside of the apparatus main body. It can be anything.

Furthermore, although the toner replenishing section 16 has been described as being located at one end of the main body of the apparatus, it is not limited thereto, and may be located over almost the entire width of the apparatus as in many conventional examples. In this case guide 15
It is clear that the specific shape of the figure will be somewhat different from that of the embodiment. The magnetic shielding plate 20 may not be provided if the influence of leakage magnetic flux is extremely weak. The rotating directions of the magnetic rolls 5, 6 as well as the stirring shafts 13, 14 are not limited to the directions shown in the embodiments. Any rotation direction suitable for the device may be used. Of course, the embodiments are not only effective for magnetic brush developing devices, but can also be applied to other types of developing devices. Not only copy machines but also similar principles
The present invention can also be applied to facsimile and electronic printer devices having a mechanism, for example.

In addition, it goes without saying that the present invention can be modified in various ways without departing from the gist of the invention.

As explained above, according to the present invention, since the developer collected by the developer collection means is dropped into the flow of developer that is circulated in a loop by a combination of a plurality of stirring shafts and guides, The developing device is designed to efficiently stir and circulate the developer without causing it to partially stagnate, and to prevent the occurrence of imbalances in the toner specific density due to large unevenness in the distribution of toner replenishment or copying. It is possible to maintain the developer concentration within the container in an even and balanced state at all times. In addition, the collected developer is mixed with the collected developer without being partially stagnated and becomes ready to be supplied, which is especially useful for small-sized developing devices where the amount of developer is small and the cycle time before resupply is short. It produces the same effect.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a longitudinal side view, FIG. 2 is an explanatory diagram showing the state of developer circulation in the collecting and agitating section, and FIG. 3 is a toner replenishing section and a toner collecting section. It is a perspective view of a stirring part. 4... Collection stirring section, a... Developer, 13... First screw-shaped stirring shaft, 14... Second screw-shaped stirring shaft, 5... Developing means (magnetic roll for development), 9... ...Developer recovery means (scraper), 15
...Guide, 15a...Rising wall section.

Claims (1)

[Scope of Claims] 1. A developer supplying means for supplying the developer collected in the collecting and agitating section to the development position; and after the developer supplying means supplies the developer to the development position, the developer that remains after the developer is supplied to the development position. a developer collecting means for collecting developer and re-supplying the developer to the collecting and agitating section, each of which is perpendicular to a first direction in which the developer collecting means supplies the developer to the collecting and agitating section; first and second screw-shaped agitation shafts that are rotatably provided to move the developer in a second direction and in opposite directions, and at the same time allow the developer to pass in the first direction; The screw-shaped stirring shaft is provided at least on the first screw-shaped stirring shaft of these first and second screw-shaped stirring shafts, and guides the developer along the second direction of the axial direction of the first screw-shaped stirring shaft. It has a bottom surface and a side wall erected approximately midway between the second screw-like agitating shaft, and the side wall allows the developer guided along the second direction to gradually move. a guide configured to gradually become lower in height so as to pass over the second screw-like stirring shaft; and a replenishing developer disposed corresponding to the upstream portion of the developer guide in the second direction in the guide. a developer supplying means, and when the developer recovery means supplies the developer to the collection and agitation section along the first direction,
A developing device characterized in that the developer is guided so that the center of the developer flow path corresponds to a substantially intermediate portion of each of the first and second screw-like stirring shafts.