JPH03174174A - Toner replenishment control method - Google Patents

Abstract

PURPOSE:To stabilize the quality of a copied image by intermittently forming the toner image of a standard mark plate in an image forming device provided with a toner recycling means. CONSTITUTION:In the copying machine provided with the toner recycling devices 52 and 53, the latent image of the standard mark plate 22 with reference density which is formed on an image carrier 10 is developed and then the density of the toner image of the plate 22 is detected. By processing the detected information, the replenishment of toner to a developing means 30 is controlled. In such a case, the latent image of the plate 22 is formed every N copies so as to reduce the returning quantity of recycled toner. Thus, the excellent quality of the copied image is stably obtained by the copying machine provided with the toner recycling devices 52 and 53.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method of controlling toner replenishment to a developing unit of an image forming apparatus such as an electrophotographic copying machine that forms an image using an electrophotographic method, and particularly relates to a method for controlling toner replenishment to a developing device. The present invention relates to a toner replenishment control method for an image forming apparatus equipped with a means for controlling toner replenishment.

[Background of the invention]

In an image forming apparatus such as an electrophotographic copying machine, a rotating image bearing member (also referred to as a photosensitive drum) has charging means such as a corona charger, an exposure means for forming a latent image by irradiating a light image, and A static eliminating device that performs irradiation using an LED or the like to form an image frame, a developing device that develops the latent image portion to form a toner image, a transfer device that transfers the toner image onto recording paper, and a transfer device that remains on the image carrier after the transfer. A cleaning means or the like for removing toner is provided.

As the cleaning means, a cleaning blade or the like which slides on the photoreceptor drum is often used, and residual toner adhering to the image bearing member is scraped off and collected into a cleaning device. When toner is used for a long time, the amount gradually increases and it becomes impossible to store it in the cleaning device. Therefore, a separate toner collection box is provided, and the collected toner is transferred to the toner collection box, and the collection box collects the collected toner. When it is filled with something, it has been done to take it out and dismiss it. Furthermore, toner recycling means has been provided to automatically return the collected toner to the developing device, thoroughly stir it with the developer in the developing device, and reuse the collected toner. For example, Japanese Utility Model Publication No. 55-18843 discloses a toner recycling device.

Regarding the developing means, in a developing device that uses a two-component developer, the carrier and toner are sufficiently stirred in the developing container, and the toner is electrostatically adhered to the carrier, forming a developer that is coated on the circumferential surface of the developing sleeve. The developer in the developing area develops the latent image on the image bearing member, and the toner is electrostatically attached to the latent image area to be developed. (toner image). Toner is consumed during development, and when the toner ratio in the developer falls below a certain range, a good toner image cannot be obtained. When the toner ratio falls below a certain range and a good toner image cannot be obtained, it is necessary to detect this and promptly supply new toner into the developing device. Japanese Patent Publication No. 43-16199 is a proposal regarding this. An electrostatic latent image of a standard type plate having a reference density is formed on a portion of the photoreceptor drum that does not contact the recording paper, this is developed, and the reflection density of the obtained toner image is measured from a light emitting element and a light receiving element. A control means is provided for detecting the toner by a sensor and replenishing the developing device with toner based on the output signal of the sensor. This toner replenishment control is obtained by a sensor; if the density of the toner image on the standard plate is lower than a certain set value, it is determined that the toner ratio in the developing device has decreased, and new toner is supplied from the hopper to the developing device. By replenishing toner and not replenishing new toner if the density of the toner image is sufficient, the image recorded on the recording paper is maintained at a certain level of density or higher.

Such a toner supply control method has generally been achieved by providing a standard plate image near the leading edge of the image area. In order to do this, a standard plate with a reference density is pasted close to the document table of the copying machine, etc., and when the optical system scans the document surface, the standard plate is scanned at the same time and the image is placed on the image carrier. A latent image of the standard plate has been formed. Therefore, in many cases, a standard board image is created for each copy, and the shading of the toner image on the standard board is checked for each copy to turn on/off toner supply.
Efforts have been made to determine F.

However, it is not always necessary to check the toner density every copy, extra toner is consumed to create a toner image on the standard plate, and the standard plate that has been formed must be cleaned every time. Because this puts a load on the cleaning section, it is necessary to
However, there is also a copying machine that creates a toner image on a standard plate when N>1). It is also disclosed, for example, in Japanese Patent Application Laid-Open No. 57-195256.

[Purpose of the invention]

Since the collected toner is recycled and reused in a copying machine equipped with a toner recycling device, there is no need to take into account the large amount of toner collected in the cleaning section. Therefore, all conventional copiers equipped with toner recycling devices are constructed to form a toner image on a standard plate every copy. This is because control and other aspects are simpler if a toner image is formed on the standard plate every l copies than when a toner image is formed on the standard plate every N copies.

However, the inventors conducted many experiments,
It has been found that copying machines equipped with toner recycling devices are more likely to suffer from defects in copy image quality than ordinary copying machines. It was also observed that the copy image quality tended to become unstable between copies.

The present inventors have discovered that in order to obtain good copy images similar to those of general copying machines with a copying machine equipped with a toner recycling device, it is possible to improve the toner replenishment control method. SUMMARY OF THE INVENTION An object of the present invention is to provide a toner replenishment control method that can stably obtain good copy image quality in a copying machine equipped with a toner recycling device.

[Structure of the invention]

The above object has a toner recycling means for conveying toner collected by a cleaning means to a developing means, and after developing a latent image on a standard plate of a standard density formed on an image carrier, the toner on the standard plate is In a toner replenishment control method in which the density of an image is detected and the detected information is processed to control toner replenishment to the developing means, the toner image on the standard plate to be formed is >1),
This is achieved by a toner replenishment control method characterized by reducing the amount of recycled toner returned.

[Detailed description of the invention]

In a copying machine equipped with a toner recycling device, the toner in the developing device is the sum of new toner and recycled toner, and as long as the ratio of recycled toner to new toner is low, good copy images can be obtained. When normal copying is being done, there are almost no problems. However, when the proportion of recycled toner increases, the toner becomes charged and the binding force of the carrier decreases, causing deterioration in copy image quality such as toner scattering and fogging. Although this has not received any attention in the past, for originals with low toner consumption, the toner consumption of the standard board portion accounts for a relatively large proportion of the toner consumption of the image portion, and the It was discovered that when a toner image of a standard type plate is provided, the ratio of recycled toner increases as a result of copying a large number of sheets, and the quality of the copied image deteriorates.Based on the results of this research, the present invention was made.

〔Example〕

No. 111ffl shows the configuration of a copying machine equipped with a toner recycling device to which the present invention is applied.

In the figure, lO is an image carrier (photosensitive drum) that rotates in the direction of the arrow (clockwise), and a charger 11. Static eliminator 12. Image exposure section 20. Developing device 30. Transfer device 13, separator 14. Sensor 40. A cleaning section 50 is provided.

The image exposure unit irradiates an original plate 21 made of a glass plate on which the original Do is placed, a standard plate 22 which is located near the original plate 21 and has a reference density, and the scanning portion of the original Do from below. Illumination lamp 23, reflective mirrors 24A, 24B, 2
There are 4C, 24D and an imaging lens 25. lighting lamp 23
The reflecting mirror 24A is attached to the first optical unit 26, and the reflecting mirrors 24B and 24C are attached to the second optical unit 27.
7 moves and scans in the direction of the arrow at a speed ratio of 2=1, and the original image Do is formed on the photoreceptor drum 10. Image exposure section 2
0 simultaneously scans and images the image of the standard plate 22 provided near the leading edge of the original Do.

The rotating photosensitive drum 10 is uniformly charged by a charger 10 and passes through a static eliminator 12 . The static eliminator 12 is the controller 1
00, the frame portion outside the image portion, excluding the image portion of the standard board 22, is irradiated with LED to eliminate static.

In the present invention, a latent image of the standard board 22 is created every N copies.For example, when the static eliminator 12 is controlled to create a latent image of the standard board 22 every 6 copies. teeth,
For the first copy, perform LED irradiation as described above and continue 5
For the second copy, the frame portion of the image portion, including the image portion of the standard board 22, is irradiated with LED to eliminate static electricity.

There is a two-component developer inside the developing device 30, which is stirred by stirring screws 33A and 33B, and then transferred to a magnet roller 32 and a rotating developing sleeve 3 located outside of the magnetic roller 32.
It is attached to the outer circumference of the photoreceptor drum 10, and development is performed in a development area facing the photoreceptor drum IO. That is, the image area and the latent images on the standard plate 22 for every N copies are developed and become toner images.

The recording paper P is discharged one by one by a paper feed roller 15, and guided to a transfer section below the transfer device 13 by a synchronously operating paper feed roller 16. In the transfer section, the image area toner image on the photosensitive drum 10 is transferred onto the recording paper P. The recording paper P on which the image portion toner image has been transferred is separated from the photoreceptor drum 10 by a separator 14, fixed by a fixing device (not shown), and discharged outside the apparatus.

The reflection density of the standard plate toner image for every N copies is read by a sensor 40 comprising a light emitting element 41 and a light receiving element 42. This detection information is compared with a preset value, and when the toner concentration is high (dark), it remains as is, and when the toner concentration is low (light), the control unit 100 rotates the toner replenishing roller 35 to rotate the toner T in the flopper 34. By doing so, the developing device 30 is replenished. In addition, 36 is a toner scraping plate, which is attached to the hopper 34 together with the toner supply roller 35.
This prevents toner from falling due to toner coagulation.

The rotating photosensitive drum 10 carrying the standard plate toner image whose density has been detected and the image area toner remaining after transfer reaches the cleaning section 50, and the toner scraped off by the cleaning blade 51, for example, is removed by the toner conveying screw. 5
After being collected in one direction by 2, the toner is moved inside a toner conveying pipe 53 having a rotating screw or the like inside.
The recycled toner is transported into the developing device 30.

FIG. 2 shows a 70-chart of the toner replenishment method described above.

First, it is set (2-1) whether or not a standard form board is to be created along with image formation for each copy, and the number of copies N is initialized to N=O (2-2), and the copying is performed (2-3). Once a copy is made, the count increases 2-4), N
Copies are made up to the P-1 copy (2-5a). Np
When it comes to copying (2-5b), the image is formed and a standard board is formed outside the screen (2-6). The density of the standard board is read by a sensor, and when it is determined that the toner density is higher than the reference density (2-7a), the process of forming the standard board for each copy is repeated. Also, the toner density on the standard plate is lighter than the standard density (
2-7b), toner is replenished.

When a standard board was created every time an image was formed (this is indicated by C-B on the graph), and when the present invention created a standard board for every N copies (this is indicated by C-B). (shown as C-A on the graph) will be explained using a graph.

Figure 3 (a) is a graph showing the relationship between the number of copies and the total amount of toner recycled.Compared to when a standard sheet was created every time an image was formed, a standard sheet was created every N copies. In this case, the total amount of recycled toner returned to the developing device is l/
This shows that the result is N. (C-A) Figure 3(b) shows the condition without toner control.
In other words, it shows the change in image density as the number of copies increases when a fixed amount of toner is replenished.If a standard chart is created each time an image is formed, the amount of recycled toner in the replenished toner increases. It is observed that as the amount increases, the image density decreases. (C-B) Figure 3 (C) shows the change in toner concentration (toner ratio in developer) as the number of copies increases under the toner control state. It is shown that when the toner density is created, the toner concentration gradually increases. (C-B) That is, if a standard board is created every time an image is formed,
The ratio of recycled toner in the supplied toner increases. As the ratio of recycled toner in the supplied toner increases, the image density of the developed standard plate becomes lower, as is clear from FIG. 3(b). It is incorrectly determined that the toner density is low. Toner is replenished based on this misjudgment, and the toner concentration within the developing device remains higher than normal and deviates from the control range. (C-B) If a standard plate is created each time an image is formed in this way, the toner concentration in the developing device will increase, and the proportion of recycled toner will increase. Copy image quality deteriorates due to the occurrence of slippage.

Now, in the flowchart of the present invention shown in FIG. 2, toner replenishment (2-8) during the copy cycle is performed continuously for M copies (where M>1).

FIG. 4(a) shows an example of a continuous copy cycle, in which the density of the toner image on the standard slip plate is detected once every 6 copies (N). If it is determined that the toner image density is lower than a certain set density, the toner replenishing roller 35 rotates continuously during the subsequent five copies (M) to replenish toner. By continuously/dividingly replenishing toner for several copies, it is possible to easily stir the developer in the developing device 30 and to easily send the developer with uniform toner concentration to the developing area. Furthermore, while the replenishment roller 35 is rotating, the toner scraping plate 36 operates continuously, and this operation supplies a fixed amount of toner.

Note that it is desirable to set the relationship between N and M such that N>M as described above. This is because if set to N(M, toner is replenished based on the previous detection result even while the density of the standard plate toner image is being detected, causing an error in the judgment result. Therefore, if set to N(M, toner is replenished based on the previous detection result. It is also possible to create a program inside that prohibits detection and measurement of the standard board.

Also, when toner is replenished, the next detection and measurement of the toner image density on the standard plate is prohibited, taking into consideration the agitation of the developer and the time delay until it reaches the development area. It is also possible to use a program, or a program that does not form a latent image on the next standard plate (pauses once) when toner is replenished.

In addition, the control unit 100 of this embodiment has a non-volatile memory 11.
0, and the previous history of toner image formation formed every N copies and the previous history of the number of consecutive toner replenishments are stored in the memory, and are stored at the end of the copying operation or when the power is turned off. However, the memory of the previous history is retained, and when the next copy starts, the copy state will be as if the previous copy was being continued.

In FIG. 4(a), for example, when the copy operation is completed at the time of SA or the power supply is turned off to 0FFt, (a) regarding the previous history of toner image formation on the standard plate, the copy corresponding to (6-3) is stored in memory, and (b) the toner image is Regarding the previous history of the number of replenishments, three times corresponding to (5-2) are stored in memory. Therefore, when the copying operation starts again, as shown in FIG. 4(b), (a) standard plate toner images are not created for the initial three copies, and (b) the initial toner image is not created for I/toner replenishment. Continuously replenish toner for 3 copies.

As explained above, the state at the time copying is stopped is memorized so that when copying is started again, it is performed in the same state as if it were continuing. It is necessary to maintain a stable toner ratio and always obtain good images, and is particularly effective when N is set large.

〔Effect of the invention〕

When using the toner replenishment control method of the present invention, toner images on a standard plate are intermittently created in an image forming apparatus equipped with a toner recycling means, so toner consumption is small (N copies). Since the ratio of recycled toner in the majority does not increase, the fluidity of the developer will not deteriorate.If the ratio of recycled toner is kept low, the cycle of replenishing, stirring, and transporting the developer will be maintained normally. This resulted in stable copy image quality being maintained over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an image forming apparatus to which the present invention is applied. FIG. 2 is a 70-chart diagram of the toner replenishment control method of the present invention. Figure 3 shows when a standard board is created for each image formation (C-B
) is a graph showing the difference between the standard form board created once for every N copies (C-A), and Figure 3 (
a) is the relationship between the number of copies and the total amount of toner recycled;
Figure (b) shows Tonercon! -Relationship between the number of copies and image density in the non-rolling state; FIG. 3(C) shows the relationship between the number of copies and toner density in the toner control state. FIG. 4 is an explanatory diagram showing the timing of forming a toner image on a cut plate and the timing of replenishing toner. lO... Image carrier (photosensitive drum) 11... Charger 12... Static eliminator 20...
・Image exposure section 21... Original table 22... Standard plate 30... Developing device 31... Developing sleeve 34... Hopper 35... Toner supply roller 36... Toner scraping plate 40...Sensor 41...Light emitting element 42.
...Light receiving element 50...Cleaning section 52.
... Toner conveyance screw 53 ... Toner conveyance pipe

Claims (5)

[Claims] (1) It has a toner recycling means for conveying the toner collected by the cleaning means to the developing means, and after developing the latent image on the standard plate of the standard density formed on the image carrier, the toner image on the standard plate In the toner replenishment control method, the toner image on the standard plate to be formed is detected every N copies (where N> 1) A toner replenishment control method characterized by reducing the amount of returned recycled toner. (2) The toner replenishment control method according to claim 1, wherein the density detection of the standard plate toner image is performed for each toner image. (3) The toner replenishment control method according to claim 1 or 2, characterized in that when toner replenishment is performed, it is performed continuously over a plurality of copies. (4) The formation history of the toner image formed every N copies is retained even when the copying operation ends or when the power is turned off. Toner supply control method. (5) The toner replenishment control method according to claim 3, wherein the history of the number of consecutive toner replenishments is maintained even when the copying operation ends or when the power is turned off.