JP2021071623A - Developing device and image forming apparatus - Google Patents

Abstract

To discard a larger amount of deteriorated developer than a non-deteriorated developer.SOLUTION: A developing device 22 of the present invention comprises a developer storage unit 31 that supplies a developer to a developing roller 27 while conveying the developer through a supply conveyance path 31A provided in parallel with the developing roller 27, and conveys the developer in the opposite direction through a reflux conveyance path 31B to return the developer to the supply conveyance path 31A, to thereby circulate the developer. A control unit sets a developer discard mode for discarding the developer on the supply conveyance path 31A to a photoreceptor drum 4 with the developing roller 27, controls formation of an electrostatic latent image carried on the photoreceptor drum 4, and increases the amount of discarded developer on the downstream side in a developer conveyance direction of the supply conveyance path 31A compared with that on the upstream side in the conveyance direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to a developing apparatus and an image forming apparatus including the developing apparatus, and more particularly to a technique for discarding a deteriorated developer in the developing apparatus.

In this type of developing apparatus, the developer is conveyed while stirring, and the developer is applied to the electrostatic latent image of the image carrier via a developing roller to obtain the electrostatic latent image of the image carrier as a visible image. (Image of developer) is being developed. Further, since an unused developer remains and the remaining developer is deteriorated by thermal pressure stress, the developer is supported on the image carrier via a developing roller when the image forming process is not performed. The visible image (image of the developing agent) of this image carrier was cleaned and discarded.

However, the larger the amount of the developer discarded, the more effectively the developer is refreshed, but the undegraded developer is also wasted, which is not preferable. In addition, due to the effects of global warming in recent years, the developing device may be used in a high-temperature environment that exceeds the guaranteed range of the operating environment. In this case, the image density may decrease due to deterioration of the developer, or development may occur. Vertical white streaks and the like were generated due to the aggregation of the agent.

Therefore, in Patent Document 1, toner (developer) is discarded by different methods according to five environmental conditions based on temperature and humidity. For example, a visible image is formed on the entire surface of the image carrier and the toner is discarded, or a visible image is formed only on both ends of the image carrier and the toner is discarded.

JP 2015-004837

Here, in the developing apparatus, the developer is supplied to the developing roller while being conveyed through the supply transfer path arranged in parallel with the developing roller, and the developer is further conveyed in the reverse direction through the reflux transfer path to be conveyed in the supply transfer path. The developer is circulated.

The degree of deterioration of the developer differs between the upstream side and the downstream side in the transport direction of the developer in the supply transport path, and the developer on the downstream side receives more or longer heat pressure stress, and the downstream side The degree of deterioration of the developer is large. Therefore, when disposing of the developer as described above, it is preferable to increase the amount of the developer discarded on the downstream side in the transport direction of the developer in the supply transport path.

However, conventionally, since the developer is uniformly applied to the entire developing roller and the developer of the developing roller is discarded to the image carrier, the developer is transferred from the upstream side to the downstream in the supply transport path. The amount of developer discarded becomes uniform toward the side. For this reason, the same amount of the developer with a small degree of deterioration as the developer with a large degree of deterioration was discarded.

Further, in Patent Document 1, since a visible image is formed on the entire surface of the image carrier and the toner is discarded, the developer having a small degree of deterioration is discarded by the same amount as the developer having a large degree of deterioration. Will be done. Further, when a visible image is formed only on both ends of the image carrier and the toner is discarded, the developer is not applied to the central portion of the image carrier and the slightly deteriorated developer is not discarded at all. Become.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable more disposal of a deteriorated developer than a non-deteriorated developer.

The developing apparatus according to one aspect of the present invention comprises a developing roller that applies a developing agent to an electrostatic latent image formed on an image carrier to develop the electrostatic latent image into a visible image, and the developing agent. While transporting along the developing roller, the developer is received from one end of the supply transport path for supplying the developer to the developing roller and the developer on the downstream side in the transport direction of the developer in the supply transport path and transported. A developer accommodating unit that has a reflux transfer path for returning the developer to the other end on the upstream side in the transfer direction of the developer in the supply transfer path, and circulates the developer through the supply transfer path and the reflux transfer path. , The developer disposal mode in which the developer in the supply transport path is discarded to the image carrier via the developing roller is set, and the formation of the electrostatic latent image supported by the image carrier is controlled. It is provided with a control unit that increases the amount of the developer to be discarded on the downstream side in the transport direction rather than on the upstream side in the transport direction of the developer in the supply transport path.

Further, the image forming apparatus according to one aspect of the present invention uses the developing apparatus of the present invention and a visible image of the image carrier formed by applying a developing agent from the developing roller of the developing apparatus on a recording paper. It includes a transfer unit to be transferred.

According to the present invention, more degraded developer can be discarded than non-degraded developer.

It is sectional drawing which shows one Embodiment of the image forming apparatus of this invention. It is a vertical cross-sectional view which shows the photoconductor drum, the developing apparatus and the like in the image forming apparatus of this embodiment. It is sectional drawing which shows the developer accommodating part of a developing apparatus. It is a functional block diagram which shows the main internal structure of an image forming apparatus. (A) and (B) are diagrams showing two types of uneven distribution patterns of electrostatic latent images formed on the surface of a photoconductor drum. It is a figure which shows the uniform pattern of the electrostatic latent image formed on the surface of a photoconductor drum. It is a flowchart which shows the control procedure for discarding the developer in the supply transport path of the developer accommodating part of a developing apparatus. (A), (B), and (C) are diagrams showing three types of uneven distribution patterns of electrostatic latent images formed on the surface of the photoconductor drum, respectively.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 10 includes an image reading unit 11 and an image forming unit 12.

The image reading unit 11 has an image sensor that optically reads an image of the manuscript paper, and the analog output of the image sensor is converted into a digital signal to generate image data indicating the image of the manuscript paper.

The image forming unit 12 prints the image indicated by the image data on the recording paper, and has an image forming unit 3M for magenta, an image forming unit 3C for cyan, an image forming unit 3Y for yellow, and black. The image forming unit 3Bk of the above is provided. In each of the image forming units 3M, 3C, 3Y, and 3Bk, the surface of the photoconductor drum 4 is uniformly charged, the surface of the photoconductor drum 4 is exposed, and an electrostatic latent image is formed on the surface of the photoconductor drum 4. Is formed, the electrostatic latent image on the surface of the photoconductor drum 4 is developed into a visible image (image of a developer), and the visible image on the surface of the photoconductor drum 4 is transferred to the intermediate transfer belt 5. As a result, a visible image of color is formed on the intermediate transfer belt 5. This color visible image is secondarily transferred to the recording paper P conveyed from the paper feed unit 14 through the transfer path 8 in the nip area N between the intermediate transfer belt 5 and the secondary transfer roller 7. The photoconductor drum 4 is an example of an image carrier within the scope of claims. Further, the intermediate transfer belt 5 and the secondary transfer roller 6 are examples of transfer portions within the scope of claims.

After that, the recording paper P is heated and pressurized by the fixing device 15, the visible image on the recording paper P is fixed by thermocompression bonding, and the recording paper P is further discharged to the discharge tray 17 through the discharge roller 16.

FIG. 2 is a vertical cross-sectional view showing a set of photoconductor drums 4 and a developing device 22 in each image forming unit 3M, 3C, 3Y, and 3Bk. Further, FIG. 3 is a cross-sectional view showing a developer accommodating portion 31 of the developing apparatus 22.

As shown in FIG. 2, a photoconductor drum 4, a developing device 22, a primary transfer roller 6, and the like are provided for each of the image forming units 3M, 3C, 3Y, and 3Bk. Around the photoconductor drum 4, a static eliminator 24 that eliminates static electricity on the surface of the photoconductor drum 4, a cleaning unit 25 that cleans the toner remaining on the surface of the photoconductor drum 4, and the surface of the photoconductor drum 4 are uniformly charged. The charged portion 26, the exposed portion 23 that forms an electrostatic latent image on the surface of the photoconductor drum 4, and the like are provided. The developing apparatus 22 is provided with a developing roller 27, a layer regulating member 28, a developing agent accommodating portion 31 accommodating a developing agent, two spiral feeders 32 for circulating and conveying the developing agent, and the like.

In this embodiment, a one-component magnetic toner is used as the developing agent contained in the developing agent accommodating portion 31 of the developing apparatus 22. The developing roller 27 includes a sleeve, a magnet provided inside the sleeve, a developing electrode, a layer regulating electrode, and the like. Further, the surface of the sleeve of the developing roller 27 is formed with irregularities having a predetermined roughness for stabilizing the transfer of the developing agent. The layer regulating member 28 is composed of a magnetic blade and a magnet, generates a magnetic field between the magnet and the layer regulating electrode of the magnet in the developing roller 27, and develops on the surface of the developing roller 27 by a gap with the sleeve of the developing roller 27. Form a thin layer of agent.

As shown in FIGS. 2 and 3, the developer accommodating portion 31 has two supply transport paths 31A and a reflux transport path 31B arranged side by side with respect to the developing roller 27 and partitioned by a partition wall 29. The supply transport path 31A and the reflux transport path 31B are connected through the connecting paths 31C and 31D at both ends to form a circulation transport path through which the developer circulates. Spiral feeders 32 are provided in the supply transport path 31A and the reflux transport path 31B, respectively. Each spiral feeder 32 is rotationally driven in the direction of the arrow by a drive mechanism (not shown).

In the supply transport path 31A, the developer is subjected to the spiral feeder 32 of the supply transport path 31A from the upstream side in the transport direction of the developer to the downstream side in the transport direction (from one end side to the other end side of the developing roller 27) in the arrow direction. It is agitated while being transported to the developing roller 27, supplied to the developing roller 27, and sent out to the reflux transport path 31B through one of the connecting paths 31C. Further, in the reflux transfer path 31B, the developer is agitated while being conveyed by the spiral feeder 32 of the reflux transfer path 31B in the direction opposite to the transfer direction in the supply transfer path 31A, and is agitated while being conveyed in the direction opposite to the transfer direction in the supply transfer path 31A. Returned to 31A. As a result, the developer is supplied to the developing roller 27 while being circulated and conveyed.

The developer accommodating unit 31 is provided with a developer replenishment port (not shown), and the amount of the developer contained in the developer accommodating unit 31 is maintained by replenishing the developer through the replenishment port. Will be done.

The developing roller 27 and the photoconductor drum 4 are rotationally driven in the direction of the arrow by a driving mechanism (not shown). A developer is supplied to the sleeve surface of the developing roller 27, a thin layer of the developer is formed on the sleeve surface of the developing roller 27 by the layer regulating member 28, and the developer on the sleeve surface of the developing roller 27 is the photoconductor drum 4. A visible image (image of a developing agent) is formed on the surface of the photoconductor drum 4 by being applied to an electrostatic latent image formed on the surface.

Next, the configuration related to the control of the image forming apparatus 10 will be described. FIG. 4 is a functional block diagram showing a main internal configuration of the image forming apparatus 10. As shown in FIG. 4, the image forming apparatus 10 includes an image reading unit 11, an image forming unit 12, a display unit 41, an operation unit 42, a temperature detection unit 43, a storage unit 44, a control unit 45, and the like. These components are capable of transmitting and receiving data or signals through the bus to each other.

The display unit 41 is a display device such as a liquid crystal display (LCD) or an organic EL (OLED: Organic Light-Emitting Diode) display.

The operation unit 42 includes hard keys such as a numeric keypad, an enter key, and a start key that are input and operated by the user.

The temperature detection unit 43 is a temperature sensor that detects, for example, the internal temperature Ti of the image forming apparatus 10 as the temperature around the developer. The temperature detection unit 43 is arranged at a predetermined position inside the image forming apparatus 10. Since the internal temperature Ti affects the temperature of the developer stored in the developer accommodating portion 31 of the developing apparatus 22, the higher the internal temperature Ti, the higher the temperature of the developer.

The storage unit 44 is a storage device such as a RAM or a large-capacity HDD (Hard Disk Drive), and stores various data and programs.

The control unit 45 is composed of a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an MPU (Micro Processing Unit), or the like. The control unit 45 functions as the control unit 46 when the control program stored in the ROM or the storage unit 44 is executed by the processor.

The control unit 45 controls the overall control of the image forming apparatus 10. Further, the control unit 45 is connected to an image reading unit 11, an image forming unit 12, a display unit 41, an operation unit 42, a temperature detection unit 43, a storage unit 44, and the like, and controls these components and controls each of these components. Sends and receives signals or data to and from components.

The control unit 46 serves as a processing unit that executes various processes, and also has a function of controlling the display unit 41.

Here, in the supply transport path 31A of the developer accommodating portion 31 of the developing apparatus 22 shown in FIGS. 2 and 3, a part of the developing agent is not supplied to the photoconductor drum 4 via the developing roller 27. It is repeatedly subjected to thermal pressure stress by the developing roller 27, the layer regulating member 28, etc., and returned to the supply transport path 31A, and gradually deteriorates.

Further, since the number of times and the time of receiving thermal pressure stress is longer or longer on the downstream side in the transport direction than on the upstream side in the transport direction of the developer in the supply transport path 31A, development is performed on the upstream side in the transport direction of the developer. The degree of deterioration of the agent is small, the degree of deterioration of the developer is large on the downstream side in the transport direction, and the degree of deterioration of the developer is further on the downstream side in the transport direction.

Further, when the temperature of the developer is low, the developer is unlikely to deteriorate, when the temperature of the developer is high, the developer deteriorates quickly, and as the temperature of the developer increases, the developer deteriorates faster. Therefore, when the temperature of the developer is low, there is almost no difference in the degree of deterioration of the developer between the upstream side in the transport direction and the downstream side in the transport direction in the supply transport path 31A, and when the temperature of the developer is high, the upstream side in the transport direction. There is a large difference in the degree of deterioration of the developer between and the downstream side in the transport direction.

Therefore, in the present embodiment, the control unit 46 sets a developer disposal mode for refreshing the developer in the supply transport path 31A when the image forming process for recording the visible image on the recording paper is not performed. .. Then, when the developer disposal mode is set, the control unit 46 acquires the internal temperature Ti of the image forming apparatus 10 detected by the temperature detection unit 43, and compares this internal temperature Ti with the preset temperature threshold Tc. When the internal temperature Ti becomes equal to or higher than the temperature threshold Tc (Ti ≧ Tc), it is considered that the temperature of the developer is high, and the developer in the supply transport path 31A is discarded and the developer is discarded. The amount is increased on the downstream side in the transport direction than on the upstream side in the transport direction of the developer in the supply transport path 31A.

As a result, the amount of the developer having a small degree of deterioration on the upstream side in the transport direction in the supply transport path 31A is reduced, and the amount of the developer having a large degree of deterioration on the downstream side in the transport direction is large, so that the developer is wasted. It is possible to select and dispose of more deteriorated developer while suppressing the above.

Specifically, the control unit 46 controls the exposure unit 23 to form a predetermined electrostatic latent image on the surface of the photoconductor drum 4, and the developing roller 27 of the developing device 22 causes the surface of the photoconductor drum 4 to form a predetermined electrostatic latent image. The electrostatic latent image is developed into a visible image (image of the developing agent), the visible image on the surface of the photoconductor drum 4 is removed by the cleaning unit 25, and the developing agent in the supply transport path 31A is discarded. Therefore, the developer is discarded in the order of supply transport path 31A → developing roller 27 → photoconductor drum 4 → cleaning unit 25. Further, the discarded developer is transported through a route (not shown) and stored in a waste box.

Further, when the temperature of the developer is high (Ti ≧ Tc) as described above, the control unit 46 controls the exposure unit 23 to obtain a predetermined electrostatic latent image of the surface of the photoconductor drum 4. , An electrostatic latent image is formed in which the area of the electrostatic latent image gradually increases or gradually increases from the upstream side in the transport direction to the downstream side in the transport direction of the developer in the supply transport path 31A. Hereinafter, the pattern of this electrostatic latent image will be referred to as an uneven distribution pattern.

The uneven distribution pattern of the electrostatic latent image formed on the surface of the photoconductor drum 4 is, for example, when the surface of the photoconductor drum 4 is developed in a plane shape as shown in FIGS. 5A and 5B. It becomes a triangular pattern PT1 or a multi-stage pattern PT2 formed by connecting a plurality of rectangular patterns of different sizes.

By forming such an electrostatic latent image of the uneven distribution pattern PT1 or PT2 on the surface of the photoconductor drum 4, the electrostatic latent image is formed on the downstream side in the transport direction rather than the upstream side in the transport direction of the developer in the supply transport path 31A. The amount of the developer to be applied is large, so that the amount of the developer with a small degree of deterioration on the upstream side in the transport direction is small, and the amount of the developer with a large degree of deterioration on the downstream side in the transport direction is large. The developer at 31A can be efficiently refreshed.

On the other hand, when the internal temperature Ti of the image forming apparatus 10 detected by the temperature detecting unit 43 is less than the temperature threshold Tc (Ti <Tc), the control unit 46 considers that the temperature of the developer is low. By controlling the exposure unit 23, an electrostatic latent image is formed on the surface of the photoconductor drum 4 so that the area of the electrostatic latent image becomes uniform from the upstream side in the transport direction to the downstream side in the transport direction of the developer in the supply transport path 31A. .. Hereinafter, the pattern of this electrostatic latent image will be referred to as a uniform pattern.

The uniform pattern of the electrostatic latent image formed on the surface of the photoconductor drum 4 becomes a rectangular pattern PT3 when the surface of the photoconductor drum 4 is developed in a plane as shown in FIG. 6, for example. ..

When such an electrostatic latent image of the uniform pattern PT3 is formed on the surface of the photoconductor drum 4, the electrostatic latent image is imparted to the electrostatic latent image from the upstream side in the transport direction to the downstream side in the transport direction of the developer in the supply transport path 31A. The amount of the developer becomes uniform, and thus the amount of the developer discarded from the upstream side in the transport direction to the downstream side in the transport direction in the supply transport path 31A becomes uniform.

As a result, when the temperature of the developer is low and there is almost no difference in the degree of deterioration of the developer from the upstream side in the transport direction to the downstream side in the transport direction in the supply transport path 31A, the developer from the upstream side in the transport direction to the downstream side in the transport direction. The developing agent in the supply transport path 31A can be efficiently refreshed by making the amount of waste to be uniform.

Next, the control procedure for discarding the developer in the supply transport path 31A of the developer accommodating unit 31 as described above will be organized and described with reference to the flowchart shown in FIG.

First, the control unit 46 sets the developer disposal mode when the image forming process for recording the visible image on the recording paper is not performed (S101), and the image forming apparatus 10 detected by the temperature detecting unit 43. The internal temperature Ti is acquired (S102), and it is determined whether or not the internal temperature Ti is equal to or higher than the preset temperature threshold value Tc (S103). The control unit 46 has elapsed a predetermined set period from the time when the power of the image forming apparatus 10 is turned on or the time when the previous developer disposal mode is set after the elapse of the predetermined set period (for example, the time when the power of the image forming apparatus 10 is turned on). The developer disposal mode may be set (S101) at a later time) and when the image forming process for recording the visible image on the recording paper has not been performed.

For example, when the control unit 46 determines that the internal temperature Ti is less than the temperature threshold Tc (S103 “No”), the control unit 46 considers that the temperature of the developer in the developer accommodating unit 31 is low and controls the exposure unit 23. Then, an electrostatic latent image of the uniform pattern PT3 shown in FIG. 6 is formed on the surface of the photoconductor drum 4 (S104), and the electrostatic of the uniform pattern PT3 on the surface of the photoconductor drum 4 is generated by the developing roller 27 of the developing apparatus 22. The latent image is developed into a visible image (image of a developer) (S105). The image of the developer of the uniform pattern PT3 formed on the surface of the photoconductor drum 4 is removed from the surface of the photoconductor drum 4 by the cleaning unit 25 and discarded, and further transported through a route (not shown) and stored in the disposal box. (S106). The above S104, S105, and S106 are performed a preset number of times (at least once) to end the process of FIG. 7.

Further, when the control unit 46 determines that the internal temperature Ti is equal to or higher than the temperature threshold Tc (S103 “Yes”), the control unit 46 considers that the temperature of the developer in the developer accommodating unit 31 is high and controls the exposure unit 23. Then, an electrostatic latent image of the uneven distribution pattern PT1 or PT2 shown in FIGS. 5A and 5B is formed (S107), and the uneven distribution pattern PT1 or the surface of the photoconductor drum 4 is formed by the developing roller 27 of the developing apparatus 22. The electrostatic latent image of PT2 is developed into a visible image (image of a developing agent) (S108). The image of the developer of the uneven distribution pattern PT1 or PT2 is removed from the surface of the photoconductor drum 4 by the cleaning unit 25 and discarded, and further, the image is conveyed through a route (not shown) and stored in the disposal box (S106). S107, S108, and S106 are performed a preset number of times (at least once) to end the process of FIG. 7.

As described above, in the present embodiment, when the internal temperature Ti of the image forming apparatus 10 becomes equal to or higher than the temperature threshold Tc (Ti ≧ Tc), it is considered that the temperature of the developing agent is high, and the electrostatic latent of the uneven distribution pattern PT1 or PT2. An image is formed, the electrostatic latent image is developed into a visible image (image of the developer), the image of the developer is cleaned, and the developer is discarded, so the amount of the developer to be discarded is supplied. It is possible to select and dispose of more deteriorated developer while suppressing wasteful disposal of the developer by increasing the amount of the developer in the transport path 31A on the downstream side in the transport direction rather than on the upstream side in the transport direction. It is possible to maintain high quality.

Here, for comparison with the above embodiment, in the image forming apparatus 10 having the same configuration as the above embodiment, even if the internal temperature Ti of the image forming apparatus 10 becomes equal to or higher than the temperature threshold Tc (Ti ≧ Tc), it is uniform. An electrostatic latent image of the pattern PT3 was formed on the surface of the photoconductor drum 4, and the amount of the developing agent discarded from the upstream side in the transport direction to the downstream side in the transport direction in the supply transport path 31A was made uniform. It was confirmed that the image density decreased as the number of printed sheets increased, and the drop in the image density at one end of the developing roller 27 corresponding to the downstream side in the transport direction of the developer became remarkable. In addition, image defects such as vertical white streaks due to aggregation of the developer were also observed, making it difficult to maintain image quality. Although it is possible to avoid such a problem by extremely increasing the amount of the developer to be discarded, the amount of the developer that has not deteriorated is also increased, and the developer is wasted. Become.

<Modification example 1>
In the first modification, in addition to the uniform pattern PT3 of the electrostatic latent image as shown in FIG. 6 and the two types of uneven distribution patterns PT1 and PT2 of the electrostatic latent image as shown in FIGS. Another three types of uneven distribution patterns PT4, PT5, and PT6 of the electrostatic latent image as shown in FIGS. 8A, 8B, and 8C are used.

The uneven distribution pattern PT4 of the electrostatic latent image shown in FIG. 8A is formed only in the region on the downstream side in the transport direction of the developer in the supply transport path 31A when the surface of the photoconductor drum 4 is developed in a plane. It becomes a rectangular pattern. Further, the uneven distribution pattern PT5 of the electrostatic latent image shown in FIG. 8B shows only the region on the downstream side in the transport direction of the developer in the supply transport path 31A when the surface of the photoconductor drum 4 is developed in a plane. A triangular pattern is formed in which the area gradually increases toward the downstream side in the transport direction in the region, and the uneven distribution pattern PT6 of the electrostatic latent image shown in FIG. 8C is the surface of the photoconductor drum 4. Is developed in a planar shape, a multi-step pattern in which the developer is formed only in the region downstream of the transport direction of the developer in the supply transport path 31A, and the area gradually increases toward the downstream side of the transport direction in the region. It becomes.

Further, in each of the uneven distribution patterns PT4, PT5, and PT6, the width (vertical width) in the circumferential direction of the photoconductor drum 4 is appropriately set, and the amount of the developer applied to the electrostatic latent image and discarded is adjusted. It is assumed that it has been done.

For example, the control unit 45 acquires the internal temperature Ti of the image forming apparatus 10 detected by the temperature detection unit 43, and sets the internal temperature Ti as preset first to third temperature thresholds Tc1, Tc2, and Tc3 (Tc1). When it is determined that the internal temperature Ti ≦ the first temperature threshold Tc1 as compared with <Tc2 <Tc3), it is considered that the temperature of the developer is low, and the exposure unit 23 is controlled to statically display the uniform pattern PT3 shown in FIG. An electrolatent image is formed on the surface of the photoconductor drum 4, and an electrostatic latent image of a uniform pattern PT3 on the surface of the photoconductor drum 4 is developed into a visible image (image of a developer) by a developing roller 27 of the developing apparatus 22. And discard the developer. Further, when the control unit 45 determines that the first temperature threshold Tc1 <internal temperature Ti ≦ the second temperature threshold Tc2, it considers that the temperature of the developing agent is slightly higher, and controls the exposure unit 23 to control the drawing. The electrostatic latent image of the uneven distribution pattern PT4 shown in 8 (A) is formed on the surface of the photoconductor drum 4, and the electrostatic latent image of the uneven distribution pattern PT4 on the surface of the photoconductor drum 4 is visualized (developed) by the developing roller 27. Develop into an image of the agent) and discard the developer. Further, when the control unit 45 determines that the second temperature threshold Tc2 <internal temperature Ti ≦ the third temperature threshold Tc3, it considers that the temperature of the developing agent is higher, and controls the exposure unit 23 to control the drawing. The electrostatic latent image of the uneven distribution pattern PT5 or PT6 shown in 8 (B) and (C) is formed on the surface of the photoconductor drum 4, and the electrostatic of the uneven distribution pattern PT5 or PT6 on the surface of the photoconductor drum 4 is formed by the developing roller 27. The latent image is developed into a visible image (image of the developer), and the developer is discarded. Further, when the control unit 45 determines that the third temperature threshold Tc3 <internal temperature Ti, it considers that the temperature of the developer is extremely high, and controls the exposure unit 23 to control FIG. An electrostatic latent image of the uneven distribution pattern PT1 or PT2 shown in B) is formed, and the electrostatic latent image of the uneven distribution pattern PT1 or PT2 on the surface of the photoconductor drum 4 is converted into a visible image (image of a developing agent) by the developing roller 27. Develop and discard the developer.

Instead of switching and using the uneven distribution patterns PT1, PT2, PT4, PT5, and PT6, only the uneven distribution patterns PT1 or PT2 shown in FIGS. 5 (A) and 5 (B) are used, and the uneven distribution patterns PT1 or PT2 are deformed. May be good. For example, the control unit 45 sets the uneven distribution pattern PT1 or PT2 so that the area becomes wider on the downstream side in the transport direction than on the upstream side in the transport direction of the developer in the supply transport path 31A as the internal temperature Ti of the image forming apparatus 10 becomes higher. Transform. As a result, the higher the internal temperature Ti, the larger the amount of the developer discarded on the downstream side in the transport direction.

<Modification 2>
In the second modification, the temperature of the developer is determined based on the internal temperature Ti detected by the temperature detection unit 43 as described above, and the electrostatic force formed on the surface of the photoconductor drum 4 according to the temperature of the developer. The pattern of the latent image is changed, but instead, the print rate of the recording paper on which the visible image is recorded is calculated based on the electrostatic latent image on the surface of the photoconductor drum 4, and the calculated print rate is used. Based on this, the pattern of the electrostatic latent image is changed. When this printing rate is small, the amount of the developer supplied from the developing apparatus 22 to the photoconductor drum 4 is small, the degree of deterioration of the remaining developer in the supply transport path 31A is large, and the upstream in the transport direction in the supply transport path 31A. The difference in the degree of deterioration of the developer between the side and the downstream side in the transport direction also becomes large. On the contrary, when the printing rate is high, the amount of the developer supplied from the developing device 22 to the photoconductor drum 4 is large, the degree of deterioration of the remaining developer in the supply transport path 31A is small, and the transfer in the supply transport path 31A is small. The difference in the degree of deterioration of the developer between the upstream side in the direction and the downstream side in the transport direction is also small.

For example, the control unit 45 calculates the print rate each time a visible image is printed on the recording paper, obtains the print rate average value Qi of a predetermined number of recording papers, and sets the print rate average value Qi in advance. When this print rate average value Qi is lower than the print rate threshold Qc (Qi <Qc) as compared with the printed print rate threshold Qc, development is performed on the upstream side in the transport direction and the downstream side in the transport direction in the supply transport path 31A. Considering that the difference in the degree of deterioration of the agent is large, the exposed portion 23 is controlled to form an electrostatic latent image of the uneven distribution pattern PT1 or PT2 shown in FIGS. The electrostatic latent image of the uneven distribution pattern PT1 or PT2 on the surface of the drum 4 is developed into a visible image (image of the developer), and the developer is discarded. Further, when the average print rate Qi is equal to or higher than the print rate threshold Qc (Qi ≧ Qc), the control unit 45 determines the degree of deterioration of the developer on the upstream side in the transport direction and the downstream side in the transport direction in the supply transport path 31A. Considering that the difference is small, the exposure unit 23 is controlled to form an electrostatic latent image of the uniform pattern PT3 shown in FIG. 6, and the developing roller 27 produces an electrostatic latent image of the uniform pattern PT3 on the surface of the photoconductor drum 4. Develop into a visible image (image of the developer) and discard the developer.

Further, the average print rate value Qi is compared with the preset first to third print rate thresholds Qc1, Qc2, and Qc3 (Qc1 <Qc2 <Qc3), and the average print rate value Qi ≥ the third print rate threshold Qc3. In this case, it is considered that the difference in the degree of deterioration of the developer between the upstream side in the transport direction and the downstream side in the transport direction in the supply transport path 31A is small, and the electrostatic latent image of the uniform pattern PT3 shown in FIG. When the developer is discarded by developing the electrostatic latent image and the second print rate threshold Qc2 ≤ print rate average value Qi <third print rate threshold Qc3, the developer is transported to the upstream side in the transport direction. Considering that the difference in the degree of deterioration of the developer is slightly large on the downstream side in the direction, an electrostatic latent image of the uneven distribution pattern PT4 shown in FIG. 8 (A) is formed on the surface of the photoconductor drum 4, and the electrostatic latent image is formed. When the developer is discarded by the development of the above and the first print rate threshold Qc1 ≤ print rate average value Qi <second print rate threshold Qc2, the degree of deterioration of the developer on the upstream side in the transport direction and the downstream side in the transport direction The electrostatic latent image of the uneven distribution pattern PT5 or PT6 shown in FIGS. 8 (B) and 8 (C) is formed on the surface of the photoconductor drum 4 and developed by developing the electrostatic latent image. When the agent is discarded and the average printing rate Qi <first printing rate threshold Qc1, it is considered that the difference in the degree of deterioration of the developer between the upstream side in the transport direction and the downstream side in the transport direction is extremely large, and FIG. An electrostatic latent image of the uneven distribution pattern PT1 or PT2 shown in A) and (B) may be formed, and the developer may be discarded by developing the electrostatic latent image.

Instead of switching and using the uneven distribution patterns PT1, PT2, PT4, PT5, and PT6, only the uneven distribution patterns PT1 or PT2 shown in FIGS. 5 (A) and 5 (B) are used, and the uneven distribution patterns PT1 or PT2 are deformed. May be good. For example, the control unit 45 deforms the uneven distribution pattern PT1 or PT2 so that the area becomes wider on the downstream side in the transport direction than on the upstream side in the transport direction of the developer in the supply transport path 31A as the average printing rate Qi becomes lower. As a result, the lower the average printing rate Qi, the larger the amount of developer discarded on the downstream side in the transport direction.

By the way, in the above-described embodiment and the first modification, the internal temperature Ti of the image forming apparatus 10 detected by the temperature detection unit 43 is acquired, and the high or low temperature of the developer is determined based on the internal temperature Ti. The temperature detection unit 43 may directly detect the temperature of the developer stored in the developer storage unit 31 of the developing apparatus 22.

Further, the control unit 46 controls the exposure unit 23 so that the density of the visible image is as an electrostatic latent image on the surface of the photoconductor drum 4 from the upstream side in the transport direction of the developer in the supply transport path 31A to the downstream in the transport direction. An electrostatic latent image may be formed that gradually increases or gradually increases toward the side. By adjusting the density of the visible image in this way, it is possible to reduce the amount of the developer on the upstream side in the transport direction and increase the amount of the developer on the downstream side in the transport direction in the supply transport path 31A. ..

Further, as a developer housed in the developer accommodating portion 31, a one-component developer such as a one-component magnetic toner is exemplified, but it is a two-component developer formed by mixing toner and a carrier. Also, the present invention can be applied.

Further, in the above-described embodiment, the multifunction device is exemplified as an embodiment of the image forming apparatus of the present invention, but this is only an example, and may be a copy machine, a printer, a facsimile machine, or the like.

Further, the above-described embodiment and the configurations of the modified examples 1 and 2 described with reference to FIGS. 1 to 8 are merely examples of the present invention, and the present invention is not intended to be limited to the configurations.

4 Photoreceptor drum (image carrier)
5 Intermediate transfer belt (transfer section)
6 Secondary transfer roller (transfer section)
10 Image forming device 11 Image reading unit 12 Image forming unit 22 Developing device 27 Developing roller 31 Developer accommodating unit 31A Supply transport path 31B Circulation transport path 32 Spiral feeder 41 Display unit 42 Operation unit 43 Temperature detection unit 44 Storage unit 45 Control unit 46 Control unit

Claims (11)

A developing roller that applies a developer to the electrostatic latent image formed on the image carrier and develops the electrostatic latent image into a visible image.
A supply transport path for supplying the developer to the developing roller while transporting the developer along the developing roller, and one end of the supply transport path on the downstream side of the developer in the transport direction. Development that has a reflux transfer path that receives and conveys and returns to the other end on the upstream side of the developer in the transfer transfer path, and circulates the developer through the supply transfer path and the reflux transfer path. Agent storage and
A developer disposal mode in which the developer in the supply transport path is discarded to the image carrier via the developing roller is set, and the formation of an electrostatic latent image carried by the image carrier is controlled. A developing apparatus including a control unit that increases the amount of the developer to be discarded on the downstream side in the transport direction rather than on the upstream side in the transport direction of the developer in the supply transport path. In the control unit, as an electrostatic latent image of the image carrier, the area of the visible image gradually increases from the upstream side in the transport direction to the downstream side in the transport direction of the developer in the supply transport path, or is stepwise. The developing apparatus according to claim 1, wherein an electrostatic latent image is formed. In the control unit, as an electrostatic latent image of the image carrier, the concentration of the visible image gradually increases from the upstream side in the transport direction to the downstream side in the transport direction of the developer in the supply transport path, or is stepwise. The developing apparatus according to claim 1, wherein an electrostatic latent image is formed. The first aspect of the present invention, wherein the control unit does not form an electrostatic latent image of the image carrier in a region on the upstream side in the transport direction of the developer in the supply transport path, but forms in a region on the downstream side in the transport direction. Developing equipment. The control unit is formed as an electrostatic latent image of the image carrier only in a region on the downstream side of the developer in the supply transport path in the transport direction, and is visible as the region is further downstream in the transport direction. The developing apparatus according to claim 1, wherein an electrostatic latent image is formed in which the area of the image gradually increases or gradually increases. The control unit controls the formation of an electrostatic latent image of the image carrier in a state where the developer disposal mode is set, and determines the amount of the developer to be discarded in the transport direction of the developer in the supply transport path. The electrostatic latent image of the uneven distribution pattern, which is more on the downstream side in the transport direction than on the upstream side, and the uniform amount of the waste developer are made uniform from the upstream side in the transport direction to the downstream side in the transport direction of the developer in the supply transport path. The developing apparatus according to claim 1, wherein any of the electrostatic latent images of the pattern is formed. A temperature detector for detecting the temperature of the developer or the temperature around the developer is provided.
The developing apparatus according to claim 6, wherein the control unit selects either the uneven distribution pattern or the uniform pattern based on the temperature detected by the temperature detection unit. When the control unit selects the uneven distribution pattern, the higher the temperature detected by the temperature detection unit, the more the amount of the developer discarded on the downstream side in the transport direction of the developer in the supply transport path. The developing apparatus according to claim 7, wherein an electrostatic latent image having many unevenly distributed patterns is formed. The control unit calculates the print rate of the recording paper on which the visible image is recorded based on the electrostatic latent image of the image carrier, and based on the calculated print rate, either the uneven distribution pattern or the uniform pattern. The developing apparatus according to claim 7. When the control unit selects the uneven distribution pattern, the lower the calculated printing rate, the larger the amount of the developer discarded on the downstream side in the transport direction of the developer in the supply transport path. The developing apparatus according to claim 9, wherein the electrostatic latent image of the above is formed. The developing apparatus according to any one of claims 1 to 10.
An image forming apparatus including a transfer unit for transferring a visible image of the image carrier formed by applying a developing agent from a developing roller of the developing apparatus to a recording paper.

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