JPH1063075A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the change of electrification property of a developer in a developing vessel from the initial stage to the end, by containing the two component developer including a carrier whose electrification property is lower than that of the carrier replenished from the developer replenishing port as the start developer at the initial setting time of the developer vessel use starting. SOLUTION: The developing vessel 41 provided with a developer replenishing port 42 and a developer discharging port 43 houses a developing roll 64, two component developer and the developer feeding members 61 to 63. The developer feeding members 61 feed the two component developer on the developing roll 64. Then, at the initial setting time of the use starting of the developer vessel 41, the two component developer including the same carrier as the feeding carrier, however the carrier whose electrification property is lowered by such as the toner adhesion, is contained in the developing vessel 41 as the start developer. In such a manner, the electrification property of the developer in the developing vessel 41 can be maintained unchanging, therefore the stable image quality can be maintained from the service start until the service life termination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing device for an image forming apparatus such as an electrophotographic copying machine or a laser printer.
In particular, the present invention relates to a developing device that stores a two-component developer including a toner and a carrier.

2. Description of the Related Art Conventionally, for example, in a dry copying machine, etc.,
2. Description of the Related Art Developing devices that visualize an electrostatic latent image on the surface of a photoreceptor using a two-component developer including a toner and a carrier, that is, perform development, are frequently used. In such a developing device, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing device. Therefore, as the frequency of agitation of the carrier stirred with the toner in the developing device increases, a situation such as adhesion of the toner to the surface occurs, and the carrier is contaminated and deteriorated. As a result, the charging performance of the developer gradually decreases. This causes image quality defects such as fogging,
This causes the image quality to be significantly reduced.

Heretofore, it has been necessary to periodically replace the developer in the developing unit at intervals that do not cause image quality defects such as fogging. In addition, a great deal of maintenance work was required to replace the developer. Therefore, for the purpose of non-replacement of the developer, a developer composed of a mixture of a carrier and a toner is supplied to the developing tank in the developing device, and the deteriorated developer having the reduced charging performance is discharged from the developing tank, and the charging performance is reduced. There has been proposed a device capable of suppressing the reduction. As such a device, for example, the following technology (J01) is conventionally known. (J01) Japanese Patent Publication No. 221591 (JP-A-59-1004)
In the apparatus described in Japanese Patent Application Publication No. 71), a new carrier is replenished in the developing tank separately from the replenishment of the consumed toner, and the excess developer in the developing tank is removed from the developing tank wall. Are discharged from a developer discharge port provided in the waste developer container and collected in a waste developer container. By successively repeating such supply and discharge of the carrier and the deteriorated developer, the developer that is contaminated and deteriorated in the developing tank is sequentially replaced with a newly supplied toner and carrier. It maintains the charging performance and suppresses deterioration in image quality. According to this proposal, the occurrence of image quality defects can be suppressed without performing a developer replacement operation, and the reduction of service cost, which was the original purpose, was realized to some extent.

Further, as an apparatus for suppressing the deterioration of the developer and gradually reducing service costs such as maintenance time caused by replacement of the developer, for example, the following apparatus (J.
02) The technology is known. (J02) JP-B-2-21591 (Japanese Unexamined Patent Publication No. 59-1004)
The technology described in Japanese Patent Application Laid-Open No. 71) discloses a technology in which a new developer or carrier replenishing unit is provided separately from a replenishing unit for toner consumed by a developing operation. Then, by providing a developer collecting section for collecting the deteriorated developer in the developing tank which becomes excessive due to the replenishment, the deteriorated developer in the developing tank is discharged in accordance with the deterioration of the developer. As a result, the original purpose of reducing the service cost can be realized.

[0004]

[Problems to be solved by the invention]

(Problem of (J02)) In the technique described in (J02), as shown in FIG. 8, after a certain time T has elapsed from the initial (new setting time at which the use of the developing container is started), the end (developer) It is possible to maintain the charging performance until the end of use due to the lifetime of the toner). However, it is not possible to suppress a decrease in the charging performance from the initial time to a certain time T, so that there is a problem that the charging performance of the developer changes. One of the requirements for a future image forming apparatus such as an electrophotographic copying machine or a laser printer is to improve the image quality. However, even if the initial setting is optimized with a new developer and high image quality is achieved, the high image quality achieved by changing the charging performance of the developer after the initial can not be maintained to the end, satisfying customers. It is not possible to realize an image forming apparatus that causes the image forming apparatus to operate. Even if the charging performance from the initial time after a lapse of a predetermined time T to the end is kept constant and good, the charging performance changes until the lapse of a certain time T from the initial. Is difficult to keep constant.

In view of the above circumstances, the present invention provides the following (O01)
Is the subject of the description. (O01) To reduce the change in the charging performance of the developer in the developing container from the initial to the end in the developing device using the two-component developer.

[0006]

Next, the present invention devised to solve the above-mentioned problems will be described. Elements of the present invention are used to facilitate correspondence with elements of the embodiments described later. , The reference numerals of the elements of the embodiment are enclosed in parentheses. Note that a symbol in parentheses connected by a + symbol indicates that a combination of a plurality of elements of the embodiment corresponds to an element of the present invention. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention and not to limit the scope of the present invention to the embodiments.

According to the present invention, in order to solve the above-mentioned problems, a developing device of the present invention has the following requirements. (A01) Two components comprising a toner and a carrier in a developing area (Q2) A developing roll (64) for transporting the developer,
The two-component developer and a developer supply member (61-63) for supplying a developer to the developing roll (64) are accommodated therein, and a developer supply port (42) and a developer discharge port (4) are provided.
(A02) A toner carrier replenishing device (42 + 44 to 47 + 51 to 54 + C + M + SN1 + S) for replenishing toner and carrier to the developer replenishing port (42) in accordance with consumption of toner in the developing operation (A02).
N2), (A03) a collecting container (59) for collecting the developer discharged from the developer discharging port (43), and (A04) developing in the developing container (41) in accordance with consumption of the toner by the developing operation. A developer discharging device (43 + 56 to 58+) for discharging the developer from the developer discharging port (43) to the collection container (59) to maintain the amount of the developer in the developing container (41) at a predetermined value;
C), (A05) At the time of new setting for starting use of the developing container (41), a two-component developer including a carrier having a lower charging performance than a carrier supplied from the developer supply port (42) is started and developed. The developer container (41) for containing the developer.

[0008]

Next, the operation of the present invention having the above-mentioned features will be described. In the developing device of the present invention having the above-described features, the developing container (41) having the developer replenishing port (42) and the developer discharging port (43) includes the developing roll (64), the two-component developer, and the developer. The supply members (61 to 63) are accommodated. The developer supply members (61 to 63) are connected to the developing roll (64) by two.
Supply the component developer. The developing roll (64) applies a two-component developer composed of toner and carrier to a developing area (Q).
Convey to 2). The toner transported to the development area (Q2) is consumed by the development operation. A toner carrier replenishing device (42 + 44) in accordance with the consumption of the toner by the developing operation.
47 + 51 + 54 + C + M + SN1 + SN2) replenishes toner and carrier to the developer replenishment port (42).
The developer discharging device (43 + 56 to 58 + C) discharges the developer in the developing container (41) from the developer discharging port (43) to the collecting container (59) in accordance with consumption of the toner during the developing operation. The developer amount in the developing container (41) is maintained at a predetermined value. The collection container (59) collects the developer discharged from the developer discharge port (43).

As described above, since the deterioration of the carrier occurs in accordance with the consumption of the toner by the developing operation, the toner and the carrier are replenished in accordance with the consumption of the toner by the developing operation, and the developing container (41) is used. By discharging the developer in parentheses), it is possible to prevent a decrease in the charging performance of the carrier. Also, at the time of new setting for starting use of the developing container (41), the developer supply port (42)
A two-component developer containing a carrier having a lower charging performance than a carrier supplied from the developer container is accommodated in the developing container (41) as a start developer. For this reason, the developing container (4)
During the entire period from the start of use to the end of use in 1), the two-component developer in the developing container (41) contains both a low-charge carrier and a novel high-charge carrier. . For this reason, the developer can be maintained at a constant charging performance during the entire use period of the developing container (41). Since the charging performance of the developer in the developing container (41) can be kept constant, stable image quality can be maintained from the start of use to the end of use due to life.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Embodiment 1 of the developing device of the present invention
(A06) A two-component developer containing the same carrier as the replenishing carrier and having a reduced charging performance due to toner adhesion or the like as a start developer. The developing container (41) to be housed.

(Effect of Embodiment 1) In Embodiment 1 of the developing device of the present invention, when a new setting for starting use of the developing container (41) is made, the same carrier as the carrier to be replenished is used. The two-component developer containing the carrier whose charging performance has been lowered is stored as a start developer in the developing container (41). For this reason, during the entire period from the start of use to the end of use of the developing container (41), the two-component developer in the developing container (41) contains a low-charge carrier and a new high-charge carrier. Will be included. Thereby, the developing container (4)
During the entire use period of 1), the developer can be maintained at a constant charging performance. Since the charging performance of the developer in the developing container (41) can be kept constant,
It is possible to provide an image forming apparatus capable of maintaining stable image quality until the end of use due to the life.

(Embodiment 2) Embodiment 2 of the developing device of the present invention is characterized by having the following requirements in the present invention: (A07) A carrier different from the replenishing carrier. The developing container (41) containing a two-component developer containing a carrier having a lower charging performance than the carrier to be replenished as a start developer.

(Operation of the Second Embodiment) In the second embodiment of the developing device of the present invention, as in the first embodiment, during the entire period from the start of use to the end of use of the developing container (41). The two-component developer in the developing container (41) contains both a carrier having low charging performance and a new carrier having high charging performance. Thereby, the developer can be maintained at a constant charging performance during the entire use period of the developing container (41). Since the charging performance of the developer in the developing container (41) can be kept constant, it is possible to provide an image forming apparatus capable of maintaining stable image quality from the start of use to the end of use due to life.

(Example) Next, an example (example) of an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following example.

(Embodiment 1) FIG. 1 is a view showing the overall arrangement of an image processing apparatus U provided with a developing apparatus according to Embodiment 1 of the present invention. FIG. 2 is an enlarged explanatory view of a main part of the first embodiment. FIG. 3 is a block diagram of the first embodiment. In FIG. 1, an image forming apparatus U has a platen glass (transparent platen) on its upper surface.
A digital copier A as an image forming apparatus main body having A1 and an automatic document feeder B detachably mounted on the platen glass A1 are provided. The automatic document feeder B sequentially takes out the documents stored in the document feed tray B1, conveys them to a copy position on the platen glass A1, and discharges the copied documents to a document discharge tray B2. It is configured.

The copying machine A includes the platen glass A1
, An image input terminal IIT (hereinafter, IIT) as an image reading unit and an image output terminal IOT (hereinafter, IOT) as an image recording operation unit.

The IIT has an exposure scanning optical system 1 below the platen glass A1. The exposure scanning optical system 1 has an exposure lamp 2 for document illumination mounted on a full rate carriage and a first mirror 3. Further, the exposure scanning optical system 1 has a second mirror 4 and a third mirror 5 mounted on a half-rate carriage that moves at half the moving speed of the full-rate carriage. It has an imaging lens 6 supported. The imaging lens 6 reflects from the original on the platen glass A1 and further reflects the first, second,
It has a function of converging the original reflected light reflected by the three mirrors 3 to 5 on a CCD (solid-state imaging device). The CCD has a function of converting the original reflected light converged on the imaging surface into an electric signal. The IIT has an image data output unit 7 for outputting an electric signal obtained by the CCD as image data, and a user interface UI for a user to input an operation command signal such as a copy start signal. The user interface UI includes a display unit UIa shown in FIG. 3, a copy start button UIb,
The display unit UIa has a copy setting number input key UIc and the like, and displays information relating to the current setting state of the image forming apparatus U.

In FIG. 1, the IOT includes a laser drive circuit 8 for converting image data output from the image data output unit 7 into a laser drive signal,
A laser writing device 9 that emits a laser beam L for writing an image in accordance with a laser drive signal output from the printer. Laser beam L emitted from laser writing device 9
1 is incident on the surface of the image carrier 11 at a latent image writing position Q1 set on the movement path of the surface of the image carrier 11 rotating in the direction of the arrow in FIG. A charger 12 is arranged along the surface of the image carrier 11 on the rotationally upstream side of the latent image writing position Q1.

An electrostatic latent image formed on the surface of the image carrier 11 is converted into a toner image in a developing area Q2 on the downstream side in the rotation direction of the latent image writing position Q1 along the surface of the image carrier 11. A developing device D for developing (details will be described later) is provided. The transfer position Q3 set on the downstream side of the developing device D includes:
A transfer device 14 is provided. Further, a static eliminator 15 and a cleaner unit 16 are disposed further downstream in the rotation direction of the transfer device 14. Below the transfer device 14,
Paper feed trays 21 to 25 are arranged in multiple stages. The paper feed tray 23 is an intermediate tray used when circulating the recording sheet (hereinafter, sheet) S on which the first copy has been performed at the time of double-sided copying, multiple copying, or the like, and re-transmitting it to the transfer position Q3.

The sheets S of the paper feed trays 21 to 25 are conveyed to the transfer position Q3 through a first sheet conveying path 26. The transfer device 14 is disposed at the transfer position Q3, and the transfer device 14 transfers the toner image I on the surface of the image carrier 11 to the sheet S passing through the transfer position Q3. The transfer position Q3 along the surface of the image carrier 11
The developing toner concentration sensor SN2 is arranged at a position on the upstream side of. The developed toner density sensor SN2 detects the density of the toner image I and outputs it to the controller C (see FIG. 3). Image carrier 1 that has passed the transfer position Q3
The one surface is neutralized by the static eliminator 15, and the toner remaining on the surface is collected by the cleaner unit 16, and then uniformly charged again by the charger 12.

At the end of the first sheet transport path 26, the transported sheet S is temporarily stopped upstream of the transfer position Q3 in the sheet transport direction, and then temporarily stopped at the transfer position Q3.
Roll 27 and register gate 28 for carrying in
Is arranged. The sheet S to which the toner image has been transferred at the transfer position Q3 is conveyed to a fixing position Q4 through a second sheet conveying path 29 connected to the sheet discharge tray TR. The heating roll 31 and the pressure roll 32 of the fixing device F are arranged at the fixing position Q4, and heat and fix the unfixed toner image on the sheet S passing through the fixing position Q4. A discharge roller 33 for discharging sheets to the sheet discharge tray TR is provided in the second sheet transport path 29 downstream of the fixing position Q4.

In the second sheet conveying path 29, a switching gate 34 is disposed upstream of the discharge roller 33.
The switching gate 34 is used when switching the sheet conveyance direction on the second sheet conveyance path 29 to the sheet circulation path 36 or the sheet discharge tray TR.

FIG. 2 is an explanatory view of a main part of the developing device according to the first embodiment of the present invention. 2, the developing device D has a developing container 41. The developing container 41 is provided with the developer supply port 4.
2, and a developer outlet 43. The toner stored in the toner storage container 44 is stored in the developer supply port 42.
It is configured to be replenished from the toner transport auger 45. At the time of a new setting (initial) when the use of the developing container 41 is started, a two-component mixture of a deteriorated (low-charging) developer and a new (high-charging) developer is mixed in the developing container 41. The developer is stored.
In FIGS. 2 and 3, an auger rotating shaft 46 that supports the toner conveying auger 45 is rotated by a developing device motor M via a clutch 47. At the right end of the auger rotation shaft 46, an encoder 48 for detecting the rotation amount of the toner transport auger 45 is provided.

In FIG. 2, the motor M for the developing device is driven by a motor driving circuit 49 for the developing device controlled by a controller C for controlling the operation of the copying machine A. While the developing device motor M is being driven, when the clutch 47 is on, the auger rotating shaft 46 and the toner conveying auger 4
5 is driven to rotate. At this time, the toner transport auger 4
5, the toner for replenishment stored in the toner storage container 44 is replenished into the developing container 41 from the developer replenishing port 42. This toner replenishment is performed by a toner concentration sensor SN1 (see FIGS. 2 and 3) in the developing container disposed in the developing container 41.
This is performed when the toner concentration in the container detected by the above-mentioned method is lower than the reference value. The toner supply is also performed when the developing toner concentration detected by the developing toner concentration sensor SN2 (see FIG. 1) is equal to or lower than a reference value. Reference numerals 42, 44 to 4
7, 51 to 54, C, M, SN1, SN2, the toner carrier replenishing device (42+
44 to 47 + 51 to 54 + C + M + SN1 + SN2). An encoder 48 for detecting the rotation amount of the toner transport auger 45 is provided with a toner carrier replenishing device (42 + 44 to 47 + 51 to 54 + C + M +
It has a function as a drive amount detector 48 for detecting the drive amount of (SN1 + SN2).

The rotation amount of the toner conveying auger 45 detected by the encoder 48 is input to the controller C. The toner supply amount into the developing container 41 is proportional to the rotation amount of the toner transport auger 45, and the controller C calculates the toner supply amount determined according to the rotation amount of the toner transport auger 45 as the toner consumption amount. Has functions. Therefore, the encoder 48 and the controller C constitute a toner consumption detecting means (48 + C) for detecting the toner consumption of the developing container.

Above the developer supply port 42, a carrier storage container 51 and a carrier supply shutter 52 are disposed. The carrier supply shutter 52 is opened and closed by a carrier supply solenoid 53. While the carrier supply shutter 52 is open, the supply carrier stored in the carrier storage container 51 is configured to drop toward the developer supply port 42. In FIG. 3, the carrier supply solenoid 53 is used.
Is operated by a carrier supply solenoid driving circuit 54 controlled by the controller C. The developer storage container (44 + 51) of the first embodiment is constituted by the toner storage container 44 and the carrier storage container 51.

The developer discharge port 43 is provided with a developer discharge shutter 56. Developer discharge shutter 5
6 is opened and closed by a developer discharge solenoid 57. In FIG. 3, a developer discharge solenoid 57 is operated by a developer discharge solenoid drive circuit 58 controlled by the controller C. A collection container 59 for collecting the discharged developer is disposed below the developer discharge port 43.
By the elements indicated by the reference numerals 43, 56 to 58, and C, the developer in the developing container 41 is discharged from the developer discharging port 43 to the collection container 59 to reduce the amount of the developer in the developing container 41. A developer discharging device (43+
56 to 58 + C).

In FIG. 2, a stirring auger 6 for stirring the two-component developer in the developing container 41 is provided inside the developing container 41.
1, 62, developer supply paddle 63, and developing roll 6
4 is rotatably supported. The stirring auger 6
The developer supply members (61 to 63) are configured by the developer supply paddles 1 and 62 and the developer supply paddle 63. Developing roll 64
Is constituted by a conventionally known fixed magnet roller 65 and a sleeve 66 rotating around its outer periphery.

In FIG. 2 and FIG.
1, 62, developer supply paddle 63, and developing roll 6
4 is rotationally driven via the clutch 68 by the developing device motor M. The augers 61 and 62 for stirring are 2
The component developer is stirred while transporting the component developers in opposite directions (in FIG. 2, the direction from the front to the back of the paper and the opposite direction), and the developer supply paddle 63 transfers the stirred two-component developer to the developing roll 64. To supply. In the developing container 41, there is provided a layer thickness regulating member 69 which regulates the layer thickness of the two-component developer which is adhered to the outer surface of the developing roll 64 and conveyed to the developing area Q2. Layer thickness regulating member 69 of this embodiment
Is formed in two layers by a laminated non-magnetic member 69a and a magnetic member 69b, but various conventionally known layer thickness regulating members such as a non-magnetic member having a single layer structure can be used. The layer thickness regulating member 69 is disposed at a position facing the magnetic pole of the magnet roller 65.

In FIG. 3, a controller C has a CPU
(Central processing unit), ROM (read only memory),
It is constituted by a microcomputer having a RAM (random access memory), an I / O (input / output interface) and the like. The controller C receives a copy start signal and a set copy number input from the UI, an encoder detection signal (toner replenishment amount detection signal) 48a, a toner density signal SN1a in the container, a development toner density signal SN2a, and other input signals. Has been entered. The controller C controls the motor drive circuit 49 for the developing device according to the input signal.
Solenoid drive circuit for carrier replenishment, solenoid drive circuit for developer discharge 58, replenishment clutch actuation circuit 7
1. It outputs control signals for the developing clutch operating circuit 72 and other operating circuits.

The ROM of the controller C stores a program that operates according to each of the input signals and necessary data. The controller C operated by the program includes a toner replenishing amount calculating unit C1, a copy number counter C2, a carrier replenishing amount calculating unit C3, a developer discharging amount calculating unit C4, and a ten-sheet counter C5 for calculating the toner amount to be replenished. Function. The toner replenishment amount calculating means C1 calculates the amount of toner to be replenished in accordance with the toner concentration signal SN1a in the developing container and the developed toner concentration signal SN2a. In order to supply the calculated toner amount, the toner supply auger 45 needs to be driven for a predetermined time. Therefore, the amount of toner to be replenished depends on the driving time of the toner replenishing auger 45, that is, the clutch 4
7 is the operation time.

The carrier replenishment amount calculating means C3 calculates the amount of carrier to be replenished in accordance with the encoder detection signal (toner replenishment amount detection signal) 48a. The amount of carrier to be replenished is the opening time of the carrier replenishing shutter 52, that is, the operating time of the carrier replenishing solenoid 53. The developer discharge amount calculating means C4 calculates a developer discharge amount to be discharged according to the encoder detection signal (toner replenishment amount detection signal) 48a. The developer discharge amount to be discharged is the opening time of the developer discharge shutter 56, that is, the operation time of the developer discharge solenoid 57. The ten sheet counter C5 is a counter used for forming a toner image for density detection on the image carrier 11 every time ten continuous copies are performed.

(Operation of Embodiment 1) The surface of the image carrier 11 is uniformly charged to a negative polarity by the charging device 12.
Next, image exposure is performed by the laser writing device 9, and an electrostatic latent image is formed on the surface of the image carrier 11. Developing device D
The agitating augers 61 and 62 in the developing container 41 rotate in directions opposite to each other, agitate and transport the toner and the carrier supplied from the developer supply port 42, and perform the mixing action of the toner and the carrier. It is a triboelectrically charged homogeneous two-component developer. The uniformly mixed two-component developer is deposited in a layer on the peripheral surface of the developing roll 64 by the developer supply paddle 63. The developer on the surface of the developing roll 64 is formed into a uniform layer by the layer thickness regulating member 69. The uniform developer layer formed on the surface of the developing roll 64 develops the electrostatic latent image on the image carrier 11 into a toner image in the developing area Q2.

A sheet S such as recording paper or a transparent transfer material on which the toner image is transferred is taken out from the paper feed trays 21 to 25 and is conveyed. Is transferred to the transfer position Q3 between the image carrier 11 and the transfer device 14 at the timing shown in FIG. At the transfer position Q3, the toner image on the image carrier 11 is transferred onto the sheet S by the transfer device 14.
Then, the sheet S on which the toner image has been transferred is fixed to the fixing device F.
Is heated and fixed, and is conveyed to the sheet discharge tray TR. After the transfer of the toner image, the surface of the image carrier 11 is then subjected to static elimination by the static eliminator 15 to remove the cleaner unit 1.
The toner remaining on the surface is scraped off by 6, and the surface is uniformly charged again to a negative polarity by the charger 12.

When the above copying operation is repeated,
The toner in the developer accommodated in the developing container 41 of the developing device D in FIG. 2 is gradually consumed, and the ratio of the toner to the carrier, that is, the toner concentration decreases.
This change in toner density is detected by a toner density sensor SN1 provided in the developing container 41. When the toner concentration falls below the proper range required for development, the controller C turns on the clutch 47 to drive the toner transport auger 45 to supply toner in the toner storage container 44 from the developer supply port 42. Is supplied into the developing container 41.

On the other hand, the carrier in the developer in the developing container 41 is not consumed by the developing operation, but is agitated together with the toner in the developing container 41, influenced by the magnetic force of the magnet roller 65, and Due to the influence of contact with the image carrier 11 and the toner, the toner sticks to the carrier surface, and the surface is gradually contaminated and deteriorated. When the carrier deteriorates in this way, the charging performance of the developer is reduced, and a predetermined amount of charge cannot be given to the toner, and the image quality is reduced.

FIG. 4 is an explanatory diagram showing the relationship between the developer charging performance and the amount of toner consumption. FIG. 4A shows that the charging performance of the developer increases as the amount of toner consumption increases (as the time during which the developing operation is performed increases). FIG. 4B is a graph showing that the higher the supply ratio of the carrier into the developer, the lower the rate of decrease of the developer charging performance, which decreases with the consumption of toner. It is. In FIG. 4A, as the toner consumption increases, the carrier charging performance decreases due to the deterioration of the carrier. In order to maintain the charging performance of the developer in the optimum range, when the toner consumption falls within the predetermined range, development is performed while exchanging a new developer containing a new carrier and a developer containing a deteriorated carrier. There is a need. By appropriately controlling the replacement amount of the developer, it is possible to maintain the developer charging performance constant. In the case where development is performed while replacing the carrier in FIG. 4B, the developer charging performance is reduced to a steady value due to the toner consumption amount, and the steady value increases as the carrier replacement amount increases. It turns out that. As can be seen from FIGS. 4A and 4B, in order to maintain the developer charging performance in the optimum range, it is necessary to exchange the carrier in a corresponding amount or the developer containing the carrier.

In the first embodiment, a developer in which a developer having a reduced charging performance is mixed with a new developer is used as a start developer. FIG. 5 shows a case where a developer obtained by mixing a developer with reduced chargeability and a new developer is used as a start developer (hereinafter, referred to as a “mixed start developer”), and only a new developer is used as a start developer. FIG. 6 is a diagram showing a relationship between developer charging performance and toner consumption time in the case of performing the above. In FIG. 5, when the mixed start developer is used (solid line), the developer charging performance does not decrease as sharply as when a new developer is replaced as the start developer. As described above, when the mixed start developer is used, it is possible to suppress a decrease in developer charging performance and maintain a constant charging performance. Therefore, in the present embodiment using a developer obtained by mixing a developer having a reduced charging performance and a new developer as a start developer, a constant charging performance can be maintained from the initial to the end, so that a stable high performance can be achieved. An image of high quality can be obtained.

Next, the method of replacing the developer according to the first embodiment will be described with reference to FIG. Figure 6 shows UI (user interface)
Copier A when the copy start button is pressed
4 is an operation control flow of FIG. In FIG. 6, when a copy start button is turned on, a density detection toner image is developed on the image carrier 11 in step ST1, and the developed toner density (the density of the developed toner image) Ta is used as the developed toner density. It is detected by the sensor SN2 (see FIG. 1).
Next, in step ST2, the detection value Ta of the developing toner concentration is obtained.
Is greater than or equal to the set reference value Tao.
If the determination in step ST2 is NO (N), the process proceeds to step ST3, in which toner is supplied in an amount corresponding to the difference between Tao and Ta, and then the process returns to step ST1. The toner replenishment in step ST3 is performed by the toner carrier replenishing device (42 + 44 to 47 + 51 to 54 + C + M + SN1).
+ SN2).

In step ST2, yes (Y)
In the case of, the process moves to step ST4. In step ST4, the developing container 4 is detected by the toner concentration sensor SN1 in the developing container.
1 is detected. Since the detected value Tb at this time is the toner concentration in the developing container when the detected value Ta of the developed toner concentration is equal to or higher than the set reference value Tao, the detected value Tb is set to the toner concentration reference value Tb in the container.
Set to o. Next, in step ST5, the count value of the ten-sheet counter n is set to “0”. That is, n = 0
And Next, in step ST6, it is determined whether or not Tb ≧ Tbo. Since Tb = Tbo was set in the step ST4, the answer is initially yes (Y). If yes (Y), copy is performed in step ST7. If no (N), copying is performed in step ST8, and at the same time, an amount of toner corresponding to the difference between Tbo and Tb is supplied.

Next, in step ST9, the count value of the ten-sheet counter n is incremented by "1".
Next, in step ST10, it is determined whether or not copying has been completed. This determination is made based on whether or not copying of the set number of copies input from the UI has been completed. If no (N), the process moves to step ST11. Next, in step ST11, n
= 10 is determined. If no (N), the process moves to step ST12. After detecting the in-container toner concentration Tb in step ST12, the process returns to step ST6. If yes (Y) in step ST11, it means that 10 copies have been made, and the process returns to step ST1.

In step ST10, if the answer is yes (Y), the process proceeds to step ST13. Step ST13
, The toner consumption Vt is calculated. Next, in step ST14, a carrier supply amount and a developer discharge amount corresponding to the toner consumption amount Vt are calculated. These calculations are performed by the carrier replenishment amount calculation means C3 and the developer discharge amount calculation means C4. Next, in step ST15, carrier supply and developer discharge are performed. Carrier replenishment is performed by the toner carrier replenishing device (42 + 44 to
7 + 51-54 + C + M + SN1 + SN2), and the developer is discharged by a developer discharge device (43 + 56-58 + C).
Performed by

As described above, the developing toner density Ta is detected by the developing toner density sensor SN2 at the start of copying and when 10 continuous copies are made. Then, when the developing toner concentration Ta is appropriate (when Ta ≧ Tao), the toner concentration Tb in the container is detected by the toner concentration sensor SN1 in the container, and the detected value Tb at that time is used as the reference value Tb of the toner concentration in the container.
determined to o. During the copying operation, the toner concentration Tb in the container is controlled such that the toner concentration Tb in the container is equal to or higher than the reference value Tbo. That is, when the toner in the developing container 41 is consumed by the developing operation, the developing container 41
The toner concentration Tb in the container detected by the toner concentration sensor SN1 inside the container decreases. When the toner concentration Tb falls below the reference value Tbo, toner is supplied. The toner supply amount Vt is detected as toner consumption by the toner consumption detecting means (48 + C). Then, at the end of copying, the supply of the carrier and the discharge of the developer are performed according to the detected toner consumption Vt. For this reason, the deterioration of the charging performance of the developer in the developing container 41 is suppressed, and the charging performance can be maintained within a certain range, so that high image quality can be stably realized.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described. In the description of the second embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The second embodiment differs from the first embodiment in the following points, but has the same configuration as the first embodiment in other points. In the first embodiment, as the start developer, a developer obtained by mixing a developer whose charging performance has been reduced to a certain level and a new developer is used.
As the start developer, a developer having a charging performance different from that of the developer to be supplied is used. In this case, the two types of carriers having different charging performances are carriers whose charge amounts are adjusted by changing the mixing ratio of coating agents (polymethyl methacrylate and polyperfluoroalkyl methacrylate) having two different charging performances. A relatively low charge carrier is used for the agent carrier, and a relatively high charge carrier is used for the replenishment carrier. Next, a specific configuration of the carrier used in this embodiment will be described. Start developer carrier 65 μm Ferrite particles 1000 parts by weight Polymethyl methacrylate 4 parts by weight Polyperfluoroalkyl methacrylate 6 parts by weight Replenishment carrier 65 μm ferrite particles 1000 parts by weight Polymethyl methacrylate 8 parts by weight Polyperfluoroalkyl methacrylate 2 parts by weight

(Effect of Embodiment 2) FIG. 7 shows developer charging when a developer having a charging performance different from that of a replenishing developer is used as a start developer and when only a new developer is used as a start developer. FIG. 4 is a diagram illustrating a relationship between performance and toner consumption time. In FIG. 7, when the toner is not replaced by using a developer having a different charging performance from the replenishing developer as the start developer (indicated by a dashed line), the charging performance of the start developer is reduced below the image quality defect occurrence boundary. High image quality cannot be maintained. However, when a carrier having a high charging performance is used as a replenishing developer and the carrier is exchanged, and when a different carrier having a low charging performance is used as a start developer (solid line), the same charging carrier is used. When only the developer is replaced (broken line)
It can be seen that the developer charging performance is kept constant without abruptly decreasing. Therefore, by using a developer having a different charging performance as the start developer, a reduction in the charging performance can be suppressed, a constant charging performance can be realized from the initial to the end, and a high image quality can be stably maintained. Become.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. Modified embodiments of the present invention will be exemplified below. (H01) The present invention can be applied to analog copying machines, printers, facsimile machines, etc., in addition to digital copying machines. (H02) The developer storage container (44
+51) instead of the toner storage container 44 and the carrier storage container 51, it is possible to configure the toner storage container and the two-component developer storage container.
Further, the developer storage container can be constituted by only one two-component developer storage container storing a two-component developer having a high toner concentration.

[0048]

According to the developing device of the present invention, the following effects can be obtained. (E01) In a developing device using a two-component developer, a change in the charging performance of the developer from initial to end can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image processing apparatus U including a developing device according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a main part of the developing device according to the first embodiment of the present invention.

FIG. 3 is a block diagram of the first embodiment.

FIG. 4 is an explanatory diagram of the relationship between developer charging performance and toner consumption. FIG. 4A shows that the charging performance of the developer increases as the toner consumption increases (to increase the time during which the developing operation is performed). FIG. 4B shows that as the supply ratio of the carrier into the developer increases, the rate of decrease of the developer charging performance decreases with the consumption of the toner. FIG.

FIG. 5 is a diagram illustrating developer charging when a developer in which charging performance is reduced and a new developer are used as a start developer and when only a new developer is used as a start developer; FIG. 4 is a diagram illustrating a relationship between performance and toner consumption time.

FIG. 6 is a developer replacement flow of the copying machine A that operates when a copy start button of a UI (user interface) is input.

FIG. 7 is a diagram illustrating a case where a developer including a carrier having a low charging performance, which is different from a carrier included in a replenishing developer, is used as a start developer, and the same developer as the replenishing developer is used. FIG. 7 is a diagram illustrating a relationship between developer charging performance and toner consumption time when used as a start developer.

FIG. 8 is a diagram illustrating a relationship between toner consumption time and developer charging performance.

[Explanation of symbols]

Q2: Development area, 41: Development container, 42: Developer supply port, 43: Developer discharge port, 44: Toner storage container, 51
... Carrier storage container, 59 ... Collection container, 64 ... Developing roll, (42 + 44-47 + 51-54 + C + M + SN1 +
SN2) toner supply device, (43 + 56-5)
8 + C): a developer discharge device; (61 to 63): a developer supply member;

Claims (3)

[Claims] 1. A developing device having the following requirements: (A01) a developing roll for transporting a two-component developer including a toner and a carrier to a developing area; the two-component developer; and the developing roll. (A02) a developer container containing a developer supply member for supplying a developer to the developer supply port and having a developer supply port and a developer discharge port; (A03) a collection container for collecting the developer discharged from the developer discharge port,
(A04) A developer discharging device that discharges the developer in the developing container from the developer discharging port to the collection container in accordance with consumption of the toner by the developing operation, and maintains the developer amount in the developing container at a predetermined value. (A05) The developing container which contains, as a start developer, a two-component developer containing a carrier whose charging performance is lower than that of the carrier supplied from the developer replenishing port at the time of new setting for starting use of the developing container. 2. The developing device according to claim 1, wherein the developing device has the following requirements: (A06) The developing device includes the same carrier as the carrier to be replenished, the carrier having reduced charging performance due to toner adhesion or the like. The developing container containing a component developer as a start developer. 3. The developing device according to claim 1, wherein the developing device has the following requirements: (A07) The developing device includes a carrier that is different from the replenishing carrier and has a lower charging performance than the replenishing carrier. The developing container containing a two-component developer as a start developer.