JP2006301538A - Developing apparatus and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus where a developer replacing work is unnecessary, and also, image definition is maintained even when the apparatus is installed in an inclined place, and to provide an image forming apparatus equipped with the developing apparatus. <P>SOLUTION: A developer quantity regulating member 20 which regulates the quantity of developer held and carried by a developing roller 17 is formed to a cylindrical shape, and also, the member 20 is rotatably arranged facing the developing roller 17. At least a part of the member 20 is constituted of a conductive body, and the member 20 also functions as a developer discharging mechanism of attracting the developer held and carried by the developing roller 17 toward the member 20 and sticking the developer to the member 20 as a bias voltage is applied by bias voltage parts 39a and 39b in between the member 20 and the developing roller 17, thereafter, discharging the developer from a developer tank 16, that is, discharging the deteriorated developer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile, and more specifically, a two-component system comprising an electrostatic latent image formed on an image carrier and a toner and a carrier. The present invention relates to a developing device that develops using the developer and an image forming apparatus including the developing device.

  In an electrophotographic image forming apparatus, a developing apparatus that visualizes (develops) an electrostatic latent image on the surface of a photoreceptor (image carrier) using a two-component developer composed of a carrier and a toner is often used. ing. In the case of a developing device using such a two-component developer, the toner is sequentially consumed by the developing operation, but the carrier is not consumed and remains in the device. Therefore, the carrier stirred together with the toner in the developing device deteriorates due to the spent such as peeling of the resin coating layer on the surface and adhesion of the toner to the carrier surface as the stirring frequency increases. Charging performance gradually decreases.

  Therefore, conventionally, the deteriorated developer (including the deteriorated carrier) in the developing tank is extracted and replaced with a new developer (total replacement). However, replacement of the developer including the carrier is a heavy labor. In addition, the toner, which is a fine powder, soars and may be sucked in, resulting in poor maintainability.

  In order to solve such a problem, for example, in Patent Document 1, not only the toner consumed by the developing operation but also the carrier in the developing device is replenished little by little to suppress the deterioration of the charging performance of the developer. A developing device configured as described above is disclosed. In the developing device, when the carrier is replenished, the developer in the developing tank (container for containing the developer) becomes excessive, and the excessive developer is provided on the wall surface of the developing tank. It overflows from the agent overflow outlet and is discharged.

By sequentially repeating such replenishment / discharge, the deteriorated developer in the developing tank is replaced with newly supplied toner and carrier, which requires maintenance to completely replace the developer. Therefore, the charging performance can be maintained and the deterioration of the image quality can be suppressed. Note that a developing device in which such supply and discharge of developer is sequentially repeated is referred to as a trickle developing device.
Japanese Patent Publication No. 2-21591 (Public Notice: May 15, 1990)

  However, the configuration of Patent Document 1 does not require the replacement of the developer and improves the maintainability. However, the developer in the developing tank cannot be maintained at an appropriate amount due to the inclination of the developing tank, and the image quality is lowered. Moreover, even if the developer in the developing device can be maintained at an appropriate amount, the developer in the developer tank is not sufficiently replaced, and the total replenishment amount is the same as the total developer amount to be replaced. In addition, there is a problem in that high image quality cannot be maintained as much as a configuration in which total replacement is performed.

  In other words, the developer discharging mechanism for discharging the deteriorated developer in Patent Document 1 is simply provided with a developer overflow outlet on the side wall of the developing tank, so that the discharge amount from the developing tank is inclined to the developing tank. However, it is difficult to discharge the developer in the designed amount when the developing tank is inclined.

  For example, when the image forming apparatus is moved and the side opposite to the developer overflow port becomes inclined, the ground condition of the installation location is bad, or the top of the desk to be installed is inclined. When the image forming apparatus is installed in an inclined state, a large amount of developer is discharged from the developer overflow outlet. In such a case, the amount of developer in the developing device is greatly reduced relative to the appropriate amount, and good image quality cannot be obtained.

  Also, since the developer overflow outlet is simply provided on the side wall of the developer tank, the fresh carrier just replenished to the developer tank can be discharged from the developer overflow outlet without being used sufficiently in the developer tank. Can happen. Therefore, even if the developer in the developing tank is not sufficiently replaced and the developer can be discharged in the designed amount, the carrier in the developing tank has deteriorated significantly with long-term use. Medium carrier, brand new carrier with almost no deterioration, etc. are mixed. In such a state, the apparent progress of carrier deterioration stops and the characteristics of the developer as a whole are stabilized, but the stable level is considerably worse than the initial state of the developer, and the replacement amount is reduced. However, the developer cannot be maintained at a high level, and the running cost is high in that the amount of developer to be replenished increases.

  The present invention has been made in view of the above problems. A first object of the present invention is to provide a developing device that does not require a developer replacement operation and that can maintain image quality even when installed in an inclined place. The second object of the present invention is to provide an image forming apparatus equipped with the image forming apparatus, and the second object is that no developer replacement work is required, the image quality can be maintained even when installed at an inclined place, and development is possible even with a small supply amount. It is an object of the present invention to provide a developing device capable of maintaining the developer in the apparatus at a high level and an image forming apparatus including the developing device.

  In order to solve the above problems, a developing device according to the present invention is a developing device that develops an electrostatic latent image formed on an image carrier using a two-component developer composed of a toner and a carrier. A developer tank that contains the developer, a developer carrier that is rotatably disposed opposite to the image carrier, carries the developer in the developer tank, and conveys the developer to the image carrier. In the developing device in which the toner and the carrier are replenished from the replenishing device in the developing tank, and the developer is sequentially discharged from the developing tank by the developer discharging mechanism. The developer amount regulating member that regulates the amount of the developer that is conveyed is formed in a cylindrical shape, and is rotatably disposed to face the developer carrying member. The developer amount on the developer carrier is regulated by the above developer amount. By adhering to the wood it is characterized by being composed by discharging from the developing tank.

  Conventionally, in a developing device, in order to make the amount of developer conveyed to an image carrier constant, a developer that regulates the amount of developer on the developer carrier facing the developer carrier. A quantity regulating member is arranged. The shape of the developer amount regulating member is generally a blade shape.

  In the above configuration, such a developer amount regulating member is formed in a cylindrical shape and rotatably disposed, and the developer carried on the developer carrier is attached to the developer amount regulating member from the developer tank. By discharging, a developer discharging mechanism is configured.

  Developer discharge using such a developer amount regulating member can be controlled by the amount of developer adhering to the developer amount regulating member, so that development using the developer overflow described above is possible. As with the agent discharge mechanism, the discharge amount does not fluctuate in the inclined state of the developing tank, and even if the image forming apparatus equipped with the developing device is tilted when moved or installed on an inclined surface As a result, it is possible to discharge the developer in the same amount, and to keep the developing amount in the developing tank constant.

  In the developing device according to the present invention, at least a part of the developer amount regulating member is made of a conductor, and a deteriorated carrier is interposed between the developer amount regulating member and the developer carrying member by a bias unit. The deteriorated developer can be discharged by applying a bias voltage that generates an electric field that electrostatically moves the developer from the developer carrying member to the developer amount regulating member.

  In the developer used for a long time, the toner spent with the toner fixed on the surface of the carrier has progressed, and the high-resistance toner adheres, so that the resistivity of the carrier becomes high, and the deteriorated carrier has a friction compared to the initial carrier. Charge holding power increases.

  In the above configuration, the high frictional charge holding force of the deteriorated carrier is utilized, and a bias voltage is applied between the developer amount regulating member and the developer carrier to remove the deteriorated carrier. An electric field that is electrostatically moved from the developer carrying member to the developer amount regulating member is generated, and the high-resistance deteriorated carrier is attracted to the developer amount regulating member side to be attached and discharged. At this time, the deteriorated carrier tends to be separated from the toner and the developer carrier due to the spacer effect of the external additive due to the increase in the amount of the external additive attached, and is more effectively attracted to the developer amount regulating member. Will be.

  In such discharge, since the deteriorated carrier is the discharge target, the deteriorated carrier can be efficiently replaced with a new carrier as compared with the developer discharge mechanism using the overflow of the developer described above, and the developing device can be used even with a small amount of carrier replacement It is possible to maintain the developer contained in the high level state, and the running cost can be reduced.

  In this case, the DC bias voltage is more preferably applied by the bias means, and the DC bias voltage to be applied is more preferably changed.

  As a bias voltage applied between the developer amount regulating member and the developer carrying member, a DC bias voltage and a superimposed bias voltage obtained by superimposing an AC bias voltage on the DC bias voltage can be considered. However, when the carrier is moved at a reverse potential using the superimposed bias voltage, even if the amplitude potential of the component of the superimposed AC bias voltage is large, even the carrier with low resistance and not much deteriorated is on the developer amount regulating member side. It will be moved to.

  On the other hand, by making the bias voltage between the developer amount regulating member and the developer carrier a direct current bias voltage, the carrier that has not deteriorated is hardly moved to the developer amount regulating member side. The movement of the carrier having deteriorated resistance toward the developer amount regulating member side becomes dominant.

  Therefore, with such a configuration, the deteriorated carrier can be preferentially discharged to the developer amount regulating member side, so that the running cost can be further reduced.

  Further, by adopting a configuration in which the DC bias voltage to be applied is variable, the developer discharge amount can be freely set.

  The developing device according to the present invention further includes an attached developer removing mechanism that removes the developer attached to the developer amount regulating member and conveys the developer to a developer collecting container provided outside the developing device. You can also.

  According to this, the developer adhering to the developer amount regulating member is removed from the developer amount regulating member by the adhered developer removing mechanism and conveyed to the developer collection container outside the apparatus. The quantity regulating member can always be kept fresh.

  As a result, the amount of developer on the developing carrier can be always regulated to be constant. Further, it becomes possible to discharge the deteriorated developer with high accuracy by the electric field, and the new developer and the deteriorated developer can be replaced at a certain ratio, and good development performance can be maintained.

  In the developing device according to the present invention, it is preferable that the rotational peripheral speed of the developer amount regulating member is faster than the rotational peripheral speed of the developer carrier.

  According to this, since the rotational peripheral speed of the developer amount regulating member is set faster than the rotational peripheral speed of the developer carrying member, the developer amount regulating member and the developer carrying member are always kept fresh. It becomes possible to keep in a state.

  As a result, the amount of developer on the developing carrier can be always regulated to be constant. Further, it becomes possible to discharge the deteriorated developer with high accuracy by the electric field, and the new developer and the deteriorated developer can be replaced at a certain ratio, and good development performance can be maintained.

  In the developing device according to the present invention, a replenishing developer in which a carrier is mixed with toner is replenished from the replenishing device to the developing tank, and replenished from the replenishing device to the developing tank after every image formation. A replenishment amount predicting means for predicting the replenishment amount of the replenishing developer, and the developer discharge mechanism controls the discharge amount of the developer based on the replenishment amount predicted by the replenishment amount predicting means; You can also

  In a developing device using a two-component developer, it is important to keep the toner concentration of the developer contained in the developer tank constant, so that the same amount of toner as that consumed in image formation is replenished. Therefore, it is necessary to change the amount of carrier in the developing tank to a constant amount so as not to change the toner density. Further, in a configuration in which a replenishment developer obtained by mixing a small amount of carrier with toner is replenished from the replenishing device, the amount of carrier replenished into the developing device after every image formation depends on the toner consumption, that is, the image density. It will be.

  Therefore, in the above configuration, a replenishment amount predicting unit for predicting the replenishment developer amount replenished to the developing tank after every image formation is provided, and the developer discharge mechanism is predicted by the replenishment amount predicting unit. Since the developer discharge amount is controlled based on the replenishment amount, an amount of developer containing the same amount of carrier as the carrier contained in the replenishment developer is discharged by the developer amount regulating member, and any image area Even after image formation over a long period of time, the amount of developer accommodated in the developing device can be stably maintained.

  Here, the replenishment amount prediction means includes, for example, dot count means for detecting an integrated value of the number of pixels of the image formed on the image carrier, and the integrated value detected by the dot count means is calculated. Based on this, it can be configured to predict the replenishment amount replenished after image formation.

  Since the dot count means detects the integrated value of the number of pixels of the image formed on the image carrier, the image density of the printed matter is predicted from the detected value (the integrated value of the number of pixels of the image). Can do. Since the toner amount consumed for the image formation can be predicted from the image density, as a result, the replenishment amount replenished after each image formation by the dot count unit can be predicted. The developing device of the present invention can be easily realized.

  As another configuration, the replenishment amount predicting means includes replenishment time detecting means for detecting a replenishment time during which the replenishment developer is replenished from the replenishing device to the developing device. The replenishment amount to be replenished after each image formation can be predicted based on the replenishment time detected by the above.

  The replenishment time detecting means detects a replenishment time during which the replenishment developer is replenished from the replenishing device to the developing device. The replenishment amount of the replenishment developer from the replenishing device to the developing device is normally controlled by the rotation time of the replenishing roller and the replenishment amount can be predicted from the replenishment time. Therefore, with such a configuration, the developing device of the present invention can be easily realized.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a developing device that develops an electrostatic latent image on an image carrier using a two-component developer composed of a toner and a carrier. In the image forming apparatus in which the toner and the carrier are replenished from the replenishing device in the developing device, and the developer in the developing device is sequentially discharged by the developer discharging mechanism, the developing device of the present invention is used as the developing device. A developing device is provided.

  As already described, the developing device of the present invention does not require a developer replacement operation, and can maintain image quality even when installed in an inclined place. Since it is possible to maintain the developer in the developing device at a high level, by providing such a developing device, it is excellent in maintainability and can maintain image quality even if installed in an inclined place. The image forming apparatus has an advantage that the running cost is low.

  As described above, the developing device and the image forming apparatus of the present invention are developing devices that develop an electrostatic latent image formed on an image carrier using a two-component developer composed of a toner and a carrier. A developer tank that contains the developer, a developer carrier that is rotatably disposed opposite to the image carrier, carries the developer in the developer tank, and conveys the developer to the image carrier. In the developing device in which the toner and the carrier are replenished from the replenishing device in the developing tank, and the developer is sequentially discharged from the developing tank by the developer discharging mechanism. The developer amount regulating member that regulates the amount of the developer that is conveyed is formed in a cylindrical shape, and is rotatably disposed to face the developer carrying member. The developer amount on the developer carrier is regulated by the above developer amount. By adhering to the timber it is constituted by discharging from the developing tank.

  Therefore, there is an effect that it is possible to provide a developing device that does not require a developer replacement operation and can maintain image quality even when installed at an inclined place, and an image forming apparatus including the developing device.

  Further, in this case, at least a part of the developer amount regulating member is made of a conductor, and the biasing means removes the deteriorated carrier from the developer carrying member between the developer amount regulating member and the developer carrying member. By applying a bias voltage that generates an electric field that moves electrostatically to the developer amount regulating member, the developer contained in the developing device is maintained at a high level even with a small amount of carrier replacement. This also has the effect of reducing running costs.

  An embodiment of the present invention will be described below with reference to FIGS.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are examples embodying the present invention, and do not limit the technical scope of the present invention.

  First, the operation of the entire image forming apparatus will be described with reference to the configuration diagram of FIG. Here, an analog image forming apparatus including an analog optical system is illustrated as the exposure optical system 2, but a digital image forming apparatus including a digital optical system including a CCD sensor may be used. Good.

  As shown in FIG. 2, in the image forming apparatus, a document placing table 1 is provided on the upper surface portion, and an exposure optical system 2 is disposed below the document placing table 1. The exposure optical system 2 includes a light source lamp 3 that scans while irradiating light on a document (not shown) placed on the document placing table 1, and reflected light from the document on a photosensitive member (image carrier) 4. It comprises a plurality of reflecting mirrors 5 for guiding, and a lens unit 6 arranged in the optical path of the reflected light.

  On the outer periphery of the photoreceptor 4, a charging charger 7 for charging the surface thereof to a predetermined potential, an interimage eraser (not shown), a developing device 8 for developing an electrostatic latent image formed on the surface of the photoreceptor 4, and a photosensitive member. A transfer charger 9 for transferring the toner image on the surface of the body 4 to a sheet (sheet), a cleaning device 10 for collecting residual toner on the surface of the photoconductor 4, a static eliminator (not shown), and the like are provided.

  A timing roller 11 for supplying paper at a predetermined timing, a transport roller 12, a paper feed cassette 13, and a paper feed roller 14 are provided on the paper input side with respect to the photoconductor 4, while on the paper output side with respect to the photoconductor 4. Is provided with a fixing device 15 for fixing the toner image transferred onto the paper to the paper.

  The process unit 36 (see FIG. 5) is configured by members provided around the photoreceptor 4 including the exposure optical system 2 and the fixing device 15, and includes a timing roller 11, a transport roller 12, and a paper feed cassette 13. The paper feed roller 14 constitutes a paper transport unit 37 (see FIG. 5).

  As shown in FIG. 3, the developing device 8 has a resin-molded developer tank 16 that constitutes a container for containing the developer. In the developer tank 16, the developer is transported and stirred. Agitating and conveying screws (rotating members) 18 and 19 for performing the above and a developing roller (developer carrying member) 17 for magnetically adsorbing and conveying the developer supplied by the agitating and conveying screw 18 are rotatably provided. .

  The developer tank 16 contains a predetermined amount (for example, 400 g) of developer. The developer tank 16 is made of a carrier and a toner, and the carrier made of a magnetic material is a resin that suppresses adhesion of the toner to the surface. It has a coat layer. When the carrier and the toner are agitated by the agitating and conveying screws 18 and 19, the toner is frictionally charged.

  As is well known, the developing roller 17 is configured to rotationally drive a cylindrical non-magnetic sleeve in the direction of the arrow so as to cover a magnet having a large number of magnetic poles provided on the peripheral surface. Therefore, the developer is attracted to the sleeve surface by the magnetic force of the magnet and is conveyed along the rotation direction of the sleeve. Specifically, the carrier is attracted to the developing roller 17 by magnetic force to form a magnetic brush, and the toner adheres to the carrier by Coulomb force.

  The developing roller 17 is provided so that a part of the developing roller 17 is exposed from the opened opening of the developing tank 16, and faces the photosensitive member 4 that is rotated at the exposed portion. This facing position is the developing position, and the carrier forming the magnetic brush by sliding the developer conveyed by the rotation of the developing roller 17 against the electrostatic latent image formed on the surface of the photoreceptor 4. The toner attached to the toner is attracted by the electrostatic force of the electrostatic latent image, and the electrostatic latent image is developed.

  Here, before the developer is transported to the developing position where it is rubbed against the photoreceptor 4, the excess amount adsorbed by the developing roller 17 by the developer amount regulating member 20 so that the amount thereof is always constant. Things are going to be removed. Although details will be described later, in the present image forming apparatus, the developer amount regulating member 20 is used for discharging the deteriorated developer.

  On the other hand, as shown in FIG. 4, a developer supply opening 26 is formed in the upper wall portion of the developing tank 16, and a carrier developer supply device (supply device) 25 is inserted into the supply opening 26 from above. It is inserted. The carrier developer replenishing device 25 accommodates, for example, a carrier developer which is a replenishing developer in which a carrier and toner are mixed at a predetermined ratio. As an example of the mixing ratio, the weight ratio can be increased by about 1: 9 (carrier: toner). As can be seen from this ratio, the toner ratio in the carrier developer is higher than that in the developer tank 16. The ratio in the carrier developer should be appropriately adjusted depending on the charge amount of the toner, the carrier particle size, the configuration of the image forming apparatus, and the like.

  A carrier developer supply screw 22 that is driven and controlled by a control device 32 (see FIG. 5), which will be described later, is provided at the bottom of the carrier developer supply device 25. When the carrier developer supply screw 22 is driven to rotate, the carrier developer flows down from the carrier developer supply device 25 by an amount corresponding to the drive time of the carrier developer supply screw 22 and is supplied into the developing tank 16. Then, it is agitated and conveyed by the agitating and conveying screws 18 and 19.

  Further, as shown in FIG. 4, the developing tank 16 is provided with a toner concentration sensor 34 that detects the toner density in the developing tank 16. The toner concentration sensor 34 is composed of, for example, a magnetic permeability sensor, detects the magnetic permeability by contacting the carrier, and obtains the ratio of the toner to the carrier from the detected magnetic permeability. The toner density sensor 34 detects that the toner ratio in the developer in the developing tank 16 is high, that is, the toner density is high when the amount of carrier contacting the toner density sensor 34 is small, while the toner density sensor 34 contacts the toner density sensor 34. When the amount of carrier to be carried out is large, it is detected that the toner ratio in the developer in the developing tank 16 is low, that is, the toner concentration is low. Then, the detection signal (detection result) of the toner concentration sensor 34 is sent to a control device 32 (see FIG. 5) which will be described later, and the control device 32 carries out the carrier of the carrier developer supply device 25 based on this detection signal. The developer supply screw 22 is driven to supply the developer into the developer tank 16.

  Next, a copy operation in the image forming apparatus having the above configuration will be described. When a power switch (not shown) is turned on, a warm-up process is first performed. After this is completed, when a later-described start switch 31 (see FIG. 5) is turned on, the document placed on the document placement table 1 is scanned by the light source lamp 3 of the exposure optical system 2. Reflected light from the original at this time is applied to the photoconductor 4 through the reflecting mirror 5... And the lens unit 6, and an electrostatic latent image is formed on the surface of the photoconductor 4 charged to a predetermined potential by the charging charger 7. It is formed.

  Next, the electrostatic latent image is developed with toner supplied from the developing device 8. The toner image on the surface of the photosensitive member 4 is transferred to a sheet supplied from the sheet feeding cassette 13 by the transfer charger 9 and is thermally fixed on the sheet by the fixing device 15. As a result, a copy image corresponding to the original image is formed on the paper.

  Such a series of copying operations is a control center for controlling each part of the image forming apparatus shown in FIG. 5, and is controlled by a control device 32 including a CPU, a ROM, and a RAM. FIG. 5 is a block diagram illustrating a configuration of a control system in the image forming apparatus.

  An ON operation signal for the start switch 31 is input to the control device 32. Further, the image forming apparatus includes an image forming counter (measuring unit) 33 that counts the cumulative number of image forming operations and a dot count device 35 that detects an integrated value of the number of pixels of an image formed on the photosensitive member 4. These count values (hereinafter referred to as image forming count values and dot count values) are also input to the control device 32.

  When the copying operation as described above is repeated, the toner in the developer stored in the developing tank 16 of the developing device 8 is gradually consumed, and the ratio of the toner to the carrier, that is, the toner density is lowered. I will do it. The toner density sensor 34 detects the change in the toner density, and the control device 32 controls the driving of the carrier developer supply screw 22 based on the detection signal of the toner density sensor 34.

  That is, the control device 32 starts driving the carrier developer replenishing screw 22 when it is detected from the detection signal of the toner concentration sensor 34 that the toner concentration has dropped to the lower limit of the appropriate range necessary for development. As a result, the carrier developer of the carrier developer supply device 25 is supplied into the developing tank 16 and the toner concentration in the developing tank 16 is increased. When it is detected from the detection signal of the toner density sensor 34 that the toner density has reached the upper limit value of the appropriate range, the control device 32 stops driving the carrier developer supply screw 22. By such control, the toner concentration in the developing tank 16 is maintained within the appropriate range. The carrier developer replenished into the developing tank 16 is agitated with the developer existing in the developing tank 16, controlled to a constant charge amount, supplied to the photoreceptor 4, and used for development.

  On the other hand, the carrier in the developer is not consumed like toner, and is used repeatedly. Therefore, the carrier is gradually agitated by the developing roller 17 and the agitating and conveying screws 18 and 19 and in contact with the photoreceptor 4. Deteriorating. As the carrier deteriorates in this way, a predetermined charge amount cannot be imparted to the toner, resulting in a decrease in image quality.

  Therefore, conventionally, a new carrier is newly supplied to the developing tank 16, while the developer is sequentially discharged from the developing tank 16, and the deteriorated carrier in the developing tank 16 is sequentially replaced with a new carrier. In this image forming apparatus, as described above, the developer amount regulating member 20 is used to discharge such developer.

  That is, the shape of the developer amount regulating member is generally a blade, but the developer amount regulating member 20 in the present image forming apparatus has a cylindrical shape as shown in FIG. It is provided so as to be rotatable. The developer carried on the surface of the developing roller 17 is adhered to the surface and discharged from the developing tank 16 (developer discharging mechanism).

  In such a method of attaching and discharging to the developer amount regulating member 20, the discharge amount can be managed by the amount of developer attached to the developer amount regulating member 20, so that the developer overflow described above is used. As in the developer discharging mechanism, the image forming apparatus equipped with the developing device 8 is tilted when it is moved or installed on an inclined surface without the discharge amount fluctuating in the inclined state of the developing tank 16. Even so, the set amount of developer can be discharged, and the developing amount in the developing tank 16 can be kept constant.

  In this image forming apparatus, the developer amount regulating member 20 is a conductive roller made of a conductive material such as stainless steel, and a bias voltage is applied between the developer amount regulating member 20 made of a conductive roller and the developing roller 17. In the part 39, a bias voltage is applied to generate an electric field for electrostatically moving the deteriorated carrier from the developing roller 17 to the developer amount regulating member 20. The bias voltage unit 39 includes a bias voltage unit 39 a that applies a voltage to the developer amount regulating member 20 and a bias voltage unit 39 b that applies a voltage to the developing roller 17. It is to be controlled.

  The deterioration of the developer due to long-term use has progressed in the toner spent where the toner adheres to the carrier surface, and the resistivity of the deteriorated carrier to which the toner having a high resistivity adheres is higher than the resistance value of the initial carrier. . In the developing tank 16, the carrier is agitated with the toner and frictionally charges the toner. At this time, the carrier itself is charged with a polarity opposite to that of the toner. If the carrier is an initial carrier (new carrier), the resistivity is low. Therefore, the charged carrier is gradually attenuated by discharging it into the developing roller 17 or the air, but the deteriorated carrier has a high resistivity due to toner spent. Then, it is difficult to attenuate, and the frictional charge holding force is higher than that of the initial carrier.

  Such a deteriorated carrier having a high frictional charge holding force is applied with a bias voltage, and an electric field is generated that electrostatically moves the deteriorated carrier from the developing roller 17 to the developer amount regulating member 20. The developer is attracted to and attached to the developer amount regulating member 20 (the potential at which a force is applied to the carrier from the developing roller 17 toward the developer amount regulating member 20), and is discharged. At this time, since the deteriorated carrier has a large amount of external additive attached, it is easily separated from the toner and the developing roller 17 due to the spacer effect and is easily attracted.

  In such a discharge method, since the deteriorated carrier is a discharge target, the deteriorated carrier can be replaced with a new carrier more efficiently than the developer discharge mechanism using the overflow of the developer described above, and the amount of carrier replacement is small. However, the developer stored in the developing device 8 can be maintained at a high level, and the running cost can be reduced.

  Here, the developer amount regulating member 20 is a conductor roller. However, the developer amount regulating member 20 may be discharged so that the deteriorated developer can be discharged from at least a part of the surface, preferably the entire axial direction of the developing roller 17. It is only necessary that a part of the region extending in the entire axial direction is made of a conductor. However, in view of the function of restricting the rise of the magnetic brush formed on the surface of the developing roller 17, it is necessary to be a rigid body.

  By the way, as a bias voltage applied between the developer amount regulating member 20 and the developing roller 17, a direct current (DC) bias voltage and a direct current (DC) bias voltage superimposed on an alternating current (AC) bias voltage ( DC + AC) bias voltage. However, when the carrier is moved at a reverse potential using the superimposed bias voltage, even if the amplitude potential of the component of the superimposed AC bias voltage is large, even the carrier with low resistance and not much deteriorated is on the developer amount regulating member side. Therefore, only the carrier having a high resistance deteriorated cannot be attached to the developer amount regulating member 20.

  Therefore, in the present image forming apparatus, the bias voltage unit 39 applies a DC bias voltage between the developer amount regulating member 20 and the developing roller 17. As a result, it is unlikely that carriers that have not deteriorated so much adhere to the developer amount regulating member 20 side, and the electrostatic developer amount regulating member 20 on the electrostatic developer amount regulating member 20 side due to the reverse potential of the deteriorated high-resistance carrier. Adhesion becomes dominant. As a result, the deteriorated carrier can be preferentially discharged to the developer amount regulating member side, and the developer in the developing tank 16 can be maintained at a higher level, further reducing the running cost. I can plan.

  Further, in the present image forming apparatus, as shown in FIG. 5, the bias voltage unit 39 is configured to be able to variably control the bias voltage applied by the control device 32. By making the bias voltage value variable, the amount of developer discharged by using the developer amount regulating member 20 is changed by changing the above-described reverse potential to which the deteriorated carrier is moved to the developer amount regulating member 20 and attached. Can be set freely.

  Further, in this image forming apparatus, as shown in FIG. 1, the developer adhering to the developer amount regulating member 20 is removed and conveyed to a developer recovery container (not shown) provided outside the developing device 8. An attached developer removing mechanism 38 is provided.

  Here, the attached developer removing mechanism 38 includes a scraper 21 that peels off the deteriorated developer attached to the developer amount regulating member 20, and a receiving unit 23 that receives the developer that is peeled off and dropped by the scraper 21. It comprises a deteriorated developer recovery screw 24 that conveys the developer recovered in the receiving portion 23 into a developer recovery container.

  By providing such an attached developer removing mechanism 38, the developer attached to the developer amount regulating member 20 is removed from the developer amount regulating member 20 and conveyed to the developer collection container. The agent amount regulating member 20 can always keep a fresh state, and the developer amount on the developing roller 17 can be always regulated to be constant. Further, it becomes possible to discharge the deteriorated developer with high accuracy using the above-mentioned electric field, and the new developer and the deteriorated developer can be replaced at a certain ratio, and good development performance can be maintained.

  Further, in order to keep the developer amount regulating member 20 and the developing roller 17 in a fresh state at all times, such an adhered developer removing mechanism 38 is provided and the rotational peripheral speed of the developer amount regulating member 20 is also provided. Is preferably set faster than the rotational peripheral speed of the developing roller 17.

  Further, in this image forming apparatus, the amount of carrier developer to be replenished from the carrier developer replenishing device 25 to the developing tank 16 is predicted, and the developer discharge amount is controlled based on the predicted amount of replenishment. It is supposed to be.

  Specifically, a dot count device (dot count means) 35 shown in FIG. 5 is provided as means for predicting the replenishment amount. The dot count device 35 detects an integrated value of the number of pixels of the image formed on the photoconductor 4. From the integrated value of the number of pixels of the image detected by the dot count device 35, an approximate image density is obtained. The amount of toner consumed for image formation can be predicted from the image density. That is, by using such a dot count device 35, the amount of carrier developer to be replenished after every image formation can be predicted.

  The output (dot count value) of the dot count device 35 is input to the control device 32, and the control device 32 obtains a predicted image density based on the dot count value, and uses the predicted image density to perform the image formation. The estimated toner consumption consumed is obtained, and the amount of carrier developer to be replenished thereafter is predicted for each image formation (each printed matter).

  Then, the control device 32 calculates the amount of developer to be discharged based on the predicted amount of carrier developer, that is, the amount of developer containing the same amount of carrier as the carrier contained in the carrier developer, and controls the amount of developer. The bias voltage unit 39 applies a bias voltage at which the member 20 has a reverse potential at which the calculated amount of developer can be discharged.

  As a result, an amount of developer containing the same amount of carrier as the carrier contained in the carrier developer can be discharged onto the developer amount regulating member 20, and the developing tank 16 can be used after image formation over a long period of any image area. The amount of developer contained in the toner can be stably maintained.

  Note that the developer discharge using the developer amount regulating member 20 may be performed at a timing other than the time of image formation, such as between printed materials.

  Here, the present invention will be described in more detail with reference to an embodiment of the image forming apparatus. The image forming apparatus of the present embodiment is structurally the same as the image forming apparatus shown in FIG. The photosensitive member 4 is uniformly charged to −650V by the charging charger 7, and the image forming area on the photosensitive member 4 is exposed to writing light to become −100V. The developing bias applied between the photosensitive member 4 and the developing roller 17 when developing the image forming area is a superimposed (DC + AC) bias voltage obtained by superimposing an alternating current (AC) bias voltage on a direct current (DC) bias voltage. When the amplitude potential of the AC component is 1000 V (peak-peak), the DC component potential is −450 V, and the development potential difference is 350 V, the toner adheres to the electrostatic latent image on the photoconductor 4 and development is performed. Further, while the photosensitive member 4 rotates in the clockwise direction, the developing roller 17 rotates in the counterclockwise direction, and the developer amount regulating member 20 also rotates in the counterclockwise direction (see FIG. 1).

In the image forming apparatus having such a configuration, the cylindrical developer amount regulating member 20 is made of stainless steel which is a rigid body and at least a part is a conductor, and the developer amount regulating member 20 is opposed to the magnetic pole of the developing roller 17. When the gap is arranged at a gap of 0.8 mm to 0.9 mm, a uniform and non-uniform transport amount of approximately 30 to 40 mg / cm ² can be obtained, and a stable image with uniform density can be obtained. .

  In such a configuration, when the developer is discharged, a DC bias of −350 V is applied to the developing roller 17 and −850 V is applied to the developer amount regulating member 20, so that the deteriorated carrier that has generated toner spent is preferentially applied. It was possible to discharge.

  In FIG. 6, in the image forming apparatus according to the present exemplary embodiment, a reverse potential generated on the developer amount regulating member 20 side by applying a bias voltage and a carrier amount (carrier adhesion amount) attached to the developer amount regulating member 20. The result of investigating the relationship with is shown. As can be seen from FIG. 6, by setting the reverse potential to 350 V or more, the carrier starts to adhere to the developer amount regulating member 20, and the adhesion amount increases as the reverse potential increases.

  FIG. 7 shows a case where the voltage applied to the developing roller 17 when discharging the developer is a DC bias voltage (DC bias voltage) and an AC + DC bias voltage (superimposed bias voltage) in the image forming apparatus of this embodiment. In each case, the results of examining the relationship between the number of image formations and the weight of toner spent on the carrier in the collected deteriorated developer are shown.

  In FIG. 7, the horizontal axis represents the number of image formations, and the vertical axis represents the toner weight spent on the carrier 1g. It can be seen that when the developer is discharged with the DC developing bias compared to the AC + DC developing bias, the carrier having a large amount of toner spent, that is, the deteriorated carrier is discharged preferentially. It can be seen that the state of the developer in the developing tank 16 is maintained at a higher level when the developer is discharged.

  Further, FIG. 8 shows the result of examining the relationship between the reverse potential generated on the developer amount regulating member 20 side and the carrier adhesion amount on the entire developer amount regulating member 20 in the image forming apparatus of this embodiment. . From FIG. 8, the carrier adhesion amount on the entire developer amount regulating member 20 depends on the reverse potential, and increases as the reverse potential increases.

  Based on the relationship between the reverse potential and the total deteriorated discharged carrier amount by the developer amount regulating member 20, the control device 32 causes the discharged carrier amount to be the same as the carrier included in the replenished developer amount predicted. A reverse potential is determined for the bias voltage unit 39, and the voltage output of the bias voltage unit 39 is controlled so that the determined reverse potential is obtained.

  Here, for example, when the image density detected by the dot counting device 35 is 5%, the developing device 8 is supplied with 5 mg of carrier, so the control device 32 sets the reverse potential to 500 V and reverses 500 V. The output of the bias voltage unit 39 is controlled so as to become a potential. On the other hand, when the image density detected by the dot counting device 35 is 15%, since 15 mg of carrier is supplied to the developing device 8, the reverse potential is set to 540V, and the bias voltage unit 39 is set to have a reverse potential of 540V. Control the output.

In the image forming apparatus of the present embodiment, the above-described adhered developer removing mechanism 38 is provided,
Since the rotational speed of the developer amount regulating member 20 is set to 400 mm / s with respect to the rotational speed of the developing roller 17 being 200 mm / s, the state between the developer amount regulating member 20 and the developing roller 17 is always fresh. I was able to keep it.

  The numerical values raised in this embodiment are merely examples. For example, the developer conveyance amount in the developing roller 17 should be appropriately adjusted according to the toner charge amount, the carrier particle size, the configuration of the image forming apparatus, and the like. Therefore, it is not always necessary to follow this numerical value, and the same applies to the potential of the photosensitive member 4, the values of the developing bias and the reverse potential, the peripheral speed values of the developing roller 17 and the developer amount regulating member 20, and the like. It is.

  Next, another embodiment according to the present invention will be described with reference to FIG. For convenience of explanation, members having the same functions as those used in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the case of the image forming apparatus of the above-described embodiment, the replenishment amount predicting means for predicting the amount of the carrier developer replenished to the developing tank 16 after each image formation is constituted by the dot count device 35 and the control device 32. . On the other hand, the replenishment amount predicting unit in the image forming apparatus according to the present embodiment includes only the control device 32 ′ shown in FIG. 9 having a function as a replenishment time detecting unit. After the image formation, the amount of carrier developer supplied from the carrier developer supply device 25 is detected from the drive time (rotation time) of the carrier developer supply screw 22. Since other configurations are the same as those of the image forming apparatus of the above-described embodiment, members having the same functions as those used in the above-described embodiment are denoted by the same reference numerals for convenience of explanation. Description is omitted.

  As described above, when it is detected from the detection signal of the toner density sensor 34 that the toner density has dropped to the lower limit of the appropriate range necessary for development, the control device 32 ′ drives the carrier developer supply screw 22. After that, when it is detected from the detection signal of the toner density sensor 34 that the toner density has reached the upper limit of the above appropriate range, the driving of the carrier developer supply screw 22 is stopped.

  Therefore, by measuring the drive time of the carrier developer supply screw 22 and obtaining the replenishment amount per unit drive time in advance, the amount of carrier developer replenished after every image formation can be obtained.

  In other words, the present invention can also be expressed as follows. In other words, the developing device of the present invention is rotatably disposed at a position facing the latent image carrier and a developer housing in which a developer composed of carrier and toner is accommodated, and the developer is carried and conveyed. A developer carrying body, and a stirring and conveying means for stirring and carrying the developer to the developer carrying body, and sequentially replenishing the developer housing with a new developer including at least a carrier from a developer supply container, In a developing device that sequentially discharges a deteriorated developer from a developing housing, the developer is opposed to the developer carrying member and is capable of rotating to regulate the amount of the developer carried on the developer carrying member. A cylindrical developer amount regulating member is provided, and the deteriorated developer is collected in the developer amount regulating member.

  In the developing device, the carrier in the developer transported by the developer carrier is moved from the developer carrier to the developer amount regulating member between the developer carrier and the developer amount regulating member. There is provided a means for causing an electric field.

  In the developing device, the electric field means for moving and collecting the developer carrying member from the developer carrying member to the developer amount regulating member is a DC bias, and the toner spent on the surface layer is preferentially discharged so that the carrier having a high resistance value is discharged. It can also be configured.

  The present invention can be applied to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile machine, which includes a developing device that develops using a two-component developer composed of toner and a carrier.

1 is a cross-sectional view illustrating a mechanism for discharging a deteriorated developer from the inside of a developing device mounted in an image forming apparatus according to an embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part structure of the said image forming apparatus. FIG. 2 is a longitudinal sectional view illustrating a main configuration of a developing device mounted on the image forming apparatus and a replenishing device attached to the developing device. FIG. 2 is a plan view showing a state where an upper wall portion in a developing device mounted on the image forming apparatus is viewed. FIG. 2 is a block diagram illustrating a main configuration of a control system of the image forming apparatus. 6 is a graph showing the relationship between the reverse potential generated on the developer amount regulating member side and the carrier adhesion amount on the developer amount regulating member in the image forming apparatus of the embodiment of the present invention. In the image forming apparatus according to the embodiment of the present invention, when the voltage applied to the developing roller when discharging the developer is a DC bias voltage and when the voltage is an AC + DC bias voltage, the number of times of image formation and the collected deteriorated developer 6 is a graph showing the relationship with the toner weight spent on the carrier. 6 is a graph showing the relationship between the reverse potential generated on the developer amount regulating member side and the carrier adhesion amount on the entire developer amount regulating member in the image forming apparatus of the embodiment of the present invention. FIG. 2 is a block diagram illustrating a main configuration of a control system of the image forming apparatus.

Explanation of symbols

4 Photoconductor (image carrier)
8 Developing Device 17 Developing Roller (Developer Carrier)
20 Developer restriction member (Developer discharge mechanism)
22 Carrier developer supply screw 25 Carrier developer supply device (supply device)
32 Control device (replenishment amount prediction means, dot count means, bias application means)
32 'control device (replenishment amount prediction means, replenishment time detection means, bias application means)
38 Adhering developer removing mechanism 39 Bias applying unit (bias applying means)
34 toner density sensor 35 dot count device (replenishment amount prediction means, dot count means)

Claims (10)

A developing device for developing an electrostatic latent image formed on an image carrier using a two-component developer composed of toner and carrier, the developer tank containing the developer, and the image carrier A developer carrier that is rotatably disposed opposite to the developer tank and carries the developer in the developer tank and conveys the developer to the image carrier, and toner and a carrier are supplied in the developer tank. On the other hand, in the developing device in which the developer is sequentially discharged from the developer tank by the developer discharging mechanism,
A developer amount regulating member that regulates the amount of developer carried and conveyed by the developer carrying member is formed in a cylindrical shape, and is disposed rotatably to face the developer carrying member.
The developer discharge mechanism is configured to cause the developer carried on the developer carrier to be transported to adhere to the developer amount regulating member and to be discharged from the developer tank. apparatus.   The developer amount regulating member is at least partially made of a conductor, and the biasing means controls the deteriorated carrier from the developer carrier to the developer amount between the developer amount regulating member and the developer carrier by the biasing means. 2. The developing device according to claim 1, wherein the developer that has deteriorated is discharged by applying a bias voltage that generates an electric field that is electrostatically moved to the member.   The developing device according to claim 2, wherein the bias unit applies a DC bias voltage.   4. The developing device according to claim 3, wherein a DC bias voltage in the bias unit is variable.   2. The developing device according to claim 1, further comprising an attached developer removing mechanism that removes the developer attached to the developer amount regulating member and conveys the developer to a developer collecting container provided outside the developing device. .   The developing device according to claim 1, wherein a rotational peripheral speed of the developer amount regulating member is faster than a rotational peripheral speed of the developer carrier. From the replenishing device to the developing tank, a replenishment developer in which a carrier is mixed with toner is replenished,
Replenishment amount predicting means for predicting the replenishment amount of the replenishment developer replenished from the replenishing device to the developing tank after each image formation;
The developing device according to claim 1, wherein the developer discharge mechanism controls a developer discharge amount based on the supply amount predicted by the supply amount prediction unit.   The replenishment amount prediction means includes dot count means for detecting an integrated value of the number of pixels of an image formed on the image carrier, and image formation is performed based on the integrated value detected by the dot count means. The developing device according to claim 7, wherein a replenishment amount to be replenished later is predicted.   The replenishment amount predicting means includes replenishment time detecting means for detecting a replenishment time during which the replenishment developer is replenished from the replenishing device to the developing device, and the replenishment time detected by the replenishment time detecting means. The developing device according to claim 7, wherein a replenishment amount replenished after image formation is predicted based on each image formation. A developing device that develops the electrostatic latent image on the image carrier using a two-component developer composed of toner and carrier, and the toner and carrier are replenished from the replenishing device in the developing device, In the image forming apparatus in which the developer in the developing device is sequentially discharged by the developer discharging mechanism,
An image forming apparatus comprising the developing device according to claim 1 as the developing device.

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