JP2005099134A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize image quality by stably maintaining developer in a developing device to an appropriate quantity by solving the problem of variation in ejected quantity of excessive developer due to oscillation or shock in a device main body in a developing device automatically refreshing 2 component developer by a 2 component developer replenishing means for a developing container and a developer ejecting opening 7 overflowing the excessive developer inside the developer container. <P>SOLUTION: The developing device is provided with: the developer container 2 partitioned into a developing chamber storing developer T containing toner and carrier and constituting a circulating path for the developer and an agitating chamber; a developer carrier carrying the developer in the developing chamber to a developing part; the ejecting opening 7 ejecting the excessive developer produced by developer replenishing; and a circulating means provided with a carrying member 4 agitating and carrying the developer inside the agitating chamber and circulating the developer in the circulating path. The carrying member 4 is provided with a first carrying part b with a great carrying ability for developer and a second carrying part c with a smaller carrying ability than the first carrying part (b). The ejecting opening 7 is installed facing the second carrying part (c). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device that develops an electrostatic image formed on an image carrier using a developer in which toner and a carrier are mixed in a copying machine, a laser printer, or the like.

  2. Description of the Related Art Conventionally, in a dry copying machine or the like, a developing device for visualizing an electrostatic latent image on the surface of an image carrier, that is, developing toner with a two-component developer composed of toner and carrier is 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, the carrier stirred together with the toner in the developing device is contaminated and deteriorated as the stirring frequency increases and the toner sticks to the carrier surface. Therefore, the charging performance of the developer gradually decreases, and thus fog (toner charged with a reverse polarity is generated when the charging performance of the developer decreases, and the non-image portion on the photoreceptor is developed during development. This causes image quality defects such as a phenomenon that toner adheres, and causes a significant decrease in image quality.

  Until now, it has been necessary to periodically replace the deteriorated developer in the developing container in order to prevent image quality defects such as fogging. In order to replace the developer, a great amount of maintenance work is required.

  Therefore, in order to eliminate the need to replace the developer, a developer consisting of a mixture of carrier and toner is replenished into the developer container, and the deteriorated developer whose charging performance has deteriorated is discharged from the developer container and charged. There has been proposed a developing device capable of suppressing a decrease in performance. As this type of technique, a technique described in Patent Document 1 called “trickling development method” is conventionally known.

In this technology, a new carrier is replenished into the developer container separately from the replenishment of consumed toner, and the developer in the developer container that has become excessive overflows from the developer outlet provided on the wall surface of the developer container. And is collected in a developer collection container. By repeatedly supplying and discharging the carrier and the deteriorated developer, the developer that is contaminated and deteriorated in the developing container is replaced with newly supplied toner and carrier. As a result, the charging performance of the developer is maintained, and the deterioration of the image quality is suppressed.
Japanese Patent Publication No. 2-21591

  An example of a developing apparatus employing the trickle developing system will be described with reference to FIGS. As shown in FIG. 10, the developing device 1 includes a developing container 2 containing a two-component developer T made of a mixture of carrier and toner, and a developing container while conveying and stirring the two-component developer in the developing container. Two parallel first and second developer transport members 3 and 4 that circulate in the container longitudinal direction and the stirred two-component developer are supported on an image carrier D such as an electrophotographic photosensitive member. A developer carrying member (developing roll) 5 for applying the electrostatic latent image on the surface of the image carrier as a toner image, a high concentration two-component developer replenishing device 6 for the inside of the developing container, and an excessive amount from the developing container 2 A developer discharge port (developer recovery port) 7 for overflowing the developer, a waste developer storage container 8 for storing the developer overflowed from the developer discharge port, and the like.

  In the two-component developer T in the developing container 2, a decrease in toner concentration due to toner consumption due to the developing operation of the electrostatic latent image on the surface of the image carrier D is detected by a detection unit (not shown), and the toner concentration is lower than the reference concentration. Then, a two-component developer (toner + carrier) having a high toner concentration is supplied from the high-density two-component developer supply device 6 into the developing container 2. The replenished high-concentration two-component developer is stirred and mixed in the two-component developer T in the developer container 2 while being transported by the developer transport members 3 and 4, and the toner of the two-component developer T in the developer container 2 is obtained. Concentration increases. The increase in the toner density is detected by the detecting means, and the high-density two-component developer is supplied from the high-density two-component developer supply device 6 into the developing container 2 until the toner density is restored to the reference density. As a result, the toner density of the developer T in the developing container 2 is maintained within the reference density range.

  On the other hand, by supplying the high-concentration two-component developer to the inside of the developing container 2, the amount of the developer T in the developing container 2 is increased by adding a carrier that is not consumed. Excess developer in excess of the standard developer amount overflows from the developer discharge port 7 to the outside of the developing container 2 and is stored in the waste developer storage container 8.

  As a result, the two-component developer T in the developing container 2 is automatically replaced little by little as the high-density two-component developer supply device 6 repeatedly supplies the high-density two-component developer into the developing container 2. Auto refreshed.

  The excess developer overflow operation will be described with reference to FIGS. FIG. 7 is a partial cross-sectional model view of the developing device 1 on the developer discharge port 7 side. The second developer conveying member 4 is a screw member provided with screw blades b spirally along the central axis a, and both end portions of the central axis a are respectively located at both longitudinal end portions of the developing container 2. The container wall 2a is rotatably supported through a bearing 9 and is disposed in the developing container 2. The screw member 4 is rotationally driven in a predetermined direction, and the developer T along the screw member 4 is conveyed in the arrow A direction along the screw member 4 while being stirred by the screw blade b. The screw-shaped direction of the screw blade portion c on the downstream side of the developer conveying direction of the screw member 4 is opposite to the screw-shaped direction of the screw blade portion b on the upstream side of the developer conveying direction. . This reverse screw blade portion (returned screw blade portion) c is in contact with the bearing 9 by the developer in the downstream portion of the screw member 4 in the developer conveyance direction by the flow of the developer T conveyed by the screw blade portion b. It is provided to prevent intrusion between the central axis a. FIG. 8 is a partial external perspective view of the screw member 4 as the second developer conveying member.

  The first developer conveying member 3 is also a screw member having the same structure as that of the second developer conveying member 4. However, the transport direction of the developer T by the first screw member 3 is opposite to that of the second screw member 4.

  The two-component developer T in the developing container 2 is circulated and conveyed in the longitudinal direction of the developing container 2 while being stirred by the rotation of the first and second screw members 3 and 4.

  The developer discharge port 7 is provided on the wall surface of the developer container at a position corresponding to the screw screw portion c of the second screw member 4 that is returned. The height of the lower end (lower edge) of the developer discharge port 7 is the height of the crest Ta generated on the developer surface of the screw blade portion c returned when the developer amount in the developer container 2 is a standard developer amount. It is set higher than the height (FIG. 7A).

  When the amount of the developer T in the developer container 2 increases due to the supply of the high-density two-component developer from the high-density two-component developer supply device 6 into the developer container 2, the developer surface level in the developer container 2 increases. The developer amount in the developer container 2 is higher than that in the standard developer amount, and the height of the peak Ta generated on the developer surface of the return screw blade portion c of the second screw member 4 is shown in FIG. As shown in b), the height of the developer discharge port 7 becomes higher than the lower end, and an excess amount of the developer T overflows from the developer discharge port 7 to the outside of the developer container 2 and is stored in the waste developer storage container 8. The

  1) Since the screw members 3 and 4 as the developer conveying members have a helical screw shape, the developer surface along the screw member of the developer T in the developer container 2 is aligned with the rotation of the screw. As shown in FIGS. 7A and 7B, a wave-like uneven portion is generated, and the uneven surface moves while the developer surface moves up and down. Further, since the developer T is rich in fluidity, the convex portion (mountain) Ta generated on the developer surface has a property of easily collapsing due to vibration or impact. Copiers and printers equipped with such a developing device have a number of sources that give vibration and shock to the entire device. For example, when picking up paper during paper feeding or as shown in FIG. When the developing device stops at the developing position in the developing rotary type color printer, a large vibration and impact are transmitted to the developing device. Depending on the generation timing of such vibration and impact, the convex shape generated on the developer surface may be destroyed. Then, in contrast to FIG. 7B, when a portion Tb where the convex portion Ta is flattened due to the collapse of the unevenness of the developer surface as shown in FIG. A phenomenon occurs in which the developer surface does not reach the developer discharge port 7 and thus the developer that should be discharged is not discharged from the developer discharge port 7.

  In particular, if the situation where the discharge amount is small continues, the total amount of the developer T in the developing container 2 increases too much, and it becomes difficult to rotate the screw members 3 and 4 as the developer conveying member. There arises a problem that the driving force is insufficient for the load and stops. Alternatively, the total amount of the developer T is excessively increased, the developer surface is significantly increased, the amount of developer coated on the surface of the developer carrier 5 is increased, and the developer thickness on the developer carrier 5 is increased. By increasing and coming into contact with the image carrier D, the developer falls off the surface of the developer carrier and contaminates the inside of the main body outside the developing device.

  2) Further, as shown in FIG. 9, in the color printer which is the developing rotary type developing unit 54 in which a plurality of developing devices 1 (Y, M, C, Bk) are held by the rotating body 54a, the developing device 1 (Y. Since M, C, and Bk) rotate, a valve is provided to prevent the developer from being discharged from the developer discharge port 7 during rotation. FIG. 10 is a main sectional view when the developing device 1 (Y, M, C, Bk) of the developing rotary type developing unit is in a position for developing the image carrier D, and a valve 10 is attached. The valve 10 has a fulcrum 11 for rotating, and the fulcrum 11 is above the developing device. When the developing device is not at the developing position in FIG. 10, the valve 10 closes the developer discharge port 7 with its own weight. However, when the developer is transported in the direction in which the rotation direction of the screw member 4 as the second developer conveying member is closed in the developing position as shown in FIG. It moves in the closing direction by movement, and the operation of discharging the excess developer, which is the original function of the discharge port, cannot be performed.

  Note that the development rotary color printer shown in FIG. D is a rotating drum type electrophotographic photosensitive member as an image carrier, 52 is a charger that uniformly charges the surface of the photosensitive member D, and 53 is an optical image exposure device that forms an electrostatic latent image on the uniformly charged surface. A laser scanner 54 is a developing unit that develops the electrostatic latent image as a toner image. The developing unit 54 is a developing rotary type, and four color developing devices 1Y, 1M, 1C, and 1BK of yellow, magenta, cyan, and black are mounted on a rotating body 54a, and the rotation of the rotating body 54a is controlled. The required developing device is moved to a position for developing the photosensitive member D. 55 is an intermediate transfer belt, 56 is a primary transfer device, 57 is a secondary transfer device, 58 is a photoreceptor cleaner, 59 is a paper feed mechanism, 60 is a fixing device, and 62 is a paper discharge tray.

  The present invention has been proposed in view of the above items 1) and 2). For a developing device having an auto-refresh function for automatically replacing a two-component developer, the vibration of the main body as in 1) above. The object is to solve the problem of fluctuations in the amount of excess developer discharged due to impact and to stably maintain the developer in the developing device at an appropriate amount and to stabilize the image.

  In addition, as described in 2) above, even when the developing device is provided with a valve for preventing leakage of the developer from the developer discharge port during rotation of the developing device in the developing rotary system, the valve is obstructed. An object of the present invention is to stably discharge an excess developer without causing any trouble.

  The present invention is a developing device having the following configuration.

  (1) A developer container containing a developer containing toner and a carrier and constituting a developer circulation path and partitioned into a developing chamber and a stirring chamber, and carrying the developer in the developing chamber and transporting it to the developing unit A developer carrying member, a discharge port for discharging surplus developer accompanying developer replenishment from the stirring chamber, and a transport member for stirring and transporting the developer in the stirring chamber, and circulating the developer in the circulation path. A developing device having a circulation means, wherein the conveying member includes a first conveying unit having a large developer conveying capability and a second conveying unit having a small conveying capability, and the discharge port is provided in the second conveying unit. A developing device provided to face each other.

  (2) The first transport unit transports the developer in the circulation direction of the stirring chamber, and the second transport unit is configured to transport the developer in a direction opposite to the circulation direction of the stirring chamber. (2) The developing device according to (1), wherein the transport unit and the discharge port are provided in a developer communication area from the stirring chamber to the developing chamber.

  (3) The developing device according to (1) or (2), wherein the conveying member is a screw member having a screw pitch of the second conveying unit smaller than that of the first conveying unit.

  (4) having an on-off valve that prevents the developer from leaking out of the discharge port as the developing device rotates, so that the on-off fulcrum of the on-off valve is on the upper side when the developing device is in the developing position. The developing device according to any one of (1) to (3).

  According to the above inventions (1), (2), and (3), it is possible to stably discharge the excess developer according to the total amount of the developer. The amount of developer in the developing container is always kept appropriate, and problems such as defective images and increased driving torque can be avoided. In other words, since the deteriorated developer can always be discharged from the developing container by an appropriate amount, a constant charging performance can be stably maintained, and high image quality can be maintained.

  Further, according to the invention of (4), it is possible to stably discharge excess developer even in a developing rotary type developing device and image forming apparatus, and the amount of developer in the developing container is always kept appropriately. Problems such as sagging, defective images, and driving torque can be avoided. That is, even in the case where a valve is provided at the developer discharge port in the development rotary type developing device, the deteriorated developer can be discharged in an appropriate amount in the same manner, so that a constant charging performance can be stably maintained, High image quality can be maintained.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration model diagram of an image forming apparatus in this embodiment. The image forming apparatus U of this example is a copying machine using a transfer type electrophotographic process and a laser scanning exposure method. In this copying machine U, a document placing table 21 is provided on the upper surface, and an exposure optical system 22 is disposed under the document placing table. When a document is placed and set on the document placement table 21 with the image surface facing downward and the copy button is pressed, the exposure optical system 22 performs photoelectric reading processing on the downward image surface of the document placed and set on the document placement table 21.

  D is a rotating drum type electrophotographic photosensitive member as an image carrier. On the outer periphery of the photosensitive member D, a charger 24 for charging the surface thereof to a predetermined potential, a developing device 1 for developing an electrostatic latent image formed on the surface of the photosensitive member D, and a toner image on the surface of the photosensitive member D. A transfer charger 26 for transferring to a sheet and a cleaning device 27 for collecting residual toner on the surface of the photoreceptor are provided.

  Further, on the paper entering side with respect to the photosensitive member D, a pair of timing rollers 28, a pair of transport rollers 29 and 30 for supplying paper at a predetermined timing, the first and second paper feed cassettes 31A and 31B, and the paper feed rollers 32A and 32A. 32B is provided. On the other hand, a fixing device 33 for fixing the toner image transferred onto the paper to the paper is provided on the paper output side with respect to the photoreceptor D.

  First, the surface of the photoconductor D that has been rotationally driven is uniformly charged by a charger 24, and then scanned and exposed with a laser beam 25a from a laser scanner 25 as an exposure device, so that the surface of the photoconductor D is statically exposed. An electrostatic latent image is formed, and the latent image is developed by the developing device 1 to form a toner image on the photoreceptor D. The laser scanner 25 outputs a laser beam 25a modulated in accordance with the time-series electric digital pixel signal of the original image photoelectrically read by the exposure optical system 22 to generate an electrostatic latent image corresponding to the original image on the surface of the photoconductor D. Write form.

  On the other hand, one sheet of recording paper P is separated and fed from the first or second paper feed cassette 31A or 31B by the paper feed rollers 32A or 32B, and the photosensitive paper passes through the transport roller pairs 30 and 29 and the timing roller pair 28. The toner image on the photoconductor D is sequentially transferred onto the recording paper P by the transfer bias applied to the transfer charger 26 at a predetermined timing and transferred to the transfer portion between the photoconductor D and the transfer charger 26. . The recording paper P onto which the toner image has been transferred is sent to the fixing device 33, where the toner image is fixed by pressurization and heating, is made into a permanent image, and is discharged onto the paper discharge tray 34.

  Further, the toner remaining on the photoreceptor D after the transfer of the toner image to the recording paper P is removed by the cleaning device 27 to prepare for the next image formation.

(2) Developing device 1
2 is an enlarged model view of the developing device portion of FIG. 1, and FIG. 3 is a longitudinal plan view of the developing container portion of the developing device. This developing device 1 is a developing device that employs a trickle developing system in the same manner as the developing device 1 of FIGS. 7 to 10 described above, and most of the device configuration is the same as the developing device 1 of FIGS. 7 to 10. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.

  The mixing ratio of the non-magnetic toner and the magnetic carrier of the two-component developer contained in the developing container 2 is, for example, about 1: 9 by weight. This ratio should be appropriately adjusted depending on the charge amount of the toner, the particle diameter of the carrier, the configuration of the image forming apparatus, and the like, and does not necessarily follow this value.

  The developing container 2 has an opening at a portion of the developing region facing the photoreceptor D, and a magnet (a magnet roll having a plurality of magnetic poles on a cylindrical surface) so as to be partially exposed to the opening 2b. A developing sleeve (developing roll) 5 as a developer carrying member 5a arranged non-rotatably is rotatably installed. The developing sleeve 5 is made of a non-magnetic material, and rotates in the direction of the arrow in FIG. 2 during the developing operation, holds the two-component developer T in the developing container 2 and regulates it to a predetermined thickness by the blade 12, thereby developing region The developer is supplied to the photoconductor D in the development area, and the electrostatic latent image formed on the photoconductor D is developed. A predetermined developing bias is applied to the developing sleeve 5. The developer after developing the latent image is collected in the developing container 2 as the developing sleeve 5 rotates.

  In the developing container 2, there are a screw member 3 (a side near the developing sleeve 5) as a first developer conveying member and a screw member 4 (a side far from the developing sleeve 5) as a second developer conveying member. Installed in parallel. As shown in FIG. 3, the first and second screw members 3 and 4 have gears G1 and G2 respectively fixed to the shaft ends on the back side thereof and meshed with the gears G1 and G2. When a rotational force is transmitted from a drive gear (not shown), the first and second screw members 3 and 4 are rotationally driven in conjunction with each other. The first and second screw members 3 and 4 rotate in the direction of the arrow shown in FIG.

  Then, the developer T in the developing container 2 is stirred and mixed by the rotation of the first and second screw members 3 and 4, and is conveyed by the first screw member 3 in the first direction indicated by the arrow in FIG. The second screw member 4 is conveyed in the second direction indicated by the arrow in FIG. 3 opposite to the first direction, and is conveyed and circulated in the developing container 2 along the circulation path indicated by the broken line in FIG. The

  A partition wall 13 is provided between the first and second screw members 3 and 4 so that the developer T can be smoothly circulated between the first and second screw members 3 and 4. Openings 14 and 15 for delivering the developer are provided on the back side and the near side of the partition wall 13. The areas where the first screw member 3 and the second screw member 4 are stirred by the partition wall 13 are a developer chamber (first developer stirring area) 16 and a stirring chamber (second developer stirring area), respectively. ) 17.

  The high-concentration two-component developer supply device 6 includes a developer bottle mounting portion that detachably mounts a developer bottle 6a containing a high-density two-component developer for replenishment, and a stirring member ( And a replenishment mechanism 6b for replenishing the developer container 2 from the replenishment port 18 provided in the developer container 2 in sequence by driving the unillustrated developer bottle 6a.

  The supply port 18 is located above the second screw member 4 as shown by a two-dot chain line in FIG. 3 and on the upstream side of the developer flow in the stirring chamber 17, and the supplied developer is placed in the stirring chamber 17. After being dropped and supplied and stirred, it passes through the opening 15 and is conveyed into the developing chamber 16.

  The supply of new developer from the high-concentration two-component developer supply device 6 into the developing container 2 is not illustrated in the same manner as described above, and the toner concentration decrease due to the toner consumption of the two-component developer T in the developing container 2 is not shown. When detected by the detecting means and the toner density is lower than the reference density, the two-component developer (toner + carrier) having a higher toner concentration is supplied into the developing container 2 from the high-density two-component developer supply device 6. By this replenishment, an increase in toner density is detected by the detection means, and the high-density two-component developer is replenished from the high-density two-component developer replenishing device 6 into the developing container 2 until the toner density returns to the reference density. . As a result, the toner density of the developer T in the developing container 2 is maintained within the reference density range.

  Excess developer in the developer container 2 due to the developer replenishment is caused by overflow from the developer discharge port (developer recovery port) 7 as described above. The developer discharge port 7 is provided on the wall of the developer container on the downstream side of the developer in the stirring chamber 17 and far from the developing sleeve 5, and excess developer from the developer discharge port 7 is outside the developer container. And is collected in a waste developer storage container (collection container) 8.

  As shown in FIG. 4A, a downstream screw blade portion c (FIG. 4) in which the direction of the screw is reversed is provided at the downstream portion of the second screw member 4, and the flow of the developer in this region is reversed. Thus, the developer trying to enter between the bearing 9 and the shaft portion a of the second screw member 4 is intended to return to the developer communication region (opening portion 15) from the stirring chamber 17 to the developing chamber. Fulfill. Therefore, the flow of the developer is in the directions of the two arrows A and B, and the amount of the developer at the changing point where the directions of the screw blade portion b and the screw blade portion c change increases, but in FIG. The blade d scraping out the developer in any direction carries the developer increased in this region in the direction of the opening 15 shown in FIG. At this time, the distance m between the end face of the blade d and the wall of the developer container in the developer downstream direction is the width of the opening 15, that is, the distance between the partition wall 13 and the wall 2a of the developer container in the developer downstream direction. It is preferably smaller than n (FIG. 3).

  The height of the upper portions of the screw blade portions b and c of the second screw member 4 is lower than the lower end of the developer discharge port 7 and the amount of developer in the developing container 2 is within a predetermined range. As shown in 4 (a), the developer surface does not reach the developer discharge port 7, and the developer is not discharged. The screw blades of the screw member 4 have a helical shape with a pitch L, and when rotated once, the developer between the blades of the L interval is carried by L. The highest point of the blade, that is, the upper part of the blade closest to the developer surface has a convex shape like a mountain, and the middle part of the convex and convex shape has a concave shape. The pitch between the protrusions is also L, and the surface of the agent becomes wavy and uneven at that pitch. FIG. 4B is a state diagram in which the developer is transported by a distance of ½ × L from the state of FIG. 4A, and the uneven shape is also transported by a distance of ½ × L.

  When the developer surface does not exceed the lower end of the developer discharge port 7 as shown in FIGS. 4A and 4B, the developer is not discharged from the developer discharge port 7, but as shown in FIG. Further, the total amount of the developer increases and the height of the developer surface increases, and the convex portion of the agent wave reaches the lowest point of the developer discharge port 7 and is discharged from the developer discharge port 7. When the screw member 4 rotates, the convex portion of the developer reaches the developer discharge port 7 in order, and is discharged each time. Finally, the developer surface is lowered to an appropriate position, and the developer The amount settles in a state where it is stably maintained at an appropriate amount.

  However, since a copying machine equipped with this developing device is accompanied by operations such as paper feeding, vibrations and shocks caused by the paper feeding operation etc. are transmitted to the developing device, causing a phenomenon that the pile of the agent is destroyed. Get up. FIG. 4C is a diagram in a state where the convex portion of the developer is positioned in the vicinity of the developer discharge port 7. If the screw member 4 is rotated as it is and the convex shape of the developer advances in the direction of the arrow, the developer peak Ta can be exactly in the middle of the discharge port 7, and the developer can be discharged from the discharge port 7. 4C, when vibration or impact is applied and the convex shape Ta collapses to the state Tb in FIG. 4D, the development in FIG. The convex shape Ta of the developer is leveled as in the state Tb of FIG. 4D, and the developer does not enter the developer discharge port 7 even if the screw member 4 is rotated.

  Therefore, in this embodiment, the following configuration is used to reliably discharge excess developer to the developer discharge port 7 without being affected by vibration and impact.

  In FIG. 5A, the pitch of the return screw blade portion c of the second screw member 4 is 1/3 of the length of the screw blade portion b that is provided on the upstream side of the second screw member 4 and conveys the developer in the forward direction. Therefore, the developer conveyance amount in the returning screw blade portion c when the screw member 4 makes one rotation is 1/3 of the other screw blade portion b. In other words, the screw blade portion b and the screw blade portion c are respectively provided in the second screw member 4 as the conveying member in the stirring chamber 17, the first conveying portion having a large developer conveying capability and the second conveying member having a small conveying capability. Corresponds to the transport section. Therefore, the difference in level of the unevenness of the developer surface of the returning screw blade portion c is 1/3 of that of the other screw blade portions b, and is almost flat. However, since the convex portion disappears and the discharge amount from the developer discharge port 7 decreases, in that case, the height of the developer discharge port 7 is adjusted to be lower as shown in FIG. It should be possible to ensure proper emissions.

  As described above, when the pitch of the returning screw blade portion c is reduced, vibration and impact are transmitted to the developing device 1 so that the convex portion Ta of the developer surface in FIG. 5B is in a state Tb in FIG. 5C. Even if it collapses, the difference in level of the unevenness of the developer surface is small, so the variation in the amount of developer discharged from the developer discharge port 7 becomes small, and the amount of excess developer discharged also in the state Tb in FIG. The advantage of being stable is born.

  Further, when the developer discharge port 7 is arranged at a position facing the changing point of the screw screw portion c of the return screw and the other screw blade portion b, as shown in FIG. As shown in FIG. 5C, the developer discharge port 7 has a screw blade portion c returning from the changing point at which the direction of the screw is reversed. Should be placed in the area. The developer discharge port 7 is preferably provided in a region facing the opening 15.

  In the developing rotary type color printer in which the developing devices 1 (Y, M, C, and Bk) are held on the rotating body 54a as shown in FIG. 9 described above, the developing device rotates and rotates. A valve is provided to prevent the developer from being discharged from the developer discharge port 7. FIG. 6 is a main cross-sectional view when the developing rotary type developing device is at a position where the photosensitive member D is developed (hereinafter referred to as a developing position). The valve 10 has a fulcrum 11 for turning. The fulcrum 11 is above the developing device. When the developing device is not in the developing position, the valve 10 closes the discharge port 7 by its own weight. When in the developing position, the rotation direction of the screw member 4 as the second developer conveying member carries the developer in a direction in which the valve 10 is opened, and the entire valve 10 is rotated in the opening direction by the movement of the developer. Therefore, when the amount of the developer increases from a predetermined amount, the valve 10 is opened by the rotation of the screw member 4, and excess developer is discharged from the developer discharge port 7 without being obstructed by the valve 10.

[Others]
1) Regarding the sequential replenishment of a new two-component developer to the developing container 2, in the above embodiment, a high-density two-component developer consisting of a mixture of toner and a carrier previously mixed with a large amount of toner is used for two-component development in the developing container. A high-concentration two-component developer replenishing device 6 is replenished for each toner density correction operation that accompanies a decrease in the toner concentration of the developer, and a toner replenishing device that replenishes toner and carrier separately to the developing container 2 A carrier replenishing device may be provided, and both the replenishing devices may be controlled in a coordinated manner to maintain the toner concentration of the two-component developer in the developing container and to perform auto refresh of the developer. In the present invention, this form is also a category of developer replenishing means for replenishing a new two-component developer in the developing container.

  2) The second screw member 4 as the conveying member in the agitating chamber 17 has the first conveying portion b having a large conveying capability of the developer and the second conveying portion c having a small conveying capability. The conveying part c of 2 does not need to be in the form of a returning screw blade part, and is a screw blade in the same direction as the screw blade part of the first conveying part b, and the screw pitch is the screw blade part of the first conveying part b It is also possible to reduce the developer conveying capacity by making the size smaller. Further, the conveying members 3 and 4 are not limited to screw members.

  3) Of course, the image forming principle and process of the image forming apparatus are not limited to the transfer type electrophotographic system of the embodiment. A direct type electrophotographic system using photosensitive paper may be used, or a transfer type or direct type electrostatic recording system using a dielectric as an image carrier may be used.

  In addition, an electrophotographic photosensitive member or an electrostatic recording dielectric is used as a rotating belt type as an image end body, and a toner image of required image information is formed on this by forming and developing a latent image, and the toner image forming portion is read. There is also an image display device that displays an image positioned on a display unit. Such an image display device is also included in the image forming apparatus of the present invention.

  Although various embodiments and modified embodiments of the present invention have been shown and described above, those skilled in the art should not limit the spirit and scope of the present invention to the specific description and drawings in this specification. Rather, it will be understood that the invention extends to various modifications and changes, which are all set forth in the appended claims.

1 is a schematic configuration model diagram of an image forming apparatus of an embodiment. FIG. 2 is an enlarged model view of a developing device portion in FIG. 1. FIG. 6 is a longitudinal plan view of a developing container portion of the developing device. FIG. 6 is an explanatory view of discharging a surplus developer. 6 is an explanatory diagram of a developer discharge port function of the developing device of Embodiment 1. FIG. FIG. 10 is an explanatory diagram of a developer discharge port function of the developing device according to the second embodiment. It is explanatory drawing of the developer discharge port function of the conventional image development apparatus, and its problem. FIG. 10 is a partial external perspective view of a screw member as a second developer conveying member. It is a schematic configuration model diagram of a color copying machine using a conventional developing device. It is sectional drawing of the image development rotary type developing apparatus which uses the image development apparatus of a prior art example.

Explanation of symbols

  1: developing device, 2: developing container, T: two-component developer, Ta: convex surface of developer, Tb: flat surface of developer surface, 3: first developer agitating and conveying screw, 4: second developer agitating Conveying screw, c: return screw blade part, 5: developing sleeve, 5a: magnet, 6a: developer supply device, 6a: developer bottle, 7: developer recovery port, 8: recovery container, 9: bearing, 10 : Valve, 11: fulcrum, 12: blade, 13: partition, 14/15: opening, 16: developing chamber, 17: stirring chamber, 18: toner supply port, 21: document mounting table, 22: exposure optical system, D: photoreceptor, 24: charger, 25: exposure device, 26: transfer charger, 27: cleaning device, 28: timing roller pair, 29-30: transport roller pair, 31A / 31B: paper feed cassette, 32A / 32B: paper feed roller, 33: fixing Location, 54a: rotating body

Claims (4)

A developer container containing a developer containing toner and a carrier and constituting a developer circulation path and partitioned into a developing chamber and a stirring chamber, and a developer carrying the developer in the developing chamber and carrying the developer to the developing unit A circulating member that circulates the developer in the circulation path, comprising: a carrier; a discharge port that discharges excess developer accompanying developer replenishment from the agitation chamber; and a conveying member that agitates and conveys the developer in the agitation chamber; In a developing device having
The transport member includes a first transport unit having a large developer transport capability and a second transport unit having a small transport capability, and the discharge port is provided to face the second transport unit. Development device.   The first transport unit transports the developer in the circulation direction of the stirring chamber, and the second transport unit is configured to transport the developer in a direction opposite to the circulation direction of the stirring chamber. The developing device according to claim 1, wherein a portion and the discharge port are provided in a developer communication region from the stirring chamber to the developing chamber.   The developing device according to claim 1, wherein the conveying member is a screw member having a screw pitch of the second conveying unit smaller than that of the first conveying unit.   An opening / closing valve for preventing the developer from leaking out of the discharge port as the developing device rotates, and the opening / closing fulcrum of the opening / closing valve is on the upper side when the developing device is in the developing position; The developing device according to claim 1, wherein

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