JP5640664B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a facsimile, and a printer that forms an image using toner, and more particularly to operation control of a developing device.

  A developing device included in an electrophotographic image forming apparatus is an apparatus that develops and visualizes an electrostatic latent image formed on an image carrier using a two-component developer composed of toner and a carrier. Inside the developing device, the developer in which the developing process is completed in the developing region and the toner is consumed is collected, mixed and stirred with the replenished toner, and again used for development. The developer used in such a developing device needs to maintain a constant toner density and charge amount in order to obtain a stable toner image. The toner density is adjusted by the toner consumed by the image formation and the replenishment toner, and the charge amount is given by frictional charging when the carrier and the toner are mixed. In a developing device using a two-component developer, the toner image is stabilized by sufficiently stirring the toner and the carrier to make the toner density distribution uniform and to charge the toner.

In a general developing device, the toner is dispersed and charged using the stirring effect of the rotation of the two conveying screws in a short time until the replenished toner is pumped up to the developing roller. In particular, when the toner balance is large, the replenished toner is not sufficiently dispersed and is pumped up by the developing roller, which causes a problem in image quality such as background contamination and toner scattering.

  In order to solve this problem, a developing unit and a developer stirring unit are separately arranged to improve stirring performance. In this developing device, there are less uncharged and weakly charged toner in the developing unit compared to a conventional developing device that uses a screw and agitation and conveyance at the same time, and it is less likely to cause toner scattering and scumming during toner replenishment. However, since the developing unit and the developer agitating unit are separated from each other, a means for circulating the developer between the developing unit and the developer agitating unit is required. As this developer circulating means, those using an air conveyance system using an air pump or a Mono pump are disclosed in, for example, “Patent Document 1” and “Patent Document 2”.

When the developer is continuously transported into the pipe using air, the transport amount may change depending on the state of the developer. For example , the powder characteristics of the developer change depending on the deterioration degree of the developer, temperature, humidity, and the like. When the developer transport amount decreases and the developer capacity of the developing unit decreases, the amount of developer pumped up by the developing roller becomes insufficient and an image defect occurs. In particular, when the developing device is a one-way circulation system, the developer is supplied to the developing roller from the supply screw arranged in parallel with the developing roller, and all the supplied developer is transported to the recovery screw after the developing operation. The amount of developer in the vicinity of the screw decreases (the volume decreases) toward the downstream side in the developer transport direction. Therefore, when the developer transport amount decreases, a depletion state occurs in which the developer is not supplied to the developing roller on the downstream side in the developer transport direction. In order to prevent the occurrence of this depletion state, it is conceivable to control the developer transport amount by detecting the developer amount in the vicinity of the supply screw.

  Therefore, it is necessary to detect the powder level and bulk of the developer inside the developing device, and to control the developer transport amount by air based on the result. Therefore, for example, "Patent Document 3" and "Patent Document 4" disclose a developing device using a piezoelectric vibration element or a magnetic permeability detection method as a developer bulk detecting means.

  In the above technique, the piezoelectric vibration element can detect whether or not the powder level of the developer is equal to or higher than a predetermined height. However, in a developing device that includes a supply screw and a recovery screw, and the developer supplied from the supply screw to the developing roller is not supplied again to the developing roller, the powder level of the developer is lower on the downstream side of the supply screw than on the upstream side. Because the height is very low, the powder level fluctuates along the inclination of the screw and the height of the powder level is not constant, the output becomes unstable and it is difficult to detect the powder level accurately. There is a problem that there is. Further, when the magnetic permeability sensor is used as the powder level detection means, the output changes depending on both the powder level height and the toner concentration, so the powder level cannot be detected unless the accurate toner concentration is known. There is a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that solves the above-mentioned problems, can detect developer depletion more reliably with a simple configuration, and can stabilize the developer conveyance amount. And

  According to the first aspect of the present invention, the developer carrier is disposed near the image carrier and circulates the developer therein and supplies the developer to the image carrier, and the developer carrier while transporting the developer. A developing unit having a rotatable developer supplying member that supplies the developer and a developer collecting member that collects the developer that has not been developed, and a developer stirring unit that is disposed at a position different from the developing unit. A developer conveying means for conveying the developer from the developer agitating unit to the developing unit by air conveying in the developer conveying path, and circulating in the developing unit via the developer discharge channel. In the developing device for returning the developed developer to the developer agitation unit, the developer supply member and the developer recovery member are communicated with each other, and have an opening in the vicinity of the developer supply member. By the developer supply member At the conveying direction downstream side of the developer, and having a developer detecting means for detecting whether or not the developer in the vicinity of the developer supply member is present.

According to a second aspect of the present invention, in the developing device according to the first aspect, the developer detecting means is configured so that the developer on the developer detecting means falls to the opening due to its own weight when the developer is reduced. It is arranged to be inclined toward the opening.

According to a third aspect of the present invention, in the developing device according to the first aspect , the developer supply member and the developer recovery member are further downstream of the developer detection unit in the direction of transport of the developer by the developer supply member. And a second opening that communicates with each other.

  According to a fourth aspect of the present invention, in the developing device according to the third aspect, the developer detecting means further has a margin with respect to the lower limit developer transport amount in which the excess developer is depleted in the developing section. It is detected that it does not exist, and the area of the opening is set to ensure the margin.

  According to a fifth aspect of the present invention, in the developing device according to the third or fourth aspect of the present invention, the developer is further provided in the vicinity of the developer supply member and in the vicinity of the developer supply member at a position corresponding to the second opening. And a second developer detecting means for detecting whether or not the toner is present.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the developer to the developing unit by the developer conveying means is further based on the detection result of the developer detecting means. The carrying amount is controlled.

  According to a seventh aspect of the present invention, in the developing device according to the sixth aspect, when the developer detecting means detects that no developer is present in the vicinity of the developer supply member, the developer conveying means The developer transport amount to the developing section is increased.

  According to an eighth aspect of the present invention, in the developing device according to the fifth aspect, the developer conveying means to the developing unit by the developer conveying means based on the detection results of the developer detecting means and the second developer detecting means. It is characterized by controlling the amount.

  According to a ninth aspect of the present invention, in the developing device according to any one of the sixth to eighth aspects, the developer conveying means further includes an air pump, and the developer is increased by increasing an air supply amount of the air pump. The carrying amount is increased.

  According to a tenth aspect of the present invention, in the developing device according to any one of the sixth to eighth aspects, the developer conveying means further includes a rotary feeder, and development is performed by increasing the number of rotations of the rotary feeder. It is characterized by increasing the amount of agent transport.

  An eleventh aspect of the invention is an image forming apparatus having the developing device according to any one of the first to tenth aspects.

  According to the present invention, it is possible to reliably detect the occurrence of the developer depletion state in advance with a simple configuration, and based on the detection result from the developer detection means, the developer to the developing unit by the developer conveying means By controlling the transport amount, the developer can be stably and continuously supplied to the developer carrying member, and good image formation can be continuously performed.

1 is a schematic front view of an image forming apparatus employing an embodiment of the present invention. 1 is a schematic perspective view of a developing device used in an embodiment of the present invention. FIG. 2 is a schematic front view illustrating a developing unit used in one embodiment of the present invention. It is a schematic sectional drawing explaining the image development part used for the 1st Embodiment of this invention. It is the schematic explaining the developer stirring part used for one Embodiment of this invention. It is the schematic explaining the flow of the developer in one Embodiment of this invention. FIG. 3 is a schematic diagram illustrating the behavior of a developer in a developing unit according to the first embodiment of the present invention. FIG. 3 is a schematic diagram illustrating the behavior of a developer in a developing unit according to the first embodiment of the present invention. It is a schematic sectional drawing explaining the image development part used for the 2nd Embodiment of this invention. It is the schematic explaining the behavior of the developer in the image development part in the 2nd Embodiment of this invention. It is the schematic explaining the behavior of the developer in the image development part in the 2nd Embodiment of this invention. It is a schematic sectional drawing explaining the image development part used for the modification of the 2nd Embodiment of this invention.

  FIG. 1 shows an image forming apparatus to which an embodiment of the present invention can be applied. In FIG. 1, an image forming apparatus 1 is a so-called tandem type image forming apparatus, and is divided into four colors of yellow (Y), magenta (M), cyan (C), and black (K) along the lower side of the intermediate transfer belt 2. Corresponding image forming units 3Y, 3M, 3C and 3K are provided. The image forming units 3Y, 3M, 3C, and 3K have the same configuration, and the photosensitive drum 4 as an image carrier, the charging unit 5, the developing unit 6 that constitutes the developing device, the primary transfer member 7, and the cleaning device 8. Etc.

  In the image forming apparatus 1, when the image forming operation is started, the photosensitive drums 4 of the image forming units 3Y, 3M, 3C, and 3K are uniformly charged by the charging unit 5, and then formed by a writing unit (not shown). An electrostatic latent image corresponding to the image to be formed is formed on the surface of the photosensitive drum 4, and toner is supplied to the electrostatic latent image from the developing unit 6, so that each color toner image is formed on each photosensitive drum 4. Each color toner image formed on each photoconductive drum 4 is superimposed and transferred onto the intermediate transfer belt 2 by each primary transfer member 7, whereby a four-color full-color toner image is formed on the intermediate transfer belt 2. This full-color toner image is collectively transferred by the secondary transfer unit 10 to transfer paper supplied from the paper feed cassette 9 by a pair of paper feed rollers and registration rollers, and the transfer paper on which the toner image is transferred passes through the fixing unit 11. After the toner image is fixed by heat and pressure, the toner image is discharged to the paper discharge unit 12. Each photosensitive drum 4 after the toner image transfer has its surface remaining toner removed by a cleaning device 8, and the intermediate transfer belt 2 after toner transfer has its residual toner removed by a belt cleaning device 13.

  The image forming apparatus 1 is characterized by a developing device. In a normal developing device, a developer used for development is agitated and mixed with toner and a carrier inside the developing unit. Developer agitating units 14 are disposed at locations away from the developing units 6 provided in the units 3Y, 3M, 3C, and 3K. The developer agitation unit 14 reliably performs mixing and agitation of the developer and the replenishment toner, and stably disperses and charges the toner. The toner agitation and the charge amount are stabilized by the action of the developer agitating unit 14 and stable image formation can be performed. In each developing unit 6 of each of the image forming units 3Y, 3M, 3C, and 3K, the developer after the developing operation is sent from the developing unit 6 to the developer stirring unit 14 through the developer discharge channel 15. New toner is replenished in the developer agitation unit 14, and the developer sufficiently agitated in the developer agitation unit 14 is discharged quantitatively by a rotary feeder (not shown). The discharged developer is conveyed by the pressure of air sent from an air pump 16 that is a developer conveying means, and is returned to the developing unit 6 through the developer conveying path 17. Replenishment of new toner to the developer stirring unit 14 is performed by supplying toner from a toner hopper (or toner cartridge) 18 little by little. In FIG. 1, reference numeral 19 denotes an air suction port of the air pump 16, reference numeral 20 denotes an external air suction path, reference numeral 21 denotes a dehumidifier, and reference numeral 22 denotes an air intake port.

  FIG. 2 shows a developing device 23 used in an embodiment of the present invention. As described above, the developing device 23 includes the developing unit 6 that is disposed in the vicinity of the photosensitive drum 4 and the developer stirring unit 14 that is disposed at a position different from the developing unit 6. The developer is transported from the section 14 to the developing section 6 via the developer transport path 17, and a two-component developer obtained by mixing toner and carrier is used as the developer.

  The developer conveyed by air from the developer agitation unit 14 is supplied to the development unit 6 and used for development, and falls by its own weight in the developer discharge passage 15 connecting the development unit 6 and the developer agitation unit 14. By being returned to the developer agitating unit 14, it is configured to circulate between the developing unit 6 and the developer agitating unit 14. The developer discharge channel 15 is formed in a tube shape from a flexible material such as silicon.

  As shown in FIG. 3, the developing unit 6 includes a developing roller 27 that is a developer carrying member and two conveying screws 28 and 29 in a casing 30. The developing roller 27 has a magnet inside, and has a known configuration in which the toner is adhered to the electrostatic latent image formed on the surface of the photosensitive drum 4 by attracting and conveying the developer. The conveying screw 28 as a developer supply member is rotationally driven so as to convey the developer from the front to the back in FIG. 3, and the conveying screw 29 as the developer collecting member moves the developer from the back to the front in FIG. It is rotationally driven so as to be conveyed toward the front. The inside of the casing 30 is divided into two by a partition plate 31, and the conveying screws 28 and 29 are respectively arranged in the divided spaces. The developing roller 27 and the two conveying screws 28 and 29 are rotationally driven by a motor (not shown) provided outside the casing 30 via a drive transmission mechanism (not shown).

  As shown in FIG. 4, the partition plate 31 has an opening 25 at the end on the back side in FIG. 3, and is configured so that the developer can move from the transport screw 28 toward the transport screw 29. 3, a developer supply port 26 is provided at an end on the front side. A doctor blade 32 for restricting the developer adhering to the developing roller 27 to a certain amount is disposed in the casing 30 located in the vicinity of the outer peripheral surface of the developing roller 27.

  As shown in FIGS. 2 and 5, the developer agitating portion 14 is provided with a casing 35 in which the diameter becomes narrower toward the lower portion and the developer is stored inside. A developer supply port 33 is provided, and a discharge port 34 is provided at the bottom. Inside the casing 35, a screw 36 for conveying the developer from below to above and a pair of stirring members 37 are rotatably provided. The screw 36 is disposed at the center position of the casing 35, and each stirring member 37 is disposed symmetrically outside the screw 36. The screw 36 and each stirring member 37 rotate in opposite directions to each other in the casing 35. Of developer is mixed.

  The screw 36 and the stirring member 37 are rotationally driven by a motor 38 as a developer conveying means. The screw 36 is directly connected to a motor 38, and each stirring member 37 is decelerated and rotated through a reduction gear train composed of a plurality of gears 39. The developer is transported from the developer replenishing port 33 to the discharge port 34 by gravity, so that the developer is always present in the developer stirring unit 14 so that unmixed developer is not discharged as it is. It is configured. The developer lifted upward from below by the rotation of the screw 36 moves downward along with the rotation of each stirring member 37 that rotates outside the screw 36 and is gathered around the screw 36 again. Thus, the developer is constantly convected in the casing 35, and the entire developer in the casing 35 is uniformly mixed by the convection.

  The developer used in this embodiment is a two-component developer, and the toner is charged by friction with the carrier. Therefore, in order to obtain the charge amount quickly, the contact efficiency between the toner and the carrier is improved. Although it is important that the developer is convected in the casing 35, the contact efficiency is increased and the damage to the developer is small. As the toner is consumed, new toner is replenished to the casing 35 from the toner hopper 18, and new toner is replenished by driving a motor 40 to rotate a small conveyance screw (not shown) disposed inside the toner supply path 41. As a result, new toner in the toner hopper 18 is conveyed into the casing 35. The small conveying screw (not shown) is configured so that a certain amount of new toner in the toner hopper 18 can be conveyed by rotation, and the replenishment amount of toner is attached to the vicinity of the most downstream position of the conveying screw 29 in the developer conveying direction. It is determined by a control means (not shown) according to the detection result of the toner density sensor (not shown).

  A rotary feeder 42 as a developer conveying means is disposed below the developer stirring unit 14 as shown in FIG. The rotary feeder 42 is disposed so as to communicate with the casing 35, and has a function of discharging a constant amount of developer from the casing 35. The rotary feeder 42 has a casing 43 and an impeller 44 rotatably provided therein, and the impeller 44 is rotated by a motor 45 shown in FIG. To discharge.

  A junction 46 is provided below the impeller 44. An air passage 47 connected to the supply port of the air pump 16 and an inlet 48 serving as one end of the developer transport path 17 connected to the developing unit 6 are connected to the merging unit 46 and discharged by the impeller 44. The fixed amount of developer is carried on the air supplied from the air pump 16 and is conveyed to the developing unit 6 by air. That is, the developer discharged by a certain amount from the rotary feeder 42 is transported by the air inside the developer transport path 17 by the air pressure supplied from the air pump 16 and returned to the developing unit 6. The developer transport path 17 is formed in a tube shape from a flexible material such as silicon.

  As shown in FIG. 4, the developer G that has flowed in from the supply port 26 via the developer conveyance path 17 is conveyed in the direction of arrow B by the conveyance screw 28, and the layer thickness is increased by the doctor blade 32 as shown in FIG. Is supplied to the developing roller 27 while being regulated. Here, the developer (excess developer) that has not been supplied to the developing roller 27 falls from the opening 25 shown in FIG. 4 and is delivered to the conveying screw 29. The transport screw 29 receives the collected developer sent from the transport screw 28 and transports it in the direction of arrow A, and the transported developer is discharged from the discharge port 24 and is passed through the developer discharge flow path 15 to a developer agitation unit. 14 is sent.

  Here, the characteristic part of this invention is demonstrated. First, the bulk of the developer in the developing unit 6 will be described. In the one-way circulation type developing unit as shown in FIG. 4, the developer is consumed from the upstream side to the downstream side in the developer conveying direction of the conveying screw 28, so that development is performed from the upstream side to the downstream side. The bulk of the agent is reduced. On the other hand, the bulk of the transport screw 29 increases toward the upstream side in the developer transport direction of the transport screw 28 (limited to the development width region). Therefore, when the developer runs out on the downstream side of the transport screw 29 in the developer transport direction, the developer becomes depleted and the developer is not supplied to the developing roller 27.

  In order to prevent the occurrence of the above-described problems, it is common to supply an excessive amount of developer to generate surplus developer and to provide a margin for depletion. However, in the configuration of the present invention, the developer is pneumatically conveyed from the outside to the developing unit 6, and in the pneumatic conveyance, the conveyance amount may vary depending on the state of the developer (toner concentration, environmental conditions, deterioration state). Therefore, if the transport amount decreases, the above-described depletion state may occur, so this must be detected in advance to prevent the occurrence of the depletion state. For this purpose, it is effective to detect the volume of the developer in the vicinity of the conveying screw 28. However, as described in the section “Problems to be solved by the invention”, it is necessary to accurately grasp the powder level of the developer. Is very difficult. However, since it is easy to detect the presence or absence of the developer by a digital method (binary method) and it can be accurately grasped, in the first embodiment of the present invention, a depletion state is obtained by the binary method. As shown in FIG. 4, a sensor 49 as a developer detecting means is disposed at a downstream position in the developer transport direction by the transport screw 28 of the opening 25 as a method for detecting this in advance. As the sensor 49, a piezoelectric sensor using a piezoelectric element, a magnetic permeability sensor for detecting the magnetic permeability of the developer, a capacitance sensor, or the like can be used.

  The arrangement position of the sensor 49 is a place where the developer must be present in the image area, and the depletion state cannot be detected in advance. If there is no developer on the sensor 49 except for the position where it is impossible to determine whether or not depletion has occurred, it can be reliably detected that the depletion state has occurred. It is set at a certain position. FIG. 7 shows a state in which the depletion has not occurred, and FIG. 8 shows a state in which the amount of developer transport is decreasing (including the case where the depletion is about to occur).

In the state shown in FIG. 7, a part of the excess developer falls from the opening 25, and a part that cannot be dropped moves over the opening 25 and moves to the end of the conveying screw 28, and this developer is detected by the sensor 49. Detected. A method for detecting the depletion state in advance will be described by taking as an example a case where the developer transport amount gradually decreases. As the developer transport amount decreases, the surplus developer amount also decreases, and all of the surplus developer falls from the opening 25. At this time, since there is no developer on the sensor 49 , the sensor 49 outputs no developer. Further, when the developer decreases, the exhaustion state occurs. However, the sensor 49 can grasp the decrease state of the developer before the exhaustion occurs.

  With the above-described configuration, it is possible to reliably detect the occurrence of the developer depletion state in advance with a simple configuration, and based on the detection result from the sensor 49, it is detected that there is no developer in the vicinity of the conveying screw 28. In such a case, the amount of developer transported to the developing unit 6 by the developer transport means is controlled, that is, the air supply amount of the air pump 16 is increased, the rotational speed of the motor 38 is increased, the rotational speed of the rotary feeder 42 is increased, etc. By increasing the amount of developer conveyed to the developing unit 6 by this, the developer can be stably and continuously supplied to the developing roller 27, and good image formation can be continued. It becomes. In the above configuration, as shown in FIGS. 4, 7, and 8, the sensor 49 is arranged to be inclined toward the opening 25, so that the developer on the sensor 49 moves to the opening 25 by its own weight when the developer is reduced. Therefore, it is possible to prevent erroneous detection due to the developer remaining on the sensor 49, and to reliably detect the state of no developer.

  FIG. 9 shows a second embodiment of the present invention. In the second embodiment, the second opening 50 is provided at a position downstream of the sensor 49 in the developer conveying direction by the conveying screw 28. FIG. 10 shows a state in which the depletion has not occurred in the second embodiment, and FIG. 11 shows a state in which the developer transport amount is decreasing (including the case where the depletion is about to occur). In the state shown in FIG. 10, a part of the surplus developer falls from the opening 25, the rest is conveyed to the sensor 49 side, and further falls from the opening 50 to the conveyance screw 29. As shown in FIG. 11, when the developer transport amount decreases, the developer falls only from the opening 25, and the developer no longer exists on the sensor 49. Even in this configuration, when it is detected that no developer is present in the vicinity of the transport screw 28 based on the detection result from the sensor 49, the amount of the developer transported to the developing unit 6 is increased. The same effects as those of the first embodiment can be obtained.

  In the second embodiment, excess developer is allowed to pass (drop) so that the developer that is desired to ensure the area of the opening 25 as a margin with respect to the developer transport amount (flow rate) at the lower limit of depletion remains in the developing unit 6. It may be a size. For example, if the normal developer transport amount is 100 g / sec, the developer transport amount at the depletion lower limit (minimum necessary for development) is 80 g / sec, and the developer transport amount to be secured as a margin is 10 g / sec, the opening The area of the portion 25 is an area through which a 10 g / sec developer passes. When the developer transport amount becomes 90 g / sec or less, the sensor 49 outputs no developer. Specifically, when the developer transport amount is 100 g / sec (excess developer 20 g / sec), 10 g / sec of developer falls from the opening 25 and the remaining 10 g / sec of developer is detected by the sensor. When the developer transport amount is 90 g / sec (excess developer 10 g / sec), 10 g / sec of developer drops from the opening 25. The sensor 49 outputs no developer on the sensor 49 without being conveyed. In this way, by setting the area of the opening 25 so that the developer amount for plus alpha stays in the developing unit 6 with respect to the developer conveyance amount reaching the depleted state, the margin of the developer conveyance amount can be accurately set. Therefore, the occurrence of the developer depletion state can be reliably detected in advance.

  FIG. 12 shows a modification of the second embodiment. This modification is a second developer detecting means for detecting whether or not the developer is present in the vicinity of the conveying screw 28 in the vicinity of the upper portion of the conveying screw 28 and corresponding to the second opening 50. The second embodiment is different from the second embodiment only in that the sensor 51 is provided. In each of the above-described embodiments, a problem that occurs when the transport amount of the developer is reduced is addressed. However, when the transport amount is increased, the developer is supplied from the opening 25 and the second opening 50. There is a possibility that the developer cannot be dropped and clogged with developer at the end of the conveying screw 28. When the developer clogging occurs, the conveyance of the developer by the conveyance screw 28 is hindered, and not only a problem occurs in the image forming operation but also the developing unit 6 may break down. At this time, since the developer contacts the sensor 51, it is possible to detect the occurrence of the above-described malfunction phenomenon. When the developer is detected by the sensor 51, the developer conveyance amount is reduced by reducing the air supply amount of the air pump 16, the rotational speed of the motor 38, the rotational speed of the rotary feeder 42, and the like. It is possible to continue image formation.

  In the above-described embodiment, an example in which a color printer is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited to this, and other apparatuses such as a copying machine, a plotter, a facsimile machine, and a multi-function machine thereof. The present invention can also be applied to an image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Image carrier (photosensitive drum)
6 Developer 14 Developer Stirrer 15 Developer Discharge Channel 16 Developer Conveying Means (Air Pump)
17 developer transport path 23 developing device 25 opening 27 developer carrier (developing roller)
28 Developer supply member (conveying screw)
29 Developer recovery member (conveying screw)
38 Developer transport means (motor)
42 Developer conveying means (rotary feeder)
49 Developer detection means (sensor)
50 Second opening 51 Second developer detecting means (sensor)

Japanese Patent No. 3733496 Japanese Patent No. 3349286 JP-A-8-36294 JP 2009-198967 A

Claims (11)

A developer carrier that is disposed near the image carrier and circulates the developer therein and supplies the developer to the image carrier, and a rotatable developer that supplies the developer to the developer carrier while transporting the developer A developing unit having a supply member and a developer collecting member that collects the developer that has not been used for development; and a developer stirring unit disposed at a position different from the developing unit; A developer conveying means for conveying the developer from the developer agitating unit to the developing unit by air conveying, and the developer circulated in the developing unit via a developer discharge channel. In the developing device for returning to the stirring section,
An opening that communicates the developer supply member and the developer recovery member, and is near the lower part of the developer supply member and downstream of the opening in the developer transport direction by the developer supply member from the opening. And a developer detecting means for detecting whether or not the developer is present in the vicinity of the developer supply member. The developing device according to claim 1,
The developer detecting means is arranged so as to be inclined toward the opening so that the developer on the developer detecting means falls to the opening due to its own weight when the developer is reduced. apparatus. The developing device according to claim 1 ,
2. A developing device comprising: a second opening communicating the developer supplying member and the developer collecting member downstream of the developer detecting means in the developer transport direction by the developer supplying member. The developing device according to claim 3.
The developer detecting means detects that the developer does not exist with a margin with respect to the lower limit developer transport amount in which the excess developer is depleted in the developing section, and the opening portion is to secure the margin. A developing device characterized in that the area is set. The developing device according to claim 3 or 4,
A second developer detecting unit configured to detect whether or not the developer is present in the vicinity of the developer supply member at a position corresponding to the second opening near the upper side of the developer supply member; A developing device. The developing device according to any one of claims 1 to 5,
2. A developing device according to claim 1, further comprising: controlling a developer conveyance amount to the developing unit by the developer conveying unit based on a detection result of the developer detecting unit. The developing device according to claim 6.
When the developer detecting means detects that no developer is present in the vicinity of the developer supply member, the developer carrying amount to the developing section by the developer carrying means is increased. Development device. The developing device according to claim 5, wherein
2. A developing apparatus according to claim 1, wherein a developer transport amount to the developing unit by the developer transport unit is controlled based on detection results of the developer detecting unit and the second developer detecting unit. In the developing device according to any one of claims 6 to 8,
The developer conveying means includes an air pump, and the developer conveying amount is increased by increasing an air supply amount of the air pump. In the developing device according to any one of claims 6 to 8,
The developing device according to claim 1, wherein the developer conveying means includes a rotary feeder, and the developer conveying amount is increased by increasing the number of rotations of the rotary feeder.   An image forming apparatus comprising the developing device according to claim 1.

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