JP5256937B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, a process cartridge including the developing device, and an image forming apparatus.

Conventionally, in an electrophotographic image forming apparatus, a developing device using a two-component developer composed of toner and a magnetic carrier has been widely used. In this developing apparatus, a two-component developer (hereinafter referred to as a developer) that is agitated and mixed in a developer accommodating portion that accommodates the developer and frictionally charged is supported on the developer carrier, and the image carrier is supported by the developer. A toner image is obtained by selectively attaching toner to the upper electrostatic latent image. The toner is consumed by such development, and when the toner concentration in the developer is lowered, a high density image cannot be obtained.
On the other hand, if the toner concentration in the developer is too high, background staining or the like occurs. Thus, in order to obtain a high-quality image, it is necessary to control the toner concentration of the developer in the developer container supplied to the developer carrier within a certain range. In view of this, there are some which include a toner replenishing device for replenishing toner in the developer accommodating portion. In such a developing device, a toner concentration detecting device (hereinafter referred to as a toner concentration sensor) as a detecting means for detecting the toner concentration in the developer accommodating portion, and a toner replenishing amount for controlling the toner replenishing amount to the developer accommodating portion. A control device is provided to control toner replenishment into the developer accommodating portion.

As the toner concentration sensor, a magnetic detection type is known in which a part of the inner wall surface of the developer accommodating portion is used as a detection surface, and a change in permeability in the developer around the detection surface is detected. In this toner concentration sensor, if the developer stays on the detection surface, it becomes impossible to detect the accurate toner concentration, which causes a malfunction of the toner replenishment amount control device.
Therefore, in Patent Document 1, the flat plate member is fixed so as to be parallel to the shaft portion at a position facing the detection surface of the shaft portion of the conveying screw that conveys the developer in the developer accommodating portion while stirring. A material in which an elastic sheet is fixed to the flat plate member in parallel is proposed. Then, the flat plate member and the elastic sheet rotate together with the conveying screw, and the elastic sheet rubs the detection surface to stir the developer on the detection surface. In this way, by stirring the developer on the detection surface, it is possible to prevent erroneous detection due to the developer remaining on the detection surface of the toner density sensor.
JP 05-150650 A

However, when the developer on the detection surface is stirred by the elastic sheet as described in Patent Document 1, the toner density sensor of the toner density sensor is adjusted in accordance with the period in which the elastic sheet rubs the detection surface during the stirring operation. The detected value changes periodically. This is because the developer density of the developer on the detection surface changes before and after the elastic sheet slides on the detection surface. That is, before the elastic sheet rubs against the detection surface, the elastic sheet presses the developer against the detection surface and the agent density on the detection surface increases. Further, since the elastic sheet springs up the developer near the detection surface when the elastic sheet rubs the detection surface, after the elastic sheet rubs the detection surface, a gap is generated in the vicinity of the detection surface. The agent density on the detection surface decreases.
If the difference in the agent density on the detection surface during such a stirring operation is large, the detection accuracy of the toner concentration sensor is lowered. Therefore, it is desirable to reduce the difference in agent density on the detection surface. In addition, the difference in agent density on the detection surface during the agitation operation varies due to disturbances in usage conditions such as the number of rotations of the conveying screw, installation environment, and developer aging, and the agent density on the detection surface during the agitation operation. If the difference is large, the toner density detection system varies depending on the use conditions of the user, so that it is desired to reduce the difference in the agent density on the detection surface.
The present invention has been made in view of the above problems, and the object of the present invention is to provide a detection surface during a stirring operation while preventing erroneous detection due to developer remaining on the detection surface of the toner concentration sensor. It is an object of the present invention to provide a developing device capable of reducing the difference in the agent density of the toner, a process cartridge and an image forming apparatus using the developing device.

In order to solve the above-mentioned problems, the invention of claim 1 is a developer carrying a developer containing toner and a carrier, and containing a developer carrier used for development and a developer supplied to the developer carrier. A casing that forms the agent accommodating portion, and a conveyance screw that conveys the developer in the casing in the axial direction while stirring the developer in the casing by rotating about the shaft portion having a spiral wing portion. A developing device including a toner concentration detecting unit configured to detect a toner concentration in the developer using a part of the inner wall surface of the casing parallel to the shaft portion of the conveying screw as a detection surface; A detection surface stirring member that is disposed on the shaft portion at a position and stirs the developer on the detection surface by rotation of the conveying screw, and the detection surface stirring member projects in a radial direction from the shaft portion. The plate-like support portion disposed in parallel with the shaft portion rotating without contacting the detection surface by the rotation of the conveying screw, and the detection by extending in the radial direction of the shaft portion from the tip of the support portion A stirring portion that elastically slidably contacts the surface, and the support portion has an opening that allows the developer to pass therethrough by rotation of the conveying screw, and corresponds to the detection surface of the upper lid portion of the casing. By forming a protrusion projecting toward the shaft portion on the inner wall surface, a plane perpendicular to the shaft portion of the developer transport path that is surrounded by the inner wall surface and transports the developer by the transport screw is provided. Compared to the cross-sectional area upstream of the detection surface in the transport direction of the transport screw, the cross-sectional area is reduced on the detection surface, and the spiral pitch width of the wing portion corresponding to the detection surface The above Compared to the upstream side of the helical pitch with respect to the detection plane in the conveying direction of the feed screw of the developer, characterized by being narrowed.
According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the support portion has a rigidity that is not deformed by a stirring operation of the developer.
The invention according to claim 3 is the developing device according to claim 1 or 2, wherein the opening of the support portion is formed in a central portion of the support portion, and is formed by a frame portion of the support portion. It is characterized by being a through hole.

According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the stirring unit is an elastic sheet that is in sliding contact with the detection surface while being elastically deformed by the rotation of the conveying screw. It is characterized by being.
According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the detection surface is formed on a part of a bottom inner wall surface of the casing.
A sixth aspect of the present invention is the developing apparatus according to any one of the first to fifth aspects, wherein a plurality of the detection surface agitating members protrude in a radial direction from the shaft portion.
The invention according to claim 7 is the developing device according to claim 6, wherein the plurality of detection surface agitating members are respectively arranged on the shaft portion at positions shifted along the developer conveying direction of the conveying screw. It is provided .

Also, the invention of claim 8, at least an image bearing member on which an electrostatic latent image is formed on the surface, a developing device for toner Zoka supplies toner to the electrostatic latent image on the image bearing member In the process cartridge integrally connected to each other, the developing device is the developing device according to any one of claims 1 to 7 .
According to a ninth aspect of the invention, there is provided an image carrier on which an electrostatic latent image is formed on the surface, and a developing device that supplies toner to the electrostatic latent image on the image carrier to form a toner image. The image forming apparatus is characterized in that the developing device is the developing device according to any one of claims 1 to 7 .
According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect , the image carrier and the developing device are integrally connected, and are configured to be detachable from the image forming apparatus main body. It is a cartridge.

  According to the present invention, the detection surface agitating member is provided in the shaft portion at a position facing the detection surface and agitates the developer on the detection surface by rotation of the conveying screw. A plate-like support portion that is arranged in parallel with the shaft portion that protrudes in a radial direction from the shaft portion and rotates without contacting the detection surface by rotation of the conveying screw, and a shaft portion from the tip of the support portion A stirring portion that extends in the radial direction of the sheet and elastically slidably contacts the detection surface, and the support portion has an opening that allows the developer to pass through by rotation of the conveying screw. , Developing device capable of reducing difference in agent density on detection surface during stirring operation while preventing erroneous detection due to developer staying on detection surface of toner concentration sensor, and process cartridge using the same And image shape It is possible to provide a device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an electrophotographic printer (hereinafter simply referred to as a printer 100) which is an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the printer 100 generates toner images of yellow (Y), magenta (M), cyan (C), and black (K) (hereinafter referred to as Y, M, C, and K), respectively. Four process cartridges 6Y, 6M, 6C, and 6K described later are provided. These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached.
Taking a process cartridge 6Y for generating a Y toner image as an example, as shown in FIG. 2, the process cartridge 6Y has a drum-shaped photosensitive member 1Y as a center, and a drum cleaning device 2Y and a charge eliminating device ( (Not shown), the charging device 4Y, the developing device 5Y and the like are integrally connected to the photoreceptor 1Y. Accordingly, the process cartridge 6Y is detachable from the printer 100 main body, and the photosensitive member 1Y, the drum cleaning device 2Y, the static eliminator (not shown), the charging device 4Y, and the developing device 5Y are pulled out from the printer 100 main body for maintenance. In addition, inspection can be performed and consumable parts such as a drum cleaning device 2Y, a static eliminator (not shown), a charging device 4Y, and a developing device 5Y can be replaced at a time. In the process cartridge 6Y, it is not always necessary to integrally connect the photosensitive member 1Y, the drum cleaning device 2Y, the static eliminator (not shown), the charging device 4Y, and the developing device 5Y. Any process cartridge in which the body 1Y and the developing device 4Y are integrally connected may be used.

The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1Y is exposed and scanned by the laser beam LY to carry an electrostatic latent image for Y. This Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner.
The Y toner image formed on the photoreceptor 1Y is intermediately transferred onto the intermediate transfer belt 8 by the primary transfer bias roller 9Y. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the primary transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. In the other process cartridges 6M, 6C, and 6K, M, C, and K toner images are similarly formed on the photoreceptors 1M, 1C, and 1K, and are intermediately transferred onto the intermediate transfer belt 8.

In FIG. 1, the exposure device 7 is disposed below the process cartridges 6Y, 6M, 6C, and 6K. The exposure device 7 serving as an electrostatic latent image forming unit emits laser beams LY, LM, LC, and LK emitted based on image information to the respective photoreceptors 1Y, 1M, 1C, and 6K in the process cartridges 6Y, 6M, 6C, and 6K. Expose to 1K. By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K, respectively. The exposure device 7 irradiates the photosensitive member through a plurality of optical lenses and mirrors while scanning the laser beams LY, LM, LC, and LK emitted from the light source with polygon mirrors that are rotationally driven by a motor. It is.
At the lower side of the exposure apparatus 7 in FIG. 1, paper supply means having a paper storage cassette 26, a paper supply roller 27 incorporated therein, a registration roller pair 28, and the like is disposed. The paper storage cassette 26 stores a plurality of transfer papers P as recording bodies, and a paper feed roller 27 is in contact with the uppermost transfer paper P.
When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is fed toward the rollers of the registration roller pair 28. The registration roller pair 28 rotationally drives both rollers to sandwich the transfer paper P, but once the transfer paper P is sandwiched, the rotation is temporarily stopped. Then, the transfer paper P is sent out toward a secondary transfer nip described later at an appropriate timing. In the sheet feeding unit having such a configuration, a conveying unit is configured by a combination of the sheet feeding roller 27 and the registration roller pair 28 corresponding to the timing roller. This transport means transports the transfer paper P from a paper storage cassette 26 serving as a storage means to a secondary transfer nip described later.

In the upper part of the process cartridges 6Y, 6M, 6C, and 6K in FIG. 1, an endless intermediate transfer belt 8 that is an intermediate transfer member is stretched over a secondary transfer backup roller 12, a cleaning backup roller 13, and a tension roller 14 to An intermediate transfer unit 15 that is moved endlessly in the direction of arrow A by the rotation of the next transfer backup roller 12 is disposed. The intermediate transfer unit 15 includes, in addition to the intermediate transfer belt 8, four primary transfer bias rollers 9Y, 9M, 9C, and 9K, a cleaning device 10, and the like.
The primary transfer bias rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 that is moved endlessly in this manner from the photoreceptors 1Y, 1M, 1C, and 1K to form primary transfer nips. These primary transfer bias rollers 9Y, 9M, 9C, and 9K are of a system that applies a transfer bias having a polarity opposite to that of toner (for example, plus) to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All the rollers other than the primary transfer bias rollers 9Y, 9M, 9C, and 9K disposed on the back surface (loop inner peripheral surface) of the intermediate transfer belt 8 are electrically grounded.
The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, C, and Y on the photoreceptors 1Y, 1M, 1C, and 1K. K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred onto the transfer paper P at the secondary transfer nip. Transfer residual toner that has not been transferred to the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10.
In the secondary transfer nip, the transfer paper P is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction, and is conveyed in the opposite direction to the registration roller pair 28 side. When the transfer paper P sent out from the secondary transfer nip passes between rollers of the fixing device 20, the four-color toner image transferred to the surface is fixed by heat and pressure. Thereafter, the transfer paper P is discharged out of the apparatus through a pair of paper discharge rollers 29. A stack unit 30 is formed on the upper surface of the main body of the printer 100, and the transfer sheets P discharged to the outside by the pair of discharge rollers 29 are sequentially stacked on the stack unit 30.
A bottle container 31 is disposed between the intermediate transfer unit 15 and the stack unit 30 located above the intermediate transfer unit 15. The bottle container 31 houses toner bottles 32Y, 32M, 32C, and 32K as replenishment toner storage units that store Y, M, C, and K toners. The toner bottles 32Y, 32M, 32C, and 32K are installed on the bottle container 31 so as to be placed from above for each toner color. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are supplied to the developing devices 5Y, 5M, and 5C of the process cartridges 6Y, 6M, 6C, and 6K by a toner replenishing device as a toner transport unit, which will be described later. 5K is replenished appropriately. These toner bottles 32Y, 32M, 32C, and 42K are detachable from the main body of the printer 100 independently of the process cartridges 6Y, 6M, 6C, and 6K.

Next, the configuration of the developing device 5Y provided in the process cartridge 6Y will be described. FIG. 2 is a schematic cross-sectional view of the process cartridge 6Y shown in FIG. 1 as viewed from the axial direction of the rotation shaft 6aY of the photosensitive member. A control unit 57Y and a drive motor 41Y, which will be described later, are schematically shown. FIG. 3 is a top view of the developing device 5Y shown in FIG. 2 with the upper cover 67Y removed.
The developing device 5Y includes a magnetic field generating means inside, and a developing sleeve 51Y as a developer carrying member that carries and conveys a two-component developer containing magnetic particles and toner on the surface, and is carried on the developing sleeve 51Y. And a developer doctor 52Y as a developer regulating member that regulates the layer thickness of the developer conveyed. Below the developing sleeve 51Y, there is a developer accommodating portion surrounded by the casing 55Y. The first developer accommodating portion 53Y that supplies the developer to the developing sleeve 51 by the partition wall 59Y, and the toner from the toner replenishing portion 58Y. The second developer containing portion 54Y that receives the replenishment is partitioned. A first conveying screw 61Y for agitating and conveying the toner is provided in the first developer accommodating portion 53Y, and a second conveying screw 62Y is provided in the second developer accommodating portion 54Y. The second conveying screw 62Y has a structure in which a spiral wing portion 62bY is fixed to the shaft portion 62aY (see FIG. 3), and the first conveying screw 61Y has the same configuration.

Further, the developer in the first developer accommodating portion 53Y is transported from right to left (in the direction of arrow B in FIG. 3 and from the near side to the far side in FIG. 2) by the rotation of the first transport screw 61Y. Then, the developer in the second developer accommodating portion 54Y is conveyed from left to right (in the direction of arrow C in FIG. 3 and from the back side to the near side in FIG. 2) by the rotation of the second conveying screw 62Y. . Then, both end portions of the partition wall 59Y in the axial direction of the conveying screw (left and right direction in FIG. 3) are openings 59aY and 59bY, and the developer G is stored in the first developer through these openings 59aY and 59bY. It circulates between the portion 53Y and the second developer accommodating portion 54Y.
A toner concentration sensor 56Y that detects the toner concentration of the developer in the second developer accommodating portion 54Y is attached to the lower outer wall surface 55aY of the case 55Y of the second developer accommodating portion 54Y. The bottom inner wall surface 55bY of the case 55Y where the toner concentration sensor 56Y is attached to the outer wall surface serves as a detection surface 80Y as a detection region for detecting the toner concentration of the toner concentration sensor 56Y. A detection surface stirring member 70Y, which will be described in detail later, is fixed at a position facing the detection surface 80Y of the rotation shaft 62aY of the second conveying screw 62.

The toner density sensor 56Y is a non-contact type toner density sensor that can detect the toner density without providing a part of the sensor at a position in contact with the developer. As such a toner density sensor, for example, one described in JP-A-2004-139038 can be used. Further, the toner concentration sensor 56Y is not limited to the non-contact sensor, and for example, a contact type sensor that is attached in such a manner that the sensor surface projects inward from the outside of the casing 55Y to the inner wall surface 55bY of the casing 55Y is used. May be. Further, it may be arranged on the inner wall surface of the casing 55Y.
Further, as the detection surface 80Y, a developer container in a region detected by the toner density sensor 56Y when detecting the toner density in the developer container (second developer container 54Y in the present embodiment) is used. This is the inner wall surface 55bY of the casing 55Y to be formed, and no special member is provided as a detection surface.

Next, the operation of this developing device will be described. In the developing device 5Y, the developer G in the developer accommodating portions 53Y and 54Y contains a carrier and toner, and the toner is taken into the developer so as to be within a predetermined toner concentration range. The toner passes from the toner bottle 32Y through the toner transport pipe 43Y of the toner transport device (not shown), and is replenished from the toner replenishing portion 58Y to the second developer accommodating portion 54Y. Thereafter, the toner is agitated by the second conveying screw 62Y and the first conveying screw 61Y, taken into the developer, and charged by frictional charging with the carrier.
The developer G containing charged toner in the first developer accommodating portion 53Y is supplied to the surface of the developing sleeve 51Y having a magnetic pole therein, and is carried by forming a developer layer by magnetic force. The developer layer carried on the developing sleeve 51Y is conveyed in the direction of the arrow as the developing sleeve 51Y rotates. In the middle, after the developer doctor 52Y regulates the layer thickness of the developer layer, the developer is transported to the developing area facing the photoreceptor 1Y. In the development area, toner is supplied to the electrostatic latent image formed on the photoreceptor 1Y for development.
The developer layer remaining on the developing sleeve 51Y is conveyed to the upstream portion in the developer conveying direction of the first developer accommodating portion 53Y as the developing sleeve 51Y rotates. When the toner is consumed by the development and the toner density in the developing device 5Y is lowered, the toner density of the developer around the detection surface 80Y is also lowered, and the toner density sensor 56Y at the lower bottom of the second developer containing portion 54Y is used. Detecting a drop in Based on the detection result, the control unit 57Y drives a drive motor 41Y of a toner replenishing device (not shown) and replenishes toner from the toner transport pipe 43Y.

Next, the detection surface stirring member 70Y according to the first embodiment, which is a characteristic part of the present invention, will be described with reference to FIG. FIG. 4 is an enlarged perspective view of a portion to which the detection surface stirring member 70Y of the first embodiment used in the developing device 5Y according to the embodiment of the present invention is fixed.
FIG. 5 is an enlarged cross-sectional view of the second developer accommodating portion 54Y at a position where the toner concentration sensor 56Y is provided. 61cY and 62cY indicated by broken lines in FIG. 5 are trajectories drawn by the radially outer ends (61eY and 62eY in FIG. 5) of the wing portion 61bY of the first conveying screw 61Y and the wing portion 62bY of the second conveying screw 62Y, respectively. Is shown.
As shown in FIG. 4, the detection surface agitating member 70Y according to the first embodiment rotates together when the second conveying screw 62Y rotates in the direction of arrow D in the drawing, and is on the detection surface 80Y (see FIG. 3). The developer G is removed and stirred. And the detection surface stirring member 70Y of this embodiment protrudes from the shaft part 62aY of the second conveying screw 62Y in the radial direction, and is a fin that is a support part as a plate-like planar member disposed in parallel with the shaft part 62aY. 72Y, and an elastic sheet 71Y attached to the fin 72Y so as to extend in the radial direction of the shaft portion 62aY from the tip of the fin 72Y.
The fin 72Y has a quadrangular opening 72aY at the center, and a frame 72bY is formed on the outer periphery of the opening 72aY. Therefore, when the second conveying screw 62Y rotates, the developer can pass through the openings 72aY of the fins 72Y. Further, since the tip end portion 71aY of the elastic sheet 71Y slides on the detection surface 80Y, the developer G is reliably stirred without staying in the vicinity of the detection surface 80Y, and the change in the density of the developer G can be suppressed.

Further, the tip 71aY of the elastic sheet 71Y can be elastically slidably contacted with the detection surface 80Y to clean the detection surface 80Y. By using such a detection surface agitating member 70Y, when the developer on the detection surface 80Y is agitated by the elastic sheet 71Y, the developer can pass through the openings 72aY of the fins 72Y. It is possible to suppress the difference in developer density caused by the jumping up of the toner and to appropriately prevent the developer from staying in the vicinity of the detection surface 80Y.
In this case, it is preferable that the fins 72Y have rigidity that is not deformed by the stirring operation of the developer G in order to appropriately stir the developer G by the elastic sheet 71Y. In order to provide such rigidity, the opening ratio of the opening 72aY formed in the fin 72Y (the area ratio of the opening 72aY to the planar area of the fin 72Y) is preferably 40% to 80%. When the opening ratio is less than 40%, the amount of developer passing through the opening 72aY decreases, and it becomes difficult to suppress the variation in the agent density.
On the other hand, when the opening efficiency exceeds 80%, the rigidity of the fin 72Y becomes small, and it becomes difficult for the developer to pass through the opening 72aY appropriately. The shape of the opening 72aY may be any shape such as a circle, an ellipse, or a quadrangle, but a square opening 72aY is formed at the center, and a frame 72bY is formed on the outer periphery of the opening 72aY. The shape of the formed fin 72Y is preferable because the rigidity of the fin 72Y and the passage of the developer G can be appropriately performed.
The elastic sheet 71Y can be a synthetic resin sheet such as a urethane sheet or a polyester sheet, but the length of the sliding contact portion with the detection surface 80Y is half or less of the length of the detection surface 80Y. It is preferable to do so. If the length of the sliding contact portion is a length that covers the entire detection surface 80Y, the density of the developer G varies, which is not preferable.

In addition, the 1st conveyance screw 61Y and the 2nd conveyance screw 62Y which concern on this embodiment consist of synthetic resins, and the shape which attached the wing | blade part 61bY and 62bY to the axial part 61aY and 62aY is produced by integral molding. The second conveying screw 62Y has a shape in which the fin 72Y is also formed by integral molding, and the fin 72Y is fixed to the shaft portion 62aY. The elastic sheet 71Y is affixed and fixed to the fins 72Y with an adhesive or the like.
As shown in FIG. 5, the detection surface agitating member 70Y shown in the first embodiment is fixed to the shaft portion 62aY of the second conveying screw 62Y, and is affixed to the fins 72Y and 72Y having the rectangular openings 72aY. And an elastic sheet 71Y. When the second conveying screw 62Y rotates in the direction of arrow D in the figure, the developer G on the detection surface 80Y is agitated by the elastic sheet 71Y.
An elastic sheet 71Y shown by a broken line in FIG. 5 is a virtual depiction of the elastic sheet 71Y in a state where it is not elastically deformed. In practice, the elastic sheet 71Y is attached to the fin 72Y and developed. When loaded in the apparatus 5Y, the elastic sheet 71Y slides on the detection surface 80Y in a state of being elastically deformed as indicated by the solid line in FIG. Thereby, the developer on the detection surface can be removed, and the developer on the detection surface can be stirred.

Further, the width in the axial direction of the detection surface agitating member 70Y indicated by the symbol W in FIG. 3 is configured to be wider than the detection surface 80Y, and the second detection screw 80Y rotates so that the entire detection surface 80Y is formed. The developer G can be stirred. A conventional developing device using an elastic sheet as a detection surface stirring member for removing the developer on the detection surface 80Y of the toner density sensor is described in Patent Document 1 and the like. Also in these developing devices, similarly to the developing device 5Y of the present embodiment, an elastic sheet is provided on the shaft portion of the conveying screw, and the elastic sheet is brought into contact with the detection surface of the toner detection unit to wipe off the attached developer. I am doing so.
However, in such a developing device, when the developer on the detection surface is stirred with the elastic sheet, there is a problem that a difference in developer density that occurs before and after the tip of the elastic sheet passes through the detection surface becomes large. This is considered due to the fact that the elastic sheet, which is the detection surface stirring member, stirs a large amount of developer at a time. Further, the developer density difference varies due to disturbances such as the linear speed mode, environment, developer fluidity, and the like, and therefore, the toner density detection accuracy varies depending on the use conditions of the user.

On the other hand, the developing device 5Y of the present embodiment has an opening 72aY in the fin 72Y as shown in FIG. With such a configuration, the developer passes up through the opening 72aY although the developer is flipped up by the elastic sheet 71. Therefore, rapid fluctuations in developer density can be suppressed. That is, the developer on the detection surface can be surely cleaned and stirred by the elastic sheet 71, and the fluctuation of the gradually increasing density can be reduced before and after the elastic sheet 71 passes.
As a result, the developer density on the detection surface 80Y immediately before the tip of the elastic sheet 71Y having the maximum agent density passes through the detection surface 80Y, and the tip of the elastic sheet 71Y having the minimum agent density is detected. A decrease in the developer density on the detection surface 80Y immediately after passing through the surface 80Y can be suppressed. Since an increase in the maximum value of the agent density and a decrease in the minimum value can be suppressed, a difference in developer density that occurs before and after the tip of the elastic sheet 71Y passes through the detection surface 80Y can be suppressed. Further, since the difference in developer density can be suppressed, in the developing device 5Y of this embodiment, variations in the developer density difference due to disturbances such as the linear speed mode, the environment, and the developer fluidity can be suppressed.

Next, a second embodiment of the developing device 5Y according to the present invention will be described with reference to FIG. FIG. 6 is an explanatory diagram of a configuration for lowering the inner wall surface of the upper cover 67Y near the detection surface 80Y used in the developing device according to the embodiment of the present invention. FIG. 6A is a side sectional view of the second developer accommodating portion 54Y of the second developer accommodating portion 54Y of the developing device 5Y viewed from the direction of arrow E in FIG. 3, and FIG. These are the top views which mounted the inner wall surface of the upper cover 67Y upward.
In such a developing device, when the bulk density of the developer in the vicinity of the toner density sensor detection region fluctuates, the magnetic flux density of the developer changes even at the same toner density, which causes a detection error. In order to improve such a problem, in the second embodiment, the cross-sectional area in the plane perpendicular to the shaft portion of the developing conveyance path in the vicinity of the installation position of the toner density sensor and the vicinity thereof is set as the upper cover 67Y of the developing device. By reducing the position of the inner surface of the developer, the bulk density variation of the developer is reduced by making it smaller than the cross-sectional area of the other developer transport path.
As shown in FIG. 6, the upper cover 67Y is such that the inner wall surface (ceiling) of the upper cover 67Y at a position facing the detection surface stirring member 70Y of the second developer containing portion 54Y is lower than the ceiling of the other part. Is provided with a ceiling convex portion 67aY. As shown in FIG. 5, the cross-sectional shape of the ceiling convex portion 67aY is a shape along a trajectory drawn by the radially outer end portion 62eY of the wing portion 62bY. At the position where such a ceiling convex portion 67aY is provided, the cross-sectional area is narrower than the other positions of the second developer accommodating portion 54Y, the developer is clogged more than the other positions, and the bulk density of the developer is reduced. Fluctuation is less likely to occur.

Thereby, since the detection surface 80Y is in a position facing the detection surface agitating member 70Y, by providing the ceiling convex portion 67aY as described above, the bulk density of the developer near the detection surface 80Y is prevented from fluctuating. doing. Thus, even if it is the structure which suppresses the fluctuation | variation of a bulk density, the fluctuation | variation of a bulk density cannot be prevented by pressing the developer G on the detection surface 80Y by the detection surface stirring member 70Y, and jumping up. .
In the present embodiment, the developer on the detection surface 80Y is stirred by the elastic sheet 71Y which is the detection surface stirring member 70Y, and the fin 72 has an opening 72aY. By providing the opening 72aY as described above, the developer G can pass through the opening 72aY when the developer is stirred.
That is, even if the developer G is flipped up by the elastic sheet 71, the developer G can pass to the rear of the fins 72, so that the detection surface stirring member 70Y does not have the opening 72aY. In comparison, it is possible to prevent fluctuations in the bulk density due to the stirring operation of the detection surface stirring member 70Y.
In the above-described embodiment, the yellow developing device 5Y and the process cartridge 6Y using yellow (Y) toner have been described. However, the same configuration can be used for toner using other color toners.

Next, a developing device 5Y according to a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is an enlarged explanatory view in the vicinity of a portion where the detection surface stirring member 70Y of the second conveying screw 62 provided in the developing device 5Y according to the third embodiment is fixed. In the third embodiment, only the configuration of the detection surface stirring member 70Y is different from the first embodiment, and the other configurations are the same as those in the first embodiment. Therefore, the different configurations will be described below, and the common configurations will be described. Description of is omitted.
As shown in FIG. 7, in the third embodiment, a plurality of detection surface stirring members 70Y described in the first embodiment are attached to the second conveying screw 62Y. Although FIG. 7 illustrates a case where two detection surface stirring members 70YA and 70YB are attached as a specific example, the number of detection surface stirring members 70Y is not limited to this. When the second conveying screw 62Y rotates in the direction of arrow D in the figure, the developer on the detection surface 80Y is agitated by the elastic sheets 71YA and 71YB.
Similarly to the first embodiment, the toner concentration sensor 56Y is attached to the outer wall surface 55aY of the casing 55, and the inner wall surface 55bY of the case casing 55Y where the toner concentration sensor 56Y is provided is a detection region of the toner concentration sensor 56Y. As a detection surface 80Y.

The fins 71YA and 71YB of the detection surface agitating members 70YA and 70YB are attached so as to be shifted from each other in the axial direction of the second conveying screw 62Y. is there. This is because the detection surface 80Y is reliably agitated and cleaned, and the elastic sheet is unexpectedly damaged in an unintended direction during assembling or driving of the image forming apparatus, so that the entire detection surface 80Y cannot be cleaned. To prevent.
Further, as described in the first embodiment, by providing the openings 71aYA and 71aYB in the fins 71YA and 71YB, the area of the detection surface 80Y that is stirred and cleaned by the elastic sheets 71YA and 71YB at a time is reduced. Therefore, fluctuations in developer density can be further prevented. Therefore, fluctuations in the bulk density due to the stirring operation of the detection surface stirring members 70YA and 70YB can be prevented.
The detection surface agitating members 70YA and 70YB of the third embodiment have a difference in developer density that occurs before and after the tips of the elastic sheets 71YA and 71YB pass the detection surface 80, as in the case of the first embodiment. Can be suppressed. In addition, since the developer density difference can be suppressed in this way, the variation in the developer density difference due to disturbances such as the linear speed mode, environment, developer fluidity, and the like can be avoided as in the first embodiment. Can be suppressed.

In the developing device 5Y of the third embodiment, unlike the first embodiment, two fins 71 are attached instead of one, and the two fins 71YA and 71YB are the second ones. It is shifted in the axial direction of the conveying screw 62Y. This makes it possible to reduce the amount of developer agitated and cleaned by one detection surface stirring member 70YA, 70YB, thereby further suppressing the difference in developer density.
By adopting the configuration as described above, it is possible to reduce the developer density fluctuation that occurs before and after stirring by the detection surface stirring members 70YA and 70YB, and to eliminate the retention of the developer that may occur in the developer having lowered fluidity. Is possible. The detection surface agitating members 70YA and 70YB of the third embodiment have a difference in developer density that occurs before and after the tips of the elastic sheets 71YA and 71YB pass the detection surface 80Y, as in the first embodiment. Can be suppressed. Further, since the difference in developer density can be suppressed, variation in the developer density difference due to disturbances such as the linear velocity mode, environment, developer fluidity, and the like can be suppressed as in the first embodiment. .

In the second embodiment described above, the ceiling convex portion 67aY is formed as a configuration that suppresses fluctuations in the bulk density of the developer on the detection surface 80Y, and the vicinity of the detection surface 80Y is located in the other area around the second developer containing portion 54Y. The cross-sectional area is narrower than the position. Here, a fourth embodiment having a configuration different from that of the second embodiment as a configuration for suppressing the fluctuation of the bulk density of the developer on the detection surface 80Y will be described with reference to FIG. FIG. 8 is a top view of the developing device 5Y according to the fourth embodiment with the upper cover 67Y removed.
As shown in FIG. 8, the second conveying screw 62Y of the developing device 5Y according to the fourth embodiment has a wing portion 62cY that narrows the pitch width of the wing portion 62bY in the region W in the vicinity of the detection surface 80Y than other positions. It has a configuration. By forming the wing portion 62cY having a narrow pitch width in this manner, the developer G can be retained in the region W, and the developer is clogged more than other positions, and the bulk density of the developer varies. Is less likely to occur. And the detection surface stirring member 70Y is formed in the axial part 62aY between the wing | blade part 62cY which narrowed this pitch width. Therefore, since the detection surface 80Y is at a position facing the detection surface agitating member 70Y, in the fourth embodiment as well as in the case where the ceiling convex portion 67aY is provided in the second embodiment, It is possible to suppress fluctuations in the bulk density of the developer.
In addition, as the detection surface stirring member 70Y in the fourth embodiment, a plurality of detection surface agitating members 70Y may be formed as in the third embodiment described above, or a ceiling protrusion 67aY is provided as shown in the second embodiment. It is good also as a composition.
In the above embodiment, the detection surface agitating member 70Y is formed on the second conveying screw 62Y. However, the toner concentration detection sensor 56 is attached to the bottom outer wall portion of the first developer accommodating portion 53Y, and the detection surface agitation is performed. The member 70Y may be attached to the first conveying screw 61Y.

1 is a diagram illustrating a schematic configuration of an electrophotographic printer that is an image forming apparatus according to an embodiment of the present invention. FIG. FIG. 2 is a schematic cross-sectional view of the process cartridge shown in FIG. 1 as viewed from the axial direction of the rotating shaft of the photoreceptor. FIG. 3 is a top view of the developing device shown in FIG. 2 with an upper cover removed. FIG. 4 is an enlarged perspective view of a portion to which a detection surface stirring member of the first embodiment used in the developing device according to the embodiment of the present invention is fixed. FIG. 3 is an enlarged cross-sectional view of a second developer accommodating portion at a position where a toner concentration sensor of the developing device shown in FIG. 2 is provided. FIG. 6 is an explanatory diagram of a configuration in which an inner wall surface of an upper cover in the vicinity of a detection surface used in a developing device according to an embodiment of the present invention is lowered, (a) shows a second developer accommodating portion of the developing device with an arrow in FIG. FIG. 6B is a side sectional view of the second developer accommodating portion viewed from the E direction, and FIG. 5B is a plan view in which the inner wall surface of the upper cover is placed upward. It is an expansion explanatory view of the vicinity of the portion to which the detection surface stirring member of the second conveyance screw with which the developing device concerning a 3rd embodiment by the present invention is provided was fixed. It is a top view of the state which removed the upper cover of the developing device concerning a 4th embodiment by the present invention.

Explanation of symbols

  1Y, 1M, 1C, 1K photoconductor, 2 cleaning device, 4 charging device, 5Y, 5M, 5C, 5K developing device, 6Y, 6M, 6C, 6K process cartridge, 7 exposure device, 8 intermediate transfer belt, 9Y, 9M 9C, 9K Primary transfer bias roller, 19 Secondary transfer roller, 20 Fixing device, 51Y Developer sleeve, 52Y Developer doctor, 53Y First developer container, 54Y Second developer container, 55Y Casing, 55aY outer wall, 55bY inner wall, 56Y toner density sensor, 57Y control unit, 58Y toner supply unit, 59Y partition wall, 61Y first conveying screw, 62Y second conveying screw, 62aY shaft, 62bY, 62cY wing, 67Y upper cover, 67aY ceiling Convex part, 70Y, 70YA, 70YB Detection surface stirring member, 7 Y, 71YA, 71YB elastic sheet, 72Y, 72YA, 72YB fins, 72aY, 72aYA, 72aYB opening, 72BY frame portion, 80Y sensing surface

Claims (10)

A developer carrying member that carries a developer containing toner and a carrier and is used for development;
A casing forming a developer accommodating portion for accommodating a developer to be supplied to the developer carrying member;
A conveying screw that conveys in the axial direction of the shaft portion while stirring the developer in the casing with the wing portion by rotating around a shaft portion having a spiral wing portion;
In a developing device comprising: a toner concentration detecting means for detecting a toner concentration in the developer using a part of the inner wall surface of the casing parallel to the shaft portion of the conveying screw as a detection surface;
A detection surface stirring member that is disposed in the shaft portion at a position facing the detection surface and stirs the developer on the detection surface by rotation of the conveying screw;
The detection surface agitating member protrudes in a radial direction from the shaft portion, and is provided in a plate-like support portion disposed in parallel with the shaft portion that rotates without contacting the detection surface by rotation of the conveying screw, A stirring portion extending in a radial direction of the shaft portion from the tip of the support portion and elastically slidingly contacting the detection surface;
The support has an opening that allows the developer to pass through by rotation of the transport screw ;
Development that conveys the developer by the conveying screw surrounded by the inner wall surface by forming a protrusion protruding toward the shaft portion on the inner wall surface corresponding to the detection surface of the upper lid portion of the casing. The cross-sectional area in the plane orthogonal to the shaft portion of the agent transport path is smaller on the detection surface than the cross-sectional area upstream of the detection surface in the transport direction of the transport screw, and
The developing device characterized in that the spiral pitch width of the wing corresponding to the detection surface is narrower than the spiral pitch width upstream of the detection surface in the developer transport direction of the transport screw. . The developing device according to claim 1,
The developing device according to claim 1, wherein the support portion has rigidity that does not deform due to a stirring operation of the developer. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein the opening of the support portion is a quadrangular through hole formed in a central portion of the support portion and formed by a frame portion of the support portion. 4. The developing device according to claim 1, wherein the stirring unit is an elastic sheet that is in sliding contact with the detection surface while being elastically deformed by rotation of the conveying screw. 5. The developing device according to any one of claims 1 to 4,
The developing device according to claim 1, wherein the detection surface is formed on a part of a bottom inner wall surface of the casing. The developing device according to any one of claims 1 to 5,
The developing device according to claim 1, wherein a plurality of the detection surface agitating members protrude in a radial direction from the shaft portion. The developing device according to claim 6.
The developing device, wherein the plurality of detection surface agitating members are respectively disposed on the shaft portion at positions shifted along a developer conveying direction of the conveying screw. At least in a process cartridge in which an image carrier on which an electrostatic latent image is formed on a surface and a developing device that supplies toner to the electrostatic latent image on the image carrier to form a toner image are integrally connected.
The developing apparatus, a process cartridge, which is a developing device according to any one of claims 1 to 7. An image forming apparatus comprising: an image carrier on which an electrostatic latent image is formed on a surface; and a developing device that supplies toner to the electrostatic latent image on the image carrier to form a toner image.
The developing device, an image forming apparatus which is a developing device according to any one of claims 1 to 7. The image forming apparatus according to claim 9 .
The image forming apparatus, wherein the image carrier and the developing device are a process cartridge that is integrally connected and detachable from the image forming apparatus main body.

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