JP2009122202A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of efficiently wiping off developer stuck to the detection face of a toner concentration sensor and detecting a toner concentration without degrading cleaning performance for the detection face of the toner concentration detecting part even if an agglomeration of developer is generated due to a decrease in developer flowability with time. <P>SOLUTION: A cleaning blade 28b is abutted on the detection face 24a of the toner concentration sensor 24 so as to form an acute angle between the detection face 24a and the face of the cleaning blade, which is opposite the contact area in the rotating direction R of the cleaning blade on the detection face 24a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device that is used in a copying machine, a printer, a fax machine, and the like using electrophotography, and visualizes an electrostatic latent image pattern using a developer containing toner and a carrier, In particular, the present invention relates to developer agitation and toner density detection.

  An image forming apparatus using an electrophotographic system is provided with a developing device that visualizes a latent image pattern by attaching toner to the electrostatic latent image pattern formed on the surface of the electrostatic latent image carrier.

  In general, as a developer used for development, a two-component developer composed of a toner and a magnetic carrier is widely used. In the case of a developing device using a two-component developer, the toner concentration, which is a mixing ratio of toner amount / carrier amount, is important. When the toner density is lower than the set value, the image density is lowered. On the contrary, when the toner density is higher than the set value, an image defect occurs due to toner scattering due to a decrease in toner charge amount.

  Accordingly, in order to achieve a stable image density, it is important to keep the toner density constant, and a toner density detector (hereinafter referred to as a toner density sensor) that detects the toner density of the developer is provided in the developing device. It is arranged. At the time of image output, the toner density in the developing container is reduced by detecting the changed toner density according to the toner consumed in the developing area and replenishing the developer container with new toner from the toner cartridge. Hold constant. The toner concentration sensor is generally a method for detecting the magnetic permeability in the developer.

  Conventionally, in a toner concentration sensor, when the developer is stirred, the developer adheres to and accumulates on the detection surface, and the toner concentration in the stirred developer cannot be accurately detected. There is.

  In order to solve this problem, for example, as shown in FIG. 12, a stirring plate 128a is fixed at a position facing the detection surface of the toner concentration sensor 124 in the shaft portion 129b of the stirring member, and the stirring plate 128a is fixed to the stirring plate 128a. A detection surface cleaning member has been proposed in which a blade-like elastic member 128b is fixed (see, for example, Patent Document 1). In this apparatus, the detection surface cleaning member rotates together with the agitation member, and the elastic member 128b rubs the detection surface to remove the developer on the detection surface and agitate it to the detection surface of the toner density sensor. It is possible to prevent erroneous detection caused by the stay of the developer.

  In addition, in order to prevent the cleaning blade from bending, the bending stiffness of the elastic member base region and the tip region of the cleaning member is made different so that the bending stiffness of the root region is larger than the bending stiffness of the tip region. There has been proposed a developing device that prevents the occurrence of toner agglomerates in a member, removes the developer on the detection surface of the toner density sensor, and stirs (see Patent Document 2).

Patent Document 3 proposes a configuration in which a conductive charge-removing member is disposed in the vicinity of the toner concentration sensor in order to discharge toner particles that are frictionally charged by stirring the developer. As a result, it is possible to prevent the magnetic permeability from being increased by the developer containing the charged toner and causing wrinkles in the toner density value detected by the toner density sensor.
Japanese Patent Laid-Open No. 5-150650 (released on June 18, 1993) JP 2006-154001 A (released on June 15, 2006) Japanese Patent Laid-Open No. 4-166964 (released on June 12, 1992)

  However, when an attempt is made to remove the developer by rubbing the detection surface with an elastic member having a uniform bending rigidity as described in Patent Document 1, depending on the value of the bending rigidity, agglomerated toner is generated. End up. Further, if the bending rigidity is high, stress is generated in the developer, resulting in a decrease in the fluidity of the developer, and the output image has an image defect such as a density defect. On the other hand, when the bending rigidity is low, the bending is caused by the load of the developer accumulated on the inner wall of the developer container. The bent cleaning member rotates without coming into contact with the detection surface of the toner density sensor, so that an accurate toner density cannot be detected, and the output image causes a density defect.

  Further, in the technique described in Patent Document 2, in a small particle diameter toner and carrier corresponding to high image quality, the toner and carrier slip through between the cleaning blade and the detection surface of the toner concentration sensor. In addition, it is impossible to wipe off the small particle size toner adhering to the detection surface of the toner density sensor, and furthermore, the scratching defect due to the deterioration of the developer fluidity due to the deterioration of the developer over time occurs. Cannot be obtained, and an appropriate toner density cannot be detected.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to efficiently wipe away the developer adhering to the detection surface of the toner concentration sensor that detects the toner concentration of the developer including toner and carrier. Is to realize a developing device capable of detecting the toner concentration without deteriorating the cleaning performance of the detection surface of the toner concentration detecting section even when the developer aggregates are generated due to the decrease in developer fluidity in the toner. .

  In order to solve the above-described problems, the developing device according to the present invention includes a developer container that contains a developer containing toner and a carrier, and a stirring blade formed on a rotating shaft. A developer conveying member that conveys the developer in the container in a fixed direction while stirring; a toner concentration detecting means that is disposed on the inner wall of the developer container and detects the toner concentration in the developer container; and the toner A cleaning blade that is provided on the developer conveying member facing the density detecting means, contacts the detection surface of the toner density detecting means as the developer conveying member rotates, and removes the developer on the detecting surface; When the cleaning blade comes into contact with the detection surface, the cleaning blade is on the opposite side of the detection surface to the rotation direction of the cleaning blade. The angle between which is characterized in that in contact with the detection surface so that an acute angle.

  In the case of the conventional configuration, the cleaning blade comes into contact with the detection surface in the trading direction by bending. When abutting in the trading direction, it is necessary to apply a certain amount of pressure to abut the cleaning blade against the detection surface so that the cleaning blade is not pushed up by the developer. In this case, when a part of the developer is sandwiched between the cleaning blade and the detection surface, a phenomenon occurs in which the developer undergoes mechanical deterioration and is fused to the detection surface.

  Further, the toner and the carrier are different in size, and the carrier is larger. Therefore, toner may slip through when the cleaning blade is pushed up by the carrier. That is, even if the carrier attached to the detection surface can be removed, the toner attached to the detection surface cannot be removed. In particular, when a developer aggregate is formed due to a decrease in the fluidity of the developer over time, it tends to adhere to the detection surface.

  However, in the above configuration of the present invention, when the cleaning blade comes into contact with the detection surface, an angle formed by a surface of the detection surface that is opposite to the rotation direction of the cleaning blade with respect to the contact portion. Is in contact with the detection surface so as to have an acute angle. That is, the cleaning blade contacts the detection surface of the toner density sensor in the counter direction. Therefore, the cleaning blade is not pushed up by the developer. When the cleaning blade is brought into contact with the detection surface, it is not necessary to apply pressure as in the case of contacting in the trading direction. Therefore, the developer is not subjected to mechanical deterioration.

  Further, since the cleaning blade applies a force in the direction of biting into the detection surface, it does not occur that the small-sized toner slips through.

  As a result, the developer adhering to the detection surface of the toner concentration sensor is efficiently wiped off, and even if developer agglomeration occurs due to a decrease in developer fluidity over time, the cleaning performance of the detection surface of the toner concentration detection unit is improved. A developing device capable of detecting the toner concentration without deteriorating can be realized.

  Further, the developing device of the present invention is provided on the rotation shaft of the developer conveying member facing the toner density detecting means, and the developer conveying member rotates to thereby remove the developer in the developer container. The toner concentration detecting means detects the toner density at the timing when the compression member applies pressure to the developer on the detection surface of the toner density detecting means. It is preferable.

  When stirring the developer, air is likely to be mixed into the developer. If the toner density is measured in a state where air is mixed, the measured value deviates from the actual toner density.

  However, according to the above configuration, pressure is applied to the developer on the detection surface by the compression member. Therefore, air is removed from the developer on the detection surface. Since the toner concentration detecting means detects the toner concentration at the timing when such pressure is applied, it is possible to output the toner concentration without the influence of air.

  In addition, the developing device of the present invention includes a convex member provided on the rotation shaft of the developer conveying member facing the toner density detecting unit, and the convex member is arranged in the rotational direction from the cleaning blade. Along the first region having a predetermined angular range and the other second region, and the distance from the center of the rotation axis of the developer conveying member is greater on the surface of the first region than on the surface of the second region. It is preferable that the toner concentration detection unit detects the toner concentration at a timing when the developer conveying member is rotated to a position where the first region of the convex member faces the detection surface of the toner concentration detection unit. .

  According to the above configuration, when the developer conveying member rotates, the second area and the first area of the convex member face the detection surface of the toner density detecting means in this order. Here, the distance from the center of the rotation axis of the developer conveying member is greater on the surface of the first region than on the surface of the second region. Therefore, after the cleaning blade passes through the detection surface, the distance between the detection surface and the convex member gradually becomes shorter as the developer transport member rotates. As a result, mechanical pressure is applied to the developer on the detection surface. The toner concentration detection unit detects the toner concentration at the timing when the first region of the convex member comes to a position facing the detection surface, that is, when the pressure is applied to the developer. As a result, it is possible to output a toner concentration without the influence of air.

  In addition, the developing device of the present invention includes a convex member provided on the rotation shaft of the developer conveying member facing the toner density detecting unit, and the convex member is arranged in the rotational direction from the cleaning blade. The distance from the center of the rotation axis of the developer conveying member gradually decreases, and the toner concentration detecting means can detect the toner concentration immediately before the cleaning blade passes the detection surface. preferable.

  According to the above configuration, after the developer conveying member rotates and the cleaning blade passes through the detection surface of the toner density detection unit, the distance between the detection surface and the convex member gradually decreases. As a result, mechanical pressure is applied to the developer on the detection surface. Then, immediately before the cleaning blade passes the detection surface, that is, at the timing when the pressure is applied to the developer, the toner concentration detecting means detects the toner concentration. As a result, it is possible to output a toner concentration without the influence of air.

  Further, the developing device of the present invention includes a partition plate perpendicular to the rotation axis of the developer conveying member at a terminal portion of the developer conveying member in the developer conveying direction, and the toner concentration detecting means includes It is preferable that it is located upstream of the partition plate in the developer transport direction and next to the partition plate.

  According to the above configuration, the developer transported by the developer transport member collides with the partition plate, and temporarily stays on the upstream side in the transport direction of the partition plate. On the other hand, since the developer is further conveyed from the upstream side while the developer conveying member is driven to rotate, pressure is applied to the developer on the upstream side in the conveyance direction of the partition plate. Since the toner concentration detecting means is disposed upstream of the partition plate in the developer transport direction and next to the partition plate, the toner concentration of the developer in a state where pressure is applied. Will be measured. As a result, it is possible to output a toner concentration without the influence of air.

  Furthermore, in the developing device of the present invention, the cleaning blade is preferably an elastic body having a JIS-A hardness of 50 ° to 70 °.

  According to said structure, a developer does not produce a mechanical deterioration and does not produce the aggregate of a developer. As a result, the developer adhering to the detection surface of the toner concentration detection means can be removed even better.

Furthermore, in the developing device of the present invention, the cleaning blade preferably has a volume resistance value of 1 × 10 ⁸ Ωcm or less.

  According to the above configuration, it is possible to remove the developer electrostatically adhering to the detection surface of the toner concentration detection unit, and the developer on the detection surface of the toner concentration detection unit can be further improved. Can be removed.

  Furthermore, in the developing device of the present invention, it is preferable that the compression member or the convex member has conductivity.

  According to the above configuration, even in a developer having a high charge amount, the toner concentration can be accurately detected without being affected by the presence of air between particles by the stirring operation and the electric repulsive force by frictional charging. it can.

  The image forming apparatus of the present invention includes any one of the developing devices described above. Therefore, even if the developer adhering to the detection surface of the toner concentration sensor is efficiently wiped off and the developer aggregates due to the decrease in developer fluidity over time, the cleaning performance of the detection surface of the toner concentration detection portion is deteriorated. It is possible to detect the toner concentration without causing the toner concentration.

  In the developing device according to the present invention, when the cleaning blade comes into contact with the detection surface of the toner concentration detection unit, the cleaning blade is in contact with the surface on the opposite side of the rotation direction of the cleaning blade from the contact portion. It abuts on the detection surface so that the angle formed is an acute angle. As a result, the developer adhering to the detection surface of the toner concentration sensor is efficiently wiped off, and even if developer agglomeration occurs due to a decrease in developer fluidity over time, the cleaning performance of the detection surface of the toner concentration detection unit is improved. The toner density can be detected without deteriorating.

Embodiment 1
An embodiment of the present invention will be described. The developing device according to the present embodiment is provided in an image forming apparatus that forms an image using a two-component developer containing toner and a carrier.

(1) Configuration of Image Forming Apparatus FIG. 2 is an explanatory diagram showing the configuration of the image forming apparatus A according to the present embodiment. The image forming apparatus A forms a multicolor or single color image on a sheet (recording paper) based on image data input from the outside or image data obtained by reading a document.

  As shown in the figure, the image forming apparatus A includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a charger 5, a cleaner unit 4, an intermediate transfer belt unit 8, a fixing unit 12, a sheet conveyance path S, a supply path. A paper tray 10 and a paper discharge tray 15 are provided.

  The image data of a color image handled in the image forming apparatus A corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, the developing device 2 (2a, 2b, 2c, 2d), the photosensitive drum 3 (3a, 3b, 3c, 3d), the charger 5 (5a, 5b, 5c, 5d), the cleaner unit 4 (4a, 4b, 4c and 3d) are provided four by four so as to form four types of latent images corresponding to the respective colors. The symbols a to d correspond to a being black, b being cyan, c being magenta, and d being yellow. It is configured.

  In the image station, the photosensitive drum 3 is disposed on the upper part of the image forming apparatus A. The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. As the charger 5, in addition to the contact type roller type shown in FIG. 2, a contact type brush type or a charger type may be used.

  The exposure unit 1 includes, for example, an EL or LED writing head in which light emitting elements are arranged in an array, in addition to a method using a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror as shown in FIG. Some techniques are used. The exposure unit 1 exposes the charged photosensitive drum 3 according to the input image data, thereby forming an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 3.

  Each developing device 2 visualizes the electrostatic latent image formed on each photoconductor drum 3 with K, C, M, and Y toners. The cleaner unit 4 removes and collects the toner remaining on the surface of the photosensitive drum 3 after the development and image transfer processes.

  An intermediate transfer belt unit 8 is disposed above the photosensitive drum 3. The intermediate transfer belt unit 8 includes an intermediate transfer roller 6 (6a, 6b, 6c, 6d), an intermediate transfer belt 7, an intermediate transfer belt driving roller 71, an intermediate transfer belt driven roller 72, an intermediate transfer belt tension mechanism 73, and an intermediate transfer belt. A transfer belt cleaning unit 9 is provided.

  The intermediate transfer roller 6, the intermediate transfer belt drive roller 71, the intermediate transfer belt driven roller 72, the intermediate transfer belt tension roller 73, etc. stretch the intermediate transfer belt 7 and rotate it in the direction of arrow B.

  The intermediate transfer roller 6 is rotatably supported by an intermediate transfer roller mounting portion in the intermediate transfer belt tension mechanism 73 of the intermediate transfer belt unit 8. The intermediate transfer roller 6 provides a transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 7.

  The intermediate transfer belt 7 is provided so as to be in contact with each photosensitive drum 3. A color toner image (multicolor toner image) is formed on the intermediate transfer belt 7 by sequentially transferring the toner images of the respective colors formed on the photosensitive drum 3 in a superimposed manner. The intermediate transfer belt 7 is formed in an endless shape using a film having a thickness of about 100 μm to 150 μm.

  Transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 7 is performed by the intermediate transfer roller 6 in contact with the back side of the intermediate transfer belt 7. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 6 in order to transfer the toner image. The intermediate transfer roller 6 is formed based on a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm, and the surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, the intermediate transfer roller 6 can uniformly apply a high voltage to the intermediate transfer belt 7. In this embodiment, a roller-shaped transfer electrode (intermediate transfer roller 6) is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic latent images on the respective photoreceptors 3 are visualized with toners corresponding to the respective hues to become toner images, and these toner images are laminated on the intermediate transfer belt 7. As described above, the stacked toner images are moved to the contact position between the conveyed sheet and the intermediate transfer belt 7 by the rotation of the intermediate transfer belt 7, and the transfer roller 11 arranged at this position moves the sheet onto the sheet. Is transcribed. In this case, the intermediate transfer belt 7 and the transfer roller 11 are pressed against each other at a predetermined nip, and a voltage for transferring the toner image onto the paper is applied to the transfer roller 11. This voltage is a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner.

  In order to obtain the nip constantly, either the transfer roller 11 or the intermediate transfer belt drive roller 71 is made of a hard material such as a metal, and the other is a soft material such as an elastic roller (an elastic rubber roller or a foaming resin roller). ).

  The toner adhering to the intermediate transfer belt 7 due to the contact between the intermediate transfer belt 7 and the photosensitive drum 3 and the toner image remaining on the intermediate transfer belt 7 without being transferred when the toner image is transferred from the intermediate transfer belt 7 to the sheet. The toner is removed and collected by the intermediate transfer belt cleaning unit 9 because it causes toner color mixing in the next process. The intermediate transfer belt cleaning unit 9 is provided with a cleaning blade as a cleaning member that comes into contact with the intermediate transfer belt 7. The portion of the intermediate transfer belt 7 in contact with the cleaning blade is supported by an intermediate transfer belt driven roller 72 from the back side.

  The paper feed tray 10 is for storing sheets used for image formation, for example, recording paper, and is provided below the image forming unit and the exposure unit 1. On the other hand, the paper discharge tray 15 provided on the upper part of the image forming apparatus A is for placing printed sheets face down.

  Further, the image forming apparatus A is provided with a sheet conveyance path S for sending the sheet in the paper feed tray 10 and the sheet in the manual feed tray 20 to the paper discharge tray 15 via the transfer unit 11 and the fixing unit 12. . In a portion from the sheet feeding tray 10 to the sheet discharge tray 15 in the sheet conveying path S, a pickup roller 16, a registration roller 14, a transfer unit including a transfer roller 11, a fixing unit 12, a conveying roller 25, and the like are arranged. Yes.

  The conveyance rollers 25 are small rollers for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 25 are provided along the sheet conveyance path S. The pickup roller 16 is a pull-in roller that is provided at an end portion of the sheet feeding tray 10 and supplies sheets from the sheet feeding tray 10 to the sheet conveyance path S one by one. The registration roller 14 temporarily holds the sheet conveyed in the sheet conveyance path S, and conveys the sheet to the transfer unit at a timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned.

  The fixing unit 12 includes a heat roller 31, a pressure roller 32, and the like. The heat roller 31 and the pressure roller 32 rotate with a sheet interposed therebetween. The heat roller 31 is controlled by a control unit (not shown) so as to have a predetermined fixing temperature. This control unit controls the heat roller 31 based on a detection signal from a temperature detector (not shown). The heat roller 31 heat-presses the sheet together with the pressure roller 33 to melt, mix, and press the color toner images transferred to the sheet, and heat-fix the sheet. The sheet on which the multicolor toner image (each color toner image) has been fixed is conveyed to the reverse sheet discharge path of the sheet conveyance path S by the plurality of conveyance rollers 25 and is reversed (the multicolor toner image is on the lower side). Are discharged onto the paper discharge tray 15.

(2) Regarding Configuration of Developing Device Next, the developing device 2 will be described. The developing device 2 is mounted on an electrophotographic image forming apparatus A as shown in FIG. The developing device 2 is for supplying toner to the photosensitive drum 3.

  FIG. 3 is a longitudinal sectional view of the developing device 2 of the present embodiment. FIG. 4 is a cross-sectional view of the developing device 2. As illustrated, the developing device 2 includes a developer storage container (developer container) 21 and two developer transports for transporting the developer stored in the developer storage container 21 while stirring. Members 22a and 22b, a developing roller 23 for supplying toner to the photosensitive drum 3, and a toner concentration sensor (toner concentration detecting means) 24 for detecting the toner concentration in the developer container 21 are provided. Yes.

  As shown in FIGS. 3 and 4, the developer storage container 21 is an elongated rectangular parallelepiped extending in the axial direction of the photosensitive drum 3. The developer storage container 21 has a partition plate 27 extending in the extending direction at the center thereof. The developer storage container 21 is partitioned by the partition plate 27 into two spaces (developer storage spaces 26a and 26b) for storing the developer.

  The partition plate 27 has openings 27a and 27b at both ends for connecting the two developer storage spaces 26a and 26b. Thus, the developer can move between the two developer storage spaces 26a and 26b through the openings 27a and 27b.

  A toner supply port for supplying toner is formed on the upper surface of one end of the developer storage space 26a. A toner cartridge is mounted above the toner supply port, and toner is supplied from the toner cartridge to the developer storage space 26a via the toner supply port.

  The developer conveying members 22a and 22b are accommodated in the developer accommodating spaces 26a and 26b, respectively, and have a structure in which a spiral screw (agitating blade) 30b is formed around the rotation shaft. The developer is transported by rotating the developer transport members 22a and 22b around the rotation shaft. In the present embodiment, in the developer storage space 26a, the developer conveying member 22a rotates so that the toner supplied from the toner replenishing port is conveyed toward the end on the side where the toner replenishing port is not formed. Is done. On the other hand, in the developer storage space 26b, the developer transport member 22b is rotated so that the developer transport direction C is opposite to the developer storage space 26a. And as above-mentioned, the partition plate 27 has opening part 27a * 27b in both ends. As a result, the developer is circulated and conveyed in the developer storage container 21 while being stirred.

  The developing roller 23 is a cylindrical roller whose axial direction is the same as that of the photosensitive drum 3, and is installed obliquely above the developer storage space 26b. Part of the developing roller 23 is exposed from the opening area of the developing device (the opening including the developing area in FIG. 3). The exposed portion is provided so as to face the photosensitive drum 3. The developing roller 23 carries the developer accommodated in the developer accommodating space 26b, and conveys the developer to a portion facing the photosensitive drum 3 in the exposed portion. Thus, toner can be attached to the electrostatic latent image formed on the photosensitive drum 3, and the electrostatic latent image can be developed to form a toner image. Note that the rotation direction of the developing roller 23 is opposite to the rotation direction of the photosensitive drum 3.

  The toner concentration sensor 24 is a sensor that detects the toner concentration in the developer storage container 21. The toner concentration sensor 24 is a magnetic permeability sensor (manufactured by TDK) that measures the magnetic permeability on the detection surface 24a. FIG. 5 is a graph showing the relationship between the output value of the toner density sensor 24 and the toner density of the developer. As shown in FIG. 5, the toner density and the output value of the toner density sensor 24 are in a proportional (linear) relationship. Therefore, the toner density can be confirmed by the output value of the toner density sensor 24.

  The toner concentration sensor 24 is attached to the bottom of the developer storage space 26b near the developing roller 23, and the detection surface 24a is a part of the bottom surface of the developer storage space 26b. Therefore, the detection surface 24a is in contact with the developer.

(3) Cleaning Mechanism for Toner Density Sensor Next, a cleaning mechanism for the detection surface 24a of the toner concentration sensor 24 will be described. FIGS. 1A and 1B are schematic views showing the developer transport member 22b installed in the developer storage space 26b in which the toner density sensor 24 is attached. FIG. 1A is a cross-sectional view when a surface perpendicular to the rotation shaft 29b of the developer conveying member 22b is formed at a position where the toner density sensor 24 is attached. FIG. 1B is a side view of the developer conveying member 22b.

  As shown in FIGS. 1A and 1B, a cleaning member 28 is attached to the developer conveying member 22b as the cleaning mechanism. The cleaning member 28 rotates in accordance with the rotation of the developer conveying member 22b, and removes the developer on the detection surface 24a by having the tip thereof abut on the detection surface 24a of the toner density sensor 24.

  The cleaning member 28 includes a cleaning blade 28b that can contact the detection surface 24a of the toner density sensor 24, and a support member 28a that supports the cleaning blade 28b and is fixed to the developer conveying member 22b.

  The support member 28a has a plate shape. The support member 28a is attached to a portion of the rotation axis 29b of the developer conveying member 22b facing the detection surface 24a of the toner density sensor 24.

  The cleaning blade 28 b has a plate-like shape in which the tip part comes into contact with the detection surface 24 a of the toner density sensor 24. The cleaning blade 28b is attached to the surface on the rotation direction (movement direction) side of the support member 28a. As a material of the cleaning blade 28b, for example, an elastic body such as urethane rubber or silicon rubber, a metal having flexibility when formed into a plate shape, or the like can be used.

  In the present embodiment, the support member 28a is bent so that the cleaning blade 28b contacts the detection surface 24a of the toner concentration sensor 24 in the counter direction. Here, the cleaning blade 28b comes into contact with the detection surface 24a of the toner density sensor 24 in the counter direction. When the cleaning blade 28b comes into contact with the detection surface 24a, the detection blade 24b comes into contact with the cleaning blade 28b. This means that the cleaning blade 28b comes into contact with the detection surface 24a so that an angle formed between the surface of the cleaning blade 28b opposite to the moving direction (rotation direction) of the cleaning blade 28b and the cleaning blade 28b is an acute angle.

  In this embodiment, as shown in FIG. 1A, the bent portion of the support member 28a is more than the surface connecting the tip of the cleaning blade 28b and the axial center of the developer transport member 22b. It exists in the direction opposite to the rotation direction of 22b. The angle formed by the cleaning blade 28b and the surface connecting the tip of the cleaning blade 28b and the axial center of the developer conveying member 22b is set to 20 °. That is, when the cleaning blade 28b comes into contact with the detection surface 24a, the surface of the detection surface 24a that is on the opposite side of the moving direction (rotation direction) of the cleaning blade 28b from the contact point with the cleaning blade 28b; An angle formed by the cleaning blade 28b (hereinafter referred to as a contact angle) is 70 °. In addition, the said contact angle is not limited to 70 degrees, What is necessary is just an acute angle.

  Thus, in this embodiment, the cleaning blade 28b of the cleaning member 28 is brought into contact with the detection surface 24a of the toner density sensor 24 in the counter direction. As a result, the developer that adheres to the detection surface 24a of the toner density sensor 24, which is the object of the present invention, can be wiped off more efficiently than before, and a developing device in which the change in the output value of the toner density sensor 24 is small is realized. Can be achieved. Hereinafter, this mechanism will be described.

  In the case of a conventional configuration such as Patent Documents 1 and 2, the cleaning blade 28b is bent to contact the detection surface 24a in the trading direction. Here, the contact in the trading direction means that when the cleaning blade 28b is in contact with the detection surface 24a, the cleaning blade 28b is closer to the moving direction side of the detection surface 24a than the contact point with the cleaning blade 28b. This means that the surface makes contact with the detection surface 24a so that the angle formed by the cleaning blade 28b is an acute angle.

  When contacting in the trading direction as described above, it is necessary to apply a certain pressure so that the cleaning blade 28b contacts the detection surface 24a so that the cleaning blade 28b is not pushed up by the developer. In this case, when a part of the developer is sandwiched between the cleaning blade 28b and the detection surface 24a, a phenomenon occurs in which the developer is fused to the detection surface 24a due to mechanical deterioration.

  Further, the toner and the carrier are different in size, and the carrier is larger. Therefore, toner may slip through when the cleaning blade 28b is pushed up by the carrier. That is, even if the carrier attached to the detection surface 24a can be removed, the toner attached to the detection surface 24a cannot be removed. In particular, when a developer aggregate is formed due to a decrease in the fluidity of the developer over time, it tends to adhere to the detection surface 24a.

  However, in the configuration of the present embodiment, since the cleaning blade 28b is brought into contact with the detection surface 24a of the toner density sensor 24 in the counter direction, the cleaning blade 28b is not pushed up by the developer. For this reason, when the cleaning blade 28b is brought into contact with the detection surface 24a, it is not necessary to apply pressure as in the case of contacting in the trading direction. Therefore, the developer is not subjected to mechanical deterioration.

  Further, since the cleaning blade 28b applies a force in the direction of biting into the detection surface 24a, it does not occur that small-sized toner slips through.

  With the above mechanism, according to the present embodiment, the developer attached to the detection surface 24a of the toner density sensor 24 is efficiently wiped off, and a developing device in which the output value of the toner density sensor 24 is small with time is realized. Can be achieved.

  6 (a) and 6 (b) show a toner density sensor using the developing device having the developer conveying member 22b of the present embodiment shown in FIG. 1 and the conventional developing device shown in FIGS. 12 (a) and 12 (b). It is the result of having measured the time-dependent change of 24 output values. FIG. 6A shows a developing device according to Embodiment 1, and FIG. 6B shows a conventional developing device. The measurement was performed in an image forming apparatus equipped with a developing device with no toner consumption. That is, the toner density in the developing device was actually changed.

  Note that urethane rubber was used as the material of the cleaning blade 28b.

  As shown in FIG. 6, in the conventional developing device, the output value of the toner density sensor 24 tends to decrease with time, that is, the toner density tends to be higher than actual. This indicates that the proper toner concentration cannot be measured as a result of the developer adhering to the detection surface 24a of the toner concentration sensor 24.

  On the other hand, in the developing device of the present embodiment, the output value of the toner density sensor 24 shows a substantially constant value. From this, it can be seen that there is no adhesion of the developer to the detection surface 24a of the toner concentration sensor 24, and the toner concentration is properly measured.

(4) About the material of the cleaning blade In the above, as the material of the cleaning blade 28b, for example, an elastic body such as urethane rubber or silicon rubber, a metal having flexibility when formed into a plate shape, or the like can be used. Explained. However, the material of the cleaning blade 28b is preferably an elastic body, and more preferably an elastic body having a hardness measured using a JIS-A hardness meter of 50 ° or more and less than 70 °.

  An elastic rubber material having a JIS-A hardness of less than 50 ° causes the developer to slip through, and the developer on the detection surface 24a of the toner density sensor 24 cannot be wiped off. On the other hand, an elastic rubber material having a hardness higher than JIS-A hardness of 70 ° is likely to cause mechanical deterioration with respect to the developer, and the developer agglomerates in the vicinity of the toner concentration sensor 24 or on the surface of the toner concentration sensor 24. Toner fusion is likely to occur. Accordingly, it is preferable to use a rubber elastic body having a JIS-A hardness of 50 ° to 70 °.

The cleaning blade 28b preferably has a volume resistivity of 1 × 10 ⁸ Ωcm or less.

  In some cases, the developer adheres to the detection surface 24a of the toner density sensor 24 due to an electrical adhesion force. The electrically attached developer may slip through the cleaning blade 28b, and the developer on the detection surface 24a of the toner density sensor 24 may not be completely wiped off. Furthermore, when the developer is stirred, an electric repulsive force acts even when the toner charge amount is high, the gap between particles in the developer increases, and the bulk density of the developer decreases. When such a phenomenon occurs, the toner concentration sensor 24 outputs an output value indicating that the magnetic permeability is low. That is, the output value of the toner density sensor 24 may output a false detection signal that the toner amount has increased even when the toner is not supplied.

Therefore, by using the cleaning blade 28b having a volume resistance value of 1 × 10 ⁸ Ωcm or less, it becomes possible to reduce part of the charge amount of the toner in the developer, and the bulk density of the developer due to the electric repulsion. Can be suppressed. Further, the developer adhesion due to the electric force on the detection surface 24a of the toner density sensor 24 can be completely wiped off. As a result, the output value of the toner density sensor 24 can be further stabilized.

The cleaning blade 28b having a volume resistance value of 1 × 10 ⁸ Ωcm or less can be implemented, for example, by containing carbon black as a conductive agent in urethane rubber. However, the material is not limited to such a material, and other materials such as silicon rubber containing a conductive material may be used. In addition, since a static elimination effect is small when a volume resistance value is higher than 10 ⁸ Ωcm, 1 × 10 ⁸ Ωcm or less is preferable.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIGS. 7 (a) and 7 (b). For convenience of explanation, members having the same functions as those in the drawings described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  The present embodiment is different from the first embodiment in that the positions of the toner density sensor 24 and the cleaning member 28 are different, and a partition plate 31 perpendicular to the rotary shaft 29b is provided at the end of the screw of the developer conveying member 22b. It differs in the point to prepare. Other configurations are the same as those of the first embodiment, and thus the description thereof is omitted here.

  7A and 7B are schematic views showing the developer conveying member 22b and the toner density sensor 24 according to the present embodiment, where FIG. 7A is a sectional view and FIG. 7B is a side view. As shown in FIG. 7B, a disc-shaped partition plate 31 perpendicular to the rotation shaft 29b is formed at the end of the developer conveyance direction C of the screw 30b of the developer conveyance member 22b. Note that the end of the developer conveying member 22b in the developer conveying direction of the screw 30b is located near the opening 27a of the partition plate 27 (see FIG. 4). Therefore, the partition plate 31 is also located in the vicinity of the opening 27a.

  The toner concentration sensor 24 and the cleaning member 28 are disposed on the upstream side in the transport direction from the partition plate 31 and next to the partition plate 31.

  As a result, the developer conveyed by the developer conveying member 22b collides with the partition plate 31 and temporarily stays upstream in the conveyance direction of the partition plate 31. On the other hand, since the developer is further conveyed from the upstream side while the developer conveying member 22b is being driven to rotate, pressure is applied to the developer on the upstream side in the conveying direction of the partition plate 31. As a result, the air contained in the developer is removed in the vicinity of the partition plate 31. However, a cleaning member 28 is provided next to the partition plate 31. Further, the partition plate 31 is located in the vicinity of the opening 27 a of the partition plate 27. Therefore, when the cleaning member 28 passes over the detection surface 24 a of the toner density sensor 24, the temporarily retained developer moves to the adjacent developer transport space through the opening of the partition plate 27.

  Therefore, in this embodiment, the toner concentration sensor 24 sets the toner concentration of the developer from which the air has been removed by setting the measurement timing of the toner concentration sensor 24 immediately before the cleaning member 28 passes the detection surface 24a. Will be measured. Here, “immediately before the cleaning member 28 passes through the detection surface 24a” means, for example, a timing within a period of ¼ of the rotation period of the developer conveying member 22b before the cleaning member 28 passes through the detection surface 24a. is there. As a result, the toner concentration sensor 24 can accurately measure the toner concentration without being affected by the change in permeability due to air.

Also in the present embodiment, the cleaning blade 28b is preferably an elastic body having a JIS-A hardness of 50 ° to 70 °. The volume resistance value is preferably 1 × 10 ⁸ Ωcm or less.

[Embodiment 3]
Another embodiment of the present invention will be described below with reference to FIGS. 8 (a) and 8 (b). For convenience of explanation, members having the same functions as those in the drawings described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the present embodiment, in addition to the cleaning member 28 of the first embodiment, a convex member 32 for applying pressure to the developer is provided on the rotation shaft 29b facing the detection surface 24a of the toner density sensor 24. This is different from the above embodiment. Since other configurations are substantially the same as those of the second embodiment, description thereof is omitted here.

  FIG. 8 is a schematic view showing the developer conveying member 22b and the toner concentration sensor 24 according to the present embodiment, in which (a) is a cross-sectional view and (b) is a side view.

  As shown in FIG. 8, the rotation shaft 29 b extends along the rotation direction of the developer conveying member 22 b from the position where the cleaning member 28 is formed on the rotation shaft 29 b facing the detection surface 24 a of the toner density sensor 24. A convex member 32 is formed so that the distance from the center gradually decreases. However, the convex member 32 may have an angular range in which the distance from the axis center is the same with respect to the center of the rotation shaft 29b.

  In this embodiment, in the range of 90 ° along the rotation direction R from the location where the cleaning member 28 is formed, the distance from the axial center is the same, and the rotation direction R from the location where the cleaning member 28 is formed. In the range of 90 ° to 270 ° along, the distance from the axial center continuously decreases monotonously along the rotation direction R.

  In other words, the convex member 32 is a convex member formed on the rotation shaft 29b of the developer conveying member 22b facing the detection surface 24a of the toner density sensor 24, and the cleaning member 28 is formed thereon. A first region within a range of a predetermined angle (90 ° in this case) and a second region other than that (the cleaning member 28 is formed) along the rotation direction R of the rotation shaft 29b. It can be said that the distance from the axial center of the developer conveying member 22b is larger in the first region than in the second region. .

  Thereby, when the developer transport member 22b rotates in the rotation direction R, the distance from the detection surface 24a to the developer transport member 22b is long immediately after the cleaning member 28 passes through the detection surface 24a. As the transport member 22b rotates, the distance from the detection surface 24a to the developer transport member 22b gradually decreases. Therefore, when the cleaning member 28 is rotated to just before the detection surface 24a, the first region of the convex member 32 faces the detection surface 24a. The developer on the detection surface 24 a is in a state where pressure is applied to the detection surface 24 a side by the first region of the convex member 32. That is, the convex member 32 is provided on the rotation shaft 29b of the developer transport member 22b, and can be said to be a compression member that applies pressure to the developer as the developer transport member 22b rotates. Thereby, excess air is removed from the developer on the detection surface 24a, and the bulk density is increased.

  Therefore, in this embodiment, the toner concentration sensor 24 sets the toner concentration of the developer from which the air has been removed by setting the measurement timing of the toner concentration sensor 24 immediately before the cleaning member 28 passes the detection surface 24a. Will be measured. Here, the time immediately before the cleaning member 28 passes through the detection surface 24a is, for example, when the developer conveying member 22b is rotated to a rotation position where the first region of the convex member 32 faces the detection surface 24a. This is a timing within a quarter of the rotation period of the developer conveying member 22b before the cleaning member 28 passes through the detection surface 24a. That is, the distance from the detection surface 24a to the convex member 32 is the timing within the period in which the shortest distance is maintained. As a result, the toner concentration sensor 24 can accurately measure the toner concentration without being affected by the change in permeability due to air.

  Further, in the present embodiment, as shown in FIG. 8B, a screw is not formed at a position where the cleaning member 28 and the convex member 32 are formed on the rotating shaft 29b of the developer conveying member 22b. I have to.

  Therefore, the developer layer thickness on the detection surface 24a is not affected by the screw, and the detection timing of the toner density sensor 24 is fixed at a predetermined rotational position of the developer conveying member 22b, thereby detecting at the time of detection. The layer thickness of the developer on the surface 24a can be made constant. As a result, the output value of the toner density sensor 24 is further stabilized.

  In addition, although demonstrated as a form which has the partition plate 31 here, the structure which provides the convex-shaped member 32 like this embodiment in the form which does not have the partition plate 31 like Embodiment 1 may be sufficient.

Also in the present embodiment, the cleaning blade 28b is preferably an elastic body having a JIS-A hardness of 50 ° to 70 °. The volume resistance value is preferably 1 × 10 ⁸ Ωcm or less.

Furthermore, it is preferable that the convex member 32 has conductivity (specifically, 10 ⁷ Ωcm or less). As a result, a part of the toner in the developer staying between the toner concentration sensor 24 and the convex member 32 is neutralized, so that the bulk density of the developer on the detection surface 24a of the toner concentration sensor 24 is eliminated. Becomes higher. As a result, the detection accuracy of the toner density sensor 24 is further improved.

[Modification]
In Embodiment 1-3 described above, when the cleaning blade 28b contacts the detection surface 24a, the movement direction (rotation direction) of the cleaning blade 28b is opposite to the contact position of the detection surface 24a with the cleaning blade 28b. A specific example is shown in which the angle (contact angle) formed by the surface in the direction and the cleaning blade 28b is 70 °. However, it is not limited to this specific example.

  For example, as shown in FIGS. 9A to 11B, the support member 28a may be bent so that the contact angle is 20 °. 9A and 9B are modifications of the first embodiment, FIGS. 10A and 10B are modifications of the second embodiment, and FIGS. 11A and 11B are the modifications of the third embodiment. It is a modified example of.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be applied to a developing device that is used in a copying machine, a printer, a fax machine, or the like using an electrophotographic method, and visualizes an electrostatic latent image pattern using a developer containing toner and a carrier.

2A and 2B are schematic views illustrating a developer conveying member according to an embodiment of the present invention, in which FIG. 1 is an explanatory diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a longitudinal sectional view of a developing device according to an embodiment of the present invention. FIG. 4 is a transverse sectional view of the developing device shown in FIG. 3. 6 is a graph showing a relationship between an output value of a toner density sensor and a toner density. FIG. 4 shows the results of measuring the change over time in the output value of the toner density sensor, where (a) shows the developing device of Embodiment 1 and (b) shows the conventional developing device. 4A and 4B are schematic diagrams illustrating a developer conveying member and a toner density sensor according to Embodiment 2, where FIG. 5A is a cross-sectional view, and FIG. 4A and 4B are schematic diagrams illustrating a developer conveying member and a toner density sensor according to Embodiment 3, where FIG. 5A is a cross-sectional view, and FIG. 4A and 4B are schematic diagrams illustrating a developer conveying member and a toner density sensor according to a modification of Embodiment 1, where FIG. 5A is a cross-sectional view, and FIG. FIG. 9 is a schematic diagram illustrating a developer conveying member and a toner density sensor according to a modification of Embodiment 2, where (a) is a cross-sectional view and (b) is a side view. FIG. 10 is a schematic diagram illustrating a developer conveying member and a toner density sensor according to a modification of Embodiment 3, wherein (a) is a cross-sectional view and (b) is a side view. It is the schematic which shows the prior art example of a developer conveyance member and a toner concentration sensor, (a) is sectional drawing, (b) is a side view.

Explanation of symbols

2 Developing device 3 Photosensitive drum 21 Developer storage container (developer container)
22b Developer conveying member 23 Developing roller 24 Toner density sensor (toner density detecting means)
24a Detection surfaces 26a and 26b Developer storage space 27 Partition plate 28 Cleaning member 28a Support member 28b Cleaning blade 29b Rotating shaft 30b Screw (stirring blade)
31 Partition plate 32 Convex member (compression member)
A Image forming apparatus C Conveying direction R Rotating direction

Claims (10)

A developer container containing a developer containing toner and a carrier;
A developer conveying member that conveys the developer in the developer container in a certain direction while stirring by forming a stirring blade on the rotating shaft and rotating;
A toner concentration detecting means disposed on the inner wall of the developer container for detecting the toner concentration in the developer container;
Cleaning that is provided on the developer conveying member facing the toner concentration detecting means, contacts the detection surface of the toner concentration detecting means as the developer conveying member rotates, and removes the developer on the detecting surface. In a developing device comprising a blade,
When the cleaning blade comes into contact with the detection surface, an angle formed between the detection surface and a surface on the opposite side to the rotation direction of the cleaning blade from the contact portion becomes an acute angle. A developing device that abuts. Compression provided on the rotation shaft of the developer conveying member facing the toner concentration detecting means, and capable of applying pressure to the developer in the developer container by rotating the developer conveying member. Comprising a member,
2. The developing device according to claim 1, wherein the toner density detecting means detects the toner density at a timing when the compression member applies pressure to the developer on the detection surface of the toner density detecting means. . A convex member provided on the rotation axis of the developer conveying member facing the toner concentration detecting means;
The convex member includes a first region having a predetermined angular range along the rotational direction from the cleaning blade and a second region other than the first region, and a distance from the center of the rotation axis of the developer conveying member is the first region. The surface of one region is larger than the surface of the second region,
The toner density detecting means detects the toner density at a timing when the developer conveying member is rotated to a position where the first region of the convex member faces the detection surface of the toner density detecting means. The developing device according to claim 1. A convex member provided on the rotation axis of the developer conveying member facing the toner concentration detecting means;
The surface of the convex member has a shape in which the distance from the center of the rotation axis of the developer conveying member gradually decreases along the rotational direction from the cleaning blade,
The developing device according to claim 1, wherein the toner concentration detection unit detects the toner concentration immediately before the cleaning blade passes the detection surface. At the end of the developer transport direction of the developer transport member, a partition plate perpendicular to the rotation axis of the developer transport member is provided,
5. The toner density detection unit according to claim 1, wherein the toner density detection unit is disposed upstream of the partition plate in the developer transport direction and adjacent to the partition plate. The developing device according to 1.   The developing device according to claim 1, wherein the cleaning blade is an elastic body having a JIS-A hardness of 50 ° to 70 °. The developing device according to claim 1, wherein the cleaning blade has a volume resistance value of 1 × 10 ⁸ Ωcm or less.   The developing device according to claim 2, wherein the compression member has conductivity.   The developing device according to claim 3, wherein the convex member has conductivity.   An image forming apparatus comprising the developing device according to claim 1.

Images