JP2011022514A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device and the like capable of accurately detecting toner concentration. <P>SOLUTION: This developing device includes: a developer container storing a developer formed by mixing toner with magnetic carrier and forming a carrying passage for the developer; a concentration sensor having a detecting part for detecting the toner concentration in the developer; a rotating shaft; a carrying member having a spiral blade provided around the rotating shaft and a plate-like member provided opposite to the detecting part extending over the whole region in the direction of carrying the developer with the spiral blade, both ends thereof in the carrying direction being formed to be continuous to the spiral blade; and a magnetic plate mounted on the plate-like member, provided opposite to the detecting part extending over the whole region in the carrying direction and disposed at a space from a part of the plate-like member that is continuous to the spiral member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus.

  A developing device having a structure that includes a sensor for detecting the presence or absence of an internal magnetic toner, a notch in a stirring blade of a stirring body for stirring magnetic toner, and a magnetic metal body on a rotating shaft is known. (For example, refer to Patent Document 1). In addition, in a developing device provided with a toner density sensor for reading the toner density of the developer, a magnet provided on a shaft (core) of a member for mixing the developer is known (see, for example, Patent Document 2). .

JP 2002-62720 A Japanese Patent Laid-Open No. 5-197290

  An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus that can detect an accurate toner density.

The developing device according to claim 1 is:
A developer container that contains a developer in which toner and a magnetic carrier are mixed and forms a transport path for the developer;
A density sensor having a detection unit for detecting the toner density in the developer;
A rotating shaft, a spiral blade provided around the rotating shaft, and both ends of the developer in the transport direction are provided so as to face the detection unit over the entire region in the transport direction of the developer by the spiral blade. A conveying member having a plate-like plate-like member formed continuously with the spiral blade, and
A magnetic plate provided on the plate-like member, provided to face the detection unit over the entire conveyance direction, and continuous with the spiral member of the plate-like member. It is characterized by comprising a magnetic plate arranged at an interval with respect to the part.

  According to a second aspect of the present invention, in the developing device, the distance between the end of the plate-like member on the upstream side in the transport direction and the magnetic plate is equal to the end of the plate-like member on the downstream side in the transport direction. It is characterized by being arranged narrower than the distance between.

  According to a third aspect of the present invention, an end portion of the plate-like member on the upstream side in the transport direction and the magnetic plate are arranged so that the magnetic brush formed on the magnetic plate in the developer does not reach the spiral blade. It is characterized by being.

  A developing device according to a fourth aspect is characterized in that the magnetic plate is provided on a surface of the plate-like member on the side where the developer is pushed by the rotation of the conveying member.

  According to a fifth aspect of the present invention, in the developing device according to the fifth aspect, the distance between the end of the plate-like member upstream in the transport direction and the magnetic plate is detected by the magnetic plate in a posture in which the plate-like member faces the detector. It is arrange | positioned in the position larger than the distance of a part and a magnetic board, It is characterized by the above-mentioned.

The process cartridge according to claim 6 is:
An image carrier that holds the image in response to formation of an image on the surface;
A developing device for developing the electrostatic latent image formed on the image carrier with toner,
The developer is
A developer container that contains a developer in which toner and a magnetic carrier are mixed and forms a transport path for the developer;
A density sensor having a detection unit for detecting the toner density in the developer;
A rotating shaft, a spiral blade provided around the rotating shaft, and both ends of the developer in the transport direction provided to face the detection unit over the entire region of the developer transport direction by the spiral blade. A conveying member having a plate-like plate-like member formed continuously with the spiral blade, and
A magnetic plate provided on the plate-like member, provided to face the detection unit over the entire conveyance direction, and continuous with the spiral member of the plate-like member. It is characterized by comprising a magnetic plate arranged at an interval with respect to the part.

An image forming apparatus according to claim 7 is provided.
An image carrier that holds the image in response to formation of an image on the surface;
A latent image forming unit that forms an electrostatic latent image on the image carrier;
A developing unit for developing the latent image formed on the image carrier by the latent image forming unit with toner;
The developer is
A developer container that contains a developer in which toner and a magnetic carrier are mixed and forms a transport path for the developer;
A density sensor having a detection unit for detecting the toner density in the developer;
A rotating shaft, a spiral blade provided around the rotating shaft, and both ends of the developer in the transport direction are provided so as to face the detection unit over the entire region in the transport direction of the developer by the spiral blade. A conveying member having a plate-like plate-like member formed continuously with the spiral blade, and
A magnetic plate provided on the plate-like member, provided to face the detection unit over the entire conveyance direction, and continuous with the spiral member of the plate-like member. It is characterized by comprising a magnetic plate arranged at an interval with respect to the part.

  According to the developing device of the first aspect, it is possible to detect an accurate toner concentration in the developer as compared with the case where the magnetic plate is not spaced from each end of the plate-like member.

  According to the developing device of the second aspect, the accurate toner concentration in the developer is stably detected as compared with the case where the interval from the upstream end to the magnetic plate is wider than the interval from the downstream end to the magnetic plate. be able to.

  According to the developing device of the third aspect, the toner in the developer is more accurate as compared with the case where the gap between the both ends of the plate-like member and the magnetic plate is a distance at which the magnetic brush reaches the blade portion. The density can be detected.

  According to the developing device of the fourth aspect, it is possible to accurately detect the toner concentration in the developer as compared with the case where the magnetic plate is not provided on the surface on the pressing side of the developer.

  According to the developing device of the fifth aspect, the toner density can be detected more accurately than in the case where the present configuration is not provided.

  According to the process cartridge of the sixth aspect, the image quality is improved as compared with the case where the magnetic plate is not spaced from both ends of the plate-like member.

  According to the image forming apparatus of the seventh aspect, the image quality is improved as compared with the case where the magnetic plate is not spaced from both ends of the plate-like member.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. It is the figure which looked at the developing device shown in Drawing 1 from the upper part. FIG. 3 is a diagram illustrating a state where a second agitation transport member is removed from the developing device illustrated in FIG. 2. FIG. 4 is a sectional view taken along line 4-4 of the developing device 13 shown in FIG. FIG. 5 is a cross-sectional view of the developing device shown in FIG. 4 taken along line 5-5. It is a graph which shows distribution in the 2nd conveyance direction of the developer near a paddle. It is a figure explaining the reference example with which the magnetic board was provided in the whole surface of the paddle.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a printer according to an embodiment of the present invention.

  The printer 1 shown in FIG. 1 forms an electrostatic latent image by irradiating a photoconductor 10, a charging roll 11 for applying a charge to the surface of the photoconductor 10, and exposure light based on image data. An exposure unit 12 that develops an electrostatic latent image with toner to form a toner image, a paper cassette 16 that stores recording paper, and a paper transport device that pulls out and transports the recording paper from the paper cassette 16 17, a transfer roll 14 for transferring the toner image onto the recording paper, a fixing device 15 for fixing the toner image on the recording paper by heating and pressurizing the toner image on the recording paper, a toner cartridge 18, A cleaning device 19 that cleans the surface of the photoconductor 10 and a control unit 1A that controls each unit in the printer 1 are provided. The photoconductor 10 has a cylindrical surface, and a rotating shaft 10 a extends in the front-rear direction of the printer 1. The photoconductor 10, the charging roll 11, the developing device 13, and the cleaning device 19 are provided in the process cartridge 1B, and the process cartridge 1B is attached to the printer 1 in a replaceable manner. The developing device 13 is opposed to the photoreceptor 10 and rotates while the developer roll 131 conveys the developer to a region between the photoreceptor 10 and two agitating conveyances that convey the developer in the developing device 13 while stirring. Members 132 and 133 are provided.

  Here, the photoconductor 10 corresponds to an example of an image carrier according to the present invention, and the combination of the charging roll 11 and the exposure device 12 corresponds to an example of a latent image forming unit according to the present invention.

  Here, an image forming method in the printer 1 will be briefly described.

  In the printer 1 shown in FIG. 1, a charge is applied to the surface of the photoreceptor 10 that rotates in the direction of arrow a about the rotation axis 10a by the charging roll 11, and the surface of the photoreceptor 10 to which the charge is applied is externally applied. An electrostatic latent image is formed on the surface of the photoreceptor 10 by irradiating the exposure device 12 with laser light based on the transmitted image data. Toner 13 is supplied from the toner cartridge 18 to the developing device 13. In the developing device 13, a developer containing toner is supplied to the developing roll 131 and is carried to a region between the developing roll 131 and the photoreceptor 10. As the toner adheres onto the latent image, the electrostatic latent image on the surface of the photoreceptor 10 is developed. The photoreceptor 10 holds a toner image formed by development, and the toner image is transferred by a transfer roll 14 onto a recording sheet conveyed in the direction of arrow b, and is recorded by a fixing device 15 that heats and pressurizes the toner image. The toner image on the paper is melted and fixed on the recording paper. The developer remaining on the surface of the photoreceptor 10 is removed by the cleaner 19. The printer 1 is a monochrome image dedicated machine, but the present invention may be applied to a color image machine.

  FIG. 2 is a view of the developing unit shown in FIG. 1 as viewed from above.

  The developing device 13 includes a developer containing device 130 that contains the developer, a developing roll 131, a first stirring and conveying member 132 that conveys the developer inside the developer containing device 130, and a second stirring and conveying member. 133. The developer container 130 includes a container main body 134 and a developer supply and discard unit 135 provided on the front F side of the printer main body 134 of the container main body 134. FIG. 2 shows a state in which the cover on the upper portion of the container main body 134 is removed. Since the container main body 134 and the developer supply / disposal unit 135 are fixed and integrated with each other, the developer container 130 will be described as long as it is not necessary to distinguish between them.

  The developer container 130 contains a developer in which toner and a magnetic carrier are mixed, and the inside of the developer container 130 is a wall 1301 extending in parallel with the developing roller 131 and the first storage chamber 130a and the second storage chamber. 130b. The first storage chamber 130a is adjacent to the developing roll 131, and the second storage chamber 130b is disposed on the opposite side of the developing roll 131 with the first storage chamber 130a interposed therebetween. The developer container 130 is provided with a density sensor 137 (see FIG. 4) that detects the density of toner in the developer, and the detection unit 137a of the density sensor 137 is exposed at the bottom of the second storage chamber 130b. ing. A first agitation transport member 132 is disposed in the first storage chamber 130a, and a second agitation transport member 133 is disposed in the second storage chamber 130b. A toner supply port 130c that opens upward is provided at the front F end of the first storage chamber 130a, and a developer discharge port 130d that opens downward is provided behind the toner supply port 130c. .

  The two agitating / conveying members 132 and 133 include rotating shafts 1321 and 1331 extending in parallel with the developing roller 131 and spiral blades 1322 and 1332 provided around the rotating shafts 1321 and 1331, respectively. The first agitating and conveying member 132 and the second agitating and conveying member 133 are rotatably supported by rolling bearings 136 at both end portions of the respective rotating shafts 1321 and 1331. The rear B ends of the rotating shafts 1321 and 1331 are connected to a gear G that transmits a driving force from a motor (not shown). The developing roll 131 and the two agitating / conveying members 132 and 133 are rotated by driving of a motor (not shown).

  The first agitation transport member 132 rotates around the axis of the rotation shaft 1321 to transport the developer in the first storage chamber 130a in the first transport direction indicated by the arrow d. The second stirring / conveying member 133 rotates around the rotation axis 1331 in the same direction as the first stirring / conveying member 132, thereby causing the developer in the second storage chamber 130b to move in the arrow e opposite to the first conveying direction. It conveys in the 2nd conveyance direction shown. In the present embodiment, the first conveyance direction d by the first agitation conveyance member 132 is forward F, and the conveyance direction e by the second agitation conveyance member 133 is backward B.

  Discharge windows 1301a and 1301b are provided on the wall 1301 that partitions the first storage chamber 130a and the second storage chamber 130b, and the developer stored in the developer container 130 passes through the discharge windows 1301a and 1301b. And circulates around the wall 1301.

  Here, the developer container 130 corresponds to an example of a developer container according to the present invention, and the second storage chamber 130b corresponds to an example of a conveyance path according to the present invention. Moreover, the 2nd stirring conveyance member 133 corresponds to an example of the conveyance member said to this invention, and the 2nd conveyance direction e by the 2nd stirring conveyance member 133 corresponds to an example of the conveyance direction said to this invention.

  The spiral blade 1322 of the first stirring and conveying member 132 has four types of spiral blade portions 1322a, 1322b, 1322c, and 1322d that are provided around the rotation shaft 1321 and have different shapes. A main stirring blade portion 1322a is provided at a position of the first stirring / conveying member 132 corresponding to the developing roll 131 (see FIG. 2). A forward conveying blade portion 1322b whose direction of rotation is opposite to that of the main stirring blade portion 1322a is provided in the front F of the main stirring blade portion 1322a, and the main stirring blade is further forward F of the reverse conveying blade portion 1322b. The discharge conveyance blade portion 1322c having the same turning direction as that of the portion 1322a is provided, and a supply blade portion 1322d having a rotation direction opposite to that of the main stirring blade portion 1322a is provided further forward F of the discharge conveyance blade portion 1322c. Is provided.

  The spiral blade 1332 of the second stirring and conveying member 133 is provided between the blade portions 1332a and 1332b and the blade portions 11332a and 1332b of which the turning direction is opposite to that of the main stirring blade portion 1322a of the first stirring and conveying member 132. And a plate-like member 1332c that extends linearly in the second transport direction e, that is, the axial direction of the rotary shaft 1331. The plate-like member 1332c is erected on the rotation shaft 1331, and the blade portions 1332a and 1332b are respectively connected to both ends of the plate-like member 1332c in the second conveyance direction e, and upstream and downstream in the second conveyance direction e. Extends to the side. The plate-like member 1332c is provided at a position facing the detection unit 137a of the density sensor 137 (see FIG. 4), and is longer than the length of the detection unit 137a in the second transport direction e.

  FIG. 3 is a diagram illustrating a state in which the second agitating / conveying member is removed from the developing device illustrated in FIG. 2. 4 is a cross-sectional view of the developing device shown in FIG. 2 taken along line 4-4.

  The density sensor 137 shown in FIG. 4 is attached to the outside of the developer container 130, but the detection unit 137a of the developer container 130 is fitted into a hole provided in the bottom of the second storage chamber 130b. And exposed at the bottom of the second storage chamber 130b. The density sensor 137 detects the toner density in the developer around the upper portion of the detection unit 137a. The toner concentration is the ratio of toner in the developer. Specifically, the density sensor 137 detects the toner density by detecting the magnetic permeability determined by the density of the magnetic carrier contained in the developer. The density sensor 137 supplies a signal representing the detected toner density to the control unit 1A (see FIG. 1). The control unit 1A adjusts the concentration of toner in the developer in the developer 13 by causing the toner cartridge 18 to supply toner to the developer 13 based on the detected toner concentration. Since the amount of toner in the developing device 13 is controlled according to the detection result of the density sensor 137, the accuracy of detection by the density sensor 137 affects the amount of toner in the developing device 13, and the developing device 13 is formed. This affects the image quality of the toner image, that is, the image quality of the image formed on the recording paper by the printer 1.

  The density sensor 137 is also used to detect that the toner in the toner cartridge 18 is empty. If the toner density in the developing device 13 does not increase after instructing the toner cartridge 18 to supply toner, the control unit 1A determines that the toner cartridge 18 is empty. As a result, the user is notified of the replacement of the toner cartridge 18 and the image formation is stopped. Therefore, accurate detection by the density sensor 137 is also required in order to replenish toner normally.

  Returning to FIG. 2, the description of the second stirring and conveying member 133 will be continued. The plate-like member 1332c extends linearly in the second transport direction e. For this reason, when the second stirring / conveying member 133 rotates, the plate-like member 1332c pushes the developer around the rotation axis, but does not push in the rotation axis direction, that is, the second conveyance direction e. For this reason, the developer conveyed in the second conveyance direction e by the blade portion 1332b on the upstream side in the second conveyance direction e accumulates in the plate-like member 1332c, and a developer accumulation is formed. Therefore, a sufficient amount of developer for accurate toner density detection is ensured around the detection unit 137a. The toner density is detected in synchronization with the timing at which the plate-like member 1332c passes in front of the detection unit 137a.

  A magnetic plate 138 is provided on the plate-like member 1332c. The magnetic plate 138 is a plate-like rubber compounded with a magnet, and is attached to a surface of the plate-like member 1332c that pushes the developer as the second stirring / conveying member 133 rotates. The magnetic plate 138 forms a magnetic brush made of a magnetic carrier in the developer around it. As the second stirring / conveying member 133 rotates, the magnetic plate 138 passes in front of the detection unit 137a of the concentration sensor 137. At this time, the detection unit 137a is brushed by a magnetic brush. As a result, the developer placed on or attached to the detection unit 137a is removed.

  FIG. 5 is a sectional view taken along line 5-5 of the developing device shown in FIG. However, in FIG. 5, in order to make it easy to see the positional relationship between the magnetic plate 138 and the detection unit 137a, the second stirring / conveying member 133 is half-rotated from the state shown in FIG. 4 and the plate-like member 1332c is positioned below. It is shown.

  The length L2 of the plate-like member 1332c in the second conveyance direction e is longer than the length L1 of the detection unit 137a, and the plate-like member 1332c extends over the entire area of the detection unit 137a in the second conveyance direction e. In addition, the length L3 of the magnetic plate 138 in the second transport direction e is longer than the length L1 of the detection unit 137a and shorter than the length L2 of the plate-like member 1332c. In the assembly of the developing device 13 of the present embodiment, the magnetic plate 138 is arranged with the position facing the detection unit 137a as a target. Therefore, the length L3 of the magnetic plate 138 is less than the length L1 of the detection unit 137a even if there is an error in the mounting position of the magnetic plate 138 or play in the second transport direction e of the second stirring transport member 133. The detection part 137a is formed in such a length that it does not protrude from the magnetic plate 138 in the second transport direction e.

  The magnetic plate 138 extends over the entire area of the detection unit 137a in the second transport direction e. Further, the magnetic plate 138 is shorter than the length L2 of the plate-like member 1332c, and is arranged at intervals G1, G2 from both ends E1, E2 of the plate-like member 1332c. More specifically, the gap between the both ends E1, E2 of the plate-like member 1332c and the magnetic plate 138 is such that the magnetic brush M formed on the magnetic plate 138 by the magnetic carrier does not reach the blade portions 1332a, 1332b. G1 and G2 are formed. For example, when it is assumed that the magnetic brush M is formed from the magnetic plate 138 to a range of 1.5 mm, the intervals G1 and G2 are wider than 1.5 mm. Further, the magnetic plate 138 is disposed on the upstream side in the second transport direction e of the plate-like member 1332c. More specifically, in the magnetic plate 138, the gap G1 from the upstream end E1 on the upstream side in the transport direction e of both ends of the plate-like member 1332c is larger than the gap G2 from the downstream end E2 on the opposite side to the upstream end E1. It is arranged in a narrow position. This arrangement corresponds to the distribution of the developer amount accumulated in the plate-like member 1332c. Further, the magnetic plate 138 has a distance between the end of the plate-like member on the upstream side in the conveyance direction and the magnetic plate 138 such that the plate-like member 1332c faces the detection unit 137b as shown in FIG. It is arranged at a position larger than the distance from the magnetic plate 138.

  Here, since the magnetic brush M formed on the magnetic plate 138 by the magnetic carrier has the gaps G1 and G2 that do not reach the blade portions 1332a and 1332b, the toner concentration of the developer assumed as the image forming apparatus and Judgment is made based on whether or not the blades 1332a and 1332b are in contact with the conveying member immersed in the developer having substantially the same density in a state where the rotation axis of the conveying member is arranged perpendicular to the direction of gravity. ing. In this embodiment, since the target density of the developing device is set to be about 7 to 9.5%, the determination is made by immersing in 8.5% developer.

  FIG. 6 is a graph showing the distribution in the second transport direction of the developer near the paddle. An arrangement in which the plate-like member 1332c and the blade portions 1332a and 1332b on both sides are developed in the circumferential direction of the rotating shaft is schematically shown on the graph of FIG.

  When the second stirring / conveying member 133 rotates, the developer is pushed to the end E1 of the plate-like member 1332c in the second carrying direction e by the upstream blade portion 1332b, and reaches the plate-like member 1332c. Since the plate-like member 1332c does not push the developer in the second transport direction e, the amount of the developer increases on the plate-like member 1332c and a developer pool is formed. However, since the developer tends to have a uniform thickness on the plate-like member 1332c, the developer drifts in the second transport direction e. The developer that has reached the downstream end E2 is then pushed by the downstream blade 1332a and conveyed in the second conveying direction e. Downstream from the downstream end E2, the developer is removed by the downstream blade 1332a and the amount of the developer is reduced. Therefore, in the downstream portion of the plate member 1332c, the developer layer collapses in the second transport direction e. Therefore, the toner amount is significantly reduced before reaching the end E2. For this reason, the distribution of the developer amount on the plate-like member 1332c is largely inclined on the downstream end E2 side and becomes unstable as shown in the graph of FIG.

  In the magnetic plate 138 of the present embodiment, the gap G1 from the upstream end E1 on the upstream side in the transport direction e to the magnetic plate 138, of both ends of the plate-like member 1332c, is from the downstream end E2 on the opposite side to the upstream end E1. Since it is arranged at a position narrower than the gap G2 to the magnetic plate 138, the developer distribution is stable. Therefore, a portion of the developer having a stable distribution passes through the detection unit 137a, so that the toner density is stably detected by the density sensor 137.

  Further, since the magnetic plate 138 is disposed with a gap G1 from the upstream end E1 of the plate-like member 1332c, the magnetic plate 138 extends to the end E1 of the plate-like member 1332c in the second transport direction e along the upstream blade portion 1332b. The developer that has been conveyed hits the side surface of the magnetic brush M formed on the magnetic plate 138.

  FIG. 7 is a diagram illustrating a reference example in which the magnetic plate is provided on the entire surface of the paddle.

  In the case where the magnetic plate 338 is provided on the entire surface of the plate-like member 3332c and arranged without being spaced from the ends E1 ′ and E2 ′ of the plate-like member 3332c as in the reference example shown in FIG. The magnetic brush M ′ formed above is formed on the entire surface of the plate-like member 3332c and reaches the upstream blade portion 3332b. In this case, the developer conveyed to the end E1 ′ of the plate-like member 3332c along the upstream blade portion 3332b does not hit the side surface of the magnetic brush M ′ and moves so as to lick the upper surface of the magnetic brush M ′. To do. For this reason, the developer forming the magnetic brush M ′ remains attached to the magnetic plate 338 and is not easily replaced. Therefore, an accurate toner density does not appear in the detection result of the sensor.

  In the present embodiment shown in FIG. 6, the replacement of the developer contained in the magnetic brush M is promoted by the developer conveyed along the upstream blade portion 1332 b and hitting the side surface of the magnetic brush M via the gap G <b> 1. For this reason, the density sensor 137 detects an accurate toner density reflecting the latest state of the developer in the developing device 13. As a result, since the amount of toner supplied to the developing device 13 is accurately controlled based on the detection result of the toner density, an image with good image quality with suppressed density fluctuations is formed. Also, the replacement timing of the toner cartridge is appropriately notified.

  In addition, the magnetic plate 138 in the present embodiment is attached to the surface of the plate-like member 1332c on the side where the developer is pressed in accordance with the rotation of the second stirring / conveying member 133, so the magnetic plate 138 presses the developer. This further promotes the replacement of the developer of the magnetic brush M.

  In the above-described embodiment, as an example of the magnetic plate according to the present invention, a plate-like rubber containing a magnet is shown. However, the present invention is not limited to this, and for example, a magnetic metal plate is used. There may be.

  In the above-described embodiment, an example of a printer is shown as the image forming apparatus. However, the image forming apparatus referred to in the present invention is not limited to a printer, and may be a copying machine or a facsimile, for example.

  In the above-described embodiment, an example of a photoreceptor having a cylindrical surface is shown as the image carrier referred to in the present invention. However, the image carrier referred to in the present invention is not limited to this, and is, for example, a belt-shaped member. May be. Further, the image carrier referred to in the present invention is not limited to a photoconductor, and for example, a potential corresponding to an image may be directly applied from an electrode.

  In the above-described embodiment, the latent image forming unit according to the present invention is configured with a charging roll and an exposure device. However, the latent image forming unit according to the present invention is not limited to this, for example, charging Instead of the roll, it may have a corona discharger, or instead of the exposure unit, it may be from a means in which a plurality of light emitting diodes are formed in an array.

DESCRIPTION OF SYMBOLS 1 Printer 1B Process cartridge 13 Developer 130 Developer container 130b 2nd storage chamber 133 2nd stirring conveyance member 137 Concentration sensor 137a Detection part 13 Magnetic plate 1332 Spiral blade 1331 Rotating shaft 1332c Plate-shaped member 1332a, 1332b Blade part

Claims (7)

A developer container that contains a developer formed by mixing toner and a magnetic carrier and forms a transport path for the developer;
A density sensor having a detection unit for detecting the toner density in the developer;
A rotating shaft, a spiral blade provided around the rotating shaft, and both ends of the developer in the transport direction provided to face the detection unit over the entire region of the developer transport direction by the spiral blade. A conveying member having a plate-like plate-like member formed continuously with the spiral blade, and
A magnetic plate provided on the plate-like member, is provided so as to face the detection unit over the entire conveyance direction, and is continuous with the spiral member of the plate-like member. A developing device comprising a magnetic plate arranged at a distance from a portion.   The magnetic plate is disposed such that the distance between the end of the plate-like member on the upstream side in the transport direction and the magnetic plate is narrower than the distance between the end of the plate-like member on the downstream side in the transport direction and the magnetic plate. The developing device according to claim 1, wherein the developing device is one.   An end portion of a plate-like member on the upstream side in the transport direction and a magnetic plate are arranged so that a magnetic brush formed on the magnetic plate in the developer does not reach the spiral blade. Item 3. The developing device according to Item 1 or 2.   4. The developing device according to claim 1, wherein the magnetic plate is provided on a surface of the plate-like member that pushes the developer by the rotation of the conveying member. 5.   In the magnetic plate, the distance between the end of the plate-shaped member on the upstream side in the transport direction and the magnetic plate is larger than the distance between the detection unit and the magnetic plate in a posture in which the plate-shaped member faces the detection unit. The developing device according to claim 1, wherein the developing device is arranged at a large position. An image carrier that holds the image in response to formation of an image on the surface;
A developing device for developing the electrostatic latent image formed on the image carrier with toner,
The developer is
A developer container that contains a developer in which toner and a magnetic carrier are mixed and forms a transport path for the developer;
A density sensor having a detection unit for detecting the toner density in the developer;
A rotating shaft, a spiral blade provided around the rotating shaft, and both ends of the developer in the transport direction are provided to face the detection unit over the entire region of the developer transport direction by the spiral blade. A conveying member having a plate-like plate-like member formed continuously with the spiral blade, and
A magnetic plate provided on the plate-like member, is provided so as to face the detection unit over the entire conveyance direction, and is continuous with the spiral member of the plate-like member. A process cartridge comprising a magnetic plate disposed at a distance from a portion. An image carrier that holds the image in response to formation of an image on the surface;
A latent image forming unit that forms an electrostatic latent image on the image carrier;
A developing unit for developing the latent image formed on the image carrier by the latent image forming unit with toner;
The developer is
A developer container that contains a developer in which toner and a magnetic carrier are mixed and forms a transport path for the developer;
A density sensor having a detection unit for detecting the toner density in the developer;
A rotating shaft, a spiral blade provided around the rotating shaft, and both ends of the developer in the transport direction are provided to face the detection unit over the entire region of the developer transport direction by the spiral blade. A conveying member having a plate-like plate-like member formed continuously with the spiral blade, and
A magnetic plate provided on the plate-like member, is provided so as to face the detection unit over the entire conveyance direction, and is continuous with the spiral member of the plate-like member. An image forming apparatus comprising: a magnetic plate disposed at a distance from a portion.

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