JP2009186799A - Developing device, image forming device and stirring member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device, and image forming device capable of accurately detecting the density of toner in the developing device using a simple constitution, and to provide stirring member thereof. <P>SOLUTION: The developing device comprises the stirring member for stirring developing agent containing toner and carrier on the carrying path in a developing tank while conveying it; a developer carrier, arranged adjacent to the stirring member for supplying the developer which is stirred and conveyed to an electrostatic image carrier; a toner concentration detecting sensor for detecting the toner concentration in the developer tank. The stirring member is a rotating screw body, and while centering a rotational axis, in a detection region on the conveying path opposite to the toner concentration detection sensor, a decelerating screw part for decelerating the conveying speed of the developer; and on the upstream region of the conveying path positioning, prior to the detection region, a regular speed screw part is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus of a two-component development system that supplies a two-component developer comprising a toner and a carrier to an electrostatic latent image on a photosensitive member for development, and an image in which the developing device is incorporated. The present invention relates to a forming device and a stirring member used by being incorporated in the developing device.

  An image forming apparatus of a two-component development system using toner and a carrier imparts a charge to the toner by frictional charging generated between the carrier and the toner, and electrostatically applies the charged toner to the latent image. An image is formed by adhering.

  In the image forming apparatus, since the toner contained in the developer is consumed by the development, the toner density in the developing apparatus gradually decreases. Then, when the toner concentration detection sensor detects that the toner concentration in the developing device has become a predetermined value or less, the toner replenishing operation is performed so that the toner concentration in the developing device is kept constant. It is configured.

  As the toner concentration detection sensor, a magnetic sensor that detects the amount of a magnetic substance, that is, a carrier contained in the developer, and an optical sensor that detects the amount of reflected light from the toner contained in the developer are mainly used. It has been.

  In the case of using either an optical sensor or a magnetic sensor, it is necessary to detect the toner concentration in the developing device as accurately as possible in order to keep the toner concentration in the developing device constant.

  In order to accurately detect the toner density in the developing device, the developing device of Patent Document 1 is provided with a stirring plate between the pitches of the stirring screw, and the width dimension of the stirring plate in the vicinity of the sensor is determined accordingly. It has been proposed to configure the stirring plate to be larger than the width dimension of the stirring plate in the other region. According to such a configuration, the conveying force of the stirring screw is reduced (that is, the developer conveying speed is reduced), and the liquid level of the developer is increased in the region near the sensor (that is, the developer is In this way, the developer is supplied to the sensor provided on the side surface of the developing tank.

Further, in the developing device of Patent Document 2, only the developer is stirred by the stirring blade (circulating piece) of the stirring means in the toner concentration detection portion, and the diffusion blade and the stirring blade (circulating piece) of the stirring means in the other portions. It is proposed that the developer is reliably stirred in the toner density detection portion by performing diffusion (conveyance) and stirring of the developer.
JP 2001-345825 A JP 2006-091704 A

  However, in the developing device disclosed in Patent Document 1, when the liquid level of the developer is increased by rotating the wide stirring plate, the developer is pressed against the inner wall surface of the developing tank. So there are the following problems. That is, when the detection surface of the toner density sensor is exposed from the wall surface of the developing tank, the detection surface may be damaged by the pressed developer, or the detection surface may be contaminated by the fusion of the developer. As a result, it is difficult to accurately detect the toner concentration. Further, when the toner concentration sensor is attached to the outside of the developing tank, it is preferable to reduce the wall thickness of the developing tank to improve detection sensitivity, but the thin wall is a deformation of the wall of the developing tank. Or it has the problem of being easy to cause destruction. The complicated structure of providing a stirring plate between each pitch of the stirring screw has a problem of increasing the manufacturing cost of the stirring screw.

  In addition, since the developing device disclosed in Patent Document 2 is intended to only stir (mix) the developer in the toner concentration detection portion, it actively diffuses the developer in the toner concentration detection portion ( (Conveyance) is not performed. Diffusion (conveyance) of the developer to the detection portion is performed by an inertial diffusion (conveyance) force by a diffusion blade located upstream of the toner density detection portion. Therefore, in the developing device of Patent Document 2, since the diffusion (conveyance) to the detection portion is inertial diffusion (conveyance) by the upstream diffusion blade, the amount of developer diffusion (conveyance amount) in the detection portion tends to vary. Therefore, there is a problem that the detection error of the toner density becomes large.

  Moreover, since the diffusion blade shown in Patent Document 2 is a plate-like body that stands upright in the direction perpendicular to the axis of rotation, that is, in the radial direction, like the stirring plate of Patent Document 1, it is conveyed in the axial direction. The developer is pushed in the direction perpendicular to the axis, that is, in the radial direction. Therefore, the developing device of Patent Document 2 has the same problem as that described in Patent Document 1.

  Furthermore, in a trickle-type two-component developing device that discharges deteriorated developer little by little and supplies new developer little by little to keep the carrier charging performance substantially constant, the toner density once increased Since the new developer is not replenished until the value falls to the predetermined value, the amount of the developer present in the developing device varies greatly during operation. For this reason, in the trickle type two-component developing device, even if the toner concentration is the same, the bulk density of the developer changes depending on the amount of the developer present in the developing device. There is a peculiar problem that the error is likely to occur.

  Therefore, a technical problem to be solved by the present invention is to provide a developing device, an image forming apparatus, and a stirring member that can accurately detect the toner density in the developing device with a simple configuration.

Means and actions / effects for solving the problems

In order to solve the technical problem, according to the present invention,
A stirring member that stirs the developer including toner and carrier while transporting the developer in the transport path in the developing tank;
A developer carrier that is disposed adjacent to the stirring member and supplies the stirred and conveyed developer to the electrostatic latent image carrier;
A toner concentration detection sensor for detecting a toner concentration in the developing tank;
The agitating member is a screw body that rotates about a rotation shaft, and a detection screw portion for reducing the developer conveyance speed is provided in a detection region of the conveyance path facing the toner concentration detection sensor, and is detected. A developing device is provided that includes a normal screw portion that transports the developer at a normal transport speed in an upstream region of the transport path positioned in front of the region.

  The basic idea of the present invention is that a stirring member, which is a screw body that rotates about a rotation shaft, is a reduction screw for reducing the developer conveyance speed in the detection region of the conveyance path facing the toner concentration detection sensor. And a normal screw part for conveying the developer at a normal conveyance speed in the upstream area of the conveyance path located in front of the detection area, and the developer conveyance speed in the detection area By decelerating from the conveyance speed in the developer area, the developer bulk density in the detection area is made larger than the developer bulk density in the upstream area, and the variation in the developer filling state (bulk density) in the detection area is varied. It is to reduce. Since the toner concentration is detected by the toner concentration detection sensor for the developer that is compacted (densified) in the detection region and has a stable filling state (bulk density), variation in detection values obtained by the toner concentration detection sensor Can be suppressed. Moreover, since the deceleration screw part also has a screw shape like the normal screw part, the stirring member maintains the screw shape as a whole. Therefore, the stirring member can be easily manufactured, and the manufacturing cost of the stirring member is hardly increased.

  As a specific form of the reduction screw part, the pitch of the reduction screw part is smaller than the pitch of the normal screw part, and / or the inclination angle with respect to the rotation axis of the reduction screw part is relative to the rotation axis of the normal screw part. It is configured to be larger than the inclination angle and smaller than 90 degrees.

  As a more specific form of the reduction screw part, it is preferable that there is a relationship of 0.2Y ≦ X ≦ 0.8Y between the reduction screw part (X) and the pitch (Y) of the normal screw part.

  As a more specific form of the reduction screw part, it is more preferable that there is a relationship of 0.4Y ≦ X ≦ 0.6Y between the reduction screw part (X) and the pitch (Y) of the normal screw part.

  As a more specific form of the reduction screw part, there is a relationship of b + 5 ° ≦ a between the inclination angle (a) of the reduction screw part with respect to the rotation axis and the inclination angle (b) of the normal screw part with respect to the rotation axis. It is preferable.

  As a more specific form of the reduction screw part, there is a relationship of b + 10 ° ≦ a between the inclination angle (a) of the reduction screw part with respect to the rotation axis and the inclination angle (b) of the normal screw part with respect to the rotation axis. More preferably.

  The developing device described above is used by being incorporated in an image forming apparatus further including a rotatable electrostatic latent image carrier that carries an electrostatic latent image on a peripheral surface.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. Further, in the image forming apparatus 1 and the developing device 34 described below, the same reference numerals are used for the same or similar components.

  The image forming apparatus 1 according to an embodiment of the present disclosure and the developing device 34 used in the apparatus will be described with reference to FIGS. Although a so-called trickle type two-component developing device will be described as an embodiment of the present invention, it is needless to say that the present invention can be applied to other two-component developing devices having no trickle mechanism.

[Image forming apparatus]
FIG. 1 shows portions related to image formation of an electrophotographic image forming apparatus 1 according to the present invention. The image forming apparatus 1 may be any of a copier, a printer, a facsimile machine, and a multi-function machine having a combination of these functions. The image forming apparatus 1 includes a photoreceptor 12 that is an electrostatic latent image carrier. In the embodiment, the photoconductor 12 is formed of a cylindrical body, but the present invention is not limited to such a form, and an endless belt type photoconductor can be used instead. The photosensitive member 12 is drivingly connected to a motor (not shown), and is rotated in the direction of the arrow based on the driving of the motor. Around the photoconductor 12, a charging device 26, an exposure device 28, a developing device 34, a transfer device 36, and a cleaning device 40 are arranged along the rotation direction of the photoconductor 12.

  The charging device 26 charges the photoreceptor layer, which is the outer peripheral surface of the photoreceptor 12, to a predetermined potential. In the embodiment, the charging device 26 is represented as a cylindrical roller. However, instead of this, other types of charging devices (for example, a rotary or fixed brush-type charging device or a wire-discharge-type charging device) may be used. Can be used. The exposure device 28 disposed in the vicinity of the photoreceptor 12 or away from the photoreceptor 12 emits image light 30 toward the outer peripheral surface of the charged photoreceptor 12. On the outer peripheral surface of the photoconductor 12 that has passed through the exposure device 28, an electrostatic latent image is formed that includes a portion where the image light 30 is projected and a portion where the potential is attenuated and a portion where the charged potential is substantially maintained. In the embodiment, the portion where the potential is attenuated is the electrostatic latent image portion, and the portion where the charged potential is substantially maintained is the electrostatic latent image non-image portion. The developing device 34 visualizes the electrostatic latent image using the developer 3 described later. Details of the developing device 34 will be described later. The transfer device 36 transfers the visible image formed on the outer peripheral surface of the photoconductor 12 to a paper 38 such as paper or film. In the embodiment shown in FIG. 1, the transfer device 36 is illustrated as a cylindrical roller, but other types of transfer devices (for example, a wire discharge transfer device) may be used. The cleaning device 40 collects untransferred toner remaining on the outer peripheral surface of the photoconductor 12 without being transferred onto the paper 38 by the transfer device 36 from the outer peripheral surface of the photoconductor 12. In the embodiment, the cleaning device 40 is illustrated as a plate-shaped blade, but other types of cleaning devices (for example, a rotary or fixed brush type cleaning device) may be used instead.

  When the image forming apparatus 1 having such a configuration forms an image, the photoconductor 12 rotates, for example, counterclockwise based on driving of a motor (not shown). At this time, the outer peripheral portion of the photoreceptor 12 that passes through the charging device 26 is charged to a predetermined potential by the charging device 26. The image light 30 is exposed to the outer peripheral portion of the charged photoconductor 12 by the exposure device 28 to form an electrostatic latent image. The electrostatic latent image is conveyed to the developing device 34 along with the rotation of the photosensitive member 12 and is visualized by the developing device 34. The visualized toner image is conveyed to the transfer device 36 along with the rotation of the photoconductor 12 and transferred to the paper 38 by the transfer device 36. The paper 38 to which the toner image has been transferred is conveyed to the fixing device 20 and the toner image is fixed to the paper 38. The outer peripheral portion of the photosensitive member 12 that has passed through the transfer device 36 is conveyed to the cleaning device 40, and the toner remaining on the outer peripheral surface of the photosensitive member 12 without being transferred to the paper 38 is scraped off from the photosensitive member 12.

[Development equipment]
The developing device 34 includes a two-component developer including a non-magnetic toner (hereinafter simply referred to as toner) and a magnetic carrier (hereinafter simply referred to as carrier), and a developing tank 66 that accommodates various members. . The developing tank 66 has an opening that is open toward the photosensitive member 12, and a developing roller 48 is provided in a space formed in the vicinity of the opening. The developing roller 48 as a developer carrying member is a cylindrical member, and is pivotally supported in parallel with the photosensitive member 12 and through a predetermined developing gap with the outer peripheral surface of the photosensitive member 12.

  The developing roller 48 is a so-called magnet roller having a magnet body 48a that is fixed so as not to rotate, and a cylindrical sleeve 48b (first rotating cylinder body) that is rotatably supported around the magnet body 48a. . Above the sleeve 48b of the developing roller 48, a regulating plate 62 that is fixed to the developing tank 66 and extends in parallel with the central axis of the sleeve 48b of the developing roller 48 is disposed to face with a predetermined regulating gap therebetween. . The magnet body 48a inside the developing roller 48 has five magnetic poles N1, S2, N3, N2, and S1 along the rotation direction of the sleeve 48b. Of these magnetic poles, the main magnetic pole N <b> 1 is disposed to face the photoconductor 12. N2 and N3 of the same polarity that generate a repulsive magnetic field for peeling off the developer on the sleeve 48 b are disposed opposite to each other inside the developing tank 66. The sleeve 48b of the developing roller 48 rotates in the direction opposite to the rotation direction of the photosensitive member 1 (in the counter direction).

  FIG. 2 is a schematic cross-sectional view of the developing device 34 as viewed from above. As shown in FIG. 2, a developer stirring and conveying chamber 67 is formed behind the developing roller 48. The developer stirring and conveying chamber 67 partitions the second conveying path 70 formed in the vicinity of the developing roller 48, the first conveying path 68 away from the developing roller 48, the first conveying path 68 and the second conveying path 70. Partition wall 76. A developer supply tank 80 is disposed above the upstream side of the first conveyance path 68 in the conveyance direction, and communicates with the first conveyance path 68 through a supply port 82. The developer supply tank 80 is filled with a supply developer 2 containing toner as a main component and containing a carrier. The carrier ratio of the replenishment developer 2 is preferably 5 to 40% by weight, more preferably 10 to 30% by weight. A developer recovery tank 90 is disposed below the second transport path 70 on the downstream side in the transport direction, and communicates with the second transport path 70 through a recovery port 92.

  At the bottom of the developer supply tank 80, a developer supply roller that is driven and controlled by the control unit 100 is disposed. When the developer supply roller is driven to rotate, an amount of new replenishment developer 2 corresponding to the driving time flows down and is supplied to the first transport path 68 of the developing tank 66.

  A first screw 72 that is a stirring member that transports the developer 3 while stirring the developer 3 is rotatably supported in the first transport path 68. A second screw 74 that transports the developer 3 from the first transport path 68 to the developing roller 48 while being stirred is rotatably supported on the second transport path 70. In this case, two upper and lower communication passages are formed by cutting out the upper portions of the partition walls 76 located at the end portions of the first conveyance path 68 and the second conveyance path 70, respectively. The developer 3 that has reached the downstream end in the transport direction of the first transport path 68 is sent to the second transport path 70 through the left connecting passage, and reaches the downstream end of the second transport path 70 in the transport direction. The reached developer 3 is fed into the first conveyance path 68 through the right communication path. As a result, the developer 3 circulates in the developer agitating / conveying chamber according to the arrow direction in FIG.

  As shown in FIG. 4, a detection area 68c for detecting the toner concentration in the developing tank 66 is provided downstream of the first conveyance path 68 and in front of the left communication path. A toner concentration detection sensor 78 is provided on the lower surface of the bottom wall 93 of the developing tank 66 corresponding to 68c. The detection area 68c is a place where the developer 3 is more easily filled as compared with other places such as the upstream area 68b located before (on the upstream side) the first transport path 68 than the detection area 68c. The toner concentration detection sensor 78 is installed directly below the bottom wall 93, or on an oblique side surface than the position directly below the bottom wall 93 (for example, on the side surface at an angle smaller than approximately 30 degrees with respect to the position directly below the bottom wall 93). Can be installed.

  In the detection area 68c, if the developer 3 is excessively compressed and the filling degree of the developer 3 becomes too large, the developer 3 stays in the detection area 68c, so that the toner density detection response to the change in toner density It becomes worse. On the contrary, if the developer 3 is not compressed so much and the filling degree of the developer 3 is not significantly different from the filling degree of the developer 3 in other places of the first conveying path 68 such as the upstream region 68b, the effect of the present invention is achieved. Cannot be obtained. Therefore, although the developer 3 does not stay in the detection region 68c, it is preferable that the developer 3 is appropriately compressed and filled in order to detect the toner density without any detection error.

  The first screw 72 and the second screw 74 are spiral screws in which spiral blades are fixed to a shaft at a predetermined pitch. FIG. 4 is a schematic cross-sectional view of the characteristic portion of the developing device 34 according to the first embodiment as viewed from the side, and shows the detection region 68 c and the peripheral portion thereof in the first transport path 68.

  As shown in FIG. 4, the first screw 72 includes a shaft 72 a extending along the first conveyance path 68, a normal screw portion 72 b that conveys the developer 3 at a normal conveyance speed, and a normal conveyance speed. And a deceleration screw portion 72c that conveys the developer 3 at a reduced deceleration speed. The pitch X of the reduction screw part 72c shown in FIG. 4 is configured to be smaller than the pitch Y of the normal screw part 72b. When comparing the normal screw part 72b and the reduction screw part 72c, only the magnitude of the pitch of the screw is different, and the other configurations are the same. Since the conveyance speed of the developer 3 decreases as the screw pitch decreases, the conveyance speed of the developer 3 is such that the developer conveyance speed (deceleration conveyance speed) in the detection area 68c <the developer conveyance in the upstream area 68b. There is a relationship of speed (normal transport speed).

  The toner concentration detection sensor 78 is, for example, a magnetic sensor that detects the magnetic permeability of the developer 3 transported in the developer agitation transport chamber 67 from a change in coil inductance. From the magnetic permeability detected by the toner concentration detection sensor 78, the amount of carrier, which is a magnetic material, is detected, and the ratio of the toner to the developer 3, that is, the toner concentration is obtained indirectly. For example, when the amount of carrier contained in the developer 3 is small, it is detected that the toner ratio is high. On the other hand, when the amount of carrier contained in the developer 3 is large, it is detected that the toner ratio is low. The voltage signal output from the toner concentration detection sensor 78 is input to the control unit 100. Based on the detection signal, a necessary supply amount is calculated and the developer supply roller of the developer supply tank 80 is calculated. Is driven, and a predetermined amount of the replenishment developer 2 is replenished into the developing tank 66. The magnetic sensor as the toner concentration detection sensor 78 is arranged at a position downstream of the detection region 68c so that the detection magnetic flux of the sensor does not go out of the detection region 68c.

  Here, since the developing device 34 described as an embodiment of the present invention employs a so-called trickle system, it has an outflow portion 75 for allowing excess developer 3 to flow out. That is, the outflow part 75 is formed by providing the notch 75 in which the upper part of the side wall located at the downstream end (right end) in the transport direction of the second transport path 70 is partially cut out. The developer 3 transported by the second screw 74 is transported from the second transport path 70 to the first transport path 68 by being blocked by the reverse screw portion in a normal state. When the developer 3 in the developing tank 66 increases and the liquid level in the developing tank 66 rises, the developer 3 gets over the outflow part 75 provided at the upper part of the side wall against the anti-skid action of the reverse screw part. Overflows to the adjacent developer reservoir 79. The developer reservoir 79 has a relatively large internal volume so that the developer in the reservoir discharged from the second conveyance path 70 can be temporarily stored. The excess developer 3 overflowing to the developer reservoir 79 is conveyed to the recovery port 92 and is recovered (discarded) to the developer recovery tank 90 through the recovery port 92.

  If the hole diameter of the recovery port 92 is too large, the developer in the reservoir is discharged at a stroke toward the developer recovery tank 90 without being temporarily stored. Conversely, if the hole diameter of the recovery port 92 is too small, clogging will occur. Therefore, in the horizontal state, the hole diameter of the recovery port 92 is sized so that an appropriate amount of developer in the reservoir is discharged to the developer recovery tank 90, in other words, so that the developer in the reservoir is discharged. Has been.

  In the developing device 34, when the toner density of the circulating developer 3 is reduced by the printing operation, the replenishment developer 2 containing toner and a small amount of carrier is replenished from the developer replenishment tank 80. The supplied replenishment developer 2 is conveyed along the first conveyance path 68 and the second conveyance path 70 of the developer stirring and conveying chamber 67 while being mixed and stirred with the developer 3 that already exists. Basically, the toner is consumed by the photoconductor 12, whereas the carrier is stored in the developing device 34, but the charging performance of the carrier gradually decreases. Since the replenishment developer 2 contains a small amount of carrier bulkier than the toner, the amount of the developer 3 in the developing device 34 gradually increases as the replenishment developer 2 is replenished. Then, the increased developer 3 circulates in the developer agitating and conveying chamber 67. Excess developer 3 that cannot circulate through the developer agitating / conveying chamber 67 gets over the reverse screw part and flows out from the outflow part 75 provided at the downstream end (right end) in the conveying direction of the second conveying path 70. It flows out and is collected in the developer collection tank 90 through the collection port 92.

  The replenishment amount of the replenishment developer 2 includes the toner concentration of the developer 3 detected by the toner concentration detection sensor 78, image information at the time of image formation (dot counter), and replenishment development in the developer replenishment tank 80. It is determined based on the carrier ratio with respect to Agent 2. The carrier ratio with respect to the replenishment developer 2 in the developer replenishment tank 80 is adjusted to the extent that the deterioration of the carrier in the developing device 34 is suppressed and the cost is not increased. As the toner is replenished, the carrier is supplied little by little.

  FIG. 3 is a control block diagram relating to the developing device 34 of the image forming apparatus 1.

  The control unit 100 as a control unit includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 104, a RAM (Random Access Memory) 106, and the like. The CPU 102 centrally controls various operations in the image forming apparatus 1 according to various processing programs and tables stored in the ROM 104. In the ROM 104, for example, a toner density calculation table for converting / calculating the voltage detected by the toner density detection sensor 78 into the toner density of the developer 3, or the actual toner density and reference toner density of the developer 3 is stored. A developer replenishment table for calculating the amount of developer to be replenished based on the difference between them is stored. The RAM 106 forms a work area for temporarily storing various programs executed by the control unit 100 and data related to these programs.

  A developing device 34, a developer supply tank 80, and a counter 108 are connected to the CPU 102. The operations of the developer agitating members 72 and 74, the toner density detection sensor 78, and the developing roller 48 constituting the developing device 34 are controlled by the CPU 102 of the control unit 100. The toner concentration of the developer 3 detected by the toner concentration detection sensor 78, image information at the time of image formation, the carrier ratio with respect to the replenishment developer 2 in the developer replenishment tank 80, and the like are temporarily stored in the RAM 106. Is remembered.

(Developer)
The two-component developer contains toner and a carrier for charging the toner. In the present invention, known toners that have been generally used in the image forming apparatus 1 can be used. The particle size of the toner is, for example, about 3 to 15 μm. A toner containing a colorant in a binder resin, a toner containing a charge control agent and a release agent, and a toner holding an additive on the surface can also be used.

  The toner is produced by a known method such as a pulverization method, an emulsion polymerization method, or a suspension polymerization method.

  The binder resin used for the toner is not limited. For example, styrene resin (monopolymer or copolymer containing styrene or styrene-substituted product), polyester resin, epoxy resin, vinyl chloride resin, phenol resin. , Polyethylene resin, polypropylene resin, polyurethane resin, silicone resin, or any mixture of these resins. The binder resin preferably has a softening temperature in the range of about 80 to 160 ° C. and a glass transition point in the range of about 50 to 75 ° C.

  For the colorant, use a known material such as carbon black, aniline black, activated carbon, magnetite, benzine yellow, permanent yellow, naphthol yellow, phthalocyanine blue, first sky blue, ultramarine blue, rose bengal, lake red, etc. Can do. In general, the addition amount of the colorant is preferably 2 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

  As the charge control agent, materials conventionally known as charge control agents can be used. Specifically, for the positively charged toner, for example, nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds, imidazole compounds, and polyamine resins can be used as charge control agents. For the negatively charged toner, metal-containing azo dyes such as Cr, Co, Al, and Fe, salicylic acid metal compounds, alkyl salicylic acid metal compounds, and curixarene compounds can be used as charge control agents. The charge control agent is preferably used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the release agent, a known release agent conventionally used as a release agent can be used. As the material for the release agent, for example, polyethylene, polypropylene, carnauba wax, sazol wax, or a mixture of them as appropriate is used. The release agent is preferably used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  Furthermore, a fluidizing agent that promotes fluidization of the developer may be added. As the fluidizing agent, for example, inorganic fine particles such as silica, titanium oxide, and aluminum oxide, and resin fine particles such as acrylic resin, styrene resin, silicone resin, and fluorine resin can be used. In particular, it is preferable to use a material hydrophobized with a silane coupling agent, a titanium coupling agent, silicon oil or the like. The fluidizing agent is preferably added at a ratio of 0.1 to 5 parts by weight with respect to 100 parts by weight of the toner. The number average primary particle size of these additives is preferably 9 to 100 nm.

  As the carrier, a known carrier that has been generally used can be used. Either a binder type carrier or a coat type carrier may be used. The carrier particle size is not limited, but is preferably about 15 to 100 μm.

  The binder type carrier is obtained by dispersing magnetic fine particles in a binder resin, and those having fine particles or a coating layer charged positively or negatively on the surface can be used. The charging characteristics such as the polarity of the binder type carrier can be controlled by the material of the binder resin, the chargeable fine particles, and the type of the surface coating layer.

  Examples of the binder resin used for the binder-type carrier include thermoplastic resins such as vinyl resins, polyester resins, nylon resins, polyolefin resins, and the like typified by polystyrene resins, and curable resins such as phenol resins. .

  Magnetic fine particles of the binder type carrier include spinel ferrite such as magnetite and gamma iron oxide, and magnets such as spinel ferrite and barium ferrite containing one or more metals other than iron (Mn, Ni, Mg, Cu, etc.). Plumbite type ferrite, iron or alloy particles having an oxide layer on the surface can be used. The shape of the carrier may be granular, spherical, or needle-shaped. In particular, when high magnetization is required, it is preferable to use iron-based ferromagnetic fine particles. In consideration of chemical stability, it is preferable to use ferromagnetic fine particles of magnetoplumbite type ferrite such as spinel ferrite and barium ferrite containing magnetite and gamma iron oxide. A magnetic resin carrier having a desired magnetization can be obtained by appropriately selecting the type and content of the ferromagnetic fine particles. The magnetic fine particles are suitably added in an amount of 50 to 90% by weight in the magnetic resin carrier.

  Silicone resin, acrylic resin, epoxy resin, fluorine resin, etc. are used as the surface coating material for the binder type carrier. The charge imparting ability of the carrier can be improved by coating and curing these resins on the carrier surface to form a coat layer.

  For example, the charging fine particles or the conductive fine particles are fixed to the surface of the binder-type carrier by, for example, mixing the magnetic resin carrier and the fine particles uniformly, adhering these fine particles to the surface of the magnetic resin carrier, and then mechanically / thermally. This is done by driving fine particles into the magnetic resin carrier by applying a strong impact force. In this case, the fine particles are not completely embedded in the magnetic resin carrier, but are fixed so that a part thereof protrudes from the surface of the magnetic resin carrier. Organic and inorganic insulating materials are used for the chargeable fine particles. Specifically, organic insulating materials include polystyrene, styrene-based copolymers, acrylic resins, various acrylic copolymers, nylon, polyethylene, polypropylene, fluororesin, and cross-linked products thereof such as organic insulating fine particles. is there. The charge imparting ability and the charge polarity can be adjusted to the material of the chargeable fine particles, the polymerization catalyst, the surface treatment and the like. As the inorganic insulating material, negatively charged inorganic fine particles such as silica and titanium dioxide, and positively charged inorganic fine particles such as strontium titanate and alumina are used.

  The coat type carrier is a carrier in which carrier core particles made of a magnetic material are coated with a resin, and like the binder type carrier, chargeable fine particles that are charged positively or negatively can be fixed to the surface of the carrier. The charging characteristics such as the polarity of the coated carrier can be adjusted by selecting the type of the surface coating layer and the electrifying fine particles. As the coating resin, the same resin as the binder resin of the binder type carrier can be used.

  The mixing ratio of the toner and the carrier of the developer 3 is adjusted so that a desired toner charge amount is obtained. The toner ratio of developer 3 is preferably 3 to 20% by weight, more preferably 4 to 15% by weight, based on the total amount of toner and carrier. The replenishment developer 2 filled in the developer replenishment tank 80 contains toner and a small amount of carrier, and the carrier ratio of the replenishment developer 2 is preferably 1 to 50% by weight. More preferably, it is 5 to 30% by weight.

  The operation of the developing device 34 configured as described above will be described.

  During image formation, the sleeve 48b of the developing roller 48 rotates in the direction of the arrow (counterclockwise) based on the driving of a motor (not shown). By the rotation of the first screw 72 and the rotation of the second screw 74, the developer 3 existing in the developer stirring and conveying chamber 67 is agitated while being circulated and conveyed through the first conveying path 68 and the second conveying path 70. As a result, the toner contained in the developer and the carrier are in frictional contact with each other and are charged with opposite polarities. In the embodiment, it is assumed that the carrier is positively charged and the toner is negatively charged. The chargeability of the toner and carrier used in the present invention is not limited to such a combination. The outer dimension of the carrier is considerably larger than that of the toner. Therefore, the negatively charged toner adheres around the positively charged carrier mainly based on the electrical attraction force of both.

  The charged developer 3 is supplied to the developing roller 48 while being transported to the second transport path 70 by the second screw 74. The developer is held on the surface side of the sleeve 48 b by the magnetic force of the magnet body 48 a inside the developing roller 48, rotates in the counterclockwise direction together with the sleeve 48 b, and is a regulation plate provided facing the developing roller 48. After the passage amount is restricted at 62, the sheet is conveyed to a development area facing the photoconductor 12. In the developing area, a head (magnetic brush) is formed by the magnetic force of the main magnetic pole N1 of the magnet body 48a. In the development region, the toner is caused by the force applied to the toner by the electric field (electric field in which alternating current is superimposed on direct current) formed between the electrostatic latent image on the photoreceptor 12 and the developing roller 48 to which the developing bias is applied. It moves toward the electrostatic latent image on the photoconductor 12, and this electrostatic latent image is developed into a visible image. The developer that has consumed the toner in the developing region is conveyed toward the developing tank 66 and is developed by the repulsive magnetic field of N3 and N2 of the magnet body 48a provided facing the second conveying path 70 of the developing tank 66. It is peeled off from above and collected into the developing tank 66. The collected developer is mixed with the developer 3 being conveyed through the second conveyance path 70.

  When the toner is forcibly consumed from the developer 3 by such image formation, it is preferable that the toner 3 is replenished with an amount corresponding to the consumed amount. Therefore, as described above, the developing device 34 includes the detection region 68c for accurately detecting the toner concentration of the developer 3 existing in the developer stirring and conveying chamber 67.

  As shown in FIG. 4, the developer 3 transported along the first transport path 68 is transported from the upstream region 68b to the detection region 68c. In the upstream area 68b, the developer 3 is conveyed at a normal conveyance speed, whereas in the detection area 68c, the developer 3 is conveyed at a decelerating speed that is lower than the normal conveyance speed. In the vicinity of the boundary with the region 68c, the developer 3 becomes a little jammed and the compacted state of the developer 3 starts. When the developer 3 is further transported in the detection area 68c, the developer 3 is gradually compressed in the detection area 68c to become a compacted state (high density). The toner concentration of the developer 3 in the compacted state (densified) is detected by a toner concentration detection sensor 78 provided on the downstream side of the detection region 68c. Since the toner density is detected by the toner density detection sensor 78 with respect to the developer 3 that has been consolidated (densified) in the detection area 68c and has a stable bulk density, variation in the detection value obtained by the toner density detection sensor 78 is detected. Can be suppressed.

  In order to confirm the effect of the present invention, in the trickle-type two-component developing device, when the amount of the developer 3 existing in the developing tank 66 is changed, the detection value obtained by the toner concentration detection sensor 78 is detected. The variation was examined and the result is shown in FIG. As experimental conditions, the toner concentration in the developing tank 66 was set to 6% by weight, and the amount of the developer 3 contained in the developer stirring and conveying chamber 67 was changed in the range of 150 g to 240 g.

  In FIG. 7, the horizontal axis represents the amount (g) of the developer 3 present in the developing tank 66, and the vertical axis represents the toner density detection error (%). FIG. 7 shows a case where the pitch X of the reduction screw part 72c is smaller than the pitch Y of the normal screw part 72b. In FIG. 7, ◯, □, △, and ◇ (all indicated by solid lines) indicate that the pitch X of the speed reduction screw portion 72c and the pitch Y of the normal screw portion 72b are respectively X = 0.2Y. , X = 0.4Y, X = 0.6Y, and X = 0.8Y, an embodiment according to the present invention configured to satisfy the relations is shown. Moreover, * mark in FIG. 7 has shown the comparative example with which the 1st screw 72 is comprised only with the normal screw part 72b, and there is no change part.

  As apparent from FIG. 7, when the speed reducing screw portion 72c is provided downstream of the normal screw portion 72b and the pitch X of the speed reducing screw portion 72c is between 0.2Y and 0.8Y, Even if the amount of the developer 3 fluctuated, the toner density detection error was less than 0.6% at the maximum, and it was confirmed that the detection error was small. That is, it is effective to have a relationship of 0.2Y ≦ X ≦ 0.8Y in order to reduce the toner density detection error.

  Furthermore, in the case of □ (X = 0.4Y) and △ (X = 0.6Y), the toner density detection error is less than 0.3%, and it is confirmed that the toner density detection error is very small. We were able to. That is, it is more effective to have a relationship of 0.4Y ≦ X ≦ 0.6Y for reducing the toner density detection error.

  On the other hand, in the case of the comparative example (marked with *) in which the first screw 72 is constituted only by the normal screw portion 72b, the detection error of the toner density is maximized when the amount of the developer 3 in the developing tank 66 varies. It was about 1.5%, and the detection error was very large.

  Therefore, as in the present invention, by developing the pitch X of the speed reduction screw portion 72c smaller than the pitch Y of the normal screw portion 72b, the development of the detection region 68c which is consolidated (densified) and has a stable bulk density. Since the toner concentration is detected by the toner concentration detection sensor 78 with respect to the agent 3, the variation in the detection value obtained by the toner concentration detection sensor 78 can be suppressed.

  Next, the developing device 34 and the operation thereof according to the second embodiment will be described with reference to FIG. 5, but the differences from the developing device 34 according to the above embodiment will be mainly described, and overlapping portions will be described. Omitted.

  FIG. 5 is a schematic cross-sectional view of the characteristic portion of the developing device 34 according to the second embodiment of the present invention as viewed from the side, and shows the detection region 68 c and the peripheral portion thereof in the first transport path 68.

  As in the first embodiment described above, a detection area 68c for detecting the toner concentration in the developing tank 66 is provided downstream of the first conveyance path 68 and in front of the left communication path. A toner concentration detection sensor 78 is provided on the lower surface of the bottom wall 93 of the developing tank 66 corresponding to the detection region 68c.

  As shown in FIG. 5, the first screw 72 includes a shaft 72 a extending along the first conveyance path 68, a normal screw portion 72 b that conveys the developer 3 at a normal conveyance speed, and a normal conveyance speed. And a deceleration screw portion 72c that conveys the developer 3 at a reduced deceleration speed. As shown in FIG. 5, the inclination angle a of the speed reduction screw portion 72c with respect to the shaft 72a is larger than the inclination angle b of the screw portion 72b with respect to the shaft 72a. At the same time, since the developer 3 needs to be conveyed downstream, the inclination angle a is smaller than 90 ° (that is, the inclination angle a is an acute angle when viewed from the downstream side in the conveyance direction). It is configured. When comparing the normal screw portion 72b and the reduction screw portion 72c, only the magnitudes of the inclination angles a and b of the screws 72b and 72c with respect to the shaft 72a are different, and the other configurations are the same. As the inclination angle of the screw portion with respect to the shaft 72a is increased, the transport speed of the developer 3 is decreased. Therefore, the transport speed of the developer 3 is determined by the developer transport speed (decelerated transport speed) in the detection region 68c <the upstream region 68b. The developer transport speed (ordinary transport speed) is established.

  As shown in FIG. 5, the developer 3 transported along the first transport path 68 is transported from the upstream region 68b to the detection region 68c. In the upstream area 68b, the developer 3 is conveyed at a normal conveyance speed, whereas in the detection area 68c, the developer 3 is conveyed at a decelerating speed that is lower than the normal conveyance speed. In the vicinity of the boundary with the region 68c, the developer 3 becomes a little jammed and the compacted state of the developer 3 starts. When the developer 3 is further transported in the detection area 68c, the developer 3 is gradually compressed in the detection area 68c to become a compacted state (high density). The toner concentration of the developer 3 in the compacted state (densified) is detected by a toner concentration detection sensor 78 provided on the downstream side of the detection region 68c. Since the toner density is detected by the toner density detection sensor 78 with respect to the developer 3 that has been consolidated (densified) in the detection area 68c and has a stable bulk density, variation in the detection value obtained by the toner density detection sensor 78 is detected. Can be suppressed.

  In order to confirm the effect of the present invention, in the trickle-type two-component developing device, when the amount of the developer 3 existing in the developing tank 66 is changed, the detection value obtained by the toner concentration detection sensor 78 is detected. The state of the variation was examined, and the result is shown in FIG. As experimental conditions, the toner concentration in the developing tank 66 was set to 6% by weight, and the amount of the developer 3 contained in the developer stirring and conveying chamber 67 was changed in the range of 150 g to 240 g.

  In FIG. 8, the horizontal axis represents the amount (g) of the developer 3 present in the developing tank 66, and the vertical axis represents the toner concentration detection error (%). FIG. 8 shows a case where the inclination angle a of the deceleration screw portion 72c is larger than the inclination angle b of the normal screw portion 72b and is acute. In FIG. 8, ◯, □, Δ, and ◇ (all indicated by dotted lines) indicate that the inclination angle a of the reduction screw portion 72c and the inclination angle b of the normal screw portion 72b are respectively a = b + 5. An embodiment according to the present invention configured to satisfy the relationships of °, a = b + 6 °, a = b + 10 °, and a = b + 12 ° and so that the inclination angle a is an acute angle when viewed from the downstream side in the conveyance direction is shown. . Moreover, the * mark in FIG. 8 has shown the comparative example with which the 1st screw 72 is comprised only with the normal screw part 72b, and there is no change part.

  As is clear from FIG. 8, a reduction screw portion 72c is provided downstream of the normal screw portion 72b, and the inclination angle a of the reduction screw portion 72c is in the range of 5 ° to 12 ° relative to the inclination angle b of the normal screw portion 72a. When the amount of the developer 3 in the developing tank 66 is fluctuated, the toner density detection error is less than 1.1% at the maximum, and it was confirmed that the detection error was small. In other words, it is effective to have a relationship of b + 5 ° ≦ a <90 ° to reduce the toner density detection error.

  Further, in the case of Δ mark (a = b + 10 °) and ◇ mark (a = b + 12 °), it should be confirmed that the toner density detection error is less than 0.4% and the toner density detection error is very small. I was able to. That is, it is more effective to have a relationship of b + 10 ° ≦ a <90 ° in reducing the toner density detection error.

  Therefore, as in the present invention, the inclination angle a of the reduction screw part 72c is larger than the inclination angle b of the normal screw part 72b, and the inclination angle a is an acute angle when viewed from the downstream side in the conveying direction. Since the toner concentration is detected by the toner concentration detection sensor 78 with respect to the developer 3 in the detection region 68c having a high density and a stable bulk density, variation in detection values obtained by the toner concentration detection sensor 78 is detected. Can be suppressed.

  Next, the developing device 34 and the operation thereof according to the third embodiment will be described with reference to FIG. 6, but the differences from the developing device 34 according to the above embodiment will be mainly described, and overlapping portions will be described. Omitted.

  FIG. 6 is a schematic cross-sectional view of the characteristic portion of the developing device 34 according to the third embodiment of the present invention as seen from the side, and shows the detection region 68c and its peripheral portion in the first transport path 68.

  Similar to the above-described embodiment, a detection region 68c for detecting the toner concentration in the developing tank 66 is provided downstream of the first conveyance path 68 and in front of the left communication path. A toner concentration detection sensor 78 is installed on the lower surface of the bottom wall 93 of the developing tank 66 corresponding to the region 68c.

  As shown in FIG. 6, the first screw 72 includes a shaft 72 a extending along the first conveyance path 68, a normal screw portion 72 b that conveys the developer 3 at a normal conveyance speed, and a normal conveyance speed. And a deceleration screw portion 72c that conveys the developer 3 at a reduced deceleration speed. As shown in FIG. 6, in addition to the pitch X of the reduction screw part 72c being smaller than the pitch Y of the normal screw part 72b, the inclination angle a of the reduction screw part 72c with respect to the shaft 72a The portion 72b is configured to be larger than the inclination angle b with respect to the shaft 72a, and the inclination angle a is an acute angle when viewed from the downstream side in the transport direction. That is, the first screw 72 according to the third embodiment shown in FIG. 6 includes the first screw according to the first embodiment shown in FIG. 4 and the first screw according to the second embodiment shown in FIG. It has a combined configuration. The speed of the developer 3 in the detection area 68c is controlled by superimposing the speed reduction effect by reducing the pitch of the speed reduction screw portion 72c and the speed reduction effect by increasing the inclination angle of the speed reduction screw portion 72c. Speed (decelerated transport speed) << Developer transport speed (normal transport speed) in the upstream region 68b.

  As shown in FIG. 6, the developer 3 transported along the first transport path 68 is transported from the upstream region 68b to the detection region 68c. In the upstream area 68b, the developer 3 is conveyed at a normal conveyance speed, whereas in the detection area 68c, the developer 3 is conveyed at a decelerating speed that is lower than the normal conveyance speed. In the vicinity of the boundary with the region 68c, the developer 3 becomes a little jammed and the compacted state of the developer 3 starts. When the developer 3 is further transported in the detection area 68c, the developer 3 is gradually compressed in the detection area 68c to become a compacted state (high density). The toner concentration of the developer 3 in the compacted state (densified) is detected by a toner concentration detection sensor 78 provided on the downstream side of the detection region 68c. Since the toner density is detected by the toner density detection sensor 78 with respect to the developer 3 that has been consolidated (densified) in the detection area 68c and has a stable bulk density, variation in the detection value obtained by the toner density detection sensor 78 is detected. Can be suppressed.

  In order to confirm the effect of the present invention, in the trickle-type two-component developing device, when the amount of the developer 3 existing in the developing tank 66 is changed, the detection value obtained by the toner concentration detection sensor 78 is detected. The variation was examined and the result is shown in FIG. As experimental conditions, the toner concentration in the developing tank 66 was set to 6% by weight, and the amount of the developer 3 contained in the developer stirring and conveying chamber 67 was changed in the range of 150 g to 240 g.

  In FIG. 9, the horizontal axis represents the amount (g) of the developer 3 present in the developing tank 66, and the vertical axis represents the toner density detection error (%). In FIG. 9, the pitch X of the reduction screw part 72c is smaller than the pitch Y of the normal screw part 72b, and the inclination angle a of the reduction screw part 72c is larger than the inclination angle b of the normal screw part 72b and is acute. Shows the case. In FIG. 9, ◎, ▽, ☆, and + indicate the pitch X of the reduction screw portion 72c and the pitch Y of the normal screw portion 72b, and the inclination angle a of the reduction screw portion 72c and the normal screw portion 72b, respectively. The inclination angle b is X = 0.2Y and a = b + 5 °, X = 0.4Y and a = b + 5 °, X = 0.2Y and a = b + 10 °, and X = 0.4Y and a = b + 10 ° An embodiment according to the present invention is shown in which the relationship is satisfied and the inclination angle a is an acute angle when viewed from the downstream side in the transport direction. Moreover, the * mark in FIG. 9 has shown the comparative example with which the 1st screw 72 is comprised only with the normal screw part 72b, and there is no change part.

  As is apparent from FIG. 9, the pitch X of the reduction screw portion 72c is in the range of 0.2Y to 0.4Y, and the inclination angle a of the reduction screw portion 72c is 5 than the inclination angle b of the normal screw portion 72a. When the angle is large in the range of 10 ° to 10 °, even if the amount of the developer 3 in the developing tank 66 fluctuates, the toner density detection error is less than 0.5% at the maximum, and the toner density detection error is very large. I was able to confirm that it was small. That is, a combination of narrowing the pitch of the speed reduction screw portion 72c and increasing the inclination angle of the speed reduction screw portion 72c is more effective for reducing the toner density detection error.

  Therefore, as in the present invention, by combining the narrowing of the pitch of the reduction screw part 72c and the increase in the inclination angle of the reduction screw part 72c, the bulk density is stabilized and the bulk density is stabilized. Since the toner concentration detection sensor 78 detects the toner concentration with respect to the developer 3 in the detection region 68c, variations in the detection value obtained by the toner concentration detection sensor 78 can be suppressed.

  In the embodiment described above, the magnetic sensor is used as the toner concentration detection sensor 78 because the magnetic sensor is very susceptible to the fluctuation of the bulk density, so that the remarkable effect of the present invention can be obtained. is there. Even the optical sensor that detects the amount of reflected light from the toner of the developer 3 is affected by the fluctuation of the bulk density, so that the effect of the present invention can be obtained. Therefore, an optical sensor may be used as the toner concentration detection sensor 78. Is possible.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the developing device of the image forming apparatus shown in FIG. 1 as viewed from above. FIG. 3 is a block diagram relating to a developing device of the image forming apparatus shown in FIG. 2. FIG. 2 is a schematic cross-sectional view of a characteristic portion of the developing device of the image forming apparatus according to the first embodiment as viewed from the side. FIG. 6 is a schematic cross-sectional view of a characteristic portion of a developing device of an image forming apparatus according to a second embodiment as viewed from the side. FIG. 10 is a schematic cross-sectional view of a characteristic portion of a developing device of an image forming apparatus according to a third embodiment as viewed from the side. 6 is a graph showing a toner density detection result according to the first embodiment. 6 is a graph showing a toner density detection result according to the second embodiment. 10 is a graph showing a detection result of toner density according to a third embodiment.

Explanation of symbols

1: Image forming apparatus 2: Developer for replenishment 3: Developer 12: Photoconductor 20: Fixing device 22: Fixing roller 26: Charging device 28: Exposure device 30: Image light 34: Developing device 36: Transfer device 38: Paper 40: Cleaning device 48: Developing roller (developer carrier)
48a: Magnet body 48b: Sleeve 62: Restriction plate 66: Developing tank 67: Developer stirring and conveying chamber 68: First conveying path 68b: Upstream area 68c: Detection area 70: Second conveying path 72: First screw (stirring member) )
72a: shaft 72b: normal screw portion 72c: deceleration screw portion 74: second screw (stirring member)
75: Notch (outflow part)
76: partition wall 78: toner concentration detection sensor 79: developer reservoir 80: developer supply tank 82: supply port 90: developer recovery tank 92: recovery port 93: bottom wall 100: control unit 102: central processing unit ( CPU)
104: Read-only memory (ROM)
106: Read / write memory (RAM)
108: Counter X: Pitch of reduction screw part Y: Pitch of normal screw part a: Inclination angle of reduction screw part with respect to shaft b: Inclination angle of normal screw part with respect to shaft

Claims (18)

A stirring member that stirs the developer including toner and carrier while transporting the developer in the transport path in the developing tank;
A developer carrier that is disposed adjacent to the stirring member and supplies the stirred and conveyed developer to the electrostatic latent image carrier;
A toner concentration detection sensor for detecting a toner concentration in the developing tank;
The agitating member is a screw body that rotates about a rotation shaft, and a detection screw portion for reducing the developer conveyance speed is provided in a detection region of the conveyance path facing the toner concentration detection sensor, and is detected. A developing device comprising: a normal screw portion for transporting a developer at a normal transport speed in an upstream region of a transport path positioned in front of the region.   The pitch of the reduction screw part is smaller than the pitch of the normal screw part, and / or the inclination angle of the reduction screw part with respect to the rotational axis is larger than the inclination angle of the normal screw part with respect to the rotational axis and 90. The developing device according to claim 1, wherein the developing device is smaller than the degree. When the pitch of the deceleration screw part is X and the pitch of the normal screw part is Y,
0.2Y ≦ X ≦ 0.8Y
The developing device according to claim 2, wherein: When the pitch of the deceleration screw part is X and the pitch of the normal screw part is Y,
0.4Y ≦ X ≦ 0.6Y
The developing device according to claim 2, wherein: When the inclination angle with respect to the rotation axis of the deceleration screw part is a, and the inclination angle with respect to the rotation axis of the normal screw part is b,
b + 5 ° ≦ a
The developing device according to claim 2, wherein: When the inclination angle with respect to the rotation axis of the deceleration screw part is a, and the inclination angle with respect to the rotation axis of the normal screw part is b,
b + 10 ° ≦ a
The developing device according to claim 2, wherein: A rotatable electrostatic latent image carrier carrying an electrostatic latent image on a peripheral surface;
A stirring member that stirs the developer including toner and carrier while transporting the developer in the transport path in the developing tank;
A developer carrier that is disposed adjacent to the stirring member and supplies the stirred and conveyed developer to the electrostatic latent image carrier;
A toner concentration detection sensor for detecting a toner concentration in the developing tank;
The agitating member is a screw body that rotates about a rotation shaft, and a detection screw portion for reducing the developer conveyance speed is provided in a detection region of the conveyance path facing the toner concentration detection sensor, and is detected. An image forming apparatus comprising: a normal screw portion that conveys a developer at a normal conveyance speed in an upstream region of a conveyance path positioned in front of the region.   The pitch of the reduction screw part is smaller than the pitch of the normal screw part, and / or the inclination angle of the reduction screw part with respect to the rotational axis is larger than the inclination angle of the normal screw part with respect to the rotational axis and 90. The image forming apparatus according to claim 7, wherein the image forming apparatus is smaller than the degree. When the pitch of the deceleration screw part is X and the pitch of the normal screw part is Y,
0.2Y ≦ X ≦ 0.8Y
The image forming apparatus according to claim 8, wherein: When the pitch of the deceleration screw part is X and the pitch of the normal screw part is Y,
0.4Y ≦ X ≦ 0.6Y
The image forming apparatus according to claim 8, wherein: When the inclination angle with respect to the rotation axis of the deceleration screw part is a, and the inclination angle with respect to the rotation axis of the normal screw part is b,
b + 5 ° ≦ a
The image forming apparatus according to claim 8, wherein: When the inclination angle with respect to the rotation axis of the deceleration screw part is a, and the inclination angle with respect to the rotation axis of the normal screw part is b,
b + 10 ° ≦ a
The image forming apparatus according to claim 8, wherein: An agitating member for agitating a developer containing toner and a carrier in a developing device,
The agitating member is a screw body that rotates about a rotation shaft, and a detection screw portion for reducing the developer conveyance speed is provided in a detection region of the conveyance path facing the toner concentration detection sensor, and is detected. An agitation member comprising: a normal screw portion that conveys the developer at a normal conveyance speed in an upstream region of the conveyance path positioned in front of the region.   The pitch of the reduction screw part is smaller than the pitch of the normal screw part, and / or the inclination angle of the reduction screw part with respect to the rotational axis is larger than the inclination angle of the normal screw part with respect to the rotational axis and 90. The stirring member according to claim 13, wherein the stirring member is smaller than the degree. When the pitch of the deceleration screw part is X and the pitch of the normal screw part is Y,
0.2Y ≦ X ≦ 0.8Y
The stirring member according to claim 14, wherein the stirring member has a relationship of When the pitch of the deceleration screw part is X and the pitch of the normal screw part is Y,
0.4Y ≦ X ≦ 0.6Y
The stirring member according to claim 14, wherein the stirring member has a relationship of When the inclination angle with respect to the rotation axis of the deceleration screw part is a, and the inclination angle with respect to the rotation axis of the normal screw part is b,
b + 5 ° ≦ a
The stirring member according to claim 14, wherein the stirring member has a relationship of When the inclination angle with respect to the rotation axis of the deceleration screw part is a, and the inclination angle with respect to the rotation axis of the normal screw part is b,
b + 10 ° ≦ a
The stirring member according to claim 14, wherein the stirring member has a relationship of

Images