JP2010025987A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a trickle system developing device using a two component developer, the device being capable of forming excellent images in a long period of time even if the level of the volume of the developer varies, and to provide an image forming apparatus thereof. <P>SOLUTION: A developing device includes a stirring member, which conveys and stirs a developer in a developing tank, and a developer carrying body. In addition, the device includes a developer feeding tank and a trickle system discharging mechanism. The discharging mechanism includes a blade reversal member having a spiral part, which is reversely wound against the spiral part of the adjacent stirring part, so as to return the excessive developer in the developing tank to the developing tank side, and the pitches of the spiral part of the blade reversal member are variable. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device used in an electrophotographic image forming apparatus and an image forming apparatus using the developing device. The present invention particularly relates to a trickle-type developing device that supplies a new developer little by little and discharges a deteriorated developer little by little, and an image forming apparatus using the developing device.

  As a developing method used in an electrophotographic image forming apparatus, a one-component developing method using toner as a main component of a developer and a two-component developing method using toner and a carrier as main components of a developer are known. Yes.

  In the two-component development method using toner and carrier, both toner and carrier are charged with a predetermined polarity by frictional contact between the toner and carrier, so that the stress received by the toner is higher than that in the one-component development method using one-component developer. It has the feature that there are few. Since the surface area of the carrier is larger than that of the toner, the carrier is less likely to become dirty due to the toner adhering to the surface of the carrier. However, due to long-term use, dirt (spent) adhering to the carrier surface increases, and as a result, the ability to charge the toner gradually decreases. As a result, the problem of fogging and toner scattering occurs. In order to extend the life of the two-component developing device, it is conceivable to increase the amount of carrier accommodated in the developing device, but this is not desirable because it leads to an increase in the size of the developing device.

  In order to solve the above-mentioned problems related to the two-component developer, Patent Document 1 discloses that a new developer is gradually supplied into the developing device and a developer whose charging performance is deteriorated is gradually discharged from the developing device. Discloses a so-called trickle-type developing device that suppresses an increase in deteriorated carriers. This developing device is configured to discharge the excess deteriorated developer by using the fluctuation in the developer volume and to keep the developer bulk level in the developing device substantially constant. According to this trickle-type developing device, the deteriorated carrier in the developing device is gradually replaced with a new carrier, and the charging performance of the carrier in the developing device can be kept substantially constant.

  In the trickle type developing device, the developer is replenished while discharging the developer in the developing device, so that the amount of the developer present in the developing device fluctuates and exists in the developing device. The amount of developer is not always constant.

  Further, when the developer bulk level fluctuates in the developing device, for example, when the developing device is inclined, when the fluidity of the developer changes, or when the operating speed of the developing device changes, Since the balance between the discharging force for discharging the developer and the discharging preventing force for blocking the developer in the developing device is lost, the amount of the developer present in the developing device varies.

  That is, when the discharge force exceeds the discharge prevention force and the developer is easily discharged, the developer present in the developing tank gradually decreases. In addition, when the discharge prevention force is greater than the discharge force and it is difficult to discharge the developer, the developer present in the developing tank gradually increases.

  When the developer is excessively reduced in the developing tank, the amount of developer supplied to the developer carrying member is reduced, which causes problems such as image defects and poor developer supply.

  An excessive increase in the developer in the developer tank adversely affects the agitation / conveyance in the developing device, which causes problems such as local image fogging and uneven toner concentration in the developer. cause.

In order to solve the above problem, it has been proposed to provide a shutter mechanism for adjusting the developer discharge amount in the vicinity of the discharge port (for example, Patent Document 2).
JP 59-1000047 A Japanese Patent Laid-Open No. 10-186829

  However, the technique disclosed in Patent Document 2 adjusts the developer discharge amount according to the degree of opening and closing of the shutter, but has the following problems.

  That is, when the shutter is in a closed approximate state close to the closed state, the developer to be discharged may stay in the vicinity of the slightly opened discharge port, and in the worst case, the discharge slightly opened by the retained developer. It happens that the exit is blocked. As a result, there is a problem that the original purpose of adjusting the developer discharge amount is not achieved.

  Even when the shutter is completely closed, the bulk level of the developer slightly fluctuates. Then, since the excess developer stays in the vicinity of the shutter when the bulk level becomes the maximum among the fluctuations, there is a problem that the vicinity of the shutter is pressed and solidified by the excess developer, thereby hindering the opening and closing of the shutter. is there.

  Therefore, the technical problem to be solved by the present invention is that a trickle-type developing device using a two-component developer can form a good image over a long period of time even if the bulk level of the developer fluctuates. It is an object of the present invention to provide a developing device and an image forming apparatus that can be performed.

Means and actions / effects for solving the problem

In order to solve the technical problem, according to the present invention,
An agitating member that agitates the developer in the developing tank containing the toner and the carrier while being conveyed in the developing tank, and the developer in the developing tank that is disposed adjacent to the agitating member and is agitated is supplied to the electrostatic latent image carrier. A developer carrying member, and a developing device comprising:
A developer supply tank for supplying toner and carrier to the developer tank;
A discharge mechanism provided in the developing tank and configured to discharge the developer in the developing tank exceeding the predetermined amount when the amount of the developer in the developing tank exceeds a predetermined amount. ,
The discharge mechanism includes a reverse blade member having a spiral portion wound in a reverse direction with respect to the spiral portion of the adjacent stirring member in order to return the developer in the developing tank that has exceeded to the developing tank side,
A developing device is provided in which the spiral portion of the reverse blade member is configured to be variable in pitch.

  According to the developing device, the spiral portion of the reverse blade member provided in the discharging mechanism is configured to be variable in pitch, so that the developer is discharged in accordance with the change in the state where the developing device is placed. It is possible to appropriately adjust the discharge prevention force for preventing the emission. Therefore, if the balance between the discharge force for discharging the developer and the discharge prevention force for blocking the developer is lost, the pitch of the spiral portion of the reverse blade member is appropriately changed. By doing so, it is possible to return to a balanced state.

As a configuration for making the pitch of the spiral portion of the reverse blade member variable, for example,
The spiral portion of the reverse blade member is sandwiched between the adjacent stirring member and the discharge conveyance member movable in the axial direction,
Both ends of the spiral portion of the reverse blade member are fixed to the adjacent stirring member and the discharge conveyance member, respectively, and the spiral portion of the reverse blade member is separated from the shaft portion of the adjacent stirring member. .

In order to detect the state change and automatically execute the variable pitch of the spiral portion of the reverse blade member in accordance with the detected state change,
A state detection device for detecting a state where the developing device is placed, and a drive device for driving the discharge conveyance member in the axial direction,
When it is detected by the state detection device that the developer is easily discharged, the drive unit increases the pitch of the spiral portion of the reverse blade member,
When it is detected by the state detection device that the developer is likely to stay, the pitch of the spiral portion of the reverse blade member is reduced by the driving device.

  The state detection device detects the tilt angle in the axial direction of the stirring member, detects the toner density in the developing tank, detects the number of printed outputs, detects the temperature of the place where the developing device is installed, and develops Detect the humidity of the installation location of the device, detect the rotation speed of the developer carrier, detect the replenishment amount of the replenished toner and carrier, detect the carrier ratio in the replenished toner and carrier, etc. This is for detecting the image density or detecting the image printing rate.

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

  Hereinafter, preferred embodiments of the present invention will be described 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.

[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 that 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 in the developing tank 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 48 b of the developing roller 48, a restricting plate 62 fixed to the developing tank 66 and extending in parallel with the central axis of the sleeve 48 b of the developing roller 48 is disposed to face with a predetermined restricting gap 63. Yes. 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. And a 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. As the replenishment developer 2, toner and carrier may be replenished separately. 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 via 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 rotationally driven, a new replenishment developer 2 corresponding to the drive 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 in the developing tank while stirring the developer 3 in the developing tank is rotatably supported in the first transport path 68. A second screw 74 that rotatably conveys the developer 3 in the developing tank from the first conveyance path 68 to the developing roller 48 while being stirred is rotatably supported on the second conveyance path 70. In this case, the communication path is formed by cutting out the upper portions of the partition walls 76 located at both ends of the first transport path 68 and the second transport path 70. The developer 3 in the developing tank that has reached the downstream end of the first transport path 68 in the transport direction is sent to the second transport path 70 through the communication path, and the downstream end of the second transport path 70 in the transport direction. The developer 3 in the developing tank that has reached 1 is fed into the first transport path 68 through the communication path. As a result, the developer 3 in the developing tank circulates in the developer agitating / conveying chamber according to the direction of the arrow in FIG.

  The first screw 72 and the second screw 74 are spiral screws in which spiral blades are fixed to a rotating shaft at a predetermined pitch. The second screw 74 extends to the right side (downstream side) of FIG.

  The second screw 74 includes a shaft portion 74 a, a normal blade portion 74 b, a reverse blade member 77 adjacent to the normal blade portion 74 b, and a discharge screw 79 adjacent to the reverse blade member 77.

  The shaft portion 74a has a cylindrical shape extending from the upstream end (left end in FIG. 2) to the downstream end (right end in FIG. 2) in the transport direction (right arrow in FIG. 2). The rod-shaped body is made of a high-rigidity material made of a metal material such as stainless steel or a resin material such as PC or ABS.

  The forward blade portion 74b disposed in the second transport path 70 is a forward direction of the developer 3 in the developing tank 3 (hereinafter, the forward direction of the transport direction is the transport direction in the second transport path 70). It is a spiral regular blade configured to be conveyed. The regular blade portion 74b is manufactured by injection molding of a resin material such as ABS, or cutting out a metal material such as SUS, and is fixed to the shaft portion 74a by fitting or bonding. The regular blade portion 74b extends in the axial direction from the upstream end portion (left end portion in FIG. 2) in the transport direction to the downstream communication passage.

  A reverse passage member 77 disposed at a position corresponding to the communication path from the second conveyance path 70 to the first conveyance path 68 and the downstream side end of the first conveyance path 68 conveys the developer 3 in the developing tank. It is a spiral reverse blade configured to transport in the direction opposite to the direction (hereinafter, the direction opposite to the transport direction refers to the direction opposite to the transport direction in the second transport path 70). The reverse blade member 77 is manufactured by injection molding of a resin material such as ABS or cutting out a metal material such as SUS. The reverse blade member 77 is inserted into the shaft portion 74a, and the upstream end thereof is fixed to the shaft portion 74a or the normal blade portion 74b by welding, adhesion, or fitting, and the downstream end. The part is fixed to the discharge screw 79 by welding, adhesion or fitting. That is, the reverse blade member 77 is separated from the shaft portion 74 a and is sandwiched between the forward blade portion 74 b and the discharge screw 79. Since the reverse blade member 77 is displaced in the forward direction or the reverse direction of the conveying direction of the shaft portion 74a in conjunction with the axial movement of the discharge screw 79, that is, the forward or reverse movement of the conveying direction, the reverse blade member 77 pitches can be reduced or increased.

  The discharge screw 79 disposed in the collection chamber is formed at the downstream end (right end in FIG. 2) in the transport direction. The discharge screw 79 includes a ring shaft portion 79a having a generally annular shape, and a regular blade portion 79b fixed on the ring shaft portion 79a by fitting or bonding. The ring shaft portion 79a having a generally annular shape is inserted into the downstream end portion of the shaft portion 74a. The regular blade portion 79b is a spiral regular blade portion 79b configured to transport the developer 3 in the developing tank in the forward direction of the transport direction. A driving device 50 is provided outside the discharge screw 79 on the downstream side. The drive device 50 drives the discharge screw 79 by air pressure, a cam mechanism, or the like, as will be described later. The drive device 50 causes the discharge screw 79 to slide along the shaft portion 74a in the axial direction, that is, in the forward or reverse direction of the transport direction.

  Further, the pitch of the regular blade portion 74 b of the second screw 74 is larger than the pitch of the regular blade portion 79 b of the discharge screw 79. Further, a reverse blade member 77 is provided for transporting the developer 3 in the developing tank 3 in the reverse direction while the developer 3 in the developing tank is transported in the forward direction of the transport direction by the forward blade portion 74 b. Accordingly, when the second screw 74 rotates, the height of the developer 3 in the developing tank at the downstream end (right end) in the transport direction of the second screw 74 becomes higher than the other portions. That is, the rising of the developer 3 in the developing tank is formed at the downstream end (right end) in the transport direction of the second transport path 70.

  Here, since the developing device 34 employs a so-called trickle system, the developing device 34 has an outlet 75 for allowing the excess developer 3 in the developing tank to flow out. That is, the outflow port 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 conveyed by the second screw 74 is blocked by the discharge prevention force of the reverse blade member 77 in a normal state, so that the second conveying path 70 to the first conveying path 68 as indicated by the solid line arrow in FIG. It is conveyed to. When the developer 3 in the developing tank increases in the developing tank and the liquid level in the developing tank 66 rises, the outflow port 75 provided at the upper portion of the side wall against the damming action of the reverse blade member 77 is developed in the developing tank. Agent 3 gets over and overflows to the adjacent collection chamber. The excess developer 3 in the developing tank overflowing into the collection chamber is conveyed to the collection port 92 by the discharge screw 79 and is collected (discarded) to the developer collection tank 90 through the collection port 92.

  The developer agitation transport chamber 67 is provided with a toner concentration detection sensor 78 that detects the current toner density in the developer agitation transport chamber 67. For example, the toner concentration detection sensor 78 detects the magnetic permeability of the developer 3 in the developing tank conveyed in the developer agitating / conveying chamber 67 from a change in inductance of the coil. From the magnetic permeability detected by the toner concentration detection sensor 78, the ratio of the toner to the developer 3 in the developing tank is obtained. For example, when the amount of carrier contained in the developer 3 in the developing tank 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 in the developing tank 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.

  In the developing device 34, when the toner concentration of the developer 3 in the developing tank is lowered 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 replenishment amount of the replenishment developer 2 includes the current toner concentration of the developer 3 in the developing tank detected by the toner concentration detection sensor 78, the printing rate (dot counter) at the time of image formation, and the developer replenishment tank 80. The carrier ratio with respect to the replenishment developer 2 is determined. 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.

  The supplied replenishment developer 2 is conveyed along the first conveyance path 68 and the second conveyance path 70 of the developer agitation conveyance chamber 67 while being mixed and stirred with the developer 3 in the developing tank. The 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 tank in the developing device 34 gradually increases as the replenishment developer 2 is replenished. To do. The developer 3 in the developing tank having an increased volume circulates in the developer agitating / conveying chamber 67. The surplus developer 3 in the developing tank that cannot circulate through the developer agitating / conveying chamber 67 gets over the reverse blade member 77 and is provided at the downstream end (right end) in the transport direction of the second transport path 70. It flows out from the outlet 75 and is collected in the developer collection tank 90 through the collection port 92.

  Various sensors and devices such as a toner density detection sensor 78 are incorporated in the image forming apparatus 1 or the developing device 34. As will be described later, these sensors and devices are used as state detection devices for detecting the state where the image forming apparatus 1 (developing apparatus 34) is placed.

  Further, the scanner 124 is used as an image reading sensor for reading a document and as a state detection device for measuring a printing rate of an image, and based on a scan signal (image signal) of the scanner 124, the control unit 100. The CPU 102 calculates the printing rate in a predetermined area of the document. Here, the printing rate is a ratio of the area of the portion on which the toner is placed when the total area constituting the image is 100%. In other words, it is related to the toner adhesion amount in image formation. . Since an image of an original is formed by laser dots having a diameter of several tens of μm, the printing rate is calculated by analyzing the ratio of the laser dots in a predetermined area of the image.

  The replenishment amount detection sensor 126 as a state detection device detects the replenishment amount of toner and carrier to the developing tank 66 by counting the rotation amount (drive time) of a replenishment motor provided in the developer replenishment tank 80. .

  The carrier ratio detection sensor 120 as a state detection device detects the carrier ratio in the supplied toner and carrier as a change in magnetic permeability and converts it into an electrical signal.

  An image density detection sensor 122 as a state detection device detects the image density (contrast) of the toner image transferred onto the intermediate transfer roller as a change in reflectance and converts it into an electrical signal.

  The inclination sensor 112 as the state detection device detects, for example, a change in the liquid level proportional to the inclination angle in the axial direction of the first screw 72 or the second screw 74 as a change in capacitance and converts it into an electrical signal. .

  A toner concentration detection sensor 78 as a state detection device detects a change in toner concentration in the developing tank 66 as a change in magnetic permeability and converts it into an electrical signal.

  A counter 108 as a state detection device detects the number of printed output sheets.

  The temperature sensor 114 as a state detection device detects the temperature of the place where the developing device 34 is installed.

  The humidity sensor 116 as a state detection device detects the humidity at the place where the developing device 34 is installed.

  A rotation speed detection sensor 118 as a state detection device counts the rotation speed of the developing roller 48.

  The replenishment amount detection sensor 126 as a state detection device counts the replenishment amount of the replenishment developer 2 to the developing tank 66 by counting the rotation amount (drive time) of a replenishment motor provided in the developer replenishment tank 80. To detect.

  The carrier ratio detection sensor 120 as a state detection device detects the ratio of carriers in the supplied replenishment developer 2 as a change in magnetic permeability and converts it into an electrical signal.

  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. The ROM 104 stores, for example, a toner density calculation table for converting and calculating the voltage detected by the toner density detection sensor 78 to the current toner density of the developer 3 in the developing tank, and the current toner density of the developer 3 in the developing tank. A developer replenishment table for calculating the amount of developer to be replenished from the toner density difference between the reference toner density and the reference toner density is stored.

  Various devices, devices, and sensors related to image formation are connected to the CPU 102 of the control unit 100. That is, the developing device 34, the developer supply tank 80, the counter 108, the inclination sensor 112, the temperature sensor 114, the humidity sensor 116, the rotation speed detection sensor 118, the carrier ratio detection sensor 120, the image density detection sensor 122, the scanner 124, and the like are controlled. The CPU 100 of the unit 100 is connected. 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, respectively. That is, the CPU 102 has a function as a control unit that controls a developing operation, a replenishing operation, an image forming operation, a scanning operation of a scanner (image reading unit), and the like.

  The RAM 106 has a work area for temporarily storing various programs executed by the control unit 100 and data related to these programs.

  Various state detection information obtained from the sensors and devices described above, that is, the inclination angle of the developing device 34, the toner concentration in the developing tank 66, the number of printed output, and the environment in which the developing device 34 is installed. The temperature and humidity, the rotation speed of the developing roller 48, the ratio of the carrier to the replenishing developer 2 in the developer replenishing tank 80, the image density, the printing rate (image information) at the time of image formation, etc. Is temporarily stored.

(Developer)
The two-component developer contains toner and a carrier for charging the toner. In the present invention, a known toner that has 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, 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. should be used. 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 can be fixed to the surface of the binder type carrier by, for example, mixing the magnetic resin carrier and the fine particles uniformly and adhering the fine particles to the surface of the magnetic resin carrier. 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 in the developer 3 in the developing tank is adjusted so as to obtain a desired toner charge amount. The toner ratio of the developer 3 in the developing tank 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 basic 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). Due to the rotation of the first screw 72 and the rotation of the second screw 74, the developer 3 in the developer tank existing in the developer stirring and transporting chamber 67 is stirred while being circulated and transported through the first transport path 68 and the second transport path 70. Is done. 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 in the developing tank 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 in the developing tank being transported through the second transport path 70.

  When toner is consumed from the developer tank developer 3 by such image formation, an amount of toner corresponding to the consumed amount is supplied to the developer tank developer 3. For this purpose, the developing device 34 includes a toner concentration detection sensor 78 that measures the ratio of the toner to the developer 3 in the developing tank existing in the developer agitating / conveying chamber 67. A developer supply tank 80 is provided above the first conveyance path 68.

  Next, the configuration and operation of the developing device 34 according to the first embodiment will be described with reference to FIGS.

  FIG. 4 is a diagram for explaining a main part of the present invention. (A) shows the case where the pitch P of the reverse blade member 77 is large, and (B) shows the case where the pitch P ′ of the reverse blade member 77 is small. FIG. 5 is a diagram for explaining a drive mode of the reverse blade member 77 according to the first embodiment. (A) shows the case where the pitch P of the reverse blade member 77 is large, and (B) shows the case where the pitch P ′ of the reverse blade member 77 is small.

  FIG. 4A shows the pitch of the reverse blade member 77 by transmitting the axial driving force of the driving device 50 to be described later to the reverse blade member 77 via the discharge screw 79 movable in the axial direction. It is shown that P is positioned so as to increase. 4B also shows that the driving device 50 positions the reverse blade member 77 so that the pitch P ′ is reduced.

  FIG. 5 illustrates a driving mode of the reverse blade member 77 by the driving device 50 using air pressure. The right end portion of the shaft portion 74a has a hollow structure having a hollow portion inside the shaft portion 74a and having an outer shell formed on the outer peripheral portion. A syringe 53 is mounted in the hollow structure. The ring shaft 79a of the discharge screw 79 is connected to the internal moving plate 79c through an axial groove (not shown) formed on the left side of the outer shell. The internal moving plate 79c and the pressing end surface 54 of the syringe 53 are integrated. Accordingly, when the internal movement plate 79c moves in the axial direction as the syringe 53 contracts or expands, the discharge screw 79 also moves along the outer shell at the right end portion of the shaft portion 74a. Further, since the reverse blade member 77 is clamped while being fixed to the ring shaft portion 79a or the normal blade portion 79b and the shaft portion 74a or the normal blade portion 74b, the discharge screw 79 is forward or reverse in the transport direction. When moving, the pitch of the reverse blade member 77 changes.

  The air pressure adjusting device 51 is a compressor that provides pressurized air or a vacuum pump that provides decompressed air. From the air pressure adjusting device 51, pressurized air or reduced air pressure is provided to the syringe 53 through the communication unit 52.

  When the decompressed air is provided from the air pressure adjusting device 51, the syringe 53 contracts. Therefore, as shown in FIG. 5A, the pressing end surface 54 of the syringe 53 moves in the forward direction of the internal movement plate 79c. (Right side of FIG. 5). As a result, the discharge screw 79 moves in the forward direction of the conveyance direction, and the pitch P of the reverse blade member 77 is increased.

  When pressurized air is provided from the air pressure adjusting device 51, the syringe 53 expands, and therefore, as shown in FIG. 5B, the internal moving plate 79c is moved in the direction opposite to the conveying direction (left side in FIG. 5). Move. As a result, the discharge screw 79 moves in the direction opposite to the conveying direction, and the pitch P ′ of the reverse blade member 77 is reduced.

  Various state detection information obtained from the sensors and devices described above, that is, the inclination angle of the developing device 34, the toner concentration in the developing tank 66, the number of printed outputs, the temperature of the environment in which the developing device 34 is installed, Humidity, the number of rotations of the developing roller 48, the replenishment amount of the replenishment developer 2, the ratio of the carrier to the replenishment developer 2 in the developer replenishment tank 80, the image density, and the printing rate during image formation Based on (image information), as shown in Table 1, the pitch of the reverse blade member 77 is appropriately changed.

  When the developing device 34 is inclined in the direction opposite to the transport direction, the developing device 34 is placed in a state where it is difficult for the developer 3 in the developing tank to be discharged. In order to promote, the discharge screw 79 is driven so as to weaken the discharge prevention force of the reverse blade member 77, that is, to reduce the pitch of the reverse blade member 77. Conversely, when the developing device 34 is inclined in the forward direction of the transport direction, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the toner concentration in the developing tank 66 is lower than a predetermined value, the flowability of the developer 3 in the developing tank becomes high, the bulk specific gravity of the developer 3 in the developing tank becomes large, and more in a certain volume. Since the developer 3 in the developing tank stays, in order to promote the discharge of the developer 3 in the developing tank, the discharge prevention force of the reverse blade member 77 is weakened, that is, the pitch of the reverse blade member 77 is reduced. The discharge screw 79 is driven. Conversely, when the toner concentration in the developing tank 66 is higher than a predetermined value, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the number of printed output is large at the endurance stage, the flowability of the developer 3 in the developing tank becomes high, the bulk specific gravity of the developer 3 in the developing tank becomes large, and the developer in the developing tank increases in a certain volume. 3 stays, the discharge screw 79 is arranged so as to weaken the discharge prevention force of the reverse blade member 77 in order to promote the discharge of the developer 3 in the developing tank, that is, to reduce the pitch of the reverse blade member 77. Driven. Conversely, when the number of printed output sheets is small at the initial stage, the discharge screw 79 is driven to increase the pitch of the reverse blade member 77.

  When the temperature in the installation environment of the image forming apparatus 1 is high, the flowability of the developer 3 in the developing tank is increased, the bulk specific gravity of the developer 3 in the developing tank is increased, and the developer in the developer tank is more in a certain volume. 3 stays, the discharge screw 79 is arranged so as to weaken the discharge prevention force of the reverse blade member 77 in order to promote the discharge of the developer 3 in the developing tank, that is, to reduce the pitch of the reverse blade member 77. Driven. Conversely, when the temperature in the installation environment of the image forming apparatus 1 is low, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the humidity in the installation environment of the image forming apparatus 1 is high, the flowability of the developer 3 in the developing tank becomes high, the bulk specific gravity of the developer 3 in the developing tank increases, and the developer in the developing tank increases in a certain volume. 3 stays, the discharge screw 79 is arranged so as to weaken the discharge prevention force of the reverse blade member 77 in order to promote the discharge of the developer 3 in the developing tank, that is, to reduce the pitch of the reverse blade member 77. Driven. Conversely, when the humidity in the installation environment of the image forming apparatus 1 is low, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the developing device 34 is driven to rotate at a low speed, the second screw 74 is driven at a low speed to make it difficult for the developer 3 in the developing tank to be discharged. Therefore, the discharge screw 79 is driven so as to weaken the discharge prevention force of the reverse blade member 77, that is, to reduce the pitch of the reverse blade member 77. Conversely, when the developing device 34 is driven to rotate at a high speed, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the replenishment amount of the replenishment developer 2 is large, more carriers are replenished at the same time, the bulk of the developer tank developer 3 is increased, and more developer tank 3 remains in a certain volume. Therefore, the discharge screw 79 is driven so as to weaken the discharge prevention force of the reverse blade member 77 in order to promote the discharge of the developer 3 in the developing tank, that is, to reduce the pitch of the reverse blade member 77. Conversely, when the replenishment amount of the replenishment developer 2 is small, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the ratio of the carrier to the replenishment developer 2 in the developer replenishment tank 80 is high, more carriers are replenished at the same time to increase the bulk of the developer tank developer 3, and more developer tanks in a certain volume. Since the inner developer 3 stays, the discharge prevention force of the reverse blade member 77 is weakened to promote the discharge of the developer 3 in the developing tank, that is, the discharge of the reverse blade member 77 is reduced. The screw 79 is driven. Conversely, when the ratio of the carrier to the replenishment developer 2 in the developer replenishment tank 80 is low, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the image density is high, the amount of toner consumed increases, so the amount of toner to be replenished, that is, the amount of replenishment developer 2 to be replenished, increases. As a result, more carriers are replenished at the same time, and the bulk of the developer tank developer 3 is increased, so that more developer tank developer 3 remains in a certain volume. In order to promote discharge, the discharge screw 79 is driven so as to weaken the discharge blocking force of the reverse blade member 77, that is, to reduce the pitch of the reverse blade member 77. Conversely, when the image density is low, the discharge screw 79 is driven so as to increase the pitch of the reverse blade member 77.

  When the image printing rate is high, the amount of toner consumed increases, so that the replenishment amount of the replenished toner, that is, the replenishment developer 2 increases. As a result, more carriers are replenished at the same time, and the bulk of the developer tank developer 3 is increased, so that more developer tank developer 3 remains in a certain volume. In order to promote discharge, the discharge screw 79 is driven so as to weaken the discharge blocking force of the reverse blade member 77, that is, to reduce the pitch of the reverse blade member 77. Conversely, when the image printing rate is low, the discharge screw 79 is driven to increase the pitch of the reverse blade member 77.

  Next, the configuration and operation of the developing device 34 according to the second embodiment will be described with reference to FIG. 6. The description will focus on differences from the first embodiment described above.

  FIG. 6 is a view for explaining a drive mode of the reverse blade member 77 according to the second embodiment. (A) shows the case where the pitch P of the reverse blade member 77 is large, and (B) shows the case where the pitch P ′ of the reverse blade member 77 is small.

  FIG. 6 illustrates a driving mode of the reverse blade member 77 by the driving device 50 using the cam mechanism 55. The right end portion of the shaft portion 74a has a hollow structure having a hollow portion inside the shaft portion 74a and having an outer shell formed on the outer peripheral portion. A compression spring 59 is mounted in the hollow structure. The ring shaft 79a of the discharge screw 79 is connected to the internal moving plate 79d through an axial groove (not shown) formed on the left side of the outer shell. Therefore, when the internal moving plate 79d moves in the axial direction, the discharge screw 79 also moves along the outer shell at the right end portion of the shaft portion 74a. Further, since the reverse blade member 77 is clamped while being fixed to the ring shaft portion 79a or the normal blade portion 79b and the shaft portion 74a or the normal blade portion 74b, the discharge screw 79 is forward or reverse in the transport direction. When moving, the pitch of the reverse blade member 77 changes.

  The cam mechanism 55 includes a generally elliptical cam having a short axis and a long axis, a motor that rotationally drives the cam, and a connecting rod 56 that is in sliding contact with the contour curve of the cam. The connecting rod 56 is connected to the internal moving plate 79 d through the guide hole 58 of the shaft wall 57. As the cam rotates, the connecting rod 56 slidably contacting the approximately elliptical cam moves in the axial direction. The internal moving plate 79d is biased toward the cam mechanism 55 by the compression spring 59.

  When the short shaft of the cam comes to the short shaft position where it abuts on the connecting rod 56, the internal moving plate 79d is moved in the forward direction (right side in FIG. 6) in the transport direction as shown in FIG. As a result, the discharge screw 79 moves in the forward direction of the conveyance direction, and the pitch P of the reverse blade member 77 is increased.

  When the long axis of the cam comes to the long axis position where it abuts the connecting rod 56, the internal moving plate 79d is moved in the direction opposite to the conveying direction (left side in FIG. 6) as shown in FIG. As a result, the discharge screw 79 moves in the direction opposite to the conveying direction, and the pitch P ′ of the reverse blade member 77 is reduced.

  In the above embodiment, the driving device 50 uses air pressure or a cam mechanism, but other driving methods may be used. For example, a driving method using a rack and pinion or a crank is also possible. In addition, although the internal moving plates 79c and 79d provided in the shaft portion 74a are to be driven, the right end portion of the ring shaft portion 79a of the discharge screw 79 may be driven directly. .

  Next, a subroutine for pitch control of the reverse blade member 77 of the present invention will be described with reference to FIG. While this subroutine is being executed, normal print output is repeatedly executed.

  In step S112, this subroutine starts. In step S114, various state information relating to the developing device 34 and the image forming apparatus 1 is detected by the sensors and devices described above. In step S116, it is determined whether the state of the developing device 34 and the image forming apparatus 1 has changed. If there is no change in state and NO is selected, the process returns to the state detection step of step S114.

  If there is a change in state in step S116, YES is selected. In step S118, the pitch of the reverse blade member 77 is enlarged or reduced in accordance with the change in the state of the developing device 34 or the image forming apparatus 1.

  In step S120, it is determined whether or not the pitch of the reverse blade member 77 has been changed appropriately. When the change of the pitch of the reverse blade member 77 is inappropriate and NO is selected, the process returns to the state detection step of step S114.

  If the pitch of the reverse blade member 77 is appropriately changed in step S120, YES is selected. In step S122, it is determined whether or not the amount of the developer 3 in the developing tank has changed. If the amount of the developer 3 in the developing tank has not changed and NO is selected, the process returns to the state detection step of step S114.

  If the amount of developer 3 in the developing tank has changed in step S122, YES is selected. In step S124, it is determined whether or not the amount of the developer 3 in the developing tank is an appropriate amount. When the amount of the developer 3 in the developing tank is not an appropriate amount and NO is selected, the process returns to the pitch variable processing step in step S118.

  In step S124, YES is selected if the amount of the developer 3 in the developing tank is an appropriate amount. In step S126, the subroutine for pitch control of the reverse blade member 77 ends, and the process returns to the original main routine.

  As described above, the spiral portion of the reverse blade member 77 provided in the discharge mechanism is configured to be variable in pitch, so that it matches the change in the state where the developing device 34 and the image forming apparatus 1 are placed. Thus, it is possible to appropriately adjust the discharge prevention force for preventing discharge of the developer 3 in the developing tank. Therefore, the spiral portion of the reverse blade member 77 is assumed to be in a state where the balance between the discharge force for discharging the developer 3 in the developing tank and the discharge prevention force for blocking the developer discharge is lost. By making the pitch of this variable, it is possible to return to a balanced state.

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. It is a figure explaining the principal part of this invention. (A) shows the case where the pitch of the reverse blade member is large, and (B) shows the case where the pitch of the reverse blade member is small. It is a figure explaining the drive form of the reverse blade member which concerns on 1st embodiment. (A) shows the case where the pitch of the reverse blade member is large, and (B) shows the case where the pitch of the reverse blade member is small. It is a figure explaining the drive form of the reverse blade member which concerns on 2nd embodiment. (A) shows the case where the pitch of the reverse blade member is large, and (B) shows the case where the pitch of the reverse blade member is small. It is a flowchart of the subroutine regarding the pitch control of a reverse blade member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Image forming device 2: Developer for replenishment 3: Developer in developing tank 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 50: Drive device 51: Air pressure adjusting device 52: Communication portion 53: Syringe 54: Pushing end surface 55: Cam 56: Connecting rod 57: Shaft wall 58: Guide hole 59: Compression spring 62: Restriction Plate 63: Restriction gap 66: Developing tank 67: Developer stirring and conveying chamber 68: First conveying path 70: Second conveying path 72: First screw (stirring member)
74: Second screw (stirring member)
74a: Shaft portion 74b: Positive blade portion 75: Notch (outlet)
76: partition wall 77: reverse blade member 78: toner concentration detection sensor 79: discharge screw (discharge conveyance member)
79a: Ring shaft portion 79b: Front blade portion 79c: Internal moving plate 79d: Internal moving plate 80: Developer supply tank 82: Supply port 90: Developer recovery tank 92: Recovery port 100: Control unit 102: Central processing unit (CPU)
104: Read-only memory (ROM)
106: Read / write memory (RAM)
108: Counter 112: Inclination sensor 114: Temperature sensor 116: Humidity sensor 118: Rotation speed detection sensor 120: Carrier ratio detection sensor 122: Image density detection sensor 124: Scanner 126: Replenishment amount detection sensor P: Enlarged pitch P ′ : Reduced pitch

Claims (14)

An agitating member that agitates the developer in the developing tank containing the toner and the carrier while being conveyed in the developing tank, and the developer in the developing tank that is disposed adjacent to the agitating member and is agitated is supplied to the electrostatic latent image carrier. A developer carrying member, and a developing device comprising:
A developer supply tank for supplying toner and carrier to the developer tank;
A discharge mechanism provided in the developing tank and configured to discharge the developer in the developing tank exceeding the predetermined amount when the amount of the developer in the developing tank exceeds a predetermined amount. ,
The discharge mechanism includes a reverse blade member having a spiral portion wound in a reverse direction with respect to the spiral portion of the adjacent stirring member in order to return the developer in the developing tank that has exceeded to the developing tank side,
A developing device, wherein the spiral portion of the reverse blade member is configured to have a variable pitch. The spiral portion of the reverse blade member is sandwiched between the adjacent stirring member and the discharge conveyance member movable in the axial direction,
Both ends of the spiral portion of the reverse blade member are fixed to the adjacent stirring member and the discharge conveyance member, respectively, and the spiral portion of the reverse blade member is separated from the shaft portion of the adjacent stirring member. The developing device according to claim 1, wherein: A state detection device for detecting a state where the developing device is placed, and a drive device for driving the discharge conveyance member in the axial direction,
When it is detected by the state detection device that the developer is easily discharged, the drive unit increases the pitch of the spiral portion of the reverse blade member,
The developing device according to claim 1, wherein when the state detection device detects that the developer is likely to stay, the driving device reduces the pitch of the spiral portion of the reverse blade member.   The developing device according to claim 3, wherein the state detection device detects an inclination angle in the axial direction of the stirring member.   The developing device according to claim 3, wherein the state detection device detects a toner density in the developing tank.   The developing device according to claim 3, wherein the state detection device detects the number of printed output sheets.   The developing device according to claim 3, wherein the state detecting device detects a temperature of a place where the developing device is installed.   The developing device according to claim 3, wherein the state detecting device detects humidity at a place where the developing device is installed.   The developing apparatus according to claim 3, wherein the state detection device detects the number of rotations of the developer carrying member.   The developing device according to claim 3, wherein the state detection device detects a supply amount of the supplied toner and carrier.   The developing device according to claim 3, wherein the state detection device detects a carrier ratio in the supplied toner and carrier.   The developing device according to claim 3, wherein the state detection device detects an image density.   The developing device according to claim 3, wherein the state detection device detects an image printing rate.   An image forming apparatus comprising: the developing device according to claim 1; and a rotatable electrostatic latent image carrier that bears an electrostatic latent image on a peripheral surface thereof.

Images