JP2009036926A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device satisfactorily carrying a developer while preventing air from blowing into a developing section. <P>SOLUTION: The developing device 100 is composed of: the developing section 2 disposed near an image carrier 1; and a developer stirring section 40 disposed in a place different from the developing section 2. The developing device 100 conveys developer through air conveyance within a developer conveyance passage 5 from the developer stirring section 40 to the developing section 2 via a developer injecting section 6. In this device 100, a developer pool D in which developer accumulates is disposed in the lower part 8A of the developer injecting section 6. An air discharging section 8B is disposed in the upper part of the developer injecting section. The exit 5B of the developer conveyance passage is connected between the developer pool D of the developer injecting section 6 and the discharging section 8B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having at least two functions, and in particular, a developer stirring unit is arranged apart from the developing unit, The present invention relates to a developing device using air conveyance for circulating developer.

  The developing device provided in the electrophotographic image forming apparatus is such that the supply of the developer (toner) to the photosensitive member as the image carrier, the stirring and mixing of the developer, and the stirring and mixing of the replenishing toner are all performed in a single developing device. A configuration that is performed simultaneously is common. In such a developing device, there are at least two conveying screws, and each conveying screw is configured to convey the developer in opposite directions. The developer is transported in one direction by one transport screw and transported in the reverse direction by the other transport screw and circulates inside the developing device.

  Recently, there is a system in which a part of the developing device where the developer is stirred is separated from the developing unit, and the developer is sufficiently stirred before being sent to the developing unit. In this system, since the developer agitating unit is provided at a position away from the developing unit, there is an advantage that the volume of the developing container occupying around the photosensitive member can be reduced as much as possible with the developing unit as a minimum volume. In addition, as a means for stably transporting a large amount of developer with a free path and a simple configuration, an air transport system that transports the developer together with an air flow is used for transporting the developer from the developer agitating unit that is remote. It is valid. Examples of such a developing device include Patent Documents 1 and 2.

Japanese Patent No. 3391926 Japanese Patent No. 3349286

  Using an air conveyance method as a developer conveying means used in the developing device is a simple method using a flexible tube and an air pump, and is an excellent method in that it can be conveyed to a remote place by a free path. In the case where the conveyed developer is supplied to a container having an opening part (such as an opening around the developing sleeve) such as a developing unit, if the air used for conveyance is blown into the container, the developer and toner inside the container There is a concern about the occurrence of problems such as blowout from the opening and scattering around the container, or scattering on the image to be formed. Such a blow-out of the developer stains the inside of the apparatus and becomes a factor that deteriorates the quality of the output image.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and an image forming apparatus capable of transporting a good developer while preventing air from being blown into a developing unit.

  Accordingly, the invention of claim 1 is constituted by being divided into a developing unit disposed in the vicinity of the image carrier and a developer stirring unit disposed at a position different from the developing unit, and from the developer stirring unit to the developing unit. In the developing device in which the developer is transported by air transport from the developer transport path to the developer transport path, a developer reservoir is provided at the lower portion of the developer feed section, and the developer An air discharge portion is provided above the input portion, and an outlet portion of the developer transport path is connected to the developer input portion located between the developer reservoir portion and the discharge portion.

  According to a second aspect of the present invention, in the developing device according to the first aspect, a filter member that allows only air to pass through is provided in the discharge portion.

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, the developer reservoir portion is formed on an upper portion of the developer stirring screw in the developing portion, and the rotational speed of the developer stirring screw is controlled. Thus, the amount of developer accumulation is controlled.

  According to a fourth aspect of the present invention, in the developing device according to the first, second, or third aspect, an opening / closing member that opens and closes a path to the developing unit is disposed in the developer reservoir.

  According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, when the deposit amount of the developer deposited on the opening / closing member exceeds a specified value, the path is opened in accordance with the weight of the deposited developer. It is characterized by being configured to be closed.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the outlet portion of the air conveying portion is centered on the charging portion so that the discharged air is fed while rotating to the developer charging portion. It is characterized by being offset from the arrangement.

  A seventh aspect of the invention is characterized in that the developing device according to any one of the first to sixth aspects is provided.

  According to the present invention, in the developer transporting path from the developer agitating unit to the developing unit, the developer is supplied by air transporting via the developer charging unit, and the developer reservoir is provided below the developer charging unit. However, an air discharge part is provided in the upper part, and the outlet part of the developer transport path is connected to the developer charging part located between the developer reservoir part and the discharge part, and is used for transporting the developer. Since the air is sealed against the developing unit side by the developer reservoir, it does not enter the developing unit and is discharged from the upper discharging unit. Conveyance is possible, and the contamination inside the apparatus due to the scattering of the developer and the quality of the output image can be reduced and suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The image forming apparatus shown in FIG. 1 includes a drum-shaped photosensitive member 1 (hereinafter referred to as “photosensitive drum 1”) as an image carrier, a developing device 100, a charging unit, an optical writing unit, and a recording material (not shown). An image forming apparatus of an electrophotographic system provided with an image transfer unit, a cleaning unit, and a fixing unit. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by the charging unit and the optical writing device, visualized by the developer of the developing device 100, transferred to the recording material by the transfer unit, and then fixed by the fixing unit. An output image is obtained by fixing the toner to the recording material. In this embodiment, a two-component developer including a toner and a carrier is used as the developer.

  The developing device 100 includes a developing unit 2 that faces the photosensitive drum 1 and is disposed in the vicinity of the photosensitive drum 1, and a developer stirring unit 40 that is disposed at a position different from the developing unit 2. The developer is conveyed from the stirring unit 40 to the developing unit 2 by air conveyance via the developer conveyance path 5 and the developer charging unit 6.

  The developing unit 2 is provided with a developing supply unit 7 to which a developer charging unit 6 is connected and a developer discharging unit 3. The developer conveyed by air from the developer agitation unit 40 is supplied from the developer input unit 6 to the development unit 2 via the development supply unit 7 and used for development, and the developer discharge unit 3, the developer agitation unit 40, and the like. So as to circulate between the developing unit 2 and the developer stirring unit 40 by dropping into the developer discharging flow path 4 provided so as to connect to the developer stirring channel 40 and being introduced into the developer stirring unit 40. It is configured.

  In the developing unit 2, a developing sleeve 20 and conveying screws 21 and 22 for stirring the developer are disposed in the casing 23. The developing sleeve 20 has a well-known configuration in which a magnet is disposed therein, and the developer is attracted and conveyed to adhere toner to the electrostatic latent image on the surface of the photosensitive drum 1. The conveying screw 21 is rotationally driven so as to convey the developer from the front side to the back side in the drawing. The transport screw 22 is rotationally driven so that the developer is transported from the back to the front in the drawing. The inside of the casing 23 is divided into two by a partition plate 24, and the conveying screw 21 and the conveying screw 22 are respectively arranged in the divided space.

  The partition plate 24 in FIG. 2 is interrupted so that the developer can move from the conveying screw 21 toward the conveying screw 22 at the end on the far side in the drawing. A developer discharge unit 3 for discharging the developer to the outside is provided on the front side of the conveyance screw 22, and a development supply unit for supplying the agitated developer into the casing on the front side of the conveyance screw 21. 7 are provided. In the vicinity of the outer peripheral surface of the developing sleeve 20, a doctor blade 25 for leveling the developer adhering to the developing sleeve 20 to a certain amount is supported by the casing 23. The casing 23 covers the periphery of the conveying screws 21 and 22, but a portion facing the photosensitive drum 1 is opened to supply developer from the developing sleeve 20 to the photosensitive drum 1. A gap is formed between the casing 23 and the developing sleeve 20. When air is blown into the developing unit 3, the developer is blown out of the casing 23 through the opening through the gap.

  As shown in FIGS. 1 and 3, the developer stirring section 40 has a casing 40 </ b> A in which the diameter becomes narrower toward the discharge port 34, such as an inverted conical shape, and the developer is accommodated therein. . The casing 40A is provided with a developer supply port 33 on its upper surface and a discharge port 34 on its lower surface. Inside the casing 40A, a screw 43 for conveying the developer from the bottom to the top and two stirring members 44 are rotatably provided. The screw 43 is disposed at the center of the casing 40A, and the stirring member 44 is disposed outside the screw 43, and the developer in the casing 40A is mixed by rotating them.

  The screw 43 and the stirring member 44 are rotationally driven by a motor 45 serving as a driving unit. Specifically, the screw 43 is directly connected to the motor 45, and the stirring member 44 is decelerated and rotated via a reduction gear train composed of gears 46a to 46d. The developer is transported from the replenishment port 33 to the discharge port 34 in the developer agitation unit 40 using gravity. Since developer always exists as a buffer in the developer agitating unit 40, it is configured so that unmixed developer is not discharged as it is. The developer lifted upward from the bottom by the rotation of the screw 43 moves downward along with the rotation of each stirring member 44 rotating outside the screw 43, and is collected around the screw 43 again. Thus, the developer is constantly convected in the casing 40A. By this convection, the entire developer in the casing 40A is uniformly mixed. Further, since the developer of this embodiment is a two-component toner, the toner is charged by friction between the toner and the carrier. Therefore, it is important to increase the contact probability between the toner and the carrier in order to quickly obtain the charge amount. However, as a result of the study by the inventors of the present application, it has been found that the contact probability increases due to the convection of the developer in the casing 40A, and the damage to the developer is small.

  A rotary feeder 50 is disposed below the developer stirring unit 40 so as to communicate with the casing 40A. The rotary feeder 50 has a function of discharging a constant amount of developer from the casing 40. That is, the rotary feeder 50 is arranged with the impeller 51 rotatably supported inside the casing 50A as shown in FIG. The impeller 51 is configured to discharge a certain amount of developer downward by being rotated by the motor 55 shown in FIG.

  A junction 52 is disposed below the impeller 51. An air passage 33 connected to a supply port 60A of an air pump 60 serving as an air supply unit and an inlet portion 5A serving as one end of a developer transport path 5 connected to the developer charging unit 6 are connected to the junction 52. The fixed amount of developer discharged by the impeller 51 is carried on the air supplied from the air pump 60 and is conveyed by air to the developer charging unit 6.

  New toner is supplied from the toner hopper 30 to the casing 40A of the developer agitating unit 40 as the toner is consumed. Toner replenishment to the developer stirring unit 40 is performed by rotating a small conveying screw disposed in the toner supply path 31 connected to the developer discharge flow path 4 when the drive motor 32 is driven to rotate. This is performed by transporting new toner in the hopper 30. When the conveying screw (not shown) is rotated, new toner in the toner hopper 30 can be conveyed by a certain amount.

  That is, the developer that is quantitatively discharged from the rotary feeder 50 is transported by the air inside the developer transport path 5 by the air pressure supplied from the air pump 60, and is supplied from the developer charging unit 6 of the developing unit 3. Returned to part 7.

  Next, a characteristic configuration of the present invention will be described.

  In the developing device 100 of this embodiment, the developer used for development in the developing unit 3 is sent from the developer discharging unit 3 through the developer discharging channel 4 to the developer stirring unit 40, where toner is replenished. In addition, the developer that is sufficiently stirred and mixed and appropriately charged is returned to the developing unit 3 via the developer transport path 5 for stable development. It is a feature of the present invention to devise the developer charging portion 6 so that the toner is not fed into the casing 23.

  As shown in FIG. 4, the end portion of the conveying screw 21 is arranged inside the developing supply unit 7, and the developer supplied from the developer conveying path 5 is conveyed in the right direction in the drawing. . The developer charging unit 6 includes a cylindrical part 8 that is provided at the top of the development supply unit 7 and extends in the vertical direction in the drawing. The cylindrical portion 8 has a lower portion 8A communicating with the developing supply portion 7, an upper portion opened to the atmosphere and provided with a discharge portion 8B. The developer is charged between the developer reservoir portion D and the discharge portion 8B. For example, a cylindrical outlet portion 5B serving as the other end of the developer transport path 5 is connected in the vicinity of the central portion 8D of the portion 8 from the lateral direction. For this reason, as shown by an arrow A, a mixed air stream of developer and air conveyed by air conveyance is introduced into the developer introduction unit 6 from the lateral direction.

  The cylindrical portion 8 according to this embodiment is provided so that a developer reservoir portion is formed so that the developer always remains in the lower portion 8A of the cylindrical portion 8 as indicated by a symbol D in FIG. . If the developer reservoir D is formed in the lower part 8A of the cylindrical part 8, it functions to seal so that the air supplied from the outlet part 5B does not enter the developing part 3 side. Further, the amount of developer remaining in the developer reservoir D is maintained in a balance between the amount of developer supplied together with air from the outlet 5B and the conveyance amount conveyed by the conveyance screw 21. In this embodiment, the number of rotations of the screw 21 is set in accordance with the input amount from the outlet portion 5B.

  In this way, the developer reservoir D is formed in the lower part 8A of the cylindrical part 8, and the developer having a large specific gravity falls downward in the cylindrical part 8 as indicated by the arrow B due to its own weight. Since the upper part of the part 8 is a discharge part 8B opened to the atmosphere, the air does not flow downward but flows upward as indicated by the arrow C and is discharged from the discharge part 8B.

  In this way, the developer reservoir D is provided at the lower part of the developer charging part 6 and the air discharge part 8B is provided at the upper part, so that the air used for transporting the developer is developed on the developing arm side. Since it is sealed by the developer reservoir D and does not enter the developing unit 3 but is discharged from the upper discharge unit 8B, it is possible to transport the developer while preventing air from being blown into the developing unit 3. In addition, it is possible to reduce and suppress dirt in the machine due to the scattering of the developer and the quality of the output image.

  The toner separated from the carrier may flow upward along with the air, but by placing the filter 10 in front of the discharge portion 8B, the floating toner can be captured so as not to go outside. The filter 10 uses a filter member having such a characteristic that only air is allowed to pass therethrough without allowing floating matters such as toner to pass therethrough. Further, since the toner captured by the filter 10 falls due to vibration or the like by providing the filter 10 on the upper part, the filter 10 can be used for a long period of time. Reference numeral 11 denotes a ring serving as a fixing member for fixing the filter 11.

  Further, by disposing the screw 21 in the lower portion 8A of the cylindrical portion 8, since the developer is blocked by the screw 21 when the rotation of the screw 21 is stopped, the developer reservoir portion D can be maintained. Further, even when the screw 21 rotates, it is possible to control so that a constant amount of developer is held in the developer reservoir D by maintaining the balance between the rotational speed and the amount of developer fed by air conveyance. .

  Next, regarding the positional relationship between the discharge portion 8B and the outlet portion 5B of the developer transport path 5 with respect to this, the center line O of the cylindrical outlet portion 5B and the center O1 of the cylindrical portion 8 are made to coincide. However, in this case, the air blown out from the discharge portion 8B and the developer have a high impact when hitting the inner wall surface of the cylindrical portion 8 facing the discharge portion 8B. It is also supposed to cause damage.

  Therefore, as shown in FIG. 5, when viewed from the axial direction of the cylindrical portion 8, the center line O of the cylindrical outlet portion 5B and the center O1 of the cylindrical portion 8 are offset by the dimension indicated by the symbol E. May be arranged. By doing in this way, the developer put into the cylindrical portion 8 from the outlet portion 5B together with the air does not hit the inner wall surface 8C of the cylindrical portion 8 vertically, and the inner wall surface as indicated by the arrow F It is thrown in while rotating (turning) along the phase of 8C, that is, air is sent to the developer throwing section 6 while being rotated, and there is little damage to the developer. Since the agent moves downward while rotating, and the air is exhausted upward while rotating, it is possible to improve the separation between them.

  6, 7, and 8, an opening / closing valve 12 serving as an opening / closing member that opens and closes the path to the developing unit 3 is arranged in the developer reservoir D. Specifically, the on-off valve 12 is disposed inside the cylindrical member 8 between the screw 21 and the outlet portion 5B. The on-off valve 12 is wound around the shaft 13 supported by the cylindrical member 8, semicircular valve bodies 14 and 15 rotatably supported by the shaft 13, and the both ends of the valve body 14, It is comprised by the torsion coil spring 16 as an urging | biasing means latched by 15 and urging | biasing the valve bodies 14 and 15 to an opening direction. A stopper 17 that defines the open position of the valve bodies 14 and 15 is disposed inside the cylindrical member 8 located above the on-off valve 12 so as to contact the valve bodies 14 and 15. The valve bodies 14 and 15 are attached to the shaft 13 and are opened by the action of the torsion coil spring 16. The valve bodies 14 and 15 become substantially circular when the stopper 17 is in a substantially horizontal open state to partition the inside of the cylindrical member 8 in the vertical direction. When the closed state in which 14 and 15 are close to each other and face each other is formed, the inside (path) of the cylindrical member 8 is configured to open. The on-off valve 12 uses a developer for opening and closing. The on-off valve 12 normally spreads horizontally as shown by a solid line in FIG. 6 and is in a closed state. When developer is accumulated on the upper part thereof, it moves as shown by a broken line in FIG. Become. That is, when the amount of developer deposited on the opening / closing valve 12 becomes equal to or greater than a prescribed value against the spring force of the torsion coil spring 16, the opening / closing valve 12 has the inside of the cylinder member 8 (path) by the weight of the deposited developer. ) Is configured to close in the opening direction.

  By providing the on-off valve 12 having such a configuration, the conveying amount of the screw 21 increases, the developer reservoir D is eliminated, or the developer in the developer reservoir D flows out when the developer 3 is tilted. Even if such a situation occurs, the normal on-off valve 12 occupies an open state in which the inside of the cylindrical member 8 is closed, so that air can be prevented from being blown into the developing unit 3. In addition, since the on-off valve 12 does not open the inside of the cylindrical member 8 due to the accumulation of a certain amount of developer, the open state that closes the inside of the cylindrical member 8 is maintained even if a small amount of accumulation occurs temporarily. Thus, it is possible to more reliably prevent air from being blown into the developing unit.

1 is a perspective view illustrating a schematic configuration of an image forming apparatus to which the present invention is applied and a configuration of a developing device. 1 is a front view illustrating a schematic configuration of an image forming apparatus to which the present invention is applied and a configuration of a developing device. FIG. 3 is a partial cross-sectional view illustrating a configuration of a developer stirring unit. It is an enlarged view showing a configuration of a developer charging unit. FIG. 4 is a plan view showing an offset state of a developer conveyance path and a developer charging unit. FIG. 4 is an enlarged cross-sectional view illustrating a configuration of a developer charging unit having an opening / closing member. It is an expanded sectional view which shows the structure and arrangement | positioning of an opening-and-closing member. It is an expansion perspective view which shows the structure and operation | movement of an opening-and-closing member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing part 5 Developer conveyance path 5B Exit part of developer conveyance path 6 Developer input part 8A Lower part of developer input part 8B Discharge part 10 Filter member 12 Opening and closing member 21 Developer stirring screw 40 Developer Stirrer 100 Developing device D Developer reservoir

Claims (7)

The developer conveying path is configured to be divided into a developing unit disposed in the vicinity of the image carrier and a developer stirring unit disposed at a position different from the developing unit, and from the developer stirring unit to the developing unit. In the developing device in which the developer is transported through the developer charging unit by air transport inside,
A developer reservoir for depositing developer is provided at the lower portion of the developer charging portion, and an air discharge portion is provided at the upper portion of the developer charging portion, and the development located between the developer reservoir and the discharging portion. A developing device characterized in that an outlet portion of the developer conveyance path is connected to the agent charging portion.   The developing device according to claim 1, wherein a filter member that allows only air to pass is provided in the discharge portion.   The developer reservoir is formed on an upper part of a developer agitating screw in the developer, and a developer reservoir amount is controlled by controlling a rotation speed of the developer agitating screw. Item 3. The developing device according to Item 1 or 2.   4. The developing device according to claim 1, wherein an opening / closing member that opens and closes a path to the developing unit is disposed in the developer reservoir.   The opening / closing member is configured to close in a direction to open the path according to the weight of the deposited developer when the accumulation amount of the developer accumulated on the upper portion becomes a predetermined value or more. The developing device according to claim 4.   6. The outlet part of the air conveying part is arranged to be offset with respect to the center of the charging part so that air is sent to the developer charging part while rotating. The developing device according to 1.   An image forming apparatus comprising the developing device according to claim 1.

Images