JP5074869B2 - Development device - Google Patents

Description

  The present invention is configured to form a toner image along an electrostatic latent image formed in advance on the surface of an image carrier by supplying toner toward the image carrier provided in the image forming apparatus. The present invention relates to a developed developing device.

  Conventionally, a developing device as described in Patent Document 1 is known. The developing device supplies toner toward an image carrier provided in the image forming apparatus to form a toner image along an electrostatic latent image formed in advance on the surface of the image carrier. Is. Such a developing device includes a developing unit having a toner carrier whose peripheral surface is opposed to the surface of the image carrier, and a toner storage unit for supplying toner to the developing unit.

When the toner in the developing unit is consumed and reduced for forming a toner image on the surface of the image carrier, the toner is replenished from the toner storage unit to the developing unit. By repeating such toner replenishment, the developing unit can perform development processing on the image carrier until the toner storage unit becomes empty.
JP 2000-250302 A

  By the way, when a small amount of toner remains in the developing portion, the remaining toner is in a deteriorated state due to repeated circulation movement in the developing portion. When a large amount of new toner is replenished in the presence of the deteriorated toner, the deteriorated toner is reversely charged. As a result, the residual toner is exposed to the outside during replenishment due to electrostatic repulsion between the residual toner and the new toner. This causes the inconvenience of scattering toward the camera. Further, when the toner is reversely charged, there arises a disadvantage that a so-called fog phenomenon occurs in which a dot image is formed in a portion where a toner image should not be formed on the surface of the image carrier.

  The present invention has been made in order to eliminate the conventional inconvenience, and is intended for one using a one-component developer, and prevents the residual toner from scattering when the toner is supplied to the developing unit. Another object of the present invention is to provide a developing device that can suppress fogging.

According to the first aspect of the present invention, there is provided a developing unit for supplying a one-component toner to the surface of an image carrier on which an electrostatic latent image is formed to form a toner image along the electrostatic latent image, and the developing A replenishing unit for replenishing toner to the image forming unit, and a toner amount in the developing unit is less than a set value set in consideration of a minimum amount of toner necessary for normally performing image forming processing on the image carrier. the thereby replenishing the toner to the developing unit with respect to the supply portion when the toner amount detecting means for detecting the toner amount detecting means that the amount of toner in the developing unit becomes less than the set value is detected to be the Control means for controlling the toner, and when the toner amount detection means detects less than the set value, the control means remains in the developing portion prior to replenishment of toner from the replenishing portion to the developing portion. Toner to the image carrier The toner amount detection means controls the density sensor for detecting the density of the toner image on the image carrier, and the duty of the development AC bias on the image carrier over the normal development conditions. In the lowered state, when the density of the blank pattern image is detected to be higher than the density of the 100% solid pattern image by the forming means for forming a 100% solid pattern image and a blank pattern image and the density sensor And a judging means for judging that the amount of toner in the developing section is less than the set value .

  In the present invention, the necessary minimum toner amount is an amount in which the image density in the axial direction of the developing roller, which is a component of the developing unit, cannot be maintained uniformly, or the amount of deteriorated toner is increased. It is the amount when it becomes a state that cannot be maintained.

  The required minimum toner amount can be determined by detecting the density using a sensor that detects the density of a toner image on an image carrier such as a photosensitive drum or an intermediate transfer body. Specifically, a 100% solid pattern image and a blank paper pattern image are formed on the image carrier with a development bias duty that is lower than the normal development conditions at a predetermined timing, and each image density is detected and 100% solid When the density of the pattern image and the blank pattern image is reversed from the normal development condition, it is determined that the toner in the developing device has reached the minimum toner amount.

  Incidentally, the developing bias duty will be described. For example, when the developing bias duty is 40%, the ratio of the positive direction is 40% when the electric field direction in the direction in which the toner moves from the developing roller onto the photosensitive member is the positive direction. It is an AC bias whose reverse direction is 60%. When the duty is reduced to 15%, for example, the time during which the electric field for moving the toner in the direction of the photoreceptor is applied is shortened, and the time for returning to the developing roller side is lengthened.

  At this time, if the amount of so-called deteriorated toner charged to a charge opposite to that of normal is increased, the application time of the electric field for moving the reversely charged toner to the photosensitive member side becomes longer, and the density of the blank paper pattern image is increased. The density of the 100% solid pattern image increases and decreases. If the density at this time is reversed, it can be determined that the ratio of the reversely charged toner in the toner increases and is likely to exceed 50%. Therefore, it can be determined that it is difficult to maintain the density with a normal developing bias.

  As another method for determining the minimum toner amount, a plurality of 100% solid pattern images are formed in the developing roller axial direction, the density difference between them is detected, and this density difference is detected as the minimum necessary amount in the developing device. A method that can be used as a material for determining the limit amount of toner can be used.

  According to the first aspect of the present invention in which such a necessary minimum toner amount is a constituent requirement, it becomes less than a set value set in consideration of a minimum necessary toner amount capable of performing normal image forming processing. Until the developing unit, toner is not supplied from the replenishing unit. Accordingly, when a large amount of new toner is supplied from the replenishing unit in a state where there is a small amount of residual toner in the developing unit that does not interfere with the image forming process, the residual toner deteriorated due to this is supplied. However, in the invention of claim 1, a very small amount of residual toner is generated in the image forming process. Since new toner is replenished in the existing state, occurrence of such inconvenience can be suppressed.

Further , when the toner amount sensor detects that the toner amount sensor is less than the set value, the control means removes the toner remaining in the developing unit prior to replenishment of toner from the replenishing unit to the developing unit. It controls to make it discharge | emit toward.

  According to such a configuration, the residual toner remaining in the developing unit is completely removed except for the toner that is fixed in the developing unit, and new toner is supplied from the replenishing unit in a state where the developing unit is substantially emptied. Since the replenished toner is replenished in the developing unit where new toner is replenished, there is no reversely charged deteriorated residual toner and the developing unit is reset to the initial state. Therefore, the toner in the developing unit is prevented from being deteriorated even when the developing device is used for a long time, and the initial quality of the toner is always maintained.

According to a second aspect of the present invention, in the first aspect of the present invention, the control means is provided on the entire surface of the surface of the image carrier to be developed by the developing unit so as to correspond to the discharge of the toner. It is controlled to form a solid solid electrostatic latent image.

  According to such a configuration, when the amount of stored toner in the developing unit becomes less than the set value, the control unit causes the solid electrostatic latent image to be uniform on the entire surface to be developed by the developing unit of the image carrier. Therefore, all of the toner less than the set value is supplied to the solid electrostatic latent image, which makes it possible to easily and reliably empty the developing unit.

  According to the developing device of the present invention, since a very small amount of toner remains in the developing portion, new toner from the replenishing portion is replenished to the developing portion. Therefore, the deteriorated and reversely charged residual toner becomes the new toner. On the other hand, it is possible to suppress as much as possible the occurrence of inconveniences such as repelling and scattering to the outside, or fogging phenomenon occurring in the image forming process.

  In particular, prior to replenishment of toner from the replenishing unit to the developing unit, the deteriorated toner remaining in the developing unit is discharged toward the image carrier, so that the residual toner in the developing unit is discharged to the outside. The occurrence of scattering and fogging can be reliably prevented.

  FIG. 1 is an external perspective view showing an embodiment of a printer to which a developing device according to the present invention is applied. FIG. 1A shows a state in which a maintenance lid is closed, and FIG. FIG. 1C shows a state where the maintenance lid is opened, and a state where the maintenance lid is opened and the toner container is removed. In FIG. 1, the XX direction is referred to as the left-right direction, and the YY direction is referred to as the front-rear direction. In particular, the -X direction is referred to as the left, the + X direction is referred to as the right, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear.

  As shown in FIG. 1, a printer (image forming apparatus) 10 is configured to be capable of color printing, and has various types described later in a printer main body 11 as a casing having a substantially cubic shape in appearance. It is configured by mounting equipment. The printer main body 11 has a rounded shape as a whole, and is designed so as to give a visually friendly and compact impression to the user. The printer main body 11 is provided with a paper discharge tray 161 on the upper surface, a maintenance lid 112 is provided on the upper front surface facing the user, and a detachable paper cassette 121 is disposed below the maintenance lid 112. This makes it extremely easy to use in consideration of usability.

  The paper discharge tray 161 receives the paper P on which printing processing has been performed, and can receive the paper P discharged from a paper discharge port 162 formed facing the front at the rear of the upper surface of the printer main body 11. It is formed by an inclined surface that is arcuate and forwardly inclined toward the front.

  The maintenance lid 112 is normally closed as shown in FIG. 1A, and is opened as shown in FIGS. 1B and 1C when a toner container (replenisher) 30 described later is replaced. Is done. The maintenance lid 112 is pivotally supported around a support shaft 122a installed slightly above the paper cassette 121 between the front positions of the pair of side plates 111 of the printer main body 11, and is supported around the support shaft 122a. A closed posture Q1 (FIG. 1A) in which the front opening 110 of the printer main body 11 is closed by reverse rotation, and an open posture Q2 (FIG. 1B) and FIG. 1 in which the front opening 110 of the printer main body 11 is opened. (C)) and the posture can be changed.

  The maintenance lid 112 is provided with a manual feed tray 122 that is pivotally supported around the support shaft 122a. The manual feed tray 122 is used when manually feeding the printing paper P to the printer 10, and the maintenance lid 112 is set in a closed posture Q1 (indicated by a solid line in FIG. 1A). By being rotated clockwise around the support shaft 122a in this state, it is pulled out from the maintenance lid 112 as shown by a two-dot chain line in FIG.

  The toner container 30 includes a black container 30K filled with black toner, a cyan container 30C filled with cyan toner, a magenta container 30M filled with magenta toner, and a yellow container 30Y filled with yellow toner. Four types are adopted. The black to yellow containers 30K, 30C, 30M, and 30Y face the front opening 110 in the printer main body 11 from the left to the right, and the black container 30K, the cyan container 30C, the magenta container 30M, and the yellow container. They are arranged in the order of 30Y.

  Therefore, the user opens the maintenance lid 112 to face the black to yellow containers 30K, 30C, 30M, and 30Y as shown in FIG. When the black to yellow containers 30K, 30C, 30M, and 30Y are removed from the printer main body 11 for replacement in this state, the state shown in FIG.

  In the present embodiment, a non-magnetic one-component toner can be used as the toner. Alternatively, magnetic one-component toner may be employed.

  The paper cassette 121 is for storing printing paper P, and is detachably attached to the printer main body 11. In the example shown in FIG. 1, the paper cassette 121 is provided in two stages, but it may be one stage or three or more stages.

  FIG. 2 is a side sectional view illustrating an embodiment of the internal structure of the printer 10 shown in FIG. In addition, the direction display by Y in FIG. 2 is the same as that in FIG. 1 (−Y: forward, + Y: backward). As shown in FIG. 2, the printer 10 includes a paper feeding unit 12 that feeds the paper P to an image forming unit 13 described later, and a toner image on the paper P while conveying the paper P sent from the paper feeding unit 12. The image forming unit 13 to be transferred, the fixing unit 14 that performs a fixing process on the toner image transferred to the paper P by the image forming unit 13, and the discharge destination of the paper P that has been subjected to the fixing process by the fixing unit 14 are switched. A discharge destination switching unit 15 and a paper discharge unit 16 that discharges the paper P that has been printed are mounted on the printer main body 11.

  The paper feed unit 12 includes the paper cassette 121 capable of storing a plurality of sheets P, which is detachably attached to a lower portion of the printer main body 11, and the manual feed used when manually feeding the sheets P. And a tray 122.

  A pickup roller 123 is provided at an upper position on the front side of each paper cassette 121, and the paper P stored in the paper cassette 121 is picked up one by one by driving the pickup roller 123 toward the image forming unit 13. Sent out.

  The image forming unit 13 can rotate around an axial center extending in a left-right direction (a direction perpendicular to the paper surface of FIG. 2) in which an electrostatic latent image and a toner image are formed along the electrostatic latent image on the peripheral surface. A photosensitive drum (image carrier) 131, a charging roller 132 for forming a uniform charge on the peripheral surface of the photosensitive drum 131 by applying a charging process, and a uniform charging roller 132. An exposure device 133 that forms an electrostatic latent image on the peripheral surface by irradiating the peripheral surface of the photosensitive drum 131 to which an appropriate charge is applied with laser light based on image information, and the electrostatic latent image is formed A developing device 10a that forms a toner image on the peripheral surface of the photosensitive drum 131 by supplying toner to the peripheral surface of the photosensitive drum 131; a transfer belt 134 to which the toner image formed on the peripheral surface of the photosensitive drum 131 is transferred; , Photosensitive drum 1 The toner image on the transfer belt 134 is electrostatically peeled off and transferred onto the surface of the transfer belt 134, and the toner image on the transfer belt 134 is electrostatically peeled off and fed from the paper feeding unit 12. A secondary transfer roller 136 to be transferred onto the paper P, a drum cleaning device 137 for cleaning the peripheral surface of the photosensitive drum 131 after being transferred to the transfer belt 134, and a surface of the transfer belt 134 after being transferred to the paper P A belt cleaning device 138 for performing a cleaning process.

  The charging roller 132 is configured such that charges having a predetermined polarity are formed on the peripheral surface by a high voltage applied from a power source (not shown). Since the peripheral surface of the charging roller 132 is in contact with the peripheral surface of the photosensitive drum 131, uniform charges are formed on the peripheral surface of the photosensitive drum 131.

  The exposure device 133 irradiates the peripheral surface of the photosensitive drum 131 uniformly charged by the charging roller 132 with laser light based on image data input from a computer (not shown). An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 131 by the light irradiation. By supplying the toner from the developing device 10a to the electrostatic latent image, a toner image is formed on the peripheral surface of the photosensitive drum 131, and the toner image is transferred to the rotating transfer belt 134.

  The developing device 10a is adjacent to the photosensitive drum 131, and a rotary developing device (developing unit) 20 that supplies toner to the photosensitive drum 131, and the rotary developing device 20 is supplied with toner. And a toner container (replenisher) 30 that is detachably attached to the printer main body 11.

  The rotary developing unit 20 is formed in a circular shape in a side view (as viewed from a direction perpendicular to the paper surface of FIG. 2), and is mounted on the rotary frame 21 at an equal pitch in the circumferential direction. The unit developing device 22 is provided. The rotating frame 21 is pivotally supported at a rear position of the photosensitive drum 131 so as to be rotatable about a frame shaft 211 disposed in parallel with the axis of the photosensitive drum 131 and at substantially the same height level. Has been. The rotating frame 21 is equally divided into four sections in the circumferential direction by four partition plates 212 protruding in the radial direction from the frame shaft 211, and a unit developing device 22 is mounted in each section. Yes.

  The unit developing unit 22 includes a black unit developing unit 22K filled with black toner, a cyan unit developing unit 22C filled with cyan toner, a magenta unit developing unit 22M filled with magenta toner, and a yellow unit. There are four types, yellow unit developer 22Y filled with toner. When forming a toner image with yellow toner on the peripheral surface of the photosensitive drum 131, the yellow unit developer 22 </ b> Y is opposed to the photosensitive drum 131 by the rotation of the rotating frame 21 around the frame axis 211. The position is set, and in this state, the photosensitive drum 131 makes a round, and a yellow toner image is formed on the circumferential surface. This yellow toner image is immediately transferred to the rotating transfer belt 134.

  The magenta, cyan, and black toner images are formed on the peripheral surface of the photosensitive drum 131 in the same manner as in the case of yellow, and the unit developing device 22 filled with toner of the target color is arranged around the photosensitive drum 131. The toner image of the next color is sequentially transferred to the peripheral surface of the photosensitive drum 131 that is opposed to the surface and has the toner image disappeared by the transfer process to the transfer belt 134.

  A color image is formed on the surface of the transfer belt 134 by appropriately synchronizing the rotation of the transfer belt 134 and the toner image forming operation of the photosensitive drum 131. The color image is transferred to the paper P fed from the paper feeding unit 12 by the action of the secondary transfer roller 136, whereby color printing is performed on the paper P.

  A registration roller pair 124 (FIG. 2) is provided at a position immediately upstream of the secondary transfer roller 136, and the sheet P sent from the paper feeding unit 12 to the image forming unit 13 is transferred by the registration roller pair 124. The conveyance timing is adjusted. The color image on the transfer belt 134 is transferred to an appropriate position on the paper P by adjusting the conveyance timing by the registration roller pair 124.

  3A and 3B are diagrams showing an embodiment of the unit developing device 22, in which FIG. 3A is a perspective view and FIG. 3B is an enlarged sectional view taken along line IIIB-IIIB in FIG. 3A. The direction display by X and Y in FIG. 3 is the same as in FIG. 1 (X is the left-right direction (−X: leftward, + X: rightward), Y is the front-back direction (−Y: forward, + Y: backward)). It is.

  First, as shown in FIG. 3A, the unit developing device 22 is sandwiched between a pair of front and rear fan-shaped side plates 221 whose center angle is set to 90 ° in a side view, and the pair of fan-shaped side plates 221. A toner storage container 222, a developing sleeve 223 installed between a pair of fan-shaped side plates 221 at a lower portion in the toner storage container 222 in FIG. 3, and a pair of fan-shaped at a lower portion in the toner storage container 222 in FIG. A stirring and conveying member 224 is provided between the side plates 221 and extends in parallel with the developing sleeve 223.

  In the present embodiment, the stirring and conveying member 224 is interposed between a screw feeder 224a provided at the left corner of FIG. 3B and between the screw feeder 224a and the developing sleeve 223. It consists of a relay roller 224b. A partition plate 226 extending from the arc top plate 222b of the toner storage container 222 is provided between the screw feeder 224a and the relay roller 224b. The first chamber 222c is divided into a second chamber 222d on the relay roller 224b side.

  At least a pair of front and rear communication openings 226a are provided at appropriate positions of the partition plate 226, and the screw feeder 224a and the relay roller 224b are driven and rotated around the shaft center by driving of a drive motor (not shown), thereby the toner storage container. The toner replenished in 222 circulates between the first chamber 222c and the second chamber 222d through these communication openings 226a.

  The toner introduced into the second chamber 222d and being carried toward the developing sleeve 223 by the peripheral surface of the relay roller 224b extends from the arc top plate 222b toward the peripheral surface of the developing sleeve 223. The toner of the predetermined layer thickness is supplied from the peripheral surface of the developing sleeve 223 to the peripheral surface of the photoconductive drum 131 by diving from the tip of the blade 227 to the peripheral surface of the photoconductive drum 131. A toner image is formed along the electrostatic latent image.

  A toner introduction opening 222 a for introducing the toner into the unit developer 22 is formed at an appropriate position on the circumferential surface of curvature of the toner storage container 222. The toner introduction opening 222a is provided with a sheet-like cover 225 made of an elastic material such as rubber for closing the toner introduction opening 222a. A slit 225a for inserting a tip of a toner transfer pipe 51 described later is provided at a substantially central position of the sheet-like lid 225.

  Then, when the toner loading cylinder 53 (FIG. 5) of the toner transfer pipe 51 is inserted into the slit 225a, the toner from the toner container 30 is loaded into the toner storage container 222.

  Returning to FIG. 2, the transfer belt 134 is provided on the primary transfer roller 135, an idle roller 134 c provided slightly behind the primary transfer roller 135, and slightly below the photosensitive drum 131. It is wound around a driving roller 134a that rotates by driving of a driving motor (not shown) and a driven roller 134b that faces the driving roller 134a at a front position below the photosensitive drum 131.

  The driven roller 134b is urged toward the direction away from the drive roller 134a by the urging force of an urging member 134d such as a coil spring, whereby the tension state of the transfer belt 134 is maintained. The secondary transfer roller 136 is disposed opposite to the drive roller 134a via the transfer belt 134 at a position directly below the drive roller 134a.

  A bias voltage for electrostatically peeling off the toner image on the transfer belt 134 is applied to the secondary transfer roller 136 from a power source (not shown). Accordingly, the toner image on the transfer belt 134 is transferred onto the paper P passing between the transfer belt 134 and the secondary transfer roller 136.

  Between the driving roller 134a and the idle roller 134c, a belt cleaning device 138 for cleaning the surface of the transfer belt 134 after the transfer processing on the paper P is provided, and the belt cleaning device 138 performs the cleaning processing. The applied transfer belt 134 goes to the photosensitive drum 131 to receive the next transfer process.

  The fixing unit 14 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 13. The fixing unit 14 is disposed opposite to the fixing roller 141 heated by an energized heating element, and below the fixing roller 141. And a pressure roller 142 whose peripheral surface is pressed against and in contact with the peripheral surface of the fixing roller 141.

  The sheet P that has been transferred by the transfer belt 134 in the image forming unit 13 is guided to the circumference of the transfer belt 134 while being sandwiched between the transfer belt 134 and the secondary transfer roller 136, and is then fixed to the fixing unit 14. The toner image is fixed on the paper P by heating when passing between the fixing roller 141 and the pressure roller 142.

  The paper P after the fixing process is led to the paper discharge conveyance path 101 by driving the first discharge roller pair 143, and the paper discharge conveyance path 101 is raised by the forward drive of the second discharge roller pair 102, and the paper discharge outlet 162. The paper is discharged to a paper discharge tray 161 provided at the top of the printer main body 11.

  The discharge destination switching unit 15 is used when double-sided printing is performed on the paper P. The paper P once sent from the fixing unit 14 to the paper discharge conveyance path 101 after the one-side fixing process is completed. Is returned to the image forming unit 13 again with the front and back reversed. The discharge destination switching unit 15 includes a return roller 151 disposed opposite to a lower end portion of the paper discharge conveyance path 101 so that a peripheral surface of the lower portion of the first discharge roller pair 143 comes into contact with each other, and the return roller 151. A return conveyance path 152 extending from the lower part of the sheet to the upstream side (the right side in FIG. 2) of the registration roller pair 124 through the fixing unit 14.

  When performing double-sided printing on the paper P, the paper P after the fixing process for which single-sided printing has been completed is led out to the paper discharge conveyance path 101 until the trailing edge passes through the first discharge roller pair 143, and the second printing is continued. The discharge roller pair 102 is reversely driven. In this way, the sheet P on which single-sided printing has been completed is guided by the drive of the return roller 151, and is sent back to the return conveyance path 152, and passes through the return conveyance path 152 to the registration roller pair 124 with the front and back sides reversed. Therefore, the printing process is performed on the back side of the paper P in the image forming unit 13 thereafter.

  The toner container 30 is different from the black unit developer 22K, cyan unit developer 22C, magenta unit developer 22M, and yellow unit developer 22Y (FIG. 1B) of the rotary developer 20, respectively. Each color toner is stored in order to supply each color toner, and four units are employed corresponding to the black to yellow unit developing units 22K, 22C, 22M, and 22Y.

  As shown in FIGS. 1B and 1C, these four toner containers 30 are placed on a base 40 provided so as to extend in the left-right direction at a substantially middle position in front of the printer main body 11. It is detachably attached. Between each toner container 30 and the rotary developing device 20, a toner transfer mechanism 50 for sending the toner in the toner container 30 to each unit developing device 22 is provided.

  FIG. 4 is a schematic perspective view showing a relative positional relationship among the rotary developing device 20, the toner container 30, the pedestal 40, and the toner transfer mechanism 50. In addition, the direction display by X and Y in FIG. 4 is the same as that in FIG. 1 (X is leftward and rightward (-X: leftward, + X: rightward), Y is front-back direction (-Y: forward, + Y: backward). ).

  As shown in FIG. 4, on the pedestal 40, a black container 30K, a cyan container 30C, a magenta container 30M, and a yellow container 30Y are mounted in parallel from left to right.

  The toner transfer mechanism 50 includes four toner transfer pipes 51 whose upstream ends (front ends) are connected to the black to yellow containers 30K, 30C, 30M, and 30Y via the pedestals 40, and the toner transfer pipes. And four toner loading devices 52 respectively connected to the downstream end (rear end) of 51.

  The toner transfer pipe 51 is formed of a flexible material made of rubber, soft synthetic resin, or the like, and can follow a predetermined operation of the toner loading device 52 by elastic deformation. Inside the toner transfer pipe 51, a spiral feeder 511 made of a coil spring that can be driven and rotated around an axis by a predetermined driving means is mounted. Then, the toner from the toner container 30 moves in the toner transfer pipe 51 by the driving rotation in the predetermined direction around the axis of the spiral feeder 511 and is loaded into the unit developer 22 through the toner loading device 52. The

  Four toner loading devices 52 are arranged in the left-right direction so as to correspond to the respective sheet-like lids 225 of the black to yellow unit developing devices 22K, 22C, 22M, and 22Y above the rotary developing device 20. It is installed. The toner transferred through the toner transfer pipe 51 in a state where a part of the toner loading device 52 penetrates the slit 225 a of the sheet-like lid 225 and enters the unit developing device 22 passes through the toner loading device 52. Are supplied to the unit developing device 22.

  FIG. 5 is a cross-sectional view showing an embodiment of the toner loading device 52. FIG. 5A is a state in which the toner loading cylinder 53 is set at the retracted position T1, and FIG. Each of the cylinders 53 is shown in the loading position T2. As shown in FIG. 5, the toner loading device 52 includes a toner loading cylinder 53 to which the downstream end of the toner transfer pipe 51 is connected, and a driving means (not shown) which is concentric with the cylinder core and is built in the toner loading cylinder 53. The screw feeder 54 that rotates around the axis by the drive, the retraction position T1 (FIG. 5A) where the toner loading cylinder 53 is spaced upward from the unit developing device 22, and the loading that has entered the unit developing device 22. An elevating mechanism 55 that elevates between the position T2 (FIG. 5B) is provided.

  The toner loading cylinder 53 has a double structure including an inner cylinder 531 and an outer cylinder 532 that is externally fitted to the inner cylinder 531 in a sliding contact state. The downstream end of the toner transfer pipe 51 is connected to the inner cylinder 531, and the outer cylinder 532 rotates forward and backward around the inner cylinder 531 within a predetermined range without interfering with the toner transfer pipe 51. Can move.

  The lower ends of the inner cylindrical body 531 and the outer cylindrical body 532 are both tapered and formed in a conical shape, and openings (inner cylindrical openings provided in the inner cylindrical body 531 are provided in the conical portions, respectively. 531a and an outer cylinder opening 532a provided in the outer cylinder 532), and the openings 531a and 532a overlap each other (that is, the shutter is open as shown in FIG. 5B) in the toner loading cylinder 53. The fed toner is led out through the openings 531a and 532a.

  On the other hand, when the outer cylinder 532 rotates around the inner cylinder 531 by a predetermined angle from this open state, the wall surface of the outer cylinder 532 closes the inner cylinder opening 531a (that is, the shutter closed state shown in FIG. 5A). State) and toner leakage is prevented. The rotating operation of the outer cylinder 532 is performed in conjunction with the lifting operation of the toner loading cylinder 53 by the lifting mechanism 55.

  When the toner loading cylinder 53 is set at the retracted position T1, the lower end portion of the toner loading cylinder 53 is in a state where the inner cylinder opening 531a is closed by the outer cylinder 532 as shown in FIG. In FIG. 5B, the toner loading cylinder 53 is moved to the loading position T2 while being separated from the sheet-like lid 225 of the unit developing device 22. The lower end portion of the sheet enters into the first chamber 222c of the unit developing device 22 from the slit 225a of the sheet-like lid 225 with the inner cylinder opening 531a opened to overlap the outer cylinder opening 532a.

  Accordingly, when the toner loading cylinder 53 is set at the retracted position T1, the toner in the toner loading cylinder 53 is prevented from leaking from the inner cylinder opening 531a, while the toner loading cylinder 53 is positioned at the loading position T2. In the set state, the toner in the toner loading cylinder 53 is supplied into the first chamber 222c of the unit developing device 22 through the inner cylinder opening 531a and the outer cylinder opening 532a.

  In the present embodiment, the angle θ between the direction in which the cylinder center of the toner loading cylinder 53 extends and the horizontal line is set to be larger than the repose angle of the toner, whereby the toner introduced into the toner loading cylinder 53 Clogging in the toner loading cylinder 53 is prevented. Incidentally, the repose angle of the toner is about 40 °, but the angle θ is set to about 70 °.

  The screw feeder 54 includes a screw shaft 541 concentric with the cylindrical center of the toner loading cylinder 53, and screw fins 542 that are formed concentrically and integrally on the peripheral surface of the screw shaft 541. The upper end portion of the screw shaft 541 protrudes from the toner loading cylinder 53 to the outside, and the screw gear 543 is fixed concentrically to the protruding portion. Then, the screw gear 543 is rotated around the axis by driving means (not shown), whereby the screw fins 542 are integrally rotated around the screw shaft 541, whereby the toner fed from the toner transfer pipe 51 is moved downward. It is forcibly moved toward.

  The elevating mechanism 55 applies a driving force to the pinion 552 via a rack 551 formed on the peripheral surface of the inner cylinder 531 and extending in the cylinder center direction, a pinion 552 that meshes with the rack 551, and a predetermined relay gear. And a drive motor (not shown). On the other hand, the outer cylinder 532 is provided with a notch window at a portion corresponding to the rack 551, and the rack 551 is exposed to the outside through the notch window. The notch window is set to have a circumferential length longer than the width dimension (circumferential length) of the rack 551, and can thereby rotate relative to the rack 551 around the cylinder center within a predetermined range.

  In addition, a guide projection (not shown) is provided at an appropriate position of the outer cylinder 532, and a cylindrical cam member surrounding the outer cylinder 532 is provided. A spiral cam groove is formed in which the guide protrusion is fitted in the sliding contact state. When the inner cylinder 531 moves up and down through the predetermined relay gear, pinion 552 and rack 551 by driving the drive motor, the toner loading cylinder 53 also moves up and down following this, and the toner loading cylinder 53 moves up and down. The guided projection is guided in the spiral cam groove of the cam member, and thereby the outer cylinder 532 rotates forward and backward around the cylinder center.

  In the present embodiment, the inner cylinder opening 531 a of the inner cylinder body 531 is moved by the outer cylinder body 532 due to the rotation of the outer cylinder body 532 in a predetermined direction when the toner loading cylinder 53 is set at the retracted position T1. On the other hand, the inner cylinder opening 531a of the inner cylinder 531 is rotated by the rotation of the outer cylinder 532 in the reverse direction when the toner loading cylinder 53 is set at the loading position T2. Overlapping with 532a is released.

  Next, returning to FIG. 3, the unit developing device 22 detects that the toner amount in the toner storage container 222 is equal to or less than a preset minimum toner amount necessary for performing image forming processing. The toner amount sensor 60 is provided. In the present embodiment, a light emitting member 61 including a light emitting element as a toner amount sensor 60, and a light receiving member 62 including a light receiving element that receives light emitted from the light emitting member 61 and converts the light into an electric signal. A so-called optical sensor consisting of:

  The toner amount sensor 60 is positioned slightly above the position where the developing sleeve 223 and the relay roller 224b are opposed to each other in the second chamber 222d of the toner storage container 222 in the unit developing device 22 in a state of facing the photosensitive drum 131. The installation position is set to detect whether toner is present at the remaining amount detection position. Specifically, as shown in FIG. 3 (A), the light emitting member 61 is installed through the portion of the front sector side plate 221 corresponding to the remaining amount detection position of the second chamber 222d, while the rear sector side plate. A light receiving member 62 is provided in a penetrating manner at a position facing the light emitting member 61 in the front-back direction of 221.

  By doing so, the remaining amount detection in the second chamber 222d of the unit developing unit 22 in a state where the unit developing unit 22 faces the photosensitive drum 131 (that is, a state in which the unit developing unit 22 is set to face the photosensitive drum). When the toner is not present at the position, the light emitted from the light emitting member 61 toward the light receiving member 62 is received by the light receiving member 62, so that the second chamber 222d of the toner storage container 222 is lower than the remaining amount detection position. It can be detected that toner is present only at the level.

  On the other hand, when the unit developing unit 22 is set in the posture opposite to the photosensitive drum and the toner exceeding the remaining amount detection position exists in the second chamber 222d of the unit developing unit 22, The light emitted from the light emitting member 61 toward the light receiving member 62 is blocked by the toner and is not received by the light receiving member 62, thereby causing the second chamber 222 d of the toner storage container 222 to be higher than the remaining amount detection position. The presence of toner can be detected at the level.

  The position at which the light emitting member 61 and the light receiving member 62 are provided (remaining amount detection position) is set in the second chamber 222d of the unit developing device 22 in a state where the unit developing device 22 is set to face the photosensitive drum. It is set so that the minimum amount of toner that can normally perform image forming processing on the peripheral surface of the photosensitive drum 131 can be secured by the remaining toner.

  The power supply to the light emitting member 61 is performed via a not-shown annular power line that is disposed to face the front surface of the rotary developing device 20 from a predetermined power supply device and is slidably contacted with the contact of the light emitting member 61. At the same time, the detection signal from the light receiving member 62 is output via an unillustrated annular signal line that is slidably contacted with the contact point of the light receiving member 62.

  In the present embodiment, the second chamber 222d of the unit developing device 22 is set in a state in which any of the four unit developing devices 22 is set to face the photosensitive drum. When the toner in the toner becomes less than the minimum required toner amount, the image forming process of this job is completed for the time being, and the toner remaining in the second chamber 222d of the unit developer 22 is removed from the photosensitive drum. Control for discharging toward the peripheral surface of 131 is performed.

  Then, new toner is supplied from the toner container 30 to the unit developing unit 22 in a state where the unit developing unit 22 is completely emptied.

  In order to perform such control, a control means 70 is provided at an appropriate position in the printer main body 11. Hereinafter, the control of the control means 70 will be described based on FIGS. 6 to 8 with reference to FIGS. FIG. 6 is a block diagram for explaining the control by the control means 70, and FIG. 7 is a flowchart for explaining the control by the control means 70.

  FIG. 8 is an explanatory diagram in cross-sectional view showing the state of toner in the unit developing device 22 set in a posture opposite to the photosensitive drum, and FIG. 8A is a diagram in which the toner storage container 222 is full. FIG. 8B shows a state where a minimum amount of toner remains in the toner storage container 222, and FIG. 8C shows a state where the residual toner in the toner storage container 222 is discharged. Each state is shown.

  First, as shown in FIG. 6, the control means 70 includes a CPU (central processing unit) 71 which is an arithmetic processing unit, and a read-only ROM (read only memory) 72 attached to the CPU 71. It has a basic configuration including a RAM (random access memory) 73.

  The ROM 72 stores a program for executing this control, and the program is read by the CPU 71 each time the printer 10 is turned on, and thereafter remains in the toner storage container 222 based on this program. Control for discharging the toner is executed. On the other hand, the RAM 73 is used as an area for temporarily writing and reading various data used temporarily in the control operation.

  The CPU 71 determines, based on the detection result of the toner amount sensor 60, whether or not the amount of toner in the unit developing device 22 set to the posture opposite to the photosensitive drum is less than the minimum required toner amount. A determination unit 711 and a control signal output unit 712 that outputs a control signal to various places based on the determination result of the toner amount determination unit 711 are provided.

  When the detection signal from the light receiving member 62 indicating that the light from the light emitting member 61 has been received is input to the toner amount determination unit 711, the toner amount determination unit 711 actually sets the posture of the unit developer 22 to be opposed to the photosensitive drum. It is determined that the amount of stored toner has become less than the minimum necessary toner amount, and a message to that effect is output to the control signal output unit 712.

  When the command signal from the toner amount determination unit 711 is input, the control signal output unit 712 continues execution to the end of the image forming process for one sheet that is currently being executed. The rotary developing device 20 (specifically, the rotary developing device 20 is driven) so that the unit developing device 22 whose toner amount has become the minimum required toner amount is set in a posture facing the photosensitive drum. A control signal is output to the drive motor (the same applies hereinafter). As a result, the target unit developing device 22 is set in a posture facing the photosensitive drum.

  In order to perform such control, the control signal output unit 712 outputs predetermined control signals associated with each other to the paper feeding unit 12, the image forming unit 13, and the fixing unit 14, and thereby the paper feeding unit 12 and the image forming unit 12 The unit in which the image forming process for one sheet P currently being executed by the linkage operation of the unit 13 and the fixing unit 14 is smoothly executed, and the toner amount thereafter becomes less than the minimum necessary toner amount. A predetermined process for the developing unit 22 is executed. In the series of these controls, the amount of stored toner, in particular, is less than the minimum required toner amount. A description will be given focusing on the control related to the unit developer 22 that faces each other.

  First, the control signal output unit 712 outputs a control signal to the charging roller 132 in a state where the target unit developing device 22 faces the peripheral surface of the photosensitive drum 131, and thereby the target unit development. Uniform light from the exposure device 133 is applied to the peripheral surface of the photosensitive drum 131 corresponding to the device 22 in a solid manner. By doing so, all of the residual toner remaining in the unit developing device 22 in accordance with the synchronous rotation of the photosensitive drum 131 and the developing sleeve 223 except for the toner deposited on the inner wall surface of the toner storage container 222 is light. The solid image is discharged to the peripheral surface of the photosensitive drum 131 irradiated with the solid, and a solid image with the toner is formed on the peripheral surface of the photosensitive drum 131. The solid image on the peripheral surface of the photosensitive drum 131 is transferred to the paper P fed from the paper feeding unit 12, fixed on the paper P by the fixing unit 14, and then discharged with the paper P. Are discharged to the paper discharge tray 161.

  Then, in a state where the unit developing device 22 is completely emptied (this state is realized by forming a solid image on the peripheral surface of the photosensitive drum 131), the control signal output unit 712 performs toner transfer. A control signal for lowering the toner loading cylinder 53 is output toward the driving means of the elevating mechanism 55 of the mechanism 50. By this control signal, the toner loading cylinder 53 is lowered and the leading end thereof is inserted into the slit 225a of the unit developing unit 22, and preparation for toner replenishment is completed.

  Subsequently, the control signal output unit 712 outputs a drive signal to the drive unit of the spiral feeder 511 of the toner transfer mechanism 50. The spiral feeder 511 is driven and rotated by this drive signal, and the toner in the toner container 30 is supplied into the unit developing device 22 via the toner transfer pipe 51 and the toner loading cylinder 53.

  A toner amount full sensor (not shown) that detects the full amount of toner in the unit developer 22 is provided in the first chamber 222c of the unit developer 22 in the vicinity of the slit 225a. When the amount sensor detects the full amount, the toner supply from the toner container 30 to the unit developing device 22 is stopped, but detailed description thereof is omitted.

  Hereinafter, the control flow by the control means 70 will be described based on the flowchart of FIG. 7 with reference to FIG. First, in a state where the full toner is loaded in the toner storage container 222 of the unit developer 22, as shown in FIG. 8A, the unit developer 22 has approximately 90% of the first chamber 222c. Are filled with the toner T, and the second chamber 222d is completely filled with the 100% toner T.

  In this state, since the light receiving member 62 of the toner amount sensor 60 is buried in the toner T, the light emitted from the light emitting member 61 cannot reach the light receiving member 62. Is not output.

  When the image forming process is executed in this state, the relay roller 224b is rotated clockwise around the roller center, and the developing sleeve 223 is also rotated clockwise around the axis, whereby the second roller 224b is rotated clockwise. The toner T in the chamber 222d is supplied to the peripheral surface of the photosensitive drum 131 from the peripheral surface of the developing sleeve 223 through the blade 227 with a predetermined layer thickness. That is, the printer 10 is set to the normal mode in which normal image forming processing is executed.

  In such a state, first, the toner T is required by the toner amount sensor 60 provided in the unit developing device 22 for the unit developing device 22 set in the posture facing the photosensitive drum in step S1. It is detected whether or not the toner amount is less than the minimum amount.

  In step S2, there is a unit developing unit 22 in which the toner T is less than the minimum necessary toner amount among the four unit developing units 22 (black to yellow unit developing units 22K, 22C, 22M, 22Y). If there is a unit developing device 22 in which the toner T is less than the minimum necessary toner amount in any unit developing device 22 (that is, YES in step S2), Which of the unit developers 22K, 22C, 22M, and 22Y for black to yellow is stored in the RAM 73 (step S3), and the next step S4 is subsequently executed. On the other hand, if the unit developer 22 is not less than the minimum necessary toner amount (NO in step S2), the process proceeds to step S4.

  Incidentally, as shown in FIG. 8B, the unit developing device 22 in which the toner T is the residual toner T ′ less than the necessary minimum toner amount is located above the position where the relay roller 224b and the developing sleeve 223 are opposed to each other. In addition, the light receiving member 62 is positioned below the light receiving element.

  In step S4, it is asked whether or not the detection processing by the toner amount sensor 60 has been performed for the four unit developing devices 22 of black to yellow 22K, 22C, 22M, and 22Y, and the detection processing is still executed. If there is a unit developer 22 that is not present (NO in step S4), the process returns to step S1.

  On the other hand, when the detection processing has been completed for all of the four black to yellow unit developers 22K, 22C, 22M, and 22Y (YES in step S4), the minimum necessary toner amount in step S5. It is determined whether or not there are less unit developing units 22 (this determination is made based on whether or not the unit developing unit 22 for which color of interest is stored in the RAM 73).

  If it does not exist (NO in step S5), the process returns to step S1, whereas if it exists (YES in step S5), the image for the currently executed sheet is targeted. After the formation process is completed, the printer 10 changes the processing mode from the normal mode to the toner supply mode (step S6).

  Subsequently, in step S7, the unit developing device 22 having a toner amount less than the necessary minimum toner amount is sequentially changed to the posture opposite to the photosensitive drum, and the residual toner T ′ in the second chamber 222d of the toner storage container 222 is removed from the photosensitive member. A process of discharging toward the peripheral surface of the drum 131 is executed. By doing so, as shown in FIG. 8C, toner T does not exist at all except for the toner fixed and accumulated on the inner wall surface of the toner storage container 222, etc.

  Next, the toner T from the toner container 30 is supplied to the unit developing device 22 that has discharged the residual toner T ′ (step S8). In this replenishment, the toner loading cylinder 53 is lowered by driving the elevating mechanism 55 according to the control signal from the control signal output unit 712 and the leading end thereof is inserted into the unit developing device 22, and then the toner container is driven by the rotation of the spiral feeder 511. This is done by feeding the toner in 30 into the unit developer 22. When the replenishment is completed, the printer 10 is returned from the toner replenishment mode to the normal mode, and a normal image forming process can be performed.

  In this embodiment, when the unit developer 22 is full immediately after the toner T is replenished (see FIG. 8A), the full toner amount is 40 g. Further, when empty in the unit developer 22 is detected by the toner amount sensor 60 (that is, when the toner amount in the unit developer 22 becomes less than the minimum required toner amount (see FIG. 8B)). The amount of toner in the unit developer 22 was 12 g. The amount of toner remaining in the unit developer 22 after the residual toner T ′ in the unit developer 22 was discharged toward the photosensitive drum 131 was 9 g. This is a deteriorated toner in which 3 g of toner, which is a value obtained by subtracting 9 g from 12 g, is discharged from the toner storage container 222.

  As can be seen from the above description, in the present invention, after detecting that the developing device (unit developing unit 22 in this embodiment) is in a so-called toner empty state, the unit developing unit 22 is immediately replenished with toner. Instead, the toner remaining in a small amount in the unit developing device 22 is forcibly discharged to the photosensitive drum 131 side, and the residual toner amount in the unit developing device 22 is made substantially zero, and then the toner T is transferred to the unit developing device 22. It is configured to replenish.

That is, the present invention has the following two important feature points.
(1) After detecting that the inside of the unit developing device 22 is in a toner empty state, the residual toner still remaining in the unit developing device 22 is forcibly discharged and then transferred from the toner container 30 to the unit developing device 22. Control so that toner is replenished.
(2) The toner empty is an amount (a necessary minimum toner amount) such that the toner T cannot be supplied so that the image density can be maintained over the entire length of the developing sleeve 223 in the axial direction. It must remain inside.

  On the other hand, the concept of toner empty of the conventional developing device indicates a state in which the amount of toner that can be printed on several sheets of paper P remains in the developing device even if it becomes empty.

  Also, in a conventional developing device that replenishes toner from a toner container, toner is replenished from the toner container so that the toner amount is always substantially constant, and the developing device becomes empty after the toner container becomes empty. On the other hand, in the developing device of the present invention (rotary developing device 20 in this embodiment), the toner amount in the unit developing device 22 is not maintained constant, and the toner T in the unit developing device 22 is empty. In this case, the toner is forcibly discharged and then the toner T is supplied from the toner container 30.

  As described above in detail, the rotary developing device 20 according to this embodiment supplies one-component toner to the surface of the photosensitive drum 131 on which the electrostatic latent image is formed, and follows the electrostatic latent image. A plurality of unit developing devices 22 for forming a toner image, a plurality of toner containers 30 for supplying toner to the corresponding unit developing devices 22, and the amount of toner in the unit developing device 22 is normally imaged on the photosensitive drum 131. The toner amount sensor 60 that detects that the toner amount is less than the minimum necessary amount necessary for performing the forming process, and the toner amount sensor 60 detects that the inside of the unit developer 22 is less than the minimum toner amount necessary. The control means 70 is configured to control the toner container 30 to supply the toner to the unit developing device 22 based on the detection signal only when the detection signal is detected.

  The control unit 70 is configured to control the remaining toner to be discharged toward the photosensitive drum 131 when the toner amount sensor 60 detects that the toner amount is less than the minimum necessary amount.

  Accordingly, since the toner is not supplied from the toner container 30 to the unit developing device 22 until the toner amount becomes less than the minimum necessary amount capable of performing normal image forming processing, the toner is still present in the unit developing device 22. When toner is supplied from the toner container 30, a large amount of replenishment toner and a large amount of residual toner are mixed with each other, and the charged state and the magnetized state of the toner are disturbed, thereby causing a fog phenomenon in the image forming process. However, the present invention can effectively prevent the occurrence of such inconvenience.

  In addition, the control means 70 controls the remaining toner to be discharged toward the photosensitive drum 131 when the toner amount sensor 60 detects that the amount of toner is less than the minimum necessary amount, thereby remaining in the unit developer 22. The remaining toner that has been used is completely removed except for the toner fixed in the unit developing device 22, and new toner is supplied from the toner container 30 in a state where the unit developing device 22 is substantially empty. Therefore, when there is a residual toner less than the necessary minimum toner amount in the unit developing unit 22, a small amount of the residual toner is reversely charged, and the toner is generated by electrostatic repulsion between the residual toner and the new toner. During the replenishment, the residual toner in the unit developing device 22 does not scatter toward the outside, and the inconvenience that the scattered toner is contaminated in the image forming apparatus. It is possible to prevent.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the printer 10 has been described as an example of the image forming apparatus to which the developing device according to the present invention is applied. The present invention is also applicable to copying machines and facsimile machines.

  (2) In the above embodiment, the rotary developing device 20 for color printing composed of a plurality of unit developing devices 22 is adopted as the developing device. However, in the present invention, the developing device is for monochrome printing. Even if it is for color printing, it is not limited to the rotary developing device 20, but a so-called tandem developing device in which unit developing devices of each color are arranged in parallel in the horizontal direction. Also good.

  (3) In the above-described embodiment, an example in which a so-called photosensor including a light receiving member 62 including a light receiving element is employed as the light emitting member 61 including the light emitting element as the toner amount sensor 60 has been described. Instead of this, a limit switch type that mechanically detects the presence of toner by kicking the striker, and a capacitance type that detects the presence or absence of toner by detecting the electrostatic capacity of the toner in the unit developing device 22. The thing etc. can also be used.

1A and 1B are perspective views of an appearance of a printer to which a developing device according to the present invention is applied, in which FIG. 1A is a state in which a maintenance lid is closed, and FIG. 2B is a state in which a maintenance lid is opened. , (C) respectively show a state where the maintenance lid is opened and the toner container is removed. It is explanatory drawing of the side sectional view which shows one Embodiment of the internal structure of the printer shown in FIG. 2A and 2B are diagrams illustrating an embodiment of a unit developing device, in which FIG. 3A is a perspective view and FIG. 3B is an enlarged sectional view taken along line IIIB-IIIB in FIG. FIG. 3 is a schematic perspective view illustrating a relative positional relationship among a rotary developing device, a toner container, a pedestal, and a toner transfer mechanism. 2A and 2B are cross-sectional views illustrating an embodiment of a toner loading device, in which FIG. 3A illustrates a state in which the toner loading cylinder is set at a retracted position, and FIG. 3B illustrates a state in which the toner loading cylinder is set at a loading position. Each is shown. It is a block diagram for demonstrating control by a control means. It is a flowchart for demonstrating control by a control means. FIG. 4 is a cross-sectional explanatory view showing a state of toner in a unit developing device set in a posture opposite to a photosensitive drum, (A) is a state where a full toner is loaded in a toner storage container; ) Shows a state where the minimum necessary toner remains in the toner storage container, and (C) shows a state where the residual toner in the toner storage container is discharged.

10 Printer (image forming device)
DESCRIPTION OF SYMBOLS 11 Printer main body 101 Discharge conveyance path 102 Discharge roller pair 110 Front opening 111 Side plate 112 Maintenance lid 12 Paper feed part 121 Paper cassette 122 Tray 122a Support shaft 123 Pickup roller 124 Registration roller pair 13 Image forming part 131 Photosensitive drum (image carrier) body)
132 charging roller 133 exposure device 134 transfer belt 134a driving roller 134b driven roller 134c idle roller 134d biasing member 135 primary transfer roller 136 secondary transfer roller 137 drum cleaning device 138 belt cleaning device 14 fixing unit 141 fixing roller 142 pressure roller 143 Discharge roller pair 15 Discharge destination switching unit 151 Return roller 152 Return conveyance path 16 Paper discharge unit 161 Paper discharge tray 162 Paper discharge port 10a Developing device 20 Rotary developer (developing unit)
21 Rotating frame 211 Frame shaft 212 Partition plate 22 Unit developing unit 22K Black unit developing unit 22C Cyan unit developing unit 22M Magenta unit developing unit 22Y Yellow unit developing unit 221 Fan-shaped side plate 222 Toner storage container 222a Toner introduction opening 222b Arc top plate 222c First chamber 222d Second chamber 223 Developing sleeve 224 Agitating and conveying member 224a Screw feeder 224b Relay roller 225 Sheet-like lid 225a Slit 226 Partition plate 226a Contact opening 227 Blade 30 Toner container (replenisher)
30K Black container 30C Cyan container 30M Magenta container 30Y Yellow container 40 Base 50 Toner transfer mechanism 51 Toner transfer pipe 511 Spiral feeder 52 Toner loading device 53 Toner loading cylinder 531 Inner cylinder 531a Inner cylinder opening 532 Outer cylinder 532a Outer cylinder opening 54 Screw feeder 541 Screw shaft 542 Screw fin 543 Screw gear 55 Lifting mechanism 551 Rack 552 Pinion 60 Toner amount sensor 61 Light emitting member 62 Light receiving member 70 Control means 71 CPU
711 Toner amount determination unit 712 Control signal output unit 72 ROM
73 RAM P Paper Q1 Closed position Q2 Opened position T Toner T 'Residual toner T1 Retraction position T2 Loading position

Claims (2)

A developing unit for supplying a one-component toner to the surface of the image carrier on which the electrostatic latent image is formed to form a toner image along the electrostatic latent image;
A replenishing unit for replenishing toner to the developing unit;
A toner amount detecting means for detecting that the toner amount in the developing unit is less than a set value set in consideration of a minimum toner amount necessary for normally performing image forming processing on the image carrier; ,
Control means for controlling the replenishing unit to replenish toner to the developing unit when the toner amount detecting unit detects that the toner amount in the developing unit is less than the set value ;
When the toner amount detecting unit detects that the toner amount is less than the set value, prior to the replenishment of the toner from the replenishing unit to the developing unit, the control unit transfers the toner remaining in the developing unit to the image carrier. Control it to exhale,
The toner amount detection means includes
A density sensor for detecting the density of the toner image on the image carrier;
Forming means for forming a 100% solid pattern image and a blank pattern image on the image carrier in a state in which the duty of the development AC bias is lower than the normal development conditions;
Judgment means for judging that the toner amount in the developing unit is less than the set value when the density sensor detects that the density of the blank pattern image is higher than the density of the 100% solid pattern image. And a developing device. The control means controls to form a uniform solid electrostatic latent image on the entire surface of the image carrier to be developed by the developing unit so as to correspond to the discharge of the toner. The developing device according to claim 1, wherein:

Images