JP2008299229A - Developing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of efficiently cooling a developer to prevent the formation of a lump of the developer due to the melting of toner and capable of reducing the temperature rise of a toner concentration sensor to carry out stable toner supply control, and to provide an image forming device. <P>SOLUTION: The developing device 20 includes: a receiving carrier screw 35 carrying the spent developer received from a developing roll 21 to a rotation axis direction; an agitating carrier screw 38 receiving the developer supplied from the receiving carrier screw 35 and carrying it to the rotation axis direction; and a feeding carrier screw 32 receiving the developer supplied from the agitating carrier screw 38 and supplying it to the developing roll 21 while carrying it in the rotation axis direction. A ventilating means 47 is provided on the outside of a member constituting a developer agitation chamber 29 in which the agitating carrier screw 38 is enclosed, to ventilate upstream from downstream in the developer carrying direction of the agitating carrier screw 38. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device that supplies a developer to a developer carrier such as a developing sleeve while conveying the developer with a conveying screw, and an image forming apparatus using the developing device.

2. Description of the Related Art Conventionally, in a developing device using a developer containing toner and a magnetic carrier, a developer carrying member is conveyed in the direction of its rotation axis by a supply and carrying screw disposed on the side of the developer carrying member. What supplies to the whole area of the longitudinal direction of is known. In this type of developing device, the developer that has contributed to the development is recovered from the developer carrier while the developer is supplied to the developer carrier by the supply and transport screw. Then, the developer transported to the downstream end of the supply transport screw in the agent transport direction is transferred to another transport screw. Next, after the transferred developer is transported while being mixed with the replenishing toner, the developer is returned to the upstream end of the supply transport screw in the agent transport direction. By carrying out such a circulating conveyance of the developer, the developer whose toner concentration has been recovered by replenishing the toner while the developer whose toner concentration has been reduced by the development is recovered from the developer carrier, the developer carrier. Can be supplied to.
However, in such a configuration, the developing density may be gradually reduced from the upstream side to the downstream side in the agent conveyance direction of the supply conveyance screw. In the vicinity of the upstream of the supply conveyance screw in the agent conveyance direction, most of the developer is occupied by the developer immediately after the concentration recovery, whereas as it goes downstream in the agent conveyance direction, used developer recovered from the developer carrier is collected. This is because the ratio of the developer increases.
On the other hand, Patent Document 1 describes a developing device that performs recovery of a developer from a developer carrying member and supply of the developer to the developer carrying member using separate transport screws.
The developing device includes a supply conveyance screw that supplies developer to the developer carrying member, a receiving conveyance screw disposed immediately below the developer conveyance body, and a side of these screws aligned in the vertical direction, and is oblique to the horizontal direction. And an inclined conveying screw arranged to take a posture. Then, toner is supplied to the used developer received from the developer carrying member by the receiving and conveying screw to restore the toner density of the developer, and then transferred to the inclined conveying screw. The inclined conveying screw conveys the developer sent from the receiving and conveying screw with an ascending gradient and sends it to a supply conveying screw disposed immediately above the receiving and conveying screw.

In such a configuration, the developer pumped up from the supply conveyance screw to the developer carrier is collected by the receiving conveyance screw and does not return to the supply conveyance screw, so that the amount of developer decreases in the supply conveyance screw as it goes downstream. . Therefore, uneven development density corresponding to the screw pitch is likely to occur downstream of the supply / conveyance screw.
In order to prevent uneven development density downstream of the supply / conveyance screw, a method is considered in which the rotation speed of the supply / conveyance screw and other conveyance screws is set to a high value so that a sufficient amount of developer is secured downstream of the supply / conveyance screw. It is done. However, when the number of rotations of the conveying screw is increased, the amount of heat generated by the developer increases, and there is a problem that the toner melts and the developer is likely to lump. Furthermore, there is a problem in that the toner density sensor is erroneously detected due to the influence of the temperature rise of the developer, and the toner replenishment control becomes unstable.

JP 2001-249545 A

  Accordingly, the present invention has been made in view of the above problems, and the problem is that the developer can be efficiently cooled to prevent the toner from melting and the developer from clumping, and to a toner concentration sensor. It is an object of the present invention to provide a developing device and an image forming apparatus capable of reducing toner temperature rise and performing stable toner supply control.

The features of the present invention, which is a means for solving the above problems, are listed below.
The developing device of the present invention includes a developer carrying member for developing a latent image on a latent image carrying member with a developer containing toner and a carrier carried on the surface, and a used development received from the developer carrying member. A receiving and conveying screw that conveys the agent in the direction of the rotation axis, a stirring and conveying screw that receives the developer sent from the receiving and conveying screw and that conveys the developer in the direction of the rotating axis, and a developer that is sent from the agitating and conveying screw In a developing device including a supply and transport screw that supplies the developer carrying member while transporting in the direction of the rotation axis, the stirring and transport screw is outside the member constituting the agent stirring chamber in which the stir and transport screw is housed. A ventilation means for ventilating from the downstream to the upstream in the developer conveying direction is provided.
Further, the developing device of the present invention detects the proportion of toner in the developer in the developing device at a position corresponding to the downstream of the stirring and conveying screw in the developer conveying direction and upstream of the ventilation direction. A member is arranged.
Further, in the developing device of the present invention, the agitating and conveying screw is disposed obliquely so that the downstream of the agitating and conveying screw is higher in the upstream direction than the upstream in the developer conveying direction, and further the agitating and conveying screw is accommodated. The heat dissipating fins are formed outside the members constituting the agent stirring chamber, and the height of the heat dissipating fins increases from the upstream to the downstream in the developer transport direction of the stirring transport screw. To do.

  Further, the image forming apparatus of the present invention is an image forming apparatus comprising at least an image carrier that forms an electrostatic latent image and a developing device that develops the electrostatic latent image to make it visible. The apparatus includes the developing device described above.

  According to these inventions, the developer can be efficiently cooled to prevent the toner from melting and the developer from clumping, and the toner concentration sensor can be prevented from rising in temperature and stably controlled to supply toner. In addition, an image forming apparatus can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic color laser printer (hereinafter simply referred to as a printer) will be described.
First, a basic configuration of the printer according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram showing a main part of a printer according to an embodiment of the present invention.
This printer includes four toner image forming units 1M, C, Y, and K for forming toner images of respective colors of magenta, cyan, yellow, and black (hereinafter referred to as M, C, Y, and K). Yes. Further, a transfer unit 50 is provided on the side of the toner image forming portions 1M, 1C, 1Y, and 1K arranged in the vertical direction.
The toner image forming units 1M, C, Y, and K have substantially the same configuration except that the color of the toner used is different. The M toner image forming unit 1M for forming an M toner image will be described. The toner image forming unit 1M includes a process unit 2M, an optical writing unit 10M, and a developing unit 20M.

The process unit 2M for M has a charging device 4M, a drum cleaning device 5M, a static elimination lamp 6M, etc. around a drum-shaped photoconductor 3M that is driven to rotate counterclockwise in the figure. It is held in a common casing and can be integrally attached to and detached from the printer body.
The photoreceptor 3M is obtained by coating an organic photosensitive layer on an element tube such as aluminum.
The charging device 4M uniformly charges the surface of the photosensitive member 3M, which is driven to rotate counterclockwise in the drawing, to a negative polarity, for example, by corona charging.
The optical writing unit 10M includes a light source composed of a laser diode or the like, a regular hexahedral polygon mirror, a polygon motor for rotationally driving the mirror, an fθ lens, a lens, a reflection mirror, and the like. A laser beam L emitted from a light source driven on the basis of image information sent from a personal computer (not shown) is reflected on the polygon mirror surface and deflected as the polygon mirror rotates, so that the photosensitive member 3M. To reach. As a result, the surface of the photoreceptor 3M is optically scanned, and an electrostatic latent image for M is formed on the surface of the photoreceptor 3M.

The developing unit 20M for M has a developing roll 21M that exposes a part of the peripheral surface from an opening provided in the casing.
The developing roll 21M has a developing roll 21 made of a non-magnetic pipe that is driven to rotate by a driving means (not shown), and a magnet roller (not shown) that is included so as not to rotate. In the developing unit 20M, an M developer (not shown) including a magnetic carrier and a negatively chargeable M toner is included. The M developer is agitated and conveyed by an agitating and conveying screw to be described later, and while the frictional charging of the M toner is promoted, the M developer is attracted to the surface of the developing roll 21 rotating the developing roll 21M by the magnetic force of the magnet roller in the developing roll 21M. Pumped up. Then, after passing through the position facing the developing doctor 25M as the developing roll 21 rotates, the layer thickness is regulated, and then the sheet is transported to the developing region facing the photoreceptor 3M.
In this development area, negative M toner is latently transferred from the sleeve side between the developing roll 21 to which a negative development bias output from a power source (not shown) is applied and the electrostatic latent image on the photoreceptor 3M. A developing potential for electrostatically moving to the image side acts. Further, a non-developing potential for electrostatically moving the negative M toner from the background side to the sleeve side acts between the developing roll 21 and the uniformly charged portion (background portion) of the photoreceptor 3M. The M toner in the M developer on the developing roll 21 is separated from the sleeve by the action of the developing potential and transferred onto the electrostatic latent image on the photoreceptor 3M. By this transfer, the electrostatic latent image on the photoreceptor 3M is developed, and an M toner image is formed. The M developer that has consumed M toner by the development is returned to the casing as the developing roll 21 rotates. Further, the M toner image on the photoreceptor 3M is intermediately transferred onto an intermediate transfer belt 51 of a transfer unit 50 described later.

  The developing unit 20M has a toner concentration sensor (not shown) composed of a magnetic permeability sensor. This toner concentration sensor outputs a voltage having a value corresponding to the magnetic permeability of the M developer accommodated in the agent stirring chamber described later of the developing unit 20M. Since the magnetic permeability of the developer shows a good correlation with the toner concentration of the developer, the toner concentration sensor outputs a voltage having a value corresponding to the toner concentration. The value of the output voltage is sent to a toner supply control unit (not shown). This toner replenishment control unit is provided with storage means such as a RAM, in which M Vtref, which is a target value of the output voltage from the M toner density sensor, and toner density mounted in other developing units. Vtref data for C, Y, M, which is a target value of the output voltage from the sensor, is stored. For the M developing unit 20M, the output voltage value from the M toner density sensor is compared with the M Vtref, and the M toner replenishing device (not shown) is driven for a time corresponding to the comparison result. As a result, M toner for replenishment is replenished into the agent recovery chamber of the developing unit 20M. By controlling the driving of the M toner replenishing device in this way (toner replenishment control), an appropriate amount of M toner is replenished to the M developer whose M toner density has been reduced along with development, and the inside of the developing unit 20M. The M toner concentration of the M developer is maintained within a predetermined range. The same toner replenishment control is performed for the developing units 20C, 20Y, and 20K.

The M toner image developed on the photoreceptor 3M is transferred to the front surface of an intermediate transfer belt 51 described later. Untransferred toner that has not been transferred onto the intermediate transfer belt 51 adheres to the surface of the photoreceptor 3M that has undergone the transfer process. This transfer residual toner is removed by the drum cleaning device 5K. The surface of the photoreceptor 3M from which the transfer residual toner has been removed in this way is discharged by the discharging lamp 6M and then charged again by the charging device 6K.
The toner image forming unit 1M for M has been described in detail. However, in the toner image forming units 1C, Y, and K for other colors, C, Y, and K toners are formed on the surfaces of the photoreceptors 3C, Y, and K by the same process. An image is formed.
A transfer unit 50 is disposed on the right side of the toner image forming portions 1M, 1C, 1Y, and 1K arranged in the vertical direction. The transfer unit 50 includes a driving roller 52, a tension roller 53, and a driven roller 54 inside a loop of an endless intermediate transfer belt 51. Then, while the intermediate transfer belt 51 is stretched by these three rollers, it is moved endlessly in the clockwise direction in the drawing by the rotational drive of the drive roller 52. The intermediate transfer belt 51 moved endlessly in this manner has its front surface on the left side of the drawing in contact with the M, C, Y, and K photoconductors 3M, C, Y, and K, respectively. This forms primary transfer nips for M, C, Y, and K.

In addition to the three rollers described above, four transfer chargers 55M, C, Y, and K are disposed inside the loop of the intermediate transfer belt 51. These transfer chargers 55M, C, Y, and K are disposed on the back side of the primary transfer nip for M, C, Y, and K so as to apply charges to the back surface of the intermediate transfer belt 51. By applying this electric charge, the toner is transferred in the primary transfer nip for M, C, Y, K in such a direction that the toner is electrostatically moved from the photoconductor 3M, C, Y, K side to the belt front side. An electric field is formed. A transfer roller to which a transfer bias is applied may be used instead of the corona charge type transfer charger.
The M, C, Y, and K toner images formed on the photoreceptors 3M, C, Y, and K of the respective colors are placed on the belt from the photoreceptor side by the influence of the nip pressure and the transfer electric field in the primary transfer nip of each color. The image is moved to the surface side and transferred onto the intermediate transfer belt 51 in a superimposed manner. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 51.
A secondary transfer bias roller 56 is in contact with the driving roller 52 on the intermediate transfer belt 51 from the belt front surface side, thereby forming a secondary transfer nip. A secondary transfer bias is applied to the secondary transfer bias roller 56 by a voltage applying means including a power source and wiring (not shown). As a result, a secondary transfer electric field is formed between the secondary transfer bias roller 56 and the grounded driving roller 52. The four-color toner image formed on the intermediate transfer belt 51 enters the secondary transfer nip as the belt moves endlessly.

The printer includes a paper feed cassette (not shown), and accommodates a recording paper bundle in which a plurality of recording papers P are stacked therein. Then, the uppermost recording paper P is sent out to the paper feed path at a predetermined timing. The fed recording paper P is sandwiched between the rollers of the registration roller pair 60 disposed at the end of the paper feed path.
The registration roller pair 60 rotates both rollers in order to sandwich the recording paper P sent from the paper feed cassette between the rollers. However, as soon as the leading edge of the recording paper P is sandwiched, both rollers rotate. Stop. Then, the recording paper P is sent toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 51. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 51 are collectively transferred onto the recording paper P by the action of the secondary transfer electric field and the nip pressure. A full color image is formed in combination with the white color of the recording paper P. The recording paper P on which the full-color image is formed in this manner is discharged from the secondary transfer nip, and then sent to a fixing device (not shown) to fix the full-color image.
The secondary transfer residual toner adhering to the surface of the intermediate transfer belt 51 after passing through the secondary transfer nip is removed from the belt surface by a belt cleaning device 57 that sandwiches the intermediate transfer belt 51 with the driven roller 54. Is done.

(First embodiment)
FIG. 2 is a longitudinal sectional view showing the configuration of the developing unit. FIG. 3 is a cross-sectional view taken along the line AA ′ of the developing unit, and is a configuration diagram showing the developing unit and the photoconductor of the toner image forming unit. FIG. 4 is a cross-sectional view taken along the line BB ′ of the developing unit and is a cross-sectional view showing one end side of the three conveyance chambers in the developing unit. FIG. 5 is a cross-sectional view taken along the line CC ′ of the developing unit and is a cross-sectional view showing the other end side of the three conveyance chambers. Here, similarly to the above, an M toner developing unit and the like are shown.
The developing device of the present invention is provided with a ventilation path that is outside of the agent stirring chamber in which the stirring and conveying screw is housed and vents from the downstream to the upstream in the rotation axis direction for conveying the developer of the stirring and conveying screw. It was.
In FIG. 2, the drum-shaped photoconductor 3M is arranged in such a posture that its axial direction extends in a direction perpendicular to the drawing sheet. The developing unit 20M has a developing chamber 26M, an agent supply chamber 27M, an agent recovery chamber 28M, and an agent agitating chamber 29M, and M developer (not shown) is accommodated in these chambers.
Further, the developing roll 21M described above is rotatably accommodated in the developing chamber 26M. Further, a supply / conveying screw 32M is rotatably accommodated in the agent supply chamber 27M. In addition, a receiving and conveying screw 35M is rotatably accommodated in the agent recovery chamber 28M. In the agent stirring chamber 29M, a stirring / conveying screw 38M is rotatably accommodated.
As described above, the developing roll 21M includes the developing roll 21 made of a non-magnetic pipe that is driven to rotate in the clockwise direction in the drawing by a driving unit such as a motor or a drive transmission system (not shown). And a magnet roller (not shown) included.

The developing chamber 26M that accommodates the developing roll 21M has an opening in the wall on the side facing the photoconductor 3M, and a part of the peripheral surface of the developing roll 21 is exposed therefrom. The developer supply chamber 27M and the agent recovery chamber 28M communicate with each other on the opposite side of the developing chamber 26M from the side facing the photoreceptor 3M over the entire area in the axial direction of the developing roll 21M. The agent supply chamber 27M is disposed directly above the agent recovery chamber 28M in the vertical direction. Both of the agent supply chamber 27M and the agent recovery chamber 28M extend across the entire length in the longitudinal direction on the right side (photoconductor side) in the drawing. It communicates with the developing chamber 26M.
The supply / conveying screw 32M accommodated in the agent supply chamber 27M has a posture extending in the horizontal direction, like the photoreceptor 3M and the developing roll 21M. Then, the rod-shaped rotary shaft member 33M and the screw blade 34M that is spirally provided on the peripheral surface of the rod-shaped rotary shaft member 33M are integrated in a counterclockwise direction in the figure by driving means such as a motor or a drive transmission system (not shown). Is driven to rotate.

Similarly to the photosensitive member 3M, the developing roll 21M, and the supply and transport screw 32M, the receiving and transporting screw 35M accommodated in the agent recovery chamber 28M also takes a posture extending in the horizontal direction. Then, the rotating shaft member 36M and the screw blade 37M are integrally rotated in the clockwise direction in the drawing by a driving means (not shown).
An agent stirring chamber 29M is adjacent to the developer supply chamber 27M and the agent recovery chamber 28M on the side opposite to the developing chamber 26M side. Unlike the other chambers, the agent stirring chamber 29M is formed to extend in a posture inclined from the horizontal direction. Further, the stirring and conveying screw 38M in which the screw blade 40M is erected on the peripheral surface of the rotating shaft member 39M also extends in an inclined posture in the agent stirring chamber 29M, and is shown in the drawing by a driving means (not shown). It is driven to rotate counterclockwise. Most of the agent stirring chamber 29M is partitioned from the agent supply chamber 27M and the agent recovery chamber 28M by a partition wall 30M. However, a part is communicated with the agent supply chamber 27M and the agent recovery chamber 28M through an opening (not shown) provided in the partition wall 30M.
In the agent supply chamber 27M, the M developer (not shown) held in the blades of the supply / conveyance screw 32M moves from the front side to the back side in the direction perpendicular to the drawing sheet as the supply / conveyance screw 32M rotates. Be transported. In the course of this conveyance, the M developer is sequentially supplied to the developing roll 21 in the developing chamber 26M as indicated by an arrow A in the drawing, and is pumped up to the developing roll 21 by the magnetic force of the magnet roller in the developing roll 21M. The M developer transported to the vicinity of the downstream end in the agent transport direction of the supply transport screw 32M (near the rear end in the figure) without being pumped up by the developing roll 21, as indicated by the arrow C in FIG. It falls into the agent recovery chamber 28M from a drop opening provided in the bottom wall of the supply chamber 27M.

In FIG. 2 described above, the M developer that has been transported to the above-described development area and contributed to the development as the developing roll 21 rotates, and then the developing chamber 26 </ b> M and the agent recovery as the developing roll 21 rotates. It is conveyed to the communication position with the chamber 28M. Then, after separating from the sleeve surface due to the influence of the repulsive magnetic field formed by the magnet roller, it falls into the agent recovery chamber 28M as indicated by an arrow B in the figure.
In FIG. 3, in the agent recovery chamber 28M, the M developer (not shown) held in the blades of the receiving and conveying screw 35M is moved from the front side in the direction perpendicular to the drawing sheet with the rotation of the receiving and conveying screw 35M. It is conveyed to the side. In the course of this conveyance, M toner is supplied by the above-described toner supply device. Further, the M developer falling from the drop opening of the agent supply chamber 27M is taken in. Thereafter, the M developer transported to the vicinity of the downstream end of the receiving transport screw 35M in the agent transport direction (near the rear end in the figure) passes through the opening 31M of the partition wall 30M as indicated by an arrow D in FIG. Then, it enters the agent stirring chamber 29M.
The M developer that has entered the agent stirring chamber 29M is taken into the upstream end of the stirring and conveying screw 38M in the agent conveying direction. Then, along with the rotation of the agitating and conveying screw 38M disposed in an obliquely upward posture from the upstream to the downstream in the developer conveying direction, the developer is conveyed with an ascending gradient as indicated by an arrow G in FIG. When transported to the vicinity of the downstream end of the stirring and transporting screw 38M in the agent transport direction, as shown by an arrow H in FIG. 5, it returns to the agent supply chamber 27M through the return opening 43M provided in the partition wall 30M. And it is taken in into the agent conveyance direction upstream edge part of the supply conveyance screw 32M. An area indicated by a symbol W in FIG. 4 indicates an image formable area in the axial direction of the photosensitive member.

In the printer having the above configuration, each of the four photosensitive members 3M, 3C, 3Y, and 3K functions as a latent image carrier that carries a latent image on a surface that moves endlessly by rotation. Further, the optical writing units 10M, C, Y, and K function as a latent image forming unit that forms a latent image on the surface of the uniformly charged photoreceptor. The developing units 20M, C, Y, and K for the respective colors function as developing devices that develop the latent images on the surfaces of the photoreceptors 3M, C, Y, and K, respectively.
Next, a characteristic configuration of the printer will be described.
In the developing unit of the printer, as shown in FIGS. 3 to 6, the members constituting the agent recovery chamber 28M in which the recovery conveyance screw 32M is accommodated and the agent agitation chamber 29M in which the agitation conveyance screw 38M is accommodated. In the lower part of the drawing, a ventilation path 47M for suppressing heat generation of the developing unit 20M and the M developer is constituted by a case 41M. Even if this ventilation path 47M is provided, air flows and the agent stirring chamber 29M and the like in contact with it can be cooled.
Further, a ventilation means 46M for ventilating the stirring and conveying screw 29M from the downstream to the upstream in the developer conveying direction may be provided. A fan is preferably used as the ventilation means 46M. The device is simple and can be miniaturized. In the present embodiment, as shown in FIG. 6 to be described later, the ventilation means 46M is installed on the downstream side in the developer conveying direction of the stirring and conveying screw 29M. However, the ventilation means 46M is arranged in the developer conveying direction of the stirring and conveying screw 38M. It may be installed upstream.

  The developer is transferred to the supply and transport screw 35M downstream of the agitating and conveying screw 38M in the developer conveying direction, but the developer stays downstream of the agitating and conveying screw 38M because the developer conveying path is folded back. The developer tends to generate heat due to frictional heat between the developers and members constituting the agent stirring chamber 29M. For this reason, by installing the ventilation means 46M that vents the agitating / conveying screw 38M from the downstream to the upstream in the developer conveying direction, the agitating / conveying screw 38M in which the low-temperature air outside the developing unit 20M is liable to cause the developer friction. Since the developer passes from the downstream side in the developer conveyance direction, the developer can be cooled efficiently, and the toner can be prevented from melting and the developer from being lumped.

[Second Embodiment]
FIG. 6 shows a second embodiment of the present invention. As shown in FIG. 6, a toner concentration sensor 45M is installed near the downstream of the stirring and conveying screw 38M in the agent conveying direction, that is, at a position corresponding to the upstream of the agitating and conveying screw 38M passing from the downstream to the upstream in the developer conveying direction. Yes. In such a configuration, since the toner density sensor 45M is installed on the upstream side in the ventilation direction, air having a low temperature outside the developing unit 20M passes through the vicinity of the toner density sensor 45M, so that the temperature of the toner density sensor 45M is increased. It can be reduced, and performance modulation due to temperature change can be prevented. Further, by installing the toner concentration sensor 45M near the downstream of the stirring and conveying screw 38M in the agent conveyance direction, the toner replenished from the toner replenishing device (not shown) passes through the toner concentration sensor 45M while being sufficiently agitated with the developer. Since the toner density can be detected, stable toner supply control can be performed.

[Third Embodiment]
3 to 6 show a third embodiment of the present invention. As shown in FIGS. 3 to 6, the stirring and conveying screw 38M is disposed obliquely so that the downstream of the stirring and conveying screw 38M is higher upward than the upstream in the developer conveying direction, and the stirring and conveying screw 38M is accommodated. The heat dissipating fins 42M are formed outside the members constituting the agent stirring chamber 29M. Since the agitating and conveying screw 38M is arranged so that the downstream side is higher than the upstream side in the developer conveying direction, the space below the agent agitating chamber 29M is larger in the downstream side than in the upstream in the developer conveying direction. The height of the heat dissipating fins 42M can be increased from the upstream in the developer conveying direction of the stirring and conveying screw 38M to the downstream. The cooling efficiency can be improved by increasing the surface area of the heat radiation fin 42M.
As described in the first embodiment, the developer is transferred to the supply and conveyance screw 32M downstream of the stirring and conveying screw 38M. However, since the developer conveying path is folded, the developer is downstream of the stirring and conveying screw 38M. Then, the developer tends to stay, and the developer tends to generate heat due to frictional heat between the developers and members constituting the agent stirring chamber 29M. Since the cooling efficiency of the heat dissipating fins 42M can be improved downstream of the agitating and conveying screw 38M in which the developer friction is likely to occur, the developer can be efficiently cooled, and the toner can be melted and the developer melted. It is possible to prevent lumps from occurring.

  So far, a so-called tandem printer that obtains a full-color image by superimposing and transferring toner images of each color formed by a plurality of toner image forming units has been described. However, an image forming apparatus that forms a full-color image by a single method has been described. In addition, the present invention can be applied. In this single system, a plurality of developing means for each color are arranged around a latent image carrier such as a photoconductor, and visible images of respective colors formed on the latent image carrier while sequentially switching the developing means to be used. Is transferred onto the intermediate transfer member in sequence. The present invention can also be applied to an image forming apparatus that forms only a single color image.

1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment of the present invention. FIG. 2 is an enlarged configuration diagram illustrating a developing unit of a toner image forming unit for M and a photoconductor in the printer. It is a cross-sectional view showing one end side of the conveyance three chambers in the developing unit. It is a longitudinal cross-sectional view which shows the same conveyance 3 chamber. It is a cross-sectional view which shows the other end side of the same conveyance 3 chamber. It is a longitudinal cross-sectional view which shows the same conveyance 1 chamber.

Explanation of symbols

3: Photoconductor (latent image carrier)
20: Developing unit (developing device)
21: Developing roll (developer carrier)
29: Agent stirring chamber 30: Partition wall 31: Opening portion 32: Supply conveyance screw 33: Rotating shaft member 34: Screw blade 35: Receiving conveyance screw 36: Rotating shaft member 37: Screw blade 38: Stirring conveyance screw 39: Rotating shaft Member 40: Screw blade 41: Case 42: Heat radiation fin 45: Toner concentration sensor 46: Ventilation means 47: Ventilation path

Claims (5)

A developer carrying body for developing a latent image on the latent image carrying body with a developer containing toner and carrier carried on the surface;
A receiving and conveying screw for conveying the used developer received from the developer carrying member in the rotation axis direction;
A stirring and conveying screw that receives the developer sent from the receiving and conveying screw and conveys it in the direction of the rotation axis; and
In a developing device comprising: a supply conveying screw that receives the developer sent from the stirring and conveying screw and supplies the developer to the developer carrying member while conveying the developer in the rotation axis direction;
The stirring and conveying screw is disposed obliquely so that the downstream of the stirring and conveying screw is higher in the upward direction than the upstream in the developer conveying direction, and
A development characterized in that a ventilation path is provided outside the agent agitating chamber in which the agitating and conveying screw is housed, and vents from downstream to upstream in the rotation axis direction for conveying the developer of the agitating and conveying screw. apparatus. 2. The developing device according to claim 1, further comprising a ventilating unit configured to ventilate the developer of the stirring and conveying screw from the downstream side toward the upstream side in the rotation axis direction. Downstream of the agitating and conveying screw in the developer conveying direction, and
The developing device according to claim 1, wherein an electronic member that detects a ratio of toner in the developer in the developing device is disposed at a position corresponding to the upstream in the ventilation direction. A fin for heat dissipation is configured outside the agent stirring chamber in which the stirring and conveying screw is housed,
The developing device according to claim 1, wherein a height of the heat dissipating fin increases from an upstream side to a downstream side in the developer conveying direction of the stirring and conveying screw. In an image forming apparatus comprising at least an image carrier that forms an electrostatic latent image and a developing device that develops the electrostatic latent image to make it visible.
The image forming apparatus includes the developing device according to claim 1.