JP5609446B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that develops an electrostatic latent image on an image carrier, a copying machine including the developing device, a printer, a facsimile, a plotter, and an image forming apparatus such as a multifunction peripheral including at least one of them. About.

In an image forming apparatus that performs development with a two-component developer containing toner and a magnetic carrier, the developing device is provided outside the developing unit and a developing unit that visualizes the electrostatic latent image on the image carrier as a toner image. The developer agitation part (developer storage part) is divided and the triboelectric charging function of the developer is shared by the developer agitation part (see Patent Document 1).
Part of the developer in which the toner has been consumed in the developing unit is discharged and introduced into the developer stirring unit, and the introduced used developer and the newly replenished toner are stirred and mixed, By adjusting the charge amount to a desired value and supplying it to the developing unit, charging failure in the developing unit can be eliminated and the speed can be increased.
The developer stirred by the developer stirring unit is transported upward in the transport path by an air transport unit provided below the developer stirring unit, and is supplied to the developing unit.
When the developing unit and the developer stirring unit are separated from each other, the system layout of the developing device increases, and therefore, the space in the height direction is generally used to achieve compactness. For this reason, the transport path for transporting the developer from the developer agitating unit to the developing unit is configured to rise substantially vertically in the vertical direction as disclosed in FIG. It is designed to be transported upward.

However, in the method of transporting upward substantially vertically, there are the following concerns.
For example, as shown in FIG. 14A, the developer agitating unit 40 is located below the developing unit (not shown), and the developer discharged from the developer agitating unit 40 is conveyed to the developing unit by air. In this case, the conveyance path 70 between the developer agitating unit 40 and the developing unit has a vertical part (including the concept of an upward inclined part), and the developer is conveyed against the gravity against the vertical part. When the developing section stops, the developer circulation also stops. At this time, the developer present in the vertical section drops due to gravity because there is no air supply from below, and as shown in FIG. It stays in the lower bent part.

That is, the conveyance path 70 is separated into a portion where the developer is filled with a high bulk density and a portion where only air exists. After that, when the developing system (developing apparatus) is started again and the developer is conveyed by air, excessive pressure is required to move (convey) the part having a higher bulk density.
Normally, when the developer is transported along the transport path (in the tube), as shown in FIG. 14C, the developer flows, and the entire tube is not filled with the developer. The conveyance pressure in such a case is lower than that in the state where the inside of the pipe is completely filled. This is because if there are many (long) completely filled states, the movement of the developer is limited, and a large force is required to break and move the developer.
Accordingly, the transport pressure during developer transport rises to an extremely high pressure (described later). The longer the vertical part, the higher this tendency.
In addition, since the developing operation is started after the developer is conveyed to the developing unit, if it takes time from the conveyance driving ON to the actual conveyance starting, the developing unit is driven during that time. There is a problem that the driving time of the developing device in a state in which the developer is not supplied from the developer stirring unit becomes long, and the deterioration of the developer is likely to proceed.

  The present invention has been made in view of such circumstances, and in a developing device having a transport path for transporting upward from a developer stirring unit to a developing unit, the amount of developer staying in a bent portion immediately after the start of transport is reduced. The main object of the present invention is to provide a developing device that can reduce the transport load related to air transport and can suppress the deterioration of the developer in the developing unit, and hence the deterioration of the image quality.

In order to achieve the above object, the invention according to claim 1 is provided with a developing unit that visualizes the electrostatic latent image on the image carrier as a toner image, and is provided outside the developing unit and discharged from the developing unit. A developer agitating unit that agitates and mixes the developer to be supplied and toner that is replenished in accordance with a change in toner density in the developing unit; and the developer is conveyed by air upward from the developer agitating unit to the developing unit In a developing device having an upward conveyance path, two or more bent portions whose conveyance direction changes upward are provided in the upward conveyance path, and the lengths of the vertical conveyance paths starting from the bending portion are equal. The bent portion is provided as described above .

According to a second aspect of the present invention, in the developing device according to the first aspect, the developer stirring unit is disposed below the developing unit, and the developer is transported downward from the developing unit to the developer stirring unit. It has the downward conveyance path which carries out.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the upward conveying path is formed of a silicon tube .
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, an entrance and an exit in the conveyance direction of the bent portion are connected by a curve .
A fifth aspect of the present invention is an image forming apparatus including the developing device according to any one of the first to fourth aspects.

According to the present invention, since the developer stays in a plurality of bent portions when the drive is stopped, the amount of developer that accumulates in one bent portion is reduced, and the transport load immediately after the start of transport is reduced. Can be small.
Even if the standing time is long, there is almost no increase in the transport pressure when the next transport is started.
As a result, it is possible to suppress the deterioration of the developer in the developing section, and hence the deterioration of the image quality.
When the upward conveyance path is made of a silicon tube, the toner resistance is excellent, and even when image formation is repeated, the developer and the toner are less adhered to the tube and stable developer conveyance is possible.
When the bent portion has a curved shape, it is easy to transport because the developer transport direction changes gently.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. It is a general | schematic perspective view of a developing device. It is sectional drawing of a developing agent stirring part. It is sectional drawing of a image development part. It is a figure which shows the bending part of an upward conveyance path | route. It is a figure which shows the change of the conveyance pressure by having provided the bending part. It is a schematic block diagram of the developing device in 2nd Embodiment. It is a schematic block diagram of the developing device in 3rd Embodiment. It is a schematic block diagram of the developing device in 4th Embodiment. FIG. 6 is a diagram illustrating a state where a developer is accumulated due to a difference in angle of a bent portion. It is a schematic block diagram of the developing device in 5th Embodiment. It is a schematic block diagram of the developing device in 6th Embodiment. FIG. 6 is a diagram illustrating a state where a developer is accumulated when the bent portion is bent at a substantially right angle. It is a figure for demonstrating the problem of the upward conveyance path | route of the conventional developing apparatus. It is a figure which shows the change of the conveyance pressure in the upward conveyance path | route of the conventional developing device.

Embodiments of the present invention will be described below with reference to the drawings. The second to fifth embodiments are reference examples.
The first embodiment will be described with reference to FIGS. First, an outline of a configuration of an image forming apparatus including a developing device (developing system) according to the present embodiment will be described with reference to FIG.
Opposite to the lower surface of the intermediate transfer belt 8 as an unfixed image carrier in the intermediate transfer unit 10, image forming units 6Y, 6M, 6C, and 6Bk corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel. ing. These image forming units 6Y, 6M, 6C, and 6Bk have the same structure except that the color of the toner used in the image forming process is different.
Each image forming unit 6 includes a photosensitive drum 1 as an image carrier, a charging unit (not shown) disposed around the photosensitive drum 1, a developing device 5, a cleaning unit (not shown), and the like.

An image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1, and a desired toner image is formed on the photosensitive drum 1.
The photosensitive drum 1 is rotationally driven in the clockwise direction in the figure by a driving unit (not shown), and the surface is uniformly charged at the position of the charging means (charging process).
Thereafter, the surface of the photosensitive drum 1 reaches an irradiation position of a laser beam emitted from an exposure unit (not shown), and an electrostatic latent image is formed by exposure scanning at this position (exposure process).
Thereafter, the surface of the photosensitive drum 1 reaches a position facing the developing device 5, and the electrostatic latent image is developed at this position to form a desired toner image (developing process).
Thereafter, the surface of the photosensitive drum 1 reaches a position facing the intermediate transfer belt 8 and the primary transfer bias roller 9, and the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 8 at this position. (Primary transfer process).
Thereafter, the surface of the photoreceptor 1 reaches a position facing the cleaning unit, and untransferred toner remaining on the photoreceptor drum 1 is collected at this position (cleaning step). After cleaning, the surface of the photosensitive drum 1 is initialized with the potential of a neutralizing roller (not shown). Thus, a series of image forming processes performed on the photosensitive drum 1 is completed.

  As shown in FIG. 1, the image forming process described above is performed by each of the four image forming units 6Y, 6M, 6C, and 6Bk. That is, laser light based on image information from an exposure unit (optical writing device) (not shown) disposed below the image forming unit is applied to the photosensitive drums of the image forming units 6Y, 6M, 6C, and 6Bk. Irradiated toward. Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

The four primary transfer bias rollers 9Y, 9M, 9C, and 9Bk respectively sandwich the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, and 1Bk to form a primary transfer nip. The primary transfer bias rollers 9Y, 9M, 9C, and 9Bk are applied with a transfer bias having a polarity opposite to the polarity of the toner.
The intermediate transfer belt 8 runs in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 9Y, 9M, 9C, and 9Bk. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1Bk are primarily transferred while being superimposed on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 onto which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19 as a secondary transfer unit. The color toner image formed on the intermediate transfer belt 8 is transferred onto a transfer sheet P as a recording medium conveyed to the secondary transfer nip position.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed.
A plurality of transfer sheets P are stored in a paper feeding unit 26 disposed in the lower part of the apparatus main body 100, and are separated and fed one by one by a paper feeding roller 27. The fed transfer paper P is temporarily stopped by the registration roller pair 28, and after the oblique deviation is corrected, it is conveyed toward the secondary transfer nip by the registration roller pair 28 at a predetermined timing. As described above, a desired color image is transferred onto the transfer paper P at the secondary transfer nip.

The transfer paper P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the fixing unit 20, where the color image transferred to the surface is fixed by heat and pressure generated by the fixing roller and the pressure roller. The
After the fixing, the transfer paper P is discharged as an output image to the paper discharge unit 30 formed on the upper surface of the apparatus main body by the paper discharge roller pair 29 and stacked. Thus, a series of image forming processes in the image forming apparatus is completed.
In FIG. 1, the code | symbol 32 has shown the reading part.

Next, the configuration of the developing device (developing system) 5 containing a two-component developer composed of toner and carrier will be described in detail.
FIG. 2 shows the overall configuration of the developing device 5. In FIG. 1, only the developing unit of the developing device 5 is shown.
In the developing device 5, the developing means 3 constituting the developing unit is independently above a developer stirring unit (also referred to as developer storage unit or developer storage unit) 40 that stirs and mixes the developer and toner. It is an arranged configuration.

As a developer transport path, a downward transport path 33 that communicates between the upper developing unit 3 and the lower developer stirring unit 40 and transports the developer downward from the developing unit 3 to the developer stirring unit 40. And an upward conveying path 31 for conveying the developer upward from the developer stirring unit 40 to the developing means 3.
The upward conveyance path 31 includes a portion constituted by a pipe. A discharge port of an air pump 60 as a power unit having a developer conveying ability that pushes up the developer against gravity is connected to an end portion of a pipe constituting the upward conveying path 31, The air pump 60 is driven to circulate the developer between the developing means 3 and the developer agitating unit 40.

The air pump 60 is suitable as a means for agitating and conveying the developer. The upward conveying path 31 for conveying the developer upward from the developer agitating unit 40 to the developing unit 3 has a plurality of bent portions that extend horizontally from the developer agitating unit 40 and then change the conveying direction upward. Yes.
In FIG. 2, the developing device 5 collects the developer from the developing unit 3 that executes a developing process with a two-component developer in which a carrier and toner are mixed with the photosensitive drum 1, and collects and supplies the developer from the developing unit 3. A developer stirring unit 40 that stirs and mixes with the toner and a circulation system that transports the developer that has been stirred to a predetermined charge amount toward the developing means 3 are provided.
The developing unit 3 is a unit for developing the electrostatic latent image on the photosensitive drum 1 with a developer (toner) to form a toner image. The electrostatic latent image on the photosensitive drum 1 provided facing the developing unit 3 is visualized as a toner image by the developing unit 3, and the toner image is transferred to a transfer paper P as a recording medium. The image is output by being fixed on the transfer paper by the fixing unit 20.

As shown in FIG. 4, the developing means 3 is provided with a developer carrying member made of a rotating member that is in close proximity to the photosensitive drum 1 and supplies the developer to the photosensitive drum 1 to visualize the latent image. (Developing roller) 11 is provided.
Inside the developing means 3, there are transport members 13, 14 such as a collecting screw for supplying the developer to the developer carrier 11 while transporting the developer in parallel with the axis of the developer carrier 11 and collecting the developer. It is arranged so that the developer is circulated and conveyed through the downstream developer agitating unit 40 while being agitated and conveyed.

A circulation system in which the developer is collected from the developing unit 3, stirred and mixed by the developer stirring unit 40, and then transferred to the developing unit 3 again will be described. Since the toner in the two components is consumed by the development, the developer having a reduced toner concentration is developed through the downward conveying path 33 that connects the developing means 3 and the developer stirring unit 40 as shown in FIG. It is transferred to the agent stirring unit 40.
As shown in FIG. 3, the developer stirring unit 40 has a cylindrical stirring container that is long in the vertical direction, and includes a stirring means inside. The stirring means is driven by a motor 45. To the side of the developer stirring section 40, a toner transport pipe 21 for replenishing the shortage of toner consumed by development is connected. A toner container 22 (see FIG. 2) containing replenished toner is connected to the toner transport tube 21.

When the toner density shortage is detected, as shown in FIG. 2, a screw (not shown) as a conveying means provided in the toner conveying tube 21 is driven by a motor 28, and the replenishing toner in the toner container 22 becomes developer. It is supplied to the stirring device 40.
The amount of toner replenished by the toner conveying tube 21 is determined by a control means (not shown) according to the detection result of the toner density sensor attached to the downward conveying path 33 or the vicinity of the recovery screw of the developing means 3.
Inside the developer agitation unit 40, the replenishing toner supplied from the toner container 22 via the toner conveyance tube 21 and the developer discharged from the developing means 3 via the downward conveyance path 33 are agitated and mixed. Dispersion and charging of the toner are performed.
As shown in FIG. 3, the developer after stirring in the developer stirring unit 40 falls to a rotary feeder (rotary impeller) 50 that is a developer feeding means located below the developer stirring unit 40, Further, by rotation of the rotary feeder 50 driven by the motor 55, the rotary feeder 50 is discharged to a discharge portion 54 that is located below the rotary feeder 50 and is surrounded by a side wall.

The discharge portion 54 communicates with the tube 35 that is a discharge pipe of the air pump 60, and the discharge portion 54 also communicates with the developing unit 3 via the upward conveyance path 31.
The developer discharged from the developer stirring section 40 to the discharge section 54 is generated by the air pump 60 and is sent to the developing means (developing section) 3 through the upward conveying path 31 together with the air flow of the compressed air sent through the tube 35. Carried. The casing of the developing means 3 is provided with an air vent hole through a filter (not shown).

The developer agitation unit 40 is provided with agitation members 43 and 44 for agitating the developer, and the developer is agitated by the rotation by the driving force transmitted through the motor 45 and the gear train (G1 to G4), and the toner Is distributed.
The stirring member 43 is directly connected to the motor shaft in the form of a screw, and rotates in a direction to lift the developer from the bottom to the top. The stirring member 44 is a stirring blade that is formed of a plate-like resin, metal, or the like and moves along the container inner peripheral surface of the developer stirring unit 40. Agitating member 44 is rotated at a low speed by a gear train to transmit the rotation of the motors 45.
Both agitating members are rotated by the motor 45, and the replenished toner is sufficiently dispersed with the existing developer.
The rotary feeder 50 sequentially discharges the developer by a rotating rotor 51 that serves to quantitatively supply the developer discharged from the developer stirring unit 40 to the lower conveyance path. The developer discharged from the rotary feeder 50 falls to the discharge unit 54 where the air and the developer merge, and is conveyed to the developing unit 3 through the upward conveying path 31 by the compressed air flow supplied from the air pump 60. The air pump 60 is an example of a power unit having a developer conveying capability, and a compressor, a blower, or the like can be used instead.

  As shown in FIG. 2, each end of the downward conveying path 33 and the upward conveying path 31 in the developing unit 3 is connected to the end in the longitudinal direction of the developing unit 3. . The developer transport amount to the developing means 3 is determined by the rotational speed of the rotary feeder 50 and the flow rate of the air pump 60. The developer is transported by the downward transport path 33 using gravity. The downward conveyance path 33 and the upward conveyance path 31 are formed of flexible tubes such as silicon, for example, because of the ease of assembling work that crawls between members. Silicon has high toner resistance, and toner and developer are difficult to adhere to the inside, so that stable developer conveyance can be performed.

FIG. 4 is a cross-sectional view of the developing unit.
In FIG. 4, a developer carrying member 11 disposed close to and opposite to the photosensitive drum 1 includes a non-magnetic cylindrical developing sleeve constituting the outer peripheral portion and magnetic field generating means (a plurality of magnetic sleeves) disposed on the inner side. A developing roller comprising a magnet roller having a magnetic pole magnetized or a plurality of magnets), wherein the developing sleeve is driven to rotate around a fixed (non-rotating) magnet, and the developer is driven by a magnetic force. (Development sleeve) This is for developing a latent image on the photoreceptor 1 with toner in a developer while being held on the surface to form a toner image.
The conveying screw 13 is a screw that collects and conveys the developer used for development, and the collected developer is sent out toward the downward conveying path 33 from an opening provided at the most downstream side. The supply screw 14 is a screw that supplies the developer after stirring to the developer carrier 11. In FIG. 4, reference numeral 25 denotes a doctor blade for regulating the developer layer thickness on the developing sleeve.

As shown in FIG. 5, in this embodiment, two bent portions 31 a are provided in the upward conveyance path 31. The bent portion here means a bent portion in which the transport direction changes upward after the developer passes through the bent portion.
In FIG. 5, the upward conveyance path 31 is bent four times, but the number of bent portions is two because the conveyance direction changes upward at two places. When the conveyance is stopped at the bent portion 31a in which the conveyance direction changes upward, the developer that has been conveyed along the conveyance path that extends upward from the bent portion starts, and the developer accumulates. In the present invention, attention is paid to the portion where the developer accumulates when the conveyance is stopped, and thus the bent portion 31b where the conveyance direction changes to other than upward such as horizontal is not noted.

The developer conveyance from the developer stirring unit 40 to the developing unit 3 is performed as follows. After being transported horizontally from the developer agitating unit 40 and rising in the vertical direction at the bent portion 31a, it is transported horizontally at the bent portion 31b and again transported in the vertical direction at the second bent portion 31a. Then, it is conveyed horizontally to the supply screw 14.
As described above, there are two conveyance paths extending upward from the bent portion 31a. By providing a plurality of bent portions 31a whose transport direction changes upward in the path for transporting the developer from the bottom to the top, it is possible to suppress an increase in transport pressure when air is supplied again after the drive is stopped and transport is started. It has become possible.

Next, a description will be given of the movement of the developer in the transport path from when the driving is stopped to when the air is supplied again and transport is started.
The developer in the upward conveyance path 31 is conveyed by air generated by the air pump 60.
When the conveyance is stopped, the supply of air into the conveyance path is stopped, and the developer in the conveyance path falls due to gravity and accumulates in the bent portion 31a. The developer accumulated in the bent portion has a higher bulk density than during conveyance.
Next, when the conveyance is started, the developer accumulated by the pressure of the air is pushed out, and then the next developer conveyance is started. Therefore, the larger the amount of developer, the more pressure is required for conveyance, and the conveyance load of the air pump that starts conveyance increases.
Therefore, in the present invention, a plurality of bent portions are provided in the transport path, and a plurality of paths for transporting from the bottom to the top are provided, thereby reducing the amount of developer accumulated in one bent portion. Since the conveyance pressure is proportional to the amount of developer accumulated in the bent portion, an increase in the conveyance pressure can be suppressed by providing a plurality of bent portions.

For example, when there is one bent portion as shown in FIG. 14, the amount of developer that accumulates in the bent portion is M. When the air supply is started, as shown in FIG. 15, the conveyance pressure rises to the maximum value P while the state of the developer in the conveyance path remains in the region (a), and conveyance is started. When the conveyance is started, air and the developer are mixed from behind as in the area (b), and the bulk density of the developer is lowered. When air is taken into all of the M developer, it is conveyed at a low density as in region (c) and the pressure is stabilized. In this case, the maximum pressure of the air pump needs to be P or more.
On the other hand, as shown in FIG. 5, when two bent portions 31a are provided so as to divide the upward transport path 31 transported in the vertical direction into two equal parts, as shown in FIG. 6, development that collects in one bent portion. The amount of the developer becomes M / 2, the transport pressure rises to P / 2 to transport the developer in the first bent portion 31a, and after the developer pressure is lowered to the steady state transport pressure, the tip of the developer is bent next. In order to transport the developer accumulated in the bent portion at the timing when the portion 31a is reached, the height rises to P / 2.

After the developer passes through the two bent portions, the developer is settled at a steady conveying pressure. The state of the developer in the transport path is changed from region (a) to region (c). In the area (a) until the developer at the first bent portion starts to move, the developer does not move. After the pressure rises to P / 2 and the developer staying in the first bent portion starts to move, the developer flows in a steady state between the discharge portion and the first bent portion. Between the first bent portion and the second bent portion, as shown in the region (b), the developer accumulated in the first bent portion is conveyed while being gradually loosened by air. After the developer flow reaches the second bent portion and the developer staying in the bent portion starts to move, it becomes a steady state with a low bulk density, and as shown in region (c), the air is stably conveyed. Is done.
Thus, it can be seen that when two bent portions 31a are provided, the maximum value of the pressure is lowered, and the load of the air pump is smaller than in the case where there is one bent portion. Therefore, it becomes possible to carry with a small air pump compared with the case where there is one bent portion.

In this embodiment, the case where there are two bent portions has been described. However, as the number of bent portions increases, the amount of developer that accumulates in one bent portion decreases. Can be suppressed.
However, increasing the number of bent portions may increase the conveying path in some cases and increase the conveying pressure in a steady state, so the number of bent portions can be determined within an appropriate range according to the characteristics of the air pump. desirable.
Since the developer in the conveying path extending upward from the bent portion is accumulated in the bent portion, it is preferable to provide the bent portion so as to equally divide the conveying path. Since the increase in pressure is proportional to the amount of developer accumulated in the bent portion, the increase in pressure can be suppressed most when the bent portion is provided so as to equally divide the conveyance path.

FIG. 7 shows a second embodiment. In addition, the same part as the said embodiment is shown with the same code | symbol, The description on the structure and function which were already demonstrated is abbreviate | omitted as long as there is no special need, and only the principal part is demonstrated (same in other following embodiment).
In the present embodiment, the upward conveying path 31 for conveying from the bottom to the top is formed in a spiral shape. When the conveyance is stopped, the developer mainly accumulates in the spiral portion.
When transporting in a spiral shape, the length of the path is longer than that of a single vertical path, so that the amount of developer staying in the entire path is large. The amount of developer that accumulates in the spiral portion is small, and an increase in pressure at the start of conveyance can be suppressed.
When the spiral angle is set to be equal to or smaller than the repose angle of the developer, the developer is accumulated in the entire spiral portion without slipping down the path when transport is stopped, so that an increase in pressure at the start of transport can be suppressed.
Another unit may be placed inside the spiral. FIG. 8 shows an example (third embodiment) in which the upward conveyance path 31 is formed in a spiral shape along the outer periphery of the stirring unit. Since almost no space for forming the spiral portion is required, the space can be used effectively.

9 and 10 show a fourth embodiment.
In the present embodiment, as shown in FIG. 9, a plurality of paths that convey the upward conveying path 31 obliquely upward are combined. When the conveyance path is slanted, the length of the path may be shorter than the path that combines the vertical and horizontal directions to convey upward.
As shown in FIG. 10A, when the angle of the bent portion 31a is set to be equal to or smaller than the repose angle of the developer, the developer is accumulated in the entire path when transport is stopped, and the fall to the bent portion is reduced.
Therefore, in addition to a small increase in pressure at the start of transport, the time from the start of transport to the stabilization of the transport state is shortened, and the developing operation can be started quickly after the start of transport.
As shown in FIG. 11, a conveyance path in which a plurality of bent portions 31 a can be formed by combining spiral, oblique, and vertical and horizontal conveyance paths may be used (fifth embodiment).

12 and 13 show a sixth embodiment.
In this embodiment, as shown in FIG. 12, the path connecting the entrance and exit of the bent portion is formed by a curve. As shown in FIG. 13 (a), when the bent portion is formed with a curve, the conveyance direction changes more slowly than when the bent portion bends 90 degrees (FIG. 13 (b)). Is small and can be transported smoothly. 13A and 13B show the state of the bent portion immediately after the conveyance is stopped.
In FIG. 13A, since the conveyance direction changes gently at the bent portion, the developer accumulated in the bent portion is easily pushed upward when air is supplied next time. On the other hand, as shown in FIG. 13B, when the conveyance direction changes 90 degrees at the bent portion, the developer is accumulated in the path above the bent portion after the conveyance is stopped, and the air is supplied from the horizontal direction. It is not preferable to transport the developer accumulated in the bent portion upward because the load is large.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum as an image carrier 3 Developing part 5 Developing apparatus 31 Upward conveyance path 31a Bending part 33 Downward conveyance path 40 Developer stirring part

JP 2008-003561 A JP 2007-94374 A

Claims (5)

A developing unit that visualizes the electrostatic latent image on the image carrier as a toner image, and a developer that is provided outside the developing unit and replenished according to changes in the developer discharged from the developing unit and the toner density of the developing unit In a developing device having a developer agitating unit for agitating and mixing the toner to be mixed, and an upward conveying path for conveying the developer by air upward from the developer agitating unit to the developing unit,
In the upward conveying path, two or more bent parts whose conveying direction changes upward are provided , and the bent parts are provided so that the lengths of the vertically conveying paths from the bent part are equal. A developing device. The developing device according to claim 1,
The developing device, wherein the developer agitating unit is disposed below the developing unit, and has a downward conveyance path for conveying the developer downward from the developing unit to the developer agitating unit. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein the upward conveying path is formed of a silicon tube . In the developing device according to any one of claims 1 to 3 ,
2. A developing device according to claim 1, wherein an entrance and an exit in the conveyance direction of the bent portion are connected by a curve . An image forming apparatus comprising the developing device according to claim 1 .

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