JPH11212345A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the miniaturization of a developing unit, the extension of the life of developer, and improvement in the image quality of an image formed from the developer having a small particle-diameter. SOLUTION: In a particular area of a developer carrying path 47A communicating with a toner replenishment means, a blocking member 400 for blocking the developer carrying path 47A is disposed. The blocking member 400 is a member higher than a carrying upper face TH defined by the developer being carried along the path. The developer carried along the carrying path 47A stays in front of the blocking member 400 to be stirred, thereafter passes through a carrying path 470 provided above the blocking member 400, and falls downstream in the carrying path 47A. During this, in the developer, a mass of toner breaks, the toner and carrier are stirred, and toner concentration is, therefore, made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine and a printer, and more particularly to an image forming apparatus provided with a developing device using a two-component developer composed of a toner and a carrier.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for color copying machines and printers. In order to obtain a color image in an image forming apparatus such as a copying machine or a printer,
In general, a plurality of developing devices are installed to develop a plurality of color toners, and the plurality of color toners are superimposed on a recording medium. As a color image forming apparatus, a plurality of developing devices are arranged around a photoconductor, only a developing device for developing is brought into contact with the photoconductor, and a so-called retract method in which others are separated, a plurality of developing devices are rotatably held. Various methods have been proposed and put into practical use, such as a so-called rotary method in which a developing device of a required color is opposed to a photoreceptor by a rotating operation, and a so-called tandem method in which at least a plurality of main development parts including a photoreceptor and a developing device are arranged in parallel. Have been.

In these developing units, a developing system using a two-component developer composed of a non-magnetic toner and a magnetic carrier is often used. In this method, it is necessary to uniformly mix the newly supplied non-magnetic toner with the carrier before reaching the developing area with the latent image carrier, and to sufficiently charge the toner required for development. The stirring of the toner and the carrier is performed by circulating the developer in the housing by two stirring and conveying members that are driven to rotate in opposite directions. For example, a toner supply port is provided near the start of transport of the auger far from the developing roll (developer carrying member), and charging and uniforming are performed by stirring in a circulation path before the toner is attached to the developer carrying member. After a final layer is formed and charged by a regulating member, development is performed in a development area.

[0004] With the spread of full-color copying machines and printers, demands for higher image quality from the market are increasing. Among various image quality items, especially in color photographic images, graininess is regarded as a major factor in determining quality. In particular, in digital images, it is important to faithfully develop each pixel of an electrostatic latent image formed by a laser beam, and it is necessary to uniformly develop with a toner having a diameter as small as possible and uniform in particle diameter. Therefore, the development conditions for suppressing the selective development of the particle size are selected, and the width of the particle size distribution of the toner is narrowed, and the particle size is significantly reduced. Good image quality could be obtained. Also, in the magnetic brush developing method using a two-component developer, in an image in which a high-density image portion is arranged adjacent to a low-density image in the process direction from the front of the process direction, the adjacent low-density portion is applied. In the low-density image area, image quality defects such as the trailing edge are a serious problem. This defect is greatly improved by using a small-diameter carrier,
Good image quality can be provided.

[0005]

However, when the particle size of the toner and the carrier is reduced, the fluidity of the powder deteriorates. Therefore, the toner and the carrier are hardly mixed in the stirring step, and the toner cannot be sufficiently charged. was there.
As described above, when the particle size of the toner is reduced, the total charge amount tends to be small, and fogging is likely to occur in image formation using toner that is not sufficiently charged. In particular, when copying high-density image samples continuously, a large amount of replenished toner is not mixed sufficiently evenly and is not sufficiently charged, resulting in uneven density and fogging of the background. There has occurred. Further, as described above, if the size of the developing device is reduced due to the demand for downsizing the image forming apparatus such as a printer, the amount of developer stored is reduced. As the absolute amount of toner in the developing device decreases, the circulation speed of the developer must be increased. The time required for the replenishment toner to reach the developer carrier is shortened by increasing the toner conveyance speed, and the amount of replacement of the toner with the developer per unit increases. The occurrence of uneven fogging has become even greater. Further, in the conventional configuration, the developer stagnates on the upstream side of the developer regulating member, giving stress to the developer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing apparatus which solves the above-mentioned problems and achieves a reduction in the size of a developing device, a long life of the developer, and an improvement in image quality with a small particle size developer. It is.

[0007]

According to a first aspect of the present invention, there is provided a developing device, comprising: a first developer conveying path communicating with a toner replenishing unit; On the upstream side of the transfer section to the second transport path, which is a supply area to the carrier, a shielding member that shields the transport path is provided, and the developer transported in the transport path stays in front of the shielding member, It is provided with a configuration of being transported over the shielding member.

(Operation) The developer in the developing device circulates while being stirred in the first and second transport paths arranged in parallel. In this circulation path, the developer in the first transport path is blocked by the shielding member, so that the developer stays in front of the shielding member. Further, the pressure of the stagnant portion is gradually increased by the developer sent from the rear, and the developer is lifted upward along the wall surface of the shielding member. Then, after passing through the transport path above the shielding member, it falls from above onto the transport path downstream of the shielding member, is transported again, and is supplied to the developing area. During this time, the toner replenished from the replenishing means is deteriorated in powder fluidity due to the reduction of the particle diameter of the carrier and the toner, so that the toner is not sufficiently disintegrated and reaches the vicinity of the shielding member without being mixed. However, the pressure applied during the movement of the developer pool from the developer pool to the conveyance path before the shielding member dissolves the toner mass and sufficiently mixes with the carrier. Further, since the developer that has passed over the shielding member drops to the downstream transport path, the developer largely moves, and a moving operation in the vertical direction occurs, so that the toner concentration of the developer can be made uniform. . Further, even in the staying portion where pressure is applied, since all the developer flows, no excessive stress is applied to a part of the developer, and the life of the developer can be compatible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an electrophotographic image forming apparatus equipped with a developing device of the present invention. A general image forming process will be described with reference to FIG. The surface of the electrostatic latent image carrier 1 is uniformly charged to a negative polarity by the charger 2. Next, image exposure corresponding to the image is performed by the laser exposure device 3, and an electrostatic latent image corresponding to the image is formed on the surface of the electrostatic latent image carrier 1. The developing device 4 selectively moves the toner onto the electrostatic latent image carrier 1 while the magnetic brush rubs the electrostatic latent image to form a toner image. Next, a transfer material 5 such as paper or a transparent sheet is conveyed from a paper feed tray (not shown) by a feed roll, and once stopped at the leading end by a registration roll, is sent to a transfer position at a predetermined timing. . The transferred transfer material 5 comes into close contact with the toner image on the electrostatic latent image carrier 1, and the toner image on the electrostatic latent image carrier 1 is transferred onto the transfer material 5 by the operation of the transfer device 6. After the toner image is fixed on the transfer material 5 by a fixing device (not shown), the toner image is carried out of the image forming apparatus. The electrostatic latent image carrier 1 after the transfer is
Thereafter, after a pre-cleaning process 10 is performed as necessary, the toner remaining on the surface is scraped off by the cleaning device 9.

FIG. 2 is a schematic structural view of the inside of the developing device, and a process until the developer in the developing device is developed will be described with reference to the drawing. Developer carrier (developing roll) 41 of developing device 4
A fixed magnet roll 412 is contained inside a rotatable developing sleeve 410, and is rotatably driven while maintaining a predetermined interval between the developing roller 410 and the peripheral surface of the electrostatic latent image carrier 1.
On the opposite side of the developer carrier (developing roll) 41 from the side facing the electrostatic latent image carrier 1, a developer agitating / conveying device 44 is provided. The developer stirring and conveying device 44 includes a first developer stirring and conveying member 45A and a second developer stirring and conveying member 45B.
It has. The first developer stirring and conveying member 45A, the second
The developer stirring and conveying member 45B has a screw structure, rotates in opposite directions to convey and circulate the developer, sufficiently stirs and mixes the toner and the carrier, and conveys the toner and the developer to the developing sleeve 410. The first and second developer stirring and conveying members 45A and 45B serve as stirring members rotating in directions opposite to each other. The first and second developer stirring and conveying members 45A and 45B convey the toner by the thrust of the stirring screw and mix the toner with the magnetic carrier. By performing the action, triboelectric charging is performed. The circulating two-component developer adheres in a layer on the peripheral surface of the developing sleeve 410. Then, the developer regulating member 42 provided opposite the magnet roll 412 with a predetermined gap is formed to have a uniform layer thickness. The developer regulating member 42 is formed of a non-magnetic member having rigidity or a member having magnetism. In the present embodiment, a member having a double structure made of a non-magnetic material and a magnetic material is used. The developer on the developer carrier 41 having the layer formed in this manner is conveyed to the developing area by the rotation of the developing sleeve 410, and a developing bias in which an AC component is superimposed on a DC component is applied to the developer. Only the toner is moved toward the latent image on the peripheral surface of the carrier 1 to form a toner image on the electrostatic latent image carrier 1.

In the case of toner images formed in this manner, in photographic images and the like frequently used in color copying, the graininess of the low-density image portion is regarded as a major factor in determining the quality of the copy image. Particularly in digital images, it is important to faithfully develop each pixel of an electrostatic latent image formed by a laser beam, and it is necessary to perform uniform development with toner having a diameter as small as possible and uniform in particle diameter. Therefore, the development conditions for suppressing the selective development of the particle size are selected, and the width of the particle size distribution of the toner is narrowed. Can be obtained. Also, in a magnetic brush developing method using a two-component developer, image omission of a low-density part near an adjacent boundary between a low-density image and a high-density image due to a process direction, and image quality of a rear end of a low-density image part in the process direction. Defects are greatly improved by reducing the particle size of the carrier. Therefore, in the present embodiment, the center (average) particle size of the toner is 6.5 μm.
m, a developer having a carrier (average) particle size of 3.5 μm was used. In order to solve problems such as deterioration of powder fluidity due to a decrease in diameter of toner and carrier and insufficient charging caused by insufficient mixing due to deterioration of powder fluidity, the developing device of the present invention employs the following developer stirring and conveying device. It has.

(Embodiment 1) FIGS. 3, 4 and 5 show Embodiment 1 of a developer stirring and conveying apparatus. The developing device 4 includes a developing roll 41
The developer agitating and conveying device 44 is housed and arranged in the housing 40. The developer stirring / conveying device 44 includes a central partition plate 49.
And a developer transport path separated by. The transport path includes a first transport path 47A that communicates with the toner supply port 53 from the toner supply device 50 and a second transport path 47B that supplies the developer to the developing roll 41. A first stirring and conveying member 4 having a screw structure is provided in the first conveying path 47A.
5A, and a second stirring / transporting member 45B having a screw structure is disposed in the second transport path 47B. First stirring and conveying member 45A and second stirring and conveying member 4
5B are arranged in parallel so as to convey the developer in mutually different directions. The center partition plate 49 is disposed at both ends in the longitudinal direction so as to have a gap between the center partition plate 49 and the housing 40. The developer in the developer agitating / conveying device 44 is transferred from the first conveying path 47A to the second conveying path 47B via the transfer section 43B on the downstream side. 47B
And further circulates to the first transport path 47A through the upstream transfer section 43A. In this circulation route,
First stirring and conveying member 45A farther from developing roll 42
A toner supply port 53 is provided near the transfer section 43A, and new toner is supplied from the supply device 50 to the first transport path 47A.

Further, a shielding member 400 is provided downstream of the toner supply port 53 in the developer transport direction and upstream of the delivery section 43B to the second transport path 47B.
The material of the shielding member 400 is not particularly limited as long as it is a non-magnetic member having rigidity. The shielding member 400 is provided so as to penetrate the rotation shaft 46A of the first stirring and conveying member 45A through the bearing 410 and to be orthogonal to the first stirring and conveying member 45A. The arrangement height of the shielding member 400 is higher than the transport upper surface TH of the developer transported by the first stirring transport member 45A. Normally, the developing device 4
In the developer toner concentration within the use range, the stirring and conveying members 45A, 45A,
The amount of developer is large enough to cover the rotary shafts (shafts) 46A and 46B of 45B. Therefore, the shielding member 400
Is the shaft 46 of the stirring and conveying members 45A and 45B at least.
A has a height projecting by a dimension h or more with respect to the arrangement height from the bottom of the housing 40 of A. In this embodiment, when a stirring and conveying member having a shaft diameter of 7.5 mm and a screw diameter of 20 mm is used, a shielding member having a height dimension protruding from the tip of the stirring and conveying member, h = 2 to 10 mm, is provided. .

The first stirring and conveying member 45A is rotatably supported by a bearing 410 fitted in the shielding member 400. In this embodiment, the first stirring and conveying member 45A is shown as being integrally formed before and after the shielding member 400, but may be formed of a plurality of members. In any case, the first stirring and conveying member 45A is rotated in the same direction by the same driving source before and after the shielding member 400.

The housing 40 is provided above the shielding member 400.
Is formed in a mountain shape, and a weir 470 is formed in the first transport path 47A. The size of the weir portion 470 of the housing 40 is set to an appropriate size according to the screw diameter of the stirring and conveying member 45A, the number of screw pitches, the number of rotations of the stirring and conveying member 45A, the volumes of the conveying paths 47A and 47B, and the like. In other words, depending on the transport capacity of the developer, for example, when the transport amount is large, the dam section 470 requires a large space (volume).

Next, the process of stirring and mixing the toner in this configuration will be described. From the supply port 53 to the first transport path 4
7A is supplied to the first stirring and conveying member 45A.
Is transported in the downstream arrow s direction while being stirred by the rotation of. However, due to the deterioration of the powder fluidity due to the small diameter of the toner and the carrier, the first stirring and conveying member 45A cannot be sufficiently mixed by the rotation of the first stirring and conveying member 45A, and is conveyed to the vicinity of the shielding member 400 in a state having the toner mass. . Shielding member 4
The developer conveyed to just before 00 is blocked by the shielding member 400, and the accumulation of the developer occurs before the shielding member 400. The developer is further pushed by the pressure of the developer sent from the rear, gradually rises along the shielding member 400, is pushed up to the weir 470 on the upper surface of the shielding member 400, and moves in the direction of the arrow u. Since the developer receives pressure during the movement to the staying portion before the shielding member 400 and the weir portion 470, the toner mass and the like are released, and the frictional charging with the carrier is sufficiently performed.

Next, the developer that has moved along the shielding member 400 falls as shown by an arrow d on the upper surface of the stirring and conveying member 45A downstream of the first conveying path 47A over the weir portion 470. At the time of the drop, developers having different toner densities are replaced with each other, so that the toner densities are made uniform.

Further, since the developer immediately after dropping is subjected to a moving operation in the up and down direction, the developer is stirred more efficiently, and the charging to the toner and the uniformity of the toner concentration are achieved.
In order to achieve efficient stirring and uniform toner distribution in the first transport path 47A, as described above, in accordance with the configuration and transport conditions of the stirring transport member 45A, the upstream and downstream of the shielding member 400 are provided. It is necessary to optimize the cross-sectional area of the straddling weir 470. If the cross-sectional area of the weir 470 is too large, the pressure between the developers in the pool in front of the shielding member 400 will be weakened, the toner mass will not be disassembled, and the triboelectric charging with the carrier will not be sufficiently performed. Since the particles pass through, the effects of charging and atomization cannot be obtained. Therefore, if the amount of developer transferred before and after the shielding member is made appropriate, the entire amount of developer must be increased.
There is a fear that the stirring performance of the stirring and conveying member may be reduced. Conversely, if the cross-sectional area of the weir portion 470 is too small, the amount of the developer conveyed downstream at this portion is excessively limited, and image quality defects due to insufficient developer supply to the developing sleeve 410 are caused. I will. Therefore, in the stirring and conveying device 44, the amount of the developer to be conveyed is controlled by the shielding member 40.
Although the upper surface TB of the developer just before is raised, the amount of the developer in the transport paths 47A and 47B is maintained to the extent that the upper surface of the rotating shaft 46A is just hidden. Thus, the cross-sectional area of the weir 470 is formed.

Further, since the developer in the stagnant portion of the first transport path 47A in front of the shielding member 400 forms a flow without stopping due to the rotation of the stirring transport member, only a part of the developer is formed. No excessive pressure is applied to the Further, the first transport path 47 </ b> A
The developer that has dropped to the downstream side of the toner is being uniformed and the chunks are collapsed while falling and falling to the conveying member 45A. The developer proceeds downstream as the conveying member 45A rotates, and the developer is transferred to the most downstream side. From the part 43B, it advances in the direction of the arrow t and flows into the second transport path 47B. The developer that has flowed into the second transport path 47B is supplied to the second stirring transport member 45B.
The toner is conveyed in the direction of the arrow v on the downstream side while being agitated by the rotation of. Then, the developer that has consumed the toner flows into the first transport path 47A from the transfer section 43A on the most upstream side, receives a supply of new toner, and receives the first transport path 47A and the second transport path 47A.
In the transport path 47B.

Since the amount of the developer flowing into the second transport path 47B is uniform, granulated and has an appropriate amount, the amount of the toner transferred to the developing roll 41 is an appropriate amount. Thus, the layer formed on the sleeve 410 does not become excessively thick. Therefore, the stress applied to the developer can be reduced as compared with the conventional method of applying pressure upstream of the developer regulating member 42.

Further, as shown in FIG.
A configuration in which a plate-shaped stirring member 60 disposed perpendicularly to the axial direction of the rotation shaft 46A of the stirring / transporting member 45A is provided on the rotation shaft 46A of the first conveyance member 45A facing the weir portion 470 on the front side is also possible. good. In this configuration, the plate-like stirring member 60 rakes up the developer by rotating the stirring and conveying member 45A.
The transfer of the developer to the stagnation portion can be prevented, and application of an unnecessarily large pressure in the stagnation portion can be prevented. By arranging a plurality of the stirring members 60 so as to extend radially, the force for scraping up the developer by rotation is increased, and the movement of the developer becomes smooth. As described above, the developing device 4 shown in this embodiment can achieve both the reduction of the stress on the developer and the admittance performance.

(Embodiment 2) In this embodiment, the arrangement position of the shielding member is changed. 7 and 8, the developing device 4 includes a developing roll 41 and a developer stirring / conveying member 44 parallel to the developing roll 41, as in the first embodiment. In the developer stirring and conveying member 44, the first conveying member 45A and the second conveying member 45B are separated by a partition plate 69. Then, an upstream transfer section 43A without a partition plate is formed on the upstream side communicating with the toner supply port 53, and a transfer section with the second transfer path 47B is provided downstream of the first transfer path 47A. Instead, the shielding member 70 is provided in this portion. The shielding member 70 is a partition plate 6
9, which is provided so as to shield the gap between the end of the partition plate 69 and the housing 40. The disposition height of the shielding member 70 is at least the first conveying member 45.
The dimension H is set higher than the upper portion of the toner conveyance of A. The housing 40 in this portion has a projection 480 projecting in a mountain shape.
Is formed, and a weir portion 490 is formed above the shielding member 70.

The developing device 4 configured as described above agitates the developer replenished with the toner supplied from the toner supply device 50 while being transported along the first transport path 47A by the first transport member 45A. Mixed. Then, the developer transported to the most downstream side of the first transport path 47A is blocked by the shielding member 70 and stays at the most downstream end. The developer is further pushed by the pressure of the developer sent from the rear, gradually rises along the shielding member 70, is pushed up to the weir 490 on the upper surface of the shielding member 70, and moves in the arrow x direction. Since the developer receives pressure during the movement to the staying portion before the shielding member 70 and the weir portion 490, the toner mass and the like are released, and the frictional charging with the carrier is sufficiently performed.

The developer moved along the shielding member 70 drops over the weir portion 490 onto the upper surface of the stirring and conveying member 45B of the second conveying path 47B as shown by an arrow y.
Replacement of developers having different toner densities occurs, and the toner densities are made uniform. As described above, the developer of this embodiment is provided with the weir 49 extending vertically in the transport path.
Pass through zero. Then, the supplied toner is efficiently mixed with the carrier before being supplied to the developing sleeve 42,
It is charged.

The conveying device 44 in this configuration can achieve high image quality by using a small particle size toner and a carrier without generating image quality defects such as fogging and unevenness. There is no need to provide a support mechanism, and the shielding member 70 is
Since it can be integrated with the device, the number of parts can be reduced and the size and cost can be reduced. Further, since the configuration is simple, reliability can be improved. As described above, one developing device is shown in this embodiment, but the same operation and effect can be achieved in a rotary type or tandem type developing device.

[0026]

The developing device of the present invention can improve the stirring and mixing performance of the toner and the carrier and the charging performance of the toner by the carrier without applying excessive stress to the developer. Further, it is possible to provide a current apparatus capable of obtaining a very good image free from problems such as unevenness and fogging in image formation using a small-diameter toner and a carrier, which is essential for improving image quality defects and improving image quality. In addition, a similar effect can be obtained in a device in which a shielding member is provided in a transfer section of a transport path, such as an effect of improving developer agitation and toner agitation performance, and a developing device having a relatively simple configuration. The miniaturization and the cost reduction can be achieved, and further, since the developer does not deteriorate due to the stress, it is possible to cope with a longer life of the developer.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus.

FIG. 2 is a sectional view taken along line aa of FIG. 3 of the developing device of the present invention.

FIG. 3 is an internal top view of the developing device.

FIG. 4 is a sectional view taken along line bb in FIG. 3;

FIG. 5 is an explanatory view of transporting a developer in a shielding member disposition portion.

FIG. 6 is an explanatory view showing another embodiment.

FIG. 7 is an internal top view of the developing device according to the second embodiment.

FIG. 8 is a sectional view taken along line cc of FIG. 7;

[Explanation of symbols]

1 electrostatic latent image carrier (photoconductor), 2 charging device, 3
Laser exposure device, 4 developing device, 5 transfer drum, 6 peeling static eliminator, 7 transfer charger, 8 fixing device, 9 cleaning device, 10 cleaning pretreatment device, 40 housing, 41 developing roll,
410 developing sleeve, 420 magnet roll, 42
Developer layer regulating member, 43 transfer section, 44 developer stirring and conveying device, 45 developer stirring and conveying member, 46
Rotary axis, 47 transport path, 49 central partition,
70,400 shielding member, 470,490 weir,
50 toner supply device, 53 toner supply port, 53
Toner supply port, 60 stirring member.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomio Onuki 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Taku Aoshima 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Ai Ito 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Motoki Noya 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (3)

[Claims] 1. A developer carrying member, a developer stirring / conveying means disposed in parallel with the developer carrying member to carry a two-component developer composed of a toner and a carrier, and supplying toner to the developer stirring / conveying means. A developer agitating / conveying means which communicates with the toner replenishing means, wherein the developer agitating / conveying means communicates with the toner replenishing means. And a second transport path facing the developer carrier. The first transport path and the second transport path are arranged in parallel and transport the developer in different directions from each other. And the developer is configured to circulate through the first transport path and the second transport path via the transfer unit on the downstream side of the transport,
The first transport path is provided with a shielding member that closes the first transport path downstream of the communication port with the toner replenishing means in the developer transport direction and upstream of the transfer section to the second transport path. ,
A developing device configured such that the developer conveyed along the first conveyance path is blocked by the shielding member and then conveyed over the shielding member. 2. A developer agitator / transporter disposed parallel to the developer carrier and transporting a two-component developer including a toner and a carrier, and supplying toner to the developer agitator / transporter. A developer agitating / conveying means which communicates with the toner replenishing means, wherein the developer agitating / conveying means communicates with the toner replenishing means. And a second transport path facing the developer carrier. The first transport path and the second transport path are arranged in parallel and transport the developer in different directions from each other. And the developer is configured to circulate through the first transport path and the second transport path via the transfer unit on the downstream side of the transport, and to transfer the developer from the first transport path to the second transport path. At the delivery section, a shielding member that closes the delivery passage Developer conveyed to the first conveyance path, after being blocked in the shielding member, made is configured to be transported to the second transport path over the shielding member developing device. 3. The shielding member is formed so as to protrude to a position higher than the upper surface of the developer conveyed in the first conveyance path,
3. The developing device according to claim 1, wherein a developer transport path through which the developer can pass is formed at an upper portion of the shielding member.