JPH06332345A - Image forming unit - Google Patents

Abstract

PURPOSE:To easily remove a foreign matter recovered in a recovery container and to easily eliminate paper powder or the like accumulated at an elimination means simultaneously together in the case where the foreign matter or the like discharged through a slit provided on a developing device is recovered in the recovery container and the paper powder or the like attached on a timing roller is eliminated from the timing roller by the elimination member. CONSTITUTION:In an image forming unit having a developing device provided with a slit 37 where the foreign matter or the like is discharged at the lower part of a developing sleeve 31 and a guide unit 4 guiding a transfer material to an image carrier 1 at the lower part of the developing device 3; a guide plate guiding the transfer material between timing rollers 43, an upper timing roller 43a, an elimination member 44 eliminating the paper powder or the like attached on the roller 43a and a recovery container 46 where the foreign matter or the like discharged through the slit 37 is recovered are provided in the guide unit 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming unit used in an image forming apparatus such as a copying machine or a printer, and has a foreign substance or an uncharged toner under a developing sleeve for supplying a developer to an image carrier. The present invention relates to an image forming unit having a developing device provided with a slit for discharging the above and the like, and a guide unit below the developing device for guiding a transfer material to the image carrier side.

[0002]

2. Description of the Related Art In recent years, in image forming apparatuses such as copying machines and printers, the purpose has been to reduce the size of the image forming apparatus and to facilitate its maintenance.
A developing device, an image carrier, and the like used in this image forming apparatus are appropriately combined to form a unit, and the image forming unit thus formed is attached to the image forming apparatus for use. Came to be.

Further, in the image forming apparatus as described above, after the toner image is transferred from the image carrier to the transfer material, the toner remaining on the image carrier is removed from the image carrier by the cleaning device. And in the past,
The toner thus removed is generally collected in a waste toner box or the like and discarded.

However, in such a case, the toner is not effectively used, and there is a problem of environmental pollution due to waste of the toner, and also in the image forming apparatus, the toner removed as described above is collected. However, there is a problem in that the image forming apparatus becomes large accordingly.

Therefore, in recent years, in the image forming apparatus as described above, the toner removed by the cleaning device as described above is returned to the developing device and used again for development.

However, the toner removed from the image carrier by the cleaning device as described above generally contains a large amount of foreign matter such as paper dust, and the toner containing a large amount of such foreign matter is placed in the developing device. When it is returned and used for development again, additives and the like contained in the paper powder are combined with the developer, resulting in poorly charged toner with low chargeability, and such foreign matter accumulates in the developing device and hardens. There has been a problem that the image formed is adversely affected by clogging between the developing sleeve and the spike height regulating plate.

Therefore, in the conventional image forming apparatus as described above, a slit is provided below the developing sleeve for supplying the developer to the image carrier, and a recovery container is arranged under the slit to develop the image. A foreign substance such as paper dust contained in the agent, a toner having a poor charging, or the like is collected in the collecting container through the slit.

Here, when the foreign matter, the poorly charged toner and the like in the developing device are collected in the collecting container as described above, the foreign matter and the poorly charged toner and the like gradually accumulate in the collecting container, Since the foreign matter, the poorly charged toner, and the like fill the collection container, it is necessary to discard the foreign matter, the poorly charged toner, and the like collected in the collection container.

However, in the conventional image forming unit, when the collecting container as described above is provided in the image forming unit, it is generally impossible to remove such a collecting container, or it is very difficult to remove it. Difficult to
When removing the collection container, there was a problem that the collected foreign matter, poorly charged toner, and the like spilled out of the collection container.

Further, conventionally, in order to reduce paper dust or the like on the transfer paper from adhering to the image carrier, the paper dust or the like on the transfer paper is adhered to the timing roller for feeding the transfer paper to the image carrier side. In addition, a removing member is provided so as to be in contact with the timing roller, and the paper dust or the like attached to the timing roller is removed from the timing roller by the removing member.

When the removing member removes the paper dust or the like adhering to the timing roller in this manner, the paper dust or the like gradually accumulates on the removing member to remove the paper dust or the like adhering to the timing roller. The ability to remove is reduced, and as a result, the paper dust, etc. on the transfer paper is not sufficiently removed by the timing roller, and a large amount of paper dust, etc. is supplied to the image carrier, resulting in poor cleaning of the image carrier. In addition, the toner removed from the image carrier contains a large amount of foreign matter such as paper dust, and when such toner is returned to the developing device, a large amount of poorly charged toner or the like is generated and an image is formed on the formed image. The problem of various adverse effects arose.

For this reason, conventionally, the paper dust and the like accumulated in the removing member has been removed, but in the image forming unit as described above, the work of removing the paper dust and the like accumulated in the removing member. Is troublesome and difficult, and such removal work is generally forgotten, and as a result, paper dust, etc. accumulates on the removal member, reducing the ability to remove the paper dust, etc. adhering to the timing roller. As mentioned above, various problems have occurred.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems in an image forming unit in which a developing device and the like are appropriately combined and unitized.

That is, according to the present invention, a developing device is provided with a slit for discharging foreign matters, poorly charged toner and the like below a developing sleeve for supplying a developer to an image carrier, and a transfer material is provided below the developing device. In the image forming unit provided with the guide unit for guiding to the image carrier side, the timing of collecting the foreign matter discharged from the slits, the poorly charged toner and the like in the collecting container and guiding the transfer material to the image carrier. When the paper dust, etc. adhering to the roller is removed from the timing roller by the removing member, the paper dust removed from the timing roller by the discharging / removing member of the foreign matter and the poorly charged toner collected in the above-mentioned collecting container. It is an object of the present invention to make it possible to easily remove all of the above at once.

[0015]

According to the present invention, in order to solve the above problems, a slit is provided below a developing sleeve for supplying a developer to an image bearing member to discharge foreign matters and uncharged toner. And a guide unit for guiding the transfer material to the image carrier side under the developing device, the guide unit guiding at least the transfer material between the pair of timing rollers. A plate, an upper timing roller above the timing roller, and a removing member for removing paper dust and the like adhering to the upper timing roller,
A collecting container for collecting foreign matters discharged from the slits, poorly charged toner, and the like is provided.

[0016]

In the image forming unit according to the present invention, the developing device is provided with a slit below the developing sleeve for supplying the developer to the image carrier to discharge foreign matters and poorly charged toner. Attached to a guide unit for guiding the transfer material to the image carrier side below the apparatus, a guide plate for guiding the transfer material between a pair of timing rollers, an upper timing roller above the timing roller, and an upper timing roller. A removing member for removing paper dust and the like, and a collecting container for collecting foreign matters discharged from the slits, poorly charged toner, and the like are provided.

Then, the guide material of the guide unit guides the transfer material between the pair of timing rollers, and the pair of timing rollers sends the transfer material to the image carrier side. Along with the removal by the roller, the paper dust or the like attached to the timing roller is removed by the removing member.

With this configuration, when the transfer material is guided to the image carrier to perform the transfer, the amount of paper dust and the like adhering from the transfer material to the image carrier is reduced, and therefore the image carrier is cleaned by the cleaning device. The amount of paper powder contained in the toner and the like removed from the paper is reduced.

Further, when the toner etc. removed from the image bearing member by the cleaning device as described above is returned to the developing device and used again for development, a non-charged toner is caused by foreign matter such as paper dust contained in the toner. It happens, but
When such a foreign substance, poorly charged toner, or the like is supplied to the developing sleeve, it is collected in the collecting container provided in the guide unit through the slit provided below the developing sleeve. It is less likely that an image formed by a foreign substance inside the toner, a poorly charged toner, or the like will be adversely affected.

Further, in the image forming unit according to the present invention, the guide unit is provided with the removing member for removing the paper dust and the like adhering to the upper timing roller and the collecting container as described above. With the unit separated from the developing device, it is possible to discharge the foreign matter collected in the collection container, the poorly charged toner, and the like, and simultaneously remove the paper dust and the like accumulated in the removing member.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An image forming unit according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

Image forming unit A in this embodiment
In FIG. 1, as shown in FIG. 1, a cylindrical image carrier 1 is rotatably provided in the center of the housing 10, and a surface of the image carrier 1 is provided above the image carrier 1. Is provided with a scorotron charging charger 2 and a developer is supplied to the image carrier 1 at a position downstream of the charging charger 2 in the rotation direction of the image carrier 1 to form a toner image on the image carrier 1. The developing device 3 for forming the image is provided.

Here, in the above-described developing device 3, as shown in the figure, the opening portion of the developing tank 30 facing the image carrier 1 is provided inside so as to face the image carrier 1. A developing sleeve 31 provided with a magnet roller (not shown) is rotatably provided, and a smoke prevention plate 32 is provided above the developing sleeve 31 to prevent the developer from scattering from the developing device 3 to the outside. In addition, the amount of the developer supplied onto the developing sleeve 31 at a position upstream of the position facing the image carrier 1 in the rotation direction of the developing sleeve 31 via the outer peripheral surface of the developing sleeve 31 at a predetermined interval. The height control plate 33 for controlling is provided.

A partition wall 34 is provided in the developing tank 30. The partition wall 34 mixes and stirs the developer with a developer supply chamber 35 located in the vicinity of the developing sleeve 31. It is divided into a developer transport chamber 36 for sending to the developer supply chamber 35, and a bucket roller 35a for supplying the developer to the developing sleeve 31 while mixing and stirring the developer is provided in the developer supply chamber 35, while the developer transport chamber 36 is provided. A transport screw 36a for transporting the developer into the developer supply chamber 35 while mixing and stirring the developer is provided therein.
A slit 37 is provided in the developing tank 30 below the developing sleeve 31 along the axial direction of the developing sleeve 31.

In the developing device 3, the carrying screw 36 provided in the developer carrying chamber 36 is provided.
The developer is conveyed into the developer supply chamber 35 while being mixed and stirred by a, and the developer thus conveyed is supplied to the bucket roller 35a provided in the developer supply chamber 35.
To supply to the developing sleeve 31.

Then, the developer thus supplied is guided to the image carrier 1 side by the rotation of the developing sleeve 31, and the amount of the developer on the developing sleeve 31 is adjusted to the above-mentioned height control plate 33 in the middle thereof. Then, the toner in the developer is supplied from the developing sleeve 31 to the electrostatic latent image portion of the image carrier 1 to form a toner image on the image carrier 1, and the toner is contained in the developer. Impurities such as paper dust and poorly charged toner are discharged through a slit 37 provided below the developing sleeve 31.

Further, in the image forming unit A in this embodiment, below the developing device 3,
As shown in FIGS. 1 and 2, a guide unit 4 for guiding the transfer paper to the image carrier 1 side is provided.

Here, in the image forming unit A, at the upstream end for guiding the transfer paper to the image carrier 1 side, a long hole along the traveling direction of the transfer paper is formed on both side walls of the housing 10. 11 is provided, pins 41 are projected on both sides of the guide unit 4, and the pins 41 are inserted into the elongated holes 11 so that the guide unit 4 slides on the housing 10 below the developing device 3. It was attached so as to be rotatable.

Further, in this guide unit 4,
A pair of transfer papers is sent to the image carrier 1 at a predetermined timing to a position downstream of the transfer plate in the transfer paper feed direction from a guide plate 42 that guides the transfer paper from the upstream end in the transfer paper feed direction to the image carrier 1 side. The upper timing roller 43a is provided above the timing roller 43 of FIG.
The upper timing roller 43a is brought into contact with the upper timing roller 43a.
A removing member 44 for removing the paper dust and the like adhering to the sheet is provided.

Further, in this embodiment, in the guide unit 4, the second guide plate for guiding the transfer paper to the image carrier 1 is located at a position downstream of the upper timing roller 43a in the transfer paper feeding direction. 45 is provided,
On the second guide plate 45, below the slit 37 in the developing device 3, a collecting container 46 for collecting foreign matter discharged from the slit 37, toner having a poor charge, and the like.
It was made to hold.

The guide unit 4 is slidably and rotatably attached to the housing 10 as described above, and the spring 47 is provided between the guide plate 42 and the developing device 3 in the guide unit 4. The guide unit 4 is held by the spring 47, and the spring 47 is held at the time of image formation.
Thus, the guide unit 4 is biased downward so that the upper timing roller 43a is brought into pressure contact with the lower timing roller 43b provided on the main body side of the electrophotographic apparatus B.

Further, in the image forming unit A of this embodiment, as shown in FIG. 1, the toner image is transferred to a position downstream of the developing device 3 in the rotational direction of the image carrier 1. A separation claw 6 for separating the paper from the image carrier 1 is rotatably provided, and the separation claw 6 allows the image carrier 1 to be separated.
Of the image carrier 1 after transfer at a position on the downstream side in the rotation direction of the
A cleaning device 7 for removing the toner and the like remaining on the surface of the sheet is provided.

Here, in the above-mentioned cleaning device 7, as shown in the figure, the cleaning blade 72 is brought into pressure contact with the surface of the image carrier 1 by the blade pressure contact spring 71, and the surface of the image carrier 1 is transferred after the transfer. The residual toner or the like is removed by the cleaning blade 72 from the image carrier 1.
The toner and the like thus removed are collected in the collecting unit 73.

As for the toner and the like collected in the collecting section 73 in this way, as shown in FIG. 3, the collected toner feeding coil 75 provided in the collected toner feeding pipe 74 causes the developing device 3 side. The toner and the like is sent to the toner replenishment section 39 through a recovery toner replenishment section 39a provided in the toner replenishment section 39 that replenishes the toner to the developing device 3, and is supplied to the toner replenishment section 39 from the toner replenishment opening 39b. Developing device 3 with new toner
I tried to put it back inside.

Next, the image forming unit A of this embodiment
The case of setting and using in the electrophotographic apparatus B will be described.

Here, when the image forming unit A as described above is set in the electrophotographic apparatus B, FIG.
As shown in FIG. 5, the bearings 43c on both sides of the upper timing roller 43a provided on the guide unit 4 in the image forming unit A are respectively
In the electrophotographic apparatus B, the lower timing roller 43b is fitted into the guides 81 provided on the pair of side plates 80 that rotatably supports the upper timing roller 43a provided on the guide unit 4 by the spring 47. The image forming unit A was set at a predetermined position of the electrophotographic apparatus B so as to be pressed against the lower timing roller 43b.

In the image forming unit A of this embodiment, the pin 41 provided on the guide unit 4 as described above is inserted into the elongated hole 11 provided on the housing 10 so that the guide unit 4 is formed. Since it is slidably attached to the housing 10, the guide unit 4 is attached to the elongated hole 1 even if the dimensions of the unit A for image formation are not uniform.
It was possible to set the image forming unit A in the electrophotographic apparatus B by appropriately sliding it in the range of 1 so that the upper timing roller 43a and the lower timing roller 43b were brought into good pressure contact with each other.

Then, while rotating the image carrier 1 provided in the image forming unit A by a driving means (not shown), the charging charger 2 causes the image carrier 1 to rotate.
Thus, the surface of the rotating image carrier 1 is uniformly charged.

Next, the original set on the original platen 100 is irradiated with light from the exposure lamp 101, and the reflected light is charged as described above through the mirrors 102, 103, 104 and 106 and the lens 105. The surface of the image carrier 1 is irradiated to form an electrostatic latent image on the surface of the charged image carrier 1 according to the image of the original.

Then, the developer is supplied from the developing sleeve 31 of the developing device 3 to the surface of the image carrier 1 on which the electrostatic latent image is formed in this way, and the developer is supplied onto the image carrier 1. A toner image is formed on the formed electrostatic latent image portion.

On the other hand, for the transfer paper, the paper feed tray 11
1 is drawn out by the paper feed roller 112, and the transfer paper drawn out in this way is transferred to each of the intermediate rollers 1.
15, 118 and intermediate guides 113, 114, 11
6, 117 to the guide plate 42 provided in the image forming unit A, and between the pair of timing rollers 43a, 43b in the state of being pressed by the spring 47 as described above via the guide plate 42. I sent it to.

When the transfer paper is guided between the pair of timing rollers 43a and 43b in this way, the paper dust or the like on the transfer paper adheres to the timing rollers 43a and 43b and is removed to some extent, and the paper dust or the like on the transfer paper is removed. The quantity has decreased. Also, in this way, the upper timing roller 43
For the paper dust and the like adhering to a, the timing roller 43
Along with the rotation of a and 43b, the removing member 44 provided so as to come into contact with the upper timing roller 43a removed from the upper timing roller 43a.

Next, when the image carrier 1 on which the toner image is formed rotates as described above and the portion on which the toner image is formed is guided to a position facing the transfer charger 5, in synchronization therewith, The transfer paper is sent along the second guide plate 45 between the transfer charger 5 and the image carrier 1 on which the toner image is formed by the timing rollers 43a and 43b, and the transfer charger 5 causes the image carrier 1 to move. After transferring the toner image formed on the surface of the to this transfer paper,
The transfer paper on which the toner image has been transferred is separated from the image carrier 1 by the separation claw 6. In this case, the amount of paper dust or the like adhering to the image carrier 1 is reduced because the paper dust or the like on the transfer paper is removed to some extent and reduced as described above.

Then, the transfer paper separated from the image carrier 1 in this way passes through the conveyor belt 121 and the fixing roller 12
Then, the toner image transferred onto the transfer paper is fixed between the fixing rollers 122, and then the transfer paper is ejected to the paper ejection tray 124 by the paper ejection roller 123.

On the other hand, after the transfer paper is separated from the image carrier 1 as described above, the toner or the like remaining on the surface of the image carrier 1 is cleaned by the cleaning blade provided in the cleaning device 7. The toner, etc., removed from the surface of the image carrier 1 by 72 and collected in the collection unit 73, is returned to the developing device 3 through the collected toner feed pipe 74 as shown in FIG. And was used again for development.

After removing the toner and the like remaining on the surface of the image carrier 1 in this manner, the image carrier 1 is removed.
The surface of the image carrier 1 was irradiated with light from the eraser 130 to cancel the residual potential on the surface of the image carrier 1.

When image formation is repeated in this manner, impurities such as paper powder and poorly charged toner in the developer supplied to the developing sleeve 31 are provided below the developing sleeve 31 as described above. The removal member 44 that collects the impurities in the collection container 46 through the slit 37 and gradually accumulates the impurities in the collection container 46, and also removes the paper dust and the like adhering to the upper timing roller 43a as described above, The paper dust and the like removed from the upper timing roller 43a gradually accumulated.

Here, in the image forming unit A in this embodiment, there are a time when foreign matter, a poorly charged toner and the like are accumulated in the collecting container 46 as described above, and a time when paper dust and the like are accumulated in the removing member 44. The size and the like of the recovery container 46 were adjusted so that the same period was reached.

Then, as described above, when the foreign material, the poorly charged toner and the like are accumulated in the collecting container 46 to some extent, and the paper dust and the like are accumulated in the removing member 44, the image forming unit A is removed from the electrophotographic apparatus B. The guide unit 4 in the image forming unit A is taken out and separated from the developing device 3 to dispose of the foreign matters and badly charged toner collected in the collection container 46, and the removing member 44.
The paper dust and the like accumulated in the above are removed from the removing member 44.

By doing so, only by separating the guide unit 4 from the developing device 3, the foreign substances collected in the collecting container 46, the uncharged toner and the like are discharged, and the paper dust and the like accumulated in the removing member 44 are removed. And can be done at the same time,
Compared to the case where these are performed separately, the operation can be performed easily.

In addition, after the foreign matters and the poorly charged toner collected in the collecting container 46 as described above are discarded and the paper dust and the like accumulated in the removing member 44 are removed, On the contrary, the recovery container 46 is held on the second guide plate 45 as described above, the guide unit 4 is attached to the developing device 3, and the image forming unit A is attached to the electrophotographic device as described above. Set to B,
The image is formed again.

When the image is formed in this manner, the foreign material, the poorly charged toner, etc. are filled in the collection container 46, and the foreign material, the poorly charged toner, etc. are not collected in the collection container 46, and the removing member 44 is used. The paper dust or the like on the transfer paper is not sufficiently removed by the timing roller 43a, and good image formation can be stably performed.

In the image forming unit A in this embodiment, in the above guide unit 4,
The second guide plate 45 is integrally provided at a position downstream of the upper timing roller 43a in the transfer paper feeding direction, and the recovery container 46 is held on the second guide plate 45. However, as shown in FIG. The second guide plate 45 may be provided separately from the guide unit 4, and only the recovery container 46 may be attached to the guide unit 4.

If the second guide plate 45 is provided separately from the guide unit 4 as described above, when the image forming unit A is set in the electrophotographic apparatus B, the guide unit 4 slides as described above. Even if this is done, this second guide plate 45
The transfer paper sent out by the timing roller 43 can be stably guided to the image carrier 1 by the second guide plate 45 without being displaced.

Further, in the image forming unit A in this embodiment, the image carrier 1, the charging charger 2, the developing device 3, the guide unit 4, the separating claw 6, the cleaning device 7 and the like are united together. However, in the image forming unit A according to the present invention, as long as it includes at least the developing device 3 and the guide unit 4 as described above, how other components are combined with each other. May be

[0056]

As described in detail above, in the image forming unit according to the present invention, the slits for discharging foreign matters, uncharged toner, etc. below the developing sleeve for supplying the developer to the image carrier in the developing device. In addition, since the guide unit for guiding the transfer material to the image carrier side under the developing device is provided with the collecting container for collecting the foreign matters discharged from the slits and the poorly charged toner, the cleaning device Even when the toner or the like removed from the carrier is returned to the developing device and used again for the development, the foreign matter contained in the returned toner or the poorly charged toner is passed through the slit in the developing device to the guide unit. Images collected by the above-mentioned collection container provided on the That influence is gone.

Further, in the image forming unit according to the present invention, a guide unit for guiding the transfer material to the image carrier side under the developing device, a guide plate for guiding the transfer material between the pair of timing rollers, and Since the upper timing roller above the timing roller and the removing member for removing the paper dust and the like adhering to the upper timing roller are provided, the paper dust and the like on the transfer material guided by the guide plate can be adjusted to the above-mentioned upper timing roller. Along with the removal to a certain extent by adhering to the roller, the paper dust and the like adhering to the upper timing roller will be removed by the removing member, and the amount of paper dust and the like applied to the image carrier from the transfer material will decrease. If the image carrier has poor cleaning, or if the toner removed from the image carrier contains a large amount of foreign matter such as paper dust. When the toner is returned to the developing device and used for development, a large amount of poorly charged toner and the like are not generated, and various adverse effects on the formed image are reduced. It was

Further, in the image forming unit according to the present invention, as described above, a collecting container for collecting foreign matters discharged from the guide unit through the slit provided in the developing device, toner having a bad charging, and the upper timing roller. Since a removing member for removing the paper dust and the like adhering to the collecting unit is provided together with the removing unit, the foreign matter collected in the collecting container and the uncharged toner can be discharged while the guide unit is separated from the developing device. At the same time, it becomes possible to remove the paper dust and the like accumulated in the removing member at the same time.

As a result, in the image forming unit according to the present invention, the work of discharging the foreign matter collected in the collection container, the toner having a bad charging, and the like, and the work of removing the paper dust accumulated in the removing member can be performed. These operations are remarkably simpler than those of the conventional image forming unit, and there is no need to forget the operation of removing the paper dust accumulated in the removing member, so that good image formation can be stably performed. Became.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view of an image forming unit according to an embodiment of the present invention.

FIG. 2 shows an image forming unit according to the embodiment,
FIG. 6 is a partially enlarged cross-sectional explanatory view showing a state in which a guide unit is provided below the developing device.

FIG. 3 is an exploded perspective view showing a state in which toner and the like collected from a surface of an image carrier by a cleaning device is returned to a developing device in the image forming unit of the embodiment.

FIG. 4 is a partially exploded perspective view showing a state in which the upper timing roller provided in the guide unit is attached to the lower timing roller provided in the electrophotographic apparatus in a pressure contact manner in the image forming unit of the embodiment. It is a figure.

FIG. 5 is a schematic cross-sectional view showing a state in which the image forming unit of the embodiment is set in the electrophotographic apparatus.

FIG. 6 is a partial enlarged cross-sectional explanatory view showing a state in which a second guide plate is provided separately from the guide unit in the image forming unit according to another embodiment of the present invention.

[Explanation of symbols]

 A image forming unit 1 image carrier 3 developing device 4 guide unit 31 developing sleeve 37 slit 42 guide plate 43 timing roller 43a upper timing roller 43b lower timing roller 44 removing member 46 collecting container

Claims (1)

[Claims] 1. A developing device provided with a slit for discharging foreign matters, uncharged toner and the like below a developing sleeve for supplying a developer to an image carrier, and a transfer material on the image carrier side below the developing device. In an image forming unit having a guide unit for guiding, a guide plate for guiding at least a transfer material between a pair of timing rollers in the guide unit, an upper timing roller above the timing roller, and an upper timing roller. An image forming unit, comprising: a removing member for removing paper dust and the like adhering to the sheet; and a collecting container for collecting foreign matters and poorly charged toner discharged through the slits.