JP3797494B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention is an electrophotographic copying machine, relates to an image forming apparatus such as a printer, in particular, to a developing device disposed in the image forming apparatus so as not to leak the developing powder out of a developing device, a developing device The present invention relates to an improvement of an image forming apparatus in which a seal member is provided in a gap between a housing and an image carrier.
[0002]
[Prior art]
As is well known, an image forming apparatus is electrostatically applied to the surface of an image carrier by the action of an image forming unit including a corona charger, an exposure device, a developing device, a transfer device, and the like disposed around the image carrier such as a photosensitive drum. A latent image is formed, and the developing powder in the developing device is attracted to the surface of the image carrier with respect to the electrostatic latent image to make a visible image , and then the visible image by the developing powder is transferred by the transfer device. It is transferred onto the material . Furthermore, the visible image transferred onto the transfer material by the fixing device is fixed , and image formation is performed on the transfer material . In order to achieve the downsizing of the image forming apparatus described above, even in the image forming unit compaction is performed, a corona charger, the spacing between the exposure device, a developing device, said transfer device device is very narrow .
[0003]
On the other hand, a certain gap is provided between the opening of the housing of the developing device facing the image carrier and the image carrier so as not to damage the image carrier due to the contact of the housing . For this reason, the developing powder that has risen by stirring and transport inside the developing device leaks out of the gap to the outside of the developing device, and the peripheral devices, particularly the above-described compaction, are developed. densely arranged eraser lamp in proximity to the device, an exposure device, a corona charger or the like is contaminated by the developing powder described above leakage.
[0004]
Such eraser lamp, in order to prevent the exposure apparatus, the leakage of the developer powder to peripheral devices such as a corona charger, the conventional image forming apparatus, as shown in FIG. 3, the surface of the image carrier 1 And a sealing member 5 is provided between the opening end of the housing 3 of the developing device 2. The seal member 5 has one end fixed to a part of the housing 3 positioned on the upstream side with respect to the moving direction of the image carrier 1 and the other end in contact with the image carrier 1. The seal member 5 used is, for example, a polyethylene film or a rubber blade, and blocks leakage of toner from the inside of the developing device 2 to the upstream side of the image carrier 1. Eraser lamp 11 the sealing member 5, as, for preventing the leaks of the developer powder soared in the developing device to a developing device 2 externally, in particular located upstream of the developing device 2, an exposure device 7, Contamination to the corona charger 6 is prevented.
[0005]
[Problems to be solved by the invention]
However, when the seal member 5 made of the above-described material is used, even if the seal member 5 is brought into contact with the surface of the image carrier with a weak force, the seal member 5 and the moving image carrier 1 are rubbed. an electrostatic latent image sealing member 5 itself is formed on an image bearing member will be frictionally charged or disturb electrostatically, and furthermore, the suction seal member 5 on the surface of the image bearing member 1 by the frictional electrification as described above Therefore, an excessive load is applied to the image carrier 1 and the image carrier is damaged. This not only depend on the material of the sealing member 15, the surface of the seal member 15 becomes large contact area to the image bearing member to a smooth surface, the sealing member is also a reason tends to be frictionally charged.
[0006]
The present invention has been made in view of the above-described problems. By blocking the developing powder from leaking from the developing device with a simple configuration, the damage to the image carrier is minimized, and It is an object of the present invention to provide an image forming apparatus capable of performing good image formation without disturbing an electrostatic latent image on an image carrier.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is to fix one end of an image on the upstream end with respect to the moving direction of the image carrier of the housing of the developing device arranged facing the image carrier. In an image forming apparatus provided with a seal member that is in contact with the carrier and blocks leakage of developer powder from the inside of the developing device to the upstream side of the image carrier, the sponge is formed in a thin plate shape A surface portion of the sponge member other than the end portion on the downstream side with respect to the moving direction of the image carrier is provided in contact with the image carrier, and one end of the sponge member is a free end. It is characterized by a shape that becomes gradually thinner toward the surface.
[0008]
The sponge member is urethane foam rubber, and the pressure of the sponge member in contact with the image carrier is 20 to 1000 (mg / cm), preferably 50 to 300 (mg / cm). It is characterized by being .
[0009]
[Action]
In such a configuration, the developing powder is agitated and conveyed by the agitating screw in order to cause the developing powder to be triboelectrically charged and attracted to the electrostatic latent image on the image carrier in the developing device. The charged developer powder is supplied to a developing roller to form a magnetic brush having a uniform thickness on the developing roller, and development is performed with the magnetic brush in contact or non-contact with the surface of the image carrier. Is called. At this time, the developer powder rises due to stirring and conveyance in the developing device. However, leakage of the developer powder is prevented by a sponge member having one end fixed to the end on the upstream side with respect to the moving direction of the image carrier of the housing of the developing device and a part in contact with the surface of the image carrier. Minimize leakage to the outside of the developing device. For this reason, it is possible to prevent contamination of the eraser lamp, the exposure device, the corona charger, and the like located upstream of the developing device by the developer powder . Minimum Moreover, the sponge member, by using i.e. porous member, the contact area between the image bearing member, compared with the sealing member having a conventional smooth surface, damage to the image carrier to become very small To the limit.
[0010]
【Example】
A preferred embodiment of the present invention will be described with reference to the drawings.
A schematic cross section of an image forming apparatus according to the present invention is shown in FIG. In the figure, an image forming apparatus projects a corona charger 6 that uniformly charges the surface of the image carrier 1 around the image carrier 1 that can rotate in the direction of the arrow , and projects an original image on the image carrier 1. An optical device 7 for forming an electrostatic latent image on the surface, a developing device 2 for developing the latent image, a transfer corona discharger 8, a separation corona discharger 9, and a developing powder on the surface of the image carrier 1 remaining after transfer. And an eraser lamp 11 for making the surface potential of the surface of the image carrier 1 uniform, and these are arranged so as to act on the image carrier 1 in sequence.
[0011]
The developing device 2 includes a developing roller 12 and a stirring screw 13, which are disposed in a housing 3 having an opening with respect to the image carrier 1 . Further, developer powder is stored inside the housing 3, and a magnetic brush is formed by adsorbing the developer powder on the surface of the sleeve 14 of the developing roller 12 that is rotated by a driving source (not shown). The electrostatic latent image formed on the image carrier 1 is developed by bringing the toner into contact with the image carrier 1 or slightly spaced for flight development .
[0012]
At one end of the housing 3 positioned on the upstream side with respect to the rotation direction of the image carrier 1, for example, a thin plate shape having a thickness of 0.5 to 3 mm, preferably 1 to 2 mm, and substantially the width of the image carrier 1. A flexible sponge member 4 having substantially the same length as that of the sponge member 4 is fixed, and is a thin plate-like surface of the sponge member 4 other than the end portion on the downstream side with respect to the moving direction of the image carrier of the sponge member portion of the surface is in contact over the width direction of the image carrier 1. Further, in addition to a flat sponge member having substantially the same thickness as shown in FIG. 1, the sponge member 4 is formed in a wedge shape, that is, gradually thinned toward the free end as shown in FIG. Also good.
[0013]
For the sponge member 4, foamed urethane rubber is preferably used, and in particular, a closed-cell urethane sponge is preferably used for preventing leakage of the developer powder. By making the sponge member an independent foam, the developing powder is not allowed to pass from the developing device 2 without changing the elasticity of the sponge member. The pressure of the sponge member 4 that contacts the image carrier 1 is set to 20 to 1000 (mg / cm), preferably 50 to 300 (mg / cm). Thus, the relatively weak pressure and the reduction of the contact area due to the foam minimize the damage to the image carrier, and the sponge member 4 can substantially prevent leakage due to the rising of the developer powder. it can.
[0014]
As for the operation, image formation is performed by a known method, the image carrier 1 carrying the electrostatic latent image reaches the position of the developing device 2, and the developing powder is applied to the image carrier 1 by the action of the developing roller 12. By supplying, an image corresponding to the electrostatic latent image on the surface of the image carrier 1 is formed on the image carrier 1. While developing powder in the developing device 2 is soared by agitation also transport, the soaring developing powder in order blocked by the sponge member 4 described above, leakage to the outside of the apparatus is prevented.
[0015]
In the above-described embodiment, the sponge member 4 is directly fixed to a part of the housing 3, but may be fixed via an indirect member as shown in FIG. The indirect member in the example shown in FIG. 2 is a regulating member 15 that regulates the thickness of the magnetic brush formed on the sleeve 14. Even if the sponge member is fixed via the regulating member 15, the same effect is obtained. In the embodiments, the drum photoconductor is used as the image carrier, but a belt-type photoconductor may be used.
[0016]
The sponge member 4 is particularly effective when the image carrier is an organic photoreceptor. This reduction in charge potential towards the organic photoreceptor as compared with inorganic photoconductive selenium photoconductor or the like due to light attenuation is slow, for which, in the time of development electrostatically between the developing powder and the image bearing member adhesive force is still strong, I or mutually挨that the contact area be a sponge member contacts the image bearing member Ru slightly der not substantially affected the electrostatic latent image on the image carrier surface Because.
[0017]
【The invention's effect】
In the image forming apparatus of the present invention, one end of the image forming apparatus can be fixed to the housing of the developing device, and the size of the apparatus can be reduced by a sponge member provided so that the surface portion at the other end is in contact with the image carrier. it is possible to prevent the device outer leakage to from other, it is possible to minimize the damage to the image carrier. Therefore, substantially good image formation can be performed without the exposure device, the corona charger, and the eraser lamp located upstream of the developing device being contaminated by the developing powder.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of an image forming apparatus according to the present invention.
FIG. 2 is a schematic sectional view showing another embodiment.
FIG. 3 is a schematic cross-sectional view of an image forming apparatus showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing apparatus 3 Housing | casing 4 Sponge member 5 Seal member 6 Corona charger 7 Optical apparatus 8 Transfer corona discharger 9 Separation corona discharger 10 Cleaning device 11 Eraser lamp 12 Developing roller 13 Stirring screw 14 Sleeve 15 Restriction member

Claims (1)

One end is fixed to the upstream end of the housing of the developing device arranged facing the image carrier in the moving direction of the image carrier, and a part of the image carrier is brought into contact with the image carrier, so that the image is developed from the inside of the developing device. In a magnetic brush developing type image forming apparatus provided with a seal member that blocks leakage of developer powder to the outside upstream of the carrier, the seal member is made of urethane foam rubber formed in a thin plate shape , A sponge member having substantially the same length as the width of the drum-shaped image carrier , and a surface portion of the sponge member other than the downstream end in contact with the moving direction of the image carrier is in contact with the image carrier. One end of the sponge member has a shape that gradually decreases toward the free end, and the pressure of the sponge member that contacts the image carrier is 20 to 1000 (mg / cm), preferably Is 50-300 (mg / cm) An image forming apparatus wherein there.

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