JP3067406B2 - Image forming device - Google Patents

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 provided with a suction duct for sucking and removing developer powder generated near a developing device.

[0002]

2. Description of the Related Art Conventionally, as a two-color image forming apparatus in an electrophotographic copying machine, a printer, or the like, a first electrostatic latent image first formed on an electrostatic latent image carrier is firstly colored. Developing using a toner, and then forming a second electrostatic latent image formed on the image carrier into a second electrostatic latent image having the same polarity as the first color toner.
2. Description of the Related Art A device that develops with a color toner is known. FIG. 1 shows a cross-sectional view of such a conventional apparatus. In this apparatus, a first charging charger 2, a first developing device 3, a second
Charging charger 4, second developing device 5, transfer charger 6,
The cleaner device 7 and the eraser device 8 are arranged in order. Each of the charging chargers is a scorotron charger having a grid electrode. Each of the developing devices is a magnetic brush type developing device. A first developing device stores a two-component developer including a red toner and a carrier, and a second developing device includes a black toner and a carrier. A two-component developer is stored. In this apparatus, a two-color image is formed by the following process.

[0003] (a) The surface of the photosensitive drum 1 is charged to a predetermined potential by the first charging charger 2.

(B) Exposure is performed by irradiating light corresponding to the document image by an appropriate exposure means as shown by an arrow B in the figure to form a first latent image.

(C) The first developing device 3 develops the first latent image using a two-component developer containing a red toner and a carrier.

(D) Next, the surface of the photosensitive drum 1 is recharged using the second charging charger 4.

(E) Further, a second latent image is formed by irradiating light corresponding to the document image by an appropriate exposure means to perform exposure.

(F) The second developing device 5 develops the second latent image using a two-component developer containing black toner and carrier.

(G) The obtained two-color toner image is transferred to the paper 11 by the transfer charger 6.

(H) Separating the paper 11 from the drum 1
The toner image is fixed by an appropriate fixing unit, and the paper 11 after the transfer of the toner image is discharged by an appropriate discharging unit.

After the residual toner is removed from the photosensitive drum 1 after the transfer of the toner image by the cleaner device 7, the residual charge is erased by the eraser device 8, and the process returns to the start.

Image formation by the above process 2
In the color image forming apparatus, the corona wire, the grid electrode, and the inner surface of the shield case of the second charging charger 4 are seriously stained by the toner dust generated from the two developing units, and the surface of the photosensitive drum 1 is contaminated. There was a problem that charging failure was caused.

On the other hand, an image forming apparatus including a duct for sucking air in the apparatus main body for the purpose of removing toner dust generated from a developing device has been widely known. For example, Japanese Unexamined Utility Model Publication No. 4-16459 discloses a suction duct in which the distal end portion covers the shield case from the outside and is formed between the duct wall surface and the shield case wall surface. An apparatus is disclosed in which air near the photoconductor is sucked through the gap.

[0014]

By the way, the developer powder generated from the developing device is not uniformly floating,
Its existence varies from place to place. For example, the inventor of the present application has found that the state of existence of powder smoke generated from the developing device differs at least in the upstream and downstream of the developing device with respect to the rotation direction of the photosensitive drum. FIG. 2 shows a schematic diagram of this smoke generation situation. 2, reference numeral 10c denotes a developing sleeve of the developing device 10. The developer dust is generated with the rotation of the photosensitive drum 1 indicated by the arrow A and the rotation of the developing sleeve 10c indicated by the arrow D. The dust is mainly downstream of the developing device 10 near the surface of the photosensitive drum 1. It occurs in a wide area near the developing device 10 upstream. Moreover, the former generates more than the latter. Developing device 1
The powder dust generated toward the downstream of zero is also generated in a relatively small amount but partially in a wide range.

[0015] However, there is no conventional device having a configuration that takes into account the presence of the various types of powder smoke described above. For example, the apparatus described in Japanese Utility Model Laid-Open No. 4-16459 is not configured to have a suction port corresponding to the above-mentioned various types of smoke having different existence states, and thus it is difficult to suck the smoke without fail. . If it is desired to suck the smoke with this device without fail, it is necessary to increase the opening area of the suction port and to suck the smoke with an extremely large suction air volume. This poses a problem in terms of power consumption. SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus provided with a suction port according to the presence of developer powder in order to solve the above problems.

[0016]

That is, according to the present invention, there is provided an image carrier in a main body of the apparatus, a first developing device provided opposite to the image carrier, and suctioning air near the developing device. A suction port having an opening area different from each other depending on the presence of a developer plume generated from the developing device at the end of the duct. A plurality is formed in the rotation direction.

[0017]

According to the present invention, for example, powder smoke scattered over a wide area is sucked by the suction port having a wide opening area, and the powder smoke having a limited distribution position has an opening surface close to the powder smoke existing portion. Smoke generated by the suction port
By using a suction port that matches the situation of powder smoke, such as making the opening area relatively small or making the suction area with a larger cross-sectional area of the ventilation path leading to the suction port and increasing the suction air volume to suction. It sucks smoke without fail. However, the suction port is formed by cutting the ventilation path by one plane, and this plane is called an opening surface.

[0018]

Embodiment 1 An embodiment of the present invention will be described below with reference to the accompanying drawings. The basic configuration of the apparatus main body of the present invention is the same as that shown in FIG.

The detailed structure near the second charger 4 of the present invention will be described with reference to the cross-sectional view shown in FIG. A corona wire 4b is stretched on the second charging charger 4 in parallel with the rotation axis of the photosensitive drum 1.
Are surrounded by a conductive shield case 4a, except for the surface facing the surface of. A grid electrode 12 is provided on the surface of the shield case 4a facing the photoconductor. On the other hand, the suction duct 9 for sucking the air in the vicinity of the developing device is provided such that the tip of the duct is located between the two developing devices 3 and 5, and the tip of the duct is further divided into two vertically. It is branched so that the upper side is a first ventilation path and the lower side is a second ventilation path.

Each air passage is formed between two wall surfaces of the duct 9 parallel to the drum rotation axis. For example, the first ventilation path is formed between the wall surfaces 13 and 14. Therefore,
In the following description, the term “air passage width” refers to the distance between the two duct wall surfaces.

The first air passage is formed between two parallel wall surfaces of the duct and is disposed between the first developing device 3 and the second charging charger 4, and has a width of the air passage. a
Is constant. A first suction port 9a is provided at the end of the first ventilation path, and its opening surface is parallel to the rotation axis of the photosensitive drum 1 and is close to and opposed to the surface of the photosensitive member 1. In this embodiment, the distance from the surface of the photoconductor 1 to the first suction port 9a is 1 mm.

The second air passage is provided between the second charging charger 4 and the second charging device.
It is formed between the developing unit 5. Of this second ventilation path,
The cross section perpendicular to the rotation axis of the drum 1 has a trumpet shape that becomes wider toward the tip of the second ventilation path. A second suction port 9b is provided at the tip of the second ventilation path, and its opening surface is parallel to the rotation axis of the drum 1 and further directed to a development site of the second developing device 5 below the rotation axis. I have.

In this embodiment, the minimum widths f and g of the ventilation passages near the division point from the duct body are substantially the same. That is, the cross-sectional area of the first ventilation path at the division point from the duct 9 main body is substantially the same as the cross-sectional area of the second ventilation path at the division point from the duct 9 main body. However, in the opening surface of the second suction port 9b,
The air passage width b of the second air passage is larger than the air passage width a of the first air passage on the opening surface of the first suction port 9a. That is, the opening area of the second suction port 9b is larger than that of the first suction port 9a.

Further, the surface of the drum 1 and the first suction port 9a
And the shortest distance d between the surface of the drum 1 and the second suction port 9b are both the shield case 4a and the drum 1
Is configured to be equal to or less than the distance e from the surface of the.

FIG. 4 shows the state of the generated smoke and the manner in which the suction duct 9 sucks the smoke. The operation of this embodiment will be described with reference to FIG. With the rotation of the developing sleeve 10a of the first developing unit 3 and the photosensitive drum 1, smoke is generated from the vicinity of the developing site of the sleeve 10a toward the downstream side. On the other hand, with the rotation of the developing sleeve 10b of the second developing unit 5 and the drum 1, smoke is generated from the vicinity of the developing portion of the sleeve 10b toward the upstream. The former produces more smoke.

Dust smoke flowing downstream from the first developing unit 3 is mainly generated near the surface of the photosensitive drum 1. This powder smoke is sucked by the first suction port 9a provided near the photoconductor 1. In addition, the powder smoke going upstream of the second developing device 5
It scatters widely over the vicinity of the developing device 5. This smoke is
It is arranged toward the developing site of the developing device 5 and b> a
The second suction port 9b whose opening area is larger than that of the first suction port 9a is sucked without leakage.

Further, the difference in the opening area described above appears as a difference in the suction force of each suction port. That is, the first suction port 9
The suction force of a is larger than that of the second suction port 9b. Therefore, a large amount of smoke is generated by the first suction port 9 having a large suction force.
a, and a small amount of powder smoke is supplied to the second suction port 9 having a small suction force.
Efficient suction can be performed by appropriately allocating the suction force such as suction in b. The suction force referred to here indicates an air volume per unit area at the opening. In this embodiment, the minimum air passage widths f and g near the division point of each air passage from the main body of the duct 9 are substantially the same, but the suction force of the first suction port 9a is further increased as f> g. It is also possible.

Furthermore, since the position of each suction port is closer to the photosensitive member 1 than the shield case 4a, dust does not enter the inside of the shield case, so the inside of the shield case 4a, the corona wire 4b, the grid electrode 12 can be prevented.

FIG. 5 is a cross-sectional view of the apparatus when an opening 4c is provided on the back surface of the shield case 12 of the second charger 4 and a third suction port 9c is provided in the suction duct 9 so as to overlap the opening 4c. Shown in As described above, the smoke generated from the first developing device 3 and the second developing device 5 is supplied to the first suction port 9a and the second suction port 9 disposed above and below the second charger 4.
Since the developing device smoke is completely absorbed by b, the developing device smoke is not sucked from the third suction port 9c. Therefore, it is possible to suck and remove corona products such as ozone generated by corona discharge from the charger 4 while avoiding contamination of the developing device powder inside the charger 4.

[0030]

Second Embodiment In the first embodiment, the smoke scattered to the downstream side is treated as scattered along the photoreceptor drum. However, in fact, not all of the smoke scatters along the photoreceptor. It scatters widely over the vicinity of the developing device. Usually, a small amount of powder smoke is scattered over a wide range, and therefore, the same as in the first embodiment may be used. However, when the ratio of powder smoke scattered over a wide range among the powder smoke generated from the first developing device to the downstream side under various conditions becomes large, it is necessary to provide a suction port corresponding to this powder smoke. . Therefore, in the present embodiment, a description will be given of an apparatus capable of sucking powder dust generated in a wide area downstream of the developing device.

The structure of this embodiment will be described with reference to FIG. This embodiment is the same as the first embodiment except that a third suction port is further provided on the first suction port.

The distal end of the suction duct 9 disposed upstream of the second charger 4 is divided into two upper and lower air passages by a rib 16 parallel to the rotation axis of the drum 1. The first suction port 9d has a third suction port 9f thereon.
Are formed respectively. Therefore, in the following description, the width of the ventilation path refers to the distance between the duct wall surface and the rib 16.

The third suction port 9f has an opening surface parallel to the rotation axis of the photosensitive drum 1 and is provided toward a developing portion of the first developing unit 3 located upstream of the rotation axis. 1st suction port 9d
Is provided close to the photosensitive drum 1 with its opening surface facing.

Further, in the opening surface of the third suction port 9f,
The air passage width h of the upper air passage is larger than the air passage width a 'of the lower air passage on the opening surface of the first suction port 9d. That is, the third suction port 9f has a larger opening area than the first suction port 9d. Furthermore, the minimum ventilation path width f ′ near the division point from the main body of the duct 9 in the ventilation path leading to the first suction port 9d is near the division point from the duct main body in the ventilation path leading to the third suction port 9f. Is configured to be larger than the minimum ventilation path width i. The second suction port 9e is used in the second embodiment.
Is the same as

Next, the operation of this embodiment will be described.
FIG. 7 is a schematic diagram showing the operation of the second embodiment of the present invention.
As the developing sleeve 10a of the first developing device 3 and the photosensitive drum 1 rotate, dust smoke is generated from the vicinity of the developing portion of the sleeve 10a toward the downstream side. This smoke mainly occurs near the drum 1, but a part of the smoke widely occurs near the developing device 3. Further, similarly to the first embodiment, the second developing device 5 is also moved upstream from the developing sleeve 10b of the second developing device 5.
A wide range of powder smoke is generated in the vicinity.

Among the powder smoke going downstream from the first developing device 3, the one scattered over a wide area is disposed toward the developing site of the first developing device 3 and has the third suction port 9 f having a wide opening area. Is sucked by The powder smoke generated in the vicinity of the photosensitive drum 1 is sucked by a first suction port 9d provided near the drum 1. The powder smoke going upstream from the second developing device 5 is sucked by the second suction port 9e.

Further, as f ′> i, the first suction port 9 d
The cross-sectional area of the ventilation path leading to the third suction port 9f at the division point from the duct body is larger than the cross-sectional area of the ventilation path leading to the third suction port 9f at the division point from the duct body, and the opening of the first suction port 9d. Since the area is smaller than the opening area of the third suction port 9f, the first suction port 9d is
Smoke dust can be sucked with a stronger suction force than the suction port 9f. Accordingly, the suction power is appropriately distributed, such that a large amount of dust smoke is sucked through the first suction port 9d having a large suction force, and a small amount of dust smoke is suctioned through the third suction port 9f having a small suction force. And efficient suction can be performed. In this embodiment, since the opening areas of the suction ports are different, f ′ = i
The minimum width of each air passage near the division point from the duct body may be the same.

Further, when the amount of smoke generated from the second developing unit 5 is small, as shown in FIG. 8, instead of providing the second suction port 9e, the upper surface of the second developing unit is exposed to light. A polyester film 15 may be provided on the upper surface of the second developing device so as to substantially block the gap between the surface of the body drum 1 and the developer may be prevented from being scattered by the polyester film 15. .

In this embodiment, the number of toner suction ports is three, but four or more toner suction ports may be provided in accordance with the presence of powder smoke. Further, an image forming apparatus having three or more developing units in the apparatus main body and a charger between these developing units has the same configuration as that shown in the first and second embodiments. Suction ports may be provided upstream and downstream of each charger. Further, the apparatuses shown in the first and second embodiments are capable of removing dust in the apparatus main body even if the image forming apparatus does not include a charger between two developing units. It is valid.

[0040]

According to the present invention, various types of developer smoke generated from a developing device can be adjusted according to various situations of smoke.
By the plurality of suction ports having different opening areas, it is possible to perform suction removal without leakage. Accordingly, it is possible to minimize the contamination in the apparatus main body and the contamination of the charger disposed near the developing device. In addition, since the air volume can be appropriately distributed according to the status of the smoke, the smoke can be removed with a minimum suction force, which leads to power saving.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an apparatus according to first and second embodiments of the present invention.

FIG. 2 is an explanatory diagram showing a state of generation of developer fumes.

FIG. 3 is a sectional view of a main part of the first embodiment of the present invention.

FIG. 4 is an explanatory view showing the operation of the first embodiment of the present invention.

FIG. 5 is a sectional view of an apparatus according to another embodiment of the first embodiment of the present invention.

FIG. 6 is an enlarged view of a main part of a second embodiment of the present invention.

FIG. 7 is an explanatory view showing the operation of the second embodiment of the present invention.

FIG. 8 is a sectional view of an apparatus according to another embodiment of the second embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photosensitive drum 2 first charging charger 3 first developing device 4 second charging charger 5 second developing device 9 suction ducts 9a, 9b, 9d, 9e, 9f

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/08 G03G 15/00 303

Claims (7)

(57) [Claims] 1. An image forming apparatus comprising: an image carrier in an apparatus main body; a first developing device provided to face the image carrier; and a duct for sucking air near the developing device. In the apparatus, at the tip of the duct, a plurality of suction ports having opening areas different from each other are formed in the rotation direction of the image carrier according to the presence state of the developer plume generated from the developing device. An image forming apparatus comprising: A second developing device provided downstream of the first developing device in the direction of rotation of the image carrier, wherein the plurality of suction ports are provided between the first developing device and the second developing device. The plurality of suction ports are provided with a first suction port provided so that an opening surface is close to the image carrier, and a plurality of suction ports are provided such that the opening surface faces a developing portion of the second developing device. 2. The image forming apparatus according to claim 1, further comprising a second suction port provided, wherein the second suction port has a larger opening area than the first suction port. 3. The method according to claim 1, wherein the first developing device and the second developing device are
A charging unit for charging the surface of the image carrier; the first suction port is disposed between the first developing device and the charging unit; and the second suction port is connected to the second developing device. 3. The image forming apparatus according to claim 2, wherein said image forming apparatus is disposed between said charging unit and said charging unit. 4. A plurality of suction ports are provided downstream of the first developing device in a rotation direction of the image carrier, and the plurality of suction ports are arranged such that an opening surface is close to the image carrier. A first suction port provided, and a second suction port disposed so that an opening surface faces a development site of the first developing device, wherein the second suction port is located at a position closer to the first suction port than the first suction port. 2. The image forming apparatus according to claim 1, wherein the opening area is large. 5. The image forming apparatus according to claim 4, further comprising a charging unit for charging the surface of the image carrier downstream of the first suction port and the second suction port in the rotation direction of the image carrier. 6. A sectional area of a ventilation passage communicating with the first suction port at a division point from the duct main body, which is defined by the second passage.
The image forming apparatus according to claim 2, wherein a cross-sectional area of a ventilation path leading to the suction port at a division point from the duct main body is larger. 7. A corona discharge device in which a corona wire is stretched in a conductive shield case, wherein a portion of each of the suction ports closest to the image carrier, the charging device includes: 6. The image forming apparatus according to claim 3, wherein a distance of the image forming apparatus is equal to or shorter than a distance between the shield case and the image carrier.