JP2006276092A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which develops an electrostatic latent image on a photoreceptor by a development roller of a developing unit to transfer a formed toner image to a running transfer belt and easily and inexpensively suppresses scattering of smoke toner generated in accordance with development of the electrostatic latent image on the photoreceptor. <P>SOLUTION: The image forming apparatus develops the electrostatic latent image to be formed on the photoreceptor drum 11 by the development roller 141 of the developing unit 14 to make it into a the toner image and transfers the toner image to the transfer belt 4. A part 142 of a developing unit case faces a photoreceptor drum 11 and the transfer belt 4. An air current control board 5 is arranged between the photoreceptor drum 11 and the part 142 of the developing unit case. The air current control board 5 guides air current which flows and folds back in the direction of the transfer belt 4 along the photoreceptor drum 11 from the development roller 141 mainly from between the part 142 of the case and the air current control board 5 in the direction of the development roller 141. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using toner, such as a copying machine, a printer, a facsimile machine, a multifunction machine that combines two or more of these.

  As an image forming apparatus that forms an image using toner, an electrostatic latent image corresponding to a document image is formed on a rotating photosensitive member by image exposure, and the electrostatic latent image is developed by a developing roller that rotates a developing device. A visible toner image is widely known. The toner image on the photoreceptor is transferred to a recording medium and fixed by a fixing device.

  In transferring the toner image on the photosensitive member to the recording medium, the toner image on the photosensitive member may be directly transferred onto the recording medium, but two or more color images (typically full-color images) may be transferred. In the image forming apparatus capable of forming, each color toner image formed on the photosensitive member is sequentially primary-transferred onto an intermediate transfer body (for example, a traveling transfer belt) in order for each color toner image, and then the intermediate transfer A multiple toner image is secondarily transferred from the body onto the recording medium and fixed. Of course, in a color image forming apparatus, it is also possible to form a monochrome image using a single color toner (for example, black toner).

  In any case, in an image forming apparatus that forms an image using toner, if the device is not devised, dust toner is generated in the developing area where the electrostatic latent image on the photoreceptor is developed by the developing device, and this is developed. The aircraft will be scattered over a wide area and contaminated inside the aircraft. For this reason, a seal member for suppressing toner scattering is provided in the developing device so that the toner does not splash from the developing device, and the toner scattering is suppressed by configuring the developing device to prevent the internal pressure from rising. Attempts have been made (Japanese Patent Laid-Open No. 60-120376).

Japanese Patent Application Laid-Open No. 60-120376

However, the method of providing the seal member in the developing device requires the addition of the seal member in the development of the developing device, and the seal member is connected to the other members of the developing device so that the toner scattering suppression effect is exhibited. The cost of the developing device has been increased due to the necessity of adjusting the positional relationship between the two and the like. As disclosed in Japanese Patent Application Laid-Open No. 60-120376, even when the developing device is configured to prevent an increase in pressure inside the developing device, the developing device is expensive.
In particular, in an image forming apparatus provided with a developing device for each color toner, such as the above-described color image forming device, the number of developing devices is large, so that the image forming device becomes more expensive.

  Accordingly, the present invention is configured to develop an electrostatic latent image formed on a rotating photosensitive member using a developing roller that rotates a developing device to form a toner image, and to transfer the toner image to a traveling transfer belt. It is an object of the present invention to provide an image forming apparatus that can easily and inexpensively suppress scattering of dust toner that occurs with development of an electrostatic latent image on a photoreceptor by a developing device. To do.

The present inventor has conducted research in order to solve the above problems, and has obtained the following knowledge.
An image forming apparatus configured to develop an electrostatic latent image formed on a rotating photosensitive member using a developing roller that rotates a developing device to form a toner image, and to transfer the toner image to a running transfer belt For example, in a tandem type color image forming apparatus, the rotation direction of the developing roller is opposite to the rotation direction of the photosensitive member, and the traveling direction of the transfer belt is the moving direction of the surface of the photosensitive member facing the transfer belt And a part of the case of the developing unit faces both the photoconductor and the transfer belt from the upstream side in the running direction of the transfer belt, and the developing roller of the developing unit is attached to the developing unit case. There is an image forming apparatus that is provided on the photosensitive drum at a position farther from the transfer belt than a part thereof.

  In such an image forming apparatus, an airflow control plate in which one end portion is located on the transfer belt side and the other end portion is located on the developing roller side between the photosensitive drum and a part of the developing device case. The air flow control plate causes the air flow to flow from the developing roller to the transfer belt along the photosensitive drum, and to return the air flow mainly from between the part of the developing device case and the air flow control plate. If directed toward this direction, it is possible to suppress a wide range of scattering to the periphery of the dust toner generated in the development region.

  Moreover, the airflow control plate can be disposed substantially independently from the developing device main body outside the developing device main body, regardless of whether the airflow control plate is arranged separately from the developing device or is attached to the developing device. In addition, an inexpensive airflow control plate material can be selected and adopted, and accordingly, the airflow control plate material can be arranged simply and inexpensively.

  Based on this knowledge, the present invention develops an electrostatic latent image formed on a rotating photosensitive member using a developing roller that rotates a developing device to form a toner image, and transfers the toner image to a transfer belt that runs. An image forming apparatus configured to perform the rotation of the developing roller in a direction opposite to the rotation direction of the photosensitive member, and the traveling direction of the transfer belt corresponds to the surface portion of the photosensitive member facing the transfer belt. The developing unit case partly faces both the photoconductor and the transfer belt from the upstream side in the transfer belt traveling direction, and the developing roller of the developing unit is the developing unit. The photosensitive drum is disposed on the photosensitive drum at a position farther from the transfer belt than a part of the case, and one end portion is located on the transfer belt side between the photosensitive drum and a part of the developing device case. And the other end is An airflow control plate located on the developing roller side is disposed. The airflow control plate flows from the developing roller along the photosensitive member toward the transfer belt, and mainly returns the airflow to the developing device case. Provided is an image forming apparatus which is a control plate that leads from a part of the airflow control plate to the developing roller.

  According to the inventor's research, the airflow control by the airflow control plate is performed by transferring the position of the plate surface on the photoconductor side of the airflow control plate or the position of the plate surface on the partial side of the developing device case, The position of the plate surface on the photosensitive member side, the position of the plate surface on the partial side of the developing device case at the one end portion on the belt side, and a part of the photosensitive member and the developing device case in the one end region of the airflow control plate It is greatly affected by the distance between them, and is also influenced by the position of the one end portion of the airflow control plate with respect to the transfer belt and the gap distance between a part of the developing device case and the transfer belt.

  Therefore, the distance from the plate surface to the photoconductor on the vertical line standing on the plate surface facing a part of the developing device case at one end portion of the airflow control plate is A, and the one end portion of the airflow control plate The distance from the plate surface to a part of the developing device case on the perpendicular line standing on the plate surface facing the photoconductor is B, and the plate surface facing the part of the developing device case at one end of the airflow control plate When the distance from the photoconductor to a part of the developing device case on the perpendicular line is C ≦ A ([2/3) · C] and B ≦ [(2/3) · C] It is desirable to satisfy. In this case, the lower limits of A and B are of course within a range where an airflow control plate having a thickness can exist.

  When the distance A is larger than (2/3) · C, the distance between a part of the developing device case and the airflow control plate becomes too small, and the transfer belt extends along the photosensitive member from the developing roller. The airflow flowing back and returning mainly returns between the airflow control plate and the photoconductor along the airflow control plate, and the airflow between the airflow control plate and the photoconductor may be disturbed. If the distance A is further increased, it becomes difficult to obtain the airflow control effect by the airflow control plate.

  Further, when the distance A becomes larger than (2/3) · C, the airflow control plate is more contaminated on the surface of the photosensitive member, and the airflow control plate is provided in a manner attached to the developing unit. When the airflow control plate is also attached and detached together with the developing device main body when the developing device is replaced, dirt on the surface of the airflow control plate on the photosensitive member side easily touches the user's hand and contaminates the user. From this point of view, it can be said that it is desirable to suppress contamination of the plate surface on the photosensitive member side of the airflow control plate as A ≦ [(2/3) · C].

When the distance B is larger than (2/3) · C, the distance between the photoconductor and the airflow control plate becomes too small, and a smooth airflow flowing from the developing roller along the photoconductor toward the transfer belt is generated. It becomes difficult to get. When B is further increased, it becomes difficult to obtain the airflow control effect by the airflow control plate.

  Further, when the shortest distance between the airflow control plate and the transfer belt is D and the shortest distance between a part of the developing device case and the transfer belt is E, 1 [mm] ≦ (D−E) is satisfied. It is desirable to make it.

When (DE) becomes smaller than 1 mm, the position of one end of the airflow control plate on the transfer belt side approaches the same surface position as the surface of the developing device case facing the transfer belt, or the developing device When the position of the surface of the case facing the transfer belt is exceeded, the airflow that flows from the developing roller to the transfer belt along the photosensitive member is turned between the transfer belt and a part of the developer case. It becomes easy to flow in and the dust toner is easily scattered.
However, if (DE) is too large, the effect of providing the airflow control plate cannot be obtained. Therefore, although depending on other conditions, (DE) may be about 5 mm or less. .

  In any case, an airflow filter may be provided between the airflow control plate and a part of the developing device case in order to capture the dust toner as much as possible and suppress the scattering thereof.

  As described above, according to the present invention, the electrostatic latent image formed on the rotating photosensitive member is developed using the rotating developing roller of the developing device to form a toner image, and the toner image is transferred to the transfer belt. Provided is an image forming apparatus configured to transfer, and capable of easily and inexpensively suppressing scattering of dust toner generated by development of an electrostatic latent image on a photoreceptor by a developing device. can do.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a tandem full-color image forming apparatus as an example of an image forming apparatus according to the present invention.
The image forming apparatus includes an endless intermediate transfer belt 4 which is wound around rollers (pulleys) 31, 32 and 33 and is driven to rotate counterclockwise (in the direction of the arrow in the figure) by the driving roller 31. Yes. A cleaner CL for removing residual toner and the like on the intermediate transfer belt 4 faces the lower left roller 32 in the figure, and a secondary transfer roller 6 faces the roller 31 on the right side in the figure. A fixing device 8 is installed above the secondary transfer roller 6.

Between the rollers 32 and 31, the yellow image forming unit Y, the magenta image forming unit M, the cyan image forming unit C, and the black image forming unit K are arranged in this order along the intermediate transfer belt 4 from the rollers 32 to 31. Is arranged in.
Each image forming unit includes a drum-type photoconductor 11, and a charging device 12, an image exposure device 13, a developing device 14, a primary transfer roller 2, and residual toner on the photoconductor around the photoconductor. The cleaners 15 to be removed are arranged in this order. The primary transfer roller 2 faces the photoconductor 11 with the intermediate transfer belt 4 in between. Each image forming unit is provided with an airflow control plate 5. The airflow control plate 5 will be described in detail later.

  A predetermined high voltage for charging the photosensitive member is applied to the charging device 12 of each image forming unit at a predetermined timing from a power supply (not shown). A predetermined developing bias is applied to the developing roller 141 of the developing unit 14 of each image forming unit at a predetermined timing from a developing bias power source for the image forming unit (not shown).

The primary transfer roller 2 of each image forming unit receives a toner image on the photoconductor 11 from the primary transfer power source for the image forming unit (not shown) to the intermediate transfer belt 4. Applied at the timing of primary transfer.
A secondary transfer voltage is applied to the secondary transfer roller 6 from a secondary transfer power supply (not shown) at the timing of secondary transfer of the toner image on the intermediate transfer belt 4 to the recording medium S.

According to the image forming apparatus shown in FIG. 1, image formation is performed as follows.
An image is formed in at least one of the image forming portions Y, M, C, and K according to the image to be finally formed.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and the primary transfer is performed on the intermediate transfer belt 4. Is done.

  That is, in the yellow image forming portion Y, the photoconductor 11 is rotated in the clockwise direction in the drawing, and the surface of the photoconductor 11 is uniformly charged to a predetermined potential by the charging device 12, and the image exposure device 13 is placed in the charged area. Then, image exposure for yellow image is performed, and an electrostatic latent image for yellow is formed on the photoreceptor 11. This electrostatic latent image is developed into a visible yellow toner image by a developing roller 141 that is applied with a developing bias of a developing unit 14 having yellow toner and is driven to rotate counterclockwise in the figure, and the toner image is converted into a visible yellow toner image. The image is transferred onto the intermediate transfer belt 4 by the primary transfer roller 2 to which the primary transfer voltage is applied.

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the intermediate transfer belt 4, and a cyan toner image is formed and transferred to the intermediate transfer belt 4 in the cyan image forming unit C. A black toner image is formed at K and transferred to the intermediate transfer belt 4.

Yellow, cyan, magenta, and black toner images are formed at a timing at which these toner images are transferred onto the intermediate transfer belt 4 in an overlapping manner.
Thus, the multiple toner image formed on the intermediate transfer belt 4 moves toward the secondary transfer roller 6 by the rotation of the intermediate transfer belt 4.

  On the other hand, the recording medium S is supplied from a recording medium supply unit such as transfer paper (not shown) to the timing roller pair 7 and further synchronized with the multiple toner images on the intermediate transfer belt 4 from the timing roller pair 7. Thus, the multiple toner image is transferred onto the recording medium S by the secondary transfer roller 6 supplied between the transfer belt 4 and the secondary transfer roller 6 and applied with the secondary transfer voltage. Thereafter, the recording medium S is passed through the fixing device 8, where the multiple toner images are fixed to the recording medium S under heat and pressure, and a predetermined color image is formed.

The airflow control plate 5 in each of the image forming units Y, M, C, and K of the image forming apparatus described above is arranged as shown in FIG.
As shown in FIG. 2, in each image forming unit, the rotation direction of the developing roller 141 is opposite to the rotation direction of the photoconductor 11, and the transfer belt 4 faces the running direction of the transfer belt 4. The direction of movement of the surface portion of the photoconductor 11 is the same. Further, a part 142 of the case 140 of the developing unit 14 faces both the photoconductor 11 and the transfer belt 4 from the upstream side in the transfer belt running direction. The developing roller 141 is provided on the photosensitive drum 11 at a position farther from the transfer belt 4 than the case portion 142.

The airflow control plate 5 is disposed between the photoconductor 11 and the case portion 142 so that the upper end portion is located on the transfer belt 4 side and the lower end portion is located on the developing roller 141 side.
At the upper end portion of the airflow control plate 5, the distance from the plate surface to the photosensitive member 11 is A on a vertical standing on the plate surface on the side facing the developing device case portion 142. Similarly, at the upper end portion of the airflow control plate 5, the distance from the plate surface to the developing device case portion 142 is B on a vertical line standing on the plate surface on the side facing the photoconductor 11. Further, the distance from the photoconductor 11 to the case portion 142 on the vertical line on the plate surface on the side facing the developing device case portion 142 at the upper end of the airflow control plate is C.

  Although not limited thereto, in the illustrated control plate 5, the plate surface on the side facing the developing device case portion 142 and the plate surface on the side facing the photoconductor 11 at the upper end of the control plate 5 are parallel. The perpendiculars that stand on the plate surfaces for measuring the distances A, B, and C coincide with each other. In the illustrated control plate 5, the plate surface on the side facing the developing device case portion 142 at the upper end of the control plate 5 and the plate surface facing the photoconductor 11 are both on the control plate 5. It is perpendicular to the end face. A ≦ [(2/3) · C] and B ≦ [(2/3) · C] are set.

Further, the shortest distance between the upper end 5a of the airflow control plate 5 and the transfer belt 4 is D, and the shortest distance between the developing device case portion 142 and the transfer belt 4 is E, and 1 [mm] ≦ (DE). ≦ 5 [mm].
The airflow control plate 5 in the illustrated example is gradually formed thinner from the upper end portion to the lower end portion.
An airflow filtering filter FL is provided between the airflow control plate 5 and the developing device case portion 142 in order to capture the dust toner and suppress its scattering.

When the airflow control plate 5 for the image forming unit is not provided, as shown in FIG. 4 as a comparative example, when the transfer belt 4 runs for image formation and the photosensitive drum 11 and the developing roller 141 rotate, Airflows f1 ′, f2 ′, f3 ′, etc. are generated. That is, as the transfer belt 4 travels, an air flow f3 ′ that flows to the vicinity of the contact nip N between the transfer belt 4 and the photoconductor 11 and returns there along the upper surface 142a of the developer case portion 142 is generated. As it occurs, it flows from the developing roller 141 toward the transfer belt 4 along the photoconductor 11 to the vicinity of the nip portion N, and then turns back to generate airflows f1 ′ and f2 ′ that mainly flow out together with the airflow f3 ′. .
At this time, the dust toner generated as the electrostatic latent image on the photoconductor 11 is developed by the developing roller 141 of the developing device 14 is scattered over a wide area around the developing area on the air currents f1 ′ and f2 ′. End up.

  However, in the image forming apparatus shown in FIG. 1, when the transfer belt 4 travels for image formation in the image forming unit and the photosensitive drum 11 and the developing roller 141 rotate, as shown in FIG. While traveling, the airflow f3 flows to the vicinity of the nip portion N and then turns back and returns along the upper surface of the developer case portion 142, while the airflow f3 is generated from the developing roller 141 toward the transfer belt 4 along the photoconductor 11. The air flows to the vicinity of the nip portion N, is folded back there, flows mainly between the developing device case portion 142 and the air flow control plate 5, and further generates air flows f1 and f2 guided toward the developing roller 141.

  The dust toner generated as the electrostatic latent image on the photoconductor 11 is developed by the developing roller 141 of the developing device 14 returns to the developing roller 141 along the airflow control plate 5 and flows to the developing roller 141. It is restrained that it travels on the surface and scatters over a wide area from the development area to the periphery.

  FIG. 5 shows a case where an airflow control plate 5 'having the distance A larger than (2/3) · C is provided. In this case, as shown in FIG. 5, the air flow f2 (5 ′) flowing from the developing roller 141 along the photoconductor 11 toward the transfer belt 4 and returning is mainly the air flow control plate 5 ′ and the photoconductor. 11, the air flow between the air flow control plate 5 ′ and the photoconductor 11 may be disturbed. If the distance A is further increased, the air flow control plate It becomes difficult to obtain the airflow control effect by 5 '.

  Further, the surface of the airflow control plate 5 ′ on the side of the photoconductor 11 becomes more dirty, and the airflow control plate 5 ′ is provided in such a manner as to be attached to the developing device 14, and the airflow control plate 5 ′ is also developed when the developing device is replaced. In the case of being attached and detached together with the main body 14, dirt on the plate surface of the airflow control plate 5 ′ on the photoconductor side easily touches the user's hand and contaminates the user.

Although not shown, when the distance B is greater than (2/3) · C, it is difficult to obtain a smooth airflow that flows from the developing roller 141 along the photoconductor 11 toward the transfer belt 4. If the distance B is further increased, it becomes difficult to obtain the airflow control effect by the airflow control plate.
Therefore, in the image forming apparatus of FIG. 1, the distances A and B related to the airflow control plate 5 are
The conditions of A ≦ [(2/3) · C] and B ≦ [(2/3) · C] are satisfied.

FIG. 6 shows an example in which (D−E) is 0 which is 1 mm or less with respect to the distances D and E, that is, in the example of FIG. 6, the upper end 5a ″ faces the transfer belt 4 of the developing device case portion 142. The case where the airflow control plate 5 ″ which is substantially the same position as the upper surface 142a is employed is shown.
As described above, when (DE) becomes smaller than 1 mm, the air flow f2 (5 ″) that flows from the developing roller 141 toward the transfer belt 4 along the photosensitive member 11 and returns is mainly transferred. The toner flows into between the belt 4 and the upper surface 142a of the developing device case portion 142, and the dust toner on the belt 4 is scattered widely around the developing region.

Therefore, in the image forming apparatus of FIG. 1, 1 [mm] ≦ (DE) is set.
Note that the distance between the lower end portion of the airflow control plate and the developing roller 141 has a small influence on the airflow, and therefore may be appropriately determined within the range where the airflows f1 and f2 in FIG. 3 are obtained.

  The present invention is configured such that an electrostatic latent image formed on a rotating photoreceptor is developed using a rotating developing roller of a developing device to form a toner image, and the toner image is transferred to a running transfer belt. In the image forming apparatus, for example, a tandem type color image forming apparatus, it can be used for suppressing the dust toner generated in the developing area from being scattered widely around the developing area and contaminating the inside of the apparatus.

1 is a diagram showing an outline of an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an arrangement and the like of an airflow control plate in each image forming unit of the image forming apparatus in FIG. 1. It is a figure which shows the airflow control by arrangement | positioning of the airflow control board shown in FIG. 2, and by extension, a dust toner scattering suppression state. FIG. 2 is a diagram illustrating an airflow when an airflow control plate is not provided in the image forming unit of the image forming apparatus of FIG. 1. It is a figure which shows the example of an airflow in the case of arrange | positioning the airflow control board by making distance A larger than 2C / 3. It is a figure which shows the example of an airflow in case distance (DE) is made smaller than 1 mm, and an airflow control board is arrange | positioned.

Explanation of symbols

Y Yellow image forming portion M Magenta image forming portion C Cyan image forming portion K Black image forming portion 11 Photoconductor 12 Charging device 13 Image exposure device 14 Developer 141 Developer roller 140 Developer case 142 Part of developer case 142a Developer Upper surface 15 of the case portion 142 Cleaner 2 Primary transfer rollers 31, 32, 33 Transfer belt roller (pulley)
4 Intermediate transfer belt CL Cleaner 5, 5 ', 5 "Airflow control plate 5a Upper end 5a" of airflow control plate 5 Upper ends f1, f2, f3 of airflow control plate 5 "Airflow FL by airflow control plate 5 Airflow filter f1' , F2 ′, f3 ′ Airflow f2 (5 ′) without airflow control plate Folded airflow f2 (5 ″) by airflow control plate 5 ′ Folded airflow 6 by airflow control plate 5 ″ Secondary transfer roller 7 Timing roller pair 8 Fixing device S Recording medium

Claims (4)

An image forming apparatus configured to develop an electrostatic latent image formed on a rotating photosensitive member using a developing roller that rotates a developing device to form a toner image, and to transfer the toner image to a running transfer belt The rotation direction of the developing roller is opposite to the rotation direction of the photoconductor, and the running direction of the transfer belt is the same as the movement direction of the surface of the photoconductor facing the transfer belt, A part of the case of the developing unit faces both the photoconductor and the transfer belt from the upstream side in the running direction of the transfer belt, and the developing roller of the developing unit is more than the part of the developing unit case. A first end located on the transfer belt side and the other end on the developing roller side between the photosensitive drum and a part of the developing device case. Airflow located at A control plate is disposed, and the airflow control plate flows from the developing roller along the photosensitive drum toward the transfer belt, and returns the airflow mainly between a part of the developer case and the airflow control plate. An image forming apparatus, wherein the image forming apparatus is a control plate that guides the developing roller toward the developing roller. A distance from the plate surface to the photoconductor on a perpendicular standing on a plate surface facing a part of the developing device case at one end of the airflow control plate is A, and the photoconductor at one end of the airflow control plate. The distance from the plate surface to a part of the developing device case on a vertical line standing on the plate surface facing the surface of the developing device case is B, and the one end portion of the airflow control plate stands on the plate surface facing the part of the developing device case. The distance from the photosensitive drum to a part of the developer case on the vertical line is C, and satisfies A ≦ [(2/3) · C] and B ≦ [(2/3) · C]. The image forming apparatus according to claim 1. The shortest distance between the airflow control plate and the transfer belt is D, and the shortest distance between a part of the developing device case and the transfer belt is E, which satisfies 1 [mm] ≦ (D−E). The image forming apparatus according to claim 1 or 2. The image forming apparatus according to claim 1, wherein an airflow filter is provided between the airflow control plate and a part of the developing device case.