JP2016090879A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress a toner from dropping off while reducing scattering of toner through installation of a suction duct.SOLUTION: An image forming apparatus includes a developing device that develops an electrostatic latent image on the surface of an image carrier with a toner, a suction duct that is used to suck a toner scattering from the inside of the developing device, and blowing means for blowing the air to a wall surface of the suction duct, and removes a toner adhered to the wall surface by blowing the air.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus using toner.

  In recent years, in an image forming apparatus using an electrophotographic process, toner consumption tends to increase as a result of progress in colorization and speeding up. As toner consumption increases, toner scattering outside the developing device also increases.

  Since the scattered toner contaminates the inside of the image forming apparatus and causes defects such as image smearing, an image forming apparatus provided with a suction duct for sucking and removing the scattered toner is known. Thus, the toner scattered from the developing device is sucked and removed through the suction duct, and contamination in the image forming apparatus is suppressed.

JP 2008-39965 A JP-A-11-143223

  Although the toner scattering can be reduced by installing the suction duct as described above, the scattered toner accumulates on the wall surface of the suction duct (especially the wall surface near the opening) and peels off when vibration is applied for some reason. May fall. When a phenomenon (referred to as “toner spillage”) in which the lump of toner that has been peeled off adheres to the surface of the photoreceptor or the like occurs, it causes image defects.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of suppressing toner spillage while reducing toner scattering by installing a suction duct.

  An image forming apparatus according to the present invention includes a developing device that develops an electrostatic latent image on the surface of an image carrier with toner, a suction duct that is used to suck toner scattered from within the developing device, and a wall surface of the suction duct. Spraying means for spraying air, and removing the toner adhering to the wall surface by spraying the air.

  According to this configuration, it is possible to suppress toner spillage while reducing toner scattering by installing a suction duct.

  More specifically, in the above configuration, the suction duct has an opening that opens toward the space between the image carrier and the developing device, and the spraying means is near the opening in the suction duct. It is good also as a structure which blows air on the wall surface.

  More specifically, the spraying unit may spray air onto the wall surface at a timing within which the toner image is not formed. More specifically, the spraying means may be configured to spray air onto the wall surface through an air injection member disposed in the vicinity of the opening.

  Further, in the image forming apparatus having the above-described configuration, which includes a fan that generates an air flow in the suction duct and sucks the scattered toner by rotating the fan in a predetermined direction, the spraying unit includes the fan and the fan. It is good also as a structure which blows air on the said wall surface by rotating in the direction opposite to a predetermined direction. More specifically, the air flow path may be switched between when the spraying means blows air onto the wall surface and when the scattered toner is sucked.

  More specifically, in the above configuration, as a fan for generating an air flow in the suction duct, a first fan for generating an air flow in a direction for sucking the scattered toner, and an air flow in a direction for blowing air on the wall surface. A second fan to be generated may be provided separately, and the blowing means may be configured to blow air onto the wall surface using the second fan.

  More specifically, the above configuration may be configured such that the toner adhering to the axial end portion is removed by jetting air to the axial end portion of the developing sleeve in the developing device. More specifically, the above-described configuration may include a setting unit that variably sets the air volume of air blowing by the blowing unit.

  Further, in the image forming apparatus having the above-described configuration that performs printing on a sheet using the toner image, the setting unit is configured such that when the printing rate for a predetermined period falls below a predetermined reference condition, or exceeds a predetermined reference condition. It is good also as a structure which sets the said air volume large.

  According to the image forming apparatus of the present invention, it is possible to suppress toner spillage while reducing toner scattering by installing a suction duct.

1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. It is a block diagram of the image formation unit which concerns on this embodiment. 1 is a configuration diagram of a developing device according to a first embodiment and its surroundings. It is explanatory drawing regarding arrangement | positioning of an air injection nozzle. 2 is a configuration diagram of another type of developing device according to Example 1 and its surroundings. FIG. FIG. 6 is a configuration diagram of a developing sleeve and a periphery thereof according to a second embodiment. FIG. 10 is a configuration diagram of another form of a developing sleeve according to Example 2 and its periphery. It is the block diagram seen from the developing sleeve shown in FIG. 7, and its periphery from another direction. FIG. 10 is a configuration diagram of a developing device according to a third embodiment and its surroundings. FIG. 10 is a configuration diagram of another type of developing device according to Example 3 and its periphery. FIG. 10 is a configuration diagram of a developing device according to a fourth embodiment and its surroundings. 10 is a flowchart relating to setting of wind speed according to a fifth embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, the content of the present invention is not limited to the embodiment.

1. Example 1
[Overall configuration of image forming apparatus]
First, Example 1 will be described. FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus 1 according to the present embodiment. As shown in the figure, the image forming apparatus 1 includes an image forming unit 2, a paper feeding unit 3, a printing unit 4, a control unit 5, and the like. As a basic operation, the image forming apparatus 1 receives an input of image data from the outside (for example, a PC), and executes a printing operation for discharging the printed (printed) paper to the outside based on this.

  The image forming unit 2 plays a role of creating a toner image based on the image data and supplying the toner image to the printing unit 4 (conveyed by an intermediate transfer belt). The image forming apparatus 1 has both color printing and monochrome printing functions. For example, the image forming apparatus 1 has a plurality of toners corresponding to yellow (Y), magenta (M), cyan (C), and black (K) toners. An image forming unit 2 is provided. The configuration of the image forming unit 2 will be described in detail again.

  Note that the image forming apparatus 1 is configured to alternatively set a monochrome print mode or a color print mode as a print mode for performing printing in accordance with an instruction from the outside. In the monochrome printing mode, basically, only the black (K) image forming unit 2 is used, and printing of one black color is performed. On the other hand, in the color printing mode, the image forming units 2 for the respective colors are used, and printing in color is performed.

  The paper feed unit 3 includes a paper tray for storing paper, and supplies the paper to the printing unit 4 at the timing when the toner image is supplied. The printing unit 4 transfers and fixes the supplied toner image onto a sheet. The paper printed in this way is discharged to a paper discharge tray provided in the image forming apparatus 1.

  The control unit 5 is configured by a microcomputer, for example, and controls each unit so that various operations of the image forming apparatus 1 are appropriately executed.

  Next, the detailed configuration of the image forming unit 2 will be described. FIG. 2 is a configuration diagram of the image forming unit 2 (including a transfer roller and an intermediate transfer belt). As shown in the figure, the image forming unit 2 is provided with a photosensitive drum 11, a charging unit 12, an exposure unit 13, a developing device 14, a transfer roller 15, an intermediate transfer belt 16, and a cleaning unit 17.

  The photosensitive drum 11 is rotationally driven in a predetermined direction (counterclockwise direction in FIG. 2), and serves as an image carrier that forms and carries a toner image.

  The charging unit 12, the exposure unit 13, the developing device 14, the transfer roller 15, and the cleaning unit 17 are arranged in this order around the photosensitive drum 11 in the rotation direction (from the upstream side to the downstream side of the rotation). They are arranged side by side.

  The charging unit 12 serves to charge the photosensitive drum 11. The exposure unit 13 exposes the charged surface of the photosensitive drum 11 according to image data. As a result, the exposure device 13 forms an electrostatic latent image on the photosensitive drum 11 according to the image data.

  The developing device 14 supplies toner to the photosensitive drum 11 via a developing sleeve 141 (developing roller) that rotates in a predetermined direction (counterclockwise direction in FIG. 2). Thereby, the electrostatic latent image on the photosensitive drum 11 is developed (that is, a toner image is formed on the photosensitive drum 11).

  The transfer roller 15 is provided in contact with the intermediate transfer belt 16 at a position facing the photosensitive drum 11 with the intermediate transfer belt 16 interposed therebetween. The transfer roller 15 serves to transfer the toner image formed on the photosensitive drum 11 to the intermediate transfer belt 16.

  The toner image transferred to the intermediate transfer belt 16 is transferred to the paper in the subsequent printing unit 4 to achieve printing on the paper. The cleaning unit 17 plays a role of collecting and cleaning the toner remaining on the surface of the photosensitive drum 11.

[Peripheral configuration of developing device, etc.]
Next, the configuration of the developing device 14 and its periphery will be described in detail. FIG. 3 is a configuration diagram of the developing device 14 and its surroundings. As shown in this figure, in addition to the developing sleeve 141 described above, a suction duct 142, a compressor 31, an air injection nozzle 32, and the like exist in the developing device 14 or its periphery.

  The suction duct 142 is installed near the upper lid of the developing device 14 and opens toward the space between the photosensitive drum 11 and the developing device 14 (in other words, around the toner image forming area on the photosensitive drum 11). Has an opening. The opening is formed by an end region 143 a of the upper cover of the developing device 14 and an end region 143 b of the ceiling portion of the suction duct 142 (hereinafter, sometimes collectively referred to as “wall surface near the opening”).

  The inside of the suction duct 142 can generate an air flow in the suction direction (right direction in FIG. 3) using, for example, a fan. Thereby, the toner scattered from the developing device 14 is sucked and removed from the opening through the suction duct, and contamination in the image forming apparatus 1 is suppressed.

  However, when the scattered toner is sucked, a part of the toner adheres to the wall surface near the opening of the suction duct 142. Since such toner adhesion causes toner spillage, in this embodiment, there is provided means for blowing air onto the wall surface in the vicinity of the opening (hereinafter sometimes referred to as “spraying means”). . By spraying air by the spraying means, it is possible to remove the adhered toner and prevent toner spillage as much as possible.

  The spraying means of the present embodiment is realized by the compressor 31, the air injection nozzle 32, and the like. As an air blower using such a compressor, for example, the air blower disclosed in JP2013-142787A may be applied, and in addition, the air blower disclosed in JP-A-3-134676, Or the air blower using the fan disclosed by Unexamined-Japanese-Patent No. 2013-218144 etc. may be applied.

  The compressor 31 is connected to an air injection nozzle 32 (air injection member) so that air is injected from the tip of the air injection nozzle 32. The air injection nozzle 32 is attached to the vicinity of the opening of the suction duct 142 (for example, the ceiling of the suction duct 142).

  The air injected from the air injection nozzle 32 is blown to each wall surface (143a, 143b) in the vicinity of the opening of the suction duct 142, as indicated by solid arrows in FIG. As a result, the toner T adhering to these wall surfaces is removed. 4 shows an installation form of the air injection nozzle 32 when viewed from the viewpoint A shown in FIG. As shown in FIG. 4, the air injection nozzles 32 are supported by a nozzle support member, and a plurality of air injection nozzles 32 are arranged so as to be aligned in the same direction as the axial direction of the developing sleeve 141.

  As described above, in this embodiment, air is blown onto the wall surface of the suction duct 142 via the air injection nozzle 32 disposed in the vicinity of the opening of the suction duct 142. In addition, a fan may be used as a part of the blowing means instead of the compressor 31 described above. FIG. 5 exemplifies a configuration diagram of the developing device 14 and its periphery in such a configuration. In this case, air is ejected from the air ejection nozzle 42 as the fan 41 rotates. The point that the injected air blows to each wall surface (143a, 143b) near the opening of the suction duct 142 is the same as in the case of FIG.

  The timing at which the air is blown by the blowing means, the amount of air blown, and the like are appropriately controlled by the control unit 5. More specifically, the control unit 5 recognizes a period during which no toner image is formed (period during which image formation is not performed), and causes air to be blown at a timing within the period.

  During the period when the toner image is not formed, the cleaning unit 17 does not affect the image quality even if the toner lump that is peeled off by the air blowing adheres to the developing sleeve 141 or the photosensitive drum 11. Removed. Note that the air blowing by the spraying unit may be performed immediately before the image formation is performed after the image forming apparatus 1 enters the predetermined image stabilization adjustment mode.

2. Example 2
Next, Example 2 will be described. The second embodiment is basically the same as the first embodiment except that air is also blown to the end portion of the developing sleeve 141. In the following description, emphasis is placed on the description of parts different from the first embodiment, and description of common parts may be omitted.

  FIG. 6 is a configuration diagram of the developing sleeve 141 and its periphery in the present embodiment. 6 corresponds to the axial direction of the developing sleeve 141. As shown in the drawing, the developing sleeve 141 has a regulating plate 145 that regulates the amount of toner transport, and air jet nozzles 52 are provided in the vicinity of both axial ends of the developing sleeve 141.

  The air injection nozzles 52 are set so as to inject air to both end portions in the axial direction of the developing sleeve 141 (particularly portions of the regulation plate 145 in this embodiment). As a result, it is possible to remove the toner adhering to both ends of the developing sleeve 141 in the axial direction. The wind speed of the said injection is set to 10-13 m / s, for example in an injection nozzle position.

  The means for injecting air to both ends in the axial direction of the developing sleeve 141 can be realized by a blower using a compressor, for example. As an air blower using such a compressor, for example, the air blower disclosed in JP2013-142787A may be applied, and in addition, the air blower disclosed in JP-A-3-134676, Or the air blower using the fan disclosed by Unexamined-Japanese-Patent No. 2013-218144 etc. may be applied.

  A blower using a fan can also be applied as means for injecting air to both axial ends of the developing sleeve 141. The configuration of the developing sleeve 141 and its periphery in such a case is illustrated in FIG. 7 (a diagram in which the left-right direction is made coincident with the axial direction) and FIG. 8 (a diagram when viewed in the axial direction). In this configuration, air is ejected from the tip of the air ejection nozzle 62 as the fan 61 rotates. It should be noted that a scattered toner suction device is provided as in Example 3 to be described later, and air may be jetted from the tip of the air jet nozzle 62 using the fan.

  The timing and frequency of injecting air to both end portions in the axial direction of the developing sleeve 141 are equal to the timing and frequency of air blowing by the blowing means described in the first embodiment (means for blowing air to the wall surface of the suction duct 142). It may be different as necessary. In addition, the configuration in which air is jetted to the end portion in the axial direction of the developing sleeve 141 as in this embodiment can be applied to each embodiment described later.

3. Example 3
Next, Example 3 will be described. The third embodiment is basically the same as the first embodiment except for the form of the spraying means and the portion related thereto. In the following description, emphasis is placed on the description of parts different from the first embodiment, and description of common parts may be omitted.

  FIG. 9 is a configuration diagram of the developing device 14 and its periphery according to the present embodiment. As shown in the drawing, on the downstream side of the suction duct 142 in the suction direction, a scattered toner suction device 71, a fan 72, a backflow prevention valve 73, and three switching valves (75a to 75c) are provided.

  The scattered toner suction device 71 is provided with a filter 74 therein, and is a device that sucks and collects scattered toner flowing from the backflow prevention valve 73 side. The fan 72 is provided in the vicinity of the opening on the side opposite to the backflow prevention valve 73 in the scattered toner suction device 71, and generates an air flow in the suction duct 142 by rotating. Moreover, each switching valve (75a-75c) is a valve for switching the path | route of airflow. The fan 72 and the switching valves (75a to 75c) are controlled by the control unit 5.

  When sucking the scattered toner, the control unit 5 controls the fan 72 and the switching valves (75a to 75c) so that an air flow indicated by a solid arrow α in FIG. 9 is generated. That is, the fan 72 is rotated, the switching valve 75a is closed, the switching valve 75b is opened, and the switching valve 75c is closed. Thereby, the scattered toner can be removed by suction through the suction duct 142.

  On the other hand, when air is blown onto the wall surface of the suction duct 142 (that is, when the blowing means is functioned), the control unit 5 causes the fan 72 and each switching so that an air flow indicated by a dotted arrow β in FIG. 9 is generated. Control the valves (75a-75c). That is, the fan 72 is rotated in the opposite direction to the case where the scattered toner is sucked, the switching valve 75a is opened, the switching valve 75b is closed, and the switching valve 75c is opened.

  As a result, the toner adhering to the wall surface of the suction duct 142 can be removed. Note that the strength of the airflow in this case is set so that, for example, the wind speed is 15 to 18 m / s at the position where the scattered toner on the upper cover of the developing device 14 is deposited. As described above, in the present embodiment, the path of the airflow is switched between when the blowing means blows air on the wall surface of the suction duct 142 and when the scattered toner is sucked.

  Furthermore, in the present embodiment, the suction duct 142 is used as an air flow path by the blowing means. As another form of such a configuration, a fan (injection fan) that generates an airflow in the direction of sucking scattered toner and a fan (back-injection fan) that generates an airflow in the direction of blowing air to the wall surface of the suction duct 142. ) May be provided separately. FIG. 10 is a configuration diagram of the developing device 14 and its periphery in such a configuration.

  On the downstream side in the suction direction of the suction duct 142 shown in FIG. 10, a scattered toner suction device 81, a jet fan 82, a backflow prevention valve 83, a switching valve 85, and a reverse jet fan 86 are provided.

  In the case of this configuration, when sucking the scattered toner, the control unit 5 controls the ejection fan 82 and the switching valve 85 so as to generate the air flow indicated by the solid line arrow α in FIG. On the other hand, when the air is blown onto the wall surface of the suction duct 142 (when the blowing means is made to function), the control unit 5 causes the reverse injection fan 86 and the air flow shown by the dotted arrow β in FIG. The switching valve 85 is controlled. Thus, the blowing means blows air onto the wall surface of the suction duct 142 using the reverse injection fan 86.

4). Example 4
Next, Example 4 will be described. The fourth embodiment is basically the same as the third embodiment except for the portion related to the developing sleeve air jetting means. In the following description, emphasis is placed on the description of parts different from the third embodiment, and description of common parts may be omitted.

  FIG. 11 is a configuration diagram of the developing device 14 and its periphery according to the present embodiment. As shown in the drawing, a developing sleeve air ejecting means 146 is provided in the vicinity of the developing device 14. The developing sleeve air ejecting means 146 allows air to pass from the rear end toward the front end, the rear end is connected to the air flow path on the fan 72 side, and the front end is the end of the developing sleeve 141 in the axial direction. It opens toward the part (one end or both ends).

  Further, the switching valve 75c of the present embodiment includes a position “d” (a position where the fan 72 and the suction duct 142 are blocked) and a position “e” (the fan 72 and the developing sleeve air injection means shown in FIG. It is possible to switch between the position 146 and the position where the space between the 146 side is cut off. The fan 72 and the switching valves (75a to 75c) are controlled by the control unit 5.

  When sucking the scattered toner, the control unit 5 controls the fan 72 and the switching valves (75a to 75c) so that an air flow indicated by a solid arrow α in FIG. 11 is generated. That is, the fan 72 is rotated, the switching valve 75a is closed, the switching valve 75b is opened, and the switching valve 75c is set to the position “d”. Thereby, the scattered toner can be removed by suction through the suction duct 142.

  On the other hand, when air is blown onto the wall surface of the suction duct 142 (when the blowing means is made to function), the control unit 5 causes the fan 72 and each switching valve to generate an air flow indicated by a dotted arrow β in FIG. (75a-75c) is controlled. That is, the fan 72 is rotated, the switching valve 75a is opened, the switching valve 75b is closed, and the switching valve 75c is set to the position “e”. As a result, the toner adhering to the wall surface of the suction duct 142 can be removed.

  Further, when air is blown to the axial end portion of the developing sleeve 141, the control unit 5 turns on the fan 72 and each switching valve (75a to 75c) so that an air flow indicated by a one-dot chain line arrow γ in FIG. 11 is generated. Control. That is, the fan 72 is rotated, the switching valve 75a is opened, the switching valve 75b is closed, and the switching valve 75c is set to the position “d”. As a result, it is possible to remove the toner adhering to the end portion of the developing sleeve 141 in the axial direction.

  As described above, in the present embodiment, the timing of air injection to the wall surface of the suction duct 142 and the timing of air injection to the axial end of the developing sleeve 141 are made different, and switching is performed according to which injection is performed. The valve 75c is switched. Note that the strength of the air flow indicated by the dotted arrow β is set such that the wind speed is 15 to 18 m / s at the position where the scattered toner accumulates on the upper lid of the developing device 14, for example. The strength of the air flow indicated by the one-dot chain line arrow γ is set such that the wind speed is 10 to 18 m / s at the ejection port position of the developing sleeve air ejecting means 146, for example.

5. Example 5
Next, Example 5 will be described. The fifth embodiment is basically the same as the fourth embodiment except for the part related to the setting of the wind speed. In the following description, emphasis is placed on the description of parts different from the fourth embodiment, and description of common parts may be omitted.

  The control unit 5 according to the present embodiment sets the wind speed (air volume) when air is blown to the wall surface of the suction duct 142 based on the information on the average printing rate (coverage) in the image forming apparatus 1. The flow of the operation will be described in detail with reference to the flowchart shown in FIG.

  After entering the stabilization adjustment mode, the control unit 5 calculates an average printing rate in printing for 2000 pages immediately before image formation, for example (step S1). Note that one side here corresponds to one side (one side) of A4 paper. Then, the control unit 5 determines whether or not the calculated average printing rate is within a range of 3 to 20% (step S2).

  When the calculated average printing rate is within the range of 3 to 20% (Yes in Step S2), the control unit 5 sets the wind speed to 15 to 18 m / s (Step S3). In addition, when the calculated average printing rate is not within the range of 3 to 20% (No in Step S2), the control unit 5 sets the wind speed to 20 to 23 m / s (Step S4).

  Thus, the control part 5 sets the air volume of the air blowing by a blowing means variably. Specifically, the control unit 5 determines when the printing rate for a predetermined period falls below a predetermined reference condition (in this embodiment, when the average printing rate falls below a reference range of 3 to 20%) or predetermined When the reference condition is exceeded (in the case of this embodiment, when the average printing rate exceeds the reference range of 3 to 20%), the wind speed is set to be large.

  The purpose of setting the wind speed as described above is as follows. If the printing rate continues to be low, the toner in the developing device 14 is likely to deteriorate and toner that tends to scatter is likely to be generated, so that the toner tends to accumulate. Therefore, in such a case (when the average printing rate is below the reference range of 3 to 20%), the air volume is increased so that the accumulated toner is more reliably removed.

  On the other hand, if the printing rate continues to be high, the chargeability of the toner itself remains high. However, the charge cannot catch up, and as a result, the toner tends to scatter and the toner tends to accumulate. . Therefore, even in such a case (when the average printing rate exceeds the reference range of 3 to 20%), the air volume is increased so that the accumulated toner is more reliably removed. Note that the process of setting the air volume as in the present embodiment is applicable to any of the embodiments described above.

6). Performance Evaluation In order to evaluate the toner spill suppression performance of each of the above examples, a performance evaluation test including a comparative example was performed. Here, the comparative example has the same configuration as that of Example 1 except that the installation of the air injection nozzle 42 is omitted.

  The contents of the performance evaluation test include combinations of conditions for the total number of printed pages (9 levels from 10,000 to 100,000) and the printing rate (2 levels of 0.3% and 25%). The settings were made as shown in the left column, and printing on A3 paper was performed under the conditions for each of the examples and comparative examples. The number of toner spills that occurred on the A3 sheet was integrated for 1,000 sheets (A4 conversion) immediately before the end of printing over the total number of prints, and this integrated value was used as an evaluation index. The smaller the integrated value, the lower the toner spill frequency and the higher the toner spill suppression performance.

The carrier in the developer has a particle size of 33 μm and a specific gravity of 5 g / cm ³ in any of the examples and comparative examples, and the toner has a particle size of 6.5 μm, a specific gravity of 1.1 g / cm ³ , and The charge amount was 30 to 40 μC / g. Further, regarding the environment, in any of the examples and comparative examples, the air temperature was 20 ° C. and the relative humidity was 50%.

  The right column of Table 1 shows the results of the performance evaluation test corresponding to the conditions in the left column. As shown in the table, in the comparative example, toner spillage started to be noticeable from the total number of printed surfaces of about 20,000. On the other hand, in Examples 1 and 3, toner spillage was sufficiently suppressed as compared with the comparative example, but when the total number of printed surfaces reached 50,000, noticeable toner spillage with a major axis of about 5 mm was confirmed. In this case, the toner accumulated at the end of the developing sleeve 141 falls.

  In Examples 2 and 4, noticeable toner spillage exceeding 0.5 mm did not occur until the total number of printed surfaces reached about 50,000. In Examples 1 to 4, since the total number of printed surfaces exceeded 70,000, the amount of scattered toner started to increase as a whole, and the number and size of toner spills slightly increased. On the other hand, in the case of Example 5, it was found that toner spillage did not occur until the total number of printed surfaces reached 100,000, and the toner spillage suppression performance was very high.

7). Summary As described above, the image forming apparatus 1 of each embodiment scatters from the developing device 14 that supplies toner to the photosensitive drum 11 (image carrier) on which the toner image is formed, and the developing device 14. A suction duct 142 used for sucking toner and spraying means for blowing air onto the wall surface of the suction duct 142 are provided, and the toner adhering to the wall surface is removed by the air blowing. Therefore, it is possible to suppress toner spillage while reducing toner scattering by installing a suction duct.

  The spraying means sprays air onto the wall surface of the suction duct 142 at a timing within a period during which no toner image is formed. For this reason, even if the toner removed by the blowing of air falls on the photosensitive drum 11, it is collected by the cleaning means 17 without affecting the image formation.

  Particularly in the second and fourth embodiments, the toner adhering to the axial end portion is removed by injecting air to the axial end portion of the developing sleeve 141 in the developing device 14. Therefore, it is possible to remove the toner before it accumulates on the axial end portion of the developing sleeve 141, thereby preventing the toner spillage or suppressing the toner to an inconspicuous size.

  In the third and fourth embodiments, the air blowing for removing the accumulated scattered toner is performed using the suction duct 142, so that a new installation is required for the conventional configuration. It is possible to reduce the number of members. In particular, when the scattered toner suction fan and the air blowing fan are used in common, the cost and space for installing the fan can be reduced as much as possible.

  Further, in the embodiment 5, it is possible to remove the scattered toner more reliably by increasing the air blowing speed in a situation where the low printing rate or the high printing rate in which the toner is likely to be scattered continues. Further, since the wind speed is not increased except in such a situation, it is possible to reduce the risk that the carrier goes out of the developing device 14 by increasing the wind speed more than necessary.

  As mentioned above, although the specific example was given and demonstrated about embodiment of this invention, this invention is not limited to the content. The present invention can be implemented in various specific forms without departing from the spirit of the present invention.

  The present invention is applicable to an image forming apparatus such as a printer.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming unit 3 Paper feed unit 4 Printing unit 5 Control part 11 Photosensitive drum 12 Charging means 13 Exposure means 14 Developing apparatus 141 Developing sleeve (developing roller)
142 Suction duct 143a End region of upper cover of developing device 143b End region of ceiling part of suction duct 145 Restriction plate 15 Transfer roller 16 Intermediate transfer belt 17 Cleaning means 31 Compressor 32, 42, 52, 62 Air injection nozzle 71, 81 , Scattered toner suction device 41, 61, 72, fan 73, 83, backflow prevention valve 74, 84, filter 82 injection fan (first fan)
86 Fan for reverse injection (second fan)
75a-75c, 85 selector valve

Claims (10)

A developing device for developing the electrostatic latent image on the surface of the image carrier with toner;
A suction duct used to suck toner scattered from within the developing device;
Spray means for blowing air to the wall surface of the suction duct,
An image forming apparatus, wherein the toner adhered to the wall surface is removed by blowing air. The suction duct has an opening that opens between the image carrier and the developing device;
The image forming apparatus according to claim 1, wherein the spraying unit sprays air onto a wall surface near the opening in the suction duct.   The image forming apparatus according to claim 2, wherein the spraying unit sprays air onto the wall surface at a timing within a period in which the toner image is not formed.   The image forming apparatus according to claim 3, wherein the spraying unit sprays air onto the wall surface via an air ejecting member disposed in the vicinity of the opening. A fan for generating an air flow in the suction duct;
The image forming apparatus according to claim 3, wherein the scattered toner is sucked by rotating the fan in a predetermined direction.
The image forming apparatus that blows air on the wall surface by rotating the fan in a direction opposite to the predetermined direction.   The image forming apparatus according to claim 5, wherein the path of the airflow is switched between when the blowing unit blows air onto the wall surface and when the scattered toner is sucked. As a fan that generates airflow in the suction duct,
A first fan for generating an airflow in a direction for sucking the scattered toner;
Separately provided with a second fan that generates an airflow in a direction of blowing air to the wall surface;
The image forming apparatus according to claim 3, wherein the blowing unit blows air onto the wall surface using a second fan.   8. The image forming apparatus according to claim 1, wherein the toner adhering to the axial end portion is removed by jetting air to the axial end portion of the developing sleeve in the developing device.   The image forming apparatus according to claim 1, further comprising a setting unit configured to variably set an air volume of air blowing by the blowing unit. The image forming apparatus according to claim 9, wherein printing is performed on a sheet using the toner image.
The setting means includes
An image forming apparatus in which the air volume is set to be large when a printing rate in a predetermined period falls below a predetermined reference condition or exceeds a predetermined reference condition.