Developing device and image forming apparatus

Abstract

To provide a developing device that can prevent blowout of toner.SOLUTION: A developing device comprises: a developing tank 50 that stores developer; a developing roller 40 that carries the developer; a first screw 61 and a second screw 62 that convey the developer and supply it to the developing roller 40; an exhaust port 50e through which air inside the developing tank 50 is exhausted; and a filter 70 that is provided in the exhaust port 50e. The developing tank 50 has a first storage part SY1 that is provided with the first screw 61, a second storage part SY2 that is provided with the second screw 62, a partition wall 53 that separates the first storage part SY1 and the second storage part SY2 from each other; and a first circulation port 54a and a second circulation port 54b that open the partition wall 53 and circulate the developer between the first storage part SY1 and the second storage part SY2. The first storage part SY1 and the exhaust port 50e are partitioned by a blocking part 55, and the second storage part SY2 is connected with the exhaust port 50e.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a developing device having a developing tank and an image forming apparatus.

Background Art

[0002] Conventionally, an electrophotographic image forming apparatus is known, and in such an image forming apparatus, a developing device having a developing container (developing tank) for storing a developer is applied. The developing device is provided with a developing roller and a stirring member, but when these are rotated, air is sucked into the developing container from the outside, the internal air pressure rises, and there is a risk that the developer will scatter to the outside. Therefore, a technique has been proposed in which a duct for discharging air is provided to suppress the scattering of the developer (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional developing devices include a first stirring chamber and a second stirring chamber that are partitioned by a partition portion and arranged in parallel with each other, and a communication portion that allows the two to communicate with each other on both end sides in the longitudinal direction of the first stirring chamber and the second stirring chamber. It also includes a developing container that houses a developer containing toner to be supplied to the image carrier, a first stirring member and a second stirring member that are rotatably supported inside each of the first stirring chamber and the second stirring chamber, convey the developer while stirring it in opposite directions along the axial direction of rotation, and circulate it in a predetermined circulation direction, and a developer carrier (developing roller) that is rotatably supported on the developing container so as to face the image carrier and supplies the toner in the second stirring chamber to the image carrier. The developing container is arranged adjacent to the second stirring chamber and includes a duct that allows the air in the second stirring chamber to flow out to the outside, an air inlet that opens along the longitudinal direction of the second stirring chamber and communicates the inside of the second stirring chamber with the inside of the duct, a first filter that covers the air inlet, and a second filter that is arranged on the downstream side in the air flow direction inside the duct with respect to the first filter and covers the air flow path.

[0005] However, in conventional developing devices, since the air in the second stirring chamber flows into the duct through the vicinity of the developer carrier, there is a risk that toner may be ejected from the gap between the developer carrier and the developing container.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a developing device and an image forming apparatus capable of suppressing toner ejection.

Means for Solving the Problems

[0007] The developing device according to the present disclosure includes a developing tank that stores a developer containing toner, a developer carrier that carries the developer, a first conveying member and a second conveying member that are arranged with their rotation axes facing each other in parallel, stir and convey the developer in the developing tank, and supply the developer to the developer carrier, an exhaust port through which air inside the developing tank is discharged, and a filter provided at the exhaust port for recovering the developer contained in the exhaust gas. The developing tank includes a first accommodating portion provided with the first conveying member and arranged on the side close to the developer carrier, a second accommodating portion provided with the second conveying member and arranged on the side far from the developer carrier, a partition wall that partitions the first accommodating portion and the second accommodating portion, and a circulation port provided at an end portion in the axial direction along the rotation axis, opening the partition wall, and allowing the developer to flow between the first accommodating portion and the second accommodating portion. The space between the first accommodating portion and the exhaust port is partitioned by a blocking portion, and the second accommodating portion is connected to the exhaust port.

[0008] In the developing device according to the present disclosure, in the conveying direction of the developer in the developing tank, the circulation port facing the downstream end portion of the first conveying member may be configured to have a larger opening area than the other circulation port.

[0009] In the developing device according to the present disclosure, the developer carrier may be provided above the first conveying member, and a ventilation port may be provided in a portion of the partition wall that faces the developer carrier in the horizontal direction and is open.

[0010] In the developing device according to the present disclosure, the developer carrier may be provided above the first conveying member, and the blocking portion may be provided above the developer carrier.

[0011] In the developing device according to the present disclosure, the exhaust port may be provided at the upper part of the developing tank and extend in the axial direction.

[0012] In the developing device according to the present disclosure, the exhaust port may be provided so as to straddle the upper parts of the first accommodating portion and the second accommodating portion.

[0013] In the developing device according to the present disclosure, the exhaust port may be connected to a duct that allows air to pass through via the filter, and an intake fan that sucks air from the developing tank may be provided in the duct.

[0014] In the developing device according to the present disclosure, the intake fan may be configured to suck air from the developing tank after image formation.

[0015] The developing device according to the present disclosure includes a printing rate determination unit that determines the printing rate on the paper for image formation and a sheet number counting unit that counts the number of sheets of paper for image formation, and the intake fan may be configured to suck air from the developing tank based on the printing rate and the number of sheets in image formation.

Advantages of the Invention

[0016] According to the present disclosure, by blocking the air flowing from the first accommodating portion to the exhaust port with the blocking portion and guiding it to flow to the exhaust port through the second accommodating portion, the airflow toward the developer carrier can be eliminated. Thereby, it is possible to suppress the toner from ejecting from near the developer carrier.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0018] (First Embodiment) Hereinafter, an image forming apparatus according to the first embodiment of the present disclosure will be described with reference to the drawings.

[0019] FIG. 1 is a schematic side view of an image forming apparatus according to the first embodiment of the present disclosure.

[0020] An image forming apparatus 1 according to the first embodiment of the present disclosure includes an exposure device 11, a developing device 12, a photosensitive drum 13 (an example of an image carrier), a cleaner device 14, a charger 15, an intermediate transfer belt device 16, a fixing device 17, a paper feed tray 18, a paper discharge tray 19, and a paper conveyance path S, and forms multi-color and monochromatic images on a predetermined sheet according to image data transmitted from the outside.

[0021] The image data handled in the image forming apparatus 1 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Therefore, the developing device 12, the photosensitive drum 13, the charger 15, and the cleaner device 14 are each provided in four units so as to form four types of latent images corresponding to each color, and are respectively set to black, cyan, magenta, and yellow, and four image stations Pa, Pb, Pc, and Pd are configured by these.

[0022] The photosensitive drum 13 is disposed substantially at the center of the image forming apparatus 1. The charger 15 uniformly charges the surface of the photosensitive drum 13 to a predetermined potential. The exposure device 11 exposes the surface of the photosensitive drum 13 to form an electrostatic latent image. The developing device 12 develops the electrostatic latent image on the surface of the photosensitive drum 13 to form a toner image on the surface of the photosensitive drum 13. By the above-described series of operations, toner images of respective colors are formed on the surface of each photosensitive drum 13. The cleaner device 14 removes and collects the residual toner on the surface of the photosensitive drum 13 after development and image transfer. Note that the structure of the developing device 12 will be described in detail with reference to FIGS. 2 to 5 described later.

[0023] The intermediate transfer belt device 16 is disposed above the photosensitive drum 13 and includes an intermediate transfer belt 21, an intermediate transfer belt driving roller 22, an intermediate transfer belt driven roller 23, an intermediate transfer roller 24, and an intermediate transfer belt cleaning device 25. Note that four intermediate transfer rollers 24 are provided corresponding to the respective color image stations for YMCK.

[0024] The intermediate transfer belt driving roller 22, the intermediate transfer belt driven roller 23, and the intermediate transfer roller 24 are configured to stretch the intermediate transfer belt 21 and move the surface of the intermediate transfer belt 21 in a predetermined direction (direction of arrow C in the figure).

[0025] The intermediate transfer belt 21 circulates in the direction of arrow C, the residual toner is removed and collected by the intermediate transfer belt cleaning device 25, and the toner images of respective colors formed on the surface of each photosensitive drum 13 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 21.

[0026] The image forming apparatus 1 further includes a secondary transfer device 26 including a transfer roller 26a. A nip area is formed between the transfer roller 26a and the intermediate transfer belt 21, and the paper conveyed through the paper conveyance path S is sandwiched and conveyed in the nip area. When the paper passes through the nip area, the toner image on the surface of the intermediate transfer belt 21 is transferred.

[0027] The paper feed tray 18 is a tray for storing the paper used for image formation, and is provided below the exposure device 11. The paper discharge tray 19 is provided above the image forming apparatus 1 and is a tray for placing the paper on which the image has been formed.

[0028] The paper conveyance path S includes a main path S1 provided in an S shape and a reverse path S2 that branches off and rejoins in the middle of the main path S1. Along the main path S1, a pickup roller 31, a pre-registration roller 33, a registration roller 32, a secondary transfer device 26, a fixing device 17, and a paper discharge roller 34 are arranged. The reverse path S2 branches off between the fixing device 17 and the paper discharge roller 34 and rejoins between the pre-registration roller 33 and the registration roller 32 via a plurality of conveyance rollers 35.

[0029] The pickup roller 31 is provided near the end of the paper feed tray 18 and is a suction roller that supplies the paper from the paper feed tray 18 to the paper conveyance path S one by one. The registration roller 32 temporarily holds the paper being conveyed from the paper feed tray 18 and conveys the paper to the transfer roller 26a at the timing when the leading edge of the toner image on the photosensitive drum 13 and the leading edge of the paper are aligned. The pre-registration roller 33 is a small roller for assisting and promoting the conveyance of the paper.

[0030] The fixing device 17 is of a belt fixing type, and a fixing belt 44 is wound around a fixing roller 41 and a heating roller 43. In the fixing device 17, a pressure roller 42 is pressed against the fixing roller 41 via the fixing belt 44. The fixing device 17 receives the paper on which the unfixed toner image has been formed, sandwiches the paper between the fixing belt 44 and the pressure roller 42, and conveys it. The paper after fixing is discharged onto the paper discharge tray 19 by the paper discharge roller 34.

[0031] Also, when forming an image not only on the front surface of the paper but also on the back surface, the paper is conveyed in the reverse direction from the paper discharge roller 34 to the reverse path S2 to reverse the front and back surfaces of the paper, and the paper is guided to the registration roller 32 again. Then, an image is formed on the back surface in the same manner as on the front surface, and the paper is discharged to the paper discharge tray 19.

[0032] Next, the structure of the developing device 12 will be described with reference to FIGS. 2 to 5.

[0033] FIG. 2 is an external perspective view of the developing device.

[0034] The developing device 12 has a developing tank 50 that houses a developer containing toner. In the developing tank 50, a developing roller 40 (an example of a developer carrier) that carries the developer is rotatably supported. Specifically, the developing tank 50 is a substantially rectangular parallelepiped container having the axial direction L along the rotation axis of the developing roller 40 as the longitudinal direction, and the developer is housed in a cavity provided inside. Hereinafter, for the sake of explanation, one end in the axial direction L of the developing tank 50 may be referred to as the tank first end 50a, the other end in the axial direction L may be referred to as the tank second end 50b, and the bottom surface may be referred to as the tank bottom surface 50c.

[0035] In the image forming apparatus 1, a cartridge for housing toner is detachably provided, and the toner is appropriately supplied from the cartridge to the developing device 12. In the developing tank 50, a supply port 51 for supplying toner is provided at a position close to the tank second end 50b. Also, in the developing tank 50, the developing roller 40 is attached to a portion facing the photosensitive drum 13, and an opening is provided around the developing roller 40 to form a roller facing port 52. The roller facing port 52 is provided at the upper part of one side surface of the developing tank 50.

[0036] On the upper surface of the developing tank 50, a duct 80 through which air is discharged to the outside is provided. An intake fan (not shown) for sucking air from the developing tank 50 is provided in the duct 80. In FIG. 2, a part of the duct 80 is shown, and it may be structured to be connected to the remaining part not shown to extend the duct 80, and the intake fan may be attached to the extended part. In this way, by attaching the intake fan to the duct 80, air can be efficiently discharged.

[0037] In addition to the above-described components, the developing device 12 may have members for reinforcing each part, members for detachably supporting itself with respect to the image forming device 1, members for transmitting power for rotating each part, etc. attached to the developing tank 50.

[0038] The developing roller 40 is provided so as to contact the photosensitive drum 13 when the developing tank 50 is attached to the image forming device 1, and supplies toner to the photosensitive drum 13. In the present embodiment, the developing roller 40 is disposed above the developing tank 50, but is not limited thereto. The developing roller 40 may be provided facing a portion of the developing tank 50 that supplies toner to the outside.

[0039] FIG. 3 is a schematic cross-sectional view showing a cross-section of the developing device as viewed from the end side in the axial direction, FIG. 4 is a schematic cross-sectional view showing a cross-section of the developing device as viewed from above, and FIG. 5 is a schematic cross-sectional view showing a cross-section of the developing device as viewed from the side along the axial direction.

[0040] In FIGS. 3 to 5, the main parts of the developing device 12 are extracted and shown, and some members are omitted in consideration of the ease of viewing the drawing. In FIG. 4, the position of the developing roller 40 is shifted so as not to overlap with the first screw 61 or the like.

[0041] In the developing tank 50, a first screw 61 (an example of a first conveying member) and a second screw 62 (an example of a second conveying member) having spiral blades provided on the outer periphery of the rotating shaft are incorporated. The first screw 61 and the second screw 62 are arranged with their rotating shafts parallel to each other and rotate to circulate the developer within the developing tank 50. And the developing tank 50 is provided with a first accommodating portion SY1 incorporating the first screw 61 and a second accommodating portion SY2 incorporating the second screw 62, and the first accommodating portion SY1 and the second accommodating portion SY2 are partitioned by a partition wall 53.

[0042] The partition wall 53 has portions corresponding to both ends in the axial direction L of the first accommodating portion SY1 and the second accommodating portion SY2 open, and circulation ports (a first circulation port 54a and a second circulation port 54b) for circulating the developer are provided between the first accommodating portion SY1 and the second accommodating portion SY2.

[0043] As shown in FIG. 4, the developer is conveyed so as to circulate within the developing tank 50. And the direction (circulation direction E) in which the developer circulates varies appropriately depending on the position within the developing tank 50. Specifically, in the first accommodating portion SY1, the circulation direction E is the direction from the first tank end 50a (the right end in FIG. 4) to the second tank end 50b (the left end in FIG. 4), and the developer conveyed to the second tank end 50b moves to the second accommodating portion SY2 through the second circulation port 54b. Also, the circulation direction E in the second accommodating portion SY2 is the direction from the second tank end 50b to the first tank end 50a, and the developer conveyed to the first tank end 50a moves to the first accommodating portion SY1 through the first circulation port 54a.

[0044] The above-described first circulation port 54a is provided near the first end portion 50a of the tank, and the second circulation port 54b is provided near the second end portion 50b of the tank. The width (first opening width KW1) at which the first circulation port 54a opens is larger than the width (second opening width KW2) at which the second circulation port 54b opens. That is, in the developing agent conveyance direction (circulation direction E) in the developing tank 50, the second circulation port 54b facing the downstream end portion of the first screw 61 has a larger opening area than the first circulation port 54a. In the developing tank 50, air easily flows along the conveyance direction of the developing agent. By enlarging the second circulation port 54b, it becomes easier to draw air into the second storage portion SY2, and by reducing the first circulation port 54a, the flow of air returning to the first storage portion SY1 can be suppressed.

[0045] In the developing device 12, it is adjusted so that an appropriate amount of the developing agent is stored in the developing tank 50, and it is preferable that the height of the stored developing agent (liquid level of the developing agent) does not exceed the first screw 61 and the second screw 62. Regarding the height at which the first circulation port 54a and the second circulation port 54b open, it may be adjusted as appropriate, and it is set to be slightly higher than the upper ends of the first screw 61 and the second screw 62 from the tank bottom surface 50c and slightly higher than the liquid level of the developing agent.

[0046] In the first storage portion SY1, the developing roller 40 is disposed above the first screw 61, and the partition wall 53 extends to a position slightly higher than the developing roller 40. In the second storage portion SY2, an exhaust path 50d extending upward along the partition wall 53 is provided. The exhaust path 50d is formed by the housing constituting the developing tank 50, and the side wall extends so as to provide a gap with the partition wall 53.

[0047] An exhaust port 50e for discharging the internal air is provided at the upper part of the developing tank 50. A filter 70 for recovering the developing agent contained in the exhaust gas is provided at the exhaust port 50e, and it is connected to a duct 80 via the filter 70.

[0048] The exhaust port 50e extends in the axial direction L (see, for example, FIG. 5) and is provided so as to straddle the upper part of the first accommodating portion SY1 and the second accommodating portion SY2 (see, for example, FIG. 3). The second accommodating portion SY2 is connected to the exhaust port 50e via an exhaust path 50d. A blocking portion 55 is provided between the first accommodating portion SY1 and the exhaust port 50e. Specifically, the blocking portion 55 is at the upper part of the first accommodating portion SY1 and is attached by connecting to the partition wall 53, blocking the direct flow of air between the first accommodating portion SY1 and the exhaust port 50e. In the present embodiment, a thin plate member formed of PET is separately provided as the blocking portion 55 and attached to the housing constituting the developing tank 50, but it is not limited thereto, and it may be a part of the housing surrounding the first accommodating portion SY1 and a portion where the partition wall 53 extends laterally. That is, the blocking portion 55 may be integrated with the housing constituting the developing tank 50.

[0049] In the developing device 12, when the developing roller 40 is rotated during image formation or the like, air is sucked into the developing tank 50 from the outside, and the internal air pressure gradually increases. Therefore, by discharging air through the exhaust port 50e, the air pressure is reduced. At this time, in the first accommodating portion SY1, since the blocking portion 55 blocks the space between the exhaust port 50e, as shown by the arrow F1, air flows into the second accommodating portion SY2 through the circulation port. The air that has entered the second accommodating portion SY2 is discharged from the exhaust port 50e through the exhaust path 50d. Further, when passing through the exhaust port 50e, the developer contained in the exhaust is collected by the filter 70.

[0050] As described above, by blocking the air flowing from the first accommodating portion SY1 to the exhaust port 50e with the blocking portion 55 and guiding it to flow to the exhaust port 50e through the second accommodating portion SY2, the air flow toward the developing roller 40 can be eliminated. Thereby, the ejection of toner from the vicinity of the developing roller 40 can be suppressed. Further, since the blocking portion 55 is provided so as to block a wide space including the periphery of the developing roller 40, the air flow toward the developing roller 40 can be more reliably eliminated.

[0051] According to the configuration of the present disclosure, by providing an exhaust port 50e at the upper part of the developing tank 50, it is possible to suck up only the exhaust while reducing the influence on the accommodated developer. Further, by making the area of the exhaust port 50e as wide as possible, a large amount of air can be discharged.

[0052] The image forming apparatus 1 includes a control unit (for example, a CPU or the like) that controls various operations, and performs an operation of operating an intake fan according to an instruction from the control unit to discharge air from the developing tank 50. As the timing for operating the intake fan, for example, after image formation is performed, by exhausting the scattered toner generated during image formation, the scattering of toner during the next image formation can be reduced.

[0053] Further, the control unit may also have functions of a printing rate determination unit that determines the printing rate on the paper for image formation and a sheet number counting unit that counts the number of sheets of paper for image formation, and may operate the intake fan based on the printing rate and the number of sheets in image formation. For the printing rate and the number of sheets, a threshold value, a table associating the two, or the like may be set, and the toner consumption amount (and replenishment amount) may be estimated by referring to them. In the image forming apparatus 1, as the image with a high printing rate is formed, the toner consumption amount increases, and the toner is likely to scatter from the developing device 12. Therefore, by exhausting at the timing when the toner consumption amount exceeds the reference value in consideration of the printing rate and the number of sheets in image formation, the scattering of toner can be reduced.

[0054] (Second Embodiment) Next, an image forming apparatus according to the second embodiment of the present disclosure will be described with reference to the drawings.

[0055] In the second embodiment, the configuration of the partition wall 53 is different from that of the first embodiment. Since the second embodiment has substantially the same configuration as the first embodiment shown in FIGS. 1 to 5, the description will be omitted, and only the different points will be described.

[0056] FIG. 6 is a schematic cross-sectional view showing a cross-section of the developing device according to the second embodiment of the present disclosure as viewed from the end side in the axial direction, and FIG. 7 is a schematic cross-sectional view showing a cross-section of the developing device according to the second embodiment of the present disclosure as viewed from the side along the axial direction.

[0057] The second embodiment is different from the first embodiment in that a ventilation opening 56 is provided in the partition wall 53. Specifically, the ventilation opening 56 is formed by opening a portion of the partition wall 53 that faces the developing roller 40 in the horizontal direction. That is, the ventilation opening 56 is provided at a height similar to that of the developing roller 40 and at a position higher than the liquid level of the developer. Therefore, the ventilation opening 56 allows air to pass from the first accommodating portion SY1 to the second accommodating portion SY2 (exhaust path 50d) as indicated by the arrow F2 without passing through the developer conveyed by the first screw 61 and the second screw 62. In this way, by providing the ventilation opening 56 and actively drawing the air around the developing roller 40 into the second accommodating portion SY2, toner scattering can be reduced.

[0058] It should be noted that all the embodiments disclosed this time are illustrative in all respects and do not serve as a basis for a limiting interpretation. Therefore, the technical scope of the present disclosure is not interpreted only by the above-described embodiments, but is defined based on the description in the claims. Also, all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0059] 1 Image forming apparatus 12 Developing device 13 Photoconductor drum 40 Developing roller (an example of a developer carrier) 50 Developing tank 50d Exhaust path 50e Exhaust port 51 Supply port 52 Roller facing port 53 Partition wall 54a First flow port (one of the flow ports) 54b Second flow port (the other of the flow ports) 55 Blocking portion 56 Vent 61 First Screw (an example of the first conveying member) 62 Second Screw (an example of the second conveying member) 70 Filter 80 Duct L Axis direction SY1 First housing part SY2 Second housing part

Claims

1. A developing tank that houses a developer containing toner, A developer carrier that supports the developer, A first transport member and a second transport member that are arranged with their rotation axes parallel and facing each other, stir and transport the developer in the developing tank, and supply it to the developer carrier, An exhaust port through which air inside the developing tank is discharged, A developing device comprising a filter provided at the exhaust port for recovering the developer contained in the exhaust gas, wherein The developing tank has A first accommodating portion provided with the first transport member and arranged on the side closer to the developer carrier, A second accommodating portion provided with the second transport member and arranged on the side farther from the developer carrier, A partition wall that partitions the first accommodating portion and the second accommodating portion, A flow port provided at an end in the axial direction along the rotation axis, opening the partition wall, and allowing the developer to flow between the first accommodating portion and the second accommodating portion, The space between the first accommodating portion and the exhaust port is partitioned by a blocking portion, The second accommodating portion is connected to the exhaust port A developing device characterized by the above.

2. The developing device according to claim 1, wherein In the transport direction of the developer in the developing tank, the flow port facing the downstream end of the first transport member has a larger opening area than the other flow port A developing device characterized by the above.

3. The developing device according to claim 1, wherein The developer carrier is provided above the first transport member, Among the partition walls, a ventilation port is provided that opens a portion facing the developer carrier in the horizontal direction A developing device characterized by the above.

4. The developing device according to claim 1, wherein The developer carrier is provided above the first transport member, The blocking portion is provided above the developer carrier A developing device characterized by the above.

5. The developing device according to claim 1, wherein The exhaust port is provided at the upper part of the developing tank and extends in the axial direction A developing device characterized by the above.

6. The developing device according to claim 5, wherein The exhaust port is provided so as to straddle the upper parts of the first accommodating portion and the second accommodating portion A developing device characterized by the above.

7. An image forming apparatus comprising the developing device according to claim 1, wherein The exhaust port is connected to a duct for passing air through the filter, An intake fan for sucking air from the developing tank is provided in the duct An image forming apparatus characterized by the above.

8. The image forming apparatus according to claim 7, wherein the intake fan sucks air from the developing tank after image formation. An image forming apparatus characterized by the above.

9. The image forming apparatus according to claim 7, comprising a printing rate determination unit that determines the printing rate on the paper for image formation, and a sheet number counting unit that counts the number of sheets of paper for image formation, wherein the intake fan sucks air from the developing tank based on the printing rate and the number of sheets in image formation. An image forming apparatus characterized by the above.

Images