JP5755172B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a dew condensation prevention mechanism in an image forming apparatus such as a printer or a copying machine using an electrophotographic system.

  2. Description of the Related Art As an output device for a computer or workstation, an electrophotographic image forming apparatus that forms an image on a recording medium using a developer or the like is known. In this image forming apparatus, for example, an electrostatic latent image is formed on a photosensitive drum, the electrostatic latent image is developed with a developer to form a developed image, and the developed image is applied to a recording medium such as transfer paper. The transferred image is transferred to form a transferred image, and the transferred image is fixed on the recording medium using heat or pressure. In this fixing, a fixing device in which a fixing roller having a built-in heating element and a pressure roller that presses and presses a recording medium against the fixing roller is generally incorporated in a casing (casing). .

  In the fixing device, the recording medium on which the transfer image is formed is heated and pressed by being sandwiched between the fixing roller and the pressure roller, and the transfer image is fixed on the recording medium. The recording medium on which the transferred image is fixed passes through the fixing device and is discharged out of the device by the carry-out roller.

  By the way, the inside of the fixing device is heated by the heat of the fixing roller. Accordingly, when the humidity around the fixing device is high or the temperature around the fixing device is low, water is easily evaporated from the recording medium and water vapor is easily generated. Furthermore, water vapor tends to be generated when the recording medium that has absorbed moisture passes through the fixing device.

  In general, the periphery of the fixing device is cooler than the inside, so that water vapor generated during fixing is rapidly cooled when discharged from the fixing device. Due to this temperature drop, water droplets adhere (condensate) to the peripheral members and parts of the fixing device. In addition, water droplets may adhere to the transport roller. Since the amount of water droplets attached in this manner increases every time the recording medium passes through the fixing device, it may fall and adhere to the recording medium or the transport roller when the amount of water droplets exceeds a certain amount.

  When water droplets adhere to the recording medium, the recording medium is easily broken or the recorded image is disturbed. In addition, when water droplets adhere to the transport roller, the water droplets may move to the recording medium and the image may be disturbed, and the frictional force on the surface of the transport roller may change and paper discharge may not occur smoothly, causing a paper jam. Sometimes.

  In order to solve these problems, conventionally, an image forming apparatus that forms a blade on a rotating shaft of a conveying roller that discharges a recording medium that has passed through a fixing device to the outside of the apparatus, and exhausts by rotating the conveying roller to prevent condensation. Is well known (see, for example, Patent Document 1).

JP 2001-175153 A

  However, in the image forming apparatus configured as described above, the steam exhaust efficiency can be increased as the rotation speed of the transport roller is increased and the blades are rotated at a higher speed. However, since the conveyance roller rotates at the timing when the recording medium is conveyed from the fixing device to the outside of the apparatus, the rotation speed of the conveyance roller cannot be set regardless of the conveyance speed of the recording medium.

  Therefore, when only one recording medium is transported (printed out), after the recording medium passes through the fixing device, the transport roller is rotated at a high speed, while a plurality of recording media are continuously discharged ( In the case of continuous printing), the rotation efficiency of the conveyance roller is controlled so that the conveyance roller is rotated at high speed only between the preceding recording medium and the succeeding recording medium (between paper), thereby increasing the exhaust efficiency. A device was made when it was not.

  However, even if the exhaust efficiency is increased only between the papers, the exhaust during the paper passing, in which condensation easily occurs, is insufficient. Further, in order to increase the rotational speed of only the transport roller, another motor is required, which increases the cost and makes the control complicated. Furthermore, since it is necessary to form the blades in a range that does not interfere with the recording medium, in addition to the low degree of freedom in design, the direction of the wind cannot be controlled because the rotation direction of the transport roller is one direction. Further, in an image forming apparatus that forms an image at a low speed, it is difficult to perform sufficient exhaustion because the rotation speed of the transport roller is also slow.

  Accordingly, the present invention has been made in view of, for example, the above-described problems, and an object of the present invention is to increase the steam exhaust efficiency and perform sufficient exhaust regardless of the rotation speed of the transport roller. An object of the present invention is to provide an image forming apparatus capable of preventing condensation.

  In order to solve the above-described problems, the present invention includes a fixing device that heats a recording medium to fix the transfer image on the recording medium, and fixes the transfer image by the fixing device to form an image. And a transport roller that discharges the recording medium on which the image is formed to the outside of the fixing device, and an exhaust rotator that exhausts air by rotating with the rotation of the transport roller. It is characterized by.

  According to the above configuration, since the exhaust rotator does not contact the recording medium, the degree of freedom in designing the exhaust rotator is increased, and the exhaust volume of the exhaust rotator is reduced within a range in which the exhaust rotator and the recording medium do not interfere with each other. Can be increased. As a result, the exhaust rotator rotates each time the conveyance roller is rotated to discharge the recording medium to the outside of the fixing device, and water vapor generated from the recording medium can be efficiently exhausted. As a result, it is possible to prevent harmful effects caused by condensation due to water vapor or the fall of condensed water droplets.

  At this time, it is preferable that the exhaust rotator is in pressure contact with the transport roller.

  According to the above configuration, it is not necessary to change the configuration of the transport roller, the rotational force of the transport roller can be transmitted to the exhaust rotator, and the pressing surface of the exhaust rotator with respect to the transport roller can be easily formed. .

  Further, it is preferable that a pair of the transport rollers that form a nip portion by pressure contact with each other is provided, and the exhaust rotator is disposed on the opposite side of the nip portion with the transport roller interposed therebetween.

  According to the above configuration, it is possible to prevent the recording medium being discharged from interfering with the exhaust rotator.

  Moreover, it is preferable that the said exhaust rotary body is equipped with the rotating shaft press-contacted to the said conveyance roller, and the blade | wing formed in the outer periphery of the said rotating shaft.

  According to the above configuration, the exhaust rotator can be obtained with a simple configuration.

  Moreover, it is preferable that the rotating shaft of the said exhaust rotary body is smaller than the outer diameter of the said conveyance roller.

  According to the said structure, the rotation speed of an exhaust rotary body can be raised rather than the rotation speed of a conveyance roller, and the exhaust_gas | exhaustion efficiency of water vapor | steam can be improved.

  According to the present invention described above, the exhaust efficiency of water vapor can be increased, and sufficient exhaust can be performed regardless of the rotation speed of the transport roller to prevent condensation.

1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a longitudinal sectional view illustrating a schematic configuration of a fixing device according to a first embodiment of the present invention. It is a side view which shows schematic structure of the exhaust rotary body which concerns on the 1st Embodiment of this invention, and a conveyance roller. 1 is a perspective view showing a schematic configuration of an exhaust rotator according to a first embodiment of the present invention. FIG. 4 is a longitudinal sectional view illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention. It is a side view which shows schematic structure of the exhaust rotary body which concerns on the 2nd Embodiment of this invention, and a conveyance roller.

(First embodiment)
First, the overall configuration of the multifunction machine 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating an outline of a configuration of a multifunction peripheral according to the first embodiment of the present invention. Hereinafter, for convenience, the front side in FIG. 1 will be described as the front side of each member.

  As shown in FIG. 1, the multifunction machine 1 includes a box-shaped apparatus main body 2, and a paper feed cassette 3 that accommodates transfer paper (not shown) as a recording medium is provided below the apparatus main body 2. A paper discharge tray 4 is provided above the apparatus main body 2. An exposure unit 5 composed of a laser scanning unit (LSU) and a laser beam from the exposure unit 5 (see arrow P) are provided between the paper feed cassette 3 and the paper discharge tray 4 in the apparatus body 2. And an image forming unit 6 disposed on the optical path.

  A photosensitive drum 7 is rotatably provided in the image forming unit 6, and around the photosensitive drum 7, a charger 8, a developing device 10, a transfer roller 11, and a cleaning device 12 are provided. Arranged in the order of the transfer process. A container 9 as a toner container is provided on one side (right in the drawing) of the developing device 10 obliquely above.

  A transfer paper transport path 13 is provided on one side of the apparatus main body 2 (left side in the drawing). A paper feed unit 14 is provided at the upstream end of the conveyance path 13, a transfer unit 15 is provided in the middle portion of the conveyance path 13, and the transfer unit 15 is opposed to the photosensitive drum 7. A fixing unit 16 is provided, and a paper discharge port 17 is provided at the downstream end of the conveyance path 13.

  Next, an image forming operation of the multifunction machine 1 having such a configuration will be described. When the MFP 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing unit 16 is executed. When image data is input from a computer or the like connected to the multifunction machine 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 7 is charged by the charger 8, exposure corresponding to the image data is performed on the photosensitive drum 7 by the laser light P from the exposure device 5, and the surface of the photosensitive drum 7 is thus obtained. An electrostatic latent image is formed. Next, the developing device 10 develops the electrostatic latent image into a toner image with toner. The toner and electric charge remaining on the photosensitive drum 7 are removed by the cleaning device 12 and a static eliminator (not shown).

  On the other hand, the transfer paper taken out from the paper supply cassette 3 or the hand tray (not shown) by the paper supply unit 14 is conveyed to the transfer unit 15 in synchronism with the above-described image forming operation. The toner image on the photosensitive drum 7 is transferred onto the transfer paper by the transfer roller 11. The transfer paper onto which the toner image has been transferred is transported downstream in the transport path 13 and enters the fixing unit 16 where the toner image is fixed on the transfer paper. The transfer paper on which the toner image is fixed is discharged from the paper discharge port 17 onto the paper discharge tray 4.

  Next, details of the fixing unit 16 will be described. As shown in FIG. 2, the fixing unit 16 includes a pressure roller 18, a fixing roller 19 disposed opposite to the pressure roller 18, and a separation claw that separates the transfer paper that is in close contact with the fixing roller 19 from the fixing roller 19. 20 are accommodated inside a casing 21 in which upper and lower openings 21a and 21b serving as transfer paper conveyance paths 13 are opened. The fixing unit 16 is disposed to face the pressing surface in the upper opening 21 a, and a pair of conveying rollers 22 and 23 that discharge the transfer paper to the outside of the fixing unit 16. An exhaust rotator 24 that rotates to exhaust air and a fixing cover 25 (see FIG. 1) that covers these are provided outside the casing 21.

  The pressure roller 18 is urged toward the fixing roller 19 by an urging means such as a spring (not shown) and sandwiches the transfer paper while pressing the transfer paper with the fixing roller 19.

  Inside the fixing roller 19, a heater 26 is provided as a heat source. The fixing roller 19 is provided in a non-contact manner in an image area located at the center in the longitudinal direction of the fixing roller 19 by being energized by applying a voltage from a voltage supply unit (not shown). Based on a thermistor signal, the temperature is controlled to a predetermined temperature at which the toner image can be fixed on the transfer paper.

  The conveyance rollers 22 and 23 have a rotation shaft 27 extending in a direction orthogonal to the conveyance path 13 (the front-rear direction in FIG. 2), and four rubber rollers 28 fixed to the rotation shaft 27. As shown in FIG. 3, the four rubber rollers 28 are arranged at a predetermined distance from each other. The outer diameter of the rubber roller 28 (indicated by reference sign d1 in FIG. 3) is set to 14 mm. The pair of transport rollers 22 and 23 formed in this way forms a nip portion 29 that presses against each other to sandwich the transfer paper, and rotates in the opposite direction when the transfer paper is discharged (in FIG. 2). In addition, the rotation direction of the conveyance roller 22 is indicated by a symbol A, and the rotation direction of the conveyance roller 23 is indicated by a symbol B). The exhaust rotator 24 is pressed against the outer periphery of the rubber roller 28 of the transport roller 22 near the paper discharge tray 4 out of the pair of transport rollers 22 and 23.

  The exhaust rotator 24 is arranged on the opposite side of the nip portion 29 with the transport roller 22 in between, and rotates as the transport roller 22 rotates. The exhaust rotator 24 extends parallel to the rubber roller 28 and is in pressure contact with the rubber roller 28, and a blade 31 disposed at a position outside the rubber roller 28 on the outer periphery of the rotary shaft 30. ,have. The shaft diameter (indicated by reference sign d2 in FIG. 3) of the rotary shaft 30 is set to 2 mm. Therefore, the exhaust rotator 24 can obtain a rotational speed (rotational speed) seven times that of the transport roller 22.

  The blades 31 are formed in a rectangular plate shape that extends along the rotation shaft 30. The blades 31 are erected in a cross shape from the outer periphery of the rotating shaft 28, and the blades 31 a formed between the rubber rollers 28 and the blades 31 b formed outside the rubber rollers 28 at both ends are in total. Five sets are formed. The length of the blade 31b in the longitudinal direction is set longer than the length of the blade 31a in the longitudinal direction. In the exhaust rotator 24 formed in this way, the rotation shaft 30 pressed against the conveyance roller 22 is opposite to the rotation direction A of the conveyance roller 22 by the rotation of the conveyance rollers 22 and 23 when discharging the transfer paper. The direction of rotation (indicated by reference numeral C in FIG. 2), the blades 31a and 31b formed on the rotating shaft 30 are also rotated.

  The exhaust rotator 24 is supported on the casing 21 by a linear support spring 32. The support spring 32 is bent in a substantially U shape when viewed from the side, a central portion is fixed to the casing 21, and both ends are wound around a half of the outer periphery of the rotating shaft 30. As a result, the support spring 32 urges toward the transport roller 22 while holding the exhaust rotator 24 in a rotatable state.

  Here, in the casing 21 of the fixing unit 16 or the inner side of the fixing cover 25 and in the vicinity of the downstream side of the upper opening 21a of the casing 21, moisture may evaporate from the transfer paper to generate water vapor. When a large amount of water vapor is generated in the casing 21, the generated water vapor may adhere to the inner surface of the fixing cover 25 and liquefy. When water droplets are generated on the inner surface of the fixing cover 25 in this way, the water droplets may fall and adhere to the transport rollers 22 and 23. In addition, water droplets may fall on the transfer paper being discharged.

  However, in the fixing unit 16 of the present invention, the blades 31 a and 31 b rotate around the rotation shaft 30 when the exhaust rotator 24 pressed against the transport roller 22 rotates as the transport roller 22 rotates. For this reason, the air inside the fixing unit 16 is discharged to the outside of the image forming apparatus 1, and the moisture evaporated from the transfer paper is also discharged to the outside of the image forming apparatus 1 along with this discharge. Further, the water vapor evaporated from the transfer paper is sprayed again onto the transfer paper, whereby the water vapor is absorbed by the transfer paper, and the water vapor is discharged to the outside of the image forming apparatus 1.

  Therefore, the humidity inside or around the fixing unit 16 does not increase, and water droplets are not generated on the surface of the inside of the fixing unit 16 or the surrounding members. As a result, the water evaporated from the transfer paper does not adhere to the transfer paper or the transport rollers 22 and 23. Therefore, the image of the transfer paper is not disturbed due to the water droplets, and the frictional force on the surfaces of the transport rollers 22 and 23 is not changed to cause a paper jam.

  Further, since the exhaust rotator 24 is pressed against the transport roller 22 by the support spring 32, there is no need to change the configuration of the transport roller 22, and the rotational force of the transport roller 22 can be transmitted to the exhaust rotator 24. In addition, it is possible to easily form the pressing surface of the exhaust rotator 24 against the transport roller 22. Further, since the exhaust rotator 24 is disposed on the opposite side of the nip portion 29 with the conveying roller 22 interposed therebetween, it is possible to prevent the transfer paper being discharged from interfering with the exhaust rotator 24. Further, since the exhaust rotator 24 includes the rotating shaft 30 and the blades 31 formed on the outer periphery of the rotating shaft 30, the exhaust rotator 24 can be obtained with a simple configuration.

  Furthermore, since the rotating shaft 30 of the exhaust rotator 24 is smaller in diameter than the outer diameter of the rubber roller 28 of the transport roller 22, the rotational speed of the exhaust rotator 24 can be made higher than the rotational speed of the transport roller 22. The exhaust efficiency of water vapor can be increased. Thereby, it is possible to prevent condensation by performing sufficient exhaustion regardless of the rotation speed of the transport roller 22.

(Second Embodiment)
By the way, as shown in FIGS. 5 and 6, a pair of exhaust rotators 35, 35 having propeller-shaped blades 34 formed on the outer periphery of the rotating shaft 30 are arranged with the blades 34 facing away from each other and spaced apart from each other. It is also possible to configure the air to flow from the center of the rotating shaft 30 to the side (left and right direction in the drawing) (this flow is indicated by a thick arrow in FIG. 6). In this case, the blades 34 of each exhaust rotating body 35 are formed one by one on both sides of the outer periphery of the rotating shaft 30 with the rotating shaft 30 interposed therebetween, and five sets are formed in total.

  Furthermore, it is also possible to arrange the exhaust rotator cover 33 covering the exhaust rotator 24 with a gap between the casing 21 and the exhaust rotator cover 33. The exhaust rotator cover 33 is formed in a bowl shape extending in parallel to the rotation shaft 30, and both ends thereof are opened and the inner surface thereof is disposed toward the exhaust rotator 24.

  Accordingly, when the exhaust rotator 35 is rotated, air is taken in from the gap between the exhaust rotator cover 33 and the casing 21, and the taken air is discharged from the openings at both ends of the exhaust rotator cover 33. As a result, the amount of air discharged from the openings at both ends of the exhaust rotator cover 33 can be increased.

  In the above-described embodiment, the blades 31 and 34 are formed on the outer periphery of the rotating shaft 30, but the shape, the number, and the arrangement of the blades 31 and 34 are not limited to the example described above. That is, as long as the blades 31 and 34 are rotatable without interfering with other members such as the rotation shaft 27 of the transport roller 22, the shape, number and arrangement of the blades 31 and 34 may be changed.

  Further, a tooth shape that meshes with the outer periphery of the rotation shaft 27 of the transport roller 22 and the outer periphery of the rotation shaft 30 of the exhaust rotator 24 so that the exhaust rotator 24 rotates as the transport roller 22 rotates. It is also good. Thereby, the rotational force of the conveyance roller 22 can be reliably transmitted to the exhaust rotator 24.

  The heater 26 may be a halogen heater, a ceramic heater, or an IH coil.

1 MFP (image forming device)
16 Fixing part (fixing device)
22 Conveying roller 23 Conveying roller 24, 35 Exhaust rotating body 29 Nip part 30 Rotating shaft 31, 34 Blade

Claims (4)

In an image forming apparatus that includes a fixing device that heats a recording medium to fix the transfer image on the recording medium, and fixes the transfer image by the fixing device to form an image.
A conveyance roller for discharging the recording medium on which the image is formed to the outside of the fixing device;
An exhaust rotating body that exhausts air by rotating with the rotation of the transport roller ,
2. The image forming apparatus according to claim 1, wherein the exhaust rotator includes a rotation shaft that is pressed against the transport roller, and a blade formed on an outer periphery of the rotation shaft .   The image forming apparatus according to claim 1, wherein the exhaust rotator is pressed against the transport roller. Comprising a pair of the transport rollers that press against each other to form a nip portion;
The image forming apparatus according to claim 1, wherein the exhaust rotator is disposed on a side opposite to the nip portion with the conveyance roller interposed therebetween. The rotating shaft of the exhaust rotary body, an image forming apparatus according to any one of claims 1 to 3, characterized in diameter der Rukoto than the outer diameter of the conveying roller.