JP4507792B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a function of forming a recorded image on both sides of a recording sheet with a printer, a copying machine, or the like using an electrophotographic method, and a fan for discharging heat generated by the constituent devices to the outside of the apparatus. The present invention relates to detection means for detecting a recording sheet passing through a path.

Japanese Patent Laid-Open No. 11-296053

  In the image forming apparatus using the electrophotographic system, the fixing device is kept at a high temperature for fixing the toner image, and it is necessary to cool the surrounding atmosphere or the peripheral device heated by the heat radiated from the fixing device. If this cooling is not performed, the toner is melted before being transferred to the recording paper, and deterioration of peripheral members of the fixing device proceeds. Therefore, it is common to provide a fan for exhausting the atmosphere around the fixing device in an image forming apparatus using an electrophotographic system.

  In addition, in an image forming apparatus capable of forming a recorded image on both sides of a recording sheet, a detecting unit is provided for detecting the recording sheet conveyed on the reverse path after fixing the toner image on one side of the recording sheet. ing. The detecting means is disposed on a reversing path where the leading edge of the recording paper reaches the detecting means when the trailing edge of the recording paper passes through the fixing device.

  As an image forming apparatus provided with a fan for exhausting the ambient atmosphere of the fixing device, a fan for cooling the double-sided unit to the double-sided unit and circulating cooling air to the inside of the image forming apparatus main body is used. There has been proposed an image forming apparatus that is equipped with a double-sided unit and can cool the inside of the image forming apparatus according to the needs of the user (Japanese Patent Laid-Open No. 11-296053). The duplex unit is provided with a reversing path through which the recording paper is conveyed in the vertical direction, and the reversing path is disposed at a position facing the fixing device. Further, the fan provided in the duplex unit is disposed at a position substantially facing the fixing device between the fixing device and the reverse path. As described above, when the fixing device, the reversing path, and the fan are provided, for the convenience of the length of the reversing path, the position of the detection unit that detects the recording paper conveyed through the reversing path is provided. The position where the fan is disposed often overlaps, and there is a problem that the ventilation of the fan is blocked by the detection means.

  The present invention has been made in view of such problems, and an object of the present invention is to interfere with the arrangement position of the recording paper detection means provided in the reversing path and the arrangement position of the fan. Even in such a case, it is an object of the present invention to provide an image forming apparatus capable of efficiently exhausting heat generated from a fixing device.

In order to achieve the above object, an image forming apparatus according to the present invention includes an apparatus housing, an image forming unit that transfers a toner image corresponding to image data to a recording sheet, and the recording sheet while conveying the recording sheet upward in the vertical direction. a fixing device for fixing the toner image transferred to the recording paper, in the case of forming a recorded image on both sides of the recording sheet, after the toner image is fixed on one side of the recording sheet, the recording sheet the image A reversing path that conveys the forming unit vertically downward , a lever that protrudes from the reversing path and that rotates as the leading end of the recording paper that is conveyed to the reversing path passes, and detects the rotation of the lever a detection sensor for an image forming apparatus composed of a fan that exhausts heat generated by the device housing to a device outside of the housing, the fan is a side of the fixing device, approximately pairs across the reverse path Together they are arranged at positions to form an exhaust passage for exhausting from the substantially horizontal direction to the flow side of the device in the apparatus, the lever, and the fixing device, between the fan and the front Sharing, ABS airflow The rotating shaft is connected to one end of a connecting shaft extending into and out of the exhaust flow path, and the detection sensor rotates at the other end of the connecting shaft. as can be detected, and is characterized in that it is disposed before the outer Sharing, ABS air passage.

  In such an image forming apparatus of the present invention, the image forming unit includes a toner storage unit that stores toner of each color, a rotating photoconductor of each color, and a plurality of surfaces that uniformly charge the surface of the photoconductor. A charger, a plurality of exposure means such as ROS and LED array for exposing the surface of the photoreceptor uniformly charged by the charging means to form an electrostatic latent image, and a toner image corresponding to the electrostatic latent image. A plurality of developing units formed on the photosensitive member, an intermediate transfer member on which toner images of respective colors are transferred from the photosensitive member, and a transfer for transferring the toner image onto a recording sheet. What is necessary is just to be comprised from the apparatus and the waste toner accommodating part etc. which accommodate the toner which became unnecessary. Here, as the intermediate transfer member, an intermediate transfer belt on which a recording image formed on the surface of each color photoconductor is transferred in a tandem color image forming apparatus, or a recording sheet is electrostatically adsorbed and conveyed. Each color photosensitive member may be disposed at a position opposite to the conveyance belt, and the recording image of each color may be electrostatically transferred to the recording paper in sequence as the recording paper is conveyed.

  The fixing device may be any one that is generally applied in an electrophotographic image forming apparatus. For example, by inserting the recording paper having the toner image transferred thereon between a pair of heating rolls and a pressure roll, heat and pressure are applied to the recording paper, and the recording paper The toner image is fixed.

  In general, when a recording sheet is transported along a transport path, a pair of transporting means such as a pair of transporting rollers transports the recording sheet so as to sandwich a center line parallel to the recording sheet transport direction. Send in the direction. Therefore, when the leading edge of the recording sheet conveyed to the reversing path passes through the lever, the lever is rotated while the central portion of the side orthogonal to the recording sheet conveying direction is in contact with the lever. It is preferable to be disposed at a position. Further, the lever must be biased with a force that allows it to rotate even when a thin recording sheet passes through.

The detection sensor is preferably disposed at a position away from the lever and at a position not interfering with the fan, and should be able to detect the rotation of the lever. In the present invention, said lever, said the sensor is connected by a connecting shaft, Ru is rotated the lever around the connecting shaft. Here, since the lever is disposed between the fixing device and the fan and in the exhaust passage by the fan, the lever slightly blocks the exhaust by the fan. However, with this configuration, unlike the conventional detection means in which the lever and the detection sensor are configured as an integrated object, the detection sensor does not block the ventilation by the fan and is emitted within the device casing. Heat can be flowed out of the device casing and efficiently exhausted. Further, since the arrangement of the fans is not restricted by the arrangement of the detection sensors , the image forming apparatus can be downsized. Furthermore, the fan can be moved closer to the inside of the apparatus housing by the space of the detection sensor , compared to the case where it is configured as a conventional integrated body, and can be further downsized as necessary.

Since the lever is disposed in the exhaust flow path by the fan, when the recording paper is transported through the reverse path, the leading edge of the recording paper flows in the direction of the exhaust flow path. At this time, it is desirable to rotate the lever in a stable state at the leading edge of the recording paper in consideration of the detection accuracy of the detection sensor . Therefore, when the leading edge of the recording paper enters the exhaust flow path by the fan, the fan is preferably exhausted in a direction in which the leading edge of the recording paper is slidably contacted with the reverse path. It is preferable to set the direction of the exhaust gas to be perpendicular to the inversion path. As a result, the leading edge of the recording paper approaches the lever while being in sliding contact with the inversion path, and the distance from the lever is kept constant. Therefore, the timing at which the lever is rotated by the recording paper is also constant, and the detection of the recording paper by the lever and the detection sensor can be stabilized.

The devices constituting the image forming apparatus are arranged close to each other in the apparatus casing, and the image forming apparatus is miniaturized. Here, it is preferable that the lever and the detection sensor are arranged at positions close to each other for the purpose of transmitting the rotation of the lever to the detection means. Further, the lever protrudes from the reversing path provided in a narrow space between the fixing device and the fan, and is further disposed at a position facing the fixing device together with the fan. The fan is disposed at a position close to the fan. Therefore, it is preferable to provide holding means for integrally holding the lever, the detection sensor, the connecting shaft, and the fan, and attach these devices to the holding means. As a result, the positional relationship between the devices is stabilized, the assembly in the production process is facilitated, and the maintenance work of the image forming apparatus can be easily performed.

  According to the image forming apparatus of the present invention configured as described above, even if the disposition position of the recording paper detection means provided in the reversing path interferes with the disposition position of the fan, It is possible to efficiently exhaust the heat generated from the fixing device.

  Hereinafter, an image forming apparatus of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of a full-color laser beam printer to which the present invention can be applied. The full-color printer 1 includes an image forming unit 2 that forms a recording image corresponding to image information on the recording paper P, and a paper feeding cassette 50 that supplies the recording paper P to the image forming unit 2. Yes.

  A process cartridge 21 for forming a toner image by an electrophotographic process is mounted on the image forming unit 2, and a raster scanning unit 3 is provided adjacent to the process cartridge 21. The process cartridge 21 includes four photosensitive drums corresponding to yellow Y, magenta M, cyan C, and black K, and these photosensitive drums are arranged in a vertical row. The raster scanning unit 3 emits four laser beams modulated according to the image information of each color, and these laser beams expose the photosensitive drums of the respective colors, respectively, and the image information is formed on the photosensitive drums according to the image information. An electrostatic latent image is formed. On the other hand, around each photosensitive drum of the process cartridge 21, a charging roll for charging the photosensitive drum to a uniform background potential prior to the exposure with the laser beam, and an electrostatic latent formed on the photosensitive drum. A developing unit for developing the image with toner and a cleaner for cleaning the photosensitive drum are provided, and a toner image corresponding to image information of each color is formed on the photosensitive drum by an electrophotographic process.

  Of the four photosensitive drums, two photosensitive drums corresponding to yellow Y and magenta M are in contact with the first primary intermediate transfer drum 22, and yellow Y and magenta formed on these photosensitive drums. The M toner image is primarily transferred to the first primary intermediate transfer drum 22. The two photosensitive drums corresponding to cyan C and black K are in contact with the second primary intermediate transfer drum 23, and the cyan C and black K toner images formed on these photosensitive drums are the second. Primary transfer drum 23 is primarily transferred. Further, the first and second primary intermediate transfer drums 22 and 23 are in contact with the secondary intermediate transfer drum 24, and the two-color multiple toner images formed on the primary intermediate transfer drums 22 and 23 are secondary intermediate images. Secondary transfer is performed to the transfer drum 24, and a multi-toner image of four colors is formed on the secondary intermediate transfer drum 24 so as to overlap each other. The four-color multiple toner images transferred onto the secondary intermediate transfer drum 24 in this way are transferred onto the recording paper P by the final transfer roll 25.

  The recording paper P is supplied from the paper feed cassette 50 housed in the lower part of the apparatus housing 1 a to the image forming unit 2 of the printer, specifically, the transfer position between the secondary intermediate transfer drum 24 and the final transfer roll 25. The A sheet feeding device 5 is provided below the image forming unit 2, and the apparatus housing 1 a is stacked on the sheet feeding device 5. The apparatus housing 1a is formed in a substantially rectangular shape and has a through hole for mounting the paper feed cassette 50. The paper feed cassette 50 is located on the front side with respect to the through hole of the apparatus housing 1a. It is configured to be pushed in and set from the left side (the left side of FIG. 1). In addition, a pickup roll 51 for pulling out the recording paper P accommodated in the cassette 50 is provided on the upper part of the paper feeding cassette 50 set in the apparatus housing 1a, and a paper feeding roll for conveying the recording paper P. 53 and a retard roll 52 that faces the paper feed roll 53 and prevents double feeding of the recording paper P is provided.

  The recording paper P thus supplied from the paper feed cassette 50 is aligned with the transfer timing of the toner image by the registration roll 26 disposed in front of the final transfer roll 25, and then the secondary intermediate transfer. It is conveyed between the drum 24 and the final transfer roll 25, and a four-color multiple toner image corresponding to the image information is transferred onto the recording paper P. Then, the recording paper P onto which the toner image has been transferred is inserted into the fixing device 6 and the toner image is fixed. Then, the recording paper P passes through the discharge roll 61 and enters the recording paper discharge portion 1b provided on the upper portion of the apparatus housing 1a. Ejected face down.

  Devices such as the fixing device 6, the power source, and the electric circuit constituting the image forming apparatus generate heat when the apparatus is operating. The heat rises while passing through the gaps between the components arranged in the apparatus housing 1a, and the heat is stagnated in the upper part of the apparatus housing 1a. If this state is left as it is, the temperature in the apparatus casing 1a rises, and the toner in the developing device and the cleaner melts, which may affect the image formed on the recording paper P. Therefore, a cooling fan 4 is disposed in the vicinity of the fixing device 6 in order to exhaust the heat stagnating in the upper part of the apparatus housing 1a to the outside of the apparatus. In addition, an air inlet 7 is provided in the side surface of the apparatus housing 1 a corresponding to the upper portion of the raster scanning unit 3, and an exhaust port 8 is provided in the side surface of the apparatus housing 1 a corresponding to the cooling fan 4. Yes. The cooling fan 4 is arranged in a direction to blow air from the right to the left in the figure, and by rotating the cooling fan 4, first, air outside the apparatus housing 1a is sucked from the air inlet 7 (in the figure). Arrow A). Thereafter, the sucked air passes through the upper part of the image forming unit 2 and the lower part of the fixing device 6 and is exhausted from the exhaust port 8 to the outside of the apparatus housing 1a (arrow B in the figure). In this way, by creating an air flow as indicated by arrows A and B in the apparatus housing 1a, the heated air at the top of the image forming unit 2 and the ambient atmosphere of the fixing device 6 are removed from the outside of the apparatus housing 1a. The temperature inside the apparatus housing 1a can be prevented from rising.

  When recording images are formed on both sides of the recording paper P, the recording paper P discharged from the fixing device 6 is once sent to the discharge roll 61, but is not discharged to the recording paper discharge portion 1b, and the discharge roll 61 is reversed. It is sent to the inversion path 62 by rotating. The reversing path 62 passes between the cooling fan 4 and the fixing device 6, and the detection lever 9 is provided in the exhaust passage of the cooling fan 4 in the reversing path 62. When the leading edge of the recording paper P passes through the detection lever 9, the detection lever 9 is rotated (not shown) to detect that the recording paper P is conveyed to the reversing path 62. Further, after the recording paper P passes through the detection lever 9, it is transported again to the registration roll 26, and the recording image is formed on the surface where the recording image is not formed.

  FIG. 2 shows the operation of the detection lever before and after the recording paper conveyed on the reverse path passes through the detection lever. Both the partial diagrams (a) and (b) show the periphery of the detection lever 9, and the reversing path 62 is disposed so as to pass between the cooling fan 4 and the fixing device 6. The detection lever 9 is disposed in the reversing path 62 in the exhaust passage (not shown) of the cooling fan 4. Further, an exhaust port 8 is provided in a side surface portion of the apparatus housing 1 a corresponding to the cooling fan 4.

  Part (a) shows a state in which the leading end of the recording paper P conveyed to the reversing path 62 in the direction of the arrow in the drawing approaches the detection lever 9. At this time, the detection lever 9 remains in a state of protruding to the reversing path 62. Then, the recording paper P is further conveyed to the tip of the reversing path 62, and the leading edge of the recording paper P reaches the detection lever 9. Part (b) shows a state in which the recording paper P passes through the detection lever 9. At this time, the detection lever 9 rotates about the connecting shaft 9a in the direction of the arrow in the figure. As a result, the detection sensor (not shown) connected to the connecting shaft 9a stops in a state where the connecting shaft 9a is rotated, that is, the recording paper P is passing through the detecting lever 9. It can be detected.

  FIG. 3 shows an example in which the leading edge of the recording paper conveyed along the reverse path by the cooling fan is brought into sliding contact with the reverse path. Here, both the partial diagrams (a) and (b) show the state in which the recording paper P is approaching the detection lever 9. In addition, regarding the arrangement positions of the cooling fan 4, the fixing device 6, the reversing path 62, the exhaust port 8, and the detection lever 9, which are arranged in the apparatus housing 1 a in both the divided drawings (a) and (b) Since it is not different from FIG. 2, its description is omitted.

  In the partial diagram (a), the cooling fan 4 blows air in the direction of arrow B, and the heat of the fixing device 6 is exhausted from the exhaust port 8. Here, when the recording paper P approaches the detection lever 9 and enters the exhaust flow path, the leading edge of the recording paper P is flowed in the direction of the arrow B and contacts the guide 62a near the apparatus housing 1a of the reversing path 62. To do. The leading edge of the recording paper P is further conveyed so as to be in sliding contact with the guide 62a, and the detection lever 9 is rotated. In this way, by sliding the leading edge of the recording paper P on the guide 62a, the distance between the leading edge of the recording paper P approaching the detection lever 9 and the detection lever 9 is kept constant, and detection is performed by the leading edge of the recording paper P. The timing at which the lever 9 is rotated can be kept constant, and the detection of the recording paper P conveyed through the reversing path 62 can be stabilized.

  On the other hand, in the partial drawing (b), the cooling fan 4 blows air in the direction of arrow A which is opposite to that in the partial drawing (a), and the air outside the apparatus housing 1a is sucked from the exhaust port 8. That is, in this figure, the exhaust port 8 functions as the intake port 7 in FIG. Here, when the recording paper P approaches the detection lever 9 and enters the intake flow path, the leading edge of the recording paper P is flowed in the direction of arrow A and contacts the guide 62b near the fixing device 6 of the reversing path 62. . The leading edge of the recording paper P is further conveyed so as to be in sliding contact with the guide 62b, and the detection lever 9 is rotated. Thus, by sliding the tip of the recording paper P on the guide 62b, the position where the tip of the recording paper P approaching the detection lever 9 contacts the detection lever 9 is kept constant. The timing at which the detection lever 9 is rotated can be kept constant, and the detection of the recording paper P conveyed through the reversing path 62 can be stabilized. This configuration is particularly effective when the recording paper P having a low stiffness is conveyed to the reversing path 62.

FIG. 4 shows a holding frame that holds the detection lever, the detection sensor , the connecting shaft, and the cooling fan. The holding frame 11 constitutes a part of a guide 62a near the apparatus housing 1a of the reversing path 62 in FIG. 3, and the guide 62a is formed so as to protrude above the holding frame 11. The detection lever 9 is disposed at a position corresponding to the center of the side orthogonal to the conveyance direction (arrow in the figure) of the recording paper P shown in the lower part of the figure. One end of the connecting shaft 9a passes through the detection lever 9, and the detection lever 9 and the detection sensor 10 are connected by the connecting shaft 9a. Accordingly, when the recording paper P passes the detection lever 9, the detection lever 9 is rotated about the connecting shaft 9a, and the detection sensor 10 detects the passage of the recording paper P. In addition, a receiving portion 4a to which a cooling fan (not shown) is fixed is erected at the central portion of the holding frame 11, and the cooling fan is fixed so as to be received in the receiving portion 4a. Since 10 is fixed outside the receiving portion 4a, the detection sensor 10 does not block the ventilation of the cooling fan. Further, an opening 11 a is provided in the upper part of the main body of the holding frame 11 to allow a fixing means such as a screw to pass through when the holding frame 11 is fixed to the image forming apparatus.

As described above, the holding frame 11 can integrally hold the cooling fan (not shown), the connecting shaft 9a, the detection lever 9 and the detection sensor 10 which are arranged close to each other in the apparatus housing 1a. It is not necessary to provide a frame for fixing each device in the apparatus housing 1a. In addition, since these devices are fixed to one holding frame 11, the mounting accuracy can be improved and the positional relationship between the devices can be stabilized as compared with the case where each device is fixed to a separate frame. Is possible. Further, once each device is fixed to the holding frame 11, each device can be attached or detached at the same time, and assembly in the production process and maintenance work of the image forming apparatus can be easily performed.

It is a figure which shows an example of the full color laser beam printer which can apply this invention. FIG. 10 is a diagram illustrating the operation of the detection lever before and after the recording paper conveyed through the reverse path passes through the detection lever. FIG. 10 is a diagram illustrating an example in which a leading edge of a recording sheet conveyed along a reverse path by air blowing from a cooling fan is brought into sliding contact with the reverse path. It is a figure which shows the holding | maintenance flame | frame which hold | maintains a detection lever, a detection sensor , a connection shaft, and a cooling fan.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Apparatus housing, 4 ... Cooling fan, 6 ... Fixing device, 8 ... Exhaust port, 9 ... Detection lever, 9a ... Connecting shaft, 62 ... Reverse path

Claims (3)

An apparatus housing, an image forming unit that transfers a toner image according to image data to a recording sheet, a fixing device that fixes the toner image transferred to the recording sheet while conveying the recording sheet upward in the vertical direction ; When forming a recorded image on both sides of the recording sheet, a reversing path for fixing the toner image on one side of the recording sheet and then transporting the recording sheet to the image forming unit vertically downward; and the reversing path And a lever that rotates as the leading end of the recording paper that is conveyed to the reversing path passes through, a detection sensor that detects the rotation of the lever, and heat generated in the apparatus casing. In an image forming apparatus composed of a fan that exhausts outside the body,
The fan is disposed on a side surface of the fixing device at a position substantially opposite to the reversing path, and forms an exhaust passage for exhausting from the side surface of the device in a substantially horizontal direction.
The lever, with said fixing device, between the fan and, together are arranged prior Sharing, ABS air flow path, one end of the connecting shaft axes of the rotation is to be drawn in and out the exhaust passage Connected to
The sensor is at the other end of the connecting shaft, the rotation so that it can detect the image forming apparatus characterized by being arranged before outside Sharing, ABS air passage. The image forming apparatus according to claim 1, wherein the fan exhausts the recording sheet conveyed along the reversing path in a direction in which the leading end of the recording sheet is in sliding contact with the reversing path. The image forming apparatus according to claim 1 , further comprising a holding unit that holds the lever, the detection sensor , the connecting shaft, and the fan.

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