JP4298557B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms images by sequentially forming images with a plurality of color image forming units, such as a color printer and a color copier, and more specifically, the inside of the apparatus, particularly a plurality of image carriers and The present invention relates to an image forming apparatus provided with a cooling means for cooling a belt member.

  In recent years, with the widespread use of electrophotographic color image forming apparatuses, in addition to the demand for color image printing quality, there has been an increasing demand for speeding up color output. To meet this demand, several image forming methods have been developed. Has been proposed. Among them, there is a color image forming method called a tandem type. In this method, toner images of black, cyan, magenta, and yellow are formed on a drum-shaped image carrier, and are sequentially transferred by transfer means to a transfer material conveyed by a transfer belt. Alternatively, each color toner image is directly transferred to a transfer belt to form a color image, and the color image is collectively transferred to a transfer material. Then, the toner image transferred to the transfer material is heated and fixed by a fixing device.

  As a method for transferring the image of each color image carrier onto a transfer material, a transfer material is conveyed by a belt called a transfer conveyance belt, and the image is directly transferred onto the transfer material, and an intermediate transfer belt. One example is one in which each color image is sequentially transferred to a so-called belt and then transferred onto transfer paper.

  In a tandem type color image forming apparatus, it is necessary to increase the number of driving units and the accompanying increase in power supply size, and the toner must be mixed and fixed in a fixing device that fixes the toner image on the transfer material. It was. For this reason, a large amount of heat was generated.

  Further, in the case of performing continuous double-sided printing, the transfer material that has once performed single-sided printing and passed through a high-temperature fixing device passes through the image forming unit again with high heat, whereby the image carrier or The temperature of the image forming unit, the transfer belt unit, etc. will rise. For these reasons, the tandem type color image forming apparatus has to be designed in consideration of the temperature rise in the apparatus main body.

  Specifically, a clearance is provided between each image carrier or between the fixing device and the image carrier, natural cooling is performed, a heat insulating material is provided around a heat source such as a fixing device or a power source, In order to prevent heat from being transmitted to the image forming unit by installing a fan and blowing air, it has been devised. In addition, for the temperature rise during continuous printing on both sides, if the throughput of double-sided continuous printing is lower than that for single-sided continuous printing or the temperature rises, the temperature near the image carrier in the machine is detected by a temperature sensor etc. For example, a specification that does not perform double-sided printing until the temperature falls can be mentioned.

JP 2003-295739 JP JP 2003-29540 JP

  However, in recent years, tandem color image forming apparatuses have been reduced in size and increased in output speed, and it has become impossible to secure clearance between image carriers and around a heat source and to reduce the throughput of duplex printing. For this reason, the temperature of the image forming unit exceeds the allowable temperature, and it is possible to stably form an image on the image carrier by fixing the toner in the toner container or the temperature rise, and to remove the toner image formed on the image carrier. There is a possibility that the image cannot be reliably transferred onto the transfer material.

  Also, the temperature of the transfer belt portion arranged along the image carrier rises, and the belt running speed becomes unstable due to the expansion of the diameter and thickness of the roller that drives the transfer belt, causing color misregistration between colors. There was a thing.

  The present invention has been made in view of the above problems, and its purpose is to provide an image carrier, an image forming unit, a belt member, and the like even when continuous printing is performed in the most severe environment for temperature rise in the machine, in a printing mode. An image forming apparatus capable of reliably cooling and suppressing the influence of heat from a heat source or a transfer material is provided.

Typical means of the present invention for solving the above problems includes a plurality of cartridges with a rotatable image bearing member for bearing a toner image, respectively, are arranged to face the plurality of image bearing members, said plurality In an image forming apparatus having a transfer belt member for transferring a toner image carried on the image carrying member and a cooling means for flowing air to cool the inside of the apparatus, adjacent ones of the plurality of cartridges. The outer wall of one of the two cartridges is provided with a rib protruding toward the outer wall of the other cartridge and extending along the rotational axis of the image carrier, and the outer wall of the two adjacent cartridges and the The space surrounded by the transfer belt member and the rib is an air path along the rotation axis direction of the image carrier through which the air flowing by the cooling means passes. Formed, characterized in that.

According to the present invention, the outer wall of two adjacent cartridges, the transfer belt member, and the rib provided on the outer wall of one of the two adjacent cartridges along the rotation axis direction of the image carrier are surrounded. By creating an air path in the space , the inside of the apparatus main body can be surely cooled, and a high-output and high-quality image can be obtained without causing toner sticking due to temperature rise inside the apparatus main body and image defects associated therewith.

  Next, an image forming apparatus according to an embodiment of the present invention will be described by exemplifying a full color laser beam printer. As an embodiment of the present invention, the transfer material is conveyed by a belt called a transfer conveyance belt and transferred directly onto the transfer material, but each color image is sequentially transferred to a belt called an intermediate transfer belt. Then, it can also be applied to a material transferred onto a transfer material. The present invention can also be applied to a color copying machine provided with a plurality of photosensitive drums. Therefore, the image forming apparatus of the present invention is not limited to a full color laser beam printer.

[Overall configuration of full-color laser beam printer]
First, the overall configuration of the printer will be described. FIG. 1 is a longitudinal sectional view showing an overall configuration of a full-color laser beam printer (hereinafter simply referred to as “printer”) 100 which is an embodiment of a multicolor image forming apparatus.

  The printer 100 includes photosensitive drums 1 (1a, 1b, 1c, 1d) as four image carriers arranged in parallel in the apparatus main body 101 in the vertical direction. Each photosensitive drum 1 is individually rotated counterclockwise in the figure by a driving unit (not shown). Around each photosensitive drum 1, a charging device 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum in order according to the rotation direction of each photosensitive drum, and a laser beam based on image information , A scanner unit 3 (3a, 3b, 3c, 3d) which is an exposure means for forming an electrostatic latent image on the photosensitive drum, and a developing device for developing the toner image by attaching toner to the electrostatic latent image 4 (4a, 4b, 4c, 4d), an electrostatic transfer device 5 that transfers the toner image on the photosensitive drum to the sheet S as a transfer material, and removes transfer residual toner remaining on the surface of the photosensitive drum after transfer. A cleaning device 6 (6a, 6b, 6c, 6d) or the like is disposed.

  The photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 each form a process cartridge 7 (7a, 7b, 7c, 7d) that is integrally formed into a cartridge. Examples of the sheet include plain paper and OHP sheet.

  The photosensitive drum 1 is formed, for example, by applying an organic optical conductor layer (OPC photosensitive member) to the outer peripheral surface of an aluminum cylinder. Both ends of the photosensitive drum 1 are rotatably supported by a support member. A rotational force from a drive motor (not shown) is transmitted to one end of the photosensitive drum 1. Therefore, the photosensitive drum 1 is rotated counterclockwise by the drive motor.

  The charging device 2 employs a contact charging method in which a charging roller having a charging member formed in a roller shape is brought into contact with the photosensitive drum 1. By applying a charging bias voltage to the conductive roller, the surface of the photosensitive drum 1 is uniformly charged.

  The scanner unit 3 is arranged in a substantially horizontal direction with respect to the photosensitive drum 1, and image light corresponding to an image signal is rotated at high speed by a scanner motor (not shown) by a laser diode (not shown). , 9b, 9c, 9d). The image light reflected from the polygon mirror 9 selectively exposes the surface of the charged photosensitive drum 1 through the imaging lens 10 (10a, 10b, 10c, 10d). As a result, an electrostatic latent image is formed on the photosensitive drum 1.

  The developing device 4 has a developing device that stores toners of each color of yellow, magenta, cyan, and black, and develops the latent image formed on the photosensitive drum 1 with each color toner to make a visible image.

  The electrostatic transfer device 5 electrostatically attracts the sheet S by an electrostatic transfer belt 11 which is an endless belt member, and transfers a toner image by conveying the transfer material to a position facing each photosensitive drum 1. is there.

  The electrostatic transfer belt 11 of the present embodiment is stretched over four rollers, a driving roller 13, driven rollers 14a and 14b, and a tension roller 15, and is in contact with all the photosensitive drums 1a, 1b, 1c, and 1d. It circulates in the direction of the arrow in FIG. The electrostatic transfer belt 11 circulates in order to electrostatically attract the sheet S to the left outer peripheral surface shown in FIG. 1 and bring the sheet S into contact with the photosensitive drum 1. At that time, the toner image on the photosensitive drum 1 is transferred to the sheet by applying a transfer bias to the transfer roller 12 (12a, 12b, 12c, 12d).

  The sheet supply unit 16 conveys the sheet S to an image forming unit (image forming unit) such as the process cartridge 7. A plurality of sheets S are stored in the sheet supply cassette 17. At the time of image formation, the half-moon shaped sheet supply roller 18 rotates according to the image forming operation, separates the sheets S in the sheet supply cassette 17 one by one, and feeds them to the registration roller pair 19. ing.

  The fixing device (fixing means) 20 fixes the toner images of a plurality of colors transferred to the sheet S to the sheet S. The fixing device 20 includes a heating roller 21a that rotates and applies heat to the sheet, and a pressure roller 21b that presses the sheet and applies pressure to the sheet S.

  Note that the printer 100 of the present embodiment can form images on both sides of a sheet. Therefore, in order to form a toner image on the other surface of the sheet on which the toner image is formed on one surface by the process cartridge 7, the sheet refeeding and transporting mechanism for reversing the sheet and feeding it to the image forming unit again. (Sheet refeed conveyance means) 50 is provided. If the sheet is formed only on one side of the sheet, the sheet refeeding and conveying mechanism 50 is not necessarily required.

  When the image forming signal is input to the printer having the above-described configuration, the sheet S is fed from the sheet feeding cassette 17 by the sheet feeding unit 16 and is electrostatically attracted to the electrostatic transfer belt 11 and conveyed to the image forming unit. The photosensitive drum 1 rotates in synchronization with the sheet conveyance, and the yellow, magenta, cyan, and black color toner images formed on the respective photosensitive drums are sequentially transferred onto the conveyed sheet by electrophotography. Then, after the sheet is conveyed to the fixing device 20 and the toner image is heated and fixed, the sheet is discharged and stacked on the discharge unit 39 at the upper part of the apparatus by the sheet discharge roller pair 23. The sheet discharged to the discharge unit 39 is heated when the toner is fixed, but is cooled by the air blown from the cooling fan 37.

[Cooling means]
The printer of the present embodiment is provided with a cooling unit in order to suppress a temperature rise in the apparatus main body. Next, the arrangement of the cooling means, which is a characteristic part of the present invention, will be described with reference to FIGS.

  As shown in FIG. 2, four openings 65 (65a) for sending cooling air into the apparatus to left and right side plate frames 60 and 61 as support members for supporting the process cartridge 7 including the photosensitive drum 1 in the apparatus main body 101 are shown. , 65b, 65c, 65d) and four openings 66 (66a, 66b, 66c, 66d) for exhausting the air inside the machine to the outside of the machine. Each of the openings 65 and 66 is provided for each of the plurality of process cartridges 7 and is composed of a process cartridge 7 containing the adjacent photosensitive drums 1 and the electrostatic transfer belt 11 as shown in FIG. The first space A and the second space B for performing exposure for forming an electrostatic latent image on the photosensitive drum 1 are provided at the same phase. In the present embodiment, the openings 65 and 66 are formed so as to cool both the spaces A and B of the spaces A and B, but only one of them may be formed.

  Further, as shown in FIG. 3, a blower duct 56 (56a) in which a blower fan 55 (55a, 55b) for taking cooling air outside the machine and feeding it into the machine is attached to the left plate frame 60 at the rear end of the main unit. , 56b) are arranged. The other end of the air duct 56 is connected to the opening 65 of the left side plate frame 60. As shown in FIG. 4, the blowing direction from the opening 65 by the blowing duct 56 is set so as to be approximately 40 ° with respect to the rotation axis direction of the photosensitive drum 1. As a result, air flows on both the surface of the photosensitive drum 1 and the surface of the electrostatic transfer belt 11 in the process cartridge 7, and the cleaning device unit 6, the charging device unit 2, the developing device unit 4 near the photosensitive drum 1, The electrostatic transfer belt unit 11 is set to be particularly cooled.

  Further, as shown in FIG. 3, a suction fan 57 is disposed on the upper right rear side of the apparatus main body in order to exhaust the air in the apparatus to the outside through the opening 66 of the right plate frame 61. The suction fan 57 and the right side plate frame 61 are covered with a right exterior part 58 of the apparatus main body provided outside the right side plate frame 61 and an upper exterior part (not shown) to form a suction duct. It is configured so that it can be efficiently exhausted outside the apparatus.

  Next, the flow of air for cooling the inside of the apparatus main body will be described with reference to FIG. Outside air in the apparatus main body flows from a blower fan 55 provided behind the blower duct. Thereafter, the air passes through the air duct 56 in the direction of the arrow and is blown to the process cartridge unit 7 through the opening 65 of the left side plate frame 60.

  The air sent to the process cartridge unit 7 passes through the spaces A and B (see FIG. 1), thereby cooling the vicinity of the photosensitive drum and the electrostatic transfer belt unit 11, and an opening provided in the right plate frame 61. Passing through 66, the air is sucked into the suction fan 57 and exhausted outside the apparatus.

  As a result, even if the internal temperature rises repeatedly by continuous double-sided printing or the like, it is efficiently cooled by the air flow by the cooling means. In this embodiment, for example, the temperature in the vicinity of the photosensitive drum 1 of the process cartridge was 60.8 ° C. before the cooling means of this embodiment was adopted, but the cooling means of this embodiment described above is adopted. As a result, the temperature was lowered to 42.8 ° C.

  Here, in the present embodiment, as shown in FIG. 1, the first space A functions as a guide for forming the air flow in the rotation axis direction of the photosensitive drum 1 on the outer wall of the cartridge 7. Cooling air from the duct 56 is effectively sent.

  In the present embodiment, an intermediate plate 63 is provided at the boundary between the mounting area of the cartridge 7 and the scanner unit 3, and when the air sent into the apparatus passes through the first space A and the second space B, an image is displayed. The forming member is efficiently cooled.

As described above, in the present embodiment, an electrostatic latent image is formed on the photosensitive drum 1 and the first space A composed of the plurality of photosensitive drums 1 adjacent to the electrostatic transfer belt 11. by making the flow of air in the direction of the rotation axis of the photosensitive drum 1 into the second space B for performing exposure of an internal device body reliably cooled, Ya decrease in throughput due to temperature increase in the apparatus main body It is possible to obtain a high-output and high-quality image that does not cause image defects such as toner fixation.

  Further, since the air blowing direction with the air duct 56 is set so that air flows through both the photosensitive drum 1 and the electrostatic transfer belt 11, the influence of heat on the photosensitive drum 1 and the toner can be minimized. .

  Further, by using the openings 65 and 66 provided in the left and right side plate frames 60 and 61 for supporting the photosensitive drum 1 with the air duct 56 and the suction duct, the cost of the image forming apparatus can be increased without newly providing a cooling means. The inside of the apparatus can be cooled while suppressing an increase in size.

  Further, the openings 65 and 66 provided in the left and right side plate frames 60 and 61 are connected to the fans 55 and 57 provided in the apparatus main body and the duct, and the air blown and sucked by the fans is blown and sucked into the openings. The space in the left and right plate frames 60 and 61 can be reliably cooled.

  Further, by causing the outer wall of the cartridge 7 loaded in the apparatus main body to function as a guide for forming an air flow in the direction of the rotation axis of the photosensitive drum 1, it is possible to newly provide a duct inside the apparatus main body. It becomes possible to secure the air flow without increasing the cost, and the cooling efficiency can be improved.

  In the above-described embodiment, the air duct 56 is disposed outside the left and right side plate frames 60 and 61. However, the air duct 56 may be disposed inside the left and right side plate frames.

  Further, as shown in FIG. 5, by providing ribs 64 (64a, 64b) in the direction along the air flow on the outer wall of the cartridge 7, it is possible to reduce the air volume of the cooling air at the place where cooling is desired. The air blowing effect can be enhanced, and the in-machine temperature due to the in-machine temperature rise can be lowered.

1 is a longitudinal sectional view showing an overall configuration of a full-color laser beam printer which is an embodiment of an electrophotographic image forming apparatus according to an embodiment of the present invention. 2 is a perspective view showing a main body frame of the image forming apparatus. FIG. 2 is a schematic perspective view of a main body frame and a cooling unit of the image forming apparatus. FIG. It is a schematic top view which shows the flow of the air by a cooling means. It is a schematic perspective view of a process cartridge provided with a rib.

Explanation of symbols

A, B ... space S ... sheet 1 ... photosensitive drum 2 ... charging device 3 ... scanner unit 4 ... developing device 5 ... electrostatic transfer device 6 ... cleaning device 7 ... process cartridge 9 ... polygon mirror
10… Imaging lens
11… Electrostatic transfer belt
12… Transfer roller
13… Drive roller
14a, 14b ... driven roller
15… Tension roller
16 ... Sheet supply section
17… Sheet supply cassette
18 ... Sheet supply roller
19… Registration roller pair
20… Fixer
21a ... Heating roller
21b… Pressure roller
23… Sheet discharge roller pair
37… Cooling fan
39… discharge section
50… Sheet refeeding mechanism
55… Blower fan
56… Blower duct
57… Suction fan
58… Right exterior parts
60… Left side frame
61… Right side frame
63 ... Middle plate
64… ribs
65, 66… opening
100 ... Printer
101 ... Main unit

Claims (3)

A plurality of cartridges each having a rotatable image carrier for carrying a toner image; and a plurality of cartridges arranged to face the plurality of image carriers and for transferring the toner images carried on the plurality of image carriers. In an image forming apparatus having a transfer belt member and cooling means for flowing air to cool the inside of the apparatus,
The outer wall of one of two adjacent cartridges of the plurality of cartridges is provided with a rib that protrudes toward the outer wall of the other cartridge and extends along the rotation axis of the image carrier,
A space surrounded by the outer walls of the two adjacent cartridges, the transfer belt member, and the ribs forms an air path along the rotation axis direction of the image carrier through which the air flowing by the cooling means passes. An image forming apparatus. 2. The electrostatic transfer belt according to claim 1, wherein the transfer belt member is an electrostatic transfer belt that electrostatically attracts and conveys a sheet and transfers toner images carried on the plurality of image carriers onto the conveyed sheet. The image forming apparatus according to 1. The cooling means is a blower fan for taking in air outside the apparatus and sending it into the apparatus,
  The blowing direction of the air blown into the air path along the rotation axis direction of the image carrier by the blower fan is directed toward the surface of the transfer belt member facing the plurality of image carriers. The image forming apparatus according to claim 1, wherein the image forming apparatus is inclined with respect to a rotation axis direction of the image forming apparatus.

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