JP2009156901A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device for preventing useless thermal conduction from a nip part to the other parts of a heat roller, raising temperature of the nip part of the heat roller up to predetermined temperature quickly, and heating only the nip part of the heat roller required for fixing operation in a concentrated manner to improve thermal efficiency of a heater. <P>SOLUTION: The heater is arranged inside a roller core of the heat roller. The roller core is composed of a main tube part constituting the nip part and supporting tube parts on both sides of the main tube part. Heat insulating parts for preventing thermal conduction from the main tube part to the supporting tube parts are provided in parts adjacent to the main tube part and the supporting tube parts. A plurality of heat insulating holes are formed in the peripheral direction of a cylindrical wall of the heat insulating parts and cross sectional area of the heat insulating parts is set to be smaller than cross sectional area of the main tube part to prevent useless thermal conduction from the main tube part to the supporting tube parts by the heat insulating parts. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention has a heat roller and a press roller that constitute a nip portion for subjecting a recording sheet to heat and pressure treatment, and while heating the nip portion with a heater built in the heat roller, The present invention relates to a fixing device that pressurizes a recording sheet to fix a toner image on the recording sheet.

  A fixing device applied to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine heats and presses a recording paper on which a toner image is formed at a nip portion, thereby converting the toner image onto the recording paper. Established. In such a fixing device, it is required to raise the temperature of the heat roller to a predetermined temperature in a short time and to heat the heat roller efficiently.

  With respect to this type of request, in Patent Document 1, both ends of the fixing roller are supported by a bearing member made of a thermoplastic resin having low thermal conductivity, and the heat of the fixing roller is wastedly dissipated to a bearing, a drive gear, a housing, and the like. Prevents the heating time. In Patent Document 2, a heat insulating member is provided between the fixing roller and the bearing member. In this case, the heat of the fixing roller heated by the halogen heater is prevented from escaping to the bearing member by the heat insulating member, thereby improving the thermal efficiency of the fixing device.

JP-A-6-161313 (paragraph number 0011, FIG. 3) JP 2002-214949 A (paragraph number 0052, FIG. 3)

  According to Patent Documents 1 and 2, it is possible to prevent heat from escaping from both ends of the fixing roller to a bearing and the like, and to achieve a certain degree of shortening of the temperature raising time and improvement of thermal efficiency. However, in this type of fixing device, the entire fixing roller including the nip portion composed of the fixing roller and the press roller is overheated with a heat source. Therefore, the fixing roller is heated unnecessarily to a portion that is not necessary for the fixing operation, and there is a corresponding amount of waste. Further, there is a disadvantage that the time required for raising the temperature of the fixing roller becomes long. Naturally, the heat efficiency of the fixing device is lowered and the power consumption is increased by the amount of wasted heating.

  An object of the present invention is to obtain a fixing device that can prevent wasteful heat conduction from the nip portion of the heat roller to other portions and quickly raise the nip portion of the heat roller to a predetermined temperature. . An object of the present invention is to intensively heat only the nip portion of the heat roller necessary for the fixing operation to eliminate unnecessary energy consumption, thereby obtaining a fixing device that can improve the thermal efficiency of the heater and contribute to energy saving. There is.

  The present invention is directed to a fixing device that includes a heat roller and a press roller that constitute a nip portion for subjecting a recording sheet to heat and pressure, and fixes a toner image onto the recording sheet. The heat roller is composed of a hollow cylindrical roller core, and a heater is disposed inside the roller core. The roller core is composed of a main pipe part constituting the nip part, and a support pipe part provided at both ends of the main pipe part and rotatably supported by bearings. Thus, a heat shield part that prevents heat conduction from the main pipe part to the support pipe part is provided in an adjacent part between the main pipe part and the support pipe part.

  Specifically, the cross-sectional area of the heat shield part is made smaller than the cross-sectional area of the main pipe part to prevent heat conduction from the main pipe part to the support pipe part.

  More specifically, a plurality of heat shield holes are formed in the circumferential direction of the cylindrical wall of the heat shield part so that the cross sectional area of the heat shield part is smaller than the cross sectional area of the main pipe part. Alternatively, a heat shield groove is recessed in the circumferential direction of the cylindrical wall of the heat shield part so that the cross sectional area of the heat shield part is smaller than the cross sectional area of the main pipe part. In this case, the heat shield groove can be formed in a circular shape.

  Heat conduction can be prevented in a form different from the above embodiment, in which the heat shield part is formed of a heat insulating material, and the main pipe part and the support pipe part are connected via the heat shield part, Prevents heat conduction from the main tube to the support tube.

  In the fixing device according to the present invention, since the heat shield portion is provided adjacent to the main tube portion and the support tube portion constituting the nip portion, the heat of the main tube portion heated by the heater is blocked from being conducted to the support tube portion. It is possible to prevent the heat of the main pipe portion from being unnecessarily conducted to a portion other than the nip portion by blocking the heat portion. Thereby, the temperature drop of the main pipe part accompanying useless heat conduction from the main pipe part to the support pipe part side can be largely suppressed, and the nip part of the heat roller can be quickly heated to a predetermined temperature. In addition, since only the main pipe portion of the heat roller corresponding to the nip portion is intensively heated by the heater, there is no waste in the heating mode of the heat roller, and the heat efficiency of the heater can be improved correspondingly, thereby contributing to energy saving.

  According to the fixing device that makes the cross-sectional area of the heat shield part smaller than the cross-sectional area of the main pipe part, the heat conduction area is made small by the small cross-sectional area of the heat shield part, and it tries to conduct from the main pipe part to the support pipe part The total amount of heat can be reduced. As a result, the temperature drop of the main pipe part due to wasteful heat conduction from the main pipe part to the support pipe part side can be largely suppressed, and the nip part of the heat roller can be quickly raised to a predetermined temperature. In addition, by applying simple machining such as drilling and grooving to the heat roller, the cross-sectional area of the heat shield can be reduced and heat conduction can be prevented, so there is no need to change the basic structure of the heat roller. An increase in cost for adding a heat conduction blocking function can be suppressed. Even with an existing heat roller, a heat conduction blocking function can be added by simply performing additional work.

  According to the fixing device that forms the heat shield portion by forming a plurality of heat shield holes in the circumferential direction of the cylindrical wall, the cross-sectional area can be reduced simply by cutting the roller core. Therefore, the heat roller can be manufactured at a lower cost and the increase in the cost of the fixing device can be suppressed as compared with the case where heat conduction is prevented by using a heat insulating component formed of a heat insulating material.

  According to the fixing device that forms the heat shield portion by forming the heat shield groove in the circumferential direction of the cylindrical wall, the heat roller can be manufactured at a low cost as described above. Further, when the heat shield portion is constituted by a plurality of heat shield holes, it is advantageous in that the heat inside the heat roller can be prevented from being dissipated through the heat shield portion. In particular, when the heat shield groove is formed in a circular shape, since the heat shield portion can be formed by turning, an increase in manufacturing cost accompanying the addition of the heat shield portion can be remarkably suppressed. In use, it is inevitable that the heat of the main pipe part is conducted to the support pipe part through the heat shield part, but if the heat shield groove is formed in a circular shape, the amount of heat conduction in the circumferential direction of the heat shield part is made uniform. Therefore, it is possible to eliminate the uneven heat distribution in the circumferential direction of the main pipe portion adjacent to the heat shield portion.

  According to the fixing device in which the heat shield part is formed of a heat insulating material and the heat shield part is arranged between the main pipe part and the support pipe part, wasteful heat conduction from the main pipe part to the support pipe part side is further effectively performed. Can be prevented. Therefore, the nip portion of the heat roller can be quickly raised to a predetermined temperature, and the heat efficiency of the heater can be improved by the amount that can prevent useless consumption of the heater heat, thereby further contributing to energy saving of the fixing device.

First Embodiment FIGS. 1 to 4 show an embodiment in which a fixing device according to the present invention is applied to a fixing device of a multifunction machine having a copy function and a facsimile function. In FIG. 2, the multi function device 1 displays a toner image on a paper feed cassette 2 on which a group of sheet papers (hereinafter simply referred to as paper) P is placed, and on the paper P sent from the paper feed cassette 2. An image recording unit 3 that performs image formation by transfer, and a fixing device 4 that heats and pressurizes the paper P subjected to image forming processing in the image recording unit 3 to fix the toner image on the paper P. The image recording unit 3 and the image reading unit 5 disposed above the fixing device 4 are included. On the upper surface of the image reading unit 5, an operation panel 6 having various operation buttons and an automatic document feeder (ADF) 7 are provided.

  Inside the multi-function device 1, a paper transport path R is formed from the paper feed cassette 2 through the image recording unit 3 to the paper discharge unit 8. At the time of image formation accompanying a copy operation or the like, the paper P is fed out to the transport path R one by one by rotationally driving the paper feed roller 9 disposed at the upper end of the paper feed cassette 2. The image recording unit 3 includes a photoconductor unit 10 including a charging drum 11 and a toner cartridge 12 that supplies toner to the photoconductor unit 10.

  As shown in FIG. 3, the fixing device 4 includes a heat roller 15 and a press roller 16, and a nip portion N that performs a heating and pressing process on the paper P is formed between the rollers 15 and 16. The heat roller 15 includes a heater 17 for heating the nip portion N via the heat roller 15, specifically a halogen heater. The region heated by the heater 17 is almost the same as the region of the nip portion N, and in FIG. 1, this effective heating region is illustrated as a large-diameter pipe portion. The heat roller 15 is formed by applying a coating treatment with polytetrafluoroethylene (PTFE) on the outer peripheral surface of a roller core 18 formed of a metal having a high thermal conductivity such as aluminum in a hollow cylindrical shape for the purpose of improving toner releasability. Become.

  The press roller 16 arranged in parallel with the heat roller 15 is formed with an elastic body layer 20 made of silicon rubber or the like on the outer peripheral surface of the rotating shaft 19, and the PTFE coating process similar to the above is performed on the outer peripheral surface. It is given. By urging both ends of the rotating shaft 19 with compression springs 21 and 21, the elastic body layer 20 of the press roller 16 is always pressed against the heat roller 15. The two rollers 15 and 16 at the time of image formation rotate in a direction to feed the paper P fed to the nip portion N to the paper discharge portion 8. These heat roller 15 and press roller 16 are assembled into a square box-like case 22 to form unit parts.

  The roller core 18 includes a main pipe portion 24 constituting the nip portion N, support pipe portions 25 and 25 supported by bearings 27 and 27 fixed to the case 22, and shields disposed adjacent to both ends of the main pipe portion 24. It consists of heat parts 26 and 26. One support tube portion 25 is equipped with a gear 28 that meshes with a final gear of a drive unit (not shown), and the heat roller 15 is rotationally driven by receiving a rotational driving force from the drive unit.

  The heat shields 26 and 26 are provided to intensively heat the nip N of the heat roller 15 by preventing heat conduction from the main pipe 24 to the support pipes 25 and 25. As shown in FIGS. 1 and 4, the heat shield portions 26 and 26 are configured by forming eight oval heat shield holes 31 in the cylindrical wall of the roller core 18 at regular intervals. The heat shield hole 31 is formed by milling the roller core 18. Thus, by forming the heat shield holes 31 at regular intervals in the circumferential direction of the cylindrical wall, the main pipe portion 24 and the support pipe portion 25 are only bridge portions 32 between the heat shield holes 31 adjacent in the circumferential direction. It will be continuous through. As a result, the cross-sectional area of the heat shield part 26 can be made smaller than that of the main pipe part 24. Therefore, the heat of the main pipe part 24 heated by the heater 17 can only be conducted through the previous bridging part 32, and the amount of heat conducted to the support pipe part 25 can be reduced to prevent the temperature drop of the main pipe part 24.

  The number of the heat shield holes 31 is not limited to eight and can be changed as appropriate. Although the heat shielding holes 31 are formed in only one row, a plurality of rows may be used. In the case of multiple rows, the phase of the heat shield holes 31 in each row can be shifted.

Second Example FIG. 5 shows a second embodiment of a fixing device according to the present invention. Since the configuration of the fixing device 4 is the same as that of the first embodiment, the description thereof is omitted. In this case, a heat shield groove 33 is provided around the cylindrical peripheral wall of the roller core 18 to form the heat shield part 26, and the cross sectional area of the heat shield part 26 is made smaller than that of the main pipe part 24. The heat shield groove 33 is formed by cutting the roller core 18. The heat of the main pipe portion 24 heated by the heater 17 can only be conducted through the bridge portion 32 at the bottom of the heat shield groove 33, thereby delaying the heat conduction to the support pipe portion 25. Therefore, the temperature drop of the main pipe portion 24 can be prevented accordingly.

  Although the heat shield groove 33 is formed on the outer peripheral surface, it may be an inner peripheral surface. Although only one row of the heat shield grooves 33 is formed, a plurality of rows may be used. The heat shield groove 33 can be formed in an intermittent state, and the heat shield groove 33 in that case is preferably formed by milling the roller core 18 in the same manner as the previous heat shield hole 31.

  As described above, if a plurality of heat shield holes 31 and heat shield grooves 33 are provided in each of the heat shield portions 26 and 26 to reduce the cross-sectional area of the heat shield portion 26, the amount of heat conduction in the heat shield portion 26 is reduced. it can. Therefore, the temperature drop of the main pipe part 24 due to heat conduction to the support pipe part 25 side can be prevented, and the nip part N of the heat roller 15 can be quickly heated to a predetermined temperature. In addition, the nip portion N of the heat roller 15 can be intensively heated by the heater 17 while reducing the heat loss by an amount that can prevent the temperature drop of the main pipe portion 24, thereby improving the thermal efficiency of the heater 17 and saving energy. Can contribute.

  When the heat shield part 26 is configured by the heat shield hole 31 or the heat shield groove 33, the cross-sectional area can be reduced only by cutting the roller core 18. Therefore, it can be manufactured at a lower cost than when a separate heat insulating member is used, and an increase in the cost of the fixing device can be suppressed.

Third Example FIG. 6 shows a third embodiment of a fixing device according to the present invention. In this case, the heat shield part 26 is formed of a heat-resistant plastic material (heat insulating material) having a low thermal conductivity, and the main pipe part 24 and the support pipe part 25 are connected via the heat shield part 26, whereby the main pipe part 24. Heat conduction to the support tube portion 26 can be prevented. The heat shield part 26 is made of a cylindrical body having the same outer diameter as that of the main pipe part 24, and includes thin connecting cylinder parts 35 that are fitted into the main pipe part 24 and the support pipe part 25 on both sides. Although not shown, the main pipe part 24, the support pipe part 25, and the connecting cylinder part 35 are fastened and fixed with screws. In addition, as a heat insulating material which forms the heat shielding part 26, materials other than plastics, such as a fiber reinforced composite plastic material which has heat resistance, ceramics, rubber | gum, are applicable.

1 is a cross-sectional view of a main part showing a first embodiment of a fixing device according to the present invention. 1 is an overall configuration diagram of an image forming apparatus to which a fixing device according to the present invention is applied. 1 is an overall configuration diagram of a fixing device. It is the sectional view on the AA line in FIG. It is sectional drawing of the heat roller which shows 2nd Example of the fixing device which concerns on this invention. It is sectional drawing of the heat roller which shows 3rd Example of the fixing device which concerns on this invention.

Explanation of symbols

4 fixing device 15 heat roller 16 press roller 17 heater 18 roller core 27 bearing 24 main pipe part 25 support pipe part 26 heat shield part 31 heat shield hole 33 heat shield groove N nip part P recording sheet

Claims (6)

A fixing device having a heat roller and a press roller constituting a nip portion for subjecting a recording sheet to heat and pressure, and fixing a toner image on the recording sheet,
The heat roller is composed of a hollow cylindrical roller core, and a heater is disposed inside the roller core,
The roller core is composed of a main pipe part that constitutes the nip part, and a support pipe part that is provided at both ends of the main pipe part and is rotatably supported by a bearing,
A fixing device, wherein a heat shielding portion for preventing heat conduction from the main tube portion to the support tube portion is provided in an adjacent portion between the main tube portion and the support tube portion.   The fixing device according to claim 1, wherein a cross-sectional area of the heat shield portion is made smaller than a cross-sectional area of the main pipe portion to prevent heat conduction from the main pipe portion to the support pipe portion.   The fixing device according to claim 2, wherein a plurality of heat shield holes are formed in a circumferential direction of the cylindrical wall of the heat shield part, and a cross-sectional area of the heat shield part is smaller than a cross-sectional area of the main pipe part.   4. The fixing device according to claim 2, wherein a heat shield groove is recessed in a circumferential direction of a cylindrical wall of the heat shield portion so that a cross-sectional area of the heat shield portion is smaller than a cross-sectional area of the main pipe portion.   The fixing device according to claim 4, wherein the heat shield groove is formed in a circular shape.   The fixing device according to claim 1, wherein the heat shield part is formed of a heat insulating material, and the main pipe part and the support pipe part are connected via the heat shield part.

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