JP2010282035A - Fixing pressure roller, fixing device with the same, and image forming apparatus having the fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing pressure roller that further shortens a "rise-up time' and prevents "a temperature decrease in passage of paper" and to provide a fixing device with the same, and an image forming apparatus with the fixing device. <P>SOLUTION: The fixing pressure roller 4 has, on the same axis, a first metal core 41 formed in a cylindrical shape and a second metal core 44 formed in a cylindrical shape on the first metal core 41. In the roller 4, a cylindrical clearance 43 is provided between the first and second metal cores 41 and 44. The clearance 43 is held at a pressure lower than the atmospheric pressure. The clearance 43 side surface of the first metal core 41 and the clearance 43 side surface of the second metal core 44 are preferably formed to have a mirror surface. In Fig.1, reference numerals 42, 45, and 46 are a spacer, an elastic layer, and a releasing layer respectively. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fixing pressure roller used as a pressure roller for fixing an unfixed toner image in an electrophotographic copying machine, printer, facsimile, or the like, a fixing device having the fixing roller, and an image formation having the fixing device. Relates to the device.

  2. Description of the Related Art Image forming apparatuses employing an electrophotographic system such as a copying machine, a printer, and a facsimile are provided with a fixing device that heats and fixes an unfixed toner image developed on a recording material such as transfer paper or OHP. In such a fixing device, a heat roll method has been widely used so far. In such a heat roll system, a pressure roller is brought into pressure contact with a heated fixing roller to form a nip portion, and a recording material is passed through the nip portion to fix an unfixed toner image.

  When an unfixed toner image is to be heat-fixed using the heat roll method, the heat capacity of the fixing roller and the pressure roller increases, so that the nip portion formed between the fixing roller and the pressure roller is a toner. There is a problem that the time required for the temperature rise to the fixing temperature at which the toner is melted, that is, the rise time (hereinafter referred to as “rise time” in this specification), becomes long. In addition, since it takes time to recover from the temperature drop during paper passing, the temperature drop during continuous paper feeding in the fixing roller (hereinafter referred to as “temperature drop during continuous paper feeding” in this specification). It will occur. Therefore, when a “temperature drop during continuous sheet feeding” occurs in the fixing roller, the number of sheets to be passed is reduced in order to ensure the fixing property, and the amount of heat taken by the recording sheet is given to the fixing roller. There is a problem that productivity is lowered because the temperature must be returned.

  Therefore, in order to solve the above problem, the heat capacity of the pressure roller is reduced to take measures against the “rise time” and the “temperature drop during sheet passing” (Patent Document 1 and Patent Document 2). See).

  That is, according to the technique described in Patent Document 1, an induction heating method with high heat generation efficiency is employed to heat and fix an unfixed toner image, and the shafts of the core bars of the fixing roller and the pressure roller are arranged on the axis. A hollow part in the direction is provided, and the hollow part is evacuated to try to reduce the heat capacity. However, in the pressure roller, since the core metal is required to have rigidity sufficient not to be deformed even at the atmospheric pressure when being evacuated in addition to the pressure at the nip portion, the core metal has not been considered so far. In order to reduce the heat capacity, the core metal has to be thickened, which is contradictory.

  In addition, according to the technique described in Patent Document 2, heat insulation is achieved by laminating a film with unevenness between a core metal and a surface layer in a pressure roller, and forming a space between the film with unevenness. It is as a layer. However, in the pressure roller, since the core metal and the convex portion of the film are in contact with each other even in the body portion of the pressure roller, heat conduction occurs. There was a problem of damage. Moreover, the air layer which comprises the space formed between the said uneven | corrugated film had the problem that heat conductivity was high.

  The present invention aims to solve this problem.

  That is, the present invention provides a fixing pressure roller, a fixing device having the fixing roller, and an image forming apparatus having the fixing device, in which the “rise time” is further shortened and the “temperature drop during sheet passing” is prevented. The purpose is that.

  In order to achieve the above object, the first aspect of the present invention provides a first metal core formed in a cylindrical shape and a second metal formed in a cylindrical shape provided on the first metal core. In the fixing pressure roller having the same core metal, a gap formed in a cylindrical shape is provided between the first core metal and the second core metal, and the gap section Is maintained at a pressure lower than atmospheric pressure.

  The invention described in claim 2 is the invention described in claim 1, wherein the surface of the first cored bar side and the surface of the second cored bar side are mirror surfaces. It is characterized by being formed.

  The invention described in claim 3 is the invention described in claim 1 or 2, wherein an elastic layer is provided on the second cored bar.

  The invention described in claim 4 is the invention described in claim 3, wherein a release layer is provided on the elastic layer.

  According to a fifth aspect of the present invention, there is provided a fixing device including: a fixing roller disposed on a conveyance path through which the transfer paper is conveyed; and a fixing pressure roller that contacts a surface of the fixing roller. A fixing device comprising the fixing pressure roller according to any one of claims 1 to 4 as the pressure roller for use.

  According to a sixth aspect of the invention, there is provided the fixing belt according to the fifth aspect, wherein the fixing belt is rotatably provided between the fixing roller and a heating roller provided in parallel to the fixing roller. It is characterized by that.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising the fixing device according to the fifth or sixth aspect.

  According to the invention described in claim 1, the first cored bar formed in a cylindrical shape, and the second cored bar formed in a cylindrical shape provided on the first cored bar, In the fixing pressure roller having the same axis, a gap formed in a cylindrical shape is provided between the first core bar and the second core bar, and the gap is a pressure lower than atmospheric pressure. Therefore, it is possible to reduce heat convection in the gap and prevent heat transfer due to air convection from the second metal core to the first metal core. By fixing the cored bar to the heated part, it is possible to reduce the heat capacity of the second cored bar. Therefore, the “rise time” is shortened and the “temperature drop during paper feeding” is prevented. A pressure roller can be provided. According to the first aspect of the present invention, the cored bar in the fixing pressure roller has a double structure of the first cored bar and the second cored bar. The rigidity of the core metal can be improved without being fleshed.

  According to the invention described in claim 2, since the surface of the first cored bar on the gap side and the surface of the second cored bar on the gap side are formed in a mirror surface, Heat transfer due to radiation (radiation) from the second cored bar to the first cored bar can be further prevented. For this reason, the “rise time” is further shortened and the “temperature drop during paper feeding” is reduced. It is possible to provide a fixing pressure roller that further prevents the above-described problem.

  According to the third aspect of the present invention, since the elastic layer is provided on the second metal core, there is no unevenness in the image, and therefore a high-quality image can be obtained.

  According to the fourth aspect of the present invention, since the release layer is provided on the elastic layer, the release property for the recording paper can be improved.

  According to the fifth and sixth aspects of the present invention, a fixing device having a fixing roller disposed on a conveyance path through which the transfer paper is conveyed, and a fixing pressure roller that abuts on the surface of the fixing roller. In addition, since the fixing pressure roller according to claim 1 is used as the fixing pressure roller, the “rise time” is shortened and the fixing pressure roller is used. It is possible to provide a fixing device that prevents the “temperature drop during paper passing” of the roller and also prevents heat radiation from the fixing pressure roller to the atmosphere, thereby improving the energy saving effect.

According to the seventh aspect of the present invention, since the fixing device according to the fifth or sixth aspect is provided, the “rise time” is shortened, and the “fixing roller” of the fixing pressure roller is shortened. It is possible to provide an image forming apparatus that prevents a “temperature drop” and prevents heat radiation from the fixing pressure roller to the atmosphere, thereby improving the energy saving effect.

1A and 1B are cross-sectional views of a fixing pressure roller showing an embodiment of the present invention, in which FIG. 1A is a vertical cross-sectional view and FIG. 1B is a cross-sectional view. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the fixing device which shows one embodiment of this invention, Comprising: (a) is provided with a surface heater, (b) is provided with a reflecting plate. FIG. 3 is an explanatory diagram of a fixing belt in a fixing device according to an embodiment of the present invention. 1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention. 6 is a graph showing the relationship between the time from turning on the power of the copying machine and the surface temperature before the fixing belt nip.

  Next, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 10 denotes a fixing pressure roller 4. The fixing pressure roller 4 coaxially connects a first metal core 41 formed in a cylindrical shape and a second metal core 44 formed in a cylindrical shape provided on the first metal core 41. Have. Further, a hollow portion 43 formed in a cylindrical shape is provided between the first core bar 41 and the second core bar 44, and the gap portion 43 is held at a pressure lower than atmospheric pressure. Yes. The gap 43 is provided with a spacer 42 formed in a ring shape at a portion corresponding to the vicinity of both ends of the second core metal 44 between the first core metal 41 and the second core metal 44. , Formed by welding them.

The first metal core 41 formed in the cylindrical shape is preferably made of stainless steel or carbon steel, and its thickness is preferably 0.3 to 5 mm. The second cored bar 44 formed in the cylindrical shape is preferably made of stainless steel or carbon steel, and the thickness thereof is preferably 0.3 to 1 mm. The second core metal 44 is attached to the first core metal 41 by welding via a spacer 42 made of ring-shaped stainless steel or carbon steel. An air vent hole is provided in the spacer 42 or the second cored bar 44 in order to evacuate the air from the gap portion 42 and make a vacuum, that is, a pressure lower than the atmospheric pressure. When it is provided on the first cored bar 41, it is necessary to provide it in the vicinity of the end that is a non-sheet passing part, so that there is a drawback that the entire length of the fixing pressure roller 4 is increased. The thickness of the gap 43 is preferably 3 to 20 mm. When the thickness of the gap 43 is reduced, the outer diameter of the first cored bar 41 can be increased and the wall thickness can be increased, so that the strength of the fixing pressure roller 4 can be improved. The “pressure lower than atmospheric pressure” (vacuum) is preferably a pressure of 10 ⁻² Pa or less. The air vent hole is sealed (ie, closed) with a stopper made of an elastic material having high heat resistance such as silicone rubber or fluororubber. In addition, the air vent hole is sealed by releasing air from the opening portion and simultaneously welding the opening portion with a low melting point material than a metal such as glass. A material having a lower melting point than a metal such as glass can be sealed more firmly than a stopper using the elastic material.

  In this way, the first cored bar 41 formed in a cylindrical shape and the second cored bar 44 formed in a cylindrical shape provided on the first cored bar 41 are coaxial. In the pressure roller 4, a gap portion 43 formed in a cylindrical shape is provided between the first core bar 41 and the second core bar 44, and the pressure of the gap portion 43 is lower than atmospheric pressure. , It is possible to reduce the convection of air in the gap 43 and prevent heat transfer due to the convection of air from the second cored bar 44 to the first cored bar 41. The second cored bar 44 can be limited to a heating part, and the heat capacity of the second cored bar 44 can be reduced. Therefore, the “rise time” can be shortened and the “temperature during paper feeding” can be reduced. It is possible to provide the fixing pressure roller 4 in which the “decrease” is prevented. According to the first aspect of the present invention, the cored bar in the fixing pressure roller 4 has a double structure of the first cored bar 41 and the second cored bar 44. The rigidity of the core bar can be improved without increasing the thickness of the gold.

  In the present invention, the surface of the first cored bar on the side of the gap 43 and the surface of the second cored bar 44 on the side of the gap 43 are preferably formed in a mirror surface. The surface of the first cored bar formed on the mirror surface on the side of the gap 43 and the surface of the second cored bar 44 on the side of the gap 43 are glossy like nickel to prevent oxidation. Glossiness can be improved by applying metal plating having Similarly, the surface of the spacer 42 provided to form the gap portion 43 can be similarly plated with a metal such as nickel to improve the glossiness and improve the heat insulation.

  Thus, when the surface of the first cored bar 41 on the side of the gap 43 and the surface of the second cored bar 44 on the side of the gap 43 are formed in a mirror surface, the second cored bar Heat transfer due to radiation (radiation) from 44 to the first core bar 41 side can be further prevented. For this reason, the “rise time” is further shortened, and “temperature drop during paper feeding” is further reduced. It is possible to provide the fixing pressure roller 4 that is prevented.

  In the present invention, an elastic layer 45 is provided on the second cored bar 44. As described above, when the elastic layer 45 is provided on the second cored bar 44, image unevenness is eliminated, and a high-quality image can be obtained. In the present invention, a release layer 46 is provided on the elastic layer 45. As described above, when the release layer 46 is provided on the elastic layer 45, the release property with respect to the recording paper 7 can be improved.

  Next, the elastic layer 45 and the release layer 46 will be described in detail.

  As shown in FIGS. 1 and 2, in the fixing pressure roller 4, an elastic layer 45 is formed on the second core metal 44, and a release layer 46 is formed on the elastic layer 45. When the fixing pressure roller 4 is mounted on the fixing device 40, the fixing pressure roller 4 presses the fixing roller 2 through the fixing belt 3 to form a fixing nip portion N. Will be. The outer diameter of the fixing pressure roller 4 is preferably 30 to 40 mm, and the thickness and hardness of the elastic layer 45 are preferably 0.3 to 5 mm and 20 to 50 ° (Asker hardness). Has been. Moreover, the thickness of the release layer 46 is preferably 10 to 100 μm. In the present invention, the fixing pressure roller 4 bites into the fixing roller 2 (and the fixing belt 3) by making the fixing pressure roller 4 harder than the fixing roller 2. This biting causes the recording material 8 to have a curvature that cannot be along the surface of the fixing belt 3 at the exit of the nip portion. For this reason, the releasability of the recording material 7 from the surface of the fixing belt 3 can be improved. .

  In FIG. 2, reference numeral 40 denotes a fixing device. The fixing device 40 includes a fixing roller 2 disposed on a conveyance path through which the recording paper 7 is conveyed, and a fixing pressure roller 4 that contacts the surface of the fixing roller 2. The fixing device 40 includes the fixing pressure roller 4 according to claim 1 as the fixing pressure roller 4. As described above, in the fixing device 40 having the fixing roller 2 disposed on the conveyance path along which the transfer paper 7 is conveyed and the fixing pressure roller 4 in contact with the surface of the fixing roller 2, When the pressure roller 40 for fixing described in any one of claims 1 to 4 is used as the pressure roller 40, the “rise time” is shortened and the pressure roller 4 for fixing is fixed. It is possible to provide the fixing device 40 that prevents the “temperature drop at the time of passing the paper” and prevents the heat from the fixing pressure roller 4 to the atmosphere and improves the energy saving effect.

  Next, the fixing device 40 will be described in detail.

  As shown in FIG. 2, the fixing device 40 of the present invention includes a heating roller 1 having a halogen heater 5 therein, a fixing roller 2 disposed in parallel with the heating roller 1, and the heating roller 1. And an endless belt-like fixing belt 3 that is stretched between the fixing roller 2 and rotated in the direction of arrow A by the rotation of any of these rollers, and is pressed against the fixing roller 2 via the fixing belt 3 and is fixed. The fixing pressure roller 4 rotates in the forward direction with respect to the belt 3. As shown in FIG. 2 (a), the fixing device 40 is provided with a surface heater 6a for heating the outer peripheral surface of the fixing pressure roller 4. As shown in FIG. 2 (b). As described above, a reflecting plate 6b that heats the outer peripheral surface of the fixing pressure roller 4 and has a halogen heater on the inner side may be provided.

  The heating roller 1 is provided to transfer heat from the halogen heater 5 inside to the abutting fixing belt, and the inner surface of the heating roller 1 is coated with black so that the heat from the halogen heater can be transferred. The light can be efficiently collected and the heat generation efficiency of the heating roller 1 can be improved. The heating roller 1 is made of a metal such as aluminum or carbon steel. Since the aluminum is a metal having a high thermal conductivity, it can be said that the heating roller 1 is suitable for the constituent material of the heating roller. Further, it is preferable that the sliding surface of the heating roller 1 with the fixing belt substrate 31 is covered with a resin having a small friction coefficient such as a fluororesin to reduce wear.

  The fixing roller 2 includes, for example, a cored bar 21 made of a metal such as stainless steel or carbon steel, and an elastic member 22 covered with the cored bar 21 in a solid or foamed heat-resistant silicone rubber or the like. It consists of. Then, a contact portion (fixing nip portion N) having a predetermined width is formed between the fixing pressure roller 4 and the fixing roller 2 by the pressing force from the fixing pressure roller 4. The outer diameter of the fixing roller 2 is preferably 30 to 40 mm, the thickness of the elastic member is preferably 3 to 10 mm, and the hardness of the elastic member is preferably 10 to 50 mm. ° (JIS-A).

  As shown in FIG. 3, the fixing belt 3 includes a base material 31, an elastic layer 32 provided on the base material 31, and a release layer 33 provided on the elastic layer 32. Become. The properties required for the base material 31 include mechanical strength and flexibility when the fixing belt 3 is pasted, and heat resistance that can withstand use at a fixing temperature. In order to inductively heat the heating roller 1, the base material 31 is preferably made of an insulating heat-resistant resin material, a resin such as polyimide, polyimide amide, PEEK, PES, PPS, or fluorine resin. The thickness of the base material 31 is preferably 30 to 200 μm. Thus, when the thickness of the base material 31 is 30 to 200 μm, it is possible to maintain a sufficient heat capacity and a sufficient strength.

  The elastic layer 32 in the fixing belt 3 is formed for the purpose of giving flexibility to the belt surface in order to obtain a uniform image without uneven glossiness. The rubber hardness is preferably 5 to 50 ° (JIS). -A hardness), and the thickness is preferably 50 to 500 μm. The elastic layer 32 is made of heat-resistant rubber such as silicone rubber or fluorosilicone rubber from the viewpoint of heat resistance at the fixing temperature. The release layer 33 is preferably made of tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (EEP). ) And the like, a mixture of these resins, or a heat-resistant resin in which these fluorine resins are dispersed.

  When the release layer 33 covers the elastic layer 32, the toner release property is improved without using silicone oil or the like, and the paper powder can be prevented from sticking (oilless). However, since these resins having releasability generally do not exhibit elasticity like rubber materials, the surface of the fixing belt 3 is formed when the release layer 33 is formed thick on the elastic layer 32. This will impair the flexibility and cause uneven glossiness. In order to make the releasability and flexibility of the fixing belt 3 compatible, the thickness of the release layer 33 is preferably 5 to 50 μm, and more preferably 10 to 30 μm. In the fixing belt 3, a primer layer may be provided between the layers as desired, and a layer for improving durability during sliding may be provided on the inner surface of the base material 31.

  As shown in FIG. 4, the image forming apparatus of the present invention has the fixing device 40 according to claim 5 or 6. Thus, when the fixing device 40 according to claim 5 or 6 is provided, the “rise time” is shortened and the fixing pressure roller (see 4 in FIG. 1) “when paper is passed. In addition, an image forming apparatus can be provided that prevents a decrease in temperature and prevents heat radiation from the fixing pressure roller to the atmosphere, thereby improving the energy saving effect.

  Next, the fixing device 40 will be described in detail.

  As shown in FIG. 4, the image forming apparatus according to the present invention is a photosensitive drum 1Y, 1M, 1C, 1Bk (image carrier) corresponding to four color toner images of yellow, magenta, cyan, and black, respectively. In order to form on the surface, four sets of image forming units 10Y, 10M, 10C, and 10Bk (image forming means) of an electrophotographic system are provided. Below these image forming units 10Y, 10M, 10C, and 10Bk, a conveying belt 20 for conveying a sheet (recording material) through the image forming units is stretched. The photosensitive drums 1Y, 1M, 1C, and 1Bk of the image forming units 10Y, 10M, 10C, and 10Bk are respectively placed in contact with the conveyance belt 20 so that paper (recording material) is statically placed on the surface of the conveyance belt 20. It is adsorbed electrically. The four sets of image forming units 10Y, 10M, 10C, and 10Bk have substantially the same structure. Therefore, here, the yellow image forming unit 10Y disposed on the most upstream side in the sheet conveying direction will be described as a representative, and the other color image forming units 10M, 10C, and 10Bk are denoted by the same reference numerals. A detailed description will be omitted.

  The image forming unit 10Y has a photosensitive drum 1Y that is in rolling contact with the conveying belt 20 at a substantially central position. Around the photosensitive drum 1Y, a charging device 2Y for charging the surface of the photosensitive drum 1Y to a predetermined potential, the charged drum surface is exposed based on the color-separated image signal, and the drum surface is exposed. An exposure device 3Y that forms an electrostatic latent image, a developing device 4Y that supplies yellow toner to the electrostatic latent image formed on the drum surface and develops it, and a sheet on which the developed toner image is conveyed via the conveyance belt 20 A transfer roller 5Y (transfer device) for transferring the toner, a cleaner 6Y for removing residual toner remaining on the drum surface without being transferred, and a charge eliminating lamp for removing electric charge remaining on the drum surface (not shown) are provided on the photosensitive drum 1Y. Are arranged in order along the rotation direction.

  A paper feed mechanism 30 for feeding paper onto the transport belt 20 is disposed on the lower right side of the transport belt 20 in the drawing. The fixing device 40 according to the above-described embodiment of the present invention is disposed on the left side of the conveyance belt 20 in the drawing (excitation coils and the like are omitted in this drawing). The paper transported by the transport belt 20 is transported to a transport path that continuously extends from the transport belt 20 through the fixing device 40 and then passes through the fixing device 40. The fixing device 40 heats and presses the conveyed paper, that is, the paper on which the toner image of each color is transferred on the surface, thereby melting the toner image of each color. Then, the melted toner images of the respective colors are permeated into the paper and fixed. Next, the paper is discharged to the downstream side of the conveyance path of the fixing device 40 via a paper discharge roller.

Example 1
A first cylinder having a diameter of 30 mm, a length of 370 mm and a thickness of 0.8 mm made of stainless steel SUS304, and a second cylinder having a diameter of 40 mm, a length of 320 mm and a thickness of 0.8 mm made of stainless steel SUS304; A ring-shaped spacer made of SUS304 having an inner diameter of 22 mm and an outer diameter of 39 mm was prepared. The spacer and both cylinders are easily aligned in the axial direction by inlay processing applied to the end of the cylinder. Then, an extra space is formed between the first cylinder and the second cylinder by extrapolating the second cylinder to the first cylinder and inserting the spacer from both ends of the first cylinder. At the same time, the second cylindrical body was temporarily assembled with respect to the first cylindrical body. Next, each of the spacers is welded and fixed to the first cylindrical body and the second cylindrical body by TIG welding, and then air is extracted from an air vent hole provided in advance in one of the spacers. After setting the pressure in the gap to 10 ⁻³ Pa, the air hole was sealed with silicone rubber to form a cored bar. Next, a heat-resistant metal primer is applied to the surface of the second metal core in the core metal thus formed to form a coating layer, and this coating layer is baked at 150 ° C. for 10 minutes to form a primer layer. After forming a silicone rubber [Toray Dow Corning Silicone Co., Ltd., DY35-363 (thermal conductivity: 0.8 × 10 ⁻³ cal / cm · sec · ° C.)] on the surface of the primer layer The coating layer containing the coating is applied to form a coating layer, and the silicone rubber constituting the coating layer is vulcanized (cured) to form an elastic layer, and the elastic layer is 0.2 mm thick with a cylindrical grinder Grinded. And the silane coupling agent (Toray Dow Corning Silicone make, DY39-067) was spray-coated on this elastic layer, and it was made to dry and the coating film by a silane coupling agent was formed. Next, 1 part by weight of anatase-type titanium oxide is added as a photocatalytic substance to 100 parts by weight of the fluororesin powder coating, and this is powder-coated on the coating film using the silane coupling agent to form a 20 μm-thick powder coating layer. After the formation, this powder coating layer was subjected to heat treatment, and the fluororesin powder was baked, melted, and cooled and cured to obtain a roller having a diameter of 40 mm. Next, a low-pressure mercury lamp that emits light of 184.9 nm (manufactured by Sen Special Light Source Co., Ltd., high-purity synthetic quartz low-pressure mercury lamp EUV200NS-7 (output 200 W)) is used for the release layer of this roller. Was applied to obtain a pressure roller for fixing.

(Example 2)
Pressing for fixing in the same manner as in Example 1 except that the surface on the gap side of the first cored bar and the surface on the gap side of the second cored bar are previously mirror-finished. Got Laura.

(Example 3)
The surface of the first core bar on the gap side and the surface of the second core bar on the gap side are preliminarily mirror-finished, and the thickness of the first core bar is 1.5 mm. A fixing pressure roller was obtained in the same manner as in Example 1 except that.

Example 4
The surface of the first cored bar side and the surface of the second cored bar side are mirror-finished in advance, and the thickness of the second cored bar is 1 mm. In the same manner as in Example 1, a fixing pressure roller was obtained.

(Comparative Example 1)
A pressure roller for fixing was obtained in the same manner as in Example 1 except that a cored bar made of carbon steel having a diameter of 40 mm, a length of 320 mm, and a thickness of 1 mm was used.

  As described above, the fixing pressure roller obtained in Examples 1 and 2 and Comparative Example 1 is incorporated in the fixing device, and the fixing device is mounted on the copying machine and the power is turned on, and then the surface of the fixing belt melts the toner. The time (second) until the fixing temperature was reached, that is, the “rise time” (second) was measured. Then, following the measurement of the “rise time”, the surface temperature drop (° C.) of the fixing belt when continuous paper feeding was performed, that is, “temperature drop during continuous paper feeding” (° C.) was measured. Next, a specific measuring method thereof will be described with reference to FIG.

  In FIG. 5, the vertical axis represents the surface temperature before the nip of the fixing belt, and the horizontal axis represents the time from the power-on of the copying machine. First, when the copier power is turned on, the fixing device starts to heat up in the rising mode, and then the temperature before the nip reaches 200 ° C. When the temperature before the nip reaches 200 ° C., the rising ends. judge. Next, after entering the paper passing mode, the paper feeding is started. Although the temperature before the nip decreases with the start of the sheet passing, the temperature before the nip stops and the temperature before the nip returns as each fixing member is sufficiently heated. In measuring the “rise time” (seconds) and “temperature drop during continuous paper feeding” (° C.) in this example and the comparative example, the “rise time” is the time until the temperature before the nip reaches 200 ° C. Time is defined, and “temperature drop during continuous sheet feeding” is defined as the lower limit temperature of the temperature before nip when 50 sheets are continuously fed.

  The measurement results are shown in Table 1 below.

  From Table 1, it can be seen that when the pressure roller for fixing obtained in Examples 1 to 4 is used, “rise time” and “temperature drop during continuous paper feeding” can be improved. The fixing pressure roller obtained in Example 4 has the same thickness as that of the fixing pressure roller obtained in the comparative example. However, the “rise time” and “temperature drop during continuous paper feeding” are shown. It was confirmed that the heat insulating effect of the present invention was high. Further, from the comparison between the fixing pressure roller obtained in Example 2 and the fixing pressure roller obtained in Example 3, the influence of the thickness of the first metal core is not recognized, so that the present invention It can be seen that the heat transfer from the second metal core to the first metal core is well blocked by the heat insulation effect of the second metal core, and the contribution to the temperature characteristics before the nip It was confirmed that the influence of the gold thickness was large.

DESCRIPTION OF SYMBOLS 1 Heating roller 2 Fixing roller 3 Fixing belt 4 Fixing pressure roller 5 Halogen heater 6a Surface heater 6b Reflecting plate 7 Recording paper N Nip part T Toner image 40 Fixing device 41 First core metal 42 Spacer 43 Gap part 44 Second Core metal 45 Elastic layer 46 Release layer

JP 10-740007 A JP 2005-157303 A

Claims (7)

A pressure roller for fixing having a first cored bar formed in a cylindrical shape and a second cored bar formed in a cylindrical shape provided on the first cored bar,
A hollow portion formed in a cylindrical shape is provided between the first core metal and the second core metal, and
The pressure roller for fixing according to claim 1, wherein the gap is held at a pressure lower than atmospheric pressure.   The pressure for fixing according to claim 1, wherein a surface of the first cored bar on the gap side and a surface of the second cored bar on the gap side are formed on a mirror surface. roller.   The pressure roller for fixing according to claim 1, wherein an elastic layer is provided on the second metal core.   The pressure roller for fixing according to claim 3, wherein a release layer is provided on the elastic layer.   A fixing device having a fixing roller disposed on a conveyance path through which transfer paper is conveyed and a fixing pressure roller in contact with a surface of the fixing roller, wherein the fixing pressure roller is used as the fixing pressure roller. 5. A fixing device comprising the pressure roller for fixing described in any one of 4 above.   The fixing device according to claim 5, further comprising a fixing belt rotatably provided between the fixing roller and a heating roller provided in parallel to the fixing roller.   An image forming apparatus comprising the fixing device according to claim 5.

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