JP2004252348A - Image fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent wrinkles when a fixing belt enters a 2nd heating body. <P>SOLUTION: The fixing device is provided with the fixing belt 8 for carrying a recording medium, a heating roller 2 which is positioned in the engagement start position S of the recording medium with reference to the fixing belt 8 and around which the fixing belt 8 is wound, and the heating body 3 positioned inside the fixing belt 8 and for heating the fixing belt 8 at a position opposed to the passing path of the recording medium which is carried by the fixing belt 8, and a distance X between the heating roller 2 and the heating body 3 is set to be ≤20mm in a non-contact state. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a belt fixing device having an endless belt provided in an image forming apparatus such as a copying machine, a facsimile, a printer, and the like, and to such an image forming apparatus having such a fixing device.
[0002]
[Prior art]
2. Description of the Related Art There has been an increasing demand for energy saving from the viewpoint of environmental protection, and energy saving has also been required for image forming apparatuses such as copying machines, facsimile machines, and printers. An image forming apparatus generally has a fixing device for fixing a toner image on a sheet-shaped recording medium on which a toner image as a fixed image is formed, but since the power consumption in the fixing device is high, In order to achieve energy saving, the fixing temperature has been lowered.
[0003]
As a method of lowering the fixing temperature, there is a method of lowering the softening point and the melting point of the toner. However, even when the same toner is used, the fixing temperature changes depending on the configuration of the fixing device, and the energy consumption also changes. Therefore, in order to achieve energy saving, it is necessary to provide a configuration of a fixing device having a low fixing temperature and low energy consumption.
[0004]
As described in Patent Literature 1 and Patent Literature 2, the fixing device includes a heating roller internally having a heater as a heat source as a heating unit and rotationally driven by a driving unit (not shown). A pressure roller pressed against the heating roller and rotated by the heating roller. The recording medium passes through a nip formed by the heating roller and the pressure roller by rotation of the heating roller and the pressure roller. There are known fixing devices of a roller facing type, a heat roller pair type, and the like that fix a toner image formed of unfixed toner by heating and conveying while pressing.
[0005]
Generally, the heat fixing is performed by heating and pressing the toner transferred on the recording medium, and the toner in a molten state thereby being adhered to the recording medium. Here, considering the roller-facing type fixing device, when heating, heat is transferred from the heating roller to the toner and the recording medium. The amount of heat flowing from the heating roller to the toner and the recording medium depends on the temperature of the heating roller. The higher the temperature, that is, the higher the set temperature of the heating roller with respect to the environmental temperature and the larger the thermal gradient, the faster and more heat can be moved. However, if the set temperature is high and the amount of heat supplied to the recording medium is large, energy consumption inevitably increases, which is not preferable.
[0006]
Therefore, in the roller-facing type fixing device, the hardness of the rubber and sponge of the pressure roller is reduced to secure the nip width with the heating roller and thereby increase the heating time, but the nip width between the heating roller and the pressure roller is increased. Since there is a limit in the relationship of the curvature of these rollers, the heating time is greatly limited, and it is difficult to provide a sufficient amount of heat. It is conceivable to secure the nip width by increasing the diameter of the roller. However, an excessively large heating roller has an excessively large heat capacity, and the heat dissipation area also increases the energy consumption.
[0007]
Therefore, in a roller-facing fixing device, the temperature of the toner is raised in a short time corresponding to a narrow nip width. I had to raise it and use it. However, in this case, since it is necessary to raise the temperature to a temperature at which the toner can be melted and fixed, the temperature of the heating roller is extremely high, and the temperature of the heating roller is raised to a surface temperature of the recording medium which does not need to be heated. Because of the large thermal gradient, the temperature inside the paper was increased more than necessary.
[0008]
As described above, in the roller-facing type fixing device in which the nip width can be reduced to a necessary minimum, the set temperature of the heating roller becomes higher than necessary, and excessive heat radiation occurs due to a large thermal gradient of the roller with respect to the environment. However, because the set temperature of the heating roller is higher than necessary, there is more heat transfer to the recording medium than necessary, and the consumption of extra energy is large. there were.
[0009]
As a means for solving the problem of such a roller-facing type fixing device, a method of heating a recording medium for a long time by passing a heating body through a fixing belt can be considered. This is referred to as a belt-type fixing device, a belt fixing device, or the like. As described in [Patent Document 3], [Patent Document 4], [Patent Document 5], and the like, a fixing belt includes a driving roller and a driven roller. , A heating element is disposed inside the fixing belt to heat the fixing belt, the fixing belt and the driven roller are driven to rotate by the driving roller, and are disposed to face the driven roller via the fixing belt. By following rotation of the pressure roller, the recording paper is passed through a nip formed by the fixing belt and the pressure roller, and is heated and pressed at the same time as the roller-facing type fixing device and conveyed. Thus, a configuration for fixing a toner image is known.
[0010]
The belt-type fixing device heats the recording medium through the fixing belt in close contact with the toner for as long as necessary to reach a predetermined temperature, so that the fixing is performed at a lower temperature than the fixing device of the roller facing type. It is possible to do. Since the set temperature of the heating element is lower than that of the roller facing type fixing device, the thermal gradient is small, and it takes time for the toner on the recording medium to reach a predetermined temperature. Unlike the apparatus, there is no need to raise the set temperature more than necessary than the temperature at which the toner can be fixed, and energy saving can be achieved.
[0011]
That is, although the heating temperature is low, it takes time for the toner to reach the predetermined temperature, but since the toner continues to be kept warm while passing through the heating unit, the toner on the recording medium is fixed to the roller facing type fixing device at the end of heating. It is possible to reach the same temperature as in the case of fixing in a high temperature and in a short time as described above, thereby enabling fixing, and furthermore, the set temperature of the heating element is low, and the heat gradient with respect to the environment of the heating element is low. Is small, the amount of heat radiation is small, and the set temperature is low, so the thermal gradient with respect to the recording medium is small.As a result, the total amount of heat received by the recording medium is also small, preventing excessive heating of the recording medium and reducing energy consumption. it can.
[0012]
However, although it is true that energy can be saved by fixing using this method, heating by simply contacting the pre-heated fixing belt slows down the temperature rise of the toner on the recording medium and causes However, there is a problem that the temperature of the toner in the area where the toner does not rise sufficiently does not sufficiently increase the adhesive strength to the recording medium, and the image is displaced by the stress applied to the recording medium during the paper passing process.
[0013]
Further, the heating of the fixing belt is performed only while the fixing belt is in close contact with the heating element, and the temperature of the fixing belt is reduced during one rotation, so that the fixing belt is configured to have a uniform temperature distribution. A problem that the expected heating element is cooled by the fixing belt at the leading edge where the cooled fixing belt re-enters, causing a temperature gradient from the leading edge to the trailing edge of the heating element, preventing the uniformity of the surface temperature of the heating element. However, although the temperature is not as high as that of the roller-facing type fixing device, the temperature setting must be made slightly higher, and there is a problem that energy saving is hindered.
[0014]
Since this problem occurs when the fixing belt cooled by heating the recording medium enters the heating element, the cooled fixing belt may be preheated before entering the heating element. That is, as described in [Patent Document 5], when the heating body is divided into two stages, only the fixing belt is heated by the first heating body, and the heating is performed by the second heating body in contact with the recording medium. According to the configuration in which the surface of the fixing belt is heated to a predetermined temperature, the fixing belt temperature required for fixing can be secured, and the fixing performance can be stabilized while saving energy without excessive heating. .
[0015]
Here, when the first heating element is a planar fixed heating element, when the cooled fixing belt enters the first heating element, the belt temperature rises and thermal expansion begins. The friction between the surface of the fixed planar heating element, which is the first heating element, and the fixing belt hinders the expansion of the fixing belt, and there is a problem that wrinkles easily enter the fixing belt. As described above, a technique has been proposed in which, by rotating the first heating element in a roller shape, a force that tends to spread in the width direction due to expansion of the fixing belt is released, and wrinkles are prevented from entering. .
[0016]
[Patent Document 1]
JP 2001-51530 A
[Patent Document 2]
JP 2001-56616 A
[Patent Document 3]
JP-A-9-80969
[Patent Document 4]
JP-A-11-133800
[Patent Document 5]
JP 2001-166618 A
[0017]
[Problems to be solved by the invention]
However, if the first heating element is formed in a roller shape, wrinkling of the fixing belt on the first heating element can be certainly prevented, but the second heating element is a fixed heating element. It was found that the fixing belt stochastically wrinkled between the first heating element and the fixed second heating element, and the fixing performance was reduced.
[0018]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device that prevents wrinkles generated when a fixing belt enters a second heating element, and an image forming apparatus having the fixing device.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided an endless fixing belt for conveying a recording medium on which a toner is fixed, and the fixing belt positioned at a position where the recording medium starts engaging with the fixing belt. A heating roller wound around the fixing belt, a guide roller positioned at a position where the engagement of the recording medium with the fixing belt ends, and a guide roller wound around the fixing belt, and recording inside the fixing belt and being conveyed by the identification attaching belt. In a fixing device having a heating body for heating the identification attachment belt at a position opposed to a medium passage path, and a pressing member occupying the engagement start position and urged toward the fixing belt, The distance between the heating roller and the heating element is not more than 20 mm and is in a non-contact range.
[0020]
According to a second aspect of the present invention, in the fixing device of the first aspect, a distance between the heating element and the guide roller is set to 20 mm or less and a non-contact range.
[0021]
According to a third aspect of the present invention, in the fixing device according to the first or second aspect, a length of the fixing belt wound around the heating roller is 0.2 to 200 mm.
[0022]
According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the heating is performed after the identification attaching belt is engaged with the heating roller while the fixing belt makes one rotation. The time required for the engagement with the body to be released is 50 msec or more.
[0023]
According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, pre-fixing is performed at a position where the pressing member and the heating roller face each other, and the heating of the fixing belt is performed. The main fixing is performed at a portion engaged with the body.
[0024]
According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the heating element is an immovable member.
[0025]
According to a seventh aspect of the present invention, in the fixing device according to any one of the first to sixth aspects, the heating element rotates in the same direction as the rotation direction of the fixing belt at a position facing the fixing belt. It is an endless heating belt.
[0026]
The invention according to claim 8 is the fixing device according to any one of claims 1 to 7, wherein the fixing belt is a metal belt or a resin belt.
[0027]
According to a ninth aspect of the present invention, in the fixing device according to any one of the first to eighth aspects, the thickness of the fixing belt is 1 to 300 μm.
[0028]
According to a tenth aspect of the present invention, in the fixing device according to any one of the first to ninth aspects, the fixing device is wound around the pressing member and extends at least from the engagement start position to the engagement end position. And an endless transport belt for transporting the recording medium.
[0029]
According to an eleventh aspect of the present invention, in the fixing device according to the tenth aspect, the transport belt is a metal belt or a resin belt.
[0030]
According to a twelfth aspect of the invention, in the fixing device according to any one of the first to eighth aspects, the thickness of the transport belt is 1 to 300 μm.
[0031]
According to a thirteenth aspect of the present invention, there is provided an image forming apparatus having the fixing device according to any one of the first to twelfth aspects.
[0032]
【Example】
FIG. 1 schematically shows an image forming apparatus to which the present invention is applied. The image forming apparatus may be any known one such as a copying machine, a facsimile, and a printer, but the image forming apparatus in this embodiment is a printer. The image forming apparatus of the present embodiment forms a color image.
[0033]
The image forming apparatus 100 includes, in addition to plain paper generally used for copying and the like, 90K paper such as an OHP sheet, a card, and a postcard, and a basis weight of about 100 g / m. ² Any of so-called special sheets having a larger heat capacity than plain paper, such as considerable thick paper and envelopes, can be used for forming an image as a sheet-shaped recording medium. The size of the recording medium is generally a size conforming to a general standard such as A4 size or A3 size, but may be a size outside the standard.
[0034]
The image forming apparatus 100 is a tandem-type color image forming apparatus, and is a cylindrical rotating body that is driven to rotate in the direction of arrow A, and uses a photoconductor using an organic semiconductor (OPC) as an image carrier. A drum (hereinafter, referred to as “photoconductor”) 101, a charging device (not shown) for charging the photoconductor 101, and an exposure (not shown) for emitting a laser beam for forming a latent image on the charged photoconductor 101 and performing optical scanning. It has an apparatus and a developing device (not shown) for developing a latent image on the photoconductor 101 after exposure.
[0035]
The image forming apparatus 100 further includes a transfer roller 111 that is disposed to face the photoconductor 101 and that transfers a toner image on the photoconductor 101 obtained by development by the developing device to a recording sheet as a recording medium. A transfer device 105, a cleaning device (not shown) that cleans the surface of the photoreceptor 101 after the transfer, a charge removal device (not shown) that removes the charge of the photoreceptor 101 before charging by the charging device, And a paper tray 102.
[0036]
The image forming apparatus 100 also moves the recording paper stacked on the paper feed tray 102 toward a transfer area 107, which is a region where the photoconductor 101 and the transfer device 105 face each other and where the photoconductor 101 and the transfer roller 111 abut. A registration roller 109 that conveys the toner image at a predetermined timing, a fixing device 108 as a fixing unit that fixes the toner image on the recording paper onto which the toner image on the photoconductor 101 has been transferred by the transfer device 105, and an image forming apparatus 100 And a discharge tray 103 which is located outside the main body and on which the fixed recording paper is stacked.
[0037]
An image forming system composed of the photoconductor 101, the charging device, the exposure device, the developing device, the transfer device 105, the cleaning device, and the charge removing device is, for example, for each color of cyan, magenta, yellow, and black, respectively. Although shown along the recording paper transport path 110 shown in FIG. 1, only one of them is shown as a representative.
[0038]
The photoreceptor 101 and the transfer roller 111 are respectively driven to rotate in the A and B directions by a motor as a drive source (not shown). The direction B is a direction in which the photosensitive drum 101 moves in the same direction as the direction A at a position facing the photosensitive member 101. The toner image on the photoconductor 101 is transferred and carried on the recording paper in a transfer area 107 formed by the photoconductor 101 and the transfer roller 111 rotating in this manner.
[0039]
As illustrated in FIG. 2, the fixing device 108 includes an endless fixing belt 8 that is an endless belt for conveying a recording sheet on which toner constituting a toner image is fixed, and starts engagement of the recording sheet with the fixing belt 8. A heating roller 2 which is a first heating element which is located at a position S and around which the fixing belt 8 is wound, and a guide roller 9 which is located at a position E where the recording paper is engaged with the fixing belt 8 and at which the fixing belt 8 is wound. have.
[0040]
The fixing device 108 also includes a heating element 3 serving as a second heating element for heating the fixing belt 8 at a position inside the fixing belt 8 and opposed to a passage of the recording sheet conveyed by the fixing belt 8. A planar heating element 4 integrated with the heating element 3 from the opposite side of the fixing belt 8 to heat the heating element 3, a tension roller 5 that contacts the fixing belt 8 and applies a predetermined tension to the fixing belt 8, The pressure roller 6 occupies the engagement start position S and is urged toward the fixing belt 8 and the heating roller 2 as shown by an arrow C in the drawing. And a spring 7 as urging means for urging toward the heating roller 2.
[0041]
The guide roller 9 is a driving roller and is rotationally driven in the direction of arrow D by a motor as driving means (not shown), and the fixing belt 8 and the heating roller 2 are driven to rotate in directions of arrows F and G, respectively. A heater 10 as heating means is disposed inside the heating roller 2 to heat the heating roller 2. The heating element 3 is an immovable member and is fixed at a position where it is in sliding contact with the back surface of the fixing belt 8. The pressure roller 6 is disposed to face the fixing roller 9 with the fixing belt 8 interposed therebetween. The pressure roller 6 comes into contact with the fixing belt 8 at a position facing the fixing roller 9 including the engagement start position S. The nip portion 12 is formed. Note that the engagement start position S substantially coincides with the position where the fixing belt 8 is separated from the heating roller 2.
[0042]
The fixing device 108 causes the nip portion 12 to pass the recording paper in the recording paper conveyance direction indicated by the arrow H by the rotation of the fixing belt 8 and the pressure roller 6 driven and rotated by the fixing belt 8, and heat and pressurize the recording paper at the same time. This is a so-called belt type fixing device in which pre-fixing is performed, main fixing is performed in a portion where the fixing belt 8 is engaged with the heating element 3 in the process of being conveyed by the fixing belt 8, and toner is fixed on recording paper. In the pre-fixing, the toner is softened by heating and is crushed on the recording paper by the pressure between the fixing belt 8 and the pressure roller 6, and in the main fixing, the toner is further heated and melted and adhered on the recording paper. .
[0043]
If the first heating element is formed into a roller shape like the heating roller 2, wrinkling of the fixing belt 8 on the first heating element can be prevented, but as described above, the second heating element Since the heating element 3 is fixed, it has been found that, in the related art, the fixing belt 8 is wrinkled stochastically between the heating roller 2 and the heating element 3 and the fixing performance is reduced. The inventors of the present invention have conducted intensive studies, and found that the cause of such wrinkles is that when the fixing belt 8 enters the fixed heating element 3 serving as the second heating element, the fixing belt 8 moves stably due to stochastic fluctuation of the fixing belt 8. It has been found that the timing at which the fixing belt 8 comes into contact with the fixed heating element 3 changes depending on the position corresponding to the position, and that the previously touched portion is quickly braked.
[0044]
The inventors have further studied and found that if the distance between the heating roller 2 and the heating element 3 is set to 20 mm or less, stochastic blurring of the fixing belt 8 is suppressed and wrinkles are prevented. The distance between the heating roller 2 and the heating element 3 is the distance indicated by the symbol X in FIG. 1, that is, the downstream side of the point S in the rotation direction F of the fixing belt 8 and the start of the engagement between the fixing belt 8 and the heating element 3. It is indicated by the distance of the portion on the upstream side from the position S ′. Therefore, in this embodiment, the distance X is set to 20 mm or less in a range where the heating roller 2 and the heating element 3 are not in contact with each other.
[0045]
Here, further careful observation revealed that the same wrinkles between the heating roller 2 and the heating member 3 as in the heating belt 3 and the guide roller 9 were stochastically entered into the fixing belt 8. As a result, it was found that if the distance between the heating element 3 and the guide roller 9 is set to 20 mm or less, the stabilization of the fixing belt 8 is suppressed and wrinkles are prevented.
[0046]
The distance between the heating element 3 and the guide roller 9 is the distance indicated by the reference character Y in FIG. 2, that is, the distance downstream of the engagement end position E ′ between the fixing belt 8 and the guide roller 9 in the rotation direction F of the fixing belt 8. , And the distance on the upstream side of the point E. Therefore, in this embodiment, the distance Y is set to 20 mm or less in a range where the heating element 3 and the guide roller 9 are not in contact with each other.
[0047]
The shorter the distances X and Y are, the more effective the prevention of wrinkling of the fixing belt 8 is. 3, the heating roller 2 and the guide roller 9 are damaged, and the rotation speed of the fixing belt 8 fluctuates, thereby hindering satisfactory fixing. Therefore, the distances X and Y are more preferably 1 to 10 mm, and further preferably 2 to 5 mm.
[0048]
Further, the fixing device is a belt fixing device like a fixing device 108, and includes a heating roller 2 for performing pre-fixing by raising the fixing belt 8 to a predetermined temperature in advance and a heating element 3 for performing main fixing. If the fixing belt 8 is preheated by the heating roller 2 in a configuration in which the heating is performed by the divided heating means, the temperature of the heater 3 does not decrease due to the heat absorption of the fixing belt 8. As a result of a detailed study of such preheating, as a result of heating the fixing belt 8 to a predetermined temperature by heating by the heating roller 2, a stage before the recording paper contacts the heating roller 2, that is, in the rotation direction F of the fixing belt 8. It was found that the fixing belt 8 should be in contact with the heating roller 2 at a length of 0.2 to 200 mm on the upstream side of the point S.
[0049]
If the length is less than 0.2 mm, the residual heat of the fixing belt 8 is not enough, and if the length exceeds 200 mm, the fixing device 108 becomes too large and the heat radiation area becomes too large, which is not preferable. Therefore, in this embodiment, the length of the portion of the fixing belt 8 wound around the heating roller 2 is set to 0.2 to 200 mm. Such a length is preferably 1 to 100 mm, more preferably 2 to 50 mm, and still more preferably 5 to 40 mm. In this embodiment, the length of the portion of the fixing belt 8 wrapped around the heating roller 2 is the length from the point S ″ at which the fixing belt 8 starts engaging with the heating roller 2 to the point S. .
[0050]
The fixing member may be used as the pressing member at the point S in addition to a roller-shaped member such as the pressing roller 6. In order to prevent the heat of the recording paper from being taken away by the pressing member, it is desirable to apply heat to the pressing member by a heating means such as a heater. However, even when the recording paper enters the nip portion 12 in a low temperature such as in winter, it is preferable because stable fixing can be performed.
[0051]
In the embodiment shown in FIG. 2, the heating is performed from the back side of the recording paper and the fixing belt 8 is located below the recording paper conveyance path, similarly to a general fixing device. As shown in FIG. 3, heating is performed from the back surface of the recording paper, that is, the surface not carrying the toner, but the fixing belt 8 is located above the recording paper transport path. Is provided with an endless transport belt 13 for transporting the recording paper because the transport of the recording paper by the fixing belt 8 is not performed smoothly.
[0052]
The transport belt 13 is wound around the drive roller 14 and the auxiliary roller 15 together with the pressure roller 6, and extends from the point S in the rotation direction F of the fixing belt 8 to a position downstream from the point E. When the driving roller 14 is driven to rotate in the direction of arrow I by a driving means (not shown), the transport belt 13 is driven to rotate in the direction of arrow J, and the pressure roller 6 and the auxiliary roller 15 also move in the directions of arrow K and arrow L, respectively. It is driven and rotated. By supporting the recording paper with the transport belt 13 and transporting the recording paper together with the fixing belt 8, the floating of the recording medium on the recording paper with respect to the fixing belt 8 is prevented, and the fixing property of the fixing belt 8 is improved.
[0053]
Even in the configuration including the transport belt 13, the transport belt 13 is a configuration for simply transporting the recording paper, and therefore, the heating roller 2 and the pressure roller 6 face each other to press the recording paper and the toner. This is the pressing force of the pressure roller 6 in the nip portion 12, where pre-fixing is performed in the same manner as described above, and main fixing is performed in the portion opposed to the heating element 3 as described above. Note that in FIG. 3, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
[0054]
As shown in FIG. 4, the heating member disposed inside the fixing belt 8 is not a fixed member because of its immovable form, and has the same direction as the rotation direction F of the fixing belt 8 at a position facing the fixing belt 8. The endless heating belt 16 rotating in the direction M may be used. The heating belt 16 is wound around rollers 17 and 18 and contacts the inside of the fixing belt 8 downstream of the heating roller 2 and upstream of the guide roller 9 in the rotation direction of the fixing belt 8, and the contacted portion fixes the fixing belt 8. The belt 8 is driven to rotate. Inside the heating belt 16, a plurality of heaters 4 as heating means are arranged in parallel.
[0055]
Even when the heating body is the immovable heating body 3 as shown in FIGS. 2 and 3, wrinkles are prevented as described above, but the fixing belt 8 is rubbed against the surface of the heating body 3 Although the torque increases due to the rotation, if the heating element is the heating belt 16, such an increase in torque does not occur. To further reduce the torque, the heating belt 16 may be driven to rotate at substantially the same speed as the fixing belt 8 by using one of the rollers 17 and 18 as a driving roller. In FIG. 4, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description is omitted.
[0056]
If the pressing force in the nip portion 12 is too small, the effect of fixing the toner to the recording paper cannot be expected, and if it is too large, wrinkling of the recording paper or the recording paper is compressed, and the texture of the recorded matter is reduced. It is not preferable because there is a problem to change. Accordingly, the pressure is preferably 2 to 200 N in total pressure, more preferably 5 to 150 N, further preferably 10 to 100 N, and still more preferably 20 to 80 N. It is possible to prevent the image from shifting. Therefore, in the present embodiment, the applied pressure is set to 20 to 80 N by selecting the spring 7 having an appropriate urging force.
[0057]
Since the fixing belt 8 is heated and pressed to perform heat fixing, the material of the fixing belt 8 is required to have heat resistance and toughness. Therefore, the fixing belt 8 is desirably a metal belt such as nickel or stainless steel, or a resin belt such as a polyimide resin or a polybenzimidazole resin. The thickness of the fixing belt 8 is preferably thinner in consideration of the response to heat, but is preferably thicker in consideration of strength durability. Therefore, the thickness of the fixing belt 8 is preferably 1 to 300 μm, preferably 2 to 200 μm, more preferably 5 to 100 μm, and still more preferably 10 to 60 μm.
[0058]
Therefore, in this embodiment, the fixing belt 8 is a metal belt made of nickel having a thickness of 30 μm. Further, in the configuration using the transport belt 13 as shown in FIGS. 3 and 4, the transport belt 13 is a 30 μm-thick metal belt made of nickel from the same requirement. Further, as shown in FIG. 4, in the configuration using the heating belt 16 as the heating element, the heating belt 16 is a 30 μm thick metal belt made of nickel from the same requirement.
[0059]
Since the fixing belt 8 is provided to give an appropriate amount of heat to the recording paper and the toner and perform good fixing, the fixing belt 8 is used to perform such good fixing by the heating roller 2 and the heating element 3 or the heating belt 16. Needs to be given a predetermined amount of heat. However, for example, when the rotation speed of the fixing belt 8 is very high or when the length from the point S ′ to the point E ′ is short, a sufficient amount of heat cannot be supplied to the fixing belt 8.
[0060]
The inventors have examined that the time from when the fixing belt 8 is engaged with the heating roller 2 until the engagement with the heating element 3 or the heating belt 16 is released during one rotation of the fixing belt 8 is determined. It was found that a sufficient amount of heat could be supplied to the fixing belt 8 if the heating time was 50 msec or more. Therefore, in the present embodiment, the rotation speed of the fixing belt 8 and the heating member 3 or the heating belt are adjusted so that the time from the point S ″ to the point E ′ during one rotation of the fixing belt 8 is 50 msec. The length from point S ′ to point E ′ of 16 was adjusted, for example, when the image forming apparatus 100 is a high-speed machine, it is necessary to increase the rotation speed of the fixing belt 8. Increases the length of the heating member 3 or the heating belt 16 from the point S ′ to the point E ′, and secures a time 50 msec from the point S ″ to the point E ′ during one rotation of the fixing belt 8. .
[0061]
As will be described below, the embodiment shown in FIG. 2 is compared with the following comparative examples shown in FIGS. 5 to 7, and the embodiment shown in FIG. In comparison with each of the examples described above, a fixing test by a comparative example using a roller-facing type fixing device was performed to verify the effects of the present invention. In FIGS. 5 to 7, the same components as those in FIGS. 2 to 4 are denoted by the same reference numerals, and the description is omitted.
[0062]
-Example 1
In Example 1, the fixing test was performed under the following conditions using the configuration shown in FIG. 2 and setting the distance X to 10 mm and the distance Y to 10 mm.
Nip time 10msec
Total long heating time 80msec
Pressing force 10N on one side (total pressure 20N when pressurized on both sides)
Set temperature of heating roller 2 120 ° C
Set temperature of heating element 3 120 ° C
[0063]
The nip time is a time required for the recording paper to pass through the nip portion 12. The total long heating time is the time from when the fixing belt 8 is engaged with the heating roller 2 to when the engagement with the heating element 3 is released during one rotation of the fixing belt 8. The pressure is the pressure applied by the pressure roller 6, one side is the pressure applied to one end of the rotation shaft provided on the pressure roller 6, and both sides pressure is the pressure applied to both ends of the rotation shaft. It is.
[0064]
As a result of the test, drawing was performed with a drawing tester, but the toner hardly fell off, the fixing property was good, and the fixing belt 8 did not wrinkle. However, when the distance X was 30 mm and the distance Y was 30 mm, rarely wrinkling was observed on the heating element 3. Therefore, when both the distance X and the distance Y were larger than 20 mm, it was confirmed that there was a conventional problem.
[0065]
-Comparative example 1
Comparative Example 1 uses the configuration shown in FIG. That is, the pre-heating is performed using the heating roller 2, but the guide roller 19 that is not pressed toward the heating roller 2 is used, and the nip portion is not formed. Other conditions are the same as in the first embodiment. The fixing belt 8 is sufficiently heated by the heating roller 2 to come into contact with the recording paper, and then is heated and heated by the heating body 3 to perform fixing. The image was drawn by a drawing tester, and the toner was hardly removed and the fixability was good, but the image shift was remarkable. Therefore, as a result of the test, it was confirmed that a pressure member was required for good fixing and that pre-fixing was required.
[0066]
-Comparative example 2
Comparative Example 2 uses the configuration shown in FIG. 6, and has a release claw 20 that forcibly separates the recording paper that has passed through the nip portion 12 from the fixing belt 8 as compared with Example 1. The main purpose is to verify the effect of the heat retention and heating after the pre-fixing, that is, the effect of the main fixing by the heating element 3. The paper passing speed is the same as in the first embodiment.
[0067]
Nip time 10msec
Total long heating time 10msec
Set temperature of heating roller 2 120 ° C, 140 ° C, 150 ° C, 160 ° C
The fixing test was performed under the following conditions. Other conditions are the same as in the first embodiment. Since the recording paper immediately after passing through the nip portion 12 is forcibly peeled off from the fixing belt 8 by the peeling claw 20, the total long heating time matches the nip time and is shortened. The reason why the set temperature of the heating roller 2 is changed is to increase the amount of heat given by the heating roller 2 instead of performing heating by the heating element 3 and to check a fixing state corresponding to this.
[0068]
The relationship between the temperature of the heating roller 2 and the fixing state was as follows.
120 ° C Cold offset without fixing
130 ° C Cold offset does not occur, but toner falls off when rubbed with finger
140 ° C Scratches considerably with a drawing tester.
Good fixability with almost no problem at 150 ℃ drawing tester
[0069]
As a result of the test, it is necessary to perform heating by the heating element 3 in order to perform good fixing while keeping the temperature of the heating roller 2 constant. That is, it is necessary to perform main fixing, and the heating time during one rotation of the fixing belt 8 is reduced. It was confirmed that heating should be performed for a long time while securing 50 msec. Further, it has been confirmed that in order to perform satisfactory fixing by heating only the heating roller 2, it is necessary to increase the temperature of the heating roller 2 as compared with the case where heating is performed together with the heating element 3, and energy consumption increases. The conventional problem that it is different was confirmed.
[0070]
-Comparative example 3
Comparative Example 3 uses the configuration shown in FIG. 7. Compared to Example 1, the heating element is not divided into the first heating element 2 and the second heating element 3, The main difference is that the fixing is performed only by the flat heating element 21 described above, and the effect of the pre-fixing is verified. The conditions were the same as in Example 1 except that the heating temperature by the heating element 21 was changed. The reason why the set temperature of the heating roller 2 is changed is that the amount of heat given by the heating element 21 is increased instead of performing the heating by the heating roller 2, and a fixing state corresponding thereto is examined.
[0071]
The relationship between the temperature of the heating element 21 and the fixing state was as follows.
120 ° C Scratches considerably when rubbed with a drawing tester.
Good fixability with almost no problem at 130 ℃ drawing tester
As a result of the test, it was found that when the heating by the heating body 21 was performed at the same temperature of 120 ° C. as in the configuration of Example 1 in which the pre-fixing was performed, the fixing performance was reduced. This is because there is no heating roller 2 as the first heating element for performing the pre-fixing, so that a temperature gradient is generated in the surface temperature of the heating element 21 as the second heating element which is a planar heating element. It is thought to be caused by
[0072]
In addition, as a result of the test, it was confirmed that heating by the first heating element was required to perform satisfactory fixing while keeping the temperature of the second heating element constant, that is, pre-fixing should be performed. Furthermore, it has been confirmed that in order to perform satisfactory fixing by heating only one heating element 21, the temperature of the one heating element 21 must be increased as compared with the case of performing pre-fixing, and energy consumption is reduced. The conventional problem that it will increase was confirmed.
[0073]
-Example 2
In Example 2, a fixing test was performed using the configuration shown in FIG. 3 under the same conditions as in Example 1 as follows. As described above, the configuration shown in FIG. 3 is provided with an endless belt as a support so as to hold and convey the back surface of the recording paper so that the conveyance of the recording paper is stabilized.
[0074]
Nip time 10msec
Total long heating time 80msec
Pressing force 10N on one side (total pressure 20N when pressurized on both sides)
Set temperature of heating roller 2 120 ° C
Set temperature of heating element 3 120 ° C
[0075]
As a result of the test, as in Example 1, with respect to the fixing performance, the image was drawn with a drawing tester, but the toner hardly dropped off, and the fixing property was good. Regarding the conveyance of the recording paper, in the first embodiment, the recording paper rarely rises from the fixing belt 8 and a partial fixing failure may occur, but the recording paper is conveyed by the conveyance belt 13 shown in FIG. In the method of transporting the recording paper, there was no problem such as the floating of the recording paper.
[0076]
In particular, in the first embodiment, the fixing surface of the recording paper, that is, the surface on which the toner is carried and fixed, faces upward, whereas in the second embodiment, the fixing surface of the recording paper faces downward. In the configuration including the transport belt 13 as in No. 2, it has been demonstrated that the fixing surface can be turned upside down without considering the influence of gravity.
[0077]
When the distance X was 5 mm and the distance Y was 3 mm, wrinkles of the fixing belt 8 on the fixed heating element 3 were not observed, but when A was 50 mm and B was 30 mm, the fixing belt 8 was fixed. It was observed that wrinkles always formed on the heated body 3. Therefore, it was more clearly confirmed than in Example 1 that there was a conventional problem when both the distance X and the distance Y were larger than 20 mm.
[0078]
-Example 3
In Example 3, a fixing test was performed using the configuration shown in FIG. 4 under the same conditions as in Example 1 as follows. As already described, the configuration shown in FIG. 4 is configured as a heating belt 16 in which the heating element is not fixed but has an endless belt shape.
[0079]
Nip time 10msec
Total long heating time 80msec
Pressing force 10N on one side (total pressure 20N when pressurized on both sides)
Set temperature of heating roller 2 120 ° C
Set temperature of heating element 3 120 ° C
[0080]
As a result of the test, similarly to Example 1, the fixing performance was the same as that of Example 2, and the image was drawn with a drawing tester. With respect to the torque of the fixing belt 8, the driving torque was reduced by 20% as compared with Example 2, and it was confirmed that the load on driving was reduced. Further, in the second embodiment, the back surface of the fixing belt 8 is easily scratched by rubbing with the fixed heating element 3, whereas in the third embodiment, the back surface of the fixing belt 8 is not damaged and Stability was improved.
[0081]
-Comparative example 4
Comparative Example 4 is a conventional roller-facing type fixing device not shown in the drawings, that is, a heating roller internally provided with a heater as a heat source serving as a heating unit, which is driven to rotate by a driving unit, and which is pressed against the heating roller. A pressure roller that is driven by the heating roller to rotate. The recording medium is passed through a nip formed by the heating roller and the pressure roller by the rotation of the heating roller and the pressure roller, and is heated and simultaneously heated. The fixing property was examined under the following conditions using the same toner as the toner used in the fixing device 108 of the first to third embodiments by a fixing device that fixes the toner by pressing and conveying the toner.
[0082]
Nip time 10msec
Pressing force 10N on one side (total pressure 20N when pressurized on both sides)
The nip time is the time required for the recording paper to pass through the nip. The pressing force is a pressing force by a pressing roller, one side is a pressure applied to one end of a rotating shaft provided in the pressing roller, and both-side pressing is a pressure applied to both ends of the rotating shaft. .
[0083]
The relationship between the temperature of the heating roller and the fixing state was as follows.
130 ℃ Cold fixing without fixing
140 ° C No cold offset, but toner falls off when rubbed with finger
150 ° C Scratches considerably with a drawing tester.
Good fixability with almost no problem at 160 ° C drawing tester
The reason why the set temperature of the heating roller is changed is that, instead of performing heating with the heating roller 2 and the heating body 3 or the heating body 16 in the embodiment, the amount of heat given only by the heating body roller is increased, and accordingly, This is to check the fixing state.
[0084]
The results of the test were compared with those in the examples. In order to perform good fixing by heating and pressing only with a heating roller in the roller facing type, it is necessary to perform heating in two stages for a long time as in the examples. It was confirmed that the temperature of the heating roller had to be increased as compared with the above, and the conventional problem that the consumed energy was increased was confirmed. From the test results, it was found that excellent fixing can be performed in the examples even when the set temperature is lowered by about 40 ° C., as compared with the roller facing type. Therefore, according to the fixing device 108 of the embodiment, energy consumption can be significantly reduced.
[0085]
The image forming apparatus 100 is configured as described above, and includes the fixing device 108 according to any one of the first to third embodiments. The power of the image forming apparatus 100 is turned on by a predetermined operation by an operator. Alternatively, when the operator shifts from the standby state to the operating state and performs a known operation of starting image formation, in the image forming system of each color, the photoreceptor 101 uniformly charged by the charging process by the charging device is indicated by an arrow A. A latent image formation in an exposure process by a laser beam irradiated according to data input from the outside by a rotation in a direction, a development process performed by development by a development device, a transfer process by a transfer device 105, a cleaning process by a cleaning device, After the charge elimination step by the charge eliminator, the process proceeds to the charging step again.
[0086]
Such a transfer step is performed in synchronization with the timing of conveyance of the recording paper conveyed along the conveyance path 110, and in the course of conveyance along the conveyance path 110, the toner image is transferred onto the recording paper by superposition transfer in all the transfer steps. Then, the image is fixed on the recording paper by a fixing process in the fixing device 108. The recording paper on which the color image is formed by fixing the toner image is discharged out of the image forming apparatus 100. In such an image forming process, in the fixing process, wrinkles of the fixing belt 8 are prevented, and the recording paper is stably transported, so that the fixing is performed satisfactorily.
[0087]
As described above, the image forming apparatus to which the present invention is applied has been described. However, the image forming apparatus is not limited to forming a color image, but may be configured to form a single color image. The configuration using the heating belt can be applied not only to the case where the transport belt is used but also to the case where the recording paper is transported only by the fixing belt 8. The configuration using the transport belt may be applied not only to the case where the fixing surface of the recording paper is facing downward but also to the case where the fixing surface of the recording paper is facing upward, as long as the fixing property is not deteriorated.
[0088]
【The invention's effect】
The present invention provides an endless fixing belt for conveying a recording medium to which toner is fixed, a heating roller positioned at a position where engagement of the recording medium with the fixing belt is started, and a fixing roller wound around the fixing belt, A guide roller around which the fixing belt is wound at a position where the engagement of the recording medium with respect to the recording medium is terminated, and an identification attachment at a position inside the fixing belt and opposed to a passage of the recording medium conveyed by the identification attachment belt. In a fixing device having a heating member for heating a belt and a pressing member occupying the engagement start position and urged toward the fixing belt, a distance between the heating roller and the heating member is set to 20 mm. Since the non-contact range is set below, it is possible to prevent wrinkles generated when the fixing belt enters the heating body, thereby stably improving the conveyance of the recording medium. To perform, it is possible to provide a fixing device capable of performing a good fixing.
[0089]
When the distance between the heating element and the guide roller is set to 20 mm or less and in a non-contact range, it is possible to prevent the fixing belt from wrinkling between the heating element and the guide roller, thereby more stably conveying the recording medium. Thus, it is possible to provide a fixing device that can perform the fixing well and perform the fixing better.
[0090]
When the length of the portion of the fixing belt that is wound around the heating roller is 0.2 to 200 mm, it is possible to prevent the apparatus from being enlarged and suppress heat radiation to reduce energy consumption. To provide a fixing device capable of sufficiently supplying heat to the fixing belt by means of the recording medium and preventing a decrease in the temperature of the heating element due to heat absorption of the fixing belt by the recording medium and performing satisfactory fixing. it can.
[0091]
If the time from the engagement of the identification belt to the heating roller to the release of the engagement to the heating body during one rotation of the fixing belt is assumed to be 50 msec or more, a sufficient amount of heat for the fixing belt is provided. By supplying the fixing device, it is possible to provide a fixing device capable of performing good fixing.
[0092]
If pre-fixing is performed at the position where the pressure member and the heating roller are opposed to each other, and main fixing is performed at the portion of the fixing belt that is engaged with the heating element, fixing is performed in two stages, pre-fixing and main fixing. By doing so, the heating roller sufficiently supplies heat to the fixing belt, preventing the temperature of the heating element from being lowered due to the heat absorption of the fixing belt by the recording medium, and fixing the toner over a relatively long distance. Provided is a fixing device that can perform satisfactory fixing by supplying a sufficient amount of heat to a recording medium, and can set the temperature of a heating roller and a heating element to a relatively low temperature and reduce energy consumption. Can be.
[0093]
If the heating element is an immovable member, it is possible to provide a fixing device that can perform satisfactory fixing with a heating element having a relatively simple structure.
[0094]
If the heating element is an endless heating belt that rotates in the same direction as the rotation direction of the fixing belt at a position facing the fixing belt, the torque of the fixing belt due to the engagement of the heating belt with the fixing belt is suppressed. Therefore, it is possible to provide a fixing device capable of performing satisfactory fixing while suppressing energy consumption by setting the driving system of the fixing belt to low torque.
[0095]
If the fixing belt is a metal belt or a resin belt, it is possible to provide a fixing device that has high heat resistance and durability, can be used for a long time, and has high user reliability.
[0096]
If the thickness of the fixing belt is 1 to 300 μm, it is possible to provide a fixing device that has high durability and can be used for a long period of time and has high user reliability.
[0097]
If an endless transport belt for transporting the recording medium is provided, which is wound around the pressing member and extends at least from the engagement start position to the engagement end position, not only the fixing belt but also the transport belt Also, by conveying the recording medium, it is possible to provide a fixing device capable of preventing the floating of the recording medium, favorably conveying the recording medium, and performing satisfactory fixing.
[0098]
If the transport belt is a metal belt or a resin belt, it is possible to provide a fixing device that has high heat resistance and durability, can be used for a long time, and has high user reliability.
[0099]
If the thickness of the transport belt is 1 to 300 μm, a fixing device having high durability and long-term use and high user reliability can be provided.
[0100]
Since the present invention resides in an image forming apparatus having the fixing device according to any one of claims 1 to 12, it is possible to obtain a high-quality image formed article having a fixing device having the above-described effects. An image forming apparatus that can be provided.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing an image forming apparatus to which the present invention is applied.
FIG. 2 is a side view illustrating a configuration example of the fixing device illustrated in FIG. 1;
FIG. 3 is a side view illustrating another example of the configuration of the fixing device illustrated in FIG. 1;
FIG. 4 is a side view showing another example of the configuration of the fixing device shown in FIG. 1;
FIG. 5 is a side view showing a configuration of a fixing device as a comparative example compared with the fixing device according to the present invention.
FIG. 6 is a side view showing another configuration of a fixing device as a comparative example compared with the fixing device according to the present invention.
FIG. 7 is a side view showing still another configuration of a fixing device as a comparative example compared with the fixing device according to the present invention.
[Explanation of symbols]
2 Heating roller
3 Heating body as immovable member
3, 16 heating element
6 Pressure member
8 Fixing belt
9 Guide roller
12 Opposing position of pressure member and heating roller
13 Endless transport belt
16 Heating body as endless heating belt
100 Image forming apparatus
108 Fixing device
F Fixing belt rotation direction
E End position of recording medium engagement with fixing belt
S Start position of engagement of recording medium with fixing belt
X Distance between heating roller and heating element
Y Distance between heating element and guide roller

Claims (13)

An endless fixing belt for conveying a recording medium on which the toner is fixed,
A heating roller that is positioned at an engagement start position of the recording medium with respect to the fixing belt and around which the fixing belt is wound;
A guide roller wound around the fixing belt and positioned at an engagement end position of the recording medium with the fixing belt,
A heating element for heating the identification attachment belt at a position inside the fixing belt and opposed to a passage path of the recording medium being conveyed by the identification attachment belt,
A fixing member that occupies the engagement start position and is urged toward the fixing belt.
A fixing device, wherein the distance between the heating roller and the heating element is 20 mm or less and is in a non-contact range. 2. The fixing device according to claim 1, wherein a distance between the heating element and the guide roller is set to 20 mm or less and a non-contact range. 3. The fixing device according to claim 1, wherein a length of the fixing belt wound around the heating roller is 0.2 to 200 mm. 4. The fixing device according to claim 1, wherein the fixing belt is engaged with the heating roller after the fixing belt makes one rotation, and then the engagement with the heating element is released. A time required for the fixing device to be 50 msec or more. 5. The fixing device according to claim 1, wherein pre-fixing is performed at a position where the pressing member and the heating roller are opposed to each other, and a fixing portion of the fixing belt is engaged with the heating element. A fixing device for performing fixing. The fixing device according to claim 1, wherein the heating element is an immovable member. 7. The fixing device according to claim 1, wherein the heating element is an endless heating belt that rotates in the same direction as the fixing belt at a position facing the fixing belt. Characteristic fixing device. The fixing device according to any one of claims 1 to 7, wherein the fixing belt is a metal belt or a resin belt. 9. The fixing device according to claim 1, wherein the thickness of the fixing belt is 1 to 300 [mu] m. The fixing device according to any one of claims 1 to 9, wherein the fixing device is configured to convey a recording medium wound around the pressing member and extending at least from the engagement start position to the engagement end position. A fixing belt having an endless transport belt. 11. The fixing device according to claim 10, wherein the transport belt is a metal belt or a resin belt. The fixing device according to any one of claims 1 to 8, wherein the transport belt has a thickness of 1 to 300 m. An image forming apparatus comprising the fixing device according to claim 1.

Images