JP2004198659A - Image fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image fixing device capable of stabilizing the fixing property of a toner image by supplying sufficient heat to a recording paper sheet. <P>SOLUTION: In a rotatable fixing roll 10 by which an unfixed image on the recording paper 35 is fixed, a belt-shaped area L in a longitudinal direction having a length in the outer peripheral direction of the surface of the fixing roll 10 is heated from outside by an external heating member 50. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image fixing device, and more particularly, to an image fixing device used for an image forming apparatus using, for example, an electrophotographic method.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus such as a copying machine or a printer using an electrophotographic method, for example, uniformly charges a photosensitive member formed in a drum shape, and exposes the photosensitive member with light controlled based on image information. An electrostatic latent image is formed on a photoreceptor, this electrostatic latent image is made a visible image with toner, and this visible image is transferred to recording paper, and then fixed by an image fixing device to form an image. I have.
[0003]
As shown in FIG. 7, an image fixing device used in such an image forming apparatus has a core made of a cylinder such as SUS covered with silicon rubber, and a halogen heater as a heating element provided inside the core. The fixing roll 101 and a similarly configured pressure roll 102 are pressed against each other. The rotationally driven fixing roll 101 and the pressure roll 102 driven and rotated by the fixing roll 101 form a nip portion 103 having a fixed width at a pressure contact portion. Then, the recording paper 104 onto which the toner image 105 has been transferred passes through the nip portion 103, so that the toner image 105 is heated and pressed, and is fixed on the recording paper 104.
[0004]
Here, as a conventional technique, there is a technique for fixing a toner image while nipping the fixing image between a fixing roll and a pressure roll (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-10-240060 (page 4, FIG. 2)
[0006]
[Problems to be solved by the invention]
However, in the conventional image fixing device, when the recording paper passes through a nip portion formed by a heating roll and a pressure roll, heat is transferred from the heating roll and the pressure roll to the recording paper, so that each surface of the recording paper is heated. As the temperature drops, sufficient heat cannot be supplied to the rear end of the recording paper. For this reason, the fixability of the toner image is reduced, and particularly in the case of 256 GSM of mirror coated paper, there is a technical problem that the process speed must be set to a low speed.
Also, when the power to the heater is increased to increase the amount of heat supplied from the heating roll and the pressure roll to the recording paper, a phenomenon occurs in which the silicone rubber coated on the heating roll and the pressure roll is peeled off, and the heater There was also a technical problem that there was a certain limit to the amount of electric power supplied to the system.
[0007]
Note that the technique described in Patent Document 1 does not disclose an effective technique for supplying a sufficient amount of heat to recording paper and stabilizing the fixability of a toner image.
[0008]
Accordingly, the present invention has been made based on such a technical problem, and an object of the present invention is to provide an image fixing device that supplies a sufficient amount of heat to a recording sheet and stabilizes the fixing property of a toner image. Is to do.
[0009]
[Means for Solving the Problems]
With this object in mind, the image fixing device of the present invention has a rotatable fixing unit for fixing an unfixed image formed on a recording material, the external fixing unit having a length in the outer peripheral direction of the surface of the fixing unit. By heating the belt-shaped region extending in the longitudinal direction from the outside, a sufficient amount of heat is supplied to the recording paper, and the fixing property of the toner image can be stabilized.
[0010]
That is, the image fixing device of the present invention includes a rotatable fixing unit that fixes an unfixed image formed on a recording material, a pressing unit that presses the fixing unit, and an outer surface of the fixing unit that is on the surface of the fixing unit. External heating means for externally heating a belt-shaped region having a length in the direction and extending in the longitudinal direction. Further, the external heating means may be provided so as to heat a belt-shaped region having a length of 5 mm or more in the outer peripheral direction of the fixing means. Further, the external heating means may be provided so as to be in contact with the fixing means at the belt-shaped region. In particular, the external heating unit may be configured to be able to contact and separate from the fixing unit. Further, a plurality of external heating means may be provided. Further, the external heating means may be provided so as to be in non-contact with the fixing means. In particular, the external heating means may include a heating element that radiates infrared rays.
[0011]
Further, the image fixing device of the present invention is configured such that a rotatable fixing roll for fixing an unfixed image formed on a recording material, a pressing member for pressing a fixing unit, and a plurality of rolls, An external heating belt that contacts the surface at a predetermined area and externally heats the fixing roll is provided. Further, the external heating belt may be characterized in that heat is supplied from a heating element disposed on one or more of the plurality of rolls. Further, the external heating belt may further include a deviation preventing member for preventing deviation of the belt. Further, the external heating belt may be configured so as to be able to contact and separate from the fixing unit.
[0012]
Further, the present invention is regarded as an image forming apparatus, and an unfixed image forming unit that forms an unfixed image according to image information on a recording material, and a rotatable fixing member that fixes the unfixed image formed on the recording material. And an external heating member that externally heats a belt-like region extending in a longitudinal direction on the surface of the fixing member and having a length in the outer peripheral direction of the fixing unit. And means. Further, the image fixing means may be characterized in that the amount of heat of the heating element disposed on the external heating member is made variable. Further, the image fixing means can be characterized in that the external heating member is configured to vary the amount of heat of the heating element according to the recording material.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on an embodiment shown in the accompanying drawings.
◎ Embodiment 1
FIG. 1 is a diagram illustrating an image fixing device according to the present embodiment. The image fixing device 1 includes a fixing roll 10 having a built-in heating source, an endless belt 30 stretched over three support rolls 20, 21, and 22 and pressed against the fixing roll 10, and a predetermined range of the endless belt 30 fixed to the fixing roll 10. The fixing device 10 includes a pressure applying member 40 that abuts against the belt 10 from the inner peripheral surface side and presses the same, and an external heating member 50 that externally heats the fixing roll 10.
[0014]
The fixing roll 10 is formed of an elastic layer 12 made of an elastic material and a heat-resistant elastic material on a cylindrical cored bar 11 made of a metal having a high thermal conductivity such as aluminum. This is a roll having a diameter of 65 mm, which is formed by laminating the surface layer 13. Two halogen heaters 14 as heating sources are disposed inside the cylinder of the cored bar 11. A temperature sensor 15 for measuring the surface temperature of the fixing roll 10 is provided on the surface of the fixing roll 10.
The fixing roll 10 is rotatably supported by a support mechanism (not shown), and is rotated at a predetermined speed in a direction indicated by an arrow in the figure by a driving device (not shown). In addition, the halogen heater 14 is controlled by a temperature control unit (not shown) based on the measurement signal of the temperature sensor 15, and the surface temperature of the fixing roll 10 is maintained at a predetermined temperature (for example, 160 ° C.).
[0015]
The endless belt 30 is formed of a resin film such as a polyimide film. And it is installed in a state of being stretched around three support rolls 20, 21 and 22 which are rotatably supported.
The support roll 20 is located downstream of the lowermost point of the fixing roll 10 in the rotation direction, and is rotatably disposed in a state of being pressed against the fixing roll 10 by a pressing mechanism (not shown). The support roll 21 is located on the upstream side in the horizontal direction from the lowest point of the fixing roll 10, and is rotatably disposed. In order to prevent a sudden temperature drop of the fixing roll 10 due to heat conduction from the fixing roll 10 to the endless belt 30 when the image fixing device 1 is started, the endless belt 30 is kept at a predetermined temperature inside the support roll 21. A halogen heater 23 for keeping the temperature higher is provided.
[0016]
Further, the support roll 22 has one end supported by a fixed bearing, and the other end supported by a bearing that can be moved in the horizontal direction by a displacement drive mechanism. The support roller 22 is moved in a direction in which the displacement driving mechanism is controlled by a drive control unit that operates based on a detection signal from a sensor (not shown) that detects the meandering traveling of the endless belt 30, and the meandering of the endless belt 30 is suppressed. It is configured to move by a fixed amount.
[0017]
In this way, the endless belt 30 is stretched while applying a predetermined tension to the three support rolls 20, 21, and 22. In particular, the outer peripheral surface of the endless belt 30 is supported by the two support rolls 20 and 21 so as to be pressed against the surface of the fixing roll 10 while being wound by a predetermined amount. As a result, a nip N in which the recording paper 35 carrying the unfixed toner image is held between the recording paper 35 and the fixing roll 10 is formed. Further, the support roll 22 supports the endless belt 30 located on the side opposite to the fixing roll 10 from the support roll 20 and the support roll 21, and suppresses the meandering of the endless belt 30.
[0018]
Further, the endless belt 30 is provided with a cleaning roll 24 that rubs the endless belt 30 to clean the surface of the endless belt 30. The cleaning roll 24 includes a cored bar and a porous sponge layer formed on the surface of the cored bar. The sponge layer is impregnated with a release agent such as dimethyl silicone oil, amino-modified silicone oil, or polyester wax to prevent toner from adhering to the surface of the endless belt 30. In addition, the sponge layer formed on the surface of the cored bar may be formed of PTFE (a porous body of fluororesin) whose surface is covered with Gore-Tex (trade name).
[0019]
An entrance guide 27 for guiding recording paper 35 carrying an unfixed toner image to the nip N is provided upstream of the support roll 21. Further, on the downstream side of the support roll 20, there is provided a paper discharge guide 28 for guiding the recording paper 35 that has passed through the nip N and is separated from the fixing roll 10. Is discharged.
[0020]
As shown in FIG. 2, the pressure applying member 40 has a support having a split structure of a support plate 41 and a support plate receiver 42, both of which are formed of stainless steel or the like and has a smooth upper surface. An elastic layer 43 made of silicone rubber (rubber hardness 23 °) is attached, and a low friction layer 44 made of a glass fiber sheet (FGF-400-4 manufactured by Chuko Kasei) impregnated with polytetrafluoroethylene.
[0021]
The support plate 41 has a T-shaped cross section, and has a convex portion 41a formed on the lower surface thereof along the axial direction of the fixing roll 10. The support plate receiver 42 has an upper surface formed with a concave groove 42a in which the convex portion 41a on the lower surface of the support plate 41 is fitted, and an extended portion 42b formed at a portion of the lower surface slightly excluding both end portions. Have been. The elastic layer 43 is formed in a curved shape such that the upper surface thereof is along the surface of the fixing roll 10, and is formed so as to extend to near the contact portion between the support roll 20 and the fixing roll 10. Thus, the endless belt 30 is configured to be able to securely adhere along the surface of the fixing roll 10 within a range where the nip N is formed. The low friction layer 44 is attached in a state where the support plate 41, the support plate receiver 42, and the elastic layer 43 are integrated and wound around the entire periphery thereof.
[0022]
In addition, the pressure applying member 40 is configured such that the support plate 41 to which the elastic layer 43 is attached is fitted to the support plate receiver 42, integrated with screws or the like, and detachably attached to the pressure frame 45. One end of the pressure frame 45 is swingably attached to a support shaft (not shown) of the main body of the image fixing device 1 through a shaft hole 45b, and the lower side of the pressure frame 45 is directed toward the fixing roll 10 by a coil spring 46. It is designed to be urged at a predetermined pressure.
[0023]
Next, the external heating member 50 will be described. The external heating member 50 stretches the heat belt 51 that is driven by the fixing roll 10 while being in contact with the fixing roll 10, stretches the heat belt 51, and stretches the heat belts 51 and 52, which heats the heat belt 51. In addition, a metal roll 54 for driving the heat belt 51 is provided.
[0024]
The heat belt 51 is an endless belt whose original shape is formed in a cylindrical shape with a diameter of 80 mm. The heat belt 51 has a structure in which a 50 μm-thick nickel electroformed belt is coated with a 100 μm-thick silicone rubber having a hardness of Hs33, or a 75 μm-thick polyimide is coated with a silicone rubber having a hardness of Hs33. It is constituted by coating with 100 μm.
The heat rolls 52 and 53 are configured by coating a core metal made of a metal such as aluminum or iron with a fluorine-coated 20 μm-thick PFA. Inside the cored bar, halogen heaters 55 and 56 each having a capacity of 300 W are provided. The metal roll 54 is a roll formed of a metal such as aluminum or iron.
[0025]
The heat belt 51 is stretched between the heat rolls 52 and 53 and the metal roll 54, and is in contact with a belt-shaped region extending in the outer circumferential direction on the surface of the fixing roll 10 while being in contact with the fixing roll 10. It is configured to follow. That is, the area where the heat belt 51 contacts the fixing roll 10 has a length L in the outer peripheral direction of the surface of the fixing roll 10, and the longitudinal direction of the fixing roll 10 is formed to have a length at least equal to or greater than the maximum image width. It is an area that spreads like a belt. The belt-shaped region has a width L of 5 mm or more in the outer circumferential direction of the fixing roll 10.
[0026]
Here, for example, consider a case where a simple roll is pressed against the fixing roll 10 having a diameter of 65 mm. Although there is a difference depending on the material of the roll, generally, the nip width formed by the roll can be about 3 to 4 mm. In the present embodiment, by setting the length in the outer peripheral direction to be longer than the nip width formed by the roll, sufficient heat can be transmitted to the fixing roll 10.
[0027]
Here, the heat belt 51 is provided with a deviation prevention member 60 for adjusting the inclination of the heat belt 51 in the width direction in order to prevent the deviation of the heat belt 51. FIG. 3 is a cross-sectional view illustrating the deviation prevention member 60. The bias preventing member 60 includes a tension roll 61 that presses the heat belt 51, a bearing 62 that supports the tension roll 61, a support 63 that supports the tension roll 61 via the bearing 62, and the heat belt 51 of the tension roll 61. Is constituted by a positioning member 64 for determining the contact position.
[0028]
The tension roll 61 is configured such that a core bar made of a metal such as aluminum or iron is coated with fluorine-coated PFA having a thickness of 20 μm. After the inclination of the tension roll 61 is adjusted, the tension roll 61 is fixed to a fixing member 65 provided in the main body of the image fixing device 1 by a screw or the like by a positioning member 64. This makes it possible to set the heat belt 51 so as not to be shifted to the left or right with respect to the traveling direction. Further, a halogen heater is provided inside the tension roll 61, and the heat belt 51 can receive heat from the tension roll 61.
[0029]
Further, the external heating member 50 is provided with a contact / separation mechanism (not shown) for setting the state in which the external heating member 50 is in contact with the fixing roll 10 and the state in which the external heating member 50 is separated. Then, the external heating member 50 can be separated from the fixing roll 10 in a case where the image fixing device 1 performs a jam process or a case where dirt such as toner attached to the heat belt 51 is cleaned.
[0030]
Next, the operation of the image fixing device 1 will be described. First, upon receiving a start signal of an image forming operation from an image forming apparatus (not shown), the surface of the fixing roll 10 is heated to a predetermined temperature by the halogen heater 14, and the fixing roll 10 starts rotating in the direction of the arrow. In synchronization with this, the endless belt 30 starts rotating in the direction of the arrow following the fixing roll 10 while being stretched over the three support rolls 20, 21, and 22. Further, the heat belt 51 of the external heating member 50 starts rotating in the direction of the arrow following the fixing roll 10 while being stretched over the heat rolls 52 and 53 and the metal roll 54.
[0031]
At this time, the endless belt 30 rotates in a state where a nip N is formed between the endless belt 30 and the fixing roll 10 by the support by the support rolls 20 and 21 and the pressing by the pressure applying member 40. Then, the recording paper 35 carrying the toner image is conveyed to and passed through the nip N, so that the toner constituting the toner image is heated and pressurized and fixed on the recording paper 35. After passing through the region of the elastic layer 12 of the fixing roll 10 which is elastically deformed by the pressing of the support roll 20, the recording paper 35 after the fixing process is naturally separated from the surface of the fixing roll 10 without using a peeling device. Is discharged to the paper discharge guide 28.
[0032]
On the other hand, in the external heating member 50, heat is transmitted to the heat belt 51 by heating of the heat rolls 52 and 53, and further, heat is supplied to the fixing roll 10. Specifically, in the heat rolls 52 and 53, the heat belt 51 is heated to 175 ° C., which is higher than the surface temperature 160 ° C. of the fixing roll 10 by 15 °. The heated heat belt 51 can supply heat to the fixing roll 10 and quickly recover the surface temperature of the fixing roll 10 to a predetermined temperature.
[0033]
That is, when the recording paper 35 carrying the unfixed toner image is heated and fixed at the nip N, the heat is taken away by the recording paper 35, and after the fixing roll 10 passes through the nip N, the fixing roll 10 Surface temperature decreases. In particular, when printing is performed continuously, or when printing thick paper or an OHP sheet having a large heat capacity, the surface temperature of the fixing roll 10 significantly decreases. On the other hand, in the image fixing device 1 according to the present embodiment, the heat belt 51 heated by the external heating member 50 is separated from the surface of the fixing roll 10 in the longitudinal direction having a length L in the outer circumferential direction of the fixing roll 10. Since the contact is made in the belt-like region extending over the belt, it is possible to immediately and sufficiently supply heat to the fixing roll 10. For this reason, even if the temperature of the fixing roll 10 decreases after passing through the nip N, the heat is sufficiently transmitted from the external heating member 50 during one rotation of the fixing roll 10, so that the heat reaches the nip N again. During this time, the temperature of the fixing roll 10 can be restored to a predetermined temperature. Therefore, sufficient fixability can be obtained even when printing continuously or when printing thick paper or an OHP sheet.
[0034]
Here, FIG. 4 is a diagram showing a change in the surface temperature of the fixing roll 10 from the start when the external heating member 50 is provided and when the external heating member 50 is not provided. As shown in FIG. 4, when the external heating member 50 is not provided, the surface temperature of the fixing roll 10 gradually decreases as the printing operation is repeated, but when the external heating member 50 is provided. Even if the printing operation is repeated, the surface temperature of the fixing roll 10 can be stabilized at approximately 190 ° C.
[0035]
Also, by changing the amount of heat for heating the heat belt 51, the gloss of the fixed image on the recording paper 35 can be adjusted. As the amount of heat applied to the heat belt 51 increases, the gloss of the fixed image can be increased. For example, as the halogen heaters 55 and 56 provided on the heat rolls 52 and 53, heaters of 500 W each are provided and the heat belt 51 is heated with a total heat of 1 kW, and heaters of 1 kW are provided respectively. In comparison with the case where the heat belt 51 was heated with a total amount of heat of 2 kW, the gloss on the mirror-coated paper could be obtained by 20 different by the 75-degree method with 2 kW than with 1 kW. Further, a constant gloss can be obtained at the leading end and the trailing end of the recording paper 35, and the entire fixed image can be formed with flat gloss.
[0036]
Therefore, it is possible to adjust the fixed image to a desired gloss by selecting the rating of the halogen heaters 55 and 56 or making the supplied power variable. Further, by adjusting the power supplied to the halogen heaters 55 and 56 according to the type of the recording paper 35 as the recording material, the amount of heat generated by the heat rolls 52 and 53 can be controlled to adjust the gloss of the fixed image. It is possible.
[0037]
In the present embodiment, the halogen heater 56 is provided on the heat roll 53, but may be omitted. On the other hand, the metal roll 54 is not provided with a halogen heater, but may be provided.
Further, in the present embodiment, the heat belt 51 is stretched by three rolls of the heat rolls 52 and 53 and the metal roll 54, but is not limited to this. That is, it may be stretched by three or more rolls, and the number of rolls on which the halogen heater is provided can be set as appropriate.
[0038]
Further, the external heating member 50 is configured such that the heat belt 51 is in contact with the surface of the fixing roll 10 in a belt-shaped region having a length L in the outer circumferential direction of the fixing roll 10 and extending in the longitudinal direction. The belt 51 may be configured such that a part of the belt 51 facing the fixing roll 10 is provided with a region that is not in contact with the fixing roll 10. Further, it is preferable that the contact area between the heat belt 51 and the fixing roll 10 is configured to be as large as possible in order to form a large heat transfer area. In addition, it is preferable that the external heating member 50 be disposed near the nip N on the upstream side in the rotation direction of the fixing roll 10 so that the heat supplied to the fixing roll 10 is not lost by radiation. Further, a plurality of external heating members 50 including at least one heat roll 52 and a heat belt 51 stretched by at least two rolls may be provided around the fixing roll 10.
[0039]
◎ Embodiment 2
In the first embodiment, heat rolls 52 and 53 are disposed inside a heat belt 51 that is driven by the fixing roll 10 while being in contact with the fixing roll 10, and the heat belt 51 is heated, so that the heat belt 51 is The image fixing apparatus 1 provided with the external heating member 50 for supplying heat to the fixing roll 10 while making contact with the surface of the fixing roll 10 in a belt-shaped region having a length L in the outer circumferential direction and having a length L in the longitudinal direction has been described. . In the second embodiment, external heating that supplies heat to a belt-shaped region having a length L in the outer circumferential direction of the fixing roll 10 by radiation from a heating element arranged in non-contact with the fixing roll 10. The image fixing device 2 including the member 70 will be described. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.
[0040]
FIG. 5 is a diagram illustrating an image fixing device according to the present embodiment. The image fixing device 2 includes a fixing roll 10 having a built-in heating source, an endless belt 30 that is driven while being pressed against the fixing roll 10, and a predetermined range of the endless belt 30 facing the fixing roll 10 from the belt inner peripheral surface side. The fixing device includes a pressure applying member 40 that contacts and presses, a guide 47 that supports the endless belt 30, and an external heating member 70 that externally heats the fixing roll 10.
The endless belt 30 runs around the guide 47 in accordance with the driving force caused by friction with the fixing roll 10. The portion of the nip N sandwiched between the fixing roll 10 and the pressure applying member 40 is deformed according to the deformation of both.
[0041]
The external heating member 70 includes three flash lamps 71 and a reflection plate 72. Part of the infrared light emitted from the flash lamp 71 directly irradiates the fixing roll 10, and part of the infrared light is reflected by the reflection plate 72 and collected on the fixing roll 10, and the outer periphery of the fixing roll 10 on the surface of the fixing roll 10. Infrared radiant heat is supplied to a band-like region extending in the longitudinal direction having a length L in the direction.
In the image fixing device 2 according to the present embodiment, the flash lamp 71 of the external heating member 70 is immediately applied to the belt-shaped region having the length L in the outer peripheral direction of the fixing roll 10 on the surface of the fixing roll 10. And it is possible to supply sufficient heat. For this reason, even if the temperature of the fixing roll 10 decreases after passing through the nip N, the heat is immediately and sufficiently supplied from the external heating member 70 during one rotation of the fixing roll 10, and the heat reaches the nip N again. By this time, the temperature of the fixing roll 10 can be restored to a predetermined temperature. Therefore, sufficient fixability can be obtained even when printing continuously or when printing thick paper or an OHP sheet.
Note that a light source that emits infrared light such as a radiant or a halogen lamp can be used as a heat source in addition to a flash lamp.
[0042]
◎ Embodiment 3
Next, a color image forming apparatus including the image fixing device 1 according to the first embodiment will be described. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.
FIG. 6 shows a color image forming apparatus according to the present embodiment. The color image forming apparatus 100 includes four photosensitive drums 101A, 101B, 101C, and 101D arranged around an intermediate transfer belt 107. Each of the photosensitive drums 101A, 101B, 101C, and 101D, for example, a charger 102A that uniformly charges the photosensitive drum 101A around the photosensitive drum 101A, and an LED that exposes light controlled based on image information. A print head (LPH) 103A, a developing unit 120A for developing a latent image formed on the photosensitive drum 101A, a primary transfer roll 112A for transferring a toner image to the intermediate transfer belt 107, and a transfer residual toner from the photosensitive drum 101A And a static eliminator 106A for removing the remaining charge on the photosensitive drum 101A. Further, a secondary transfer roll 113 for transferring the toner image transferred on the intermediate transfer belt 107 to the recording paper 35, a paper transport belt 110 for transporting the recording paper 35, and a fixing device for fixing the toner image on the recording paper 35 1 is provided. In addition, the periphery of the photosensitive drums 101B, 101C, and 101D has the same configuration.
[0043]
The charger 102A is formed of a conductive roll or a charging roll formed by laminating a conductive sponge and a conductive rubber, and is connected to a power supply (not shown) and supplied with a voltage. Then, the surface of the photosensitive drum 101A is uniformly charged at a constant voltage. The LPH 103A irradiates light controlled based on image data from a host computer (not shown) to form a latent image on the photosensitive drum 101A.
[0044]
The developing device 120A transports the developer, in which the toner and the carrier as the magnetic particles are mixed, to the photosensitive drum 101A while supporting the developer on the developer carrying member, and converts the latent image formed on the photosensitive drum 101A to yellow. Develop with the toner of (Y) to form a toner image. The developing devices 120B, 120C, and 120D are provided with developers using magenta (M), cyan (C), and black (K) toners, respectively. , K are formed.
[0045]
The primary transfer roll 112A is formed by laminating a conductive rubber or a conductive sponge and a conductive rubber, and is connected to a power supply (not shown) and supplied with a voltage. Then, the toner image is transferred onto the intermediate transfer belt 107. The cleaner 105A includes a cleaning blade and a cleaner housing. The cleaning blade abuts in the counter direction with respect to the rotation direction of the photosensitive drum 101A, scrapes off the transfer residual toner remaining on the photosensitive drum 101A at the time of transfer, and stores it in the cleaner housing.
[0046]
The static eliminator 106A is formed by laminating conductive rubber or conductive sponge and conductive rubber, and is connected to a power supply (not shown) and supplied with a voltage. Then, the electric charge remaining on the photosensitive drum 101A is removed, and the surface potential on the photosensitive drum 101A is made uniform to almost 0V. The intermediate transfer belt 107 is made of a flexible film such as polyimide, and moves while being held between the photosensitive drums 101A to 101D and the primary transfer rolls 112A to 112D. Then, the Y, M, C, and K toner images formed on the respective photosensitive drums 101A to 101D are transferred onto the intermediate transfer belt 107 by the primary transfer rolls 112A to 112D while being aligned by the registration sensor 108. Synthesized.
[0047]
The color toner image transferred to and synthesized on the intermediate transfer belt 107 is collectively transferred to the recording paper 35 by the secondary transfer roll 113. Then, the recording paper 35 is transported to the fixing device 1 by the paper transport belt 110. The toner remaining on the intermediate transfer belt 7 as transfer residue is removed by the cleaner 114.
[0048]
When the fixing device 1 receives the start signal of the image forming operation from the image forming apparatus 100, the surface of the fixing roll 10 is heated to the predetermined temperature by the heating of the halogen heater 14, and the fixing roll 10 starts rotating in the direction of the arrow. In synchronization with this, the endless belt 30 starts rotating in the direction of the arrow following the fixing roll 10 while being stretched over the three support rolls 20, 21, and 22. On the other hand, the color toner images formed on the respective photosensitive drums 101A to 101D are transferred onto the recording paper 35 and synthesized. Then, the recording paper 35 is conveyed to the fixing device 1.
[0049]
At this time, the endless belt 30 rotates in a state where a nip N is formed between the endless belt 30 and the fixing roll 10 by the support by the support rolls 20 and 21 and the pressing by the pressure applying member 40. Then, the recording paper 35 carrying the toner image is conveyed to and passed through the nip N, so that the color toner image is heated and pressed and fixed on the recording paper 35 to form a color image.
[0050]
Here, in the external heating member 50, heat is transmitted to the heat belt 51 by heating the heat rolls 52 and 53, and further, heat is supplied to the fixing roll 10. Since the heat belt 51 of the external heating member 50 comes into contact with the surface of the fixing roll 10 in a belt-like region having a length L in the outer peripheral direction of the fixing roll 10 and extending in the longitudinal direction, the heat belt 51 contacts the fixing roll 10 immediately and immediately. It is possible to supply sufficient heat. For this reason, even if the temperature of the fixing roll 10 decreases after passing through the nip N, the heat is sufficiently transmitted from the external heating member 50 during one rotation of the fixing roll 10, so that the heat reaches the nip N again. During this time, the temperature of the fixing roll 10 can be restored to a predetermined temperature. Therefore, even when printing continuously or when printing thick paper having a large heat capacity, a sufficiently fixed color image can be formed without reducing the process speed of the image forming apparatus 100.
[0051]
Also, by changing the amount of heat for heating the heat belt 51, the gloss of the fixed image on the recording paper 35 can be adjusted. As the amount of heat applied to the heat belt 51 increases, the gloss of the fixed image can be increased. . Further, uniform gloss can be obtained on the entire surface including the leading end and the trailing end of the recording paper 35, and the entire fixed image can be formed with flat gloss. Further, by adjusting the power supplied to the halogen heaters 55 and 56 according to the type of the recording paper as the recording material, the amount of heat generated by the heat rolls 52 and 53 can be controlled to adjust the gloss of the fixed image. It is.
The same effect can be obtained not only in the color image forming apparatus of the present embodiment but also in an image forming apparatus that forms a black and white image.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to supply a sufficient amount of heat to the recording paper and to stabilize the fixability of the toner image.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an image fixing device.
FIG. 2 is a diagram illustrating a pressure applying member.
FIG. 3 is a cross-sectional view illustrating a deviation prevention member.
FIG. 4 is a diagram showing a change in the surface temperature of a fixing roll from the time of startup.
FIG. 5 is a diagram illustrating an image fixing device.
FIG. 6 is a diagram illustrating a color image forming apparatus.
FIG. 7 is a diagram illustrating a conventional image fixing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fixing roll, 14 ... Halogen heater, 15 ... Temperature sensor, 20, 21, 22 ... Support roll, 24 ... Cleaning roll, 30 ... Endless belt, 40 ... Pressure applying member, 50 ... External heating member, 51 ... Heat belt , 52, 53: Heat roll, 54: Metal roll, 55, 56: Halogen heater, 60: Deviation prevention member, 61: Tension roll, 62: Bearing, 63: Support, 64: Positioning member, 70: External heating Member, 71: flash lamp, 72: reflector

Claims (14)

Rotatable fixing means for fixing an unfixed image formed on the recording material,
Pressing means for pressing the fixing means,
An image fixing apparatus, comprising: an external heating unit that externally heats a band-shaped region extending in a longitudinal direction having a length in a peripheral direction of the fixing unit on a surface of the fixing unit. 2. The image fixing apparatus according to claim 1, wherein the external heating unit is arranged to heat the belt-shaped region having a length of 5 mm or more in an outer peripheral direction of the fixing unit. 2. The image fixing device according to claim 1, wherein the external heating unit is disposed so as to be in contact with the fixing unit in the band-shaped region. 4. The image fixing device according to claim 3, wherein the external heating unit is configured to be able to contact and separate from the fixing unit. 2. The image fixing device according to claim 1, wherein a plurality of the external heating units are provided. 2. The image fixing device according to claim 1, wherein the external heating unit is disposed in non-contact with the fixing unit. The image fixing device according to claim 6, wherein the external heating unit includes a heating element that radiates infrared rays. A rotatable fixing roll for fixing an unfixed image formed on the recording material,
A pressure member that presses the fixing unit,
An image fixing device, comprising: an external heating belt that is stretched by a plurality of rolls, contacts the surface of the fixing roll at a predetermined area, and heats the fixing roll from the outside. 9. The image fixing device according to claim 8, wherein the external heating belt is supplied with heat from a heating element disposed on one or more of the plurality of rolls. 9. The image fixing device according to claim 8, wherein the external heating belt further includes a deviation preventing member that prevents deviation of the belt. 9. The image fixing device according to claim 8, wherein the external heating belt is configured to be able to contact and separate from the fixing unit. Unfixed image forming means for forming an unfixed image according to image information on a recording material,
A rotatable fixing member for fixing an unfixed image formed on the recording material, a pressing member for pressing the fixing member, and a length on the surface of the fixing member in the outer circumferential direction of the fixing unit. And an external heating member for externally heating the belt-shaped region extending in the longitudinal direction. 13. The image forming apparatus according to claim 12, wherein the image fixing unit is configured to change a calorific value of a heating element disposed on the external heating member. 14. The image forming apparatus according to claim 13, wherein in the image fixing unit, the external heating member is configured to change the amount of heat of the heating element according to the recording material.

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