JP4207558B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device of a type in which a recording sheet carrying a toner image to be fixed is pressed while being in close contact with a heated and rotating endless fixing belt, and then peeled off. The present invention relates to a fixing device capable of performing high-speed fixing by quickly and accurately heating a belt to a desired fixing temperature.
[0002]
[Prior art]
In recent years, as a fixing device used in an image forming apparatus such as a printer, a copying machine, or a multi-function printer using an electrophotographic method, an electrostatic recording method, etc., a rotating and tensioning fixing belt is used. A type of belt that is heated and heated while the recording paper carrying an unfixed toner image is pressed against the belt surface and is kept in close contact with the belt surface, and is cooled by cooling means and then peeled off from the belt. Fixing devices have been proposed (Patent Documents 1, 2, and 3).
[0003]
According to this type of fixing device, the toner image on the recording paper follows the smooth surface of the fixing belt, and after being cooled and solidified with the surface being smooth, is peeled off from the fixing belt side. Excellent fixed images can be obtained. Further, since the toner is peeled off from the fixing belt after being cooled and solidified, the toner is less likely to be offset to the fixing belt.
[0004]
[Patent Document 1]
JP-A-5-72926
[Patent Document 2]
Japanese Unexamined Patent Publication No. 7-2110019
[Patent Document 3]
JP 2002-99158 A
[0005]
[Problems to be solved by the invention]
However, the fixing device having such a fixing belt and cooling means has the following problems.
[0006]
That is, in such a fixing device, there are various obstacles when trying to realize faster fixing (for example, a fixing processing speed of 60 sheets per minute or more when using recording paper such as plain paper). Have difficulty.
[0007]
For example, in order to realize the high-speed fixing, the fixing belt that has passed through the cooling means and has been cooled to about the softening temperature of the toner can be fastened to the melting temperature of the toner in a short time for the next fixing. Must be heated rapidly. However, in the conventional fixing device, the heating of the fixing belt is simultaneously performed in the pressurizing unit with the recording paper (Patent Documents 1 and 2), and in addition, the belt on the upstream side in the belt rotation direction from the pressurizing unit. Since the form (patent document 3) performed from the inner peripheral surface side is adopted, such a quick heating cannot be handled.
[0008]
In particular, if the outer peripheral surface of the fixing belt is to be heated to a sufficient temperature, a temperature difference in the thickness direction of the belt is likely to occur or it is difficult to heat the belt without excess or deficiency. In addition, since the inner circumferential surface of the fixing belt becomes too hot and the recording paper is heated more than necessary even after passing through the pressure unit, excessive water vapor is generated from the paper. The paper stays at the interface with the fixing belt, so that the paper is partially peeled off from the fixing belt, and the paper (toner image) portion cannot sufficiently follow the smooth flat surface of the fixing belt, resulting in uneven gloss. There is a case. The latter problem occurs more significantly when heated rapidly in the pressurizing section. Also, the fixing belt passes through the pressure part did If the recording paper and the toner image are kept at a high temperature afterwards, the recording paper and the toner image cannot be sufficiently cooled by the cooling means, and it is difficult to peel off the fixing belt from the fixing belt particularly with a thin recording paper.
[0009]
In order to avoid these problems, the rotational movement speed of the fixing belt may be set to a sufficiently low speed, but this makes high-speed fixing impossible. Although it is conceivable to reduce the thickness of the fixing belt, in this case, sufficient strength as a fixing belt that rotates at high speed cannot be maintained, and wrinkles are easily generated in the fixing belt. Rich settlement is impossible.
[0010]
The present invention has been made in view of such circumstances, and the main object of the present invention is to fix a fixing belt to a desired fixing without inducing problems such as uneven heating, uneven gloss, and poor paper peeling. It is an object of the present invention to provide a fixing device capable of performing high-speed fixing by heating quickly and accurately to a temperature.
[0011]
[Means for Solving the Problems]
The fixing device of the present invention (first invention) includes, as illustrated in FIG. 1 a, an endless fixing belt 2 that rotates in a fixed direction, a heating unit 3 that heats the fixing belt 2, and a heating unit 3. Pressurizing means 4 that presses the recording paper P carrying the toner image T to be fixed on the surface of the heated fixing belt 2, and the recording paper that is pressed by the pressing means 4 and remains in close contact with the fixing belt 2 On the premise of the fixing device 1 provided with a cooling means 5 for cooling P and a paper peeling means 6 for peeling the recording paper P from the fixing belt 2 after passing through the cooling means 5, the heating means 3 is a fixing belt. 1 and at least one inner heating means 3A for heating from the inner peripheral surface side of the belt, and 1 for heating from the outer peripheral surface side of the belt. With the above outer heating means 3B It is characterized in that. A one-dot chain line with an arrow in the figure indicates a general conveyance path of the recording paper P.
[0012]
According to the fixing device 1 of the first invention as described above, the fixing belt 2 after passing through the sheet peeling means 6 and completing the fixing operation 1 is inside in the section E1 until it reaches the pressure means 4 again. Heating is performed from both the inner and outer peripheral surfaces of the belt by the heating means 3A and the outer heating means 3B. As a result, before the recording paper P to be subsequently fixed reaches the fixing nip portion between the fixing belt 2 and the pressurizing unit 4, the fixing belt 2 which has passed through the cooling unit 5 and is in a low temperature state is again desired. As a result, the fixing belt 2 can be efficiently heated to the fixing temperature, and as a result, the fixing belt 2 can be rotated at high speed to perform high-speed fixing.
[0013]
In addition, since the fixing belt 2 can be heated to a desired fixing temperature in a stage before reaching the fixing nip portion, it is not particularly necessary to heat the fixing belt 2 at the fixing nip portion. There is no risk of heating, and the paper does not peel off from the belt surface due to excessive water vapor generation.
[0014]
Here, the positional relationship of the heating means 3A, 3B with respect to the rotational movement direction of the fixing belt is not particularly limited because there are a positional relationship shifted forward and backward with respect to the rotational movement direction, the same position facing each other, and the like. . With respect to this positional relationship, from the standpoint that the final adjustment of the heating state of the fixing belt 2 can be performed quickly and accurately, at least one outside of the heating means 3A and 3B is disposed. It is preferable to arrange the heating means 3B at the most downstream position in the belt rotational movement direction.
[0015]
Also, high-speed fixing means that, for example, fixing using a recording sheet whose base material portion is composed of a synthetic resin sheet such as an OHP sheet or the like is 40 sheets per minute or more by A4 plate sheet lateral feed. This refers to fixing performed at a processing speed. For fixing using other recording papers and paper (pulp) sheets other than synthetic resin sheets, the A4 printing paper is fed at least 60 sheets per minute. Fixing performed at a processing speed. In the fixing device of the present invention, when fixing is performed using the recording paper other than the above, the fixing processing speed can be set to the same speed regardless of conditions such as the type and thickness of the paper. preferable. This makes it possible to perform more ideal high-speed fixing.
[0016]
In the fixing device 1 according to the first aspect of the present invention, the temperature detecting means 7 for detecting the temperature of the portion of the fixing belt 2 before contacting the recording paper P is installed, and the outside heating is performed according to the detection information of the temperature detecting means 7. It is good to comprise so that the heating operation of the means 3B may be controlled.
[0017]
In this case, as a result of appropriately adjusting the heating temperature on the outer peripheral surface of the fixing belt 2 by the outer heating means 3B, the fixing belt 2 arrives at the fixing nip portion in a state where the fixing belt 2 is heated to a desired fixing temperature quickly and accurately. It becomes like this. The portion of the fixing belt 2 before coming into contact with the recording paper P is a position on the near side where the fixing belt 2 reaches the fixing nip portion, and at least the state in which the fixing belt 2 is heated by the heating means 3 is defined as the fixing nip portion. Any position can be used as long as it can be finally confirmed immediately before reaching.
[0018]
Further, in each of the fixing devices 1 of the first invention, it is preferable that the outer heating unit 3B is a non-contact type heating unit that heats the fixing belt 2 in a non-contact state.
[0019]
In this case, as compared with the contact-type heating unit that heats the fixing belt 1 in contact, it is possible to avoid damaging the outer peripheral surface that affects the fixing result of the fixing belt 2, and the heating unit 3B is reached. The heating means 3B can be appropriately heated without being directly affected by the low temperature state of the outer peripheral surface of the fixing belt 2, which is advantageous for high-speed fixing.
[0020]
Further, in each of the fixing devices 1 of the first invention, the temperature detecting means 8 for detecting the temperature of the portion of the fixing belt 2 after passing through the paper peeling means 6 is installed, and the detection information of the temperature detecting means 8 is included. Accordingly, the cooling operation of the cooling means 6 may be controlled.
[0021]
In this case, the temperature state of the fixing belt 2 when reaching the sheet peeling means 6 is appropriately managed by adjusting the cooling operation (cooling capacity, presence / absence of cooling, etc.). As a result, even if the fixing belt 2 is kept at a high temperature even after passing through the fixing nip portion, the cooling belt is appropriately cooled by the cooling means. However, since the cooling is appropriately performed until the paper peeling means 6 is reached, good peeling from the fixing belt 2 is ensured.
[0022]
On the other hand, the fixing device of the present invention (second invention) is the fixing device 1 as a premise of the first invention as shown in FIG. Adjusting heating means 3C for adjusting and heating the belt 2 disposed at a position on the near side reaching, and powerful heating for strongly heating the belt 2 disposed at a position upstream of the adjusting heating means 3C in the belt rotation direction And means 3D.
[0023]
According to the fixing device 1 of the second invention as described above, at least within the section E1 until the fixing belt 2 after passing through the sheet peeling means 6 and completing the fixing operation 1 reaches the pressure means 4 again. After being heated strongly by the strong heating means 3D, it is adjusted and heated by the adjustment heating means 3C. As a result, before the recording paper P to be subsequently fixed reaches the fixing nip portion between the fixing belt 2 and the pressurizing unit 4, the fixing belt 2 which has passed through the cooling unit 5 and is in a low temperature state is again desired. The fixing temperature can be efficiently and accurately heated. As a result, the fixing belt 2 can be rotated at high speed to perform high-speed fixing.
[0024]
Further, as in the case of the fixing device of the first invention, the fixing belt 2 can be heated to a desired fixing temperature at a stage before reaching the fixing nip portion. Further, there is no possibility that the recording paper is heated more than necessary when it passes through the fixing nip portion, and the paper does not peel off from the belt surface due to excessive water vapor generation.
[0025]
Here, the heating means 3C, 3D is not particularly limited as to which side is heated from the outer peripheral surface and the inner peripheral surface of the fixing belt 2 (or both surfaces thereof). However, from the standpoint that the final adjustment of the heating state of the fixing belt 2 can be performed quickly and accurately, the adjustment heating means 3C is configured to be heated at least from the outer peripheral surface side of the fixing belt 2. It is preferable.
[0026]
In the fixing device 1 according to the second aspect of the present invention, the temperature detecting means 7 for detecting the temperature of the outer peripheral surface portion of the fixing belt 2 before contacting the recording paper P is provided, and the temperature detecting means 7 is arranged according to the detection information of the temperature detecting means 7. It is good to comprise so that the heating operation of the adjustment heating means 3C may be controlled.
[0027]
In this case, as a result of appropriately adjusting the heating temperature on the outer peripheral surface of the fixing belt 2 by the adjusting heating unit 3C, the fixing belt 2 arrives at the fixing nip portion in a state where the fixing belt 2 is heated to a desired fixing temperature quickly and accurately. It becomes like this. The portion of the fixing belt 2 before coming into contact with the recording paper P is the same as that in the first invention described above.
[0028]
Further, in each of the fixing devices 1 of the second invention, the adjustment heating unit 3C is preferably a non-contact type heating unit that heats the fixing belt 2 in a non-contact state.
[0029]
In this case, as in the case of the first invention described above, it is possible to avoid damaging the outer peripheral surface that affects the fixing result of the fixing belt 2 as compared with the contact heating unit, and the adjustment heating unit 3C The heating means 3C can be appropriately heated without being directly affected by the low temperature state of the outer circumferential surface of the fixing belt 2 that arrives, which is advantageous for high-speed fixing.
[0030]
Further, in each of the fixing devices 1 of the second invention, the temperature detecting means 8 for detecting the temperature of the portion of the fixing belt 2 after passing through the paper peeling means 6 is installed, and the detection information of the temperature detecting means 8 is included. Accordingly, the cooling operation of the cooling means 6 may be controlled. In this case, the same effects as those in the first invention described above can be obtained.
[0031]
In the first and second inventions described above, the recording paper is not limited to ordinary paper as long as the recording paper can be conveyed in the fixing device and can fix the toner image, and is not limited to normal paper. Such a member is included. The toner constituting the toner image is a fine powder made of a binder resin containing a colorant or the like, and is generally used as a one-component or two-component developer.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
FIG. 2 is a schematic configuration diagram showing a main part of the fixing device 10 according to the first embodiment of the present invention. The fixing device 10 is used as a fixing unit in an image forming apparatus such as a printer or a copying machine. Solid arrows in the figure indicate the rotation directions of the main rotating parts.
[0033]
The fixing device 10 includes an endless fixing belt 20 that rotates in the direction of an arrow, heating rolls 30 and 31 that heat the fixing belt, and a predetermined distance in the same direction while being pressed against the surface of the fixing belt 20 to be heated. The endless pressure belt 40 that rotates in a straight line and the heat circulator 50 that is disposed in the inner peripheral surface of the fixing belt 20 constitute the main part.
[0034]
The fixing belt 20 further includes an elastic layer made of a silicone copolymer (hardness: for example, 24 °) having a thickness of about 60 μm on a belt base material having a thickness of about 50 μm made of polyimide or the like containing carbon black. A surface release layer having a thickness of about 1 to 100 μm made of a synthetic resin exhibiting releasability is formed in this order as necessary. As a belt base material, it is possible to use a sheet material having a high heat resistance generally having a thickness of 10 to 100 μm. From a polyester, polyethylene terephthalate, polyethersulfone, polyetherketone, polysulfone, polyimideamide, polyamide, etc. Can be used. As the synthetic resin for forming the surface release layer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polytetrafluoroethylene, and the like are applicable.
[0035]
The fixing belt 20 is stretched around the first heating roll 30, the second heating roll 31, the first pressure roll 45, the plurality of belt support rolls 27a to 27e, and the like, and is also used as a driving roll. One heating roll 30 rotates in the direction of arrow A. The belt 20 has a circumference of about 1300 mm and a width of about 360 mm.
[0036]
The belt support roll 27c supports the fixing belt 20 so that the fixing belt 20 moves while being bent sharply, and thereby plays a role of peeling the recording paper P in close contact with the fixing belt 20 by its own strength. Functions as a peeling roll. The second heating roll 31 functions as a steering roll that corrects meandering travel (position) of the fixing belt 20 by displacing one end side of the rotation shaft in a predetermined direction. The meandering control mechanism using the second heating roll 31 operates to displace one end of the heating roll 31 by a predetermined amount based on detection information from a position measurement sensor that detects the position of the end of the fixing belt 20.
[0037]
The first heating roll 30 has a structure in which a heating source 32 such as a halogen lamp is arranged inside a cylindrical metal (aluminum or the like) roll having an outer diameter of 50 to 60 mm. Heat from the inner surface. In addition, the first heating roll 30 is configured to use a larger number or a higher heating capability as the heating source 32 than the second heating roll 31 so that the fixing belt 2 can be heated strongly. In this example, three halogen lamps are installed as the heating source 32 to enhance the heating capacity.
[0038]
The second heating roll 31 has a structure in which a heating source 33 such as a halogen lamp is disposed inside a cylindrical metal roll having an outer diameter of 80 to 100 mm, and the fixing belt 20 is arranged from the outer peripheral surface side. Heat. Further, the second heating roll 31 is configured to use, for example, a small number or a lower heating capability as the heating source 33 compared to the first heating roll 30 so that the fixing belt 2 can be heated while being finely adjusted. Has been. In this example, two halogen lamps are installed as the heat source 33.
[0039]
The fixing belt 20 is looped around the first heating roll 30 and the second heating roll 31 in an S shape so as to secure as many wrap areas as possible with the respective heating rolls 30 and 31. Efficient heating by the heating rolls 30 and 31 is performed. Further, a winding web type release agent supply device 60 is disposed on the surface of the second heating roll 31, and the release agent such as silicone oil impregnated in the web 61 covers the surface of the heating roll 31. Thus, a very small amount (“1 μl / A4 size sheet” or less) is supplied to the outer peripheral surface of the fixing belt 20.
[0040]
The pressure belt 40 has an elastic layer of about 45 μm thickness made of silicone rubber or the like on a belt base material of about 80 μm thickness made of polyimide or the like, and a surface release layer made of synthetic resin or the like if necessary. The structure is formed by stacking in this order. This surface release layer is formed of a synthetic resin, for example, a silicone resin, which exhibits good release properties, particularly for both the recording paper P and the surface release layer 23 of the fixing belt 20. The belt 40 has a circumference of about 900 mm and a width of about 360 mm. The pressure belt 40 is stretched around a second pressure roll 46, a drive roll 47, a plurality of belt support rolls 48a to 48c, and the like, and is rotated by the drive roll 47 in the arrow B direction. . The pressure belt 40 rotates in the same direction in contact with the outer peripheral surface of the fixing belt 20 in a predetermined section between the second pressure roll 46 and the belt support roll 48a.
[0041]
Each of the pressure rolls 45 and 46 is a heat resistant elastic layer having a thickness of about 6 mm made of silicone rubber (hardness: about 17 degrees) or the like on a cylindrical metal (aluminum etc.) roll base having an outer shape of 80 mm or the like. And a predetermined pressurizing force (for example, a nip pressure of 3.5 × 10 6 by a pressurizing mechanism not shown). ^Five It is installed so that its nip width is about 20 mm. In addition, the pressure rolls 45 and 46 are provided with a heating source such as a halogen lamp in the internal space, and perform heating only during so-called warm-up that raises the roll to the temperature during the fixing operation (heating during the fixing operation). Do not).
[0042]
The drive roll 47 functions as a steering roll for correcting the meandering travel of the pressure belt 40 by displacing one end side of the rotation shaft. The meandering control mechanism using the drive roll 47 operates based on detection information from a position measurement sensor that detects the position of the end of the pressure conveying belt 40 as in the meandering control mechanism using the second heating roll 31. To do.
[0043]
The heat circulator 50 includes a first metal plate 51 that contacts the inner peripheral surface of the fixing belt 20 within a predetermined interval between the first pressure roll 45 and the belt support roll 27c, a belt support roll 27e, and a first heating roll. 30, the second metal plate 52 that is in contact with the inner peripheral surface of the fixing belt 20, and the first metal plate 51 and the second metal plate 52, and heat of the first metal plate 51 is transferred to the second metal plate 52. It is comprised with the heat transport body 53 made to move and circulate.
[0044]
Each of the metal plates 51 and 52 is a plate formed of a metal such as aluminum, and the belt contact surface protrudes at least outward and is a curved surface gently curved in the belt running direction (from a predetermined radius of curvature). A curved surface). For this reason, the fixing belt 20 is held in a state where it is curved toward the outer peripheral surface side by the contact of the metal plates 51 and 52 (FIG. 2). As the heat transporter 53, a plurality of heat pipes are used in which a liquid is decompressed and sealed in a tube, and the heat resistance is very small, and a large amount of heat can be transported to a low temperature side even at a small temperature difference. Yes. The heat pipe is used by being assembled in a substantially rectangular annular shape that circulates between the plates while touching and passing the inner surfaces of the metal plates 51 and 52.
[0045]
When the heat circulator 50 takes heat from the fixing belt 20 in a state where the first metal plate 51 is heated, the heat is transferred to the first metal plate 51 by the heat conduction action of the heat pipe as the heat transporter 53. Is transmitted to the second metal plate 52 side in a low temperature state. Thus, the fixing belt portion in contact with the first metal plate 51 absorbs heat and is cooled to a predetermined temperature, while the fixing belt portion in contact with the second metal plate 52 is heated to a predetermined temperature.
[0046]
As described above, in the fixing device 10, the fixing belt 20 is heated during the fixing operation by the first metal plate 52 (first stage heating) and the first heating roll 30 (second stage heating) of the heat circulator 50. Heating) and the second heating roll 31 (third stage heating) are performed in this order by three heating means.
[0047]
In the fixing device 10, as shown in FIG. 2, a first temperature sensor 71 that detects the surface temperature of the first heating roll 30 and a second temperature sensor 72 that detects the surface temperature of the second heating roll 31. The heating operation of each heating roll 30, 31 is directly controlled according to the detection information of each sensor 71, 72.
[0048]
That is, as shown in FIG. 3, each of the temperature sensors 71 and 72 is connected to a system controller 75 composed of a microcomputer or the like that comprehensively manages and controls each operation of the entire fixing device 10, and detects each detection. Information (electrical signal) is transmitted. In the system controller 75 to which the detection information of the temperature sensors 71 and 72 is input, the heating sources 32 and 33 are held so as to be held at the heating temperatures preset for the heating rolls 30 and 31. Predetermined control signals relating to the heating operation are respectively transmitted to the first heating source controller 76 and the second heating source controller 77 for controlling the heating operation (power supply ON / OFF operation).
[0049]
In particular, in this embodiment, the first heating is performed so that the second stage heating by the first heating roll 30 can be performed more strongly (steeply) than the second stage heating by the first metal plate 52 of the heat circulator 50. The heating temperature of the roll 30 is set to a value (for example, a value that is higher by about 50 to 60 ° C.) than the heating temperature by the first metal plate 52.
[0050]
Further, in the fixing device 10, the fixing is performed such that the pressure rolls 45 and 46 pass between the belt support roll 27 b and the support roll 27 a before reaching the fixing nip portion where the pressure belt 45 and the pressure conveyance belt 40 are pressed against each other. A non-contact type third temperature sensor 70 for detecting the temperature of the outer peripheral surface of the belt 20 is disposed, and a second heating for adjustment heating is performed according to detection information of the sensor 70 (surface temperature of the fixing belt immediately before the fixing nip portion). The heating operation of the heating roll 31 is controlled twice.
[0051]
That is, as shown in FIG. 3, the third temperature sensor 70 is connected to the system controller 75 and transmits its detection information (electrical signal). In the system controller 80 to which the detection information of the temperature sensor 70 is input, the control signal for adjusting the heating operation is sent to the second heating source controller 77 so that the surface temperature of the fixing belt 20 becomes a desired fixing temperature. A predetermined control signal based on the detection information of the second temperature sensor 72 is transmitted together.
[0052]
Further, in the fixing using the OHP sheet, the fixing device 10 rotates the fixing belt 20 or the like so that a fixing processing speed of 40 sheets per minute is obtained by lateral feeding of A4 size paper, and other recording is performed. In fixing using paper, the fixing belt 20 and the like are set to rotate so that the fixing processing speed is 80 sheets per minute by A4 size paper lateral feed.
[0053]
In such a fixing device 10, fixing is performed as follows on the recording paper P onto which the toner image T has been transferred on the image forming unit side of the image forming apparatus.
[0054]
That is, first, the recording sheet P to which the toner image T has been transferred is in a posture in which the toner image carrying surface is in contact with the fixing belt 20, and the fixing nip while the fixing belt 20 and the pressure belt 40 are overlapped with each other. Part (belt nip part).
[0055]
During the fixing operation, the fixing belt 20 is heated through a plurality of stages as follows while rotating. First, the belt is heated from the belt inner peripheral surface side to a predetermined temperature by heat circulated when passing through the second metal plate 52 of the heat circulator 50, and then passes through the first heating roll 30. At that time, the belt is strongly heated from the belt inner peripheral surface side to a predetermined temperature, and finally adjusted and heated from the belt outer peripheral surface side to the fixing temperature when passing through the second heating roll 31.
[0056]
At this time, the heating operation of the first heating roll 30 and the second heating roll 31 is controlled according to each detection information of the first temperature sensor 71 and the second temperature sensor 72 as described above. Further, the fixing belt 20 is heated to a desired fixing temperature by controlling the heating operation of the second heating roll 31 according to the detection information of the third temperature sensor 70.
[0057]
Then, the recording paper P carrying the toner image is heated in contact with the heated fixing belt 20 at the fixing nip portion, and at the same time, is pressed by the pressure rolls 45 and 46.
[0058]
Subsequently, the recording sheet P is sandwiched between the fixing belt 20 and the pressure belt 40 and conveyed while being in close contact with the fixing belt 20, and the first metal plate from which heat is removed by the thermal circulation of the thermal circulator 50. When passing through 51, the toner image and the toner image are cooled to a predetermined temperature. This cooling solidifies the toner image. The recording paper P that has passed through the first metal plate 51 of the heat circulator 50 is peeled off from the fixing belt 20 together with the toner image by the strength of the paper itself at the paper peeling portion constituted by the belt support roll 27c. The The peeled recording paper P is discharged out of the apparatus. As a result, the toner image is fixed on the recording paper.
[0059]
The image fixed in this manner is obtained as an image having a rich glossiness that is smoothed especially on the surface of the fixing belt 20. In addition, in the fixing device 10, the first metal plate 51 and the second metal plate 52 of the heat circulator 50 come into contact with the fixing belt 20 to perform good heat circulation, so that the temperature environment for the toner image is also improved. The image quality is improved.
[0060]
Further, in the fixing device 10, the fixing belt 20 cooled by the first metal plate 51 of the heat circulator 50 reaches the fixing nip portion, and the first metal plate 52 of the heat circulator 50 performs the first operation. Since the heating is sequentially performed in a plurality of times of the stage heating, the second stage heating by the first heating roll 30, and the third stage heating by the second heating roll 31, the heating is quickly performed again to the fixing temperature.
[0061]
In addition, since the heating at this time is first heated twice from the belt inner peripheral surface side and then from the belt outer peripheral surface side, there is almost no temperature difference in the thickness direction of the fixing belt 20. Heated uniformly and efficiently. In addition, the second heating by the first heating roll 30 causes a rapid heating to near the fixing temperature, and then the final heating is performed while adjusting the degree of heating by the second heating roll 30. Heated stably.
[0062]
Further, in this embodiment, the strong heating is performed by the first heating roll 30 relatively far from the fixing nip portion, and the fixing roll is not heated by the pressure rolls 45 and 46 when entering the fixing operation. The fixing belt 20 is not heated more than necessary at the nip portion. Thereby, there is no possibility that the recording paper P sandwiched and conveyed between the fixing belt 20 and the pressure conveying belt 40 is heated more than necessary and generates excessive water vapor, thereby peeling off the fixing belt 20.
[0063]
Therefore, with this fixing device 10, even if high-speed fixing is performed at the fixing processing speed as described above, it is possible to perform good fixing without causing problems such as uneven heating, uneven gloss, and poor paper peeling. It becomes.
[0064]
<Test>
Hereinafter, tests performed using the fixing device 10 will be described.
[0065]
As shown in FIG. 4, the heating temperature by the first metal plate 52 of the heat circulator 50, the heating temperature by the first heating roll 30, and the heating temperature by the second heating roll 31 are set and plural types of recording paper P are set. Were used, and high-speed fixing (fixing processing speed: 80 sheets per minute by A4 sideways feed) was performed, and fixing results (image quality, gloss, etc.) were examined (Example 1 and Comparative Example 1). The results are shown in FIG.
[0066]
The fixing temperature at this time was set to 175 ° C. Moreover, the cooling temperature by the 1st metal plate (cooling plate) 51 of the heat circulator 50 was set to 100 degrees C or less (preferably 90 degrees C or less). “S paper” as the recording paper is 56 gsm (gram per square meter) thin paper (made by Fuji Xerok), “J paper” is 82 gsm plain paper exclusively for color copying (made by Fuji Xerok), “coated paper” "Is 104.7 and 127.9 gsm coated paper (Oji Paper: OK Top Coated Paper), and" Platinum Paper "is 256 gsm high gloss coated paper (Oji Paper: Mirror Coated Platinum Paper).
[0067]
From the results shown in FIG. 4, it was possible to perform high-speed fixing with high gloss and no gloss unevenness in any of the S paper, J paper and coated paper with good image quality. On the other hand, when the heating temperature of the first heating roll 30 was set to about 130 ° C. (Comparative Example 1), there was no problem in the case of S paper, but fixing in the case of J paper and coated paper. Cold offset occurred due to insufficient temperature (insufficient fixing belt heating).
[0068]
In the case of this comparative example 1, the heating temperature (the temperature detected by the third temperature sensor 70) before the fixing nip portion of the fixing belt 20 was unstable (increase / decrease) with respect to the fixing temperature of 175 ° C. In particular, it was confirmed that the heating temperature in front of the fixing nip is about 15 ° C. lower than the fixing temperature in the initial fixing stage of up to several tens of sheets when performing continuous fixing. In contrast, in Example 1, even when continuous fixing is performed, the heating temperature before the fixing nip portion is within ± 5 ° C. with respect to the fixing temperature of 175 ° C. during all fixing operations including the initial stage. It has also been confirmed that the temperature is maintained.
[0069]
In Example 1, in the case of platinum paper, the amount of toner was large, and a cold offset occurred in a high density portion of multiple colors. Accordingly, the fixing temperature is changed to 185 ° C., and accordingly, the heating temperature of the second heating roll 31 is changed to 185 ° C., and the heating temperature of the first heating roll 30 is changed to 170-180 ° C. A test was performed (Example 2). As a result, it was possible to perform high-speed fixing with high gloss without unevenness and good gloss without unevenness.
[0070]
Moreover, while using an OHP sheet (Fuji Xerox Co., Ltd .: V556) and setting each heating temperature as shown in FIG. 5, high-speed fixing for an OHP sheet (fixing processing speed: 40 mm / min by A4 plate lateral feed) (Example 3). As a result, it was possible to perform high-speed fixing with high gloss without unevenness and good gloss without unevenness. On the other hand, when the heating temperature of the first heating roll 30 is set to about 130 to 140 ° C. (Comparative Example 2), the occurrence of cold offset at a high density of the toner image due to insufficient heating of the fixing belt and the light transmittance. Such as a drop in image quality (image darkening occurs during projection). Such a result is considered to be because the temperature of the fixing belt 20 in front of the fixing nip becomes unstable as in the case of Comparative Example 1.
[0071]
<< Embodiment 2 >>
FIG. 6 is a schematic configuration diagram showing a main part of the fixing device 10 according to Embodiment 2 of the present invention. The fixing device according to this embodiment has the same configuration as the fixing device 10 according to the first embodiment except that a non-contact type heating lamp 35 is used instead of the second heating roll 31. In the figure, components that are the same as those in the first embodiment are denoted by the same reference numerals.
[0072]
The non-contact type heating lamp 35 is a radiant heating device having a structure in which a lamp heating source 37 such as a halogen lamp is disposed inside a reflecting plate 36 having a reflecting surface toward the fixing belt 20. The heating lamp 35 is disposed at a predetermined distance on the outer peripheral surface side of the fixing belt 20 that passes between the first heating roll 30 and the support roll 27a.
[0073]
The heating lamp 35 is also used for adjusting and heating the fixing belt 20. For this reason, the heating operation of the heating lamp 35 is controlled in accordance with detection information from the third sensor 70 (FIG. 3). The control of the lamp heating source 37 of the heating lamp 35 is not based on the ON / OFF operation of the power supply, but is always in the ON state and the power supply amount (current or voltage) is changed.
[0074]
In the fixing device 10 to which such a non-contact type heating lamp 35 is applied, the outer peripheral surface of the fixing belt 10 may not be touched as compared with the contact type heating means such as the second heating roll 31, which may cause damage. Therefore, the smoothness of the belt surface can be maintained. For this reason, fixing with an excellent gloss feeling is achieved by fixing along the smooth surface of the fixing belt 20. Other than this, the same fixing performance as that of the fixing device 10 according to the first embodiment was obtained, and high-speed fixing was also possible.
[0075]
<< Embodiment 3 >>
FIG. 7 is a schematic configuration diagram showing a main part of the fixing device 10 according to the third embodiment of the present invention. The fixing device according to this embodiment has the same configuration as the fixing device 10 according to the first embodiment except that a heat sink 55 with air blow is used instead of the heat circulator 50. In this fixing device, the first stage heating by the second metal plate 52 is eliminated due to the non-use of the heat circulator 50, but the fixing belt 20 can be heated at a similar level. In the figure, components that are the same as those in the first embodiment are denoted by the same reference numerals.
[0076]
The heat sink 55 with blower includes a contact heat radiating plate portion 56 that abuts on the inner peripheral surface of the fixing belt 20 between the pressure roll 45 and the support roll 27 c, and a plurality of heat radiating fins 57 erected from the heat radiating plate portion 56. The air is blown from the blower fan 58 through a duct (a portion indicated by a two-dot chain line) between the heat sink body composed of the above and the heat radiation fins 57 of the heat sink. The lower surface of the contact heat radiating plate 56 is in contact with the inner peripheral surface of the fixing belt 20.
[0077]
In addition, the heat sink 55 is provided with a fourth temperature sensor 80 that detects the temperature of the outer peripheral surface of the fixing belt 20 that has passed through the belt support roll 27 c serving as a peeling roll, and a blower fan according to the detection information of the temperature sensor 80. 58 is controlled to adjust the cooling operation by the heat sink. The fourth temperature sensor 80 is connected to the system controller 75 as shown by a two-dot chain line in FIG. 3, and rotates the drive motor (ON / OFF operation, rotation speed, etc.) of the blower fan 58 from the system controller 75. A predetermined control signal is transmitted to the motor driver 86 to be controlled. The control at this time is performed so as to be maintained at a preset cooling temperature (for example, 100 ° C. or lower, preferably 90 ° C. or lower).
[0078]
In the fixing device 10 to which such a heat sink 55 with air blow is applied, the recording paper and the toner image are cooled by the heat sink 55 at a desired cooling temperature, so that thin paper is used as the recording paper. However, good peeling from the fixing belt 20 is possible, and as a result, high-speed fixing is also possible.
[0079]
In this embodiment, as shown by a two-dot chain line in FIG. 7, the fourth temperature sensor 80 is installed on the downstream side of the contact heat sink plate 56 of the heat sink body in the belt rotational movement direction. You may comprise so that temperature may be detected and the ventilation operation | movement of the ventilation fan 58 may be controlled based on this detection information.
[0080]
<< Other Embodiments >>
In the first to third embodiments, the pressure belt 40 may not be provided, and the first pressure roller 45 and the second pressure roller 46 may constitute a fixing device. Further, the cooling means may be installed on the belt inner peripheral surface side between the peeling support roll 27c and the support roll 27d.
[0081]
【The invention's effect】
As described above, according to the fixing device of the present invention, the fixing belt can be quickly and accurately heated to a desired fixing temperature without inducing problems such as uneven heating, uneven gloss, and paper peeling failure. Therefore, it is possible to perform fixing at a higher speed.
[Brief description of the drawings]
FIG. 1A is a conceptual diagram illustrating a fixing device according to a first invention, and FIG. 1B is a conceptual diagram illustrating a fixing device according to a second invention.
FIG. 2 is a schematic configuration diagram showing a main part of the fixing device according to the first embodiment.
FIG. 3 is a schematic block diagram illustrating a configuration of a main control system related to a fixing belt heating system.
FIG. 4 is a chart showing conditions and results of tests (Examples 1 and 2, Comparative Example 1).
FIG. 5 is a chart showing conditions and results of tests (Example 3, Comparative Example 2).
FIG. 6 is a schematic configuration diagram illustrating a main part of a fixing device according to a second embodiment.
FIG. 7 is a schematic configuration diagram illustrating a main part of a fixing device according to a third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,10 ... Fixing device, 2,20 ... Fixing belt, 3A ... Inner heating means, 3B ... Outer heating means, 3C ... Adjusting heating means, 3D ... Strong heating means, 4 ... Pressurizing means, 5 ... Cooling means, 6 ... paper peeling means, 7, 8 ... temperature detection means, 27c ... support roll, 30 ... first heating roll (inner heating means, strong heating means), 31 ... second heating roll (outer heating means, adjustment heating means), DESCRIPTION OF SYMBOLS 40 ... Pressurization conveyance belt (pressurization means), 50 ... Thermal circulator (heating means and cooling means), 55 ... Heat sink with ventilation (cooling means), 70 ... 3rd temperature sensor (temperature detection means), 80 ... 1st 4 temperature sensors (temperature detection means), T ... toner image, P ... recording paper, E1 ... section.

Claims (4)

An endless fixing belt rotating in a certain direction;
Heating means for heating the fixing belt;
The fixing belt after passing through the heating means is pressed against the outer peripheral surface of the fixing belt heated by the heating means by pressurizing a pressure roll disposed so as to sandwich the fixing belt from the outer peripheral surface and the inner peripheral surface . A pressurizing unit that presses a recording paper carrying a toner image to be fixed;
A cooling means for cooling the recording paper that is pressed against the pressure belt and kept in close contact with the fixing belt;
In a fixing device comprising a paper peeling means for peeling the recording paper from the fixing belt after passing through the cooling means,
One or more inner heating means for heating from the belt inner peripheral surface side and heating from the belt outer peripheral surface side in the section from the passage of the fixing belt through the sheet peeling means to the pressure means. And a fixing device having one or more outer heating means.   2. The fixing according to claim 1, further comprising a temperature detecting unit configured to detect a temperature of a portion of the fixing belt before contacting the recording paper, and controlling a heating operation of the outer heating unit according to detection information of the temperature detecting unit. apparatus.   The fixing device according to claim 1, wherein the outer heating unit is a non-contact type heating unit that heats the fixing belt in a non-contact state.   The temperature detection means for detecting the temperature of the portion of the fixing belt after passing through the paper peeling means is installed, and the cooling operation of the cooling means is controlled according to the detection information of the temperature detection means. The fixing device described.

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