JP3818809B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device provided in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine. In particular, even when the type of transfer paper is changed, an appropriate amount of heat can be obtained only by switching the nip width. The present invention relates to a fixing device of an image forming apparatus that can perform image processing.
[0002]
[Prior art]
In general, a fixing method of a fixing device provided in an image forming apparatus such as a copying machine or a printer is a method in which an unfixed toner image is fixed on a transfer sheet by heating and pressing. First, the conventional fixing device will be briefly described with reference to FIG. That is, as shown in FIG. 1, the fixing device 1 includes a fixing roller 2 and a pressure roller 3 that is in pressure contact with the fixing roller 2, and the pressure roller 3 is a pressure spring 5 provided on the pressure arm 4. It is pressed against the fixing roller 2 side by a strong pressurizing force due to the urging force. Further, fixing heaters 6 and 6 for heating are provided inside the fixing roller 2. As a result, the unfixed toner on the transfer paper conveyed to the fixing device 1 is pressed and fixed by heating by the fixing heater 6 and a predetermined “nip width” formed between the rollers 2 and 3.
[0003]
By the way, there are many types of paper used as transfer paper such as tracing paper (hereinafter referred to as “trepe”) and polyester film (hereinafter referred to as “polyfilm”) in addition to plain paper. . And, when the transfer paper is a trepe, unlike the plain paper, the cellulose fibers are fine and the fiber layer is formed in the vertical direction. Therefore, especially when this trepe is a roll, as shown in FIG. Further, contraction in the lateral direction (X direction in the figure) may occur on the near side of the nip width region, and so-called “conveying wrinkles” may occur. Conventionally, in order to solve this problem, it is necessary to prevent heat evaporation halfway and to secure a heat amount capable of uniformly evaporating the moisture content. Adjustments such as increasing the nip width are made. In addition, when the transfer paper is a poly film, if the amount of heat is large, the film itself is softened (plastically deformed) by heating. Therefore, as shown in FIG. May occur. Therefore, in this case, it is necessary to individually set the fixing roller temperature and the nip width fixing conditions that provide the minimum amount of heat applied to the polyfilm.
[0004]
Further, as this type of fixing device, Japanese Patent Laid-Open No. 8-305212 discloses a fixing device in which the nip width in the longitudinal direction is changed for each sheet width. That is, as shown in FIG. 8, the fixing device 1 of this conventional example is a transfer sheet used with a nip width adjusting means 8 for adjusting the nip width and a nip width controlling means 9 for controlling the adjustment amount. Use condition setting means 10 in which the use conditions are preset, and use condition determination means 11 for determining whether the transfer paper is a small size paper or a large size paper, The nip width is varied depending on the size of the transfer paper to be discriminated. In this case, since the nip width corresponding to the temperature change in the longitudinal direction of the fixing roller 2 is set, even when the transfer paper is a small size paper or a large size paper, no fixing failure or hot offset occurs. Good conveyance and image quality can be obtained.
[0005]
[Problems to be solved by the invention]
However, the conventional fixing device has the following problems. That is, as described above, conventionally, the fixing roller temperature and the nip width as the fixing conditions are individually switched according to the type of transfer paper, but an appropriate amount of heat is determined according to each transfer paper. Therefore, for example, when fixing plain paper with the fixing condition (205 ° C.) of Trepe, the amount of heat applied to the plain paper becomes excessive, which causes the problem of toner sticking. Become. Here, it can be considered that the nip width is variable, but conventionally, the nip width that can be changed by adjustment is extremely small. Further, when the plain paper is fixed with the polyfilm fixing condition (175 ° C.), the amount of heat is naturally insufficient, which causes a fixing failure. For this reason, in order to ensure the transport quality of various types of transfer papers, the set temperature region of the fixing roller must be set in a wide range, but when the set temperature region of this fixing roller is set in a wide range, The temperature setting of the fixing roller is affected by the ambient environmental temperature. In particular, switching of the fixing conditions has a problem that the standby time required for switching becomes longer as the temperature change range during heating or cooling becomes larger. It will occur.
[0006]
Further, in the case of the above publication, since it does not correspond to the change of the transfer paper type but corresponds to the change of the size of the transfer paper, the standby time is changed when the change of the transfer paper type still being used is switched. This increases the length and causes problems in conveyance and image quality.
[0007]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problems of the conventional fixing device as described above, and to ensure the conveyance and image quality of various types of transfer papers as well as the types of transfer papers during copying operations. It is an object of the present invention to provide a fixing device that can prevent the standby time from becoming longer and shorten the time even when the change is made.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 includes a fixing roller, a pressure roller, and a fixing unit that adjusts a nip width between the fixing roller and the pressure roller. In the apparatus, the pressure adjusting means includes a pressure spring for pressing the pressure roller against the fixing roller, a bracket connected to one end of the pressure spring, and a bracket substantially parallel to the expansion / contraction direction of the pressure spring. And a rotating shaft provided so as to penetrate the bracket. The rotation of the rotating shaft causes the bracket to move in the expansion / contraction direction of the pressure spring to change the nip width of the fixing roller.
[0010]
The invention of claim 2 is the invention according to claim 1, actuating a pressure regulating means when the type of the transfer sheet to the second sheet type is changed after fixing the first paper type It is characterized by.
The invention according to claim 3 is the invention according to claim 2 , wherein the transfer paper whose fixing roller setting temperature is lower than the first paper type is the third paper type. The pressure adjusting means is operated when the transfer paper type is changed to the second paper type after the third paper type copying operation.
The invention according to claim 4 is the invention according to claim 3 , wherein the transfer paper type is the first, second, and third paper types, and the fixing condition of the second paper type is the first and third paper types. In the fixing roller temperature region under the fixing condition of the paper type, the pressure adjusting means is operated without changing the set temperature of the fixing roller.
[0011]
According to a fifth aspect of the invention, in the second, third, or fourth aspect of the invention, a transfer paper type discriminating unit that discriminates the type of the transfer paper, and a determination condition by the transfer paper type discriminating unit are added. And a control device for controlling the pressure adjusting means.
According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising the fixing device according to the first, second , third , fourth or fifth aspect.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an embodiment of the present invention. FIG. 1 is a side view showing the overall configuration of the fixing device, and FIG. 2 is a longitudinal sectional view of the fixing device. As shown in FIG. 1, the fixing device 1 includes a fixing roller 2 and a pressure roller 3 that is in pressure contact with the fixing roller 2, and one end portion (left side in FIG. 1) of the pressure arm 4 is pivotally supported. In addition, a pair of pressure springs 5 are attached to the other end (right side in FIG. 1). For this reason, the pressure roller 3 is in pressure contact with the fixing roller 2 side by a strong pressure applied by the urging force of the pressure spring 5. Further, fixing heaters 6 and 6 for heating are provided inside the fixing roller 2. As a result, the unfixed toner on the transfer paper conveyed to the fixing device 1 is pressed and fixed by heating and the nip width formed between the rollers 2 and 3. Further, reference numeral 12 denotes a transfer paper type discriminating means, and 13 denotes a control device. As will be described later, the control device 13 performs control based on the transfer paper type discriminating result by the transfer paper type discriminating means 12 as a pressure adjusting means. Therefore, the control device 13 stores in advance a control amount corresponding to the type of each transfer paper. The transfer paper type discriminating means 12 can discriminate the paper type designated by the control panel of the operation unit.
[0013]
Here, a feature of the present invention is that the variable amount (range) of the nip width is increased as compared with the conventional case in order to cope with the fixing conditions for various types of transfer paper. Therefore, as shown in FIG. 1, the fixing device 1 is provided with a pressure adjusting means 15. The pressure adjusting means 15 has a stepping motor 16 and a movable bracket 17 whose urging force by the pressure spring 5 can be varied. One end of the pressure spring 5 (in FIG. 1) is provided at the lower end of the movable bracket 17. The other end (the lower side in FIG. 1) is attached to the pressure arm 4 side. Reference numeral 18 denotes a screw-shaped rotating shaft provided so as to penetrate substantially the center of the movable bracket 17. By rotating the rotating shaft 18, the movable bracket 17 can be moved up and down. Accordingly, since the extension amount of the pressure spring 5 is changed by the vertical movement of the movable bracket 17, the urging force can be varied. Here, the stepping motor 16 is driven by the control of the control device 13 based on the transfer paper type discrimination result by the transfer paper type discrimination means 12.
[0014]
On the other hand, as shown in FIG. 2, a small-diameter rotary gear 20 is fixed to the upper portion of the rotary shaft 19 of the stepping motor 16, and this rotary gear 20 meshes with a relay gear 21. It meshes with a rotating gear 22 fixed at the top. Accordingly, the rotation of the stepping motor 16 is transmitted from the rotation gear 20 to the rotation gear 22 and the rotation shaft 18 via the relay gear 21, and the movable bracket 17 moves up and down as the rotation shaft 18 rotates. Reference numeral 24 denotes a detection sensor. The detection sensor 24 is operated (ON / OFF) when the detection piece 17a fixed to one side of the movable bracket 17 shields the detection sensor 24. Here, the movable bracket 17 The state in which the pressure spring 5 that is the uppermost position is extended to the maximum is detected. Accordingly, the pressure applied by the pressure adjusting means 15 is maximized when detected by the detection sensor 24.
[0015]
FIG. 3 shows fixing conditions for trepe (first paper type) and plain paper (second paper type), FIG. 4 shows fixing conditions for polyfilm and plain paper, and FIG. 5 shows trepe and polyfilm (first paper type). 3 is a diagram illustrating the fixing conditions of the third paper type) and plain paper as embodiments. In each of these drawings, the vertical axis indicates the set value which is the transition of the fixing roller temperature (° C.) and the nip width (mm) according to the type of transfer paper, and the horizontal axis indicates the type of transfer paper. . Here, the optimum heating amount of Trepe is “1.9 J / cm ² ”, the optimum heating amount of plain paper is “1.3 J / cm ² ”, and the optimum heating amount of poly film is “1.2 J”. / cm ² ". Hereinafter, the details of the fixing device of the present invention will be described with reference to FIGS.
[0016]
First, as shown in FIG. 3, in the present invention, when changing from a copying operation using a trepe to a plain paper, the fixing roller temperature (° C.) is kept at about 205 ° C., and only the nip width is set to about 10 mm to 5 mm. Perform variable control. As a specific operation of the fixing device, when the user gives an instruction to change from trepe to plain paper, this paper selection is discriminated by the transfer paper type discriminating means 12 (FIG. 1). The rotation of the stepping motor 16 is started by a control signal from the control device 13 according to the determination condition by the means 12. Here, as shown in FIG. 1, the position where the applied pressure by the applied pressure adjusting means 15 is the maximum is the reference, so that the movable bracket 17 is lowered by the rotation of the stepping motor 16. The urging force due to is weakened and the nip width is reduced, and the nip width is adjusted to a predetermined value. At this time, as shown in FIG. 3 described above, since the fixing roller temperature (° C.) is not changed, the standby time required for adjustment can be shortened. In addition, the nip width is reduced by this adjustment, so that even when the fixing roller temperature is high (205 ° C), hot offset etc. on plain paper can be avoided, and transfer paper transfer and image quality are ensured. can do.
[0017]
Further, as shown in FIG. 4, when changing from poly film to plain paper, the fixing roller temperature (° C.) is kept at about 175 ° C., and only the nip width is increased to about 6 mm to 7 mm. As a specific operation of the fixing device, the rotation of the stepping motor 16 is started by the control signal from the control device 13 and the movable bracket 17 is raised, and accordingly, the urging force by the pressure spring 5 is increased and the nip is increased. The width is also increased and adjusted to a predetermined nip width. At this time, as shown in FIG. 4 as described above, since the fixing roller temperature (° C.) is not changed, the waiting time required for adjustment can be shortened. Also, since the nip width is increased by adjustment at this time, fixing failure on plain paper can be avoided even if the fixing roller temperature is low (175 ° C), and transfer paper transfer and image quality are ensured well. can do.
[0018]
Further, as shown in FIG. 5, when the fixing condition of the plain paper is within the fixing roller temperature region in the fixing condition of the trepe and the poly film, the nip width is switched by the pressure adjusting means 15 without changing the set temperature of the fixing roller. An appropriate amount of heat can be obtained only with this. In other words, in the case of plain paper positioned between the fixing conditions between the trepe and the polyfilm, it can be always used when the image forming apparatus is capable of copying. As a result, the fixing roller temperature (° C.) is not naturally changed, so that the standby time required for adjustment can be shortened.
[0019]
【The invention's effect】
The present invention is as described above, and the invention according to claim 1 includes a fixing roller, a pressure roller, and a pressure adjusting means for adjusting a nip width between the fixing roller and the pressure roller. The pressure adjusting means includes a pressure spring for pressing the pressure roller against the fixing roller, a bracket connected to one end of the pressure spring, and a penetrating through the bracket substantially parallel to the expansion / contraction direction of the pressure spring. The rotation axis of the rotation shaft can move the bracket in the direction of expansion and contraction of the pressure spring and change the nip width of the fixing roller. In addition, the image quality can be ensured satisfactorily, and the waiting time can be prevented from becoming long even when the transfer paper is switched.
[0021]
The inventions according to claims 2 to 4 also ensure good transport of various types of transfer papers and image quality, and prevent the waiting time from becoming long even when the transfer papers are switched. There is an effect that it can be planned. The invention according to the fifth aspect has an effect that it is possible to accurately determine the type according to various types of transfer paper and to accurately adjust the pressing force. The invention described in claim 6 can further provide an image forming apparatus including the fixing device described in claim 1, 2 , 3 , 4 or 5 .
[Brief description of the drawings]
FIG. 1 is a side view showing an overall configuration of a fixing device according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of the identification wearing apparatus.
FIG. 3 is an explanatory diagram showing fixing conditions for tracing paper and plain paper.
FIG. 4 is an explanatory diagram showing fixing conditions for a polyester film and plain paper.
FIG. 5 is an explanatory diagram showing fixing conditions for tracing paper, polyester film, and plain paper.
FIG. 6 is a perspective view showing tracing wrinkles of tracing paper.
FIG. 7 is a perspective view showing a roller mark of a polyester film.
FIG. 8 is a schematic configuration diagram illustrating an example of a conventional fixing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing roller 3 Pressure roller 4 Pressure arm 5 Pressure spring 6 Fixing heater
12 Transfer paper type discrimination means
13 Control device
15 Pressure adjusting means
16 Stepping motor
17 Movable bracket
17a Detection piece
18, 19 Rotating shaft
20, 22 Rotating gear
21 Relay gear
24 detection sensor

Claims (6)

In a fixing device comprising a fixing roller, a pressure roller, and a pressure adjusting means for adjusting a nip width between the fixing roller and the pressure roller.
The pressure adjusting means is
A pressure spring for pressing the pressure roller against the fixing roller, a bracket connected to one end of the pressure spring, and a penetrating direction of the pressure spring so as to penetrate the bracket. A rotating shaft ,
The fixing device according to claim 1, wherein the bracket moves in the expansion / contraction direction of the pressure spring by rotation of the rotation shaft to change a nip width of the fixing roller. 2. The fixing device according to claim 1 , wherein the pressure adjusting means is operated when the transfer paper type is changed to the second paper type after fixing the first paper type. When the transfer paper whose fixing roller setting temperature is lower than that of the first paper type is used as the third paper type, the transfer paper to the second paper type after copying the third paper type The fixing device according to claim 2 , wherein the pressure adjusting means is operated when the type of the fixing member is changed. When the transfer paper type is the first, second, and third paper types and the fixing condition of the second paper type is within the fixing roller temperature region in the fixing conditions of the first and third paper types, the set temperature of the fixing roller The fixing device according to claim 3 , wherein the pressure adjusting means is operated without changing the pressure. A transfer sheet type discriminating means for discriminating the type of the transfer sheet, according to claim 2 and 3 in accordance with the determination conditions by the transfer sheet type discriminating means, and having a control device for controlling the pressure regulating means Or the fixing device according to 4 ; An image forming apparatus having a fixing device according to claim 1, 2, 3, 4 or 5,.

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