JP6648494B2 - Fixing device and image forming device - Google Patents

Description

  The present invention relates to a fixing device for fixing an unfixed toner image and an image forming apparatus using the fixing device.

  In recent years, market demands for energy saving and speeding up of image forming apparatuses such as printers, copiers, and facsimile machines have become stronger. In the above image forming apparatus, an unfixed toner image is formed on a recording material sheet, printed paper, photosensitive paper, electrostatic recording by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. It is formed on a recording medium such as paper (hereinafter, referred to as “paper”).

  By the way, in the above-described image forming apparatus, a fixing device for fixing an unfixed toner image is used. As such a fixing device, a contact heating system such as a heat roller system, a film heating system, or an electromagnetic induction heating system is employed.

  As the above-described fixing device, there is one having a configuration disclosed in Patent Documents 1 and 2. The fixing device disclosed in Patent Document 1 is of a belt type, and it is desired to further reduce the warm-up time and the first print time (Problem 1). The “warm-up time” refers to a time required from a normal temperature state to a predetermined printable temperature (reload temperature) such as when the power is turned on. The “first print time” refers to the time from when a print request is received to when a print operation is performed after a print preparation and a paper discharge is completed.

  Further, with the high-speed processing of the image forming apparatus, the number of sheets passed per unit time has increased, and the required amount of heat has increased. For this reason, there is a problem that the amount of heat is insufficient particularly at the beginning of continuous printing (a so-called temperature drop) (Problem 2).

  The fixing device disclosed in Patent Literature 2 is of a surf fixing (film fixing) type using a ceramic heater, and has a lower heat capacity and a smaller size than the above-described belt type fixing device by adopting the surf fixing method. Becomes possible. However, in the surf fixing method, since only the nip portion is locally heated, the other portions are not heated, and the belt is the coldest at the entrance of the nip paper and the like, and fixing defects are likely to occur. Problem. In particular, in high-speed processing in which the rotation of the belt is fast and the heat radiation of the belt other than at the nip is increased, there is a problem that fixing defects are more likely to occur (problem 3).

  For the purpose of solving the above problems 1 to 3, there is a configuration disclosed in Patent Document 3 under the name of a heating device. FIG. 5 is a schematic sectional view illustrating a schematic configuration of the heating device disclosed in Patent Document 3. In the heating device shown in FIG. 5, a pipe-shaped metal heat conductor 2 is fixed inside an endless belt 1 so as to guide the movement of the endless belt 1, and the heat source inside the metal heat conductor 2 is fixed by the metal heat conductor 2. 3, the endless belt 1 is indirectly heated.

  Further, a pressure roller 4 that forms a nip portion N in contact with the metal heat conductor 2 via the endless belt 1 is provided, and the endless belt 1 is rotated around the rotation of the pressure roller 4. Move in the direction. Reference numeral 5 denotes a metal roller, and reference numeral 6 denotes an elastic layer.

  That is, the heating device disclosed in Patent Document 3 has a configuration using the endless belt 1 and heats the entire endless belt 1. According to this configuration, it is possible to reduce the first print time from the heating standby time, and to eliminate the shortage of heat during the high-speed rotation processing, and to achieve a good fixing even when mounted in a high-production image forming apparatus. It is possible to obtain the nature.

  However, in the heating device disclosed in Patent Document 3, although the above-described first print time can be shortened, it is necessary to further improve the thermal efficiency in order to further improve the energy saving and the first print time. is there.

  In each of the above-described conventional fixing devices and the like, by directly heating the endless belt 1, energy saving is high, and the first print time from the heating standby time can be further reduced. On the other hand, it has been clarified that the temperature controllability is degraded by the temperature of the pressure roller itself without a heater, which was not a problem in the past. In other words, when the sheet passes through the nip when the pressurizing temperature is high, the power supplied to the fixing member immediately before that is small. When the sheet passes through the nip in this state, the temperature of the pressure roller sharply drops. As a result, the temperature of the fixing member being controlled also drops unnecessarily, causing a drop. This causes a temperature ripple, which deteriorates the temperature controllability for several seconds thereafter. On the other hand, when the pressurizing temperature is low, the temperature of the pressurizing temperature does not drop so much even when the paper passes, and since a relatively large amount of electric power is supplied until immediately before, the drop does not occur.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of obtaining stable image quality by reducing the temperature ripple while reducing the heat capacity and the return time, and an image forming apparatus using the fixing device.

  According to an aspect of the present invention, there is provided a fixing member for fixing unfixed toner to a recording medium, a heating source for heating the fixing member, and a fixing member. A pressure member for pressing a recording medium; a nip forming member for forming a nip between the pressure member; a power control circuit for controlling power supplied to the heating source; and detecting a temperature of the pressure member. In the fixing device having a pressure temperature sensor that performs heating, the power supply to the heating source is increased or decreased according to the pressure temperature detected by the pressure temperature sensor, and the intended power supply timing is delayed. It is characterized by having a supply power correcting means for performing a quick correction.

  According to the present invention, stable image quality can be obtained by reducing the temperature ripple as well as reducing the heat capacity and the return time.

FIG. 1 is a schematic side sectional view illustrating a configuration of an image forming apparatus using a fixing device according to an embodiment of the present disclosure. FIG. 2 is an enlarged front view illustrating a main configuration of the fixing device according to the first embodiment. It is a schematic diagram which shows the transition of the pressurization temperature in the conventional structure which does not correct the electric power supply to a heating source, (A) is a schematic diagram which shows the temperature transition when a pressurization temperature is low, (B) is a schematic diagram. It is a schematic diagram which shows a temperature transition in case pressure pressure is high. It is a schematic diagram which shows the transition of the pressurization temperature in this apparatus which corrects the electric power supply to a heating source, (A) is a schematic diagram which shows the temperature transition when a pressurization temperature is low, (B) is a pressurization. It is a schematic diagram which shows a temperature transition in case temperature is high. FIG. 11 is a schematic sectional view illustrating a schematic configuration of a heating device disclosed in Patent Document 3.

  Hereinafter, a fixing device according to the present invention and an image forming apparatus using the fixing device will be described with reference to the drawings. FIG. 1 is a side sectional view showing a schematic configuration of an image forming apparatus using a fixing device according to an embodiment of the present invention. In the drawings, the same or corresponding parts are denoted by the same reference characters, and their description will be appropriately simplified or omitted.

  Hereinafter, a color laser printer (hereinafter, simply referred to as a “printer”) will be described as an example of the image forming apparatus. The printer 10 shown in FIG. 1 is provided with four image forming units 11Y, 11M, 11C, and 11K in the center of the printer body. Each image forming unit 11Y is similar except that it contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (BK) corresponding to the color separation components of the color image. Configuration.

  Each of the image forming units 11Y, 11M, 11C, and 11K includes a drum-shaped photoconductor 12, a charging device 13 for charging the surface of the photoconductor 12, a developing device 14, a cleaning device 15, and the like. The developing device 14 supplies toner to the surface of the photoconductor 12, and the cleaning device 15 cleans the surface of the photoconductor 12.

  In FIG. 1, only the photoconductor 12, the charging device 13, the developing device 14, and the cleaning device 15 included in the black image forming unit 11K are denoted by reference numerals, and the other image forming units 11Y, 11M, 11C is omitted.

  An exposure device 16 for exposing the surface of each photoconductor 12 is disposed below the image forming units 11Y, 11M, 11C, and 11K. The exposure device 16 has a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 12 with laser light based on image data.

  A transfer device 17 is provided above the image forming units 11Y, 11M, 11C, and 11K. The transfer device 17 includes an intermediate transfer belt 18, four primary transfer rollers 19, a secondary transfer roller 20, a secondary transfer backup roller 21, a cleaning backup roller 22, a tension roller 23, and a belt cleaning device 24.

  The intermediate transfer belt 18 is formed in an endless shape, and is stretched by a secondary transfer backup roller 21, a cleaning backup roller 22, and a tension roller 23. Here, as the secondary transfer backup roller 21 is driven to rotate, the intermediate transfer belt 18 travels (rotates) in the direction indicated by the arrow in the drawing.

  The four primary transfer rollers 19 form a primary transfer nip by sandwiching the intermediate transfer belt 18 between each of the photosensitive members 12. A power supply is connected to each primary transfer roller 19 so that a predetermined DC voltage or AC voltage is applied.

  The secondary transfer roller 20 forms a secondary transfer nip by sandwiching the intermediate transfer belt 18 between the secondary transfer roller 20 and the secondary transfer backup roller 21. Further, similarly to the primary transfer roller 19, a power source is connected to the secondary transfer roller 20, and a predetermined DC voltage or AC voltage is applied.

  The belt cleaning device 24 has a cleaning brush and a cleaning blade arranged so as to contact the intermediate transfer belt 18. The waste toner transfer hose extending from the belt cleaning device 24 is connected to the entrance of the waste toner container.

  A bottle accommodating portion 25 is provided at an upper portion of the printer main body, and four toner bottles 25Y, 25M, 25C, and 25K accommodating toner for replenishment are detachably mounted in the bottle accommodating portion 25. .

  A supply path is provided between each of the toner bottles 25Y, 25M, 25C, and 25K and each of the developing devices 14. The toner is supplied from each of the toner bottles 25Y, 25M, 25C, and 25K to each of the developing devices 14 via the supply path.

  On the other hand, at the lower part of the printer main body, there are provided a paper feed tray 26 containing the paper P, a paper feed roller 27 for carrying out the paper P from the paper feed tray 26, and the like. Here, the paper P includes, in addition to plain paper, thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like. Further, a manual paper feed mechanism may be provided.

  A transport path R for discharging the paper P from the paper feed tray 26 through the secondary transfer nip to the outside of the printer main body is provided in the printer main body. In the transport path R, a pair of registration rollers 28 for transporting the sheet P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 20 in the sheet transport direction.

  Further, a fixing device A for fixing an unfixed image transferred to the sheet P is disposed downstream of the position of the secondary transfer roller 20 in the sheet conveyance direction. Further, a pair of paper discharge rollers 29 for discharging the paper P to the outside of the printer main body is provided downstream of the fixing device A in the paper transport direction of the transport path R. Further, on the upper surface of the printer main body, there is provided a paper discharge tray 9 for stocking the paper P discharged out of the printer main body by the pair of paper discharge rollers 29.

  Next, a fixing device A according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is an enlarged front view illustrating a main configuration of the fixing device A according to the embodiment of the present disclosure. The fixing device A mainly includes a pressing roller 30 as a pressing member, a fixing belt 40 as a fixing member, a heating source 50, and a nip forming member 60.

  The fixing belt 40 is formed in an endless shape, and the heating source 50 and the nip forming member 60 described above are disposed inside the fixing belt 40. In this configuration, the fixing belt 40 is directly heated by the heating source 50 from the inner peripheral side. The fixing belt 40 uses a metal belt such as nickel or SUS or a base material 41 using a resin material such as polyimide. The surface layer of the fixing belt 40 is formed by coating a release layer 42 made of PFA, PTFE, or the like, and has a release property so that toner does not adhere.

  An elastic layer formed of a silicone rubber layer or the like may be provided between the base material 41 of the fixing belt 40 and the release layer 42. In the absence of the silicone rubber layer, the heat capacity is reduced and the fixability is improved. There is a problem that skin-like gloss unevenness (yuzu skin image) remains. In order to improve this, it is necessary to provide a silicone rubber layer having a thickness of 100 [μm] or more. Due to the deformation of the silicone rubber layer, minute unevenness is absorbed, so that it is possible to improve the skin image of Yuzu.

  The heating source 50 shown in the present embodiment uses a halogen heater, but is not limited to this. For example, an IH, a resistance heating element, a carbon heater, or the like can be used. The nip forming member 60 is disposed so as to form a nip with the pressure roller 30 opposed to the fixing belt 40 via the fixing belt 40, and is in direct sliding contact with the inner peripheral surface of the fixing belt 40. . In addition, you may make it slide indirectly via a sliding sheet.

  The nip forming member 60 shown in the present embodiment has a nip portion N formed on a flat surface, but may have a concave shape or another shape. When the nip is formed in a concave shape, the discharge direction of the leading end of the paper P is closer to the pressure roller 30 and the separability is improved, so that the occurrence of jam can be suppressed.

  A support member (stay) 61 for supporting the nip portion N is provided inside the fixing belt 40, which prevents the nip forming member 60 that receives pressure from the pressure roller 30 from bending, and is uniform in the axial direction. Nip width. The support member 61 is held and fixed to a holding member (flange) 62 at both ends and positioned. On the inner wall surface side of the support member 61, a reflecting member 63 for blocking radiant heat from the heating source 50 and the like is arranged along the inner wall surface. This suppresses wasteful energy consumption due to the heating of the support member 61 by radiant heat from the heating source 50 or the like. Note that the same effect can be obtained by performing heat insulation or mirror finishing on the inner surface of the support member 61 instead of the reflection member 63.

  The above-described fixing belt 40 is rotated by the pressure roller 30. That is, when the pressure roller 30 shown in FIG. 2 is rotated by the driving source, the driving force is transmitted to the fixing belt 40 in the nip portion N, and the fixing belt 40 is driven to rotate. The fixing belt 40 rotates at both ends except the nip portion N while being guided by the holding members 62. With such a configuration, it is possible to realize the fixing device A that is inexpensive and quickly warms up.

  The pressure roller 30 is formed by forming an elastic rubber layer 32 on an outer peripheral portion of a cored bar 31, and has a release layer (PFA or PTFE layer) on the surface to obtain releasability. The pressure roller 30 is configured to rotate by transmitting a driving force via a gear from a driving source such as a motor provided in the printer body.

  Further, the pressure roller 30 is pressed toward the fixing belt 40 by a spring or the like, and has a predetermined nip width as the elastic rubber layer 32 is crushed and deformed. The pressure roller 30 may have a hollow structure, or a configuration in which a heating source such as a halogen heater is provided inside the pressure roller 30. The elastic rubber layer 32 may be solid rubber, but if no heating source is provided inside the pressure roller 30, sponge rubber may be used. The use of sponge rubber is more preferable because the heat insulating property is enhanced and the heat of the fixing belt 40 is hardly deprived.

  By the way, the pressure roller 30 is provided with a pressure temperature detection sensor S1 for detecting the temperature of the pressure roller 30, and a power control circuit 70 is connected to the heating source 50. The control unit 80 has a function of controlling power supplied to the heating source 50 by executing a required program. A pressurized temperature detection sensor S1 is connected to the input side of the control unit 80, and the heating source 50 is connected to the output side. The control unit 80 shown in the present embodiment has the following functions.

  A function of increasing / decreasing the power supply to the heating source 50 in accordance with the pressurized temperature detected by the above-described pressurized temperature detection sensor S1, and correcting the intended power supply timing early or late. This function is referred to as “supply power correcting means 80a”. Specifically, a fixed power determined according to a predetermined process condition is set, and the fixed power is increased or decreased according to the pressurized temperature obtained by the pressurized temperature detection sensor S1. The “predetermined process conditions” include the thickness, linear velocity, color mode, process linear velocity, etc. of the recording medium. The “fixed power” is determined in accordance with a predetermined process condition, and is output in a fixed manner with respect to a paper-passing mode required according to the predetermined process condition. 80 is stored in the memory.

The supply power correction means 80a corrects the increase / decrease based on the fixed power according to the pressurized temperature detected by the pressurized temperature detection sensor S1. Also, the power supply timing is corrected early or late with respect to the intended power supply timing according to the pressurized temperature detected by the pressurized temperature detection sensor S1. The “ expected power supply timing” is when the paper P enters the fixing nip. Specifically, the correction is performed so that the supply power increases as the pressurization temperature increases, and decreases as the pressurization temperature decreases. Further, from the intended power supply timing, the power supply timing is advanced as the pressurization temperature rises, and the supply power timing is delayed as the pressurization temperature decreases. Further, the correction is performed when a predetermined time has not elapsed since the paper P enters the fixing nip. That is, by detecting the temperature after the rotation is stabilized, the appropriate heat storage state of the fixing device A can be determined.

  FIGS. 3A and 3B are schematic diagrams showing a transition of a pressurized temperature in a conventional configuration in which power supply to a heating source is not corrected. FIG. 3A is a schematic diagram showing a transition of a temperature when a pressurized temperature is low, and FIG. () Is a schematic diagram showing a temperature transition when the pressurization temperature is high. In the figure, the vertical axis indicates temperature, and the horizontal axis indicates time.

  As shown in FIGS. 3A and 3B, when the first sheet enters a place where the pressing temperature is high toward the first sheet of paper P, a drop occurs due to the first sheet. However, the temperature controllability deteriorates for a while due to the influence. This problem is more likely to occur as a more prominent problem when the pressurizing temperature is high in the usage modes up to that time. Further, when the target temperature is low, for example, when the paper is passed at a low speed, the influence is small, but the temperature controllability is deteriorated due to the same cause.

  FIGS. 4A and 4B are schematic diagrams illustrating a transition of the pressurized temperature in the present apparatus for correcting the power supply to the heating source. FIG. 4A is a schematic diagram illustrating a transition of the temperature when the pressurized temperature is low, and FIG. FIG. 3 is a schematic diagram showing a temperature transition when a pressurization temperature is high.

  As shown in FIGS. 4A and 4B, the fixed output is corrected according to the detection result of the pressurized temperature. The output of the fixed output is made earlier as the pressurization temperature becomes higher. Thereby, a desired temperature controllability can be obtained.

That is, for the fixed output power, the fixed power that is always required in the paper passing mode may be determined in advance according to the above-described predetermined process conditions such as the process linear velocity, the color mode, and the thickness of the paper P. It becomes necessary, and the increase / decrease of the supply power is corrected based on the fixed power. It is desirable that the intended power supply timing is defined based on the timing at which the leading edge of the paper P enters the nip. However, if the timing of the correction is too early, the controllability is deteriorated due to the temperature ripple that is excessively heated before the sheet is passed. Therefore, it is desirable to perform an evaluation in advance and use an optimum value in each image forming apparatus and the fixing apparatus. .

  As described above, when a sheet is passed from a state where the pressurization temperature is high, the temperature drop of the first sheet is remarkable, so it is necessary to prevent the offset due to the drop of the first sheet. Therefore, the required lighting duty is corrected according to the pressurized temperature. As a result, the user can obtain stable image quality in various use situations while preventing the temperature drop and offset of the first sheet, reducing the heat capacity and shortening the recovery time.

10 Image forming apparatus (printer)
11Y to 11K Each image forming unit 12 Each photoconductor 13 Charging device 14 Each developing device 15 Cleaning device 18 Intermediate transfer belt 19 Primary transfer roller 21 Secondary transfer backup roller 24 Belt cleaning device 25 Bottle storage unit 25Y to 25K Toner bottle 28 Resist Roller 29 Discharge roller 30 Pressure roller 31 Metal core 40 Fixing belt 41 Base material 50 Heat source 60 Nip forming member 61 Support member 62 Holding member 63 Reflecting member 80 Control unit 80a Supply power correction means P Recording medium (paper)
R transport path S1 Pressurized temperature detection sensor

JP 2004-286922 A JP-A-4-44032 JP 2007-334205 A

Claims (8)

A fixing member for fixing the unfixed toner to the recording medium,
A heating source for heating the fixing member,
A pressure member for pressing the recording medium between the fixing member and
A nip forming member that forms a nip between the pressing member and
A power control circuit for controlling power supplied to the heating source,
And a pressure temperature detection sensor for detecting the temperature of the pressure member.
In accordance with the pressurized temperature detected by the pressurized temperature detection sensor, power supply to the heating source is increased or decreased, and an intended power supply timing when the recording medium enters the fixing nip is corrected. A fixing device comprising a supply power correction unit. A fixed power determined according to the predetermined process conditions is set,
2. The fixing device according to claim 1, wherein the supply power correction unit performs increase / decrease correction based on the fixed power according to the pressurized temperature. 3.   3. The fixing device according to claim 1, wherein the supply power correction unit corrects the power supply timing according to the pressurized temperature with respect to the intended power supply timing. 4.   The said supply power correction means corrects so that supply power may be increased according to the rise of the pressurization temperature and may be reduced as the pressurization temperature falls. The fixing device according to claim 1.   5. The power supply timing according to claim 3, wherein the power supply timing is advanced according to an increase in the pressurized temperature, and the supply power timing is delayed according to a decrease in the pressurized temperature from the intended power supply timing. 6. Fixing device. The fixing device according to claim 5, wherein the supply power correction unit performs the correction when a predetermined time has not elapsed after a recording medium enters the fixing nip.   The fixing device according to claim 2, wherein the predetermined process condition includes a thickness of a recording medium, a linear velocity, and a color mode.   An image forming apparatus using the fixing device according to claim 1.

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