JP6303652B2 - Fixing device, heating control method, and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device used in an electrostatic recording image forming apparatus such as a copying machine, a facsimile machine, or a printer, and performs fixing processing on transfer paper or the like at a nip portion between an endless fixing member and a pressure member. The present invention relates to an apparatus and an image forming apparatus equipped with the fixing device.

  In recent years, there has been an increasing market demand for energy saving and high speed for image forming apparatuses such as printers, copiers, and facsimiles. In an image forming apparatus, an unfixed toner image is transferred to a recording material sheet, printing paper, photosensitive paper, electrostatic recording paper, etc. by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, and magnetic recording. Formed on recording material. As a fixing device for fixing an unfixed toner image, a contact heating method fixing device such as a heat roller method, a film heating method, and an electromagnetic induction heating method is widely used.

  As an example of such a fixing device, a belt-type fixing device (for example, Japanese Patent Application Laid-Open No. 2004-286922) and a surf fixing (film fixing) fixing device (for example, Japanese Patent No. 2,861,280) using a ceramic heater are known. ing.

  In the belt-type fixing device, in recent years, further reduction in warm-up time and first print time has been desired (Problem 1). The warm-up time is the 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 is a time from when a print request is received to when a print operation is performed through a print preparation and paper discharge is completed. In addition, as the speed of image forming apparatuses increases, the number of sheets to be passed per unit time increases and the required amount of heat increases, so that there is a problem that the amount of heat is insufficient (so-called temperature drop), particularly at the beginning of continuous printing. (Problem 2).

  As a method for solving the problem of the problem 1, surf fixing using a ceramic heater has been proposed. With this method, it is possible to reduce the heat capacity and reduce the size as compared with a belt-type fixing device. However, since only the nip portion is locally heated, the other portions are not heated, and the belt is in the coldest state at the entrance of the nip paper and the like. . In particular, in a high-speed machine, there is a problem that fixing failure is more likely to occur because the belt rotates fast and the heat radiation of the belt outside the nip increases (problem 3).

  In order to solve the problems 1 to 3 as described above, for example, a technique such as Japanese Patent Application Laid-Open No. 2007-334205 has been proposed. This technology makes it possible to warm the entire belt in a configuration using an endless belt, shortens the first print time from the heating standby time, and eliminates the shortage of heat during high-speed rotation. As a result, this is a technique of a fixing device that can obtain good fixability even when mounted on a high-production image forming apparatus.

  However, it is necessary to further improve the thermal efficiency in order to further improve energy saving and the first print time. From the configuration in which the endless belt is indirectly heated through the metal heat conductor, the endless belt (metal heat conductor) It is conceivable to employ a configuration in which heating is performed directly (without going through). In this way, by adopting a configuration in which the endless belt is directly heated, energy saving is high, and it is possible to further shorten the first print time from the heating standby time. However, since the heat capacity is low and there is almost no heat conduction in the thrust direction, there is a new problem that the temperature rise (edge temperature rise) in the area outside the paper size cannot be suppressed when the heater emission length is different from the paper size. ing.

  An object of the present invention is to suppress a temperature rise at an end portion in the nip width direction in a fixing device.

The fixing device according to claim 1 is disposed so as to face the fixing member, an endless flexible fixing member that can rotate around an axis in the width direction, a heating source that heats the fixing member, and the fixing member. A pressure member, a nip forming member that forms a nip portion facing the pressure member inside the fixing member, a temperature detecting unit that detects a temperature of the fixing member, and a radiation light from the heating source is shielded. A light shielding member, a light shielding member driving means for rotating the light shielding member about an axis parallel to the axis, and a heat source driving means for rotating the heating source about an axis parallel to the axis. The heating source is a heating source including a central heater having a heat generating part at the center in the axial direction and an end heater having a heat generating part at the end in the axial direction. Having the central heater on the upstream side, and the downstream side Part has a heater, and controlling rotation and said light shielding member and the heating source.

  According to the image forming apparatus of the first aspect, since the rotation of the light shielding member and the heat source is controlled, the temperature rise at the end in the nip width direction can be suppressed.

1 is a configuration diagram of a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a side view of a main part of the fixing device according to the embodiment. FIG. 2 is a perspective view and a block configuration diagram of a main part of a fixing device according to an embodiment. FIG. 4 is a perspective view of a light shielding member, a flange, and a guide member of the fixing device in the embodiment. FIG. 3 is a perspective view of a light shielding member driving mechanism of the fixing device in the embodiment. FIG. 2 is a schematic diagram illustrating a front view of a light shielding member and a heating source of a fixing device and a configuration of a heat generating portion of a halogen heater of the heating source in the embodiment. It is a figure explaining the range of the efficiency heated by the heat source in embodiment. It is a figure which shows an example of the temperature distribution of a thrust direction when not moving the heating source in the embodiment.

  Hereinafter, embodiments of an image forming apparatus and a fixing apparatus to which the present invention is applied will be described. First, the schematic configuration and operation of the image forming apparatus of the present embodiment will be described with reference to FIG. The image forming apparatus 100 of this embodiment is a color laser printer, and four image forming units 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each of the image forming units 4Y, 4M, 4C, and 4K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that.

  Each of the image forming units 4Y, 4M, 4C, and 4K supplies a drum-shaped photosensitive member 5 as a latent image carrier, a charging device 6 that charges the surface of the photosensitive member 5, and a toner to the surface of the photosensitive member 5. A developing device 7 and a cleaning device 8 for cleaning the surface of the photoreceptor 5 are provided. In FIG. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4 </ b> K are denoted by reference numerals. In the other image forming units 4 </ b> Y, 4 </ b> M, and 4 </ b> C, The reference numerals are omitted.

 Under the image forming units 4Y, 4M, 4C, and 4K, an exposure device 9 that exposes the surface of the photoreceptor 5 is disposed. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data. A transfer device 3 is disposed above the image forming units 4Y, 4M, 4C, and 4K. The transfer device 3 includes the following members. An intermediate transfer belt 30 as a transfer member, four primary transfer rollers 31 as primary transfer means, and a secondary transfer roller 36 as secondary transfer means. In addition, a secondary transfer backup roller 32, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

  The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, when the secondary transfer backup roller 32 is driven to rotate, the intermediate transfer belt 30 runs (rotates) in the direction indicated by the arrow in the figure.

  Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31.

  The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Similarly to the primary transfer roller 31, a power source (not shown) is also connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It has become so.

  The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

  A bottle container 2 is provided in the upper part of the printer main body, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are detachably attached to the bottle container 2. A replenishment path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each development from each toner bottle 2Y, 2M, 2C, 2K is performed via this replenishment path. The toner is supplied to the device 7.

  On the other hand, at the lower part of the printer main body, a paper feed tray 10 containing transfer paper P as a recording medium, a paper feed roller 11 for carrying the transfer paper P out of the paper feed tray 10, and the like are provided. Here, the transfer paper P includes, in addition to plain paper, thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Although not shown, a manual paper feed mechanism may be provided.

  In the printer main body, a conveyance path is provided for discharging the transfer paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path, a pair of registration rollers 12 as a transport unit that transports the transfer paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the transfer paper transport direction.

  A fixing device 20 for fixing the unfixed image transferred to the transfer paper P is disposed on the downstream side in the transport direction of the transfer paper P from the position of the secondary transfer roller 36. Further, a pair of paper discharge rollers 13 for discharging the transfer paper P to the outside of the apparatus is provided downstream of the fixing device 20 in the transport direction of the transfer paper P in the transport path R. A discharge tray 14 for stocking the transfer paper P discharged outside the apparatus is provided on the upper surface of the printer main body.

  Next, the configuration of the fixing device 20 in the embodiment will be described. 2 is a side view of a main part of the fixing device 20 in the embodiment, FIG. 3 is a perspective view and a block diagram of the main part of the fixing device 20, and FIG. 4 is a perspective view of a light shielding member, a flange and a guide member of the fixing device 20. . FIG. 5 is a perspective view of the light shielding member driving mechanism of the fixing device 20, FIG. 6 is a front view of the light shielding member and the heating source of the fixing device 20 (FIG. 6A), and the configuration of the heat generating portion of the halogen heater of the heating source. It is a schematic diagram (FIG. 6B).

  The fixing device 20 has a substantially cylindrical shape and a flexible “fixing member” as a rotatable “fixing member” 21, and pressurization as a “pressurizing member” provided so as to be rotatable facing the fixing belt 21. A heating source 23 for heating the roller 22 and the fixing belt 21 is provided. The fixing device 20 includes the following members for improving the fixing efficiency of the transfer paper P. Specifically, a nip forming member 24 disposed inside the fixing belt 21, a stay 25 that supports the nip forming member 24, and a reflecting member 26 that reflects light emitted from the heating source 23 to the fixing belt 21 are provided. Further, a stay member 27 (flange) that holds and fixes the stay 25 that supports the nip forming member 24 at both ends in the longitudinal direction, a pressure unit (not shown) that pressurizes the pressure roller 22 to the fixing belt 21, and the like. It also has.

  Further, the fixing device 20 includes a light shielding member 40 having an arc-shaped cross section whose longitudinal direction is a direction perpendicular to the moving direction of the fixing belt 21. The light shielding member 40 is disposed so as to face the reflection member 26 with the heating source 23 interposed therebetween, and is a member that restricts the fixing belt 21 from being irradiated with radiation light (including infrared rays) from the heating source 23. It is.

  The heating source 23 includes a central heater 23 </ b> A and an end heater 23 </ b> B each composed of a halogen heater, and the heating source 23 directly heats the fixing belt 21 at a place other than the nip portion of the fixing belt 21. As shown in FIG. 6B, the central heater 23A has a central region in the longitudinal direction as a heating target, and a heat generating portion 23A1 shown in FIG. 6B is provided at the center. The end heater 23B is heated at both end regions in the longitudinal direction, and heat generating portions 23B1 shown in FIG. 6B are provided at both ends.

  The pressure roller 22 includes a cored bar 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, or fluororubber provided on the surface of the cored bar 22a, and PFA provided on the surface of the elastic layer 22b. It is constituted by a release layer 22c made of PTFE or the like. The pressure roller 22 is pressed toward the fixing belt 21 by a pressure unit (not shown) and is in contact with the nip forming member 24 via the fixing belt 21. At the location where the pressure roller 22 and the fixing belt 21 are in pressure contact with each other, the elastic layer 22b of the pressure roller 22 is crushed to form a nip portion N having a predetermined width.

  The pressure roller 22 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the main body of the image forming apparatus. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate. The fixing belt 21 rotates along with the pressure roller 22. That is, the pressure roller 22 is rotated by a driving source (not shown), and the driving force is transmitted to the belt at the nip portion N, whereby the fixing belt 21 is rotated. Further, the fixing belt 21 is guided by the holding member 27 at both ends other than the nip portion and travels. As described above, the fixing belt 21 is an endless and flexible fixing member that can rotate around the central axis L (FIG. 2) in the width direction. Then, when the transfer paper P onto which the toner T is transferred passes through the nip portion N, the toner image is fixed. With the above configuration, it is possible to realize a fixing device that is inexpensive and has a fast warm-up.

  As shown in FIG. 3, the fixing device 20 includes a light shielding member driving unit 50, a heating source driving unit 60, and a temperature sensor 70 including a thermistor as a “temperature detection unit”. As shown in FIG. 5, the light shielding member driving means 50 includes a gear unit 50A including a first gear 51, a second gear 52, and a third gear 53, and a motor 50B that drives the gear unit 50A by a worm gear 54. Yes. Then, by driving the motor 50B, the rotational force of the gear unit 50A is transmitted to the guide member 55, and the light shielding member 40 is rotated in the circumferential direction of the fixing belt 21 as indicated by an arrow R shown in FIG. Further, as shown in FIG. 3, the heat source driving means 60 includes a gear unit 60A and a motor 60B similar to the light shielding member driving means 50, and is driven by the motor 60B via the gear unit 60A. Is rotated and moved as indicated by an arrow S in FIG.

  In this embodiment, the light shielding member 40 and the heating source 23 rotate around the axis L. The light shielding member 40 and the heating source 23 may be rotated about an axis parallel to the axis L (for example, the axis LP). The light shielding member 40 may be rotated about the axis L, while the heating source may be rotated about the axis LP. The light shielding member 40 may be driven to rotate about the axis L, and the heating source 23 may be rotated about the center (for example, the axis 23L) between the center heater 23A and the end heater 23B. The axis is “parallel” even if it is coaxial.

  The temperature sensor 70 includes a contact type thermistor and detects the temperature of the pressure roller 22. Thus, the temperature sensor 70 detects the temperature of the fixing belt 21 (fixing means) via the pressure roller 22.

  As shown in FIG. 3, the light shielding member driving unit 50 and the heat source driving unit 60 of the fixing device 20 are driven and controlled by a controller 80. The controller 80 is connected to the main controller on the main body side of the image forming apparatus, receives various data such as paper size, number of sheets, and printing time from the main controller, and detects the temperature of the pressure roller 22 from the temperature sensor 70. To do. Then, the controller 80 controls the rotation of the light shielding member 40 and the heating source 23 via the light shielding member driving means 50 and the heating source driving means 60 based on various data such as the temperature, the paper size, the number of sheets, and the printing time. I do.

  As shown in FIGS. 3, 4, 5, and 6 (A), the shape of the light shielding member 40 is a stepped shape having a light shielding area corresponding to the width of each transfer paper. And it arrange | positions so that it may rotate without contact as mentioned above along the inner side of the fixing belt 21, and it rotates to the position corresponding to each paper width, and shields the area | region unnecessary for heating. As a result, even when transfer paper with a narrow width is continuously fed, the non-sheet passing area does not become overheated, and control such as reducing productivity to cancel the overheated area is minimized. You can stay. When the light shielding member 40 is rotated, the light shielding edge portion 40a (FIGS. 3, 4, 5, and 6A) has an oblique shape so that the light shielding region in the width direction (thrust direction) changes. Accordingly, it is not necessary to prepare a halogen heater as a heating source for each paper width (paper size).

  An example of the rotation control method of the light shielding member 40 and the heating source 23 and an example of the heating control method will be described below. Before the printing is started, the heat storage state of the fixing device 20 is determined from the elapsed time from the previous printing, the temperature of the pressure roller 22, and the like, and the position of the light shielding member 40 (the position in the rotation direction) at the start of printing is designated. To do. As a result, it is possible to avoid problems such as the temperature rise at the end portion being so fast that the light shielding member 40 cannot be rotated in time, and problems such as poor fixing at the start of printing due to excessive light shielding.

  Further, the temperature of the fixing belt 21 is detected, and the position of the light-shielding member is determined while observing the temperature of the fixing belt 21 during printing (when the fixing operation is performed). The temperature rise at the inner end can be suppressed.

  In addition, the position of the light shielding member may be made variable according to conditions such as the paper width (paper size) and paper type of the transfer paper to be printed. In addition, since the position of the light shielding member 40 is moved when the temperature of the edge rises during printing, an optimal light shielding state can be maintained according to each paper width (paper size) without shading lightly.

  The arrangement of the central heater 23A and the end heater 23B of the heating source 23 is the central heater 23A upstream in the rotation direction and the end heater 23B downstream. This is because light shielding is easier when the central heater 23 is on the top when small-size paper is passed. The central heater 23A and the end heater 23B are connected.

As shown in FIG. 7, it is the central position in the rotational direction that can radiate the radiation light (infrared rays) to the fixing belt 21 most efficiently among the openings of the light shielding member 40, and goes upstream or downstream from the center. The efficiency decreases. This is because the angle at which the fixing belt 21 is directly warmed is maximized when the fixing belt 21 is at the center in the rotational direction. This is because the component that warms the fixing belt 21 directly decreases as the distance from the center decreases, and the components of the primary reflected light and the secondary reflected light increase. The reflectance of the reflecting member 26 is about 98%. Therefore, the heating source 23 (central heater 23A, end heater 23B) is rotated (changed in position) in conjunction with the rotation of the light shielding member 40.

  For example, when printing large-size transfer paper, the light shielding member 40 is rotated in the opening direction. However, since the most end portion is subject to temperature sag and easily causes fixing failure, the end heater 23B is interlocked with the light shielding member 40. The heating source 23 is rotated so as to be in an efficient position.

  Further, when printing a small size transfer paper, the heating source 23 is rotated so that the central heater 23A is in an efficient position in conjunction with the rotation of the light shielding member 40 in the direction of narrowing the heating region. . This is because the end heater 23B is turned off and only the central heater 23A is turned on when the size is small, and the position where the efficiency of the central heater 23A is maximized is optimal. As a result, the fixing state can be kept good without consuming wasteful power.

  More specifically, when printing from a state in which the fixing device 20 is cold, the light shielding member 40 is in a position (position) where the light shielding rate is the lowest at the start of printing. For example, when printing of A6 size transfer paper is started, the temperature sensor 70 detects the temperature of the pressure roller 22 on the outer side when viewed in the width direction (thrust direction) than the A6 size paper width. When the controller 80 detects that the detected temperature is a certain temperature or higher (for example, 160 ° C. or higher), the controller 80 blocks the light from the heating source 23 (the surface area facing the heating source 23 is more relative). The light shielding member 40 is moved in the direction in which the printing speed is increased, and printing is continued while suppressing the temperature rise in the non-sheet passing area. The position of the light shielding member 40 and the temperature of the non-sheet passing area are paired, and the controller 80 has three sets of data sets of the position of the light shielding member 40 and the temperature of the non-sheet passing area. In the above example, when 170 ° C. is detected, the light shielding member 40 is moved to a position where light shielding is performed more than when 160 ° C. is detected.

  In addition, when printing a transfer sheet having a paper width in which the temperature increase in the non-sheet passing area cannot be detected by the arrangement of the temperature sensor in the thrust direction, the position of the light shielding member 40 is determined according to the time from the start of printing. The position of the light shielding member 40 and the time from the start of printing are also paired, and the controller 80 has three sets of data sets of the position of the light shielding member 40 and the time from the start of printing. You may control based not on the time from the start of printing but on the number of printed sheets and the cumulative lighting time (duty integration) of the heating source 23.

  When printing is started from a state in which the fixing device 20 is warm (the temperature detected by the temperature sensor 70 that detects the temperature of the pressure roller 22 is already 170 ° C. or higher), the following is performed. Before the start of printing, the light blocking member 40 is moved from a position with the lowest light blocking rate to a position with a high two-step light blocking rate.

  Further, when the position of the temperature sensor 70 in the thrust direction is changed, moved, or added to print B4 size transfer paper, the thrust direction is different from when printing A6 size transfer paper. Refer to the temperature sensor in position. The combination of the temperature at which the light shielding member 40 is moved and the position of the light shielding member 40 may be set differently from the A6 size printing.

  Further, since the temperature of the light shielding member 40 itself rises when continuous paper is passed, the light shielding member 40 is moved to a position where it does not receive infrared rays (heater light) from the heating source 23 when the number of sheets reaches a certain number or more. You may let them. Thus, it is possible to continue printing in combination with control such as reducing productivity.

  FIG. 8 is a diagram illustrating an example of a temperature distribution in the thrust direction when the heating source 23 is moved and when the heating source 23 is not moved. The horizontal axis indicates the position in the thrust direction, and the vertical axis indicates the temperature. Compared to the case where the heating source 23 is not fixed and moved as described above, the temperature distribution in the thrust direction can be further averaged by moving the heating source 23.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention. That is, the shape of each member of the fixing device 20 is not limited.

21 fixing belt 22 pressure roller 23 heating source 24 nip forming member 40 light shielding member 50 light shielding member driving means 60 heating source driving means 70 temperature sensor 80 controller

Japanese Patent Laid-Open No. 2004/286922 Japanese Patent No. 2861280 JP 2007-334205 A

Claims (7)

An endless flexible fixing member that is rotatable about an axis in the width direction;
A heating source for heating the fixing member;
A pressure member disposed to face the fixing member;
A nip forming member that forms a nip portion facing the pressure member inside the fixing member;
Temperature detecting means for detecting the temperature of the fixing member;
A light blocking member that blocks radiation from the heating source;
Light shielding member driving means for rotationally driving the light shielding member around an axis parallel to the axis;
Heating source driving means for rotating the heating source around an axis parallel to the axis;
With
The heating source is a heating source including a central heater having a heat generating portion at the center in the axial direction and an end heater having a heat generating portion at the end in the axial direction, and is upstream of the rotation direction of the fixing member. The central heater on the side, the end heater on the downstream side,
A fixing device that controls rotation of the light shielding member and the heating source. A fixing device heating control method for controlling heating of the fixing member of the fixing device according to claim 1,
A heating control method for a fixing device, wherein the heating source is rotated in conjunction with the light shielding member. A fixing device heating control method for controlling heating of the fixing member of the fixing device according to claim 1,
A heating control method for a fixing device, wherein the heating source is rotationally controlled during a fixing operation on a transfer sheet. A fixing device heating control method for controlling heating of the fixing member of the fixing device according to claim 1 ,
A heating control method for a fixing device, wherein when the light shielding member is rotated in a direction to reduce a light shielding region by the light shielding member, the heating source is rotated in a direction in which the efficiency of the end heater of the heating source is increased. . A fixing device heating control method for controlling heating of the fixing member of the fixing device according to claim 1 ,
A heating control method for a fixing device, wherein when the light shielding member is rotated in a direction to increase a light shielding area by the light shielding member, the heating source is rotated in a direction in which the efficiency of the central heater of the heating source is increased. A fixing device, wherein the heating control method for a fixing device according to claim 2 is performed.   An image forming apparatus comprising the fixing device according to claim 1.

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