JP6319468B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes an image on a recording medium, and an image forming apparatus including the fixing device.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, an unfixed image transferred and carried on a recording medium such as paper is heated and fixed to copy or copy Records can be obtained.

  At the time of fixing, a recording medium carrying an unfixed image is heated while being nipped and conveyed by a fixing member and a pressure member, so that a developer, particularly toner, contained in the unfixed image is melted. Softening and penetration into the recording medium are performed, and toner is fixed on the recording medium.

  Further, when heating the fixing member to a predetermined temperature with a heat source, if the heating time to the predetermined temperature is sufficiently short, the preheating step in the standby state can be omitted, and the energy consumption can be greatly reduced. In order to achieve this, a low heat capacity member such as a thin roller or belt composed of a metal substrate and an elastic rubber layer is widely used as the fixing member. In addition to the halogen heater that heats the fixing member with radiant heat, the heat source also uses a ceramic heater, an IH system with high heating efficiency, or the like to achieve rapid heating. For example, Patent Documents 1 to 4 disclose fixing devices having these configurations.

  Among these fixing devices, a fixing belt and a heating roller are installed on a fixing belt, a heating device is heated by an IH method, and a fixing member is locally heated by biasing the installation position of a built-in halogen heater. In the thing (partial heating method), the heating region heated by the heating source and the fixing nip portion are different in position. Therefore, even when the fixing member is heated relatively high in the heating region, the heat amount of the fixing member is taken away by the recording medium passing through the fixing nip portion when the image fixing operation is performed. Although the temperature does not become abnormally high, when the image forming device suddenly stops due to paper jams or other reasons, the image forming device is turned off, the fixing device is in off mode / sleep mode, or in energy saving mode. In the state where the rotation of the fixing member stops, the fixing member may be overheated due to the residual heat (residual heat) of the heating source even if the power supply to the heating source is stopped. Alternatively, even when the remaining heat of the heating source does not matter so much, the surface may be heated after the rotation is stopped due to the remaining heat of the reflector, the stay, and the hot internal air. Furthermore, if the heating area and the fixing nip are separated, the heating area has a higher portion so that the amount of heat required for fixing can be secured when the belt heated in the heating area moves to the fixing nip. Since it is heated, the belt portion is damaged if the belt portion is not deprived of heat. In particular, in a fixing device including a fixing member that is further thinned and has a low heat capacity in order to shorten the warm-up time and reduce energy consumption, such a problem tends to occur in the fixing member.

  When an image forming apparatus equipped with a partial heating type fixing device suddenly stops, the fixing member is deprived of heat by the pressure member or the recording medium in a range where it is in contact with the pressure member or the recording medium, In particular, in the range before entering the fixing nip portion including the heating area, the heat transfer in the circumferential direction is relatively slow, so that the heat is stored and the range is particularly thermally expanded. The temperature deviation in the circumferential direction of the fixing member is large, and there is a difference in the amount of thermal expansion between the high temperature region and the low temperature region, and if it goes too far, the kink (plastic indentation formed on the fixing member) Crushing) occurs. Since the occurrence of kinks is due to local thermal expansion, it depends on the material constituting the thin fixing member and its thickness, but when the fixing member generates kinks, it develops into an abnormal image and further fixing. It also leads to the destruction of members.

  The present invention does not cause a kink to occur on the fixing member even when the fixing member suddenly stops abnormally due to a jam or a heater, etc. and the fixing member suddenly stops abnormally. Is an issue.

In order to solve the above problems, the present invention provides a heating source, a rotatable fixing member that is heated by the heating source and heats a recording medium, and press-contacts the fixing member and includes a nip between the fixing member and the fixing member. In a fixing device configured to include a rotatable pressure member that forms a portion, and a rotation driving unit that rotates the fixing member or the pressure member, the fixing member has a nip forming member therein A belt, the nip forming member is opposed to the pressure member at the nip portion via the fixing member, the heating source is a radiant heater, and the nip is formed in the circumferential direction of the fixing member. When the fixing member other than the portion is heated and the fixing member stops for a reason other than the end of the fixing process in the apparatus power-on state, the power supply to the heating source is stopped, Its establishment At least a predetermined amount of the fixing member after the timber is stopped, the is rotated by the pressure member, the rotational speed of the fixing member when the fixing member after fixing member is stopped by a predetermined amount of rotation, following the rotational speed before the fixing member stopped it is proposed that is.

  According to the present invention, when the fixing member stops abnormally and suddenly, the fixing member rotates and moves before the portion of the fixing member partially heated by the heating source generates kinks due to thermal expansion. The temperature deviation in the circumferential direction can be suppressed, and the occurrence of kinks can be avoided.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram of a fixing device mounted in an image forming apparatus. It is a schematic block diagram of a fixing device provided with only one halogen heater as a heating source. It is a schematic block diagram of a fixing device provided with three halogen heaters as heating sources. FIG. 2 is a diagram conceptually showing a heating source (halogen heater) and temperature detection means (thermopile, thermistor) of a fixing device. FIG. 3 is a diagram illustrating a temperature control circuit of the fixing device. FIG. 7A is a graph showing a temperature change of the fixing belt. FIG. 7A shows a temperature change when the fixing belt is rotated until the paper discharge roller stops after the heater is turned off, and FIG. The temperature change when the fixing belt is stopped at substantially the same timing as FIG. 6 is a graph showing a temperature change of the fixing belt when the temperature of the fixing belt is monitored and the belt is rotated as necessary after the fixing motor is stopped. 6 is a graph showing a temperature distribution in the circumferential direction when the image forming apparatus suddenly stops and the fixing belt stops rotating. 6 is a graph showing a temperature distribution in the circumferential direction when the fixing belt is forcibly rotated by L ₁ -L ₂ when the image forming apparatus stops suddenly and the fixing belt stops rotating. It is a kink avoidance flow at the time of forward rotation operation. It is a kink avoidance flow at the time of reverse operation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings for explaining the embodiments of the present invention, components such as members and components having the same function or shape are given the same reference numerals as much as possible to simplify the explanation. To do.

First, an overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
The image forming apparatus 1 is a tandem color laser printer, and four image forming units 4Y, 4M, 4C, and 4K are provided at 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. It is the same composition except being.

  More specifically, each of the image forming units 4Y, 4M, 4C, and 4K includes 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 photosensitive member 5. A developing device 7 for supplying toner to the surface and a cleaning device 8 for cleaning the surface of the photoreceptor 5 are provided. In FIG. 1, only for the black image forming unit 4K, the reference numerals are given to the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8, and the other image forming units 4Y, 4M, and 4C are omitted. doing.

  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 an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, a secondary transfer backup roller 32, and a cleaning device. A 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 is like that.

  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 developing device 7 is connected from each toner bottle 2Y, 2M, 2C, 2K via this replenishment path. The toner is replenished.

  On the other hand, at the bottom of the printer main body, a paper feed tray 10 that stores paper P as a recording medium, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like are provided. Here, the concept of the recording medium includes, in addition to plain paper, thick paper, postcard, envelope, 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 transport path R is provided for discharging the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, on the upstream side of the secondary transfer roller 36 in the paper transport direction, a timing adjusting roller 12 called a pair of registration rollers is disposed as a transport means for transporting the paper P to the secondary transfer nip. ing.

  Further, a fixing device 20 for fixing the unfixed image transferred onto the paper P is disposed downstream of the secondary transfer roller 36 in the paper transport direction. An inlet sensor 40 and an outlet sensor 41 for detecting the passage of the paper are disposed on the upstream side and the downstream side in the paper transport direction with respect to the fixing device 20.

  Further, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. The fixing motor M1 that drives the fixing device 20 and the paper discharge motor M2 that drives the paper discharge roller 13 can be driven independently of each other. In addition, a paper discharge tray 14 for stocking paper discharged outside the apparatus is provided on the upper surface of the printer main body.

  Next, the basic operation of the printer according to this embodiment will be described. When the image forming operation is started, the respective photoconductors 5 in the respective image forming units 4Y, 4M, 4C, and 4K are rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 5 is charged by the charging device 6. Are uniformly charged to a predetermined polarity. The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5. At this time, the image information to be exposed on each photoconductor 5 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, whereby the electrostatic latent image is visualized (visualized) as a toner image. .

  When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated by the arrow in the figure. Then, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 31. As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

  Thereafter, when each color toner image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the toner image on each photoconductor 5 is generated by the transfer electric field formed in the primary transfer nip. Are successively superimposed and transferred onto the intermediate transfer belt 30. Thus, a full color toner image is carried on the surface of the intermediate transfer belt 30. The toner on each photoconductor 5 that has not been transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Thereafter, the surface of each photoconductor 5 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  In the lower part of the image forming apparatus, the paper feed roller 11 starts to rotate, and the paper P is sent out from the paper feed tray 10 to the transport path R. The sheet P sent to the transport path R is timed by the registration roller 12 and sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip. .

  Thereafter, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 rotates, the transfer electric field formed in the secondary transfer nip causes the toner image on the intermediate transfer belt 30 to move. The toner images are transferred onto the paper P all at once. At this time, the residual toner on the intermediate transfer belt 30 that has not been transferred to the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and stocked on the paper discharge tray 14.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single-color image is formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. Of course, it is possible to form a two-color or three-color image using two or three image forming units.

  Next, the configuration of the fixing device 20 will be described. As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a rotatable fixing member, a pressure roller 22 as a pressure member rotatably provided facing the fixing belt 21, and fixing. A halogen heater 23 as a heating source for heating the belt 21, a nip forming member 24 and a stay 25 as support members disposed inside the fixing belt 21, and light emitted from the halogen heater 23 to the fixing belt 21. The sheet is separated from the fixing belt 21, the reflecting member 26 that reflects, the thermopile 27 that detects the temperature of the fixing belt 21, the thermistor 29 that detects the temperature of the pressure roller 22, and the fixing belt 21. A separation member 28 and a pressure / pressure release means (not shown) for pressing the pressure roller 22 to the fixing belt 21 are provided.

  The fixing belt 21 is composed of an endless belt member (including a film) that is thin and flexible. More specifically, the fixing belt 21 includes a base material on the inner peripheral side made of a material having high thermal expansion such as nickel or SUS, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or polytetrafluoroethylene. It is comprised by the mold release layer of the outer peripheral side formed with (PTFE) etc. Further, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

  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 22. And 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 a 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 printer main body. 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.

In the present embodiment, the pressure roller 22 is a hollow roller, but it may be a solid roller. Further, a heating source such as a halogen heater may be disposed inside the pressure roller 22 . Elastic layer 22b may be a solid rubber, but if there is no heat source inside the pressing roller 22 may be with a sponge rubber. Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is hardly taken away. In addition, the fixing member and the pressure member are not limited to being in pressure contact with each other, and may be configured to simply contact without pressing.

  In this embodiment, the halogen heater 23 is composed of two halogen heaters 23A (first halogen heater) and 23B (second halogen heater), and each halogen heater 23A, 23B has a fixing device 20 at both ends. Is fixed to a side plate (not shown). The halogen heaters 23A and 23B are configured to generate heat by being output controlled by a power supply unit provided in the printer body, and the output control is based on the detection result of the surface temperature of the fixing belt 21 by the thermopile 27. Done. By such output control of the heaters 23A and 23B, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired value. As shown in FIG. 3, the halogen heater can be a single heater capable of heating the entire paper-passable area as shown in FIG. Three or more heaters may be used, and the heating source for heating the fixing belt 21 may be a heating element other than the halogen heater, for example, a ceramic heater.

  The nip forming member 24 is disposed long in the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22, and is fixedly supported by a stay 25. Thereby, the pressure from the pressure roller 22 is supported, the situation where the nip forming member 24 is bent is prevented, and a uniform nip width is obtained in the axial direction of the pressure roller 22. The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the function of preventing the nip forming member 24 from bending. Furthermore, by forming the stay 25 so as to have a horizontally long cross section extending in the pressure direction of the pressure roller 22, the section modulus is increased, and the mechanical strength of the stay 25 can be improved. .

  The nip forming member 24 is formed of a heat resistant member having a heat resistant temperature of 200 ° C. or higher. This prevents the nip forming member 24 from being deformed by heat in the toner fixing temperature range and ensures a stable state of the nip portion N, thereby stabilizing the output image quality. For the nip forming member 24, polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), polyether ether ketone (PEEK), etc. It is possible to use a typical heat resistant resin. In this embodiment, LCP is used.

  The nip forming member 24 has a low friction sheet 240 on the surface thereof. When the fixing belt 21 rotates, the fixing belt 21 slides with respect to the low friction sheet 240, whereby the driving torque generated in the fixing belt 21 is reduced, and the load due to the frictional force on the fixing belt 21 is reduced.

  The reflection member 26 is disposed between the stay 25 and the halogen heater 23. By arranging the reflection member 26 in this way, the light emitted from the halogen heater 23 toward the stay 25 is reflected to the fixing belt 21. As a result, the amount of light applied to the fixing belt 21 can be increased, and the fixing belt 21 can be efficiently heated. Further, it is possible to suppress radiant heat from the halogen heater 23 from being transmitted to the stay 25 and the like, and energy saving can be achieved.

In addition, the fixing device 20 according to the present embodiment is devised in various configurations in order to further improve energy saving and first print time.
Specifically, the fixing belt 21 can be directly heated at a place other than the nip portion N by the halogen heater 23 (direct heating method). In this embodiment, nothing is interposed between the halogen heater 23 and the fixing belt 21 between the left side portions in FIG. 2, and the radiant heat from the halogen heater 23 is directly applied to the fixing belt 21 in that portion. .

  Further, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is made thinner and smaller in diameter. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in the ranges of 20 to 100 μm, 100 to 300 μm, and 5 to 50 μm. The diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, the thickness of the entire fixing belt 21 is desirably 0.4 mm or less, and more desirably 0.2 mm or less. The diameter of the fixing belt 21 is desirably 30 mm or less. The fixing belt is obtained by baking an elastic layer on a base material and coating a release layer.

  In this embodiment, the diameter of the pressure roller 22 is set to 20 to 40 mm, and the diameter of the fixing belt 21 and the diameter of the pressure roller 22 are configured to be equal. However, it is not limited to this configuration. For example, the fixing belt 21 may be formed so that the diameter thereof is smaller than the diameter of the pressure roller 22. In that case, since the curvature of the fixing belt 21 at the nip portion N is larger than the curvature of the pressure roller 22, the recording medium discharged from the nip portion N is easily separated from the fixing belt 21.

  Further, as a result of reducing the diameter of the fixing belt 21, the space inside the fixing belt 21 is reduced. However, in this embodiment, the stay 25 is formed in a concave shape bent at both ends, and the inside of the portion formed in the concave shape. By accommodating the halogen heater 23, the stay 25 and the halogen heater 23 can be arranged even in a small space.

  Further, in order to dispose the stay 25 as large as possible even in a small space, the nip forming member 24 is formed compact on the contrary. Specifically, the width of the nip forming member 24 in the sheet conveyance direction is formed smaller than the width of the stay 25 in the sheet conveyance direction. Further, in FIG. 2, the heights of the nip forming member 24 at the upstream end 24a and the downstream end 24b in the sheet conveying direction with respect to the nip N (or its virtual extension line E) are h1 and h2, respectively. When the maximum height with respect to the nip portion N (or its virtual extension line E) in the portion of the nip forming member 24 other than the end portion 24a and the downstream end portion 24b is h3, h1 ≦ h3 and h2 ≦ h3. doing. With this configuration, the upstream end 24 a and the downstream end 24 b of the nip forming member 24 are interposed between the bent portions on the upstream and downstream sides of the stay 25 in the sheet conveying direction and the fixing belt 21. Therefore, each bent portion can be disposed close to the inner peripheral surface of the fixing belt 21. As a result, the stay 25 can be disposed as large as possible in a limited space in the fixing belt 21, and the strength of the stay 25 can be ensured. As a result, it is possible to prevent the nip forming member 24 from being bent by the pressure roller 22 and to improve the fixability.

  The basic operation of the fixing device according to this embodiment will be described below. When the power switch of the printer main body is turned on, power is supplied to the halogen heater 23 and the pressure roller 22 starts to rotate clockwise in FIG. As a result, the fixing belt 21 is driven to rotate counterclockwise in FIG. 2 by the frictional force with the pressure roller 22.

  Thereafter, the paper P carrying the unfixed toner image T in the image forming process described above is conveyed in the direction of the arrow A1 in FIG. 2 while being guided by the guide plate 37, and sent to the nip portion N that is in a pressure contact state. Is done. Then, the toner image T is fixed on the surface of the paper P by heat from the fixing belt 21 heated by the halogen heater 23 and pressure applied between the fixing belt 21 and the pressure roller 22.

  The paper P on which the toner image T is fixed is carried out from the nip portion N in the direction of the arrow A2 in FIG. At this time, the paper P is separated from the fixing belt 21 by the leading edge of the paper P coming into contact with the leading edge of the separation member 28. Thereafter, the separated paper P is discharged out of the apparatus by the paper discharge roller as described above, and stocked on the paper discharge tray.

  In the printer according to the present embodiment, the fixing motor M1 is stopped immediately after the trailing edge of the paper P has escaped from the fixing nip N and while the paper P is being transferred by the paper discharge roller 13, thereby fixing the paper. The rotation of the belt 21 is stopped. In a conventional image forming apparatus, the fixing device and the paper discharge roller are driven by a common motor, and the fixing belt / fixing roller and the paper discharge roller are usually rotated simultaneously or stopped simultaneously. In contrast, in this example, the pressure roller 22 and the paper discharge roller 13 are rotationally driven by independent motors M1 and M2, so that the pressure roller 22 can be stopped while the paper discharge roller 13 is rotating. Therefore, it is possible to control to temporarily stop the fixing motor M1 while the paper discharge motor M2 is rotating.

  In this manner, the fixing motor M1 is stopped immediately after the trailing edge of the sheet exits the fixing nip N, so that the pressure roller is driven as compared with the conventional apparatus in which the fixing device and the discharge roller are simultaneously driven and stopped. Time can be shortened. Since the fixing motor M1 needs to drive not only the pressure roller but also the fixing belt, and the fixing belt receives resistance by sliding with the nip forming member fixed to the side plate, the power consumption of the fixing motor M1 is large. Therefore, as described above, if the entire sheet escapes from the fixing nip N and the fixing motor M1 is temporarily stopped while the paper discharge motor M2 is being driven, the driving time of the fixing motor M1 can be shortened and saved. Electricity can be achieved. The temporary stop of the fixing motor M1 can be performed not only at the time of individual paper passing during continuous paper passing but also after the passage of a plurality of papers.

  Such an effect can be obtained when both rollers can be driven and stopped independently. Therefore, the present invention is not limited to a configuration in which the paper discharge roller and the pressure roller are driven by separate motors M1 and M2. For example, even if both rollers are driven by a common motor, a clutch is arranged in the torque transmission path from the motor to both rollers, and the rotation and stop of both rollers are controlled independently by switching the clutch. However, similar effects can be obtained.

  Hereinafter, heating in the axial direction of the fixing belt 21 by the two halogen heaters 23A and 23B will be described. As can be seen from FIG. 5, the positions of the heat generating portions of the first halogen heater 23A and the second halogen heater 23B are different. That is, the first halogen heater 23A has a heat generating portion (light emitting portion) 23A1 disposed over a predetermined range from the central portion in the longitudinal direction. In the present embodiment, the heat generating portion 23A1 is provided in a range of 200 to 220 mm symmetrically from the center in the longitudinal direction of the first halogen heater 23A. On the other hand, the second halogen heater 23B has heat generating portions (light emitting portions) 23B1 at both ends in the longitudinal direction. In the present embodiment, the heat generating portion 23B1 is provided to cover both ends of the belt width outward in the longitudinal direction from the region corresponding to the heat generating portion 23A1 of the first halogen heater 23A. Here, the passing width of A3 size paper or A4 size paper in landscape orientation is 297 mm, and the total length of the length of the heat generating portion 23A1 of the first halogen heater 23A and the length of the heat generating portion 23B1 of the second halogen heater 23B. Is set to be 300 to 330 mm, so that it is longer than the sheet passing width. This is because the amount of heat generation decreases in the outer end region of the heat generating portion 23B1 (the light emission intensity becomes weak), and a temperature drop occurs. Therefore, a portion where the heat generation amount (heat generation strength) exceeds a predetermined value is used as the paper passing region. This is necessary.

  In this embodiment, two thermopiles 27 that detect the temperature of the fixing belt 21 are provided. The first thermopile 27A detects the temperature of the central region of the fixing belt 21 corresponding to the heat generating part 23A1 of the first halogen heater 23A, and the second thermopile 27B corresponds to the heat generating part 23B1 of the second halogen heater 23B. Thus, each thermopile is installed so as to detect the temperature of the end region of the fixing belt 21.

  FIG. 6 shows a configuration example of the temperature control circuit of the fixing device 20. The electric power supplied from the power supply unit 51 is supplied to the halogen heaters 23A and 23B via the relay 52 and the triacs 53A and 53B, respectively. The relay 52 is turned on (closed) during warm-up, print job execution, ready standby, etc., and is turned off (opened) during other power-off, off-mode, energy-saving mode, sudden stop, etc. The The triacs 53A and 53B control the energization amount to the first halogen heater 23A and the second halogen heater 23B, respectively, and feed back the temperature information of the fixing belt 21 detected by the first thermopile 27A and the second thermopile 27B. The fixing belt 21 is maintained at a predetermined temperature. The ready standby is a state in which printing can be started immediately upon receiving a print job instruction. The software / hardware that operates the machine, such as the controller and engine software, has already been started. In this state, the fixing motor is generally stopped, but the fixing member is maintained at a constant temperature. Can pass through immediately.

The temperature control unit 54 includes a relay control unit 54A that controls the relay 52, a triac control unit 54B that controls the triacs 53A and 53B, and an overtemperature protection circuit that outputs an abnormal stop signal when the fixing belt 21 is overheated. 54C. The temperature control unit 54 receives temperature information of the center region and the end region of the fixing belt 21 detected by the first thermopile 27A and the second thermopile 27B as temperature information values (voltage values) D ₁ and D _2. . In the present embodiment, relay control section 54A based on the temperature information value _D 1, _{D 2,} and outputs the ON / OFF control signals _{S 1} to the relay 52, the drive control to the drive control unit 60 of the pressing roller 22 outputs a signal _{S 2,} the triac control unit 54B, based on the temperature information values D1, D2, triacs 53A, and outputs an energization control signal _{S 3} to 53B, overheat protection circuit 54C, the temperature information value _{D 1} , D ₂ , an abnormal stop signal S ₄ is output to the relay control unit 54 A. However, it is not limited to such a configuration.

  In the fixing device according to the present embodiment, the fixing belt 21 with a reduced heat capacity is directly heated as described above, and the heat irradiation range for the fixing belt 21 is limited by the reflecting member 26. Therefore, if heating by the halogen heater 23 is continued in a state where the fixing belt 21 is stopped by stopping the driving of the fixing motor M1, the fixing belt 21 may be instantaneously overheated and the belt may be damaged. In order to prevent such a problem, when the fixing motor M1 is temporarily stopped, the halogen heater 23 is turned off (stopped) before the fixing motor M1 is stopped, and the halogen heater 23 is always turned off when the fixing motor M1 is stopped. To. This switching is performed by giving a control signal from the temperature control unit 54 to the triac 53. The halogen heater 23 may be turned off after the paper P has completely passed through the fixing nip N, or in a state where the rear end of the paper P exists in the fixing nip N.

  By the way, the halogen heater 23 has a configuration in which a heater and a halogen are enclosed in a glass tube, and heat accumulated in the glass tube is released even after the heater is turned off. Therefore, when a halogen heater is used as a heating source, the fixing belt 21 is temporarily heated by the residual heat of the glass tube even after the heater is turned off. Further, while the sheet is passing through the fixing nip N, the sheet P is deprived of heat. However, after the trailing end of the sheet has escaped from the fixing nip N (the completion of sheet passing), heat is not released via the sheet P. Temperature rises. 7A shows the temperature change of the fixing belt when the fixing belt 21 is rotated after the halogen heater 23 is turned off until the paper discharge roller 13 stops. FIG. 7B shows the halogen heater 23 turned off. The temperature change of the fixing belt when the rotation of the fixing belt 21 is stopped at substantially the same timing as FIG. FIGS. 7A and 7B show a case where the sheet passing is completed at the same time as the halogen heater is turned off.

  In the fixing device having the configuration corresponding to FIG. 7A, heat is dissipated by the rotation of the fixing belt 21 even after the heater is turned off, so that the temperature rise of the fixing belt 21 becomes moderate. On the other hand, in the fixing device having the configuration corresponding to FIG. 7B, since the rotation of the fixing belt 21 is stopped at the same time as the heater is turned off, the temperature of the fixing belt rapidly increases without performing heat dissipation. Depending on the heat storage state, the upper limit temperature may be exceeded and the belt may be damaged.

  Therefore, the fixing device according to the present embodiment is configured to radiate heat from the fixing belt 21 based on the detected value of the thermopile 27 that is a temperature sensor after the rotation of the fixing belt 21 is stopped. The heat radiation can be performed, for example, by rotating the fixing belt 21 by the fixing motor M1. Specifically, as shown in FIG. 8, the temperature of the fixing belt 21 is monitored for a certain time (for example, 10 seconds) after the fixing motor M1 is stopped, and the temperature conversion value D of the fixing belt 21 is smaller than the upper limit temperature. When the temperature reaches the specified temperature or higher, the fixing motor M1 is started, and the fixing belt 21 is rotated to radiate heat. As a result, as shown by the solid line in FIG. 8, it is possible to prevent overheating of the fixing belt 21. The broken line in the figure shows the assumed temperature change of the fixing belt 21 when the fixing belt 21 is stopped simultaneously with the heater stop and the fixing belt 21 is kept stopped thereafter.

  When a printer having the above-described fixing device is suddenly stopped by relaying off during image processing due to a paper jam or the like, the power supply to the halogen heaters 23A and 23B is stopped while the fixing device power is on. The fixing belt is also stopped. FIG. 9 shows the circumferential temperature distribution of the fixing belt at that time. The heating area of the fixing belt is defined by the residual heat of the halogen heater 23 as a heating source (defined by the end of the reflection member 26 and the position of the halogen heater 23, and heated by direct radiation of the halogen heater 23 and reflection by the reflection member 26. The belt inner peripheral range) is further heated. As described above, unless the heated area moves to the fixing nip and is deprived of heat by the pressure member or the paper, the heated area remains at a high temperature and thermally expands to an overheated state (particularly heated). A) closest to the source A). On the other hand, the belt portion other than the heating region does not thermally expand because of low thermal conductivity. In particular, the position B on the upstream side in the belt rotation direction with respect to the heating region has the lowest temperature, and plays a role of suppressing the movement of the portion A to expand at the B position, and the portion A is not fully expanded and is recessed inside. (Kink occurs). That is, the temperature difference between the locations A and B causes kinking.

Therefore, in order to avoid the occurrence of kink, when the printer suddenly stops and the fixing belt also stops rotating, the fixing motor M1 is started and the fixing belt 21 is forcibly rotated to release heat. For example, as shown in FIG. 2, when the length of the heating region in the belt circumferential direction is L ₂ and the circumferential length of the entire fixing belt is L ₁ , fixing is performed by L ₁ −L ₂ (= L). When the belt 21 is rotated forward, the entire circumference of the fixing belt receives the residual heat of the halogen heater, the entire belt is thermally expanded, and the occurrence of kinks can be suppressed. FIG. 10 shows the circumferential temperature distribution of the fixing belt at that time. In this embodiment, it was confirmed that kinks are generated when the temperature difference between A and B is about 90 ° C. to 110 ° C., and that kinks can be avoided by rotation of L ₁ −L ₂ (= L). The rotation amount of L is defined in the case of the endless fixing belt 21 that is thin and flexible, and may be equal to or less than L in a configuration other than the fixing belt 21. The length of L ₂ is intended to be defined from the mutual position relationship between the heater 23 and the reflector 26 the fixing belt 21.

If there is no paper P between the fixing entrance sensor 40 and the fixing exit sensor 41 when the image forming apparatus is suddenly stopped, the rotation distance of the fixing belt is set without limitation, and the residual heat of the halogen heater is uniformly absorbed throughout the belt. it can. The forward rotation operation is selected because it is stable as the operation of the fixing member. However, there is no problem even if the reverse rotation operation is selected as long as it is a fixing device in which the reverse rotation operation is stable. However, if there is a sheet between the fixing entrance sensor and the fixing exit sensor when the image forming apparatus is suddenly stopped, if the normal rotation operation is performed, the sheet is wound around the fixing belt, and the user cannot perform jam processing. Therefore, when there is a sheet between the fixing entrance sensor and the fixing exit sensor, the reverse operation should be selected.

  FIG. 11 shows a kink avoidance flow when the forward rotation operation is performed when there is no paper P between the fixing entrance sensor 40 and the fixing exit sensor 41. After detecting a jam, stop the heater and turn off the relay. At the same time, the fixing motor control is changed to the normal rotation linear speed and the normal rotation operation is started. Stop the motor after rotating forward distance. After stopping the motor, release the pressure and complete the operation.

  Next, FIG. 12 shows a kink avoidance flow when the sheet P is present at the fixing entrance sensor 40 and the fixing exit sensor 41 when the sheet is reversely operated. After detecting a jam, stop the heater and turn off the relay. At the same time, the fixing motor is stopped. After confirming that the brake control time (guaranteed value until complete stop, for example, several tens of milliseconds) has elapsed, the fixing motor is surely stopped. After the brake control time has elapsed, the progress of the rotation stop waiting time (= margin for securing the time from switching from forward rotation to reverse rotation) is checked. Reverse rotation starts after the rotation stop waiting time has elapsed. Stop motor after reverse rotation distance. After stopping the motor, release the pressure and complete the operation. The reverse rotation distance here is defined in a range in which no kink occurs and the jammed paper P does not damage the image forming apparatus. The reason is that if the reverse rotation distance is too large, the jammed paper P may hit the intermediate transfer belt 30 and be damaged, or may enter the gap in the image forming apparatus. It is to become. In order to prevent a problem caused by the reversal distance being too large, for example, the distance from the rear end of the jammed paper P to the secondary transfer nip may be considered as the upper limit of the reversal distance. The upper limit is calculated according to the length of the paper in the conveyance direction.

  In order to prevent kinks, it is effective to increase the rotation time, so it is preferable to decrease the linear speed and increase the rotation time. Therefore, the forward rotation and the reverse rotation linear velocity are set so as to be equal to or lower than the rotation speed before the fixing device suddenly stops.

  When there is a sheet between the fixing entrance sensor and the fixing exit sensor when the image forming apparatus is suddenly stopped, and this sheet is a strong thick paper, the sheet is conveyed to the fixing device when the fixing belt is operated in reverse. There is a possibility that the sheet pierces the members (in the present embodiment, the intermediate transfer belt 30 and the secondary transfer roller 36) located on the upstream side of the path, and damages the upstream members. Therefore, the amount of reverse rotation is calculated from the length in the longitudinal direction of the paper (length in the paper conveyance direction) so that the paper does not pierce the upstream member, and control is performed so that the paper is reversely operated by the calculated amount. By controlling in this way, it is possible to suppress the occurrence of kinks while protecting the upstream member.

  The above describes a configuration that avoids the situation where kinks are generated due to the residual heat of the heating source. However, even if the residual heat of the heating source itself is not a problem, the heating area is affected by the residual heat of the reflector, stay, and hot internal air. The temperature of the heating region may cause kinking when the fixing belt stops. In order to avoid this, it is preferable to move the heating area when the fixing belt is stopped to the fixing nip portion and take heat away by a pressure roller or the like. At least the most advanced part of the heating area or the part closest to the heating source is moved to the fixing nip part.

  The present invention is applicable to other types of fixing devices such as a belt type fixing device in which a fixing belt is installed between a fixing roller and a heating roller, and a pressure roller is pressed against the fixing roller via the fixing belt. Is also applicable. When the fixing belt is constructed by the fixing roller and the heating roller, the heating roller may be driven. Further, the fixing device according to the present invention is not limited to the color laser printer shown in FIG. 1, but can be mounted on a monochrome image forming apparatus or other electrophotographic image forming apparatus.

20 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (Pressure member)
23 Halogen heater (heating source)
23A First halogen heater 23B Second halogen heater 24 Nip forming member (support member)
25 Stay (support member)
27 Thermopile (temperature detection means)
27A 1st thermopile 27B 2nd thermopile 51 Power supply unit 52 Relay 53A Triac 53B Triac 54 Temperature control unit 54A Relay control unit D ₁ Temperature information value from the 1st thermopile D ₂ Temperature information value from the 1st thermopile L ₁ Fixing belt ( Fixing member) Perimeter L ₂ Fixing belt (fixing member) heating range N Nip part P Paper (recording medium)

JP 2007-79040 A JP 2010-32625 A JP 2007-334205 A JP 2008-129517 A

Claims (21)

A heating source;
A rotatable fixing member that is heated by the heating source and heats the recording medium ;
A rotatable pressure member that presses against the fixing member and forms a nip portion with the fixing member;
In a fixing device configured to include a rotation driving unit that rotates the pressure member,
The fixing member is a belt having a nip forming member therein, the nip forming member is the nip portion and faces the pressure member through the fixing member, and the heating source is a radiant heater. Yes, in the circumferential direction of the fixing member, the portion of the fixing member other than the nip portion is heated ,
When the fixing member is stopped for a reason other than the end of the fixing process when the apparatus power is on, the power supply to the heating source is stopped, and the fixing member is pressed at least by a predetermined amount after the fixing member is stopped. Rotate following the member ,
The fixing device according to claim 1, wherein a rotation speed of the fixing member when the fixing member is rotated by a predetermined amount after the fixing member is stopped is equal to or lower than a rotation speed before the fixing member is stopped . A heating source;
A rotatable fixing member that is heated by the heating source and heats the recording medium ;
A rotatable pressure member that presses against the fixing member and forms a nip portion with the fixing member;
In a fixing device configured to include a rotation driving unit that rotates the fixing member or the pressure member,
The fixing member is a belt having a nip forming member therein, the nip forming member is the nip portion and faces the pressure member through the fixing member, and the heating source is a radiant heater. Yes, in the circumferential direction of the fixing member, the portion of the fixing member other than the nip portion is heated ,
When the fixing member stops for a reason other than the end of the fixing process when the apparatus power is on, the power supply to the heating source is stopped, the relay is turned off, and the fixing member is at least a predetermined amount after the fixing member is stopped. Rotate ,
The fixing device according to claim 1, wherein a rotation speed of the fixing member when the fixing member is rotated by a predetermined amount after the fixing member is stopped is equal to or lower than a rotation speed before the fixing member is stopped . A heating source;
A rotatable fixing member that is heated by the heating source and heats the recording medium;
A rotatable pressure member that presses against the fixing member and forms a nip portion with the fixing member;
Rotation driving means for rotating the pressure member;
In a fixing device configured to include:
The fixing member is a belt having a nip forming member therein, the nip forming member is the nip portion and faces the pressure member through the fixing member, and the heating source is a radiant heater. Yes, in the circumferential direction of the fixing member, the portion of the fixing member other than the nip portion is heated,
When the fixing member is stopped for a reason other than the end of the fixing process when the apparatus power is on, the power supply to the heating source is stopped, and the fixing member is pressed at least by a predetermined amount after the fixing member is stopped. Rotate following the member,
Detecting means for detecting the temperature of the fixing member, and the fixing means when the detecting means detects that the fixing member has reached a predetermined temperature after the fixing member is stopped for the reason of completion of the fixing process. A fixing device that rotates a member. A heating source;
A rotatable fixing member that is heated by the heating source and heats the recording medium;
A rotatable pressure member that presses against the fixing member and forms a nip portion with the fixing member;
Rotation driving means for rotating the fixing member or the pressure member;
In a fixing device configured to include:
The fixing member is a belt having a nip forming member therein, the nip forming member is the nip portion and faces the pressure member through the fixing member, and the heating source is a radiant heater. Yes, in the circumferential direction of the fixing member, the portion of the fixing member other than the nip portion is heated,
When the fixing member stops for a reason other than the end of the fixing process when the apparatus power is on, the power supply to the heating source is stopped, the relay is turned off, and the fixing member is at least a predetermined amount after the fixing member is stopped. Rotate
Detecting means for detecting the temperature of the fixing member, and the fixing means when the detecting means detects that the fixing member has reached a predetermined temperature after the fixing member is stopped for the reason of completion of the fixing process. A fixing device that rotates a member. The predetermined amount, upon stop of the fixing member, portions of the fixing member in contact recently the heating source, any of claims 1 to 4, characterized in that the quantity necessary to move to the nip the fixing device according to an item or. The fixing member has a circumferential length L _1, the range of the fixing member heated by the heating source is a L _2, claim 1, wherein the predetermined amount is characterized in that the L ₁ -L ₂ the fixing device according to any one of to 4. When a recording medium detection unit is provided on each of the upstream side and the downstream side of the recording medium conveyance path in the nip portion, and it is determined that there is no recording medium between the recording medium detection units when the fixing member is stopped. the fixing device according to any one of claims 1 to 6, characterized in that to forward the fixing member. When a recording medium detection unit is provided on each of the upstream side and the downstream side of the recording medium conveyance path in the nip portion, and it is determined that there is a recording medium between the recording medium detection units when the fixing member is stopped. the fixing device according to any one of claims 1 to 6, characterized in that reversing the fixing member. 9. The storage device according to claim 8 , further comprising: a storage device that stores a length of the recording medium in a recording medium conveyance direction, wherein the reverse rotation amount of the fixing member is changed according to the length of the recording medium stored in the storage device. The fixing device described. 8. The fixing device according to claim 6 , wherein an upper limit is set for the reverse rotation of the fixing member in accordance with a length in a conveyance direction of the recording medium.   An image forming apparatus comprising the fixing device according to claim 1. The fixing device includes a discharge roller, the first motor rotates drives the fixing member, the fixing according to claim 1 or 2 second motor and drives rotating the sheet discharge rollers apparatus.   The image forming apparatus according to claim 11, wherein the image forming apparatus includes a paper discharge roller on a downstream side of the fixing device.   The image forming apparatus includes a first motor that rotationally drives the fixing member and a second motor that rotationally drives the paper discharge roller, and the first motor and the second motor are independent motors. The image forming apparatus according to claim 13, wherein the image forming apparatus is provided. The image forming apparatus according to claim 13 , wherein a motor for rotating the fixing member and a motor for rotating the discharge roller are common . The fixing device according to claim 1 or 2 the thickness of the fixing member is a belt, characterized in that it is 0.4mm or less. The fixing device according to claim 1 or 2 the thickness of the fixing member is a belt, characterized in that it is 0.2mm or less. The diameter of the fixing member fixing device according to claim 1 or 2, characterized in that a 20 to 40 mm. The diameter of the fixing member fixing device according to claim 1 or 2, characterized in that it is 30 mm. The fixing member is a belt fixing device according to claim 1 or 2, characterized in that it consists substrate and the elastic layer and the releasing layer. The fixing member is a belt has a nip forming member and the supporting member inside the fixing device according to claim 1 or 2, wherein the nip forming member is characterized by being supported by the support member.

Images