JP2015028507A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to properly detect a current or electric power to be applied to a heat source, and to prevent a temperature of a fixing member from being significantly increased due to heat generated in the heat source.SOLUTION: The fixing apparatus includes: a fixing member 21; an opposite member 22 which comes into contact with the fixing member 21 to form a nip part N; heat sources 23A, 23B for heating the fixing member 21; and detection means which detects a current or electric power to be applied to the heat sources 23A, 23B. A recording medium P with an unfixed image T carried thereon is conveyed to the nip part N, to fix the unfixed image T to the recording medium P. When the detection means detects the current or electric power to be applied to the heat sources 23A, 23B, the current or electric power is applied to only one of the heat sources 23A and 23B.

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 various image forming apparatuses such as a copying machine, a printer, a facsimile, or a complex machine of these, a copy or a recorded material is obtained by heating and fixing an unfixed image transferred and supported on a recording medium such as paper. 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.

  Also, when heating the fixing member to a predetermined temperature with a heat source, if the heating time to the predetermined temperature is sufficiently short, even if the preheating step in the standby state is omitted, the user's usability is not greatly affected. Energy consumption can be greatly reduced. In order to achieve these, a low heat capacity member such as a thin roller or a thin belt formed of a metal base and an elastic rubber layer is used as the fixing member. Moreover, in addition to the halogen heater as the heat source, rapid heating is realized by using an IH method having high heating efficiency.

  By the way, the input voltage of the commercial power supply may vary depending on the user, and the input voltage from the commercial power supply may be higher than the rated voltage of the image forming apparatus. In this case, if the temperature control of the fixing unit is performed under the same conditions, more power than necessary is supplied from the heating source, and the temperature of the fixing member excessively increases.

  For this reason, for example, in Patent Document 1 and Patent Document 2, the voltage applied to the heating source is detected, and the duty of the energization time and the non-energization time per unit time of the heating source is controlled according to the detected voltage. Thus, a technique for controlling power consumption is disclosed.

  Although it is possible to detect the voltage without applying a voltage to the heating source at a position close to the commercial power source and estimate the input power, it is possible to energize the fixing device or use other electronic equipment that uses the same power source. There is a possibility that the applied current and input power fluctuate due to fluctuations in the applied voltage to the fixing device. However, in order to detect more accurate power in a state where the fixing device is energized, it is necessary to turn on the heating source with 100% duty for 1 to 2 seconds. A voltage higher than the rated voltage is applied to the heating source, If the heating source is turned on with 100% duty when an excessively applied current and power are applied to the heating source, the fixing member may be overheated. In particular, when a thin roller or belt is used for the fixing member, the temperature of the fixing member is likely to rise, and the problem of excessive temperature rise becomes significant. Also, when a voltage higher than the rated voltage is applied, the power cord and lead wires may exceed the current resistance, leading to failure. However, voltage detection can detect accurate current values such as inrush current. Absent.

  Therefore, in view of such circumstances, the present invention can accurately detect the applied current or input power to the heating source and prevent an excessive temperature rise of the fixing member due to heat generated by the heating source at that time. The present invention is intended to provide a fixing device capable of preventing failure due to overcurrent and an image forming apparatus including the fixing device.

  In order to solve the above problems, the present invention provides a fixing member, a facing member that contacts the fixing member to form a nip portion, a plurality of heating sources that heat the fixing member, and an applied current to the heating source. Or a detecting device that detects input power, and transports a recording medium carrying an unfixed image to the nip portion to fix the unfixed image on the recording medium, the detecting device When detecting the applied current or input power to the heating source, only a part of the heating source is applied with current or supplied with power.

  According to the present invention, when detecting the applied current or input power to the heating source, a current higher than the rated current is applied to the heating source by applying the current to only a part of the heating sources or supplying power. Even in this case, the temperature rise of the fixing member due to the heat generated by the heat source can be suppressed. This makes it possible to accurately detect the current or power without excessively raising the temperature of the fixing member.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. 2 is a cross-sectional side view of a fixing device mounted on the image forming apparatus. FIG. FIG. 2 is a schematic plan view of a fixing device. 2A and 2B are diagrams illustrating a configuration of an end portion of the fixing belt, in which FIG. 3A is a perspective view, FIG. 2B is a plan view, and FIG. 2 is a block diagram of a control system of a fixing device. FIG. It is a figure which shows the flowchart of an electric current detection method. It is a block diagram of other embodiments of the control system. It is a schematic block diagram of a fixing device provided with three halogen heaters. FIG. 2 is a schematic configuration diagram of a fixing device in which a fixing belt is stretched between a fixing roller and a heating roller. FIG. 2 is a schematic configuration diagram of a fixing device using a fixing roller instead of a fixing belt.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, constituent elements such as members and components having the same function or shape are described once by giving the same reference numerals as much as possible. Then, the explanation is omitted.

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.
An image forming apparatus 1 shown in FIG. 1 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.

  Specifically, each of the image forming units 4Y, 4M, 4C, and 4K has a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and a surface of the photoconductor 5. A developing device 7 for supplying toner 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 an intermediate transfer belt 30 as a transfer member, 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 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 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 recording medium includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. 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, a pair of registration rollers 12 serving as transport means for transporting the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the paper transport direction.

  Further, a fixing device 20 for fixing the unfixed image transferred onto the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper transport direction. 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. A discharge tray 14 for stocking sheets discharged outside the apparatus is provided on the upper surface of the printer main body.

  Next, a basic operation of the printer according to the present embodiment will be described with reference to FIG. 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 sequentially 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. Further, the toner on each photoconductor 5 that could not be 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 charge 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 a transfer on the intermediate transfer belt 30. 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 could not be transferred onto 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 can be formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. Two or three image forming units can be used to form a two-color or three-color image.

Next, the configuration of the fixing device 20 will be described with reference to FIGS.
2 is a cross-sectional side view of the fixing device, FIG. 3 is a schematic plan view thereof, FIG. 4 is a diagram showing a configuration of an end portion of the fixing belt, (a) is a perspective view, and (b). (C) is a side view seen from the direction of the axis of rotation of the fixing belt.

  As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member, a pressure roller 22 as an opposing member facing the fixing belt 21, and two heating sources as heating sources for heating the fixing belt 21. Halogen heaters 23A and 23B, a nip forming member 24 disposed inside the fixing belt 21, a stay 25 as a support member for supporting the nip forming member 24, and light emitted from the halogen heaters 23A and 23B. A reflection member 26 that reflects to the fixing belt 21, two thermopiles 27A and 27B as temperature detection means for detecting the temperature of the fixing belt 21, and a thermistor 29 as temperature detection means for detecting the temperature of the pressure roller 22. A separation member 28 that separates the sheet from the fixing belt 21 and a pressure unit (not shown) that pressurizes the pressure roller 22 to the fixing belt 21. Eteiru.

  The fixing belt 21 is composed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 21 includes a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI), and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Or it is comprised by the release layer of the outer peripheral side formed with polytetrafluoroethylene (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 fluorine rubber provided on the surface of the cored bar 22a, and a PFA provided on the surface of the elastic layer 22b. Alternatively, 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 place where the pressure roller 22 and the fixing belt 21 are in pressure contact, 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. Also, when there is no elastic layer, the heat capacity is reduced and the fixability is improved. It can happen. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing an elastic layer having a thickness of 100 μm or more, minute unevenness can be absorbed by elastic deformation of the elastic layer, so that occurrence of uneven gloss can be avoided. The elastic layer 22b may be solid rubber, but if there is no heat source inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is less likely to be taken away. Further, the fixing member and the facing member are not limited to being brought into pressure contact with each other, and may be configured to simply contact each other without applying pressure.

  The halogen heaters 23A and 23B are fixed to side plates (not shown) of the fixing device 20 at both ends. In FIG. 3, when the lower halogen heater 23A is referred to as a first halogen heater and the upper halogen heater 23B is referred to as a second halogen heater for convenience, the first halogen heater 23A and the second halogen heater 23B generate heat. The position of the part is different. Specifically, the heat generating portion of the first halogen heater 23A is disposed over a predetermined range from the central portion in the longitudinal direction, while the heat generating portion of the second halogen heater 23B is disposed on both ends in the longitudinal direction. It is arranged over a predetermined range.

  In the present embodiment, the heat generating portion of the first halogen heater 23A is disposed within a range of 200 to 220 mm with the central portion in the longitudinal direction as the axis of symmetry, and each heat generating portion of the second halogen heater 23B has its longitudinal length. It is disposed outside the width of 200 to 220 mm with the center in the direction as the axis of symmetry and within the width of 300 to 330 mm. Here, the sheet passing width of the A3 portrait and A4 landscape of the paper size used in this machine is 297 mm, but the combined light emission length of the first and second halogen heaters 23A and 23B is 300 to 330 mm. Yes, longer than the paper passing width. This is because generally the halogen heater has a lower emission intensity at the end of the light emitting part, so in order to prevent the temperature drop at the end of the paper passing area at the completion of warm-up or at the start of paper passing, This is because the light emission length needs to be longer than the paper passing width.

  As shown in FIG. 3, of the two thermopiles 27 </ b> A and 27 </ b> B, the first thermopile 27 </ b> A is disposed at the axial center of the fixing belt 21, and the second thermopile 27 </ b> B is the axial end of the fixing belt 21. It is arranged on the part side. The first thermopile 27A is provided corresponding to the heat generating part at the center of the first halogen heater 23A, and the second thermopile 27B is provided corresponding to the heat generating part at the end of the second halogen heater 23B.

  Each of the halogen heaters 23A and 23B is 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 27A and 27B. Based on. By controlling the output of the heaters 23A and 23B, the temperature of the fixing belt 21 (fixing temperature) is controlled to a desired temperature. In addition to the halogen heater, an IH, a resistance heating element, a carbon heater, or the like may be used as a heating source for heating the fixing belt 21.

  As shown in FIG. 2, the nip forming member 24 includes a base pad 241 and a sliding sheet (low friction sheet) 240 provided on the surface of the base pad 241. The base pad 241 is continuously disposed in the longitudinal direction over the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22, and receives the pressure from the pressure roller 22 to change the shape of the nip portion N. It is a decision. The base pad 241 is fixedly supported by the stay 25. Thus, the nip forming member 24 is prevented from being bent by the pressure of the pressure roller 22, 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. The base pad 241 is also preferably made of a material that is hard to some extent to ensure strength. As a material for the base pad 241, a resin such as a liquid crystal polymer (LCP), a metal, a ceramic, or the like can be used.

  The base pad 241 is made 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 base pad 241, general materials such as polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), polyetheretherketone (PEEK), etc. It is possible to use a heat resistant resin.

  The sliding sheet 240 may be disposed on at least the surface of the base pad 241 that faces the fixing belt 21. As a result, when the fixing belt 21 rotates, the fixing belt 21 slides with respect to the low friction sheet, so that 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 In addition, it is also possible to set it as the structure which does not have a sliding sheet | seat.

  The reflection member 26 is disposed between the stay 25 and the halogen heaters 23A and 23B. Examples of the material of the reflecting member 26 include aluminum and stainless steel. By arranging the reflecting member 26 in this way, the light emitted from the halogen heaters 23A and 23B 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, since it is possible to suppress the radiant heat from the halogen heaters 23A and 23B from being transmitted to the stay 25 and the like, 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 locations other than the nip portion N by the halogen heaters 23A and 23B (direct heating method). In the present embodiment, nothing is interposed between the halogen heaters 23A, 23B and the left side portion of the fixing belt 21 in FIG. I have to.

  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 a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is set. It is set to 1 mm or less. 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 0.2 mm or less, and more desirably 0.16 mm or less. The diameter of the fixing belt 21 is desirably 30 mm or less.

  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 smaller 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.

  As described above, as a result of reducing the diameter of the fixing belt 21, the space inside the fixing belt 21 is reduced. However, in the present embodiment, the stay 25 is formed in a concave shape bent at both ends, and the concave shape is formed in the concave shape. By accommodating the halogen heaters 23A and 23B inside the formed portion, the stay 25 and the halogen heaters 23A and 23B 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 base pad 241 in the sheet conveyance direction is formed to be smaller than the width of the stay 25 in the sheet conveyance direction. Further, in FIG. 2, the heights of the base pad 241 upstream end 24a and downstream end 24b in the sheet conveying direction with respect to the nip portion N (or its virtual extension line E) are h1 and h2, respectively. If the maximum height with respect to the nip portion N (or its virtual extension line E) in the portion of the base pad 241 other than the portion 24a and the downstream end portion 24b is h3, h1 ≦ h3 and h2 ≦ h3 are configured. Yes. With this configuration, the upstream end 24 a and the downstream end 24 b of the base pad 241 are not 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 fixing property.

  Further, in order to ensure the strength of the stay 25, in this embodiment, the stay 25 comes into contact with the nip forming member 24 and extends in the paper transport direction (vertical direction in FIG. 2), and the base portion 25a. And a rising portion 25b extending in the contact direction of the pressure roller 22 (left side in FIG. 2) from the upstream and downstream ends of the sheet conveyance direction. That is, by providing the stay 25 with the rising portion 25b, the stay 25 has a horizontally long cross section extending in the pressure direction of the pressure roller 22, and the section modulus is increased, so that the mechanical strength of the stay 25 is increased. Can be improved.

  In addition, the strength of the stay 25 is improved by forming the rising portion 25b longer in the contact direction of the pressure roller 22. Therefore, it is desirable that the leading end of the rising portion 25 b is as close as possible to the inner peripheral surface of the fixing belt 21. However, during rotation, the fixing belt 21 may be shaken (disturbance in behavior) regardless of whether it is large or small. Therefore, if the leading end of the rising portion 25b is too close to the inner peripheral surface of the fixing belt 21, the fixing belt 21 is moved to the leading end of the rising portion 25b. There is a risk of contact. In particular, in the configuration using the thin fixing belt 21 as in the present embodiment, since the swinging width of the fixing belt 21 is large, care must be taken in setting the position of the leading end of the rising portion 25b.

  Specifically, in the case of this embodiment, the distance d in the contact direction of the pressure roller 22 between the tip of the rising portion 25b and the inner peripheral surface of the fixing belt 21 is at least 2.0 mm, preferably 3.0 mm or more. It is preferable to set. On the other hand, when the fixing belt 21 has a certain thickness and almost no vibration, the distance d can be set to 0.02 mm.

  In this way, the rising portion 25b is disposed long in the contact direction of the pressure roller 22 by disposing the leading end of the rising portion 25b as close as possible to the inner peripheral surface of the fixing belt 21. Can do. Accordingly, the mechanical strength of the stay 25 can be improved even in the configuration using the small-diameter fixing belt 21.

  As shown in FIG. 4A or 4B, a belt holding member 40 is inserted into the end of the fixing belt 21, and the end of the fixing belt 21 is rotatably held by the belt holding member 40. Has been. Here, only the configuration of one end is shown, but the configuration is the same in the opposite end.

  As shown in FIG. 4C, the belt holding member 40 is formed in a C-shape that is opened at the position of the nip portion (position where the nip forming member 24 is disposed). The end of the stay 25 is fixed to the belt holding member 40 and positioned.

  Further, as shown in FIG. 4A or 4B, a protective member that protects the end portion of the fixing belt 21 between the end surface of the fixing belt 21 and the opposite surface of the belt holding member 40 facing the fixing belt 21. A slip ring 41 is provided. As a result, when the fixing belt 21 is displaced in the axial direction, the end portion of the fixing belt 21 can be prevented from coming into direct contact with the belt holding member 40, and the end portion can be prevented from being worn or damaged. it can. Further, the slip ring 41 is fitted to the belt holding member 40 with a margin with respect to the outer periphery. For this reason, when the end of the fixing belt 21 comes into contact with the slip ring 41, the slip ring 41 can be rotated with the fixing belt 21, but the slip ring 41 does not rotate and is stationary. I do not care. As a material of the slip ring 41, it is preferable to apply a so-called super engineering plastic excellent in heat resistance, for example, PEEK, PPS, PAI, PTFE and the like.

  Although not shown in the drawings, shielding members for shielding heat from the halogen heaters 23A and 23B are disposed between the fixing belt 21 and the halogen heaters 23A and 23B at both axial ends of the fixing belt 21. Yes. Thereby, in particular, an excessive temperature rise in the non-sheet passing region of the fixing belt during continuous sheet feeding can be suppressed, and deterioration and damage of the fixing belt due to heat can be prevented.

Hereinafter, the basic operation of the fixing device according to the present embodiment will be described with reference to FIG.
When the power switch of the printer main body is turned on, power is supplied to the halogen heaters 23A and 23B, 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. It is fed into the nip N of the roller 22. 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 heaters 23A and 23B 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.

FIG. 5 is a block diagram of a control system of the fixing device.
The electric power supplied from the power supply unit 55 is supplied to the first halogen heater 23A and the second halogen heater 23B via the relay 56, the current detection unit (detection unit) 57, and the triac 58. The triac 58 controls energization (lighting rate) to the halogen heaters 23A and 23B based on the detected temperatures of the thermopiles 27A and 27B, and maintains the fixing belt 21 at a predetermined temperature. The relay 56 is turned on when starting up when the printer is turned on, when passing paper, and the like. When the relay 56 is turned on and the triac 58 is also turned on, electric power is supplied from the power supply unit 55 to the halogen heaters 23A and 23B for the first time. On the other hand, when the printer is turned off, in a standby state, or when an abnormality occurs, the relay 56 is turned off and the power supply to the halogen heaters 23A and 23B is cut off.

  The “standby state” here is a state in which, after a predetermined time has passed after the image forming apparatus is turned on, a part of power supply is stopped or reduced, and a return command is waited for. In addition, a state called an energy saving mode for saving power is also included. “Return” means that power necessary for image formation is supplied from the power source and printing is possible. The “energy saving mode” includes, for example, a “low power mode” that stops power supply and lowers the fixing temperature except for a part of the engine system load when a certain time has elapsed since the last use of the device. ”,“ Sleep mode ”to stop the power supply to the engine system load when the operation is not continued after shifting to the low power mode, and when the device is not used for the set time, all the engine system load The controller system load includes “off mode” in which power supply is stopped except for a part.

  The current detection unit 57 detects the current applied to the halogen heaters 23A and 23B at the time of start-up operation after the power is turned on or when returning from the standby state. The maximum lighting rate of the halogen heaters 23A and 23B is adjusted based on the result of current detection by the current detection unit 57. For example, when the current is high, the maximum lighting rate of the halogen heaters 23A and 23B is set low.

Hereinafter, the current detection method which is a characteristic part of the present invention will be described.
In the present embodiment, in order to detect an accurate current, current detection is performed in a state where the halogen heater is turned on for 1 to 2 seconds at a 100% duty. However, in the case of the configuration using the thin fixing belt 21 as in the present embodiment, if both of the two halogen heaters 23A and 23B are turned on at 100% duty for 1 to 2 seconds, it is higher than the rated current. When current is applied to the halogen heater, the temperature of the fixing belt 21 is excessively increased, which may cause deterioration or damage of the fixing belt 21.

  Therefore, when current detection is performed, current is applied only to some of the halogen heaters so that the temperature of the fixing belt 21 does not rise too much. In the present embodiment, of the two halogen heaters 23A and 23B, the first halogen heater 23A having a heat generating portion at the center is lit for 1 to 2 seconds at 100% duty, and the current at that time is detected.

  Instead of the first halogen heater 23A, it is also possible to detect the current by energizing the second halogen heater 23B in the same manner. However, since the second halogen heater 23B is a heater that is used less frequently than the first halogen heater 23A, it is preferable to perform current detection using the first halogen heater 23A that is mainly used. Further, lighting of the halogen heater for 1 to 2 seconds for current detection also serves as a heat supply for heating the fixing belt 21 to a predetermined temperature, but the second halogen heater 23B is more than the first halogen heater 23A. The output is also set low. For this reason, when the second halogen heater 23B is turned on for current detection, the amount of heat supplied to the fixing belt 21 is smaller than when the first halogen heater 23A is turned on. Warm time becomes longer. For this reason, from the viewpoint of shortening the temperature raising time, it is preferable to turn on the first halogen heater 23A for current detection.

  As described above, it is possible to suppress an excessive temperature rise of the fixing belt 21 by energizing only some of the halogen heaters and detecting the current. However, in this case, since the amount of heat supplied to the fixing belt 21 by lighting is reduced as compared with the case where both halogen heaters are turned on, the temperature raising time of the fixing belt 21 is prolonged. Therefore, in this embodiment, in order to prevent the extension of the temperature raising time from the extension of the waiting time of the user or the like, current detection is performed as follows.

The current detection method of this embodiment will be described with reference to the flowchart shown in FIG.
The current detection of the halogen heater is performed at the start-up operation when the printer power is turned on or when the printer is returned from the standby state. First, the printer is turned on or from the standby state. It is confirmed whether or not to return (S1).

  When the printer is turned on, it is necessary to start up the controller. In the present embodiment, it takes 20 seconds to start up the controller, but the time required for the normal heating time of the fixing belt is 10 seconds or less. In other words, even if the current detection is performed and the temperature rise time of the fixing belt is extended, a series of operations from the start of current detection to the completion of the temperature increase of the fixing belt can be performed within the startup operation time of the controller. is there. For this reason, when the printer is turned on, current detection is performed during the startup operation.

  On the other hand, when returning from the standby state, the controller has already been started up. Therefore, when returning from the standby state, there is basically less time margin than when starting up when the power is turned on. However, when an image forming adjustment operation (process control) is performed at the time of return, the operation takes about 15 seconds, so that a time margin for current detection can be provided. Here, the image forming adjustment operation is, for example, an operation of detecting the photosensitive member potential and toner density and adjusting process conditions such as a charging grid and a developing bias of the photosensitive member based on the detection results. In this embodiment, immediately after the start of the return operation, the control unit of the printer determines whether or not any of the following conditions (1) to (5) is satisfied (S2). Perform the image adjustment operation.

(1) When the temperature change of the use atmosphere (in-machine temperature of the image forming apparatus) from the standby state to the return is 10 deg or more.
(2) When the humidity change of the use atmosphere (in-machine humidity of the image forming apparatus) from the standby state to the return is 30% or more at the time of return.
(3) At the time of return, when the standby time from the standby state to return is 5 hours or more.
(4) When returning, the cumulative number of black prints since the previous image adjustment operation is 500 or more.
(5) When returning, the cumulative number of color prints since the previous image formation adjustment operation is 200 or more.
In addition, the conditions and numerical values shown in (1) to (5) are examples, and are not limited to these. The printer also includes a temperature detection unit, a humidity detection unit, a standby time measurement unit (timer), and a printed sheet number storage unit (counter) (not shown) for detecting each of the above conditions.

  When it is determined that any one of the above conditions is satisfied and the image forming adjustment operation is executed, current detection is performed during the image forming adjustment operation. On the other hand, when the image forming adjustment operation is not executed, no current is detected because there is no time margin.

  As described above, in this embodiment, when there is a time margin, that is, when the image forming adjustment operation is performed at the start-up operation when the printer power is turned on or at the return from the standby state, Even in these cases, current detection is not performed when the temperature of the fixing belt or the pressure roller is high before the energization of the halogen heater is started. When the temperature of the fixing belt or the pressure roller is high from the beginning, the current is detected, and although only some of the halogen heaters are turned on for a predetermined time with 100% duty, the temperature of the fixing belt is excessively increased. This is because there is a risk of losing. Therefore, in this embodiment, before conducting the current detection, the printer control unit confirms whether the detected temperatures of the first thermopile and the second thermopile are both 60 ° C. or less (S3). Current detection is performed only when the detected temperature is 60 ° C. or lower. Conversely, when at least one of the detected temperatures of the first thermopile and the second thermopile exceeds 60 ° C., current detection is not performed.

  As described above, according to the present invention, a current higher than the rated current is applied to the halogen heater by lighting only a part of the plurality of halogen heaters with a 100% duty for a predetermined time (1 to 2 seconds). Even in such a case, an accurate current can be detected without excessively heating the fixing belt. As a result, deterioration and damage of the fixing belt due to heat can be prevented, and the fixing temperature can be accurately managed based on an accurate current detection result.

  In particular, in the configuration using a thin fixing belt for reducing the heat capacity as in the above-described embodiment, the temperature of the fixing belt is likely to increase. Therefore, the configuration of the present invention is applied to the fixing device having such a configuration. A greater effect can be expected.

  In addition, when only some of the halogen heaters are turned on, the temperature increase time of the fixing belt becomes longer. In the above embodiment, the temperature increase time is increased by performing the current detection when there is a time margin. It is possible to avoid or reduce the extension of the waiting time due to the increase of the time. Thereby, current detection can be performed without impairing ease of use. In the above-described embodiment, even if there is a time margin, overheating of the fixing belt is surely prevented by not detecting the current when the temperature of the fixing belt is high from the beginning.

  Further, in place of the current detection unit 57, as shown in FIG. 7, a power detection unit (detection unit) 59 for detecting the power supplied to the halogen heater may be provided. In this case as well, as in the case of current detection, only a part of the plurality of halogen heaters is turned on at a 100% duty for a predetermined time (1 to 2 seconds) during power detection, thereby overloading the fixing belt. Accurate power can be detected without increasing the temperature. Further, in the power detection, by adopting the same method as the detection method shown in the flowchart of FIG. 6, it is possible to avoid or reduce the waiting time due to the increase in the temperature rising time, and the fixing belt. It is possible to reliably prevent overheating.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. For example, as shown in FIG. 8, the present invention can be applied to a fixing device including three or more halogen heaters 23. In this case, the number of halogen heaters 23 to be turned on at the time of current detection or power detection may be one or may be two (a plurality) as in the above embodiment. 8 is a sheet metal provided so as to surround the nip forming member 24. In this case, the nip forming member 24 is supported by the stay 25 via the sheet metal 250. Other configurations are basically the same as those of the embodiment shown in FIG.

  Further, in the present invention, as shown in FIG. 9, a fixing device in which the fixing belt 21 is stretched by a heating roller 64 including a fixing roller 63 and a halogen heater 23, or a fixing belt 21 as shown in FIG. Thus, the present invention can also be applied to a fixing device using a fixing roller 63 having a halogen heater 23 therein. Also in these fixing devices, by turning on only some of the halogen heaters 23, it is possible to perform accurate current detection or power detection while preventing overheating of the fixing belt 21, the fixing roller 63, and the like. is there. This is particularly effective when the heating roller 64 and the fixing roller 63 are thin and easily rise in temperature.

  In addition, the fixing device according to the present invention is not limited to the color laser printer shown in FIG. 1, and can be mounted on a monochrome image forming apparatus, other printers, copiers, facsimiles, or complex machines thereof. .

20 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (opposing member)
23A Halogen heater (heating source)
23B Halogen heater (heating source)
57 Current detector (detection means)
59 Power detection unit (detection means)
N nip P Paper (recording medium)

JP 2008-65002 A Japanese Patent Laid-Open No. 2005-257831

Claims (10)

A fixing member;
An opposing member that contacts the fixing member and forms a nip portion;
A plurality of heating sources for heating the fixing member;
Detecting means for detecting an applied current or input power to the heating source,
A fixing device that conveys a recording medium carrying an unfixed image to the nip portion and fixes the unfixed image on the recording medium,
A fixing device, wherein when the detection means detects an applied current or input power to a heating source, only a part of the heating source is applied with current or input power.   The fixing device according to claim 1, wherein when an image forming adjustment operation is performed when returning from a standby state, current or power is detected during the image forming adjustment operation.   3. The fixing device according to claim 2, wherein the image forming adjustment operation is performed when the temperature of the use atmosphere from the standby state to the return is changed by a predetermined value or more when returning from the standby state. .   The fixing device according to claim 2, wherein the image forming adjustment operation is performed when the humidity of the use atmosphere from the standby state to the return is changed by a predetermined value or more when returning from the standby state. .   3. The fixing device according to claim 2, wherein the image forming adjustment operation is performed when a standby time after returning from the standby state to the return is equal to or longer than a predetermined time when returning from the standby state.   The fixing device according to claim 2, wherein the image forming adjustment operation is performed when the accumulated number of prints since the previous image forming adjustment operation is equal to or greater than a predetermined number when returning from the standby state.   The fixing device according to claim 1, wherein when the power of the image forming apparatus is turned on, current or power is detected during the startup operation.   8. The fixing device according to claim 1, wherein the current or power is detected only when the temperature of the fixing member or the counter member before starting to energize the heating source is equal to or lower than a predetermined value. .   The fixing device according to claim 1, wherein the fixing member is an endless fixing belt.   An image forming apparatus comprising the fixing device according to claim 1.

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