JP2014026072A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus having a short warm-up time and capable of preventing problems such as breakage of a fixing member or a fixing failure.SOLUTION: The fixing device includes a fixing belt 21, a pressurizing roller 31 disposed on an outer circumference side of the fixing belt 21, a heater 25 heating the fixing member, and a control unit controlling a transferred amount of heat to the fixing member by heating, and thereby setting a temperature on the outer surface of the fixing member to a predetermined temperature; and the fixing device feeds a sheet carrying an unfixed toner image into a nip 26 formed by press-contact between the fixing belt 21 and the pressurizing roller 31, and heats and fixes the image. The fixing device further includes displacement detection means 27 that detects a degree of deformation in an outer surface 21a of the fixing belt 21. If the displacement detection means 27 detects deformation in a degree exceeding a predetermined range during a warm-up period of the fixing device 20, the control unit suppresses the transferred amount of heat to the fixing belt 21.

Description

  The present invention relates to a fixing device and an image forming apparatus. More specifically, the present invention relates to a fixing device that fixes a toner image formed on an image carrier onto a recording medium, and an image forming apparatus including the fixing device.

  Various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copiers, printers, facsimiles, and their combined machines, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. The image is formed by a process in which the transferred image is transferred onto a recording paper (also referred to as paper, recording material, or recording medium) by a transfer device to carry the image, and a toner image on the recording paper is fixed by a fixing device using pressure, heat, or the like Yes.

  In the fixing device, a fixing member and a pressure member constituted by opposing rollers or belts or a combination thereof are disposed so as to contact each other to form a nip portion. And a pressure is applied to fix the toner image on the recording paper.

  For example, a belt fixing type fixing device 110 as shown in FIG. 6 includes a pressure roller 113 having a heater 111 as a heat source, a fixing belt 117 including a fixing roller 115 provided with a rubber layer on the surface layer, and fixing. The transferred toner image is heated and pressed in the process of passing the toner-transferred recording medium (recording paper) P through the nip portion (fixing nip portion) N formed by the pressure roller 119 in contact with the belt 117. It will be fixed.

  Further, as the above-described fixing device used in the image forming apparatus, there is a fixing device disclosed in Patent Document 1 having a fixing member that is in sliding contact with the inner surface of a rotating body. This fixing device is shown in FIG. The fixing device 20 is in contact with the metal heat conductor 22 via the fixing member (fixing belt) 21, the metal heat conductor (heating member) 22 provided inside the fixing belt 21, the heat source 25, and the fixing belt 21. And a pressure roller 31 that forms a nip, and a fixing device that performs a fixing process by heating and pressing a material to be fixed that passes through the nip. According to the invention of Patent Document 1, since the entire fixing belt 21 constituting the fixing device 20 can be heated, the warm-up time (heating standby time) and the first print time can be shortened, that is, the apparatus is speeded up. can do.

  However, the fixing device having the configuration shown in Patent Document 1 has a configuration in which a fixing belt, which is a fixing member, is provided so as to be detachable along a metal thermal conductor, so that the fixing belt is driven by rotation from a pressure roller. Sag occurs in the fixing belt in the downstream direction of the fixing member. For this reason, a temperature difference occurs between the upstream side and the downstream side of the above-described fixing member of the metal thermal conductor, and the metal thermal conductor is thermally deformed into a convex shape near the central portion in the axial direction on the downstream side of the fixing member. However, a gap is formed between the both ends of the fixing belt and a so-called belt floating state. As a result, there is a problem that the metal thermal conductor generates abnormal heat, and the fixing belt may be deformed and damaged.

  The present invention has been made in order to solve the above-described problems. Even when the fixing member has a high heating efficiency and has a short warm-up time and a high-speed apparatus, the above-described fixing is performed. It is an object of the present invention to provide a fixing device that does not cause problems such as member breakage and fixing failure, and an image forming apparatus using the same.

  In order to achieve such an object, the fixing device according to claim 1 includes an endless fixing member having flexibility, and a pressure member arranged to be able to press the fixing member on the outer peripheral side of the fixing member. A heating unit that heats the fixing member, and a control unit that sets the temperature of the outer surface of the fixing member to a predetermined temperature by controlling the amount of heat transfer to the fixing member by heating, the fixing member and the pressure member In a fixing device that heats and fixes a sheet carrying an unfixed toner image through a nip portion between a fixing member and a pressure member formed by pressure contact with the fixing member, the degree of deformation of the outer surface of the fixing member is reduced. Displacement detecting means for detecting is further provided, and the controller detects the deformation of the outer surface of the fixing member having a size exceeding a predetermined range when the fixing device is warmed up. It suppresses heat transfer.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus that do not cause problems such as breakage of a fixing member or defective fixing even in the case of an apparatus with a short warm-up time and a high speed. .

1 is a schematic configuration diagram of an image forming apparatus according to an exemplary embodiment. 1 is a schematic configuration diagram of a fixing device according to a first embodiment. FIG. 3 is a top view of the fixing device according to the first embodiment. FIG. 6 is a flowchart relating to the operation of the fixing device according to the present embodiment. FIG. 5 is a schematic configuration diagram of a fixing device according to a second embodiment. It is a schematic block diagram of the conventional fixing device. It is a schematic block diagram of the conventional fixing device.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

(Configuration and operation of image forming apparatus)
First, the configuration and operation of the entire image forming apparatus of the present embodiment will be described with reference to FIG. As shown in FIG. 1, an image forming apparatus (apparatus main body) 1 in this embodiment is a tandem type color printer. In the bottle accommodating portion 101 above the image forming apparatus 1, four toner bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable). Yes.

  An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

  The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 1 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser beam emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (This is an exposure process.)

  Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). .) Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photoconductive drums 5Y, 5M. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

  Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78.

  Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by the three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

  The four primary transfer bias rollers 79Y, 79M, 79C, and 79K respectively sandwich the intermediate transfer belt 78 between the photosensitive drums 5Y, 5M, 5C, and 5K to form a primary transfer nip. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

  Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing.

  Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

  Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing belt 21 and the pressure roller 31. Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The recording medium P to be transferred discharged out of the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. Thus, a series of image forming processes in the image forming apparatus is completed.

1. First Embodiment Next, a fixing device according to a first embodiment of the present invention will be described with reference to FIGS.

  The fixing device (20) according to the present embodiment includes an endless fixing member (fixing belt 21) having flexibility, and a pressure member (pressurizing member) disposed on the outer peripheral side of the fixing member so as to be able to press the fixing member. Pressure roller 31), driving means for driving the fixing member, heating means for heating the fixing member (heater 25), temperature detecting means for detecting the temperature of the outer surface of the fixing member (temperature sensor 40), and heating A control unit (50 (not shown)) that sets the temperature of the outer surface of the fixing member to a predetermined temperature by controlling the amount of heat transfer to the fixing member, and press-contacting the fixing member and the pressure member Detecting the magnitude of deformation of the outer surface of the fixing member in a fixing device that performs heating and fixing by passing a sheet carrying an unfixed toner image through a nip portion N between the fixing member and the pressure member formed by Displacement detecting means (27) is further provided, Control unit, at the time of warm-up of the fixing device, when the displacement detection means detects the deformation of the outer surface of the size of the fixing member exceeds a predetermined range, and suppresses the amount of heat transferred to the fixing member.

(Configuration of fixing device)
FIG. 2 is a schematic sectional view of the fixing device according to the first embodiment. Specifically, FIG. 2A shows the fixing device in a cold (stationary) state before heating. 2B is a cross-sectional view showing a first deformation (first position), which will be described later, after heating and rotation driving, and FIG. 2C is a second-stage deformation after heating and rotating driving (first position). It is sectional drawing which shows a 2nd position. FIG. 3 is a schematic top view of the fixing device.

  As shown in FIG. 2A, a fixing device 20 includes a fixing belt 21 as a fixing member, a metal heat conductor (also referred to as a metal pipe or a heating pipe) 22, a reinforcing member 23, a heater 25 as a heat source, and a nip portion N. A nip forming member 26 for forming the pressure, a displacement detection means 27, a pressure roller 31 as a pressure member, a temperature sensor (temperature detection means) (not shown) for detecting the temperature of the outer surface 21a of the fixing belt 21, and similarly not shown. It is comprised by the control part. Hereinafter, each configuration will be described in detail.

[Fixing belt]
The fixing belt 21 as a fixing member is a thin and flexible endless belt (or film), and rotates together with an external roller. In the example shown in FIG. 2, the pressure roller 31 is rotated by a driving unit (not shown), and the driving force is transmitted to the belt at the nip portion N, whereby the fixing belt 21 is rotated.

  The fixing belt 21 is formed by sequentially laminating an elastic layer and a release layer on a base material, and the entire thickness thereof is set to 1 mm or less. The base material of the fixing belt 21 has a layer thickness of 30 to 50 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide.

  The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. When there is no elastic layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image and the image has a crusty skin-like shape. There is a problem that marks remain. On the other hand, by providing the elastic layer, minute irregularities on the surface of the fixing belt 21 in the nip portion are not formed, and heat is uniformly transmitted to the toner image on the recording medium P, thereby preventing the generation of a scum skin image.

  The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm, such as PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), and the like. Made of material. By providing the release layer, the releasability (peelability) for the toner image is secured.

  The diameter of the fixing belt is usually set in a range of 15 to 120 mm, and in this embodiment, the diameter of the fixing belt 21 is set to 30 mm. Inside the fixing belt 21 (inner peripheral surface side), a metal heat conductor 22, a reinforcing member 23, a heater 25, a nip forming member 26, and the like are fixed.

[Nip forming member]
The nip forming member 26 is fixed on the inner peripheral surface side of the fixing belt 21 and abuts against the pressure roller 31 via the fixing belt 21 to form the nip portion N. The sliding contact surface between the nip forming member 26 and the fixing belt 21 is formed of a material having a low friction coefficient so that the wear of the fixing belt 21 is reduced even if the nip forming member 26 and the fixing belt 21 are in sliding contact. It is preferable. Further, a sliding sheet may be provided between the nip forming member 26 and the inner peripheral surface of the fixing belt 21.

[heater]
Here, it is assumed that the heater 25 serving as a heat source uses a halogen heater, and both ends thereof are fixed to side plates (not shown) of the fixing device 20. Then, the metal heat conductor 22 is heated by the radiant heat of the heater 25 whose output is controlled by the power supply unit of the image forming apparatus 1. Further, the fixing belt 21 is entirely heated by the metal heat conductor 22, and heat is applied to the toner image on the recording medium from the surface of the heated fixing belt 21.

  The output control of the heater 25 is controlled by the control unit based on the detection result of the outer surface 21a of the fixing belt 21 by the temperature sensor 40 such as a thermistor facing the surface of the fixing belt 21. Further, the temperature of the fixing belt 21 (fixing temperature) can be set to a predetermined temperature by such output control of the heater 25. Normally, when the temperature is stabilized at a predetermined temperature (fixing temperature), the control unit permits paper feeding, and the fixing device 20 starts paper feeding.

  The heat source is not limited to the halogen heater, and induction heating means (IH coil), resistance heating element, carbon heater, or the like may be used.

[Metal heat conductor]
The hollow metal heat conductor 22 is fixed so as to face the inner peripheral surface of the fixing belt 21 at a position excluding the nip portion, and is heated by the radiant heat of the heater 25 to heat the fixing belt 21 (heat is absorbed). Tell). In addition, as a material of the metal thermal conductor 22, a material having thermal conductivity such as aluminum, iron, and stainless steel can be used. In this embodiment, SUS having excellent strength is used. In the example shown in FIG. 2, the metal heat conductor 22 has a circular shape, but is not limited to this, and has other cross-sectional shapes such as a circular shape or a square shape whose top portion is crushed. May be.

  Even if the speed of the apparatus is increased because the fixing belt 21 is heated over a wide range in the circumferential direction by the metal heat conductor 22 without locally heating only a part of the fixing belt 21. The fixing belt 21 is sufficiently heated to prevent the occurrence of fixing failure.

  Further, even when the metal heat conductor 22 is thinned to improve the heating efficiency of the fixing belt 21, the metal heat conductor 22 is separated from the nip forming member 26 that receives pressure from the pressure roller 31. Therefore, a problem that the metal heat conductor 22 is bent and the inner peripheral surface of the fixing belt 21 is rubbed strongly, a problem that the metal heat conductor 22 is bent and the driving torque of the fixing belt 21 is increased, and the like are suppressed. The

  As described above, in the fixing device 20, the fixing belt 21 is heated over a wide range in the circumferential direction by the metal heat conductor 22, so that the fixing belt 21 is sufficiently heated even when the speed of the device is increased. Therefore, it is possible to suppress the occurrence of fixing failure. That is, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time are shortened, and the size of the apparatus is reduced.

  The difference in outer diameter between the fixing belt 21 and the metal heat conductor 22 is preferably within 1 mm. As a result, the area in which the metal heat conductor 22 and the fixing belt 21 are in sliding contact with each other is increased, and the problem that the wear of the fixing belt 21 is accelerated is suppressed, and the metal heat conductor 22 and the fixing belt 21 are separated from each other too much. A problem that the heating efficiency of the belt 21 is reduced can be suppressed. Furthermore, since the metal heat conductor 22 is placed close to the fixing belt 21, the circular posture of the flexible fixing belt 21 is maintained to some extent, so that deterioration and breakage due to deformation of the fixing belt 21 can be reduced. Can do.

  Further, the sliding surface of the metal heat conductor 22 may be formed of a material having a low friction coefficient so that the wear of the fixing belt 21 is reduced even if the metal heat conductor 22 and the fixing belt 21 are in sliding contact. good. Further, a lubricant such as silicone oil or fluorine grease is applied to the interface between the fixing belt 21 and the metal thermal conductor 22.

[Reinforcing material]
It is also preferable to provide a reinforcing member 23 that supports the nip forming member 26 in the nip portion N and reinforces the strength inside the metal heat conductor 22. Further, when the reinforcing member 23 is heated by the radiant heat of the heater 25 or the like, it is also preferable to heat-insulate or mirror-treat the surface. Thereby, excessive heating can be prevented and useless energy consumption can be suppressed.

[Pressure roller]
The pressure roller 31 as a pressure member has a diameter of 30 mm and is formed by forming an elastic layer on a hollow cored bar. The elastic layer of the pressure roller 31 is made of a material such as foamable silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE, or the like can be provided on the surface layer of the elastic layer. The pressure roller 31 is pressed against the fixing belt 21 by a spring or the like, and the rubber layer is crushed and deformed to form a desired nip portion between both members.

  Note that when the elastic layer of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the pressure applied to the nip portion can be reduced, so that the bending that occurs in the metal heat conductor 22 is reduced. Can be further reduced.

  In this embodiment, the fixing belt 21 has a diameter equal to that of the pressure roller 31, but the fixing belt 21 has a diameter smaller than the pressure roller 31. You can also. In this case, since the curvature of the fixing belt 21 at the nip portion N is smaller than the curvature of the pressure roller 31, the recording medium P sent out from the nip portion N is easily separated from the fixing belt 21.

  The pressure roller 31 is rotated by a driving force transmitted from a driving unit such as a motor through a gear. Further, the pressure roller 31 may be a solid roller, but the hollow roller may have a smaller heat capacity. Further, a heat source such as a heater may be provided on the pressure roller 31 side. If there is no heater inside the pressure roller, sponge rubber may be used. Sponge rubber is more desirable because it increases heat insulation and makes it difficult for the fixing belt to lose heat.

[Displacement detection means]
A deformation detection member 27 serving as a displacement detection means for detecting the magnitude of deformation of the outer surface 21 a of the fixing belt 21 is a central portion in the axial direction of the fixing belt 21 and within a range heated by the heater 25. The displacement (deformation) of the outer surface 21a of the position is arranged at a position where it can be detected. As shown in FIGS. 2A to 2C, in the case of the fixing device 20, the position within the range heated by the heater 25 can detect the displacement of the outer surface 21 a near the lower surface of the fixing belt 21. Is arranged. Therefore, it is possible to detect the position where the deformation is most significant in the fixing belt 21 when heated by the heater 25.

  The deformation detection member 27 includes a belt deformation detection unit 27b at one end of the rotation shaft 27a, and has a rod-shaped first filler 27c and a second filler 27d at the other end. The belt deformation detection unit 27b has a contact roller at the tip, and detects the degree of deformation of the fixing belt 21 at the above-mentioned position in a stepwise manner as will be described later. In the top view of FIG. 3, the belt deformation detection unit 27b of the deformation detection member 27 is drawn at a position on the side of the fixing belt so that the contact roller can be seen, but the actual arrangement is shown in FIG. In this way, the contact roller is disposed below the fixing belt 21.

  A first contact detection sensor 27e for detecting a first deformation described later is disposed at the tip of the first filler 27c, and a second contact detection for detecting a second deformation described later is provided at the tip of the second filler 27d. A sensor 27f is provided. The first filler 27c and the second filler 27d are shifted in the axial direction so that the magnitude of the displacement can be detected stepwise.

  The first contact detection sensor 27e and the second contact detection sensor 27f are transmissive photoimplotters and have a U-shape in which a light emitting portion and a light receiving portion are opposed to each other. When the tip of the first filler 27c or the second filler 27d is inserted between the opposed light emitting part and the light receiving part of the first contact detection sensor 27e or the second contact detection sensor 27f, the light emitting part moves to the light receiving part. On the other hand, the light emitted is blocked. Based on this principle, the magnitude of deformation of the fixing belt 21 is detected.

  Here, the deformation size of the fixing belt 21 that may be damaged by heating when the fixing device 20 is warmed up is set to 1 mm or more. When the displacement (the magnitude of deformation) in the cross-sectional direction of the fixing belt 21 is 1 mm, the fixing belt 21 is set to the first position (first deformation) 21b (FIG. 2B). Further, when the above displacement exceeds 1 mm (about 1 mm to 2 mm), the second position (second deformation) 21c is set (FIG. 2C).

  During the warm-up described above, the outer surface 21a of the fixing belt 21 is deformed by heating, and the deformation causes the contact roller of the belt deformation detection unit 27b to be pushed downward (FIG. 2B). At this time, the first filler 27c and the second filler 27d rotate around the rotation shaft 27a. At this time, when the displacement by which the contact roller of the belt deformation detection unit 27b is pushed is 1 mm, the first filler 27c is inserted between the light emitting unit and the light receiving unit of the first contact detection sensor 27e, thereby A position 21b is detected.

  Similarly, when the displacement by which the contact roller of the belt deformation detection unit 27b is pressed is 1 mm to 2 mm, the second filler 27d is inserted between the light emitting unit and the light receiving unit of the second contact detection sensor 27f, so that the first 2 position 21c is detected.

  In the fixing device 20 according to the first embodiment, the metal heat conductor 22 is disposed on the inner peripheral side of the fixing belt 21, so the heater 25 heats the metal heat conductor 22 and the fixing belt 21. The deformation detection member 27 detects the magnitude of deformation of the outer surface of the metal heat conductor 22 via the fixing belt 21 by detecting the magnitude of deformation of the outer surface 21 a of the fixing belt 21. Suppose you are.

(Fixing device control)
Next, an operation related to the control unit and the displacement detection unit 27 in the fixing device 20 according to the first embodiment of the present invention will be described. The following processing is started on the condition that the apparatus main body 1 is turned on and the user presses the copy start button from the operation panel.

  According to the fixing device of the present invention, when the fixing device 20 is warmed up, the control unit detects the deformation of the outer surface 21a of the fixing belt 21 whose deformation detecting member (displacement detecting means) 27 exceeds the predetermined range. When this occurs, the amount of heat transfer to the fixing belt 21 is suppressed.

  In the present embodiment, the paper feed permission in step S17 described later is performed when the temperature of the outer surface 21a of the fixing belt 21 is stabilized at a predetermined temperature (fixing temperature) in step S16 described later. In the process until the fixing temperature reaches a predetermined temperature, the lighting rate of the heater 25 is controlled so that the deformation of the fixing belt 21 due to heating falls within a range where there is no damage.

  Hereinafter, an example of a detailed control operation will be described with reference to the flowchart of FIG.

  The control unit issues an instruction to start power supply to a heater driving circuit (not shown) at a maximum lighting rate of 100% (step S10). Next, the control unit determines whether or not the deformation detection member (displacement detection means) 27 has detected the first position 21b (FIG. 2B) (step S11).

  Here, it is assumed that the deformation detection by the deformation detection member (displacement detection means) 27 is performed at a predetermined interval, for example, an interval of 0.01 seconds, if necessary. When the displacement detector 27 does not detect the first position 21b, the controller controls the heater drive circuit to supply power at a maximum lighting rate of 100% (step S14).

  Then, when the temperature sensor confirms that the temperature of the outer surface 21a of the fixing belt 21 is stabilized at a predetermined temperature (step S16), the control unit issues a paper feed permission (step S17), and paper feeding is started. The

  On the other hand, when the displacement detector 27 detects the first position 21b, the process proceeds to step S12.

  Next, the control unit determines whether or not the displacement detection unit 27 has detected the second position 21c (FIG. 2C) (step S12). When the displacement detector 27 does not detect the second position 21c, the controller controls the heater drive circuit to supply power with a lighting rate of 75% (step S15).

  On the other hand, when the displacement detection unit 27 detects the second position 21c, the control unit controls the heater drive circuit to make the lighting rate 0%, cuts off the power supply (stops heating), and again performs S11. (Step S13).

  Next, the control unit determines whether or not the fixing temperature has reached a predetermined temperature (step S16). When the temperature sensor detects the temperature of the outer surface 21a of the fixing belt 21 and confirms that the fixing temperature is equal to or higher than the predetermined temperature, the control unit permits paper feeding (step S17).

  In this manner, by extending the paper feed permission until the second position 21c is no longer detected, there is a problem such as a fixing failure due to the passage of paper while the amount of heat transfer to the fixing belt 21 is suppressed. Can be prevented.

  On the other hand, when the fixing temperature is equal to or lower than the predetermined temperature, the process returns to step S11. Next, the control unit determines whether the paper passing is completed (step S18). Specifically, the determination is made based on whether or not the last recording medium is no longer detected by a paper discharge sensor (not shown). When the signal from the paper discharge sensor is detected, the control unit moves to step S11, and when the signal from the paper discharge sensor is not detected, the control unit ends the operation.

  As is apparent from the above description, according to the fixing device 20 of the first embodiment, when the deformation detecting member (displacement detecting means) 27 detects a deformation exceeding a predetermined range, the fixing belt. Since the amount of heat transfer to 21 is suppressed, problems such as breakage of the fixing belt due to abnormal heat generation of the metal heat conductor 22 can be prevented. Also, by extending the paper feed permission until the second position 21c is no longer detected, it is possible to prevent problems such as poor fixing due to paper passing while the amount of heat transfer to the fixing belt 21 is suppressed. be able to.

2. Second Embodiment Next, a fixing device according to a second embodiment of the present invention will be described with reference to FIG. FIGS. 5A to 5C are schematic cross-sectional views of the fixing device according to the second embodiment, and are illustrated following FIGS. 2A to 2C.

  The fixing device 20 a according to the second embodiment has a configuration in which the inner peripheral surface of the fixing belt 21 is painted black and is directly radiated and heated by the heater 25 without using the metal heat conductor 22. . In the case of such a fixing belt, there is an advantage that the temperature rise time from the start of heating to the fixing temperature is fast. Since the fixing device 20 a does not have the configuration in which the metal heat conductor 22 is disposed, the deformation detecting unit 27 detects the deformation of the fixing belt 21 itself.

  Since other configurations and operations are the same as those in the first embodiment, detailed description thereof is omitted. In the fixing device 20a of the second embodiment, the same effect as that of the fixing device 20 of the first embodiment can be expected.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the fixing device using the pressure roller 31 as the pressure member has been described as an example. However, the fixing device is not limited thereto. For example, a pressure belt or a pressure pad is used as the pressure member. It is also preferable. In addition, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Exposure part 4 Image formation part 5 Photoconductor drum 12 Paper feed part 20, 20a Fixing apparatus 21 Fixing belt 21a (Fixing belt) outer surface 21b 1st position (1st deformation)
21c Second position (second deformation)
22 Metal thermal conductor (metal pipe)
23 Reinforcing member 25 Heater (heating means)
26 Nip forming member 27 Deformation detecting member (displacement detecting means)
27a Rotating shaft 27b Belt deformation detection section 27c First filler 27d Second filler 27e First contact detection sensor 27f Second contact detection sensor 31 Pressure roller 40 Temperature sensor (temperature detection means)
50 control unit 75 charging unit 76 developing unit 77 cleaning unit 78 intermediate transfer belt 79 primary transfer bias roller 80 intermediate transfer cleaning unit 82 secondary transfer backup roller 83 cleaning backup roller 84 tension roller 85 intermediate transfer unit 89 secondary transfer roller 97 Paper feed roller 98 Registration roller pair 99 Paper discharge roller pair 100 Stack part 101 Bottle storage part 102 Toner bottle N Nip part P Recording medium

JP 2009-3410 A

Claims (7)

An endless fixing member having flexibility;
A pressure member arranged to be able to press the fixing member on an outer peripheral side of the fixing member;
Heating means for heating the fixing member;
A control unit that sets the temperature of the outer surface of the fixing member to a predetermined temperature by controlling the amount of heat transfer to the fixing member by heating;
With
In a fixing device that heats and fixes a sheet carrying an unfixed toner image through a nip portion between the fixing member and the pressure member formed by pressure contact between the fixing member and the pressure member,
Displacement detecting means for detecting the magnitude of deformation of the outer surface of the fixing member further comprises
The controller is
When the fixing device is warmed up,
A fixing device that suppresses the amount of heat transfer to the fixing member when the displacement detection unit detects a deformation of the outer surface of the fixing member having a size exceeding a predetermined range. A pipe-shaped metal heat conductor fixed in proximity to the inner peripheral side of the fixing member;
The heating means heats the metal thermal conductor and the fixing member,
The displacement detection means detects the magnitude of deformation of the outer surface of the metal heat conductor via the fixing member by detecting the magnitude of deformation of the outer surface of the fixing member. The fixing device according to claim 1.   The fixing device according to claim 1, wherein an inner peripheral surface of the fixing member is black. The displacement detection means includes
2. The center portion in the axial direction of the fixing member and disposed at a position where the displacement of the outer surface can be detected at a position within a range heated by the heating means. Item 4. The fixing device according to Item 3. When the deformation of the outer surface of the fixing member having a size exceeding the predetermined range is set stepwise as a first deformation and a second deformation larger than the first deformation,
The controller is
When the first deformation is detected by the displacement detection means, the amount of heat transferred to the fixing belt due to the heating is reduced, and when the second deformation is detected, the heating is stopped. The fixing device according to claim 1, wherein an amount of heat transfer to the fixing member is suppressed. When the displacement detection unit detects the second deformation, the detection of the deformation is repeated at a predetermined interval until the second deformation is not detected in the state where the heating is stopped,
The fixing device according to claim 5, wherein the paper feed permission of the fixing device is extended to a point in time when the second deformation is no longer detected.   An image forming apparatus comprising the fixing device according to claim 1.