JP2017044863A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the rotation of a fixing belt without imposing a load on the fixing belt with a simple configuration.SOLUTION: A fixing device comprises: an endless fixing belt 22; a pressure roller 23 that is in pressure contact with the fixing belt 22; a belt assisting part 25 that is provided inside the fixing belt 22 and receives a press contact pressure from the pressure roller 23 via the fixing belt 22; a heater 24 that heats the fixing belt 22; a rotating member 28 that is provided at an end of the fixing belt 22 and rotates with the fixing belt 22; and a photosensor 27 that detects the rotation of the rotating member 28.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device and an image forming apparatus for fixing an image formed on a recording sheet by sandwiching the recording sheet in a nip region between an endless fixing belt and a pressure roller.

  As a fixing device, a pressure roller is pressed against an endless fixing belt, a nip area is formed between the fixing belt and the pressure roller, and the fixing belt is heated by a heater provided inside the fixing belt. In some cases, the recording paper is sandwiched in a nip area and an image (unfixed toner image) on the recording paper is fixed by thermocompression.

  In such a fixing device, since the pressure roller is driven to rotate and the fixing belt pressed against the pressure roller is driven to rotate, the fixing belt stops when the fixing belt slides against the pressure roller. To do. When the fixing belt is stopped, only a part of the fixing belt is excessively heated by the heater, and the fixing belt is damaged. Alternatively, when an overload is applied to the fixing belt, the fixing belt may be broken, and members around the fixing belt may be excessively heated by the heater.

  For this reason, for example, in Patent Document 1, a roller is brought into contact with the peripheral surface of the fixing belt and rotated, and the rotation of the roller is transmitted to an impeller-like member through a plurality of gears. Is detected by the photo sensor, and when the fixing belt stops and the impeller-like member also stops, the stop of the fixing belt is determined based on the detection output of the photo sensor, and the heat generation of the heater is stopped. .

JP 2010-72480 A

  However, in the configuration in which the rotation of the roller is transmitted to the impeller-like member via a plurality of gears as in Patent Document 1, each gear is thermally expanded as the temperature rises, and there is no play between the gears. The torque required to rotate the gear increases, the torque applied to the roller also increases, the load on the fixing belt received from the roller increases, and the fixing belt rotates poorly or the fixing belt is damaged. . Or, even if the play between each gear is set large, the torque required to rotate each gear fluctuates due to the expansion and contraction of each gear accompanying the temperature change, and the torque applied to the rollers also fluctuates. The fixing belt load received from the roller fluctuates, and the rotation operation of the fixing belt becomes unstable.

  In addition, the number of gears, rollers, and parts that rotatably support these gears increases, requiring a large space around the fixing belt and increasing the size of the fixing device.

  SUMMARY An advantage of some aspects of the invention is that it is possible to detect rotation of a fixing belt without applying a load to the fixing belt, although the configuration is simple.

  A fixing device according to an aspect of the present invention is provided with an endless fixing belt, a pressure roller pressed against the fixing belt, and an inner side of the fixing belt. A belt auxiliary unit received via the fixing belt, a heat generating unit for heating the fixing belt, a rotating member provided at an end of the fixing belt and rotating together with the fixing belt, and detecting rotation of the rotating member And a rotation detection unit.

  An image forming apparatus according to an aspect of the present invention includes the fixing device according to the present invention described above and an image forming unit that forms an image on a recording sheet, and the fixing apparatus includes the recording sheet and the fixing belt. This is an image forming apparatus that is sandwiched in a nip region between pressure rollers and thermocompression-bonds an image formed on the recording paper.

  According to the present invention, it is possible to detect the rotation of the fixing belt without applying a load to the fixing belt, although the configuration is simple.

1 is a perspective view illustrating an appearance of an image forming apparatus to which a fixing device according to an embodiment of the present invention is applied. 1 is a cross-sectional view schematically showing an image forming unit and a fixing device in an image forming apparatus according to an embodiment of the present disclosure. 1 is a front view illustrating a fixing device according to an exemplary embodiment. FIG. 2 is a cross-sectional view illustrating a fixing device of the present embodiment. FIG. 4 is a perspective view showing a periphery of one end of the fixing belt by breaking the fixing belt in the fixing device of the present embodiment. FIG. 3 is a perspective view showing the vicinity of one end of the fixing belt. FIG. 7 is a perspective view showing the vicinity of one end of the fixing belt, and shows a state where the rotational position of the fixing belt is different from FIG. 6. FIG. 2 is a block diagram illustrating a functional configuration of a fixing device. 6 is a flowchart illustrating a control procedure of the fixing device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing an external appearance of an image forming apparatus to which a fixing device according to an embodiment of the present invention is applied. The apparatus main body 2 of the image forming apparatus 1 as shown in FIG. 1 is provided with a plurality of components for realizing various functions of the image forming apparatus 1. For example, the apparatus main body 2 is provided with an image forming unit, a fixing device, a data communication unit, an operation unit 3, a paper feeding unit 4, a discharge tray 5, and the like.

  The data communication unit receives image data from an external terminal such as a personal computer via a network. The image forming unit forms (prints) the image indicated by the image data received by the data communication unit on the recording paper supplied from the paper feeding unit 4. The recording paper on which the image has been formed is discharged to the discharge tray 5 after undergoing fixing processing by the fixing device.

  The operation unit 3 includes, for example, a start key, a determination key (enter key) for confirming an operation input, a numerical value input key for inputting a numerical value, and the like, and gives instructions from the operator for various operations and processes. Accept. The operation unit 3 includes a display unit that displays operation guidance to the operator.

  FIG. 2 is a cross-sectional view schematically showing an image forming unit and a fixing device in the image forming apparatus according to the embodiment of the present disclosure.

  The image forming unit 11 is for forming a toner image on the recording paper P supplied from the paper feeding unit 4 by an electrophotographic method. The image forming unit 11 rotates in the direction of an arrow, and the surface of the photoconductive drum 12. Is generated on the surface of the photosensitive drum by the exposure from the neutralizing unit 13 for removing static electricity, the cleaning unit 14 for cleaning the surface of the photosensitive drum 12, the charging unit 15 for uniformly charging the surface of the photosensitive drum 12, and the exposure unit. And a developing unit 16 for developing the electrostatic latent image into a toner image.

  The photosensitive drum 12 is pressed against a transfer roller 18 provided below the photosensitive drum 12 to form a nip region between the photosensitive drum 12 and the transfer roller 18.

  When the recording paper P is supplied from the paper supply unit 4, the recording paper P is transported in the direction of arrow A through the transport path 17. The recording paper P is passed through the nip area between the photosensitive drum 12 and the transfer roller 18, and the toner image on the surface of the photosensitive drum 12 is transferred. Subsequently, the recording paper P is conveyed to the fixing device 21, and the recording paper P is heated and pressurized by the fixing device 21, whereby the toner image on the recording paper P is fixed. Further, the recording paper P is transported from the fixing device 21 through a transport path 17 curved upward, and is discharged to a discharge tray 5 provided on the upper side of the image forming apparatus 1.

  Next, the fixing device 21 of this embodiment will be described in detail. FIG. 3 is a front view showing the fixing device 21. FIG. 4 is a cross-sectional view showing the fixing device 21.

  3 and 4, the fixing device 21 includes a fixing belt 22, a pressure roller 23, a heater 24, a belt auxiliary member 25, a temperature sensor 26, a photo sensor 27, a rotating member 28, and each holding frame 29. I have.

  The fixing belt 22 is an endless belt, and is a sheet-like one in which a base material layer made of metal, synthetic resin, etc., an elastic layer made of silicone rubber, etc., a release layer made of synthetic resin, etc. are laminated. , Has flexibility.

  Cylindrical portions 29 a of the respective holding frames 29 are inserted inside both ends of the fixing belt 22. Each holding frame 29 is fixed to frames 30 (shown in FIGS. 5 to 7) on both sides of the fixing device 21, and the fixing belt 22 is held in a substantially cylindrical shape by inserting the cylindrical portion 29 a of each holding frame 29. I'm leaning.

  In addition, the inner diameter of the fixing belt 22 is sufficiently larger than the outer diameter of the cylindrical portion 29 a of each holding frame 29, and a gap is formed between the inner peripheral surface of the fixing belt 22 and the outer peripheral surface of the cylindrical portion 29 a of each holding frame 29. The fixing belt 22 is rotatably supported by the cylindrical portion 29a of each holding frame 29.

  Further, a heater 24 and a belt auxiliary member (belt auxiliary portion) 25 extending in the longitudinal direction of the fixing belt 22 are provided inside the fixing belt 22. The belt auxiliary member 25 is a columnar body, the upper surface thereof is a reflecting surface 25b, and the lower surface thereof is a bowl-shaped concave surface 25a. The heater 24 is, for example, a halogen lamp, and the radiant heat of the heater 24 is directly applied to the fixing belt 22 and is reflected by the reflecting surface 25b of the belt auxiliary member 25 to be applied to the fixing belt 22, and the fixing belt 22 is heated. Is done.

  The pressure roller 23 is obtained by covering the outer peripheral surface of a metal cylinder or column with a layer made of synthetic resin or the like, and is provided in parallel with the fixing belt 22. Specifically, the shaft 23 a of the pressure roller 23 is supported so as to be parallel to an imaginary line passing through the center of the cylindrical portion 29 a of each holding frame 29 that rotatably supports the fixing belt 22. Further, the curvature of the bowl-shaped concave surface 25 a of the belt auxiliary member 25 is set slightly smaller than the curvature of the outer peripheral surface of the pressure roller 23.

  Here, the pressure roller 23 is disposed below the fixing belt 22. Then, the shaft 23 a of the pressure roller 23 is urged upward by a spring or the like (not shown) to approach the fixing belt 22, and the pressure roller 23 is pressed against the fixing belt 22. At this time, the fixing belt 22 is greatly deformed and depressed at the pressure contact portion of the pressure roller 23, and the pressure roller 23 is pressed against the hook-shaped concave surface 25 a of the belt auxiliary member 25 via the fixing belt 22. The pressure contact pressure is received by the bowl-shaped concave surface 25 a of the belt auxiliary member 25. Thereby, the outer peripheral surface of the pressure roller 23 and the outer peripheral surface of the fixing belt 22 are pressed against each other in a wide range, and a nip region N is formed in this wide range.

  Then, when the rotational driving force of the motor 32 (shown in FIG. 8) is transmitted to the pressure roller 23 through a gear unit (not shown) and the pressure roller 23 is rotationally driven in the direction of the arrow, this additional force is applied. The fixing belt 22 pressed against the pressure roller 23 is driven to rotate in the direction opposite to that of the pressure roller 23. At this time, the fixing belt 22 is in sliding contact with the bowl-shaped concave surface 25a of the auxiliary member 25, and the nip area N between the pressure roller 23 and the fixing belt 22 is maintained.

  Further, the fixing belt 22 is heated by causing the heater 24 to generate heat. At this time, the temperature sensor 26 detects the temperature of the end portion of the fixing belt 22, and the heater 24 is on / off controlled based on the detected temperature, thereby adjusting the temperature of the fixing belt 22 to a specified temperature suitable for fixing. To do.

  In this state, when the recording paper P is conveyed to the nip area N, the recording paper P is heated and pressurized in the nip area N, and the toner image on the recording paper P is fixed by thermocompression bonding.

  By the way, in such a fixing device 21, when the fixing belt 22 slips with respect to the pressure roller 23, the rotation of the fixing belt 22 stops. When the fixing belt 22 is stopped, various inconveniences occur.

  Therefore, in the present embodiment, the rotation of the fixing belt 22 is detected, and when the rotation of the fixing belt 22 is stopped, the heat generation of the heater 24 and the rotation of the pressure roller 23 are stopped. Next, the configuration for detecting the rotation of the fixing belt 22 and the control procedure of the fixing device 21 will be described in detail.

  FIG. 5 is a perspective view showing the periphery of one end of the fixing belt 22 by breaking the fixing belt 22. 6 and 7 are perspective views showing the periphery of one end portion of the fixing belt 22 and show respective states in which the rotation position of the fixing belt 22 is different.

  As shown in FIGS. 5 to 7 and also in FIGS. 3 and 4, a rotation member 28 is provided at one end of the fixing belt 22. The rotating member 28 includes, for example, six cylindrical portions 28a that protrude from the one end of the cylindrical portion 28a to the outside in the radial direction of the cylindrical portion 28a and are arranged at regular intervals in the circumferential direction of the cylindrical portion 28a. And a protrusion 28b.

  The cylindrical portion 28 a of the rotating member 28 is inserted inside one end portion of the fixing belt 22 and is disposed between the fixing belt 22 and the cylindrical portion 29 a of each holding frame 29. The outer peripheral surface of the cylindrical portion 28 a of the rotating member 28 is in contact with the inner peripheral surface of one end region of the fixing belt 22. Further, an anti-slip portion is provided on the inner peripheral surface of one end region of the fixing belt 22 to be subjected to anti-slip processing. For example, by forming a layer having a large coefficient of friction on the inner peripheral surface of one end region of the fixing belt 22 or by performing unevenness processing on the inner peripheral surface of one end region of the fixing belt 22, The anti-slip portion is provided. For this reason, when the fixing belt 22 rotates, the rotating member 28 rotates together with the fixing belt 22, and each protrusion 28b also rotates. Note that the portion where the anti-slip portion is formed (anti-slip processing) is more end than the nip region N formed between the fixing belt 22 and the pressure roller 23 in the direction in which the shaft 23 a of the pressure roller 23 extends. It is more desirable that the position be the part side (outside). By forming the anti-slip portion at this position, the anti-slip portion is disengaged from the nip portion, so that the load on the fixing belt 22 is reduced.

  One end of the cylindrical portion 28a protrudes from one end of the fixing belt 22 to the outside of the fixing belt 22, and each protruding portion 28b protrudes from the protruding end. Each protrusion 28b rotates together with the fixing belt 22. However, when the fixing belt 22 is shifted left and right (in the direction in which the shaft 23a extends), the end of the fixing belt 22 hits the protrusion 28b. There is an effect to prevent. Further, the end of the fixing belt 22 is in contact with each protrusion 28b. However, in the present embodiment, there are only six places where the end of the fixing belt 22 contacts with the protrusion 28b. Therefore, the burden on the end portion of the fixing belt 22 due to the contact is small.

  In addition, the photosensor 27 is disposed so as to face the rotation track surface of each projection 28 b through the opening 30 a of the frame 30. The photosensor 27 includes a light emitting element and a light receiving element, and is, for example, a reflection type optical sensor. The photosensor 27 emits light from the light emitting element to the rotation orbital surface of each protrusion 28b and reflects the light reflected by the protrusion 28b. Light is received by the light receiving element. FIG. 6 shows a state in which light from the light emitting element passes between the protrusions 28b, and light reflected by the protrusions 28b is not received by the light receiving element. FIG. 7 shows light from the light emitting element. This shows a state in which the light reflected by 28b is received by the light receiving element.

  For this reason, when each protrusion 28b is rotating, the light reception output of the light receiving element alternately changes between a high level and a low level, and when each protrusion 28b is stopped, the light reception output of the light receiving element is at a high level. Or it is maintained at a low level and does not change. Therefore, it can be determined whether the fixing belt 22 and the rotating member 28 are rotating based on the detection output of the photosensor 27 (light reception output of the light receiving element).

  It is also possible to determine the rotational speeds of the fixing belt 22 and the rotating member 28 based on the period at which the light reception output of the light receiving element changes between high level and low level.

  FIG. 8 shows a configuration for controlling the fixing device 21. In FIG. 8, the control unit 31 inputs the detection output of the temperature sensor 26 and the detection output of the photosensor 27, and controls driving of the motor 32 for turning on / off the heater 24 and rotating the pressure roller 23. The fixing process is executed, and the operation of the fixing device 21 is stopped when an abnormality occurs.

  The heater 24 is an example of a heat generating unit in the claims, the photo sensor 27 is an example of a rotation detecting unit in the claims, and the temperature sensor 26 is an example of a temperature detecting unit in the claims. .

  Next, the control procedure of the fixing device 21 will be described with reference to the flowchart shown in FIG.

  First, during the operation of the image forming unit 11, the control unit 31 drives and controls the motor 32, rotationally drives the pressure roller 23, and rotates the fixing belt 22 (step S11).

  Further, the control unit 31 inputs the detection output of the temperature sensor 26, controls the heater 24 on and off based on the temperature of the end of the fixing belt 22 indicated by the detection output, and adjusts the heat generation amount of the heater 24, The temperature of the fixing belt 22 is adjusted to a specified temperature suitable for fixing (step S12).

  In this state, the recording paper P passes through the nip area N between the pressure roller 23 and the fixing belt 22, and the toner image on the recording paper P is fixed by thermocompression bonding.

  At this time, the control unit 31 inputs the detection output of the photosensor 27, and determines whether or not the fixing belt 22 and the rotating member 28 are rotating based on the detection output (step S13). If the controller 31 determines that the fixing belt 22 and the rotating member 28 are rotating (“Yes” in step S13), the controller 31 continues the rotation driving of the pressure roller 23 and the on / off control of the heater 24.

  Subsequently, the control unit 31 determines whether an abnormality of the fixing belt 22 has occurred based on the detection output of the photo sensor 27 and the detection output of the temperature sensor 26 (step S14), and the abnormality has occurred in the fixing belt 22. If it is determined that there is not (“No” in step S14), the processing from step S11 is repeated.

  If the control unit 31 determines that the rotation of the fixing belt 22 and the rotation member 28 has stopped based on the detection output of the photosensor 27 (“No” in step S13), the control unit 31 stops the on / off control of the heater 24, and the heater The heat generation of 24 is stopped (step S15), the motor 32 is further stopped, and the pressure roller 23 and the fixing belt 22 are stopped (step S16).

  As a result, it is possible to avoid a state in which the fixing belt 22 slips and stops with respect to the pressure roller 23, and only a part of the fixing belt 22 is excessively heated by the heater 24, so that the fixing belt 22 is The situation of being damaged can be prevented.

  Also, when the control unit 31 determines that the abnormality of the fixing belt 22 has occurred based on the detection output of the photo sensor 27 and the detection output of the temperature sensor 26 (“Yes” in step S14), the heater 24 is turned on / off. The control is stopped, the heat generation of the heater 24 is stopped (step S15), the motor 32 is further stopped, and the pressure roller 23 and the fixing belt 22 are stopped (step S16).

  Here, when the fixing belt 22 is overloaded and torn and cracked, even if one end side of the fixing belt 22 (one end side where the photo sensor 27 is provided) is rotating, The other end side of the fixing belt 22 (the other end side where the temperature sensor 26 is provided) may be almost stopped, and at this time, the other end of the fixing belt 22 detected by the temperature sensor 26 is brought about. An abnormal temperature occurs at the end. For example, when the other end side of the fixing belt 22 is almost stopped, only a part of the fixing belt 22 is intensively heated by the heater 24, and the temperature detected by the temperature sensor 26 is temporarily abruptly increased. Get higher.

  That is, when the fixing belt 22 is overloaded and torn and cracked, even if one end side of the fixing belt 22 is rotating, the other end side of the fixing belt 22 is almost stopped, and the temperature sensor 26 The detected temperature temporarily increases rapidly.

  For this reason, the control unit 31 determines that the fixing belt 22 and the rotating member 28 are rotating based on the detection output of the photosensor 27, but the other end portion of the fixing belt 22 based on the detection output of the temperature sensor 26. When the temperature abnormality is determined, it is determined that an abnormality has occurred in the fixing belt 22 (“Yes” in step S14). Then, the control unit 31 stops the heat generation of the heater 24 (Step S15), and stops the pressure roller 23 and the fixing belt 22 (Step S16).

  As a result, it is possible to avoid a situation in which the fixing belt 22 is torn and members around the fixing belt 22 are excessively heated by the heater 24.

  As described above, in the present embodiment, the cylindrical portion 28 a of the rotating member 28 is inserted inside one end of the fixing belt 22, the rotating member 28 is rotated together with the fixing belt 22, and the rotating member 28 is rotated by the photosensor 27. Each protrusion 28b is detected to determine whether or not the fixing belt 22 and the rotating member 28 are rotating. The rotating member 28 and the photosensor 27 do not apply a load to the fixing belt 22, and the load on the fixing belt 22 does not increase or fluctuate. For this reason, the fixing belt 22 is not damaged, and the rotation operation of the fixing belt 22 is not disturbed. Further, the number of parts is small, no special space is required, and the fixing device 21 is not increased in size.

  Further, when it is determined that the rotation of the fixing belt 22 has stopped, the heating of the heater 24 is stopped and the fixing belt 22 is stopped, so that the fixing belt 22 can be prevented from being damaged.

  Further, since the photo sensor 27 detects the rotation of one end of the fixing belt 22 and the temperature sensor 26 detects the temperature of the other end of the fixing belt 22, the detection output and temperature of the photo sensor 27 are detected. The abnormality of the fixing belt 22 is determined based on the detection output of the sensor 26, and this abnormal state can be avoided.

  In the above embodiment, the cylindrical portion 28 a of the rotating member 28 is inserted inside one end of the fixing belt 22, but the diameter of the cylindrical portion 28 a is increased so that the cylindrical portion 28 a is connected to the fixing belt 22. You may fit in the outer side of one edge part. Further, instead of the photosensor, other types of sensors may be applied, and the shape, configuration, material, and the like of the rotating member may be changed as appropriate according to the type of sensor.

  The image forming apparatus according to the present invention has been described using a monochrome printer, but this is only an example, and other color printers and other electronic devices such as multifunction peripherals, copiers, facsimile machines, and the like. An image forming apparatus may be used.

  Further, the configuration and processing described with reference to FIGS. 1 to 9 are only one embodiment of the present invention, and are not intended to limit the present invention to the configuration and processing.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Apparatus main body 3 Operation part 4 Paper feeding part 5 Output tray 11 Image forming part 21 Fixing apparatus 22 Fixing belt 23 Pressure roller 24 Heater 25 Belt auxiliary member 26 Temperature sensor 27 Photo sensor 28 Rotating member 29 Holding frame 31 Control unit

Claims (6)

An endless fixing belt,
A pressure roller pressed against the fixing belt;
A belt auxiliary portion provided inside the fixing belt and receiving the pressure contact pressure by the pressure roller via the fixing belt;
A heat generating part for heating the fixing belt;
A rotating member provided at an end of the fixing belt and rotating together with the fixing belt;
And a rotation detection unit that detects rotation of the rotation member. The rotating member has a cylindrical portion inserted inside an end portion of the fixing belt, and a plurality of projecting portions protruding in a radial direction from the cylindrical portion and arranged in a circumferential direction of the cylindrical portion,
The fixing device according to claim 1, wherein the rotation detection unit detects the protrusions that rotate as the rotation member rotates.   The fixing device according to claim 2, wherein a slip stopper for the rotating member is provided in an end region in contact with a cylindrical portion of the rotating member on an inner peripheral surface of the fixing belt.   The fixing device according to claim 1, further comprising a control unit that determines a rotation state of the fixing belt based on a detection output of the rotation detection unit. A temperature detection unit for detecting the temperature of the other end of the fixing belt opposite to the end of the fixing belt provided with the rotating member;
The fixing device according to claim 4, wherein the control unit determines an abnormality of the fixing belt based on a detection output of the rotation detection unit and a detection output of the temperature detection unit. A fixing device according to any one of claims 1 to 5,
An image forming unit that forms an image on recording paper,
The fixing device is an image forming apparatus in which the recording paper is sandwiched in a nip region between the fixing belt and the pressure roller, and an image formed on the recording paper is thermocompression bonded.