JP2016166918A - Fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device and the like capable of suppressing fixation failure that occurs when an annular belt becomes the unstable state before the belt reaches a fixation pressure-contact part formed by pressing the belt against the outer peripheral surface of a heating roller.SOLUTION: A fixation device comprises: a heating roller which rotates; an annular belt which is brought into contact with the outer peripheral surface of the heating roller to interlockingly rotate; and a pressure member provided with a pressing part which forms a fixation pressure-contact part by pressing the outer peripheral surface of the annular belt against a portion along the axial direction of the outer peripheral surface of the heating roller, an inlet guide part which is provided in a shape of protruding so as to approach the outer peripheral surface of the heating roller at the position on the upstream side in the rotation direction of the heating roller from the pressing part and guides the annular belt so as to come into contact with the portion along the axial direction of the outer peripheral surface of the heating roller before reaching the fixation pressure-contact part, and at least one intermediate guide part which is provided in a shape of protruding so as to approach the outer peripheral surface of the heating roller at the intermediate position between the pressing part and the inlet guide part and guides the annular belt so as to approach the portion along the axial direction of the outer peripheral surface of the heating roller to pass.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In an image forming apparatus that forms an image composed of a developer, a fixing device of a type that forms a fixing pressure contact portion by pressing an annular belt against an outer peripheral surface of a rotary roll may be applied. As a fixing device of this type, there is a fixing device that takes measures to prevent fixing failure and image quality failure caused by using an annular belt.

  For example, an endless belt rotating body suspended on at least two fixing members, and a heating fixing belt suspended on the belt rotating body and at least one member and subjected to a heating action, There is known a fixing device in which a belt rotating body is configured to come into pressure contact with a pressure member via a heat fixing belt (Patent Document 1).

Japanese Patent Laid-Open No. 2004-184753

  The present invention relates to a fixing device capable of suppressing a fixing failure caused by an unstable state before the annular belt reaches a fixing pressure contact portion formed by being pressed against an outer peripheral surface of a heating roll, and the fixing device. An image forming apparatus including the above is provided.

The fixing device of the present invention (A1)
A rotating heating roll;
An annular belt that rotates around in contact with the outer peripheral surface of the heating roll;
A pressing portion that presses the outer peripheral surface of the annular belt against a portion along the axial direction of the outer peripheral surface of the heating roll to form a fixing pressure contact portion; and the heating roll at a position upstream of the pressing portion in the rotation direction of the heating roll. An inlet guide portion that is provided in a shape protruding so as to approach the outer peripheral surface of the guide roller and guides the annular belt to start contacting a portion along the axial direction of the outer peripheral surface of the heating roll before reaching the fixing pressure contact portion; It is provided in a shape protruding so as to approach the outer peripheral surface of the heating roll at a position intermediate between the pressing portion and the inlet guide portion, and the annular belt is brought close to a portion along the axial direction of the outer peripheral surface of the heating roll. And a pressure member having at least one intermediate guide portion that guides it to pass.

  In the fixing device of the invention (A2), in the fixing device of the invention A1, at least one of the intermediate guide portions is closer to the entrance guide portion than a central position between the entrance guide portion and the pressing portion. Is provided.

  The fixing device according to the invention (A3) is the fixing device according to the invention A1 or A2, in which the intermediate guide portion has a distance that is less than or equal to the interval between the heating roll and the inlet guide portion. It is configured.

  The image forming apparatus according to the present invention (B1) includes the fixing device according to any one of the above inventions A1 to A3.

  According to the fixing device of the invention A1, it is possible to suppress a fixing failure that occurs due to an unstable state before the annular belt reaches the fixing pressure contact portion formed by being pressed against the outer peripheral surface of the heating roll. .

  In the fixing device of the invention A2, the effect of the invention A1 can be obtained with certainty while reducing the impact when the leading end of the recording medium on which the toner image to be fixed is in contact with the annular belt.

  In the fixing device of the invention A3, the effect of the invention A1 can be obtained more reliably than in the case where the distance between the intermediate guide portion and the heating roll is wider than the distance between the inlet guide portion and the heating roll.

  According to the image forming apparatus of the invention B1, the fixing failure caused by the unstable state before the annular belt reaches the fixing pressure contact portion formed by being pressed against the outer peripheral surface of the heating roll in the fixing device is suppressed. As a result, it is possible to suppress the deterioration of image quality due to such a fixing failure.

1 is a conceptual diagram illustrating an overall configuration of an image forming apparatus including a fixing device according to Embodiment 1. FIG. FIG. 2 is a partial cross-sectional explanatory diagram showing an enlarged overall configuration of a fixing device in the image forming apparatus of FIG. 1. FIG. 3 is a partial cross-sectional explanatory view showing an enlarged main part (pressure member and its peripheral part) in the fixing device of FIG. 2. FIG. 3 is a perspective view showing an entire pressure member in the fixing device of FIG. 2. It is explanatory drawing for demonstrating the structure of each site | part in a pressurization member. FIG. 3 is an explanatory diagram conceptually showing main operation states of the fixing device of FIG. 2. It is explanatory drawing which shows notionally the other structural example of the pressurization member in a fixing device. It is explanatory drawing which shows notionally another structural example of the pressurization member in a fixing device.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “embodiments”) will be described with reference to the accompanying drawings.

[Embodiment 1]
1 and 2 show an image forming apparatus including the fixing device according to the first embodiment. FIG. 1 conceptually shows the overall configuration of the image forming apparatus, and FIG. 2 shows the overall configuration of the fixing device. Arrows indicated by reference signs X, Y, and Z in each drawing such as FIG. 1 are orthogonal coordinate axes (directions) indicating respective directions of the width, height, and depth of the three-dimensional space assumed in each drawing.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 forms an image composed of a developer on a recording sheet 9 which is an example of a recording medium. For example, the image forming apparatus 1 receives image information input from an external device such as an information terminal and receives an image. The printer is configured to perform formation.

  The image forming apparatus 1 has a casing 10 having a box-like appearance as a whole, and the interior space of the casing 10 is configured with toner as a developer as shown in FIG. An image forming unit 20 for forming a toner image, an intermediate transfer device 30 for transferring the toner image formed by the image forming unit 20 after the primary transfer, and finally transferring the toner image onto the recording paper 9; A paper feeding device 40 that receives and feeds the recording paper 9 supplied to the secondary transfer position, a fixing device 5 that fixes the toner image secondary-transferred by the intermediate transfer device 30 to the recording paper 9, and the like are arranged. On the upper surface of the housing 10, there is provided a discharge storage portion 12 for discharging the recording paper 9 after the image is formed and storing it in a stacked state. A one-dot chain line shown in FIG. 1 is a main conveyance path of the recording paper 9.

  The image forming unit 20 according to the first embodiment includes four image forming units that individually form four color developer (toner) images of yellow (Y), magenta (M), cyan (C), and black (K). It is composed of image units 20Y, 20M, 20C, and 20K. Also, these image forming units 20 (Y, M, C, K) are arranged in a state (inclined state) in which the position gradually increases in the order of black, cyan, magenta, and yellow in the internal space of the housing 10. ing.

  Each of the four image forming units 20 (Y, M, C, K) has a photosensitive drum 21 that is a drum-shaped photosensitive member that is rotationally driven in a direction indicated by an arrow A, and an outer periphery that serves as an image forming area of the photosensitive drum 21. A charging device 22 in the form of a roll for charging the surface to a required potential and the outer peripheral surface of the photosensitive drum 21 after charging are irradiated with light separated into each color component based on required image information to An exposure device 23 that forms an electrostatic latent image, and a developing device 24 (Y, Y) that develops the electrostatic latent image with toner of each color component and visualizes it as a toner image of each color (Y, M, C, K). M, C, K) and unnecessary toner such as toner remaining on the outer peripheral surface of the photosensitive drum 21 after primary transfer of the toner image on the photosensitive drum 21 to the intermediate transfer device 30 (the intermediate transfer belt 31) is removed. Drum cleaning device 26 etc. for cleaning There.

In each of the image forming units 20 (Y, M, C, K), when an image formation request is received, the outer peripheral surface of each photosensitive drum 21 that starts rotating is charged to a required potential by each charging device 22. Thereafter, light corresponding to the image signal of each color component is irradiated from the exposure device 23 onto the outer peripheral surface of the charged photosensitive drum 21 to form an electrostatic latent image of each color component.
Subsequently, with respect to the electrostatic latent image of each color component formed on the outer peripheral surface of each photosensitive drum 21, the four colors (Y, M, C, K) in the corresponding developing device 24 (Y, M, C, K). The four color toner images are formed on the respective photosensitive drums 21 by developing with any one of the toners.

The intermediate transfer device 30 is slightly inclined at a position on the upper side in the gravity direction of the four image forming units 20 (Y, M, C, K) corresponding to the arrangement of the image forming units 20 group in an inclined state. Arranged in a state.
The intermediate transfer device 30 includes an endless intermediate transfer belt 31 that can transfer and hold a toner image formed on the photosensitive drum 21 of the image forming unit 20 (Y, M, C, K) by electrostatic action. A plurality of support rolls 32 a to 32 e that support the intermediate transfer belt 31 so as to rotate by sequentially passing through the primary transfer positions of the image forming unit 20 (Y, M, C, K), and the inner side of the intermediate transfer belt 31. And a roller that primarily transfers each toner image formed on the photosensitive drum 21 of each image forming unit 20 (Y, M, C, K) to the outer peripheral surface of the intermediate transfer belt 31 by an electrostatic action or the like. A primary transfer device 34 in a form, a secondary transfer device 35 in a roll form or the like for secondary transfer of the toner image primarily transferred to the intermediate transfer belt 31 to the recording paper 9 by electrostatic action, etc., and a secondary transfer The rear intermediate transfer belt 31 To remove unnecessary substances such as toner remaining on the peripheral surface and a belt cleaning device 36 or the like for cleaning.

  Of these, the support roll 32a is configured as a drive roll and secondary transfer backup roll, the support roll 32c is configured as a tension applying roll, the support rolls 32d and 32e are configured as surface rolls, and the support roll 32b is configured as a cleaning backup roll. Yes.

The paper feeding device 40 is disposed at a position on the lower side in the gravity direction of the four image forming units 20 (Y, M, C, K).
The paper feed device 40 is attached to the housing 10 so as to be freely drawn out, and stores a paper storage body 41 for storing recording paper 9 of a desired size and type on the stacking plate 42, and a paper storage A feeding device 43 for feeding the recording paper 9 from the body 41 one by one is provided. In the paper feeding device 40, when an image is formed, the required recording paper 9 is sent out one by one from the paper container 41 by the sending device 43. The recording paper 9 sent out from the paper feeding device 40 advances along a conveyance path indicated by a one-dot chain line, and the intermediate transfer device 30 is matched with the secondary transfer timing by a conveyance timing adjustment roll pair 44 arranged on the conveyance path. Are finally fed to the secondary transfer position (position between the intermediate transfer belt 31 and the secondary transfer device 35).

In the intermediate transfer device 30, when an image is formed, each color toner image formed on each photosensitive drum 21 in the image forming unit 20 (Y, M, C, K) is subjected to the transfer action of the primary transfer device 34 and is intermediate. The primary transfer is sequentially performed while being aligned with the outer peripheral surface of the transfer belt 31. At this time, in the image forming unit 20 (Y, M, C, K), the outer peripheral surface of the photosensitive drum 21 after the primary transfer is cleaned by the drum cleaning device 26.
Subsequently, the intermediate transfer belt 31 conveys the primarily transferred toner image to a secondary transfer position facing the secondary transfer device 35. Thereafter, in the intermediate transfer device 30, the toner image on the intermediate transfer belt 31 is subjected to the transfer action of the secondary transfer device 35 on the recording paper 9 supplied from the paper supply device 40 to the secondary transfer position. Transcript. At this time, in the intermediate transfer device 30, the outer peripheral surface of the intermediate transfer belt 31 after the secondary transfer is cleaned by the belt cleaning device 36.

The fixing device 5 is disposed at a position on the upper side in the gravity direction of the secondary transfer portion of the intermediate transfer device 30 (the portion where the secondary transfer device 35 of the intermediate transfer belt 31 is disposed).
The fixing device 5 includes a heating roll 51 that is driven to rotate in a direction indicated by an arrow B in the internal space of the box-shaped housing 50 and is heated by the heating unit 501 to keep the surface temperature at a required temperature. An annular pressure belt 52 that rotates in contact with the outer peripheral surface of the heating roll 51 and a portion along the axial direction of the outer peripheral surface of the heating roll 51 (direction along the direction of the coordinate axis Z). A pressure member 53 having a portion that forms a fixing pressure contact portion (FN) by being pressed with a required pressure is mainly installed.

The housing 50 is provided with an inlet (opening) 50a through which a recording paper 9 holding a toner image to be fixed is introduced, and an outlet (opening) 50b through which the recording paper 9 after fixing is discharged. In FIG. 2, reference numeral 56 denotes an introduction guide member for guiding the recording paper 9 onto which the toner image has been secondarily transferred to the fixing pressure contact portion FN, and reference numeral 57 denotes the recording paper 9 after completion of fixing toward the outlet 50b. A discharge guide member that guides the heating roll 51, a temperature measuring device 58 for measuring the surface temperature of the heating roll 51, and a reference 59 attached so as to swing up and down around the fulcrum portion 59 a, ensuring the passage of the recording paper 9. And a transport path constituent member that switches destinations.
When the recording paper 9 after the completion of fixing is discharged, the conveyance path constituting member 59 swings in the upward direction indicated by the double-pointed arrow about the fulcrum portion 59a by being pushed by the discharged recording paper 9. The outlet 50b is opened to the extent that the recording paper 9 can pass through (the state indicated by the two-dot chain line in FIG. 2). Further, when the recording paper 9 after completion of fixing does not pass or when double-sided image formation is performed, the conveyance path constituting member 59 swings downward about the fulcrum portion 59a due to its own weight or the like, and the outlet 50b is It is kept in a state (state indicated by a solid line) that forms a path for transporting the recording paper 9 for double-sided image formation.
Further details of the fixing device 5 will be described later.

  In the fixing device 5, at the time of image formation, the recording paper 9 onto which the toner image T is secondarily transferred by the intermediate transfer device 30 advances along the conveyance path indicated by a one-dot chain line and passes through the inlet 50 a of the housing 50. Thereafter, the sheet is fed into a fixing pressure contact portion FN formed between the rotating heating roll 51, the pressure belt 52, and the pressure member 53. The fixing device 5 melts and fixes the toner image T on the recording paper 9 by applying heat and pressure when the recording paper 9 passes through the fixing pressure contact portion FN.

  After the fixing, the recording paper 9 passes through the outlet 50b of the casing 50 and is discharged, and then advances along the conveyance path indicated by the alternate long and short dash line, and the casing 9 by the discharge roll pair 48 disposed at the end of the conveyance path. It is carried out of the body 10 and finally accommodated in the discharge accommodating portion 12. Incidentally, in the case of double-sided image formation, the recording paper 9 on which image formation (fixing) on one side has been completed is transferred from the rear end portion of the recording paper 9 by the reverse rotation conveyance operation of the discharge roll pair 48 to the conveyance path constituting member 59. It is guided along the upper end guide part so as to be returned to the paper conveyance path. Reference numeral 50c shown in FIG. 2 is a retransmission guide member that constitutes a part of a reverse retransmission path (not shown) that retransmits the recording paper 9 to the paper feed conveyance path in a state in which the recording paper 9 is reversed at the time of double-sided image formation.

  According to this image forming apparatus 1, by selecting and operating all or a part (at least a plurality of color toners) of the image forming unit 20 (Y, M, C, K), four colors (Y, M, A color image constituted by combining all or part of the toners of C, K) can be formed. Further, by operating one of the image forming device units 20 (Y, M, C, K), it is also possible to form a single color image composed of one color toner such as black.

<Configuration of fixing device>
The fixing device 5 includes the heating roll 51, the pressure belt 52, and the pressure member 53 described above in the housing 50. In particular, the pressure member 53 having the following configuration is provided. Applicable.

That is, as shown in FIGS. 2 to 4 and the like, the pressurizing member 53 is an elongated plate-like member that extends along the axial direction of the heating roll 51, and the surface on the side facing the heating roll 51. The following pressing portion 61, entrance guide portion 62 and intermediate guide portion 63 are provided.
Specifically, the pressing member 53 presses the outer peripheral surface of the pressure belt 52 against a portion along the axial direction (almost along the coordinate axis Z) of the outer peripheral surface of the heating roll 51 to form a fixing press contact portion FN. 61 and a shape protruding from the pressing portion 61 at the upstream side in the rotation direction B of the heating roll 51 so as to approach the outer peripheral surface of the heating roll 51, and the pressure belt 52 reaches the fixing pressure contact portion FN. The inlet guide 62 that guides to start contacting the portion along the axial direction of the outer peripheral surface of the heating roll 51 before, and approaches the outer peripheral surface of the heating roll 51 at an intermediate position between the pressing portion 61 and the inlet guide 62. It has an intermediate guide portion 63 that is provided in such a protruding shape and guides the pressure belt 52 to pass close to a portion along the axial direction of the outer peripheral surface of the heating roll 51.

  Here, the heating roll 51 is made of a material such as metal, and has a cylindrical roll body having an axial length larger than the maximum feed width of the recording paper 9 used for image formation, and the inside of the roll body. It comprises a heating means 501 such as a halogen heater arranged along the axial direction of the space. In addition, the heating roll 51 is rotatably attached to the casing 50 so that the rotary power from a rotary drive device (not shown) is transmitted to the heating roll 51 in the direction indicated by the arrow B. It has become.

  The pressure belt 52 is made of a material such as polyimide, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), and has a length (width) substantially corresponding to the axial length of the heating roll 51. An annular (single cylinder) belt material. The pressure belt 52 has a guide portion provided on a belt guide support member 54 whose inner peripheral surfaces at the left and right end portions in the rotation direction are disposed on the left and right end portions of the pressure belt 52, and the belt guide support. The member 54 is supported so as to be able to rotate by being guided while being in contact with a part of the pressure member 53 disposed at the opening facing the heating roll 51 of the member 54. In addition, the pressure belt 52 is in a state in which the outer circumferential surface thereof is pressed against and contacted with the outer circumferential surface of the heating roll 51 by the pressing portion 61 of the pressing member 53, so that the rotational force of the heating roll 51 is transmitted. It is adapted to follow and rotate in the direction indicated by arrow C (FIG. 3). The belt guide support member 54 is attached so that both ends in the longitudinal direction (the axial direction of the heating roll 51) are fixed to the housing 50.

  The pressure member 53 is formed into a desired shape using a material made of a synthetic resin such as polyethylene terephthalate (PET) or liquid crystal polymer (LCP). The pressurizing member 53 in the first embodiment has a size corresponding to a region in which the entire width dimension along the rotation direction of the heating roll 51 is about 1/4 of the entire circumference of the heating roll 51. The overall length dimension along the axial direction of the heating roll 51 is equal to or larger than the length of the maximum area used when the heating roll 51 is fixed.

  As shown in FIG. 3 to FIG. 5 and the like, the pressing portion 61 in the pressing member 53 is near the end portion on the downstream side in the rotation direction B of the heating roll 51 in the surface facing the heating roll 51 of the pressing member 53. In FIG. 4, the heating roll 51 is provided in a raised shape so as to come into contact with the portion along the axial direction of the outer peripheral surface with a required width W (FIG. 4). The cross-sectional shape of the protruding portion of the pressing portion 61 is, for example, such that its outline draws a curved line.

  Further, the pressing portion 61 is pressed with a required pressure by the pressing body 55, so that the pressing portion 61 is applied to a portion along the axial direction of the outer peripheral surface of the pressure roll 51 (through the pressure belt 52) with substantially equal pressure. It is comprised so that it may contact. The pressing body 55 includes a groove 68 formed linearly along the axial direction of the heating roll 51 on the surface opposite to the surface facing the heating roll 51 of the pressing member 53 and the inner wall surface of the belt guide support member 54. Arranged between. Specifically, the pressing body 55 is made of a plate material having an L-shaped cross section, and the distal end of the relatively long plate portion is fitted in the groove portion 68 in the pressure member 53, and the relative In particular, the short plate portion is disposed in close contact with the inner wall surface of the belt guide support member 54.

  As shown in FIG. 3 to FIG. 5 and the like, the inlet guide portion 62 in the pressing member 53 is connected to the heating roll 51 from the pressing portion 61 (center position of the width W) on the surface of the pressing member 53 facing the heating roll 51. 1 at the position along the axial direction of the outer peripheral surface of the heating roll 51 at a position (near the end on the upstream side) that is separated by a required distance L (see FIG. 5) upstream in the rotational direction B. (Refer to FIG. 5). The cross-sectional shape of the protruding portion of the entrance guide portion 62 is, for example, a shape that draws a triangular shape having an obtuse angle. Incidentally, as shown in FIG. 5 and the like, the inlet guide portion 62 is moved from a central position D of the width W of the pressing portion 61 to a position D where the central angle is 90 ° on the upstream side in the rotation direction B of the heating roll 51. It exists in the state which exists in the area | region R. A symbol O in FIG. 5 indicates a rotation center point of the heating roll 51.

  As shown in FIGS. 3 to 5 and the like, the intermediate guide portion 63 in the pressure member 53 is located between the pressing portion 61 and the inlet guide portion 62 on the surface of the pressure member 53 facing the heating roll 51 ( In the middle position), the heating roll 51 is provided in a shape protruding so as to approach the portion along the axial direction of the outer peripheral surface of the heating roll 51 with a required second interval K2 (see FIG. 5). The cross-sectional shape of the protruding portion of the intermediate guide portion 63 is, for example, a shape that draws a triangular shape having an acute angle.

  Further, as shown in FIG. 5, the intermediate guide portion 63 is located at the entrance more than the center position P (position L / 2) between the pressing portion 61 and the entrance guide portion 62 (separation distance L on the arc). It is provided at a position close to the guide part 62. In other words, the position at this time is a position upstream of the central position P in the rotational direction B of the heating roll 51. Further, as shown in FIG. 5, this position is defined such that the separation distance on the arc with respect to the inlet guide portion 62 of the intermediate guide portion 63 is m1, and the separation distance on the arc with the pressing portion 61 of the intermediate guide portion 63 is m2. In this case, the two separation distances M1 and M2 are also positions where the magnitude relationship of “m1 <m2” is satisfied.

  Further, as shown in FIG. 5, the intermediate guide portion 63 has a dimension in which the distance K2 from the heating roll 51 is smaller than the distance K1 from the inlet guide portion 62 to the heating roll 51 (“K2 <K1”). Relationship). Incidentally, the distance K2 between the intermediate guide portions 63 is at least a lower limit value from the viewpoint that it is necessary to allow the pressure belt 52 and the recording paper 9 to pass between the intermediate guide portion 63 and the heating roll 51 at the same time. The size is set to be larger than the total thickness of the pressure belt 52 and the recording paper 9. Further, the interval K1 of the entrance guide portion 62 is set so that the lower limit value thereof is equal to or smaller than the interval at which heat can be transferred from the heating roll 51 to the recording paper 9 from the viewpoint of improving the fixing property.

Further, in this pressurizing member 53, as shown in FIG. 5 and the like, the pressurizing belt 52 heats a portion (end portion) upstream from the inlet guide portion 62 in the rotation direction B of the heating roll 51. From the viewpoint of being guided smoothly so as to approach the outer peripheral surface of the roll 51, it is formed as an entrance slope in a state of gradually approaching the outer peripheral surface of the heating roll 51. Further, the portion 66 of the pressure member 53 from the inlet guide portion 62 to the intermediate guide portion 63 is formed as an inclined surface that gradually moves away from the outer peripheral surface of the heating roll 51 from the inlet guide portion 62 to the intermediate guide portion 63. doing. Further, the portion 67 from the intermediate guide portion 63 to the pressing portion 61 of the pressing member 53 is formed as an inclined surface that gradually approaches the outer peripheral surface of the heating roll 51 from the intermediate guide portion 63 to the pressing portion 61. ing.
Accordingly, between the pressure member 53 and the heating roll 51, as shown in FIG. 5 and the like, the inclined portion 66 and the outer periphery of the heating roll 51 are interposed between the inlet guide portion 62 and the intermediate guide portion 63. A first space S1 mainly surrounded by the surface, and a second space S2 mainly surrounded by the inclined portion 67 and the outer peripheral surface of the heating roll 51 between the intermediate guide portion 63 and the pressing portion 61. Exists.

  The pressure member 53 is attached to the belt guide support member 54 fixed to the housing 50 as described above. Reference numeral 71 in FIGS. 3 and 4 denotes a guide plate for regulating and guiding the position of the side end portion (meandering travel) of the pressure belt 52 provided at both end portions in the longitudinal direction of the slope portion 66. It is. In addition, in order to reduce the sliding resistance generated between the pressure member 53 of the pressure belt 52 and the surface of the pressure member 53 facing the heating roll 51 and the inner peripheral surface of the pressure belt 52. In addition, it may be arranged so that a sliding sheet (not shown) exists. As the sliding sheet, for example, a member in which a sheet base material such as a glass cloth is impregnated with a fluororesin is applied. Reference numeral 69 in FIG. 3 or the like is used, for example, as a part to which an upstream end of the sliding sheet is attached. In the sliding sheet having the upstream end attached to the attachment portion 69, the downstream portion is present between the surface of the pressure member 53 facing the heating roll 51 and the inner peripheral surface of the pressure belt 52. Are arranged as follows.

<Operation of fixing device>
Next, the operation of the fixing device 5 will be described.

  In the fixing device 5, when the image is formed, the heating roll 51 is heated to a predetermined temperature by the heating unit 501, and is rotationally driven in a direction indicated by an arrow B by receiving rotational power from a rotational driving device (not shown). In addition, the heating belt 52 is driven to rotate in the direction indicated by the arrow C by transmitting the rotational force generated by the rotational drive of the heating roll 51 at a portion (fixing pressure contact portion FN) that contacts the outer peripheral surface of the heating roll 51. .

At this time, the pressure belt 52 is guided and supported by the belt guide support member 54 and the like, and passes through the pressure member 53 in the following state.
That is, as shown in FIGS. 3, 6, etc., the pressure belt 52 has an outer periphery of the heating roll 51 by an inlet guide portion 62 that first exists at a position where the pressure belt 52 of the pressure member 53 moves by rotation. Passed by being guided close to the surface. Subsequently, the pressure belt 52 passes through the pressure member 53 in a state in which the pressure belt 53 is reliably close to the outer peripheral surface of the heating roll 51 by the intermediate guide portion 63 that exists next to the inlet guide portion 62. Finally, in the pressure belt 52, the outer circumferential surface of the pressure belt 52 extends along the axial direction of the outer circumferential surface of the heating roll 51 by the pressing portion 61 that finally exists after passing through the intermediate guide portion 63 in the pressure member 53. The portion is pressed at least with a width W and guided so as to form a fixing pressure contact portion FN. Strictly speaking, the pressure belt 52 passes through the outer peripheral surface formed of the cylindrical curved surface of the heating roll 51 at a position before reaching the fixing pressure contact portion FN formed by the pressing portion 61.

As a result, in the fixing device 5, the pressure belt 52 extends along the axial direction of the outer peripheral surface of the heating roll 51 by the inlet guide portion 62 before reaching the fixing pressure contact portion FN formed by the pressing portion 61 of the pressure member 53. It passes in a state of approaching the portion and passes in a state of contact at a position before reaching the fixing pressure contact portion FN. In addition, the pressure belt 52 is securely attached to a portion along the axial direction of the outer peripheral surface of the heating roll 51 before reaching the fixing pressure contact portion FN by the intermediate guide portion 63 existing between the inlet guide portion 62 and the pressing portion 61. It will pass in the state of approaching.
Accordingly, the pressure belt 52 passes so as to be stably kept close to the outer peripheral surface of the heating roll 51 before reaching the fixing pressure contact portion FN, and is heated before reaching the fixing pressure contact portion FN. It is possible to suppress an unstable state that flutters up and down in a space existing between the outer peripheral surface of the roll 51 and the pressure member 53.

  In the fixing device 5, the recording sheet 9 on which the toner image T to be fixed is secondarily transferred is guided from the inlet 50 a of the housing 50 to the introduction guide member 56 and introduced toward the fixing pressure contact portion FN. And the outer peripheral surface of the pressure belt 52 that passes between the inlet guide portion 62 and the intermediate guide portion 63 of the pressure member 53 after the leading end 9a of the recording paper 9 contacts the outer peripheral surface of the pressure roll 51. After that, it moves toward the fixing pressure contact portion FN while being sandwiched between the heating roll 51 and the pressure belt 52. Subsequently, the fixing device 5 fixes the toner image T onto the recording paper 9 by heating and pressurizing the recording paper 9 when it enters and passes through the fixing pressure contact portion FN. Finally, in the fixing device 5, the recording paper 9 that has been fixed by passing through the fixing pressure contact portion FN is discharged from the outlet 50 b of the housing 50 while being guided by the discharge guide member 57.

At this time, in the fixing device 5, when the recording sheet 9 on which the toner image T is secondarily transferred is introduced, the pressure is applied after the leading end 9 a of the recording sheet 9 passes through the inlet guide portion 62 of the pressing member 53. Since it contacts the outer peripheral surface of the belt 52, the pressure belt 52 receives an impact and swings up and down in the space between the outer peripheral surface of the heating roll 51 and the pressure member 53. Here, the position at which the recording paper 9 first comes into contact with the pressure belt 52 is the central position P between the pressing portion 61 of the pressure member 53 and the inlet guide portion 62 (separation distance L on the arc). It has been confirmed that the position is closer to the entrance guide 62 than the position (L / 2).
However, in the fixing device 5, the pressure belt 52 is reliably attached to the outer peripheral surface of the heating roll 51 by the intermediate guide portion 63 existing on the way from the inlet guide portion 62 to the fixing pressure contact portion FN formed by the pressing portion 61. Since the guide is guided so as to approach, it is possible to suppress the pressure belt 52 from swinging up and down and becoming unstable even when receiving an impact due to the contact of the recording paper 9.
For this reason, in the fixing device 5, the recording paper 9 also follows the pressure belt 52 that travels in a stable state, and is sent to and passed through the fixing pressure contact portion FN. The occurrence of a fixing failure due to an unstable state such as swinging up and down in the space between the outer peripheral surface of the heating roll 51 and the pressure member 53 is suppressed. Incidentally, the fixing failure in this case is specifically a defect such as fixing the toner image transferred to the recording paper 9 in a shifted state.

In the fixing device 5, as described above, the intermediate guide portion 63 of the pressure member 53 is provided at a position closer to the entrance guide portion 62 than the central position P between the pressing portion 61 and the entrance guide portion 62. So there are the following advantages.
That is, even if the recording paper 9 first contacts the outer peripheral surface of the pressure belt 52 at a position closer to the inlet guide portion 62 than the central position P in the pressure member 53, the pressure belt 52 is moved by the intermediate guide portion 63. Since it is guided in a state of reliably approaching the outer peripheral surface of the heating roll 51, the pressure belt 52 at that time swings up and down in the space S2 existing between the inlet guide portion 62 and the intermediate guide portion 63, etc. The unstable state is appropriately suppressed. As a result, the recording paper 9 is fed into the fixing pressure contact portion FN in a more stable state.

Further, the fixing device 5 is configured such that the distance K2 between the heating roll 51 and the heating guide 51 is smaller than the distance K1 between the entrance guide 62 and the heating roll 51 as described above. .
That is, before the pressure belt 52 reaches the fixing pressure contact portion FN, the inlet guide portion 62 and the intermediate guide portion 63 of the pressure member 53 are sequentially passed. At this time, the inlet guide portion 62 and the intermediate guide portion 63 Since the distances K1 and K2 with respect to the heating roll 51 are gradually reduced (K1> K2), the pressure belt 52 also moves in a state of gradually and reliably approaching the outer peripheral surface of the heating roll 51. An unstable state such as swinging up and down before reaching the fixing pressure contact portion FN is reliably suppressed. Also by this, the recording paper 9 is sent to the fixing pressure contact portion FN in a more stable state.

  In the image forming apparatus 1 provided with the fixing device 5, the fixing failure caused by the unstable state before the pressure belt 51 reaches the fixing pressure contact portion FN in the fixing device 5 is suppressed. Therefore, it is possible to suppress the deterioration of the image quality due to such fixing failure.

[Other embodiments]
In the first embodiment, the configuration example in which one intermediate guide portion 63 is provided as the pressure member 53 in the fixing device 5 has been described. However, as the pressure member 53, for example, as illustrated in FIG. It is possible to apply a pressing member 53B provided with two intermediate guide portions 63 and 64. Incidentally, in the pressure member 53B illustrated in FIG. 7, the inlet guide portion 62 is positioned at a position D where the central angle is 90 ° from the central position D of the width W of the pressing portion 61 to the upstream side in the rotation direction B of the heating roll 51. It is provided in a state of facing.

  In this case, it is desirable to provide one (first) intermediate guide portion 63 at a position closer to the entrance guide portion 62 than the central position P between the pressing portion 61 and the entrance guide portion 62 in the pressure member 53B. . Further, the other (second) intermediate guide portion 64 may be provided at a position between the first intermediate guide portion 63 and the pressing portion 61. Furthermore, even if the distance K2 between the first intermediate guide portion 63 and the heating roll 51 and the distance K3 between the second intermediate guide portion 64 and the heating roll 51 are set to be the same size (“K2 = K3”). Alternatively, the interval K3 of the second intermediate guide portion 64 may be set to be smaller than the interval K2 of the first intermediate guide portion 63 (“K2> K3”). In addition, about the intermediate | middle guide part, if necessary, it is also possible to provide three or more.

  In the first embodiment, the case where the distance K2 between the intermediate guide portion 63 and the heating roll 51 of the pressure member 53 is set to be smaller than the distance K1 between the inlet guide portion 62 and the heating roll 51 is exemplified. However, the present invention is not limited to this, and it may be set so as to have the same dimensions (“K2 = K1”).

  Furthermore, in the first embodiment, it is also effective to attach the elastic member 70 to the inlet guide portion 62 of the pressure member 53 so as to face the heating roll 51. The elastic member 70 is a member having elasticity such as a silicon pad or a nonwoven fabric. The elastic member may be in contact with the surface of the heating roll 51 with its own elastic force.

  When the elastic member 70 is mounted, the pressure belt 52 passes through the inlet guide portion 62 of the pressure member 53 while being in contact with the surface of the heating roll 51 by the elastic force of the elastic member. Thus, the vehicle travels to the fixing pressure contact portion FN in a more stable state. In addition, the entrance guide unit 62 can more actively heat the toner image, which contributes to improvement in fixing performance.

Further, in the fixing device 5, a pressure member 53 (for example, the above-described pressure member) is arranged such that the entrance guide portion 62 is disposed at a central angle that is 90 ° or more than the central position D of the pressing portion 61. If the member 53B) is to be employed, the distance (K1) between the inlet guide 62 and the heating roll 51 is greatly affected by the travelability and fixing performance of the pressure belt 52, and the distance between them is determined. Setting management of (K1) was difficult. As a countermeasure, an attempt has been made to lightly contact the inlet guide 62 of the pressure member 53 with the surface of the heating roll 51. In this case, however, the gloss caused by the toner image to be fixed being displaced on the recording paper 9 is detected. Since image quality defects (so-called haze) such as (gloss) unevenness and density unevenness occur, there is a limit to adopting the pressure member 53 (B) as described above.
In this regard, when the elastic member 70 is attached, even when the pressure member 53 (B) in which the inlet guide portion 62 is disposed at the position as described above is employed, the occurrence of the image quality defect is suppressed. It becomes like this.

  In addition, the image forming apparatus to which the present invention is applied is not limited to the image forming apparatus of the type that forms the color image exemplified in the first embodiment. For example, a monochrome image (for example, a black and white image) is also formed. It is also possible to use an image forming apparatus of the type.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 5 ... Fixing apparatus 51 ... Heating roll 52 ... Pressure belt (annular belt)
53 ... Pressure member 61 ... Pressing part 62 ... Inlet guide part 63 ... Intermediate guide part (intermediate guide part in one case)
FN: Fixing pressure contact portion B: Rotating direction P of the heating roll ... Center position K1: Spacing of the inlet guide section with the heating roll K2: Spacing of the intermediate guide section with the heating roll

Claims (4)

A rotating heating roll;
An annular belt that rotates around in contact with the outer peripheral surface of the heating roll;
A pressing portion that presses the outer peripheral surface of the annular belt against a portion along the axial direction of the outer peripheral surface of the heating roll to form a fixing pressure contact portion; and the heating roll at a position upstream of the pressing portion in the rotation direction of the heating roll. An inlet guide portion that is provided in a shape protruding so as to approach the outer peripheral surface of the guide roller and guides the annular belt to start contacting a portion along the axial direction of the outer peripheral surface of the heating roll before reaching the fixing pressure contact portion; It is provided in a shape protruding so as to approach the outer peripheral surface of the heating roll at a position intermediate between the pressing portion and the inlet guide portion, and the annular belt is brought close to a portion along the axial direction of the outer peripheral surface of the heating roll. And a pressing member having at least one intermediate guide portion that guides the passage.   The fixing device according to claim 1, wherein at least one of the intermediate guide portions is provided at a position closer to the entrance guide portion than a central position between the entrance guide portion and the pressing portion.   The fixing device according to claim 1, wherein the intermediate guide unit is configured such that a distance between the intermediate guide unit and the heating roll is equal to or smaller than a distance between the inlet guide unit and the heating roll.   An image forming apparatus comprising the fixing device according to claim 1.

Images