JP7110945B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus, and is suitable for application to, for example, an electrophotographic image forming apparatus and a fixing device included in such an image forming apparatus.

An electrophotographic image forming apparatus transfers an image formed with a developer (also called a developer image) to a medium such as paper, and then attaches the transferred image (developer image) to the medium using a fuser as a fixing device. is fixed to the medium by

In a fixing device provided in such an image forming apparatus, a fixing member such as a roller or a belt and a pressure member such as a roller or a belt are rotated while they are in contact with each other, and the conveyed medium is rotated. The image (developer image) formed on the medium is heat-melted and fixed on the medium by applying heat and pressure to the nip portion formed between the fixing member and the pressure member. ing.

Conventionally, such a fixing device includes a separating member that separates (that is, peels off) the medium from the fixing member so that the medium that has passed through the nip portion between the fixing member and the pressure member does not wind around the fixing member. There is one provided (see, for example, Patent Document 1). Further, conventionally, a fixing device can change the contact pressure (nip pressure) of the nip portion between the fixing member and the pressure member by displacing the fixing member in a direction toward or away from the pressure member. There is also In addition, the operation of displacing the fixing member in the direction toward or away from the pressure member is hereinafter referred to as the contact-separation operation.

JP 2015-210351 A

By the way, in order to detect whether or not the medium is wound around the fixing member, a medium detection member that detects the medium that has passed through the nip portion between the fixing member and the pressure member and is separated from the fixing member by the separation member. can be provided in the fixing device, but the conventional fixing device does not have a structure corresponding to both the detection of the medium by the medium detection member and the contact/separation operation of the fixing member. In other words, the conventional fixing device does not have both the fixing member contact/separation operation and the medium detection (that is, take-up detection).

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and proposes a fixing device and an image forming apparatus having both a fixing member contact/separation operation and a medium detection.

According to the present invention, a fixing device includes a rotatable pressure member, a fixing member that contacts an outer peripheral surface of the pressure member and rotates together with the pressure member, and a space between the fixing member and the pressure member. a separation member that separates the medium that has passed through the nip portion from the fixing member; a medium detection member that detects the medium that has passed through the nip portion between the fixing member and the pressure member ; the fixing member and the fixing member; and a support portion for supporting the end portion in the rotation axis direction of the pressure member, and the unit is supported by the support portion by rotating around a rotation axis parallel to the rotation axis of the pressure member. The fixing member is displaced in a direction toward and away from the pressure member, a part of the supporting portion has a shape along the outer peripheral surface of the fixing member, and the separation member A fixing member facing portion facing an outer peripheral surface of a member and a contact portion contacting the support portion are provided, and the contact portion is attached to the support portion while maintaining a positional relationship with the medium detection member. The displacement of the fixing member is followed by moving so as to come into contact with a portion of the fixing member .

By doing so, the medium detection member can accurately detect the medium separated from the fixing member by the separation member even if the fixing member is displaced due to the contacting/separating operation.

The present invention can realize a fixing device and an image forming apparatus having both the contact/separation operation of the fixing member and the detection of the medium.

1 is a side view showing the overall configuration of an image forming apparatus according to a first embodiment; FIG. 1 is a perspective view showing the configuration of a fixing device according to a first embodiment; FIG. 1 is a perspective view showing the configuration of a fixing device according to a first embodiment; FIG. 1 is a perspective view showing the configuration of a fixing device according to a first embodiment; FIG. 2 is a rear view showing the configuration of the fixing device according to the first embodiment; FIG. 2 is a cross-sectional view showing a cross section of the fixing device according to the first embodiment; FIG. It is a perspective view showing the configuration of a flange according to the first embodiment. 2 is an enlarged perspective view of a portion of the fixing device according to the first embodiment; FIG. 4 is a cross-sectional view showing a cross-section of the fixing device when the belt unit according to the first embodiment is at the decompression position; FIG. 4 is a cross-sectional view showing a cross section of the fixing device when the belt unit according to the first embodiment is at the release position; FIG. FIG. 8 is a perspective view showing the configuration of a flange according to the second embodiment; FIG. 11 is a cross-sectional view showing a cross section of the fixing device when the belt unit according to the second embodiment is at the nip position; FIG. 11 is a cross-sectional view showing a cross section of the fixing device when the belt unit according to the second embodiment is at the release position;

EMBODIMENT OF THE INVENTION Hereinafter, the form (this is called embodiment hereafter) for implementing invention is demonstrated in detail using drawing.

[1. First Embodiment]
[1-1. Overall Configuration of Image Forming Apparatus]
FIG. 1 shows an outline of the overall configuration of an image forming apparatus 1 according to the first embodiment. 1 is a side view showing the overall configuration of the image forming apparatus 1. As shown in FIG. As shown in FIG. 1, the image forming apparatus 1 is an electrophotographic printer and has a substantially box-shaped device housing 2 . Here, the right side of the device housing 2 in the drawing is the front surface, and the left side of the drawing is the rear surface. The direction from the bottom to the top is the upward direction, the direction from the top to the bottom of the device housing 2 is the downward direction, the direction from the front side to the back side of the device housing 2 in the drawing is the right direction, and the device housing 2, the left direction is the direction from the back side to the front side in the drawing.

In the upper part of the apparatus housing 2, a plurality of color developers (for example, four color toners of black (K), yellow (Y), magenta (M), and cyan (C) that are handled by the image forming apparatus 1 are provided. ) are arranged in the front-rear direction along the transport path R of the paper P.

Each image forming unit 3 (3K, 3Y, 3M, 3C) has a photosensitive drum 4 (4K, 4Y, 4M, 4C) and a toner cartridge 5 (5K, 5Y, 5M, 5C). Each image forming unit 3 (3K, 3Y, 3M, 3C) irradiates and exposes the surface of the photosensitive drum 4 (4K, 4Y, 4M, 4C) to expose the surface of the photosensitive drum 4 (4K, 4Y). , 4M, 4C), and then the toner supplied from the toner cartridges 5 (5K, 5Y, 5M, 5C) is adhered to the electrostatic latent image. It is a device that forms a toner image on the surface of (4K, 4Y, 4M, 4C).

Further, inside the apparatus housing 2, a transfer unit 6 is provided below the image forming units 3 (3K, 3Y, 3M, 3C). The transfer unit 6 includes an annular conveying belt 7 which is freely runnable along the conveying path R (to the left in the figure), and photosensitive drums 4 (4K, 4Y, 4M, 4C) and transfer rollers 8 (8K, 8Y, 8M, 8C) arranged opposite to each other.

The transfer rollers 8 (8K, 8Y, 8M, 8C) separate the paper P from toner when the paper P passes between the photosensitive drums 4 (4K, 4Y, 4M, 4C) and the conveying belt 7. It is a member that transfers the toner image of each color formed on the photoreceptor drum 4 (4K, 4Y, 4M, 4C) to the paper P by charging it with opposite polarity.

Further, inside the apparatus housing 2, a tray 9 for storing the paper P is provided below the transfer unit 6 (that is, the lower portion of the apparatus housing 2). Further, in the vicinity of the tray 9, a hopping roller 10 is provided for feeding out the sheets P contained in the tray 9 to the transport path R one by one. Furthermore, a pair of transport rollers for transporting the paper P is provided on the transport path R between the tray 9 and the transfer unit 6 inside the apparatus housing 2 .

Further, inside the apparatus housing 2, a fixing device 11 is provided on the downstream side (that is, rearward) of the transfer unit 6 in the paper conveying direction. The fixing device 11 includes a fixing belt 12 on the upper side and a pressure roller 13 on the lower side. is a device that fixes a toner image on a sheet of paper P by heating and pressurizing the . A detailed configuration of the fixing device 11 will be described later.

Further, a stacker 14 for discharging the paper P is provided at the upper end of the device housing 2 . Furthermore, inside the apparatus housing 2, a pair of discharge rollers for discharging the paper P to the stacker 14 and the like are provided on the transport path R between the fixing device 11 and the stacker 14. FIG. Furthermore, medium detection sensors for detecting the paper P are provided at a plurality of locations on the transport path R inside the apparatus housing 2 . The overall configuration of the image forming apparatus 1 is as described above. Although not shown in FIG. 1, the apparatus housing 2 also includes a control section for controlling the operation of each section, a thermistor for detecting the temperature of the fixing device 11, a motor for driving each roller, and the like. there is Further, an operation unit for receiving user's operation is also provided outside the apparatus housing 2 .

Here, the printing operation of the image forming apparatus 1 will be briefly described. The image forming apparatus 1 feeds out the sheets P stored in the tray 9 one by one to the transport path R by the hopping rollers 10 . The paper P fed out to the transport path R is transported to the transfer unit 6, and transported by the transport belt 7 of the transfer unit 6 to the image forming units 3K, 3Y, 3M, and 3C in order. The image forming units 3K, 3Y, 3M, and 3C form toner images of respective colors on the surfaces of the photosensitive drums 4K, 4Y, 4M, and 4C. The toner images thus formed on the surfaces of the photosensitive drums 4K, 4Y, 4M and 4C are transferred onto the paper P by the transfer rollers 8K, 8Y, 8M and 8C. is formed.

The paper P on which the color toner image is formed is conveyed from the transfer unit 6 to the fixing device 11 . The fixing device 11 fixes the color toner image on the paper P. As shown in FIG. As a result, a color image is printed on the paper P. FIG. After that, this paper P is conveyed to the stacker 14 and discharged onto the stacker 14 . Although the details will be described later, the fixing device 11 displaces the fixing belt 12 toward and away from the pressure roller 13 by the contact pressure between the fixing belt 12 and the pressure roller 13 . A certain nip pressure can be changed. The printing operation of the image forming apparatus 1 is as described above.

[1-2. Configuration of Fixing Device]
Next, the configuration of the fixing device 11 will be described in detail with reference to FIGS. 2 to 10. FIG. 2 to 10 are diagrams in which part of the fixing device 11 is omitted or simplified as appropriate. Specifically, FIGS. 2, 3, and 4 are perspective views of the fixing device 11, FIG. 5 is a rear view of the fixing device 11 as seen from the rear side, and FIGS. 7 and 8 are perspective views enlarging a part of the fixing device 11. FIG.

As shown in FIGS. 2 to 5, the fixing device 11 includes a left side frame 20L positioned at the left end of the fixing device 11, a right side frame 20R positioned at the right end, a lower portion of the left side frame 20L and the right side frame 20R. and a center upper frame 20U connecting the upper portion of the left side frame 20L and the upper portion of the right side frame 20R. Note that the central upper frame 20U and the central lower frame 20D are separated in the vertical direction so that paper can pass between them.

As shown in FIGS. 2 to 5, the fixing device 11 includes a belt unit 21 having the fixing belt 12, a pressure roller shaft 22 serving as a rotating shaft of the pressure roller 13, and the fixing belt 12. A release unit 23 that rotates the belt unit 21 in a direction away from the pressure roller 13 , and the paper that has passed through the nip portion between the fixing belt 12 and the pressure roller 13 is separated from the fixing belt 12 and transported to the transport path R (FIG. 1), a lower transport guide 25 that guides the sheet that has passed through the nip portion to the transport path R together with the separator unit 24, and a nip portion between the fixing belt 12 and the pressure roller 13. It supports a paper detection lever 26 for detecting paper that has passed through.

As shown in FIG. 2, the pressure roller 13 is a cylindrical roller having a pressure roller shaft 22 that extends in the left-right direction and is rotatably supported by the lower portion of the left side frame 20L and the lower portion of the right side frame 20R. is fixed to Three gears 30, 31, and 32, which are a drive system for the pressure roller 13, are provided on the outer side (that is, the right side) of the right side frame 20R. The right end of the pressure roller shaft 22 extends to the outer side of the right side frame 20R through a hole (not shown) provided in the right side frame 20R and is fixed to the gear 32. As shown in FIG. In the drive system of the pressure roller 13 , the gear 30 is connected to the gear on the main body side of the image forming apparatus 1 , and when the gear on the main body side rotates, the rotation of the gear 30 , the gear 31 , and the gear 32 . The pressure roller 13 rotates together with the pressure roller shaft 22 fixed to the gear 32 .

As shown in FIG. 2, the belt unit 21 has a left plate 40L positioned at the left end of the belt unit 21, a right plate 40R positioned at the right end, and the fixing belt 12. As shown in FIG. The left plate 40L and the right plate 40R are attached to the inner surfaces of the central portion of the left side frame 20L and the central portion of the right side frame 20R of the fixing device 11, respectively, and are cylindrical (annular) fixing belts extending in the left-right direction. 12 are rotatably supported.

Here, as shown in FIG. 6, which is a cross-sectional view of the fixing device 11 taken along line AA shown in FIG. . As shown in the perspective view of FIG. 7, the flange 41 is provided on a substantially cylindrical belt support portion 41s having a substantially C-shaped cross section and on one end side of the belt support portion 41s. It is composed of a belt restricting portion 41r having a substantially C-shaped cross section and a substantially disc-shaped belt regulating portion 41r that widens in the direction of the belt. That is, the flange 41 has a substantially C-shaped cross section as a whole, and the portion corresponding to the inner side of the C-shape is a groove 41g.

As shown in FIG. 6, the flange 41 has the groove 41g directed downward (specifically, toward the pressure roller 13), and the belt support portion 41s protrudes from the left plate 40L toward the right plate 40R. Thus, the belt restricting portion 41r is fixed to the left plate 40L. Here, a surface 41u of the belt regulating portion 41r fixed to the left plate 40L, which faces the right plate 40R, is called a flange surface 41u. Although not shown, the right plate 40R also has a flange 41 fixed to its inner surface (that is, right side surface) so as to be bilaterally symmetrical with the left plate 40L side.

In the belt unit 21, the belt support portions 41s of the left and right flanges 41 fixed to the left plate 40L and the right plate 40R enter inside the left and right ends of the fixing belt 12 and come into contact with the inner peripheral surfaces of the left and right ends. support the left and right ends of the fixing belt 12 so as to be rotatable. Further, the belt unit 21 regulates the lateral position of the fixing belt 12 between the left and right flange surfaces 41u. Further, as shown in FIG. 6, the flange 41 fixed to the left plate 40L has a portion 41rp on the rear side of the outer peripheral surface of the belt restricting portion 41r that extends along the outer peripheral surface of the fixing belt 12, although details will be described later. It has a substantially arc shape. That is, the outer peripheral surface of the fixing belt 12 and the portion 41rp of the outer peripheral surface of the belt restricting portion 41r are substantially parallel, and the distance between them (the distance in the direction orthogonal to the outer peripheral surface of the fixing belt 12) is also substantially constant. . Although not shown, the flange 41 fixed to the right plate 40R also has a portion 41rp on the rear side of the outer peripheral surface of the belt regulating portion 41r formed in a substantially arc shape along the outer peripheral surface of the fixing belt 12. ing.

Further, as shown in FIG. 6, the left plate 40L is formed with a round hole 42 near the front of the flange 41. The round hole 42 is provided at the front end of the central portion of the left side frame 20L. A rotating shaft 43 parallel to the roller shaft 22 is inserted. In this manner, the left plate 40L is rotatably supported by the left side frame 20L. Further, the left plate 40L is moved in the direction indicated by the arrow Ar1 in FIG. ). Although not shown, the right plate 40R is also rotatably supported by the right side frame 20R so as to be bilaterally symmetrical with the left plate 40L side, and in the same direction as the left plate 40L ( In other words, it is urged in the direction in which the fixing belt 12 it supports is pressed against the pressure roller 13 .

In this manner, the fixing device 11 presses the fixing belt 12 together with the belt unit 21 against the pressure roller 13, and when the pressure roller 13 is rotated, the fixing belt pressed against the pressure roller 13 is pressed. 12 are designed to be carried around.

As shown in FIGS. 3 and 4, the release unit 23 includes a laterally extending shaft 50 rotatably supported by the upper rear end of the left side frame 20L and the upper rear end of the right side frame 20R; 50 and a cam 51 fixed thereto. Three gears 33, 34, and 35, which are the drive system of the release unit 23, are provided on the outer side (that is, the right side) of the right side frame 20R. The right end of the shaft 50 extends to the outer surface side of the right side frame 20R through a hole (not shown) provided in the right side frame 20R and is fixed to the gear 35. As shown in FIG. In the drive system of the release unit 23, the gear 33 is connected to the gear on the main body side of the image forming apparatus 1, and when the gear on the main body side rotates, the rotation is transmitted to the gear 33, the gear 34, and the gear 35. , and the cam 51 rotates together with the shaft 50 fixed to the gear 35 . The gear 33 is coaxial with the gear 30 and independent of the gear 30, and the gear 35 is a two-stage gear.

Cams 51 are fixed to the shaft 50 at two left and right positions near the inner surface of the left side frame 20L and near the inner surface of the right side frame 20R. Here, as shown in FIG. 6, the left cam 51 is arranged to face rearwardly of a cam contact surface 45 provided at the upper rear end of the left plate 40L of the belt unit 21 . The outer peripheral surface of the cam 51 has a shortest portion 51s with the shortest distance from the central axis of the cam 51, and a longest portion 51g with the longest distance from the central axis. and an intermediate portion 51c whose distance from the central axis is longer than the shortest portion 51s and shorter than the longest portion 51g.

As shown in FIG. 6, when the shortest portion 51s of the left cam 51 rotates to a position facing the cam contact surface 45 of the left plate 40L, the shortest portion 51s and the cam contact surface 45 are separated. (That is, it does not contact the cam contact surface 45). At this time, although not shown, the right cam 51 is also rotated to a position where the shortest portion 51s faces the cam contact surface 45 of the right plate 40R. The contact surface 45 is separated. At this time, the left plate 40L and the right plate 40R of the belt unit 21 do not receive the force from the cam 51, but are urged by the spring 44 in the direction indicated by the arrow Ar1 in FIG. direction). Therefore, at this time, the nip pressure between the fixing belt 12 and the pressure roller 13 becomes maximum. The position of the belt unit 21 (that is, the position of the fixing belt 12) at this time is called a nip position. The image forming apparatus 1 normally performs a printing operation with the belt unit 21 positioned at this nip position.

As shown in FIG. 9A corresponding to FIG. 6, when the intermediate portion 51c of the left cam 51 rotates to a position facing the cam contact surface 45 of the left plate 40L, the intermediate portion 51c contacts the cam. It abuts on the contact surface 45 . At this time, although not shown, the right cam 51 is also rotated to a position where the intermediate portion 51c faces the cam contact surface 45 of the right plate 40R. The contact surface 45 abuts. At this time, the cam contact surface 45 of the left plate 40L and the right plate 40R of the belt unit 21 is pushed forward by the intermediate portion 51c of the cam 51 so as to resist the biasing force of the spring 44. 9 (that is, the direction in which the fixing belt 12 moves away from the pressure roller 13). At this time, the nip pressure between the fixing belt 12 and the pressure roller 13 is smaller than that at the nip position. The position of the belt unit 21 (that is, the position of the fixing belt 12) at this time is called a decompression position. The image forming apparatus 1 positions the belt unit 21 at this depressurized position when printing on specific paper such as envelopes and thick paper.

Further, as shown in FIG. 10A corresponding to FIG. 6, when the left cam 51 rotates to the position where the longest portion 51g faces the cam contact surface 45 of the left plate 40L, the longest portion 51g is in contact with the cam. It abuts on the contact surface 45 . At this time, although not shown, the right cam 51 is also rotated to a position where the longest portion 51g faces the cam contact surface 45 of the right plate 40R. The contact surface 45 abuts. At this time, the left plate 40L and the right plate 40R of the belt unit 21 are pushed forward by the longest portion 51g of the cam 51, so that the left plate 40L and the right plate 40R of the belt unit 21 are pushed forward by the longest portion 51g of the cam 51. The fixing belt 12 rotates in the direction opposite to the indicated direction (that is, the direction in which the fixing belt 12 separates from the pressure roller 13). At this time, the nip pressure between the fixing belt 12 and the pressure roller 13 becomes even smaller than that at the decompression position. The fixing belt 12 and the pressure roller 13 may be completely separated and the nip pressure may be zero. The position of the belt unit 21 at this time is called a release position. The image forming apparatus 1 positions the belt unit 21 at this release position when it is not in operation, such as during transportation.

As shown in FIGS. 4 and 6, the paper detection lever 26 is provided at the center in the left-right direction on the rear surface 20Db of the center lower frame 20D. A rear surface 20Db of the central lower frame 20D is positioned behind the pressure roller 13. As shown in FIG. The paper detection lever 26 extends upward from the rear surface 20Db of the central lower frame 20D, and a rotating shaft 26r provided at the lower end thereof and extending in the horizontal direction is connected to a bearing portion 60 provided on the rear surface 20Db of the central lower frame 20D. is inserted into the In this manner, the paper detection lever 26 is rotatably supported by the rear surface 20Db of the central lower frame 20D.

Further, the paper detection lever 26 is biased in a direction to be pressed against the rear surface 20Db of the central lower frame 20D by a torsion spring 61 (FIG. 4) attached to the rotating shaft 26r. As shown in FIG. 6, the paper detection lever 26 is pressed against the rear surface 20Db of the central lower frame 20D, and at this time, the upper portion thereof is positioned further in the conveying direction than the nip portion Np between the fixing belt 12 and the pressure roller 13. It blocks the transport path (hereinafter referred to as internal transport path) Rf inside the fixing device 11 located downstream (rear). When the front end of the paper passing through the nip portion Np between the fixing belt 12 and the pressure roller 13 collides with the upper portion of the paper detection lever 26, the paper detection lever 26 rotates so as to fall backward, thereby allowing the paper to pass through. After the paper passes through, it returns to its original position.

Further, as shown in FIG. 4, a rotation detection sensor 62 is provided on the rear surface 20Db of the central lower frame 20D to detect that the sheet detection lever 26 has been rotated from being pressed against the rear surface 20Db so as to fall backward. It is When the rotation detection sensor 62 detects the rotation of the paper detection lever 26, the control unit of the image forming apparatus 1 determines that the paper is being conveyed normally. If the rotation of 26 is not detected, it is determined that the paper is wrapped around the fixing belt 12, and the printing operation is stopped, for example.

As shown in FIGS. 3, 5, and 6, the lower transport guide 25 is attached between the lower rear end of the left side frame 20L and the lower rear end of the right side frame 20R, and is attached to the fixing belt 12. It forms the lower side of the internal transport path Rf positioned downstream (rearward) in the transport direction from the nip portion Np with the pressure roller 13 . Incidentally, as shown in FIG. 3, the lower transport guide 25 covers the rear side of the paper detection lever 26. As shown in FIG. Further, the lower transport guide 25 is provided with a space for the paper detection lever 26 in the central portion in the left-right direction, and the paper detection lever 26 rotates within this space.

As shown in FIGS. 4, 6 and 8, the separator unit 24 is located at the rear end of the central portion of the left side frame 20L (behind the fixing belt 12) and the rear end of the central portion of the right side frame 20R (behind the fixing belt 12). ) extending in the left-right direction (that is, parallel to the pressure roller shaft 22), a plate separator 71 attached to the shaft 70 and separating the paper from the fixing belt 12; An upper transport guide 72 is attached to the plate separator 71 and guides the sheet separated from the fixing belt 12 along the inner transport path Rf together with the lower transport guide 25 .

As shown in FIG. 8, the plate separator 71 is an elongated sheet metal member having a length slightly shorter than the interval between the left side frame 20L and the right side frame 20R (not shown in FIG. 8). is fixed and integrated with the upper transport guide 72 . The plate separator 71 has its left end portion and right end portion bent toward one side (upper conveying guide 72 side), and the left and right bent portions (which are called bent portions) 71s are provided with shaft insertion holes. 71h is provided. The plate separator 71 is attached to the shaft 70 by inserting the shaft 70 into the left and right shaft insertion holes 71h with one surface on the rear side (the upper transport guide 72 on the rear side) and the other surface on the front side. ing.

As shown in FIG. 6, the shaft insertion hole 71h is an oval-shaped (also called a racetrack-shaped) elongated hole composed of opposing straight portions and opposing circular arc portions, and the distance between the opposing straight portions is It is about the same as the diameter of shaft 70 and the distance between opposing arcuate portions is greater than the diameter of shaft 70 . That is, the plate separator 71 is rotatably and slidably supported by the shaft 70 inserted through the oval shaft insertion hole 71h. The shaft insertion hole 71h is not limited to an oval shape, and may be a long rectangular hole. Further, the longitudinal direction of the shaft insertion hole 71h is the slide direction of the plate separator 71. As shown in FIG.

Furthermore, as shown in FIG. 8, torsion springs 73 are attached to both left and right ends of the shaft 70 (only the left end in FIG. 8). Each of the left and right torsion springs 73 has one arm 73a in contact with the rear surface 20Ub of the central upper frame 20U, and the other arm 73b of the left and right torsion springs 73. is adapted to abut on the The notch 71sd is provided at a position closer to one surface of the plate separator 71 than the shaft insertion hole 71h. The torsion spring 73 exerts a biasing force on the plate separator 71 to rotate it clockwise in FIG. 6 around the shaft 70 .

On the other hand, the plate separator 71 is provided with a convex portion 74 projecting upward at a predetermined position on the upper end thereof. It is designed not to rotate in the middle clockwise direction. In other words, the plate separator 71 is in a state in which the projecting portion 74 is always pressed against the lower surface 20Ud of the central upper frame 20U by the biasing force of the torsion spring 73 . At this time, as shown in FIG. 6, the plate separator 71 slides in the front-rear direction because the longitudinal direction of the shaft insertion hole 71h is the front-rear direction (more precisely, the direction is slightly inclined with respect to the front-rear direction). In addition, due to the component in the front-rear direction of the biasing force of the torsion spring 73, a force to slide forward (in the direction approaching the fixing belt 12) acts.

As shown in FIG. 6, since the lower surface 20Ud of the central upper frame 20U is not parallel to the longitudinal direction of the shaft insertion hole 71h, the plate separator 71 slightly rotates when sliding in the front-rear direction. . In other words, although the plate separator 71 is restricted in rotation, it does not rotate at all.

Further, as shown in FIG. 8, the plate separator 71 has a bent portion 71b in which the lower end portion is bent forward (ie, toward the fixing belt 12). A front end surface 71bf of the bent portion 71b has a stepped shape in which left and right end portions 71bs are recessed one step with respect to the central portion 71bc. A center portion 71bc of the front end surface 71bf of the bent portion 71b is a portion for separating the paper from the fixing belt 12, and left and right end portions 71bs of the front end surface 71bf are formed between the flanges 41 positioned on both left and right sides of the fixing belt 12. A lower end surface 71bd of the bent portion 71b, which is a portion that abuts on the portion 41rp, is a guide surface that guides the sheet separated from the fixing belt 12 to the upper transport guide 72 at the rear. Here, the left and right end portions 71bs of the plate separator 71 are called separator side contact portions 71bs, the portion 41rp of the flange 41 is called the flange side contact portion 41rp, and the lower end surface of the bent portion 71b of the plate separator 71 is called a flange side contact portion 41rp. 71bd is called a guide surface 71bd. Incidentally, the guide surface 71bd of the bent portion 71b is, for example, inclined such that the rear end side is positioned slightly higher than the front end side, and is parallel to the longitudinal direction of the shaft insertion hole 71h. Below the guide surface 71bd and the upper transport guide 72, the lower transport guide 25 is positioned. The upper part of the paper detection lever 26 is positioned between the guide surface 71bd and the lower transport guide 25 .

The plate separator 71 is prevented from sliding further forward by contacting the flange-side contact portions 41rp of the left and right flanges 41 with the separator-side contact portions 71bs. In other words, the plate separator 71 is urged in the direction in which the separator side contact portion 71bs is pressed against the flange side contact portion 41rp of the flange 41 by the biasing force of the torsion spring 73, and the separator side contact portion 71bs is always pressed against the flange side contact portion 41rp. is pressed against the flange side contact portion 41rp. Here, the plate separator 71 has a gap between the center portion 71bc of the front end surface 71bf and the outer peripheral surface of the fixing belt 12 when the separator side contact portion 71bs contacts the flange side contact portion 41rp of the flange 41. The dimensions of each part are selected so that a constant gap is formed. That is, the separator-side contact portion 71bs of the plate separator 71 is pressed against the flange-side contact portion 41rp of the flange 41, so that the center portion 71bc of the front end surface 71bf approaches the outer peripheral surface of the fixing belt 12, thereby The paper can be separated from the The front end face 71bf of the plate separator 71 can easily separate the paper from the fixing belt 12 when it is closer to the fixing belt 12 at a position closer to the nip portion Np. Therefore, it is desirable that the flange-side contact portion 41rp of the flange 41 is also provided at a position as close to the nip portion Np as possible.

Further, as will be described later in detail, when the position of the belt unit 21 is changed by the contacting/separating operation, the plate separator 71 slides following the displacement of the flange 41 at this time, so that the separator-side abutting portion 71bs is constantly maintained. is brought into contact with the flange side contact portion 41rp of the flange 41 .

Further, as shown in FIG. 5, the plate separator 71 has a portion (hereinafter referred to as a lever insertion portion) 75 into which the front end of the paper detection lever 26 is inserted into the center portion in the left-right direction of the bent portion 71b at the lower end. is provided, and the tip of the paper detection lever 26 is inserted into the lever insertion portion 75 . That is, as shown in FIG. 6, the paper detection lever 26 is arranged such that the tip thereof protrudes upward (opposite to the lower transport guide 25 side) from the guide surface 71bd of the bent portion 71b of the plate separator 71. It overlaps so that it penetrates the internal transport path Rf in the vertical direction and reliably closes it. On the other hand, the plate separator 71 is slidable in the front-rear direction while the tip of the sheet detection lever 26 is inserted into the lever insertion portion 75 .

That is, as shown in FIG. 6, in the plate separator 71, the longitudinal direction of the shaft insertion hole 71h and the guide surface 71bd of the bent portion 71b are parallel (or substantially parallel), and the guide surface of the bent portion 71b is parallel. By sliding along the surface 71bd, the tip of the paper detection lever 26 remains inserted into the lever insertion portion 75 (that is, the paper detection lever 26 is positioned between the guide surface 71bd of the plate separator 71 and the lower transport guide 25). , while blocking the internal transport path Rf between them). From another point of view, the longitudinal direction of the shaft insertion hole 71h of the plate separator 71 is parallel (or substantially parallel) to the paper transport direction in the internal transport path Rf, and the plate separator 71 slides along the paper transport direction. As a result, the tip of the paper detection lever 26 can be slid while being inserted into the lever insertion portion 75 .

From another point of view, the plate separator 71 slides while maintaining a state in which the guide surface 71bd of the bent portion 71b is positioned closer to the rotation shaft 26r of the paper detection lever 26 than at least the tip position of the paper detection lever 26. As a result, the tip of the paper detection lever 26 can be slid while being inserted into the lever insertion portion 75 . From another point of view, the plate separator 71 slides so as to keep the distance between the upper transport guide 72 and the lower transport guide 25 substantially constant, so that the tip of the paper detection lever 26 reaches the lever insertion portion 75. It can be slid while inserted.

In this manner, the plate separator 71 can slide while maintaining the positional relationship with the paper detection lever 26 (that is, the positional relationship in which the tip of the paper detection lever 26 protrudes upward from the guide surface 71bd). The configuration of the fixing device 11 is as described above.

Here, the operation of the fixing device 11 will be briefly described. The operation of the fixing device 11 is controlled by a controller (not shown) of the image forming apparatus 1 . That is, the fixing device 11 rotates the belt unit 21 to a designated position (nip position or decompression position) by the drive system of the release unit 23 , raises the temperature of the fixing belt 12 to the set temperature, and increases the temperature of the pressure roller 13 . The pressure roller 13 is rotated by the driving system. In the fixing device 11 , when the pressure roller 13 rotates, the fixing belt 12 pressed against the pressure roller 13 rotates in the direction opposite to the pressure roller 13 . The fixing device 11 heats and presses the paper when the paper passes through the nip portion Np between the fixing belt 12 and the pressure roller 13, thereby fixing the toner image on the paper.

After passing through the nip portion Np, the sheet is separated from the fixing belt 12 by the plate separator 71, and is moved by the guide surface 71bd of the plate separator 71, the upper transport guide 72, and the lower transport guide 25 while tilting the sheet detection lever 26. It is guided and transported to the transport path R outside the fixing device 11 through the internal transport path Rf. At this time, the fixing device 11 sends the detection result of the rotation detection sensor 62 to the controller (not shown) of the image forming apparatus 1 . The operation of the fixing device 11 is as described above.

[1-3. Operation of plate separator]
Next, the operation of the plate separator 71 when the belt unit 21 of the fixing device 11 changes its position by the contacting/separating operation will be described in detail. First, as shown in FIG. 6, assume that the belt unit 21 is in the nip position. At this time, the separator-side contact portion 71bs ( FIG. 8 ) of the plate separator 71 comes into contact with a predetermined portion of the flange-side contact portion 41rp of the flange 41 of the belt unit 21 .

Thus, when the belt unit 21 is in the nip position, the plate separator 71 contacts the flange-side contact portion 41rp of the flange 41 with the separator-side contact portion 71bs, so that the central portion 71bc of the front end face 71bf is Close to the outer peripheral surface of the fixing belt 12 . At this time, the plate separator 71 is in a state in which the tip of the sheet detection lever 26 is inserted into the lever insertion portion 75 . By doing this, the fixing device 11 at the nip position can reliably separate the paper from the fixing belt 12 by the plate separator 71 that is close to the outer peripheral surface of the fixing belt 12, and the paper detection lever 26 that blocks the internal transport path Rf. can accurately detect the paper.

Next, as shown in FIG. 9A and FIG. 9B, which is a cross-sectional view of the fixing device 11 taken along the line BB shown in FIG. Assume that the nip position is changed to the depressurization position by rotating in the direction opposite to the direction indicated by the middle arrow Ar1. At this time, in the plate separator 71, as the flange side contact portion 41rp of the flange 41 moves upward and slightly obliquely backward, the separator side contact portion 71bs in contact with the flange side contact portion 41rp moves rearward. By being pushed, it slides backwards (more precisely, backwards slightly diagonally).

The separator-side contact portion 71bs of the plate separator 71 contacts the flange-side contact portion 41rp of the flange 41 at a position shifted downward (toward the groove 41g of the flange 41) from the nip position. . Here, the flange side contact portion 41rp of the flange 41 has a substantially arc shape along the outer peripheral surface of the fixing belt 12 . Therefore, as the flange 41 is displaced together with the fixing belt 12, even if the location where the separator-side contact portion 71bs of the plate separator 71 contacts changes on the flange-side contact portion 41rp of the flange 41, the plate separator 71 is The distance between the central portion 71bc of the front end surface 71bf and the outer peripheral surface of the fixing belt 12 does not change.

In this way, even when the belt unit 21 is at the depressurizing position, the separator-side contact portion 71bs of the plate separator 71 contacts the flange-side contact portion 41rp of the flange 41, so that the front end surface 71bf of the plate separator 71 is reduced. The central portion 71bc of the fixing belt 12 is close to the outer peripheral surface of the fixing belt 12 . In other words, even if the belt unit 21 transitions from the nip position to the depressurization position, the size of the gap formed between the central portion 71bc of the front end surface 71bf of the plate separator 71 and the outer peripheral surface of the fixing belt 12 does not change. At this time, the plate separator 71 slides while maintaining the positional relationship with the paper detection lever 26, so that the tip of the paper detection lever 26 is inserted into the lever insertion portion 75 as in the nip position. becomes. By doing this, the fixing device 11 at the depressurized position can reliably separate the paper from the fixing belt 12 by the plate separator 71 adjacent to the outer peripheral surface of the fixing belt 12 as in the case of the nip position. The paper can be accurately detected by the paper detection lever 26 that blocks Rf.

Next, as shown in FIGS. 10A and 10B corresponding to FIGS. 9A and 9B, the belt unit 21 of the fixing device 11 further rotates in the direction opposite to the arrow Ar1 in FIG. As a result, the pressure reduction position is changed to the release position. At this time, the plate separator 71 slides forward (precisely, forward and slightly diagonally downward) by the biasing force of the torsion spring 73 as the flange-side contact portion 41rp of the flange 41 moves upward and slightly diagonally forward. . The plate separator 71 contacts the flange-side contact portion 41rp of the flange 41 at a location where the separator-side contact portion 71bs is displaced further downward (toward the groove 41g of the flange 41) than in the decompression position. touch.

In this way, even when the belt unit 21 is in the release position, the separator-side contact portion 71bs of the plate separator 71 contacts the flange-side contact portion 41rp of the flange 41, so that the center portion 71bc of the front end face 71bf is moved. approaches the outer peripheral surface of the fixing belt 12 . In other words, even if the belt unit 21 transitions from the decompression position to the release position, the size of the gap formed between the central portion 71bc of the front end surface 71bf of the plate separator 71 and the outer peripheral surface of the fixing belt 12 does not change. At this time, the plate separator 71 slides while maintaining the positional relationship with the paper detection lever 26, so that the tip of the paper detection lever 26 is inserted into the lever insertion portion 75 of the plate separator 71, as in the nip position. It is inserted.

In the image forming apparatus 1, for example, when the paper detection lever 26 of the fixing device 11 detects paper jam, the fixing device 11 is moved to the release position, and the user removes the jammed paper. . Here, even when the fixing device 11 is in the release position, the tip of the paper detection lever 26 is inserted into the lever insertion portion 75 of the plate separator 71. It is possible to accurately detect whether the paper has been removed.

[1-4. Summary and Effects]
As described above, the fixing device 11 according to the first embodiment changes the position of the belt unit 21 to the nip position or the pressure reduction position by the contacting/separating operation, so that the pressure between the fixing belt 12 and the pressure roller 13 is reduced. Changed the nip pressure.

Then, when the fixing belt 12 and the flange 41 are displaced due to the position change of the belt unit 21 , the fixing device 11 slides the plate separator 71 so as to follow the displacement of the fixing belt 12 and the flange 41 . The separator-side contact portions 71bs located at both the left and right ends of the front end surface 71bf are always in contact with the flange-side contact portions 41rp of the flange 41 .

When the fixing belt 12 and the flange 41 are displaced, the location where the separator-side contact portion 71bs of the plate separator 71 abuts on the flange-side abutment portion 41rp of the flange 41 changes. By forming the portion 41rp into a substantially arc shape extending along the outer peripheral surface of the fixing belt 12, no matter where on the flange side contact portion 41rp of the flange 41 the separator side contact portion 71bs of the plate separator 71 contacts, , the distance between the central portion 71bc of the front end surface 71bf of the plate separator 71 and the outer peripheral surface of the fixing belt 12 can be kept constant.

In this manner, the fixing device 11 can always keep the distance between the central portion 71bc of the front end surface 71bf of the plate separator 71 and the outer peripheral surface of the fixing belt 12 constant (that is, bring them close to each other) without depending on the contacting/separating operation. , the central portion 71bc of the front end face 71bf of the plate separator 71, the paper can be reliably separated from the fixing belt 12. As shown in FIG.

Further, when the plate separator 71 slides following the displacement of the fixing belt 12 and the flange 41 , the fixing device 11 changes the positional relationship between the paper detection lever 26 and the plate separator 71 (positional relationship projecting upward from the guide surface 71bd).

As a result, in the fixing device 11, for example, a gap is created between the tip of the paper detection lever 26 and the guide surface 71bd of the plate separator 71, and the paper passes through this gap without tilting the paper detection lever 26. Such a situation can be prevented, and the paper can be accurately detected by the paper detection lever 26. As a result, whether or not the paper is wrapped around the fixing belt 12 can be accurately detected.

As described above, in the fixing device 11 of the first embodiment, when the fixing belt 12 is displaced by the contact/separation operation, the plate separator 71 is fixed while maintaining the positional relationship between the paper detection lever 26 and the plate separator 71. Since the plate separator 71 slides following the displacement of the belt 12 , the paper can be reliably separated from the fixing belt 12 , and the paper separated from the fixing belt 12 can be accurately detected by the paper detection lever 26 . can be detected. Thus, it can be said that the fixing device 11 has a structure in which both the attachment/detachment operation of the fixing belt 12 and the sheet detection are performed.

[2. Second Embodiment]
Next, a second embodiment will be described. This second embodiment is an embodiment in which the configuration of the flange 41 is different from that of the first embodiment. Therefore, only the configuration of the flange 41 will be mainly described here. The flange 41 of the second embodiment is hereinafter referred to as a flange 41x.

[2-1. Configuration of Flange]
As shown in FIG. 11 corresponding to FIG. 7 of the first embodiment and FIG. 12A corresponding to FIG. 6 of the first embodiment, the flange 41x of the second embodiment is a flange The shape of the side contact portion 41rp is different from that of the flange 41 of the first embodiment. That is, in the flange 41 of the first embodiment, the flange-side contact portion 41rp is generally arc-shaped along the outer circumference of the fixing belt 12, whereas in the second embodiment, the flange-side contact portion 41rp is substantially arcuate. Reference numeral 41x denotes a flange-side contact portion 41rp that is formed by a substantially arc-shaped first portion (hereinafter referred to as an arc portion) 100u that extends along the outer peripheral surface of the fixing belt 12, and an arc-shaped first portion 100u that extends along the outer peripheral surface of the fixing belt 12; It is formed of a linear second portion (referred to as a linear portion) 100d extending in a direction away from the outer peripheral surface of the fixing belt 12 .

As shown in FIG. 12A, the straight portion 100d of the flange side contact portion 41rp is provided below the arc portion 100u (on the side of the groove 41g). Here, the arc portion 100u of the flange-side contact portion 41rp is substantially parallel to the outer peripheral surface of the fixing belt 12, and the distance from the outer peripheral surface of the fixing belt 12 (the distance in the direction orthogonal to the outer peripheral surface of the fixing belt 12). is almost constant, the straight portion 100d is not parallel to the outer peripheral surface of the fixing belt 12, and the distance from the outer peripheral surface of the fixing belt 12 increases as the distance from the arc portion 100u increases. there is

The circular arc portion 100u of the flange side contact portion 41rp is a portion with which the separator side contact portion 71bs of the plate separator 71 contacts when the belt unit 21 is positioned at the nip position and the decompression position. A linear portion 100d is a portion with which the separator-side contact portion 71bs of the plate separator 71 contacts when the belt unit 21 is positioned at the release position. The configuration of the flange 41x of the second embodiment is as described above.

[2-2. Operation of plate separator]
Next, the operation of the plate separator 71 when the belt unit 21 of the fixing device 11 changes its position by the contacting/separating operation will be described in detail. The second embodiment differs from the first embodiment in the operation of the plate separator 71 when the belt unit 21 transitions to the release position. Therefore, a detailed description of the operation of the plate separator 71 when the belt unit 21 is positioned at the nip position or the depressurization position will be omitted.

First, as shown in FIG. 12(A) and FIG. 12(B), which is a partially enlarged view of FIG. 12(A), it is assumed that the belt unit 21 is in the nip position. At this time, the separator-side contact portion 71bs of the plate separator 71 contacts the arc portion 100u of the flange-side contact portion 41rp of the flange 41x. Therefore, at this time, the center portion 71bc of the front end surface 71bf of the plate separator 71 approaches the outer peripheral surface of the fixing belt 12 . At this time, the tip of the paper detection lever 26 is inserted into the lever insertion portion 75 of the plate separator 71 , although this is omitted in FIG. 12 . Likewise, when the belt unit 21 is at the pressure reducing position, the separator side contact portion 71bs of the separator unit 24 contacts the arc portion 100u of the flange side contact portion 41rp of the flange 41x.

On the other hand, as shown in FIGS. 13A and 13B, it is assumed that the belt unit 21 transitions from the nip position or pressure reduction position to the release position. At this time, in the plate separator 71, as the flange-side contact portion 41rp of the flange 41x moves upward and slightly obliquely, the separator-side contact portion 71bs moves toward the straight portion 100d of the flange-side contact portion 41rp of the flange 41x. abut. Here, since the straight portion 100d of the flange-side contact portion 41rp is farther from the outer peripheral surface of the fixing belt 12 than the arc portion 100u, the plate separator 71 is located at the nip position and the depressurization position. , the central portion 71bc of the front end surface 71bf moves away from the outer peripheral surface of the fixing belt 12. As shown in FIG.

That is, the plate separator 71 is configured such that when the belt unit 21 transitions to the release position, the gap between the central portion 71bc of the front end surface 71bf and the outer peripheral surface of the fixing belt 12 becomes larger than when the belt unit 21 is in the nip position and the depressurization position. slide to.

[2-3. Summary and Effects]
As described above, in the fixing device 11 of the second embodiment, the flange-side contact portion 41rp of the flange 41x is formed into a substantially arc-shaped arc portion 100u extending along the outer peripheral surface of the fixing belt 12, and the fixing portion 100u. A linear portion 100d extending in a direction away from the outer peripheral surface of the belt 12 is formed.

When the belt unit 21 is in the nip position or the pressure reduction position, the fixing device 11 brings the separator-side contact portion 71bs of the plate separator 71 into contact with the arc portion 100u of the flange-side contact portion 41rp of the flange 41x, thereby When the unit 21 is in the release position, the separator-side contact portion 71bs of the plate separator 71 is brought into contact with the straight portion 100d of the flange-side contact portion 41rp of the flange 41x.

By doing so, in the fixing device 11 of the second embodiment, when the belt unit 21 is at the release position, the central portion 71bc of the front end face 71bf of the plate separator 71 is more likely to be removed than when the belt unit 21 is at the nip position and the depressurization position. , the gap from the outer peripheral surface of the fixing belt 12 can be increased.

By the way, in the image forming apparatus 1, for example, when the fixing device 11 is not operated, the fixing device 11 is set to the release position. Specifically, in the image forming apparatus 1 , for example, when the paper detection lever 26 of the fixing device 11 detects a paper jam, the fixing device 11 is moved to the release position to stop the operation of the fixing device 11 . At this point, the user removes the jammed paper inside the fixing device 11 . At this time, if the distance between the plate separator 71 and the fixing belt 12 is too close, for example, the user's hand hits the plate separator 71 and the plate separator 71 contacts the fixing belt 12, and the fixing belt 12 may be scratched or damaged. there is a possibility to do so.

Further, in the image forming apparatus 1, the fixing device 11 is set to the release position during transportation. At this time, if the distance between the plate separator 71 and the fixing belt 12 is too close, for example, due to vibration during transportation, the position of the plate separator 71 will move and come into contact with the fixing belt 12, and the fixing belt 12 will be scratched or damaged. There is a possibility of doing so.

Therefore, in the fixing device 11 of the second embodiment, when the belt unit 21 is at the release position, the central portion 71bc of the front end surface 71bf of the plate separator 71 and the fixing belt 21 are larger than when the belt unit 21 is at the nip position and the depressurization position. 12, even if the user's hand touches the plate separator 71 or the position of the plate separator 71 changes due to vibration, the plate separator 71 does not come into contact with the fixing belt 12. , the fixing belt 12 can be prevented from being scratched or damaged. Thus, the fixing device 11 of the second embodiment can improve reliability by making the fixing device 11 less likely to break down than the fixing device 11 of the first embodiment.

[3. Other embodiments]
[3-1. Other Embodiment 1]
In the above-described first and second embodiments, the plate separator 71 is rotatably and slidably supported by the shaft 70, and the protrusion 74 of the plate separator 71 is pushed by the biasing force of the torsion spring 73 to the central upper frame. By being pressed against the lower surface 20Ud of 20U, the plate separator 71 slides while its rotation is restricted.

As a mechanism for sliding the plate separator 71, a mechanism different from the mechanisms of the first and second embodiments described above may be used. For example, at least a portion of the shaft 70 of the plate separator 71 (the portion inserted into the shaft insertion hole 71h) may be shaped like a square bar with a square cross section. In this case, the length from one surface of the square bar-shaped portion of the shaft 70 to the other surface on the opposite side is made approximately the same as the distance between the opposed linear portions of the shaft insertion hole 71h. By doing so, the opposing straight portions of the shaft insertion hole 71h abut on one surface and the other surface of the square bar-shaped portion of the shaft 70, thereby restricting the rotation of the plate separator 71 and only allowing it to slide.

[3-2. Other Embodiment 2]
Further, in the first and second embodiments described above, when the fixing belt 12 and the flange 41 are displaced by changing the position of the belt unit 21, the plate separator 71 is slid so as to follow the displacement of the fixing belt 12 and the flange 41. I tried to let Not limited to this, for example, the position of the shaft 70 of the separator unit 24 is provided at a position coaxial with the rotation shaft 26r of the paper detection lever 26 or at a position near the rotation shaft 26r, and the plate separator 71 is provided at the left and right sides of the plate separator 71. The bent portion 71s may be extended downward to the position of the shaft 70 so as to be rotatably (but not slidably) supported by the shaft 70, and the projection 74 may be omitted from the plate separator 71. FIG. In this case, the plate separator 71 rotates so that the guide surface 71bd follows the rotational trajectory of the leading end of the paper detection lever 26 (a chain double-dashed line in FIG. 6), thereby maintaining the positional relationship with the paper detection lever 26. It is possible to follow the displacement of the fixing belt 12 as it is.

[3-3. Other embodiment 3]
Furthermore, in the first embodiment described above, the left and right separator-side contact portions 71bs of the plate separator 71 are brought into contact with the flange-side contact portions 41rp of the left and right flanges 41 . The separator-side contact portion 71bs may be brought into contact with a portion other than the flange 41 as long as it is provided in the belt unit 21 and displaced together with the fixing belt 12 . Incidentally, the portion with which the separator-side contact portion 71bs is contacted may be shaped along the outer peripheral surface of the fixing belt 12, similarly to the flange-side contact portion 41rp. Similarly, in the second embodiment, the separator-side contact portion 71bs may be brought into contact with a portion other than the flange 41x.

[3-4. Other embodiment 4]
Furthermore, in the above-described first and second embodiments, the paper that has passed through the nip portion Np between the fixing belt 12 and the pressure roller 13 is detected by the paper detection lever 26 as a medium detection member. . Alternatively, for example, an optical sensor may be provided instead of the paper detection lever 26, and the paper may be detected by this optical sensor. In this case, for example, a light receiving portion is provided on the bent portion 71b of the plate separator 71, and a light emitting portion is provided below the light receiving portion (for example, the rear surface 20Db of the central lower frame 20D). The optical axis is vertically pierced through the internal transport path Rf. Also in this case, in the fixing device 11, the plate separator 71 slides so as to keep the distance between the upper transport guide 72 and the lower transport guide 25 (that is, the length of the internal transport path Rf in the height direction) substantially constant. As a result, the distance between the light receiving portion and the light emitting portion can be kept substantially constant, and the paper can be accurately detected. An optical sensor having a light emitting/light receiving portion and a reflector may be used instead of the optical sensor having the light emitting portion and the light receiving portion.

Further, in the first and second embodiments described above, the paper detection lever 26 having a mechanism that tilts backward when in contact with paper is used, but the present invention is not limited to this, and any mechanism that displaces when in contact with paper is used. For example, a paper detection lever having a mechanism different from the paper detection lever 26 may be used.

[3-5. Other embodiment 5]
Furthermore, in each of the embodiments described above, the present invention is applied to the fixing device 11 having the fixing belt 12 as the fixing member and the pressure roller 13 as the pressure member. The present invention is not limited to this, and the present invention can be applied to a fixing device having a configuration different from that of the above-described fixing device 11, as long as the fixing device is capable of moving the fixing member toward and away from the pressure member. may apply. For example, a fixing device in which the position of the fixing belt 12 can be changed to a nip position, two or more pressure reduction positions with different nip pressures, and a release position (that is, the fixing belt 12 can be changed to four or more positions). may be applied to Also in this case, the separator-side contact portion 71bs of the plate separator 71 should always be in contact with the flange-side contact portion 41rp of the flange 41, as in each embodiment described above.

[3-6. Other embodiment 6]
Furthermore, in each of the embodiments described above, the present invention is applied to the image forming apparatus 1, which is an electrophotographic color printer. The present invention is not limited to this, and the present invention may be applied to an image forming apparatus having a configuration different from that of the image forming apparatus 1 described above, as long as the image forming apparatus has a fixing device capable of separating and contacting a fixing member. For example, it may be applied to an image forming apparatus that is a monochrome printer or an image forming apparatus that has an intermediate transfer belt. It may be applied to a forming device.

[3-7. Other embodiment 7]
Further, in each of the above-described embodiments, the pressure roller 13 is used as a specific example of the pressure member. For example, a pressure member made of a belt may be used instead of the roller. Furthermore, in each of the above-described embodiments, the fixing belt 12 is used as a specific example of the fixing member. For example, instead of the belt, a fixing member made of a roller may be used.

Furthermore, in each of the above-described embodiments, as a specific example of the separation member, the plate separator 71 having the front end surface 71bf, which is a specific example of the fixing member facing portion, and the separator-side contact portion 71bs, which is a specific example of the contact portion. However, a separating member different from the plate separator 71 may be used as long as the medium can be separated from the fixing member. Furthermore, in each of the above-described embodiments, the flanges 41 and 41x are used as specific examples of the supporting portions that support the ends of the fixing member in the rotation axis direction. A support portion different from the flanges 41 and 41x may be used as long as it can support the portion.

[3-8. Other Embodiment 8]
Furthermore, the present invention is not limited to the embodiments described above. That is, the scope of the present invention is applicable to embodiments obtained by arbitrarily combining a part or all of the above-described first and second embodiments and other embodiments, and embodiments extracting a part thereof. It is the one that reaches.

INDUSTRIAL APPLICABILITY The present invention can be widely used in a fixing device capable of separating and contacting a fixing member, and an image forming apparatus such as a printer having such a fixing device.

1 image forming apparatus 11 fixing unit 12 fixing belt 13 pressure roller 21 belt unit 23 release unit 24 separator unit 25 lower transport Guide 26...Paper detection lever 41, 41x...Flange 41rp...Flange side contact portion 42...Round hole 43...Rotating shaft 71...Plate separator 71b, 71s...Bending Part 71bf Front end surface 71bc Center part 71bs Separator side contact part 71bd Guide surface 61, 73 Torsion spring 75 Lever insertion part 100u Arc part , 100d: Straight portion, Np: Nip portion.

Claims (9)

a rotatable pressure member;
a fixing member that contacts an outer peripheral surface of the pressure member and rotates together with the pressure member;
a separating member that separates the medium that has passed through the nip portion between the fixing member and the pressure member from the fixing member;
a medium detection member that detects a medium that has passed through a nip portion between the fixing member and the pressure member ;
a unit having the fixing member and a support portion that supports an end portion of the fixing member in the rotation axis direction;
with
Said unit is
displacing the fixing member supported by the support portion in directions approaching and separating from the pressure member by rotating around a rotation axis parallel to the rotation axis of the pressure member;
The support part is
a portion of which has a shape along the outer peripheral surface of the fixing member;
The separating member is
A fixing member facing portion facing an outer peripheral surface of the fixing member and a contact portion contacting the support portion are provided, and the contact portion contacts the support portion while maintaining a positional relationship with the medium detection member. follows the displacement of the fixing member by moving in contact with the portion of the
A fixing device characterized by: The separating member is
The fixing device according to claim 1 , wherein the contact portion is biased in a direction of pressing against the portion of the support portion. The separating member is
a guide surface for guiding the medium separated from the fixing member;
The medium detection member is
A portion is provided between the guide surface and a conveying guide provided at a position facing the guide surface, and one end on the guide surface side protrudes from the guide surface,
The separating member is
3. The fixing device according to claim 1 , wherein the one end of the medium detection member moves following displacement of the fixing member while maintaining a positional relationship in which the one end of the medium detection member protrudes from the guide surface. The separating member is
By sliding along the guide surface , the displacement of the fixing member is followed while maintaining a positional relationship in which the one end of the medium detection member protrudes from the guide surface. A fixing device as described. The separating member is
It has an oval-shaped long hole extending along the guide surface through which a shaft parallel to the rotation axis of the pressurizing member is inserted. 5 . The fixing device according to claim 4 , wherein the displacement of the fixing member is maintained while maintaining a positional relationship in which the one end of the fixing member protrudes from the guide surface. Said unit is
By rotating the fixing member about a rotation axis parallel to the rotation axis of the pressure member, the fixing member is moved to a nip position where the nip pressure between the fixing member and the pressure member is maximum. moving to either a decompression position where the nip pressure is reduced or a release position where the fixing member and the pressure member are separated;
The separating member is
The fixing device according to any one of claims 3 to 5 , wherein the fixing device moves following the position of the fixing member while maintaining the positional relationship with the medium detection member. Said unit is
By rotating the fixing member about a rotation axis parallel to the rotation axis of the pressure member, the fixing member is moved to a nip position where the nip pressure between the fixing member and the pressure member is maximum. moving to either a decompression position where the nip pressure is reduced or a release position where the fixing member and the pressure member are separated;
The separating member is
When the fixing member moves to the nip position or the pressure reduction position, the fixing member moves following the position of the fixing member while maintaining the positional relationship with the medium detection member, and the fixing member moves to the release position. 3. When the fixing member is at the nip position or the depressurization position, the fixing member moves so that the gap between the fixing member facing portion and the outer peripheral surface of the fixing member becomes larger than when the fixing member is at the nip position or the pressure reduction position. 6. The fixing device according to any one of 1 to 5 . The support part is
The portion in contact with the separating member is composed of a substantially arc-shaped first portion extending along the outer peripheral surface of the fixing member and a linear second portion extending in a direction away from the outer peripheral surface of the fixing member. The separation member is formed with
When the fixing member is at the nip position or the depressurization position, the contact portion moves to contact the first portion of the support portion, and when the fixing member is at the release position, the contact. 8 . The fixing device according to claim 7 , wherein the portion moves so as to contact the second portion of the support portion. An image forming apparatus comprising the fixing device according to any one of claims 1 to 8 .

Images