Fixing device and image forming apparatus

Abstract

The invention provides a fixing device and an image forming apparatus. The fixing device includes a fixing member, a pressing member, a discharge roller pair, a discharge guide, and an actuator. The fixing member is heated by a heat source. The pressing member forms a pressing region between the pressing member and the fixing member, the pressing region heating and pressing a sheet to which a toner image is transferred. The discharge roller pair includes an upper discharge roller and a lower discharge roller, and conveys the paper passing through the pressing region. The discharge guide guides the sheet passing through the pressing region toward the discharge roller pair. The actuator has a rotating shaft supported by the discharge guide so as to be rotatable and movable in the axial direction, and a detection piece extending in the radial direction from the rotating shaft, and the paper passing through the pressing region is brought into contact with the detection piece to rotate the actuator about the rotating shaft, thereby detecting the paper. The discharge guide has a slit that accommodates the detection sheet and restricts the movement of the detection sheet in the width direction of the sheet. Therefore, the paper jam can be safely processed.

Description

Technical Field

[0001] The present invention relates to a fixing device for fixing a toner image on a paper and an image forming apparatus having the fixing device. Background Art

[0002] As one of the heating methods of the fixing part in the fixing device, there is a known method of using a heating body (planar heater) formed with a resistance heating element on a ceramic substrate to heat only the pressurized area. This method has a high temperature rise performance and only heats the required part, so it is energy-efficient. In this method, the temperature rise performance of the fixing part is high, so in terms of safety, measures need to be taken to prevent the user from contacting the fixing part.

[0003] Therefore, the image forming apparatus may include a fixing shutter that is movable between a closed position that covers the heat source and an open position that exposes the heat source. The fixing shutter is arranged on the entrance side of the paper into the pressurizing region.

[0004] However, in the above-mentioned image forming apparatus, there is no baffle on the discharge side where the paper is discharged from the pressurized area. When a paper jam occurs in the pressurized area, the jammed paper is removed from the discharge side in most cases. Therefore, it is necessary to prevent the heater or the fixing component from being exposed even on the discharge side.

[0005] In addition, a discharge guide that guides the paper to the discharge roller pair is sometimes provided on the discharge side where the paper is discharged from the pressure area. An actuator that detects the paper passing through the pressure area is sometimes provided on the discharge guide. In this case, when dealing with a paper jam in the pressure area, when the jammed paper is removed from the discharge side, the paper sometimes hits the actuator and the position of the actuator changes. As a result, the actuator can no longer accurately detect the paper. Summary of the invention

[0006] In view of the above circumstances, an object of the present invention is to provide a fixing device and an image forming apparatus having the fixing device, which can suppress the change in the position of the actuator and is configured so that a user does not come into contact with the heater and the fixing component on the discharge side of the paper discharged from the pressurized area.

[0007] In order to solve the above technical problems, the fixing device of the present invention comprises a fixing component, a pressure component, a discharge roller pair, a discharge guide and an actuator. The fixing component is heated by a heat source. The pressure component forms a pressure area between the fixing component and the fixing component for heating and pressurizing the paper with the toner image transferred thereon. The discharge roller pair comprises an upper discharge roller and a lower discharge roller, which convey the paper passing through the pressure area. The discharge guide guides the paper passing through the pressure area to the discharge roller pair. The actuator comprises a rotating shaft and a detection piece, wherein the rotating shaft is supported on the discharge guide in a rotatable and axially movable manner, the detection piece extends radially from the rotating shaft, and the paper passing through the pressure area abuts against the detection piece, causing the actuator to rotate around the rotating shaft as the center, thereby detecting the paper. The discharge guide has a slit, which accommodates the detection piece and limits the movement of the detection piece in the width direction of the paper.

[0008] The image forming device of the present invention comprises an image forming unit, the fixing device and a cover. The image forming unit transfers a toner image to a sheet of paper. The fixing device fixes the toner image transferred by the image forming unit to the sheet of paper. The cover is provided in an openable and closable manner, and the fixing device is exposed on the discharge side of the sheet of paper discharged from the pressurized area by opening. The image forming device can be powered on even in a state where the cover is opened. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a front view schematically showing the internal structure of the image forming apparatus according to one embodiment of the present invention.

[0010] Figure 2A This is a perspective view of the fixing device (in a state where the lower roller assembly is closed) according to the embodiment of the present invention as viewed from the rear side.

[0011] Figure 2B This is a perspective view of the fixing device (in a state where the lower roller assembly is opened) according to the embodiment of the present invention as viewed from the rear side.

[0012] Figure 3A It is a cross-sectional view showing a fixing device (a state in which the lower roller assembly is closed) according to an embodiment of the present invention.

[0013] Figure 3B It is a cross-sectional view showing a fixing device (a state in which the lower roller assembly is opened) according to an embodiment of the present invention.

[0014] Figure 4 This is a perspective view of a fixing housing and a discharge guide fixed to the fixing housing, as seen from the front side, in a fixing device according to an embodiment of the present invention.

[0015] Figure 5 This is a perspective view of a lower roller assembly viewed from the rear side in the fixing device according to the embodiment of the present invention.

[0016] Figure 6 This is a perspective view of a discharge guide as viewed from the rear side in the fixing device according to the embodiment of the present invention.

[0017] Figure 7 This is a front view of a discharge guide as viewed from the front side in the fixing device according to the embodiment of the present invention.

[0018] Figure 8 This is a diagram schematically showing a structure in which a rotating shaft of an actuator is supported by a discharge guide in a fixing device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] Next, refer to the attached Figure 1 The image forming apparatus and fixing device of the present invention will be described.

[0020] First, use Figure 1 The overall structure of the image forming apparatus 1 will be described. Figure 1 It is a front view schematically showing the internal structure of the image forming apparatus 1. Fr, Rr, L, and R shown in each figure respectively represent the front side, the rear side, the left side, and the right side of the image forming apparatus.

[0021] The image forming apparatus 1 has a hollow housing 3. Inside the housing 3 are: a paper feed cassette 5 for storing paper; a paper feed device 7 for feeding paper from the paper feed cassette 5; an image forming unit 9 for transferring a toner image onto paper by an electrophotographic method; a fixing device 11 for fixing the toner image onto the paper; a discharge device 13 for discharging paper; and a paper discharge tray 15 for stacking discharged paper.

[0022] The paper feed cassette 5 is arranged at the lower part of the housing 3. The paper feed device 7 is arranged above the front end of the paper feed cassette 5. The image forming unit 9 is arranged behind the paper feed device 7. The fixing device 11 is arranged behind the image forming unit 9. The discharge device 13 is arranged above the fixing device 11.

[0023] Inside the housing 3, a conveying path 17 for the paper S is formed from the paper supply device 7 through the image forming unit 9 and the fixing unit 11 to the discharge unit 13. The conveying path 17 is formed so as to bend upward from the paper supply device 7 and then extend backward toward the image forming unit 9, extend backward from the image forming unit 9 and toward the fixing unit 11, and bend upward from the fixing unit 11 and toward the discharge unit 13. The direction in which the paper is conveyed along the conveying path 17 is defined as the conveying direction, and the width direction (left-right direction) of the paper intersecting the conveying direction is defined as the width direction. In addition, a reverse conveying path 18 is formed inside the housing 3, and the reverse conveying path 18 branches from the conveying path 17 on the downstream side of the fixing unit 11 and merges with the conveying path 17 on the downstream side of the paper supply device 7.

[0024] When forming an image, the paper supplied from the paper cassette 5 by the paper supply device 7 is conveyed to the image forming unit 9 along the conveying path 17, and a toner image is formed on the paper in the image forming unit 9. The paper is conveyed to the fixing device 11 along the conveying path 17, and the toner image is fixed on one surface of the paper in the fixing device 11. The paper is conveyed to the discharge device 13 along the conveying path 17, and discharged to the paper discharge tray 15 by the discharge device 13. In the case of double-sided printing, the paper on which the toner image is fixed on one surface by the fixing device 11 is turned back by the discharge device 13, and is conveyed again along the conveying path 17 through the reverse conveying path 18, and a toner image is formed on the other surface in the image forming unit 9. Thereafter, the paper is conveyed to the fixing device 11 along the conveying path 17, and the toner image is fixed on the other surface of the paper by the fixing device 11. The paper is conveyed to the discharge device 13 along the conveying path 17, and discharged to the paper discharge tray 15 by the discharge device 13.

[0025] The conveying path 17x between the fixing device 11 and the discharge device 13 is formed between the surface of the rear side of the housing 3 and the rear cover 19, and the rear cover 19 is supported rotatably around the lower end portion on the surface of the rear side of the housing 3. By rotating (opening) the rear cover 19 downward, the surface of the fixing device 11 on the downstream side in the conveying direction of the paper is exposed, and the conveying path 17x between the fixing device 11 and the discharge device 13 is opened. According to this, it is possible to handle a paper jam that occurs in the fixing device 11 or the conveying path 17x. In this way, the rear cover 19 is an example of a cover that is set in an openable and closable manner and exposes the fixing device 11 by opening.

[0026] Next, refer to Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 4 The fixing device 11 will be described. Figure 2A and Figure 2Bis a perspective view of the fixing device 11 as viewed from the rear side. Figure 3A and Figure 3B is a cross-sectional view showing the fixing device 11, Figure 4 It is a perspective view of the fixing housing 21 and the discharge guide 27 as viewed from the front side.

[0027] The fixing device 11 includes a fixing housing 21 (see Figure 2A and Figure 2B , Figure 4 The fixing housing 21 supports a fixing unit 23 (see Figure 3A and Figure 3B ), which fixes the toner image on the paper; the discharge roller pair 25 (refer to Figure 2A and Figure 2B , Figure 3A and Figure 3B ), which conveys the paper through the fixing unit 23 along the conveying path 17; and the discharge guide 27 (refer to Figure 2A and Figure 2B , Figure 3A and Figure 3B ) which guides the paper that has passed through the fixing unit 23 toward the discharge roller pair 25.

[0028] First, the main reference Figure 4 The fixing housing 21 is described. The fixing housing 21 includes left and right side plates 31L and 31R facing each other in the width direction (left-right direction), and a beam member 33 provided between the left and right side plates 31L and 31R. The left and right side plates 31L and 31R have notches 31a extending downward from the upper end.

[0029] Next, the main reference Figure 3A and Figure 3B The fixing unit 23 is described below. The fixing unit 23 includes a fixing belt 41 as a fixing member, a planar heater 43 as a heat source for heating the fixing belt 41, and a pressure roller 45 as a pressure member, which forms a pressure region N between the pressure roller 45 and the fixing member to press and heat the paper.

[0030] The fixing belt 41 is an endless belt having a predetermined inner diameter and a width longer than the width of the paper. The fixing belt 41 is made of a flexible material and has a base layer; an elastic layer disposed on the outer peripheral surface of the base layer; and a release layer disposed on the outer peripheral surface of the elastic layer. The base layer is formed of a metal such as SUS or Ni. The elastic layer is formed of silicone rubber or the like. The release layer is formed of a PFA tube or the like. In some cases, a sliding layer is formed on the inner peripheral surface of the base layer. The sliding layer is formed of polyamide-imide, PTFE or the like.

[0031] The two ends of the fixing belt 41 are rotatably supported by end holders (not shown). The two end holders are supported by notches 31a (mounting holes) of the left and right side plates 31L and 31R of the fixing housing 21. Figure 4 ). The stay 47 penetrates the hollow portion of the fixing belt 41. Both ends of the stay 47 are supported by end holders.

[0032] The planar heater 43 is a flat component having a width equal to that of the fixing belt 41, and a predetermined length and thickness. The planar heater 43 has a laminated structure in which a substrate made of stainless steel or ceramic, an electrical insulating layer made of glass, a resistive heating layer having electrodes, and a protective layer are laminated in sequence from the inner side to the outer side. The surface of the protective layer is formed flat and serves as a sliding surface in contact with the inner peripheral surface of the fixing belt 41. The resistive heating layer is heated by energizing the resistive heating layer using the electrodes. As described above, the planar heater 43 has a high temperature rise property and can heat the fixing belt 41 only on the sliding surface.

[0033] The planar heater 43 is held together with the stay 47 by a holding member 49, and the holding member 49 is supported by an end holding frame. The holding member 49 is a substantially semi-cylindrical member having a width equal to that of the fixing belt 41 and a predetermined length in the circumferential direction. The planar heater 43 is housed in a recess formed at the top of the holding member 49. The holding member 49 is formed of a heat-resistant resin such as a liquid crystal polymer, for example.

[0034] The pressure roller 45 includes a core bar, an elastic layer provided on the outer peripheral surface of the core bar, and a mold release layer provided on the outer peripheral surface of the elastic layer. The elastic layer is formed of silicone rubber or the like. The mold release layer is formed of a PFA tube or the like.

[0035] The pressure roller 45 is rotatably supported by the left and right side plates 31L and 31R of the fixing housing 21 (see Figure 4 ), and is pressed against the planar heater 43 from below the fixing belt 41. Accordingly, a pressurized area N is formed between the fixing belt 41 and the pressurized roller 45. The pressurized roller 45 is driven to rotate by a motor (not shown). When the pressurized roller 45 is driven to rotate by the motor, the fixing belt 41 is driven to rotate in the opposite direction to the pressurized roller 45. Accordingly, the paper conveyed along the conveying path 17 passes through the pressurized area N.

[0036] Next, the discharge roller pair 25 will be described. Figure 2A and Figure 2B , Figure 3A and Figure 3B As shown, the discharge roller pair 25 includes an upper roller assembly 51 and a lower roller assembly 61 , and is supported by the fixing housing 21 at a position downstream of the pressing region N in the conveying direction.

[0037] First, the upper roller assembly 51 is described. The upper roller assembly 51 includes an upper roller 53 and an upper guide plate 55. The upper roller 53 includes a rotating shaft and two roller bodies arranged on the rotating shaft at a predetermined interval in the width direction. Both ends of the rotating shaft are rotatably supported by the left and right side plates 31L and 31R of the fixing housing 21. The rotating shaft can be driven to rotate by a motor (not shown).

[0038] The upper guide plate 55 is disposed between the left and right side plates 31L and 31R of the fixing housing 21. Figure 2A , Figure 2B As shown in FIG. 1 , a plurality of ribs 55a are provided in the vertical direction at predetermined intervals in the width direction on the rear surface (the surface on the downstream side in the conveying direction) of the upper guide plate 55. Two rectangular notches are formed at predetermined intervals in the center of the width direction at the lower end of the upper guide plate 55. The two roller bodies of the upper roller 53 are housed in these two notches.

[0039] Next, the main reference Figure 5 The lower roller assembly 61 will be described. Figure 5 The bottom roller assembly 61 is a perspective view of the bottom roller assembly 61 viewed from the rear side. The bottom roller assembly 61 includes a bottom roller 63 and a bottom guide member 65 supporting the bottom roller 63. The bottom roller 63 includes a rotation axis and two roller bodies arranged on the rotation axis at a predetermined interval in the width direction. The two roller bodies are arranged at the same position as the two roller bodies of the top roller 53 in the width direction (see FIG. Figure 2A ).

[0040] The lower guide member 65 includes left and right side plates 65L, 65R, and a lower guide plate 65X disposed between the left and right side plates 65L, 65R. At the lower end portions of the outer surfaces of the left and right side plates 65L, 65R, left and right fulcrum pins 67 protrude in the width direction. The rear surface of the lower guide plate 65X (the surface on the downstream side in the conveying direction) includes a rear guide surface for guiding the paper along the reverse conveying path 18. On the rear guide surface, a plurality of guide ribs 69 are formed in the up-down direction at predetermined intervals in the width direction. On the opposite side of the rear guide surface, a reinforcing rib 71 is formed in the up-down direction and the width direction (at the Figure 5 The diagram is omitted, see Figure 3A and Figure 3B ) Two rectangular notches 73 are formed at the upper end of the lower guide plate 65X at a predetermined interval in the center in the width direction.

[0041] Both ends of the rotating shaft of the lower roller 63 are rotatably supported by upper ends of left and right side plates 65L and 65R of the lower guide member 65. The two roller bodies are housed in two notches 73 of the lower guide plate 65X.

[0042] The left and right fulcrum pins 67 of the lower guide member 65 are inserted into the substantially central portion in the height direction of the left and right side plates 31L and 31R of the fixing housing 21. Accordingly, the lower guide member 65 is rotatably supported by the left and right side plates 31L and 31R. The lower roller assembly 61 is in the conveying position (refer to Figure 2A and Figure 3A ), and the open position where the roller body of the lower roller 63 is separated from the roller body of the upper roller 53 from the rear (refer to Figure 2B and Figure 3B ). The lower roller assembly 61 is supported in a temporarily immovable manner at the conveying position and the open position by a holding mechanism (not shown). Thus, the lower guide member 65 is an example of a supporting member, which rotatably supports one of the discharge rollers (lower roller 63) in the discharge roller pair 25, and can rotate the discharge roller in a direction away from the other discharge roller (upper roller 53).

[0043] Next, the main reference Figure 6 The discharge guide 27 will be described. Figure 6 2 is a perspective view of the discharge guide 27 viewed from the rear. The discharge guide 27 includes left and right side plates 81L, 81R, and a guide plate 81X disposed between the left and right side plates 81L, 81R. Left and right bosses 83 protrude in the width direction at the upper end portions of the outer surfaces of the left and right side plates 81L, 81R.

[0044] The front surface of the upper half of the guide plate 81X (the surface on the upstream side in the conveying direction) forms a front guide surface that is inclined upward from the pressure area N toward the discharge roller pair 25. Along the front guide surface, the paper is guided from the pressure area N to the discharge roller pair 25. On the front guide surface, a plurality of guide ribs 85 are formed along the vertical direction at predetermined intervals in the width direction (see also FIG. Figure 3A and Figure 3B ). On the opposite side of the front guide surface, a reinforcing rib 87 is formed along the vertical direction and the left-right direction (see also Figure 3A and Figure 3B ).

[0045] The rear surface of the lower half of the guide plate 81X (the surface on the downstream side in the conveying direction) forms a rear guide surface for guiding the paper during double-sided conveying. Figure 6 As shown, on the rear guide surface, a plurality of guide ribs 89 along the vertical direction are formed at predetermined intervals in the width direction. On the opposite side of the rear guide surface, reinforcement ribs (not shown) along the vertical direction and the left-right direction are formed.

[0046] A slit 93 cut from the upper end is formed in the middle portion in the width direction of the upper end portion of the guide plate 81X. A rectangular opening 95 is formed in the lower portion of the middle portion in the width direction of the guide plate 81X.

[0047] like Figure 3A As shown in FIG. 1 and FIG. 2 , the discharge guide 27 is arranged such that the upper half of the guide plate 81X is located between the fixing unit 23 and the discharge roller pair 25, and the lower half of the guide plate 81X (at the position closer to the fixing unit 23 than the lower roller assembly 61) is located. Figure 3A , Figure 3B (the lower half is omitted in the figure) is located below the lower roller assembly 61 (see also Figure 2A and Figure 2B ).

[0048] like Figure 4 As shown, the left and right bosses 83 of the left and right side plates 81L and 81R of the discharge guide 27 are inserted into the left and right side plates 31L and 31R of the fixing housing 21. In addition, the guide plate 81X of the discharge guide 27 is fixed to the beam member 33 of the fixing housing 21 with a plurality of screws B at the center of the width direction.

[0049] like Figure 2A and Figure 3A As shown in FIG. 1 , when the lower roller assembly 61 of the discharge roller pair 25 is rotated to the conveying position, the lower half of the discharge guide 27 is exposed below the lower roller assembly 61. Furthermore, the rear guide surface of the lower guide plate 65X of the lower guide member 65 of the lower roller assembly 61 and the rear guide surface of the guide plate 81X of the discharge guide 27 are continuous. In particular, as shown in FIG. Figure 2A As shown, the guide ribs 69, 89 of the two guide surfaces are continuous in the conveying direction.

[0050] like Figure 2B and Figure 3B As shown in FIG. 1 , when the lower roller assembly 61 is rotated to the open position, the space between the upper and lower rollers 53, 63 of the upper and lower roller assemblies 51, 61 is opened, and the upper half of the guide plate 81X of the discharge guide 27 (the reinforcing rib 87 on the rear side) and the gap G between the upper guide plate 55 of the upper roller assembly 51 and the guide plate 81X of the discharge guide 27 are exposed from between the upper and lower rollers 53, 63 (see FIG. 1 ). Figure 3B ). The gap G communicates with the pressurized area N. The gap G is set to a level that a user's finger cannot be inserted into (for example, 5 to 8 mm).

[0051] Next, the main reference Figure 7 and Figure 8 The actuator 101 supported by the discharge guide 27 will be described. Figure 7 This is a front view of the discharge guide 27 as seen from the front side. Figure 81 is a diagram schematically showing a structure in which a rotating shaft 103 of an actuator 101 is supported by a discharge guide 27. The actuator 101 rotates when a sheet of paper comes into contact therewith, thereby detecting the passage of the sheet of paper.

[0052] The actuator 101 includes a rotating shaft 103, a main actuator piece 105 (detection piece) and a double-sided actuator piece 107 (detection piece) extending radially from the rotating shaft 103, and a detected piece 109. The rotating shaft 103 has a length of about half the width of the guide plate 81X of the discharge guide 27. The main actuator piece 105 and the double-sided actuator piece 107 are provided at the left end of the rotating shaft 103 so as to extend in opposite radial directions. The detected piece 109 is provided at the right end of the rotating shaft 103.

[0053] The rotating shaft 103 is rotatably supported at the upper end of the surface on the front side of the guide plate 81X of the discharge guide 27 (the surface on the upstream side in the conveying direction). Specifically, at the left end of the rotating shaft 103, a left support portion 103L is formed at a position to the left of the main actuator plate 105 and the double-sided actuator plate 107. A circular left bearing hole 96 for supporting the left support portion 103L is formed on the discharge guide 27. The left support portion 103L is inserted into the left bearing hole 96 along the axial direction of the rotating shaft 103. On the rotating shaft 103, a force applying component 110 is sleeved between the left support portion 103L and the main actuator plate 105 and the double-sided actuator plate 107. As an example, the force applying component 110 is a torsion coil spring. From Figure 7 When viewed from the right side, the force applying component 110 applies force to the actuator 101 in the counterclockwise direction around the rotation axis 103.

[0054] A right support portion 103R is formed at the right end portion of the rotating shaft 103 at a position to the left of the detection piece 109. Figure 8 As shown, the right support portion 103R has a shape in which a circle is cut with two parallel straight lines to form a notch when viewed from the axial direction, and has a pair of arc surfaces 103Ra facing each other and a pair of flat surfaces 103Rb facing each other. The discharge guide 27 has a side plate 86 formed in a direction orthogonal to the rotation axis 103. A right bearing portion 97 for supporting the right support portion 103R is formed on the side plate 86. The right bearing portion 97 has a groove portion 97a and an opening portion 97b, wherein the groove portion 97a is arranged from the edge of the side plate 86 in a direction orthogonal to the axial direction of the rotation axis 103, and the opening portion 97b is connected to the groove portion 97a. The width (height) of the groove portion 97a is approximately equal to the distance between the two flat surfaces 103Rb of the right support portion 103R. The inner diameter of the opening portion 97b is approximately equal to the diameter of the imaginary circle formed by the two arc surfaces 103Ra of the right support portion 103R.

[0055] Next, the installation of the actuator 101 to the discharge guide 27 is described. First, the force member 110 is inserted through the rotating shaft 103. Then, the left support portion 103L is arranged on the right side of the left bearing hole 96, and the rotating shaft 103 is rotated in a direction to overcome the load force of the force member 110, and the right support portion 103R is inserted into the right bearing portion 97. In detail, the right support portion 103R is maintained in a posture where the two flat surfaces 103Rb are horizontal (see Figure 8 The right bearing 97 is inserted into the groove 97a of the right bearing 97 along the direction along the two flat surfaces 103Rb. When the right support 103R reaches the opening 97b of the right bearing 97 (the arc surface 109Ra contacts the inner surface of the opening 97b), the left support 103L is inserted into the left bearing hole 96. Then, the rotating shaft 103 is moved in the axial direction until the main actuator piece 105 overlaps with the gap 93 of the guide plate 81X. Finally, the main actuator piece 105 is forced by the force applying member 110 to be accommodated in the gap 93 (refer to Figure 8 solid line).

[0056] Thus, the main actuator piece 105 is housed in the slit 93 of the guide plate 81X, and protrudes upward from the guide plate 81X (see also FIG. Figure 6 ). An example of the width of the main actuator sheet 105 is 4 mm, and an example of the width W of the slit 93 is 6 mm. That is, a gap W of 1 mm is provided between the main actuator sheet 105 and the two side surfaces of the slit 93 in the width direction. The double-sided actuator sheet 107 is housed in the opening 95 of the guide plate 81X and protrudes to the rear side (downstream side in the conveying direction) of the guide plate 81X (see also Figure 6 ). The detected piece 109 protrudes outward (rearward) in the width direction of the guide plate 81X. The rotating shaft 103 is supported by the left bearing hole 96 and the right bearing portion 97 in a rotatable and axially movable manner. The axial movement of the main actuator piece 105 is limited within the range of the width W of the gap 93, and therefore, the axial movement of the actuator 101 is limited.

[0057] Next, the operation of the actuator 101 will be described. The paper passing through the pressurizing area N is guided along the front guide surface of the discharge guide 27 and finally abuts against the main actuator piece 105. Then, the main actuator piece 105 is pressed by the paper, thereby rotating the rotation shaft 103 (see Figure 8 The detected sheet 109 also rotates together with the rotating shaft 103. A light sensor (not shown) is provided on the fixing housing 21 to cut off or form a light path through the detected sheet 109. The light sensor cuts off or forms a light path through the detected sheet 109, and sends a signal to the control unit (not shown) accordingly. The control unit determines that the paper has passed through the pressurizing area N based on the signal.

[0058] Similarly, when the paper conveyed in the reverse conveying path 18 abuts against the double-sided actuator piece 107, the double-sided actuator piece 107 is pressed by the paper, and the rotating shaft 103 rotates together with the detected piece 109. The detected piece 109 cuts off or forms the optical path, and the optical sensor sends a signal to the control unit accordingly. The control unit determines that the paper has passed through the reverse conveying path 18 based on the signal.

[0059] Reference Figure 2A , Figure 2B , Figure 3A , Figure 3B The fixing operation of the fixing device 11 having the above structure is described. First, in the fixing unit 23, the pressure roller 45 is driven by the motor to rotate, and the fixing belt 41 is driven by the pressure roller 45 to rotate in the direction opposite to the rotation direction of the pressure roller 45 ( Figure 3A At the same time, the planar heater 43 is driven to heat the fixing belt 41. The fixing belt 41 is heated to a predetermined control temperature (for example, 160° C.). After the fixing belt 41 is heated in this way, the paper S to which the toner image is transferred is transported to the pressurizing area N.

[0060] When the paper S passes through the pressurizing area N, it is heated by the fixing belt 41 and pressurized by the pressurizing roller 45 and the fixing belt 41, whereby the toner image is fixed on the paper S. The paper S with the toner image fixed thereon is guided from the pressurizing area N to the discharge roller pair 25 along the front guide surface of the guide plate 81X of the discharge guide 27. Thereafter, the paper is conveyed to the discharge device 13 along the conveying path 17 by the discharge roller pair 25. At this time, the rotating shaft 103 is rotated by the paper abutting against the main actuator piece 105 of the actuator 101, and the control unit determines that the paper has passed through the pressurizing area N.

[0061] When a paper jam occurs in the pressurized area N, first, open the rear cover 19 (see Figure 1 ). So, if Figure 2A As shown in FIG. 1 , the rear surface of the fixing device 11 (the surface on the downstream side in the conveying direction) is exposed. After that, the lower roller assembly 61 is rotated from the conveying position to the open position. Figure 2B and Figure 3B As shown in FIG. 1 , a gap G is exposed between the upper guide plate 55 of the upper roller assembly 51 and the guide plate 81X of the discharge guide 27. The paper can be taken out through this gap G.

[0062] As described above, according to the fixing device 11 of the present invention, as described above, the height of the gap G is such that the user's fingers cannot enter, so the possibility of the user contacting the fixing belt 41 is low. That is, even if the lower roller assembly 61 is rotated to the open position, since the discharge guide 27 is present on the rear side of the fixing unit 23, the gap G where the fixing belt 41 or the pressurizing area N is exposed can be made as narrow as possible. Specifically, it can be narrowed to such an extent that the user's fingers cannot enter. Therefore, even when using the planar heater 43 with high temperature rise performance, paper jams can be handled safely.

[0063] The left and right bosses 83 of the left and right side plates 81L and 81R of the discharge guide 27 are inserted into the left and right side plates 31L and 31R of the fixing housing 21, and the guide plate 81X is fastened to the beam member 33 of the fixing housing 21 by screws (see FIG. Figure 4 ). In addition, reinforcing ribs 87 are formed on the front and rear surfaces of the discharge guide 27 along the vertical direction and the width direction, and the rigidity of the discharge guide 27 becomes high. Therefore, when a finger is inserted into the gap G, even if the discharge guide 27 is pressed toward the pressurized area N, the discharge guide 27 is not easily deformed, and the gap G is not easily opened. Therefore, paper jams can be handled more safely.

[0064] Furthermore, the interval between the main actuator piece 105 and both sides of the gap 93 in the width direction is 1 mm, so fingers cannot be inserted through the gap. Thus, the gap that allows access to the pressurized area N or the fixing belt 41 can be made as narrow as possible, thereby increasing the safety of paper jam handling.

[0065] In addition, even when the planar heater 43 is used, the paper jam can be handled safely in this way, so, for example, there is no need to provide an interlock switch on the rear cover 19. That is, when the planar heater 43 is used, in consideration of safety, when the rear cover 19 is opened when handling a paper jam in the pressurized area N, the interlock switch may be activated to cut off the power supply of the image forming apparatus 1. In the present invention, it is difficult to enter the pressurized area N or the fixing belt 41 as described above, so the paper jam can be handled even in the state where the power is turned on. Therefore, the workability of handling the paper jam can be improved.

[0066] Furthermore, the above description of the embodiments of the present invention describes suitable embodiments of the present invention, and therefore, various technically preferred limitations may be added. However, the technical scope of the present invention is not limited to these aspects unless otherwise specified.

Claims

1. A fixing device, characterized in that: The invention has a fixing member, a pressing member, a discharge roller pair, a discharge guide and an actuator, wherein: The fixing member is heated by a heat source; The pressurizing member forms a pressurizing area between the pressurizing member and the fixing member for heating and pressurizing the paper to which the toner image is transferred; The discharge roller pair includes an upper discharge roller and a lower discharge roller, and conveys the paper passing through the pressure area; The discharge guide guides the paper passing through the pressure area toward the discharge roller pair; The actuator comprises a rotating shaft and a detection piece, wherein the rotating shaft is supported on the discharge guide member in a manner that the rotating shaft can rotate and can move in the axial direction, and the detection piece extends radially from the rotating shaft, and the paper in the pressurized area abuts against the detection piece to rotate the actuator around the rotating shaft, thereby detecting the paper. The discharge guide has a slit, and the slit accommodates the detection piece and restricts the detection piece from moving in a width direction of the paper.

2. The fixing device according to claim 1, characterized in that: The device further comprises a support member, the support member being arranged on a side farther from the pressurizing area than the discharge guide, rotatably supporting the lower discharge roller of the discharge roller pair and being capable of rotating the lower discharge roller in a direction away from the upper discharge roller. The discharge guide is arranged so as to form a gap between the discharge guide and the upper discharge roller into which a finger cannot be inserted.

3. The fixing device according to claim 1, characterized in that: The heat source is a planar heater.

4. The fixing device according to claim 1, characterized in that: The interval between the slit and the actuator in the width direction is 1 mm.

5. The fixing device according to claim 1, characterized in that: The apparatus further comprises a housing having a pair of side plates facing the width direction of the paper and a beam member disposed between the pair of side plates, wherein the housing supports the fixing member and the pressing member. The discharge guide has a pair of bosses, and the pair of bosses protrude in opposite directions along the width direction of the paper. The discharge guide is fastened to the beam member by screws, and the pair of bosses are inserted into through holes formed in the pair of side plates.

6. The fixing device according to claim 1, characterized in that: The discharge guide has a reinforcement rib.

7. An image forming device, characterized in that: A device comprising an image forming unit, the fixing device according to claim 1, and a cover, wherein: The image forming unit forms a toner image on a sheet of paper; The fixing device fixes the toner image transferred by the image forming section onto the paper; The cover is provided in an openable and closable manner, and when opened, the fixing device is exposed at the discharge side where the paper is discharged from the pressurizing area. The image forming apparatus can be powered on even in a state where the cover is opened.

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