JP2014063010A - Image forming device - Google Patents

Abstract

An image forming apparatus capable of smoothly transporting a recording sheet from a fixing unit frame in a transport direction.
In a state in which a fixing unit frame 83 is fixed to a side frame on the upstream side in the conveyance direction of a recording sheet with respect to a paper discharge unit frame 95, three fixing units are arranged at equal intervals in the longitudinal direction of the fixing unit frame 83. Each protrusion 83B of the rib 83A comes into contact with the contact surface 95B of the paper discharge unit cover 96 constituting a part of the paper discharge unit frame 95, so that the warp in the longitudinal direction of the fixing unit frame 83 is brought into contact with the contact surface 95B. Corrected and reduced. As a result, the recording paper is smoothly conveyed from the fixing unit frame 83 toward the paper discharge unit frame 95.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus including a fixing unit frame.

  In general, an image forming apparatus such as a laser printer or a digital copying machine includes a fixing unit that thermally fixes a developer image on a recording sheet. As this type of fixing unit, for example, Patent Document 1 discloses a recording roller in which a developer image is thermally fixed, and a heating roller and a pressure roller that thermally fix the developer image on the recording sheet by sandwiching and rotating the recording sheet. A structure is disclosed that includes a pair of discharge rollers for feeding out a sheet, and a heating roller, a pressure roller, and a frame that rotatably supports the discharge rollers.

JP-A-6-27752

  By the way, the frame of the fixing unit that rotatably supports the heating roller, the pressure roller, the discharge roller, and the like is generally made of synthetic resin that is injection-molded into a shape in which the axial direction of these rollers is the longitudinal direction. Warpage is likely to occur in the direction. If warpage occurs in the longitudinal direction of the frame, for example, the contact pressure of the pair of discharge rollers becomes non-uniform in the axial direction, and the recording sheet may not be discharged smoothly in the discharge direction.

  In addition, when the frame of the paper discharge unit is arranged adjacent to the frame of the fixing unit, if the fixing frame is warped, the fixing unit frame interferes with the paper discharge unit frame, or the fixing unit frame There is a possibility that the interval between the discharge unit frame is not stable and the recording sheet discharged from the fixing unit cannot be accurately received by the discharge unit.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can smoothly convey a recording sheet from a fixing unit frame in a conveyance direction.

  An image forming apparatus according to the present invention for solving the above-described problems is an image forming apparatus having a fixing unit for thermally fixing a developer image on a recording sheet, and a heating member for heating the recording sheet A fixing unit frame having a pressing member configured to press the recording sheet against the heating member, a side frame to which the fixing unit frame is fixed, and a downstream side of the fixing unit frame in the conveyance direction of the recording sheet And a paper discharge unit frame for discharging the recording sheet. The fixing unit frame has a protrusion that reduces warpage of the fixing unit frame by abutting against the paper discharge unit frame.

  In this image forming apparatus, the fixing unit frame is fixed to the side frame on the upstream side in the conveyance direction of the recording sheet with respect to the paper discharge unit frame, and if the fixing unit frame is warped, the fixing unit frame protrudes. As the portion comes into contact with the paper discharger frame, the fixing unit frame is corrected by the paper discharger frame and the warpage of the fixing unit frame is reduced.

  In the image forming apparatus described above, when a plurality of protrusions of the fixing unit frame are arranged in the width direction orthogonal to the conveyance direction of the recording sheet, the fixing unit frame is corrected by the discharge unit frame over the width direction of the recording sheet, This is preferable because warpage of the fixing unit frame is reduced in the width direction of the recording sheet.

  Here, the fixing portion frame fixed to the side frame can be configured to include two contact surfaces for positioning with respect to the side frame and two screwing portions for fixing to the side frame.

  In this case, if the two contact surfaces are spaced apart from each other in the width direction of the recording sheet, the fixing unit frame is stably positioned in the front-rear direction over the width direction of the recording sheet by the two contact surfaces. preferable.

  Further, the two screwing portions are arranged apart from each other in the width direction of the recording sheet, and are arranged in parallel with the two contact surfaces by providing a pressing margin for pressing the two contact surfaces in the contact direction. This is preferable because the fixing unit frame is stably fixed by the two screwing portions in the width direction of the recording sheet and the two contact surfaces are pressed in parallel and without looseness.

  Further, when the two contact surfaces are disposed between the two screwing portions in the width direction of the recording sheet, the fixing unit frame is difficult to bend at a portion between the two contact surfaces in the width direction of the recording sheet. Therefore, it is preferable.

  Here, two screwing parts can each be set as the structure which has the boss | hub hole provided in the side frame, ie, the boss | hub hole fitted to the boss | hub provided in the side frame so that a screw may be screwed in.

  In this case, if the boss hole of one screwing part is a round hole and the boss hole of the other screwing part is a long hole whose longitudinal direction is the width direction of the recording sheet, the fixing part frame is connected to one screw. It is preferable because it is positioned in the width direction of the recording sheet by the round boss hole of the stop portion, and the thermal expansion along the width direction of the recording sheet is absorbed by the long boss hole of the other screw fastening portion. .

  On the other hand, it is preferable that the side frame has an assembly guide portion that guides the screwing portion in the contact direction of the contact surface. In this case, when the fixing unit frame is assembled and fixed to the side frame, the fixing unit frame is guided to the contact direction of the contact surface by the side frame assembly guide unit, so that the fixing unit frame becomes the side frame. Can be easily assembled at a predetermined position.

  In the image forming apparatus according to the present invention, the protrusion of the fixing unit frame abuts on the paper discharge unit frame, whereby the fixing unit frame is corrected to the paper discharge unit frame, and warping of the fixing unit frame is reduced. Therefore, according to the image forming apparatus of the present invention, the recording sheet can be smoothly conveyed from the fixing unit frame toward the sheet discharge unit frame on the downstream side in the conveyance direction. Further, it is possible to avoid inconveniences such as the fixing unit frame interfering with the paper discharge unit frame or the interval between the fixing unit frame and the paper discharge unit frame being unstable.

1 is a side sectional view showing a schematic configuration of a color printer as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a fixing unit and a paper discharge unit illustrated in FIG. 1. FIG. 3 is a perspective view of the fixing unit shown in FIG. 2 as viewed from the front upper side. FIG. 3 is a perspective view of the fixing unit shown in FIG. 2 as viewed from the upper rear side. FIG. 5 is a partially enlarged side view illustrating a contact state between a left contact surface of the fixing unit frame illustrated in FIG. 4 and a left receiving surface of the side frame. It is a figure explaining the right side screwing part of the fixing | fixed part flame | frame shown in FIG. 3, horizontal sectional view (a) and vertical sectional view (b) before tightening a screw, and vertical sectional view after tightening a screw ( c). FIG. 5 is a perspective view of an assembly guide portion of a side frame that guides a left screwing portion of the fixing portion frame shown in FIG. 4.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of an image forming apparatus according to the invention will be described in detail with reference to the drawings as appropriate. An image forming apparatus according to an embodiment is embodied as a color printer 1 as illustrated in FIG. 1, for example. In the following description, the side facing the user who uses the color printer 1, that is, the left side of the sheet of FIG. 1 is “front”, the right side is “rear”, the vertical direction is “up / down”, and the front side is “ “Right” and the back side “Left”.

<Schematic configuration of color printer>
As shown in FIG. 1, the color printer 1 mainly includes a paper feed unit 20, an image forming unit 30, a fixing unit 80, and a paper discharge unit 90 in a main body frame 10. On the upper side of the main body frame 10 is provided an upper cover 12 that can be opened and closed up and down with the rear side as a rotation center. The main body frame 10 has side frames 100 for supporting members such as the image forming unit 30 and the fixing unit 80 on both the left and right sides.

  The paper feeding unit 20 is provided in the lower part of the main body frame 10. The paper feed unit 20 includes a paper feed tray 21 that accommodates a recording paper P as an example of a recording sheet, a paper pressing plate 22, a paper feed roller 23, and a separation provided on a conveyance path 24 for the recording paper P. A roller 25, a separation pad 26, a paper dust removing roller 27, and a registration roller 28 are mainly provided.

  The recording paper P in the paper feed tray 21 is brought close to the paper feed roller 23 by the paper pressing plate 22 and sent out by the paper feed roller 23. The fed recording paper P is separated one by one by the separation roller 25 and the separation pad 26, and after a certain amount of paper dust is collected by the paper dust removing roller 27, it is supplied to the image forming unit 30 by the registration roller 28.

  The image forming unit 30 mainly includes four LED units 40, four process cartridges 50, and a transfer unit 70. Each process cartridge 50 includes a photoconductor cartridge 51 and a developing cartridge 61 that is detachably attached to the photoconductor cartridge 51.

  The LED unit 40 is disposed above the photosensitive drum 53 and includes a plurality of LEDs (light emitting diodes) (not shown) arranged in the left-right direction at the lower end thereof. The LED unit 40 exposes the surface of the photosensitive drum 53 by blinking the LED based on the image data. The LED unit 40 is held by the upper cover 12 and is separated from the photosensitive drum 53 by opening the upper cover 12.

  A plurality of process cartridges 50 are arranged side by side in the front-rear direction between the upper cover 12 and the paper feed tray 21, and are exchangeably mounted on the main body frame 10 in a state where the upper cover 12 is opened. It is the composition which becomes.

  Each photoconductor cartridge 51 mainly includes a photoconductor drum 53, a charger 54, and a collection roller 55. The collection roller 55 is a roller for collecting the transfer residual toner attached on the photosensitive drum 53.

  Each of the developing cartridges 61 includes a developing roller 63, a supply roller 64, a layer thickness regulating blade 65, an agitator 66, and an accommodating portion 67 that accommodates a positively chargeable toner as an example of a developer. It is comprised.

  The transfer unit 70 is provided between the paper feed tray 21 and the process cartridge 50, and mainly includes a driving roller 71, a driven roller 72, an endless conveyance belt 73, and four transfer rollers 74. ing. The conveying belt 73 is stretched between the driving roller 71 and the driven roller 72, and is disposed to face the photosensitive drum 53 on which the outer surface is arranged. The transfer roller 74 corresponds to the inner side of the conveying belt 73. A conveying belt 73 is disposed between the photosensitive drum 53 and the photosensitive drum 53.

  The fixing unit 80 is provided behind the four process cartridges 50 of the image forming unit 30. The fixing unit 80 includes a heating roller 81 as a heating member for heating the recording paper P, and a pressure roller 82 as a pressure member for pressing the recording paper P between the heating roller 81. And. The heating roller 81 and the pressure roller 82 constitute the main part of the fixing device, and are rotatably supported by the fixing unit frame 83.

  The paper discharge unit 90 is provided continuously behind the fixing unit 80. The paper discharge unit 90 records at least the recording paper P conveyed from the fixing unit 80 along the paper discharge path 91 to the discharge port 92, and records from the discharge port 92 onto the paper discharge tray 13. A discharge roller 94 for discharging the paper P is rotatably supported by the paper discharge unit frame 95. A sheet discharge path 91 is formed between the sheet discharge unit frame 95 and the sheet discharge unit cover 96.

  In the image forming unit 30, the surface of the photosensitive drum 53 is uniformly positively charged by the charger 54 and then exposed by the LED unit 40, whereby the electrostatic latent image based on the image data is formed on the photosensitive drum 53. Is formed. Further, the toner in the container 67 is supplied to the developing roller 63 to which the developing bias is applied via the supply roller 64 while being agitated by the agitator 66, and enters between the developing roller 63 and the layer thickness regulating blade 65. Then, it is carried on the developing roller 63 as a thin layer having a constant thickness. When the developing roller 63 comes into contact with the photosensitive drum 53, toner is supplied from the developing roller 63 to the photosensitive drum 53, whereby the electrostatic latent image is visualized and developed on the photosensitive drum 53. A toner image as an agent image is formed.

  Thereafter, the recording paper P supplied to the image forming unit 30 is conveyed between the photosensitive drum 53 and the conveying belt 73, so that the toner image formed on the photosensitive drum 53 is transferred onto the recording paper P. Is done. The recording paper P to which the toner image has been transferred is conveyed to the fixing unit 80, and the toner image is thermally fixed while passing between the heating roller 81 and the pressure roller 82, whereby the image is formed on the recording paper P. It is formed. Then, the recording paper P on which the image is formed is conveyed along the paper discharge path 91 by the transport roller 93 and the discharge roller 94, passes through the discharge port 92 of the paper discharge unit frame 95, and is discharged from the main body frame 10. It is discharged onto the tray 13.

<Detailed structure of fixing unit>
As shown in the enlarged sectional view of FIG. 2, a discharge roller 84 and a pinch roller 85 are disposed behind the heating roller 81 and the pressure roller 82 of the fixing unit 80. The paper discharge roller 84 and the pinch roller 85 are rotatably supported by the fixing unit frame 83 and discharge the recording paper P on which the toner image is thermally fixed between the heating roller 81 and the pressure roller 82. It is transported toward 90 transport rollers 93.

  The heating roller 81 is composed of a cylindrical metal tube having a halogen heater (not shown) therein. The heating roller 81 is rotatably supported at both ends in the axial direction by the fixing unit frame 83 via a bearing (not shown). A pressure roller 82 is disposed obliquely below and behind the heating roller 81.

  The pressure roller 82 is formed by thickening a urethane rubber layer around the core metal, and applies a desired nip pressure between the pressure roller 82 and the heating roller 81. Both ends of the pressure roller 82 are supported by a swing arm (not shown) that is swingably supported by the fixing unit frame 83, and the swing arm is biased upward by a spring (not shown). Thus, the heating roller 81 is pressed with a predetermined force.

<Detailed structure of fixing unit frame>
As shown in the perspective views of FIGS. 3 and 4, the fixing unit frame 83 has a longitudinal direction in the left-right direction along the axial direction of the heating roller 81, that is, the left-right width direction orthogonal to the conveyance direction of the recording paper P. It consists of a synthetic resin injection molded into a shape. A single exhaust fan F for cooling the heating roller 81 is attached to the right end of the fixing unit frame 83. Further, a non-contact thermistor TH that detects the surface temperature of the heating roller 81 in a non-contact state is disposed at the center in the longitudinal direction of the fixing unit frame 83.

  As shown in FIG. 2, the fixing unit frame 83 includes an upper frame 86 that covers a portion from above to the front of the heating roller 81, a plate-like upper sheet guide 87 that extends forward from the front end of the upper frame 86, The lower sheet guide 88 is disposed to face the lower side of the upper sheet guide 87.

  The plate-like upper sheet guide 87 extends in the width direction perpendicular to the conveyance direction and the vertical direction of the recording paper P, with the upstream side in the conveyance direction of the recording paper P being the front and the downstream side in the conveyance direction being the rear. The pressure roller 82 is disposed in front of the pressure roller 82.

  The front end of the upper sheet guide 87 is adjacent to the photosensitive cartridge 51 that forms the lower portion of the process cartridge 50 shown in FIG. The upper sheet guide 87 has reinforcing ribs 87A that protrude upward and extend in the left-right width direction.

  Here, a rib 83A that protrudes upward in the front-rear direction is formed on the upper surface of the rear portion of the fixing unit frame 83, and a protrusion 83B is formed integrally with the rib 83A on the upper end of the rib 83A. ing. The protruding portion 83B of the rib 83A is below the contact surface 95B so as to be able to contact the contact surface 95B provided on the lower surface of the rear portion of the paper discharge unit frame 95 of the paper discharge unit 90. It is provided opposite to.

  As shown in the perspective views of FIGS. 3 and 4, a plurality of ribs 83 </ b> A having protrusions 83 </ b> B at the upper end are arranged in the longitudinal direction of the fixing unit frame 83, that is, in the width direction orthogonal to the conveyance direction of the recording paper P. Yes. For example, in the example shown in FIGS. 3 and 4, three ribs 83 </ b> A are arranged at equal intervals in the longitudinal direction of the fixing unit frame 83. The ribs 83 </ b> A reduce the warpage in the longitudinal direction of the fixing unit frame 83 by the protrusions 83 </ b> B coming into contact with the contact surface 95 </ b> B of the paper discharge unit frame 95.

  Further, as shown in the perspective views of FIGS. 3 and 4, the fixing unit frame 83 has a front and rear assembling structure with respect to the left and right side frames 100 (only the left side is shown in FIGS. 5 and 7 and the right side is not shown). It has a right abutment surface 83C and a left abutment surface 83D for positioning, and a right screwing portion 83E and a left screwing portion 83G for fixing with screws.

  On the other hand, the side frame 100 includes a right receiving surface (not shown) on which the right abutting surface 83C of the fixing unit frame 83 abuts, a left receiving surface 101 (see FIG. 5) on which the left abutting surface 83D abuts, and a right screwing portion. A screw boss 102 (see FIGS. 6A and 6B) fixed by screwing to 83E, a screw boss 103 fixed to the left screwing portion 83G (see FIG. 7), and a left screwing And an assembly guide 104 for guiding the portion 83G.

  As shown in FIG. 3, the right contact surface 83 </ b> C and the left contact surface 83 </ b> D of the fixing unit frame 83 are spaced apart in the longitudinal direction (width direction) of the fixing unit frame 83 in the vicinity of the middle portion in the vertical direction of the fixing unit frame 83. It is arranged near the left and right ends. The right contact surface 83C and the left contact surface 83D are formed in parallel to each other as planes orthogonal to the front-rear direction of FIG.

  Further, as shown in FIG. 4, the right screwing portion 83E and the left screwing portion 83G of the fixing unit frame 83 are formed on the right and left contact surfaces 83C and 83D in the longitudinal direction (width direction) of the fixing unit frame 83, respectively. It is arranged slightly outside. In other words, the right contact surface 83C and the left contact surface 83D are disposed inside the right screw portion 83E and the left screw portion 83G in the longitudinal direction (width direction) of the fixing unit frame 83.

  The right screw portion 83E and the left screw portion 83G of the fixing unit frame 83 are arranged in parallel to each other along a plane orthogonal to the front-rear direction in FIG. That is, the right screwing portion 83E and the right contact surface 83C are arranged in parallel with each other, and the left screwing portion 83G and the left contact surface 83D are arranged in parallel with each other.

  The right screwing portion 83E has a long boss slot 83F on the left and right sides into which the screw bosses 102 (see FIGS. 6A and 6B) of the side frame 100 are inserted. On the other hand, the left screwing portion 83G has a boss round hole 83H into which the screw boss 103 (see FIG. 7) on the side frame 100 side is inserted.

  FIGS. 6A and 6B show a right screwing portion 83E fixed by screwing a screw S into the screw boss 102 on the side frame 100 side. Before fixing the fixing unit frame 83 to the side frame 100 with the screw S, the right screwing portion 83E has a seating surface with a pressing margin C of a predetermined screw S behind the seating surface 102A of the screw boss 102. Is opened and placed. The pressing allowance C functions as a predetermined pressing allowance for pressing the right contact surface 83C (see FIG. 3) in the contact direction. Although illustration is omitted, the seating surface of the left screwing portion 83G is also arranged rearward from the seating surface of the screw boss 103 with a predetermined pressing margin C open.

  Here, as shown in FIG. 7, the assembly guide 104 on the side frame 100 side includes a lateral upper assembly guide 104A that guides the upper side portion of the left screwing portion 83G on the fixing unit frame 83 side in the front-rear direction. A horizontal lower assembly guide 104B that guides the lower side portion of the left screwing portion 83G in the front-rear direction, and a vertical left-right direction group that guides the guide groove 83J formed in the upper side portion of the left screwing portion 83G in the front-rear direction. Attachment guide 104C. The front-rear direction in which the assembly guide 104 guides the left screwing portion 83G is a direction along the contact surface of the protrusion 83B of each rib 83A described above.

<Operation at fixing unit>
In the color printer 1 as the image forming apparatus according to the present embodiment, when the fixing unit frame 83 of the fixing unit 80 is assembled and fixed to the side frame 100, first, as shown in FIG. The left screwing portion 83G is engaged with 104. That is, the guide groove 83J of the left screwing portion 83G is engaged with the vertical mounting guide 104C in the vertical direction, the upper side portion of the left screwing portion 83G is engaged with the upper mounting guide 104A, and the left screwing portion 83G is engaged. Is engaged with the lower assembly guide 104B.

  Then, the fixing unit frame 83 is pushed forward with respect to the side frame 100 while maintaining this engaged state. Since the pressing direction of the fixing unit frame 83 is a direction along the contact surface of the protrusion 83B of each rib 83A described above, the fixing unit frame 83 can be smoothly pressed forward with respect to the side frame 100. .

  Subsequently, the right abutting surface 83C of the fixing unit frame 83 shown in FIG. 3 is brought into contact with a right receiving surface (not shown) on the side frame 100 side, and the left abutting surface 83D is contacted with the left receiving surface 101 on the side frame 100 side. (See FIG. 5). Then, the screw boss 102 on the side frame 100 side is inserted into the boss slot 83F of the right screwing portion 83E (see FIGS. 6A and 6B), and the boss round hole of the left screwing portion 83G is inserted. The screw boss 103 on the side frame 100 side is inserted into 83H (see FIG. 7).

  In this state, the screw S is screwed into the screw boss 102, and the right screw fixing portion 83E is fixed to the screw boss 102. Similarly, the screw S is screwed into the screw boss 103, and the left screwing portion 83G is fixed to the screw boss 103 (see FIG. 7). In this way, the fixing unit frame 83 can be easily assembled at a predetermined position of the side frame 100.

  In this case, as shown in FIG. 6C, the screw S is screwed in by a screwing allowance corresponding to the pressing allowance C after the seating surface comes into contact with the seating surface of the right screwing portion 83E. The seating surface of the screw abuts against the seating surface 102 </ b> A of the screw boss 102. Similarly, on the left side, after the seat surface of the screw S comes into contact with the seat surface of the left screwing portion 83G, the screw S is screwed in by a screwing allowance corresponding to the pressing allowance C, and the seat surface of the screw S is used for the screw. It abuts against the seating surface of the boss 103. As a result, the right abutting surface 83C is pressed against the right receiving surface (not shown) of the side frame 100 with a force corresponding to the predetermined pressing allowance C, and the left abutting surface 83D is the left receiving surface 101 of the side frame 100 (see FIG. 5). ) With a force corresponding to a predetermined pressing allowance C.

  In this way, the fixing unit frame 83 is not loosened in the front-rear direction over the width direction of the recording paper P with respect to the side frame 100 by the right side contact surface 83C and the left side contact surface 83D that are spaced apart in the longitudinal direction. Positioned stably. Further, the fixing unit frame 83 is stably fixed to the side frame 100 in the width direction of the recording paper P by the right side screwing portion 83E and the left side screwing portion 83G which are spaced apart from each other in the longitudinal direction. Is done. For this reason, since the positional relationship with the transfer unit 70 that transports the recording paper P to the fixing unit 80, particularly the parallelism across the left and right, is improved, the recording paper P can be transported stably from the transfer unit 70 to the fixing unit 80. Can do.

  Here, the right contact surface 83C and the left contact surface 83D of the fixing unit frame 83 are disposed inside the right screwing portion 83E and the left screwing portion 83G in the longitudinal direction (width direction) of the fixing unit frame 83. Therefore, in the fixing unit frame 83, the portion between the right contact surface 83C and the left contact surface 83D in the longitudinal direction (width direction) is difficult to bend.

  Further, as shown in FIG. 4, since the right screwing portion 83E of the fixing unit frame 83 has a long boss hole 83F and the left screwing portion 83G has a round boss hole 83H, the fixing unit frame 83 is positioned in the longitudinal direction (width direction) by the boss round hole 83H of the left screwing portion 83G, and the thermal expansion along the longitudinal direction (width direction) is absorbed by the boss long hole 83F of the right screwing portion 83E. Is done.

  As described above, in a state where the fixing unit frame 83 is fixed to the side frame 100, even if the fixing unit frame 83 warps upward, the fixing unit frame 83 is arranged at equal intervals in the longitudinal direction of the fixing unit frame 83. The protrusions 83B of the three ribs 83A come into contact with the contact surface 95B of the paper discharge unit frame 95, whereby the warpage of the fixing unit frame 83 is corrected to the contact surface 95B and reduced.

  Therefore, according to the color printer 1 of the present embodiment, the recording paper P can be smoothly conveyed from the fixing unit frame 83 toward the paper discharge unit frame 95 on the downstream side in the conveyance direction. Further, inconveniences such as the fixing unit 83 frame interfering with the paper discharge unit frame 95 or a gap between the fixing unit frame 83 and the paper discharge unit frame 95 can be avoided.

  Further, since the upper sheet guide 87 has reinforcing ribs 87A that protrude upward and extend in the width direction, warpage in the vertical direction is suppressed, and a predetermined interval is maintained between the upper sheet guide 87 and the lower sheet guide 88. As a result, the recording paper P is smoothly drawn between the upper sheet guide 87 and the lower sheet guide 88.

  The image forming apparatus according to the embodiment of the present invention has been described above. However, the image forming apparatus of the present invention is not limited to the embodiment, and the specific configuration is within the scope of the present invention. It can be changed as appropriate.

  For example, the fixing unit 80 may include a fixing roller in which an endless heating belt is stretched between the fixing roller and the endless fixing film is driven to rotate around the heating member. It is good also as a structure provided with the film-type heating rotary body. The pressure member pressed by the heating rotator does not necessarily need to be a rotatable roller. For example, a plate-shaped member may be pressed by the heating rotator.

  In the color printer 1 as an embodiment of the image forming apparatus, the recording sheet P such as a thick sheet, a postcard, and a thin sheet is exemplified as the recording sheet. However, the recording sheet is not limited to the recording sheet, and may be an OHP sheet, for example. Good.

  The image forming apparatus of the present invention can be applied not only to the color printer 1 but also to a monochrome printer, a copying machine, a multifunction machine, and the like.

1 Color printer P Recording paper P
DESCRIPTION OF SYMBOLS 10 Main body frame 30 Image formation part 80 Fixing part 81 Heating roller 82 Pressure roller 83 Fixing part frame 83A Rib 83B Protrusion part 83C Right side contact surface 83D Left side contact surface 83E Right side screwing part 83F Boss long hole 83G Left side screwing part 83H Round hole for boss 84 Paper discharge roller 85 Pinch roller 90 Paper discharge part 100 Side frame 101 Left receiving surface 102 Screw boss 103 Screw boss 104 Assembly guide 104A Upper assembly guide 104B Lower assembly guide 104C Left and right assembly guide S thread

Claims (7)

An image forming apparatus including a fixing unit for thermally fixing a developer image to a recording sheet,
A fixing unit frame having a heating member for heating the recording sheet, and a pressure member configured to press the recording sheet against the heating member;
A side frame to which the fixing unit frame is fixed;
A discharge unit frame provided on the downstream side in the conveyance direction of the recording sheet with respect to the fixing unit frame, for discharging the recording sheet,
The image forming apparatus according to claim 1, wherein the fixing unit frame includes a protrusion that reduces a warp of the fixing unit frame by contacting the fixing unit frame.   The image forming apparatus according to claim 1, wherein a plurality of the protrusions are arranged in a width direction orthogonal to a conveyance direction of the recording sheet. The fixing unit frame includes two contact surfaces for positioning with respect to the side frame, and two screwing portions for fixing to the side frame,
The two contact surfaces are spaced apart from each other in the width direction,
The two screwing portions are arranged to be spaced apart from each other in the width direction, and are arranged in parallel with the two contact surfaces by providing a pressing margin for pressing the two contact surfaces in the contact direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 3, wherein the two contact surfaces are disposed between the two screwing portions in the width direction.   5. The image forming apparatus according to claim 3, wherein each of the two screwing portions has a boss hole provided in the side frame and fitted into a boss into which a screw is screwed.   The boss hole of one screwing part of the two screwing parts is a round hole, and the boss hole of the other screwing part is a long hole whose longitudinal direction is the width direction. The image forming apparatus according to claim 5.   The image forming apparatus according to claim 3, wherein the side frame includes an assembly guide portion that guides the screwing portion in a contact direction of the contact surface.

Images