JP2024010695A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can achieve prevention of a trouble that an arm is deformed in a width direction due to the weight of a second fixing member and an improvement in the degree of freedom in design of a fixing unit.

SOLUTION: A fixing unit 7 has a fixing frame 80 that supports a first fixing member 30, and arms 60 that are rotatably supported on the fixing frame 80 and press a second fixing member 40 toward the first fixing member 30. The second fixing member 40 has a contact surface 41 that is in contact with a recording sheet SH, and parts to be pressed 44 that project outward in a width direction beyond the contact surface 41 and are pressed by the arms 60. The image forming apparatus 1 further comprises regulation surfaces 95 that are provided in an apparatus body 9, located on the outside in the width direction of the arms 60 and on the inside in the width direction of outside ends in the width direction of the parts to be pressed 44, and are directed inward in the width direction, the regulation surfaces 95 at least partially overlapping the arms 60 within rotation ranges of the arms 60 when seen along the width direction.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Patent Document 1 discloses a color printer that is an example of a conventional image forming apparatus. In this color printer, the fixing device is housed in the housing body. In the fixing device, the fixing belt is wound around two rollers each extending in the width direction. The pressure roller also extends in the width direction. The fixing belt and the pressure roller sandwich the recording paper and heat it to thermally fix the toner image onto the recording paper.

More specifically, the fixing device includes a fixing frame and a pressure lever. The fixing frame rotatably supports the two rollers described above. Further, the fixing frame supports the bearing of the pressure roller so that it can approach and separate from the fixing belt. The pressure lever is rotatably supported by the fixing frame. The pressure lever presses the pressure roller toward the fixing belt.

In the fixing frame, the lower frame is provided with a first regulating section, and the front frame is provided with a second regulating section.

When the casing body receives acceleration in the width direction due to a fall or collision, and the weight of the pressure roller that shifts in the width direction acts on the pressure lever, the width of the pressure lever is Directional movement is restricted.

Japanese Patent Application Publication No. 2009-69701

However, in the above-mentioned conventional image forming apparatus, since the fixing device is provided with the first regulating section and the second regulating section, it is necessary, for example, to secure an arrangement space in the fixing frame or to make a part of the fixing frame protrude more than the other part. This may limit the degree of freedom in designing the fixing device.

The present invention has been made in view of the above-mentioned conventional situation, and is aimed at suppressing the problem that the arm that presses the second fixing member toward the first fixing member is deformed in the width direction due to the weight of the second fixing member. An object of the present invention is to provide an image forming apparatus that can realize the following: , and an improved degree of freedom in designing a fixing unit.

The image forming apparatus of the present invention includes an apparatus main body,
a fixing unit housed in the apparatus main body, the fixing unit heating the recording sheet while sandwiching it between a first fixing member and a second fixing member each extending in the width direction, and thermally fixing the toner image onto the recording sheet; An image forming apparatus comprising:
The fixing unit includes a fixing frame that supports the first fixing member;
an arm rotatably supported by the fixing frame and pressing the second fixing member toward the first fixing member;
The second fixing member has a contact surface that contacts the recording sheet, and a pressed portion that protrudes outward in the width direction from the contact surface and is pressed by the arm,
A regulating surface provided on the apparatus main body, located outside the arm in the width direction and inside the width direction of the outer end of the pressed portion in the width direction, and facing inward in the width direction. The control surface further includes the regulating surface that at least partially overlaps the arm in a rotation range of the arm when viewed along the width direction.

In the image forming apparatus of the present invention, when the main body of the apparatus receives acceleration in the width direction due to a drop or collision, and the weight of the second fixing member that shifts in the width direction acts on the arm, the regulating surface is applied to the arm from the outside in the width direction. come into contact with This prevents the arm from shifting excessively in the width direction.

In addition, since this image forming apparatus has a regulating surface provided on the main body of the apparatus, for example, it is necessary to secure a space for arranging the regulating surface on the fixing frame, or to make a part of the fixing frame protrude more than the other part so that the regulating surface can be placed. There is no need to form it.

Therefore, the image forming apparatus of the present invention can suppress the problem that the arm is deformed in the width direction due to the weight of the second fixing member, and can improve the degree of freedom in designing the fixing unit.

The fixing unit may include a cam that is rotatably supported by the fixing frame and acts on the arm. The cam moves the arm between a first position where the nip pressure between the first fixing member and the second fixing member is a predetermined value and a position where the nip pressure is smaller than the first position or between the first fixing member and the second fixing member. The structure may be such that the member is rotated to a second position where the member is separated from the member. In this case, when the arm is in the second position, the nip pressure is smaller than in the first position or is zero, so the second fixing member is likely to shift in the width direction. It is possible to prevent the arm from shifting excessively in the width direction.

When viewed along the width direction, the regulating surface may be configured to overlap with the arm in the second position, but not overlap with the arm in the first position. In this case, when the arm is at the first position, the nip pressure is greater than at the second position, so the second fixing member is less likely to shift in the width direction. Therefore, even if the regulating surface does not regulate the arm in the first position, the arm is prevented from shifting excessively in the width direction. Furthermore, the restriction surface does not affect the movement of the arm in the first position.

The regulating surface may have an inclined surface that is inclined outward in the width direction so that the distance in the width direction from the arm is the shortest when the arm is in the second position. In this case, the arm in the first position is shifted in the width direction, and when the arm is rotated from that state to the second position, the inclined surface comes into sliding contact with the arm, returning the arm to its original position in the width direction. It can be returned.

The contact surface may be a roller. The pressed portion may include a rotating shaft that rotates integrally with the roller and a bearing that rotatably supports the rotating shaft. In this case, due to the configuration in which the arm presses the pressed portion consisting of the rotating shaft and the bearing, rotation of the roller is unlikely to be inhibited.

The arm may be configured to support a bearing. In this case, relative displacement in the width direction between the second fixing member and the arm can be suppressed with high reliability. Note that the weight of the second fixing member that shifts in the width direction due to acceleration in the width direction acts directly on the arm, but even in that case, the regulating surface can prevent the arm from shifting excessively in the width direction. .

When viewed along the width direction, the regulating surface may be located on the opposite side of the first fixing member with respect to the rotation center of the rotating shaft. In this case, the arm can be suitably regulated by the regulating surface near the point of action where the arm presses the second fixing member. Note that since the point of action is located far from the center of rotation of the arm and the point of force to which the biasing spring is connected in the arm, it is difficult to provide a regulating surface in the above arrangement on the fixing frame, but it is easy to provide on the main body of the apparatus.

The contact surface may be an endless belt. The pressed portion may be a belt support member that supports the endless belt from the inner circumference. In this case, the endless belt facilitates increasing the nip width when the first fixing member and the second fixing member sandwich the recording sheet.

The arm may be made of a metal plate having a surface perpendicular to the width direction. In this case, even if the arm is made of so-called sheet metal, the problem of deformation in the width direction due to the regulating surface can be suppressed.

The apparatus main body may have a main body frame that supports the fixing frame. The regulating surface may be provided on the main body frame. In this case, when the fixing unit is housed in the apparatus main body, the regulating surface provided on the main body frame can suitably prevent the arm from shifting excessively in the width direction.

The apparatus main body may include a main body frame that supports the fixing frame, and a cover that is openably and closably supported by the main body frame and has a regulating surface. In a state where the cover is closed, the regulating surface may be configured to overlap the arm when viewed along the width direction. In this case, when the fixing unit is taken out from the apparatus main body or housed in the apparatus main body with the cover open, the regulating surface is less likely to interfere with the fixing unit.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. FIG. 2 is a partial schematic sectional view of the image forming apparatus according to the embodiment, showing a state in which the rear cover and the fixing cover are opened. 3(a) shows the normal pressure contact mode of the heating roller and the pressure roller, FIG. 3(b) shows the light pressure contact mode of the heating roller and the pressure roller, and FIG. 3(a) shows the heating roller and the pressure roller in the light pressure contact mode. The separation mode of the pressure roller is shown. FIG. 4 is a schematic rear view of the fixing unit housed in the apparatus main body. FIG. 5 is a cross-sectional view taken along the line AA in FIG. 4, showing the arm and the like in the first position. FIG. 6 is a cross-sectional view similar to FIG. 5, showing the arm and the like in the second position. FIG. 7 is a cross-sectional view similar to FIG. 5, showing the arm and the like in the third position. FIG. 8 is a partial perspective view showing a part of the fixing frame and a switching lever. FIG. 9 is a perspective view showing the switching lever. FIG. 10 is a cross-sectional view similar to FIG. 5, showing the relative relationship between the fixing cover that opens and closes and the arm. FIG. 11 is a schematic rear view of the fixing unit housed in the apparatus main body. FIG. 12 is a cross-sectional view taken along line BB in FIG. 11, showing the arm and the like in the second position.

Embodiments embodying the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an image forming apparatus 1 according to the embodiment is an example of a specific embodiment of the image forming apparatus of the present invention. The image forming apparatus 1 is a color printer that forms images in multiple colors on a recording sheet SH using an electrophotographic method.

<Schematic configuration of image forming apparatus>
The image forming apparatus 1 includes an apparatus main body 9 having a substantially box-like shape, an image forming section 3 housed in the apparatus main body 9, a sheet tray 9C, a feeding section 20, a pair of post-fixing conveyance rollers 26, and a pair of ejection auxiliary rollers 28. and a pair of discharge rollers 29.

The sheet tray 9C is located below the image forming section 3. The sheet tray 9C stores recording sheets SH on which images are not formed in a stacked state. The recording sheet SH is paper, an OHP sheet, or the like.

A discharge tray 9T is formed on the upper surface of the apparatus main body 9. The discharge tray 9T supports the recording sheet SH on which image formation has been completed.

The feeding section 20 is located in front of the image forming section 3. The post-fixing conveyance roller pair 26 , the ejection auxiliary roller pair 28 , and the ejection roller pair 29 are located at the rear of the image forming section 3 .

The width direction of the device main body 9 is a direction perpendicular to the front-rear direction and the up-down direction. The front-rear direction, up-down direction, and width direction shown in each figure after FIG. 2 are shown corresponding to FIG. 1.

The feeding section 20 includes a feeding roller 21, a separating roller 22, a separating pad 22A, a first pair of conveying rollers 23, and a second pair of conveying rollers 24, which are arranged along the feeding path P1.

The feeding path P1 is a path that proceeds forward and upward from the front end of the sheet tray 9C, then makes a U turn, and proceeds backward to reach the image forming section 3.

The supply roller 21 sends out the recording sheet SH stored in the sheet tray 9C to the feeding path P1. The separation roller 22 and the separation pad 22A separate the recording sheets SH sent out by the supply roller 21 one by one when a plurality of recording sheets SH are overlapped.

The first transport roller pair 23 and the second transport roller pair 24 nip the recording sheets SH separated one by one by the separation roller 22 and the separation pad 22A, and transport them toward the image forming section 3.

The image forming section 3 is of a direct transfer color electrophotographic type. The image forming section 3 includes a process cartridge 4, a transfer belt 6, a scanner section 8, a fixing unit 7, and the like.

The process cartridge 4 corresponds to toner of four colors, black, yellow, magenta, and cyan, and is an assembly of four cartridges arranged in series in the front-rear direction. The process cartridge 4 includes four photoreceptors 5 corresponding to each color of toner, a developing roller (not shown), a charger, a toner storage section, and the like. The rotational axis of the photoreceptor 5 extends in the width direction of the apparatus main body 9. The transfer belt 6 faces each photoreceptor 5 from below.

The scanner unit 8 includes a laser light source, a polygon mirror, an fθ lens, a reflecting mirror, and the like. The scanner unit 8 irradiates each photoreceptor 5 in the process cartridge 4 with a laser beam from above.

In the process cartridge 4, the surface of each photoreceptor 5 is uniformly positively charged by a charger as it rotates, and then exposed by high-speed scanning with a laser beam irradiated from a scanner section 8. As a result, an electrostatic latent image corresponding to the image to be formed on the recording sheet SH is formed on the surface of each photoreceptor 5.

Next, toner is supplied from the toner storage portion to the surface of each photoreceptor 5 in correspondence with the electrostatic latent image, thereby forming a toner image. Then, when the recording sheet SH passes through the image forming section 3, the upwardly facing surface of the recording sheet SH faces the photoreceptor 5. Then, the toner image carried on the surface of each photoreceptor 5 is transferred to the upwardly facing surface of the recording sheet SH.

The fixing unit 7 is located behind the process cartridge 4. Although the specific configuration of the fixing unit 7 will be described later, the fixing unit 7 includes a first fixing member 30 and a second fixing member 40, each extending in the width direction.

The first fixing member 30 includes a heating roller 31 and a heater 32. The heating roller 31 is a hollow rotating body in which a thin elastic layer is formed on the surface of a thin metal cylinder extending in the width direction, and a release layer is formed on the surface of the elastic layer. The heating roller 31 contacts the recording sheet SH through its release layer. The heater 32 is a halogen heater extending in the width direction, and heats the heating roller 31 from the inner circumference. The heating roller 31 of the first fixing member 30 is driven to rotate.

The second fixing member 40 has a rotating shaft 45 and a pressure roller 41. The pressure roller 41 is an example of the "contact surface" and "roller" of the present invention.

The rotating shaft 45 is a metal round bar extending in the width direction. The pressure roller 41 has a thin resin layer formed on the surface of a thick foamed elastic layer that extends in the width direction and covers the rotating shaft 45 . The pressure roller 41 contacts the recording sheet SH through its resin layer. Pressure roller 41 is pressed toward heating roller 31 . The pressure roller 41 of the second fixing member 40 is driven by the heating roller 31 and rotates integrally with the rotating shaft 45 .

The fixing unit 7 heats and presses the recording sheet SH, onto which the toner image has been transferred, by sandwiching it between a heating roller 31 and a pressure roller 41, thereby thermally fixing the toner image onto the recording sheet SH.

The post-fixing conveyance roller pair 26 is located behind and above the heating roller 31 and the pressure roller 41. The post-fixing transport roller pair 26 includes a drive roller 26A and a pinch roller 26P.

The drive roller 26A is held by the fixing unit 7. The pinch roller 26P is held by a fixing cover 97, which will be described later.

The post-fixing transport roller pair 26 transports the recording sheet SH that has passed through the fixing unit 7 of the image forming section 3 along the discharge path P2.

The discharge path P2 guides the recording sheet SH upward, which passes through the fixing unit 7 of the image forming section 3 and is conveyed by the pair of conveyance rollers 26 after fixing, and makes a U-turn so that the surface on which the image is formed faces downward. This is the route for discharging the paper onto the discharge tray 9T.

The discharge auxiliary roller pair 28 is located above the post-fixing conveyance roller pair 26. The ejection roller pair 29 is located forward of the ejection auxiliary roller pair 28 and above the rear end of the ejection tray 9T.

The pair of discharge auxiliary rollers 28 nip the recording sheet SH conveyed along the discharge path P2 and convey it toward the pair of discharge rollers 29, and the pair of discharge rollers 29 nip the recording sheet SH and convey it to the discharge tray 9T. Discharge.

<Rear cover>
As shown in FIGS. 1 and 2, the device main body 9 has a rear cover 99. The rear cover 99 is swingable at its lower end around an opening/closing axis X99 extending in the width direction.

As shown in FIG. 1, the rear cover 99 closes an opening 9H formed in the rear surface of the device main body 9 in an upright state, and constitutes a part of the rear surface of the device main body 9.

As shown in FIG. 2, the rear cover 99 opens the opening 9H by swinging its upper end backward and downward. Thereby, the user can perform maintenance work and the like to remove the recording sheet SH that is jammed in the discharge path P2.

<Normal pressure mode, light pressure mode, and separation mode of heating roller and pressure roller>
By approaching or separating the heating roller 31 and the pressure roller 41, the normal pressure contact mode shown in FIG. 3(a), the light pressure contact mode shown in FIG. 3(b), and the mode shown in FIG. 3(c) are performed. It can be switched to the remote mode shown.

Switching between the normal pressure contact mode, the light pressure contact mode, and the separation mode is performed by the user manually operating a switching lever 70, which will be described later with reference to FIGS. 4 to 9.

The normal pressure contact mode shown in FIG. 3A is a mode in which the nip pressure between the heating roller 31 and the pressure roller 41 is a predetermined size suitable for plain paper having a typical thickness.

The light pressure contact mode shown in FIG. 3(b) is a mode in which the nip pressure between the heating roller 31 and the pressure roller 41 is smaller than the nip pressure in the normal pressure contact mode, and is suitable for envelopes, cardboard, etc. that are thicker than plain paper. In this mode, the nip pressure is increased. The compressive deformation of the pressure roller 41 in the light pressure contact mode is smaller than the compressive deformation of the pressure roller 41 in the normal pressure contact mode.

The separation mode shown in FIG. 3(c) is a mode in which the heating roller 31 and the pressure roller 41 are separated and no nip pressure is applied between them. If the recording sheet SH is jammed between the heating roller 31 and the pressure roller 41 which are in the normal pressure contact mode or the light pressure contact mode, the heating roller 31 and the pressure roller 41 can be switched to the separation mode. The jammed recording sheet SH can be extracted from between the heating roller 31 and the pressure roller 41.

<Body frame of the device body>
As shown in FIG. 4, the device main body 9 includes a pair of main body frames 90. As shown in FIG. The main body frame 90 located on one side in the width direction extends in the front-back direction and the up-down direction along one side of the device main body 9. The main body frame 90 located on the other side in the width direction extends in the front-back direction and the up-down direction along the other side surface of the device main body 9.

Although not shown, the device main body 9 has a plurality of connection frames each extending in the width direction and connecting a pair of main body frames 90.

<Fusing frame of the fusing unit>
As shown in FIGS. 4 and 5, the fixing unit 7 has a fixing frame 80 extending in the width direction. Fixing frame 80 is a resin molded product. As shown in FIG. 4, the pair of main body frames 90 support the outer ends of the fixing frame 80 in the width direction. The outer ends of the fixing frame 80 in the width direction are fastened to a pair of main body frames 90 with screws (not shown) or the like.

<Fuser cover>
As shown in FIGS. 1 and 2, the apparatus main body 9 includes a fixing cover 97. As shown in FIGS. The fixing cover 97 is an example of the "cover" of the present invention. The fixing cover 97 is swingable at its lower end around an opening/closing axis X97 extending in the width direction.

The fixing cover 97 is supported so as to be openable and closable by a fixing cover support portion 90G of the main body frame 90 shown in FIG.

As shown in FIG. 1, when the fixing cover 97 is in an upright state, it closes a portion of the fixing unit 7 located behind the pressure roller 41, and brings the pinch roller 26P into contact with the drive roller 26A.

As shown in FIG. 2, the fixing cover 97 opens a portion of the fixing unit 7 that is located behind the pressure roller 41 by swinging its upper end backward and downward.

With the rear cover 99 and the fixing cover 97 open, the user can remove the fixing unit 7 from the apparatus main body 9 by removing the screws or the like that fasten the fixing frame 80 to the pair of main body frames 90. This allows the user to replace the fixing unit 7 with a new one if a problem occurs with the fixing unit 7.

<Specific configuration of fixing unit>
As shown in FIG. 4, in the fixing unit 7, a pair of supported members 31G are connected to the outer ends of the heating roller 31 of the first fixing member 30 in the width direction. The supported member 31G is a cylinder centered on the rotation center X31 of the heating roller 31 and having a larger diameter than the heating roller 31.

As shown in FIG. 5, the fixing frame 80 supports the heating roller 31 so as to be rotatable around the rotation center X31 by surrounding the supported member 31G with a plurality of heating roller supporting parts 80G in a slidable manner.

Although not shown, the heating roller 31 is rotationally driven by the driving force of the motor being transmitted to the supported member 31G located on one side in the width direction via a transmission mechanism including a plurality of gear groups.

<Arm>
As shown in FIG. 4, the fixing unit 7 has a pair of arms 60. The pair of arms 60 are located outside the pressure roller 41 of the second fixing member 40 in the width direction.

The arm 60 is made of a metal plate having a surface perpendicular to the width direction. In this embodiment, the arm 60 is a sheet metal member formed by punching a steel plate.

In FIGS. 5 to 7, the arm 60 located on one side in the width direction is shown, and the arm 60 located on the other side in the width direction has the same configuration as the arm 60 located on one side in the width direction, so illustration thereof is omitted.

As shown in FIG. 5, the arm 60 has a generally L-shape when viewed from the side, extends rearward from its front end, is bent, and extends upward to reach its upper end. The arm 60 is formed with a rotation shaft hole 61, a bearing support hole 62, a spring locking hole 63, a convex portion 64, and a cap fitting portion 65.

The rotation shaft hole 61 is formed at the front end of the arm 60, and a portion thereof is opened by a notch. An arm support portion 86 is formed in a portion of the fixing frame 80 located at the front and lower side.

The arm support portion 86 has a shaft portion centered on the rotation axis X60 extending in the width direction, and a retaining portion protruding from the tip of the shaft portion in a radial direction outward of the rotation axis X60. There is.

The shaft part of the arm support part 86 is inserted into the rotation shaft hole 61, and the retaining part of the arm support part 86 prevents the front end of the arm 60 from coming off, so that the arm 60 is supported by the fixing frame 80 and rotates. It is rotatable around the moving axis X60.

As shown in FIG. 4, the second fixing member 40 has a pressed portion 44 that protrudes outward from the pressure roller 41 in the width direction. The pressed portion 44 includes the above-mentioned rotating shaft 45 and a pair of bearings 47.

The pair of bearings 47 rotatably support a portion of the rotating shaft 45 that protrudes outward in the width direction from the pressure roller 41 about the rotation center X41. The bearing 47 has a large diameter portion and a small diameter portion located outside the large diameter portion in the width direction and having a smaller diameter than the large diameter portion.

The outer end of the pressed portion 44 in the width direction is the outer end of the rotating shaft 45 in the width direction, or the outer end of the small diameter portion of the bearing 47 in the width direction. In this embodiment, since the outer end of the rotating shaft 45 in the width direction protrudes briefly outward in the width direction from the small diameter portion of the bearing 47, the outer end of the pressed portion 44 in the width direction is is the outer edge of

As shown in FIG. 5, the bearing support hole 62 of the arm 60 is formed in a bent portion of the arm 60. In the arm 60, the small diameter portion of the bearing 47 fits into the bearing support hole 62, and as shown in FIG. is supported.

As shown in FIG. 5, the spring locking hole 63 of the arm 60 is formed at an intermediate portion between the bent portion and the upper end of the arm 60. One end of a tension coil spring 69 is locked in the spring locking hole 63 .

A spring locking convex portion 89 is formed in the front and upper portion of the fixing frame 80 . The other end of the tension coil spring 69 is locked to the spring locking convex portion 89 .

The tension coil spring 69 exerts a biasing force to rotate the arm 60 around the rotation axis X60 in the clockwise direction in the drawing of FIG. The arm 60 receives the urging force of the tension coil spring 69 and presses the rotating shaft 45 and the bearing 47 of the pressed portion 44 so as to approach the rotation center X31 of the heating roller 31. As a result, the arm 60 presses the pressure roller 41 of the second fixing member 40 toward the heating roller 31 of the first fixing member 30 .

The convex portion 64 of the arm 60 protrudes forward and upward from an intermediate portion between the spring locking hole 63 and the upper end of the arm 60 . The convex portion 64 has a surface adjacent to the fixing frame 80 in the width direction, and restricts movement of the upper end side of the arm 60 in the width direction.

The position of arm 60 shown in FIG. 5 is the first position. The first position of the arm 60 is a position where the heating roller 31 and the pressure roller 41 are switched to the normal pressure contact mode shown in FIG. This is the position that determines the size.

As shown in FIGS. 4 and 5, the cap fitting portion 65 of the arm 60 is formed at the upper end of the arm 60. The arm 60 has a cap 66 made of resin. The cap 66 is fitted into the cap fitting portion 65.

The front and upward facing surface of the cap 66 is a contact surface 66B. The bottom surface of the concave portion of the cap 66 that is recessed rearward and downward from the abutment surface 66B is a surface that extends substantially parallel to the abutment surface 66B and faces forward and upward, and serves as an abutment surface 66A.

<Switching lever and cam>
As shown in FIG. 4, the fixing unit 7 has a pair of switching levers 70. The pair of switching levers 70 are located above the caps 66 of the pair of arms 60.

In FIGS. 5 to 7, the switching lever 70 located on one side in the width direction is illustrated, and the switching lever 70 located on the other side in the width direction has the same configuration as the switching lever 70 located on one side in the width direction, so the illustration is not made. Omitted.

As shown in FIGS. 5, 8, and 9, the switching lever 70 is a resin molded product in which a cam 71 and an operating portion 79 are integrally formed. The cam 71 has a shaft gripping portion 72, cam surfaces 73A and 73B, and reinforcing ribs 74. The switching lever 70 rotates around a cam support shaft 87 provided on the fixing frame 80.

The shaft gripping portion 72 is formed at the front end of the cam 71. The shaft gripping portion 72 has a cylindrical inner circumferential surface, and has a substantially C-shape in side view with a cutout at the front portion of the inner circumferential surface.

The cam surface 73A is a rearward-facing end surface of a rib that projects downward from the lower surface of the cam 71 and extends in the front-rear direction. The cam surface 73B is the rear surface of the cam 71 and is located above the cam surface 73A.

The reinforcing rib 74 projects upward from the front portion of the upper surface of the cam 71 and extends in the front-rear direction to reinforce the upper portion of the shaft gripping portion 72 .

The operating portion 79 is connected to a rear and upper portion of the cam 71 and protrudes rearward. The distance from the cam support shaft 87 to the operating section 79 is greater than the distance from the cam support shaft 87 to the cam 71.

As shown in FIGS. 5 and 8, a pair of opposing walls 85, a cam support shaft 87, and a cam stopper 88 are formed in the rear and upper portion of the fixing frame 80.

The inner width of the pair of opposing walls 85 is slightly larger than the outer width of the cam 71. The cam support shaft 87 extends in the width direction between the pair of opposing walls 85, and both ends of the cam support shaft 87 in the width direction are connected to the pair of opposing walls 85.

The cam stopper 88 extends in the width direction between the upper ends of the pair of opposing walls 85, and both ends of the cam stopper 88 in the width direction are connected to the upper ends of the pair of opposing walls 85. The cam stopper 88 has a relief portion 88A that is recessed upward from the lower surface at the center in the width direction.

The cam 71 of the switching lever 70 is rotatably supported by the fixing frame 80 by the shaft gripping portion 72 gripping the cam support shaft 87 . When the user manually operates the operating section 79 of the switching lever 70 with the rear cover 99 open, the cam 71 rotates. With the configuration in which the distance from the cam support shaft 87 to the operating portion 79 is greater than the distance from the cam support shaft 87 to the cam 71, the operating force by the user can be reduced.

The cam stopper 88 comes into contact with the upper surface of the cam 71 when the user moves the operating section 79 upward, and restricts rotation of the cam 71 . At this time, the upper end of the reinforcing rib 74 enters the relief portion 88A of the cam stopper 88, so the position of the cam stopper 88 can be lowered.

The reinforcing rib 74 reliably suppresses deformation of the shaft gripping portion 72 when the user applies too much operating force to move the operating portion 79 upward. As a result, the shaft gripping portion 72 is difficult to come off from the cam support shaft 87.

The cam 71 acts on the cap 66 of the arm 60 to rotate the arm 60 between a first position shown in FIG. 5, a second position shown in FIG. 6, and a third position shown in FIG. The second position and the third position are examples of the "second position" of the present invention.

As shown in FIG. 5, when the cam surfaces 73A and 73B of the cam 71 are separated from the contact surfaces 66A and 66B of the cap 66, the arm 60 is in the first position.

As shown in FIG. 6, when the operating portion 79 is pushed downward and the cam surface 73A of the cam 71 comes into contact with the contact surface 66A of the cap 66, the arm 60 moves from the first position around the rotation axis X60. It rotates counterclockwise in the paper of FIG. The arm 60 resists the biasing force of the tension coil spring 69 and moves the rotating shaft 45 and bearing 47 of the pressed portion 44 slightly away from the rotation center X31 of the heating roller 31. As a result, the arm 60 weakens the pressing force that presses the pressure roller 41 of the second fixing member 40 toward the heating roller 31 of the first fixing member 30 .

The position of the arm 60 when the cam surface 73A contacts the contact surface 66A is the second position. The second position of the arm 60 is a position where the heating roller 31 and the pressure roller 41 are switched to the light pressure contact mode shown in FIG. This is the position where the nip pressure is smaller than the nip pressure in the mode.

As shown in FIG. 7, when the operating portion 79 is further pushed downward and the cam surface 73B of the cam 71 contacts the contact surface 66B of the cap 66, the arm 60 moves to the second position around the rotation axis X60. 7 in the counterclockwise direction on the paper in FIG. The arm 60 resists the biasing force of the tension coil spring 69 and further moves the rotating shaft 45 and the bearing 47 of the pressed portion 44 away from the rotation center X31 of the heating roller 31. As a result, the arm 60 separates the pressure roller 41 of the second fixing member 40 from the heating roller 31 of the first fixing member 30 .

The position of the arm 60 when the cam surface 73B contacts the contact surface 66B is the third position. The third position of the arm 60 is a position where the heating roller 31 and the pressure roller 41 are switched to the separation mode shown in FIG. This is the position where no nip pressure is applied to the

The limit of the rotation range when the arm 60 rotates counterclockwise in the drawing of FIG. 7 around the rotation axis X60 is determined by the contact between the cam surface 73B and the contact surface 66B.

When the operating portion 79 is pushed upward from the state shown in FIG. 7 to the state shown in FIG. 6, the arm 60 rotates from the third position to the second position. When the operating portion 79 is pushed upward from the state shown in FIG. 6 to the state shown in FIG. 5, the arm 60 rotates from the second position to the first position. The rotation range of the arm 60 is the range shown in FIGS. 5 to 7.

<Regulatory Department and Regulation>
As shown in FIG. 4, the image forming apparatus 1 further includes a pair of regulating sections 94. The regulating portion 94 located on one side in the width direction is provided on the main body frame 90 located on one side in the width direction of the device main body 9 . The regulating portion 94 located on the other side in the width direction is provided on the main body frame 90 located on the other side in the width direction of the device main body 9 .

In this embodiment, the regulating portion 94 is a separate member from the main body frame 90 and is assembled to the main body frame 90. Note that the restricting portion 94 may be integrally formed with the main body frame 90.

The pair of regulating portions 94 protrude inward in the width direction at a position below the pressure roller 41. The pair of regulating portions 94 have regulating surfaces 95 .

The regulating surface 95 is located outside the arm 60 in the width direction and inside the width direction of the outside end of the pressed portion 44 (the outside end of the rotating shaft 45 in the width direction). facing.

The regulating surface 95 is a flat surface perpendicular to the width direction, and has an inclined surface 95S on its upper end side. The inclined surface 95S extends upward and is inclined outward in the width direction.

The arm 60 shown in solid lines in FIG. 4 corresponds to the first position shown in FIG. The lower end of the arm 60 shown by the two-dot chain line in FIG. 4 corresponds to the second position shown in FIG. The inclined surface 95S is inclined outward in the width direction so that the distance in the width direction from the arm 60 is the shortest when the arm 60 is in the second position.

As shown in FIGS. 5 to 7, the regulating surface 95 at least partially overlaps the lower end of the bent portion of the arm 60 in the rotation range of the arm 60 when viewed along the width direction.

More specifically, as shown in FIGS. 6 and 7, when viewed along the width direction, the regulating surface 95 overlaps the lower end of the bent portion of the arm 60 in the second and third positions. On the other hand, as shown in FIG. 5, when viewed along the width direction, the regulating surface 95 does not overlap the lower end of the bent portion of the arm 60 in the first position.

When viewed along the width direction, the regulating surface 95 is located on the opposite side of the first fixing member 30 with respect to the rotation center X41 of the rotating shaft 45. More specifically, when viewed along the width direction, the regulating surface 95 is located at a position overlapping the imaginary line K1 passing through the rotation center X31 of the heating roller 31 and the rotation center X41 of the rotating shaft 45.

<Effect>
In the image forming apparatus 1 , when the main body 9 of the apparatus receives acceleration in the width direction due to a fall or a collision, the weight of the pressure roller 41 , rotating shaft 45 , and bearing 47 of the second fixing member 40 that shifts in the width direction acts on the arm 60 . There are cases where In this case, as shown in FIGS. 6 and 7, the regulating surface 95 contacts the lower end of the bent portion of the arm 60 in the second or third position from the outside in the width direction. This prevents the arm 60 from shifting excessively in the width direction.

Further, in this image forming apparatus 1, a pair of regulating portions 94 having regulating surfaces 95 are provided on a pair of main body frames 90 of the apparatus main body 9. Therefore, in the image forming apparatus 1, for example, it is necessary to secure a space for arranging the regulating surface 95 in the fixing frame 80, or to form the regulating surface 95 by making a part of the fixing frame 80 protrude more than the other part. do not have.

Therefore, the image forming apparatus 1 can suppress the problem that the arm 60 is deformed in the width direction due to the weight of the second fixing member 40 and can improve the degree of freedom in designing the fixing unit 7.

In this image forming apparatus 1, the cam 71 of the switching lever 70 is configured to move the arm 60 to a first position where the nip pressure between the heating roller 31 and the pressure roller 41 is a predetermined value, and a position where the nip pressure is lower than the first position. and a third position where the heating roller 31 and the pressure roller 41 are separated from each other. With this configuration, when the arm 60 is at the second position or the third position, the nip pressure is smaller than that at the first position or is zero, so that the pressure roller 41 and the like of the second fixing member 40 are moved in the width direction. However, even in that case, since the regulating surface 95 contacts the lower end of the bent portion of the arm 60 in the second or third position from the outside in the width direction, the arm 60 may shift excessively in the width direction. can be suppressed.

Further, in this image forming apparatus 1, when viewed along the width direction, the regulating surface 95 is located at the lower end of the bent portion of the arm 60 in the second position shown in FIG. 6 or the third position shown in FIG. However, it does not overlap with the lower end of the bent portion of the arm 60 in the first position shown in FIG. When the arm 60 is in the first position, the nip pressure is greater than in the second position, so the pressure roller 41 and the like of the second fixing member 40 are less likely to shift in the width direction. Therefore, even if the regulating surface 95 does not regulate the arm 60 in the first position, the arm 60 is prevented from shifting excessively in the width direction. Moreover, the regulating surface 95 does not affect the movement of the arm 60 in the first position.

Further, in this image forming apparatus 1, as shown in FIG. 4, the regulating surface 95 is arranged on the outer side in the width direction so that the distance in the width direction to the arm 60 is the shortest when the arm 60 is in the second position. It has an inclined surface 95S that is inclined toward. With this configuration, when the arm 60 in the first position is shifted in the width direction and the arm 60 is rotated from that state to the second position, the inclined surface 95S slides into contact with the lower end of the bent portion of the arm 60. This allows the arm 60 to be returned to its original position in the width direction.

Furthermore, in this image forming apparatus 1, the contact surface of the second fixing member 40 that contacts the recording sheet SH is the pressure roller 41, and the arm 60 presses the pressed portion 44 consisting of the rotating shaft 45 and the bearing 47. With this configuration, rotation of the pressure roller 41 is not easily inhibited.

In addition, in this image forming apparatus 1, the arm 60 has a small diameter portion of the bearing 47 fitted into the bearing support hole 62, as shown in FIG. 5, and faces inward in the width direction of the arm 60, as shown in FIG. The surface supports the bearing 47 by being adjacent to the large diameter portion of the bearing 47. With this configuration, the image forming apparatus 1 can suppress relative displacement in the width direction between the pressure roller 41 and the like of the second fixing member 40 and the arm 60 with high reliability. Note that the weight of the pressure roller 41 and the like of the second fixing member 40 that shifts in the width direction due to the acceleration in the width direction acts directly on the arm 60, but even in that case, the regulating surface 95 prevents the arm 60 from moving. Excessive deviation in the width direction can be suppressed.

Further, in this image forming apparatus 1, as shown in FIG. 5, the regulating surface 95 is located on the opposite side of the first fixing member 30 with respect to X41 of the rotating shaft 45 when viewed along the width direction. ing. More specifically, when viewed along the width direction, the regulating surface 95 is located at a position overlapping the imaginary line K1 passing through the rotation center X31 of the heating roller 31 and the rotation center X41 of the rotating shaft 45. With this configuration, the arm 60 can be suitably regulated by the regulating surface 95 in the vicinity of the point of action where the arm 60 presses the pressed portion 44 of the second fixing member 40 . Note that the point of action is located far from the rotation axis X60 of the arm 60 and the force point to which the tension coil spring 69 is connected in the arm 60, that is, the spring locking hole 63, so that the regulating surface 95 in the above arrangement is not connected to the fixing frame. Although it is difficult to provide it in the device body 9, it is easy to provide it in the device body 9.

Further, in this image forming apparatus 1, the arm 60 is made of a metal plate having a surface perpendicular to the width direction. In this way, even if the arm 60 is made of a so-called sheet metal, the problem of deformation in the width direction due to the regulating surface 95 can be suppressed.

Furthermore, in this image forming apparatus 1, the apparatus main body 9 includes a pair of main body frames 90 that support the fixing frame 80. A pair of restriction portions 94 having restriction surfaces 95 are provided on a pair of main body frames 90 . With this configuration, when the fixing unit 7 is housed in the apparatus main body 9, the regulating surfaces 95 provided on the pair of main body frames 90 can suitably prevent the arm 60 from shifting excessively in the width direction.

As shown in FIG. 10, the image forming apparatus 1 is configured to include a regulating portion 294 and a regulating surface 295 provided on a fixing cover 97 instead of a regulating portion 94 and a regulating surface 95 provided on a main body frame 90. You can.

In the configuration shown in FIG. 10, a pair of regulating portions 294 are provided at the outer ends of the fixing cover 97 in the width direction.

The pair of regulating portions 294 protrude forward toward the bent portion of the arm 60 when the fixing cover 97 is closed. The pair of regulating portions 294 have regulating surfaces 295.

Although not shown, the regulating surface 295 is located outside the arm 60 in the width direction and at the outer end in the width direction of the pressed portion 44 (at the rotating shaft 45), similarly to the regulating surface 95 provided on the main body frame 90. It is located on the inner side in the width direction than the outer end in the width direction, and faces inward in the width direction.

The position of arm 60 shown in FIG. 10 is the first position. When the fixing cover 97 is closed, the regulating surface 295 overlaps the bent portion of the arm 60 in the first position when viewed along the width direction.

Although not shown, when the fixing cover 97 is closed, the regulating surface 295 also overlaps with the bent portion of the arm 60 in the second position or the third position when viewed along the width direction.

When the fixing cover 97 is open, the pair of restricting portions 294 are separated from the bent portion of the arm 60 by a large distance rearward.

In the configuration shown in FIG. 10, the restriction portion 294 and the restriction surface 295 provided on the fixing cover 97 prevent the arm 60 from deforming in the width direction due to the weight of the second fixing member 40, and provide freedom in designing the fixing unit 7. It is possible to improve the degree of

In addition, in the configuration shown in FIG. 10, when the fixing unit 7 is taken out from the apparatus main body 9 or housed in the apparatus main body 9 with the fixing cover 97 open, the pair of restriction parts 294 having the restriction surfaces 295 are removed. It becomes difficult to interfere with the fixing unit 7. Therefore, the user can easily attach and detach the fixing unit 7 to and from the apparatus main body 9.

In the configuration shown in FIGS. 11 and 12, a second fixing member 340 having an endless belt 341 and a belt support member 345 is used instead of the second fixing member 40 having the pressure roller 41. As shown in FIG. 12, a pressed part support hole 362 is formed in the arm 60 instead of the bearing support hole 62.

As shown in FIG. 11, the endless belt 341 is an example of the "contact surface" of the present invention. The belt support member 345 is an example of the "pressed portion" of the present invention.

The endless belt 341 is a heat-resistant and flexible cylindrical body made of a thin plate of resin such as polyimide or a thin plate of metal such as stainless steel, and contacts the recording sheet SH. Although illustration is simplified, the belt support member 345 includes a resin member and an elastic member that extend in the width direction and support the endless belt 341 from the inner periphery, and a metal member that extends in the width direction and reinforces the resin member etc. , is composed of.

The belt support member 345 has a pair of flange portions 345F and a pair of protrusion portions 345A.

The pair of flange portions 345F adjoin the endless belt 341 from the outside in the width direction, and restrict the endless belt 341 from shifting in the width direction. The pair of protruding portions 345A protrude outward in the width direction from the pair of flange portions 345F.

The outer end in the width direction of the belt support member 345, which is the pressed portion, is the outer end in the width direction of the pair of protrusions 345A.

As shown in FIG. 12, the protruding portion 345A passes through the pressed portion support hole 362 of the arm 60. The cross-sectional shape of the protruding portion 345A is a substantially rectangular shape that is elongated in the direction approaching the rotation center X31 of the heating roller 31.

Under the urging force of the tension coil spring 69, the arm 60 rotates the heating roller 31 by rotating the protruding portion 345A of the belt support member 345, which is the pressed portion, by the edge of the pressed portion support hole 36 that is farthest from the heating roller 31. Press it so that it approaches the center X31. As a result, the arm 60 presses the endless belt 341 of the second fixing member 340 toward the heating roller 31 of the first fixing member 30 .

As shown in FIG. 11, a pair of protrusion guides 383 are provided at a lower end of the fixing frame 80 located on the outer side in the width direction than the pair of arms 60. As shown in FIG.

As shown in FIG. 12, the protrusion guide 383 has a guide hole 383G. The guide hole 383G guides the protrusion 345A toward and away from the rotation center X31 of the heating roller 31.

As shown in FIG. 11, the regulating surface 95 is located outside the arm 60 in the width direction and at the outside end in the width direction of the belt support member 345 which is the pressed portion (the outside end in the width direction of the pair of protrusions 345A). It is located on the inside in the width direction and faces inside in the width direction.

The position of the arm 60 shown in FIG. 12 is the second position. Although not shown, the arm 60 rotates to the first position and the third position.

When viewed along the width direction, the regulating surface 95 overlaps with the lower end of the bent portion of the arm 60 in the second position shown in FIG. 12 or the third position not shown, while it is in the first position not shown. It does not overlap with the lower end of the bent portion of the arm 60 in the state.

When viewed along the width direction, the regulating surface 95 is located on the opposite side of the rotation center X31 of the heating roller 31 with respect to the protrusion 345A.

In the configurations shown in FIGS. 11 and 12, the problem of deformation of the arm 60 in the width direction due to the weight of the endless belt 341 and the belt support member 345 of the second fixing member 340 can be suppressed, and the degree of freedom in designing the fixing unit 7 can be improved. and can be realized.

Furthermore, the endless belt 341 facilitates increasing the nip width when the first fixing member 30 and the second fixing member 340 sandwich the recording sheet SH.

Further, when viewed along the width direction, as shown in FIG. 12, the regulating surface 95 is located on the opposite side of the rotation center X31 of the heating roller 31 with respect to the protruding portion 345A. With this configuration, the arm 60 can be suitably regulated by the regulating surface 95 in the vicinity of the point of action where the arm 60 presses the belt support member 345, which is the pressed portion of the second fixing member 340.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention can be modified and applied as appropriate without departing from the spirit thereof.

In the embodiment, the first fixing member 30 has a heating roller 31 and the second fixing member 40 has a pressure roller 41, and the first fixing member 30 has a heating roller 31 and the second fixing member 40 has a pressure roller 41. 40 has an endless belt 341. However, the present invention is not limited to this configuration. For example, both the first and second fixing members may have endless belts. Further, the first fixing member may include an endless belt, and the second fixing member may include a roller.

In the embodiment, the second fixing member 40, 340 is pressed toward the first fixing member 30 having the heater 32, but the present invention is not limited to this configuration. For example, a second fixing member having heating means may be pressed toward the first fixing member.

In the embodiment, the cam 71 acting on the arm 60 is part of the switching lever 70 and is rotated by manual operation, but the present invention is not limited to this configuration. For example, the cam acting on the arm 60 may be rotated by being driven by a motor or the like. The cam acting on the arm 60 may rotate in conjunction with the rocking of the fixing lever 97 and the rear cover 99.

In the embodiment, the cover is a fixing cover 97 that opens and closes by swinging, but the present invention is not limited to this configuration. For example, the cover may be opened and closed by sliding. Further, the cover may be an exterior cover of the device main body.

INDUSTRIAL APPLICATION This invention can be utilized for an image forming apparatus, a multifunctional machine, etc. which are equipped with an image forming function and an image reading function.

1, 2, 3... Image forming apparatus, 9... Apparatus main body, 7... Fixing unit 30... First fixing member, 40, 340... Second fixing member SH... Recording sheet, 80... Fixing frame, 60... Arm 41, 341 ...Contact surface (41...roller (pressure roller), 341...endless belt)
44, 345...Pressed part (345...Belt support member)
45...Rotating shaft, 47...Bearing, 95, 295...Restricting surface 71...Cam, 95S...Slanted surface, X41...Rotation center of rotating shaft 90...Main frame, 97...Cover (fixing cover)

Claims (11)

The device body,
a fixing unit housed in the apparatus main body, the fixing unit heating the recording sheet while sandwiching it between a first fixing member and a second fixing member each extending in the width direction, and thermally fixing the toner image onto the recording sheet; An image forming apparatus comprising:
The fixing unit includes a fixing frame that supports the first fixing member;
an arm rotatably supported by the fixing frame and pressing the second fixing member toward the first fixing member;
The second fixing member has a contact surface that contacts the recording sheet, and a pressed portion that protrudes outward in the width direction from the contact surface and is pressed by the arm,
A regulating surface provided on the device main body, located outside the arm in the width direction and inside the width direction of the outer end of the pressed portion in the width direction, and facing inward in the width direction. The image forming apparatus further includes the regulating surface that at least partially overlaps the arm in a rotation range of the arm when viewed along the width direction. The fixing unit includes a cam that is rotatably supported by the fixing frame and acts on the arm;
The cam moves the arm between a first position where the nip pressure between the first fixing member and the second fixing member is a predetermined value, and a second position where the nip pressure is smaller than the first position, or the first fixing position where the nip pressure is smaller than the first position. The image forming apparatus according to claim 1, wherein the image forming apparatus is rotated to a second position where the member and the second fixing member are separated from each other. The image forming apparatus according to claim 2, wherein when viewed along the width direction, the regulating surface overlaps with the arm in the second position, but does not overlap with the arm in the first position. . The regulating surface has an inclined surface that slopes outward in the width direction so that the distance to the arm in the width direction is the shortest when the arm is in the second position. Item 2. Image forming apparatus according to item 2. the contact surface is a roller;
5. The image forming apparatus according to claim 1, wherein the pressed portion includes a rotating shaft that rotates integrally with the roller, and a bearing that rotatably supports the rotating shaft. The image forming apparatus according to claim 5, wherein the arm supports the bearing. The image forming apparatus according to claim 5, wherein the regulating surface is located on the opposite side of the first fixing member with respect to the rotation center of the rotation shaft when viewed along the width direction. the contact surface is an endless belt;
The image forming apparatus according to any one of claims 1 to 4, wherein the pressed portion is a belt support member that supports the endless belt from an inner periphery. 5. The image forming apparatus according to claim 1, wherein the arm is made of a metal plate having a surface perpendicular to the width direction. The device main body has a main body frame that supports the fixing frame,
The image forming apparatus according to any one of claims 1 to 4, wherein the regulating surface is provided on the main body frame. The device main body includes a main body frame that supports the fixing frame;
a cover that is openably and closably supported by the main body frame and has the regulating surface;
5. The image forming apparatus according to claim 1, wherein when the cover is closed, the regulating surface overlaps the arm when viewed along the width direction.

Images