JP7040342B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming device using the fixing device, and particularly to a device using a fixing belt.

Conventionally, in a belt-type fixing device, a fixing unit having a fixing belt and a pressure unit having a pressure belt have a configuration in which the relative positional relationship changes in the direction of separation and contact depending on the printing mode. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-36391 (page 17, FIG. 14)

However, if the nip state (relative positional relationship of the nip portion between the fixing belt and the pressure belt) is changed depending on the thickness and type of the medium, the environment of rotational movement of the belt changes and comes into contact with the flange surface. The shearing force generated in the radial direction of the end face of the belt causes cracks in the end face of the belt, and the tension of the belt increases more than necessary due to the change in the movement path, resulting in an increase in rotational load torque. there were.

The fixing device according to the present invention is a fixing device including a first fixing belt unit and a second fixing belt unit that can move in a direction in which the first fixing belt unit is brought into contact with and separated from the first fixing belt unit.
The first fixing belt unit is
An endless first fixing belt, a first roller inside the first fixing belt, which rotates in contact with the inner surface of the first fixing belt, and the inside of the first fixing belt. A first pressurizing member that presses the inner surface of the first fixing belt is provided.
The second fixing belt unit is
The movable plate that can move in the contacting and separating directions, the endless second fixing belt, and the first fixing belt and the first fixing belt that are inside the second fixing belt and are supported by the movable plate. A second roller that faces the first roller via the fixing belt 2 and presses against the inner side surface of the second fixing belt to rotate, and the movable inside of the second fixing belt. A second pressurizing member that is supported by the plate, faces the first pressurizing member via the first fixing belt and the second fixing belt, and presses the inner surface of the second fixing belt. A path setting member that is inside the second fixing belt and is deployed on the movable plate to determine the rotational movement path of the second fixing belt, and the movable inside of the second fixing belt. It is provided with a movable guide member that is supported by the plate and guides the inner surface of the second fixing belt.
The movable guide member is rotatably held by the movable plate and includes a contact portion that abuts on the second fixing belt and an engaging portion, and the contact portion is attached to the second fixing belt. A third urging member urging in a direction away from the above and the engaging portion of the movable guide member are engaged to regulate the rotation of the movable guide member by the third urging member. It is provided with an engaged portion fixed to the fixing device main body, and is provided with an engaged portion.
As the movable plate moves in the direction of contact and separation, the movable guide member rotates to change the guide position of the contact portion with respect to the second fixing belt.

According to the present invention, even when the relative positional relationship of the second fixing belt with respect to the first fixing belt changes, it is possible to always guide the second fixing belt to an appropriate rotational movement path in an appropriate state. It is possible to suppress malfunctions and the like.

It is a schematic block diagram which shows schematic the structure of the main part of the image forming apparatus of Embodiment 1 which adopts the fixing apparatus by this invention. It is a block diagram of the main part of the fixing device of Embodiment 1 by this invention. It is sectional drawing of the upper fixing belt. It is an external perspective view of the upper flange and the lower flange constituting the fixing device seen from diagonally above. It is a block diagram which shows the relative position of the upper flange and the lower flange at the time of operation (plain paper printing) of a fixing device, (a) is a plan view seen from the minus side of a Y axis, and (b) is a plan view. , Is a side view seen from the plus side of the X-axis. It is a figure which provides the explanation of the movement of the movable guide rib when the lower flange moves in the Z-axis direction with the movable plate with respect to the upper flange, and (a) shows the state of a fixing device at the time of non-printing. (B) shows the state of the fixing device during the thick paper printing operation. (A) shows the holding mechanism of the lower pressure member when the movable plate is in the plain paper printing position, and (b) is the holding mechanism of the pressure roller when the movable plate is also in the plain paper printing position. Is shown. (A) shows the holding mechanism of the lower pressure member when the movable plate is in the thick paper printing position, and (b) shows the holding mechanism of the pressure roller when the movable plate is also in the thick paper printing position. .. It is a figure which provides the explanation of the operation state at the time of printing the recording paper of a different thickness in the fixing apparatus of Embodiment 1, (a) is the operation state at the time of printing a plain paper of a general thickness. (B) shows an operating state when printing thick recording paper. It is a main part block diagram of the fixing device of Embodiment 2 based on this invention. It is a block diagram which shows the motor control part which drives a stepping motor. In the operation explanatory view of the fixing device provided with the guide rib fixed to the lower flange, (a) shows the state of the lower fixing belt in the operating state of forming the upper fixing belt and the nip portion as shown in FIG. (B) is a partially enlarged view of the dotted circle portion in (a).

Embodiment 1.
FIG. 1 is a schematic configuration diagram schematically showing a configuration of a main part of an image forming apparatus according to the first embodiment in which the fixing apparatus according to the present invention is adopted.

The image forming apparatus 100 shown in the figure has a configuration as, for example, a color electrophotographic printer, and a paper feed cassette 104 for storing a recording paper 101 as a recording medium is mounted inside the apparatus, and the recording paper 101 is fed. A paper feed roller 105 taken out from the cassette 104 and a resist roller 106 for feeding the recording paper 101 to the image forming unit at a predetermined timing are arranged. Further, in the image forming apparatus 100, as an image forming portion, a developing apparatus 110K for forming an image of toner as a black (K) developer, a developing apparatus 110Y for forming a yellow (Y) toner image, and a magenta (Mazeda) ( The developing device 110M for forming the toner image of M) and the developing device 110C for forming the toner image of cyan (C) (may be simply 110 if it is not necessary to distinguish between these developing devices). They are arranged in order from the upstream side along the transport path of the recording sheet 101. These developing devices 110 have the same configuration except that toner of a predetermined color is used.

For example, as shown in the developing device 110K using black (K) toner, each developing device 110 has a photoconductor drum 111 as an electrostatic latent image carrier and its surroundings from the upstream side in the rotation direction (arrow direction). The charging device 112 that supplies and charges the surface of the photoconductor drum 111, which is arranged in order, and the surface of the charged photoconductor drum 111 are selectively irradiated with light based on the image data to perform electrostatic latency. The exposure device 113 that forms an image, the developer supply device 114 that develops an electrostatic latent image formed on the photoconductor drum 111 with the toner to form a toner image, and the toner remaining on the surface of the photoconductor drum 111. A cleaning device 115 or the like arranged in contact with the photoconductor drum 111 for removal is provided.

Further, in the image forming apparatus 100, as a belt type transfer apparatus 120, the recording paper 101 is conveyed, and the toner image formed by each developing apparatus is sequentially transferred to the conveying recording paper 101. The drive roller 122, which is rotated from a drive unit (not shown) to drive the endless transfer belt 121 in the direction of the arrow, and the tension roller 123, which is paired with the drive roller 122 and stretches the endless transfer belt 121, are provided.

Then, the fixing device 10 for fixing the toner image formed on the recording paper 101 by applying heat and pressure, and the recording paper 101 passing through the fixing device 10 are conveyed, and the recording paper 101 on which the image is fixed is stored. The transport rollers 131 and 132 to be discharged are arranged in the paper discharge loading unit 130. The fixing device 10 will be described in detail later.

Each axis of X, Y, and Z in FIG. 1 has an X axis in the transport direction when the recording paper 101 passes through the image forming portion, and a Y axis in the rotation axis direction of the photoconductor drum 111. The Z axis is taken in the direction orthogonal to both of these axes. Further, when each axis of X, Y, and Z is shown in another figure described later, it is assumed that these axial directions indicate a common direction. That is, the X, Y, and Z axes of each figure indicate the arrangement direction when the depiction portion of each figure constitutes the image forming apparatus 100 shown in FIG. Further, here, it is assumed that the Z axis is arranged so as to be substantially in the vertical direction.

In the above configuration, the outline of the printing operation of the image forming apparatus will be described with reference to FIG. The dotted line arrow in the figure indicates the transport direction of the transportable recording sheet 101.

When the image forming apparatus 100 receives a print command from a higher-level device (not shown), the recording paper 101 stored in the paper feed cassette 104 is taken out from the paper feed cassette 104 by the paper feed roller 105, and is slanted by the resist roller 106. After the rows are corrected, they are conveyed to an image forming unit including four developing devices 110 and a transfer device 120 at predetermined timings.

At this time, as the photoconductor drum 111 rotates in the direction of the arrow, the surface of the photoconductor drum 111 of each developing device 110 is charged by the charging device 112 to which a voltage is applied by a power supply device (not shown). Subsequently, when the surface of the charged photoconductor drum 111 reaches the vicinity of the exposure device 113, the surface of the photoconductor drum 111 is exposed by the exposure device 113, and an electrostatic latent image corresponding to the image information is formed on the surface of the photoconductor drum 111. This electrostatic latent image is developed by the developer supply device 114, and a toner image corresponding to each color is formed on the surface of the photoconductor drum 111.

The recording paper 101 conveyed to the image forming unit is attracted to the endless transfer belt 121 and conveyed in the arrow direction, and is sequentially sandwiched between the photoconductor drum 111 rotating in the arrow direction of each developing device 110 and the endless transfer belt 121. In the process, the toner images of each color of black (K), yellow (Y), magenda (M), and cyan (C) formed at a predetermined timing are sequentially superimposed and transferred, and the toner of each color is transferred onto the recording paper 101. A color image is formed by. The photoconductor drum 111 is subjected to the next charging after the residual toner remaining on the photoconductor drum 111 after transfer is scraped off by the cleaning device 115 and cleaned.

Subsequently, the recording paper 101 on which a color image of toner of each color is formed is conveyed to the fixing device 10. The toner image on the recording paper 101 is pressurized and heated by the fixing device 10 to be melted and fixed on the recording paper 101. Further, the recording paper 101 is discharged to the paper discharge loading unit 130 by the transport rollers 131 and 132, and the printing operation is completed.

FIG. 2 is a configuration diagram of a main part of the fixing device 10, FIG. 3 is a cross-sectional view of the upper fixing belt 210, and FIG. 4 shows an upper flange 201 and a lower flange 251 constituting the fixing device 10 from diagonally above. It is an external perspective view as seen.

The upper fixing belt 210 and the lower fixing belt 260 are endless belts extending so as to include a recording area in the width direction (Y-axis direction) of the recording sheet 101 conveyed in the arrow A direction. When mounted on a belt, its cross-sectional shape is supported in a rice ball shape by a straight portion and an arc portion as shown in FIG. Hereinafter, the extending direction of these fixing belts 210 and 260 may be referred to as the longitudinal direction of the fixing device 10.

As shown in the cross-sectional view of FIG. 3, the upper fixing belt 210 as the first fixing belt has a laminated structure in which the elastic layer 210b is formed on the base material 210a and the release layer 210c is formed on the elastic layer 210b. It has become. Since the upper fixing belt 210 and the lower fixing belt 260 as the second fixing belt are the same at least in the cross-sectional configuration, the upper fixing belt 210 will be described here.

The base material 210a can be formed of a metal such as Ni or SUS or a PI resin having a thickness in the range of 30 μm to 50 μm. Here, a 50 μm SUS material is used. The elastic layer 210b can be formed of silicon rubber having a thickness in the range of 100 μm to 350 μm. Here, it is set to 300 μm. A PFA (perfluoroalkoxy alkane) layer is formed as the release layer 210c. The base material 210a is inside the endless belt.

The elastic upper fixing belt 210 is supported from the inside at three points by a drive roller 211 and tension rollers 212, 213 as first rollers arranged so as to be in contact with the inner side surface thereof. Halogen lamps 211 and 222 that also extend in the longitudinal direction are arranged inside the upper fixing belt 210, and the inside of the upper fixing belt 210 is supported between the drive roller 211 and the tension roller 212, which will be described later. An upper pressurizing member 215 as a first pressurizing member forming a nip region is arranged so as to be formed, and further, between the halogen lamps 211 and 222 and the drive roller 211, the upper pressurizing member 215, and the tension roller 212. The upper reflector 223 is arranged so as to separate them from each other.

On the other hand, the elastic lower fixing belt 260 is supported from the inside at three points by a pressure roller 261 as a second roller and tension rollers 262 and 263 as a routing member arranged so as to be in contact with the inner side surface thereof. ing. A halogen lamp 271 that also extends in the longitudinal direction is disposed inside the lower fixing belt 260, and the inside of the lower fixing belt 260 is supported between the pressure roller 261 and the tension roller 262, which will be described later. A lower pressurizing member 265 is arranged as a second pressurizing member forming the nip region, and further, between the halogen lamp 271 and the pressurizing roller 261 and the lower pressurizing member 265 and the tension roller 262. The lower reflector 273 is arranged so as to separate them from each other.

As shown in FIG. 2, the drive roller 211 and the pressure roller 261 and the upper pressure member 215 and the lower pressure member 265 are arranged so as to face each other via the upper fixing belt 210 and the lower fixing belt 260, respectively. As will be described later, the upper fixing belt 210 and the lower fixing belt 260 are configured to be pressure-contactable so as to form a nip portion in an operating state.

Both ends of the upper fixing belt 210 are further regulated by a pair of upper flanges 201 arranged at both ends in the longitudinal direction. Since these pair of upper flanges 201 are formed plane-symmetrically with respect to a virtual center plane that intersects vertically at the center in the longitudinal direction, for example, the upper flanges 201 arranged on the back side in FIG. 2 are described here. Will be explained.

FIG. 4 is an external perspective view of the upper flange 201 and the lower flange 251 described later as viewed from diagonally above.

As shown in the figure, the upper flange 201 is mainly formed of a flat plate-shaped member formed in a substantially arc shape, and is a cross-sectional circle extending perpendicularly to the flat surface portion 201a from the inner end portion of the flat surface portion 201a. A pair of arc-shaped upper guide ribs 202 and 203 are formed. As shown in FIG. 2, the upper flange 201 is arranged such that the upper guide ribs 202 and 203 are inside the upper fixing belt 210 and guide the inner side surface thereof at the inner end portion of the upper fixing belt 210. The flat surface portion 201a of the upper flange 201 abuts on the inner end portion of the upper fixing belt 210 to restrict movement in the same direction.

Therefore, the upper fixing belt 210 rotates while being guided by the drive roller 211, the upper pressurizing member 215, the tension rollers 212, 213, and the upper guide ribs 202, 203 that guide only both ends thereof.

The upper fixing belt 210 does not move in the position in the apparatus, whereas the lower fixing belt 260 can move in the direction of contact with the upper fixing belt 210 (here, the Z-axis direction) as described later. It is configured. Therefore, the pressure roller 261, the tension roller 262, 263, the lower pressure member 265, the halogen lamp 271, and the lower reflector 273 arranged inside the lower fixing belt 260 are all movable together with the lower flange 251 described later. It is arranged on the plate 310. In FIG. 2, for the sake of simplicity, the movable plate 310 schematically shows only the outer shape of both lower end portions.

Both ends of the lower fixing belt 260 are further regulated by a pair of lower flanges 251 arranged at both ends in the longitudinal direction. Since these pair of lower flanges 251 including the movable guide rib 253 are formed plane-symmetrically with respect to a virtual center plane that intersects vertically at the center in the longitudinal direction, for example, the back side in FIG. 2 is shown. The lower flange 251 and the movable guide rib 253 arranged in the above will be described.

FIG. 4 is an external perspective view of the lower flange 251 and the upper flange 201 as viewed from diagonally above.

As shown in the figure, the lower flange 251 is mainly formed of a flat plate-shaped member formed in a substantially shape, and the predetermined portion of the flat surface portion 251a has a cross section extending perpendicularly to the flat surface portion 251a. An arc-shaped lower fixed guide rib 252 and a movable guide rib 253 as a movable guide member rotatably held with respect to the flat surface portion 251a are arranged. At the tip of the movable guide rib 253, a contact portion 253a that abuts on the inside of the lower fixing belt 260 is formed. The movable guide rib 253 will be described in detail later.

As shown in FIG. 2, the lower flange 251 has a lower fixing guide rib 252 and a movable guide rib 253 inside the lower fixing belt 260 at the inner end portion of the lower fixing belt 260, and guides the inner side surface thereof. The flat surface portion 251a of the lower flange 251 abuts on the inner end portion of the lower fixing belt 260 to restrict movement in the same direction.

Therefore, the lower fixing belt 260 will be described later while being guided by the pressure roller 261, the lower pressure member 265, the tension rollers 262, 263, and the lower fixed guide rib 252 that guides only both ends thereof, and the movable guide rib 253. Rotate and move like.

Therefore, in an operating state in which the drive roller 211 and the pressure roller 261 are in pressure contact with each other, when the drive roller 211 receives a rotational force via a drive source and a drive transmission mechanism (not shown) and rotates in the direction of the arrow, the rotational force increases. The upper fixing belt 210 and the lower fixing belt 260 are transmitted to the fixing belt 210, the lower fixing belt 260, and the pressure roller 261 and move in the same direction (arrow direction), and the pressure roller 261 is also provided in the arrow direction. Turn around. The movement of the upper fixing belt 210 and the lower fixing belt 260 at this time while rotating may be hereinafter referred to as rotational movement.

Further, in the operating state where the drive roller 211 and the pressure roller 261 are in pressure contact with each other, the drive roller 211 and the pressure roller 261 are sandwiched by the pressure contact portion and the upper pressure member 215 and the lower pressure member 265. The upper fixing belt 210 and the lower fixing belt 260 formed a nip portion in this region. At this time, the upper fixing belt 210 and the lower fixing belt 260 are supported so that their cross-sectional shapes are onigiri-shaped so that the straight portion forming the nip portion can be formed relatively long, as shown in FIG. ing.

The thermopile 230 is installed at a position where the temperature detection unit faces the upper fixing belt 210 in order to detect the temperature of the upper fixing belt 210, and the thermopile 280 detects the temperature of the lower fixing belt 260. Is installed at a position facing the lower fixing belt 260.

The movable plate 310 slides in the same direction with respect to the main body of the fixing device 10 so that the lower fixing belt 260 to be held can move in the direction in which the lower fixing belt 260 is separated from the upper fixing belt 210 (here, the Z-axis direction). It is held freely and is driven and moved by a pair of cam gears 301, 302 that mesh with each other. The upper fixing belt 210 and the member arranged inside the upper fixing belt 210 and acting on the upper fixing belt 210 are referred to as the upper fixing belt unit 304 as the first fixing belt unit, and the movable plate 310 and the movable plate 310 have the upper fixing belt unit 304. A member that is held and moves together may be referred to as a lower fixing belt unit 305 as a second fixing belt unit.

That is, the movable plate 310 is provided with an engaging portion (not shown) that engages with the cam guide 301a of the cam gear 301 and the cam guide 302a of the cam gear 302 above the rotation axis of each gear. The movable plate 310 moves in the Z-axis direction according to the rotation of the cam guide 301a and the cam guide 302a. At this time, it is assumed that the movable plate 310 is urged in the negative direction of the Z axis by its own weight or urging means. Here, these cam gears 301 and 302 are rotationally driven by a drive motor provided in the main body of the fixing device 10, and this drive motor is from a control unit (not shown) that controls the entire image forming apparatus 100. It is rotationally driven based on the command.

The configuration of the movable guide rib 253 and its movement will be further described. FIG. 5 is a configuration diagram showing the relative positions of the upper flange 201 and the lower flange 251 when the fixing device 10 is in operation (printing on plain paper), and FIG. 5A is a view from the minus side of the Y axis. It is a plan view, and the figure (b) is a side view seen from the plus side of the X axis.

As shown in FIGS. 2, 4, and 5, the movable guide rib 253 is rotatably held by the rotation shaft 254 planted from the lower flange 251 and is also provided on the rotation shaft 254 so that both ends are locked. The contact portion 253a is urged in the arrow B direction (counterclockwise direction) by the torsion spring 267 as a third urging member mounted on the post 268 and the movable guide rib 253.

Further, the movable guide rib 253 includes an engaging piece 253b extending at a tip portion substantially at a right angle to the radial direction. As shown in FIGS. 4 and 5, the engaging piece 253b is arranged on the back side of the lower flange 251 (the side opposite to the contact portion 253a) in the longitudinal direction (Y-axis direction). On the other hand, the upper flange 201 is provided with a restricting member 201b as an engaged portion at a position where the engagement piece 253b can be brought into contact with the upper flange 201b.

FIG. 6 is a diagram for explaining the movement of the movable guide rib 253 when the lower flange 251 moves in the Z-axis direction with the movable plate 310 with respect to the upper flange 201, and FIG. 6A is a diagram. The state of the fixing device 10 when the paper is not passed is shown, and FIG. 3 (b) shows the state of the fixing device 10 when the thick paper printing operation is performed.

FIG. 6A shows the state of the fixing device 10 when the paper is not passed. At this time, the lower flange 251 that moves in the Z-axis direction along with the movable plate 310 is most separated from the upper flange 201. The standby position is set, and the engaging piece 253b of the movable guide rib 253 is separated from the restricting member 201b of the upper flange 201. At this time, the movable guide rib 253 urged in the direction of arrow B by the torsion spring 267 is restricted from rotating in the same direction by a restricting member (not shown), and stays at the initial rotation position shown in FIG. There is.

FIG. 6B shows the state of the fixing device 10 during the thick paper printing operation. At this time, the lower flange 251 that moves in the Z-axis direction along with the movable plate 310 and the movable plate 310 is relative to the upper flange 201. The position is closer to the thick paper printing position. In this moving process, the engaging piece 253b of the movable guide rib 253 comes into contact with the regulating member 201b of the upper flange 201, and is further pushed down by the regulating member 201b.

As a result, the movable guide rib 253 rotates around the rotation shaft 254 in the direction of arrow C (clockwise) against the urging force of the torsion spring 267, and the contact portion 253a thereof moves in the plus direction of the X axis. It is displaced to the overhanging thick paper printing rotation position.

FIG. 5 shows a state of the fixing device 10 during a plain paper printing operation. At this time, the lower flange 251 that moves in the Z-axis direction along with the movable plate 310 and the movable plate 310 is larger than the above-mentioned thick paper printing position. It is a plain paper printing position that is closer to the upper flange 201. In this moving process, the engaging piece 253b of the movable guide rib 253 is relatively further pushed down by the regulating member 201b.

As a result, the movable guide rib 253 further rotates around the rotation shaft 254 in the direction of arrow C (clockwise) against the urging force of the torsion spring 267, and the contact portion 253a is at the thick paper printing rotation position. Further, it is displaced to the position of rotation of plain paper printing overhanging in the positive direction of the X-axis.

Next, a method of holding the lower pressurizing member 265 and the pressurizing roller 261 by the movable plate 310 will be described. FIG. 7A shows a holding mechanism of the lower pressure member 265 when the movable plate 310 is in the plain paper printing position, and FIG. 7B shows a holding mechanism when the movable plate 310 is also in the plain paper printing position. The holding mechanism of the pressure roller 261 is shown. Further, FIG. 8A shows a holding mechanism of the lower pressure member 265 when the movable plate 310 is in the thick paper printing position, and FIG. 8B shows a holding mechanism when the movable plate 310 is also in the thick paper printing position. The holding mechanism of the pressure roller 261 is shown.

As shown in FIG. 7A, a first rotating arm 352 for deploying a fixing portion 353 for fixing the lower pressurizing member 265 is rotatable on the rotating base 350 to be planted on the movable plate 310. It is held in. The first rotating arm 352 has a tip portion 352a hung on the other end of a first compression spring 354 as a first urging member whose one end is hung on a movable plate 310. Is urged in the clockwise direction (arrow direction).

Therefore, when the movable plate 310 is in the plain paper printing position, the lower pressure member 265 fixed to the fixing portion 353 holds the upper fixing belt 210 and the lower fixing belt 260 as shown in FIG. 9A described later. It is in a state of being in pressure contact with the upper pressurizing member 215 via the above, which restricts the rotation of the first rotating arm 352 in the same direction.

Further, as shown in FIG. 7 (b), the rotating base shaft 350 planted on the movable plate 310 has a second rotation arm 352 coaxial with the first rotating arm 352 and rotatably holds the pressure roller 261. The rotating arm 362 of the above is rotatably held. The second rotating arm 362 has an engaging projection 362a formed at the tip thereof, and the other end of the second compression spring 364 as a second urging member whose one end is hung on the movable plate 310. It is urged in the clockwise direction (arrow direction) in the figure.

Therefore, when the movable plate 310 is in the plain paper printing position, the pressure roller 261 rotatably held by the second rotating arm 362 is the upper fixing belt 210 and the upper fixing belt 210 as shown in FIG. 9A described later. It is in a state of being in pressure contact with the drive roller 211 via the lower fixing belt 260, whereby the rotation of the second rotating arm 362 in the same direction is restricted.

Although the first rotating arm 352 and the second rotating arm 362 are arranged adjacent to each other in the Y-axis direction, the second rotating arm 362 is arranged on the minus side of the Y axis. , Here, in order to facilitate the explanation of the configuration, they are described in separate drawings. Therefore, the second rotating arm 362 is formed with a notch opening 362b for avoiding the fixing portion 353 fixed to the first rotating arm 352 and planted in the Y-axis direction.

On the other hand, during thick paper printing, the movable plate 310 is moved from the plain paper printing position shown in FIG. 7 to the thick paper printing position shown in FIG. 8 by the cam gears 301 and 302. Only move vertically downward.

However, since the first rotating arm 352 is urged in the arrow direction (clockwise direction) by the first compression spring 354, the lower pressurizing member 265 to hold the first rotating arm 352 is shown in FIG. 9 (b) described later. As shown in FIG. 8A, the state of being slightly rotated in the same direction is maintained while the state of pressure contact with the upper fixing belt 210 and the lower fixing belt 260 with respect to the upper pressing member 215 is maintained.

Further, since the second rotating arm 362 rotatably held by the rotating base shaft 350 is urged in the arrow direction (clockwise direction) by the second compression spring 364, it is vertically downward of the movable plate 310. Along with the movement to, the pressure roller 261 to be held starts rotating in the direction of the arrow while maintaining the pressure contact state with respect to the drive roller 211 via the upper fixing belt 210 and the lower fixing belt 260.

However, the amount of rotation of the second rotating arm 362 is limited by the regulating projection 370 as a regulating member provided on the movable plate 310. That is, when the movable plate 310 starts moving from the plain paper printing position shown in FIG. 7B to the thick paper printing position shown in FIG. 8B, the second rotating arm 362 starts rotating in the arrow direction. However, during the movement, the restricting projection 370 of the movable plate 310 abuts on the engaging projection 362a of the second rotating arm 362 to restrict the rotation of the second rotating arm 362, and is integrated downward as it is. Moving.

Therefore, when the movable plate 310 reaches the thick paper printing position, the pressure roller 261 held by the second rotating arm 362 is slightly smaller than the drive roller 211 as shown in FIG. 9B described later. Keep the position moved in the direction away from (vertically below).

As described above, although the lower pressurizing member 265 and the pressurizing roller 261 are held by the movable plate 310, they are displaced differently with respect to the movement of the movable plate 310 in the Z-axis direction (vertical direction). ..

In the above configuration, the operation of the fixing device 10 during the printing operation by the image forming device 100 will be further described.

When the image forming apparatus 100 receives a printing command from a higher-level device (not shown), the fixing device 10 moves the movable plate 310 upward (plus side of the Z axis) by rotating the cam gear 301 and the cam gear 302, and moves upward. The fixing belt 210 and the lower fixing belt 260 are brought into pressure contact with each other to form a nip portion as shown in FIG.

After that, when the drive roller 211 receives a rotational force via a drive source and a drive transmission mechanism (not shown) and rotates in the direction of the arrow, the pressurizing roller 261 rotates in the direction of the arrow, and the upper fixing belt 210 and the lower portion are sandwiched. The fixing belt 260 rotates and moves in the same direction (arrow direction).

When the upper fixing belt 210 and the lower fixing belt 260 start to rotate, the current supply to the halogen lamps 221, 222, 271 is started, and each halogen lamp generates heat and starts warming up. As a result, the surface temperatures of the upper fixing belt 210 and the lower fixing belt 260 increase. The surface temperature of the upper fixing belt 210 is detected by the thermopile 230 and the temperature is controlled so that the detected temperature becomes a predetermined temperature, and the surface temperature of the lower fixing belt 260 is detected by the thermopile 280 and the detected temperature is the predetermined temperature. Is controlled to be.

When the warm-up operation is completed, the image forming apparatus 100 main body moves the movable plate 310 up and down according to the set thickness and type of the recording paper 101, and brings it to the optimum position.

Next, before explaining the operation of the fixing device 10 in which the movable guide rib 253 is displaced according to the stop position of the movable plate 310, here, the nip of the upper fixing belt 210 and the lower fixing belt 260 at the time of printing. The phenomenon that occurs in each fixing belt will be described in the section with reference to FIG. 12, taking the case of the lower fixing belt 260 as an example. Here, the movable guide rib 253 will be described as a fixed guide rib 553.

FIG. 12 is an operation explanatory view at the time of printing of a fixing device provided with a guide rib 555 fixed to the lower flange 251. FIG. 12A shows an upper fixing belt 210 and a nip portion formed as shown in FIG. The operating state of the lower fixing belt 260 is shown, and FIG. 2B is a partially enlarged view of the dotted circle portion 500 in FIG. 6A. The fixing device shown in FIG. 7 is mainly different from the fixing device 10 shown in FIG. 2 in that the guide rib 553 is fixed to the lower flange 251.

Since the lower fixing belt 260 transfers the carried-in recording paper in the paper direction (arrow A direction), the lower fixing belt 260 on the upstream side of the nip portion when rotating in the arrow direction shown in FIG. Is pulled in the paper-passing direction and the tension becomes stronger, so that the paper rotates and moves in contact with the lower fixed guide rib 252 located upstream of the nip portion and guiding this portion.

On the other hand, in the lower fixing belt 260 on the downstream side of the nip portion, the tension is weakened by the belt portion always pushed out from the nip portion, so that the rotational movement position swells as shown by the dotted line in FIG. It passes through the rotational movement position outside. Moreover, this overlap amount is not always constant, and changes with a fluctuation width W between the guide rib position regulated by the guide rib 553 and the maximum overlap position due to the pressure change when the recording paper is passed.

Further, the lower fixing belt 260 moves in any direction in the longitudinal direction when the fixing device is operated, but the flat surface portion 251a of the lower flange 251 located at both ends in the longitudinal direction (see FIG. 4, only the back side is shown). ) Restricts the movement of both ends in the longitudinal direction in the same direction, so that either end is always in contact with the corresponding flat surface portion 251a (only one end side is shown). Therefore, the lower fixing belt 260 always receives a shearing force in the direction perpendicular to the peripheral surface, and cracks occur at the end of the belt over time, which may cause breakage.

This overlap amount will change even when the lower fixing belt 260 is displaced with respect to the upper fixing belt 210 according to the thickness of the paper to be printed, as in the fixing device 10 of the present embodiment. However, one object of the fixing device 10 of the present embodiment is to suppress the fluctuation width W of this overlap regardless of the displacement of the lower fixing belt 260.

As shown in FIG. 2, when the lower fixing belt unit 305 is displaced with respect to the upper fixing belt unit due to the thickness of the recording paper or the like, for example, from the above-mentioned plain paper printing position (see FIG. 5) to the thick paper printing position (see FIG. 5). When moving to FIG. 6B), the amount of movement of the pressurizing roller 261 and the lower pressurizing member 265 urged to form the nip portion is small, whereas the amount of movement is small in other places, the movable plate 310. Moves downward (minus direction of the Z axis) together with. Therefore, when the guide rib 553 is fixed as in the fixing device shown in FIG. 12, the tension of the lower fixing belt 260 changes depending on the position of the lower fixing belt unit 305, and the overlap amount changes.

FIG. 9 is a diagram for explaining an operating state when printing recording papers having different thicknesses in the fixing device 10 of the present embodiment, and FIG. 9A is a diagram of plain paper having a general thickness. The operation state at the time of printing is shown, and FIG. 3 (b) shows the operation state at the time of printing a thick recording paper.

As shown in FIG. 3A, the movable plate 310 of the fixing device 10 for printing plain paper is moved to the uppermost position by the cam gears 301 and 302, and accordingly, the movable plate 310 is moved to the uppermost position. The fixedly held lower flange 251 is in a state of being moved to the plain paper printing position shown in FIG.

Then, as shown in FIG. 5, the movable guide rib 253 at this time is restricted to the normal printing rotation position by the engaging piece 253b as the engaging portion abutting on the regulating member 201b of the upper flange 201. .. This normal printing rotation position is the position where the contact portion 253a projects most in the positive direction of the X-axis, but it is unnecessary by slightly contacting the rotating lower fixing belt 260 without pressing. It is considered in advance so that the position is such that the fluctuation width W is minimized without generating a large tension.

Further, when the movable plate 310 is in this plain paper printing position, as described above, the lower pressurizing member 265 presses against the upper pressurizing member 215 via the upper fixing belt 210 and the lower fixing belt 260 to pressurize. The roller 261 is in a state of being in pressure contact with the drive roller 211 via the upper fixing belt 210 and the lower fixing belt 260.

On the other hand, as shown in FIG. 3B, the movable plate 310 of the fixing device 10 for printing thick recording paper is moved vertically downward by the cam gears 301 and 302, and is movable accordingly. The lower flange 251 fixedly held by the plate 310 is in a state of being moved to the thick paper printing position shown in FIG. 6 (b).

When the movable plate 310 is in this thick paper printing position, as described above, the lower pressure member 265 presses against the upper pressure member 215 via the upper fixing belt 210 and the lower fixing belt 260, but its pressure contact force is high. The pressure roller 261 is reduced and keeps a position moved in a direction (vertically downward) slightly separated from the drive roller 211. In this state, the lower fixing belt 260 is pulled downward by the tension roller 263 or the like, and the bulge of the rotational movement position around the movable guide rib 253 is reduced.

When printing on thick paper, the pressing force of the lower pressurizing member 265 is weakened, the pressing force of the pressurizing roller 261 on the drive roller 211 is weakened, and the pressure is lowered to a position where the pressure roller 261 is slightly separated from the printing on plain paper. , Suppressing the recoil when passing through thick paper, etc., to obtain the appropriate nip pressure for each.

However, at this time, as shown in FIG. 6B, the movable guide rib 253 restricted to the thick paper printing rotation position by the engaging piece 253b abutting on the restricting member 201b of the upper flange 201 is the same. The contact portion 253a is at a position retracted in the negative direction of the X-axis from the case of the normal printing rotation position. Due to this rotational displacement, the contact portion 253a slightly contacts the lower fixing belt 260 that rotates and moves at this time without being pressed, so that the fluctuation width W is not generated without unnecessary tension. It is considered in advance so that the position is such that the position is minimized.

As described above, according to the fixing device of the present embodiment, even when the path of rotational movement of the lower fixing belt 260 changes due to the displacement of the lower fixing belt in the direction in which the lower fixing belt is separated from the upper fixing belt 210. Since the fluctuation width W can be maintained to the minimum, deterioration of the lower fixing belt 260 over time can be suppressed due to fluctuations in the rotational movement path and the like. Further, since unnecessary tension due to urging force or the like is not applied to the lower fixing belt 260, it is possible to suppress malfunction due to an increase in rotational load torque.

Embodiment 2.
FIG. 10 is a configuration diagram of a main part of the fixing device 400 of the second embodiment based on the present invention.

The main difference between the fixing device 400 and the fixing device 10 of the first embodiment shown in FIG. 2 is that the stepping motor is driven by the rotation of the movable guide rib 453 (corresponding to the movable guide rib 253 in FIG. 2). This is the point to be done in 401. Therefore, the parts of the image forming apparatus that employ the fixing apparatus 400 that are common to the image forming apparatus 100 (FIG. 1) of the first embodiment are designated by the same reference numerals, or the description is omitted by omitting the drawings. However, I will focus on the differences. Since the main part configuration of the image forming apparatus of the present embodiment is the same as the main part configuration of the image forming apparatus 100 of the first embodiment shown in FIG. 1 except for the fixing device, refer to FIG. 1 as necessary. do.

As shown in FIG. 10, the movable guide rib 453 here is configured such that its rotation shaft 454 is rotationally driven in both directions by a stepping motor 401 capable of forward / reverse rotation, either directly or via a reduction gear. ing.

FIG. 11 is a block diagram showing a motor control unit 450 as a drive control unit for driving the stepping motor 401.

The motor control unit 450 has a standby mode corresponding to non-passing paper, a thick paper printing mode corresponding to thick paper printing operation, and a plain paper printing mode corresponding to plain paper printing operation from a control unit (not shown) that controls the entire image forming apparatus. In response to each mode, the movable guide rib 453 receives the operation mode signal 451 indicating any of the above, and the movable guide rib 453 has the above-mentioned initial rotation position (see FIG. 6A) and the thick paper printing rotation position (FIG. 6B). ), And the drive pulse signal 452 is output to the stepping motor 401 so as to rotate to the plain paper printing rotation position (see FIG. 5A).

As described above, according to the fixing device of the present embodiment, even when the path of rotational movement of the lower fixing belt 260 changes due to the displacement of the lower fixing belt in the direction in which the lower fixing belt is separated from the upper fixing belt 210. Since the fluctuation width W can be maintained to the minimum, wear of the lower fixing belt 260 over time can be suppressed due to fluctuations in the rotational movement path and the like. Further, since unnecessary tension due to urging force or the like is not applied to the lower fixing belt 260, it is possible to suppress malfunction due to an increase in rotational load torque. Further, since the rotation position of the movable guide rib 453 is determined by electric drive, the mechanical configuration can be simplified, and it becomes easy to set each rotation position of the movable guide rib 453 to a desired position more finely.

Further, in the description of the claims and the embodiments described above, the terms "top", "bottom", "left", "right", "front", and "rear" are used, but these are for convenience. However, it does not limit the absolute positional relationship in the state where the fixing device is arranged.

In the above-described embodiment, an example in which the present invention is adopted as an image forming apparatus as a color printer is shown, but the present invention is not limited to this, and the copier, the facsimile, and the MFP provided with a fuser. It can also be used for image processing devices such as. Further, although the color printer has been described, it may be a monochrome printer.

10 Fixing device, 100 image forming device, 101 recording paper, 104 paper feed cassette, 105 paper feed roller, 106 resist roller, 110 developing device, 111 photoconductor drum, 112 charging device, 113 exposure device, 114 developer supply device, 115 Cleaning device, 120 Transfer device, 121 Endless transfer belt, 122 Drive roller, 123 Tension roller, 130 Paper discharge loading part, 131 Transfer roller, 132 Transfer roller, 201 Upper flange, 201a Flat part, 201b Regulatory member, 202 Upper guide rib, 203 Upper guide rib, 210 Upper fixing belt, 210a base material, 210b elastic layer, 210c release layer, 211 drive roller, 212 tension roller, 213 tension roller, 215 upper pressurizing member, 221 halogen lamp, 222 halogen lamp , 223 Upper reflector, 230 Thermopile, 251 Lower flange, 251a Flat surface, 252 Lower fixed guide rib, 253 Movable guide rib, 253a Abutment part, 253b Engagement piece, 254 Rotating shaft, 260 Lower fixing belt, 261 Pressurizing roller , 262 Tension Roller, 263 Tension Roller, 265 Lower Pressurizing Member, 267 Torsion Spring, 268 Locking Post, 271 Halogen Lamp, 273 Lower Reflector, 280 Thermopile, 301 Cam Gear, 301a Cam Guide, 302 Cam Gear, 302a Cam Guide , 304 Upper fixing belt unit, 305 Lower fixing belt unit, 310 Movable plate, 350 Rotating base shaft, 352 1st rotating arm, 352a Tip part, 353 fixing part, 354 1st compression spring, 362 2nd rotation Dynamic arm, 362a engaging protrusion, 362b opening, 364 second compression spring, 370 regulating protrusion, 400 fixing device, 401 stepping motor, 450 motor control unit, 451 operation mode signal, 452 drive pulse signal, 453 movable guide rib, 454 rotating shaft.

Claims (5)

In a fixing device including a first fixing belt unit and a second fixing belt unit that can move in a direction in which the first fixing belt unit is brought into contact with and separated from the first fixing belt unit.
The first fixing belt unit is
With the endless first fixing belt,
A first roller inside the first fixing belt that rotates in contact with the inner surface of the first fixing belt.
It is provided with a first pressurizing member inside the first fixing belt and pressing the inner side surface of the first fixing belt.
The second fixing belt unit is
A movable plate that can move in the direction of contact and separation,
With the endless second fixing belt,
Inside the second fixing belt, supported by the movable plate, facing the first roller via the first fixing belt and the second fixing belt, the second fixing belt of the second fixing belt. A second roller that presses against the inner surface and rotates,
Inside the second fixing belt, supported by the movable plate, facing the first pressure member via the first fixing belt and the second fixing belt, the second fixing. A second pressurizing member that presses the inner surface of the belt,
A path setting member that is inside the second fixing belt and is provided on the movable plate to determine the rotational movement path of the second fixing belt.
A movable guide member which is inside the second fixing belt and is supported by the movable plate and guides the inner surface of the second fixing belt is provided.
The movable guide member includes a contact portion that is rotatably held by the movable plate and abuts on the second fixing belt, and an engaging portion.
A third urging member that urges the abutting portion in a direction away from the second fixing belt.
With the engaged portion fixed to the fixing device main body, which engages with the engaging portion of the movable guide member and regulates the rotation of the movable guide member by the third urging member.
Equipped with
As the movable plate moves in the direction of contact and separation, the movable guide member rotates to change the guide position of the contact portion with respect to the second fixing belt. .. The second pressurizing member is displaceably held by the movable plate and urged by the first urging member in a direction approaching the first pressurizing member.
The fixing device according to claim 1, wherein the second roller is displaceably held by the movable plate and is urged by a second urging member in a direction approaching the first roller. .. The second pressurizing member is held by a first rotating arm rotatably held by the movable plate, and the second roller is rotatably held by the movable plate. 2. The fixing device according to claim 2, wherein the fixing device is held by a rotating arm of the above. The fixing device according to claim 3, wherein the second rotating arm is restricted in the amount of rotation by a regulating member arranged on the movable plate. An image forming apparatus comprising any of the fixing devices according to claims 1 to 4 .

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