JP2013195683A - Fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of stabilizing behavior of a fixing belt in the vicinity of a separation plate, properly maintaining a gap between the fixing belt and the separation plate, and stabilizing separability of paper.SOLUTION: A fixing device comprises: a pressure roller 20 that rotates in a predetermined direction; an endless fixing belt 21 that is heated by a heat source 22 and is brought into pressure contact with the pressure roller 20 to form a fixing nip N2 and to be driven in conjunction with the pressure roller 20; separation means 27 that is provided on the downstream side of the fixing nip N2 to separate a recording medium passing the fixing nip N2 from the fixing belt 21; and regulation means 30 that contacts the outer peripheral surface of the fixing belt 21 to prevent the fixing belt 21 from approaching the separation means 27 side.

Description

  The present invention relates to a fixing device that fixes an unfixed image on a recording medium, and an image forming apparatus.

Conventionally, an image forming apparatus using an electrophotographic method is known.
In the image forming process in such an image forming apparatus, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and the electrostatic latent image is developed with a toner or the like as a developer to be visualized. This process is established by a process in which the developed image is transferred onto a recording sheet by a transfer device to carry the image, and a toner image on the recording sheet is fixed by a fixing device using pressure, heat, or the like.
In the fixing device, a fixing rotator constituted by opposing rollers, belts, or a combination thereof is disposed, and the recording paper is sandwiched and heat and pressure are applied to fix the toner image on the recording paper.

FIG. 8 is a diagram illustrating an example of a configuration of a fixing device that employs a belt fixing method which is one of fixing methods.
A fixing device 100 shown in FIG. 8 has a fixing belt (fixing body) including a heating roller 101 having a heater 102 as a heat source body therein and a fixing roller 103 having a rubber layer as a surface layer as a fixing rotating body. 104 and a pressure roller (pressure body) 105 that contacts the fixing belt 104 are housed in a fixing cover 115.
The surface temperature of the heater 102 is measured by temperature detection means (thermistor) 110.
The recording paper 106 that has reached the fixing device 100 and has undergone toner transfer enters the fixing nip 107 of the fixing belt 104 and the pressure roller 105, and the transferred toner image is heated while the recording paper 106 passes through the fixing nip 107. And pressed to fix.
The fixing belt 104 is tensioned by a tension roller 109 urged by a spring 108 on the outer peripheral surface thereof.
A separation plate 111 for separating the recording paper 106 from the fixing belt 104 is provided in the vicinity of the outlet downstream of the fixing nip formed by the fixing belt 104 and the pressure roller 105.

Incidentally, the fixing device shown in FIG. 8 has the following problems of durability and stability of the belt temperature.
For example, the wear resistance due to sliding between the ceramic heater (heating roller 101) that is a heat source and the inner surface of the fixing belt 104 is insufficient, and the surface that repeats continuous friction is roughened when operated for a long time, increasing the frictional resistance. Phenomena such as unstable running or an increase in driving torque of the fixing device occur. As a result, there arises a problem that the transfer material forming the image slips and the image shifts or the stress on the drive gear increases to cause the gear to be damaged.
On the other hand, it has a fixing member (metal pipe) as a guide for the fixing belt, which is in sliding contact with the inner surface of the rotating body (endless belt), rather than stretching the endless fixing belt between the fixing roller and the heating roller. A fixing device is known (for example, Patent Document 1).

FIG. 9 is a diagram showing the configuration of a film fixing type fixing device having such a configuration.
The fixing device shown in FIG. 9 has a nip formed by sandwiching a heat-resistant film (fixing film) 121 as a fixing belt between a ceramic heater 122 as a heating element and a pressure roller 120 as a pressure member. A nip portion is formed between the fixing film 121 and the pressure roller 120 by the member 125. A mesh-like lubricating sheet 124 is disposed in the nip portion.
The inner part of the fixing film 121 is made of a pipe-shaped metal, is in sliding contact with the inner surface of the fixing film 121 (fixed and does not rotate), and is fixed by being heated by the radiant heat (radiant light) of the heater 122 provided therein. A pipe-shaped metal body 123 is provided as a heating member that heats the belt 121.
The surface temperature of the fixing film 121 is measured by a temperature detecting means (thermistor) 128.

Then, a recording material on which an unfixed toner image to be image-fixed is formed and supported is introduced between the film in the fixing nip portion and the pressure roller 120, and is nipped and conveyed together with the film. The heat of the ceramic heater 122 is applied to the recording material through the fixing film 121, and the unfixed toner image is fixed to the recording material surface by heat and pressure by the pressure of the fixing nip portion.
In addition to the heater 122, a support 127 that supports the nip forming member 124 is provided in the pipe-shaped metal body 123. The pipe-shaped metal body 123 has a function of maintaining the shape of the fixing belt. Also have.
This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a member having a low heat capacity as a film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. It is only necessary to generate heat at a predetermined fixing temperature, the waiting time before the image forming apparatus can be executed after the power is turned on is short (quick start property), and the power consumption during standby is also low. There are advantages such as significantly smaller (power saving).

However, the fixing device shown in FIG. 9 has a problem that the configuration is complicated because a pipe-shaped metal member is provided inside the fixing belt as a traveling guide for the fixing belt and as a heating member for heating the fixing belt. is there.
However, when the fixing belt is heated by removing the pipe-shaped metal member and radiating the heat of the heater with the reflecting plate, the behavior of the fixing belt is not stable in the vicinity of the separating plate, and the separating plate with the fixing belt However, the gap is not an appropriate distance, and the separation property of the recording material becomes unstable.
Patent Document 2 describes a configuration in which flanges at both ends of the belt are used as rotation guides for the fixing belt. In this configuration, a fixing belt separation plate other than the flange portion (such as the central portion) in the longitudinal direction of the fixing belt is described. There is a problem that it is difficult to control the behavior of the neighborhood.
In view of such problems, the present invention can stabilize the behavior of the fixing belt in the vicinity of the separation plate, maintain the gap between the fixing belt and the separation plate appropriately, and stabilize the paper separation property. An object of the present invention is to provide a fixing device and an image forming apparatus having the same.

  In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that a pressurizing means rotating in a predetermined direction and heated by a heat source and being brought into contact with the pressurizing means while forming a fixing nip portion. An endless belt member, a separation unit that separates the recording medium that passes through the fixing nip from the belt member, and a regulation unit that regulates the belt member from approaching the separation unit. Features.

  Since it is configured as described above, according to the present invention, it is possible to suppress the flapping of the fixing belt by providing the restricting means for restricting the belt member from approaching the separating means. Stabilize and secure stable separation

1 is a diagram illustrating an example of a configuration of an image forming apparatus to which a fixing device according to an exemplary embodiment can be applied. FIG. 4 is a diagram illustrating a comparative example of a fixing device according to the present embodiment. FIG. 3 is a view showing a longitudinal section of a fixing belt in the fixing device shown in FIG. 2. The enlarged view of the area | region A in FIG.2 (b). The figure which shows the relationship between a fixing belt and a separating plate when a fixing belt bends. 1 is a diagram illustrating a configuration of a fixing device according to an embodiment. The enlarged view of the area | region B in FIG.6 (b). FIG. 3 is a diagram illustrating an example of a configuration of a fixing device that employs a belt fixing method. FIG. 3 is a diagram illustrating an example of a configuration of a film fixing type fixing device.

Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a diagram illustrating an example of the configuration of an image forming apparatus to which the fixing device according to the present embodiment can be applied.
The image forming apparatus shown in FIG. 1 is an apparatus that forms one image from four color toners of yellow (Y), magenta (M), cyan (C), and black (K), each of which contacts the intermediate transfer belt 3. However, four photosensitive drums 2Y, 2M, 2C, and 2K as image bearing members that are rotationally driven in the direction A in the figure, and charging devices 7Y, 7M, 7C, and 7K that uniformly charge these photosensitive drums, A writing unit 8 for forming an electrostatic latent image by exposing and scanning the charged photosensitive drum with a laser beam and developing devices 4Y, 4M, 4C, and 4K for developing the electrostatic latent image on each photosensitive member are provided. ing.
Further, toner bottles 11Y, 11M, 11C, and 11K filled with yellow, magenta, cyan, and black toners to be supplied to the developing devices 4Y, 4M, 4C, and 4K of the respective colors by a predetermined replenishment amount by a conveyance path (not shown) are also provided. I have.

A process of obtaining a color image in the image forming apparatus 1 will be described.
A transfer material P such as paper set in the transfer material cassette 5 is fed by a paper feed roller 6 and conveyed to a nip N 1 between the secondary transfer roller 13 and the intermediate transfer belt 3.
Next, a voltage is applied to the transfer rollers 9Y, 9M, 9C, and 9K, and the toner on the photosensitive drums 2Y, 2M, 2C, and 2K is sequentially transferred onto the intermediate transfer belt 3.
At this time, the image forming operation for each color is executed while shifting the timing from the upstream side in the transport direction of the intermediate transfer belt 3 toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 3. Is done.
The image formed on the intermediate transfer belt 3 is conveyed to the position of the secondary transfer roller 13 and secondarily transferred to the transfer material P.
The transfer material P on which the toner image of each color is transferred is conveyed to a fixing device 10 as a fixing unit, thermally fixed, and discharged by a paper discharge roller 12.

The fixing device 10 according to the embodiment of the present invention includes a pressure roller (an example of a pressure unit) 20 and a fixing belt (an example of a belt member) 21, and the transfer material P is formed by both of these rotating bodies. In the fixing nip portion, heat fixing is performed.
In this respect, the fixing device 10 of the present embodiment has a configuration similar to that of the fixing device described with reference to FIG. 9, but the fixing belt 21 of the present embodiment has the same fixing belt as that of FIG. The pipe-shaped metal member that functions as a rotation guide for the fixing belt 21 and a heating means for heating the fixing belt 21 is not provided.
As a heating unit for the fixing belt 21, a reflection plate is provided on the inner surface side of the fixing belt 21, and radiant heat from a heating source is reflected on the inner surface of the fixing belt 21 to heat the fixing belt 21.
Then, as a means for stabilizing the behavior of the fixing belt 21 during rotation (running), regulation that restricts the running of the fixing belt 21 by contacting the fixing belt 21 (regulating that the fixing belt 21 approaches the separation plate 27). Means.

Here, prior to describing the characteristics of the fixing device according to the present embodiment, in the configuration of the present embodiment in which a pipe-shaped member serving as a rotation guide is not provided on the inner surface side of the fixing belt 21, the fixing belt travels. A problem that occurs when a regulating member for regulating is not provided will be described.
In addition, the structure demonstrated below is the same structure as this embodiment except the point which does not provide a limitation member.
2A and 2B are diagrams for explaining problems that occur when a metal pipe serving as a rotation guide for the fixing belt 21 is not provided on the inner surface side of the fixing belt. FIG. 2A is a schematic perspective view of the fixing device, and FIG. These are sectional drawings of a rotating shaft direction. In FIG. 2, the fixing cover that accommodates the fixing belt and the pressure roller is not shown.
3 is a diagram showing a longitudinal section of the fixing belt 21 in FIG.
Further, FIG. 4 is an enlarged view of a region A in FIG.

A fixing device 10 shown in FIG. 2 includes a pressure roller (an example of a pressure unit) 20 and an endless fixing belt 21 driven by rotation of the pressure roller inside the fixing cover.
On the inner peripheral surface side of the fixing belt 21, a radiation heating source (hereinafter referred to as a heater) 22 such as a halogen heater is in direct contact with the inner surface of the fixing belt 21 (or indirectly through a sliding sheet). A nip forming member (nip forming means) 23 that forms a fixing nip N2 with the pressure member 20, a metal structure (pressure stay) 24 that receives a load applied to the nip forming member 23, and FIG. As shown, a resin or metal flange 25 that holds the fixing belt 21 at both ends, and a reflection plate 26 as a reflection means for reflecting the radiant heat of the heater 22 radiated to the opposite side of the fixing belt 21 to the fixing belt 21. And a separation plate 27 provided in the vicinity of the outlet (downstream) of the nip N2 as separation means for separating the transfer material from the fixing belt 12.
The flange 25 preferably has an opening for allowing the heater 22 and the pressure stay 24 to rotate while being passed through the fixing belt 21.

In FIG. 2B, the shape of the nip N2 is a concave shape, but may be a flat shape or other shapes.
However, when the nip shape is concave, the discharge direction of the transfer material tip is closer to the pressure roller 20 and the separation property of the transfer material from the fixing belt 21 is improved, so that jamming can be suppressed. .

The pressure roller 20 is formed with a silicone rubber layer 20b on the surface of a hollow metal roller 20a, and in order to obtain releasability, a release layer (PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) is further formed on the surface. Or a PTFE (polytetrafluoroethylene) layer).
The pressure roller 20 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus 1 via a gear 20c provided at an end portion in the longitudinal direction.
The pressure roller 20 is pressed against the fixing belt 21 by a spring or the like (not shown), and has a predetermined nip width when the surface silicone rubber layer 20b is crushed and deformed.
Further, the pressure roller 20 (metal roller 20a) may be a solid roller, but the hollow case has an advantage that the heat capacity can be reduced. Further, the pressure roller 20 may have a heating source such as a halogen heater.

The silicone rubber layer 20b may be solid rubber, but if there is no heater inside the pressure roller 20, sponge rubber may be used. Sponge rubber is more desirable because it increases heat insulation and makes it difficult for the fixing belt to lose heat.
Further, as the pressure roller 20, there are many examples in which an elastic layer is provided on a hollow metal shaft portion and a release layer is further provided on the surface thereof. In such a pressure roller 20, only an end portion outside the sheet passing range is provided. There is also a fixing device configured to rotate the fixing belt 21 by removing the release layer and exposing the elastic layer (hereinafter referred to as a grip portion) to make the surface layer highly frictional. There may be a step between the release layer on the surface and the grip portion.

The fixing belt 21 is a metal belt such as nickel or SUS (stainless steel) or an endless belt (or film) using a resin material such as polyimide, and has a release layer such as a PFA or PTFE layer on its surface layer. Release properties are provided so that toner does not adhere.
An elastic layer formed of a silicone rubber layer or the like may be provided between the base material of the fixing belt 21 and the PFA or PTFE layer.
Without this silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, the subtle irregularities on the belt surface are transferred to the image and the image has a crusty skin-like shape. There is a problem that marks remain.
In order to improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, subtle irregularities are absorbed and the skin image is improved.
The pressure stay 24 is made of a metal such as stainless steel or aluminum.
As the reflecting plate 26, in this embodiment, a material obtained by evaporating silver on the surface of an aluminum substrate is used. Since silver has a low emissivity, the heat absorption efficiency of the fixing belt 21 can be improved by reflecting the radiant heat toward the pressure stay irradiated from the halogen heater 22.
In the example shown in FIG. 2, the reflecting plate 26 is fixed to the pressure stay 24, but the reflecting plate 26 may be movable. Of course, the material of the reflecting plate 26 is not limited to a material obtained by vapor-depositing silver on an aluminum base material.

As shown in detail in FIG. 4, in the fixing device, a separation plate 27 such as a metal plate is disposed with a minute gap 28 of approximately 1 mm or less from the fixing belt 21 at the ideal position 21 </ b> A. .
This is provided so that the transfer material P is forcibly separated when the transfer material P cannot be naturally separated from the fixing belt 21 and is not wound around the fixing belt.
The separation plate 27 needs to keep the fixing belt 21 and an appropriate gap 28. This is because if the gap is too wide, the transfer material cannot be separated.

However, in the case of the fixing device using the thin fixing belt 21, the strength of the fixing belt 21 is low, and therefore there is no guide (metal pipe) when the fixing belt 21 rotates (runs) as shown in FIG. Then, the fixing belt 21 is bent and fluttered, and the gap 28 between the separation plate 27 and the fixing belt 21 is not stable.
Therefore, if the gap 28 between the separation plate 27 and the fixing belt 21 is small, the fixing belt 21 approaches the separation plate 27 as shown in FIG. There is a risk of damage.
However, if the gap 28 of the separating plate 27 is set large in advance so that the fixing belt 21 does not come into contact with the separating plate 27 in anticipation of variations in the running behavior of the fixing belt 21, the margin of separation of the transfer material is reduced. There's a problem.
Therefore, as described above, in the present embodiment, a regulating member for suppressing variation in running behavior of the fixing belt 21 is provided on the outer peripheral surface side of the fixing belt 21.

6A and 6B are diagrams illustrating a configuration of the fixing device according to the present exemplary embodiment, in which FIG. 6A is a schematic perspective view of the fixing device, and FIG. 6B is a cross-sectional view in the rotation axis direction.
As in FIG. 2, the fixing cover that accommodates the fixing belt and the pressure roller is not shown.
As shown in FIG. 6, in this embodiment, the running behavior of the fixing belt is regulated by contacting the outer peripheral surface of the fixing belt 21 in the vicinity of the tip of the separation plate 27 (the fixing belt 21 approaches the separation plate 27. A regulating member (contact member) 30 is provided.

FIG. 7 is an enlarged view of region B in FIG.
Except that the contact member 30 is provided, the configuration is almost the same as that of FIG. 2, and the common members are denoted by the same reference numerals and the description thereof is omitted.
By providing the contact member 30, as shown in FIG. 6, the behavior of the fixing belt 21 during rotation (running) is stabilized, and both the gaps of the fixing belt 21 do not approach the separation plate 27. Since it is maintained appropriately, stable separation by the separation plate 27 can be ensured.
As the contact member 30, a roller-shaped rotating body is adopted, which facilitates the arrangement and is suitable for being difficult to become a sliding load of the fixing belt 21.

Further, if the surface of the contact member 30 is a releasable member such as a fluororesin, an abnormal image due to toner adhesion / fixation is less likely to occur, and the frictional resistance is small, so the load on the fixing belt 21 is reduced. It can be reduced to prevent damage (such as scratches) to the fixing belt.
The contact member 30 may be pressed (pressed) against the fixing belt 21 by a pressure member (not shown), or may be rotationally driven by a drive mechanism (not shown).
By pressing or driving the contact member 30, the rotation of the contact member 30 is stabilized, and a load is applied to the fixing belt 21 due to a difference in linear velocity from the fixing belt 21. Can be prevented.
If the contact member 30 is not provided with a drive mechanism, the product cost can be reduced.
When the contact member 30 is not pressed against the fixing belt 21, the load on the fixing belt 21 can be reduced as much as possible, and the product cost can be reduced. Uneven rotation of the contact member 30 that occurs when the parallelism between the fixing belt 21 and the contact member 30 is poor, or damage to the fixing belt 21 when it does not rotate can be prevented.
Note that the regulating member 30 may be provided not in contact with the fixing belt 21 but with an arbitrary gap from the fixing belt 21.

1 image forming apparatus, 2 (Y, M, C, K) photosensitive drum, 3 intermediate transfer belt,
4 (Y, M, C, K) Developing device, 5 Transfer material cassette, 6 Paper feed roller, 7 (Y, M, C, K) Charging device, 8 Writing unit, 9 (Y, M, C, K) Transfer roller,
10 fixing device, 11 (Y, M, C, K) toner bottle, 12 discharge roller, 13 secondary transfer roller, N2 fixing nip, 20 pressure roller, 20a metal roller, 20b silicone rubber layer, 20c gear, 21 Fixing belt, 22 Halogen heater, 23 Nip forming member, 24 Pressure stay, 25 Flange, 26 Reflecting plate, 27 Separating plate, 28 Gap, 30 Contact member

JP 2010-286815 A JP 2010-020247 A

Claims (8)

Pressurizing means rotating in a predetermined direction;
An endless belt member that is heated by a heat source and is rotated while forming a fixing nip portion in pressure contact with the pressure unit;
Separating means for separating the recording medium passing through the fixing nip portion from the belt member;
Restricting means for restricting the belt member from approaching the separating means;
A fixing device comprising:   The fixing device according to claim 1, wherein the restricting unit is a roller-shaped rotating body.   3. The fixing device according to claim 1, wherein the fixing nip portion is formed by press-contacting a nip forming unit in contact with an inner peripheral surface of the belt member and the pressurizing unit via the belt member. A fixing device.   4. The fixing device according to claim 1, wherein the belt member includes a reflection unit configured to reflect radiant heat of the heat source on an inner peripheral surface side. 5. In the fixing device according to any one of claims 1 to 4,
A fixing device comprising a release member on a surface of the regulating means. The fixing device according to any one of claims 1 to 5,
The fixing device, wherein the regulating member is pressurized against the fixing member. In the fixing device according to any one of claims 1 to 6,
The fixing device is characterized in that the regulating member is rotationally driven by a drive source.   An image forming apparatus comprising the fixing device according to claim 1.

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