JP6784175B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction device thereof, and a fixing apparatus installed therein.

Conventionally, in a fixing device in an image forming apparatus such as a copier or a printer, the recording medium after the fixing step is surely separated without being wound around the fixing rotating body without damaging the fixing rotating body such as a fixing roller. In addition, a technique of bringing a brush-shaped rotating body (brush-shaped peeling means) into contact with the surface of the fixing rotating body is widely known (see, for example, Patent Document 1).

Specifically, in the fixing device in Patent Document 1, a pressure rotating body (pressurized roll) is in pressure contact with the fixing rotating body (fixing roll), and a nip portion (fixing nip) through which a recording medium is conveyed is formed. Has been done. Then, the toner image on the recording medium conveyed to the nip portion is fixed on the recording medium by the heat received from the fixing rotating body and the pressure of the nip portion. Then, even if the recording medium sent out from the nip portion is in a state of being attracted to the fixing rotating body, it is fixed by the brush-shaped rotating body (brush-like peeling means) that comes into contact with the fixing rotating body on the outlet side of the nip portion. It is forcibly separated from the rotating body and transported toward the paper discharge transport path.

Since the conventional fixing device described above uses a soft brush-shaped rotating body (brush-shaped peeling means) as the separating member, there is a problem that the surface of the fixing rotating body is damaged as compared with the case where a hard separating claw is used as the separating member. Can be expected to have the effect of reducing.
However, in the above-mentioned conventional fixing device, the separability of the recording medium with respect to the fixing rotating body becomes low depending on the thickness and type of the recording medium conveyed to the nip portion, or the recording medium comes into contact with the brush-shaped rotating body. Sometimes it got scratched.
Further, such a problem can occur in the same manner even when the brush-shaped rotating body is installed so that the recording medium after the fixing step is separated without being wound around the pressurized rotating body.

The present invention has been made to solve the above-mentioned problems, and the separability of the recording medium with respect to the fixing rotating body or the pressurized rotating body becomes low depending on the thickness and type of the recording medium conveyed to the nip portion. It is an object of the present invention to provide a fixing device and an image forming device, which are less likely to cause a problem that the recording medium is scratched due to contact with a brush-shaped rotating body.

The fixing device in the present invention includes a fixing rotating body that heats a toner image and fixes it on the surface of a recording medium, and a pressurized rotating body that forms a nip portion through which the recording medium is conveyed by pressure contacting the fixing rotating body. At a position downstream of the nip portion in the transport direction of the recording medium, the fixing rotating body or the surface of the pressurized rotating body is in contact with or opposed to the surface of the recording medium, and the tip of the recording medium is delivered from the nip portion. A brush-shaped rotating body that abuts in the width direction to separate the recording medium from the fixed rotating body or the pressurized rotating body is provided, and the recording medium is conveyed to the nip portion according to the thickness or type of the recording medium. One of the plurality of the brush-shaped rotating bodies formed so that the elastic forces of the brush-shaped portions that abut on the tip of the recording medium are different from each other is selected, and the selected brush-shaped rotating body is used as the recording medium. It is moved to a position where it can come into contact with the tip of the.

According to the present invention, depending on the thickness and type of the recording medium conveyed to the nip portion, the separability of the recording medium with respect to the fixed rotating body or the pressurized rotating body may be lowered, or the recording medium may come into contact with the brush-shaped rotating body for recording. It is possible to provide a fixing device and an image forming device that are less likely to cause a problem that the medium is scratched.

It is an overall block diagram which shows the image forming apparatus in embodiment of this invention. It is a block diagram which shows the fixing device. It is the schematic which shows the fixing roller and the brush-shaped roller in the width direction. (A) an enlarged view showing a state in which the first brush-shaped roller is in contact with the fixing roller, and (B) an enlarged view showing a state in which the second brush-shaped roller is in contact with the fixing roller. It is an enlarged view which shows the main part of the fixing device as a modification 1. It is an enlarged view which shows the main part of the fixing device as a modification 2. It is a block diagram which shows the fixing device as a modification 3.

<Embodiment>
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

First, FIG. 1 describes the overall configuration and operation of the image forming apparatus 1.
In FIG. 1, 1 is a tandem color copier as an image forming apparatus, 2 is a writing unit that emits a laser beam based on input image information, 3 is a document conveying unit that conveys a document D to a document reading unit 4, and 4 is a document conveying unit. The document reading unit for reading the image information of the document D is shown.
Further, 7 is a paper feed unit for accommodating a recording medium P such as paper, 9 is a registration roller (timing roller) for adjusting the transfer timing of the recording medium P, and 11Y, 11M, 11C, and 11BK are colors (yellow, magenta, etc.). A photoconductor drum, on which a toner image of (cyan, black) is formed, is shown.

Further, 12 is a charging portion for charging the surface of each of the photoconductor drums 11Y, 11M, 11C, 11BK, and 13 is a development for developing an electrostatic latent image formed on the surface of each of the photoconductor drums 11Y, 11M, 11C, 11BK. Units 14 are primary transfer bias rollers that transfer toner images formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on the surface of the recording medium P, and 15 are photoconductor drums 11Y, 11M. A cleaning unit for collecting untransferred toner remaining on the surfaces of 11C and 11BK is shown.
Further, 16 is an intermediate transfer belt cleaning unit for cleaning the intermediate transfer belt 17, 17 is an intermediate transfer belt on which toner images of a plurality of colors are superimposed and transferred, and 18 is an intermediate transfer belt on which the color toner image on the intermediate transfer belt 17 is transferred on the recording medium P. A secondary transfer bias roller for transferring to, 20 is a fixing device for fixing a toner image (unfixed image) on the recording medium P.

Hereinafter, the operation of the image forming apparatus during normal color image forming will be described.
First, the document D is conveyed from the platen by the transfer roller of the document transfer unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating the light emitted from the illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read by a color sensor for each RGB (red, green, blue) color separation light, and then converted into an electrical image signal. Further, based on the RGB color separation image signal, the image processing unit performs processing such as color conversion processing, color correction processing, and spatial frequency correction processing to obtain color image information of yellow, magenta, cyan, and black.

Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. Then, a laser beam (exposure light) based on the image information of each color is emitted from the writing unit 2 toward the surfaces of the corresponding photoconductor drums 11Y, 11M, 11C, and 11BK, respectively.

On the other hand, the four photoconductor drums 11Y, 11M, 11C, and 11BK are each rotating counterclockwise in FIG. Then, first, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portion facing the charging portion 12 (the charging step). In this way, a charging potential is formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK.
After that, the surfaces of the charged photoconductor drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams (exposure step). Specifically, in the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a different optical path for each of the yellow, magenta, cyan, and black color components.

The laser beam corresponding to the yellow component irradiates the surface of the photoconductor drum 11Y, which is the first from the left side of the paper surface. At this time, the laser beam of the yellow component is scanned in the rotation axis direction (main scanning direction, width direction) of the photoconductor drum 11Y by the polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photoconductor drum 11Y after being charged by the charging unit 12.

Similarly, the laser beam corresponding to the magenta component is applied to the surface of the photoconductor drum 11M second from the left on the paper surface to form an electrostatic latent image corresponding to the magenta component. The cyan component laser beam is applied to the surface of the photoconductor drum 11C, which is the third from the left on the paper surface, to form an electrostatic latent image of the cyan component. The laser beam of the black component is applied to the surface of the photoconductor drum 11BK, which is the fourth from the left on the paper surface, to form an electrostatic latent image of the black component.

After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color are formed reach the positions facing the developing unit 13, respectively. Then, toners of each color are supplied from each developing unit 13 to the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK, and the latent images formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are developed. (It is a development process.).
After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the developing step reach the facing portions with the intermediate transfer belt 17, respectively. Here, a primary transfer bias roller 14 is installed on each of the opposing portions so as to abut on the inner peripheral surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, toner images of each color formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred on the intermediate transfer belt 17 (primary transfer). It is a transfer process.).

Then, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the transfer step reach the positions facing the cleaning unit 15, respectively. Then, the cleaning unit 15 collects the untransferred toner remaining on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK (this is a cleaning step).
After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK pass through the static elimination unit, and a series of image forming processes on the photoconductor drums 11Y, 11M, 11C, and 11BK are completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are superimposed and transferred (supported) travels in the clockwise direction of FIG. 1 and is transferred to the secondary transfer bias roller 18. Reach the opposite position of. Then, the color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at the position facing the secondary transfer bias roller 18 (this is the secondary transfer step).
After that, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning portion 16. Then, the untransferred toner adhering to the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 are completed.

Here, the recording medium P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (which is the secondary transfer nip) is conveyed from the paper feed unit 7 via the resist roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feed roller 8 is guided to the resist roller 9 from the paper feed unit 7 that houses the recording medium P after passing through the transport path. The recording medium P that has reached the resist roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, a color image (toner image) is fixed to the surface of the recording medium P at the nip portion (fixing nip) between the fixing roller and the pressurizing roller (the fixing step).
Then, the recording medium P after the fixing step is discharged as an output image to the outside of the apparatus main body 1 by the paper ejection roller, and a series of image forming processes is completed.

Next, with reference to FIGS. 2 to 4, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail.
As shown in FIGS. 2 to 4, the fixing device 20 includes a fixing roller 21 as a fixing rotating body, a heater 25 as a heating means, a temperature sensor 40, a pressure roller 31 as a pressure rotating body, and a brush-shaped rotating body. It is composed of brush-shaped rollers 36A and 36B, a first arm 37, a second arm 38, a tension spring 39 (a urging member), a guide plate 35, and the like.

Here, the fixing roller 21 (fixing member) as the fixing rotating body is a roller member having a multi-layer structure in which an elastic layer and a release layer are sequentially laminated on a core metal 21a having a hollow structure made of a metal material such as stainless steel. The nip portion (fixing nip) is formed by pressure contact with the pressure roller 31 as the pressure rotating body.
The elastic layer of the fixing roller 21 is formed of an elastic material such as fluororubber, silicone rubber, or foamable silicone rubber. The release layer of the fixing roller 21 is formed of PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer resin) or the like. By providing the release layer on the surface layer of the fixing roller 21, the release property (peeling property) with respect to the toner T (toner image) is ensured. The fixing roller 21 is rotationally driven in the clockwise direction of FIG. 2 by a drive mechanism.

A heater 25 (heat source) as a heating means is fixedly installed inside the hollow structure fixing roller 21 (core metal 21a).
The heater 25 (heating means) is a halogen heater, and both ends thereof are fixed to the side plates of the fixing device 20. Then, with the main switch of the image forming apparatus main body 1 turned on, electric power is supplied from the power supply unit to the heater 25. Then, the fixing roller 21 is heated by the radiant heat from the heater 25 whose output is controlled by the control unit, and heat is applied to the toner image T on the recording medium P from the surface of the further heated fixing roller 21.
The output control of the heater 25 is performed based on the detection result of the roller surface temperature by the temperature sensor 40 facing the surface of the fixing roller 21 in a non-contact manner. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the temperature sensor 40 (thermopile). By controlling the output of the heater 25 in this way, the temperature (fixing temperature) of the fixing roller 21 can be adjusted and controlled to a desired temperature (target control temperature).

Further, the pressure roller 31 (pressurizing member) as the pressure rotating body is mainly composed of a core metal 32 and an elastic layer 33 formed on the outer peripheral surface of the core metal 32 via an adhesive layer. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, fluororubber, or silicone rubber. A thin mold release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
Then, the pressurizing roller 31 is pressed against the fixing roller 21 by the pressurizing mechanism. In this way, a desired nip portion (a portion surrounded by a broken line in FIG. 4) is formed between the pressure roller 31 and the fixing roller 21.
The pressurizing roller 31 rotates in the counterclockwise direction of FIG. 2 as the fixing roller 21 rotates.

With reference to FIG. 2, guide plates 35 for guiding the transfer of the recording medium P are provided on the inlet side and the outlet side of the contact portion (nip portion) between the fixing roller 21 and the pressurizing roller 31, respectively. It is arranged. The guide plate 35 is fixed to the side plate of the fixing device 20.
Further, a brush-shaped roller 36A (a brush-shaped rotating body) as a brush-shaped rotating body that functions as a separating member is located near the outlet side of the nip portion (fixing nip) at a position facing the outer peripheral surface of the fixing roller 21 (fixing rotating body). 36B) is arranged. By installing the brush-shaped roller 36A (36B), it is possible to reduce the problem that the recording medium P after the fixing step is wound around the fixing roller 21 along with the traveling of the fixing roller 21. The brush-shaped rollers 36A (36B) will be described in more detail later.
In addition, the fixing device 20 is provided with a first arm 37, a second arm 38, and a tension spring 39 (a urging member), which will be described in detail later.

The fixing device 20 configured as described above operates as follows.
When the main switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) to the heater 25.
Then, when the print command (print request) is input, the drive mechanism starts the clockwise rotational drive of the fixing roller 21, and the counterclockwise driven rotation of the pressurizing roller 31 is started. After that, the recording medium P is fed from the paper feed unit 7, and the toner image on the intermediate transfer belt 17 is supported on the recording medium P as an unfixed image at the position of the secondary transfer bias roller 18. The recording medium P on which the unfixed image T (toner image) is supported is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portions of the fixing roller 21 and the pressure roller 31 in the pressure contact state. Then, the toner image T is fixed on the surface of the recording medium P by the heating by the fixing roller 21 and the pressing force of the fixing roller 21 and the pressure roller 31. After that, the recording medium P sent out from the nip portion by the rotating fixing roller 21 and the pressure roller 31 is separated by the brush-shaped roller 36A (36B) and conveyed in the direction of the arrow Y11.

Hereinafter, the characteristic configuration and operation of the fixing device 20 (image forming device 1) according to the present embodiment will be described in detail.
With reference to FIGS. 2 to 4, the fixing device 20 in the present embodiment has a fixing roller 21 (fixing rotating body) at a position downstream of the nip portion (fixing nip) in the transport direction of the recording medium P. A brush-shaped roller 36A (36B) as a brush-shaped rotating body is installed so as to come into contact with the surface. The brush-shaped roller 36A (36B) hits the tip of the recording medium P sent out from the nip portion over the width direction (the direction perpendicular to the paper surface of FIGS. 2 and 4 and the left-right direction of FIG. 3). It functions as a separating member that comes into contact with and separates the recording medium P from the fixing roller 21.
Then, a plurality of brush-shaped portions 36A2 and 36B2 formed so that the elastic forces of the brush-shaped portions 36A2 and 36B2 that abut on the tip portion of the recording medium P are different from each other according to the thickness of the recording medium P conveyed to the nip portion (fixing nip). One of the brush-shaped rollers 36A and 36B (brush-shaped rotating body) is selected, and the selected brush-shaped roller is moved to a position where it can come into contact with the tip of the recording medium P.

Specifically, the fixing device 20 is provided with two brush-shaped rollers 36A and 36B (brush-shaped rotating bodies) that can be switched as separating members. That is, the first state (the state shown in FIGS. 2 and 4A) in which the first brush-shaped roller 36A is brought into contact with the fixing roller 21 to function as a separating member, and the second brush-shaped roller 36B Is switched between the second state (the state shown in FIG. 4B) in which the is brought into contact with the fixing roller 21 to function as a separating member, and the control of the motor 51 (stepping motor) by the control unit 50. It is configured in.

More specifically, with reference to FIG. 4, the first arm 37 is rotatably held by the first brush-shaped roller 36A on one end side, and the second brush-shaped roller 36B is rotatable on the other end side. It is held in. The first arm 37 is rotatably held with respect to the second arm 38 about the rotation shaft 37a. Further, the rotating shaft 37a of the first arm 37 is directly connected to the motor shaft of the motor 51 (see FIG. 2) (or is connected to the inter-connection via a gear train). With such a configuration, the first arm 37 is rotated about the rotation shaft 37a by the control of the motor 51 by the control unit 50, and the first state shown in FIG. 4A and FIG. 4B ), And the second state shown in) will be appropriately switched.
Further, the second arm 38 is rotatably held about the support shaft 38a with respect to the housing of the fixing device 20. Further, in the second arm 38, the first arm 37 is held on one end side of the support shaft 38a, and one end side of the tension spring 39 is connected to the other end side. The other end of the tension spring 39 is connected to the housing of the fixing device 20. With such a configuration, the brush-shaped roller 36A (36B) is urged by the urging force of the tension spring 39 in the direction of pressing against the fixing roller 21 via the second arm 38, and is desired on the surface of the fixing roller 21. It will come into contact with the pressure contact force.

Here, in the brush-shaped rollers 36A and 36B (brush-shaped rotating bodies), brush-shaped portions 36A2 and 36B2 made of a plurality of flexible hair-like members are provided around the outer peripheral surfaces of the shaft portions 36A1 and 36B1. It is a thing. Specifically, brush bristles made of resin fibers such as nylon, rayon, acrylic, vinylon, polyester, and vinyl chloride are planted on the base cloth and wound spirally on shafts 36A1 and 36B1 made of a metal material. The brush-shaped portions 36A2 and 36B2 are formed. Further, as shown in FIG. 3, in the brush-shaped rollers 36A and 36B in the present embodiment, the lengths of the brush-shaped portions 36A2 and 36B2 in the width direction are substantially the same as the lengths of the fixing rollers 21 in the width direction. The brush-shaped portions 36A2 and 36B2 are configured to abut against the fixing roller 21 in the width direction.

Further, in the present embodiment, the elastic force of the brush-shaped portion 36B2 of the second brush-shaped roller 36B is set to be larger than the elastic force of the brush-shaped portion 36A2 of the first brush-shaped roller 36A. ..
Here, the "elastic force" of the brush-shaped portions 36A2 and 36B2 is a force exerted by the brush-shaped portions 36A2 and 36B2 that are deformed by applying an external force as a reaction. Therefore, in the second state where the second brush-shaped roller 36B is in contact with the fixing roller 21 as shown in FIG. 4 (B), the first brush-shaped roller 36A is the fixing roller as shown in FIG. 4 (A). Compared to the first state in which the brush-shaped roller is in contact with the fixing roller 21, the brush-shaped roller is in contact with the fixing roller 21 with a stronger force.

The difference in elastic force between the two brush-shaped portions 36A2 and 36B2 can be formed by providing a difference in the material, density, length and the like of the brush bristles constituting the brush-shaped portions 36A2 and 36B2.
Further, in the present embodiment, the brush-shaped portions 36A2 and 36B2 are made of a plurality of flexible hair-like members. On the other hand, the brush-shaped portions 36A2 and 36B2 are formed by forming a plurality of notches in a plurality of flexible strip-shaped members (for example, a film-shaped member made of a material such as thin PET) in the circumferential direction. It can be arranged side by side to form a brush.)

Then, in the present embodiment, when the thickness of the recording medium P conveyed to the nip portion is thin, compared with the case where the recording medium P conveyed to the nip portion is thick. Of the plurality of brush-shaped rollers 36A and 36B (brush-shaped rotating bodies), the brush-shaped roller 36B having a large elastic force in the brush-shaped portion is selected.
Specifically, in the present embodiment, when the recording medium P to be passed is thin paper (recording medium P having a basis weight of 40 g / m ² or less), the second brush-shaped roller 36B is separated. The motor 51 is controlled by the control unit 50 so that it is selected to be used as a member and is in the second state shown in FIG. 4 (B). On the other hand, when the recording medium P through which the paper is passed is a medium other than thin paper (the recording medium P having a basis weight of more than 40 g / m ² ), the first brush-shaped roller 36A is used as a separating member. The motor 51 is controlled by the control unit 50 so that it is selected to be used and is in the first state shown in FIG. 4 (A).

As a means for detecting the thickness of the recording medium P to be passed through, a paper thickness sensor 53 that directly detects the thickness of the recording medium P can be used, or the thickness of the recording medium P is indirectly determined. An operation panel 52 that detects the target can also be used.
A known paper thickness sensor 53 can be used, and the paper thickness sensor 53 is installed at a predetermined position in the transport path from the paper feeding unit 7 to the fixing device 20, and directly determines the thickness of the recording medium P passing through that position. It detects the target. Further, the operation panel 52 is installed on the exterior portion of the image forming apparatus main body 1 and indirectly detects the thickness of the recording medium P based on the information of the recording medium P input by the user.
Then, the control unit 50 determines which of the two brush-shaped rollers 36A and 36B is used as the separating member according to the detected thickness of the recording medium P, and controls the motor 51 as described above. It will be.

As described above, in the present embodiment, as the separating member for preventing the recording medium P sent out from the nip portion from winding around the fixing roller 21, a separating claw having no flexibility is not used. Brush-shaped rollers 36A and 36B having flexibility are used. Therefore, even if the brush-shaped rollers 36A and 36B come into contact with the recording medium P and the fixing roller 21, the problem that the recording medium P and the fixing roller 21 are scratched is less likely to occur.
Further, the brush-shaped rollers 36A and 36B have a tip portion of the recording medium P so that the brush bristles of the flexible brush-shaped portions 36A2 and 36B2 enter the gap between the recording medium P and the fixing roller 21 in the width direction. The recording medium P is separated from the fixing roller 21 in contact with the fixing roller 21. Here, since the tip end portion of the recording medium P is a marginal region where the toner image is not supported, the adhesion to the fixing roller 21 is weaker than that of the other portions, and the tip portion is between the fixing roller 21 and the fixing roller 21. A relatively wide gap will be formed. Therefore, the brush-shaped portions 36A2 and 36B2 described above can enter the gaps between the brush bristles, and the function (separability) as a separating member is ensured. That is, the problem that the recording medium P after the fixing step winds around the fixing roller 21 and causes a jam (paper jam) is reduced.

As described above, the brush-shaped rollers 36A and 36B generally function as separating members without damaging the recording medium P or the fixing roller 21. However, if the elastic force of the brush-shaped portion is too strong, the tip portion of the recording medium P is likely to be scratched by the brush-shaped roller depending on the thickness (or type) of the recording medium P through which the paper is passed. Further, if the elastic force of the brush-shaped portion is too weak, it becomes difficult to function as a separating member depending on the thickness (or type) of the recording medium P through which the paper is passed.
The recording medium P (thin paper) having a thin thickness has low rigidity and easily wraps around the fixing roller 21. Therefore, in the present embodiment, when a thin recording medium P (thin paper) is passed through the paper, a second brush-shaped roller 36B having a relatively large elastic force is used as a separating member to improve the separability. ing. As a result, it is possible to prevent the thin paper from wrapping around the fixing roller 21 even when the thin paper is passed through. Further, in such a case, the elastic force of the second brush-shaped roller 36B tends to cause scratches on the tip of the recording medium P, but the elastic force is not set to be too strong, so that the recording medium P is not set. Due to the low rigidity of the (thin paper), bending occurs so as to escape when it comes into contact with the brush-shaped portion 36B2, and large scratches are not formed.
Further, the recording medium P other than the thin paper has a certain degree of rigidity and is difficult to wind around the fixing roller 21. Therefore, in the present embodiment, when a recording medium P (plain paper or thick paper) other than thin paper is passed, the first brush-shaped roller 36A having a relatively small elastic force is used as a separating member. It maintains its separability. As a result, even when the recording medium P other than the thin paper is passed through the paper, it is possible to prevent the recording medium P from being wound around the fixing roller 21. Further, in such a case, the small elastic force of the first brush-shaped roller 36A makes it difficult for the tip of the recording medium P to be scratched, and also makes it difficult for the surface of the fixing roller 21 to be scratched.
As described above, in the present embodiment, it is possible to efficiently and surely improve the separability of the recording media P having different thicknesses while minimizing the damage to the recording medium P and the fixing roller 21.

In the present embodiment, it is also possible to control to select one of the two brush-shaped rollers 36A and 36B according to the type of the recording medium P.
Specifically, when the type of recording medium P conveyed to the nip portion has low separability with respect to the fixing roller 21, the type of recording medium P conveyed to the nip portion P has high separability with respect to the fixing roller 21. Of the plurality of brush-shaped rollers 36A and 36B, the brush-shaped roller 36B having a larger elastic force of the brush-shaped portion is selected as compared with the case where the brush-shaped rollers 36A and 36B are made. More specifically, the type (paper type) of the recording medium P having low separability is stored in advance in the storage unit of the control unit 50, and is separable based on the input information regarding the recording medium P to the operation panel 52. The motor 51 is selected so that a second state (the state of FIG. 4B) is selected instead of the first state when it is determined that a low-type recording medium P is to be passed. Will be controlled.
Even when such control is performed, it is possible to efficiently and surely improve the separability of different types of recording media P while minimizing damage to the recording medium P and the fixing roller 21.

Here, with reference to FIG. 4, in the present embodiment, the brush-shaped rollers 36A and 36B (brush-shaped rotating bodies) are configured to rotate in the same direction as the rotation direction of the abutting fixing roller 21. ing.
Specifically, the drive motor 55 is connected so that even if any of the two brush-shaped rollers 36A and 36B comes into contact with the fixing roller 21, the drive motor 55 can be driven and transmitted to the brush-shaped roller. Then, the brush-shaped roller is rotationally driven in the clockwise direction of FIG. That is, the brush-shaped rollers 36A and 36B rotate in the counter direction at the contact position with respect to the fixing roller 21 that rotates clockwise.
By rotating the brush-shaped rollers 36A and 36B in the counter direction in this way, the recording medium P wound around the fixing roller 21 is separated along the rotation of the brush-shaped rollers 36A and 36B. That is, the function (separability) as a separating member is enhanced.

Further, in the present embodiment, the brush-shaped rollers 36A and 36B (brush-shaped rotating bodies) are configured to rotate at a peripheral speed equal to or higher than the peripheral speed of the abutting fixing roller 21.
Specifically, the drive motor 55 rotationally drives the brush-shaped rollers 36A and 36B so that the linear velocity ratio at the contact position with the fixing roller 21 is 1 or more.
By setting the rotation speeds of the brush-shaped rollers 36A and 36B high in this way, the recording is wound around the fixing roller 21 so as to follow the rotation of the brush-shaped rollers 36A and 36B at a speed faster than the speed of being caught in the fixing roller 21. The medium P will be separated. That is, the function (separability) as a separating member is enhanced.

Further, in the present embodiment, the brush-shaped rollers 36A and 36B (brush-shaped rotating bodies) guide the recording medium P delivered from the nip portion so as to be conveyed in the conveying direction.
Specifically, the brush-shaped rollers 36A and 36B are arranged along the transport path on the downstream side of the fixing device 20, and are rotated along the transport direction.
As a result, the recording medium P after being separated from the fixing roller 21 by the brush-shaped rollers 36A and 36B is guided along the rotation of the brush-shaped rollers 36A and 36B to the transport path on the downstream side of the fixing device 20. As a result, the transportability of the recording medium P after the fixing step is improved.

<Modification example 1>
FIG. 5 is an enlarged view showing a main part of the fixing device 20 as a modification 1, and is a view corresponding to FIG. 4 (A) in the present embodiment.
As shown in FIG. 5, in the first modification, a cleaning blade 60 is installed as a cleaning member for removing foreign matter adhering to the brush-shaped portion 36A2 of the brush-shaped roller 36A (brush-shaped rotating body).
Specifically, the cleaning blade 60 (cleaning member) is a substantially plate-shaped member made of a rubber material or a metal material, and is arranged so as to enter the brush bristles of the brush-shaped portion 36A2. As a result, when the brush-shaped roller 36A is rotationally driven, the cleaning blade 60 is in sliding contact with the brush-shaped portion 36A2 of the brush-shaped roller 36A, and foreign matter such as toner and paper dust adhering to the brush-shaped portion 36A2 is removed from the cleaning blade 60. Is mechanically removed by. The removed foreign matter falls downward and is collected in the case in which the cleaning blade 60 is held. As a result, it is possible to prevent problems such as foreign matter adhering to the brush-shaped roller 36A, deterioration of the function as a separating member, and damage to the recording medium P.
Note that FIG. 5 illustrates the first state in which the first brush-shaped roller 36A is in contact with the fixing roller 21, but in the second state in which the second brush-shaped roller 36B is in contact with the fixing roller 21. Even if there is, the cleaning blade 60 is configured to come into contact with the second brush-shaped roller 36B.

<Modification 2>
FIG. 6 is an enlarged view showing a main part of the fixing device 20 as the second modification.
As shown in FIG. 6, in the second modification, the brush-shaped rollers 36A and 36B (brush-shaped rotating bodies) come into contact with the surface of the fixing roller 21 as the fixing rotating body to separate the recording medium P from the fixing roller 21. Instead of functioning as a separating member, it is configured to function as a separating member that abuts on the surface of the pressure roller 31 as a pressure rotating body and separates the recording medium P from the pressure roller 31. Further, also in the second modification, as in the case of the present embodiment, one of the two brush-shaped rollers 36A and 36B having different elastic forces is selected according to the thickness and type of the recording medium P to be passed. Will be done.
When configured in this way, while minimizing damage to the recording medium P and the pressurizing roller 31, the separability from the pressurizing roller 31 efficiently and reliably with respect to the recording media P having different thicknesses and types. Can be enhanced.

<Modification example 3>
FIG. 7 is a configuration diagram showing a fixing device 20 as a modification 3.
In the present embodiment, the present invention is applied to the roller type fixing device 20 of the heat heater type, but the fixing device 20 to which the present invention is applied is not limited to such a type, and various types are applied. It can be installed in a type fixing device.
For example, as shown in FIG. 7A, the present invention is also applied to a heat heater type belt type fixing device 20 (a fixing device in which a fixing belt 22 is used as a fixing rotating body). You can also. In such a case, the fixing belt 22 is stretched and supported by a plurality of roller members such as a fixing auxiliary roller 23, a heating roller 24, and a tension roller. Further, the fixing auxiliary roller 23 is pressed against the pressure roller 31 via the fixing belt 22 to form a nip portion. Further, the heater 25 is fixedly installed inside the heating roller 24 having a hollow structure.
Further, as shown in FIG. 7B, the present invention can also be applied to the roller type fixing device 20 of the electromagnetic induction type (IH type). In such a case, in the fixing roller 21, an elastic layer, a heat generating layer electromagnetically induced and heated by an induction heating unit 70 around which an exciting coil is wound, a mold release layer, and the like are laminated on the core metal portion. It becomes a thing.
Further, although not shown, the present invention can also be applied to a roller type fixing device of a resistance heat generation type. In such a case, the fixing roller is installed so that the resistance heating element comes into contact with the hollow portion of the core metal portion, and an elastic layer, a mold release layer, or the like is laminated on the core metal portion.
And even in such a case, almost the same effect as that of the present embodiment can be obtained.

As described above, the fixing device 20 in the present embodiment abuts on the tip end portion of the recording medium P sent out from the nip portion in the width direction to separate the recording medium P from the fixing roller 21 (fixing rotating body). Brush-shaped rollers 36A and 36B (brush-shaped rotating bodies) are provided. Then, one of the plurality of brush-shaped rollers 36A and 36B formed so that the elastic forces of the brush-shaped portions 36A2 and 36B2 are different from each other according to the thickness and type of the recording medium P conveyed to the nip portion is used. It is selected and the selected brush-shaped roller is moved to a position where it can come into contact with the tip end portion of the recording medium P.
As a result, depending on the thickness and type of the recording medium P conveyed to the nip portion, the separability of the recording medium P with respect to the fixing roller 21 may be lowered, or the recording medium P may be in contact with the brush-shaped rollers 36A and 36B to be scratched. It is possible to prevent problems such as sticking.

In the present embodiment, the pressure roller 31 is used as the pressure rotating body, but a pressure belt can also be used as the pressure rotating body.
Then, even in such a case, the same effect as that of the present embodiment can be obtained.

Further, in the present embodiment, the brush-shaped rollers 36A and 36B are brought into contact with the fixing roller 21 to function as a separating member, but the brush-shaped rollers 36A and 36B are minutely attached to the fixing roller 21. It can also function as a separating member by facing each other with a large gap. As described above, since the tip of the recording medium P does not completely adhere to the fixing roller 21 due to the margin, the brush-shaped rollers 36A and 36B face the fixing roller 21 in a non-contact manner with a minute gap. Even so, since the brush bristles of the brush-shaped rollers 36A and 36B can be inserted into the gap at the tip of the recording medium P, such a configuration is possible.
Then, even in such a case, the same effect as that of the present embodiment can be obtained. In particular, since the brush-shaped rollers 36A and 36B are not in contact with the fixing roller 21, the surface of the fixing roller 21 does not need to be further damaged.

Further, in the present embodiment, two brush-shaped rollers 36A and 36B having different elastic forces are used, but three or more brush-shaped rollers 36A and 36B having different elastic forces can also be used.
Then, even in such a case, the same effect as that of the present embodiment can be obtained. In particular, by using three or more brush-shaped rollers 36A and 36B, finer texture control can be performed according to the thickness and type of the recording medium P to be passed.

It is clear that the present invention is not limited to the present embodiment, and within the scope of the technical idea of the present invention, the present embodiment may be appropriately modified in addition to the suggestions in the present embodiment. is there. Further, the number, position, shape, etc. of the constituent members are not limited to the present embodiment, and can be a suitable number, position, shape, etc. for carrying out the present invention.

In the present application, the "width direction" is defined as a direction orthogonal to the transport direction of the recording medium.
Further, in the present application, the "recording medium" is defined to include all sheet-shaped recording media such as coated paper, label paper, transparencies, and films, in addition to ordinary paper (paper).

1 Image forming apparatus (image forming apparatus main body),
20 Fixing device,
21 Fixing roller (fixing rotating body),
25 heater (heating means),
31 Pressurized roller (pressurized rotating body),
36A 1st brush-like roller (brush-like rotating body),
36A1 shaft part, 36A2 brush-like part,
36B 2nd brush-like roller (brush-like rotating body),
36B1 shaft part, 36B2 brush-like part,
37 1st arm,
38 Second arm,
39 Tensile spring (biasing member),
60 Cleaning blade (cleaning member),
P Recording medium.

Japanese Unexamined Patent Publication No. 60-76779

Claims (9)

A fixing rotating body that heats the toner image and fixes it on the surface of the recording medium,
A pressurized rotating body that forms a nip portion through which the recording medium is conveyed by pressure contacting the fixing rotating body, and
At a position downstream of the nip portion in the transport direction of the recording medium, the width of the tip portion of the recording medium sent out from the nip portion abuts or faces the surface of the fixing rotating body or the pressurized rotating body. A brush-shaped rotating body that abuts in a direction and separates the recording medium from the fixed rotating body or the pressurized rotating body.
With
Among the plurality of brush-shaped rotating bodies formed so that the elastic forces of the brush-shaped portions that abut on the tip end portion of the recording medium differ from each other according to the thickness or type of the recording medium conveyed to the nip portion. A fixing device characterized in that one is selected and the selected brush-shaped rotating body is moved to a position where it can come into contact with the tip end portion of the recording medium. When the thickness of the recording medium conveyed to the nip portion is thin, the thickness of the recording medium conveyed to the nip portion is thicker than that of the plurality of brush-shaped rotating bodies. The fixing device according to claim 1, wherein a brush-shaped rotating body having a large elastic force of the brush-shaped portion is selected. When the type of recording medium conveyed to the nip portion is low in separability from the fixing rotating body or the pressurized rotating body, the type of recording medium conveyed to the nip portion is the fixing rotating body or the fixing rotating body. A claim characterized in that a brush-shaped rotating body having a larger elastic force of the brush-shaped portion is selected from the plurality of brush-shaped rotating bodies as compared with the case where the reversible property with respect to the pressurized rotating body is high. The fixing device according to item 1 or claim 2. The method according to any one of claims 1 to 3, wherein the brush-shaped rotating body rotates in the same direction as the rotation direction of the fixed rotating body or the pressurized rotating body that abuts or faces each other. Fixing device. Any of claims 1 to 4, wherein the brush-shaped rotating body rotates at a peripheral speed equal to or higher than the peripheral speed of the fixed rotating body or the pressurized rotating body that abuts or faces each other. Fixing device described in. The fixing device according to any one of claims 1 to 5, wherein the brush-shaped rotating body guides the recording medium sent out from the nip portion so as to be conveyed in the conveying direction. The fixing device according to any one of claims 1 to 6, further comprising a cleaning member for removing foreign matter adhering to the brush-shaped portion of the brush-shaped rotating body. The brush-shaped rotating body is characterized in that the brush-shaped portion composed of a plurality of hair-like or strip-shaped members is provided around the outer peripheral surface of the shaft portion. The fixing device according to any one. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 8.

Images