JP7091882B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming device.

As an image forming apparatus such as a copying machine, a facsimile, and a printer, an image forming apparatus using an electrophotographic method is known. In the image forming process, an electrostatic latent image is formed on the surface of a photosensitive drum which is an image carrier, and the electrostatic latent image is developed with a developer such as toner to make a visible image, and the developed image is obtained. It is established by the process of transferring an image to a recording medium (also referred to as recording material, paper, recording paper) by a transfer device, supporting the image, and fixing an unfixed toner image on the recording medium by a fixing device using pressure, heat, or the like. There is.

The fixing device includes, for example, a fixing member (fixing roller) having a heat source inside and a pressure member (pressurizing roller) that presses against the fixing member, and is formed by pressure contact between the pressure member and the fixing member. It is known that a recording medium carrying an unfixed toner image is heated and fixed by a fixing nip portion (nip portion) while being sandwiched and conveyed.

In such a fixing device, the surface of the fixing member is devised to prevent toner adhesion. However, it is known that a phenomenon called offset occurs in which toner slightly adheres to the fixing member from the transmitted recording medium depending on the type of recording medium, the image formed, the installation environment, and the like. Since this offset toner (also referred to as offset toner) remains on the fixing member or the pressurizing member, it may be back-transferred to a recording medium or the like and stain the image.
There is an aspect that the offset of the toner is likely to occur due to the tendency of lowering the melting point of the toner accompanying the energy saving of the fixing device in recent years and reducing the particle size of the toner for improving the image quality.

In addition, paper dust such as calcium carbonate and filler contained in the transfer paper, which is a recording medium, may adhere to the surface of the fixing member, and further, these and toner (wrapping around from the fixing member to the pressure member). However, it may be combined with (including offset toner) to grow and stick.

In order to prevent such a phenomenon, a fixing device provided with a cleaning member for removing toner or the like adhering to or fixed to the fixing member or the pressure member is known (see, for example, Patent Documents 1 and 2). .. As the cleaning member, for example, a cleaning roller as a rotating member, a brush roller, and the like are known.

However, the toner removed by the cleaning member and deposited on the cleaning member may be remelted by heat. There is a problem that the remelted toner is reverse-transferred to the fixing member, the pressure member, or the recording medium (paper).
Remelting of toner is a phenomenon that occurs remarkably when, for example, a small size paper is passed as compared with the maximum size paper that can be passed. Since the area in contact with the fixing roller is small for small-sized paper, the temperature is taken only in a narrow range of the fixing roller, and as a result, the temperature of the fixing roller in the non-passing part rises, and the cleaning member of the corresponding part also becomes hot. This is because the adhered toner melts away. Reverse transfer of the remelted toner may cause image stains and jams.

A cleaning device capable of suppressing such adverse effects and effectively removing stains adhering to the rotating member of the fixing device for a long period of time has been proposed (see, for example, Patent Document 3).

Patent Document 3 describes a rotary cleaning member for cleaning dirt adhering to a rotary member included in a fixing device, a deposit removing member for removing adhered deposits by abutting on the rotary cleaning member, and a deposit removing member. A cleaning device including a contact separation control means for performing contact separation control for contacting and separating the deposit removing member with and separated from the rotary cleaning member according to the temperature around the rotary cleaning member or the rotary cleaning member is disclosed. In the temperature range where the removal effect of the deposit is large, the deposit removing member is brought into contact with the rotary cleaning member, and in the temperature region where the removal effect of the deposit is small, the deposit removing member is separated from the rotary cleaning member. ..

According to the apparatus of Patent Document 3, when the temperature around the deposit removing member that comes into contact with the rotary cleaning member that is the cleaning member is too high, the deposit removing member is separated to soften and melt and have high adhesiveness. It is said that it is possible to prevent the toner that has come to show the above or is in a fluidized state from adhering to the rotary cleaning member again and deteriorating the cleaning effect.

However, when the fixing device is continuously operated and the temperature is sufficiently high, the molten deposits only move while diffusing from the recovery roller to the rotary cleaning member (brush roller), and the deposits are not removed. It is difficult to suppress the occurrence of stains and jams on the image.

Therefore, the present invention provides a fixing device capable of preventing reverse transfer to a pressure roller and a fixing roller due to remelting of toner or the like removed by a cleaning member, and suppressing image stains and jams. The purpose is.

In order to solve the above problems, the fixing device according to the present invention is provided between a fixing member rotatably provided, a heating means for heating the fixing member, and a rotatably provided fixing member. The pressure member for forming the portion and the cleaning member for cleaning the pressurizing member are provided, and the toner image is recorded on the recording medium by passing a recording medium carrying an unfixed toner image on the nip portion. In the fixing device to be fixed above, a heat absorbing member for contacting with the cleaning member to absorb heat and cooling is further provided, and the cleaning member is rotatable and contactably arranged with the pressure member. It is a member, and when the surface temperature of the pressurizing member continuously exceeds a predetermined temperature for a predetermined time, it is separated from the pressurizing member, and the heat absorbing member is separated from the pressurizing member by the cleaning member. It is characterized in that it comes into contact with the cleaning member during the operation.

According to the present invention, there is provided a fixing device capable of preventing reverse transfer to a pressure roller and a fixing roller due to remelting of toner or the like removed by a cleaning member, and suppressing image stains and jams. be able to.

It is a schematic block diagram which shows the image forming apparatus equipped with the fixing apparatus which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the fixing device which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the fixing device which concerns on one Embodiment of this invention. It is a schematic block diagram which shows a part of the driving means of the fixing device which concerns on one Embodiment of this invention. It is a schematic block diagram which shows an example of the conventional fixing apparatus.

Hereinafter, the fixing device and the image forming device according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments shown below, and can be modified within the range conceivable by those skilled in the art, such as other embodiments, additions, modifications, and deletions. However, as long as the action and effect of the present invention are exhibited, it is included in the scope of the present invention.

(Image forming device)
FIG. 1 is an overall schematic view of an image forming apparatus 1 provided with the fixing apparatus according to the present embodiment.
In the center of the color image forming apparatus 1 shown in FIG. 1, an image forming unit 2 to which four process units 9Y, 9M, 9C, and 9K are detachably provided is arranged. Each process unit 9Y, 9M, 9C, 9K accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specific process units 9 include a photoconductor drum 10 which is a drum-shaped rotating body capable of supporting toner as a developer on the surface, and a charging roller 11 which uniformly charges the surface of the photoconductor drum 10. And a developing device 12 having a developing roller 13 that supplies toner to the surface of the photoconductor drum 10.

Toner bottles 26Y, C, M, and K filled with yellow, cyan, magenta, and black toners are detachably provided on the upper part of the image forming apparatus 1. Then, the toner of each color is replenished to the developing device 12 of each color through the replenishment path provided between the toner bottles 26Y, C, M, and K with the developing device 12.

An exposure unit 3 is arranged below the process unit 9. The exposure unit 3 is configured to emit laser light based on the image data.

A transfer unit 4 is arranged above the image forming unit 2. The transfer unit 4 includes an endless intermediate transfer belt 16, a primary transfer roller 17 arranged at a position facing the photoconductor drum 10 of each process unit 9 with the intermediate transfer belt 16 interposed therebetween, and a transfer member. It includes a secondary transfer roller 18, a secondary transfer backup roller 14 as an opposing member, a cleaning backup roller 15, a tension roller 27, and a belt cleaning device 28.

The intermediate transfer belt 16 is an endless belt, and is stretched by a secondary transfer backup roller 14, a cleaning backup roller 15, and a tension roller 27. Here, by rotationally driving the secondary transfer backup roller 14, the intermediate transfer belt 16 orbits (rotates) in the direction indicated by the arrow A in the figure.

Each of the four primary transfer rollers 17 sandwiches an intermediate transfer belt 16 with each photoconductor drum 10 to form a primary transfer nip. Further, a power supply is connected to each primary transfer roller 17, and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to each primary transfer roller 17.

The secondary transfer roller 18 sandwiches the intermediate transfer belt 16 with the secondary transfer backup roller 14 to form a secondary transfer nip M as a transfer nip. Further, similarly to the primary transfer roller 17, a power supply is also connected to the secondary transfer roller 18, and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the secondary transfer roller 18. It has become like.

The belt cleaning device 28 has a cleaning brush and a cleaning blade arranged so as to be in contact with the intermediate transfer belt 16. The waste toner collected by the belt cleaning device 28 is stored in the waste toner container via the waste toner transfer hose.

The paper feed unit 5 is located at the lower part of the image forming apparatus 1, and is a feed cassette 19 accommodating a recording medium (hereinafter, also referred to as “paper”) P, or a paper feed cassette 19 for carrying out the paper P. It consists of a paper roller 20 and the like.

The transport path 6 is a transport path for transporting the paper P carried out from the paper feed section 5, and the transport roller pair is in the middle of the transport path 6 up to the paper discharge section 8 described later in addition to the pair of resist rollers 21. It is arranged appropriately in.

The fixing device 7 according to the present invention has a fixing roller 31 as a fixing member heated by a heating source, a pressure roller 32 as a pressure member capable of pressurizing the fixing roller 31, and the like. The fixing roller 31 forms a fixing nip (hereinafter referred to as a nip portion) N with the pressure roller 32.

The paper ejection unit 8 is provided at the most downstream side of the transport path 6 of the image forming apparatus 1. The paper ejection unit 8 is provided with a pair of paper ejection rollers 24 for ejecting the paper P to the outside and a paper ejection tray 25 for stocking the ejected paper P.

The image forming unit 2, the exposure unit 3, the transfer unit 4, and the like are image forming means for forming an image on the paper P.

Hereinafter, the basic operation of the image forming apparatus 1 will be described with reference to FIG.
When the image forming operation is started in the image forming apparatus 1, an electrostatic latent image is formed on the surface of the photoconductor drum 10 of each process unit 9Y, 9C, 9M, 9K. The image information exposed on each photoconductor drum 10 by the exposure unit 3 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. An electrostatic latent image is formed on each photoconductor drum 10, and the toner stored in each developing device 12 is supplied to the photoconductor drum 10 by a drum-shaped developing roller 13, so that the electrostatic latent image is formed. It is visualized as a toner image (developer image) which is a manifest image.

In the transfer unit 4, the intermediate transfer belt 16 is driven to travel in the direction of the arrow A in the figure by the rotational drive of the secondary transfer backup roller 14. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 17. As a result, a transfer electric field is formed at the primary transfer nip, and the toner images formed on each photoconductor drum 10 are sequentially superimposed and transferred on the intermediate transfer belt 16 at the primary transfer nip.

On the other hand, when the image forming operation is started, in the lower part of the image forming apparatus 1, the paper feeding roller 20 of the paper feeding unit 5 is rotationally driven, so that the paper P accommodated in the paper feeding cassette 19 is moved to the transport path 6. Be sent out. The paper P sent out to the transport path 6 is timed by the resist roller 21 and sent to the secondary transfer nip between the secondary transfer roller 18 and the secondary transfer backup roller 14. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner image on the intermediate transfer belt 16 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

The paper P on which the toner image is transferred is conveyed to the fixing device 7, and the paper P is heated and pressed by the fixing roller 31 and the pressure roller 32 to fix the toner image on the paper P. Then, the paper P on which the toner image is fixed is separated from the fixing roller 31, is conveyed by the transport roller pair, and is discharged to the paper discharge tray 25 by the paper discharge roller 24 at the paper discharge unit 8.

The above description is an image forming operation when forming a full-color image on paper P, but a single-color image can be formed by using any one of four process units 9Y, 9C, 9M, and 9K. It is also possible to use two or three process units 9 to form a two-color or three-color image.

(Fixing device)
2 and 3 are schematic views of the main configuration of the fixing device according to the present embodiment.
The fixing device 7 shown in FIGS. 2 and 3 is rotatably provided with a fixing member (hereinafter, also referred to as “fixing roller”) 31 rotatably provided, and a heating means 29 for heating the fixing member 31. The nip portion N is provided with a pressurizing member (hereinafter, also referred to as “pressurizing roller”) 32 that forms a nip portion N between the fixing member 31 and a cleaning member 33 that cleans the pressurizing member 32. It is a device that passes a recording medium P carrying an unfixed toner image and fixes the toner image on the recording medium P.

The fixing device 7 further includes a heat absorbing member (hereinafter, also referred to as “heat absorbing roller”) 34 for contacting with the cleaning member 33 to absorb heat and cool it.
The cleaning member 33 is a rotatable member arranged so as to be contactable and detachable from the pressurizing member 32, and the endothermic member 34 hits the cleaning member 33 when the cleaning member 33 is separated from the pressurizing member 32. Contact.
Examples of the cleaning member 33 include a brush member (brush roller). In this embodiment, an embodiment in which the cleaning member 33 is a brush roller will be described.

Further, the fixing device 7 includes a mold release agent coating member (hereinafter, also referred to as “release agent coating roller”) 35 that applies a mold release agent to the heat absorbing member 34.
The mold release agent application member 45 is a rotatable member, and is rotated by a driving means.
The endothermic roller 34 comes into contact with the release agent application roller 35, and is driven to rotate by the rotation of the release agent application roller 35.

In the figure, the rotation direction of the fixing roller 31, the pressure roller 32, the brush roller 33, the heat absorbing roller 34, and the mold release agent coating roller 35, and the conveying direction of the recording medium P are indicated by arrows.

FIG. 2 shows a state in which the brush roller 33, which is a cleaning member, is in contact with the pressure roller 32. In this case, the brush roller 33 is separated from the heat absorbing roller 34.
FIG. 3 shows a state in which the brush roller 33, which is a cleaning member, is separated from the pressure roller 32. In this case, the brush roller 33 is in contact with the heat absorbing roller 34, and the heat absorbing roller 34 is also in contact with the mold release agent applying roller 35.

The brush roller 33 may be configured to be separated from the pressure roller when the surface temperature of the pressure roller 32 continuously exceeds the predetermined temperature for a predetermined time.
For example, a means capable of detecting the surface temperature and the passage of time of the pressure roller 32 is arranged, and when the temperature exceeding the reference time is continuously detected for exceeding the reference time, the brush roller 33 is pressed by the pressure roller 32. The operation can be controlled so as to come into contact with the heat absorbing roller 34 at a distance from the heat absorbing roller 34.
Here, the reference temperature and time can be appropriately selected according to the printing conditions, the environment, and the like as long as the toner can be prevented from remelting. For example, the state where the surface temperature is 145 to 200 ° C. can be continued for 5 minutes or more.

Further, the brush roller 33 may be configured so that the recording medium P comes into contact with the pressure roller 32 while passing through the nip portion N and is separated from the pressure roller 32 after the recording medium P passes through the nip portion N. ..
In this case, for example, a means for detecting the passage of the rear end portion of the recording medium P is arranged on the downstream side of the nip portion N, and there is no recording medium P through which the recording medium P passes and passes through the nip portion N. If this is the case, the operation can be controlled so that the brush roller 33 is separated from the pressure roller 32 and comes into contact with the heat absorbing roller 34.

Examples of the brush roller 33 include a core metal and a large number of brush fibers provided on the outer peripheral surface of the core metal. Foreign matter on the surface such as offset toner of the pressure roller 32 can be entangled and recovered by the brush fiber.
The material of the brush fiber is preferably heat resistant, and examples thereof include polyimide (PI) and polyphenylene sulfide (PPS).

The heat absorbing roller 34 is a rotating member having a heat pipe inside as a heat absorbing means. For example, a roller member having a heat pipe inside and having a metal such as aluminum on the outside can be mentioned.
By providing a heat pipe, a uniform temperature distribution in the direction of the rotation axis can be realized.

The mold release agent coating roller 35 is a mold release agent coating means containing a mold release agent, and is, for example, composed of a core metal and a coating member in which the outer peripheral surface of the core metal is impregnated with the mold release agent. Further, there is a case where a control layer for controlling the amount of exudation is provided on the surface layer.
The coating member may be any as long as it can exude the impregnated mold release agent and can be applied to the contact target (heat absorbing roller 34), and examples thereof include foams and non-woven fabrics.

The drive of the release agent application roller 35 will be described with reference to FIG.
As shown in FIG. 4, the fixing device 7 of the present embodiment has a pressure gear 36 for driving a pressure roller 32, an idler gear 37 connected to the pressure gear, and a coating roller gear for driving a mold release agent application roller 35. It is equipped with 38.

The drive is transmitted from the motor of the image forming apparatus main body (not shown) to the pressurizing gear 36. As a result, the pressure roller 32 is rotationally driven. Alternatively, a pressure gear 36 driven from a fixing gear (not shown) is supported as an idler gear by a bearing on the pressure roller 32 shaft. Further, the drive is transmitted to the coating roller gear 38 via the connected idler gear 37, whereby the release agent coating roller 35 is rotationally driven.
Then, the endothermic roller 34 is driven to rotate in contact with the release agent application roller 35.

As described above, the fixing device 7 of the present embodiment is provided with a brush roller 33 that directly cleans foreign matter such as toner on the pressure roller 32 so as to be detachable, and the brush roller 33 can be brought into contact with the heat absorbing roller 34. Therefore, it is possible to suppress the temperature rise of the brush roller 33 and prevent the removed toner and the like from being remelted. As a result, it is possible to prevent the occurrence of reverse transfer due to the melted toner, and it is possible to suppress the occurrence of stains on the image and jam around the fixing portion.

Further, the release agent is applied to the pressure roller 32 by the brush roller 33 that holds the release agent by coming into contact with the release agent application roller 35 via the heat absorbing roller 34, and the amount of offset toner generated. Can be reduced.

FIG. 5 shows an example of a fixing device (device of Patent Document 3) provided with a conventional cleaning means.
As shown in FIG. 5, in the conventional fixing device, the pressure roller 32 is in contact with the roller member 134 for the purpose of cleaning and soaking heat. A brush roller 133 for removing foreign matter is in contact with the roller member 134. The roller member 134 is always in contact with the pressure roller 32. For this reason, the recovered toner or the like may melt out, causing stains or jams on the image due to reverse transfer.

On the other hand, in the fixing device 7 according to the present invention, as shown in FIGS. 2 and 3, the foreign matter on the pressure roller 32 is directly cleaned by the brush roller 33, and the pressure roller 32 has a predetermined high temperature. When the conditions are satisfied, the brush roller 33 is separated from the pressure roller 32 and brought into contact with the heat absorbing roller 34 to lower the temperature, and at the same time, the removing agent from the mold removing agent applying roller 35 is applied to the heat absorbing roller 34. It is configured to receive via.
As a result, it is possible to suppress the melting of toner due to the temperature rise of the brush roller 33, and it is possible to further reduce the amount of offset toner generated.

1 Image forming device 7 Fixing device 31 Fixing member (fixing roller)
32 Pressurizing member (pressurizing roller)
33 Cleaning member (brush roller)
34 Endothermic member (endothermic roller)
35 Release agent application member (release agent application roller)
36 Pressurizing gear 37 Idler gear 38 Coating roller gear 39 Heating means N Nip part P Recording medium (paper)

Japanese Unexamined Patent Publication No. 2006-6744 Japanese Patent No. 3608969 Japanese Unexamined Patent Publication No. 2017-3759

Claims (7)

With the fixing member provided rotatably,
A heating means for heating the fixing member and
A pressurizing member that is rotatably provided and forms a nip portion between the fixing member and the fixing member.
A cleaning member for cleaning the pressure member is provided.
In a fixing device in which a recording medium carrying an unfixed toner image is passed through the nip portion and the toner image is fixed on the recording medium.
Further provided with a heat absorbing member for contacting with the cleaning member to absorb heat and cooling the cleaning member.
The cleaning member is a rotatable member displaceable from the pressurizing member, and when the surface temperature of the pressurizing member continuously exceeds a predetermined temperature for a predetermined time, the pressurization is performed. Separated from the member,
The endothermic member is a fixing device characterized in that the cleaning member comes into contact with the cleaning member when the cleaning member is separated from the pressurizing member. The fixing device according to claim 1, wherein the cleaning member is a brush member. The fixing device according to claim 1 or 2, wherein the heat absorbing member is provided with a mold release agent coating member. The fixing device according to claim 3, wherein the mold release agent coating member is a rotatable member and is rotated by a driving means. The fixing device according to any one of claims 1 to 4, wherein the heat absorbing member is a rotating member having a heat pipe inside as a heat absorbing means. Claim 1 is characterized in that the cleaning member comes into contact with the pressurizing member while the recording medium passes through the nip portion, and separates from the pressurizing member after the recording medium passes through the nip portion. The fixing device according to any one of 5 to 5 . An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 6 .

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