JP6494208B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device, and is suitable for an electrophotographic image forming apparatus in which a toner image formed on a recording material using an electrophotographic image forming process is melted by heat and fixed on the recording material. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine and an electrophotographic printer (laser beam printer, LED printer, etc.).

  An image forming apparatus using an electrophotographic process is equipped with a fixing device that performs heat fixing processing on a toner image formed on a recording material. In recent years, many constituent materials for electrophotographic toners contain release wax. This is added to adjust the glossiness of the printed image, impart effects such as pigment dispersibility, and prevent fixing offset.

  Here, there are several types of fixing offset phenomena as shown below. In the process of fixing to the recording material, if the heating of the toner by the fixing member is insufficient (low temperature), the toner is not sufficiently melted and the fixing force to the recording material is reduced. It will stick. This phenomenon is called cold offset, and the portion where the toner adheres to the fixing member appears as an image defect on the recording material. Further, since the fixing toner has a weak fixing force, it may be peeled off from the recording material by friction or the like.

  On the other hand, if the temperature of the fixing member is too high, the toner is sufficiently melted, but the toner viscosity is lowered more than necessary, so that part of the molten toner is peeled off from the recording material and contaminates the surface of the fixing member. Resulting in. This phenomenon is called hot offset and results in image loss on the recording material, similar to cold offset.

  Thus, as a method for preventing these fixing offsets, Patent Document 1 proposes to add a wax component to the toner as a release agent. By encapsulating the release wax in the toner, the release wax moves to the interface between the molten toner and the fixing member at the time of heat-fixing, and the anti-offset performance is improved. Furthermore, Patent Document 2 proposes a technique of adding two or more types of release waxes to the toner in order to improve the anti-offset performance.

  However, it has been found that release wax evaporates when heated above a certain level. When this release wax adheres to the conveyance guide in the fixing device, it becomes conveyance resistance, and when it adheres to the conveyance roller, it reduces the friction coefficient of the roller, thereby reducing the conveyance performance, It can also cause problems.

JP-A-8-184992 JP 2000-3070 A

  Here, as a method for suppressing the discharge amount of the wax vaporizing component from the fixing device, it is conceivable to narrow the airflow path along the route, which is a route for discharging the wax vaporizing component in the fixing device. However, when the component (inner wall member) constituting the air flow path is brought close to the fixing member along the path to obtain the effect, the component (inner wall member) constituting the air flow path is affected by the heat of the fixing member. There is a possibility that an adverse effect of thermal deformation and contact with the fixing member may occur. Further, there is a possibility that interference with parts (inner wall members) constituting the air flow path during assembly of the fixing member may occur.

  An object of the present invention is to prevent a wax vaporizing component from passing through a discharge portion with a simple configuration without a harmful effect as in the case where an inner wall member is brought close to a fixing member along a route in order to narrow an air flow route. An object of the present invention is to provide a fixing device that can be used.

In order to achieve the above object, a fixing device according to the present invention includes a first rotating body, and a counter body that faces the first rotating body and forms a first nip portion together with the first rotating body. And a second rotating body that forms a second nip portion together with the first rotating body, heating means for heating the first rotating body, the first rotating body, and the second rotating body. A cover member surrounding at least a part of the rotating body, and sandwiching and conveying a recording material carrying a toner image formed using toner containing wax in the first nip portion, In the fixing device for heat-fixing on the recording material, in the air flow path led to the discharge portion through the inner space of the cover member of the component vaporized from the wax by being heated in the first nip portion, Of the first rotating body and the second rotating body. There is a restricting member that restricts the passage of the vaporized component at a position opposed to at least one of the first position for restricting the passage, and a second position retracted from the first position. The tip of the restricting member at the first position is an inner space of an outer tangent line between the first rotating body and the second rotating body, and The first rotator is located upstream of the second nip portion in the rotation direction of the first rotator, and is located at a position corresponding to a confluence portion of the airflow by the first and second rotators .

  According to the present invention, there is no adverse effect as in the case where the inner wall member is brought close to the fixing member along the path in order to narrow the air flow path, and the passage of the wax vaporizing component to the discharge portion can be suppressed with a simple configuration. it can.

1 is a cross-sectional view illustrating an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. FIG. 2 is a schematic view around a fixing device according to an exemplary embodiment of the present invention. (A) is a schematic diagram showing the flow of the airflow in the fixing device of the comparative example, (b) is a schematic diagram showing the flow of the airflow in the fixing device according to the first embodiment of the present invention. FIG. 3 is a schematic view when the fixing device according to the first embodiment is assembled. (A) is a schematic diagram of the periphery of a fixing device according to a second embodiment of the present invention, and (b) is a perspective view of a regulating member that regulates the amount of vaporized components that pass in the second embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
(Image forming device)
An image forming apparatus 1 shown in FIG. 1 is an intermediate transfer belt type color image forming apparatus equipped with a fixing device according to an embodiment of the present invention. The image forming apparatus 1 includes drum-shaped electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 1a, 1b, 1c, and 1d. The photosensitive drums 1a, 1b, 1c, and 1d have a predetermined peripheral speed (process speed). Driven by rotation.

  In this rotation process, the photosensitive drums 1a, 1b, 1c, and 1d are uniformly charged to predetermined polarities and potentials by the charging rollers 2a, 2b, 2c, and 2d, and then subjected to image exposure by the image exposure unit 3. Thereby, an electrostatic latent image corresponding to each color component image of the target color image is formed. Next, the electrostatic latent image is developed by the developing devices 4a, 4b, 4c, and 4d for each color at the development position, and visualized as a toner image.

  The intermediate transfer belt 10 is an endless belt (endless belt) and is stretched by tension members (a driving roller 11, a counter roller 12, a tension roller 13, and an auxiliary roller 18). The photosensitive drums 1a, 1b, 1c, and 1d are rotationally driven at substantially the same peripheral speed so that the photosensitive drums 1a, 1b, 1c, and 1d move in the same direction as the photosensitive drums at positions where they abut against the photosensitive drums.

  The toner image of the first color formed on the photosensitive drum 1a passes through a contact portion (hereinafter referred to as a primary transfer nip) between the photosensitive drum 1a and the intermediate transfer belt 10 and is transferred onto the intermediate transfer belt 10. (Primary transfer). Here, a primary transfer voltage is applied to the primary transfer rollers 14a, 14b, 14c, and 14d. The primary transfer residual toner remaining on the surface of the photosensitive drum 1a is cleaned and removed by the cleaning device 5a, and then subjected to an image forming process below charging.

  Thereafter, similarly, a second color toner image, a third color toner image, and a fourth color toner image are formed and sequentially transferred onto the intermediate transfer belt 10 to correspond to the target color image. A composite color image is obtained.

  The four color toner images on the intermediate transfer belt 10 are collectively applied to the surface of the sheet S fed by the sheet feeding means 50 in the process of passing through the secondary transfer nip between the intermediate transfer belt 10 and the secondary transfer roller 20. Transferred (secondary transfer). Here, a secondary transfer voltage is applied to the secondary transfer roller 20 by a secondary transfer power source. Thereafter, the sheet S carrying the four-color toner images is introduced into the fixing device 30, where the four-color toners are melted and mixed and fixed (fixed) on the sheet S by being heated and pressurized. Through the above operation, a full-color print image is formed and discharged outside the apparatus by the discharge roller 34.

  Further, the secondary transfer residual toner remaining on the surface of the intermediate transfer belt 10 is cleaned and removed by the transfer belt cleaning device 16.

(Fixing device)
In the fixing device 30 of the present embodiment shown in FIG. 2, a fixing roller 31 as a first rotating body, which is a fixing member for heating the sheet S to which the toner image is transferred, can rotate around a rotation shaft 31a. Is provided. Then, a first nip portion (fixing nip portion) N1 is formed in pressure contact with a pressing means 33 as a counter member below the fixing roller 31, and the sheet S as a recording material is nipped and conveyed.

  Further, the fixing device 30 of the present embodiment employs an external heating method, and in order to heat the fixing roller 31, a heating unit 32 is provided above the fixing roller 31 and comes into contact with the fixing roller 31 to be the second. The nip portion (heating nip portion) N2 is formed. A heater 32 h as a heating source is provided inside the heating unit 32.

  Heat is transmitted to the fixing roller 31 by the second nip portion N2 by running the heat-resistant film 32f as the second rotating body between the heater 32h and the fixing roller 31 facing the heater 32h. It is done. The heat is transmitted to the first nip portion N1, and the sheet S carrying the unfixed toner image is nipped and conveyed to heat and fix the unfixed toner image on the sheet. The fixed sheet S is guided to the guide members 36 a and 36 b and is discharged out of the apparatus by the paper discharge roller 34.

(Generation of wax vaporization component)
Next, with reference to FIG. 3, the occurrence state of the wax vaporizing component in the fixing device according to the present embodiment will be described. The toner image formed using the toner containing the wax used in the present embodiment is heated at the first nip portion (fixing nip portion) N1 to generate a wax vaporizing component. Therefore, it is important to keep the wax vaporization component generated in the fixing device in the fixing device 30.

  There is an influence of an air current on the wax vaporizing component being discharged out of the fixing device through the discharging portion of the fixing device, and the air current in the vicinity of the heat-resistant film 32f will be described with reference to FIG. 3A shows the flow of airflow in the fixing device of the comparative example, and FIG. 3B shows the flow of airflow in the fixing device of this embodiment.

  As shown in FIG. 3A, since the fixing roller 31 and the heat resistant film 32f rotate in the direction of the arrow, air currents indicated by arrows X1 'and X2' are generated in the vicinity of the fixing roller 31 and the heat resistant film 32f. On the other hand, the airflow staying in the image forming apparatus or the fixing device is an upward airflow caused by heat, and an airflow indicated by an arrow Y 'is generated. Even if the gap between the guide member 36a functioning as the inner wall member, the fixing roller 31, and the heat-resistant film 32f is narrowed, the wax vaporizing component is moved out of the fixing device by the ascending air current Y 'and the air current X2' generated by the rotation of the heat-resistant film 32f. And discharged.

  Therefore, in FIG. 3B, the gap filling member 37 as a regulating member movably provided on the guide member 36a is joined at the junction of the fixing roller 31 and the heat-resistant film 32f, and the outer shape of the fixing roller 31 and the heat-resistant film 32f. Arranged in the inner space (heating nip side) from the tangent (first position). That is, the first position is at the junction of the airflows (arrows X1 ′ and X2 ′) by the first and second rotating bodies that are about to approach each other on the upstream side of the heating nip portion (second nip portion). In the corresponding position. Such a gap filling member 37 is positioned by a guide member 36a or a fixing frame (not shown).

  Due to the arrangement of the gap filling member 37, the flow of the rising airflow Y is inhibited by the joining portion of the airflows X <b> 1 and X <b> 2 due to the rotation of the fixing roller 31 and the heat resistant film 32 f, and the airflow of the rising airflow Y can be retained. As a result, the wax vaporizing component is suspended in the space for a long time, and the wax vaporizing component aggregates with each other or is captured by the surface of the cover member 35 surrounding at least a part of the first and second rotating bodies. For this reason, it is possible to obtain an effect of suppressing the amount of the wax vaporizing component discharged outside the fixing device and suppressing the wax vaporizing component adhering to the sheet conveying portions of the guide members 36a and 36b.

  Here, the gap filling member 37 is movable to a first position that restricts the passage of vaporized components and a second position that is retracted from the first position.

(When assembling the fixing device)
Next, FIG. 4 shows an explanation when the fixing device is assembled. During the fixing process, the gap filling member 37 was in the first position (FIG. 3B) that narrows the gap between the fixing roller 31 and the heating member 32, but during assembly, the gap filling member 37 was retracted from the first position. 2 (see FIG. 4). FIG. 4 shows a state where the cover member 35 is removed for assembly.

  At the time of assembly, the pressure unit 33, the fixing roller 31, and the heating unit 32 are assembled from the direction of the arrow in FIG. At that time, the gap filling member 37 moves to the second position retracted from the first position, and the gap filling member 37 interferes with other members such as the pressure unit 33, the fixing roller 31, and the heating unit 32 during assembly. It will be a position not to. For this reason, problems such as scratches, dents and breakage due to contact with the gap filling member 37 can be avoided.

  It should be noted that the gap filling member 37 is not storable in the guide member 36a as shown in FIG. 4 (the second position retracted from the guide surface as the inner wall surface), but the inner wall surface at the retracted second position. It is good also as a structure which serves as the guide surface of a guide member.

  When the assembly is completed and the arrangement with respect to the gap filling member 37 is changed from the state shown in FIG. 4 (when assembled) to FIG. 3B (when fixing processing), the gap filling member 37 suspended in the gravitational direction has its own weight. Return from the second position retracted to the first position.

(Effect of this embodiment)
In the fixing device according to the present embodiment, airflow along the rotation direction of the first and second rotating bodies can be suppressed while assembling is ensured. As a result, the wax vaporizing component can be retained in the fixing device. By allowing the wax vaporization component to float in the fixing device for a long time, the wax vaporization components aggregate with each other or are captured by the collection member, so that adhesion to the transport member can be suppressed.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described. The basic configuration is the same as that of the first embodiment, but shows a configuration in which the shape is divided in consideration of thermal deformation of the gap filling member. FIG. 5 is a schematic diagram of the fixing device according to the present embodiment. As shown in FIG. 5A, the gap filling member 37 is divided (37a, 37b, 37c) in the longitudinal direction (direction perpendicular to the recording material conveyance direction) and arranged side by side through a shaft 38 which is a shaft member. To do. The shaft 38 is positioned on a component that can guarantee accuracy, such as a fixing frame (not shown).

  Thereby, the influence of the warp at the time of shaping | molding the clearance gap member 37, and the deformation | transformation by a heat | fever can be suppressed, and it can arrange | position with high position accuracy. Although the gap filling member 37 is divided into three in FIG. 5, it may be divided into any number depending on the material and the longitudinal width. At the first position where the passage of the component vaporized from the wax is restricted, the tip position of the gap filling member 37 may be deformed by heat in the fixing device, but the divided structure can suppress deformation due to heat. For this reason, in the first position, a state where the air flow path to the outside of the fixing device is narrowed can be maintained, and the discharge of the wax vaporizing component can be stably suppressed.

<< Third Embodiment >>
In the first and second embodiments, as a heating method in the fixing device, a surf by a combination of a heat resistant film 32f that is a hollow (cylindrical) rotating body and a fixing roller 31 that is a solid (columnar) rotating body. The fixing method was adopted. On the other hand, in the present embodiment, as a heating method in the fixing device, a heat roller fixing method using a combination of a fixing roller and a heating roller, both of which are solid (cylindrical) rotating bodies, is used. Other points are the same as those in the first and second embodiments, and thus the description thereof is omitted.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Modification 1)
In the embodiment described above, the heater that contacts the inner surface of the cylindrical film is used as a heating source, but the present invention is not limited to this. That is, when using a lamp (such as a halogen lamp) provided in the center of the cylindrical film internal space, the cylindrical film is heated by IH (induction heating method) using electromagnetic induction, or by energizing the film. The same applies to the case where the film is directly heated.

(Modification 2)
Further, in the above-described embodiment, the pressure roller is used as the pressure member that is the opposing body, but the present invention is not limited to this, and a case where a pressure belt is used instead of the pressure roller as the rotating body or The same can be applied to the case where a fixed pressure pad is used instead of the rotating body.

31..Fixing roller (first rotating body), 32f..Heat resistant film (second rotating body),
33 ..Pressure member (opposing body) 35 ..Cover member 37 ..Gap filling member (regulation member), N 1 ..First nip portion (fixing nip portion), N 2 ..Second nip portion (Heating nip)

Claims (7)

A first rotating body;
An opposing body facing the first rotating body and forming a first nip portion with the first rotating body;
A second rotating body that forms a second nip portion together with the first rotating body, and heating means for heating the first rotating body;
A cover member surrounding at least a part of the first rotating body and the second rotating body;
Have
A fixing device that sandwiches and conveys a recording material carrying a toner image formed using toner containing wax in the first nip portion, and heat-fixes the toner image on the recording material;
The first rotating body and the second rotating body in an air flow path that is guided to the discharge section through the inner space of the cover member of the component vaporized from the wax by being heated in the first nip section. A regulating member that regulates the passage of the vaporized component at a position facing at least one of
The restricting member is movable to a first position for restricting the passage and a second position retracted from the first position,
The tip of the restricting member at the first position is an inner space of an outer tangent line between the first rotating body and the second rotating body, and the first nip portion with respect to the second nip portion. A fixing device, wherein the fixing device is located at a position corresponding to a confluence portion of airflows by the first and second rotating bodies that are about to approach each other on the upstream side in the rotation direction of the rotating body . The second position is a position where the restricting member does not interfere with any of the first rotating body, the opposing body, and the second rotating body when the fixing device is assembled. The fixing device according to 1 . The regulating member, a fixing device according to claim 1 or 2, wherein the a shape divided in a longitudinal direction perpendicular to the conveying direction of the recording material. The regulating member is provided with a longitudinal to the shaft member perpendicular to the conveying direction of the recording material, according to any one of claims 1 to 3, characterized in that it is suspended from the gravitational direction the shaft member Fixing device. The regulating member, a fixing device according to any one of claims 1 to 4, characterized in that movement to the first position from the second position by its own weight. Said second rotary member, a fixing device according to any one of claims 1 to 5, characterized in that it comprises a heat source therein. The fixing device according to claim 6 , wherein the second rotating body is formed of a cylindrical film, and the heating source is a heater that contacts an inner surface of the cylindrical film.