JP2006337656A - Heat fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the load on a heating body of rotation and to prolong the lifetime of the heating body of rotation by keeping a cleaning member contactless with the heating body of rotation. <P>SOLUTION: A conductive body of rotation 23 as an attaching and detaching means is arranged on the surface of a film unit 20 which is the heating body of rotation of the heat fixing device in a contactless state. The paper dust (affix) 37 sticking to the surface of the film unit 20 is attracted by the conductive body of rotation 23 to detach the paper dust 37. The paper dust 37 stuck to the conductive body of rotation 23 is removed by the cleaning member like a cleaning blade 25. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat fixing device for fixing a visible image formed with toner on a recording material such as paper to the recording material.

  2. Description of the Related Art Conventionally, many image forming apparatuses such as copying machines and printers that employ an electrophotographic method employ a thermal fixing method as a means for performing a fixing process on a recording material carrying an unfixed image. A fixing device is provided.

  As an example of a fixing device, a fixing film that rotates along a film guide, a heating source that is provided in the fixing film and that heats the fixing film, and a heat-resistant elastic layer formed on a metal core made of aluminum or iron. The thing provided with the pressure roller is mentioned.

  In this fixing device, a pressure roller is pressed against a fixing film by a spring or the like, and a recording material carrying an unfixed image is passed through a heating nip formed by the pressing to heat and apply. By pressing, an unfixed image is fixed on the recording material.

  In the upstream of the conveying direction of the fixing device, a transfer step of applying a bias of reverse polarity to the toner from the back surface of the recording material by a transfer roller to which a predetermined bias voltage is applied in order to transfer the toner image on the image carrier to the recording material Is done. For this reason, the recording material before passing through the fixing device is charged in the opposite polarity to the toner. In this state, the recording material is conveyed into the fixing device. Deposits such as paper dust adhere to the recording material, and these deposits are charged to the same polarity as the recording material.

  On the other hand, a fixing bias is applied to the surface of the fixing film for the purpose of preventing so-called tailing and offset. Therefore, an electrostatic force acts on the charged deposit between the fixing film surface and the recording material, and the deposit adheres electrostatically to the fixing film surface. Thereby, even if the fluororesin excellent in mold release property is used for a fixing film, mold release property falls. As a result, there is a problem that the toner adheres not to the recording material side but to the fixing film side and affects the quality of the recorded image.

In order to solve this problem, conventionally, a method has been used in which a cleaning member such as a web, a roller, or a brush is brought into contact with the surface of the fixing film to directly remove the adhered matter (Patent Documents 1, 2, and 3). .
JP 10-161450 A JP 2001-117407 A JP 2000-315033 A

  However, in the above method, the cleaning member is brought into direct contact with the fixing film to peel off the adhered matter, so that the fixing film is easily damaged. Due to this scratch, the surface property of the fixing film is deteriorated and the releasability is deteriorated. For this reason, toner adheres to the surface of the fixing film, and the adhered toner deteriorates the thermal conductivity and lowers the fixability. This causes a cold offset and further causes toner to adhere. As a result, problems such as image contamination on the recording material, pressure roller contamination, and a reduction in the life of the fixing film occurred.

  The present invention has been made in such a background, and the object thereof is to eliminate the load on the heating rotator by making the cleaning member for the heating rotator non-contact and prevent image smearing on the recording material. Another object of the present invention is to provide a heat fixing device capable of extending the life of the heating rotator and an image forming apparatus provided with the heat fixing device.

  In the heat fixing apparatus according to the present invention, the recording material on which the unfixed toner image is formed is passed between the nips where the heating rotator and the pressure rotator are pressed against each other, and the unfixed toner image is placed on the recording material. In the heat-fixing apparatus for fixing to the surface, a detaching means that is arranged in a non-contact state with respect to the surface of the heating or pressure rotator and attracts the adhered matter adhering to the rotating body to detach the adhered matter from the rotating body It is provided with.

  The detaching means attracts the deposits in a non-contact state with respect to the surface of the rotator to detach it from the rotator, so that the surface of the rotator is not damaged.

  Moreover, the said detachment | leave means can be comprised with the rotary body which attracts | sucks the said deposit | attachment with an electrostatic force, for example. The adhering matter adhering to the detaching means can be constituted by a cleaning member such as a cleaning blade or a cleaning brush that comes into contact with a rotating body and physically removes the adhering matter. Even if the rotating member constituting the detaching means is damaged by the contact of the cleaning member, there is no particular problem.

  The rotating body that attracts the adhering matter by electrostatic force is a conductive rotating body to which a predetermined bias is applied. For example, this bias has a reverse polarity to the transfer bias of the unfixed toner image. The deposit is charged with the same polarity as the transfer bias. By setting the conductive rotator to the opposite polarity to the transfer bias, the deposit can be detached from the conductive rotator by electrostatic force.

  The non-contact surfaces where the conductive rotating body and the heating rotating body face each other preferably travel in the same direction and at substantially the same speed. Thereby, the detachment | desorption characteristic by the electrostatic force of a deposit | attachment becomes favorable.

  The image forming apparatus according to the present invention includes the heat fixing device having any one of the above-described configurations.

  According to the present invention, the adhering material can be removed in an electrostatic non-contact state without contacting the cleaning member to the heating rotator for fixing, so that the load on the heating rotator is eliminated and the heating rotation by the cleaning member is performed. It is possible to eliminate scratches on the belt surface. As a result, image contamination on the recording material can be prevented and the life of the heating rotator can be extended.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
(First embodiment)

  FIG. 1 is a diagram showing a main part of image formation of an image forming apparatus provided with a heat fixing device of the present invention, and showing the flow of image formation.

  As a flow of image formation, first, the image carrier 3 is charged to a predetermined constant potential from the charging high-voltage power source 1 by the charging roller 2, and a point on the image carrier 3 on which the image is formed is exposed by the exposure unit 4. The potential is lowered. Then, the toner in the developing container 5 is uniformly placed on the developing sleeve 6 and the difference between the lowered potential on the image carrier 3 and the potential applied to the developing sleeve 6 (that is, the action of the electric field) is used. Charged toner is deposited on the image carrier 3 to visualize the electrostatic latent image on the surface of the image carrier 3.

  The toner image attached on the image carrier 3 moves to a predetermined transfer region as the image carrier 3 rotates. On the other hand, a transfer material such as a sheet is fed by a sheet feeding means and conveyed to a predetermined transfer area along the pre-transfer guide 7. The toner image on the image carrier 3 is transferred onto the transfer material by the transfer roller 8 in this transfer region. Thereafter, the transfer material such as paper is conveyed along the fixing inlet guide 11, fixed by the fixing device 12, and discharged. The toner that adheres to the image carrier 3 and cannot be transferred is scraped off and collected in the waste toner storage space 10 by the cleaning blade 9.

  FIG. 2 is a diagram illustrating a configuration example of the fixing device 12 in the present embodiment.

  The fixing device 12 includes a film unit 20 and a pressure roller 21. The film unit 20 includes a heating source 19, a fixing film 15, a film guide 13, a T stay 14, and a temperature detection element 18.

  In this example, the heating source 19 is a ceramic heater, which is composed of a heating element in which a heating paste is printed on a ceramic substrate, a glass coating layer for ensuring protection and insulation of the heating element, and the like. An AC current whose power is controlled is supplied to the heating element to generate heat. The fixing film 15 is made of polyimide and has a substantially cylindrical shape with a thickness of about 64 μm, and efficiently transfers heat from a heating source to the toner 17 on the paper 16. The film guide 13 has a number of ribs in the longitudinal direction, thereby assisting the circumferential movement of the fixing film 15 while suppressing resistance to the fixing film 15. The T stay 14 is made of a steel plate and receives the applied pressure uniformly.

  The temperature detection element 18 on the back of the ceramic substrate is a thermistor and detects a temperature change. Based on the detection result, the target temperature of the heater is determined, the heater driving means is controlled to control the power to the heater, and the heater temperature is maintained at the target temperature (printing temperature). In addition, the pressure roller 21 is formed by covering a cored bar made of aluminum with silicon rubber.

  The pressure roller 21 is brought into pressure contact with a heating source (heater) 19 with a predetermined pressure (nip pressure) via a fixing film 15 by a spring to form a heating nip portion 22 composed of the film unit 20 and the pressure roller 21. ing. The pressure roller 21 is driven to rotate by a pressure roller driving unit (not shown), and the fixing film 15 is driven to rotate, and the paper 16 introduced into the heating nip 22 is in close contact with the fixing film 15. It is transported by. As the sheet 16 is conveyed to the heating nip portion 22 in this way, the unfixed toner image formed and supported on the sheet is fixed by the heat of the heater member and the nip pressure.

  As described above, upstream of the fixing device 12 in the conveying direction, the toner image on the image carrier 3 is transferred onto the paper, and thus reverses the toner polarity (negative in this example) from the back of the paper via the transfer roller 8. A polarity bias (up to about +4 KV in this example) is applied. For this reason, the paper before fixing is in a state (about +200 V) charged with a polarity opposite to that of the toner. In this state, the paper is conveyed into the fixing device. On the other hand, a fixing bias (about −500 V) is applied to the surface of the fixing film 15 for the purpose of preventing so-called tailing and offset. Therefore, for example, paper dust on the paper as a charged deposit is electrostatically acted between the surface of the fixing film and the paper, and the paper dust is electrostatically attached to the surface of the fixing film 15. When paper dust adheres to the surface of the fixing film, its releasability is reduced, and toner adheres not to the paper 16 side but to the fixing film 15 side, affecting the image quality.

  In the conventional method, the cleaning member is directly brought into contact with the fixing film, and the paper dust is peeled off to prevent the paper dust from adhering to the surface of the fixing film. As the toner deteriorates, the toner adheres, the adhered toner deteriorates the thermal conductivity and the fixability is lowered, thereby generating a cold offset and further attaching the toner. As a result, image staining on the recording material occurs and there is a problem that the life of the fixing film is shortened.

  Therefore, the present invention is intended to eliminate the load on the fixing film by disposing the cleaning member on the fixing film in a non-contact state, prevent image smearing, and extend the life of the fixing film.

  FIG. 3 shows the configuration of the fixing device 12 in the embodiment of the present invention. In this example, the configuration of the fixing device 12 including the film unit 20 and the pressure roller 21 is the same as that shown in FIG. 2, but a cylindrical conductive rotating body 23 made of aluminum is disposed downstream of the heating nip portion 22. Installed close to each other in a non-contact state, a transfer bias (positive in this example) applied to the transfer roller 8 is applied to the conductive rotating body 23 by a high-voltage power source 24 (negative in this example). . In this example, an elastic cleaning blade 25 made of urethane is brought into contact with the conductive rotating body 23 as a cleaning means for collecting the paper dust 37 removed from the surface of the fixing film 15 and adhered to the conductive rotating body 23. The paper dust 37 is physically removed and collected.

  FIG. 4 illustrates a configuration example of the conductive rotating body 23.

  A driving force is obtained from the pressure roller 21 using the driving gear 26, a metal core 27 made of aluminum having a predetermined diameter (Φ8 mm in this example) and the driving gear 26 are connected, and the conductive rotating body 23 is rotated. The width 28 of the conductive rotating body 23 is set to the same width as that of the fixing film 15. The diameter 29 of the conductive rotating body 23 is set to 20 mm. The diameter of the conductive rotating body 23 may be the same as that of the fixing film 15. In this example, the bias is applied to the conductive rotating body 23 through the cored bar 27.

  Table 1 shows the presence or absence of the cleaning effect when the distance between the fixing film and the conductive rotating body and the bias applied to the conductive rotating body are changed.

  In the present embodiment, −500 V is applied to the fixing film 15 side, and the distance between the fixing film 15 and the conductive rotating body 23 is changed to 0.5 mm, 1 mm, 3 mm, and 5 mm. Bias of -500 V, -1 KV, and -1.5 KV was applied. As a result, in the case of −500 V, since the applied bias was weak, the cleaning effect could not be obtained at all distances (0.5 mm, 1 mm, 3 mm, and 5 mm) between the fixing film 15 and the conductive rotating body 23.

  Next, in the case of −1 KV, the effect could not be obtained when the distance between the fixing film 15 and the conductive rotor 23 was 1 mm, 3 mm, and 5 mm, but an efficient cleaning effect could be obtained at 0.5 mm.

  In the case of −1.5 KV, the applied bias tends to be slightly strong when the distance between the fixing film 15 and the conductive rotating body 23 is 0.5 mm, and conversely, when 3 mm and 5 mm, the applied bias is weak and an efficient effect can be obtained. Although not possible, an efficient cleaning effect could be obtained at 1 mm.

  From the above, when the distance between the fixing film 15 and the conductive rotor 23 is 0.5 mm, the applied bias is 1 KV, and when the distance between the fixing film 15 and the conductive rotor 23 is 1 mm, the applied bias is 1.5 KV. I can say that. However, when the distance between the fixing film 15 and the conductive rotator 23 is 0.5 mm, it is easily affected by the size of the paper powder 37. Therefore, the distance between the fixing film 15 and the conductive rotator 23 is 1 mm, and the applied bias is 1.5 KV. And

  FIG. 5 illustrates the relationship between the conductive rotating body 23 and the fixing film 15. The rotation speed and rotation direction 30 of the fixing film 15 are the same as the rotation speed and rotation direction 31 of the conductive rotating body 23. The interval 32 between the fixing film 15 and the conductive rotor 23 is 1 mm.

FIG. 6 shows a modification of the cleaning means in the first embodiment. In the example described above, the cleaning blade 25 is used as the cleaning means, but in the example of FIG. 6, the cleaning brush 33 is used. The cleaning brush 33 is a rotary brush formed by winding aluminum around 6 mm in diameter, winding conductive fibers around it, and then cutting the fiber length to 6 mm. Although FIG. 6 shows an example in which the fixing roller 36 is used instead of the fixing film 15 as the heating rotator, the cleaning brush 33 may be used in a fixing device using the fixing film 15. The configuration of the fixing roller 36 shown in the figure is a heating and fixing device that controls the energization of a halogen heater 35 incorporated in a cylindrical metal roller 34 and maintains the surface of the cylindrical metal roller 34 at a predetermined temperature. Although the cleaning means in the present invention shows the cleaning blade 25 and the cleaning brush 33, any configuration can be used as long as the paper dust 37 adhering to the surface of the heating rotator can be removed.
(Second Embodiment)

  A second embodiment of the present invention will be described with reference to FIG. The same reference numerals are given to the same elements as those in the configuration of the first embodiment, and the duplicate description is omitted. In this configuration, the belt unit 40 is used as the conductive rotating body. The belt unit 40 includes a conductive endless belt 41 stretched between a conductive roller 42 and another roller 43. A voltage from the power source 24 is applied to the conductive roller 42, and the endless belt 41 is charged. The polarity and voltage of the bias applied to the roller 42 are the same as those in the first embodiment. Further, although the cleaning blade 25 is arranged on the roller 43 side as the cleaning means in this example, the arrangement position may be on the roller 42 side. Further, instead of the cleaning blade 25, a cleaning brush 33 may be used.

  The preferred embodiments of the present invention have been described above, but various modifications and changes other than those mentioned above can be made. For example, the endless belt 41 shown in FIG. 7 is not necessarily endless. Although the bias is applied to the conductive rotator through the mandrel, it may be directly applied to the conductive rotator. Further, a combination in which the conductive rotating body is a metal brush and the cleaning member is a blade may be used. Furthermore, although only the detachment of the deposit from the heating rotator has been described, the present invention can also be applied to the detachment of the deposit from the pressure rotator.

FIG. 3 is a diagram illustrating a main part of image formation of the image forming apparatus including the heat fixing device of the present invention, and illustrating a flow of the image formation. FIG. 2 is a diagram illustrating a configuration example of a fixing device according to an embodiment of the present invention. 2 illustrates a configuration of a fixing device according to an exemplary embodiment of the present invention. FIG. 4 is a diagram illustrating a configuration example of a conductive rotator illustrated in FIG. 3. It is a figure for demonstrating the relationship between the electrically conductive rotary body and fixing film in embodiment of this invention. It is a figure which shows the modification of the cleaning means in embodiment of this invention. It is a figure which shows the structural example of the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... High-voltage power supply 2 ... Charging roller 3 ... Image carrier 4 ... Exposure part 5 ... Developing container 6 ... Developing sleeve 7 ... Pre-transfer guide 8 ... Transfer roller 9 ... Cleaning blade 10 ... Waste toner storage space 11 ... Fixing entrance Guide 12 ... Fusing device
13 ... Film guide 14 ... T stay 15 ... Fixing film 16 ... Paper (transfer material)
DESCRIPTION OF SYMBOLS 17 ... Toner 18 ... Temperature detection element 19 ... Heat source 20 ... Film unit 21 ... Pressure roller 22 ... Heating nip part 23 ... Conductive rotator 24 ... High voltage power supply 25 ... Cleaning blade 26 ... Drive gear 27 ... Core metal 28 ... Conductive Rotating body width 29... Conductive rotating body diameter 30... Fixing film rotating speed 31... Conducting rotating body rotation speed 32... Fixing film-to-conductive rotating body interval 33. Cleaning brush 34. Cylindrical metal roller 35. Heater 36 ... fixing roller 37 ... paper powder 40 ... belt unit 41 ... endless belts 42, 43 ... roller

Claims (8)

In the heating and fixing apparatus, the recording material on which the unfixed toner image is formed is passed through a nip where the heating rotator and the pressure rotator are pressed against each other, and the unfixed toner image is fixed on the recording material.
It is arranged in a non-contact state with respect to the surface of the heating or pressure rotating body, and has a detaching means for attracting the adhered matter attached to the rotating body and detaching the adhered matter from the rotating body. Heat fixing device.   The heating and fixing apparatus according to claim 1, wherein the detaching unit is configured by a rotating body that sucks the deposit by electrostatic force.   The heat fixing apparatus according to claim 2, wherein the rotating body that attracts the attached matter by electrostatic force is a conductive rotating body to which a predetermined bias is applied.   The bias applied to the conductive rotator is opposite in polarity to the transfer bias of the unfixed toner image with respect to the transfer bias used to transfer the unfixed toner image from the image carrier to the recording material before the heat fixing. The heat fixing apparatus according to claim 3.   The heat fixing apparatus according to claim 3, wherein the non-contact surfaces where the conductive rotating body and the rotating body face each other travel in the same direction and at substantially the same speed.   The heat fixing apparatus according to claim 1, further comprising a cleaning member that contacts the detaching unit and removes the attached matter.   The heat fixing apparatus according to claim 6, wherein the cleaning member is a cleaning blade or a cleaning brush.   An image forming apparatus comprising the heat fixing device according to claim 1.

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