JP2008129060A - Image heating and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the offset of unfixed toner due to charging of the surface of a rotary body for pressurizing. <P>SOLUTION: The image heating and fixing device has a rotary body for heating 21 and the rotary body for pressurizing 22 which comes into contact with the rotary body for heating to form a nip portion N and heats and fixes an unfixed toner image t on a recording material P, while sandwiching and conveying the recording material carrying the unfixed toner image in the nip portion. In the image heating and fixing device, a charge eliminating member 51 for eliminating charges from the surface of the rotating body for pressurizing 22 is oppositely arranged to the surface of the rotary body for pressurizing in a non-contact manner across a rotating member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image heat fixing apparatus suitable for use as a heat fixing apparatus mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  As an image heating and fixing device mounted on an electrophotographic copying machine or printer, a heater having an energized heating element on a ceramic substrate, a fixing film that moves while contacting the heater, a heater and a nip portion via the fixing film There are some which have a pressure roller for forming the. Patent Documents 1 and 2 describe this type of fixing device. The recording material carrying the unfixed toner image is heated while being nipped and conveyed by the nip portion of the fixing device, whereby the image on the recording material is heated and fixed on the recording material. This fixing device has an advantage that the time required for starting energization of the heater and raising the temperature to the fixable temperature is short. Therefore, a printer equipped with this fixing device can shorten the time (FPOT: first printout time) after the print command is input until the first image is output. This type of fixing device also has an advantage that power consumption during standby for waiting for a print command is small.

  In the fixing device described above, it is ideal that all of the unfixed toner images carried on the recording material are appropriately heated and melted and fixed on the recording material. However, when the unfixed toner image on the recording material is heat-fixed, a part of the toner is not fixed but adheres to the fixing film side, and may be transferred to the recording material side at the next round of the fixing film. A phenomenon in which a part of the toner is not fixed and adheres to the fixing film side is called offset. It is well known that when an offset occurs, the quality of an image formed on a recording material is affected.

  Various factors can be considered as the cause of the offset, and the electrostatic force exerted on the toner from the outer peripheral surface (surface) of the pressure roller is one of the major factors. That is, the surface of the pressure roller in contact with the non-carrying surface (back surface) opposite to the carrying surface (front surface) of the recording material carrying the unfixed toner image continuously conveys the recording material, thereby causing a high potential on the negative side. May be charged up to In that case, offset occurs because the surface of the pressure roller and the negatively charged toner repel electrostatically. Generally, the surface of the pressure roller is made of an insulating material such as a fluororesin in order to ensure releasability with respect to the recording material. For this reason, the pressure roller surface may be charged to about minus several kV due to frictional charging with a recording material, a fixing film, etc., and offset is likely to occur.

  In order to prevent such charging of the pressure roller surface, attempts have been made to disperse a conductive material such as carbon in a fluororesin on the surface of the pressure roller. However, since the surface property of the pressure roller is deteriorated, the releasability is lowered, and there is a problem that the toner adheres to the surface of the pressure roller, the toner is discharged to the recording material, and the like, and is not adopted in many cases. .

Therefore, the neutralization brush made of SUS or amorphous metal or the neutralization needle made of sawtooth conductive plate (static elimination member) is opposed to the surface of the pressure roller in a non-contact manner, and the pressure roller surface is neutralized to prevent offset. Have been proposed (Patent Documents 3 and 4). Among these, the static elimination needle is cheaper than the static elimination brush, and is effective in preventing offset caused by charging of the pressure roller surface.
JP-A-63-313182 JP-A-4-44075 JP-A-7-295427 JP 2006-126805 A

  The present invention is a further development of the above prior art. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image heating and fixing device capable of preventing the offset of unfixed toner due to charging of the surface of the pressing rotary member.

A typical configuration of an image heating apparatus according to the present invention includes a heating rotator and a pressurizing rotator that forms a nip portion in contact with the heating rotator, and is not fixed at the nip portion. In an image heating and fixing apparatus that heats and fixes an unfixed toner image on a recording material while sandwiching and conveying the recording material carrying the toner image,
A static elimination member that neutralizes the pressurizing rotator, the static elimination member disposed along a surface of the pressurizing rotator in a longitudinal direction of the pressurizing rotator perpendicular to the recording material conveyance direction;
A rotatable rotating member that is in contact with the surface of the pressurizing rotator or a rotation center axis of the pressurizing rotator and holds a gap that can be neutralized between the charge eliminating member and the surface of the pressurizing rotator;
An image heating fixing device characterized by comprising:

  According to the present invention, since the gap that can be neutralized can be maintained between the static eliminator and the surface of the pressurizing rotator by the rotating member, the neutralization performance of the surface of the pressurizing rotator by the static eliminator is stabilized. As a result, offset of unfixed toner due to charging of the surface of the pressurizing rotating body can be prevented.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 1 is an overall configuration diagram of an example of an image forming apparatus in which the image heat fixing apparatus according to the present invention can be mounted as an image heat fixing apparatus (fixing device). This image forming apparatus is an electrophotographic laser beam printer.

  A drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 is obtained by forming a photosensitive material such as OPC, amorphous Se, or amorphous Si on a cylindrical conductive drum base such as aluminum or nickel. is there.

  The photosensitive drum 1 is rotated in the direction indicated by the arrow R1. The outer peripheral surface (surface) of the photosensitive drum 1 is uniformly charged by a charging roller 2 as a charging means. Next, the charged surface on the surface of the photosensitive drum 1 is subjected to scanning exposure with a laser beam E that is ON / OFF controlled according to image information by a laser scanning device 3 as an exposure unit. An electrostatic latent image corresponding to the image information is formed. The electrostatic latent image is developed with the developing toner by the developing device 4 and visualized. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and image exposure and reversal development are often used in combination.

  On the other hand, recording materials (hereinafter referred to as transfer materials) P loaded and stored in the feeding cassette 5 are fed one by one by the pickup roller 6 and conveyed to the registration roller pair 7. Next, the transfer material P is sent to the transfer nip T between the photosensitive drum 1 and the transfer roller 8 as transfer means by the roller pair 7, and is nipped and conveyed by the photosensitive drum 1 and the transfer roller 8 at the transfer nip T. In the conveying process, the toner image visualized on the surface of the photosensitive drum 1 is transferred onto the transfer material P by the transfer roller 8.

  The transfer material P that has received the transfer of the toner image and carries the unfixed toner image is conveyed to the fixing device 9. As the transfer material P passes through the fixing device 9, the unfixed toner image is heated and fixed on the transfer material P as a permanent image. The transfer material P exiting the fixing device 9 is discharged by a discharge roller pair 10 and 11 to a discharge tray 12 provided at the upper part of the device.

  The transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image onto the transfer material P is removed by a cleaning device 13 as a cleaning unit.

  By repeating the above operation, image formation (printing) can be performed one after another.

  The image forming apparatus according to the present exemplary embodiment can perform printing at a printing speed of 600 dpi, 22 sheets / minute (LTR longitudinal feed: process speed of about 126 mm / sec).

(2) Fixing Device In the following description, with respect to the fixing device and its constituent members, the longitudinal direction refers to the direction orthogonal to the transfer material conveyance direction on the surface of the transfer material. The width direction (short direction) refers to the transfer material conveyance direction on the surface of the transfer material. The width refers to a dimension in the transfer material conveyance direction.

  FIG. 2 is a schematic longitudinal sectional view of the fixing device 9. FIG. 3 is a front model view of the fixing device 9.

  The fixing device 9 has a cylindrical thin-walled film (hereinafter referred to as a film) 21 having flexibility and heat resistance as a heating rotator. The fixing device 9 is in contact with the film 21 to form a fixing nip portion N. An elastic pressure roller 22 is provided as a pressure rotating body. The fixing device 9 includes a ceramic heater 23 that heats the film 21 as a heating body, a heater holder 24 as a heating body holding member that holds the heater 23, and a regulating member that regulates the movement of the film 21 in the longitudinal direction. Fixing flanges 25a and 25b. The film 21, the pressure roller 22, the heater 23, and the holder 24 are all elongated members in the longitudinal direction.

  FIG. 4 is a cross-sectional view illustrating the layer structure of the fixing film 21. 5 is a diagram showing a method of applying a bias to the fixing film 21. FIG. 6 is a diagram showing the configuration of the heater and the temperature control system.

  The film 21 has a sleeve-like low heat capacity heat-resistant resin film layer as a base layer 21a, a conductive primer layer as an intermediate layer 21b on the base layer 21a, and a release layer 21c on the intermediate layer 21b. (FIG. 4). As the base layer 21a, a heat-resistant resin film layer having a low heat capacity such as polyimide, polyamideimide, PEEK, PES, PPS, PFA, PTFE, and FEP is used. A conductive primer layer 132 is used as the intermediate layer 21b. As the release layer 21c, a release layer obtained by mixing a conductive member such as carbon into PFA, PTFE, FEP or the like is used.

  The film 21 preferably has a thickness of 100 μm or less in order to enable quick start. Further, the film 21 having a sufficient strength for constituting the fixing device 21 having a long durability life and excellent in durability needs to have a thickness of 20 μm or more. Therefore, the thickness of the film 21 is optimally 20 μm or more and 100 μm or less.

  Further, a fixing bias is applied to the film 21 in order to prevent image defects caused by an offset or the like. As shown in FIG. 5, a method of applying a fixing bias to the film 21 is such that a primer layer 21b is exposed at the longitudinal end portion of the outer peripheral surface (surface) of the film 21, and a power supply member such as a conductive brush is provided on the primer layer 21b. 41 is brought into contact. A fixing bias is applied to the power supply member 41 from the high-voltage DC power source 42 (FIG. 2) via the resistor 43.

  In the present embodiment, the film 21 is used as a heating rotator, but a metal sleeve may be used as the heating rotator. As the metal sleeve, a thin sleeve-shaped metal element tube such as stainless steel is used as a base layer, and the outer peripheral surface (surface) of the metal element tube is coated with the release layer via the primer layer. be able to. In this case, a part of the longitudinal end portion of the surface of the metal base tube is exposed for grounding the heating rotator and applying a fixing bias to the heating rotator.

The heater 23 has an elongated substrate 23a made of a material having electrical insulation, good thermal conductivity, and heat resistance, such as Al ₂ O ₃ or AlN. Then, on one surface of the substrate 23a, energized heat generating resistance layers 23b1, 23b2 made of silver palladium or the like are provided in parallel along the longitudinal direction via the connecting electrode 23c, and the resistance layers 23b1, 23b2 are covered so as to cover the resistance layers 23b1, 23b2. A protective layer 23d that protects the layers 23b1 and 23b2 is provided. The protective layer 23d is formed of a thin glass layer. The resistance layers 23b1 and 23b2 provided in parallel are electrically connected to current-carrying electrodes 23e and 23f provided at the ends of the substrate 23a opposite to the connecting electrode 23c, respectively. The heater 23 is formed such that the heat generation area of the resistance layer is larger than the maximum width of the recording material P introduced into the fixing nip N.

  The holder 24 is formed in a vertical cross-section with a heat-resistant resin, and is disposed in the film 21. As the material of the holder 24, liquid crystal polymer, phenol resin, PPS, PEEK, or the like is used. In the holder 24, a substrate 23a of the heater 23 is held in a groove provided in the center of the lower surface in the width direction with the protective layer 23d facing downward. The holder 24 is loosely fitted on the film 21 with a margin. The film 21 is loosely fitted on the holder 24 holding the heater 23 with a sufficient circumferential length. As will be described later, since the inner peripheral surface (back surface) of the film 21 rotates while sliding on the outer surface of the protective layer 23 d of the heater 23 and the outer surface of the holder 24, the friction between the outer surface of the protective layer 23 d and the outer surface of the holder 24 and the rear surface of the film 21. It is necessary to keep resistance low. Therefore, a small amount of lubricant such as heat-resistant grease is interposed on the outer surface of the protective layer 23d and the outer surface of the holder 24 so as to keep the frictional resistance small. Thereby, the film 21 can rotate smoothly.

  The pressure roller 22 has an elastic layer 22b formed by foaming heat-resistant rubber such as insulating silicone rubber or fluorine rubber or heat-resistant rubber on the outside of a metal core 22a serving as a rotation center axis. A release layer 22c such as PFA, PTFE, or FEP is provided on the elastic layer 22b. The pressure roller 22 is rotatably supported at both ends of the cored bar 22a by first side plate pairs 32a and 32b of the apparatus frame via bearings 31a and 31b. On the upper side of the pressure roller 22, both end portions of the holder 24 holding the heater 23 are held by the second side plate pairs 33a and 33b of the apparatus frame. The first side plate pair 32a, 32b is pressed against the second side plate pair 33a, 33b with a predetermined pressure by a not-shown pressurizing spring (pressurizing means). As a result, the surface of the pressure roller 22 is pressed against the heater 23 with the film 21 in between, and the back surface of the film 21 abuts against the surface of the protective layer 23d of the heater 23, thereby causing a predetermined width between the surface of the film 21 and the surface of the pressure roller 22. A nip portion N is formed. Further, the flanges 25 a and 25 b attached to the second side plate pair 33 a and 33 b in a state of being fitted to the end portion of the holder 24 have restriction surfaces 25 a 1 and 25 b 1 facing the longitudinal end portion of the film 21. And the movement of the film 21 in the longitudinal direction is regulated by the end of the rotating film 21 coming into contact with the regulation surfaces 25a1, 25b1.

(3) Heat Fixing Operation of Fixing Device In FIGS. 2 and 3, the fixing device 9 has a driving force applied to the driving gear G provided at the end of the cored bar 22 a of the pressure roller 22 by the rotation driving unit (rotation driving means) M. , The pressure roller 22 is rotated at a predetermined peripheral speed in the direction of the arrow. Due to the rotation of the pressure roller 22, a rotational force acts on the film 21 by a frictional force between the surface of the pressure roller 22 and the surface of the film 21 in the nip portion N. With this rotational force, the back surface of the film 21 is in close contact with the surface of the protective layer 23d of the heater 23 in the nip portion N and slides around the holder 24 in the arrow direction at a peripheral speed equal to the rotational peripheral speed of the pressure roller 22. Followed rotation.

  When the heater 23 is energized from the temperature control unit (temperature control means) 44 to the resistance layer 23b, the resistance layer 23b generates heat and quickly rises in temperature. That is, the temperature controller 44 energizes the path of the conductive electrode 23e, the resistance layer 23b1, the connecting electrode 23c, the resistance layer 23b2, and the conductive electrode 23f, and the resistance layers 23b1 and 23b2 generate heat. The temperature of the heater 23 is detected by a thermistor as temperature detecting means 25 provided on the other surface of the substrate 23a. The detected temperature is fed back to the temperature control unit 44. The temperature control unit 44 controls energization to the heater 23 so that the temperature detected by the thermistor 25 is maintained at a fixed fixing temperature (target temperature). As a result, the heater 23 is heated and adjusted to the fixing temperature.

  The transfer material P carrying the unfixed toner image t is introduced into the nip portion N while the heater 23 rises to the fixing temperature and the rotational peripheral speeds of the pressure roller 22 and the film 21 are stable. Here, K is a transfer material conveyance direction. In the process in which the transfer material P is nipped and conveyed at the nip portion N, the toner image t is heated and fixed to the transfer material P by applying the heat of the heater 23 and the nip pressure of the nip portion N to the toner image t.

  The transfer material P exiting the nip portion N is separated from the surface of the film 22 and guided to the discharge roller 10 (FIG. 1) by the discharge guide 51. The discharge guide 51 is attached to the first side plate pair 32a, 32b of the apparatus frame.

(4) Static electricity holding member gap holding structure In the fixing device 9 described above, when a static elimination needle is provided as a static elimination member for neutralizing the surface of the pressure roller 22, the distance between the static elimination needle and the pressure roller 22 surface (hereinafter referred to as “static discharge needle”). The static elimination performance varies greatly depending on the gap). For this reason, the static elimination capability is insufficient due to variations in the mounting position of the static elimination needle, and offset is likely to occur.

  For example, let us consider a case where a static elimination needle is attached to an introduction guide (not shown) provided on the transfer material introduction side of the fixing device 9 or the discharge guide 51 in the transfer material conveyance direction K. In that case, it is necessary to dispose the static elimination needle at a position where the tip of the static elimination needle does not contact the surface of the pressure roller 22 in consideration of the installation position tolerance of the introduction guide and the discharge guide 51 and the outer diameter tolerance and thermal expansion of the pressure roller 22. There is. However, the gap between the charge eliminating needle and the surface of the pressure roller 22 is increased depending on the tolerance of each component such as the introduction guide, the discharge guide 51, the charge eliminating needle, and the pressure roller 22, and the pressure roller 22 is increased. The surface may not be sufficiently neutralized and offset may occur.

  Therefore, in this embodiment, as shown in FIG. 2 and FIG. 7, the surface of the static elimination needle 51 and the surface of the pressure roller 22 using the abutment roller 52 as a rotating member that rotates in contact with the surface of the pressure roller 22. A gap d1 that can be neutralized is held between them.

  (A) of FIG. 7 is explanatory drawing showing the relationship between the static elimination needle 51 provided in the static elimination needle holder 62, and the pressure roller 22 surface, (b) is an enlarged view of the A section shown to (a).

  As the static elimination needle 51, an elongated SUS sheet metal having a thickness of 0.1 mm is used. The static elimination needle 51 is arranged along the surface of the pressure roller 22 in the longitudinal direction of the pressure roller 22 on the lower surface of the static elimination needle holder 62 as a static elimination member holding member provided in the discharge guide 61, and the tip thereof is pressurized. It faces the surface of the roller 22 in a non-contact manner (FIG. 7A). The shape of the tip of the static elimination needle 51 facing the surface of the pressure roller 22 is a sawtooth shape. In this embodiment, the shape of the tip of the static elimination needle 51 is a sawtooth shape. The size of the sawtooth shape at the tip of the static elimination needle 51 is such that the interval between adjacent peaks is 2 mm, and the height of the peaks is 3 mm.

  The static elimination needle 51 is provided at a position where the surface potential is highest in the pressure roller 22, that is, at a position downstream of the fixing nip portion N in the transfer material conveyance direction K. It is preferable to provide the static elimination needle 51 at that position because the surface of the pressure roller 22 can be efficiently neutralized. In this embodiment, the static elimination efficiency is further improved by grounding the static elimination needle 51. Not limited to this, it is possible to ground the static elimination needle 51 via a diode or to apply a bias to the static elimination needle 51 to further improve the static elimination efficiency.

  The rollers 52 are rotatably held at both ends of the static elimination needle holder 62 in the longitudinal direction of the pressure roller 22. The two rollers 52 provided at both ends of the static elimination needle holder 62 have an outer peripheral surface (surface) in contact with the surface of the pressure roller 22, and a gap d 1 capable of static elimination is provided between the tip of the static elimination needle 51 and the surface of the pressure roller 22. Form (FIG. 7A). Here, the distance L between the two rollers 52 is larger than the maximum width W of the transfer material P introduced into the nip portion N. That is, the two rollers 52 are arranged at positions that do not hinder the transfer of the transfer material P. The smaller the gap d1, the higher the charge eliminating effect on the surface of the pressure roller 22. In this embodiment, considering the undulation of the surface of the pressure roller 22 and the outer diameter tolerance of the roller 52, the gap d1 is set to 0.7 mm so that the tip of the static elimination needle 51 does not contact the surface of the pressure roller 22.

  The roller 52 is rotatable about a shaft 62 a provided in the static elimination needle holder 62, and is disposed in the static elimination needle holder 62 so as to protrude from the tip of the static elimination needle 51 to the surface of the pressure roller 22. The static elimination needle holder 62 is rotatably held by the discharge guide 61. The static elimination needle holder 62 is urged toward the pressure roller 22 by a spring 63 as an urging member against the discharge guide 61, and the surface of the roller 52 is brought into contact with the surface of the pressure roller 22 with a predetermined urging force. Since the surface of the roller 52 is brought into contact with the surface of the pressure roller 22 by the spring 63, the outer diameter of the pressure roller 22 changes due to variations in the outer diameter of the pressure roller 22 or thermal expansion of the pressure roller 22. The change can be absorbed by the spring 63. Therefore, the gap d1 between the tip of the static elimination needle 51 and the surface of the pressure roller 22 can be kept constant.

  As the material of the roller 52, PFA resin or PTFE resin, which is difficult to transfer and adhere to the unfixed toner attached to the surface of the pressure roller 22 due to jam or the like, is used. In addition, the same effect can be obtained by coating a heat resistant resin such as LCP or PPS with PFA or PTFE.

  A specific experiment was conducted on the relationship between the static elimination needle 51 and the offset. An experimental example will be described. FIG. 8 is a view showing the fixing device used in the experiment, and is a view showing the fixing device in which the static elimination needle 51 is directly arranged on the discharge guide 61.

  When the surface of the pressure roller 22 is not neutralized (no static eliminator), when the static eliminator 51 is directly arranged on the discharge guide 61 (FIG. 8), the static eliminator 51 is opposed to the surface of the pressure roller 22 via the roller 52. Table 1 shows the results of comparing the offset levels for each case (FIG. 2).

  As shown in FIG. 8, in the configuration in which the discharge needle 61 is directly provided on the discharge guide 61, the tip of the discharge needle 51 is added in consideration of the outer diameter tolerance of the pressure roller 22, the thermal expansion, the installation tolerance of the discharge needle 51, and the like. The gap d1 is set to 2.0 mm so as not to contact the surface of the pressure roller 22.

  The confirmation of the offset level was performed after introducing 100 sheets of paper (Xx4024 standing paper) with high resistance in a low-temperature and low-humidity environment where the pressure roller 22 surface is easily charged into the nip portion N. Further, as an image pattern, a halftone image composed of 600 dpi isolated one dot was used so that static elimination unevenness could be easily confirmed.

  As can be seen from Table 1, when the static elimination needle 51 is not provided, the surface potential of the pressure roller 22 is charged to −3.0 kV or more, and an NG level offset occurs.

  When the static elimination needle 51 is arranged on the discharge guide 61 as shown in FIG. 8, the surface potential of the pressure roller 22 decreases to about −2.0 to −2.5 kV, and the offset is improved, but it is completely Did not go away.

  On the other hand, in the case of the configuration of this embodiment (FIG. 2), the surface potential of the pressure roller 22 decreased to about −1.0 to −1.5 kV, and no offset occurred.

  In this embodiment, the surface of the roller 52 is brought into contact with the surface of the pressure roller 22 in the fixing device 9, but the present invention is not limited to this. FIG. 9 is a schematic longitudinal sectional view of a modification of the fixing device 9 of the present embodiment.

  In the pressure roller 22, when the elastic layer 22b is relatively thin and thermal expansion is small, the surface of the roller 52 is brought into contact with the surface of the cored bar 22a at both ends of the pressure roller 22 as shown in FIG. Also good. Even if such a configuration is adopted, the same effect can be obtained.

  According to the present embodiment, the charge elimination needle 51 can be brought close to the surface of the pressure roller 22 in a non-contact manner via the roller 52 so that the tip of the charge elimination needle 51 can be brought as close as possible without contacting the surface of the pressure roller 22. . That is, since the gap d1 that can be neutralized can be maintained between the static elimination needle 51 and the pressure roller 22 surface by bringing the roller 52 surface into contact with the pressure roller 22 surface, the static elimination of the pressure roller 22 surface by the static elimination needle 51 is possible. Performance is stable. As a result, offset of unfixed toner due to charging of the pressure roller 22 surface can be prevented.

  In addition, since PFA resin or PTFE resin is used as the material of the roller 52, there is an effect that unfixed toner is difficult to transfer and adhere.

  Another example of the image heating and fixing apparatus according to the present invention will be described.

  In this embodiment, members and portions that are common to those of the fixing device of Embodiment 1 are denoted by the same reference numerals, and repetitive description of the members and portions is omitted. The same applies to Example 3.

  The fixing device 9 shown in the present embodiment is configured to divide the static elimination needle 51 into a plurality of parts in the longitudinal direction of the pressure roller 22. FIG. 10 is a diagram illustrating the fixing device according to the present exemplary embodiment, and is an explanatory diagram illustrating a relationship between the pressure roller 22 and the static elimination needle 51 divided into a plurality of portions.

  The specifications of the image forming apparatus equipped with the fixing device 9 of this embodiment are a process speed of 201 mm / s and a print speed of 35 sheets / min (LTR longitudinal feed).

  In the image forming apparatus equipped with the fixing device 9 using the film 21, paper having a narrow paper width (hereinafter referred to as “small size paper”) such as an envelope is used as the transfer material P. In some cases, continuous printing is performed at the same print interval as the large size paper. In that case, it is known that the temperature of the area where the small-size paper does not pass (hereinafter referred to as a non-paper passing area) rises excessively than the area where the small-size paper of the heater 23 passes (hereinafter referred to as the paper passing area). It has been. Due to excessive temperature rise in the non-sheet passing area, the temperature of the non-sheet passing portion on the surface of the pressure roller 22 corresponding to the non-sheet passing area also rises, and the outer diameter of the pressure roller 22 is increased due to thermal expansion in the non-sheet passing area. Become.

  When the outer diameter of the pressure roller 22 increases at the non-sheet passing portion on the surface of the pressure roller 22, the sheet passing portion on the surface of the pressure roller 22 corresponding to the small size paper passing region of the heater 23 and the pressure roller 22. The gap between the tip of the static elimination needle 51 and the surface of the pressure roller 22 differs depending on the non-sheet passing portion on the surface. FIG. 11 exaggerates the appearance of the outer diameter increasing at the non-sheet passing portion on the surface of the pressure roller 22. That is, as shown in the figure, the gap d2 between the tip of the static elimination needle 51 in the paper passing portion on the surface of the pressure roller 22 and the surface of the pressure roller 22 is the static elimination needle in the non-paper passing portion on the surface of the pressure roller 22. 51 is larger than the gap d1 between the tip and the pressure roller 22 surface (d1 <d2). In that case, there is a possibility that the paper passing portion on the surface of the pressure roller 22 cannot be sufficiently discharged and an offset occurs in the paper passing portion. Similarly, when a pressure roller 22 having a reverse crown shape in which the outer diameter of both longitudinal ends is larger than the outer diameter of the central portion between the both longitudinal ends is used as the pressure roller 22, the surface of the pressure roller 22 is similarly passed. There is a possibility that an offset occurs in the paper portion.

  Therefore, in this embodiment, as shown in FIG. 10, in the longitudinal direction of the pressure roller 22, the static elimination needle 51 is divided into three corresponding to the paper passing portion and the non-paper passing portion on the surface of the pressure roller 22. Yes. The static elimination needle 51 is disposed in the static elimination needle holder 62 and is opposed to the paper passing portion and the non-paper passing portion on the surface of the pressure roller 22 through the roller 52 in a non-contact manner. That is, the gap d2 is set to the gap d1 by bringing the static elimination needle 51 corresponding to the paper passing portion on the surface of the pressure roller 22 closer to the surface of the pressure roller 22 than the other two static elimination needles 51 corresponding to the non-paper passing portion. An equal gap d21 can be obtained. Accordingly, a gap d1 (= d21) that can be neutralized can be maintained between the static elimination needle 51 and the surface of the pressure roller 22 in the sheet passing portion and the non-sheet passing portion on the surface of the pressure roller 22.

  Accordingly, even when the outer diameter of the pressure roller 22 is increased at the non-sheet passing portion on the surface of the pressure roller 22, the charge removal is performed between the charge eliminating needle 51 and the surface of the pressure roller 22 in both the sheet passing portion and the non-sheet passing portion. A possible gap d1 can be maintained, and the sheet passing portion and the non-sheet passing portion can be sufficiently discharged. Therefore, also in this embodiment, it is possible to prevent the offset of unfixed toner due to the charging of the surface of the pressure roller 22.

  Also in the present embodiment, a specific experiment was performed on the relationship between the charge elimination needle 51 and the offset. An experimental example will be described.

  When the static elimination needle 51 is not divided (no static elimination needle division), each of the three static elimination needles 51 is opposed to the sheet passing portion and the non-sheet passing portion on the surface of the pressure roller 22 via the roller 52, respectively. The results of comparing the offset levels are shown in Table 2.

  The offset is confirmed by introducing 50 sheets of paper (envelope leaving paper) with high resistance in a low-temperature and low-humidity environment into the nip portion N after the normal size paper (Xx4024 (LTR) leaving paper) is placed in the nip portion as in the first embodiment. N was introduced.

  As can be seen from Table 2, in the case where there was no neutralization needle division, the potential of the sheet passing portion on the surface of the pressure roller 22 was −2.5 to −3.0 kV, and offset occurred. However, in the non-sheet passing portion, the potential decreased to about -1.0 to -1.5 kV, and no offset occurred.

  On the other hand, in the case of the configuration of this embodiment (FIG. 10), the potential of the paper passing portion and the non-paper passing portion on the surface of the pressure roller 22 is reduced to about −1.0 to −1.5 kV, Offsets no longer occur.

  From the results shown in Table 2, when the neutralization needle is not divided, the paper passing portion on the surface of the pressure roller 22 corresponding to the small size paper passing area is not sufficiently discharged by introducing the small size paper into the nip portion N. It can be seen that an offset occurs.

  In contrast, in the case of the configuration of the present embodiment, the pressure roller 22 corresponding to the non-sheet passing area of the small size paper and the paper passing portion of the surface of the pressure roller 22 corresponding to the small size paper passing area. It can be seen that the non-sheet passing portion of the surface is sufficiently neutralized and no offset occurs.

  In the present embodiment, the example in which the static elimination needle 51 is divided into three in the longitudinal direction has been described. Since the number of divisions of the static elimination needle 51 depends on image forming conditions such as the image formation speed, the corresponding paper size, the outer diameter shape of the pressure roller 22, etc., the static elimination needle 51 is divided into two or more than four. However, similar effects can be obtained.

  According to the present embodiment, the static elimination needle 51 arranged along the surface of the pressure roller 22 in the longitudinal direction of the pressure roller 22 is divided into a plurality of parts, and the static elimination needle 51 is provided with a roller 52 on the pressure roller 22 surface. It is made to oppose non-contact through. As a result, even when the outer diameter difference occurs in the longitudinal direction of the pressure roller 22, the gap d <b> 1 that can be neutralized can be maintained between the surface of the pressure roller 22, the static elimination needle 51, and the surface of the pressure roller 22. Accordingly, in this embodiment, the same operation and effect as those of the fixing device 9 of Embodiment 1 can be obtained.

  Another example of the image heating and fixing apparatus according to the present invention will be described.

  The fixing device 9 shown in this embodiment includes a cleaning member 53 that cleans the surface of the roller 52 that contacts the surface of the pressure roller 22. 12A and 12B are diagrams illustrating a fixing device according to the present exemplary embodiment, in which FIG. 12A is a view of the relationship among the static elimination needle 51, the pressure roller 22, the roller 52, and the cleaning member 53 as viewed from the longitudinal direction, and FIG. It is the figure which looked at (a) from the cleaning member 53 side.

  The specifications of the image forming apparatus equipped with the fixing device 9 of this embodiment are a process speed of 266 mm / s and a print speed of 45 sheets / min (LTR longitudinal feed). In this embodiment, it is assumed that the number of sheets of transfer material P that pass through (the number of transfer materials P introduced into the nip portion N) is 400,000 as the durable life of the fixing device 9.

As described above, the first embodiment employs a configuration in which dirt such as toner does not adhere to the surface of the roller 52 by using PFA resin or PTFE resin as the material of the roller 52.
However, when the endurance life is relatively long as in the fixing device 9 of this embodiment, the releasability of the surface of the roller 17 is lowered, and the toner or the like may adhere to the surface of the roller 17 and cause dirt. FIG. 13 exaggerates the appearance of toner smearing due to toner or the like adhering to the surface of the roller 17. 13A is a view of the relationship between the static elimination needle 51, the pressure roller 22, the roller 52, and the toner stain from the longitudinal direction side, and FIG. 13B is a view of FIG. 13A viewed from the static elimination needle 51 side. . As shown in the figure, when toner contamination occurs on the surface of the roller 17, the tip of the static elimination needle 51 and the surface of the pressure roller 22 are separated from each other by a gap d1 or more, and the surface of the pressure roller 22 cannot be sufficiently eliminated. May occur.

  Therefore, in this embodiment, as shown in FIG. 12, a polyimide sheet having a thickness of 0.5 mm is brought into contact with the surface of the roller 52 as the cleaning member 53. The cleaning member 53 is formed in a rectangular shape wider than the surface of the roller 52, the end opposite to the roller 52 is coupled to the charge eliminating needle 51 or the charge eliminating needle holder 62, and the free end on the roller 52 side is connected to the surface of the roller 52. It is in contact. The cleaning member 53 can remove the toner stain on the surface of the roller 52, so that the toner 52 and the like can be prevented from adhering to the roller 52, and a good image with no offset can be obtained throughout the life of the fixing device 9.

  Table 3 shows changes in the offset level depending on the number of sheets that pass when the roller 52 has the cleaning member 53 and when the roller 52 does not have the cleaning member 53.

  The offset is confirmed by introducing 50 sheets of paper (envelope leaving paper) with high resistance in a low-temperature and low-humidity environment into the nip portion N after the normal size paper (Xx4024 (LTR) leaving paper) is placed in the nip portion as in the first embodiment. N was introduced.

  From Table 3, it can be seen that when the roller 52 does not have the cleaning member 53, the surface of the pressure roller 22 cannot be sufficiently neutralized from the time when 300,000 sheets are passed, and offset starts to occur.

  On the other hand, in the configuration of the present embodiment, even when 400,000 sheets of the durable life of the fixing device 9 were passed, no neutralization failure occurred on the surface of the pressure roller 22 and no offset occurred.

  In this embodiment, a polyimide sheet is used as the cleaning member 53 of the roller 52. However, the same effect can be obtained with a configuration using a sheet such as PET or a configuration in which a felt or the like is contacted.

  According to the present embodiment, the surface of the roller 52 that holds the gap d <b> 1 that can be neutralized between the static elimination needle 51 arranged along the surface of the pressure roller 22 in the longitudinal direction of the pressure roller 22 and the surface of the pressure roller 22. Can be cleaned by the cleaning member 53. As a result, toner contamination on the surface of the roller 52 can be prevented, and the gap d1 between which the charge removal needle 51 and the pressure roller 22 can be discharged is maintained. As a result, it is possible to prevent the occurrence of offset due to insufficient neutralization of the surface of the pressure roller 22 throughout the durable life of the fixing device 9.

Overall configuration diagram of an example of an image forming apparatus Model of longitudinal section of the fixing device of Example 1 Front model diagram of the fixing device of Example 1 Sectional view showing layer structure of fixing film Diagram showing bias application method to fixing film Diagram showing heater configuration and temperature control system (A) is explanatory drawing showing the relationship between a static elimination needle and a pressure roller surface, (b) is an enlarged view of the A section shown in (a). It is a figure showing the fixing device used for experiment, and is a figure showing the fixing device which has arranged the static elimination needle directly on the discharge guide Fig. 4 is a longitudinal cross-sectional model view of a modification of the fixing device according to the first embodiment. FIG. 6 is a diagram illustrating a fixing device according to a second embodiment, and is an explanatory diagram illustrating a relationship between a pressure roller and a plurality of charge elimination needles. The figure showing the relationship between the static elimination needle which is not divided and the pressure roller surface when the outside diameter of the non-sheet passing part becomes large 6A and 6B are diagrams illustrating a fixing device according to a third exemplary embodiment, in which FIG. 5A is a view of a relationship between a static elimination needle, a pressure roller, a roller, and a cleaning member as viewed from the longitudinal direction, and FIG. Viewed from It is a figure showing a mode that toner dirt occurred on a roller surface, (a) is a figure which looked at the relation between a static elimination needle, a pressure roller, a roller, and toner dirt from the longitudinal direction side, and (b) shows (a). View from static elimination needle side

Explanation of symbols

9: fixing device, 21: fixing film, 22: elastic pressure roller, 51: static elimination needle, 52: abutting roller, 53: cleaning member, N: nip portion, P: transfer material

Claims (5)

A recording material having a heating rotator and a pressurizing rotator that is in contact with the heating rotator to form a nip portion, and sandwiching and transporting a recording material carrying an unfixed toner image at the nip portion In an image heating and fixing apparatus that heats and fixes an unfixed toner image on the top,
A static elimination member that neutralizes the pressurizing rotator, the static elimination member disposed along a surface of the pressurizing rotator in a longitudinal direction of the pressurizing rotator perpendicular to the recording material conveyance direction;
A rotatable rotating member that is in contact with the surface of the pressurizing rotator or a rotation center axis of the pressurizing rotator and holds a gap that can be neutralized between the charge eliminating member and the surface of the pressurizing rotator;
An image heating fixing device comprising:   2. The image heating and fixing apparatus according to claim 1, wherein a shape of a tip portion of the charge eliminating member facing the surface of the pressing rotary member is a sawtooth shape. 3. The image heating and fixing apparatus according to claim 1, wherein a material of the rotating member is PFA resin or PTFE resin.   4. The image heating and fixing apparatus according to claim 1, wherein the charge eliminating member is divided into a plurality of parts in the longitudinal direction of the heating rotating body. 5.   5. The image heating fixing apparatus according to claim 1, further comprising a cleaning member that cleans the surface of the rotating member that is in contact with the surface of the pressurizing rotating body.

Images