JP2015232597A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve energy saving by preventing a warm-up time from getting long and to prevent an abnormal image by cleaning a pressing roller.SOLUTION: A fixing device includes a fixing belt 38 which comes into contact with a paper sheet Pa, a pressure roller 30 which forms a fixing nip part SN between the pressure roller 30 and the fixing belt 38, a resistance heating element 31 which heats the fixing belt 38, a pressing roller 40 which is formed by covering a core metal with an elastic layer and brought into contact with the resistance heating element 31 through the fixing belt 38, and a cleaning pad 41 which is arranged in the vicinity of the pressing roller 40. The cleaning pad 41 is arranged so that the pressing roller 40 and the cleaning pad 41 are separated from each other and when the temperature of the pressing roller 40 becomes high and the pressing roller 40 is thermally expanded, the pressing roller 40 and the cleaning pad 41 come into contact with each other.

Description

  The present invention relates to a fixing device and an image forming apparatus. More specifically, the present invention relates to a fixing device mounted on an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, a printer, or a complex machine thereof.

  Various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines, facsimile machines, printers, or their combined machines, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner or the like as a developer to be visualized. The developed image is transferred onto a recording material (also referred to as paper, recording paper, or recording medium) such as paper or an OHP sheet by a transfer device to carry the image, and unfixed on the recording material by a fixing device using heat and pressure This is established by the process of fixing the toner image.

  Various types of fixing devices have been proposed. For example, a heat roller type fixing device has a nip between a fixing roller heated by a heating member such as a halogen heater or an induction heating coil and a pressure roller. The toner is melted and fixed by heat and pressure by forming a portion and passing a recording material carrying an image through the nip portion. This heat roller type fixing device is widely used from the viewpoints of safety and compatibility with high speed machines.

  Also, belt systems and film systems are often used as fixing devices for realizing energy saving.

  For example, Patent Document 1 proposes a heating device that applies heat energy to a recording material by sandwiching the film and the recording material so that the film and the recording material are brought into close contact with a pressure member by a plate-shaped heating body that contacts the heat resistant film. . The film can be thinned to about 100 μm or less, and the start-up time can be reduced by simply raising the temperature of the heating element with a small heat capacity, so that the start-up time can be shortened and preheating power can be reduced. it can.

  Also, based on the image information formed on the recording material, the control temperature of the heating body and the heating area are changed to selectively heat only the image area, and the non-image area (the image in the image forming area does not exist) A method that enables energy saving by reducing the energy supply to (part) has been proposed.

  For example, in Patent Document 2, the temperature of each element of the heating element in the thermal head is measured and the appropriate heat is supplied, so that the influence of the ambient temperature is taken into consideration, and the toner applies heat only to the toner portion on the paper surface. A fixing method is disclosed.

  In addition, there has been proposed a method in which a resistance heating heater and a pressing roller (pressing member) are provided so as to face the resistance heating heater via a fixing belt.

  For example, in Patent Document 3, a resistance heating heater is disposed on the inner surface of the belt, and a fixing roller is disposed as a pressing member that presses the belt against the resistance heating heater from the outside of the belt in order to efficiently transfer heat to the belt. Is disclosed.

  In the fixing device disclosed in Patent Document 3, when the belt is stretched between the arc-shaped heater and the nip member by providing a counter roller, the arc-shaped heater and the belt can be used without burdening the belt with excessive tension. Therefore, the belt deformation at the corners and edges of the arc-shaped heater and the nip member is limited to elastic deformation, and plastic deformation that leads to belt breakage can be eliminated. Further, the inner surface of the belt is not rubbed strongly by the arc-shaped heater or the corners and edges of the nip member.

  However, when the pressing member is arranged outside the belt as in Patent Document 3, the pressing member is contaminated by a slight amount of offset toner, and an abnormal image is generated when the accumulated offset toner adheres to the belt again. There is a fear.

  As for the problem that the fixing member is contaminated with a small amount of offset toner as described above, although it is a heat roller type fixing device, in Patent Document 4, a cleaning roller provided in contact with and away from the fixing roller is brought into contact. A fixing device that collects offset toner on the fixing roller on the cleaning roller is disclosed.

  Here, in a method in which a pressing member is disposed outside the belt as in Patent Document 3, when a configuration in which a cleaning member such as a cleaning roller is in contact with the pressing member is considered, heat escapes from the pressing member to the cleaning member. There is a problem that the warm-up time is increased and the power consumption is increased, so that the energy saving performance is impaired.

  In addition, it is conceivable to provide a mechanism that allows the cleaning member to be brought into and out of contact with the pressing member as in Patent Document 4, but a part such as a motor is required as the contact and separation mechanism for making contact and separation, and the cost It will lead to high.

  Accordingly, the present invention provides a fixing device including a pressure roller and a member for cleaning the pressure roller, preventing an increase in warm-up time, saving energy, and without using a contact / separation mechanism having a motor or the like. It is an object to provide a fixing device capable of cleaning a roller.

  In order to achieve such an object, a fixing device according to the present invention includes a fixing member that contacts a recording medium that holds an unfixed image, a pressure member that forms a fixing nip portion between the fixing member, and the fixing device. A heating member that heats the member, and a pressure roller that is formed by covering a cored bar with an elastic layer and is in contact with the heating member via the fixing member; and in the vicinity of the pressure roller A pressure roller contact member that is disposed, the pressure roller and the pressure roller contact member are separated from each other, and the pressure roller and the pressure roller contact member when the pressure roller is thermally expanded at a high temperature The pressing roller contact member is arranged so that the contact with the roller is in contact.

  According to the present invention, it is possible to prevent the warm-up time from becoming long, save energy, and clean the pressing roller to prevent abnormal images.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus. FIG. 2 is a side view illustrating a basic configuration of a fixing device. FIG. 3 is a side view of the fixing device according to the present embodiment, and shows a room temperature state. FIG. 6 is a side view of the fixing device according to the present embodiment, and is a diagram illustrating an operation in a cleaning mode. FIG. 3 is a side view of a fixing device having a cleaning roller, showing a room temperature state.

  Hereinafter, the configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

(Image forming device)
FIG. 1 is a schematic configuration diagram illustrating the overall configuration of an embodiment of an image forming apparatus according to the present invention. The outline and operation of the internal configuration of the image forming apparatus will be described with reference to FIG.

  As shown in FIG. 1, the image forming apparatus 1 includes a paper feeding unit 4, a registration roller pair 6, a photosensitive drum 8 as an image carrier, a transfer unit 10, a fixing device 12, and the like. .

  The paper feeding means 4 feeds the paper Pa as recording material stored in a stacked state and the paper Pa stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16 and the like. The paper Pa sent out by the paper supply roller 16 is temporarily stopped by the registration roller pair 6, and after the positional deviation is corrected, it is formed on the photoconductive drum 8 at a timing synchronized with the rotation of the photoconductive drum 8. The toner image is sent to the transfer portion N by the registration roller pair 6 at the timing when the leading edge of the toner image coincides with the predetermined position at the leading edge of the paper Pa in the transport direction.

  Around the photosensitive drum 8, in the rotation direction indicated by the arrows, a charging roller 18 as a charging unit, a mirror 20 constituting a part of an exposure unit (not shown), a developing unit 22 including a developing roller 22a, A transfer unit 10 and a cleaning unit 24 including a cleaning blade 24a are disposed. Between the charging roller 18 and the developing means 22, exposure light Lb is irradiated to the exposure unit 26 on the photosensitive drum 8 via the mirror 20 and scanned.

  In this image forming apparatus 1, when the photosensitive drum 8 starts to rotate, the surface of the photosensitive drum 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated and scanned on the exposure unit 26 based on the image information. Thus, an electrostatic latent image corresponding to the image to be created is formed. The electrostatic latent image is moved to the developing means 22 by the rotation of the photosensitive drum 8, where toner is supplied to be visualized to form a toner image. The toner image formed on the photosensitive drum 8 is transferred onto the paper Pa that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer means 10.

  The paper Pa carrying the toner image is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged and stacked on a paper discharge tray (not shown). The configuration of the fixing device 12 will be described later.

  Next, the residual toner remaining on the photosensitive drum 8 without being transferred at the transfer portion N reaches the cleaning means 24 as the photosensitive drum 8 rotates, and while passing through the cleaning means 24, the cleaning blade 24a. Is scraped off and cleaned. Thereafter, the residual potential on the photosensitive drum 8 is removed by a neutralizing unit (not shown), and is prepared for the next image forming process.

(Fixing device)
Next, a fixing device provided in the image forming apparatus will be described. First, with reference to FIG. 2, a basic configuration and control as a premise of the fixing device according to the present embodiment will be described. FIG. 2 is a schematic side view of the fixing device 12. The fixing device 12 includes a fixing belt 38 as a fixing member, a pressure roller 30 as a pressure member that forms a fixing nip SN between the fixing belt 38, a resistance heating element 31 as a heating member, and the like. Have.

  The fixing belt 38 is an endless seamless belt, and has a base and an elastic layer coated on the surface of the base. The substrate is made of, for example, SUS and has an outer diameter of 40 mm and a thickness of 40 μm. The substrate may be made of polyimide (PI) resin or a metal substrate such as iron or nickel.

  The elastic layer has a layer thickness of about 50 to 200 μm, and silicone rubber, fluorine rubber, foamable silicone rubber, or the like can be used. For example, it is made of silicone rubber and has a thickness of 100 μm.

  Further, the surface of the fixing belt 38 is made of a fluorine-based material such as PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene) in order to enhance durability and ensure releasability. A release layer having a resin thickness of 5 to 50 μm is formed. Further, polyimide, polyetherimide, PES (polyethersulfone), or the like can also be used.

  A nip support member 61 is provided on the inner peripheral side of the fixing belt 38, and a nip forming member 60 is installed at a position where the nip portion SN is formed. A fixing nip portion SN is formed at a location where the fixing belt 38 and the pressure roller 30 are in contact with each other by the nip forming member 60. The nip support member 61 is supported by an external member (side plate) (not shown) and supports the nip forming member 60.

  The pressure roller 30 has a cored bar and an elastic layer coated on the surface of the cored bar. The pressure roller 30 is pressed against the fixing belt 38 by a pressure roller urging means 35. The core metal of the pressure roller 30 is made of, for example, iron and has an outer diameter of 40 mm and a thickness of 2 mm. A heat source such as a heater may be fixed inside the cored bar.

  The elastic layer is made of, for example, silicone rubber and has a thickness of 5 mm. Moreover, it is preferable to form a fluororesin layer having a thickness of about 40 μm on the surface of the elastic layer in order to improve the releasability.

  The resistance heating element 31 is a resistance heating element whose base material is formed of ceramics, for example, and is supplied with power from a power supply unit 39 connected to a commercial power source.

  The resistance heating element 31 and the power supply unit 39 constitute a heating means, and the heating control means 37 controls the heating means. Further, a thermistor 34 as a temperature detecting means is provided at a position in contact with the inner peripheral surface side of the fixing belt 38 and detects the temperature of the fixing belt 38.

  The heating control means 37 is constituted by a microcomputer including a CPU, ROM, RAM, I / O interface, and the like, and controls the power supply unit 39 to supply predetermined electric power to the resistance heating element 31. The heating control unit 37 controls energization of the power supply unit 39 so as to maintain the fixing belt 38 at a desired temperature based on the detection result detected by the thermistor 34.

  The resistance heating element 31 is supported by the heater folder 32. The heater folder 32 is supported by a heater support member 33, and the heater support member 33 is supported by a nip support member 61.

  Since the heater folder 32 receives heat from the resistance heating element 31, the heater folder 32 tends to become high temperature. For this reason, it forms with resin with high heat resistance, such as LCP (liquid crystal polymer). The heater support member 33 is, for example, SECC (electrogalvanized steel sheet) and has a thickness of 1.6 mm.

  The pressing roller 40 is provided at a position facing the resistance heating element 31 with the fixing belt 38 interposed therebetween, and is a pressing member that presses the fixing belt 38 against the resistance heating element 31 from the outside of the fixing belt 38. Take around.

  The pressing roller 40 has a cored bar and an elastic layer coated on the surface of the cored bar. The pressing roller 40 may be, for example, a rubber roller having an outer diameter of 20 mm in which a core metal has a diameter of 10 mm and 5 mm thick silicone rubber is wound around the core metal. Moreover, it is preferable to form a fluororesin layer having a thickness of about 40 μm on the surface of the silicone rubber in order to improve the releasability.

  The pressure roller 40 is pressed against the resistance heating element 31 through the fixing belt 38 by the pressure roller urging means 43.

  In the fixing device 12, as shown in FIG. 2, the paper Pa carrying the unfixed toner image T is guided to the fixing nip portion SN formed by the fixing belt 38 and the pressure roller 30, and the paper Pa is The toner image T is fixed at the fixing nip portion SN and then discharged.

  Here, when the pressing roller 40 is disposed on the outer peripheral side of the fixing belt 38 as in the fixing device 12 shown in FIG. 2, the pressing roller 40 is contaminated by a slight amount of offset toner, and the accumulated offset toner is An abnormal image may occur due to adhesion to the fixing belt 38. In order to clean the pressure roller 40, it is desirable to provide a cleaning member (referred to as a pressure roller contact member) such as a cleaning roller or a cleaning pad that comes into contact with or comes into contact with the pressure roller 40. When the contact is always made, the heat escapes from the pressure roller 40 to the pressure roller contact member, so that the warm-up time of the fixing device 12 is lengthened and the power consumption is increased, so that the energy saving performance is impaired. Further, although it is conceivable that the pressing roller contact member can be brought into and out of contact with the pressing roller 40 by a contact / separation mechanism equipped with a motor or the like, this leads to high cost.

  Therefore, the fixing device (fixing device 12) according to the present embodiment, as shown in FIG. 3 and the like, is a fixing member (fixing belt 38) that comes into contact with a recording medium (paper Pa) that holds an unfixed image (toner image T). ) And a fixing member, a pressure member (pressure roller 30) that forms a fixing nip portion (fixing nip portion SN), and a heating member (resistance heating element 31) that heats the fixing member. In the apparatus, a pressure roller (pressure roller 40) that is formed by covering a cored bar with an elastic layer and is brought into contact with a heating member via a fixing member, and a pressure roller contact member (cleaning) disposed in the vicinity of the pressure roller Pad 41 and cleaning roller 42), the pressure roller and the pressure roller contact member are separated from each other, and the pressure roller and the pressure roller contact member come into contact with each other when the pressure roller is thermally expanded. A is obtained by placing the pressing roller contact member. In addition, the code | symbol in embodiment and an application example are shown in a parenthesis.

  FIG. 3 is a side view of the fixing device 12 according to the present embodiment, and is an explanatory view showing the fixing device 12 having a cleaning pad as a pressing roller contact member in a room temperature (20 ° C.) state. Hereinafter, differences from the basic configuration shown in FIG. 2 will be described. In addition, room temperature is the temperature range which can be taken indoors normally, for example, is the range of 1-30 degreeC.

  As shown in FIG. 3, the fixing device 12 has a cleaning pad 41 fixed in the vicinity of the pressing roller 40. The cleaning pad 41 is, for example, a pad member formed by winding a nonwoven fabric around the surface of a member such as LCP having high heat resistance.

  Further, as shown in FIG. 3, in the room temperature state, the cleaning pad 41 and the pressing roller 40 are disposed at positions that are separated from each other with a predetermined gap (gap g).

  When the pressure roller 40 rises from room temperature to a printing temperature (for example, 150 ° C.), the elastic layer thermally expands. Further, when the pressure roller 40 rises to a cleaning mode operating temperature higher than the printing temperature (for example, 200 ° C.), it is elastic. The layer expands further.

Here, when the thickness of the elastic layer of the pressing roller 40 is 5 mm and the linear expansion coefficient is 5 × 10 ⁻⁴ , the heat of about 0.7 mm is obtained when the temperature rises from room temperature (20 ° C.) to 150 ° C. which is the printing temperature by 130 degrees. Inflate. Furthermore, when the temperature rises to 200 ° C., which is an operating temperature in a cleaning mode described later, the film expands by about 1.1 mm.

  Therefore, in the present embodiment, the gap g between the pressure roller 40 and the cleaning pad 41 in the room temperature state is not in contact with thermal expansion at the printing temperature, but is in contact with thermal expansion at the operating temperature in the cleaning mode, for example, It arrange | positions so that it may be set to 0.9 mm. Thereby, during the printing operation, the pressing roller 40 and the cleaning pad 41 do not contact each other, but the pressing roller 40 and the cleaning pad 41 start to contact before reaching the operating temperature in the cleaning mode.

  Therefore, it is possible to prevent heat from the pressing roller 40 from being transferred to the cleaning pad 41 during the printing operation. At least at room temperature, the pressing roller 40 and the cleaning pad 41 are arranged so as to have a predetermined gap and are in contact at the operating temperature in the cleaning mode, so that they are in contact during the printing operation. However, it is possible to prevent the heat of the pressing roller 40 from being transferred to the cleaning pad 41 from the start of the warm-up operation until the start of contact.

  FIG. 4 is a side view of the fixing device 12 according to the present embodiment, and is an explanatory view showing a cleaning mode operation of the fixing device 12 having a cleaning pad as a pressing roller contact member.

  Here, the fixing device 12 executes a cleaning mode (cleaning operation) during the non-printing operation. In the cleaning mode, for example, the fixing belt 38 is rotated for 60 seconds while the temperature detected by the thermistor 34 is maintained at 220 ° C. At that time, the pressure roller 40 rises to 220 ° C. which is substantially the same as that of the fixing belt 38. Then, the pressing roller 40 comes into contact with the cleaning pad 41 due to thermal expansion beyond the gap g.

  Thereby, the offset toner adhered to the surface of the pressing roller 40 can be scraped off by the nonwoven fabric on the surface of the cleaning pad 41. Further, even for offset toner that could not be collected by the nonwoven fabric, the fixed offset toner is easily peeled off from the pressing roller 40, and therefore adheres to the paper Pa in small amounts via the fixing belt 38 during the next printing. It was possible to discharge from the pressing roller 40.

  3 and 4, the example in which the cleaning pad 41 is used as the pressing roller contact member has been described. However, the cleaning roller 42 may be used as the pressing roller contact member.

  The fixing device 12 shown in FIG. 5 has a cleaning roller 42 fixed in the vicinity of the pressing roller 40. The cleaning roller 42 is made of, for example, aluminum. FIG. 5 shows a state at room temperature, and the gap (gap g) between the pressing roller 40 and the cleaning roller 42 is formed at 0.9 mm. Thus, the thermal expansion of the pressing roller 40 during the printing operation does not contact the pressing roller 40 and the cleaning roller 42, but the pressing roller 40 and the cleaning roller 42 are in contact in the cleaning mode.

(Conditions for cleaning mode)
Hereinafter, the execution conditions when the image forming apparatus 1 performs the cleaning mode will be described.

[Implementation condition (1)]
It is preferable that the image forming apparatus 1 includes a print number storage unit that counts the number of prints and executes the cleaning mode for each predetermined print number.

  In the cleaning mode, an operation of rotating at a high temperature for 60 seconds is performed, so that the user has a waiting time and a load is applied to the components of the fixing device 12 during that period. For this reason, it is preferable to minimize the number of times the cleaning mode is performed.

  Here, the number of executions of the cleaning mode is determined using the data of the number of prints stored in the image forming apparatus 1. For example, it was found that the offset toner can be maintained on the surface of the pressing roller 40 without being fixed by performing the cleaning mode once for every 5000 printed sheets.

[Condition (2)]
Further, it is preferable that the image forming apparatus 1 includes a cumulative area storage unit that stores a cumulative image area, and executes the cleaning mode for each predetermined cumulative image area.

  Since the use application of the image forming apparatus 1 varies depending on the user, it is conceivable that the conditions for performing the cleaning mode cannot be determined in general by the number of prints. Therefore, the number of executions of the cleaning mode may be determined using data on the accumulated image area stored in the image forming apparatus 1. For example, the average image area ratio is 10%, and the cumulative image area when 5000 sheets of A4 size and 10% image area ratio are printed is defined as a threshold (threshold). The cleaning mode is performed.

[Implementation condition (3)]
The image forming apparatus 1 preferably includes a print number storage unit and a cumulative area storage unit, and preferably executes the cleaning mode when the cumulative image area does not reach a predetermined value during a predetermined number of prints.

  Here, it has been found that if printing with an extremely small image area continues, paper dust and toner are likely to adhere to the pressing roller 40. This is because fine paper dust and offset toner adhering to the fixing belt 38 are attracted to the image portion toner, so that the fixing belt 38 is kept in a clean state (so-called self-cleaning), but only for a print with a small image area. This is because paper dust and offset toner remaining on the fixing belt 38 are difficult to occur and accumulate on the pressing roller 40.

  Therefore, for example, when the number of printed sheets is lower than a predetermined value with a cumulative image area every 1000 sheets (for example, a cumulative image area when 1000 sheets of an A4 size image area ratio of 2% are printed) is the cleaning mode. It is preferable to implement.

  As described above, the fixing device 12 according to the present embodiment includes the pressing roller 40 that is formed by covering the cored bar with the elastic layer and is in contact with the resistance heating element 31 via the fixing belt 38. And a pressure roller contact member (cleaning pad 41, cleaning roller 42) disposed in the vicinity of 40, the pressure roller 40 and the pressure roller contact member are separated from each other, and the pressure roller 40 is thermally expanded due to high temperature. Sometimes, the pressing roller contact member is arranged so that the pressing roller 40 and the pressing roller contact member are in contact with each other.

  Specifically, the thermal expansion amount of the pressing roller 40 is proportional to the temperature of the pressing roller 40, and the pressing roller 40 in contact with the fixing belt 38 becomes a temperature close to the fixing belt 38. In the room temperature state, the pressure roller 40 and the pressure roller contact member are arranged so that there is a gap between them, and at the printing temperature, the thermal expansion of the pressure roller 40 is still small and the pressure roller 40 and the pressure roller contact member are not in contact with the pressure roller contact member. Thus, the thermal expansion amount is increased at the time of the operation of the cleaning mode in which the temperature is higher than the printing temperature, and the heat roller is disposed at a position where the pressure roller contact member comes into contact.

  In this manner, the pressure roller 40 and the pressure roller contact member are separated from each other at room temperature and during a normal printing operation, and during the cleaning operation in which the fixing belt 38 is rotated at a higher temperature than during the printing operation, the thermal expansion of the pressure roller 40 is performed. To make contact.

  For this reason, during the printing operation, the pressure roller 40 and the pressure roller contact member are separated from each other, so that heat does not escape from the pressure roller 40 to the pressure roller contact member, thereby preventing an increase in warm-up time. Therefore, it is possible to save energy by reducing power consumption.

  Further, at the time of the cleaning operation, an abnormal image can be prevented by removing the offset toner and the like adhering to the pressure roller 40 when the pressure roller 40 and the pressure roller contact member come into contact with each other. At this time, since the pressing roller contact member only needs to be fixed, it is not necessary to provide a contact / separation mechanism such as a motor for moving the pressing roller contact member, so that the cost can be reduced.

  Therefore, both energy saving performance and cleaning performance can be achieved at low cost.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Paper feed means 6 Registration roller pair 8 Photosensitive drum 10 Transfer means 12 Fixing apparatus 14 Paper feed tray 16 Paper feed roller 18 Charging roller 20 Mirror 22 Development means 22a Development roller 24 Cleaning means 24a Cleaning blade 26 Exposure part 30 Pressure roller 31 Resistance heating element 32 Heater folder 33 Heater support member 34 Thermistor 35 Pressure roller biasing means 37 Heating control means 38 Fixing belt 39 Power supply unit 40 Pressing roller 41 Cleaning pad 42 Cleaning roller 43 Pressing roller biasing means 60 Nip forming member 61 Nip supporting member g Gap Lb Exposure light N Transfer site Pa Paper SN Fixing nip T Toner image

JP-A-6-95540 JP 2005-181946 A JP 2008-70737 A JP-A-8-166739

Claims (8)

A fixing member in contact with a recording medium holding an unfixed image;
A pressure member that forms a fixing nip with the fixing member;
A fixing device having a heating member for heating the fixing member,
A pressure roller that is formed by coating a cored bar with an elastic layer, and is in contact with the heating member via the fixing member;
A pressing roller contact member disposed in the vicinity of the pressing roller,
The pressing roller and the pressing roller contact member are separated from each other,
The fixing device, wherein the pressing roller contact member is arranged so that the pressing roller and the pressing roller contact member come into contact with each other when the pressing roller is hot and thermally expands.   The temperature of the pressure roller when the pressure roller is thermally expanded and the pressure roller and the pressure roller contact member start to contact each other is higher than the temperature of the pressure roller during a printing operation. The fixing device according to 1.   The fixing device according to claim 1, wherein the pressing roller contact member is a cleaning pad or a cleaning roller.   An image forming apparatus comprising the fixing device according to claim 1.   A cleaning mode in which, under a predetermined condition, the temperature of the fixing member is maintained at a temperature higher than that during the printing operation, is rotated for a predetermined time, and the pressure roller is cleaned by bringing the pressure roller and the pressure roller contact member into contact with each other. The image forming apparatus according to claim 4, further comprising:   6. The image forming apparatus according to claim 5, further comprising a print number storage unit for counting the number of prints, wherein the cleaning mode is executed every predetermined number of prints. 6. The image forming apparatus according to claim 5, further comprising cumulative area storage means for storing a cumulative image area, wherein the cleaning mode is executed for each predetermined cumulative image area. A print number storage means for counting the number of prints;
Cumulative area storage means for storing the cumulative image area;
The image forming apparatus according to claim 5, wherein the cleaning mode is executed when the accumulated image area does not reach a predetermined value during a predetermined number of prints.