JP2014153480A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus capable of accelerating the start-up of a portion of a fixing member corresponding to an image area to a fixing temperature, while achieving energy saving.SOLUTION: A fixing device includes an endless belt-like fixing member that is rotatably provided, a pressure member that is rotatably provided and brought into pressure contact with the fixing member to form a nip part with the fixing member, and heating means provided in contact with the fixing member for heating the fixing member. The heating means are provided in plurality each having a heat source and cover the entire image formation area in a paper width direction orthogonal to a recording material conveyance direction of the recording material, and include image area heating means for changing an area heated by the heat source according to an image area on the recording material where a toner image is formed and heating a portion of the fixing member corresponding to the image area to a fixing temperature, and entire area heating means for heating the entire image formation area of the fixing member at a temperature lower than the fixing temperature.

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the fixing device.

  Conventionally, in an image forming apparatus, a latent image on an image carrier is developed with toner supplied from a developing device, and a toner image as a visible image is formed on the image carrier. The toner image on the image carrier is transferred to a recording material by a transfer device and fixed on the recording material by a fixing device.

  In the fixing device described in Patent Document 1, a pressure roller that is rotatably provided and a fixing belt that is a flexible endless belt member provided to face the pressure roller are brought into pressure contact with each other. Thus, a nip portion is formed. In addition, a heating unit that contacts the inner peripheral surface of the fixing belt and heats the fixing belt is provided on the inner peripheral surface side of the fixing belt corresponding to the nip portion. Then, the fixing belt is heated by the heating means so as to apply heat only to the portion of the fixing belt corresponding to the image area where the toner image exists on the paper, so that the toner on the paper conveyed to the nip portion is removed. Fix to paper with heat and pressure. In this way, by applying heat only to the portion corresponding to the image area of the fixing belt and heating it to the fixing temperature, it is possible to save energy compared to heating the entire fixing belt to the fixing temperature.

  However, when the heating unit starts heating the portion corresponding to the image area of the fixing belt, if the temperature of the fixing belt is too low, a large amount of heat is required to raise the temperature to the fixing temperature. Therefore, there arises a problem that the rise to the fixing temperature of the portion corresponding to the image area of the fixing belt is not in time.

  The present invention has been made in view of the above-described problems, and a purpose thereof is a fixing device capable of quickly starting up a fixing temperature of a portion corresponding to an image area of a fixing member while saving energy. An image forming apparatus including the fixing device is also provided.

  In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that an endless belt-shaped fixing member provided rotatably and a nip portion between the fixing member rotatably provided and pressed against the fixing member. And a heating means provided in contact with the fixing member for heating the fixing member, allowing the recording material to pass through the nip portion, and the toner on the recording material by heat and pressure. In the fixing device for fixing an image to the recording material, a plurality of heating means having a heat source occupying the entire image forming region in the paper width direction perpendicular to the recording material conveyance direction of the recording material are provided. An image area heating means for heating a portion corresponding to the image area of the fixing member to a fixing temperature by changing a heating area by the heat source in accordance with an image area on which the toner image is formed; and a temperature lower than the fixing temperature. so It is characterized in that it has a whole heating means for heating the image forming area throughout the serial fixing member.

  Here, the “image forming area” is an area set so that an image can be formed. In the image forming area, an area where an image exists is an “image area”, and an area where no image exists is “ “Non-image area”.

  In the present invention, the entire area of the image forming area of the fixing member is heated by the entire area heating means at a temperature lower than the fixing temperature, and the area corresponding to the image area of the fixing member is heated to the fixing temperature by the image area heating means. Thus, by heating the entire image forming area of the fixing member at a temperature lower than the fixing temperature, the portion corresponding to the image area of the fixing member is compared with the case where the entire image forming area of the fixing member is not heated. It is possible to reduce the amount of heat required when heating the toner to the fixing temperature. Accordingly, it is possible to speed up the start up to the fixing temperature of the portion corresponding to the image area of the fixing member. Further, since the entire image forming area of the fixing member is heated at a temperature lower than the fixing temperature, energy saving can be achieved as compared with the case where the entire image forming area of the fixing member is heated to the fixing temperature.

  As described above, according to the present invention, there is an excellent effect that the rise to the fixing temperature of the portion corresponding to the image area of the fixing member can be accelerated while energy saving is achieved.

2 is a schematic configuration diagram of a fixing device according to Configuration Example 1. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. 2A is an external view of a fixing device according to Configuration Example 1, and FIG. 2B is a schematic diagram of a heating member. The top view which shows an image formation pattern. The top view which shows an image formation pattern. The graph which shows the relationship between the 1st target temperature with respect to an image area | region and a non-image area | region, and a 2nd target temperature. FIG. 6 is a schematic configuration diagram of a fixing device according to Configuration Example 2; FIG. 10 is a schematic configuration diagram of a fixing device according to Configuration Example 3. FIG. 10 is a schematic configuration diagram of a fixing device according to Configuration Example 4; FIG. 10 is a schematic configuration diagram of a fixing device according to Configuration Example 5;

FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the present embodiment.
As shown in FIG. 2, a printer as an example of an image forming apparatus according to the present embodiment includes a paper feeding device 4, a registration roller pair 6, a photosensitive drum 8 as an image carrier, a transfer device 10, It has a fixing device 12 and the like.

  The paper feeding device 4 feeds the paper S as a recording material stored in a stacked state and the paper S stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16 and the like.

  The sheet S sent out by the sheet feeding roller 16 is temporarily stopped by the registration roller pair 6 to correct the posture deviation. Thereafter, at the timing synchronized with the rotation of the photosensitive drum 8, that is, at the timing at which the leading edge of the toner image formed on the photosensitive drum 8 coincides with the predetermined position of the leading edge of the sheet S in the transport direction. The pair 6 is sent to the transfer portion N.

  Around the photosensitive drum 8, the charging roller 18, the mirror 20 constituting a part of the exposure unit, the developing device 22 including the developing roller 22a, the transfer device 10, and the cleaning are arranged in order of the photosensitive drum rotation direction. A cleaning device 24 provided with a blade 24a is disposed. Between the charging roller 18 and the developing device 22, exposure light Lb is irradiated to the exposure unit 26 on the photosensitive drum 8 through the mirror 20 and scanned.

  The image forming operation in the printer is performed in the same manner as in the past. That is, 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 to create an image to be created. A latent image corresponding to is formed. The latent image is moved to a position facing the developing device 22 by the rotation of the photosensitive drum 8, where toner is supplied from the developing device 22 to the latent image to be visualized to form a toner image.

  The toner image formed on the photosensitive drum 8 is transferred onto the paper S that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer device 10.

  The sheet S on which the toner image has been transferred is conveyed toward the fixing device 12, and after the toner image is fixed on the sheet S by the fixing device 12, the sheet S is discharged to a discharge tray (not shown) and stacked.

  Residual toner remaining on the photosensitive drum 8 without being transferred from the photosensitive drum 8 to the paper S at the transfer portion N reaches the cleaning device 24 as the photosensitive drum 8 rotates, and is scraped off by the cleaning blade 24a. Thus, the surface of the photosensitive drum is cleaned. Thereafter, the residual potential on the photosensitive drum 8 is removed by a neutralizing unit (not shown) and prepared for the next image forming step.

  Here, conventionally, as a fixing device used in an image forming apparatus, a heat roller type is known. In the heat roller type fixing device, a nip portion is formed by a fixing roller having a heat source such as a halogen heater or an induction heating coil inside and a pressure roller, and a recording material on which a toner image is formed is formed in the nip portion. The toner is fixed to the recording material by heat and pressure.

  As a fixing device that heats the fixing roller from the outside, for example, as described in JP-A-2001-343860, the toner is melted by heat accumulated in the vicinity of the surface of the fixing roller by heating the fixing roller from the outside. I do. This has the advantage that the rise time to the fixing temperature is short and the energy loss is small compared to the internal heating method in which the fixing roller is heated from the inside.

  The fixing roller method is widely used from the viewpoints of safety and compatibility with high speed machines. However, since the core of the fixing roller is made of metal and has a large heat capacity, it takes several minutes to reach a predetermined fixing temperature. For this reason, even in a standby state where no image forming operation is performed, heating is performed so that the fixing roller is maintained at a certain temperature.

  As a fixing device for realizing energy saving, a belt method or a film method is often used, and a technique for selectively heating only an image region based on image information has been proposed.

  As a film-type fixing device, for example, as described in JP-A-6-95540, a plate-like heating body that comes into contact with a thin cylindrical heat-resistant film, and a pressure roller, a film and a recording material In such a manner that the thermal energy is applied to the recording material. Since the film thickness is as thin as about 100 [μm], the start-up time up to the fixing temperature can be reduced by simply increasing the temperature of the plate-like heating body with a small heat capacity, so the start-up time can be shortened and the preheating power can be reduced. Can be reduced.

  Furthermore, in accordance with the toner image formed on the recording material, the control temperature of the heating body and the heating area are changed to reduce the heating to the non-image area where the image does not exist in the image forming area. A configuration that enables energy saving is known. In Japanese Patent Laid-Open No. 2005-181946, by measuring the temperature of each element of the heating element of the thermal head and supplying appropriate heat, the influence of the ambient temperature is taken into consideration and only the toner portion on the recording material is heated. The structure which adds is disclosed.

  In a fixing device that selects and heats a portion corresponding to an image region of a fixing belt, a surface heating element such as a thermal head that rapidly increases in temperature is used as a heat source that heats the image region. Such a heat source needs to quickly heat the image area and raise the temperature of the fixing belt. However, if the heat capacity of the heat source itself is large, a heat amount enters the heat source itself, the heat amount does not enter the fixing belt, and the rise to the fixing temperature of the fixing belt is delayed. In addition, if the temperature of the fixing belt is too low at the start of heating the portion corresponding to the image area of the fixing belt by the heat source, a large amount of heat is required to raise the temperature to the fixing temperature. As a result, the rise to the fixing temperature of the portion corresponding to the image area of the fixing belt is not in time.

[Configuration example 1]
FIG. 1 is a schematic configuration diagram of a fixing device 12 according to this configuration example. 3A is an external view of the fixing device 12, and FIG. 3B is a schematic diagram of the heating members 56A and 56B.

  As shown in FIG. 1, the fixing device 12 includes a fixing belt 38, a pressure roller 30 as a pressure member that forms a fixing nip portion SN between the fixing belt 38, and planar heat generation such as a thermal heater. It has heating members 56A and 56B which are bodies. The pressure roller 30 is urged toward the fixing belt 38 by an urging means (not shown) and is pressed against the fixing belt 38.

  The heating member 56 </ b> A and the heating member 56 </ b> B are attached to the stay-like member 57 and are arranged side by side along the fixing belt rotation direction at a position in contact with the inner peripheral surface of the fixing belt 38. By providing the heating members 56A and 56B in contact with the inner surface of the fixing belt 38, the outer circumferential surface of the fixing belt 38 that contacts the toner image on the paper S is prevented from being scratched by the heating members 56A and 56B. And the life of the fixing belt 38 can be extended.

  The heating members 56A and 56B are provided with a heater 55 so as to occupy the entire image forming region in the paper width direction orthogonal to the paper transport direction of the paper P. As shown in FIGS. 3A and 3B, the heating member 56A has a heater 55A divided into seven in the paper width direction, and each heater 55Aa, 55Ab, 55Ac, 55Ad, 55Ae, 55Af, 55Ag can heat the fixing belt 38 independently. In the heating member 56B, the heater 55B is divided into three in the paper width direction, and each of the heaters 55Ba, 55Bb, and 55Bc can heat the fixing belt 38 independently.

  In this configuration example, the heater 55A of the heating member 56A is divided into seven parts in the paper width direction (longitudinal direction), and the heater 55B of the heating member 56B is divided into three parts in the paper width direction (longitudinal direction). It is not limited. For example, when the heater 55B of the heating member 56B is divided into three in the paper width direction, the number of divisions in the paper width direction of the heater 55A of the heating member 56A may be four or more. By making the number of divisions in the paper width direction of the heater 55B of the heating member 56B smaller than the number of divisions in the paper width direction of the heater 55A of the heating member 56A, the power supply 39 supplies the heater 55B of the heating member 56B to that amount. Wiring can be reduced.

  The heating member 56A heats each heater 55A independently according to the image area where the toner image on the paper S is formed, and changes the heating area to heat the portion corresponding to the image area of the fixing belt 38 to the fixing temperature. Image area heating means. The heating member 56B is a whole area heating unit that heats the entire image forming area of the fixing belt 38 at a temperature lower than the fixing temperature. The heating member 56B may be configured to be able to heat the entire area of the fixing belt 38 in the sheet width direction.

  As temperature detection means for detecting the surface temperature of the fixing belt 38 in the vicinity of the heating member 56B, downstream of the fixing nip portion SN in the fixing belt rotation direction and upstream of the heating members 56A and 56B in the fixing belt rotation direction. Thermistor 34 is provided.

Further, thermistors 36a and 36b as temperature detecting means for detecting the temperature of the heating members 56A and 56B are provided on the surface of the heating members 56A and 56B opposite to the side in contact with the inner peripheral surface of the fixing belt 38. Yes.

  A power source 39 is provided to supply power to the heating members 56A and 56B. When power is supplied from the power source 39 to the heaters 55A and 55B of the heating members 56A and 56B, the heaters 55A and 55B of the heating members 56A and 56B are provided. Generates heat. Further, based on the temperature information detected by the thermistor 34 and the thermistors 36a and 36b, the control device 37 controls the power supply 39, and the power supply 39 supplies power to the heaters 55A and 55B of the heating members 56A and 56B. The control device 37 can control power supply by the power source 39 independently in each of the heaters 55A and 55B divided by the heating members 56A and 56B. The control device 37 is a microcomputer including a CPU, a ROM, a RAM, an I / O interface, and the like.

  The fixing belt 38 has a stainless steel base 38a having an outer diameter of 40 [mm] and a thickness of 40 [μm], and an elastic layer 38b coated on the surface of the base 38a. The elastic layer 38b is made of silicone rubber and has a thickness of 100 [μm]. Further, on the surface of the elastic layer 38b, in order to enhance the durability of the fixing belt 38 and to ensure the releasability, the release with a fluorine resin such as PFA or PTFE having a thickness of 5 [μm] to 50 [μm]. A layer 38c is formed. The base 38a of the fixing belt 38 may be polyimide.

  Inside the fixing belt 38, in addition to the heating members 56A and 56B, a belt support member 61 that supports the fixing belt 38, and a nip that forms the pressure roller 30 and the fixing nip portion SN with the fixing belt 38 interposed therebetween. A member 60 is provided. These members are connected to and supported by a device side plate (not shown).

  The pressure roller 30 includes an iron core 30a having an outer diameter of 40 [mm] and a thickness of 2 [mm], and an elastic layer 30b covered on the surface of the core 30a. The elastic layer 30b is made of silicone rubber and has a thickness of 5 [mm]. In addition, it is desirable to form a fluororesin layer having a thickness of about 40 [μm] on the surface of the elastic layer 30b in order to improve releasability.

  At a position facing the heating members 56A and 56B via the fixing belt 38, an elastic roller 40, which is a pressing member that is pressed by the biasing means (not shown) and presses the fixing belt 38, is pressed against the fixing belt 38. Is provided. Thereby, the contact state between the fixing belt 38 and the heating members 56A and 56B can be kept good.

  The elastic roller 40 includes an iron cored bar 40a having an outer diameter of φ15 [mm] to 30 [mm] and an outer diameter of φ8 [mm], and an elastic layer 40b covered on the surface of the cored bar 40a. Have. The elastic layer 40b is made of silicone rubber and has a thickness of 3.5 [mm] to 11 [mm]. It is desirable to form a fluororesin layer having a thickness of about 40 [μm] on the surface of the elastic layer 40b in order to improve the releasability.

  The pressing member that presses the fixing belt 38 at a position facing the heating members 56A and 56B via the fixing belt 38 is not limited to an elastic roller. For example, a mechanism such as a pad or brush that can maintain a good contact state between the fixing belt 38 and the heating members 56A and 56B can be used.

  In the fixing device 12 of this configuration example, the control device 37 controls power supply from the power source 39 to the heaters 55A and 55B of the heating members 56A and 56B based on image information for forming an image on the paper S. In this way, energy saving is achieved by changing the heating ratio of the heating members 56A and 56B. An example of this control operation is shown below.

  FIG. 4A shows an image forming pattern in which an image area a, a non-image area b, and an image area a ′ are present on the sheet S in order from the leading end side in the sheet conveyance direction. The image area a and the image area a 'need to be fixed, but the non-image area b does not need to be fixed because there is no toner to be fixed.

  Image information of the image forming pattern is input to the control device 37 from an image processing device (not shown). Then, the control device 37 sets the heating member 56A so that the temperature of the part corresponding to the non-image area b of the fixing belt 38 is lower than the temperature of the part corresponding to the image area a and the image area a ′ of the fixing belt 38. , 56B are controlled. In other words, in the portion corresponding to the image region a and the image region a ′, the heating member 56A is supplied with electric power to obtain the fixing temperature, and in the portion corresponding to the non-image region b, the heating member 56A is not supplied with electric power. The electric power which can obtain the temperature lower than the fixing temperature is supplied to 56B.

  Note that “corresponding to an image region” and “corresponding to a non-image region” mean a position where the fixing belt 38 is in close contact, and hereinafter, it is also expressed as “contact” as appropriate.

  FIG. 4B shows an image forming pattern in which an image area a and a non-image area b exist on the paper S in order from the leading end side in the paper transport direction. Also in this case, as in FIG. 4A, the control device 37 causes the temperature of the portion corresponding to the non-image area b of the fixing belt 38 to be lower than the temperature of the portion corresponding to the image area a of the fixing belt 38. Thus, the heating members 56A and 56B are controlled. In other words, in the portion corresponding to the image region a, power that provides a fixing temperature is supplied to the heating member 56A, and in the portion corresponding to the non-image region b, no power is supplied to the heating member 56A and the heating member 56B is supplied with the fixing temperature. Supplying electric power that can obtain a low temperature.

  Here, it is conceivable that the power supply to the heating members 56A and 56B is completely stopped (turned off) at a portion corresponding to the non-image area b of the fixing belt 38. If the temperature of the fixing belt 38 is excessively lowered, The rise to the fixing temperature in the image area is not in time. Therefore, in this configuration example, the sheet of the fixing belt 38 is heated by the heating member 56B so that the second target temperature is lower than the first target temperature that is the fixing temperature and higher than the room temperature, as shown in FIG. Heat the entire width. In this way, the temperature of the portion corresponding to the non-image area b of the fixing belt 38 is also maintained at the second target temperature. In the present configuration example, while detecting the temperature of the heating member 56B by the thermistor 36b, the heating member 56B supplies the heat amount for maintaining the second target temperature also to the non-image area b of the fixing belt 38.

  As a result, even the portion corresponding to the non-image area b of the fixing belt 38 is heated by supplying power to the heating member 56B, but the temperature of the portion corresponding to the non-image area b of the fixing belt 38 is changed to the first temperature. Power consumption can be reduced as compared with the case where the target temperature is set to one. That is, since the power supplied in the region P ′ is smaller than the power supplied in the region P shown in FIG. 6, energy saving is possible.

  FIG. 5A shows an image forming pattern in which an image area c and a non-image area d are mixed on the paper S in the paper width direction. FIG. 5B shows an image forming pattern in which an image area a and a mixed area h in which an image area c and a non-image area d are mixed in the sheet width direction are present on the sheet S in order from the leading end side in the sheet conveying direction. Is shown.

  Similarly, in this case, the control device 37 causes the temperature of the portion of the fixing belt 38 corresponding to the non-image area d to be lower than the temperature of the portion of the fixing belt 38 corresponding to the image area a and the image area c. The heating members 56A and 56B are controlled. That is, the power corresponding to the image region a and the image region c is supplied with electric power to obtain the fixing temperature to the heating member 56A, and the portion corresponding to the non-image region d is not supplied with electric power to the heating member 56A. Is supplied with electric power that provides a temperature lower than the fixing temperature.

  When the portion corresponding to the image area a of the fixing belt 38 is heated by the heating member 56A, all the heaters 55Aa, 55Ab, 55Ac, 55Ad, 55Ae, and 55Af included in the heating member 56A shown in FIG. , 55Ag. On the other hand, when the portion corresponding to the image region c of the fixing belt 38 is heated by the heating member 56A, power is supplied to the heaters 55Aa, 55Ab, 55Ac, and 55Ad included in the heating region e shown in FIG. . And electric power is not supplied to heater 55Ae, 55Af, and 55Ag contained in the heating area | region f.

  Further, in this configuration example, when power is supplied to the heating member 56A, as shown by the hatched portions in FIGS. 4 and 5, the image area is a portion before entering the fixing nip portion SN in the sheet conveyance direction. Electric power is supplied from the power source 39 so as to preheat the preheating region g. This preheating region g is a region that is necessary because the heating length in the circumferential direction of the heating member 56A and the heating member 56A itself also require a temperature raising time. The preheating region g is desirably as small as possible from the viewpoint of energy saving.

  As described above, the heat amount supply source necessary for maintaining the temperature of the non-image area, the heat amount supply source necessary for maintaining the temperature of the image area, and power control are divided. As a result, the heat capacity of the heating source necessary for maintaining the temperature of the image area can be reduced, the heating time of the heating member 56A itself is shortened, and as a result, the heating temperature of the fixing belt 38 is shortened, and preheating is performed. The region g can be reduced.

  Further, since the temperature raising time of the fixing belt 38 is shortened, the set temperature (second target temperature) of the non-image area can be set low.

  When the paper S having a small paper width is continuously passed, the end of the fixing belt 38 in the paper width direction may rise excessively. In this case, for example, the energization amount to the heaters 55Aa, 55Ab, 55Af, 55Ag and the heaters 55Ba, 55Bc in the heat generation regions at both ends of the heating member 56A and the heating member 56B in the paper width direction is reduced. In this way, by controlling the temperature at both ends of the fixing belt 38 in the sheet width direction, it is possible to suppress an excessive increase in temperature at the ends of the fixing belt 38 in the sheet width direction.

  Since the heater 55B of the heating member 56B is not controlled to heat the image area, if the problem of the temperature rise at both ends in the sheet width direction of the fixing belt 38 as described above occurs, the problem is not generated. What is necessary is just to make it the division | segmentation number of the heating area | region (heater 55B) which can be suppressed. That is, the number of divisions of the heating area (heater 55B) in the paper width direction does not have to be the same as that of the heating member 56A, and the number of divisions of the heating member 56B may be smaller than that of the heating member 56A.

[Configuration example 2]
In this configuration example, as shown in FIG. 7, the heating member 56 </ b> A divided into seven in the paper width direction and the heating member 56 </ b> B not divided in the paper width direction are arranged along the rotation direction of the fixing belt 38. Has been placed.

  When the paper S having a small paper width is continuously passed, there is no image information at the end in the paper width direction outside the paper passing area, and thus there is no control by the heating member 56A. Therefore, if the temperature rise at the end is not a problem as compared with a fixing device other than the partial heating method based on image information, the heating member 56B is moved in the paper width direction in the partial heating method fixing device 12 based on the image information. It is not necessary to divide. Since the heating member 56B is not divided, wiring from the power source 39 to the heating member 56B can be reduced as compared with the case where the heating member 56B is divided, and space saving and cost reduction can be achieved.

[Configuration example 3]
In this configuration example, as illustrated in FIG. 8, the heating member 56 </ b> A and the heating member 56 </ b> B are attached to the stay-like member 57, and are aligned along the fixing belt rotation direction at positions where they contact the outer peripheral surface of the fixing belt 38. Is arranged in. In addition, it is desirable to coat the surface of the heating members 56A and 56B on the side in contact with the outer peripheral surface of the fixing belt 38 to prevent toner adhesion.

  By providing the heating members 56A and 56B in contact with the outer peripheral surface of the fixing belt 38, the temperature rise of the outer peripheral surface of the fixing belt targeting the image area is accelerated. Therefore, the configuration is suitable from the viewpoint of energy saving, and is also suitable for a high-speed machine having a large number of printed sheets per unit time. Of course, it goes without saying that the fixing device 12 of this configuration example may be used for a low-speed machine.

[Configuration Example 4]
In this configuration example, the heating member 56B shown in FIG. 9 serves as a heat source that heats the entire sheet width of the fixing belt 38 to the temperature of the non-image area (second target temperature). The heating member 56A serves as a heat source that heats each heating area independently to the fixing belt 38 to the fixing temperature in accordance with position information where an unfixed image is formed on the paper S. is there. The heating member 56A is provided in contact with the outer peripheral surface of the fixing belt 38, and the heating member 56B is provided in contact with the inner surface of the fixing belt 38.

  By reducing the contact width in the fixing belt rotation direction between the heating members 56A and 56B and the fixing belt 38, it is easy to obtain a good contact pressure between the heating members 56A and 56B and the fixing belt 38, and the temperature of the fixing belt 38 is stabilized. Control becomes possible. Further, since the image area is heated by the heating member 56A from the outer peripheral surface side of the fixing belt 38, the temperature rise of the image area is quick.

[Configuration Example 5]
In this configuration example, the heating member 56B shown in FIG. 10 serves as a heat source that heats the entire sheet width of the fixing belt 38 to the temperature of the non-image area (second target temperature). The heating member 56A serves as a heat source that heats the fixing belt 38 to the fixing temperature independently in each heating region in accordance with position information on which an unfixed image is formed on the paper S. The heating member 56A is provided in contact with the outer peripheral surface of the fixing belt 38, the heating member 56B is provided in contact with the inner surface of the fixing belt 38, and the heating member 56A and the heating member 56B are sandwiched between the fixing belt 38. They are placed facing each other.

  In this configuration, the heating member 56A and the heating member 56B function as backup members for contact with the fixing belt 38. Therefore, a separate backup member is provided for each of the heating member 56A and the heating member 56B, the amount of heat that escapes from the fixing belt 38 to the backup member can be reduced, and energy saving can be achieved.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
Pressurization that forms a nip portion such as a fixing nip portion SN between a fixing member such as an endless belt-like fixing belt 38 provided rotatably and the fixing member provided in pressure contact with the fixing member. A pressure member such as a roller 30; and a heating unit that is provided in contact with the fixing member and heats the fixing member. The recording material such as the sheet S is passed through the nip portion, and is heated on the recording material by heat and pressure. In a fixing device such as the fixing device 12 for fixing the toner image on the recording material, a plurality of heating means having a heat source such as a heater 55 occupying the entire image forming region in the paper width direction perpendicular to the recording material conveyance direction of the recording material is provided. The heating member 56A for heating the portion corresponding to the image area of the fixing member to the fixing temperature is changed in accordance with the image area where the toner image on the recording material is formed. With the image area heating unit, and the entire heating means such as heating member 56B to heat the image forming area entire area of the fixing member at a temperature lower than the fixing temperature. According to this, as described in the above embodiment, it is possible to speed up the start up to the fixing temperature of the portion corresponding to the image area of the fixing member while saving energy.
(Aspect B)
In (Aspect A), in the heating means, the heat source is divided into a plurality of parts in the recording material width direction, and the division width of the heat source in the recording material width direction is different for each heating means. According to this, as described in the above embodiment, the number of wirings can be reduced, and space saving and cost reduction can be achieved.
(Aspect C)
In (Aspect A), in the image area heating means, the heat source is divided into a plurality of parts in the recording material width direction, and at least one of the whole area heating means is divided in the recording material width direction. . According to this, as described in the above embodiment, the number of wirings can be reduced, and space saving and cost reduction can be achieved.
(Aspect D)
In (Aspect A), (Aspect B) or (Aspect C), the heating means is provided in contact with the outer peripheral surface of the fixing member. According to this, as described in the above embodiment, the temperature rise of the outer peripheral surface of the fixing member aimed at the image area can be accelerated.
(Aspect E)
In (Aspect A), (Aspect B) or (Aspect C), the heating means is provided in contact with the inner peripheral surface of the fixing member. According to this, as described in the above embodiment, it is possible to prevent the outer peripheral surface of the fixing member in contact with the toner image on the recording material from being scratched by the heating means, thereby extending the life of the fixing member. Can do.
(Aspect F)
In (Aspect A), (Aspect B) or (Aspect C), at least one of the heating means is provided in contact with the outer peripheral surface of the fixing member, and at least one of the heating means is provided on the inner periphery of the fixing belt. Provided in contact with the surface. According to this, as described in the above embodiment, it is easy to obtain a good contact pressure between the heating means and the fixing member, and stable temperature control of the fixing member is possible.
(Aspect G)
In (Aspect F), the image area heating means is provided in contact with the outer peripheral surface of the fixing member, the entire area heating means is provided in contact with the inner peripheral surface of the fixing member, and the recording material width of the heat source is provided. The number of divisions in the direction is larger in the image area heating means than in the whole area heating means. According to this, as described in the above embodiment, the temperature rise of the outer peripheral surface of the fixing member aimed at the image area can be accelerated.
(Aspect H)
In (Aspect F) or (Aspect G), the heating means provided in contact with the outer peripheral surface of the fixing member and the heating means provided in contact with the inner peripheral surface of the fixing member sandwich the fixing member. Were placed facing each other. According to this, as described in the above embodiment, the image area heating unit and the entire area heating unit function as a backup member for contacting the fixing member. Therefore, a backup member is separately provided for each of the image region heating unit and the entire region heating unit, and the amount of heat that escapes from the fixing member to the backup member can be reduced, and energy saving can be achieved accordingly.
(Aspect I)
An image carrier such as a photosensitive drum 8; a toner image forming unit comprising a charging roller 18, a developing device 22 and an exposure unit 26 for forming a toner image on the image carrier; and the toner image on the image carrier. In the image forming apparatus, the image forming apparatus includes a transfer unit such as a transfer device 10 that transfers the toner image from the recording medium to a recording medium, and a fixing unit such as a fixing device 12 that fixes the toner image transferred onto the recording medium to the recording medium. As the means, the fixing device of (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G) or (Aspect H) is used. According to this, as described in the above embodiment, while saving energy, the portion corresponding to the image area of the fixing member is quickly raised to the fixing temperature to prevent the occurrence of fixing failure, and good image formation is achieved. It can be carried out.

DESCRIPTION OF SYMBOLS 4 Paper feeder 6 Registration roller pair 8 Photosensitive drum 10 Transfer device 12 Fixing device 14 Paper feed tray 16 Paper feed roller 18 Charging roller 20 Mirror 22 Developing device 22a Developing roller 24 Cleaning device 24a Cleaning blade 26 Exposure unit 30 Pressure roller 30a Metal core 30b Elastic layer 34 Thermistor 36a Thermistor 36b Thermistor 37 Controller 38 Fixing belt 38a Base body 38b Elastic layer 38c Release layer 39 Power supply 40 Elastic roller 40a Core metal 40b Elastic layer 55 Heater 56A Heating member 57B Heating member 57B Heating member 56B Member 60 Nip forming member 61 Belt support member

JP-A-6-138793

Claims (9)

An endless belt-shaped fixing member provided rotatably;
A pressure member that is rotatably provided and presses against the fixing member to form a nip portion with the fixing member;
Heating means provided in contact with the fixing member and heating the fixing member;
In the fixing device for passing the recording material through the nip portion and fixing the toner image on the recording material to the recording material by heat and pressure,
A plurality of heating means having a heat source occupying the entire image forming region in the paper width direction perpendicular to the recording material conveyance direction of the recording material;
An image area heating means for changing a heating area by the heat source in accordance with an image area on the recording material on which the toner image is formed, and heating a portion corresponding to the image area of the fixing member to a fixing temperature; And a whole-area heating unit that heats the entire image forming area of the fixing member at a temperature lower than the temperature. The fixing device according to claim 1.
The heating means is divided into a plurality of the heat sources in the recording material width direction,
The fixing device according to claim 1, wherein a divided width of the heat source in the recording material width direction is different for each heating unit. The fixing device according to claim 1.
In the image area heating means, the heat source is divided into a plurality in the recording material width direction,
At least one of the whole area heating means is characterized in that the heat source is not divided in the recording material width direction. The fixing device according to claim 1, 2 or 3.
A fixing device, wherein the heating means is provided in contact with the outer peripheral surface of the fixing member. The fixing device according to claim 1, 2 or 3.
A fixing device, wherein the heating means is provided in contact with an inner peripheral surface of the fixing member. The fixing device according to claim 1, 2 or 3.
At least one of the heating means is provided in contact with an outer peripheral surface of the fixing member, and at least one of the heating means is provided in contact with an inner peripheral surface of the fixing belt. The fixing device according to claim 6.
The image area heating means is provided in contact with the outer peripheral surface of the fixing member, and the entire area heating means is provided in contact with the inner peripheral surface of the fixing member;
The fixing device according to claim 1, wherein the number of divisions of the heat source in the recording material width direction is larger in the image area heating unit than in the whole area heating unit. The fixing device according to claim 6 or 7, wherein
The heating means provided in contact with the outer peripheral surface of the fixing member and the heating means provided in contact with the inner peripheral surface of the fixing member are arranged to face each other with the fixing member interposed therebetween. Fixing device. An image carrier;
Toner image forming means for forming a toner image on the image carrier;
Transfer means for transferring the toner image from the image carrier onto a recording medium;
An image forming apparatus comprising: a fixing unit that fixes the toner image transferred onto the recording medium to the recording medium;
An image forming apparatus using the fixing device according to claim 1, 2, 3, 4, 5, 6, 7, or 8 as the fixing unit.

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