JP2014157175A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a temperature of fixing members to a low temperature even in a place where image areas have a small interval, so as to improve energy saving characteristics.SOLUTION: A fixing device 12 includes fixing members 28 and 38 that are rotated while being brought into contact with an unfixed image, a pressure member 30 that forms a fixing nip part with the fixing member, heating means 56 for heating the fixing member with power from a power source 40 and having a plurality of heating areas divided in a direction orthogonal to a recording material conveyance direction, and external heating control means 42 for controlling the heating means; and passes a recording material carrying an unfixed image through the fixing nip part SN to perform fixing. The external heating control means has a heating mode of maintaining a temperature of a portion of the fixing member corresponding to a non-image area on the recording material at a temperature lower than that of a portion on the fixing member corresponding to an image area, while controlling a linear velocity of the fixing member to be slower than a normal process linear velocity, and selectively controls the respective heating areas in the heating mode on the basis of image information on the recording material.

Description

  The present invention relates to a thermal fixing device in an electrophotographic image forming apparatus, and an image forming apparatus such as a copying machine, a printer, and a facsimile equipped with the fixing device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed on an image carrier based on image information, the toner image is transferred onto a recording material such as paper or an OHP sheet, and the toner image is carried. The recorded material is passed through a fixing device, and the toner image is fixed on the recording material by heat and pressure.

  A heat roller type fixing device forms a nip portion with a fixing roller heated by a heating source such as a halogen heater or an induction heating coil and a pressure roller, and passes a recording material carrying an image through the nip portion, The toner is melted and fixed by heat and pressure. 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, there is a problem that a large amount of energy is consumed because it is necessary for the standby heat to maintain the fixing roller at a certain temperature even when not in use.

  Belt and film systems are frequently used as energy-saving fixing devices. A system that heats the heat insulation roller from the outside and a technology that selectively heats only the image area based on image information are proposed. ing.

There is a film method as an energy-saving fixing method.
For example, as described in Patent Document 1, the recording material is sandwiched so that the film and the recording material are in close contact with a plate-like heating body and a pressure roller that are in contact with the thin cylindrical heat-resistant film, and heat energy is applied to the recording material. It is a configuration to give. Since the film is as thin as about 100 μm, it is only necessary to raise the temperature of the plate-like heating body having a small heat capacity for the start-up time. For this reason, rise time can be shortened and preheating electric power can be reduced.

  Furthermore, energy saving is achieved by changing the control temperature and heating area of the heating body in accordance with the image formed on the recording material, and reducing the energy supply to the non-image area (the area where no image exists in the image forming area). The structure which enables is disclosed.

  Patent Document 2 discloses a configuration in which the temperature of each element of the heating element of the thermal heater is measured to supply appropriate heat so that the influence of the ambient temperature is taken into consideration and heat is applied only to the toner portion on the paper surface. Has been.

  Patent Document 3 employs a fixing method in which a roller is heated from the outside. By heating from the outside, the toner can be melted by the heat stored in the vicinity of the surface layer of the fixing roller. Therefore, there are advantages in that the rise time is short and energy loss is small as compared with the internal heating method in which the entire fixing roller is heated. Similar to Patent Documents 1 and 2, a configuration is disclosed in which only the image area is selectively heated and the second set temperature is lower than the fixing set temperature.

  Conventionally, the maximum energy supply amount is set to the fixing device so that sufficient fixing can be performed even when an image is formed on the entire surface of the recording material, and a belt, film, or the like so as not to exceed the rated power of the device. The rated power of a fixing member such as a roller is set. This also applies to the configurations in Patent Documents 1, 2, and 3 that selectively heat the image area.

  Now, one method for improving energy saving in a configuration in which the image area is selectively heated is to make the temperature of the fixing member corresponding to the non-image area as low as possible. In Patent Document 3, the fixing member temperature corresponding to the non-image area is set to a second set temperature lower than the first set temperature for melting the toner in the image area. However, in order to improve energy saving In this case, the second set temperature may be set to a lower temperature.

  When a certain part of the fixing member comes into contact with the non-image area of the first recording material and makes one rotation and then comes into contact with the image area of the next recording material, the part is moved from the second set temperature to the first temperature. Needs to rise rapidly. At this time, the second set temperature is determined by how quickly the temperature of the fixing member can be raised, and thus energy saving is determined.

  However, at locations where the interval between image areas in the paper conveyance direction is narrow, it is necessary to keep the fixing member temperature as the second set temperature, but it is necessary to continue to maintain the first set temperature. There was a problem that it was difficult to obtain.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the fixing member temperature to a low temperature even at a position where the interval between image areas is narrow, and to improve energy saving.

  In order to solve this problem, the present invention provides a fixing member that rotates in contact with an unfixed image, a pressure member that forms a fixing nip portion between the fixing member, and the fixing member using electric power from a power source. A heating unit having a plurality of heating regions divided in a direction perpendicular to the recording material conveyance direction and an external heating control unit for controlling the heating unit, and carrying an unfixed image in the fixing nip portion. The external heating control means controls the fixing member at a linear speed slower than a normal process linear speed, and corresponds to a non-image area on the recording material. A heating mode for maintaining the fixing member portion at a temperature lower than the fixing member portion corresponding to the image region, and selectively controlling each heating region by the heating mode based on image information on the recording material; A fixing device characterized by Suggest.

  According to the present invention, it is possible to reduce the heating temperature of the heating unit even in a non-image region with a shorter interval and / or further reduce the heating temperature of the heating unit in a non-image region other than the non-image region with a shorter interval. Therefore, it is possible to reduce the heating power and save energy compared to the prior art.

1 is a schematic diagram of a cross section of an image forming apparatus. FIG. 2 is a schematic view of a cross section of a fixing device. 1 is a schematic perspective view of a fixing device. It is a figure which shows the image area | region and non-image area | region formed on the paper. It is a figure which shows the image area | region and non-image area | region formed on the paper. It is a schematic diagram of a cross section of another fixing device. It is a schematic diagram of the heater divided | segmented into ten pieces. It is a schematic diagram of a cross section of another fixing device. It is a schematic diagram of a cross section of another fixing device. It is a schematic diagram of an external heating type fixing device. It is a figure which shows the image area | region and non-image area | region formed on the paper. It is a figure which shows the relationship between the target temperature of a fixing member, and a position. It is a figure which shows 1st Embodiment for improving energy saving property. It is a figure which shows 2nd Embodiment for improving energy saving property. It is a figure which shows 3rd Embodiment for improving energy saving property. It is a figure which shows 4th Embodiment for improving energy saving property. FIG. 6 is an enlarged view showing a change in the surface temperature of the fixing member in a preheating region d.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of the image forming apparatus. As shown in the drawing, a printer 2 as an example of an image forming apparatus according to the present embodiment 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. Have.

  The paper feeding means 4 feeds the paper P as a recording material stored in a stacked state and the paper P 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 P delivered by the paper supply roller 16 is temporarily stopped by the registration roller pair 6 to correct the posture deviation. Thereafter, the sheet P is synchronized with the rotation of the photosensitive drum 8, that is, at the timing when the leading end of the toner image formed on the photosensitive drum 8 and the predetermined position of the leading end of the sheet P in the transport direction coincide with each other. It is sent to the transfer site N by the registration roller pair 6.

  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, the exposure unit 26 on the photosensitive drum 8 is irradiated with the exposure light Lb via the mirror 20 and scanned.

  The image forming operation in the printer 2 is performed in the same manner as before. 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. An electrostatic latent image corresponding to 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 make the electrostatic latent image visible and a toner image is formed. The toner image formed on the photosensitive drum 8 is transferred onto the paper P that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer means 10. The paper P 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).

  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 is scraped off by the cleaning blade 24 a while passing through the cleaning means 24. To be 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.

  As shown in FIGS. 2 and 3, the fixing device 12 as the first embodiment is an external heating method. The fixing device 12 includes a fixing roller 28 as a fixing member that rotates in contact with an unfixed image, a pressure roller 30 as a pressure member that forms a fixing nip portion SN with the fixing roller 28, and a commercial power source. And a thermal heater 56 as a heating means for heating the fixing roller with the electric power. The thermal heater 56 and the power source 40 constitute an external heating means.

  The thermal heater 56 has a plurality (seven in this embodiment) of heaters 56a, 56b, 56c, 56d, 56e, 56f, and 56g arranged at equal intervals in the width direction of the paper P. Each heater 56a, 56b, 56c, 56d, 56e, 56f, 56g corresponds to each heating region and can be heated independently.

  Power is supplied to the thermistor 34 as temperature detecting means for detecting the surface temperature downstream of the fixing nip SN of the fixing roller 28 and upstream of the heater 56, the thermistor 36 as temperature detecting means for detecting the temperature of the heater 56, and the heater 56. Power supply 40 and external heating control means 42 for controlling the power supply 40 based on the detection information of the thermistors 34 and 36 are provided.

  Here, the external heating control means 42 means a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

  The fixing roller 28 has an aluminum cored bar 28a having an outer diameter of 50 mm and a thickness of 3 mm, and a heat insulating layer 28b coated on the surface of the cored bar 28a. The heat insulating layer 28b is made of silicon rubber and has a thickness of 4 mm. The heat insulating layer 28b may be formed of foamed silicon rubber with less heat diffusion in order to further enhance its heat insulating function.

  On the heat insulating layer 28b of the fixing roller 28, a good heat conductive layer 28c made of nickel is formed. However, the good heat conductive layer 28c is not limited to nickel, and may be an iron-based alloy such as stainless steel, a metal-based material such as aluminum or copper, a graphite sheet, or the like as long as the thermal conductivity is at least higher than that of the heat insulating layer 28b.

  By forming the good heat conductive layer 28 c on the fixing roller 28, local temperature unevenness of the surface temperature of the fixing roller 28 due to uneven heat generation of the thermal heater 56 is reduced. Even in areas where heat is not generated between the heaters 56a, 56b, 56c, 56d, 56e, 56f, and 56g, heat is quickly transmitted, thereby reducing unevenness in image fixing.

  In addition, since the temperature of the region slightly larger than the region heated by the thermal heater 56 is raised by the action of the good heat conductive layer 28c, there is an advantage that a slight deviation from the image can be compensated. In other words, there is an advantage that the degree of freedom in design is large in setting the size and interval of each of the heaters 56a, 56b, 56c, 56d, 56e, 56f, and 56g constituting the thermal heater 56.

  In addition, in order to improve the durability of the fixing roller 28 and ensure the releasability, a release layer having a thickness of 20 to 80 μm may be formed on the surface of the heat insulating layer 28b with a fluorine-based resin such as PFA or PTFE. .

  The pressure roller 30 has an iron cored bar 30a having an outer diameter of 50 mm and a thickness of 4 mm, and an elastic layer 30b coated on the surface of the cored bar 30a. The elastic layer 30b is made of silicon rubber and has a thickness of 5 mm. It is desirable to form a fluororesin layer having a thickness of about 50 μm on the surface of the elastic layer 30b in order to improve the releasability.

  The pressure roller 30 is pressed against the fixing roller 28 by an urging means (not shown). The heater 56 is pressed against the surface of the fixing roller 28 by an urging means (not shown).

  As described below, energy saving can be realized by controlling the heaters 56a, 56b, 56c, 56d, 56e, 56f, and 56g in accordance with the image information.

  When the heating efficiency of the thermal heater 56 is low and it is difficult to raise the surface temperature of the fixing roller 28 to a predetermined fixing temperature, the halogen heater 58 inside the fixing roller 28 is heated to a temperature slightly lower than the fixing temperature. In addition, energy consumption can be reduced by raising the temperature of the part corresponding to the image area by the thermal heater 56.

  When an image is formed on the entire image forming area on the paper P, the entire fixing roller 28 is heated, so that heating control based on image information is not necessary. In such a case, only the halogen heater 58 is used. The temperature may be raised to the fixing temperature. In addition, the startup time may be shortened by energizing both the halogen heater 58 and the thermal heater 56 simultaneously only during startup.

Next, heating control will be described.
The external heating control means 42 changes the heating rate of the thermal heater 56 based on image information for forming an image on the paper P.

  First, FIG. 4 is a diagram showing an image area and a non-image area formed on the paper P. FIG. 4A shows an image formation pattern in which an image area a, a non-image area b, and an image area a ′ are present in order from the leading end side in the conveyance direction of the paper P. The image area a and the image area a ′ where the toner to be fixed exists needs to be fixed, but the non-image area b where no toner exists does not need to be fixed.

  FIG. 4B shows an image forming pattern in which an image area a and a non-image area b exist in order from the leading end side in the conveyance direction of the paper P. The image area a where the toner to be fixed exists needs fixing, but the non-image area b where no toner exists does not need fixing.

  FIG. 5 is a diagram showing an image area and a non-image area formed on the paper P. FIG. 5A shows an image forming pattern in which an image region c and a non-image region d exist in a direction orthogonal to the conveyance direction of the paper P (longitudinal direction of the fixing roller). The image area c where the toner to be fixed exists needs fixing, but the non-image area d where no toner exists does not need fixing.

  FIG. 5B shows an image forming pattern in which an image area g in the conveyance direction of the paper P, an image area surrounded by h and e, and a non-image area surrounded by h and f exist. The image areas e and f where the toner to be fixed exists needs fixing, but the non-image area h where no toner exists does not need fixing.

  In FIG. 4A, when image information of the above pattern is input to the external heating control means 42 from an image processing device (not shown), the temperature of the part of the fixing roller 28 corresponding to the non-image area b is changed to the image area a, The external heating control means 42 controls the power supply 40 and the heater 56 so as to be lower than the temperature of the fixing roller 28 corresponding to a ′.

  Here, the portion of the fixing roller 28 corresponding to the image region or the non-image region means the portion of the fixing roller 28 that is in close contact with the image region or the non-image region. In other words, power is supplied to the entire area of the heaters 56a to 56g so that the roller portion corresponding to the image area a distributed over the entire sheet width can obtain a predetermined fixing temperature, while the roller corresponding to the non-image area b. The power supply is reduced at the site. Then, power is again supplied to the heaters 56a to 56g so that the roller portion corresponding to the image area a 'at the rear end of the paper reaches the fixing temperature.

  Similarly in FIG. 4B, power is supplied to the entire area of the heaters 56a to 56g so that the roller portion corresponding to the image region a can obtain a predetermined fixing temperature, while the roller corresponding to the non-image region b. The power supply is reduced at the site.

  In FIG. 5A, electric power is supplied to the heaters 56a to 56g so that the roller portion corresponding to the image region c distributed over half the paper width can obtain a predetermined fixing temperature. Specifically, the external heating control means 42 is arranged so that the temperature of the part of the fixing roller 28 corresponding to the non-image area d is lower than the temperature of the part of the fixing roller 28 corresponding to the image area c. The supply power of 56e-g is made smaller than the supply power of heaters 56a-d.

  In FIG. 5B, power is supplied to the entire area of the heaters 56a to 56d so that the roller portion corresponding to the image region g distributed substantially over the entire sheet width can obtain a predetermined fixing temperature. After that, for example, the power supplied to the heaters 56a to 56d is supplied to the heaters 56e to 56g so that the roller portion corresponding to the image region surrounded by h and e distributed substantially over half the sheet width can obtain a predetermined fixing temperature. Make it larger than the power supply.

  As the heating control, the power supply may be completely stopped at a portion corresponding to the non-image area surrounded by the non-image areas b, d, and h and f. However, if the temperature is too low, the next image area (see FIG. In 4 (a), the rising responsiveness to the fixing temperature in the image area a ′) is deteriorated. Therefore, it is desirable to keep the temperature of the fixing roller 28 at a predetermined value or higher by blinking the heater or supplying low power to the heater.

  As described above, the heater is also supplied to the roller portion corresponding to the non-image area surrounded by the non-image areas b, d, and h and f, but the power supply is reduced, so that energy saving is possible.

  In this embodiment, the heater 56 is brought into contact with the surface of the fixing roller 28 for heating, but the external heating control means 42 may be constituted by a coil and an inverter, and may be a non-contact heating method by the IH method. The exciting coil is obtained by winding a litz wire obtained by twisting about 50 to 500 conductor wires having a diameter of about 0.05 to 0.2 mm with an insulating coating, for example, 5 to 15 times. Also in this method, the temperature of the fixing roller 28 can be controlled based on the image information, so that energy saving is realized as described above.

Next, the fixing device 12 as the second embodiment will be described with reference to FIGS. 6 and 7.
In the fixing device 12 in the present embodiment, the heater 56 is configured by a thermal heater, a ceramic heater, or the like in which a heating resistor is mounted on a plate-like substrate. The heater 56 is disposed inside the belt (film), and heats the belt (film) to increase the temperature of the belt (film), thereby heating and fixing the unfixed image conveyed to the fixing nip portion SN.

  The thermal heater 56 is disposed upstream of the fixing nip SN. This is because it takes some time for the heat from the heater 56 arranged inside the belt (film) to reach the surface of the fixing roller 28. However, the heater 56 may be disposed in the vicinity of the fixing nip SN. The same applies to the external heating method.

  As shown in FIG. 7, the heater 56, which is a plate-like heating means, has a plurality of heating regions divided in the direction perpendicular to the paper transport direction, and each heater 56 can be controlled independently. In this embodiment, the heater is divided into ten pieces.

  The fixing belt 38 as a fixing member includes a SUS base 38a having an outer diameter of 50 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 silicon rubber and has a thickness of 100 μm.

  On the surface of the fixing belt 38, a release layer 38c having a thickness of 20 to 80 [mu] m is formed by a fluorine-based resin such as PFA or PTFE in order to enhance durability and secure release properties. The fixing belt base 38a may be made of polyimide.

  There is a support member 61 inside the fixing belt, and a pressing member 60 is installed at a position of the nip portion SN, and is connected to an external member (not shown) to support the fixing member.

FIG. 8 shows a fixing device 12 as the third embodiment. As shown in the figure, the heater 56 that is a plate-like heating means may be disposed at the fixing nip portion SN, whereby the heater 56 can also function as a pressing member. Other configurations are the same as those in FIG.
Although not shown, the belt or film configuration shown in FIG. 6 may be heated by an external heating method shown in FIG.

FIG. 9 is a cross-sectional view showing the fixing device 12 as the fourth embodiment.
As shown in the figure, the fixing device 12 includes a fixing belt 38 as a fixing rotating body, a pressure roller 30 as an opposing member (or an opposing rotating body) that contacts the fixing belt 38 and forms a nip portion SN, And a heater 56 as a heating member for heating the fixing belt 38. The heater 56 is in contact with the fixing belt 38 on a substantially flat surface.

  The fixing belt 38 is formed of an endless belt member (including a film) that is thin and flexible. Specifically, the fixing belt 38 includes an SUS base material 38a having an outer diameter of 40 mm and a thickness of 40 μm, an elastic layer 38b made of silicon rubber having a thickness of 100 μm covering the outer peripheral surface of the base material 38a, and an elastic member. It is composed of a release layer 38c made of a fluororesin such as PFA or PTFE having a thickness of 5 to 50 μm covering the outer peripheral surface of the layer 38b. The base material 38a of the fixing belt 38 may be made of a resin material such as polyimide.

  The pressure roller 30 includes an iron cored bar 30a having an outer diameter of 40 mm and a thickness of 2 mm, and an elastic layer 30b covering the outer peripheral surface of the cored bar 30a. The elastic layer 30b of the pressure roller 30 is made of silicon rubber and has a thickness of 5 mm. Moreover, in order to improve mold release properties, a mold release layer made of a fluorine-based resin having a thickness of about 40 μm may be disposed on the outer peripheral surface of the elastic layer 30b.

  A nip forming member 60 as a pressing member is disposed at a position facing the pressure roller 30 on the inner peripheral side of the fixing belt 38. The nip forming member 60 is supported by side plates (not shown) of the fixing device 12 at both ends thereof. When the pressure roller 30 is brought into pressure contact with the nip forming member 60 by pressure means such as a pressure lever, a nip portion SN having a predetermined width is formed at the pressure contact portion between the fixing belt 38 and the pressure roller 30. ing. Note that the fixing rotator and the opposing member may be simply brought into contact with each other without applying pressure.

  The pressure roller 30 is configured to be rotationally driven in the direction of arrow B in the figure by a drive source such as a motor (not shown). When the pressure roller 30 is rotationally driven, the driving force is transmitted to the fixing belt 38 at the nip portion SN, and the fixing belt 38 is driven to rotate in the direction of arrow C in the figure. A belt support member 61 that supports the fixing belt 38 is disposed on the inner peripheral side of the fixing belt 38.

  The heater 56 is composed of a planar or plate-like heating element such as a thermal heater or a ceramic heater. A stay 35 as a support member is disposed on the inner peripheral side of the fixing belt 38, and the stay 35 causes the heater 56 to be upstream of the nip portion SN in the sheet conveyance direction A, and the fixing belt 38. It is supported so as to face the inner peripheral surface. In addition, a power source 40 is connected to the heater 56, and power is supplied from the power source 40 to the heater 56. The output of the power source 40 is controlled by the external heating control means 42. The external heating control means 42 is composed of a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

  The fixing device 12 includes a first thermistor 36 as a heater temperature detecting unit that detects the temperature of the heater 56 and a second thermistor 34 as a belt temperature detecting unit that detects the temperature of the fixing belt 38. The first thermistor 36 is disposed so as to be in direct contact with the heater 56, and the second thermistor 34 is opposed to the outer peripheral surface of the fixing belt 38 on the upstream side in the belt rotation direction C with respect to the heater 56. It is arranged. The temperature information detected by each thermistor 36, 34 is input to the external heating control means 42, and the external heating control means 42 controls the output of the power source 40 based on this input information. It is configured.

  A pressing roller 39 as a pressing member that presses the fixing belt 38 is disposed at a position facing the heater 56 on the outer peripheral side of the fixing belt 38. The pressing belt 39 presses the fixing belt 38 toward the heater 56 from the outer peripheral side, so that the fixing belt 38 comes into contact with the heater 56. The pressure roller 39 has an outer diameter of 15 mm to 30 mm, an iron core metal 39a having an outer diameter of 8 mm, and an elastic layer made of silicon rubber having a thickness of 3.5 mm to 11 mm covering the outer peripheral surface of the core metal 39a. 39b. Further, in order to improve the mold release property, a mold release layer made of a fluororesin having a thickness of about 40 μm may be disposed on the outer peripheral surface of the elastic layer 39b. Here, the pressing roller 39 is pressed against the fixing belt 38 by a pressing unit (not shown). However, the pressing roller 39 may be simply brought into contact without being pressed by the pressing unit.

The basic operation of the fixing device will be described with reference to FIG.
When the power switch of the main body of the image forming apparatus is turned on, power is supplied from the power source 40 to the heater 56, and the pressure roller 30 starts to rotate in the direction of arrow B in the figure. As a result, the fixing belt 38 is driven to rotate in the direction of arrow C in the figure by the frictional force with the pressure roller 30.

  Thereafter, when the sheet P carrying the unfixed toner image G through the image forming process is conveyed to the nip portion SN between the fixing belt 38 and the pressure roller 30, the sheet P is heated and heated. The toner image G on the paper P is fixed. Then, after the sheet P is carried out from the nip portion SN, it is discharged out of the apparatus.

  As described above, each heating region of the heater 56 is heated independently. That is, each part of the fixing member 38 corresponding to the image area in the width direction of the paper P perpendicular to the conveyance direction of the paper P can be independently heated by each heating area of the heater.

Next, the control operation in the embodiment will be described.
When the image forming pattern shown in FIG. 5 is fixed using the heater 56 shown in FIG. 7, the part of the fixing member 38 corresponding to the image areas c and e among the plurality of heating areas of the heater 56 is the heater 56A. A fixing member corresponding to the non-image areas d and h is a heater 56B.

  When image information of the pattern shown in FIG. 5 is input to the external heating control unit 42 from an image processing apparatus (not shown), the external heating control unit 42 supplies power to obtain a fixing temperature to the heater 56A and supplies the heater 56B with power. Stop or reduce the power supply. The external heating control means 42 controls each heating of the heater so that the temperature of the part of the fixing member 38 corresponding to the non-image areas d and h is lower than the temperature of the part of the fixing member 38 corresponding to the image areas c and e. Control the area.

  The heating areas of the heaters 56 need not be arranged on a straight line, but may be arranged in a staggered manner so as to partially overlap in the width direction of the paper P. With such an arrangement, a shortage of heat that may occur in the gap between the heaters positioned linearly in the width direction of the paper P is compensated by the heaters displaced in the circumferential direction of the fixing members 28 and 38, and uneven heating temperature is generated. Less.

  When the size and image information of the paper P are set from the operation panel (not shown) of the printer 2, the external heating control means 42 corresponds to the portions of the fixing members 28 and 38 corresponding to the non-image areas based on the information. Stop or reduce the power supply to the heater.

  Thus, energy saving can be achieved by controlling the temperature of the part corresponding to the non-image region to be low based on the image information. Further, it is possible to prevent the durability of the fixing members 28 and 38 and the pressure roller 30 from being deteriorated due to an abnormally high temperature in the non-sheet passing region, which is a problem with this type of fixing device, and the thermal adverse effect on the peripheral members.

  In each of the embodiments described above, energy saving is achieved by reducing the input power to the non-image area. However, a high-speed machine or the like has a high process line speed and may not obtain sufficient power. In this case, the energy saving effect is lowered.

Here, the reason why the energy saving effect is lowered will be described with reference to FIGS.
FIG. 10 is a schematic diagram of an external heating type fixing device, where X is a fixing roller, Y is a pressure roller, and Z is a heater that is an external heating means. The fixing device 12 may be configured to heat the fixing belt 38 from the inside as shown in FIG.

  FIG. 11 shows an image formation pattern in which an image area a, a non-image area b or b ′, and an image area a ′ are present in order from the leading end side in the paper conveyance direction.

FIG. 12 is a diagram showing the relationship between the target temperature and position of the fixing roller at the normal process linear speed.
The horizontal axis represents the surface position of the fixing roller X, and the vertical axis represents the control target temperature at that position. The positions a, b, a ′ of the fixing roller X in FIG. 12A correspond to the image areas a, b, a ′ in FIG. 11A, respectively, and the position a of the fixing roller X in FIG. , B ′, a ′ correspond to the non-image areas a, b ′, a ′ of FIG.

  In FIG. 12A, a region P is a region for supplying power and is wider than the image region a. This is because the surface temperature of the fixing roller and the fixing belt (temperatures at positions a and a ′) corresponding to the image area a is set due to the heater width H and the response time until the heater is heated as shown in FIG. This is because a preliminary heating region d for preliminary heating is necessary to raise the temperature sufficiently. Here, P = a + d = a ′ + d is established. Although not shown in FIG. 11, the preheating area d is located in front of the image area a and in the non-image areas b and b ′ and in front of the image area a ′.

  When the non-image region b is sufficiently wide as shown in FIG. 11A, the non-image is maintained while maintaining the first target temperature for the image regions a and a ′ as shown in FIG. 12A. Due to the region b, it can be lowered to a second target temperature lower than the first target temperature and higher than room temperature. By controlling the surface temperature of the fixing member to a second target temperature lower than the first target temperature, power consumption can be suppressed. For example, the first target temperature is 120 ° C., and the second target temperature is 90 ° C.

  However, when the non-image area b ′ is not sufficiently wide as shown in FIG. 11B, the first target temperature or a little lower than this is also obtained in the non-image area b ′ as shown in FIG. Since it is necessary to maintain a low temperature, it is difficult to reduce power consumption in this region.

Next, a first embodiment for improving energy saving will be described with reference to FIG.
In the present embodiment, the external heating control means 42 selectively fixes each heating region of the heater divided into a plurality of parts while controlling the fixing members 28 and 38 to a first linear speed slower than the normal process linear speed. It has the 1st heating mode heated to the 1st target temperature which is temperature, or the 2nd target temperature below this. As a result, an energy saving effect can be obtained even when the image shown in FIG. 11B is fixed.

  FIG. 13 shows the surface temperature (target temperature) of the fixing members 28 and 38 at this time. When comparing FIGS. 12A and 12B with FIG. 13, the size of the preheating region d is different. In the case shown in FIG. 13 where the fixing members 28 and 38 are controlled at a first linear speed slower than the normal process linear speed, compared to the case shown in FIG. 12 where the fixing members 28 and 38 are controlled at a normal process linear speed. In addition, the preheating region d is small. FIG. 17 is an enlarged view showing a change in the surface temperature of the fixing member in the preheating region d. The temperature change of this embodiment is a line along points C, B, and A. This is because the size of the preheating region is substantially proportional to the linear velocity.

  That is, distance (position) = linear velocity × time. If the time is constant, the distance (position) decreases as the linear velocity decreases. For example, when the normal linear velocity is 200 mm / s, the size of the preheating region is approximately half the length by setting the first linear velocity to 100 mm / s. In other words, since the linear velocity is reduced, the distance required to increase the temperature to the first target temperature is also reduced. The conventional temperature change is a line along points C and A.

  As shown in FIG. 13, when the linear velocity is decreased, the preheating area d becomes smaller. Therefore, even when the size of the non-image area b ′ is smaller, the temperature can be lowered to the second target temperature. Can be lowered. Note that the external heating control means 42 may determine whether the print command is an urgent command, and may select a low speed if a low speed is acceptable.

  FIG. 14 shows a second embodiment for improving energy saving. This embodiment recognizes an image area and a non-image area, and determines a heating area and a non-heating area, and can be applied independently or in combination with other embodiments.

  As shown to Fig.14 (a), in this embodiment, the heater 56 is divided | segmented into six. First, the external heating control means 42 divides the image information on the paper into a predetermined size in the paper transport direction in a partial region (axial direction unit region) perpendicular to the paper transport direction. Next, the external heating control means 42 determines whether or not an unfixed image is formed for each divided area, and the divided area where the unfixed image is formed is a heated part, and the non-formed divided area is a non-heated part. to decide.

  The determination of the heating region / non-heating region is determined by the heating response time until the fixing members 28 and 38 make one rotation. In the case of belt fixing, the belt heat capacity, the heating time of the heating member, the supply power, the linear velocity, etc. Affected by.

  In FIG. 14B, the linear velocity is slower and can be applied particularly advantageously to the first heating mode. Since the linear velocity is low, the temperature of the fixing member can be raised in time, so the heating resolution is high. Therefore, as shown in the figure, the size of the divided area in the paper transport direction can be made smaller than that in the case of FIG. In FIG. 14 (a), there is only one divided area as the non-heated area B without an unfixed image, but in FIG. 14 (b) with high resolution, the number of divided areas as the non-heated areas D and F is increased to three. ing. Since the power supplied to the heater 56 is reduced or stopped in the non-heating region, the power reduction effect is increased. A, C, and E are heating regions.

  As described above, when the linear velocity is low and the heat responsiveness of the fixing members 28 and 38 is sufficiently high, the size of the divided region can be further reduced, and energy saving can be achieved. Instead, the resolution may be increased if the power supply can be increased and the heating response of the fixing member is high.

Next, a third embodiment for enhancing energy saving will be described based on FIG.
FIG. 15 shows the surface temperature of the fixing members 28 and 38. In the present embodiment, when fixing the image shown in FIG. 11B, the process linear velocity is made slower than the normal linear velocity as in the first embodiment, but the non-heating area other than the non-image region b ′ is not used. The fixing member temperature corresponding to the region (region other than region P) is set to a third target temperature lower than the second target temperature. Here, the external heating control means 42 selectively controls each heating region of the divided heaters at the fixing temperature while controlling the fixing members 28 and 38 to a first linear speed that is slower than the normal process linear speed. A second heating mode for heating to a first target temperature or a third target temperature lower than the second target temperature at the normal process linear velocity is provided.

  Comparing FIG. 12B and FIG. 15, the size of the region P for supplying power is the same. The size of the preheating region d in FIG. 15 is the same as that in FIG. 12B, but the first target temperature and non-image region for the image region is the case in FIG. The third target temperature difference for can be increased. This is because the temperature difference in the same preheating region is substantially proportional to the linear velocity. In FIG. 17, the temperature change of this embodiment is a line along points E, B, and A.

  As shown in FIG. 15, since the temperature of the fixing member rises in time when the linear velocity is slowed down, the temperature can be lowered to the third target temperature in the non-image region other than the non-image region b ′. Can be lowered.

Next, a fourth embodiment for enhancing energy saving will be described with reference to FIG.
FIG. 16 shows the surface temperature of the fixing members 28 and 38. In the present embodiment, when fixing the image shown in FIG. 11B, a second linear velocity that is slower than the first linear velocity in the first embodiment (FIG. 13) is set, and a non-image area is further set. The fixing member temperature corresponding to b ′ is set to a third target temperature lower than the second target temperature. Here, the external heating control means 42 selectively controls each heating region of the divided heaters at the fixing temperature while controlling the fixing members 28 and 38 to a second linear speed slower than the first linear speed. A third heating mode for heating to a first target temperature or a third target temperature lower than the second target temperature at the normal process linear velocity is provided.

  Comparing FIG. 13 and FIG. 16, the size of the region P for supplying power is the same. The size of the preheating region d in FIG. 16 is the same as that in FIG. 13, but the first target temperature for the image region and the third target temperature for the non-image region are the same in FIG. It can be seen that the difference between In FIG. 17, the temperature change of the present embodiment is a line along points D and A.

  As shown in FIG. 16, by further reducing the linear velocity, the temperature is decreased to the third target temperature in the non-image area and is also decreased to the third target temperature (area corresponding to the non-image area b ′). ) Can be increased, and the overall energy consumption can be further reduced.

  Although not shown, in the fifth embodiment, the first embodiment is performed when the interval between the image areas in the paper transport direction is equal to or greater than a predetermined distance based on image information input to the external heating control means 42 such as a CPU. The linear velocity reduction operation of the fixing members 28 and 38 in the fourth to fourth embodiments is not performed.

  That is, even if the user selects one of the heating modes and performs an energy saving operation in which the linear velocity is slow, the target temperature may not be lowered in the case of a solid image having almost no non-image area. In this case, the energy saving effect is limited, and the paper feeding speed is reduced, so that the productivity is lowered. Therefore, when the external heating control means 42 determines that the disadvantages generated are greater than the advantages obtained by the heating mode with reference to the image information, the external heating control means 42 performs an operation of maintaining productivity without shifting to these heating modes.

  That is, the external heating control unit 42 controls the fixing members 28 and 38 at a normal process linear speed when the interval between the image areas in the paper conveyance direction is equal to or larger than a predetermined distance, and the part of the fixing member corresponding to the image area. Is maintained at a first target temperature that is a fixing temperature, and a normal heating mode is maintained in which a portion of the fixing member corresponding to the non-image area is maintained at a second target temperature that is equal to or lower than the first target temperature. The external heating control means 42 selectively controls each heating area by this normal heating mode.

  In this manner, when power reduction cannot be expected even by shifting to each heating mode, productivity and user convenience can be ensured by suppressing switching of the heating mode.

  The present invention has been described above with reference to the illustrated examples. However, the components of the present invention are not limited to these, and various modifications can be made without departing from the scope of the technical idea of the present invention.

12 Fixing device 28 Fixing roller (fixing member)
30 Pressure roller (Pressure member)
38 Fixing belt (fixing member)
40 Power supply 42 External heating control means 56 Heater (heating means)
P paper (recording material)

JP-A-6-95540 JP 2005-181946 A JP 2001-343860 A

Claims (7)

A fixing member that rotates in contact with an unfixed image, a pressure member that forms a fixing nip portion with the fixing member, and the fixing member that is heated by power from a power source, in a direction perpendicular to the recording material conveyance direction A fixing device that includes a heating unit having a plurality of heating regions divided into a plurality of heating regions and an external heating control unit that controls the heating unit, and performs fixing through a recording material carrying an unfixed image in the fixing nip portion. And
The external heating control means controls the fixing member to a linear speed slower than a normal process linear speed, and the fixing member corresponding to the non-image area on the recording material corresponds to the image area. A fixing device having a heating mode for maintaining the temperature at a temperature lower than that of the region, and selectively controlling each heating region by the heating mode based on image information on the recording material.   The external heating control means controls the fixing member to a first linear velocity that is lower than a normal process linear velocity, and sets a portion of the fixing member corresponding to an image area on the recording material to a first fixing temperature. And a first heating mode for maintaining a portion of the fixing member corresponding to the non-image area at a second target temperature that is equal to or lower than the first target temperature, on the recording material The fixing device according to claim 1, wherein each heating region is selectively controlled by the first heating mode based on image information.   The external heating control means controls the fixing member to a first linear velocity that is lower than a normal process linear velocity, and sets a portion of the fixing member corresponding to an image area on the recording material to a first fixing temperature. A second heating mode in which the fixing member corresponding to the non-image area is maintained at a third target temperature lower than the second target temperature at a normal process linear speed; The fixing device according to claim 1, wherein each heating region is selectively controlled by the second heating mode based on image information on the recording material.   The external heating control means controls the fixing member to a second linear velocity slower than a first linear velocity slower than a normal process linear velocity, and a portion of the fixing member corresponding to an image area on the recording material Is maintained at the first target temperature that is the fixing temperature, and the third target temperature that is lower than the second target temperature at the normal process linear speed is maintained at the third target temperature corresponding to the non-image area. The fixing device according to claim 1, wherein each heating region is selectively controlled by the third heating mode based on image information on the recording material.   The external heating control unit divides the image information on the recording material into unit regions in the recording material conveyance direction, determines the unit region with the image information as a heating portion, and determines the unit region without the image information as the unit region. The fixing device according to claim 1, wherein the fixing device is determined as a non-heated portion.   The external heating control means refers to the image information on the recording material, and when the interval between the image areas in the recording material conveyance direction is a predetermined distance or more, while controlling the fixing member at a normal process linear speed, The portion of the fixing member corresponding to the image area on the recording material is maintained at a first target temperature that is a fixing temperature, and the portion of the fixing member corresponding to the non-image area is equal to or lower than the first target temperature. A normal heating mode for maintaining the second target temperature is provided, and each heating region is selectively controlled by the normal heating mode based on image information on the recording material. The fixing device according to claim 1.   An image forming apparatus comprising the fixing device according to claim 1.

Images