JP2014109600A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device which stabilizes fixing quality without increasing the size of the device and to provide an image forming apparatus using the same.SOLUTION: A fixing device comprises: heating means having a first heating part which is controlled according to the temperature of a fixing member and a second heating part which is divided into a plurality of regions in a longitudinal direction perpendicular to a conveyance direction of recording materials and is controlled according to position information of image regions regardless of the temperature of the fixing member; and heating control measures which controls the temperature of the fixing member by controlling each heating part independently according to position information of an unfixed image formed on a recording medium and controls the heating temperature of a non-image region where the unfixed image is not present to be lower than that of an image region where the unfixed image is present.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly, 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. About.

  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 recording material is passed through a fixing device, and the toner image is fixed on the recording material by heat and pressure. OHP is an abbreviation for Over Head Projector.

"Thermal roller system"
In a heat roller type fixing device, a fixing roller heated by a heating source such as a halogen heater or an induction heating coil and a pressure roller form a nip portion, and a recording material carrying an image is passed through the nip portion. The toner is melted and fixed by heat and pressure.
The fixing roller system is widely used from the viewpoint of 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 energy consumption is high due to standby heat that maintains the fixing roller at a certain temperature even when not in use.

  As a fixing device for realizing energy saving, a belt and a film system are often used, and a system for heating the heat insulating roller from the outside and a technique for selectively heating only an image area based on image information have been proposed. (For example, refer to Patent Documents 1 to 3.)

"Image area selective heating by film method"
There is a film system as an energy saving fixing configuration.
As described in Patent Document 1, for example, this film system is sandwiched between a plate-like heating body that comes into contact with a thin cylindrical heat-resistant film and a pressure roller so that the film and the recording material are brought into close contact with each other. In this configuration, energy is applied to the recording material. Since the film is as thin as about 100 μm, the start-up time can be substantially increased only by increasing the temperature of the plate-like heating body having a small heat capacity, so that the start-up time can be shortened and the preheating power can be reduced.
Further, a configuration is disclosed that enables energy saving 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.

  Japanese Patent Application Laid-Open No. 2004-228688 has a configuration in which the temperature of each element of the heating element of the thermal head is measured and supplied with 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. It is disclosed.

"Image area selective heating with external heating roller system"
The invention described in Patent Document 3 is a fixing configuration in which a roller is heated from the outside. This is because the toner is melted by the heat stored in the vicinity of the surface of the fixing roller by heating from the outside, so that the rise time is shorter and the energy loss is less than the internal heating method in which the entire fixing roller is heated. .
Patent Document 3 discloses a configuration in which only the image area is selectively heated, as in the inventions described in Patent Documents 1 and 2, and the second set temperature is lower than the fixing set temperature.

In a fixing device that selects and heats an image area, a thermal head or the like that rapidly increases in temperature as in the invention described in Patent Document 2 is used as a heat source that heats an image area.
While such a heat source is suitable for quickly heating the toner portion, there is a problem that the temperature rise is too rapid and it is difficult to stably control the target temperature, and the fixing quality is not stable due to the temperature variation.

As a countermeasure against the above-described problem, as in the invention described in Patent Document 3, it is an effective means to separate a heat source that heats stably and a heat source that heats aiming at an image portion.
However, if the heat source that heats the image area as in Patent Document 3 is on the image surface side, the toner fixing surface may be scratched due to contact with the heat source, or the apparatus may be enlarged because the heat source is outside. There was a problem such as doing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that stabilizes the fixing quality without increasing the size of the device, and an image forming apparatus using the fixing device.

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a fixing member that rotates in contact with an unfixed image, a pressure member that forms a nip portion between the fixing member, and the unfixed image. A fixing device comprising: a heating unit that heats the recording material when the carried recording material passes through the nip portion to fix the unfixed image; and a heating control unit that controls the heating unit, The heating unit is divided into a first heating unit controlled according to the temperature of the fixing member and a plurality of regions in a longitudinal direction orthogonal to the conveyance direction of the recording material, regardless of the temperature of the fixing member. A second heating unit that is controlled according to position information of the image area, and the heating control unit controls each heating unit according to the position information on which the unfixed image is formed on the recording material. Independently controlling the temperature of the fixing member, The heating temperature of the non-image area Chakugazo is not present, and to control lower than the image area in which the unfixed image is present.

  According to the present invention, fixing quality can be stabilized without increasing the size of the apparatus.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. FIG. 3 is a diagram illustrating an example of a fixing device according to an embodiment. It is an example of paper Pa having a non-image portion a and an image presence portion b. (A), (b) is a figure which shows the relationship between the image absence part a of the paper Pa, the image presence part b, and the temperature of a nip part. FIG. 6 is a diagram illustrating a state in which a toner image in which characters and photographs are mixed is formed on paper Pa. It is a figure which shows the relationship between the photo presence part of a paper Pa, a character presence part, a no-image part, and the temperature of a nip part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Embodiment 1>
Roller external heating configuration [Overall configuration of image forming apparatus]
FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment.
As shown in FIG. 1, a printer as an example of an image forming apparatus according to the present embodiment includes a paper feeding unit 4, a registration roller pair, a photosensitive drum 8 as an image carrier, a transfer unit 10, and a fixing device 12. Have.

The paper feeding means 4 feeds the paper P as a recording material stored in a stacked state, and the paper Pa stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16.
The paper Pa sent out by the paper feed roller 16 is temporarily stopped by the registration roller pair 6 to correct the posture deviation. When the posture deviation is corrected, the paper Pa is sent to the transfer portion N at a timing synchronized with the rotation of the photosensitive drum 8. That is, the paper Pa is sent to the transfer portion N by the registration roller pair 6 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 paper Pa in the transport direction coincide.

  Around the photosensitive drum 8, a charging roller 18 as a charging unit, a mirror 20 for an exposure unit (not shown), a developing unit 22 having a developing roller 22a, a transfer unit 10, and a cleaning blade 24a are provided in the direction of the arrow. A cleaning means 24 is arranged.

Between the charging roller 18 and the developing means 22, exposure light Lb is irradiated to the exposure unit 26 on the photosensitive drum 8 via the mirror 20 and scanned.
The image forming operation in the printer is performed in the same manner as a general image forming operation.

That is, when the photosensitive drum 8 rotates, the surface of the photosensitive drum 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated to the exposure unit 26 based on the image information and scanned to form an image to be created. A corresponding electrostatic latent image is formed.
The electrostatic latent image is moved to the developing unit 22 by the rotation of the photosensitive drum 8, and is supplied with toner by the developing unit 22 to be visualized to form a toner image.
The toner image formed on the photosensitive drum 8 is transferred onto the paper Pa that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer means 10.
The paper Pa carrying the toner image is conveyed toward the fixing device 12, fixed by the fixing device 12, discharged to a discharge tray (not shown), and stacked.

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.
After cleaning, the residual potential on the photoconductive drum 8 is removed by a neutralizing means (not shown) and prepared for the next image forming process.

[Fixing device]
An example of a fixing device according to an embodiment is shown in FIG.
The heating device of the fixing device shown in FIG. 2 includes a heating control unit 1, a heating control unit 2, a power source A, a power source B, a pressure roller 30, a heating source 31, a fixing belt 38 as a fixing member, and a plate-like heating unit 56. Have
The heating control unit 1 is a unit that controls the voltage of the power source A of the heating source 31 as the first heating unit based on a signal from the sensor 34.
The heating control means 2 is a means for controlling the voltage of the power source B of the plate-like heating means 56 as the second heating unit based on the image information.
The first heating unit and the second heating unit may heat the surface of the fixing member that does not contact the unfixed image.

The power source A and the power source B are, for example, commercial power sources of 100V50Hz, 100V60Hz, 200V50Hz, and 200V60Hz for domestic use, but are not limited to those for foreign countries. That is, a known voltage conversion circuit may be provided so as to be compatible with either 50 V or 60 Hz of 110 V, 115 V, 120 V, 127 V, 220 V, 230 V, and 240 V depending on the country or region.
The heating source 31 is controlled based on the temperature of a sensor 34 that measures the surface temperature of the fixing belt 38. A halogen lamp was used as the heating source 31.
The heat generated by the heating source 31 is absorbed and diffused by the belt support member 61 to apply heat to the base material 38a of the fixing belt 38 in a wide range.

  The heating control means 1 is a control device that performs PID (Proportional Integral Differential) control based on the temperature of the sensor 34, and is configured to control the fixing belt 38 at a stable temperature. However, the control target temperature of the heating control means 1 is controlled to be about 40 ° C. lower than the temperature at which the toner melts.

The heating control unit 2 controls each heating unit independently of the temperature of the fixing member in accordance with position information where an unfixed image is formed on the paper Pa, and controls the heating temperature of the non-image area to be lower than that of the image area. To do.
The heating control means 2 counts the number of dots representing pixels formed by irradiating the writing laser in each color of YMCK with respect to a certain area of the paper Pa, sums up the pixel count values of the four colors, and adds them to the paper Pa. The amount of toner is calculated as the weight per unit area. Y is yellow, M is magenta, C is cyan, and K is black.
The plate-like heating means 56 is a thermal head, a ceramic heater, or the like that is disposed in the longitudinal direction orthogonal to the conveyance direction of the paper Pa and has a resistance heating element formed on the plate-like substrate.
The plate-like heating means 56 is disposed inside the film and raises the temperature of the film or belt by about 40 ° C. with the heat to heat and fix the unfixed image conveyed to the nip portion SN.
Although only one plate-like heating means 56 is shown in the drawing, it has a region divided into a plurality of directions in a direction perpendicular to the paper conveyance direction, that is, a direction perpendicular to the drawings of this specification. The area can be independently controlled by heating.
The plate-like heating means 56 determines the heating amount and the heating timing from the image position information and the toner amount information at the image position.

The fixing belt 38 as a fixing member includes, for example, a base 38a made of SUS (stainless steel) 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. The fixing belt 38 rotates in contact with the unfixed image.
On the surface of the fixing belt 38, a release layer 38 c having a thickness of 5 to 50 μm is formed with a fluorine-based resin such as PFA or PTFE in order to enhance durability and secure release properties.
PFA is a perfluoroalkoxy fluororesin, and PTFE is polytetrafluoroethylene (also referred to as tetrafluorinated resin).

The substrate 38a of the fixing belt 38 may be polyimide.
A belt support member 61 is provided inside the fixing belt 38, and a pressing member and a pressure member 30 are installed at the nip portion SN, and connected to an external member (not shown) to support the fixing member.
As shown in FIG. 2, the plate-like heating means 56 may function as a pressing member and may be arranged at the nip portion SN.
As described above, each heating part of the heating member is independently heated, and the heating is controlled according to the image information as described above.

<Embodiment 2>
Embodiment 2 will be described.
FIG. 3 is an example of the paper Pa having the non-image portion a and the image presence b.
FIGS. 4A and 4B are diagrams showing the relationship among the non-image portion b, the image presence portion a, and the temperature of the nip portion of the paper Pa.

A case will be described in which an image presence portion b and an image absence portion a as shown in FIG. 3 enter a nip portion (not shown) in the direction of the arrow. The non-image portion a is a non-image region where no unfixed image exists, and the image-present portion b is a region including an image region where an unfixed image exists.
As shown in FIG. 4A, when the heater control is performed at the timing when the image present portion b reaches the nip portion, the actual temperature arrives with a delay corresponding to the passage through the fixing belt 38, and the image present portion b is reached. Deviation occurs between the temperature peak part.

  Therefore, as shown in FIG. 4B, the phase between the presence / absence of the image and the change in the nip temperature is adjusted by applying the image information earlier than the target position. In other words, the heating unit starts heating before the unfixed image passes through the nip portion. As a result, the deviation between the image present portion b and the temperature peak portion is eliminated, and the fixing quality can be stabilized without increasing the size of the apparatus.

<Embodiment 3>
A third embodiment will be described.
FIG. 5 is a diagram illustrating a state where a toner image in which characters and photographs are mixed is formed on the paper Pa. FIG. 6 is a diagram illustrating the relationship between the temperature of the photo-pasted portion, the text-present portion, the non-image portion, and the nip portion of the paper Pa.

  In the case of an image in which characters and photographs are mixed as shown in FIG. 5, in addition to the image position information, the position of the photograph is recognized using image type information, and as shown in FIG. Increase the voltage or heating body energization time to be higher than the part.

The heating means heats longer when the amount of toner as a weight per unit area of the unfixed image is large, and heats short when the amount of toner per unit area of the unfixed image is small.
Here, a large amount of toner and a small amount of toner mean a relative relationship between the amounts of toner. For example, for one color and two colors of toner, the heating time for two colors is longer than that for one color. Meaning.
The heating means controls the voltages of the power source A and the power source B so that the temperature of the unfixed image is higher than that of the character portion in the photograph portion. As a result, an image with a high glossiness of the photographic part can be obtained.

<Effect>
According to the present embodiment, a system having two heating bodies controlled by the temperature of the fixing member and a divided heating body that heats the image portion as a target is more stable than the case of only the divided heating body. Fixing quality can be obtained.

  According to the present embodiment, in addition to the above-described configuration, the two heating bodies are arranged in the fixing roller, so that the fixing roller can be prevented from being scratched on the image surface.

  According to the present embodiment, in addition to the above configuration, since it takes time until the heat of the partial heating body that heats the image portion as a target passes through the fixing roller and comes out to the image surface, a heating method is used in advance. Thereby, the heating delay of a partial heating body can be prevented.

  According to the present embodiment, in addition to the above-described configuration, a control method for increasing the amount of heat generated by the partially heated body in a portion where the toner is large and decreasing in a portion where the toner is small is shown. If the amount of toner is small, the amount of heating can be reduced and energy can be saved.

  According to the present embodiment, in addition to the above configuration, the temperature of the photograph part is set higher than that of the character part. Since the photograph part is required to have a higher gloss than the character part, the gloss can be increased by setting the character part to a higher temperature.

That is, according to this embodiment, it is possible to obtain a fixing device that saves energy and has a stable fixing quality.
According to the present embodiment, there is no flaw on the image surface of the fixing roller, and an energy-saving fixing device can be obtained.
According to this embodiment, it is possible to provide a fixing device that saves energy and has stable fixing quality.
According to this embodiment, when the amount of the toner portion is small, the heating amount can be reduced, and a more energy-saving fixing device can be obtained.
According to this embodiment, it is possible to provide a fixing device having high photographic part glossiness while saving energy.
According to this embodiment, an energy-saving image forming apparatus can be obtained.

<Others>
The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention. is there.

DESCRIPTION OF SYMBOLS 1, 2 Heat control means 4 Paper feed means 6 Registration roller pair 8 Photosensitive drum 10 Transfer means 12 Fixing device 14 Paper feed tray 16 Paper feed roller 18 Charging roller 20 Mirror 22 Development means 22a Development roller 24 Cleaning means 24a Cleaning blade 28 Heating roller 30 Pressure roller 31 Heating source 34 Sensor 38 Fixing belt 38a Base material 38b Elastic layer 38c Release layer 40 Power supply B
56 Plate heating means 61 Belt support member Pa Paper SN Nip part

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 nip portion with the fixing member;
Heating means for fixing the unfixed image by heating the recording material when the recording material carrying the unfixed image passes through the nip portion;
A heating control means for controlling the heating means,
The heating unit is divided into a first heating unit controlled according to the temperature of the fixing member and a plurality of regions in a longitudinal direction orthogonal to the conveyance direction of the recording material, regardless of the temperature of the fixing member. A second heating unit that is controlled according to the position information of the image area,
The heating control unit controls the temperature of the fixing member independently for each heating unit in accordance with position information where the unfixed image is formed on the recording material, and a non-image in which the unfixed image does not exist A fixing device characterized in that a heating temperature of an area is controlled to be lower than an image area where the unfixed image exists. The fixing device according to claim 1,
The fixing device according to claim 1, wherein the first heating unit and the second heating unit heat a surface of the fixing member that does not contact an unfixed image. The fixing device according to claim 1, wherein:
The fixing device, wherein the heating means starts heating before an unfixed image passes through the nip portion. The fixing device according to any one of claims 1 to 3,
The heating device heats longer when the weight per unit area of the unfixed image is large, and heats shorter when the weight per unit area of the unfixed image is small. The fixing device according to any one of claims 1 to 3,
The heating means increases the voltage applied to the heating body when the weight per unit area of the unfixed image is large, and decreases the voltage applied to the heating body when the weight per unit area of the unfixed image is small. A fixing device characterized by the above. The fixing device according to any one of claims 1 to 3,
The heating device controls the unfixed image so that the temperature of the photographic part is higher than that of the character part.   An image forming apparatus using the fixing device according to claim 1.

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