JP2007108372A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that fixes an unfixed toner image to a transfer material by the application of heat and pressure thereto, the fixing device being designed such that a temperature difference caused in the widthwise direction of the peripheral face of a heating rotator is reduced, the heating rotation body is efficiently heated and a warmup period is shortened. <P>SOLUTION: A built-in heat source 23 is disposed in the heating rotator 21. On the outside of it, an external heating source 24 is disposed for heating a range narrower than the heating range of the built-in heating source 23. On the peripheral face of the heating rotator 21, a first temperature detecting means 26 and a second temperature detecting means 27 are disposed within and outside, respectively, the heating range of the external heating source 24. Based on the detection value of the first temperature detecting means, ON/OFF of the external heating source 24 or internal heating source 23 is controlled to maintain the heating rotator at a temperature suitable for fixing. In addition, the built-in heating source or external heating source is selected based on the detection value of the second temperature detecting means, thereby heating the heating rotator. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in an image recording apparatus such as a printer, a copying machine, or a facsimile, and uses a fixing device that heats and presses an unfixed toner image carried on a transfer material to fix it on the transfer material, and the fixing device. The present invention relates to an image forming apparatus.

As a fixing device of an image forming apparatus that forms a visible image using toner, one having a heating roll as a heating rotator and a pressure roll as a pressure member is widely used. In this fixing device, the heating roll and the pressure roll are rotationally driven while being pressed against each other, the transfer material is sent to the press contact portion (nip portion), and the unfixed toner image carried on the transfer material is heated.・ It is to be crimped.
The heating roll has a hollow cylindrical cored bar such as aluminum and a heating source provided therein, for example, a halogen lamp, and the peripheral surface of the heating roll has a temperature suitable for fixing a toner image. Heated.

  Such a heating roll needs to be preheated (warmed up) to a predetermined temperature at the start of use of the image forming apparatus, and the preheating time is required to be shortened. It is also required to reduce the amount of power consumed for heating. For this reason, the heating roll needs to reduce the wall thickness of the cylindrical core bar, reduce the heat capacity, and efficiently transfer heat from the built-in heating source to the cylindrical core bar. Furthermore, when the heat capacity is reduced, when the size of the transfer material is small, a difference in the peripheral surface temperature of the heating roll tends to occur between the transfer material passing region and the non-passing region. That is, there is an amount of heat that moves to the transfer material in the passage region of the transfer material, and a temperature difference occurs when uniformly heated.

Under such circumstances, Patent Documents 1 and 2 disclose a fixing device including a plurality of heaters having different heating regions inside a heating roll. This device controls ON / OFF of these heaters according to the warm-up, small size transfer material, and large size transfer material, respectively, and the temperature difference that occurs in the axial direction of the heating roll. Is to reduce.
JP-A-8-220932 JP 2001-201978 A

  However, since the apparatus described in Patent Document 1 or Patent Document 2 includes a plurality of heaters as heating sources inside the heating roll, when one heater is turned on, the other heaters are turned on. Absorbing the radiant heat from the heated heater or blocking the radiant heat from the heater in the ON state causes temperature unevenness on the peripheral surface of the heating roll. For this reason, shortening of warm-up time may be inhibited. In addition, since a plurality of heaters are built in the heating roll, it is difficult to assemble the heating roll, and the heater may come into contact and break during the work. For this reason, simplification of the assembly process is also required.

  The present invention has been made to solve such a problem, and an object of the present invention is to use a fixing device capable of efficiently heating a heating rotator and shortening the warm-up time, and the fixing device. An image forming apparatus is provided.

  In order to solve the above-mentioned problems, a heating rotator with a built-in heating source and an endless peripheral surface that circulates, and a transfer that is in pressure contact with the peripheral surface of the heating rotator and passes between the heating rotators. A pressure member that presses a material against the circumferential surface of the heating rotator, and the heating incorporated in the heating rotator in the width direction of the circumferential surface of the heating rotator outside the heating rotator. An external heating source that heats a range narrower than a range heated by a source (hereinafter referred to as “built-in heating source”) is disposed, and when the external heating source is turned on, the built-in heating source is turned off. The fixing device is characterized by being controlled as described above.

This fixing device has a heating rotator that radiant heat from the built-in heating source is not absorbed or blocked by other heating sources, so this radiant heat is efficiently supplied from the inside to the heating rotator. And can warm up quickly. Moreover, heat can be supplied uniformly in the width direction of the peripheral surface, and the peripheral surface can be heated uniformly. Further, the external heating source corresponds to the sheet passing width of a small size transfer material, and when the external heating source is turned on, the internal heating source is controlled to be turned off. By appropriately switching these heating sources, even when fixing a toner image on a transfer material having a small size, it is possible to prevent the temperature difference between the sheet passing area and the non-sheet passing area from becoming excessive. Can do.
Further, at the time of assembling the heating rotator, only one heating source needs to be arranged inside, and the assembly becomes easy.

  In addition, the heating rotator includes first temperature detecting means for detecting the temperature of the peripheral surface within a range where the external heating source in the width direction of the peripheral surface heats, and the detected value is within a predetermined range. It is possible to control ON / OFF of the external heating source or the built-in heating source so as to be maintained. Thus, even when a small-size transfer material passes and heat is supplied to the heating rotator by an external heating source, even when a large-size transfer material passes and is heated by the internal heating source, the heating rotator Can be maintained at a temperature at which satisfactory fixing is possible (hereinafter referred to as “fixable temperature”).

  The heating rotator has a second temperature detecting means in addition to the first temperature detecting means, and the second temperature detecting means is disposed outside the heating range of the external heating source. can do. Then, based on the detection value by the second temperature detection means, the selection of the heating source to be used, that is, the energization to the external heating source or the energization to the built-in heating source is performed. As a result, when using a small size transfer material, it is possible to prevent the outside of the region through which the transfer material passes from being excessively heated, and to suppress the temperature difference in the width direction of the peripheral surface of the heating rotator. It becomes.

  In this fixing device, switching between the external heating source and the built-in heating source can be controlled based on the size of the transfer material to be conveyed. That is, based on image information input from the external device to the image forming apparatus, image information read by the image reading apparatus or the like, or information on the size of the transfer material input by the operator of the image forming apparatus, the external heating source Or it can be switched to select either of the built-in heating sources. As a result, an external heating source that heats a narrow range is used when the size of the transfer material used is small, and an internal heating source is used when a large size transfer material is used, so that a part of the heating rotator is excessive. Can be prevented from being heated. In addition, power consumption can be reduced.

  In the image forming apparatus provided with the fixing device as described above, the radiant heat from the built-in heating source built in the heating rotator is efficiently supplied to the heating rotator, so that the warm-up can be quickly performed. The waiting time at the start of use is shortened. In addition, it is possible to suppress the temperature difference in the width direction of the peripheral surface of the heating rotator, to eliminate the use of power for heating unnecessary portions to a high temperature, and to reduce the power consumption of the entire device. it can.

  As described above, in the fixing device according to the present invention and the image forming apparatus using the fixing device, the heating rotator includes the built-in heating source and heats a range narrower than the range heated by the built-in heating source. Since the external heating source is provided outside the heating rotator, there is nothing to absorb or block the heat of the built-in heating source when warming up by the built-in heating source. It can be carried out. In addition, the external heating source is set to a heating range corresponding to the small size of the transfer material used, and the heating rotator is heated by switching between the internal heating source and the external heating source. be able to. Accordingly, it is possible to maintain the region through which the transfer material passes at a temperature suitable for fixing, and to prevent the temperature difference in the width direction of the peripheral surface from becoming excessive.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
This image forming apparatus includes an image reading apparatus 1 that reads image information from a document, a receiving unit 2 that is connected to an external device such as a personal computer via a communication line, and receives the image information, and the receiving unit 2 or the image reading apparatus 1. The image recording control unit 3 that converts image information from the digital image signal to perform image processing and the like, and the image forming unit 4 that forms an image based on information output from the image recording control unit 3 are provided. .

  The image forming unit 4 includes a cylindrical photosensitive drum 11 on which a latent image is formed on the surface by irradiation with image light after uniform charging, and around the photosensitive drum 11. A charging device 12 for uniformly charging the surface of the photosensitive drum 11, an exposure device 13 for irradiating the photosensitive drum 11 with image light to form a latent image on the surface, and a latent image on the photosensitive drum 11. A developing device 14 for selectively transferring toner to form a toner image, a transfer device 15 for transferring the toner image formed on the photosensitive drum 11 to a recording sheet (transfer material), and after transferring the toner image A cleaning device 16 that removes the toner remaining on the photosensitive drum 1, and a static elimination exposure device 17 that neutralizes the photosensitive drum and initializes the potential.

  The photosensitive drum 11 is a photosensitive material made of various inorganic photosensitive materials such as Se, a-Si, a-SiC, and Cds, an organic photosensitive material, an amorphous selenium photosensitive material, an amorphous silicon photosensitive material, etc. on the surface of a metal drum. What formed the body layer can be used.

  The charging device 12 is formed by coating a metal roll having conductivity, such as stainless steel or aluminum, with a coating of a high resistance material. The charging device 12 is in contact with the photosensitive drum 11 and is driven to rotate. When a predetermined voltage is applied, a continuous discharge is generated in a minute gap near the contact portion between the roll and the photosensitive drum 11, and the surface of the photosensitive drum 4 is charged almost uniformly. It is.

  The exposure device 13 includes a laser generator that blinks for each pixel based on an image signal output from the image recording control unit 3, and exposes and scans the peripheral surface of the photosensitive drum 11 with a polygon mirror. is there. As a result, the potential of the exposed portion is attenuated on the peripheral surface of the photosensitive drum 11, and a latent image is formed due to the difference in electrostatic potential.

  The developing device 14 has a developer carrier having a toner thin layer formed on the surface thereof at a position close to and facing the photosensitive drum 11, and between the developer carrier and the photosensitive drum 11. The toner is transferred to the latent image within the electric field generated in the above to form a visible image.

  The transfer device 15 is disposed so as to face the photoconductor drum 11 and forms an electric field between the photoconductor drum 11 and the photoconductor on the recording sheet conveyed in contact with the photoconductor drum 11. The toner image on the drum is electrostatically transferred.

  A fixing device 18 that heats and pressurizes the toner image on the recording sheet and presses the toner image on the recording sheet is provided on the downstream side of the transfer device 15. A paper discharge roller (not shown) for feeding a recording sheet from the inside of the apparatus is provided on the downstream side of the fixing device 18, and this paper discharge roller discharges the recording sheet to a paper discharge tray. .

  As shown in FIGS. 2 and 3, the fixing device 18 includes a heating roll 21 that is supported so as to be rotatable around a central axis, a pressure roll 22 that rotates while being pressed in parallel with the heating roll 21, and A built-in heating source 23 built in the heating roll 21, an external heating source 24 arranged in a non-contact manner outside the heating roll 21, a reflector 25 provided so as to cover the back side of the external heating source, and an external First temperature detecting means 26 for detecting the temperature of the outer peripheral surface of the heating roll 21 within the heating width of the heating source 24, and detecting the temperature of the outer peripheral surface of the heating roll 21 outside the range of the heating width of the external heating source 24. The second temperature detection means 27 constitutes a main part. When a recording sheet P (transfer material) carrying an unfixed toner image is sent to the pressure contact portion between the heating roll 21 and the pressure roll 22 that are rotationally driven, the toner image is transferred by the heat transfer from the heating roll 21. It heats and pressurizes and press-bonds onto the recording sheet.

  The heating roll 21 includes a metal cylindrical core bar 21a having conductivity and a surface release layer 21b laminated on the core bar 21a. An image is formed by a flange and a support shaft (not shown). The main body frame of the forming apparatus is rotatably supported.

  The cylindrical cored bar 21a of the heating roll 21 can be made of a metal such as aluminum, iron, and stainless steel having excellent thermal conductivity and rigidity. In this embodiment, a cylindrical body made of aluminum having an outer diameter of 65 mm is used as the core metal, and the surface release layer 21b is powder-coated with PTFE resin in which silicon carbide powder having a thickness of 30 μm is dispersed on the peripheral surface of the core metal. After that, it is formed by baking.

  The built-in heating source 23 is a halogen lamp having substantially the same length as that of the heating roll 21 in the axial direction, and supplies heat to the heating roll 21 over substantially the entire length in the axial direction.

  As the external heating source 24, a halogen lamp disposed in a non-contact manner facing the outer peripheral surface of the heating roll 21 is used, and the heating roll is heated by heat radiated from the halogen lamp. . In addition, the reflector 25 provided on the opposite side of the surface facing the heating roll is configured to efficiently radiate the radiant heat from the halogen lamp to the peripheral surface of the heating roll 21. And as shown in FIG. 2, it arrange | positions in the upstream of the nip part by which the heating roll 21 and the pressurization roll 22 are press-contacted, and the surrounding surface before reaching the press-contact part with the pressurization roll 22 efficiently Heat. The external heating source 24 heats a range narrower than the range heated by the built-in heating source 23, and supplies heat to a sheet passing area when a small-size recording sheet is used. Yes. Note that the image forming apparatus of the present embodiment is a so-called center register that controls the position of the recording sheet at its center, so the external heating source 24 heats a predetermined width near the center in the axial direction of the heating roll 21. It is supposed to be. On the other hand, a so-called side registration image forming apparatus that controls the position of a recording sheet by its side edge is arranged to heat a predetermined width from one end in the axial direction of the heating roll.

  As shown in FIG. 3, the first temperature detection means 26 is disposed in contact with the outer peripheral surface of the heating roll 21 at a substantially central portion in the axial direction of the heating roll 21. That is, the temperature on the outer peripheral surface of the heating roll 21 is detected in an area through which recording sheets of all sizes used in the image forming apparatus pass. As shown in FIG. 4, the first switch 28 operates based on the detection value of the first temperature detection means 26. The first switch 28 controls ON / OFF of power supply to the built-in heating source 23 or the external heating source 24. When the temperature falls below a predetermined temperature range, the first switch 28 is turned on, and the temperature is within the predetermined range. It is set to be in the OFF state when it is higher.

  The second temperature detection means 27 is arranged so as to detect the temperature of the outer peripheral surface of the heating roll 21 outside the range of the heating width of the external heating source 24. That is, the position at which the temperature is detected by the second temperature detecting means 28 is a range through which a large-sized recording sheet passes, but deviates from the range through which a small-sized recording sheet passes and is close to the side edge. ing. The second switch 29 is operated based on the detection value of the second temperature detection means 27. By switching the second switch 29, the internal heating source 23 or the external heating source is switched from the power source 30. Electric power is supplied to any one of 24.

  The first temperature detecting means and the second temperature detecting means measure the temperature in contact with the peripheral surface of the heating roll 21, and have a large thermocouple using the Seebeck effect and a large temperature coefficient of resistance. A thermistor using an element is used. Since these contact-type temperature sensors are inexpensive, the cost of the apparatus can be reduced.

  In this embodiment, a non-contact halogen lamp is used as the external heating source 24 on the outer peripheral surface of the heating roll 21, but the heating source is not necessarily limited to the halogen lamp. Further, heat can be supplied by contacting the peripheral surface of the heating roll 21. Furthermore, in this embodiment, the heating roll 21 is used as the heating rotator, but an endless belt or the like can also be used.

  The pressure roll 22 has a metal cylindrical cored bar 22a as a core, an elastic layer 22b such as sponge or rubber provided on the surface of the cored bar, and a release layer 22c made of a fluororesin on the surface. It is a laminated one. In this embodiment, a 12 mm-thick silicone rubber layer is formed as an elastic layer on a metal core, and a conductive PFA resin tube in which 30 μm of carbon is dispersed is covered as a release layer.

Next, operations of the image forming apparatus and the fixing apparatus will be described.
When image information is input to the image recording control unit 3 from the receiving unit 2 to which an external device such as the image reading device 1 or a personal computer is connected through a communication line, image processing or the like is performed based on the image information. The image forming unit 4 forms a toner image based on the processed digital image signal. At this time, the image information includes size information of the recording sheet on which the image is recorded.

  In the image forming unit 4, the peripheral surface of the photosensitive drum 11 that is rotated by the charging device 12 is charged to a uniform negative polarity. Then, the exposure device 13 emits a laser beam corresponding to the image signal input from the image recording control unit 3, and scans the peripheral surface of the photosensitive drum 11 to form an electrostatic latent image corresponding to the image. Is done. The electrostatic latent image is conveyed to a position facing the developing device 14 by the rotation of the photosensitive drum 11, and the toner is transferred to the exposure unit to form a toner image. The toner image on the photosensitive drum 11 is conveyed to a position facing the transfer device 15 by the rotation of the photosensitive drum 11. At the same time, a recording sheet is conveyed from a paper tray (not shown) at a predetermined timing and brought into contact with the toner image on the photosensitive drum 11. The toner image is transferred to the recording sheet within the electric field formed by the transfer device 15 and sent to the fixing device 18. In the fixing device, a recording sheet carrying an unfixed toner image is heated and pressed, and the softened toner image is pressed onto the recording sheet.

  In the fixing device 18, when the image forming apparatus is driven, the built-in heating source 23 of the heating roll 21 is turned on and warm-up is started. At this time, the first temperature detecting means 26 measures the temperature, and is heated until reaching a predetermined temperature, that is, a temperature at which an appropriate toner image can be fixed. When the predetermined temperature is reached, the power supply to the built-in heating source 23 is turned off by the first switch 28.

  When the temperature detected by the first temperature detecting means 26 reaches a preset fixing temperature, a toner image is formed according to the image information, and the recording sheet P carrying the toner image is sent to the fixing device 18. Then, the fixing operation is performed. At this time, heat is transferred from the heating roll 21 to the recording sheet, and the temperature of the heating roll 21 decreases. When the first temperature detection unit 26 detects that the temperature of the sheet passing area has dropped, the first switch 28 is turned on to heat the heating roll again. By such control of the first switch 28, the sheet passing area of the heating roll 21 is maintained within a preset fixing temperature range.

  When the toner image fixing operation as described above is performed, when the recording sheet is in contact with almost the entire length of the heating roll 21 in the axial direction, that is, when the size of the recording sheet is large, the heating roll 21 is spread over the entire area in the axial direction. Heating is performed almost uniformly, heat transfer to the recording sheet P occurs almost evenly, and the temperature distribution becomes substantially uniform in the axial direction. Therefore, the temperature detected by the second temperature detection means 27 is substantially the same as the detection value of the first temperature detection means 26.

  On the other hand, even when the size of the recording sheet sent to the fixing device is small, ON / OFF of the built-in heating source 23 is controlled based on the detected value of the first temperature detecting means 26, and the center of the heating roll 21 in the axial direction is controlled. The temperature of the section, that is, the paper passing area is controlled. As a result, even when a recording sheet having a small size is used, good fixing is performed. However, in the vicinity of both ends of the heating roll 21, that is, in the region where the recording sheet does not pass due to the small size of the recording sheet, the recording sheet does not cause heat transfer, and the temperature does not decrease much. On the other hand, the supply of heat from the built-in heating source 23 is performed substantially uniformly in the axial direction of the heating roll 21, so that the temperature near both ends rises from the center. When the second temperature detecting means 27 detects that the temperature of the non-sheet passing area has risen to a predetermined value, the second switch 29 is switched based on this detection signal, and power supply is built-in. The heating source 23 is switched to the external heating source 24. The external heating source 24 supplies heat to a range corresponding to the width of the small-sized recording sheet. The temperature rise at both ends of the heating roll 21 is suppressed, and the recording sheet passes through the range. Necessary heat is supplied.

  Thereafter, the temperature of the central portion through which the recording sheet passes is detected by the first temperature detecting means 26 in the same manner as when heated by the built-in heating source 23, and the first switch 28 has a predetermined temperature range. Controlled by ON / OFF. And when the detection value by the 2nd temperature detection means 27 falls below predetermined value, it heats by the 2nd switch 29 so that the external heating source 24 may be turned off and the internal heating source 13 may be turned on. The source is switched again. Thereby, the peripheral surface of the heating roll 21 is maintained at a substantially uniform temperature in the axial direction.

  Note that, when the image forming and the recording sheet are not supplied and in the standby state, the first switch 28 is controlled based on the value detected by the first temperature detecting means 26, and the built-in heating source 23 The supply or stop of heat is controlled. As a result, the heating roll 21 is maintained at a lower temperature over the entire length than when the toner image is fixed. The set temperature at the time of standby is a temperature that can be raised to a temperature at which fixing can be performed in a short time, and is set so that power consumption for maintaining this temperature is as small as possible.

  As described above, the first switch 28 is controlled based on the detection value by the first temperature detection means 26, and the second switch 29 is controlled based on the detection value by the second temperature detection means 27. . As a result, even if the size of the supplied recording sheet is different, the temperature of the peripheral surface of the heating roll 21 can be maintained at a small temperature difference in the axial direction, so that stable image fixing can be performed and the heating roll can be kept in excess. Heating can be prevented.

  In the embodiment described above, the second temperature detecting means 27 for detecting the temperature of the end portion of the heating roll is provided, and the selection of the external heating source 24 or the built-in heating source 23 is controlled based on the detected value. However, the selection of the heating source can be controlled based on the image information. For example, based on information relating to the size of the recording sheet output from the image recording control unit 3, the built-in heating source 23 is turned on when a large recording sheet is supplied. When small-sized recording sheets are continuously supplied, the internal heating source 23 is turned off and the external heating source 24 is turned on.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 3 is a schematic perspective view showing a heat source provided in the fixing device of FIG. 2. FIG. 3 is a schematic diagram illustrating a configuration for controlling a heating state of a heating roll in the fixing device of FIG. 2.

Explanation of symbols

1: image reading device, 2: receiving unit, 3: image recording control unit, 4: image forming unit,
11: Photosensitive drum, 12: Charging device, 13: Exposure device, 14: Developing device, 15: Transfer device, 16 Cleaning device, 17: Static elimination exposure device, 18: Fixing device,
21: Heating roll, 22: Pressurizing roll, 23: Built-in heating source, 24: External heating source, 25: Reflecting plate, 26: First temperature detecting means, 27: Second temperature detecting means, 28: First 29: second switch, 30: power supply,

Claims (5)

A heating rotator with a built-in heating source and an endless peripheral surface moving around,
A pressure member that is pressed against the peripheral surface of the heating rotator and presses the transfer material passing between the heating rotator and the peripheral surface of the heating rotator;
The outside of the heating rotator has a narrower range than the range in which the heating source built in the heating rotator (hereinafter referred to as “built-in heating source”) heats in the width direction of the peripheral surface of the heating rotator. An external heating source to heat is arranged,
When the external heating source is turned on, the built-in heating source is controlled to be turned off. First temperature detecting means for detecting the temperature of the outer peripheral portion of the heating rotator within the heating range of the external heating source in the width direction of the peripheral surface of the heating rotator,
2. The ON / OFF of the external heating source or the built-in heating source is controlled so that the detection value of the first temperature detection means is within a predetermined range. Fixing device. A second temperature detecting means for detecting the temperature of the outer peripheral portion of the heating rotator outside the heating range of the external heating source in the width direction of the heating rotator circumferential surface;
The selection as to whether the external heating source or the built-in heating source is turned on is controlled based on a detection value of the second temperature detection means. Item 3. The fixing device according to Item 2. The selection as to whether the external heating source or the built-in heating source is turned on is as follows:
The fixing device according to claim 1, wherein the fixing device is controlled based on a size of a transfer material to be conveyed. An image forming means for forming a toner image by transferring toner to a latent image due to a difference in electrostatic potential;
A transfer means for transferring the toner image directly to the transfer material or to the transfer material via an intermediate transfer member;
Fixing means for heating and fixing the toner image by passing the transfer material onto which the toner image has been transferred between a heating rotator and a pressure member that are pressed against each other;
Inside the heating rotator, there is a built-in heating source for heating the width of the maximum size transfer material that can be used in the image forming apparatus,
Outside the heating rotator, an external heating source for heating a range narrower than the maximum size,
The image forming apparatus, wherein when the external heating source is turned on, the built-in heating source is controlled to be turned off.

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