JP5190209B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that melts and fixes a toner image on the surface of a recording medium when a recording medium on which an unfixed toner image is formed is conveyed, and an image forming apparatus including the same.

  Electrophotographic image forming apparatuses are widely used as, for example, copiers, printers, and facsimile machines because they can form high-quality images in a short time and with easy maintenance. Yes. An electrophotographic image forming apparatus includes, for example, a photoreceptor, a charging device, an exposure device, a developing device, a transfer device, a fixing device, and a cleaning device. The photoreceptor is a roller-like member having a photosensitive film formed on the surface thereof. The charging device receives a voltage and charges the surface of the photoreceptor to a predetermined potential. The exposure apparatus irradiates the charged photoreceptor surface with signal light corresponding to image information to form an electrostatic latent image. The developing device supplies toner to the electrostatic latent image on the surface of the photoreceptor to develop the toner image. The transfer device transfers the toner image on the surface of the photoreceptor to a recording medium. The fixing device fixes, for example, a toner image on a recording medium. As a result, an image is formed on the recording medium. The cleaning device is a blade-like member provided so as to be in contact with the surface of the photoreceptor, and removes toner remaining on the surface of the photoreceptor after the toner image is transferred to the recording medium.

  The fixing device includes a pair of rollers (a fixing roller and a pressure roller) that are in pressure contact with each other, and the roller pair is fixed by a heating device including a halogen heater or the like disposed in both or one of the rollers. A configuration of a heat roller fixing system in which a recording paper on which an unfixed toner image is formed is passed through a pressure contact portion (fixing nip portion) after being heated to a temperature and the toner image is fixed by heat and pressure is often used. ing.

  In particular, in a fixing device for full-color image formation, it is common to use an elastic roller provided with an elastic layer made of silicon rubber or the like on the surface layer of the fixing roller.

  By using an elastic roller as the fixing roller, the surface layer of the fixing roller is elastically deformed according to the unevenness of the unfixed toner image and comes into contact with the toner image so as to cover the toner image. Thus, it is possible to satisfactorily heat-fix the unfixed toner image. In addition, the releasability of the color toner that is more likely to be offset than the monochrome toner can be improved due to the strain relief effect of the elastic layer at the fixing nip. Furthermore, since the nip shape of the fixing nip is convex upward, so-called reverse nip shape, the paper peeling performance is improved and the paper can be peeled off without using a peeling nail or other peeling means (self Strip) and image defects caused by peeling means can be eliminated.

  However, the fixing roller provided with the elastic layer has a very low thermal conductivity of the elastic layer itself. Therefore, when a heating device is provided inside the fixing roller, the heat transfer efficiency is lowered and the warm-up time is long. And the fixing roller temperature does not follow when the speed is increased.

  In order to solve such a problem, a configuration of an external heating fixing system in which an external heating device is brought into contact with the surface of the fixing roller and the fixing roller is heated from the outside is known. A belt heat fixing method has been proposed.

  The fixing device described in Patent Document 1 is a fixing device using an external belt heating fixing method. As an external heating device, a 400 W halogen heater is disposed inside each of two stretching rolls, and is heated by the halogen heater. The tension roll is heated via the endless belt. Moreover, the structure which detects the surface temperature of a tension roll with the thermistor provided outside is described.

JP 2005-292714 A

  When a plurality of heat sources such as halogen heaters are provided, a thermistor and a thermostat are also provided for each heat source. However, the apparatus configuration becomes complicated and the cost increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus including the fixing device that can simplify the device configuration and reduce the cost even when a plurality of external heating members are provided.

The present invention includes a recording medium having a pair of fixing members pressed against each other and a plurality of external heating members for heating the fixing member from the outside, and an unfixed toner image formed on the surface thereof. In a fixing device that melts and fixes a toner image on the surface of a recording medium when conveyed between a pair of fixing members,
The plurality of external heating members are each a plurality of heating rollers each having a heat source and rotatable about an axis.
The heat generation amounts of the plurality of heat sources are configured to be the same, and the heat capacities of the plurality of heating rollers are configured to be the same.
The plurality of heat sources are electrothermal conversion heat sources that generate heat by power supplied from a power source,
A regulating member that regulates the calorific value of the plurality of heat sources to be within a certain range;
A detection member for detecting the temperature of the external heating member;
A control unit that controls the operation of the power source based on the temperature of the external heating member detected by the detection member;
The fixing member is inserted between the plurality of heat sources, is connected in series with the plurality of heat sources with respect to the power source, and is provided at a position equidistant from each external heating member. Device.

  The present invention further includes an endless belt that is suspended from the plurality of heating rollers and is pressed against the outer surface of the fixing member by the heating rollers.

  In the invention, it is preferable that the regulating member is provided in a region surrounded by the endless belt.

The present invention also provides a photoreceptor having a photosensitive layer on the surface;
Charging means for charging the photosensitive layer to a uniform potential;
Exposure means for irradiating the surface of the charged photoreceptor with signal light to form an electrostatic latent image; and
Developing means for supplying toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image;
Transfer means for transferring a toner image on the surface of the photoreceptor to a recording medium;
An image forming apparatus including the fixing device.

According to the present invention , each of the plurality of external heating members includes a plurality of heating rollers each having a heat source therein and rotatable around an axis, and the heat generation amounts of the plurality of heat sources are configured to be the same. The plurality of heating rollers are configured to have the same heat capacity, and the plurality of heat sources are electrothermal conversion heat sources that generate heat by electric power supplied from a power source, and the heat generation amounts of the plurality of heat sources are constant. A control member for controlling the power supply to be within the range, a detection member for detecting the temperature of the external heating member, and a control for controlling the operation of the power source based on the temperature of the external heating member detected by the detection member The regulating member is inserted between the plurality of heat sources, is connected in series with the plurality of heat sources with respect to the power source, and is equidistant from each external heating member. Established That.

Thereby, the control means of a plurality of external heating members can be shared, and the apparatus configuration of the fixing device itself can be simplified. Further, by simplifying the device configuration, the device cost can be reduced.
In addition, since the temperatures of the plurality of external heating members become uniform, the configuration of the fixing device can be simplified by sharing the control means.
Moreover, it has a control member which controls so that the emitted-heat amount of these heat sources may become in a fixed range. The regulating member is realized by, for example, a thermostat or a thermal fuse. Since the plurality of heat sources are controlled to operate in the same manner, if at least one restricting member is provided, the control can be controlled, and the apparatus configuration can be simplified.
Furthermore, it has a detection member which detects the temperature of the said external heating member. The detection member is realized by a thermistor, for example. Since the plurality of heat sources are controlled to operate in the same manner, if at least one detection member is provided, it can be controlled, and the apparatus configuration can be simplified.
By connecting in series with the power supply, the start and end timing of heat generation and the amount of heat generated during heat generation can be easily controlled to be the same.
In addition, since the restriction member is provided at a position equidistant from each external heating member and is equally affected by the heat generated from each external heating member, the restriction member is provided for a plurality of external heating members. Can be shared.

  According to the invention, there is further provided an endless belt that is suspended by the plurality of heating rollers and is in pressure contact with the outer surface of the fixing member by the heating rollers.

  By mediating the heat transfer from the external heating member to the fixing member with the endless belt, the temperature of the plurality of heating means can be made more uniform.

According to the invention, the regulating member is provided in a region surrounded by the endless belt.
Thereby, since it does not receive to the influence of heat from those other than external heating members, such as an external environment, a control member can be operated more rapidly and accurately.

  According to the invention, when the exposure unit irradiates the charged photosensitive member surface with signal light to form an electrostatic latent image, the developing unit applies toner to the electrostatic latent image on the photosensitive member surface. To form a toner image. The transfer unit transfers the toner image on the surface of the photosensitive member to the recording medium, and the fixing unit fixes the toner image on the recording medium to the recording medium.

  As a result, the apparatus configuration of the fixing device is simplified and the cost is reduced, so that the apparatus configuration of the image forming apparatus itself can be simplified and the cost can be reduced.

  The fixing device according to the present invention fixes a toner image on a recording sheet by heat and pressure on a recording sheet on which an unfixed toner image is formed. An unfixed toner image is a developer such as a non-magnetic one-component developer composed of a non-magnetic toner, a non-magnetic two-component developer composed of a non-magnetic toner and a carrier, and a magnetic developer composed of a magnetic toner. It may be called “toner”).

  FIG. 1 is a schematic diagram illustrating a configuration of a fixing device 10 according to a first embodiment of the present invention. As shown in FIG. 1, the fixing device 10 includes a fixing roller 11, a pressure roller 12, an external heating belt 13 that is an endless belt for heating the fixing roller from the outside, and an endless belt for heating the external heating belt 13. The first heating roller 14, the second heating roller 15, the first heater lamp 16 as a heat source for heating the first heating roller 14, the second heater lamp 17 as the heat source for heating the second heating roller 15, A thermistor 18 for detecting the surface temperature of the heating belt 13 and a thermostat 19 for controlling the temperatures of the first and second heater lamps 16 and 17 are included.

  The fixing roller 11 and the pressure roller 12, which are a pair of fixing members, are pressed against each other with a predetermined load (for example, 600 N), and the fixing roller 11 and the pressure roller 12 are in contact with each other between them. A fixing nip portion (for example, 9 mm width) is formed. The recording paper P having an unfixed toner image formed on the surface is fixed by passing through the fixing nip portion. When the recording paper P passes through the fixing nip portion, the fixing roller 11 contacts the toner image forming surface of the recording paper P, and the pressure roller 12 contacts the surface opposite to the toner image forming surface of the recording paper P. It is like that.

  A third heater lamp 20 that directly heats the fixing roller 11 is disposed inside the fixing roller 11. When a control device (not shown) controls the operation of the DC power supply and energizes the third heater lamp 20, the third heater lamp 20 emits light and infrared rays are emitted. As a result, the inner peripheral surface of the fixing roller 11 is heated by absorbing the emitted infrared rays, and the entire fixing roller 11 is heated.

  Further, separately from the third heater lamp 20, the first and second heater lamps 16 and 17 which are electrothermal conversion heat sources are controlled, are energized by a DC power source, emit light, and emit infrared rays. As a result, the inner peripheral surfaces of the first heating roller 14 and the second heating roller 15 which are external heating members are heated by absorbing the emitted infrared rays, and the heated first heating roller 14 and the second heating roller 15 are heated. The external heating belt 13 is heated. The external heating belt 13 contacts the surface of the fixing roller 11 between the first heating roller 14 and the second heating roller 15 to heat the fixing roller 11 from the outside.

  The external heating belt 13 is provided so as to come into contact with the surface of the fixing roller 11 on the opposite side across the axis of the fixing nip portion, and is configured to be pressed against the fixing roller with a predetermined pressing force (for example, 40 N). A heating nip portion (for example, a width of 20 mm) is formed between the external heating belt 13 and the fixing roller 11.

  The fixing roller 11 is rotated around the axis by a rotation driving device (not shown). The external heating belt 13 rotates according to the rotation of the fixing roller 11 due to the frictional force between the outer surface thereof and the surface of the fixing roller 11. The first heating roller 14 and the second heating roller 15 are driven to rotate according to the rotation of the external heating belt 13 due to the frictional force between the outer surface thereof and the inner surface of the external heating belt 13.

  In this way, the heated external heating belt 13 heats the surface of the fixing roller 11 that is in contact with rotation, and heats the fixing roller 11 to a predetermined temperature (for example, 180 ° C.).

  The fixing roller 11 has a three-layer structure in which a metal core, an elastic layer, and a release layer are formed in this order from the inside. For the core metal, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used.

  For example, silicon rubber is used for the elastic layer, and fluorine resin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is used for the release layer.

  Similarly to the fixing roller 11, the pressure roller 12 has an elastic layer such as silicon rubber on the outer peripheral surface of steel, stainless steel, aluminum or the like, and a release layer such as PFA is further formed thereon.

  As the external heating belt 13, a synthetic resin material having excellent heat resistance and releasability as a release layer on the surface of a hollow cylindrical base material made of a heat resistant resin such as polyimide or a metal material such as stainless steel or nickel ( For example, it has a two-layer structure in which a fluorine resin such as PFA or PTFE is formed. Further, in order to reduce the shifting force, the inner peripheral surface may be coated with a fluororesin or the like.

  The 1st heating roller 14 and the 2nd heating roller 15 consist of a cylindrical metal core material comprised with aluminum and an iron-type material. In addition, in order to reduce the offset force of the external heating belt 13, the surface of the metal core material may be coated with a fluorine resin or the like.

  A thermistor is disposed in the vicinity of the external heating belt 13, and the outer peripheral surface temperature of the external heating belt 13 is detected. Based on the detected temperature, the control device controls the DC power supply to control the first and second. The heater lamps 16 and 17 are caused to emit light.

  The recording paper P on which the unfixed toner image is formed is conveyed to the fixing nip portion at a predetermined fixing speed and copying speed, and is fixed by heat and pressure.

  The fixing speed is a process speed, for example, 355 mm / sec. The copying speed is the number of copies per minute, for example 70 sheets / minute.

  A configuration example of the external heating belt 13, the fixing roller 11, the pressure roller 12, the first heating roller 14, and the second heating roller 15 is shown.

  The external heating belt 13 is, for example, coated on a surface of a base material of polyimide having a thickness of 90 μm (trade name: Upilex S, manufactured by Ube Industries, Ltd.) with a fluorine resin blended with PTFE and PFA as a release layer to a thickness of 20 μm. An endless belt can be used.

  The fixing roller 11 is made of an aluminum cored bar coated with a 3 mm thick silicon rubber layer and a 30 μm thick PFA tube.

  As the pressure roller 12, a 2 mm thick silicon rubber layer coated on an aluminum cored bar and a 30 μm thick PFA tube coated thereon are used.

  Both the fixing roller 11 and the pressure roller 12 have an outer diameter of 50 mm. The first heating roller 14 and the second heating roller 15 are both made by coating the surface of an aluminum cored bar having a thickness of 0.75 mm with a fluorine resin blended with PTFE and PFA to a thickness of 20 μm. The outer diameter of both the first heating roller 14 and the second heating roller 15 is 15 mm. The distance between the axes of the first and second heating rollers is 23.0 mm. The peripheral length (inner diameter) of the external heating belt 13 is 94.24 mm at room temperature. The external heating belt 13 is suspended by two heating rollers having a fixed center distance, and is brought into pressure contact with the fixing roller 11 with a load of 40N.

FIG. 2 is a schematic diagram showing the configuration of the fixing device 10 according to the second embodiment of the present invention.
The present embodiment is different from the first embodiment only in the configuration that does not include the external heating belt 13. The fixing roller 11 is heated from the inside by the third heater lamp 20, and each of the first heating roller 14 and the second heating roller 15 contacts the fixing roller 11 and is also heated from the outside.

FIG. 3 is a block diagram illustrating an electrical configuration of the fixing device 10.
The second heater lamp 17, the thermostat 19, and the first heater lamp 16 are connected in series to the DC power source 21 in this order. The control unit 22 controls the DC power source 21 based on the surface temperature of the external heating belt 13 detected by the thermistor 18 that is a detection member, thereby causing the first heater lamp 16 and the second heater lamp 17 to have a predetermined same temperature. It is controlled to become.

  Since the second heater lamp 17, the thermostat 19 and the first heater lamp 16 are connected in series, the first heater lamp 16 and the second heater lamp 17 are simultaneously turned on and heated at the same time by supplying power from the DC power supply 21. Start. During lighting, the same electric power is supplied to the first heater lamp 16 and the second heater lamp 17, so that the same temperature is maintained. The thermostat 19 as a regulating member temporarily cuts the circuit when a predetermined threshold temperature is reached, and connects the circuit when the temperature falls below the threshold temperature, thereby regulating the heat generation amount of the heater lamp within a certain range. However, also in this case, since the first heater lamp 16 and the second heater lamp 17 are connected in series, the first heater lamp 16 and the second heater lamp 17 are turned off simultaneously. When one of the lamps is disconnected, the power supply to the other lamp is stopped, so that the first heater lamp 16 and the second heater lamp 17 are turned off simultaneously.

  The first heating roller 14 and the second heating roller 15 are configured so as to have the same heat capacity, and are configured by the same material and the same size, for example, as described above. By doing so, the first heating roller 14 and the second heating roller 15 are heated to substantially the same temperature, so there is no problem even if the thermistor 18 is installed only on the second heater lamp 17 side.

  FIG. 4 is a block diagram illustrating another electrical configuration of the fixing device 10. Although FIG. 3 shows the case where the first heater lamp 16 and the second heater lamp 17 are connected in series to the DC power source 21, the first heater lamp 16 and the second heater lamp 17 can be connected in parallel. is there.

  In the case of parallel connection, even if one of the heater lamps is disconnected, the other lamp remains lit. Therefore, it is necessary to control so that the lit heater lamp does not overheat.

  Therefore, when connecting in parallel, as shown to Fig.4 (a), the 1st thermostat 19a and the 2nd thermostat 19b are connected in series with respect to the 1st heater lamp 16 and the 2nd heater lamp 17, respectively. Even if one of the lamps is disconnected, the thermostat connected to the other lamp is controlled so as not to overheat because the circuit is temporarily disconnected when a predetermined temperature is reached.

  Further, when controlling by one thermostat 19, as shown in FIG. 4B, two first heater lamps 16 and second heater lamps 17 connected in parallel and one thermostat 19 are connected in series. . By connecting in this way, even if one of the lamps is disconnected, the thermostat 19 is controlled so as not to overheat because the circuit is temporarily disconnected when a predetermined temperature is reached.

  As the first heater lamp 16 and the second heater lamp 17, a heat source by radiant heat such as a halogen heater is used, and those having the same output such as wattage are used.

  FIG. 5 is a diagram showing the arrangement position of the thermostat 19. The thermostat 19 is preferably arranged at a position that is substantially equidistant from the plurality of heater lamps. As shown in FIG. 5A, an intermediate position between the first heater lamp 16 and the second heater lamp 17. Placed in. By doing so, the thermostat 19 can be shared because it is equally affected by the heat generated from the first heater lamp 16 and the second heater lamp 17.

  Further, when the external heating belt 13 is used, as shown in FIG. 5B, the external heating belt 13 is located at an equal distance from the first heater lamp 16 and the second heater lamp 17. It is preferable to arrange inside. By disposing inside the belt, the thermostat 19 can be operated more quickly and accurately because it is not affected by heat other than the first heater lamp 16 and the second heater lamp 17 such as the external environment.

FIG. 6 is a view showing the arrangement position of the thermostat 19 when there are three heating rollers.
FIG. 6A shows a case where all three heating rollers are in contact with the fixing roller 11, and the thermostat 19 is arranged at a predetermined interval on the opposite side of the heating roller located in the middle from the fixing roller 11. Is done. In FIG. 6B, two of the three heating rollers are arranged so as to press the external heating belt 13 against the fixing roller 11, and the remaining one heating roller includes two heating rollers pressed against the fixing roller 11. The heating roller is disposed at an equal distance from the fixing roller 11 so as to be in contact with the external heating belt 13 at a position away from the fixing roller 11. The thermostat 19 is equidistant from the three heating rollers and is disposed inside the external heating belt 13.

  As for the arrangement of the thermistor 18, as shown in FIGS. 1 and 2, it is preferable that the thermistor 18 be arranged in the vicinity of the heating roller arranged downstream in the rotation direction of the fixing roller 11, in the present embodiment, the second heating roller 15. . In particular, when the external heating belt 13 is used, the heating roller arranged on the downstream side in the rotation direction of the fixing roller 11 among the plurality of arranged heating rollers is best in the contact state with the external heating belt 13. Therefore, such a configuration is preferable from the viewpoint of temperature detection accuracy.

  Moreover, as a thermostat used in order to achieve the objective of this invention, the CR-7 series by a Wako Electronics company is mentioned, for example. Examples of the thermistor used to achieve the object of the present invention include the thermistor sensor HF series and ND sensor F type series for information communication equipment manufactured by Ishizuka Electronics Co., Ltd., which are either contact type or non-contact type. Can be used.

  In addition to the thermostat, a temperature fuse can be used as the temperature control element of the heat source. Since the thermostat has a size larger than that of the thermal fuse, it is preferable to use the thermal fuse when the installable area is narrow inside the external heating belt 13. However, since the thermal fuse cannot be used after it has been blown, it can be said that it is preferable to use a thermostat as much as possible in order to suppress an increase in work load due to component replacement and an increase in the period during which the apparatus cannot be used.

  FIG. 7 is a schematic diagram illustrating a configuration of the image forming apparatus 100 including the fixing device 10. The image forming apparatus 100 forms a multicolor or single color image on a predetermined recording sheet based on image data transmitted from each terminal device on the network, for example.

  The image forming apparatus 100 includes a fixing device (heating device) 10, a recording paper transport unit 30, a supply tray 40, a visible image forming unit 50 (50Y / 50M / 50C / 50K), and a paper discharge tray 60.

  In the image forming apparatus 100, four visible image forming units 50Y, 50M, 50C, and 50B are arranged in parallel corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). ing. The visible image forming unit 50Y forms an image using yellow (Y) toner, the visible image forming unit 50M forms an image using magenta (M) toner, and the visible image forming unit 50C. Performs image formation using cyan (C) toner, and the visible image forming unit 50B performs image formation using black (K) toner. A specific arrangement is a tandem type in which four sets of visible image forming units 50 are arranged along a conveyance path connecting the supply tray 40 of the recording paper P and the fixing device 10.

  The visible image forming unit 50 has substantially the same configuration except for the color of the toner to be handled, that is, the photosensitive drum 51, the charging device 52, the laser beam irradiation means 53, the developing device 54, the transfer device. A roller 55 and a cleaner unit 56 are provided, and multiple color toner images are transferred onto the conveyed recording paper P.

  The photoconductive drum 51 carries an image to be formed. The charger 52 uniformly charges the surface of the photosensitive drum 51 to a predetermined potential. The laser beam irradiation unit 53 exposes the surface of the photosensitive drum 51 charged by the charger 52 according to the image data input to the image forming apparatus 100 to form an electrostatic latent image on the surface of the photosensitive drum 51. . The developing device 52 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 51 with toner of each color. The transfer roller 55 is applied with a bias voltage having a polarity opposite to that of the toner, and transfers the formed toner image onto the recording paper P conveyed by the recording paper conveying means 30 described later. The cleaner unit 56 removes and collects the toner remaining on the surface of the photosensitive drum 51 after the development processing in the developing device 54 and the transfer of the toner image formed on the photosensitive drum 51. The transfer of the toner image onto the recording paper P as described above is repeated four times for four colors.

  The recording paper conveyance means 30 includes a driving roller 31, an idling roller 32, and a conveyance belt 33, and conveys the recording paper P so that the toner image formed by the visible image forming unit 50 is transferred to the recording paper P. . The driving roller 31 and the idling roller 32 stretch the endless conveyance belt 33, and the endless conveyance belt 33 is rotated by the drive roller 31 being controlled to rotate at a predetermined peripheral speed. The conveying belt 33 generates static electricity on the outer surface, and conveys the recording paper P while being electrostatically attracted.

  The recording paper P is thus transported to the transport belt 33 and a toner image is transferred to the surface thereof. Then, the recording paper P is peeled off from the transport belt 33 by the curvature of the drive roller 31 and transported to the fixing device 10. The fixing device 10 applies a suitable heat and pressure to the recording paper P, melts the toner, and fixes it to the surface of the recording paper P, thereby forming a robust image.

  Since the device configuration of the fixing device 10 is simplified and the cost is reduced, the device configuration of the image forming apparatus 100 itself including the fixing device 10 can be simplified and the cost can be reduced.

1 is a schematic diagram illustrating a configuration of a fixing device 10 according to a first embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a configuration of a fixing device 10 according to a second embodiment of the present invention. 2 is a block diagram illustrating an electrical configuration of the fixing device 10. FIG. Is a reference block diagram illustrating an electrical configuration of another fixing equipment. FIG. 4 is a view showing the arrangement position of a thermostat 19. It is a figure which shows the arrangement position of the thermostat 19 in the case of three heating rollers. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 100 including a fixing device 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fixing device 11 Fixing roller 12 Pressure roller 13 External heating belt 14 First heating roller 15 Second heating roller 16 First heater lamp 17 Second heater lamp 18 Thermistor 19 Thermostat 30 Recording paper conveying means 40 Supply tray 50 Visible image Forming unit 60 Output tray

Claims (4)

A recording medium having a pair of fixing members pressed against each other and a plurality of external heating members for heating the fixing members from the outside, on which an unfixed toner image is formed, is formed on the pair of fixing members. In a fixing device that melts and fixes a toner image on the surface of a recording medium when conveyed between
The plurality of external heating members are each a plurality of heating rollers each having a heat source and rotatable about an axis.
The heat generation amounts of the plurality of heat sources are configured to be the same, and the heat capacities of the plurality of heating rollers are configured to be the same.
The plurality of heat sources are electrothermal conversion heat sources that generate heat by power supplied from a power source,
A regulating member that regulates the calorific value of the plurality of heat sources to be within a certain range;
A detection member for detecting the temperature of the external heating member;
A control unit that controls the operation of the power source based on the temperature of the external heating member detected by the detection member;
The fixing member is inserted between the plurality of heat sources, is connected in series with the plurality of heat sources with respect to the power source, and is provided at a position equidistant from each external heating member. apparatus. The fixing device according to claim 1, further comprising an endless belt that is suspended by the plurality of heating rollers and is pressed against the outer surface of the fixing member by the heating rollers. The fixing device according to claim 2, wherein the regulating member is provided in a region surrounded by the endless belt. A photoreceptor having a photosensitive layer on the surface;
Charging means for charging the photosensitive layer to a uniform potential;
Exposure means for irradiating the surface of the charged photoreceptor with signal light to form an electrostatic latent image; and
Developing means for supplying toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image;
Transfer means for transferring a toner image on the surface of the photoreceptor to a recording medium;
An image forming apparatus comprising a fixing device according to any one of claims 1-3.

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