JP2004240002A - Heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve temperature control accuracy and image quality. <P>SOLUTION: In the heating device, the fixing roller 51 is heated by a heater 54 incorporated in it and an external heat roller 53. The external heat roller 53 can be brought into contact with the fixing roller 51 and separated from it. When sheet conveyance is stopped for a fixed interval or longer after consecutive conveyance of sheets, the heating device separates the external heat roller 53 from the fixing roller 51. This prevents such a condition that only the temperature of the surface of the fixing roller 51 is high and the temperature of the inside of the fixing roller 51 is low. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image on a sheet, such as a copying machine, a printer, or a facsimile apparatus, and more particularly, to a heating apparatus that is provided in such an apparatus and applies heat to a sheet. is there.
[0002]
[Prior art]
By using a known image forming process, an image is formed on a sheet using a toner composed of a heat-soluble resin or the like, and a heating device is applied to a so-called fixing device to fix the unfixed toner image. The toner can be melted and fixed.
[0003]
The fixing device also includes a pressing unit that presses the sheet in addition to the heating by the heating device, and applies heat and pressure to fix the unfixed toner image.
[0004]
Further, in order to apply a surface treatment to a sheet having a porous polymer layer formed on its surface, for example, after forming an image by a so-called inkjet method, heating the sheet to melt the porous polymer layer. Alternatively, a heating device can be applied.
[0005]
As described above, the heating device is appropriately applied to the image forming apparatus according to various purposes.
[0006]
Hereinafter, a case where the heating device is applied as a fixing device will be described in more detail.
[0007]
2. Description of the Related Art An image forming apparatus using an electrophotographic method generally fixes a toner image formed of a resin, a magnetic material, a colorant, and the like, which is electrostatically carried on a transfer material (sheet), by pressing and rotating each other. It has a fixing device that applies heat and pressure while nipping and transporting at a pressure contact portion between a roller and a pressure roller to perform fusing and fixing.
[0008]
Conventionally, in such a fixing device, a halogen lamp or the like is used as a heat source for heating, and a method of heating from the inside by a heat source arranged inside the fixing roller, and a method of heating from the outside by a heat source arranged outside the fixing roller. The method can be roughly divided into a heating method.
[0009]
In the internal heating method in which the fixing roller is heated from the inside, during the fixing operation, a heat source is operated to keep the surface temperature of the roller surface that applied heat to the transfer material and toner constant. There is a time lag until the surface temperature starts to rise. Therefore, when performing continuous copying, the temperature of the roller surface temporarily drops. In addition, when the copy speed increases, the temperature of the roller surface decreases sharply, and there is a possibility that fixing failure may occur.
[0010]
On the other hand, there are various external heating methods for heating the fixing roller from the outside.However, considering the safety in the event of paper jam, a material with a built-in heat source and high thermal conductivity is used. The most common method is to heat the heated heater roller by pressing it against the surface of the fixing roller.
[0011]
In this external heating system, since the structure is such that heat is actively supplied to the vicinity of the surface of the fixing roller, the amount of heat lost by applying heat to the transfer material and the toner during the fixing operation is directly supplied to the surface of the fixing roller. be able to. Therefore, there is a characteristic that control responsiveness is better than a configuration in which heating is performed from the inside.
[0012]
However, in this configuration, since heat is applied only to a fixed area on the surface of the fixing roller, it is difficult to keep the temperature of the fixing roller constant during standby, and it is necessary to perform sufficient pre-rotation before starting the copying operation. And the copying operation cannot be started immediately. Further, even during the copying operation, since the temperature inside is lower than the surface of the fixing roller, heat given from the outside escapes to the inside of the fixing roller. Therefore, heat must be supplied in excess of the heat lost to the transfer material, which is not efficient.
[0013]
For this reason, a configuration having a heat source both inside and outside the fixing roller is common.
[0014]
A typical conventional example having a heat source inside and outside such a fixing roller will be described with reference to FIG. FIG. 6 is a schematic diagram illustrating a main configuration of a fixing device according to the related art.
[0015]
As shown in FIG. 6, a fixing roller 1 has a heater 4 serving as a heat source, and an external heating roller 3 having a heater 5 therein so as to be in contact with the fixing roller.
[0016]
Further, a first temperature detecting means 6 which comes into contact with the fixing roller 1 and detects the temperature of the roller surface, and a second temperature detecting means which comes into contact with the external heating roller 3 and detects the temperature of the roller surface 7 to detect the surface temperature of each roller.
[0017]
Based on these detection results, the heaters 4 and 5 are turned on so that the surface temperature of each roller becomes a predetermined temperature (fixing roller 1: 170 ° C., external heating roller 3: 200 ° C. in this example).・ Off is controlled.
[0018]
Further, when the recording material 8 on which the unfixed toner 9 is formed passes through the fixing roller 1 and the pressing portion (nip portion) of the pressing roller 2 which rotates while pressing against the fixing roller 1, heat is removed from the fixing roller 1 to fix the fixed image. Get.
[0019]
However, in the above configuration, even when the supply interval of the recording material is temporarily changed due to image adjustment or the like during the continuous copying operation, the heater 4 inside the fixing roller 1 and the heater 5 from the external heating roller 3 generate heat. The first temperature detecting means 6 which detects the surface temperature of the fixing roller 1 detects a predetermined temperature (170 ° C. in this example), so that the heater 4 inside the fixing roller 1 is turned off. I will.
[0020]
That is, the temperature inside the fixing roller 1 decreases, but the surface temperature of the fixing roller 1 is maintained at a predetermined temperature by the external heating roller 3.
[0021]
In such a situation, when the copying operation starts again and returns to the normal recording material supply interval, the recording material removes heat from the surface of the fixing roller 1 and the surface temperature of the fixing roller 1 becomes lower than a predetermined temperature (170 ° C.). Only after that, the heater 4 inside the fixing roller is turned on. However, the heater 4 causes a time lag until the temperature inside the fixing roller 1 is increased, and as a result, the temperature of the fixing roller 1 is reduced.
[0022]
Such a problem of the temperature control may occur in a heating device for performing a surface treatment on the sheet on which the porous polymer layer is formed.
[0023]
[Problems to be solved by the invention]
As described above, in a heating device having a heating source inside and outside a heating roller, temperature control is insufficient. In addition, when the temperature control is insufficient, the quality of an image to be formed is adversely affected.
[0024]
An object of the present invention is to provide a heating device for improving the accuracy of temperature control and an image forming device for improving the image quality.
[0025]
[Means for Solving the Problems]
In order to achieve the above object, in a heating apparatus according to the present invention, in a configuration in which a first heating source is provided inside a heating roller and a second heating source is provided outside the heating roller, a second heating source is provided. Is configured such that it can be moved toward and away from the surface of the heating roller by a driving unit, and the contact and separation operation is controlled by a drive control unit in accordance with the sheet conveyance status.
[0026]
Here, since the first heating source heats the heating roller from the inside of the heating roller, there is an advantage that the entire roller can be uniformly heated, but a disadvantage that a time lag until the roller surface reaches a desired temperature is relatively long. Having.
[0027]
On the other hand, the second heating source directly heats a part of the surface of the heating roller, and thus has an advantage that a time lag for bringing the roller surface to a desired temperature is short, but has a disadvantage that the entire roller cannot be uniformly heated.
[0028]
Since the heating device of the present invention includes both the first heating source and the second heating source, by compensating for each other's disadvantages, the heating device uniformly heats the entire heating roller and a time lag for bringing the roller surface to a desired temperature. Can be shortened.
[0029]
In the present invention, the drive control means controls the contact / separation operation of the second heating source with respect to the surface of the heating roller.
[0030]
Therefore, it is possible to form a state in which the second heating source is kept away from the surface of the heating roller.
[0031]
Accordingly, the heating roller is not affected by the second heating source (or is less affected by the heating source), that is, it can be set to a temperature heated by only the first heating source.
[0032]
Therefore, the first heating source can be controlled so as not to be affected by the second heating source or to be less affected by the second heating source, and the accuracy of the temperature control can be improved. That is, when the heating roller is affected by being heated by the second heating source, it may be erroneously detected that the desired temperature is achieved even if the heating by the first heating source is insufficient. However, by eliminating the influence of the second heating source, such erroneous detection can be prevented, and thereby the temperature control can be improved.
[0033]
A specific configuration for controlling each heating source will be described.
[0034]
First temperature detecting means for detecting the surface temperature of the heating roller is provided. When the temperature detected by the detecting means is equal to or less than a predetermined value, a first heating source provided inside the heating roller is provided. Is turned on, and if it is equal to or greater than the predetermined value, the first heating source is controlled to be turned off.
[0035]
Further, a second temperature detecting means for detecting a surface temperature of a second heating source provided outside the heating roller is provided, and when the temperature detected by the detecting means is equal to or less than a predetermined value, The second heating source is turned on, and if it is equal to or more than the predetermined value, the second heating source is controlled to be turned off.
[0036]
By performing such control, the surface temperature of the heating roller and the surface temperature of the second heating source can be kept constant.
[0037]
Here, the “predetermined predetermined value” which is a threshold value for turning on or off each heating source is a predetermined temperature itself or a value converted into the temperature (for example, temperature detection Output voltage value output from the means). In addition, the predetermined value may be determined in a range other than one value. That is, when the predetermined value is set in the range, there is a difference between the threshold value when the heating source is turned on from off and the threshold value when the heating source is turned on from off.
[0038]
In addition, turning off the heating source means not only stopping the function of the heating source so that the heating operation is not completely performed, but also comparing the heating function with turning on the heating source. (Reducing the output).
[0039]
In the present invention, as described above, the drive control means controls the contact / separation operation of the second heating source with respect to the heating roller surface, so that the second heating source is separated from the heating roller surface. The state can now be formed.
[0040]
Accordingly, since the heating roller is not affected by the second heating source or has little effect, it is possible to set the temperature to a temperature heated only by the first heating source. In other words, when affected by the second heating source, even if the internal temperature of the heating roller is insufficient, the surface temperature of the heating roller is increased by the second heating source. Therefore, if the temperature detected by the first temperature detecting means for detecting the surface temperature of the heating roller is equal to or higher than a predetermined value, the first heating source is turned off. In addition, heating by the first heating source is not performed.
[0041]
On the other hand, in the case of the present invention, by keeping the second heating source away from the surface of the heating roller, the heating roller is not affected by the second heating source or its influence is reduced. It is possible to appropriately control the first heating source.
[0042]
Here, the control for separating the second heating source from the heating roller is performed according to the sheet conveyance status, and a specific case will be described.
[0043]
As described above, the reason why the second heating source is separated from the heating roller is that the surface temperature of the heating roller is reduced by the second heating source even though the internal temperature of the heating roller is lower than a desired temperature. This is for avoiding a state where the temperature is maintained at a desired temperature.
[0044]
Therefore, when such a state can occur, control may be performed to separate the second heating source from the heating roller.
[0045]
Such a state occurs when a large amount of heat is taken from the heating roller. For example, when a sheet is continuously conveyed, a large amount of heat is taken by the sheet.
[0046]
Therefore, the sheet interval of the continuously conveyed sheets (which may be based on the distance between the trailing end of the sheet and the leading end of the succeeding sheet or may be based on the time between them) is set to a predetermined value. If it exceeds, it is preferable to perform control for separating the second heating source from the heating roller.
[0047]
With this configuration, the sheet is continuously conveyed, and in a state where the internal temperature of the heating roller is lowered, then, while the sheet is not conveyed for a certain period or more, the second heating source is separated from the heating roller. By doing so, the control of the first heating source is not affected by the second heating source, and the internal temperature of the heating roller can be set to a desired temperature. Thus, the sheet conveyed thereafter can be sufficiently heated.
[0048]
Here, if the surface temperature of the heating roller does not reach a certain temperature, it is not preferable to separate the second heating source from the heating roller. In a case where the temperature exceeds a predetermined value and the surface temperature of the heating roller exceeds a predetermined value, it is more preferable to perform control for separating the second heating source from the heating roller. .
[0049]
By applying the heating device according to the present invention configured as described above as a fixing device in an image forming apparatus, or by applying it as a device for performing a surface treatment of a sheet having a porous polymer layer, The quality of the formed image is improved.
[0050]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless otherwise specified. Absent.
[0051]
The heating device according to the embodiment of the present invention is applied to an image forming apparatus such as a copying machine. However, since the image forming apparatus is a known technique, a detailed description thereof is omitted, and the heating apparatus is simply described. explain.
[0052]
In the following embodiments, a case will be described in which a heating device is applied as a so-called fixing device provided in an electrophotographic image forming apparatus.
[0053]
To briefly explain the configuration in this case, a fixing device is used to form an unfixed toner image on a sheet by a known electrophotographic process, and then heat and press the sheet to fix the toner image. It is provided.
[0054]
Note that a heating device as a fixing device described below can be applied as it is to a surface treatment device for performing a surface treatment of a sheet having a porous polymer layer formed on the surface.
[0055]
To briefly explain the configuration in this case, an image is formed on a sheet having a porous polymer layer by a so-called inkjet method, and then, the sheet is heated to melt the porous polymer layer. A surface treatment device is provided to perform the surface treatment.
[0056]
(First Embodiment)
With reference to FIGS. 1 to 4, a fixing device as a heating device according to a first embodiment of the present invention and an image forming apparatus provided with the fixing device will be described.
[0057]
First, an image forming apparatus provided with a fixing device will be described with reference to FIGS. 2 and 3 using a four-drum laser beam printer (hereinafter simply referred to as a printer) having a plurality of optical scanning units as an example. FIG. 2 is a schematic sectional view of the entire image forming apparatus according to the present embodiment. FIG. 3 is an enlarged view of an image forming process part in FIG.
[0058]
The printer shown in FIG. 2 includes an image forming station (Pa, Pa) serving as an image forming unit including a developing device and the like around an electrophotographic photosensitive member (hereinafter, referred to as a “photosensitive drum”) serving as a latent image carrier. Pb, Pc, and Pd) are provided. Then, an image formed on each of the image forming stations on the photosensitive drum is a recording material (hereinafter, referred to as a transfer sheet) such as a transfer sheet (sheet) on a transport unit that moves and passes adjacent to the photosensitive drum. It is configured to be transferred to P.
[0059]
As shown in FIG. 3, photosensitive drums 1a, 1b, 1c, 1d are arranged on image forming stations Pa, Pb, Pc, Pd for forming images of magenta, cyan, yellow, and black, respectively. Each photosensitive drum is rotatable in the direction of the arrow.
[0060]
Further, around the photosensitive drums 1a, 1b, 1c, 1d, potential control devices 11a, 11b, 11c, 11d for controlling the charging potentials of the chargers 12a, 12b, 12c, 12d and the photosensitive drums, and developing. The devices 2a, 2b, 2c, 2d, the on-photosensitive-drum image density measuring devices 21a, 21b, 21c, 21d for controlling the image density, and the cleaners 4a, 4b, 4c, 4d are sequentially arranged along the rotation direction of the photosensitive drum. It is arranged.
[0061]
A transfer unit 3 is provided below each photosensitive drum. The transfer section 3 has a transfer bell 31 as a recording material conveying means common to each image forming station and transfer chargers 3a, 3b, 3c, 3d.
[0062]
In the printer as described above, the transfer paper P supplied from the paper supply cassette 61 as the recording material supply means shown in FIG. 2 is supported on the transfer belt 31 and conveyed to each image forming station, where The toner images of each color formed on the drum are sequentially transferred. When the transfer step is completed, the transfer paper P is separated from the transfer belt 31 and is conveyed to the fixing device 5 by the conveyance belt 62 serving as recording material guiding means.
[0063]
Next, the fixing device 5 will be described in more detail with reference to FIG.
[0064]
The fixing device 5 mainly includes a fixing roller 51 as a heating roller having a heater 54 therein as a first heating source, and a nip for forming a nip for nipping and conveying the recording material between the fixing roller 51 and the fixing roller 51. The image forming apparatus includes a pressure roller 52 and an external heating roller 53 disposed outside the fixing roller 51 and serving as a second heating source for heating the roller surface while being in contact with the surface of the fixing roller 51. The external heating roller 53 has a heater 55 inside.
[0065]
As a specific example of the fixing roller 51, an iron core metal cylinder having a thickness of 3 [mm] is coated with HTV silicon rubber having a thickness of 6 [mm] and JIS-A hardness of 30 to 60 degrees. Is set to 50 [mm]. Further, for example, a layer of PTFE 20 to 70 [μm] or PFA 50 to 100 [μm] may be provided in order to enhance the surface releasability.
[0066]
As a specific example of the pressure roller 52, an aluminum cylinder having an outer diameter of 50 [mm] and a thickness of 2 [mm] and having a surface layer coated with a fluororesin in order to enhance releasability is used. it can.
[0067]
As a specific example of the external heating roller 53, an aluminum cylinder having an outer diameter of 28 [mm] and a thickness of 2 to 4 [mm], in which a fluororesin is provided on a surface layer to enhance releasability, is used. be able to. Further, it is preferable that the inner surface of the cylinder be coated with black paint (each product name is also different).
[0068]
As the heaters 54 and 55, halogen lamps disposed along the rotation axis direction at the central portions in the fixing roller 51 and the external heating roller 53 can be used.
[0069]
Further, a first temperature sensor 56 as a first temperature detecting means is provided at a central portion along the rotation axis direction of the fixing roller 51 so as to contact the fixing roller surface. The surface temperature of the fixing roller 51 can be detected by the first temperature sensor 56.
[0070]
Further, a second temperature sensor 57 as a second temperature detecting means is provided on the external heating roller 53 so as to abut on the surface of the external heating roller 3 at the center in the roller rotation axis direction. The surface temperature of the external heating roller 3 can be detected by the second temperature sensor 57.
[0071]
The detection information of each of these temperature sensors is input to a temperature control device (not shown).
[0072]
The maximum electric power supplied to the heater is, for example, 800 to 2000 [W] in total, and the electric power is supplied based on the detection signals of the first temperature sensor 56 and the second temperature sensor 57. Is automatically controlled so that the temperature of the surface becomes a predetermined constant temperature.
[0073]
In addition, as a specific example of the first temperature sensor 56 and the second temperature sensor 57, an element such as a thermistor or a thermocouple can be used.
[0074]
In the present embodiment, the external heating roller 53 is configured to be able to contact and separate from the roller surface of the fixing roller 51. In the present embodiment, the contact / separation cam 58 is used as a driving means for performing the contact / separation operation. Further, a contact / separation control device 59 is provided as drive control means for controlling the contact / separation cam 58.
[0075]
With the above configuration, when the transfer paper P is conveyed, the fixing roller 51 and the pressure roller 52 rotate at a constant speed, and at the same time, the contact / separation cam 58 is rotated by the contact / separation control device 59 so that the external heating roller 53 is moved. The fixing roller 51 is brought into contact with the fixing roller 51. When the transfer paper P passes between the fixing roller 51 and the pressure roller 52, the transfer paper P is pressed and heated with a substantially constant pressure from both the front and back surfaces, and the unfixed toner image on the transfer paper surface is removed. It is fused and fixed, and a full-color image is formed on the transfer paper P.
[0076]
The transfer paper P on which the image is fixed is separated from the pressure roller 52 by the lower separation claw, and is discharged outside the machine.
[0077]
In the image forming apparatus configured as described above, the passage timing of the recording material (transfer paper or sheet) may be temporarily delayed during continuous copying due to control such as image density adjustment and potential control on the drum. .
[0078]
As described above, in order to suppress a decrease in the temperature of the fixing roller that occurs when the recording material is temporarily stopped and then restarted, in the embodiment of the present invention, the contact and separation of the external heating roller 53 are performed. Control is performed as follows.
[0079]
FIG. 1 shows the state of the control of contact and separation of the external heating roller and the change of the surface temperature of each roller in the fixing device according to the first embodiment of the present invention.
[0080]
In the present embodiment, the temperature of each roller surface is detected by the first temperature sensor 56 and the second temperature sensor 57 shown in FIG.
[0081]
When the detected temperature is higher than a predetermined temperature control point, control is performed to repeat the operation of turning off the heater and turning on the heater when the temperature becomes low.
[0082]
Thus, in the area A (in a state where copying is possible and no sheet is conveyed) in FIG. 1, the roller surface temperature of each roller is controlled within a certain fixed width range.
[0083]
Then, when copying is started, the external heating roller 53 comes into contact with the fixing roller 51, and thereafter, the sheet is conveyed, and the sheet loses heat. Region B in FIG. 1).
[0084]
Then, after a while, the control for temporarily stopping the continuous copy operation is started as described above (C area in FIG. 1).
[0085]
Here, if the surface temperature of the fixing roller 51 exceeds a certain value (in this case, 170 ° C.), the heater 54 is turned off, so that the internal temperature becomes insufficient, and the temperature of the fixing roller drops when restarting. I will.
[0086]
Therefore, in the embodiment of the present invention, the control is performed such that the external heating roller 53 is separated when the recording material is temporarily stopped, that is, when the interval between the continuous recording materials becomes longer than that during normal image formation.
[0087]
By performing such control, the surface temperature of the fixing roller 51 is not affected by the external heating roller 53 or is less affected. That is, the fixing roller 51 is heated only by the heater 54 provided therein.
[0088]
Accordingly, it is possible to suppress a phenomenon that only the surface of the fixing roller 51 has a predetermined temperature (here, 170 ° C.) and the temperature inside the fixing roller drops.
[0089]
Then, when continuous copying starts again, the external heating roller 53 is brought into contact with the fixing roller 51 again, so that the influence of heat being taken away by the conveyed sheet can be reduced, and the temperature of the fixing roller 51 can be reduced. It is possible to perform stable control (D region in FIG. 1).
[0090]
As described above, in the system in which the copying operation is temporarily stopped during the continuous copying, the accuracy of the temperature control can be improved by controlling the external heating roller to be separated from the fixing roller during the stop. it can. This makes it possible to always obtain a good copy image.
[0091]
(Second embodiment)
FIG. 5 shows a second embodiment of the present invention. In the first embodiment, whether or not the external heating roller is separated from the fixing roller is determined only by the interval of the conveyed sheets.
[0092]
However, it is not desirable to separate the external heating roller from the fixing roller even though the surface temperature of the fixing roller has not reached a certain temperature.
[0093]
Therefore, in the present embodiment, a configuration is described in which both the sheet interval and the surface temperature of the fixing roller are considered as factors for determining whether or not to separate the external heating roller from the fixing roller.
[0094]
In addition, since the basic configuration and operation of the image forming apparatus and the fixing device are the same as those of the first embodiment, the description thereof is omitted.
[0095]
FIG. 5 shows how the external heating roller is controlled to contact and separate and how the surface temperature of each roller changes in the fixing device according to the second embodiment of the present invention.
[0096]
In the first embodiment, the separation of the external heating roller is controlled by changing the interval of the recording material that continuously passes through the fixing device. However, in the present embodiment, the interval of the recording material changes. Further, when the output from the temperature detecting means of the fixing roller is equal to or more than a predetermined value, the separation control is performed.
[0097]
In the present embodiment, as shown in FIG. 5, when the control enters the continuous copy operation area B from the standby area A and then enters a control for temporarily stopping the continuous copy operation, the surface temperature of the fixing roller becomes a predetermined temperature (the Until the temperature reaches 170 ° C. in the embodiment, the external heating roller keeps the contact state (region C). Then, when the temperature of 170 ° C. is detected, the separation control of the external heating roller 53 is performed (D area). This makes it possible to quickly stabilize the temperature of the fixing roller to a predetermined temperature, so that it is possible to cope with a short stop time.
[0098]
The embodiments of the present invention also include the following embodiments.
[0099]
(Embodiment 1)
A heating roller (e.g., corresponding to the fixing roller 51) having a first heating source (e.g., corresponding to the heater 54) therein;
Pressing means (for example, corresponding to the pressing roller 52) for forming a nip for conveying the sheet while nipping the sheet between the heating roller and the heating roller;
A second heating source (e.g., corresponding to the external heating roller 53) for heating the heating roller while abutting the heating roller surface;
Driving means (e.g., corresponding to the contact / separation cam 58) for causing the second heating source to move toward and away from the surface of the heating roller;
A heating device, comprising: a drive control unit (e.g., corresponding to the contact / separation control device 59) that controls the drive unit in accordance with a sheet conveyance state.
[0100]
(Embodiment 2)
A heating roller (e.g., corresponding to the fixing roller 51) having a first heating source (e.g., corresponding to the heater 54) therein;
First temperature detecting means (for example, corresponding to the first temperature sensor 56) for detecting the surface temperature of the heating roller;
A first heating unit that turns on the first heating source when the temperature detected by the first temperature detection unit is equal to or lower than a predetermined value, and turns off the first heating source when the temperature is equal to or higher than the predetermined value; Source control means;
Pressing means (for example, corresponding to the pressing roller 52) for forming a nip for conveying the sheet while nipping the sheet between the heating roller and the heating roller;
A second heating source for heating the heating roller while abutting against the heating roller surface;
Second temperature detecting means (for example, corresponding to the second temperature sensor 57) for detecting the surface temperature of the second heating source,
A second heating unit that turns on the second heating source when the temperature detected by the second temperature detection unit is equal to or lower than a predetermined value, and turns off the second heating source when the temperature is equal to or higher than the predetermined value; Source control means;
Driving means (e.g., corresponding to the contact / separation cam 58) for causing the second heating source to move toward and away from the surface of the heating roller;
A heating device, comprising: a drive control unit (e.g., corresponding to the contact / separation control device 59) that controls the drive unit in accordance with a sheet conveyance state.
[0101]
(Embodiment 3)
When the sheet interval of the continuously conveyed sheet exceeds a predetermined value, the drive control unit performs control to separate the second heating source from a heating roller. 3. The heating device according to 1 or 2.
[0102]
(Embodiment 4)
The drive control means is provided when the sheet interval of the continuously conveyed sheets exceeds a predetermined value, and when the surface temperature of the heating roller exceeds a predetermined value. 3. The heating apparatus according to claim 1, wherein control is performed to separate the second heating source from a heating roller.
[0103]
(Embodiment 5)
Image forming means for forming an unfixed toner image on a sheet (e.g., corresponding to an image forming station (Pa, Pb, Pc, Pd)), and a sheet on which an unfixed toner image is formed by the image forming means Transport means for transporting the heating device according to any one of embodiments 1 to 4,
An image forming apparatus, wherein an unfixed toner image formed on a conveyed sheet is heated and fixed by the heating device.
[0104]
(Embodiment 6)
An image forming means for forming an image on a sheet having a porous polymer layer, and a sheet on which an image is formed by the image forming means is conveyed to the heating device according to any one of embodiments 1 to 4. Transport means, and
An image forming apparatus, wherein the conveyed sheet is heated by the heating device to melt the porous polymer layer and perform a surface treatment.
[0105]
【The invention's effect】
As described above, according to the heating device of the present invention, the accuracy of temperature control is improved. According to the image forming apparatus provided with the heating device of the present invention, the image quality is improved.
[Brief description of the drawings]
FIG. 1 is a time chart illustrating a state of control of contact and separation of an external heating roller and a change in a surface temperature of each roller in a fixing device according to a first exemplary embodiment of the present invention.
FIG. 2 is a schematic sectional view of the entire image forming apparatus according to the embodiment of the present invention.
FIG. 3 is an enlarged view of an image forming process part in FIG. 2;
FIG. 4 is a main configuration diagram of a fixing device according to the embodiment of the present invention.
FIG. 5 is a time chart illustrating a state of control of contact and separation of an external heating roller and a change in a surface temperature of each roller in a fixing device according to a second exemplary embodiment of the present invention.
FIG. 6 is a main configuration diagram of a fixing device according to the related art.
[Explanation of symbols]
51 Fixing roller
52 pressure roller
53 External heating roller
54, 55 heater
56 1st temperature sensor
57 2nd temperature sensor
58 Connecting / disconnecting cam
59 Contact / separation control device

Claims (1)

A heating roller having a first heating source therein;
Pressing means for forming a nip for conveying the sheet while nipping the sheet between the heating roller,
A second heating source for heating the heating roller while abutting against the heating roller surface;
Driving means for moving the second heating source toward and away from the surface of the heating roller;
A heating control unit that controls the driving unit in accordance with a sheet conveyance state.

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