JP2009036930A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which enables the low heat conductivity member of a heat transfer roller to come into sure contact with the surface of a fixing roller, when the movement of the surface of the fixing roller is stopped, and to provide an image forming apparatus provided with the fixing device. <P>SOLUTION: In the heat transfer roller 11, a heat insulating layer 12 made of a heat resistant resin such as polyimide resin is formed on the surface of a metal core which serves as a rotating shaft 11a and is made of metal such as aluminum. On the surface of the heat insulating layer 12, a heat transfer layer 15 where a high conductivity member 13 which is divided equally into sixteen in a peripheral direction, has predetermined heat conductivity (236W/m K) and is made of aluminum metal and the low conductivity member 14 which is made of iron metal and has heat conductivity (83.5W/m K) smaller than that of the high conductivity member 13 are alternately arranged is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a fixing unit that heats an unfixed toner image on a recording medium and a pressing unit that presses the fixing unit, and at least the fixing unit includes a surface of the fixing unit and a surface of the pressing unit. The present invention relates to a fixing device that heats and pressurizes the unfixed toner image while moving the surface thereof and fixes the image on a recording medium, and an image forming apparatus including the fixing device.

In an image forming apparatus using an electrophotographic system, a heat roller type fixing device is often used as a fixing device for fixing an unfixed toner image transferred onto a recording medium such as recording paper on the recording medium. This fixing device has a heat source inside, and press-rotates a pressure roller and a fixing roller formed of a material having releasability with respect to toner, such as silicon rubber or fluorine resin, so that the pressure-contact portion of both rollers is The unfixed toner image on the recording medium passing through the nip is fixed by heating and pressing. In this heat roller type fixing device, since the surface of the fixing roller and the unfixed toner image on the recording medium come into contact with each other under pressure, the thermal efficiency when fusing the unfixed toner image on the recording medium is extremely good. Fast fixing can be performed and is very effective in a high-speed electrophotographic copying machine.
However, when an unfixed toner image is continuously formed on a recording medium having a size smaller than the fixing roller width (axial direction: length in the longitudinal direction) and passed through the fixing device, the fixing does not contact the recording medium. When the temperature of the roller end is excessively increased, the fixing roller and the pressure roller surface layer are deteriorated at an early stage. Further, since the heat energy generated from the heating source is used to increase the temperature of the portion where the recording paper does not pass, the energy efficiency becomes very poor.
In order to deal with such problems, the heat of the regions on both ends of the fixing roller is recorded by bringing a high heat conductive roller made of a material having good heat conductivity such as aluminum into contact with the surface of the fixing roller. It has been proposed that the temperature distribution on the surface of the fixing roller is made substantially uniform in the axial direction by conduction to a region where heat is taken away in contact with the medium. (For example, see Patent Document 1)

6A and 6B are diagrams illustrating a schematic configuration of a conventional fixing device, in which FIG. 6A is a cross-sectional view, and FIG. 6B is a side view. The fixing device includes a fixing roller 1 that incorporates a halogen heater 3 in the center and rotates in the direction of arrow A, and a pressure roller 2 that presses the fixing roller 1 and rotates in the direction of arrow B. A transfer sheet 5 as a recording medium having an unfixed toner image 6 on the surface guided and conveyed by the guide 8 from the direction of the arrow C is heated and pressed by the fixing roller 1 and the pressure roller 2 to be transferred. A toner image is fixed on the top.
In this case, as shown in FIG. 6B, when the transfer paper 5 having a width of W is sandwiched between the fixing roller 1 and the pressure roller 2, the surface of the fixing roller 1 that comes into contact with the transfer paper 5 is used. In the area X1, the heat of the surface of the fixing roller 1 is absorbed by the transfer paper 5 and the temperature decreases, whereas the areas X2 and X3 at the end of the fixing roller 1 that do not contact the transfer paper 5 are in the transfer paper. Since the heat is not absorbed by 5, the temperature rises and the surface layers of the fixing roller 1 and the pressure roller 2 are easily deteriorated, and the energy efficiency is poor. Such a problem is that a temperature detection member 4 for detecting the surface temperature of the fixing roller 1 is installed in the center of the fixing roller 1 in the axial direction, and the surface temperature of the fixing roller 1 detected by the temperature detection member 4 is controlled. In this case, the temperature difference between the center portion and the end portion of the fixing roller 1 becomes large and becomes remarkable.

Therefore, in this fixing device, a heat transfer roller provided on the surface of the fixing roller 1 with a heating means and a heat pipe disposed in the hollow cylindrical tube from the material having good heat conductivity such as aluminum in the axial direction. 9 is brought into contact with the fixing roller 1 to rotate. By doing so, the heat absorbed in the high temperature regions X2 and X3 is conducted and released to the low temperature region X1, so that the temperature distribution on the surface of the fixing roller 1 is made substantially uniform in the axial direction. It has become.
When such a heat transfer roller 9 is used, the temperature distribution on the surface of the fixing roller 1 can be boiled almost uniformly when the transfer paper 5 is placed in the paper passing state. Deterioration of the surface layer of the roller 2 can be suppressed. However, when the transfer sheet 5 is not passed between the fixing roller 1 and the pressure roller 2 and the rotation of the fixing roller 1 is stopped, the high heat transfer roller 9 absorbs heat from the surface of the fixing roller 1 and Since the surface temperature of the fixing roller 1 is lowered, the surface temperature of the fixing roller 1 has to be raised when the transfer paper 5 is passed, and the energy efficiency is not good.
In order to improve such a problem, the inventor uses a heat transfer roller 9 in which a high heat conductivity material and a low heat conductivity material are alternately arranged on the outer periphery of a resin heat insulating layer. The pressure roller 2 is brought into contact with the pressure roller 2, rotated with the rotation of the pressure roller 2, and the pressure roller 2 is brought into contact with the pressure roller 2 when the rotation of the pressure roller is stopped. It was proposed to suppress the absorption of heat from the surface of No. 2 to suppress the decrease in the surface temperature of the pressure roller and the fixing roller. (See Patent Document 2)
JP 2005-99136 A JP 2007-65416 A

However, in the device described in Patent Document 2, it is difficult to appropriately control the temperature of the end surface of the fixing roller, which is a heating source, in order to bring the heat transfer roller into contact with the pressure roller 2. Since the transmission roller rotates along with the rotation of the pressure roller 2, the low thermal conductivity material of the heat conduction roller does not properly come into contact with the surface of the pressure roller 2 when the rotation of the pressure roller stops. There is a problem that the heat insulating action may not be sufficiently exhibited.
The present invention has been made in consideration of the above circumstances, and when the movement of the surface of the fixing means such as the fixing roller is stopped, the low thermal conductivity member of the heat transfer roller surely contacts the surface of the fixing roller. It is an object of the present invention to provide a fixing device and an image forming apparatus including the same.

In order to solve the above problems, the invention described in claim 1 includes a fixing unit that heats an unfixed toner image on a recording medium, and a pressing unit that presses the fixing unit, and the surface of the fixing unit. In a fixing device that heats and pressurizes the unfixed toner image while moving at least the surface of the fixing unit with the surface of the pressure unit, and fixes the toner image on a recording medium, a peripheral surface abuts on the surface of the fixing unit. A heat transfer roller is disposed, and the heat transfer roller is adjacent to a member having a predetermined heat conductivity and a member having a smaller heat conductivity along the circumferential direction of the heat transfer roller. The members having different heat conductivity of the heat transfer layer are extended along the axial direction of the heat transfer roller, and the heat transfer roller is rotated by driving means. Driven When the heat transfer roller is rotated by the drive unit, the heat transfer roller includes a position detection unit that detects a circumferential position of a member having a different heat transfer coefficient, and when the movement of the surface of the fixing unit is stopped, A position detecting unit detects a position of a peripheral surface of the member having a low thermal conductivity, and includes a control unit that controls the driving unit so as to contact the surface of the fixing unit based on the detection signal. And
According to a second aspect of the present invention, in the fixing device according to the first aspect, a heat insulating layer is disposed between the heat transfer layer of the heat transfer roller and the rotating shaft.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect, when a recording medium having a maximum allowable width as a size width in the longitudinal direction of the fixing unit is transferred to the surface of the fixing unit, The rotation of the heat transfer roller is controlled by the control means so that only the peripheral surface of the heat transfer roller having a small thermal conductivity contacts the surface of the fixing means.
According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the member having a predetermined thermal conductivity of the heat transfer roller is made of an aluminum-based material, and the predetermined heat The member having a lower thermal conductivity than the member having the conductivity is characterized by being composed of at least one material selected from iron-based materials, resin materials, rubber materials, and ceramic materials.
According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the heat transfer layer of the member having a smaller thermal conductivity than the member having the predetermined thermal conductivity. A space layer is formed.
According to a sixth aspect of the present invention, in the fixing device according to the fifth aspect, the space is a space having an atmospheric pressure of 1/500 or less of the atmospheric pressure.
According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising the fixing device according to any one of the first to sixth aspects.

  According to the present invention, the heat transfer roller whose peripheral surface is in contact with the surface of the fixing unit is disposed, and the heat transfer roller has a predetermined thermal conductivity along the circumferential direction of the heat transfer roller. And a member having different thermal conductivity adjacent to each other, and members having different thermal conductivities of the heat transfer layer are respectively arranged along the axial direction of the heat transfer roller. Position detection for detecting a circumferential position of a member having a different heat transfer coefficient when the heat transfer roller is rotated by a drive unit and the heat transfer roller is rotated by the drive unit. And when the movement of the surface of the fixing unit is stopped, the position detecting unit detects the position of the peripheral surface of the member having a low thermal conductivity, and based on the detection signal, the surface of the fixing unit is detected. To abut By providing the control means for controlling the drive means, when the movement of the surface of the fixing means such as the fixing roller is stopped, the low thermal conductivity member of the heat transfer roller is surely brought into contact with the surface of the fixing roller. It is possible to provide a fixing device that can be used and an image forming apparatus including the same.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view conceptually showing an image forming apparatus such as an electrophotographic copying machine or printer according to the present invention. The image forming apparatus according to the present embodiment mainly includes a reading unit 111 that reads a document, an image forming unit 112 that forms an image, an automatic document feeder (ADF) 113, and a document on which documents sent from the ADF 113 are stacked. A paper discharge tray 114, a paper supply unit 119 including paper supply cassettes 115 to 118, and a paper discharge unit (discharge tray 120) for stacking recording paper are configured.
When the document P is set on the document table 121 of the ADF 113 and an operation unit (not shown), for example, a print key is pressed, the uppermost document P is sent in the direction of the arrow B 1 by the rotation of the pickup roller 122. Then, by the rotation of the document conveying belt 123, the paper is fed onto the contact glass 124 fixed to the image reading unit 111 and stops there. The image of the document P placed on the contact glass 124 is read by a reading device 125 positioned between the image forming unit 112 and the contact glass 124. The reading device 125 includes a light source 126 that illuminates the original P on the contact glass 124, an optical system 127 that forms an original image, a photoelectric conversion element 128 that includes a CCD that forms an original image, and the like. After the image reading is completed, the document D is transported in the direction of arrow B2 by the rotation of the transport belt 123 and discharged onto the paper discharge tray 114. Thus, the original P is fed one by one onto the contact glass 124 and the original image is read by the reading device 125.

  On the other hand, inside the image forming unit 112, a drum-shaped photoreceptor 130 as an image carrier is disposed. The photoconductor 130 is driven to rotate clockwise in the drawing, and the charging device 131 charges the surface to a predetermined potential. Further, the writing unit 132 emits laser light L that is light-modulated in accordance with image information read by the reading device 125, and the surface of the charged photosensitive member 130 is exposed with the laser light L, whereby the photosensitive member is exposed. An electrostatic latent image is formed on the surface 130. The electrostatic latent image is developed into a toner image on the surface of the photoconductor 130 by toner supplied from the development device 133 to the photoconductor 130 when passing through the development device 133. The unfixed toner image developed on the surface of the photoreceptor 130 in this manner is transferred to the recording device 130 between the photoreceptor 130 and the transfer device 134 by the transfer device 134 facing the surface of the photoreceptor 130. It is transferred to transfer paper P that is a medium. The surface of the photoreceptor 130 after the toner image transfer is cleaned by removing the residual toner by the cleaning device 135.

The plurality of paper feed cassettes 115 to 118 arranged at the lower part of the image forming unit 112 contain transfer paper P of different sizes, and the transfer paper P is transferred from any of the paper feed cassettes 115 to 118 in the direction of arrow B3. The unfixed toner image formed on the surface of the photoreceptor 130 as described above is transferred onto the surface of the transfer paper P. Next, the transfer paper P passes through the fixing device 10 in the image forming unit 112 as indicated by an arrow B4, and the unfixed toner image transferred onto the surface of the transfer paper P by the action of heat and pressure is fixed. The transfer paper P that has passed through the transport roller pair 136 is transported by the discharge roller pair 137, discharged to the paper discharge tray 120 as shown by an arrow B5, and stacked.
In the image forming apparatus according to the present embodiment, an example in which a single photosensitive member 130 for black is provided as a photosensitive member is not limited to such a monochrome image forming device, but yellow, magenta, Needless to say, the image forming apparatus may form a color toner image using a plurality of toners such as cyan and black.

In the present invention, the configuration of the fixing device 10 is characteristic. Next, a fixing device according to an embodiment of the present invention will be described with reference to the drawings.
2A and 2B are diagrams showing a configuration of a fixing device according to an embodiment of the present invention, in which FIG. 2A is a schematic sectional view, and FIG. 2B is a side view. In the present embodiment, the fixing device includes a fixing roller 1 that is a fixing unit including a halogen heater 3 that is a heating source, a pressure roller 2 that is a pressing unit that is pressed against the fixing roller 1, and the fixing roller 1. A temperature detecting member 4 such as a thermistor for detecting the temperature of the fixing roller 1 and a heat transfer roller 11 pressed against the surface of the fixing roller 1. The heater 3 is controlled to have a constant temperature by a temperature control device based on a temperature detected by a temperature detection member 4 (not shown).
The fixing roller 1 is formed with an elastic layer such as silicon rubber on the outer periphery of a cylindrical tube made of, for example, aluminum having good thermal conductivity, and has a releasing property such as fluororesin (PFTE) on the surface of the elastic layer. A film of material is formed. At both ends, a rotating shaft 1a is formed by projecting a cylindrical tube from the end face, and the rotating shaft 1a is rotated in the direction of arrow A by a driving means 15 such as a motor.
In addition, the pressure roller 2 is formed with an elastic layer made of an elastic material such as silicon rubber on a core metal that becomes the rotation shaft 2 a, and the surface 2 b of the elastic layer is elastically formed with the surface 1 b of the fixing roller 1. A nip portion N is formed that presses and heats and presses the transfer paper 5 having the unfixed toner image 6 therebetween. In the nip portion N, the transfer paper 5 having the unfixed toner image 6 is fed to the surface conveyed from the direction of the arrow C, the unfixed toner 6 is melted, and is fixed to the transfer paper 5 by receiving pressure. The transfer paper 5 is conveyed in the paper discharge direction (arrow B5 direction) by the rotation of the pressure roller that rotates along with the rotation of the fixing roller 1 in the arrow B direction.

In the present embodiment, the temperature detection member 4 is disposed at the longitudinal end of the fixing roller 1 and detects the surface temperature at the end of the fixing roller 1. The heat transfer roller 11 is disposed upstream of the temperature detection member 4 of the fixing roller 1 in the rotation direction of the fixing roller 1 and downstream of the nip portion N between the fixing roller 1 and the pressure roller 2. . The heat transfer roller 11 is disposed at a position avoiding directly above the heater 3 that is a heat source of the fixing roller 1, that is, obliquely above the heater 3.
As shown in FIG. 3, the heat transfer roller 11 has a heat insulating layer 12 made of a heat resistant resin such as a polyimide resin on the surface of a cored bar made of a metal such as aluminum as the rotating shaft 11a. On the surface of the heat insulating layer 12, a high thermal conductivity member 13 made of aluminum metal and a predetermined thermal conductivity (236 W / m · K) divided into 16 parts in the circumferential direction and a high thermal conductivity member 13 made of iron metal. The heat transfer layer 15 in which the low thermal conductivity members 14 having a smaller thermal conductivity (83.5 W / m · K) are alternately arranged is formed. As shown in FIG. 2B, the high thermal conductivity member 13 and the low thermal conductivity member 14 of the heat transfer layer 15 each extend from one end to the end along the axial direction (arrow D direction). The rotating shaft 11a of the heat transfer roller 11 and the rotating shaft 1a of the fixing roller 1 are attached in parallel so that the outer peripheral surface 15a of the heat transfer layer 15 contacts the surface 1b of the fixing roller 1. It has become. Therefore, when the outer peripheral surface 13 a formed of the high thermal conductivity member 13 of the heat transfer layer 15 comes into contact with the surface 1 b of the fixing roller 1, the temperature becomes high without contacting the transfer paper 5 at the end of the fixing roller 1. The heat of the surface 1b of the fixing roller 1 in the areas X2 and X3 is absorbed and cooled by the outer peripheral surface 13a formed by the high thermal conductivity member 13, and comes into contact with the transfer paper 5 of the fixing roller 1 thereby Heat is transferred toward the low temperature region X2, and the surface of the region X2 of the fixing roller 1 is heated.

On the other hand, when the outer peripheral surface 14a formed of the low thermal conductivity member 14 comes into contact with the front surface 1b of the fixing roller 1 and the back surface of the transfer paper 5, the heat absorption from the front surface 1b of the fixing roller 1 is high thermal conductivity. It is smaller than the heat absorption on the outer peripheral surface 13a formed by the index member 13, and is almost insulative, so that a decrease in the surface temperature of the fixing roller 1 is suppressed.
A rotation driving means 18 such as a motor is connected to one of the rotation shafts 11 a of the heat transfer roller 11, and is rotated in the direction of arrow E by the rotation of the rotation driving means 18. Accordingly, by rotation of the heat transfer roller 11, the outer peripheral surface 13a formed of the high thermal conductivity member 13 and the outer peripheral surface 14a formed of the low thermal conductivity member 14 are alternately brought into contact with the surface 1a of the fixing roller 1. As a result, heat absorption and heat insulation by the outer peripheral surface 13a formed by the high thermal conductivity member 13 are alternately generated, and an excessive temperature rise on the end surface of the fixing roller 1 is suppressed. A decrease in the surface temperature of the fixing roller 1 is also appropriately suppressed.

  Further, as shown in FIGS. 4A and 4B, a filler 21 is connected to the other rotary shaft 11a of the heat transfer roller 11. The filler 21 is constituted by a wing-like member 21 a extending radially from the rotary shaft 11 a at a position corresponding to the outer peripheral surface 14 a of the low thermal conductivity member 14 of the heat transfer layer 15 of the heat transfer roller 11. Accordingly, the wing member 14a shields the projection light beam of the photosensor 22 installed with the filler 21 interposed therebetween, thereby detecting the position of the wing member 14a and detecting the position of the wing member 14a, thereby reducing the heat. The outer peripheral surface 14a of the conductivity member 14 is detected. The photosensor 22 is set at a contact position between the surface 1b of the fixing roller 1 and the outer peripheral surface 15a of the heat transfer roller 11, and when the photosensor 22 detects the wing member 14a, the low thermal conductivity. The outer peripheral surface 14 a of the member 14 is in contact with the surface 1 b of the fixing roller 11.

Since the position of the outer peripheral surface 14a of the low thermal conductivity member 14 is detected in this way, the detection means 16 including the position detection means 16a by the filler 21 and the photosensor 22 as shown in FIG. Thus, it is possible to detect the material of the thermal conductivity member at the contact position between the surface 1b of the fixing roller 1 and the outer peripheral surface 15a of the heat transfer roller 11. Therefore, when the material of the outer peripheral surface 15 a at the contact position between the surface 1 b of the fixing roller 1 and the outer peripheral surface 15 a of the heat transfer roller 11 when the rotation of the fixing roller 1 is stopped is the high thermal conductivity member 13. The heat transfer roller 11 is rotated by the driving means 18 so that the outer peripheral surface 15a of the heat transfer roller 11 at the contact position between the surface 1b of the fixing roller 1 and the outer peripheral surface 15a of the heat transfer roller 11 is the outer periphery of the low thermal conductivity member 14. The control unit 17 controls the surface 14a.
As described above, when the unfixed toner image 6 on the transfer sheet 5 is fixed by the fixing device 10 and the rotation of the fixing roller 1 is stopped, the position detection unit 16a causes the surface 1b of the fixing roller 1 and the heat transfer roller 11 to be stopped. The material of the thermal conductivity member at the position of contact with the outer peripheral surface 15a is detected, and the rotation of the heat transfer roller 11 is controlled by the position signal of the position detecting means 16a to always maintain the outer peripheral surface 14a of the low thermal conductivity member 14. Is in contact with the surface 1 b of the fixing roller 1. Therefore, when the rotation of the fixing roller 1 is stopped, the heat absorbing action from the fixing roller 1 by the heat transfer roller 11 is suppressed, and the decrease in the surface temperature of the fixing roller 1 can be suppressed. Although the filler 21 and the photo sensor are used as the position detection means 16a, the material of the heat conductivity member is not limited to this, and the material of the heat conductivity member at the contact position between the surface 1b of the fixing roller 1 and the outer peripheral surface 15a of the heat transfer roller 11 Other configurations may be used as long as they detect the above.

  Further, in the fixing device according to the present embodiment, when the transfer paper 5 uses an allowable width having the maximum size width, for example, A3 size transfer paper 5, the end of the fixing roller 1 as described above is used. Since abnormal temperature rise is unlikely to occur, the heat absorbing action by the outer peripheral surface 13a of the high thermal conductivity member 13 of the heat transfer roller 11 is not required, but rather fixing by the contact between the outer peripheral surface 13a of the high thermal conductivity member 13 and the fixing roller 1. Since the temperature of the roller 1 is lowered, it is preferable that the outer peripheral surface 14 a of the low thermal conductivity member 14 of the heat transfer roller 11 is in contact with the fixing roller 1. Therefore, in the present embodiment, when the transfer paper 5 having such a maximum allowable width is used, at least the surface 1b of the fixing roller 1 and the outer periphery of the heat transfer roller 11 are in contact with the transfer paper 5 at least. The rotation of the heat transfer roller 11 is stopped so that the contact position with the surface 15a becomes the outer peripheral surface 14a of the low thermal conductivity member 14, and only the rear surface of the transfer paper 5 and the outer peripheral surface 14a of the low thermal conductivity member 14 slide. It is possible to make contact.

  Specifically, the detection unit 16 shown in FIG. 2A is provided with a size detection unit 16 b that detects the size of the transfer paper 5 conveyed to the fixing device 10. Based on the detection signal of the size detection means 16b, it is determined whether or not the size of the transfer paper 5 to be used is the maximum allowable size. If yes, the surface 1b of the fixing roller 1 in the detection means 16 and the heat transfer roller are determined. The material of the thermal conductivity member at the contact position is detected by the position detecting means 16a that detects the material of the thermal conductivity member at the contact position with the outer peripheral surface 15a. The position detecting means 16a stops the rotation of the heat transfer roller 11 so that the outer peripheral surface 15a of the heat transfer roller 11 at the contact position becomes the outer peripheral surface 14a of the low thermal conductivity member 14, and the transfer paper 5 is fixed to the fixing roller. Control means so as to maintain the contact between the outer peripheral surface 14a of the low thermal conductivity member 14 and the surface 1b of the fixing roller 1 while applying braking until it passes through the nip portion N between the pressure roller 1 and the pressure roller 2. The drive means 18 is controlled by 17. In addition to the size detection unit 16b and the position detection unit 16a, the detection unit 16 also includes an end detection unit 16c that detects the start and end of the transfer paper 5. The start end of the transfer paper 5 is used as the nip portion N. The rotation of the fixing roller 1 is started immediately before being supplied to the printer, and the rotation of the fixing roller 1 is stopped by detecting the end of the transfer paper 5 immediately after passing through the nip portion N.

As the high thermal conductivity member 13 of the heat transfer layer 15 of the heat transfer roller 11, the thermal conductivity of aluminum material such as copper metal (thermal conductivity: 403 W / m · K), aluminum metal, aluminum alloy or the like is 230 W / Those having m · K or more are preferable, and an aluminum-based material that is particularly lightweight is preferable.
Examples of the low thermal conductivity member 14 of the heat transfer layer 15 of the heat transfer roller 11 include iron-based metal materials such as stainless steel (thermal conductivity: 83.5 W / m · K), polyamide (thermal conductivity: 0.73 W / heat resistant resin such as m · K), rubber material such as silicon rubber (thermal conductivity: 0.28 W / m · K), ceramics (thermal conductivity: 31 W / m · K) material, etc. can be used. A mixture of these materials can also be used. In particular, when a heat-resistant resin material is used, it is preferable because the heat conductive layer 15 can be formed by being integrally formed with a metal material that becomes a high thermal conductivity member.
Further, when a heat-resistant resin material is used as the low thermal conductivity member 14 of the heat transfer layer 15 of the heat transfer roller 11 and the space portion 16 extending in the axial direction is formed as shown in FIG. It becomes possible to exhibit a more excellent heat insulation effect by reducing the thermal conductivity. In particular, it is preferable that the space portion 16 is sealed and the atmospheric pressure in the space is set to a vacuum state of 1/500 atm or less because the thermal conductivity can be further reduced.

Further, in the heat transfer roller 11 in the present embodiment, a heat insulating layer 12 made of polyamide resin or the like is interposed between the cored bar and the heat conductive layer 15. Therefore, it is possible to suppress the heat applied to the heat transfer layer 15 from being transferred to the core metal, and it is possible to prevent the heat insulation effect of the low thermal conductivity material 14 of the heat transfer layer 15 from being reduced.
In the heat transfer roller 11 according to the present embodiment, the heat transfer layer 15 is divided into 16 equal parts in the circumferential direction, eight high heat conductivity members 13, eight low heat conductivity members 14, a plurality of high heat conductivity members, and low heat. It is not necessary to alternately arrange a plurality of high thermal conductivity members 13 and low thermal conductivity members 14 one by one. However, at least the high thermal conductivity members 13 and It is sufficient to use the low thermal conductivity members 14 one by one and to adjoin these materials in the circumferential direction. Further, the distances d1 and d2 in the circumferential direction do not need to be equal, and the length of d1 or d2 can be increased as necessary.

Further, the fixing roller 1 is used as the fixing means in the present embodiment, but an endless fixing belt is stretched between the heating roller and the fixing roller, and the fixing belt heated by the heating roller is interposed therebetween. It is also possible to heat and press at the nip N between the fixing roller 1 and the pressure roller 2. In this case, the heat transfer roller 1 may be brought into contact with the surface of the fixing belt as fixing means.
Similarly, the pressure roller 2 is used as the pressure unit in the present embodiment, but a pressure belt that is stretched around a plurality of rollers and presses the fixing unit may be used, or an elastic pad that does not rotate. May be.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1A and 1B are diagrams illustrating a schematic configuration of a fixing device according to an embodiment of the present invention, in which FIG. It is sectional drawing of the heat-transfer roller used with the fixing device of one Embodiment by this invention. 2A and 2B are diagrams illustrating a schematic configuration of a heat transfer roller position detection unit used in a fixing device according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view, and FIG. It is sectional drawing which notched some heat transfer rollers of other embodiment used with the fixing device of one Embodiment by this invention. 2A and 2B are diagrams illustrating a schematic configuration of a conventional fixing device, in which FIG. 1A is a cross-sectional view and FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing roller, 1a Rotating shaft, 1b Surface, 2 Pressure roller, 3 Heater, 4 Temperature detection member, 5 Transfer paper, 6 Unfixed toner image, 10 Fixing device, 11 Heat transfer roller, 11a Rotating shaft, 12 Heat insulation layer , 13 High thermal conductivity member, 13a outer peripheral surface, 14 Low thermal conductivity member, 14a outer peripheral surface, 15 heat transfer layer, 15a outer peripheral surface, 16 space portion, 21 filler, 22 photosensor, 112 image forming portion, 130 photoconductor, 131 charging device, 132 optical writing unit, 133 developing device, 134 transfer device, 135 cleaning device

Claims (7)

A fixing unit that heats an unfixed toner image on a recording medium; and a pressing unit that presses the fixing unit, and at least the surface of the fixing unit is moved by the surface of the fixing unit and the surface of the pressing unit. While fixing the unfixed toner image on a recording medium by heating and pressurizing,
A heat transfer roller whose peripheral surface abuts on the surface of the fixing unit is disposed, and the heat transfer roller has a member having a predetermined thermal conductivity along the circumferential direction of the heat transfer roller and the peripheral surface. A member having a smaller heat conductivity is disposed adjacent to the heat transfer layer, and members having different heat conductivities of the heat transfer layer are respectively extended along the axial direction of the heat transfer roller. The heat transfer roller is rotationally driven by a drive means, and when the heat transfer roller is rotated by the drive means, the heat transfer roller includes a position detection means for detecting a circumferential position of a member having a different heat transfer coefficient, When the movement of the surface of the fixing unit is stopped, the position detecting unit detects the position of the peripheral surface of the member having a low thermal conductivity, and contacts the surface of the fixing unit based on the detection signal. Said driving means Fixing apparatus characterized by comprising a control means for controlling. The fixing device according to claim 1.
A fixing device, wherein a heat insulating layer is disposed between a heat transfer layer of the heat transfer roller and a rotating shaft. The fixing device according to claim 1 or 2,
When a recording medium having a maximum allowable width as a size width in the longitudinal direction of the fixing unit is transferred to the surface of the fixing unit, only the peripheral surface of the heat transfer roller having a small thermal conductivity is the surface of the fixing unit. The fixing device is characterized in that the rotation of the heat transfer roller is controlled by the control means so as to come into contact with the fixing device. The fixing device according to any one of claims 1 to 3,
The member having a predetermined thermal conductivity of the heat transfer roller is made of an aluminum-based material, and the member having a smaller thermal conductivity than the member having the predetermined thermal conductivity is an iron-based material, a resin material, or a rubber material And a fixing device comprising at least one material selected from ceramic materials. The fixing device according to any one of claims 1 to 4, wherein:
A fixing device, wherein a space layer is formed in the heat transfer layer of a member having a thermal conductivity smaller than that of the member having the predetermined thermal conductivity. The fixing device according to claim 5.
The fixing device according to claim 1, wherein the space is a space having an atmospheric pressure of 1/500 or less of the atmospheric pressure.   An image forming apparatus comprising the fixing device according to claim 1.

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