JP2015075567A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that prevents unnecessary energy consumption, has a high energy saving property, and has the long life and high durability.SOLUTION: In a fixing device including a fixing belt 21, a nip forming member 24, a pressure roller 22, and a heat source 23 that heats the fixing belt, a thermoelectric transducer (Peltier element 70), which has a cooling surface the temperature of which is reduced and a heating surface the temperature of which is increased upon energization, is provided between the nip forming member 24 and its supporting member 25. With this configuration, an increase in temperature of members not required for achieving fixability can be suppressed and the consumption of unnecessary energy and unnecessary heat accumulation can be prevented.

Description

  The present invention relates to a fixing device that fixes an image on a recording medium, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copiers, printers, facsimiles, and multifunction peripherals thereof are provided with a fixing device that fixes a toner image carried on a recording medium such as paper. Generally, a fixing device includes a fixing member that is heated by a heating source such as a heater, and an opposing member that forms a nip portion in contact with the fixing member. When the image forming operation is started in the image forming apparatus and the toner image is transferred to the sheet, the sheet passes through the nip portion between the fixing member heated to a predetermined temperature and the opposing member. The toner carried on the paper is heated and melted to fix the image.

  In order to save energy and improve the first print time, it is necessary to further improve the thermal efficiency. Therefore, a configuration in which the endless belt is directly heated is proposed, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2007-233301).

  In the configuration described in Patent Document 1, as shown in FIG. 12, a plate-like nip forming member 500 is provided inside the endless belt 100 at a position facing the pressure roller 400. In the case of this configuration, the endless belt 100 can be directly heated by the heat source 300 at a place other than the place where the nip forming member 500 is disposed, so that the heat transfer efficiency is greatly improved and the power consumption is reduced. This makes it possible to further shorten the first print time from the heating standby time. In this fixing device, the nip forming member 500 is supported by a support member 600 such as stainless steel, and the strength of the nip forming member 500 against the pressure applied by the pressure roller 400 is increased.

  However, in the fixing device shown in FIG. 12, a small-diameter belt having a diameter of about 30 mm is used as the endless belt 100 in order to improve thermal efficiency. In such a configuration, the endless belt 100 is disposed in the endless belt 100. The size of the supporting member 600 tends to be smaller. As a result, sufficient strength of the nip forming member 500 cannot be obtained, and when the nip forming member 500 is bent due to the pressure applied by the pressure roller 400, the surface pressure distribution and the nip width of the nip portion N vary, thereby fixing. There is a risk of failure. Therefore, a fixing device has been devised that improves the strength of the support member and prevents the nip forming member from bending.

  13 includes a rotatable endless fixing belt 100, a nip forming member 500 disposed inside the fixing belt, and a pressure roller that forms a nip portion between the fixing belt. 400, a heating source 300 that directly heats the fixing belt at a place other than the nip portion, and a support member 600 that supports the nip forming member. In this configuration, the support member 600 includes the pair of rising portions 625 extending in the pressing direction of the pressure roller 400, whereby the strength of the support member 600 can be improved. As a result, the nip forming member 500 can be prevented from bending due to the contact of the pressure roller 400, so that the nip width can be formed uniformly in the axial direction of the counter rotating body, which is favorable. An image can be obtained.

  However, the conventional fixing device does not take into consideration the heating rate and heat storage property of the members constituting the fixing unit, and the temperature of the members that are not essentially required for the fixing property is increased, resulting in wasted energy. There is a problem that the fixing device may be damaged due to consumption or unnecessary heat storage.

  An object of the present invention is to solve the above-described problems in the conventional fixing device, to prevent wasteful energy consumption, and to provide a fixing device with high energy saving, long life and high durability.

  In order to solve the above-described problems, the present invention provides a rotatable endless fixing belt, a nip forming member disposed inside the fixing belt, and abutting the nip forming member via the fixing belt. And a heating source that heats the fixing belt at a location other than the nip portion, and a recording medium carrying an unfixed image in the nip portion. In a fixing device that transports and fixes an unfixed image on the recording medium, a thermoelectric device that has a cooling surface that cools when energized and a heating surface that heats up between the nip forming member and the support member. A conversion element is provided.

  According to the fixing device of the present invention, the heat energy stored in the fixing device, particularly when images are continuously fixed on the recording medium, is configured not to be stored in the fixing device more than necessary. Long life and high durability can be achieved.

  Further, according to the image forming apparatus of the present invention, it is possible to provide an image forming apparatus equipped with a fixing device having excellent energy saving and long life and high durability.

1 is a cross-sectional configuration diagram schematically illustrating a color laser printer that is an example of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram illustrating an embodiment of a fixing device. It is a figure which shows the state which moved the shielding member to the retracted position. It is a disassembled perspective view which shows the structure of a thermoelectric conversion element periphery. It is a perspective view of the Peltier device simple substance which comprises a thermoelectric conversion element. It is a graph which shows the temperature change of the nip formation member with respect to continuous operation time. It is a graph which shows the relationship between the operation | movement time integrated within the predetermined time, and the temperature of a nip formation member. It is a graph which shows the temperature change of the nip forming member with respect to the continuous number of paper passing. 6 is a graph showing the relationship between the accumulated number of sheets passed within a predetermined time and the temperature of the nip forming member. It is a figure which shows the fixing device provided with the temperature detection means which detects the temperature of a thermoelectric conversion element. It is a disassembled perspective view which shows the thermoelectric conversion element periphery in a structure provided with the temperature detection means. It is a schematic block diagram of the conventional fixing device. It is a schematic block diagram of another conventional fixing device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional configuration diagram showing an outline of a color laser printer which is an example of an image forming apparatus according to the present invention. The overall configuration and operation of the color laser printer 1 shown in this figure will be described later, and the fixing device will be described first.

  As shown in FIG. 2, the fixing device 20 mounted on the color laser printer 1 includes a fixing belt 21 as a fixing member, a pressure roller 22 as an opposing member in contact with the outer peripheral surface of the fixing belt 21, and A halogen heater 23 as a heating source for heating the fixing belt 21, a nip forming member 24 that contacts the pressure roller 22 from the inner peripheral side of the fixing belt 21 to form the nip portion N, and the nip forming member 24 are supported. A stay 25 as a support member, a reflection member 26 that reflects heat from the halogen heater 23 to the fixing belt 21, a shielding member 27 that shields heat from the halogen heater 23, and temperature detection that detects the temperature of the fixing belt 21. A temperature sensor 28 as a means is provided.

  The fixing belt 21 is composed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 21 includes a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI), and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Or it is comprised by the release layer of the outer peripheral side formed with polytetrafluoroethylene (PTFE) etc. Further, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

  Also, when there is no elastic layer, the heat capacity is reduced and the fixability is improved. It can happen. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing an elastic layer having a thickness of 100 μm or more, minute unevenness can be absorbed by elastic deformation of the elastic layer, so that occurrence of uneven gloss can be avoided.

  In this embodiment, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is thin and has a small diameter. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is set. It is set to 1 mm or less. The diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, the thickness of the entire fixing belt 21 is desirably 0.2 mm or less, and more desirably 0.16 mm or less. The diameter of the fixing belt 21 is desirably 30 mm or less.

  The pressure roller 22 includes a cored bar 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, or fluorine rubber provided on the surface of the cored bar 22a, and a PFA provided on the surface of the elastic layer 22. Alternatively, it is constituted by a release layer 22c made of PTFE or the like. The pressure roller 22 is pressed toward the fixing belt 21 by a pressure unit (not shown) and is in contact with the nip forming member 24 via the fixing belt 21. At the place where the pressure roller 22 and the fixing belt 21 are in pressure contact, the elastic layer 22b of the pressure roller 22 is crushed to form a nip portion N having a predetermined width. Note that the fixing member and the facing member are not limited to being in pressure contact with each other, and may be configured to simply contact without pressing.

  The pressure roller 22 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the printer main body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate.

  In the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heating source such as a halogen heater may be disposed inside the pressure roller 22. The elastic layer 22b may be solid rubber, but if there is no heat source inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is less likely to be taken away.

  The halogen heater 23 is disposed on the inner peripheral side of the fixing belt 21 and on the upstream side of the nip portion N in the sheet conveyance direction. Specifically, in FIG. 2, assuming that a virtual straight line passing through the center Q of the nip portion N in the paper transport direction and the rotation center O of the pressure roller 22 is L, the halogen heater 23 is closer to the paper transport direction than the virtual straight line L. It is arranged on the upstream side (lower side in FIG. 2). The halogen heater 23 is configured to generate heat by being output controlled by a power supply unit provided in the printer body, and the output control is performed based on the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 28. Is called. By such output control of the heater 23, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature. A temperature sensor (not shown) for detecting the temperature of the pressure roller 22 is provided in place of the temperature sensor for detecting the temperature of the fixing belt 21, and the temperature of the fixing belt 21 is predicted based on the temperature detected by the temperature sensor. You may make it do.

  In this embodiment, two halogen heaters 23 are provided, but the number of halogen heaters 23 may be one or three or more according to the size of the paper used in the printer. In addition to the halogen heater, a resistance heating element, a carbon heater, or the like can be used as a heating source for heating the fixing belt 21.

  The nip forming member 24 includes a base pad 241 and a low friction sliding sheet 240 provided on a surface of the base pad 241 facing the fixing belt 21. The base pad 241 is disposed in a longitudinal shape over the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22. The shape of the nip portion N is determined by the base pad 241 receiving the pressure applied by the pressure roller 22. In the present embodiment, the shape of the nip portion N is flat, but may be a concave shape or other shapes. The sliding sheet 240 is provided to reduce sliding friction when the fixing belt 21 rotates. Note that when the base pad 241 itself is formed of a low-friction member, the sliding sheet 240 may not be provided.

  The base pad 241 is made of a heat-resistant member having a heat-resistant temperature of 200 ° C. or more, prevents deformation of the nip forming member 24 due to heat in the toner fixing temperature region, and ensures a stable state of the nip portion N for output. Stabilizes image quality. Examples of the material of the base pad 241 include polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), and polyether ether ketone (PEEK). A general heat resistant resin can be used.

  The base pad 241 is fixedly supported by the stay 25. Thus, the nip forming member 24 is prevented from being bent by the pressure of the pressure roller 22, and a uniform nip width is obtained in the axial direction of the pressure roller 22. The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the function of preventing the nip forming member 24 from bending. The base pad 241 is also preferably made of a material that is hard to some extent to ensure strength. As a material for the base pad 241, a resin such as a liquid crystal polymer (LCP), a metal, a ceramic, or the like can be used.

  The reflection member 26 is fixedly supported by the stay 25 so as to face the halogen heater 23. By reflecting the heat (or light) radiated from the halogen heater 23 to the fixing belt 21 by the reflecting member 26, the heat is suppressed from being transmitted to the stay 25 and the like, and the fixing belt 21 is efficiently heated. At the same time, we are trying to save energy. As the material of the reflecting member 26, aluminum, stainless steel or the like is used. In particular, in the case of using a material obtained by vapor-depositing silver having a low emissivity (high reflectivity) on an aluminum base material, the heating efficiency of the fixing belt 21 can be improved.

  The shielding member 27 is configured by forming a metal plate having a thickness of 0.1 mm to 1.0 mm into an arc-shaped cross-sectional shape along the inner peripheral surface of the fixing belt 21. The shielding member 27 is movable in the circumferential direction of the fixing belt 21 as necessary. In the present embodiment, in the circumferential region of the fixing belt 21, a direct heating region in which the halogen heater 23 directly heats the fixing belt 21 is heated, and other than the shielding member 27 between the halogen heater 23 and the fixing belt 21. There are non-direct heating regions where members (reflecting member 26, stay 25, nip forming member 24, etc.) intervene, but when it is necessary to shield heat, shield member 27 is directly heated region as shown in FIG. It is arranged at the shielding position on the side. On the other hand, when there is no need for heat shielding, as shown in FIG. 3, the shielding member 27 is moved to the retracted position on the non-direct heating region side, and the shielding member 27 is retracted to the back side of the reflecting member 26 and the stay 25. Is possible. Moreover, since the shielding member 27 requires heat resistance, it is preferable to use a metal material such as aluminum, iron, stainless steel, or ceramic as the material.

Next, a characteristic configuration of the present invention will be described.
The fixing device 20 according to the present invention includes a thermoelectric conversion element 70 in the gap between the stay 25 and the nip forming member 24. In the embodiment, a Peltier element is used as the thermoelectric conversion element 70. As shown in FIG. 4, the thermoelectric conversion element 70 of the present embodiment has a configuration in which five Peltier elements 70A to 70E are arranged in parallel. All the Peltier elements 70A to 70E are the same. In addition, it is good also as a structure which accommodates the Peltier elements 70A-70E in a box-shaped metal. In addition, the number of Peltier elements may be changed as appropriate according to the size of the device to be applied and the Peltier element to be used. You may arrange | position with the structure of a row | line | column or a checkered pattern (staggered arrangement | positioning).

  A perspective view of a single Peltier element 70 used in the embodiment is shown in FIG. The Peltier element 70 has a flat, rectangular parallelepiped shape as a whole. When energized from a lead wire (not shown), one principal surface 71 cools down to become a cooling surface, and the other principal surface 72 rises in temperature. It becomes the heating surface. Further, when a temperature difference is generated between the main surfaces 71 and 72, an electromotive force is generated (between the lead wires) due to the Seebeck effect. As the Peltier element 70 used here, a known modularized element may be used.

  All of the Peltier elements 70 </ b> A to 70 </ b> E are configured to bring the cooling surface 71 into close contact with the nip forming member 24. This is to increase the heat transfer efficiency, and it is also effective to increase the adhesion by interposing a heat-resistant grease or the like between the cooling surface 71 and the nip forming member 24. Also, as shown in FIG. 4, a plurality of Peltier elements 70A to 70E arranged in parallel are connected in series by a wiring (not shown).

Next, the energization timing to the thermoelectric conversion element (Peltier element) 70 will be described.
In order to fix the toner on the recording medium (paper), the toner carried on the paper is heated and melted by passing through the nip portion between the fixing member heated to a predetermined temperature and the opposing member. That's fine. In the fixing device of FIG. 2, the fixing belt 21 and the pressure roller 22 are in contact with each other with a nip portion N having a predetermined width, so that the fixing belt 21 and the pressure roller 22 have a heat amount sufficient to heat and melt the toner. At the start of image formation from the cold time, the heat amount from the halogen heater 23 is applied to the fixing belt 21, and a part of the heat amount of the fixing belt 21 is transferred to the pressure roller 22 so that the toner is removed. It is sufficient that the amount of heat is sufficient for heating and melting. At this time, it is not necessary to store heat in the stay 25 and the nip forming member 24, the fixing belt 21 has a low heat capacity as described above, and the pressure roller 22 includes the core metal 22a and the core metal 22a. Since it is composed of an elastic layer 22b made of foamable silicone rubber, silicone rubber, fluorine rubber or the like provided on the surface, and a release layer 22c made of PFA or PTFE or the like provided on the surface of the elastic layer 22, Only the release layer 22c is heated for the heat insulation effect of the elastic layer 22b, and it is possible to fix the toner to the sheet with the minimum amount of heat, in other words, the minimum amount of energy.

  The stay 25 does not need to actively store heat, but when the sheet is fixed continuously, heat may be transferred from the halogen heater 23 or the stored fixing belt 21. For this reason, it is desirable that the halogen heater 23 and the stay 25 be separated from each other as much as possible. However, if the stay 25 is warmed, the amount of heat transferred from the halogen heater 23 to the stay 25 is reduced. Therefore, it is one method to always energize the Peltier element 70 during operation.

Next, control for switching the energization of the thermoelectric conversion element (Peltier element) 70 from OFF to ON at a predetermined timing during paper feeding will be described.
When the sheet is continuously fixed, especially when the fixing device fixes the sheet continuously for a long time, the amount of heat moves from the fixing belt 21 to the nip forming member 24 or the amount of heat from the halogen heater 23 increases. The heat is transmitted to the reflecting member 26 and the stay 25, and the constituent members of the fixing device are gradually stored. When the temperature of each component in the fixing device is in an equilibrium state, it is desirable that the temperature of the stay 25 is high and the heat is stored. In this state, the stay 25 can behave as a medium for applying heat to the fixing belt 21 like the halogen heater 23 to the fixing device, and the heat generation amount per unit time of the halogen heater 23 is smaller than that in the cold state. Sufficient fixability can be obtained in a small state.

  Further, since the amount of heat taken away from the fixing belt 21 by storing the nip forming member 24 is reduced, it is possible to prevent fixing problems due to temperature drop at the nip portion N. However, since the nip forming member 24 is made of resin and is lower than the heat resistant temperature of the stay 25 made of metal, the apparatus configuration may be such that the temperature of the nip forming member 24 is lower than the temperature of the stay 25. desirable. As described above, the base pad 241 is made of a heat-resistant member having a heat-resistant temperature of 200 ° C. or higher. However, due to the widespread use of low-temperature fixing toner, the fixing belt temperature 21 does not have to be 200 ° C. at the nip portion N. The temperature of the forming member 24 should also be maintained equal to or less than the temperature at the nip N of the fixing belt temperature 21.

  The temperature at the nip portion N of the fixing belt 21 in the image forming apparatus of the embodiment is 165 ° C., and the operation of the thermoelectric conversion element (Peltier element) 70 is controlled with this temperature as a target. The temperature of the Peltier element 70 is controlled by a CPU (not shown).

  FIG. 6 is a graph showing a temperature change of the nip forming member 24 with respect to continuous operation time. The nip forming member 24 reaches 150 ° C. at time A in the curve (a) which is the operation state at the standard speed, and at time B in the curve (b) which is the operation state at the half speed. In the image forming apparatus according to the embodiment, if the nip forming member 24 is maintained at 150 ° C., the heat amount is not substantially deprived from the fixing belt 21, and the temperature at which the nip forming member 24 itself is damaged by heat resistance. not. From the above, if the operation of the Peltier element 70 is controlled with the temperature as a target at time A and time B according to the operating conditions, it is possible to achieve both energy saving and durability. That is, the Peltier element 70 is energized when a continuous operation time reaches a predetermined time (for example, time A or time B).

  FIG. 7 is a graph showing the relationship between the accumulated operation time within a predetermined time and the temperature of the nip forming member 24. For example, in the case of fixing operation when image formation is continuously performed for 30 minutes and in the case of fixing operation when image formation is continuously performed for 15 minutes twice at 1 second intervals under the same image formation conditions, nip formation is performed. The temperature of the member 24 is substantially the same. However, if the operation of the Peltier element 70 is controlled only in the continuous time of FIG. 6, the Peltier element 70 is not energized even though the temperature of the nip forming member 24 actually exceeds 150 ° C. Become. By accumulating the operating time within a predetermined time and energizing the Peltier element 70, it becomes possible to control with high accuracy. That is, the Peltier element 70 is energized when the operation time accumulated within a predetermined time reaches a predetermined time (for example, time C). Accumulation conditions for a predetermined time can be further improved, for example, by resetting or subtracting the integrated value when an operation interval of a predetermined time or longer occurs. The integration condition is a value unique to the apparatus.

  FIG. 8 is a graph showing the temperature change of the nip forming member 24 with respect to the continuous sheet passing number. The nip forming member 24 reaches 150 ° C. at time D in the curve (d) which is the standard image forming state and at time E in the curve (e) which is the image forming state at half speed. In the image forming apparatus according to the embodiment, if the nip forming member 24 is maintained at 150 ° C., the heat amount is not substantially deprived from the fixing belt 21, and the temperature at which the nip forming member 24 itself is damaged by heat resistance. not. As described above, if the operation of the Peltier element 70 is controlled at the time D and time E according to the image forming conditions (so that the nip forming member 24 is at this temperature), both energy saving and durability are achieved. It becomes possible to do. That is, the Peltier element 70 is energized when the number of continuous sheets to be fed reaches a predetermined number.

  FIG. 9 is a graph showing the relationship between the accumulated number of sheets passed within a predetermined time and the temperature of the nip forming member 24. For example, the temperature of the nip forming member 24 is substantially the same when 1000 images are continuously formed and when 500 images are continuously formed at intervals of 1 second under the same image forming conditions. However, if the operation of the Peltier element 70 is controlled only by the number of continuous sheets in FIG. 8, the peltier element 70 is not energized even though the temperature of the nip forming member 24 actually exceeds 150 ° C. It will be. By accumulating the number of sheets passed within a predetermined time, it becomes possible to control with high accuracy. Accumulation conditions for the predetermined number of sheets can be further improved in accuracy by resetting or subtracting the integrated value when an image forming interval of a predetermined time or longer occurs, for example. The integration condition is a value unique to the apparatus.

  FIG. 10 is a diagram illustrating a fixing device including a temperature detecting unit that detects the temperature of the thermoelectric conversion element. FIG. 11 is an exploded perspective view showing the periphery of the thermoelectric conversion element in the configuration including the temperature detecting means. The configuration other than the provision of the temperature detecting means is the same as that of the fixing device of FIG.

  As shown in FIGS. 10 and 11, the temperature detection means 75 is provided on the main surface (cooling surface) 71 side of the Peltier element 70 that is a thermoelectric conversion element, and the temperature is detected, so that it is appropriate based on the detected temperature. It is possible to control the Peltier element 70 with higher accuracy so that the temperature is set to a low temperature (for example, 150 ° C.). That is, when the temperature detected by the temperature detecting means 75 reaches a predetermined temperature, the Peltier element 70 is energized.

  In this embodiment, by using a Peltier element as the thermoelectric conversion element, the thermoelectric conversion element can be mounted and applied as a small and low-cost thermoelectric conversion element, and the present invention can be embodied.

  In addition, although not shown, it is also possible to store a direct current output from the thermoelectric conversion element (Peltier element 70) by including a secondary battery as a storage means. In this case, the output to the Peltier element 70 may be performed from the secondary battery, or the commercial AC power source may be converted to DC depending on the amount of stored electricity or the like.

  By using the fixing device according to the present invention described above for an image forming apparatus, it is possible to prevent useless energy consumption, and to provide an image forming apparatus with high energy saving, long life and high durability. .

Finally, the overall configuration and operation of the color laser printer 1 shown in FIG. 1 will be described.
An image forming apparatus 1 shown in FIG. 1 is a color laser printer, and four image forming units 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each of the image forming units 4Y, 4M, 4C, and 4K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that.

  Specifically, each of the image forming units 4Y, 4M, 4C, and 4K has a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and a surface of the photoconductor 5. A developing device 7 for supplying toner and a cleaning device 8 for cleaning the surface of the photoreceptor 5 are provided. In FIG. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4 </ b> K are denoted by reference numerals. In the other image forming units 4 </ b> Y, 4 </ b> M, and 4 </ b> C, The reference numerals are omitted.

  Under the image forming units 4Y, 4M, 4C, and 4K, an exposure device 9 that exposes the surface of the photoreceptor 5 is disposed. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data.

  A transfer device 3 is disposed above the image forming units 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer member, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, a secondary transfer backup roller 32, and a cleaning device. A backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

  The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, when the secondary transfer backup roller 32 is driven to rotate, the intermediate transfer belt 30 runs (rotates) in the direction indicated by the arrow in the figure.

  Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31.

  The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Similarly to the primary transfer roller 31, a power source (not shown) is also connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It has become so.

  The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

  A bottle container 2 is provided in the upper part of the printer main body, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are detachably attached to the bottle container 2. A replenishment path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each development from each toner bottle 2Y, 2M, 2C, 2K is performed via this replenishment path. The toner is supplied to the device 7.

  On the other hand, at the lower part of the printer main body, a paper feed tray 10 that stores paper P as a recording medium, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like are provided. Here, the recording medium includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. Although not shown, a manual paper feed mechanism may be provided.

  In the printer main body, a transport path R is provided for discharging the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, a pair of registration rollers 12 serving as transport means for transporting the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the paper transport direction.

  Further, a fixing device 20 for fixing the unfixed image transferred onto the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper transport direction. Further, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. A discharge tray 14 for stocking sheets discharged outside the apparatus is provided on the upper surface of the printer main body.

Next, a basic operation of the printer according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the respective photoconductors 5 in the respective image forming units 4Y, 4M, 4C, and 4K are rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 5 is charged by the charging device 6. Are uniformly charged to a predetermined polarity. The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5. At this time, the image information to be exposed on each photoconductor 5 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, whereby the electrostatic latent image is visualized (visualized) as a toner image. .

  When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated by the arrow in the figure. Then, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 31. As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

  Thereafter, when each color toner image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the toner image on each photoconductor 5 is generated by the transfer electric field formed in the primary transfer nip. Are sequentially superimposed and transferred onto the intermediate transfer belt 30. Thus, a full color toner image is carried on the surface of the intermediate transfer belt 30. Further, the toner on each photoconductor 5 that could not be transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Thereafter, the surface of each photoconductor 5 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  In the lower part of the image forming apparatus, the paper feed roller 11 starts to rotate, and the paper P is sent out from the paper feed tray 10 to the transport path R. The sheet P sent to the transport path R is timed by the registration roller 12 and sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip.

  Thereafter, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 rotates, the transfer electric field formed in the secondary transfer nip causes a transfer on the intermediate transfer belt 30. The toner images are transferred onto the paper P all at once. At this time, the residual toner on the intermediate transfer belt 30 that could not be transferred onto the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and stocked on the paper discharge tray 14.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single color image can be formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. Two or three image forming units can be used to form a two-color or three-color image.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. The configuration of the fixing device can be appropriately changed within a range where the present invention can be applied. For example, the shape or configuration of the nip forming member or its supporting member can adopt a form different from the illustrated example. Also, appropriate materials can be used for the nip forming member and its supporting member. The number and type of heaters are also arbitrary.

  Further, the configuration of the image forming apparatus can be changed as appropriate, and the present invention is not limited to one using four color toners, and is also applicable to a full color machine using three color toners, a multicolor machine using two color toners, or a monochrome apparatus. Can be applied. Of course, the image forming apparatus is not limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having a plurality of functions.

1 Color laser printer (image forming device)
20 Fixing device 21 Fixing belt 22 Pressure roller (opposite rotating body)
23 Halogen heater (heating source)
24 Nip forming member 25 Stay (support member)
26 Reflecting member 27 Shielding member 28 Temperature sensor (temperature detecting means)
70 Peltier element (thermoelectric conversion element)
71 Cooling side main surface 72 Heating side main surface 75 Temperature detection means 240 Sliding sheet (low friction sheet)
241 Base pad N Nip part P Paper (recording medium)

Japanese Patent Laid-Open No. 2007-233011

Claims (12)

A rotatable endless fixing belt, a nip forming member disposed inside the fixing belt and supported by a support member, and the fixing belt by contacting the nip forming member via the fixing belt. A counter-rotating body that forms a nip portion, and a heating source that heats the fixing belt,
In the fixing device for transporting a recording medium carrying an unfixed image to the nip portion and fixing the unfixed image on the recording medium,
A fixing device comprising: a thermoelectric conversion element having a cooling surface that cools when energized and a heating surface that heats up when energized between the nip forming member and the support member.   The fixing device according to claim 1, wherein the thermoelectric conversion element is energized when a predetermined condition is satisfied during operation.   The fixing device according to claim 2, wherein the thermoelectric conversion element is always energized during operation.   The fixing device according to claim 2, wherein the thermoelectric conversion element is energized when a continuous operation time reaches a predetermined time.   The fixing device according to claim 2, wherein the thermoelectric conversion element is energized when an operation time accumulated within a predetermined time reaches a predetermined time.   The fixing device according to claim 2, wherein the thermoelectric conversion element is energized when a continuous sheet passing number reaches a predetermined number.   The fixing device according to claim 2, wherein the thermoelectric conversion element is energized when the number of sheets passed within a predetermined time reaches a predetermined number.   The thermoelectric conversion element includes a temperature detection unit on the nip forming member side, and the thermoelectric conversion element is energized when a temperature detected by the temperature detection unit reaches a predetermined temperature. The fixing device according to 1.   The fixing device according to claim 1, wherein the thermoelectric conversion element and the nip forming member side are in close contact with each other.   The fixing device according to claim 1, further comprising a power storage unit configured to store power generated by the thermoelectric conversion element.   The fixing device according to claim 1, wherein the thermoelectric conversion element is a Peltier element. An image forming apparatus comprising the fixing device according to claim 1.

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