JP4255760B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a fixing device having a fixing member heated by a heating means, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine including the fixing device.
[0002]
[Prior art]
  A fixing device is mounted on an electrophotographic image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least one of these functions. The fixing device includes a fixing member heated by a heating unit, and a pressure member in pressure contact with the fixing member, and a recording material on which a toner image is transferred is formed in a nip portion formed by the fixing member and the pressure member. In general, a method of fixing a toner image on a recording material by passing the toner is used. Since the fixing member has an elastic layer and a release layer laminated on a metal core and has a relatively large heat capacity, the rise time required for heating from room temperature to a set temperature becomes long.
[0003]
  As a heating method for the fixing member, there are a case where heating means such as a halogen heater is provided inside the fixing member and heating is performed from inside, or a case where heating means is provided outside the fixing member and heating is performed from outside. As a fixing device that heats the fixing member from the inside, there is Patent Document 1, and as a fixing device that heats the fixing member from the outside, Patent Document 2 can be cited.
[0004]
[Patent Document 1]
  JP 11-184291 A
[Patent Document 2]
  JP 2002-40855 A
[Problems to be solved by the invention]
[0005]
  Since the fixing member is generally formed longer in the longitudinal direction than the width of the recording material, if the recording material having a size smaller than the length of the fixing member is continuously fixed, the temperature of the non-sheet passing portion is determined. May go up and be destroyed. In addition, when trying to fix a large size sheet immediately after passing a small size sheet continuously, the non-sheet passing part is hotter than the sheet passing part. Unevenness may occur, causing problems such as wrinkles, uneven glossiness, and hot offset. Further, when heating from the inside of the fixing member as in Patent Document 1, the rise time required for heating from the room temperature to the set temperature becomes longer than when the fixing member is heated from the outside.
[0006]
  The present invention relates to a fixing device having a short rise time while preventing the heat of the fixing member from being efficiently released to suppress the temperature rise and preventing the occurrence of hot offset of the toner, the destruction of the fixing member, wrinkles, uneven gloss, and the like. And an image forming apparatus.
[0007]
[Means for Solving the Problems]
  In order to set the above object, the invention of claim 1 provides a fixing member heated by a heating means and a pressure member in pressure contact with the fixing member, and a recording material onto which a toner image is transferred, and a fixing member. In a fixing device that performs fixing by passing a nip formed by a pressure member, the fixing member isIt has a metal core bar having a cavity inside thereof and open at both ends, and a heat insulating member provided on the surface inside the cavity of a portion where the thickness of the core bar is thinner than a predetermined thickness,It has a fan that forcibly moves the heat in the cavity from the opening to the outsideIt is characterized by that.
[0008]
  According to a second aspect of the present invention, in the fixing device according to the first aspect,A control unit that changes and controls the driving state of the fan based on the paper size detected by the paper size detecting means for detecting the paper size and the number of passed sheets counted by the passed sheet number counting means for counting the number of passed sheets. HaveIt is characterized by that.
[0009]
  The invention of claim 3An image forming apparatus comprising: an image carrier; a transfer unit that transfers a toner image formed on the image carrier to a recording material; and a fixing device that fixes the toner image transferred to the recording material to the recording material.
The fixing device according to claim 1 or 2 is used as the fixing device.It is a feature.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
  Background of the Invention
  In the fixing device, shortening the rise time of the temperature of the fixing member is important for energy saving. By reducing the thickness of the metal core and the elastic layer, the apparatus can have a low heat capacity and the rise time can be shortened. As a result, the rise time can be considerably shortened, but when the heating means is inside, there is a time loss in transferring heat by heat conduction from the inner surface to the surface of the fixing member. In particular, in a fixing device corresponding to a color image that requires a sufficiently thick elastic layer, this time loss is large. For this reason, there are problems such as a delay in the rise time and a time taken to recover from a decrease in the temperature of the fixing member when the paper is passed, and the fixing property is deteriorated because the temperature of the fixing member is lowered when the paper is continuously passed.
[0011]
  As a countermeasure against this, an external heating method has been proposed in which a heating unit is arranged on the surface side of the fixing member and the surface of the fixing member is directly heated as described in Patent Document 2. In the external heating method, since only the surface layer that needs to be heated is heated, the rise time is very fast, and the response from the temperature drop at the time of paper passing is good. However, since the actual heat of the surface layer escapes to the inside of the member that does not need to be heated, the pressure member, etc., the rise time is later than the theoretical value of heating only the surface layer.
[0012]
  For this reason, a heat insulating layer is provided under the surface layer, and the rise time is shortened by improving the heat insulating property. As a member having good heat insulation, a member containing a gas such as air having low thermal conductivity is generally used. For example, in Japanese Unexamined Patent Publication No. 2000-206815, foamed silicone rubber is often used. Foamed silicone contains air and thus has a low thermal conductivity and good heat insulation, but is compressed in the nip portion to reduce the air content and increase the thermal conductivity. In addition, there is a problem that high surface pressure cannot be applied because of compressive deformation, and deterioration with time is caused by repeated deformation. Further, since the radius of rotation changes due to compression, there is a disadvantage that it is not suitable as a driving side member for conveying a recording material or the like at a constant speed. As a heat insulating material having high rigidity and small deformation, porous ceramics described in JP-A No. 2002-40855, porous resins described in JP-A No. 2000-275996, or hollow particles are mixed with a binder. Can be mentioned.
[0013]
  Based on such a background, the configuration and operation of the fixing device and the image forming apparatus according to the present invention will be described. In claim 1, the fixing member includes a cavity inside the maximum temperature portion, and the release member in the cavity is released. The amount of heat is varied in the longitudinal direction of the fixing member. In this case, since the temperature of the part where the heat dissipation amount is high is likely to escape, by increasing the heat dissipation amount inside the part corresponding to the non-sheet passing portion, the occurrence of uneven internal temperature in the fixing member is suppressed and the temperature unevenness is suppressed. It is possible to prevent defects such as wrinkles, gloss unevenness, and hot offset caused by the above.
[0014]
  When the fixing member has a metal core, the heat insulating member is provided on the surface inside the cavity where the thickness of the core is thinner than a predetermined thickness. When a heat insulating member is provided, heat is not easily transmitted to the inside of the cavity. Therefore, when the core metal corresponding to the paper passing part is thinned, the heat of the part corresponding to the paper passing part can be provided by providing the heat insulating member inside. Is more difficult to escape and can quickly rise in temperature. Further, since there is no heat insulating member for the heat corresponding to the non-sheet passing portion, it is easy to escape and the temperature rise can be suppressed.
[0015]
  Claim1Then, a heat transfer part for releasing heat to the outside of the fixing member is provided in the cavity. Therefore, the heat in the cavity of the fixing member can be released to the outside of the fixing member, the inside of the fixing member is cooled, and an increase in the internal temperature can be suppressed. For this reason, the occurrence of uneven internal temperature in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented. Examples of the heat transfer unit include an opening that communicates the cavity and the outside of the fixing member, and a heat pipe that communicates the cavity and the outside of the fixing member. In the case of a fixing member provided with an opening, if a fan for forcibly moving the heat in the cavity from the opening to the outside is provided, the cooling efficiency inside the fixing member is increased, and an increase in the internal temperature can be suppressed. The occurrence of non-uniformity in internal temperature can be suppressed, and problems due to temperature non-uniformity can be prevented.
[0016]
  Claim2Then, the drive state of the fan is changed and controlled on the basis of the paper size detected by the paper size detecting means for detecting the paper size and the number of passed sheets counted by the passed sheet number counting means for counting the number of passed sheets. A control unit is provided. This is because when the size of the transfer material is large or when the size is small and the number of sheets is small, the edge temperature rise hardly occurs, and the necessity of driving the fan is reduced. Therefore, the degree of increase in the end temperature of the fixing member is estimated from the paper size and the number of sheets to be passed, and when it is not necessary, the fan is stopped, and when necessary, the fan is driven to reduce the power consumption. While reducing, it becomes possible to cool without waste.
[0017]
  Claim3In the image forming apparatus, the above-described fixing device is used. By using such a fixing device, it is possible to achieve a power saving image forming apparatus with a short rise time while preventing occurrence of hot offset of the toner, destruction of the fixing member, wrinkles, gloss unevenness, and the like. it can.
[0018]
【Example】
  The image forming apparatus shown in FIG. 13 is one form of an electrophotographic full-color printer. This printer includes a photoconductor unit 502Y, 502M, 502C, 502BK provided with a plurality of photoconductor drums 504Y, 504M, 504C, 504BK as image carriers in a box-shaped apparatus main body 500, and photoconductor drums 504Y, 504M, 504C, and 504BK, and a transfer unit 560 having a transfer conveyance belt 503 as a transfer conveyance body that conveys a sheet P as a transfer material, and a photosensitive drum 504Y on the sheet P conveyed by the transfer conveyance belt 503. , 504M, 504C, and 504BK are provided as transfer rollers 501Y, 501M, 501C, and 501BK as transfer means for transferring toner images on the toner images.
[0019]
  The transfer / conveying belt 503 is provided so as to be driven to rotate in a direction indicated by an arrow A, spanned by a plurality of rollers to which rotational driving force is transmitted. The transfer conveyance belt 3 is disposed so as to be in pressure contact with the surface of each photosensitive drum. Developing devices 505Y, 505M, 505C, and 505BK are arranged on the side facing each photosensitive drum. Each developing device includes a two-component developer having a plurality of colors, for example, yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as K) toner and a carrier. The electrostatic latent images are respectively supplied to the electrostatic latent images formed on the photosensitive drums 504Y, 504M, 504C, and 504BK, and each electrostatic latent image is developed.
[0020]
  A writing device 506 as an exposure unit is disposed above the photoreceptor units 502Y, 502M, 502C, and 502K, and a duplex unit 507 is disposed below the photoreceptor units 2Y, 2M, 2C, and 2K. Below the duplex unit 7, paper feed cassettes 513 and 514 that can store transfer materials P of different sizes are disposed. A reversing unit 508 is disposed on the left side of the apparatus main body 500, and a manual feed tray 515 is provided on the right side of the apparatus main body 1 so as to be openable and closable in the arrow B direction. A fixing device 509 is disposed between the transfer conveyance belt 503 and the reversing unit 508. A reverse conveyance path 510 is branched and formed on the downstream side of the fixing device 9 in the transfer material conveyance direction, and the sheet-like transfer material P is discharged at the upper portion of the apparatus by a discharge roller 511 disposed in the reverse conveyance path 10. Guide to the paper tray 512.
[0021]
  Each photoconductor unit is a unit for forming a toner image corresponding to each color of Y, M, C, and BK on each photoconductor drum. Each photoconductor unit is provided with a charging device (not shown) that uniformly charges the surface of each photoconductor drum, and a cleaning device that cleans the surface of the photoconductor drum with a brush roller and a cleaning blade. Each photoconductor unit and each charging device have the same configuration except for a place in the apparatus main body 1.
[0022]
  The writing device 506 includes a Y laser beam modulated by Y image data from a laser diode as a laser light source (not shown), an M laser beam modulated by M image data, and a C laser beam modulated by C image data. The photosensitive drum is irradiated with BK laser light modulated by the BK image data through a lens and a mirror (not shown) to form an electrostatic latent image on the drum surface.
[0023]
  In the duplex image forming mode in which the duplex unit 507 forms an image on both sides of the paper P, the image is formed on one side and then conveyed to the reversal conveyance path 544 of the reversing unit 508 to be switched back and reversed. The received paper P is received and re-conveyed to a transfer portion formed between each photosensitive drum and the transfer conveyance belt 503.
[0024]
  The reversing unit 508 includes a plurality of conveying rollers and a plurality of conveying guide plates. In the double-sided image forming mode, the reversing unit 508 reverses the front and back of the transfer material and sends it to the double-sided unit 507. It has a function of discharging the subsequent transfer material out of the apparatus in the same orientation, and a function of discharging the transfer material after image formation outside the apparatus with its front and back reversed. In the paper feed unit in which the paper feed cassettes 513 and 514 are arranged, separation paper feed units 545 and 546 for separating and feeding the paper P on the paper feed cassettes 13 and 14 one by one are provided. .
[0025]
  In this embodiment, when image formation is instructed by an operation unit (not shown), each photosensitive drum is rotated by a drive source (not shown) to rotate clockwise. Each charging device applies a charging bias from a power source (not shown) to uniformly charge each photosensitive drum. Each uniformly charged photosensitive drum is exposed by a writing device 506 with laser light modulated with image data of each color of Y, M, C, and K, and an electrostatic latent image is formed on each surface. The These electrostatic latent images on the photoconductive drum are developed by rotating the drum and a developing sleeve (not shown) included in each developing device by a driving source (not shown) to generate each of the Y, M, C, and K colors. It becomes a toner image.
[0026]
  One sheet P is separated from the selected one of the sheet cassettes 513 and 514, and is supplied to a registration roller 551 disposed closer to the sheet feed unit than the photosensitive unit 502Y. Paper. In this embodiment, a manual feed tray 515 is disposed on the right side portion of the apparatus main body 500, and paper can be fed from the manual feed tray 515 to the registration rollers 551. The registration roller 551 feeds each sheet onto the transfer / conveying belt 503 at a timing when the toner image of each photosensitive drum coincides with the leading edge thereof. The fed paper P is electrostatically adsorbed by the transfer conveyance belt 3 charged by the paper suction roller 52 around which the transfer conveyance belt 503 is wound, and is conveyed to each transfer unit.
[0027]
  The conveyed paper P receives transfer rollers 501Y, 501M, 501C, and 501BK supplied with a transfer bias from a power source (not shown) when sequentially passing through the respective transfer units, whereby Y, The toner images of M, C, and K colors are sequentially superimposed and transferred to form a four-color superimposed full-color toner image. The full color toner image is fixed on the paper P on which the full color toner image is formed by the fixing device 509, and then the paper P is discharged to the paper discharge tray 512 through the paper discharge path corresponding to the designated mode. From the apparatus 509, it goes straight through the reversing unit 508 and is discharged straight.
[0028]
  In the image forming apparatus, when the double-sided image forming mode is selected, the recording medium P has a reversal conveyance path 544 in the reversing unit 508 after a toner image is formed on one side and the toner image is fixed by the fixing device 509. Then, after being switched back, the sheet is conveyed to the duplex unit 507, and is fed again from there, and an image is formed on the back surface and discharged in the same manner as in the front surface image formation.
[0029]
  The above image forming operation is an operation when the full color mode for superimposing four colors is selected by an operation unit (not shown). However, when the full color mode for superimposing three colors is selected by the operation unit, a K toner image is formed. Is omitted, and a full-color image is formed on the paper P by superimposing Y, M, and C three color toner images. When the monochrome image forming mode is selected on the operation unit, only the K toner image is formed and a monochrome image is formed on the paper P.
[0030]
  FIG. 1 is a schematic configuration diagram of the fixing device 509. The fixing device 509 shown here has a fixing member 2 in the form of a roller as a fixing member, and a roller-shaped pressing member 14 that is pressed against the fixing member 2 by a spring 15, and these members are in pressure contact with each other. By doing so, the nip portion N is formed. The pressure member 14 is rotated by being driven by a drive motor (not shown), and the driving force is transmitted to the fixing member 2 to be rotated. Outside the fixing member 2, a halogen heater 5 and a reflection plate 6 are installed as heating means. The reflection plate 6 reflects the heat of the heater toward the fixing member 2. The surface 2 a of the fixing member 2 is controlled to reach a set temperature by radiant heat from the halogen heater 5 and radiant heat reflected by the reflecting plate 6. As the fixing operation, the sheet P to which unfixed toner is attached is heated and pressed while being nipped and transported with the central portions of the fixing member 2 and the pressure member 14 as a reference, and is fixed.
[0031]
  The fixing member 2 has a roller shape with an outer diameter of 30 mm and extends in the paper width direction. As shown in FIG. 4, the fixing member 2 is formed of a metal cored bar 4 and a plurality of hollow fibers wound around the cored bar 4. It is comprised from the heat insulation layer 3 made. That is, the fixing member 2 has a cavity 4a therein. Examples of the hollow fiber include hollow structures such as polyester, polyimide, polyamideimide, polybenzimidazole, polybenzobisoxazole, polyphenylene sulfide, glass, ceramics, and metal. The material is not limited in terms of increasing the heat insulating effect, but in this example, polyimide hollow fiber is adopted in consideration of heat resistance, thermal conductivity of the material itself, and strength. The polyimide hollow fiber has an outer total of 230 μm and an inner total of 150 μm, and has high heat insulation and rigidity by tightly winding this hollow fiber. In the vicinity of the surface layer of the fixing member 2, as shown in FIG. 2A, there is a silicone rubber layer having a thickness of 0.1 mm as the elastic layer 12, and a 15 μm-thick PFA tube is coated on the surface layer as the release layer 13. is there.
[0032]
  The pressing member 14 has a roller diameter of 30 mm and extends in the paper width direction, and is configured by winding a hollow fiber around a metal core 4 in a layer of about 2 mm as shown in FIG. ing. A 1 mm silicone rubber layer 17 is formed on the hollow fiber layer 16 as an elastic layer, and a 15 μm PFA tube is coated on the surface layer as a release layer 18. With such a configuration, when the fixing member 2 and the pressure member 14 are pressed against each other so as to have a surface pressure of 2 kg / cm 2, the hollow fiber layer is hardly deformed and a uniform nip portion N can be formed.
[0033]
  The lengths of the fixing member 2 and the pressure member 14 in the longitudinal direction (paper width direction) indicated by the arrow C are formed longer than the width of the normally used paper P. Both ends of the fixing member 2 are opened to form heat transfer portions 12 and 13 for releasing heat to the outside of the fixing member in the cavity 4a.
[0034]
  Next, the operation will be described. When the conventional fixing member as shown in FIG. 3 is used, for example, in a fixing device capable of passing a normal size paper P, a paper P smaller than the normal size is continuously passed. In such a case, in the paper passing area, the paper and toner are deprived of heat and then reheated, so that the temperature becomes substantially constant. However, since the non-sheet passing area is not deprived of heat by the sheet P and is kept heated, it becomes high temperature, the heat insulating layer and the elastic layer are deteriorated, and the normal size sheet is removed after the small sheet is continuously passed. When the paper is passed, the non-sheet passing portion is at a high temperature, so that toner hot offset, paper wrinkles, and the like occur.
[0035]
  As shown in FIG. 4, the fixing member 2 according to the present invention has an elastic layer 3 positioned on the end portions 2a and 2b side of the fixing member 2 which becomes a non-sheet passing portion when a small size sheet is passed. The thickness is made smaller than the central portion 2c which is a paper portion, and the thermal resistance from the surface layer of the fixing member 2 to the cored bar 4 is different between the end portions 2a and 2b and the central portion 2c. That is, the temperature difference between the surface side 3 a and the inner surface side 3 b of the heat insulating layer 3 is different in the longitudinal direction of the fixing member 2. Since a highly rigid hollow fiber is used for the heat insulating layer 3, the heat insulating layer 3 has high rigidity, and even if the thickness of the heat insulating layer 3 is changed, the amount of deformation due to the pressure hardly changes, and the paper conveyance direction of the nip portion N There is little variation in width. The surface layer of the fixing member 2 is heated by the radiant heat of the halogen heater 5 shown in FIG. 1, and the heat is retained on the surface layer by the heat insulating layer 3. When paper is passed in this state, the heat of the surface layer moves to the paper P and toner T through which the paper has passed, and is fixed. In this way, the heat of the surface layer is taken away by the paper P and the toner, reheated by the radiation of the halogen heater 5, and can be continuously fixed by repeating this.
[0036]
  As described above, in the case of a short heat-fixing span, the heat of the surface layer is immediately taken away by the paper P and the toner T and hardly conducted into the fixing member 2. However, when there is a paper passing portion and a non-paper passing portion for a relatively long time as in the continuous fixing operation of small size paper, the temperature gradient (temperature) between the non-paper passing portion surface layer of the fixing member 2 and the cored bar 4 portion. The difference) increases, and the heat of the non-sheet passing portion surface layer is conducted to the cored bar 4. In particular, since the heat insulating layer 3 in the non-sheet-passing region is thinner than the center portion, the heat of the surface layer is conducted to the cored bar 4 faster than the center portion, and the temperature rise of the surface layer in the non-sheet-passing region can be suppressed. Furthermore, since the thickness of the cored bar 4 is thicker at the end portions 2a and 2b than at the central portion 2c, the heat capacity is large and the temperature is not easily saturated. For this reason, the temperature rise of the surface layer in the non-sheet passing area is suppressed for a long time, and the temperature difference between the sheet passing portion and the non-sheet passing portion is kept small, thereby causing hot offset of the toner T, destruction of the fixing member 2, wrinkles and gloss. Generation of unevenness can be prevented. Further, since heat escapes from the heat transfer portions 12 and 13 to the outside of the fixing member in the cavity 4a, an increase in the internal temperature of the fixing member 2 can be reduced. Here, for example, the standard size is assumed to be A3 size paper and the small size paper is A4 size. However, the paper size is not limited, and the standard size paper as shown in FIG. A configuration in which the thickness of the heat insulating layer 3 is changed stepwise so as to correspond to the type of size, or the thickness of the heat insulating layer 3 may be continuously changed as shown in FIG. In this example, the maximum temperature portion of the fixing member 2 is the entire surface layer in a broad sense and the end surface layer located in a non-sheet passing portion in a narrow sense. The low temperature portion is the entire surface of the cavity 4a in a broad sense and the surface of the cavity 4a located in the central portion 2c in a narrow sense.
[0037]
  The fixing member 2 shown in FIG.,A fan 8 is provided in the vicinity of the opening of the end portions which are the heat transfer portions 12 and 13 of the fixing member 2 to cool the cored bar 4 inside the fixing member 2.In FIG.Air is blown into the cavity 4 a of the fixing member 2 by the fan 8. For this reason, the temperature of the cored bar 4 is less likely to be saturated, the temperature rise of the surface layer in the non-sheet passing region can be suppressed for a long time, and the temperature difference between the sheet passing portion and the non-sheet passing portion can be kept small. It is possible to prevent the occurrence of offset, destruction of the fixing member, wrinkles and gloss unevenness. In this example, air is blown into the cavity 4a of the fixing member 2 by the fan 8, but the air in the cavity 4a may be sucked by the fan 8 to release heat.
[0038]
  The fixing member 2 shown in FIG.,The surface area of the cored bar 4 was made larger at the end than at the center. Because the surface area of the cored bar 4 is increased by mechanically roughening the surface of the cored bar 4 or by providing fins.,Can be cooled more efficiently. Moreover, as shown in FIG. 9, according to the thickness of the heat insulation layer 3, for example, the surface area may be changed stepwise or continuously from the central portion 2c to the end portions 2a, 2b. With this configuration, the temperature rise of the surface layer in the non-sheet passing area can be suppressed for a long time, and the temperature difference between the sheet passing portion and the non-sheet passing portion can be kept small, thereby causing hot offset of toner, destruction of the fixing member, Generation of wrinkles and uneven gloss can be prevented.
[0039]
  (Example1)
  The fixing member 2 shown in FIG.,A heat insulating sheet 9 made of foamed silicone is provided only in the central part 4b of the cored bar 4. By disposing the heat insulating sheet 9 in this manner, only the end portions 2a and 2b can be cooled while preventing the temperature of the central portion 2c from being lowered, and therefore only the temperature rising portion of the non-sheet passing portion can be cooled.
[0040]
  (Example2)
  In this example, the sheet size detected by a sheet size sensor 19 serving as a sheet size detecting unit that detects the sheet size and the sheet passing number counting unit 20 serving as a sheet passing number counting unit that counts the number of sheets P passing through the sheet P are counted. Based on the number of sheets passed, the drive state of the fan 8 is changed and controlled by the controller 10 as a control unit.
[0041]
  The controller 10 is configured by a well-known computer. When paper feeding starts, the controller 10 takes in paper size information from the paper size sensor 19, determines whether the paper size is a normal size or a small size, and measures the number of papers to be passed. The information on the number of passing sheets counted by the container 20 is taken in. When the paper size is the normal size, the fan 8 is not driven regardless of the number of sheets to be passed. Further, when it is determined that the paper P is a small size and the number of sheets to be passed becomes a predetermined number or more, the fan 8 is driven to cool the core 4 of the fixing member 2. Thus, by controlling the drive of the fan 8 according to the paper size and the number of sheets to be passed, it is possible to save power and to avoid unnecessary cooling operation.
[0042]
  As shown in FIG. 12, a temperature sensor 11a serving as a first temperature detecting means for detecting the temperature of the end 4c inside the cavity 4a, and a second temperature detecting means for detecting the temperature of the central part 4b inside the cavity 4a. The temperature sensor 11b is provided, and the drive state of the fan 8 is changed and controlled by the controller 14 serving as a control unit based on the difference in temperature information detected by the temperature sensors 11a and 11b.
[0043]
  The controller 14 is composed of a known computer, and when the difference in temperature information from the temperature sensors 11a and 11b is equal to or greater than a predetermined temperature difference, the temperature at the end of the fixing member 2 is increased. Then, the fan 8 is driven. In this way, the fan 8 is driven only when the temperature difference between the end 4c and the center 4b in the cavity 4a is equal to or greater than a predetermined temperature difference, so that power saving can be achieved and unnecessary cooling operation can be avoided.
[0044]
  In each example, the paper passing portion is the paper P.ContactThe non-sheet passing portion refers to the end portions 2a and 2b positioned outside the width of the sheet P. In each of the above embodiments, the fixing member 2 has been described as having a roller shape. However, as shown in FIGS. 14 and 15, the fixing member 2 and the tension roller 17 are also applied to a fixing device in which the fixing belt 16 is stretched. it can. When the fixing belt 16 is used, the belt may be heated by the halogen heater 5. Note that the fixing member 2 shown in FIG.AhThus, the fixing belt 16 is in sliding contact with the fixed state.
[0045]
【The invention's effect】
  According to the present invention, the fixing member is formed with a part where heat is easily transmitted and a part where heat is not easily transmitted in the longitudinal direction, and the temperature rise is suppressed at the part where heat is easily transmitted. Generation of temperature unevenness in the member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented.
[0046]
  According to the present invention, the heat insulation rate of the heat insulation layer is different, and by reducing the heat insulation rate of the end portion of the fixing member that becomes a non-sheet passing portion, heat can easily escape and temperature rise can be suppressed. Therefore, occurrence of temperature unevenness in the fixing member is suppressed, and problems such as wrinkles, gloss unevenness, and hot offset due to temperature unevenness can be prevented.
[0047]
  According to the present invention, since the heat radiation amount in the cavity of the fixing member varies in the longitudinal direction of the fixing member, the temperature of the portion with a high heat radiation amount is easily escaped. By increasing the heat radiation amount, the occurrence of uneven internal temperature in the fixing member is suppressed, and problems such as wrinkles and gloss unevenness due to temperature unevenness, and hot offset can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fixing device to which the present invention is applied.
2A is a partially enlarged sectional view of a fixing member, and FIG. 2B is a partially enlarged sectional view of a pressure member.
FIG. 3 is a schematic cross-sectional view showing a configuration of a conventional fixing member.
[Fig. 4]ConstantFIG. 3 is a schematic cross-sectional view of a fixing member in a landing apparatus.
[Figure 5]ConstantFIG. 5 is a schematic cross-sectional view of another fixing member in the attaching device.
[Fig. 6]ConstantFIG. 5 is a schematic cross-sectional view of another fixing member in the attaching device.
[Fig. 7]ConstantFIG. 3 is a schematic cross-sectional view of a fixing member in a landing apparatus.
[Fig. 8]ConstantFIG. 3 is a schematic cross-sectional view of a fixing member in a landing apparatus.
FIG. 9ConstantFIG. 5 is a schematic cross-sectional view of another fixing member in the attaching device.
FIG. 10 shows an embodiment of the present invention.1It is a schematic sectional drawing of the fixing member in the fixing device shown in FIG.
FIG. 11 shows an embodiment of the present invention.22 is a schematic configuration diagram showing a fixing member and its control system in the fixing device shown in FIG.
FIG. 12 is a schematic configuration diagram showing a fixing member and its control system in the fixing device.
FIG. 13 is a schematic configuration diagram of an image recording apparatus equipped with the fixing device of the present invention.
FIG. 14 is a schematic configuration diagram of a fixing device using a belt-like fixing member to which the present invention is applied.
FIG. 15 is a schematic configuration diagram of another fixing device using a belt-shaped fixing member to which the present invention is applied.
[Explanation of symbols]
  2 Fixing member
  2a, 2b Longitudinal end
  2c Longitudinal center
  3 Insulation layer
  3a Surface side of heat insulation layer
  3b Inner surface side of heat insulation layer
  4 cored bar
  4a cavity
  4b Center of the cavity
  4c End of cavity
  5 Heating means
  8 fans
  9 Insulation material
  10, 14 Control unit
  11a First temperature detection means
  11b Second temperature detecting means
  12, 13 Heat transfer part
  14 Pressure member
  19 Paper size detection means
  20 Number of paper passing counting means
  504Y, 504M, 504C, 504BK Image carrier
  509 Fixing device
  560 transfer means
  T Toner image
  P Recording material
  N Nip part
  C Longitudinal direction of fixing member

Claims (3)

A fixing member heated by a heating unit and a pressure member in pressure contact with the fixing member, and a recording material on which a toner image is transferred pass through a nip formed by the fixing member and the pressure member. In the fixing device for fixing by
The fixing member includes a metallic core bar having a cavity inside thereof and an opening at both ends, and a heat insulating member provided on a surface inside the cavity where the thickness of the core bar is smaller than a predetermined thickness. Have
A fixing device having a fan for forcibly moving heat in the cavity from the opening to the outside . The fixing device according to claim 1.
Control for changing and controlling the driving state of the fan based on the paper size detected by the paper size detecting means for detecting the paper size and the number of passed sheets counted by the passed sheet number counting means for counting the number of passed sheets a fixing device characterized in that it comprises a part. An image forming apparatus comprising: an image carrier; a transfer unit that transfers a toner image formed on the image carrier to a recording material; and a fixing device that fixes the toner image transferred to the recording material to the recording material. ,
An image forming apparatus using the fixing device according to claim 1 or 2 as the fixing device .

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