JP2005107201A - Heating device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent tear/break of a film end part, to increase edge heating nature (fixability) and to reduce drive torque, etc. in a tension-free type (pressure roller drive type) heating device of film heating system. <P>SOLUTION: In the heating device having a heating object, film 2 which slides with the heating object and a pressure roller 6 having an elastic layer 6a on a shaft 6b, which is pressure-contact with the heating object via the film 2, forms a nip N, driven and rotated, carries, conveys a heated member by the nip N and heats the heated member by heat from the heating object via the film 2, when the axial direction of the pressure roller 6 is considered as the longitudinal direction of each component, at least one edge f of the longitudinal direction of the film 2 exists at the same position as one edge g in the longitudinal direction of the elastic layer 6a of the pressure roller 6 or the inside of the edge g. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a film heating suitable for use as a fixing device (fixing device) for heating and pressure-fixing an unfixed toner image formed and supported on a recording material in an image forming apparatus such as an electrophotographic system. The present invention relates to a heating apparatus of the type, and an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer provided with the heating apparatus as an image heating fixing unit.

  In general, in various types of information, video equipment, and the like, an image forming apparatus that specifically substantiates an image in an intangible information format on a recording material such as paper is used as its final output form.

  In such an image forming apparatus such as a copying machine, a coloring agent or the like is fixed on a recording material according to an image pattern by drawing or drawing, scanning or recording an object, or generating an image generated by communication transfer or the like. By doing so, an appropriate image is reproduced on the paper.

  Further, in this image forming apparatus, fine toner powder is used as a colorant (developer). In order to stably fix the toner arranged in an image pattern on the paper, simplicity, etc. Therefore, the heating method is widely used.

  Conventionally, an electrothermal roller type fixing device has been widely used as a fixing device as a heating device. However, such a fixing device takes a long time to start operation and consumes a relatively large amount of power. Inconvenience occurred.

  That is, in this fixing device, a halogen lamp is disposed inside a metal roller, and the halogen lamp is heated to heat the entire metal roller, so that the entire metal roller has a uniform temperature. Since it takes time to become operable, the time required for start-up of the operation is slow, and since the entire metal roller having a relatively large heat capacity is always heated, power consumption is also increased.

  Therefore, a resistance heating element pattern is directly formed on a ceramic substrate with excellent heat resistance and durability to form a heating element, which is used as a heat source and a sheet of paper etc. via a thin heat resistant film. A configuration method of a heating device of a film heating method that uniformly heats a heated material by contacting the heated material is disclosed in Patent Document 1 and the like.

  Further, as disclosed in Patent Document 2 and the like, a tension that allows the film to be driven with respect to the pressure roller by loosely fitting the film on the film guide and driving the pressure roller as the pressure means. A free type (pressure roller drive type) film heating type heating device often employs this heating device because the number of parts is small.

According to such a film heating type heating apparatus, since the heat capacity of the heating substrate and the film itself is small, it is possible to shorten the time required to raise the temperature up to a predetermined temperature and to reduce power consumption.
JP-A-63-313182 JP-A-4-44075

  In recent years, copying machines and printers using an electrophotographic method have greatly increased the number of printable sheets per unit time, and as a result, the speed of image forming apparatuses has been increased.

  When the speed is increased, the time required for the recording material to pass through the fixing device is increased. Therefore, when the developer is fixed on the recording material as before, the speed is increased. It is necessary to give more heat and pressure than the above structure.

  In addition, it is necessary to widen the fixing area by widening the nip portion for nipping and conveying the recording material. In order to widen the nip width, there is a method of increasing the pressure or decreasing the hardness of the heat-resistant elastic layer of the pressure roller.

  In the case of a tension-free type film heating type fixing device (heating device), if the pressure is simply increased, the nip width will widen, but the pressure roller itself will bend by the pressure, so the nip width in the longitudinal direction It becomes difficult to maintain a uniform thickness, resulting in uneven fixing in the longitudinal direction. Therefore, in order to keep the nip width straight in the longitudinal direction, a method of lowering the hardness of the heat resistant elastic layer of the pressure roller is preferable. However, if the hardness is lowered too much, the force to support the film itself will weaken, so the flange will support the film at both ends by sliding and moving due to a slight difference in pressure in the longitudinal direction. The end of the film is pressed against. If the length of the fixing film is long and the end is outside the end of the heat-resistant elastic layer of the pressure roller, the end of the fixing film cannot be supported. Has occurred.

  In addition, the resistance heating element in the heating body is housed in the nip, so that when the heating element is exposed from the nip portion, the heating body is prevented from cracking due to local temperature rise in the exposed portion. When the length of the heat-resistant elastic layer in the longitudinal direction is short, it is necessary to shorten the length of the resistance heating element of the heating body, and in that case, it becomes difficult to secure the fixing property at the longitudinal end. As a result, uneven fixing occurred in the longitudinal direction.

  Therefore, an object of the present invention is to prevent the above-mentioned problem of tearing and tearing of the film in a tension-free type (pressure roller drive type) film heating type heating apparatus.

  Another object is to prevent tearing and tearing of the film, and further to prevent heating unevenness (fixing unevenness) in the longitudinal direction.

  Still another object is to prevent tearing and tearing of the film and to further improve the slidability of the pressure roller.

  Still another object is to provide an image forming apparatus capable of providing a high-quality image by providing the heating device of the present invention as a heat fixing device.

  The present invention is a heating apparatus and an image forming apparatus having the following configurations.

(1) A heating element, a film that slides with the heating element, and an elastic layer on the mandrel, pressurizing the heating element through the film to form a nip, and being rotationally driven A heating apparatus that sandwiches and conveys the member to be heated at the nip, and heats the member to be heated by heat from the heating body via the film,
When the axial direction of the pressure roller is the longitudinal direction of each constituent member, at least one end in the longitudinal direction of the film is at the same position as one end in the longitudinal direction of the elastic layer of the pressure roller, or A heating device, wherein the heating device exists inside one end portion in the longitudinal direction of the elastic layer of the pressure roller.

(2) A heating body, a film sliding with the heating body, an elastic layer on a cored bar, pressurizing with the heating body via the film to form a nip, and pressurizing to rotate A heating apparatus that sandwiches and conveys the member to be heated at the nip, and heats the member to be heated by heat from the heating body via the film,
When the axial direction of the pressure roller is the longitudinal direction of each component, the length in the longitudinal direction of the film is L1, and the length in the longitudinal direction of the elastic layer of the pressure roller is L2, L1 ≦ A heating apparatus, wherein the relationship of L2 is established, and an end portion in the longitudinal direction of the film is present at the same position or in the longitudinal direction as an end portion in the longitudinal direction of the elastic layer of the pressure roller.

(3) A heating element provided with a resistance heating element, a film that slides with the heating element, an elastic layer on a cored bar, and press-contacted with the heating element via the film to form a nip, A heating roller that rotates and drives the heated member in the nip, and heats the heated member by heat from the heating body via the film,
When the axial direction of the pressure roller is the longitudinal direction of each constituent member, the length in the longitudinal direction of the film is L1, the length in the longitudinal direction of the elastic layer of the pressure roller is L2, and the length on the heating body When the length in the longitudinal direction of the resistance heating element is L3, the relationship of L1 ≦ L3 ≦ L2 holds, and the longitudinal end of the resistance heating element is the longitudinal end of the elastic layer of the pressure roller. The heating device is present at the same position or inside in the longitudinal direction.

  (4) In the heating device according to any one of (1) to (3), the friction coefficient of the surface of the heating body in contact with the elastic layer of the heating body and the pressure roller is the friction of the surface in contact with the film of the heating body. A heating device characterized by being smaller than the coefficient.

  (5) In an image forming apparatus having an image forming means for forming and carrying an unfixed image on a recording material and a heat fixing means for fixing the unfixed image on the recording material, the heat fixing means according to claims 1 to 4. An image forming apparatus comprising the heating device according to claim 1.

  According to the configuration of the above (1), in order to hold the end portion of the film with the pressure roller elastic layer, the spread in the direction perpendicular to the length of the film at the end portion is suppressed and the trumpet-like tearing and tearing are prevented. Is possible.

  According to the configuration of (2) above, in order to hold the end portion of the film with the pressure roller elastic layer, the spread of the film at the end portion in the direction perpendicular to the length of the film is suppressed, and the trumpet-like tearing and tearing are prevented. Is possible.

  According to the configuration of the above (3), in order to hold the end portion of the film with the pressure roller elastic layer, the spread in the direction perpendicular to the length of the film at the end portion is suppressed and the trumpet-like tearing and tearing are prevented. Is possible. Moreover, since it becomes possible to increase the calorie | heat amount of the heating apparatus of the to-be-heated member edge part by making the length of the resistance heating element on a heating body longer than a film, it can prevent the heating nonuniformity in a longitudinal direction. In addition, in the heat fixing device, it is possible to prevent a fixing failure at the image end portion.

  According to the configuration of (4) above, the frictional force at the portion where the pressure roller and the heating element come into contact is reduced, so that the rotational torque of the pressure roller can be reduced, and the operating load of the entire heating device can be reduced. Become.

  According to the configuration of (5), an image forming apparatus capable of preventing the fixing film from being broken, reducing the operation load of the heat fixing apparatus itself, and providing a high-quality image without fixing unevenness in the longitudinal direction is provided. It becomes possible to do.

  According to the present invention described above, it is possible to prevent tearing and tearing of the film in a tension-free type (pressure roller drive type) film heating type heating apparatus. Further, it is possible to prevent the film from being torn and torn, and further to prevent heating unevenness in the longitudinal direction (fixing unevenness in the heat fixing apparatus). Furthermore, the film can be prevented from being torn and torn, and the rotational torque of the pressure roller can be reduced, thereby reducing the operating load of the entire heating device. Further, it is possible to provide an image forming apparatus that can prevent the fixing film from being broken, reduce the operation load of the heat fixing apparatus itself, and can provide a high-quality image without fixing unevenness in the longitudinal direction.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic view of a main part of a laser beam printer as an image forming apparatus according to an embodiment of the present invention.

  Reference numeral 101 denotes an organic photosensitive drum as an image carrier, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed. The peripheral surface of the organic photosensitive drum 101 that is rotationally driven is uniformly charged to a predetermined polarity and potential by a charging roller 102 to which a predetermined charging bias is applied from the power source E1. In this example, negative charging is performed to a predetermined potential.

  Next, laser scanning exposure L of image information is performed on the uniformly charged surface by the laser exposure device 103. The laser exposure device 103 scans and exposes the uniformly charged surface of the organic photosensitive drum 101 by outputting laser light modulated in accordance with the time-series electric digital pixel signal of the image information. Reference numeral 103 a denotes a mirror that deflects the output laser light to the exposure unit of the organic photosensitive drum 101. By this laser scanning exposure L, an electrostatic latent image corresponding to the scanning exposure pattern of the image information is formed on the surface of the organic photosensitive drum 101.

  Next, the electrostatic latent image is developed as a toner image by the developing device 104. The developing device 104 of this example is a reversal developing device using a one-component magnetic toner or a two-component developer composed of a mixture of toner and a magnetic carrier as the developer T, and the toner has a negative polarity. The developer T is magnetically held on the peripheral surface of the developing sleeve 104a as a developer carrying member rotated in the counterclockwise direction indicated by the arrow, and the layer thickness is regulated by a blade 104b as an application amount regulating member. By the rotation of the sleeve 104a, the photosensitive drum 101 is conveyed to a developing area which is a facing portion of the developing sleeve 104a. A predetermined developing bias is applied to the developing sleeve 104a from the power source E2. As a result, the negatively charged toner on the developing sleeve 104a side selectively moves and adheres to the surface of the organic photosensitive drum 101 corresponding to the electrostatic latent image pattern in the developing region, and the electrostatic latent image is reversely developed as a toner image. The

  On the other hand, the recording material P stacked and stored in the sheet feeding cassette 110 is separated and fed by the sheet feeding roller 111, which is a contact portion between the organic photosensitive drum 101 and the transfer roller 106 from the sheet path 112. The sheet is fed to the transfer nip portion at a predetermined control timing, and is nipped and conveyed through the transfer nip portion. A predetermined positive transfer bias having a polarity opposite to the charging polarity of the toner is applied to the transfer roller 106 from the power source E3. As a result, the toner image on the surface of the organic photosensitive drum 101 is sequentially transferred onto the surface of the recording material P at the transfer nip portion.

  The recording material that has exited the transfer nip is separated from the surface of the organic photosensitive drum 101 and is introduced from the sheet path 113 into the heat fixing device 107 and undergoes a toner image fixing process. The recording material that has exited the heat fixing device 107 passes through a sheet path 114 and is discharged as a print to a discharge unit 115 outside the apparatus.

  On the other hand, the surface of the organic photosensitive drum 101 after separation of the recording material is cleaned by a cleaning blade 105a of the cleaning device 105 to remove residual deposits such as transfer residual toner and paper dust, and is repeatedly used for image formation. .

  Reference numeral 116 denotes a process cartridge that can be attached to and detached from a predetermined location 1001 in the printer main body 1000. In this example, the four image forming process devices, ie, the organic photosensitive drum 101, the charging roller 102, the developing device 104, and the cleaning device 105 are collectively configured as a process cartridge that can be attached and detached.

(2) Heat fixing device 107
FIG. 2 is an enlarged schematic cross-sectional view of the main part of the heat fixing device (heat fixing device) 107. The heat fixing device 107 of this example is a tension-free type (pressure roller drive type) film heating type heating device using a cylindrical film.

  Reference numeral 100 denotes a fixing film unit, and reference numeral 6 denotes a pressure roller. A fixing nip portion N is formed by pressure contact between the two 100 and 6.

  In the fixing film unit 100, reference numeral 3 denotes a ceramic heater as a heating body, which is a horizontally long and thin member having a low heat capacity and having a longitudinal direction as a longitudinal direction in the drawing. Reference numeral 1 denotes a horizontally long stay made of a heat-resistant resin having a substantially semicircular arc shape in cross section, and serves as an inner surface guide member of a cylindrical film to be described later. The heating body 3 is fixedly held by being fitted into a heating body fitting groove formed along the length of the horizontal stay 1 at the center of the lower surface of the horizontal stay 1. Reference numeral 2 denotes a cylindrical film, which is loosely fitted on the horizontally long stay 1 on which the heating body 1 is fixed and held as described above. Reference numeral 7 denotes a horizontally long pressurizing stay with a U-shaped cross section that is inserted into the inside of the horizontally long stay 1. The both ends of the horizontally long pressure stay 7 protrude outwardly from the both ends of the film 2. It is. Reference numeral 10 denotes a flange for regulating the end portion of the film 2, which is assembled to both end portions of the horizontally long pressure stay 7 projecting outward from both end portions of the film 2 (FIG. 3). The end of the film 2 is received by the surface to restrict the movement of the film 2 along the length of the horizontally long stay 1.

  In order to reduce the heat capacity and improve the quick start property, the film 2 has a total thickness of about 100 μm or less and has PTFE, PFA, FEP having heat resistance, releasability, strength, durability, etc. Or a full-layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of polyimide, polyamideimide, PEEK, PES, PPS or the like. In this embodiment, the heat-resistant film 2 was coated with a polyimide film of 50 μm, PTFE of 10 μm, and a layer thickness of 60 μm. The inner peripheral surface side of the film 2 is coated with grease in order to improve slidability.

  The assembly of the horizontally long stay 1, the heating body 3, the cylindrical fixing film 2, the horizontally long pressure stay 7 and the flange 10 is a fixing film unit 100.

  The pressure roller 6 includes an aluminum cored bar 6b having an outer diameter of 13 mm, and a heat-resistant elastic layer of silicone foam having a length L = 240 mm and a thickness of 3 mm, which is coated on the cored bar 6b in a roller shape. 6a. As shown in FIG. 3, both end portions of the cored bar 6b are rotatably held between the side plates (not shown) of the fixing device via bearings 8 so as to be rotatably supported. Further, a gear G is fixedly disposed on one end side of the cored bar 6b, and a driving force from a driving motor M of a driving device is transmitted to the gear G so that the elastic pressure roller 6 is rotationally driven. Yes.

  Then, the fixing film unit 101 is arranged on the upper side of the pressure roller 6 in parallel with the elastic pressure roller 6 with the heating body 3 facing downward, and as shown in FIG. The pressure block 10a integrated with the flange is pressed downward by a predetermined force against the elasticity of the pressure roller 6 by the pressure spring 10b. As a result, the horizontally long pressure stay 7 and the horizontally long stay 1 are pushed down against the elasticity of the elastic pressure roller 4, and the heating body 3 and the pressure roller 6 are pressed against each other with the film 2 sandwiched therebetween. A fixing nip portion N having a predetermined width is formed by the elastic strain of the elastic layer 6a.

  The film 2 receives rotational torque due to frictional force at the fixing nip portion N by the rotational driving of the pressure roller 6, and the film at a predetermined peripheral speed while the inner surface of the fixing nip portion N closely contacts and slides on the surface of the heating element 3. The outer periphery of the horizontally long stay 1 serving as the inner surface guide member is in a driven rotation state.

  The energization of the heating body 3 is started, the pressure roller 6 is driven to rotate, and the cylindrical film 2 is rotated in accordance with the rotation of the pressure roller 6, and the heating body 3 rises to a predetermined temperature and enters a temperature control state. In a state where the rotation of the pressure roller 6 and the film 2 is stabilized, the recording material P carrying the unfixed toner image T between the film 2 and the pressure roller 6 in the fixing nip portion N is an entrance side guide member. 11 is guided, guided and transported by the sheet 11, the unfixed toner image carrying surface of the recording material P is in close contact with the outer surface of the film 2, and the recording material P passes through the fixing nip portion N in a state of being overlapped with the film 2. To go.

  In the process of passing the recording material P through the fixing nip, the recording material P is heated by receiving the heat of the heating body 3 through the film 2 and the unfixed toner image T is fixed to the surface of the recording material P by heating and pressing. The recording material P is separated from the outer surface of the film 2 at the recording material outlet portion of the fixing nip portion N, guided by the outlet side guide member 12, and discharged and conveyed.

FIG. 4 is a structural model diagram of the heating element 3 used in this example. This heating element 3 is
1) Alumina substrate a having a width of 7 mm, a length of 270 mm, and a thickness of 1 mm as a heater substrate (ceramic substrate);
2) An electric resistance material such as Ag / Pd (silver palladium), for example, is applied and formed on the surface side of the heater substrate a by screen printing to a thickness of about 10 μm and a width of 1 to 3 mm. In addition, two reciprocating parallel resistance heating elements b,
3) A conductive pattern c in which one end portions of the two reciprocating parallel resistance heating elements b are electrically connected in series;
4) An electrode pattern d for feeding that is electrically connected to the other end of each resistance heating element b.
5) Insulating protective sliding layer e such as thin glass or fluororesin provided to cover resistance heating element b and conductive pattern c on the surface side of heater substrate a,
Etc.

  A thermistor 4 as a temperature detecting element for monitoring the temperature of the heating body is disposed on the back side of the heater substrate a.

  Then, the heating body 3 is fitted and fixed to the heating body fitting groove formed along the length of the member at the center of the lower surface of the horizontally long stay 1 so that the surface of the heating body is exposed to the outside. is there.

  Reference numeral 13 denotes a power supply connector fitted to the heating element 3 on the power supply electrode pattern d side. The heating element 3 is heated rapidly by the power supply from the AC power supply 14 to the resistance heating element b via the power supply connector 13 and the power supply electrode pattern d, and the resistance heating element b generates heat over the entire length. The temperature rise of the heating body 3 is detected by the thermistor 4, and the detected temperature information is input to the control circuit 15. Based on the detected temperature information, the control circuit 15 controls the power supplied from the AC power source 14 to the resistance heating element b by phase, wave number control, etc., and controls the temperature of the heating element 3 to a predetermined temperature.

  Next, the relationship in the longitudinal direction of the film 2 and the pressure roller 6 in the heat fixing device 107 of this embodiment will be described with reference to FIG. Here, the axial direction of the pressure roller 6 is the longitudinal direction of the constituent members of the apparatus.

  In this embodiment, the length in the longitudinal direction of the film 2 is L1 = 225 mm, the length in the longitudinal direction of the silicone rubber foam portion 6a that is the elastic layer of the pressure roller 6 is L2 = 240 mm, and the relationship of L1 <L2 is satisfied. It is said. Further, the end portion f of the film 2 is configured to exist inside the end portion g of the silicone rubber foam portion 6 a of the pressure roller 6.

  By the way, when there is a slight pressure difference in the longitudinal direction of the fixing nip N and a difference in hardness of the pressure roller 6 on the film 2, the film 2 is shifted toward the longitudinal direction of the horizontally long stay 1 that is a film guide member. Force is generated. In that case, the film 2 slides along the longitudinal direction of the horizontally long stay 1 and moves in the longitudinal direction, and the end portion f in the offset direction is pressed against the inner surface of the flange 101 to be received, thereby restricting the movement of the film. . However, if the pressing force is too strong, the film end f buckles, and the film end opens in a trumpet shape, resulting in a problem that eventually breaks the film.

  In particular, so-called medium- and high-speed machines with a large number of prints per fixed time are designed to increase the width of the fixing nip portion N and widen the fixing area in order to ensure the fixing performance. In this case, since the hardness of the heat-resistant elastic layer 6a of the pressure roller 6 is kept low, the force for pressing the film itself does not work, and the film 2 tends to move toward the longitudinal end portion.

  However, as in the present embodiment, by maintaining the relationship between the length L1 of the film 2 and the length L2 in the longitudinal direction of the heat-resistant elastic layer 6a of the pressure roller 6 as described above, the film 2 is in the longitudinal end direction. The force in the pressing direction from the heat-resistant elastic layer 6a of the pressure roller 6 to the film end acts even when the force to move toward the flange increases and the pressing force against the flange 101 increases, so the film end Will open in a trumpet shape in the direction perpendicular to the longitudinal direction and will not tear or tear.

  Therefore, an endurance test of 50,000 sheets was performed using the image forming apparatus provided with the heat fixing device 107 having this configuration, and it was confirmed whether or not the film 2 had the lifetime of the image forming apparatus main body.

  The main body of the image forming apparatus of this example was an image forming apparatus main body having a process speed of 140 mm / s and a throughput of 25 ppm. In order to secure the fixing performance, the Asker C hardness of the pressure roller 6 is kept low for the purpose of securing the fixing nip width. The hardness of the silicone rubber foam 6a of the pressure roller 6 is measured at a total of 8 points, 10 mm from both ends in the longitudinal direction and 4 points in the circumferential direction. The average is considerably low as 42 °, and the nip width N = 9 mm. It is said. It is very difficult to produce the silicone rubber foam 6a with exactly the same hardness in one, and hardness variations of about 1 ° to 2 ° may occur even within the same pressure roller. Many. Also in this embodiment, the pressure roller has a left-right hardness difference, and the driving side is 41.3 ° and the non-driving side is 42.7 °.

  As Comparative Example 1, a fixing device having a configuration in which the length L1 of the film 2 in the longitudinal direction L1 = 225 mm and the length of the silicone rubber foam 6a of the pressure roller 6 in the longitudinal direction L2 = 218 mm as shown in FIG. A durability test was conducted. As described above, the relationship is L1> L2, and the longitudinal end g of the silicone rubber foam 6a of the pressure roller 6 is located inside the film end f. The hardness of the silicone rubber foam portion 6a of the pressure roller 6 was 42 ° asker C hardness (41.6 ° on the driving side and 42.4 ° on the non-driving side) as in this embodiment.

  Table 1 shows the state of the film at the endurance of the image forming apparatus main body.

  In Comparative Example 1, film breakage occurred at a little less than 27,000 sheets, and durability was stopped. First, the Asker C hardness of the silicone rubber foam portion 6a of the pressure roller 6 is low, and a force by which the film 2 slides in the longitudinal direction due to a slight left-right hardness difference acts, and the film end f is pressed against the flange 10. Power works. Furthermore, since the length L1 of the film 2 in the longitudinal direction is shorter than the length L2 of the silicone rubber foam 6a of the pressure roller 6 (FIG. 5), the pressure roller 6 becomes free when the end of the film becomes free. Since the force to press the film end in the pressurizing direction does not work with the silicone rubber foam part 6a, the film end pressed against the flange 10 is buckled, and the film end f opens in a trumpet shape. Tearing and tearing will occur.

  In Example 1, 50,000 sheets were passed without film breakage. This is because the pressure roller 6 itself has a left-right hardness difference in the silicone rubber foam portion 6 a as in Comparative Example 1, and the film 2 also has a sliding force in the longitudinal direction, and the film end f is pressed against the flange 10. Power works. However, since the length L2 of the silicone rubber foam portion 6a of the pressure roller 6 is longer than the longitudinal length L1 of the film 2 and outside the film end f (FIG. 3), the film end f is In the fixing nip portion N, a force that presses the film end in the direction perpendicular to the longitudinal direction works, and the film end f pressed against the flange 10 does not become a trumpet and does not break.

  In this way, the longitudinal length L2 of the heat resistant elastic layer portion 6a of the pressure roller 6 is made longer than the longitudinal length L1 of the film 2, and the end portion of the heat resistant elastic layer 6a of the pressure roller 6 is set. By making g outside the edge f of the film 2, it is possible to completely prevent film breakage and to provide a high-quality image until the life of the image forming apparatus main body. .

  In this embodiment, the length L2 of the heat-resistant elastic layer 6a of the pressure roller 6 is longer than the length L1 in the longitudinal direction of the fixing film 2, and the end of the heat-resistant elastic layer 6a of the pressure roller 6 is set. Although g is present outside the end f of the fixing film 2, at least one end g of the heat-resistant elastic layer 6 a of the pressure roller 6 is at the same position as the end f of the fixing film 2. However, the same effect can be obtained. Further, even if at least one end portion g of the heat-resistant elastic layer 6a of the pressure roller 6 is present on the inner side of the end portion f of the fixing film 2, the fixing film 2 is on the other side. Similar effects can be obtained. Furthermore, although the material of the heat resistant elastic layer 6a of the pressure roller 6 is a silicone rubber foam, it is not limited to this as long as the same effect can be obtained. Furthermore, the length L1 of the film 2 is limited to 225 mm, and the length L2 of the heat-resistant elastic layer 6a of the pressure roller 6 is limited to 240 mm. However, it is not limited to this as long as the same effect can be obtained.

  In this embodiment, the length L3 (FIG. 3) in the longitudinal direction of the resistance heating element b on the heating body 3 of the first embodiment described above is made longer than the length L1 of the film 2, and the heat resistance of the pressure roller 6 is increased. The elastic elastic layer 6a is shorter than the length L2. Further, the end g of the heat-resistant elastic layer 6 a of the pressure roller 6 exists outside the end h of the resistance heating element b and the film end f of the heating body 3.

  That is, the relationship of L1 <L3 <L2 is satisfied, and the end g of the heat-resistant elastic layer 6a of the pressure roller 6 is outside the end h of the resistance heating element b of the heating body 3, and the resistance heating of the heating body 3 is performed. The end h of the body b has an outer relationship than the film end f.

  Since the configuration of the fixing device and the configuration of the image forming apparatus other than the above-described related configurations are the same as those in the first embodiment, the description thereof will be omitted.

  According to the above-described apparatus configuration of the present embodiment, not only film tearing that occurs at the film edge f can be prevented, but also the fixability of the image at the edge can be improved, and fixing unevenness in the longitudinal direction can be prevented.

  Therefore, an endurance test of 50,000 sheets was performed using the main body of the image forming apparatus provided with the heat fixing device of this configuration, and whether or not the film 2 has the life of the main body and further the ability of fixing was confirmed.

  The main body of the image forming apparatus of this example was an image forming apparatus main body having a process speed of 140 mm / s and a throughput of 25 ppm. In order to secure the fixing performance, the Asker C hardness of the pressure roller is kept low for the purpose of securing the nip width. The hardness of the silicone rubber foam 6a of the pressure roller 6 is measured at a total of 8 points, 10 mm from both ends in the longitudinal direction and 4 points in the circumferential direction. = 9 mm. Silicone rubber foams are very difficult to manufacture with the same hardness in one piece, and hardness variations of about 1 ° to 2 ° often occur even within the same pressure roller. . Also in this embodiment, the pressure roller has a left-right hardness difference, and the driving side is 40.9 ° and the non-driving side is 42.1 °.

  The longitudinal relationship of the fixing device is that the length L1 of the film 2 is 225 mm, the length L2 of the silicone rubber foam 6a of the pressure roller 6 is 240 mm, and the length of the resistance heating element b of the heating body 3 is L3 = 231 mm. And the relationship of L1 <L3 <L2 is established.

  Also, the end g of the silicone rubber foam 6 a of the pressure roller 6 is outside the end h of the resistance heating element b of the heating body 3, and the end h of the resistance heating element b of the heating body 3 is the end of the film 2. It is outside the part f.

  As Comparative Example 2, the longitudinal length L1 of the film 2, the longitudinal length L2 of the silicone rubber foam 6a portion of the pressure roller 6, and the length of the resistance heating element b of the heating body 3 as shown in FIG. A similar durability test was performed using a fixing device having a configuration of L3. L1 = 225 mm, L2 = 218 mm, L3 = 216 mm, and L1> L2> L3, and the longitudinal end g of the silicone rubber foam 6a of the pressure roller 6 is inside the film end f. In addition, the end h of the resistance heating element b of the heating body 3 is located inside the end g of the silicone rubber foam 6a of the pressure roller 6.

  If the resistance heating element b does not fit within the fixing nip formed by the pressure roller 6 and the fixing film unit 100, the resistance heating element b may abnormally generate heat at a portion where it does not fit, causing cracking of the heating element.

  Further, the hardness of the silicone rubber foam portion 6a of the pressure roller 6 was 42 ° in Asker C hardness (41.8 ° on the driving side and 42.2 ° on the non-driving side) as in the example.

The fixability is an average value of samples of 1 to 100 sheets, and represents a density reduction rate before and after rubbing with a halftone fixing rubbing tester. In this durability test, Fox River Bond 75 g / m ² paper (letter size) was used as the paper type.

  Table 2 shows the state of the film and the fixability in the life of the image forming apparatus main body.

  If the fixing density reduction rate exceeds 20%, it is NG level, and if it is within 20%, it is OK level.

  In Comparative Example 2, film breakage occurred at a little over 27,000 sheets, and the durability was stopped. First, the Asker C hardness of the silicone rubber foam portion 6a of the pressure roller 6 is low, and a force by which the film 2 slides in the longitudinal direction due to a slight left-right hardness difference acts, and the film end f is pressed against the flange 10. Power works. Furthermore, since the length L1 of the film 2 in the longitudinal direction is shorter than the length L2 of the silicone rubber foam part 6a of the pressure roller 6 (FIG. 5), the film end f becomes free so that the pressure roller Since the rubber part 6a of 6 does not exert a force to hold the film end f in the pressing direction, the film end f pressed against the flange 10 is buckled, and the film end f opens in a trumpet shape. The tears will occur.

  Regarding the fixing property, the fixing property at the center is 12.1%, which is an OK level, but the fixing property at the end is an NG level. This is because the length L3 of the resistance heating element b of Comparative Example 2 is shorter than the length L2 of the rubber portion 6a of the pressure roller 6 and further 2 mm longer than the letter-size lateral width 216 mm. This is because if it escapes, the fixing property at the edge of the image will deteriorate.

  In Example 1, the film breakage is 50,000 sheets OK. As described above, the pressure roller 6 itself has a left-right hardness difference in the silicone rubber foam portion 6a as in Comparative Example 1, and the film 2 also has a sliding force in the longitudinal direction. The force pressed against the flange 10 works. However, since the length L2 of the rubber portion 6a of the pressure roller 6 is long and the rubber portion end g is outside the film end f (FIG. 3), the film end f is elongated at the fixing nip portion N. The force that presses the film end f in the direction perpendicular to the direction acts, and the film end f pressed against the flange 10 does not become a trumpet and does not break.

  Regarding the fixing property, the fixing property at the center is 10.2%, which is OK level, and the fixing property at the edge is also OK level, but the fixing property at the edge is 19.5%, and there is almost no margin. First, the length L3 of the resistance heating element b of Example 1 (FIG. 3) is only 2 mm longer than the letter-size lateral width 216 mm as in Comparative Example 2 (FIG. 5). Since the length L2 of this is longer than that of the comparative example 2, the heat escape is smaller than that of the comparative example 2, and the end fixability is better than that of the comparative example 2. However, since the length L3 of the resistance heating element b is short, the fixability of the end portion tends to be lowered.

  In Example 2, 50,000 sheets were passed without film breakage. This is because the pressure roller 6 itself has a left-right hardness difference in the silicone rubber foam portion as in Comparative Example 1, the film 2 also has a sliding force in the longitudinal direction, and the film end f is pressed against the flange 101. Work. However, since the length L2 of the rubber portion 6a of the pressure roller 6 is long and the rubber portion end g is outside the film end f, the film end f is film in the nip portion N in the direction perpendicular to the longitudinal direction. The force which presses down the edge part f works, and the film edge part f pressed against the flange 10 is torn without becoming a trumpet shape and does not break.

  In terms of fixability, both the center and the edge of the image are at the OK level. This is because the length L3 of the resistance heating element b of the heating element 3 is sufficiently long and 15 mm longer than the image width 216 mm, so that the image can be sufficiently fixed at the image end even if heat escapes from the end. Because it is. Further, since the resistance heating element b is present in the rubber portion 6a of the pressure roller 6, there is no local abnormal heat generation, and the heating element does not crack.

  In this way, the length L2 of the heat-resistant elastic layer portion 6a of the pressure roller 6 in the longitudinal direction is made longer than the length of the resistance heating element b of the heating element 3, and the length L3 of the resistance heating element b of the heating element 3 is set. Is longer than the length L1 of the film 2 in the longitudinal direction, and the end g of the heat-resistant elastic layer 6a of the pressure roller 6 is placed outside the end h of the resistance heating element b of the heating body 3, By making the end h of the resistance heating element b outside the end f of the film 2, it is possible to completely prevent the occurrence of film breakage, and further improve the fixing property of the image end, Fixing unevenness in the direction can be completely eliminated. That is, it is possible to provide a high-quality image until the lifetime of the image forming apparatus main body.

  In the present embodiment, the end h of the resistance heating element b of the heating element 3 is located inside the end g of the heat-resistant elastic layer 6a of the pressure roller 6, but the resistance heating element b The same effect can be obtained even if the position of the end h of the heat-resistant elastic layer and the end of the heat-resistant elastic layer g of the pressure roller 6 are the same. Moreover, although the material of the heat resistant elastic layer 6a of the pressure roller 6 is a silicone rubber foam, it is not limited to this as long as the same effect can be obtained. Further, the length L1 of the film 2 is limited to 225 mm, the length L2 of the heat resistant elastic layer 6a of the pressure roller 6 is limited to 240 mm, and the length L3 of the resistance heating element b of the heating element 3 is limited to 231 mm. Of course, it is not limited to this as long as it is obtained.

  A feature of the present embodiment is that in the first and second embodiments, the heating element 3 and the heat-resistant elastic layer 6a of the pressure roller 6 are in direct contact with each other without the film 2 (between N1 and N2 in FIG. 3). The coefficient of friction of the surface of the heating body is made smaller than the portion j where the heating body 3 and the heat-resistant elastic layer 6a of the pressure roller 6 are not in direct contact (the portion corresponding to L1 where the film 2 is interposed) j. It is. Since the configuration of the fixing device and the configuration of the image forming apparatus other than those described above are the same as those in the first and second embodiments, the description thereof will be omitted.

  In this embodiment, the insulating protective sliding layer e of the heating body 3 is processed to reduce the friction coefficient of the portion i where the heating body 3 and the heat-resistant elastic layer 6a of the pressure roller 6 are in direct contact. Yes. In this embodiment, the insulating protective sliding layer e of the heating body 3 is a glass layer, and as a specific processing method for reducing the friction coefficient of the portion i of the glass layer e, the glass surface, the pressure roller surface layer, Since the frictional force decreases when the contact area is smaller, the glass surface of the heating element 3 is polished with a fine file in the same direction as the rotation direction of the pressure roller 6. The glass layer portion j other than the portion i is not polished with a file. The friction coefficient μ of the glass layer portion j not polished with the file is 0.3, whereas the friction coefficient μ of the glass layer portion j polished with the file is 0.2.

  Using the heating element 3 of this configuration, the torque in the heat fixing device was measured. As a comparative example, the entire friction coefficient μ of the glass layer e remains at 0.3 without performing the above-described processing of the surface portion j of the heating layer 3 in direct contact with the pressure roller 6 of the glass layer e. A thing was used.

  In the torque measuring method, a torque measuring device is connected to the pressure roller 6 itself, and the heating body 3 is idling while the temperature is adjusted to 180 ° C., and the torque value of only the heat fixing device is measured. The torque value itself is an average value when it is continuously rotated for 5 minutes from the start of idling.

  Table 3 shows the measured torque values of Example 3 and Comparative Example 3 when measured under the above conditions.

  When Example 3 and Comparative Example 3 are compared, it can be seen that the torque value is clearly lower in Example 3. This is because the friction coefficient of the portion i where the heating body surface and the pressure roller are in direct contact with each other is lowered, so that the frictional force between the heating body 3 and the pressure roller 6 is reduced, resulting in a reduction in torque. It is.

  Thus, by reducing the friction coefficient of the surface of the heating body at the portion i where the heating body 3 and the pressure roller 6 are in contact with each other, it is possible to reduce the frictional force between the heating body 3 and the pressure roller 6 and heat fixing. The torque of the device can be reduced. Furthermore, the operation load of the entire image forming apparatus can be reduced, and it is not necessary to use an expensive and high-power drive device.

  In this embodiment, the surface of the heating element is polished with a file in order to reduce the friction coefficient. However, the present invention is not limited to this method as long as the same effect can be obtained.

[Others]
1) The heating device of the present invention is not limited to the heat fixing device of the embodiment, but an image heating device that heats a recording material carrying an image to improve surface properties such as gloss, an image heating device that is supposed to be worn, It can be widely used as a means / device for heat-treating a material to be heated, such as a heating / drying device or a heating laminating device.

  2) Of course, the structure of the ceramic heater as the heating element 3 is not limited to the structure shown in the embodiment. The heating element 3 is not limited to a ceramic heater, and other types of heating elements such as an electromagnetic induction heating member and a nichrome heater can also be used.

1 is a schematic view of a main part of a laser beam printer as an image forming apparatus according to an embodiment of the present invention. It is a cross-sectional enlarged model view of the main part of the heat fixing device. It is a figure (Examples 1-3) showing the relationship of the longitudinal direction of a heat fixing apparatus. It is a configuration explanatory view of a heating body incorporated in a heat fixing device. It is a figure showing the relationship of the longitudinal direction of the heat fixing apparatus of Comparative Examples 1-3.

Explanation of symbols

  1 .. Stay 2 .. Film 3.. Heating element b b Resistance heating element 4 Thermistor 6 Pressure roller 6a Heat-resistant elastic layer 6b Pressure roller 6b Pressure roller core, T ... toner, P ... recording material, 101 ... photoconductor, 102 ... charging roller, 103 ... laser exposure device, 104 ... developing device, 105a ... cleaning blade, 106 ..Transfer roller 107 ..Fusing device 100 ..Fixing film unit

Claims (5)

A heating body, a film that slides with the heating body, a pressure roller that has an elastic layer on the core, forms a nip in pressure contact with the heating body via the film, and is driven to rotate. A heating device that sandwiches and conveys the member to be heated at the nip, and heats the member to be heated by heat from the heating body via the film,
When the axial direction of the pressure roller is the longitudinal direction of each constituent member, at least one end in the longitudinal direction of the film is at the same position as one end in the longitudinal direction of the elastic layer of the pressure roller, or A heating device, wherein the heating device exists inside one end portion in the longitudinal direction of the elastic layer of the pressure roller. A heating body, a film that slides with the heating body, a pressure roller that has an elastic layer on the core, forms a nip in pressure contact with the heating body via the film, and is driven to rotate. A heating device that sandwiches and conveys the member to be heated at the nip, and heats the member to be heated by heat from the heating body via the film,
When the axial direction of the pressure roller is the longitudinal direction of each component, the length in the longitudinal direction of the film is L1, and the length in the longitudinal direction of the elastic layer of the pressure roller is L2, L1 ≦ A heating apparatus, wherein the relationship of L2 is established, and an end portion in the longitudinal direction of the film is present at the same position or in the longitudinal direction as an end portion in the longitudinal direction of the elastic layer of the pressure roller. A heating element provided with a resistance heating element, a film that slides with the heating element, and an elastic layer on a core metal, and press-contacted with the heating element through the film to form a nip, which is driven to rotate. A heating roller that sandwiches and conveys the heated member at the nip, and heats the heated member by heat from the heating body via the film,
When the axial direction of the pressure roller is the longitudinal direction of each constituent member, the length in the longitudinal direction of the film is L1, the length in the longitudinal direction of the elastic layer of the pressure roller is L2, and the length on the heating body When the length in the longitudinal direction of the resistance heating element is L3, the relationship of L1 ≦ L3 ≦ L2 holds, and the longitudinal end of the resistance heating element is the longitudinal end of the elastic layer of the pressure roller. The heating device is present at the same position or inside in the longitudinal direction.   The heating device according to any one of claims 1 to 3, wherein the friction coefficient of the surface of the heating body in contact with the elastic layer of the heating body and the pressure roller is made smaller than the friction coefficient of the surface in contact with the film of the heating body. A heating device characterized by.   5. An image forming apparatus comprising: an image forming unit that forms and supports an unfixed image on a recording material; and a heat fixing unit that fixes an unfixed image on the recording material. An image forming apparatus comprising the heating device described above.

Images