JP6395570B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device used in an image forming apparatus employing an image forming process such as an electrophotographic system or an electrostatic recording system such as a copying machine, a laser beam printer, and an LED printer.

  A fixing device using a film is known as a fixing device provided in an image forming apparatus such as an electrophotographic system or an electrostatic recording system. This fixing device is a device that has a cylindrical film and a heater that comes into contact with the inner surface of the film, and fixes the toner image formed on the recording material to the recording material using the heat of the film.

  This fixing device has an advantage that the warm-up time is short because the heat capacity of the film is small. However, when a small size recording material is continuously fixed, a temperature increase in the non-sheet passing portion in which the temperature of the non-sheet passing portion, which is an area through which the recording material does not pass, rises excessively easily occurs. Therefore, Patent Document 1 discloses a device that suppresses the temperature rise of the non-sheet passing portion by bringing a long thin aluminum plate into contact with the heater in the longitudinal direction to promote the movement of heat in the non-sheet passing portion. Yes.

JP 11-260533 A

  However, since the metal plate of Patent Document 1 is formed in an elongated shape (aluminum plate having a length of 230 mm, a width of 10 mm, and a thickness of 1.0 mm) according to the size of the heater, it is easily warped, and the metal plate has May affect adhesion. Therefore, in order to suppress the warpage of the metal plate, a configuration in which the metal plate is divided into a plurality of parts in the longitudinal direction can be considered, but depending on the way of division, the movement of heat between the central portion and the end portion by the metal plate is hindered. There is a problem that there may be cases.

  One of the preferred embodiments for solving the above problems is a cylindrical film, a heater that contacts the inner surface of the film, and a surface of the heater opposite to the surface that contacts the inner surface of the film. A fixing device that heats a toner image formed on a recording material by using heat of the film and fixes the toner image on the recording material. And one of them is in contact with the heater continuously from the center to the end of the heating area of the heater in the bus direction.

  According to the present invention, in a fixing device having a film, a heater in contact with the inner surface of the film, and a heat conduction member in contact with the heater, heat between the central portion and the end portion in the longitudinal direction by the heat conduction member can be obtained. The structure which divided | segmented the heat conductive member can be implement | achieved, without preventing a movement.

1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment. Schematic sectional view of the fixing device according to the first embodiment. (A) Side view of the heater according to the first embodiment, (b) Front view of the heater according to the first embodiment. The figure which shows the position of the heat conductive member which concerns on Example 1. FIG. The figure which shows the position of the heat conductive member which concerns on the comparative example 2 FIG. 3 is a diagram of the fixing device according to the first embodiment when viewed from the recording material conveyance direction. The figure which shows the temperature distribution of a film in Example 1 and Comparative Examples 1 and 2.

  An embodiment of the present invention will be described with reference to FIGS.

(Image forming device)
A schematic cross-sectional view of a laser beam printer as an image forming apparatus according to the present embodiment is shown in FIG.
The printer includes a process cartridge that holds a drum-type electrophotographic photosensitive member (hereinafter “photosensitive member”) 1 as an image carrier, a charging unit 2, and a developing unit 4. In addition, a laser scanner unit 3 is provided that forms an electrostatic latent image corresponding to the image information on the outer peripheral surface of the photoconductor by an exposure processing step corresponding to the input image information. The image forming apparatus further includes a transfer unit 5 that transfers an image to the recording material P, and a fixing unit (fixing device) 7 that performs a fixing process on the recording material P to which the image has been transferred by heating and pressing.

  When the printer receives the print signal, the photosensitive member 1 starts to rotate. The photoreceptor 1 is rotationally driven in the direction of arrow A at a predetermined peripheral speed. At that time, a bias is applied to the charging unit 2 from a power source (not shown), and the surface of the photoreceptor 1 is charged to a predetermined surface potential.

  Next, scanning and exposure are performed by the scanner unit 3 on the charged portion of the surface of the photoconductor according to the image information, and an electrostatic latent image according to the image information is formed on the photoconductor 1. Formed on the surface. The electrostatic latent image thus formed is developed by the developing unit 4 and visualized as a toner image.

On the other hand, the feeding roller 9 is driven and separated from the recording material loaded with the recording material P from the paper feeding cassette 13 and fed. The recording material P is conveyed by a registration roller pair 10 to a transfer nip portion formed by the photoreceptor 1 and the transfer portion 5 at a predetermined timing. The toner image formed on the photoreceptor 1 is transferred to the recording material P while the recording material P is conveyed at the transfer nip portion. Then, the recording material P that has been subjected to the transfer process is sent to the fixing unit 7 and is discharged to the outside of the printer via the paper discharge unit 8.
The image forming process has been described above.

(Fixing device)
Next, the fixing device 7 will be described with reference to FIG. In FIG. 2, 201 is a cylindrical film, 202 is a pressure roller as a backup member. Reference numeral 203 denotes a heater that contacts the inner surface of the film 201. Reference numeral 300 denotes a metal plate as a heat conducting member that contacts the heater 203. Reference numeral 204 denotes a heater holder as a support member that supports the heater 203 via the metal plate 300. The metal plate 300 is sandwiched between the heater 203 and the heater holder 204. 211 is a stay 211 for improving the bending rigidity of the support member 204. The heater 203 forms a nip portion for conveying the recording material together with the pressure roller 202 through the film 201. In the description of the fixing device, the longitudinal direction is the same direction as the generatrix direction of the film 201.

  The film 201 has a base layer and a surface layer formed outside the base layer. The base layer is formed of a resin such as polyimide (PI) or polyether ether ketone (PEEK), or a metal such as stainless steel (SUS) or nickel. The surface layer is formed of a material having excellent releasability such as a fluororesin.

  As shown in FIG. 2, the pressure roller 202 includes a cored bar 202a, a rubber layer 202b formed outside the cored bar 202a, and a release layer 202c formed outside the rubber layer. The core metal 202a is formed of a metal such as iron or aluminum. The rubber layer 202b is formed of silicone rubber, silicone sponge, or the like. The release layer 202c is formed of a fluororesin or the like. As shown in the schematic diagram of the fixing device 7 in FIG. 6, the cored bar 202a of the pressure roller 202 is provided with a gear G for receiving a driving force from a driving source (not shown) at one end. The length of the cored bar 202a of the pressure roller 202 is as follows because of the space for providing the gear G in the cored bar 202a. The length (distance L1) of the cored bar 202a from the center of the recording material conveyance area to the end (one end) on the side where the gear G is provided is the end (others) on the side where the gear G is not provided. It is longer than the length (distance L2) of the cored bar 202a to the end). Hereinafter, of the cored bar 202a of the pressure roller 202, the side on which the gear G is provided is referred to as the long axis side, and the side on which the gear G is not provided is referred to as the short axis side. In this embodiment, it is assumed that the central portion of the recording material conveyance region in the pressure roller 202 (nip portion) coincides with the central portion of the heat generation region of the heater 203.

  The heater holder 204 shown in FIG. 2 is formed of a resin having high heat resistance such as polyphenylene sulfide (PPS) or liquid crystal polymer (LCP). The heater holder 204 also functions as a guide member that guides the film 201 from the inner surface while supporting the heater 203.

  The configuration of the heater 203 will be described with reference to FIG. FIG. 3A is a side view of the heater 203, and FIG. 3B is a front view of the front side of the heater 203. The heater 203 includes a substrate 203a, a heating resistor 203b formed on the substrate 203a, a protective layer 203d that protects the heating resistor 203b, and an electrode portion 203c that is electrically connected to the heating resistor 203b. Have. The substrate 203a is formed of a ceramic such as alumina or aluminum nitride. The heating resistor 203b is formed on the substrate 203a by screen printing using silver / palladium alloy or the like. The electrode part 203c is formed of silver or the like. The protective layer 203d is a glass coat, and contributes to an improvement in slidability with the film 201.

  In the heater 203 according to the present embodiment, two silver palladium (Ag / Pd) pastes are formed in the longitudinal direction as a heating resistor 203b on a substrate 203a formed of alumina having a thickness of 1 mm. Further, at the end on the short axis side of the substrate 203a, the ends of the two heating resistors 203b are electrically connected by applying and baking silver. In addition, an electrode portion 203c is formed by applying and baking silver on an end portion on the long axis side of the substrate 203a. The heating resistor 203b has a configuration in which two heating resistors 203b are connected in series, and is adjusted so that the total resistance of the two heating resistors 203b is 18Ω. A connector C shown in FIG. 6 is connected to the electrode portion 203c, and power is supplied from a power source (not shown). A glass coat 203 d is applied on the heating resistor 203 b of the heater 203.

  Next, the configuration of the metal plate 300 of this embodiment will be described with reference to FIG. The upper diagram of FIG. 4 is the same as FIG. 3A, and the lower diagram of FIG. 4 is a diagram of the heater 203 and the metal plate 300 viewed from the support member 203 side. The metal plate 300 of the present embodiment is divided into two parts 300a and 300b in the longitudinal direction. The metal plates 300a and 300b are in contact with the surface opposite to the surface that contacts the inner surface of the film 201 of the heater 203. The metal plate 300a has a length of 150 mm, a width of 5 mm, and a thickness of 0.1 mm, and the metal plate 300b has a length of 90 mm, a width of 5 mm, and a thickness of 0.1 mm. By dividing the metal plate 300 in this way, the size of the metal plate is reduced to suppress warpage, and the adhesion between the metal plate 300 and the heater 203 is improved. Each of the metal plate 300a and the metal plate 300b has a bent portion (not shown) formed by bending both ends in the longitudinal direction to a side where the heater holder 204 is provided, and the bent portion is provided in the heater holder 204. The movement in the longitudinal direction is restricted by being inserted into the.

  The metal plate 300a and the metal plate 300b have an asymmetric shape with respect to the central portion of the heat generating region. The metal plate 300a is continuously in contact with the heater 203 from the center of the heat generating area of the heater 203 (area where the heat generating resistor 203b is provided) to the end on the side where the electrode section 203c is provided in the longitudinal direction. On the other hand, in the longitudinal direction, the metal plate 300b is in contact with the heater 203 continuously to the end portion of the heat generation area where the electrode portion 203c is not provided at a predetermined interval from the end portion of the metal plate 300a. . In the longitudinal direction, the metal plate 300 a is provided on the long axis side of the pressure roller 202 in FIG. 6, and the metal plate 300 b is provided on the short axis side of the pressure roller 202. Note that the heat conductivity (200 W / mk) of the metal plate (aluminum plate) 300 is higher than the heat conductivity (20 W / mk) of the substrate (alumina) 203a of the heater 203. A diffusion effect is obtained.

  On the metal plate 300a, as shown in FIG. 4, a thermistor Th as a temperature detection member is provided closer to the electrode portion 203c than the center of the heat generating region. The thermistor Th is for detecting the temperature of the heater 203 through the metal plate 300a. The electric power supplied to the heater 203 is controlled by a control unit (not shown) so that the temperature detected by the thermistor th becomes the target temperature.

  Next, the fixing process operation of the fixing device 7 according to the present embodiment will be described. The pressure roller 202 is rotated by a driving force transmitted from a driving source (not shown) via a gear G shown in FIG. The film 201 rotates following the pressure roller 202 by the frictional force received from the pressure roller 202 rotating at the nip portion. At this time, power is supplied from the power source (not shown) to the heating resistor 203b via the electrode portion 203c, and the heating resistor 203b generates heat, thereby heating the film 201. After the temperature of the thermistor Th reaches a fixable target temperature, the toner image is heated using the heat of the film 201 while conveying the recording material P on which the toner image is formed at the nip portion, and the toner image is recorded on the recording material P A fixing process for fixing to P is performed.

(Effect of this embodiment)
The effect of this embodiment will be described using the fixing devices of this embodiment, Comparative Example 1, and Comparative Example 2. Here, the structure of the comparative example 1 and the comparative example 2 is demonstrated. Comparative Example 1 is a fixing device that does not include the metal plate 300, and the other configuration is the same as that of the present embodiment. Comparative Example 2 is a fixing device in which the shape of the metal plate 300 is different from that of the present example, and the other configuration is the same as that of the present example. The shape of the metal plate 300 of the comparative example 2 is demonstrated using FIG. The metal plate 300 of the comparative example 2 is divided into two in the longitudinal direction, a metal plate 300a and a metal plate 300b. The metal plate 300a and the metal plate 300b have the same size (length 120 mm, width 10 mm, thickness 0.1 mm). In the longitudinal direction, the boundary between the metal plate 300 a and the metal plate 300 b (region where the metal plate 300 is not in contact with the heater) coincides with the central portion of the heat generation region of the heater 203. That is, the metal plate 300a and the metal plate 300b have a symmetrical shape with respect to the central portion of the heat generation region.

FIG. 7 and Table 1 show the results of measuring the surface temperature of the film 201 after the fixing treatment under the conditions shown below. For the measurement of the surface temperature of the film 201, a non-contact thermometer (which can detect infrared rays and display a temperature distribution) was used.
Type of recording material: XEROX Business 4200 (basis weight 75 g / m2, LETTER size)
Surface speed of the pressure roller 202 (printer process speed): 100 mm / s
Target temperature: 190 ° C. (detection temperature of temperature detection element Th)
FIG. 7 shows the temperature distribution of the film 201 in the heat generation region of each heater 201 of Comparative Example 1, Comparative Example 2, and Example 1 at an interval of one sheet in 5 seconds. . The horizontal axis in FIG. 7 is the position in the longitudinal direction of the film 201, and the vertical axis is the temperature of the film 201. As for the position in the longitudinal direction, the major axis side and the minor axis side are shown in the figure so that the correspondence with the pressure roller 202 becomes clear.

  Table 1 shows the central portion of the heat generation area of the films 201 of Comparative Example 1, Comparative Example 2, and Example 1, and measured temperatures on the long axis side and the short axis side. Table 1 shows the results of evaluation of good (◯) and slightly inferior (Δ) regarding the fixability of the image subjected to the fixing process together with the measured temperature.

  According to FIG. 7, in any fixing device, the temperature of the film 201 at the temperature detection position by the thermistor Th is the target temperature (190 ° C.). In any fixing device, as shown in FIG. 7 and Table 1, the temperature at both ends of the heat generation area of the film 201 is lower than the temperature at the center. This is because, when fixing a large size recording material such as LETTER, both ends in the longitudinal direction of the film 201 are deprived of heat by the recording material in the same way as the central portion, and more than the central portion. This is because it is close to the outside of the device and easily radiates heat.

  Comparative Example 1 shows that the temperature on the long axis side (183 ° C.) of the film 201 is lower than the temperature on the short axis side (186 ° C.). As a result, the fixing property of the end portion on the long axis side of the image fixed by the apparatus of Comparative Example 1 was inferior to that of the end portion on the central portion and the short axis side. This is because the shaft 202a of the pressure roller 202 is longer on the long axis side than on the short axis side and has a larger heat capacity, so the heat of the film 201 is on the longer axis side than on the short axis side of the pressure roller 202. It is because it is easy to escape. In addition to this, since the electrode 203c is provided on the substrate 203a on the long axis side of the heater 203 and a connector is connected to the electrode 203c, the film has a structurally larger heat capacity than the short axis side. The heat of 201 is easy to move.

  The temperature of the film 201 in the comparative example 2 is lower than that of the comparative example 1 in the central portion of the heat generating region, and the temperatures at both ends are high. This is because the heat in the vicinity of the central portion is transmitted to both ends having a low temperature due to the thermal diffusion effect of the metal plates 300a and 300b. However, the fixability at the end on the long axis side of the image fixed by the apparatus of Comparative Example 2 is inferior to that at the center and the end on the short axis side, and the temperature on the long axis side of the film 201 (184 ° C.). ) Is not enough.

  On the other hand, the temperature on the long axis side of the film 201 in Example 1 was 186 ° C., and the fixability of the image edge portion was also good. In the apparatus according to the first embodiment, the metal plate 300a continuously contacts the heater 203 from the central part of the heat generation area of the heater 203 to the end on the long axis side, and the heat at the central part is longer than that on the short axis side. This is because more can be transmitted to the shaft side. On the other hand, in the apparatus of Comparative Example 2, since the central portion of the heat generating region and the boundary region between the metal plates 300a and 300b coincide with each other in the longitudinal direction, the heat at the central portion of the heater 203 is a metal. The structure is difficult to move to the end via the plate 300. Further, in the configuration of Comparative Example 2, the metal plate 300a and the metal plate 300b are symmetrical with respect to the central portion of the heat generating region in the longitudinal direction. Therefore, the metal plate 300 of the comparative example transfers almost the same amount of heat to the end on the long axis side and the end on the short axis side of the heat at the center of the heater 203, and one of the heat is applied in the longitudinal direction. It is difficult to correct the heat generation distribution of a device having a heat capacity at one end larger than that at the other end.

  As described above, in this embodiment, in the fixing device in which the heat conducting member is brought into contact with the heater, the heat conducting member is divided without hindering the heat transfer between the central portion and the end portion in the longitudinal direction by the heat conducting member. There is an effect that can be done.

(Modification of this embodiment)
A modification of this embodiment will be described. In the first modification of the present embodiment, the sizes of the metal plate 300a and the metal plate 300b are the same as in the present embodiment, but are formed of materials having different thermal conductivities. The metal plate 300a is a copper plate (thermal conductivity 420 w / mk), and the metal plate 300b is an aluminum plate (200 w / mk). Example: By making the thermal conductivity of the metal plate 300a larger than that of the metal plate 300b, an uneven temperature distribution of the film 201 due to an imbalance of heat capacity at one end and the other end in the longitudinal direction of the apparatus The effect is that correction becomes easier than 1.

  Further, as a second modification, a configuration in which the metal plate 300b is a copper plate (thermal conductivity 420 w / mk) and the metal plate 300a is an aluminum plate (200 w / mk) is also conceivable. In this embodiment, since the metal plate 300b is not in contact with the central portion of the heat generating region of the heater 203, the function of transferring heat from the central portion to the end portion by the metal plate 300b is inferior to that of the metal plate 300a. Therefore, by making the thermal conductivity of the metal plate 300b higher than that of the metal plate 300a, the function of moving the heat of the heater 203 by the metal plate 300b from the central portion to the end portion can be improved.

  Moreover, even if the materials of the metal plate 300a and the metal plate 300b are the same, the same effects as those of the first and second modifications can be obtained by making the thickness or the width in the short direction different.

  Moreover, in the present Example and the modification, although the metal plate 300 was divided into two, it is not limited to this. The effect can be obtained even if the metal plate 300b is further divided into a plurality of parts. In the present embodiment and the modification, the long axis side of the pressure roller and the side on which the heater electrode is provided are the same side in the longitudinal direction. However, when these are opposite to each other in the longitudinal direction, the metal plate 300a of the present embodiment is provided on the long axis side of the pressure roller.

  In addition, a present Example and modification do not necessarily presuppose the imbalance of the heat capacity of the one end part of the apparatus and the other end part. In the present embodiment, when fixing a large size recording material, the heat at the central portion of the heater 203 can be easily moved to one of the end portions, so that the end fixability can be improved. Because it plays.

  Further, in this embodiment and the modification, a metal plate (a plate material made of metal) is used as the heat conducting member, but the present invention is not limited to this as long as the heat conductivity is higher than that of the heater substrate. For example, the same effect can be obtained even with a plate or sheet made of graphite.

  Further, in the fixing devices of the present embodiment and the modification, the heater forms the nip portion together with the pressure roller through the film, but is not limited to this configuration. For example, a fixing device in which a heater contacts an inner surface of a film and a nip portion forming member different from the heater forms a nip portion together with a pressure roller via the film may be used. Or the structure which heats the fixing roller which forms a nip part with a film, the heater which contacts the inner surface of a film, and a pressure roller from the outside may be sufficient.

DESCRIPTION OF SYMBOLS 201 Film 202 Pressure roller 202a Metal core of pressure roller 203 Heater 204 Heater holder 300 (300a, 300b) Thermal conduction member

Claims (6)

A tubular film,
A heater in contact with the inner surface of the film;
A roller having a shaft portion that forms a nip portion for conveying a recording material together with the film, and a plurality of rollers in contact with the surface of the heater opposite to the surface in contact with the inner surface of the film. A heat conduction member divided into
In the a fixing device for fixing a recording material the toner image by heating the thermal toner image formed on a recording material by using the film, the shaft portion of the roller, in the generatrix direction, The distance from the center of the heat generation area of the heater to one end is longer than the distance to the other end,
One of the heat conducting members is in contact with the heater continuously from the central portion of the heat generating area of the heater in the bus bar direction to an end portion on the same side as the one end .   The fixing device according to claim 1, further comprising: a support member that supports the heater via the heat conductive member, the heat conductive member being sandwiched between the support member and the heater.   The fixing device according to claim 1, wherein the heat conducting member is a plate material. The heater board and the fixing device according to any one of claims 1 to 3, characterized in that it has a, a heating resistor formed on the substrate. The fixing device according to claim 4 , wherein a thermal conductivity of the thermal conductive member is larger than a thermal conductivity of the substrate. The heater is electrically connected to the heating resistor, and has an electrode portion provided only at one end in the longitudinal direction of the substrate,
One of the heat conducting members is in contact with the heater continuously from a central portion of the heat generating region of the heater to an end portion on the same side as the side on which the electrode portion is provided. Item 6. The fixing device according to Item 4 or 5 .