JP5253603B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device mounted on an image forming apparatus using electrophotographic technology such as a copying machine or a printer.

  In a general image forming apparatus, an electrostatic latent image is formed on the surface of a photosensitive drum based on image information. The photosensitive drum is charged with a predetermined polarity, and when light is irradiated based on image information, the charge in that portion is removed to form an electrostatic latent image. A developing device for storing toner is provided adjacent to the photosensitive drum. The toner is charged with the same polarity as that of the photosensitive drum, and is adsorbed on an uncharged portion of the surface of the photosensitive drum. The recording material onto which the toner image is transferred is conveyed to a nip portion between the photosensitive drum and the transfer roller by a conveyance unit including a paper feed roller and a conveyance roller. A transfer roller is also provided adjacent to the photosensitive drum, and applies a charge having a polarity opposite to that of the toner from the back surface of the recording material to attract and transfer the toner on the surface of the photosensitive drum onto the recording material. The recording material onto which the toner image has been transferred is conveyed to a nip portion of a fixing unit that includes a heating roller incorporating a heating device and a pressure roller pressed against the heating roller. After fixing the toner image on the recording material by applying heat and pressure by the fixing means, the recording material is conveyed by a pair of conveying rollers and discharged from the recording material discharge port to the recording material stacking portion.

  Examples of fixing means include a heat roller method and a film heating and pressing method. In the heat roller method, a rotating roller pair is formed by a heat roller (hereinafter, a fixing roller) and a pressure roller. A heat source such as a halogen lamp is built in the fixing roller, the fixing roller is heated to a predetermined fixing temperature and the temperature is adjusted, and a recording material on which an unfixed toner image is formed and supported is introduced into the nip portion of the rotating roller pair. In this case, the unfixed toner image is fixed on the recording material by being nipped and conveyed. The film heating method uses a film with a small heat capacity, nipping and transporting the recording material between the film and the pressure roller, and heating and adjusting the temperature of the heater provided on the inner surface of the film to a predetermined fixing temperature. It is means for fixing the toner image on the recording material. In addition, in order to improve the pressure contact state between the fixing roller or film and the pressure roller in the fixing nip portion, there are also those in which an elastic layer is coated on the fixing roller or film.

  In these contact-type heat and pressure fixing systems, the phenomenon of offset is unavoidable. There are several types of offsets. The low temperature offset is caused by insufficient fixing of the toner to the recording material due to insufficient melting of the toner. The high temperature offset is a contamination of the fixing roller and the film due to the molten toner at the time of fixing crying between the recording material and the fixing roller. In addition, there is a so-called electrostatic offset. These offsets can be caused by short-term / temporary image contamination on the front / back of the recording material, and secondary accumulation and transfer of contamination due to repeated use. There was a problem of paper jam and shortening of the fixing device life.

  As countermeasures against the offset phenomenon, as countermeasures from the fixing device, an attempt is made to improve the releasability of the surface of the fixing roller to suppress toner adhesion as much as possible, and according to the charging polarity of the toner on the fixing roller and the pressure roller. Attempts have been made to suppress the offset with respect to the fixing roller by applying a bias charge or removing the charge. Attempts to improve the releasability on the surface of the fixing roller include a configuration in which a fluororesin is coated or a release material is applied to the surface of the fixing roller. When a release material is stably applied to the surface of the fixing roller for a long time, it is necessary to provide an auxiliary cleaning member such as a winding type cleaning web or a cleaning pad, which increases the size and complexity of the fixing device. It was. Considering recent demands for miniaturization and weight reduction, it is necessary and preferable to remove these auxiliary devices. In other words, unless the offset resistance of the toner is improved, it has been impossible to meet the demands for reduction in size and weight. Therefore, as a countermeasure from the toner, a toner including a release wax has been proposed (Patent Document 1). By embedding the release wax in the toner, the release wax moves to the interface between the molten toner and the fixing roller during heat fixing, and prevents the molten toner from crying to the fixing roller side, thereby improving the anti-offset performance. ing. Furthermore, in order to improve anti-offset performance, a technique for adding two or more types of release wax to the toner (Patent Document 2) and a technique for optimizing the thermal characteristics of the release wax (Patent Document 3) have been proposed. Yes.

  Although the fixing roller method has been described, the above countermeasure is the same for the film heating and pressing method and is not limited to the fixing roller method.

JP-A-8-184992 JP 2000-3070 A Japanese Patent Laid-Open No. 11-327340

  The release wax contained in the toner is liquefied at the time of heat fixing, and a part thereof becomes a gas. The wax component cooled immediately after vaporization solidifies again and moves on the wind flowing in the machine. Then, there was a phenomenon that the solidified wax component was liquefied again and adhered at various points in the machine where the temperature rose by passing paper. In the machine, the temperature tends to rise at the point where the recording material comes into contact. That is, the wax component tends to adhere to the recording material conveyance guide and the conveyance roller. If wax components adhere to the recording material conveyance guide or conveyance roller, the recording material conveyance may be hindered or the friction coefficient of the roller may be reduced. A special response was necessary.

  Recently, there is an increasing demand for laser beam printers that are faster and more compact. Regardless of the heat roller method or the film heating and pressing method, higher heat energy and pressure are required in order to perform image formation at a higher speed and satisfy the fixing property. If an attempt to increase the speed is achieved only by increasing the pressing force, a structure that can withstand the pressing force is required, and thus there is a possibility that the request for miniaturization may not be sufficiently satisfied. For this reason, it is necessary to cope with speeding up and downsizing while balancing the increase of heat energy and pressure. As a method for increasing the thermal energy applied to the recording material, a method of increasing the heating time and a method of increasing the heating temperature can be considered, but in any case, the thermal energy applied to the toner on the recording material increases. As the heat energy applied to the toner increases, the amount of release wax that vaporizes also increases.

  In recent years, the thermal energy applied to the toner tends to increase in order to cope with higher speeds and downsizing, and the amount of release wax that vaporizes also increases. The frequency is expected to increase. Therefore, it is important to develop technology for collecting the wax component contained in the toner in the heat and pressure fixing device.

In order to solve the above-described problems, the present invention provides a fixing nip portion forming member that forms a fixing nip portion that heats a recording material carrying a toner image formed by using toner containing a release wax while nipping and conveying the recording material. When, in the fixing device having a frame for accommodating the fixing nip forming member, between the frame and the fixing nip forming member, a component vaporized from the release wax is heated in the fixing nip portion have a collecting member for collecting the collecting member, the radiation heat from the fixing nip forming member, by keeping the temperature of the vaporized component is liquid phase, collecting the vaporized component characterized in that it.

According to the present invention, it is possible to suppress the release wax from adhering to the paper guide or the conveyance roller.

FIG. 3 is a cross-sectional view of an image forming apparatus main body on which a fixing device is mounted. 1 is a cross-sectional view of a fixing device according to a first exemplary embodiment. 1 is a perspective view of a fixing device according to Embodiment 1. FIG. FIG. 3 is a detailed configuration explanatory diagram of a collecting member 113 according to the first embodiment. FIG. 3 is a detailed configuration explanatory view of a collecting member 115 according to the first embodiment. FIG. 6 is a detailed configuration explanatory view of a collecting member 114 according to the first embodiment. Explanatory drawings of heat capacities of the collecting members 113 to 115, the stay 108, the base plate 109, and the front lower cover 112 of the first embodiment. 3 is a detailed explanatory diagram of a sleeve 105 and a pressure roller 102 according to Embodiment 1. FIG. FIG. 3 is a measurement diagram of the melting point and sublimation point of the release wax of Example 1. 5 is a temperature profile of the collecting member 113 and the stay 108 according to the first embodiment. 4 is a temperature profile of the collecting member 114 and the front lower cover 112 according to the first embodiment. The temperature profile of the collection member 115 of Example 1. FIG. The detailed structure explanatory drawing of the collection members 113-115 of Example 2. FIG.

Example 1
First, a full color laser beam printer which is an image forming apparatus equipped with the fixing device of the present invention will be described. Although a full-color laser beam printer provided with a plurality of photosensitive drums is taken up as the image forming apparatus, the present invention can also be applied to a monochrome copying machine including a single photosensitive drum and a fixing device mounted on the printer. Therefore, the image forming apparatus equipped with the fixing device of the present invention is not limited to a full color laser beam printer. FIG. 1 is a longitudinal sectional view showing the overall configuration of a full-color laser beam printer 1 (hereinafter, printer 1).

  A cassette 2 is housed in a lower portion of the printer 1 so as to be drawable. A manual feed unit 3 is disposed on the right side of the printer 1. Recording materials are stacked and accommodated in the cassette 2 and the manual feed unit 3, respectively, and the recording materials are separated one by one and fed to the registration rollers 4. The printer 1 includes an image forming unit 5 in which image forming stations 5Y, 5M, 5C, and 5K corresponding to each color of yellow, magenta, cyan, and black are arranged in a horizontal row. The image forming unit 5 includes photosensitive drums 6Y, 6M, 6C, and 6K (hereinafter, unified with the photosensitive drum 6) as image carriers, and charging devices 7Y, 7M, and 7C that uniformly charge the surface of the photosensitive drum 6. 7K, a scanner unit 8 for forming an electrostatic latent image on the photosensitive drum 6 by irradiating a laser beam based on image information, a developing device 9Y for developing the toner image by attaching toner to the electrostatic latent image, 9M, 9C, and 9K, and primary transfer portions 11Y, 11M, 11C, and 11K (hereinafter unified with the primary transfer portion 11) for transferring the toner image on the photosensitive drum 6 to the electrostatic transfer belt 10 are provided. The toner image on the transfer belt 10 onto which the toner image has been transferred by the primary transfer unit 11 is transferred to the recording material by the secondary transfer unit 12. Thereafter, when the recording material passes through a nip formed by the heating unit 101 and the pressure roller 102 pressed against the heating unit 101, the recording material passes through the fixing device 100 that fixes the transferred image. Thereafter, the conveyance path is switched by the double-sided flapper 13 and conveyed to either the discharge roller pair 14 or the switchback roller pair 15. The recording material conveyed to the switchback roller pair 15 side is reversely conveyed by the switchback roller pair 15 part, and again passes through the registration roller 4, the secondary transfer unit 12, and the fixing device 100, and then the discharge roller pair 14 side. It is conveyed to. After passing through the discharge roller pair 14, the recording material is discharged to the recording material stacking unit 16.

  Next, a detailed configuration of the fixing device 100 mounted on the printer 1 will be described with reference to FIGS. FIG. 2 is a longitudinal sectional view of the fixing device 100, and FIG. 3 is a perspective view of the inside of the fixing device 100.

  In the fixing device 100, 101 is a heating unit, and 102 is a pressure roller. The heating unit 101 has a heater 103. The heater 103 is supported by a heater holder 104 as a support member. The heater holder 104 is formed of a heat resistant resin having heat resistance and sliding properties such as a liquid crystal polymer. A fixing sleeve (endless belt) 105 is externally mounted on the heater holder 104. The fixing sleeve 105 has substantially the same peripheral length as the pressure roller 102, and both end portions of the fixing sleeve 105 are rotatably held on the outer periphery of the pair of sleeve flanges 106. Further, both end portions of the heater holder 104 are also held by the sleeve flange 106. The pair of sleeve flanges 106 are supported by the side plate pair 107. The pressure roller 102 is brought into pressure contact with the fixing sleeve 105 with a predetermined pressing force T so as to face the heater 103 supported by the heater holder 104. As a result, a fixing nip portion N is formed between the fixing sleeve 105 and the pressure roller 102. As described above, the fixing nip portion forming member includes the endless belt, the heater that contacts the inner surface of the endless belt, and the pressure roller that forms the fixing nip portion together with the heater via the endless belt. The fixing nip portion is a region where a recording material carrying a toner image formed using toner containing a release wax is heated while nipping and conveying the recording material.

  The heating unit 101 and the pressure roller 102 are surrounded by a pair of side plates 107, a stay 108, and a base plate 109, and are all sheet metal members. These three parts are frames constituting the fixing device 100, which ensure the rigidity of the fixing device 100 and accommodate a fixing nip portion forming member. The side plate pair 107, the stay 108, and the base plate 109 are surrounded by the rear cover 110, the upper cover 111, the front lower cover 112, and the left and right covers 117, and the user connects the side plate pair 107, the stay 108, and the base plate 109 from the outside. It cannot be touched. Since the lower part of the front lower cover 112 directly faces the heating unit 101, the front lower cover 112 also has a function as a frame constituting the fixing device 100. A collecting member 113 is provided on the surface of the stay 108 on the fixing sleeve 105 side, a collecting member 114 is provided on the surface of the front lower cover 112 on the fixing sleeve 105 side, and a collecting member is provided on the surface of the base plate 109 on the pressure roller 102 side. 115 is installed, and the collection members 113 to 115 are all configured so that the user cannot touch them. The gap between the collection member 113, the collection member 114, and the fixing sleeve 105 is 3 mm, and the gap between the collection member 115 and the pressure roller 102 is 1.5 mm. Although the details will be described later, the collecting member is a member that collects the release wax generated by being heated at the fixing nip portion while being maintained at a temperature between the melting point and the sublimation point of the release wax. The collecting member is provided between the fixing nip portion forming member and the frame that houses the fixing nip portion forming member.

  Next, the detailed structure of the collection member 113, the collection member 114, and the collection member 115 is demonstrated based on FIGS. The collection member 113, the collection member 114, and the collection member 115 are all PBT containing glass with a thickness of 1 mm, and the load deflection temperature is 207 ° C. (1.82 MPa (test method: ISO075-1, 2)). Since the collecting member is thin, the possibility of short-circuiting during injection molding is extremely high. However, if the injection pressure, mold temperature, or resin temperature is increased to prevent short-circuiting, the “warping” of the component increases, and there is a concern that it may come into contact with the fixing sleeve 105 or the pressure roller 102. Therefore, the collecting member 113, the collecting member 114, and the collecting member 115 are not in a shape having a long width, but are configured in such a manner that two short-shaped members are used side by side (however, a machined product) This is not the case when using extruded sheet materials, punched sheet materials, etc.).

  As shown in FIG. 4, the collection member 113 includes ribs 113a at both ends and a central part, and claws 113b in the vicinity of the ribs 113a. The catching member 113 is fixed to the stay 108 by hooking the claw 113b and the stopper 113c into the square hole provided in the stay 108. The claw 113b regulates the X direction and the Z direction, and the stopper 113c regulates the Y direction. . Only the inner surfaces of the rib 113a and the claw 113b are in contact with the stay 108. Other portions are not in contact with each other, and a gap is provided. The contact area between the collecting member 113 and the stay 108 is reduced, and the stay 108 and the gap are provided in portions other than the rib 113a and the claw 113b, thereby preventing heat conduction from the collecting member 113 to the stay 108.

  The attachment structure of the collection member 115 to the base plate 109 is exactly the same as the attachment structure of the collection member 113 to the stay 108 (see FIG. 5). Therefore, the explanation here is omitted.

  As shown in FIG. 6, the collecting member 114 is fixed to the hole 114 a provided in the collecting member 114 by the snap fit 116 through the boss 112 a provided in the front lower cover 112 (3 at both ends and the central portion). Place). The collecting member 114 and the front lower cover 112 are in contact only with the counterbore surface (the mesh hatched surface in FIG. 6) around the boss 112a, and a gap is provided in the other portions. Similar to the collecting member 113 and the collecting member 115, the contact area between the collecting member 114 and the front lower cover 112 is reduced, and a gap is provided in other portions, so that the collecting member 114 is moved to the front lower cover 112. The heat conduction is suppressed. That is, the space between the collecting member and the member to which the collecting member is attached is thermally insulated by the gap.

Next, the heat capacity C of each component is shown in FIG. Heat capacity C is C = mc
Heat capacity: C [J / K], mass: m [g], specific heat: c [J / g · K]
It is represented by As shown in FIG. 7, the collecting member 113 is compared with the stay 108 to which the collecting member 113 is attached, and the collecting member 114 is compared with the front lower cover 112 to which the collecting member 114 is attached. 115 has a very small heat capacity compared to the base plate 109 to which the collecting member 115 is attached. In addition, the heat capacity shown here is one heat capacity (for example, two of the collection members 113 attached to the stay 108) of the plurality attached to the members to which the collection members 113 to 115 are attached. 1 of the heat capacity). In order to quickly raise the temperature to the temperature equal to or higher than the melting point after the printing is started, it is necessary to stabilize the temperature of the fixing sleeve 105 during paper passing. Therefore, it is desirable that the heat capacities of the collecting members 113 to 115 provided near the fixing sleeve 105 are as small as possible. That is, when the heat capacity of the collecting member is C1 and the heat capacity of the member to which the collecting member is attached is C2, it is preferable that the relationship of C1 <C2 is satisfied.

  Next, detailed configurations of the fixing sleeve 105 and the pressure roller 102 will be described with reference to FIG. The fixing sleeve 105 includes an endless base layer 105a, a primer layer 105b provided on the outer periphery of the base layer 105a, an elastic layer 105c provided on the outer periphery of the primer layer 105b, and a release layer 105d provided on the outer periphery of the elastic layer 105c. (A in FIG. 8). The base layer 105a is a base layer made of metal such as SUS (stainless steel) having excellent thermal conductivity, and has sufficient strength to withstand a heat stress and a mechanical stress and to have a long durability life. , And a thickness of about 30 μm. The primer layer 105b is formed by applying a conductive primer having an appropriate amount of conductive particles such as carbon dispersed on the base layer 105a to a thickness of about 5 μm. The toner image carried on the recording material P can be wrapped by the elasticity of the elastic layer 105c, and uniform heating and pressure fixing can be realized. The release layer 105d is made of a PFA resin having a thickness of about 20 μm as a fluororesin having excellent releasability and high heat resistance in order to prevent adhesion of toner and paper powder and to ensure separation performance of the recording material P from the fixing sleeve 105. It is formed by coating.

  The pressure roller 102 includes a metal (aluminum or iron) metal core 102a, an elastic layer 102b formed of silicon rubber or the like outside the metal core 102a, and a release layer 102c that covers the surface of the elastic layer 102b. (B in FIG. 8). Both ends of the core metal 102a are rotatably supported by the side plate pair 107. As the elastic layer 102b, a solid rubber layer formed of silicon rubber or the like, or a sponge rubber layer formed by foaming silicon rubber to have a heat insulating effect, or the like is used. The release layer 102c is made of a fluororesin such as PFA and covered with a tube.

  A heater drive control circuit as a control means includes a power feeding device and a CPU for controlling the power feeding device. In the heater drive control circuit, the CPU inputs a print signal and performs on / off control of the power supply device, thereby energizing and heating the heating resistor of the heater 103. The heater 103 is rapidly heated by energization heating of the heating resistor. Based on the temperature detected by a thermistor (not shown) as temperature detecting means provided on the back surface of the heater 103 (the surface opposite to the fixing nip portion N), the heater 103 is set to a predetermined target set temperature. The temperature is controlled and the fixing sleeve 105 is heated to that temperature. The set temperature in this embodiment is 180 ° C.

  In this state, the recording material P carrying the unfixed toner image S is introduced into the fixing nip portion N from the recording material conveyance direction indicated by the arrow X direction, and the recording material P is nipped and conveyed by the nip portion N (FIG. 2). . In this embodiment, the front end of the recording material P reaches the fixing nip N 7.3 seconds after the print signal is input. During this conveyance process, the heat of the heater 103 is applied to the recording material P through the fixing sleeve 105. The unfixed toner image S is fixed on the surface of the recording material P by the heat of the heater 103 and the nip pressure. The recording material P exiting the nip portion N is separated from the surface of the fixing sleeve 105 by the curvature, and is conveyed to the paper discharge roller pair 14 or the switchback roller pair 15.

  Next, the melting point and the sublimation point of the release wax contained in the toner will be described. The peak temperature of the maximum endothermic peak of the release wax is measured according to ASTM D3418-82 using a differential scanning calorimeter “Q1000” (manufactured by TA Instruments). The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. Specifically, about 10 mg of toner is precisely weighed, put in an aluminum pan, an empty aluminum pan is used as a reference, and the temperature rising rate is 1 in a measurement temperature range of 30 to 200 ° C. Measurement is performed at ° C / min. In the measurement, the temperature is once raised to 200 ° C., subsequently lowered to 30 ° C., and then the temperature is raised again. The maximum endothermic peak of the DSC curve in the temperature range of 30 to 200 ° C. in the second temperature raising process is defined as the maximum endothermic peak of the endothermic curve in the DSC measurement of the release wax, and this temperature is defined as the melting point (Tm). To do.

  The sublimation point of the release wax is measured using a particle counter “Handheld 3016” (manufactured by Lighthouse). Specifically, in a space sealed with a 30 cm × 30 cm × 30 cm box, measurement is performed by heating 10 mg of precisely weighed toner. In this measurement, the temperature at which counting starts at the particle counter is defined as the sublimation point (Ts). The release wax used in this example has a melting point Tm of 76.08 ° C. (a in FIG. 9) and a sublimation point Ts of 140 ° C. (b in FIG. 9).

  Next, the temperature profile of the collection member 113 and the stay 108 is shown in FIG. The temperature profile of the collection member 113 is T113, and the temperature profile of the stay 108 is T108.

<T113, T108 measurement conditions>
Temperature: 23 ° C
Humidity: 50%
Recording material: 75 gsm, LTR size Paper feeding conditions: Leave the image forming apparatus for 24 hours under the above environment → Leave for 60 minutes after turning on the main unit → Single side continuous paper feeding

  The collecting member 113 is heated by the radiant heat radiated from the fixing sleeve 105. At the time of standby for waiting for a print signal, the heater 103 is temperature-controlled at 120 ° C., and its peripheral components are warmed, so the temperature of the collecting member 113 does not become the environmental temperature where the printer 1 is placed. Therefore, as shown to a in FIG. 10, the temperature Ts113 before the print signal input of the collection member 113 is changing at 59-60 degreeC. When the print signal is input and the heater 103 starts rapid temperature increase, the collection member 113 also starts rapid temperature increase. The temperature TN113 of the collecting member 113 when the leading edge of the recording material P reaches the nip portion N is raised to 81 ° C. and reaches the melting point Tm of the release wax. Thereafter, the temperature of the collecting member 113 rises, but the temperature curve gradually becomes gentler, and finally the temperature rise disappears below the sublimation point Ts. The temperature rise speed and the ultimate temperature of the collecting member 113 can be easily changed by adjusting the heat capacity C113 by changing the gap amount between the collecting member 113 and the fixing sleeve 105, the material and volume of the collecting member 113, and the like. Is possible. Therefore, the temperature of the collection member 113 can be set between the melting point and the sublimation point of various types of release wax until the leading edge of the recording material P reaches the nip portion N. As described above, in the fixing device of the present embodiment, the temperature of the collecting member reaches the melting point of the release wax or more before the leading edge of the recording material reaches the fixing nip portion. Further, the temperature of the collecting member is kept in a temperature range not lower than the melting point of the release wax and not higher than the sublimation point during the printing period (during the fixing process).

  On the other hand, the stay 108 is farther from the fixing sleeve 105 than the collecting member 113, and the heat capacity C108 of the stay 108 is about eight times the heat capacity C113 of the collecting member 113. The temperature is lower than the temperature of the collecting member 113 and is about 45 ° C. The rise in temperature after the print signal is input is very slow and does not reach the melting point Tm even after 100 seconds. That is, the heat of the collecting member 113 is not conducted so much to the stay 108, and the temperature of the stay 108 does not increase so much because the heat capacity C108 is large.

  As described above, the temperature of the collecting member reaches or exceeds the melting point of the release wax before the leading edge of the recording material reaches the fixing nip portion, whereas the temperature of the stay reaches the melting point of the release wax. It turns out that it has not reached.

  Next, b in FIG. 10 shows a temperature profile T113 'of the collecting member 113 when the paper is continuously fed immediately after the main body power is turned on.

<T113 'measurement conditions>
Temperature: 23 ° C
Humidity: 50%
Recording material: 75 gsm, LTR size Paper passing condition: The image forming apparatus is left for 24 hours under the above environment.

  The heater 103 is heated to a state where the fixing process can be performed immediately after the main body power is turned on, and the collecting member 113 also starts to rapidly rise in temperature. Thereafter, the pre-print signal input temperature Ts113 'of the collecting member 113 changes at 71 to 73 ° C. The temperature TN113 ′ of the collecting member 113 when the leading edge of the recording material P reaches the nip portion N is 88 ° C. and reaches the melting point Tm of the release wax. After that, the same profile as T113 is shown. The same heating operation is performed not only after the main body power is turned on, but also after restoration after JAM processing, after restoration of the energy saving mode, and the like. Therefore, when the printer 1 is in any state, such as after standby, after the main body power is turned on, after recovery after JAM processing, or after recovery of the energy saving mode, the collecting member 113 is reached when the leading edge of the recording material P reaches the nip portion N. The temperature has reached 76.08 ° C. or higher.

  Next, the temperature profile of the collection member 114 and the front lower cover 112 is shown in FIG. The temperature profile of the collecting member 114 is T114, and the temperature profile of the front lower cover 112 is T112. The measurement conditions are exactly the same as <T113, T108 measurement conditions>.

  Since the temperature of the collecting member 114 reaches 76.08 ° C. or higher (TN114 = 82 ° C.) by the time the leading end of the recording material P reaches the nip portion N, it is almost the same as the collecting member 113. The temperature profile is similar (T114). Therefore, detailed description is omitted. The temperature profile of the front lower cover 112 also shows the same tendency as that of the stay 108, and it can be seen that heat is not conducted so much from the collecting member 114 to the front lower cover 112. The heat capacity C114 of the collecting member 114 is about 1/24 of the heat capacity C112 of the front lower cover 112. If heat is easily conducted from the collecting member 114 to the front lower cover 112, or if the front lower cover 112 is to have the function of the collecting member 114, the front lower cover 112 becomes hot, and the JAM There is a concern that the user may touch the high temperature portion of the front lower cover 112 at the time of processing or fixing device replacement.

  Next, the temperature profile (T115) of the collection member 115 and the temperature profile (T109) of the base plate 109 are shown in FIG. The measurement conditions are exactly the same as <T113, T108 measurement conditions>. The collecting member 113 and the collecting member 114 are heated by the radiant heat radiated from the fixing sleeve 105, whereas the collecting member 115 is heated by the radiant heat radiated from the pressure roller 102. When the print signal is input and the heater 103 is energized and heated to start rapid heating, the collecting member 115 also starts rapid heating. When the leading edge of the recording material P reaches the nip portion N, the temperature TN115 of the collecting member 115 is 92 ° C. However, when the recording material P is nipped by the nip portion N, heat is taken away by the recording material P, and the temperature of the pressure roller 102 decreases. Along with this, the temperature of the collecting member 115 also drops to a peak at Tp immediately after TN115. During the passage of paper, the fixing sleeve 105 is always supplied with heat from the heater 103. In contrast, the pressure roller 102 has no heat supply source other than the heater 103. For this reason, the recording material P is deprived of heat, and the temperature of the pressure roller 102 decreases. However, since the amount of heat taken away by the recording material P is always constant, the temperature of the pressure roller 102 does not continue to decrease, and changes at a certain temperature during the sheet passing. Therefore, although the temperature of the collection member 115 also decreases at the peak Tp, it continues to shift in a certain region of 80 to 83 ° C. Further, the heat capacity C115 of the collecting member 115 is set to about 1/13 of the heat capacity C109 of the base plate 109. For this reason, the temperature rise speed of the base plate 109 after the print signal is input is very slow. If at least one of the plurality of collecting members present in the fixing device 100 has reached the melting point Tm when the leading edge of the recording material P reaches the nip portion N, the release wax is collected. Is possible.

  The wax component heated and vaporized by the fixing means is cooled immediately after vaporization and solidifies again. As described above, the melting point Tm of the release wax contained in the toner used in this embodiment is 76.08 ° C. and the sublimation point Ts is 140 ° C. Therefore, the release wax is 76.08 to 140 ° C. It becomes a liquid phase state in the region. In the liquid phase state, “wetting” occurs on the collecting members 113 to 115, and an intermolecular force acts between the releasing wax and the collecting members 113 to 115, thereby making it possible to adsorb the releasing wax. . That is, it is possible to collect the release wax by the collecting members 113 to 115 by setting the temperature of the collecting members 113 to 115 to the melting point Tm or more and bringing the wax component re-solidified after vaporization into a liquid phase state again. It can be done. When the temperature of the collection members 113 to 115 is equal to or lower than the melting point Tm, the release wax is in a solid phase, and “wetting” does not occur on the collection members 113 to 115. Since the intermolecular force acting between the release wax and the collection members 113 to 115 is very small, the release wax cannot be adsorbed to the collection members 113 to 115. Moreover, if the temperature of the collection members 113 to 115 exceeds the sublimation point Ts, the collected release wax is sublimated from the collection members 113 to 115 again. For the above reasons, by keeping the temperature of the collecting members 113 to 115 in the same region (76.08 to 140 ° C.), the release wax that has been liquefied and solidified after being heated and sublimated in the fixing nip portion is collected. It can be liquefied again by the members 113 to 115 and adsorbed. In addition, in order to collect the release wax stably even when printing a small number of sheets such as when one sheet is printed intermittently, the temperature of the collecting members 113 to 115 is rapidly increased after a print signal is input. The temperature of the collecting members 113 to 115 needs to reach the melting point Tm of the release wax before the leading end of the recording material P reaches the nip portion N. By allowing the temperature of the collecting members 113 to 115 to reach the melting point Tm of the release wax before the leading edge of the recording material P reaches the nip portion N, the release wax can be stably obtained in any paper passing mode. Can be adsorbed to the collecting members 113 to 115.

  When a plurality of release waxes are used, it is desirable to change the temperature of the collecting members 113 to 115 in the temperature range from the highest melting point to the lowest sublimation point among the release waxes. .

  The effects of the embodiment will be described below. A recording material guide and a conveyance roller are obtained by positively adsorbing release wax on the heating unit 101, the stay 108, the front lower cover 114, and the collecting members 113 to 115 provided between the pressure roller 102 and the fixing base 109. It is possible to suppress conveyance failure due to adhesion of the release wax to the surface. Then, by setting the temperature of the collecting members 113 to 115 to the melting point Tm or higher until the leading edge of the recording material P reaches the nip portion N, the release wax is captured regardless of the number of printed sheets in one job. It is possible to collect. The collecting member 113 has a heat capacity as small as possible with respect to the stay 108, the collecting member 114 with respect to the front lower cover 112, and the collecting member 115 with respect to the base plate 109. It is possible to shorten the time from the input of the print signal to the start of printing by increasing the time for starting up to the melting point of the release wax. A gap is provided between the collecting members 113 to 115, the stay 108, the base plate 109, and the front lower cover 112 to suppress heat conduction, and the heat absorption amount of the collecting member 113 and the collecting member 114 is set to a constant amount. By suppressing the temperature, it is possible to stabilize the temperature of the fixing sleeve 105 during paper passing and to secure stable fixing performance with power saving. In addition, it is possible to prevent the front lower cover 112 that can be contacted by the user from becoming high temperature. Moreover, since the space | gap is utilized as a heat insulation member, it is possible to implement | achieve the collection structure of a release wax with low cost.

(Example 2)
Next, the fixing device according to the second embodiment will be described. The characteristic portions inside the fixing device which are mainly different from the first embodiment will be described.

  In the fixing device 100 according to the second embodiment, a heat-resistant nonwoven fabric 118 that can be impregnated with a release wax is attached to the surfaces of the collecting member 113, the collecting member 114, and the collecting member 115 (FIG. 13). ). The heat-resistant non-woven fabric 118 is an aggregate of fibers having an average diameter of several tens of μm, and has an extremely large outer surface area compared to a normal resin part. By attaching a heat-resistant nonwoven fabric 118 that can be impregnated with a release wax on the surfaces of the collection members 113 to 115 and increasing the outer surface area, it is possible to increase the collection amount of the release wax.

DESCRIPTION OF SYMBOLS 1 Printer 5 Image formation part 100 Fixing device 101 Heating unit 102 Pressure roller 108 Stay 109 Base plate 112 Front lower cover 113-115 Collection member 118 Heat resistant nonwoven fabric

Claims (8)

A fixing nip portion forming member that forms a fixing nip portion that heats a recording material that carries a toner image formed using toner containing a release wax while nipping and conveying the recording material, and a frame that houses the fixing nip portion forming member In a fixing device having
Between the frame and the fixing nip portion forming member, said heated at the fixing nip portion to have a collecting member for collecting the components vaporized from the release wax, the collecting member, the fixing nip portion A fixing device that collects the vaporized component by maintaining a temperature at which the vaporized component is in a liquid phase state by radiant heat from a forming member . The fixing device according to claim 1, wherein the temperature of the collecting member reaches a temperature at which the liquid phase state is reached before a leading end of the recording material reaches the fixing nip portion.   3. The fixing device according to claim 1, wherein a relationship of C1 <C2 is satisfied, where C1 is a heat capacity of the collecting member and C2 is a heat capacity of a member to which the collecting member is attached. The fixing device according to claim 1, wherein a non-woven fabric that can be impregnated with the release wax is provided on a surface of the collecting member. The fixing device according to any one of claims 1 to 4 between members the collecting member and the collecting member is mounted is characterized in that it is insulated. The fixing device according to claim 1, wherein the collecting member is a plate-like member, and is attached to the frame in a state where a gap is provided between the collecting member and the frame. . The said collection member is a plate-shaped member, The flat part of the said collection member is provided so that the said fixing nip part formation member may be opposed, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. The fixing device described. The fixing nip portion forming member includes an endless belt, a heater that contacts an inner surface of the endless belt, and a pressure roller that forms the fixing nip portion together with the heater via the endless belt. The fixing device according to any one of claims 1 to 7 .

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