JP3970044B2 - Heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a heating body is adhered to an inner surface side of a heat-resistant elastic belt provided with an elastic layer on a heat-resistant substrate belt, and a heated object is adhered to the outer surface side, and the heat energy of the heating body is received through the heat-resistant elastic belt. The present invention relates to a belt heating type heating device applied to a heating body.
[0002]
This apparatus is an image fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, or a fax machine, that is, a toner made of heat-meltable resin by an appropriate image forming process means such as electrophotography, electrostatic recording, and magnetic recording. Corresponding to the target image information formed by the direct or indirect (transfer) method on the surface of the recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) The unfixed toner image can be used as an apparatus for heat-fixing the permanent image as a permanently fixed image on the surface of the recording material carrying the image.
[0003]
Further, the present invention is not limited to the fixing device, and can be widely used as a means / device for heat-treating a material to be heated, such as a device for modifying a surface property by heating a recording material carrying an image, or a device for assumed wearing.
[0004]
[Prior art]
Conventionally, as a fixing device for fixing an unfixed image on a recording material in an image forming apparatus such as a copying machine, a printer, and a fax machine using an electrophotographic method, a fixing device of a contact heating method having good thermal efficiency and safety In recent years, in particular, from the viewpoint of promoting energy saving, as a method of high heat transfer efficiency and quick start-up of the device, a belt heating type fixing device that heats through a belt having a small heat capacity has attracted attention. .
[0005]
Recently, with the progress of colorization of electrophotographic technology, soft fixing is required as a requirement for a fixing member in contact with a recording material. In the conventional fixing device, the toner particles are crushed due to the rigidity of the surface layer made of a releasable resin such as a fluororesin, and the resolution of the image is deteriorated, or the color mixture at the time of fixing the color toner image in which the toner layers are stacked in layers. Problems such as defects have been pointed out, and as a means for solving these problems, a method using a heat-resistant elastic belt in which an elastic layer is provided between a base layer and a surface layer instead of a film is disclosed in JP-A-10-10893, This is proposed in Japanese Patent Laid-Open No. 11-15303.
[0006]
Specifically, as shown in FIG. 7, the heat-resistant elastic belt 5 has a heat-resistant elastomer layer as an elastic layer 5b formed on the outer surface of a thin metal tube or heat-resistant plastic tube as the belt base layer 5a. The surface layer (release layer) 5c has a laminated structure in which a layer of silicone rubber or fluororesin is formed.
[0007]
On the other hand, as a direction of this type of belt fixing method, for the purpose of obtaining a preheating effect for efficiently heating the recording material, for example, as described in JP-A-6-314041 and Japanese Patent No. 2769727, etc. There has been proposed a recording material that aims at a preheating effect of a recording material that is brought into contact with a belt immediately before the material enters the nip portion.
[0008]
[Problems to be solved by the invention]
However, the belt heating type fixing device using the heat-resistant elastic belt 5 has the following problems.
[0009]
a. Since the elastic layer 5b having a lower thermal conductivity than the base layer 5a is provided, the thermal responsiveness at the nip portion is lowered, and the temperature rise at the nip portion is delayed with respect to the heat generated by the heating element.
[0010]
b. When a ceramic heater is used as the heating element, the ceramic heater is installed within the nip width, so that the heater may be damaged if the applied pressure is increased to improve the fixability.
[0011]
Accordingly, an object of the present invention is to solve the problems a and b in the belt heating type heating apparatus.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a heating apparatus having the following configuration.
A cylindrical belt provided with an elastic layer on a base layer, a ceramic heater that contacts the inner circumferential surface of the belt and heats the belt, and is disposed on the inner circumferential surface side of the belt and supports the ceramic heater A heating assembly having a supporting member; and a pressing member that forms a press-contact nip portion together with the heating assembly, wherein the ceramic is heated while nipping and conveying the material to be heated in the press-contact nip portion. The heater is not provided in the pressure nip portion and is supported by the support member on the upstream side in the belt rotation direction with respect to the pressure nip portion, and the pressure nip portion does not rotate toward the inner peripheral surface side of the belt. The heating device is formed by the support member and the pressure member fixedly arranged in this manner via the belt.
According to the present invention, 1) the ceramic heater is disposed on the inner peripheral surface side of the belt, so that the entire apparatus can be made compact. 2) the support member and the pressure member that support the ceramic heater are members that form the press-contact nip portion. Therefore, it is not necessary to apply excessive pressure to the ceramic heater. 3) Since the support member is fixedly arranged so as not to rotate toward the inner peripheral surface side of the belt, a pressure nip is provided by a roller that warms the entire surface. Compared to the configuration that forms the part, the amount of heat that escapes from the belt to the support member side at the pressure nip part can be suppressed, and the advantages of a heating device that uses a ceramic heater can be taken advantage of. 4) The outer peripheral surface of the belt Since the heat given by the heater is generated on the belt surface when the arbitrary position reaches the pressure nip portion, the power consumption can be suppressed. It is possible to achieve the effect that at the same time.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
<Example 1>
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus in which the heating device according to the present invention is mounted as an image heating and fixing device.
[0023]
This image forming apparatus is a tandem type full-color printer using an electrophotographic process.
[0024]
Y, M, C, and B are first to fourth color toner image forming stations arranged in order from right to left on the drawing.
[0025]
Each of the color toner image forming stations Y, M, C, and B has a rotating drum type electrophotographic photosensitive member 11 as an image carrier, a charging device 12, an exposure device 13 such as a laser scanner or an LED array, a developing device 14, and the like. An electrophotographic process mechanism including a cleaning device 15 and the like. The photoconductor 11 is rotationally driven at a predetermined peripheral speed in the clockwise direction of the arrow.
[0026]
The first color toner image forming station Y forms a full-color yellow component toner image on the surface of the photoconductor 11. The second color toner image forming station M forms a magenta component toner image of a full color image on the surface of the photoconductor 11. The third color toner image forming station C forms a cyan component toner image of a full color image on the surface of the photoreceptor 11. The fourth color toner image forming station B forms a black toner image on the surface of the photoconductor 11. Since the principle and process of toner image formation at each color toner image forming station are known, the description thereof will be omitted.
[0027]
A transfer belt 16 is suspended from a plurality of support rollers 17 and stretched under the first to fourth color toner image forming stations Y, M, C, and B to the all color toner image forming stations. It is arranged in a slanting manner. The transfer belt 16 is rotationally driven in a counterclockwise direction indicated by an arrow at a peripheral speed corresponding to the peripheral speed of the photoconductor 11.
[0028]
Reference numeral 18 denotes a transfer electrode roller. In each of the first to fourth color toner image forming stations Y, M, C, and B, the transfer belt 16 is pressed against the lower surface of the photoconductor 11 to form a transfer nip portion. is doing. Reference numeral 19 denotes a transfer bias application power source for each transfer electrode roller 18, which applies a predetermined voltage having a polarity opposite to the charging polarity of the toner at a predetermined control timing as a transfer bias.
[0029]
Reference numeral 20 denotes a sheet feeding path. A recording material (transfer material) P separated and fed from a sheet feeding mechanism (not shown) is fed to the end of the transfer belt 16 on the first color toner image forming station Y side. To feed. The transfer belt 16 electrostatically attracts and holds the fed recording material P or grips it with a chuck, and each transfer nip portion of the first to fourth visible image forming stations Y, M, C, and B Are transported sequentially. As a result, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred in the aligned state on the surface of the same recording material P to form a full-color toner image.
[0030]
The recording material P transported and passed through the transfer nip portion of the fourth visible image forming station B is separated from the transfer belt 16, introduced into the heat fixing device 21, and subjected to heat fixing processing of an unfixed toner image. It is discharged and conveyed.
[0031]
(2) Heat fixing device 21
FIG. 2 is an enlarged cross-sectional model view of the heat fixing device 21 portion. The heat fixing device 21 of the present embodiment is a pressure roller driving type belt heating type heating device using an endless (cylindrical) heat-resistant elastic belt.
[0032]
Reference numeral 1 denotes a heating assembly as a fixing member, and reference numeral 2 denotes a heat-resistant elastic pressure roller as a pressing member, which forms a nip portion (fixing nip portion) N by being pressed against each other.
[0033]
A heating assembly 1 as a fixing member includes a heating element (heating element) 3, a heating element (a heating element) 3 that holds the heating element, and a cylindrical (endless belt-like) heat-resistant elastic belt (fixing belt) 5 that is rotatably fitted with a margin. It is an assembly comprising a heat insulating stay holder 4 as a support member and a rigid stay 6 having a U-shaped cross section downwardly inserted through the heat insulating stay holder 4.
[0034]
The heat-resistant elastic pressure roller 2 as a pressure member includes a cored bar 2a and an elastic layer 2b formed by foaming heat-resistant rubber such as silicone rubber or fluorine rubber or silicone rubber on the outer side thereof. A release layer 2c such as PFA, PTFE, or FEP may be formed on 2b. The pressure roller 2 of the apparatus of this example has a diameter of 20 mm.
[0035]
The heating assembly 1 as the fixing member and the heat-resistant elastic pressure roller 2 as the pressure member are arranged in parallel in the vertical direction, and the pressure roller 2 is elastic in the direction of the heating assembly 1 by a pressure means (not shown). The belt 5 is sandwiched between the lower surface portion of the heat insulating stay holder 4 on the heating assembly 1 side and the pressure roller 2 and is energized against the elasticity of the layer 2b. The pressure is controlled so as to form a pressure nip N having a width necessary for heat fixing from both ends in the direction.
[0036]
The pressure roller 2 is rotationally driven by the driving means M in the counterclockwise direction of the arrow b. As the pressure roller 2 is driven to rotate, the inner surface of the belt 5 slides on the lower surface of the heat insulating stay holder 4 at the pressure nip portion N, and the belt 5 is rotated in the clockwise direction indicated by the arrow a.
[0037]
A recording material P carrying an unfixed toner image t as a material to be heated is introduced between the belt 5 and the pressure roller 2 in the pressure nip N and is nipped and conveyed. c is the heated material conveyance direction.
[0038]
The heating element 3 is a ceramic heater in the apparatus of this example, and this heater 3 is fixedly supported on the outer surface of the heat insulating stay holder 4 on the upstream side in the heated material conveyance direction from the pressure nip N. FIG. 3 is an enlarged model view of the heater 3 portion. The heater 3 heats the inner surface of the belt 5 upstream of the pressure nip N in the heated conveyance direction, and is nipped and conveyed between the belt 5 and the pressure roller 2 when the belt 5 passes through the pressure nip N. Heat is applied to the recording material P, and the toner image t on the recording material P is melted and fixed. In this example apparatus, the heater 3 is installed at a position 8 mm away from the upstream end of the pressure nip N in the recording material conveyance direction upstream.
[0039]
The heat-insulating stay holder 4 is a semicircular saddle-shaped member having a transverse cross section, holds the heater 3, prevents heat radiation to the inside of the belt, functions as a rotation guide for the belt 5, liquid crystal polymer, phenol resin, PPS, PEEK, etc. It is formed by.
[0040]
Belt 5 is required to suppress the frictional resistance between the heater 3 and the heat insulating stay holder 4 and the belt 5 to rotate while rubbing on the inner side near Ruhi over data 3 and the heat insulating stay holder 4. For this reason, a small amount of lubricant such as heat-resistant grease is interposed on the surfaces of the heater 3 and the heat insulating stay holder 4. As a result, the belt 5 can rotate smoothly.
[0041]
1) Heating body 3
FIG. 4 is a structural diagram of an example of the ceramic heater 3 as a heating body. (A) is a partially cut-out plan model view on the heater surface side, and (b) is a plan model diagram on the heater back side.
[0042]
This heater 3 has (1). A horizontally long, highly insulating ceramic substrate 3a (thickness of about 0.64 mm) made of alumina, aluminum nitride, silicon carbide, or the like, whose longitudinal direction is the direction orthogonal to the heated material conveyance direction,
(2). For example, Ag / Pd (silver palladium), RuO ₂ formed by coating on the surface side of the substrate 3a in the form of a line or a thin strip having a thickness of about 10 μm and a width of about 1 to 5 mm by screen printing or the like along the length. , Current-carrying resistance layer 3b such as Ta ₂ N,
(3). Electrode portions 3c and 3c formed of Ag / Pt (silver / platinum), which are electrically connected to both ends in the longitudinal direction of the energization heating resistor layer 3b;
(4). An insulating protective layer 3d, such as a thin glass coat, provided on the surface of the energization heating resistor layer 3b, which is electrically insulated and capable of withstanding rubbing against the belt 5.
(5). A temperature sensing element 3e such as a thermistor provided on the back side of the substrate 3a;
Etc.
[0043]
The heater 3 is fixedly supported by fitting the heater in a fitting groove 4 a provided in advance in the holder longitudinal direction at a predetermined position on the outer surface of the heat insulating stay holder 4.
[0044]
The electrode portions 3c and 3c of the heater 3 are connected to a power supply portion (not shown) via a power supply connector (not shown), and power is supplied from the power supply portion to the energization heating resistor layer 3b, so that the heater 3 can be quickly operated. Raise the temperature. The temperature sensing element 3e detects the temperature of the heater 3 and feeds back the temperature information to the power feeding unit.
[0045]
A temperature sensing element 7 such as a thermistor for sensing the temperature of the surface of the belt 5 is disposed downstream of the pressure nip portion N in the conveyance direction of the heated material. Then, by appropriately controlling the voltage and wave number applied to the energization heating resistor layer 3b according to the temperature detection signal of the temperature detection element 7 or the temperature detection element 3e on the back side of the heater, or both, Heating necessary for fixing the toner image t on the recording material P is performed while keeping the temperature control temperature in the press nip N substantially constant.
[0046]
2) Belt 5
The heat-resistant elastic belt 5 is a three-layer belt having a belt base layer 5a, an elastic layer 5b, and a surface layer 5c, as in the belt shown in FIG.
[0047]
The base layer 5a which is the innermost surface is made of a resin such as polyimide or polyamideimide, or a metal belt such as SUS or nickel. In order to construct a long-life heat fixing apparatus, it is necessary to have sufficient strength and excellent durability, and therefore, a layer having a strength such as polyimide may be further provided on the inner surface. On top of this, an elastic layer 5b is provided in order to secure the fixing property of the color image, and a heat-resistant rubber layer such as silicone rubber or fluorine rubber is used. Further, in order to prevent offset and to ensure separation of the recording material, the surface layer 5c is coated with a heat-resistant resin having good release properties such as PFA, PTFE, FEP, silicone resin or the like alone or coated. In this embodiment, a belt 5 having an inner diameter of 30 mm was used.
[0048]
Thus, with the above-described apparatus configuration, the temperature of the belt 5 rises when heated from the heater 3 while the belt 5 is slidingly rotated, but the outermost surface immediately passes through the heater section. However, the temperature does not rise to a temperature at which sufficient fixability is ensured, and heat is sufficiently transferred when it rotates to the point where it passes through the pressure nip N, which is good for the recording material P at the pressure nip N. Secure fixing property can be secured.
[0049]
Therefore, as shown in FIG. 5, the heater 3 has a higher thermal efficiency than the heating device in which the heater 3 is installed in the press-contact nip portion N and the heat generating area of the heater is provided. Secure fixability.
[0050]
Specifically, in a heating apparatus having a configuration in which the heater 3 is installed in the pressure nip N as shown in FIG. 5, a process speed of 120 mm / sec and an A4 standard heated object are continuously provided at intervals of 12 sheets per minute. When the paper is inserted, a maximum of 600 W is required at the time of paper passing to obtain a sufficient fixing property. On the other hand, when a similar test is performed with the apparatus of the present invention shown in FIG. Can be secured, and more than 10% of power can be saved.
[0051]
<Example 2>
Next, a second specific example of the present invention will be described. The configuration inside the heat fixing apparatus is the same as that shown in FIG.
[0052]
FIG. 6 shows an enlarged cross-sectional view around the heating element, which is a feature of this example. In this example, the cross-sectional shape of the surface of the heater 3 has a curved surface, and the curved surface shape is in close contact with the inner surface of the belt 5 or slides in conformity thereto. Therefore, the heat generated from the heater 3 is transmitted well to the belt 5, and the wait time can be further shortened compared to the planar heater 3 shown in FIGS.
[0053]
Rotation and heating were started from room temperature, and the time until the belt surface temperature at the downstream side of the material to be heated from the pressure nip N reached 180 ° C. was measured. When a flat heater was used Was 22 seconds. On the other hand, when a curved heater was used, it could be shortened to 20 seconds.
[0054]
Further, since the heat transfer efficiency from the heater 3 to the belt 5 is increased, the rapid temperature rise in the vicinity of the heater can be mitigated, and damage to the heater 3 and the heat insulating stay holder 4 can be prevented.
[0055]
Further, by arranging the heater 3 attachment position upstream of the pressure nip portion N in the heated material conveyance direction (upstream side of the belt rotation direction), the upper position indicated by a two-dot chain line 3 ′ in FIG. Compared to the case where the heater 3 is attached to a position on the downstream side of the heated material conveyance direction (downstream side of the belt rotation) or the like from the pressure nip portion N as indicated by a two-dot chain line 3 ", the belt 5 and the heater 3 Heat transfer efficiency is improved because it becomes easier to contact, leading to a reduction in wait time.
[0057]
<Others>
1) Although the ceramic heater having the structure shown in FIG. 4 is used as the heating element 3 in the embodiment, a ceramic heater having a structure different from this may be used.
[0058]
2) Although the contact type thermistor is used as the temperature sensing elements 3e and 7 in the embodiment, there is no problem with the non-contact type sensing element that senses by radiation or the like, and the arrangement position is also different from the embodiment. Temperature control is possible even if it is attached to other different places.
[0059]
3) Although the rotation of the belt 5 is driven rotation by driving the pressure roller in the embodiment, a driving roller is provided inside the belt, and the belt is rotated by driving the driving roller to rotate the belt. I can do it.
[0060]
4) The pressure member is not limited to a roller body, and may be a rotating endless belt body.
[0061]
5) The heating device of the present invention is not limited to the heat-fixing device of the embodiment, but an image heating device that is supposed to be worn, an image heating device that reheats a recording material carrying an image to improve the surface properties such as gloss, Sheet-like material to be heated other than the recording material can be passed through and used as a heat treatment apparatus such as drying, heat laminating, hot press wrinkle removal, hot press curl removal, etc.
【The invention's effect】
As described above, according to the present invention, even in a heating device of a belt heating method using a belt having an elastic body with low thermal conductivity, the heat generated by the heating body preheats the belt. Thus, the material to be heated can be efficiently applied to the pressure contact nip portion through the, and the wait time can be shortened.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an example of an image forming apparatus. FIG. 2 is a schematic configuration diagram showing an embodiment of a heating and fixing apparatus as a heating apparatus according to the present invention. FIG. 3 is an enlarged model diagram of a heating body portion. FIG. 5 is a schematic configuration diagram of an apparatus in which a heating body is disposed in the pressure nip portion. FIG. 6 is an enlarged model view of a heating body portion of the heating apparatus of Example 2. FIG. 7 has an elastic body. Belt layer model diagram [Explanation of symbols]
1. Fixing member 2. Pressure member (pressure roller) Heating body 3a. Ceramic substrate 3b. Energized heating resistor layer 3c. Electrode part 3d. Insulating protective layer 4. 4. Support member (insulated stay holder) 5. Heat-resistant elastic belt Rigid stay 7. Temperature sensing element 2a. Core 2b. Elastic layer 2c. Release layer 5a. Belt base layer 5b. Heat resistant elastomer layer 5c. Release layer

Claims (1)

A cylindrical belt provided with an elastic layer on a base layer, a ceramic heater that contacts the inner circumferential surface of the belt and heats the belt, and is disposed on the inner circumferential surface side of the belt and supports the ceramic heater A heating device having a support member, and a pressure member that forms a pressure nip portion together with the heating assembly, and heating the material to be heated while nipping and conveying the material to be heated at the pressure nip portion .
The ceramic heater is not provided in the pressure nip portion and is supported by the support member on the upstream side in the belt rotation direction with respect to the pressure nip portion, and the pressure nip portion is located on the inner peripheral surface side of the belt. A heating apparatus , wherein the support member and the pressure member fixedly arranged so as not to rotate are formed via the belt .

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