JP4048361B2 - Oven fixing device of printing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oven fixing device of a printing apparatus such as a printer for fixing a non-fixed toner image on one or both sides of a continuous recording medium such as paper or sheet-like plastic film in a non-contact manner.
[0002]
[Prior art]
In a printing apparatus for forming an image on a web, roller fixing with a heat source is generally known as a means for permanently fixing the image on the web. In the case of the roller fixing method, it is generally possible to cope with a range from low speed to high speed, and in terms of image quality, the state of toner crushing can be reduced by covering the surface of the heating roll with an elastic body. To some extent. Further, double-sided printing using a continuous web can be handled by tandem printing by arranging two apparatuses. However, there are some problems in the tandem printing using the roll fixing method and the roll fixing method described above. In roll fixing, a web is sandwiched and conveyed by a heating roll having a heat source and a pressure roll that pressurizes from the opposite side of the web, and this causes a change in image quality over time due to wear of the roll itself and a problem of component life. In particular, in order to cope with high image quality, in the case of roll fixing having an elastic body on the roll surface, the life becomes even more remarkable. In the case of roll fixing, it is necessary to apply oil such as silicone in order to secure the releasability between the roll surface and the toner, so that consumables such as oil increase including the roll, which increases running costs. It is a factor. Furthermore, roll fixing is not easy for double-sided printing in a single case on continuous paper. Both the pair of heat and pressure rollers have a heat source and cover an elastic body excellent in releasability, but the thickness of the elastic body prevents thermal deterioration at the boundary between the elastic body and the core metal. The thickness is 1 mm or less. However, since the nip width cannot be increased in the above configuration, problems such as poor fixing occur.
[0003]
Therefore, in order to solve the above-mentioned problem, a non-contact fixing method means such as an oven or flash fixing that does not contact with a heated object is known.
[0004]
[Problems to be solved by the invention]
By the way, in the case of non-contact fixing in which the web and the heat source are not in contact, there is no mechanical toner fixing to the web due to pressure other than heat like roller fixing, and the fixing to the web is only heat for melting the toner. Therefore, the fixing strength is greatly affected by the web temperature. Moreover, since it is non-contact, thermal efficiency is generally about 20 to 30%. Therefore, although the temperature of the heat source depends on the printing speed and the paper basis weight, it is necessary to set the temperature to approximately 250 ° C. or higher.
[0005]
The structure of the heating plate used under the high temperature condition as described above is mainly composed of a heater as a heat source and a base made of a material such as aluminum, SUS, ceramics, etc., and radiant heat from the heating surface and heat via air. The web and toner are heated and fixed by transmission. If the heating plate is aluminum and a sheathed heater is used as the heater, the sheathed heater pipe material is SUS, so it does not expand in the same way due to the difference in the coefficient of thermal expansion. The plate itself is thermally deformed. Usually, since it warps in the longitudinal direction of the heating plate, the gap with the web changes between the central portion and the end portion, and a temperature gradient occurs in the amount of heat received by the web. This results in poor fixing at the end. In order to avoid the above, if the gap in the central part is set narrow, when the paper passes through the inside of the fixing, because of the high temperature, the difference in shrinkage due to the non-uniformity of the moisture content and the non-uniformity of the original paper ( When heat is applied to the formation or fiber composition, the entire surface of the paper becomes undulated and a phenomenon of losing flatness occurs, resulting in image disturbance due to contact with the heating plate.
[0006]
In order to suppress the deformation of the heating plate, it is possible to arrange the base aluminum and the sheathed heater symmetrically. However, the heating plate has a large weight and a large heat capacity, resulting in problems of response and power consumption increase. It will be. On the other hand, if SUS or ceramics is used as the base material, the problem of thermal deformation is eliminated, but it becomes a problem in terms of more important thermal response and power consumption.
[0007]
In the case of this non-contact fixing, the heat received by the web is largely due to radiation, but the heat radiation at the end of the heating plate (longitudinal direction) escapes to the outside. This also results in poor fixing of the edges. In order to avoid the above, there is a method of lengthening the longitudinal direction of the heating plate to overlap the heat generation area of the heater with the web or reducing the falling of the end of the heating plate by providing a coarse and dense heater. In any case, problems such as large weight of the heating plate, large heat capacity, and increased cost arise.
[0008]
Accordingly, a first object of the present invention is to provide an efficient heating plate by reducing the power consumption by reducing the weight of the heating plate and reducing the heat capacity.
[0009]
A second object is to provide a double-sided simultaneous fixing device that secures stable fixing properties over the entire area of the web by reducing the temperature drop at the edge of the web and obtaining a uniform temperature distribution.
[0010]
[Means for Solving the Problems]
The object is to provide a web conveying means for conveying a continuous web, an image recording means having a toner carrier, and transferring a toner image formed on the surface of the toner carrier to one or both sides of the web, and the web A fixing device for fixing the toner image transferred to the web, wherein the fixing device is a printing device such as a printer having a heating plate having a heating source disposed in a non-contact manner on both surfaces of the web. The shape of the heating surface of the plate is concave along the web width direction at normal temperature, and is formed so as to be flat along the web width direction by thermal deformation during printing, and at a position close to both side edges of the heating plate This is achieved by providing a heat shielding member on the surface.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an electrophotographic double-sided printing apparatus using an oven fixing system equipped with a web temperature measuring means of the present invention. First, the overall configuration of a double-sided printing apparatus to which the present invention is applied will be described with reference to FIG.
[0012]
A continuous web 3 such as paper or sheet-like plastic film wound in a roll shape is sent from the paper feeding device 1 to the conveying roller 2. The web 3 fed out from the conveying roller 2 passes through a tension control unit 4 that applies tension to the web 3, a regulating unit 5 that regulates the feeding position in the width direction of the web 3, and a driven roller 6, and then a toner image forming unit. 8a and 8b. The driven roller 6 provided in the preceding stage of the image forming unit is provided with detection means 7 such as an encoder for detecting the actual web conveyance speed, and controls the speed of the discharge roller 33 so that the web contracts after passing through the fixing unit. The web 3 is conveyed at a constant speed in consideration of the influence of the above. The toner image forming portions 8 a and 8 b for forming the toner image 9 are arranged so as to form images on both surfaces of the web 3. The toner image forming sections 8a and 8b for forming the toner image 9 are provided with a toner carrier 10 in which a photoreceptor layer is coated on a metal drum surface in a rotatable manner, and the surface of the toner carrier 10 is provided on the outer periphery of the toner carrier 10. A charger 11 for uniformly charging the toner, an optical unit 12 for forming an electrostatic latent image on the toner carrier 10, a developing device 13 for developing the electrostatic latent image with toner and forming a toner image, A transfer unit 14 for transferring the toner image to the recording medium 3 and a cleaning unit 15 for removing residual toner after transfer on the toner carrier 10 are provided. The web 3 passes through the toner image records 8a and 8b, the toner image 9 is formed on both sides, and the web 3 on which the toner image 9 is formed is a heating that internally includes a heater 17 and a temperature detection sensor 18 that are disposed to face the web 3. Passing between the plates 16 in a non-contact manner with an appropriate gap, a permanent image is formed on both sides. In FIG. 1, two pairs of the heating plates 16 arranged to face each other are described. However, it is easy to arrange a plurality of heating plates 16 depending on the web conveyance speed and the web basis weight.
[0013]
In the present invention, a heat shielding plate 19 is provided on the side surface of the heating plate 16 disposed opposite from the fixing entrance to the exit. In addition, a heating plate 16 having a concave shape in the longitudinal direction of the heating surface of the heating plate 16 is provided. The web 3 is driven by a discharge roller 20 via a web 3 driven roller 6 on which a permanent image is formed, and the printing process is completed.
[0014]
In FIG. 1, a roller method is used for the web conveyance method, but the same effect can be obtained in an electrophotographic printing apparatus using a tractor method for the conveyance method. The same effect can be obtained even when the toner carrying member of the image forming unit is in the form of a belt or there are a plurality of toner carrying members.
[0015]
The configuration of the fixing device of the present invention will be described in detail with reference to FIGS. 2, 3, and 4.
[0016]
FIG. 2 shows a side view of the fixing device. The surface temperature of the heating plate 16 disposed opposite to the web 3 is controlled to 250 ° C. or higher, and the heat transfer from the heating plate 16 to the web 3 is made to have an emissivity that matches the surface of the heating plate with the absorption wavelength of the web 3. And heat transfer through the air layer by bringing the heating plate 16 close to the web 3. Therefore, the surface of the heating plate described above is preferably black body color. The structure of the heating plate 16 includes a heater 17 such as a sheathed heater in a member having high thermal conductivity such as aluminum, a temperature detection sensor 18 such as a thermistor for detecting the temperature of the heating plate, and a heating plate (not shown). Are provided with a heat insulating material, a heat insulating cover, a power supply line to the heating plate, and a signal line that block heat radiation from the back surface of the heat sink. The heating portion of the heater 17 is divided into two parts in the web width direction, and temperature detection sensors 18 for detecting the temperature of the heating plate are also provided at two locations as shown in the figure. With the above configuration, the temperature of the heating plate 16 can be controlled independently on the left and right sides of the drawing, and even when the web size changes, a uniform temperature distribution in the width direction can be achieved.
[0017]
Heat shield plates 19 are provided on both sides of the heating plate 16 on the side surface of the heating plate 16 configured as described above and in proximity to the heating plate 16. Further, as shown in FIG. 3, the heating surface of the heating plate 16 has a concave shape with respect to the web 3. The above shape is the same for the opposite heating plate disposed oppositely.
[0018]
Here, the effects of the present invention will be described with reference to FIGS. 3 and 4 are views of the fixing device as viewed from above. FIG. 3 shows the shape of the heating plate at room temperature. At room temperature, the shape of the heating plate is concave, and the gap with the web 3 is wide at the center and narrow at the end. Here, the set value of the gap is set at the end position. The heater is turned on and the state during printing is the state shown in FIG. Since the heating plate 16 has a high temperature of 250 ° C. or higher, the central portion of the heating plate 16 protrudes, and thermal deformation occurs that warps in the longitudinal direction. At this time, the heating surface that is concave in the normal temperature state has a shape close to a flat shape, and the gap with the web 3 can be ensured to be the same in the longitudinal direction.
[0019]
Further, by providing the heat shielding plate 19 on the side surface of the heating plate 16, the radiant heat radiated from the heating surface is reflected by the heat shielding plate 19 and returns to the heating plate as shown in FIG. It is possible to reduce the drop in temperature drop at the end without reducing the amount of heat received. Here, it is desirable that the surface of the heat shield plate is closer to a mirror surface state.
[0020]
FIG. 5 is a top view showing a state of escape of the radiant heat when there is no heat shielding plate. Although the radiant heat from one point at the end spreads radially, the heat toward the outside of the heating plate escapes to the outside as it is, so the amount of heat received by the web decreases compared to the center. Therefore, a temperature difference Δt occurs between the center and the end in the width direction. In order to reduce the temperature difference Δt described above, there is a method of using a range in which the heat generating part is made longer with respect to the web 3 and the temperature drop is small as shown in FIG. 6, but this increases the size of the apparatus and the heating plate. It will cause adverse effects of weight and heat capacity.
[0021]
On the other hand, for the shape of the heating plate, the shaded portion is reduced as shown in FIG. 7 in order to reduce the weight and heat capacity, but the heater position is asymmetric with respect to the aluminum base. As shown in FIG. 8, the thermal deformation that warps and the gap δ1> δ2 between the central portion and the end portion occurs. In order to avoid thermal deformation, as shown in FIG. 9, it is only necessary to arrange the heater position symmetrically (A = B) without reducing the thickness, but with this, the heat capacity is large and the response is slowed and the power consumption is increased. This results in an inefficient fixing device.
[0022]
In the above description, the double-sided monochrome configuration has been described. However, when applied to a printing apparatus that forms color images on both sides of the web, an image forming unit may be further added. Further, the printing unit is not limited to the electrophotographic process, and may be a printing unit using an ink jet recording method, or may be used as a drying unit for drying ink.
[0023]
【The invention's effect】
According to the present invention, the heating plate can be reduced in weight and the heat capacity can be reduced, so that power consumption can be reduced and an efficient fixing device can be provided. Further, since the temperature drop at the edge of the web can be reduced and a uniform temperature distribution can be obtained, it is possible to provide a double-sided simultaneous fixing device that ensures stable fixing properties over the entire area of the web.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire duplex printing apparatus to which an oven fixing device of a printing apparatus according to the present invention is applied.
FIG. 2 is a side view showing a configuration of an oven fixing device of the printing apparatus according to the present invention.
FIG. 3 is a top view showing a normal temperature state of the oven fixing device of the printing apparatus according to the present invention.
FIG. 4 is a top view showing a printing state of the oven fixing device of the printing apparatus according to the present invention.
FIG. 5 is a schematic diagram showing a heat transfer state.
FIG. 6 is a side view and a graph of an oven fixing device showing an example of a conventional temperature distribution uniformizing method.
FIG. 7 is a cross-sectional view showing a conventional heating plate shape.
FIG. 8 is a schematic diagram showing a state of thermal deformation during heating. FIG. 9 is a schematic diagram showing an example of preventing conventional thermal deformation.
[Explanation of symbols]
3 is a web, 16 is a heating plate, 17 is a heater, 18 is a heating plate temperature detection sensor, and 19 is a heat shielding plate.

Claims (2)

A web conveying means for conveying a continuous web, an image recording means having a toner carrier, and transferring a toner image formed on the surface of the toner carrier to one or both sides of the web, and transferred to the web A fixing device for fixing the toner image, and the fixing device is a printing device such as a printer including a heating plate having a heating source disposed in a non-contact manner on both surfaces of the web.
The shape of the heating surface of the heating plate is concave along the web width direction at normal temperature, and is formed so as to be flat along the web width direction by thermal deformation at the time of printing, and close to both side edges of the heating plate An oven fixing device for a printing apparatus, wherein a heat shielding member is provided at the position.   The oven fixing device for a printing apparatus according to claim 1, wherein the surface of the heat shielding member is a metal member having a mirror surface.

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