JP3833104B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a cylindrical fixing film, an energization heating element on a ceramic substrate, and a glass coat layer covering the energization heating element, so that the glass coating layer is in contact with an inner peripheral surface of the fixing film. A heater disposed inside the film, a pressure roller that forms a fixing nip portion together with the heater via the fixing film, and a support member that supports the fixing film and the pressure roller, The present invention relates to a so-called film heating type fixing device that fixes an image on a recording material while nipping and conveying the recording material at a fixing nip portion .
[0002]
[0003]
[0004]
[Prior art]
Such film heating type fixing devices are proposed in, for example, Japanese Patent Laid-Open Nos. 63-313182, 2-157878, 4-44075, 4-204980, and the like. ing.
[0005]
[0006]
[0007]
[0008]
The fixing device of the film heating type, it is possible to configure the apparatus of on-demand type with a member of low heat capacity as a Heater and the fixing film, energized seen Heater at the time of image formation performed in the image forming apparatus Thus, it is sufficient to generate heat at a predetermined fixing temperature, and the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is significantly reduced. There are advantages such as (power saving).
[0009]
As a driving method of Fixing film, a method for driven rotation of the fixing film in guiding the peripheral surface film guide fixing film which is pressed by the (film support member) and pressure roller by the rotation of the pressure roller (pressurizing A pressure roller driving method) and a method of rotating the pressure roller by driving an endless fixing film stretched between a driving roller and a tension roller (fixing film driving method).
[0010]
The contact surface of the fixing film of the heater, the gas Rasukoto layer for the purpose of insulation protection or the like is provided, proposes its thickness from problems such as leakage heat conducting-runaway, for example, in JP-A 06-301303 JP It has been optimized as it is.
[0011]
[Problems to be solved by the invention]
However, in recent years, image forming apparatuses such as copiers and printers have been demanded to further speed up and save power, and in order to ensure toner fixing property to a recording material while speeding up, a heater is used. It is necessary to further increase the thermal efficiency from the energization heating element to the recording material.
[0012]
Therefore, in the past, thinning of the fixing film and thinning of the glass coat layer have been performed, but thinning of the fixing film cannot be rotated along the support member due to a decrease in the physical strength of the film, The film is twisted, bent, dented, etc., and the recording material cannot be normally conveyed. Or rotation durability may lead to damage of the film and further the heating device itself. Further, the resistance value of the film cannot be managed at the time of manufacture, and it becomes difficult to electrically control the unfixed toner when the recording material is conveyed. In addition, when the glass coat layer is made thinner, the surface property of the heater is lowered, and as a result, the degree of adhesion between the heater, the fixing film, and the recording material is lowered, so that the thermal efficiency is never improved.
[0013]
[0014]
In addition, when the glass coat layer is made thinner, the current applied to the heater may leak from the glass coat layer / fixing film.
[0015]
SUMMARY OF THE INVENTION An object of the present invention is to obtain a film heating type fixing device that can cope with speeding up and power saving without lowering fixing property and dielectric strength .
[0016]
[Means for Solving the Problems]
The present invention is a fixing device having the following configuration.
[0017]
(1) A cylindrical fixing film, an energization heating element on a ceramic substrate and a glass coat layer covering the energization heating element, and the fixing film so that the glass coating layer is in contact with the inner peripheral surface of the fixing film A fixing roller that forms a fixing nip portion together with the heater via the fixing film, and a support member that supports the fixing film and the pressing roller. In the fixing device for fixing the image on the recording material while nipping and conveying the recording material at the nip portion, the fixing film and the pressure roller are supported by the support member via an insulating member, and the glass coat layer is A glass paste that is thicker than the thickness of the energization heating element is printed twice so as to cover the energization heating element, and then formed by firing once. That the fixing device.
[0018]
(2) The fixing device according to (1), wherein the total thickness of the glass coat layer is 20 to 34 μm.
[0019]
[0020]
[0021]
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below.
[0023]
(Reference example)
First, a reference example will be described. Fixing device in this reference example is an Fixing device of a film heating system using a pressure roller driving type.
[0024]
Figure 1 is a longitudinal sectional view showing a schematic configuration of a laser beam printer as an example of images forming apparatus. The image forming apparatus includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier. The photosensitive drum 1 is rotatably supported by the apparatus main body M, and is rotationally driven at a predetermined process speed in the direction of arrow R1 by a driving means (not shown).
[0025]
Around the photosensitive drum 1, a charging roller (charging device) 2, an exposure unit 3, a developing device 4, a transfer roller (transfer device) 5, and a cleaning device 6 are disposed almost in order along the rotation direction. .
[0026]
A sheet feeding cassette 7 that stores a sheet-like recording material P such as paper is disposed below the apparatus main body M, and the sheet feeding roller 15 is sequentially arranged from the upstream side along the conveyance path of the recording material P. , conveying rollers 8, a top sensor 9, the conveyance guide 10, a constant Chakusochi 11, transport rollers 12, discharge rollers 13, the sheet discharge tray 14 is disposed.
[0027]
Next, the operation of the image forming apparatus having the above configuration will be described.
[0028]
The photosensitive drum 1 that is rotationally driven in the direction of arrow R1 by a driving means (not shown) is uniformly charged to a predetermined polarity and a predetermined potential by a charging roller 2. The photosensitive drum 1 after charging is subjected to image exposure L based on the image information by the exposure means 3 such as a laser optical system on the surface, and the charge of the exposed portion is removed to form an electrostatic latent image.
[0029]
The electrostatic latent image is developed by the developing device 4. The developing device 4 includes a developing roller 4a. A developing bias is applied to the developing roller 4a, and toner is attached to the electrostatic latent image on the photosensitive drum 1, thereby developing the toner image (a visible image). ).
[0030]
The toner image is transferred to the recording material P such as paper by the transfer roller 5. The recording material P is stored in a paper feed cassette 7, fed and transported by a paper feed roller 15 and a transport roller 8, and a transfer nip between the photosensitive drum 1 and the transfer roller 5 via a top sensor 9. It is conveyed to the part. At this time, the leading edge of the recording material P is detected by the top sensor 9 and synchronized with the toner image on the photosensitive drum 1. A transfer bias is applied to the transfer roller 5, whereby the toner image on the photosensitive drum 1 is transferred to a predetermined position on the recording material P.
[0031]
The recording material P carrying the unfixed toner image on the surface by transfer is transported to the fixing device 11 along the transport guide 10, where the unfixed toner image is heated and pressurized and fixed on the surface of the recording material P. . The fixing device 11 will be described in detail later. The recording material P after the toner image is fixed is transported and discharged onto a paper discharge tray 14 on the upper surface of the apparatus main body M by a transport roller 12 and a discharge roller 13.
[0032]
On the other hand, the photosensitive drum 1 after the toner image transfer, toner over the remaining on the surface without being transferred onto the recording material P is removed by a cleaning blade 6a of the cleaning device 6, ready for the next image formation. By repeating the above operations, image formation can be performed one after another.
[0033]
Next, the fixing device 11 will be described in detail with reference to FIG. This figure is a longitudinal sectional view along the conveyance direction (arrow K direction) of the recording material P.
[0034]
The fixing device 11 shown in the figure, the ceramic heater 20 as a heating element for heating the toner, the heater 20 fixing fill arm 2 5 enclosing the fixing film 25 abuts against the pressure roller 26 and the heater 20, The temperature control means 27 for controlling the temperature and the rotation control means 28 for controlling the conveyance of the recording material P are main constituent members.
[0035]
The heater 20 is supported by a heater holder 22 attached to the apparatus main body M, on which a conductive heating element pattern 20b is formed, for example, by thick film printing on a heat-resistant substrate 20a such as alumina. The heater holder 22 is a member formed in a semicircular shape with heat-resistant resin, and also acts as a guide member for guiding the rotation of the fixing film 25.
[0036]
The fixing film 25 is formed of a heat-resistant resin such as polyimide in a cylindrical shape, and encloses the heater 20 and the heater holder 22 described above. The fixing film 25 is pressed against the heater 20 by a later-described pressure roller 26 so that the back surface of the fixing film 25 comes into contact with the lower surface of the heater 20. The fixing film 25 is configured to rotate in the arrow R25 direction as the recording material P is conveyed in the arrow K direction by the rotation of the pressure roller 26 in the arrow R26 direction. Note that the left and right ends of the fixing film 25 are regulated by guide portions (not shown) of the heater holder 22 so that they do not come off in the longitudinal direction of the heater 20. Further, grease is applied to the inner surface of the fixing film 25 in order to reduce sliding resistance between the heater 20 and the heater holder 22.
[0037]
The pressure roller 26 is provided with a heat-resistant release layer 26b having elasticity such as silicone rubber on the outer peripheral surface of a metal cored bar 26a. The fixing film is formed from below by the outer peripheral surface of the release layer 26b. 25 is pressed against the heater 20 to form a fixing nip portion N with the fixing film 25. When the width (nip width) in the rotation direction of the pressure roller 26 in the fixing nip portion N is a, the nip width a is set to such an extent that the toner on the recording material P can be suitably heated and pressed. Has been.
[0038]
The rotation control unit 28 includes a motor 29 that rotates the pressure roller 26 and a CPU 30 that controls the rotation of the motor 29. As the motor 29, for example, a stepping motor or the like can be used, and the pressure roller 26 can be continuously rotated in the direction of the arrow R26, or can be intermittently performed by a predetermined angle. That is, the recording material P can be stepped while the pressure roller 26 is repeatedly rotated and stopped.
[0039]
The temperature control means 27 includes a thermistor (temperature detection element) 21 attached to the back surface of the heater 20, and a CPU 23 that controls the triac 24 based on the temperature detected by the thermistor 21 and controls energization of the heater 20. .
[0040]
As described above, the fixing device 11 heats the toner on the recording material P by the heater 20 while the recording material P is nipped and conveyed at the fixing nip portion N by the rotation of the pressure roller 26 in the direction of the arrow R26. At this time, by controlling the rotation of the pressure roller 26 by the rotation control means 28, the feeding of the recording material P can be controlled appropriately, and the temperature of the heater 20 is controlled appropriately by the temperature control means 27. It is something that can be done.
[0041]
Figure 3 is a schematic diagram of Heater 20, a thick film printing method on the ceramic substrate 20a made of alumina or the like using the (screen printing), a conductive thick film paste such as Ag / Pd, as the thickness of 5μm The energization heating element 20b is printed and fired, and the glass coat layer 20c is printed and fired with an insulating glass thick film paste thereon.
[0042]
Figure 4 is the fixing of the fixing device film 25, shows the support structure of the pressure roller 26, the fixing Phil arm 2 5 containing therein a heater 20, a pressure roller 26 which is pressed to the fixing film 25 insulating member 35 The fixing film 25 and the pressure roller 26 are pressed by a pressing unit 37 to form a pressure nip N.
[0043]
With this configuration, an ammeter 38 is provided between the support member 36 and the ground E (unit support member), and a withstand voltage test is performed in which AC 1800 V is applied for 3 seconds from the power source 39 between the heater 20 and the ground E to measure the leakage current. Even if it went, leak from the fixing film, film guide, roller cored bar, roller surface and the like as well as leakage from the heater 20 did not occur at all.
[0044]
In this way, the fixing film 25 and the pressure roller 26 are in an insulated state, that is, the fixing film 25 and the pressure roller 26 are supported by the support member 36 via the insulating member 35, thereby preventing current leakage. Above, the glass coat layer is made into two layers.
[0045]
Further, when the fixability was measured using the heater 20 without glass coating (no coating), a result of hardly fixing (poor fixability) was obtained. FIG. 5 shows the relationship between the number of times of coating (printing) of the glass coat layer and the fixing property.
[0046]
The film pressure that can be applied at one time is 10 to 17 μm, and the film thickness is formed every 1 μm in the range of 10 to 17 μm for one time printing, 20 to 34 μm for two times printing, and 30 to 51 μm for three times printing. Is possible.
[0047]
Conventional three-layer coating (three times coating) 50 μm fixability (density reduction rate) was about 18%, but by reducing the glass coating layer to about 16.5 by 45 μm, 40 μm, 35 μm, 30 μm. %, About 15%, about 13.5%, and about 12%, and the fixing property is improved.
[0048]
Further, the fixing property of each film was measured by firing in each printing to increase the film thickness. As shown in FIG. 5, it was found that the fixing property was different depending on the number of times of printing as shown in FIG. For example, even with the same 30 μm, the fixability is improved by about 13% in the three-time printing, and about 8% in the two-time printing. However, even if the film thickness is reduced by printing once, the fixability is not improved, and it is understood that the film thickness reduction by printing twice is appropriate. This is because the heating element convex portion of about 5 μm affects the surface of the glass coat layer and the surface properties of the glass coat layer are deteriorated.
[0049]
In the above reference example, the fixing film 25 and the pressure roller 26 are kept insulated from the apparatus main body by the insulating member 35 , and two glass coat layers are printed twice between the fixing film 25 and the heater 20 at 10 μm. Since it was formed by performing, it was possible to form an optimum glass coat thickness, and it became possible to improve the fixability by about 7%. Of course, the fixability varies depending on various factors such as the fixing temperature, the pressing force, and the rotation speed. In addition, it is possible to ensure thermal efficiency that can speed up without securing the fixing film and fixing device while ensuring electrical safety.
[0050]
(Example)
In the above reference example, firing was performed every time the glass coat layer was printed. However, in this embodiment, the fixing property is further improved by optimizing the number of firings.
[0051]
Although traditional apparatus tended breakdown voltage by reducing the firing times is disadvantageous, in the present invention as shown in FIG. 4, the fixing film 2 5, the support member pressure roller 2 6 via the insulating member 35 since the is supported by the 36, it is possible to reduce the firing times without having to worry about the breakdown voltage.
[0052]
In the experiment, as shown in FIG. 6, it can be seen that the fixing property is improved by reducing the number of firings. Thus, by reducing the once fired number in this embodiment, it is possible to improve the fixing property to about 4%, more depending on the configuration of the heating data 2 0, film of the lower layer coating as shown in FIG. 3 By changing the thickness according to the thickness of the heating body, the smoothness of the surface of the glass coat layer can be further maintained.
[0053]
In this embodiment, since the energization heating element 20b is about 5 μm, it is desirable to print the lower layer coat to 10 μm. The upper layer coat can be printed on a thickness of 10 to 17 μm, although it varies depending on the heating element pattern as long as the surface property can be secured. Although the upper and lower layers have different film thicknesses, the above fixability can be ensured if the two layers are in the range of 20 to 34 μm. Of course, it varies depending on various factors such as fixing temperature, pressure, and rotation speed, so this measurement uses the same reference examples and conditions. According to the present embodiment, it is possible to further ensure thermal efficiency.
[0054]
【The invention's effect】
As described above, according to the present invention, there is an effect that it is possible to obtain a film heating type fixing device that can cope with speeding up and power saving without lowering the fixing property and withstand voltage .
[0055]
[0056]
[0057]
[0058]
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an example of an image forming apparatus .
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a fixing device. FIG. 3 is a schematic configuration diagram of a heater.
FIG. 4 is a diagram illustrating a support structure of a fixing film and a pressure roller.
FIG. 5 is a graph showing the relationship between the film thickness and the fixing property depending on the number of times of printing.
FIG. 6 is a relationship diagram between the number of firings and the fixability depending on the number of printings.
[Explanation of symbols]
1 Image carrier (photosensitive drum)
2 Charging device (charging roller)
3 Exposure means 4 Developing device 5 Transfer device (transfer roller)
6 Cleaning Device 7 Paper Feed Cassette 8 Carrying Roller 9 Top Sensor 10 Carrying Guide 11 Fixing Device 12 Carrying Roller 13 Paper Ejecting Roller 14 Paper Ejecting Tray 15 Paper Feeding Roller 20 Heating Body (Ceramic Heater)
21 Temperature sensing element (Thermistor)
22 Heater holder 23 CPU
24 Triac 25 Fixing Rotator (Fixing Film)
26 Fixing Rotator (Pressure Roller)
27 Temperature control means 28 Rotation control means 29 Motor 30 CPU
N Fixing nip P Recording material

Claims (2)

A cylindrical fixing film, an energizing heating element on a ceramic substrate, and a glass coat layer covering the energizing heating element are provided inside the fixing film so that the glass coat layer is in contact with the inner peripheral surface of the fixing film. A heater that is disposed, a pressure roller that forms a fixing nip portion together with the heater via the fixing film, and a support member that supports the fixing film and the pressure roller. In a fixing device for fixing an image on a recording material while nipping and conveying the recording material,
The fixing film and the pressure roller are supported by the support member via an insulating member, and the glass coat layer is formed by stacking a glass paste thicker than the thickness of the energization heating element so as to cover the energization heating element. A fixing device which is formed by printing twice and then firing once. The fixing device according to claim 1, wherein the total thickness of the glass coat layer is 20 to 34 μm.

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