JPH0764425A - Image forming device - Google Patents

Abstract

PURPOSE:To enable the fixing rate of toner to be enhanced and to enable both warm-up time and power consumption to be reduced by forming the base of a heater roller from a specific conductive ceramic. CONSTITUTION:A heater roller 1 has a volume specific resistance of 0.1 to 10OMEGA.cm and has a cylindrical base 2 made from ceramics of a perovskite crystal structure. A plating layer of an electrically conductive metal, such as Ni, Ag or Al, is formed on the surface of each end of the base 2 to provide electrodes 3, and brushes 4 are brought into sliding contact with the electrodes 3 so that the heater roller 1 carries current. The surface of the base 2 except the electrodes 3 is coated with a layer 5 of mold releasing agent by electrostatic coating or by flame spraying. The ceramics from which the base 2 of the heater roller 1 is made is heated by itself because of its conductivity. Therefore the overall surface of the heater roller 1 can be heated evenly, and the fixing rate of toner 40 can be greatly enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus incorporated in a copying machine and a printer machine (LED printer, laser printer, liquid crystal shutter printer, etc.).

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus in a copying machine or a printer has a photosensitive drum 3 as shown in FIG.
The charging device 32 and the developing device 34, which are arranged on the outer peripheral surface of 1, and the exposing device 33 such as an LED printer head, perform charging, exposure,
Development is performed, toner 40 (developer) is attached to the outer peripheral surface of the photosensitive drum 31, and the toner 40 is transferred to the printing paper 45 by the transfer colon 35. Then, when the printing paper 45 to which the toner 40 is transferred is sent between the heater roller 1 and the pressure roller 36 which form the fixing unit, the toner 40 on the printing paper 45 is melted by the heat of the heater roller 1 and the pressure of the pressure roller 36. Then, it is fixed on the printing paper 45.

In the heater roller 1 of the fixing portion, a release material layer 52 is formed on the surface of a base pipe 50 made of an aluminum alloy as shown in FIG. 5, and a plurality of halogen lamps 53 are built in the base pipe 50. The heater roller 1 is heated by the heat generated by the halogen lamp 53. However, the heater roller 1 having the above structure requires a large amount of electric power, and the waiting time from power-on to reaching the set temperature (hereinafter, referred to as start-up time) is very long. Further, since the halogen lamp 53 is built in as a heating element, the size of the heater roller 1 is restricted, and there is a problem that the size cannot be reduced.

Therefore, as means for solving these problems, Japanese Patent Laid-Open Nos. 62-200379 and 62-2 are known.
As shown in Japanese Patent No. 00380, a large number of plate-shaped heating elements 63 are formed at equal intervals by print printing on the outer peripheral surface of a cylindrical substrate 60 made of ceramics as shown in FIG. 4, and insulation is provided thereon. The heater roller 1 having a multi-layer structure in which the layer 61 is formed to embed the heating element 63 and the release material layer 62 such as silicon rubber is formed on the outermost peripheral surface is used. Then, the brush 65 is brought into contact with the exposed portions of both ends of the heating element 63, and a voltage is applied through the brush 65 to heat the heater roller 1.

[0005]

However, such a heater roller 1 has the following problems.

That is, even if the heating element 63 of the heater roller 1 is energized, the surface A above the heating element 63 is immediately heated to the set temperature and generates heat, but the surface B where the heating element 63 is not embedded does not reach the set temperature. Since it is not heated and uneven heat is generated, the start-up time cannot be shortened in order to make the temperature distribution on the surfaces A and B of the heater roller 1 uniform. For this reason, even if the power of a copying machine or the like using this heater rotor 1 is turned on, it cannot be used immediately. Moreover, the plate-shaped heating element 63 is the tubular base 6
Since they are formed at intervals of 0, it is difficult to make the temperatures of the surfaces A and B of the heater roller 1 uniform even if electricity is applied for a long time, and uneven heat generation occurs. Therefore, the fixing rate of the toner 40 is improved. I couldn't.

Further, since the heater roller 1 has a multi-layer structure, each layer has a different coefficient of thermal expansion, and there is a risk of distortion or cracking due to the difference in thermal expansion between the layers.
If the distortion or crack occurs, the printing paper 45 may be scratched, and the temperature distribution on the surfaces A and B of the heater roller 1 may become more uneven, so that the fixing rate of the toner 40 may be increased. There was also a problem of worsening.

Therefore, in order to eliminate the unevenness of heat generation, there is proposed a heater roller 1 in which a heat generating layer 63 is formed on the entire circumference of the surface of the cylindrical substrate 60 by a method such as pressure film printing. However, in the end, the difference in thermal expansion between the layers does not match, which may cause distortion or cracking. Moreover, in manufacturing, in order to reduce unevenness of heat generation, the thickness of each layer to be adhered to the tubular substrate 60 must be constant, so that cutting must be performed each time one layer is formed, Further, when forming the layer, there is a problem that the working time and the processing cost are increased because the layer must be formed thicker in consideration of the cutting process.

Moreover, although nickel, chromium, etc. are used as the material of the heating element or the heating layer 63, since the heat loss of these materials is large, the power consumption of the heater roller 1 cannot be reduced and the life of the heater roller 1 is reduced. There was also the problem of being short.

On the other hand, in order to obtain stable fixing of the toner 40, it is necessary to keep the surfaces A and B of the heater roller 1 at the set temperature at the time of use. The temperature of the heater roller 1 had to be constantly kept at the set temperature regardless of the presence or absence of print output. Therefore, it is necessary to always apply a voltage to the heater roller 1, and it is difficult to reduce power consumption.

[0011]

In view of the above problems, therefore, in the present invention, a heater roller is made of a rare earth chromite oxide-based ceramic having a volume resistivity of 0.1 to 10 Ω · cm and a perovskite type crystal structure. The substrate is formed and the heater roller is arranged in the image forming apparatus.

Examples of the rare earth chromite oxide-based ceramics include LaCrO ₃ , PrCrO ₃ , and NdCrO.
₃ , SmCrO ₃ , GdCrO ₃ , DyCrO ₃ , Ho
Examples include ceramics such as CrO ₃ and EoCrO ₃ .

[0013]

According to the present invention, since the base of the heater roller is made of conductive ceramics, the base itself can be used as a heating element. Therefore, when the base is energized, it can be heated immediately, and the surface of the heater roller can be uniformly heated. Moreover, since the above-mentioned ceramics have a volume specific resistance value of 0.1 to 10 Ω · cm, it is possible to generate the amount of heat necessary for fixing the toner.

The above-mentioned ceramic is mainly composed of a rare earth chromite oxide having a perovskite type crystal structure. Since this ceramic has excellent heat resistance and does not deteriorate in characteristics even at high temperatures, its performance is maintained for a long time. be able to.

Therefore, the image forming apparatus of the present invention can improve the fixing rate of the toner, shorten the start-up time, and reduce the power consumption, and maintain its performance for a long period of time. Can be maintained.

[0016]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a diagram showing an operating state of an image forming apparatus having a heater roller according to an embodiment of the present invention, and FIG. 2 is a perspective view in which a part of the heater roller shown in FIG. 1 is cut away. However, the same parts as those in the conventional example are indicated by the same reference numerals.

The image forming apparatus shown in FIG.
The outer peripheral surface of the photosensitive drum 31 is charged by the charging device 32 arranged on the outer peripheral surface of the toner 1, and the toner 40 is discharged by the developing device 34.
Are supplied to the outer peripheral surface of the photosensitive drum 31, and light is emitted from the exposure device 33 disposed inside the photosensitive drum 31 to the toner 4
By irradiating 0 onto the outer peripheral surface of the photosensitive drum 31, the toner 4
0 is attached, and the toner 40 is printed by the transfer colon 35 arranged on the opposite side with the printing paper 45 sandwiched therebetween.
It is designed to be transferred on top. Then, the printing paper 45 on which the toner 40 is transferred is sent to a fixing portion which is provided thereafter and is composed of the heater roller 1 and the pressure roller 55, and is sent between the heater roller 1 and the pressure roller 55, whereby the heater roller 1 The toner 40 on the printing paper 45 is heated by the heat and the pressure from the pressure roller 55.
Is melted and fixed.

On the other hand, the heater roller 1 provided in such an image forming apparatus is, as shown in FIG.
A cylindrical base 2 is formed of ceramics having a volume resistivity value of cm and having a perovskite type crystal structure, and Ni, Ag, Al are formed on both end surfaces of the base 2.
A conductive metal plating layer is formed as an electrode 3, and a brush 4 is slidably contacted with the electrode 3 to energize the electrode 3, and a release material layer 5 is provided on the surface of the base 2 excluding the electrode 3. The thickness t is 15 to 25 μm by a method such as electrostatic coating or thermal spraying.
It is coated in the range of m. A bearing 6 is fixed to the inner holes of both ends of the base body 2 by a key 9 or the like, and a shaft 8 having a gear 7 at one end is inserted and fixed to the bearing 6. Then, by driving the gear 7 using a motor (not shown), the heater roller 1
Is designed to rotate.

In this heater rotor 1, since the ceramics forming the substrate 2 is conductive, the ceramics themselves generate heat. Therefore, the entire surface of the heater roller 1 can be uniformly heated, and the fixing rate of the toner 40 can be significantly improved. Moreover, the volume resistivity of ceramics is 0.1 to 10 Ω · cm,
Since the size of the heater roller 1 is determined by the size of the printing paper 45, the outer diameter is approximately 15 × the inner diameter 12 × the length 260.
A size of about mm is used. Therefore, when calculated from the amount of heat generation required to fix the toner 40, the volume resistivity of the ceramics forming the substrate 2 is 0.1 to 1
It is important that it is 0 Ω · cm. That is, when the volume resistivity value is less than 0.1 Ω · cm, the heat generation amount becomes too large, so that the toner 40 is melted too much and the printing paper 45
On the contrary, if the volume resistivity value is larger than 10 Ω · cm, the predetermined heat generation amount cannot be obtained, so that the toner 40 cannot be melted and the image is formed on the printing paper 45. This is because the toner 40 cannot be fixed on the sheet.

The substrate 2 itself generates heat and is exposed to high temperature. However, it is excellent in heat resistance because it is made of ceramics having a perovskite type crystal structure.
The characteristics hardly deteriorate even at high temperatures. Therefore, it is not necessary to replace the heater roller 1 for a long period of time, and the image forming apparatus including the heater roller 1 has a long life.

Further, the heater roller 1 has a simple structure in which the outer peripheral surface of the base body 2 is coated with the release material layer 5, so that the heater roller 1 is easy to manufacture and the thickness h of the heater roller 1 can be reduced. Therefore, the heat transfer can be accelerated, and as a result, the start-up time can be shortened.

The release material layer 5 is made of a fluororesin. If this material is used, the release material layer 5 has an electric insulation property and evenly adheres to the surface of the base 2 even when heat is applied. It is possible to obtain the surface accuracy almost equal to the surface accuracy of, and it is most suitable as a release material.

The ceramics forming the base 2 are as follows:
Lanthanum chromite (LaCrO ₃ ), praseodymium chromite (PrCrO ₃ ), neodymium chromite (Nd
CrO ₃ ), samarium chromite (SmCrO ₃ ),
Gadolinium chromite (GdCrO ₃ ), dysprosium chromite (DyCrO ₃ ), holmium chromite (HoCrO ₃ ), erbium chromite (ErC)
It is possible to use rO ₃ ) or a rare earth chromite oxide-based ceramic compounding these. These ceramics have a volume resistivity of 0.1 to 10 Ω.
Since it is in the range of cm, it is most suitable as the heat-generating substrate of the heater roller 1. Further, among the above ceramics, for ceramics whose volume resistivity is not within the range of 0.1 to 10 Ω · cm, by substituting a part of the rare earth element,
A volume resistivity value of 0.1 to 10 Ω · cm can be obtained. That is, in the above ceramics, a part of the rare earth element is replaced with a Group 2a element of the periodic table such as Ca, Sr, or Ba to form a lattice defect and contribute to hopping conduction such as Mn or Cr. As described above, the conductivity can be increased, and thus the ceramic having a volume specific resistance value of 0.1 to 10 Ω · cm can be obtained by adjusting the substitution amount.

Further, since these ceramics have a perovskite type crystal structure, they are excellent in heat resistance,
The characteristics hardly deteriorate even at high temperatures. However, since a trace amount of Cr component evaporates at high temperatures and the characteristics may be gradually deteriorated, when the heater roller 1 that can be used for a longer period of time is required, C of the above ceramics is used.
By substituting a part of r with an element such as Mn, Co, Fe, Ni, Ce, or Zr or Group 3A or 4A of the periodic table, C
It is also possible to use the heater roller 1 having a long life in which the evaporation of the r component is suppressed and the characteristic deterioration is suppressed.

Moreover, since the specific heat of these ceramics is as small as 0.2 cal / ° C. or less, the heat capacity of the heater roller 1 can be reduced and the coefficient of thermal expansion is 1 ×.
It is about 10 ^-7 / ° C, which is smaller than that of alumina or silicon carbide. Therefore, the power consumption can be reduced, the start-up time can be shortened, and the expansion of the heater roller 1 does not apply an extra pressure to the toner 40 sandwiched between the drum 31 and the heater roller 1. Toner 4
A stable toner 4 that can always apply a constant pressure to 0
Fixing of 0 can be performed.

Further, the porosity is set to 10 in order to have a thermal shock resistance which is practically no problem as a heater to be rapidly heated.
It may be set to -30%. This is because if the porosity is lower than 10%, the thermal shock resistance is lowered, and it is easily damaged during rapid heating. Conversely, if the porosity is higher than 30%, the mechanical strength is decreased and the damage is likely to occur during handling. Is.

Among the above ceramics, LaC
The heater roller 1 formed of ceramics based on rO ₃ will be described.

In order to set the volume resistivity to 0.1 to 10 Ω · cm, a part of La of LaCrO ₃ is Ca.
Alternatively, in order to further suppress the characteristic deterioration by substituting with Sr, Cr
Is partially replaced with Mn.

This optimum substitution amount is represented by the site ratio X: Y, and the ratio is (La _1-X A _X ) (Cr _1-Y B _Y ) O ₃ 0 ≦ X ≦ 0.7 0 ≦ Y ≦ 0.6 A: Ca or Sr, B: Mn is preferable, and the ceramics made of lanthanum chromite (LaCrO ₃ ) substituted in this range have a volume resistivity of 0. 1-10
It is in the range of Ω · cm.

[0031]

[Table 1]

Heater roller 1 made of this ceramic
Is manufactured by using La ₂ O ₃ and C as the ceramic raw materials.
r ₂ O ₃ is mixed, and SrO or C is added to enhance conductivity.
AO and a predetermined amount of Mn ₂ O ₃ are added as a substitute material in order to suppress deterioration of characteristics. Then, an organic binder or the like is added to these raw materials and kneaded, a tubular body is formed by using an extruder, and the obtained tubular body is cut to a predetermined size and then fired in an oxidizing atmosphere. Thus, the cylindrical substrate 2 forming the heating element can be obtained. After that, the surface of the substrate 2 is finished with a center line average roughness (Ra) of 1 to
The desired cylindrical substrate 2 can be obtained by polishing to 2.5 μm. Here, the surface roughness of the substrate 2 is 1 to the center line average roughness.
The reason for polishing to 2.5 μm is that the release agent layer 5 coated on this surface is so thin that the surface roughness of the surface directly affects the surface roughness of the base body 2 as the base. This is because when the line average roughness is smoother than 1 μm, the heater roller 1 idles and the printing paper 45 cannot be stably conveyed. When the center line average roughness is 2.5 μm, the surface is This is because the temperature distribution on the surface of the heater roller 1 is not uniform because it is too coarse, and stable fixing of the toner 40 cannot be performed.

Next, Ni is formed on both end surfaces of this cylindrical substrate 2.
The heater roller 1 according to the present invention can be obtained by forming a plated layer to form the electrode 3 and coating the surface of the substrate 2 excluding the electrode 3 with a fluororesin having a thickness t of about 15 μm.

By the way, the heater roller 1 according to the present invention
Can be used not only in the image forming apparatus that separately transfers and fixes the toner 40, but also in the image forming apparatus as shown in FIG. 3 that simultaneously transfers and fixes the toner.

In the image forming apparatus shown in FIG. 3, an exposing device 33, which is a head such as an LED or a laser, is arranged inside the photosensitive drum 31 so as to emit light in the horizontal direction. A developing device 34 is provided at a position opposed to the developing device 34, and the toner 40 fed from the upper portion of the developing device 34 is attached to the outer peripheral surface of the photosensitive drum 31 and fed. It has a structure in which the heater roller 1 is arranged with 45 interposed therebetween. That is, the photosensitive drum 31 and the heater roller 1 form a conveying device, and when the printing paper 45 is inserted into the gap between the photosensitive drum 31 and the heater roller 1 and the heater roller 1 is rotated, the printing paper 45 becomes the photosensitive drum 31. The photosensitive drum 31 is conveyed by the pressing force of the heater roller 1 and
The upper toner 40 is fixed on the printing paper 45 by the heat and pressure of the heater roller 1 simultaneously with the transfer.

By disposing the heater roller 1 according to the present invention in such an image forming apparatus, the size of the apparatus can be greatly reduced, and when a voltage is applied, the surface of the heater roller 1 is heated to a set temperature in a short time. Since it can generate heat up to, it can be used soon after the power is turned on. Moreover, since the temperature distribution on the surface of the heater roller 1 is always uniform, an excellent fixing rate of the toner 40 can be obtained, and the heat capacity is small, so that the power consumption can be reduced.

Since the heater roller 1 according to the present invention has a very short start-up time, it is possible to turn off the power supply of the heater at times other than printing, and it is possible to save a large amount of electric power. is there.

Experimental Example A heater roller according to the present invention,
As a comparative example, a heater having a halogen lamp in an alumina tube shown in FIG. 5 and a heater having an insulating layer and a plate-like heat generating layer formed on the surface of a cylindrical substrate made of alumina ceramics shown in FIG. Experiments were conducted on the temperature rise time and power consumption.

In the heater roller of the present invention, a cylindrical substrate is formed from the three types of lanthanum chromite oxide ceramics shown in Table 1, Ni electrodes are provided on both ends of this cylindrical substrate, and the portions other than the electrodes are made of fluororesin. A coated heater roller was used. Further, in a comparative example, a heater roller whose cylindrical substrate is made of alumina ceramics is laid with a heating plate-like body made of a plurality of W (tungsten), an insulating layer of silicone rubber is formed on the heating plate-like body, and a fluororesin is formed on the outermost layer. Was used.

Each heater roller has an outer diameter of 15 m.
m, wall thickness 1.5 mm, length 260 mm.
However, the heater roller with a built-in halogen lamp has an outer diameter of 20 mm. Then, by applying a voltage of 100 V to these heater rollers, the set temperature of 180 V is applied.
The temperature rising time until the temperature reached to ° C and the power consumption were measured.

The respective results are shown in Table 2.

[0042]

[Table 2]

As can be seen from Table 2, the heater of sample 5 required 65 seconds to raise the temperature, and the electric power consumed in one hour was 850.
It was W. Moreover, even with the heater of sample 4, it takes 25
Seconds are required and power consumption is 650W.

On the other hand, the heaters of Samples 1 to 3 according to the present invention have a heating time of 12 seconds, which is about 80% less than that of the heater of Sample 5. It can be seen that it can be reduced by about 50% even for the heater of No. 4. Also, it can be seen that the power consumption is 560 W, which can also reduce the power consumption.

Further, when the heater rollers of Samples 1 to 4 were respectively incorporated in the image forming apparatus, a temperature difference of about 40 ° C. was generated on the surface of the heater roller of Sample 4, and the printing paper on which toner was transferred was printed. When toner is sent to the fixing unit, the ratio of toner fixing (toner fixing ratio) is 92.
%Met.

On the other hand, with the heater rollers of Samples 1 to 3 according to the present invention, it was found that the toner fixing rate can be improved to 99% or more, and more stable printing is possible.

[0047]

According to the present invention, since the base body of the heater roller provided in the image forming apparatus is formed of the rare earth chromite oxide-based ceramics having the perovskite type crystal structure, it has excellent heat resistance and high temperature characteristics. It can be made less deteriorated.

Further, since this ceramic is electrically conductive and has a volume resistivity of 0.1 to 10 Ω · cm, it is possible to obtain a predetermined amount of heat generation by applying a voltage, and moreover, a specific heat is obtained. Since it is small, startup time can be shortened and power consumption can be reduced.

Further, since the base body itself functions as a heating element, it is not necessary to have a conventional multi-layer structure, and it is possible to contribute to miniaturization. Therefore, the image forming apparatus of the present invention including the heater roller can improve the fixing rate of toner, can be used in an early stage by turning on the power, and can reduce power consumption. As described above, it can have very excellent performance.

[Brief description of drawings]

FIG. 1 is a diagram showing an operating state of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view showing a heater roller that constitutes an image forming apparatus according to the present invention.

FIG. 3 is a diagram showing an operating state of another image forming apparatus according to the present invention.

FIG. 4 is a partially cutaway perspective view showing a conventional heater roller.

FIG. 5 is a partially cutaway perspective view showing a conventional heater roller.

[Explanation of symbols]

 1 Heater Roller 2 Substrate 3 Electrode 5 Release Material Layer 6 Bearing 7 Gear 8 Shaft 9 Key 31 Photosensitive Drum 32 Charger 33 Exposure Device 34 Developer 40 Printing Paper 45 Toner 65 Brush

Claims (1)

[Claims] 1. An image forming apparatus comprising a heater roller for fixing toner, wherein a heater roller substrate is formed of a rare earth chromite oxide ceramics having a volume resistivity of 0.1 to 10 Ω · cm.