JP2003167463A - Fixing unit and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower the surface temperature of the metal core of a heating roller to prevent the dissipation of heat from a pressure roller. <P>SOLUTION: The rubber thickness of a fixing roller having an outside diameter of 46 mm is 2.1 mm and the rubber of the pressure roller having an outside diameter of 43 mm is 1.9 mm, and their relationship is established by λ1>λ2, wherein λ1 is the heat conductivity coefficient of the surface layer of the fixing roller and λ2 is the heat conductivity coefficient of the surface layer of the pressure roller. In addition, in the case each surface layer is formed from a plurality of layers, the sum of the heat conductivity coefficients of the layers is calculated, and a relationship is established by λ1'>λ2', wherein λ1' is the heat conductivity coefficient of the plurality of surface layers of the fixing roller and λ2' is the heat conductivity coefficient of the plurality of surface layers of the pressure roller. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device,
In particular, it relates to a color fixing device for an electrophotographic apparatus.

The present invention relates to an image heating device for heating a roller by utilizing the radiant heat of a halogen heater.

This device is a fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer or a fax machine, that is, a heat-meltable resin by an appropriate image forming process means such as electrophotography, electrostatic recording or magnetic recording. The present invention relates to an apparatus for heat-fixing an unfixed toner image directly or indirectly formed on a surface of a recording material using a toner such as the above as a permanently fixed image on the surface of the recording material.

[0004]

2. Description of the Related Art FIG. 5 is a diagram for explaining a conventional technique.
It is a schematic sectional view of a laser beam printer in which electrophotographic technology is applied to a printer. The operation of this device will be described below.

The intensity of the laser beam from the scanner 13 is modulated by the image information signal sent from the host computer to form an electrostatic latent image on the photosensitive drum 11. The intensity of the laser light and the irradiation spot diameter are appropriately set according to the resolution of the image forming apparatus and the desired image density, and the electrostatic latent image on the photosensitive drum 11 has the bright portion potential VL in the portion irradiated with the laser light. , The other part is the primary charger 12
It is formed by being held at the dark portion potential VD which is charged by. The photosensitive drum 11 rotates in the direction of the arrow, and the electrostatic latent image is sequentially developed by the developing device 14. The toner in the developing device 14 is a developing sleeve 140 that is a toner supply rotating member.
2 and the developing blade 1401 control the toner height and tribo and form a uniform toner layer on the developing sleeve 1402. The developing blade 1401 is usually made of metal or resin, and the resin blade is in contact with the developing sleeve 1402 with an appropriate contact pressure. The toner layer formed on the developing sleeve 1402 faces the photosensitive drum 11 as the developing sleeve 1402 itself rotates, and the electric field formed by the voltage Vdc applied to the developing sleeve 1402 and the surface potential of the photosensitive drum 11 causes VL of VL. Selectively visualize only a part. The toner image on the photosensitive drum 11 is sequentially transferred by the transfer device 15 onto the paper sent from the paper feeding device. As a transfer device, in addition to the corona charger shown in the figure, there is a transfer roller system in which a current is supplied from a power source to a conductive elastic rotating member to convey a paper while applying a transfer charge. The paper on which the toner image is transferred is sent to the fixing device 10 as the photosensitive drum 11 rotates, and becomes a permanent fixed image by being heated and pressed.

As an image heating apparatus represented by a heat fixing apparatus, a film heating method has been widely used in addition to the heat roller method shown in FIG.

In the heat roller system, a heat source such as a halogen heater is generally used in the roller, but in addition to this, the heat roller itself has an electric resistance to supply electric power to the heat roller for heating. A method has also been devised.

As a film heating method, a method of heating a film having a small heat capacity by using a ceramic heater as a heat source is widely practiced. In Japanese Patent Laid-Open No. 7-114276, a metal film is used for electromagnetic induction. Also discloses an induction heating method of self-heating with an eddy current.

As a temperature control method of the heat roller system, a temperature detecting element such as a thermistor is brought close to the roller and a halogen heater is turned on / off in accordance with the detected temperature to control the temperature of the roller to an appropriate temperature. Also, in the self-heating roller system, a technique of controlling the self-temperature by using a PTC material as a heating element is also disclosed.

As a film type temperature control method, a temperature detecting element such as a thermistor is brought close to the ceramic heater, and the ceramic heater is turned on / off by the detected temperature to control the film temperature at the nip to an appropriate temperature. To do.

[0011]

However, the fixing device of the above heat roller system has a problem that not only the heat capacity of the fixing roller is large, the power required for heating is large, but also the wait time is long.

In particular, when a fixing roller having a large heat capacity using an elastic layer such as silicone rubber on the roller surface layer is used in a full-color image recording apparatus, a delay occurs in temperature control and temperature rise on the surface of the fixing roller. However, problems such as improper fixing, uneven gloss and offset, and high temperature at the interface between the roller core metal and the elastic layer have caused the problem of peeling of the elastic layer due to thermal deterioration. Further, when the elastic layer of the roller surface layer is made thin in order to reduce the heat capacity, a sufficient nip width cannot be secured, so that the same phenomenon as described above occurs due to insufficient heat quantity.

Further, in a self-heating type fixing device, since a temperature difference is apt to occur between the temperature detecting element and the roller or film surface in the nip portion, if ordinary feedback control is performed, uneven gloss, improper fixing and offset will occur. However, there is a problem in that such problems are likely to occur.

In the film heating system, since the heat capacity of the heating element is small, on-demand fixing is possible.
If the normal on / off control is performed, the film temperature vibrates, and there is a problem that uneven gloss, improper fixing, offset, etc. are likely to occur.

[0015]

The present invention is an image forming apparatus having the following configuration.

(1) The rotating fixing roller and the fixing roller
A pressure roller that is in pressure contact with the roller,
And the surface of the pressure roller is covered with an elastic body,
A heating source is provided on one of the rollers, and the surface of the fixing roller is
And the unfixed developer image was carried on the pressure contact portion of the pressure roller.
By sandwiching and transporting the recording material, the unfixed developer image
In a fixing device for fixing on the recording material, the fixing roller
Thermal conductivity of elastic body λ ₁, Thermal conduction of elastic body of pressure roller
Rate λ_TwoAnd then λ₁> Λ_TwoTo satisfy the relational expression of
And a fixing device.

(2) The thermal conductivity λ ₁ of the fixing roller is 0.44 [W / m · K] ≦ λ ₁ , and the thermal conductivity λ ₂ of the pressure roller is 0.22 [W / m · K]. ] ≦ λ ₂ ≦ 0.44
[W / m · K] The fixing device as described in (1) above.

(3) When the thickness t _{1 of} the elastic body of the fixing roller and the thickness t ₂ of the elastic body of the pressure roller are t ₂ , 1.5 [mm] ≦ t ₁ ≦ 2. 5 [mm], 1.
The fixing device according to any one of (1) and (2), characterized in that 5 [mm] ≦ t ₂ ≦ 2.5 [mm].

(4) The elastic bodies of the fixing roller and the pressure roller are composed of at least one kind of composite elastic body, and the thermal conductivity λ ₁ ′ of the elastic body of the fixing roller and the thermal conductivity of the elastic body of the pressure roller. _'when a, lambda _1' conductivity lambda ₂ fixing device according to the satisfies the relation of> λ _{2 '(1).}

(5) The thermal conductivity λ ₁ ′ of the fixing roller is 0.44 [W / m · K] ≦ λ ₁ ′, and the thermal conductivity λ ₂ ′ of the pressure roller is 0.22 [W / m · K] ≦ λ ₂ ′ ≦ 0.
The fixing device described in (1) or (4) is characterized in that it is set to 44 [W / mK].

(6) When the thickness of the elastic body of the fixing roller is t ₁ ′ and the thickness of the elastic body of the pressure roller is t ₂ ′, 1.5 [mm] ≦ t ₁ ′. ≦ 2.5 [m
m] and 1.5 [mm] ≦ t ₂ ′ ≦ 2.5 [mm], the fixing device according to (1) or (5).

(7) The fixing device according to any one of claims (1) to (6), characterized in that the hardness of the elastic body of the fixing roller and the pressure roller is 15 ° or less according to JIS-A standard.

(8) Forming a permanent image by forming a heat-softening colored powder (hereinafter referred to as toner) image on a recording material and passing the recording material bearing this toner image through a fixing device. An image forming apparatus, wherein the fixing device is one of the fixing devices (1) to (7).

<Operation> The heat conductivity of the fixing roller is made larger than that of the pressure roller, the heat conductivity of the fixing roller is 0.44 [W / m · K] or more, and the heat conductivity of the pressure roller is high. The rate is 0.22 [W / m · K] or more and 0.44 [W / m ·
K] or less, the thickness of the elastic body of the fixing roller and the pressure roller is 1.5 [mm] or more and 2.5 [mm] or less, and the hardness of the elastic body of the fixing roller and the pressure roller is JIS-A. By setting the standard to 15 ° or less, problems such as poor fixing, uneven gloss, and offset can be solved without delay in temperature control and temperature rise of the fixing roller surface.

Further, since the rise in the interface temperature between the roller core metal and the elastic layer can be suppressed, the problem of peeling of the elastic body due to heat deterioration can be solved.

Further, since the elastic layer of the roller surface layer is not made thin so as to reduce the heat capacity, a sufficient nip width can be secured, and problems such as poor fixing, uneven gloss and offset due to insufficient heat quantity can be solved. .

Therefore, it is possible to provide a full-color image forming apparatus having a good thermal response and having high performance in which fixing defects, uneven gloss, and offset do not occur.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a drawing showing the features of an embodiment of the present invention. 101 is a fixing roller, and 1011 is a core metal such as aluminum. Reference numeral 103 denotes a heater as a heat source, and 1012 denotes an elastic layer which is a base layer formed on the surface of the core metal 1011 and has a thickness (several to several tens of μ) of multi-color toner of a single color to four colors in a color image.
m), the layer thickness is several tens of μm or more. If the elasticity of the elastic layer 1012 is small, the resolution of the toner may be reduced due to unfixed toner recesses or crushed toner. Therefore, the material of the elastic layer 1012 is methyl-based or methylvinyl-based liquid silicone rubber RTV, L.
It is preferable that the TV type has elasticity.

The hardness of the elastic layer 1012 is 15 ° (J
IS-A) or less, more preferably 10 ° (JIS-A)
The following is good. The thermal conductivity of the elastic layer 1012 is 0.
44 [W / m · K] or more is preferable. Thermal conductivity λ is 0.44
When it is smaller than [W / m · K], the thermal resistance is large and the temperature rise in the surface layer of the fixing roller 101 becomes slow.

A release layer (not shown), which is a surface layer, is formed on the elastic layer 1012. As the release layer (not shown), in addition to fluororesins such as PFA, PTFE and FEP, silicone resin, A material having good releasability and heat resistance such as silicone rubber, fluororubber, or silicone rubber can be selected. The release layer (not shown) has a thickness of 20 to 100 μm.
If the thickness of the release layer (not shown) is less than 20 μm, uneven coating may cause a part with poor releasability.
Problems such as insufficient durability occur. In addition, if the release layer exceeds 100 μm, there is a problem that heat conduction deteriorates. Particularly, in the case of a resin release layer, the hardness becomes too high, and the effect of the elastic layer 1012 is lost.

Reference numeral 102 denotes a pressure roller, which is the fixing roller 1.
Similar to 01, an elastic layer 1022 is provided on a core metal 1021 including a heater 103. The thickness of the elastic layer 1022 is the same as that of the fixing roller 101.
In order to follow the thickness (several to several tens of μm) of the multi-color toner of four colors, it has a layer thickness of several tens of μm or more. If the elasticity of the elastic layer 1022 is small, unfixed toner recesses or collapse of the toner may cause a decrease in resolution.
For this reason, it is preferable that the material of the elastic layer 1022 is a methyl-based or methylvinyl-based liquid silicone rubber RTV or LTV type having elasticity.

The hardness of the elastic layer 1022 is 15 ° (J
IS-A) or less, more preferably 10 ° (JIS-A)
The following is good. Regarding the thermal conductivity of the elastic layer 1022, since heat is not directly applied to the image surface, it can be made smaller than that of the fixing roller and is 0.22.
The range of [W / m · K] or more and 0.44 [W / m · K] or less is preferable. When the thermal conductivity λ is smaller than 0.22 [W / m · K], the thermal resistance is large and the temperature rise in the surface layer of the pressure roller 102 becomes slow. Also, 0.44 [W
/ M · K], the thermal resistance is small and the heat storage effect in the surface layer of the pressure roller 102 is small.

A release layer (not shown), which is a surface layer, is formed on the elastic layer 1022 in the same manner as the fixing roller 101, and PFA, PTFE, FE are used as the release layer (not shown).
In addition to fluororesins such as P, silicone resins, silicone rubbers, fluororubbers, silicone rubbers, and other materials with good mold release and heat resistance can be selected. The thickness of the release layer (not shown) may be equal to or larger than that of the fixing roller, but if it exceeds 100 μm, the hardness becomes too high, especially in the case of a resin-based release layer, and the effect of the elastic layer 1022 is obtained. It's gone.

The fixing roller 101 and the pressure roller 102 are pressed by a pressure spring (not shown), and the total pressing force is 50 to 50.
A fixing nip width of about 8.0 to 9.0 mm is obtained at 70 kgf. Reference numeral 104 denotes a thermistor, which is brought into contact with each surface of the fixing roller 101 and the pressure roller 102 as a temperature detector, and based on the detected roller surface temperature, a roller driving circuit (not shown) controls the roller surface temperature at the time of standby and Ripple ± so that the target temperature for printing is reached.
Temperature control is controlled in the range of several degrees Celsius. In this embodiment, the temperature control target temperature during standby is 165 ° C., the temperature control target temperature during printing is 175 ° C., and the ripple is controlled at ± 5 ° C. The temperature control target temperature of 165 ° C. during standby is determined from the viewpoint of the temperature rise inside the machine and the fixing failure (below this, fixing failure occurs). In the conventional full-color image recording apparatus that requires a large amount of power for temperature control, the heaters 103 of the fixing roller and the pressure roller are simultaneously turned on at the time of startup, standby, and printing. However, due to energy saving, high speed, and high thermal efficiency, the heater 103 of the pressure roller is
It was more effective to control to obtain a large amount of heat by turning on the light only during standby and adding the power used for the pressure roller heater to the fixing roller heater at the time of startup and printing. Also in this embodiment, the heater of the pressure roller is turned on only in the standby mode, and is turned off in the printing mode. 10
Reference numeral 3 denotes a heater, which is preferably 500 [W] or more for heating the fixing roller having a large heat capacity, and more preferably 900 to 1300 [W] from the viewpoint of shortening the wait time. Further, the pressure roller that is turned on only in the standby mode can be made smaller than the heater power of the fixing roller, and is 200 to 400 [W]
Good. In this embodiment, 900 [W] (100 [V] rating) for the fixing roller 101 and the pressure roller 10 are used.
As 200, 200 [W] (100 [V] rating) is used. Reference numeral 105 denotes a thermoswitch, which is disposed as a safety element in the vicinity of the fixing roller 101 and the pressure roller 102, and is a non-contact type thermoswitch in order to prevent scratches on the roller surface.

The operation and effect of the image heating apparatus when it is used as a fixing device of a four-color image forming apparatus will be described below together with the operation of the image forming apparatus.

FIG. 2 is a sectional view of an electrophotographic color printer using the present invention. Reference numeral 11 is a photoconductor drum made of an organic photoconductor, 12 is a charging device for uniformly charging the photoconductor drum 11, and 13 is a signal from an image signal generator (not shown) for turning on / off a laser beam. Is a laser optical box that converts the light into an electrostatic latent image on the photosensitive drum 11. 1
Reference numeral 101 is a laser beam, and 1102 is a mirror. The electrostatic latent image on the photosensitive drum 11 is visualized by selectively adhering toner by the developing device 14. The developing device 14 is composed of a color developing device for yellow Y, magenta M, and cyan C and a developing device B for black, and develops the latent image on the photosensitive drum 11 one color at a time and develops the toner image on the intermediate transfer drum 16 A color image is obtained by sequentially superimposing them on top. Intermediate transfer drum 16
Has a medium resistance elastic layer and a high resistance surface layer on a metal drum, and applies a bias potential to the metal drum to transfer a toner image by a potential difference from the photosensitive drum 11. On the other hand, the recording material P sent from the paper feed cassette by the paper feed roller is sent between the transfer roller 15 and the intermediate transfer drum 16 in synchronization with the electrostatic latent image on the photoconductor drum 11. The transfer roller 15 transfers the toner image on the intermediate transfer drum 16 onto the recording material P by supplying an electric charge having a polarity opposite to that of the toner from the back surface of the recording material P. In this way, the recording material P on which the unfixed toner image is placed is subjected to heat and pressure by the heat fixing device 10, is permanently fixed on the recording material P, and is discharged to a paper discharge tray (not shown). . The toner and the paper dust remaining on the photoconductor drum 11 are removed by the cleaner 17, and the toner and the paper dust remaining on the intermediate transfer drum 16 are removed by the cleaner 18. repeat.

The above-mentioned fixing device is used as the fixing device 10. At a process speed of about 120 mm / sec, the recording material P is heated and conveyed at the nip to fix the toner image and separated at the nip outlet.

Although the four-color image forming apparatus has been described in this embodiment, it may be used in a monochrome or one-pass multi-color image forming apparatus. In this case, the elastic layer 1012 can be omitted in the fixing roller 101.

Next, the features of this embodiment will be described together with the operating principle.

When the heat conductivity of the elastic layer 1012 of the fixing roller 101 is small, a delay occurs between the temperature adjustment and the temperature rise of the fixing roller surface. Therefore, in order to adjust the temperature of the fixing roller surface to a predetermined temperature, heating is required. It requires a large amount of power. as a result,
The interface temperature between the core metal 1011 and the elastic layer 1012 was excessively raised, and the elastic layer 1012 was thermally deteriorated and peeled off. Therefore, in order to improve this, the elastic layer 101
It is necessary to increase the thermal conductivity of No. 2 so as to improve the thermal response and suppress the excessive temperature rise of the interface temperature. In this embodiment,
For the elastic layer 1012 and the elastic layer 1022, a low hardness silicone rubber having a JIS-A standard of 15 ° or less is used in order to secure a fixing nip width for obtaining a sufficient fixing property. Further, although the silicone rubber is excellent in heat resistance, the temperature at which it thermally deteriorates in proportion to the hardness becomes high, and the temperature at which the silicone rubber used in this embodiment thermally deteriorates is approximately 240 ° C., The interface temperature between the core metal 1011 and the elastic layer 1012 needs to be 240 ° C. or lower.

The pressure roller 102 is made of an elastic layer 1022.
If the heat conductivity of the toner is large, the heat storage effect during printing is reduced, so that the surface temperature of the pressure roller is drastically lowered, resulting in defective fixing, uneven gloss, and offset.

Therefore, the elastic layer 101 of the fixing roller 101
The thermal conductivity of 2 is λ₁The elastic layer 102 of the pressure roller 102
The thermal conductivity of 2 is λ_TwoAnd then λ₁> Λ_TwoRelational expression of
Is satisfied, 0.44 [W / m · K] ≦ λ₁, And 0.2
2 [W / m · K] ≦ λ_Two≤0.44 [W / mK] or less
And the thickness of the elastic layer 1012 of the fixing roller 101 is
t ₁, The thickness of the elastic layer 1022 of the pressure roller 102 is t_Two
Is 1.5 [mm] ≦ t₁≦ 2.5 [m
m], 1.5 [mm] ≦ t_Two≤2.5 [mm], constant
The hardness of the elastic layer 1012 of the forming roller 101 is h₁, Pressure
The hardness of the elastic layer 1022 of the roller 102 is h_TwoIf you do
h₁≤15 ° (JIS-A), h_Two≤15 ° (JIS-
By setting A), the temperature control and the temperature rise on the surface of the fixing roller are delayed.
Poor fixing, uneven gloss, and offset without spreading
It is possible to solve such problems.

Next, in the fixing devices A to U, the interface temperature between the core metal of the fixing roller and the elastic layer, the lowest point of the surface temperature of the pressure roller during printing, durability, fixing property, and wait time were examined. .

[0044]

[Table 1]

The measuring methods 1 to 3 shown in Table 1 and respective fixing devices will be described.

FIG. 3 is a view of the fixing device of this embodiment as seen from the paper discharge direction. As shown in FIG. 3, since it is difficult to actually measure the interface temperature between the core metal 1011 and the elastic layer 1012, the elastic layer 1012 in the central portion of the fixing roller 101 is peeled off, and the temperature of the portion A is measured to measure the core. A relative comparison was made as the interface temperature between the gold 1011 and the elastic layer 1012. As the measurement conditions, 105 g paper (40 manufactured by Xerox Co., Ltd., which is the maximum basis weight used as plain paper in this image forming apparatus) is used.
24 sheets, Ledger size) were continuously fed at a throughput of 12 sheets per minute, and the value when sufficiently stable was measured.

FIG. 4 is a view of the fixing device of this embodiment as seen from the paper discharge direction. As shown in FIG. 4, the temperature of the central portion B of the pressure roller 102 is measured and compared as the surface temperature of the elastic layer 1022. The measurement conditions are the same as in 105 g paper which is the maximum basis weight used as plain paper in this image forming apparatus (4024 paper manufactured by Xerox,
Ledger size) was continuously fed at a throughput of 12 sheets per minute, and the value showing the lowest point (minimum temperature) was measured.

The number of sheets passed until the roller is peeled and destroyed. As the paper passing conditions, 4024 sheets (75 g paper, Letter size) manufactured by Xerox Co., Ltd. are continuously passed at a throughput of 24 sheets per minute, and the number of sheets to be passed until the elastic layer 1012 of the fixing roller 101 is peeled off and destroyed. I counted. Incidentally, a fixing device which cannot be fixed due to its fixability and wait time has not been measured.

It was judged whether the fixability was good or bad. As the measurement conditions, the maximum basis weight of 105 g paper (Xerox 4024 paper, Ledger size) used as plain paper in this image forming apparatus is set to 12 per minute as in
The lowest point (lowest temperature) with continuous throughput at the throughput of one sheet
The toner image on the sheet showing "1" was rubbed through Silbon C or the like, and the density decrease rate of 20% or less was determined.

The wait time was determined. Input voltage 10
At 0 [V], it was determined that the time from the room temperature to the printable temperature (the temperature control target temperature during standby) was within 3 minutes.

From the above-mentioned measurement results of-, the effect levels were evaluated as ⊚, ∘ and ×. ⊚ indicates a fixing device that has a good fixing property and satisfies the high durability of 200k sheets or more, and ○ indicates a fixing device that satisfies the fixing property and a durability of 150k sheets or more, x Is not fixative,
Alternatively, a fixing device with 60 or less sheets passed is shown.

According to the fixing devices A, B and C, the thermal conductivity λ ₁ of the elastic layer 1012 of the fixing roller 101 is 0.44 [W.
/ M · K] (fixing device C), core metal 10
11 and the elastic layer 1012 have an interface temperature of 241 ° C.,
The temperature has risen to the heat deterioration temperature of the silicone rubber, and the durability is 60 k or less. When the thermal conductivity λ ₁ is 0.44 [W / m · K] or more (fixing devices A and B)
In addition, the interface temperature between the core metal 1011 and the elastic layer 1012 is 22
The temperature is 6 ° C. or lower, which satisfies the heat deterioration temperature of the silicone rubber or lower, and the durability is as high as about 200 k sheets.
Therefore, t ₁ = 2.0 [mm], h ₁ = 10 ° (JIS
-A), λ ₂ = 0.33 [W / m · K], t ₂ = 2.0
Under the condition of [mm] and h ₂ = 10 ° (JIS-A), the fixing roller 101 has a thermal conductivity λ ₁ of 0.44 [W / m ·
K] or more, high durability is obtained.

Next, according to the fixing devices D, E, F and G, the thermal conductivity λ ₂ of the elastic layer 1022 of the pressure roller 102 is 0.
When it is larger than 44 [W / mK] (fixing device D),
The central portion B of the pressure roller 102 reaches 160 ° C., and the temperature is lowered to a temperature at which the fixing failure occurs or less, and the fixing failure occurs. Further, the thermal conductivity λ ₂ is 0.22 [W / m
・ If it is smaller than K] (fixing device G), the pressure roller 1
02 has a poor thermal response and has a long wait time. The thermal conductivity λ ₂ is 0.22 [W / m ·
When K] ≦ λ ₂ ≦ 0.44 [W / m · K] (fixing devices E and F), the central portion B of the pressure roller 102 is 167 ° C. or higher, which satisfies the temperature at which fixing failure occurs or higher. is doing. Therefore, λ ₁ = 0.50 [W / m · K], t ₁ =
2.0 [mm], h ₁ = 10 ° (JIS-A), t ₂ =
Under the condition of 2.0 [mm] and h ₂ = 10 ° (JIS-A), the thermal conductivity λ ₂ of the pressure roller 102 is 0.22 [W /
Good fixability is obtained by setting m · K] ≦ λ ₂ ≦ 0.44 [W / m · K].

Next, according to the fixing devices H, I, J and K, the thickness t ₁ of the elastic layer 1012 of the fixing roller 101 is 2.5.
When it is larger than [mm] (fixing device H), the core metal 101
The interface temperature between 1 and the elastic layer 1012 is 247 ° C., and the temperature has risen to the heat deterioration temperature of the silicone rubber, and the durability is 60 k or less. Also, the thickness t ₁ is 1.5
When it is smaller than [mm] (fixing device K), the fixing nip width becomes small, and the heat for sufficiently melting the toner T cannot be supplied, so that fixing failure occurs. When the thickness t ₁ is 1.5 [mm] ≦ t ₁ ≦ 2.5 [mm] (fixing devices I and J), the interface temperature between the core metal 1011 and the elastic layer 1012 is 227 ° C. or less, Satisfying the heat deterioration temperature of the silicone rubber or lower, the durability is as high as about 200k sheets. Therefore, λ ₁ = 0.50 [W / m · K], h
_{1 = 10 ° (JIS-A} ), λ 2 = 0.33 [W / m ·
K], t ₂ = 2.0 [mm], h ₂ = 10 ° (JIS-
Under the condition A), the fixing roller 101 obtains high durability by setting the thickness t ₁ of the elastic layer 1012 to 1.5 [mm] ≦ t ₁ ≦ 2.5 [mm].

Next, according to the fixing devices L, M, N and O, the thickness t ₂ of the elastic layer 1022 of the pressure roller 102 is 2.5.
If it is larger than [mm] (fixing device L), the thickness t ₂ is too large and a delay occurs in the temperature rise on the surface of the pressure roller 102, resulting in a long wait time. Also, the thickness t ₂
Is less than 1.5 [mm] (fixing device O), the central portion B of the pressure roller 102 reaches 160 ° C., which is below the temperature at which fixing failure occurs, and fixing failure occurs. . Then, the thickness t ₂ is 1.5 [mm] ≦ t ₂
In the case of ≦ 2.5 [mm] (fixing devices M and N), the central portion B of the pressure roller 102 is 165 ° C. or higher, which satisfies the temperature at which fixing failure occurs or higher. Therefore, λ ₁ =
0.50 [W / m · K], t ₁ = 2.0 [mm], h ₁
= 10 ° (JIS-A), λ ₂ = 0.33 [W / m ·
K], h ₂ = 10 ° (JIS-A), the pressure roller 102 sets the thickness t ₂ of the elastic layer 1022 to 1.5 [m.
Good fixability is obtained by setting m] ≦ t ₂ ≦ 2.5 [mm].

Next, according to the fixing devices P, Q and R, the hardness h ₁ of the elastic layer 1012 of the fixing roller 101 is 15 ° (JI
If it is larger than (S-A) (fixing device P), the fixing nip width becomes small, and heat that sufficiently melts the toner T cannot be supplied, so that fixing failure occurs. The hardness h ₁ is 1
When it is less than 5 ° (JIS-A) (Fixing device Q, R)
In addition, the interface temperature between the core metal 1011 and the elastic layer 1012 is 21
The temperature is 1 ° C. or lower, which satisfies the heat deterioration temperature of the silicone rubber or lower, and the durability is high at about 200 k sheets.
Therefore, λ ₁ = 0.50 [W / m · K], t ₁ = 2.0
[Mm], λ ₂ = 0.33 [W / m · K], t ₂ = 2.
Under the condition of 0 [mm] and h ₂ = 10 ° (JIS-A),
The fixing roller 101 sets the hardness h ₁ of the elastic layer 1012 to h ₁ ≦
High durability is obtained by setting it to 15 ° (JIS-A).

Next, according to the fixing devices S, T and U, the pressure roller is
Hardness h of the elastic layer 1022 of the roller 102_TwoIs 15 ° (JI
S-A) (fixing device S), the fixing nip
The width becomes smaller and the heat that melts the toner T sufficiently can be supplied.
No fixing failure has occurred. Also, hardness h_TwoIs 1
When it is less than 5 ° (JIS-A) (Fixing device T, U)
In addition, the central portion B of the pressure roller 102 is 165 ° C. or higher.
The temperature is above the temperature at which fixing failure occurs. Obey
, Λ₁= 0.50 [W / mK], t₁= 2.0 [m
m], h₁= 10 ° (JIS-A), λ_Two= 0.33
[W / mK], t _Two= 2.0 [mm]
The pressure roller 102 has a hardness h of the elastic layer 1022._TwoH_Two≤1
Good fixability is obtained by setting it to 5 ° (JIS-A).

As described above, by adopting this embodiment, it is possible to obtain a fixing device having a good thermal response and having no defective fixing, uneven gloss, and offset.

(Second Embodiment) The configurations of the fixing device and the image forming apparatus are the same as those described above.

A feature of the present invention is that, in addition to the above control method,
Elastic layer 101 of fixing roller 101 and pressure roller 102
2 and the elastic layer 1022 are a plurality of layers, and the fixing roller 10
₁ the thermal conductivity of the first composite elastic layer 1012 lambda when a ', the thermal conductivity of the composite elastic layer 1022 of the pressure roller 102 lambda _2', where satisfies the relationship of lambda ₁ '> lambda _2' It is in.

In this example, as in the first embodiment, 0.4
4 [W / m · K] ≦ λ ₁ ′, and 0.22 [W / m ·
K] ≦ λ ₂ ′ ≦ 0.44 [W / m · K] or less, the thickness of the elastic layer 1012 of the fixing roller 101 is t ₁ ′, and the thickness of the elastic layer 1022 of the pressure roller 102 is t ₂ ′. Is set to 1.5 [mm] ≦ t ₁ ′ ≦ 2.5 [mm], 1.5
[Mm] ≦ t ₂ ′ ≦ 2.5 [mm], and the fixing roller 1
01, the hardness of the elastic layer 1012 is h ₁ ′, the pressure roller 10
When the hardness of the second elastic layer 1022 is h ₂ ′,
h ₁ ′ ≦ 15 ° (JIS-A), h ₂ ′ ≦ 15 ° (JI
By adopting S-A), the delay between the temperature control and the temperature rise on the surface of the fixing roller does not occur, and problems such as defective fixing, uneven gloss and offset can be solved. In addition, since the choice of elastic layer materials increases, inexpensive materials can also be used,
It is possible to provide a highly durable fixing device having good thermal response while reducing costs.

[0062]

As described above, according to the first and second inventions of the present application, it is possible to improve the thermal responsiveness and durability of the heat roller fixing device requiring a large amount of heat. Moreover, it is possible to realize uniform fixing by supplying heat accurately to the recording material.

Further, the image forming apparatus using the image heating apparatus having the features of the first and second inventions can shorten the wait time, perform image formation with low power consumption, and produce a full-color image. High image quality can be maintained even for images with a large amount of toner.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating a first embodiment of the present invention.

FIG. 2 is a schematic sectional view illustrating a color image forming apparatus using the fixing device of the present invention.

FIG. 3 is a measurement diagram according to the first embodiment of the present invention.

FIG. 4 is a measurement diagram according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a usage example of a conventional example of the present invention.

[Explanation of symbols]

101 fixing roller 102 pressure roller 103 heater 104 thermistor 105 thermo switch 1011 and 1021 core metal 1012, 1022 elastic body

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Sano             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Nana Taki Hideo             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation F-term (reference) 2H030 AD04 BB23 BB42 BB63                 2H033 AA02 AA09 AA10 AA24 AA30                       BB06 BB15 BB29 BB30                 3J103 AA02 AA51 AA85 BA03 BA41                       FA01 FA12 GA02 GA57 GA58                       GA60 HA04 HA12

Claims (8)

[Claims] 1. A rotating fixing roller, and a pressure roller that is in pressure contact with the fixing roller, the surfaces of the fixing roller and the pressure roller are covered with an elastic body, and at least one roller is provided with a heating source. A fixing device for fixing the unfixed developer image on the recording material by sandwiching and transporting the recording material carrying the unfixed developer image on the surface of the fixing roller and the pressure contact portion of the pressure roller. thermal conductivity lambda ₁ of the elastic body of the _roller, when the thermal conductivity lambda ₂ of the elastic body of the pressure roller, fixing device, characterized by satisfying the λ _1> λ ₂ relationship. 2. The thermal conductivity λ ₁ of the fixing roller is 0.4.
4 [W / m · K] ≦ λ ₁ , thermal conductivity λ of the pressure roller
₂ is 0.22 [W / m · K] ≦ λ ₂ ≦ 0.44 [W /
m · K], the fixing device according to claim 1. 3. When the thickness t _{1 of} the elastic body of the fixing roller and the thickness t ₂ of the elastic body of the pressure roller are t ₂ , 1.5 [mm] ≦ t ₁ ≦ 2.5. [Mm], 1.
The fixing device according to claim 1 or _{2, wherein} 5 [mm] ≦ t ₂ ≦ 2.5 [mm]. 4. The elastic body of the fixing roller and the pressure roller is composed of at least one kind of composite elastic body, and the thermal conductivity λ ₁ ′ of the elastic body of the fixing roller and the thermal conductivity of the elastic body of the pressure roller. The fixing device according to claim 1, wherein a relational expression of λ ₁ ′> λ ₂ ′ is satisfied when the ratio is λ ₂ ′. 5. The thermal conductivity λ ₁ ′ of the fixing roller is set to 0.
44 [W / m · K] ≦ λ ₁ ′, the thermal conductivity λ ₂ ′ of the pressure roller is 0.22 [W / m · K] ≦ λ ₂ ′ ≦ 0.44
The fixing device according to claim 1 or 4, wherein [W / m · K] is set. 6. When the thickness of the elastic body of the fixing roller is t ₁ ′ and the thickness of the elastic body of the pressure roller is t ₂ ′, 1.5 [mm] ≦ t ₁ ′ ≦ 2.5 [m
m], 1.5 [mm] ≦ t ₂ ′ ≦ 2.5 [mm], Claim 1 or 4, 5
The fixing device according to the item. 7. The fixing device according to any one of claims 1 to 6, wherein the hardness of the elastic body of the fixing roller and the pressure roller is 15 ° or less according to JIS-A standard. 8. An image forming apparatus for forming a thermosoftening colored powder (hereinafter referred to as toner) image on a recording material, and passing the recording material bearing this toner image through a fixing device to make a permanent image. An image forming apparatus, wherein the fixing device is the fixing device according to any one of claims 1 to 7.