JPH03161783A - Heat fixing device for electrophotography - Google Patents

Abstract

PURPOSE:To provide the lower electric power consumption and the longer life of an image forming device by forming a heat generating part as a unidirectional heat generating part and forming a heat fixing part of a heat fixing belt consisting of a film-shaped endless belt. CONSTITUTION:The heat generating part is formed as the unidirectional heat generating part 1 and the heat fixing part is formed of the heat fixing belt 2. The heat capacity of the heat fixing part is extremely decreased in this case and the lowering of the temp. of the heat fixing part 2 in the part exclusive of a heating region 5 is possible. In addition, the need for previously warming up the heat fixing part 2 so as to be ready for use is eliminated. The electric power consumption is reduced in this way. Since the heat capacity of the heat fixing part is small, the abrupt temp. rise in the image forming device by the heat transfer from the heat fixing part after the stop of the power source of the image forming device is prevented and the thermal deterioration of the parts which are disposed in the device and vulnerable to high temp. is prevented. The life of the image forming device is thus prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat fixing device for electrophotography, and more particularly, the present invention relates to a heat fixing device for electrophotography, and in particular, a heat fixing device that fixes a fixing medium to which a toner image has been transferred is heated by a heat generating section and a pressure section. This relates to a heat fixing device for electrophotography that is inserted between the media and heat fixes a toner image onto a fixing medium. [Prior Art] As shown in FIG. 4, for example, a conventional heat fixing device for electrophotography includes a heat generating section consisting of a halogen lamp 4l, a heat fixing section consisting of a heat fixing roller 42, and a pressure roller 43. The main part was constructed from the pressurized part. In such a conventional electrophotographic heat fixing device, a heat fixing roller 42 that receives radiant heat from a halogen lamp 41 and a pressure roller 43 rotate in the direction shown by the arrow while being in pressure contact with each other to form a toner image. The transferred toner image is placed between the fixing medium S and the toner image is thermally melted and fixed on the fixing medium S. By the way, in the conventional heat fixing device for electrophotography, the heat fixing section is formed by the heat fixing roller 42 made of a hollow cylinder, and the cross-sectional thickness t' of the heat fixing roller 42 is sufficiently large thermally. The heat capacity of the fixing roller 42 had to be extremely large.

Furthermore, since it is necessary to press the heat fixing roller 42 and the pressure roller 43 into pressure contact to form a heating region 44 having a certain nip width Therefore, the heat capacity of the heat fixing roller 42 has to be increased. Furthermore, since the thermal capacity of the heating fixing roller 42 is large, it is necessary to keep the heating fixing roller 42 warmed up at all times even when the toner image is not actually being thermally fixed onto the medium S to be fixed. In addition, although the surface temperature of the heat fixing roller 42 is sufficient if only the heating area 44 has the necessary heating temperature, since the heat generating part is non-directional, such as the halogen lamp 41, it is difficult to The temperature at each location was almost equally high compared to the surrounding area. Therefore, a large amount of heat escapes from the surface of the heat fixing roller 42 to the surroundings due to two types of heat transfer: heat radiation indicated by A' and heat transfer indicated by B'. This heat loss occurs because the diameter of the heat-fixing roller 42 inevitably becomes larger than a certain diameter, and therefore the surface area of the heat-fixing roller 42 inevitably becomes larger than necessary compared to the heating area 44. It was further increased by.

[Problem to be solved by the invention]

In the conventional electrophotographic heat fixing device described above, the heat fixing section is formed by the heat fixing roller 42, and the heat capacity and surface area of the heat fixing roller 42 have to be larger than necessary. In addition, a large amount of heat is lost due to heat radiation and heat transfer from the surface of the heat fixing roller 42, resulting in a problem that the electrophotographic heat fixing device consumes a large amount of power. Furthermore, since the heat capacity of the heat fixing roller 42 was larger than necessary, when the power of the image forming apparatus equipped with the electrophotographic heat fixing device is stopped, the heat of the electrophotographic heat fixing device is forcibly discharged. The exhaust fan that generates heat also stops, and as a result, the temperature inside the image forming apparatus temporarily rises rapidly due to heat transfer from the heat fixing roller 42, which has a sufficiently large heat capacity (heat storage amount), which is a so-called overshoot. There is a problem in that this phenomenon causes thermal deterioration of parts that are sensitive to high temperatures, such as photoreceptors, which are arranged inside the image forming apparatus. By using a unidirectional heat generating section and using a heat fixing belt made of a film-like endless belt for the heat fixing section, the heat capacity of the heat fixing section can be reduced and various conventional r!11M points can be solved at once. [Means for Solving the Problems] The present invention provides a heat fixing device for electrophotography in which a fixing medium to which a toner image is transferred is heated by a heat generating section. In an electrophotographic heat fixing device that is inserted between a heat fixing unit and a pressure unit to heat fix a toner image on a fixing medium, a unidirectional heat ray is emitted by directing the heat generating unit in one direction. The present invention is characterized in that the heating unit is a heating unit, and the heating fixing unit is a heating fixing belt formed of a film-like endless belt.

[Effect]

In the electrophotographic heat fixing device of the present invention, the unidirectional heat generating section emits heat rays in one direction, and the heat fixing belt is heated intensively by the heat rays from the unidirectional heat generating section to form a toner image. is melted with heat and fixed on the fixing medium. [Example] Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the structure of an electrophotographic heat fixing device according to an embodiment of the present invention. The electrophotographic heat fixing device of this embodiment includes a unidirectional heat generating section 1, a heat fixing belt 2 serving as a heat fixing section, and four belt transfer shafts 3 that extend and transport the heat fixing belt 2. , the main part thereof is separated from the pressure roller 4 which is the pressure part. As shown in FIG. 2, the unidirectional heat generating unit 1 includes a halogen lamp 6 and a concave mirror 7 having a parabolic curved surface, an involute curved surface, etc., which arranges the halogen lamp 6 near the focal position.
This is because of this. This unidirectional heating section l is configured to emit heat rays C emitted from the halogen lamp 6 by reflecting them on a concave mirror 7 in a concentrated manner in one direction. It is arranged so as to face the pressure roller 4 with the heating fixing belt 2 in between so that the back side facing the area 5 is irradiated intensively. The heat fixing belt 2 is made of PTFE (boritetrafluoroethylene). It is formed into an endless shape using a thin film-like belt made of silicone rubber or the like, or a belt made of a thin stainless steel plate coated with PTFE. It goes without saying that the cross-sectional thickness t of the heat-fixing belt 2 is considerably thinner than the cross-sectional thickness t° of the heat-fixing roller 42. Also,
The circumferential length of the heat fixing belt 2 can also be made considerably shorter than the circumferential length of the heat fixing roller 42 for the same nip width X of the heating area 5. Next, the operation of the electrophotographic heat fixing device of this embodiment configured as described above will be explained. When a fixing medium S such as paper onto which a toner image has been transferred is fed by a feeding means (not shown), the belt transfer shaft 3 is rotated clockwise (as viewed in FIG. 1) in conjunction with this. Then, the heat fixing belt 2 is transported in the direction of the arrow at a transport speed approximately equal to the feeding speed of the fixing medium S. At the same time, the pressure roller 4 is rotated in the direction of the arrow at a circumferential speed approximately equal to the feeding speed of the fixing medium S. Then, just before the leading edge of the fixing medium S is inserted between the heat fixing belt 2 and the pressure roller 4, the halogen lamp 6 is turned on and the unidirectionality is set. Heat wire C from heat generating part 1
is irradiated onto the back side of the heating area 5 of the heating fixing belt 2. Since the cross-sectional thickness t of the heating fixing belt 2 is so thin that it can be almost ignored thermally, the heat radiated from the heating wire C reaches the heating region 5 instantaneously. Therefore, the toner image on the medium S to be fixed is thermally fused by the heat applied from the heat fixing belt 2 heated to a high temperature, and the toner image thermally fused by the pressure applied by the pressure roller 4 is to be fixed. It is fixed on the medium S. After that, the heating fixing belt 2 is exposed to the outside space by being transferred in the direction of the arrow, but since its heat capacity is small, the surface temperature drops immediately, and the heat loss A due to heat radiation also increases due to heat transfer. Both loss B and heating fixing roller 4
A much smaller amount is required compared to case 2. Here, the length (width) of the heat fixing belt 2 in the axial direction is L.
1 Assuming that the thickness is t, the transfer speed is V, the specific heat is C, and the density is ρ, the required amount per unit time to raise the temperature of the heat fixing belt 2 from the ambient temperature θ to the required heating temperature θ2 is: Amount of heating Q. is Qs ”C.xρXVXLX t
X (θ2−θ,)[W]. Now, suppose that the circumferential length of the heat-fixing belt 2 is extended to infinity, and the maximum heat is such that the surface temperature of the heat-fixing belt 2 becomes equal to the ambient temperature θ1 from the required heating temperature θ2 by emitting heat to the external space. Even if we consider a model that is prone to loss, the amount of heat loss = required heating amount 10. Therefore, L=340
mm, v=5Qmm/see, θg-160”C, θ.
=20"C, assuming a silicon rubber belt of t-30μm, Cs of silicone rubber =1.4X10'J
oule/kg-deg and ρxQ. 9X10-”k
g/mm3G7, Ql k” 1 0 0 [W].In other words, the amount of heat loss Q, no matter how large, is I
It is below OOW. However, in reality, the circumferential length of the heat-fixing belt 2 can be shortened (it is a finite length), so the decrease in the surface temperature of the heat-fixing belt 2 is greater than the difference between the required heating temperature θ2 and the ambient temperature θ. This will be a small value. That is, the heat loss B due to heat transfer decreases as the surface temperature of the heat fixing belt 20 decreases, and the heat loss A due to heat radiation decreases as the surface temperature of the heat fixing belt 20 decreases.
Expressing the surface temperature as an absolute temperature, it is proportional to the fourth power of the absolute temperature. Therefore, if the surface temperature of the heat-fixing belt 2 decreases even slightly, it will decrease dramatically. circumference), the surface temperature of the heating fixing belt 2 returns to the heating area 5 without decreasing much. Therefore, the actual required heating amount Ql is 50W or less. In other words, the actual amount of heat loss Q. is less than 50W. By the way, in the conventional electrophotographic heat fixing device, the cross-sectional thickness 1 of the heat fixing roller 42 is sufficiently large thermally, and as a result, the heat capacity of the heat fixing roller 42 is also extremely large. are uniformly equal.

For this reason, for example, the heating fixing roller 42 with a diameter of 4 Qmm
Let Q be the amount of heat loss when using the heated fusing roller 42. Even if this heated fusing roller 42 is used in an ideal manner where no forced air cooling effect is generated by an exhaust fan, etc., the fusing conditions are the same as described above. Therefore, the QIq becomes 120 to 150 [W], which is a much larger amount of heat loss than the amount of heat loss Q@ in the electrophotographic heat fixing device of this embodiment.
I know it will become precious.

The lamp heat amount of the halogen lamp 6 is actually the required heating amount Q. It is determined that on/off control is performed using approximately twice the amount of lamp heat. Therefore, in the electrophotographic heat fixing device of this embodiment, the heat loss IQI can be reduced from the heat loss amount Qm of about 150 W in the conventional electrophotographic heat fixing device to about 50 W. The lamp heat amount can also be reduced by about 200 W compared to the lamp heat amount of a 4-liter halogen lamp in a conventional electrophotographic heat fixing device. As a result, it is possible to reduce the maximum power consumption of the electrophotographic heat fixing device by approximately 200W. In addition, since the thermal capacity of the heat fixing belt 2 is small and the heat generating part is made into the unidirectional heat generating part 1, the warm-up time of the heat fixing device for electrophotography is extremely short. It is no longer necessary to keep the heat-fixing belt 2 on standby with a constant warm amplifier before the start of feeding, and from this point of view as well, the power consumption of the electrophotographic heat-fixing device can be reduced. Furthermore, because the thermal capacity of the heat fixing belt 2 is small, there is almost no sudden temperature rise inside the image forming apparatus after the power is turned off, and there is a risk that components sensitive to high temperatures inside the image forming TC apparatus will deteriorate due to heat. There is no. By the way, as shown in FIG. 1, the unidirectional heating section 1 does not necessarily need to be located inside the heat fixing belt 2. For example, as shown in FIG. In the case where there are three belts, the unidirectional heat generating section 1 may be arranged near the outside of the heat fixing belt 2 on the side into which the fixing medium S enters. That is, the unidirectional heat generating section 1 may be placed at any position as long as it is near the heating area 5 and can heat the heat fixing belt 2 to the required heating temperature θ2 in the heating area 5. Even if the unidirectional heat generating section 1 is arranged in the position shown in FIG. 3, the heat fixing belt 2 heated by the unidirectional heat generating section 1 immediately reaches the heating area 5, so that the position shown in FIG. It goes without saying that almost the same functions and effects as the electrophotographic heat fixing device of the embodiment shown in 2 can be obtained. In each of the above embodiments, the unidirectional heating section 1 was made up of a halogen lamp 6 and a concave mirror 7.
The unidirectional heating section l may be of any construction as long as it can radiate heat rays in one direction. For example, a mirror surface may be placed directly on the glass surface of a halogen lamp. [Effects of the Invention] As explained above, according to the present invention, the heat generating section is a unidirectional heat generating section and the heat fixing section is a heat fixing belt, so that the heat capacity of the heat fixing section is extremely small. The temperature of the heat fixing section can be lowered in areas other than the heating area, eliminating the need for the heat fixing section to warm up and standby, and reducing unnecessary heat loss to the outside space. This has the effect of reducing the power consumption of the electrophotographic heat fixing device. In addition, the small heat capacity of the heat fixing unit prevents a sudden temperature rise inside the image forming apparatus due to heat transfer from the heat fixing unit after the image forming apparatus is powered off. This has the effect of preventing thermal deterioration of components that are vulnerable to high temperatures and extending the life of the image forming device in which the electrophotographic heat fixing device is installed.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of an electrophotographic heat fixing device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an enlarged view of the unidirectional heating section in FIG. 3 is a schematic sectional view showing the width of a heat fixing device for electrophotography according to another embodiment of the present invention, and FIG. 4 is an example of a conventional heat fixing device for electrophotography. FIG. In the figure, l...unidirectional heat generating section, 2...heat fixing belt, 3...belt transfer shaft, 4...pressure roller, 5...heating area, 6...halogen Lamp, 7... Concave mirror, S... Fixing medium.

Claims (1)

[Scope of Claims] An electrophotographic heat treatment device that heats and fixes the toner image onto the fixing medium by inserting the fixing medium onto which the toner image has been transferred between a heat fixing unit heated by a heat generating unit and a pressure unit. In the fixing device, the heat generating section is a unidirectional heat generating section that emits heat rays in one direction, and the heat fixing section is a heat fixing belt formed of an endless belt in the form of a film. Photographic heat fixing device.