JPH04270361A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the influence of heat on a photosensitive body, etc., without reducing the heat efficiency of a thermal fixing device in an image forming device and to prolong the life of the device. CONSTITUTION:Plural Peltier elements 32 are arranged on a fixing cover for the fixing device 14, and an electric current is made to flow to the Peltier elements 32 by a power supply 33 so as to generate a cooling effect. Then, among the heat generated by a fixing roller 20 heated by a heater 19 in the fixing device 14, only the heat which is about to radiate from the position where the Peltier elements 32 are arranged on the fixing cover 27 is cooled, so that the photosensitive body, etc., arranged nearby and which is weak in heat is prevented from being influenced without reducing the thermal efficiency of the fixing device 14.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is a laser printer (L
PB), plain paper copier (PPC), facsimile machine (
The present invention relates to an image forming apparatus equipped with a heat fixing device such as a FAX).

0002

[Prior Art] Conventionally, in an image forming apparatus equipped with such a heat fixing device, the heat generated by the heat fixing device is transmitted to the photoreceptor and shortens its life, so an exhaust fan or the like is installed near the heat fixing device. was installed to release the heat to the outside of the image forming apparatus. Further, a heat insulating material is provided between the heat fixing device and the photoreceptor to block heat radiation from the heat fixing device to the photoreceptor.

0003

However, if a photoreceptor or the like that is sensitive to heat is placed near the heat fixing device, heat radiation by the exhaust fan alone cannot sufficiently prevent the effects of heat. There was a problem that the life of the photoreceptor etc. was reduced. In addition, if the air volume of the exhaust fan is increased to ensure sufficient heat dissipation, the airflow discharged outside the image forming apparatus will become stronger and take more heat than necessary from the entire heat fixing device, causing the heat fixing device to There was a problem that the thermal efficiency of the

For example, in an image forming apparatus in which a photoreceptor 29 and a fixing device 28 are located close to each other as shown in FIG. Even if you try to drain it,
Since there are physical limits to the shape of the exhaust duct 30, a sufficient heat dissipation effect cannot be obtained. Furthermore, if the air volume of the exhaust fan 31 is increased in order to increase the heat dissipation effect, more heat than necessary will be taken away from the fuser 28.
This will reduce the thermal efficiency of the

Furthermore, even if a heat insulating material is provided between the heat fixing device and the photoreceptor, a sufficient heat insulation effect on the photoreceptor cannot be obtained. The present invention has been made in view of the above points, and an object of the present invention is to prevent the influence of heat on a photoreceptor, etc., and extend the life of the heat fixing device without reducing its thermal efficiency.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an image forming apparatus including a photoreceptor and a heat fixing device, in which the heat fixing device is locally cooled on an outer cover of the heat fixing device. It is equipped with a thermoelectric effect element. Further, a thermoelectric effect element for locally cooling the photoreceptor is disposed inside the photoreceptor at a position facing the heat fixing device.

[0007]

[Operation] In the image forming apparatus according to the present invention, a thermoelectric effect element is disposed on the outer cover of the heat fixing device, and the cooling effect of the thermoelectric effect element suppresses the heat generated by the heat fixing device from being released to the surroundings. The heat does not affect the photoreceptor, etc., which is sensitive to heat, in the vicinity of the heat fixing device.

Furthermore, a thermoelectric effect element is provided on the inside of the photoreceptor at a position facing the heat fixing device, and the cooling effect of the thermoelectric effect element suppresses heat generation on the outside of the photoreceptor due to heat dissipation from the heat fixing device from the inside. Therefore, the heat does not affect the photoreceptor or the like, which is sensitive to heat, in the vicinity of the heat fixing device.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic diagram of a laser printer which is an embodiment of an image forming apparatus according to the present invention.

In this laser printer 1, a printer control section 8 sequentially controls each section based on information given from a host system such as a word processor or a computer, and a photosensitive drum 9 is rotated in the direction of the arrow by a drive motor (not shown). At this time, the surface of the photosensitive drum 9 is uniformly charged by the charging charger 10, and the laser optical system 11 irradiates the photosensitive drum 9 with a laser beam modulated according to the video signal while main scanning in the axial direction of the photosensitive drum 9 for exposure. , an electrostatic latent image is formed on the surface of the photosensitive drum 9, and toner is adhered onto the photosensitive drum 9 by a developing roller 12a of a developing device 12 to develop the electrostatic latent image into a visible image.

On the other hand, the recording paper P stored in the upper paper feed cassette 2A or the lower paper feed cassette 2B is fed in the direction of arrow A by the pickup roller 3, and is registered one by one by the feed roller 4 and the reverse roller 5. When the recording paper P is conveyed to the roller pair 6 and detected by the registration sensor 7, it waits at the position where it is held between the registration roller pair 6, and the leading edge of the recording paper P is aligned by the registration roller pair 6, and the recording paper P is placed in a predetermined position. The paper is fed to the transfer section at the timing of , and brought into contact with the toner image on the photoreceptor drum 9, and the toner image is transferred to the recording paper P by the action of the transfer charger 13.
Transfer to.

Thereafter, the recording paper P is conveyed to the fixing device 14 and subjected to a heat fixing process for fixing the toner, and then discharged in the direction of arrow B and stocked on the paper discharge section 15. . Further, residual toner on the photosensitive drum 9 is removed by a cleaning blade 16 in preparation for the next image formation, and the removed toner is collected in a toner collection tank 17.

FIG. 1 is an external perspective view of the fixing device 14 of the laser printer 1 shown in FIG. 3, and FIG. 2 is a side view thereof. This fixing device 14 includes a fixing heater 19 (for example, 4
A pressure lever 22 biased by a pressure spring 23 presses a pressure roller 21 onto a fixing roller 20 having a built-in roller (00W), and both rollers 20 and 21 rotate in contact with each other. A plurality of separation claws 24 are in contact with the recording paper P to prevent the recording paper P from being wrapped around the recording paper P.

Furthermore, the fixing thermistor 26 that detects the surface temperature of the fixing roller 20 comes into contact with the fixing roller 20, and a thermal fuse 25 for safety is disposed slightly away from the fixing roller 20, so that when the temperature rises abnormally, (For example, 1 at ambient temperature
50°), the fuse blows out, functions as a temperature switch, and cuts off the voltage supply to the fixing heater 19.

In this laser printer 1, since the unfixed toner image after transfer is in an unstable state on the recording paper P, it is guided by the guide plate 18 and transferred to the recording paper P into the fixing device 14. Heat and pressure are applied by the fixing roller 20 and the pressure roller 21 to fix the toner onto the recording paper P.

[0016] In a part of the fixing device cover 27 where a malfunction may occur due to heat emitted from the fixing device cover 27, such as the part facing the photosensitive drum 9 of the fixing device 14,
A large number of Peltier elements 32, which are thermoelectric effect elements, are arranged in two rows, and each Peltier element 32 is connected in series and powered by a power source 33.

When the plurality of Peltier elements 32 receive power, the cooling effect of each Peltier element 32 cools only the portion of the fuser cover 27 facing the photosensitive drum 9, and the heat emitted therefrom is sufficiently absorbed. This prevents heat from affecting the photosensitive drum 9 in the vicinity of the fixing device 14 without reducing the thermal efficiency of the fixing device 14. Therefore, a heat dissipation duct and a fan for removing heat emitted from the fixing device 14 are unnecessary, and it is also possible to downsize the machine and reduce costs.

Next, another embodiment of the image forming apparatus according to the present invention will be described. The image forming apparatus in this embodiment uses a belt-shaped photoreceptor, and differs from the previous embodiment in the arrangement position of the thermoelectric effect element. FIG. 4 is an external perspective view of a fixing device and a photoreceptor portion in this embodiment, and parts common to those in FIG.

In this embodiment, three rollers 35a and 35b are installed so that the photoreceptor belt 34 is slightly extended from the inner side.
, 35c, and each of the rollers 35a, 3
5b and 35c rotate in the same direction, thereby rotating the photoreceptor belt 34 in the direction of the arrow.

A large number of Peltier elements 32, which are thermoelectric effect elements, are arranged in two rows on the inner surface of the photoreceptor belt 34 at a position facing the fixing device 14, and each Peltier element 32 is connected in series. Power is supplied by a power source 33. Therefore, the fixing device 14 is attached to the outer surface of the photoreceptor belt 34.
Even if the heat is dissipated, the inner surface of the belt 34 in that area is cooled by the cooling effect of each Peltier element 32.
The influence of heating on the photoreceptor belt 34 can be prevented without reducing the thermal efficiency of the fixing device 14.

Furthermore, when a plurality of Peltier elements are provided on the fixing cover of the fixing device as in the above embodiment, a storage space is required between the fixing device and the photoreceptor.
If each Peltier element is provided inside the photoreceptor as in this embodiment, there is no need to newly secure storage space for the Peltier element, and the apparatus can be downsized and cost reduced. Note that in the case of a drum-shaped photoreceptor, a similar effect can be obtained even if a thermoelectric effect element is provided inside the drum-type photoreceptor.

Next, the cooling effect of the Peltier element will be explained in detail. Generally, the following equations 1 are known as equations expressing the relationship between thermoelectric effects.

[0023]

[Math 1]

In equations 1 to 1, S, π, and τ are the Seebeck coefficient, Peltier coefficient, and Thomson coefficient, respectively, and κ and ρ are the thermal conductivity and electrical resistivity, respectively.
E, I, Q, Q0 are the vector quantity, heat quantity, and heat absorption rate that indicate the magnitude of the electric field and current, respectively, T is the temperature, and gra
dT is the temperature gradient.

[0025] In the formula (■), the vector quantity E indicating the magnitude of the electric field when there is no temperature gradient is equal to the value E = ρ・I, which is usually found by the well-known Ohm's law, and there is a temperature gradient. The vector quantity E, which indicates the magnitude of the electric field at a time, is that since electrons in a place with a high temperature have a large momentum, electrons flow from a place with a high temperature to a place with a low temperature. The lower one has a negative potential,
In the case of a hole, the opposite is true, and the second term (S·gradT) corresponding to the value is added to the first term (ρ·I).

Therefore, as shown in FIG. 5, in a circuit in which a Peltier element 32 made by joining dissimilar metals M and N is connected to a power source 33 (for example, a DC power source such as a storage battery), the power source 33
When the current I is not flowing, the vector quantity indicating the magnitude of the electric field is E=S・gradT according to equation (2).If a temperature difference of (T1-T2) is given to the metal M in the center by the metals N on both sides, then As a result, a potential difference (V1-V2) is generated. This is the principle of a thermoelectric generator.

[0027] In the formula, the amount of heat when a current I is passed without a temperature gradient is Q = π・I, which means that electrons flow from a substance with electrons with low energy to a substance with electrons with high energy. When you extract , only high-energy electrons come out, leaving behind electrons with low energy. Considering the amount of heat at that time, there will be a difference in heat flow between the two materials, resulting in a lower energy The temperature of substances that have electrons decreases. This is the Peltier effect. Since the Peltier heat Q at this time is carried in the same direction as the current I, the Peltier coefficient π takes a positive or negative sign depending on the direction of the current I.

When a current I is applied to the Peltier element 32 by the power source 33, an amount of heat of Qm=πm·I flows in the region of the metal M of the Peltier element 32, and Qm=πm·I flows in the region of the metal N of a different type from the metal M. Since the amount of heat of πn・I flows, (πm−πn)・I at the junction of metals M and N
There will be a difference in the amount of heat. This amount of heat generates heat on one side of the joint and absorbs heat on the other, and the difference changes the temperature of the joint, so when this is negative, it becomes the principle of electronic cooling.

Here, in order to make a Peltier element with good thermoelectric efficiency, the ratio of the heat removed from the load to the consumed power, that is, the cooling effect coefficient COP (Coeffic
performance of a
refrigerator).

[0030]

[Math 2]

In Equation 2, Z is called a figure of merit and is used to judge the quality of the thermoelectric material, and Tc, Th, Tm
are the temperature of the cold junction, the temperature of the hot junction, and the average temperature of the cooling element, respectively. Actual Peltier elements are made using metals such as Bi, Sb, Bi2, Te3, and Bi+Te based on these values.

In the above-described embodiment, a Peltier element was used as the thermoelectric effect element, but an element having the Thomson effect as shown in Equation (2) of Equation 1 may also be used, in which the same kind of metals are bonded. Furthermore, this invention is not limited to laser printers.
The present invention can be applied to all image forming apparatuses equipped with a fixing device, such as various optical printers, electrophotographic copying machines, and facsimile machines.

[0033]

As described above, according to the image forming apparatus of the present invention, the life of the photoreceptor can be extended by preventing the influence of heat on the photoreceptor, etc., without reducing the thermal efficiency of the heat fixing device. As a result, there is no need to provide a duct or an exhaust fan for discharging the heat generated by the heat fixing device, and it is possible to downsize the image forming device and reduce manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a fixing device 14 of the laser printer shown in FIG. 3. FIG.

FIG. 2 is a side view of the same.

FIG. 3 is a schematic configuration diagram of a laser printer which is an embodiment of an image forming apparatus according to the present invention.

FIG. 4 is an external perspective view of a fixing device and a photoreceptor portion in another embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a circuit diagram for explaining the thermoelectric effect of a Peltier element.

FIG. 6 is a schematic diagram showing a process section of a conventional image forming apparatus.

[Explanation of symbols]

1 Laser printer 2A, 2B
Paper feed cassette 3 Pick up roller 4
Feed roller 5 Reverse roller 6 Registration roller pair 7 Registration sensor 8 Printer control section 9 Photosensitive drum 10 Electrostatic charger 11 Laser optical system 12 Developing device 13 Transfer charger 14 Fixing device 15 Paper discharge section 18
Guide plate 19 Fixing heater 20 Fixing roller 21 Pressure roller 22 Pressure lever 23 Pressure spring 24 Separation claw
25 Thermal fuse 26 Thermistor 27 Fuser cover 32 Peltier element (thermoelectric effect element)
33 Power supply 34 Photoreceptor belt 35a, 35b
, 35c Roller P Recording paper M, N
Metals that make up Peltier elements

Claims (2)

[Claims] 1. An image forming apparatus comprising a photoreceptor and a heat fixing device, characterized in that a thermoelectric effect element for locally cooling the heat fixing device is disposed on an outer cover of the heat fixing device. Forming device. 2. An image forming apparatus including a photoreceptor and a heat fixing device, wherein a thermoelectric effect element for locally cooling the photoreceptor is disposed inside a position of the photoreceptor facing the heat fixing device. An image forming apparatus characterized by: