JP2003323099A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To steadily form an image of satisfactory quality by preventing, by means a simple structure, the temperature of peripheral members from increasing due to heat generated from a heat generating part in an apparatus. <P>SOLUTION: Heat generated by a fixing unit 7 is received and diffused by the heat sink 14 of a heat insulating device 13 and transferred to a heat pipe 15. The heat transferred to the heat pipe 15 is further transferred to a heat radiation member 16 by the heat pipe 15, so that the heat is radiated. Thus, the heat generated by the fixing unit 7 is prevented from being transferred to a developing unit 4 near the fixing unit 7, and an image of satisfactory quality can be steadily formed. <P>COPYRIGHT: (C)2004,JPO

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 such as a copying machine or a printer, and more particularly to prevention of temperature rise of surrounding members due to heat generated from a heat generating section in the apparatus.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine or a printer using an electrophotographic system is internally provided with many units such as a scanner unit, a writing unit, a fixing unit and a power supply unit which generate heat during operation. . Among them, the fixing unit has a halogen lamp heater built-in, in order to heat-bond the developer to the recording paper.
Since it is heated and maintained at 50 ° C, a large amount of heat is generated.
Further, the scanner unit irradiates the original with a halogen lamp and reads the original pattern with its reflectance. When the original is read, heat is also generated in the halogen lamp. The generated heat causes the temperature of other units around the unit to rise. In particular, it is necessary to avoid thermal influences on the transfer unit and the developing unit, etc., which have the photoconductors arranged in the vicinity of the fixing unit, and the heat generated by the fixing unit, etc. Effective thermal measures are needed to prevent transmission.

The conventional image forming apparatus can be designed with a relatively large housing, but in recent years, it has been multifunctional in spite of demand for higher speed and full colorization. It is being miniaturized. In order to meet the demand for miniaturization, various units in the device are miniaturized and arranged in high density. Therefore, it becomes difficult to secure a flow path duct provided to cool the inside of the device with a fan, and it becomes impossible to cool the heat generating part with air by providing a fan, which causes a problem that the temperature inside the device rises. It was

In order to solve this problem, for example, as disclosed in Japanese Unexamined Patent Publication No. 5-341677, the heat generated in the fixing unit is covered by a heat collecting plate covering the upper portion of the fixing unit and a heat pipe connected to the heat collecting plate. Heat is transported to a heat dissipation plate provided near the opening of the cover, and air is cooled by a fan or natural convection to prevent the temperature inside the device from rising.

[0005]

However, since the heat collecting plate is provided above the fixing unit, a large amount of heat is applied to the heat collecting plate from the fixing unit having a high temperature, and the heat pipe cannot be cooled. However, there is a disadvantage that the heat radiation effect is reduced. In addition, the heat of the fixing unit easily escapes to the heat collecting plate, and the electric power supplied to the halogen lamp heater increases in order to keep the fixing temperature constant, resulting in an increase in power consumption.

The present invention solves the above disadvantages, prevents the temperature of the surrounding members from rising due to the heat generated from the heat generating portion in the apparatus with a simple structure, and can stably form a high quality image. It is intended to provide.

[0007]

An image forming apparatus according to the present invention includes a heat sink for shielding and diffusing heat generated in a fixing unit, a plurality of heat pipes arranged along the surface of the heat sink, and a heat sink. A heat insulating device that has a heat dissipation member connected to one end of the heat pipe is placed between the fixing unit and a unit where it is desired to prevent thermal effects from the fixing unit This heat is received by the heat sink, diffused and transferred to the heat pipe, and then transferred to the heat dissipation member via the heat pipe to dissipate heat, and the heat generated in the fixing unit is transferred to other units near the fixing unit. prevent.

In the heat insulating device, the heat pipe is arranged on the fixing unit side, and the heat accumulated in the heat sink is quickly transmitted by the heat pipe.

The surface of the heat sink facing the fixing unit has an infrared reflectance of 50% or more,
Absorption of infrared rays generated in the fixing unit is reduced to suppress the temperature rise of the heat sink.

Further, the heat sink and the heat pipe are connected so that the contact thermal resistance of the heat sink and the heat pipe is 5 ° C./W or less, and the heat of the heat sink is efficiently transmitted to the heat pipe to enhance the cooling efficiency of the heat sink.

Further, the contact heat resistance of the heat dissipating member to the heat pipe and the heat sink is set to 1 ° C./W or less to efficiently transfer heat to the heat dissipating member. The emissivity of this heat dissipation member is 50
% Or more to improve cooling efficiency.

[0012]

1 is a block diagram of an image forming apparatus of the present invention. As shown in the figure, an image forming apparatus 1 using an electrophotographic system is provided with a reading unit 2 and a writing unit 3.
It has a developing unit 4, a transfer unit 5, a paper feeding unit 6, a fixing unit 7, a paper discharging unit 8 and a double-sided unit 9. The reading unit 2 has a carriage having a light source, a plurality of mirrors, a lens, and a CCD, and scans and reads a document. The writing unit 3 has a laser light source, a polygon mirror, etc., and irradiates the photoconductor of the developing unit 4 with a laser beam containing image information to form a latent image. Development unit 4
Visualizes the latent image formed on the photoreceptor with a developer.
The transfer unit 5 transfers the visible image formed on the photoconductor of the developing unit 4 onto the recording paper conveyed from the paper feeding unit 6. The fixing unit 7 fixes the visible image on the recording paper, to which the visible image is transferred and is conveyed by the conveying belt 10, by heat and pressure. The paper discharge unit 8 discharges the recording paper on which the visible image is fixed. The double-sided unit 9 reverses the recording sheet having the visible image fixed and sends it to the transfer unit 5 when double-sided printing of the recording sheet is designated.

The fixing unit 6 of the image forming apparatus 1 includes a fixing roller 12 having a heater 11 of 850 W and 140 W, for example. The surface temperature of the fixing roller 12 is about 185.
It is kept heated at ℃. The heat generated from the fixing unit 6 has a thermal effect on the surrounding units, but it is the developing unit 4 that the temperature rise is most desired to be avoided. Therefore, the heat insulating device 13 is arranged between the fixing unit 6 and the developing unit 4 to prevent the heat generated in the fixing unit 6 from being transferred to the developing unit 4.

As shown in the perspective view of FIG. 2, the heat insulating device 13 has a heat sink 14, a plurality of heat pipes 15, and a plurality of heat radiation members 16 having fins for heat radiation. The heat sink 14 is made of a metal having good thermal conductivity, for example, a plate material having a large area of 2 mm to 3 mm, such as aluminum or copper, and is processed so as to cover the fixing unit 6 which is a heat source. The surface of the heat sink 14 on the fixing unit 6 side is mechanically polished so as to have a reflectance of infrared rays of 50% or more, thereby increasing the reflectance.
The heat pipe 15 is arranged in parallel along the heat sink 14, and is fixed to the fixing unit 6 side of the heat sink 14 by soldering, brazing, screwing, or the like,
The contact thermal resistance between the heat sink 14 and the heat pipe 15 is 5
The heat pipe 15 is in close contact with the heat sink 14 so that the temperature becomes less than or equal to ° C / W. The heat dissipation member 16 has a contact thermal resistance of 1 ° C. at the tips of the heat pipes 15 and the heat sink 14.
It is fixed by soldering or brazing so as to be less than / W. Further, the heat dissipation fins of the heat dissipation member 16 are formed such that the surface thereof is made black by heat-resistant black paint or alumite treatment and the emissivity is 50% or more.

The heat dissipating member 16 of the heat insulating device 13 is arranged in the vicinity of the opening of the housing exterior cover of the image forming apparatus 1, and the heat sink 14 having the heat pipe 15 is attached to the fixing unit 6.
And the developing unit 4 between them. This heat sink 1
By disposing 4 between the fixing unit 6 and the developing unit 4, heat generated by the fixing roller 12 of the fixing unit 6 is transferred to the heat sink 14. This fixing unit 6
If the heat sink 14 absorbs a large amount of infrared rays emitted from the heat sink 14, the temperature of the heat sink 14 rises too much, and the heat affects the developing unit 4. Therefore, the reflectance of the heat sink 14 is set to 50% or more so that the heat sink 14
The temperature rise is suppressed within a certain range and the heat generated in the fixing unit 6 is blocked so as not to be transferred to the developing unit. The heat transferred to the heat sink 14 is efficiently transferred to the heat pipe 15 which is in close contact with the heat sink 14 so that the contact thermal resistance is 5 ° C./W or less, and the heat pipe 15 having a large thermal conductance transfers the heat to the heat dissipation member 16. To do. The heat transferred to the heat dissipation member 16 is cooled by the airflow near the opening of the housing exterior cover. When cooling the heat radiating member 16, the heat radiating fin of the heat radiating member 16 has a black surface and is formed to have an emissivity of 50% or more, so that heat can be efficiently radiated. Therefore, the temperature rise of the developing unit 4 due to the heat generated in the fixing unit 6 can be suppressed, and a high quality image can be stably formed.

[0016]

EXAMPLE The reflectance of the heat sink 14 was changed, the wavelength λ was measured at 0.8 μm to 10 μm by the photometer, and the surface temperature of the heat sink 14 was measured. Small rise,
For example, even if the heat source is heated and held at 100 ° C,
When the reflectance is 50%, the surface temperature of the heat sink 14 is 60.
C., and when the reflectance is 60%, the surface temperature of the heat sink 14 is as low as 40.degree. On the other hand, when the reflectance of the heat sink 14 is as low as about 45%, the surface temperature of the heat sink 14 rises to 70 ° C. and the cooling efficiency decreases. When it is assumed that the heat pipe 15 is brought into contact with the heat sink 14 and air cooling is performed by natural convection, the heat sink 14 when the reflectance of the heat sink 14 is 50%.
Since the surface temperature of 60 ° C. is the cooling limit, the reflectance of the heat sink 14 is set to 50% or more.

Further, the heat sink 14 and the heat pipe 1
When the heat sink 14 is heated by radiation and convection by changing the contact thermal resistance of the heat sink 14 of FIG.
The results of measuring the temperature of the heat pipe 15 are shown in the table below.

[0018]

[Table 1]

Assuming that the allowable temperature rise inside the image forming apparatus 1 is up to 23 ° C. with respect to room temperature, as shown in the above table, the contact thermal resistance between the heat sink 14 and the heat pipe 15 should be 5 ° C./W or less. For example, the temperature of the heat pipe 15 is 5
The temperature is 0 ° C. or less, and for example, even when the room temperature is 27 ° C., the temperature inside the image forming apparatus 1 can be kept within the allowable value.

The results of measuring the temperature of the heat pipe 15 and the temperature of the heat radiating member 16 when the heat radiating member 16 is air-cooled by changing the contact thermal resistance between the heat pipe 15 and the heat radiating member 16 are shown in the following table.

[0021]

[Table 2]

As shown in the above table, the temperature of the heat dissipation member 16 can be lowered to 30 ° C. by setting the contact thermal resistance between the heat pipe 15 and the heat dissipation member 16 to 1 ° C./W or less. Therefore, the heat can be efficiently transferred to the heat dissipation member 16, and the cooling efficiency can be improved.

The following table shows the results of measuring the temperature of the heat radiating member 16 by changing the emissivity by changing the paint on the surface of the heat radiating member 16 and air-cooling by natural convection while applying a certain amount of heat to the heat radiating member 16. Show.

[0024]

[Table 3]

As shown in the above table, when the emissivity of the heat dissipation member 16 is 50 or more, the allowable value of the temperature rise inside the image forming apparatus 1 can be satisfied.

In the above description, the heat radiating member 16 is attached to the heat insulating device 13.
However, structural members such as a housing cover and columns of the image forming apparatus 1 may be used as the heat dissipation member 16. By using the structural member such as the housing cover or the pillar as the heat dissipation member 16 as described above, the heat dissipation area can be increased and the cooling efficiency can be further enhanced.

[0027]

As described above, according to the present invention, the heat generated in the fixing unit is received by the heat sink, diffused and transferred to the heat pipe, and then transferred to the heat radiating member through the heat pipe to radiate the heat. Since the heat generated in step 1 is prevented from being transferred to other units near the fixing unit, it is possible to suppress the temperature rise of other units near the fixing unit and stably form a high-quality image. be able to.

In the heat insulating device, the heat pipe is arranged on the fixing unit side, and the heat accumulated in the heat sink is quickly transmitted by the heat pipe, so that the cooling efficiency of the heat sink is improved.

Further, by forming the surface of the heat sink facing the fixing unit so that the infrared reflectance is 50% or more, absorption of infrared rays generated in the fixing unit can be reduced and the temperature rise of the heat sink can be suppressed. it can.

Furthermore, by connecting the heat sink and the heat pipe so that the contact thermal resistance between the heat sink and the heat pipe is 5 ° C./W or less, the heat of the heat sink is efficiently transmitted to the heat pipe to enhance the cooling efficiency of the heat sink. be able to.

By setting the contact heat resistance of the heat dissipation member to the heat pipe and the heat sink to be 1 ° C./W or less, heat can be efficiently transferred to the heat dissipation member and the cooling efficiency can be improved. By setting the emissivity of the heat dissipation member to 50% or more, heat can be rapidly dissipated from the heat dissipation member and the cooling efficiency can be further improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a configuration of a heat insulating device.

[Explanation of symbols]

1; image forming apparatus, 2; reading unit, 3; writing unit, 4; developing unit, 5; transfer unit, 6; paper feeding unit, 7; fixing unit, 8; paper discharging unit, 9; duplex unit, 12 Fixing roller, 13; heat insulating device, 1
4; heat sink, 15; heat pipe, 16; heat dissipation member.

Claims (6)

[Claims] 1. An image forming apparatus using an electrophotographic method, wherein a heat sink for shielding and diffusing heat generated in a fixing unit, a plurality of heat pipes arranged along the surface of the heat sink, a heat sink and a heat pipe. An image forming device characterized in that a heat insulating device having a heat radiation member connected to one end of the fixing unit is arranged between the fixing unit and a unit which is provided in the vicinity of the fixing unit and which is desired to prevent a thermal influence from the fixing unit. apparatus. 2. The image forming apparatus according to claim 1, wherein the heat insulating device is arranged with a heat pipe on a fixing unit side. 3. The image forming apparatus according to claim 1, wherein a surface of the heat sink facing the fixing unit has an infrared reflectance of 50% or more. 4. The image forming apparatus according to claim 1, wherein the heat sink and the heat pipe are connected so that the contact heat resistance between the heat sink and the heat pipe is 5 ° C./W or less. 5. The contact thermal resistance of the heat dissipation member to the heat pipe and the heat sink is 1 ° C./W or less.
5. The image forming apparatus according to any one of 4 to 4. 6. The image forming apparatus according to claim 1, wherein the heat dissipation member has an emissivity of 50% or more.