JPH11338331A - Heat shield device for image forming equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the heat shielding device of an image forming device where noise is reduced and heat from a heat source is efficiently used for the acceleration of a natural convection. SOLUTION: At the heat shielding device shielding the transfer of the heat from the heat source part 21 at the inside of the image forming device to a part to be protected 3, a ventilating duct 4 having an exhaust port 42 on the upper side of the heat source part 21 and an intake port 41 on the lower side of the exhaust port 42 is provided between the heat source part 21 and the part to be protected 3. This device possesses a heat insulating part 5 on the side of the heat source part between the heat source part 21 and the ventilating duct 4 and a heat radiating part 6 on the side of the ventilating duct between the heat source part 21 and the ventilating duct 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to an electrophotographic image forming apparatus such as a printer, and more particularly to measures against heat generated in such an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic image forming apparatus of this type, there has been widely used an apparatus which forms a toner permanent image on a recording sheet by respective steps of charging, exposure, development, transfer, fixing and cleaning. Are known. by the way,
Such heat generated in the image forming apparatus may cause various problems, and measures against heat are an important problem in designing the image forming apparatus.

For example, in a fixing step of forming an image on a recording sheet, an unfixed toner image held on the recording sheet is fixed on the recording sheet by the action of heat and pressure. The heat generated may cause problems such as melting and sticking of the toner in the cleaning device and the developing device, promoting deterioration of the photoconductor material, and causing malfunction of electronic components.

Therefore, as a countermeasure against heat in the image forming apparatus, a technique has been proposed in which air is blown by an exhaust fan to forcibly cool the cleaning device, as described in, for example, JP-A-5-142911. ing.
Further, Japanese Patent No. 2626031 proposes a technique for exhausting hot air using natural convection without providing such an exhaust fan.

[0005]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No.
In the technique described in Japanese Patent No. 42911, the exhaust is performed by using the exhaust fan, so that the noise tends to be a problem. In particular, it is difficult to apply to an image forming apparatus installed in a quiet environment such as a library.

In the technology described in Japanese Patent No. 2626031, noise can be reduced, but it does not necessarily effectively promote natural convection of hot air. In some cases, it may be impossible to sufficiently exhaust hot air.
In particular, if the size of the image forming apparatus is further reduced and a fixing device that generates heat in the image forming apparatus, a cleaning device, and the like are provided close to each other, there is a possibility that such technology cannot cope with the problem.

Further, in the technique described in Japanese Patent No. 2626031, heat from a fixing device, which is a main heat source, is only taken away, and extra power is required to maintain a constant temperature, so that energy is saved. It is not preferable from a viewpoint. That is, when the heat source is a fixing device, it is preferable to radiate the heat from the fixing device in order to promote natural convection, but from the viewpoint of energy saving, it is preferable that the heat radiated from the fixing device is as small as possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a heat shield device for an image forming apparatus, which has low noise and can use heat from a heat source to promote natural convection without waste. Is to provide.

[0009]

That is, the present invention relates to a heat shield device for blocking the transfer of heat from a heat source portion to a protected portion in an image forming apparatus. A ventilation duct having an air inlet below the heat source section and the protected section; a heat insulation section on the side of the heat source section between the heat source section and the ventilation duct; A heat radiating section is provided on the side of the ventilation duct between the duct and the duct. By configuring the heat shield device of the image forming apparatus in this manner, first, in the initial state, the heat generated from the heat source is held by the heat insulating portion, and can be prevented from being transmitted to the protected portion. Secondly, even when the image forming apparatus is continuously operated, the heat released by the heat insulating portion without being able to hold the heat effectively heats the air in the ventilation duct by the heat radiating portion, and the heat source, the intake port, the exhaust port and the like. Due to the positional relationship described above, natural convection of air flowing from the intake port to the exhaust port of the ventilation duct is generated, and the flow of air can prevent transmission of heat to the protected portion. Further, since no motor such as a fan is used, there is no problem of noise.

In this case, the heat radiating portion may constitute a part of the ventilation duct. In this case, a heat shield device having the above-mentioned function can be provided with a simpler structure.

In the case where the heat source section is located in the fixing device of the image forming apparatus, the fixing device has first and second intake ports near the sheet feeding side and the sheet discharging side, respectively. In this case, relatively cool air is drawn in from a first suction port provided near the sheet feeding side of the fixing device, and a second suction port provided near the sheet discharging side of the fixing device. Relatively hot air heated in the fixing device is taken in from the air, and a natural convection can be generated more effectively in the ventilation duct due to a temperature difference of the air taken in from each of them, thereby providing a heat shielding effect. Can be enhanced.

Further, the image forming apparatus may have an opening / closing control means for controlling the opening / closing of the intake port in accordance with the operating state of the image forming apparatus. In this case, when the image forming apparatus is operating, it is discharged from the fixed recording sheet. In addition to effectively taking in the generated heat into the ventilation duct, at the time of stop or standby, the heat transmitted from the heat radiating section does not leak to the outside from the intake port, and natural convection can be effectively promoted. In addition, the control of the intake port by the opening / closing control means may be simply controlling the opening and closing of the intake port or controlling the degree of opening and closing of the intake port.

The fixing device has a paper feed port for feeding a recording sheet and a paper discharge port for discharging a recording sheet.
The opening and closing control device may also control the opening and closing of the paper feed port and / or the paper discharge port according to the operation state of the image forming apparatus. In this case, when the image forming apparatus is operating, the heat leaking from the paper feed port and / or the paper discharge port of the fixing device is effectively taken into the ventilation duct, and the heat transmitted from the heat radiating unit is stopped or stopped. Natural convection can be effectively promoted without leaking to the outside. Note that the control of the paper feed port and / or the paper discharge port by the opening / closing control means may be simply opening and closing, or may be controlling the degree of opening and closing.

Further, it is also possible to have a structure in which a part of the ventilation duct has an exhaust fan for assisting natural convection. In this case, the flow of air in the ventilation duct can be more effectively controlled by the exhaust fan. Since it can be generated, the heat shielding effect on the protected portion can be further enhanced. In addition, since the rotation of the exhaust fan assists natural convection generated in the ventilation duct due to heat, a sufficient heat shielding effect can be obtained at low speed rotation, so that noise is relatively small.

Further, the image forming apparatus may have exhaust fan control means for controlling the rotation of the exhaust fan in accordance with the operating condition of the image forming apparatus. In this case, there are conflicting demands for a heat shielding effect and noise prevention. Can be satisfied together. Note that the control of the exhaust fan by the exhaust fan control means may be a method of simply turning on / off the rotation of the exhaust fan, or a method of controlling the rotation speed in multiple stages or continuously.

[0016]

Next, a preferred embodiment of the present invention will be described based on an embodiment of the present invention. First Embodiment FIG. 1 illustrates an entire image forming apparatus to which a heat shield according to a first embodiment of the present invention is applied. The image forming apparatus includes a photosensitive drum 12, a charging roll 121,
Exposure device 122, rotary developing device 123, primary transfer roll 124, drum cleaning device 125, intermediate transfer belt 13, stretching roll 131, secondary transfer roll 13
2, fixing device 2, recording sheet tray 14, transport roll 1
5 and the like.

The color image forming operation of the image forming apparatus will be briefly described. The surface of the photosensitive drum 12 uniformly charged by the charging roll 121 is exposed to the exposure device 12.
2 is exposed to laser light corresponding to each color to form an electrostatic latent image. The electrostatic latent image is developed into the color by the rotary developing device 123 to form a toner image, and is transferred onto the intermediate transfer belt 13 by the primary transfer roll 124. This process is repeated for each color with a certain timing, so that four color toner images of yellow, cyan, magenta, and black are superimposed on the intermediate transfer belt 13.
In accordance with the timing, the recording sheet is transferred from the recording sheet tray 14 via the transport roll 15 to the secondary transfer roll 1.
32, and the toner image is secondarily transferred from the intermediate transfer belt 13 to a recording sheet. The unfixed toner image held on the recording sheet is conveyed to the fixing device 2, fixed on the recording sheet by the action of heat and pressure, becomes a permanent image, and is discharged out of the image forming apparatus, and a color permanent image is formed. Get an image.

FIG. 2 shows the periphery of the heat shield device according to this embodiment. This heat shield device is a heat shield device that blocks the transmission of heat from the heat source unit 21 in the image forming apparatus to the protected unit 3.
And a ventilation duct 4 having an intake port 41 below the exhaust port 42 is provided between the heat source section 21 and the protected section 3, and a heat source section between the heat source section 21 and the ventilation duct 4 is provided. A heat insulating section 5 is provided on the side of the heat source section 21 and a heat radiating section 6 is provided on the side of the ventilation duct 4 between the heat source section 21 and the ventilation duct 4.

The heat source section 21 is a heating roll (heat roll) of the fixing device 2 in this embodiment. The protected portion 3 is a cleaning device, a developing device, various electronic circuit boards, and the like, which are generally devices easily affected by heat. FIG. 3A shows an example of a more specific embodiment of the protected portion 3. In this embodiment, the protected portion 3
It is assumed that the lower part 31 of the rotary developing device 123 is used. Also, although not shown in FIG.
3 does not necessarily need to exist above the heat source section 21, and may be, for example, as shown in FIG. Also,
FIG. 3B assumes that the protected portion 3 is the vicinity 33 of the electronic circuit board.

The ventilation duct 4 is provided between the heat source section 21 and the protected section 3. Further, the exhaust port 42 is provided above the heat source section 21 and the protected section 3, and the intake port 41 is provided on a side surface section of the heat source section 21 below the exhaust port 42. The shape, size, and the like of the ventilation duct 4 can be arbitrarily designed depending on the internal structure of the image forming apparatus to which the ventilation duct 4 is applied. It is desirable to form as vertically as possible over the mouth 42,
In particular, a configuration in which the air in the ventilation duct 4 near the intake port 41 at the lower portion is heated is most preferable.

On the other hand, the ventilation duct 4 is provided between the heat source section 21 and the protected section 3, and needs to be provided in consideration of the positional relationship with other devices in the image forming apparatus. Therefore, in this embodiment, as shown in FIG. 2, a crank-shaped shape including a vertical portion A, a horizontal portion B, and a vertical portion C is adopted. As described above, even when the shape of the ventilation duct 4 cannot be formed vertically due to the positional relationship with other devices in the image forming apparatus, the length of the horizontal portion B is increased from the viewpoint of promoting natural convection in the ventilation duct 4. Is preferably as short as possible. If possible, the horizontal portion B is preferably inclined upward with respect to the flow of air in the ventilation duct 4, and conversely, it is not preferable to arrange the horizontal portion B downward with respect to the flow of air. Further, it is preferable that the boundary between the vertical portion A and the horizontal portion B and the boundary between the horizontal portion B and the vertical portion C are formed as smoothly as possible and have a large radius of curvature. Further, the length of the vertical portion C having the exhaust port 42 at the upper end is preferably made as long as possible, and it is desirable to warm the air in the ventilation duct 4 near the lower end of the vertical portion C.

The heat insulating portion 5 can be made of a fiber material such as wool, felt, paper or the like, and the other material can be made of a heat insulating material such as urethane foam. Further, since the heat insulating portion 5 holds the heat of the heating roll as much as possible, it is desirable to use a large amount of heat insulating material in order to enhance the heat insulating efficiency. It is desirable to use less heat insulating material. Therefore, in the present embodiment, the limited space is effectively used by providing the heat insulating portion 5 in the upper portion of the fixing device 2 where the heat from the heating roll is most concentrated.

A heat radiating plate is fixedly provided as a heat radiating portion 6 above the heat insulating portion 5, in this embodiment, on the upper outer wall of the fixing device 2. The heat radiating portion 6 is used to efficiently heat the heat leaked through the heat insulating portion 5 to the air in the ventilation duct 4, and the heat radiating material is made of iron, aluminum, etc. having excellent heat conductivity. Metals can be used. In this embodiment, as shown in FIG. 2, a heat radiating plate is provided at a position facing the heat insulating portion 5, and a heat radiating plate is not provided at a position where the heat insulating portion 5 is not provided. This is because the heat inside the fixing device 2 is not unnecessarily taken away.

In this embodiment, the rail 12 is connected to the ventilation duct 4 so that the fixing device 2 can be detached from the image forming apparatus when the fixing device 2 is maintained.
a and b, and a base frame 11 of the image forming apparatus.
Are provided with guides 11a and 11b.

FIG. 4 is a graph illustrating the effect of the heat shield device according to this embodiment. FIG. 5 shows a comparative example, which is the same as the heat shield device according to the present embodiment except that it does not have the heat insulating portion 5 and the heat radiating portion 6 (heat radiating plate). In the graph of FIG. 4, the solid line indicates a time change of the temperature of the heating roll as the heat source unit 21 according to the present embodiment and the comparative example. The solid line represents the temperature change at the point P1 in FIG. 4 below the ventilation duct 4 of the heat shield device according to the comparative example, and the solid line represents the lower portion of the ventilation duct 4 of the heat shield device according to the present embodiment.
Temperature changes at two points are shown.

As shown in FIG. 4, at the time T1, the temperature of the heating roll is lower than that of the lower part of the ventilation duct 4 according to the comparative example.
The temperature at one point reaches a constant temperature H at time T2, and the temperature at point P2 below the ventilation duct 4 according to the present embodiment reaches a constant temperature H at time T4. Here, the temperature change at the point P2 at the lower portion of the ventilation duct 4 according to the present embodiment is relatively moderate due to the provision of the heat insulating portion 5. For example, when the temperature at the point P1 in the comparative example reaches H at a certain time T3. On the other hand, the temperature at the point P2 is h lower than that.
For this reason, up to the time T4, the temperature rise in the ventilation duct 4 can be suppressed due to the heat insulating portion 5, and as a result, the adverse effect of heat on the protected portion 3 can be effectively prevented.

Further, this means that the heat generated from the heating roll is hard to escape, that is, the amount of heat (hatched portion in the graph of FIG. 4) which is lost during the time T0 to T4 can be saved. As a result, power for maintaining the heating roll at a constant temperature can be saved.

Further, after time T4, heat generated from the heating roll escapes as in the comparative example. On this occasion,
In the case of the comparative example, this heat is radiated into the image forming apparatus, but in the case of the heat shield device according to the present embodiment, the heat is heated by the heat radiating portion 6 to heat the air in the ventilation duct 4. In this case, natural convection is promoted, and hot air does not stay in the ventilation duct 4. As a result, the adverse effect of heat on the protected portion 3 can be effectively prevented.

As described above, in the heat shield device according to the present embodiment, the devices that produce the contradictory effects of heat insulation and heat radiation are skillfully combined to save the power consumption of the heating roll, and to adversely affect the protected portion 3 due to the heat. However, in order to obtain this effect, the ventilation duct 4 of the heat shield device,
It is necessary to design the configurations of the heat insulating unit 5 and the heat radiating unit 6 according to the characteristics of the image forming apparatus. For example, ventilation duct 4
If the size and shape of the fixing device 2 are suitable for promoting natural convection, the heat insulating portion 5 can be configured to be small, and the fixing device 2 can be reduced in size. Conversely, when the configuration of the ventilation duct 4 is not a configuration suitable for promoting natural convection, the heat-insulating portion 5 is made of a member having a high heat-insulating effect and the size thereof is made large, and the heat source portion 21 is made as large as possible. In addition to delaying the transmission of heat from the heat radiation unit 6, even if heat leaks from the heat insulating unit 5 due to the use of the image forming apparatus for a long time, the heat radiating unit 6 promotes the natural convection in the ventilation duct 4 as much as possible. It is desirable to take measures such as increasing the surface area or providing more heat radiating portions 6 at the portion near the lower end of the vertical portion C of the ventilation duct 4 in FIG.

FIG. 6 shows a state in which the fixing device 2 is removed from the image forming apparatus to which the heat shielding device according to the present embodiment is applied, and the heat shielding device is viewed from the direction of arrow V1 in FIG. It is a view of the surroundings. In such an image forming apparatus, the fixing device 2 is preferably configured to be detachable for repair, inspection, and the like, but a rail 12 including a rail on the side of the heat radiating section 6 and a rail receiving section on the side of the ventilation duct 4. a, b, guide portion 11 on base frame
By providing a and b, the fixing device 2 can be removed. FIG. 6A shows a state in which the fixing device 2 is attached to the image forming apparatus.
(B) shows a state in which it is detached, and is attached in the direction of arrow V2 after completion of repair work or the like. When the image forming apparatus is used, the lower part of the ventilation duct 4 and the heat radiating plate are in contact with each other.
The contact can be easily released, and workability at the time of repair, inspection, and the like can be improved.

(Modification 1) As a modification of the first embodiment, the heat radiating portion 6 may be a part of the ventilation duct 4 as shown in FIG. That is, the vertical part a and the horizontal part b of the heat sink constitute a part of the ventilation duct 4. In the first embodiment, the heat leaked from the heat insulating portion 5 is used to heat the air in the ventilation duct 4 via the heat radiating plate and the lower surface of the ventilation duct 4. ) Alone, the air in the ventilation duct 4 is warmed, so that the air in the ventilation duct 4 can be more effectively warmed and natural convection can be promoted.

(Modification 2) As a further modification, FIG.
As shown in (2), the heat insulating section 5 may be provided outside the fixing device 2. That is, the heat insulating portion 5 may be provided around the upper portion of the fixing device 2, and the heat insulating portion 5 may surround the heat insulating portion. In this case, the heat insulating portion 5 can be retrofitted to the conventional fixing device 2 and the heat insulating portion 5 is not provided inside the fixing device 2, so that the fixing device 2 itself can be downsized. it can.

(Modification 3) As a further modification, FIG.
As shown in FIG. 7, the heat radiating portion 6 may have heat sinks 61a and 61b provided on the heat radiating plate in addition to the heat radiating plate. In this case, the heat leaking from the heat insulating portion 5 is used to more effectively warm the air in the ventilation duct 4, and natural convection can be promoted. The materials, size and shape of the heat sinks 61a and 61b can be arbitrarily selected, but it is desirable that the materials have high thermal conductivity for the purpose. The size of the heat sinks 61a and 61b is preferably large in order to improve heat dissipation. However, if the size is too large, natural convection of the air in the ventilation duct 4 may be hindered. It is desirable to set appropriately in consideration of the inner diameter and the like.
As the shape of the heat sinks 61a and 61b, it is preferable to select a shape having a large surface area such as a plurality of fins as in this modified example from the viewpoint of improving heat dissipation. The shape of the ventilation duct 4 does not hinder the natural convection of the ventilation of the ventilation duct 4.
It is desirable to provide it in parallel with the convection flow inside.

(Modification 4) As a further modification, FIG.
As shown in FIG. 0, an exhaust fan 81 for assisting natural convection in the ventilation duct 4 may be provided at the exhaust port 42 of the ventilation duct 4. By using the exhaust fan 81, natural convection in the ventilation duct 4 is assisted, and a more reliable and powerful air flow is formed in the ventilation duct 4, and heat is trapped in the ventilation duct 4 to be protected. An adverse effect of heat on the portion 3 can be reliably prevented. The exhaust fan 81 can be appropriately selected depending on the inner diameter of the ventilation duct 4, the required air volume, and the like. The purpose is to assist natural convection generated in the ventilation duct 4 due to heat from the heat source 21. Therefore, the rotation is sufficiently effective at an extremely low speed, and the problem of noise hardly occurs.

For example, according to an experiment by the present inventor, the noise of the conventional exhaust fan 81 is 40 to 45 dB [A], whereas the noise of the exhaust fan 81 of the present embodiment is 30 to 45 dB [A].
It was found that the noise was reduced to about 35 dB [A], and the noise could be reduced by about 10 dB while maintaining a sufficient heat shielding ability. In the experiment, the exhaust fan was an axial flow fan with SANYO's Blancless DC motor: SANAC
The height of the hollow portion of the horizontal portion B of the ventilation duct 4 was 16 mm using E25.

The second embodiment relates to an improvement of the heat shield device of the image forming apparatus according to the present embodiment, and the vicinity of the sheet feeding side of the fixing device 2 of the image forming apparatus to which the heat shield device is applied and the paper discharge. The first and second intake ports 41a and 41b are provided near the side, respectively, and the other configuration is the same as that of the first embodiment. FIG.
1 shows the periphery of the heat shield device according to the present embodiment.

The fixing device 2 of the image forming apparatus to which the heat shield device is applied has a heating roll and a pressure roll therein,
The recording paper or the like holding the unfixed toner image is conveyed and passed through the nip portion to fix the toner image on the recording paper. Therefore, the fixing device 2 has a paper feed port 23 and a paper discharge port 24 through which recording paper enters and is discharged on the paper feed side and the paper discharge side, respectively.

In the heat shield device according to this embodiment, the hot air of the recording sheet discharged from the fixing device 2 and the hot air discharged from the paper discharge port 24 of the fixing device 2 are supplied to the second intake port provided in the vicinity thereof. The natural convection in the ventilation duct 4 is further promoted by taking in the ventilation duct 4 from 41b.
In particular, when the second intake port 41b exists at the lower end of the vertical portion A of the ventilation duct 4 as in this embodiment, the effect of promoting natural convection is high.

(Modification 1) This modification has opening / closing control means 7 for opening and closing the second intake port 41b of the ventilation duct 4. The opening / closing control means 7 includes an opening / closing lid 71 attached to the ventilation duct 4, a main controller (not shown) of the image forming apparatus main body, an opening / closing controller (not shown), a solenoid (not shown), and a pulling device. The opening / closing control unit is configured by a spring (not shown) or the like, and receives a signal indicating operation of the image forming apparatus from a main control device of the image forming apparatus main body,
The opening / closing control unit energizes the solenoid based on the signal,
The opening / closing lid 71 opens against the tension of the tension spring. Conversely, the power supply to the solenoid is cut off by a signal from the main controller indicating the stop or standby of the image forming apparatus, and the opening / closing lid 71 is closed by the tension of the tension spring.

FIG. 12A shows the state of the heat shield device during the operation of the image forming apparatus. During the operation of the image forming apparatus, the heat inside the fixing device 2 is released from the paper discharge port 24 of the fixing device 2 together with the recording sheet passing through the nip between the heating roll and the pressure roll of the fixing device 2. Here, the hot air is drawn in from the second suction port 41b of the ventilation duct 4 provided on the sheet discharge port 24 side of the fixing device 2, and natural convection in the ventilation duct 4 is promoted.

FIG. 12B shows the state of the heat shield device when the image forming apparatus is stopped or when it is on standby. When the image forming apparatus is stopped or on standby, the heat released from the paper discharge port 24 of the fixing device 2 is relatively small.
When the second intake port 41b of the ventilation duct 4 is closed, the heat conducted through the heat sink and the heat sink 61 is transferred to the second intake port 4b.
1b is prevented, and as a result, natural convection in the ventilation duct 4 is promoted. Although the opening and closing of the first intake port 41a is not controlled in this modification, the opening and closing of the first intake port 41a may be controlled similarly to the second intake port 41b.

(Modification 2) In this modification, as shown in FIG. 13, an exhaust fan for assisting natural convection in the ventilation duct 4 is provided at the exhaust port 42 of the ventilation duct 4 of the heat shield according to the modification 1. 81, and has exhaust fan 81 control means for controlling the rotation of the exhaust fan 81 in accordance with the operation state of the image forming apparatus. In this modification, the first and second intake ports 41a, 41b are controlled by the opening / closing control means 7. Here, the exhaust fan control unit includes a main controller (not shown) of the image forming apparatus main body, an exhaust fan controller (not shown), and the like, and performs image formation from the main controller of the image forming apparatus. The exhaust fan control unit starts and stops the rotation of the exhaust fan 81 based on a signal indicating the operation of the device.

FIG. 13A shows the state of the heat shield device during the operation of the image forming apparatus. During operation of the image forming apparatus, the opening and closing control means 7 controls the ventilation duct 4.
The first and second intake ports 41a and 41b are both opened, and the exhaust fan 81 is rotated by the exhaust fan control means. By the rotation of the exhaust fan 81, convection in the ventilation duct 4 is further promoted, and the heat shielding effect can be enhanced. Further, the exhaust fan 81 is connected to the ventilation duct 4.
Because it assists natural convection in the inside, even if the rotation speed is set to be much lower than that of the conventional one, a sufficient heat shielding effect can be obtained, so that a noise problem hardly occurs.

On the other hand, FIG. 13B shows the state of the heat shield device when the image forming apparatus is stopped or when it is on standby. When the image forming apparatus is stopped or on standby, the opening and closing control means 7 controls the first and second intake ports 4 of the ventilation duct 4.
1a and 1b are closed, and the exhaust fan 81 is stopped by the exhaust fan control means. In this case, the fixing device 2
Is relatively small, the heat conducted through the first and second intake ports 41a and 41b of the ventilation duct 4 and the heat sink and the heat sink 61 is closed.
Escape from the ventilation duct 4
Promotes natural convection within. Further, since the exhaust fan 81 is stopped, no noise is generated.

The rotation of the exhaust fan 81 may be controlled, for example, when the image forming apparatus is in operation, during standby (when no image is formed for a certain period of time), or when stopped (when the power of the image forming apparatus is turned off). In this state, the number of rotations may be controlled in multiple stages, such as normal rotation, low-speed rotation, and stop, or the number of rotations may be continuously changed according to the number of image formations. It may be something.

(Variation 3) As shown in FIG. 14, this variation is directed to the first and second intake ports 41a, 41b of the ventilation duct 4.
Further, the fixing device 2 includes an opening / closing control unit 7 for opening and closing the sheet feeding port 23 and the sheet discharging port 24 of the fixing device 2. The opening / closing control means 7 includes opening / closing lids 71a and 71b attached to the fixing device 2, a main control device (not shown) of the image forming apparatus main body, opening / closing control section 72, solenoids 73a and 73b, tension springs 74a and 74b, and the like. It is constituted by.

FIG. 14A shows the state of the heat shield device during the operation of the image forming apparatus. When the image forming apparatus is in operation, the paper feed port 23 and the paper discharge port 2 of the fixing device 2
4 and the first and second intake ports 41a and 41b of the ventilation duct 4 are also opened. Therefore, heat mainly from the fixed recording sheet can be sucked in from the second air inlet 41, and natural convection in the ventilation duct 4 can be promoted. In this case, since heat leaking from the paper feed port 23 of the fixing device 2 is relatively small,
3 need not necessarily be open. In the case of this modification, the openable lids 71a and 71b also serve as chutes on the recording sheet transport path.

FIG. 14B shows a state of the heat shield device when the image forming apparatus is stopped or in a standby state.
When the image forming apparatus is stopped or on standby, the paper feed port 23 and the paper discharge port 24 of the fixing device 2 are closed, and the first and second intake ports 41 of the ventilation duct 4 are also closed. That is, the paper feed port 23 of the fixing device 2 and the first intake port 41 of the ventilation duct 4 are connected to the paper discharge port 24 of the fixing device 2 and the ventilation duct 4.
And the second intake port 41 are joined by the opening / closing lid 71, respectively. With such a state, when the image forming apparatus is stopped or on standby, heat leaking from the fixing device 2 is effectively taken into the exhaust duct, and natural convection in the ventilation duct 4 is promoted. In particular, immediately after the image forming apparatus is stopped or on standby, a large amount of heat leaks out of the fixing device 2, which is effective in promoting natural convection in the ventilation duct 4. On the other hand, when a long time has elapsed since the power of the image forming apparatus main body was turned off or when a long time has elapsed since the image forming apparatus (fixing apparatus) was stopped, the heat leaking from the fixing apparatus 2 is small. The paper feed port 23 and the paper discharge port 24 may be opened.

[0049]

According to the first aspect of the present invention, since the heat from the heat source portion is used to promote natural convection in the ventilation duct to protect the protected portion from the heat, the noise is reduced and the heat shielding property is reduced. A heat shield device of an image forming apparatus having excellent heat resistance can be provided.

According to the second aspect of the present invention, the heat from the heat source can be utilized more effectively to promote natural convection in the ventilation duct, and the structure of the apparatus is simplified.

According to the third aspect of the present invention, the heat released from the paper discharge port and the paper supply port of the fixing device can be used to effectively promote natural convection in the ventilation duct. In particular, heat from the heated recording sheet after fixing can be taken in from the second air inlet.

According to the fourth aspect of the present invention, when the amount of heat released from the heat source portion is small according to the operation status of the image forming apparatus, the heat is not released to the outside, and the inside of the ventilation duct is effectively prevented. And natural convection can be promoted as a result.

According to the fifth aspect of the present invention, when the heat release from the heat source portion is small according to the operating condition of the image forming apparatus, the heat can be prevented from being released to the outside more effectively. The heat can be taken into the ventilation duct and natural convection can be promoted as a result.

According to the invention of claim 6, since the convection of air in the ventilation duct is assisted, the heat shielding effect can be further enhanced and the noise of the exhaust fan can be minimized.

According to the seventh aspect of the invention, it is possible to achieve both a heat shielding effect and a reduction in noise of the exhaust fan.

[Brief description of the drawings]

FIG. 1 schematically shows an image forming apparatus to which a heat shield device according to a first embodiment is applied.

FIG. 2 shows the entire heat shield device according to the first embodiment.

FIG. 3 shows a more specific example of a protected portion.

FIG. 4 is a time-heat graph for explaining the effect of the heat shield device according to the first embodiment.

FIG. 5 shows the entire heat shield device for comparison with the heat shield device according to the first embodiment.

FIG. 6 is a diagram illustrating a state in which the heat source unit is removed from the heat shield device according to the first embodiment.

FIG. 7 shows the entirety of a first modification of the heat shield device according to the first embodiment.

FIG. 8 shows an entirety of a second modification of the heat shield device according to the first embodiment.

FIG. 9 shows the entirety of a third modification of the heat shield device according to the first embodiment.

FIG. 10 shows an entirety of a modification 4 of the heat shield device according to the first embodiment.

FIG. 11 shows the whole and operation of a heat shield device according to a second embodiment.

FIG. 11 shows the whole and operation of a first modification of the heat shield device according to the second embodiment.

FIG. 13 shows the whole and operation of a second modification of the heat shield device according to the second embodiment.

FIG. 11 shows the whole and operation of Modification 3 of the heat shield device according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Fixing device, 21 ... Heat source part (heating roll), 3 ... Protected part, 4 ... Ventilation duct, 41 ... Intake port, 42 ... Exhaust port, 5 ... Heat insulation part, 6 ... Heat dissipation part , 61: heat sink, 7: open / close control means, 71: open / close lid, 72 ...
Opening / closing control unit, 73: solenoid, 73: tension spring,
81: Exhaust fan, 8: Exhaust fan control means

Claims (7)

[Claims] 1. A heat shield device for blocking transmission of heat from a heat source portion to a protected portion in an image forming apparatus, comprising: an exhaust port above the heat source section and an intake port below the exhaust port. A ventilation duct is provided between the heat source section and the protected section, a heat insulating section on a heat source section side between the heat source section and the ventilation duct, and a ventilation duct side between the heat source section and the ventilation duct. A heat shield for an image forming apparatus, comprising: a heat radiating unit; 2. The heat shield device according to claim 1, wherein the heat radiating part forms a part of a ventilation duct. 3. The fixing device according to claim 1, wherein the heat source section is provided in a fixing device of the image forming apparatus, and the ventilation duct has first and second intake ports near a sheet feeding side and a sheet discharging side of the fixing device. Item 3. A heat shield device for an image forming apparatus according to any one of Items 1 and 2. 4. An opening / closing control means for controlling opening / closing of said air inlet in accordance with an operation state of the image forming apparatus.
3. The heat shield device of the image forming apparatus according to any one of 3. 5. The fixing device has a paper feed port for feeding a recording sheet and a paper discharge port for discharging a recording sheet. 5. The heat shielding device for an image forming apparatus according to claim 4, wherein the opening and closing of the paper discharge port is controlled. 6. A heat shield device for an image forming apparatus according to claim 1, further comprising an exhaust fan for assisting natural convection in a part of said ventilation duct. 7. The heat shield device for an image forming apparatus according to claim 6, further comprising exhaust fan control means for controlling rotation of said exhaust fan in accordance with an operation state of the image forming apparatus.