JP2006317530A - Heat exhausting structure and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide heat exhausting structure equipped with constitution capable of securing a necessary air current of radiated heat and simultaneously restraining noise made when securing the air current. <P>SOLUTION: The heat exhausting structure aiming at the constitution using an external heating source 101A arranged near a member to be heated 14E for the member to be heated 14E is equipped with: a housing 101 for a heat source which has space for housing the external heating source 101A and where a duct is coupled with one end and the other end in the extension direction of the space; and a blower device 102 provided at one end in the extension direction of the space so as to generate the air current in the space. The duct 103 positioned at the other end in the extension direction of the space out of the ducts is set so that its length extended from the other end in the extension direction of the space may be ten or more times as long as a hydraulic diameter (4×average area of the duct/average cross-sectional periphery length of the duct). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust heat structure and an image forming apparatus, and more particularly to an exhaust heat structure used in a fixing device equipped in the image forming apparatus.

  As is well known, one of image forming methods is an electrophotographic method. In this system, when an electrostatic latent image formed on a photoconductor corresponding to a latent image carrier is subjected to visible image processing upon receiving toner from a developing device, the toner image is recorded on a recording medium such as recording paper. The transferred toner image is fixed by a melting / penetrating action using heat and pressure in a fixing device.

In the fixing device, apart from a configuration in which a fixing roller having an internal heat source and a pressure roller are used to heat and fix the recording sheet while being nipped and conveyed, a belt that can reduce the heat capacity unlike the roller is wound between the rollers. There is a configuration to be used.
When the surface of the belt used in this configuration is heated not from the inside of the roller but from the outside, the rise of the surface temperature of the belt that contacts the unfixed toner can be accelerated. Therefore, an electromagnetic induction method can be used as an external heating source (Non-Patent Document 1).

  By the way, in the image forming apparatus, as a heat generating source in the image forming apparatus like the above-described fixing apparatus, electromagnetic devices such as a motor and a clutch, and a microchip used for control are included. However, the heat from the fixing device having a large calorific value may cause an increase in the ambient temperature in the image forming apparatus, which may have a thermal adverse effect on the equipped equipment.

  For example, since toner is used as a developer in the developing device, there is a possibility that the desired developer supply control cannot be performed due to the solidification of the toner due to the temperature rise in the developing device. Also, in an optical system, since an optical lens such as an fθ lens is often made of resin, a regular imaging optical path is changed due to thermal deformation or the like, and an abnormal image such as a color shift is generated. Defects may occur.

  Therefore, conventionally, a configuration for discharging the heat generated in the fixing device to the outside has been adopted. As this configuration, it is a general configuration to arrange a heat exhaust fan near the fixing device (for example, Patent Document 1).

  In addition, an airflow passage using a duct is formed between the position near the fixing device and the outer wall of the image forming apparatus main body, a fan is provided on the entrance side of the airflow passage, and air from the vicinity of the fixing device is provided in a part of the duct. There is also a configuration in which notch that can be taken in is formed and hot air in the vicinity of the fixing device can be taken into the duct (for example, Patent Document 2).

  Furthermore, as a configuration for preventing thermal deformation of the optical system parts, a configuration has been proposed in which each optical device is collectively provided with a duct that can be arranged in the airflow passage, and heat isolation and heat dissipation are performed using the duct (for example, Patent Document 3).

July 14, 2000 Post office of the Ministry of Internal Affairs and Communications “Title: Document copy printing machine using electromagnetic induction heating added to type designation” (materials for consultation with the Radio Control Council regarding partial revision of the Radio Law Enforcement Regulations) JP-A-11-231760 (paragraph "0009" column) JP 2000-98857 A (paragraph 0017 column) JP 2001-22151 A (paragraph “0025” column)

In recent years, it has been desired to shorten the time required to start up the image forming apparatus, and there is a tendency that the fixing apparatus also needs to shorten the warm-up time until it reaches a predetermined fixing temperature.
For this reason, in addition to using a belt having a small heat capacity, a heating method that quickly rises to the heating temperature may be used. As this heating method, there is the above-described electromagnetic induction heating (induction heating (IH)) method. .

  In the electromagnetic induction heating method, a metal housing containing a magnetic force generating coil is disposed in the vicinity of the belt surface, and radiant heat from the housing side is generated by using eddy currents generated by magnetic lines transmitted through the metal housing. Thus, the belt can be heated.

However, when the electromagnetic induction heating method is used, there are the following problems.
When heating is performed from the side of the metal housing disposed in the vicinity of the belt surface, the heat retention on the roller side is small unlike the case where the heating source for the belt is provided on the roller side. For this reason, the heat from the metal housing used for electromagnetic induction heating easily spreads to the peripheral part, leading to a temperature rise in the peripheral space. As a result, as described above, the optical system and the developing device side are adversely affected. Effect.

  On the other hand, the magnetic force generating coil used for electromagnetic induction heating changes the insulation performance as the temperature rises, and may cause insulation failure depending on the temperature. For this reason, in order to prevent the temperature rise in a peripheral part and the overheating state of the coil for magnetic force generation, it is possible to perform heat dissipation by the air current as disclosed in the patent document.

However, when airflow is used, the flow rate may be increased in accordance with the size of the heat dissipation range, but since the current flowing through the magnetic force generating coil and the amount of heat generated are in a square relationship, the warm-up rise is shortened. In order to obtain a calorific value for this purpose, it is necessary to pass a corresponding amount of current, and accordingly, the flow rate of the cooling airflow for suppressing the influence of heat on the peripheral part must also be increased. As a result, when the flow rate of the cooling airflow is increased, the airflow noise and the fan driving noise tend to increase, which may cause a new environmental noise problem. In particular, the inside of a metallic housing with a coil for generating magnetic force may have a small airflow passage space because many parts including not only the coil but also structural parts such as ferrite are arranged at high density. For this reason as well, there is a possibility that noise generation becomes significant by securing the flow rate of the cooling airflow and increasing the flow velocity for securing this flow rate.
In view of the problems in the conventional heat exhaust structure and the apparatus including the same, it is an object of the present invention to be able to secure a necessary radiating airflow and simultaneously suppress noise generated when securing the airflow. And an image forming apparatus including a fixing device using the same.

  In order to achieve this object, the invention according to claim 1 is an exhaust heat structure intended for a configuration using an external heat source disposed in the vicinity of a member to be heated, wherein the external heat source is disposed. And a heat source housing having a duct for connecting the duct to one end and the other end in the extension direction of the space, and generating an air flow in the space provided at one end of the space extension direction. Among the ducts, a duct located at the other end in the extension direction of the space has a length extending from the other end in the extension direction of the space having a hydraulic diameter (4 × average area of the duct). The average cross-sectional circumference of the duct) is set to 10 times or more.

  According to a second aspect of the present invention, in the exhaust heat structure according to the first aspect, the external heating source provided in the heat source housing is an electromagnetic induction heating device provided with a magnetic force generating coil. .

  According to a third aspect of the present invention, in the exhaust heat structure according to the first or second aspect, a sirocco fan is used as the blower.

  According to a fourth aspect of the present invention, in the exhaust heat structure according to the first or third aspect, the air blower generates a positive pressure in the space.

  According to a fifth aspect of the present invention, in the exhaust heat structure according to any one of the first to fourth aspects, a replaceable filter is provided on a side where air from outside is introduced in the extending direction of the space. It is characterized by having.

  According to a sixth aspect of the present invention, the image forming apparatus includes the fixing device using the heat exhaust structure according to any one of the first to fifth aspects.

  According to the first aspect of the present invention, the airflow that has passed through the space portion is not directly discharged to the outside from the end portion in the extension direction of the space portion. Thereby, the emission sound by the momentum of the airflow discharged | emitted from a space part does not arise. In particular, the emission sound can be reduced by reducing the momentum when the airflow that has passed through the space portion is further discharged from the duct by using velocity attenuation caused by further passing through the duct.

  According to the second aspect of the present invention, it is possible to prevent the generation of noise when the cooling effect by the airflow is obtained when the external heating source uses an electromagnetic induction heating device having a magnetic force generating coil.

  According to the third and fourth aspects of the invention, the use of the sirocco fan makes it possible to reduce the installation space of the blower device and to secure an air volume sufficient for positive pressure in the space. By compressing, it becomes possible to secure an air flow in a space where the component arrangement is densified.

  According to the fifth aspect of the invention, it is possible to prevent foreign matter from entering the space, thereby preventing adverse effects on the magnetic force generating coil disposed in the space, and ensuring a predetermined heat generation state. Is possible.

  According to the sixth aspect of the invention, not only is it possible to shorten the warm-up time at the time of fixing by the electromagnetic induction heating method, but it is also possible to prevent abnormal overheating that occurs when the electromagnetic induction heating method is used. It is possible to prevent a thermal adverse effect on the crisis arranged around the fixing device.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is an external view of an image forming apparatus 1 using an exhaust heat structure according to an embodiment of the present invention. The image forming apparatus 1 shown in FIG. 1 is a color printer having the configuration of the image forming processing unit shown in FIG. The present invention is not limited to a color printer, but includes a facsimile machine, a printing machine, and the like.

  The color printer 1 includes a document scanning device 20 at the upper part of the housing with the image forming unit shown in FIG. 2 in the vertical direction, and a paper feeding device 21 having a plurality of paper feeding trays 21A and 21B at the lower part. The upper surface of the housing below the document scanning device 20 is provided with a paper discharge tray 1A that forms an in-body paper discharge portion, thereby eliminating the need for a paper discharge space outside the device. An operation panel 20 </ b> A is provided on the front surface of the document scanning device 20.

  Covers 22 and 23 that can be opened and closed are provided on the side surface of the apparatus housing on the upper portion of the paper feed cassette 21A and on the wall surface in a direction perpendicular to the position, for example, replacement or maintenance of a unit that forms an image forming processing section described later. It can be opened at the time of.

  FIG. 2 is a diagram showing the configuration of the image forming processing unit. In FIG. 2, the document scanning device 20 located at the upper portion and the paper feeding device 21 located at the lower portion are omitted.

  In FIG. 2, the image forming processing unit 2 is provided with an image forming unit 2 capable of forming an image for each color separation (for convenience, initials Y, M, C, and B meaning yellow, magenta, cyan, and black are attached to reference numeral 2. Are displayed side by side, and the exposure unit 3 is disposed below the image forming units 2Y, 2M, 2C, and 2B.

Each of the image forming units 2Y, 2M, 2C, and 2B has the same configuration. Now, the configuration of a unit that forms a yellow image will be described as follows.
The image forming unit 2Y includes a rotatable photosensitive drum 4Y that is a latent image carrier, and an image forming process is performed around the photosensitive drum 4Y along the clockwise rotation direction in FIG. A charging device 5Y for execution, an incident portion 6Y for writing light from the exposure unit 3, a developing device 7Y, a transfer device 8, and a cleaning device 9Y are arranged.

  In FIG. 2, the developing device 7Y uses a two-component developer containing toner and a carrier, and discharges the old developer by supplying the carrier in addition to supplying the toner for correcting the concentration of the developer. A trickle development system in which the developer can be replaced is adopted.

  In FIG. 2, the transfer device 8 includes a transfer belt 8A that can move while facing and facing the photosensitive drum of each image forming unit, and is positioned at a position facing the photosensitive drum 4Y across the transfer belt 8A. A transfer roller 8Y capable of applying a transfer bias is provided.

  The transfer device 8 in this embodiment is superposed on the primary transfer process in which the visible images carried on the photosensitive drums in the respective image forming units 2Y, 2M, 2C, and 2B are sequentially superimposed and transferred onto the transfer belt 8A. The secondary transfer process is performed in which the transferred image is collectively transferred to a recording sheet or the like fed out from the paper feeding device 10. For this reason, a secondary transfer device 11 including a transfer roller to which a transfer bias can be applied is disposed at a position where the secondary transfer process can be performed.

The paper feeding device 10 is provided with a paper feeding cassette 10A for storing recording paper and a registration roller 10B arranged in the feeding path. The registration roller 10B is introduced from a manual paper feeding tray 10C. The recording paper conveyance path is provided at a position where it merges with the conveyance path from the paper feed cassette 10A.
In FIG. 2, reference numeral 12 denotes a cleaning device for the transfer belt 10A, and reference numeral 13 denotes a static elimination device for the transfer belt 10A.

In the image forming processing unit shown in FIG. 2, the color images respectively formed in the image forming units 2Y, 2M, 2C, and 2B are sequentially superimposed and transferred to the transfer belt 8A of the transfer device 8 by the primary transfer process. Are collectively transferred onto the recording paper in the secondary transfer process and then fixed in the fixing device 14.
As shown in FIG. 1, the recording paper on which the image is fixed is discharged onto a paper discharge tray 1A that is provided inside the apparatus and forms a cylinder discharge portion.

Inside the color printer 1, the space above the image forming units 2Y, 2M, 2C, and 2B is shared with the toner replenishing portions 15Y, 15M, 15C, and 15B used in the trickle developing method described above and the respective toner replenishing portions. A carrier replenishing unit 16 is disposed.
In FIG. 2, the fixing device 14 includes rollers 14B and 14C arranged in the circumferential direction of the pressure roller 14A, and a heating roller provided at a position facing the pressure roller 14A across the rollers 14B and 14C. A fixing belt 14E wound around 14D is provided, and the fixing belt 14E is heated by an electromagnetic induction heating source 100 as an external heating source disposed in the vicinity of the surface.
FIGS. 3A and 3B are diagrams showing the configuration of the electromagnetic induction heating device 100, where FIG. 3A shows an appearance, and FIG. 3B shows a state where the exterior panel in FIG.
In the drawing, an electromagnetic induction heating device 100 has a space for arranging a magnetic force generating coil 100A inside, and a heat source in which a part of the outer shell can surround the heating roller 14D (see FIG. 2). The magnetic force generating coil 100A is extended in a direction parallel to the width direction of the recording paper passing through the fixing device 14, and a plurality of locations are provided in the heat source housing 101 along the extending direction. It is supported.

  The heat source housing 101 is an airflow passage space in which the space between the heat source housing 101 and the exterior panel 101B (see FIG. 3A) extends in the extending direction except for the support position of the magnetic force generating coil 100A in the internal space. 3B, outside air is introduced from one end in the extending direction and can be discharged from the other end in the extending direction, as indicated by an alternate long and short dash line in FIG.

  One end of the heat source housing 101 in the extending direction is an outside air intake side. As shown in FIG. 4, the end of the heat source housing 101 has a sirocco fan 102 that can introduce the outside air into a positive pressure. A duct is connected, and a chimney-like duct 103 is connected to the other end in the extending direction.

Unlike the axial fan, the sirocco fan 102 is an advantageous member in that it can secure a relatively desired flow rate even if it is small. In this embodiment, the sirocco fan 102 also has a recording size to be fixed. However, a relationship of 0.03 m ³ /min<Q<0.15 m ³ / min is set as the flow rate (Q) of the sirocco fan 102.
FIG. 5 is a diagram for explaining the reason for setting the flow rate.
In the same figure, in the electromagnetic induction heating apparatus 100, the heat source housing 101 (shown on the left side) has an airflow discharge part (FIG. 5A) on the other end side in the extension direction, and an outside air introduction part (FIG. 5A) on the one end side in the extension direction. 5 (B)), the flow velocity distribution in the central portion in the extending direction (FIG. 5C), which is one of these end portions, is shown.
In FIG. 5, the flow velocity is shown in contour lines, and the smaller the contour, the higher the flow velocity. Specifically, the portion with the smallest contour is about 3.5 m / s, and the outside of the portion with the largest contour is 0 m / s.
FIG. 5 (A) shows the result of measuring the velocity at a position 1 cm inward from the other end in the extension direction, which is the airflow discharge portion, and FIG. 5 (B) is 1 cm from one end in the extension direction, which is the outside air introduction portion. It is the result of measuring the speed at a position closer to the inside.

In FIG. 5, in the range from the one end to the other end along the extending direction, the maximum velocity can be obtained by setting the above-described flow rate in the penetrating portion (shown by the symbols α1 and α2 for convenience) serving as an airflow passage space. 3.6 m / s was obtained, and an overall speed of 1 to 3 m / s was obtained.
The temperature on the surface of the exterior panel at each part due to the airflow at this speed passing through the penetration part, in other words, the cooling state by heat radiation is almost uniform, and cooling is performed over the entire extension direction of the heat source housing 101. Is made uniform so as not to cause an extreme overheating state in the peripheral portion.

The inventor conducted experiments on the air volume based on the air flow velocity and the temperature change in each part of the heat source housing 101, and obtained the results shown in FIGS.
FIG. 6 shows the airflow temperature at the other end in the extending direction corresponding to the airflow discharge portion in the heat source housing 101, the air volume, the allowable temperature set in the heat source housing 101, and the ambient temperature around the fixing device. FIG. 7 shows a change state from the map of FIG. As is clear from this result, by using a simple configuration that only sets the wind speed, an overheating state in the electromagnetic induction heating device 100 can be prevented, and thermal adverse effects such as a temperature rise in the peripheral portion can be prevented. Can be suppressed.

  On the other hand, the exhaust duct 103 provided at the other end in the extension direction of the heat source housing 101 has a length from the other end in the extension direction to the end portion of the hydraulic diameter (4 × average area of the duct / average cross-sectional circumference of the duct). (Long) is set to 10 times or more.

  By setting the length of the exhaust duct 103, the airflow that has passed through the heat source housing 101 is not directly released to the outside, so the sound that is emitted when it is directly released to the outside and the airflow that passes through the inside Sound does not leak outside. This is because, when passing through the exhaust duct 103, the velocity of the airflow is attenuated due to the viscous resistance and frictional resistance between the airflow and the inner surface of the duct, thereby reducing the momentum when the air is discharged from the exhaust duct 103. This can be considered as a rough reason.

The inventor conducted an experiment on how the noise value at the outlet of the exhaust duct changes when the length of the exhaust duct 103 is changed. As shown in FIG. It was confirmed that the noise standard value or less could be maintained if the hydraulic diameter was 10 times or more. In this case, although the length of the exhaust duct is set to 10 times or more the hydraulic diameter, it does not mean that the length of the exhaust duct 103 may be increased to a dark cloud, and the conditions such as the capacity of the sirocco fan and the installation space The upper limit naturally exists depending on the selection range of the lower limit when the noise reference value is reached.
In FIG. 8 described above, as shown in FIG. 9, the length of the exhaust duct 103 is 182 mm, and the hydraulic diameter in the cross section of the exhaust duct 103 indicated by symbol S in FIG. The result in the case of (16 mm × 20 mm) / 72 = 17 mm is shown. The length of the exhaust duct 103 described above is 10 times or more with respect to the hydraulic diameter, and the noise value can be kept below the reference value.

  An exchangeable filter (not shown) is provided at the outside air introduction portion, which is one end in the extending direction of the electromagnetic induction heating device 100, and foreign matter to be introduced, for example, toner powder scattered around the periphery is magnetically applied. The coil is prevented from entering the position where the generating coil is disposed, thereby preventing adhesion to the coil or internal fouling.

  Since the present embodiment is configured as described above, the electromagnetic induction heating device 100 provided in the fixing device 14 supports both ends in the extension direction on the support walls 1A and 1B of the color printer 1 as shown in FIG. Is done. A sirocco fan 102 having a duct connected to one end in the extending direction of the heat source housing 101 is attached to the outside of the one supporting wall 1A.

  In the electromagnetic induction heating device 100, the foreign space contained in the outside air introduced by the sirocco fan 102 is collected by the filter, so that the internal space and the magnetic force generating coil are kept clean. As a result, a short circuit and fouling due to adhesion of foreign matter to the magnetic force generating coil are prevented, and a heat generation state for shortening warming up can be maintained.

  On the other hand, since the outside air introduced into the heat source housing 101 is brought into a positive pressure state by the sirocco fan 102, the airflow is obstructed even if there are members arranged at high density in the heat source housing. It is possible to pass through the inside by forcibly pushing without any trouble, and in particular, the flow rate is maintained at a predetermined speed. As a result, a uniform cooling effect can be expected in the extending direction of the heat source housing 101 without deteriorating the heat dissipation efficiency due to airflow retention.

  Further, the airflow that has passed through the inside of the heat source housing 101 and moved into the exhaust duct 103 causes a speed decay due to the length of the exhaust duct 103. Thus, unlike the case where the heat source housing 101 is directly discharged to the outside, the moving momentum is reduced, so that the pressure at the time of discharge is reduced and no sound pressure recognized as noise is generated. The generation of environmental noise can be reliably prevented.

  In the above embodiment, the configuration using the electromagnetic induction heating method is shown as the configuration of the external heat source. However, the present invention is not limited to this, and the present invention is also applicable to a lighting overheating method external heat source using a coil. The invention can be provided.

1 is an external view showing an example of an image forming apparatus equipped with a fixing device adopting a heat exhaust structure according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a configuration of an image formation processing unit in the image forming apparatus shown in FIG. 1. 2A and 2B are diagrams for explaining a configuration of a part of an electromagnetic induction heating device used for a fixing device in the image forming apparatus shown in FIG. 1, in which FIG. The state where the inside is exposed is shown. It is an external view which shows the structure of the housing for heat sources of the electromagnetic induction heating apparatus which is the characteristic part in a present Example. It is a figure for demonstrating the distribution state of the airflow speed in the extension direction of the housing for heat sources shown in FIG. 4, (A), (B), (C) in each part of the extension direction of the housing for heat sources, respectively. The distribution of air velocity is shown. It is a map which shows the result of having experimented the relationship between the air volume by airflow velocity, and a temperature change. FIG. 7 is a diagram showing the experimental result shown in FIG. 6 as a change state. It is a diagram for demonstrating the relationship between the length of an exhaust duct, and a noise value. FIG. 9 is a mechanism diagram for explaining conditions for obtaining the relationship shown in FIG. 8, where (A) shows the length of the exhaust duct and (B) shows the cross-sectional dimension of the exhaust duct. It is a figure which shows the state in which the electromagnetic induction heating apparatus shown in FIG. 4 was integrated in the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A, 1B Support wall board 2 Image forming unit 14 Fixing apparatus 14A Pressure roller 14B, 14C Roller 14D Heating roller 14E Fixing belt 100 Electromagnetic induction heating apparatus 101 Heat source housing 102 Sirocco fan 103 Exhaust duct

Claims (6)

An exhaust heat structure intended for a configuration using an external heat source disposed in the vicinity of a heated member,
A heat source housing having a space for arranging the external heating source therein, and a duct connected to one end and the other end in the extending direction of the space;
A blower provided at one end in the extending direction of the space and causing an air flow in the space;
Of the ducts, the duct located at the other end in the extension direction of the space has a hydraulic diameter (4 × average area of the duct / average cross-sectional circumference of the duct). ) Is set to be 10 times or more of the above. The exhaust heat structure according to claim 1,
The exhaust heat structure according to claim 1, wherein the external heating source provided in the heat source housing is an electromagnetic induction heating device having a magnetic force generating coil. The exhaust heat structure according to claim 1 or 2,
A heat exhaust structure using a sirocco fan as the blower. The exhaust heat structure according to claim 1 or 3,
The exhaust air structure is characterized in that the air blower generates a positive pressure in the space. The exhaust heat structure according to any one of claims 1 to 4,
An exhaust heat structure characterized in that a replaceable filter is provided on a side where air from the outside is introduced in the extending direction of the space. An image forming apparatus comprising: a fixing device using the exhaust heat structure according to claim 1.

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