JP2004021213A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with stable performance by preventing end part temperature from rising and efficiently cooling various devices which are arranged inside. <P>SOLUTION: A flapper 102 which changes an air path is arranged between the passage of a recording medium 94 which is about to enter a fixing device 30 and a suction fan 88. The flapper 102 is opened and closed blocking the air path 92a around a shaft 102a extending in parallel to the passage of the recording medium 94. When the suction fan 88 rotates, the flapper 102 is opened as shown by a two-dot chain line. Air flowing through the air path 92a is not blocked. When the suction fan 88 reverses, the flapper 102 is closed as shown by a solid line with air from the outside. Consequently, the majority of the air introduced from the outside blows to both the lengthwise end parts of a fixing roller 30a more securely to cool it. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image by heating and fixing a developed image on a recording medium.
[0002]
[Prior art]
Conventionally, an image forming apparatus that forms an image on a recording medium using an electrophotographic image forming process has been known. Examples of such an image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer and a laser beam printer), an electrophotographic facsimile machine, an electrophotographic word processor, and the like. An example of an electrophotographic printer will be described with reference to FIG.
[0003]
FIG. 5 is a schematic diagram showing an example of a conventional electrophotographic printer.
[0004]
At the lower part of the electrophotographic printer 10, a cassette tray 14 on which a recording medium 12 is loaded is detachably mounted. The recording medium 12 is fed one by one by a feed roller 16, and further conveyed by a conveying roller 18 to a registration roller pair 20. The recording medium 12 that has reached the registration roller pair 20 is temporarily stopped by the registration roller pair 20.
[0005]
On the other hand, a laser beam 52 carrying image information is emitted from the laser scanner unit 50 and irradiates the photosensitive drum 22. Thus, the electrostatic latent image is written on the photosensitive drum 22. The registration roller pair 20 starts rotating and the recording medium 12 starts to be conveyed again so that the timing at which the electrostatic latent image is written on the photosensitive drum 22 and the timing at which the recording medium 12 is conveyed coincide.
[0006]
The electrostatic latent image formed on the photosensitive drum 22 is developed by the developing device 24, and a developed image is formed on the photosensitive drum 22. This developed image is transferred as a toner image by the transfer roller 26 onto the surface of the recording medium 12 sent to the photosensitive drum 22. The recording medium 12 onto which the toner image has been transferred is conveyed along a conveyance path 28 by the photosensitive drum 22 and the transfer roller 26 and reaches the fixing device 30. The recording medium 12 conveyed to the fixing device 30 is conveyed while being nipped by the fixing roller 30a and the pressure roller 30b, so that the toner image is fixed on the recording medium 12 by heat and pressure. As a result, an image is formed on the recording medium 12. The recording medium 12 on which the image is formed is discharged while being nipped by the discharge rollers 32.
[0007]
A configuration for irradiating the photosensitive drum 22 with the laser beam 52 from the laser scanner unit 50 will be described.
[0008]
A laser beam 52 emitted from a laser emitting unit (not shown) of the laser scanner unit 50 is scanned by a polygon mirror (hereinafter, referred to as a polygon mirror) 56 rotated by a polygon motor 54 of the deflection scanning device. The light passes through the imaging lens system of one or a plurality of fθ lenses 58, and irradiates the photosensitive drum 22 of the photosensitive unit 40 arranged on the side of the laser scanner unit 50 to form an image on the surface thereof. The polygon motor 54, the polygon mirror 56, the fθ lens 58, and the like are built in the optical frame 60 of the laser scanner unit 50. The optical frame 60 is made of resin, and is sealed to prevent sound from leaking and dust from entering the inside.
[0009]
Since the polygon motor 54 rotates at about 22,000 rotations, it easily generates heat, and also generates heat from a substrate (not shown) that forms the laser beam 52. For this reason, the temperature inside the optical frame 60 tends to rise. When the internal temperature of the optical frame 60 increases, the refractive indices of the plurality of fθ lenses 58 change, and an electrostatic latent image may not be formed at an appropriate position on the photosensitive drum 22. For this reason, a fan 70 for cooling the laser scanner unit 50 is arranged in the electrophotographic printer 10.
[0010]
The fixing roller 30a of the fixing device 30 has a built-in heater (not shown) for heating and fixing an unfixed developed image. This heater rises to about 170 ° C. There is also a fixing device using an endless film instead of the fixing roller 30a (direct heating type). In this direct heating type, a heater is disposed inside the endless film, and the temperature of the heater becomes high as in the type using the fixing roller 30a (indirect heating type).
[0011]
By the way, in recent years, there has been a need to turn off the power of the fixing heater when not using various electrophotographic apparatuses, due to the increasing awareness of energy saving and environmental protection. For this reason, the electrophotographic apparatus automatically turns off the heater power when the non-use state continues for a long time, and automatically turns on the heater power by detecting the approach of the user by a power saving sensor or the like. Some types have a function to turn it on.
[0012]
In such an energy saving type electrophotographic apparatus, it is required that the temperature of the fixing roller can be quickly raised after the heater power is turned on. In order to satisfy this requirement, there is a fixing roller whose thickness is reduced to 1 mm or less.
[0013]
[Problems to be solved by the invention]
However, in the fixing device capable of rapidly raising the temperature of the fixing roller as described above, there is a problem of “end temperature rise”. This “end temperature rise” means that a width (for example, a width when the B5 size is made vertical) smaller than a maximum paper passing width (a width when the A3 size is made vertical in a popular machine) in the electrophotographic apparatus is continuously used. Means that the temperature at both ends in the longitudinal direction of the fixing roller rises excessively when fixing is performed. The reason for this “end temperature rise” is that when a recording medium having a small width is continuously fixed, heat from the heater is transmitted to the recording medium in contact with the longitudinal center of the fixing roller. This is because the recording medium does not come into contact with both ends, so that heat is not transmitted and accumulates, so that both ends in the longitudinal direction rise too much.
[0014]
Due to the above “end temperature rise”, the life of the bearing that holds both ends in the longitudinal direction of the fixing roller may be shortened. Further, when a recording medium having a large width is fixed after the “end temperature rise”, both ends in the width direction of the recording medium (portions corresponding to both ends in the longitudinal direction of the fixing roller) become higher than a set temperature and are fixed. There is a possibility that an error occurs or a transport error occurs. Such “end temperature rise” is a problem common to both the indirect heating type fixing device and the direct heating type fixing device described above.
[0015]
SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus which prevents "end temperature rise" and efficiently cools various devices arranged therein and has stable performance.
[0016]
[Means for Solving the Problems]
The image forming apparatus of the present invention for achieving the above object,
(1) a casing having a predetermined shape in which a first side wall and a second side wall facing each other are formed;
(2) a first vent formed in the first side wall and through which air passes;
(3) a second vent formed in the second side wall and through which air passes;
(4) By rotating in a predetermined forward rotation direction, external air is sucked from the first ventilation port, passes through the inside of the housing, and is discharged from the second ventilation port. It is disposed near the second air vent, which is rotated in the opposite reverse rotation direction to suck external air from the second air vent, pass through the inside of the housing, and discharge from the first air vent. Suction fan and
(5) The image forming apparatus further includes a fixing device disposed inside the housing for heating and fixing the developed image on a recording medium that blocks an air passage of the air passing through the inside of the housing.
[0017]
Here, the suction fan is
(6) When the recording medium passing through the inside of the housing is larger than a predetermined size, the recording medium rotates forward in a predetermined direction. It may rotate in the opposite direction to the direction.
[0018]
Also,
(7) The fixing device may be arranged near the suction fan.
[0019]
further,
(8) A flapper may be provided to change an air path through which the external air sucked by the suction fan flows.
[0020]
Furthermore,
(9) The flapper is arranged between the suction fan and the fixing device, and changes an air path so that external air is applied to both longitudinal ends of the fixing roller of the fixing device. May be used.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
[0022]
A first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.
[0023]
FIG. 1 is a schematic diagram showing a first embodiment of the image forming apparatus of the present invention. FIG. 2 is a perspective view showing a part of the image forming apparatus of FIG. FIG. 3 is a schematic diagram illustrating the flow of air when the suction fan is rotated in the reverse direction. In these drawings, the same components as those shown in FIG. 5 are denoted by the same reference numerals.
[0024]
The electrophotographic printer 80 has a rectangular housing 81. The fixing device 30 and the laser scanner unit 50 are housed inside the housing 81. The housing 81 has a first side wall 82 and a second side wall 84 facing each other.
[0025]
The first side wall 82 has first ventilation ports 82a and 82b through which air passes. The first ventilation port 82a is formed in a portion of the first side wall 82 above the laser scanner unit 50, and includes a number of holes. Therefore, the air passing through the first vent 82 a passes over the laser scanner unit 50. The first ventilation port 82b is formed in a portion of the first side wall 82 below the laser scanner unit 50, and includes a number of holes. Therefore, the air passing through the first vent 82b passes below the laser scanner unit 50.
[0026]
The second side wall 84 is formed with a second ventilation port 84a through which air passes. Outside the second side wall 84, a third side wall 86 extending in parallel with the second side wall 84 is formed. A third vent 86a is formed in a portion of the third side wall 86 facing the second vent 84a. Therefore, the air passing through the second vent 84a is discharged to the outside through the third vent 86a. Conversely, the air sucked from the outside passes through the third vent 86a and then passes through the second vent 84a to enter the inside of the housing 81.
[0027]
As shown in FIGS. 1 and 2, a suction fan 88 is fixed inside and near the second ventilation port 84a. The suction fan 88 rotates forward or backward according to the size of the recording medium conveyed to the fixing device 30. Here, when the recording medium has a large size (the maximum size in which an image can be formed by the electrophotographic printer 80 or a size slightly smaller than the maximum size), the suction fan 88 rotates forward. On the other hand, when the recording medium has a small size, the suction fan 88 rotates in the reverse direction.
[0028]
When the suction fan 88 is rotated forward, as shown in FIG. 1, external air passes through the first ventilation ports 82a and 82b and enters the inside of the housing 81. The air 90a (air passage 90a) that has passed through the first ventilation opening 82a cools the laser scanner unit 50 and the photoreceptor unit 40 while passing over them, and further passes between the fixing device 30 and the photoreceptor unit 40. The cooling air reaches the suction fan 88 while being cooled, and is discharged to the outside through the second ventilation port 84a and the third ventilation port 86a.
[0029]
On the other hand, the air 90b (the air passage 90b) that has passed through the first ventilation port 82b cools them while passing below the laser scanner unit 50 and the photoconductor unit 40. In this case, the polygon motor 54, which is one of the heat sources, is efficiently cooled. The air 90b further passes below the developing device 24 of the photoreceptor unit 40 and reaches the suction fan 88 while cooling it, and is discharged to the outside through the second vent 84a and the third vent 86a. .
[0030]
When the suction fan 88 rotates in the reverse direction, as shown in FIG. 3, external air is sucked into the suction fan 88 through the third ventilation port 86a and the second ventilation port 84a. The sucked air collides with the photoreceptor unit 40 and the like and branches up and down, so that three air paths 92a, 92b and 92c are formed as shown in FIG.
[0031]
The air flowing through the air path 92a passes through the paper passage 30c of the fixing device 30, enters the inside of the fixing device 30, cools the fixing roller 30a and the pressure roller 30b, and is then discharged from the paper discharge opening. In this case, as shown in FIG. 2, when a small-sized recording medium 94 is being conveyed to the fixing device 30, the central portion of the air passage 92 a is blocked by the recording medium 94. For this reason, the air flowing through the air passage 92a enters the fixing device 30 from both ends in the width direction of the paper passage opening 30c, hits both ends in the longitudinal direction of both the fixing roller 30a and the pressure roller 30b, and cools both ends in the longitudinal direction. . Further, the air flowing through the air passage 92a has just entered from the outside, and is not heated. As a result, both ends in the longitudinal direction of both the fixing roller 30a and the pressing roller 30b are efficiently cooled, so that a temperature increase in both ends in the longitudinal direction is suppressed. In addition, a waste heat hole for discharging air that has cooled the fixing roller 30a and the pressure roller 30b may be formed on the side wall of the fixing device 30.
[0032]
The air flowing through the air passage 92b cools the air passing through the space between the fixing device 30 and the photoreceptor unit 40, and further cools the air passing over the laser scanner unit 50. It is discharged to the outside through 82a. Both ends of the photoconductor unit 40 in the width direction (a direction perpendicular to the paper surface of FIG. 3) are likely to become hot due to radiant heat from both ends in the longitudinal direction of the fixing roller 30a. Both ends in the width direction are efficiently cooled when the air passes between them.
[0033]
The air flowing through the air passage 92c passes below the developing device 24 of the photoconductor unit 40 to cool it, and further cools them while passing below the photoconductor unit 40 and the laser scanner unit 50. In this case, the polygon motor 54, which is one of the heat sources, is cooled. Thereafter, the air passes through the first vent 82b and is discharged to the outside.
[0034]
As described above, by appropriately rotating the one suction fan 88 forward or backward, not only the both ends in the longitudinal direction of the fixing roller 30a but also the parts and devices arranged inside the housing 81 can be efficiently processed. Since cooling can be performed, an electrophotographic printer 80 having stable performance can be obtained. Further, since one suction fan 88 is used, the number of parts does not need to be increased, and the cost can be reduced.
[Second embodiment]
[0035]
A second embodiment of the present invention will be described with reference to FIG.
[0036]
FIG. 4 is a perspective view showing a second embodiment of the image forming apparatus of the present invention.
[0037]
A feature of the electrophotographic printer 100 according to the second embodiment is that a flapper 102 for changing an air path is disposed between the passage of the recording medium 94 and the suction fan 88 immediately before entering the fixing device 30.
[0038]
The flapper 102 opens and closes around a shaft 102a extending parallel to the passage of the recording medium 94 so as to block the air path 92a. When the suction fan 88 is rotating forward, the air path shown in FIG. 1 is formed, so that the flapper 102 opens as shown by the two-dot chain line. Therefore, the air flowing through the air passage 92a is not blocked.
[0039]
On the other hand, when the suction fan 88 is rotating in the reverse direction, as shown in FIG. 3, the flapper 102 closes as indicated by a solid line due to air entering from outside. For this reason, much of the air introduced from outside hits the both ends in the longitudinal direction of the fixing roller 30a more reliably and cools it.
[0040]
【The invention's effect】
As described above, in the image forming apparatus of the present invention, the fixing device is cooled by the air passing through the inside of the housing. Further, the recording medium conveyed while being sandwiched between the fixing roller and the pressure roller incorporated in the fixing device blocks the air path of the air passing through the inside of the housing. For this reason, when the recording medium is not in contact with both ends in the longitudinal direction of the fixing roller, air is applied to both ends in the longitudinal direction of the fixing roller, and both ends in the longitudinal direction are cooled. Temperature rise is suppressed. In addition, by appropriately rotating the suction fan in the normal or reverse direction, the components and devices in the housing can be efficiently cooled, so that an image forming apparatus with stable performance can be obtained.
[0041]
Here, when the fixing device is arranged in the vicinity of the suction fan, when the suction fan is rotated in the reverse direction, the external air sucked by the suction fan quickly hits the fixing device. For this reason, since the fixing device is cooled quickly, both ends in the longitudinal direction of the fixing roller can be cooled more efficiently.
[0042]
In the case where a flapper is provided to change the air path through which the external air sucked by the suction fan flows, the air path can be changed by the flapper, so that components and members arranged inside the housing can be cooled.
[0043]
Further, the flapper is disposed between the suction fan and the fixing device, and changes an air path so that external air is applied to both longitudinal ends of the fixing roller of the fixing device. If the fixing roller is used, both ends in the longitudinal direction of the fixing roller can be cooled even more efficiently.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a first embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a perspective view showing a part of the image forming apparatus of FIG.
FIG. 3 is a schematic diagram showing a flow of air when a suction fan is rotated in a reverse direction.
FIG. 4 is a perspective view illustrating a second embodiment of the image forming apparatus of the present invention.
FIG. 5 is a schematic view showing an example of a conventional electrophotographic printer.
[Explanation of symbols]
30 Fixing device 80, 100 Electrophotographic printer 81 Case 82 First side wall 82a, 82b First vent 84 Second side wall 84a Second vent 88 Suction fan 102 Flapper

Claims (5)

A casing having a predetermined shape in which a first side wall and a second side wall facing each other are formed;
A first vent formed in the first side wall and through which air passes;
A second vent formed in the second side wall and through which air passes;
By rotating in a predetermined forward rotation direction, external air is sucked from the first ventilation port, passes through the inside of the housing, and is discharged from the second ventilation port, and is opposite to the normal rotation direction. A suction fan disposed in the vicinity of the second ventilation port, wherein the suction fan is disposed near the second ventilation port, wherein the external air is sucked from the second ventilation port by rotating in a rotational direction, passes through the inside of the housing, and is discharged from the first ventilation port. When,
An image forming apparatus, comprising: a fixing device disposed inside the housing for heating and fixing a developed image on a recording medium passing through the inside of the housing. The suction fan,
When the recording medium passing through the inside of the housing is larger than a predetermined size, it rotates forward in a predetermined direction,
2. The image forming apparatus according to claim 1, wherein when the recording medium passing through the inside of the housing is smaller than the predetermined size, the recording medium rotates in a direction opposite to the predetermined direction. The fixing device includes:
The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged near the suction fan. The image forming apparatus according to claim 1, further comprising a flapper configured to change an air path through which the external air sucked by the suction fan flows. The flapper is
The fixing device is disposed between the suction fan and the fixing device, and the air passage is changed so that external air is applied to both ends in the longitudinal direction of the fixing roller of the fixing device. The image forming apparatus according to claim 4, wherein

Images