JPH04340561A - Recording sheet cooling device - Google Patents

Abstract

PURPOSE:To satisfactorily cool a recording sheet without increasing the number and the area of the cooling fin of a heat pipe, to prevent the occurrence of curl or a blocking phenomenon and to efficiently perform the cooling by providing the heat pipe which has the cooling fin at the end and rotates to perform self-cooling in a cooling device. CONSTITUTION:Relay guiding plates 21 are respectively provided at positions opposed to paper ejecting rollers 13 and 14, and the heat pipe 27 rotatably supported and a carrying roller 22 which rotates in contact with the lower part of the pipe 27 are provided behind the cooling guiding plates 21. Then, the cooling fin, whose shape is like a propeller, is attached to one end of the pipe 27, and an air current is generated when the heat pipe 27 rotates. In such a case, the air current makes hot air inside a machine and cool air outside the machine circulate so as to enhance the heat radiation effect of the cooling fin in virtue of the cool outside air. The cooling fin is formed of aluminum for example, which is excellent in heat conductivity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording sheet cooling device for an image recording machine having a heat fixing device, such as a printer or a facsimile machine.

0002

2. Description of the Related Art An image recording machine having a conventional heat fixing device and a recording sheet cooling device will be described with reference to an embodiment of the present invention shown in FIG. Each device is shown.

[0003] A recording sheet 5 is loaded with an unfixed toner image transferred by a transfer section (not shown) into a thermal fixing device 1, and is conveyed into a nip between a fixing roller 2 and a pressure roller 4, and is then pressed. The unfixed toner image is fixed on the recording sheet 5 by pressing the pressure roller 4 against the fixing roller 2 by heating and pressurizing it. The fixing roller 2 has a built-in heater 3 and its temperature is normally controlled at 185° C. by a thermistor 8, and the pressure roller 4 has a 5 mm thick rubber layer provided on its surface.

By the way, the recording sheets 5 that have been fixed in this way are hot and tend to curl, and if they are ejected to the paper output tray 50 and stacked as they are, heat will accumulate between the recording sheets 5 when they are continuously passed through. occurs, recording sheet 5
A so-called blocking phenomenon may occur in which the toner fixed on the recording sheet 5 becomes sticky and sticks to the back side of the next recording sheet 5. This is a phenomenon that often occurs particularly when the recording sheets 5 after fixing are stacked together before they have sufficiently cooled down, such as in a high-speed machine. Then, when the recording sheets 5 stuck in this manner are taken out from the paper discharge tray 50, a problem arises in that they make a clicking sound and must be peeled off one by one.

[0005] In order to solve this problem,
The recording sheet 5 that has been fixed is separated by a separating claw 11 and conveyed to discharge rollers 13 and 14 via an exit guide plate 12. At this time, the recording sheet 5 is at around 120°C.
Thereafter, the recording sheet is cooled and conveyed by a recording sheet cooling device having a pair of upper and lower cooling rollers (not shown) and a conveyance roller using the relay guide plate 21 .

[0006]

[Problems to be Solved by the Invention] In such a conventional recording sheet cooling device, since the contact time between the recording sheet and the cooling roller is short, it is difficult to cool the recording sheet to a satisfactory level.
Therefore, there is a problem in that it is not possible to effectively correct curls or prevent the blocking phenomenon from occurring.Also, since the thermal conductivity of the cooling roller and the heat transport capacity of the heat pipe are not determined in advance, it is not possible to effectively correct curls or prevent the blocking phenomenon. In the case of a high-speed image recording machine, there is a problem that there is excessive cooling, and in the case of a high-speed image recording machine, there is insufficient cooling, and a cooling effect corresponding to different linear velocities cannot be obtained. Furthermore, in some cases, a heat pipe is used for the cooling roller, and cooling fins are provided at the ends of the heat pipe to dissipate heat, but there is a problem in that cooling efficiency is poor if only the cooling fins are provided. As a solution to this problem,
In order to increase the cooling effect, it is necessary to increase the number of cooling fins or increase the area of the cooling fins. If this is done, there is a problem that the cost increases and the machine becomes larger.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the conventional recording sheet cooling device as described above, to cool the recording sheet to a satisfactory degree, and to correct curls and prevent the blocking phenomenon. can be done effectively,
In addition, the thermal conductivity of the cooling roller and the heat transport capacity of the heat pipe are determined in advance, which may result in excessive cooling in the case of a low-speed image recording machine or insufficient cooling in the case of a high-speed image recording machine. In addition, since cooling effects corresponding to different linear velocities can be obtained, cooling efficiency is good without increasing the number of cooling fins installed on the heat pipe or increasing the area of the cooling fins, which increases costs and increases the size of the machine. The purpose of the present invention is to provide a recording sheet cooling device that does not require any additional work.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a heat pipe in which a cooling fin 30 is provided at one end of a cooling conveyance roller in the above-mentioned conventional recording sheet cooling device. 27, the heat pipe 27 is rotatably provided, and is characterized in that it cools itself by rotating the heat pipe 27. The heat pipe 27 is supported so that the cooling fin 30 side is higher, and the cooling fin 30 is characterized in that it has a propeller shape.

[0009]

[Operation] In this invention as described above, the recording sheet fixed by the heat fixing device is conveyed to the recording sheet cooling device in the same manner as in the conventional device described above, and is conveyed by the conveyance roller and the heat pipe. while cooling. In this case, the heat pipe is provided with cooling fins at the end, and the cooling fins are in the shape of a propeller, and the heat pipe is rotatable, allowing for self-cooling, and because the heat pipe is slanted, Effective cooling of the recording sheet is achieved. In addition, a belt is provided as a conveying member in place of the conveying roller, and a pair of rollers are provided which are stretched around the belt and rotate to convey the recording sheet and cool it.

0010

[Embodiment] In the embodiment of this invention shown in the drawings, FIG.
Since the first embodiment shown in to 4 and the other second to fourth embodiments have many parts in common, the same reference numerals as in the first embodiment will be used for these parts and the explanation thereof will be omitted. However, we will mainly explain the different parts. This first
The recording sheet cooling device 20 according to the embodiment includes relay guide plates 2 at positions facing the paper ejection rollers 13 and 14, respectively.
A heat pipe 27 is rotatably supported behind the cooling guide plate 21, and a conveying roller 22 that rotates in contact with the heat pipe 27 is provided below the heat pipe 27.

A cooling fin 30 shown in FIG. 2 is attached to one end of the heat pipe 27, and the cooling fin 30 has a propeller shape as shown in FIG. to occur. This airflow circulates hot air inside the machine and cold air outside the machine, thereby increasing the heat dissipation effect of the cooling fins 30 by using the cold air outside. In this embodiment, the cooling fins 30 are made of a material having good thermal conductivity, such as aluminum or copper. Furthermore, in order to further increase the heat conduction efficiency of the heat pipe 27, the side of the heat pipe 27 on which the cooling fins 30 are attached is sloped upward, as shown in FIG. This inclination angle θ
The heat pipe 27 is rotatably supported by the front and rear side frames of the machine frame (not shown) at an angle of about 1 to 10 degrees, preferably about 2 to 3 degrees, with respect to the horizontal. When this heat pipe 27 cools the recording sheet 5 and absorbs heat, the fluid within the heat pipe 27 is naturally heated. If the heat pipe 27 is horizontal, the heated fluid will not move smoothly within the heat pipe 27, causing the fluid to stagnate between the heating section and the cooling section, resulting in cooling. Although there is a problem of low effectiveness,
When the heat pipe 27 is tilted and the protruding end to be cooled is at the upper side as in this embodiment, the heating fluid rises and the cooling fluid descends, creating convection, and the movement is smooth, resulting in improved cooling efficiency. Rise. Due to these actions, the cooling section 2
The temperature of the recording sheet 5 cooled at 0° C. drops to about 60° C., which is below the softening point of toner. Even when stacked, there is no toner blocking phenomenon, and the sheets are never too hot to hold in your hand. Note that 24 indicates a paper discharge guide plate.

The recording sheet 5 on which the unfixed toner has been fixed by the thermal fixing device 1 is processed in the same manner as in the conventional device described above.
The recording sheet is transported to such a recording sheet cooling device 20. The recording sheet 5 that has been conveyed is cooled while
It is transported by a transport roller 22 whose surface is provided with an elastic body for forming a nip with the heat pipe 27 . Then, the recording sheet 5 that has been conveyed is transferred to a heat pipe 27.
The heat pipe 27 is cooled by cooling fins 30 and cold air circulated from outside the machine, and the recording sheet is efficiently transported by the transport roller 22 in contact with the heat pipe 27. cooled down.

A second embodiment shown in FIG.
There is no difference from the first embodiment except that the position of the conveyance roller 22 is upside down.

The third embodiment shown in FIG. 6 employs a conveyor belt 39 in place of the conveyor roller 22 of the first embodiment, and there is no difference from the first embodiment, including its function. In this embodiment, 40 and 41 are conveyor belts 3.
9 indicates a stretched roller.

The fourth embodiment shown in FIG. 7 is similar to the third embodiment except that the positions of the heat pipe 27 and the conveyor belt 39 are upside down.

[0016]

Effects of the Invention The present invention is as described above, and the cooling device of the present invention is provided with propeller-shaped cooling fins at the end thereof, and is rotatable for conveying and cooling the recording sheet. A heat pipe that is tilted and supported so that the attached end is on the upper side, and a conveyor roller or conveyor belt made of an elastic body that comes into contact with the heat pipe to form a nip are installed, so that the propeller-shaped heat pipe is installed. Air currents generated by the cooling fins can circulate air inside and outside the machine, increasing cooling efficiency, and since the ends of the heat pipes with the cooling fins are tilted upwards, the cooling fins of the heat pipes are The cooling effect can be further enhanced without increasing the number of sheets or the area thereof, and the recording sheets can be cooled satisfactorily, so that curling and blocking phenomena do not occur.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional view of a main part of the heat pipe according to the above embodiment.

FIG. 3 is a front view of the cooling fin of the embodiment same as above.

FIG. 4 is a perspective view of the heat pipe of the embodiment same as above.

FIG. 5 is a vertical sectional view of a main part of a second embodiment of the invention.

FIG. 6 is a vertical sectional view of a main part of a third embodiment of the invention.

FIG. 7 is a vertical cross-sectional view of a main part of a fourth embodiment of the present invention.

[Explanation of symbols]

1 Fixing device 20 Cooling device 21 Relay guide plate 22 Conveyance roller 24 Paper discharge guide plate 27 Heat pipe 30 Cooling fins 39 Conveyor belt 40, 41 Conveyor belt roller

Claims (3)

[Claims] 1. In a recording sheet cooling device that cools and conveys a recording sheet on which an image has been fixed by a heat fixing device, one of the cooling conveyance rollers is constituted by a heat pipe provided with cooling fins at one end, and the heat pipe is configured to rotate. A recording sheet cooling device characterized in that the recording sheet cooling device is freely movable and cools itself by rotating the heat pipe. 2. The recording sheet cooling device according to claim 1, wherein the heat pipe is supported such that the cooling fin side thereof is raised. 3. The recording sheet cooling device according to claim 1, wherein the cooling fins are propeller-shaped.