JPH04340577A - Fixing device for copying machine - Google Patents

Abstract

PURPOSE:To make a temperature nearly even low over the entire width of a pressure roller with an easy construction, and to prevent hot offset, blocking and the wrinkle of a transferring paper from occurring by providing a cooling means pressured by a fixing roller having a heating source and cooling the pressure roller which is actuated when a second surface is copied. CONSTITUTION:A fixing device for a copying machine equiped with the fixing roller 1 having the heating source and the pressure roller 2 pressured by the fixing roller 1 is provided with the cooling means 11 to cool the pressure roller 2 actuated when the second surface is copied. The cooling means 11 is provided with a ventilator 13 opening on a position close to the pressure roller 2 on the upstream side of a fixing part in the carrying direction of the transferring paper, and a fan 14 is set inside the ventilator 13. In this case, the cooling means 11 cools the pressure roller 2 by ventilating the pressure roller 2 at copying time, and the hot offset or the blocking on a paper ejecting tray is prevented from occurring by this cooling. It is better to execute the cooling of the pressure roller 2 by the cooling means 11 when the second surface is copied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, and more particularly to an image forming apparatus for a copying machine capable of double-sided copying.

0002

2. Description of the Related Art Conventionally, as a copying machine capable of double-sided copying, a fixing roller 1 having a heating source 3 is used as shown in FIGS.
An image forming apparatus equipped with a pressure roller 2 that presses the fixing roller 1 and a thermistor 4 that detects the temperature of the fixing roller 1 is used. In such a copying machine, when copying the first side, as shown in FIG. 12, when the transfer paper 5 carrying the toner 6 passes between the rollers 1 and 2, it is heated and pressurized by them to form an image. 7 is formed. During the subsequent copying of the second side, the image shown in FIG.
Transfer paper 5 with new toner 6 on it is reversed as shown in
The image 7 is formed on the surface in the same manner as described above. During such second-side copying, hot offset, toner peeling off from the transfer paper in the paper ejection tray, or so-called blocking is likely to occur, so care must be taken to prevent this from occurring. Because the first
The transfer paper 5 after side copying has already passed through the fixing section, so it has a considerable amount of heat, and when it enters the second side copying process and reaches the fixing section in this state, further heat is added. Hot offset is likely to occur, and when the copied transfer paper is stacked on the paper output tray after being ejected, the toner on the transfer paper faces each other and has a large amount of heat, so blocking is likely to occur. There's a problem.

[0003] In addition to the temperature, pressure, and nip of the fixing roller 1, the temperature of the pressure roller 2 also plays an important role in fixing the image 7 on the transfer paper 5. That is, when the temperature of the pressure roller 2 is low, the amount of heat supplied from the back side of the transfer paper 5 decreases, resulting in poor fixing performance. Further, if the temperature distribution of the pressure roller 2 becomes non-uniform, the nip amount also becomes non-uniform, causing a problem that wrinkles and uneven fixing occur on the transfer paper 5. On the other hand, when copying the second side, which is performed subsequently, hot offset and blocking on the paper output tray are likely to occur as described above, and in the case of thin transfer paper 5, there is a problem that wrinkles are likely to occur if the temperature is too high. Therefore, the temperature of the pressure roller 2 is preferably lower than the normal temperature. Normally, the pressure roller 2 is often made of a silicone rubber layer or a fluorine rubber layer that has poor thermal conductivity, so if a small-sized transfer paper 5 with a width narrower than the pressure roller 2 is continuously passed through , the temperature of the paper passing section of the pressure roller 2 becomes lower,
The temperature in the non-sheet passing area tends to be high and non-uniform. As a result, there is a difference in the nip formed with the fixing roller 1, and after the small size transfer paper 5 passes, the large size transfer paper 5
When the paper is passed through, there are problems such as wrinkles appearing on the transfer paper 5 and uneven fixing properties.

0004

[Problem to be solved by the invention] Therefore, as a method that can solve such problems,
There is a device as disclosed in Japanese Patent No. 43, which is provided with a pressure means that can variably set the pressure force of a pressure roller,
The objective is to lower the pressing force when copying the second side compared to the pressing force when copying the first side. However, in such a device, the structure is complicated and expensive, and the pressing force and nip amount when copying on the second side changes, so the amount of heat applied is small, and while the fixing is performed reliably, the fixing roller There is a problem in that it is extremely difficult to set conditions to prevent a hot offset from occurring.

An object of the present invention is to solve the problems of the conventional image forming apparatus as described above, to provide a low temperature that is almost uniform over the entire width of the pressure roller with a simple structure, and to prevent offset and blocking from occurring. There is no need to provide a fusing device for copiers.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the invention according to claim 1 includes a fixing roller having a heat source and a pressure roller pressurized by the fixing roller. The fixing device of the copying machine is characterized in that a cooling means is provided for cooling the pressure roller that operates when copying the second side. Further, the invention according to claims 2 and 3 provides a fixing device for a copying machine that includes a fixing roller having a heat source and a pressure roller that applies pressure to the fixing roller, further comprising: a heat pipe that contacts the pressure roller; This heat pipe is characterized by having cooling fins and a fan that blows outside air onto the cooling fins.
It is designed to operate when copying. Furthermore, claim 4
The invention provides a fixing device for a copying machine that includes a fixing roller having a heat source and a pressure roller that applies pressure to the fixing roller, and a heat pipe that contacts the pressure roller and rotates as the pressure roller rotates. The heat pipe has a surface made of metal, and is characterized in that it is provided with a cleaning means for cleaning the surface of the heat pipe.

[0007]

[Operation] In the invention of claim 1 as described above, the pressure roller that is pressed against the fixing roller during second side copying is cooled by the cooling means, and the pressure roller is brought to a low temperature by this cooling, so that hot offset or ejection can be performed. Blocking in the paper tray is prevented. Claims 2 and 3 as above
In the invention, the pressure roller that is pressed against the fixing roller during second-side copying is cooled by a heat pipe, and this cooling keeps the pressure roller at a constant temperature, and when necessary, the fan is activated to apply cooling fins to the pressure roller. Cool by blowing air against the
In this way, the temperature of the pressure roller is prevented from rising, and occurrence of hot offset or blocking on the paper ejection tray is prevented. In the invention of claim 4 as described above, the pressure roller that is pressed against the fixing roller during second side copying is cooled by a heat pipe, and the pressure roller 2 is cooled to a constant temperature by this cooling. This prevents the temperature of the pressure roller from rising, prevents hot offset or blocking on the paper output tray, and cleans toner, etc. that has adhered to the surface of the heat pipe with a cleaning means, and improves heat conduction by the adhesion of toner, etc. pressure roller 2.
This prevents the image from being re-transferred.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In each of the embodiments shown below, the same reference numerals will be used to refer to the same parts as in the conventional image forming apparatus, and the explanation will be omitted, and the explanation will mainly be given to the different parts. In the embodiment of the invention of claim 1 shown in FIGS. 1 and 2, reference numeral 11 denotes a cooling means for the pressure roller 2, and this cooling means 11 is the pressure roller on the upstream side of the fixing section in the conveyance direction of the transfer paper 5. The air blower 13 has a duct 12 that opens at a position close to the air blower 2, and a fan 14 is installed inside the air blower 13. The cooling means 11 blows air to the pressure roller 2 to air-cool it during copying, and this cooling prevents occurrence of hot offset or blocking on the paper discharge tray. It is preferable that the pressure roller 2 be cooled by the cooling means 11 when copying the second side.

Next, in the embodiment of the invention according to claims 2 and 3 shown in FIGS.
It has a heat pipe 17 that is in pressure contact with the pressure roller 2 on the upstream side of the fixing section, and this heat pipe 17 has cooling fins 19 on the outer extension of its rotating shaft 18. A blower 21 is provided to blow air to the cooling fins 19, and the blower 21 has a blower box 23 having a duct 22 opening toward the cooling fins 19. A fan 24 is installed inside the blower box 23. The heat pipe 17 cools the pressure roller 2 during copying,
This cooling keeps the pressure roller 2 at a constant temperature,
When necessary, the fan 24 is operated to blow air to the cooling fins 19 to cool them, thus preventing the temperature of the pressure roller 2 from rising, thereby preventing the occurrence of hot offset or blocking on the paper output tray. . It is preferable that the cooling fins 19 be cooled by the fan 24 when copying the second side.

In FIG. 5, the overall width is L as shown in FIG.
, the temperature distribution in the pressure roller 2 whose paper passing portion has a width l is shown, and the temperature T1 is the temperature of the non-paper passing portion of the pressure roller 2 of a conventional image forming apparatus without the cooling means 16. T2
indicates the temperature of the paper passing section, and it can be seen that the temperature of the non-paper passing section is considerably higher than the temperature of the paper passing section. On the other hand, in this invention, the heat pipe 1 is operated without operating the fan 24.
When the fan 24 is cooled, the temperature becomes T3, and when the fan 24 is operated, the temperature becomes T4, and these temperatures T3 and 4 are almost uniform throughout the paper passing section and the non-paper passing section.

In this embodiment, in order to improve the releasability from the fixing roller 1, an oil coated felt 27 is used.
The oil in the oil sump 26 is applied to the fixing roller 1 and is made uniform by the metering blade 28 to prevent toner and paper dust from adhering to the fixing roller 1 as much as possible. Note that 29 indicates a cleaning blade.

Next, since the embodiment of the invention of claim 4 shown in FIG. Where it can be omitted, it will be omitted. 31 is pressure roller 2
This cooling means 31 has a heat pipe 32 that is in pressure contact with the pressure roller 2 by a spring 37, as in the previous embodiment, and the surface of this heat pipe 32 is made of metal. There is. And this heat pipe 3
2 cools the pressure roller 2 during copying, and this cooling cools the pressure roller 2 to a constant temperature, thus preventing the temperature of the pressure roller 2 from rising and preventing hot offset or discharge from the fixing roller 1. Blocking in the paper tray is prevented. It is preferable that the cooling fins 19 be cooled by the fan 24 when copying the second side.

FIG. 9 shows a heat pipe 32 of this embodiment.
The widths L, l and temperatures T1, T2 of the pressure roller 2 are the same as those in the embodiments of the invention of claims 2 and 3; The temperature T3 in the example is the temperature T3 through the paper passing section and the non-paper passing section.
It becomes almost uniform between T1 and T2.

This embodiment is provided with a cleaning means 33 for cleaning the surface of the heat pipe 32, and the cleaning means 33 in the embodiment of FIG. It has a felt 34 in contact with it, and instead of this felt 34,
A rotating brush 36 as shown in another embodiment of FIG. 7 may also be used. In this embodiment, an oil coated felt 27 is provided on the fixing roller 1 as in the embodiments of the invention according to claims 2 and 3.
Although oil is applied to the fuser roller 1 to prevent toner and paper dust from adhering to the fuser roller 1, these particles still offset the fuser roller 1 and wrap around the pressure roller 2. Toner and the like are cleaned by the heat pipe 32. If the toner, etc. that has adhered to the surface of the heat pipe 32 is left as it is, the thermal conductivity of the adhered portion will deteriorate, the effect of making the temperature uniform will be weakened, and it will be retransferred to the pressure roller 2. It is possible to do so. Furthermore, as shown in Figures 10 and 11, dirt 4
Considering the state in which 0 is concentrated and adhered to one place, the heat pipe 32 has a large diameter only in that part, and the other parts do not come into contact with the pressure roller 2 and do not function as a heat pipe. is possible. By the way, in this embodiment, a cleaning means 33 is provided, and a felt 34 or a rotating brush 36 is in contact with the heat pipe 32, and the surface of the heat pipe 32 is cleaned by these, thereby preventing such occurrence. It prevents

[0015]

Effects of the Invention The present invention is as described above, and the invention according to claim 1 is such that the pressure roller that is pressed against the fixing roller having a heat source during second side copying is cooled by the cooling means. The pressure roller is cooled to a low temperature by cooling, thereby preventing occurrence of hot offset or blocking on the paper discharge tray, and has the advantage that the structure is simple. The invention according to claims 2 and 3 cools the pressure roller that is pressed against the fixing roller during copying on the second side using a heat pipe, maintains the pressure roller at a constant low temperature, and operates the fan when necessary. Air is blown to the cooling fins to cool them, thereby preventing the temperature of the pressure roller from rising, thereby making it possible to prevent hot offset or blocking on the paper ejection tray. According to the fourth aspect of the invention, the pressure roller 2, which is pressed against the fixing roller during copying on the second side, is cooled by a heat pipe to maintain the pressure roller 2 at a constant low temperature. This prevents hot offset or blocking from occurring on the paper output tray, and the cleaning means cleans the toner etc. adhering to the surface of the heat pipe to prevent thermal conductivity from worsening due to adhesion of toner etc. , the temperature may become uneven, or the pressure roller 2
This has the effect of preventing re-transfer.

[Brief explanation of the drawing]

FIG. 1 is a partially longitudinal front view of an embodiment of the invention according to claim 1.

FIG. 2 is a longitudinal sectional side view of the main parts of the same as above.

FIG. 3 is a partially vertical front view of an embodiment of the invention according to claims 2 and 3;

FIG. 4 is a vertical sectional side view of the main parts of the same as above.

FIG. 5 is a temperature distribution diagram of the pressure roller same as above.

FIG. 6 is a partially vertical front view of an embodiment of the invention according to claim 4;

FIG. 7 is a side view of the main parts of the same as above.

FIG. 8 is a front view of a part of another embodiment same as the above.

FIG. 9 is a temperature distribution diagram of the pressure roller same as above.

FIG. 10 is an explanatory diagram of one phenomenon that occurs when the cleaning means is removed from the same as above.

FIG. 11 is a side view of the heat pipe same as above.

FIG. 12 is an explanatory diagram of this type of fixing device when copying the first side.

FIG. 13 is an explanatory diagram when copying the second side of the same as above.

[Explanation of symbols]

1 Fixing roller 2 Pressure roller 5 Transfer paper 7 Image 11, 16, 31 Cooling means 12, 22 Duct 13, 21 Blower 14, 24 fan 17, 32 Heat pipe 19 Fin 33 Cleaning means

Claims (4)

[Claims] 1. In a fixing device for a copying machine, which includes a fixing roller having a heat source and a pressure roller that applies pressure to the fixing roller, cooling means for cooling the pressure roller that operates when copying a second side. A fixing device for a copying machine, characterized in that it is provided with. 2. A fixing device for a copying machine comprising a fixing roller having a heat source and a pressure roller that applies pressure to the fixing roller, wherein a heat pipe is provided in contact with the pressure roller, and the heat pipe is A fixing device for a copying machine, comprising cooling fins and a fan that blows outside air onto the cooling fins. 3. The fixing device for a copying machine according to claim 2, wherein the fan operates during copying on the second side. 4. A fixing device for a copying machine comprising a fixing roller having a heat source and a pressure roller that applies pressure to the fixing roller, wherein a heat roller that contacts the pressure roller and rotates as the pressure roller rotates. 1. A fixing device for a copying machine, comprising a pipe, the surface of the heat pipe being made of metal, and a cleaning means for cleaning the surface of the heat pipe.