JPH08227240A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device which minimizes an amount of heat which is taken away by a fixing device and saves energy, and achieves satisfactory fixing. CONSTITUTION: The image forming device comprises the fixing device 13 of a heat roller system consisting of a fixing roller 6 and a pressure roller 7 and having a fixing cover 8 covering at least the fixing roller 6, and a carrying part consisting of guide plates 4 and 5 which guide transfer paper 1 with a toner image held on it to the fixing device 13. The device is equipped with a heating means 9 for heating the guide plates 4 and 5 or their atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an electrophotographic image forming apparatus used in a facsimile or the like and having a heat roller type fixing device.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus generally employs a heat roller method in which a toner image is transferred onto a transfer sheet and then the fixing device applies heat to the toner image to fix the toner image. Has been done. In this heat roller type fixing device, heat is applied to the toner image on the transfer paper with a heat roller or the like to melt the toner and fix the toner on the transfer paper. At this time, the toner is fixed by the temperature of the transfer paper or the toner itself. It is well known that there are differences in sex.
That is, the higher the temperature of the transfer paper or the toner, the better the fixability after passing through the fixing device. This is because the amount of heat taken by the transfer paper from the fixing unit is reduced. If the amount of heat taken from the fixing unit can be reduced, energy saving at the time of fixing can also be achieved. This energy saving is also an important issue in recent OA equipment. Therefore, for example, in Japanese Patent Application Laid-Open No. 61-135358, an auxiliary heating roller is provided upstream of the nip portion of the fixing device in addition to the heating roller of the fixing device and surrounds the fixing device and its conveying path. There is disclosed a fixing device which preheats the transfer paper by inserting it.

[0003]

However, in the above-mentioned conventional image forming apparatus (fixing device), the peripheral surface of the auxiliary heating roller is only brought close to the transfer sheet, and therefore the transfer sheet is preheated. There was a problem that the effect was not so good. Further, although it is known that a heat pipe is provided inside the fixing device, it is usually used to exhaust the heat to suppress the temperature rise of the fixing device and is not used as a preheating means. . So, this invention
An image forming apparatus having a fixing device capable of solving the above-mentioned conventional problems, suppressing the amount of heat taken by the fixing device as much as possible, achieving energy saving, and performing good fixing The task is to do.

[0004]

SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a heat roller type fixing device comprising a fixing roller and a pressure roller, and provided with a fixing cover for covering at least the fixing roller. In the image forming apparatus having a conveying unit including a plurality of guide plates for guiding the transfer paper carrying the toner image to the fixing device, a heating unit for heating the guide plate or its atmosphere is provided, According to a second aspect of the present invention, the heating means is a heat transfer means for moving the heat inside the fixing cover to the transport section. Further, in the third aspect, the heat transfer means has one end of the fixing cover. It is a heat pipe installed inside, and the other end is arranged in contact with the guide plate or integrated with the guide plate, and in claim 4, the transfer unit is at least,
The heat transfer means is composed of an upper guide plate on the side of the transfer paper on which the toner image is carried and a lower guide plate on the back side of the transfer paper, and the heat transfer means moves air from above the upper guide plate toward the upper guide plate. To form a flow, and in claim 5, as the heating means, a heater disposed in contact with at least one of the guide plates is adopted.

[0005]

Therefore, in claim 1, by the heating means,
Since the guide plate or its atmosphere is warmed, the transfer paper is warmed before entering the fixing device, and the amount of heat taken by the transfer paper from the fixing device is reduced. Further, in claim 2, the heat of the fixing device is efficiently used by moving the heat inside the fixing cover to the conveying section by the heat transfer means. Further, according to claim 3, one end of the fixing device is installed inside the fixing cover, and the other end of the fixing cover is arranged in contact with the guide plate, or a heat pipe as the heat transfer means integrated with the guide plate is used to heat the fixing device. Move efficiently and the transfer paper is warmed before entering the fusing device. Further, in claim 4, the heat transfer means forms an air flow from above the upper guide plate toward the upper guide plate, thereby warming the surface side of the transfer paper on which the toner image is carried, so that the toner temperature is increased. Rises. Further, in claim 5, the temperature of the guide plate easily rises even when the temperature of the fixing device is low by the heater, which is the heating means arranged in contact with at least one of the guide plates, and the transfer paper enters the fixing device. Warmed before.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a photosensitive drum 2 which is an image carrier
A transfer charger 3 is arranged as a transfer portion of the transfer charger 3 in the vicinity thereof. A transport unit A including an upper guide plate 5 and a lower guide plate 4 is provided on the downstream side of the transfer unit, and the fixing device 13 is disposed on the downstream side. The fixing device 13 includes a fixing roller 6 having a heater 12 built therein and a pressure roller 7 abutting against the fixing roller 6, which are surrounded by a fixing upper cover 8 and a fixing lower cover 10.

Then, as shown in FIG. 2, from the fixing upper cover 8 to the lower guide plate 4 through the non-sheet passing portion B,
A heat pipe 9 as a heating and heat transfer means is arranged in contact with these. A pair of paper discharge rollers 14 is arranged on the downstream side of the fixing device 13. In this configuration, the transfer paper 1 carries the toner image untransferred from the photoconductor drum 2 in the transfer charger 3 of the transfer unit, carries the unfixed toner image, and is sent to the fixing device 13 through the transport unit A. The transport unit A guides the transfer sheet 1 between the fixing roller 6 and the pressure roller 7 by the lower guide plate 4, and the transfer sheet 1 is given heat to fix the toner image.

In the carrying section A, the heat of the heat pipe 9 is transferred to the lower guide plate 4, and the lower guide plate 4 serves as a heat radiating plate. The temperature of the upper part of the fixing device 13 is usually 1
The temperature is 00 ° C, and the fixing upper cover 8 is also 60-100.
Although the temperature is close to 0 ° C., the ambient temperature of the lower guide plate 4 and its vicinity is the same as room temperature. Therefore, heat is transferred from the fixing upper cover 8 to the lower guide plate 4 via the heat pipe 9.
As a result, the temperature of the fixing upper cover 8 decreases, and the ambient temperature of the lower guide plate 4 and its vicinity rises. In this state, the temperature of the transfer paper 1 and the toner image carried on the transfer paper 1 rises as the transfer paper 1 passes through the transport section A, and the amount of heat taken by the transfer paper 1 and the toner image from the fixing roller 6 decreases.

Next, another embodiment will be described with reference to FIG. In the figure, the basic structure is the same as that of the above-mentioned embodiment, except that an opening 8a is provided in a part of the fixing upper cover 8 instead of providing the heat pipe 9, and this opening 8a is provided. The point is that the fan 15 is attached and the duct 16 leading to the upper guide plate 5 is arranged between the fixing upper cover 8 and the upper guide plate 5. The fan 15 and the duct 16 constitute heat transfer means. In this configuration, the heated air in the fixing upper cover 8 is conveyed to the vicinity of the upper guide plate 5 via the duct 10 by the rotation of the fan 15, and the upper guide plate 5 is warmed. This is less efficient than the embodiment of FIG. 1 in raising the temperature of the guide plate, but by blowing the air flow from above the upper guide plate 5 to the upper guide plate 5, heat above the guide plate 5 can be removed. You can eliminate the escape. Further, in this case, the side of the transfer paper 1 on which the toner image is carried is warmed, and there is also an advantage that the toner can be reliably preheated.

Next, still another embodiment will be described with reference to FIG. In the figure, the basic structure is the same as that of the above-mentioned embodiment, except that the lower guide plate 5 is provided with a heater 11 as a heating means instead of the heat pipe 9. With this configuration, the lower guide plate 5
Is heated directly by the heater 11, its heating efficiency is good,
Moreover, if a temperature detecting element is attached to the lower guide plate 5, it is possible to control the temperature of the lower guide plate 5.

Next, the temperature change of the fixing roller 6 in this embodiment will be described. First, FIG. 5 shows how the temperature of the fixing roller 6 decreases when the transfer paper 1 is continuously fed when the heater 11 is not provided. In the figure, the solid line indicates the temperature of the transfer paper 1 is 20 ° C., and the alternate long and short dash line indicates 30.
C., the chain double-dashed line is 40.degree. C., and as the temperature of the transfer paper 1 rises, the temperature decrease slows. In this condition, the set temperature of the fixing roller 6 is 180 ° C. and the heater 1 of the fixing roller 6 is set.
2 is always lit and settles down at about 160 ° C.

Further, when the heater 11 is provided and its capacity is sufficiently given, the temperature of the fixing roller 6 settles down to the set temperature as shown in FIG. 6, but when the first sheet passes, it is heated. The pressure roller 7 also takes away heat, and the temperature once drops. The amount of this drop varies depending on the temperature of the transfer paper 1 (toner) (each line is the same as in FIG. 5), but the temperature when it falls may be equal to or higher than the temperature that can maintain the fixing property shown by the broken line. As in this embodiment, by preheating the transfer paper 1 with the heater 11, it is possible to maintain the fixing property of the transfer paper 1 even if the temperature of the fixing roller 6 is lowered. The configuration itself can be further lowered.

[0013]

As described above, according to the first aspect, since the heating means for heating the guide plate or its atmosphere is provided, the transfer paper can be heated before entering the fixing device.
The amount of heat taken from the fixing device by the transfer paper can be reduced, and energy saving of the device can be achieved. Further, even if the amount of heat is small, good fixing can be performed, and the set temperature of the fixing roller can be lowered. Further, according to claim 2, since the heating unit is a heat transfer unit that transfers the heat inside the fixing cover to the transport unit,
The heat of the fixing unit can be efficiently used. Further, according to claim 3, the heat transfer means is a heat pipe having one end installed inside the fixing cover and the other end in contact with the guide plate or integrated with the guide plate, so that the heat transfer means is efficient. Heat can be transferred, and in particular, the temperature difference can be increased by bringing one end of the heat pipe into contact with the guide plate, which facilitates heat transfer and can efficiently raise the temperature of the guide plate.

According to a fourth aspect of the present invention, the guide plate comprises at least an upper guide plate on the side of the transfer sheet on which the toner image is carried and a lower guide plate on the back side of the transfer sheet.
Moreover, the heat transfer means forms an air flow from above the upper guide plate toward the upper guide plate, so that
The surface side of the transfer paper bearing the toner image can be warmed, and a sufficient preheating effect can be obtained. According to the fifth aspect, since the heating means is a heater arranged in contact with at least one of the guide plates, the temperature of the guide plate can be easily increased and the amount of heat taken from the fixing roller can be reduced. Since the setting temperature of the fixing roller can be set low by reducing the amount or preheating, the power can be saved and the energy saving effect can be obtained, and the temperature can be raised from the normal temperature to the setting temperature in a short time. Further, even when the fixing roller is not sufficiently warmed immediately after rising, the lower guide plate and its atmosphere can be heated, and stable preheating and fixability can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement configuration of a heat pipe according to claim 3;

FIG. 3 is a schematic configuration diagram showing an embodiment based on claims 2 and 4.

FIG. 4 is a schematic configuration diagram showing an embodiment according to claim 5.

FIG. 5 is a characteristic diagram showing a temperature change of the fixing roller during continuous sheet feeding.

FIG. 6 is a characteristic diagram showing a temperature change of the fixing roller when the lower guide plate is heated by a heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer paper 4 Upper guide plate 5 Lower guide plate 6 Fixing roller 7 Pressure roller 8 Fixing cover 9 Heat pipe (heating means: heat transfer means) 11 Heater (heating means) 13 Fixing device 15, 16 Heat transfer means

Claims (5)

[Claims] 1. A heat roller type fixing device comprising a fixing roller and a pressure roller and having a fixing cover covering at least the fixing roller, and a plurality of transfer papers carrying a toner image to the fixing device. An image forming apparatus comprising: a guide plate; and a conveyance unit, wherein the guide plate or a heating unit for heating the atmosphere thereof is provided. 2. The image forming apparatus according to claim 1, wherein the heating unit is a heat transfer unit that transfers heat inside the fixing cover to the transport unit. 3. The heat transfer means is a heat pipe having one end installed inside the fixing cover and the other end arranged in contact with the guide plate, or a heat pipe integrated with the guide plate. Item 2. The image forming apparatus according to item 2. 4. The transport section comprises at least an upper guide plate on the side of the transfer sheet on which the toner image is carried and a lower guide plate on the back side of the transfer sheet, and the heat transfer means includes the upper transfer plate. The image forming apparatus according to claim 2, wherein an air flow is formed from above the guide plate toward the upper guide plate. 5. The image forming apparatus according to claim 1, wherein the heating means is a heater arranged in contact with at least one of the guide plates.