JP2001249562A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device equipped with shutter structure having a high heat insulating effect at a paper passing aperture part and capable of restraining power consumption at the standby time to be low. SOLUTION: This fixing device is equipped with a fixing roller incorporating a heat source, a pressure roller press-contacting with the fixing roller and a fixing frame covering both rollers and functioning also as a device outside frame, and a recording medium carrying an unfixed image is made to pass between both rollers along a paper passing guide. Then, the device is provided with a shutter capable of shielding the aperture part of the fixing frame through which the recording medium passes at a position not along the side wall of the fixing frame inside the aperture part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device which is mounted on an image forming and recording apparatus such as a copying machine, a printer, a facsimile and fixes an unfixed toner on a recording medium.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile, etc., as a fixing device for fixing an unfixed image formed by a toner made of a heat-meltable resin or the like transferred onto a recording sheet to the recording sheet. A fixing device of a heat roller type, in which a fixing roller having a built-in heater and a pressure roller are brought into pressure contact with each other to fix an unfixed toner image by heat and pressure while nipping and transporting a recording sheet by both rollers, is generally known. I have.

[0003] Further, in the image forming apparatus, high speed and high image quality as well as low power consumption are major technical issues.
After the power is turned on, the operation state of the image forming apparatus changes from warming up to printing, and then to the print standby mode. Efforts to reduce power consumption in each operation mode include reducing the time by using an immediate heat fixing method during warm-up, using low-temperature fixing toner during printing, and insulating the fixing device during standby.

FIG. 5 shows an example of a conventional heat roller type fixing device. In the fixing device shown in FIG. 5, the fixing roller 1 is installed on both sides of a frame 3 of the fixing device via bearings (not shown), and has a heater 4 built therein. The fixing roller 1 is heated by the heater (halogen lamp) 4, and the outer peripheral surface of the fixing roller is temperature-controlled and controlled to a predetermined fixing temperature. The pressure roller 2 has a shaft (not shown) movable vertically in a state of being mounted on a pressure arm, and is normally mounted in a state of being pressed against the fixing roller 1.

At the time of printing, the fixing roller 1 is driven to rotate in the forward direction of the sheet at the same peripheral speed as the speed of the sheet introduced into the fixing device, and the pressure roller 2 rotates following the rotation. The sheet conveyed from the transfer unit side is guided by the sheet passing guide 5, contacts the fixing roller 1 and passes through the nip, whereby the unfixed toner image is melted by heat and fixed on the sheet surface. During printing standby, the rotation of the fixing roller 1 and the pressure roller 2 is stopped, and the temperature of the outer peripheral surface of the fixing roller is controlled so as to maintain a predetermined standby temperature.

Here, the heat released from the fixing roller is externally transmitted through the frame 3 or through the paper passage opening 6 due to convection generated in the internal space of the fixing device, as indicated by arrows in FIG. Released to Approximately 40% of the power consumed by the fixing device during standby is intensively dissipated from the paper passage opening, so that measures to insulate the paper passage opening are most effective for energy saving. Further, as is apparent from the state of convection generated outside the fixing device as indicated by the arrow in FIG. 5, the upward flow generated by the heat released from the surface of the fixing roller 1 and transferred to the outside through the frame 3 It rises along the side wall surface, goes around to the upper surface of the frame, and rises.

In order to solve the above-mentioned problem of low power consumption, Japanese Patent Laid-Open No. Hei 7-6 discloses a technique of providing a sheet passing shutter during standby.
No. 4422. This is shown in FIG.
Here, a structure in which a shutter that can be opened and closed can be installed on a frame (exterior member) of a fixing device is described.

[0008]

However, in the above method, although the generation of the airflow flowing from the inside of the fixing device to the outside through the paper passage opening can be suppressed, the airflow rising along the shutter surface outside the fixing device can be suppressed. Is formed and heat transfer is promoted, so that there is a problem that a sufficient power consumption reduction effect cannot be obtained.

As shown in FIG. 6, the convection generated outside the fixing device in which the shutter structure is installed on the frame indicates that
The flow that has risen along the frame wall surface is
It can be seen that it flows along the surface and promotes heat transfer from the shutter to the outside.

In view of the above, the present invention proposes a method capable of reducing heat outflow caused by convection around a fixing device, which cannot be achieved by a conventional shutter structure, thereby suppressing the position and power consumption of a shutter having a high heat insulating effect. It is an object of the present invention to provide a fixing device that can perform the fixing.

[0011]

According to a first aspect of the present invention, there is provided a fixing roller having a built-in heat source, a pressure roller which is pressed against the fixing roller, and a fixing frame which covers the rollers and also serves as an outer frame of the apparatus. In a fixing device having a recording medium carrying an unfixed image between both rollers along a paper guide, and fixing the unfixed image to the recording medium by heat and pressure, the recording medium passes therethrough. A blocking member for shielding the opening is provided inside the opening of the fixing frame and not along the side wall of the fixing frame.

Further, the second invention of the present invention is characterized in that, in the first invention, the blocking member is rotatably supported.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a fixing device according to the present invention. In FIG. 1, a fixing device of the present invention includes a fixing roller 1 having a built-in heater 4, a pressure roller 2 pressed against the fixing roller 1,
A frame 3 which covers both rollers and also serves as an outer frame of the apparatus. The frame 3 has a paper passing guide 5 (5a to 5a-5) for passing paper on which an unfixed image is formed before and after the fixing roller 1.
d) is provided.

In the present invention, a position inside the paper passage opening 6 of the frame 3 through which the recording medium passes and not along the side wall of the frame 3, ie, here, the end of the paper passage guide 5 on the roller 1, 2 side. Further, a shutter 7 capable of blocking the paper passage opening 6 is provided. By providing the shutter 7 at a more appropriate position, it is possible to increase the thermal resistance value of the heat radiation path through the paper passage opening 6 and reduce the amount of heat radiation.

FIG. 1 also shows the state of convection in the fixing device of the present invention. As shown in FIG. 1, in addition to the effect of suppressing the heat flow that tends to flow out from the paper passage opening 6 as in the conventional case, the shutter 7 is arranged inside the side wall surface of the frame 3 and thus rises along the frame 3. It is possible to prevent the flowing flow from touching the surface of the shutter 7 and promoting heat transfer on the surface of the shutter 7.

Next, the structure of the shutter 7 will be described. The shutter 7 is formed of a heat-resistant resin having a low thermal conductivity, and is rotatably supported by a rotation support shaft 9 provided at a side end of the fixing roller 1 of the paper passing guides 5a and 5c. As the shutter opening / closing means, a solenoid, a stepping motor, a cam member, an elastic spring, a fluid valve, and others are used.
Electrical, magnetic, mechanical and fluid means are conceivable.

The shutter 7 is opened only during printing, and when the shutter is opened, the shutter 7 is arranged along the surface of the paper passing guides 5a and 5c.

At the time of printing, the recording sheet is guided by a sheet passing guide 5b on the pressure roller 2 side, enters between the rollers 1 and 2, and is discharged along the sheet passing guide 5c on the fixing roller 1 side. Therefore, during printing, the shutter 7 does not interfere with paper passing.
On the paper input side, the shutter 7 is attached to the paper passing guide 5a on the fixing roller 1 side. On the other hand, with respect to the paper ejection side, either the fixing roller 1 side or the pressure roller 2 side
5c may be used.

When the shutter is closed, the gap between the end of the shutter 7 and the guide 5 is small, and the higher the airtightness, the higher the heat insulating effect. Therefore, an elastic material such as a heat insulating sponge is attached to the end of the shutter 7. It is good to attach.

[Analysis] Next, in order to compare the effect of the fixing device of the present invention with a conventional example, evaluation was made by numerical analysis. The analysis conditions were as follows: the fixing roller surface temperature was kept constant at 175 ° C., and the ambient temperature was kept constant at 20 ° C., and heat and flow were calculated in consideration of heat transfer between components and heat transfer with air.

The members used for the analysis will be described. For the shutter 7, a 2 mm silicon sponge was attached on a sheet metal having a thickness of 0.5 mm. The upper paper passing guides 5a and 5c and the upper frame 3a are made of PET mixed with 50% glass fiber.
(PolyEthyleneTerephthalat
e), and the lower paper passing guides 5b and 5d and the lower frame 3
b is a sheet metal. The pressure roller 2 uses silicon rubber. The contact area between the pressure roller 2 and the fixing roller 1, that is, the nip was assumed to be 2 mm in width.

FIG. 2 schematically shows the convection around the fixing device when the shutter 7 is provided inside the frame 3 of the present invention, that is, near the fixing roller 1. FIG. 3 schematically shows a convection state of the fixing device when a conventional shutter structure (a shutter is provided outside the frame 3, that is, at a position apart from the fixing roller 1) is used as a comparative example.
Note that the fixing cover 8 covers the fixing device, so that a further heat insulating effect can be expected.

When these analysis results are compared with each other, it is confirmed in FIG. 3 that the flow rising from the lower side surface of the frame 3b rises along the surface of the shutter 7, thereby promoting heat transfer on the surface of the shutter 7. Was done. On the other hand, in FIG.
By adopting the shutter structure of the present invention, it has been confirmed that the flow resistance near the shutter 7 surface is increased, and the flow rising from the lower side surface of the frame 3b is prevented from flowing along the shutter 7 surface. Was. Therefore, the thermal resistance of the surface of the shutter 7 increases, and the amount of heat radiation is reduced.

Further, under the above conditions, the fixing roller 1
As a result of calculating the amount of heat radiation from the conventional example, the amount of heat radiation of the conventional example is 43.
In contrast to 0 W, the heat radiation amount of the present invention was 38.3 W, and the power consumption was reduced by about 11% as compared with the related art. In the case of the conventional technology using no shutter, the heat radiation amount is 4
The power consumption is 5.8 W, and the power consumption can be reduced by about 16%.

[Measurement] Next, the fixing device of the present invention was set to 30 ×
It was incorporated in a urethane board box of 30 × 55 cm (longitudinal direction of the fixing roller), and the power consumption of the fixing device during standby was measured. The measurement was performed in a test room where the surface temperature of the fixing roller was kept constant at 175 ° C. as in the analysis and the room temperature was controlled at 20 ° C.

The power consumption of the present invention is 51.1 W, compared to the power consumption of 54.8 W when the shutter structure is not provided in the paper passage opening 6, and the power consumption can be reduced by about 7%. . The power consumption when the shutter was provided on the outside was 53.6 W, which was about 5% lower than that of the present invention.

Further, the fixing device of the present invention was incorporated in a copying machine main body, and the power consumption of the fixing device during standby was measured. The measurement was performed at 175 ° C as in the analysis of the fixing roller surface temperature.
The test was performed by setting a copying machine in a test room maintained at a constant room temperature of 20 ° C.

The power consumption of the present invention is 72.6 W, compared to the power consumption of 78.3 W when the shutter structure is not provided in the paper passage opening 6, and the power consumption can be reduced by about 7%. . The power consumption when the shutter was provided outside was 76.4 W, which was about 5% lower than that of the present invention.

Although the numerical values are different between the analysis result and the measurement result, the effect that the provision of the shutter position inside the frame contributes to the reduction in power consumption can be understood from both results.

FIG. 4 shows another fixing device of the present invention. Since the structure of the fixing device is the same as that of FIG. 1, only the differences will be described here. The same members as those in FIG. 1 are denoted by the same reference numerals.

As in FIG. 1, the shutter 7 is used only during printing.
For example, it is opened by a solenoid, and both ends thereof are rotatably supported by a rotating shaft 9 provided on a side plate.
Here, to open and close the shutter 7 smoothly,
The adiabatic shutter and the support shaft 12 are rotatably joined, and an elastic spring 13 is attached so that the adiabatic shutter surface is arranged at a fixed position when the adiabatic shutter is closed.

In a general fixing device, the paper passing guide 5 attached to the paper discharge side has a shape such that the path narrows in the direction of travel of the recording paper, and the shutter is opened and closed through the paper discharge path. Is difficult. Therefore, the heat insulating shutter 7 is provided only in the paper passage opening 6 on the paper entry side. In the case of this configuration, the shutter 7 is disposed above the fixing device at the time of printing as shown by an arrow in the drawing, and does not hinder the sheet passing. Therefore, there is no problem even if the thickness of the member of the heat insulating shutter 7 is large.

An experiment was conducted by assembling the above-described configuration, that is, a case in which only one of the paper passing openings was blocked by an adiabatic shutter, incorporated in a copying machine. The power consumption of the present invention is 74.7 W, compared to the power consumption of 78.3 W when the shutter structure is not provided in the paper passing portion, and the power consumption can be reduced by about 5%. It was confirmed that the same heat-insulating effect as in the case of having was obtained.

If the material of the heat insulating shutter 7 is a thick heat insulating sponge, the heat resistance value of the heat insulating shutter 7 itself becomes larger than that shown in the above-described embodiment, and the heat insulating shutter 7 and the paper passing guide 5 are in close contact with each other. Since the performance can be easily increased, it is possible to obtain a greater heat insulating effect.

[0036]

According to the present invention, the heat flow flowing out through the opening can be suppressed, and the flow rising along the outer wall surface of the fixing frame can be prevented from being along the surface of the blocking member, thereby blocking the flow. Since heat radiation from the member surface can be prevented, the power consumption of the fixing device can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a fixing device of the present invention.

FIG. 2 is a diagram showing a state of convection in the fixing device of the present invention.

FIG. 3 is a diagram illustrating a state of convection in a fixing device provided with a conventional adiabatic shutter.

FIG. 4 is a diagram illustrating another example of the fixing device of the present invention.

FIG. 5 is a diagram illustrating a conventional heat roller type fixing device.

FIG. 6 is a diagram illustrating a fixing device provided with a conventional shutter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Fixing frame 4 Heater 5 Paper passing guide 6 Paper passing opening 7 Thermal insulation shutter 8 Fixing cover 9 Rotating support shaft 12 Support shaft 13 Elastic spring

Claims (2)

[Claims] 1. A fixing roller having a built-in heat source, a pressure roller pressed against the fixing roller, and a fixing frame covering both rollers and also serving as an outer frame of the apparatus, and an unfixed image is provided between the two rollers. In a fixing device for passing a recording medium carrying the recording medium along a paper guide and fixing an unfixed image on the recording medium by heat and pressure, wherein the fixing frame is located inside an opening of the fixing frame through which the recording medium passes. A fixing member for shielding the opening at a position not along the side wall of the fixing device. 2. The fixing device according to claim 1, wherein the blocking member is rotatably supported.