JPH07271227A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device constituted so that wasteful power consumption is reduced and a temperature at the position of fixing is precisely controlled. CONSTITUTION:The fixing device is provided with a heat roller 10 and a backup roller 30. The roller 10 is provided with a hollow roller member which is turnable with respect to a device main body and the inside of the roller member is provided with a heating means 12 fixed to the device main body. Then, only a prescribed range of the inside circumferential surface of the roller member in the rotating direction thereof is heated by the heating means 12 extending over the almost whole area thereof in the axial direction. Besides, a detection means 20 detecting the temperature of the roller 10 is provided near a position corresponding to the position of the fixing action and outside the prescribed range of the inside circumferential surface of the roller member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a fixing device of an image forming apparatus using electrophotography, such as a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, as a fixing device for image formation using an electrophotographic method, a method of melting and fixing a toner image transferred to a recording paper by heating and pressurizing has been known. Such a fixing device generally has a pair of fixing rollers. The fixing roller is composed of a heat roller heated to a predetermined temperature and a backup roller provided so as to sandwich the recording paper.

The recording paper on which the toner image has been transferred passes through a nip (press contact portion: fixing operation position) so as to be sandwiched between a heat roller and a backup roller. At this time, the toner is melted by the heat of the heat roller, and a predetermined pressure is applied by the heat roller and the backup roller to fix the toner on the recording paper.

A halogen lamp is generally used as a heat source of the heat roller. The halogen lamp is provided inside the heat roller along the rotation axis of the heat roller, and radiates heat uniformly to the inner peripheral surface of the heat roller.

[0005]

The fixing device as described above has the following problems. In places other than the nip where the fixing action is performed, the heat radiated from the halogen lamp to the inner peripheral surface of the fixing roller is radiated from the outer peripheral surface of the fixing roller. That is, electric power is wasted without contributing to the fixing action. The halogen lamp consumes a considerable part of the power consumption of the image forming apparatus, and it is not preferable that the halogen lamp consumes waste power.

Further, in order to maintain the temperature of the fixing roller at the optimum temperature for the fixing action, a temperature sensor is usually provided. For accurate temperature control, it is preferable to detect the temperature of the fixing roller near the nip position (fixing position) and control the output of the halogen lamp. However, since the recording paper passes near the nip position, it is unavoidable to measure the temperature at a position separated to some extent. However, as described above, since the heat is constantly radiated from the surface of the fixing device and the heat taken by the recording paper is present, it is not possible to know the exact temperature at the nip position. Therefore, the output of the halogen lamp could not be perfectly controlled.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a fixing device capable of suppressing unnecessary power consumption and accurately controlling the temperature at the fixing operation position.

[0008]

Therefore, in the fixing device of the present invention, which has a heat roller and a backup roller, the heat roller has a hollow roller member rotatable with respect to the main body of the device. Inside the roller member, there is a heating means fixed to the apparatus body,
It is characterized in that the heating means heats the inner peripheral surface of the roller member over substantially the entire area in the axial direction of the roller member, and only in a predetermined range in the rotational direction of the roller member. Further, a detection means for detecting the temperature of the heat roller is provided near the position corresponding to the fixing operation position on the inner peripheral surface of the roller member and outside the predetermined range. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view showing a schematic configuration of a fixing device 1 as an embodiment of the present invention. Further, FIG. 2 is a schematic top view showing a state in which the heat roller 10 is supported by the main body by a supporting member provided in the main body. The fixing device 1 includes a heat roller 10 and a backup roller 30. The heat roller 10 has a hollow cylindrical shape. As shown in FIG. 2, the pair of supporting members 41 and 42 is a main body (fixing unit).
The heat roller 10 is rotatably supported by the pair of support members 41 and 42.

The gear 1 is attached to one end of the heat roller 10.
5 is fixed to the heat roller 10, and is driven by a driving mechanism (not shown) at a predetermined speed synchronized with the conveyance of the recording paper. Furthermore, a pair of support members 4
Second support members 51 and 52, which are also fixed to the main body, are provided on the outside of the units 1 and 42. The third support members 61 and 62 are attached to the second support member in a fixed state. The third support member, which will be described in detail later, is inserted into the heat roller 10 by a predetermined amount to fix the member arranged inside the heat roller 10.

As shown in FIG. 1, the backup roller 3
0 is arranged in a state of being urged by the heat roller 10 with the recording paper 2 interposed therebetween. The backup roller 30 is driven by the rotation of the heat roller 10. When the recording paper on which the toner image is transferred is sandwiched between the backup roller 30 and the heat roller 10, the heat roller 1
The toner is melted by the heat of 0, and a predetermined pressure is applied at the nip position (fixing action position) between the backup roller 30 and the heat roller 10 to perform the fixing process.

The inside of the heat roller 10 has a structure as shown in FIG. The halogen lamp 12 extends in the rotation axis direction of the heat roller 10 (direction perpendicular to the paper surface). The reflecting mirror 11 is provided so as to extend parallel to the halogen lamp 12. Both the halogen lamp 12 and the reflector 11
The length in the axial direction of the heat roller 10 is
The length corresponds to the width of the portion that contributes to the fixing action of. As shown in FIG. 2, the halogen lamp 12 and the reflecting mirror 11 are both fixed to the third supporting members 61 and 62. The reflecting mirror 11 has a parabolic shape in a plane perpendicular to the rotation axis of the heat roll 12. Further, the halogen lamp 12 is installed so as to be positioned at the focal point of the parabola drawn by the cross section of the reflecting mirror 11 in the plane perpendicular to the rotation axis of the heat roll 12. Light emitted by the halogen lamp 12 (heat)
Becomes almost parallel rays and irradiates a predetermined range on the inner peripheral surface of the heat roller 10. The predetermined irradiation range is located upstream of the nip position (fixing position) in the rotation direction of the heat roll 10.

The heat roll 1 is more than the predetermined irradiation range.
A thermistor 20 is provided near the nip position (fixing position) on the downstream side in the rotational direction of 0. Conventionally, the halogen lamp in the heat roller irradiates the entire inner peripheral surface of the roller with light. Therefore, the thermistor cannot be provided inside the heat roller 10. When a thermistor is installed outside the heat roller, the heat roller, the backup roller, and the recording paper sandwiched between them have their respective drive mechanisms, so it is not possible to install temperature detection means such as the thermistor near the nip position. It was Therefore, the temperature detected by the thermistor was the temperature at a position greatly apart from the fixing action position.

However, in the case of this embodiment, since the light of the halogen lamp is irradiated in a limited range, it is possible to install the thermistor in the vicinity of the fixing operation position outside the range. It was Moreover, since the inside of the heat roll is almost sealed, it is possible to obtain the effect of preventing dust from adhering between the thermistor and the inner peripheral surface of the roller.

FIG. 3 is a diagram for explaining the temperature control of the heat roller 10 configured as described above.

(A) shows that when the heat capacity of the heat roller 10 is assumed to be zero, according to the rotation of the heat roller 10,
A state where a predetermined point on the outer peripheral surface is changed by light irradiation of the halogen lamp 12 is shown. Since the heat capacity is assumed to be zero, the temperature rises when the predetermined point enters the light irradiation area of the halogen lamp, and the temperature returns to the initial value when the predetermined point exits the light irradiation area. The interval between the peaks in the graph corresponds to one rotation (one cycle) of the heat roller 10.

(B) is a graph showing a temperature change at a predetermined point on the heat roller 10 in consideration of the heat capacity of the heat roller 10 and the heat loss due to heat radiation. The temperature increased in the light irradiation area gradually decreases due to heat radiation.

(C) shows a temperature drop caused by heat being absorbed by the recording paper at the nip position (fixing position).

(D) is a combination of the graph of (b) and the graph of temperature drop at the fixing action position shown in (c). The temperature of the heat roller 10 that has risen in the light irradiation region gradually decreases due to heat dissipation, the heat is taken by the recording paper 2 at the fixing action position, and the temperature largely descends stepwise, and then gradually decreases again.

In order to ensure the fixing, the temperature at the fixing working position may be a predetermined fixing temperature. Therefore, in the graph of (d) above, the output of the halogen lamp may be controlled so that the temperature T when lowered at the nip position becomes the above-mentioned predetermined fixing temperature. As described above, in the present embodiment, since the thermistor is provided near the nip position, feedback control is performed so that the temperature detected by the thermistor reaches a predetermined fixing temperature, so that the nip point can be easily and accurately determined. The temperature can be controlled. Further, since the recording paper is conveyed by being sandwiched by the pair of rollers, the recording paper does not meander and the fixing process can be performed reliably.

[0021]

As described above, according to the fixing device of the present invention, since only the predetermined area of the heat roller on the upstream side of the fixing position is intensively heated, the thermal efficiency can be improved and the power consumption can be improved. Can be made smaller. Moreover, the heating range is immediately before the position where the fixing action is performed, and the fixing action is performed before the temperature of the heated portion is lowered by heat radiation, so that the efficiency is high. Further, as the heating means, the halogen lamp extending parallel to the rotation axis of the heat roller and the light collecting means for collecting the light generated by the halogen lamp in a predetermined range are provided, so that the halogen lamp is effectively generated. The heat can be utilized, and the output of the halogen lamp may be smaller than that of the conventional configuration.
Further, since the thermistor for detecting the temperature of the heat roller can be arranged near the fixing action position, accurate temperature control is possible.

[Brief description of drawings]

FIG. 1 is a schematic side view illustrating a configuration of a fixing device.

FIG. 2 is a schematic top view showing a mounted state of a heat roller.

FIG. 3 is a graph showing a temperature change of a heat roller.

[Explanation of symbols]

 1 Fixing Device 10 Heat Roller 11 Reflector 12 Halogen Lamp 20 Thermistor 30 Backup Roller 41, 42 First Support Member 51, 52 Second Support Member 61, 62 Third Support Member

Claims (7)

[Claims] 1. A heat roller and a backup roller, wherein the heat roller has a hollow roller member rotatable with respect to the apparatus main body, and is fixed inside the roller member with respect to the apparatus main body. A heating means, wherein the heating means heats the inner peripheral surface of the roller member over substantially the entire axial direction of the roller member, and only in a predetermined range in the rotation direction of the roller member, Fixing device. 2. The predetermined range is a range upstream of a fixing action position where the heat roller and the backup roller sandwich a recording paper in the rotating direction of the heat roller. Fixing device. 3. The heating means includes a halogen lamp extending parallel to the rotation axis of the heat roller, and a condensing means for condensing the light generated by the halogen lamp in the predetermined range. The fixing device according to claim 1 or 2. 4. The fixing device according to claim 3, wherein the light condensing means has a mirror member extending substantially parallel to the halogen lamp. 5. The mirror member is characterized in that a cross-sectional shape perpendicular to a rotation axis of the heat roller is a parabola, and the halogen lamp is located at a substantially focal point of the parabola.
The fixing device according to claim 4. 6. An inner peripheral surface of the roller member, in the vicinity of a position corresponding to the fixing action position and outside the predetermined range,
The fixing device according to claim 1, further comprising a detection unit that detects the temperature of the heat roller. 7. The fixing device according to claim 6, further comprising control means for controlling the heating means so that the temperature detected by the detection means becomes a predetermined temperature.