JPS59216172A - Heat fixing device - Google Patents

Abstract

PURPOSE:To shorten a preheating time greatly and improve the reliability of a temperature sensor by installing a plate type heating body in parallel to a guide member for a couple of fixing rolls, and providing the temperature sensor the surface of the heating body. CONSTITUTION:The plate type heating body 12 is arranged in parallel to the paper feed guide 4 for the fixing roll couple, and the temperature sensor 13 is fitted to its surface. When a supporting body 5 holding a toner image is conveyed, the heating body 12 generates heat to heat the toner image 6 to temperature above a softening point, so excellent fixation is performed. Then, the heat capacity set electric power of the heating body 12 are approximated to the characteristics of a heat roll 1 to control the surface temperature of the heat roll 1 through the sensor 13. Thus, the preheating time is shortened greatly and no toner sticks to the sensor 13, whose reliability is therefore improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention fixes a toner image formed on a support such as paper in an electronic copying machine, a printer, etc. between a pair of rolls, at least one of which has a heating mechanism, that rotates in pressure contact with each other. The present invention relates to a heat fixing device.

As one of the fixing devices in an image forming apparatus, there is a heat roll type which is equipped with a metal core with good heat conductivity and a heat source such as an infrared lamp, a halogen lamp, or a nichrome wire inside, a heating roll, and a pressure roll. Heat fixing devices are known. (For example, JP-A-49-81041, JP-A-53-145)
635, Japanese Patent Publication No. 54-19347, etc.) FIG. 1 is a schematic sectional view showing an example of this type of heat fixing device. In the case of this extreme heat fixing device, a sensor for controlling the surface temperature is generally installed on the surface of the heating roll. In FIG. 1 of the sensor, 1 is a heating roll, 2 is a pressure roll, 3 is a side plate that supports both rolls with bearings (not shown) at both ends, 4 is a paper feed guide, and 5 is a support for a toner image 6. The covering support is shown in each case. The heating roll 1 is formed by covering the outer peripheral surface of a metal hollow core 8, which has heat 17 inside, with a heat-resistant release layer 9'c. On the other hand, the pressure roll 2 is formed by covering the outer peripheral surface of a metal hollow core 10 with a heat-resistant elastic layer 11. Further, the heating roll 1 and the pressure roll 2 are pressed against each other by a pressing mechanism (not shown), and a predetermined contact width is formed at the pressed portion.

According to this configuration, by supplying power to the heat source 7, the maximum amount of heat necessary for fixing is supplied to the surface of the heating roll 1, the heating roll 1 and the pressure roll 2 are rotated in the direction of the arrow shown in the figure, and the support body 5 is rotated. The toner image 6 is conveyed along the paper feed guide 4 (in the red stamp direction shown in the figure), and the toner image 6 is fixed on the support 5.

According to the above fixing device, other heat fixing devices (oven type,
It is advantageous in that it requires fewer consumable horns and enables high-speed fixing compared to a flash lamp, etc.; The time it takes to reach 200°C (about 200°C)
Below is the preheating time (at least 1 minute).
There is a problem.

In order to shorten the preheating time, it is conceivable to reduce the heat capacity of the heating roll by, for example, reducing the diameter and thinning of the metal hollow core. However, in the case of levers, it is necessary to increase the pressing force (0.5 to IK (about 1/Cm)) in order to form a predetermined contact width to obtain the contact time necessary for fixing. As a result, the rigidity to withstand this pressing force is insufficient, and sufficient pressing force and contact width cannot be obtained in the longitudinal center of the hollow metal core, resulting in poor fixing. If the input power is increased, the overshoot of the temperature with respect to the set temperature will become large, and the time required for the temperature to stabilize at the set temperature will become longer, so that the preheating time will not be shortened as a result.

Therefore, in order to shorten the preheating time, for example,
-27550, 50-93658, 50-16
No. 1244, No. 51-9547, No. 54-83440
Although it is possible to use an auxiliary heat source as described in various publications such as No. 1, there are problems such as a fire occurring if the back side of the paper comes into contact with the preheater and poor thermal efficiency, so it has not been put into practical use. not present.

Therefore, there is a problem that the toner adhering to the surface of the heating roll 1 adheres to the surface of the temperature sensor 13, and the adhering toner damages the surface of the heating roll 1, further deteriorating the responsiveness.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat fixing device that can eliminate the drawbacks of the prior art described above, shorten the preheating time, and improve the reliability of the temperature sensor.

The heat fixing device of the present invention includes a pair of rotatable fixing rolls, at least one of which has a heat generating function on its surface and the other of which is covered with a heat-resistant layer so as to be elastically deformable. A pressure contact portion having a predetermined contact width is formed by pressing each other, and a support supporting a toner image is passed through the pressure contact portion, and when viewed from the conveyance direction of the support, In a heat fixing device including a guide portion, a plate-shaped heating element having a length corresponding to the axial length of the fixing roll is installed substantially parallel to the guide member, and It is characterized by a temperature sensor installed on the surface.

The details of the present invention will be explained below with reference to the drawings.

FIG. 2 is a schematic sectional view of a heat fixing device according to an embodiment of the present invention, and the same functional parts as in FIG. 1 are designated by the same reference numerals.

In Fig. 2, the heating roll 1 and the pressure roll 2 have the same structure and are arranged in the same way as in Fig. 1. It differs from the one shown in Fig. 1 in that it uses a metal hollow core.Also, in Fig. 2, a plate with approximately the same length as the heating roll is placed opposite the paper feed guide 4. A shaped heating element 12 is installed.

According to such a configuration, when the support body 5 holding the toner image 6 is conveyed in the direction of the arrow shown in the figure, the support body moves toward the paper feed guide 4.
, toward the pressure contact area between the heating roll 1 and the pressure roll 2. At this time, electric power is supplied to the plate-shaped heating element 12 to generate heat, and the toner image 6 on the support 5 is heated to a temperature higher than the softening point of the toner (usually 100 to 130 DEG C.). Therefore, since the toner image 6 is already in a semi-molten state due to the radiant heat of the plate-shaped heating element 12 before fixing, it is possible to perform good fixing without increasing the fixing pressure and the contact width of both U-ru. .

In this case, since the plate-shaped heating element 12 is close to the heating roll 1, the surface temperature of the plate-shaped heating element 12 is equal to or lower than the heat-resistant temperature of the heat-resistant release layer 8 formed on the surface of the heating roll 1.
For example, in the case of tetrafluoroethylene resin, it is necessary to set the temperature to 250° C. or lower, and also from the viewpoint of power consumption, it is necessary to set the surface humidity so that it is not too high. In addition, it is advantageous in terms of thermal efficiency to install the plate-shaped heating element 12 as close as possible to the paper feed guide 5 (preferably 20111 m or less). In other words, the surface temperature can be set low and power can be saved, but the plate-shaped heating element If the distance a between the body 12 and the paper feed guide 5 is too narrow, jam trouble will easily occur, so the distance a should be determined taking this into consideration.

Furthermore, depending on the heat capacity and the set power of the plate-shaped heating element 12, the temperature rise and temperature drop characteristics with respect to the heating time can be brought close to the characteristics of the heating roll 1.The temperature sensor 13 is installed on the surface of the plate-shaped heating element 120. Thus, the surface heights of the root-shaped heating element 12 and the heating roll 1 can be controlled simultaneously.

The present invention will be explained in detail below.

In FIG. 2, the heating roll 1 has an outer diameter of 27 mmφ,
Apply 20~3% Teflon (trade name) to the outer circumferential surface of a stainless steel pipe with a wall thickness of 1mm (but with shafts at both ends).
A fixing section with a length of 28 mm is coated uniformly to a thickness of 5 μI, and a halogen lamp capable of generating heat uniformly over a length of 280 mm is installed inside the hollow core 8.
0mm). The pressure roll 2 was formed by uniformly coating the outer peripheral surface of an aluminum alloy pipe with a silicone rubber layer. 8 with a width of 50 mm as the plate-shaped heating element 12
A vine plate heater was used to heat the samples uniformly over the entire length of the four sizes, and they were installed so that the spacing a was 7 m n+.

Then, the pressure roll 2 is pressed against the heating roll 1 with a linear pressure of 0.5K (J/cm), and the pressure roll 1 is rotated by a drive source (not shown) (the pressure roll 2 is in contact with the outer peripheral surface of the heating roll 1). (rotates due to frictional force), with a thickness of 10 mm as the support 5
Use 0μm plain paper (84 size) and set the paper feed speed to 150.
As a result of fixing under the conditions shown in Table 1 with a setting of mn+//sec, no jam trouble occurred and a high-quality fixed image without side offsets or fixing defects was obtained. Moreover, it was confirmed that fixing could be started 25 seconds after starting power supply to the halogen lamp 7 and the freight heater. Note that the pressure roll 2 has an outer diameter of 20 to 30 mm.
Although the φ and the pressing length were varied in the range of 260 to 280 mm, and the contact width was in the range of 3.0 to 3.5 mm, good results were obtained in all cases. Also, the toner is
(NO2) described in Example 1 of Specification No. 7-73033
Magnetic Table 1 Furthermore, when the temperature sensor 13 is installed on the surface of the plate-shaped heating element 12 and the temperature is set at 160°C, the relationship between the surface temperature of the plate-shaped heating element 12 and the heating time is as shown in Fig. 3. It has been found that the relationship between the surface temperature of the heating roll 1 and the heating time can be controlled as shown in FIG. 4.

As described above, according to the present invention, it is possible to significantly shorten the preheating time in heat roll type heat fixing, and to obtain a good fixed image, and furthermore, by controlling the surface temperature of the plate-shaped heating element, , it is possible to achieve the effect that the surface temperature of the heating roll can be indirectly controlled.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional heat fixing device, FIG. 2 is a schematic sectional view of a heat fixing device according to an embodiment of the present invention, and FIG. 3 is a relationship between the surface temperature of a plate-shaped heating element and heating time. FIG. 4 is a diagram showing the relationship between the surface temperature of the heating roll and the heating time. 1: heating roll, 2: pressure roll, 4: paper feed guide, 5
: Support, 6: Toner image, 12: Plate heating element, 13: Humidity sensor Figure 1

Claims (1)

[Claims] 1. A pair of rotatable fixing rolls, at least one of which has a heat-generating function on its surface and the other covered with an elastically deformable heat-resistant layer; A pressure contact portion having a contact width of In the heat fixing device, a plate-shaped heating element having a length corresponding to the axial length of the fixing roll is installed substantially parallel to the guide portion I, and the surface temperature of the plate-shaped heating element is maintained at a constant temperature. A heat fixing device characterized in that a sensor for controlling is installed, and the surface temperature of a fixing roll having a heat generating function is also controlled by this sensor.