JP2944282B2 - Heat roller fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, by the fixing roller and this pressure contact rotating pressure roller, while conveying the recording material carrying the toner image, the heat roller fixing device for thermally fixed on the recording material the toner image It is about.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic system such as a copying machine, an efficient heat roller fixing device is often used in order to fix a toner image on a recording material.

As shown in FIG. 16, one example of a conventional heat roller fixing device is a fixing roller 11 containing a heating source such as a halogen lamp 13 and a pressure roller having an elastic layer pressed against the fixing roller 11. The fixing is performed by pressing and heating the toner image P onto the transfer material P via the fixing roller 11 with heat from a heating source.

[0004]

In such a conventional heat roller fixing device, it is desirable to make the temperature distribution in the longitudinal direction of the fixing roller as uniform as possible, but such control is actually difficult. .

For example, since both ends of a fixing roller containing a heat source have openings, heat escapes from the openings and the temperature at both ends of the roller tends to be low. For this reason, especially at the time when the fixing operation has just started from the standby state before the fixing, the fixing property becomes insufficient at both ends of the roller.

Further, if the size of the recording material to be passed is smaller than the roller length, heat is accumulated on the roller surface (non-sheet passing portion) through which the paper does not pass, and the roller temperature rises abnormally. (Hereinafter referred to as “non-sheet passing portion temperature increase”). For this reason, the separation claw, the cleaning unit, the release agent applying unit, etc., which are arranged in contact with the peripheral surface of the roller, are thermally damaged in the temperature raising unit.

SUMMARY OF THE INVENTION The present invention solves the problems of the conventional apparatus, and does not cause a temperature drop at the end of the roller when the fixing device enters the fixing state from the standby state. An object of the present invention is to provide a heat roller fixing device that does not cause excessive temperature rise in a non-sheet passing portion.

[0008]

According to the present invention, an object of the present invention is to provide a recording medium carrying a toner image by a pair of nipping and conveying members.
A roller and a heater for heating at least one of the pair of rollers.
And the amount of heat generated per unit length is large near the paper passing standard.
The first heater and the heating value per unit length are
A second heater large in an area deviated from the vicinity of
Control means for controlling lighting of the heater and the second heater;
In the heat roller fixing device having
During the fixing operation standby state, a small number of the pair of rollers
A table of the area that is out of the vicinity of at least one roller
The second heat so that the surface temperature becomes higher than near the paper passing reference
The first heater is turned on during the fixing operation.
Is achieved by turning on .

[0009]

According to the present invention, by performing control using such a heater, the roller immediately after the standby state is copied.
Is higher in a region outside the vicinity of the paper passing reference, so that the temperature drop due to the heat radiation from the opening at the end face of the roller is compensated, and the fixing property is secured. During the copying operation, the roller temperature is controlled by the first heater.
Even when passing small-size paper, since the heat distribution of the first heater is equal to or smaller than the vicinity of the paper passing reference in the above area ,
The amount of excess heat accumulated in the area is reduced by the heat radiation from both ends of the roller, and as a result, the temperature rise of the non-sheet passing portion is suppressed to a level that does not cause a problem. Thus, when fixing, the recording material
Stable fixability is obtained regardless of the size of

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a fixing roller,
A heat-resistant and highly releasable material such as fluororesin or silicon rubber is applied to a single-layer or multi-layer coat on a hollow core having good thermal conductivity such as aluminum or iron. 2
Is a pressure roller that rotates by pressing against the fixing roller, has an elastic layer, and forms a nip portion by pressing against the fixing roller 1.

Inside the fixing roller 1, two halogen lamps 3 and 4 are provided as heaters, and the temperature is controlled to a predetermined temperature by a temperature control element 5 in contact with the outer peripheral surface of the fixing roller 1. Separate claws, temperature fuses, oil (release agent) applying means, cleaning means, and the like are also provided on the outer peripheral surface of the fixing roller 1 as necessary.

FIG. 2 is a sectional view of such a fixing device, in which only the fixing roller 1 is shown in cross section. In this example, a system is adopted in which the paper as the recording material is passed regardless of its size, with one side passing the reference line indicated by the arrow L in the drawing. Paper). As schematically shown in the drawing, the first heater 3 has a smaller amount of heat distribution on the non-sheet passing reference side (on the side opposite to the reference line L) than the other portions. Conversely, the two heaters are set so that the heat distribution amount on the non-sheet passing reference side is larger than the other portions. The extent to which the amount of heat distribution is regulated is determined based on the temperature distribution that appears on the roller surface when each heater is used alone. The roller surface temperature distribution is shown in FIGS. In the case where the first heater is used alone, as shown in FIG.
The roller surface temperature becomes lower than other parts. On the other hand, in the case of the second heater alone, the heat distribution is set such that the temperature is higher at the non-sheet passing end portion than at other portions as shown in FIG. The total power of the two heaters is, of course, within the allowable power.

Next, control of the two heaters 3 and 4 composed of such a combination will be described.

When the power of the copying machine is turned on, power is supplied to both heaters 3 and 4 and the temperature control element 5 is turned on.
However, power supply is continued in principle until a predetermined temperature is detected (at startup).

When the control element 5 detects a predetermined temperature, the first heater 3 is turned off and the second heater 4 alone controls to maintain this temperature. This is a so-called standby state. When the copy button is pressed, the second heater 4 is turned off, and the first heater 3 controls the fixing roller 1 to a predetermined temperature during copying. After the copying is completed, the process returns to the standby state again, and the temperature of the fixing roller 1 is controlled only by the second heater 4.

FIGS. 5 to 7 show how the temperature distribution in the longitudinal direction of the fixing roller changes by the above control. In the standby state after startup, the fixing roller 1
Is temperature-controlled by the second heater 4, the larger amount of heat distribution at the end compensates for the amount of heat radiation from the end face, and as a result, FIG.
As shown in (2), the temperature distribution of the roller is slightly higher at the end than at the center. When copying is started on a large-sized sheet of paper from such a state, the temperature control is started by the first heater 3 as described above, so that the temperature at the end portion is lower than that at the center as described in FIG. There is a tendency. See FIG. But,
Since the temperature at the start is increased at the ends, the fixing failure does not occur at both ends immediately after the start of copying as seen in the conventional example. In the case of continuous copying, the temperature of the end portion decreases as the number of sheets advances. However, since the entire fixing device including the pressure roller 2 warms, even if the temperature of the end portion decreases to some extent, the fixing is performed. Sex is well compensated. Therefore, there is no problem with the fixing property in a large-size copy.

Next, when copying is performed on small-sized paper (especially continuous copying), excess heat tends to accumulate in the non-sheet passing portion. Since the heat distribution is smaller than the other parts on the non-sheet passing side, the amount of heat accumulated along with the heat radiation from the roller end surface is much smaller than that of the conventional example,
Therefore, the temperature rise in the non-sheet passing portion remains within an allowable range. See FIG. Therefore, thermal damage to the separation claw provided on the outer peripheral portion of the fixing roller does not occur.

<Experimental Example 1> Fixing roller; 1.5 mm Alumi metal core coated with PTFE; pressure roller; 5 mm thick silicon rubber layer First heater; Paper passing side 5
0 mm has a smaller amount of heat distribution by about 20% than that of the center. Second heater;
0 mm has a heat distribution about 50% larger than the center. Control temperature Tc; 180 ° C. When the temperature distribution of the fixing roller was measured under these conditions,
During standby, the end on the non-paper passing reference side is about 10 ° compared to the center.
It was as high as C.

When 100 sheets of A3 size paper were passed from this state, the temperature on the non-sheet passing reference side finally became lower by about 15 ° C. than the central part. There was no problem from the 1st sheet to the 100th sheet.

Further, when 250 sheets of B5 size paper are continuously fed vertically from the standby state, the maximum temperature in the non-sheet passing area on the non-sheet passing reference side is about 230 ° C. No thermal damage occurred.

<Comparative Example 1> The distribution of heat distribution of the heater with respect to the above-described fixing, pressure roller, and set temperature was compared as follows. First heater; heater having a light emitting portion of 300 mm, which is 20% larger than the portion of the heat distribution amount on the non-sheet passing reference side of 50 mm. Second heater; heater having a light emitting portion of 300 mm and having a substantially uniform heat distribution in the longitudinal direction. When the temperature distribution was observed according to the same sequence as in the above embodiment, the temperature of the end portion was about 10 ° compared to the center during standby, as much as heat was released from the end face.
Low near C.

When the A3 size paper is continuously fed, although the amount of heat distribution at the end of the first heater is large, a slight decrease in the temperature is observed on the way, but the temperature distribution is almost uniform, and there is no problem in the fixability. As can be seen from this, if the temperature of the end portion is low during standby, it is essential to increase the heat distribution amount of the first heater at the end portion.

However, when the B5 paper is continuously fed in the longitudinal feed, the amount of heat distribution at the end of the first heater is large, so that the temperature rise in the heater paper passing area exceeds 260 ° C. Thermal deformation was observed in the separation claw and the like in contact with the area.

<Comparative Example 2> The same fixing and pressing roller pair as in Experimental Example 1 was used, and the heater having the following heat distribution was used. The first heater; the light emitting portion is 300 mm, and the heat distribution amount is smaller by about 20% on the non-sheet passing reference side 50 mm than the central portion (the same heater as the experimental example). The second heater; An experiment was performed in the same sequence as in the above example using the heater described above, and the temperature distribution on the roller surface during standby was almost uniform. Was.

Thereafter, when A3 size continuous paper was passed, the fixing ability of several sheets at the initial stage was insufficient on the non-paper passing reference side. This is because the heat is rapidly taken away at the start of paper passing and the temperature drops greatly, whereas the amount of heat distribution is smaller than that at the center, so that the supply of heat to the rollers cannot be completed in time. However, in the case of B5 longitudinal continuous paper passing, the temperature rise in the non-paper passing area was 230 ° C. as in the experimental example, and there was no problem.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG.

Although the cross-sectional structure of the fixing device is the same as that of FIG. 1, in the present embodiment, the center line of the paper in the longitudinal direction is substantially the predetermined value at the center of the roller regardless of the size of the paper. This shows a case where a so-called center paper passing standard system that passes through a line is adopted. Therefore, the first heater 3 is set such that the heat distribution is substantially symmetrical with respect to the paper passing reference line and the amount of distributed heat is higher at the center than at both ends, as schematically shown in the drawing. ing. On the other hand, secondly, the heater 4 is set so that the amount of heat distribution at both ends is larger than that at the center. When these heaters 3 and 4 are used alone for the fixing roller, the temperature distribution appearing on the roller surface at the time of saturation is shown in FIGS. As shown in FIG. 9, the first heater 3 has a temperature distribution in which both ends are lower than the center. On the other hand, in the second heater 4, as shown in FIG. 10, both ends show a higher temperature distribution than the center. In this example, it is necessary to use a heater exhibiting such a temperature distribution. The control when such a heater is used is performed in the same manner as in the above example.

FIGS. 11 to 13 show the effect of the heater and the control on the temperature distribution.

The temperature distribution in the standby state after the start-up of the apparatus is controlled by the second heater 4 as shown in FIG. 11, so that the temperature distribution at both ends is higher than at the center. When continuous copying of A3 size paper is started from this state, the temperature at both ends gradually decreases (FIG. 12).
However, since the temperature at both ends is high in the early stage of paper passing, there is no problem in the fixing performance including the center. In the latter half, there is sufficient fixing device. There was no problem. When B5 size paper is continuously copied, the temperature of the non-sheet passing areas formed at both ends increases (see FIG. 13), but the heat distribution amount of the first heater is originally set to be small at both ends. Therefore, the temperature rise in the non-sheet passing portion, in combination with the heat radiation from the roller end surface, remains within a range that does not pose a practical problem. Therefore, there is no influence on the separation claw and the like.

<Experimental Example 2> The fixing and pressure rollers were used in Experimental Example 1.
The same as was used. The first heater has a light emission length of 300 mm and has a large amount of heat distribution of about 20% at both ends 70 mm each on both sides of the paper passing reference line. The second heater has a light emission length of 320 mm and each 60 mm both ends compared to other parts. The heat distribution is about 50% larger. Control temperature: 180 ° C. When the temperature distribution on the fixing roller was observed under the above conditions, the temperature at both ends was higher by 15% ° C. than in the center during standby. When A3 size paper was continuously fed in this state, a steady temperature distribution was obtained for about 60 sheets. At that time, the temperature at both ends was lower than that at the center by about 10 ° C. There was no problem in the early stage of the paper and the late stage of the paper passing. On the other hand, when the B5 size paper was passed vertically and continuously from the standby state, the temperature in the non-sheet passing area was 240 ° C., and there was no thermal damage to the nails and the like.

<Third Embodiment> Up to the above example, two heaters were built in the same fixing roller. However, in this embodiment, an example in which one heater is built in each of the upper and lower parts is shown in FIGS. This will be described with reference to FIG. In this example, the central reference sheet passing is used as in the above example.

FIG. 14 is a cross-sectional view of such a fixing device, in which both the fixing roller 1 and the pressure roller 2 are made of a hollow metal core, and have heaters 3 and 4 respectively built therein. Except for this point, it is the same as the above example. FIG. 15 is a cross-sectional view, in which the temperature control element 5 (thermistor or the like) is located substantially at the center of the fixing roller 1 in the longitudinal direction. The amount of heat distribution is set large. On the other hand, the heater 4 in the pressure roller 2 is set so that the amount of heat distribution is higher at both ends than at the center. Further, looking at the temperature distribution at the time of saturation of the roller surface with respect to each of the heaters 3 and 4, when the fixing roller has a lower temperature distribution at both ends, the pressure roller has a lower temperature distribution. Both ends are set to be higher. In the fixing device having such a setting, the temperature distribution of the fixing roller 1 is low at both ends and the pressure roller 2 is high at both ends during the standby state as described above. However, in the initial state of paper passing, the temperature at both ends of the pressure roller 2 is high, so that sufficient fixing property can be obtained. Absent. On the other hand, when the small size paper such as B5 is passed after the standby, the amount of heat distribution at both ends of the first heater is originally small, so that the temperature rise remains within a range where there is no practical problem.

<Experimental Example 3> Fixing roller; pressure roller provided with 1 mm thick silicon rubber layer of 2 mm aluminum core; 1.5 m above aluminum core at 3 mm
a first heater provided with a silicon rubber layer having a thickness of m; having a light emission length of 320 mm in the fixing roller; In the roller, it has a light emission length of 320 mm, and the heat distribution amount is about 40% larger at each end of 80 mm than at the center. Control temperature: 170 ° C. When the temperature control element 5 in contact with the fixing roller 1 detects the control temperature (170 ° C.) using the two heaters 3 and 4, the control temperature is maintained using the two heaters 3 and 4. ON / OFF as needed, and control is performed only by the first heater 3 during copying.

In this control, the temperature of the surface of the fixing roller 1 during standby was lowered by about 5 to 10 ° C. because the amount of heat from the first heater 3 was small especially at both ends. On the other hand, the surface temperature of the pressure roller 2 was higher than the center by 15 ° C. or more at both ends because of the great influence of the second heater 4.
When continuous copying is started on A3 paper in this state, the surface temperatures of the fixing roller 1 and the pressure roller 2 are both lower than those in the standby state. Since the temperature of the roller 2 is high at both ends (even if the temperature of the fixing roller 1 is low at both ends), there is no problem in the fixing property, and the whole system including both the rollers 1 and 2 is warmed in the latter half of the sheet passing. We did not interfere. If B5 paper is passed vertically and continuously from standby, the first heater 3
Since the amount of heat distribution at both ends was small, the temperature rise was 235 °, which was not a problem.

Although the heater is provided inside the roller in the above examples, the present invention can be applied to a so-called external heating system in which the heater is provided outside the roller.

[0038]

As described above, according to the present invention,
A pair of rollers for nipping and transporting a recording material carrying a toner image
And a heater for heating at least one of the pair of rollers.
The amount of heat generated per unit length is large near the paper passing standard.
Heating amount per heater and unit length is near the paper passing standard
A second heater which is larger in an area outside of the first heater and a first heater
And control means for controlling lighting of the second heater.
In the heat roller fixing device, the control unit controls the fixing operation.
In the operation standby state, at least one of the pair of rollers
Surface temperature of the area of one of the rollers outside the standard
Above the second heater so that
Turns on and only the first heater above is turned on during the fixing operation
As a result, it is possible to secure the fixability when passing large-size paper, prevent the temperature of the non-paper passing portion from rising when passing small-size paper, and to determine the size of the recording material and the number of continuous fixing when fixing.
Resulting in a stable effect of Ru to give the fixability was that not suppressed non-sheet passing portion Atsushi Nobori matter.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the apparatus in FIG. 1;

FIG. 3 is a diagram of a temperature distribution appearing on a roller surface when only a first heater is used in the apparatus of FIG. 1;

FIG. 4 is a diagram of a temperature distribution appearing on a roller surface when only the second heater is used in the apparatus of FIG. 1;

FIG. 5 is a diagram of a temperature distribution showing a change in the surface temperature of the fixing roller of the apparatus shown in FIG. 1 (during standby).

6 is a diagram of a temperature distribution showing a change in the surface temperature of the fixing roller of the apparatus shown in FIG. 1 (during large-size paper copying).

FIG. 7 is a diagram of a temperature distribution showing a change in surface temperature of the fixing roller of the apparatus shown in FIG. 1 (during small-size paper copying).

FIG. 8 is a sectional view of the device of the second embodiment.

FIG. 9 is a diagram of a temperature distribution appearing on the roller surface when only the first heater is used in the apparatus of FIG. 8;

FIG. 10 is a diagram of a temperature distribution appearing on the roller surface when only the second heater is used in the apparatus of FIG. 8;

11 is a diagram of a temperature distribution showing a change in surface temperature of the fixing roller of the apparatus shown in FIG. 8 (during standby).

FIG. 12 is a diagram of a temperature distribution showing a change in the surface temperature of the fixing roller of the apparatus shown in FIG. 8 (when copying large-size paper).

13 is a diagram of a temperature distribution showing a change in the surface temperature of the fixing roller of the apparatus shown in FIG. 8 (during small-size paper copying).

FIG. 14 is a side view of the third embodiment device.

FIG. 15 is a sectional view of the device of the third embodiment.

FIG. 16 is a sectional view of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 First heater 4 Second heater 5 Temperature control element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-185482 (JP, A) JP-A-62-223674 (JP, A) JP-A-64-84271 (JP, A) 70258 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/20 G03G 15/20

Claims (1)

(57) [Claims] 1. A recording material carrying a toner image is nipped and conveyed.
Heat a pair of rollers and at least one of the pair of rollers
Heater that generates heat per unit length with paper passing standards
Nearly large first heater and heating value per unit length
A second heater that is large in an area deviating from the vicinity of the paper passing standard;
A control means for controlling lighting of the first heater and the second heater
A heat roller fixing device having a step
When the fixing operation standby state is set,
An area outside the vicinity of at least one of the rollers
So that the surface temperature of
The first heater is turned on during the fixing operation.
A heat roller fixing device characterized in that only the light is turned on .