JPS62253182A - Fixing device - Google Patents

Abstract

PURPOSE:To uniform the temperature distribution of the surface of a heat roller and to obtain safe, stable fixation characteristics by setting the temperature of the heat roller on a reference position side to a temperature gradient which is 30-100% higher than the other side. CONSTITUTION:The heating rate of the internal heater H1 of the heat roller of a fixing device where paper is fed based on one side P position is set to the temperature gradient which is 30-100% higher at the side of the position P than at the other end. Consequently, when the form of small size is fed, the surface temperature of a paper nonfeed side roller is prevented from rising abnormally and when the temperature of the paper nonfeed side drops owing to the feeding of a form of large side, a copying speed is only switched to a slow speed. Thus, the temperature distribution of the roller surface is uniformed and safe, stable fixation characteristics are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fixing device, and more particularly to a fixing device applicable to copying machines, facsimile machines, various printers, and the like.

(Prior Art) A so-called one-sided reference type fixing device is known in which the reference position when passing a sheet carrying a toner image is set at one end of the heat roller in the longitudinal direction of the shaft. The heat roller used for this purpose is, for example, as shown in FIG. 3, and is heated by a heater built into the heat roller. In the diagram, the code A is A4 horizontal size, and the code B is B
4 horizontal size, symbol C indicates a sheet passing area from a reference position P set at the left end, for example, for a sheet of A3 horizontal size.

The luminescence distribution of this old heater is as shown in Figure 2, and the luminescence rate is in the range of TI = 15 to 30% compared to the center in the region of length L1 = 30 to 1100II1 at both ends of the luminescence length. In other words, the temperature is set to be high, and the temperature distribution is symmetrical.

However, regarding a heat roller that exhibits such a luminescence distribution,
When passing small size sheets, heat is taken away from the reference position P side, which is the paper passing section, so temperature rise is not a problem.
The temperature on the side opposite to the reference position, which is the non-traffic paper portion, may rise too much and cause, for example, damage to the bearing or other problems.

(Objective) Therefore, an object of the present invention is to provide an improved fixing device that can uniformize the temperature distribution of the heat roller during passing of small size sheet 1 and obtain safe and stable fixing performance. be.

(Structure) In order to achieve the above object, the present invention relates to the temperature distribution of the heat source installed in the heat roller, and the temperature at the reference position when paper is passed through the heat roller is set to 3.
It is characterized in that it is set to have a temperature gradient that increases from 0 to 100%.

Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

In the present invention, for example, as shown in Figure 1, the light emission distribution (heat generation distribution) before the heater is set to a temperature gradient where the light emission rate is 72 = 30 to 100% higher on the reference position IF side when paper is passed than on the opposite side. .

In this way, even when a small-sized sheet is passed, the surface temperature of the roller on the non-paper passing side is prevented from rising abnormally, and the temperature of the roller surface on the reference position P side is prevented from decreasing. As a result, it is possible to increase the number of sheets guaranteed to be fixed and to ensure good fixing performance.

Note that when passing large-sized sheets and there is a concern that the temperature on the non-sheet passing side may drop, the copying speed may be changed to a lower value to increase the number of sheets that can be fixed.

FIG. 6 shows a comparison of the state of the heat roller surface temperature in the conventional example and in the example of the present invention when small size (A4 landscape size) copies are made at a rate of 63 sheets per minute. It is.

In the figure, numeral 1 is the temperature on the non-paper passing side in the conventional example, numeral 2 is the temperature on the non-paper passing side in the embodiment of the present invention, numeral 3 is the temperature at the central part of the heat roller in the embodiment of the present invention, and numeral 4 is the temperature in the present invention. Reference numeral 5 indicates the temperature at the reference position in the embodiment according to the present invention, reference numeral 5 indicates the temperature at the reference position in the conventional example, and reference numeral 6 indicates the temperature on the paper passing side in the conventional example.

When the heater of the heat roller generates heat during paper passing, in the conventional example, the temperature on the non-paper passing side increases by 30 to 40°C.

On the other hand, the temperature on the paper passing side is absorbed by the sheet and drops to near the temperature at which fixing is possible.

On the other hand, if the temperature distribution is as shown in the embodiment of the present invention (Fig. 1), the energy on the non-paper passing side is utilized on the paper passing side, as shown in Fig. 6, and the temperature rise on the non-paper passing side is reduced. At the same time, it is possible to reduce the temperature drop on the paper passing side.

Next, other embodiments of the present invention will be described.

In this example, as shown in FIG. 4, two heaters H3 and H3 are installed inside the heat roller.

During sheet feeding, only heater 3 generates heat due to the power constraints given to the copying machine, and there is sufficient power during startup (warm-up) and standby periods other than fusing. The heater H3 and the heater H4 are made to generate heat at the same time.

In such a heat roller, as mentioned above, the heater H3,
The heaters 114 are controlled separately so that, for example, the temperature distribution of the heater H3 has a temperature gradient 7 such that T3 is 30 to 100% higher at the reference position than on the opposite side of the reference position P, as shown in FIG. If the temperature distribution of the old heater is set to =4-, the temperature distribution of the heater 113
The temperature gradient 8 is set to be approximately symmetrical to the above.

This prevents the surface temperature of the heat roller on the side opposite to the reference position P (non-sheet passing side) from rising abnormally when passing small-sized sheets, and also prevents the surface temperature of the heat roller on the side opposite to the reference position P (paper passing side In addition to increasing the guaranteed number of sheets to be fixed by reducing the drop in the surface temperature of the heat roller at the heater H4 (temperature gradient 8
) Depending on the temperature distribution, the reference position P at startup and standby
The surface temperature of the heat roller on the opposite side (non-paper passing side) is at the reference position P.
It is possible to increase the number of large-sized sheets that can be guaranteed to be fixed by maintaining the temperature so that it does not become significantly lower than the side, thereby minimizing the drop in temperature when passing large-sized sheets.

FIG. 7 shows the distribution of the heat roller surface temperature at the time of startup.

In the figure, reference numeral 10 indicates the temperature change at the reference position P when only the heaters 1 and 3 have the temperature gradient 7 shown in FIG. 5, and the heater 114 has the temperature distribution as shown in FIG. Further, reference numeral 11 indicates a temperature change on the opposite side of the reference position P under the same conditions as above.

On the other hand, reference numeral 12 indicates the temperature on the reference position P side and the opposite side when both the two heaters in the heat roller have the temperature distribution as shown in FIG. 113. For (2), the temperatures on the reference position P side and on the opposite side of the garden are shown when the temperature distribution is as shown in FIG. 5, respectively.

According to this FIG. 7, regarding the effect during paper feeding, it is sufficient to change the temperature distribution of only the heater H3 as shown in FIG. This creates a temperature difference between the two sides. This temperature difference may not be a problem in some cases, but if it becomes a problem, in order to correct this temperature difference, the heat generation distribution of the heater H4, which generates heat only during startup and standby, should be made to be approximately symmetrical to the temperature distribution of the heater 113. Therefore, safe and stable fixing can be achieved with the same temperature difference as in the conventional case.

In the embodiments described above, the reference position when passing the sheet carrying a toner image is the so-called central reference type, which is set at one end in the longitudinal direction of the heat roller axis. The standard type fixing device can also be implemented using the same concept.

In other words, regarding the luminous efficiency distribution of a heat source built into the heat roller, such as a heater, the central portion, which is the reference position for paper feeding, is
It is set so as to draw a convex shape as shown in FIG. 8, in which the luminous efficiency is 30 to 100% higher than that of the other end portions.

In this way, even in the central reference type fixing device, when a small size sheet is passed through, the surface temperature of the rollers at both ends on the non-sheet passing side can be prevented from rising abnormally, and the roller surface temperature at the reference position can be prevented. By suppressing the drop in the center roller surface temperature, it is possible to increase the number of sheets guaranteed to be fixed and to ensure good fixing performance.

Note that if a small number of sheets are to be passed through and there is a concern that the temperature may drop on the non-sheet passing side, the copying speed may be changed to a lower value to increase the number of sheets that can be fixed.

In this way, in the center reference type fixing device, the temperature drop in the center area due to paper feeding is reduced by making the luminescence rate of the heater, which is the heat source, an upwardly convex luminescence distribution, as described above. It is possible to improve the fixing properties of.

On the other hand, depending on how the temperature is set, the temperature at both ends is lower than the temperature at the center, so there is a possibility that a fixing failure may occur due to a drop in temperature at both ends.

Regarding this point, when examining the pressure distribution of the pressure roller 21 which forms a pair with the roller 20 and is pressed against it as shown in FIG. 1
As shown in Figure 0, it is common for ΔP to be set larger by 10 to 50%, and the nip width distribution at this pressure distribution is
As shown in Figure 1, the ratio of the width Q2 at the center to the width Q2 at both ends is Ω2/Q1=1.1 to 1.5, and in order to obtain a good fixing effect, Since thermal and pressure factors are involved, even if the temperature at both ends is lower than the temperature at the center, the pressure applied to the roller is higher at both ends than at the center, so it is possible to obtain the same fixing effect as at the center. Can be done.

In other words, if the temperature conditions of the heat roller are set so that the same degree of fixing effect as in the center can be obtained, taking into account the difference in fixing performance due to the above-mentioned pressure distribution characteristics between the rollers, Compared to the conventional technology in which the temperature distribution is the same, it is possible to extend the number of sheets to be fixed (one hour of copying) before a fixing failure occurs, and to increase the number of sheets guaranteed to be fixed.

In addition, during the so-called startup period immediately after starting the fixing device, the heat dissipated from both ends of the heat roller is greater than during standby.
Generally, the temperature at the core decreases and the temperature difference becomes such that the compensation effect of the fixing performance due to the pressure distribution where the pressure is higher at both ends than at the center as described above cannot be sufficiently covered. .

To deal with this, a heat source is also provided for the pressure roller 21 (see Figure 9), and the temperature distribution is turned on at the time of startup so that the temperature distribution is convex and high at both ends, as shown in Figure 12. Bye. It is assumed that the heater of the heat roller 20 is always turned on for heating.

Here, further regarding the heating timing when heating the pressure roller 21, during startup and standby, for example, the exposure light source is not emitting light, and the accompanying drive system is also feeding paper. As a result, the power consumption of the copier as a whole is low.

Therefore, by allocating electric power to heat the fixing device during startup and standby to heat the pressure roller 21, heating can be accelerated by compensating for the temperature drop due to heat dissipation from both ends during startup. Not only
Due to the heat storage effect, it is possible to further extend the time until fixing failure occurs during continuous copying or the like.

By the way, if the temperature of the heating roller is not controlled as described above and the temperature distribution of the heating roller is constant in the width direction, as shown in FIG. In contrast, the temperature distribution of the heat roller is such that the central part is higher than both ends, and the temperature of the heat roller is set to 12 during standby and startup. If heating is performed in the manner shown in the figure, the time it takes for the temperature at the center of the roller and at both ends of the roller to drop to the upper limit of the fixing failure temperature will be significantly extended, as shown in Figure 14. be able to.

In FIG. 14, the upper limit of the fixing failure temperature at both ends of the roller is lower than the fixing failure temperature upper limit at the center of the roller, which means that the fixing performance is improved due to the effect of the nip pressure.

Due to recent user needs, even medium- and high-speed machines with a processing capacity of 40 sheets per minute or more require low power consumption (for example, 1f15A).
100V), this type of low-power copying machine has problems such as the long time it takes to warm up the fixing section and the short time it takes for fixing failure due to an early drop in temperature. This is convenient because it also eliminates the problem.

(Effects) According to the present invention, in the heat roller fixing device, it is possible to prevent an abnormal temperature rise in the non-conducting paper portion when passing small size sheets, to make the temperature distribution uniform, and to obtain safe and stable fixing performance.

[Brief explanation of drawings]

1 and 5 are heater temperature distribution diagrams as one embodiment of the present invention, and FIG. 2 is a heater temperature distribution diagram according to a conventional example,
Figures 3 and 4 are cross-sectional views of a heat roller suitable for carrying out the present invention, Figures 6 and 7 are diagrams of the heat roller surface temperature comparing the embodiment and the conventional example, respectively, and Figure 8. 9 is an explanatory diagram of a pair of rollers constituting the fixing device; FIG. 10 is a diagram of pressure distribution acting between the rollers in the same figure; FIG. 11
Figure 12 is a diagram explaining the nip width, Figure 12 is a temperature distribution diagram on the pressure roller, Figure 13 is a diagram explaining the change in roller temperature in the conventional example, and Figure 14 is a diagram explaining the change in roller temperature according to the present invention. It is a diagram. H3, H4...Heater, P...Reference position. 3rd ward, 4th figure, P, 5th figure, 4σZ

Claims (1)

[Scope of Claims] In a fixing device in which the reference position when passing a sheet carrying a toner image is set at the center or one end side in the longitudinal direction of the heat roller axis, the temperature of a heat source built into the heat roller is provided. Regarding the distribution, a fixing device characterized in that the temperature at the reference position of the heat roller is set to have a temperature gradient such that the temperature on the reference position side is 30 to 100% higher than on the other side.