JPH05297760A - Fixing device - Google Patents

Abstract

PURPOSE:To optimize setting from warming up a fixing device till starting fixing by controlling the rotation of a roller and the flickering of a heat source. CONSTITUTION:This fixing device is provided with a control means which makes set temperature higher than usual in the case that the heat source repeats to be turned on/off at intervals of previously decided time so as to perform heating to attain the warm-up set temperature and a printing signal is inputted in the middle of warm-up while a heat roll 1 and a pressure roll 7 start to rotate after heating for a specified time from turning on a power source, and continue to rotate till attaining the warm-up temperature previously decided. Therefore, the warm-up time is shortened, and overshoot is difficult to occur. Even when the printing signal is inputted in the middle of warm-up, even a 1st sheet obtains sufficient fixing intensity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner image on a transfer material onto the transfer material by passing it between a heating roll and a pressure roll for heating and fixing.

[0002]

2. Description of the Related Art Conventionally, in such a fixing device, the publication No. As shown in Japanese Patent Laid-Open No. 63-64071, the heating roll and the pressure roll do not rotate after the power is turned on. As shown in 59-72464, both rolls start rotating immediately after the power is turned on. When the temperature of the heating roll is raised after the power is turned on, the heating roll is continuously heated until the warm-up set temperature is reached. There is a known method of continuing.

Furthermore, the warm-up set temperature is usually set to a constant value, and even when a print signal is input during the warm-up, when the first first sheet is fixed, the fixing is started at the normal warm-up set temperature. There are many things.

[0004]

However, in the case of a fixing device in which the heating roll and the pressure roll do not rotate after the power is turned on, the entire pressure roll does not uniformly warm while the temperature of the heating roll is rising. It can only be partially warmed, centered on the part that contacts the heating roll. For this reason, when both rolls rotate and perform heat fixing after the start of printing, the pressure roll has temperature unevenness, and the heat applied from the heating roll to warm the low temperature part is removed, and Cannot give a sufficient amount of heat to the toner image of. As a result, the melting of the toner becomes insufficient, which causes defective fixing. Further, since the pressure roll is stationary up to the set temperature, the roll is likely to be deformed.

Further, in the fixing device in which the heating roll and the pressure roll rotate immediately after the power is turned on, the heat transfer from the heating roll to the pressure roll is performed from the beginning, so that FIG.
As shown in FIG. 1, the gradient of the temperature rise of the heating roll indicated by l1 ′ is gentler than l1 which shows the normal temperature change shown in FIG. 1, and it takes a very long time to reach the set temperature. In addition, there is a drawback that it constantly emits noise. Further, the toner offset to the roll during the previous fixing is solidified on the roll surface when the power is turned on, but this toner may damage both rolls.

When the heating roll is continuously heated until the warm-up set temperature is reached, an overshoot occurs in which the temperature rises above the warm-up set temperature as shown by l3 in FIG. High heat makes it easy to damage, and shortens the life of the heating roll and the pressure roll.

Further, even when a print signal is input during the warm-up time, in the case of a fixing device in which the warm-up set temperature is the same as usual, if the printing is started immediately after the warm-up is completed, the device is at a low temperature, Since the heat taken by the pressure roll is still large, the amount of heat applied to the toner image is not sufficient, and fixing failure is likely to occur.

The problem to be solved by the present invention is to prevent the occurrence of defective fixing, to obtain a fixed image with sufficient fixing strength, to shorten the warm-up time until reaching the set temperature, and to prevent roll damage. The object is to obtain a fixing device that extends the life of the roll.

[0009]

SUMMARY OF THE INVENTION The present invention is a fixing device having a heating roll having a heat source and a pressure roll rotating in contact with the heating roll. And that the pressure roll starts rotating, after the heating roll and the pressure roll start rotating,
Continue to rotate both rolls until the heating roll temperature reaches a preset warm-up set temperature T1, and after the heating roll and the pressure roll start rotating, the heat source is turned on at a preset time interval, Repeated OFF to raise the temperature to the warm-up set temperature T1. If a print signal is input during warm-up after the power is turned on, the warm-up set temperature is changed to a temperature T2 higher than usual and the set temperature is maintained. After that, the control means is provided so that the first fixing is started.

[0010]

【Example】

(Embodiment 1) The fixing device used in this embodiment is constituted by a heating roll 1 and a pressure roll 7 as shown in FIG. The heating roll 1 has a fluoride 3 on the surface of the metal cylinder 2.
And a halogen lamp 4 is arranged inside. The pressure roll 7 is composed of the central metal shaft 5 and the silicon rubber 6 around the metal shaft 5 formed by injection molding. In the temperature detection, the upper part of the heating roll temperature is measured by the thermometer 8, and the temperature is constantly controlled to the set temperature based on the surface temperature.

FIG. 1 is a diagram showing the relationship between the surface temperature of the heating roll and the pressure roll of the fixing device of the present invention and time. In this apparatus, when warming up, the timer starts counting immediately after turning on the power, and both rolls do not rotate for X0 seconds, and the halogen lamp in the heating roll lights up to heat the heating roll. After X0 seconds, the timer finishes counting and is activated to start the rotation of the heating roll and the pressure roll. The temperature of the heating roll at this time is indicated by T0, but this is not a specific temperature but a value that can vary depending on the material and size of the roll, the operating environment of the fixing device, and the time.

After the heating roll and the pressure roll start rotating, the halogen lamp in the heating roll repeats lighting and extinguishing at a predetermined time interval, for example, an interval of t seconds. The halogen lamp continues to be turned on and off until the heating roll reaches the set temperature T1, and after X1 seconds when the heating roll reaches the set temperature T1, the halogen lamp changes to the control to maintain the set temperature and the fixing state is established. Become. Until this point,
The rotation of both rolls may be continued, and then the heat may be fixed for some time after the heat stabilization. In this case, since the heating roll temperature l1 is moderately briefly heated from X0 to X1, the overshoot after reaching T1 is very small,
Although the temperature rise rate between X0 and X1 is slightly lowered, it is shortened to the warm-up time X1 as a whole. Further, the pressure roll temperature l2 is as high as T0 at the start of rotation of both rolls, so that the temperature rise between X0 and X1 is rapid for a short time. The heat dissipation loss from was extremely small and a highly efficient fixing device was realized.

The values of X0, X1, t, and T1 above are
It is determined by the material and configuration of the heating roll and pressure roll, other components and toner, and is not particularly limited.

Comparative Example 1 Using the same fixing device as in Example 1, the heating roll and the pressure roll were controlled to start rotating immediately after the power was turned on. At that time,
The relationships between the surface temperature of the heating roll and the pressure roll and the time are shown as l1 'and l2' in FIG. 2, respectively. When the heating roll and the pressure roll start to rotate immediately after the power is turned on, the gradient of the surface temperature l1 'of the heating roll with respect to time becomes gentle as compared with l1.

This is because when the rotation starts immediately after the power is turned on, the heat radiation from the pressure roll is large, and as a result, the rise of the temperature of the heating roll is delayed and the time required to reach the set temperature becomes long. Therefore, the warm-up time of the fixing device is long, and the time until the first printing of the image forming apparatus is limited, so that it cannot be said to be an appropriate control method.

(Comparative Example 2) Using the same fixing device as in Example 1, the halogen lamp is lit without repeating lighting and extinguishing even after the heating roll is heated and the surface temperature becomes about the same as T0. Then, the temperature was raised to the set temperature T1. The relationship between time and temperature at this time is indicated by l3 in FIG. The surface temperature of the heating roll continues to rise for a while even after reaching T3, and overshoots. After reaching a temperature higher than T1, the temperature begins to drop, but the overshoot is completed and a stable state is reached. X3 (X3> X1)
It took time. At this time, the temperature reached reached a region above the high temperature offset temperature to cause offset.

(Embodiment 2) A fixing device having the same structure as that of Embodiment 1 but with the temperature control changed as described below is used.
A test was conducted to check the occurrence of fixing failure. When the warm-up is started after the power is turned on and the print signal is input within the time X1 seconds, the temperature T2 is maintained at 0,10,20 ° C higher than the normal warm-up set temperature T1 for X1-X2 seconds. The temperature control was changed so that.

Using such a fixing device, a print signal was input within X1 seconds after the power was turned on, and fixing was performed after X2 seconds after the warm-up was completed. A graph showing the temperature change of the heating roll with respect to the time change at this time is l4 in FIG. Repeating the process of turning on the power, inputting the print signal, fixing after the warm-up, turning off the power, and cooling the device, fixing 100 sheets under the same conditions, and measuring the fixing ratio of the print sample created to determine the occurrence of print defects. I checked. The fixing rate was measured by a rubbing test using an eraser, the rate of change in the OD value before and after rubbing was examined, and a fixing rate of 60% or less was determined as fixing failure.

The results are shown in Table 1. From this result, it was found that the printing failure occurred very often when the warm-up set temperature remained at the normal set temperature, and almost never when the set temperature was set higher than 10 ° C.

[0020]

[Table 1]

[0021]

As described above, in a fixing device having a heating roll having a heat source and a pressure roll rotating in contact with the heating roll, the heating roll and the heating roll are heated after a lapse of a certain time from the start of heating. The pressure roll starts rotating, the heating roll and the pressure roll start rotating, and then both rolls continue to rotate until the temperature of the heating roll reaches a preset warm-up set temperature T1, After the pressure roll starts rotating, the heat source repeats ON and OFF at predetermined time intervals to raise the temperature to the warm-up set temperature T1, and the print signal is input during the warm-up after the power is turned on. In this case, the control means for changing the warm-up set temperature to a temperature T2 higher than usual and maintaining the set temperature for the first fixing operation. According to the fixing device, characterized in that it comprises, warm-up time is shortened, power consumption has become possible to lower. Moreover, there was almost no overshoot, and the desired set temperature could be smoothly achieved. Further, the heating roll and the pressure roll of the fixing device are less damaged, the life can be extended, and even when a print signal is input during the warm-up, the print failure occurs from the first fixing of the first sheet. The probability of occurrence has decreased, and stable fixing strength can be secured.

[Brief description of drawings]

FIG. 1 is a diagram showing temperature changes of a heating roll and a pressure roll with time of a fixing device of the present invention.

FIG. 2 is a diagram showing a temperature change of a heating roll and a pressure roll with respect to time change when both rolls start to rotate immediately after the power supply of a conventional fixing device is turned on.

FIG. 3 is a diagram showing a temperature change of the heating roll with respect to time in the case of the fixing device of the present invention and when the heating roll is continuously heated after X0 seconds.

FIG. 4 is a diagram showing a change in heating roll temperature with respect to time when a print signal is input during a warm-up time in the fixing device of the present invention.

FIG. 5 is a schematic view of a fixing device of the present invention.

[Explanation of symbols]

 1 Heating Roll 2 Metal Cylinder 3 Fluoride 4 Halogen Lamp 5 Metal Shaft 6 Silicon Rubber 7 Pressure Roll 8 Thermometer

Claims (4)

[Claims] 1. In a fixing device having a heating roll having a heat source and a pressure roll rotating in contact with the heating roll, the heating roll and the pressure roll are rotated after a lapse of a certain time from the start of heating. A fixing device having control means for starting. 2. A control means for continuing the rotation of both rolls after the heating roll and the pressure roll start rotating until the temperature of the heating roll reaches a preset warm-up set temperature T1. The fixing device described. 3. The heat source is turned on and off at a predetermined time interval after the heating roll and the pressure roll start rotating.
2. The fixing device according to claim 1, further comprising control means for repeating the FF to raise the warm-up set temperature T1. 4. When a print signal is input during warm-up after turning on the power, the warm-up set temperature is changed to a temperature T2 higher than usual, and after the set temperature is maintained, the first fixing is started. The fixing device according to claim 1, further comprising: