JPH01282585A - Temperature control method for heat roller fixing device - Google Patents

Abstract

PURPOSE:To obtain uniform fixing performance from right after a warm-up to stability by setting the set temperature of a fixing roller higher right after the warm-up than in stability and lowering the temperature gradually to the temperature in stability. CONSTITUTION:The set temperature T of the fixing roller right after the warm-up is set higher than the set temperature Tc in stability. Consequently, the surface temperature of the fixing roller right after the warm-up is high, so even if the heat of the fixing roller is absorbed by toner, a pressure roller, etc., heat conducted to a form and the toner is equal to that in stability, so the excellent fixing performance is obtained. When the set temperature T of the fixing roller right after the warm-up is varied to the set temperature Tc in stability, the temperature is varied gradually, stepwise, or continuously and then the heat conducted to transfer paper and the toner is nearly constant to cause neither excessive fixation nor deficient fixation. Copy quantities right after the warm-up, in stability, and at an intermediate point are nearly equal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method for a heat roller fixing device of an electrostatic recording device.

[As shown in FIG. 11, a fixing device for an electrostatic recording device such as an electrophotographic copying machine, a facsimile machine, or an electrostatic printer uses a fixing roller 2 with a built-in heater 1 that can be energized when the main switch is turned on. A heat roller fixing device that fuses the toner image to the surface of the transfer paper by nipping and conveying the transfer paper 4 carrying an unfixed toner image between a pressure roller 3 that is in pressure contact with the heat roller fixing device is widely used.

Conventionally, in this type of fixing device, the surface temperature of the fixing roller is detected by a temperature detecting means 5 such as a thermistor, and the heater 1 is controlled on/off based on the signal to maintain the surface temperature of the fixing roller 2 at a set temperature. It is controlled to perform fixing, and it is controlled to stop copying when the surface temperature of the fixing roller falls below a predetermined fixable lower limit temperature due to heat being absorbed by the paper and toner due to continuous sheet feeding.

When the main switch is turned on and the heater in the fixing roller is energized until the temperature reaches the predetermined set temperature, the fixing roller and pressure roller are normally stopped, so if the temperature of the fixing roller rises, Only the portion of the circumferential surface of the pressure roller that contacts the fixing roller locally increases in temperature due to heat conduction, but since the material of the pressure roller is made of a poor heat conductor such as silicone rubber, other parts Therefore, as shown in Fig. 12, when the surface temperature of the fixing roller rises from the room temperature TO to the predetermined set temperature Tc, copying is started, fusing is performed, and the temperature of the fixing roller increases. Even if the surface temperature is detected and the heater is controlled on and off using the signal to maintain the set temperature Tc,
When continuous paper feeding is performed, the heat from the fixing roller is used not only to heat the transfer paper and the rollers 1 to 1, but also to heat the surface of the pressure roller 9, which has not yet reached a sufficient temperature, resulting in poor fixing performance. In addition, the surface temperature of the fixing roller is as shown in the curve ■ in Figure 13.
As shown by , the temperature decreases rapidly and reaches the fixable lower limit temperature Tρ relatively quickly. However, if continuous copying is started at point ■ in Figure 12 in a stable state after a considerable number of sheets have been fixed after reaching the -Wataru set temperature, the surface temperature of the pressure roller will be evenly distributed around the entire circumference. Because the temperature is rising, the heat from the fusing roller is used exclusively to heat the paper and toner, resulting in good fusing performance.
The surface temperature of the fixing roller gradually decreases as shown by curve 2 in FIG. 13, and the number of continuous copies increases until the temperature drops to the lowest fixable temperature. For example, immediately after warming up, 5
The minimum temperature is reached with 0 copies, but when it is stable it is 500
The temperature reaches the lower limit with one sheet.

In view of the above facts, as a method to ensure that good fixing is possible immediately after warm-up as well as when the temperature is stable, and at the same time prevents the number of continuous copies whose temperature is below the minimum fixable temperature during continuous copying from decreasing, for example, 31462
In Japanese Patent Publication No. 61-31463, it has been proposed to idle the fixing roller and pressure roller during warm-up to warm the pressure roller over its entire circumference, thereby creating conditions similar to when it is stable. There is. However, in order to idle the pair of fixing rollers, most parts of the entire machine also rotate, which generates noise even when no copying is being performed, and causes unnecessary rotation. This also adversely affects the durability of each drive component.

In view of the above-mentioned problems of conventionally implemented or proposed heating methods for heat roller fixing devices, the present invention has been made to achieve a gradual fixing performance from immediately after warm-up to a stable state, and to provide a heating method using a heater. To provide a temperature control method for a heat roller fixing device that enables continuous copying of the same number of sheets as when stable immediately after warm-up even in a fixing device with a small capacity.

In order to achieve the above object, the temperature control method of the present invention sets the set temperature of the fixing roller immediately after warm-up higher than the temperature at a stable time, and controls the set temperature to gradually lower the set temperature to the temperature at a stable time. It is characterized by

Embodiments of the present invention will be described in detail below with reference to the drawings.

In the first embodiment, which shows a fixing roller set temperature curve and a fixing roller temperature drop curve in FIGS. 1 and 2, respectively, the fixing roller set temperature T immediately after warm-up is set to a higher value than the set temperature Tc at a stable time. has been done. As a result, the surface temperature of the fixing roller is high immediately after warm-up, so even if the heat of the fixing roller during fixing is absorbed not only by the paper and toner but also by the pressure roller, the heat given to the paper and toner remains the same as when it is stable. Good fixing properties can be obtained. In addition, since the initial temperature is high, the number of continuous copies until the temperature drops to the minimum fixable temperature Tρ is as shown by the curve ■ in Figure 2, and the fixing roller temperature shown by the curve ■ when stable is from T to the minimum fixable temperature. The number of copies remains the same as the number of copies until it drops to Tβ. However, the value T when the set temperature stabilizes to 1 degree below the value immediately after warming up.
When iT and II fil are applied so as to change to c, and when fusing is performed at the time point ■ just before the change, the temperature of the fixing roller is higher than the steady state, and the pressure rollers are also mutually spaced all around. As the temperature rises, the number of sheets that can be continuously copied increases as shown by curve 2 in FIG. 2, which is good, but it results in excessive fixation.

Therefore, as shown in FIGS. 3, 4, 5, and 6, the fixing roller set temperature T immediately after warm-up is changed to the stable set temperature Tc, gradually, in several steps, or When controlled to change continuously, the surface temperature of the pressure roller gradually increases according to the elapsed time after warm-up, but the surface temperature of the fixing roller gradually decreases.
As a result, the heat applied to the transfer paper and toner is generally constant, and excessive fixing and poor fixing do not occur.

Furthermore, as shown in Figures 4 and 6, the number of copies from the start of continuous fixing until the lowest temperature for fixing is reached is approximately the same regardless of whether it is immediately after warm-up, when it is stable, or in between. Furthermore, the fixing properties are sufficient under all conditions, and over-fixing and under-fixing are prevented.

Even after arriving at Warm 711, if you haven't used the machine at all since the evening before, such as first thing in the morning, turn off the main switch and then turn it on again soon. The temperature state of the pressure roller and surrounding members is different when the ohm is turned on and when the ohm-up is completed.

In consideration of this point, it is preferable that when the main switch is turned on, the set temperature of the fixing roller immediately after warm-up is changed depending on the energization ratio during a predetermined period of time before that. By doing so, it is possible to prevent the time required to reach the copy-enabled point from becoming longer than necessary.

FIG. 7 is a flowchart showing the flow of operations from turning on the main switch in the 4th position until copying is displayed. In the diagram, T is the set temperature immediately after warm-up T1 is the maximum set temperature (set temperature when not used for a long time) K1 is the correction coefficient 2 is 11 (for example, 0.5Kt) 11 is the past 1
The energization ratio L2 for 0 minutes is the energization ratio Ts for the past 60 minutes is the temperature detected by the thermistor.

FIG. 8 is a control block diagram in that case. The past energized and de-energized states are stored in a part of the memory, and are input to the D CIII 8 section when the main switch is turned on, and the set temperature T immediately after warm-up is determined by the calculation formula shown in Figure 7.
is calculated, and when the fixing roller surface temperature Ts detected by the thermistor reaches T, the heater is turned off and the message ``Ready to copy'' is displayed.

Instead of calculating the set temperature T immediately after warm-up from the energization ratio for a predetermined time after the main switch is turned on, temperature detection means such as a thermistor is used to detect the temperature of the pressure roller that changes due to the energization ratio before the main switch is turned on. The fixing roller temperature setting immediately after warm-up may be controlled to be changed based on the detected signal. FIGS. 9 and 10 are a flowchart and a control block diagram, respectively, from turning on the main switch to displaying that copying is possible in that case.

In the figure, Set temperature immediately after ohm up T1 is the maximum set temperature is the correction factor t is pressure roller temperature It is.

In either case, depending on the set temperature immediately after warm-up, it is appropriate that the time to shift to the set temperature in a stable state is shorter than the shift time during warm-up after not using the product for a long time. .

The difference between the set temperature immediately after warm-up and the set temperature when stable, and the time required to shift from the set temperature immediately after warm-up to the set temperature when stable, etc. are determined by the heater capacity, the heat capacity of the fixing roller and heating roller, and the heat It is necessary to set it on a case-by-case basis depending on various factors such as conductivity and copy speed.

Effects - As described above, according to the present invention, uniform fixing performance can be obtained from immediately after ohm-up until the time of stabilization, and,
It is possible to keep the number of continuous copies possible at the same level as when it is stable.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a line section showing changes over time in the set temperature of the fixing roller according to the method of the first embodiment of the present invention, a curve diagram showing the relationship between the number of continuous copies and a decrease in the fixing roller temperature, and FIG. 4 and 4 are similar views of the second embodiment of the invention, FIGS. 5 and 6 are similar views of the third embodiment of the invention, and FIG. 7 is a similar view of the third embodiment of the invention. A flowchart for changing the set temperature immediately after warm-up according to the energization ratio, Fig. 8 is a control block diagram thereof, Fig. 9
The figure is a flowchart for changing the set temperature immediately after warm-up depending on the pressure roller temperature when the main switch is turned on, FIG. 10 is a control block diagram thereof, and FIG. 11 is a configuration of a heat roller fixing device to which the present invention is applied. FIG. 12 is a side sectional view showing an example, and FIG. 12 is a graph of the set temperature of the fixing roller of a conventional apparatus versus time. FIG. It is a curve diagram showing a relationship. 1... Heater (heat source), 2... Fixing roller, 3...
・Pressure roller, 4... Transfer paper, 5... Thermistor Fig. 1 @ Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 9 Fig. 8 Fig. 10 Large volume]

Claims (3)

[Claims] (1) The transfer paper carrying the unfixed toner image is conveyed between the fixing roller, which has a built-in heat source that can be energized when the main switch is turned on, and the pressure roller that comes into pressure contact with the fixing roller, and fixing is carried out, and the surface temperature of the fixing roller is is detected and the heat source is controlled on/off based on the signal to maintain the surface temperature of the fixing roller at the set temperature, and recording is stopped when the surface temperature of the fixing roller falls below the predetermined lower limit temperature for fixing due to continuous paper feeding. In a temperature control method for a heat roller fixing device of an electrostatic recording device that is controlled to A temperature control method characterized by controlling the temperature to lower the temperature. (2) The temperature control method according to claim 1, wherein the temperature setting of the fixing roller immediately after warm-up is changed according to the energization ratio during a predetermined period of time before the main switch is turned on. (3) The temperature control method according to claim 1, wherein the temperature setting of the fixing roller immediately after warm-up is changed depending on the surface temperature of the pressure roller when the main switch is turned on.