JPH06149122A - Temperature control method on thermal fxing device - Google Patents

Abstract

PURPOSE:To make the fluctuating width of the temperature of a fixing roll in a thermal fixing device used for a very high speed printer or a copying machine small. CONSTITUTION:In this temperature control method for the thermal fixing device using the fixing rolls 1 and 2 whose surfaces are covered with releasable materials 12 and 22, just after an operation is started, a heater 6 is almost fully energized until the surface temperature of the heating roll 1 is transferred to a rise from a drop, while a paper passes in a normal thermal fixing operation, the energization of the heater 6 is controlled based on a constant energizing quantity to automatically control the temperature, and when the operation is completed, the energization of the heater 6 is turned off before the completion of the operation. The current value of the surface temperature of the heating roll 1 is compared with the previous value to decide the transfer to the rise by using a sampling control system, the energizing quantity of the heater 6 is controlled by changing the duty ratio of the energization and it is decided that the left number of papers to pass becomes a prescribed value, so that the energization of the heater 6 can be turned off as well. Further, after the energization is completed, the heating roll 1 is allowed to run idle by a prescribed number of times, as will.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control method for a heat fixing device used in a printer, a copying machine or the like.

[0002]

2. Description of the Related Art Generally, in order to maintain the temperature of a heating roll within a certain temperature fluctuation range, the temperature of the heating roll is detected by a temperature sensor such as a thermistor, and when the upper limit temperature is exceeded, the heater is energized. Is turned off or the energization duty is decreased to lower the temperature of the heating roll, and when the temperature falls below the lower limit temperature, the energization of the heater is turned on or the duty ratio is increased to increase the temperature of the heating roll. It is controlled to raise.

[0003]

The problem in performing such feedback control is that the response of the temperature sensor and the heat conduction to the surface of the heating roll have a time delay, and therefore the actual response is delayed. That is, the temperature fluctuation range becomes large. In particular, in an ultra-high speed copying machine of 100 sheets / minute class, when silicone rubber is used as a coating material for a heating roll, this delay becomes a serious problem, and sometimes a copy with improper fixing is discharged. There was even a thing.

[0004] Figure 4 shows the time variation of the heating roll temperature of heat fixing the respiratory conventional temperature control, for example by a copying machine, the sheet feeding is started in accordance with the copy start command at time t _o The fixing roll rotates, heat is taken from the heating roll side to the pressure roll side in contact with the fixing roll, and the temperature sharply drops from the standby temperature T _s . And
Feedback control is activated after the lower limit temperature _TL is exceeded to increase the energization energy of the heater of the heating roll, but the response of the sensor is slow, and the silicone rubber coated on the surface of the heating roll has poor thermal conductivity. Therefore, the surface temperature of the heating roll continues to decrease, and the lower limit temperature T _L
After the temperature has dropped to the lower temperature T _{ll, the} temperature gradually rises. Then, at the subsequent time t ₂ , the temperature becomes gradually higher than the lower limit temperature T _L. 10 sheets from t _o to t ₂
A low-speed machine of the minute class cannot pass even one sheet of paper, but when using an ultra-high-speed machine of the 100-sheet / minute class, about 5 sheets of paper will pass through the fuser, so a copy with a bad fixing Will be discharged.

Next, at the end of the copying operation, after the time t _e when all the sheets have passed, the paper which has absorbed heat from the surface of the heating roll is no longer supplied. The temperature is suddenly increased by losing the destination of heat release and easily exceeds the standby temperature T _s . Further, in the ultra-high-speed machine, the standby temperature T _s is set to be high in order to compensate for the temperature drop immediately after the start of copying, so if the temperature rises above that, the life of the silicone rubber that is the coating material will be shortened. It is not preferable.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and reduce the fluctuation range of the temperature of the fixing roll in an ultra high speed printer or copying machine.

[0007]

According to the present invention, in a temperature control method of a heat fixing device using a fixing roll whose surface is coated with a releasing material, the surface of the heating roll is started immediately after the start of operation. The heater is almost fully energized until the temperature falls from rising to rising, and the heater energization is controlled centering on a constant energization amount during paper passing during the steady thermal fixing operation to perform automatic temperature control. Then, the power to the heater is turned off.

A sampling control system is used to compare the current value of the surface temperature of the heating roll with the previous value to determine that the temperature has risen, and to control the energization amount to the heater, the duty ratio of energization is changed. In addition, it is possible to turn off the power supply to the heater by determining that the remaining number of passed sheets reaches a predetermined value. Further, it is also possible to rotate the heating roll a predetermined number of times even after the completion of paper passing.

[0009]

According to the above-mentioned structure of the present invention, the temperature drop width immediately after the start of the thermal fixing operation can be suppressed to a small extent to prevent the fixing failure, and the temperature change width centering on a single reference value during the paper passing. Can be suppressed narrowly, and at the end, the accumulated heat of the heating roll can be sufficiently released to prevent unnecessary temperature rise. Thereby, the temperature change range of the heating roll can be suppressed to be small as a whole.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a hardware block diagram of a control device for a heat fixing device for carrying out a temperature control method for a heat fixing device according to the present invention. A thermal fixing device is configured. The heating roll 1 is connected to the drive motor 3, so that when the drive motor 3 rotates, the heating roll 1 also rotates, and the pressure roll 2 in contact with the heating roll 1 also rotates.

The heating roll 1 and the pressure roll 2 are respectively composed of cylindrical cores 11 and 21 and releasable coating layers 12 and 22 such as silicon rubber covering the outsides thereof. A heater 6 is provided inside the heating roll 1, and the heating roll 1 is heated by the heater 6. The heat accumulated in the heating roll 1 is also transferred to the pressure roll 2 in contact with each other, but the surface temperature of the two rolls is equalized to each temperature by being rotated by the drive motor 3. .

The surface temperature of the heating roll 1 is detected by a temperature sensor 4 which is, for example, a thermistor, and the controller 10
Be transmitted to. The control unit 10 is, for example, a microcomputer system, and the CUP 10 is centered around the bus 101.
2, a memory 103, an input interface 104 and an output interface 105. The detection result of the temperature sensor 4 is captured by the control unit 10 via the input interface 104.

The drive motor 3, the heater 6 and the paper feeding section 20
Is supplied with power from an AC or DC power supply unit 30, and three switches 41, 42, and 43, which are solid-state relays, are provided between the drive motor 3, the heater 6, and the paper supply unit 20 and the power supply 30. They are interposed, and power supply to them is controlled to be turned on / off. These three switches 41, 42 and 43 are the output interface 1
The on / off state is controlled by an operation command output from 05. In particular, the energization control to the heater 6 needs to control the energization amount per unit time, and is realized by changing the duty ratio of the energization.

The paper 50 taken in by the paper feeding section 20 is formed in the direction of arrow X after the image is formed by the toner 51 while passing through the paper feeding path, and is sandwiched between the heating roll 1 and the pressure roll 2. And is fixed by heat. Figure 2
Is a flowchart of temperature control, which is executed by a so-called sampling control system that operates at a fixed sampling period.

[0015]

[Table 1]

The above table shows an example of ranking according to the ratio of energization on / off times within a unit time when the duty ratio of energization is changed in order to control the energization amount per unit time to the heater 6. ing. For example, in rank 14, the duty ratio is 70, that is, the ratio of on time to off time is 14: 6. More specifically, for example, the AC half-wave is set to 1, electricity is supplied for 14 periods, and it is turned off for 6 periods.
20 AC half-waves in the case of 50H _z, since 200 milliseconds, which means that repeating the 200 ms as one period.

FIG. 3 shows the time change of the surface temperature of the heating roll when the control according to the present invention is performed. The temperature control operation according to the present invention will be described below with reference to Table 1 and FIG. 3 along the flow of FIG. When a thermal fixing operation start command is issued in accordance with the start of copying or printing (step a in FIG. 2, the same applies hereinafter), the drive motor 3 is driven to rotate the fixing rolls 1 and 2 (step b),
The heater 6 is almost fully energized (step c). "Almost full energization" means, for example, rank 18 or higher in Table 1, that is, a duty ratio of 90% or higher. Since the heat is taken from the heating roll 1 to the pressure roll 2 even if the power is almost fully energized,
As shown in FIG. 3, the surface temperature of the heating roll 1 continues to drop. Eventually, the temperature of the pressure roll 2 also rises, the amount of heat taken from the heating roll 1 decreases, and the effect of almost full energization appears, and the temperature of the heating roll 1 starts to rise at time t ₁ ′, and Unlike the case, it stays above T _L.

The step of almost full energization can be executed at the same time as the paper passing for thermal fixing, but it is executed before the start of the paper passing and the paper is passed after the transient change of the temperature. You can also During this period, the difference between the current surface temperature T _c of the heating roll 1 and the temperature T _{B one} minute before in the sampling cycle is monitored, and when it is determined that the temperature has stopped falling and has started to rise (step d), the energization rank is changed. For example, the rank is lowered to rank 14 in Table 1 (step e). Rank 14 is on time 14 vs. off time 6 as shown in Table 1.
It has a typical duty ratio in which the temperature of the heating roll does not fluctuate significantly during sheet feeding.

Thereafter, automatic temperature control during sheet passing is performed as a steady heat fixing operation (step f). The difference between the current temperature T _c and the reference temperature T _o is _calculated, and if it is ± 1 ° C. or less, the current rank is maintained. If the current value is higher, the rank is lowered by 1 to 2 according to the difference, the ratio of the power-off time is increased, and the heating energy is reduced. If the current is lower,
Increase the rank by 1 to 2 to increase the ratio of energization on time and increase heating energy. By controlling in this way, it is possible to control within ± 2 ° C.

Since the paper continuously absorbs heat energy during the passage of the paper, a substantially equilibrium state can be maintained. After passing the paper, there is nothing that absorbs thermal energy, so
Even if the heater is de-energized, the sensor's response delay and the silicone rubber's poor thermal conductivity cause the heat accumulated up to that point to reach the heating roll surface with a delay, thus reducing the surface temperature. It raises unnecessarily (Fig. 1
See t _e ). Therefore, in the present invention, when the remaining number of sheets becomes, for example, two (step g), the heater is de-energized (step h), and the last sheet is fixed by releasing the accumulated heat. Further, even after the last sheet of paper is discharged (step i), the fixing roll is idled for several rotations (step j), and the heating roll 1 and the pressure roll 2 are rotated.
Heat is released by transmitting heat to the surface to prevent unnecessary rise in surface temperature. After that, the temperature control during standby is performed (step k). Rank 6 or above during standby
After raising the temperature to the standby temperature T _s using 10,
The ranks 1 to 3 are used to maintain the standby temperature T _s .

[0021]

As described above, according to the present invention,
Since heating is performed without waiting for the temperature effect of the heating roll at the start of the thermal fixing operation, there is an effect that the width of the falling temperature is suppressed to a low level and the fixing property is improved. Since the duty ratio is only slightly changed during the passage of the paper, the temperature change width can be narrowed. Further, since the heating is stopped without waiting for the temperature rise at the end, it is possible to prevent an unnecessary temperature rise and there is an effect of preventing deterioration of the heating roll.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a hardware configuration of a heat fixing device control device for carrying out the present invention.

FIG. 2 is a flowchart showing a flow of temperature control according to the present invention.

FIG. 3 is a diagram showing a time change of a heating roll temperature in temperature control according to the present invention.

FIG. 4 is a diagram showing a time change of a heating roll temperature in conventional temperature control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heating roll 2 ... Pressurizing roll 3 ... Drive motor 4 ... Temperature sensor 6 ... Heater 10 ... Control part 11, 21 ... Core metal 12, 22 ... Releasable coating layer 20 ... Paper feed part 30 ... Power supply 41, 42 , 43 ... Switch 50 ... Paper 51 ... Toner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Hayashi 1-741 Kugayama, Suginami-ku, Tokyo Iwasaki Tsushin Co., Ltd. (72) Inventor Satoshi Suzuki 1-41-1 Kugayama, Suginami-ku, Tokyo Iwasaki Communication machine Co., Ltd.

Claims (5)

[Claims] 1. A heating roll whose surface is coated with a releasing material layer, and a heating roll which is arranged so as to come into contact with the heating roll and to perform paper passage for thermal fixing between the heating roll and the surface of the releasing material layer. A pressure roll coated with the temperature sensor, a temperature sensor that detects the surface temperature of the heating roll, a heater that heats the heating roll, and a temperature control unit that controls energization to the heater based on the output of the temperature sensor. (B) Immediately after the start of the heat fixing operation, the heater is controlled regardless of the output of the temperature sensor until the surface temperature of the heating roll finishes decreasing and starts to rise. (B) Around the full power supply, and (b) During the paper passing during the steady thermal fixing operation, the heater is fed to the heater according to the difference between the output of the temperature sensor and the reference temperature, centering on the predetermined amount of power supply per unit time. Control the amount of electricity Temperature control method and Rukoto, in the heat fixing device which comprises a and turning off the power supply to the heater before the end (c) heat-fixing operation. 2. A sampling control system is used to compare the current temperature with the temperature immediately before, and it is determined that the surface temperature of the heating roll has finished decreasing and has started increasing. 2. A temperature control method in the heat fixing device according to 1. 3. The temperature control method in a thermal fixing device according to claim 1, wherein the energization amount is controlled by changing the duty ratio of energization to the heater. 4. The heat fixing device according to claim 1, wherein the heater is turned off when it is determined that the number of remaining sheets to be heat-fixed has reached a predetermined value. Temperature control method in. 5. The temperature control in the heat fixing device according to claim 1, wherein the heating roll is idled a predetermined number of times even after the completion of the paper passage for heat fixing. Method.