JPH01210982A - Fixing device drive control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a drive control method for a fixing device, and in particular, a method for controlling the drive of a fixing device, and in particular, a method for controlling the drive of a fixing device by coordinating a fixing roller with a built-in heating means and a pressure roller that is pressed against the fixing roller at a predetermined timing. The present invention relates to a drive control method of a fixing device, which controls the drive of the fixing device so as to rotate the fixing device.

(Prior Art) Various image forming apparatuses such as copiers are provided with a fixing device to fix a toner image adhered to a recording paper. This fixing device is equipped with a fixing roller that has a built-in heating means and a pressure roller that is pressed against the fixing roller, and both of the rollers work together at a predetermined timing when starting up after the electric press. The drive is controlled so that it is rotated so that it can be fixed. That is, after the power is turned on, when the temperature of the fixing roller is started to increase and the temperature of the fixing roller reaches a predetermined temperature of 1 degree T3, if the temperature of the pressure roller is lower than the fixable temperature T1, both rollers are operated together. The pressure roller is rotated to reach a predetermined temperature T2 higher than the fixable temperature T1, and when T2 is detected as the temperature of the pressure roller, both rollers are stopped.

However, the conventional fixing device drive control method as described above has the following problems. First, when a faster fixing speed is required as the image forming speed (copying speed) increases, the set temperature of the pressure roller must be increased to ensure fixing performance. However, as shown in FIG. 6, when the pressure roller exceeds the critical temperature T5 and approaches the saturated temperature state, the temperature increase of the pressure roller rapidly slows down, and as a result, the temperature detection of the pressure roller becomes difficult. This error has a large effect on the control time for performing the cooperative rotation, and the variation in the drive control operation of the cooperative rotation becomes large. Specifically, if the temperature detection data of the pressure roller becomes even slightly higher than the actual temperature, the time for co-rotation will be significantly shorter than the originally required time, resulting in poor fixing.
H will come. Conversely, if the temperature detection data of the pressure roller is even slightly lower than the actual temperature, the time for cooperative rotation will be significantly longer than the originally required time, and the state will become ready for fusing. This will result in extra waiting time.

(Purpose) Therefore, the present invention is capable of appropriately controlling the cooperative rotational movement of the fixing roller and the pressure roller, and in particular, raising the temperature of the pressure roller to a necessary and sufficient temperature in a short period of time. An object of the present invention is to provide a drive control method for a fixing device.

(Structure) In order to achieve the above object, the present invention provides a fixing device that controls the drive of a fixing roller having a built-in heating means and a pressure roller that is in pressure contact with the fixing roller so that they rotate together at a predetermined timing. In the drive control method, when the temperature of the fixing roller is started to rise and the fixing roller reaches a predetermined temperature T3, if the temperature of the pressure roller is lower than the fixable temperature T1, both rollers are controlled to cooperate. The pressure roller is rotated to reach a predetermined temperature T2 higher than the fixable temperature T1, and after that, both rollers are stopped after co-rotating for a certain period of time.

In the control system having such a configuration, cooperative rotation is performed for a certain period of time after it is detected that the pressure roller has reached a predetermined temperature T2 higher than the fixable temperature T1. Even if there is some temperature detection error, the temperature of the pressure roller is maintained at a constant temperature or higher during a constant rR.

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

First, an example of a fixing device to which the present invention is applied will be explained with reference to FIG. A fixing roller 2 and a pressure roller 3 are provided in the housing 1, and the lower part of the fixing roller 2 is pressed against the pressure roller 3. A toner image is attached to the nip between these rollers 2 and 3. The recorded paper is fed in. A heater 2a serving as a heating means is built into the center of the fixing roller 2, and a coated felt 2b for applying a release agent is pressed onto the outer periphery of the fixing roller 2. Further, a fixing mold 2C is disposed in contact with the exit portion of the fixing roller 2 to separate the recording paper from the surface of the fixing roller 2, and
A thermistor 20 for detecting the surface temperature of the fixing roller 2 is arranged at the entrance of the fixing roller 2 .

Furthermore, a fuse 2f is installed above the fixing roller 2 to shut off the power to the heater 2a when the fixing roller 2 becomes abnormally heated. On the other hand, a pressure cam 3a is pressed against the shaft portion of the pressure roller 3, and the pressing of the pressure cam 3a causes the pressure roller 3 to press against the fixing roller 2 with a predetermined pressing force. It is now possible to do so.

At the entrance part of this pressure roller 3, the pressure roller 3 is
A thermistor 3b is arranged to detect the surface temperature of.

FIG. 2 shows a control circuit attached to the fixing device. In the figure, reference numeral 11 indicates a commercial power supply, and reference numeral 12 indicates a zero-cross detection circuit for detecting the zero-cross point of the commercial power supply 11. This zero cross detection circuit 12 detects the "old" state at the zero cross point.
The zero cross signal is input to an external interrupt terminal iNT of a microcomputer 13 equipped with a circuit for controlling the temperature of the fixing roller 2. The microcomputer 13 used is μC0M7818G, which is an A/
1-chip 8-bit microcomputer with D converter, 8-bit CPU, ROM (4 bits), RAM (256 bytes), A/D converter (8 analog inputs), multi-function 16-bit timer /
Event counter (2 pieces, 8 pins) ~ Timer (
2), a general-purpose serial interface, an I10 port (40 bits), an interrupt function (3 external, 8 internal), etc. are integrated into one chip. When the boat P1 of the microcomputer 13 is set to "0", the switching element 23 is made conductive by the trigger circuit 19, and power is supplied to the heater 2a installed on the fixing roller 2. There is. A thermistor 20 that detects the surface temperature of the fixing roller 2 is connected to the A/D of the microcomputer 13 through a temperature detection circuit 20.
The thermistor 3b, which is input to the port ANO and which detects the surface temperature of the pressure roller 3, is connected to the A/D of the microcomputer 13 through the temperature detection circuit 21.
It is input to boat AN1. Each of the above temperature detection circuits 2
0.21, one end of each thermistor 2e, 3b is grounded, and the other end is connected to a power source of τ5V via a predetermined resistor. Also, each thermistor 2
The voltage across e and 3b is the microcomputer-13
is input to the A/D boat of

Further, reference numeral 15 indicates a drive motor, and when the port P2 of the microcomputer 13 is set to "LO,:", the trigger circuit 22 causes the switching element 24 to
is brought into conduction, and the drive motor 15 is driven to rotate. The input shafts of the fixing roller 2 and the pressure roller 3 are connected to the output shaft of the drive motor 15 via a chain, and both the rollers 2.3 are rotated together by the driving force of the drive motor 15. It looks like this.

Next, an embodiment of the present invention using a control device like the one above will be described. FIG. 3 explains the main flow in one embodiment of the present invention. As shown in this figure, when the power is turned on, initial settings are first performed in step 1-1. This initial setting turns off each port, clears all RAM, and disables all interrupts.

Next, in step 2, frequency detection is performed.

In other words, wait until the zero cross signal becomes "old", wait Oo, l5EC from the time it becomes "1 old", and then when the zero cross signal becomes "old", start 0.5 from that point.
A counter (FRQCNT) is incremented each time a rising edge of the zero-crossing signal is detected during SEC. When 0.5SEC has elapsed, (FRQCNT
) is checked, and if (FRQCNT) is over 55, it is set to 60H2, and (FRQCNT) is 55.
In the following cases, it is set as 50H7. Then, if it is 50H2, 100 is set in the 1 SEC counter (HETCNT), and if it is 60H2, 120 is set in the I SEC counter (HETCNT). The zero-cross interrupt mask is released after the shop.

In step 1-3, the ISEC counter (HETC
NT) is checked and waits until (HETCNT) becomes O. Here, (HETCNT) is decremented by the zero-crossing interrupt process every zero-crossing, and (HETCNT)
CNT) becomes 0, reset is performed in step 1-4 (50H2: 100, 60H7: 120
), then (HETCNT) is made O for each TI SEC.

Furthermore, in step 1-4, (HETCN
T) is reset and duty calculation is performed. That is, the number of on-cycles (ONCYC) is determined based on the temperature of the fixing roller using the following formula.

(ONCYC) - (ONCYC) + (EM)---
−・■(EM)=KP(PT)+Kl(IT)+K
d(DT)...■(PT)=(TNl)+('
TNO)・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・■(IT)・(ST)-(TNO
)・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・■(DT)=(PT)−((TN2)
÷(TNll)・・・・・・・・・・・・■Here, the above 0
(ONCYC) on the right side of the equation is the previous number of on cycles, and (ONCYC) on the left side is the current number of on cycles. The on-cycle unit is a half wave of the AC waveform. Note that (ST) represents the target temperature data of the fixing roller, (TNO') represents the current temperature data of the fixing roller, and (TNI) represents the 1S temperature data of the fixing roller.
It represents the temperature data before EC, and (TN2) represents the temperature data of the fixing roller 2 SEC before. Also K
P, Kl, and Kd represent constants determined by the characteristics of the fixing roller.

(ONCYC) newly updated by the above formula 0 is:
It is set in the on-cycle counter (ON CNT). The temperature of the fixing roller is AN at each zero cross.
Invert the data read from O and write (TOH) (TO
L). Then, in step 1-4, the above (TOH) (TOL) is divided by the number of sampling times to obtain the current fixing roller W degree (TNO). The number of sampling times is 100 in the case of 50H2, and 120 in the case of 60)-17. Similarly, the temperature of the pressure roller is obtained by dividing the added temperature (TlH) by the number of sampling times, and this data is taken as the temperature of the pressure roller.

In steps 1-5, flag 1 (FLAGl) is checked, and if (FLAGl) is rOJ, step 1-
If (FLAGl) is "1", the process moves to step 1-10. At the beginning (FLAGl
) is "0", the process moves to step 1-6.

In step 1-6, the temperature of the fixing roller is checked, and when the temperature of the fixing roller reaches 170 degrees Celsius or higher, the process moves to step 1-7. If the temperature has not reached 170 degrees Celsius, the process returns to step 1-3.

In step 1-7, flag 1 (FLAGI) is set.

In step 1-8, the temperature of the pressure roller is checked, and if the pressure roller is above 60 degrees Celsius, step 7
-3, and if the temperature is lower than 60 degrees C, the process proceeds to step 1-9.

In step 1-9, the motor ON flag (MOTON
) is set, and the process returns to step 1-3.

In step 1-10, the motor ON flag (MOTO
N> is xy'). (If MOTON> is “1”, the process moves to step 1-11, but (MO, TON
) is rOJ, the process returns to step 1-3.

In step 1-11, the temperature of the pressure roller is checked, and if the pressure roller reaches 100 degrees Celsius, the process proceeds to step 1-12, and if it is below 100 degrees Celsius, the process proceeds to step 1-3. be returned.

In step 1-12, flag 2 (FLAG2) is checked, and if (FLAG2) is an rOJ body, step 1
-13, and if (FLAG2) is "1", the process moves to step 1-14.

In step 7-73, flag 2 (FLAGI) is set, and a predetermined time T is set in the timer, which is then started. Then, the process returns to step 1-3.

In step 1-14, it is determined whether or not the timer (T) has expired. If the timer (T) has not expired, step 1-14
Returned to 3. If completed, the motor ON flag (M
OTON) is reset, and the process returns to step 1-3.

Next, zero cross interrupt processing (ZCINT) will be explained based on FIG. Zero-crossing interrupt processing is called on the rising edge of the zero-crossing signal when external interrupts are unmasked.

In step 2-1, 1 SEC counter (HETCN
T) is decremented.

In step 2-2, the on-cycle counter (ONC
NT) is checked, and if (ONCNT) is not 0, the process moves to step 2-3, and (ONCNT)
If is O, the process moves to step 2-4.

In step 2-3, (ONCNT) is decremented and the fixing roller heater is turned on to heat the fixing roller.

In step 2-4, heaters 1 to riggers of the fixing roller are turned off.

In step 2-5, the motor ON flag (MOTON
) is checked, and if (MOTON) is "1", the process moves to step 2-6, but if (MOTON) is "O", the process moves to step 2-7.

In step 2-6, the motor trigger is turned on,
Both rollers are rotated together.

In step 2-7, the motor trigger is turned off,
Both rollers are stopped.

In step 2-8, the voltage input to the ANO is
The temperature data of the fixing roller obtained by converting and inverting the data is added to an addition register (TOH>(TOL>).

Further, in step 2-9, temperature data of the pressure roller obtained by A/D converting the voltage input to the ANI and inverting the data is added to the addition registers (TOH) (TOL) and returned.

In the control method in this embodiment, as shown in FIG. 1, the power is turned on at time to and the temperature of the fixing roller 2 starts to rise. When the fixing roller 2 reaches a predetermined temperature T3, that is, at time t1, if the temperature of the pressure roller 3 is lower than the fixable temperature T1, both the rollers 2.3 are rotated together, and the pressure roller 3 is made to reach a predetermined temperature T2 higher than the fixable temperature T1. After it is detected that the pressure roller 3 has reached the predetermined temperature T2, which is higher than the fixable temperature T1, cooperative rotation is performed for a certain period of time T, and then both rollers are stopped. Then, the fixing operation starts from there.

In this way, even if there is some error in detecting the temperature of the pressure roller 3, the temperature of the pressure roller 3 will be increased to a certain level or higher within a certain period of time. Specifically, when the temperature detection data of the pressure roller 3 becomes somewhat higher than the actual temperature, the cooperative rotation is performed for a certain period of time after the temperature detection of the pressure roller 3, so the cooperative rotation time is A temperature that allows fixing can be obtained without causing a situation where the time is significantly shorter than originally required.

Conversely, if the temperature detection data of the pressure roller 3 is slightly lower than the actual temperature, the cooperative rotation will only be performed for a certain period of time after the temperature of the pressure roller 3 is detected, so the cooperative rotation time will be The time does not become significantly longer than originally required, and a situation where extra waiting time is required until the fixing is possible can be avoided.

(Effects) As described above, in the drive control method of the fixing device according to the present invention, even if there is some temperature detection error for the pressure roller whose temperature is raised by cooperative rotation, the pressure roller can be controlled for a certain period of time. After the pressure roller reaches a predetermined temperature by cooperative rotation between the fixing roller and the pressure roller, the pressure roller is rotated cooperatively for a certain period of time, and then both rollers are rotated together. Since the fixing roller and the pressure roller are stopped, the cooperative rotation of the fixing roller and the pressure roller can be controlled to be constant regardless of the temperature detection error. The temperature can be raised to the necessary and sufficient temperature in a time of .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing temperature changes of a fixing roller and a pressure roller based on a drive control method in an embodiment of the present invention, and FIG. 2 is a block diagram showing an outline of a control device for carrying out the present invention. Diagrams, Figures 3 and 4 are
A main flow diagram showing a procedure for implementing the control device shown in the figure, a flow chart showing a zero-cross interrupt, FIG.
The figure is a diagram showing temperature changes of a fixing roller and a pressure roller based on a conventional drive control method. 2-...Fixing row 7-. 2a...Heater, 2e...
・Thermistor, 3... Pressure roller, 3b... Thermistor, 13... Microcomputer-120
゜21...Temperature detection circuit. (1 person outside) Location I Figure ￥1ηI! 7 buddhas

Claims (1)

[Claims] In a drive control method for a fixing device, the fixing roller having a built-in heating means and a pressure roller that is in pressure contact with the fixing roller are controlled so as to rotate together at a predetermined timing. When the fixing roller reaches a predetermined temperature T3, if the temperature of the pressure roller is lower than the fixable temperature T1, both rollers are rotated together to raise the pressure roller to a temperature higher than the fixable temperature T1. A method for controlling the drive of a fixing device, characterized in that both rollers are stopped after reaching a predetermined temperature T2 and then causing cooperative rotation for a certain period of time.