JPH0486781A - Method for controlling heating of roller type thermal fixing device - Google Patents

Abstract

PURPOSE:To smoothly make temperature rise to control reference temperature by executing the rotation/stop control of a pair of rollers based on the length of time until the temperature arrives at the control reference temperature after a power source is turned on. CONSTITUTION:A heater 10 is incorporated in a heating roller 1a and a thermister 2 is arranged closely to the surface of the roller 1a. A CPU 4 executes the heating control of the heater 10 through an SSR 5 based on a pulse signal generated based on a comparison signal. Count values corresponding to a first and a second set time (t1 > t2) which are shorter than the time until the temperature arrives at the reference temperature from the normal temperature are set in the CPU 4. Besides, the control references of the rotation and stop of a pair of rollers according to the case that the rising time (t) until the temperature arrives at the control reference temperature is (t1 > t> t2) and the case that it is (t2 > t) are set. Thus, even in the case that the temperature is made to rise from the normal temperature and in the case that the power source is turned on immediately after reset, the generation of noise and overshooting are started and the temperature is smoothly made to rise to the control reference temperature.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method of controlling the temperature of a heat fixing device used in an image forming apparatus, and more specifically relates to a heating roller having a built-in heater and a heating roller that is in contact with the heating roller. The present invention relates to a temperature control method for a roller type heat fixing device configured such that a recording material can be inserted between a pair of pressure rollers that rotate together.

``Prior Art'' Conventionally, a roller-type heat fixing device is well known, which fixes an unfixed toner image by passing a recording material carrying an unfixed toner image between a pair of fixing rollers consisting of a heating roller and a pressure roller. In recent years, this type of device has become widely used in the field of various image forming machines that utilize electrophotographic technology because it can fix toner images safely, reliably, and quickly with low energy consumption, and the temperature can be easily controlled. It is used in many ways.

In such a device, the diameter of the roller pair is reduced in order to achieve miniaturization, and the heater capacity is set to be large in order to improve the heating start-up speed. The heat storage capacity is relatively reduced, and overshoot is likely to occur when the temperature is raised, and the overshoot is further amplified due to the detection delay by the thermistor.

For this reason, a technology has been developed in which the temperature is raised while rotating the pair of rollers in cooperation with each other at the same time as the power is turned on. However, in this technology, heat is also dissipated from the pressure roller from the time the power is turned on. As a result, the heat dissipation area increases, resulting in a slow temperature rise rate.

In order to eliminate this drawback, a first set temperature lower than the standby reference temperature is set, the pair of rollers are rotated together until the set temperature is reached, and the rotation of the pair of rollers is stopped after reaching the set temperature. A technique has also been disclosed in which the device is started up to the standby temperature.

However, in such a technique, when the power is turned on again at a temperature higher than the first set temperature, such as when removing a jam, the temperature must be raised while the rotation of the pair of rollers is stopped, resulting in overshoot. is also likely to occur.

Therefore, a second reference temperature is further provided between the first reference temperature and the standby temperature, and contrary to the above, the rotation of the roller pair is stopped until the first set temperature is reached, and the temperature is raised. After reaching the set temperature, the pair of rollers is rotated in cooperation with each other until a second set temperature is reached, and further, after reaching the set temperature, the rotation of the pair of rollers is stopped and the temperature is raised to a standby temperature. The technology used for this purpose is also disclosed.

(Japanese Patent Publication No. 61-31463) ``Technical Problem to be Solved by the Invention'' However, even in this prior art, when the power is turned on again after a short power interruption time, such as when clearing a jam, the first -The power is often turned on again between the second set temperature, and for this reason, when turning on again after clearing a jam, the roller pair always rotates, making a lot of noise, which can be a problem in offices etc. where noise is a problem. Not only is this often the case, but the rotation of the roller pair also slows down the start-up speed.

In view of the drawbacks of the prior art, the present invention provides smooth control while avoiding elbow noise and overshoot as much as possible, whether the temperature is raised from room temperature or the power is turned on again after clearing a jam. The purpose of the present invention is to provide a temperature control method for a roller type heat fixing device that can be brought up to a reference temperature.

The present invention does not control the rotation/stop of the roller pair based on the temperature as in the above-mentioned prior arts, but rather controls the rotation/stop of the roller pair based on the temperature. The three cases of turning the power back on immediately after turning it off (hereinafter referred to as the third startup) are distinguished depending on the amount of time it takes to reach the control standard temperature after turning on the power. The first and second set times (t
1) Set t2), and in the case of the first start-up after turning on the power, overshoot will be large if the roller is started up to the control reference temperature with the roller stopped, so at least the control should be started after the first set time has elapsed. Rotate the roller until it reaches the reference temperature to prevent overshoot.

In the case of the second start-up, since the start-up width is small to some extent, overshoot will not be a problem even if the roller is stopped and started up to the control reference temperature, but the heat distribution on the pressure roller side is uneven. However, if the fixing operation is proceeded as is, fixing failure may occur.

The rear roller is rotated, the number of crosses between the control reference temperature and the detected temperature caused by the rotation is counted, and the pair of rollers is stopped based on the count value, thereby making the heat distribution uniform.

Furthermore, in the case of the third start-up, since the start-up width is very small, there is no problem of overshoot or non-uniform heat distribution on the pressure roller side even if the roller is started up to the control reference temperature while the roller is stopped.

Therefore, when the start-up time t is (t2) t ), it is determined that the third start-up is performed, and even after the control reference temperature is reached, the temperature is maintained with the roller pair stopped.

Note that the control reference temperature is not limited to the standby temperature or the fixing target temperature, and can be set to any reference temperature that does not exceed the fixing target temperature due to overshoot, for example.

"Effect" Therefore, the invention described in claim 1 claims the entire heating control system, and the invention can be used to start up from any temperature point, or in other words, when the temperature is started up from room temperature. Even when the power is turned on again after clearing a jam, or when the power is turned on again immediately after a reset, the control reference temperature is maintained smoothly and without any fixing failure while avoiding noise and overshoot as much as possible. can be launched.

Furthermore, the invention described in claim 2 provides a temperature control method that is suitable when the power is turned on again after the temperature has decreased to a certain extent, such as during jam processing, although it is not from room temperature. In order to suppress the temperature as much as possible, the roller pair is rotated after reaching the control reference temperature, but instead of setting the rotation time using a fixed time, the number of crosses between the control reference temperature and the detected temperature caused by the rotation is controlled. By counting, it is possible to quickly grasp the point in time when the heat distribution toward the pressure roller side has become uniform, and to stop the pair of rollers based on the count value.

Note that the control reference temperature is maintained using proportional control, 0N10FF.
Any temperature control method may be adopted.

"Example" An example of the present invention will be described in detail below based on one drawing. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. Not too much.

FIG. 1 is a schematic block diagram showing the main circuit configuration around a fixing device incorporated in an electrophotographic printer according to an embodiment of the present invention. The heating roller a has a heater 0 built therein along the axial direction, and a thermistor 2 is disposed close to the surface thereof.

The detected electric sweat corresponding to the temperature detected by the thermistor 2 is input to a temperature detection circuit 3, and in the detection circuit 3, a reference voltage corresponding to a set temperature such as a fixing target temperature or a standby reference temperature inputted from the CPU 4, The detected voltages are compared, and the comparison signal is amplified and output to the CPU 4.

The CPU 4 performs heating control of the heater 0 via the SSR5 based on the pulse signal generated based on the comparison signal, so that the roller surface temperature can be maintained at the control target temperature (TI, T2) described later. It is configured.

On the other hand, the CPU 4 has first and second set times (tl>
t2), a timer 6 for counting the start-up time after the power is turned on for the CPU 4, and the control reference temperature T and the detected temperatures S, Sl, and S2.
A counter 7 is attached to count the number of crosses.

Next, the operation of this embodiment will be explained based on the flowchart of FIG. 2 and the temperature time chart of FIG. 3.

A. When starting up from room temperature (- First, in Routine A, after turning on the power, start timer t, turn on the motor flag, and turn on (S
(TEPI), if the detected temperature has not reached the first set temperature TI (standby temperature) (STEP 2) and the timer 6 indicates t<tl, heater heating control is performed with the motor stopped (STEP 3). and the timer t
If the temperature still does not reach the first set temperature after the first set time t1 has elapsed (STEP 4), turn the motor ONI (STEP 4).
EP5) Continue heater heating control without rotating the roller pair. (STEP 6) Then, after continuing the above state until the first set temperature TI is reached, and setting the count value at the time when the temperature reaches the first set temperature TI (STEP 7), the heater control routine (B) is entered.
The temperature is maintained by repeating FF control, and the count value is updated every time the heater is turned off.5TEP21)
, when the count value reaches the reference count value (S
TEP 8) Stop the motor and send the heater ready signal (STEP 9) L, move to the fixing operation, and as shown in (STEP 22) of the heater control routine (B), the above 0
Maintenance control of the second set temperature (fixing target temperature) is performed based on N10FF control.

B. When the power is turned on again after the temperature has dropped to a certain extent, such as when clearing a jam, although not from normal temperature (S1) First, after turning on the power, start the timer 6, turn on the motor flag, and set the detected temperature to the first set temperature. The operation is the same as that described above in that if TI has not been reached and the timer indicates t≧tl, heater heating control is performed with the motor stopped.

When the timer t reaches the first set temperature within the first set time t1 and the timer t is longer than the second set time t2, the count value is set (STEP 7) and the motor is turned on (STEP 5). ) Perform heater heating control without rotating the roller (STEP 6).

That is, the heater control repeats the 0N10FF control in order to maintain the first set temperature in the case of standby operation as shown in the heater control routine (B) in the same way as the above operation.
Update the count value every time the heater is turned off 5TEP2
1) When the count value reaches the reference count value, the heater ready signal should be sent as it is 5TEP9),
Shift to fixing operation, and maintain control of the second set temperature based on the ON10FFM control described above (STEP 22)
.

C1 When turning on the power again immediately after turning off the power (S2) First, after turning on the power, start the timer, turn on the motor flag, and make sure that the detected temperature has not reached the first set temperature (standby temperature) and the timer is t≧t
In case 1, the heater heating control is performed with the motor stopped, which is the same as the above operation.

When the timer t reaches the first set temperature within the first and second set times t1, the motor ON flag is set to 0FFL (STEPIO), the count value is set (STEPII), and the motor is turned off (STEPIO).
PI2) Perform heater heating control and repeat 0N10FF control to maintain the first set temperature, and update the count value every time the heater is turned off.5TEP21)
When the count value reaches the reference count value, the heater ready signal is directly transmitted (STEP 9), the process moves to the fixing operation, and the second set temperature is maintained based on the 0N10FF control described above (STEP 22).

Therefore, according to such embodiments, the effects of the present invention can be smoothly achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the main circuit configuration around the fixing device of an electrophotographic printer according to an embodiment of the present invention, and FIGS. 2 and 3 are a flowchart showing its operation and temperature. It is a time chart figure.

Claims (1)

[Claims] 1) Roller type thermal fixing in which a recording material carrying an unfixed toner image is inserted between a roller pair consisting of a heating roller with a built-in heater and a pressure roller to fix the toner image. In a heating control method for a device, at least one control reference temperature that can be maintained at a predetermined temperature by heating control of a heater, a first set time (t1) smaller than the time required to reach the reference temperature from room temperature, and the first set time (t1) If a second set time (t1>t2) is set smaller than the first set time, and the first set time is reached before the control reference temperature is reached after the power is turned on, at least the control reference temperature is set after the set time is reached. Rotate the roller until the temperature reaches the temperature, and if the start-up time t from turning on the power until reaching the control reference temperature is (t1>t>t2), rotate the roller after reaching the control reference temperature, and then rotate the roller until the control reference temperature is reached. counting the number of crosses between the control reference temperature and the detected temperature caused by the above, and stopping the roller pair based on the count value, and further stopping the roller pair if the start-up time t is (t2>t). 2) A heating control method for a roller type thermal fixing device characterized by controlling heating in a state in which the recording material has an unfixed toner image carried between a pair of rollers consisting of a heating roller with a built-in heater and a pressure roller. In a heating control method for a roller-type heat fixing device that fixes the toner image while the toner image is inserted, the control method is performed when the time t from when the power is turned on until the control reference temperature is reached is within an arbitrarily set reference time range. After the reference temperature is reached, heating control is performed while rotating the roller pair, and the number of crosses between the control reference temperature and the detected temperature caused by the heating control is counted, and the roller pair is stopped based on the count value. A heating control method for a roller type heat fixing device characterized by