JPH06202526A - Heating device - Google Patents

Abstract

PURPOSE:To prevent a roller from being abnormally heated after the rotation of the roller is stopped by setting the driving control means of a pair of rollers so that a pair of rollers is stopped based on the signal of a temperature detection means after the temperature of a heating body becomes the prescribed temperature or under. CONSTITUTION:When a recording material is not carried to a device, sensors 16 and 17 are turned off and the temperature of the heating roller is kept lower than the temperature suitable for fixing. When the recording material is carried to the device, the sensor 16 is turned on first. Then, a signal S10 to a motor 15 is turned on and a signal S13 is selected by a control part 1. That means, the signal S13 is inputted from an A/D converter 28 by setting a control target voltage to Vref2 and a signal S11 from an A/D converter 6 and the signal S13 are compared. Then, the temperature is controlled by the temperature suitable for fixing the recording material. When the signal S11 from the converter 6 arrives at the value of a signal S12 corresponding to a control target voltage Vref1, the signal S10 to the motor 15 is turned off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device used in an image forming apparatus such as an electrophotographic device and an electrostatic recording device. Particularly, the present invention relates to a heating device suitable for heating and fixing an unfixed image.

[0002]

2. Description of the Related Art A heating method, especially a heat roller fixing method, is widely used for fixing an unfixed image. In this method, basically, a heating roller and a pressure roller that is in pressure contact with the heating roller are integrally formed, and a recording material supporting an unfixed image is passed between them to perform fixing. In this configuration, normally, the roller is stopped when the recording material is not conveyed, and when the recording material is conveyed, the roller starts to rotate by a signal from a sensor or the like before reaching the roller. Then, when the roller is rotated, temperature control is performed at a temperature suitable for heat fixing, and after the trailing edge of the recording material passes through the roller,
Immediately the rotation of the roller has stopped.

FIG. 10 shows an image heating apparatus for performing the above-mentioned heat fixing. In the apparatus shown in FIG. 10, the recording material 1 is conveyed in the direction of the arrow and supports the unfixed powder toner image.
2 is conveyed by the conveyor belt 13 and passes through the sensor 16. As a result, the motor 15 connected to the heating roller 10 and the pressure roller 11 starts driving, and the heating roller 10
Then, the pressure roller 11 starts to rotate. Then, the recording material 12
Is conveyed to the nip portion between the heating roller 10 and the pressure roller 11, is heated and pressed at the nip portion, and is discharged.
Passes through the sensor 17. As a result, the signal of the sensor 17 changes from on to off, and the driving of the motor 15 is stopped.

On the other hand, the heating in the nip portion is performed by supplying electric power to the halogen heater 5 contained in the heating roller 10 to generate heat, and a temperature detecting element provided in contact with the surface of the heating roller. The energization to the halogen heater 5 is controlled so that the resistance value of the thermistor 9 is constant with respect to the reference value. As a result, the heating roller 10 maintains the temperature required for fixing, and good fixing is performed.

However, if the temperature of the heating roller 10 is constantly maintained at the temperature required for fixing, power consumption increases and abnormal overheating of the roller may occur. Therefore, in the above apparatus, when the roller is stopped. The temperature is controlled to be lower than that during rotation. Hereinafter, this temperature control method will be described.

FIG. 11 shows an example of the temperature control circuit and roller drive circuit for the heating roller. In FIG. 11, 6 is an A / D converter for obtaining a digital value S11 from the voltage VT obtained by the voltage dividing ratio of the thermistor 9 and the resistor R1. 27 is an A / D converter for obtaining a digital value S12 from the control target voltage Vref1,
28 is an A / D converter for obtaining the digital value S13 from the control target voltage Vref2. That is, the A / D converter 6 detects the actual temperature of the heating roller, and
The D converter 27 detects the reference temperature at the time of fixing, and further A
The / D converter 28 is for detecting the reference temperature when the rollers are stopped.

The A / D converter 6 and the A / D converter
Digital values S11, S12, S13 output by the D converter 27 and the A / D converter 28, respectively.
Is input to the control unit 21. As shown in FIG. 12, which will be described later, the control unit 21 follows the inputs of the sensors 16 and 17,
The motor 15 is turned on / off by the control signal S10, and the halogen heater 5 is turned on / off by selecting and inputting the digital values S12 and S13 at any time.

Control of the halogen heater 5 is performed via the electric power energization pattern generator 3. The power energization pattern generator 3 outputs a heater control signal S4 to the heater drive circuit 4 based on the energization pattern signal S3 of the control section 21, and the heater drive circuit 4 outputs the halogen heater 5 based on the heater control signal S5. AC drive.

Next, the operation of the above control circuit will be described. First, when the recording material is not conveyed to the apparatus, the sensors 16 and 17 are in the off state,
As shown in FIG. 12, the control unit 21 turns off the control signal S10 of the motor 15 and controls the temperature based on the signal S12 from the A / D converter 27. This signal S12
Is a digital value of the control target voltage Vref1 corresponding to a temperature lower than a temperature suitable for fixing the recording material, whereby the temperature of the heating roller is the temperature T as shown in FIG.
Is kept at 1.

When the recording material is conveyed to the apparatus,
First, the sensor 16 is turned on.
2, the signal S10 to the motor 15 is turned on,
Temperature control is performed based on the signal S13 from the A / D converter 28. This signal S13 is a digital value of the control target voltage Vref2 corresponding to the temperature suitable for fixing,
As a result, the temperature of the heating roller becomes the temperature T2 as shown in FIG.

Further, while the sensor 16 or 17 is on, the recording material is in the vicinity of the roller, so the control unit 2
1, the signal S10 to the motor 15 is turned on as shown in FIG. 12, and the signal S13 from the A / D converter 28 is used as a reference. As a result, the temperature of the heating roller maintains the above T2, and good fixing is performed.

The above operation will be described with reference to the flowchart of FIG. First, the states of the sensor 16 and the sensor 17 are determined (step 201), and when either the sensor 16 or the sensor 17 is on or both sensors are on, the signal S10 to the motor 15 is turned on (steps 201 to 201). 202). Then, S13 is selected as the reference signal for temperature control (step 20).
3). On the other hand, when both the sensor 16 and the sensor 17 are off, the signal S10 to the motor 15 is turned off (steps 201 to 204), and S12 is selected as a reference signal for temperature control (step 20).
5). After selecting the reference signal for temperature control as described above, temperature control is performed based on the selected signal (step 206).

[0013]

However, according to the above-mentioned conventional example, since the temperature of the heating roller is maintained at the temperature T2 just before the roller rotation is stopped, the roller temperature after the stop is shown by ΔT1 in FIG. However, there is a problem in that the heating roller is deformed, deteriorated, or has an offensive odor, and the life of the roller is significantly shortened. There was also a risk of ignition due to abnormal overheating of the rollers.

An object of the present invention is to solve the above problems and to provide a heating device capable of preventing abnormal overheating of a roller after the rotation of the roller is stopped.

[0015]

According to the present invention, the above object is to provide a roller pair of a heating roller and a pressure roller which are rotatably arranged while being in pressure contact with each other, and a heating body included in the roller pair. A temperature detecting means for detecting the temperature of the heating member, a recording material detecting means for detecting the presence or absence of a recording material guided by the pressure contact portion of the roller pair and discharged from the pressure contact portion, and the recording material detecting means. Based on the signal of, when the recording material approaches the pressure contact portion of the roller pair, the roller pair is rotated,
Roller pair drive control means set to stop the roller pair after the recording material is discharged from the pressure contact portion;
The temperature of the heating element is maintained at a predetermined target temperature based on the temperature detected by the temperature detecting means, and the target temperature is set to a fixing temperature necessary for fixing as the recording material approaches the pressure contact portion. Further, in the heating device provided with a temperature control means for setting the temperature lower than the fixing temperature in association with the discharge from the pressure contact portion, the roller pair drive control means is configured to control the temperature of the heating body based on a signal from the temperature detection means. This is achieved by setting the roller pair to be stopped after it is determined that the temperature has become equal to or lower than the predetermined temperature.

[0016]

According to the present invention, when the recording material approaches the pressure contact portion formed by the roller pair of the heating roller and the pressure roller,
The roller pair starts to rotate, and the heating element in the roller pair is driven to reach a predetermined fixing temperature. Therefore,
The recording material is conveyed while being heated and pressed by the roller pair, and is discharged from the pressure contact portion. Then,
The heating element is driven to reach a predetermined temperature lower than the fixing temperature, and gradually lowers the temperature. Then, when the temperature reaches a predetermined temperature, the roller pair is stopped and put in a standby state. At this time, the amount of heat given during the fixing operation is accumulated in the roller pair, and an overshoot occurs due to the amount of heat, but the roller pair is rotated and fixed as described above before entering the standby state. Since the temperature is maintained at a predetermined temperature lower than the temperature, the temperature of the entire roller pair is uniformly low, and the overshoot is suppressed to a low level.

[0017]

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

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. 1 is a temperature control circuit of a heating device according to a first embodiment of the present invention. The same parts as those of the conventional example shown in FIGS. 10 to 14 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, reference numeral 1 indicates the ON / OFF control of the motor 15 and the halogen heater 5 according to the inputs of the sensors 16 and 17 and the digital value of the signal S11 from the thermistor 9.
Is a control unit for performing on / off control of.

The control method in the control circuit shown in FIG. 1 will be described below. First, when the recording material is not conveyed to the apparatus, the sensors 16 and 17 are in the off state, and the heating roller is kept at a temperature lower than the temperature suitable for fixing. Therefore, the control target voltage is Vref1, and the control unit 1 controls the A / D converter 27 as shown in FIG.
The signal S12 from is selected and the temperature control is performed by comparing S11 and S12.

Next, when the recording material is conveyed to the apparatus,
First, the sensor 16 is turned on, and the control unit 1 turns on the signal S10 to the motor 15 and selects the signal S13 as shown in FIG. That is, the control target voltage is set to Vref2
Input the signal S13 from the A / D converter 28 as
By comparing S11 and S13 from the A / D converter 6, temperature control is performed at a temperature suitable for fixing the recording material.

While the sensor 16 or 17 is on, the recording material is in the vicinity of the roller, so the control unit 1 turns on the signal S10 to the motor 15 as shown in FIG.
The signal S13 is selected. That is, the control target voltage is Vre
Temperature control is performed as f2. However, after that, the sensor 17
Is turned off, the control unit 1 controls the signal S1 as shown in FIG.
2 is selected, the control target voltage is set to Vref1, and temperature control is performed at a temperature lower than the temperature suitable for fixing. Then, when the signal S11 from the A / D converter 6 further reaches the value of the signal S12 corresponding to the control target voltage Vref1, the signal S10 to the motor 15 is turned off.

The above control will be described with reference to the flowchart of FIG. First, the states of the sensors 16 and 17 are detected (step 101), the sensor 16 or the sensor 17 is turned on, or the signal S10 to the motor 15 is turned on when both sensors are turned on (steps 101 to 10).
2). Next, S13 is selected as a signal serving as a reference for temperature control (step 103). On the other hand, when all the sensors are off, the control target voltage is changed from Vref2 to Vre.
As a result of setting to f1, it is judged whether or not the value of the signal S11 has reached the value of the signal S12 corresponding to Vref1 (step 101 to step 104), and if not, the signal S10 to the motor 15 is turned on. (Step 105),
S12 is selected as a signal that serves as a reference for temperature control (step 106). If it has been reached, the signal S10 to the motor 15 is turned off (step 107),
S12 is selected as a signal that serves as a reference for temperature control (step 108).

After selecting the temperature control reference signal as described above, temperature control is performed based on the signal (step 109).

FIG. 4 shows a temperature change of the heating roller when the control operation of the present embodiment as described above is performed. As can be seen from this figure, when the motor is stopped, the temperature of the overshoot of the temperature of the heating roller is suppressed within a predetermined range.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5, even if the first embodiment is applied, the temperature overshoot may still be large.
In this embodiment, in order to prevent this, the set temperature for turning on the motor is changed.

FIG. 6 shows a temperature control circuit of the heating apparatus of this embodiment. In FIG. 6, 6 is an A / D converter for obtaining a digital value S1 from the voltage VT obtained by the voltage dividing ratio of the thermistor 5 and the resistor R1. Reference numeral 7 is an A / D converter for obtaining the digital value S2 from the control target voltage Vref. This control target voltage Vref is variable,
It can be changed by controlling the signal S by the control unit 2. The A / D converter 6 and the A / D converter 7 output digital values S1 and S2 to the control unit 2, respectively. The control unit 2 turns on and off the motor and sets the control target voltage Vref according to the input of the sensor.

A control method in the control circuit of this embodiment as described above will be described. First, when the recording material is not conveyed to the apparatus, the sensors 16 and 17 are in the off state, and the control unit 2 turns off the signal S10 to the motor 15 to set the target control voltage Vref as shown in FIG. The control target voltage Vref (1) corresponding to the temperature T1 shown in FIG. 9 is set, and the A / D converter 6 is controlled by the signal S. Then, the A / D converter 6 controlled in this way
The signals S2 and S1 are compared to control the temperature. Here, the temperature T1 is a temperature lower than the temperature suitable for fixing.

Next, when the recording material is conveyed to the apparatus,
First, the sensor 16 is turned on, the control unit 2 turns on the signal S10 to the motor 15 as shown in FIG. 7, and sets the control target voltage to Vref corresponding to the optimum temperature T2 for fixing.
Set to (2). Then, the A / D converter 6 is controlled in the same manner as described above, and the temperature control is performed at a temperature suitable for fixing the recording material while comparing the signals S2 and S1.

While the sensor 16 or the sensor 17 is on, the recording material is in the vicinity of the roller, so the control unit 2
Turns on the signal to the motor 15 as shown in FIG. 7, and sets the control target voltage to Vref corresponding to the temperature T2 suitable for fixing.
Set so as to be (2).

However, when the sensor 17 is turned off thereafter, the control target voltage is set to Vref (Ta). This Vref (Ta) is obtained as follows. First, the overshoot value ΔT2 generated after the previous fixing as shown in FIG. 5 is held, and the held value ΔT2 is obtained from the temperature (T1 in the case of FIG. 9) set by Vref (1) after the previous fixing. The temperature Ta is obtained by subtracting from, and Vref (Ta) is set so as to correspond to this temperature Ta. That is, overshoot is prevented by lowering the temperature after fixing from the previous time.

In this way, the control target voltage is set to Vref (T
After setting to a), the signal S2 from the A / D converter 6
And the signal S1 are compared, and when the value of the signal S1 reaches the value of the signal S2, the signal to the motor 15 is turned off.

After that, the overshoot of the heating roller from the limit temperature that does not affect the life of the roller is measured, and thereafter, the temperature corresponding to Vref (1) is maintained.

Next, the control of this embodiment will be described with reference to the flowchart of FIG. First, the control target voltage Vref
(Ta) is set to a value corresponding to Vref (1) (step 300). Next, the states of the sensors 16 and 17 are detected (step 301), the sensor 16 or the sensor 17 is turned on, or the signal S10 to the motor 15 is turned on when both sensors are turned on (step 302), and the control target voltage is reached. Is Vref (2).

If all the sensors are off,
As a result of changing the control target voltage from Vref (2) to Vref (Ta), it is determined whether or not the temperature of the heating roller has reached the temperature Ta with respect to Vref (Ta). The signal S10 to the motor 15 is turned off (step 305), and the control target voltage is set to Vref.
Set to (1). On the other hand, if you have never reached
The signal S10 to the motor 15 is turned on (step 30
7) The control target voltage is set to Vref (Ta) (step 308). In this way, after setting the control target voltage in steps 306 and 308, respectively, the overshoot temperature ΔT2 is measured and the temperature Ta is calculated.

After setting each target control voltage as described above, temperature control is performed while comparing the signals S1 and S2.

According to this embodiment, as shown in FIG. 9, the overshoot of the heating roller can be further reduced.

[0039]

As described above, according to the present invention, since the rotation of the roller is stopped after the temperature of the roller reaches a predetermined low temperature, the roller temperature after the stop does not become abnormally high and the heating is performed. The roller was not deformed, deteriorated, or had an offensive odor, and the roller life was extended. Also, there is no danger of ignition due to abnormal overheating of the rollers.

[Brief description of drawings]

FIG. 1 is a diagram showing a temperature control circuit of a heating device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing selection of a set temperature and a motor on / off for a sensor input by a control unit in the circuit of FIG.

3 is a flowchart showing a flow of control by a control unit in the circuit of FIG.

FIG. 4 is a diagram showing an example of a temperature change of the heating roller according to the first embodiment of the present invention.

FIG. 5 is a diagram showing another example of temperature changes of the heating roller according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a temperature control circuit of a heating device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing selection of set temperature and motor on / off for a sensor input by the control unit in the circuit of FIG. 6;

8 is a flowchart showing a flow of control by a control unit in the circuit of FIG.

FIG. 9 is a diagram showing another example of temperature changes of the heating roller according to the second embodiment of the present invention.

FIG. 10 is a cross-sectional view of a conventional image heating apparatus that performs heat fixing.

FIG. 11 is a diagram showing a conventional heating roller temperature control circuit and a roller driving circuit.

12 is a diagram showing selection of a set temperature for a sensor input and ON / OFF of a motor by a control unit in the circuit of FIG. 11.

13 is a flowchart showing a flow of control by a control unit in the circuit of FIG.

FIG. 14 is a diagram showing another example of temperature change of a conventional heating roller.

[Explanation of symbols]

1, 2 Control Unit (Temperature Control Unit, Roller Pair Drive Control Unit) 5 Halogen Heater (Heating Body) 9 Thermistor (Temperature Detection Unit) 10 Heating Roller 11 Pressurizing Roller 12 Recording Material 16, 17 Sensor (Recording Material Detection Means)

Claims (2)

[Claims] 1. A roller pair of a heating roller and a pressure roller, which are rotatably arranged while being in pressure contact with each other, a heating body included in the roller pair, and a temperature detecting means for detecting the temperature of the heating body. A recording material detecting means for detecting the presence or absence of a recording material guided to the pressure contact portion of the roller pair and discharged from the pressure contact portion, and a recording material pressure contact portion of the roller pair on the basis of a signal from the recording material detection means. The roller pair drive control means set to stop the roller pair after the recording material is discharged from the pressure contact portion when the recording material is discharged from the pressure contact portion, and the temperature detected by the temperature detection means. Based on the above, the temperature of the heating body is maintained at a predetermined target temperature, the target temperature is set to a fixing temperature necessary for fixing as the recording material approaches the pressure contact portion, and the discharge from the pressure contact portion is performed. Accordingly, the temperature lower than the fixing temperature In the heating device having a temperature control unit for setting the temperature of the roller pair, the roller pair drive control unit determines that the temperature of the heating body has become equal to or lower than a predetermined temperature based on the signal of the temperature detection unit, A heating device, which is set to be stopped. 2. The predetermined temperature for stopping the roller pair is
The heating device according to claim 1, which is determined by a difference between a maximum temperature of the heating element and a standby temperature during standby.