JP2881713B2 - Heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for fixing a toner used in an image forming apparatus.

[0002]

2. Description of the Related Art A conventional thermal heating device for fixing a toner used in an image forming apparatus has a configuration shown in FIG.
In the figure, reference numeral 1 denotes a heating roller, which is heated by a heater 2. Reference numeral 3 denotes a pressure roller, which is in contact with the heating roller 1 with a predetermined pressure. The heating roller 1 and the pressure roller 3 rotate in the direction of the arrow, and the contact portions of the two rollers 1 and 3 convey the recording paper across the recording paper. At this time, the unfixed toner on the recording paper is fixed by heat and pressure. 5 is an AC power supply.

The power supplied to the heater 2 is controlled by a solid state relay (SSR) 6.
That is, when an ON signal is input from the microcontroller 9 to the SSR 6 through the buffer 8, the SSR 6 is turned on, and power is supplied to the heater 2. A thermistor 4 is mounted on the heating roller 1, and a voltage applied to the thermistor 4 is input to an AD converter 7. Since the voltage value of the thermistor 4 changes according to the surface temperature of the heating roller 1, the microcontroller 9 can know the surface temperature from the digital value received from the AD converter 7.

[0004] The microcontroller 9 includes a heating roller 1.
If it is determined that the surface temperature is lower than the target temperature, SSR6
Is turned on. Conversely, if it is determined that the surface temperature is higher than the target temperature, the SSR 6 is turned off. Thus, the surface temperature of the heating roller 1 is kept constant. The microcontroller 9 includes a microprocessor, RO
The sequence is controlled in accordance with a program stored in the ROM, including the M and RAM.

[0005]

However, in many cases, the AC power supply 5 of the heating device is directly supplied from a commercial power supply. The voltage of the commercial power supply supplied to such an image forming apparatus varies from country to country. For example, 100 in Japan
V, 115 V in North America, 220 V and 240 V in Europe.

For this reason, conventionally, in order to keep the power consumption of the heater constant even when the power supply voltage is different, the resistance value of the heater is changed according to the power supply voltage. However, this method complicates production management and increases production costs.

In order to avoid this problem, if the unit value of the heater is adapted to the power supply voltage of each country, the power consumption of the heater will be different between the countries. Therefore, 100V-2
If the power supply voltage up to 40V can be covered, 2
At 40 V, the power consumption becomes unnecessarily large.
Furthermore, after turning on the power, when the heating roller is cold,
Excessive current flows.

The present invention has been made to solve such a conventional problem, and provides a heating device capable of reducing the power consumption of a heating element to a predetermined value or less regardless of a power supply voltage. With the goal.

[0009]

The heating device provided by the present invention is the following three devices.

(1) A heating element that generates heat by applying a voltage, power control means connected in series with an AC power supply to perform an ON / OFF operation to energize the heating element, and to be placed near the heating element. A heating object to be heated, a temperature detection means attached to the heating object to detect a temperature thereof, and a temperature control means for controlling a conduction angle of a power control means based on an output value of the temperature detection means. An apparatus, wherein when the temperature control unit recognizes that the temperature of the object to be heated is lower than a target temperature based on an output value of the temperature detection unit, the power control unit is turned ON / OFF at a zero crossing point, A rate of temperature rise per unit time of the heating body at that time is measured, and when the rate of temperature rise is higher than a first predetermined value, a predetermined low conduction angle is gradually increased to thereby increase the temperature of the object to be heated. of The temperature rise rate per much time second
And when the temperature rise rate is lower than the first predetermined value, the power control means is turned on / off at a zero crossing point.
A means for keeping the rate of temperature rise per unit time of the object to be heated at a second predetermined value.

(2) A heating element that generates heat by applying a voltage, power control means connected in series with an AC power supply to perform an ON / OFF operation to energize the heating element, and to be disposed near the heating element. A heating object to be heated, a temperature detection means attached to the heating object to detect a temperature thereof, and a temperature control means for controlling a conduction angle of a power control means based on an output value of the temperature detection means. An apparatus for turning on / off the power control means at a predetermined conduction angle when the temperature control means recognizes from the output value of the temperature detection means that the temperature of the object to be heated is higher than a target temperature. Then, a rate of temperature rise per unit time of the heating element at that time is measured, and when the rate of temperature rise is higher than a first predetermined value, a predetermined low conduction angle is gradually increased to thereby increase the temperature. Heating body The temperature rise rate per much time second
And when the temperature rise rate is lower than the first predetermined value, the power control means is turned on / off at a zero crossing point.
A means for keeping the rate of temperature rise per unit time of the object to be heated at a second predetermined value.

(3) In the heating device according to the above (1), a first storage means for storing a temperature rise rate of the object to be heated,
A second storage means for storing the conduction angle at that time; and means for determining the conduction angle based on signals from the first storage means and the second storage means.

[0013]

According to the present invention, even if the voltage of the commercial power supply supplied to the image forming apparatus is different, the power consumption of the heating element can be reduced to a predetermined value or less regardless of the voltage.

[0014]

【Example】

(Embodiment 1) FIG. 1 is a circuit diagram of a heating apparatus according to a first embodiment of the present invention. In the figure, reference numerals 1 to 9 denote the same parts as those in the conventional heating apparatus shown in FIG. That is, 1 is a heating roller that rotates in the direction of the arrow, and receives heat from the heater 2. 3 is a pressure roller,
It is in contact with the heating roller 1 with a predetermined pressure. The heating roller 1 and the pressure roller 3 rotate in the direction of the arrow,
The contact section 3 conveys the recording paper across the recording paper. At this time, the unfixed toner on the recording paper is fixed by heat and pressure. 5 is an AC power supply.

The electric power supplied to the heater 2 is controlled by a solid state relay (hereinafter, referred to as SSR) 6. That is, when an ON signal is input from the microcontroller 9 to the SSR 6 through the buffer 8, the SSR 6 is turned on, and power is supplied to the heater 2. Here, the SSR 6 is of a type that does not incorporate a zero-cross function. When the SSR 6 is turned on, the conductive state is maintained as long as the voltage does not approach near zero volt.
Therefore, once the SSR 6 is turned ON, it remains ON for at least a half cycle.

A thermistor 4 is mounted on the heating roller 1, and a voltage applied to the thermistor 4 is input to an AD converter 7. Since the voltage value of the thermistor 4 changes according to the surface temperature of the heating roller 1, the microcontroller 9 can know the surface temperature from the digital value received from the AD converter 7.

The microcontroller 9 includes the heating roller 1
If it is determined that the surface temperature is lower than the regulated temperature, SSR6
Is turned on. Conversely, if it is determined that the surface temperature is higher than the regulated temperature, the SSR 6 is turned off. Thus, the surface temperature of the heating roller 1 is kept constant. The microcontroller 9 includes a microprocessor, RO
The sequence is controlled in accordance with a program stored in the ROM, including the M and RAM.

In this embodiment, the amount of electricity supplied to the heater 2 is
How to control conduction angle and keep conduction angle at 180 ° SS
It is controlled by a method of controlling the ratio between the ON period and the OFF period of R6.

In order to control the conduction angle of the SSR 6, the phase of the power supply voltage must be detected. The phase detection circuit diagram includes the resistor 11 and the diode stack 1 shown in FIG.
7, a photocoupler 14, and a resistor 13. 1
Reference numeral 6 denotes a power switch.

FIG. 2 shows the operation waveforms of the above-mentioned phase detection circuit.
A power supply voltage having a voltage waveform as shown in FIG. 2A is supplied from the power supply 5 to the diode stack 17. A full-wave rectified current flows through the input of the photocoupler 14, and its output is turned on / off. The ON / OFF waveform is
As shown in FIG. 2B, the power supply voltage waveform (FIG. 2A)
Becomes a high level near the zero cross. The pulse signal is referred to as an AINT signal. The AINT signal is input to an interrupt port of the microcontroller 9. Then, the microcontroller 9 is interrupted in synchronization with the rise of the AINT signal, and the interrupt routine is executed. In the interrupt routine, a predetermined timer is started. And when the timer counts up,
A pulse having a predetermined width is output to SSR6. Assuming that the pulse drive signal is an FDRV signal, the signal waveform is shown in FIG.
(C). SS in synchronization with this FDRV signal
R6 is turned on, and a heater current as shown in FIG. The power supplied to the heater 2 can be controlled by changing the time from the zero crossing to the heater ON. The conduction angle of the heater 2 is controlled from 0 ° (completely OFF) to 180 ° (completely ON).
As described above, the heater current flows in each cycle after a predetermined time from the zero cross of the power supply voltage.

On the other hand, when the conduction angle θ = 180 °, the O
The ratio between the N period and the OFF period is controlled by the FDRV signal shown in FIG. 2E and the heater current shown in FIG. FD
The RV signal is always output in synchronization with the AINT signal. SS
R6 turns ON in synchronization with the FDRV signal, and a heater current as shown in FIG. SSR6 ON
The power supplied to the heater 2 can be controlled by changing the ratio between the period and the OFF period.

In this embodiment, the control is performed as follows to limit the power to the heater 2 and control the temperature of the heating roller 1. This control flow will be described with reference to FIGS. In both figures, A and B indicate connection points of the flow.

When the power is turned on (step 401),
The temperature T on the heating roller 1 is measured. If the temperature T is lower than the target temperature Ta, the conduction angle is set to 180 ° and the heater 2 is turned on (steps 401 to 404).
Next, the timer is started and it is determined whether or not the count is up. After counting up, the temperature difference between when the timer is started and when the timer counts up is measured (steps 405 to 407). If the temperature difference ΔT in Step 407 is smaller than the first predetermined value ΔT1, the conduction angle is set to 180 ° and the timer is started (Steps 408 to 410).
Then, if the timer counts up, a temperature difference between the time when the timer is started and the time when the timer counts up is measured (step 4).
11, step 412). Temperature difference ΔT in step 412
Is larger than a second predetermined value ΔT2, the heater is turned on,
If it is smaller, it is turned off (steps 413 to 41)
5). Steps 413 to 415 are repeated to keep the temperature rise rate of the heating roller 1 at the second predetermined value ΔT2. Next, it is determined whether or not the temperature T of the heating roller 1 is the temperature regulation temperature Tm. If the temperature is the temperature control temperature Tm, the ON period and the OFF period ratio of the SSR 6 are changed and maintained at the temperature control temperature Tm (step 431). If not, the process returns to step 410 (step 429).

At step 408, if the temperature difference ΔT is larger than the first predetermined value ΔT1, the conduction angle is set to the predetermined value θa. Then, the same operation as in steps 405 to 406 is repeated (steps 416 to 419). If the temperature difference ΔT is smaller than the second predetermined value ΔT2 in Step 420, θb is added to the current conduction angle (Step 421). If the temperature difference ΔT is larger than the second predetermined value ΔT2, θb is added from the current conduction angle to θb.
(Step 422). The operations of steps 420 to 422 are repeated to maintain the temperature rise rate of the heating roller 1 at the second predetermined value ΔT2. Next, it is determined whether or not the temperature T of the heating roller 1 is the temperature regulation temperature Tm. If the temperature is the controlled temperature Tm, the conduction angle is controlled to maintain the controlled temperature Tm (step 43).
1). If not, the process returns to step 417 (step 430).

If the temperature of the heating roller 1 is higher than the target temperature Ta in step 402, the conduction angle θ is set to θ1, the heater is turned on, and the same operations as in steps 410 to 413 are repeated (steps 423 to 42).
7). Next, if the temperature rise rate ΔT of the heating roller 1 is larger than the third predetermined value ΔT3, the process proceeds to step 416 (step 428), and the operations of steps 416 to 422 are repeated. On the other hand, if the temperature rise rate ΔT of the heating roller 1 is smaller than the third predetermined value ΔT3, the process proceeds to step 409, and the operations of steps 409 to 415 are repeated. FIG. 5 shows a temperature transition of the surface of the heating roller 1 when the above control is performed.

According to the routine of steps 402 to 422, if the temperature T of the heating roller 1 is lower than a predetermined value, the heating roller 1 is turned on at a conduction angle of 180 °. If the temperature rise rate at this time is larger than the first predetermined value ΔT1, the conduction angle θ
Is maintained at the second predetermined value ΔT2 (first predetermined value ΔT1 ≧ second predetermined value ΔT2). When the temperature rise rate is smaller than the first predetermined value ΔT1, the conduction angle θ is maintained at 180 ° and the ratio of the ON period to the OFF period of the SSR 6 is changed to reduce the temperature rise rate to the second predetermined value ΔT1.
It is kept at T2. On the other hand, when the temperature T of the heating roller 1 is higher than the predetermined value, the temperature rise rate is measured at the conduction angle θ1. Thereafter, the same routine as described above is performed to maintain the temperature rise rate at the second predetermined value ΔT2.

In the above routine, the rate of temperature rise after the power is turned on is limited. That is, when the power supply voltage is high, the conduction angle is controlled, and when the power supply voltage is high, the conduction angle θ
Is maintained at 180 °, and the ratio between the ON period and the OFF period of the SSR 6 is changed.

(Embodiment 2) In the first embodiment, control is performed so that the temperature rise rate of the heating roller 1 becomes a predetermined value when the power is turned on. Therefore, if the heating roller 1 is cold when the power is turned on and there is enough time to reach the target temperature Ta, the routine of the temperature rise rate at the time of turning on the power is effective. However, if the temperature T of the heating roller 1 has already risen to near the target temperature Ta when the power is turned on, the effect is not sufficiently exhibited. The second embodiment solves this problem.

FIG. 6 is a circuit diagram of a heating device according to a second embodiment.
1 is different from that of FIG. 1 in that an EEPROM 18 is added, and the other configuration is the same as that of FIG. The microcontroller 9 has a function of writing the determined conduction angle data.

The control method in this embodiment will now be described with reference to FIG.
This will be described with reference to FIG. In both figures, A,
B and C indicate flow connection points. Power on (Step 6
01) Then, it is determined whether the temperature T of the heating roller 1 is lower than a predetermined value. If it is lower, the same control as in the first embodiment is performed. If it is higher, the conduction angle data θe is stored in the EEPROM
18 and the conduction angle data θe is 180 °
(Step 602, Step 623,
Step 624). If θe is 180 °, the heater 2 is turned on at this conduction angle (step 626), and step 60
Go to 9. Thereafter, the same control as in the first embodiment is performed. On the other hand, if θe is not 180 °, the EEPROM 1
The heater 2 is turned on with the conduction angle data θe read from the heater 8. Thereafter, the same control as in the first embodiment is performed.

In the second embodiment, if the temperature T of the heating roller 1 at the time of turning on the power is equal to or higher than a predetermined value, the initial value of the conduction angle is read from the EEPROM 18, and the conduction of the heater 2 is thereby determined based on the previously measured value. Since the angle is set, the temperature can be quickly adjusted at a desired temperature.

[0032]

As described above, when power is turned on, θ =
The temperature rise rate of the heated body per unit time is detected at a conduction angle of 180 ° (full lighting), and when the temperature rise rate of the heated body at this time is larger than a predetermined value, gradually from a predetermined low conduction angle. By increasing the conduction angle, the temperature rise rate of the object to be heated is maintained at a predetermined value. On the other hand, when the temperature rise rate of the object to be heated is smaller than the predetermined value, the power control means is controlled at a conduction angle of θ = 180 °. By turning ON / OFF, the temperature rise rate of the object to be heated is maintained at a predetermined value.
When a heating device for each country ranging from C100V to AC240V is provided, the power consumption of the heating element can be reduced to a predetermined value or less regardless of the power supply voltage.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a heating device according to a first embodiment.

FIG. 2 is a circuit diagram of a phase detection circuit for a power supply voltage in FIG. 1;

FIG. 3 is a flowchart showing the operation of the first embodiment.

FIG. 4 is a flowchart showing the operation of the first embodiment.

FIG. 5 is a graph showing a change in the surface temperature of the heating roller in the first embodiment.

FIG. 6 is a circuit diagram of a heating device according to a second embodiment.

FIG. 7 is a flowchart showing the operation of the second embodiment.

FIG. 8 is a flowchart showing the operation of the second embodiment.

FIG. 9 is a circuit diagram of a conventional heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating roller 2 Heater 4 Thermistor 5 AC power supply 6 Solid state relay (SSR) 7 AD converter 9 Microcontroller 14 Photocoupler 18 EEPROM

Claims (3)

(57) [Claims] 1. A heating element that generates heat by applying a voltage, a power control means connected in series with an AC power supply to perform an ON / OFF operation to energize the heating element, and is disposed near the heating element. A heating device comprising: a body to be heated; a temperature detection unit attached to the body to be heated to detect a temperature thereof; and a temperature control unit for controlling a conduction angle of a power control unit based on an output value of the temperature detection unit When the temperature control unit recognizes that the temperature of the object to be heated is lower than a target temperature based on an output value of the temperature detection unit, the power control unit is turned ON / OFF at a zero crossing point,
Measure the temperature rise rate per unit time of the heating body at that time, when the temperature rise rate is higher than a first predetermined value, by gradually increasing a predetermined low conduction angle,
By keeping the temperature rise rate per unit time of the object to be heated at a second predetermined value, and when the temperature rise rate is lower than the first predetermined value, turning on / off the power control means at a zero crossing point, A heating apparatus comprising means for maintaining a rate of temperature rise of the object to be heated per unit time at a second predetermined value. 2. A heating element that generates heat by applying a voltage, power control means connected in series with an AC power supply to perform an ON / OFF operation to energize the heating element, and is disposed near the heating element. A heating device comprising: a body to be heated; a temperature detection unit attached to the body to be heated to detect a temperature thereof; and a temperature control unit for controlling a conduction angle of a power control unit based on an output value of the temperature detection unit When the temperature control unit recognizes that the temperature of the object to be heated is higher than a target temperature based on the output value of the temperature detection unit, the power control unit is turned on / off at a predetermined conduction angle. ,
Measure the temperature rise rate per unit time of the heating body at that time, when the temperature rise rate is higher than a first predetermined value, by gradually increasing a predetermined low conduction angle,
By keeping the temperature rise rate per unit time of the object to be heated at a second predetermined value, and when the temperature rise rate is lower than the first predetermined value, turning on / off the power control means at a zero crossing point, A heating apparatus comprising means for maintaining a rate of temperature rise of the object to be heated per unit time at a second predetermined value. 3. The heating device according to claim 1, wherein a first storage means for storing a rate of temperature rise of the object to be heated, a second storage means for storing a conduction angle at that time, and the first storage means. And a means for determining a conduction angle based on a signal from the second storage means.