JP2003068427A - Heater drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to monitor whether the power supply is suitable for a heater or not. SOLUTION: Trial drive of the heater 21b is carried out supplying only the voltage, which is reduced the effective value by a diode 12, by making the temperature control switch 11 turn OFF and making the switch 13 for inspection turn ON. And, CPU 14 judges whether the power supply means 3 and the heater 21b suit or not based on the temperature change by this trial drive of the heater 21b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater drive circuit which is applied to, for example, a heat fixing device of an electrophotographic apparatus and controls the temperature of a heater.

[0002]

2. Description of the Related Art A heater driving circuit of this type monitors the temperature of a heater and intermittently supplies electric power from a power source to the heater so that the temperature reaches a predetermined temperature.

In electrophotographic apparatuses, there are cases where there are a plurality of series of products that use heaters having different ratings. For example, a product series that uses a heater with a rating of 100V (hereinafter referred to as 100V system) and a rating of 200V
There is a case where there is a product series (hereinafter referred to as a 200V system) that uses the heater of.

Even when such a plurality of sequences exist,
The heater drive circuit can be compatible with a common configuration. For this reason, if the same heater drive circuit is commonly used for each series, it is inevitable that each series has a common connector shape and the like, and different series of heaters can be attached to the product body of one series. .

[0005]

With such a configuration, there is a possibility that the product body and the heater may be mounted in an incorrect combination. In such a case, the power source and the heater are incompatible with each other, which may cause various problems. That is, for example, when a 100V heater is attached to a 200V product body, an excessive voltage is applied to the heater, which shortens the life of the heater or damages the heater. Could occur. Further, for example, when a 200V heater is mounted on a 100V product body, a sufficient voltage is not supplied to the heater, so that it takes a lot of time to raise the heater temperature to a target temperature. There is a possibility that a problem may occur such that the temperature of the heater cannot be raised to the target temperature, or the temperature of the heater cannot be stably controlled to the target temperature.

The present invention has been made in consideration of such circumstances, and an object thereof is to provide a heater drive circuit capable of monitoring whether or not a power source and a heater are compatible with each other. To do.

[0007]

In order to achieve the above object, a first aspect of the present invention is a heater drive circuit for controlling heat generation of a heater which is operated by receiving power supply from a power supply means. Turn on / off the power supply to the heater
A first switch means to be turned off, a voltage reducing means such as a diode, which is inserted between the power source means and the heater in parallel with the first switch means, and the power source via the voltage reducing means. Second switch means for turning ON / OFF power supply from the means to the heater, and the first switch means.
A determination means is provided for determining compatibility between the power supply means and the heater based on a temperature change of the heater when the switch means is OFF and the second switch means is ON.

By taking such means, the voltage reduced by the voltage reducing means is supplied to the heater so that the power supply means outputs a voltage higher than the rated voltage of the heater. Also, the heater is experimentally heated in a state where an excessive voltage is not supplied to the heater, and the compatibility between the power supply means and the heater is determined based on the temperature change at this time.

In addition to the first aspect of the present invention, the second aspect of the invention is based on the determination that the power source means and the heater are not compatible with each other, and the first switch is subsequently provided. A prohibition means for prohibiting turning on the means is provided.

By taking such means, when the power supply means and the heater are incompatible, the power supply means does not directly supply the electric power to the heater without the voltage reduction means.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a main part of a heater drive circuit according to this embodiment.

In this figure, a portion indicated by reference numeral 1 is a heater driving circuit. In this embodiment, the heater drive circuit 1
Are used to control the temperature of the heat fixing device 2 in the electrophotographic apparatus.

The heat fixing device 2 comprises a heat roller 21 and a press roller 22. The heat roller 21 is further
A heater 21b is arranged in an internal space of a hollow roller 21a (a cross section is shown in the figure). The heat roller 21 is a sheet P that is inserted between the heat roller 21 and the press roller 22.
On the other hand, the heat generated by the heater 21b is transmitted through the hollow roller 21a. As a result, the heat roller 21 melts and fixes the toner image formed on the paper P by the electrophotographic process processing unit (not shown). The heater 21b
Operates by receiving power supply from an AC power supply 3 as power supply means.

The temperature of the heat roller 21 is detected by the thermistor 4, resistor 5 and A / D converter 6. The thermistor 4 is arranged in a state of being close to the surface of the heat roller 21. Further, one end of the thermistor 4 is connected to the power supply line of a predetermined reference voltage Va, and the other end is connected to the resistor 5. The resistor 5 is the thermistor 4
The terminal on the side opposite to that connected to is grounded. Thus, the resistor 5 and the thermistor 4 form a voltage dividing circuit for dividing the reference voltage Va at a ratio according to the resistance value of the thermistor 4. The A / D converter 6 converts the potential of the connection point between the thermistor 4 and the resistor 5, that is, the voltage value obtained by dividing the reference voltage Va by the thermistor 4 and the resistor 5 into a digital value.

The heater drive circuit 1 includes a temperature control switch 11, a diode 12, an inspection switch 13 and a CP.
It has U14, ROM15 and RAM16. Then, the temperature control switch 11, the inspection switch 13, C
The PU 14, the ROM 15, and the RAM 16 are connected to each other via a bus 17. An A / D converter 6 is also connected to the bus 17.

The temperature control switch 11 is inserted between the AC power supply 3 and the heater 21b, and turns ON / OFF the power supply from the AC power supply 3 to the heater 21b. That is, the temperature control switch 11 corresponds to the first switch means.

Diode 12 and test switch 13
Are connected in series. Further, the diode 12 and the inspection switch 13 are inserted in parallel with the temperature control switch 11 between the AC power supply 3 and the heater 21b.
Thus, in the diode 12, the inspection switch 13 is turned on.
At this time, half-wave rectification is performed on the electric power supplied from the AC power supply 3 to the heater 21b. As a result, the effective voltage supplied from the AC power supply 3 to the heater 21b is reduced, and the diode 12 corresponds to a voltage reducing means. Further, the inspection switch 13 turns on / off the power supply from the AC power supply 3 to the heater 21b via the diode 12.
It corresponds to the second switch means.

The CPU 14 operates on the basis of an operation program stored in the ROM 15, and generally controls each unit to realize temperature control.

The ROM 15 stores and holds an operation program of the CPU 14 and various data necessary for temperature control.

The RAM 16 temporarily stores various data used by the CPU 14 to perform various processes.

Now, the CPU 14 performs software processing based on the operation program stored in the ROM 15 so as to serve as a processing means for controlling the temperature of the heat roller 21 to a predetermined target temperature, and also a judging means and a prohibiting means. To work as.

Here, the judging means is the temperature control switch 11
The suitability between the AC power supply 3 and the heater 21b is determined based on the temperature change of the heat roller 21 in a state where the switch is OFF and the inspection switch 13 is ON.

Further, the prohibiting means prohibits the temperature control switch 11 from being subsequently turned on when the determining means determines that the AC power supply 3 and the heater 21b are incompatible.

Next, the operation of the heater drive circuit 1 configured as described above will be described.

For example, when the controller (not shown) of the electrophotographic apparatus to which the heater driving circuit 1 is applied instructs the activation, the CPU 14 responds to the instruction to start the inspection process as shown in FIG.

In this inspection processing, the CPU 14 first
The value output from the A / D converter 6, that is, the detected temperature at the present time is fetched and is substituted into the variable T1 (step ST1). Thus, the variable T1 indicates the temperature of the heat roller 21 in the initial state.

After that, the CPU 14 turns on the inspection switch 13 (step ST2). The temperature control switch 11 and the inspection switch 13 are off when the CPU 14 does not perform on control. Therefore, a state is formed in which the temperature control switch 11 is OFF and the inspection switch 13 is ON. Then, in this state, the CPU 14 waits for the end of the predetermined inspection period (step ST3).

When it is confirmed that the inspection period has ended, the CPU 14 takes in the detected temperature at that time and substitutes it into the variable T2 (step ST4). Further, the CPU 14 turns off the inspection switch 13 (step ST5). Then, the CPU 14 confirms whether the difference between the variable T2 and the variable T1, that is, the amount of increase in the detected temperature during the inspection period is within a predetermined effective range (step ST6).

Now, the output voltage of the AC power supply 3 and the heater 21
It is assumed that a change in the temperature of the heat roller 21 in a state where the rated voltage of b is 100 V or 200 V (hereinafter, referred to as a conforming state) is a characteristic represented by a symbol A in FIG. At this time, the output voltage of the AC power supply 3 is 100V,
And when the rated voltage of the heater 21b is 200V,
Since the voltage supplied to the heater 21b is insufficient,
The change in the temperature of the heat roller 21 has a characteristic of lying down as compared with the conforming state, as indicated by the symbol B in FIG. On the other hand, the output voltage of the AC power supply 3 is 200 V and the heater 2
If the rated voltage of 1b is 100V, the heater 21b
Since the voltage supplied to the heat roller 2 is excessive,
The change in the temperature of 1 is a characteristic that occurs as compared with the conforming state, as indicated by the symbol C in FIG.

Therefore, the temperature rise amount during the inspection period is as follows: the output voltage of the AC power supply 3 is 100 V and the heater 2
When the rated voltage of 1b is 200 V, it becomes smaller than the increase amount Ta in the adapted state, as indicated by Tb in FIG. In addition, the temperature rise during the inspection period depends on the AC power supply 3
When the output voltage is 200 V and the rated voltage of the heater 21b is 100 V, the increase amount Ta is larger than the increase amount Ta in the conforming state as shown by Tc in FIG.

Therefore, the effective range is set in consideration of the characteristics shown in FIG. 3 by setting the range in which it can be discriminated whether or not the temperature rise exhibits characteristics close to the characteristics indicated by the symbol A. In the confirmation processing in step ST6 described above, it is confirmed whether or not it is in the conforming state.

If it is confirmed in step ST6 that the amount of temperature rise during the inspection period is within the predetermined range, that is, in the conforming state, the CPU 14 sets the operation permission mode (step ST7). The operation permission mode is a mode for permitting the drive control of the heater 21b by controlling the temperature control switch 11.
After setting this operation permission mode, the CPU 14
Starts a well-known temperature control process for actually controlling the temperature of the heat roller 21 to a predetermined target temperature as a process of another routine (step ST8), and ends the current inspection process.

However, if it is confirmed in step ST6 that the amount of increase in temperature during the inspection period is not within the predetermined range, that is, that it is not in the conforming state, the CPU 14
Sets the operation prohibition mode (step ST9). This operation prohibition mode is a mode for prohibiting the drive control of the heater 21b by controlling the temperature control switch 11. Therefore, if this operation prohibition mode is set, C
The PU 14 ends this inspection processing without activating the temperature control processing.

As described above, according to this embodiment, electric power is supplied to the heater 21b on a trial basis, and it is determined whether or not the AC power source 3 and the heater 21b are compatible with each other based on the amount of temperature rise caused by the electric power supply. To do. As a result, the output voltage is 10
A 200V heater 2 having a rated voltage of 200V with respect to a 100V product body having an AC power source 3 of 0V
When the heat roller 21 having 1b is mounted, or the rated voltage is 100V, the rated voltage is 100V with respect to the main body of a 200V system equipped with the AC power supply 3 having an output voltage of 200V.
When the heat roller 21 having the system heater 21b is mounted, it is possible to judge it when it is in an incompatible state. Therefore, the heater drive circuit 1 of the present embodiment is designed to have a common connector so that the heater drive circuit 1 can be used in both 100V and 200V product series.
It is possible to judge the non-conforming state as described above, and it is possible to take measures against the non-conforming state by utilizing the judgment result by an appropriate method.

In the present embodiment, when performing the inspection as to whether or not it is in the conforming state, the diode 12 performs half-wave rectification to supply a voltage whose effective value is reduced to half to the heater 21b. Even when the heat roller 21 having the 100V-type heater 21b is attached to the product body of the above, the excessive voltage that damages the heater 21b is not applied, and the heat roller 21 is not applied during the inspection period. No failure or abnormal operation will occur.

Further, according to the present embodiment, since the diode 12 is used to reduce the voltage applied to the heater 21b, it can be realized extremely easily and inexpensively.

Further, according to the present embodiment, when it is determined that the non-conforming state is found, the temperature control thereafter is prohibited and the heater 21b is not driven. It is possible to reliably prevent a failure or an abnormal operation due to continued use.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the subsequent driving of the heater 21b is prohibited when it is determined that the heater is not in conformity. However, it is also possible to perform another treatment such as, for example, notifying the user of the non-conforming state by a display or the like, or a plurality of treatments may be performed respectively. Alternatively, the determination result may be output to the outside, and appropriate processing such as notification may be performed outside.

Further, in the above embodiment, the diode 12 is used as the voltage reducing means, but the configuration may be arbitrary such as using other element such as a triac.

Further, in the above embodiment, the heater drive circuit 1
Although the heater 21b in the thermal fixing device 2 is driven, the present invention can be used to drive a heater other than the heater 21b in the thermal fixing device 2.

Besides, various modifications can be made without departing from the scope of the present invention.

[0043]

According to the first aspect of the present invention, the voltage reduced by the voltage reducing means is supplied to the heater, so that the power source means outputs a voltage higher than the rated voltage of the heater. Even if the heater is heated experimentally without supplying an excessive voltage to the heater, and the compatibility between the power supply means and the heater is determined based on the temperature change at this time, the power supply and the heater are The heater drive circuit is capable of monitoring whether or not it is suitable.

Further, according to the second aspect of the present invention, when the power supply means and the heater are incompatible, the power supply means does not directly supply power to the heater without the voltage reduction means. It is possible to prevent the product from being continuously used in an incompatible state.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of a heater drive circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure at the time of inspection processing by a CPU 14 in FIG.

3 is a diagram showing how the detected temperature changes when electric power is supplied to the heater 21b in FIG.

[Explanation of symbols]

1 ... Heater drive circuit 11 ... Temperature control switch 12 ... Diode 13 ... Switch for inspection 14 ... CPU 15 ... ROM 16 ... RAM 17 ... Bus 2 ... Heat fixing device 21 ... Heat roller 21a ... Hollow roller 21b ... heater 22 ... Press roller 3 ... AC power supply 4 ... Thermistor 5 ... Resistor 6 ... A / D converter

Claims (3)

[Claims] 1. A heater drive circuit for controlling heat generation of a heater which operates by receiving power supply from a power supply means, wherein power supply from the power supply means to the heater is turned ON / OF.
F switch means, voltage reducing means inserted between the power source means and the heater in parallel with the first switch means, and the heater from the power source means via the voltage reducing means. Second switch means for turning on / off the power supply to the heater, and the power source means and the heater based on the temperature change of the heater when the first switch means is off and the second switch means is on. A heater driving circuit, comprising: a determining means for determining compatibility. 2. A prohibition means for prohibiting subsequent turning on of the first switch means in response to the judgment means judging that the power supply means and the heater are incompatible with each other. The heater drive circuit according to claim 1, which is characterized in that. 3. The heater drive circuit according to claim 1, wherein the power supply means supplies alternating current power, and the voltage reduction means is a diode.