JPH0667485A - Image recorder - Google Patents

Abstract

PURPOSE:To protect a device from a failure with a simple constitution, in each part of an image recorder such as a copying machine, etc., provided with a thermal fixing unit, a cooling fan and their driving power sources. CONSTITUTION:The temperature of the heater H of the thermal fixing unit is detected by a thermistor TH and the signal of the detection is inputted into a microcomputer control circuit 2. Further, the rotation of the cooling fan F driven by a switching power source 5 is detected by a rotation sensor S and the signal of the detection is inputted into the microcomputer 2. On the other hand, the output current of the switching power source 5 is detected by a current detecting circuit 6. Then, when the microcomputer 2 detects the abnormality of the thermal fixing unit or the cooling fan F from each input signal or the current detecting circuit 6 detects the abnormality of the output of the switching power source 5, stops the operation of the switching power source 5 to stop the energization of the thermal fixing unit and the cooling fan F.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus such as a copying machine provided with a thermal fixing device and a cooling fan, and a driving power source for driving them.

[0002]

2. Description of the Related Art An image recording apparatus such as a copying machine is provided with a heat fixing device for fixing a toner image on a transfer sheet and a cooling fan for cooling the inside of the apparatus. If the thermal fixing device fails, there is a risk of an excessive temperature rise. Therefore, a safety circuit as shown in FIG. 4 is provided.

In FIG. 4, reference numeral 1 is an AC power source for driving the thermal fixing device, and 2 is a microcomputer (CPU) for controlling the energization of the heater H of the thermal fixing device, and a plurality of input ports (INPORTA, B ... ) And output port (OUT
PORTA, B ...). TH is a thermistor installed in or near the heater H and has a resistance R1.
At the same time, a detection signal obtained by dividing the control voltage is input to the microcomputer 2. Reference numeral 3 is a triac (two-way three-terminal thyristor) interposed between the heater H and the AC power supply 1, and its gate terminal is connected to the output terminal of the microcomputer 2.

Reference numeral 4 is a relay whose contact point 4a is connected between the AC power supply 1 and the triac 3, Q1 is a transistor which is turned on and off by the output of the microcomputer 2, and its collector is connected to the base of the transistor Q2. The collector of Q2 is the coil 4b of the relay 4 described above.
It is connected to the. C1 and R2 are a capacitor and a resistor connected between the base and emitter of the transistor Q2.

In the circuit shown in FIG. 4, the contact 4a of the relay 4 is normally used.
Is closed, and when the energization signal is output from the microcomputer 2, the triac 3 is turned on, the heater H of the thermal fixing device is energized, and the toner image can be thermally fixed. Here, if the thermal fixing device fails and exceeds a predetermined temperature,
The microcomputer 2 detects the signal from the thermistor TH and turns on the transistor Q1. As a result, the transistor Q2 is turned off, and the energization of the coil 4b of the relay 4 is stopped. Therefore, the contact 4a of the relay 4 is opened, and the energization of the heater H is stopped.

Further, even if the cooling fan fails, the inside of the apparatus is brought into an abnormal temperature rise state. Therefore, a similar safety circuit is provided to prevent this. When the cooling fan fails, the copy operation is stopped and the device is prevented from being destroyed.

[0007]

However, in the image recording apparatus as described above, since the thermal fixing device, the cooling fan and the driving power source are provided with the respective protection circuits,
There are problems that the circuit becomes complicated, the number of elements used is large, and the cost becomes high.

The present invention has been made in view of the above problems, and it is possible to obtain an inexpensive image recording apparatus which can protect the apparatus with a simple circuit structure, use a small number of elements. Has an aim.

[0009]

An image recording apparatus of the present invention has a thermal fixing device and a cooling fan, a driving power source for driving them, a temperature sensor for detecting the temperature of the thermal fixing device, and the cooling device. A rotation sensor that detects the rotation of the fan, a detection circuit that detects the output of the driving power supply of the cooling fan and controls the operation of the driving power supply, and the operation of the driving power supply of the cooling fan based on the output of each sensor. And a control circuit for controlling the.

A switching power supply is used as a drive power source for the cooling fan, and a control circuit outputs an abnormality detection signal in response to a signal from each sensor. The abnormality detection signal or the abnormality detection signal from the detection circuit causes the control circuit to output the abnormality. It is configured to stop the oscillation of the switching power supply.

Further, a relay driven by the output of the switching power source is provided, and the contact of this relay is connected in series with the thermal fixing device.

[0012]

In the image recording apparatus of the present invention, the output signal of the temperature sensor of the heat fixing device and the output signal of the rotation sensor of the cooling fan are input to the control circuit. When the control circuit detects an abnormality from these signals, the abnormality detection is performed. Output a signal. And
The operation of the drive power supply is controlled by the abnormality detection signal or the abnormality detection signal from the output circuit of the drive power supply, and the power supply is stopped when the thermal fixing device or the cooling fan fails.

[0013]

1 is a circuit diagram showing the configuration of an embodiment of the present invention, and the same reference numerals as those in FIG. 4 denote the same components.
In the figure, reference numeral 1 denotes an AC power supply, which serves as a drive power supply for the heater H of the thermal fixing device and also supplies an AC voltage to the switching power supply 5 which is a drive power supply for the cooling fan F.

Reference numeral 2 denotes the output of a thermistor (temperature sensor) TH for detecting the temperature of the heater H and rotation of the cooling fan F.
A microcomputer (control circuit) that controls the operation of the switching power supply 5 based on the output of the rotation sensor S that detects a stop outputs an abnormality detection signal when the outputs of the sensors TH and S are abnormal, and outputs the switching power supply 5 Stop the oscillation of. 3 is a triac connected in series with the heater H, 4 is a relay driven by the output (+ 12V) of the switching power supply 5, and the contact 4a of this relay 4 is connected in series with the heater H.

Reference numeral 6 is a current detection circuit for detecting the output current of the switching power supply 5 and controlling the operation of the switching power supply 5. Here, the current of the power supply line of + 5V is detected, and it is inserted in the power supply line. The resistor R3, the resistors R4 and R5 for voltage division, and the comparator Q3. The output port of the current detection circuit 6 is an output port (OUTPO) of the abnormality detection signal of the microcomputer 2.
RTB), these ports are OR-coupled, and the oscillation stop signal input terminal (E) of the switching power supply 5 is connected.
rr terminal). When the output current of the switching power supply 5 is abnormal, the current detection circuit 6 outputs an abnormality detection signal.
Oscillation is stopped.

In the circuit configured as described above, the thermistor TH installed near the heater H of the heat fixing device.
Converts the temperature of the heater H into a voltage value and inputs it to the input port (INPORTA) of the microcomputer 2. The rotation sensor S of the cooling fan F also sends a detection signal to the input port (INPORTB) of the microcomputer 2.
Are typing in. The microcomputer 2 monitors these input signals, and when either of them is in an abnormal state, that is, when the temperature of the heat fixing device is excessively increased or the cooling fan F is stopped, the oscillation of the switching power supply 5 from the output port (OUTPORTB). Output an abnormality detection signal to the stop terminal. As a result, the oscillating operation of the switching power supply 5 is stopped, and the power supply to the thermal fixing device and the cooling fan F is stopped.

Further, the current detection circuit 6 detects the output current of the switching power supply 5, and when the output becomes an overcurrent state, the output of the comparator Q3 is inverted. At this time, since the output line of the comparator Q3 is wire-connected to the output line of the abnormality detection signal, the oscillating operation of the switching power supply 5 is also stopped by the inverted output (abnormality detection signal) of the comparator Q3, and the thermal Power supply to the fixing device and the cooling fan F is stopped.

As described above, when any abnormal state such as an abnormal temperature rise of the heat fixing device, a stop of the cooling fan F, or an overcurrent of the switching power supply 5 occurs, the operation of the switching power supply 5 is stopped and the power supply to each part is stopped. The supply is stopped and damage to the device is prevented. At that time, a part of the protection circuit of each part of the heat fixing device, the cooling fan F and the switching power source 5 is shared, and the destruction of the device due to the failure of three places is prevented at the same time. Therefore, the circuit configuration is simplified, the number of elements used is small, and the cost can be reduced.

FIG. 2 shows the internal structure of the switching power supply 5. The alternating current from the alternating current power supply 1 is full-wave rectified by the diode stack 7, smoothed by the capacitor C2, and then intermittently applied to the primary winding of the transformer T by the switching operation of the transistor Q4. And
The alternating current generated in the two secondary windings of the transformer T is rectified by the diodes D1 and D2, and the capacitor C3.
Smoothed by C4 and output as + 12V and + 5V DC.

The switching operation of the transistor Q4 is controlled by the output D of the oscillator (OSC) 8, and the output of the auxiliary winding of the transformer T is rectified and smoothed by the diode D3 and the capacitor C5. Things are supplied as power. The oscillation of the oscillator 8 is controlled by the potential of SD. When the potential exceeds the first reference potential, the oscillation is stopped, and when it falls below the second reference potential, the oscillation operation is performed (first reference potential> second Reference potential).

On the other hand, the signal input from the above-mentioned oscillation stop terminal is sent to the oscillator 8 via the resistor R6 and the photocoupler 9.
And the potential of the SD is controlled by this input signal. At that time, when a failure occurs, a signal charge is stored by the capacitor C6 and plays a role of a memory so that the failure state is not cleared by turning on / off a power switch (not shown). R7 is a resistor connected to the output side of the photocoupler 9, and R8 is a resistor connected in parallel with the capacitor C6.

FIG. 3 is a circuit diagram showing the configuration of another embodiment of the present invention, and the same reference numerals as those in FIG. 1 denote the same components. In the figure, 10 is a voltage detection circuit for detecting the output voltage of the switching power supply 5, which is composed of resistors R9 and R10 for voltage division, a series circuit of a Zener diode ZD and a resistor R11 which are constant voltage elements, and a comparator Q5.

In the above embodiment, the current detection circuit 6 is provided to protect the switching power supply 5 from overcurrent, but in this embodiment, the voltage detection circuit 10 is used to protect against overvoltage. That is, when the voltage detection circuit 10 detects an overvoltage, an abnormality detection signal is output to the oscillation stop terminal of the switching power supply 5 to stop the oscillation operation of the switching power supply 5.

With such a structure, the operation of the switching power supply 5 is stopped when an abnormal state such as an abnormal temperature rise of the thermal fixing device, a stop of the cooling fan F, or an overvoltage of the switching power supply 5 occurs. Power supply to each part is stopped. Therefore, the same effect as that of the embodiment of FIG. 1 can be obtained, and it is possible to prevent the device from being broken due to the failure at three locations.

It should be noted that a configuration combining the embodiment of FIG. 1 and the embodiment of FIG. 3, that is, a configuration in which both a current detection circuit 6 for detecting an overcurrent of the switching power supply 5 and a voltage detection circuit 10 for detecting an overvoltage are provided. Also good. In this case, it is possible to prevent the device from being damaged due to the abnormal temperature rise of the heat fixing device, the stop of the cooling fan F, and the overcurrent and overvoltage of the switching power supply 5.

[0026]

As described above, according to the present invention, the abnormal states of the thermal fixing device and the cooling fan are detected from the output signals of the respective sensors, and the abnormality detection signal or the abnormal state of the driving power source is detected. Since the operation of the drive power supply is controlled by the detection signal, it is possible to prevent the damage of the device due to the failure of the thermal fixing device, the cooling fan and the drive power supply, and to protect the device with a simple circuit configuration. It is possible to obtain the effect of being less expensive and cheaper.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an internal configuration of a switching power supply.

FIG. 3 is a circuit diagram showing a configuration of another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 AC power supply (driving power supply) 2 Microcomputer (control circuit) 4 Relay 4a contact point 5 Switching power supply (driving power supply) 6 Current detection circuit 10 Voltage detection circuit

Claims (3)

[Claims] 1. A thermal fixing device and a cooling fan, a driving power source for driving them, a temperature sensor for detecting a temperature of the thermal fixing device, a rotation sensor for detecting rotation of the cooling fan, and the cooling device. A detection circuit that detects the output of the driving power supply of the fan and controls the operation of the driving power supply; and a control circuit that controls the operation of the driving power supply of the cooling fan based on the output of each sensor. Image recording device. 2. A driving power supply for the cooling fan uses a switching power supply, and a control circuit outputs an abnormality detection signal in response to a signal from each sensor, and the switching is performed by the abnormality detection signal or the abnormality detection signal from the detection circuit. The image recording apparatus according to claim 1, wherein the oscillation of the power supply is stopped. 3. The image recording apparatus according to claim 2, further comprising a relay driven by an output of a switching power supply, and a contact of the relay is connected in series with a thermal fixing device.