JPH0228537Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a toner fixing device.

In recent years, flash discharge lamps have come to be used in toner fixing devices for facsimile machines and copying machines because they enable high-speed fixing and do not require waiting time. In such a fixing device, the toner is melted and fixed by the energy generated by the flash of the flash discharge lamp.

FIG. 1 shows an example of a conventional toner fixing device using a flash discharge lamp, and 1 is a charging circuit connected to an AC power source AC via a power switch SW. A charging/discharging capacitor 2 is connected, and a flash discharge lamp 3 is connected to both ends of the charging/discharging capacitor 2. 31 is a trigger electrode arranged along the tube wall of the flash discharge lamp 3, and the trigger circuit 4 is connected to this trigger electrode 31. P is an input terminal for a trigger circuit drive signal for operating the trigger circuit 4, and a trigger signal is input to this input terminal P in synchronization with the conveyance of a fixing material such as paper on which unfixed toner has adhered. A circuit drive signal is input. 5 is a discharge circuit, and this discharge circuit 5 is constituted by a series connection body of a discharge resistor R connected in series to both ends of the charging/discharging capacitor 2, and a switch such as a relay contact ry. RY is a relay coil that is integrated with relay contact ry to form a relay, and this relay coil RY is connected to input terminal a of AC power supply AC,
The relay contact ry is a normally closed contact. 6 is a charging start signal generating circuit for driving the charging circuit 1, and while receiving the charging start signal from the charging start signal generating circuit 6, charge is supplied from the charging circuit 1 to the charging/discharging capacitor 2. be done.

According to this toner fixing device, the power switch
When SW is closed, relay coil RY
is activated and the relay contact ry is open, and when a charge start signal is supplied from the charge start signal generation circuit 6 to the charging circuit 1, the charging/discharging capacitor 2 is set to a predetermined voltage, that is, toner fixation by the charging circuit 1. is charged to a voltage that can provide the required flash energy. Next, when a trigger circuit drive signal is input to the input terminal P, the trigger circuit 4 is activated and a high voltage is applied to the trigger electrode 81, which breaks the insulation between the discharge electrodes of the flash discharge lamp 3 and causes charging and discharging. The charge in the capacitor 2 is instantly released and a flash of light is generated. The radiant energy of this flash melts and fixes the unfixed toner on the fixing material.

On the other hand, when the device is at rest, the power switch SW is opened, and at this time, the operation of the relay coil RY is stopped and the relay contact RY is closed. When the relay contact ry closes in this way, the charging/discharging capacitor 2
The residual charge is discharged via the discharge resistor R, and the voltage across the charging/discharging capacitor 2 becomes zero, resulting in a safe state.

However, since the charging voltage of the charging/discharging capacitor 2 is relatively high, for example, about 2000 V, the relay contact ry is easily welded and damaged, and the opening/closing operation may not always be performed well. When the power switch SW is closed, if the relay contact ry does not open completely and a part of it is in contact, when a charging start signal is supplied to the charging circuit 1, the relay contacts ry will be directed to the charging/discharging capacitor 2. The charging charge is supplied, but at this time, both ends of the charging/discharging capacitor 2 are short-circuited by the discharging circuit 5, so the charging charge is not stored in the charging/discharging capacitor 2, but flows to the discharging resistor R, and as a result, discharging occurs. There is a problem that the resistor R is fused due to heat and the discharge circuit 5 is destroyed.

In the above example, the switch in the discharge circuit 5 is configured with a relay, but even if the switch is configured with other configurations, such as a manual switch or a semiconductor switching element, the same problem as described above will occur if the switch breaks down. It has points.

The present invention was developed based on the above-mentioned circumstances, and an object of the present invention is to provide a toner fixing device that can prevent damage to the discharge resistor due to overheating even if the switch of the discharge circuit fails. Its features are a flash discharge lamp for toner fixing equipped with a trigger electrode, a charging/discharging capacitor connected to both ends of this flash discharge lamp, and a charging device that supplies charge to the charging/discharging capacitor. a trigger circuit for supplying a trigger voltage to a trigger electrode of a flash discharge lamp; a discharge circuit comprising a series connection of a discharge resistor and a switch connected to both ends of the charging/discharging capacitor; and charging by the charging circuit. The present invention further includes a charging stop circuit that stops the charging operation by the charging circuit when the operation is started and a current flows through the discharging resistor of the discharging circuit.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an explanatory circuit diagram showing an embodiment of the present invention, in which 1 is a charging circuit, 2 is a charging/discharging capacitor, 3 is a flash discharge lamp, 4 is a trigger circuit, 5 is a discharging circuit, and 6 is a charging circuit. This is a start signal generating circuit, and its configuration is the same as that shown in FIG.

7 is a charging stop circuit, and this charging stop circuit 7
is a voltage dividing resistor R1 inserted between the discharge circuit 5 and the charging/discharging capacitor 2, a capacitor C1 connected to both ends of the voltage dividing resistor R1, and a gate on the positive side of the capacitor C1. Thyristor Th whose cathode is connected to the negative side, a series circuit of resistor R2 and DC power supply DC connected in series between the anode and cathode of thyristor Th, and between the anode of thyristor Th and the negative side of DC power supply DC. It consists of a resistor R3 and a light emitting diode LED connected to the charge start signal generating circuit 6 and a phototransistor PHT inserted in one side of the signal transmission path from the charging start signal generating circuit 6 to the charging circuit 1. Coupler PH is configured. Although a switch for the DC power source DC is not shown, the DC power source DC is opened and closed in conjunction with the opening and closing of the power switch SW.

According to the above embodiment, when the relay contact ry operates well, when the power switch SW is closed, the relay coil RY is activated and the relay contact ry is in an open state. At this time, in the charging stop circuit 7, the voltage across the resistor R1 is zero, so the thyristor Th is in the off state, and therefore, current flows through the closed circuit consisting of the DC power supply DC, the resistor R2, the resistor R3, and the light emitting diode LED. Photocoupler PH turns on. When a charge start signal is generated from the charge start signal generating circuit 6 in this state, the signal is supplied to the charging circuit 1 via the phototransistor PHT, and the charging/discharging capacitor 2 is charged.

On the other hand, the relay contact ry became defective and the power switch
When the relay contacts do not open completely even when the SW is closed, and some of them are in contact with each other, and the discharge circuit 5 is not cut off, the charging operation by the charging circuit 1 is started and the discharge circuit 5 is closed. When a current flows through the discharge resistor R, the charging stop circuit 7 is activated and the charging operation by the charging circuit 1 is stopped.

In other words, when the power switch SW is closed, the DC power supply DC is closed in conjunction with this, but at this time, the charging/discharging capacitor 2 has already been discharged and no current flows through the discharge resistor R and resistor R1. Since the trigger voltage is not generated, the thyristor Th of the charging stop circuit 7 is in the off state and the photocoupler
PH is on. Therefore, when the charging start signal generation circuit 6 generates a charging start signal in this state, this signal is supplied to the charging circuit 1 and the charging operation is started.

However, even if the charging circuit 1 starts charging, the relay contact ry is not completely open, so current flows not only to the charging/discharging capacitor 2 but also to the discharging resistor R and the resistor R1. .
At this time, the thyristor of the charging stop circuit 7 is activated by the trigger voltage generated by the discharge resistor R and the resistor R1.
Th shifts to the on state and the photocoupler PH turns off. As a result, the charging start signal is cut off and the charging operation of the charging circuit 1 is stopped.

Even if the relay contact ry malfunctions and the current from the charging circuit 1 flows into the discharging resistor R of the discharging circuit 5, the charging stop circuit 7 prevents the charging circuit 1 from operating properly. Since the discharge resistor R is stopped immediately, damage to the discharge resistor R due to overheating can be prevented.

Although one embodiment of the present invention has been described above, the present invention can be modified as appropriate. For example, the switch of the discharge circuit 5 may be configured with a manual switch, a semiconductor switching element, etc. in addition to a relay. . Further, the configuration of the charging stop circuit 7 is not limited to the above-mentioned embodiments, and various changes can be made.

As described above, the present invention consists of a flash discharge lamp for toner fixing equipped with a trigger electrode, a charging/discharging capacitor connected to both ends of the flash discharge lamp, and a charging circuit supplying charge to the charging/discharging capacitor. a trigger circuit that supplies a trigger voltage to a trigger electrode of a flash discharge lamp; a discharge circuit that is connected to both ends of the charging and discharging capacitor and includes a series connection of a discharge resistor and a switch; and a charging operation by the charging circuit. The toner fixing device is characterized by comprising a charging stop circuit that stops the charging operation by the charging circuit when the charging circuit starts and current flows through the discharging resistor of the discharging circuit. Even if the discharge resistor fails, damage to the discharge resistor due to overheating can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory circuit diagram showing an example of a conventional toner fixing device, and FIG. 2 is an explanatory circuit diagram showing an embodiment of the present invention. AC...alternating current power supply, SW...power switch, 1
...Charging circuit, 2...Charging/discharging capacitor, 3...
...Flash discharge lamp, 4...Trigger circuit, 5...Discharge circuit, 6...Charging start signal generation circuit, R...Discharge resistor, RY...Relay coil, ry...Relay contact, 7...Charging stop circuit , R1, R2, R3...
Resistor, Th...thyristor, PH...photocoupler, DC...DC power supply.

Claims (1)

[Scope of utility model registration request] A flash discharge lamp for toner fixing equipped with a trigger electrode, a charging and discharging capacitor connected to both ends of this flash discharge lamp, a charging circuit that supplies charging charge to this charging and discharging capacitor, and a trigger electrode of the flash discharge lamp. a trigger circuit that supplies a trigger voltage to the
A discharge circuit consisting of a series connection body of a discharge resistor and a switch is connected to both ends of the charge/discharge capacitor, and when a charging operation by the charge circuit is started and current flows through the discharge resistor of the discharge circuit, the discharge circuit is connected to both ends of the charge/discharge capacitor. A toner fixing device comprising: a charging stop circuit that stops charging operation by a charging circuit.