JPH05914Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a toner fixing device equipped with a flash lamp used in image forming apparatuses such as copying machines and facsimile machines.

[Prior art]

In a toner fixing device equipped with a flash lamp, a flash lamp such as a xenon lamp is usually housed in a lamp cover that has a reflective mirror surface on its inner surface and an opening of the size necessary for fixing, and the opening is covered with a lamp cover. A cover glass is provided. Fixing is carried out by sequentially passing an image support, such as a transfer paper, carrying an unfixed toner image on its surface along the opening surface of the lamp cover. This is done by turning on the flash lamp every time the fixing device moves by the effective fixing width. That is, the light emitted from the flash lamp is reflected either directly or by the reflective mirror surface on the inner surface of the lamp cover, and some of the light hits the toner image on the transfer paper and the other part hits the margin, and the light that hits the toner image on the transfer paper ( In particular, heat rays) are absorbed and heat the toner. On the other hand, the light that hits the margins of the transfer paper other than the toner image is reflected and hits the reflective mirror surface of the lamp cover, where it is reflected again and hits the transfer paper, and the operation is repeated. In this way, most of the light emitted from the flash lamp is absorbed by the toner image as it is repeatedly reflected between the transfer paper and the reflective mirror surface of the lamp cover. As a result, the toner image is molten and liquefied, and then solidified and fixed onto the transfer paper.

The flash lamp is turned on by charging a main capacitor for energy supply with the luminous energy required for fixing the toner, and then instantaneously supplying the charging energy of the main capacitor to the flash lamp. It is useful to use an electrolytic capacitor as the main capacitor because it is easy to obtain a large capacity capacitor, but at the start of lighting, the voltage between the electrodes of the flash lamp usually needs to be about several hundred V or more. A single electrolytic capacitor has a maximum withstand voltage of about 350V, and cannot hold the high voltage mentioned above, so the main capacitor is usually constructed by connecting two or more electrolytic capacitors in series. be done.

[Problem that the invention attempts to solve]

When two or more electrolytic capacitors are connected in series to form the main capacitor, repeated rapid charging and discharging may cause leakage current in each electrolytic capacitor or changes in capacitance over time. Therefore, an abnormally high voltage is applied to a particular electrolytic capacitor during charging, and in the worst case, the electrolytic capacitor may exceed its withstand voltage and be destroyed, resulting in an extremely dangerous accident.
This phenomenon becomes more significant as the number of electrolytic capacitors increases.

For this reason, an overvoltage detection circuit is usually provided that detects the charging voltage of the electrolytic capacitor and generates an overvoltage detection signal before the charging voltage reaches a voltage exceeding an allowable limit. In this case, the overvoltage detection circuit is constructed using a photocoupler that combines a light emitting diode that emits light when the charging voltage of the electrolytic capacitor reaches an overvoltage and a phototransistor that receives light from the light emitting diode. Ru.

However, when using a photocoupler, the light emitting diode and phototransistor are extremely close to each other as one element, even though a high voltage of about 1000V may be applied between the light emitting diode and the phototransistor. Because of this arrangement, the insulation resistance between the two is low, resulting in insufficient insulation, and as a result, there is a problem in that high voltage flows into the control circuit system, causing serious damage.

[Purpose of the invention] The present invention was made based on the above-mentioned circumstances, and its purpose is to configure a main capacitor by connecting two or more electrolytic capacitors in series, and to increase the charging voltage of the electrolytic capacitor. The overvoltage detection signal is generated before the voltage exceeds the permissible limit, and the insulation resistance between the overvoltage detection part and the detection signal generation part in the overvoltage detection circuit is sufficiently high to prevent high voltage from entering the control circuit system. To provide a highly safe toner fixing device that does not go around.

[Means for solving problems]

The toner fixing device of the present invention includes a flash lamp, a discharge circuit including a main capacitor and a supply circuit that supplies charging energy from the main capacitor to the flash lamp, a trigger circuit that triggers the flash lamp, and a discharge circuit that includes a main capacitor and a supply circuit that supplies charging energy from the main capacitor to the flash lamp. A toner fixing device comprising a charging circuit for charging a capacitor and an overvoltage detection circuit for detecting an overvoltage of the main capacitor, and fixing a toner image on an image support by irradiating light from the flash lamp. The capacitor is formed by connecting two or more electrolytic capacitors in series, and the overvoltage detection circuit divides the series connection of the electrolytic capacitors into two or more groups and independently detects the overvoltage of the electrolytic capacitor for each group. A divided detection section including a light emitting element that detects and generates light before the start of discharge, an optical fiber that conducts the light of the light emitting element of each divided detection section, and when the light of the light emitting element is received from the optical fiber. and a detection signal generation section including a light receiving element that is electrically connected to generate a detection signal.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an outline of an example of a toner fixing device according to the present invention. Reference numeral 1 denotes a flash lamp made of, for example, a xenon flash lamp. The lamp cover 23 is housed in a lamp cover 23 having an opening surface 22 with a width L ₁ formed therein, and a transparent cover glass 24 is provided on the opening surface 22 of the lamp cover 23 . Although not shown, a trigger wire wound spirally, for example, is disposed on the outer wall surface of the flash lamp 1. Reference numeral 12 denotes a separation and conveyance tank for transfer paper, which is a support for the transferred toner image, made of paper, for example, and reference numeral 13 denotes a rear reflecting plate that also serves as the surface of the tank. Further, 14 is a drive roller of the separation conveyance belt 15, 16 is a transmission roller thereof,
17 is a paper ejection roller.

When the transfer paper, on which the toner image has been transferred, is conveyed on the separation conveyance belt 15 in the direction of arrow A, the conveyance switch 18 provided at the inlet of the fixing section of the separation conveyance tank 12 outputs a fixing control signal. Timing detection is performed. When the leading edge of the transfer paper turns on the conveyance switch 18 and enters the fixing area Q of the effective fixing width _L2 of the flash lamp 1,
The flash lamp 1 is emitted to fix the toner on the transfer paper. Thereafter, until the trailing edge of the transfer paper finishes passing through the fixing section, the flash lamp 1 is emitted every time the transfer paper advances a distance of the effective fixing width L ₂ to fix the entire area. . In addition, 1 in the figure
9 is a paper discharge detection switch.

FIG. 2 is an explanatory circuit diagram showing an electric circuit portion that causes the flash lamp 1 to emit light.

3 is a charging circuit, which includes a step-up transformer 32, a solid state relay (SSR) 31 inserted between the primary side of the step-up transformer 32 and the AC power supply, and a charge circuit of the step-up transformer 32. Detection by a rectifier 33 connected to the secondary side, voltage dividing resistors 34 and 35 for detecting the charging voltage of the main capacitor 4 for energy supply, which will be described later, and a capacitor charging signal CHG and voltage dividing resistors 34 and 35, which will be described later. The charging voltage control circuit 36 controls the charging voltage of the main capacitor 4 by controlling the opening/closing operation of the solid state relay 31 based on the voltage V ₀ . 37,
38 is a capacitor and inductor for power factor improvement, and 39A and 39B are circuit breakers. In the solid state relay 31, when the signal to the input terminal 31D is low level (L level), the AC side terminals 31A, 31B
During this conduction period, the main capacitor 4 is charged by the power supplied from the AC power source AC.On the other hand, when the signal to the input terminal 31D is at a high level (H level), the AC side terminal 31A ,3
1B is cut off and the supply of power from the AC power source AC is stopped.

4 is a main capacitor for energy supply, and in this example, four electrolytic capacitors 41, 42, 4
3 and 44 are connected in series.

Reference numeral 100 denotes an overvoltage detection circuit, which in this example is configured to generate an overvoltage detection signal when the charging voltage of any one of the electrolytic capacitors 41, 42, 43, and 44 reaches an abnormally high overvoltage. Details will be described later. In this example, in this overvoltage detection circuit 100, when an overvoltage detection signal is generated, the contacts 201 and 202 inserted in the front stage of the solid state relay 31 are opened by the electromagnetic switch 200, and the power from the AC power supply AC is interrupted. Supply is cut off. This electromagnetic switch 20
0 contacts 201 and 202 are closed when the input terminal 203 of the electromagnetic switch 20 is at L level.
AL is an alarm terminal, and this terminal AL is connected to an alarm lamp, an alarm sound generator, etc., and an alarm is announced when an overvoltage detection signal is generated.

5 is a supply circuit for supplying charging energy of the main capacitor 4 to the flash lamp 1;
Anode terminal 1 of flash lamp 1 is connected from positive terminal 4A of main capacitor 4 to air core reactor 51.
The part leading to 0A and the negative terminal 4 of the main capacitor 4
It consists of a portion from B to the cathode terminal 10B of the flash lamp 1. The air core reactor 51 is
It has a function of suppressing the peak value of the discharge current of the flash lamp 1 to a low value.

A discharge circuit 6 is constituted by the main capacitor 4, the supply circuit 5, and the discharge path of the flash lamp 1, and the discharge circuit 6 is closed when the flash lamp 1 emits light.

Reference numeral 11 denotes a trigger wire, which is wound spirally around the outer wall surface of the flash lamp 1, for example.

7 is a trigger circuit that triggers the flash lamp 1. The high voltage side output terminal 7D of this trigger circuit 7 is connected to the trigger wire 11, and when the trigger signal TG is input to the input terminal 7B, the flash is output from the output terminal 7D. The high voltage pulse required to trigger the lamp 1 is generated, which is applied to the trigger wire 11 which causes the flash lamp 1 to be triggered.
is triggered. The resistor 81 and the constant voltage element 82 constitute a voltage stabilizing circuit for supplying a driving voltage to the trigger circuit 7.

The charging voltage control circuit 36 is basically composed of a comparator 361 and a transistor 362 that controls the start and stop of the operation of the comparator 361, as shown in FIG. The output terminal is connected to the output terminal 36A via a resistor 363, the base of the transistor 362 is connected to the input terminal 36B via a resistor 364, and the non-inverting input terminal of the comparator 361 is connected to the input terminal 36A via a resistor 365.
6C, and its inverting input terminal is connected via a resistor 366 to a reference voltage source composed of resistors 367, 368, and 369. E is a voltage source, 370,
371 and 372 are diodes and capacitors for preventing malfunction, respectively; a capacitor 373, a Zener diode 374, and a resistor 375 are components of a voltage stabilizing circuit. This charging voltage control circuit 3
6, during the period when the capacitor charging signal CHG input to the terminal 36B is at L level, the transistor 362 is off, and at this time the comparator 361 is in the operating state, and the main capacitor 4, which is not being charged at this time, is Since the detection voltage V ₀ is smaller than the reference voltage Vr, the comparator 36
1 is at the L level, which is supplied to the input terminal 31D of the solid state relay 31.
A and 31B are electrically connected, and charging of the main capacitor 4 by the charging circuit 3 is started. With this charging,
When the charging voltage of the main capacitor 4 reaches the set voltage V ₁ necessary for fixing the toner, the detection voltage V ₀ becomes the reference voltage Vr.
When the output of the comparator 361 is inverted and becomes the H level, the signal to the input terminal 31D of the solid state relay 31 becomes the H level, and the signal to the input terminal 31D of the solid state relay 31 becomes the H level.
A and 31B are cut off, and the charging operation of the main capacitor 4 by the charging circuit 3 is stopped. One terminal 36
During the period when the capacitor charging signal CHG input to B is at H level, the transistor 362 is on, and at this time, the operation of the comparator 361 is stopped, and its output becomes H level regardless of the magnitude of the detection voltage _V0 . As a result, the connection between the terminals 31A and 31B of the solid state relay 31 is cut off, and the charging operation by the charging circuit 3 is stopped.

The trigger circuit 7 is basically composed of a charging/discharging capacitor 71, a high-voltage pulse transistor 72, and a thyristor 73 as a switching element, as an example of which is shown in FIG. During the operation period, element 7A,
The capacitor 71 is charged by the drive voltage applied between the terminals 7C and 7C, and then the trigger signal TG is applied from the terminal 7B to the gate of the thyristor 73, turning on the thyristor 73. At this time, the capacitor 71
The charged electric charge instantaneously flows to the primary side of the high voltage pulse transformer 72, and as a result, the high voltage pulse transformer 72
A high voltage pulse of, for example, 10 to 20 KV is generated on the secondary side of the flash lamp 1, and when this is applied to the trigger wire 11, the flash lamp 1 starts emitting light. 74 and 75 are protection diodes, 76 is a constant voltage element for overvoltage prevention, and 77 is a charging resistor.

As an example of the overvoltage detection circuit 100 is shown in FIG. Divided detection units 110A, 110B, 1 each including a light emitting element such as a light emitting diode that independently detects overvoltage of an electrolytic capacitor and emits light for each group.
10C, 110D and their division detection unit 110
An optical fiber 130 that conducts light from the light emitting diodes 111A, 111B, 111C, and 111D of A, 110B, 110C, and 110D;
111B, 111C, and 111D. A light emitting element, for example, a phototransistor 1, which becomes conductive and generates a detection signal when it receives at least one of the lights.
41. The division detection units 110A, 110B, 11
0C and 110D have completely similar configurations, and to explain the divided detection section 110A as an example, there are resistors 112 at both ends of the electrolytic capacitor 41.
A, light emitting diode 111A, transistor 11
4A are connected in series, and the anode of a Zener diode 115A is connected to the base of the transistor 114A.
The cathode of is connected to one of the voltage dividing resistors 116A, 117A, and 118A connected to both ends of the electrolytic capacitor 41.
Connected to 17A. 119A is a resistor connected between the base and emitter of transistor 114A, and 120A is a capacitor connected between the cathode of Zener diode 115A and the emitter of transistor 114A.
The light receiving end of the optical fiber 130 is divided into four parts, and these light receiving ends 131A, 131B, 13
1C and 131D are light emitting diodes 111, respectively.
A, 111B, 111C, and 111D are arranged close to the light emitting parts, and the light sending end 132 is connected to the detection signal generating part 14.
The phototransistor 141 is placed close to the light receiving portion of the phototransistor 141. The detection signal generating section 140 includes a phototransistor 141, a resistor 142 connected between the emitter of the phototransistor 141 and ground (GND), and the phototransistor 14.
A resistor 143 and a transistor 144 connected between the collector of 1 and the ground (GND), and a base of this transistor 144 and a phototransistor 1
A resistor 145 connected between the emitter of 41
, a resistor 146 connected between the collector and emitter of a transistor 144, and a transistor 147 whose base and emitter are connected to both ends of the resistor 146 and whose collector is connected to the electromagnetic switch 200.

To explain the operation of this overvoltage detection circuit 100, the charging voltage of at least one of the electrolytic capacitors 41, 42, 43, and 44, for example, the electrolytic capacitor 41, is an abnormally high voltage, for example, an overvoltage V ₃ of about the rated voltage of the capacitor. When this happens, the Zener diode 115A becomes conductive due to the voltage V ₄ generated by the voltage dividing resistor 117A, thereby turning on the transistor 114A and causing the light emitting diode 111A to emit light. This light emitting diode 111
When A emits light, the light passes through the optical fiber 130 from the light receiving end 131A and irradiates the light receiving part of the phototransistor 141 from the light sending end 132, thereby making the phototransistor 141 conductive.
When the phototransistor 141 becomes conductive, a base current flows to turn the transistor 144 on, thereby shorting the base and emitter of the transistor 147, turning the transistor 147 off. When this transistor 147 is turned off, an H level overvoltage detection signal is generated from the terminal f, and as a result, the input terminal 203 of the electromagnetic switch 200 becomes H level, and the contacts 201 and 202
is opened and power supply from the AC power source AC is cut off.

According to the toner fixing device having the above configuration, toner is fixed in the following manner. First, when the transfer paper carrying an unfixed toner image on its surface is carried into the fixing device, the conveyance switch 18 is turned on by the leading edge of the transfer paper, which causes the capacitor charging signal to be turned on.
The timing of CHG and trigger signal TG is set. After that, before the leading edge of the transfer paper leaves the fixing area Q, the capacitor charging signal CHG, which had been at the H level, is switched to the L level, and the comparator 361 starts operating. At this time, the main capacitor 4 is not charged, so the detection signal
Since V ₀ is lower than the reference voltage Vr, the comparator 36
The signal input from the output terminal 36A of 1 to the terminal 31D of the solid state relay 31 becomes L level, and the terminal 31A of the solid state relay 31,
31B becomes conductive, the charging circuit 3 starts charging operation, and the main capacitor 4 is charged.

When the charging voltage of the main capacitor 4 exceeds the set voltage V ₁ required for fixing the toner, the detected voltage V ₀ exceeds the reference voltage Vr, and at that time, the output terminal 36A of the comparator 361 connects the solid state relay 31. The signal input to terminal 31D switches from L level to H level, and terminals 31A and 31B of solid state relay 31 are cut off.
The charging operation by the charging circuit 3 is stopped.

Next, a trigger signal TG is generated between when the leading edge of the transfer paper enters the fixing area Q and when it exits, and a high voltage pulse is supplied from the terminal 7D of the trigger circuit 7 to the trigger wire 11, and the discharge circuit 6 becomes conductive, and the charged energy of the main capacitor 4 is supplied to the flash lamp 1 to start emitting light, and the light energy at this time causes a first region of an area corresponding to the effective fixing width L ₂ on the leading edge side of the transfer paper to be The fixing of the toner image is performed in the step. Then, at the same time as the trigger signal TG is generated, or slightly before that, the capacitor charging signal CHG is temporarily switched to H level, thereby stopping the charging operation of the charging circuit 3 during the light emission and continuing the flash lamp 1. After the discharge is prevented and the light emission ends, that is, after the discharge current becomes zero, the capacitor charging signal CHG is immediately returned to the L level, and the comparator 361 becomes operational. At this time, the main capacitor 4 has been discharged and its detection voltage V ₀ is lower than the reference voltage Vr, and the charging circuit 3
The charging operation of the main capacitor 4 is started, and the main capacitor 4 is charged in the same manner as described above. And the charging voltage of main capacitor 4 is set voltage
When V ₁ is reached, the charging operation by the charging circuit 3 is stopped, and then the trigger signal TG is generated again until the rear end of the fixed first area of the transfer paper leaves the fixing area Q, and the same process as described above is generated. The toner image is fixed in a second area following the first area of the transfer paper.

Such an operation is repeated a number of times depending on the length of the transfer paper in the conveying direction, and the fixing of the entire toner image on the transfer paper is completed. In the final light emission, the capacitor charging signal CHG goes high at the same time as the trigger signal TG or slightly before it.
After that, the charging operation of the charging circuit 3 is stopped, and when the paper discharge detection switch 19 detects that the trailing edge of the transfer paper has left the fixing area Q, the capacitor charging signal CHG and the trigger signal TG are switched to When the timing setting is canceled and the conveyance switch 18 is turned on by the next conveyed transfer paper, the timings of the capacitor charging signal CHG and the trigger signal TG are newly set.

Above are electrolytic capacitors 41, 42, 43, 44
Both of these explanations assume that charging and discharging are performed in a normal state where the charging voltage does not become overvoltage, but for some reason the electrolytic capacitors 41 and 4
When the charging voltage of at least one of 2, 43, and 44 becomes an overvoltage, in the overvoltage detection circuit 100, the light emitting diode of the split detection section connected to the electrolytic capacitor that has become overvoltage emits light. conducts the phototransistor 141 of the detection signal generation section 140 through the optical fiber 130, thereby generating an overvoltage detection signal from the terminal f and closing the contacts 201 and 202 of the electromagnetic switch 200.
is opened, and the charging operation of the charging circuit 3 is stopped.

According to the above embodiment, the overvoltage detection circuit 100
, the four electrolytic capacitors 41, 42, 43, 44 constituting the main capacitor 4 are divided into four groups, and the electrolytic capacitors 41, 42, 4
3 and 44 are provided with divided detection sections 110A, 110B, 110C, and 110D for detecting the charging voltage, and the light from the light emitting diode of each divided detection section is transmitted through the optical fiber 130 to the phototransistor 141 of the detection signal emission section 140. Since the light is configured to be irradiated onto the light receiving section, the distance between the light emitting section of the light emitting diode and the light receiving section of the phototransistor is increased due to the optical fiber 130, and as a result, the insulation resistance between the light emitting diode and the phototransistor is increased. Therefore, even if a high voltage is applied between the two, this high voltage is prevented from flowing into the control circuit system, and the overvoltage detection circuit 100 detects the electrolytic capacitor 4 without causing serious damage.
1, 42, 43, and 44, the charging voltage can be prevented from exceeding the permissible limit, and as a result, a highly safe toner fixing device can be provided.

Since the optical fiber 130 is used, the detection signal generation section 140 only needs one light receiving element, that is, one phototransistor 141, and therefore the configuration of the detection signal generation section 140 is extremely simple.

[Effect of idea]

As described in detail above, the present invention comprises a flash lamp, a discharge circuit including a main capacitor and a supply circuit that supplies charging energy from the main capacitor to the flash lamp, and a trigger circuit for triggering the flash lamp. and a toner fixing device comprising: a charging circuit for charging the capacitor; and an overvoltage detection circuit for detecting overvoltage of the main capacitor, and for fixing a toner image on an image support by irradiating light from the flash lamp. , the main capacitor is formed by connecting two or more electrolytic capacitors in series, and the overvoltage detection circuit divides the series connection of electrolytic capacitors into two or more groups, and independently detects the electrolytic capacitors for each group. a divided detection section including a light emitting element that detects overvoltage before the start of discharge and generates light; an optical fiber that conducts the light of the light emitting element of each divided detection section;
Since the toner fixing device is characterized in that it has a detection signal generating section including a light receiving element that is electrically connected to generate a detection signal when the light from the light emitting element is received from the optical fiber, an electrolytic capacitor is used. Two or more are connected in series to form a main capacitor, and an overvoltage detection signal is generated before the charging voltage of the electrolytic capacitor reaches a voltage exceeding the permissible limit. It is possible to provide a highly safe toner fixing device in which the insulation resistance between the toner fixing device and the signal generating portion is sufficiently high, and high voltage does not leak into the control circuit system.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an outline of an example of a toner fixing device according to the present invention, Fig. 2 is an explanatory circuit diagram showing an electric circuit portion that causes a flash lamp to emit light, and Fig. 3 is an example of a charging voltage control circuit. FIG. 4 is an explanatory circuit diagram showing an example of a trigger circuit, and FIG. 5 is an explanatory circuit diagram showing an example of an overvoltage detection circuit. 1... Flash lamp, 21... Reflective mirror surface,
22... Opening surface, 23... Lamp cover, 24...
... Cover glass, 15 ... Separation conveyance belt, 18
...Conveyance switch, 19...Sheet discharge detection switch,
3... Charging circuit, 31... Solid state relay, 32... Transformer, 321, 322... Secondary coil, 33... Rectifier, 34, 35... Voltage dividing resistor, 36... Charging voltage control circuit, 4... Main capacitor, 41, 42, 43, 44... Electrolytic capacitor, 100... Overvoltage detection circuit, 200... Electromagnetic switch, 5... Supply circuit, 6... Discharge circuit, 11
...Trigger wire, 7...Trigger circuit, 361
... Comparator, 362 ... Transistor, 7
1... Charging/discharging capacitor, 72... High voltage pulse transformer, 73... Thyristor, 110A, 11
0B, 110C, 110D... Division detection unit, 11
1A, 111B, 111C, 111D...Light emitting diode, 130...Optical fiber, 140...
Detection signal generation section, 141...phototransistor.

Claims (1)

[Claims for Utility Model Registration] A flash lamp, a discharge circuit including a main capacitor and a supply circuit for supplying charging energy from the main capacitor to the flash lamp, a trigger circuit for triggering the flash lamp, A toner fixing device that includes a charging circuit that charges a main capacitor and an overvoltage detection circuit that detects an overvoltage of the main capacitor, and fixes a toner image on an image support by irradiating light from the flash lamp. The main capacitor is composed of two or more electrolytic capacitors connected in series, and the overvoltage detection circuit divides the series connection of the electrolytic capacitors into two or more groups and independently detects the overvoltage of the electrolytic capacitor for each group. A divided detection section including a light emitting element that detects and generates light before the discharge starts; an optical fiber that conducts the light of the light emitting element of each divided detection section; and when the light of the light emitting element is received from the optical fiber. A toner fixing device comprising: a detection signal generation section including a light receiving element that is electrically connected to a light receiving element and generates a detection signal;