JPH0245874Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] 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, the flash lamp such as a xeno lamp is usually housed in a lamp cover that has a reflective mirror surface formed on the inner surface and has an opening of the size necessary for fixing, and a lamp cover that covers the opening. A cover glass is provided. The establishment is
An image support such as a transfer paper carrying an unfixed toner image on its surface is sequentially passed along the opening surface of the lamp cover, and the transfer paper is effectively fixed as defined by the width of the opening surface of the lamp cover. This is done by turning on a flash lamp each time the width is moved. 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 advantageous 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 at least several hundred volts. However, 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 configured by connecting three or more electrolytic capacitors in series, for example. be done.

[Problem that the invention attempts to solve]

When three 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, during charging, an abnormally high voltage is applied to a particular electrolytic capacitor, and in the worst case, the withstand voltage may be exceeded and the electrolytic capacitor may be destroyed, resulting in an extremely dangerous accident.
Such development becomes significantly larger as the number of electrolytic capacitors increases.

[Purpose of invention]

The present invention was developed based on the above-mentioned circumstances, and its purpose is to configure a main capacitor by connecting three or more electrolytic capacitors in series, and to provide a simple structure with a small number of parts. An object of the present invention is to provide a toner fixing device which can perform stable charging without applying an abnormally high voltage to an electrolytic capacitor, and can perform safe and highly reliable toner fixing.

[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 fixing a toner image on an image support by irradiating light from the flash lamp, wherein the main capacitor is composed of three or more electrolytic capacitors connected in series. The charging circuit divides the series connection body of electrolytic capacitors into two or more groups and charges the electrolytic capacitors independently for each group. The transformer includes a transformer having a coil and a rectifier circuit connected to each of the secondary coils of the transformer, at least one of the rectifier circuits being a voltage doubler rectifier circuit and having the electrolyte as a part of its components. It is characterized by using a capacitor.

〔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,
A 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, in the figure,
19 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.

Reference numeral 3 denotes a charging circuit, which is a step-up transformer having a number corresponding to the number of divided groups of electrolytic capacitors constituting the main capacitor 4 for energy supply described later, that is, in this example, two secondary coils 321 and 322. 32 and this step-up transformer 32
A solid state relay (SSR) 31 inserted between the primary side of the transformer and the AC power source AC, and voltage doubler rectifier circuits 33A and 33B connected to the secondary coils 321 and 322 of the step-up transformer 32, respectively, voltage dividing resistors 34 and 35 for detecting the charging voltage of the main capacitor 4 for energy supply, which will be described later;
It consists of a charging voltage control circuit ₃₆ that controls the charging voltage of the main capacitor 4 by controlling the opening/closing operation of the solid state relay 31 based on the capacitor charging signal CHG, which will be described later, and the voltage V 0 detected by the voltage dividing resistors 34 and 35. . 37A, 37B and 38A, 3
8B is a capacitor for power factor improvement, and inductors 39A and 39B are circuit breakers. The voltage doubler rectifier circuits 33A and 33B each include four diodes and two capacitors, and these two capacitors utilize electrolytic capacitors constituting a main capacitor 4, which will be described later. That is, the electrolytic capacitor constituting the main capacitor 4 is a capacitor for charging the flash lamp 1 with the energy necessary for emitting light, and at the same time it is a capacitor for charging the AC voltage from the secondary coils 321, 322 in the voltage doubler rectifier circuits 33A, 33B. It also serves as a capacitor to obtain twice the DC voltage. 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 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, and the series connection body of these electrolytic capacitors is a first group consisting of two or more groups, for example, electrolytic capacitors 41 and 42.
Group G1 and electrolytic capacitors 43 and 44
The electrolytic capacitors 41 and 42 belonging to the first group G1 also serve as capacitors of one voltage doubler rectifier circuit 33A, and the second group G2 is divided into two groups. Electrolytic capacitors 43 and 44 belonging to
also serves as a capacitor for the other voltage doubler rectifier circuit 33B, and during charging, each electrolytic capacitor is charged independently for each group.

5 is a supply circuit for supplying charging energy of the main capacitor 4 to the flash lamp 1;
A portion from the positive terminal 4A of the main capacitor 44 to the anode terminal 10A of the flash lamp 1 via the air core reactor 51, and a portion from the negative terminal 4B of the main capacitor 4 to the cathode terminal 10B of the flash lamp 1. It becomes more. The air core reactor 51
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, and this trigger wire 11 is provided, for example, on the outer wall surface of the flash lamp 1 in a spiral manner.

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 consisting of resistors 367, 368, and 369. E is the voltage source, 370,3
71 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 36
To explain the operation, during the period when the capacitor charging signal CHG input to the terminal 36B is at L level, the transistor 362 is in the off state, 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 detected. Since the voltage Vo is smaller than the reference voltage Vr, the comparator 361
The output of the solid-state relay 31 is at the L level, and this is supplied to the input terminal 31D of the solid-state relay 31.
31B becomes conductive, and the charging circuit 3 starts charging the main capacitor 4. As a result of this charging, when the charging voltage of the main capacitor 4 reaches the set voltage V ₁ necessary for fixing the toner and the detection voltage Vo exceeds the reference voltage Vr, the output of the comparator 361 is inverted and becomes H.
As a result, the signal to the input terminal 31D of the solid state relay 31 becomes the H level, and the signal to the input terminal 31A of the solid state relay 31,
31B is cut off, and the charging operation of the main capacitor 4 by the charging circuit 3 is stopped. On the other hand, while the capacitor charging signal CHG input to the terminal 36B 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 Vo. As a result, solid state relay 31
The terminals 31A and 31B are 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 transformer 72, and a thyristor 73 as a switching element, as shown in FIG.
During the operation period of charging circuit 3, terminals 7A and 7C
The capacitor 71
is charged, and then the trigger signal TG is sent to terminal 7B.
When applied to the gate of the thyristor 73 from
On the next side, a high voltage pulse of, for example, 10 to 20 KV is generated, which is applied to the trigger wire 11 and 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.

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 detected voltage
Since Vo is lower than the reference voltage Vr, the comparator 36
The signal input from the output terminal 36A of the solid state relay 31 to the terminal 31D of the solid state relay 31 becomes L level, and the signal input from the terminal 31D of the solid state relay 31 becomes L level.
A and 31B become conductive, and the charging circuit 3 starts charging operation, and the main capacitor 4 is charged.

In charging this main capacitor 4, electrolytic capacitors 41 and 4 belonging to the first group G1
2 is charged independently of the electrolytic capacitors belonging to the second group G2 by one secondary coil 321 of the transformer 32 and the voltage doubler rectifier circuit 33A, while the electrolytic capacitors 43 and 44 belonging to the second group G2 is charged independently of the electrolytic capacitors belonging to the first group G1 by the other secondary coil 322 of the transformer 32 and the voltage doubler rectifier circuit 33B.

When the charging voltage of the main capacitor 4 exceeds the set voltage V ₁ required for fixing the toner, the detected voltage Vo exceeds the reference voltage Vr, and at that time, the output terminal 36A of the comparator 361 is connected to the terminal of the solid state relay 31. The signal input to 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 Vo 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.

According to the above embodiment, the four electrolytic capacitors 41, 42, 43, 4 constituting the main capacitor 4
4 is divided into a first group G1 and a second group G2, and the transformer 32 is provided with a number corresponding to the number of divided groups, that is, two secondary coils 321, 322. A voltage doubler rectifier circuit 33A configured using electrolytic capacitors 41 and 42 belonging to one of the secondary coils 3
21, and a voltage doubler rectifier circuit 33B configured using electrolytic capacitors 43 and 44 belonging to the second group G2 is connected to the other secondary coil 322, and each group is independently connected to each electrolytic capacitor. Because charging is carried out, the number of electrolytic capacitors belonging to each group is small, making it easier to maintain the balance of charging voltage.
The magnitude of the output voltage required for each of the secondary coils 321 and 322 is reduced, and the charging voltage to be borne by each group is reduced. Even if a high voltage is applied, its magnitude is reduced, and the probability of a dangerous accident due to destruction of the electrolytic capacitor is greatly reduced. Because it is configured using electrolytic capacitors 41, 42, 43, 44, the voltage doubler rectifier circuits 33A, 3
It is no longer necessary to provide a dedicated capacitor for 3B, and four diodes are sufficient for each of the voltage doubler rectifier circuits 33A and 33B, so the number of diodes is small, and as a result, the number of parts is reduced. With a simple configuration, the main capacitor 4 can be charged stably, and toner fixation can be performed safely and with high reliability.

The present invention has been described above in detail based on one embodiment. The number of electrolytic capacitors constituting the main capacitor is basically determined based on the energy required for toner fixation, so it is not limited to three, but may be four or more, and the number of electrolytic capacitors connected in series Even when dividing into a plurality of groups, the number of groups is not limited to two and may be three or more as necessary. All of the rectifier circuits may be voltage doubler rectifier circuits, or some may be voltage doubler rectifier circuits and the rest may be other rectifier circuits.

[Effect of idea]

As described in detail above, the present invention includes 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, and a trigger for triggering the flash lamp. circuit, and a charging circuit that charges the main capacitor, and fixes a toner image on an image support by irradiating light from the flash lamp, wherein the main capacitor includes three electrolytic capacitors. or more connected in series, and the charging circuit corresponds to the number of groups for dividing the series-connected body of electrolytic capacitors into two or more groups and charging the electrolytic capacitors independently for each group. number 2
The transformer includes a transformer having a secondary coil and a rectifier circuit connected to each of the secondary coils of the transformer, at least one of the rectifier circuits being a voltage doubler rectifier circuit as a part of its components. Since the toner fixing device is characterized by the use of electrolytic capacitors, three or more electrolytic capacitors are connected in series to form the main capacitor, and the number of parts is small and the configuration is simple. Stable charging can be performed without abnormally high voltage being applied to the electrolytic capacitor, and safe and highly reliable toner fixing can be performed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing an example of a toner fixing device according to the present invention, and FIG. 2 is an explanatory circuit diagram showing an electric circuit portion that causes a flash lamp to emit light. FIG. 3 is an explanatory circuit diagram showing an example of a charging voltage control circuit, and FIG. 4 is an explanatory circuit diagram showing an example of a trigger 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, 33A, 33B... Voltage doubler rectifier circuit, 3
4, 35...Voltage dividing resistor, 4...Main capacitor, 4
1, 42, 43, 44...electrolytic capacitor, G1
...First group, G2...Second group,
36...Charging voltage control circuit, 5...Supply circuit, 6
...Discharge circuit, 11...Trigger wire, 7...Trigger circuit, 361...Comparator, 362...
...transistor, 71...charging/discharging capacitor,
72...High voltage pulse transformer, 73...Thyristor.

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 comprising a charging circuit for charging a main capacitor and fixing a toner image on an image support by irradiating light from the flash lamp, wherein the main capacitor includes three or more electrolytic capacitors connected in series. The charging circuit divides the series connection body of the electrolytic capacitor into two or more groups and charges the electrolytic capacitor independently for each group. a transformer having a secondary coil; and a rectifier circuit connected to each of the secondary coils of the transformer, at least one of the rectifier circuits being a voltage doubler rectifier circuit, and as part of its components, A toner fixing device characterized by using an electrolytic capacitor.