JPH064002A - Flash controller - Google Patents

Abstract

PURPOSE:To detect the short-circuit failure of any capacitor when the plural capacitors are connected in series and used as the charging and discharging capacitor as for a flash controller controlling a flash lamp by the charging voltage of the capacitor in order to perform flash fixing or the like. CONSTITUTION:As for the flash controller allowing the flash lamp 23 to emit light by energey charged to the capacitor 21 by impressing the trigger voltage on the lamp 23 by a trigger generation circuit 24 after the capacitor 21 connected to the lamp 23 in parallel is charged by a charging circuit 24, the capacitor 21 is constituted of plural capacitor groups which are serially connected. Besides, a circuit 28 monitoring a time until the finish of the charging from the start of the charging of the capacitor groups by the charging circuit 20 is provided. Then, the abnormality of the capacitor groups is detected by the output of the time monitor circuit 28.

Description

Detailed Description of the Invention

(Table of Contents) Industrial Application Field of the Prior Art (FIG. 5) Problem to be Solved by the Invention Means for Solving the Problem (FIG. 1) Action Example (a) Description of the First Example ( (FIGS. 2 to 3) (b) Description of the second embodiment (FIG. 4) (c) Description of another embodiment Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash control device for flash control of a flash lamp by a capacitor charging voltage for flash fixing and the like.

In image forming apparatuses such as copying machines, printers, and facsimile machines, latent image forming type recording apparatuses such as electrophotographic apparatuses are used in order to record plain paper. In such an image forming apparatus, an electrostatic latent image is formed, developed, a toner image is transferred to a sheet, a toner image is obtained on the sheet, and a fixing device is used to fix the toner to the sheet. To be done.

There is a fixing device using a heat roller as this fixing device, but in a device having a low fixing speed and a high speed, a flash lamp capable of high-speed fixing is caused to flash and the toner is melted by light energy to fix the flash fixing device. Is used.

To make this flash lamp flash,
Although a flash control device is used, a cost-effective configuration is desired.

[0006]

2. Description of the Related Art FIG. 5 is an explanatory diagram of a conventional technique. Make a flash lamp such as a xenon lamp emit light at regular intervals,
The process of using the thermal energy to emit light from a xenon lamp in a flash fixing device at a constant cycle is shown in FIG.
As shown in (A) and (B), a constant current is supplied from the constant current source (power source) 20 to the capacitor 21 in response to a capacitor charging signal sent from a control circuit (not shown).

The power supply 20 has a circuit for detecting the terminal voltage of the capacitor 21, and when the charging voltage of the capacitor 21 reaches a predetermined voltage, the current supply is stopped and the charging of the capacitor 21 is stopped. Then, the voltage is maintained at a constant voltage, and the charge completion signal is notified to the control circuit.

When the capacitor 21 is completely charged, a trigger signal is generated from the control circuit, and a high pulse voltage for causing the lamp 23 to emit light is generated from the trigger voltage generating circuit 24 via the pulse transformer (trigger transformer) 25. , The lamp 2 by applying the trigger wire to the lamp 2
3 is activated and the lamp 23 emits light.

The light emitted from the lamp 23 is generated by the condenser 21.
The lamp 23 is discharged all at once in a short time of several hundreds of microseconds by the charged energy. If the charging energy of the capacitor 21 is small, the toner image is not fixed yet, which is an important obstacle such as the loss of print data.

For this reason, conventionally, a charging voltage detection circuit 26 for detecting the charging voltage of the capacitor 21 and a voltage monitoring circuit 27 are provided to monitor the charging energy of the capacitor 21 by the voltage and eventually the light emission of the lamp 23. The energy (fixing energy) was monitored.

[0011]

However, the prior art has the following problems. The capacitor 21 used for this charging / discharging is required to have a high capacity and a high withstand voltage, an expensive one such as a paper film capacitor is required, and the apparatus price cannot be reduced.

Therefore, when a plurality of electrolytic capacitors having a relatively small capacity and a low withstand voltage are connected in series and used, in the conventional fixing energy monitoring method, a short-circuit failure occurs in one of the plurality of capacitors. However, since the charging voltage of the capacitor can be charged to a predetermined value, it is not judged as abnormal and the capacity of the capacitor is reduced by 1/2.
The fixing energy represented by C, V, and V decreases, and troubles such as unfixed toner image occur.

Therefore, it is an object of the present invention to provide a flash control device capable of detecting a short-circuit fault of any one of capacitors when a plurality of capacitors are connected in series and used as a charge / discharge capacitor. To do.

[0014]

FIG. 1 shows the principle of the present invention. According to claim 1 of the present invention, the capacitor 21 connected in parallel to the flash lamp 23 is charged by the charging circuit 20, and then the trigger voltage is applied to the flash lamp 23 by the trigger generation circuit 24 to charge the capacitor 21. In the flash control device that causes the flash lamp 23 to emit light by the generated energy, the capacitor 21 is configured by a plurality of capacitor groups connected in series, and
A circuit 28 for monitoring the time from the start of charging of the capacitor group of the charging circuit 20 to the completion of charging is provided, and an abnormality of the capacitor group is detected by the output of the time monitoring circuit 28.

According to the second aspect of the present invention, the flash lamp 2 is provided.
After charging the capacitor 21 connected in parallel with the capacitor 3 from the charging circuit 20, a trigger voltage is applied to the flash lamp 23 by the trigger generation circuit 24 to cause the capacitor 21
With the energy charged to the flash lamp 2
In the flash control device for emitting light, the capacitor 2
1 is composed of a plurality of capacitor groups connected in series, and a circuit 29 for monitoring the charging voltage between the terminals of each capacitor constituting the capacitor group is provided. It is characterized by detecting an abnormality.

A third aspect of the present invention is characterized in that, in the first or second aspect, the flash lamp 23 is for fixing the toner on the sheet.

[0017]

In the first aspect of the present invention, the charge / discharge capacitor 21
The time from the start of charging to the completion of charging (predetermined charging voltage) changes depending on whether there is a short circuit fault in the capacitor or when there is no short circuit fault in the capacitor. The time will be shorter.

Therefore, a time monitoring circuit 28 for monitoring the charging completion time is provided to monitor the charging time of the series-connected capacitor group and detect a short circuit fault of the capacitor group.

According to a second aspect of the present invention, a circuit 29 for monitoring the charging voltage between the terminals of each capacitor of the plurality of series capacitor groups is provided, and the capacitor 29 is monitored by monitoring the charging voltage between the terminals of each capacitor of the series capacitor group. It is intended to detect a short circuit fault in a group.

According to the third aspect of the present invention, since the flash lamp 23 fixes the toner, it is possible to prevent the fixing failure due to the decrease of the fixing energy due to the short circuit of the capacitor.

[0021]

【Example】

 (a) Description of First Embodiment FIG. 2 is a block diagram of a printing apparatus according to an embodiment of the present invention.

In the electrophotographic printing apparatus, as shown in FIG. 2, the rotating photosensitive drum 10 is charged by the pre-charging device 11,
In accordance with the image data in the page buffer 30, the laser optical system 12 exposes the optical image to form an electrostatic latent image corresponding to the image, and the developing device 13 develops the toner.

The toner image on the photosensitive drum 10 is transferred from the hopper 19a to the continuous sheet conveyed by the sheet conveying section 17 by the transfer charger 14, sent to the flash fixing section 18, and flash-fixed by the fixing section 18. Stacker 19b
Housed in.

The photosensitive drum 10 after the transfer of the toner image is
After the charge is removed by the charge removing unit 15 and electrically cleaned, the cleaning air unit 16 mechanically removes the residual toner, sucks it, and mechanically cleans it for use in the next image formation on the photosensitive drum 10.

A flash fixing device using a flash lamp is used as the fixing device 18, and the flash lamp is flash-controlled. FIG. 3 is an explanatory diagram of the first embodiment of the present invention.

In the figure, the same parts as shown in FIG.
Indicated by the same symbol, 21a, 21b, and 21c are capacitors, which are connected in series, are connected in parallel to the power supply 20 and the lamp 23, and are composed of inexpensive electrolytic capacitors, and 26 is a charging voltage detection circuit. That detects the charging voltage between the terminals of the series capacitors 21a to 21c and generates a charging completion signal when the charging voltage reaches a predetermined charging voltage, 2
Reference numeral 8 denotes a charging time monitoring circuit, which counts the time from the charging signal to the power source (capacitor charging circuit) 20 to the charging completion signal of the charging voltage detection circuit 26 with a timer, and outputs an abnormal signal if the counting time is within the scheduled charging time. It occurs.

In this embodiment, three capacitors are connected in series, one end of the first capacitor 21a is connected to the output terminal of the power source (constant current source) 20, and the other end is connected to the second capacitor 21b. Then, one end of the second capacitor 21b is used as the first capacitor 21a and the other end is used as the third capacitor 2a.
1c, one end of the third capacitor 21c is connected to the second capacitor 21b, the other end is connected to the FG side of the output of the power supply 20, and between the one end of the first capacitor 21a and the other end of the third capacitor 21c. Is detected by the charging voltage detection circuit 26.

This operation will be described with reference to FIG. 5B. The power supply 20 causes the capacitor group 21a ...
21c is charged, and the charging voltage waveform becomes a trapezoid as shown in FIG. 5 (B).

The power supply 20 stops charging when the charging voltage of the capacitors 21a to 21c reaches a predetermined value, the capacitor charging voltage is held at the predetermined value, and the charging voltage detection circuit 26
While the charging voltage exceeds a predetermined value, a charging voltage detection signal is generated and output to the charging time monitoring circuit 28.

The charging time monitoring circuit 28 activates a timer in response to the charging signal supplied to the power source 20, counts the time (charging time) T until the generation of the charging voltage detection signal, and the charging time T is shorter than the specified value. In this case, it is determined that the capacitor is short-circuited and an abnormal signal is generated in the control circuit.

Specifically, the timer is set to a specified value T, the timer is stopped by the charging voltage detection signal, and if the charging voltage detection signal does not arrive after the specified value count has been exceeded, an abnormal signal is issued. To occur.

When the control circuit receives the abnormal signal, it stops the printing operation, performs processing such as displaying an abnormal state without flashing the flash lamp 23, and normalizes the toner on the paper without fixing it. Prevents output.

(B) Description of the Second Embodiment FIG. 4 is an explanatory view of the second embodiment of the present invention. In the figure, the same components as those shown in FIGS. 3 and 5 are designated by the same symbols, and 26a is a first charging voltage detecting circuit, and
First capacitor 21a from G (frame ground)
26b is a second charging voltage detecting circuit which detects a voltage at one end of the FG, converts the voltage into a digital value by an AD converter, and outputs the digital value.
Which detects the voltage at one end of the capacitor 21b, converts it into a digital value by an AD converter, and outputs the digital value, 26
Reference numeral c is a third charging voltage detection circuit, which detects the voltage from one end of the third capacitor 21c from FG (frame ground), converts it into a digital value by an AD converter, and outputs it.

Reference numeral 29a denotes a first capacitor charging voltage monitoring circuit, which detects the voltage detected by the first charging voltage detecting circuit 26a,
29b, which monitors the terminal voltage of the first capacitor 21a from the difference between the detected voltage of the second charging voltage detection circuit 26b and generates an abnormal signal if the terminal voltage is below a predetermined value, 29b
Is a second capacitor charging voltage monitoring circuit, which detects the difference between the detection voltage of the second charging voltage detection circuit 26b and the detection voltage of the third charging voltage detection circuit 26c.
The terminal voltage of b is monitored, and if the terminal voltage is equal to or lower than a predetermined value, an abnormal signal is generated. 29c is a third capacitor charging voltage monitoring circuit.
The terminal voltage of the third capacitor 21c is monitored from the difference between the detected voltage of b and the FG voltage, and if the terminal voltage is below a predetermined value, an abnormal signal is generated.

This operation will be described. When the charging of the power source 20 is completed, each of the capacitor charging voltage monitoring circuits 29a-29 is monitored.
c calculates the inter-terminal voltage of each of the capacitors 21a to 21c and compares it with a predetermined value, and each of the capacitor charging voltage monitoring circuits 29a to 29c determines that the detected inter-terminal voltage is equal to or less than the predetermined value.
An abnormal signal is generated as a short circuit of the capacitor.

When any one of the control signals is received by the control circuit, the printing operation is stopped, the abnormal state is displayed without flashing the flash lamp 23, and the toner on the paper is not fixed. Normal output is prevented.

(C) Description of Other Embodiments In addition to the above embodiments, the present invention can be modified as follows. In the above-described embodiments, the printing apparatus has been described as an electrophotographic mechanism, but it can be used as a printing mechanism for fixing a toner image (for example, an electrostatic recording mechanism).

The sheet PP is not limited to paper, but other media can be used. Although the printer is described as the printer, it may be another printer such as a copying machine or a facsimile.

Although the flash lamp is used for fixing the toner, it may be used for other purposes. The control circuit may have the time monitoring function of FIG. 3 or the voltage monitoring function of FIG.

The present invention has been described above with reference to the embodiments.
Various modifications are possible within the scope of the invention, and these modifications are not excluded from the scope of the invention.

[0041]

As described above, according to the present invention,
It has the following effects. Since the charge / discharge capacitor is composed of a plurality of series capacitors, an inexpensive electrolytic capacitor having a low withstand voltage can be used, which contributes to cost reduction.

Even in this case, it is possible to detect the short circuit abnormality of the capacitor and prevent the flash light in which the flash energy is lowered in advance.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of a printing apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 10 Photosensitive Drum (Image Carrier) 11 Charging Device 12 Optical Unit 13 Developing Device 14 Transfer Device 15 Static Eliminator 16 Cleaning Air Part 17 Paper Conveying Part 18 Flash Fixing Part 20 Charging Circuit 21, 21a-21c Capacitor 23 Flash Lamp 24 Trigger Generation Circuit 26 Charging voltage detection circuit 28 Charging time monitoring circuit 29 Charging voltage monitoring circuit

Claims (3)

[Claims] 1. A capacitor (21) connected in parallel with a flash lamp (23) is charged by a charging circuit (20), and then a trigger voltage is applied to the flash lamp (23) by a trigger generation circuit (24). In the flash control device that causes the flash lamp (23) to emit light by the energy charged in the capacitor (21), the capacitor (21) is configured by a plurality of capacitors connected in series, and the charging circuit ( 20) A flashlight characterized in that a circuit (28) for monitoring the time from the start of charging of the capacitor group to the completion of charging is provided, and an abnormality of the capacitor group is detected by the output of the time monitoring circuit (28). Control device. 2. A capacitor (21) connected in parallel with the flash lamp (23) is charged by a charging circuit (20), and then a trigger voltage is applied to the flash lamp (23) by a trigger generation circuit (24). Then, in the flash control device that causes the flash lamp (23) to emit light by the energy charged in the capacitor (21), the capacitor (21) is composed of a plurality of capacitor groups connected in series, and the capacitor group is formed. A flash control device characterized in that a circuit (29) for monitoring the charging voltage between the terminals of each of the constituent capacitors is provided, and an abnormality of the capacitor group is detected by the output of the charging voltage monitoring circuit (29). 3. The flash control device according to claim 1, wherein the flash lamp (23) is for fixing the toner on the sheet.