JP2561981B2 - UV discharge tube failure detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet discharge tube failure detection device for detecting a failure of an ultraviolet discharge tube used for flame monitoring of a combustion apparatus.

[0002]

2. Description of the Related Art Conventionally, an ultraviolet discharge tube (hereinafter referred to as a UV tube) has been used in a combustion apparatus to monitor a burner flame. The UV tube is a discharge tube configured to generate a discharge between electrodes when ultraviolet rays emitted from a flame enter.

[0003]

In the conventional UV tube, even if ultraviolet rays do not enter due to an abnormality such as deterioration,
A failure that causes self-discharge may occur for some reason. When the UV tube is used for flame monitoring, if the above-mentioned failure occurs, a flame detection signal is obtained even though there is no flame, which is extremely dangerous.
In such a case, in the past, when a complete self-discharge state was reached, a similar flame was detected and the combustion device was stopped to maintain safety, but the time until the device actually stops. It was not possible to determine whether or not the flame was a similar flame, and during this time, inconveniences such as fuel supply occurred, which was a major problem in system operation.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a UV tube failure detection device capable of early detection of self-discharge of the UV tube.

[0005]

In the UV tube failure detection apparatus according to the present invention, a shutter for blocking the incident ultraviolet rays of the UV tube is provided, and the change rate of the output of the UV tube is measured at the time of blocking the shutter, and a constant value is measured. When it is smaller than the rate of change, the signal is regarded as self-discharge and a signal such as an alarm is issued.

[0006]

[Function] When the UV tube becomes more prone to self-discharge,
Even if the shutter is closed from the incident state of ultraviolet rays, the output of the UV tube is less likely to drop. Therefore, by periodically closing the shutter while the UV tube is detecting a flame and observing changes in the UV tube during that time, You can know the breakdown.

[0007]

EXAMPLE FIG. 1 shows an example in which a UV tube is used for flame monitoring of a combustion apparatus. In FIG. 1, the flame 2 of the burner 1 is monitored by a UV tube 3. Flame 2 and UV
A shutter 4 is arranged between the tube 3 and the tube 3. Normally, the shutter 4 is opened and is in a position shown by a dotted line. When the flame 2 is present, the UV tube 3 is discharged, and the discharge current is applied to the flame detection circuit 5 as the measuring means, where it is converted into the voltage V _F. This voltage V _F is sent to the combustion control system in the subsequent stage as a flame detection signal, and A
The data is converted into digital data by the / D conversion circuit 6 and sent to the arithmetic unit 7 such as a microcomputer.

The arithmetic unit 7 controls the shutter control circuit 8 and performs a predetermined arithmetic operation based on the digital data, and outputs a failure detection signal when a failure of the UV tube 3 is detected. The shutter control circuit 8 periodically controls opening / closing of the shutter 4 by a shutter opening / closing signal V _SH based on an instruction from the arithmetic unit 7.

Next, the operation of the above configuration will be described with reference to the timing chart of FIG. The shutter 4 is controlled by a shutter opening / closing signal V _SH from the shutter control circuit 8 so as to be periodically closed for a predetermined time t _A. In the state where the burner 1 has the flame 2 and the normal combustion is performed, the flame 2 is detected by the UV tube 3 when the shutter 4 is opened, and at this time, the output voltage V _{F of the} flame detection circuit 5 is detected.
Outputs a flame detection signal having a substantially constant level V _F1 in FIG. Next, when the shutter 4 moves from this state to the position indicated by the solid line and is closed for a predetermined time t _A , the ultraviolet rays from the flame 2 incident on the UV tube 3 are blocked and the discharge is stopped, and therefore the flame detection is performed. The output voltage V _F of the circuit 5 drops from V _F1 .

At this time, if the UV tube 3 is normal,
The voltage V _F rapidly drops from V _F1 to V _{F3 in} FIG. 2, and when the shutter 4 is opened again after the time t _A has elapsed, the voltage V _F becomes V V again.
Return to _F1 . However, when the tendency of self-discharge in the UV tube 3 becomes strong, even after the shutter 4 is closed, the discharge does not stop immediately and gradually disappears.
_F gradually goes down.

[0011] In the present invention, the arithmetic unit 7 on the basis of the voltage V _F to the digital data converted by A / D converter circuit 6, measured over time voltage V _F at the predetermined time t _B from the shutter 4 is closed Then, the change rate K is calculated, and the failure of the UV tube 3 is determined based on the change rate K.

As shown in FIG. 2, the magnitude V _F2 of the voltage V _F after a predetermined time t _B from the closing of the shutter 4 is obtained. The rate of change K can be obtained from the above-mentioned V _F2 and V _F1 by K = (V _F1 −V _F2 ) / t _B. The change rate K is compared with a predetermined self-discharge determination level K _A, and when K ≧ K ₄ , it is determined that the UV tube 3 is normal, and when K <K _A , it is determined that the UV tube 3 has a failure. Output the detection signal.

The following method can be considered as a method of determining the self-discharge determination level K _A. (1) Level V _F1 of flame detection signal when shutter 4 is open
The K _A according to the above is registered in a table in advance. (2) Let K _{A be} the average value of the rate of change K obtained by opening and closing the shutter 4 several times during the initial operation of the combustion apparatus.

[0014]

According to the present invention, a shutter for blocking the ultraviolet rays entering the UV tube is provided, and the rate of change of the flame detection signal level is monitored for a predetermined time after the shutter is closed. Since it is configured to judge that the UV tube has failed when the size exceeds U,
A failure due to self-discharge of the V tube can be detected at an early stage, so that the safety of the combustion device can be improved and the maintainability can be improved, and more strict life management of the UV tube is performed. It is possible to obtain an effect such as being able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a failure detection device for an ultraviolet discharge tube according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the device.

[Explanation of symbols]

 3 Ultraviolet discharge tube 4 Shutter 5 Flame detection circuit 7 Arithmetic device

Claims (1)

(57) [Claims] 1. A measuring means for measuring a discharge current of an ultraviolet discharge tube, a shutter means for blocking ultraviolet rays incident on the ultraviolet discharge tube, and the measuring circuit when ultraviolet rays are blocked by the shutter means. Of the discharge of the ultraviolet discharge tube, the output of which is measured over time, and a signal output when the rate of change is smaller than a predetermined value.