JP3563220B2 - Flame rod abnormal state detection method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for detecting an abnormal state of a frame rod used for detecting a flame of a combustion device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a flame rod has been widely used as a flame detecting means of a combustion device. However, since the flame rod is provided in a flame, the combustion equipment is provided with a frame rod abnormal state detecting means for detecting a failure or an abnormal state of the frame rod body. As an example of such a frame rod abnormal state detecting means, a flame detecting device as disclosed in Japanese Patent Application Laid-Open No. Hei 7-260138 has been proposed. The means for detecting an abnormal state of a frame rod disclosed in Japanese Patent Application Laid-Open No. Hei 7-260138 extracts a DC current component and an AC current component as signal waveforms output from the frame rod independently, and inputs both signal waveforms to a microcomputer. Then, the insulation failure of the frame rod is detected by comparing and processing, and an abnormal state is detected from the result.
[0003]
[Problems to be solved by the invention]
However, in the frame rod abnormal state detecting means having the above configuration, there are many hardware components such as AC / DC converters and behavioral amplifiers, so that the degree of freedom in design and the cost are increased due to the increase in the number of components.
[0004]
Further, as another frame rod abnormal state detecting means, since the electrodes are short-circuited (short) when the frame rod is abnormal, the constants of the constituent elements can be determined so that a constant 0 V can be taken out as a DC component at the time of this short circuit. However, such a constant setting cannot be realized due to, for example, the detection of an abnormal state, which is another load such as the detection of an exhaust cylinder detachment.
[0005]
The present invention has been made in view of the above problems, and has as its object to provide a method for detecting an abnormal state of a frame rod, which is simple in hardware and has a configuration in which a constant setting of constituent elements can be freely determined.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, in a frame rod abnormal state detecting means including a frame rod, a charge / discharge unit, and a microcomputer, the microcomputer stores an upper limit reference value and a lower limit reference value for detecting an abnormal state. The frame rod abnormal state detection method is characterized in that it is determined that the frame rod is in an abnormal state when the predetermined number of times exceeds an upper limit value and a lower limit value. The upper limit value and the lower limit value may be changed to a value stored in advance depending on a use period.
[0007]
【Example】
FIG. 1 shows an embodiment of the method for detecting an abnormal state of a frame rod according to the present invention. In FIG. 1, a detecting portion of a frame rod 10 placed in a flame is connected to a charging / discharging portion 20 composed of a resistor 24 and a capacitor 22, and this output portion is connected to a voltage dividing resistor 32 and 34. The output is connected to the microcomputer 50 through the pressure unit 30 and to the filter unit 40 including the resistor 44 and the capacitor 42.
[0008]
FIG. 2 shows a voltage waveform diagram at each point of the above configuration. A to D shown in FIG. 2 correspond to the respective A to D portions shown in FIG. The method for detecting an abnormal state of a frame rod according to the present invention will be described with reference to FIGS. 1 and 2 described above.
[0009]
First, a normal case will be described. A commercial power supply (100 V AC: not shown) is connected to the frame rod 10, and a point A is supplied with an AC sine waveform of 100 V AC. Next, when the flame rod 10 is placed in the flame, a rectified waveform leaving a positive waveform at the point A due to the rectifying action of the flame appears at the point B as is well known. The rectified waveform B is sent to the charging / discharging unit 20 composed of the resistor 24 and the capacitor 22, so that a substantially linear voltage waveform appears at the point C, and this waveform is input to the microcomputer 50 at the subsequent stage. As described above, the C waveform can be set near 0 V by the constants of the resistor and the capacitor, but cannot be set near 0 V in the present embodiment due to other loads. The waveform C is shaped by the voltage dividing unit 30 into a waveform D near an appropriate value so that the microcomputer 50 can easily process the waveform. It is needless to say that when the flame is strong, the waveform has a high voltage value (high position), and when the flame is weak, the waveform has a low voltage value (low position).
[0010]
Next, a case where the frame rod 10 is in a short state, that is, an abnormal state will be described. As in the normal state, a commercial power supply is connected to the frame rod 10, and an AC sine waveform of AC100V is supplied to the point A. Here, if the frame rod 10 is in the short state, the rectification action by the flame is not obtained, and the sine waveform at the point A is output to the point B as it is. This is the waveform indicated by C ′ in FIG. 2, and a sine waveform that is clearly different from the linear voltage waveform at normal time is input to the microcomputer 50 at the subsequent stage.
[0011]
Next, the operation of the microcomputer 50 used in the embodiment of the present invention will be described below. The microcomputer 50 stores two reference voltages for detecting an abnormal state, and sets these reference values as an upper reference value and a lower reference value, respectively. Here, the microcomputer 50 constantly monitors the voltage waveform from the point D every millisecond. When the voltage value at the point D falls below the lower limit reference value for a predetermined time within the specified time and exceeds the upper limit reference value thereafter, it is determined that the frame rod 10 is in an abnormal state (short state), Time processing. In the present embodiment, in particular, when the time below the lower reference value is set to 3 ms or more, and when the time exceeds the upper reference value for 1 ms or more, the lower reference value and the upper reference value are similarly set as a grace period of 1 second. It is monitored whether a waveform exceeding the lower limit reference value and the waveform exceeding the upper limit reference value are output as in the previous case, and processing is performed to determine that the frame rod 10 is abnormal. This one second is equivalent to the “specified time”, and the specified time is a voltage that temporarily exceeds the lower limit reference value or the upper limit reference value due to, for example, intrusion of noise into an electric circuit. In some cases, such processing is performed as a measure to prevent this erroneous detection. The above operation is shown in FIG.
[0012]
In the present embodiment, the time exceeding the lower limit reference value and the upper limit reference value and the grace period for ensuring the abnormality detection are determined, but these times can be changed as appropriate and depend on the device. It is determined by the intensity of the flame. In some cases, such as when there is a large difference between the upper reference value and the lower reference value, the grace period is not set, and if the condition of the upper reference value and the lower reference value is satisfied at least once, the abnormality processing is set. You may. Further, the specified time (1 second) and the predetermined time (several milliseconds) used in the above embodiment can be appropriately changed.
[0013]
The upper limit value and the lower limit value can be changed according to the use state and the use period (aging period). , The abnormal state of the frame rod can always be detected in an optimal state.
[0014]
【The invention's effect】
According to the above configuration, the abnormality of the frame rod can be detected without increasing the number of hardware components such as the AC / DC converter and the behavioral amplifier, and without affecting other load controls, thereby facilitating circuit design. At the same time, it is possible to provide a frame rod abnormal state detecting means with reduced cost.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a frame rod abnormal state detecting means of the present invention.
FIG. 2 shows voltage waveform diagrams at respective points in FIG.
FIG. 3 shows an operation flowchart of a microcomputer 50.
In the drawings, the same reference numerals indicate the same or corresponding parts.
10 Frame rod 20 Charge / discharge unit 30 Voltage division unit 40 Filter unit 50 Microcomputer

Claims (3)

In a frame rod abnormal state detecting means including a frame rod, a charge / discharge unit, and a microcomputer, an upper limit reference value and a lower limit reference value for the microcomputer to detect an abnormal state are stored, and an upper limit value and a lower limit are determined a predetermined number of times within a specified time. A method for detecting an abnormal state of a frame rod, comprising determining that the frame rod is in an abnormal state when the value exceeds the value. In a frame rod abnormal state detecting means including a frame rod, a charging / discharging unit, and a microcomputer, an upper limit reference value and a lower limit reference value for the microcomputer to detect an abnormal state are stored, and the upper limit value is repeatedly determined within a specified time by an upper limit value. A frame rod abnormal state detecting method, wherein it is determined that the frame rod is in an abnormal state when the lower limit value is exceeded. The method according to claim 1 or 2, wherein the upper limit value and the lower limit value can be changed to values stored in advance depending on a use period.

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