JPH08136322A - Liquid level detection method and liquid level detector - Google Patents

Abstract

PURPOSE: To provide a liquid level detection method for making clear failure occurrence causes when detecting a liquid level by differing an output signal level when detecting the presence or absence of a liquid from that when the liquid level detector fails or is connected improperly. CONSTITUTION: In a liquid level detection method where a corresponding detection signal is outputted from a light emitting element 12 according to the presence or absence of a liquid in an optical path between the light emitting element 12 and a photo detector 14, the output signal level when detecting the presence or absence of the liquid differs from that when a liquid level detector fails or is connected improperly, thus making clear the causes of occurrence of failure when detecting the liquid level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting method and a liquid level detector for various equipment such as petroleum fan heaters, and more particularly to a liquid level detecting method for detecting the liquid level of kerosene in a tank. The present invention relates to improvement of a liquid level detector.

[0002]

2. Description of the Related Art Conventionally, this type of petroleum fan heater has a liquid level detector for detecting the presence or absence of kerosene in a tank, and a photocoupler is used as the liquid level detector.

As shown in FIG. 15, this photocoupler connects a light emitting diode LED and a phototransistor PT to a power supply voltage VDD (for example, about 5V) via a connector C and current limiting resistors R1 and R2. It is a structure.

The input signal modes that this type of conventional photocoupler can give to the microcomputer M are only the High input signal mode and the Low input signal mode. That is, when the oil level of kerosene in the tank is above a certain reference for the position of the photocoupler, the light of the light emitting diode LED of the photocoupler is diffused by kerosene or the like and does not reach the phototransistor PT. Since the transistor PT remains off, the high input signal of 5V of the power source voltage is applied to the resistor R2 to the microcomputer M.
Enter through.

On the other hand, when the oil level of kerosene in the tank is lower than a certain standard with respect to the position of the photocoupler, the light of the light emitting diode LED of the photocoupler reaches the phototransistor PT and reaches the phototransistor PT. Is turned on, and a Low input signal is input to the microcomputer M.

[0006]

However, the most common cause of defects in the conventional liquid level detector is the connecting end C of the connector C.
It is a failure due to the disconnection of 1, C2 and C3. Even if the connection ends C1, C2, C3 of the connector C are disconnected,
The microcomputer M receives a High input signal. That is, when the oil level of the kerosene in the tank is above a certain reference level, a High input signal is input to the microcomputer M, and even if the connector C is disconnected, Input signal comes in.

Therefore, the use of the conventional liquid level detector causes the following problems.

If the oil level of kerosene in the tank is lower than a certain level, a Low input signal should originally be input to the microcomputer M as described above, but the connector C is also disconnected at the same time. Receives a High input signal to the microcomputer M.
Therefore, the microcomputer M uses the normal Hig
It is recognized that the input signal mode is the h input signal, that is, the oil level of kerosene in the tank is erroneously determined to be above a certain reference level.

As a result, the oil fan heater maintains a normal combustion state even though there is almost no kerosene in the tank. If you keep the normal combustion state,
Since there is almost no kerosene in the tank, the pump sends a little kerosene and a large amount of air to the burner side. For this reason, the air in the burner becomes excessive and the pressure of the air increases, which causes a problem of abnormal red combustion.

In view of the above situation, the present invention makes the output signal level at the time of liquid level detection different from the output signal level at the time of liquid presence / absence detection and the liquid level detector failure or connection failure. An object of the present invention is to provide a liquid level detection method and a liquid level detector capable of clarifying the cause of an abnormality.

[0011]

In order to solve the above problems, the invention according to claim 1 responds from the light receiving element depending on the presence or absence of liquid in the optical path between the light emitting element and the light receiving element. In the liquid level detection method of outputting a detection signal, it is configured by making the output signal level at the time of detecting the presence or absence of the liquid different from the output signal level at the time of the liquid level detector being defective or the connection being defective.

According to a second aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the light receiving element depending on the presence or absence of the liquid in the optical path between the light emitting element and the light receiving element. A signal level shift means for making the output signal level at the time of presence / absence detection different from the output signal level at the time of the liquid level detector being defective or having a defective connection is connected to the signal output terminal of the light receiving element.

According to a third aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the collector electrode of the phototransistor in accordance with the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor.
A voltage drop means is connected between the collector electrode of the phototransistor and the anode of the light emitting diode.

According to a fourth aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of the detection liquid in the optical path between the light emitting diode and the phototransistor. In a liquid level detector formed such that the light emitting diode and the phototransistor are connected to an external circuit via a connector, a connector connecting end to which a collector electrode of the phototransistor is connected and an anode of the light emitting diode. Is connected to the connector connecting end to which is connected.

According to a fifth aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the collector electrode of the phototransistor in accordance with the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor.
A first voltage drop means is connected between the collector electrode of the phototransistor and the anode of the light emitting diode;
A second voltage drop means is connected between the collector electrode and the emitter electrode of the phototransistor.

According to a sixth aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor.
The collector electrode of the phototransistor has an anode,
In addition, the cathode of the light emitting diode has a voltage drop diode connected to the cathode, respectively.

According to a seventh aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor.
A collector electrode is connected to the collector electrode of the phototransistor, and an emitter electrode is connected to the anode of the light emitting diode.

According to an eighth aspect of the present invention, there is provided a liquid level detector which outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor.
A resistor is connected between the collector electrode of the phototransistor and the anode of the light emitting diode.

[0019]

According to the invention described in claim 1, the output signal level at the time of detecting the presence or absence of the liquid is made different from the output signal level at the time of the liquid level detector being defective or the connection being defective. The cause of the abnormal occurrence can be clarified.

According to the second aspect of the present invention, the signal level shifting means makes the output signal level at the time of detecting the presence or absence of the liquid different from the output signal level at the time of the liquid level detector being defective or the connection being defective. As a result, the signal level of the detection signal obtained from the signal output terminal of the light receiving element differs depending on the cause of the abnormality, and therefore the cause of the abnormality at the time of detecting the liquid level can be clarified.

According to the third aspect of the invention, the voltage drop means is connected between the collector electrode of the phototransistor and the anode of the light emitting diode. Therefore, when the liquid level detector is defective, for example, when the light emitting diode is short-circuited (short-circuited), a current flows through the power supply, the collector electrode of the phototransistor, the voltage drop means, and the light emitting diode, and the resistance of the light emitting diode is zero at this time. Therefore, the voltage level of the detection signal corresponds to the voltage drop generated in the voltage drop means, and does not reach the zero level as in the conventional case. Therefore, by associating the detection signal level with the short-circuit failure of the light emitting diode, the cause of the abnormality can be distinguished. When the light emitting diode has an open circuit failure (open), the potential of the collector electrode of the phototransistor (power supply potential) is output. Further, at the time of a failure such as a connection failure or a contact failure of the light emitting diode, the current path flowing through the voltage drop means disappears, so that the signal level of the detection signal becomes the potential (power supply potential) of the collector electrode of the phototransistor. Thus, it is possible to clarify the cause of the abnormality when detecting the liquid level.

According to the fourth aspect of the invention, the voltage drop means is connected between the connector connecting end to which the collector electrode of the phototransistor is connected and the connector connecting end to which the anode of the light emitting diode is connected. . Therefore, when the liquid level detector is defective, for example, when the light emitting diode is short-circuited (short-circuited), a current flows through the power source, the connector connection end, the collector electrode of the phototransistor, the voltage drop means, and the light emitting diode path. Since the resistance of No. 1 is zero, the voltage level of the detection signal corresponds to the voltage drop generated in the voltage drop means, and does not reach the zero level as in the conventional case. Therefore, by associating the detection signal level with the short-circuit failure of the light emitting diode, the cause of the abnormality can be distinguished. When the light emitting diode has an open circuit failure (open), the potential of the collector electrode of the phototransistor (power supply potential) is output. further,
In the event of a failure such as a connection failure or a contact failure at the connector connection end of the light emitting diode, the current path flowing through the voltage drop means disappears, and the signal level of the detection signal becomes the potential (power supply potential) of the collector electrode of the phototransistor.
Thus, it is possible to clarify the cause of the abnormality when detecting the liquid level.

According to the invention described in claim 5, the first voltage drop means is connected between the collector electrode of the phototransistor and the anode of the light emitting diode, and the collector electrode and the emitter electrode of the phototransistor are connected. The second voltage drop means is connected across the space. Therefore, when the liquid level detector is defective, for example, when the light emitting diode is short-circuited (short-circuited), a current flows through the path of the power source, the collector electrode of the phototransistor, the first voltage drop means, and the light emitting diode. Since the resistance can be almost ignored, the voltage level of the detection signal corresponds to the voltage drop generated in the first voltage drop means, and does not reach the zero level as in the conventional case. Therefore, by associating the detection signal level with the short-circuit failure of the light emitting diode, the cause of the abnormality can be distinguished. Also, when the light emitting diode has an open circuit failure (open), the power supply voltage is set to the first
The potential determined by the voltage division ratio of the voltage drop means and the second power supply voltage means is output. Further, when there is a failure such as a connection failure or a contact failure at the connector connection end of the light emitting diode, the current path flowing through the voltage drop means is lost, so that the signal level of the detection signal is the power supply voltage which is the same as that of the first voltage drop means and the second voltage drop means. The potential is determined by the voltage division ratio of the power supply voltage means. Thus, it is possible to clarify the cause of the abnormality when detecting the liquid level.

According to the sixth aspect of the invention, due to the presence of the voltage drop diode, the output signal level at the time of detecting the presence or absence of the liquid and the output signal level at the time of the liquid level detector being defective or the connection being defective. The cause of the abnormality at the time of detecting the liquid level can be clarified by changing the difference.

According to the invention described in claim 7, due to the existence of the voltage drop transistor, the output signal level at the time of detecting the presence or absence of the liquid and the output signal level at the time of the liquid level detector being defective or the connection being defective. Since they are made different, it is possible to clarify the cause of the abnormality when detecting the liquid level.

According to the eighth aspect of the present invention, the presence of the resistor causes the output signal level at the time of detecting the presence or absence of the liquid to be different from the output signal level at the time of the liquid level detector being defective or the connection being defective. Therefore, it is possible to clarify the cause of the abnormality when the liquid level is detected.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings.

First Embodiment First, FIG. 1 shows an example of a petroleum fan heater to which an embodiment of the liquid level detector according to the present invention is applied, and the outline thereof will be described.

In FIG. 1, kerosene 5 stored in a storage tank 1 can be sent to a burner 3 by a pump 2. The fuel cartridge tank 4 is set in the storage tank 1.

The fuel cartridge tank 4 has a valve 4
a is arranged, and kerosene 5 is successively supplied into the storage tank 1. In FIG. 1, the storage tank 1 is drawn larger than the fuel cartridge tank 4 for convenience of description.

The storage tank 1 is provided with a liquid level detector 10, and the blower sends primary air and secondary air to the burner 3. If the kerosene 5 in the storage tank 1 decreases and drops from the oil level L1 to the oil level L2, if the normal combustion operation is performed without noticing that, the pump 2 will remove the kerosene 5 from the oil level. The air in the storage tank 1 is also sucked in continuously. Eventually, the flame of the burner 3 extinguishes, but the problem is that kerosene and a large amount of air are sent into the burner 3, and the balance between air and kerosene is lost, resulting in an abnormal red fire. Therefore, it is necessary to reliably notify the user that the amount of kerosene in the storage tank 1 has become less than the predetermined amount.

FIG. 2 shows an example of a sectional structure of the liquid level detector 10 according to the present invention, and FIG. 3 shows an equivalent circuit of an electric circuit of the liquid level detector 10.
In FIG. 4, the light emitting element 12, the light receiving element 14 of the liquid level detector 10,
The cover member 16 of transparent resin is shown.

As shown in FIG. 2, the liquid level detector 10 has three connection terminals 10a, 10b and 10c. FIG.
As shown in FIG. 3, the light emitting diode 12 and the phototransistor 14 that constitute the photocoupler 15 are mounted on the mounting plate 18, surrounded by the cover member 16, and mounted in the casing 19.

If the kerosene 5 is at the oil level L1, for example, the light LT emitted from the light emitting diode 12 is diffused by the kerosene 5 and the cover member 16 and does not reach the phototransistor 14 as shown by the chain double-dashed line. The phototransistor 14 is off.

On the other hand, when the kerosene 5 in FIG. 4 is lowered to the oil level L2, the light LT emitted from the light emitting diode 12 is reflected by the cover member 16 and reaches the phototransistor 14 as shown by the solid line. Light receiving element 1
4 turns on.

FIG. 5 shows an example of an electric circuit of the liquid surface detector 10 according to the present invention. In FIG. 5, the photocoupler 15 and the voltage drop (or voltage generation) with respect to the power supply voltage VDD.
A diode D1 as a means is connected. The cathode of the diode D1 is connected between the current limiting resistor R1 and the anode of the light emitting diode 12 of the photocoupler 10. The anode of the diode D1 is connected between the other pull-up resistor R2 and the collector electrode of the phototransistor 14 of the photocoupler 10. The cathode of the light emitting diode 12 and the emitter electrode of the phototransistor 14 are grounded.

The connection point between the anode of the diode D1 and the collector of the phototransistor 14 is connected to the A / D converter 28 of the microcomputer 26. The current limiting resistor R1 is a resistor (for example, 150Ω) for passing a large current from the power source to the light emitting diode 12,
The pull-up resistor R2 is connected to the phototransistor 1 from the power supply.
Resistance for passing a small current through 4 (for example, 10-20K
Ω).

Next, the operation of the first embodiment will be described with reference to FIG. FIG. 12 illustrates the value of the input voltage to the microcomputer 26 for each embodiment and for each state (normal and abnormal).

The normal state in FIG. 12 means the light emitting diode (L
The ED 12 does not have a short circuit failure (short circuit) or an open circuit failure (open), and the phototransistor 14 does not have a short circuit failure (short circuit) or an open circuit failure (open).

When the kerosene of FIG. 4 is filled up to the oil level L1 in this normal state, the light of the light emitting diode 12 is diffused to the outside of the sensor due to the refractive index of the kerosene and the refractive index of the sensor, and leaks to the phototransistor 14. Does not reach. Therefore, in FIG. 5, the phototransistor 14 is off, and the current from the power source flows through the path of the pull-up resistor R2, the diode D1, and the light emitting diode 12. Therefore, the forward voltage VF1 (for example, 0.6 V) of the diode D1 and the forward voltage VF2 of the light emitting diode 12 are set.
Output voltage value 2.6V to which (for example, 2.0V) is added
Is input to the A / D conversion unit 28 of the microcomputer 26, and the microcomputer 26 determines that “there is kerosene in the tank”.

On the other hand, when the kerosene is reduced to the oil level L2 as shown in FIG. 4 under normal conditions, the light emitting diode 1
The light 2 is reflected inside the sensor and is reflected by the phototransistor 14
To reach. Therefore, in FIG. 5, the phototransistor 14 is turned on, and the current from the power supply drops to the ground. As a result, the collector-emitter voltage VCE (about 0.2 V) of the phototransistor 14 is input to the A / D converter 28 of the microcomputer 26, and the microcomputer 26 determines that "there is no kerosene in the tank". The above description is for the case where both the light emitting diode 12 and the phototransistor 14 are normal.

Next, an explanation will be given of an abnormal condition when the kerosene 5 is present in the tank 1 of FIG. The abnormal state is a case where the light emitting diode (LED) 12 has a short circuit failure (short circuit) or an open circuit failure (open), or the phototransistor 14 has a short circuit failure (short circuit) or an open circuit failure (open).

There is kerosene 5 in the tank 1 up to the oil level L1,
When the light emitting diode 12 is short-circuited, the power source, the collector electrode of the phototransistor 14, the voltage drop diode D
1. A current flows through the path of the light emitting diode 12, the light emitting diode 12 does not emit light, and the phototransistor 14 is off. This causes the forward voltage VF1 of the diode D1.
Only (0.6V) is the A / D of the microcomputer 26
The voltage is input to the conversion unit 28 as an input voltage.

When the kerosene 5 is in the tank 1 up to the oil level L1 and the light emitting diode 12 opens, the light emitting diode 12 does not emit light and the phototransistor 14 is off. In addition, the current path of the diode D1 is also cut off, so that the power supply voltage VDD (5V) is input to the A / D conversion unit 28 of the microcomputer 26 as an input voltage.

Furthermore, when kerosene 5 is in the tank 1 up to the oil level L1 and the phototransistor 14 is short-circuited, the zero level is zero in the A / D converter 2 of the microcomputer 26.
8 is input as an input voltage.

Further, when kerosene 5 is in the tank 1 up to the oil level L1 and the phototransistor 14 is opened, the current from the power source is pulled up by the resistor R2 and the diode D.
1, and then flows in the path of the light emitting diode 12. As a result, the forward voltage VF1 (for example, 0.6 V) of the diode D1 and the forward voltage VF2 of the light emitting diode 12 are set.
A voltage value of 2.6 V, to which (for example, 2.0 V) is added,
The voltage is input to the A / D converter 28 of the microcomputer 26 as an input voltage.

Next, a description will be given of an abnormal condition when the oil level of kerosene 5 is L2 in the tank 1 of FIG. 2 and there is no kerosene 5.

Even when there is no kerosene 5 in the tank 1, as in the case where the kerosene 5 is in the tank 1 described above,
When the light emitting diode 12 is short-circuited, the diode D1
Only the forward voltage VF1 (0.6 V) is input to the A / D converter 28 of the microcomputer 26 as an input voltage. Further, when the light emitting diode 12 is opened, the power supply voltage VDD (5V) changes to A of the microcomputer 26.
The voltage is input to the / D converter 28 as an input voltage. further,
When the phototransistor 14 is short-circuited, the zero level is input to the A / D conversion unit 28 of the microcomputer 26 as an input voltage. Furthermore, the phototransistor 1
When 4 opens, forward voltage VF of diode D1
A voltage value of 2.6 V obtained by adding 1 (for example, 0.6 V) and the forward voltage VF2 (for example, 2.0 V) of the light emitting diode 12 is input to the A / D conversion unit 28 of the microcomputer 26 as an input voltage. .

As described above, according to this embodiment, due to the presence of the diode D1 which is the signal level shifting means, the output signal level when the presence or absence of kerosene is detected and the output signal level when the liquid level detector is defective are determined. Can be different. As a result, the signal level of the detection signal obtained from the signal output terminal of the photodiode 14 differs depending on the cause of abnormality,
It is possible to clarify the cause of the abnormality when detecting the liquid level.

Second Embodiment FIG. 6 shows a second embodiment of the liquid level detector 10 according to the present invention. In FIG. 6, the same or equivalent elements as those of the first embodiment (FIG. 5) are designated by the same reference numerals and described below.

This embodiment shows an application example of the present invention when the liquid surface detector 10 shown in the first embodiment is connected via a connector 30. Such a mode is often used in actual assembly.

The connector 30 has three connecting ends 30a, 3
It has 0b and 30c. The connection end 30a electrically connects the anode of the light emitting diode 12 and the current limiting resistor R1. The connection end 30b electrically connects the collector electrode of the phototransistor 14 and the pull-up resistor R2.
0c electrically connects the cathode of the light emitting diode 12 and the emitter electrode of the phototransistor 14 to the ground. The diode D1 as the voltage drop means is provided on the external circuit side of the photocoupler 15 at the connection ends 30a and 30b.
The anode of the diode D1 is connected to the collector electrode of the phototransistor 14, and the cathode of the diode D1 is connected to the anode of the light emitting diode 12.

Next, the operation of the second embodiment will be described.

As shown in FIG. 12, the light emitting diode 12
If both and the phototransistor 14 are normal,
The value of the input voltage to the microcomputer 26 is the same as in the normal case of the principle diagram of FIG.

Further, irrespective of the presence or absence of kerosene in the tank,
Light emitting diode (LED) 12 short circuit failure (short circuit)
Alternatively, in the case of an open circuit failure (open) or an abnormality in which the phototransistor 14 has a short circuit failure (short circuit) or an open circuit failure (open), the value of the input voltage to the microcomputer 26 is the same as in the abnormal case of FIG. .

However, in this embodiment, regardless of the presence or absence of kerosene in the tank, as shown in FIG.
The case where any of the connection ends 30a, 30b, 30c of No. 1 has a poor connection or a bad contact is added as an abnormal state.

Connection end (NO. 1) 30a of the connector 30
If the connection failure or the contact failure occurs, the light emitting diode 12 becomes the same as the open state, and the phototransistor 14 is off. Therefore, the power supply voltage (5
V) is an A / D conversion unit 28 of the microcomputer 26
Input as an input voltage.

The connection end of the connector 30 (NO. 2)
If the connection or the contact failure occurs in 30b, the forward voltage VF1 (for example, 0.6 V) of the diode D1 and the forward voltage VF2 (for example, 2.0 V) of the light emitting diode 12 are generated.
The voltage value 2.6V to which V) is added is input as an input voltage to the A / D conversion unit 28 of the microcomputer 26.

Further, the connection end of the connector 30 (NO.
3) When the connection or contact of 30c becomes poor, the light emitting diode 12 becomes the same as the open state,
The power supply voltage (5V) is A / of the microcomputer 26.
The voltage is input to the D conversion unit 28 as an input voltage.

Third Embodiment FIG. 7 shows a third embodiment of the liquid level detector 10 according to the present invention. In FIG. 7, the same or equivalent elements as those of the first embodiment (FIG. 5) are designated by the same reference numerals and described below.

In this embodiment, a transistor Tr1 biased by a bias resistor R3 is provided instead of the diode D1 as the voltage drop means. The collector electrode of the transistor Tr1 is connected to the collector electrode of the phototransistor 14, and the emitter electrode of the transistor Tr1 is connected to the anode of the light emitting diode 12. Forward voltage drop VF of transistor Tr1
Is generally 0.6 to 0.7V.

When both the light emitting diode 12 and the phototransistor 14 are normal, the value of the input voltage to the microcomputer 26 is, for example, the transistor Tr1 when there is kerosene in the tank as shown in FIG.
The sum of the forward voltage and the forward voltage of the light emitting diode 12 is 2.1 V, and is 0.2 V when there is none.

Regardless of the presence or absence of kerosene in the tank, the light emitting diode (LED) 12 has a short circuit failure (short circuit) or an open circuit failure (open), or the phototransistor 1
In the case of an abnormality in which 4 is a short circuit failure (short circuit) or an open circuit failure (open), the microcomputer 2
The value of the input voltage for 6 is shown in FIG.

Fourth Embodiment FIG. 8 shows a fourth embodiment of the liquid level detector according to the present invention.
In FIG. 8, elements that are the same as or equivalent to those of the first embodiment (FIG. 5) are given the same reference numerals and described below.

In this embodiment, a resistor R4 is provided instead of the diode D1 as the voltage drop means in the first embodiment (FIG. 5). That is, the resistor R4 is connected to the collector electrode of the phototransistor 14 and the light emitting diode 12.
Connected between the anodes of. In the case of FIG.
The value of the input voltage to the microcomputer 26 is adjusted by the voltage division ratio of the two resistors R1, R2 and R4.
The resistance value of R2 and R4 is, for example, 10 KΩ.

When both the light emitting diode 12 and the phototransistor 14 are normal, the value of the input voltage to the microcomputer 26 is as shown in FIG. 12 when the kerosene is in the tank, for example, the voltage drop of the resistor R4. Minutes and the total forward voltage of the light emitting diode 12 is 2.3V
If there is not, it is 0.2V.

Regardless of the presence or absence of kerosene in the tank, the light emitting diode (LED) 12 has a short circuit failure (short circuit) or an open circuit failure (open), or the phototransistor 1
In the case of an abnormality in which 4 is a short circuit failure (short circuit) or an open circuit failure (open), the microcomputer 2
The value of the input voltage for 6 is shown in FIG.

Fifth Embodiment FIG. 9 shows a liquid level detector according to a fifth embodiment of the present invention.
In FIG. 9, the same or equivalent elements as those of the first embodiment (FIG. 5) are designated by the same reference numerals and described below.

In this embodiment, instead of the diode D1 as the voltage drop means, a Zener diode DZ1 is used.
Is provided. The other points in the configuration are the same as those in the first embodiment (FIG. 5), and thus detailed description will be omitted.

In this embodiment, when both the light emitting diode 12 and the phototransistor 14 are normal, the value of the input voltage to the microcomputer 26 is as shown in FIG.
As shown in 2, when the kerosene is in the tank, the total of the forward voltage of the Zener diode DZ1 and the forward voltage of the light emitting diode 12 is 2.6 V, and is 0.2 V when there is no kerosene.

Regardless of the presence or absence of kerosene in the tank, the light emitting diode (LED) 12 has a short circuit failure (short circuit) or an open circuit failure (open), or the phototransistor 1
In the case of an abnormality in which 4 is a short circuit failure (short circuit) or an open circuit failure (open), the microcomputer 2
The value of the input voltage for 6 is shown in FIG.

Sixth Embodiment FIG. 10 shows a sixth embodiment of the liquid level detector according to the present invention. In FIG. 10, the same or equivalent elements as those of the first embodiment (FIG. 5) are designated by the same reference numerals and described below.

In this embodiment, as apparent from comparison with the second embodiment (FIG. 6), the diode D1 is connected to the connector 3
It is arranged on the side of the photocoupler 15 via 0. In such a mode, the diode D1 is connected to the connection terminals 10a, 1
0b (see FIG. 2) or built in the casing 19.

In this embodiment, when both the light emitting diode 12 and the phototransistor 14 are normal, the value of the input voltage to the microcomputer 26 is as shown in FIG.
As shown in 2, when the kerosene is in the tank, the total of the forward voltage of the diode D1 and the forward voltage of the light emitting diode 12 is 2.6V, and is 0.2V when there is no kerosene.

Regardless of the presence or absence of kerosene in the tank, the light emitting diode (LED) 12 has a short circuit failure (short circuit) or an open circuit failure (open), or the phototransistor 1
In the case of an abnormality in which 4 is a short circuit failure (short circuit) or an open circuit failure (open), the microcomputer 2
The value of the input voltage for 6 is shown in FIG.

And, regardless of the presence or absence of kerosene in the tank,
As shown in FIG. 12, the connection ends 30a, 3 of the connector 30 are
Either 0b or 30c may cause poor connection or poor contact.

Connection end (NO. 1) 30a of the connector 30
If the connection is poor or the connection is poor, the current from the power source flows through the diode D1 to the light emitting diode 12, so that there is no problem and the forward voltage VF1 (for example, 0.6 V) of the diode D1 and the light emitting diode 12 A voltage value of 2.6 V to which the forward voltage VF2 (for example, 2.0 V) is added is input to the A / D conversion unit 28 of the microcomputer 26 as an input voltage.

The connection end of the connector 30 (NO. 2)
If the connection or contact failure of 30b occurs, the light-emitting diode 12 is in the same state as the open state, and the power supply voltage (5V) is input as an input voltage to the A / D conversion unit 28 of the microcomputer 26.

Further, the connection end of the connector 30 (NO.
3) When the connection or contact of 30c becomes poor, the light emitting diode 12 becomes the same as the open state,
The power supply voltage (5V) is A / of the microcomputer 26.
The voltage is input to the D conversion unit 28 as an input voltage.

Seventh Embodiment FIG. 11 shows a seventh embodiment of the liquid level detector according to the present invention. In FIG. 11, the same components as those of the sixth embodiment (FIG. 10) are designated by the same reference numerals and described below.

In this embodiment, as apparent from the comparison with the sixth embodiment, the voltage dividing resistor R5 is arranged between the collector electrode and the emitter electrode of the phototransistor 14 and inside the connector 30. ing. The voltage dividing resistor R5 and the pull-up resistor R2 divide the power supply voltage. The resistance R2 is, for example, 10 KΩ, and the resistance R5 is, for example, 5.
It is 1 KΩ.

In this embodiment, the sixth embodiment (see FIG. 1)
0) is different from the case where the connection end 30a of the connector 30 of the light emitting diode 12 is disconnected, as shown in FIG.
When the light emitting diode 12 is opened, the power supply voltage 5V is divided by the resistors R2 and R5, so that 3.3V is, for example, A / D converter 2 of the microcomputer 26.
8 is input as an input voltage.

Regardless of the presence or absence of kerosene in the tank, the light emitting diode (LED) 12 has a short circuit failure (short circuit) or an open circuit failure (open), or the phototransistor 14 has a short circuit failure (short circuit) or an open circuit failure (open). In case of abnormality, microcomputer 2
The value of the input voltage for 6 is shown in FIG.

In this embodiment, regardless of the presence or absence of kerosene in the tank, as shown in FIG. 12, when one of the connection ends 30a, 30b, 30c of the connector 30 of FIG. 11 has a poor connection or a poor contact. There is.

Connection end (NO. 1) 30a of the connector 30
If the connection is poor or the contact is poor, the resistors R2 and R
Input voltage (VDD × R5) /
(R2 + R5) is set to the forward voltage VF1 (for example, 0.6 V) of the voltage drop diode D1 and the light emitting diode 12
If the voltage is lower than the added voltage value 2.6V of the forward voltage VF2 (for example, 2.0V) (see formula (1) in FIG. 14), the same as when the light emitting diode 12 is opened, The input voltage is 3.3V.

Further, as shown in the equation (2) of FIG. 14, the input voltage (VDD × R5) / (R2 + R5) is set to the forward voltage VF1 (0.6 V, for example) of the voltage drop diode D1 and the forward voltage of the light emitting diode 12. Directional voltage VF2 (for example, 2.
0V) is much larger than the added voltage value of 2.6V, which is the same as the case where the connection end 30a of the connector 30 in Example 5 of FIG. 10 is disconnected, and the input voltage is 2.6V. .

The connection end of the connector 30 (NO. 2)
If the connection or contact failure of 30b occurs, the power supply voltage (5V) is input to the A / D conversion unit 28 of the microcomputer 26 as an input voltage.

Further, the connection end of the connector 30 (NO.
3) When the connection or contact of 30c becomes poor, the light emitting diode 12 becomes the same as the open state,
The power supply voltage (5V) is A / of the microcomputer 26.
The voltage is input to the D conversion unit 28 as an input voltage.

In the first embodiment (FIG. 5) to the seventh embodiment (FIG. 11), there is no kerosene in the tank and the phototransistor 14 is open in the abnormal condition shown by the black circle in FIG. In this case, the microcomputer 26 determines that "there is kerosene" in the tank, but other failures can be detected.

FIG. 13 conceptually shows that in the above-described embodiment, the liquid level detector has kerosene in the tank, no kerosene, and the failure of the liquid level detector can be distinguished by the microcomputer by the input voltage. There is.

Although the liquid level detector applied to the oil fan heater has been described as an example in the above description, the invention is not limited to this, and the forced air supply / exhaust type hot air heater, oil boiler, automobile fuel gauge, It goes without saying that the present invention can also be applied to equipment in other areas and fields such as silicon oil meters such as copying machines.

Further, in the first to seventh embodiments, when an abnormal state occurs, the microcomputer may have a warning function such as turning on a warning lamp.

[0093]

As described above, according to the invention described in claim 1, the output signal level at the time of detecting the presence or absence of the liquid and the output signal level at the time of the liquid level detector being defective or the connection being defective. Since the configurations are made different, it is possible to clarify the cause of the abnormality when detecting the liquid level. Therefore, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, abnormal red-fire combustion can be prevented, and safety can be improved.

According to the second aspect of the invention, the signal level shift means makes the output signal level at the time of detecting the presence or absence of the liquid different from the output signal level at the time of the liquid level detector being defective or the connection being defective. Since the configuration is adopted, as a result, the signal level of the detection signal obtained from the signal output end of the light receiving element differs depending on the cause of the abnormality, so that the cause of the abnormality at the time of detecting the liquid level can be clarified. Therefore, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, abnormal red-fire combustion can be prevented, and safety can be improved.

According to the third aspect of the invention, the voltage drop means is connected between the collector electrode of the phototransistor and the anode of the light emitting diode. Therefore, when the liquid level detector is defective, for example, when the light emitting diode is short-circuited (short-circuited), a current flows through the power supply, the collector electrode of the phototransistor, the voltage drop means, and the light emitting diode, and the resistance of the light emitting diode is zero at this time. Therefore, the voltage level of the detection signal corresponds to the voltage drop generated in the voltage drop means, and does not reach the zero level as in the conventional case. Therefore, by associating the detection signal level with the short-circuit failure of the light emitting diode, the cause of the abnormality can be distinguished. When the light emitting diode has an open circuit failure (open), the potential of the collector electrode of the phototransistor (power supply potential) is output. Further, at the time of a failure such as a connection failure or a contact failure of the light emitting diode, the current path flowing through the voltage drop means disappears, so that the signal level of the detection signal becomes the potential (power supply potential) of the collector electrode of the phototransistor. Thus, it is possible to clarify the cause of the abnormality when detecting the liquid level. Therefore, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, abnormal red-fire combustion can be prevented, and safety can be improved. According to the invention described in claim 4, the voltage drop means is connected between the connector connecting end to which the collector electrode of the phototransistor is connected and the connector connecting end to which the anode of the light emitting diode is connected. Therefore, when the liquid level detector is defective, for example, when the light emitting diode is short-circuited (short-circuited), a current flows through the power source, the connector connection end, the collector electrode of the phototransistor, the voltage drop means, and the light emitting diode path. Since the resistance of No. 1 is zero, the voltage level of the detection signal corresponds to the voltage drop generated in the voltage drop means, and does not reach the zero level as in the conventional case. Therefore, by associating the detection signal level with the short-circuit failure of the light emitting diode, the cause of the abnormality can be distinguished. When the light emitting diode has an open circuit failure (open), the potential of the collector electrode of the phototransistor (power supply potential) is output. Further, in the case of a failure such as a connection failure or a contact failure at the connector connection end of the light emitting diode, the current path flowing through the voltage drop means is lost, so that the signal level of the detection signal is equal to the potential (power supply potential) of the collector electrode of the phototransistor. Become. Thus, it is possible to clarify the cause of the abnormality when detecting the liquid level. Therefore, it is possible to detect the contact failure or connection failure of the connector which is actually the most frequent cause of failure. Moreover, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, and it is possible to prevent abnormal red fire combustion and improve safety.

According to the invention described in claim 5, the first voltage drop means is connected between the collector electrode of the phototransistor and the anode of the light emitting diode, and the collector electrode and the emitter electrode of the phototransistor are connected. The second voltage drop means is connected across the space. Therefore, when the liquid level detector is defective, for example, when the light emitting diode is short-circuited (short-circuited), a current flows through the path of the power source, the collector electrode of the phototransistor, the first voltage drop means, and the light emitting diode. Since the resistance is zero, the voltage level of the detection signal corresponds to the voltage drop generated in the first voltage drop means, and does not reach the zero level as in the conventional case. Therefore, by associating the detection signal level with the short-circuit failure of the light emitting diode, the cause of the abnormality can be distinguished. Also, when the light emitting diode has an open circuit failure (open), the power supply voltage is set to the first
The potential determined by the voltage division ratio of the voltage drop means and the second power supply voltage means is output. Further, when there is a failure such as a connection failure or a contact failure at the connector connection end of the light emitting diode, the current path flowing through the voltage drop means is lost, so that the signal level of the detection signal is the power supply voltage which is the same as that of the first voltage drop means and the second voltage drop means. The potential is determined by the voltage division ratio of the power supply voltage means. Thus, it is possible to clarify the cause of the abnormality when detecting the liquid level. Therefore, it is possible to detect the contact failure or connection failure of the connector which is actually the most frequent cause of failure.
Moreover, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, and it is possible to prevent abnormal red fire combustion and improve safety.

According to the sixth aspect of the present invention, due to the presence of the voltage drop diode, the output signal level when the presence or absence of the liquid is detected and the output signal level when the liquid level detector is defective or the connection is defective. Since it is configured to be different, it is possible to clarify the cause of the abnormality when detecting the liquid level. Therefore, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, abnormal red-fire combustion can be prevented, and safety can be improved.

According to the invention described in claim 7, the output signal level at the time of detecting the presence or absence of the liquid and the output signal level at the time of the liquid level detector being defective or the connection being defective are provided by the existence of the voltage drop transistor. Since the configurations are made different, it is possible to clarify the cause of the abnormality when the liquid level is detected. Therefore, even if there is almost no kerosene in the tank, the normal combustion state will not be maintained, abnormal red-fire combustion can be prevented, and safety can be improved.

According to the invention described in claim 8, due to the presence of the resistor, the output signal level at the time of detecting the presence or absence of the liquid is made different from the output signal level at the time of the liquid level detector being defective or the connection being defective. Since the configuration is adopted, it is possible to clarify the cause of the abnormality when detecting the liquid level. Therefore, it is possible to detect an abnormality during liquid level detection even with the cheapest resistor with few failures, and the normal combustion state will not be maintained even if there is almost no kerosene in the tank. It is possible to prevent fire burning and improve safety.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a petroleum fan heater including a liquid level detector of the present invention.

FIG. 2 is a vertical sectional view showing a structural example of a liquid level detector according to the present invention.

FIG. 3 is an equivalent circuit diagram of a liquid level detector FIG. 2 electric circuit according to the present invention.

FIG. 4 is an enlarged view of a photocoupler portion of the liquid surface detector according to the present invention.

FIG. 5 is an electric circuit diagram showing a first embodiment of the liquid level detector according to the present invention.

FIG. 6 is an electric circuit diagram showing a second embodiment of the liquid level detector according to the present invention.

FIG. 7 is an electric circuit diagram showing a third embodiment of the liquid level detector according to the present invention.

FIG. 8 is an electric circuit diagram showing a fourth embodiment of the liquid level detector according to the present invention.

FIG. 9 is an electric circuit diagram showing a fifth embodiment of the liquid level detector according to the present invention.

FIG. 10 is an electric circuit diagram showing a sixth embodiment of the liquid level detector according to the present invention.

FIG. 11 is an electric circuit diagram showing a seventh embodiment of the liquid level detector according to the present invention.

FIG. 12 is a diagram showing an example of the input voltage of the microcomputer in each embodiment.

FIG. 13 is a diagram conceptually showing the presence of kerosene in the tank, the absence of kerosene, and the failure of the liquid level detector by the value of the input voltage of the microcomputer.

FIG. 14 is a diagram showing a calculation example in the case where the connector is disconnected in FIG.

FIG. 15 is a diagram showing a conventional liquid level detector.

[Explanation of symbols]

5 Kerosene (liquid) 10 Photocoupler (sensor) 12 Light emitting diode (light emitting element) 14 Photodiode (light receiving element) 30 Connector 30a, 30b, 30c Connector connection end Tr1, DZ1 Voltage drop transistor (voltage drop means, signal level shift) R4 voltage drop resistor (voltage drop means, signal level shift means) 100 external circuit D1 voltage drop diode (voltage drop means, signal level shift means)

Claims (8)

[Claims] 1. A liquid level detection method for outputting a corresponding detection signal from the light receiving element in accordance with the presence or absence of liquid in the optical path between the light emitting element and the light receiving element, the output signal level at the time of detecting the presence or absence of the liquid. And a liquid level detection method, wherein the output signal level when the liquid level detector is defective or when the connection is defective is made different. 2. A liquid level detector that outputs a corresponding detection signal from the light receiving element according to the presence or absence of liquid in the optical path between the light emitting element and the light receiving element, wherein the output signal level at the time of detecting the presence or absence of the liquid And a signal level shift means for differentiating the output signal level when the liquid level detector is defective or connection failure is connected to the signal output end of the light receiving element. 3. A liquid level detector that outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor, wherein the collector electrode of the phototransistor is A liquid level detector characterized in that a voltage drop means is connected between the anode of the light emitting diode and the anode. 4. A liquid level detector which outputs a corresponding detection signal from a collector electrode of the phototransistor according to the presence or absence of a detection liquid in an optical path between the light emitting diode and the phototransistor, wherein In a liquid level detector in which a phototransistor is connected to an external circuit via a connector, a voltage is applied between a connector connecting end to which a collector electrode of the phototransistor is connected and a connector connecting end to which an anode of the light emitting diode is connected. A liquid level detector characterized by being connected with a descending means. 5. A liquid level detector that outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor, wherein the collector electrode of the phototransistor is A first voltage drop means is connected between the anode of the light emitting diode and
A liquid level detector characterized in that a second voltage drop means is connected between the collector electrode and the emitter electrode of the phototransistor. 6. A liquid level detector which outputs a corresponding detection signal from a collector electrode of the phototransistor according to the presence or absence of liquid in an optical path between the light emitting diode and the phototransistor, wherein an anode is a collector of the phototransistor. On the electrode
A liquid level detector characterized in that a cathode has a voltage drop diode respectively connected to an anode of a light emitting diode. 7. A liquid level detector that outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor, wherein the collector electrode is the phototransistor. A liquid level detector having a voltage drop transistor connected to a collector electrode and an emitter electrode to an anode of a light emitting diode, respectively. 8. A liquid level detector that outputs a corresponding detection signal from the collector electrode of the phototransistor according to the presence or absence of liquid in the optical path between the light emitting diode and the phototransistor, wherein the collector electrode of the phototransistor is A liquid level detector characterized in that a resistor is connected between the anode of the light emitting diode and the anode.