JPS597934B2 - Liquid level detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level detection device for detecting a drop in the electrolyte level of a storage battery.

Conventionally, many of these types of devices are so-called electrode-type liquid level detection devices, which apply a voltage directly from the outside to a detection electrode suspended above the electrolyte surface, and detect the liquid level by connecting and disconnecting the detection electrode and the liquid surface. It is used.

Although this method has a simple structure, depending on the type of storage battery, the current flowing into the detection electrode may cause electrodeposition on the detection electrode, which not only has an adverse effect on the storage battery, but also has a negative effect on the liquid level detection ability. There was a great risk that it would be inaccurate. In order to eliminate this drawback, a method has been proposed in which a liquid level detection electrode is connected to the primary side of the mutual induction coil, the secondary coil is used as an inductance of an oscillation circuit, and the liquid level is detected based on the presence or absence of oscillation. It was done. However, the operating principle of this method is that in the normal standby state where the electrolyte and the detection electrode are in contact,
Since the resistance between the two detection electrodes connected to the secondary coil becomes low due to the electrolyte, the load on the primary coil becomes heavy and the oscillation of the oscillation circuit of the secondary coil stops. . When the oscillation circuit of the secondary coil stops oscillating, no voltage is generated between the two detection electrodes connected to the primary coil, and the above-mentioned drawbacks are eliminated.

In addition, in an alarm state where the electrolyte and the detection electrode do not come into contact,
The resistance between the two detection electrodes connected to the primary coil becomes high, and the load on the primary coil becomes lighter.
The oscillation circuit of the next coil oscillates.

As described above, whether the oscillation circuit oscillates is determined depending on whether the load resistance of the primary coil is high or low, and depending on whether the oscillation circuit oscillates, the electrolyte and the detection electrode It is possible to detect whether it is in a non-contact state or in a contact state.

However, this method also has problems.

If the interelectrode resistance of the two detection electrodes connected to the primary coil is R, then this is the minimum value at which oscillation can be started from a stopped state in the oscillation circuit of the secondary coil. When we try to find the value of R of 2 and the maximum value of R that can stop oscillation from the oscillation state, they do not match, and there is a relationship of 1<<2, and 2 If the value of is set to an appropriate value, the value of will become a considerably low resistance. If the surface of the detection electrode becomes dirty and the contact resistance with the electrolyte becomes greater than r1, once oscillation starts, the oscillation circuit will stop oscillating even if the detection electrode is below the surface of the electrolyte. do not. In particular, in the case of oil batteries, the surface of the electrolyte is filled with insulating oil, and the surface of the detection electrode is quickly contaminated, making it impossible to accurately detect the liquid level with this method. .

The object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a device that can detect the liquid level without generating a voltage on the detection electrode in a normal standby state (a state in which the detection electrode is below the liquid surface). It is an object of the present invention to provide a liquid level detection device capable of reliably detecting the liquid level position even when the inter-electrode resistance increases due to surface deterioration or the like.

The gist of the invention to achieve the above object is as follows.

That is, in the present invention, a liquid level detection electrode is connected to the primary coil of a mutual induction coil, and the coil is used as an inductance of an oscillation circuit, and the resistance between the two detection electrodes due to the subsurface of the liquid level is significantly reduced. This method changes the oscillation power conditions of the oscillation circuit connected to the secondary side of the mutual induction wire ring, and detects the liquid level based on the presence or absence of oscillation. , stable regardless of the condition of the electrodes, etc.
It is equipped with a circuit that forcibly interrupts the oscillation of the oscillation circuit from the outside to ensure reliable operation.

As mentioned above, oscillation circuits usually have inertial characteristics. 1st
The figure shows the relationship between the interelectrode resistance R of the detection electrode and the oscillation of the oscillation circuit. As mentioned above, there is a hysteresis characteristic when starting from a stopped state of oscillation and when stopping from an oscillating state. That is, in order to stop oscillation while oscillation is continuing, R smaller than r1 is required, and conversely, in order to start oscillation while oscillation is stopped, R larger than R2 is required. However, if the surface of the detection electrode becomes dirty and the resistance R between the electrodes becomes r1 and R<R2, then for some reason (the battery shakes and the electrolyte surface is deformed, the detection electrode and electrolyte are separated for a moment). If the oscillation is started due to contact (such as no contact), the oscillation of the oscillation circuit will not stop even if the detection electrode comes into contact with the electrolyte again.

Therefore, does the oscillation circuit oscillate under the conditions of R2 and R?
It is not possible to distinguish whether oscillation is occurring under the condition of 1 or R<R2. In the present invention, in order to distinguish between the above conditions, the power to the oscillation circuit is once turned off, oscillation is forcibly stopped, and then the power is turned on again. The system distinguishes between r1, R, and R2.

However, since there is a possibility that the oscillation will start again at some timing, the circuit of the present invention periodically intermittent the lightning source so that r1<R
The oscillation under the condition <R2 is prevented from continuing.

FIG. 2 shows how the output waveform of the oscillation circuit changes when the interelectrode resistance R in the device of the present invention changes.

The observation power station is point P in Figure 3. Under the condition of R2<R, the oscillation circuit repeats stable oscillation intermittently, and the oscillation signal detection circuit at the subsequent stage detects this state as an oscillation state. Under the condition of R, R<R2, oscillation occurs and does not occur, and the oscillation waveform as a whole has many missing parts. The oscillation signal detection circuit at the subsequent stage detects such a state as a non-oscillation state. Since the oscillation circuit does not oscillate under the condition of R<r1, the oscillation signal detection circuit at the subsequent stage naturally detects that it is in a non-oscillation state. Next, a specific example of the present invention will be explained using a circuit diagram shown in FIG.

In FIG. 3, the circuit of this device can be divided into the following parts according to their functions.

Detection end and oscillation circuit 1, power supply intermittent circuit 2, oscillation signal detection circuit 3, alarm output circuit 4, power input section 5. The detection end and oscillation circuit 1 are mutual induction wire T1 field effect transistor Tr.
,, capacitors Cl, C2, C3 and resistors R,, R2
formed by.

T and T2 at the ends of the primary coil of the mutual induction coil T are detection terminals to which the liquid level detection electrode 8 shown in FIG. 4 is connected. The power supply intermittent circuit 2 is a transistor, Tr4, Tr.
5, Tr6, resistance R6, R7, R8, R,, R]0, R
3. The power supply to the oscillation circuit 1 formed by the capacitors C6 and C7 is switched on and off by a free-running multivibrator.

The oscillation signal detection circuit 3 is formed of a transistor Tr2, a diode D1, capacitors C4 and C5, and resistors R4 and R5.When the oscillation circuit 1 is oscillating, the oscillation signal at point P (
AC) is connected to the transistor 'r1- through the capacitor C4.
Based on the base of the transistor Tr2, the transistor Tr2 turns ON-OFF according to the oscillation signal. Transistor Tr2 is 0N-
When OFF, capacitor C5 is charged and capacitor C5
generates a voltage across the terminals of When the oscillation circuit 1 stops oscillating, the voltage at point P is a DC square wave voltage as shown in Figure 2, so the DC current is blocked by the capacitor C4, and the base current flows through the transistor Tr2. First, the transistor Tr2 does not turn ON.

Therefore, no voltage is generated across the capacitor C5 and the terminal. When the interelectrode resistance R is in the range of r1<R<R2, the oscillation circuit sometimes oscillates, but each time the transistor Tr2 turns ON and charges the capacitor C5, the period is short, so the capacitor C5 is charged. Not enough voltage is generated across the terminals. The alarm output circuit 4 is formed by a transistor Tr3, a relay Ry diode D2,
When a sufficient voltage is generated across the terminals of the front and rear capacitors C5, a voltage is applied to the base of the transistor Tr3, and the transistor Tr3 becomes ON. Transistor Tr3 is 0
When N is selected, relay Ry operates, and an alarm can be issued by combining contacts T5, T6, T7 of relay Ry with an alarm display means such as a buzzer lamp.

In a specific example of this device, the power supply of the oscillation circuit is periodically switched from 0N to 0F using a free-running multivibrator signal. However, the liquid level can be detected even if the power is turned OFF manually when necessary, so it is not necessary to turn the power OFF periodically.
There is no need to turn it 0FF. The present invention has the configuration described above, and since the liquid level detection electrode and the detection circuit are mounted on a mutual induction wire and can be isolated in a direct current manner, a large number of storage batteries that require liquid level detection are connected in series. Even when the detection devices are connected to each other, there is no need to pay attention to insulation between the detection devices, increasing the degree of freedom in design.

Furthermore, when the detection electrode is immersed in the liquid, the detection circuit stops oscillating, so no voltage is generated between the electrodes.
Therefore, the device of the present invention has the advantage that the electrode shape is not deformed by deposits caused by an inflow current, which is common in conventional electrode type liquid level detection devices, and the liquid level detection accuracy can be improved.
In the above, the oscillation of the oscillation circuit is periodically and forcibly intermittent from the outside to create a temporary complete oscillation stop state, but even if the oscillation of the oscillation circuit is not completely stopped from the outside,
The same effect can be obtained by simply increasing the intensity alternately. This is because the oscillation that continues even when the electrode is below the liquid level is weakened because the resistance between the electrodes absorbs the oscillation power, so the power supplied from the outside for oscillation is completely stopped. At the very least, you can stop it by just weakening it.

The oscillation of the oscillation circuit can be weakened externally by inserting a resistor Rl between the collector of the transistor Tr6 and the dividing point of the resistors R2 and R3 in FIG. It is clear that the liquid level detection device of the present invention can also be used to detect the level of conductive liquids other than batteries.

[Brief explanation of drawings]

Figure 1 shows the relationship between inter-electrode resistance and oscillation, and Figure 2 shows how the output waveform of the oscillation circuit changes when the inter-electrode resistance changes.
FIG. 3 is a circuit diagram showing an embodiment of the liquid level detection device of the present invention;
FIGS. 4A and 4B are schematic cross-sectional views for explaining the operating state of the apparatus of the present invention.

Claims (1)

[Claims] 1 Connect a liquid level detection electrode to the primary side of a mutual induction coil using the secondary coil as the inductance of the oscillation circuit,
In a device that detects the liquid level by changing the oscillation conditions depending on the presence or absence of contact between the liquid level and the electrode, the oscillation circuit generates periodic oscillation by forcibly intermittent oscillation or by alternately increasing the oscillation strength. A liquid level detection device characterized by detecting the presence or absence of contact between a liquid level and an electrode based on whether the liquid level is not sustained or not.