JPH01176917A - Liquid level detector - Google Patents

Abstract

PURPOSE:To preclude a malfunction by a simple structure by providing a trigger circuit, a display device, a state holding circuit, etc. CONSTITUTION:This device which as a liquid level sensor 4 for detecting the presence of liquid, the trigger circuit 41 for receiving the electric signal of the sensor 4, and the display device 42 driven by the circuit 41 is provided with the state holding circuit 43 which generates an output for putting the device 42 in a state before the liquid slants when the liquid receiving acceleration slants. Then when the circuit 43 sends its output to the device when detecting the acceleration applied to the liquid to hold the device 42 in the state before the liquid slants. Thus, the malfunction is precluded by the simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid level sensor, particularly a liquid level detection device for detecting the level of a liquid such as engine oil of an automobile.

2. Prior Art As shown in, for example, Japanese Utility Model Publication No. 57-491.50, in a conventional liquid level detector, one end of a cylindrical body is attached to a liquid port plug, and a detection tube is fixed to the other end of the cylindrical body. Additionally, a detection electrode is attached to the cylindrical body so that the lead wire is inserted into the inside of the cylindrical body and connected to the end of the lead wire.

In addition, the liquid level detection device shown in Japanese Patent Publication No. 58-28530 is for g!Is oscillation. It has a configuration that allows accurate measurement of the liquid level by detecting the difference between the oscillation frequencies oscillated by the oscillator and the oscillator for measuring the liquid level, which includes the interelectrode capacitance detected by the liquid level sensor. . A liquid level sensor forms an interelectrode capacitance between an outer cylinder and an inner cylinder made of conductive material such as aluminum or copper, and when the liquid level sensor is immersed in the liquid to be measured, Due to the difference between the dielectric constant of the liquid and the dielectric constant of the part other than the liquid being measured,
The difference in capacitance between the outer cylinder and the inner cylinder can be detected as the liquid level. However, this liquid level detection device requires high precision and a complicated circuit.

Furthermore, Japanese Patent Publication No. 60-35613 discloses a liquid level gauge in which an electrode is fitted into a hole formed in an insulating sleeve, and the insulating sleeve is further inserted into a hole in a conductive protective tube. When immersed in water, a current flows between the electrode and the conductive protection tube, and when the liquid level drops, the current flow decreases and the liquid level can be detected. However, this level gauge
When used as an engine oil level sensor, conventional liquid level gauges may malfunction due to oil level fluctuations, inclinations, and oil scattering during engine operation.

The problem that the invention aims to solve This state will be explained with reference to FIGS. 6 to 9.

First, as shown in FIG. 6, the liquid level detection device 1 includes a liquid level sensor 4 fixed to a container 3 containing a liquid 2 such as oil. For example, as shown in FIG. 9, the liquid level sensor 4 includes a mounting portion 11 in which a recess 11a is formed, and
a first electrode 14 having a substantially cylindrical shape and having one end 12 fitted to the top end 13 and the other end 13 being a free end; an insulator 15 that is held in a non-contact state; and an insulator 15 that extends from the mounting portion 11 while surrounding the first electrode 14;
4 and a second electrode 16 having a different polarity. The attachment part 11 is made of brass or galvanized iron, and has a head 21 with a hexagonal cross section and a threaded part 22 formed below the chain part 21.

The insulator 15 is made of PB'r (polybutylene terephthalate) resin that has extremely high insulation resistance.

The first electrode 14 and the second electrode 16 are made of aluminum, and the second electrode 16 has a plurality of holes 17 formed therein. Since the engine oil is heated to 100 to 150°C, the insulator 15 has high insulation properties in this temperature range, and the first electrode 14. The insulator 15 and the second electrode 16 have corrosion resistance against engine oil.

The first electrode 14 and the second electrode 1 that constitute the electrode section 20
6 are connected to conductive wires 18 and 19, respectively, and the current flowing between the first electrode 14 and the second electrode 16 is supplied to an amplifier (not shown). The conductive wire 19 is connected to an opening 23 formed in one head 21 . A conductive sleeve 25 is attached to the opening 23 if necessary.

The threaded portion 22 provided on the mounting portion 11 of the liquid level detection device is
It is screwed into a hole in a container 3 such as an oil pan in which oil is stored. The electrode part 20 protrudes into the oil 2 such as engine oil in the container 3, and the first electrode 14 and the second electrode 16 are connected to a positive electrode connected to a power source and the container 3, respectively.
form a negative electrode connected to. As shown in FIG. 6, when the oil 2 is present in an amount above a certain level, the electrode part 2
A current flows between the first electrode 14 and the second electrode 16 of No. 0 through the oil 2, and the presence of the oil 2 can be detected. When the oil 2 does not reach a certain level, the oil 2 and the electrode part 20 do not come into contact and no current flows, so the presence of the oil 2 is not detected.

By the way, when acceleration α is applied to container 3, oil 2
The liquid level of is inclined at an angle tanθ=α/g. In this case, if the acceleration α is large, the oil 2
Since the liquid level is separated from the liquid level sensor 4, an oil shortage state is erroneously detected even though there is sufficient engine oil. Further, as shown in FIG. 8, when acceleration is applied to the oil 2 in the direction opposite to 41g, the presence of oil is erroneously detected even though there is a lack of oil.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid level detection device that eliminates the above-mentioned drawbacks, does not cause malfunctions, and has a simple structure.

Means for Solving the Problems The liquid level detection device of the present invention includes a liquid level sensor that detects the presence of liquid, a trigger circuit that receives an electrical signal from the liquid level sensor, and a display device that is driven by the trigger circuit. A liquid level detection device having a configuration includes a state holding circuit that generates an output to maintain a display device in a state before the liquid is tilted when the liquid subjected to acceleration is tilted.

(2) When the state holding circuit detects the acceleration applied to the liquid, it provides an output to the display device to maintain the display device in the state before the liquid is tilted.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5. In these drawings, the same parts as those shown in FIGS. 6 to 9 are designated by the same reference numerals, and the explanation thereof will be omitted.

As shown in FIG. 1, the liquid level detection device of the present invention includes a liquid level sensor 4 that detects the presence of liquid, an amplifier 40 connected to the liquid level sensor 4, and a trigger that receives an electrical signal from the amplifier 40. It has a circuit 41, a display device 42 driven by the trigger circuit 41, and a state holding circuit 43 that generates an output to hold the display device 42 in the state before the liquid is tilted when the liquid subjected to acceleration is tilted. The state holding circuit 43 includes an acceleration sensor 44 (
211th! 1 and Fig. 3). Acceleration sensor 44
has, for example, a mercury switch 46.

FIG. 2 shows the state before being subjected to acceleration, and the mercury 46a is stationary. Therefore, the two contacts 46b and 46c are electrically connected by the mercury 46. However, when the acceleration sensor 44 receives acceleration, the mercury 46
Move d1 as shown in the figure.

Therefore, the two contacts 46b and 46c are electrically disconnected. In such a configuration, the state holding circuit 4
3, when detecting the acceleration applied to the liquid 2, provides an output to the display 'JNIi 142 to maintain the display device in the state before the liquid is tilted. A specific example of the circuit shown in FIG. 1 is shown in FIG.

A liquid level sensor 4 is fixed to the container 3, and the liquid level sensor 4 is connected between the resistor 50 and the container 3. The liquid level sensor 4 and the resistor 50 are connected to an inverting input terminal of a comparator 57. A non-inverting input terminal of the comparator 57 is connected between the resistors 51 and 52, and a constant divided voltage is applied thereto. The output of the comparator 57 is connected to a display device 42 such as an LED.

A transistor 53 is connected to the output line of the comparator 57. The base of the transistor 53 is connected to the acceleration sensor 44 via an amplifier 54, an inverter 55, and a retrigger timer 56. Acceleration sensor 44, transistor 53. The amplifier 54, the inverter 55, and the retrigger timer 56 constitute a state holding circuit 43.

When liquid is present in the container 3, a current flows through the liquid level sensor 4, and the inverting input terminal of the comparator 57 is given a signal at a level lower than the voltage applied to the non-inverting input terminal.

Therefore, comparator 57 produces an output. However, container 3
When no liquid is present in the liquid level sensor 4, no current flows through the liquid level sensor 4, so the voltage at the inverting input terminal of the comparator 57 is lower than the voltage at the non-inverting input terminal. Therefore, the comparator 57 does not generate an output, and therefore the display device 42 is driven by the inverter connected between the comparator 57 and the display device 42. Therefore, when acceleration is applied to the container 3, the liquid level sensor 4 is turned off, and the transistor 53 is turned on for a certain period of time through the inverter 55 and the retrigger timer 56. Therefore, since the output of the comparator 57 remains at a low level for a certain period of time, erroneous display on the display device 42 is prevented when there is a sufficient amount of liquid 2 as shown in FIG.

FIG. 5 shows another embodiment of the invention. The base of the transistor 60 constituting the trigger circuit is connected to the amplifier 40. The collector of transistor 60 is connected to a power supply via resistors 61 and 62, and the emitter is grounded. The base of transistor 60 is connected to the collector of transistor 63. The emitter of the transistor 63 is grounded, and the base is connected to a power supply via a resistor 64 and grounded via an acceleration sensor 44 . Furthermore, the base of transistor 60 is also connected to the base of transistor 65, the collector of transistor 65 is connected to the power supply via resistor 66, and the emitter is grounded. In parallel with the collector-emitter connection of the transistor 60, a series circuit including a PUT 67 constituting a state holding circuit, a light emitting diode 68 serving as a display device, and a resistor 69 is connected between the power supply and ground. The gate of PUT 67 is connected between resistors 61 and 62. Further, a series circuit of a capacitor 7o and a resistor 71 is connected in parallel with one light emitting diode 68 and a resistor 69. The base of transistor 72 is connected to the collector of transistor 65, and the collector is connected to resistor 73.
is connected to the base of transistor 74 via
The emitter is grounded. The emitter of the transistor 74 is connected to the power supply, and the collector is connected to the resistor 75 and the capacitor 7.
6 to ground. The anode of PUT77 is resistor 7
5 and a capacitor 76.

The cathode is connected between capacitor 7o and resistor 71. A series circuit of resistors 78 and 79 is connected in parallel to the series circuit of resistor 75 and capacitor 76. The gate of PUT 77 is connected between resistors 78 and 79. The collector of transistor 80 is connected to the base of transistor 72, the base is connected between resistor 64 and acceleration sensor 44, and the emitter is grounded.

In the above configuration, when liquid is present in the container 3,
The output of amplifier 40 is at a low level. Therefore, transistor 60 does not turn on. However, when the liquid in the container 3 decreases, the output of the amplifier 40 becomes high level,
Transistor 60 is turned on. For this reason, PUT67
The gate voltage of PUT67 becomes lower than the anode voltage.
is turned on. Therefore, current flows from the power supply through the PUT 67, the light emitting diode 68, and the resistor 69.

The lighting state of the one light emitting diode 68 in which the decrease in liquid is indicated by the lighting of the light emitting diode 68 continues as long as the PUT 67 remains on.

In this state, the acceleration sensor 44 normally maintains the on state shown in FIG. 2. However, when acceleration is applied to the container 3, the acceleration sensor 44 is turned off. Therefore, transistor 63 is turned on, and transistor 60
is off. At the same time, transistor 80 is turned on, so that transistors 72 and 74 are not switched on. Thus, transistors 63 and 80, which constitute PUT 67 and the switching element, can be used both in the presence and absence of liquid. The light emitting diode 68, which is a display device, maintains the display state before the acceleration is applied.

Therefore, when the liquid 2 is replenished into the container 3, the output of the amplifier 40 becomes high level. Here, if no acceleration is applied to the container 3, the acceleration sensor 44 is turned on. Therefore, transistors 72 and 74 are turned on, and PUT 77
, the oscillation circuit consisting of resistors 75, 78 and 79 and capacitor 76 starts oscillating 6. Therefore, PUT 77 generates a large output and a high voltage is applied to the cathode of PUT 67, so PUT 67 is turned off and 1 light emitting diode 68 goes out.

The above embodiments can be modified. For example, it is possible to use a piezoelectric element as an acceleration sensor, which produces a fluctuating output when acceleration occurs. Further, PUT can be changed to an equivalent circuit of a transistor or a thyristor.

As mentioned above, in this invention, when acceleration is applied to a container containing liquid and the liquid is tilted, the display device is maintained in the state before the liquid is tilted by the state holding circuit. does not result in mislabeling. Therefore, one worker can always obtain correct liquid level information.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the concept of the electric circuit of the liquid level detection device according to the present invention, Fig. 2 is a sectional view of the acceleration sensor before acceleration is applied, and Fig. 3 is a cross-sectional view of the acceleration sensor after acceleration is applied. 4 is a circuit diagram showing one embodiment of the electric circuit of the liquid level detection device according to the present invention, FIG. 5 is a circuit diagram showing another embodiment, and 6th wU is a state before acceleration is applied. Fig. 7 is a sectional view showing the state in which the liquid level sensor is attached to the container, Fig. 7 is a sectional view showing the state in which acceleration is applied to the container shown in Fig. 6, and Fig. 8 is a sectional view showing the state where the oil level sensor is attached to the container shown in Fig. 7. FIG. 9 is a cross-sectional view of the liquid level sensor when it is tilted. 20. liquid, 40. Liquid level sensor, 41. . trigger circuit, 4206 display device, 436. State holding circuit, Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Cause Fig. 7 Fig. 8 Fig. 9

Claims (5)

[Claims] (1) A liquid level detection device that has a liquid level sensor that detects the presence of liquid, a trigger circuit that receives an electrical signal from the liquid level sensor, and a display device that is driven by the trigger circuit that receives acceleration. A liquid level detection device comprising a state holding circuit that generates an output to maintain a display device in a state before the liquid is tilted when the liquid is tilted. (2) The state holding circuit includes an acceleration sensor that detects acceleration applied to the liquid, and a switching element that is connected to the acceleration sensor and blocks the operation of the trigger circuit. Liquid level detection device. (3) The liquid level detection device according to claim (1), wherein the acceleration sensor includes a mercury switch. (4) The liquid level detection device according to claim (1), wherein the trigger circuit is a transistor having a base connected to the liquid level sensor via an amplifier. (5) The liquid level detection device according to claim (1), wherein the state holding circuit includes a PUT.