JPH04113231A - Level sensor - Google Patents

Abstract

PURPOSE:To obtain a simple-structured and compact switch by detecting conduction and non-conduction of a pair of electrodes which are placed through a discharge gap and detecting whether height level of a flow behavior substance is at a required position or not. CONSTITUTION:Conductive thick films 2a and 2b are coated on a rectangular ceramic substrate 1 in parallel by screen printing, etc., the edge parts are bent inward and are opposed with a specified gap, and then the other edge parts of the conductive thick films 2a and 2b become connection edges 3a and 3b of lead wires 5, 5 with these as electrodes e, e. Then, the ceramic substrate 1 between the above electrodes 3, 3 is partially eliminated and a discharge gap g is formed between the electrodes e, e. A distance d of this discharge gap g is determined according to the applied voltage V and magnitude of electrical insulation property of a flow behavior substance to be detected, no discharge is made when covered with the flow behavior substance, and discharge is made when exposed to air.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a powder of electrically insulating fluid material, such as engine oil of an internal combustion engine, ceramic, glass, etc., as the substance to be detected, and detects its height. This invention relates to a level sensor that detects levels.

[Prior art] For example, level sensors for detecting the level of engine oil in internal combustion engines mainly include those with a built-in float switch, as well as those that use ultrasonic waves or thermal changes. etc. have also been proposed.

[Problems to be Solved by the Invention] By the way, the float type is inexpensive and highly reliable, but it has the drawback of being large.

On the other hand, ultrasonic and thermal level sensors can be made smaller, but there is a problem in that the circuitry provided in the sensor itself becomes complicated and expensive.

An object of the present invention is to provide a level sensor that is small in size, has a simple circuit, and is inexpensive.

[Means for Solving the Problems] The present invention provides a method in which a pair of electrodes are placed opposite each other with a discharge gap interposed therebetween,
The height position of the electrode pair is determined by immersing the electrode pair in an electrically insulating fluid substance, making the electrodes non-conductive with the fluid substance, and making conduction between the electrodes in air by discharging. The height level of the fluid substance is detected based on the height of the fluid substance.

[Function] In air, the electrodes are electrically connected due to discharge, but in an electrically insulating fluid substance, there is no electrical continuity between the electrodes. Therefore, it is possible to detect whether the height level of the fluid material is at the desired position by arranging the electrode pair at a required level position of the fluid material and checking the conduction state between the electrodes. Become.

[Example] An embodiment of the invention will be described with reference to FIG.

A thick conductor film 2a is formed on a rectangular ceramic substrate 1.

2b are coated and formed in parallel by screen printing or the like, and the ends thereof are bent inward to face each other at a predetermined interval, and these are used as electrodes e, e, and the other ends of the thick conductor films 2a and 2b are The connection ends 3a and 3b of the lead wires 5 and 5 are assumed to be connection ends 3a and 3b. Then, the ceramic substrate l between the pair of electrodes e and e is partially removed to form a discharge gap g between the electrodes e and e. The distance d of this discharge gap g is determined depending on the applied voltage V and the electrical insulation of the fluid substance to be detected. When covered with a fluid substance, no discharge occurs and the discharge gap is exposed to air. It is designed to discharge when the V/d23000J when used to detect engine oil for internal combustion engines
It is desirable to set it to rt/mrn. Furthermore, the surface of the ceramic substrate 1 is covered with a glass layer 4 to expose only the electrodes e, e and the connecting ends 3a, 3b, and shield the thick conductor films 2a, 2b on the other surfaces of the ceramic substrate 1. At this time, the connection end 3a.

The distance between the electrodes 3b is set to such an extent that no discharge occurs. Lead wires 5, 5 are soldered to the connecting ends 3a, 3b of this ceramic substrate 1, and after this is inserted into a cylindrical housing 10 equipped with a screw portion 11 as shown in FIG. The cylindrical housing 10
At the bottom of the cylindrical body, the electrodes e and e holes are exposed. Thus, a level sensor S is constructed. Then, this level sensor S is attached to the oil tank 12 using the screw portion 11.
etc.

FIG. 3 shows a detection circuit that is connected to the level sensor S and performs the required liquid level detection operation.

Here, the step-up transformer 20 has its primary side connected to a primary power source V that generates a pulse voltage, and its secondary side includes a level sensor S having electrodes e, e facing each other via a discharge gap d.
is connected to the connection ends 3a and 3b of
, e.

On the secondary side of the step-up transformer 20, a level sensor S and a capacitor C are connected in series via a diode D1 and a resistor R. Furthermore, the capacitor C is connected in parallel between the base terminal and the emitter terminal of the transistor T. This transistor T is a step-up transformer 2
The collector terminal is connected to the negative line on the primary side of the step-up transformer 20 via the diode D2, and the emitter terminal thereof is connected to the positive line on the primary side of the step-up transformer 20. That is, the short circuit 21 is connected to the positive and negative primary sides of the step-up transformer 20 via the transistor T.

With this configuration, when the sensor S is in oil, the gap between the pair of electrodes e and e is filled with highly electrically insulating oil, so no discharge occurs between the pair of electrodes e and e. , since no current flows, no charge accumulates in capacitor C. On the other hand, when the liquid level falls and the electrodes e and e are exposed to the air, the insulation between the electrodes e and e is broken and a current flows, which accumulates in the capacitor C, drives the shorting transistor T, and causes the shorting. The secondary circuit 21 is closed and the primary power supply V is short-circuited.

In such a configuration, for example, the level sensor S is disposed in the oil tank so that its electrodes e, e are at the lower limit liquid level position of the engine oil, and the level sensor S is placed on the primary side of the step-up transformer 20. By connecting the igniter,
As the oil decreases below the lower limit position, the igniter is short-circuited and the engine is stopped, thereby making it possible to prevent vehicle breakdowns or accidents.

Although the above embodiments used printed electrodes on a ceramic substrate as the electrode material, electrodes made of various materials or shapes can be used. In addition to short-circuiting the primary voltage of the igniter based on the detection result, various notification means may be proposed, such as causing the lamp to fall over. For example, by interposing various alarm devices at the position of the circuit 2, it becomes possible to warn of a decrease in oil.

[Effects of the Invention] As described above, the present invention allows a pair of electrodes placed opposite to each other with a discharge gap to be electrically discharged in the air to be electrically conductive, and to be electrically insulated in a fluid material having electrically insulating properties to be electrically non-conductive. , this conduction and non-conduction is detected to detect whether the height level of the fluid substance is at the required position.For this purpose, if only the electrode and its connecting end are provided, It has a simple structure, can be made smaller than a structure using a float switch, and is inexpensive because it does not require a complicated circuit.

[Brief explanation of drawings]

The accompanying drawings show embodiments of the present invention: - Fig. 1 is a perspective view of a ceramic substrate 1, Fig. 2 is a vertical sectional side view of a level sensor S, and Fig. 3 is a detection circuit diagram. S-...Level sensor e, e...Electrode l...Ceramic substrate 2a, 2b...Conductor thick film 3a, 3b-...Connection end 20...Step-up transformer 21...Short circuit

Claims (1)

[Claims] A pair of electrodes are placed opposite each other with a discharge gap in between, the electrode pair is immersed in an electrically insulating fluid substance, the fluid substance makes the electrodes non-conductive, and a discharge is caused between the electrodes in the air. A level sensor characterized in that the height level of the fluid substance is detected based on the height position of the electrode pair by making the electrode pair conductive.