JPH0525325U - Piezoelectric liquid level sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] In a piezoelectric liquid level sensor, which has a liquid sensing part formed by sticking a piezoelectric element to the inner surface of a vibrating plate on the opening side of the lower end of a protective tube, the liquid sensing part is arranged. Be able to set it in the required place. [Structure] The protection tube 1 is bent so that the liquid sensing portion can be positioned at a place where there is no liquid standing or an appropriate place where it does not interfere with various members.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a piezoelectric liquid level sensor for detecting whether or not the liquid level of various liquids such as oil of an internal combustion engine or a generator is above a predetermined level.

[0002]

[Prior Art]

 As a piezoelectric liquid level sensor, a diaphragm is placed in a liquid-tight manner with one surface exposed to the outside at the bottom opening of the protective tube, and a piezoelectric element is attached to the inner surface of the diaphragm to create a bimorph type. There has been proposed a liquid sensing unit. Such a level sensor is arranged so that the vibration plate has a height corresponding to a predetermined liquid level, and when the liquid is above a predetermined level in the container, the outer surface of the vibration plate is immersed in the liquid, The liquid pressure makes it impossible to vibrate even when an alternating voltage is applied to the upper and lower electrodes of the piezoelectric element. Further, when the liquid surface is below a predetermined level, the outer surface of the vibration plate is exposed to the air, and the application of the liquid pressure is released to enable vibration. Therefore, by detecting this vibration, it is possible to detect whether or not the liquid level of the liquid is below a predetermined level.

[0003]

[Problems to be solved by the device]

 By the way, when the piezoelectric liquid level sensor is mounted on an oil tank or the like of an automobile as described above, in order to accurately detect the level, the liquid sensing section is arranged at a stable place without liquid standing. There is a need. In addition, there are cases where various members are located below the oil injection port that is the mounting site in the tank, and the piezoelectric liquid level sensor cannot be inserted straight. Depending on the configuration, it cannot be installed. It is an object of the present invention to provide a piezoelectric liquid level sensor having the above-mentioned configuration, which is capable of easily setting a liquid sensing portion at a required location.

[0004]

In the piezoelectric liquid level sensor of the first means of the present invention, a vibration plate is liquid-tightly arranged on the lower end opening side of the protection tube with one surface exposed to the outside. A piezoelectric element is attached to the inner surface of the vibrating plate to form a bimorph type liquid sensing section, and when the exposed outer surface of the vibrating plate is not in contact with the liquid, the piezoelectric element is vibrated to detect the presence or absence of the liquid. In the piezoelectric type liquid level sensor, a protective tube is bent so that the liquid sensing portion is located at an arbitrary position. The first means is also one in which the protection tube is formed by a bendable flexible protection tube.

[0005]

[Action]

 In the first means, since the protection tube is bent at an arbitrary angle, the liquid sensing section can be appropriately arranged at a necessary place. Further, in the second means, by applying a flexible protective tube, the protective tube can be bent appropriately. Therefore, by appropriately bending the mounting portion provided at the upper end, the position of the liquid sensing portion can be arbitrarily adjusted, and optimal positioning can be performed.

[0006]

【Example】

 FIG. 1 shows an example of the piezoelectric type liquid level sensor S of the first means of the present invention, wherein 1a is an elongated protective tube made of a corrosion-resistant metal material, the main part of which is "" It is bent in a letter shape.

2 and 3 show an example of the piezoelectric liquid level sensor S'of the second means of the present invention, which is equipped with a protective tube 1b made of a flexible material.

The piezoelectric liquid level sensors S and S'have the same configuration except for the protective tubes 1a and 1b, and the structure will be described with reference to FIG. The sensor case 2 is externally fitted on the upper portions of the protection tubes 1a and 1b. The sensor case 2 is provided with a flat housing cylinder 3 on its upper part, and a printed circuit board 7 is fitted in the flat housing cylinder 3 in the longitudinal direction along the major axis. Further, as shown in FIG. 1, a circular fixed flange 4 having mounting holes 5 and 5 is formed continuously on the lower part of the flat storage cylinder 3, and a fitting cylinder 6 is formed on the lower part thereof. By fitting the upper ends of the protection tubes 1a and 1b into the inside of 6, it is possible to connect the protection tubes 1a and 1b to the sensor case 2. Then, the fixing flange 4 can be attached to an oil tank or the like by screw-fixing the mounting holes 5 and 5. Various circuit parts are mounted on the printed circuit board 7 and are connected to external devices by lead wires 8. Then, the lead wires 9a and 9b electrically connected to the electrodes of the piezoelectric element 31 which will be described later are inserted into the protective tubes 1a and 1b and are connected to the required conductive paths of the printed circuit board 7.

A rubber damper 10 made of a material such as silicone rubber, fluorosilicone rubber, fluororubber, or NBR, which opens downward, is fitted into the lower end opening 12 of each of the protection tubes 1a and 1b. The rubber damper 10 has a short cylindrical shape, and has a locking brim portion around it as a cushioning portion, and a circular pipe groove 11 that opens downward from the lower surface to the inner depth is formed. A through hole 13 is formed in the center, and a conductive tube 17 connected to the lead wire 9a is fitted into the through hole 13. A metallic cylindrical base lid 20 is fitted in the circular tube groove 11. This cylindrical base lid 20 is provided with a cylindrical portion 21 that fits in the circular pipe groove 11, and a connecting flange portion 23 that vertically contacts the locking flange portion of the rubber damper 10 is formed on the outer periphery of the lower end thereof. There is.

A vibrating plate 30 made of a thin metal plate is arranged at the lower end of the cylindrical base cover 20 so as to shield the cylindrical hole from below, with its peripheral edge joined. At the center of the inner surface of the vibrating plate 30, a piezoelectric element 31 forming a liquid sensing section together with the vibrating plate 30 is fixed. The piezoelectric element 31 comprises electrodes arranged on the front and back surfaces of a piezoelectric ceramic disk of lead zirconate titanate or the like. The piezoelectric element 31 is arranged so as to face the cylindrical hole of the base lid 20. The piezoelectric element 31 having such a structure has a two-terminal structure, but may have a three-terminal structure in which a large-area excitation electrode and a small-area feedback electrode are provided on the surface side. ..

The surface electrode of the piezoelectric element 31 is connected to the conductive tube 17 by the lead wire 33. Further, a connecting pin 25 that electrically connects to the lead wire 9b is provided on the upper end of the cylindrical base cover 20, and the back electrode of the piezoelectric element 31, the diaphragm 30, and the metal cylindrical base cover 20 are interposed therebetween. Are electrically connected. Thus, the front surface electrode of the piezoelectric element 31 is electrically connected to the lead wire 9a, and the back surface electrode thereof is electrically connected to the lead wire 9b to be connected to a required conductive path of the print substrate 7, and the lead wire 8 is used. It will be connected to an external device. The connection with the printed circuit board 7 may be performed by fitting the connector to the mouth end of the flat storage tube 3 without using the lead wire 8.

In mounting the piezoelectric type liquid level sensor S of the first means having the above-mentioned structure, by bending the protection tube 1a, the vibration plate 30 can be placed at an optimum place such as a place where liquid does not stand. It is possible to easily dispose the liquid sensing portion constituted by the piezoelectric element 31 and the piezoelectric element 31. At this time, as described above, by screw-fixing from the mounting holes 5 and 5 of the fixing flange 4, mounting on an oil tank or the like is possible without requiring a rotating operation. Therefore, the position of the liquid sensing portion is not displaced by its attachment. That is, in the conventional mounting means for screwing the liquid level sensor S into the oil inlet by rotational operation, the liquid sensing part is mounted at an appropriate position by bending the flexible protective tube 1a. Even if the is installed, its position will change due to its rotation operation. However, in the above-described embodiment, since the fixing flange 4 is attached, the rotating operation is not necessary, and such a problem does not occur.

In the piezoelectric type liquid level sensor S'of the second means shown in FIGS. 2 and 3, the protective tube 1b has a bellows structure or is made of a flexible metal material so that it can be bent. With such a configuration, the liquid sensing portion can be flexibly arranged at a required position and the surface of the diaphragm 30 can be easily inclined.

As described above, in the piezoelectric liquid level sensor S, the vibration plate 30 is tilted with respect to the liquid surface in the mounted state. Further, in the piezoelectric type liquid level sensor S ', it becomes possible to incline the diaphragm 30 at will. Therefore, the following advantages occur.

As shown in FIG. 4A, in the case of the conventional piezoelectric liquid level sensor s having the vertical protection tube 1c, when the piezoelectric liquid level sensor s is mounted in a uniform manner, the diaphragm 30 becomes horizontal. In such a state, even if the liquid surface is lower than the position of the vibration plate 30, the liquid surface may adhere to the vibration plate 30 due to the surface tension, which hinders the vibration of the vibration plate. However, it is determined that the diaphragm 30 is immersed in the liquid, which is likely to cause false detection. However, as shown in FIG. 4b, when the surface of the diaphragm 30 is inclined with respect to the liquid surface, the liquid adhering to the outer surface of the diaphragm 30 descends along the inclination, which hinders the vibration of the diaphragm 30. It will be in a state without a thing. By inclining the vibrating plate 30 in this manner, the influence of the surface tension of the liquid can be prevented.

[0016]

[Effect of the device]

 In the piezoelectric liquid level sensor S, S'of the present invention, since the protective tubes 1a, 1b are appropriately bent as described above, the liquid sensing portion arranged at the lower end of the piezoelectric liquid level sensor S, S'is It is possible to make it a proper place where various members are not disturbed, and it is possible to eliminate the adverse effect of the surface tension of the liquid due to the inclination of the liquid sensing portion. Further, in the case of using the flexible protection tube 1b, there is an excellent effect that the bending can be easily adjusted and the attachment location can be favorably dealt with.

[Brief description of drawings]

FIG. 1 is a perspective view of a piezoelectric type liquid level sensor S of a first means.

FIG. 2 is a perspective view of a piezoelectric type liquid level sensor S ′ of a second means.

FIG. 3 is a vertical sectional side view of a piezoelectric type liquid level sensor S ′ of a second means.

FIG. 4a is a schematic side view showing an influence of surface tension on a liquid sensing unit in a horizontal state.

FIG. 4b is a schematic side view showing the influence of surface tension on the liquid sensing part in the inclined state.

[Explanation of symbols]

 S, S'Piezoelectric liquid level sensor 1a, 1b Protective tube 2 Sensor case 10 Rubber damper 11 Circular tube groove 30 Vibration plate 31 Piezoelectric element

Claims (2)

[Scope of utility model registration request] 1. A liquid sensing part is constructed by arranging a vibration plate in a liquid-tight manner with one surface exposed to the outside on the opening side of the lower end of a protection tube, and attaching a piezoelectric element to the inner surface of the vibration plate. In a piezoelectric liquid level sensor that detects the presence or absence of liquid by vibrating the piezoelectric element when the exposed outer surface of the vibration plate is not in contact with the liquid, a protective tube is provided so that the liquid sensing unit is at an arbitrary position. Piezoelectric liquid level sensor characterized by being bent. 2. A liquid sensing part is constructed by arranging a vibration plate in a liquid-tight manner with one surface exposed to the outside on the opening side of the lower end of the protection tube, and attaching a piezoelectric element to the inner surface of the vibration plate. In a piezoelectric liquid level sensor that detects the presence or absence of liquid by vibrating the piezoelectric element when the exposed outer surface of the vibration plate is not in contact with the liquid, the protection tube is formed of a flexible flexible protection tube. A piezoelectric liquid level sensor characterized in that