JPS6035858Y2 - Vibration detector for internal combustion engine - Google Patents

Description

[Detailed description of the invention] This invention relates to a vibration detector for knocking, etc. in an internal combustion engine, and is immersed in a liquid such as engine cooling water or engine oil, or suspended on the liquid surface. It is an object of the present invention to provide a vibration detector equipped with a piezoelectric wave receiving element that can efficiently detect sound waves caused by engine vibration propagating on a surface and has excellent durability.

An embodiment of the present invention will be explained with reference to FIG.

1 indicates a piezoelectric receiving element, la and la are band-shaped composite piezoelectric materials made by uniformly blending ferromagnetic powder such as lead titanate or lead zirconate in synthetic rubber or synthetic resin. a pair of flexible piezoelectric sheets, 1b is the piezoelectric sheet;
1b is a flexible center electrode sheet made of conductive rubber or resin bonded between the piezoelectric sheets 1a; lc;
, lc are flexible outer electrode sheets made of conductive rubber or resin bonded to the outer surfaces of the piezoelectric sheets 1a, 1a,
These constitute a bimorph piezoelectric material.

The piezoelectric sheets 1a, 1a are polarized by applying a DC voltage between the center electrode sheet 1b and the outer electrode sheets 1c, lc.

Reference numeral 2 denotes a coated lead wire for signal conveyance connected to the center electrode sheet 1b and the outer electrode sheet IC at one end of the wave receiving element 1, and the outer end passes through a holder to be described later and connects to an external vibration detection circuit (not shown). It has been extended to (no).

Reference numeral 3 denotes a holder having a hexagonal head 3a for tightening on the upper outer periphery and a threaded part 3b for engine attachment on the lower outer periphery, and a main part of the covered lead wire 2 extending from one end of the wave receiving element 1. If necessary, the piezoelectric wave receiving element 1 is held in a suspended state by using the lead wire 2. Hold.

5 is a sponge attached to the end of the piezoelectric wave receiving element 1;
A buffer layer made of cork or the like prevents vibrations from being transmitted from the engine when it comes into contact with the engine wall, as shown in FIGS. 3 and 4, which will be described later.

In the above, in order to make the piezoelectric wave receiving element 1 a watertight structure,
A pair of electrode sheets (lc, lc) bonded to the outer surfaces of the piezoelectric sheets (la, la) are made wider than the piezoelectric sheets so that the entire surface of the piezoelectric sheets except one end is surrounded by a liquid surface, and each electrode sheet (1b, lc) is One end and the connecting part of the lead wire 2 are waterproofed with synthetic rubber or synthetic resin paint 6, and the entire circumference of the piezoelectric wave receiving element 1 and the connecting part of the lead wire 2 are integrally molded with the waterproof paint. You can also do that.

Next, Fig. 2 shows another example of the present invention, as a piezoelectric wave receiving element,
Twisted wire 1 to serve as the center electrode instead of the bimorph piezoelectric material in the previous example
On the outer periphery of b', there is a composite electrical layer la', a conductive layer lc' which becomes an outer electrode, and an insulating protective layer l made of synthetic rubber, synthetic resin, etc.
Using a cable-type piezoelectric body 1' in which d' is sequentially and coaxially coated, an insulating layer ld' coated on the outer periphery of the conductive layer lc', a connection portion between the covered lead wire 2', and an end portion of the piezoelectric body are It is the same as the embodiment shown in FIG. 1 above, except that it is surrounded by a waterproof paint 6 such as synthetic leather rubber to form a watertight structure.

Note that the external shape and structure of the piezoelectric wave receiving elements 1 and 1' are not limited to those of each of the above embodiments, but in short, a composite piezoelectric material with low acoustic impedance and excellent vibration resistance and shock resistance is used. Any structure may be used as long as it has a watertight structure.

Therefore, when using the above-mentioned vibration detector, the third
As shown in the figure, the piezoelectric wave receiving element 1.1' is inserted through the screw hole 7a provided at the key point of the water jacket 7 and immersed in the internal cooling water 8, and the holder 3 is inserted into the screw hole 7a.
The internal engine oil 10 can be installed by screwing together the threaded portions 3b of the oil pan 9, or by inserting the piezoelectric wave receiving elements 1, 1' through the screw holes 9a provided at key points in the oil pan 9, as shown in FIG. Then, holder 3 is screwed into screw hole 9a and attached.

Furthermore, when the piezoelectric wave receiving elements 1, 1' are floated on the surface of the cooling water 8 or oil 10, a float may be attached to the wave receiving element, or the buffer layer 5 itself may be used as a float.

In this way, a piezoelectric wave receiving element immersed in a liquid such as engine cooling water or oil or floating on the liquid surface receives the sound waves generated by engine vibration and propagates in the liquid or on the liquid surface, and generates electricity. This signal is sent to an external vibration detection circuit via a lead wire.

Conventionally, this type of vibration detector has a piezoelectric ceramic attached to a diaphragm,
The metal shell is peripherally supported on the inner surface of the cylinder block, and when used, the metal shell is screwed onto key points on the outer wall surface of the cylinder block, and the mechanical vibration transmitted through the outer wall surface of the block is absorbed by the diaphragm. The piezoelectric ceramic attached to the diaphragm converts the signal into an electrical signal, which is then extracted from the lead wire. However, when unexpected vibrations occur in the engine, the strong vibrations are applied to the diaphragm through the main metal, causing a relatively strong vibration. This had the disadvantage of damaging small piezoelectric ceramics and having extremely poor durability. However, as mentioned above, this proposal uses a piezoelectric wave receiving element that has a watertight structure than a composite piezoelectric material, and uses it to protect the engine from cooling water and the engine. It is immersed in a liquid such as oil or suspended on the liquid surface, and detects sound waves caused by engine vibrations that propagate in the liquid or on the liquid surface, so unlike conventional methods, strong engine vibrations are not detected. Not only will it not be easily damaged by damage, but combined with the high strength of the receiving element itself, the durability can be significantly improved.Furthermore, the piezoelectric receiving element of the present invention is made of a material with low acoustic impedance. Because it matches well with liquids such as cooling water and oil, it efficiently receives sound waves and increases sensitivity.In addition, by adding a buffer layer to the end of the piezoelectric wave receiving element, it can be used in the engine where cooling water and oil are stored. Another advantage is that by contacting the wall surface, transmission of engine vibrations to the wave receiver can be completely blocked, further increasing sensitivity.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the present invention, A is a longitudinal side view, B is an enlarged sectional view along the line E in Fig. A, and Fig. 2 is another example of the invention, A is a longitudinal side view, B is A FIG. FIG. 3 shows an embodiment in which the proposed vibration detector is attached to the water jacket of an engine, and FIG. 4 shows an embodiment in which it is attached to an oil pan. 1.1'...Piezoelectric wave receiving element, 2...Coated lead wire for signal transmission, 3...Holder for engine mounting 5...Buffer layer.

Claims (1)

[Scope of utility model registration request] A piezoelectric wave receiving element is immersed in a liquid such as engine cooling water or engine oil to detect sound waves caused by engine vibration propagating in the liquid, and the piezoelectric wave receiving element is made of a composite piezoelectric material to have a watertight structure. A coated signal carrying lead wire connected to one end of the wave receiving element is led out to the engine mounting holder, and the lead wire is suspended, and the end of the piezoelectric wave receiving element is connected to the engine wall surface. A vibration detector for an internal combustion engine, characterized in that it is equipped with a buffer material that prevents vibration transmission due to contact with the vibration detector.