JPS60158322A - Sound sensor - Google Patents

Abstract

PURPOSE:To attach a sensor to a material to be detected simply and to make the sensor operate sensitively, by a special constitution, wherein the compression of a piezoelectric element is loosened in proportion to the magnitude of vibration, and an electric signal, which is generated in proportion to the magnitude of the loosening of the compression, can be readily extracted. CONSTITUTION:In the compression stroke of a piston 24, mixed gas in a space 23 of a tube part of a cylinder 21 is compressed and ignited. When the mixed gas at the end part of the cylinder is spontaneously ignited, the abnormal local increase in pressure occurs, pressure vibration is generated and a knocking sound is generated. The abnormal pressure acts on a cylinder head 22. A rod shaped case 1, which is tightened to the head 22 is finely elongated together with the head 22. The cylinder 21 is finely moved. Compression on a piezoelectric element 11 caused by the compressing force of a push rod 7 is loosened. A voltage proportional to the loosening is generated in the piezoelectric element 11. The voltage is extracted out of the rod shaped case 1 and the push rod 7, which are contacted with the upper and lower electrode surfaces of the piezoelectric element 11. Thus the detected signal of the abnormal pressure is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides vibration generating members such as internal combustion engine cylinders having a cylinder head as a cover member, for example.
Relating to an acoustic sensor that extracts vibration (sound) generated between a vibration generating member and a cover member using an electrical signal converted into a voltage proportional to the magnitude of the vibration (sound),
The main body is a rod-shaped case whose tip is fixed to a vibration generating member and the insertion part of the cover member is fixed with a screw or the like, and an insertion hole with a bottom is formed from one end surface of the case, and the insertion hole has a bottom. A bushing rod is inserted and the rod is attached to the case, and a piezoelectric element is placed between the bottom of the insertion hole and the front end surface of the bushing rod, and vibration is generated between the vibration generating member and the cover member. Vibration (sound) is converted into slight expansion and contraction of a rod-like case through a cover member, and the expansion activates a piezoelectric element,
The object of the present invention is to provide an acoustic sensor having a special configuration suitable for relaxing the compression of a piezoelectric element by a bushing rod in proportion to the vibration (acoustic) magnitude.

A piezoelectric element is used as a sensor component in a sensor that detects knocking that occurs in a gasoline engine or measures other abnormal vibrations (abnormal noise W).
Acoustic sensors are known which extract an electrical signal generated by compression which is proportional to the magnitude of the sound. Unlike such known configurations, the present invention is suitable for loosening the compression of a piezoelectric element in proportion to the magnitude of vibration (sound) and extracting an electric signal generated in proportion to the magnitude of the loosening of the compression. The feature is that it has a special configuration.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described with reference to the accompanying drawings.

In the figure, 21 is an internal combustion engine cylinder which is a vibrating member;
2 is a cylinder head attached to the cylinder 21 with screws or the like, and constitutes a cover member of the present invention. cylinder 21
A piston 24 is fitted into the inner space 23 of the cylindrical part, and the piston 2
4, the mixed fuel gas and the like are compressed, and the compressed pressure is applied to the cylinder head 22 to cause slight vibration movement in the direction of the arrow a.

Reference numeral 1 denotes a rod-shaped case, and a screw 2 is provided on the outer periphery of the tip of the case to be screwed into the cylinder 21 and fixed in an upright position. Rod case 1
also passes through the cylinder head 22, and tightens the external thread 3 (16) on the outer periphery of this part. That is, the rod-shaped case 1 serves as a mounting screw for the cylinder 21 and the cylinder head 22.

An insertion hole 4 having a bottom portion 5 is formed at one end surface protruding from the tightening nut 16 of the rod-shaped case 1, and an elastic insulating ring 6 is provided between the insertion hole 4 and the inner surface of the insertion hole 4 to maintain a circumferential gap for electrical insulation. A retaining screw 8 is inserted into which the bushing rod 7 fitted in the upper part is inserted, and the rod 7 is screwed at the entrance of the insertion hole 40 to maintain an insulating gap 6a between the bushing rod 7 and the bushing rod 7 (see Fig. 2).
are screwed together and fixed to the rod-shaped case 1 in an electrically insulating manner.

A receiver 9 with a convex cross section is fitted into the bottom 5 of the insertion hole 4 as shown in FIG. A piezoelectric element 11 is interposed between the two. No. 12; is surrounded by the piezoelectric element II, a portion of the receiving metal 9, and a portion of the pressing metal 10. It's a rim bush. (In FIGS. 2 to 4, the number 1 receiver 9, the suppressor 10, and the insulating bushing 12 are omitted.) Compressive pressure is applied to the piezoelectric element 11 by the bushing rod 7. The pressure is adjusted by tightening the cap screw 8.

Real h1! ! For example, in the compression stroke of the piston 24,
The mixed gas in the inner space 23 of the cylinder 21 is compressed and ignited, but when the mixed gas (end gas) at the end of the cylinder spontaneously ignites, a local abnormal pressure occurs, causing pressure vibrations and knocking noise. occurs. Therefore, the abnormal pressure is applied to the cylinder head 22, and the rod-shaped case 1, whose tip end is fixed to the cylinder 21 and is tightened to the head 22 at the part passing through the cylinder head 22, is moved along the arrow line in FIG. 3 with the head 22. The cylinder 21 is slightly expanded in the direction a, and the cylinder 21 moves slightly as indicated by the arrow in the same figure, thereby loosening the pressure on the piezoelectric element 11 to which the bushing rod 7 is applying the compressive force. The loosening of the pressure occurs during each JEI stroke of the piston 24, but when knocking occurs as described above, the amount of expansion is large, +△λ, as shown in an exaggerated manner in FIG. Since a voltage is generated in the piezoelectric element 11 that is proportional to the magnitude of the pressure slack, this voltage is extracted to the outside through the rod-shaped case 1 and the bush rod 7 that are in contact with the upper and lower electrode surfaces of the piezoelectric element 11, and the actual pressure (abnormal sound) is detected. Signal. When the piston 24 moves to the ejection stroke, the piezoelectric element 11 is again compressed by 1 Δλ as shown in FIG.

In the above embodiment, if metals having the same linear expansion coefficient are used for the rod-shaped case l and the bushing rod 7, the cylinder 21
Even if there is a change in PA, etc., the compression pressure applied to the piezoelectric element 11 does not change, so the detection level of abnormal vibration (abnormal sound) does not change.

The sensor of the present invention can be used not only to detect knocks between internal combustion engines as described above, but also to measure changes in pressure inside a cylinder.

The present invention has the structure and operation clarified by the explanation in 1γ1, is suitable for relaxing the compression pressure of the piezoelectric element 11 and extracting a voltage proportional to the relaxation, and is composed of a vibration generating member and a cover member. The structure is such that a window is opened for attachment to the detection target mechanism, and the specially configured acoustic sensor can be easily attached to the detection target mechanism and can be operated sensitively.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention, and FIG. 1 is a partially cutaway side view, FIGS. 2 to 4 are explanatory views of the present invention, FIG. 4 is a vertical side view showing expansion of the piezoelectric element, and FIG. 4 is a vertical side view showing compression of the piezoelectric element.

Claims (1)

[Claims] An insertion hole with a bottom is formed from one end surface of a rod-shaped case whose tip is fixed to a vibration-generating member and the insertion portion of the cover member attached to the vibration-generating member is fixed with a screw or the like, and a bushing rod is inserted into the insertion hole. The rod is inserted into the case, and a piezoelectric element is placed between the bottom of the insertion hole and the front end of the bushing rod to reduce the vibration (acoustic) generated between the vibration generating member and the cover member. ) is converted into a slight extension of a rod-shaped case via a cover member, and the extension activates a piezoelectric element to extract an electrical signal.