JPH02660Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piezoelectric sensor that is installed on the surface of a vibrating body such as an engine cylinder block that generates vibrations due to engine knocking or fuel injection to detect the vibrations.

Conventionally, this type of piezoelectric sensor, as shown in Fig. 1, has a screw rod b protruding from the surface of a vibrating body a such as a cylinder block, and an annular piezoelectric element c having electrodes d and d on the front and back sides. A tightening nut f (pinching part) which is fitted by applying clamping washers e and e to the upper and lower surfaces respectively, and which is further screwed onto the screw rod b from above to form a screw body with the screw rod b. is tightened, and the piezoelectric element c is held between the surface of the vibrating body a and the tightening nut f, and the vibrating body a
By causing compressive strain in the piezoelectric element c due to detected vibrations occurring with knocking, fuel injection, etc., an output signal synchronized with the vibrations is extracted from the piezoelectric element c.

By the way, in the conventional device having such a configuration,
Since the tightening by the tightening nut f (pinching part) is received only by the piezoelectric element c, the nut f at the time of installation is
Fatigue accumulates due to over-tightening or continuous squeezing pressure, which tends to cause cracks and breakage of the piezoelectric element c, and has disadvantages such as a short service life.

The present invention aims to eliminate the above-mentioned conventional drawbacks, and includes arranging a pressure-resistant pipe inside or outside a piezoelectric element, and providing a pressure-receiving body above the piezoelectric element so as to cover the pressure-resistant pipe. The piezoelectric sensor is configured such that the pressure receiving body is pinched by the pinching portion of the threaded body, and the pressure accompanying the tightening of the threaded body is received by the upper surface of the piezoelectric element and the upper surface of the pressure-resistant pipe, The pressure caused by the tightening of the screw body is released through a pressure-resistant pipe to relieve the pressure on the piezoelectric element, thereby preventing damage to the piezoelectric element due to the pinching pressure of the pressure receiving body.

An embodiment of the present invention will be described with reference to the accompanying drawings.

Reference numeral 1 is an annular treading body, the upper surface of which is widened to form a locking collar 2 and a wide riding surface on the inner and outer peripheries;
On the inside, a pressure-resistant pipe 3 made of a hard metal material having the same inner diameter as the treading body 1 is placed, and on the outside thereof, a laminate 4 having the same outer diameter as the treading body 1 is placed. The pressure-resistant pipe 3 and the laminate 4 are evenly placed on the mounting surface. The laminated body 4 has an outer diameter equal to that of the tread body 1.
The piezoelectric elements 6, 6 are mounted on a damper 5 made of a soft metal such as aluminum material, which is equal to Make it higher than pipe 3. Further, an annular insulating material 8 is inscribed on the inner surface of the piezoelectric elements 6, 6, and the terminal plate 7 and the pressure-resistant pipe 3 are inscribed.
Insulate.

A pressure receiving body 9, which is made of the same shape and material as the treading body 1 and has a locking collar 10 on the inner and outer peripheral surfaces of its lower part, is mounted on the pressure-resistant pipe 3 and the laminated body 4, and pressure is applied from above to The dampers 5, 5 are compressed to make the height of the stacked body 4 equal to that of the pressure-resistant pipe 3 as shown in FIG.
Then, the outer surfaces of each member are covered with a connecting pipe 12, the upper edge of each is hung on the locking collar 2 of the treading body 1, and the lower edge of each is hooked on the locking collar 10 of the pressure receiving body 9, thereby fixing each member. Unite. As mentioned above, the connecting pipe 11,
12, the dampers 5, 5 are maintained in a proper compressed state.

The terminal plate 7 is located in the middle of the connecting pipe 12.
A conductive pipe 14 is fitted into the circular hole 13, a conductive cord 15 is inserted through the pipe 14, and the conductive wire is connected to the terminal plate 7.
Connect to. Thus, an annular piezoelectric sensor A having an insertion hole 16 is constructed.

The installation of the piezoelectric sensor will be explained.

The insertion hole 16 of the piezoelectric sensor A is inserted into a threaded rod 21 installed on the surface of a cylinder block 20 of an engine that generates detected vibrations such as knocking vibrations or vibrations associated with fuel injection, which is an example of the vibrating body a. A tightening nut 22 (squeezing part) that is fitted into the piezoelectric sensor A so that the end of the screw rod 21 protrudes from the upper surface of the piezoelectric sensor A, and forms a screw body with the screw rod at the end.
and tighten it to the upper surface of the pressure receiving body 9 of the piezoelectric sensor A to attach the piezoelectric sensor A to the cylinder block 20.
is held between the surface of the screw and the tightening nut 22. This squeezing force is transmitted as a partial pressure to the pressure-resistant pipe 3 and the laminate 4, and the pressure applied to the laminate 4 acts on the piezoelectric element 6 via the damper 5. Moreover, the piezoelectric elements 6, 6
is held between the dampers 5, 5, and since the dampers 5, 5 are softer than the pressure-resistant pipe 3 even in a compressed state, the tightening pressure is easily applied to the pressure-resistant pipe 3 side. Therefore, the piezoelectric sensor A is fixed to the vibrating body a without loosening, and at the same time, the tightening pressure acts on the piezoelectric elements 6, 6 in a relaxed manner, thereby preventing their damage.

The operation of the piezoelectric sensor having the above configuration will be explained.

When detected vibrations such as knocking occur in the cylinder block 20, the screw rod 2
1, the tightening nut 22 vibrates in a direction perpendicular to the mounting surface of the cylinder block 20, causing compressive strain in the piezoelectric elements 6, 6 of the piezoelectric sensor A in the axial direction. Therefore, a potential difference is generated between the front and back electrodes (not shown) of the piezoelectric elements 6, 6. The upper surface electrode of this upper piezoelectric element 6 and the lower piezoelectric element 6
Since the lower surface electrode is grounded to the body via the damper 5 and the pressure-resistant pipe 3, an output signal is taken out from the terminal plate 7 by the conductive cord 15. Such a signal is subjected to processing such as amplification and wave rectification by an external device such as an amplifier, thereby making it possible to detect knocking, injection timing, etc.

Instead of the tightening nut 22, a bolt may be screwed into the cylinder block 20 from the insertion hole 16 of the piezoelectric sensor A, and the head (pinching part) of the bolt may be brought into contact with the upper surface of the piezoelectric sensor A. . In addition, a spark plug or the like can also be used as the threaded body.

In the embodiment described above, the pressure-resistant pipe 3 was arranged so as to be in contact with the inner surface of the laminate 4, but it may also be arranged on the outer surface of the laminate 4. In this case,
In order to enable connection between the conducting wire of the conductive cord 15 and the terminal plate 7, it is necessary to form a slit for connection at the relevant location. Further, dampers 5, 5 are arranged on the upper and lower surfaces of the piezoelectric element 6.
The dampers 5, 5 can also be omitted by making the thickness of the pressure-resistant pipe 3 equal to that of the pressure-resistant pipe 3.
In this case, the bias stress applied to the piezoelectric elements 6, 6 will be brought about by the tightening of the threaded body.

As clarified from the above description, the present invention is such that a pressure-resistant pipe 3 is arranged on the inner or outer surface of the piezoelectric element 6, and a pressure-receiving body is arranged above the pressure-resistant pipe 3 to cover the piezoelectric element 6 and the pressure-resistant pipe 3. 12, the pressure receiving body 12 is pinched by the pinching part of the threaded body, and the pressure accompanying the tightening of the threaded body is received by the piezoelectric element 6 and the pressure-resistant pipe 3, so that the pinching force is reduced. This is because the clamping pressure applied to the piezoelectric element 6 is dispersed and alleviated, and damage to the piezoelectric element 6 when tightening the screw body and aging fatigue of the piezoelectric element 6 due to continuous application of clamping force do not occur. This has excellent effects such as being able to extend the life of the piezoelectric element 6 as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a vertical side view showing a conventional piezoelectric sensor, and FIGS. 2 and 3 show an embodiment of the present invention.
The figure is a longitudinal side view, and FIG. 3 is a sectional view taken along the line A--A in FIG. 2. DESCRIPTION OF SYMBOLS 1...Treading body, 3...Pressure pipe, 4...Laminated body, 5...Damper, 6...Piezoelectric element, 9...Pressure receiving body, 16...Insertion hole, A...Piezoelectric sensor.

Claims (1)

[Scope of utility model registration request] A piezoelectric element which has an annular shape and is fitted onto the shaft of a threaded body such as a bolt or spark plug that is threaded onto the surface of a vibrating body such as a cylinder wall of an internal combustion engine, and which is crimped onto a clamping pressure portion of the threaded body. In the piezoelectric sensor, a pressure-resistant pipe is arranged inside or outside the piezoelectric element, a pressure-receiving body is provided above the piezoelectric element and the pressure-resistant pipe so as to cover the pressure-receiving body, and a pressure receiving part of the threaded body is The piezoelectric sensor is characterized in that the pressure-receiving body is compressed by the pressure-receiving body, and the pressure accompanying the tightening of the screw body is dispersed to the pressure-resistant pipe side.