JPS58202853A - Pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a stable output with the generation of even charge on the surface of a piezo-electric body while preventing damage thereto by uniformizing pressure with a hard metal protective plate interposed between a metal pressure receiving plate and the piezo-electric body. CONSTITUTION:A pressure sensor 10 is composed of a ring-shaped buffer plate 13 made of a soft flexible metal such as copper for transmitting even pressure to a piezo-electric body 12, a ring-shaped protective plate 14 made of hard metal such as stainless steel laminated on the top thereof 13 to protect the piezo-electric body 12 from abnormal pressure and a pressure receiving plate 15 made of soft flexible metal such as copper laminated on the top of the protective plate 14 to serve as ring-shaped surface electrode. This can produce a stable output with the generation of even charge on the surface of the piezo-electric body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure sensor that has been improved to improve pressure resistance.

Pressure sensors that receive mechanical pressure and output the received pressure as electrical signals include those that are simply formed in a flat plate shape, as well as those that are formed in the cylinder part 1 of an automobile engine, for example, as shown in FIG. There are pressure sensors 4 of various shapes, such as a washer type pressure sensor 4 which is interposed in the tightening portion of the spark plug 2 or the tightening portion of the head bolt 3 and is used to detect the cylinder pressure. .

The washer type pressure sensor 4 is inserted into the threaded portion of the spark plug 2 or the head bolt 3, and is tightened and fixed onto the cylinder s11 together with the spark plug 2 or the head bolt 3. The tightening of the threaded portion of the head bolt 3 or the spring system of the bolt body that occurs as the engine burns is used to measure the cylinder pressure by detecting changes in pressure.

The pressure sensor 4 has a ring-shaped overall shape, and its structure is as shown in FIG. an electrode plate 5; a ring-shaped piezoelectric body 6 closely laminated on both sides of the internal electrode plate 5; and a ring-shaped surface laminated on the top surface of the piezoelectric body 6 so as to face the internal electrode plate 5. P is formed from a pressure receiving plate 7 which also serves as an electrode, and further,
The inner and outer peripheries of the ring shape are molded with an insulating protection member 8, and the whole is integrally formed into a washer ring shape, and the internal electrode 5 and the pressure receiving plate 7 are insulated.

In addition, in order to improve the adhesion between the surface of the pedestal or bolt and the pressure receiving surface of the pressure sensor 4 at the tightening portion of the spark plug 2 and head bolt 3, the pressure receiving plate 7 is made of a soft flexible material such as copper. metal is used.

Therefore, when the pressure sensor 4 is used to detect the cylinder pressure of the engine as described above, the torque for tightening the spark plug 2 is 1.5 to 3 k (11, and the torque for tightening the head bolt 3 is 1.5 to 3 k). Since the torque is tightened with a relatively large torque of 7 to 10 klJ, the pressure receiving plate 7 of the pressure sensor 4 is plastically deformed in accordance with the roughness of the surface of the part during tightening, so that it comes into close contact with the part. becomes.

However, in conventional pressure sensors, such as the washer-type pressure sensor 4 mentioned above, which simply has a structure in which a piezoelectric material is closely held between metal plates or electrode plates, this problem occurs. The pressure receiving surface of the pressure sensor (the pressure sensor 4
(shown in Figure 2 A), when extremely strong pressure is applied at a point or ubiquitously, the degree of plastic deformation at the received pressure becomes large, and the plastic deformation strain extends to the internal piezoelectric body. This poses a problem in that the piezoelectric body is damaged.

This invention was made in view of the above problems, and by configuring the surface of the piezoelectric body to be protected with a hard metal plate, it is possible to prevent pressure reception when strong external pressure is applied pointwise or ubiquitously to the pressure receiving surface. It is an object of the present invention to provide a pressure sensor that can prevent the piezoelectric body from being damaged due to the influence of plastic deformation of the surface, and can improve pressure resistance and output stability by equalizing the pressure applied to the piezoelectric body. purpose.

Hereinafter, one embodiment of the pressure sensor according to the present invention will be described in detail using the drawings from FIG. 3 onwards.

FIG. 3 is a sectional view showing an embodiment of the present invention, and the pressure sensor shown in the figure is a cross-sectional view showing an embodiment of the present invention. Similar to the pressure sensor 4 shown in FIG. 2, 10 is a washer-type pressure sensor for detecting the internal cylinder pressure of the engine, which is interposed in the tightening part of the ignition plug or head bolt of an automobile. ,,,,.

The pressure sensor '10 is shown in FIGS. 3 and 4.
- As shown in (enlarged view of circle B in Fig. 3), a ring-shaped metal plate internal electrode 11 with a pull-out terminal 11a protruding from a part of its outer periphery, and a tightly laminated structure on both sides of this internal electrode 11. a ring-shaped piezoelectric body 12, and a ring-shaped buffer plate 13 made of a soft flexible metal such as copper, which is laminated on the top surface of the piezoelectric body 12 and is used to uniformly transmit pressure to the piezoelectric body 12. , a ring-shaped protection plate 14 made of a hard metal such as stainless steel, which is laminated on the upper surface of this buffer plate 13 to protect the piezoelectric body 12 from abnormal pressure; and this protection plate 14.
The pressure receiving plate 15, which also serves as a ring-shaped surface electrode made of a soft and flexible metal such as copper, is laminated on the upper surface of the pressure receiving plate 15.

The pressure receiving plate 15 has internal electrodes 11 . Piezoelectric body 12
．． @It extends into the center opening 16 via an insulating protection member 17 provided on the ring-shaped inner periphery across the barrier plate 13 and the protection plate 14, and is formed into a ring shape with a cross-section. .

Further, the ring-shaped outer periphery of the pressure sensor 10 is molded with an insulating protection member 18 similar to the above-mentioned member 17, so that the entire pressure sensor 10 is integrally molded into a washer ring shape.

Incidentally, thin film electrodes made of silver are usually formed on both surfaces of the piezoelectric body 13, and when the silver electrodes 19 are relatively thick (for example, 50 microns or more), the buffer plate 13 is not particularly required.

When the pressure sensor 10 configured as described above is interposed in a part for tightening a spark plug or a head bolt of an automobile as described above, the tightening may be caused by unevenness or inclination of the part surface or intrusion of foreign matter into the pressure receiving plate 15. Even if strong pressure is applied pointwise or ubiquitously to the pressure receiving surface of the pressure receiving plate 15 and the degree of plastic deformation of the pressure receiving plate 15 increases, this plastic deformation strain is blocked by the protection plate 14 and is transmitted pointwise or ubiquitously. The pressure is dispersed throughout the protection plate 14 and converted into uniform pressure.

This distributed and homogenized pressure is evenly transmitted to the entire surface of the piezoelectric body 12 by the buffer plate 13, thereby preventing damage to the piezoelectric body 12 and spreading the pressure to the surface of the piezoelectric body 12. This makes it possible to generate a uniform electric image and obtain stable output.

Additionally, when detecting the internal pressure of an engine, it is generally better to insert the pressure sensor through the head bolt than to insert it through the spark plug, but as mentioned above, tightening the head bolt is The torque required to tighten the spark plug is greater than the torque required to tighten the spark plug, and therefore the piezoelectric body has often been damaged.However, if the above pressure sensor 10 is used by intervening in the tightening section of the head bolt, such problems can be avoided. Therefore, the required number of pressure sensors can be reduced, and manufacturing costs can be reduced.

As explained above, in the pressure sensor of the present invention,
By configuring the surface of the piezoelectric body to be protected with a hard metal protection plate, there are advantages such as being able to improve the pressure resistance and output stability of the pressure sensor.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the installed state of a pressure sensor for detecting the cylinder pressure of an automobile engine, Figure 2 is a cross-sectional view showing an example of a conventional pressure sensor, and Figure 3 is a cross-sectional view of the book. A sectional view showing an embodiment of the pressure sensor according to the invention, FIG.
It is an enlarged view of circle B in the figure. 10...Pressure sensor 11...Internal electrode 12...Piezoelectric body 14...Protective plate 15...Pressure plate Patent applicant No. 1wi Figure 82 Figure 3 Figure 4

Claims (1)

[Claims] (1) A pressure sensor having a piezoelectric body inserted between an internal electrode and a metal pressure-receiving plate, characterized in that a hard metal protection plate is interposed between the metal pressure-receiving plate and the piezoelectric body. pressure sensor.