JPS59111032A - Washer type pressure sensor - Google Patents

Abstract

PURPOSE:To enhance pressure resistance and to stabilize output, by constituting the titled pressure sensor so that pressure applied to a pressure receiving surface is mainly received by a gap holding part and a piezoelectric element receives pressure through a buffer body. CONSTITUTION:A hollow outer shell is formed by gap holding parts 13, 14 for holding the predetermined gap between an upper and a lower pressure receiving parts 11, 12 and an internal electrode plate 15 and piezoelectric elements 16, 17 are laminated in this gap in a closely contacted state. A bellows shaped spring 18 is provided to the under surface of the piezoelectric element 17 through a ring shaped spacer 19 made of a good conductive material such as copper. For example, when the pressure sensor constituted as mentioned above is interposed to the clamp part of the head bolt of an engine, the greater part of clamping torque is added to the above mentioned gap holding parts 13, 14 while pressure to the piezoelectric elements 16, 17 is buffered by the spring 18 and, therefore, a possibility such that the characteristics of the piezoelectric elements 16, 17 are attenuated or said elements are damaged is eliminated.

Description

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

Pressure sensors that receive mechanical pressure and output the received pressure as an electrical signal include those formed simply on a flat plate, as well as a washer-type pressure sensor 1 as shown in FIG. 1, for example.

For example, as shown in FIG. 2, this washer-type pressure sensor 1 is attached to a tightening part of a head bolt 5 for attaching a cylinder head 3 to a cylinder block 4 in a cylinder part 2 of an automobile engine, similar to a normal washer. It is used to measure the cylinder pressure by detecting the change in the tightening pressure that occurs as the gas burns.

As shown in FIG. 3, the structure of the conventional washer-type pressure sensor 1 includes an internal electrode 7 made of a ring-shaped metal plate with a lead terminal (t shown in FIG. 1 6) protruding from a part of the outer periphery. , a ring-shaped piezoelectric body 8 which is closely adhered to m layers on both sides of this internal electrode 7;
A ring-shaped metal pressure-receiving plate 9 is laminated on the upper surface of the piezoelectric body 8 facing the internal electrode 7, and an insulating protection member 1 covers the inner and outer peripheries of the ring-shaped laminated structure.
The internal electrode 7 and the pressure receiving part 9 are insulated.

Further, in order to improve the adhesion between the surface of the pedestal or bolt at the tightening part of the head bolt 5 and the surface of the pressure sensor 1, the pressure receiving plate 9 is made of a soft flexible metal such as copper. .

When the pressure sensor 1 is used by being interposed in the tightening part of the head bolt 5 of the engine as described above,
By tightening with a relatively large tightening torque of 7 to 10 kgm, the pressure receiving plate 9 is plastically deformed in accordance with the rough polishing of the pedestal of the tightening part and the surface of the bolt, and comes into close contact with the tightening part. , the resistance of the contact surface is reduced to improve detection accuracy.

However, since the pressure sensor 1 described above has a structure in which a piezoelectric body is simply tightly held between metal plates or electrode plates, the pressure applied to the pressure receiving surface (pressure receiving surface, plate 9 surface) is , most of it is applied to the piezoelectric body 8, and when a relatively large pressure is applied, such as the tightening torque of the head bolt 5 mentioned above, the piezoelectric characteristics are attenuated and accurate pressure detection becomes impossible. There is a risk that the piezoelectric body may be damaged.

The present invention has been made in view of the above-mentioned circumstances, and includes a pair of ring-shaped pressure-receiving parts that are arranged opposite to each other with a predetermined gap between them by a relatively rigid gap-holding part. By interposing a piezoelectric element through a buffer made of a material that has a large elastic deformation compared to the above, and providing an electrode plate in contact with this piezoelectric element, the bias pressure from the object to be measured is mainly applied to the gap. In addition to receiving pressure at the holding part, pressure fluctuations from the test object are applied to the piezoelectric element via the buffer, so that even when a relatively large pressure is applied to the pressure-receiving surface, the piezoelectric element is not damaged. There's nothing to do,
It is an object of the present invention to provide a washer type pressure sensor that can also provide a stable output.

Embodiments of the present invention will be described in detail below with reference to FIG. 4 and subsequent drawings.

FIG. 4 is a sectional view showing the structure of the first embodiment of the washer type pressure sensor according to the present invention, and its appearance is similar to the conventional one shown in FIG. It is something that

The pressure sensor shown in the figure has a pair of ring-shaped metal pressure receiving parts 11 and 12 arranged vertically opposite each other and having the same diameter, and extending integrally from the inner and outer peripheral edges of the upper pressure receiving part 11. A hollow outer shell is formed by a gap holding part 14.15 which is welded to the upper surface of the lower pressure receiving part 12 and maintains a predetermined gap between the upper and lower pressure receiving parts 11.12. ing.

The pair of gap holding parts 14.15 are both made of relatively rigid metal such as steel, and are formed in a ring shape concentric with the pressure receiving part 11.12.

An internal electrode plate 15 formed in a ring shape concentric with the pressure receiving part is inserted into the gap between the pair of pressure receiving parts. Ring-shaped piezoelectric elements 16 and 17 are closely stacked.

The piezoelectric elements 16 and 17 are made of, for example, PZT (trade name).
These piezoelectric ceramics are made of piezoelectric ceramics such as, and the polarization directions of the two are opposed so that charges of the same polarity are generated on the contact surface with the internal electrode plate 15, and the electromotive force of the piezoelectric element is
is extracted to the outside.

Further, a bellows-shaped spring 18 is installed on the lower surface of the piezoelectric element 17 via a ring-shaped spacer 19 made of a good conductor such as copper. By being compressed and held between the spacer 19, the piezoelectric elements 16 and 17, and the internal electrode plate 15 are pressed upward, and the upper surface of the piezoelectric element 16 is pressed against the upper pressure receiving part 11.
It is pressed against the inner surface of the

Therefore, the electric charge generated on the upper surface side of the piezoelectric element 16 is led out via the upper pressure receiving part 11, and the electric charge generated on the lower surface side of the piezoelectric element 17 is led out via the lower pressure receiving part 12 through the spacer 19° spring 18. It will be derived as follows.

Furthermore, piezoelectric elements 16 and 17 are disposed between the internal electrode plate 15, the inner peripheral side of the piezoelectric elements 16 and 17, and the gap holding part 14.
An insulating ring 20 is inserted to prevent short circuit between the two poles.

In the washer-type pressure sensor configured as described above, for example, when it is interposed in the tightening part of the head bolt 5 of the engine, most of the tightening torque of the head bolt 5 is In addition to the gap holding parts 13 and 14, the pressure on the piezoelectric elements 16 and 17 is buffered by the spring 19, so there is no risk that the characteristics of the piezoelectric elements 16 and 17 will be attenuated or that they will be damaged.

Next, FIG. 5 is a sectional view showing a second embodiment of the present invention.

The washer type pressure sensor shown in the figure has a ring-shaped aluminum spacer 21 in place of the spring 18 and spacer 19 in the first embodiment shown in FIG. The spacer 21 is formed to have a thickness such that the upper surface of the piezoelectric element 16 can be pressed against the lower surface of the upper pressure receiving section 11.

The Young's modulus Ea of the aluminum forming the spacer 21 is 7X 101ON/Ill 2, whereas the Young's modulus ES of the steel forming the gap holding part 13.14 is 21X10"N/m2. Therefore, the spacer 21 is easily deformed elastically with respect to the gap holding part 13.14, and exhibits the same effect as the spring 18 of the first embodiment.
The number of parts and man-hours can be reduced compared to those of the first embodiment.

Next, FIG. 6 is a sectional view showing a third embodiment of the present invention.

The washer type pressure sensor shown in the same figure is the aluminum spacer 2 in the second embodiment shown in FIG.
1, a plastic spacer 22 is inserted between the internal electrode plate 15 and the lower pressure receiving part 12, and since the plastic spacer 22 does not have conductivity, it can be used as a single piezoelectric element. The structure is such that pressure changes are detected at 16.

The Young's modulus Ep of the plastic forming the spacer 22 is 1×10”N/m2 or less, which is smaller than that of the aluminum, so that the M'fjj effect of the pressure horn applied to the piezoelectric element 13 can be further increased. .

FIG. 7 is a sectional view showing a fourth embodiment of the present invention,
The washer type pressure sensor shown in the same figure has a piezoelectric element itself which has a pressure buffering property instead of providing buffer parts such as the spring 19 and spacers 21, 22 in each of the above embodiments.

That is, it has a structure in which two upper and lower polymer piezoelectric elements 23 and 24 are sandwiched between the upper and lower pressure receiving parts 11 and 12 with an internal electrode in between.

The polymer piezoelectric elements 23 and 24 are made of a pure polymer such as polyvinylidene fluoride or a composite of polyvinylidene fluoride mixed with PZT powder. Since the ratio is about 1/100 of that of the steel, it is possible to obtain the same effects as in each of the above embodiments.

As explained in detail above, in the washer type pressure sensor according to the present invention, the pressure applied to the pressure receiving surface is mainly received by the gap holding part, and the piezoelectric element receives the pressure via the buffer body. With this configuration, voltage resistance can be further improved and a stable 1C output can be obtained.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the external appearance of a washer type pressure sensor, Figure 2 is a sectional view showing an example of applying the same pressure sensor to detect pressure inside a cylinder, and Figure 3 is a diagram showing the structure of a conventional washer type pressure sensor. 4 is a sectional view showing a first embodiment of the washer type pressure sensor according to the present invention, FIG. 5 is a sectional view showing a second embodiment of the present invention, and FIG. FIG. 7 is a sectional view showing a third embodiment of the invention, and FIG. 7 is a sectional view showing a fourth embodiment of the invention.

Claims (1)

[Claims] (1) A pair of ring-shaped pressure-receiving parts arranged vertically opposite each other to receive pressure from a test object; formed of a relatively rigid material, and with a predetermined gap between the pair of ring-shaped pressure-receiving parts. a gap holding section that holds; a piezoelectric element interposed in the gap between the pair of pressure receiving sections via a buffer made of a material having a larger elastic deformation than the gap holding section; the piezoelectric element 1. A washer-type pressure sensor comprising: an electrode plate that is in contact with the electrode plate and that outputs the electromotive force to the outside.