JPH0285738A - Pressure sensor - Google Patents

Abstract

PURPOSE:To improve the fracture toughness and flexural strength of the title sensor by providing a diaphragm composed of a metallic base body and insulating layer formed on the base body. CONSTITUTION:A resistance group is arranged so that resistances R1 and R3 can be compressed and resistances R2 and R4 can be extended to the maximum when a pressure P is applied to a diaphragm F composed of an insulating layer 1 and base body 2 in the direction from the annular hold 4 of the base body 2. Namely, the compressed resistance R3 can be arranged any place if it is positioned on a concentric circle of the bottom surface of the annular hole 4 or can be positioned to the position R3'. Then a bridge circuit with a pressure sensitive resistance is formed on the insulating layer 1 by a thick-film forming method. Since a metal which is small in Young's modulus and large in fracture toughness and flexural strength is used as the material of the diaphragm F, the sensor can be improved in pressure sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure sensor, and particularly to a diaphragm of a pressure sensor.

(Prior Art) Conventionally, a pressure sensor that forms a resistance element on a diaphragm that deforms due to pressure and detects pressure from a change in resistance value uses a thick film resistor as the material of the diaphragm. Alumina ceramics and the like are used, which have relatively high strength, are easily available, and have a proven track record of compatibility with thick film materials.

(Problems to be Solved by the Invention) The material of the diaphragm conventionally used as a thick film pressure sensor is usually alumina ceramic, and this ceramic usually contains about 96% aluminum oxide.

The problems when using alumina ceramics as a diaphragm material for thick film pressure sensors are as follows: ■ Young's modulus is as high as approximately (3.2 x 10104)/■ 2, so the thickness of the diaphragm is A large strain cannot be obtained unless the diameter is made thin and the diameter is large.
That is, this relationship is as shown by the following equation.

ε=σ/E ε: Strain a=Radius σ: Stress E: Young's modulus ■ Fracture toughness is small at about 4 MPam172, so brittle fracture is likely to occur due to large pressure changes; ■ Fracture strength is small at about 30 kg/+u+2 However, there were problems such as the inability to set a high rated pressure as a pressure sensor.

In order to overcome the above-mentioned problems, the present invention provides a diaphragm made of a material with excellent fracture toughness and bending strength.

(Means for Solving the Problems) That is, in order to solve the above-mentioned problems of conventional ceramic diaphragms, the diaphragm is made of metal such as SUS or iron as a material with excellent fracture toughness and bending strength. According to the present invention, a metal having a small Young's modulus and high fracture toughness and bending strength is used as the constituent material of the diaphragm. Therefore, it is possible to obtain a compact high-pressure pressure sensor that is highly sensitive and resistant to pressure shock.

Further, as is clear from the above formula, a pressure sensor for low pressure with high sensitivity can be obtained by reducing the thickness of the diaphragm and increasing the diameter. Furthermore, since a thick film resistor is used, thermal stability is also good.

(Examples) Examples according to the present invention will be described below with reference to the accompanying drawings.

In FIG. 1(a), reference numeral 1 denotes a hollow insulating layer formed on the upper surface of a metal base 2. In FIG. The metal base 2 is usually S
It is made of OS, iron, etc.

Hereinafter, in this specification, a member composed of the insulating layer 1 and the base 2 will be referred to as a diaphragm F.

A bridge circuit 3 is formed on the upper surface of the insulating layer l of the diaphragm F. FIG. 1(b) shows resistors R+ and R2 arranged at the bottom of the annular hole 4 provided in the diaphragm base 2.

R3 and R4 are illustrated. Resistors R2 and R4 are arranged substantially near the center of the annular hole 4, and resistors R1 and R3 are arranged on concentric circles formed by the bottom surface of the annular hole 4. Pressure P is applied from the direction of the annular hole 4 of the base 2 to the diaphragm F consisting of the insulating layer 1 and the base 2.
In the present invention, the resistor group is arranged at a position where the degree of compression is greatest so that when the resistors R1 and R3 are compressed and the resistors R2 and R are expanded at the same time. That is, as already explained, the position of the resistor R3 to be compressed is the base annular hole 4.
Any location may be used as long as it is on the concentric circle that is the bottom of the
It may also be set at the ° position.

Next, FIG. 1(C) shows a bridge circuit composed of resistors RI, R2, R3, and Ra. This circuit is well known, so a detailed explanation thereof will be omitted.

Furthermore, in the embodiment of the present invention, SuS is used as the metal substrate 2, which is subjected to cutting and polishing processing, and its upper surface is made of a thermal expansion material similar to that of the substrate 2 (SUS), which is mainly made of lead borosilicate glass. The paste waiting for the coefficient is printed and fired by a thick film method to form an insulating layer 1 having a thickness of 20 to 40 gm.

Furthermore, a bridge circuit 3 in which a pressure sensitive resistor is arranged on the insulating layer.
is formed by a thick film method. Although SUS was used for the metal base in this example, it is not limited to this and other metals may be used.The method for forming the insulating layer is as described in Example 1.
Although a thick film method was used in the above, it goes without saying that other methods such as a spray method, thermal spraying method, coating method, etc. may also be used.

Figure 2 shows a pressure-output value graph of a pressure sensor, whose diaphragm is φ10. t=1.25mm. In this figure, the conventional pressure sensor S2 with a ceramic diaphragm breaks down at a pressure of 450 kg/cs+2, but the pressure sensor S1 with the base and insulating layer according to the present invention breaks down when a pressure of 500 kg/cs+2 is applied. Also, regarding the output voltage, the pressure sensor Sl according to the present invention is 2.1 times larger than the conventional one.
Therefore, the pressure sensor S1 according to the present invention can set a larger rated pressure and obtain a larger output voltage than the conventional pressure sensor.

As explained above, the present invention provides a pressure sensor equipped with a diaphragm in which a hollow insulating layer is formed on a metal base, and its manufacturing method is relatively simple and inexpensive, and therefore mass production is possible. suitable for

Furthermore, the pressure sensor according to the present invention can be applied to cases where strain sensing with high sensitivity and good thermal stability is required, without causing destruction even under considerable pressure. Furthermore, although the present invention relates to a pressure sensor, it is of course applicable to sensors that measure changes in physical quantities such as acceleration, strain, load, and torsional moment.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and FIG. 2 is a graph showing pressure-output characteristics of the embodiment. FIG. 1(a) is a line side view of one embodiment of the pressure sensor according to the present invention, FIG. 1(b) is a plan view showing the arrangement of the resistor group as seen from the bottom of FIG. 1, and FIG. 1(c) is a Bridge circuit diagram FIG. 2 is a graph showing the characteristics of the pressure output value of the pressure sensor. F...diaphragm, l...insulating layer, 2...substrate, 3...bridge circuit, 4...annular hole patent applicant
Delphi Co., Ltd. Agent Patent Attorney Eiko Kobayashi Figure 1 Figure 2 Repulsion (kg cm)

Claims (1)

[Claims] 1. Sensing a change in resistance in the bridge circuit as a function of deformation of the diaphragm by means of a diaphragm comprising a base body and an insulating layer provided thereon, and a bridge circuit further constructed thereon. The pressure sensor has a diaphragm in which the base is made of metal and a glass insulating layer is formed on the metal surface. 2. The pressure sensor according to claim 1, further comprising a diaphragm formed by using a metal such as SUS or iron as the base and forming an insulating layer of enamel (mainly made of lead borosilicate glass) on the metal surface.