JPH04294233A - Dynamic quantity detector - Google Patents

Abstract

PURPOSE:To obtain a detector with little influence of electromagnetic induction and external noise by electrically shielding a part with high impedance and also loading electrostatic capacitance in terms of a distribution constant circuit. CONSTITUTION:Thick film distortion-sensitive resistors 3a to 3d and an electrode part 4 are coated by an insulation layer 6 using low melting point glass or the like. Although the thinner the insulation layer 6 formed, the more advantageous, thickness of approximately 15 to 30mum is optimum in order to prevent failure in isolation due to occurrence of pin holes. No insulation layer 6 is formed on a part of terminals 5a to 5d, because the terminals 5a to 5d need to be connected with exterior by means of soldering or the like. An electrode part 7 is further formed on the insulation layer 6. It is usually convenient that the electrode part 7 be larger in size than the underlying electrode part 4. The electrode part 7 is designed to be connected to the terminal 5c. The distortion- sensitive resistors 3a to 3d, the insulation layer 6 and the electrode part 7 are all manufactured by thick film printing and baking processes.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical quantity detector that includes a strain gauge using a thick film resistor and measures a physical quantity by converting it into an electrical signal.

0002

2. Description of the Related Art A conventional mechanical quantity detector of this type will be explained. An inorganic insulating layer formed on a thin ceramic or metal plate is used as a strain-generating body, and a strain-sensitive resistor is formed by forming a thick film on top of this by a process such as printing or firing. Mechanical quantity detectors have been put into practical use. Next, Fig. 4(a), Fig. 4(b), Fig. 5
A conventional pressure sensor will be explained in detail with reference to . Figure 4
In (a) and (b), a diaphragm 2 is formed in the center of the ceramic base 1 to be thin and is a strain-generating part due to receiving pressure.
form. A plurality of thick film strain-sensitive resistors 3a, 3b, 3c, and 3d are formed on the upper surface of the central portion of the diaphragm 2 and on the peripheral portion thereof. These resistors 3a to 3d are connected to thick film electrode portions 4, respectively. A portion of the electrode portion 4 is provided with terminals 5a, 5b, 5c, and 5d for connection to the outside. FIG. 5 is an electrical circuit diagram of the detector of FIG. 4. These thick film strain-sensitive resistors often have a resistance value of several tens of kilohms in consideration of the piezoresistance effect of the resistor element, current consumption, etc.

0003

[Problems to be Solved by the Invention] Conventional mechanical quantity detectors have advantages such as high sensitivity and low current consumption, but on the other hand, they have high impedance and are susceptible to electromagnetic induction and external noise. There were problems such as being unsuitable for detecting mechanical quantities.

0004

Means for Solving the Problems The present invention aims to solve the above-mentioned problems, and the means for achieving the object will be explained using the reference numerals used in the embodiments. That is, strain-sensitive resistors 3a to 3d formed of a thick film, and an insulating layer 6 formed of a thick film so as to cover part or the front part of the electric signal line such as the electrode part 4 and the terminals 5a to 5d connected thereto. This mechanical quantity detector is characterized in that a metal electrode layer 7 formed of a thick film is provided on the insulating layer 6.

[0005]

[Operation] The mechanical quantity detector according to the present invention has thick film strain-sensitive resistors 3a to 3d formed on the diaphragm 2, which is a strain generating part, and electrode parts 4 connected thereto, and signal lines including terminals 5a to 5d. A metal electrode layer 7 is formed through an insulating layer 6 having a dielectric constant ε, and by grounding this metal electrode layer 7, the thick film strain-sensitive resistors 3a to 3d and the signal lines connected thereto are electromagnetic. It is shielded from induction and external noise, and further includes thick film strain sensitive resistors 3a to 3d, signal lines connected thereto, and metal electrode layer 7.
has an electrostatic container in the form of a distributed constant circuit, which bypasses the high-frequency components of the intruding noise.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view of an embodiment of the invention. Thick film strain-sensitive resistors 3a to 3d and electrode portions 4 are formed as shown in FIG. 4, and these members 3a to 3d, 4 are covered with an insulating layer 6 made of low melting point glass or the like. The thinner the insulating layer 6 is, the more advantageous it is, but the optimal thickness is about 15 to 30 μm in order to prevent insulation defects due to pinholes. The insulating layer 6 is not formed on some of the terminals 5a to 5d. The reason for this is that the terminal groups 5a to 5d need to be connected to the outside by soldering or the like. Further, an electrode portion 7 is formed on the insulating layer 6. It is usually advantageous for the electrode section 7 to have a larger size than the electrode section 4 located below. In this embodiment, the electrode section 7 is designed to be connected to the terminal 5c. The strain sensitive resistors 3a to 3d, the insulating layer 6, and the electrode layer 7 are all manufactured by thick film printing and firing processes. FIG. 3 is a sectional view of a member made of these thick films. Also figure 2
2 illustrates the electrical circuit of the pressure sensor of FIG. 1;

[0007]

[Effect] The present invention electrically shields high impedance parts and loads capacitance using a distributed constant circuit, so it is possible to use a mechanical quantity detector that is less affected by electromagnetic induction and external noise. Obtainable. Furthermore, the structure of the main components of this detector can be manufactured by the same process as that used to form a thick film strain-sensitive resistor, which has the effect of reducing manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a plan view of a substrate on which a strain gauge of a mechanical quantity detector according to the present invention is arranged.

FIG. 2 is an electrical circuit diagram of the mechanical quantity detector of FIG. 1.

FIG. 3 is a cross-sectional view of the main components of FIG. 1;

FIG. 4(a) is a plan view of a conventional pressure detector. (b) is a side view of (a).

FIG. 5 is an electrical circuit diagram of FIG. 4;

[Explanation of symbols]

1 Ceramic base 2 Diaphragm 3a-3d Thick film sensitive strain resistance 4 Electrode part 5a-5d Terminal 6 Insulating layer 7 Electrode layer

Claims (2)

[Claims] Claim 1: A strain-sensitive resistor formed of a thick film, an insulating layer formed of a thick film so as to cover a part or front part of an electric signal line such as an electrode part or a terminal connected to the strain-sensitive resistor, and this insulating layer. A mechanical quantity detector characterized in that a metal electrode layer formed of a thick film is provided thereon. 2. The mechanical quantity detector according to claim 1, wherein the metal electrode layer is connected to a signal line of a converter or a current-carrying part of a measuring instrument connected thereto.