Measuring and testing – Fluid pressure gauge – Diaphragm
Patent
1990-03-21
1992-09-08
Woodirl, Donald O.
Measuring and testing
Fluid pressure gauge
Diaphragm
73721, 338 4, 338 42, G01L 906
Patent
active
051448432
DESCRIPTION:
BRIEF SUMMARY
Description
1. Technical Field
The present invention relates to a pressure sensor which has a structure suitable for mounting to components of hydraulic machines, i.e., hydraulic equipment such as hydraulic pipes and couplings (joints) for the hydraulic pipes, and which has a diaphragm positioned such that strain gauges in a strain detecting section provided on the diaphragm take an optimum location for high measurement accuracy, a pressure sensor manufacturing method by which the pressure sensor can simply be manufactured in a mass quantity by utilizing semiconductor manufacture technology, and to hydraulic equipment which is produced with the structure allowing the pressure sensor to be incorporated therein in advance for high practicability.
2. Background Art
Pressure sensors are one sort of sensors contained in the category of stress sensors in a broad sense that conceptually includes strain sensors, torque sensors, load sensors, etc., and are employed for measuring a pressure of a liquid, gas, etc. Such pressure sensors are often used as detector means for detecting working hydraulic pressures at various mechnical components in hydraulic machines for civil engineering and construction, for example. Pressure sensors may have various types of the structure. A pressure sensor of the diaphragm type will be described below.
The structure of a conventional diaphragm type pressure sensor is shown in FIG. 39. The pressure sensor comprises a metal-made diaphragm base 300 which is directly subjected to a pressure P, e.g., a hydraulic pressure, an insulting film 301 formed by a film forming technique, such as CVD, using silane gas or the like, four strain gauges 302 each of which has a resistance value changed dependent on a strain of the diaphragm caused by the pressure P, thin film conductors 302 serving as terminals for electric wiring, and a passivation film 304 which functions as a hermetic protection film. The metal-made diaphragm base 300 is functionally divided into to two parts. One part is a diaphragm section 305 subjected to the pressure P for developing a strain dependent on the magnitude of the pressure, and another part is a tubular support section 306 which functions to support the diaphragm section 305 and fix the pressure sensor at a certain mounting location. The diaphragm section 305 is formed at a top position of the tubular support section 306 so as to close one end face thereof. The strain gauge 302 and the thin film conductors 303 are covered by the passivation film 304 such as a SiN.sub.x or SiO.sub.2 film. Wires 307, 307 are connected at their lower ends to the thin film conductors 303, 303, respectively, as viewed on the drawing. The other ends of the wires 307 are connected to an electrical measuring unit such as a voltage meter or ampere meter via lead wires (not shown) for electrically measuring a strain developed in the diaphragm section 305. More specifically, in the no-load condition where the pressure P does not act on the diaphragm section 305, the specific resistances of the strain gauges 302 remain unchanged so that no potential difference occurs between the wires 307 and 307 and no current flows into the measuring unit. On the other hand, when a strain is developed in the diaphragm section 305 upon being subjected to the pressure P, the specific resistances of the strain gauges 302 are changed to produce a potential difference between the wires 307 and 307, whereby the measuring unit can determine the pressure applied to the diaphragm section 305.
In the pressure sensor having the structure shown in FIG. 39, the diaphragm section 305 and the support section 306 are integrally structured into the metal-made diaphragm base 300. Conventionally, however, there has also been proposed a pressure sensor in which the diaphragm section 305 and the support section 306 are structured as separate members, are disclosed in Japanese Utility Model Laid-Open 61(1986)-137242 by way of example. In this type pressure sensor, the diaphragm section 305 is formed into a metal-made thin plate diap
REFERENCES:
patent: 3935636 (1976-02-01), Mermelstein
patent: 4600912 (1986-07-01), Marks et al.
patent: 4665754 (1987-05-01), Glenn et al.
patent: 4884051 (1989-11-01), Takahashi et al.
Hashimoto Hisayoshi
Hatano Kazuyoshi
Ichiryu Ken
Sato Fujio
Tamura Morio
Hitachi Construction Machinery Co. Ltd.
Woodirl Donald O.
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