CN100399032C - Athermal Flow Velocity and Direction Sensor Based on Micromechanical System - Google Patents

Abstract

The non-thermal flow rate sensor based on the micromechanical system is a capacitive flow rate sensor that is processed by the micromechanical system and contains a support beam and a baffle body. The sensor is provided with a baffle body (2) on the substrate (7). The center of the bluff body (2) is provided with a pillar (1) fixed on the substrate (7), and a plurality of isotropic damping support beams (8 ) connection; the bluff body (2) is made of two concentric rings, connected by four connecting plates between the two concentric rings and the annular space between the two concentric rings is divided into four subspaces, The first orthogonal fixed electrode (3), the second orthogonal fixed electrode (4), the third orthogonal fixed electrode (5), and the fourth orthogonal fixed electrode (6) are respectively located between two concentric rings in the four subspaces. The sensor has the advantages of measuring two-dimensional wind direction, low power consumption, fast response, small temperature drift and good reliability.

Description

Athermal Flow Velocity and Direction Sensor Based on Micromechanical System

technical field

The invention relates to a micromechanical non-thermal flow velocity flow sensor, in particular to a capacitive flow velocity flow sensor which is processed by MEMS (micro mechanical system) and contains a support beam and a resistance body.

Background technique

Fluid measurement has important applications in industrial and agricultural production, meteorology, environmental protection, national defense, scientific research, aviation and other departments. Among them, flow velocity and direction measurement, as an important part of fluid measurement, has been developed for many years. There have been measurement methods such as wind cup and vane measurement, pitot tube measurement, float measurement, mechanical measurement, acoustic measurement, optical measurement, heat transfer measurement, and electromagnetic measurement. The micro flow rate and flow direction sensor based on MEMS processing technology has the characteristics of small size, low price and good product consistency, and it has become a hot spot in the research of fluid sensors in recent years. Van Putten proposed the first flow sensor based on silicon micromachining technology in 1974 (Putten V, Middelheok S. "Integrated silicon anemometer". Electron. Lett.1974 (21): 425-426), the working principle of this sensor It is based on heat transfer, that is, the flow velocity and direction information is measured by measuring the change of the thermal field caused by the fluid flow. After more than 30 years of development, thermal microfluidic sensors have become mainstream, especially in the field of anemometers. However, thermal microfluidic sensors also have their inherent disadvantages. For example, large power consumption, measurement errors due to thermal conduction of the substrate, zero point drift with ambient temperature, long response time, etc. In addition, because the fluid needs to be heated, the application of thermal microfluidic sensors in biology is limited. Athermal microfluidic sensors can overcome the above disadvantages. Kersjes proposed a method for measuring differential pressure (Kersjes R, Eichholz J, Langerbein A, et al. "An integrated sensor for invasive blood-velocity measurement". Sensors and Actuators A, 1993, 37(38): 674-678), Oosterbroek A method for measuring pressure drop was proposed (Oosterbroek E, Lammerink J, Berenschot W, et al. "Design, reallzation and characterization of novel capacitive pressure/flow sensor". Proc. Transducers'97, 1997: 151-154), Svedin proposed Through the method of measuring lift force (Svedin N, Stemme E, Stemme G. "A new bi-directional gas flow sensor based on lift force". Proc. Transducers'97, 1997: 145-148), Ng proposed to measure viscous force (Ng K, Shajii K, Schmidt M A. "A liquid shear stress sensor fabricated using wafer bonding technology". Proc Transducers'91, 1991.931-934). At present, the common disadvantages of flow velocity and direction sensors based on the non-thermal principle are the small measuring range and the inability to measure two-dimensional wind direction.

Contents of the invention

Technical problem: The purpose of this invention is to provide a non-thermal flow velocity and direction sensor based on micromechanical system, which has the advantages of measuring two-dimensional wind direction, low power consumption, fast response, small temperature drift and good reliability.

Technical solution: The present invention is a non-thermal flow rate and direction sensor based on a micromechanical system, which is a capacitive flow rate and direction sensor for measuring fluid flow rate and flow direction signals. The sensor includes several support beams that can provide isotropic damping, vertical baffle bodies supported on the beams, vertical electrodes arranged orthogonally, and fixed substrates and leads; The center of the fluid circle is provided with a pillar fixed on the substrate, and the pillar and the inner circumference of the bluff body are connected by a plurality of isotropic damping support beams; the bluff body is composed of two concentric rings, two concentric circles The rings are connected by four connecting plates and the annular space between the two concentric rings is divided into four subspaces, the first orthogonal fixed electrode, the second orthogonal fixed electrode, the third orthogonal fixed electrode, the second The four orthogonal fixed electrodes are respectively located in four subspaces between two concentric rings; the materials of the pillars, support beams, and baffle body are conductive N-type semiconductor silicon; the suspension support beam and the baffle body structure are bonded technology formation.

When the sensor is in the fluid, the fluid flow generates pressure on the bluff body, and the bluff body transmits the pressure to the support beam, the support beam is strained, and the vertical bluff body is displaced relative to the fixed vertical electrode, so that the gap between the two The capacitance value changes. The flow velocity and flow direction information can be obtained by measuring the change in capacitance between the four orthogonal sets of electrodes. That is, the information of the flow direction and flow velocity is obtained by measuring the differential change of the orthogonal capacitance brought about by the displacement of the bluff body caused by the fluid. The isotropically damped support beam and bluff body act both as a movable displacement member and as an electrode for measuring capacitance changes.

Beneficial effects: the present invention can be manufactured by using MEMS processing technology, the manufacturing method and structure are relatively simple, and the reliability is good. Traditional thermal fluid sensors obtain flow velocity and flow direction information by setting heating components, allowing fluid to flow through the heating components, and measuring changes in the thermal field or temperature changes of the heating components. Due to the heating of the fluid, the power consumption is large and the temperature effect is obvious. The invention adopts the principle of mechanics to measure, and obtains the flow velocity and flow direction information by measuring the displacement caused by the force of the fluid on the bluff body. Thereby avoiding this defect. Most traditional non-thermal fluid sensors use Bernoulli's principle to measure pressure difference or pressure drop, and cannot obtain two-dimensional direction information. The present invention solves this problem by arranging orthogonal fixed electrodes, and two-dimensional direction information can be obtained by respectively detecting changes in capacitance between mutually orthogonal electrodes. The invention adopts capacitive structure detection, has small temperature drift, high sensitivity and strong anti-interference ability. Using the surface oxidized N-type semiconductor silicon wafer as the structural material, the gap between the electrodes is formed by ICP (plasma enhanced etching), and then the pillars and glass are bonded to complete the fixation and leads, and finally the support beams and resistors are formed by ICP. fluid release. Compared with the traditional sacrificial layer release to form voids, this novel bonding method can form vertical electrode voids, effectively increasing the initial capacitance and sensitivity. And because the fixing and wiring are achieved through silicon and glass bonding. Can effectively reduce the parasitic capacitance.

Description of drawings

Fig. 1 is a schematic structural view of the present invention.

In the above figure, there are pillars 1, baffle body 2, first orthogonal fixed electrode 3, second orthogonal fixed electrode 4, third orthogonal fixed electrode 5, fourth orthogonal fixed electrode 6, substrate 7, each Isotropic damping support beam 8.

Detailed ways

The invention is a fluid sensor for measuring flow velocity and flow direction. Consisting of a pillar 1, a resistive body 2, a first orthogonal fixed electrode 3, a second orthogonal fixed electrode 4, a third orthogonal fixed electrode 5, a fourth orthogonal fixed electrode 6, a substrate 7, and an isotropic damping support beam 8 composition. The substrate 7 is glass, on which leads are formed. The pillar 1 is bonded to the glass, and the first orthogonal fixed electrode 3 , the second orthogonal fixed electrode 4 , the third orthogonal fixed electrode 5 , and the fourth orthogonal fixed electrode 6 are also bonded to the glass. The material of the pillar 1, the support beam 8 and the bluff body 2 is N-type semiconductor silicon, which is obtained by double-side etching twice. As shown in FIG. 1 , the conductive resistive body 2 and four fixed electrodes, that is, the first orthogonal fixed electrode 3 , the second orthogonal fixed electrode 4 , the third orthogonal fixed electrode 5 , and the fourth orthogonal fixed electrode 6 constitute four a capacitor. The bluff body 2 leads from the glass substrate 7 through the connection of the support beam 8 and the pillar 1 . When the fluid acts on the bluff body 2, the bluff body 2 receives a force, the direction of the force is the same as the flow direction, and the magnitude of the force depends on the flow velocity. The support beams 8 provide isotropic damping. The bluff body 2 produces plane displacement in the direction of flow velocity. The size of the four capacitors changes. The value of the change depends on the direction and magnitude of the displacement of the bluff body 2 . Therefore, the information of flow velocity and flow direction can be obtained by measuring the size changes of the four capacitances.

The manufacturing process of the sensor in this example is as follows: prepare N-type semiconductor silicon chip 1#; etch the N-type semiconductor silicon chip on the back to form the steps of the bluff body 2; etch the N-type semiconductor silicon chip to form the steps of the support beam 8; The back side of N-type semiconductor silicon chip 1# is bonded to glass 7; the front side of N-type semiconductor silicon chip 1# is etched to form resistance body 2, support beam 8, first orthogonal fixed electrode 3, and second orthogonal fixed electrode Electrode 4 , third orthogonal fixed electrode 5 , fourth orthogonal fixed electrode 6 and strut 1 .

The isotropic damping support beam 8 is composed of a plurality of hollow rhombuses connected in series.

The substrate 7 is made of glass material, and the pillar 1 and the bluff body 2 are made of N-type semiconductor silicon material.

Claims (2)

1. A non-thermal flow rate sensor based on a micromechanical system, the sensor includes: several support beams (8) that can provide isotropic damping, vertical bluff bodies (2) supported on the beams, and orthogonal settings The vertical electrode and the fixed substrate (7) and lead wire; The substrate (7) is provided with a bluff body (2), and the center of the bluff body (2) is provided with a pillar fixed on the substrate (7) (1), the pillar (1) and the inner circumference of the bluff body (2) are connected by a plurality of isotropic damping support beams (8); the bluff body (2) is composed of two concentric rings, two concentric The circular rings are connected by four connecting plates and the annular space between the two concentric circular rings is divided into four subspaces, the first orthogonal fixed electrode (3), the second orthogonal fixed electrode (4), The third orthogonal fixed electrode (5) and the fourth orthogonal fixed electrode (6) are respectively located in four subspaces between two concentric rings; the pillar (1), support beam (8), bluff body The material of (2) is conductive N-type semiconductor silicon; the structures of the suspended support beam (8) and the suspended resistance body (2) are formed by bonding technology. 2. The micromechanical system-based non-thermal flow velocity and direction sensor according to claim 1, characterized in that: the isotropic damping support beam (8) is composed of a plurality of hollow rhombic phases connected in series.

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