CN1818666A - Capacitor-style microfluid angular accelerometer - Google Patents

Abstract

A capacitive angular accelerometer belongs to the technical field of micro-electromechanical systems. The invention comprises: an upper shell, a fluid chamber, a differential capacitor dynamic plate, a differential capacitor fixed plate, and a lower shell. The fluid chamber is filled with dense liquid. When there is an angular accelerometer in the vertical direction, the baffle is inclined under the action of the inertial force of the sealing liquid, thereby driving the differential capacitive plate to move through the outer wall of the flexible chamber. The control circuit detects the variation of the differential capacitance, and then deduces the angular acceleration value input from the outside. The whole device can be fabricated by LIGA/quasi-LIGA process and bonding process. The capacitive angular accelerometer proposed by the invention works under the quasi-static state, has a wide detection frequency range, and also has high measurement accuracy.

Description

Capacitive microfluidic angular accelerometer

technical field

The invention relates to a device in the technical field of microelectromechanical systems, in particular to a capacitive microfluidic angular accelerometer.

Background technique

Accelerometers are commonly used to measure the second derivative of displacement with respect to time. The angular accelerometer measures the second derivative of angular displacement with respect to time, and it can be used in automotive safety control systems, hard disk anti-shock vibration and other fields. When the carrier has an angular acceleration input in a certain direction, the angular accelerometer can output an electrical signal (such as voltage) proportional to the input angular acceleration through the detection circuit. For example, the sensed angular acceleration signal can be used to judge whether the car is about to tip over, so as to take corresponding measures in time. The angular accelerometer can also be used to control the read-write head of the disk, so that the disk control system can compensate for the angular acceleration caused by severe shock or vibration, so that the disk can rotate stably and at a constant speed. Angular accelerometers can also be used in vibration control of test benches, dynamic control of robot arms and other fields.

After searching the literature of the prior art, it is found that an angular accelerometer is proposed in the U.S. Pat. No. 5,251,484 rotational accelerometer ("Rotational Accelerometer"). The central part of the accelerometer has an annular axis fixed on the base body, and connected to the annular axis are radially arranged cantilever spoke electrodes. When the angular acceleration of the carrier exists, the spoke electrodes will deform flexibly. The spoke electrodes distributed on the outer edge and the fixed reference electrodes form a differential parallel plate capacitive signal extraction scheme, and the differential output voltage will be output when the spoke movable plate deviates from the center position. The sensing capability of this angular accelerometer is limited by the amount of displacement of the flexible spoke electrodes. Structures with rotatable cantilevers generally require high structure matching to ensure predictable gain, phase and linear response. Linear sensitivity and cross-axis sensitivity (gain) are highly dependent on structural matching. In addition, the discrete capacitor plate leads will increase the complexity of the structure and the production cost.

It was also found in the search that U.S. Pat. No. 6,257,062 angular accelerometer ("AngularAccelerometer"), in an angular accelerometer mentioned in this patent, the rotating inertial mass and the base are connected through a series of support beams, An inertial mass is suspended above the chamber. This angular accelerometer can get higher accuracy than the former one. However, this angular accelerometer requires extremely high structural symmetry, which puts forward higher requirements for microfabrication methods.

Contents of the invention

The present invention proposes a capacitive microfluidic angular accelerometer aiming at the deficiencies of the above-mentioned angular accelerometer. The present invention has a simple structure, is suitable for MEMS processing technology, and the fluid is almost sealed in a cavity space; because it works through the almost sealed fluid inertial force, it has a wide frequency response bandwidth; the capacitance detection device is sensitive to the working environment temperature The sensitivity is not strong, and the working temperature range is large.

The present invention is achieved through the following technical solutions. The capacitive microfluidic angular accelerometer of the present invention includes: an upper housing, a fluid chamber, a differential capacitance dynamic plate, a differential capacitance fixed plate and a lower housing, wherein the fluid chamber The chamber is composed of the following structures: inner ring wall of the chamber, outer ring wall of the chamber, baffle plate, the outer ring wall of the chamber is surrounded by the outer ring wall of the rigid chamber and the outer ring wall of the flexible chamber together, and the outer ring of the outer chamber and the outer ring of the flexible chamber The wall is connected with a differential capacitor dynamic plate, and the differential capacitor fixed plate is located at the outer edge of the lower shell.

Distributed on the lower shell are differential capacitive dynamic plates, chamber inner ring wall, chamber outer ring wall, П-shaped fixed plate, L-shaped fixed plate, baffle plate, rigid chamber outer wall, flexible chamber outer wall, moving pole Plate connecting arm, П-shaped moving plate, П-shaped moving plate. The inner ring wall of the chamber and the lower shell form a fixed connection, the outer ring wall of the chamber is jointly surrounded by the outer wall of the rigid chamber and the outer wall of the flexible chamber, and the outer wall of the rigid chamber is much wider than the outer wall of the flexible chamber. When angular acceleration is input, the rigid baffle will drive the outer wall of the flexible chamber to deform. The outer wall of the flexible chamber drives the П-shaped moving plate to move through the connecting arm of the moving plate. The differential capacitance formed by the L-shaped fixed plate, the П-shaped fixed plate and the fingers of the П-shaped movable plate can detect the rotation of the П-shaped movable plate. The differential capacitor fixed plate forms a fixed connection with the lower shell through its lower surface.

When the present invention works, the fluid chamber is filled with high-density liquid. When there is an angular acceleration in the vertical direction on the carrier connected to the whole structure, due to the action of fluid inertial force, the baffle will have a small displacement and offset, and the outer ring wall of the flexible chamber will deform accordingly, so that it is in line with the outer ring of the flexible chamber The angular displacement of the differential capacitive plates rigidly connected to the walls. By detecting the value change of the differential capacitance, the angular acceleration of the carrier can be measured.

From the above, it can be seen that the fluid in the present invention is almost sealed in the chamber, and no large displacement will occur. At the same time, due to the small mass of the differential capacitor plates, their mass inertia effect can be ignored. Therefore, the present invention operates under quasi-static conditions with a wide range of corresponding frequencies. The difference-finger type differential capacitance detection mechanism can detect the extremely small angular displacement of the capacitance-moving plate, so the present invention can obtain higher measurement accuracy. The capacitive angular accelerometer proposed by the invention can improve the measurement accuracy of the traditional angular accelerometer, improve the frequency response range and the applicable ambient temperature range, improve the performance of the angular accelerometer, and further promote the application range of the angular accelerometer.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention;

Fig. 2 is a three-dimensional view of the structure of the present invention after removing the upper casing;

Fig. 3 is a top view of the structure of the present invention after removing the upper casing;

Fig. 4 is a partial view of the A-A perspective in Fig. 3;

Fig. 5 is a side view of the upper case.

Detailed ways

As shown in FIG. 1 , the present invention includes: an upper casing 1 , a fluid chamber 2 , a differential capacitance dynamic plate 3 , a differential capacitance fixed plate 4 , and a lower casing 5 . The upper shell 1 and the lower shell 5 are fixedly connected together by bonding materials, wherein the fluid chamber 2 is surrounded by the inner ring wall 6 of the chamber, the outer ring wall 7 of the chamber and the baffle plate 10, and the differential capacitive plate 3 passes through The outer ring wall 7 of the chamber is connected to the lower casing 5 , the differential capacitor fixed plate 4 and the lower casing 5 are fixedly connected together, and the fluid chamber 2 is filled with high-density fluid.

As shown in Fig. 2 and Fig. 3, on the lower casing 5, there are differential capacitive dynamic plates 3, chamber inner ring wall 6, chamber outer ring wall 7, П-shaped fixed pole plate 8, L-shaped fixed pole plate 9, Baffle plate 10, rigid chamber outer wall 11, flexible chamber outer wall 12, moving plate connecting arm 13, П-shaped moving plate 14, П-shaped moving plate 15. The chamber inner ring wall 6 and the lower housing 5 form a fixed connection, and the chamber outer ring wall 7 is jointly surrounded by a rigid chamber outer wall 11 and a flexible chamber outer wall 12, and the rigid chamber outer wall 11 is wider than the flexible chamber outer wall 12. Three to five times larger. When angular acceleration is input, the rigid baffle 10 will drive the outer wall 12 of the flexible chamber to deform. The outer wall 12 of the flexible chamber drives the П-shaped movable plate 14 to move through the connecting arm 13 of the movable plate. The differential capacitance formed by the L-shaped fixed pole plate 9, the П-shaped fixed pole plate 8 and the fork 15 of the П-shaped movable pole plate can detect the rotation of the П-shaped movable pole plate 14. The differential capacitor fixed plate 4 forms a fixed connection with the lower casing 5 through its lower surface.

As shown in FIG. 4 , the baffle 10 is fixedly connected to the outer wall 12 of the flexible chamber, and there is a certain gap between the baffle 10 and the upper cavity 1 , the lower cavity 5 and the inner ring wall 6 of the chamber. The entire differential capacitance moving plate 3 forms a fixed connection through the moving plate connecting arm 13 and the outer wall 12 of the flexible chamber. There is a certain gap between the differential capacitor moving plate 3 and the upper case 1 , the lower case 5 , and the differential capacitor fixed plate 4 to ensure their mobility. All the fork fingers 15 of the П-shaped movable plate are connected to each other through the root 16 of the П-shaped movable plate.

When there is angular acceleration input in the axial direction of the micro-angular accelerometer of the present invention, the fluid filled in the fluid chamber 2 will push the baffle plate 10 to tilt, thereby driving the differential capacitive plate 3 connected to the outer wall 12 of the flexible chamber to move , through the detection circuit to measure the change value of the differential capacitance to obtain the value of the input angular acceleration.

As shown in Figure 5, there is a chamber 17 in the upper casing 1, and the height of the chamber 17 is exactly the same as the height of the differential capacitor fixed plate 4, the inner ring wall 6 of the chamber, and the outer ring wall 7 of the chamber, thereby ensuring a closed Fluid chamber space.

The size of the whole device varies from several millimeters to several centimeters, and the structure and working principle of the present invention are also applicable to macroscopic large-scale structures. The differential capacitive dynamic plate 3, the differential capacitive fixed plate 4, the inner ring wall 6 of the chamber, the outer ring wall 7 of the chamber, and the baffle 10 are all structures with a high aspect ratio, wherein the baffle 10, the differential capacitive dynamic plate 3 and the lower There is a certain gap in the casing 5 , and the differential capacitance fixed plate 4 , the inner ring wall 6 of the chamber, the outer ring wall 7 of the chamber and the lower casing 5 are fixedly connected. These structures are made of the same metal material, such as copper, nickel, and the like. The standard LIGA/quasi-LIGA process is used to fabricate the structure fixed to the lower plate, and the SLIGA or sacrificial layer LIGA process is used to fabricate a movable structure with a high aspect ratio.

The material of the upper shell 1 and the lower shell 5 is crystalline silicon or glass, and the inner chamber 17 of the upper shell 1 is made by precision machining technology, and can also be processed by wet etching.

The upper casing 1 and the lower casing 5 are bonded with an adhesive, or anodic bonding can be used to form a fixed connection. Before bonding, the fluid chamber 2 needs to be filled with high-density liquid as an inertial mass.

A relatively mature differential capacitance reading circuit in the prior art is used to obtain the value and variation of the differential capacitance, and convert the capacitance signal into a voltage signal.

Claims (8)

1. A capacitive microfluidic angular accelerometer, comprising: an upper housing (1), a fluid chamber (2), a differential capacitance dynamic plate (3), a differential capacitance fixed plate (4), a lower housing (5 ), characterized in that: the fluid chamber (2) is surrounded by the chamber inner ring wall (6), the chamber outer ring wall (7) and the baffle (10), the upper casing (1) and the lower casing (5 ) are fixedly connected together by bonding materials, the differential capacitive moving plate (3) is connected to the lower shell (5) through the outer ring wall (7) of the chamber, and the differential capacitive fixed plate (4) and the lower shell (5 ) are fixedly connected together, and the fluid chamber (2) is filled with high-density fluid. 2. The capacitive microfluidic angular accelerometer according to claim 1, characterized in that a differential capacitive plate (3), a chamber inner ring wall (6), and a chamber outer ring are distributed on the lower housing (5). Wall (7), Π-shaped fixed plate (8), L-shaped fixed plate (9), baffle plate (10), rigid chamber outer wall (11), flexible chamber outer wall (12), movable plate connecting arm (13), Π-shaped movable pole plate (14), Π-shaped movable pole plate (15), the inner ring wall (6) of the chamber and the lower shell (5) form a fixed connection, and the outer ring wall (7) of the chamber is made of rigid The chamber outer wall (11) and the flexible chamber outer wall (12) are jointly enclosed, and the rigid chamber outer wall (11) is three to five times wider than the flexible chamber outer wall (12). 3. The capacitive microfluidic angular accelerometer according to claim 2, characterized in that the baffle (10) and the outer wall of the flexible chamber (12) are fixedly connected, and the baffle (10) and the upper cavity (1), There are gaps in the lower cavity (5) and the inner ring wall (6) of the cavity. 4. The capacitive microfluidic angular accelerometer according to claim 2, characterized in that all the fingers (15) of the Π-shaped movable plates are connected to each other through the roots (16) of the Π-shaped movable plates. 5. The capacitive microfluidic angular accelerometer according to claim 1 or 2, characterized in that, the entire differential capacitive moving plate (3) is fixed by the moving plate connecting arm (13) and the outer wall of the flexible chamber (12). connect. 6. The capacitive microfluidic angular accelerometer according to claim 1 or 2, characterized in that the differential capacitance dynamic plate (3) and the upper casing (1), the lower casing (5), and the differential capacitance fixed plate (4) There is a gap between them. 7. The capacitive microfluidic angular accelerometer according to claim 2 or 3, characterized in that, when an angular acceleration is input, the rigid baffle (10) will drive the deformation of the flexible chamber outer wall (12), and the flexible chamber outer wall (12) Drive the Π-shaped movable pole plate (14) to move through the movable pole plate connecting arm (13), and the L-shaped fixed pole plate (9), the Π-shaped fixed pole plate (8) and the Π-shaped movable pole plate fork ( 15) The formed differential capacitance can detect the rotation of the Π-shaped movable pole plate (14), and the differential capacitance fixed pole plate (4) forms a fixed connection with the lower casing (5) through its lower surface. 8. The capacitive microfluidic angular accelerometer according to claim 1, characterized in that there is a chamber (17) in the upper housing (1), and the height of the chamber (17) is just in line with the differential capacitance fixed plate (4 ), the chamber inner ring wall (6), and the chamber outer ring wall (7) have the same height, thereby ensuring a closed fluid chamber space.

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