RU2515378C1 - Micromechanical accelerometer - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: micromechanical accelerometer comprises a sensitive element, made of single-crystal silicon of low conductivity, an external frame with a pendulum fixed on it with the help of resilient torsions. The external frame has alternating width. In its narrow part there are U-shaped loops facing outside. The sites of fixation to glass pads on the external frame are arranged strictly on longitudinal and transverse axes of a sensitive element. In the micromechanical accelerometer there are round glass pads. This simplifies assembly and reduces labour intensiveness of the item.

EFFECT: increased accuracy with simultaneous reduction of labour intensiveness without change in mass and dimension parameters.

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Description

The invention relates to measuring technique and can be used in micromechanical linear acceleration sensors. Known micromechanical accelerometer containing a housing, a sensing element made of a frame coil, suspended in the housing on metal extensions, a displacement sensor of the frame coil.

The disadvantage of this device is the design complexity, low technology, low accuracy due to sensitivity to cross-linking [1].

Known micromechanical accelerometer containing a housing, a sensing element made of monocrystalline silicon in the form of an electrically conductive inertial mass, which is a pendulum suspended by torsion bars, which are connected to the outer frame by the other side. Torsion bars are made cross-shaped with a cross section in the form of an X-shaped profile. An external frame, uniform in width around the entire perimeter, on which there are platforms for attaching glass plates. The glass plates are rectangular, connected to the sensitive element by the method of anode landing [2].

The disadvantage of this device is that the anode connection of two glass plates with a silicon sensitive element is carried out at a temperature of over 450 ° C. After cooling the package of two glass plates and a silicon sensitive element, the deformation of the outer frame. This deformation is respectively transmitted to the elastic torsion bars. This significantly affects the stability of the elastic properties of the latter.

So, after joining, the emerging contact stresses affect the elastic suspension, due to which the instability of the zero offset increases and, as a result, the accuracy of the device as a whole decreases. Another drawback of this design is the influence of disturbing factors, in particular, plus and minus temperatures, and the design of the sensitive element will be deformed, which will lead to the emergence of instability of the zero signal, its high level. The stiffness of the torsion bars and, as a result, the steepness of the displacement transducer will also change. Another disadvantage is the use of rectangular plates. When assembling a package of two glass plates and a silicon sensitive element, difficulties arise in sequentially interfacing with each other the elements of the micromechanical accelerometer and their mutual fixation. Therefore, reduced productivity and increased complexity of the product. All this significantly reduces the accuracy of the device as a whole.

The problem to which the invention is directed, is to increase the accuracy of the micromechanical sensor and simplify the assembly of its nodes. To achieve this, in a micromechanical accelerometer containing a housing, a silicon sensitive element with an external frame mounted on it with elastic torsion pendulum, glass plates, mounting areas on the external frame, the external frame is made uneven in width, mounting areas are located on the sides and lower sides the outer frame, on the longitudinal and transverse axes of the sensing element, in its widest part, and between the lateral attachment pads and the attachment point of the elastic torsion bar on the outer U-shaped loops are formed to the outside, round glass plates are used, on which, on the one side, a recess for assembly is made on the longitudinal axis at the edge, and another recess is made in the opposite position in the place where the glass glass is welded, the tongue of the sensing element with an electric contact pad is located between two recesses intended for welding.

A sign that distinguishes the proposed micromechanical accelerometer from the known one is that the outer frame is made uneven in width with U-shaped loops facing outward, located between the side mounting pads and the fixing point of the elastic torsion bars on the outer frame. This allows you to significantly reduce the stress state on the elastic torsion bars, since a significant part of the deformation is concentrated in the connection site "mounting pad - U-shaped loop - the reverse end of the U-shaped loop". The deformations that occur in the lower wide part of the outer frame do not significantly affect the elastic torsion, because they are concentrated between the attachment sites and are transmitted again through the connection site “attachment site - U-shaped loop - back end of the U-shaped loop”. Therefore, to improve the fastening of the glass plates and simplify the assembly, the lower outer frame is formed wider in area. The use of round plates simplifies the assembly of the micromechanical accelerometer assembly, namely sequential pairing with each other of the elements of the micromechanical accelerometer and their mutual fixation with subsequent anode connection.

The proposed micromechanical accelerometer is illustrated by the drawings shown in figures 1, 2.

Figure 1 shows a silicon sensing element, where:

1 - outer frame;

2 - pendulum;

3 - elastic torsion bars;

4 - U-shaped loops;

5 - platforms for fastening to glass plates;

6 - electrical contact pad.

Figure 2 shows the sensing element with glass plates fixed to it, where:

7 - a recess for supplying an electrical conductor to the opposite lining;

8 - a recess for assembling two plates and a sensitive element into a package;

9 - language of the sensing element with an electric contact pad.

The micromechanical accelerometer contains a sensitive element made of single-crystal silicon of low conductivity, in which a pendulum 2 is fixed on the outer frame 1 through elastic torsions 3. On the outer frame 1, P is formed between the attachment points to the glass plates 5 and the attachment point of the elastic torsion 3 on the outer frame 1 -shaped loop 4 facing outward. The mountings to the glass plates 5 are located strictly on the longitudinal and transverse axes of the sensing element. The glass plates are round, mounted on the sensitive element through the mounting plate 5. On the glass plate, the recess 7 serves to lead the conductor to the opposite plate. Similarly, on the opposite cover. The recess 8 is necessary when assembling a package of two glass plates and a silicon sensing element. By sequentially interfacing with each other the elements of the micromechanical accelerometer, namely the glass plates, the silicon sensitive element and their mutual fixation, the necessary alignment accuracy is achieved, ensuring a minimum error. This configuration of the plates allows you to easily remove the snap after fixing the package in the device for anode connection. The electric contact pad 6 and the language of the sensing element with the electric contact pad 9 are used to connect with the pendulum 1 movement transducer.

Micromechanical accelerometer works as follows. When exposed to linear acceleration, the pendulum 2 of the silicon sensor deviates from its neutral position. In this case, the elastic torsion 3 is twisted at a certain angle. A signal processing circuit is implemented on the glass plates of the pendulum 2. When exposed to linear acceleration, an imbalance occurs between the top and bottom of the glass substrates. The magnitude of this imbalance is proportional to the measured acceleration.

Under the influence of harmful factors, such an arrangement of the U-shaped loops 4 and the attachment sites 5 on the outer frame 1 reduces the zero signal and its instability, and with the simultaneous action of the measured acceleration, it decreases the error of the slope of the characteristics of the device as a whole. The use of round glass lining simplifies assembly, reduces the complexity, provides the necessary alignment accuracy, reducing the error. Conducted prototype tests showed a positive effect of this device in terms of manufacturability and accuracy.

Information sources

1. Capillary accelerometer AK5-15, TU 611.781.TU. 1984 year

2. RF patent No. 106001 (prototype).

Claims (1)

A micromechanical accelerometer comprising a housing, a silicon sensing element with an external frame mounted on it with elastic torsion pendulum, glass plates, mounting areas on the external frame, characterized in that the external frame is made uneven in width, the mounting areas are located on the sides and lower sides the outer frame, on the longitudinal and transverse axes of the sensing element in its widest part, and between the lateral mounting platforms and the place of attachment of the elastic torsion bar on the outer frame U-shaped loops are formed, facing outward, using round glass plates, on which, on one side, a recess for assembly is made on the longitudinal axis at the edge, and on the opposite side, where the opposite glass plate is welded, another recess, the tongue a sensing element with an electric contact pad is located between two recesses of both plates, intended for welding.

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