RU2746112C1 - Solid state linear acceleration sensor - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment and can be used in micromechanical linear acceleration sensors. The center plate assembly located between the stationary outer plates is integrally formed. The outer frame and the inner part are formed, connected through elastic elements. An additional contour frame of variable thickness and width is attached to the outer side of the fixed outer plate. Areas of attachment to the formed substrate and to the fixed outer plate are formed.

EFFECT: improving the accuracy of measuring linear accelerations.

1 cl, 4 dwg

Description

The invention relates to measuring technology and can be used in micromechanical linear acceleration sensors.

Known is a sensitive element of an integral accelerometer, made of monocrystalline silicon, containing a pendulum, an outer frame connected to the pendulum through elastic elements, glass plates located on both sides of the outer frame, forming a pendulum displacement transducer [1].

The main function of the elastic elements is to provide the suspension of the inertial mass, while the parameters of the elastic elements must be stable during operation. The main disadvantage of this design is its high sensitivity to thermomechanical stresses. This significantly affects the stability of the zero signal and the measurement accuracy of the parameter itself, that is, the linear acceleration. As a result, the zero offset increases and, as a result, the accuracy of the instrument as a whole decreases.

Known is a sensitive element of an integral accelerometer made of monocrystalline silicon in the form of an inertial mass (pendulum) having two arms and suspended on elastic cruciform torsion bars with a cross-section in the form of an X-shaped profile operating in torsion, an external frame to which elastic torsion bars are connected, glass covers to which the outer frame is attached. At the same time, platforms for attaching glass plates are formed on the outer frame, located along the axis of the torsion bars, at the points of their conjugation with the outer frame [2].

One of the disadvantages of the sensitive element of the accelerometer is its high sensitivity to low and high temperature influences. With an increase or decrease in operating temperatures, the elastic cruciform torsion bars of the sensing element are shortened or lengthened. Since the elastic torsion bars are rigidly connected, on the one hand, with the inertial mass, and on the other hand, with the outer frame, while the latter is rigidly connected to the glass plates, the resulting deformation is applied to the inertial mass (pendulum), which ultimately deforms the latter ... As a result, a signal appears at the output of the displacement transducer, in the absence of acceleration applied to the inertial mass, or an additional signal when subjected to linear acceleration, i.e. an error in the measurement of the useful signal appears. From all this it follows that the accuracy of measuring the linear acceleration is significantly reduced.

Another disadvantage is the presence of stress concentrators at the joints "elastic torsion-inertial mass (pendulum)" and "elastic torsion-external frame". This, in turn, reduces the strength of the structure of the sensitive element as a whole, which, at certain maximum shock loads or vibrations, leads to the destruction of the sensitive element.

Another disadvantage of this device is that after the anodic connection of the silicon sensitive element of the micromechanical accelerometer with glass plates, the residual stress arising in the silicon-glass junction deforms the elastic elements that move the inertial mass, which increases the level of the zero signal. This reduces the accuracy of the instrument.

A device is known that includes first and second stationary outer plates, each of which has fixed electrodes located on the inner surfaces, and a central plate assembly located between the stationary outer plates. The center plate assembly includes an upper center plate and a lower center plate. The upper and lower center plates have an inner part, an outer frame located outward from the perimeter of the inner part, a set of springs connecting the outer frame to the inner part, and a center electrode located on the outer surface of the inner part. The set of springs is thinner than each of the inner and outer frame [3].

The disadvantage of this device is its increased sensitivity to operating temperature factors.

The problem to be solved by the invention is to increase the accuracy of measuring linear accelerations.

To achieve this, in a solid-state linear acceleration sensor, comprising, a base, first and second stationary outer plates, and a center plate assembly located between the stationary outer plates including an upper center plate and a lower center plate that include an outer frame and an inner portion, connecting with each other by elastic elements., according to the invention, the central plate assembly

located between the stationary outer plates is formed in one piece, in which the outer frame and the inner part are formed, connected through elastic elements, in addition, an additional contour frame of variable thickness and width is attached to the outer side of the stationary outer plate, consisting of flexible sections, and formed the pads for attachment to the formed substrate are located outside the additional contour frame or inside the additional contour frame. Formation of the central plate assembly in one piece improves manufacturability, since it does not require the connection of the upper and lower central plates used in the prototype. In addition, the formation of such a configuration will make it possible to form a symmetrical device. Formed additional contour frames of variable thickness and width, consisting of flexible sections, act as decoupling structures when exposed to negative and positive temperatures. In this case, the accuracy of the device is significantly increased, since the additional contour frames are micro-moved by flexible sections between the fixed outer plate and the substrate. Such a device is subject to minimal deformation when exposed to temperatures. This minimizes temperature error. Hence, it improves accuracy. Thus, the formed structure significantly increases the accuracy.

The proposed solid-state linear acceleration sensor is illustrated by the drawings shown in FIG. 1a, 1b, 2a, 2b, 2c 3a, 3b, 4. In Fig. 1a, 1b schematically depict options for a solid-state linear acceleration sensor.

FIG. 2a, 2b, 2c - schematically depicts options for an additional contour frame of variable thickness and width, in Fig. 3a, 3b schematically depict variants of the central plate assembly; FIG. 4 - the first and second fixed outer plates are schematically shown, where:

1 - inner part,

2 - outer frame,

3 - elastic elements,

4 - the first fixed outer plate,

5 - the second fixed outer plate,

6 - additional contour frame,

7 - upper electrode,

8 - lower electrode,

9 - central electrode,

10 - substrate,

11 - flexible sections,

12 - platforms for attachment to the second fixed outer plate,

13 - pads for attachment to the substrate.

The solid-state linear acceleration sensor contains an inner part 1, connected through elastic elements 3 to an outer frame 2. On one side of the outer frame 2, a first fixed outer plate is connected 4. On the other side of the outer frame 2, a second fixed outer plate 5 is connected. from separate flexible sections 11 (Fig. 2a, 2b, 2c). Moreover, the additional contour frame 6 is connected to the substrate 10 through the attachment sites to the substrate 13. Through the attachment sites to the second stationary outer plate 12, the additional contour frame 6 is connected to the second stationary outer plate 5. On both sides of the inner part 1, electrodes 9 are formed. An upper electrode 7 is formed on the outer plate 4. A lower electrode 8 is formed on the second stationary outer plate 5. The stationary outer plate 5 is connected to an additional contour frame 6, which is connected to a substrate 10 attached to a base (not shown).

The central plate assembly can be, for example, represented as a pendulum connected to the outer frame 2 through elastic elements 3. The pendulum is represented as an inner part 1 (Fig. 3a). Another example of a variant of the central plate assembly is a two-arm pendulum connected to the outer frame 2 through elastic elements 3 (Fig. 3b). The two-arm pendulum is shown as the inner part of l. Ha fig. 1a shows a variant of a solid-state linear acceleration sensor with variants of an additional contour frame 6 with the variants shown in FIG. 2a, fig. 2b - with the attachment pads 13 located outside the additional contour frame 6. FIG. 1b shows a variant of a solid-state linear acceleration sensor with a variant of an additional contour frame 6 with the variant shown in FIG. 2c - with the attachment pads 13 located inside the additional contour frame 6.

A solid-state linear acceleration sensor works as follows. Under the action of linear acceleration, the inner part 1 deviates from its neutral position. Elastic elements 3 are twisted at a certain angle. The resulting imbalance of the differential capacitive displacement transducer, implemented on the first stationary outer plate 4, the second stationary outer plate 5 and the inner part 1 with the electrodes 7, 8, 9 formed on it, is proportional to the magnitude of the measured acceleration.

When a solid-state linear acceleration sensor is exposed to harmful external factors - negative and positive temperatures, stresses arise in the base (not shown). Thermomechanical stresses are transmitted from the base through the substrate 10. The resulting deformations from these stresses are transmitted to an additional contour frame 6 then to a fixed outer plate 5. Since the additional contour frame 6 consists of separate flexible sections 11 (Fig. 2a, 2b, 2c), then the deformation of these flexible sections 11 occurs. Thus, a large proportion of the deformations are filtered by the flexible sections 11 and the minimized deformation is transmitted to the elastic elements 3. The effect of mechanical stresses on the elastic elements 3 is practically zero. The noted properties confirm the advantages of the claimed invention over the known solutions.

A solid-state linear acceleration sensor can be made of monocrystalline silicon with a wafer orientation <100> ÷ <110> by anisotropic etching or plasma etching. The prototype tests carried out showed a positive effect of both this micromechanical sensor and its assembly method both in manufacturability and accuracy, that is, in reducing the offset of the zero signal.

Information sources:

1. RF patent No. 106 001.

2. RF patent No. 225 1702.

3. US patent No. 9752900 - prototype.

Claims (1)

A solid-state linear acceleration sensor containing, a base, a first and second stationary outer plates and a central plate assembly located between the stationary outer plates, including an upper central plate and a lower central plate, which include an outer frame and an inner part, which are interconnected by elastic elements characterized in that the central plate assembly located between the stationary outer plates is formed in one piece, in which the outer frame and the inner part are formed, connected through elastic elements, in addition, the formed additional contour frame of variable thickness is attached to the outer side of the stationary outer plate and width, consisting of flexible sections, and the formed areas of attachment to the formed substrate are located outside the additional contour frame or inside the additional contour frame.

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