RU2794992C1 - Strain gauge force sensor - Google Patents

Abstract

FIELD: instrumentation

SUBSTANCE: can be used to create accurate, noise-free, compact and high-tech strain gauge sensors for measuring weight and force. The sensor can be used in weighing technology and for commercial weighing, as well as in test technology for measuring forces in two directions. The sensor is made in the form of a washer, inside of which a parallelogram mechanism, monolithically connected with it, is formed, consisting of two parallelograms operating in parallel, which are monolithically connected with the periphery of the washer at one end, and others - with the power supply node of the sensor. The parallelogram mechanism is formed with the help of two U-shaped grooves located oppositely, and four blind identical holes on both sides of the washer, arranged in pairs and symmetrically and parallel to the O-O axis of the washer and perpendicular to the grooves and connected in pairs by blind slots located parallel to the planes of the washer, on which releases are made, the height of which h is determined by the deflection of the parallelogram mechanism when exposed to one and a half times the rated load, and the diameters ∅ are two mm higher than the largest two times the size from the center to the edge of the parallelogram mechanism.

EFFECT: increased noise immunity of the sensor from parasitic torques and bending moments at its input, as well as increased measurement accuracy due to the monolithic design of the entire structure. The cylindrical shape of the sensor makes it possible to simplify the manufacturing technology and make it a group one, as well as to simplify the sealing of sensors using profiled membranes.

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Description

The invention relates to measuring technology, namely to devices for measuring weight and force.

Known strain gauge force sensor [1], containing an elastic element (UE) in the form of a parallelogram with a bridge of strain gauges (TP) and control resistors. The disadvantage of such a sensor is that the SE is not protected from a parasitic torque that twists both beams of a parallelogram, as well as from a reactive moment at the place of its attachment, which also affects the measurement accuracy.

The closest in technical essence to the proposed invention is a force sensor, consisting of two elements [2]. In it, the UE is made in the form of a double-bent beam, which is inserted into a parallelogram mechanism. This sensor is better protected from parasitic torques associated with the eccentricities of the applied loads, but its metrological performance is significantly lower due to the non-monolithic design of the parallelogram mechanism and the unstable behavior of the pinched ends of the beam.

The objectives of the invention are: improving the noise immunity and accuracy of measurements, as well as simplifying the technology of manufacturing and sealing the sensor.

The objectives are achieved by the fact that the UE is made in the form of a washer, inside of which there is a parallelogram mechanism, consisting of two parallel parallelograms, with one end monolithically connected to the periphery of the washer, and with the other ends - with a power input unit, monolithically combining two parallelograms into a single whole with the washer.

The goals are also achieved by the fact that the parallelogram mechanism is formed using two “P”-shaped grooves, which are located opposite, and four blind holes of the same diameter on both sides of the washer, located in pairs - symmetrically and parallel to the O-O axis of the washer and perpendicular to the grooves, and connected in pairs by blind slots, which are parallel to the planes of the washer.

To limit the overload on both sides of the washer, releases are made, the height of which - h is determined by the deflection of the parallelogram mechanism when exposed to one and a half times the rated load, and the diameter ∅ by 2 mm exceeds the largest two-fold size L max from the center to the edge of the parallelogram mechanism. On FIG. 1 shows the views of the sensor: front, top, section A-A, LMax, P1 and P2. On FIG. 2 - el. TP bridge circuit, adjusting resistors of the bridge-Rb, Rt, Rt, Rb, (a-b) - supply voltage of the bridge-Epit., (c-d) - sensor output signal-Uout.

The sensor consists of two monolithically connected parallelograms P1 and P2, on which strain gauges R1 and R2 are fixed on P1 and R2 and R3 on P2. Parallelograms P1 and P2 are monolithically connected at one end to the periphery of the washer, on which the resistors Rb and Rt1 are located, and at the other ends to the power supply unit, on which the resistors Rch and Rt2 are fixed.

Strain gauges R2 and R4 perceive the deformation of one sign, for example, compression, and R1 and R4 of the other - tension (the sign depends on the direction of the force). They are interconnected by a bridge. The adjusting resistor R6 is used to balance the bridge, Rt1 for temperature compensation of the zero signal, Rt2 for temperature compensation of the output signal, and Rv for normalizing the output signal. To suppress common-mode noise, RT2 and Rb are divided into two parts and included in each of the bridge power diagonals.

The operation of the sensor is as follows. When the force F is applied, the parallelogram mechanism and the strain gauges of the bridge are deformed. Their resistances change, for example: for R2 and R4 it decreases, and for R1 and R3 it increases. This leads to an imbalance in the bridge circuit, as a result, an output signal proportional to the measured force is formed on the output diagonal of the bridge. The value of the force F is judged by the value of the output signal.

In the case of a measurable force, as shown in Fig. 1 the sensor may not be fixed at its place of installation; in case of a different direction of force, the sensor should be fixed, for example, with bolts. To exclude possible overloads, releases are made on both sides of the washer, the height of which h is determined by the deflection of the end of the parallelogram mechanism when the sensor is loaded with a 1.5-fold load Fnom, and the diameter ∅ of the release should be 2 mm greater than the largest twofold size of the parallelogram mechanism.

The proposed force sensor has certain advantages in comparison with the known ones, namely:

1. Its noise immunity from parasitic torques and bending moments will increase.

2. The measurement accuracy will increase due to the solidity of the entire sensor design, as well as taking into account point 1.

3. The technology of manufacturing and sealing the sensor is simplified due to the cylindrical shape of the washer.

4. It is possible to implement a group manufacturing method.

Sources of information accepted by the author during the examination:

1. Auth. certificate No. 1198398, Mkl. G01L 1/22, 1985.

2. Pat. USA No. 3805604, class. 73-141, 1974.

Claims (2)

1. Strain gauge force sensor (TDS), containing an elastic element, a bridge of strain gauges and adjusting resistors, characterized in that the sensor is made in the form of a washer, inside of which there is a parallelogram mechanism consisting of two parallelograms operating in parallel, with one end monolithically connected to the periphery of the washer, and others - with a power-generating node, monolithically combining two branches of the parallelogram mechanism. 2. TDS according to claim 1, characterized in that the parallelogram mechanism is formed using two U-shaped grooves located oppositely, and four blind identical holes on both sides of the washer, arranged in pairs symmetrically and parallel to the O-O axis of the washer and perpendicular grooves and connected in pairs by blind slots located parallel to the planes of the washer, on which releases are made, the height of which h is determined by the deflection of the parallelogram mechanism when exposed to one and a half times the rated load, and the diameters ∅ by two mm exceed the largest twofold size from the center to the edge of the parallelogram mechanism.

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