SU690332A1 - Dynamometer - Google Patents

Description

(54) DYNAMOMETER

The invention relates to a power measuring technique and can be used as a power measuring kit in an electromechanical balance for various purposes. Known dynamometers containing a cargo-carrying beam with a bearing housing mounted on it. The beam is supported in the vertical direction by two magnetoelastic transducers mounted on the base plate. Pre-compression of the converters is provided by a tension screw spring connecting the beam to the plate and installed vertically along the lines, passing through the center of the bearing. The beam is attached to the vertical posts of the support pin by means of elastic hinges that have flexibility in the vertical direction. Magnetoelastic transducers perceive the almost completely vertical component of the force of the shaft and bearing interaction, and each converter undergoes additional compression deformation 1 during the loading of the beam. : The accuracy and sensitivity of this dynamometer is determined by the accuracy and sensitivity of magnetoelastic transducers. The linear range of measured forces is equal to the sum of the corresponding ranges of transducers. The dynamometer does not extend the working transform set, which is part of the full range, where the relative linearity error of the magnetoelastic transducer does not exceed a certain specified value. In addition, this dynamometer does not provide for the correction of additive errors due to changes in the power supply of magnetoelastic converters, fluctuations in ambient temperature and. etc. The advantage of the device is that with identical linear characteristics of the magnetoelastic transducers, the readings do not depend on the position of the point of application of the measured force in the beam.

The closest in technical essence is a dynamometer consisting of two identical bodies made in the form of a split bracket, in which magnetoelastic transformers of the transformer type with two mutually perpendicular windings are placed with preliminary compression. Shells are mounted on a base plate along its longitudinal axis. In addition, each housing is installed in a plate on two prismatic supports. A traverse with two prisms at the ends is installed in the upper part of the dynamometer. The traverse with its ends rests loosely on each body. The measured force acts on the pin, the traverse ball and through the support prisM1 g is transmitted to the housing, and each transducer in the process of loading the traverse undergoes additional compression deformation.

In this dynamometer, each body performs the function of a mechanical force divider in a given ratio, which allows stretching the linear part of the characteristics of the transducer and thereby reducing the upper limit of measurement towards higher values of the measured force. However, the expansion of the working range of the conversion does not occur, because with the expansion of the upper limit of measurement, the lower limit increases accordingly. numerically equal to the threshold of sensitivity. Correction of additive errors also does not occur.

The purpose of the acquisition. This is an increase in the accuracy of measurement by creating a dynamometer based on a monolithic beam, which has the property of expanding the operating range both upwards and downwards, has no additive errors and is not sensitive to possible landings of the point of application of the measured force along the longitudinal axis of the beam. For this purpose, the most effective and therefore widely used in practice method of extending the working range, based on the differential switch on of two converters, is commonly used. .

At one end of the beam, the support is located on the side opposite to the rule of force, and on the other.

From the end of the beam, from the side of the force, the elastic arm at the first end of the beam, which interacts with the sio-measuring transducer and sometimes, as well as the elastic shoulder at the second end of the beam, interact with the measuring transducer, side opposite to the direction of the vortex, and the elastic shoulder at the first end of the beam, interacting with the force transducer, as well as the elastic pl & at the tff end of the beam, interacting with the support and force measuring with a reformer, located in relation to the neutral layer of the beam from the action of force.-.

Fig. 1 shows an descriptive dynamometer with magnetoelastic force-measuring, transducers, general view; in fig. 2 - linear characteristics of magnetoelastic compression transducers; in fig. 3 - linear characteristics of converters with different signs of the increment of the mechanical load; in fig. 4 - linear characteristic of a dynamometric beam with differential switching on converters with linear characteristics; in fig. 5 - dynamometric beam with predvaritel1 but strained magnetoelastic devices & in fig. 6 - beam. On- . laden with measurable force; in fig. 7 (essentially nonlinear characteristics, magnetoelastic transducers of squeezing; Fig. 8 - nonlinear characteristics of the transform: bodies with different signs of increment of the mechanical load; Fig. 9 - linear characteristics of the dynamometer with differential switching of the transducers with significantly nonlinear characteristics;

The dynamometer contains a monolithic beam 1 (dynamometric beam), sleep & in its middle part with a power-receiving element 2, made in the form of a receiving platform (Fig. 1). The beam is about its ends on rack 3 through prismatic supports 4 and 5. One of the supports is fixed, the adress is self-regulating with. The ends of the beam have cuts 6 located along its neutral plane and directed from the end faces to the pentrue of the same beam, i.e. to point C. Each raerez at the end of the beam passes into a cylindrical cavity 7, designed

to install the sensing element Through the entire surface of the end face of the beam is made through the slot 8,

Thus, cut 6, cavity 7 and slot 8 form at each end of the beam of the elastic shoulder 9. Between the elastic shoulders in each cavity 7 with a mouthpiece, a sensing element 10 is installed, a magnetic-elastic transducer of the transformer type with mutually perpendicular magnetizing and signal windings. Each transducer is fixed in the corresponding cavity with the help of a clamping device consisting of a lining 11, a ball 12. and a screw 13.

In the cavity located at the left end of the beam, a magnetoelastic transducer of the positive increment of the mechanical load is installed, and in the cavity located at the right end of the bar, the magnetoelastic transducer of the negative increment of the mechanical load is installed.

The elastic arm 9 on the left end of the beam, which interacts with the transducer of the positive increment of mechanical load and the supporting prism 4 of the rack, is located relative to the neutral plane of the curved beam on the side of its stretched fibers, i.e. from the side opposite to the direction of the force. Another elastic shoulder on the left side of the beam that only interacts with the converter is located on its compressed fibers, i.e. by the action of force.

The elastic arm on the right end of the bar, interacting through the Support prism 5 with the stand and with the negative increment converter of the mechanical load, is located relative to the neutral plane of the bent beam on the side of its compressed fibers. Another elastic shoulder on the right end of the beam, which interacts only with the negative increment converter of the mechanical load, is located on its stretched fibers.

The measuring windings of magnetoelastic transducers are connected in series and counter, and the magnetizing windings are connected in parallel and powered by an alternating current of industrial windings.

nsA frequency.

The dynamometer works as follows

way ..

The magneto-elastic transducers are fitted with an iB hollow beam with a pre-screw. The tension is created with the help of a pressure screw 13 due to the elastic deformation of the arms of the 9th beam. At the same time, the elastic shoulders of the right side of the beam are bent by force 1, the preliminary tension of the transducer is 1 P, and the elastic shoulders of the left part by force 1 (the preliminary tension of the transducer

0 2 P (see Fig. 5).

The absolute magnitude of the preload tension of each converter is selected as follows.

five

If the characteristics of the transducers are straight lines of the same slope {fig. 2), then the right-side converter 1 P is clamped by the force Pjrj with a sufficiently large margin

0 linearity used in the future when unloading the converter. This force corresponds to the output voltage Ijjn of the measuring winding of the converter.

five

The left co-decorator 2 P is clamped by the RPI force so that the output voltages of the 9 signal windings of the transducers are equal in sign and the absolute value, i.e. zn.

0

If the characteristics of the transducers are curvilinear (Fig. 7), then the right transducer 1 P is clamped by a sufficiently large in magnitude by the force Rjn, which allows

5 use this converter in unloading mode to the point corresponding to its maximum sensitivity.

The left transducer 2 P is clamped by the force of Р2П so that the sensitivity of the transducer at this load point is maximum. The best option would be when the increments of LC and D (for weekends, for example,

5 Research institutes for unloading, respectively, the right and the load of the left transducers of the same force will be equal in magnitude and opposite in sign,

In the case of using nonlinear transducers, the output voltages and; the corresponding forces of the preliminary tension and of the P; p will be different in absolute value.

five

Consider each elastic shoulder as a straight spring, clamped at one end and loaded with the force of preload and other end. 7; find the first BO BO: the deformation of the shoulders (Fig. 5); The displacement of point A by the application of force Pjp is due to the deformation of the elastic arm of the RLP; the rigidity of the elastic arm at point A; shoulder length from embedment to the point of application of the force P., is the modulus of the longitudinal elasticity of the material of the timber; mmeite inertia of the cross section of the shoulder relative to the neutral axis. The initial displacements of the points b, c, and d of the application of the forces Rn and Ran are determined in a similar way. We find the quantity S, characterizing the opening of the elastic arms along the load axis of the magnetoelastic converter. For the right side of the beam we have l - - C / V / 7 tlp "-U / b -, FOR the left side of the beam:. where) l is the height of the beam. Measured force P acts on a dynamometric beam through the gruyeo receiving platform 2. At the same time, the monolithic beam from the supporting prisms 4 and 5 is acted upon by the reaction forces RI and R Under the action of these forces, the beam undergoes a deformation of the transverse bend, while the curvature of the elastic arms located on the side of the stretched fibers of the beam, decreases, and the curvature of the elastic arms located on the side of the compressed fibers of the beam increases {see FIG. b); : The force perceived by each transducer in the process of bending a monolithic beam depends on the magnitude of the deformations of that uniform arm, which interacts only with the transducer. We write down the expression for the determination of the full displacement of the point B of the elastic arm located at the left end of the beam with a hundred compressed fibers. 2 l 60 I MO L / L Т60 (AO} С Р (Р .-. МР. Л2 .П г - (p,, - (,) (: where will we find the increment of the force, szhipriyayut transforming the basic reaction RZDR, ft. Let us write an expression for determining the total displacement of the point C of an elastic arm, pa; located on the right end of the beam from its stretched outshocks. С CQ. I Cl, {4.0)) Л - Р Г fn-c, (Р, ,,) R. .. from where we find a clutch of forces; compressing the converter 1 P under the action of the support reaction R OTH. -F way, both magnetoelastic converters under the deformation of the beam under the action of the measured force P are loaded with compression By applying force, however, the sign of the increment of mechanical yagruaki, and therefore, the output voltage of them is different (Fig. b). Under the action of the measured force, the 1 P converter mounted on the right end of the beam is somewhat unloaded. With afovi, the force compressing the core of the converter, is equal to Р,, Р ,, -coeff LL. jdv / of the unit of power transfer of the right-hand transformation gel with a negative increment of mechanical load; and 5 is the distance from the point of application of the measured force to the beam to its straight supports. The output voltage of the right transducer 1 P is equal (Fig. 3 and 8). (4) Under the action of the measured force, the 2 P transducer mounted on the left end of the beam is somewhat loaded, and the force compressing the seryetchnik-preformer is equal to 6g, ДР, Р, п Л-, R., where I am transmitting left transducer with a positive increment of mechanical load. The output voltage of the left converter 2 P is equal to (Fig. 3 and 8). The resultant voltage of the two receivers with differential activation of the measuring windings is H; () - (. (((. Let's analyze the equations 1), (2), (3) (5U; and (t). If the fuzziness of the transforms is the same and their characteristics are linear (FIG. 3), then iriUnpcp s-4 and .a. A-6L prirascheni u and Lg5: m of mechanical load are equal and opposite in sign, et al. - K, P -; K P LR, Since in an atom case the increments uU h uUt of the output voltages are also opposite and opposite Here, p 32 the resulting voltage is defined as (; (/; formula (8) it follows that the sensitivity of a dynamometric differential beam is two times lower than the sensitivity of converters. The characteristic of a beam with linear, converters is also linear and goes out of origin) (Fig 4) The use of a dynamometer extends the upper measurement limit of the transducer by four times (K-.), And the lower limit due to the sensitivity threshold is only doubled. This contributes uve. the full range of FP transformations in half. The sensitivity of a dynamometer with linear transducers does not depend on the change in the position of the point of application of the measured force P to the beam, which is obvious (Fig. 3). If the characteristics of converters 1 П and 2 П are curvilinear with the same character of change in sensitivity /, then equal and opposite in sign of the increments Rp and Rp2 of the mechanical load of the transducers cause the corresponding increments U U and UU of output voltages that are opposite to the sign but not equal in magnitude ( Fig. c). The differential inclusion of non-linear transducers operating on identical parts of the output characteristics leads to the fact that the non-linearity faults, with strict equality of the sensitivities of both transducers, are mutually corrected. The characteristic of a dynamometer with non-linear converters is linear, - ao comes out from the origin of the coordinate, and with some; offset (Fig. 9). The application of the dynamometer described allows to create sufficiently accurate,. Measurement and weighing instruments and does not have an additive component of the error measured. Changes in the ambient temperature, pianos magnetizing windings, weakening in the mechanical contacts of the device pre-press the magneto-resistant transducer, the aging of the material, etc. do not cause significant zero-metering device care due to the mutual correction of additive errors of converters. This makes it possible to refuse an automatic zero-setting device before measuring in instruments of class 0.5; 1 and rougher.

This dynamometer has the property of correcting errors due to the nonlinearity of the characteristics of TNC converters. The linearity error is reduced ten or more times.

Since a dynamometric beam on two supports is a statically determinable system, the movements of the point of application of the measured force P along the load-receiving platform that are possible during operation affect only the redistribution of the reference reactions P and P and does not lead to a Change in sensitivity. This improves the measurement accuracy of statistics and dynamic. reduces the design requirements of the power-transmission device.

Formula of Invention

A dynamometer containing a monolithic bar with cuts at the ends, passing into the cavities, in which load-bearing transducers are installed with a preliminary preload;

according to the differential scheme, for example, magnetoelastic force sensors, power receiving part and supports fixing the beam on the rack, characterized in that, in order to improve the measurement accuracy, at one end of the beam the support is located on the side opposite to the direction of the force, and at the other end timber from the side of the force, the elastic arm at the first end of the beam interacting with the force-measuring transducer and the support, and the elastic arm at the second end of the beam interacting with the force measuring transducer The tree is located. with respect to the neutral layer of the beam from the side opposite to the direction of the force, a is the elastic shoulder at the first end of the beam interacting with the force-measuring transducer, and the elastic arm at the second end of the beam interacting with the support and the force-measuring transducer is positioned relative to the neutral from the side of the action of force.

Sources of information taken into account in the examination

1. US patent number 3.495.453, cl. 73-141, 1970

2. USSR autograph certificate

No. 393962, - cl. From 01-fj 1/12, 1970.

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