RU84550U1 - DEVICE FOR TORQUE MEASUREMENT - Google Patents

Abstract

1. A device for measuring torque containing a shaft located in the housing with a torsion middle part, at the ends of which there are bushings with gear discs, protrusions and depressions in the form of annular sectors, diametrically arranged respectively, are made on the inner ends of these bushings, a light source is placed between the gear discs and on the outside there are two photodetectors, characterized in that the device is equipped with a torsional vibration damper, the elements of which are placed on the cylindrical surfaces of the protrusions of the bushings ok, and the torsion part of the shaft is removable and connected to the bushings by means of clearance-free couplings, while the end parts of the shaft are integral with the bushings. ! 2. The device for measuring torque according to claim 1, characterized in that the torsion part of the shaft is made in the form of a coil spring. ! 3. The device for measuring torque according to claim 1, characterized in that the clearance-free clutch is made in the form of a ring having low bending stiffness, mounted on the inner end surfaces of the bushings at two diametric points, while the torsion part of the shaft is attached to two other diametric points .

Description

The invention relates to the testing, research and diagnosis of machines with rotating shafts and can be used to record the magnitude of the torque in power plants, for example in turbo-piston engines.

Known devices for measuring torque are a system consisting of a sensor and a recorder. The primary converter in the sensors is a cylindrical shaft (torsion shaft). The conversion of the torsion shaft twist angle is usually carried out using gear discs [1, 2, 3, 6, 8]. Further conversion is provided by an optical channel [6, 8], including using differential gears [6], as well as various sensors [2, 3]. Apply other options for converting the angle of rotation of the torsion shaft - through an elastic beam and pneumatic nozzle [4], through cams with a plunger from the spools of the hydraulic system [5]. In specialized devices, the radial load of the bearing is converted to axial [7].

A common disadvantage of the known devices for measuring torque is a narrow measuring range along its lower boundary. This is mainly due to the use of a cylindrical torsion shaft. At low torques, the diameter of the torsion shaft is so small that it becomes impossible to constructively realize the sensor, or the design becomes unacceptably complex.

Another major drawback is related to the type of function of the measured moment M = f (t). In real devices, the moment is not a constant. There are two main measurement modes: stationary, when the parameters of the device under study on the motor and load sides are constant, and transitional (non-stationary), when one or more of these parameters is changed according to a given law (for example, cyclic tests).

In transient modes, the torque function is a wide range of component frequencies. The situation is similar for the stationary mode, because there are ripples of the moment due to the kinematics of the device under study, the friction instability, and the ripple of the engine moment (for example, piston). Thus, the torque function can always be represented by the expansion in the harmonic Fourier series with a wide range of harmonics (frequencies).

Having placed the sensor in the gap of the kinematic chain of the device under study, we obtain a system consisting of three elements:

I _dv -C _p -I _heat

where I _dv is the reduced moment of inertia of the rotating parts from the engine side;

C _in - the rigidity of the torsion shaft;

I _LOAD - reduced moment of inertia of the rotating parts on the load side.

This system is an oscillating link with its own (resonant) frequency

Where

Given a wide range of frequencies of the moment function, this frequency ω will appear in the frequency spectrum of the moment. Therefore, near the frequency ω, the sensor conversion function will be non-linear, which will lead to a decrease in measurement accuracy.

Analyzing known devices for measuring torque, one can also note the high complexity [1, 6] or the presence of mechanical hysteresis due to constant (Coulomb) friction [4, 5, 7] in the kinematic pairs of sensors.

The prototype is a device for measuring torque [8]. In the sensor of this device, the sensing element, as in analogues, is a torsion shaft having a cylindrical shape. At the ends of the shaft in the bearings are bushings with gear discs. A modulator in the form of gear disks with a drive is located on the axis parallel to the shaft, and in the gear zone of the bushings of the bushings and the modulator there is a light source and two photodetectors. The photodetectors are connected to the registrar, at the inner ends of the bushings there are made diametrically arranged protrusions and troughs in the form of ring sectors. The device is equipped with a channel registering the limiting value of torque. This channel includes electrical contacts on the protrusions of the bushings and, to provide an electric circuit with a recorder, electrically insulated slip rings on the bushings and fixed brushes.

The disadvantages of the device for measuring torque [8] are:

- constructive complexity due to two circumstances.

First: The torque limit detection channel is redundant. The metrological characteristics of the device will include the value of the upper limit of the measurement range less than this limit. The channel registers only the fact of sampling the angular clearance in the protrusions-depressions of the bushings. The user does not need this information in a metrological sense. Second: It is necessary to ensure a fixed connection of the bushings with the shaft. This can be realized either by a great interference, then the problem arises of ensuring the undeformed state of the torsion (small diameter) part of the shaft with a large pressing force, or by introducing additional fixation means, for example, keyed joints, then the accuracy problem arises related to mating over several surfaces;

- narrow measurement range. Given the above design features of the known device, we can conclude that it cannot be implemented to measure small values of torque. An attempt to expand the measuring range due to the shift of the sensing element will entail the manufacture of the entire set of parts located on the shaft, i.e. almost the entire sensor;

- low measurement accuracy near the resonant frequency of the system. At the resonance frequency, it may not be possible to measure. This imposes restrictions on the applicability of the device to certain research objects.

The proposed device largely eliminates the above disadvantages. The device for measuring torque consists of two units - a sensor and a recorder. The recorder is functionally a phase meter, which is implemented in the usual way.

The invention is illustrated by drawings. Figure 1 shows an axial section of a torque sensor; figure 2 is a section aa of figure 1; figure 3 is an expanded section bb In figure 2.

In the housing 1 using bearings 2 mounted composite torsion shaft. This shaft is represented by three main parts: the middle elastic part 3 (torsion bar) in the form of a coil spring and two bushings 4, 5 having shanks 6, 7 for mounting bearings 8, 9. The ends of the torsion bar (spring) are fixed to the inner end surfaces of the bushings with couplings in the form of an elastic ring 10. This ring is fixed by two bosses 11, 12 and is fixed to the sleeve (the fastening is the same for both ends) using screws 13, 14, and the spring is fixed to the ring using two other bosses 15, 16 and screws 17, 18 . All bosses are fixed on an elastic ring e by means of expanding (Figure 3).

The bushings have gear disks 19, 20. In the gear zone of these disks, a light source 21 and two photodetectors 22, 23 are fixedly mounted on the casing. For metrological certification and periodic verification, the production batch of torque sensors is equipped with a modulator, which is shown in Figs. rotating rotor 24.

The opposite ends of the bushings have protrusions 25, 26 diametrically arranged in the form of annular sectors on the sleeve 4 and 27, 28 on the sleeve 5. In this case, the protrusions of one sleeve enter the troughs of the other, forming an angular gap δ.

Torsional vibration dampers are installed on the cylindrical part of the protrusions of the bushings. A housing 30 with a lead 31 is fixed on the protrusion of one sleeve by screws 29. At the end of this lead there is a permanent magnet 32, which with a small gap enters the annular groove of the housing 33, fixed by screws 34 on the protrusion of the other sleeve. The case with an annular groove is made of a material with high electrical conductivity (aluminum, copper). Structurally, the damper bodies can be made integral and their parts are connected by screws 35, 36.

For ease of installation of the sensor elements, the bushings 4, 5 have windows 37, 38 on cylindrical and end surfaces.

Metrological certification and periodic verification of the torque sensor are carried out using a modulator 24. This procedure is carried out in static conditions. Consistently apply to the shanks 6, 7 of the sensor shaft different values of torque in the entire measurement range. In this case, in proportion to the applied moment, the spring 3 will twist and the relative rotation of the gear disks 19, 20 equal to this twist angle. The rotating rotor of the modulator 24 provides a variable optical flux of the light source 21. Sensing this flux of the photodetector 22, 23 generates sequences of electrical pulses. The pulses in the sequence of one photodetector are shifted relative to the pulses of the sequence of another. Their relative shift — the ratio of the shift time of the pulses in the sequences to the period of the sequences — is proportional to the applied torque. Thus, the output parameter of the sensor is the phase shift of the pulse sequences of the photodetectors 22, 23.

When the sensor is operating on rotating shafts, the modulation of the luminous flux of the source 21 is provided by rotating gear disks 19, 20. Moreover, there is no need for a modulator. The sensor is installed in the gap of the kinematic circuit of the investigated device between the source of torque (engine) and load (brake). Under the action of torque, the torsion part of the shaft (coil spring) experiences angular deformation proportional to the transmitted moment. Since this moment is variable with a wide spectrum, the natural frequency of the engine-sensor-brake system is in the frequency spectrum of the moment. Resonant torsional vibrations occur. When torsional vibrations occur, a relative movement of the permanent magnet 32 and the annular groove of the housing 33 appears. Resistance arises proportional to the relative speed of this movement (viscous friction). It is due to two factors: the first - due to the flow of air through the annular gap between the magnet and the channel, the second - due to the induction of eddy currents on the walls of the channels. The damper parameters are selected in such a way as to bring the oscillatory system closer to the aperiodic link. For this reason, the sensor conversion function remains linear.

During the rotation of the sensor shaft, the disks 19, 20 modulate the luminous flux of the source 21, as a result of the photodetector 22, 23 form a sequence of electrical pulses. If the torque is not equal to zero, then these sequences are shifted one relative to the other. A recorder connected to the outputs of the photodetectors captures the phase shift of the pulses of two sequences, which is proportional to the measured torque.

The proposed design of the device for measuring torque is quite simple, it implements a linear characteristic of the conversion of the sensor, which ensures the accuracy of the measurement. The shape of the sensing element in the form of a helical coil spring allows you to expand the measurement range in the lower region. The fastening of the sensitive element through the clearance-free coupling makes it possible to complete the device with interchangeable sensitive elements (torsions) of any shape (including cylindrical), thereby covering the required measurement range.

1. A.S. USSR No. 546798, class G01L 3/04. Device for measuring torque, bull. No.6 on 02.15.77.

2. A.S. USSR No. 647561, class G01L 3/04. Device for measuring torque, bull. No.6 on 02.15.79.

3. A.S. USSR No. 773463, class G01L 3/04. Device for measuring torque, bull. No. 39 dated 23.10.80.

4. A.S. USSR No. 798517, class G01L 3/04. Device for measuring torque, bull. No 3 on 01/23/81.

5. A.S. USSR No. 1229610, class G01L 3/04. A device for measuring the torque on the shaft, bull. No.17 on 05/07/86.

6. A.S. USSR No. 1265498, cl. G01L 3/04. Device for measuring the torque of a rotating shaft, bull. No. 39 dated 23.10. 86.

7. A.S. USSR No. 1774196, cl. G01L 3/04. Device for measuring torque, bull. No. 41 dated 11/07/92.

8. A.S. USSR No. 1357731, class G01L 3/04. A device for measuring torque, Bull No. 45 dated 07.12.87. - prototype.

Claims (3)

1. A device for measuring torque containing a shaft located in the housing with a torsion middle part, at the ends of which bushings with gear discs are installed, protrusions and depressions in the form of annular sectors, diametrically located respectively, are made on the inner ends of these bushings, a light source is placed between the gear discs and on the outside there are two photodetectors, characterized in that the device is equipped with a torsional vibration damper, the elements of which are placed on the cylindrical surfaces of the protrusions of the bushings ok, and the torsion shaft part is removable and connected to the bushings by means of clearance-free couplings, while the shaft end parts are integral with the bushings. 2. The device for measuring torque according to claim 1, characterized in that the torsion part of the shaft is made in the form of a coil spring. 3. The device for measuring torque according to claim 1, characterized in that the clearance-free coupling is made in the form of a ring having low bending stiffness, mounted on the inner end surfaces of the bushings at two diametric points, while the torsion part of the shaft is attached to two other diametric points .