RU2765520C1 - Method for determining the smoothness of gearbox rotation - Google Patents

Abstract

FIELD: mechanical engineering.SUBSTANCE: invention relates to mechanical engineering. The method includes measuring the vibration parameters of the gearbox; additionally, the vibration parameters of a known-good gearbox are measured. The measured vibration signal is presented as a spectral characteristic. After that, the vibration amplitudes are compared on the spectral characteristics of the investigated and known to be working gearboxes, while the comparison is carried out in the frequency ranges of gearing and rotation frequencies of the gearbox shafts, and the vibration amplitude of a known good gearbox is used as a criterion for the smoothness of rotation of the gearbox under investigation.EFFECT: determination of the smoothness of rotation of the gearbox is provided with the simultaneous identification of the source of vibration that introduces irregularity.1 cl, 4 dwg

Description

The invention relates to mechanical engineering, namely to checking the smoothness of rotation of gearboxes used in high-precision servo drives and is intended to assess the smoothness of rotation of gearboxes.

The tracking electric drive (EA), which provides (reproduces) with a given accuracy the movement of the executive body of the working machine in accordance with an arbitrarily changing input control signal, is widely used in modern technology, including: for antennas of radio telescopes, satellite communication systems, in metalworking machines, for driving robots and manipulators, in automatic measuring devices, as well as in weapon control systems. The transmission of motion from the engine to the actuator occurs through a mechanical transmission, usually through a gearbox. Since the servo gearbox operates in reverse mode, it is necessary to ensure shockless engagement in it. This guarantees smooth and silent operation, and hence the dynamic accuracy of the entire system. Thus, such quality of dynamics as smoothness comes to the fore. Work in this direction was carried out by I.I. Artobolevsky, V.A. Besekersky, B.V. Novoselov, B.K. Chemodanov, E.P. Popov, O.P. Mikhailov, V.V. Morozov, E.A. Novikov. Under the "smoothness" of the EP, according to should be understood as the absence of jerky motion at the minimum critical speed. Non-smooth movement at low speeds is associated with the instability of the friction process that occurs in the mechanical transmission of the EP, which in turn is caused by technological manufacturing and assembly errors. The effect of these errors on the smoothness is not so noticeable at high speeds of the electric drive due to the inertia of the load, which helps to overcome wedging. But if we consider the mechanical transmission separately from the EP with the load, then the unevenness manifests itself in the entire speed range in the form of noise and vibrations. However, the method currently used by some manufacturers of gearboxes consists in assessing the smoothness of the gearbox by the difference between the largest and smallest friction torques. In this case, control takes place directly on the gearbox by rotating the input shaft through a pulley with a cable and a dynamometer, which pulls the cable at low speed and controls the readings. The dynamometer readings are recalculated taking into account the leverage of the application of force into the magnitude of the moment. Sufficient smoothness is considered if the maximum and minimum torque values differ by no more than 2 times. As practice shows, this method does not have sufficient objectivity, as it depends on several factors:

- pulley rotation speed;

- pulley diameter (i.e. its moment of inertia);

- the angle of force application.

Despite the level of development of technology and means of technical diagnostics, this method cannot be automated and, as a result, its objectivity is very low due to the factors listed above. In addition, it should be noted that there is currently no unified method for assessing the smoothness of rotation of a mechanical transmission, described in the literature. Thus, there are prerequisites for developing a method for determining smoothness, which has sufficient accuracy and objectivity.

A known METHOD FOR DETERMINING THE SMOOTH OPERATION OF THE SPINDLE OF THE LATHE HEADTOCK (see patent RU No. 2 283 729, IPC V23V 7/00, V23V 3/00, 2006). The essence of the invention lies in the fact that an oxidized cylindrical roller is installed on the machine support, the diameter of which is equal to or greater than the diameter of the mandrel, equipped with a brake device. The axis of the roller is placed parallel to the line of the centers of the machine, and the holder is rigidly fixed on the support of the machine. The active oxidized cylindrical surface of the roller is pressed against the mandrel by means of the cross feed of the caliper, creating a braking torque on the roller, and the spindle is driven, as a result of which light stripes are obtained on the oxidized cylindrical surface of the roller. The proposed method for determining the smoothness of the operation of the spindle of the headstock of lathes is simple and illustrative, allowing timely control of the kinematic accuracy of the spindle of the headstock of lathes in production conditions by a turner working on this machine; allows timely detection of inaccurately manufactured or worn spindle drive links. However, this method is not universal for smoothness control, its use is limited to lathes. In addition, this method uses light stripes on the oxidized cylindrical surface of the roller to determine the smoothness, the width and angular pitch of which are very difficult to objectively measure. Therefore, it can be stated that the objectivity of this method is at a low level.

The closest in technical essence and the achieved result to the claimed solution is a method for determining the smooth running of passenger cars (OST 24.050.16-85). Ride smoothness indicators are determined based on the results of measurements of vibration parameters in the car body in the vertical and horizontal directions over the entire speed range. Then the values of the obtained indicators of smoothness are averaged for each speed of movement using mathematical transformations. The average at a given point of the car for the corresponding direction of oscillation, the indicator of smoothness of movement at each speed of movement should be no more than:

3,25 - для пассажирских вагонов локомотивной тяги, вагонов электро- и дизельпоездов, автомотрис, груженых вагонов метрополитена;

3.25 - for passenger cars of locomotive traction, cars of electric and diesel trains, railcars, loaded subway cars;

3,4 - для порожних вагонов метрополитена

3.4 - for empty subway cars

3,5 - для трамвайных вагонов

3.5 - for tram cars

The advantage of the method is to include accurate indicators of smoothness for each type of wagon, as well as the fact that smoothness is assessed over the entire range of operating speeds.

The disadvantage of this method is its lack of information content. That is, there is no exact information about the source of increased vibration, if any, because. according to the results of tests according to this method, only a conclusion is made about the compliance or non-compliance of the wagon in terms of smoothness.

The objective of this invention is to determine the smoothness of rotation of the gearbox while simultaneously identifying the source of vibration that introduces unevenness.

This is achieved by the fact that in a method that includes measuring the vibration parameters of the gearbox, for example, using a vibration analyzer, the sensor of which is located on the gearbox housing, the vibration parameters of a known-good gearbox are additionally measured. The measured vibration signal is presented as a spectral characteristic. After that, the vibration amplitudes are compared on the spectral characteristics of the investigated and known good gearboxes, while the comparison is carried out in the ranges of gearing frequencies and speeds of the gearbox shafts, and the vibration amplitude of the known good gearbox is used as a criterion for the smoothness of rotation of the studied gearbox.

In the proposed method for determining the smoothness of rotation of the gearbox, the result is achieved by choosing a known good gearbox, i.e. having the necessary smoothness of rotation, for example, according to positive test results, it is part of a servo drive. At the same time, it is known that errors in the manufacture of parts and errors in the assembly of the gearbox lead to noise and vibrations, which characterize smoothness. Therefore, then the measurement of the vibration characteristics of a known-good gearbox is carried out, based on the results of which a reference spectrum is built by giving individual narrow ranges, corresponding to the frequency ranges of gearing and speeds of the gearbox shafts, to the maximum allowable value. Next, the vibration characteristics of the verified gearbox are measured and its amplitude is compared with the amplitude of the reference spectrum. The excess of the amplitude over the reference spectrum in the frequency range corresponding to the gearing frequency indicates the need to refine or replace this gear pair. Thus, this method allows you to determine the smoothness of rotation and identify the source of vibration in comparison with the prototype.

In FIG. 1 shows a diagram of a device that implements the proposed method, in Fig. 2 - reference spectrum, in Fig. 3 - spectrum of vibration of the researched reducer, in fig. 4 - result of comparison with the reference spectrum

The circuit includes a vibration sensor 1, a gearbox housing 2, a vibration analyzer 3, an electric motor 4, a gear of the first stage of the gearbox 5, a gear of the second stage of the gearbox 6, a gear of the first stage of the gearbox 7, a gear of the second stage of the gearbox 8, an intermediate shaft 9 and an output shaft 10 .

The implementation of the proposed method is carried out as follows. First, a known-good gearbox is selected, for example, according to the test results as part of a servo drive. Then, its vibration studies are carried out, for which the vibration sensor 1 is fixed on the housing 2 of the operating gearbox. It receives a signal proportional to the vibration acceleration of the gearbox. The vibration analyzer 3, connected to the sensor 1, receives a signal from it and processes it according to the appropriate algorithm, for example, according to the Fourier transform method. Thus, a vibration spectrum of a known good gearbox is obtained, the smoothness of rotation of which ensures the requirements for the application. Further, knowing the frequency of rotation of the motor shaft, the frequency of gearing of each stage of the gearbox and the frequency of rotation of the shafts, the limiting values of vibration are determined, on the basis of which the reference spectrum of a known-good gearbox is built. The resulting reference spectrum is then used as a smoothness criterion for gearboxes of a similar design. Rejection of gearboxes according to the criterion of smoothness of rotation occurs by comparing the reference spectrum (of a known good gearbox) and the vibration spectrum of the gearbox under study.

Example. An experimental verification of the proposed method was carried out for a two-stage gearbox as follows. According to the test results, a gearbox was selected as part of the servo drive, the smoothness of rotation of which allows meeting the requirements for the accuracy of the drive. Then, for this gearbox, using a vibration analyzer, the vibration parameters were measured in terms of vibration velocity. Using the Fourier transform, the spectrum of vibration velocity was obtained in the frequency range of gear gearing. Of the entire spectrum, the most interesting are: the rotational speed of the electric motor 4, the gearing frequencies of the gears 6, 6, the gears 7, 8 and the rotational speeds of the shafts 9, 10, determined by the formulas:

f _tooth1 =f _D ×z ₁

where f _tooth1 - gearing frequency of the first stage of the gearbox, Hz;

f _d - frequency of rotation of the motor shaft, Hz;

z ₁ - the number of teeth of the first stage gear

In our case f _tooth1 =40x22=880 Hz

The gearing frequency of the second stage will be equal to the product of the output shaft speed and the number of wheel teeth:

f _tooth2 \u003d (f _D × z ₁ / z ₂ × z ₃ / z ₄ ) × z ₄

z ₂ - the number of teeth of the wheel of the first stage

z ₃ - number of gear teeth of the second stage

z ₄ - the number of teeth of the wheel of the second stage

f _tooth2 =(40×22/78×18/66)×66=203 Hz

The speed of the intermediate shaft is equal to the product of the speed of the motor shaft and the gear ratio of the first stage:

f _prom \u003d f _{D ×} z ₁ ) / z ₂

f _prom \u003d 40 × 22 / 78 \u003d 11.3 Hz

The speed of the gearbox output shaft is defined as the product of the gearbox shaft frequency and its gear ratio:

f out \ _u003d f _D × z ₁ / z ₂ × z ₃ / z ₄

f out \ _u003d 40 × 22 / 78 × 8 / 66 \u003d 3.1 Hz

Thus, the frequencies of interest to us are: 3.1 Hz; 11.3 Hz; 40 Hz; 203 Hz; 880 Hz. For each of them, based on the results of checking a known-good gearbox, the limit values of the vibration velocity amplitude were set:

The reference spectrum was constructed from the limiting values (Fig. 2). To check the smoothness of rotation of the tested gearbox, the spectrum of its vibration velocity was obtained (Fig. 3). On the spectrum are:

f _rev - rotational frequency of the input shaft

f _tooth1 - gearing frequency of the first stage of the gearbox

f _tooth2 - gearing frequency of the second stage of the gearbox

2f _tooth2 - the second harmonic of the gearing frequency of the second stage of the gearbox

3f _tooth2 - the third harmonic of the gearing frequency of the second stage of the gearbox

Next, the spectrum of the investigated reducer and the reference spectrum were compared (Fig. 4). Exceeding the reference spectrum at the frequency of gearing of the first stage of the gearbox indicates unsatisfactory smoothness of rotation of the gearbox and the need to refine or replace the gear pair of the first stage of the gearbox. Thus, the smoothness of the gearbox operation is determined and at the same time the source of the non-smoothness is determined.

This method was tested when testing gearboxes developed as part of the Boomerang R&D, EPOHA R&D. The test results confirmed the effectiveness of the proposed method.

Claims (1)

The method for determining the smoothness of rotation of the gearbox, including the measurement of vibration parameters, characterized in that they additionally test a known-good gearbox, obtain a reference spectrum in the frequency range corresponding to gearing frequencies and shaft speeds, and use its amplitude as a criterion for the smoothness of rotation of the gearbox.

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