RU2499927C1 - Method for exclusion of resonant modes of ceramic-metal plates oscillations of hydromechanical transmission of transport vehicle - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method consists in analytical or experimental determination of frequency spectrum of engine disturbing and of eigenfrequency spectrum of ceramic-metal plate, possibility of resonant modes disturbing by equality of disturbing frequencies and eigenfrequencies. Additionally determined and compared to eigenfrequency spectrum of ceramic-metal plate is frequency spectrum of disturbance generated by hydrodynamic processes in interblade space of hydraulic transformer and pressure oscillations of operating fluid in its feeding system. Then possibility of resonant mode is determined by equality of eigenfrequencies of ceramic-metal plate and engine disturbing frequencies, disturbing frequencies generated by hydrodynamic processes in interblade space of hydraulic transformer and pressure oscillations of operating fluid in its feeding system. Subject to resonant conditions eigenfrequency spectrum of ceramic-metal plate is corrected by destruction of wave number repetition factor, which length sum corresponds to the length of circle midradius of ceramic-metal plate by provision of symmetrically arranged holes changing frequency spectrum of ceramic-metal plate.

EFFECT: increasing durability and reliability of operation of friction elements of hydromechanical transmission.

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Description

The invention relates to transport engineering and can be used in the development and modernization of transport vehicles equipped with hydromechanical transmissions.

In the process of testing experimental hydromechanical transmissions (HMTs) and operating some serial ones, a rupture of cermet disks (MCD) of friction control elements is observed after a limited period of operation. A metallographic analysis of the destroyed disks shows that the cracks are fatigue-like. This is a consequence of the resonant modes of operation that occur when one of the natural frequencies of the MCD coincides with the frequency of the disturbing effect generated by the engine. To increase the durability of MCD by eliminating resonance modes, it is necessary to determine the spectrum of its natural frequencies. Analytically determine the frequency values using approximate formulas valid for a circular ring made of a homogeneous material. In the wave theory, oscillations of a circular ring are described by partial differential equations whose solution is equality [Timoshenko SP, Young D.Kh., Weaver U. Oscillations in engineering. Publishing House: M .: Mechanical Engineering, 1985, p. 435]:

$$\omega ={\omega }_k=\frac{K\left(K^2-\mathrm{one}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="00000005.png"\; state="\{\{state\}\}">K</figure-callout>}}^2+\mathrm{one}}}\sqrt{\frac{EJ}{m_0{R}^{\mathrm{four}}}},$$

), и форму колебаний диска; Е - модуль упругости второго рода; J - момент инерции прямоугольного сечения кольца $$J=\raisebox{1ex}{$b\cdot h^3$}\!\left/ \!\raisebox{-1ex}{$12$}\right.$$

размером b·h; m₀ - погонная масса; R - средний радиус кольца.where K is an integer that determines the number of waves z of length λ that fit on the length of the ring 2πR (K = 1,2, ..., N, $$K=\raisebox{1ex}{$2\pi R$}\!\left/ \!\raisebox{-1ex}{$z\lambda $}\right.$$

), and the form of oscillation of the disk; E is the elastic modulus of the second kind; J is the moment of inertia of the rectangular cross section of the ring $$J=\raisebox{1ex}{$b\cdot {\mathrm{<figure-callout\; id="3"\; label="h"\; filenames="00000004.png,00000005.png"\; state="\{\{state\}\}">h</figure-callout>}}^3$}\!\left/ \!\raisebox{-1ex}{$12$}\right.$$

size b · h; m ₀ - linear mass; R is the average radius of the ring.

However, the MKD design is multicomponent, combining a metal disk, cermet overlays, adhesive layers, that is, heterogeneous materials with various nonlinear physical and mechanical properties. In addition, on one of the end surfaces of the MCD, a gear rim is made. Eigenfrequencies of MKD of complex shape, consisting of inhomogeneous materials, can be determined on the basis of numerical simulation (analogue - Basov K.A., Movchan D.A. ANSYS. User Manual. Publisher: DMK-Press, 2011, 640 pp. ) - determining the response of the finite-difference model of the MCD to the harmonic effect of the adjustable frequency (for example, in the NASTRAN software package). However, the reliability of the model construction is limited by the accuracy of the description of the nonlinear interaction between the MCD elements (a steel ring and ceramic-metal overlays) formed by adhesive layers. In this regard, the results of a numerical estimation of the natural frequencies of the MCD must be adjusted taking into account the experimental data obtained during tests at a special bench using the non-destructive testing method - by the reaction of the disk to a harmonic signal of adjustable frequency [Application for utility model No. 2012126204/20 (040447) from 06.22.2012 “A stand for determining the spectrum of natural frequencies of cermet disks of hydromechanical transmissions”]. The probability of excitation of resonant modes is determined by the equality of the frequencies of the perturbations of the engine and its own ring. It is proposed to provide the exclusion of resonance in the literature by varying the natural frequencies of the cermet disk in accordance with the above equation. However, the physical and mechanical properties (elastic modulus E, density of the material ρ, which determines the linear mass m ₀ , respectively, and the speed of sound in the material E / ρ) are stable for the materials used, and the variation in geometric parameters (J, R) is limited by the layout conditions of the friction disks in the transmission case.

Due to the limited possibilities of correcting the spectrum of the natural frequencies of the MCD, radial incisions are made in the discs to exclude resonance modes. The dimensions of the incisions are selected from the condition of maintaining the strength of the MCD. However, under the action of centrifugal forces, the strength condition is violated due to the high concentration of stresses in the notch zone. In addition, the disk loses its elastic stability when the wave propagation speed through the disk becomes equal to the rotation speed. Some damping of vibrations can be achieved by creating a cone-shaped or corrugated shape of steel disks working in tandem with the MCD. This leads to an increase in friction between the disks during their rotation, wear and a decrease in efficiency [Salzerman IM, Kamensky DM, Onopko AD Friction clutches and brakes of tracked vehicles. M .: Engineering, 1965, Fig. 109, p. 151].

The closest in technical essence and the achieved results is a method of eliminating resonance regimes in friction disks of hydromechanical transmissions, which consists in analytically or experimentally determining the frequency spectrum of the motor perturbation and the natural frequency spectrum of the ceramic-metal disk, as well as the probability of excitation of the resonant modes when the frequency of the perturbation and the natural (Zaitsev V.A., Zhuchkov M.G., Kryukov A.P. Vibro-shock processes in disk friction clutches // Bulletin of the Armored Tech. nicknames. - 1968. - No. 6. - p. 33-36, prototype). The frequency spectrum of the engine disturbances is determined analytically based on the calculation of the polyharmonic function of the engine torque from the indicator diagram of one cylinder, taking into account the operating procedure and design features, based on the spectral analysis of the obtained function. Another way to determine the frequency of engine disturbances is a spectral analysis of the engine torque according to the manufacturer and the determination of the main motor harmonics.

The essence of the known method is as follows.

1. The definition of the spectrum of the natural frequencies of the MCD from the analytical dependence.

2. Calculation of the function of the polyharmonic disturbance of the engine torque according to the indicator diagram of one cylinder, taking into account the operating procedure and design features; Based on the spectral analysis of the obtained function, the motor harmonics are determined.

3. Determining the possibility of a resonant mode by the equality of the natural frequencies of the disk and the motor harmonics of the engine.

Under the conditions of resonance, due to the limited possibilities of adjusting the frequencies of the motor perturbations or the natural frequencies of the disk, it is planned to reduce the stress concentration at the base of the MKD teeth and increase the bearing capacity by design and technological measures (hardening the surface hardness at the base of the tooth based on nanotechnology, laser saturation of refractory metal carbides - WC, TiC, etc.). However, in this case, resonance is not excluded; complex elements of the transmission interacting with the MCD are destroyed.

It should be noted that in the considered method when predicting the resonance mode, the generation of disturbance frequencies by hydrodynamic processes in the interscapular space and the pulsation of the working fluid pressure in the torque converter feed system is not taken into account.

The studies performed by the authors found that resonance excitation in the frequency range not previously considered occurs when the torque converter (GT) operates in the fluid coupling mode with a slight, 10 ... 15%, slipping of the turbine relative to the pump. The engine moment, the pre-transformer zone, and also the gears do not contain harmonics of such a high order (more than 700 Hz). It was established by experimental studies that high-frequency oscillations are observed when neutral in the transmission and when driving in V, VI gears with an unlocked torque converter (GT) and an engine shaft speed of more than 2050 rpm. The oscillation amplitude in the vertical and horizontal planes is 1.0 ... 1.5 g (9.8 ... 15.0 m / s ² ). As follows from the nature of the spectral density of the process, the main oscillations are concentrated in the frequency range 700 ... 730 Hz not studied before. When the torque converter is blocked, the spectral density is “white noise”, i.e. Oscillations occur in a wide spectrum of frequencies without resonances. Based on the simulation of hydrodynamic flows in the interscapular space with the relative motion of the impellers of the widely used and energy-intensive torque converter GTK-XV with the number of impeller blades for pumping wheels k _n = 28, turbine k _m = 22 it was found that in the pump-turbine transition with a relative slip of 30 ... 200 rpm there is a simultaneous interaction of two pairs of blades of the pump and turbine wheels. In this case, hydrodynamic pulses are formed with a frequency of 703 Hz, which corresponds to the frequency of oscillations recorded in the course of experimental studies of gas turbine engines (700-730 Hz).

The correctness of the determination of the spectrum of high-frequency perturbation generated by the torque converter was carried out in the study of two torque converters of different designs and sizes, but with the same number of wheel blades on the special bench indicated above. A spectral analysis of the process of changing the torque on the torque converter wheels and the working fluid pressure showed that the actual dynamic processes of turbine disturbance formation are much more complicated than those taken in the calculation. The frequency of the perturbation of the moment on the turbine corresponds to the calculated, i.e. ω = 0.5 · (k _T · k _H ) · Δn (Δn is the relative frequency of rotation of the turbine and pump wheels). At the same time, it is necessary to take into account the process of pulsation of the working fluid pressure at the inlet of the torque converter, which is formed by the gear pump of the make-up system and in frequency that closely matches the frequency of disturbances generated by hydrodynamic processes in the torque converter.

In addition, an effective way of correcting the spectrum of the eigenfrequencies of the disk oscillations is to “destroy” the number of waves whose length corresponds to the circumference of the average radius of the disk. However, this is not realized in the analyzed sources. Thus, the known methods for eliminating the resonant modes of oscillations of the MCD have the following disadvantages.

1. When predicting the resonance regime, the generation of disturbance frequencies generated by hydrodynamic processes in the interscapular space and the pulsation of the working fluid pressure in the torque converter feed system is not taken into account.

2. Methods of correcting the spectrum of natural frequencies of MCD have limited capabilities, reduce the structural strength, in addition, the disk loses its elastic stability when the wave propagation velocity through the disk becomes equal to the rotation speed.

Due to the above disadvantages, the existing method for predicting and eliminating the resonant modes of oscillations of the MCD is ineffective.

In this regard, a method is proposed for eliminating the resonance modes of oscillations of metal-ceramic disks of a hydromechanical transmission of a transport machine, which consists in analytically or experimentally determining the frequency spectrum of the motor perturbations and the natural spectrum of the ceramic-metal disk, and the possibility of exciting resonance modes by the equality of the frequency of the perturbations and the natural ones. The novelty of the method lies in the fact that the spectrum of perturbations formed by hydrodynamic processes in the interscapular space of the torque converter and the pulsations of the working fluid pressure in its feed system is determined and compared with the spectrum of the natural frequencies of the ceramic-metal disk, and the possibility of the resonance mode is determined by the equality of the natural frequencies of the ceramic-metal disk and frequencies engine disturbances, disturbance frequencies generated by hydrodynamic processes in the interscapular In addition to the torque converter and pulsations of the working fluid pressure in the feed system, when the resonance condition is met, the spectrum of the natural frequencies of the ceramic-metal disk is corrected by breaking the multiplicity of the number of waves, the sum of the lengths of which corresponds to the circumference of the average radius of the ceramic-metal disk, by making pairs of symmetrically arranged holes on this circle that change the spectrum frequencies of cermet disk.

Figure 1 shows the block diagram of the sequence of actions that determine the proposed method. Figure 2 shows the amplitude-frequency characteristics of the MCD, characterizing the effectiveness of the proposed method.

The proposed method is carried out by performing the following operations.

1. The spectrum of natural frequencies of the MCD is determined by the analytical dependence, by numerical modeling according to solid-state drawings, or by the results of an experimental study when the disk is irradiated with a sound wave of adjustable frequency.

2. The function of the polyharmonic disturbance of the engine torque is determined from the indicator diagram of one cylinder, taking into account the operating procedure and design features; Based on the spectral analysis of the obtained function, motor harmonics are determined.

3. Calculate the spectrum of frequencies excited by hydrodynamic processes in the torque converter during the formation of pair pulses from the known values of the number of wheel blades.

4. Calculate according to the dependence ω _p = F (z _w , C, m _p ) the frequency spectrum excited by the torque converter feed system, depending on the number of teeth of the gear pump z _w , spring stiffness C, mass m _{p of the} spool piston.

5. Determine the possibility of the resonant mode by the equality of the eigenfrequencies of the MCD and the frequencies of the motor harmonics of the engine, the frequencies of disturbances excited by the hydrodynamic processes of the torque converter or its feeding system.

6. When the resonance conditions are met, the spectrum of the eigenfrequencies of the disk is corrected by destroying the multiplicity of the number of waves whose sum of lengths corresponds to the circumference of the average radius of the disk. To do this, on the circumference of the average radius of the disk, pairs of symmetric located holes are used that change the spectrum of its frequencies. The number of pairs of holes is determined depending on the required offset of the spectrum of the eigenfrequencies of the disk.

The effectiveness of the proposed method for adjusting the spectrum of natural frequencies MCD is illustrated by spectral density graphs shown in figure 2, obtained experimentally by irradiating the disk with a sound wave of adjustable frequency. Graph 1 corresponds to the spectral density of the disk in the initial state, graph 2 for two pairs of holes, and graph 3 for three pairs of holes. In this case, the spectral density changes significantly. In the initial state, the maximum spectral density corresponds to a frequency of 703 Hz (graph 1); with two pairs of holes, the spectral density amplitude at a frequency of 703 Hz ceases to be dominant, since its value decreases by 60% (Figure 2). The maximum value of the amplitude shifts toward lower frequencies, while the disk does not lose elastic stability when the wave propagation velocity through the disk becomes equal to the rotation speed.

An even greater effect is observed with six pairs of holes (graph 3). The size of the holes is chosen from the condition of maintaining the strength of the MCD under the action of centrifugal forces. Thus, the proposed method takes into account the possibility of resonance not only due to perturbations of the engine, but also perturbations generated by the torque converter and pressure pulsations in its feed system. The application of the proposed method will significantly increase the durability and reliability of the friction elements of the hydromechanical transmission.

Claims (1)

The method for eliminating the resonance modes of oscillations of metal-ceramic disks of a hydromechanical transmission of a transport vehicle, which consists in analytical or experimental determination of the frequency spectrum of the disturbances of the engine and the spectrum of natural frequencies of the ceramic-metal disk, the possibility of exciting resonance modes by the equality of the frequencies of the disturbances and the natural ones, characterized in that they are additionally determined and compared with the spectrum eigenfrequencies of the cermet disk perturbation frequency spectrum formed by the hydrodynamic processes in the interscap space of the torque converter and the pulsations of the working fluid pressure in its feed system, determine the possibility of the resonance mode by the equality of the eigenfrequencies of the cermet disk and the frequencies of the disturbances of the engine, the frequencies of the disturbances generated by the hydrodynamic processes in the interscap space of the torque converter and the pulsations of the working fluid pressure in the feed system , when the resonance conditions are fulfilled, the spectrum of the proper frequency of the ceramic-metal disk by destroying the multiplicity of the number of waves, the sum of the lengths of which corresponds to the circumference of the average radius of the ceramic-metal disk, making pairs of symmetrically arranged holes on this circle that change the frequency spectrum of the ceramic-metal disk.

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