RU2144620C1 - Internal combustion engine timing gear drive - Google Patents

Abstract

FIELD: mechanical engineering; engines; base members. SUBSTANCE: timing gear has housing 4 adhesively connected in separate zones, through gasket 5 made of viscoelastic damping material, with stiffening limited rib 6. Material of gasket 5 has physical and mechanical properties predetermined by relationship. Gasket can have discrete structure and different thickness and composition, and rib can be made of different shape. Recommended sphere of application is automobile engines. EFFECT: enhanced efficiency of damping and reduced amplitude of vibration and noise radiated by walls of housing of engine mechanism drive. 5 cl, 10 dwg

Description

 The invention relates to engine building, in particular to a timing mechanism drive (timing) and its structural elements.

 Known sound-damping element for the casing of the camshaft drive belt (see Japan application N 1-247719 51 MKI 4 F 02 B 77/13, publ. 10.03.89), made of hard plastic with holes, then the holes are sequentially closed (filled) by injection pressing by two elements from soft vibration-damping plastic, due to which the effect of vibration-damping and noise reduction is achieved. The disadvantage of this device is the technological complexity of the manufacture of this soundproofing element, the low soundproofing ability of such a structure.

 The known engine timing engine ICE described in the application of Germany N 1122767, class 46cN-16/01 (F 02 F), the filing date of the application is 15.10.57. This mechanism contains a driving and driven pulleys, interconnected by a drive toothed belt, enclosed in a box-shaped casing, mounted on the motor housing, and provided with a box-shaped casing with ventilation holes. The main disadvantage of this technical solution from the point of view of sound insulation is the presence of ventilation holes that lead to additional sound emission from the drive elements in a wide frequency range, both in the low and high frequencies, due to depressurization of the casing space and direct airborne radiation from under the casing through the indicated holes.

 The development of the above technical solution was the device of the gas distribution mechanism of the internal combustion engine (see ed. St. USSR N 1346832 class 4 F 02 B 77/13, application filing date 03/27/1986). The advantage of this mechanism is the optimal location of the ventilation openings in the timing case at the nodes of the lowest intrinsic vibration modes of its air volume, which can significantly reduce the sound emission from the drive elements of the gas distribution mechanism into the environment at the lower resonant modes of the air volume enclosed under the casing. At the same time, this device has a number of significant drawbacks, both in terms of acoustics and other functional properties, since the broadband high-frequency radiation of the drive elements will be practically unimpeded to be emitted into the environment, as well as through the perforation holes in the casing, abrasive parts of dirt, water, etc. Through the holes, not only dust, dirt, water cannot be excluded, which adversely affects the abrasive wear of the pulley teeth, which reduces the durability and reliability of the drive and negatively affects its functional properties, but also, in some cases, the perforated holes are unacceptable in terms of stiffness and strength characteristics of the drive structure.

 Perforated holes made in the wall of the casing, being an effective means of reducing low- and mid-frequency noise, can lead to increased transmission by air of broadband, high-frequency noise emitted by drive elements. In addition, perforated holes are ineffective for suppressing the high-frequency case sound of the timing case caused by multi-node high-frequency vibration modes of the structure of the walls of the case itself.

 A known design of the timing engine of an internal combustion engine, comprising a polymer casing with a noise vibration damping device in the form of a developed rubber plug with an interference fit installed in a specially made casing window (see J SAE Review, No. 6, November 1981, p. 19 ... 25). The use of such a noise reduction structure, as follows from FIG. 13, p.24 of this article, it was possible to mainly reduce radiation in the low-frequency region of the spectrum not exceeding 750 Hz. In the high frequency region, the marked device has shown its low efficiency.

 A known design of the timing engine of an internal combustion engine containing a polymer casing with a highly developed fins skeleton in the form of longitudinal and intersecting stiffeners on the outer and inner surface of the casing wall is molded as a whole with the casing structure (see US patent N 4607601, class F 01 L 1 / 01, Patent Date Aug. 26, 1986). The developed finned and therefore dynamically rigid structure of the walls of the casing allows to minimize low-frequency radiation of sound, which is a positive factor. At the same time, the medium and, in particular, high-frequency radiation of sound by such a casing is not only not attenuated, but even amplified due to the resonant coincidence of the frequencies of the bending vibrations of the walls with the frequencies and harmonics of the gears of the drive units. This fact is a significant and undesirable defect in the design of the casing and the timing drive as a whole.

 Known design of the casing of the belt drive of the engine according to Japanese application N 60-12570 from 07/05/1985, class. F 01 L 1/46, in which a developed window is made, in which a plate of a porous material such as foam aluminum is inserted. The open-cell breathable foam aluminum structure promotes ventilation of the space of the drive pulleys and belt and provides partial absorption of noise generated by the drive. This design, having very limited noise-reducing characteristics, loses them during operation due to clogging of the pores of the foam by dust particles, lubricating oil, etc., which is its drawback.

 As a prototype of the inventive engine timing device of the internal combustion engine, a technical solution can be selected according to the application of Germany N 3141627, class. F 01 L 1/04, publ. 06/24/1982, In the specified device, the timing cover of the internal combustion engine is made of soft damping material such as an integrally formed fibrous material (technical felt) impregnated with phenolic resin and polyurethane foam. Moreover, the casing design on its outer surface may contain reinforcing elements such as concave grooves and corrugations to increase the rigidity of the casing structure. This design of the casing provides a sufficiently high absorption of noise emitted under the casing by timing elements, including (and mainly medium- and high-frequency noise), however, the porous structure of the walls of the casing during operation loses its original characteristics (dusting, pollution, entailing loss of sound-absorbing properties porous sound-absorbing materials, both fibrous and foam). The effect of variable high and low temperatures also negatively affects the noise-damping characteristics of such materials. All this led to the absence of the specified concepts (made of fibrous and foamy polymeric materials) in modern ICE vehicle designs of timing drive housings.

 The design of the timing case cover must satisfy at least three basic requirements: protection of the drive from external influences - ingress of dirt, dust, moisture, i.e. those adverse external factors that can lead to increased wear and, consequently, reduced durability of drive elements, heat removal of the outer surface and low noise emitted directly by the walls of the casing into the environment (low body sound).

 The solution of the technical problem involves increasing the damping efficiency of structural vibrations and noise emitted by the timing case, mainly in the medium and high frequency region (above 600 Hz), by implementing an effective mechanism for the irreversible conversion of the medium and high frequency mechanical vibrational energy of the walls into thermal.

Названная прокладка на присоединительной поверхности стенки кожуха под одним ребром может быть размещена дискретно, т.е. в виде отдельных составных частей и может иметь различную толщину и/или тип материала.The essence of the invention lies in the fact that in the known design of the timing engine of an internal combustion engine, consisting of pulleys, a gear belt, a casing, a stiffening and damping element consisting of a viscoelastic gasket and a limited stiffening rib is installed on the surface of the latter, which performs the function of reducing the amplitude of oscillations of the casing wall in the low-frequency region and damping of vibrations of the casing wall in the medium and high-frequency region, and the ratio of the elastic modulus E of the density ρ and the thickness h of the material in a viscoelastic damping pad is defined by the expression

The said gasket on the connecting surface of the casing wall under one rib can be placed discretely, i.e. in the form of separate components and may have a different thickness and / or type of material.

The invention is illustrated in the drawings (drawings)
- in FIG. 1 shows the construction of a timing drive with a tightening and damping element of the casing;
- in FIG. 2 shows a side view of the timing drive with a tightening and damping element of the casing;
- in FIG. Figure 3 shows the characteristic noise spectrum emitted by the engine timing engine in the casing zone;
- in FIG. 4 shows schematically a mechanism for suppressing low-frequency oscillations due to the presence of a tightening rib;
- in FIG. 5 shows schematically a mechanism for suppressing high-frequency oscillations due to the presence of a tightening rib;
- in FIG. 6 shows a cross section of a tightening and damping element on a wall of a timing case;
- in FIG. 7 shows the frequency dependence of the loss coefficient in the noise damping device according to the claimed design;
- in FIG. 8, 9 and 10 show variants of the structural design of the claimed device, which are characterized, respectively, paragraph 3, paragraph 4 and paragraph 5 of the claims.

 Timing drive, FIG. 1 is mounted on the front wall of the engine block 1 and contains pulleys 2, a timing belt 3, a casing 4, a viscoelastic damping pad 5 and a limited tightening rib 6. In FIG. Figure 2 shows a side view of this structure, from which it can be seen that the rib is located in the direction of the long (least bending) part of the casing, which ensures the weakening of the excitation of its first longitudinal vibration modes.

 From the point of view of providing the required degree of vibration damping, this design is intended directly to reduce the structural noise of the vibrating walls of the timing case excited mainly through its attachment to the engine block and cylinder head. The figure 3 shows the characteristic noise spectrum emitted by the engine timing engine in the area of the casing. It can be seen that the bulk of the sound energy is concentrated in the medium and high frequency region of the sound spectrum. At the same time, intense harmonics are also present in the low-frequency region in the noise spectrum.

 The essence of the proposed technical solution is to implement a noise-reducing design that provides both suppression of the amplitude of oscillations in the low-frequency region due to the introduction of a stiffening element and damping of oscillations in the medium and high-frequency region (above 600-800 Hz) due to the implementation of an effective mechanism for the irreversible conversion of vibrational energy into thermal using stiffening ribs with a deforming gasket underneath. Figure 4 schematically shows the mechanism for suppressing low-frequency vibrations of the casing wall due to the presence of tightening ribs, preventing bending deformation of high amplitudes due to a significantly increased moment of resistance to bending. During bending vibrations of the wall of the casing 4, a toughening rib 6 attached adhesively (thermo-adhesive, sticky adhesive layer) through a viscoelastic gasket 5, due to its significantly greater bending stiffness, limits the vibrational movement of the wall of the casing 4 and, thus, reduces the low-frequency sound emission of the casing into the environment.

 Examples of the use of viscoelastic damping pad materials can include: plasticized polyvinyl chloride, nitrile rubber, butyl rubber, low molecular weight epoxy resin with polyester plasticizer, filled with graphite, modified epoxy resins, etc.

 In terms of the main constituent elements, the proposed noise reduction structure (Fig. 6) does not fundamentally differ from a structure containing, for example, a layer of noise vibration damping material on its surface, as this, for example, is reflected in the German application laid out No. 3141627 class. F 16 F 15/02 publ. 24.06.82 g. The main difference of the claimed design is the use of a viscoelastic damping material of the gasket 5, adhesively connecting the surface of the casing wall and tightening the rib and having an elastic modulus, density and thickness, deliberately set to ensure high acoustic quality of a particular engine timing design.

The mechanism of effective damping of medium and high frequency vibrations in this design is as follows. If in the mechanical vibrational structure shown in FIG. 5 containing a thin-walled polymer wall of the casing, the viscoelastic damping layer of the gasket and the reinforcing reinforcing element in the form of a stiffener in the low-frequency region of vibrations (bending deformations), a sandwich-type three-layer structure damping mechanism is predominantly implemented (see Fig. 4): "plate - viscoelastic material - rigid amplifier", and the irreversible conversion of the energy of mechanical vibrations into thermal energy occurs due to the work s shear deformation of a viscoelastic damping layer structure, the proposed structure is based on a different mechanism of damping, primarily based on the realization srednevysokochastotnyh strain "tensile-compressive" of the viscoelastic layer (see. Fig. 5). A flexurally oscillating plate at higher modes excites vibrations and corresponding deformations of the damping gasket material along the structure of which elastic waves propagate in the direction of its thickness. Due to internal (molecular) losses in the structure of the viscoelastic damping material, after multiple reflections of waves from the rigid structures of the plate and amplifier, the vibrational (deformation) energy of the elements of the mechanical assembly is irreversibly converted into thermal energy scattered in the structure of the viscoelastic damping layer. The magnitude of such irreversible losses depends on the speed (with _p ) of the shear wave propagation in the damping material, which is determined by the formula (1).

где E - модуль упругости демпфирующего материала, ρ - плотность материала.

where E is the elastic modulus of the damping material, ρ is the density of the material.

и, следовательно
f_r = с_p/4h
Для эффективного демпфирования колебаний тонкостенных панелей из полимерных материалов, типа стенок кожуха привода ГРМ ДВС, в частотной области выше 600 Гц в такой конструкции узла предлагается выдерживать соотношение значений модуля упругости, плотности и толщины материла (параметров E, ρ и h) таким образом, чтобы резонансная частота, определяема по формуле (2) находилась в пределах 800 - 1000 Гц. Далее, преобразовывая формулу (2) с учетом заданных f_r = 800...1000 сек^-1 имеем:
с_p/4h 800. . . 1000 sec^-1, с учетом

имеем

или

В случае выполнения соотношения (3) реальные значения добротностей резонансов такой колебательной системы перекроют требуемый частотный диапазон начиная с 600 Гц и обеспечат, таким образом, наиболее эффективное демпфирование средне- и высокочастотного звукового излучения кожуха привода ГРМ ДВС, решая, таким образом, актуальную проблему улучшения виброакустических качеств энергетических установок автотранспортных средств. С другой стороны, в сравнении с нерезонансным демпфированием, характерным для стенок с вибродемпфирующим покрытием, максимальное рассеивание механической колебательной энергии на частотах, соответствующих максимальным амплитудам деформаций вязкоупругого слоя, обусловлено реализацией большей механической работы, преобразуемой в теплоту. В то же время, демпфирование колебаний конструкции (стенок кожуха привода ГРМ) в высокочастотной области позволяет увеличить потери в системе (по сравнению с низкочастотной областью) также за счет совершения и преобразования большей работы, совершаемой в системе (благодаря большому числу колебаний за единицу времени).The frequency dependence of the loss coefficient (η) for a structure using this principle of vibration damping is shown in Figure 7. The resonant frequency f _r , at which the loss coefficient has a maximum value, is determined provided that the material thickness (h) is equal to 1/4 of the transverse length propagated in it waves λ:

and therefore
f _r = s _p / 4h
To effectively damp vibrations of thin-walled panels made of polymeric materials, such as the walls of the timing case of an internal combustion engine, in the frequency region above 600 Hz, it is proposed to maintain the ratio of the elastic modulus, density and thickness of the material (parameters E, ρ and h) in such a way that the resonance frequency, determined by the formula (2) was in the range of 800 - 1000 Hz. Further, transforming the formula (2) with given f _r = 800 ... 1000 sec ^-1 we have:
with _p / 4h 800.. . 1000 sec ^-1 , taking into account

we have

or

If relation (3) is fulfilled, the real values of the quality factors of resonances of such an oscillatory system will cover the required frequency range starting from 600 Hz and will thus ensure the most effective damping of the medium and high frequency sound radiation of the engine timing case, thus solving the urgent problem of improving vibroacoustic qualities of power plants of vehicles. On the other hand, in comparison with non-resonant damping, which is typical for walls with a vibration damping coating, the maximum dispersion of mechanical vibrational energy at frequencies corresponding to the maximum strain amplitudes of the viscoelastic layer is due to the implementation of more mechanical work that is converted into heat. At the same time, damping of structural vibrations (walls of the timing drive casing) in the high-frequency region allows to increase losses in the system (compared to the low-frequency region) also by performing and transforming more work done in the system (due to the large number of vibrations per unit time) .

 If the introduction of a viscoelastic damping pad with a stiffener only on a part of the surface (the most vibroactive) bounded by the rib and the walls of the casing is sufficient for the necessary damping efficiency, then this introduction is also justified from the point of view of reducing the cost of the device.

 To preserve noise-vibration-damping efficiency, from layout considerations, the noise-vibration-absorbing design can be made not only in the form of a single unit, but also in several separate units distributed over the surface of the timing case, including “recessed” options, as shown in figure 8.

To increase the tightening effect and, accordingly, increase the efficiency of the structure, primarily in the low-frequency region, the rib structure can be made in the form of a corrugation, and the damping effect in the medium and high-frequency region will be achieved mainly due to the maximum thickness h _{2 of the} viscoelastic damping pad, placed in the Central part (cavity) of the ribs, as shown in figure 9.

Depending on the particular design of the timing drive casing (its dimensions, thickness and wall material, elastic modulus), to tighten the walls of the casing, a larger contact area between the walls and the rib may be required, and the toughening rib may be corrugated to the wall of the timing casing, as shown in figure 10. in this case, the central part of the node (with a thin layer of damping material ₂ h), mainly providing stiffness characteristics, suppresses low-frequency radiation, and the peripheral edge zone (with a thick layer of damping conductive material h ₁₎ - medium- and high-frequency sound emission suppression.

Claims (4)

1. The gas distribution mechanism of the internal combustion engine, containing gear drive pulleys, a gear drive belt, closed by a polymer casing with a noise vibration damping device, characterized in that the noise vibration damping device is made in the form of a limited tightening rib, adhesive bonded to the surface of the casing wall through an intermediate layer of viscoelastic damask with the corresponding ratio of the elastic modulus E, density ρ and thickness h of the viscoelastic damping material th pads, which is given by

2. The gas distribution mechanism of the internal combustion engine according to claim 1, characterized in that the viscoelastic damping pad is placed in the area between the tightening rib and the casing wall surface in the form of several discrete overlays.  3. The gas distribution mechanism of an internal combustion engine according to claims 1 and 2, characterized in that the noise vibration damping device is located on the surface of the gas distribution mechanism casing in the form of several discrete elements.  4. The drive of the gas distribution mechanism of the internal combustion engine according to paragraphs. 1 to 3, characterized in that the cross section of the stiffening ribs of the noise vibration damping device is made in the form of a corrugation.  5. The drive of the gas distribution mechanism of the internal combustion engine according to claims 1 to 4, characterized in that the tightening rib is installed with a wide part to the wall of the casing.

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