GB2242723A

GB2242723A - Suspension system for a reciprocating hermetic compressor

Info

Publication number: GB2242723A
Application number: GB9106945A
Authority: GB
Inventors: Rogerio Sangoi; Jose Lainor Driessen; Dietmar Erich Bernhard Lilie
Original assignee: Empresa Brasileira de Compressores SA
Current assignee: Empresa Brasileira de Compressores SA
Priority date: 1990-04-06
Filing date: 1991-04-03
Publication date: 1991-10-09
Also published as: FR2660703A1; ES2043479B1; ITMI910872A1; GB9106945D0; ES2043479A2; IT1247849B; BR9001772A; JPH04228883A; CN1055801A; DE4110922A1; ES2043479R; ITMI910872A0

Abstract

A motor-pump unit is held in suspension within a hermetic housing by means of helical springs whose ends are attached to the housing and to the motor-pump unit. At least one element (10, 20) is provided for absorbing high frequency vibratory energy, being attached to each helical spring and in close contact with at least part of the surface of the spring wire, along a portion of the latter, in order to absorb and damp the resonances of longitudinal propagation of the waves throughout the spring, without changing the elasticity characteristics of the spring at low frequencies. The element can be a core or sleeve of soft rubber which may be pressed against the surface of the helical spring. An alternative element is a rubber coating or a closely wound coil surrounding the wire of the helical spring. <IMAGE>

Description

9 1

SUSPENSION COMPRESSOR Background of the Invention This invention relates to a suspension system to be used in reciprocating hermetic compressors in which the fixation of the motor-pump unit to the housing is done by means of springs.

Reciprocating hermetic compressors are conventionally provided with a suspension system using springs in order to isolate the vibrations of the motor-pump unit in relation to the compressor housing.

In one of the known constructive arrangements, the motor-pump unit is attached to the compressor housing through metallic suspension springs, which operate under tension. However, these metallic suspension springs are not good high frequency insulators, due to the phenomena of longitudinal propagation of vibrations along the spring material itself, allowing these vibrations to reach the less rigid upper part of the housing and so radiating noise (due to these high frequency housing vibration).

This constructive solution of the prior art is schematically illustrated in figure i c)+ the attached drawings.

In reciprocating hermetic i -SYSTEM FOR A RECIPROCATING HERMETIC compressors with a more recent design, the conventional suspension system employing suspension metallic springs under tension has been replaced by. a suspension system using supporting metallic springs under compression which :30 are unit, attached metallic housing normally allowing located beneath a bearing point of the motor-pump as schematically illustrated in fig 2 of the drawings. In this prior art arrangement, the springs are fixed in a lower part of the presenting a dynamic stiffness which is quite higher than that of the upper part, a considerable reduction o+ the high 1 1 1 1 p frequency vibration wave propagation.

Although the use of supporting metallic springs under compression substantially reduces the high frequency vibrations transferred to the housing and is of easy execution in new products designs, this prior art system becomes of difficult execution, when adapting a product which is already available, that is, a compressor which has been manufactured with a system of suspension springs under tension, to the system of supporting springs under compression. Transforming the system of springs under tension into that using springs under compression, requires heavy changes in the manufacture process and also a new study to balance the inertia forces acting on the motor-pump unit. Sometimes, this new balancing becomes impractical, when the intention is to preserve the basic dimensions and characteristics of the motorpump unit and housing.

Besides the above inconvenience, we can still mention 20 the fact that, even in the system of supporting springs under compression, the metallic springs are the only structural interconnection elements, except for the discharge tube, between the motor-pump unit and the housing,which cannot avoid the propagation of the high frequency vibrations, from the motorpump unit to the housing. Thus, the attenuation of these higher frequency vibrations is accomplished only by fixing the springs to a more rigid portion of the hous i ng.

0-biects of the Invention A. general object of the present invention is to provide a suspension system for a reciprocating hermetic compressor which allows obtaining a considerable attenuation in the transmission of high frequency vibratory energy through the suspension springs, by means of a construction which is easy to 4 3 manufacture and to assemble, even using already available compressors, without requiring a new balancing of the motor-pump unit or significant changes in the manufacturing processes.

A further object of the present invention is to provide a suspension system of the above mentioned type which allows obtaining an effective attenuation in the transmission of high frequency vibration through the suspension springs, when working both under tension or under compression. Brief Description the Invention

These and other objects and advantages of the present invention are achieved through a suspension system applied to a reciprocating hermetic compressor which comprises an hermetic housing supporting, therewithin, a motor-pump unit which is held in suspension through helical springs with their ends being respectively and simultaneously fixed to the housing and to the motor- pump unit.

According to the present invention, it is provided at least one element for absorbing the high frequency vibratory energy, being fixed to each helical spring in a close contact with the surface of the spring wire, along an extension of the latter, in order to absorb and damp the resonances of wave longitudinal propagation in spring material throughout the spring, when the compressor is working, without changing the elasticity characteristics of the spring.

In a way of carrying out the invention, the damping 30 element is fixed to the surface of the spring wire by the joint action of partially fitting the spring wire in the contact surface of the absorbing element and of a certain pressing of said contact surface on the spring wire, sufficient to ensure the close contact between the spring and the damping element.

In another way of carrying out the invention, the 1 4 damping element is attached to the surface of the spring- wire by the friction forces assured by the radial pressing of the damping element against the spring coils.

In another way of carrying cut the invention, the damping element takes the form of an individual and continuous coating of the spring coils.

Independently from the preferred way of carrying out the invention, the provision of an absorbing element in each spring makes said element absorb the vibratory energy in high frequencies, said energy being in the form of resonances of longitudinal propagation of waves along the spring, the springs being responsible +or a substantial transmission of energy to the structure to which they are attached.

The provision of the absorbing elements, which are the subject matter of the present invention, allows that the conventional suspension springs be also high frequency insulating attenuating the vibrations reaching the compressor housing and causing the noise radiation by the vibration of said housing.

Brief Description of the Drawings The invention will hereinafter be described with 25 reference to the attached drawings, in which:

Figure 1 shows schematically a side elevational view 04 a reciprocating hermetic compressor with the motor-pump unit being attached to the housing by means of metallic suspension springs under tension; Figure 2 shows a similar view to that of figure i, but with the motor- pump unit of the compressor being fixed to the housi'ng by means of supporting metallic springs under compression; Figure 3 shows a diametrical longitudinal seccional 35 view of a metallic helical spring, of the suspension or supporting types, having its coils jointly and provided with 20 characteristics, -5externally surrounded by an absorbing element of tubular shape; Figure 3a shows a perspective view of the absorbing element of figure 3, Figure 4 illustrates a diametrical longitudinal sectional view of a helical metallic spring, of the suspension or supporting types, having its coils jointly and internally covered by an absorbing element in the form of a substantially cylindric body which is adapted within the spring; Figure 5 illustrates a diametrical longitudinal sectional view of a helical metallic spring, of the suspension or supporting types, carrying the absorbing elements shown in figures 3 and 5; Figure 6 shows an elevational side view, partially sectioned, of an absorbing element in the form of a split sleeve, which will be pressed around a suspension or supporting spring shown in dashed lines, Figure 7 shows a cross sectional view of the absorbing element of figure 6, taken according to line VIIVII of this same figure; Figure 8 illustrates a diametrical longitudinal sectional view of another absorbing element, in the form of a cylindrical plug, to be fitted by interference within a suspension or supporting spring, radially pressing the spring coils; Figure 8a illustrates an end view of the expander to be inserted into an axial hole of the plug; Figures 9 and 10 illustrate a spring with its coils being individually involved by a continuous absorbing element, in the form of a coating and a covering element, respectively; and Figure 11 shows, in a diametricallongitudinal section, the assembly of a suspension helical spring, on a support of the compressor housing. Detailed Description of the Invention As already mentioned in the background of the

1 j 6 invention, figures 1 and 2 have the function of illustrating two known manners of attaching a motorpump unit 1 within the housing 2 of a compressor, using helical metallic springs 3 which can operate 5 under tension (figure 1) or under compression (figure 2).

Since the springs are metallic and fixed by their ends to the motor-pump unit 1 and housing 2, they do not restrict in any way the propagation of the high frequency waves which are produced by the vibrations of the motor-pump unit 1 and transmitted, being amplified by spring resonances, to the housing, causing an undesirable noise, particularly in the case of the assembly arrangement of figure 1.

The present invention provides a way of imparting to the springs 3 the capacity of attenuating the transmission of such high frequency vibratory energy of the motor-pump unit 1 to the housing 2 of the compressor. Such blocking effect against the transmission of high frequency vibrations along the springs 3 is attained when the springs are aggregated with damping elements capable of absorbing the high frequency vibratory energy, transforming it into heat that is dissipated within the housing.

In the mode of execution illustrated in figure 2, the absorbing element 10 takes the form of a sleeve, with a longitudinal extension corresponding to the free length of the spring 3 and with its inner cylindric face having a slightly smaller diameter than the outer diameter of the spring. In this arrangement, the coils of the spring 3 are partially covered by the material of the absorbing element, thus improving the transmission of high frequency vibratory energy from the springs to the absorbing element.

The material of the sleeve 10 can be defined by any viscous-elastic material such as, for example, soft 1 7 rubber (expanded or not) which is able to absorb the waves propagation energy at high frequencies through the spring, transforming this vibratory energy into heat. The material of the sleeve 10 should also be sufficiently soft in order to, together with the diametral difference above mentioned in relation to the spring, its inner surface in contact with the spring coils be elastically deformed by the latter, which became partially "fitted" in the corresponding elastically lowered portions of the sleeve inner surface.

The sleeve 10 may also be longitudinally split in 12, in order to facilitate its adjustment around a spring 3 already mounted between the motor-pump unit 1 and the housing 2.

The longitudinal extension of the sleeve 10 may be dimensioned so as to permit involving only part of the extension of spring 3, provided that such dimensioning assures an adequate absorption of vibratory energy by the sleeve. Nevertheless, it should be observed that, the greater the contact area between the material of the absorbing element 10 and the spring wire, the greater will be the absorption of vibratory energy by said absorbing element.

The same principle may be applied to the exact determination of the material and of the wall thickness of the absorbing element 10. The material should be selected in such a way as to assure an absorption of vibratory energy within a wall standard which is appropriate to 'the existing spaces in the interior of a housing of a reciprocating hermetic compressor for small refrigerating machines.

In case the springs 3 are conical coils, the sleeve 10 will present a shaped inner face to externally involve the spring.

adequate 30 thickness a Concerning the known helical springs, experience has proved that a sleeve 10, with a length only slightly inferior to the free length of the spring, which is around 26mm, and with a wall thickness around E3.5mm in spongy rubber having a hardness inferior to 25 IRHD, is capable of absorbing around 4.0 dE (four decibels) of the high frequency vibratory energy in transmission through the spring.

In figure 4, it is illustrated another absorbing 10 element 20 which takes the form of an elongated body, in this case of cylindric shape, having the same len2th as the helical spring 3 and being preferably formed by a viscous-elastic material such as, for example, soft rubber (expanded or not). The cylindric body 20 has a diameter which is slightly larger than the inner diameter o+ the coils of the helical spring 3, in order to assure the necessary interference with said spring when it is fitted therewithin, the material of the absorbing element and the aforesaid diametral difference being selected to permit the same type of interference assembly described with relation to the absorbing element 10.

Figure 5 illustrates the simultaneous use of two absorbing elements in only one spring, the sleeve 10 being disposed around the spring, while the cylindric body 20 is accomodated within the spring 3.

This arrangement may be useful in situations in which it is necessary a high degree of absorption in conditions with elevated vibrations of high frequency.

It should be observed that the cylindric body 20 may have a conical shape in case the spring is in the conical coil form.

In the assembly system of the absorbing element to 35 the spring, as illustrated in figures 3, 4 and 5, the retention between the absorbing element and the 1 9 spring is obtained by interference of the spring coils with the absorbing material, so that the absorbing element can receive and retain the spring high frequency vibrations. The high frequency 3 propagation waves along the spring are transferred from the coils to the elastically lowered regions of the side surface o+ the absorbing element body, where they are absorbed and the vibratory energy is transformed into heat. In this solution, it is necessary that the side walls of the absorbing element partially embrace the spring coils, exerting a certain compression thereon, so as to guarantee that the high frequency vibrations can be physically transmitted to the absorbing element body. The sleeve 10 can further be surrounded by a retention clamp, (not shown) in order to promote the adequate pressing of the absorbing element on the spring 3.

Figures 6 and 7 illustrate an alternate construction of figures 3 and 3a, In this alternate construction.

the absorbing element takes the form of a sleeve 30 of a viscous - elastic material, such as soft or expanded rubber, said sleeve being provided with a longitudinal slat 32 and dimensioned to externally embrace the spring 3, exerting a certain radial compression on the coils, so that to assure a friction force therewith.

The radial compression of the sleeve 30 around the spring 3 can be obtained by the own deforming elastic force of the sleeve, or with the help of a pressing clamp 35 surrounding the outer side wall of the sleeve 30. The fixing between the clamp 35 and the sleeve 30 can be accomplished in different ways, including the vulcanization of the sleeve directly an the inner face of the metallic pressing clamp 35, in 3f.5 nrder to form a single piece therewith.

Figure 8 illustrates an absorbing element in the form 1 1 1 of an elongated plug 40 made of soft rubber having, in this examplei a cylindric shape and being dimensioned to be fitted within the suspension or supporting spring, with its side wall exerting a certain radial compression on the spring coils. Such compression can be obtained by the own elasticity cif the plug 40 and the degree of compression thereof within the spring and/or by inserting an expander 45 in an axial hole 43, which is provided from at least LO one of the ends of the plug 40. Concerning the sleeve 30 af figures 6 and 7 and the cylindric plug 40 of figure 8, the physical transmission of the high frequency vibrations from the spring to the absorbing element is achieved by the friction between the spring contact surfaces with the absorbing element, this friction being a function of the material of the spring and absorbing element and c+ the radial compression force between the same.

The same comments made hereinbefore about the 20 absorbing elements 10 and 20 are applied to the sleeve 30 and cylindric plug 40 concerning the material, dimensions and shape, though it should be only painted cut that, in the case of sleeve 30 and cylindric plug 40, the viscous-elastic material is not sufficiently soft to allow the partial fitting of the spring wire to the contact surface, as it occurs in the illustrations of figures 3, 3a, 4 and 5.

Another constructive embodiment for the absorbing element is illustrated in figure 9. In this embodiment, the absorbing element takes the form of a coating 501 preferably continuous, involving individually the spring coils and being made of rubber, being vulcanized or not on the spring wire, lead alloys or any other material which can absorb properly the high frequency vibrations, without affecting the spring elasticity in low frequencies.

il In figure 10, it is illustrated a variation of the embodiment shown in figure 9, where the absorbing element takes the form of a metallic card 60 as, far example, a spring with a much smaller wire diameter, surrounding helically the wire of the suspension or supporting spring.

In the embodiment shown in figure 9, the absorption effect is attained due to the close contact which is assured between the coating material and the coil wire, through a physical phenomenum similar to that existing in the embodiments of figures 6 and 7.

In the construction shown in figure 10, the absorption occurs by the metallic -Friction between the suspension spring wire and the covering spring wire, transforming the vibration energy into heat, which is dissipated to the environment where the assembly is located.

In order to increase even more the attenuation of vibratory energy through the spring towards the compressor housing, there may be provided a pad 70 (figure 1i), made of a material with a mechanical impedance which is quite different (lower) to that o+ spring 3 (impedance mismatch) as, for example, plastic or rubber, being disposed between one end of the spring and its fixing point to the motor-purnp unit i and/or housing 2. This pad 70 has the function of decreasing the transmission of high frequency vibratory energy to the compressor housing.

1 F 12 1 - Suspension

Claims

CLAIMS system for a reciprocating hermetic compressor comprising an

hermetic housing (2) supporting therewithin a motor-pump unit (i) which is held suspended by means a+ helical springs (3) with their ends being respectively and simultaneously attached to the housing (2) and to the motor-pump unit (1), characterized in that it is provided with at least one element (10, 20. 30, 40, 50, 60) for absorbing high frequency vibratory energy, being attached to at least one helical spring and in close contact with at least part of the surface of the spring wire, along an extension of the latter, in order to absorb and damp the vibration energy at the of longitudinal propagation waves the helical spring, excited when the is working, without changing the characteristics of the spring in low frequencies.

2 - Suspension system, according to claim i, wherein the absorbing element (10,20) is attached to the wire surface of the spring (3) through partial fitti'ng o+ the spring wire to the contact surf ace of the absorbing element (10,20) and a certain pressing of said contact surface an the spring wire, sufficiently to assure the close contact between the spring and the absorbing element.

3 - Suspension system, according to claim 2, wherein the partial fitting of the wire of spring (3) to the contact surface of the absorbing element (10,20) is obtained by the elastic deformation of the contact surface regions of the absorbing element pressing the wire of the spring (3).

4 - Suspension system, according to any one of claims 2 or 3, wherein pressing said contact surface on the spring wire occurs in a substantially radial resonances throughout compressor elasticity 13 direction, inwardly or outwardly, in relation to the akis of spring (3).

- Suspension system, according to claim 4, wherein the absorbing element is in the form of a sleeve (10), with its inner face defining the contact surface with the wire of the spring (3).

6 - Suspension system, according to claim 5, wherein the sleeve (L0) has an inner diameter which is slightly smaller than the outer diameter of spring (3), so that said contact surface of the absorbing element can press the spring wire radially inwardly.

Suspension system, according to claim 6, wherein the sleeve (10) is longitudinally split.

9 - Suspension system, according to claim 6, wherein the sleeve (10) is involved by a retention clamp.

9 - Suspension system, according to claim 5, wherein the inner face of the sleeve (10) presents the same shape as the ewternal contour of spring (3).

- Suspension system, according to claim 5, wherein P-O the sleeve (10) has a length which is substantially equal to the free length of the spring (3).

11 - Suspension system, according to claim 4, wherein the absorbing element has the form of an elongated body (20) with its outer side surface of revolution defining the contact surface with the wire substantially of the spring (3).

12 - Suspension system, according to claim 11, wherein the outer side surface of the elongated body (20) has a shape which is equal to the inner contour of the spring (35.

13 - Suspension system, according to claim 11, wherein the elongated body (20) has a diameter which is slightly larger than the inner diameter of spring (3), so that said contact surface of the absorbing element can press the spring wire substantially radially outwardly.

I- 14 14 - Suspension system, according to claim ii, wherein the elongated body (20) has a length which is substantially equal to the length of spring (3).

- Suspension system, according to claim 4, wherein the absorbing element (10,20) is made of viscous elastic material, sufficiently soft so as to deform elastically in the regions of its contact surface which are pressed against the wire of the spring (3).

16 - Suspension system, according to claim i, wherein the absorbing element (30, 40) is attached to the wire surface of the spring (3) by the friction between said wire and the contact surface of the absorbing element, this friction being assured by the radial pressing of the absorbing element (30,40) against the coils of the spring (3), said absorbing element being made of a viscous-elastic material sufficiently tough to avoid a relevant elastic deformation, in terms of retention, in the regions of the contact surface of the absorbing element (30,40) which press the wire of the spring (3).

17 - Suspension system, according to claim 16, wherein the absorbing element is in the form of a sleeve (30) with its inner face defining the contact surface with the wire of the spring (3) and having a shape which is equal to that of the external contour of the spring (3).

18 - Suspension system, according to claim 17, wherein the sleeve (30) is longitudinally split, having an inner diameter which is slightly smaller than the outer diameter of the coils of the spring (.3), so that the inner surface of the sleeve (30) can press the coils of the spring (3) radially inwardly.

19 - Suspension systeffi, according to claim 18, wherein the sleeve (30) is surrounded by a pressing clamp (35).

- Suspension system, according to claim 19, T 1 is wherein the sleeve (20) is incorporated, as a single piece, to the inner face a+ the pressing clamp (35).

21 - Suspension system, according to claim 17, wherein the sleeve (30) has a length which is substantially equal to the free length of the spring (3).

22 - Suspension system, according to claim 16, wherein the absorbing element is in the form of an elongated plug (40) with its outer side surface of revolution defining a contact surface with the coils of the spring (2) and having a shape which is equal to the inner contour of the spring (3).

23 - Suspension system, according to claim 22, wherein the elongated plug (40) has a diameter which is slightly larger than the inner diameter of the spring (3), so that said contact surface of the absorbing element can press the spring wire radially outwardly.

24 - Suspension system, according to claim 22, wherein the elongated plug (40) has a length which is substantially equal to the free length of the spring (3).

- Suspension system, according to claim 22, wherein the elongated plug (40) has an axial hole (43) provided from at least one of the ends of the plug and inside which it is introduced an expander (45) dimensioned to make the outer diameter o+ the elongated plug, at the region of said axial hole (43) slightly larger than the inner diameter of the spring (3).

26 - Suspension system, according to claim 1, wherein the absorbing element takes the form of a coating (50) individually surrounding the spring coils.

27 - Suspension system, according to claim 26, 35 wherein the coating (50) is continuous.

29 - Suspension system, according to claim 26, 1 p 16 wherein the coating (50) is made of rubber which is aggregated on the wire of the spring (3).

29 - Suspension system, according to claim i, wherein the absorbing element is defined by a metallic cord 5 (60) surrounding helically the wire of the spring.

- Suspension system, according to claim 1, wherein it includes a pad (70) made of a material with a mechanical impedance being quite lower to that of spring (3), situated between one end of the spring (3) and its fixing point to the motor-pump unit (i) and/or housing (2).

1 i, Published 1991 al The Patent Office. Concept House. Cardiff Road. Newport. Gwent NP9 1RH. Further copies mav be obtained from Sales Branch. Unit 6. Nine Mile Point. Cx,.,Tnfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.