WO2009079727A1

WO2009079727A1 - System for attenuating pulsation in the gas discharge of a refrigeration compressor

Info

Publication number: WO2009079727A1
Application number: PCT/BR2008/000366
Authority: WO
Inventors: Eduardo De Souza Alvarenga
Original assignee: Whirlpool S.A.
Priority date: 2007-12-26
Filing date: 2008-12-03
Publication date: 2009-07-02
Also published as: US20100310389A1; JP2011508141A; EP2235370A1; BRPI0705357A2; KR20100092512A; CN101932835A

Abstract

The attenuation system is applied to a compressor which comprises: a cylinder (2) having an end closed by a valve plate (4) provided with a discharge orifice (4a) and defining, with the cylinder (2), a compression chamber (6), a cylinder cover (5) being seated against the valve plate (4) and defining a discharge chamber (7), which communicates with the exterior of the compressor through a discharge tube (8). The attenuation system comprises: at least one intermediary chamber (10) defined in the interior of the discharge chamber (7), in order to receive, from the discharge orifice (4a), the whole discharge flow coming from the compression chamber (6); and at least one connecting tube (20) mounted in the interior of the discharge chamber (7), having a first end (21) open to the interior of the intermediary chamber (10) and a second end (22) open to the interior of the discharge chamber (7).

Description

SYSTEM FOR ATTENUATING PULSATION IN THE GAS DISCHARGE OF A REFRIGERATION COMPRESSOR Field of the Invention

The present invention refers to an attenuating pulsation system to be applied in the gas discharge of a refrigeration compressor, for example of the reciprocating hermetic type and generally driven by a linear motor. Background of the Invention Refrigeration compressors are generally provided with pulsation attenuators or acoustic filters provided in the gas discharge. Such attenuators have the purpose of attenuating the pulsation of the gases which are pumped from the compressor to the refrigeration system to which said compressors are generally coupled or, in the generic case, to the high-pressure side of the refrigeration circuit to which the compressor belongs, as well as reducing the noise irradiated by the compressor to the external ambient. The pulsation of the gases generates an excitation in the ducts and components to which the discharge of the compressor is coupled, which in turn generates noise.

The attenuation of pulsations in the gas discharge of a compressor is generally carried out by: restricting the pumped refrigerant fluid flow, by reducing the diameter of the discharge tube, obtaining attenuation through load loss; or providing one or more expansion volumes disposed in series with the discharge tube, making the acoustic impedance discontinuity reflect pulsation acoustic waves existing in said tube, thereby attenuating the transmitted pulsation. In these constructions, the pulsation attenuating devices are incorporated to the cylinder block and/or to the discharge tube. The gas flow is forced to pass through a well defined sequence of tubes, volumes and restrictions located in the cylinder block and/or in the discharge tube, whose dimensions, arrangement and particular characteristics depend on the application, on the type and size of the compressor, on the mass flow, on the working fluid, on the temperatures and operation conditions, on the noise bands which are intended to attenuate, etc.

Although this discharge system solution presenting a configuration of volumes "in series" results in greater attenuation, it has the disadvantage of producing a higher load loss. This solution further presents the disadvantage of requiring large dimensions for the cylinder block to allow machining the volumes and discharge tubes. In compact compressors, for example, of the type not presenting a massive block and in which the cylinder block that defines part of the shell is very light, such known solution is not applied, since there is no space for incorporating an attenuator integrated to the cylinder block. Summary of the Invention It is a generic object of the present invention to provide a system for attenuating pulsation in the gas discharge of a refrigeration compressor, particularly of small dimensions, which enables attenuating discharge pulsations and noise, without presenting the load loss of the conventional constructions. Another object of the present invention is to provide a system for attenuating pulsations and noise, as cited above, which is easily constructed and mounted, mainly in a compressor without a massive block, particularly of the linear type. These objects are attained through a system for attenuating pulsation in the gas discharge of a refrigeration compressor of the type which comprises : a cylinder block defining a cylinder; a valve plate closing an end of the cylinder and provided with a discharge orifice and defining, with the cylinder, a compression chamber; a cylinder cover seated against a face of the valve plate opposite to that turned to the compression chamber and defining a discharge chamber; and a discharge tube communicating the discharge chamber to the exterior of the compressor. The attenuation system of the present invention comprises: at least one intermediary chamber defined in the interior of the discharge chamber, so as to receive, from the discharge orifice, the whole discharge flow coming from the compression chamber; at least one connecting tube mounted in the interior of the discharge chamber, having a first end open to the interior of the intermediary chamber and a second end open to the interior of the discharge chamber, said connecting tube projecting, by a certain extension, to the interior of at least one of the intermediary chamber and discharge chamber. Brief Description of the Drawings

The invention will be described below, upon reference to the enclosed drawings, given by way of example of an embodiment of the invention and in which: Figure 1 schematically represents a longitudinal sectional view of part of the discharge assembly of a linear motor reciprocating compressor of the prior art, particularly of the compact type, in which the shell is defined by the cylinder block and by the cylinder cover; Figure 2 schematically represents as in figure 1, a longitudinal sectional view of a linear motor compressor with the system for attenuating discharge pulsation of the present invention;

Figure 3 schematically represents a view similar to that of figure 2, but illustrating the system for attenuating pulsation provided with more than one intermediary chamber;

Figure 4 schematically represents an enlarged longitudinal sectional view of the cylinder cover of the compressor illustrated in figure 2, in which is provided the system for attenuating discharge pulsation of the present invention, for the embodiment illustrated in figure 2 ; Figure 5 graphically represents the attenuation results obtained for a prior art gas discharge system, having only one discharge volume in the discharge chamber

(dashed line) , and for a construction having a pulsation attenuation system, according to the present invention, presenting two gas discharge volumes in the interior of the cylinder cover; and

Figure 6 graphically represents the attenuation results obtained for a gas discharge arrangement for one and for two discharge volumes in the discharge chamber, in the interior of the cylinder cover, according to one of the ways of carrying out of the present invention. Description of the Illustrated Embodiments The present invention will be described for a reciprocating hermetic compressor which comprises a motor-compressor assembly having a cylinder block 1, which defines a cylinder 2, inside which a piston 3 is axially displaced by actuation of a motor (not illustrated) . In a particular compressor construction of the type driven by a linear motor, the piston 3 is connected to a resonant spring (not illustrated) and axially displaced in the interior of the cylinder 2 by an actuating assembly (not illustrated) , which supports a magnetic component (not illustrated) and which is axially driven upon energization of the linear motor.

The cylinder 2 has an open end, through which the piston 3 is housed, and an opposite end closed by a valve plate 4, against which is seated a cylinder cover 5. The valve plate 4 carries at least one of the suction valve and discharge valve, which regulate the gas inlet and outlet in relation to the interior of the cylinder 2. In the illustrated construction, the valve plate 4 is provided with a discharge orifice 4a, closed by a corresponding discharge valve 4b, and two suction orifices 4c, closed by a valve element 4d. In this illustrated construction, the valve plate 4 carries, on each one of its opposite faces, said discharge valve 4b and suction valve 4d. The valve plate 4 defines, with the interior of the cylinder 2, a compression chamber 6. The construction illustrated in figure 1 presents a conventional way of mounting the cylinder cover 5 to a cylinder block 1, which results in the deficiencies already discussed.

The cylinder cover 5 is seated against a face of the valve plate 4, which is opposite to another face of the latter and turned to the compression chamber 6, said cylinder cover 5 defining, with the adjacent face of the valve plate 4, a discharge chamber 7, which maintains a selective fluid communication with the compression chamber 6, through the discharge orifice 4a and discharge valve 4b, and a constant fluid communication with a discharge side of a refrigeration system to which the compressor is associated, through a discharge tube 8, which communicates said discharge chamber 7 to the exterior of the compressor.

The reciprocating movement of the piston 3 in the interior of the cylinder 2, in relation to the valve plate 4, determines, respectively, the gas suction operation and the gas compression operation in the compressor.

In some constructions of a compressor driven by a linear motor, the motor-compressor assembly is mounted in the interior of a shell, which forms a hermetic environment in relation to the exterior, said mounting being usually carried out on a set of suspension springs positioned in the interior of the shell. In the compact linear compressor constructions, the cylinder block 1 and the cylinder cover 5 define part of the shell.

According to the present invention, the refrigeration compressor includes a discharge attenuation system which comprises at least one intermediary chamber 10, defined in the interior of the discharge chamber 7, so as to receive, from the discharge orifice 4a of the valve plate 4, the whole discharge flow coming from the compression chamber 7, said intermediary chamber 10 maintaining constant fluid communication with the discharge chamber 7, through at least one connecting tube 20 mounted in the interior of the discharge chamber 7 and having a first end 21 open to the interior of the intermediary chamber 10, and a second end 22 open to the interior of the discharge chamber 7, said connecting tube 20 projecting, for example, by a certain extension, to the interior of at least one of the intermediary chamber 10 and discharge chamber 7. The solution of the present invention refers to a concept for an acoustic muffler of the volume-tube- volume type, which is not provided in the cylinder block 1 or in the discharge tube 8, but in the interior of the cylinder cover 5, presenting, as a first volume, an intermediary chamber 10 in which the gas is discharged through the opening of the discharge valve 4b and, as the last volume, the one defined adjacent to the discharge tube 8 in the cylinder cover 5, at least one of said volumes maintaining communication with an adjacent volume through a connecting tube 20 having an end open to the interior of the discharge chamber 7 and an end open to an adjacent intermediary chamber, as illustrated in figure 1. The volume of each intermediary chamber and of the discharge chamber, as well as the determination of the dimensions of each connecting tube 20 (extension, shape, cross-section) and the definition of the extension projecting from the latter to the interior of each chamber in which said connecting tube actuates, are defined as a function of the attenuation effect to be obtained and the pulsation range to be attenuated. According to the present invention, in case a plurality of intermediary chambers are provided in series, as illustrated in figure 3, they can be interconnected to each other by different connecting tube constructions, the fluid communication between each two consecutive and sequential intermediary chambers being carried out by at least one connecting tube 20 presenting, between its first end 21 and its second end 22, an extension calculated at least as a function of the main pulsation mode of the gas under compression to be attenuated. In a particular construction form with volumes in series, these are provided with overlapped intermediary chambers 10, a first of which in fluid communication with the discharge orifice 4a. In another particular construction, the intermediary chambers are disposed in surrounding layers, concentric or not.

In another way of carrying out the present invention, the volumes and tubes in series can be obtained with a sequence of volumes which are spaced apart and interconnected by connecting tubes 20. In a variant for any of these constructions, as well as for those illustrated herein, the first intermediary chamber 10, which receives the compressed gas directly from the compression chamber 6, is seated against the valve plate 4. In another constructive variant, within the concept presented herein, there is provided, between the discharge orifice 4a and a first of said intermediary chambers 10, a connecting tube 20, which maintains the first of the intermediary chambers 10 spaced from a seating condition against the valve plate 4.

For any of the constructions of volumes and tubes of the present invention, these are provided in order not to interrupt an intermittent gas mass flow being discharged to the discharge chamber, during compression, while attenuating the pulsations of this gas mass under compression.

Each intermediary chamber 10 is defined by a hollow body, of rigid of flexible structure, and which affixes a portion of a connecting tube 20, for example, by means of weld or glue, or also incorporating said tube portion in a single piece. Each intermediary chamber 10 is provided in the interior of the cylinder cover 5, so' that the only fluid communication thereof with an adjacent volume of an intermediary chamber 10, or with the discharge chamber 7, is made through one or more connecting tubes 20. In order to improve the attenuation of pulsations, at least one of the parts of intermediary chamber 10 and connecting tube 20 is provided or coated with acoustic insulating material. In the constructions in which the intermediary chambers 10 are seated against the valve plate 4, each said intermediary chamber 10 is attached to the valve plate 4 by an appropriate fixation means 40, such as glue, screw, weld, etc., or by a simple mounting interference of the cylinder cover 5, said fixation being carried out so as to prevent compressed gas leakage between a peripheral edge of the intermediary chamber 10 and an adjacent face of the valve plate 4.

In a constructive form for affixing the intermediary chamber to the valve plate 4 , said intermediary chamber presents its hollow body having an opening, whose contour is defined by a peripheral edge 10a, to be seated against the valve plate 4, and from which externally projects a peripheral flange 11, for example continuous, and which allows the fixation to the valve plate 4, through, for example, screws, as illustrated in figure 4. In another constructive option, the peripheral flange of the intermediary chamber 10 presents a determined extension, which is sufficient to externally seat, in its periphery, a peripheral edge portion of the cylinder cover 5, which is affixed to the cylinder jointly with said intermediary chamber.

According to a way of carrying out the present invention, each connecting tube 20 presents its respective first and second ends 21, 22 eccentrically disposed in the intermediary chamber 10 and discharge chamber 7, the second end 22 of the connecting tube 20 being disposed spaced from an open end of the discharge tube 8, turned to the interior of the discharge chamber 7.

According to another aspect of the present invention, each connecting tube 20 presents at least one of its first and second ends 21, 22 projecting to the interior of the respective intermediary chamber 10 and discharge chamber 7, by a determined extension previously calculated as a function of the pulsation mode to be attenuated. In the illustrated constructive form, the connecting tube 20 has each of its first and second ends 21, 22 projecting to the interior of the respective intermediary chamber 10 and discharge chamber 7 by a respective extension calculated as exposed above. According to another aspect of the present invention, each connecting tube 20 can be substituted by one or more holes defined in the part provided with said holes and so that the thickness of said part defines a tube extension presenting the ends as already described, without impairing the function thereof. In this case, the attenuation curve is that illustrated in figure 6.

Each intermediary chamber 10 carries the respective connecting tube(s) 20, which are incorporated thereto by fixation or formed in a single piece with the body of said intermediary chamber 10, upon obtention of the latter.

As a function of the extension to be presented by the connecting tube, said connecting tube 20 should be provided so as to present a spiral development, to the interior of at least one of the intermediary chamber 10 and discharge chamber 7, from a portion of its extension projecting to t-he interior of the respective chamber. In the construction illustrated in figure 4, the connecting tube 20 presents a spiral development, from its first end 21, in the portion of its extension externally projecting from the hollow body of the intermediary chamber 10 that carries it. As a function of the reduced space available in the interior of the cylinder cover 5, the connecting tube 20 presents its spiral portion accompanying at least part of the outer peripheral contour of the intermediary chamber. However, it should be understood that the illustrated constructive form should not be considered as limitative for the development arrangement of the connecting tube 20, but only as a constructive option.

It should also be observed that the constructive variants described herein can be individually presented in particular constructions, or also partially or totally combined to each other.

As can be observed in figures 5 and 6, the solution for the pulsation attenuation system of the present invention presents a substantial attenuation gain in a wide band spectrum, said attenuation being of up to 50 decibel in some specific bands in relation to the prior art constructions.

Claims

1. A system for attenuating pulsation in the gas discharge of a refrigeration compressor of the type which comprises: a cylinder block (1) defining a cylinder (2) ; a valve plate (4) closing an end of the cylinder (2) and provided with a discharge orifice (4a) and defining, with the cylinder (2) , a compression chamber (6) ; a cylinder cover (5) seated against a face of the valve plate (4) opposite to that turned to the compression chamber (6) and defining a discharge chamber (7) ; a discharge tube (8) to communicate the discharge chamber (7) with the exterior of the compressor, characterized in that it comprises:

- at least one intermediary chamber (10) defined in the interior of the discharge chamber (7) , so as to receive, from the discharge orifice (4a) , the whole discharge flow coming from the compression chamber (6) ;

- at least one connecting tube (20) mounted in the interior of the discharge chamber (7) , having a first end (21) open to the interior of the intermediary chamber (10) and a second end (22) open to the interior of the discharge chamber (7) , said connecting tube (20) projecting, by a certain extension, to the interior of at least one of the intermediary chamber (10) and discharge chamber (7) .

2. The system, as set forth in claim 1, characterized in that the first and second ends (21, 22) of the connecting tube (20) are eccentrically disposed in the intermediary chamber (10) and discharge chamber (7) .

3. The system, as set forth in claim 2, characterized in that the connecting tube (20) presents, between its first end and its second end (21, 22) , an extension calculated as a function of the main pulsation mode of the gas under compression to be attenuated.

4. The system, as set forth in claim 3, characterized in that the first end (21) of the connecting tube (20) projects to the interior of the intermediary chamber (10) , by a determined extension previously calculated as a function of the pulsation mode to be attenuated.

5. The system, as set forth in claim 1, characterized in that the connecting tube (20) presents a spiral development, from its first end (21) and which extends at least along the extension of the connecting tube (20) which is internal to the discharge chamber (7) .

6. The system, as set forth in claim 1, characterized in that the connecting tube (20) is formed in a single piece with the intermediary chamber (10) .

7. The system, as set forth in claim 1, characterized in that at least one of the parts of intermediary chamber (10) and connecting tube (20) is provided in an acoustic insulating material.

8. The system, as set forth in claim 1, characterized in that the second end (22) of the connecting tube (20) is disposed spaced from the open end of the discharge tube (8) .

9. The system, as set forth in claim 1, characterized in that the intermediary chamber (10) is hermetically attached to the valve plate (4) .

10. The system, as set forth in claim 9, characterized in that the intermediary chamber (10) is a hollow body having an opening whose contour is defined by a peripheral edge (10a) to be seated and affixed against the valve plate (4) .

11. The system, as set forth in claim 10, characterized in that the hollow body is rigid.