Device for damping pressure pulsations for a compressor of a caseous fluid

A process for manufacturing a device and the device for damping pressure pulsations for a compressor of a gaseous fluid, in particular a refrigerant, in a refrigerant circuit of a motor vehicle air-conditioning system. The device exhibits a housing that encompasses a chamber and features at least two outlet openings. Here, the housing is constructed between tubular connecting lines, whose ends are aligned with one another. An insert element for reducing the cross-sectional area of the pass-through opening is arranged inside at least one of the pass-through openings.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a United States nation phase patent application based on PCT/KR2020/009307 filed on Jul. 15, 2020, which claims the benefit of German Patent Application No. 10 2019 123 902.8 filed on Sep. 5, 2019, the entire disclosures of which are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a device for damping pressure pulsations for a compressor of a gaseous fluid, in particular a refrigerant, in a refrigerant circuit of a motor vehicle air-conditioning system. The device exhibits a housing that encloses a chamber and displays at least two pass-through openings. The housing is produced between tubular connecting lines, whose ends/faces are aligned with one another.

BACKGROUND ART

Compressors for mobile applications that are known from the state of the art, particularly for air-conditioning systems in motor vehicles, and are used to pump refrigerant through a refrigerant circuit, in the following also referred to as refrigerant compressors, are often classified as variable stroke or variable displacement piston compressors or as scroll compressors, irrespective of the refrigerant. Particularly in the case of refrigerant compressors that are driven via a belt and belt pulley, the speed is determined by the speed of the motor vehicle, in particular by the rotary speed of the engine. Variable stroke piston compressors guarantee consistent operation of the air-conditioning system, as the compressor delivers a required constant or variable output regardless of the speed of the engine.

During operation of the compressor, pressure pulsations are generated and transferred to the air conditioning unit arranged in the passenger compartment via connecting lines of the refrigerant circuit. Thanks to its design, the air conditioning unit acts as a large, even surface and thereby resembles a kind of loudspeaker or amplifier for the pulsations. The noise that is generated in n circumstances, in particular at resonant frequencies, is therefore perceived directly by the driver.

For the reasons stated, conventional compressors are produced with a device for damping and reducing the pressure pulsations that occur. The function of the device for damping the pressure pulsations lies in altering a flow cross-section, in particular a sudden change in flow cross-section, for the fluid compressed by the compressor. The sudden change in flow cross-section causes an increased pressure pulsation loss, which in turn reduces the pressure pulsations that are transmitted to the vehicle interior by the connecting line of the refrigerant circuit and generate the noise.

EP 2 357 330 A1 discloses a silencer for use in a tubular component that forms a cavity with a flow channel and at least one resonator chamber. The resonator chamber is connected to the flow channel via a connection channel.

Fittings of this kind, which are installed in connecting lines, designed to act as silencers and require virtually no additional installation space, display either inadequate noise insulation or are only effective within a specific frequency range.

In addition to this, so-called reflective silencers with a housing that encloses a cylindrical volume and employs openings on the faces arranged opposite one another to allow the fluid to flow in and out are already known from the state of the art. The openings each exhibit a significantly smaller diameter than the housing, meaning that the sudden changes in diameter formed at the openings for the fluid flowing through the housing lead to a sudden change in flow cross-section. As a result of the impedance jump generated with the sudden change from the smaller internal diameter of the refrigerant circuit connecting line to the large internal diameter of the housing, or the internal volume of the silencer, the sound waves that occur as pressure pulsations in the line are damped.

As well as requiring a lot of space, the known silencers typically exhibit additional elements that need to be manufactured, as well as an internal arrangement that is complex and therefore costly to produce. This in turn increases both the time and cost of manufacturing.

DE 11 2015 000 105 T5 presents a silencer that encloses a cavity. The silencer exhibits two pot-shaped elements that are connected at open ends, which are aligned and in contact with one another, by brazing or welding. The open ends are each provided on a first face of the elements. In addition to this, a base of the pot-shaped elements is produced as a permanent component of a connecting line of a refrigerant circuit on a second face that is arranged distally to a first face. The base exhibits one pass-through opening with a smaller diameter than the connecting line.

Here, the connecting line is produced with an increased wall thickness in the area of the transition to the pot-shaped element, which, alongside increased material requirements, for example also leads to forming limitations, as well as greater costs—in particular when bending the connecting lines.

The silencers known from the state of the art require a very large installation space in order to achieve a significant damping effect. In modern motor vehicles, however, and in passenger vehicles in particular, the installation space is very limited, meaning that the intended silencers either do not achieve an adequate damping effect or that they must be removed altogether.

SUMMARY

The object of the invention lies in provision or improvement of a device for damping pressure pulsations, in particular for a compressor of a gaseous fluid in a refrigerant circuit, that offers maximum noise insulation over a broad frequency range. The objective here is in particular to achieve improved damping characteristics with improved noise damping performance over conventional silencers with the same dimensioning or at least similar damping characteristics and at least the same noise damping performance in combination with reduced device space requirements, as well as in particular to avoid a low-frequency damping drop-off. The pressure losses should be minimal. Among other things, damping of the pressure pulsations should help avoid noise emissions, which have an impact on comfort, for example for passengers sitting inside a vehicle interior. The device should exhibit a simple design, comprising a minimal number of components with minimal space requirements, minimal material usage and thereby minimal weight. In addition to this, the manufacturing and assembly costs should be minimal.

The task is solved by the subject matter with the characteristics as shown and described herein.

The task is solved by a device according to the invention for damping pressure pulsations for a compressor of a gaseous fluid, in particular a refrigerant. The device exhibits a housing that encloses a chamber with at least two pass-through openings. The housing is produced between tubular connecting lines, whose ends/faces are aligned with one another.

According to the design of the invention, an insert element for reducing the cross-sectional area of the outlet opening is arranged inside at least one of the outlet openings.

The pass-through openings, advantageously produced as openings with a circular cross-section, each preferably exhibit a diameter that corresponds to an internal diameter of the connecting lines. In particular the two pass-through openings should preferably be arranged and aligned on a common axis.

As per a further embodiment of the invention, the housing is produced with a rotation symmetrical configuration around a longitudinal axis. Here, an internal diameter of the housing is preferably larger than the internal diameter of the connecting lines.

As per an advantageous embodiment of the invention, the housing exhibits two housing elements, which are aligned with one another as first faces produced with open ends and also attached to one another on the first faces, in particular by brazing or welding. Here, each housing element can be produced as a permanent component of one end of a connecting line.

The housing elements advantageously each exhibit a base on a second face that is aligned distally to the first face in a longitudinal direction x. One pass-through opening is in particular provided within the base here.

According to another preferred embodiment of the invention, a first pass-through opening is produced as an inlet opening and a second pass-through opening is produced as an outlet opening of the chamber. The inlet opening and the outlet opening are preferably arranged and aligned on a symmetry axis of the device, in particular the longitudinal axis of the housing.

Another advantage of the invention lies in the fact that a first insert element is arranged inside the inlet opening and a second insert element is arranged inside the outlet opening to reduce the cross-sectional area of the outlet opening.

The respective insert element preferably essentially exhibits the shape of a hollow cylinder, in particular a hollow circular cylinder. Here, the insert element is preferably constructed with an external diameter that corresponds to the diameter of the pass-through opening or the internal diameter of the connecting line. After inserting the insert element into the pass-through opening, a shell surface area of the insert element is in contact with the external diameter on the perimeter wall of the pass-through opening or the internal surface of the wall of the connecting line. The insert element is held in place via an interference fit here.

As per a further embodiment of the invention, the insert element, preferably produced from a plastic, exhibits a total length Liand is arranged in such a way that it penetrates into the chamber with a certain length L0. Here, the length L0that penetrates into the chamber of the insert element is lower than the total length Liand greater than or equal to zero. Alongside the total length Liand the internal diameter, the insert element can also, depending on requirements, be constructed with a length L0that penetrates into the chamber.

With integration of the at least one insert element in the device, as well as the targeted design and arrangement of the insert element, pressure pulsations of the compressor are damped, in particular also at targeted disturbing frequencies.

According to another advantageous embodiment of the invention, the first insert element is constructed with an inlet section. The inlet section exhibits a constant external diameter and a continuously reducing internal diameter in the flow direction of the fluid. The inlet section is provided at the end of the first insert element into which fluid flows.

The second insert element is preferably constructed with an outlet section that exhibits a constant external diameter and a continuously increasing internal diameter in the flow direction of the fluid. The outlet section is provided at the end of the second insert element at which fluid flows out.

The device according to the invention for damping pressure pulsations is preferably used in a refrigerant compressor of a refrigerant circuit, in particular a motor vehicle air-conditioning system.

Here, one of the pass-through openings, in particular the outlet opening of the device, is preferably connected to an intake area of the compressor, while the inlet opening is advantageously produced as a connection to a low-pressure side of the refrigerant circuit. The device is intended for use with both electrically driven and mechanically driven compressors.

The task is also solved by an inventive method for manufacturing the device according to the invention for damping pressure pulsations for a compressor of a gaseous fluid, in particular a refrigerant. This method exhibits the following steps:Widening of one end of a connecting line up to an internal diameter of a chamber and forming the end of the connecting line as a housing element with a base and one open end or one open face.Widening of a first housing element in the area of the widened end and producing a flange of a flange connection on the housing elements in such a way that the internal diameter of the first housing element at the open end corresponds to an external diameter of the second housing element at the open end plus sufficient play for connecting the housing elements.Inserting prefabricated insert elements into pass-through openings produced in the housing elements.Assembly (insertion into one another) of the housing elements, in particular insertion of the second housing element into the first housing element at the flange connection.Fluid-tight connection of the housing elements, in particular by welding or brazing.

In summary, the device according to the invention for damping pressure pulsations for a compressor exhibits various advantages:Reduction of disturbing pressure pulsations that negatively impact the interior acoustics of a motor vehicle or avoidance of noise emissions that have a negative effect on comfort, for example for passengers inside the vehicle.Improved damping characteristics with improved noise damping performance over conventional silencers with the same dimensioning or at least similar damping characteristics with at least the same damping performance, while requiring less space.Minimal pressure losses, as well as minimal influence on the power consumed by the compressor while in operation.Simple design, comprising a minimal number of components with minimal space requirements.Minimal manufacturing and assembly costs.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG.1shows a device1′ for damping pressure pulsations for a compressor inside a chamber3enclosed by a housing2′, provided as an axial longitudinal section from the state of the art.

The produced housing2′ that encloses the chamber3exhibits a first housing element2a′ and a second housing element2b′, which are attached to one another by brazing or welding at open ends that are facing and in contact with one another. The open ends are each provided on a first face of the housing elements2a′,2b′. On a first face arranged distally relative to the second face, the housing elements2a′,2b′ each exhibit a base4a,4b. A pass-through opening6a′,6b′ is provided in the bases4a,4bof the housing elements2a′,2b′, each of which represents a permanent component of a connecting line5of a refrigerant circuit. The diameters of the pass-through openings6a′,6b′ are preferably identical and smaller than the internal diameter of the connecting line5.

The connection of the connecting line5to the base4a,4bis produced with a transition area7′ in each case. Within the transition area7′, the connecting line5exhibits a constant external diameter, which also corresponds to the external diameter of the connecting line5in sections of the refrigerant circuit located away from the device1′ and expands in the area of the base4a,4b.

The internal diameter of the connecting line5is constant in the direction of the device1′ up to the transition area7′ and then continuously decreases within the transition area7′. The internal diameter of the connecting line5is minimal in the area of the base4a,4band corresponds to the diameter of the respective pass-through opening6a′,6b′. The wall thickness of the connecting line5continuously increases in the transition area in the direction of the device1′.

FIGS.2A and2Bprovide a comparison between a conventional device1′ and a device according to the invention1for damping pressure pulsations for a compressor, each shown as an axial longitudinal section with calculation parameters.

The damping behaviour DTLof a reflective silencer, also known as the transmission loss coefficient DTL, can be calculated on the basis of the frequency or wavelength to be damped and the installation space available using the following formula (source: Wallin, H.-P., Carlsson, U., Abom, M., Boden, H., & Glab, R. (2012). Sound and vibration [Book]. Stockholm, Sweden: The Marcus Wallenberg Laboratory.):

The installation space is dictated by the internal diameter of the chamber3. The inner volume of the chamber3or the volume enclosed by the housing2′ is defined on the basis of the length L in the longitudinal direction x, as well as the cross-sectional area S2. S1corresponds to the cross-sectional area of the pass-through openings6a′,6b′ for fluid entry into the chamber3, as well as for fluid exit from the chamber3, while k corresponds to the wave number as k=2π/λ. As a result, the damping behaviour DTLof the device1′ produced as a reflective silencer is also dependent on the flow cross-section S1of the inlet opening6a′ and the outlet opening6b′, as well as the inner flow cross-section S2of the chamber3.

When fluid flows through the device1′ with the chamber3and the pass-through openings6a′,6b′, the pressure pulsations are reduced by the level of transmission loss coefficient DTL.

Consequently, the damping behaviour DTLof a reflective silencer is determined by the length of the chamber3, in particular the inner volume of the chamber3, and an expansion ratio. The expansion ratio is understood to mean the ratio between the internal diameter of the chamber3and the diameter of the pass-through openings6a′,6b′.

In order to improve the damping behaviour DTLof the reflective silencer with constant inner volume of the chamber3, in particular with consistent length L and consistent cross-sectional area S2(in other words essentially the same housing2with constant installation space), the cross-sectional area S1of the pass-through openings6a,6b, in particular inlet opening6aor outlet opening6b, can be reduced to a cross-sectional area S1*. In particular, this changes the expansion ratio.

The expansion ratio, and thereby the damping behaviour DTL, of the reflective silencers can also be kept constant with a smaller installation space.

As can in particular be seen inFIG.2B, the cross-sectional areas of the pass-through openings6a,6bof the device1are each reduced by the arrangement of an insert element8a,8b. Firstly, a length Liof the area that changes the cross-section of the insert elements8a,8bhas an effect on the damping behaviour DTL. Secondly, the damping behaviour DTLis also influenced by the insert elements8a,8breaching into the chamber3. Here, the insert elements8a,8bare arranged with a section of length L0inside the chamber3.

FIG.3Ashows an embodiment of a device according to the invention1for damping pressure pulsations for a compressor with insert elements8a,8binside a chamber3that is enclosed by the housing2, depicted as an axial longitudinal section.

The housing2is produced with a first housing element2aand a second housing element2b. The housing elements2a,2bare aligned with one another, with the open ends arranged in contact, and then connected to one another in particular by brazing or welding. Here, the housing elements2a,2bare each arranged with a first face facing each other. On a first face that is aligned distally in the longitudinal direction x to the second face, the housing elements2a,2beach exhibit a base4a,4b. The housing elements2a,2bare produced with the bases4a,4beach as a permanent component of a connecting line5of a refrigerant circuit. One pass-through opening6a,6bis provided within each of the bases4a,4b. The diameters of the pass-through openings6a,6band the internal diameters of the connecting lines5are preferably identical.

The connecting lines5are produced with both a constant external diameter and a constant internal diameter, in other words with a constant wall thickness.

With the pass-through openings6a,6b, the housing2that encloses the chamber3exhibits an inlet opening6a, as well as an outlet opening6b, each of which are produced in the base4a,4bof the housing elements2a,2b. The fluid that is to be compressed when flowing through the compressor flows through the connecting line5and the inlet opening6ain the longitudinal direction x into the chamber3of the device1and then back out the chamber3and into the connecting line5through the outlet opening6b. Here, the inlet opening6ais produced as a connection to a low-pressure side of the refrigerant circuit, while the outlet opening6bis connected to an intake area of the compressor via the connecting line5. The inlet opening6aand the outlet opening6bare aligned with one another coaxially, i.e. on a common axis, which also corresponds to the symmetry axis or the longitudinal axis of the device1.

When manufacturing the device1, a pressing tool is used to widen one end of a connecting line5up to a final diameter in a cold forming process, wherein the end of the connecting line5then represents a housing element2a,2bwith the base4a,4b.FIG.3Bshows the first housing element2aof the housing2of the device1as perFIG.3Ain four different conditions and the second housing element2bin three different conditions, each during manufacture.

After widening two connecting lines5up to an internal diameter of the chamber3to be produced later in two shown steps, the first housing element2ais widened further at the open end in a further step, in particular a third step shown, in order to produce a flange for the flange connection of the housing elements2a,2b. The first housing element2ais widened on the open face in such a way that the internal diameter then corresponds to the external diameter of the second housing element2bin the widened section plus enough play to connect the housing elements2a,2bto one another.

After inserting the prefabricated insert elements8a,8binto the housing elements2a,2band connecting the housing elements2a,2bwith one another, in particular inserting the second housing element2binto the first housing element2a, the housing elements2a,2bare, for example, brazed or welded to one another in order to guarantee a fluid-tight connection of the housing2.

The essentially hollow cylinder-shaped, specifically circular hollow cylinder-shaped, insert elements8a,8b, in particular to reduce the cross-sectional areas S1of the pass-through openings6a,6b, are preferably manufactured from a plastic and exhibit an external diameter that corresponds to the internal diameter of the connecting line5. This secures fluid-tight insertion of the insert element8a,8binto the respective housing element2a,2b, in particular via an interference fit. Here, fluid-tight insertion is understood to mean that the outer shell surface area of the insert element8a,8bis in fluid-tight contact with the internal surface of the connecting line5and thereby that the entire mass flow of the fluid is guided through the respective insert element8a,8b. Any occurrence of a bypass flow of the fluid on the outside of the insert element8a,8bis prevented. The insert elements8a,8b, preferably produced from a plastic, are to be formed very flexibly, wherein the use of other easily formable materials can be provided for the insert elements8a,8b.

The insert elements8a,8bare matched to the necessary areas of application, in particular the specific frequency ranges in which targeted damping is to be achieved, in terms of their shape, in particular with regard to their total length L1and cross-sectional area S1*. Alongside the total length L0and an internal diameter of the insert element8a,8b, the length L0of the insert element8a,8bcan also be varied inside the chamber3.

When the housing elements2a,2bhave been assembled and connected, the device1preferably exhibits a length of around 50 mm and external diameter of around 37 mm with a wall thickness of around 1.5 mm. In the area where they are connected to one another, the housing elements2a,2bare arranged with an overlap of around 5 mm to one another.

Construction of a conventional device1′ with an internal diameter of the chamber3of 48 mm and an internal diameter of the connecting lines5of 16 mm results in an expansion ratio of 3. In the case of a space-saving embodiment of the device1with an internal diameter of the chamber3of 36 mm and the same length L, the diameter of the pass-through openings6a,6bis reduced to 12 mm in order to keep the expansion ratio, and thereby also the damping behaviour DTL, constant. Alongside the same length L and expansion ratio, the device according to the invention1also delivers the same performance as the conventional device1′.

FIG.4compares transmission losses or damping behaviour based on the frequency of a reflective silencer known from the state of the art, a conventional device1′ as perFIG.1and a device according to the invention1as perFIG.3Afor damping pressure pulsations within a refrigerant circuit that employs R134a as the refrigerant.

It becomes clear here that the device according to the invention1in the space-saving embodiment can close a gap that occurs in the damping behaviour, in particular in the low frequency range, for example in the range up to around 800 Hz, between a reflective silencer known from the state of the art and the conventional device1′ as perFIG.1. Particularly in the stated frequency range, the pressure pulsation damping performance of the device1is greater than that of the conventional device1′.

FIGS.5A and5Bshow and compare detailed depictions of the device1for damping pressure pulsations for a compressor, in particular the housing elements2a,2bwith the insert elements8a,8b, under variation of the total length Liof the insert elements8a,8bwith a constant internal diameter of 12 mm, as well as the transmission losses or damping behaviour of the device1with the various insert elements8a,8bbased on the frequency inside a refrigerant circuit. The insert elements8a,8bare each arranged in such a way that they do not reach into the chamber3of the device1. The length L0of the insert elements8a,8binside chamber3is therefore zero in each case.

The total length Li, of the insert elements8a,8bvaries between 5 mm (a), 10 mm (b), 25 mm (c) and 50 mm (d), while the internal diameter exhibits the value of 12 mm.

FIG.5Bclearly shows that the damping behaviour of the device1is improved with increasing total length Li, of the insert elements8a,8b.

FIGS.6A and6Bprovide a comparison that includes detailed depictions of the device1for damping pressure pulsations for a compressor, in particular the housing elements2a,2bwith the insert elements8a,8b, under variation of the internal diameter of the insert elements8a,8b, each with constant total length Li, and constant length L0penetrating into both the volume of the device1and the connecting line5, as well as the transmission losses or damping behaviour of the devices1with the various insert elements8a,8bbased on the frequency inside a refrigerant circuit. The total length Li, of the insert elements8a,8bis 65 mm in each case, while the insert elements8a,8bare each arranged in such a way that they reach into the chamber3of the device1with a length L0of 15 mm.

The internal diameter of the insert elements8a,8bvaries between 11 mm (d), 12 mm (e) and 13 mm (f).

FIG.6Bclearly shows that the damping behaviour, in particular the high-frequency damping behaviour of the device1, is improved over a known reflective silencer above a certain frequency. In addition to this, the damping behaviour of the device1is in particular improved as the internal diameter of the insert elements8a,8bis reduced.

With the production and arrangement of the insert elements8a,8binside the housing elements2a,2b, a desired internal geometry of the device1is created which in particular increases the low-frequency pressure pulsation damping effect and, at the same time, reduces the drop in pressure when the fluid flows through the device1.

Consequently, the improved pressure pulsation damping effect primarily occurs in operating states with a low mass flow to be transported, and thereby a low compressor load, which should be considered highly critical in the context of pressure pulsations in vehicles.

As shown in particular byFIGS.5A and6A, the first insert elements8aare each produced with an inlet section. Inside the inlet section, the insert element8aexhibits an internal diameter that reduces in the flow direction of the fluid and then remains constant from the end of the inlet section, while maintaining a constant external diameter. The wall thickness of the first insert element8ainside the inlet section is therefore continuously reduced in the direction of the chamber3.

The internal diameter of the second insert element (not shown) in the flow direction of the fluid is also constant up to an outlet section and then increases continuously inside the outlet section, meaning that the wall thickness of the second insert element inside the outlet section continuously decreases in the direction away from the chamber3.

The internal diameter of each of the insert elements8a,8bis minimal in the area of the end open to the chamber3.

LIST OF REFERENCE NUMBERS

1,1′ Device2,2′ Housing2a,2a.′ First housing element2b,2b′ Second housing element3Chamber4aBase of the first housing element3a4bBase of the second housing element3b5Connecting line6a,6a.′ Pass-through opening, inlet opening, fluid flow path6b,6b′ Pass-through opening, outlet opening, fluid flow path7′ Transition area8aFirst insert element8bSecond insert elementDTLDamping behaviour, transmission loss coefficientS1Cross-sectional area of pass-through openings6a,6b,6a.′,6b′S1* Reduced cross-sectional areaS2Cross-sectional area with inner volume of chamber3in the longitudinal direction xL Length of inner volume of chamber3LiLength of altered cross-section area, length of insert element8a,8bL0Length of insert element8a,8binside chamber3k Wave numberλ Wavelengthx Longitudinal direction