The present invention relates to a coolant circuit of a cooling system with a pipe-shaped body, into which a sound absorber is inserted. A resonator sound absorber for pipes is known from DE 43 27 562 Al, for example. A sound absorber for pipes through which hot gases flow having multiple concentrically situated sound absorbing chambers is known from this publication. DE 196 47 425 Al describes an acoustic resonator which has multiple resonator chambers. The resonator chambers may be situated along the interior circumference or on the exterior circumference of the pipe.

Another sound absorber having resonator chambers situated on the exterior circumference of the pipe is known from DE 101 02 040 Al .

The above-mentioned sound absorbers have the disadvantage that they are complex and expensive to manufacture. In addition, they require a large installation space which is frequently not available, particularly in applications for the automobile industry.

DE 10 2004 029 221 Al describes a sound absorber for an air intake system of a combustion engine. The object of the present invention is to improve the sound insulation of a cooling system. This object is achieved with a coolant circuit of a cooling system with a pipe-shaped body, into which a sound absorber is inserted, whereby the body forms a cavity and whereby the sound absorber is designed as an insert which is inserted into the cavity of the pipe-shaped body and whereby the insert delimits at least one resonator chamber and a flow channel which is connected to the resonator channel via a connection channel.

This design enables effective absorption of noises by using the acoustic resonator principle. The gas volume enclosed in the resonator chamber is connected to the flow channel via the preferably narrow connection channel. A mechanical mass-spring system having a distinct natural resonance occurs due to the elasticity of the gas volume in the interior of the resonator chamber in combination with the inert mass of the gas situated in the connection channel.

Occurring noise may be effectively reduced due to this natural resonance. If the frequency of the noise source is known, the natural frequency of the resonator chamber may be adjusted to this. In order to enable absorption of noises in different frequency ranges, multiple resonator chambers each having different natural frequencies may be provided. According to the present invention, the sound absorber is designed as an insert, the insert forming the at least one resonator chamber and the flow channel. In this way, the sound absorber is particularly easily manufacturable. It is sufficient to place the insert into the pipe-shaped body. Further adaptations to the pipe-shaped body are not absolutely necessary. Moreover, the sound absorber does not require any additional installation space on the exterior of the pipe-shaped body. In this way, the assembly may be carried out particularly easily since the sound absorber is manufactured

separately and needs only be inserted into the pipe-shaped body. The manufacturing costs are also low due to the design of the sound absorber as an insert. A sound absorber of this type is particularly suitable for pipe-shaped bodies through which at least partially gas flows. The sound absorber is particularly suitable for closed circuit systems such as cooling circuits. The insert is inserted in a cooling circuit of a cooling system in order to effectively dampen the noises of the compressor. The sound absorber is particularly suitable for mobile cooling systems, e.g., in a motor vehicle. The sound absorber

according to the invention has a pipe-shaped body which is inserted in the coolant circuit of a cooling system. The pipe-shaped body may have a rigid or a flexible design. The pipe-shaped body is

advantageously a flexible hose made of plastic, for example.

According to an advantageous embodiment of the present invention, it is provided that the insert has a partition which forms the flow channel and separates it from the at least one resonator chamber. The partition may be formed here by a section of the insert which forms an inner pipe. In this way, a sound absorber is obtained which may be easily manufactured and assembled. The inner pipe forms the flow channel in the interior of the sound absorber. This may be placed coaxially in the pipe-shaped body. The inner pipe may have a round or an angular cross section. The flow channel is preferably situated in the interior of the inner pipe, while the at least one resonator chamber is formed on the exterior of the inner pipe, in the space formed between the inner pipe and the pipe-shaped body. An inner cross section area of the inner pipe advantageously changes in the axial direction of the insert. This may be achieved in particular in such a way that the inner pipe, starting from an inlet cross section area at an inlet of the sound absorber, narrows to an intermediate cross section area and expands from there to an outlet cross section area at the outlet of the sound absorber. In this way, the space for the resonator chamber or resonator chambers may be created using the insert without having to modify the pipe-shaped body. Nonetheless, a low flow resistance for a gas flowing through the flow channel may be obtained. This flow resistance is kept particularly low if the change in the inner cross section area in the axial direction does not occur suddenly. This may be achieved by a conical design of the inner pipe, at least in some sections. If the inlet cross section area and the outlet cross section area of the sound absorber correspond essentially to the inner cross section area of the pipe-shaped body, further adjustments of the insert or of the pipe-shaped body are not necessary in order to guide the fluid into the flow channel. The inner pipe advantageously fits tightly on the pipe-shaped body in the areas of the inlet and the outlet of the sound absorber.

One advantageous embodiment of the present invention provides that the insert has at least one web, pointing to the outside, for fitting on the inner wall of the pipe-shaped body, the at least one web delimiting the resonator chamber in an axial direction of the insert. The web may be situated on the exterior of the inner pipe and forms a spacer. In this way, the space required for the resonator chamber is formed between the inner pipe and the pipe- shaped body. The web may be designed as a circumferential ring-shaped bead, for example. In addition, such a web is advantageous when the sound absorber is used in a curved pipe-shaped body. With the web fitting on the pipe- shaped body, the insert is able to adapt to the radius of curvature of the pipe-shaped body even if it is manufactured without a curvature or with a different curvature.

A particularly compact configuration results when the web separates two adjacent resonator chambers. In this case, the sound absorber may have, in a simple manner, multiple resonator chambers which are attuned to different natural frequencies, which makes it possible to reduce sound in different frequency ranges. For example, in order to form multiple resonator chambers, multiple webs may be provided spaced in the axial direction, one web separating two resonator chambers.

Easy manufacture and assembly also result due to the fact that the connection channel is formed by a channel-shaped section in the partition. Additional components are not necessary in this design. The insert may advantageously be a one-piece component together with the partition and the connection channel which may be manufactured as a contiguous injection-molded part. The length and the diameter of the connection channel (or of the connection channels) may be selected according to the Helmholtz resonator principles in such a way that the respective natural frequency of the resonator chamber is in the intended frequency range. The channel-shaped section

advantageously runs in the radial direction.

A further improvement is achieved by the fact that the at least one resonator chamber has, in an axial direction of the insert, a changing inner diameter while the outer diameter remains constant. In this way, in particular the flow resistance in the flow channel may be kept low.

The usability and the assembly are further improved when the sound absorber is made of an elastically bendable material. In this way, the sound absorber may be inserted into pipe-shaped bodies having a curve or into flexible hoses. For example, an elastic plastic may be used as the elastically bendable material. In this way it may be achieved that the ends of the insert may assume a bending angle to one another of more than 5°, in particular more than 20°, and advantageously up to 90°. Effective noise absorption in multiple frequency ranges may

advantageously be achieved in that multiple resonator chambers are formed in the axial direction adjacent to one another which are each connected to the flow channel via a connection channel. Each of the resonator chambers may be attuned to a different natural frequency. It has been proven advantageous in practice to provide up to four resonator chambers adjacent to one another which make it possible to reduce the noise in a corresponding number of frequency ranges.

Depending on the application, one single resonator chamber may be sufficient or a greater number of resonator chambers may be provided.

The at least one resonator chamber is advantageously delimited on its exterior by a wall of the pipe-shaped body. In particular, the resonator chamber may be delimited to the outside by the interior of the pipe- shaped body which then forms the exterior of the resonator chamber while it is delimited to the interior by the insert. As an alternative, the insert may also have an additional wall which delimits the resonator chamber or the resonator chambers in the radial direction to the outside.

For being fixed in the pipe-shaped body, the insert advantageously has a clamping zone on its exterior, which is used for fixing the sound absorber after being inserted into the pipe-shaped body. Fixing is particularly simple if the pipe-shaped body is made of a deformable material and is fastened to the clamping zone by a clamping device such as a hose clamp, for example. The pipe-shaped body may be made of an elastically deformable material, e.g., plastic, or a ductile material, e.g., aluminum, which is stamped into the clamping zone. In order to obtain a good fastening, the clamping zone may be delimited by a clamping edge on one or both sides. This makes it possible to achieve a positive fit between the insert and the pipe-shaped body. The clamping edge may be formed by the web. A compact configuration may be achieved if the clamping edge has breakthroughs because the volume on both sides of the clamping edge may be part of a resonator chamber. The pipe-shaped body advantageously has the same diameter in the area in which the insert is situated and in the areas adjacent in the axial direction. Modifications on the pipe-shaped body, in particular a widening, in order to provide the resonator chambers there, are not necessary. The insert may simply be inserted into the pipe-shaped body, which may be continuous, for example.

Further objectives, features, advantages, and application options of the present invention arise from the following description of exemplary embodiments based on the drawing. All described and/ or depicted features by themselves or in any combination form the object of the present invention, also independently of their being combined in individual claims or of their back reference.

Figure 1 shows a sectional view of a sound absorber according to the present invention inserted into a straight pipe-shaped body.

Figure 2a shows a perspective view of a sound absorber according to the present invention from Figure 1 ;

Figure 2b shows a perspective sectional view of a sound absorber from Figure 2a; Figure 3a shows the sound absorber from Figure la inserted into a curved pipe-shaped body, the pipe-shaped body being shown in sectional view;

Figure 3b shows the sound absorber from Figure 3a, the sound absorber and the pipe-shaped body being shown in sectional view; Figure 4a shows a perspective view of another embodiment of a sound absorber according to the present invention;

Figure 4b shows a perspective sectional view of the sound absorber from Figure 4a.

Figure 1 shows a sound absorber 1 for a pipe-shaped body 2 which forms a cavity 3. Pipe-shaped body 2 may be a pipe made of plastic or metal, for example. Pipe- shaped body 2 may be made of an elastically

deformable material and may be designed as a hose, for example.

Pipe-shaped body 2 is a part of a coolant circuit of a cooling system in which the coolant circulates in the interior of the pipe-shaped body. The depicted sound absorber 1 is suitable in particular for that part of a coolant circuit in which the coolant is present in gaseous form. In this way, sound absorber 1 may effectively reduce the noise generated by a compressor (not shown). Sound absorber 1 is designed as an insert 26 which is manufactured separately and inserted during assembly into cavity 3 of pipe-shaped body 2.

Sound absorber 1 has a central flow channel 4. Flow channel 4 is situated coaxially with pipe-shaped body 2. Furthermore, four resonator chambers 5, 6, 7, 8 are provided adjacent to one another in the axial direction. Flow channel 4 and resonator chambers 5, 6, 7, 8 are separated by a partition 9 which forms flow channel 4 on its inside and separates it from the respective outside resonator chamber 5, 6, 7, and 8. Partition 9 is formed by a section of sound absorber 1 designed as an insert. Resonator chambers 5, 6, 7, 8 extend here ring- like around inner pipe 10. Furthermore, it is apparent in Figure 1 that the inner cross section area of the inner pipe changes in the axial direction of sound absorber 1. Starting from an inlet cross section area at an inlet 1 1 of sound absorber 1, the inner cross section area of inner pipe 10 narrows until it reaches an intermediate cross section area in a central area 15. From there the inner cross section area widens again up to an outlet cross section area at outlet 12 of sound absorber 1. The inlet cross section area and the outlet cross section area at inlet 1 1 and outlet 12 correspond approximately to the inner cross section area of pipe- shaped body 2. In this way, the flow may reach flow channel 4 of sound absorber 1 through pipe-shaped body 2 unhindered and with only low flow losses and may exit from there again into pipe-shaped body 2. In the shown embodiment, inner pipe 10 has two conical sections 13, 14 which connect inlet 1 1 and outlet 12 with an area 15 having the narrowest cross section. In the shown embodiment, conical sections 13 and 14 have the same axial length. Area 15 having the narrowest cross section has a cylindrical cross section.

Each resonator chamber 5, 6, 7, 8 is delimited to the inside by inner pipe 10 and to the outside by a section of pipe- shaped body 2. In addition, sound absorber 1 has webs 16, 17, 18 so that multiple resonator chambers 5, 6, 7, 8 are separated in the space formed between inner pipe 10 and pipe-shaped body 2. Each of these webs 16, 17, 18 is situated on inner pipe 10 and has a ring-like

circumferential design. The outer diameter of webs 16, 17, 18 corresponds to the inner diameter of pipe-shaped body 2 so that pipe- shaped body 2 is in tight contact with sound absorber 1 in the area of webs 16, 17, 18. The circumferential webs 16, 17, 18 point to the outside in the radial direction. Web 16 separates resonator chambers 5, 6 which are adjacent in the axial direction. Correspondingly, web 17 separates resonator chambers 6, 7 and web 18 separates resonator chambers 7, 8. Resonator chambers 5 and 8 are delimited at their outer ends by a section of inner pipe 10 which is in contact with pipe- shaped body 2. Resonator chambers 5, 6, 7, 8 have a constant outer diameter over their axial length, but a changing inner diameter.

Resonator chambers 5, 6, 7, 8 make noise reduction possible according to the Helmholtz resonator principle. For this purpose, resonator chambers 5, 6, 7, 8, each including a volume, are connected to flow channel 4 via connection channels 19 and 19', 20 and 20', 21 and 21' and 22 and 22'. In the shown embodiment, each resonator chamber 5, 6, 7, 8 is connected to flow channel 4 via two opposite connection channels 19 and 19', 20 and 20', 21 and 21 ' and 22 and 22'. Each connection channel encloses a small circular opening.

Connection channels 19, 19', 20, 20', 21, 21', 22 and 22' have different lengths for each resonator channel 5, 6, 7, 8 which makes tuning to the intended frequency range possible. In the shown embodiment, the two opposite connection channels 19, 19' have a length on the order of magnitude of the wall thickness. The two connection channels 21, 21' are slightly longer. Connection channels 22, 22' and 20, 20' have a distinctly greater length. Connection channels 19, 19', 20, 20', 21, 21', 22, 22' are formed by a channel-like section of partition 9 and inner pipe 10. Connection channels 19, 19', 20, 20', 21 , 2 , 22, 22' may be placed at an intended position on the circumference of the insert.

The shown sound absorber 1 may be made of plastic as an injection molded part. Particularly suitable is an elastic plastic material. Sound absorber 1 is then also insertable with no problem into curved pipe- shaped bodies. Moreover, the sound absorber is then able to adapt itself with no problem to a flattening or ovalization of the pipe- shaped body, which may occur in the area of a curve of the pipe-shaped body, for example.

Figures 2a and 2b show sound absorber 1 from Figure 1 prior to its insertion into the pipe-shaped body. Webs 16, 17, 18 situated on inner pipe 10 and the conical sections 13, 14 and area 15 having the narrowest cross section of inner pipe 10 are clearly recognizable.

Furthermore, connection channels 19, 19', 20, 20', 21 , 21 ', 22, 22' are clearly recognizable.

Figures 3a and 3b show sound absorber 1 inserted into a pipe-shaped body 2 having a curve. For example, the pipe- shaped body may be designed as a hose which is installed with a curve. Since sound absorber 1 is made of an elastic plastic material, it is able to adapt to the curve of pipe-shaped body 2, even if it is manufactured in the straight shape shown in Figure 2a. Also in a curved pipe-shaped body, webs 16, 17, 18 provide good contact of sound absorber 1 with the inside of the pipe-shaped body without preventing the pipe-shaped body from bending.

Figures 4a and 4b show another embodiment of the sound absorber according to the present invention prior to its insertion into a pipe- shaped body. Parts having the same function are labeled with the same reference numerals as in the preceding figures. Reference is made to the respective description which also applies to Figures 4a and 4b.

In the embodiment shown in Figures 4a and 4b, only two resonator chambers are formed which are separated by the circumferential web 36. Web 16' has, like webs 16, 17, and 18 in the above-described embodiment, a circumferential ring-like design. In addition, web 16' is situated protruding on the outside of inner pipe 10. Each of the resonator chambers is connected to flow channel 4 via two connection channels 20, 20' and 22, 22'. In the embodiment shown in Figures 4a and 4b, the inner pipe also has conical sections 13, 14. However, these sections are shorter in the axial direction than is the case in the embodiment shown in Figure 1. Accordingly, the area 15 having the narrowest cross section is correspondingly longer. In this way, a greater volume is available for the resonator chambers.

For fixing sound absorber 1, the insert has a clamping zone 23 on the outside of inner pipe 10. If the pipe-shaped body is made of a deformable material, as is the case with a hose, the pipe-shaped body having sound absorber 1 may be fastened in clamping zone 23 using a clamping device, e.g., a hose clamp. In the shown embodiment, the wall thickness of inner pipe 10 is reinforced in clamping zone 23 for this purpose. Clamping zone 23 is delimited on both sides by clamping edges 24, 24' which point to the outside. Good axial fixing is achieved in this way. In the shown embodiment, clamping edge 24 is formed by an oblique side surface of web 16'. Clamping edge 24' spaced in the axial direction from clamping edge 24 has breakthroughs 25. In this way, the space on both sides of clamping edge 24' may form a continuous resonator chamber.

List of reference numerals

1 sound absorber

2 pipe- shaped body

3 cavity

4 flow channel

5 resonator chamber

6 resonator chamber

7 resonator chamber

8 resonator chamber

9 partition

10 inner pipe

11 inlet

12 outlet

13 conical section

14 conical section

15 area having the narrowest cross section

16, 16' web

17 web

18 web

19, 19' connection channels

20, 20' connection channels

21 , 21 ' connection channels

22, 22' connection channels

23 clamping zone

24, 24' clamping edges

25 breakthrough

26 insert