Muffler comprising a Helmholtz resonator and a vehicle comprising such a muffler

Abstract

A muffler for a vehicle, where the muffler comprises a partition wall that divides the interior in a first chamber and a second chamber, where an inlet pipe comprising a perforated section arranged in the first chamber and a closed section arranged in the first chamber, where the outlet opening of the inlet pipe is arranged in the second chamber, a first outlet pipe comprising an inlet opening arranged in the first chamber and an outlet opening arranged outside of the muffler, where the muffler comprises a second outlet pipe having an inlet opening arranged in the second chamber, and where the second outlet pipe is provided with an exhaust valve adapted to open or close the exhaust gas flow through the second outlet pipe. The advantage of the invention is that a muffler with an improved low frequency noise attenuation and low backpressure is provided.

Claims

1. A muffler for an exhaust gas system of a vehicle comprising an internal combustion engine, the muffler comprising: a gas-tight housing; a partition wall dividing the interior of the housing in a first chamber and a second chamber; an inlet pipe extending through the first chamber and comprising a perforated section arranged in the first chamber and a closed section arranged in the first chamber, wherein an inlet opening of the inlet pipe is arranged outside of the housing and wherein an outlet opening of the inlet pipe is arranged in the second chamber, the outlet opening being permanently open towards the second chamber; a first outlet pipe comprising an inlet opening arranged in the first chamber and an outlet opening arranged outside of the housing; and a second outlet pipe having an inlet opening arranged in the second chamber and an outlet opening arranged outside of the housing, wherein the second outlet pipe is provided with a first exhaust valve adapted to open or close the exhaust gas flow through the second outlet pipe.

2. The muffler according to claim 1, wherein the first outlet pipe extends through the second chamber.

3. The muffler according to claim 1, wherein the muffler comprises a third outlet pipe having an inlet opening arranged in the first chamber and an outlet opening arranged outside of the housing, and where the third outlet pipe is provided with a second exhaust valve adapted to open or close the exhaust gas flow through the third outlet pipe.

4. The muffler according to claim 3, wherein the second exhaust valve is adapted to open before the first exhaust valve.

5. The muffler according to claim 1, wherein the first exhaust valve is electrically controlled.

6. The muffler according to claim 1, wherein the first exhaust valve is adapted to be opened at an engine speed of between 2000-3000 rpm.

7. The muffler according to claim 1, wherein the closed section of the inlet pipe and the second chamber constitutes a Helmholtz resonator having a centre frequency between 50-100 Hz.

8. The muffler according to claim 1, wherein the closed section of the inlet pipe and the second chamber constitutes a Helmholtz resonator having a centre frequency between 70-85 Hz.

9. The muffler according to claim 1, wherein the closed section of the inlet pipe and the second chamber constitutes a Helmholtz resonator having a centre frequency of 75 Hz.

10. The muffler according to claim 1, wherein the partition wall is airtight.

11. The muffler according to claim 1, wherein the partition wall is provided with at least one opening that is arranged to provide a controlled leakage between the first chamber and the second chamber.

12. A vehicle comprising an exhaust gas system and an internal combustion engine, the exhaust gas system comprising a muffler comprising: a gas-tight housing; a partition wall dividing the interior of the housing in a first chamber and a second chamber; an inlet pipe extending through the first chamber and comprising a perforated section arranged in the first chamber and a closed section arranged in the first chamber, wherein an inlet opening of the inlet pipe is arranged outside of the housing and wherein an outlet opening of the inlet pipe is arranged in the second chamber, the outlet opening being permanently open towards the second chamber; a first outlet pipe comprising an inlet opening arranged in the first chamber and an outlet opening arranged outside of the housing; and a second outlet pipe having an inlet opening arranged in the second chamber and an outlet opening arranged outside of the housing, wherein the second outlet pipe is provided with a first exhaust valve adapted to open or close the exhaust gas flow through the second outlet pipe.

13. The vehicle according to claim 12, wherein the first outlet pipe extends through the second chamber.

14. The vehicle according to claim 12, wherein the muffler comprises a third outlet pipe having an inlet opening arranged in the first chamber and an outlet opening arranged outside of the housing, and where the third outlet pipe is provided with a second exhaust valve adapted to open or close the exhaust gas flow through the third outlet pipe.

15. The vehicle according to claim 14, wherein the second exhaust valve is adapted to open before the first exhaust valve.

16. The vehicle according to claim 12, wherein the first exhaust valve is electrically controlled.

17. The vehicle according to claim 12, wherein the first exhaust valve is adapted to be opened at an engine speed of between 2000-3000 rpm.

18. The vehicle according to claim 12, wherein the closed section of the inlet pipe and the second chamber constitutes a Helmholtz resonator having a centre frequency between 50-100 Hz.

19. The vehicle according to claim 12, wherein the partition wall is airtight.

20. The vehicle according to claim 12, wherein the partition wall is provided with at least one opening that is arranged to provide a controlled leakage between the first chamber and the second chamber.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will be described in greater detail in the following, with reference to the attached drawings, in which:

(2) FIG. 1 shows a first example of a muffler according to the invention with the valve in a closed state,

(3) FIG. 2 shows a first example of a muffler according to the invention with the valve in an open state,

(4) FIG. 3 shows a second example of a muffler according to the invention,

(5) FIG. 4 shows a graph of the relation between attenuation and engine speed for a muffler according to the invention, and

(6) FIG. 5 shows a vehicle comprising a muffler according to the invention.

DESCRIPTION OF EMBODIMENTS

(7) The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims.

(8) FIGS. 1 and 2 show a first example of a muffler, FIG. 3 shows a further example of a muffler, FIG. 4 shows a graph of the attenuation for different mufflers and FIG. 5 shows a vehicle comprising a muffler.

(9) The muffler 1 comprises a circumferential outer surface 21, a first end wall 19 and a second end wall 20. The muffler is in the shown example provided with a cylindrical shape, but other shapes are also possible. The first end wall 19, the second end wall 20 and the outer surface 21 constitutes the housing 2 of the muffler. The muffler further comprises an inlet pipe 6, a first outlet pipe 11 and a second outlet pipe 14. The second outlet pipe 14 is provided with a first exhaust valve 17. The inlet pipe is adapted to receive the exhaust gases from the combustion engine and lead them into the muffler, and the first and the second outlet pipes are adapted to exhaust the exhaust gases from the muffler. The muffler 1 further comprises an inner partition wall 3 which divides the interior of the housing 2 in a first chamber 4 and a second chamber 5.

(10) The partition wall may be airtight or may be arranged with one or more smaller openings in the partition wall, in order to introduce a controlled leakage. The purpose of using a controlled leakage is to smooth the damping characteristics of the Helmholtz resonator. With an airtight partition wall, the damping will be relatively sharp at the tuned frequency with a high attenuation at the centre frequency, and with a relatively narrow bandwidth. This corresponds to a relatively high Q factor. With a controlled leakage, the damping characteristics will not be as high at the centre frequency, but with a wider bandwidth. Such a muffler will have a lower Q factor.

(11) The inlet pipe 6 comprises an inlet opening 9 and an outlet opening 10. The inlet opening is adapted to be connected to an exhaust pipe leading from the combustion engine and possibly from a catalyst. In the shown example, the inlet side of the inlet pipe 6 is arranged in the first end wall 19 and the outlet side is arranged in the partition wall 3 with the outlet opening 10 in the second chamber 5. The inlet pipe comprises a perforated section 7 which is provided with a plurality of holes, through which exhaust gases can pass when the first exhaust valve 17 is closed. The open area of the perforated section should for this reason be at least the same size as the area of the inlet pipe, and is preferably larger. The inlet pipe further comprises a further section which will be referred to as a closed section 8 arranged at the partition wall, with the inlet pipe extending through the partition wall 3. The closed section 8 is non-perforated, i.e. the circumferential wall of the closed section 8 is airtight. Thus, the closed section 8 may be referred to as a closed wall section 8. The closed section 8 will constitute the Helmholtz neck of the Helmholtz resonator when the first exhaust valve 17 is closed. When the first exhaust valve 17 is closed, exhaust gas will not be able to pass through the second outlet pipe 14 via the closed section 8 and the second chamber 5, but soundwaves will interact with the closed section 8 and the second chamber, thereby creating the Helmholtz effect. Thus, the inlet pipe 6 may be referred to as a hollow pipe, which allows exhaust gas to flow from the inlet opening 9 to the outlet opening 10, but when the first exhaust valve 17 is closed, no, or a very small initial amount, of exhaust gas is allowed to flow through the outlet opening 10, as the first exhaust valve 17 prevents any gas flow through the second outlet pipe 14.

(12) The first outlet pipe 11 comprises an inlet opening 12 and an outlet opening 13. The inlet opening is arranged in the first chamber 4 and is adapted to exhaust all of the exhaust gases from the inlet pipe 6 when the first exhaust valve 17 is closed, and to exhaust some of the exhaust gases when the first exhaust valve 17 is open. The diameter of the inlet pipe and the first outlet pipe are in the shown example thus substantially the same, but the first outlet pipe 11 may also have a larger diameter. The first outlet pipe 11 extends in the shown example through the second chamber 5 and through the second end wall 20, with the outlet opening 13 arranged outside of the housing 2. At lower engine speeds, when the first exhaust valve 17 is closed, all exhaust gas will exit through be the first outlet pipe 11. The exhaust gas will enter the muffler through the inlet pipe 6, pass through the perforated section 7 and will exit through the first outlet pipe 11. Due to the Helmholtz resonator created by the closed section 8 of the inlet pipe 6 and the second chamber 5, low frequency noise is attenuated.

(13) The second outlet pipe 14 comprises an inlet opening 15 and an outlet opening 16. The inlet opening is arranged in the second chamber 5 and is adapted to exhaust most of the exhaust gases from the inlet pipe 6 when the first exhaust valve 17 is open, in parallel with the first outlet pipe 6. The diameter of the inlet pipe and the second outlet pipe are in the shown example substantially the same, but the second outlet pipe may also have a different diameter that may be larger. The inlet opening 15 may be arranged relatively close to and may be aligned with the outlet opening 10 of the inlet pipe 6. The outlet opening 16 is arranged outside of the housing 2. The second outlet pipe 14 is provided with a first exhaust valve 17 which preferably is arranged outside of the housing 2. The first exhaust valve 17 is controlled by a first actuator 18, which may be an electrically controlled motor, a solenoid or another type of actuator. At lower engine speeds, the first exhaust valve 17 is closed in order to create a Helmholtz resonator. At higher engine speeds, the first exhaust valve is opened such that the muffler will function as a conventional muffler with most of the exhaust gas passing through inlet pipe 6 and the second outlet pipe 14. This is shown in FIG. 2.

(14) The first exhaust valve is opened at a predefined engine speed. In one example, the first exhaust valve is opened at an engine speed of 2600 rpm. The engine speed at which the first exhaust valve 17 is opened will depend on the design of the muffler and the engine, but is preferably in an engine speed region between 2000-3000 rpm. The Helmholtz resonator is in this example tuned to suppress a centre frequency of 75 Hz, and may e.g. be tuned to in a frequency region between 70-85 Hz. The centre frequency for the Helmholtz resonator depends e.g. on the number of cylinders of the combustion engine and is of course also dependent on the emitted low frequency caused by engine pulsations of a specific combustion engine. A four cylinder engine may e.g. have a Helmholtz resonator tuned in the frequency interval between 50-100 Hz.

(15) FIG. 4 shows an example of the attenuation for a conventional muffler with a dash-dotted line a, for a muffler with a Helmholtz resonator with a broken line b, and for a combined muffler according to the invention with a continuous line c.

(16) FIG. 3 shows a further example of a muffler according to the invention, comprising a further outlet pipe. In this example, the inlet pipe 6 is arranged through the circumferential outer surface 21 and the closed section 8 is bent. The first outlet pipe 11 is arranged through the first end wall 19. The second outlet pipe 14 is arranged as described above. The third outlet pipe 22 comprises an inlet opening 23 and an outlet opening 24. The inlet opening 23 is arranged in the first chamber 4 and the outlet opening 24 is arranged outside of the housing 2. In the shown example, the third outlet pipe is arranged through the second chamber 5. However, it should be noted that the outlet openings of the outlet pipes may be arranged in other ways, depending on the design of the muffler and the vehicle. For a vehicle having two visible exhaust ports and a muffler arranged sideways of the vehicle, it may be desirable to have an outlet pipe at each end wall of the muffler in order to simplify the exhaust piping of the vehicle. The diameter of the inlet pipe and the third outlet pipe are in the shown example substantially the same, but the third outlet pipe may have a diameter with a different cross section, depending on the design of the muffler. The third outlet pipe is provided with a second exhaust valve 25, which is controlled by a second actuator 26. The second exhaust valve is set to open at a specified engine speed, and may be opened before the first exhaust valve opens in order to reduce the back pressure of the muffler at lower engine speeds.

(17) FIG. 5 shows a vehicle 30 comprising an internal combustion engine 31 and an exhaust gas system 32 comprising a muffler 1 according to the invention. The internal combustion engine is a spark-ignited gasoline engine which may be charged with a turbo or a supercharger. The volume of the muffler is adapted to the type of vehicle used, and is e.g. dependent on the volume and the engine speed of the used internal combustion engine. A suitable volume for a passenger car may e.g. be 20-50 litres, whereas a two wheel motorbike may have a volume of e.g. 5 litres.

(18) The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims.