Patent Grant
10358956
This invention generally relates to a dual path vehicle exhaust system having active noise control and a valve to control noise in a compact configuration.
Active noise control (ANC) systems are used in many vehicle exhaust systems to control the level of sound emitted by the exhaust system. Integrating an ANC system into a vehicle exhaust system is an attractive way to achieve a lower weight in a smaller packaging area, and can provide a system that can potentially out-perform traditional exhaust systems in terms of back pressure and tailpipe noise reduction. Additionally ANC systems are beneficial because they can add noise as well as cancel noise.
Noise attenuation difficulties arise for controlling low frequency noise, such as noise below 80 HZ, for example. To effectively cancel low frequency noise, a very large speaker diameter with a significantly large back volume, e.g. an increase from 3.5 L to 16 L, is required in order to effectively reduce or cancel the exhaust sound. Also, a significant amount of speaker power and/or more than one speaker may be required in order to sufficiently address all desired noise levels. This disadvantageously requires a significant amount of packaging space, and also increases cost and weight. Additionally, this causes even further issues when there is a dual tailpipe configuration.
In one exemplary embodiment, a vehicle exhaust system includes a first exhaust gas path and a second exhaust gas path. At least one valve positioned within the first exhaust gas path and an active noise control system is associated with the second exhaust gas path.
In another exemplary embodiment, a vehicle exhaust system includes a first tailpipe providing a first exhaust gas outlet and a second tailpipe providing a second exhaust gas outlet that is separate from the first exhaust gas outlet. At least one valve is positioned within the first tailpipe and an active noise control system is associated with the second tailpipe. The active noise control system includes at least one speaker and microphone, and at least one controller manages the at least one valve and the active noise control system.
In another exemplary embodiment, a method of controlling noise generated by a vehicle exhaust system comprises: providing a first tailpipe having a first outlet and a second tailpipe having a second outlet separate from the first outlet; associating at least one valve with the first tailpipe; associating an active noise control system with the second tailpipe; and controlling the valve and the active noise control system simultaneously to control noise generated by the vehicle exhaust system.
In a further embodiment of any of the above, the first exhaust gas path has a first muffler and a first tailpipe, and wherein the valve is positioned in the first tailpipe downstream of the first muffler.
In a further embodiment of any of the above, the second exhaust gas path has a second muffler and a second tailpipe, and wherein the active noise control system is associated with the second tailpipe downstream of the second muffler.
In a further embodiment of any of the above, a third muffler is positioned upstream of the first and second mufflers.
In a further embodiment of any of the above, a transverse muffler is connected to the first and second tailpipes, and wherein the valve and the active noise control system are positioned downstream of the transverse muffler.
In a further embodiment of any of the above, an additional muffler is positioned upstream of the transverse muffler, and a first pipe portion extends from the transverse muffler to the additional muffler and a second pipe portion extends from the transverse muffler to the additional muffler.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A vehicle exhaust system 10 includes an engine 12 that generates exhaust gases that are conveyed through various components of the vehicle exhaust system 10. The exhaust system 10 includes an upstream portion that includes hot end components such as particulate filters, catalysts, e.g. SCR, DOC, etc., and other components that remove undesirable elements from the exhaust gases. The exhaust system 10 also includes a downstream portion that includes cold end components such as mufflers, resonators, X-pipes, Y-pipes, H-pipes, etc. that are used to control noise generated by the exhaust system.
At least one valve 30 is positioned within the first exhaust gas passage 14 and an active noise control system 32 is associated with the second exhaust gas passage 20. In one example, the valve 30 is positioned within the first exhaust gas passage 14 in a non-bypass configuration such that all exhaust gas must pass through the valve 30 before exiting the first exhaust outlet 16. The valve 30 and active noise control system 32 cooperate with each other to control noise generated by the exhaust system 10.
Any type of active noise control system 32 can be used within the vehicle exhaust system 10; however, the active noise control system 32 must be able to provide active sound cancelling and/or sound enhancement. In one example, the active noise control system 32 includes a speaker 34 and an anti-noise controller 36. The active noise control system 32 may optionally include one or more sensors 38 and/or a microphone 40 that communicates exhaust or sound characteristics to the controller 36. The anti-noise controller 36 then generates a control signal 42 that causes the speaker 34 to generate an out of phase sound that cancels out an exhaust system generated noise as known. Optionally, the control signal 42 can cause the speaker 34 to generate a sound that is used to enhance noise to provide a desired noise level.
In the example configuration of
The valve 30 is comprised of a valve body that is positioned within the first tailpipe 18 downstream of the first muffler 50. Optionally, the valve 30 could be upstream of the first muffler 50 (see dashed lines in
The active noise control system 32 is associated with the second tailpipe 24 downstream of the second muffler 60. This configuration allows for the second muffler 60 to be smaller than the first muffler 50, which provides for an even more compact arrangement. The microphone 40 sends feedback 86 to the anti-noise controller 36. The sensor(s) 38, such as a temperature sensor for example, also sends data back to the anti-noise controller 36 as indicated at 88. Information regarding valve position in the first exhaust gas passage 14 can also be communicated to the anti-noise controller 36 as indicated at 90.
The engine control unit/valve control unit 80 and the anti-noise controller 36 communicate with each other, as indicated at 84, to control the valve 30 and speaker 34 to simultaneously control noise within the first 14 and second 20 exhaust gas passages by attenuating low and/or high frequency noise, respectively, as needed. The engine control unit 80 can be a separate controller from the controller 36 for the active noise control system 32, or optionally, the controllers could be combined with each other as a single unit. The controllers 36 and/or 80 can also use additional information such as engine RPM, throttle position, desired noise profile, engine mode, or any other engine or exhaust system characteristics, to control the position of the valve 30 and/or the speaker output to achieve the desired noise configuration.
The system operates as follows. At low exhaust flow rates, the valve 30 is closed. This significantly improves the low frequency acoustics of the exhaust system 10. This also enables the single speaker 34 attached to the second tailpipe 24 to cancel the remaining engine noise after passing through the upstream portion of the exhaust system 10. To enable the cancellation of the engine noise emitted from the second tailpipe 24, the error microphone measures the residual noise and feeds this information to the anti-noise controller 36. The anti-noise controller 36 additionally uses inputs from the engine control unit 80 of engine speed, load, and optionally other additional data as described above, to modify the input control signal 42 to the speaker 34.
The actively controlled valve 30 is opened, or moved progressively toward the open position, in order to keep the system back pressure within acceptable levels. At some point, as the valve 30 opens, the noise emitted from the first tailpipe 18 will be louder than the noise emitted by the second tailpipe 24. At this point, noise cancellation is no longer effective and the valve 30 is controlling the minimum noise level as opposed to the speaker 34. Thus, the active noise control only works when the valve 30 is closed and up to the point where the noise emitted from the first tailpipe 18 will be louder than the noise emitted by the second tailpipe 24. As such, by combing an active valve 30 with active noise control, a lower cost system for a dual exhaust path can be achieved as compared to a two speaker system.
In addition to cancellation, noise addition is also possible. This possibility can occur simultaneously, e.g. one could cancel one frequency while enhancing another frequency. This makes it possible to cancel, for example, second and fourth EOs while enhancing 1.5, 3, and 6 EOs, which makes and I4 engine sound more like a V6 engine.
Optionally, an upstream muffler 120 is connected to the first 14 and second 20 exhaust gas passages upstream of the transverse muffler 100. The first pipe portion 102 extends to a first outlet 122 of the upstream muffler 120 and the second pipe portion 106 extends to a second outlet 124 of the upstream muffler 120. A third pipe portion 126 of the first exhaust gas passage 14 extends from the upstream muffler 120 to upstream exhaust components and a fourth pipe portion 128 of the second exhaust gas passage 20 extends from the upstream muffler 120 to upstream exhaust components.
One example of the transverse muffler 100 is shown in greater detail in
In this example, a first pipe 150 is supported by first and second baffle plates 134a, 134b to extend through the fifth chamber 144. The first pipe 150 has a first end that is open to the fourth chamber 142 and a second, opposite, end that is open to the first chamber 136. A second pipe 152 is supported by the first 134a and second 134b baffle plates, as well as by third 134c and fourth 134d baffle plates, to extend through the first 136, third 140, and fifth 144 chambers. The second pipe 152 has a first end that is open to the second chamber 138 and a second, opposite end comprises the first outlet 110. A third pipe 154 is supported by the third 134c and fourth 134d baffle plates to extend through the third chamber 140. The third pipe 154 has a first end that is open to the first chamber 136 and a second, opposite, end comprises the second outlet 112.
The first 150, second 152, and/or third 154 pipe portions may include perforated sections 160 to provide further noise attenuation as needed. The baffle plates 134 may comprise solid plates with openings for the respective pipe portions 150, 152, 154. Or, one or more of the baffle plates 134 may include sections 162 with perforations and/or other noise reducing materials.
The use of the valve 30 in first exhaust gas passage 14 of the exhaust system allows the exhaust sound emitted from this passage to be substantially deliminated. This means the active noise control system 32 need only address the noise emitted from the muffler 60. Because one of the exhaust outlets is addressed by the valve, the active noise control system can use a single “driver”, e.g. a speaker, for noise cancelling a dual outlet system. Additionally, there are some low frequency benefits of using a valve in this configuration that enables a smaller, lighter, and less expensive speaker to be utilized.
Further, by combining the active noise control system 32 in one path of a dual path exhaust configuration with the valve 30 located within the other path of the dual path exhaust configuration, it allows the overall size of the active noise control system 32 to be made very compactly. Further, by reducing the size, the energy required to power the active noise control system 32 can be significantly reduced. Also, by using only one valve 30 and one active noise control system 32 to control noise in a dual path configuration, the overall size of the exhaust system 10 can be reduced to provide a more compact arrangement.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
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