CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Korean Patent Application Number 10-2009-0118580 filed Dec. 2, 2009, the entire contents of which application is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a muffler for a vehicle that can implement sporty and dynamic sound in accelerating a vehicle. 
         [0004]    2. Description of Related Art 
         [0005]    Mufflers for vehicles in the related art have a plurality of chambers that are formed by one or more baffles in a closed muffler housing having a predetermined volume, an exhaust inflow pipe through which an exhaust gas flows inside the muffler housing, and an exhaust outflow pipe through which an exhaust gas flows outside the muffler housing, in which the exhaust gas that has flowed inside the muffler housing through the exhaust inflow pipe, flows through an exhaust channel formed in the muffler housing, and consequently flows outside the muffler through the exhaust outflow pipe, with the pressure and sound reduced. 
         [0006]      FIG. 1  shows an example of variable exhaust channel type mufflers according to the related art, in which two baffles  2  are disposed at a predetermined distance from each other longitudinally inside a muffler housing  1  which has a substantially rectangular box shape, an exhaust inflow pipe  3  through which an exhaust gas flows inside from the engine is disposed through the front of housing  1  and the two baffles, an exhaust outflow pipe  4  through which the exhaust gas having flowed inside muffler housing  1  flows outside the muffler housing extends outside through two baffles  2  and the rear of muffler housing  1 , and a valve  5  that shifts the channel for the exhaust gas in the muffler housing is provided for one of baffles  2 . 
         [0007]    Accordingly, when the engine operates at a low speed, since the exhaust gas flowing into housing  1  through exhaust inflow pipe  3  is low in pressure, the valve  5  is kept closed by an elastic member supporting it, such that the back pressure increases and the exhaust sound of the exhaust gas that has passed through the resonant chamber reduces. 
         [0008]    When the engine operates at a high speed, as shown in  FIG. 2 , since the exhaust gas flowing into housing  1  through exhaust inflow pipe  3  is high in pressure, valve  5  is opened by the pressure of the exhaust gas, such that the back pressure increases and the output of the vehicle increases. 
         [0009]    Another example of mufflers, a variable channel type muffler that shifts the exhaust channel for an exhaust gas flowing into the muffler in accordance with the operation speed of the engine, has been proposed. 
         [0010]    However, the mufflers having the configuration described above in the related art can only reduce noise or increase the engine power by changing the back pressure while expanding or contracting the exhaust gas channel, but they cannot implement sporty and dynamic sound by tuning at a desired frequency band. 
         [0011]    The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    Various aspects of the present invention are directed to provide a muffler for a vehicle that is effective in acceleration sound tuning of the vehicle and can improve commercial value of the vehicle by implementing sporty and dynamic sound. 
         [0013]    In an aspect of the present invention, the muffler apparatus for a vehicle, wherein a speaker chamber that produces sound while vibrating by pressure of an exhaust gas flowing into a muffler housing may be formed in the muffler housing, the pressure of the exhaust gas being greater than a predetermined value. 
         [0014]    The speaker chamber may be defined by a partition disposed in the muffler housing. 
         [0015]    The partition may be provided with a valve that selectively opens a flow channel to the speaker chamber by the pressure of the exhaust gas, wherein the valve is mounted to the partition and elastically supported by an elastic member at one side thereof 
         [0016]    The speaker chamber may be provided with a thin plate speaker that is vibrated by the pressure of the exhaust gas, wherein the thin plate speaker is mounted on the muffler housing and is elastically supported by elastic members at both sides on the muffler housing. 
         [0017]    According to a muffler for a vehicle of the present invention, a valve that is opened/closed by pressure of an exhaust gas is disposed in a front chamber defined by a muffler housing and a baffle inside the muffler housing and a portion of the wall of the front chamber is formed of a thin plate supported by an elastic member to function as a speaker. Therefore, when a vehicle is accelerated, the valve is opened and the thin plate is vibrated by pressure of an exhaust gas and produces sporty and dynamic sound to increase acceleration impression, and noise generated by the exhaust gas can be effectively controlled at the maximum engine power without increasing the back pressure of the exhaust gas. Further, it is possible to implement sound that makes it possible to feel power within a range above a predetermined operation speed of the engine, and to make the inside quiet when the vehicle travels at a constant speed and slowly accelerates. 
         [0018]    The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an internal cross-sectional view of a muffler according to the related art. 
           [0020]      FIG. 2  is a cross-sectional view illustrating the operation of the muffler according to the related art when an engine operates at a high speed. 
           [0021]      FIG. 3  is a cross-sectional view illustrating the operation of a muffler for a vehicle according to an embodiment of the present invention, when an engine operates at a constant speed or slowly accelerates. 
           [0022]      FIG. 4  is a cross-sectional view illustrating the operation of the muffler for a vehicle according to an embodiment of the present invention, when an engine is rapidly accelerated. 
       
    
    
       [0023]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
         [0024]    In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0026]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0027]      FIG. 3  is a cross-sectional view showing the structure of muffler according to an embodiment of the present invention, in which two baffles  2   a  and  2   b  are disposed at a predetermined distance from each other longitudinally in a muffler housing  1  having a substantially rectangular box shape, and an exhaust inflow pipe  3  through which an exhaust gas is discharged outside from the engine is disposed through the front of housing  1  and the two baffles. 
         [0028]    An exhaust outflow pipe  4  through which an exhaust gas having flowed in muffler housing  1  is discharged outside the muffler housing extends outside through two baffles  2   a  and  2   b  and the rear of muffler housing  1 . 
         [0029]    A plurality of holes  3   a  is formed at the portion between two baffles  2   a  and  2   b  of the exhaust inflow pipe and an exhaust gas guide pipe  7  is disposed through first baffle  2   a  such that a front chamber communicates with a middle chamber in order to guide that exhaust gas, which has been discharged through holes  3   a  and flowed in the middle chamber  6   a  defined by the two baffles, into the front chamber  6   b  defined by front baffle  2   a  and muffler housing  1 . 
         [0030]    Further, a partition  8  is disposed in front of front chamber  6   b  to define a speaker chamber  9  between partition  8  and the muffler housing, a through-hole is formed through partition  8 , a valve  8   a  that opens/closes speaker chamber  9  by opening/closing the through-hole is disposed to be elastically supported by a spring and an elastic member  8   b  at one side, and a thin plate speaker  9   a  is supported by elastic members  9   b  at both sides, on the front of speaker chamber  9 . 
         [0031]    Therefore, when a vehicle slowly accelerates or travels at a constant speed, some of the exhaust gas that has flowed inside muffler housing  1  through exhaust inflow pipe  3 , as shown in  FIG. 3 , flows into middle chamber  6   a  through holes  3   a , flows into front chamber  6   b  through exhaust gas guide pipe  7 , and is then discharged outside the muffler housing through exhaust outflow pipe  4 . 
         [0032]    In this process, although pressure of the exhaust gas in front chamber  6   b  is applied to valve  8   a,  the pressure is smaller than the elastic force of spring  8   b  supporting valve  8   a,  such that valve  8   a  keeps closing speaker chamber  9 . 
         [0033]    In the process of the exhaust gas flowing as described above, the exhaust gas smoothly flows through the exhaust pipes and the chambers, such that the back pressure does not increase and the engine power is improved. 
         [0034]    When the vehicle is rapidly accelerated, as shown in  FIG. 4 , the exhaust pressure of the exhaust gas in front chamber  6   b  increases, such that valve  8   a  is opened by the pressure of the exhaust gas and the exhaust gas flows into speaker chamber  9  through the channel formed by the opening, in which the exhaust gas has pressure pulsation, which vibrates thin plate speaker  9   a,  such that thin plate speaker  9   a  produces sporty and dynamic sound while dynamically vibrating. 
         [0035]    Since the exhaust gas can smoothly flow through the exhaust pipes and the chambers even if a vehicle is rapidly accelerated, as described above, the engine power increases. 
         [0036]    Further, it is easy to tune the frequency band by adjusting the material, thickness, and size etc. of thin plate speaker  9   a,  which enables a user to simply produce desired sound. 
         [0037]    Further, since the valve is kept closed, when a vehicle travels at a constant speed or slowly accelerates, noise generated by exhaust gas is reduced, thereby implementing quiet driving. 
         [0038]    The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
A muffler apparatus for a vehicle may include a speaker chamber that produces sound while vibrating by pressure of an exhaust gas flowing into a muffler housing, wherein the speaker chamber is formed in the muffler housing, the pressure of the exhaust gas being greater than a predetermined value.