Abstract:
An exhaust muffler device for an internal combustion engine includes an outer housing which defines a sealed chamber and which is connected to opposite inlet and outlet pipes, and an initial expansion subchamber and a pre-outlet subchamber disposed in the sealed chamber. The exhaust gas enters the initial expansion subchamber and mainly flows to a tubular passage in the pre-outlet subchamber to be exhausted through the outlet pipe. Portion of the exhaust gas flows into the sealed chamber and re-enters into a rejoining region of the tubular passage to be entrained in the main stream, thereby attenuating noise of the engine with minimal reduction of engine performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority of Taiwanese Patent Application No. 099103519, filed on Feb. 5, 2010, the disclosure of which is herein incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to an exhaust muffler device, more particularly to an exhaust muffler device used with an internal combustion engine. 
         [0004]    2. Description of the Related Art 
         [0005]    An exhaust muffler device is generally mounted between an exhaust manifold and a tailpipe of an internal combustion engine to reduce the noise generated by the engine as a result of the sudden expansion of combustion chamber exhaust gases. As disclosed in U.S. Pat. Nos. 6,089,347, 7,798,286 B2, and 7,243,757 B2, conventional mufflers are generally classified from the structural consideration as two basic types: a compartmentalized type which comprises a plurality of sealed, noise entrapment chambers, and a straight through muffler which comprises a perforated duct within a sealed housing. The compartmentalized type of muffler uses various volumes of different shaped or sized chambers interconnected with pipes and can dampen resonance frequency, but a relatively large volume of the chambers is required to generate resonation therein. The straight through muffler uses an offset side branch off a straight through pipe. When the sound wave reaches a closed end of the side branch, it reflects back to be dampened. However, an effect of the presence of reflector partitions and chamber walls is to produce a back pressure in the exhaust path of exhaust gas, which robs the engine of some amount of horsepower. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide an exhaust muffler device which can attenuate noise of the engine with minimal reduction of engine performance. 
         [0007]    According to this invention, the exhaust muffler device includes an outer housing having inlet-side and outlet-side walls disposed to be spaced apart from each other in a longitudinal direction to define a sealed chamber. An inlet pipe extends through the inlet-side wall to permit entry of exhaust gas into the sealed chamber. An outlet pipe is disposed in the outlet-side wall and which extends along an outlet axis into the sealed chamber. An initial expansion subchamber is disposed in the sealed chamber, and has a first proximate wall disposed to permit the inlet pipe to extend therethrough, a first distal wall spaced apart from the first proximate wall in the longitudinal direction to serve as a barrier to obstruct flow path of main stream of the exhaust gas, and a first surrounding partition wall disposed between the first proximate and distal walls. A pre-outlet subchamber is disposed in the sealed chamber, and has a second proximate wall, a second distal wall spaced apart from the second proximate wall in the longitudinal direction to permit the outlet pipe to extend therethrough, and a second surrounding partition wall disposed between the second proximate and distal walls to define a tubular passage. The tubular passage has a direction change region which is juxtaposed to the first surrounding partition wall in a direction transverse to the longitudinal direction, and which is disposed downstream of the initial expansion sub-chamber by virtue of an internal port in the second surrounding partition wall that extends through the first surrounding partition wall, and a rejoining region which is disposed downstream of the direction change region and upstream of the outlet pipe, and which extends along the outlet axis of the outlet pipe. The second surrounding partition wall has a plurality of second communicating perforations such that portion of the exhaust gas from the main stream flowing out of the second communicating perforations at an upstream side into the sealed chamber is permitted to re-enter into the rejoining region through the second communicating perforations at a downstream side to be thereby entrained in the main stream before flowing out of the outlet pipe. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which: 
           [0009]      FIG. 1  is a sectional view of the first preferred embodiment of an exhaust muffler device according to this invention; 
           [0010]      FIG. 2  is a sectional view of the second preferred embodiment of an exhaust muffler device according to this invention; 
           [0011]      FIG. 3  is a sectional view of the third preferred embodiment of an exhaust muffler device according to this invention; and 
           [0012]      FIG. 4  is a sectional view of the fourth preferred embodiment of an exhaust muffler device according to this invention. 
       
    
    
       [0013]    Before the present invention is described in greater detail, it should be noted that same reference numerals have been used to denote like elements throughout the specification. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    Before the present invention is described in greater detail, it should be noted that same reference numerals have been used to denote like elements throughout the specification. 
         [0015]    Referring to  FIG. 1 , the first preferred embodiment of an exhaust muffler device according to the present invention is shown to comprise an outer housing  2 , an inlet pipe  5 , an outlet pipe  6 , an initial expansion subchamber  31 , and a pre-outlet subchamber  32 . 
         [0016]    The outer housing  2  has inlet-side and outlet-side walls  22 ,  23  disposed to be spaced apart from each other in a longitudinal direction (A) to define a sealed chamber  21 . The inlet pipe  5  extends along an inlet axis through the inlet-side wall  22  so as to permit entry of exhaust gas into the sealed chamber  21 . The outlet pipe  6  is disposed in the outlet-side wall  23  and which extends along an outlet axis into the sealed chamber  21 . In this embodiment, the inlet axis is offset from the outlet axis. 
         [0017]    The initial expansion subchamber  31  is disposed in the sealed chamber  21 , and has a first proximate wall  314  which is spaced apart from the inlet-side wall  22  by a first distance, and which is disposed to permit the inlet pipe  5  to extend therethrough, a first distal wall  315  which is spaced apart from the first proximate wall  314  in the longitudinal direction (A) to serve as a barrier to obstruct flow path of main stream of the exhaust gas, and a first surrounding partition wall  312  which is disposed between the first proximate wall  314  and the first distal wall  315 . The first surrounding partition wall  312  has a plurality of first communicating perforations  313  disposed downstream of the inlet pipe  5  and upstream of the first distal wall  315  to divert portion of the exhaust gas from the main stream out of the initial expansion subchamber  31  into the sealed chamber  21  so as to reduce the back pressure generated in the initial expansion sub-chamber  31 . 
         [0018]    The pre-outlet subchamber  32  is disposed in the sealed chamber  21 , and has a second proximate wall  324  which is spaced apart from the inlet-side wall  22  by a second distance that is longer than the first distance, a second distal wall  325  which is spaced apart from the second proximate wall  324  in the longitudinal direction (A), and which is disposed to permit the outlet pipe  6  to extend therethrough, and a second surrounding partition wall  322  which is disposed between the second proximate wall  324  and the second distal wall  325  to define a tubular passage  321 . The tubular passage  321  is configured to have a direction change region ( 321   a ) which is juxtaposed to the first surrounding partition wall  312  in a direction (B) transverse to the longitudinal direction (A), and which is disposed downstream of the initial expansion sub-chamber  31  by virtue of an internal port  326  in the second surrounding partition wall  322  that extends through the first surrounding partition wall  312 , and a rejoining region ( 321   b ) which is disposed downstream of the direction change region ( 321   a ) and upstream of the outlet pipe  6 , and which extends along the outlet axis of the outlet pipe  6 . The second surrounding partition wall  322  has a plurality of second communicating perforations  323 . In this embodiment, the second surrounding partition wall  322  at the rejoining region ( 321   b ) is configured to diverge toward the second distal wall  325  to permit further expansion of the main stream of the exhaust gas while flowing out of the outlet pipe  6 . 
         [0019]    Further, an outer partition wall  33  is disposed to divide the sealed chamber  21  into a proximate subchamber  211  bordered by the inlet-side wall  22  and a distal subchamber  212  bordered by the outlet-side wall  23 . The outer partition wall  33  having a plurality of penetrating holes  331  communicating the proximate subchamber  211  with the distal subchamber  212 . The initial and pre-outlet subchambers  31 ,  32  are disposed in the proximate subchamber  211 . Furthermore, in this embodiment, a reflecting plate  36  is disposed in the proximate subchamber  211  between the second distal wall  325  and the outer partition wall  33  and parallel to the outer partition wall  33 , and a perforated plate  35  is disposed to extend in the longitudinal direction (A) from the outer partition wall  33  to suspend the reflecting plate  36  from the outer partition wall  33 . Thus, portion of the exhaust gas in the sealed chamber  21  is obstructed and reflected to permit an increased portion of exhaust gas in the sealed chamber  21  to re-enter into the rejoining region ( 321   b ) through the second communicating perforations  323  at the downstream side so as to facilitate flowing of the exhaust gas out of said outlet pipe  6 . By virtue of the perforated plate  35  and the reflecting plate  36 , vibration of the outer partition wall  33  generated as a result of impact of the flow of the exhaust gas in the sealed chamber  21  can be reduced. 
         [0020]    The high-pressurized exhaust gas is led to enter into the initial expansion subchamber  31  for expansion while portion of the exhaust gas from the main stream flows through the first communicating perforations  313  in the sealed chamber  21 . The main stream of the exhaust gas subsequently flows in the tubular passage  321  for further expansion while portion of the exhaust gas in an upstream side from the main stream flows through the second communicating perforations  323  into the sealed chamber  21 . The exhaust gas in the sealed chamber  21  is permitted to re-enter into the rejoining region ( 321   b ) through the second communicating perforations  323  at a downstream side to be thereby entrained in the main stream before flowing out of the outlet pipe  6 . The initial expansion sunchamber  31  can serve as a resonating chamber to produce a sound wave that cancels out a certain frequency of sound. The sealed chamber  21  is also to serve as a resonating chamber where sound is reduced by reflecting and directing portions of the exhaust gas. By virtue of the pre-outlet subchamber  32  having the second communicating perforations  323 , the exhaust gas can flow in and out the tubular passage  321  so as to generate destructive interference of sound. Meanwhile, after entering into the initial expansion chamber  31 , the main stream of the exhaust gas can continue on flowing into the direction change region ( 321   a ) by being diverted in the transverse direction (B), and subsequently flow in the rejoining region ( 321   b ) for exhausting out of the outlet pipe  6 . Thus, a smooth flow path of the main stream of the exhaust gas is produced from the inlet pipe  5  to the outlet pipe  6 . In addition, by virtue of the first communicating perforations  313 , the back pressure generated adjacent to the inlet pipe  5  can be further reduced. Accordingly, the drawback of decreasing in the output horsepower of an engine described in the prior art can be successfully eliminated. 
         [0021]    Referring to  FIG. 2 , the second preferred embodiment of the exhaust muffler device according to this invention is shown to be similar to the first preferred embodiment. In the second embodiment, an acoustic absorbing material  4  is further provided to be packed in the distal subchamber  212 . In addition, part of the first surrounding partition wall  312  is disposed to extend transversely and outwardly of the outer housing  2  so as to minimize the volume of the sealed chamber  21 , thereby reducing the accommodation space for the muffler device in a vehicle. This is particularly desirable if the muffler device is needed to be mounted under the middle part of the chassis of the vehicle. 
         [0022]    Referring to  FIG. 3 , the third preferred embodiment of the exhaust muffler device according to this invention is shown to be similar to the first preferred embodiment. In the third embodiment, a communicating subchamber  34  is further disposed in the sealed chamber  21  to communicate the initial expansion subchamber  31  with the rejoining region ( 321   b ) through the first distal wall  315  and the second surrounding partition wall  322  so as to permit portion of the main stream of the exhaust gas to pass through the communicating subchamber  34  and flow into the rejoining region ( 321   b ). The communicating subchamber  34  has a plurality of third communicating perforations  343  for further diversion of the exhaust gas into the sealed chamber  21 . 
         [0023]    Referring to  FIG. 4 , the fourth preferred embodiment of the exhaust muffler device according to this invention is shown to be similar to the first preferred embodiment. In the third embodiment, the direction change region ( 321   a ) of the tubular passage  321  is pipe-like, and the rejoining region ( 321   b ) is in communication with the initial expansion subchamber  31  through the first distal wall  315  such that the inlet axis of the inlet pipe  5  is in line with the outlet axis of the outlet pipe  6  in the longitudinal direction (A). 
         [0024]    While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.