In a vehicle, in installing a muffler that is a part of an exhaust system, the muffler is installed below a rear floor of the vehicle with a hanger rubber interposed therebetween. The hanger rubber reduces vibrations and shaking of the muffler and suppresses transmission of the vibrations to the vehicle body.
Japan Patent Application Laid-Open No. 2006-183587 discloses a known support structure.
In a prior-art support structure for an exhaust pipe, a muffler to be installed below a rear floor of a vehicle needs to be mounted at a high rigidity and stable position by a hanger rubber so as to reduce vibrations and shaking of the muffler to suppress transmission of the vibrations to the vehicle body. Moreover, it is necessary to prevent thermal deterioration of the hanger rubber caused by heat generated by the muffler.
To solve these problems, i.e., to reduce the vibrations and shakes of the muffler to suppress the transmission of the vibrations to the vehicle body, there is a prior-art structure for fixing a muffler to a high rigidity side frame by a special retaining bracket and a structure using a special mounting part for preventing shaking of the hanger rubber in order to suppress the shaking of the hanger rubber as described in Japan Patent Application Laid-Open No. 2005-120847.
However, these measures require special new parts for stably mounting the hanger rubber, which results in an increase in the number of parts and cost.
To prevent the thermal deterioration of the hanger rubber caused by the heat from the muffler, there is a prior-art structure using a hanger rubber having high heat resistance and a structure using a special heat shield part for shielding from the heat of the muffler as described in the above-described Japan Patent Application Laid-Open No. 2005-220852.
However, these structures involve an increase in cost and the number of parts.
Here, the prior-art support structure of the exhaust pipe will be described in detail.
In the support structure of the exhaust pipe, as shown in FIG. 5, a pair of left and right side frames 108 (the left side frame is not shown) are provided on a lower side of a rear floor 103 of a vehicle 101. A back panel 109 extending downward from the rear floor 103 is joined to rear end portions of the left and right side frames 108. Left and right reinforcing plates 111 (the left reinforcing plate is not shown) are joined to a wall face of the back panel 109 on a vehicle rear side in positions facing the rear end portions of the left and right side frames 108. Left and right stays 113 (the left stay is not shown) extending in a vehicle rearward direction are mounted to the left and right reinforcing plates 111. A bumper member 114 extending in a vehicle width direction is mounted to rear end portions of the left and right stays 113. A muffler 115 is disposed below the rear floor 103 and on a front side of the back panel 109 and is supported on a vehicle body 102 by a hanger rubber or rubber hanger 116.
A special retaining bracket 131 is provided on a side wall of the rear end portion of the right side frame 108. A first pin portion 132 hangs from the special retaining bracket 131. A second pin portion 133 is provided at an upper portion of a rear end face of the muffler 115. The first and second pin portions 132 and 133 are respectively inserted from vehicle front and rear sides into first and second engagement hole portions 134 and 135 formed in the hanger rubber 116 to thereby support the muffler 115 on the vehicle body 102 by the hanger rubber 116.
Exhaust gas flows through the muffler 115 when the vehicle 101 is driven and increases temperature of the muffler 115.
Then, the high-temperature muffler 115 warms a portion around it and warmed hot air rises.
At this time, as is apparent from FIG. 5, a space 118 surrounded with the right side frame 106 and the right reinforcing plate 111 is formed on vehicle rear side and upper side of the muffler 115 and the hanger rubber 116 is located in the space 118.
As a result, the hot air warmed by the muffler 115 rises and stays in the space 118 as shown by white thick arrows in FIG. 5. The hanger rubber 116 located in the space 118 is exposed to the warmed hot air and thermally deteriorates.
Some objects of the present invention are to reduce propagation of vibrations to a vehicle body, to prevent thermal deterioration of the hanger rubber, and to improve mountability of a muffler to the vehicle body in a support structure for an exhaust pipe.