Muffler

A muffler comprising:

• an inner pipe having a tubular shape;
• and
• an outer pipe having a tubular shape, the inner pipe being disposed on an inner-circumferential side of the outer pipe, the outer pipe forming a double-wall pipe with the inner pipe,
• one of a first end of the double-wall pipe or a second end of the double-wall pipe being continuous to a first channel on an upstream side in an exhaust flow direction, and the other of the first end of the double-wall pipe or the second end of the double-wall pipe being continuous to a second channel on a downstream side in the exhaust flow direction, thereby forming an exhaust channel coupling the first channel and the second channel via the inner pipe,
• a cavity being provided between the outer pipe and the inner pipe, the second end having an opening between the inner pipe and the outer pipe, the cavity being configured to communicate with the exhaust channel via the opening,
• the inner pipe having a first range and a second range, an outer side surface of the inner pipe being located at the same position as a reference in the first range, and the outer side surface of the inner pipe being disposed on an inner side relative to the reference in the second range, the reference being a position of an inner side surface of the outer pipe,
• the outer side surface of the inner pipe reaching an edge of the second end in each of the first range and the second range,
• the inner pipe and the outer pipe being disposed at a position where the outer side surface of the inner pipe and the inner side surface of the outer pipe are in contact with each other so as to close a space between the inner pipe and the outer pipe, in the first range,
• a part of the cavity being formed between the outer side surface of the inner pipe and the inner side surface of the outer pipe, and the opening being formed in a portion where the second range reaches the edge of the second end, in the second range,
• the outer pipe including an outer pipe small diameter portion forming the first end, an outer diameter of the outer pipe becoming smaller in the outer pipe small diameter portion, an outer pipe large diameter portion forming the second end, the outer diameter of the outer pipe becoming larger in the outer pipe large diameter portion, and an outer pipe enlarged diameter portion provided between the outer pipe small diameter portion and the outer pipe large diameter portion, the outer diameter of the outer pipe gradually increasing from the outer pipe small diameter portion to the outer pipe large diameter portion in the outer pipe enlarged diameter portion,
• the outer pipe large diameter portion having a length larger than a combined length of the outer pipe small diameter portion and the outer pipe enlarged diameter portion, in the exhaust flow direction,
• the inner pipe including an inner pipe small diameter portion forming the first end, an outer diameter of the inner pipe becoming smaller in the inner pipe small diameter portion, an inner pipe large diameter portion forming the second end, the outer diameter of the inner pipe becoming larger in the inner pipe large diameter portion, and an inner pipe enlarged diameter portion provided between the inner pipe small diameter portion and the inner pipe large diameter portion, the outer diameter of the inner pipe gradually increasing from the inner pipe small diameter portion to the inner pipe large diameter portion in the inner pipe enlarged diameter portion,
• the inner pipe large diameter portion having a length larger than a combined length of the inner pipe small diameter portion and the inner pipe enlarged diameter portion, in the exhaust flow direction,
• an inner side surface of the outer pipe small diameter portion and an outer side surface of the inner pipe small diameter portion being in contact with each other over the entire circumference,
• an inner side surface of the outer pipe large diameter portion and an outer side surface of the inner pipe large diameter portion being in contact with each other in some area, which is the first range, and form the cavity between each other in an other area, which is the second range, differing from the some area, and a part of the outer side surface of the inner pipe large diameter portion being disposed on an inner-circumferential side relative to a reference in a portion where the cavity is formed, the reference being a position of the inner side surface of the outer pipe large diameter portion.

A muffler comprising:

• an inner pipe having a tubular shape, and
• an outer pipe having a tubular shape, the inner pipe being disposed on an inner-circumferential side of the outer pipe, the outer pipe forming a double-wall pipe with the inner pipe,
• one of a first end of the double-wall pipe or a second end of the double-wall pipe being continuous to a first channel on an upstream side in an exhaust flow direction, and the other of the first end of the double-wall pipe or the second end of the double-wall pipe being continuous to a second channel on a downstream side in the exhaust flow direction, thereby forming an exhaust channel coupling the first channel and the second channel via the inner pipe,
• a cavity being provided between the outer pipe and the inner pipe, the second end having an opening between the inner pipe and the outer pipe, the cavity being configured so as to communicate with the exhaust channel via the opening,
• in a circumferential area with presence of an inclusion to be held between an outer side surface of the inner pipe and an inner side surface of the outer pipe, the inner pipe having a reference that is a position of an inner side surface of the inclusion, whereas in a circumferential area with no presence of the inclusion, the inner pipe having a reference that is a position of the inner side surface of the outer pipe, the inner pipe having a first range where a position of the outer side surface of the inner pipe coincides with the reference, and the inner pipe having a second range where the outer side surface of the inner pipe is located inward relative to the reference,
• in the first range, the inclusion being held between the outer side surface of the inner pipe and the inner side surface of the outer pipe so as to close a space between the inner pipe and the outer pipe,
• in the second range, a part of the cavity being formed between the outer side surface of the inner pipe and the inner side surface of the outer pipe so as to form the opening at a position closer to the second end of the double-wall pipe in the second range,
• the inner pipe including a large diameter portion having a first diameter, and a small diameter portion having a second diameter that is smaller than the first diameter,
• the part of the cavity being formed between an outer side surface of the small diameter portion and the inner side surface of the outer pipe,
• the large diameter portion being disposed at the second end and including the first range and the second range,
• the part of the cavity being formed between an outer side surface of the large diameter portion and the inner side surface of the outer pipe in the second range,
• a resonance chamber, which corresponds to the part of the cavity, being formed between the outer side surface of the small diameter portion and the inner side surface of the outer pipe,
• in the second range, a resonance pipe, which corresponds to the part of the cavity, being formed between the outer side surface of the large diameter portion and the inner side surface of the outer pipe, and
• the opening provided at one end of the resonance pipe, the resonance pipe communicating with the exhaust channel via the opening, the resonance chamber communicating with the exhaust channel via the resonance pipe, whereby the resonance pipe and the resonance chamber being configured to function as a Helmholtz resonator.