Patent Application
20060065480
The subject invention relates to a method and apparatus for attaching a heat shield to a muffler.
A vehicle exhaust system includes a plurality of exhaust components that handle exhaust gases generated by an internal combustion engine. A typical exhaust system includes an exhaust pipe that guides exhaust gases from the internal combustion engine to a muffler. A tailpipe transfers exhaust gases from the muffler to external atmosphere. In addition to guiding exhaust gases, the muffler reduces operational noise levels generated by the internal combustion engine and exhaust system. The exhaust system can include other exhaust components for processing exhaust gases or for reducing noise, such as additional silencers, a catalytic converter, or a resonator.
The exhaust components are typically routed from the internal combustion engine, located near a front portion of a vehicle, underneath a passenger compartment to a rear portion of the vehicle where the tailpipe is traditionally located. The muffler is typically positioned directly underneath the passenger compartment. As known, the exhaust gases generated by the exhaust system have high temperatures. Due to the proximity of the muffler to the passenger component, there is a concern that this heat could be transferred to the passenger compartment.
One solution to reduce effects of the heat generated by exhaust system components has been to install a heat shield between the muffler and a vehicle structure such as a vehicle floor. Many different methods have been used to attach the heat shield to the muffler. One known method involves using bands to secure the heat shield to the muffler. A banding machine typically secures a band around the heat shield at each end of the muffler. This method has some disadvantages. One disadvantage is that the bands may not be secured tightly enough to the muffler. Loose bands can generate an annoying rattle sound. Another disadvantage involves the size, maintenance, and overall cost of the banding machine.
Another known attachment method uses a weld to attach the heat shield to the muffler. Typically in this method, the heat shield is welded directly to an outer shell of the muffler. This weld interface does not accommodate thermal expansion that occurs as the muffler heats up and cools down. This can adversely affect the welds and can even result in weld failures.
Another known attachment method involves capturing ends of the heat shield under a spun end of a muffler end cap. A muffler includes an outer shell with a muffler end cap mounted to each end of the outer shell. In a spin process, ends of the outer shell and circumferential edges of the muffler end caps are spun or folded over each other to provide a secure and permanent attachment between the muffler end caps and the outer shell. Attempting to capture another layer of material, i.e. a heat shield end portion, in the muffler end cap spun end can be disruptive to the assembly process. Further, muffler leak rate properties can be degraded due to the additional layer of material at the spun joint.
Thus, there is a need for an improved attachment interface between a heat shield and a muffler assembly that can accommodate thermal expansion without degrading the attachment interfaces, and which is more reliable than prior attachment interfaces.
A muffler assembly includes an outer shell having a first end cap at one shell end and a second end cap at an opposite shell end. The first and second end caps are attached to the outer shell via a spin attachment process. A heat shield extends along a length of the outer shell and includes a first shield end attached over the first end cap at a first attachment interface and a second shield end attached over the second end cap at a second attachment interface.
In one example, the first and second attachment interfaces are provided by deforming the first and second shield ends around at least a portion of a perimeter of the first and second end caps. In another example, at least one retaining member is used to provide the first and second attachment interfaces. The retaining member could be a single clip, multiple clips, or a retaining ring that directly secures the first and second heat shield ends to the first and second end caps.
In one embodiment, the heat shield includes a plurality of convolutes that are spaced apart from each other along a length of the heat shield. Each convolute is formed as an accordion-like protrusion extending outwardly from an upper surface of the heat shield. The plurality of convolutes dissipates stress that would be generated at the first and second attachment interfaces as the muffler assembly heats up and cools down.
In another embodiment, the heat shield is made from a first component and a second component attached to the first component via an adjustable attachment interface. The adjustable attachment interface allows an overall length of the heat shield to be adjusted to any one of a plurality of overall lengths within a predetermined range of overall lengths. The adjustable attachment interface includes at least one longitudinal slot formed in at least one of the first or second components and at least one fastener received within the longitudinal slot to secure the first and second components together.
The subject invention provides an improved method and apparatus for attaching a heat shield to a muffler assembly. The improved method and apparatus can accommodate thermal expansion without degrading attachment interfaces, is more reliable than prior attachment interfaces, and has improved acoustics over prior designs. 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 muffler 10, shown in
A heat shield 18 is mounted to the muffler 10 to reduce adverse effects of heat generated by the muffler 10. The heat shield 18 has a first shield end 20 mounted to the first end cap 14 at a first attachment interface and a second shield end 22 mounted to the second end cap 16 at a second attachment interface. The heat shield 18 extends along an upper length of the outer shell 12 and is to be positioned between the muffler 10 and a vehicle structure, such as a floor (not shown).
The heat shield 18 can be attached to the first 14 and second 16 end caps in many different manners to define the first and second attachment interfaces. In one example, at least one retaining clip 24 is used to secure each of the first 20 and second 22 shield ends to the respective first 14 and second 16 end caps. A detail of the retaining clip 24 is shown in
As shown in
In this attachment configuration, the first shield end 20 directly engages an end cap portion adjacent the outer peripheral edge 30. The retaining clip 24 has a first portion 36 that directly engages the first shield end 20 and a second portion 38 that directly engages an external surface 40 of the first end cap 14.
A single retaining clip can be used to secure the heat shield 18 to the muffler 10 or a plurality of retaining clips 24, as shown in
In the attachment configuration shown in
As shown in
The retaining clip 24 can be formed from a resilient spring material that is snapped over the first end cap 14. The retaining clip 24 could also be deformed over the muffler end cap spin attachment 32 with tack welds being used if needed. An example of a tack weld location is shown at 50. The retaining clip 24 could also be staked in place using a manual or automated process. Optionally, the first end cap 14 could include a retention feature 52 that cooperates with the retaining clip 24 to provide a more secure attachment interface as needed.
Another attachment interface 54 for attaching the first shield end 20 to the first end cap 14 is shown in
Another attachment interface 60 for attaching the first shield end 20 to the first end cap 14 is shown in
As shown in
As discussed above, the heat shield 18 can be attached to the first 14 and second 16 end caps in many different manners to define the first and second attachment interfaces.
One example of a heat shield is shown generally at 70 in
Another example of a heat shield 80 is shown in
In the example shown, the first 82 and second 84 portions overlap and are connected with a series of Belleville washers 86 and fasteners, such as rivets 88. At least one of the first 82 and second 84 portions includes a series of slots 90 that receive the rivets 88. Strengthening ribs 92 are formed on the first 82 and second 84 portions. The strengthening ribs 92 extend generally parallel to a longitudinal axis L defined by the heat shield 80.
An example of a rivet 88 being received within a slot 90 is shown in
The linear movement allows adjustment of the heat shield 80 prior to attaching the heat shield 80 to the first 14 and second end caps 16 as described above. This allows a common heat shield assembly to be used for mufflers 10 of different lengths within a predetermined range. Also, mufflers of even greater or lesser lengths than the predetermined range could also benefit from this type of heat shield 80 as only one of the first 82 or second 84 portions would have to be changed to accommodate the variable length.
Further, the linear movement of the rivet 88 within the slot 90 can occur during vehicle operation. This allows for the difference in thermal expansion between the muffler 10 and the heat shield 80 generated during normal thermal cycling. This helps to dissipate stress that would otherwise attempt to degrade heat shield/end cap attachment interfaces. The Belleville washers 86 keep tension on the adjustable attachment interface 100, which allows this relative movement without having looseness or rattling.
Although a preferred 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.
