Patent Application
20150159787
The subject invention relates to welding pipe sections together for use in a vehicle exhaust system.
An exhaust system includes pipe sections that are welded together. Typically, one end of a pipe is inserted into an open end of a connecting pipe and the pipes are brazed or welded together via a peripheral joint that extends about an inner or outer circumference of the pipes at the connection interface.
As known, the pipes are not sized to fit perfectly together. As such, a clearance exists between the two pipes prior to welding. The circumferential weld provided about the periphery to connect the pipes together fills in this clearance to provide a leak free connection. However, this circumferential weld creates a stress riser that extends 360 degrees around the pipes at the connection interface. This joint is subjected to high heat and high levels of vibration which can cause cracks to be generated at the stress riser. This can result in premature wear and/or fracture of the joint.
Brazing also has some disadvantages. This connection method requires additional brazing material, requires high grade pipe material, and has temperature limits.
In one exemplary embodiment, an exhaust component assembly includes a first pipe that defines a center axis and has a first end, and a second pipe that has a second end inserted into the first end of the first pipe such that an outer surface of the second end is in contact with an inner surface of the first end. At least one axial weld connects the first and second ends together.
In a further embodiment of the above, the at least one axial weld comprises a plurality of axial welds that are spaced apart from each other circumferentially about the center axis.
In a further embodiment of any of the above, the first and second ends overlap each other by a first length, and wherein the axial welds have a second length that is less than the first length.
In another exemplary embodiment, a method of connecting a first end of a first pipe to a second end of a second pipe includes the steps of: inserting the second end into the first end; yielding at least one of the first and second ends such that an outer surface of the second pipe is in contact with the inner surface of the first pipe; and welding the first end to the second end with at least one axial weld.
In a further embodiment of any of the above, the at least one axial weld comprises a plurality of axial welds, the axial welds are circumferentially spaced apart from each other about the center axis.
In a further embodiment of any of the above, the axial welds are formed to be generally parallel to the center axis.
In a further embodiment of any of the above, the first and second ends overlap each other by a first length, and the axial welds are formed to have a second length that is less than the first length.
In a further embodiment of any of the above, at least one of the first and second ends are plastically deformed such that the first end is in abutting contact with the second end.
In a further embodiment of any of the above, at least one of the first and second ends are re-sized down by applying an external force to at least one of the first and second ends to create a line-to-line fit between the first and second ends.
In a further embodiment of any of the above, at least one of the first and second ends are expanded out by applying an internal force to at least one of the first and second ends to create a line-to-line fit between the first and second ends.
In a further embodiment of any of the above, at least one slit is provided in the first end and the at least one axial weld is welded along the at least one slit.
These and other features of this application will be best understood from the following specification and drawings, the following of which is a brief description.
Throughout the exhaust system 10 there are many different locations where two pipes 18, 20 are welded together.
In one example, the first pipe 18 defines a center axis A, and the at least one axial weld 30 comprises a plurality of axial welds 30. The axial welds 30 are circumferentially spaced apart from each other about the center axis A. In one example, the axial welds 30 are formed to be generally parallel to the center axis A; however, the axial welds could also be orientated to be at an angle relative to the center axis A.
The first 22 and second 24 ends overlap each other by a first length L1. In one example, the overlap length L1 is within a range of 25 mm to 75 mm; however, other ranges could be used. The axial welds 30 are formed to have a second length L2 that is less than the first length L1. Thus, the axial welds are small, discrete linearly extending welds that are applied to only a very small portion of the overall diameter of the overlapped pipes 18, 20.
The step of yielding at least one of the first 22 and second 24 pipe ends includes taking one or both parts past yield by plastically or permanently deforming the first 22 and/or second 24 ends such that a portion of the first end 22 is in abutting contact with a portion of the second end 24. In one example, at least one of the first 22 and second 24 ends is sized down by applying an external force F1 to the first 22 and second 24 ends to create a line-to-line fit between the first 22 and second 24 ends. In another example, both the first 22 and second 24 ends are sized down by the external force F1. Optionally, at least one of the first 22 and second 24 ends can be expanded out by applying an internal force (in a direction opposite to external force F1) to the first 22 and second 24 ends to create a line-to-line fit between the first 22 and second 24 ends. In another example, both the first 22 and second 24 ends are expanded. The intention is to have a tight, gap-free interface (or only a very small clearance) between the pipes.
Welding of the two pipes 18, 20 together could be accomplished by MIG welding, laser welding or TIG welding, for example. In another example shown in
The axial welds are formed via two layers, i.e. the first 18 and second 20 pipes, at each weld location. This is different than a circumferential weld joint where one side of the weld is through two layers, i.e. first and second pipes, and the other side of the weld is only through one layer, i.e. the first pipe. Further, with axial welds, welding variability should be easily tolerated without introducing stress risers.
Welding from the outside provides a contraction of the outside pipe 18 due to there being more heat and molten material at the weld location on the outside pipe 18 versus the inside pipe 20. After welding, as the first pipe 18 cools, the first pipe 18 contracts more tightly onto the second pipe 20. This increases strength and decreases the possibility of leaks. Thus, even if there is a slight clearance between the pipes 18, 20 after the yielding step, this clearance will be eliminated after the first pipe 18 cools after welding due to the contraction of the first pipe 18.
Sizing pipes together and then adding welds in an axial direction improves joint strength, enables the use of thinner wall tubing, simplifies welding (reduced weld position requirements), reduces joint gas leak, and does not require weld wire. One important feature is that the welding only occurs along the pipe diameter in a discrete number of locations, e.g. 4 to 8 locations for example, which are via thin wall interfaces. The majority of the diameter is undisturbed by welding making the joint very strong and less susceptible to cracking as compared to circumferential welding. Further, the high strain points always occur in a double wall thickness zone with non-welded material on both sides to add strength.
The subject invention provides several advantages over brazing too. There is no filler material required and lower cost pipe material can be used. Further, higher temperature capabilities are provided.
Although an 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.
