Friction Welded Piston Cooling Channel Design
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Solution Overview
Problem
Existing friction welding methods for producing pistons with closed circumferential cooling channels result in excessive reduction of the cooling channel volume due to radial protrusion of friction welding beads, which impedes cooling oil flow and reduces material strength.
Innovation Solution
The method involves designing the joining surfaces to absorb excess material during friction welding, avoiding sharp notches and maintaining the radial expansion of the cooling channel, thus eliminating typical friction welding beads and allowing for a functional, closed circumferential cooling channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If friction welding is used to join piston base body and piston ring element, then the piston can be produced with closed cooling channel, but friction welding beads protrude radially into the cooling channel reducing its volume
Solution Approach 1:
The joining surfaces are designed in advance with specific geometries (concave-convex configurations, stepped surfaces, or inclined surfaces) to accommodate excess material during friction welding. This preliminary design prevents material protrusion into the cooling channel by providing predetermined receptacles for the welding beads, thereby maintaining the cooling channel volume while enabling friction welding production
Solution Approach 2:
The joining surfaces are given different local geometries - one surface is made concave or stepped while the other is convex, creating a localized material absorption zone at the joining interface. This local quality differentiation allows excess welding material to be contained at the joining surface without encroaching on the cooling channel space
2Strength
If friction welding beads are formed during joining, then the piston components are connected, but sharp notches occur at the exit of rolled beads reducing material strength
Solution Approach 1:
The harmful sharp notches created by conventional friction welding beads are converted into beneficial rounded transitions by designing the joining surfaces to accommodate and reshape the excess material. The concave-convex surface configurations transform the harmful sharp edges into smooth, rounded contours that eliminate stress concentration points while maintaining the structural integrity of the welded joint
Solution Approach 2:
The joining surfaces are pre-designed with specific geometries that anticipate and control the formation of welding beads. By providing predetermined surface configurations (concave-convex pairs, stepped surfaces, or inclined surfaces) before welding, the excess material is guided into controlled positions that form smooth transitions rather than sharp notches, eliminating stress concentration points
3Volume of stationary object
If joining surfaces are designed to absorb excess material, then cooling channel volume is maintained, but the joining surface geometry becomes more complex
Solution Approach 1:
Rather than making the entire joining surface complex, only specific local zones are given special geometries (concave or convex regions, stepped areas, or inclined surfaces). The majority of the joining surface remains simple and planar, allowing for easy manufacturing while the localized complex features perform the material absorption function without significantly increasing overall complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases material strength by 85-100% of the base material, maintaining the original cooling channel volume and ensuring unimpeded cooling oil flow, enabling greater design freedom for pistons with closed cooling channels.
Implementation Method 1
the piston base body and the piston ring element are connected to one another by friction welding
Data Source
Figure 1~2
Figure 3a~4b
Figure 5~6
AI summary
The invention relates to a method for producing a piston (10) for an internal combustion engine, said piston comprising a main piston body (11) and a piston ring element (12), the main piston body (11) having at least a piston skirt (15), the piston ring element having at least a piston head (19), a circumferential fire land (21), and a circumferential ring part (22) provided with annular grooves, and the main piston body (11) and the piston ring element (12) forming a circumferential closed cooling channel (23). Said method is characterized by the following steps: (a) providing a blank (11', 111', 211') of a main piston body (11) having an outer joining surface (29, 129, 229) and an inner joining surface (31, 131, 231) and a lower cooling channel part (23a) circulating between the two joining surfaces (29, 31; 129, 131; 229, 231), (b) providing a blank (12', 112', 212') of a piston ring element (12) having an outer joining surface (32, 132, 232) and an inner joining surface (33, 133, 233) and an upper cooling channel part (23b) circulating between the two joining surfaces (32, 33; 132, 133; 232, 233), (c) forming a circumferential expansion (34a, 34b; 134b; 234a, 234b) on at least one joining surface (29, 129, 229, 31, 131, 231; 32, 132, 232, 33, 133, 233), the expansion (34a, 34b; 134b; 234a, 234b) extending to the associated cooling channel part (23a; 23b), (d) connecting the blank (11', 111', 211') of the main piston body (11) to the blank (12', 112', 212') of the piston ring element (12) by means of the joining surfaces (29, 129, 229, 31, 131, 231; 32, 132, 232, 33, 133, 233) thereof using friction welding to form a piston blank (10', 110'), (e) post-processing and/or finishing the piston blank (10', 110') to form a piston (10). The invention further relates to such a piston.