Machine element or mechanism – Elements – Pitmans and connecting rods
Patent
1996-07-22
1998-08-04
Luong, Vinh T.
Machine element or mechanism
Elements
Pitmans and connecting rods
74588, 29888092, G05G 100
Patent
active
057877637
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for producing a one-piece or multi-piece connecting rod with a connecting rod eye, connecting rod shaft and/or connecting rod head from at least one sheet metal strip, which is formed with essentially perpendicularly angled-off edge strips on both sides and is bent normally in respect to its main plane into cylindrical or semi-cylindrical support surfaces around the bearing axes of the connecting rod head and/or the connecting rod eye, and all sheet metal elements which define separating gaps in the bearing surfaces of the connecting rod are fixed in place in the immediate vicinity of the bearing surfaces. The invention furthermore relates to a connecting rod made of sheet metal.
BACKGROUND OF THE INVENTION
Connecting rods - are mostly produced by forging processes today. Forged connecting rods have a relatively great weight, which makes the balancing of the masses of the crank mechanism difficult. This problem in regard to the balancing of the masses is even increased because the finished weights of the connecting rods are subject to large variations, which are compensated by weighing the connecting rods individually and then assembling them in the crank mechanism when they have been sorted out. When employing one-piece crankshafts, connecting rods with divided connecting rod heads are required. This means that the forged connecting rod must be opened at the connecting rod head and subsequently re-assembled with difficulties arising on account of exact centering. As a whole, the forging process for producing connecting rods is elaborate and expensive.
Lately, more and more connecting rods are produced by means of the sintering method. Although this method does not provide any essential cost advantages for production, the connecting rods produced in accordance therewith are lighter and more constant in their weight than forged connecting rods. For this reason the high-cost weighing process can be omitted. For dividing the connecting rod head, its lower half is directedly broken off. The three-dimensional break structure being created in the process is used as the centering means in the assembly of the crank mechanism and is furthermore able to transmit axial and radial forces between the halves of the connecting rod head.
Titanium connecting rods are also known which do have excellent sturdiness characteristics, but which are very expensive to manufacture. For this reason they are preferably employed in job lot sizes in connection with the highest requirements.
Production methods for sheet metal connecting rods are also known, wherein the sheet metal body is located perpendicularly in respect to the bearing axes of the connecting rod eye and the connecting rod head, and shaping takes place axially in respect to the bearing axis direction, see DE-OS 30 06 240 and DE-OS 38 01 802. The connecting rods produced by means of these simple and inexpensive methods are very light, however, they have no great stiffness values. They are therefore only suitable for subordinate uses. In addition, designs with a divided connecting rod head for one-piece crankshafts are difficult to produce.
Finally, a connecting rod made of sheet metal is known from the Japanese patent application publication JP-A-57173610 (Patent Abstracts of Japan, Vol. 7, No. 16 (M-187)), wherein a sheet metal strip with edge strips is bent in the center area, normally in respect to its main plane, into a cylindrical support surface around the bearing axis of the connecting rod eye, and at the ends into a semi-cylindrical bearing surface around the bearing axis of the connecting rod head. With this shape the connecting rod shaft consists of a double layer of sheet metal, so that in this case, too, a comparatively large mass is the result. In addition, the separating gap of the connecting rod head is located normally in respect to the main load direction, which is disadvantageous.
It is the object of the invention to provide a method of the kind mentioned at the outset, which results in a lig
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Fatehpour Edison
Grimm Walter
Koch Berthold
Griwe Innovative Umformtechnik GmbH
Luong Vinh T.
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