Applicant claims priority under 35 U.S.C. §119 of German Application Serial No. 103 22 921.3 filed on May 21, 2003.
The invention relates to a method for the production of a one-piece piston for an internal combustion engine.
One piece pistons are known in the art, such as the one-piece piston shown in European Patent EP 0 027 445 B1. In that patent, the piston is formed using the casting method. To be able to better utilize the available oil amount for cooling the piston, the known piston has a cooling channel, which is partly closed, formed in its edge region, by a projection structured as an oil groove. With this design, the projection is molded partly onto the pin boss supports and partly onto the skirt connection, which has the result that the production of the known piston, using casting technology, is very complicated and requires casting dies that consist of several parts. This has the disadvantage that the production of the piston known from the state of the art is very complicated and expensive. Furthermore, the production of pistons by means of casting technology always brings the risk with it that casting voids, will form in the piston during production. These casting voids make the piston completely unusable.
Thus, the invention is based on the task of avoiding the stated disadvantages of the state of the art.
The invention relates to a method for the production of a one piece piston for a combustion engine. In this case, the method comprises forging a piston head from a piston blank wherein the piston head extends along a longitudinal axis and is formed in a substantially cylindrical manner having a radial outer region. Next, the piston head is cut to form a recess on a side of the piston head to form a ring wall and a protrusion which results in a ring shaped gap between the protrusion and the ring wall. In this case, the protrusion has an outer radial region that is radially inside of a radial inside region or ring wall by a distance (y). Next, a cooling channel is machined using a machine tool having a width that is smaller than the distance (y) wherein the cooling channel is disposed in an outer region of the piston head with a radially outer delimination formed by a ring wall molded into the piston head, and a radially inner delimination which is formed by a ring wall molded onto the piston head. In this case, the radially inner delimination is formed partly by pin boss supports and partly by skirt connections.
Next, a projection is machined by forming a groove shaped undercut, which faces towards the piston head, structured as an oil groove, which is molded partly on to the at least one pin boss support and partly onto the at least one skirt connection wherein the cooling channel is partly closed off towards a side of the pin bosses.
Next, at least one pin bore is machined in the piston head wherein this pin bore forms at least one pin boss having at least two pin boss supports and at least one face formed integral with the piston head. In this case, the pin boss supports and the face are arranged set back relative to the radial outer region of the piston head.
An outside contour of the piston can be machined wherein this step includes forming at least two skirt elements coupled to the pin boss in the piston head, via a skirt connection having at least one recess between the skirt elements and the piston head.
The ring element is for reducing the gap between the ring wall and the projection, in particular, this also results in a simple and inexpensive possibility of further improving the utilization of the available oil amount for cooling the piston.
Other optional features of the invention may include that the piston head is formed from a blank made from forgeable, heat resistant steel. Alternatively, the blank could be made from forgeable aluminum alloy.
To machine this piston blank, a lathe could be used to produce the piston head. Another optional step could include affixing a ring element on an inside face of the ring wall in a pin-boss-side region, wherein the pin bolt side edge of the ring element reaches into the cooling channel.
This ring element can have a cross-section that is shaped as a nose directed radially inward. In addition, this ring element can be formed from an elastically resilient material. Furthermore, this ring element can be formed from plastic, and wherein the step of affixing the ring element comprises gluing the ring element on a radially inside face of the ring wall.
Furthermore, the step of forming the ring element can include forming a ring element having a circumferential molded on part; and then the step of affixing the molded on part includes forming this part into a circumferential groove formed in a radially inside face of the ring wall.
Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose at least one embodiment of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.
In the drawings, wherein similar reference characters denote similar elements throughout the several views:
Turning now in detail to the drawings,
Pin boss supports 9, 9′, help form a pin boss 11, 11′, with a pin bore 3, 3′, which is molded onto piston head 4, in each instance. Faces 12 of pin bosses 11, 11′ are arranged set back relative to ring wall 7, in the direction of longitudinal piston axis 13. Pin bosses 11, 11′ are connected with one another by way of skirt elements 14, 14′, which are each molded onto piston head 4 by way of a skirt connection 10, 10′. Between skirt elements 14, 14′ and piston-head-side region 15 of piston 1, are recesses 16.
Cooling channel 6 is partly closed off, in the direction of pin bosses 11, 11′, by a circumferential projection 17 structured as an oil groove, which is molded on partly to pin boss support 9, 9′ and partly to skirt connection 10, 10′. Projection 17, together with pin-boss-side face 18 of ring wall 7, forms a gap 19.
The cross-section shown in
In a first set of method steps, according to
A first step for the production of cooling channel 6, shown in the left half of the cross-sectional diagram, takes place using lathing tool 27, in which cutting plate 31 is attached to a tool holder 34 that is angled up by approximately 30°. Using this tool, a recess 35 can be lathed into the region between ring wall 7 and pin boss support 9, 9′, for example, skirt connection 10, 10′.
With this design, a residual region 40 is left, which can be removed using the lathing tool 29, which has an arm 41 angled upward by approximately 45° in its front region. Completion of cooling channel 6 takes place using the lathing tool 30. In this case, there is arm 42 of which is angled off at a right angle, and is long enough to lathe out residual region 43. Depending on the desired height of cooling channel 6, arm 42 can be longer than the distance between top edge 37 of skirt element 14, 14′ and bottom edge 38 of ring wall 7. In this case, it is necessary to introduce lathing tool 30 into recess 39 in the region of face 12 of pin bosses 11, 11′, which are arranged set back relative to ring wall 7, to start the lathing process. A sufficiently large recess 16 then makes it possible so that the lathing process proceeds without hindrance from skirt elements 14, 14′, with arm 42 moved into recess 39 and piston 1′″ having been put into rotation.
Subsequent to this, the outside contours of piston 1′″ are lathed in a known manner, using lathing tools suitable for this purpose, not shown in
To better utilize the available oil amount for cooling of piston 1, according to
Assembly of ring element 44 takes place wherein it is bent apart and laid around piston 1 between ring wall 7 and projection 17. The gap of ring element 44 subsequently allows pressing ring element 44 together and thereby reducing its radius to such an extent that it can be introduced from below into cooling channel 6, until the molded-on part 46 of the ring element 44 catches into groove 47. If the ring element 44 is made of metal, its inherent stress is sufficient to permanently fix ring element 44 in place in cooling channel 6. If ring element 44 is made of plastic, a suitable adhesive is required to fix it in place.
Accordingly, while at least one embodiment of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
---|---|---|---|
103 22 921 | May 2003 | DE | national |
Number | Name | Date | Kind |
---|---|---|---|
6415191 | Pryor | Jul 2002 | B1 |
6487773 | Scharp et al. | Dec 2002 | B1 |
6760961 | Upadhya | Jul 2004 | B2 |
Number | Date | Country |
---|---|---|
0 027 445 | Apr 1979 | EP |
Number | Date | Country | |
---|---|---|---|
20040231631 A1 | Nov 2004 | US |