EP1920151A1

EP1920151A1 - Lightweight piston

Info

Publication number: EP1920151A1
Application number: EP06777082A
Authority: EP
Inventors: Ralf Buschbeck; Johannes Spermann; Albert Haberl; Klaus Lormes
Original assignee: KS Kolbenschmidt GmbH
Current assignee: KS Kolbenschmidt GmbH
Priority date: 2005-08-29
Filing date: 2006-08-26
Publication date: 2008-05-14
Also published as: JP2009506259A; US20080264247A1; WO2007025686A1; US7954421B2; KR20080063269A; BRPI0615298A2

Abstract

The invention relates to a piston (1) comprising a piston head (2) that is provided with a field of rings (4) and a piston shaft (3) which is disposed thereupon. The piston shaft (3) is equipped with supporting shaft wall sections (5) and rear connecting walls (6) which interconnect the shaft wall sections (5), have an arched shape, and are fitted with a bolt bore (7). An undercut free space (8) is provided below the annular field (4) in the area of the bolt bore (7), in the region of the piston head (2). An arched zone (15) is embodied in the interior of the piston (1), at the transition from the bolt bore (7) in the direction of the shaft wall section (5f).

Description

DESCRIPTION

lightweight pistons

The invention relates to a piston having a ring bottom having a piston head and a piston shaft arranged thereon according to the features of the preamble of claim 1.

Such a piston is known from DE 101 45 589 A1. This has a KoI- benboden, which consists of a ring field with several annular grooves and possibly a combustion bowl. In the direction of movement of the piston, a piston shaft is arranged below the piston head, said piston shaft consists of two the piston in operation in the internal combustion engine bearing shaft wall sections, which serve to guide the piston in the cylinder of the internal combustion engine. The shaft wall sections are connected to each other via past connecting walls, wherein the connecting walls have no connection to the running surface of the cylinder. In the piston of DE 101 45 589 A1, according to the claims 1 to 3 there, the connecting walls on a curved course, which may be convex, concave or a combination of these curvatures. Furthermore, in this known piston in the region of the connecting walls of the lower edge of the ring field over this protruding formed (supernatant) and there at least partially hollowed out, so that creates a free space in order to save weight.

The invention is based on the object to improve a generic piston in terms of its properties during operation in the internal combustion engine, in particular to increase its strength and durability.

This object is solved by the features of claim 1. According to the invention it is provided that in the interior of the piston at the transition from the pin bore in the direction of the shaft wall portion, a curved portion is provided. By means of these curved regions at the transition from the recess edge of the pin bore in the direction of the skirt wall sections, on the one hand so much material can be retained that the required strength is achieved during operation of the piston, while at the same time so much material can be taken away that a weight reduction is simultaneously optimized Durability of the piston occurs. As a result of this curved course according to the invention in the inner region of the piston, the required strength and durability of the piston is thus increased in conjunction with the outer curved profile of the supporting shaft wall sections while at the same time the piston weight is reduced. Furthermore, this construction can be continued to the effect that, starting from an annular groove of the ring field in the direction of the pin bore at least one compound is introduced into the piston. This considerably improves the operation of the piston, since the oil ring (possibly multi-part oil scraper ring) seated in the annular groove accumulates the oil present on the surface of the piston or on the surface of the cylinder wall and this is pressed into the connection and thus can be guided in the direction of the pin bore, there to cause lubrication of the bolt inserted into the pin bore. This compound is particularly advantageous in the generic piston, as this already has a low weight and improved strength due to the curved connecting walls, the compound of the invention for lubricating the bolt inserted into the pin bore the durability of the entire assembly consisting of pistons, bolts and Connecting rod, much improved. Because the supply of oil from the direction of the surface of the piston in the direction of the pin bore, the bolt inserted there is lubricated and can not eat. The bore according to the invention is either cast in and / or introduced by a drilling process (bore).

In a further development of the invention, at least one rib for supporting the ring field is arranged in the free space behind the ring field. The at least one rib advantageously has the effect that the projecting region of the annular field is effectively supported in the area of the connecting walls that are located behind, so that deformation of the piston during operation is largely reduced. In a further embodiment of the invention, a rib is in each case right and left above the pin hole in the space available. As a result, the ring field is supported on those areas to the right and left of the pin hole, which form a special stability. As a result, influences of the movement of the bolt in the pin bore during the movement of the piston are not transmitted to the ring field, if just according to the invention in each case a rib is arranged right and left above the pin bore.

In a further embodiment of the invention, the connection extends through the at least one rib, in particular through several or all ribs. In this case, both the ribs and the compounds can already be considered in the production of a piston blank. Additionally or alternatively, it is conceivable that the at least one compound is introduced only after the production of the piston blank. It is also conceivable, for example, in the case of an angled or rounded course of the connection of the annular groove in the direction of the pin bore already form part of the connection with the production of the piston blank and another, the remaining part of the compound by a subsequent machining operation, in particular a bore to contribute. If the connection is already produced with production of the piston blank, it is advisable to provide in the area of the later connection a core or also a pin, which is removed after production of the piston blank.

In a further development of the invention, at least one drainage slot extending into the free space is present in the annular groove. The clearance with the production of the piston blank (and optionally after subsequent further processing) is designed so that with introduction of the annular groove, in particular the lowermost annular groove, a connection is generated from the outside in the direction of the free space, just the sufficient in the free space drainage slot forms. This means that with introduction of the annular groove, in particular by a step of machining, the drainage slot is automatically generated. The introduced drainage slot causes the oil present on the surface of the piston or on the surface of the cylinder inner wall to be removed in the direction of the interior of the piston. The position or the structural design of this Drainage slit has a higher fatigue strength compared to previously known oil wells. In addition, there is no interruption of the ring bearing surface, so that groove wear and oil consumption are thereby reduced.

In a further embodiment, the bolt bore has a lifting groove for a retaining ring (clamping ring) for the bolt, wherein the lifting groove is arranged below the free space and at the upper vertex of the pin bore. The clearance makes it possible to arrange the lifting groove at the upper vertex of the pin bore. This has the advantage that the lifting groove is arranged in a region in which the strength of the piston is not impaired. This leads advantageously to an increase in mass-load safety.

In a further embodiment of the invention, the edge is rounded below the ring field in the region of the past connecting walls. After the production of the piston blank this is usually finished by means of machining, in particular turned off. As a consequence. That the edge below the ring field in the region of the past connecting walls is very sharp and optionally identifies a ridge that can come during handling, in particular the assembly of the piston to injuries of the assembly staff. For this purpose, this sharp edge is rounded below the ring field in an advantageous manner or has a rounding. This rounding can also be produced by machining, in particular a milling process.

Embodiments of the invention, but not limited thereto, are described below and explained with reference to the figures.

Figures 1 to 3 each show a piston 1 of an internal combustion engine, which may be configured as a lightweight piston, but does not have to. If it is a lightweight piston, first a piston blank made of a lightweight material, in particular aluminum, poured and then finished by means of machining. This piston 1 consists of a piston head 2 with an attached piston shaft 3, wherein the piston head 2 and the piston shaft 3 are integrally formed or consist of two parts, which are joined together after their preparation. Furthermore, the piston 1 has a ring field 4 with three annular grooves on the rule. The piston shaft 3 consists of the piston 1 bearing shaft wall sections 5, wherein the shaft wall sections 5 are connected by past connecting walls 6 together. The connecting walls 6 have a straight, arched or other course, with respect to the curved course of the composite walls 6 reference is made to the possible embodiments according to the patent claims 1 to 3 of DE 101 45 589 A1. Reference is made to this curved course (concave and / or convex from one skirt wall section to the other skirt wall section and / or in its course in the piston movement axis), since this process is particularly important in terms of weight saving while maintaining the required strength. Just as important but depending on the geometric design and purpose of the piston 1 straight connecting walls. The past connecting walls 6 furthermore have a bolt bore 7 for receiving a bolt for connecting the piston 1 to a connecting rod (not shown). Furthermore, it is shown in Figure 1, that in the region of the piston head 2 behind the ring field 4 and above the pin bore 7 a clearance 8 is present. In a first embodiment, as shown in FIG. 1, starting from an annular groove 9 of the annular field 4, a connection 10 extends in the direction of the pin bore 7 in order to lubricate the pin (not shown) located there. In the embodiment of the connection 10 according to FIG. 1 is a bore which is partly introduced from the direction of the annular groove 9 and partly from the direction of the piston skirt 3 in the direction of the piston crown 2. The representation at the bottom right of Figure 1 is a section AA as shown in Figure 1 above right.

FIG. 2 shows the same piston 1 according to FIG. 1, wherein a rib 11 is arranged in each case above the pin bore 7 in the free space 8 to the right and left of the pin bore 7. These ribs 11 are used to support the ring field 4 during operation of the piston 1, so that the forces acting on the piston head 2 forces are introduced via the ribs 11 in the past connecting walls 6. Furthermore, it is shown in FIG. 2 that the bolt bore 7 has a lifting groove 12 for a retaining ring (clamping ring) for the bolt, the lifting groove 12 being arranged below the clearance 8 and at the upper vertex of the bolt bore 7. In the representation of FIG. 2, on the right, a drainage slot 13 is shown, its location and arrangement is also apparent when looking at the figure 3. The drainage slot 13 is arranged in the region of the annular groove 9 so that a connection results from the annular groove 9 in the free space 8 when the annular groove 9 is introduced into the piston blank. The region of the drainage slot 13 behind the annular groove 9, that is in the region of the free space 8, may be cup-shaped. When using, in particular, a three-part oil ring in the annular groove 9, oil can be removed from the surface of the piston 1 or the cylinder running surface in the direction of the inner region of the piston 1 via the drainage slot 13. For this purpose, there are the drainage slots 13, in particular in each case a drainage slot on the right and left of the pin bore 7, in particular symmetrically arranged, in the region of the past connecting walls 6, since there is sufficient space for the discharged oil.

Although not shown in the figures, the connection 10, as shown, for example, in FIG. 1, may extend from the annular groove 9 through the rib 11 in the direction of the pin bore 7.

With regard to FIG. 3, it can be seen that curved areas 15 are provided in the inner area of the piston 1 and extend from the pin bore 7 in the direction of the shaft wall sections 5 (their inner surfaces). These curved areas 15 can have a continuous or unsteady course in the circumferential direction and / or in the course in the direction of the piston stroke axis and thus be adapted to the respective geometries of the inner area of the piston 1. These curved areas 15 can be introduced either by casting the piston 1 or by subsequent machining, in particular machining by means of milling.

The course and / or the extension of the arched area 15 also has the additional advantage that a free space is created in the interior area of the floor, which is necessary for the play requirements of a trapezoidal connecting rod, via which the piston can be connected to the crankshaft. LIST OF REFERENCE NUMBERS

1st piston

2nd piston bottom

5 3. Piston stem

4th ring field

5th shaft wall section

6. connecting wall

7. Bolt hole

10 8. Freiraum

9. annular groove

10. Connection

11th rib

12. Excavation

15 13. Drainage slot

14. Rounding off

15th arched area

Claims

PATENT APPLICATIONS

1.

A piston (1) having a piston crown (2) having a ring field (4) and a piston shaft (3) arranged thereon, further having supporting shaft wall sections (5) and connecting walls (6) which connect the shaft wall sections (5) with each other and a pin bore (7), characterized in that in the interior of the piston (1) at the transition from the pin bore (7) in the direction of the shaft wall portion (5) a curved portion (15) is provided.

Second

Piston (1) according to claim 1, characterized in that outgoing from an annular groove (9) of the annular field (4) in the direction of the pin bore (7) at least one compound (10) in the piston (1) is introduced.

Third

Piston (1) according to claim 1 or 2, characterized in that in the free space

(8) at least one rib (11) for supporting the ring field (4) is arranged.

4th

Piston (1) according to claim 3, characterized in that in each case a rib (11) on the right and left above the pin bore (7) is present.

5th

Piston (1) according to claim 3 or 4, characterized in that the connection (10) extends through the at least one rib (11).

6th Piston (1) according to one of claims 1 to 5, characterized in that in the annular groove (9) at least one in the free space (8) extending into the drainage slot (13) is present.

5 7.

Piston (1) according to one of the preceding claims, characterized in that the bolt bore (7) has a lifting groove (12) for a retaining ring, wherein the lifting groove (12) below the free space (8) and at the upper vertex of the pin bore (7). is arranged.

10

8th.

Piston (1) according to one of the preceding claims, characterized in that the edge below the ring field (4) in the region of the past connecting walls (6) is rounded.

15

9th

Piston (1) according to one of the preceding claims, characterized in that the shaft wall sections (5) have a curved course.

20 10.

Piston (1) according to one of the preceding claims, characterized in that below the annular field (4) in the region of the pin bore (7) there is a rear-cut free space (8) in the region of the piston head (2).