TWO-PIECE PISTON RING

Abstract

A piston ring has an annular base body 2, which is preferably open at a joint, with a U-shaped cross section, the open side of which faces inwards in the radial direction. A ring spring 4 is provided which runs in a meandering manner in the axial direction, and which pretensions the base body 2 outwards in the radial direction. In one section of the ring spring 4, which is located inside the base body, meandering loops 5 bear alternately against the shanks 3 of the U-shaped cross section. In one section of the ring spring 4, which protrudes out of the base body 2, meandering loops 6 bear alternately against the radially inwardly facing edges of the shanks 3 of the U-shaped cross section.

Claims

1. A piston ring (1), comprising: an annular base body (2), which is preferably open at a joint, with a U-shaped cross section, the open side of which faces inwards in the radial direction; a ring spring (4) running in a meandering manner in the axial direction, which pretensions the base body (2) outwards in the radial direction; wherein in one section of the ring spring (4), which is located inside the base body, meandering loops (5) bear alternately against the shanks (3) of the U-shaped cross section; and wherein in one section of the ring spring (4), which protrudes out of the base body (2), meandering loops (6) bear alternately against the radially inwardly facing edges of the shanks (3) of the U-shaped cross section.

2. The piston ring (1) according to claim 1, wherein the base body (2) and/or the interior of the U-shaped cross section have a rectangular shape.

3. The piston ring (1) according to one of the preceding claims, wherein the ring spring (4) has a rectangular, trapezoidal or wave-shaped meandering shape.

4. The piston ring (1) according to one of the preceding claims, wherein the piston ring (1) is a compression piston ring.

Description

SHORT DESCRIPTION OF THE FIGURES

[0018] FIG. 1 is a cross-sectional view of a conventional, one-piece piston ring with U profile;

[0019] FIG. 2 is a plan view of an embodiment of a two-part piston ring according to the invention;

[0020] FIG. 3 is a cross-sectional view through a further embodiment of a two-part piston ring according to the invention; and

[0021] FIGS. 4 and 5 show meandering profiles, which can be used in embodiments of the piston ring according to the invention.

DETAILED DESCRIPTION

[0022] FIG. 1 shows a cross section through a conventional one-piece compression piston ring having a base body 2 with a U-shaped cross section. During the working cycle of the associated engine, the lower flank 3 of the ring bears against the ring groove (not shown). The combustion pressure acts on the upper flank 3 during the working cycle of the engine, indicated by arrows. As the flank has a substantially smaller wall thickness than rectangular rings for example, owing to the U profile, a bending of the flank may result, as illustrated here.

[0023] Due to high peak loading and/or due to fatigue owing to constant bending during operation, the ring may ultimately break, for example in the region of the transition into the shank of the U profile.

[0024] Also, the one-piece U profile piston ring shown has a lower radial pressure compared to a rectangular ring with otherwise identical dimensions. The pressure on the cylinder running surface is therefore lower.

[0025] To solve these problems, the invention therefore suggests a two-part piston ring. FIG. 2 shows an embodiment of such a piston ring. The piston ring 1 has a base body 2 with U-shaped cross section. In the embodiment shown, the radially inwardly facing edges of the shanks of the U cross section are bevelled. Alternatively, right-angled and also rounded edges or combinations thereof are likewise possible.

[0026] A meandering ring spring 4 is accommodated in the inferior of the U profile. In the section of the ring spring 4, which is accommodated inside the base body 2, that is to say is located between the shanks of the U profile, the meandering loops 5 bear alternately on the upper or lower inner flank of the U profile. In the section of the ring spring 4, which protrudes out of the base body 2, the meandering loops 6 bear alternately against the radially inwardly facing edges of the shanks 3 of the U-shaped cross section.

[0027] As a result, the two-part piston ring has two advantageous properties compared to a one-part U-shaped ring. On the one hand, the radial pressure is increased by the ring spring 4, which can press the base body 2 outwards by bearing against the radial internal edges of the shanks. On the other hand, the inner sections of the ring spring 4 support the shanks or flanks 3 with respect to pressure loads in the axial direction. Ring breakage can therefore be prevented.

[0028] Slots are located at the respective meandering loops, which separate the inner meandering loops 5 from the outer meandering loops 6. The slots are for example located in the respective outer third with respect to the height. By contrast, the ring spring 4 is in one piece in the central third. Other divisions are likewise possible, as long as a sufficiently large area in the centre remains integral, in order to ensure the stability of the spring.

[0029] likewise, it is merely optional, as illustrated to use a symmetrical spring, which also has meandering loops which are separated by slots in the inner area. This may also be desirable for reasons of simplified production of the spring, even if the inner loops at the edge are then functionless.

[0030] Due to the relatively open construction of the spring, the piston ring can also preferably be used as compression or top ring. The combustion pressure can penetrate at the open points in a relatively unhindered manner to the inner base surface of the base body and thus press the piston ring onto the cylinder running surface. This is an advantage compared to more solid elements of two-part piston rings, in which gas passage of this type is not possible.

[0031] FIG. 3 shows an alternative embodiment of the piston ring in cross section. Here, an asymmetrical ring spring 4 is used, which exclusively has a (wider) inner area with meandering loops 5 and a (narrower) outer area with meandering loops 6. In the case of the cross section shown, the in each case lower meandering loops bear against the lower shank of the U profile. The loops located therebehind in the circumferential direction, when then bear against the upper shank, are shown dashed.

[0032] FIGS. 4 and 5 show alternatives for the meandering shape of the ring spring. Trapezoidal loops (solid) and rectangular loops (dashed) are shown in FIG. 4. In both cases, it is true that as a result, the bearing points on the U profile, which are only punctiform or linear in wave-shaped meandering runs, are replaced by flatter contact faces. That may be advantageous in order to introduce the forces in a more evenly distributed manner. In addition, the piston ring can be better reinforced against bending moments by means of steeper to vertical runs of the spring.

[0033] FIG. 5 shows a wave-shaped meandering run. This can also be adjusted with regards to the supporting effect, by adjusting the steepness and/or number of loops.