DE102009028390B3 - Piston for internal combustion engine, has connector fixed between ring groove or area between ring grooves and another ring groove and comprising valve i.e. ball valve, that allows gas flow only in direction of latter ring groove - Google Patents

Abstract

The piston (10) has a piston ring groove (18) arranged on a next to a piston head (16), and piston rings (22, 24) arranged in another piston ring groove (20). A connector (30) is fixed between the latter ring groove or an area (32) between the ring grooves and the former ring groove. The connector includes a valve i.e. ball valve, that allows a gas flow only in a direction of the former ring groove. The connector ends into the former ring groove at a point radially inside of one of the piston rings.

Description

Technical area

The invention relates to a piston for an internal combustion engine according to the preamble of claim 1.

In the field of internal combustion engines, it is known that unnecessary emissions may result from gas loss occurring through the piston ring system into the crankcase. The piston ring system usually has two compression rings and an oil ring and has the task to seal the resulting combustion gases in the combustion chamber as best as possible. This implementation is set by the dynamic ring movement and shock games certain limits. Too high pressures in the area between the piston rings, in particular the first (uppermost) and the second piston ring, prevent the ring movement required for sealing and thus lead to increased gas flow in the direction of the crankcase. If the ring movements are made possible by large shock plays, although the intermediate ring pressure is reduced, due to the high impact play but also occur gas flow in the direction of the crankcase and "BlowBy" on.

State of the art

The EP 0 979 352 B1 describes a piston for a two-stroke diesel engine, in which a connection between the intermediate ring portion and a portion may be provided radially inwardly of the first piston ring. Similar pistons are in the GB 2 104 621 A and the DE 195 14 918 A1 described.

The GB 123 355 A relates to a piston in which a connection from a first piston ring groove or a region between the first and second piston ring groove or from the second and third piston ring groove to the piston head is provided and provided with a check valve.

The invention has for its object to provide a piston for an internal combustion engine, which is improved in view of the reduction of blowby in the direction of the crankcase.

The solution to this problem is achieved by the piston described in claim 1.

As a result, it has at least two annular grooves, a first annular groove closest to the piston crown, and a second annular groove farther away therefrom. In these piston rings are arranged respectively. The first annular groove is also referred to below as the uppermost annular groove. The piston rings are hereinafter referred to according to their arrangement in the first or second annular groove as the first and second piston ring.

The piston according to the invention has a connection between the second annular groove and / or the region between the two annular grooves, from a location radially inward of the second piston ring and / or axially closer to the piston crown than the second piston ring, and the first annular groove. The starting point of said compound, d. H. radially within the second piston ring and / or axially above the second piston ring may be described in that this connection is opened, d. H. should not be blocked by the second piston ring when it rests, for example, during the movement of the piston upwards to expel the combustion gases, at the lower groove edge of the second annular groove. In this situation, a comparatively high pressure prevails in the area between the piston rings, which can lead to combustion gases escaping undesirably in the direction of the crankcase. The described arrangement of the starting point of said compound, which leads at least indirectly into the combustion chamber, allows the combustion gases to flow away in this area in the direction of the combustion chamber. As a result, the high pressures prevailing here are relieved, and BlowBy in the direction of the crankcase is greatly reduced.

According to the invention, the connection described has a valve which allows a gas flow only in the direction of the first annular groove. Namely, in other than the above-described situation, it is undesirable to allow gases to flow toward the second piston ring or even toward the crankcase. Therefore, the gas flow in this direction, i. H. blocked from the combustion chamber or the region of the first annular groove "down" through said valve. As described above, however, this gas flow is admitted in the direction of the first annular groove in order to achieve the described advantageous effects.

Preferred developments of the piston according to the invention are described in the further claims.

For the valve, a ball valve is currently preferred, which can be referred to as "fully automatically controlled" insofar as it is opened by a high pressure in the area between the piston rings as desired, while it is closed, for example, in the compression stroke by the combustion chamber pressure and prevented in that gas flows off in the direction of the second annular groove in this situation.

The connection described can be designed to be particularly simple and short in that it opens into the first annular groove at a location radially within the first piston ring. In the situation described, for example when expelling the combustion gases, the first piston ring is located on the lower groove flank, so that at the described junction of the connection radially within the first piston ring through the gaps radially inside the piston ring and the groove bottom and at the upper groove flank a Connection to the combustion chamber is made.

In addition, the described connection can be designed to be particularly short in the case where it is in the lower, d. H. the flank of the first annular groove further away from the combustion chamber opens.

This applies equally to the preferred embodiment in which the described compound at the top, d. H. the flank of the second annular groove located closer to the piston base begins. Alternatively, particularly good properties are expected for that embodiment in which the connection originates from the region between the piston ring grooves.

When the connection begins radially inside the second piston ring, it can advantageously be substantially axially, i. H. extending in the direction of the piston axis, are formed and thus has a minimum length.

Brief description of the drawings

Hereinafter, an embodiment shown by way of example in the drawings will be explained in more detail. Show it:

1 a sectional view of a portion of the piston according to the invention in a cylinder liner; and

2 a detail of in 1 shown piston.

Detailed description of preferred embodiments of the invention

The in 1 schematically illustrated piston 10 moves axially during operation, ie according to 1 from top to bottom and vice versa, in a cylinder liner 12 , According to the registration of 1 is the combustion chamber 14 which is attached to the piston crown 16 adjacent, above the piston 10 , Starting from the piston head are in the embodiment shown a first 18 and a second annular groove 20 trained, in which a first 22 or a second piston ring 24 are arranged. It should be noted that the gaps shown between the piston rings 22 . 24 and the grooves 18 . 20 as well as between the piston 10 and the cylinder liner 12 are shown exaggerated for clarity.

According to the invention is between the second annular groove 20 , In the case shown radially inside the second piston ring 24 and from the upper groove flank 26 starting, to the first annular groove 18 in a region radially inward of the first piston ring 22 in the lower groove flank 28 opening up, a connection 30 educated. This allows, for example, during the expulsion of combustion gases, ie, when the piston according to 1 Moves up that high pressures due to the immediately preceding combustion in the area 32 between the piston rings of this area in the first annular groove 18 and thus into the combustion chamber 14 can be derived. Also shown in dashed lines is an alternative embodiment in which the connection from the area 32 extending between the two piston ring grooves 18 . 20 is gone out. In this case, the connection thus runs essentially diagonally.

In 2 is schematically the one in the connection 30 provided valve 34 shown in the embodiment shown as a ball valve shown. This has a ball 36 on that when the pressure is above the ball 36 is higher than below it, for example because compression or combustion is taking place at the annular edge between the conduit 38 and the broadening 40 is applied. This will be the connection in this situation 30 sealed in total, ie, a gas flow from the region of the combustion chamber or the first annular groove in the direction of the second annular groove 20 will be prevented. In the reverse direction, however, the gas flow is allowed. This gas flow occurs, for example, when combustion gases are expelled, but in the area 32 (see. 1 ) between the piston rings 22 and 24 a comparatively high pressure prevails, so that the ball 36 as shown by 2 moved upwards. Here, however, no closure of the line 42 , Rather, for example, by the fact that the edge 44 between the line 42 and the broadening 40 at least partially with a recess 46 is provided, gas in the direction of the first annular groove 18 and thus in the direction of the combustion chamber 14 escape.

It should be noted that along the circumference of the piston 10 several of the connections shown 30 can be provided. To allow the necessary valve clearance, the broadening 40 advantageously formed axially higher than the diameter of the ball 36 ,

Overall, by the return of the combustion gases into the combustion chamber, a reduction of the gap widths can be made, so that gas flow in the direction of the crankcase is reduced and emissions are reduced.

Claims (6)

Piston ( 10 ) for an internal combustion engine, with at least two, a first annular groove ( 18 ) closest to the piston crown ( 16 ) is arranged, and a second annular groove ( 20 ), in each of which piston rings ( 22 . 24 ) and at least one connection ( 30 ) between the second annular groove ( 20 ) and / or an area ( 32 ) between the annular grooves ( 18 . 20 ), from a location radially within the second piston ring ( 24 ) and / or axially closer to the piston head ( 16 ) than the second piston ring ( 24 ), and the first annular groove ( 18 ), characterized in that the compound ( 30 ) at least one valve ( 34 ) having a gas flow only in the direction of the first annular groove ( 18 ) allows. Piston according to claim 1, characterized in that the valve ( 34 ) is a ball valve. Piston according to claim 1 or 2, characterized in that the compound ( 30 ) in the first annular groove ( 18 ) at a location radially inside the first piston ring ( 22 ) opens. Piston according to one of the preceding claims, characterized in that the compound ( 30 ) in the lower groove flank ( 28 ) of the first annular groove ( 18 ) opens. Piston according to one of the preceding claims, characterized in that the compound ( 30 ) from the upper groove flank ( 26 ) of the second annular groove ( 20 ) or the area ( 32 ) between the annular grooves ( 18 . 20 ). Piston according to one of the preceding claims, characterized in that the compound ( 30 ) runs largely axially.

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