DE19730399A1 - Piston for internal combustion engine with direct fuel injection - Google Patents

Abstract

The piston has several channels (6) which extend from the piston depression to the piston head. The channels are evenly distributed over the circumference of the piston depression and extend outwards at an angle from the base (5) of the piston hollow.

Description

The invention relates to a piston according to the upper Concept of claim 1 for an internal combustion engine Direct injection, both for a diesel and for an Otto internal combustion engine.

In particular with diesel internal combustion engines will increase the amount of direct fuel injection applied at the fuel is finely distributed and electronically metered into the Combustion chamber is injected. In the TDC position of the piston the combustion chamber is mainly formed by the piston bowl det. The quality of the combustion depends on this process depends on many factors. Important parameters include a. the Injection law (time of injection, injection quantity over time), the geometry of the injector, the jet angle, the geometry of the piston bowl and the inlet geometry (e.g. swirl channel).

The firing process is evaluated on the basis of the We efficiency, exhaust emissions and noise. All of the above parameters have a significant influence on the evaluation criteria. The reason for this is the retroactive effect  this parameter on the flow mixing, evaporating formation and mixture formation processes during compression, during combustion and during expansion.

In the usual direct injection process, the kinetic Energy of the air introduced into the combustion chamber to the Vermi with the fuel and to homogenize it Mixture used. The fresh gas charge is during the compression gradually almost completely into the Piston recess pushed so that there the kinetic energy the fuel injection is concentrated. While the Combustion expires and the gas expands, the gas becomes pressed out of the piston bowl into the combustion chamber. This takes place at low speeds with dissipation of the kinetic energy, resulting in poor homogenization As a result, the high local temperature peaks lead to a fat one soot-forming combustion and thereby also problems with a Causes exhaust gas recirculation.

The invention has for its object a piston Generic type to create a faster and with your more homogeneous mixture formation with reduced combustion peak temperatures and thus a reduction in HC emissions ions, the formation of soot and the formation of NOx becomes.

This object is achieved in that in the Piston is provided a plurality of channels extending from the piston bowl to the piston crown.  

In the invention is already during the compression the channels a secondary flow from the piston bowl into the Combustion chamber induced. This secondary flow causes after Fuel injection an improved homogenization of the Air-fuel mixture. With the onset of combustion this secondary flow is intensified so that the mixture similar to pre-chamber diesel engines now high speed through the channels into the combustion chamber crosses. Due to the high flow rate optimally processed the still unburned mixture and increased turbulence, resulting in higher combustion leads to dizziness.

Advantageous developments of the invention are in the sub claims specified. So the channels are preferably the same moderately distributed over the circumference of the piston bowl and they can start from the bottom of the piston bowl and the circumference of the pistons trough diagonally outwards, straight or along a curve and / or, seen in plan view of the piston crown, approximately run tangential to the piston bowl. With an internal combustion engine machine with an inlet channel, one in the piston bowl Generated swirl, the channels preferably run in the Swirl direction from the peripheral wall of the piston bowl at an angle to Piston crown. The cross-sectional profile of the channels can be designed like a nozzle or diffuser. By variation the area ratio of the channel openings to the troughs opening, the inclination and the length of the channels and by the shape of the transition between the piston bowl and the channels can be optimally adapted to the individual case  Relationships are created.

An embodiment of the invention is described below Described with reference to the drawings. It shows:

Fig. 1 is a plan view of a piston, and

FIG. 2 shows a section along line 2-2 in FIG. 1.

In the drawings, a piston 1 of a diesel or gasoline internal combustion engine with direct injection is shown, which has a piston head 2 , in the center of which a piston recess 3 is arranged, the peripheral wall of which is designated 4 and the bottom of which is designated 5 .

From the peripheral wall 4 of the piston recess 3 go near the bottom 5 of 6 channels, which extend up to the piston crown. 2 As can be seen from FIG. 1, these channels 6 are distributed uniformly over the circumference of the piston recess 3 and run approximately tangentially to the piston recess 3 . In Fig. 2, the ge-cut channel 6 is drawn rotated in the plane of the drawing to make its course more recognizable.

Is equipped with a swirl-generating inlet duct, the internal combustion engine, which in the piston cavity 3 produces a twist in the direction of arrow P, the channels 6 preferably extend, as shown in Fig. 1, in the swirl direction P obliquely upwards to the piston crown 2 down.

As described previously, the channels 6 already cause a secondary flow of air from the piston recess 3 into the remaining combustion chamber lying above the piston crown 2 , as indicated by the arrow D in FIG. 2. This secondary flow results in a very good homogenization of the fuel-air mixture after the injection of the fuel. This secondary flow is amplified with the onset of combustion, so that the mixture flows at high flow speed from the piston bowl 3 through the channels 6 in the rest of the combustion chamber. This optimally prepares the still unburned mixture and increases the turbulence in the combustion chamber.

Claims (9)

1. Piston of an internal combustion engine with direct injection, the piston crown ( 2 ) has a piston recess ( 3 ), characterized by a plurality of channels ( 6 ) which extend from the piston recess ( 3 ) to the piston crown ( 2 ). 2. Piston according to claim 1, characterized in that the channels ( 6 ) are arranged distributed uniformly over the circumference of the piston recess ( 2 ). 3. Piston according to claim 1 or 2, characterized in that the channels ( 6 ) from the circumference ( 4 ) of the piston recess ( 3 ) extend obliquely outwards. 4. Piston according to one of claims 1 to 3, characterized in that the channels ( 6 ) from the bottom ( 5 ) of the piston recess ( 3 ) extend. 5. Piston according to one of the preceding claims, characterized in that the channels ( 6 ) run in a straight line. 6. Piston according to one of claims 1 to 4, characterized in that the channels ( 6 ) run along a curve. 7. Piston according to one of the preceding claims, characterized in that the channels ( 6 ), seen in plan view of the piston crown ( 2 ), extend approximately tangentially to the piston recess ( 3 ). 8. Piston according to one of the preceding claims for an internal combustion engine with an inlet channel which produces a swirl in the piston bowl ( 3 ), characterized in that the channels ( 6 ) in the swirl direction (D) from the peripheral wall ( 4 ) of the piston bowl ( 3 ) run at an angle to the piston crown ( 2 ). 9. Piston according to one of the preceding claims, characterized in that the cross-sectional profile of the channels ( 6 ) is designed like a nozzle or diffuser.