FR3057913A1 - PISTON FOR INTERNAL COMBUSTION ENGINE WITH AERODYNAMIC CURTAIN - Google Patents

Abstract

Piston (1) intended to slide in a cylinder (2) of direct injection internal combustion engine characterized in that it comprises: - a combustion chamber (11), - a substantially planar flushing zone (13), - a channel (10) connecting the combustion chamber (11) to the flushing zone (13), this channel (10) being oriented substantially perpendicularly to the flushing zone (13) at its first end (10 ') opening on the hunting area (13).

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY

COURBEVOIE © Publication number:

(to be used only for reproduction orders)

©) National registration number

057913

60168 © Int Cl ⁸ : F02 F3 / 26 (2017.01)

PATENT INVENTION APPLICATION

A1

©) Date of filing: 20.10.16. ©) Applicant (s): RENAULT S.A.S Joint-stock company ©) Priority: simplified - FR. @ Inventor (s): HERVET JEROME, DUTFOY LAURENT and LEFORT OLIVIER. (43) Date of public availability of the request: 04.27.18 Bulletin 18/17. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents (73) Holder (s): RENAULT S.A.S Société par actions sim- related: folded. ©) Extension request (s): ©) Agent (s): NOVAIMO.

PISTON FOR INTERNAL COMBUSTION ENGINE WITH AERODYNAMIC CURTAIN.

FR 3 057 913 - A1

Piston (1) intended to slide in a cylinder (2) of an internal combustion engine with direct injection characterized in that it comprises:

- a combustion chamber (11),

- a substantially flat hunting area (13),

- A channel (10) connecting the combustion chamber (11) to the hunting zone (13), this channel (10) being oriented substantially perpendicular to the hunting zone (13) at its first end (10 j opening out on the hunting area (13).

Piston for internal combustion engine with aerodynamic curtain

The present invention relates to a piston intended to slide in a cylinder of an internal combustion engine with direct injection, as well as an internal combustion engine and a motor vehicle as such incorporating such a piston.

An internal combustion engine with direct injection of the state of the art, in particular with a diesel cycle, comprises several cylinders closed by a cylinder head, inside which pistons slide between two extreme positions, called top dead center and bottom dead center .

Such a piston has a cavity hollowed out in its upper part in which the combustion of the fuel takes place mainly, commonly called combustion chamber. This combustion chamber comprises a concave wall of revolution about an axis parallel to the axis of translation of the piston, commonly known as the bowl. The particular shape of this bowl aims to improve the diffusion of the injected fuel and combustion products in the combustion chamber, and finally to optimize the post-oxidation of the soot to achieve the most efficient combustion possible.

In general, fuel injection is carried out when the piston is in the high position, but certain variants exist around this high position, for example based on so-called late injections, in particular for implementing combustion strategies in processes. depollution. In all cases, it happens that aerodynamic movements within the combustion chamber cause a few drops of fuel near it, on the upper flat surface of the piston commonly called hunting area. Indeed, this hunting zone joins the combustion chamber by means of a simple convex radius, commonly called reentrant lip. These drops burn and form carbonaceous materials, soot, more generally residual particles, which manage to propagate between the piston and the cylinder liner. These residual particles finally mix with the engine oil, leading to a deterioration in the performance of this oil. It is necessary to program the draining of the engine oil according to a frequency adapted to the speed of its degradation. It is of course interesting to maximize the intervals between oil changes.

Thus, an object of the invention is to provide a solution for reducing the level of residual particles, such as carbonaceous materials, smoke particles and soot from combustion, in the oil of an internal combustion engine. .

In this design, the invention relates to a piston intended to slide in a cylinder of an internal combustion engine with direct injection comprising:

- a combustion chamber,

- a substantially flat hunting area,

- A channel connecting the combustion chamber to the hunting zone, this channel being oriented substantially perpendicular to the hunting zone at its first end opening onto the hunting zone.

In other embodiments:

- The channel opens into a peripheral wall of the combustion chamber;

- The orientation of the axis of the second end of the channel at the level of the combustion chamber varies from tangency to perpendicularity with respect to the peripheral wall of the combustion chamber;

- the axis of the first end of the channel has an inclination less than or equal to 20 degrees relative to the direction perpendicular to the hunting area;

- The channel is cylindrical or helical in shape;

- the hunting area is substantially annular;

- the combustion chamber has the shape of a bowl.

According to a variant of the invention, the piston comprises as many channels as jets coming from direct injection.

The invention also relates to an internal combustion engine comprising such a piston.

Finally, the invention relates to a motor vehicle comprising an internal combustion engine equipped with such a piston.

These objects, characteristics and advantages of the present invention will be described in detail in the following description of a particular embodiment and of a variant made without implied limitation in relation to the attached figures among which:

FIG. 1 represents a perspective view of a piston according to an embodiment of the invention.

FIG. 2 represents a section along A-A of a half-piston and aims to illustrate the effect obtained, during the combustion phase, of a piston according to the embodiment of the invention.

FIG. 3 represents a top view of a piston according to the embodiment of the invention.

FIG. 4 represents a section along A-A of the upper part of a half-piston according to the embodiment of the invention.

FIG. 5 represents a perspective view of a piston according to a variant of the embodiment of the invention.

FIG. 1 represents a piston 1 having a hunting zone 13, substantially planar and annular, perpendicular to the direction along the axis Z of translation of the piston 1. This hunting zone 13 comprises a plurality of holes corresponding to the first ends 10 'of channels 10 (not shown in this figure). Channels 10 have second 10 ”ends opening into the combustion chamber

11. The double arrows illustrate the gas flows generated by the arrangement of the channels 10 in the piston 1.

The directions along the X and Y axes, axes by convention perpendicular to each other, are by convention also perpendicular to the direction along the Z axis, direction in which the piston 1 translates.

FIG. 2 illustrates a phase of combustion of the piston 1 sliding in a cylinder 2 closed by a cylinder head 3.

Before combustion, jets 15 of fuel are injected into the combustion chamber 11.

The combustion of the fuel, in addition to providing translation energy to the piston 1, generates a soot pocket 16 extending substantially around an XY plane, in the space between the hunting zone 13 and the cylinder head 3 .

Gas flows are generated in the channels 10 due to the pressure difference between the peripheral wall 14 of the combustion chamber 11 and the flushing zone 13. In fact, by guiding this pressure in the channels 10, the gases relax and accelerate before entering the flushing zone 13. The gas flows leaving the first ends 10 ′ are generated substantially parallel to the direction along the axis Z, that is to say perpendicular to the direction of advance of the soot bag 16. The plurality of channels 10 creates an aerodynamic curtain which blocks the progression towards the jacket of the cylinder 2, soot 16 coming from the combustion chamber 11. The soot 16 and more generally the residual particles of combustion, in particular the carbonaceous materials, are stopped before reaching between the piston 1 and the jacket of the cylinder 2. They therefore do not reach close to the segments 4 and do not mix with the oil m host.

Once the combustion phase has ended, the vacuum generated by the descent of the piston 1 at the hunting zone 13 maintains the gas flow in the channels 10. The aerodynamic curtain is maintained which prevents the propagation of residual particles towards the cylinder liner 2 during descent of piston 1.

FIG. 3 shows an example of the location of the first ends 10 ’on the flush zone 13 of a piston 1, as well as their respective channels 10 represented by transparency. The channels 10 open almost tangentially into the peripheral wall 14. The first ends 10 ′ are distributed regularly and substantially centered between the reentrant lip and the outer circumference of the upper surface of the piston 1.

FIG. 4 illustrates in more detail the shape of the upper part of the piston 1 according to the invention, in particular the geometrical specificities of the channel 10. The first end 10 ′ of the channel 10 is located on the flush zone 13, zone comprising the half upper part of the reentrant lip and extending radially to the outer circumference of the upper surface of the piston 1 (shown in phantom). The axis of the first end 10 ′ is substantially perpendicular to the hunting zone 13. This means that the axis of the channel 10, at its point of intersection with the hunting zone 13, has a maximum angle β of 20 degrees with a straight line perpendicular to the hunting area 13. In FIG. 4, a possible inclination in the XZ plane has been shown, a similar inclination being possible in the YZ plane.

The channel 10 opens into the peripheral wall 14 of the combustion chamber 11, the peripheral wall 14 (shown in thick solid line) going from the lower half of the reentrant lip to the convex part of the bottom of the bowl 12. Depending on the desired effect on the gas flows, the axis of the second 10 ”end takes different orientations. The angle of incidence a, that is to say the orientation of the axis of the second end 10 ”relative to the perpendicular of the peripheral wall 14 can vary from the perpendicularity to the tangency (by tangency, we mean that the axis of the second end 10 ”and said perpendicular are collinear).

The channel 10 is cylindrical, helical or any other section suitable for obtaining a channel 10 in a process for manufacturing a piston 1.

FIG. 5 represents a variant in which the piston 1 comprises as many channels 10 as jets 15 coming from an injector. The gas flows represented by double arrows emerge from the first ends 10 ′ on the hunting zone 13 limiting or even stopping the progression of smoke and soot 16 by initiating two vortex-type rotation zones on each side of the jets 15, c that is to say two circular movements in opposite directions with respect to each other on the two sides of the jets 15.

When the piston 1 rises, during the compression phase, these channels 10 make it possible to extract the overpressure of air located in the hunting zone 13, thus limiting the recirculation of gases from the combustion chamber to the casing d engine oil by means of segment games (better known as the ango-saxon blow-by) at top dead center, which very significantly reduces the low-pressure part of the indicated average pressure prevailing in the cylinder during an engine cycle (better known by the expression “negative loop” and by the acronym PMI BP) and consequently improves engine efficiency. The air thus extracted from the hunting zone 13 is accelerated by passing through the channels 10 before exiting through the second ends 10 ”through the peripheral wall 14 of the combustion chamber 11, in a quasi-tangential manner, thus amplifying the swirl movement, commonly known as a swirl, already established in bowl 12.

In summary, the invention makes it possible to repel the residual particles from combustion towards their emission zones. This modification is characterized by a transport of the residual particles in the direction of the central axis of translation of the piston 1, direction opposite to the jacket of the cylinder 2. The residual particles do not reach the jacket of the cylinder 2 and even less between the piston 1 and the cylinder liner 2. This results in elimination of the transfer of residual particles to the engine oil.

As a note, the solution according to the invention therefore achieves the desired object of reducing the degradation of engine oil and has the following advantages:

- It also makes it possible to amplify the swirl movement in the bowl 12 during the compression phase. The advantage of generating swirl only by internal aerodynamics, is that one can do without the helical intake channel and the swirl flap, which generate large pressure losses upstream of the intake valve. In general, the reduction in pressure losses improves the specific consumption of the engine.

- It limits blow by, reduces PMI BP and improves engine efficiency.

- The entirety of the other parts of the piston 1, in particular the combustion chamber 11, its peripheral wall 14, the flushing zone 13, the grooves intended for the segments 4 can remain unchanged.

- The cylinder head may remain unchanged.

- It is thus compatible with existing solutions.

The invention is particularly well suited to an internal combustion engine with a diesel cycle, which experiences a problem of generation of carbonaceous material, resulting from combustion, in engine oil. Finally, it also relates to a motor vehicle as such incorporating such a piston, in particular light vehicles and industrial vehicles such as heavy goods vehicles.

Claims (11)

Claims: 1. Piston (1) intended to slide in a cylinder (2) of an internal combustion engine with direct injection characterized in that it comprises: - a combustion chamber (11), - a substantially flat hunting area (13), - A channel (10) connecting the combustion chamber (11) to the hunting zone (13), this channel (10) being oriented substantially perpendicular to the hunting zone (13) at its first end (10 ') leading to the hunting area (13). 2. Piston (1) according to claim 1, characterized in that the channel (10) opens into a peripheral wall (14) of the combustion chamber (11). 3. Piston (1) according to claim 2, characterized in that the orientation of the axis of the second end (10 ”) of the channel (10) at the combustion chamber (11) varies from tangency to perpendicular to the peripheral wall (14) of the combustion chamber (11). 4. Piston (1) according to one of the preceding claims, characterized in that the axis of the first end (10 ') of the channel (10) has an inclination less than or equal to 20 degrees relative to the direction perpendicular to the hunting area (13). 5. Piston (1) according to one of the preceding claims, characterized in that the channel (10) is of cylindrical or helical shape. 6. Piston (1) according to one of the preceding claims, characterized in that it comprises as many channels (10) as jets (15) coming from direct injection. 5 7. Piston (1) according to one of the preceding claims, characterized in that the hunting zone (13) is substantially annular. 8. Piston (1) according to one of the preceding claims, characterized in that the combustion chamber (11) has the shape of a bowl (12). 9. Internal combustion engine characterized in that it comprises a piston (1) according to one of the preceding claims. 10. Motor vehicle characterized in that it comprises a motor with 15 internal combustion according to claim 9. 1/5