DE10260938A1 - Compression ignition internal combustion engine - Google Patents

Abstract

The internal combustion engine with compression ignition has a combustion chamber 1 which is delimited on the one hand by the surface of a piston 3, which is arranged in a cylinder block, and on the other hand by the lower wall of a roof-shaped cylinder head 4, which has two separate inlet openings on a surface of the roof 13 7, 8 and has two separate outlet openings 11, 12 on the surface of the roof opposite the inlet openings; the cylinder head is provided with a recess 18, which opens into the lower wall of the cylinder head 4, and with an injection nozzle 16 for the fuel, which is arranged parallel to the axis of the cylinder 2 and opens into the upper part of the recess 18; a glow plug 17 opens laterally in the recess 18; the surface of the piston 3 is provided with a recess 30 which is arranged substantially below the recess 18; the recess 30 is surrounded by two protruding bumps 33 which are arranged symmetrically to the transverse plane of the cylinder.

Description

The present invention relates to an internal combustion engine Compression ignition, for example a diesel engine, and with Direct injection, mainly for motor vehicles. In particular, the present invention relates to shape the combustion chamber of the engine and especially the top of the piston.

French patent application No. 01-12306 (processing a conical chamber) describes a diesel engine several cylinders and with direct injection, in which the Injectors for the fuel essentially in the Axes of the cylinders are arranged and one is conical Chamber is formed in the cylinder head.

The central arrangement of the fuel injectors in the roof-shaped cylinder head has the advantage that Limit wetting of the walls (in the case where the Fuel early during the compression stroke Delay is injected during the expansion stroke), that is, the deposition of fuel droplets on the walls of the cylinder, causing a significant reduction in the Emission of pollutants such as HC and NOX as well as soot particles is achieved.

Through this publication it is known to be a glow plug insert (either in the side of the recess and in close to the injector or in the cylinder between two Valves opens).

The known flat pistons which are provided with a recess (for example, the shape of a bowl with a circumferential Have edge) together with an associated plane Cylinder heads have the disadvantage that they are not in optimally the two main requirements the operation of a diesel engine with direct injection fulfill, namely the shift operation and the homogeneous Business. As usual, the geometry of the Piston in terms of shift operation and local Concentration of fuel selected so the deteriorates Mode of operation with homogeneous operation and, conversely, the Geometry of the pistons and the cylinder head with regard to chose a homogeneous company, the deteriorates Mode of operation in shift operation.

The object of the present invention is a Internal combustion engine in the form of a diesel engine Direct fuel injection to create the top overcomes the disadvantages listed above, in particular because of the Design of a roof-shaped or conical Piston associated with the cylinder head, so that both a Shift operation as well as homogeneous operation is made possible.

To achieve this object, the invention proposes one Internal combustion engine in the form of a diesel engine, the one Combustion chamber which, on the one hand, by the Top of a piston that is confined in one Cylinder block is arranged and the other through the lower Wall of a roof-shaped cylinder head on one of the two roof openings on both roof surfaces and on the opposite side of the inlet openings Roof surface two separate outlet openings having; the engine is characterized in that the Cylinder head also with one in the bottom wall of the Cylinder head opening recess is provided, one Injector for the fuel parallel to the axis of the Cylinder is arranged and opens into the upper part of the recess and that the piston on its top with a recess is provided, which is essentially below the recess is arranged and that of two protruding humps is surrounded, which is symmetrical with respect to the transverse plane of the Cylinders are arranged.

According to another feature of the diesel engine according to the Invention, the recess consists of a main cavity, the is bounded by a floor that extends towards Front part of the injector extends as well as through a Sidewall, with a variety of secondary cavities in the lower section of the first cavity open.

According to another feature of the diesel engine according to the Invention extends the main cavity substantially along the axis of the cylinder.

According to another feature of the diesel engine according to the Invention, the main cavity essentially has one circular or elliptical cross-section.

According to another feature of the diesel engine according to the Invention, the secondary cavities extend on both sides of the Main cavity between the inlet and / or Outlet ports.

According to another feature of the diesel engine according to the Invention are the two on top of the piston and this hump surrounding both sides of the depression in one Angular sector between 90 ° and 130 ° arranged.

According to another feature of the diesel engine according to the Invention are those on the surface of the piston on both sides of the recess arranged bumps with ends that are located below the inlet and outlet openings, being designed to form areas that direct the flow towards the center of the depression.

According to another feature of the diesel engine according to the Invention, the top of the piston is provided with surfaces which are designed as inclined planes and which are extend on both sides of the depression between the humps, these surfaces being those created by the ends of the bumps Direct the flow towards the center of the depression.

According to another feature of the diesel engine according to the Invention is the glow plug above the inlet lines or the outlet lines with a predetermined inclination with respect the axis of the cylinder.

The aims, aspects and advantages of the invention are clearer from the following description of a non-limiting Embodiment of the invention in connection with the attached drawing; show in it:

Fig. 1 shows schematically a plan view of the clip combustion of a diesel engine according to the invention,

Fig. 2 is a sectional view taken along the line II-II of Fig. 1 and

Fig. 3 is a plan view of the piston shown in Fig. 2.

The one shown in the figures and described below Embodiment of the invention relates to a four-stroke Diesel engine with several cylinders, as well as with direct Fuel injection and with four valves per Cylinder.

The most important part of this internal combustion engine is the cylinder head, which is arranged above a cylinder block 24 . In this cylinder block 24 , a plurality of cylindrical bores, the cylinders, are provided which are identical to the cylinder denoted by 2 in FIG. 2. A piston 3 is arranged in each cylinder, the reciprocating movement of which is converted into a rotary movement via a connecting rod arrangement (not shown) and a crankshaft.

A combustion chamber 1 is formed in the upper section of the cylinder 2 and is delimited by the upper side of the piston 3 , a lower wall 13 in the cylinder head 4 and the walls of the cylinder 2 . The underside of the cylinder head has essentially the shape of a roof with two roof surfaces, the ridge 14 of which extends essentially parallel to the longitudinal axis of the cylinder head.

From Fig. 1 it is apparent that the cylinder head 4 is in the transverse direction for each combustion chamber 1 of two inlet lines 5, 6 through which the gases to be burned and two outlet conduits 9, 10 for the burnt gases. The inlet and outlet lines are formed on both sides of the combustion chamber and the longitudinal center plane of the cylinder head and are connected to the combustion chamber via inlet openings 7 , 8 and outlet openings 11 , 12 , which can be closed by means of controllable shaft valves.

The two inlet openings 7 , 8 are formed in the lower wall 13 of the cylinder head 4 on the same side with respect to the roof ridge 14 , while the outlet openings 11 , 12 in the lower wall 13 of the cylinder head 4 on the side opposite the inlet openings in the lower wall 13 are trained.

The one from the intake valves with the exhaust valves included angle is essentially the same of the roof.

The design of the inlet openings is selected such that they take up the largest possible inlet area in the roof 13 to limit the wall effect, the two inlet lines 5 and 6 being arranged essentially parallel to one another in the cylinder head 4 and also being dimensioned such that the filling of the combustion chamber 1 is made easier with combustion air.

According to the invention, the lower wall 13 of the cylinder head 4 is provided with a recess 18 which extends essentially parallel to the axis of the cylinder 2 . An injection nozzle 16 for the fuel and a glow plug 17 open into this recess 18 . The injection nozzle 16 is provided in a conventional manner with an unillustrated supply line for fuel under pressure. The amount of fuel injected either prematurely during the compression stroke or with a delay during the power stroke is calculated by the electronic engine control, also not shown, which determines the time of injection and the duration of opening of injector 16 in accordance with the operating conditions of the engine, in particular the load and the engine Speed, calculated.

The recess 18 consists of a main cavity 22 , which preferably extends essentially along the axis of the cylinder 2 . If it is necessary for reasons of installation, the axis of the recess 18 can also deviate from the axis of the cylinder 2 by a few millimeters. This cavity is delimited at its upper section by a wall 20 , in which the tip of the injection nozzle 16 opens, and by a side wall 19 , which essentially has the shape of a truncated cone in which the glow plug 17 opens. The lower opening of this cavity can be extended by secondary cavities 21 in the direction of the four bridge areas between the valves.

These secondary cavities 21 serve primarily to increase the volume of the recess 18 , but not the depth of the main cavity 22 . This makes it possible to define an enclosure volume of a suitable size without affecting the compact dimensions of the cylinder head or the area of the flow area.

It should be emphasized that the number of secondary cavities can be freely selected, for example three secondary cavities can be provided, one of which extends in the direction of the bridge region connecting the inlet valves and the other two extend parallel to the ridge 14 on both sides of the main cavity 22 . Likewise, the shape and dimensions of these secondary cavities can be freely selected as a function of the available installation space and the desired volume.

The configurations of the various secondary cavities 21 which surround the main cavity 22 depend on its shape. The main cavity may have a circular cross-section (in the case in which the injection openings are arranged and aligned according to a cone) or else an elliptical cross-section, as shown in the figure, wherein the major axis of the ellipse can run parallel to the ridge 14 or perpendicular to it and in this case the exit of the rays and the angle enclosed by them can be designed in such a way that the entire space is used. The bulge formed by the side wall 19 can also be reduced to the minimum determined by the technique of casting or machining in order to obtain an essentially cylindrical shape.

The fuel injector passes through the cylinder head 4 parallel to the axis of the cylinder such that the outlet tip is substantially perpendicular to the wall 20 of the recess 18 .

According to some variants of the invention, the outlet tip may also protrude or be retracted laterally into the wall 20 . The dimensions of the recess and those of the jet cone of the injected fuel are matched to one another in order to avoid any direct wetting of the side wall 19 by the fuel jets, regardless of the operating conditions of the engine. The glow plug 17 , which passes through the wall 19 laterally, is inserted into the cylinder head 4, for example, along its axial plane, either above the inlet lines 5 , 6 , as shown in the figure, or above the outlet lines 9 , 10 .

The arrangement of the glow plug 17 is suitable for facilitating a cold start. It is located at a predetermined distance h from the injection nozzle 16 such that it is struck by one of the jets emerging from the nozzle. The depth H of the recess 18 is chosen such that the distance h mentioned is substantially less than two thirds of H (h << 2/3) .H. Above all, however, the glow plug 17 is arranged above the secondary cavities 21 . This arrangement of the glow plug in the upper region of the recess 18 in the immediate vicinity of the outlet tip of the nozzle 16 enables better cold start behavior and better combustion in the phases of warming up after starting.

This is because the aerodynamic movements remain limited inside the volume determined by the recess 18 , in particular in the upper region of the recess 18 . This makes it possible to precisely control the stratification of the fuel mixture.

It is also possible, during high load operation, to bring about a first phase of limited combustion in the recess 18 , which takes place very quickly in the vicinity of an isochoric transformation, since when the flame front leaves the recess 18 to pass into the cylinder, a second one Isobaric transformation phase occurs. Such a process leads to an improved thermodynamic efficiency of the combustion at the same maximum temperature of the cycle and at the same time a reduction in the emission of nitrogen oxides and soot particles.

It should be emphasized that the secondary cavities distributed along the circumference of the main cavity 22 have the additional advantage of channeling the spreading gases. These gases are thereby guided to the exit of the main cavity 22 and thus lead to a rapid spread of the flame front into the entire combustion chamber 1 .

According to the invention, the piston 3 and in particular its surface is optimized with regard to the remaining combustion chamber and in particular its recess 18 , so that the engine can run both in homogeneous operation and in shift operation.

For this purpose, the surface of the piston 3 is provided with a concave depression 30 in the form of a ball impression. This recess 30 , which is produced by a casting process or machining, is arranged essentially in the middle of the piston below the recess 18 . The circular opening of this recess 30 has a diameter which is either smaller than half the diameter of the piston or, preferably, equal to this half. The depression 30 is surrounded by two protruding bumps 33 . The two bumps 33 are arranged on both sides of the depression 30 along the longitudinal axis of the cylinder head 4 and are symmetrical to the vertical transverse plane of the cylinder.

The bumps are also included on the circumference of the depression 30 in an angular sector, which is preferably between 90 ° and 130 °. Their shape is complementary to that of the lower wall 13 of the cylinder head 4 , whereby the remaining volume of the combustion chamber 1 when the piston is at top dead center is limited with a view to achieving a corresponding degree of compression of the gases.

The side walls of the bumps 33 opposite the depression 30 are designed such that they extend the spherical shape; the ends 32 of the bumps 33 lie below the inlet openings 7 , 8 and the outlet openings 11 , 12 and are designed in such a way that they form regions which favor the flow towards the center of the depression. In addition, the surface of the piston 3 has inclined surfaces 31 that extend between the bumps 33 on both sides of the depression 30 . The inclination of the surfaces 31 is smaller than that of the ends 32 and is selected such that it channels the flow directed from the ends 32 towards the depression 30 . In addition, the surfaces 31 , the upper edges of which delimit the opening of the depression 30 , contribute to an increase in their volume without increasing the dimensions of the piston and in particular the thickness of its head part.

Thus, the upper side of the piston 3 , when it is at the top dead center, enables a combustion chamber 1 to be maintained , which is formed by the recess 18 and by the recess 30 , which approximates a spherical shape and in which the combustion is approximately in the middle begins.

The design of the piston 3 and that of the recess 18 in the cylinder head 4 are particularly favorable to enable efficient types of shift operation and homogeneous operation of the engine with a view to increasing its efficiency and reducing emissions of pollutants such as nitrogen oxides and soot particles. The selected design advantageously influences both the internal aerodynamics and the formation and spread of the combustion. With regard to the internal aerodynamics, it should be said that the gases flowing into the combustion chamber are directed towards the center of the depression 30 , so that they maintain the energy inherent in them during the compression stroke up to the top dead center, which is increased by the compression stroke until the end of the compression stroke Flow formation towards the center of the quasi-spherical combustion chamber.

This improved internal aerodynamics enables higher combustion speeds and thus optimal thermodynamic efficiency due to the onset of combustion and its expansion. In stratified operation, the fuel injected with deceleration is concentrated in the recess 18 , a part entering the recess 30 ; this limits its dispersion in the remaining cylinder. In homogeneous operation, the fuel is injected prematurely, after which the mixture fills a reduced volume which approximates a spherical shape, with the advantage that an essentially homogeneous combustion is obtained. The combustion progresses evenly in the chamber, reaching the walls relatively late during the cycle and at about the same time. This in turn leads to lower thermal loads while maintaining a longer lasting higher combustion speed during the cycle.

It should be emphasized that the invention is in no way based on the illustrated and described embodiments is limited, which serve only for explanation, but in On the contrary, all technical equivalents of the parts described includes, and their combinations, insofar as they are part of the Invention lie.

Claims (10)

1. Combustion engine with compression ignition, which has a combustion chamber ( 1 ), which is delimited on the one hand by the top of a piston ( 3 ) which is arranged in a cylinder block and on the other hand by the lower wall of a roof-shaped cylinder head ( 4 ), which on one of the has two separate inlet openings ( 7 , 8 ) on both surfaces of the roof ( 13 ) and has two separate outlet openings ( 11 , 12 ) on the surface opposite the inlet openings, characterized in that the cylinder head is also connected to one in the lower wall of the Cylinder head ( 4 ) opening recess ( 18 ) is provided, wherein an injection nozzle ( 16 ) for the fuel is arranged parallel to the axis of the cylinder ( 2 ) and opens into the upper part of the recess ( 18 ) and wherein a glow plug ( 17 ) laterally in the Recess ( 18 ) opens and that the piston ( 3 ) is provided on its top with a recess ( 30 ) which is arranged substantially below the recess ( 18 ), the recess ( 30 ) being surrounded by two protruding bumps ( 33 ) which are arranged symmetrically with respect to the transverse plane of the cylinder. 2. Internal combustion engine according to claim 1, characterized in that the recess ( 18 ) from a main cavity ( 22 ) from the wall ( 20 ) in which the tip of the injection nozzle ( 16 ) opens and a side wall ( 19 ) is delimited and consists of at least one secondary cavity ( 21 ) which opens into the lower section of the main cavity ( 22 ). 3. Internal combustion engine according to claim 2, characterized in that the main cavity ( 22 ) extends substantially along the axis of the cylinder ( 2 ). 4. Internal combustion engine according to one of claims 2 or 3, characterized in that the main cavity ( 22 ) has a substantially circular or elliptical cross section. 5. Internal combustion engine according to one of claims 2 to 4, characterized in that the secondary cavities ( 21 ) extend on both sides of the main cavity ( 22 ) between the inlet openings ( 7 , 8 ) and / or the outlet openings ( 11 , 12 ). 6. Internal combustion engine according to one of claims 1 to 5, characterized in that on the upper side of the piston ( 3 ) on both sides around the recess ( 30 ) formed bumps ( 33 ) are arranged in an angular sector between 90 ° and 130 °. 7. Internal combustion engine according to one of claims 1 to 6, characterized in that the on the top of the piston ( 3 ) on both sides of the recess ( 30 ) formed bumps ( 33 ) are provided with ends which extend below the inlet and outlet openings and which are designed in such a way that they form regions which direct the flow towards the center of the depression ( 30 ). 8. Internal combustion engine according to claim 7, characterized in that the top of the piston ( 3 ) has flat inclined surfaces ( 31 ) which extend on both sides of the recess ( 30 ) and between the bumps ( 33 ) and which through the ends ( 32 ) the hump ( 33 ) direct the generated flow towards the center of the depression ( 30 ). 9. Internal combustion engine according to one of claims 1 to 8, characterized in that the glow plug ( 17 ) is arranged in the vicinity of a fuel jet emerging from the injection nozzle. 10. Internal combustion engine according to one of claims 1 to 8, characterized in that the glow plug ( 17 ) above the inlet lines ( 5 , 6 ) or the outlet lines ( 9 , 10 ) and inclined to the axis of the cylinder ( 2 ) is arranged.