JP2014020278A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine for satisfactorily executing pre-injection while securing the maximum fuel injection quantity, and consequently, effectively reducing combustion noise while suppressing combustion deterioration in a direct injection type internal combustion engine with a common rail type fuel injection device even with a comparatively simple and low-cost structure.SOLUTION: An internal combustion engine 100 directly injects and supplies fuel to a combustion chamber 150, comprises: a fuel injection nozzle 160 for main injection of a common rail type provided facing the combustion chamber 150 from the lower surface of a cylinder head 110; and a fuel injection nozzle 200 for pre-injection provided near the center of an inner peripheral wall of a piston combustion chamber 121 outside the fuel injection nozzle 160 for main injection. Fuel spray from the fuel injection nozzle 200 for pre-injection is diffused in a circumferential direction by swirl flow X, diffused near the center of the piston combustion chamber 121 by squish flow Y, and after that, is self-ignited.

Description

  The present invention relates to an internal combustion engine. In particular, the present invention relates to the structure of a combustion chamber of an internal combustion engine that supplies fuel directly to the combustion chamber.

Up to now, for example, in a direct injection type diesel engine (a diesel engine in which fuel is directly injected into a combustion chamber and burned), a so-called common rail type fuel injection device is provided relatively freely. Since the amount can be variably controlled, for example, 1 to ³ mm ³ / st (stroke) before the main injection of fuel injection is started by using one fuel injection nozzle provided for each cylinder. A very small amount of fuel is injected and supplied to the combustion chamber (so-called pre-injection) by opening and closing the valve for a very short time, and before the main injection starts, it self-ignites to a certain extent away from the fuel injection nozzle. By increasing the local temperature and shortening the ignition delay of the main injection, especially under low load conditions, to suppress rapid premixed combustion, thereby suppressing the rapid pressure rise in the combustion chamber Including controlling combustion noise, control taking advantage of the common rail fuel injection system have been conducted (see as an example of a diesel engine equipped with a so-called common rail fuel injection system, for example, a Patent Document 1).

JP 2009-275654 A

  Here, in the pre-injection as described above, a very small amount of fuel injection is injected and supplied, but since the fuel injection amount is only 1 to 4% of the maximum fuel injection amount, the small amount of fuel injection is reduced. Since it is very difficult to control accurately over a long period over the life cycle, the deterioration of combustion due to variations in the fuel injection amount in the pre-injection has been inevitable to some extent.

  In a direct injection type diesel engine, the premixed combustion ratio increases with the length of the ignition delay period, and the increase in the pressure in the combustion chamber after ignition suddenly increases and the combustion noise increases. In order to reduce the fuel consumption, pre-injection in which a small amount of fuel is injected into the combustion chamber prior to the main injection of fuel injection is essential.

  Note that if the fuel injection amount of the pre-injection is excessively increased, combustion in the main injection deteriorates and harmful components contained in the exhaust gas increase, so the fuel injection amount of the pre-injection reduces the combustion noise. It can be said that the smaller the better, the better.

  However, as the diesel engine has a high Pme (mean effective pressure), the required maximum fuel injection amount is increased, and it is difficult to control the minute fuel injection amount with high accuracy.

  That is, there is a situation that it is very difficult to control the minute fuel injection amount with little variation and high accuracy in the pre-injection due to the increase in the capacity of the fuel injection device accompanying the increase in the maximum fuel injection amount for increasing the Pme. .

  The present invention has been made in view of such circumstances, and in a direct injection internal combustion engine having an electronically controlled fuel injection device such as a common rail fuel injection device, while having a relatively simple and low-cost configuration. It is an object of the present invention to provide an internal combustion engine that can perform pre-injection well while ensuring a fuel injection amount, and can effectively reduce combustion noise while suppressing deterioration of combustion.

Therefore, the internal combustion engine according to the present invention is
An internal combustion engine comprising a combustion chamber surrounded by a piston top surface, a cylinder head lower surface, and an inner wall of a cylinder in which the piston is slidably accommodated, and directly injecting fuel into the combustion chamber,
A common rail fuel injection nozzle attached to the cylinder head and facing the combustion chamber from the bottom of the cylinder head;
A pre-injection fuel injection nozzle provided outside the main injection fuel injection nozzle and near the center of the inner peripheral wall of the piston combustion chamber inlet, facing the combustion chamber from the bottom surface of the cylinder head;
With
The fuel spray injected from the pre-injection fuel injection nozzle is diffused in the circumferential direction by the swirl swirl flow, and diffused toward the center of the piston combustion chamber by the squish flow, and then self-ignited.

  In the present invention, a fuel supply pump that supplies fuel to the pre-injection fuel injection nozzle is provided separately from a common rail fuel supply device that supplies fuel to the main injection fuel injection nozzle. can do.

  According to the present invention, in a direct injection internal combustion engine equipped with an electronically controlled fuel injection device such as a common rail fuel injection device, the pre-production is performed while ensuring the maximum fuel injection amount, while having a relatively simple and low-cost configuration. It is possible to provide an internal combustion engine that can perform injection well and can effectively reduce combustion noise while suppressing deterioration of combustion.

1 is a cross-sectional view in the vicinity of a top dead center of a piston of a combustion chamber of an internal combustion engine according to an embodiment of the present invention (a cross-sectional view cut along a plane substantially orthogonal to a crankshaft). It is the figure in the piston top dead center vicinity which looked at the combustion chamber of the internal combustion engine which concerns on embodiment same as the above from the cylinder head side. It is sectional drawing (sectional drawing cut | disconnected by the plane substantially orthogonal to a crankshaft) in the vicinity of 20-30 degrees (crank angle) before piston top dead center of the combustion chamber of the internal combustion engine which concerns on embodiment same as the above. It is a figure in 20-30 degree (crank angle) vicinity before piston top dead center which looked at the combustion chamber of the internal combustion engine which concerns on embodiment same as the above from the cylinder head side.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIGS. 1 and 2, an internal combustion engine 100 that is a direct injection diesel engine according to an embodiment of the present invention includes a lower surface of a cylinder head 110, a top surface (upper surface) of a piston 120, and a cylinder block. A cylinder liner is attached to the cylinder head 110 such that the tip of the fuel injection nozzle 160 faces a combustion chamber 150 defined by an inner peripheral wall surface (not shown) inserted into a cylinder liner (not shown). .

The fuel injection nozzle 160 is connected to a so-called common rail type (accumulation type) fuel injection device, and is configured to arbitrarily control the fuel injection amount, the fuel injection start timing, the fuel injection period, the fuel injection rate, and the like.
The fuel injection nozzle 160 is provided in the cylinder head 110 for each cylinder (cylinder, combustion chamber). As shown in FIG. 2, the tip of the fuel injection nozzle 160 is viewed from the reciprocating motion direction of the piston 120. It is arrange | positioned so that it may become a substantially center.

At the tip of the fuel injection nozzle 160 facing the combustion chamber 150, for example, about 5 to 10 nozzle holes are provided at predetermined intervals in the circumferential direction, and slightly downward (conical angle ( (Cone angle) is set to, for example, about 140 to 160 degrees) toward the piston combustion chamber (cavity) 121 provided in a concave shape on the top surface of the piston 120 according to the operating state (rotational speed, load, etc.) of the internal combustion engine 100 The fuel is injected and supplied at a predetermined timing with the injected fuel amount.
The fuel injection nozzle 160 is an injector for performing main injection.

  Here, in the internal combustion engine 100 according to the present embodiment, in addition to the fuel injection nozzle 160, a gasoline engine (direct injection gasoline engine) of a direct injection type (a fuel supply system that directly injects and supplies fuel into the combustion chamber). The injector (fuel injection nozzle) 200 used in the cylinder head 110 is attached to the cylinder head 110 for each cylinder so that the tip thereof faces the combustion chamber 150 as shown in FIGS. Yes.

  The injector 200 is a pre-injection fuel injection nozzle for performing pre-injection, and an injector having a general fuel pressure level of 10 MPa as an injector for a direct injection gasoline engine can be used.

  The fuel supply pump that supplies fuel to the injector 200 can be shared with a common rail fuel supply device that supplies fuel to the main injection fuel injection nozzle 160. A fuel supply pump for a direct-injection gasoline engine can be provided separately from (independently from) the common rail fuel supply device that supplies fuel.

  As shown in FIG. 2, the direction of fuel injection from the injector 200 is a direction slightly approaching the center of the combustion chamber from the inner peripheral wall of the inlet portion of the piston combustion chamber 121, and a swirl swirl flow in which the tip of the injector 200 is disposed. Fuel is injected along the swirl swirl flow X only in the downstream direction of the swirl swirl flow from a region where both X and squish flow Y are very strong.

  If the injection timing of the fuel from the injector 200 is too close to the piston top dead center (TDC), the high in-cylinder pressure (cylinder internal pressure, combustion chamber pressure) may hinder the diffusion of fuel spray in the circumferential direction. Since the squish flow Y that is desired to be used for the diffusion of the fuel spray is also weakened, as illustrated in FIGS. 3 and 4, it is somewhat early (20 to 30 ° CA BTDC) (crank angle 20 to 30 ° before top dead center). It is set to inject.

  Since only a small amount of fuel for pre-injection is injected from the injector 200, a small-capacity injector 200 used in a direct-injection gasoline engine or the like is adopted, and a nozzle injection hole is used so that fuel spray is atomized. It is set as the structure which narrowed down small.

  By narrowing down the nozzle nozzle hole, the fuel injection period becomes longer for the same fuel amount. However, as described above, fuel injection is performed in order to perform early injection at 20 to 30 ° (crank angle) before top dead center. There is no self-ignition inside.

  During the ignition delay period from the start of fuel injection of the injector 200 until the injected fuel self-ignites, the fuel spray injected from the injector 200 increases at the inlet of the piston combustion chamber 121 as shown in FIG. After being diffused in the circumferential direction by the swirled swirl flow X that has been accelerated and diffused slightly toward the center of the piston combustion chamber 121 by the squish flow Y, self-ignition is performed, so that the pre-injection (main injection of the fuel injection) An effect equivalent to that of injecting and supplying a small amount of fuel to the combustion chamber before starting can be expected.

  In the present embodiment, since it is important to diffuse the fuel spray from the injector 200 dedicated for pre-injection in the circumferential direction by the swirl swirl flow X, the shape of the intake port is such that the swirl swirl flow X is generated. It is assumed that it is formed or adjusted. Therefore, the internal combustion engine 100 according to the present embodiment is premised on an internal combustion engine capable of generating an intake swirl with a swirl ratio of about 1.5 to 2.0.

  Note that the injector 200 dedicated to pre-injection only needs to inject a small amount of fuel for pre-injection, and thus a small-capacity injector can be adopted, so that a small amount of fuel-fuel injection for pre-injection can be adopted. Quantity control can be maintained with high accuracy over a long period of time.

  In addition, since the fuel injection nozzle 160, which is an injector dedicated to main injection, does not perform pre-injection, pressure fluctuation (fuel pressure fluctuation) in the common rail (accumulation chamber) is suppressed, so that a high effective injection pressure from the beginning of main injection starts. And can contribute to shortening the fuel injection period and promoting atomization of the fuel spray.

  Moreover, since the fuel injection nozzle 160 dedicated to main injection does not perform pre-injection, pressure pulsation in the common rail (pressure accumulation chamber) is suppressed. Accordingly, variation in the injection amount of the fuel injection nozzle 160 (variation at each injection, variation among cylinders) can be suppressed, so that it is possible to improve combustion fluctuations and black smoke (soot) emission concentration. Can contribute.

  Furthermore, since the fuel injection nozzle 160 dedicated to main injection need not perform pre-injection, select the nozzle specifications corresponding to the increasing load (maximum fuel injection amount) and the accompanying increase in fuel injection pressure. Since this can be realized, the degree of freedom in design can be greatly improved.

  As described above, according to the present embodiment, in a direct injection internal combustion engine having an electronically controlled fuel injection device such as a common rail fuel injection device, the maximum fuel injection is achieved with a relatively simple and low-cost configuration. It is possible to provide an internal combustion engine that can perform pre-injection well while ensuring the amount, and can effectively reduce combustion noise while suppressing deterioration of combustion.

  In the present embodiment, the injector 200 dedicated to pre-injection is illustrated and described as a single injection hole, but the present invention is not limited to this and may be configured with a plurality of injection holes.

  In the present embodiment, the diesel engine has been described as an example. However, the present invention is not limited to this, and even a fuel other than light oil such as gasoline, natural gas, alcohol, biofuel, or the like is directly combusted. The present invention can be applied to any internal combustion engine that injects fuel into the chamber and is included in the technical scope of the present invention.

  The present invention is not limited to the embodiments of the invention described above, and various modifications can be made without departing from the gist of the present invention.

100 Internal combustion engine
110 Cylinder head 120 Piston 121 Piston combustion chamber (cavity)
150 Combustion chamber 160 Fuel injection nozzle (for main injection)
200 injector (fuel injection nozzle for pre-injection)

Claims (2)

An internal combustion engine comprising a combustion chamber surrounded by a piston top surface, a cylinder head lower surface, and an inner wall of a cylinder in which the piston is slidably accommodated, and directly injecting fuel into the combustion chamber,
A common rail fuel injection nozzle attached to the cylinder head and facing the combustion chamber from the bottom of the cylinder head;
A pre-injection fuel injection nozzle provided outside the main injection fuel injection nozzle and near the center of the inner peripheral wall of the piston combustion chamber inlet, facing the combustion chamber from the bottom surface of the cylinder head;
With
An internal combustion engine characterized in that fuel spray injected from a pre-injection fuel injection nozzle is diffused in the circumferential direction by a swirl swirl flow and diffused toward the center of a piston combustion chamber by a squish flow and then self-ignited.   2. A fuel supply pump that supplies fuel to the pre-injection fuel injection nozzle is provided separately from a common rail fuel supply device that supplies fuel to the main injection fuel injection nozzle. The internal combustion engine described in 1.