Patent Publication Number: US-2010108013-A1

Title: Gasoline Direct Injection Engine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2008-108980 filed on Nov. 4, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a gasoline direct injection engine, and more particularly to a gasoline direct injection engine having improved operability. 
     2. Description of Related Art 
     Technologies for a gasoline direct injection (GDI) engine have been studied in order to improve fuel consumption and performance of the engine. 
     The GDI engine technologies are methods in which fuel is directly injected into a combustion chamber rather than into an intake manifold. 
     Since the GDI engine concentrates air and fuel at the circumference of an ignition spark plug by directly injecting fuel into the combustion chamber so as to make a concentrated mixture, the engine is operable with a lean air/fuel ratio. 
     Therefore, cooling performance of a lateral cylinder wall is superior in comparison with a conventional intake port injection type, and thereby the fuel amount can be precisely controlled in order to enhance fuel consumption and the engine performance may be improved. 
     Various methods have been developed in order to smoothly operate the engine with a lean air/fuel ratio by mixing air and fuel homogeneously, and in order to concentrate air and fuel at a circumference of the ignition plug. 
     In an internal combustion engine, a vortex is generated about a vertical axis in a moving direction of a piston or about a horizontal axis in a moving direction of the piston, wherein the former is called tumble and the latter is called swirl. 
     Since the air/fuel ratio and the concentration thereof depend on the tumble and swirl, consideration of the tumble and swirl is required in order to improve the operation performance of a GDI engine. 
     The tumble and swirl generated by this structure depend on an angle formed between the intake manifold and the exhaust manifold in a vertical moving direction of the piston, and an angle formed between the intake/exhaust manifolds and a horizontal line. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide a gasoline direct injection engine having advantages of improving operability thereof. 
     In an aspect of the present invention, the internal combustion engine may include a piston reciprocally moving upwardly and downwardly in a cylinder, a combustion chamber defined between a piston head and the cylinder, an ignition plug disposed at the top of the combustion chamber, at least one intake manifold disposed at an upper wall of the combustion chamber so that the at least one intake manifold is not interfered with by the ignition plug, and guiding intake air into the combustion chamber, an intake port disposed at an end of the at least one intake manifold, an intake valve disposed at the intake port and configured to open and close the intake port, and an injector interposed between the intake port and another intake port below the intake ports and injecting fuel into the combustion chamber. 
     A valve angle defined as an angle between a longitudinal axis of the piston passing through a lower tip of the ignition plug and a longitudinal axis of the intake valve may be an acute angle, a tumble angle defined as an angle between the longitudinal axis of the intake valve and a longitudinal axis of the intake manifold may be an acute angle, and an incidence angle defined as an angle between the longitudinal axis of the intake manifold and a horizontal line perpendicular to the longitudinal axis of the piston may be an acute angle, wherein the valve angle is less than 30 degrees, wherein the tumble angle is less than 65 degrees, and wherein the incidence angle is less than 5 degrees. 
     An angle between the at least one intake manifold and the injector may be less than 15 degrees. 
     The piston may include a cavity formed on an upper surface thereof to be dented with a predetermined depth and an outer circumference of the input port is disposed overlapped with an outer circumference of the cavity, wherein a center of the cavity is shifted from a center of the piston toward the injector with a predetermined distance 
     Accordingly, if the gasoline direct injection engine according to an exemplary embodiment of the present invention is employed in a vehicle, operability of the GDI engine can be improved by designing it corresponding to the valve angle, tumble angle, and incidence angle. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view showing a gasoline direct injection engine according to an exemplary embodiment of the present invention. 
         FIG. 2  is a schematic view showing a main portion of a gasoline direct injection engine according to an exemplary embodiment of the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a top plan view showing a gasoline direct injection engine according to an exemplary embodiment of the present invention, and  FIG. 2  is a schematic view showing a main portion of a gasoline direct injection engine according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1  and  FIG. 2 , a gasoline direct injection engine according to an exemplary embodiment of the present invention includes a cylinder head  100  and a cylinder block  200 , and a plurality of cylinders (only one cylinder is shown in drawings for convenience of description) between the cylinder head  100  and the cylinder block  200 . 
     A piston  300  is inserted into each cylinder such that it is capable of linear reciprocation. 
     Two intake manifolds  110   a  and  110   b  and exhaust manifolds are disposed at the cylinder head  100 , and intake valves  111   a  and  111   b  and exhaust valves are mounted at intake ports  140   a  and  140   b  and exhaust ports of a combustion chamber C, respectively. 
     Further, an injector  130  is mounted between the intake port  110   a  and the intake port  110   b  so as point toward an inner center of the combustion chamber C, and an ignition plug  120  is mounted at a circumference of the injector  130  so as to ignite the fuel when receiving an electrical signal from an electronic control unit. 
     Referring to  FIG. 2 , intake valves  111   a  and  111   b  are respectively provided so as to be biased toward a vertical direction of the piston  300  at a predetermined angle (hereinafter called “valve angle”: V a , V b ). 
     In addition, a predetermined angle between the valves  111   a  and  111   b  and the intake manifolds  110   a  and  110   b  is called “tumble angle” T a , T b  hereinafter. 
     Further, an angle formed between the intake manifolds  110   a  and  110   b  and the direction perpendicular to the vertical direction of the piston  300  is called “incidence angle” I a , I b  hereinafter. 
     The valve angle Va, Vb is preferably less than 30 degrees, the tumble angle Ta, Tb is preferably less than 65 degrees, and the incidence angle  1   a,    1   b  is preferably over 5 degrees. 
     In this construction, interference caused by the intake valve  111   a ,  111   b  is minimized when intake air passes out of the intake manifolds  110   a ,  110   b  because of the structural design of the valve angle Va, Vb, the incidence angle  1   a,    1   b , and the tumble angle Ta, Tb. 
     Further, an optimum state is realized such that the fuel and air that are mixed homogeneously are close to a circumference of the ignition plug  120  by an angle of the fuel injected from the injector  130  since the injector  130  is mounted at a predetermined angle corresponding to the incidence angle  1   a ,  1   b.    
     Therefore, by designing as such, the tumble and swirl are generated more effectively. 
     Meanwhile, a cavity  320  may be formed at a piston head  310  defining a top end of the piston  300 . 
     That is, fuel injected from the injector  130  is concentrated at the center of the combustion chamber C by forming the center of the cavity  320  to be shifted toward the intake valves  111   a ,  111   b.    
     Further, the ignition plug  120  is mounted at the cylinder head  100  so as to be disposed at an end of the cavity  320  disposed at a side of the piston  300 . 
     The injector  130  is disposed between the intake manifolds  110   a  and  110   b  so as to directly inject fuel into the combustion chamber C, and is disposed at a predetermined biased angle with respect to the ignition plug  120 . 
     In this case, the slant angle of the injector  130  formed from a horizontal direction perpendicular to a longitudinal axis of the piston  300  is preferably similar to the incidence angle I a , I b , within a scope of 10 degrees. 
     As can be seen from the foregoing, the tumble and swirl generated between each of the components is promoted by minimizing interference with each other by designing the angle of the injector  130  according to the valve angle V a , V b , the tumble angle T a , T b , and the incidence angle I a , I b.    
     Therefore, operability of the GDI engine is improved, due to mixing air and fuel homogeneously, and igniting effectively. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper” and “lower” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.