JP2003027945A - Cylinder fuel injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a compression ratio in an internal combustion, engine in which a fuel injection valve 11 is installed at a part on the outside of an intake port 7 in a cylinder head 3 to inject fuel diagonally downward, and in which timing of fuel injection is set to be a point around an upper dead point in a suction stroke, and a point lower than the upper dead point in the suction stroke. SOLUTION: A swollen part 12 having an up gradient is provided at a close position to the fuel injection valve in a top surface of a piston 5, and a cavity is recessed at a part far from the fuel injection valve in the top surface of the piston. When the timing of fuel injection is around the upper dead point in the suction stroke, injected fuel is sprayed to the inclination surface of the swollen part. When the timing of fuel injection is lower than the upper dead point in the suction stroke, injected fuel reaches the cavity.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder fuel injection type internal combustion engine which directly injects and supplies fuel into a cylinder. 2. Description of the Related Art One type of in-cylinder fuel injection type internal combustion engine is provided with fuel injection into a cylinder head by, for example,
In the low rotation range, the process is performed near the top dead center in the intake stroke, while in the high rotation range, the process is performed near the top dead center in the intake stroke to form a homogeneous air-fuel mixture throughout the cylinder. Some are configured to burn. In this type of in-cylinder fuel injection type internal combustion engine, a cavity is formed in the top surface of a piston to inject fuel into the cavity, thereby promoting fuel vaporization. It is well-known that the fuel is prevented from adhering to the inner wall surface of the cylinder as much as possible. However, in general, a fuel injection valve in an in-cylinder fuel injection type internal combustion engine is provided with a fuel injection valve at a portion outside a suction port provided in a cylinder head for closing a top portion of a cylinder having a built-in piston. Since the fuel is mounted so as to inject fuel from obliquely downward, there are the following problems. That is, while the piston in the cylinder reciprocates, the angle of oblique downward injection of fuel at the fuel injector is always constant irrespective of the reciprocation of the piston. Accordingly, the position at which the fuel injected from the fuel injection valve reaches the top surface of the piston is determined from the fuel injection valve when the fuel injection supply is performed at a position lower than the top dead center in the intake stroke. When it is far away and near the top dead center in the intake stroke, it moves greatly depending on the fuel injection timing, such as being close to the fuel injection valve, so the cavity formed in the top surface of the piston is concave. At any one of the injection timings, the injection fuel must be considerably large so as to reliably enter the cavity. In other words, when the timing of fuel injection is set near the top dead center in the intake stroke and near below the top dead center in the intake stroke in accordance with the rotational speed or the like, the top surface of the piston Since the cavity formed in the recess must be considerably large in accordance with the two injection timings, the larger the cavity, the larger the clearance volume at the top dead center of the piston and the higher the compression ratio. There is a problem that can not be. In particular, this problem, that is, the inability to increase the compression ratio, was remarkable in a small-diameter bore having an inner diameter of a cylinder of about 70 mm or less. Further, reducing the depth of the cavity in order to increase the compression ratio increases the adhesion of the injected fuel to the inner wall surface of the cylinder. An object of the present invention is to solve this problem. [0010] In order to achieve this technical object, the present invention provides a fuel injection valve at a portion outside a suction port provided in a cylinder head for closing the top of a cylinder. The fuel injection valve is mounted so as to inject fuel obliquely downward, the fuel injection timing of the fuel injection valve near the top dead center in the intake stroke and near the top dead center in the intake stroke. In the in-cylinder fuel injection type internal combustion engine, the top surface of the piston reciprocating in the cylinder has a sloping surface having a slope inclined upward toward the center of the cylinder at a position close to the fuel injection valve. A portion is provided so as to protrude from the top surface of the piston, while a cavity is formed in a portion of the top surface of the piston far from the fuel injection valve, and the timing of the fuel injection is adjusted. When near the top dead center in the intake stroke, the injected fuel hits the inclined surface in the raised portion, and when the timing of the fuel injection is near the bottom dead center in the intake stroke, the injected fuel reaches the cavity. It has been configured. " In this configuration, when the fuel injection is performed near the top dead center in the intake stroke, the piston is located near the top dead center. By hitting the ascending slope in the raised portion protruding from the top surface of the piston and being guided obliquely upward along the inclined surface, it is possible to prevent the fuel from adhering to the inner wall surface of the cylinder, Fuel vaporization is promoted. On the other hand, when the fuel injection is performed at a time near a point lower than the top dead center in the intake stroke, the injected fuel enters the cavity formed in the top surface of the piston, and the fuel is injected into the cylinder. Can be prevented from adhering to the inner wall surface, and the vaporization of fuel is promoted. That is, according to the present invention, when the fuel injection timing is near the top dead center in the intake stroke, the injected fuel is blown against the inclined surface of the ridge protruding from the top surface of the piston, and the fuel injection timing It is configured such that it enters the cavity formed in the top surface of the piston only when it is lower than the top dead center during the stroke, whereby the cavity can be made smaller by the protrusion. Thus, the compression ratio can be surely improved under the condition that the vaporization of the injected fuel is promoted and the amount of the fuel attached to the inner wall surface of the cylinder is reduced as much as possible. Further, when the compression ratio is the same, the depth of the cavity can be made deeper to promote the effect of the cavity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. In this figure, reference numeral 1 denotes a cylinder block having a cylinder 2, and reference numeral 3 denotes a cylinder head fastened to the upper surface of the cylinder block 1 so as to cover the top of the cylinder 2. A combustion chamber 4 is recessed in the cylinder 2 of the lower surface of the cylinder 3, and the cylinder 2 has a small bore having an inner diameter of about 70 mm or less, and is interlocked with a crankshaft (not shown). A reciprocating piston 5 is incorporated. On one side of the cylinder head 3 across the axis 2a of the cylinder 2, two intake ports 7 each having an intake valve 6 at an opening into the combustion chamber 4 are provided. Two exhaust ports 9 each having an exhaust valve 8 are provided at an opening into the combustion chamber 4, and a portion between the two intake valves 6 and the two exhaust valves 8, An ignition plug 10 is mounted at a substantially central portion of the combustion chamber 4 so as to look into the combustion chamber 4. In this case, the two intake ports 7
Is configured to apply a tumble flow that turns vertically in the intake stroke in which the piston 5 moves downward, as shown by an alternate long and short dash line arrow A, to the intake air introduced into the cylinder 2 from the intake ports 7. ing. Reference numeral 11 denotes a fuel injection valve mounted on the cylinder head 3. The fuel injection valve 11 is formed in a plan view (FIG. 2) when viewed from the direction of the axis 2 a of the cylinder 2. 6, the fuel injection valve 11
The fuel injection valve 11 is mounted so that its tip 11a can be seen inside the combustion chamber 4 outside the intake valves 6, and the axis 11b of the fuel injection valve 11 is the same as the cylinder in plan view (FIG. 2). The cylinder 2 is mounted so as to be inclined outwardly with respect to the axis 2a of the cylinder 2 when viewed from the side (FIG. 1). Further, the fuel injection valve 11 deflects fuel from an injection hole (not shown) at the tip 11a thereof at an opening angle θ with respect to the axis 2a of the cylinder 2 as shown by an arrow B. It is configured to inject downward. The fuel injection by the fuel injection valve 11 is performed, for example, in a low rotation range.
In the intake stroke that moves downward from top dead center to bottom dead center, near the top dead center, in the high rotation range, the intake stroke near the bottom dead center, such as near bottom dead center, etc. In other words, the timing of the fuel injection in the fuel injection valve 11 is set near the top dead center in the intake stroke and near the top dead center in the intake stroke. In this case, the fuel injection timing may be set near the top dead center in the intake stroke, near the middle between the top dead center and the bottom dead center, and near the bottom dead center in the intake stroke. . The top surface 5a of the piston 5
Of the cylinder 2
Is provided so as to protrude upward from the top surface 5a of the piston 5 while a raised portion 12 having an inclined surface 12a having a relatively gentle upward slope θ1 is provided toward the center of the piston 5. A cavity 13 having a depth H is appropriately formed in a portion far from the fuel injection valve 11,
A space between the bottom surface of the cavity 13 and the apex of the raised portion 12 is formed as an arc surface 14 or an inclined surface having a gentle downward slope toward the cavity 13. In this configuration, when the fuel injection by the fuel injection valve 11 is performed near the top dead center in the intake stroke, the piston 5 is located near the top dead center as shown by the solid line in FIG. The fuel injected as shown by the arrow B hits a slope 12a of a rising slope in the raised portion 12 protruding from the top surface 5a of the piston 5,
By being guided obliquely upward as shown by the arrow C along the inclined surface 12a, the fuel can be prevented from adhering to the inner wall surface of the cylinder 2, and the vaporization of the fuel is promoted. On the other hand, when the fuel injection by the fuel injection valve 11 is performed at a time lower than the top dead center in the intake stroke, the piston 5 is moved to a position lower than the top dead center as shown by a two-dot chain line in FIG. The fuel injected as shown by the arrow B is located on the top surface 5 of the piston 5.
a into the cavity 13 formed in the recess
This prevents the fuel from adhering to the inner wall surface of the cylinder 2 and promotes the vaporization of the fuel. Further, the space between the bottom surface of the cavity 13 and the apex of the raised portion 12 is formed as an arc surface 14 or an inclined surface having a gentle downward slope toward the cavity 13 so that an arrow in the cylinder 2 is formed. The tumble flow indicated by A can be prevented from being reduced at the raised portion 12.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional front view of an essential part showing an embodiment of the present invention. FIG. 2 is a sectional view taken along the line II-II of FIG. [Description of Signs] 1 Cylinder block 2 Cylinder 3 Cylinder head 4 Combustion chamber 5 Piston 5a Piston top surface 6 Intake valve 7 Intake port 8 Exhaust valve 9 Exhaust port 10 Ignition plug 11 Fuel injection valve 12 Raised portion 12a Inclined surface 13 Cavity

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[Procedure amendment] [Date of submission] July 12, 2001 (2001.7.1)
2) [Procedure amendment 1] [Document name to be amended] Drawing [Item name to be amended] Fig. 1 [Correction method] Change [Content of amendment] [Fig. 1]

Claims (1)

Claims: 1. A fuel injection valve is provided in a portion of a cylinder head closing a top portion of a cylinder outside an intake port provided in the cylinder head, and fuel is injected obliquely downward from the fuel injection valve. In a cylinder fuel injection type internal combustion engine, the fuel injection timing of this fuel injection valve is set near the top dead center in the intake stroke and near the top dead center in the intake stroke. On the top surface of the piston that reciprocates in the cylinder, a protruding portion having an inclined surface with an ascending gradient toward the center of the cylinder is provided at a portion near the fuel injection valve so as to protrude from the top surface of the piston. A cavity is formed in a part of the top surface of the piston far from the fuel injection valve, and when the timing of the fuel injection is near a top dead center in an intake stroke, the injected fuel is An in-cylinder fuel injection type internal combustion engine, wherein the injected fuel reaches the cavity when the fuel injection timing is near the bottom dead center in the intake stroke when the fuel injection strikes the inclined surface at the starting portion. .