JPH08338250A - Piston for inside-cylinder fuel injection engine - Google Patents

Abstract

PURPOSE: To provide a piston, by which a mechanical loss in an engine is reduced and improvement in output, fuel consumption, and the like is accomplished, for an inside-cylinder fuel injection engine. CONSTITUTION: In a piston 2 reciprocating inside a cylinder bore 3 toward which a fuel feeding port 13 is opened on a cylinder inside wall face 6, two compression rings 9b, 10b are provided, while between both rings 9b, 10b, an air vent groove 12 is formed over the whole circumference of the outer circumference part of the piston 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a piston of a cylinder fuel injection engine.

[0002]

2. Description of the Related Art In recent automobile engines, in order to achieve low fuel consumption and low pollution by achieving lean burn by stratified intake air, fuel for each cylinder is directly injected and supplied into each cylinder bore. In order to obtain a stable operation of the fuel injection nozzle and a good mixture formation, the fuel injection nozzle is usually arranged on the inner wall of the cylinder. As an example,
It is disclosed in Japanese Utility Model Publication No. 63-202767.

[0003]

However, in such a prior art example, since the tip of the fuel injection nozzle is disposed in the fuel supply port so as to be recessed from the inner wall surface of the cylinder, the piston in the cylinder bore may be moved up and down. When the first compression piston ring (hereinafter referred to as the compression ring) mounted on the piston approaches the upper end portion of the fuel supply port during the reciprocating motion between the points, the sliding surface of the compression ring and the fuel supply port A gap is generated between the recesses, and a gas pressure of approximately the same magnitude as the gas pressure applied to the upper surface of the piston acts on the recess through the gap. Therefore, the piston receives lateral pressure from the fuel supply port side and is pushed by the cylinder inner wall on the opposite side, increasing the sliding resistance of the piston, and as a result,
There is a problem that the mechanical loss of the engine increases, causing a reduction in output and deterioration of fuel efficiency.

[0004]

According to the present invention, a fuel injection nozzle faces an opening of a fuel supply port formed on an inner wall surface of a cylinder, and a fuel injection nozzle is provided between a first compression piston ring and a second compression piston ring. A ventilation groove is formed around the entire circumference of the piston.

[0005]

According to the above construction, since the ventilation groove is formed around the entire circumference of the piston between the two compression rings, the first compression ring mounted on the piston moves with the reciprocating motion of the piston. When approaching the upper end of the opening of the fuel supply port, a gap is created between the sliding surface of the compression ring and the recess of the fuel supply port, through which the outer periphery of the piston facing the opening of the fuel supply port is formed. A gas pressure of about the same size as the gas pressure applied to the upper surface of the piston acts in the space surrounded by the recess of the fuel supply port, but this gas pressure acts on the entire circumference of the piston through the ventilation groove, causing the piston to move to the cylinder bore. Work to hold in the center inside.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of the present invention. In the figure, reference numeral 1 indicates a cylinder block provided with a cylinder bore 3 in which a piston 2 reciprocates, and a cylinder head 4 having a combustion chamber 5 is attached to the upper surface of the cylinder block 1. Further, the cylinder block 1 is provided with a fuel supply port 13, and an opening 15 of this port 13 is opened in the cylinder inner wall surface 6 between the top dead center and the bottom dead center of the piston 2, and this port 13 is It is formed so as to supply the fuel from the fuel injection valve 17 into the cylinder bore 3 via the injection nozzle 16 loaded from the outside. The tip of the injection nozzle 16 loaded in the port 13 is arranged so as to recede inside the cylinder inner wall surface 6, and the recessed portion 14 of the port 13 is formed in the cylinder inner wall surface 6.

On the other hand, on the outer peripheral portion of the piston 2, a first compression ring 9b and a second compression ring 9b are arranged in this order from the upper surface of the piston 2 downward.
The piston ring grooves 9a, 10a, 11a into which the compression ring 10b and the oil ring 11b are respectively fitted are provided. Then, the ring groove 9a for the first compression ring 9b and the ring groove 10a for the second compression ring 10b.
In between, a ventilation groove 12 having a groove width of about half the distance between the ring grooves 9a and 10a is formed on the outer peripheral portion of the piston 2 over the entire circumference. The distance L between the first compression ring 9b and the second compression ring 10b fitted to the piston 2 is larger than the diameter D of the opening 15 of the port 13 in the piston movement direction. The piston 2 is integrally combined with the piston ring 8 fitted in these ring grooves 9a, 10a, 11a to form the cylinder bore 3
It is loaded inside.

With the above structure, the cylinder bore 3
The intake stroke, the compression stroke, the explosion stroke, and the exhaust stroke are repeated in this order with the reciprocating movement of the piston 2 inside the cylinder. Also, during this stroke, the piston 2 and the cylinder inner wall surface 6 In general, a piston clearance 7 is provided to prevent seizure on the cylinder inner wall surface 6 due to thermal expansion and deformation of the piston 2, and a space 18 in the cylinder bore 3 above the piston 2 and in the crankcase below. Airtightness between the compression rings 9b, 10
It is the same as before that b has the function of holding, but for example, in the case where the piston 2 descends in the cylinder bore 3 in the explosion stroke, the first compression ring 9b starts to engage with the upper end of the opening 15. At this time, a gap is generated between the compression ring 9b and the opening 15, and even if the pressure of the combustion gas acts on the recess 14 of the port 13 through this, the first and second compression rings 9b and 10b are not compressed. Since the interval L is formed to be larger than the diameter D of the opening 15 in the piston movement direction, the second compression ring 10b abuts the cylinder inner wall surface 6 without contacting the opening 15 at the same time as the first compression ring 9b. And the second compression ring 10b
The airtightness inside the cylinder bore 3 located higher can be maintained.

Further, since the piston clearance 7 is usually provided in a narrow gap (for example, 50 μm or less), it is not possible to transmit a sudden pressure change, so that the piston 2 in operation may have the recessed portion 14 therein. When passing through, the pressure change in the recess 14 is not transmitted in the direction of the piston clearance 7 on the outer peripheral portion of the piston 2 between the first compression ring 9b and the second compression ring 10b. Therefore, the gas pressure acting on the recessed portion 14 is only transmitted to the ventilation groove 12 communicating therewith, and the ventilation groove 1
A gas pressure of substantially the same magnitude acts on the entire circumference of the piston 2 from 2 to act to hold the piston 2 in the center of the cylinder bore 3.

In this embodiment, the case where the present invention is applied to the four-cycle engine has been described, but the present invention can also be applied to the two-cycle engine. Further, in the description of the embodiments, the width of the ventilation groove is set to about half the distance between both compression rings, but the invention is not limited to this, and any width and depth may be used as long as pressure can be transmitted quickly. Further, the fuel supply port is not limited to the one directly opening to the inner wall surface of the cylinder,
As shown in, the diameter of the fuel supply port may be narrowed in the vicinity of the opening and may be opened.

[0011]

According to the present invention, the following effects can be obtained. In the in-cylinder fuel injection engine having the recess of the fuel supply port on the inner wall surface of the cylinder, the ventilation groove is formed all around the outer circumference of the piston between the two compression rings. The same amount of gas pressure acts on the piston to act to hold the piston in the center of the cylinder bore, resulting in a reduction in piston sliding resistance and a reduction in engine mechanical loss.
This is effective in improving output and fuel efficiency. In particular, the effect is remarkable in an engine with a high cylinder pressure such as a rapid combustion engine aiming at low fuel consumption and low pollution.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention.

FIG. 2 is a side view of the piston according to the embodiment of the present invention.

FIG. 3 is a partially enlarged sectional view of the embodiment of the present invention.

[Explanation of symbols]

 2 Piston 6 Cylinder inner wall surface 9b First compression piston ring 10b Second compression piston ring 12 Ventilation groove 13 Fuel supply port 15 Opening 16 Injection nozzle

Claims (1)

[Claims] 1. A fuel injection nozzle facing an opening of a fuel supply port formed on an inner wall surface of a cylinder,
A piston for an in-cylinder fuel injection engine, characterized in that a ventilation groove is formed around the entire circumference of the piston between the first and second compression piston rings.