JP2006316730A - Cylinder direct injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct injection type internal combustion engine preventing adherence of fuel to a substantial portion of a piston top face and a cylinder inner peripheral wall, and having a piston with small compression height and sufficient strength. <P>SOLUTION: This direct injection type internal combustion engine is provided with the flat piston of which top face virtually has no cavity, a pair of first ribs positioned on the piston top face and extended from an outer peripheral part of the piston to an outer peripheral part in the opposite side via an approximately central part, and a pair of second ribs positioned between the pair of first ribs and bridging and connecting the pair of first ribs. Fuel is injected toward a piston top face partition partitioned by the first and second ribs on the piston top face, by a fuel injection valve. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a direct injection type internal combustion engine, and more particularly to a supercharged direct injection type internal combustion engine.

  Conventionally, the direct injection type internal combustion engine includes a piston having a cavity as described in Patent Document 1 or Patent Document 2.

  In Patent Document 1, a piston provided with a protruding portion having a contact surface on the inner surface of a cavity where a fuel injected from a fuel injection valve first reaches a portion where the injected fuel hits and spreads in the lateral direction. An in-cylinder direct injection internal combustion engine is disclosed. Thereby, the problem that the injected fuel adheres to the inner surface of the cavity and adversely affects combustion, leading to an increase in HC in the exhaust gas, is solved.

  Patent Document 2 discloses a direct injection type internal combustion engine that is excellent in ignitability and fuel efficiency performance due to fuel stratification. The internal combustion engine follows a forward tumble flow formed in the combustion chamber by intake air from the intake port on both sides in the cylinder row direction in the cavity formed on the top surface of the piston and corresponding to the spark plug. Is provided with a pair of ribs facing each other. As a result, the intake guide walls are constituted by the mutually opposing side surfaces of the ribs, and the forward tumble flow in the combustion chamber is guided and guided by these intake guide walls to suppress the rollover breakdown of the forward tumble flow, and from the fuel injection valve. The injected fuel is guided to the vicinity of the spark plug.

JP 2002-180838 A JP 2000-87750 A

  However, a piston having such a cavity inevitably increases the compression height (height from the center of the piston pin shaft to the piston top surface), resulting in an increase in the overall height of the internal combustion engine and an increase in piston weight. There were drawbacks. Furthermore, since the piston has a large combustion chamber surface area, heat transfer loss increases, and as a result, there is a drawback that fuel consumption is deteriorated. On the other hand, when the compression height is reduced, the thickness of the piston top surface is reduced, causing a problem in strength. In fact, with a flat piston with a reduced compression height, there is a problem that the top surface of the piston cracks during operation.

  Furthermore, in order to avoid an adverse effect on combustion due to fuel adhering to the inner surface of the cavity, Patent Document 1 employs a protrusion having a surface against which the injected fuel strikes, but the effect is incomplete. In any of the patent documents, there is no mention of an adverse effect caused by the fuel adhering to the inner peripheral wall of the cylinder. Incidentally, the fuel adhering to the inner peripheral wall of the cylinder is scraped off by the piston ring to dilute the oil stored in the oil pan, and at the worst, causes the oil-lubricated bearings to be burned.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a direct injection internal combustion engine including a piston having a small compression height and sufficient strength without causing fuel to adhere to a substantial portion of the piston top surface and a cylinder inner peripheral wall.

According to the invention of claim 1,
In a cylinder direct injection internal combustion engine comprising a fuel injection valve that directly injects fuel into a combustion chamber and a flat piston that has substantially no cavity on the top surface,
A pair of first ribs located on the top surface of the flat piston and extending from the outer peripheral portion of the piston to the outer peripheral portion on the opposite side via a substantially central portion;
A pair of second ribs that are located between the pair of first ribs and that bridge-couple the pair of first ribs;
In-cylinder direct injection internal combustion engine, wherein fuel injection is performed by the fuel injection valve toward a piston top surface section defined by the first rib and the second rib on the top surface of the piston. Is done.

  As described above, according to the internal combustion engine of the first aspect, since the flat piston having substantially no cavity is adopted on the top surface, a piston having a small compression height is used, and as a result, the total height of the internal combustion engine is increased. Decreases, and the piston weight decreases. Since the first rib and the second rib are disposed on the top surface of the piston, the rigidity of the piston top surface is increased and the thickness of the piston top surface can be reduced. Further, since fuel is injected toward the piston top surface section formed by the ribs, the fuel adheres only to the section, and the fuel is less likely to adhere to other areas of the piston top surface and the cylinder inner peripheral wall. Therefore, incomplete combustion and oil dilution can be prevented.

According to invention of Claim 2,
2. The direct injection type internal combustion engine according to claim 1, wherein the first rib has a surface for receiving fuel spray. 3.
Thus, according to the internal combustion engine of the second aspect, since the fuel spray has a surface for receiving the fuel spray, the fuel spray is reflected by the support surface and efficiently stirred and mixed with the air in the combustion chamber, so that the mixture formation is good. It becomes.

According to invention of Claim 3,
The in-cylinder direct injection internal combustion engine according to claim 1 or 2, wherein the first rib extends in a piston pin axial direction.
As described above, according to the internal combustion engine of the third aspect, since the first rib is not disposed in the high temperature portion on the exhaust side of the piston top surface, the heat spot portion (the heat reservoir portion that becomes high temperature during operation of the internal combustion engine). Is not formed, and the occurrence of knocking can be suppressed.

According to invention of Claim 4,
An ignition plug is provided at substantially the center of the combustion chamber, the piston top surface section is located at substantially the center of the combustion chamber, and the surface for receiving fuel spray is substantially perpendicular to the piston top surface. An in-cylinder direct injection internal combustion engine according to any one of claims 1 to 3 is provided.
As described above, according to the internal combustion engine of the fourth aspect, the surface that receives the fuel spray inside the rib wall that forms the section is substantially perpendicular to the top surface of the piston, and therefore collides with and reflects the fuel spray receiving surface. The fuel spray is directed upward in the compartment. Since both the compartment and the spark plug are located in the approximate center of the combustion chamber, the spark plug exists above the compartment, and a rich air-fuel mixture is formed in the vicinity of the spark plug due to the reflected fuel spray. For this reason, the stability of fuel ignition is ensured. Further, since a rich air-fuel mixture is formed in the vicinity of the spark plug, stratified combustion becomes possible, and fuel consumption can be reduced.

According to the invention of claim 5,
The direct injection type internal combustion engine according to any one of claims 1 to 4, which performs supercharging.
As described above, according to the internal combustion engine of the fifth aspect, since the supercharged internal combustion engine has a large amount of fuel injection, the effect obtained by preventing the fuel from adhering to a substantial portion of the piston top surface and the cylinder inner peripheral wall is further improved. growing.

  According to the present invention, it is possible to obtain a direct injection type internal combustion engine having a piston with a small compression height and sufficient strength without attaching fuel to a substantial portion of the piston top surface and the cylinder inner peripheral wall.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a direct injection type internal combustion engine according to the present invention, and schematically shows the flow of fuel spray in a combustion chamber based on actual measurements. 1 is a cross-sectional view taken along the XX axis in the plan view of the piston according to the present invention shown in FIG.

  The internal combustion engine 10 is configured as, for example, an in-line four-cylinder supercharged gasoline internal combustion engine mounted on an automobile. The combustion chamber 10 a of the internal combustion engine 10 is constituted by a cylinder bore 11, a cylinder head 13, and a flat piston 12 that is reciprocally disposed in the cylinder bore 11. The piston 12 is equipped with a piston ring 21 for sealing the gas in the combustion chamber 10a. Further, a connecting rod 19 is connected to the piston 12 via a piston pin 17 so as to be swingable. The connecting rod 19 transmits the gas pressure in the combustion chamber 10a to a crankshaft (not shown) to output the engine. Is generated.

  FIG. 2 shows a cross-sectional view of the piston according to the present invention on the left side, and a plan view of the piston according to the present invention on the right side. 2 is a cross-sectional view taken along the YY axis of the plan view on the right side of FIG. On the other hand, the plan view on the right side of FIG. 2 is a plan view seen from the Z direction in the cross-sectional view on the left side of FIG. 2 or the cross-sectional view of FIG. Note that the YY axis overlaps the piston pin axis center line.

  The top surface of the flat piston 12 has substantially no cavity, and has a valve recess (a recess for avoiding interference with the valve at the top dead center) 12v, the ribs 12b and 12c according to the present invention, and the like. When viewed as a whole (compared to a conventional cavity), it is formed as a substantially flat top surface 12a. For this reason, it becomes possible to make compression height CH smaller than the piston with a cavity (refer FIG. 3). As a result, the overall height of the engine is reduced and the piston weight is reduced. In the cross-sectional view on the left side of FIG. 2, CH represents the compression height.

  On the top surface of the piston 12, a pair of first ribs 12 b extending in the piston pin axial direction from the outer peripheral portion of the piston to the outer peripheral portion on the opposite side via a substantially central portion, and between the pair of first ribs A pair of second ribs 12c that are positioned and connect the pair of first ribs in a bridging manner are disposed. The first rib 12b may extend linearly or in a curved shape. As shown in FIG. 1, the first rib 12b has a triangular cross section, and has a surface 12bx for receiving the fuel spray 23a on its inner wall. The surface 12bx that receives the fuel spray of the first rib is substantially perpendicular to the piston top surface 12a. The reason why the cross section of the first rib 12b is triangular is to reduce weight. Since the fuel spray is reflected by the receiving surface 12bx and efficiently stirred and mixed with the air in the combustion chamber, the mixture formation is improved and complete combustion is promoted.

The pair of first ribs 12b and the pair of second ribs 12c connecting the pair of first ribs in a bridging manner increase the rigidity and improve the strength of the piston top surface. As a result, the piston top wall thickness TH (see FIG. 1) can be reduced. A composite stress such as an explosion force in the combustion chamber, a thrust force, and a thermal stress is generated on the top surface of the piston.
In the experiment of the internal combustion engine, at first, when a piston having only the first rib and having no second rib was adopted, a crack was formed between the pair of first ribs and along the first rib at the base portion of the first rib. Occurred. As a countermeasure, when the piston according to the present invention in which the second rib was installed in addition to the first rib was used and the experiment was performed under the same operating condition, no crack was generated. Thereby, the actual effect by this invention was able to be confirmed.

  In addition, the first rib extends in the piston pin axial direction and is not disposed in the vicinity of the exhaust-side high temperature portion 12g on the top surface of the piston. Therefore, the heat spot portion due to the rib arrangement is not formed, and the occurrence of knocking is suppressed. Is possible.

  Returning to FIG. 1, a spark plug 14 for igniting the air-fuel mixture is disposed substantially at the center of the combustion chamber 10a. An intake valve 16 is disposed at the intake port 15 facing the combustion chamber 10a, and an exhaust valve 20 is disposed at the exhaust port 18 facing the combustion chamber 10a. An injector 23 that directly injects fuel into the combustion chamber 10a is disposed near the intake valve 16 of the combustion chamber 10a. The direction of the injection hole 23b of the injector 23 is directed to the piston top surface section 12d formed by the ribs 12b and 12c so that the fuel spray injected from the injection hole 23b collides with the section 12d. Is set to The section 12d is located substantially at the center of the piston top surface 12a.

  That is, when the fuel spray 23a injected from the injection hole 23b of the injector 23 collides with the section 12d, the surface that receives the fuel spray 23a of the first rib that is substantially perpendicular to the piston top surface 12a. While being guided by 12bx, it reflects and heads upward from the piston top surface 12a. Above that, since the spark plug 14 is disposed in the approximate center of the combustion chamber 10a, a rich air-fuel mixture is formed in the vicinity of the spark plug by the reflected spray. For this reason, the stability of fuel ignition is ensured. Further, since a rich air-fuel mixture is formed in the vicinity of the spark plug by the reflected fuel spray, stratified combustion becomes possible, and fuel consumption can be reduced.

Further, the section 12d is surrounded by the first rib and the second rib, and has a shape like a basin. For this reason, even if the fuel spray 23a collides with the section 12d, fuel is less likely to adhere to other areas of the piston top surface other than the section 12d and the cylinder inner peripheral wall 11a. Can be prevented. Since the supercharged internal combustion engine has a large amount of fuel injection, the effect obtained by preventing fuel from adhering to a substantial portion of the piston top surface and the inner peripheral wall of the cylinder becomes greater.
At the time of stratified combustion, since the fuel spray becomes a flame almost immediately after generation, the flame directly contacts with the top surface of the piston almost only in a limited section 12d. For this reason, the flat piston which concerns on this invention becomes a cooling loss smaller than a normal flat piston. Incidentally, the piston is oil cooled by receiving an oil jet on the back surface 12f.

  FIG. 3 shows a conventional piston 12 with a cavity. 12h is a cavity and 23 is an injector.

  In this way, it is possible to obtain a direct injection type internal combustion engine including a piston having a small compression height and sufficient strength without attaching fuel to a substantial portion of the piston top surface and the cylinder inner peripheral wall.

It is sectional drawing which shows schematic structure of the direct injection type internal combustion engine of this invention. A sectional view of the piston according to the present invention is shown on the left side, and a plan view of the piston according to the present invention is shown on the right side. It is a conventional piston with a cavity.

Explanation of symbols

CH Compression height TH Piston top wall thickness 10 Internal combustion engine 10a Combustion chamber 11 Cylinder bore 11a Cylinder inner peripheral wall 12 Piston 12a Piston top surface 12b First rib 12bx Surface for receiving fuel spray from the first rib 12c Second rib 12d Piston top surface Partition 12f Rear surface 12g Exhaust side high temperature portion of piston top surface 12h Cavity 12v Valve recess 13 Cylinder head 14 Spark plug 15 Intake port 16 Intake valve 17 Piston pin 18 Exhaust port 19 Connecting rod 20 Exhaust valve 21 Piston ring 23 Injector (fuel injection valve)
23a Fuel spray 23b Injection hole

Claims (5)

In a cylinder direct injection internal combustion engine comprising a fuel injection valve that directly injects fuel into a combustion chamber and a flat piston that has substantially no cavity on the top surface,
A pair of first ribs located on the top surface of the flat piston and extending from the outer peripheral portion of the piston to the outer peripheral portion on the opposite side via a substantially central portion;
A pair of second ribs that are located between the pair of first ribs and that bridge-couple the pair of first ribs;
A direct injection type internal combustion engine, wherein fuel is injected by the fuel injection valve toward a piston top surface section defined by the first rib and the second rib on the top surface of the piston.   The in-cylinder direct injection internal combustion engine according to claim 1, wherein the first rib has a surface for receiving fuel spray.   The in-cylinder direct injection internal combustion engine according to claim 1, wherein the first rib extends in a piston pin axial direction.   An ignition plug is provided at substantially the center of the combustion chamber, the piston top surface section is located at substantially the center of the combustion chamber, and the surface for receiving fuel spray is substantially perpendicular to the piston top surface. The in-cylinder direct injection internal combustion engine according to any one of claims 1 to 3.   The in-cylinder direct injection internal combustion engine according to any one of claims 1 to 4, wherein supercharging is performed.

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