JP2936803B2 - In-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection internal combustion engine.

[0002]

2. Description of the Related Art A groove is formed on the top surface of a piston, and fuel is injected from a fuel injection valve into the groove to generate a swirling flow around a cylinder axis in a combustion chamber. An in-cylinder injection type internal combustion engine in which an ignitable air-fuel mixture is formed around an engine is known.
No. 42).

[0003]

However, in this in-cylinder injection type internal combustion engine, it is essential to generate a swirling flow around the cylinder axis. Therefore, when the swirling flow around the cylinder axis is not generated, the injection is no longer performed. The method cannot be adopted. In addition, since the strength of the swirl flow varies depending on the operating state of the engine, if the formation of the air-fuel mixture around the ignition plug is entirely dependent on the swirl flow, the optimal air-fuel mixture will be ignited for any operating state of the engine There is a problem that it is difficult to form around the stopper.

[0004]

According to the present invention, an ignition plug is disposed at the center of the inner wall surface of a cylinder head, and a fuel injection valve is disposed at a peripheral portion of the inner wall surface of the cylinder head. Forming a groove on the piston top surface defined by a pair of side wall surfaces extending from the lower part of the ignition plug toward the fuel injection valve side and a substantially flat bottom wall surface, and from the fuel injection valve. The fuel is injected obliquely toward the groove bottom wall surface and the injected fuel colliding with the groove bottom wall surface is directed along the groove side wall surface toward the groove end below the spark plug, and the groove end and the fuel injection valve are connected. The fuel guide groove extending along the vertical plane including the groove is formed on the bottom wall surface of the groove, and the side wall surface of each groove extends substantially straight from the end of the groove toward the fuel injection valve.

[0005]

A part of the injected fuel is guided by the fuel guide groove to reach the end of the groove, and the other injected fuel flows toward the groove side wall surface and then flows along the groove side wall surface. In this case, when each groove side wall surface extends substantially straight from the groove end portion toward the fuel injection valve side, the flow rate of the fuel that starts toward the groove end portion along the groove side wall surface is equal to the groove end portion. The closer, the faster. Therefore, there is a time lag before each fuel flowing along the groove side wall surface reaches the groove end portion, and the fuel that has reached the groove end portion early along the groove side wall surface and the groove end portion along the fuel guide groove. A combustible air-fuel mixture is formed around the ignition plug by the fuel that has reached.

[0006]

3 and 4, reference numeral 1 denotes a cylinder block, 2 denotes a piston reciprocating in the cylinder block 1, 3 denotes a cylinder head fixed on the cylinder block 1, and 4 denotes a cylinder head. The combustion chamber formed between the wall surface 3a and the top surface of the piston 2 is shown. A concave groove 5 is formed on the cylinder head inner wall surface 3a, and a pair of air supply valves 6 are arranged on the cylinder head inner wall surface portion 3b that forms the bottom wall surface of the concave groove 5. On the other hand, the cylinder head inner wall surface portion 3c excluding the concave groove 5 is inclined and substantially flat, and three exhaust valves 7 are arranged on the cylinder head inner wall surface portion 3c. The cylinder head inner wall surface portion 3b and the cylinder head inner wall surface portion 3c are connected to each other via the peripheral wall 8 of the concave groove 5.

The peripheral wall 8 of the concave groove is located between the pair of mask walls 8a, which are disposed very close to the peripheral edge of the air supply valve 6 and extend in an arc along the peripheral edge of the air supply valve 6, and the air supply valve 6. And a pair of fresh air guide walls 8c located between the supply wall 6 and the peripheral wall of the cylinder head inner wall surface 3a. Each mask wall 8a extends toward the combustion chamber 4 below the intake valve 6 at the maximum lift position, so that the opening between the peripheral portion of the intake valve 6 located on the exhaust valve 7 side and the valve seat 9 is formed. The air supply valve 6 is closed by the mask wall 8a throughout the opening period of the air supply valve 6. In addition, each fresh guide wall 8
The fresh air guide walls 8b and 8c extend substantially parallel to a line connecting the centers of the two air supply valves 6. The ignition plug 10 is disposed on the cylinder head inner wall surface portion 3c so as to be located at the center of the cylinder head inner wall surface 3a. On the other hand, the exhaust valve 7 is not provided with a mask wall that covers the opening between the exhaust valve 7 and the valve seat 11, so that when the exhaust valve 7 is opened, the exhaust valve 7
The entire opening formed between the valve seat 11 and the valve seat 11 opens into the combustion chamber 4.

An air supply port 12 is formed in the cylinder head 3 for the air supply valve 6, and an exhaust port is formed for the exhaust valve 7.
13 is formed. On the other hand, a fuel injection valve 14 is arranged at the peripheral portion of the cylinder head inner wall surface 3 a between the two supply valves 6, and fuel is injected from the fuel injection valve 14 into the combustion chamber 4.

As shown in FIGS. 1 and 3, a recessed groove 15 is formed on the top surface of the piston 2 from below the spark plug 10 to below the tip of the fuel injection valve 14. The concave groove 15 is defined by a pair of side wall surfaces 15b extending gradually from the concave groove end 15a below the ignition plug 10 toward the fuel injection valve 14 and a substantially flat bottom wall surface 15c. As shown in FIG. 5, the concave groove end 15a has a concave cross-sectional shape that is concave toward the side opposite to the fuel injection valve 14. 1, the groove end 15a is formed on a vertical plane KK including the ignition plug 10 and the fuel injection valve 14, and each side wall surface 15b is symmetrical with respect to this vertical plane KK. It has a unique shape. Accordingly, the concave groove 15 has a symmetrical shape with respect to the vertical plane KK. Also, as shown in FIG.
A fuel guide groove 16 extending along a vertical plane KK is formed thereon. The fuel guide groove 16 has a concave cross-sectional shape as shown in FIG. As shown in FIG. 3, when the piston 2 reaches the top dead center, a squish area is provided between the top surface portion of the piston 2 located on the side opposite to the concave groove 15 with respect to the ignition plug 10 and the cylinder head inner wall surface portion 3c. 17 is formed.

As shown in FIG. 5, shown in FIGS.
In the embodiment, the exhaust valve 7 is opened before the intake valve 6 and the exhaust valve 7 is opened.
The valve 7 opens before the intake valve 6. Also, in FIG.
I _lIndicates the fuel injection timing during low engine load operation.
And I_m1And I_m2Is the fuel during medium load operation of the engine.
The fuel injection timing._hDuring engine high load operation
FIG. Fig. 5 High engine load operation
Fuel injection I at the time of rotation_hGoes around when the exhaust valve 7 closes.
The fuel injection I at the time of engine low load operation_lIs high load
It turns out that it is done much later than when driving
You. In addition, during engine middle load operation, fuel injection is divided into two
I_m1And I_m2Is performed, and at this time, the first fuel injection
I_m1Is performed at about the same time as during high-load operation of the engine.
Second fuel injection I_m2Is about the same time as when the engine is operating at low load
It can be seen that this is done.

As shown in FIG. 6, when the air supply valve 6 and the exhaust valve 7 are opened, air flows into the combustion chamber 4 via the air supply valve 6. At this time, since the opening of the air supply valve 6 on the exhaust valve 7 side is covered by the mask wall 8a, air is
The gas flows into the combustion chamber 4 from the opening of the air supply valve 6 on the side opposite to the side a. This air descends along the inner wall surface of the cylinder bore below the air supply valve 6 as indicated by the arrow W, and then travels along the top surface of the piston 2 and rises along the inner wall surface of the cylinder bore below the exhaust valve 7, and Will flow in a loop in the combustion chamber 4. The burned gas in the combustion chamber 4 is discharged through the exhaust valve 7 by the air W flowing in the loop, and the swirling flow X swirling in the vertical plane in the combustion chamber 4 by the air W flowing in the loop. Is generated. Next, when the piston 2 starts rising after passing through the bottom dead center BDC, fuel injection from the fuel injection valve 14 is started thereafter.

Next, with reference to FIGS. 7 to 10, a description will be given of a fuel injection method at the time of low load operation of the engine, at the time of medium load operation of the engine, and at the time of high load operation of the engine. FIG. 7 shows the fuel injection _Il during the low engine load operation and the second fuel injection _Im2 during the medium engine load operation.
Shows a fuel injection I _h in the first fuel injection I _m1 and engine high load operation during medium load operation the engine.

As shown in FIGS. 1 and 7, at the time of the second fuel injection during the low load operation of the engine and the middle load operation of the engine, the fuel flows from the fuel injection valve 14 along the vertical plane KK along the groove bottom wall surface 15c. Is injected obliquely toward the groove, and the injected fuel collides with the groove bottom wall surface 15c, and then proceeds on the groove bottom wall surface 15c toward the groove end portion 15a. Next, the behavior of the injected fuel at this time will be described with reference to FIG. In FIG. 9, a dashed line R indicates a collision area of the injected fuel on the groove bottom wall surface 15c. Arrows F ₁ and F ₂ show two typical flows of the injected fuel flowing toward the groove side wall surface 15b, and arrow F ₃ shows a flow along the fuel guide groove 16 toward the groove end 15a. Is shown. That is, a part of the fuel F ₃ injected from the fuel injection valve 14 advances in the fuel guide groove 16 due to the inertial force and immediately reaches the concave groove end 15a, and the remaining fuel F ₃ is injected.
₁ and F ₂ proceed in the injection direction by inertial force even after colliding on the groove bottom wall surface 15c, and then proceed to the groove side wall surface 15b and then proceed toward the groove end portion 15a along the groove side wall surface 15b. I do. Therefore, the fuels F ₁ and F ₂ that travel along the groove side wall surface 15b arrive at the groove end 15a later than the fuel F ₃ that advances in the fuel guide groove 16.

Next, paying attention to the fuels F ₁ and F ₂ , since each groove side wall surface 15 b extends almost straight from the groove end portion 15 a toward the fuel injection valve 14, the groove side wall surface 15 b
Each injection fuel F ₁ for the incident angle theta ₁ of F _2, theta ₂ becomes smaller as the injected fuel near the injection center, therefore the injected fuel F ₁ when started to start traveling along the recessed groove side wall 15b , flow velocity v ₁ of the F _2, v ₂ becomes faster as the injected fuel closer to the injection center.

On the other hand, as shown in FIG.
The contour of the concave groove 15 'formed on the top surface of the
From the fuel injection valve 14 'to the flat bottom wall 15 of the concave groove 15'.
When fuel is injected onto c ', each of the
Injected fuel F₁', F_Two'Incident angle θ₁', Θ_Two′ Is injection
The closer the injection fuel is to the center, the larger it is
Injected fuel F when it starts to proceed along 15b '
₁', F_Two'Flow velocity v₁', V_Two′ Is near the injection center
The slower the injected fuel, the slower it will be. However, like this ₁'>
v_Two′, The flow along each groove side wall surface 15b ′
The fuel or air-fuel mixture collected at the groove end 15a 'at about the same time.
And then rises along the groove end 15a 'at about the same time
As a result, an air-fuel mixture is formed around the ignition plug 10. Obedience
In this case, the ignition plug 10
A mixture is formed around the
The concentration of the mixture formed around the spark plug 10 is the fuel injection amount
Cannot be controlled by any method other than controlling
Will be. Thus, for example, when the fuel injection amount is small
Try to form the optimal mixture around spark plug 10
When the fuel injection amount increases, it is formed around the spark plug 10
The air-fuel mixture becomes excessively rich, thus
Not only can not get the ignition, even if the ignition
As a result, a large amount of unburned HC and CO is generated.

On the other hand, as shown in FIG. 9, v ₁ <
v injected fuel F ₁ even ₂ becomes associated with the injected fuel F ₂ has reached the groove end portion 15a is still in progress toward the groove end 15a, so that each injection fuel F _1, F ₂ is concave There will be a time lag to reach the groove end 15a. Further, the injected fuel as described above F ₃ are injected fuel F _2, F ₃
The injected fuels F ₁ , F ₂ , and F ₃ arrive at the groove end 15a earlier than before, so that there is a time difference in reaching the groove end 15a.

As described above, if there is a time difference between each of the injected fuels F ₁ , F ₂ and F ₃ reaching the groove end 15a, the ignition plug 10
The mixture formed around the fuel gradually becomes thicker as time elapses.Therefore, in this case, even if the fuel injection amount is constant, the ignition time is controlled by controlling the time from fuel injection to ignition. When the spark plug is made
The concentration of the air-fuel mixture formed in 10 laps can be controlled. In other words, by controlling the ignition timing or the injection timing such that an optimum concentration of the mixture is formed around the ignition plug 10 when the ignition is performed, the optimum around the ignition plug 10 is always achieved when the ignition is performed. An air-fuel mixture can be formed. Therefore, if the concave groove 15 having the shape as shown in FIG. 9 is used, it is possible to secure good ignition by the ignition plug 10 irrespective of the fuel injection amount.

On the other hand, when the injected fuel collides with the groove bottom wall surface 15c when the injected fuel is widely dispersed on the groove bottom wall surface 15c, the more widely the injected fuel is dispersed, the more the fuel is vaporized within the groove 15 and the groove is formed. The amount of fuel remaining within 15 increases. Also, in this case, the smaller the fuel injection amount, the greater the amount of heat applied to the fuel per unit volume. Therefore, the smaller the fuel injection amount, the greater the proportion of fuel vaporized in the groove 15. It is a preferable direction that the amount of fuel vaporized in the groove 15 increases. However, as the amount of fuel vaporized in the groove 15 increases, the amount of fuel reaching the groove end portion 15a decreases. Therefore, if the injected fuel is dispersed over a wide range, there is a risk that an ignitable air-fuel mixture cannot be formed around the ignition plug 10 particularly when the fuel injection amount becomes small.

However, as shown in FIG.
When the fuel guide groove 16 is formed on the upper side, the fuel injected into the fuel guide groove 16 does not diffuse to the periphery and the groove end 15
sent to a. Therefore, even when the fuel injection amount is small, a certain amount of fuel is surely fed into the groove end 15a, and thus, even when the fuel injection amount is small, it is possible to ignite around the ignition plug 10. Thus, a proper air-fuel mixture can be reliably formed.

By the way, as shown in FIG. 6, the swirling flow X generated in the combustion chamber 4 is attenuated as the piston 2 rises and the turning radius gradually decreases while decreasing. As shown, the swirling flow X is along the groove bottom wall surface 15c. When the piston 2 further approaches the top dead center, a squish flow squirts from the squish area 17 as shown by an arrow S in FIG.
Also advances along the groove bottom wall surface 15c. Therefore, these swirling flows X
The squish flow S promotes the vaporization of the injected fuel. When the bottom wall surface 15c is covered with the ceramic layer, the temperature of the bottom wall surface 15c rises. Therefore, in order to further promote the vaporization of the injected fuel, it is preferable to apply a ceramic coating on the groove bottom wall surface 15c.

On the other hand, at the time of the first fuel injection during the engine high load operation and the engine medium load operation, the fuel injection is started when the piston 2 is at the low position as shown in FIG. Therefore, at this time, the injected fuel collides over a wide area on the top surface of the piston 2, so that the fuel is well dispersed in the combustion chamber 4. During medium load operation the engine lean air-fuel mixture in the combustion chamber 4 by the fuel injection I _m1 of the first time is formed, the lean air-fuel mixture is the second fuel injection I
_The air-fuel mixture formed around the ignition plug 10 by _m2 is burned as an ignition source. On the other hand, at the time of engine high load operation, an air-fuel mixture formed in the combustion chamber 4 is ignited by the spark plug 10 by the injected fuel as shown in FIG.

Although the present invention has been described with reference to the case where the present invention is applied to a direct injection two-stroke engine, the present invention can also be applied to a direct injection four-cycle engine.

[0023]

According to the present invention, when fuel is injected into the groove formed on the top surface of the piston, when the ignition is performed, an air-fuel mixture having an optimum concentration is always produced around the ignition plug regardless of the fuel injection amount. Can be formed.

[Brief description of the drawings]

FIG. 1 is a plan view of a piston top surface.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is a side sectional view of the two-stroke engine.

FIG. 4 is a bottom view of the cylinder head.

FIG. 5 is a diagram showing a valve opening period of a supply / exhaust valve and a fuel injection timing.

FIG. 6 is a side sectional view of the two-stroke engine during a scavenging stroke.

FIG. 7 is a side cross-sectional view of a two-cycle engine showing fuel injection during low-load operation and second fuel injection during medium-load operation.

FIG. 8 is a side cross-sectional view of the two-cycle engine showing a first fuel injection during a medium load operation and a fuel injection during a high load operation.

FIG. 9 is a plan view of a piston top surface similar to FIG. 1;

FIG. 10 is a plan view of a piston top surface showing an unfavorable example.

[Explanation of symbols]

 2 ... piston 10 ... spark plug 14 ... fuel injection valve 15 ... concave groove 15a ... concave groove end 15b ... concave groove side wall surface 16 ... fuel guide groove

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eiji Ohno 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hiroaki Nihei 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Koichi Nakata 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-4-370319 (JP, A) JP-A-3-65864 (JP, U) JP-A 1-124042 (JP, U) JP-A 3-52333 (JP, U) JP-A 57-33231 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02B 23/10 F02F 3/26

Claims (1)

(57) [Claims] An ignition plug is arranged at the center of an inner wall surface of a cylinder head, a fuel injection valve is arranged at a peripheral portion of an inner wall surface of the cylinder head, and is gradually expanded from below the ignition plug toward the fuel injection valve. A groove is formed on the piston top surface defined by a pair of extending side wall surfaces and a substantially flat bottom wall surface, and fuel is obliquely injected from the fuel injection valve toward the groove bottom wall surface. The fuel injected against the bottom wall is directed toward the end of the groove below the spark plug along the side wall surface of the groove, and the fuel guide groove extending along a vertical plane including the end of the groove and the fuel injection valve is formed as a groove. An in-cylinder injection type internal combustion engine formed on a bottom wall surface and having a side wall surface of each groove extending substantially straight from an end of the groove toward a fuel injection valve.