JP2524043Y2 - Stratified combustion engine with supercharger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an engine for stratifying an air-fuel mixture in a combustion chamber using exhaust gas recirculation gas.

[Conventional technology and issues]

Conventionally, an engine disclosed in Japanese Patent Application Laid-Open No. 52-32415 is known as this type of engine. That is, during the overlap period in which both the intake valve and the exhaust valve are opened, the engine causes the burned gas in the exhaust port to flow back to the combustion chamber to form an EGR (exhaust gas recirculation) layer near the top of the piston, An air-fuel mixture is supplied to the upper portion of the air-fuel mixture from an intake port to form a gas-fuel mixture layer near the ignition plug, thereby performing stratified combustion.

However, this conventional apparatus has a problem that the burned gas and the air-fuel mixture are easily mixed at the beginning of the overlap period, and it is difficult to form a rich air-fuel mixture layer containing no burned gas around the ignition plug. Have.

An object of the present invention is to provide an engine in which a burned gas and an air-fuel mixture are hardly mixed in a combustion chamber, and a sufficiently rich air-fuel mixture layer can be formed around an ignition plug.

[Means for solving the problem]

According to the present invention, in order to solve the above problems, an exhaust valve that can be opened to about 90 ° after the intake top dead center, and a valve that opens before the intake top dead center and closes after the exhaust valve closes An intake valve that performs injection, a fuel injection valve that performs fuel injection after the exhaust valve is closed and the intake valve is open, and a supercharger that supplies air into the combustion chamber via the intake valve. A backflow burned gas guide means for guiding the burned gas flowing backward from the exhaust port into the combustion chamber to the lower region of the combustion chamber is provided to fill the lower region of the combustion chamber with the burned gas and the upper portion of the combustion chamber. The area is filled with an air-fuel mixture.

[Action]

When the intake valve opens before the intake top dead center, a fresh air layer is formed on the burned gas layer formed near the top of the piston as the piston descends. Then, fuel is injected after the exhaust valve is closed, and an air-fuel mixture layer is formed on the fresh air layer.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiment.

Referring to FIG. 1 (C), a piston 13 is slidably inserted into a cylinder bore 12 formed in the cylinder block 11, and the bore 12, the top surface of the piston 13 and the cylinder head 14 are formed.
Thus, a combustion chamber 15 is formed. The ignition plug 16 is provided on the cylinder head 14 and protrudes from the upper center of the combustion chamber 15. The intake valve 21 opens and closes an intake port 22, and the exhaust valve 23 opens and closes an exhaust port 24. The fuel injection valve 25 is attached to a downstream portion of the intake manifold and injects fuel into the intake port 22. A supercharger is provided in an intake passage 26 connected to the intake port 22.
A throttle valve 28 is provided upstream of the supercharger 27. The supercharger 27 has a pair of rotors 27a and 27b, and supercharges intake air to the combustion chamber 15.

FIG. 2 shows the shape of the cylinder head 14 in the vicinity of the intake and exhaust valves 21 and 23. The exhaust valve 23 closes the exhaust port 24 in the state shown by the solid line, and
Open 24 slightly. A wall at the center of the cylinder head 14
A valve head 14a is formed, and the valve head 23a of the exhaust valve 23 moves up and down near the wall 14a during the opening and closing operation. Therefore, when the lift amount of the exhaust valve 23 is relatively small (the state shown by a broken line in the figure),
The exhaust valve 23 opens the exhaust port 24 in a portion close to the wall surface of the bore 12, and when the lift amount of the exhaust valve 23 increases and the valve head 23a is located below the wall 14a, the exhaust valve 23 The exhaust port 24 is opened all around.

FIG. 3 shows the opening / closing timing of the intake valve 21 and the exhaust valve 23 and the fuel injection timing of the fuel injection valve 25. The exhaust valve 23 opens slightly before the intake bottom dead center and 90 after the intake top dead center.
Close the valve around °. The intake valve 22 opens before the intake top dead center, and closes after the intake bottom dead center, that is, after the exhaust valve 23 closes. In other words, the exhaust valve 23 is about
The valve is open during the 90 ° crank angle. The fuel injection valve 25 is
Fuel injection is performed before the intake bottom dead center, that is, after the exhaust valve 23 is closed and while the intake valve is open.

The operation of this embodiment will be described with reference to FIGS. 1 (a), 1 (b) and 1 (c). This figure shows the engine state in the medium load operation range. FIG. 1 (a) shows the exhaust stroke, and the intake valve
The valve 21 is closed, and the exhaust valve 23 is open. The burned gas passes around the valve head of the exhaust valve 23 and is discharged to the exhaust port 24. Next, after passing through the intake top dead center, as shown in FIG. 1 (b), the intake valve 21 opens, but the exhaust valve 23 is still open. Therefore, the burned gas flows back from the exhaust port 24 into the combustion chamber 15 due to the lowering of the piston 13,
Fresh air is supercharged into the combustion chamber 15 from the intake port 22 by the operation of 27. As described with reference to FIG. 2, since the exhaust port 24 is mainly opened at a portion close to the wall surface of the cylinder bore 12, most of the burned gas in the exhaust port 24 is bored.
It flows into the combustion chamber 15 along the 12 wall surfaces. Therefore,
The burned gas is unevenly distributed below the combustion chamber 15. In this embodiment, the exhaust valve 23 is located after the intake top dead center.
The valve closes at 90 °, whereby a sufficient amount of burned gas flows back into the combustion chamber 15, but if the supercharger 27 is not provided, the exhaust gas also flows back to the intake port 22. Therefore, stratification in the combustion chamber described later cannot be achieved. That is, it is essential to supercharge the air into the combustion chamber 15 during the intake stroke.

After 90 ° after the intake top dead center, as shown in FIG. 1 (c), the exhaust valve 23 closes to enter the intake stroke, and at this time fuel injection is performed. At this time, the fuel does not flow into the exhaust port 24 because the exhaust valve 23 is closed. In the combustion chamber 15, a layer of rich air-fuel mixture near the spark plug 16, a layer of burned gas near the top of the piston 13, and a layer of fresh air between the air-fuel mixture layer and the burned gas layer are formed. Each is formed. By such stratification, the air-fuel mixture is hardly mixed with the burned gas, and maintains a sufficiently rich state.
It becomes easy to ignite. Further, the air-fuel mixture is heated by the burned gas particularly in a portion near the burned gas. Next, in the compression stroke, the air-fuel mixture further rises in temperature to about 10
When the temperature reaches 00 ° K, self-ignition occurs without relying on the spark of the ignition plug 16. This spontaneous ignition occurs after the intake valve 21 is closed and the compression ratio is about 8
When it becomes, it occurs.

Thereafter, similarly, FIGS. 1 (a), (b) and (c)
The exhaust, intake, compression, and self-ignition are performed in the order shown in FIG. In Thus low and medium load range, the air-fuel ratio in the entire combustion chamber 15 becomes lean, and reduces the NO _x in the exhaust gas to the burned gas is re-burned. Also, due to self-ignition, extremely stable combustion is obtained, and the combustion efficiency is improved. Exhaust valve 23 even after intake top dead center
Is open, a large amount of residual gas remains in the combustion chamber 15, which reduces pumping loss and improves fuel economy. For example, when spontaneous ignition is difficult, such as in a low-load operation range in a cold state, the air-fuel mixture is ignited by the ignition plug 16, but the mixture is collected near the ignition plug 16 so that ignition is easy.

On the other hand, in the high-load operation range, since the pressure in the intake port 22 is extremely high, after the intake top dead center, while the intake and exhaust valves 21 and 23 are both open, air flows into the intake port 22 and the combustion chamber. 1
5, flows in the order of the exhaust port 24, from the exhaust port 24 to the combustion chamber 1
No backflow of the burnt gas to 5 (FIG. 1 (b)) occurs.
Therefore, the residual gas in the combustion chamber 15 is small, and the air-fuel mixture is ignited by the ignition plug 16 and burns as in the case of a normal engine.
In this case, since the intake air is supercharged by the supercharger 27, a high output is obtained.

In the high-load operation range, the residual gas in the combustion chamber 15 is smaller than in the medium-load operation range, but is larger than in a normal engine because the overlap angle of the intake and exhaust valves 21 and 23 during the valve opening period is large. If there is a large amount of residual gas in this way, knocking is likely to occur.
If the capacity of 27 is increased, fuel consumption may be reduced due to the drive of the capacity. Further, if the overlap angle of the intake and exhaust valves 21 and 23 is large, more air flows from the combustion chamber to the exhaust port, and the intake efficiency may be lower than that of a normal supercharged engine.

Therefore, in another embodiment of the present invention, a variable valve timing mechanism is provided to change the opening / closing timing of the exhaust valve 23 in the high load operation range so that the overlap angle is smaller than that in the low and medium load operation range.

Variable valve timing mechanisms are conventionally known, and one example is shown in FIGS. 4 (a) and 4 (b). In this figure, a cam (not shown) for opening and closing the exhaust valve is provided on the camshaft 31. Timing pulley 32 is camshaft 31
, And rotates in conjunction with a crankshaft (not shown) to rotate the camshaft 31. A sleeve inner 33 is integrally formed at the base of the cam shaft 31, and a sleeve outer 34 is fitted around the sleeve inner 33. The sleeve outer 34 can rotate relative to the sleeve inner 33,
The timing pulley 32 is integrally connected. Guide slits 3 on sleeve inner 33 and sleeve actor 34 respectively
5,36 are formed. The guide slit 35 is inclined with respect to the axial direction of the cam shaft 31, and the guide slit 36 is inclined in a direction opposite to the guide slit 35. The slider 37 extends in the radial direction and engages with the guide slits 35 and 36. Slider 3
7 is connected to the output shaft 39 of the step motor 38,
The camshaft 31 is configured to be displaced in the axial direction by the rotational displacement of the camshaft 31.

When the slider 37 is displaced in the axial direction, the sleeve inner 33 and the sleeve outer 34 are rotationally displaced in the opposite directions due to the engagement between the slider 37 and the guide slits 35 and 36. That is, the timing pulley 32 is relatively rotated and displaced with respect to the cam shaft 31. As a result, the relative rotation angle position between the cam (not shown) fixed to the cam shaft 31 and the timing pulley 32 changes, and the opening / closing timing of the exhaust valve changes.

FIG. 5 shows a change in the opening / closing timing of the exhaust valve by the variable valve timing mechanism shown in FIGS. 4 (a) and 4 (b). That is, the exhaust valve opens from near the bottom dead center of the exhaust to about 90 ° after the top dead center of the intake as shown by a broken line L in the low-medium load operation range. The valve opens from 65 ° before bottom dead center to 20 ° after intake top dead center.
Thus, in the high load operation range, the overlap angle of the intake and exhaust valves is reduced as in the case of a normal engine, thereby reducing residual gas and preventing the occurrence of knocking. The risk of slippage is reduced, and the intake efficiency is improved.

6A and 6B show another example of the variable valve timing mechanism. In this figure, a cam shaft 41 is provided with two cams 42 and 43 for opening and closing the exhaust valve. These cams 42, 43 have different cam profile shapes, i.e. one cam 42 is suitable for high load operation,
The other cam 43 has a profile shape suitable for low and medium load operation. The cams 42 and 43 are formed on a cam piece 44, and the cam piece 44 is formed with a guide groove formed on the cam shaft 41.
By 45, it is supported to be displaceable in the axial direction. Cam piece
44 has a flange 46 formed thereon.

The cylindrical guide shaft 51 extends parallel to the cam shaft 41, and the drive fork 52 fitted and supported on the outer peripheral surface of the guide shaft 51 is connected to the flange 46 of the cam piece 44. The drive fork 52 can be displaced along the axis of the guide shaft 51. A drive shaft 53 is inserted into the guide shaft 51, and a ring 54 is fitted between the guide shaft 51 and the drive shaft 53. The ring 54 is connected to the drive fork 52 via a bolt 62 inserted through a guide hole 61 formed in the guide shaft 51. The guide hole 61 has locking portions 61a and 61b projecting in the circumferential direction of the guide shaft 51 at both ends. Drive fork 52 is guided by spring 63
As a result, the bolt 62 is normally locked in one of the locking portions 61a and 61b, and the driving fork 52 is stopped with respect to the guide shaft 51.

The springs 55 and 56 are provided with annular protrusions 5 formed on the drive shaft 53.
It is provided between 7 and the ring 54. The drive shaft 53 can be displaced in the axial direction, and when the bolt 62 is displaced while being engaged with the engagement portion 61a or 61b, the ring 55 and the drive fork 2 are attached to the springs 55 and 56 by the guide shaft 51. A force for urging in the axial direction is generated. A guide groove 58 is provided on the outer peripheral surface of the drive shaft 53.
Is engraved. The guide groove 58 extends along the axial direction of the drive shaft 53, and has inclined portions 58a and 58b at both ends. The tip of the bolt 62 is engaged with the guide groove 58, and is released from the locking portions 61a, 61b when engaging with the inclined portions 58a, 58b.

Accordingly, when the drive shaft 53 is displaced to the right in the drawing while the bolt 62 is engaged with the left engaging portion 61a, the springs 55 and 56 bend and the ring 54 is urged rightward. When the drive shaft 53 is further displaced to the right, the bolt 62 is engaged with the inclined portion 58a and comes off the locking portion 61a. This allows
The ring 54 and the drive fork 52 are displaced rightward by the resilient force of the springs 55 and 56, and the bolt 62 is
To lock. That is, the cam piece 44 is displaced along the cam shaft 41, and the cams 42 and 43 are switched.

7 (a) and 7 (b) show the opening and closing timing of the valve by the variable valve timing mechanism of FIGS. 6 (a) and 6 (b). FIG. 7 (a) shows the exhaust valve in the high load operation range.
The valve opens from 55 ° before the bottom dead center of the exhaust to 10 ° after the top dead center of the intake as shown in FIG.
The valve opens from 55 ° before bottom dead center of exhaust to 90 ° after top dead center of intake, as shown in (2). On the other hand, the intake valve opens from 10 ° before top dead center of intake to 50 ° after bottom dead center of intake regardless of the load, so the overlap angle of the intake and exhaust valves during opening period becomes smaller at high load. 4A, 4B, the residual gas is reduced and the intake efficiency is improved. Further, in the examples of FIGS. 7 (a) and 7 (b), the valve opening period of the exhaust valve can be changed according to the magnitude of the load. The degree of freedom is increased, and the engine output under a high load can be further improved.

[Effect of the invention]

As described above, according to the present invention, at the beginning of the overlap period, the burned gas is less likely to be mixed with the rich air-fuel mixture layer formed near the ignition plug, and the effect of obtaining stable combustion is obtained. Can be

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a), 1 (b) and 1 (c) show an embodiment of the present invention, FIG. 1 (a) is a sectional view showing an exhaust stroke, and FIG. 1 (b) ) Is a sectional view showing the first half of the intake stroke, FIG. 1 (c) is a sectional view showing the vicinity of the bottom dead center of the intake stroke, FIG. 2 is a sectional view showing the vicinity of the intake and exhaust valves of the cylinder head, FIG. 4A is a graph showing the open / close state of the intake / exhaust valve in the embodiment of FIGS. 1A, 1B, and 1C, and FIG. 4A is a perspective view showing a drive unit of the variable valve timing mechanism. 5B is a cross-sectional view of the drive unit, FIG. 5 is a graph showing the open / close state of the intake / exhaust valve when the variable valve timing mechanism of FIGS. 4A and 4B is used, and FIG. ) Is a side view showing another example of the variable valve timing mechanism, FIG. 6 (b) is a cross-sectional view of the variable valve timing mechanism of FIG. 6 (a), and FIG. a) is a graph showing the opening / closing timing of the intake / exhaust valve in the high load operation range when the variable valve timing mechanism of FIGS. 6 (a) and (b) is used, and FIG. 7 (b) is the low / medium load operation range. 6 is a graph showing the opening / closing timing of the intake / exhaust valve. 21 ... intake valve, 23 ... exhaust valve, 25 ... fuel injection valve, 27 ...
... supercharger.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location F02D 13/02 F02D 13/02 K F02M 25/07 570 F02M 25/07 570A

Claims (1)

(57) [Scope of request for utility model registration] 1. An exhaust valve which can be opened to about 90 ° after intake top dead center, an intake valve which opens before intake top dead center, closes after the exhaust valve closes, and the exhaust valve A fuel injection valve for performing fuel injection after the valve is closed and while the intake valve is open; and a supercharger for supplying air into the combustion chamber via the intake valve. A backflow burned gas guide means for guiding burned gas flowing backward from the combustion chamber into the combustion chamber to the lower area of the combustion chamber is provided to fill the lower area of the combustion chamber with the burned gas and mix the upper area of the combustion chamber with the air-fuel mixture. A stratified combustion engine with a supercharger designed to satisfy the needs.