JPH11280507A - Spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize compression self ignition combustion in a low load operating region by providing a real compression ratio variable means for changing a real compression ratio decided by an operating condition of an intake valve according to an operating condition of an engine, and operating the real compression ratio variable means so as to increase real compression ratio at a low lead region side of a region where a self ignition operation is carried out. SOLUTION: A valve closing period variable mechanism 40 for changing a real compression ratio according to an operation condition of an engine is arranged on an end part of an intake cam shaft 29 as a real compression ratio variable means. In a compression self ignition operation region, a valve closing timing variable mechanism 40 for changing closing timing of a first intake valve 18 and a second intake valve 19 is operated, and is controlled in such a condition that the valve closing timing is advanced at a low load side of the engine and the valve closing timing is delayed at a high load side of the engine. As a result, a real compression ratio is increased at the low load side of the engine, the real compression ratio is reduced at the high load side of the engine, and thereby, compression self ignition combustion is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type internal combustion engine in which exhaust gas is introduced into a combustion chamber of an internal combustion engine to perform combustion, and in particular, compression utilizing backflow exhaust gas introduced from an exhaust port into the combustion chamber. The present invention relates to a spark ignition type internal combustion engine that switches between self-ignition operation and spark ignition operation using a spark plug according to an engine load.

[0002]

2. Description of the Related Art As part of purifying exhaust gas, a method of causing an internal combustion engine, for example, a spark ignition type internal combustion engine (hereinafter referred to as a gasoline engine), to perform not only a spark ignition operation by a spark plug but also a self-ignition operation by compression. Development is under consideration. According to the gasoline engine of this method, although the generation amounts of HC and NOx in the exhaust gas are greatly reduced, the timing of self-ignition depends on the air-fuel ratio of the mixture, the temperature of the mixture, and so on. It is known that it is difficult to cause self-ignition at a desired time in a wide range of load used.

As a conventional gasoline engine, for example,
There is a two-stroke gasoline engine shown in the book "94 Honda R & D Report" (published by Honda Motor Co., Ltd.). In this two-cycle gasoline engine,
During low-load operation of the engine, the exhaust port is partially blocked by a throttle valve to increase the concentration of residual exhaust remaining in the cylinder, and to increase the temperature and pressure of the air-fuel mixture in the cylinder at the start of the compression stroke. This realizes ignition combustion, thereby eliminating unstable combustion at the time of partial load peculiar to a two-stroke gasoline engine and reducing HC emissions.

A conventional gasoline engine is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 7-180515. In this gasoline engine, when the engine is running at a low load, the exhaust valve is slightly opened in the intake stroke, and the residual exhaust gas in the exhaust port flows back into the combustion chamber, so-called internal E
By performing the GR, the combustion temperature is reduced, and the emission amount of NOx is reduced.

[0005]

However, the prior art gasoline engine has the following problems.

That is, if the technique of increasing the concentration of residual exhaust in a cylinder by restricting an exhaust port by a throttle valve employed in the above-described two-cycle gasoline engine is directly applied to a four-cycle gasoline engine,
In a cycle gasoline engine, a sufficient amount of exhaust cannot be retained in the cylinder because exhaust is forcibly pushed by a piston in an exhaust stroke. As a result, there has been a problem that the temperature and pressure in the cylinder in the initial stage of the compression stroke cannot be sufficiently increased, and the compression self-ignition combustion cannot be realized.

In the gasoline engine disclosed in Japanese Patent Application Laid-Open No. 7-180515, the exhaust valve is simply opened when the engine is under partial load operation, so that a sufficient amount of exhaust gas is supplied to the combustion chamber. Can not be introduced. As a result, there has been a problem that a desired compression auto-ignition combustion cannot be realized, and that the introduced exhaust gas merely has an effect of lowering the combustion temperature due to the flame propagation.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to realize stable compression auto-ignition combustion in a wide range of operation as much as possible, such as HC, NOx, etc. It is an object of the present invention to provide a spark ignition type internal combustion engine that can significantly reduce the amount of exhaust gas.

[0009]

According to a first aspect of the present invention, there is provided a spark ignition type internal combustion engine, comprising: an intake valve for opening and closing an opening of an intake port communicating with a combustion chamber; An exhaust valve that opens and closes an opening of an exhaust port communicating with the exhaust port, and opens at least one exhaust valve in an exhaust stroke and an intake stroke to flow exhaust gas in the exhaust port back into the combustion chamber to perform self-ignition combustion. A spark ignition type internal combustion engine that selectively switches between self-ignition operation and spark ignition operation with a spark plug according to the load of the engine to operate. Actual compression ratio variable means for changing the compression ratio in accordance with the operating conditions of the engine, wherein the actual compression ratio variable means increases the actual compression ratio on the low load region side of the region where the self-ignition operation is performed. Operate , And it has a configuration.

According to a second aspect of the present invention, an intake valve for opening and closing an opening of an intake port communicating with the combustion chamber and an exhaust valve for opening and closing an opening of an exhaust port communicating with the combustion chamber are provided. At least one exhaust valve is opened in an exhaust stroke and an intake stroke to allow exhaust gas in an exhaust port to flow back into the combustion chamber to perform self-ignition combustion, and to perform self-ignition operation according to the load of the engine. A spark ignition type internal combustion engine operated by selectively switching between spark ignition operation by a spark plug and an actual compression ratio that changes an actual compression ratio determined by operating conditions of the intake valve in accordance with operating conditions of the engine. Variable means, the actual compression ratio variable means,
The operation is performed so as to reduce the actual compression ratio on the high load region side of the region where the self-ignition operation is performed.

According to a third aspect of the present invention, an intake valve for opening and closing an opening of an intake port communicating with the combustion chamber and an exhaust valve for opening and closing an opening of an exhaust port communicating with the combustion chamber are provided. At least one exhaust valve is opened in an exhaust stroke and an intake stroke to allow exhaust gas in an exhaust port to flow back into the combustion chamber to perform self-ignition combustion, and to perform self-ignition operation according to the load of the engine. A spark ignition type internal combustion engine operated by selectively switching between spark ignition operation by a spark plug and an actual compression ratio that changes an actual compression ratio determined by operating conditions of the intake valve in accordance with operating conditions of the engine. Variable means, the actual compression ratio variable means,
It operates to increase the actual compression ratio on the low load region side of the region where the self-ignition operation is performed, and decrease the actual compression ratio on the high load region side of the region where the self-ignition operation is performed.
It has a configuration.

According to a fourth aspect of the present invention, in the spark ignition type internal combustion engine according to any one of the first to third aspects, the actual compression ratio variable means is configured to reduce a region in which a spark ignition operation is performed by a spark plug. It operates to reduce the actual compression ratio in the load region.

According to a fifth aspect of the present invention, in the spark ignition type internal combustion engine according to any one of the first to fourth aspects, the actual compression ratio variable means is configured to increase a region in which a spark ignition operation is performed by a spark plug. It is configured to operate to increase the actual compression ratio in the rotation high load region.

According to a sixth aspect of the present invention, in the spark ignition type internal combustion engine according to any one of the first to fifth aspects, the actual compression ratio variable means reduces a region in which a spark ignition operation is performed by a spark plug. It operates so as to reduce the actual compression ratio in a high rotational load region.

According to a seventh aspect of the present invention, in the spark ignition type internal combustion engine according to any one of the first to third aspects, the actual compression ratio variable means changes a closing timing of the intake valve. Under the operating condition of the engine in which the exhaust valve is opened during the intake stroke, the valve closing timing variable mechanism is configured such that, as the engine operating region approaches the low load side, the intake air intake increases as compared with the high load side. The valve is operated so as to make the valve closing timing earlier.

In the spark ignition type internal combustion engine according to the present invention, the variable valve closing timing mechanism may control the rotation of the crankshaft with respect to the rotation of the crankshaft.
The rotational phase shift of an intake camshaft having an intake valve cam for opening and closing the intake valve is changed.

According to a ninth aspect of the present invention, in the spark ignition type internal combustion engine according to any one of the first to third aspects, the actual compression ratio varying means varies the lift amount of the intake valve. The variable valve lift mechanism is configured to increase the lift amount of the intake valve as the operating region of the engine approaches the low load side under the operating condition of the engine in which the exhaust valve is opened in the intake stroke. It operates so that the lift amount of the intake valve is reduced as the operating range of the engine approaches the high load side.

Also, as described in claim 10,
10. The spark ignition type internal combustion engine according to claim 9, wherein the variable valve lift mechanism includes a plurality of intake valve cams having different cam heights for driving the intake valve to open and close with respect to the intake camshaft. Selectively switching and operating the plurality of intake valve cams according to the operating conditions of
It has a configuration.

Further, as described in claim 11,
The spark ignition type internal combustion engine according to any one of claims 1 to 10, further comprising a check valve provided in the middle of the intake port to prevent the gas introduced into the combustion chamber from flowing toward the upstream side of the intake port. It has a configuration provided.

Also, as described in claim 12,
In the spark ignition type internal combustion engine according to any one of claims 1 to 11, the actual compression ratio varying means changes the actual compression ratio in a range of 9 to 12.

Further, as described in claim 13, in the spark ignition type internal combustion engine according to claims 1 to 12, the volume of the combustion chamber when the piston is located at the top dead center and the piston is moved from the bottom dead center. The theoretical compression ratio calculated from the stroke volume at the time of moving to the top dead center is set in the range of 12 to 18.

[0022]

According to the spark ignition type internal combustion engine of the first aspect of the present invention, the actual compression ratio variable means for changing the actual compression ratio of the gas introduced into the combustion chamber in accordance with the operating conditions of the engine. Since the actual compression ratio is increased in the low-load operation range of the engine, stable compression self-ignition combustion can be performed in the low-load operation range of the engine, thereby reducing the emission of HC, NOx, and the like. The amount can be greatly reduced.

That is, in the low-load operation region of the engine, a mixture of fresh air and fuel and a relatively low-temperature backflow exhaust gas flowing backward from the exhaust port during the intake stroke are introduced into the combustion chamber. Will be done. At this time, since the actual compression ratio is increased (increased) by the actual compression ratio variable means, the backflow exhaust gas having a relatively low temperature rises to a sufficiently high temperature exceeding the ignition temperature of the air-fuel mixture in the adiabatic compression change. The compressed self-ignition combustion of the air-fuel mixture occurs starting from the interface between the high-temperature backflow exhaust gas and the air-fuel mixture.

Therefore, stable compression auto-ignition combustion can be realized in the low load operation range of the engine, and HC, N
Ox emissions can be significantly reduced.

According to the spark ignition type internal combustion engine of the second aspect of the present invention, the actual compression ratio variable means for changing the actual compression ratio of the gas introduced into the combustion chamber in accordance with the operating conditions of the engine is used. Since the actual compression ratio is reduced on the high load operation region of the engine, stable compression self-ignition combustion can be performed in the high load operation region of the engine.
As a result, the emission amount of HC, NOx, and the like can be significantly reduced.

That is, in the high-load operation region of the engine, a mixture of fresh air and fuel and a relatively high-temperature backflow exhaust gas flowing backward from the exhaust port are introduced into the combustion chamber during the intake stroke, and the adiabatic compression is performed by the subsequent compression stroke. Will be done.
At this time, since the actual compression ratio is reduced (decreased) by the actual compression ratio variable means, the backflow exhaust gas having a relatively high temperature is
In the adiabatic compression change, gentle compression auto-ignition combustion of the air-fuel mixture starts at the interface between the backflow exhaust gas and the air-fuel mixture without reaching a high temperature and a high pressure at which knocking occurs.

Accordingly, stable compression auto-ignition combustion can be realized in the high load operation range of the engine, and HC, N
Ox emissions can be significantly reduced.

According to the spark ignition type internal combustion engine of the third aspect of the present invention, the actual compression ratio variable means for changing the actual compression ratio of the gas introduced into the combustion chamber according to the operating conditions of the engine is used. In the low load operation range, the actual compression ratio is increased, and in the high load operation range, the actual compression ratio is decreased, so that stable compression self-ignition combustion can be performed in a wide operating range of the engine. Thus, the emission amount of HC, NOx, etc. can be significantly reduced.

That is, in the low-load operation region of the engine, in the intake stroke, a mixture of fresh air and fuel and the relatively low-temperature backflow exhaust gas flowing backward from the exhaust port are introduced into the combustion chamber, and the adiabatic compression is performed by the subsequent compression stroke. Will be done.
At this time, the actual compression ratio is increased (increased) by the actual compression ratio variable means.
In the adiabatic compression change, the temperature of the mixture is raised to a sufficiently high temperature exceeding the ignition temperature of the mixture, and compression self-ignition combustion of the mixture occurs at the interface between the high-temperature backflow exhaust and the mixture. Become.

On the other hand, in the high load operation region of the engine, a mixture of fresh air and fuel and a relatively high temperature backflow exhaust gas flowing backward from the exhaust port are introduced into the combustion chamber during the intake stroke.
In the subsequent compression stroke, adiabatic compression is performed. At this time, the actual compression ratio is lowered (decreased) by the actual compression ratio variable means.
Without reaching high pressure, gentle compression self-ignition combustion of the air-fuel mixture will occur starting from the interface between the backflow exhaust and the air-fuel mixture.

Therefore, stable compression auto-ignition combustion can be realized in the high load operation range of the engine, and HC, N
Ox emissions can be significantly reduced.

According to the spark ignition type internal combustion engine of the fourth aspect of the present invention, the actual compression ratio is reduced (decreased) by the actual compression ratio variable means in a low load operation region in which the engine performs the spark ignition operation. Therefore, pumping loss due to compression resistance is reduced, thereby improving fuel efficiency.

According to the spark ignition type internal combustion engine according to the fifth aspect of the present invention, the actual compression ratio is increased (increased) by the actual compression ratio variable means in the high-speed high-load operation region in which the engine performs the spark ignition operation. ), The filling efficiency is increased and the output can be improved.

According to the spark ignition type internal combustion engine according to the sixth aspect of the present invention, the actual compression ratio is reduced (decreased) by the actual compression ratio variable means in the low-rotation, high-load operation region in which the engine performs the spark ignition operation. ), Stable combustion can be performed without knocking.

According to the spark ignition type internal combustion engine of the seventh aspect of the present invention, a variable valve closing timing mechanism for changing the valve closing timing of the intake valve is employed as the actual compression ratio variable means, and the exhaust valve operates during the intake stroke. Under the operating condition in which the valve is opened, that is, in the operating region in which the compression self-ignition combustion is performed, the closing timing of the intake valve is advanced earlier on the lower load side (or the closing timing of the intake valve is delayed on the higher load side). A high compression ratio can be realized on the low load operation side and a low compression ratio can be realized on the high load operation side. As a result, stable compression self-ignition combustion can be performed in a wide operating range of the engine.
The emission amount of NOx and the like can be significantly reduced.

According to the spark ignition type internal combustion engine of the present invention, as the variable valve closing timing mechanism constituting the actual compression ratio variable means, the rotational phase of the intake camshaft is shifted with respect to the rotation of the crankshaft. The mechanism that changes the compression ratio allows the actual compression ratio to be changed using existing technology without the need to design a new mechanism, etc., thereby enabling stable compression self-ignition combustion. Can be.

According to the spark ignition type internal combustion engine of the ninth aspect of the present invention, a variable valve lift mechanism for changing the lift amount of the intake valve is employed as the actual compression ratio variable means, and the exhaust valve is opened during the intake stroke. Under the operating conditions that are performed, that is, in the operation region in which the compression auto-ignition combustion is performed, the lift amount of the intake valve is increased toward the lower load side, and the lift amount of the intake valve is decreased toward the higher load side, so that the low load operation side is achieved. Thus, it is possible to realize a high compression ratio and a low compression ratio on the side of high load operation, whereby stable compression self-ignition combustion can be performed in a wide operating range of the engine.
The emission amount of NOx and the like can be significantly reduced.

According to the spark ignition type internal combustion engine of the tenth aspect of the present invention, a plurality of intake valve cams having different cam heights are selectively switched as a variable valve lift mechanism constituting the actual compression ratio variable means. The actual compression ratio can be changed using the existing technology without the need for designing a new mechanism, etc.
Stable compression self-ignition combustion can be performed.

According to the spark ignition type internal combustion engine of the present invention, since the check valve is provided in the intake port, the backflow exhaust gas introduced into the combustion chamber flows out toward the intake port. The flow into the combustion chamber again and mixing with the air-fuel mixture can be suppressed, and the stratified distribution state of the air-fuel mixture and the backflow exhaust gas can be maintained and formed in the combustion chamber. Thereby, the low load limit of the compression self-ignition combustion can be expanded.

According to the spark ignition type internal combustion engine of the twelfth and thirteenth aspects of the present invention, stable compression self-ignition combustion can be realized in a wide operating range of the engine.
As a result, the emission amount of HC, NOx, and the like can be significantly reduced.

[0041]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 and 2 are a longitudinal sectional view and a plan view, respectively, showing a schematic configuration of a spark ignition type internal combustion engine (gasoline engine) according to the present invention. In this gasoline engine 10,
As shown in FIGS. 1 and 2, the combustion chamber A includes a cylindrical bore side surface 11 a of a cylinder block 11, a crown surface 12 a of a piston 12 reciprocating along the bore side surface 11 a, and a lower surface 13 a of a cylinder head 13. The cylinder head 13 has a first intake port 14 and a second intake port 14 for introducing a mixture of fresh air and fuel into the combustion chamber A.
An intake port 15, a first exhaust port 16 and a second exhaust port 1 for discharging exhausted combustion from the combustion chamber A;
7 are formed. The cylinder head 13
The first intake valve 18 opens and closes the opening 14a of the first intake port 14, the second intake valve 19 opens and closes the opening 15a of the second intake port 15, and the opening 16a of the first exhaust port 16. A first exhaust valve 20 for opening / closing the opening and a second exhaust valve 21 for opening / closing the opening 17a of the second exhaust port 17 are reciprocally mounted. A spark plug 22 for performing spark ignition is attached to the center.

The first intake port 14 and the second intake port 15 have substantially the same shape and the same inclination angle so as to communicate with the combustion chamber A, and the upstream side merges with each other to form one intake port. An electromagnetic fuel injection valve 23 for injecting fuel is mounted in the middle of the area where the first intake port 14 and the second intake port 15 merge.

The first intake port 14 and the second intake port 15 are not limited to the above-described configuration. For example, the first intake port 14 and the second intake port 15 may be located on the first intake port 14 side in an independent area of each intake port. It is also possible to adopt a configuration in which the electromagnetic fuel injection valve 23 is mounted, and a swirl control valve (not shown) that is opened and closed according to the operating conditions of the engine is rotatably mounted on the second intake port 15 side. .

The first exhaust port 16 and the second exhaust port 17 are independent exhaust ports having substantially the same shape and having the same inclination angle and extending obliquely upward from the combustion chamber A in a substantially linear manner. It is formed as a port.

As shown in FIG. 1, an intake valve driving mechanism for opening and closing the first intake valve 18 and the second intake valve 19 includes an intake rocker shaft 2 fixed to a cylinder head 13.
5 and is swingably attached to the first intake valve 18 and the second intake valve 18.
An intake side rocker arm 27 having an abutment portion 27a that abuts on the upper end of the intake valve 19, is rotatably supported by the cylinder head 13, and comes into contact with the intake side rocker arm 27. Intake valves 18, 19
The intake camshaft 29 and the like are provided with an intake valve cam 29a that operates to open the valve.

The first exhaust valve 20 and the second exhaust valve 21
The exhaust valve drive mechanism that drives the opening and closing of the cylinder head 13
The exhaust-side rocker arm 28 and the cylinder head 13 each having a contact portion 28a that is swingably attached to an exhaust-side rocker shaft 26 fixed to the first portion and abuts on upper ends of the first exhaust valve 20 and the second exhaust valve 21, respectively. And a first exhaust valve cam 30a which contacts the exhaust side rocker arm 28 and operates to open the first and second exhaust valves 20 and 21 in the exhaust stroke, and the first in the intake stroke. And an exhaust camshaft 3 having a second exhaust valve cam 30b operable to open the second exhaust valves 20 and 21.
0 or the like. The second exhaust valve cam 30
b may be configured to open only one of the first and second exhaust valves 20, 21.

At the end of the intake camshaft 29,
A variable valve closing timing mechanism 40 is provided as actual compression ratio variable means for changing the actual compression ratio in accordance with the operating conditions of the engine. As shown in FIG. 3, the valve closing timing variable mechanism 40 is a sleeve 4 fixed to an end of the intake camshaft 29 by a bolt 41 and having outer teeth 42 a on an outer peripheral portion.
2, a driven sprocket 43 having a cylindrical shape and having inner teeth 43a on its inner peripheral portion, and a rotational driven force of a crankshaft (not shown) transmitted through a transmitting means such as a timing chain. Internal teeth 4
A cylindrical gear 44 spirally meshing with the inner teeth 43a of the driven sprocket 43 and the outer teeth 42a of the sleeve 42 having the outer teeth 4a and the outer teeth 44b; and moving the cylindrical gear 44 in the axial direction of the intake camshaft 29. It is composed of moving means and the like.

That is, by reciprocating the cylindrical gear 44, the driven sprocket 43 and the intake camshaft 29 can be relatively rotated, and by this relative rotation, the crankshaft can be rotated. In contrast, the rotational phase shift of the intake camshaft 29 can be changed.

Next, the gasoline engine 1 according to this embodiment
The operation of 0 will be described.

FIG. 4 is a map showing the assignment of the actual compression ratio to the rotation and load of the engine. Here,
The actual compression ratio is defined as the combustion chamber volume when the piston 12 is at the compression top dead center (TDC) and the stroke volume calculated from the piston stroke from the closing timing of the intake valves 18 and 19 to the compression top dead center. It is required.

First, in the region where the compression self-ignition operation is performed in FIG. 4, during the exhaust stroke, as shown in FIG.
The exhaust valve 20 and the second exhaust valve 21 are both pushed down to open, and the burned gas in the combustion chamber A is exhausted to the outside as exhaust through both the first exhaust port 16 and the second exhaust port 17. Is done. In the subsequent intake stroke, FIG.
As shown in (b), the first intake valve 18 and the second intake valve are both pushed down and opened by the operation of the intake valve cam 29a, and the fuel injected from the fuel injection valve 23 and the upstream of the intake system are opened. A mixture Gmix with the introduced fresh air (air) flows from the first intake port 14 and the second intake port 15 to the combustion chamber A.
Introduced within. In this intake stroke, the second
By the operation of the exhaust valve cam 30b, the first exhaust valve 20 and the second exhaust valve 21 are pushed down again to open, and the exhaust Gi remaining in the first exhaust port 16 and the second exhaust port 17 is opened.
n flows back into the combustion chamber A.

At this time, the air-fuel mixture Gmix is unevenly distributed on the intake valve side in the combustion chamber A, and the backflow exhaust gas Gix is unevenly distributed on the exhaust valve side in the combustion chamber A to form a stratified distribution state.

Here, the lift characteristics of the first exhaust valve 20 and the second exhaust valve 21 in the exhaust stroke and the intake stroke are as shown in FIG.

In the subsequent compression stroke, as shown in FIG. 5C, the intake valve cam 29a and the second exhaust cam 30
When the operation of b is completed, the first and second intake valves 18 and 19 and the first and second intake valves 20 and 21 are closed, and the piston 12 rises while the stratified distribution state is maintained. , FIG.
As shown in (d), the mixture Gmix and the backflow exhaust Gi
A compression of n is performed. In this compression stroke, the temperature of the backflow exhaust Gin unevenly distributed in the combustion chamber A rises to a temperature exceeding the ignition temperature of the air-fuel mixture Gmix due to adiabatic compression change, and the interface between the heated backflow exhaust Gin and the air-fuel mixture Gmix. , The compressed air-fuel mixture Gmix generates compression self-ignition combustion. In the subsequent expansion stroke, the piston 12 is depressed by the explosive force caused by the compression self-ignition combustion, and returns to the exhaust stroke again, and the above-described operation is repeated.

In this compression self-ignition operation region, a variable valve closing timing mechanism for changing the valve closing timing of the first intake valve 18 and the second intake valve 19 is operated, as shown in FIG. 6B. In addition, control is performed such that the valve closing timing is advanced on the low load side of the engine, while the valve closing timing is delayed on the high load side of the engine. As a result, the actual compression ratio increases on the low load side of the engine, while the actual compression ratio decreases on the high load side of the engine. Therefore, gentle and stable compression auto-ignition combustion occurs over a wide range of load.

In the region where the spark plug 22 performs the spark ignition operation in FIG. 4, during the exhaust stroke, as shown in FIG. 7A, the first exhaust valve cam 30a is operated to activate the first exhaust valve 20a. The second exhaust valve 21 and the second exhaust valve 21 are both pushed down to open, and the burned gas in the combustion chamber A is exhausted to the outside as exhaust gas through the first exhaust port 16 and the second exhaust port 17. Here, the lift characteristics of the first exhaust valve 20 and the second exhaust valve 21 in this exhaust stroke are shown in FIG.
As shown in FIG. In the subsequent intake stroke, as shown in FIG. 7B, the operation of the first exhaust valve cam 30a ends, the first and second exhaust valves 20, 21 close, and the operation of the intake valve cam 29a operates. As a result, both the first intake valve 18 and the second intake valve 19 are pushed down to open, and a mixture Gmix of fuel injected from the combustion injection valve 23 and fresh air (air) introduced from the upstream of the intake system. Are introduced into the combustion chamber A from the first intake port 14 and the second intake port 15, respectively. In the intake stroke, as described above, the first and second exhaust valves 20, 21 are connected to the second exhaust valve cam 30b.
Is not driven to open, and the valve is in a closed state. The closed state of the first and second exhaust valves 20, 21 is as follows.
A known cam selection mechanism (not shown) provided on the exhaust side rocker arm 28 is operated so that the operating force of the second exhaust valve cam 30b is not transmitted to the first and second exhaust valves 20 and 21. Maintained by Then, the air-fuel mixture Gmix introduced in the intake stroke is uniformly distributed in the combustion chamber A.

In the subsequent compression stroke, as shown in FIG. 7 (c), the operation of the intake valve cam 29a ends, the first and second intake valves 18, 19 close, and the mixture Gmix
The piston 12 rises while maintaining the homogeneous distribution of
This air-fuel mixture Gmix is compressed as shown in FIG.
In the vicinity of the end of the compression stroke, spark ignition is performed by the spark plug 22, and the mixture Gmix produces homogeneous combustion. The piston 12 is pushed down in the subsequent expansion stroke due to the explosive power of the spark ignition combustion,
Returning to the exhaust stroke again, the above-described operation is repeated.

In the spark ignition operation region,
The variable valve closing timing mechanism for changing the valve closing timing of the first intake valve 18 and the second intake valve 19 is operated, as shown in FIG. In the region, the valve closing timing is controlled to be delayed, while in the high rotation and high load region, the valve closing timing is controlled to be advanced.
As a result, the actual compression ratio decreases in a low load region such as an idling operation and a low rotation high load region, whereas the actual compression ratio increases in a high rotation high load region. Therefore, pumping loss can be reduced in a low-load region such as idling operation, knocking can be avoided in a low-rotation high-load region, and the filling efficiency can be increased in a high-rotation high-load region. it can.

FIG. 9 shows an embodiment in which a variable valve lift mechanism for changing the lift of the intake valve is employed as the actual compression ratio variable means. This variable valve lift mechanism 4
Reference numeral 9 denotes a switch for switching the lift characteristic of the intake valve between two stages. The intake camshaft 50 includes a low lift cam 50a having a small lift amount and a large lift amount as intake valve cams having different cam heights. A high lift cam 50b is formed side by side, and an intake side rocker arm swingably attached to the intake side rocker shaft 51 is provided with upper ends of the first intake valve 18 and the second intake valve 19, respectively. A main rocker arm 52 that abuts, a sub rocker arm 54 swingably attached to the main rocker arm 52 via a sub rocker shaft 53, and a sub rocker arm 54
55, which is always urged upward, and an engagement lever 57 which is swingably attached to the main rocker arm 52 via a pin 56 and can engage with the sub rocker arm 54.
And a spring 58 for urging the engaging lever 57 in the disengaging direction, a hydraulic piston 59 for pressing the engaging lever 57 in the engaging direction, and the like.

That is, when high-pressure oil is not supplied to the hydraulic piston 59, the engaging lever 57 is disengaged from the auxiliary rocker arm 54. When the intake camshaft 50 rotates in this state, the high-lift cam 50b is The pushed sub rocker arm 54 swings freely with respect to the main rocker arm 52, and the main rocker arm 52 pushed by the low lift cam 50a pushes down the first and second intake valves 18,19. On the other hand, when high-pressure oil is supplied to the hydraulic piston 59, the engagement lever 57 is in a locked state in which the auxiliary rocker arm 54 is prevented from swinging with respect to the main rocker arm 52 by engaging the auxiliary rocker arm 54. When the camshaft 50 rotates, the auxiliary rocker arm 54 pushed by the high lift cam 50b pushes down the first and second intake valves 18 and 19 via the main rocker arm 52.

Therefore, by controlling the operation timing of the hydraulic piston 59 in accordance with the operating conditions of the engine, the first
The lift amounts of the first and second intake valves 18 and 19 can be changed. For example, in a region where a so-called compression auto-ignition operation is performed in which the first and second exhaust valves 20 and 21 are opened in the intake stroke, FIG. As shown in FIG. 10, the hydraulic piston 59 is operated to increase the lift amount of the first and second intake valves 18 and 19 on the low load side, and the lift of the first and second intake valves is increased on the high load side. By disabling the hydraulic piston 59 so as to reduce the amount, the actual compression ratio can be increased on the low load side and decreased on the high load side.

FIGS. 11 and 12 are a longitudinal sectional view and a plan view showing another embodiment of the spark ignition type internal combustion engine (gasoline engine) according to the present invention. This gasoline engine 6
0, the gas introduced into the combustion chamber A is supplied to the gasoline engine 10 according to the above-described embodiment in the confluence region of the first and second intake ports 14 and 15 with the first and second intake ports 14. , 15 are provided with a check valve 61 for preventing the outflow toward the upstream side. The check valve 61 includes a frame body 62 having a substantially triangular prism shape, and a total of six cantilever valve bodies 63 for opening and closing the six openings 62a formed in the frame body 62, respectively. Is formed.

Then, the first and second intake ports 14, 1
When fuel and fresh air are introduced from 5, the valve body 63 bends to open the opening 62a. On the other hand, when the air-fuel mixture and the backflow exhaust are going to flow out of the combustion chamber A, the valve body 63 is closed. The opening 62a is closed by the spring returning force.

Accordingly, during the period when both the first and second intake valves 18 and 19 and the first and second exhaust valves 20 and 21 are open, the first and second intake ports 14 and 15 and the first and second intake ports 14 and 15 are connected. Due to the pressure difference generated between the second exhaust ports 16 and 17, the backflow exhaust Gin introduced into the combustion chamber A flows toward the upstream side of the first and second intake ports 14 and 15, and flows into the combustion chamber again. And mixing with the air-fuel mixture Gmix can be suppressed. As a result, in the combustion chamber A,
The stratified distribution state of the mixture Gmix and the backflow exhaust Gin can be reliably formed, and the low load limit of the compression self-ignition combustion can be expanded.

FIG. 13 is a diagram showing the effect of the actual compression ratio on compression self-ignition combustion. As shown in the figure, in the relationship between the actual compression ratio and the charging efficiency, a region (L) where the compression self-ignition combustion is not performed, a region (M) where the compression self-ignition combustion is performed, and a region after the compression self-ignition. If the actual compression ratio is smaller than 9, the compression auto-ignition combustion is not performed (L), and the charging efficiency is about 50% to about 20%. In the partial load region, when the actual compression ratio is increased from the high load side to the low load side, the engine can be operated in the region (M) where the compression self-ignition combustion is performed. It is possible to realize stable compression auto-ignition combustion in a low load region excluding the idling operation.

The volume of the combustion chamber A when the piston 12 is located at the top dead center (TDC) and the stroke volume when the piston 12 moves from the bottom dead center (BDC) to the top dead center (TDC) are determined. If the theoretical compression ratio (mechanical compression ratio) determined by calculation is set to be in the range of 12 to 18, the actual compression ratio can be easily changed in the range of 9 to 12, and as a result, stable Compression self-ignition combustion can be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a spark ignition type internal combustion engine according to the present invention.

FIG. 2 is a plan view showing one embodiment of a spark ignition type internal combustion engine according to the present invention.

FIG. 3 is a longitudinal cross-sectional view showing a variable valve closing timing mechanism as an example of an actual compression ratio variable unit that forms a part of the spark ignition type internal combustion engine according to the present invention.

FIG. 4 is a setting map of an actual compression ratio in a relationship between an engine speed and an engine load.

FIGS. 5A and 5B show the state of the engine in a compression auto-ignition operation region, where FIG. 5A shows an exhaust stroke, FIG. 5B shows an intake stroke, FIG. 5C shows a compression stroke, and FIG. It is a longitudinal cross-sectional view which shows each state.

FIGS. 6A and 6B show valve lift characteristics with respect to a crank angle in a compression self-ignition operation region, where FIG. 6A shows valve lift characteristics of first and second exhaust valves, and FIG. 6B shows first and second intake valves. FIG. 5 is a view showing valve lift characteristics of the present invention.

FIGS. 7A and 7B show the state of the engine in a spark ignition operation region, wherein FIG. 7A shows an exhaust stroke, FIG.
(C) is a longitudinal cross-sectional view showing each state near the compression top dead center, and (d) is a compression stroke.

FIGS. 8A and 8B show valve lift characteristics with respect to a crank angle in a spark ignition operation region, wherein FIG. 8A shows valve lift characteristics of first and second exhaust valves, and FIG. 8B shows valve lift characteristics of first and second intake valves. It is a figure showing valve lift characteristics.

FIG. 9 is an exploded perspective view showing a variable valve lift mechanism as another example of the actual compression ratio variable means which constitutes a part of the spark ignition type internal combustion engine according to the present invention.

FIG. 10 is a view showing valve lift characteristics of first and second intake valves with respect to a crank angle in a variable valve lift mechanism.

FIG. 11 is a longitudinal sectional view showing another embodiment of the spark ignition type internal combustion engine according to the present invention.

FIG. 12 is a plan view showing another embodiment of the spark ignition type internal combustion engine according to the present invention.

FIG. 13 is a diagram showing the influence of the relationship between the actual compression ratio and the charging efficiency on compression self-ignition.

[Explanation of symbols]

 Reference Signs List 10 gasoline engine 11 cylinder block 11a bore side surface 12 piston 12a crown surface 13 cylinder head 13a bottom surface 14 first intake port 14a opening 15 second intake port 15a opening 16 first exhaust port 16a opening 17 second exhaust port 17a opening Part 18 First intake valve 19 Second intake valve 20 First exhaust valve 21 Second exhaust valve 22 Spark plug 23 Fuel injection valve 25 Intake side rocker shaft 26 Exhaust side rocker shaft 27 Intake side rocker arm 28 Exhaust side rocker arm 29 Intake cam Shaft 29a Inlet valve cam 30 Exhaust camshaft 30a First exhaust valve cam 30b Second exhaust valve cam 40 Variable valve closing timing mechanism (actual compression ratio variable means) 41 Bolt 42 Sleeve 42a Outer teeth 43 Follower sprocket 43a Inner Tooth 4 Cylindrical gear 44a Internal teeth 44b External teeth 49 Variable valve lift mechanism (actual compression ratio variable means) 50 Intake camshaft 50a Low lift cam 50b High lift cam 51 Intake side rocker shaft 52 Main rocker arm 53 Secondary rocker shaft 54 Secondary Rocker arm 55 Spring 56 Pin 57 Engagement lever 58 Spring 59 Hydraulic piston 60 Gasoline engine 61 Check valve 62 Frame 62a Opening 63 Valve body

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 25/07 F02M 25/07 B 510 510B

Claims (13)

[Claims] An exhaust valve for opening and closing an opening of an intake port communicating with the combustion chamber; and an exhaust valve for opening and closing an opening of an exhaust port communicating with the combustion chamber. The valve is opened during the intake stroke to allow the exhaust gas in the exhaust port to flow back into the combustion chamber to perform self-ignition combustion, and to selectively perform self-ignition operation and spark ignition operation with a spark plug according to the load of the engine. A spark ignition type internal combustion engine that is operated by switching, comprising: an actual compression ratio variable unit that changes an actual compression ratio determined by an operating condition of the intake valve according to an operating condition of the engine; The means operates to increase the actual compression ratio on the low load region side of the region in which the self-ignition operation is performed. 2. An intake valve for opening and closing an opening of an intake port communicating with the combustion chamber, and an exhaust valve for opening and closing an opening of an exhaust port communicating with the combustion chamber, wherein at least one exhaust valve has an exhaust stroke and The valve is opened during the intake stroke to allow the exhaust gas in the exhaust port to flow back into the combustion chamber to perform self-ignition combustion, and to selectively perform self-ignition operation and spark ignition operation with a spark plug according to the load of the engine. A spark ignition type internal combustion engine that is operated by switching, comprising: an actual compression ratio variable unit that changes an actual compression ratio determined by an operating condition of the intake valve according to an operating condition of the engine; The means operates to reduce the actual compression ratio on the high load region side of the region in which the self-ignition operation is performed. 3. An exhaust valve for opening and closing an opening of an intake port communicating with the combustion chamber, and an exhaust valve for opening and closing an opening of an exhaust port communicating with the combustion chamber, wherein at least one exhaust valve has an exhaust stroke and The valve is opened during the intake stroke to allow the exhaust gas in the exhaust port to flow back into the combustion chamber to perform self-ignition combustion, and to selectively perform self-ignition operation and spark ignition operation with a spark plug according to the load of the engine. A spark ignition type internal combustion engine that is operated by switching, comprising: an actual compression ratio variable unit that changes an actual compression ratio determined by an operating condition of the intake valve according to an operating condition of the engine; The means is operable to increase the actual compression ratio on the low load region side of the region where the self-ignition operation is performed, and to decrease the actual compression ratio on the high load region side of the region where the self-ignition operation is performed. A spark ignition type internal combustion engine characterized by the following. 4. The actual compression ratio variable means operates to reduce the actual compression ratio in a low load region where a spark ignition operation is performed by a spark plug. A spark ignition type internal combustion engine according to any one of the preceding claims. 5. The actual compression ratio varying means operates so as to increase the actual compression ratio in a high rotation and high load region where a spark ignition operation is performed by a spark plug. 4. The spark ignition type internal combustion engine according to any one of 4 above. 6. The actual compression ratio varying means operates to reduce the actual compression ratio in a low rotation and high load region where a spark ignition operation is performed by a spark plug. 5. The spark ignition type internal combustion engine according to any one of 5. 7. The variable actual compression ratio means comprises a variable valve closing timing mechanism for changing a valve closing timing of the intake valve, wherein the variable valve closing timing mechanism is such that the exhaust valve is opened during an intake stroke. 4. The engine according to claim 1, wherein, under an operating condition of the engine, the closing timing of the intake valve is advanced as the operating range of the engine approaches the low load side as compared with the high load side. A spark-ignition internal combustion engine according to one of the preceding claims. 8. The variable valve closing timing mechanism changes a rotational phase shift of an intake camshaft having an intake valve cam for opening and closing the intake valve with respect to the rotation of the crankshaft. The spark ignition type internal combustion engine according to claim 7, wherein: 9. The variable actual valve lift mechanism comprising a variable valve lift mechanism for changing a lift amount of the intake valve, wherein the variable valve lift mechanism operates an engine in which the exhaust valve is opened during an intake stroke. Under the conditions, it operates so that the lift amount of the intake valve increases as the operation region of the engine approaches the low load side, and the lift amount of the intake valve decreases as the operation region of the engine approaches the high load side. The spark ignition type internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine operates in the following manner. 10. The variable valve lift mechanism includes a plurality of intake valve cams having different cam heights for driving the intake valves to open and close with respect to the intake camshaft. The spark ignition type internal combustion engine according to claim 9, wherein the plurality of intake valve cams are selectively switched to operate. 11. A check valve for preventing a gas introduced into the combustion chamber from flowing toward an upstream side of the intake port in the middle of the intake port. Item 11. The spark ignition type internal combustion engine according to any one of Items 1 to 10. 12. The spark ignition type internal combustion engine according to claim 1, wherein said actual compression ratio varying means changes the actual compression ratio in a range of 9 to 12. 13. The theoretical compression ratio calculated from the combustion chamber volume when the piston is located at the top dead center and the stroke volume when the piston moves from the bottom dead center to the top dead center is 1
2. The method according to claim 1, wherein the value is set in a range of 2 to 18.
13. The spark-ignition internal combustion engine according to any one of items 12 to 12.