JP2992967B2 - engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine, that is, an internal combustion engine, and more particularly, to an engine having a high thermal efficiency.

[0002]

2. Description of the Related Art In an engine, that is, an internal combustion engine, mechanical work is taken out by utilizing a pressure increase accompanying combustion of fuel supplied to a combustion chamber. Therefore, the greater the pressure rise ΔP (in-cylinder pressure rise) accompanying combustion is, the better the work is performed.

[0003] Now, the calorific value Q of the fuel is expressed by the following equation. Q = Cv · G · ΔT (1)

Here, Cv: constant volume specific heat G: mass of air-fuel mixture charged into the combustion chamber ΔT: temperature rise due to combustion (increase in cylinder temperature)

When the above equation (1) is modified, the following equation (2) is obtained. ΔT = Q / Cv · G (2) As understood from the equation (2), when Q and G are constant, ΔT increases as Cv decreases.

It is known that the constant volume specific heat Cv increases substantially in proportion to the in-cylinder temperature T (see FIG. 1). In other words, the smaller the in-cylinder temperature T, the lower the constant volume specific heat C
v is small. Therefore, the lower the in-cylinder temperature T, the greater the increase in the in-cylinder temperature ΔT due to combustion.

Here, as the rise ΔT of the in-cylinder temperature becomes larger,
Since the cylinder pressure rises greatly (大 き く P is large),
As the in-cylinder temperature T decreases, the in-cylinder pressure increases ΔP. In other words, put the same amount of fuel,
Assuming that the obtained calorific value is the same, the smaller the in-cylinder temperature T, the greater the in-cylinder pressure increase ΔP, and thus the better the work (the better the thermal efficiency).

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine in which the in-cylinder temperature is reduced to improve the thermal efficiency.

[0009]

According to the present invention, there is provided a sub-chamber formed in an engine body and opening to a combustion chamber, and a sub-chamber for opening and closing the opening of the sub-chamber. A sub-chamber valve, which is opened in the middle of the compression stroke and closed during the end of the compression stroke or the beginning of the explosion stroke.

[0010]

According to the above arrangement, the hot air-fuel mixture accompanying the compression is sealed in the sub-chamber and cooled in the sub-chamber. Then, the air-fuel mixture cooled in the sub-chamber is replaced with a part of the air-fuel mixture in the combustion chamber in the next compression stroke, and as a result, the air-fuel mixture in the combustion chamber is cooled (decrease in cylinder temperature). Therefore, the higher the temperature of the air-fuel mixture introduced into the sub-chamber, the greater the cooling effect in the sub-chamber, which makes it possible to greatly reduce the in-cylinder temperature.

When considering the closing timing of the sub-chamber valve, if the temperature rise caused by compressing the air-fuel mixture in the combustion chamber is to be utilized to the utmost, the closing timing of the sub-chamber valve is determined as the compression top dead center. do it. Alternatively, in order to make maximum use of the pressure increase due to combustion, it is better to close the sub chamber valve as late as possible (the crank angle at which the combustion maximum pressure is reached is about 30 deg after compression top dead center (ATDC)).

Here, the actual combustion state fluctuates greatly in each cycle as shown in the acupressure diagram of FIG.
Therefore, if the sub-chamber valve is opened until the in-cylinder pressure deviation (variation) is large, the pressure, density, and temperature of the air-fuel mixture confined in the sub-chamber will fluctuate in each cycle. Not preferred.

Considering FIG. 2 from this viewpoint, in the example of the engine specifications and operating conditions shown in FIG. 2, the timing at which the pressure fluctuation in the combustion chamber occurs is about 20 deg after the ignition timing.
After the time has passed. Therefore, if the sub-chamber valve is closed immediately before the deviation (variation) in the pressure rise due to combustion, it is possible to increase the cooling effect of the air-fuel mixture while suppressing the influence of the combustion fluctuation.

On the other hand, if the influence of the pressure fluctuation due to combustion is to be prevented, the sub-chamber valve may be closed near the ignition timing. That is, the sub-chamber valve may be closed at the end of the compression stroke.

The timing of opening the sub-chamber valve may be determined in detail in relation to the timing of closing the sub-chamber valve. That is, even if the sub-chamber valve is opened, the air-fuel mixture in the sub-chamber and the air-fuel mixture in the combustion chamber cannot be immediately replaced. This replacement requires a certain amount of time. However, when the sub-chamber valve is opened too early, the compression stroke is performed under the volume of the combustion chamber plus the volume of the sub-chamber, and the compression loss increases.

Therefore, the opening time of the sub-chamber valve may be set as late as possible after the start of the compression stroke (after the intake valve is closed) and the time required to replace the air-fuel mixture in the sub-chamber. The opening timing of the sub-chamber valve is the middle stage of the compression stroke. Of course, the opening timing of the sub chamber valve may be finally determined by an experiment.

Incidentally, as prior arts which are structurally similar to the present invention, Japanese Patent Application Laid-Open Nos. Sho 54-116512 and
There is an engine with a sub-chamber disclosed in Japanese Patent No. 80408 and the like.
The engine with a sub-chamber includes a sub-chamber that opens to the combustion chamber, and a sub-chamber valve that opens and closes the opening of the sub-chamber. This point is common to the present invention.

However, in this engine with a sub-chamber, the sub-chamber valve is opened in accordance with the closing timing of the intake valve, and the air-fuel mixture in the sub-chamber is used (using the differential pressure between the sub-chamber and the combustion chamber). ),
The present invention differs from the present invention in that a strong swirl is generated in the combustion chamber.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Reference numeral 1 shown in FIG. 3 denotes an engine. The engine 1 has a combustion chamber 4 defined by a piston 3 inserted into a cylinder bore 2, and an ignition plug 5 is provided facing the combustion chamber 4. ing.

An intake port 6 and an exhaust port 7 are opened in the combustion chamber 4, and an intake valve 8 is provided in the intake port 6.
An exhaust valve 9 is disposed at the exhaust port 7, and the intake valve 8 and the exhaust valve 9 are opened and closed at a predetermined timing in synchronization with an engine output shaft (not shown). You. That is, the engine 1 is a conventionally known otto-cycle gasoline four-cycle engine.

The engine 1 has a sub-chamber 10.
The sub-chamber 10 has a sub-chamber port 10a open to the combustion chamber 4, and a sub-chamber valve 11 is disposed in the sub-chamber port 10a. It can be opened and closed.

FIG. 4 shows an example of the opening / closing timing of the sub chamber valve 11. As is apparent from FIG.
Is the ABD whose closing timing is the same as the ignition timing
C160 deg, which is about 7
The sub-chamber valve 11 is opened before 0 deg. Note that the closing timing of the intake valve 8 is about 5 after the passage of the top dead center.
0 deg.

With the above configuration, a part of the air-fuel mixture in the combustion chamber 4 is confined in the sub-chamber 10 by the sub-chamber valve 11 which is opened and closed in the compression stroke. In the compression stroke, the air-fuel mixture cooled in the sub-chamber 10 is replaced with a part of the air-fuel mixture in the combustion chamber 4.

Thus, the temperature of the air-fuel mixture in the combustion chamber 4 (in-cylinder temperature) is lower than that of a normal engine having no sub-chamber 10, and the thermal efficiency of the engine 1 is improved.

In addition, the fact that the temperature in the cylinder lowers means that
It is also advantageous for knocking measures. Therefore, when the compression ratio of the engine is increased or the boost pressure is increased, it is effective as a knocking countermeasure.

Although the invention has been described with reference to an otto-cycle type engine as an example, the invention can be applied to a diesel engine. When applied to this diesel engine, there is an effect that NO _X in exhaust gas can be reduced in addition to improvement in thermal efficiency.

[0027]

As is apparent from the above description, according to the present invention, the thermal efficiency of the engine can be improved by lowering the in-cylinder temperature.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the in-cylinder temperature and the specific heat (constant volume specific heat) of an air-fuel mixture.

FIG. 2 is a typical acupressure diagram of an engine.

FIG. 3 is a schematic diagram of an engine according to the embodiment.

FIG. 4 is a diagram showing an example of an opening / closing timing of a sub-chamber valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 3 Piston 4 Combustion chamber 5 Spark plug 8 Intake valve 10 Subchamber 10a Subchamber port opening to combustion chamber 11 Subchamber valve

Continuing from the front page (72) Inventor Kenji Kashiyama 3-1 Shinchi, Funaka-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Corporation (72) Inventor Junzo Sasaki 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Corporation (56) References JP-A-54-98408 (JP, A) JP-A-54-116512 (JP, A) JP-A-57-164224 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 15/04

Claims (1)

(57) [Claims] 1. A sub-chamber formed in an engine body and opening to a combustion chamber, and a sub-chamber valve for opening and closing the sub-chamber, wherein the sub-chamber valve is opened in a middle stage of a compression stroke. ,
An engine closed during the end of the compression stroke or the beginning of the explosion stroke.