JPS58133448A - Compression-ignition engine - Google Patents

Abstract

PURPOSE:To variably arrange compression ratio at starting and warming end and improve startability, fuel consumption and exhaust characteristic of an engine, by providing an intake shut off valve in an intake passage and a closing valve and a starting passage communicated to a combustion chamber in a bypass passage of the intake shut off valve. CONSTITUTION:An intake shut off valve 11 closes an intake passage 8 on the half way of an intake stroke. While a passage 14 is formed so as to be communicated to a combustion chamber 3 by bypassing the valve 11, here a closing valve 15 is provided in the passage 14 and mechanically interlocked to a throttle valve 9 to start opening together with the valve 9 after the valve 9 is opened to a prescribed opening. Now the valve 15 is closed, if an intake valve 5 is opened to start an intake stroke as a piston 1 lowers, the passage 8 is closed by the valve 11 on the half way of the intake stroke and the piston 1 continuously lowers to reach the bottom dead center again rises to enter a compression stroke. From a point of time the valve 11 closes the passage 8, intake air is not sucked into a cylinder 2. Accordingly, if the valve 15 is closed, low compression ratio is obtained, while if the valve 15 is fully opened, high compression ratio is obtained, thus the compression ratio can be easily changed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compression ignition engine in which the compression ratio is effectively made variable by blocking intake air into the cylinder in the middle of the intake stroke.

Compression ignition engines generally use a high compression ratio from the viewpoint of engine startability, but this is still not sufficient to ensure good startability, and it is desirable to use an even higher compression ratio. ing.

However, adopting an extremely high compression ratio results in an increase in friction loss and an increase in harmful components in the exhaust gas (particularly NOx in direct injection engines), which does not have a positive effect on the fuel efficiency of the engine.

Therefore, for example, if a direct injection engine were to use an extremely high compression ratio only at the time of starting (the conventional compression ratio was 1.
7 (like 21), the startability is greatly improved.

Similarly, when starting a direct injection engine, an extremely high compression ratio is adopted (for example, 21), but after the engine has warmed up, the compression ratio is reduced to a low one (for example, 14 compared to the conventional 17). For example, harmful components in exhaust gas (especially NOx)
) will be significantly reduced.

From this point of view, the present invention attempts to improve the startability, fuel efficiency, and exhaust gas characteristics of an engine by arbitrarily changing the compression ratio, and will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a compression ignition engine according to the present invention, in which a pneumatic governor (not shown) is used as a governor, where 4 is a fuel injection valve, 9 is a throttle valve, and 1 is a fuel injection valve.
0 represents a small venturi, and the fuel injection amount is controlled by guiding the negative pressure generated in the small venturi 10 to a governor (pneumatic governor).

An intake cutoff valve 11 is provided at a predetermined position in the intake passage 8 leading to the combustion chamber 3 of the engine.
That is, the closing part 12 formed in the intake cutoff valve 11 closes the intake passage 8 in the middle of the intake stroke (for example, at a crank angle of 50 degrees before the bottom dead center of the piston 1). .

In this case, the time when the intake cutoff valve 11 opens the intake passage 8 (the time when the communication passage 13 formed in the intake cutoff valve 11 communicates with the intake passage 8) is the timing when the intake valve 5 opens (for example,
(Crankshaft angle at 30° before top dead center of piston 1)
It may be the same as , or it may be slightly faster than that.

In the figure, the intake cutoff valve 11 uses a rotary valve type.
Since the drive is decelerated to 1/2 of the rotation of the crankshaft, the intake passage 8 is opened once while the intake valve 5 is open and once when it is closed, but in any case, This intake cutoff valve 11 is designed to close the intake passage 8 in the middle of the intake stroke (in addition, it is also possible to drive the intake cutoff valve 11 by decelerating it to one-fourth of the rotation of the crankshaft. ).

On the other hand, a passage 14 is formed so as to bypass the intake cutoff valve 11 and lead to the combustion chamber 3 of the engine, and this passage 14 is equipped with a closing valve 15.

This closing valve 15 is mechanically linked to the throttle valve 9, and after the throttle valve 9 (that is, the accelerator pedal that opens and closes it) opens to a predetermined opening degree, it begins to open together with the throttle valve 9 (closed). Although the valve 15 may be fully opened at the same time as the throttle valve 9 is fully opened, it is better to fully open the valve 15 as soon as possible after it starts to open).

The opening/closing timing of the intake valve 5 is no different from the conventional one (for example, it opens at a crankshaft angle of 30 degrees before the top dead center of the piston 1 and closes at 50 degrees after the bottom dead center).

Now considering the case where the closing valve 15 is closed (fully closed) in the present invention, when the intake valve 5 opens and the intake stroke begins with the descent of the piston 1, as described above, in the middle of the intake stroke (for example, when the crank 50 degrees before the bottom dead center of the piston 1) the intake passage 8 is closed by the intake cutoff valve 11 (at this time, the intake valve 5 is still open), and the piston 1 continues to reach the bottom dead center. , it rises again and moves on to the compression stroke.

That is, after the intake air cutoff valve 11 closes the intake passage 8 during the intake stroke, no intake air is drawn into the cylinder 2 even if the piston 1 descends.

Therefore, at this time, the effective stroke of the piston 1 should be approximately from the top dead center position of the piston to the piston position at the time when the intake cutoff valve 11 closes the intake passage 8, and the compression ratio is also based on this effective stroke. I have to think about it.

On the other hand, when the closing valve 15 is fully opened, intake air is drawn into the cylinder 2 throughout the entire intake stroke, so at this time, the compression ratio is based on the piston stroke from the top dead center position of the piston 1 to the bottom dead center position. The way to think about it is the same as before.

In this way, in the present invention, the closing valve 15 is closed (fully closed).
This results in a low compression ratio, and when the closing valve 15 is fully opened, it becomes a high compression ratio, making it possible to easily change the compression ratio (when the closing valve 15 is half open, the compression ratio is considered to be in the middle). ).

Therefore, if the closing valve 15 is opened when the engine is started (by fully depressing the accelerator pedal or by some other method), the compression ratio will effectively become a high compression ratio (e.g., about 21 for a direct injection engine with a compression ratio of 17). ), the intake air temperature rises sufficiently during fuel injection, resulting in good starting performance.

Furthermore, if the closing valve 15 is closed (fully closed) after the engine has been warmed up, the compression ratio will actually become low (for example, 17), and friction loss can be suppressed as before.

In this case, since the expansion ratio is much higher than the compression ratio (the expansion ratio is always the same as the compression ratio when the closing valve 15 is fully open - for example, about 21), fuel efficiency is significantly improved.

Since the compression ratio (or expansion ratio) of a normal direct injection engine is about 17, preferred embodiments of the present invention in a direct injection engine, for example, are as follows.

That is, the compression ratio when the closing valve 15 is closed (fully closed) is approximately 14, and the compression ratio when fully opened is approximately 21.

As a result, since the closing valve 15 is fully opened when starting the engine, the compression ratio is effectively about 21, and the startability is greatly improved.

In addition, since the closing valve 15 is closed (fully closed) after the engine is warmed up (of course, the closing valve 15 is opened during high loads), the compression ratio is effectively about 14, and friction loss is kept low. This makes it possible to significantly reduce harmful components (especially NOx) in exhaust gas.

At this time, the expansion ratio is still about 21, so fuel efficiency is significantly improved.

Note that in order to prevent an increase in the ignition delay period when the closing valve 15 is closed and the compression ratio is effectively set to about 14, it is effective to appropriately heat the intake air flowing through the intake passage 8.

Further, it is preferable to gradually close the closing valve 15 while the engine is being warmed up.

As described above, according to the present invention, the startability, fuel efficiency, and exhaust gas characteristics of the engine can be significantly improved.

Next, it is preferable that the shutoff valve 15 is closed (fully closed) when the engine is under low (medium) load, and fully opened when the engine is under high (medium) load. It is designed to be mechanically linked with the throttle valve 9 (that is, with the accelerator pedal), and may also be mechanically linked with a control rack that controls the amount of fuel injection.

Another possible method is to open and close the closing valve 15 using a diaphragm device 16 operated by the negative pressure of the small venturi 10, as shown by the two-dot chain line.

That is, when the throttle valve 9 is opened and the negative pressure in the small venturi 10 becomes less than a specified value, the closing valve 15 starts to open.

Furthermore, as shown in FIG. 2, it is also possible to open and close the closing valve 15 using a switch device 18 and an electromagnet device 19 that detect the fuel injection amount control position of the control rack 17.

That is, when the engine is under low (medium) load, the internal contacts of the switch device 18 are open as shown in the figure, and therefore the closing valve 15 is closed (fully closed), but when the engine is under low (medium) load,
Under high load, when the control rack 17 moves (fuel injection amount increases) and reaches the stepped portion 20, the push rod 21 falls there, so the contacts inside the switch device 18 are closed and the electromagnet device 19 is energized. That's what I do.

As a result, the electromagnet built into the electromagnet device 19 pulls in the rod 22 against the spring, so that the closing valve 15 opens (fully opens).

FIG. 3 shows an embodiment in which the intake cutoff valve 11 is a poppet valve type like the intake valve 5.

That is, in FIG. 3, the intake cutoff valve 11 is driven by a cam (not shown), and the intake passage 8 is activated in the middle of the intake stroke (for example, at a crankshaft angle of 50 degrees before the bottom dead center of the piston).
In addition, the passage 14 bypasses the intake shutoff valve 11 and communicates with the combustion chamber of the engine.

Reference numeral 15 denotes a closing valve, which closes the passage 14 during low (medium) load after the engine has been warmed up, and by opening and closing the closing valve 15, the compression ratio can be effectively changed as shown in Fig. 1. can.

Therefore, it is possible to significantly improve the startability, fuel efficiency, and exhaust gas characteristics of the engine.

FIG. 4 shows the engine shown in FIG. 1 in which the startability of the engine according to the present invention is further improved.

That is, in FIG. 4, the starting passage 24 leading to the combustion chamber of the engine.
At the same time, this starting passage 24 is also connected to the intake cutoff valve 11.
(by another closing portion 23 formed in the intake cutoff valve 11) to open and close near the end of the intake stroke (near the bottom dead center of the piston 1).

When starting the engine, the closing valve 15 and the opening/closing valve 2 are closed as shown in the figure.
6 are both closed (fully closed), and the starter valve 25 is left fully open.

Therefore, intake air is drawn into the cylinder 2 only from the starting passage 24.

Now, when you crank the engine to start it,
Piston 1 descends to begin the intake stroke, and cylinder 2
A strong negative pressure is generated inside.

When the piston 1 approaches the bottom dead center, the intake cutoff valve 11 opens the starting passage 24, and intake air enters the cylinder 2 at high speed for a certain period of time.

At this time, the intake air enters at an extremely high speed, so due to its inertia, the intake air filled in the cylinder 2 is adiabatically compressed and increases the intake air temperature, resulting in a significant increase in the intake air temperature during fuel injection. As a result, the startability of the engine is further improved.

(At this time, the closing valve 15 is closed, but the cylinder 2 is filled with intake air near the end of the intake stroke, so the compression ratio is actually extremely high.) After the engine starts, the warm air It is best to open the on-off valves 26 one after another according to the state, and after warming up, fully open the on-off valves 26 and close the starting valves 25.
fully close.

Although it is desirable to fully close both the closing valve 15 and the opening/closing valve 26 when starting the engine, it is also conceivable to start the engine with at least one of them slightly open.

Additionally, connecting the starting passage 24 to the exhaust passage and replacing the intake air filled in the cylinder 2 from air only to exhaust gas (which contains a large amount of combustion) when starting the engine also has an effect on starting performance. It is something.

In order to further improve the startability of the engine according to the present invention shown in FIG. 3, FIG. 5 shows an engine in which a new starting passage is similarly provided.

That is, in FIG. 5, 27 is a starting intake valve driven by a cam, which is operated near the end of the intake stroke (including the beginning of the compression stroke).
The starting passage 24 is opened and closed, and the intake air filled in the cylinder is adiabatically compressed by its inertia, thereby raising the intake air temperature and further improving starting performance.

When starting the engine, the closing valve 15 and the opening/closing valve 2 are closed as shown in the figure.
Needless to say, the starting valve 25 is kept fully open or almost fully open.

In this case, a poppet valve type intake valve 27 is used to open and close the starting passage 24 near the end of the intake stroke, but a rotary valve type may also be used. This is shown in FIG.

That is, in FIG. 6, 28 is a rotary valve, which is connected to the starting passage 2.
4 is opened and closed near the end of the intake stroke, and intake air is passed through the intake valve 5.
The air enters the cylinder at an extremely high speed, and the air filled in the cylinder is adiabatically compressed.

After the engine is warmed up, the starting passage 24 is connected to the starting valve 25, for example.
It goes without saying that it is fully closed by (not shown, see FIG. 5).

As described above, the present invention is provided with an intake cutoff valve at a predetermined position of the intake passage leading to the combustion chamber of the engine, the intake passage is closed in the middle of the intake stroke by the intake cutoff valve, and further the intake cutoff valve is A closing valve is provided in the bypass passage leading to the combustion chamber of the engine, and the closing valve is kept closed during low load after the engine has been warmed up, and the starting passage leading to the combustion chamber of the engine is The starting passage is formed so that it opens and closes near the end of the intake stroke, so that when the engine starts, all or most of the intake air taken into the engine passes through the starting passage and is taken into the engine. and the starting passage is closed after the engine has warmed up.
Engine startability, fuel efficiency, and exhaust gas characteristics can be significantly improved.

[Brief explanation of the drawing]

Figures 1 and 4 are cross-sectional views of a compression ignition engine according to the present invention;
The figure shows a method of opening and closing the closing valve, and Figures 3, 5, and 6 are diagrams (schematically drawn plan views) of a compression ignition engine according to the present invention. 1 is a piston, 2 is a cylinder, 3 is a combustion chamber, 4 is a fuel injection valve, 5 is an intake valve, 6 is an exhaust valve, 7 is an exhaust passage, 8 is an intake passage, 9 is a throttle valve, 10 is a small venturi, 11 12 and 23 are intake cutoff valves, 12 and 23 are closing portions 13 are communicating passages, 14 are passages, 15 are closing valves, 16 are diaphragm devices, 17 are control racks, 18 are switch devices, 19 are electromagnetic devices, 20 are stepped portions, 21 is a push rod, 22 is a rod, 24 is a starting passage, 25 is a starting valve, 26 is an on-off valve, 27
28 is a starting intake valve, and 28 is a rotary valve. Patent applicant Shuichi Kitamura

Claims (5)

[Claims] (1) An intake cutoff valve is provided at a predetermined position in the intake passage leading to the combustion chamber of the engine, and the intake passage is closed in the middle of the intake stroke by the intake cutoff valve, and the intake passage is bypassed and A compression ignition engine characterized in that a closing valve is provided in a passage leading to a combustion chamber of the engine, and the closing valve is kept closed during low load after warming up the engine. (2) The compression ignition engine according to claim 1, wherein an intake cutoff valve is provided at a predetermined position in the intake passage upstream of the intake valve. (3) An intake cutoff valve is provided at a predetermined position in the intake passage leading to the combustion chamber of the engine, and the intake passage is closed in the middle of the intake stroke by the intake cutoff valve, and the intake passage is bypassed and the engine In a compression ignition engine, a starting passage leading to the combustion chamber of the engine is provided with a closing valve in the passage leading to the combustion chamber of the engine, and the closing valve is kept closed during low load after the engine has been warmed up. , the starting passage is made to open and close near the end of the intake stroke, so that when the engine is started, all or most of the intake air taken into the engine passes through the starting passage and is taken into the engine; A compression ignition engine characterized in that the starting passage is closed after the engine has been warmed up. (4) The compression ignition engine according to claim 3, further comprising an intake cutoff valve at a predetermined position in the intake passage upstream of the intake valve. (5) A compression ignition engine according to claim 4, wherein the starting passage is opened and closed by an intake cutoff valve.