JPS6256325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake and exhaust system for a diesel engine.

The purpose of the present invention is to change the inertia effect due to the equivalent length of the intake and exhaust pipes according to the engine load, and to increase the output particularly in the high load range and improve the fuel efficiency in the low load range. .

BACKGROUND ART Inertial supercharging means that utilizes air column vibration (pulsation) generated in intake and exhaust pipes by opening and closing intake and exhaust valves is well known in order to improve the intake efficiency of conventional engines.

In other words, on the intake pipe side, the length of the intake pipe is selected so that the peak of positive pressure due to air column vibration (pulsation) generated in the pipe reaches the vicinity of the intake valve just before the intake valve closes. This is to fill the cylinder with the highest density air, and this is called inertial supercharging.

Furthermore, the air column vibration on the exhaust pipe side is larger than the air column vibration within the intake pipe. This is because the flow velocity immediately after the exhaust valve opens is generally faster than that on the intake side, and therefore the dynamic pressure is also greater. However, the qualitative theory is the same as in the case of the intake pipe: when the exhaust valve opens, the pressure inside the cylinder suddenly drops, while the pressure inside the exhaust port near the exhaust valve suddenly rises once due to the exhaust blowing. . Pulsations are generated by the impact reciprocating within the exhaust pipe, and the waves gradually attenuate, but since the impact pressure is large, the amplitude of the pulsations is also large. At this time, the positive pressure wave is caused by the fact that the cylinder internal pressure is still high.
This has almost no effect on exhaust blowing, but the phase relationship between the positive and negative pulsating pressure, the exhaust valve closing timing, and the overlap timing with the intake valve is such that the outlet of the valve is under negative pressure during the latter half of the exhaust valve opening period. In particular, if there is a negative pressure at the time of overlap, it also serves as a scavenging action and sucks out the residual gas, increasing the volumetric efficiency and increasing the intake efficiency in the same way as the supercharging effect in the intake pipe.

When using this supercharging effect and the exhaust pipe suction effect, that is, the inertia effect, in a multi-cylinder engine,
If each cylinder is connected by a manifold, the pressure waves from the adjacent intake or exhaust pipe will interfere and become a composite wave, which will have no effect.In order to eliminate this interference, the distance from each cylinder to the converging part will be reduced. It is common that it is long.

The optimum conditions for this inertial effect depend on the engine rotation speed, so if the maximum effect can be obtained at a certain rotation speed, the conditions will be worse at other rotation speeds, so a wide range of rotation speeds should be used. It was difficult to take full advantage of this effect with ordinary automobile engines.

Therefore, if we consider this inertial effect in terms of engine load conditions, we find that if the intake efficiency is increased by the inertial effect, the output will increase at high loads, but at low loads, the output will increase more than necessary for the fuel. Extra air enters, and as a result, pumping loss increases, especially during the compression stroke, and as extra force is required, fuel efficiency at low loads deteriorates.

In view of the above problems, the present invention utilizes the inertia effect to reduce the intake efficiency in the low load range and to change the actual length of the intake pipe or exhaust pipe in accordance with the load in order to solve the above problem. This is what I did.

Embodiments of the present invention will be described below based on the drawings.
In FIG. 1, 1 is a diesel engine, 2 is an intake manifold, 3 is an intake pipe, and 4 is an air cleaner. In the present invention, the inside of the intake pipe 3 including the intake manifold 2 is partitioned in the longitudinal direction by a partition wall 5. Therefore, in the case of a 6-cylinder engine as shown in the example,
The intake system is divided into two parts for each three cylinders by the partition wall 5, forming a so-called inertial supercharging pipe.

The partition wall 5 is provided with one or more holes 6 at arbitrary positions from the root of the intake pipe 3 to the intake manifold 2, thereby providing a portion where the sections are communicated. An on-off valve 7 is provided in this hole 6, and the on-off valve 7 is operated depending on the load and rotational speed of the engine.

According to the present invention, when the on-off valve 7 is opened, the total length l2 from the position of the intake valve 8 to the end of the partition wall 5 on the air cleaner 4 side becomes a short length l1 due to the opening of the hole 6.

Therefore, by closing the on-off valve 7 in the high load and low rotation range and setting the positive pressure wave of the inertia supercharging pulsation at the full length l2 of the partition wall 5 to coincide with the closing point of the intake valve, it is possible to In the rotation range, the inertia effect increases the suction rate, resulting in increased output under high loads.
Furthermore, in a high load, high rotation range, the on-off valve 7 is opened to obtain high suction efficiency that matches the high rotation speed.

On the other hand, by opening the on-off valve 7 in a low-load, low-speed range, the actual length of the dividing wall 5 becomes a short length l1, which allows for a gap between the pulsation of inertial supercharging in the intake pipe and the closing point of the intake valve. Misalignment occurs and the air flowing into the cylinder is reduced. That is, the suction efficiency is lower than that of inertial supercharging at high loads. Therefore, when the load is low, the minimum necessary amount of air is allowed to flow in, which reduces pumping loss during the compression stroke and eliminates the need for extra force. Similarly, in the low-load, high-speed range, the on-off valve is closed to reduce suction efficiency and pumping loss.

When this situation is expressed as a fuel efficiency rate, when the intake efficiency is low, the fuel efficiency becomes a, b, and c, as shown by curve A in Figure 2, and when the intake efficiency is high, the fuel efficiency is B.
As shown by the curve, d, b, and e, but by opening and closing the on-off valve 7 at the boundary point f between the low load region and the high load region, a, These curves are curves b and e, which improve fuel efficiency.

Although the above embodiment has been described on the intake side, the same effect can be obtained on the exhaust side or on both intake and exhaust.

As described above, according to the present invention, an equivalent pipe length is constructed in which one or both of the intake and exhaust pipes is divided into two by a partition wall, and a hole for shortening the equivalent pipe length is formed in this, and this hole is Equipped with an on-off valve that opens and closes,
In the high load range, the inertia effect increases the suction efficiency, and in the low load range, the suction efficiency is conversely degraded, so it eliminates pumping loss at low loads and has the effect of improving fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of the device of the present invention, and FIG. 2 is a curve diagram of the fuel efficiency rate of the device of the present invention. 1... Engine, 2... Intake manifold, 3...
Intake pipe, 4... Air cleaner, 5... Partition wall, 6
...hole, 7...open/close valve.

Claims (1)

[Claims] 1 A partition wall is provided to divide the inside of one or both of the intake and exhaust pipes of the engine into two sections in the longitudinal direction to give an equivalent pipe length, and a communication hole between the sections is provided in this partition wall to shorten the equivalent pipe length. A suction/exhaust system for a diesel engine, characterized in that an on-off valve is provided to open and close this hole, and the on-off valve is opened and closed according to the load of the engine to reduce suction efficiency in a low load range. .