JPS6014169B2 - Intake system for multi-cylinder engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a multi-cylinder engine, and more particularly to an intake system designed to improve intake air filling efficiency.

Some internal combustion engines employ a uniform intake system called inertial supercharging or resonance supercharging. In this case, a negative pressure wave generated near the intake boat at the start of intake propagates to the intake pipe engine (in the case of a single cylinder engine) at the speed of sound, and the intake pressure vibration is returned toward the intake boat as a positive pressure wave. Taking advantage of what happens. That is, by matching the cycle of intake pressure vibration with the intake valve opening/closing cycle so that the positive pressure wave is transmitted to the intake valve just before the intake valve closes, the air that has generated the positive pressure wave is It is pushed into the cylinder by inertia, and the weekly intake due to inertia can improve the intake air filling efficiency. Incidentally, in a multi-cylinder engine, a confluence point where branches of the intake manifold connected to each cylinder converge continuously receives the negative pressure during the intake stroke of each cylinder, so that the negative pressure is always maintained at a substantially constant negative pressure.

Therefore, the confluence point has a damping function that buffers the propagation of pressure waves from the downstream side of the confluence point to the upstream side of the confluence point, and the intake pressure vibration in the intake circuit connected to the cylinder in the intake stroke is substantially reduced to the combustion chamber. A pressure wave is a vibration that propagates back and forth between the intake pressure and the confluence point, and therefore, the natural frequency of the intake pressure vibration is determined by the confluence point position.

For example, the one shown in Samurai Seki No. 48-72509 utilizes inertia supercharging equipped with a resonant tank and resonant tube, but even with this, the natural frequency of the intake passage is constant and the low speed range Only in this case can a good inertial weekly feed effect be ensured, and in the high speed range, the natural frequency is too small, so the intake air filling efficiency is rather lower than that of the intake passage of a normal engine.

Furthermore, Japanese Patent Publication No. 42-27441 discloses a method in which a passage called a balance tube connects the gathering parts of the intake manifolds connected to each cylinder group whose intake valve opening timings do not overlap, and opens and closes this passage. What has been done is shown.

However, as stated in the publication, the balance tube is provided to eliminate imbalance in the load of each cylinder due to uneven operation of the carburetor and its operating system during light loads. Even if the intake pipes are opened and closed, the intake pipes upstream from the gathering part of each intake manifold are not long enough to allow intake pressure vibrations to propagate back and forth in the low, middle and far range of the engine, resulting in so-called inertial supercharging. Furthermore, since the carburetor includes a throttle valve, it is virtually impossible to perform inertial supercharging effectively. That is, the degree of closing of the throttle valve is large at low speeds and low loads, and the propagation of intake pressure is greatly attenuated in the throttle valve section, so it is impossible to perform active inertial weekly feeding using intake pressure oscillations. The present invention has been made in view of such conventional drawbacks, and the upstream end of the intake manifold branch carries a plurality of intake passages respectively connected to each cylinder group consisting of cylinders whose intake valve opening timings do not overlap with each other. A plurality of large-volume, box-shaped gathering chambers are connected to each other, and natural vibrations are connected to the gathering chambers through the space, and inertia supercharging is performed by propagating intake pressure vibrations in the engine's low speed range. a resonant passage having a plurality of intake passages without a constriction part, and is provided with a switching device for freely switching the intermediate portions of the plurality of intake channels to open and shut off each other; By switching from shutoff to communication when the intake air pressure increases, the confluence point of these intake passages is switched from the upstream part to the downstream part, thereby ensuring good inertial supercharging throughout the entire speed range of the engine. The present invention provides an intake system for a cylinder engine.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a six-cylinder engine,
The crank angle of cylinders #1 to #6 in the engine is 120o.
The ignition order for each is #1 → #4 → #2 → #6 → #3 → #5.

Therefore, as shown in FIG. 2, the intake valve opening timings of cylinders #1, #2, and #3 (hereinafter referred to as first cylinder group 1) do not substantially overlap with each other, and cylinders #4, In #5 and #6 (hereinafter referred to as second cylinder group 2), the intake valve opening timings of each cylinder do not substantially overlap with each other, but the intake valve opening timings of first cylinder group 1 and second cylinder group 2 mutually overlap. There is a relationship in which the cylinders have overlapping timings. All these cylinders #1 to #6
Each intake manifold branch part 3 has its lower end connected to
The upstream end of the box is connected to the box-shaped gathering chamber 4.

Inside the gathering chamber 4, there is a space 4A for transporting the first cylinder group 1.
A switching valve 5 is provided which can freely cut off the space 4B connected to the second cylinder group 2 and the second cylinder group 2 as desired. Further, a resonance passage 6 whose downstream end is connected to the space 4A side of the gathering chamber 4 and a space 4B
A resonant passage 7 whose downstream end is connected via a gate is arranged in parallel on the side, and the upstream ends of both passages 6 and 7 are closed and connected to a gathering chamber 8.

These resonance passages 6 and 7 are set to have a natural frequency at which intake pressure vibrations propagate back and forth at low speeds and inertia overflow occurs.

In addition, by increasing the length of the resonance passages 6 and 7 and increasing the volume of the gathering chamber 4, the natural frequency of intake pressure vibration is reduced, and this is well matched to inertial supercharging in the low speed range of the engine. can be done.

In this way, two intake circuits are formed that are connected to each cylinder group consisting of cylinders whose intake valve opening timings do not overlap with each other, and one is the intake manifold branch of each cylinder connected to the first cylinder group 1. 3, a space 4A, and a resonance passage 6; the other one consists of the intake manifold branch part 3 of each cylinder connected to the second cylinder group 2, a space 4B, and a resonance passage 7; A switching valve 5 serving as a switching device is used to freely switch between the sections.

An intake pipe 9 is connected to the gathering chamber 8 on the upstream side. The intake pipe 9 may be opened to the atmosphere, but it may also be connected to an air cleaner, darbocharger, aftercooler, etc. located further upstream.
It is also possible to have a built-in cooler or aftercooler. Further, in this embodiment, the two intake passages are made to communicate with the atmosphere through the upstream gathering chamber 8, but it is of course possible to make the upstream ends open to the atmosphere independently. It is. In the intake passage having such a configuration, when the engine rotational speed is below a predetermined value, the switching valve 5 is closed to shut off the space 4A and the space 4B, and when the engine speed exceeds the predetermined value, the switching valve 5 is opened and the space 4 is closed.
A and the space 48 are configured to suit each other.

The open/close valve 5 may be opened/closed automatically by detecting the engine rotational speed, or may be opened/closed manually. Alternatively, a configuration may be adopted in which the engine rotational speed and load are detected and controlled. With this configuration, in a low engine speed range when the cutoff valve 5 is closed, the intake passages connected to each cylinder of the first cylinder group 1 and the intake passages connected to each cylinder of the second cylinder group 2 are located downstream. In the collecting chamber 4 on the side, the flow is blocked by the switching valve 5 and does not merge, but in the collecting chamber 8 on the upstream side across the passages 6 and 7.

The upstream collecting chamber 8 communicates with all the cylinders #1 to #6 and continuously receives the suction negative pressure from each cylinder, and is maintained at a substantially constant negative pressure.

On the other hand, since the intake valve opening timings of the cylinders in the first and second cylinder groups 1 and 2 do not substantially overlap with each other, the space 4A defined by the switching valve 5 in the downstream gathering room 4
and space 4B are affected only by the intake pressure from one cylinder in the intake stroke in the corresponding cylinder group. Therefore, in the first cylinder group 1 and the second cylinder group 2, the pressure wave of the intake pressure vibration generated from the cylinder in the intake stroke is transmitted from the combustion chamber of the cylinder to the corresponding manifold branch part 3 and the space 4A.
Alternatively, the natural frequency of the intake pressure vibration is determined by the upstream collecting chamber 8, that is, the position of the confluence of the intake air, since the intake pressure vibration propagates back and forth through the space 4B and reaches the upstream collecting chamber 8.

Therefore, by setting the natural frequency of the intake pressure vibration determined by the mounting position of the upstream gathering chamber 8 in accordance with the opening/closing cycle of the intake valve in the low speed range of the engine, intake inertia supercharging in the low speed range can be achieved. It can be done well.

On the other hand, when the switching valve 5 is opened at high engine speed, the space 4A and the space 48 are communicated with each other in the gathering chamber 4, so that the entire space inside the gathering chamber 4 continuously receives negative pressure from all cylinders #1 to #6. The pressure is maintained at a substantially constant negative pressure.

Therefore, the gathering chamber 4 has a pressure buffering function similar to that of the gathering chamber 8 in the low-speed engine, and the pressure wave of the intake pressure vibration propagates back and forth along the path from the combustion chamber of the cylinder in the intake stroke to the gathering chamber 4. It becomes a vibration.

In this case, the propagation path of the pressure wave is shortened compared to the case of a low-speed engine, so the natural frequency of intake pressure vibration increases, matching the intake valve opening/closing cycle in the high-speed engine range, and providing good performance even at high speeds. Intake inertia supercharging is performed. Therefore, the filling efficiency of the intake air with respect to the engine rotational speed N' is determined by the natural frequency of the intake pressure vibration in the engine low speed range where the switching valve 5 is closed and the engine high speed range where the switching valve 5 is closed, respectively, as shown in Fig. 3. The intake valve opening/closing cycle has extremely thick points A and B that match to achieve the best inertia weekly rate. Good intake air filling efficiency can be obtained throughout the entire speed range.

In addition, the intake passage confluence position control mechanism described in this embodiment detects the engine rotation speed and load, and in a region where the engine load exceeds a predetermined value, the confluence point is adjusted according to an increase in the engine rotation speed. The movement may be controlled to the downstream side, and when the engine load is below a predetermined value, it may be held at the upstream position value (the position when the engine rotation speed is low) regardless of the engine rotation speed.

In this way, when the load of the engine is large, the intake air filling efficiency is improved over the entire engine speed range, and the output performance is improved, and when the load of the engine that does not require much output is small, the intake air filling efficiency in the intake passage is improved. Engine rotation speed at which the natural frequency of pressure vibration and the intake valve opening/closing cycle are optimally synchronized (
Since the rotational speed (referred to as the synchronized rotational speed) is fixed in a low rotational speed range, the intake air loss at high rotational speeds can be suppressed and the fuel consumption rate at low loads can be reduced.

In addition, in this embodiment, there are two passages, a low-speed passage and a high-speed passage.
For example, by providing a switching valve in the middle of multiple resonance passages to freely switch between low speeds and shutoffs, three or more merging points that can be freely switched are provided, so that switching between three or more stages can be achieved depending on the engine speed. Alternatively, switching control may be performed.
As explained above, according to the present invention, a box-shaped collection of large volume in which the intake manifold branch is connected to a plurality of intake passages respectively connected to each cylinder group consisting of cylinders whose intake valve opening timings do not overlap with each other is formed. It is composed of a resonant passage connected to the upstream side of the intake passage, and is provided with a switching device that can selectively cut off the intermediate portions of these plurality of intake passages, and the switching device can be used to increase the engine rotational speed. The structure is configured so that the confluence point of the intake passages is switched from the upstream side to the downstream side by switching from shutoff to lotus connection depending on the situation, so the natural frequency of intake pressure vibration in the intake passage is changed in accordance with the intake valve opening/closing cycle. As a result, a good inertia weekly rate can be obtained over the entire speed range of the engine, and the intake air filling efficiency can be improved accordingly, so that the engine performance, particularly the output performance, can be significantly improved.
In particular, because it has a box-shaped gathering room space with a large volume,
The variable range of resonance rotation speed (including ultra-low speed) is extremely wide, and the resonance passage does not have a constriction part (vaporizer).
Since the inertial supercharging effect is large and there is no uneven fuel spray that occurs in engines with a carburetor, the effect of inertial weekly charging can be maximized.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional configuration diagram showing one embodiment in which the present invention is applied to a six-cylinder engine, Fig. 2 is a graph showing the intake valve relationship characteristics with respect to the crank angle of each cylinder in the same engine, and Fig. 3
The figure is a graph showing the relationship between engine rotational speed and intake air filling efficiency in the same embodiment. #1 to #6...Cylinder, 1,16...1st cylinder group, 2,1
7...Second cylinder group, 3...Intake manifold branch section, 4...Collection chamber, 5...
・Switching valve, 6, 7...Passage, 8...Collection chamber, 9...Intake introduction pipe. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In an intake system for a multi-cylinder engine that performs inertial supercharging using intake pressure vibration, a plurality of intake passages connected to each cylinder group consisting of cylinders whose intake valve opening timings do not overlap with each other are connected to intake manifold branches, respectively. A plurality of box-shaped gathering chambers with large volumes are connected to each other at their upstream ends. a resonant passage having a natural frequency at which the intake air is supplied and has no constriction part, and a switching device for freely switching the intermediate portions of the plurality of intake passages to communicate and disconnect from each other, the switching device An intake system for a multi-cylinder engine, characterized in that the merging point of these intake passages is switched from an upstream part to a downstream part by switching from cutoff to communication when the engine speed increases.