JPS60219414A - Intake device for engine - Google Patents

Abstract

PURPOSE:To provide an intake device having satisfactory efficiency of intake even in low speed by forming respective intake paths of an engine having two intake valves as swirl forming large diameter paths and opening small diameter intake paths provided with a valve controllably opened and closed according to the engine running condition in the antiswirl direction near the respective intake valves. CONSTITUTION:Air is sucked into a cylinder 22 of an engine having two intake valves 27 in two intake ports 26 through two large diameter intake paths 25 communicating to the respective intake ports 26 and two small diameter intake paths 29. The large diameter intake path 25 is of spiral type which forms high swirl in the intake port 26, and the small diameter intake path 29 has a controlling valve 30 while opening in the antiswirl direction near the intake valve 27. The valve 30 is closed in low load and air is sucked through the large diameter intake path 25 with high efficiency of intake and high swirl, and in high load the valve 30 is opened to remove the swirl while increasing the intake amount.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system that improves the control structure for the swirling vortex flow (hereinafter referred to as "swirl") of intake air in a cylinder chamber in, for example, a three-valve or four-valve direct injection diesel engine. .

For example, the cylinder head of a direct injection diesel engine is equipped with an intake boat to guide air into the cylinder chamber, and the intake valve opens and closes the intake valve seat that communicates with this intake boat in response to each stroke of the engine. It looks like this.

The air introduced into the cylinder chamber from the intake valve seat is compressed and mixed with the fuel injected from the injection nozzle, resulting in explosive combustion. It is well known that the better the mixing state of air and fuel, the better the combustion efficiency. It is.

Conventionally, various means have been used to improve the mixing state of air and fuel, one of which is H8P.
High swirl boat (forced swirl intake hole) called structure
”.

This is shown in Figures 1 and 2) and (B). In the figure, 1 is a cylinder liner, 2 is a cylinder chamber, 3 is a cylinder head, and 4 is an intake device, which consists of an intake boat 5 and an intake valve 6. Furthermore, the cylinder head 3 is equipped with a fuel injection nozzle (not shown) facing the cylinder chamber 2 (the figure shows a normal two-way valve consisting of one intake valve and one exhaust valve). (This is a valve type engine.) The intake boat 5 has a slight "eccentricity" with respect to the center of the intake valve 6, so that the intake valve 6 descends and the intake boat 5
During the suction stroke when the cylinder is opened, the suction air that has been subjected to one eccentricity by the intake boat 5 is guided to the cylinder chamber 2, where a swirl is forcibly formed along the circumferential direction. Therefore, the mixing state of this air and the fuel injected from the injection nozzle is improved, and as a result, the combustion efficiency is improved.

Note that the ratio between the rotational speed of intake air in the cylinder chamber and the engine rotational speed is referred to as a "swirl ratio," and it is desirable that this swirl ratio be variable based on various conditions as described below.

For example, when comparing engine performance by alternately setting intake boats with different swirl ratios in the same cylinder chamber, the third
The experimental results are as shown in the figure. In the figure, curve a is for a high swirl ratio, curve 6 is for a medium swirl ratio, and curve C is for a low swirl ratio. As shown in the figure, the engine performance is best when the engine speed is low with a high swirl ratio a, aS with a medium swirl ratio when the engine speed is low, and with low swirl ratio C when the engine speed is high. Become. Therefore, if the swirl ratio is constant, performance will deteriorate in some engine rotation range.

Further, exhaust gas regulations are set for automobile engines, and the amount of NOx (nitrogen oxides) generated, which is the main component in exhaust gas, is related to the swirl ratio. That is, experimental results as shown in FIG. 4 have been obtained, and they are in a substantially proportional relationship with each other, and the higher the swirl ratio, the greater the amount of NOx generated.

Furthermore, since the load on the engine is affected by the engine speed, the relationship between this and the swirl ratio must be considered. As shown in Figure 5, high swirl is optimal when the engine speed is low, medium swirl ratio is optimal when the engine speed is medium, and low swirl ratio is optimal when the engine speed is high. (Fig. 3), the hatched portion shown in the figure may have a low swirl ratio of 1 to 1 to the load. For example, if the load is low at low speed, there is no need for a high swirl ratio, and a low swirl ratio is optimal. Even at medium speeds, a low swirl ratio is sufficient from light to medium loads, and at high speeds, a low swirl ratio is optimal regardless of the load condition. That is, in the case of low speed and low load, there is a surplus of intake air, so combustion occurs regardless of the swirl ratio. In this state, rather than a high swirl ratio that increases the amount of NOx generated,
A low swirl ratio that generates a small amount is optimal. Also, the lower the swirl, the less heat loss is absorbed from the combustion gas into the cylinder wall. Particularly under light loads, the magnitude of this heat loss corresponds to deterioration or improvement of fuel efficiency, so low swirl is advantageous from this point of view as well.

Needless to say, the above is exactly the same for a three-valve engine with two intake valves and one exhaust valve, or a four-valve engine with two intake valves and one exhaust valve.

The conventional variable swirl structure in this type of engine is such that one of the two intake valves is completely closed as required.

That is, the intake valve seat opened and closed by each intake valve communicates with a branch intake boat branched from the tip of the intake boat. When one intake valve completely closes the intake valve seat and only the other intake valve opens and closes, the cross-sectional area of the intake flow path is halved, so the flow rate of the intake air flowing through this intake valve seat increases, and the cylinder chamber This will result in a high swirl state. Additionally, when both intake valves are opened and closed, the flow velocity of the intake air flowing through each intake valve seat is reduced, resulting in a low swirl state.In this way, variable swirl is also possible in 3-valve or 4-valve engines. However, there is a problem in that the volumetric efficiency in the cylinder chamber decreases, especially during high swirl. That is, since no air is taken in from one intake valve seat, the amount of intake air is significantly insufficient, which adversely affects combustion efficiency.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to easily vary the swirl state in a three-valve or four-valve engine 1 with a simple structure, and to constantly change the swirl state. The present invention aims to provide an engine intake device that can secure a sufficient amount of intake air.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in FIGS. 6 and 7, 21 is a cylinder liner for six cylinders in series, 22 is a cylinder chamber, and 23 is a cylinder liner for six cylinders in series.
is a cylinder head 24, is an intake manifold, and S is an intake device to be described later. This intake device S is provided in a cylinder head 20 and an intake manifold 24, and includes a pair of intake boats 25, 2s and intake valve seats 26, 25, respectively.
, intake valves 27.27, and a swirl control passage 29.2 having an opening 28.28 in the peripheral wall near these intake valves 27.27.
Reference numerals 9 and 31 are exhaust valve seats that branch off from the exhaust manifold 32, and the engine is of a four-valve type in which exhaust valves (not shown) are opened and closed, respectively. The above-mentioned intake boat 25 is the most suitable for obtaining a high swirl state.
"Eccentricity" is a luxury.

The intake valve 27 is connected to a timing mechanism (not shown) to open and close the intake valve seat 26 in a timely manner. An opening is opened in the peripheral wall of the terminal end 1 of the intake boat 25 at a position immediately before the slow flow is introduced into the cylinder chamber 22. Further, a midway portion of the swirl control passage 29 is along the intake boat 25, and the other end thereof opens at the upper portion thereof.

In addition, these intake boats 25 and swirl system.

The control passage 29 is integrally provided in the cylinder head 23 and the intake manifold 24 as a cast structure. The shunt valve 3o is rotatably provided at the opening at the other end of each of the swirl control passages 29, 290. To explain, this is as shown in Figures 8 and 9,
It is made by cutting the middle part of a single round bar from both sides, leaving only the part along the axial direction thin. The vertical dimension of the swirl control passage 29 is slightly smaller than the diameter dφ of the shaft valve 30. Therefore, if the thin wall portion 30g of the shaft valve 30 is oriented vertically, the swirl control passage 29 can be completely closed. By rotating it in either direction, it opens to adjust the flow rate.

Therefore, if the thin portion 30a extends in the horizontal direction, it will be in a completely open state. Shaft valve 30 formed in this way
protrudes from the intake manifold 24 only at one end, and is mechanically connected to the drive mechanism. This drive mechanism is electrically connected to a control circuit consisting of a microcomputer, etc., which receives detection signals from a sensor that detects the engine speed, a sensor that detects the depression angle of the accelerator pedal, or a sensor that directly detects the load condition. Ru. The intake manifold 24 is connected to an air cleaner (not shown) so that fresh air from outside can be guided to each intake boat 26, 25 and the swirl control passages 29, 29.

Therefore, during the suction stroke in which the intake valves 27 and 27 are simultaneously lowered and both the intake valve seats 26 and 26 are opened, the intake air that has been subjected to one eccentricity by the intake boats 25 and 25 is introduced into the cylinder chamber 22. At this point, a swirl is forcibly formed along the circumferential direction. This air mixes with the fuel injected from the injection nozzle (not shown),
Burn.

When the drive mechanism receives detection signals of the engine rotational speed and the depression angle (load) of the accelerator pedal via the control circuit, the drive mechanism rotates the shaft valve 3o as appropriate. The swirl control passages 29 and 29 are closed when a high swirl ratio of the intake air introduced into the cylinder chamber 22 is desired, and are opened when a low swirl ratio is desired. That is, the intake boat 25 has an optimal shape to obtain a high swirl state.

Therefore, the shaft valve 30 is connected to the swirl control passage 29.
By closing 29, all intake air is transferred to the intake boat 25.
The air flows through the air, creating a high swirl state and providing a sufficient amount of intake air. At this time, the opening 28 of the swirl control passage 29 faces the intake boat 25, but does not obstruct the flow of intake air. This is because the opening 28 opens in the peripheral wall of the intake boat 25 near the intake valve 27, where the main flow of intake air has already been sucked into the cylinder chamber 22, and only the remaining flow with a slow flow velocity exists. Furthermore, since the openings 28 are not convex portions but concave portions, they do not act as resistance to flow. For these reasons, the swirl performance is not adversely affected when the swirl control passage 29 does not function, such as in a high swirl state.

Swirl control passage 29.29 by rotating shaft valve 30
If the cylinder chamber 22 is opened even slightly, the swirl ratio of the cylinder chamber 22 will decrease. That is, as shown in FIG. 10, from each intake boat 25.25 to the cylinder chamber 22 via the intake valve seat 26.26, and from the swirl control passage 29.29 to the opening 28.28 and the intake valve seat 26, 26.

The intake air led from the intake boats 25 and 25 becomes a forward swirl direction component in the clockwise direction in the figure in the cylinder chamber 22, as shown by the white arrow and the white dashed line arrow in the figure. On the other hand, the intake air led from the swirl control passages 29 and 29 has a reverse swirl direction component in the counterclockwise direction in the figure in the cylinder chamber 22, as shown by the black arrow and the black dashed line arrow in the figure. These swirls collide with each other in the cylinder chamber 22 and cancel each other out. Due to the shape of each port 25 and passage 29 and the amount of intake air introduced, the forward swirl direction component is larger than the reverse swirl direction component, and although the swirl does not disappear, the swirl ratio decreases and a low swirl state is obtained. Moreover, the original intake bow) 25. ;In addition to the intake air flowing in from t5, there is also intake air from the swirl control passages 29 and 29, so the total amount of intake air is sufficiently secured. Especially when the engine is in a high rotation range, a good low swirl condition is a priority. As explained above, if the swirl control passage 29.29 is opened, a sufficient amount of intake air can be secured and the condition can be obtained at 0°C.Also, the forward high swirl from the intake boat 25.25 and the swirl control The reverse swirl from the passage 29.29 flows into the cylinder chamber 22.
They interfere with each other, producing two vortices with different rotational directions, and also producing many small vortices or disturbances around these vortices. These many vortices or turbulences remain even after the compression stroke and improve the mixing of the spray and desired air, helping to improve combustion efficiency and reduce smoke and exhaust gas. In a high swirl state, the intake air is guided smoothly and selectively along the streamlined and smooth intake boat 25.25 shape at the minimum necessary speed. Moreover, since the air is evenly introduced into the cylinder chamber 22 from the entire circumference of each intake valve seat 26, 26, the swirl is high and the intake air amount is also very large.

In the above embodiments, a direct injection diesel engine has been described, but the present invention is not limited to this, and can of course be applied to a gasoline engine as well.

In addition, in the above embodiment, there are 4 valves, 2 intake valves and 2 exhaust valves.
Although the description has been made regarding a valve type engine, the present invention is not limited thereto, and can of course be applied to a three valve type engine with two intake valves and one exhaust valve.

It goes without saying that various other modifications can be made without departing from the gist of the present invention.

As explained above, according to the present invention, in a three-valve or four-valve engine equipped with two intake valves, a pair of swirl control passages each having an opening facing the circumferential wall near each intake valve is provided, and the opening is located at a position where the air flowing in from the opening swirls in the opposite direction to the swirl direction of the intake air from the intake boat, so the swirl state can be easily varied and a sufficient amount of intake air can be ensured regardless of the spray state. This improves combustion efficiency and reduces exhaust gas and smoke. Furthermore, since the structure is simple, an inexpensive two-engine intake device can be provided without adversely affecting the cost.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the main parts of an engine showing a conventional example of the present invention;
Fig. 2 (4) is a cross-sectional plan view of the intake system, Fig. 2 (B) is a longitudinal sectional view taken along line B-B and lil in Fig. 2 (4), and Fig. 3 is a cross-sectional view of the intake system. Figure 4 is a characteristic diagram of NOx generation state as a function of swirl ratio, Figure 5 is a characteristic diagram of optimum load condition as a function of swirl ratio and engine revolution speed, and Figure 6 is a characteristic diagram of the present invention. 7 is a schematic perspective view thereof, FIG. 8 is a partially cutaway perspective view of the intake system, and FIG. 9 is a diagram illustrating its swirl control passage and shaft valve. The vertical cross-sectional view and the first θ diagram are diagrams illustrating the stool state. 22... Cylinder chamber, 27... Intake valve, 25...
Intake boat, 28...opening, 29...swirl control passage. Applicant's agent Patent attorney Takehiko Suzue〉Rotation speed - Figure 6 n

Claims (1)

[Claims] 3 with 2 intake valves and 1 exhaust valve for the cylinder chamber
In a valve-type engine or a four-valve engine equipped with two intake valves, each intake boat on the upstream side of each intake valve is provided with a swirl control passage having an opening facing a peripheral wall near the intake valve, and the opening is provided at a position where a swirl flow occurs in a direction opposite to the swirl direction of intake air that occurs when air flowing into the cylinder from the opening flows into the cylinder from the intake boat. Engine intake system.