JPH0650057B2 - Swirl control device - Google Patents

Description

The present invention relates to a control device for a suction air swirl (swirl vortex) formed in a combustion chamber (cylinder chamber) of an engine.

<Prior Art> For example, a cylinder head of a direct injection diesel engine is provided with an intake port for introducing air into a combustion chamber, and an intake valve provided in the intake port opens and closes according to each stroke of the engine. It is supposed to do.

The air introduced from the intake port into the combustion chamber is compressed and mixed with the fuel ejected from the injection nozzle for explosive combustion. It is well known that the better the mixed state of the air and the fuel, the higher the combustion efficiency. Is.

Conventionally, various means have been used to improve the mixed state of air and fuel, and one of them is a high swirl port (forced swirl inlet) called an HSP structure.

As shown in FIGS. 14 (A) and (B), this is the intake port 01
Is slightly eccentric with respect to the center of the intake valve 02, and the intake air deflected by the intake port 01 is guided to the combustion chamber 03 during the intake stroke when the intake valve 02 is lowered and the intake port 01 is opened. The swirl is forcibly formed along the direction. Therefore, the mixed state of the intake air and the fuel injected from the injection nozzle is improved, and the combustion efficiency is improved.

It is desirable that the strength of the swirl formed in the combustion chamber be variable under various conditions. The strength of the swirl is represented by the ratio of the rotational speed of the intake air in the combustion chamber to the engine speed (called the swirl ratio).

Regarding the relationship between the swirl ratio and engine performance, it is known that it is better in terms of engine performance to increase the swirl ratio when the engine speed is low and decrease the swirl ratio when the engine speed is high. There is.

It is known that the magnitude of the swirl ratio is also related to the amount of NOx (nitrogen oxide) generated, and the higher the swirl ratio, the greater the amount of NOx generated.

For the engine load, a low swirl ratio is optimal at low speeds and low loads, and a low swirl ratio from light to medium loads is sufficient even at medium speeds, and at high speeds it is low regardless of load conditions. The swirl ratio is optimal.

Further, regarding the relationship between the swirl ratio and the heat loss, the lower swirl ratio reduces the heat loss absorbed from the combustion gas into the cylinder wall. In particular, at light loads, the magnitude of this heat loss corresponds to the deterioration and improvement of the fuel efficiency, and from this point as well, the low swirl ratio is more advantageous.

Since there is an optimum swirl ratio according to various conditions as described above, in order to make the swirl ratio variable, conventionally, for example, a mechanism as disclosed in Japanese Patent Publication No. 51-7243 has been proposed. This is as shown in FIGS. 15A and 15B, in which 112 is a combustion chamber, 115 is an intake port, and 116 is
a is an intake valve seat. The intake port 115 has a structure based on a low swirl type, and is divided into left and right ports 115a and 115b by a partition wall 117, and one of the ports 115b can be opened and closed by an open / close valve 118.

When the on-off valve 118 is opened as shown in FIG. 9A, intake air is guided to both ports 115a and 115b, and the flow velocity passing through the intake valve seat 116a is low, so the combustion chamber 112 is in a low swirl state. Open / close valve 1 as shown in FIG.
When the valve 18 is closed, intake air is guided to only one port 115a. The intake passage cross-sectional area is halved, and the intake valve seat 116
aBecause it is narrowed down to more than the inner diameter area, the flow velocity of intake air becomes faster,
The combustion chamber 112 is in a high swirl state. The swirl component in each state has the direction and strength indicated by the arrow in the figure.

With this type of structure, the swirl ratio can be varied as necessary, but it has the following drawbacks. That is, in the low swirl state, as shown in FIG. 16 (A), only one rigid vortex-like swirling flow occurs in the combustion chamber 112, and in the rigid vortex shown in FIG. 16 (B). Further, since the spray F that is radially injected from the center of the combustion chamber 112 has only the effect of receiving a side wind from the rigid vortex indicated by the arrow in the figure, sufficient mixing of the spray F and air cannot be obtained. Further, in the high swirl state, the intake air is guided to one port 115a as shown in FIG.
When passing through the end portion of 17, the flow channel area is rapidly expanded. Therefore, there are several eddy currents due to separation, and there are losses such as backflow. Further, since the flow passage cross-sectional area is halved and the port 115a has a narrow cross-sectional area, a great flow passage resistance is generated and the intake air flows out into the combustion chamber 112 only from a part of the intake valve seat 116a. Insufficient amount.

As a basic concept of swirl, when it is desired to obtain a high swirl state, it is desirable to let the intake air flow into the combustion chamber in the horizontal direction (circumferential direction), and at this time, the intake air amount is small. In order to obtain a low swirl state, it is desirable to let the intake air flow into the combustion chamber in the vertical direction (axial direction), and at this time, the intake air amount becomes large.

However, in the conventional structure shown in FIGS. 15 (A) and (B),
The intake port 115 is simply divided into two parts, and the intake direction is not changed with the switching of each swirl state, and the intake amount is reduced in any state.

Although various other structures can be seen, the swirl state cannot be varied while always ensuring a sufficient intake amount, and the complicated structure adversely affects the cost.

<Problems to be Solved by the Invention> As a solution to the above-mentioned drawbacks of the conventional variable swirl structure, a main port (intake port) connected to the upstream side of the intake valve and a terminal end of the main port are provided. A variable swirl port, which is connected at a certain angle and consists of a sub-port independent of the main port, is considered, and the swirl ratio is changed by changing the amount of air flowing through the sub-port. With this swirl port, the swirl ratio can be changed without reducing the amount of intake air into the combustion chamber.

The present invention uses the variable swirl port as an intake system to obtain an optimum swirl ratio according to the various conditions described above, thereby improving engine performance and improving fuel efficiency.
The purpose is to reduce NOx.

<Means for Solving the Problems> The configuration of the present invention for achieving the above object is a main port that is connected to an upstream side of an intake valve of a combustion chamber and uses air that flows into the combustion chamber as a forward swirl flow. In addition to the main port, the intake port extends downward from above the main port and is connected near the intake valve seat so that intake air is directly guided into the combustion chamber through the intake valve seat, and the intake valve and the intake valve are connected. A sub-port for forming a reverse swirl flow opposite to the forward swirl flow in the combustion chamber by a velocity component in the direction perpendicular to the combustion chamber axis of the intake flow when flowing into the combustion chamber from the gap with the seat, A valve mechanism that changes the swirl ratio of the forward swirl flow generated from the sum of the forward swirl flow and the reverse swirl flow in the combustion chamber by changing the amount of air flowing through the sub-port, and the engine load and rotation. A valve control system that operates a valve mechanism by selecting a swirl ratio based on the number of revolutions, and a low swirl ratio is selected in the valve control system when the engine is in high rotation or low / medium load in medium rotation, and further fuel injection is performed. The swirl control device further comprises a timing control means for controlling the timing to be advanced.

<Examples> FIG. 1 shows a schematic structure of an embodiment of a swirl control device according to the present invention, FIG. 2 shows a schematic structure of a cross section of an engine along a plane, and FIG. The side section of the engine is shown.

Reference numeral 1 is an engine, 2 is its cylinder block, 3 is a cylinder liner, 4 is a piston, 5 is a cylinder head connected to the upper part of the cylinder block 2, 6 is a combustion composed of a cylinder liner 3, a piston 4 and a cylinder head 5. Chamber (cylinder chamber). A variable swirl intake system is provided in the cylinder head 5, 7 is an intake valve seat provided in the cylinder head 5, 8 is an intake valve that opens and closes the intake valve seat 7, and 9 is provided upstream of the intake valve 8. The main port, 10 is the terminal end of the main port 9 (end of winding in this embodiment)
It is a sub-port independent from the main port 9 connected to. The main port 9 is provided so as to be slightly eccentric with respect to the center of the intake valve 8 and has an optimum shape for obtaining a high swirl ratio when external air is guided into the combustion chamber 6 through the intake valve seat 7. ing. The sub-port 10 is connected to the end of the main port 9 at an angle so that the air can be smoothly supplied to the combustion chamber 6. The intake valve 8 is driven to open and close the intake valve seat 7 at a timing. Although not shown in the drawing, the cylinder head 5 is provided with an exhaust system including an exhaust valve, an exhaust port, and the like, and a fuel injection nozzle is provided so as to face the combustion chamber 6.

An intake manifold 11 is connected to the cylinder head 5, and the main air passage 12 and the sub air passage 13 of the intake manifold 11 are connected to the main port 9 and the sub port 10, respectively. The sub air passage 13 is provided with a valve body 14 that opens and closes the passage 13, and an actuator 15 for opening and closing the valve body 14 is connected to an end of the valve body 14. The valve portion 14a of the valve body 14 has a plate shape, and the passage 13 is fully opened when the valve portion 14a is substantially horizontal, and the sub air passage 13 is fully closed when the valve portion 14a is substantially vertical. . By adjusting the opening degree of the sub air passage 13 by the operation of the actuator 15, the amount of air flowing therethrough is adjusted,
That is, the amount of air entering the combustion chamber 6 from the sub port 10 is adjusted, and the swirl is changed.

During the intake stroke in which the intake valve 8 descends and the main port 9 opens, intake air is guided into the combustion chamber 6 via the intake valve seat, where a swirl is forcedly formed along the circumferential direction. Will be done. This air mixes with fuel injected from an injection nozzle (not shown) and burns.

The valve body 14 is closed when the swirl ratio of the intake air introduced into the combustion chamber 6 is desired to be high, and is opened when the swirl ratio is desired to be low. The high swirl state can be explained with reference to FIGS. 4 (A) and (B), and the low swirl state with reference to FIGS. 5 (A) and 5 (B). That is, in each figure (A), the intake valve seat 7 is divided into eight equal parts and the numbers 1 to 8 are given.
Intake is carried out to the combustion chamber 6 at the position of each number and in the direction indicated by the arrow in the figure, and the strength corresponding to the length of the arrow. The swirl components of numbers 1 to 4 are forward swirl components because the intake direction in the main port 9 also follows the clockwise direction (+) created around the center O ₁ of the combustion chamber 6 in the combustion chamber 6 as well.
These moments are forward swirl moments. The swirl components of numbers 5 to 8 are anti-swirl components because they try to rotate in the counterclockwise direction (-) around the center O ₁ , and these moments are anti-swirl direction moments. In each figure (B), the magnitude of the swirl component moment of each number is indicated by arrows in the forward and reverse directions. O ₂ is the center point of the intake valve seat 7. Fig. 4
In the cases of (A) and (B), since the auxiliary port 10 is closed, the difference between the sum of the forward swirl direction moments and the sum of the reverse swirl direction moments is sufficiently large, resulting in a high swirl state as a whole. However, in the case of FIGS. 5 (A) and 5 (B), since the auxiliary port 10 is open, the intake air is also guided from here to the combustion chamber 6, especially the moments in the reverse swirl direction near the numbers 6 and 7. Is large. The sum of moments in this direction approaches the sum of forward swirl moments. The intake air in the forward swirl direction in the combustion chamber 6 collides with the intake air in the reverse swirl direction guided from the auxiliary port 10,
And they cancel each other out to get a low swirl state. However, as the intake air flow rate, originally, the amount that flows in from the sub port 10 in addition to the amount that flows in from the main port 9 is secured.
Furthermore, since the sub-port 10 stands nearly vertically,
The intake air flows into the combustion chamber 6 smoothly. Therefore, in the low swirl state, the intake amount is sufficient. In particular, when the engine is in the high rotation range, the low swirl state is good as described above, but if the sub port 10 is opened, a sufficient intake amount can be secured and that state can be obtained. Further, as shown in FIGS. 6 (A) and 6 (B), the forward high swirl from the main port 9 (shown by a white arrow in the figure) and the sub port 1
Reverse swirls from 0 (indicated by black arrows in the figure) interfere with each other in the combustion chamber 6 to generate two vortices with different rotation directions, and many small vortices or turbulences around them. Give rise to. Many of these vortices or turbulences remain slightly after the compression stroke and improve the mixing of the sprays F ... with air as shown in FIG. 6 (C) to improve the combustion efficiency.
Helps reduce smoke and exhaust emissions. In the high swirl state, the intake air is guided smoothly along the streamlined smooth main port 9 shape as shown in FIG. 7 at the minimum necessary speed and without loss. Moreover, since it is uniformly guided to the combustion chamber 6 from the entire circumference of the intake valve seat 7, the swirl is high and the intake amount is very large. In addition, in high swirl state, sub port 10
Does not adversely affect the flow of intake air in the main port 9.

The actuator 15 is controlled to open and close by a control signal from a control unit 16 as a control system.
The control unit 16 stores an optimum swirl map M that serves as a reference for operating the actuator 15. In this swirl map M, the optimum swirl ratio in the operating state can be selected based on the load and the rotation speed of the engine 1. The load of the engine 1 is
This is performed by detecting the depression amount of the accelerator pedal 17, and the rotation speed (Ne) of the engine 1 is detected by the tachogenerator 18 and input to the control unit 16. In the figure, 19 is an injection pump.

The optimum swirl map M stored in the control unit 16 is determined so as to obtain an optimum operating state according to the load and the rotation speed of the engine 1. The relationship is shown in FIGS. 8 to 11.

Fig. 8 shows the relationship between the swirl ratio and the NOx emission amount in the 6-mode value, and Fig. 9 shows the relationship between the swirl ratio, the fuel consumption rate, and the smoke concentration at different rotation speeds at full load. As an example, Fig. 10 shows the relationship between the swirl ratio at 45% Ne (low speed) and the fuel efficiency and smoke concentration at different loads. Fig. 11 shows the engine speed and load at a certain load. The relationship between the amount of change in fuel consumption rate, the amount of change in NOx, and the amount of change in smoke concentration is shown when the swirl ratio is changed.Fig. 12 shows the amount of change in fuel consumption rate at a certain engine speed, load, and dp. Regarding the relationship between / dθ change amount and Pmax change amount, the tendency when the swirl ratio is changed is shown. 11 and 12, a, b, c ... j
Is a measurement point, and the numbers in the figure are swirl ratios as an example. Pmax in FIG. 12 is the maximum cylinder pressure,
It is easy to determine the durability required for the engine.
Further, dp / dθ shows the change of the in-cylinder pressure with respect to time, which facilitates the generation of noise. Both Pmax and dp / dθ are desirably low values.

As shown in FIG. 8, in the 6-mode value, the smaller the swirl ratio, the more NOx is reduced.

As shown in FIG. 9, when the engine speed Ne is 100% (high speed), a low swirl ratio, 65% (medium speed) is a medium swirl ratio, and 30% (low speed) is a high swirl ratio. The smoke temperature is also good.

As shown in Fig. 10, 4/4, 3 / at low speed 45% Ne
At 4 and 2/4 loads, a high swirl ratio improves the fuel efficiency and smoke concentration, but for loads below that, a low swirl ratio improves the fuel efficiency. The reason is that the lighter the load, the more susceptible it is to cooling loss. The heat transfer from the combustion gas to the cylinder liner, the piston, the lower surface of the cylinder head, etc. is proportional to the n-th power of the gas flow velocity. Therefore, at light load, the smaller the swirl speed, the better the fuel consumption rate.

Further, as shown in FIG. 11, the lower the swirl ratio, the lower the NOx in all operating conditions of the engine.

Further, as shown in FIG. 12, as the swirl ratio is lowered, Pmax and dp / dθ are lowered in all operating conditions of the engine, so that the durability of the engine can be improved and the noise can be reduced.

Therefore, in principle, select a low swirl ratio in a region where there is no great difference in performance even if the swirl ratio is changed. In addition, as the swirl ratio is reduced at high-speed and low-medium-speed partial loads, not only the fuel efficiency improves, but NOx also decreases (exhaust gas becomes clean) and Pmax decreases (engine durability improves). , Dp / dθ is also reduced (noise is reduced), which is advantageous in all respects.

The swirl map M obtained in consideration of the above has a high swirl ratio at least in the low speed and high load region and a medium and low swirl ratio in the other regions.

In the swirl map M shown in FIG. 1, low-speed / high-load regions, low-medium-speed / low-middle-high-load regions, low-medium-high-speed / low-medium-high load regions are partitioned in steps, and each is divided into high swirl ratio regions (for example, swirl ratio 4 .3), a medium swirl ratio region (for example, swirl ratio 3.3), and a low swirl ratio region (for example, swirl ratio 2.0).

Based on the above map, the optimum swirl ratio is selected according to the load and the rotational speed of the engine 1, the actuator 15 is controlled so that the swirl ratio becomes the relevant swirl ratio, and the amount of air sucked into the combustion chamber 6 from the auxiliary port 10 is reduced. It is changed, and the swirl ratio is changed.

By the way, as can be seen from FIG. 11, depending on the operating state, when the low swirl ratio is set, there is a case where there is a sufficient margin for the change amount of NOx. On the other hand, as can be seen from FIGS. 11 and 12, the performance changes by changing the fuel injection timing. In FIGS. 11 and 12, the characteristic indicated by the broken line is an injection timing change characteristic as an example. In the present invention, by adjusting the swirl ratio and the injection timing, the fuel consumption rate is further improved while the NOx change amount is suppressed within the specified value. For example, in FIG. 13, the points indicated by indicate the current swirl ratio and the fuel injection timing that satisfy the specified values for both the fuel consumption rate and the NOx emission amount, and from this point, the swirl ratio is further lowered. And NOx emissions can be reduced. However, here, if the NOx emission amount is suppressed to a specified value and the fuel injection timing is advanced, the point becomes and fuel efficiency is further improved. That is, as shown in FIG. 13, in addition to the fuel consumption reduction (A) by lowering the swirl ratio, the fuel consumption reduction B can be achieved by advancing the fuel injection timing.

The actual control is based on the engine operating condition and swirl ratio. From the diagram in each operating condition shown in Fig. 11, the fuel consumption satisfies the specified value even if the swirl ratio is increased, and the change in fuel injection timing improves fuel consumption. The area that contributes to is determined and controlled accordingly.

<Effects of the Invention> According to the swirl control device of the present invention, the swirl state can be easily changed by using the intake system as a variable swirl intake system including the main port and the auxiliary port, and at the same time, a sufficient amount of air is constantly maintained. In addition, the optimum swirl ratio can be selected according to the operating state of the engine, so that combustion efficiency can be improved, NOx in exhaust gas can be reduced, and smoke concentration can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an embodiment in which an engine is a cross section along a plane, and FIG.
Fig. 4 is a side sectional view of a part of the engine, Fig. 4 (A) is a diagram for explaining swirl components in a high swirl state, Fig. 4 (B) is a diagram for explaining swirl moment in the same state, and Fig. 5
FIG. 6A is a diagram for explaining a swirl component in a low swirl state, FIG. 6B is a diagram for explaining a swirl moment in the same state, and FIG. 6A is a perspective view for explaining a low swirl state. 7B is a perspective view for explaining the swirl state, FIG. 7C is a diagram for explaining the spray state, FIG. 7 is a perspective view for explaining the intake state, and FIGS. 8 to 12 are swirls. Fig. 13 is a diagram showing the relationship between the ratio and NOx emission amount, fuel consumption rate, smoke concentration, etc., and Fig. 13 is a diagram showing the relationship between the swirl ratio, the fuel consumption rate change amount due to changes in injection timing, and the NOx change amount. Yes, FIG. 14 (A) is a cross-sectional plan view of an ordinary intake device.
(B) is a sectional view taken along the line BB, FIG. 15 (A) and (B) are schematic plan views of a conventional variable swirl port, and FIG. 16 (A) is a schematic perspective view thereof. ) Is an explanatory view of the spray state, the same figure (C)
FIG. 4 is an explanatory diagram of an intake state. In the drawings, 1 is an engine, 6 is a combustion chamber, 8 is an intake valve, 9 is a main port, 10 is an auxiliary port, 11 is an intake manifold, 14 is a valve, 15 is an actuator, 16 is a control unit, and M is an optimal swirl map. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Komuro 4-21-1, Shimomaruko, Ota-ku, Tokyo Mitsubishi Motors Corporation Tokyo Motor Manufacturing Co., Ltd. Maruko factory (56) Reference JP-A-56-50226 (JP, A) Actual development Sho-58-132145 (JP, U) Actual development Sho-59-126132 (JP, U) Japanese patent publication Sho 57-19292 (JP, B1)

Claims (1)

[Claims] 1. A main port which is connected to an upstream side of an intake valve of a combustion chamber and has a forward swirl flow of air which flows into the combustion chamber, and a main port separate from the main port and extends downward from above the main port. A combustion chamber axis line of the intake flow when the intake air is connected to the vicinity of the intake valve seat so as to be directly guided into the combustion chamber via the intake valve seat and flows into the combustion chamber through the gap between the intake valve and the intake valve seat. With respect to the forward swirl flow in the combustion chamber by a velocity component in the vertical direction, and a sub-port that forms a reverse swirl flow that is opposite to the forward swirl flow, and the forward swirl in the combustion chamber by changing the amount of air flowing through the sub-port. Flow and a swirl ratio of the forward swirl flow generated from the sum of the reverse swirl flow, and a valve control system for operating the valve mechanism by selecting the swirl ratio based on the load and the engine speed of the engine. A swirl control, characterized in that the valve control system includes timing control means for selecting a low swirl ratio when the engine is at high rotation speed or low / medium load at middle rotation speed and further for accelerating fuel injection timing. apparatus.