JPH11350989A - Suction controller of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve decrease in intake noise and improvement in accuracy in controlling fuel injection in the delayed close mirror cycle of the engine. SOLUTION: During the delayed close mirror cycle operation, two inlet valves 3A, 3B for each cylinder are as follows. The inlet valve 3A is opened near the suction top dead center and shuts near the suction bottom dead center. The inlet valve 3B is opened near the suction bottom dead center, and shuts after the suction bottom dead center during the compression stroke. Further, this is constructed in such a way that he fuel is injected only to the inlet port on the side of the inlet valve 3A. As a result, intake air flows in only from the inlet valve 3A into the cylinder during the intake stroke. A part of the intake air in the cylinder flows backward only to the inlet valve 3B during the compression stroke. Accordingly, collision of intake airs with a different flow direction is avoided and the intake noise is prevented. Moreover, the fuel injection accuracy improves preventing the wall flow from flowing backward.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine capable of controlling intake air in a late closing Miller cycle, and more particularly to a technique for improving intake noise and fuel injection performance.

[0002]

2. Description of the Related Art In an engine in which the amount of intake air is controlled by a throttle valve, throttle loss of the throttle valve is involved, thereby deteriorating fuel economy. In order to improve this, there is known a Miller cycle engine in which the closing timing of an intake valve is controlled to control the amount of intake air while taking in intake air at atmospheric pressure. In addition to eliminating losses, reduce the effective compression ratio,
There are advantages that the thermal efficiency can be sufficiently increased by, for example, ensuring the expansion ratio as usual, and that NOx can be reduced by lowering the temperature of the combustion chamber. The Miller cycle engine has an early closing Miller cycle that shuts off the intake system and the cylinder before the intake bottom dead center by controlling the closing timing of the intake valve, and shuts off the intake system and the cylinder after the intake bottom dead center. There is a late closing Miller cycle.

[0003]

The late-closing Miller cycle can be controlled even at a high rotation where it is difficult to control the closing timing of the intake valve in the early closing Miller cycle. The intake valve closes when the piston speed before intake bottom dead center is low, so the intake flow speed to the silling is low and the fuel mixability in the cylinder is low, whereas in the slow closing Miller cycle, the piston descends Since the intake flow rate can be sufficiently increased in the stroke and sufficient agitation is performed in the piston ascent stroke, there is an advantage that the mixing property of the fuel is excellent.

An engine for performing the above-mentioned delayed closing mirror cycle is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-102982. In this engine, two intake valves are provided for each cylinder, and the intake valves are closed sufficiently later than the intake bottom dead center to perform a late closing mirror cycle operation. However, in the intake control in the conventional slow-closing Miller cycle, the intake air once taken into the cylinder enters the piston ascent stroke and is blown back to the intake port. The intake air collides with the intake air, which vibrates the intake pipe and generates intake noise.

[0005] In an engine that injects fuel into the intake port, fuel droplets and wall flow are transported from the intake port into the cylinder in accordance with the flow rate of the intake air. The air that is sometimes blown back to the intake port causes the fuel in the cylinder near the intake port opening, particularly the wall flow, to flow back to the intake port, making it difficult to control the fuel amount and the mixing ratio in the cylinder. . In addition, when the amount of residual fuel in the intake port increases, and as a result, especially when the engine rotational speed continuously fluctuates, for example, at the time of idling rotational speed control, the amount of fluctuation of the residual fuel amount increases, and In some cases, the fluctuation amount of the fuel ratio becomes large and the fuel efficiency deteriorates.

The present invention has been made in view of such conventional problems, and has as its object to reduce intake pipe vibrations and intake noise by devising the flow of intake air in a late closing mirror cycle. It is another object of the present invention to improve the control accuracy of the fuel amount and the mixing ratio in the cylinder and improve the fuel efficiency.

[0007]

According to the present invention, there is provided an intake valve driving means for driving two intake valves for each cylinder and opening and closing these intake valves at respective set opening / closing timings. And, under the condition of operating in a late closing Miller cycle, one intake valve is closed near the bottom dead center of the intake, and the other intake valve is opened almost simultaneously with the closing of the one intake valve. Opening and closing timing setting means for setting the opening and closing timing so as to close the valve after the intake bottom dead center.

According to the first aspect of the present invention, under the condition of operating in the slow closing Miller cycle, only one of the two intake valves of each cylinder is opened until the vicinity of the intake bottom dead center is reached. The intake air flows into the cylinder only through the intake valve. Next, while the other intake valve is opened almost at the same time as the closing of the one intake valve and closed after intake bottom dead center,
The intake air in the cylinder flows backward only from the other intake valve.

Here, since the other intake valve is closed up to near the intake bottom dead center, no intake air flows in the cylinder direction at the intake port connected to the other intake valve. The intake air flowing backward from the intake air flows out of the other intake valve smoothly, and the vibration of the intake pipe and the generation of intake noise due to the collision of the intake air flows can be prevented. The invention according to claim 2 is characterized in that, under the condition of operating in the late closing Miller cycle, the fuel is injected only to the intake port side connected to one intake valve whose closing timing is set before the intake bottom dead center. Features.

According to the second aspect of the present invention, under the condition of operating in the slow closing Miller cycle, the fuel injected only to the one intake port side connected to the one intake valve opens only the one intake valve. While the valve is being opened, the air flows into the cylinder by the intake air flow only from the one intake port. Here, since only the one intake port is open, 2
Since the flow rate of the intake air is faster than when one of the intake ports is opened, the fuel can efficiently flow into the cylinder, and the amount of fuel remaining in the one intake port can be reduced.

Next, when the one intake valve closes near the intake bottom dead center and the other intake valve opens almost simultaneously, the intake air in the cylinder is transferred from the other intake valve to the other intake valve as described above. Backflow into the other intake port of the series. At this time, since the one intake valve is closed, there is no reverse flow of fuel from the one intake port, and no fuel is injected into the other intake port connected to the other intake valve. There is no wall flow of fuel at the other intake port, so there is no backflow of the wall flow, and only a part of small droplets and vaporized particles having a small particle diameter floating in the intake air in the cylinder is supplied to the other intake port. , The amount of backflow fuel is greatly reduced.

As described above, since the backflow of the fuel to the intake port can be sufficiently suppressed, the control of the fuel amount and the mixing ratio in the cylinder can be performed with high accuracy. Since the amount (equilibrium residual fuel amount) can be sufficiently reduced, the air-fuel ratio control accuracy at the time of idle speed control and the like can be improved, and the fuel efficiency can be improved. The invention according to claim 3 is characterized in that the fuel injection is terminated before the closing timing of the one intake valve under the condition of operating in the late closing Miller cycle.

According to the third aspect of the present invention, when fuel is injected after the one intake valve is closed, the fuel injected after the closing of the one valve remains in the intake port as it is. The amount increases. Therefore, by ending the fuel injection before the closing timing of the one intake valve, the equilibrium residual fuel amount can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 showing an embodiment, an engine 1 has two intake valves 3A,
3B and exhaust valves 4A and 4B, and corresponding intake ports 5A and 5B and exhaust ports 6A and 6B.
The opening and closing of the intake valves 3A and 3B and the exhaust valves 4A and 4B are electronically controlled by a valve driving device 2. Here, the valve drive device 2 is configured to be able to independently control the opening and closing of at least two intake valves 3A and 3B.

A fuel injection valve 7 is mounted near a branch point between the two intake ports 5A and 5B.
It has two injection holes 7a and 7b for injecting fuel toward the two intake ports 5A and 5B, respectively.
The fuel injection can be freely switched between a case where fuel injection is performed simultaneously from a and 7b and a case where fuel injection is performed only from the injection hole 7a (see hatching in the figure).

An ignition plug 9 and an ignition coil 10 are mounted in the combustion chamber 8. In addition, the engine body outputs a reference signal at a reference crank angle of each cylinder, a crank angle sensor 11 that outputs a unit angle signal for each minute crank angle, an air flow meter 12 that detects an intake air flow rate, and a cooling water temperature. A water temperature sensor 13 to be detected is mounted. Is installed.

Signals from the various sensors are output to a control unit 14. The control unit 14 outputs a fuel injection signal to the fuel injection valve 7 based on these detection signals to perform fuel injection control, and Coil 10
To control the opening and closing of the intake valves 3A and 3B and the exhaust valves 4A and 4B by outputting a valve drive signal to the valve drive device 2.

FIG. 3 shows the structure of the valve driving device 2. In FIG. 3, a valve driving device 2 includes a housing 21 made of a non-magnetic material provided on a cylinder head, and intake valves 3A and 3B.
(Or exhaust valves 4A, 4B, hereinafter represented by intake valves 3A)
An armature 22 provided integrally with the stem 31 and freely housed in the housing 21, and an upper surface of the armature 22 so as to exert an electromagnetic force for sucking the armature 22 and closing the intake valve 3A. A valve-closing electromagnet 23 fixedly disposed in the housing 21 at a position facing the armature 22 and a lower surface of the armature 22 so as to exert an electromagnetic force for attracting the armature 22 and opening the intake valve 3A. Valve-opening electromagnet 24 fixedly arranged in the housing 21 at the position
A valve-closing-side return spring 25 that urges the armature 22 toward the valve closing direction of the intake valve 3A, a valve-opening-side return spring 26 that urges the armature 22 toward the valve opening direction of the intake valve 3A, It is comprised including. When both the valve-closing electromagnet 23 and the valve-opening electromagnet 24 are demagnetized, the valve-closing-side return spring 25 and the valve-closing-side return spring 25 are moved so that the intake valve 3 is located substantially at the center between the fully open position and the valve-closing position. When the spring force with the valve-opening side return spring 26 is set and only the valve-closing electromagnet 23 is excited, the intake valve 3A closes,
When only the valve opening electromagnet 24 is excited, the intake valve 3A is driven to open (fully open). The valve driving device 2 constitutes intake valve driving means.

Intake valves 3A, 3B by the valve drive device 2
The opening / closing timing of the exhaust valves 4A and 4B is controlled to be a target opening / closing timing set based on the operating state of the engine 1. 4), as shown in FIG. 4, one intake valve 3A opens near the intake top dead center and closes near the intake bottom dead center, and the other intake valve 3B closes the one intake valve. The valve is opened almost at the same time as the closing timing of 3A, and is controlled to close at a timing set according to the target intake air amount after the intake bottom dead center. Therefore, the control unit 12 for controlling the opening / closing timing of the intake valves 3A, 3B via the valve driving device 2 has the function of the opening / closing timing setting means in the present invention in software.

Next, the operation during the execution of the late closing mirror cycle will be described with reference to FIGS. One intake valve 3A opens near the intake top dead center, while the other intake valve 3B is kept closed. Therefore, the intake air flows into the cylinder through only one intake port 5A. Further, only one injection hole 7a of the fuel injection valve 7 is opened, and fuel is injected only into the one intake port 5A. As shown in FIG. 5, a part of the injected fuel is vaporized, a part of the fuel becomes a droplet, and a part of the fuel becomes a wall flow attached to the wall of the intake port 5A. Or it is dragged and flows into the cylinder.

Here, the intake air is supplied to one intake port 5A.
Since the fuel flows only from the two intake ports, the flow velocity is sufficiently large as compared with the case where the fuel flows from the two intake ports at the same time. Therefore, the fuel efficiently flows into the cylinder. Next, as shown in FIG. 5, the one intake valve 3A closes near the intake bottom dead center, and the other intake valve 3B opens almost simultaneously. Until the intake valve 3B closes at a set time after the intake bottom dead center, the intake air in the cylinder flows backward from the intake valve 3B into the intake port 5B due to the rise of the piston. Here, since the intake valve 3B is closed to near the intake bottom dead center,
No intake air flow in the cylinder direction is generated in the intake port 5B. Therefore, the intake air flowing backward from the cylinder flows out of the intake port 3B smoothly without colliding with the intake air flow in the cylinder direction. Vibration and intake noise can be prevented.

In addition, the intake valve 3A
Is closed, there is no backflow of fuel from the intake port 3A, and intake air in the cylinder flows backward toward the intake valve 3B. However, since no fuel is injected into the intake valve 3B side, the intake port 5B Has no fuel wall flow and therefore no wall flow backflow. Large droplets having a particle size of about 20 μm or more that move at a relative speed with respect to the backflowing air do not substantially flow back to the intake port 3B, and only the droplets having a particle size of less than about 20 μm and a part of the vaporized portion are removed. It flows backward to the intake port 3B. In this way, by eliminating the backflow of the wall flow, the amount of fuel in the cylinder and the mixing ratio can be controlled with high precision, and the amount of equilibrium residual fuel can be greatly reduced. The air-fuel ratio control accuracy is improved, and the fuel efficiency can be improved.

Compared with the conventional case where the two intake valves are opened and closed at the same timing to execute the delayed closing Miller cycle, conventionally, the two intake ports are opened while the piston descends, and these two intake ports are opened. After the intake air flows into the cylinder via the intake port, and after the piston rises, the intake air in the cylinder flows back to the two intake ports. The intake air that flows backward to the port collides, causing the intake pipe to vibrate and generate intake noise.

In addition, as shown in FIG. 7 in comparison with the present embodiment, in the conventional example, since the intake air flows into the cylinder through two intake ports, the flow velocity of the intake air into the cylinder is small. , Fuel tends to remain in the intake port. on the other hand,
After the piston rises, the wall flow, small droplets (less than about 20 μm) droplets, and vaporized gas flow back into the two intake ports in the fuel inside the cylinder, so that the wall flow fuel flows back and the backflow fuel The amount of fuel greatly increases and the control accuracy of the fuel amount and the mixture ratio in the cylinder decreases, and the amount of equilibrium residual fuel remaining in the intake port eventually increases. The control accuracy decreases, and the fuel efficiency also deteriorates.

As described above, when the late closing mirror cycle according to the present embodiment is executed, the intake ports are selectively opened during the intake stroke and the compression stroke, thereby reducing the vibration of the intake pipe and the intake noise. As a result, the amount of fuel flowing back to the intake port, particularly the wall flow rate, can be significantly reduced as compared with the conventional case, so that the amount of fuel in the cylinder and the mixing ratio can be accurately controlled, and the balance of the intake port can be improved. As a result, the amount of residual fuel can be significantly reduced, so that the air-fuel ratio control accuracy at the time of idle speed control and the like can be improved, and the fuel efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram according to an embodiment.

FIG. 2 is a partial cross-sectional view of the same system configuration diagram.

FIG. 3 is a sectional view showing the configuration of the valve drive device according to the embodiment;

FIG. 4 is a diagram showing open / close timing characteristics of two intake valves in the embodiment.

FIG. 5 is a sectional view showing a state inside the cylinder during the intake stroke of the embodiment.

FIG. 6 is a cross-sectional view showing the inside of the cylinder in the first half of the compression stroke of the embodiment.

FIG. 7 is a view showing a fuel amount characteristic in the embodiment in comparison with a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Valve drive device 3A, 3B Intake valve 4A, 4B Exhaust valve 5A, 5B Intake port 6A, 6B Exhaust port 7 Fuel injection valve 14 Control unit

Claims (3)

[Claims] 1. An air conditioner comprising: two intake valves for each cylinder; and intake valve driving means for driving the intake valves to open and close at respective set opening and closing timings, and operating under a slow-closed mirror cycle. The opening / closing timing is set so that one intake valve is closed near the bottom dead center of the intake and the other intake valve is opened almost simultaneously with the closing of the one intake valve, and is closed after the bottom dead center of the intake. An intake control device for an engine, comprising: an opening / closing timing setting unit that performs opening and closing timing. 2. An intake control system for an engine according to claim 1, wherein fuel is injected only into an intake port connected to said one intake valve under the condition of operating in the late closing Miller cycle. 3. The intake control system for an engine according to claim 2, wherein the fuel injection is terminated before the closing timing of the one intake valve under the condition of operating in the late closing Miller cycle.