JPS61126320A - Intake-air device in internal combustion engine - Google Patents

Abstract

PURPOSE:To aim at enhancing the stability of combustion upon valve opening and closing operation, by instantly operating an intake-air passage shut-off valve which opens upon high load operation of an engine having two intake valves for every engine cylinder, from its minimum opening degree to its maximum opening degree, and then by stepwisely opening the valve. CONSTITUTION:For every engine cylinder, a high speed type intake valve 11A having a long valve opening period and a low speed type intake valve 11B having a short valve opening period are provided. Further, actuators 19, 20 are provided at both ends of a rod 18 in a valve 15, and maintain a shut-off valve at its open position upon low load operation. When a control device 30 receives a rotational speed signal and an intake-air pressure signal, and therefore detects the middle load operation, it opens a solenoid valve 23 to actuate the actuator 19 with the use of vacuum from a vacuum tank 24, and instantly operates the valve 15 by a set stroke up to a predetermined opening degree to open the valve 15. Thereafter a solenoid valve 28 is opened upon operation with a load above a predetermined load to operate the actuator 20 to fully open the valve 15.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a technology for improving the intake system of an internal combustion engine having two intake valves for each cylinder.

<Prior art> As a prior art of the intake system of this type of internal combustion engine, there is, for example, the one shown in FIG.
No. 356).

This is a high-speed intake valve I with a large delay in closing timing for each cylinder.
A and a low-speed intake valve IB with a small delay in closing timing, and an on-off valve 3 is provided at the intake port 2A in which a high-speed intake valve IA is inserted, and the on-off valve 3 is closed in the low speed range of the engine and is closed in the high speed range. We are trying to open it in the area.

That is, in the low speed range, air is taken only through the intake port 2B equipped with the low speed intake valve IB with a small delay in closing timing, thereby increasing the effective compression ratio (hereinafter referred to as the actual compression ratio) and improving the intake air filling efficiency. In addition, by generating a large swirl in the combustion chamber 4 using the intake air flowing in the tangential direction, we aim to improve combustibility at low speeds. By using the intake valve IA in conjunction with the intake valve, the inertia effect of the intake air is effectively used, and by opening the two intake ports, the intake resistance is reduced and the intake air filling efficiency is increased, leading to improved output. ing.

Further, since the on-off valve 3 is opened less frequently in the normal operating range, the fuel injector 5 is provided on the side of the intake boat 2A, which is always open, in order to obtain stable air-fuel ratio control responsiveness.

Note that two exhaust valves 6A, 6B and two exhaust ports 7A, 7B are also provided.

<Problem to be solved by the invention> By the way, in such an intake system, the on-off valve 3 is closed in the medium speed range.
When the opening is instantaneously opened from the fully closed state to the maximum opening, the cross-sectional area of the intake boat doubles, so the flow velocity of the intake air is halved at once, and the intake air is combusted in approximately equal amounts from the two intake boats 2A and 2B in parallel. Since it is introduced into the combustion chamber 4, swirl generation within the combustion chamber 4 disappears.

For this reason, the diffusion of the fuel spray and the mixing with the air within the combustion chamber 4 are not performed well, and a quench layer formed by the fuel adhering to the wall surface of the combustion chamber 4 is deposited on the intake boat 2B on the side where the fuel injector 5 is installed. HC tends to be concentrated near the interposed intake valve IB, and is discharged unburnt due to the thick quench layer.
(hydrocarbons) increases. Especially in the case of an internal combustion engine with an exhaust turbo supercharger, the air-fuel ratio must be enriched to lower the exhaust temperature due to the heat resistance of the turbine rotor, which increases the quench layer and causes a noticeable increase in HC emissions. Become something.

In view of this, by gradually opening the on-off valve 3 over a wide speed range, the amount of intake air from the intake port 2B side is prevented from being halved all at once when the valve is opened, and the fuel in the combustion chamber 4 is The present applicant has proposed a method for preventing an increase in HC due to uneven distribution of the quench layer.

FIG. 6 shows the sharing ratio of the intake air amount between the low-speed side intake boat 2B and the high-speed side intake boat 2A, the air-fuel ratio of the low-speed side intake boat 2B, and the HC when the opening degree of the on-off valve 3 is gradually increased.
Shows the characteristics of generated concentration (constant engine speed).

As shown in the figure, as the opening degree of the on-off valve 3 increases, the intake bow)
The air-fuel ratio of 2B becomes enriched, but the HCrM degree rises from the moment the valve opens to a certain degree. ! Once in a while, there is almost no change.

On the other hand, the closing timing of the high-speed intake valve LA is later than the closing timing of the low-speed intake valve IB, and is set near the middle of the compression stroke. Since the intake air is also small, a backflow of intake air occurs from the high-speed intake valve IA through the on-off valve 3 at the beginning of the compression stroke, and the actual compression ratio decreases.

In this case, since the low-speed intake valve IB is already closed, the intake air whose pressure has increased due to the rise of the piston flows backward from the high-speed intake valve IA, so that the reverse flow rate increases rapidly as the opening of the on-off valve 3 increases. As a result, the actual compression ratio also has a characteristic of rapidly decreasing at the beginning of opening of the on-off valve 3.

Furthermore, when the opening degree of the on-off valve 3 is increased, the share of the intake air amount of the high-speed intake port 2A increases, and the swirl strength gradually decreases accordingly.

The decrease in the actual compression ratio and the decrease in the swirl strength lead to a decrease in the combustion speed, and therefore, as the combustion speed decreases, it is necessary to advance the ignition timing, so the ignition timing is adjusted according to the actual compression ratio as shown in Fig. 7. A characteristic is required in which the angle is greatly advanced at the beginning of the opening of the on-off valve 3, where the decrease in the opening is large, and thereafter, the angle is gradually advanced as the opening degree of the on-off valve 3 increases.

However, rapidly changing the ignition timing according to the opening degree of the on-off valve 3 at the initial stage of opening of the on-off valve 3 requires highly accurate control, and moreover, for example, the opening degree of the on-off valve 3 varies between cylinders. If this occurs (particularly in the small opening range, the degree of variation tends to increase), the ignition timing will be too advanced, causing non-king, or conversely, the ignition timing will be too late, resulting in insufficient output.

In this way, gradually changing the opening/closing valve 3 even in the early stages of opening/closing has little effect on reducing HC emissions as described above (it makes it difficult to control the accuracy of ignition timing and opening degree control of the opening/closing valve 3). Only.

The present invention has been made in view of the above-mentioned problems, and by changing the opening control method of the on-off valve, it is possible to perform simple and reliable ignition control while sufficiently achieving the function of reducing unburned HC. Further, it is an object of the present invention to provide an intake system for an internal combustion engine that allows stable drivability to be obtained.

Therefore, the present invention opens the on-off valve instantly between the minimum opening degree and a predetermined opening degree, and gradually opens the on-off valve between the predetermined angle and the maximum opening degree. Alternatively, a configuration is provided in which a valve opening degree control means for continuously opening the valve is provided.

With this configuration, there is no need for highly accurate ignition control according to the opening degree of the on-off valve at the initial stage of opening, and problems such as knocking and insufficient output due to variations in the opening degree of the valve are eliminated. is also avoided.

<Example> Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show a first embodiment, in which a high-speed intake valve 11A, a low-speed intake valve 11B, and these are interposed in each cylinder of an internal combustion engine equipped with an exhaust turbocharger (not shown). Intake boats 12A, 12B and two exhaust valves 13A, 13B
and exhaust ports 14A and 14B are provided, and the intake boat 12A is equipped with an on-off valve 15, and the intake port 12B is equipped with a fuel injector 16, respectively. 17 is a combustion chamber.

Here, the opening/closing characteristics of the high-speed intake valve 11A, the low-speed intake valve 11B, and the exhaust valves 13A and 13B are as shown in FIG. 4, and the closing timing of the high-speed intake valve 11A is delayed to the middle of the compression stroke. The closing timing of the low-speed intake valve 11B is set earlier than this, near the bottom dead center of the compression stroke.

As a configuration according to the present invention, an opening control means for the on-off valve 15 is provided as follows. The on-off valve 15 of each cylinder is fixed to a single rod 18, and at both ends of the rod 18 there are actuators 19 for driving the on-off valve 15 to a predetermined intermediate degree, and actuators 19 for driving the on-off valve 15 to a predetermined intermediate degree. The on-off valve 15 is connected to the actuator 20, and by properly using these two actuators 19 and 20, the on-off valve 15 can be fully closed (minimum opening) - intermediate opening (approximately 30°) - fully open and maximum opening near 0° to 90°. ) The opening degree is selectively controlled in three stages.

That is, the actuator 19 for intermediate opening is
/F19°"' O-/F 1B(7)-01"'"
1877°; Negative pressure working chamber 19c defined by the diaphragm 19 that engages with the elongated hole 22a of the lever 22 eccentrically supported by the rate 21 and fixes the output rod 19a.
A negative pressure inlet of the solenoid valve 23 is connected to the vacuum tank 24 via the a)a++1)+ of the solenoid valve 23.

The vacuum tank 24 introduces negative intake pressure from an intake manifold (not shown) via a check valve 25 and accumulates the intake pressure.

On the other hand, the actuator 20 for fully opening the on-off valve 15 has the same structure as the actuator 19 for intermediate opening.
The output rod 20a and the plate 26 fixed to the other end of the rod 18 are connected by a lever 27 without any play. The negative pressure working chamber 20c defined by the diaphragm 20b of the actuator 20 is connected to the boats aZ, b of the solenoid valve 28.
2 to the intermediate opening actuator 19 and the solenoid valve 23
It is connected to the piping that connects the

On the other hand, an intake pressure sensor 29 is provided to detect the intake pressure signal at the confluence of the intake boats 12A and 12B, and the intake pressure signal from this intake pressure sensor 29 and the rotational speed signal from a crank angle sensor (not shown) are input. The control unit 30 controls the on-off valve 1 by controlling the two solenoid valves 23 and 28 to turn on and off according to the engine operating range.
5 to control the opening.

That is, the intake pressure is less than a predetermined value (20On+mHg), or the engine rotation speed is a predetermined value (for example, 2800 rpm+m2).
In the low load and low speed range below
By communicating with '2, actuator 19.20
The insides of the negative pressure working chambers 19c and 20C are maintained at atmospheric pressure. As a result, the output rods 19a and 20a are in the extended position due to the urging force of the return springs 19d and 20d installed in the negative pressure working chambers 19c and 2Oc, and in this state, the on-off valve 15 is fully closed (minimum (opening).

When the intake pressure is above a predetermined value and the engine rotational speed is above a predetermined value, the solenoid valve 23 is turned ON and the solenoid valve 28 is turned O.
Hold in FF.

As a result, the boat a+ of the solenoid valve 23 is switched to communicate with the boat b1, and negative pressure from the vacuum tank 24 is introduced into the negative pressure working chamber 19c of the actuator 19, against the biasing force of the return spring 19d. Output rod 19a is retracted. In this case, lever 22
The amount of rotation of the plate 26 and the rod 18 integral therewith is reduced by the amount of play in the elongated hole 22a, and the on-off valve 5 is instantly opened to a predetermined intermediate opening degree (for example, 30 degrees). Thereafter, in the medium speed range until the rotational speed reaches about 400 rpm, the on-off valve 15 is kept precisely constant at this medium opening degree.

In this way, by opening the opening/closing valve 15 from fully closed to intermediate opening at once, the ignition timing can be advanced in steps, and the opening/closing valve 15 can be controlled with high accuracy in accordance with changes in opening. While highly accurate management of the opening degree is no longer required, advance angle control is performed simply and with high reliability, and it is possible to avoid knocking and insufficient output due to variations in the opening degree of the on-off valve 15, and to ensure stable drivability. Can be maintained.

By appropriately setting the intermediate opening, unburned H
The increase in C can be suppressed well.

Furthermore, the rotation speed increases to a predetermined high speed value (4000r
When the temperature reaches above pm), the solenoid valve 28 is also turned on.
Ports az and bz communicate with each other, and the negative pressure from the hakinem tank 24 is applied to the solenoid valves 23 (a+, b+) and the solenoid valve 2.
It is also introduced into the negative pressure working chamber 20c of the actuator 20 through ports az and bz of No. 8, and the output rod 20a is drawn in. As a result, the lever 27. Plate 26. The on-off valve 15 is switched from the intermediate opening degree to the fully open position via the rod 18 (
Maximum opening degree) - open to the air.

In such a high-speed range, the increase in intake flow velocity causes mixing of fuel and air within the intake port and combustion chamber.

Since the vaporization property is improved, the amount of unburned HC discharged can be suppressed to a sufficiently low level.

By controlling the opening degree of the on-off valve as described above, it is possible to improve fuel efficiency and output by using swirl and increasing the actual compression ratio in the low speed range, and by using inertial supercharging in the high speed range. Of course, it is possible to improve output and fuel efficiency while suppressing the occurrence of knocking.

In addition, in this embodiment, the on-off valve opening degree is divided into three stages, but control may be performed in more stages than this, and furthermore, the minimum opening degree and the intermediate opening degree may become problematic. It may be configured such that only the opening between the two openings is instantaneously opened and closed, and the opening between the intermediate opening and the maximum opening is opened and closed continuously according to changes in the rotational speed.

<Effects of the Invention> As explained above, according to the present invention, the structure is such that the change in the actual compression ratio with respect to the change in the opening of the on-off valve is instantaneously controlled from the minimum opening to a predetermined intermediate opening. , while suppressing an increase in the amount of unburned HC discharged, simple ignition advance control is performed, and good output control can be performed without causing knocking due to variations in opening/closing valve openings, etc.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the overall configuration of an embodiment of the present invention, FIG. 2 is a view taken in the direction of arrow A in FIG. 1, and FIG. 3 is a view taken in the direction of arrow B in FIG. 1.
FIG. 4 is a diagram showing the intake/exhaust valve opening characteristics of the same example as above;
Figure 5 is a sectional view showing the outline of the earlier application filed by the present applicant;
The figure shows the intake air volume sharing ratio of the two intake ports with respect to the opening/closing valve opening degree, the air-fuel ratio of the low-speed intake port, and the Hc
FIG. 7 is a diagram showing the concentration characteristics, and FIG. 7 is a diagram showing the ignition advance control value and actual compression ratio characteristics with respect to the opening degree of the on-off valve. 11A...High-speed intake valve 11B...Low-speed intake valve 12A, 12B...Intake port 15...Open/close valve
18... Rod 19... Actuator (for on-off valve intermediate opening) 20... Actuator (for on-off valve fully open) 21, 26... Plate 22.27...
Lever 22a... Long hole 23. 28... Solenoid valve 24... Vacuum tank 29... Intake pressure sensor 30... Control unit patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima Figure 2 Broom 3 Figure 4 Figure 5

Claims (1)

[Claims] Each cylinder is equipped with a high-speed intake valve with a relatively large closing timing delay, a low-speed intake valve with a relatively small closing timing, and two intake ports in which these intake valves are interposed. In an intake system for an internal combustion engine, in which an interposed intake port is provided with an on-off valve that opens and closes according to engine operating conditions, the on-off valve is instantaneously opened between a minimum opening degree and a predetermined opening degree, and 1. An intake system for an internal combustion engine, comprising a valve opening control means that opens the valve in stages or continuously between the maximum angle and the maximum angle.