JPS61286526A - Intake/exhaust valve device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve intake air filling efficiency, by a method wherein two intake ports are formed in each cylinder, a fuel feed device is situated in the one intake port, and an on-off valve in the other intake port. CONSTITUTION:Second intake ports 12A and 12B, opened and closed by first and second intake valves 11A and 11B, are formed in each cylinder, a fuel injection valve 16, feeding fuel, is positioned in the first intake port 12A, and an on-off valve 13 to the end part on the upper stream side of the second intake port 12B. First and second exhaust valves 14A and 14B, opening and closing first and second exhaust ports 15A and 15B, are positioned opposite to the intake valves 11A and 11B, respectively. With this constitution, the opening timing of the first intake valve 11A is set so that the first intake valve is opened by the phase difference alpha at an opening timing earlier than that of the second intake valve 11B, and is set to the phase difference alpha satisfying alpha<=(1/2)theta0 in relation to an overlap period theta0 in which the first intake valve 11A and the exhaust valves 14A and 14B are all opened.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applied to the intake and
This invention relates to an exhaust valve device.

<Prior Art> As a conventional example of an intake/exhaust valve device for an internal combustion engine, there is one shown in Figs. 7 and 8 (Japanese Patent Publication No. 47-3172
(See Publication No. 4 and Japanese Patent Application No. 58-225356).

That is, each cylinder of the engine has a first intake valve LA.

The second intake valve IB and the first intake valve IB. Second exhaust valves 2A and 2B are provided, the intake port is divided into a first intake port 3A and a second intake bow 1-3B, and an on-off valve 4 is provided in the second intake port 3B. The on-off valve 4 is operated by an actuator (not shown) that is operated by controlled negative pressure from a solenoid valve (not shown) by a control circuit (not shown) that detects engine operating conditions such as low speed or partial load region (hereinafter referred to as low speed region). figure)
Opening/closing is controlled by In the low speed range, by closing this on-off valve 4, the effect is essentially the same as that of the second intake valve IB, and intake air is introduced from one side to form a swirl and prevent exhaust blowback. ing. In medium/high speed/high load ranges (hereinafter referred to as medium/high speed ranges), this on-off valve 4 is opened and intake air is introduced from both the first and second intake valves LA, IB to ensure intake air filling efficiency. Since the opening/closing valve 4 is infrequently opened in the normal operation range, the fuel injection valve 5 is operated at the first intake valve that always introduces intake air into the combustion chamber 6 via the first intake valve IA in order to obtain a stable air-fuel ratio and responsiveness. 1 is provided on the intake port 3A side. 7 is a spark plug. Figure 8 is 1. The second intake valves IA, IB and the first. Second exhaust valve 2
These are the lift characteristics of A and 2B. 1st. second exhaust valve 2A,
2B have the same lift characteristics, but when comparing the lift characteristics of the first intake valve IA with the lift characteristics of the second intake valve IB,
The opening timing is slow (and the closing timing is early), and both the operating angle and maximum lift amount are small. If the first intake valve IA is used for low speeds, the second intake valve IB has lift characteristics for high speeds.

According to this configuration, in the low speed range, the on-off valve 4 is closed and air is taken only from the first intake port 3A side, and the lift characteristics of the first intake valve IA are utilized to improve fuel efficiency and stability by strengthening the swirl. In addition to improving low-speed torque, in the high-speed range, the on-off valve 4 is opened to take in air from the second intake port 3B side, and the second intake valve IB, which is set to high-speed characteristics, is lifted. We take advantage of its characteristics to ensure sufficient filling efficiency.

<Problems to be Solved by the Invention> By the way, in the above-mentioned conventional intake/exhaust valve device, the volume downstream of the on-off valve 4 cannot be reduced due to various restrictions, and the volume is 15 to 20% of the cylinder volume. Especially during idling, when the second intake valve IB closes at the beginning of the compression stroke, the inside of the second intake port 3B downstream of the on-off valve 4 becomes negative pressure of about 400 mm + I (g), and the exhaust gas When the second intake valve IB opens at the end of the stroke, the pressure difference between the exhaust gas and the air-fuel mixture causes the exhaust gas to flow into the second intake bow 3B. Therefore, the effect of suppressing exhaust gas blowback by the on-off valve 4 is small. At this time, the on-off valve 4 is only effective in improving the combustion speed due to swirl.

On the other hand, in the medium/high speed range where the on-off valve 4 is open, as shown in FIG. 8, the valve lift amount of the first intake valve IA is the lift of the second intake valve IB)! The first intake valve IA is set smaller and the first intake valve IA
Since the opening timing of the second intake valve IB is set later than that of the second intake valve IB, the amount of intake air introduced into the combustion chamber 6 via the first intake valve IA is extremely small compared to the second intake valve IB side. The intake flow velocity of the first intake port 3A through which fuel is supplied from the fuel injection valve 5 is not sufficient for vaporization and atomization of the fuel, which is unfavorable in terms of mixture formation.

By the way, in order to ensure good air-fuel mixture formation, it is preferable to open the first intake valve IA earlier than the second intake valve IB, but if the difference in the opening timing of these intake valves IA and IB is increased, the intake Filling efficiency decreases. Furthermore, when the amount of exhaust gas blowback is large, the intake air filling efficiency also decreases.

The present invention was developed in view of the above circumstances, and aims to form a mixture by reversing the opening timing of the two intake valves, and to reduce the amount of exhaust gas blowback and increase the intake air filling efficiency. The purpose of this invention is to know the limits regarding the valve overlap period during which both the opening timing of the first intake valve and the exhaust valve open, and the difference between the opening timing of the first intake valve and the second intake valve.

Means for Solving the Problems> For this reason, the present invention mainly aims at adjusting the opening timing of the first intake valve installed in the intake port to which fuel is supplied by adjusting the phase difference α from the opening timing of the second intake valve. The valve overlap period θ is such that the first intake valve and the exhaust valve are both opened. The phase difference α is set to satisfy α≦1/2θ0.

By setting the phase difference α between the two intake valves in this manner, sufficient intake air is introduced into the combustion chamber through both intake valves while reducing the residual gas concentration, resulting in sufficient intake air filling. In order to improve efficiency, the first intake valve to which fuel is supplied is opened early to ensure good mixture formation.

<Example> An example of the present invention will be described below based on FIGS. 1 and 2.

In the figure, each cylinder of an internal combustion engine is provided with first and second intake valves 11A and IIB, respectively.
12A and 12B are provided, and an on-off valve 13 is provided at the upstream end of the second intake port 12B.

Furthermore, first and second exhaust valves 14A and 14B are interposed in the first and second exhaust ports 15A and 15B, respectively, to face the first and second intake valves 11A and IIB, respectively.

The on-off valve 13 is closed in the low speed range, as in the conventional example, and is closed in the middle speed range.
The valve is configured to open at high speeds.

The opening/closing timing of the first intake valve 11A is set so that it opens around 20" before the top dead center of the intake stroke and closes around 50" after the bottom dead center of the compression stroke. The closing timing is set so that it opens around 16 degrees before the top dead center of the suction stroke and closes around 58 degrees after the bottom dead center of the compression stroke (
(see Fig. 2), and the first and second exhaust valves 14A, 14
The opening and closing timing of B is set so that it opens around 50 degrees before the bottom dead center of the expansion stroke and closes around 4 degrees after the top dead center of the suction stroke (see Fig. 2). Also, the first and second intake valves 11A.

Since the cam characteristic curves of 11B are approximately similar in terms of cam characteristics, the maximum lift amount of the first intake valve 11A is the same as that of the second intake valve 1.
It is larger than 1B.

In addition, 16 is a fuel injection valve as a fuel supply device that injects fuel toward the first intake port 12A, 17 is a combustion chamber, and 1
8 is a spark plug.

Next, the phase difference between the opening timings of the first intake valve 11A and the second intake valve 11B, and the first intake valve 11A that opens early and the valves that open both the first and second exhaust valves 14A and 14B, are as follows. 3 to 6, the results obtained using the following equations will be explained based on the overlap period and the change in the exhaust gas blowback flow rate as an adiabatic change in the compressible fluid (exhaust gas).

In other words, the exhaust blowback flow rate G for a unit crank angle
is obtained by

In the above formula, a represents the first and second exhaust valves 14A.

14B effective opening area, a2 is the first and second intake valve 11
A, IIB effective opening area, Pl is the first and second exhaust port) 15A, 15B exhaust pressure (set to atmospheric pressure here), P2 is the pressure of the combustion chamber 17, P3 is the first and second intake port Intake pressure of ports 12A and 12B (here -5
00++1lHH), g is the gravitational acceleration, k is the specific heat ratio of the exhaust gas, and v, , vz are the specific volumes of the combustion chamber and each port, respectively.

First, in this calculation, the opening timing of the first intake valve 11A and the closing timing of the first and second exhaust valves 14A, 14B are held substantially constant, and their valve overlap period is set to θ. (See FIG. 2), and the opening timing of the second intake valve 11B is changed within the range of the pulp overlap period. Then, there is a valve overlap period θ during which both the first intake valve 11A and the first and second exhaust valves 14A and 14B open. (See Figure 2) Find the change in the exhaust gas blowback flow rate G within the range.

FIG. 3 shows the second intake valve 11B and the first and second exhaust valves 14A, 14 when the opening timing of the second intake valve 11B is changed.
It shows the change in valve lift amount compared to B. Further, FIG. 4 shows the pressure change in the combustion chamber 17 at the same time as above, and FIG. It shows the change in the exhaust gas blowback flow rate G when the wrap period θ is changed.

Here, in FIGS. 3 to 5, the phase difference α (see FIG. 2) being the same phase means that the first and second intake valves 11A, IIB
is the valve overlap period θ. When the phase difference α is 0.50°, the second intake valve 11B opens from the middle of the valve overlap period, and the phase difference α is 0.50°. What is the second intake valve 11?
B opens simultaneously with the closing of the first and second exhaust valves 14A and 14B.

As is clear from FIG. 5, the exhaust blowback flow ilG reaches its maximum in the middle of the pulp overlap, and becomes approximately O in the early and late stages. This includes the first and second intake valves 11A, IIB and the first
and the second exhaust valves 14A, 14B.
When one of the valves 4A and 14B is both closed, the exhaust gas blowback flow rate G becomes O. Furthermore, as is clear from Fig. 5, as the phase difference α (see Fig. 2) increases, the exhaust blowback flow rate G decreases in the first half of the valve overlap period, and then the phase difference α decreases to 0.50°. From the moment it exceeds θ/θ, the rate of decrease decreases. >0.5, the exhaust gas blowback flow rate G hardly changes regardless of the change in the phase difference α. This means that the pressure P2 in the combustion chamber 17 is θ/θ. 0.5, the negative pressure suddenly becomes large because it is in the early stage of the intake stroke, so there is no change in the exhaust blowback flow rate G regardless of changes in the effective opening areas of the intake valves 11A and IIB.

Therefore, the phase difference α is 0.5θ. When the phase difference α increases, the exhaust gas blowback flow rate G hardly changes even if the phase difference α increases. As is clear from Fig. 6, which shows the exhaust blowback flow rate ratio Q/Q (1 (Q6 is the exhaust blowback flow it at the same phase), the total exhaust blowback starts from the vicinity where the phase difference α exceeds 0.5θ. The flow rate Q hardly decreases and remains approximately constant.As a result,
α〉0.5θ. Not only is this not effective in reducing the exhaust blowback flow rate, but it also causes a decrease in intake filling efficiency due to the delay in opening of the second intake valve 11B. Therefore, in order to increase the intake air filling efficiency, the first intake valve 11A and The phase difference α with the second intake valve 11B is α≦0.5θ. It is clear that it is desirable to set it within the range of .

Although the presence of the on-off valve 13 was not taken into consideration in this calculation, the valve over-ramp period θ of the first intake valve 11A, which has a relatively large intake port volume downstream of the on-off valve 13 and is not provided with the on-off valve 13. is larger than that of the second intake valve 11B, so the timing at which exhaust gas flows into the second intake port 12B is delayed.
This is because B is no longer filled with exhaust gas. When the valve overlap period θ0 is relatively small, the influence of the on-off valve 13 becomes even smaller and can be ignored.

Note that this phenomenon is true even in an engine equipped with one exhaust valve (two intake valves).

As explained above, if the phase difference α between the first intake valve 11A and the second rI & air valve 11B is set to α≦1/2θ0, sufficient intake air filling efficiency can be ensured. As shown in the figure, the first intake valve 11A and the second intake valve 1
The first intake valve 11A and the first and second exhaust valves 14A set the phase difference of the valve opening timing to 4° with respect to the first intake valve 11B and open first.
, 14B. is set to 24°, so that the phase difference falls within the above range (α≦2θ), so that sufficient intake air filling efficiency can be ensured. Also, the first intake valve 11A on the side to which fuel is supplied is replaced with the second intake valve 11A.
Since the valve opens earlier than B and the valve lift amount is set large, sufficient intake air is introduced from the first intake port 12A at the beginning of the intake stroke, so the flow rate increases and the fuel is supplied from the fuel injection valve 16. Fuel and intake air are sufficiently mixed, which is advantageous for forming a mixture.

<Effects of the Invention> As explained above, the present invention mainly allows the opening timing of the first intake valve to which fuel is supplied to be opened earlier than the second intake valve with a phase difference α between the first intake valve and the exhaust valve. valve overlap period θ. For α≦2θ. Since the following is satisfied, it is possible to ensure sufficient intake air filling efficiency and to ensure good mixture formation.

[Brief explanation of drawings]

Fig. 1 is a plan view of an intake/exhaust valve device showing an embodiment of the present invention, Fig. 2 is a valve characteristic diagram of the same as above, Figs. - A plan view showing a conventional example of an exhaust valve device, and FIG. 8 is a valve characteristic diagram of the same as above.

Claims (1)

[Claims] First and second intake valves are interposed in each of the two intake ports, a fuel supply device mainly supplies fuel to the intake port in which the first intake valve is interposed, and the second intake valve is interposed. In an intake/exhaust valve device for an internal combustion engine, which includes an on-off valve that is installed in an intake port and opens and closes depending on engine operating conditions, and at least one exhaust valve, the opening timing of the first intake valve is set to a second intake valve. For a valve overlap period θ_0 in which the valve is opened earlier than the valve opening timing with a phase difference α, and the first intake valve and the exhaust valve are both opened, α≦1/2θ_0.
An intake/exhaust valve device for an internal combustion engine, characterized in that the phase difference α is set to satisfy .