JPH0372818B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an intake/exhaust valve device for an internal combustion engine having two intake valves for each cylinder.

<Prior art> As a conventional example of an intake/exhaust valve device for an internal combustion engine, there is one shown in Figs.
(See Publication No. 47-31724 and Japanese Patent Application No. 58-225356).

That is, each cylinder of the engine has a first intake valve 1A,
Second intake valve 1B and first and second exhaust valves 2A, 2B
The intake port is divided into a first intake port 3A and a second intake port 3B, and the second intake port 3B is provided with an on-off valve 4. The on-off valve 4 is 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). Opening/closing is controlled by In the low speed range, closing the on-off valve 4 has the same effect as effectively closing the second intake valve 1B, introducing intake air from one side to form a swirl, and preventing exhaust blowback. There is. Medium/high speed/high load area (hereinafter referred to as medium/
In the high speed range), the on-off valve 4 is opened and intake air is introduced from both the first and second intake valves 1A and 1B 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 which always introduces intake air into the combustion chamber 6 via the first intake valve 1A 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. FIG. 8 shows the first and second intake valves 1A,
1B and the lift characteristics of the first and second exhaust valves 2A and 2B. The first and second exhaust valves 2A and 2B have the same lift characteristics, but when comparing the lift characteristics of the first intake valve 1A with the lift characteristics of the second intake valve 1B,
The opening timing is late, the closing timing is early, and both the operating angle and the maximum lift amount are small. If the first intake valve 1A is used for low speeds, the second intake valve 1B 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, making use of the lift characteristics of the first intake valve 1A to improve fuel efficiency and stability by strengthening swirl, as well as to improve torque at low speeds. In this case, the on-off valve 4 is opened and air is taken in from the second intake port 3B side, and sufficient filling efficiency is ensured by taking advantage of the lift characteristic of the second intake valve 1B, which is set to a high-speed characteristic. There is.

<Problems to be Solved by the Invention> By the way, in the conventional intake/exhaust valve device described above, the volume downstream of the on-off valve 4 cannot be made small due to various restrictions, and the volume is 15 to 15 times the cylinder volume.
20%, and especially during idling, when the second intake valve 1B closes at the beginning of the compression stroke, the inside of the second intake port 3B downstream of the on-off valve 4 increases.
At the end of the exhaust stroke, the second
When the intake valve 1B opens, the exhaust gas flows into the second intake port 3B due to the pressure difference between the exhaust gas and the air-fuel mixture. 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, the valve lift amount of the first intake valve 1A is set smaller than the lift amount of the second intake valve 1B and the first intake valve 1A is opened, as shown in FIG. Valve timing is 2nd intake valve 1
Since it is set later than B, the first intake valve 1A
The amount of intake air introduced into the combustion chamber 6 through the fuel injector 5 is extremely small compared to the second intake valve 1B side. In particular, the intake air flow rate at the first intake port 3A, which supplies fuel from the fuel injection valve 5, is reduced due to fuel vaporization and fog. The flow rate is not sufficient for this purpose, 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 1A earlier than the second intake valve 1B, but if the difference in the opening timings of the intake valves 1A and 1B 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 focuses on the opening of a first intake valve installed in an intake port to which fuel is supplied and a second intake valve installed in the other intake port. Both valve timings are set before the top dead center of the intake stroke, and the opening timing of the first intake valve is opened earlier than the opening timing of the second intake valve with a phase difference α, and the opening timing of the first intake valve is earlier than that of the second intake valve. The phase difference α is set to satisfy α≦1/2θ ₀ with respect to the pulse overlap period θ ₀ in which both the exhaust valve and the exhaust valve open.

<Function> By setting the phase difference α between the two intake valves in this way, the residual gas concentration can be reduced while
Sufficient intake air is introduced into the combustion chamber through both intake valves to achieve sufficient intake air filling efficiency, and the first intake valve to which fuel is supplied opens early to ensure good mixture formation. did. In particular, the first and second
Both intake valves are opened before the top dead center of the intake stroke to suppress the amount of exhaust gas blowback and to increase the overlap period with the exhaust valve as much as possible, increasing the intake air filling efficiency in the middle and high speed ranges where the on-off valves open. I tried to output it.

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

In the figure, each cylinder between the internal combustion engines is provided with first and second intake ports 12A and 12B each having a first and second intake valve 11A and 11B interposed therein.
An on-off valve 13 is provided at the upstream end of the intake port 12B. Further, the first and second intake valves 1
The first and second exhaust valves 14A and 14B are connected to the first and second exhaust ports 15 so as to face the ports 1A and 11B, respectively.
A and 15B are respectively interposed.

The on-off valve 13 is configured to close in a low speed range and open in a medium/high speed range, as in the conventional example.

The opening/closing timing of the first intake valve 11A is set so that it opens at around 20° before the top dead center of the intake stroke and closes around 50° after the bottom dead center of the compression stroke, and the opening/closing timing of the second intake valve 11B 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 Figure 2). Also,
The opening and closing timings of the first and second exhaust valves 14A and 14B are both set so that they start opening around 50° before the bottom dead center of the expansion stroke and close around 4° after the top dead center of the suction stroke. (See Figure 2). Further, since the cam characteristic curves of the first and second intake valves 11A and 11B are substantially similar in terms of cam characteristics, the maximum lift amount of the first intake valve 11A is larger than that of the second intake valve 11B.

In addition, 16 is a fuel injection valve as a fuel supply device that injects fuel toward the first intake port 12A;
7 is a combustion chamber, and 18 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, 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 or It is obtained by

In the above formula, a ₁ is the first and second exhaust valve 14
A, 14B effective opening area, _a2 is the effective opening area of the first and second intake valves 11A, 11B, _P1 is the first
and the exhaust pressure of the second exhaust ports 15A and 15B (set to atmospheric pressure here), P ₂ is the combustion chamber 1
7 pressure, P ₃ is the first and second intake port 12A,
12B intake pressure (set to -500mmHg here), g is gravitational acceleration, k is specific heat ratio of exhaust gas, v ₁ ,
v ₂ is the specific volume of the combustion chamber and each port, respectively.

First, in this calculation, the first intake valve 11A
Valve opening timing and first and second exhaust valves 14A, 14B
The valve closing timing of the second intake valve 11B is held approximately constant, the valve overlap period thereof is set to θ ₀ (see Fig. 2), and the valve opening timing of the second intake valve 11B is varied within the range of the valve overlap period. I tried to let him do it.
Then, the change in the exhaust gas blowback flow rate G during the valve overlap period θ ₀ (see FIG. 2) in which the first intake valve 11A and the first and second exhaust valves 14A and 14B are both opened is determined.

FIG. 3 shows changes in the valve lift amount of the second intake valve 11B and the first and second exhaust valves 14A, 14B when the opening timing of the second intake valve 11B is changed. Further, FIG. 4 shows the pressure change in the combustion chamber 17 during the same change as above, and FIG. 5 shows the valve overlap period θ ₀ of the first and second intake valves 11A, 11B. It shows the change in the exhaust gas blowback flow rate G when the overlap period θ is changed.

Here, in FIGS. 3 to 5, the phase difference α
(See Fig. 2) are in the same phase when the first and second intake valves 11A, 11B open simultaneously with the valve overlap period θ ₀ , and the phase difference α is 0.5θ ₀ . The second intake valve 11B opens from the middle of the valve overlap period, and the phase difference α is θ ₀ means that the second intake valve 11B opens the first and second exhaust valves 14A and 14B. The valve opens at the same time.

As is clear from FIG. 5, the exhaust blowback flow rate G reaches its maximum in the middle of the valve overlap, and becomes approximately 0 in the early and late stages. This is the first and second intake valve 1
1A, 11B and first and second exhaust valves 14A, 14
The exhaust gas blowback flow rate G is determined by the change in the effective opening area between the intake valves 11A and 11B and the exhaust valves 14A and 14B, and is determined by the change in the effective opening area between the intake valves 11A and 11B and the exhaust valves 14A and 14B. Furthermore, as is clear from Fig. 5, as the phase difference α (see Fig. 2) increases, the exhaust blowback flow rate G
After the phase difference α decreases, the rate of decrease decreases from the time when the phase difference α exceeds 0.5θ ₀ , and in the latter stage when θ/θ ₀ <0.5, the exhaust gas blowback flow rate G hardly changes regardless of the change in the phase difference α. This is because when the pressure P ₂ in the combustion chamber 17 is θ/θ ₀ <0.5, the negative pressure suddenly becomes large because it is in the early stage of the intake stroke. G
There is no change.

Therefore, when the phase difference α exceeds 0.5θ ₀ , the exhaust blowback flow rate G hardly changes even if the phase difference α increases. This is the total exhaust gas blowback flow rate Q/Q ₀ (Q ₀ is the exhaust gas blowback flow rate at the same phase) obtained by integrating the exhaust gas blowback flow rate G per unit crank angle at each phase difference over the entire overlap period. As is clear from Fig. 6, the phase difference α is
From the vicinity of exceeding 0.5θ ₀ , the total exhaust gas blowback flow rate Q hardly decreases and becomes approximately constant. As a result, α＜0.5θ ₀
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 It is clear that it is desirable to set the phase difference α with the second intake valve 11B in the range α≦0.5θ ₀ .

Although the presence of the on-off valve 13 was not taken into account in this calculation, the valve overlap 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 equipped with the on-off valve 13, ₀ is larger than that of the second intake valve 11B, the timing at which exhaust gas flows into the second intake port 12B is delayed, and the second intake port 12B is no longer filled with exhaust gas. If the valve overlap period θ ₀ is relatively small,
Furthermore, the influence of the on-off valve 13 is small and can be ignored. Note that this phenomenon holds 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 intake valve 11B is set to α≦1/2θ ₀ , sufficient intake air filling efficiency can be ensured. As shown in the figure, the phase difference between the opening timings of the first intake valve 11A and the second intake valve 11B is set to 4 degrees, and the first intake valve 1 opens first.
Since the valve overlap engine θ ₀ between the exhaust valve 1A and the first and second exhaust valves 14A and 14B is set to 24°, the phase difference is within the above range (α≦1/2θ ₀ ), so sufficient intake air is obtained. Filling efficiency can be ensured, and the exhaust blowback flow rate G can be significantly suppressed. In particular, since the opening timing of the first intake valve 11A and the second intake valve 11B is set before the top dead center of the intake stroke, the opening timing of the first intake valve 11A and the second intake valve 11B is set before the top dead center of the intake stroke. In addition to the overlap period with the opening timing of the exhaust valve 14A, the timing of the intake valve 11B and the second exhaust valve 14B
Since a sufficient overlap period can be ensured by adding an overlap period with the above, it is possible to significantly suppress the exhaust gas blowback flow rate G while ensuring sufficient intake air filling efficiency to improve the output. In addition, since the first intake valve 11A on the side to which fuel is supplied is opened before the second intake valve 11B and its valve lift is set large, the first intake port
Since a sufficient amount of intake air is introduced from A, its flow rate increases, and the fuel supplied from the fuel injection valve 16 and the intake air are sufficiently mixed, which is advantageous for forming an air-fuel 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, so that the first intake valve and the exhaust valve are opened earlier than the second intake valve. Valve overlap period with valve θ ₀ α≦
Since 1/2θ ₀ is satisfied, sufficient intake air filling efficiency can be ensured while greatly suppressing the exhaust blowback flow, and good mixture formation can be ensured. In particular, since the opening timing of the first and second intake valves is set before the top dead center of the intake stroke, it is possible to secure a sufficient overlap period with the exhaust valve in the middle and high speed ranges where the opening and closing valves open. Output can be improved while significantly suppressing blowback flow.

[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, and Fig. 3
Figures 6 to 6 are the above theoretical characteristic diagrams, and Figure 7 is the absorption and
FIG. 8 is 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. 11A...First intake valve, 11B...Second intake valve, 13...Opening/closing valve, 14A...First exhaust valve, 1
4B...Second exhaust valve, 16...Fuel injection valve.

Claims (1)

[Claims] 1. First and second intake valves respectively installed in two intake ports, a fuel supply device mainly supplying fuel to the intake port in which the first intake valve is installed, and a fuel supply device in which the second intake valve is installed. In the intake/exhaust valve device for an internal combustion engine, the valve opening timing of the first and second intake valves includes an on-off valve that is installed in an intake port and opens and closes depending on the engine operating state, and at least one exhaust valve. are both set before the top dead center of the intake stroke, and the opening timing of the first intake valve is opened earlier than the opening timing of the second intake valve with a phase difference α, and the first intake valve and the An intake/exhaust valve device for an internal combustion engine, characterized in that the phase difference α is set to satisfy α≦θ ₀ /2 with respect to a valve overlap period θ ₀ in which both the exhaust valve and the exhaust valve open.