JPS61205325A - Intake device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve intake charging efficiency, by setting an operating period of a valve, from a start of its opening to the maximum lift point, shorter than the operating period of the valve, from the maximum lift point to an end of the closing, in the case of the intake valve mounted to the outlet of an intake port equipped with an opening and closing valve. CONSTITUTION:Each cylinder, providing two intake valves 1A, 1B and two intake ports 2A, 2B reaching these intake valves 1A, 1B, mounts respectively a fuel injection valve 3 to the first intake port 2A further an opening and closing valve 4 to the second intake port 2B. While an engine, connecting an actuator 7 with a supporting axis 4a of the opening and closing valve 4 to be operated by a control unit 8, controls the opening and closing valve 4 so as to be closed in a low speed range while opened in an intermediate and a high speed range. Further the second intake valve 1B sets its opening period a little earlier than the top dead center similarly to the first intake valve 1A, but delays the closing period to about a half of a compression stroke. And the engine sets the period, after the second intake valve 1B starts to open till it reaches the maximum lift point, shorter than the period after the maximum lift point of the valve till it closes.

Description

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

(Prior Art) An example of an intake system for this type of internal combustion engine is the one shown in Japanese Patent Application No. 58-225356 filed by the present applicant.

This device is equipped with two intake valves for each cylinder and two intake ports leading to these intake valves.One intake port is closed in the low speed range of the engine, opens in the high speed range, and one intake port is opened in the low speed range. Vibration is absorbed only from the port, generating a strong swirl flow to improve combustibility, and in medium and high speed ranges, air is taken in from two intake ports to reduce passage resistance and improve output.

(Problems to be Solved by the Invention) By the way, in such an intake system, the closing timing of the intake valve installed at the outlet of the intake port in which the on-off valve is installed is determined by the inertia supercharging in the high speed range. In addition, by reducing the actual compression ratio and increasing the knocking resistance, in order to achieve torque, it is possible to reduce the compression stroke later than usual (TDC 55-8).
0°).

Also, during idling, burnt gas flows into the intake port downstream of the opening/closing valve and is at pressure h during the overlap period of the opening timings of the intake valve and exhaust valve, and then is re-inhaled into the combustion chamber, causing In the same way, during the overlap period between the intake valve and the exhaust valve, exhaust gas blows back into the combustion chamber from the exhaust port, resulting in deterioration of combustibility. For this reason, as shown in FIG. 5, fuel consumption during idling deteriorates, and as shown in FIG. 6, torque decreases in the medium speed range. For this reason, it is desirable to set the opening timing of the intake valve closer to the top dead center in order to reduce the overlap with the exhaust valve.

However, if the closing timing of the intake valve is delayed while the opening timing of the intake valve remains close to the top dead center, the maximum lift point will approach the bottom dead center. This is C), which is preferable in terms of suction efficiency.In other words, the speed of the piston during its downward stroke reaches its maximum at 70 to 80 degrees (crank angle) after top dead center, as shown in Figure 4, and as a result of this movement, The flow rate of the intake air into the combustion chamber is slightly slower than that at the maximum piston speed, and is approximately 10 minutes after top dead center.
It reaches its maximum near 0”.

Therefore, normally, the lift of the high-speed intake valve 1B is set to be maximum near this point, but the maximum lift point is delayed for the above-mentioned reasons, and the suction efficiency (filling efficiency) decreases.

The present invention has been made by focusing on the above-mentioned problems.The present invention solves the above-mentioned problems by changing the characteristics of the intake valve for medium and high speeds, and improves the intake efficiency as much as possible. The purpose is to provide intake equipment for engines.

Means for Solving the Problems> For this reason, the present invention improves the lift characteristics of a high-speed intake valve installed at the outlet of an intake port equipped with an on-off valve by adjusting the period from the start of valve opening to the maximum lift point. The configuration is set to be asymmetrical and shorter than the period from the maximum lift point to the end of valve closing.

<Function> With this configuration, the opening timing of the high-speed intake valve is set near top dead center to minimize the overlap with the exhaust valve, reducing the amount of residual gas, and closing the intake valve. The timing should be delayed to the middle of the compression stroke to reduce the actual compression ratio while ensuring matching with inertial supercharging at high speeds, and then move the maximum lift point closer to top dead center to match the maximum flow velocity point of the intake air. Therefore, the intake air filling efficiency can be improved as much as possible.

<Example> Hereinafter, embodiments of the present invention will be explained based on the drawings.

Each cylinder of an internal combustion engine has a first cylinder. Second intake valve IA, IB
And the first one leading to these intake valves. Second intake port 2A, 2
A fuel injection valve 3 is provided at the first intake port 2A.
, a butterfly type on-off valve 4 is installed in each of the second intake ports 2B.

In addition, two exhaust valves 5A, 5B and two exhaust valves 6A, 6B are provided for each cylinder.

An actuator 7 is connected to the support shaft 4a of the on-off valve 4 via a link mechanism, and the on-off valve 4 is operated by operating the actuator 7 in response to a signal from a control device 8.
is controlled so that it closes in the low speed range of the engine and opens in the medium and high speed range.

In addition, the lift characteristics of the first intake valve IA are set by a cam (not shown) that operates the first intake valve IA so that it starts opening slightly earlier than the top dead center and closes a little later than the bottom dead center, as shown in Fig. 2. There is.

On the other hand, the second intake valve IB, as shown in FIG. 3C,
Like the first intake valve IA, the opening timing is set slightly earlier than top dead center, but the closing timing is set delayed until near the middle of the compression stroke.

This point is similar to the above-mentioned 5th prior application example, but as a concept according to the present invention, the period (crank angle) from when the second intake valve IB starts opening until it reaches the maximum lift point is maximized. Set it so that it is shorter than the period (crank angle) from the lift point to the close.

Specifically, the opening timing is set to 10° before the top dead center, 100° after the maximum lift upper point, and the closing timing is set to about 70° after the bottom dead center. In this case, the operating angle j from valve opening to maximum lift point
! l'100°, the operating angle from Il large lift point to valve closing is 150°.

Next, the effect will be explained.

In a low speed range below a predetermined engine rotation speed, the on-off valve 4 closes and air is taken only from the first intake valve 1A via the first intake port 2B, which creates a strong swirl in the combustion chamber and reduces combustibility. In addition, the knock resistance is improved, and by setting the closing timing of the first intake valve 1A earlier, the actual compression ratio is large, so the intake air filling efficiency is increased, and the intake air filling efficiency is improved in the low speed range. Output and fuel efficiency can be improved as much as possible.

On the other hand, in medium and high speed ranges exceeding the specified rotation speed, the on-off valve 4
opens, the first intake port 2A and the second intake port 2B
Intake is performed from both through the first intake valve IA and the second intake valve IB.

As a result, the side area of the intake passage increases and intake resistance decreases, and since the lift amount of the second intake valve IB is large and the closing timing is set later, the actual compression ratio decreases and the anti-knock resistance is reduced. In addition, supercharging using the inertial force of intake air is effectively performed, and intake air filling efficiency is improved.

Further, as an effect of the configuration according to the present invention, the maximum lift point of the second intake valve IB is brought closer to the top dead center side and synchronized with the maximum point of the intake flow velocity, thereby further increasing the intake air filling efficiency. be able to.

The lift characteristics of A shown in Figure 3 for comparison are those required in a normal engine (normal rotation range of about 600 to 7000 rpm), especially in the high speed range (4000 rpm or more), but the maximum lift point is is delayed by 120 degrees after top dead center, and the intake air filling efficiency cannot be sufficiently increased.

On the other hand, as shown in B, if the valve opening timing is advanced while the valve closing timing is fixed so that the maximum lift point approaches the top dead center side, the maximum lift point is ideal, but the valve opening timing is too fast, the overlap period with the exhaust valve increases, and as a result, the amount of residual gas increases, resulting in a decrease in torque in the medium speed range, as shown in FIG. In this regard, in this embodiment, it is possible to sufficiently promote high output in the high speed range while preventing such a decrease in torque in the medium speed range.

(Effects of the Invention) As explained above, according to the present invention, the lift characteristics of the high-speed intake valve are asymmetric, and the maximum lift point is brought closer to the top dead center without changing the opening/closing timing, and the intake flow velocity is adjusted to the maximum point. This allows the intake air filling efficiency to be increased as much as possible, and has the effect of promoting an increase in output in the high speed range while preventing a decrease in torque, especially in the medium speed range.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of one embodiment of the present invention, and FIG.
The figure is a diagram showing the lift characteristics of the first intake valve in the above embodiment, Figure 3 is a diagram showing the lift characteristics of the second intake valve in the above embodiment and for comparison, and Figure 4 is a diagram showing the piston speed. Figure 5 is a diagram showing the fuel consumption characteristics during idling with respect to the overlap period between the intake valve and exhaust valve, and Figure 6 is the torque change characteristic with respect to the overlap period between the intake valve and exhaust valve. FIG. IA...First intake valve IB...Second intake valve 2
A...First intake port 2B...Second intake port 4...Opening/closing valve 7...Actuator 8
···Control device. Patent Applicant Nissan Motor Co., Ltd. Agent Patent Attorney Fujio SasashimaFigure 2Figure 3

Claims (1)

[Claims] In an intake system for an internal combustion engine, each cylinder is provided with two intake valves, two intake ports leading to these intake valves, and one intake port is provided with an on-off valve that opens and closes according to engine operating conditions. An internal combustion engine characterized in that the lift characteristic of an intake valve installed at the outlet of an intake port equipped with a valve is set such that the period from the start of opening to the maximum lift point is shorter than the period from the maximum lift point to the end of valve closing. Engine intake system.