JPS61197719A - Intake device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To stabilize combustion and prevent torque from fluctuation in an engine having an intake path for high speed in parallel to an intake path for low speed and provided near a port of said intake intake path for high speed with a switch valve opened in high speed, by providing a throttle valve opened in high speed upstream of said intake path for high speed. CONSTITUTION:An intake path 12 for low speed and an intake path 13 for high speed are branched from an intake pipe 11. Intake ports 17 branched from the intake path 13 for high speed to respective cylinders is provided with switch valves 6 opened in high speed respectively while the branch portion of intake path 13 for high speed is provided with a throttle valve 15 for high speed beginning to open from high speed rotation. Since the switch valve 6 and throttle valve 15 are closed in low speed of an engine, intake having approximately atmospheric pressure flows from said intake path 13 through a gap in the valve 6 downstream of the switch valve 6 so that negative pressurization is obviated to prevent exhaust from reversion. In high speed rotation, the switch valve 6 together with the throttle valve 15 is gradually opened so that unstable combustion due to abrupt change in intake flow can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> 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 shown in FIG. 4 (Japanese Patent Application No. 60918/1982).

To explain this, the opening timing of the low-speed intake valve 1 and high-speed intake valve 2 provided for each cylinder is changed, and the low-speed intake port 3 and high-speed intake port 4 that communicate with these intake valves 1 and 2 are changed. An on-off valve 6 is provided at the high-speed intake port 4, which is installed independently and has a high-speed intake valve 2 that overlaps greatly with the exhaust valve 5. One intake throttle valve 8 is interposed in the intake passage 7 on the side.

In an operating range where the intake air flow rate is less than a predetermined value, the on-off valve 6 is fully opened to create a strong swirl inside the combustion chamber by utilizing the airflow flowing only from the low-speed intake port 3 along the peripheral wall of the combustion chamber. The aim is to improve flammability by generating

On the other hand, when the intake air flow rate exceeds a predetermined value, as the flow rate increases, that is, the rotational speed.

As the load increases, the opening degree of the on-off valve 6 is gradually increased to gradually increase the opening area of the high-speed intake port 4, and the on-off valve 6 is approximately fully opened in the maximum output range of the engine.
Open□Close Valve 6 is aimed at improving intake air filling efficiency while suppressing an increase in the amount of unburned HC discharged immediately after opening.

By the way, in the above-mentioned device, when the on-off valve 6 is closed, the air pressure close to the atmospheric pressure on the upstream side of the intake throttle valve 8 is passed through the fresh air introduction passage 9 in which an orifice is inserted in the high-speed intake port 4 portion on the downstream side. Fresh air is sucked in from when the high-speed intake valve 2 closes to when it next opens, and the differential pressure with the exhaust pressure is reduced.Then, during the overlap period with the subsequent exhaust valve 5, the exhaust is This prevents the gas from flowing into the air port 4, significantly reducing the amount of burned gas mixed in the air-fuel mixture, and improving combustion performance.

(Problems to be Solved by the Invention) However, as described above, even in the case where the backflow of exhaust gas is prevented by introducing fresh air, as shown below,
However, there was room for improvement.

That is, in the configuration described above, since both the low-speed and high-speed intake ports 3.4 are provided downstream of the intake throttle valve 8, the upstream pressure of the on-off valve 6 becomes equal to the intake negative pressure during idling.

For this reason, when fresh air is introduced into the high-speed intake port 4 and the pressure inside the intake port 4 is increased to near atmospheric pressure, the differential pressure across the on-off valve 6 becomes large, and the sealing performance of the on-off valve 6 becomes a problem. It's coming.

By the way, when the on-off valves 6 of a plurality of cylinders are controlled to open and close by the same rotating shaft 10, the following problem occurs when the sealing performance of the on-off valves 6 is improved.

Generally, the cylinder head is made of aluminum, and the housing of the on-off valve 6 is also preferably made of aluminum in order to reduce weight.

However, it is difficult to make the rotating shaft 10 sufficiently large in diameter (which creates resistance to air intake), and the rotating shaft 10 is made of aluminum because it has to be ground down to a flat surface in order to install the on-off valve 6 and holes for the mounting screws are formed. It is difficult to use steel in terms of strength, and it is necessary to use iron-based materials.

゛ In this case, depending on the operating condition of the engine, the temperature of each component, including the cylinder head, changes over a range of about 150 degrees, from -20 degrees Celsius at the start in winter to around +130 degrees Celsius when running at high speed. , Therefore, each of the above components is affected by heat. ・The thermal expansion coefficients of iron and aluminum differ by about 1 degree,
If the on-off valve 6 is attached to the rotating shaft 10 at room temperature with almost no gap between it and the high-speed intake port 4, the axial direction of the rotating shaft 10 due to heat and expansion will occur at high speeds where the temperature increases. The difference between the amount of elongation and the amount of elongation of the housing of the on-off valve 6 in the same direction becomes large, and as a result, the on-off valve 6 bites into the wall of the high-speed intake port 4, making it impossible to open and reducing engine output. The problem arises that the

For this reason, it is necessary to provide a certain amount of clearance in advance between the on-off valve 6 and the wall of the high-speed intake port 4, which inevitably reduces the sealing performance.

If sufficient sealing performance is not achieved, the introduced fresh air will leak from the on-off valve 6 into the intake passage 7 on the upstream side, causing variations in the pressure in the high-speed intake port 4 of each cylinder. .

In this case, the proportion of residual gas differs for each cylinder, which may cause variations in combustion and unstable rotation.

The present invention was developed in view of these conventional problems, and by reducing the pressure difference between the upper and downstream sides of the on-off valve, the leakage of fresh air introduced downstream of the on-off valve is suppressed. An object of the present invention is to provide an intake device for an internal combustion engine that improves combustion performance during idling as much as possible by increasing the effect of preventing blowback of exhaust gas.

(Means for Solving Problems 1) For this reason, the present invention provides a structure in which the downstream portion of the intake passage has a low-speed intake passage having a low-speed throttle valve and communicating with the low-speed intake valve, and a high-speed throttle valve. A high-speed intake passage leading to a high-speed intake valve is provided, and an open/close valve is provided for each cylinder in the high-speed intake passage, which closes at least in the low-speed range including idling and is controlled to open and close in the high-speed range according to changes in operating conditions. A control means is provided in a port near the high-speed intake valve, and controls the opening degree of the high-speed throttle valve to increase or decrease in accordance with an increase or decrease in the engine intake air flow rate in the opening region of the on-off valve.

Effect〉 Next, the effect of this configuration will be explained.

During low-speed operation, including idling, the on-off valve and the high-speed throttle valve are at their minimum opening degrees, and only the low-speed throttle valve is open.

In this state, when the high-speed intake valve closes near the middle of the compression stroke, the inside of the high-speed intake port on the downstream side of the on-off valve is in a negative pressure state, while the upstream side of the on-off valve is in a negative pressure state through the high-speed throttle valve. It communicates with the atmosphere.

For this reason, fresh air close to atmospheric pressure flows into the high-speed intake port through the gap between the on-off valve and the high-speed intake port, and as a result, the pressure inside the high-speed intake port gradually increases until the next high-speed By the time the air intake valve opens, the pressure rises to near atmospheric pressure.

On the other hand, when the high-speed intake valve is opened, the combustion chamber is filled with residual exhaust gas at approximately atmospheric pressure.

Therefore, until the exhaust stroke reaches the top dead center of the exhaust stroke, the residual exhaust gas in the combustion chamber is prevented from blowing back into the high-speed intake port sealed by the on-off valve, and most of it is discharged to the exhaust port.

In addition, during high-speed operation, the on-off valve is switched from closed to open, and after that, the high-speed throttle valve is controlled by the control means and gradually begins to open according to the increase in the intake air flow rate, and the intake air is also drawn from the high-speed intake port. will be held.

<Example> The example shown in FIGS. 1 to 3 will be described below. still,
Elements that are the same as those in the conventional example will be described with the same reference numerals as in FIG. 4.

In the combustion chamber of each cylinder of the engine, there is a high-speed intake valve 2 that opens earlier than the closing timing of a pair of exhaust valves 5 whose opening and closing timings are equal;
A low-speed intake valve 1 whose opening timing is later than this is provided.

The intake passages leading to the low-speed and high-speed intake valves 1 and 2 are configured as follows.

That is, the downstream end of the intake pipe 11 whose upstream end is connected to an air cleaner (not shown) branches into two, and a low-speed manifold 12 and a high-speed manifold 1 are installed at the two downstream ends, respectively.
3 is connected.

A low-speed throttle valve 14 is installed at the downstream end of the intake pipe 11 to which the low-speed manifold 12 is connected, and a high-speed throttle valve 15 is installed to the downstream end of the intake pipe 11 to which the high-speed manifold 13 is connected. be done.

In addition, low speed manifold 12 and high speed manifold 1
3, each branch part is connected to a low-speed intake port 16 leading to the low-speed intake valve 1 of each cylinder, and a high-speed intake port 17 leading to the high-speed intake valve 2 of each cylinder.

As a result, the low speed intake valve 1 is passed from the branch part of the intake pipe 11 to the low speed manifold 12 and the low speed intake port 16.
A low-speed intake passage leading to the high-speed intake valve 2 is provided independently, and a high-speed intake passage similarly extends from the branch portion of the intake pipe 11 to the high-speed intake valve 2 via the high-speed manifold 13 and the high-speed intake port 17.

Further, the high-speed intake port 17 is provided with an on-off valve 6 that closes in a low-speed range including at least idling and is controlled to open and close in a high-speed range according to changes in operating conditions.

This on-off valve 6 has a predetermined leakage amount (40 to 60 It at a differential pressure of 500 mmHg) between it and the high-speed intake port 17.
It is installed with a gap formed so as to provide a leakage amount of about /l1in.

Here, the support shaft 21 of the low-speed throttle valve 14 is linked to the accelerator pedal, and the opening degree is adjusted according to the driver's intention.

Further, the support shaft 22 of the high-speed throttle valve 15 is connected to a stepping motor 23, and the stepping motor 23 is driven and controlled, for example, as shown in FIG. Ru.

In this case, in the low speed region where the on-off valve 6 is closed, the high speed throttle valve 1
5 is the minimum opening degree (however, the opening degree should be sufficiently larger than that of the on-off valve 6), but the opening degree is gradually increased from the point when the on-off valve 6 opens half way in the 0N-OFF state. It has the characteristic of fully opening in the high speed range as the intake air flow rate increases.

Note that the stepping motor 23 and the control/control circuit 24 constitute a control means.

Next, the effect of this configuration will be explained.

During low-speed operation, including idling, which is detected by the intake negative pressure detected by the pressure sensor and the engine rotational speed detected by the speed sensor, the on-off valve 6 and the high-speed throttle valve 15 are at their minimum opening degrees. Therefore, only the low speed throttle valve 14 is open.

In this state, when the high-speed intake valve 2 closes near the middle of the compression stroke, the interior of the high-speed intake port 17 on the downstream side of the on-off valve 6 is in a negative pressure state, while the upstream side of the on-off valve 6 is in a high-speed intake port 17. It communicates with an air cleaner (not shown) via a throttle valve 15.

Therefore, fresh air close to atmospheric pressure flows into the high-speed intake port 17 through the gap between the on-off valve 6 and the high-speed intake port 17, and as a result, the pressure inside the high-speed intake port 17 gradually increases. The pressure then rises to near atmospheric pressure by the time the high-speed intake valve 2 opens.

On the other hand, when the high-speed intake valve 2 is opened, the combustion chamber is filled with residual exhaust gas at approximately atmospheric pressure.

Therefore, until reaching the top dead center of the exhaust stroke, the residual exhaust gas in the combustion chamber is prevented from blowing back into the high-speed intake port 17 sealed by the on-off valve 6, and most of it is discharged to the exhaust port.

As a result, the proportion of residual exhaust gas that enters the combustion chamber in the subsequent intake stroke can be reduced as much as possible, and the combustion improvement effect can be sufficiently enhanced.

By bifurcating the downstream end of the intake pipe 11 into two and installing a low-speed throttle valve 14 in conjunction with the accelerator pedal in the low-speed intake passage, the upstream side of the on-off valve 6 is kept close to atmospheric pressure even at low speeds. Therefore, leakage of fresh air from the downstream side of the on-off valve 6 to the upstream side can be prevented.

In this way, by preventing the leakage of fresh air to the upstream side of the on-off valve 6, it is possible to suppress variations in the pressure inside the high-speed intake port 17 on the downstream side, and thereby equalize the proportion of residual exhaust gas in each cylinder and improve combustion. Variations can be eliminated and rotational stability such as idling can be maintained.

Specifically, when the upstream side of the on-off valve 6 of the high-speed manifold 13 is communicated with the atmosphere via the high-speed throttle valve 15, the high-speed intake valve 2 opens during the intake stroke, so the downstream side of the on-off valve 6 opens. Since the intake pressure is negative and the differential pressure with the upstream side is large, the ventilation stroke is only 1/4 of the total stroke, and the differential pressure can be eliminated in the remaining three strokes.

In addition, since the low-speed intake valve l is also open during one intake stroke, the high-speed intake port 17 downstream of the on-off valve 6 communicates with the low-speed manifold 12, and gas enters and exits from cylinder to cylinder. The variation in pressure is eliminated.

Furthermore, it has the advantage that a new valve can be introduced downstream by simply forming a gap between the on-off valve 6 and the high-speed intake port 17, and there is no need to provide a communication pipe like in the past, reducing costs and layout. It is also advantageous in terms of

In addition, low speed manifold 12 and low speed intake bow) 1
6 and shorten the high-speed manifold V13 and high-speed intake port 17, it is possible to match the intake pulsation characteristics at low speeds and high speeds to the respective operating ranges and improve the filling rate. This can also be finely adjusted by adjusting the opening of one high-speed throttle valve.

During high-speed rotation exceeding a predetermined value, which is detected based on the intake air negative pressure and the engine rotational speed, the on-off valve 6 is switched from closed to open by an actuator (not shown), and from then on, the control circuit opens according to the increase in the intake air flow rate. 24 sends a signal to the stepping motor 23, and the high speed throttle valve 15 begins to gradually open.

In this way, when the high-speed intake port 17 is opened,
Since intake is performed using the high-speed intake valve 2, which opens earlier than the low-speed intake valve 1 and closes much later than the low-speed intake valve 1, the compression top dead center temperature and pressure of the intake air decrease due to a decrease in the effective compression ratio. It is possible to suppress the rise in the engine speed, thereby suppressing the occurrence of knocking, and to reduce the intake air circulation resistance by opening the high-speed intake port i7, thereby improving the filling efficiency and increasing the output.

Here, in this embodiment, since the high-speed throttle valve 15 gradually changes its opening degree in response to changes in engine operating conditions, the intake air flow rate from the high-speed intake port 17 increases all at once. Therefore, it is possible to prevent the air-fuel ratio of the low-speed intake port 16 from becoming excessively enriched and the generation of unburned HC to increase, preventing engine torque fluctuations, and achieving stable characteristics.

It is also possible to omit the high-speed throttle valve 15 and gradually open the on-off valves 6, but in this case, the openings of the plurality of on-off valves 6 may vary at the beginning when the openings are small, and This causes variations in the intake air flow rate.

In this regard, in this embodiment, since the opening degree of one high-speed throttle valve 15 is controlled, variations among the cylinders are eliminated.

<Effects of the Invention> As explained above, according to the present invention, in the idling special low speed region, the on-off valve is closed, and fresh air on the upstream side is introduced into the downstream side of the on-off valve to raise it to near atmospheric pressure. , it is possible to prevent exhaust gas from blowing back and improve fuel efficiency and output characteristics.Also, by controlling the opening of the high-speed throttle valve, variations in the downstream pressure of the opening/closing valve for each cylinder, and therefore variations in combustibility, can be reduced. This problem is resolved and stable rotation performance is obtained.

[Brief explanation of drawings]

1 (A) and (B) respectively show an embodiment of the present invention, (A) is a plan sectional view showing the state at low engine speed, (B
) is a plan cross-sectional view showing the state at high engine speed, Figure 2 is a diagram showing the structure of the high-speed and low-speed throttle valve parts used in the above embodiment, and Figure 3 is the opening of the high-speed throttle valve. FIG. 4, a diagram showing the characteristics, is a plan sectional view showing a conventional intake system for an internal combustion engine.

Claims (1)

[Scope of Claims] An intake system for an internal combustion engine including a high-speed intake valve and a low-speed intake valve for each cylinder, wherein a downstream portion of the intake passage is provided with a low-speed throttle valve; A low-speed intake passage leading to the intake valve and a high-speed intake passage having a high-speed throttle valve and leading to the high-speed intake valve are branched and are closed in a low-speed range including at least idling, and are closed in a high-speed range when operating conditions change. An on-off valve that is controlled to open and close according to the engine intake air flow rate is provided at a port near the high-speed intake valve of each cylinder in the high-speed intake passage, and the high-speed An intake system for an internal combustion engine, comprising a control means for increasing and decreasing the opening degree of a throttle valve.