JPH0519010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a technology for improving combustion during idling of an internal combustion engine.

<Background Art> Conventional known technologies of this type include, for example, those shown in FIGS. 1 to 3. This changes the opening timing of the intake valves 1 and 2, which are provided two for each cylinder, and provides two independent intake ports 3 and 4 that communicate with these intake valves 1 and 2.
An on-off valve 6 is provided at the intake port 4 to which the high-speed intake valve 2 with a large overlap with the intake valve 2 is installed, and the on-off valve 6 is closed in low speed regions such as during idling to prevent exhaust gas from blowing back during the substantial valve overlap period. By preventing this, combustion is improved.

However, in such a conventional method of blocking the intake port, it is difficult to reduce the volume of the intake port 4 downstream of the on-off valve 6 due to various restrictions, and it is approximately 15 to 25% of the cylinder volume. . If the intake port volume in this part is large, the following problems will occur, especially during idling with a large intake negative pressure.

When the intake stroke ends and the intake valve 2 closes at the beginning of the compression stroke, the mixture from the beginning of the compression stroke is trapped in the intake port 4, but since the pressure of the mixture is idling, the negative pressure of about 400 mmHg It is a state of pressure. For this reason, the intake valve 2
When the valve opens, exhaust gas flows into the intake port 4 due to the pressure difference between the exhaust pressure and this negative pressure, and the pressure inside the intake port 4 rises to near the exhaust pressure.
Because the exhaust gas (burned gas), which occupies about half of the volume, mixes with the air-fuel mixture in the combustion chamber 7 during the following intake stroke,
The residual gas concentration cannot be reduced sufficiently, and the effect of improving fuel efficiency cannot be achieved as much as expected. Therefore,
As shown in FIG. 4, a communication pipe 9 has an orifice 8 interposed in the high-speed intake port 4 portion downstream of the on-off valve 6.
Atmospheric air is introduced through the high-speed intake valve 2, and fresh air is sucked in by this negative pressure between when the high-speed intake valve 2 closes and when it next opens, reducing the differential pressure with the exhaust pressure and continuing during the overlap period. The applicant of the present application has proposed a method of preventing exhaust gas from flowing into the high-speed intake port 4 and significantly reducing the amount of burned gas mixed in the air-fuel mixture. In this figure, the on-off valve 6 is controlled to open and close by an actuator 10, and the supply of control pressure to the actuator 10 is interrupted by an electromagnetic valve 11. This intermittent condition is the pressure sensor 12
The control unit 13 detects engine operating conditions such as engine speed and engine rotation speed. 14 is a limit switch that monitors the completion of actuation of the actuator 10. A portion of the high-speed intake port 4 downstream of the on-off valve 6 communicates with the upstream of the throttle valve 15 via a communication pipe 9, and the flow rate is regulated by an orifice 8. The pressure upstream of the throttle valve 15 is always close to atmospheric pressure, so when the inside of the intake port 4 is under negative pressure, fresh air upstream of the throttle valve 15 passes through the orifice 8 and flows into the intake port 4 downstream of the on-off valve 6. flow inside. When fresh air is introduced in this manner, after the high-speed intake valve 2 closes, the pressure inside the intake port 4 downstream of the on-off valve 6 gradually approaches atmospheric pressure. The orifice 8 controls the inflow amount of fresh air close to atmospheric pressure, and during the period of one crank revolution (1/10 second at 600 rpm when idling) when the high-speed intake valve 2 is closed, the orifice 8 controls the inflow of fresh air near atmospheric pressure. The size is set to be necessary and sufficient to bring the pressure sufficiently close to atmospheric pressure (the diameter of the 8 orifices is about 1 to 2φ).

In this way, at the end of the exhaust stroke when the high-speed intake valve 2 is opened, the combustion chamber 7 is filled with exhaust gas at approximately atmospheric pressure (average value). The blowback of this exhaust gas into the intake port 4 can be effectively suppressed, and combustion performance can be significantly improved.

For comparison, when fresh air is not introduced, when the high-speed intake valve 2 is closed, there is no gas flowing into or out of the intake port 4. The internal pressure of the intake port 4 is kept constant at a negative pressure of about half the atmospheric pressure. Therefore, when the high-speed intake valve 2 starts to open, the exhaust gas filling the combustion chamber 7 rapidly flows into the intake port 4 due to a large pressure difference, and the volume of the intake port 4 downstream of the on-off valve 6 is reduced. Approximately half of the exhaust gas remains at near atmospheric pressure, expands at once during the subsequent intake stroke, and enters the combustion chamber 7, so even if the on-off valve 6 is provided, a considerable amount of residual gas remains. , no significant improvement in combustion can be expected.

However, even with the above-mentioned proposal in which the backflow of exhaust gas was prevented by introducing fresh air, there was still room for improvement as described below. That is, in the above-mentioned proposal, as shown in FIG. 5, both the low-speed and high-speed intake ports 3 and 4 are provided downstream of the throttle valve 15, so the upstream pressure of the on-off valve 6 is negative during idling. equal to the pressure. 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. If sufficient sealing performance is not achieved, the introduced fresh air will leak from the on-off valve 6 to the intake manifold 16 on the upstream side, causing variations in the pressure within the intake port 4 of each cylinder. In this case, the proportion of residual gas differs from cylinder to cylinder, which may cause variations in combustion and unstable rotation.

<Purpose of the Invention> The present invention was made in view of the above-mentioned circumstances, and it suppresses the leakage of fresh air introduced downstream of the on-off valve by reducing the pressure difference between the upstream and downstream sides of the on-off valve. 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.

<Summary of the Invention> For this reason, the present invention provides a method in which the downstream portion of the intake stroke is branched into a low-speed intake passage leading to a low-speed intake valve and a high-speed intake passage leading to a high-speed intake valve,
A throttle valve is provided in the low-speed intake passage, and an on-off valve that closes in the low-speed range including idling and whose opening is controlled in the high-speed range is provided in the port portion of the high-speed intake passage near the high-speed intake valve. The high-speed intake passage and the intake passage upstream of the on-off valve are communicated via an air flow rate adjusting means.

This introduces fresh air close to atmospheric pressure into the high-speed intake passage downstream of the on-off valve, suppressing exhaust blowback, improving output and fuel efficiency during idling, and opening the upstream side of the on-off valve to the atmosphere. By doing so, the pressure difference with the downstream side is avoided as much as possible, and the sealing performance of the on-off valve is improved to eliminate variations in combustibility from cylinder to cylinder, thereby ensuring stable rotation.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

In FIGS. 6 to 9 showing one embodiment, an internal combustion engine 21 has a low-speed intake valve 23A and a high-speed intake valve 23 with different opening and closing timings in the combustion chamber 22 of each cylinder.
B, and a pair of exhaust valves 24 whose opening and closing timings are equal are provided.

The low speed intake valve 23A is a low speed cam 25.
The high-speed intake valve 23B contacts and follows the high-speed cam 25B, starts opening near the top dead center of the intake stroke, and closes near the bottom dead center of the intake stroke.
It begins to open around 30 degrees before top dead center on the exhaust stroke and closes around the middle of the compression stroke. Further, the pair of exhaust valves 24 are driven by a pair of cams 26 having the same shape, and begin to open in the latter half of the expansion stroke, and close in the early stage of the intake stroke.

And low speed and high speed intake valves 23A, 23
The intake passage leading to B is formed as follows.

The downstream end of the intake pipe 27, whose upstream end is connected to an air cleaner (not shown), branches into two, and a low-speed manifold 28A and a high-speed manifold 28B are connected to the two downstream ends, respectively. Intake pipe 27
A throttle valve 29 is interposed at the downstream end of the low-speed manifold 28A to which the low-speed manifold 28A is connected.

Then, the low-speed manifold 28A and the high-speed manifold 28B are branched by the number of cylinders,
A low speed intake port 30A leading to the low speed intake valve 23A of each cylinder and a high speed intake port 30B leading to the high speed intake valve 23B are formed.

Intake port 3 for low speed and high speed for each cylinder
0A and 30B are provided with a valve chamber 32 equipped with a butterfly-type on-off valve 31 on the high-speed intake port 30B side.

The opening/closing valve 31 has an orifice 31b opened therein for metering fresh air to flow from the upstream side to the downstream side, as will be described later.

Both ends of the support shaft 31a of the on-off valve 31 of each cylinder protrude outside the valve chamber 32, and a lever 33 is fixed to one end of the shaft 31a.
Both ends of the tension spring 34 are engaged and attached to pins 33a and 32a fixed to the ends of the valve chamber 32 and the outer wall of the valve chamber 32, respectively. As a result, the on-off valve 31 is urged in the valve opening direction by the urging force of the tension spring 34.

Further, a lever 35 is fixed to the other end of the support shaft 31a, and the lever 35 of each cylinder is supported by a rod 36 at regular intervals, and a link 37 is connected to one end of the rod 26. The output rod 38a of the diaphragm actuator 38 is connected to the output rod 38a of the diaphragm actuator 38.

The actuator 38 has an output rod 38a.
A return spring 3 is placed in a pressure operating chamber 38c partitioned on one side by a diaphragm 38b to which a return spring 3 is fixed.
8d is installed, and controlled negative pressure is supplied from an electromagnetic negative pressure control valve 39, which will be described later.

The electromagnetic negative pressure control valve 39 is a constant negative pressure control valve that forms a constant negative pressure by opening and closing a negative pressure introduction port 39a that leads intake negative pressure from the low-speed manifold 28B downstream of the throttle valve 29 via a check valve. It includes a pressure valve section 39A and a solenoid valve section 39B that controls the amount of atmospheric air introduced to dilute the constant negative pressure formed by the constant pressure valve section 39A. By controlling the duty ratio of the pulses output from the control unit 40 to the solenoid valve section 39B, a desired controlled negative pressure is formed in the controlled negative pressure extraction port 39c, and the controlled negative pressure is supplied as controlled negative pressure. The pressure is supplied to the pressure working chamber 38c of the actuator 38 via the pipe 41.

The control unit 40 inputs a pressure signal from a pressure sensor 42 that detects the intake negative pressure in the low-speed manifold 28A and an engine speed signal from a distributor (not shown), etc., and adjusts the intake negative pressure according to the engine speed. solenoid valve part 39
Set the duty ratio of the pulse output to B. In this case, as the energization duty ratio of the pulse increases, the amount of atmospheric air introduced into the controlled negative pressure outlet port 39c increases, and the absolute value of the controlled negative pressure supplied to the actuator 38 decreases. The output rod 38a gradually extends due to the biasing force of the return spring 38d, and the opening/closing valve 31 is opened through the operation of the link 37, rod 36, and lever 35.
The degree of opening increases. Specifically, during normal partial load operation, the output to the solenoid valve section 39B is
By closing port 39c as OFF,
The maximum negative pressure generated by the constant pressure valve section 39A is supplied to the pressure working chamber 38c, the on-off valve 31 is closed, and the throttle valve 2 is closed.
9 is opened to a predetermined opening degree or more and enters a high-load operating state, the energization duty ratio to the solenoid valve 39B is gradually increased to gradually open the on-off valve 31. That is, the throttle valve 29 and the on-off valve 31 are respectively operated in the same manner as the primary valve and secondary valve in a two-barrel carburetor.

Next, a series of operations of this embodiment will be explained.

During partial load operation, including idling, which is detected by the intake negative pressure detected by the pressure sensor 42 and the engine rotational speed, the control unit 40 controls the solenoid of the electromagnetic negative pressure control valve 39 as described above. The output to the valve 39B is turned OFF (energization duty ratio 0), and the on-off valve 31 is maintained in a fully closed state via the actuator 38, link 37, rod 36, and lever 35.

In this state, near the middle of the compression stroke, the high-speed intake valve 2
3B is closed, the high-speed intake port 30B on the downstream side of the on-off valve 31 is in a negative pressure state;
The upstream side of the closing valve 31 communicates with the air cleaner (or the control unit discharge side of the exhaust turbo supercharger) without passing through the throttle valve 29. For this reason,
Fresh air close to atmospheric pressure flows into the high-speed intake port 30B on the downstream side of the orifice 31b formed in the on-off valve 31, and as a result, the pressure in the high-speed intake port 30B gradually increases, and then the high-speed intake Valve 23B
The pressure rises to near atmospheric pressure by the time it opens (shown by the solid line in Figure 9; the dotted line shows the conventional example). On the other hand, when the high-speed intake valve 23B is opened, the combustion chamber 22 is filled with residual exhaust gas (burnt gas) at a pressure substantially close to atmospheric pressure.

Therefore, until the top dead center of the exhaust stroke is reached, the residual exhaust gas in the combustion chamber 22 is suppressed from blowing back into the high-speed intake port 30B sealed by the on-off valve 31, and most of it is exhausted to the exhaust port. Ru.

As a result, in the subsequent intake stroke, the combustion chamber 22
The proportion of residual exhaust gas mixed into the combustion chamber can be reduced as much as possible, and the combustion improvement effect can be sufficiently enhanced.

Furthermore, as the configuration according to the present invention, the throttle valve 29 is provided in the low-speed intake passage independent of the high-speed intake passage, so the upstream side of the on-off valve 31 is maintained close to atmospheric pressure even under low load, and the downstream side of the on-off valve 31 is maintained at near atmospheric pressure even under low load. Leakage of fresh air from the side to the upstream side can be prevented, and sufficient sealing performance can be obtained.

In this way, by improving the sealing performance of the on-off valve 31, it is possible to suppress variations in the pressure inside the downstream high-speed intake port 30B, which equalizes the proportion of residual gas in each cylinder, eliminates variations in combustion, and reduces idling, etc. Rotational stability is maintained.

Specifically, when the upstream side of the on-off valve 31 of the high-speed intake passage is opened to the atmosphere, the high-speed intake valve 23B opens during the intake stroke, so the downstream side of the on-off valve 31 becomes negative intake pressure, and the upstream side Although the pressure difference between the intake stroke and the intake stroke is large, the intake stroke is only 1/4 of the total stroke, and the remaining 3/4 stroke eliminates the pressure difference and provides a good seal.

In addition, since the low-speed intake valve 23A is also open during the intake stroke, the high-speed intake port 30B downstream of the on-off valve 31 communicates with the low-speed manifold 28A, and gas enters and exits, so the pressure for each cylinder is This will eliminate the variation in .

In this regard, in the case shown in FIG. 4, the differential pressure between the upstream and downstream sides of the on-off valve 31 is small during the intake stroke, but
Since a large pressure difference occurs in the other 3/4 strokes, it is necessary to pay attention to sealing performance, and there is a risk of pressure variation between cylinders.

Furthermore, as shown in this embodiment, there is an advantage that fresh air can be introduced downstream by simply providing an orifice 31b in the on-off valve 31, and there is no need to provide a communication pipe 9 as shown in FIG. Therefore, it is advantageous in terms of cost and layout. in this way,
When the orifice 31b is provided in the on-off valve 31, both the gap between the orifice 31b and the on-off valve 31 determines the sealing performance, so the diameter of the orifice 31a can be determined after checking the sealing performance, making it easy to ensure accuracy. can be done.

Further, as shown in FIG. 7, by lengthening the low-speed intake port 30A and shortening the high-speed intake port 30B, inertial supercharging can be effectively utilized depending on the engine rotation speed.

On the other hand, during high-speed, high-load operation detected by intake negative pressure and engine rotational speed, the energization duty ratio from the control unit 40 to the solenoid valve portion 39B increases, and the control negative pressure supplied to the actuator 38 is weakened to open/close the valve. Valve 31 begins to open.

In this way, when the high-speed intake port 30B opens, the high-speed intake valve 23 opens earlier than the low-speed intake valve 23A and closes much later.
Since intake is performed using B in combination, the reduction in the effective compression ratio suppresses the rise in the compression top dead center temperature and pressure of the intake air, suppressing the occurrence of knocking, and the use of inertial supercharging and the intake port for high speed. Due to the effect of reducing the intake flow resistance due to the opening of 30B, it is possible to improve the filling efficiency and improve the output.

As described above, since the on-off valve 31 gradually changes its opening degree in response to changes in engine operating conditions, fluctuations in engine torque are prevented.
Stable characteristics can be obtained.

<Effects of the Invention> As explained above, according to the present invention, the low-speed intake passage leading to the low-speed intake port valve which opens at a later time, and the high-speed intake passage leading to the high-speed intake valve which opens at an early time. On the other hand, a throttle valve is installed in the low-speed intake passage, and an on-off valve is installed near the high-speed intake valve of each cylinder in the high-speed intake passage. By introducing fresh air from the upstream side to the downstream side and raising it to near atmospheric pressure, it is possible to prevent exhaust blowback and improve fuel efficiency and output characteristics, as well as reduce the variation in the downstream pressure of the open/close valve for each cylinder. Therefore, variations in combustibility are eliminated and stable rotation performance is obtained.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the main parts of an example of a conventional intake system for an internal combustion engine, Fig. 2 is a graph showing the lift characteristics of the intake and exhaust valves of the same device, and Fig. 3 is a longitudinal sectional view of the main parts of the same device. , FIG. 4 is a block diagram showing the overall outline of an intake system for an internal combustion engine proposed by the applicant, FIG. 5 is a plan view of the main parts of the same device, and FIG. 6 is an overall outline of an embodiment of the present invention. 7 is a plan view of the main part of the same embodiment, FIG. 8A is a rear view of the valve chamber part of the above embodiment, FIG. 8B is a plan view, and FIG. C is a right sectional view. D is a front view, and FIG. 9 is a graph showing the characteristics of each part of the same embodiment. 21...Internal combustion engine, 23A...Low speed intake valve, 23
B...High-speed intake valve, 27...Intake pipe, 28A...Low-speed manifold, 28B...High-speed manifold,
29... Throttle valve, 30A... Low speed intake port, 30
B...High-speed intake port, 31...Opening/closing valve, 31b...
Orifice, 35...Lever, 36...Rod, 37
...link, 38...actuator, 39...electromagnetic negative pressure control valve.

Claims (1)

[Claims] 1. In the intake system of an internal combustion engine, which is equipped with a low-speed intake valve that starts to open near the top dead center of the intake stroke and a high-speed intake valve that starts to open earlier in the latter half of the exhaust stroke for each cylinder, the downstream part of the intake passage A low-speed intake passage leading to the low-speed intake valve and a high-speed intake passage leading to the high-speed intake valve are provided, and a throttle valve is interposed in the low-speed intake passage, and each of the high-speed intake passages is provided with a throttle valve interposed in the low-speed intake passage. An on-off valve that is closed at least in a low-speed region including idling and whose opening is controlled according to changes in operating conditions in a high-speed region is provided in a port near the high-speed intake valve of the cylinder, and a high-speed intake passage downstream of the on-off valve. An intake system for an internal combustion engine, characterized in that the intake passage and the intake passage upstream of the on-off valve are communicated through an air flow rate adjusting means.