JPH02115525A - Air intake device of engine - Google Patents

Abstract

PURPOSE:To decrease the difference in the amount of air intake among cylinders in a low-load range by installing a communicating passage midway in air intake branch pipes of each cylinder, installing shut-off valves on the communicating passage, inserting respective throttle valves in immediate upstream of the communicating passage openings on the air intake branch pipes of each cylinder and opening the shut-off valves while in a low-load range. CONSTITUTION:In a low-load condition, a shut-off valve 12 is practically in an opened condition. Intake air, therefore, flows in according to the opening of throttle valves 14 of air intake branch pipes 4a4d of each cylinder. Since the air intake branch pipes 4a-4d of each cylinder are mutually communicating with a communicating passage 11, the amount of filled intake air is equalized. Furthermore, since the passage capacity downstream of the throttle valve 14 is small, the additional supply of the amount of intake air to each cylinder 2 is quickly performed even when the throttle is rapidly opened, so that transient response property is improved and acceleration performance is excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for an engine that obtains a dynamic effect of intake air.

(Prior art) Conventionally, in an engine intake system, when increasing the charging efficiency by utilizing dynamic effects such as the inertia effect of intake air, it is necessary to increase the engine low When the engine is rotating, the intake passage is required to be long, and when the engine is running at high speed, the intake passage is required to be short.

In order to meet the above requirements, a communication passage was provided in the middle of the intake branch pipe of each cylinder to connect the intake branch pipes of each cylinder, and an on-off valve was provided in this communication passage to open and close depending on the operating state. The engine intake system technology was published in 1986-79
It is publicly known as seen in Publication No. 22.

(Problem to be Solved by the Invention) However, in the engine intake system as described above, in order to effectively increase the charging efficiency by utilizing the inertia of the intake air in the low speed range, a very long intake pipe length is required. In such an intake system, if the throttle valve is installed upstream of the cylinder cluster, the intake pipe volume downstream of the throttle valve will increase, which will reduce the transient response of the intake air amount during acceleration, resulting in a delay in acceleration. .

In order to deal with the above points, transient response can be improved by installing the throttle valve closer to the engine and reducing the passage volume downstream of the throttle valve, but installing a throttle valve for each cylinder is not recommended. The problem is that the difference in intake air distribution between cylinders increases in the light load range due to accuracy errors in the throttle valve.

In other words, in the region of low throttle opening, due to manufacturing or installation errors in the throttle valve installed for each cylinder, a small amount of error will occur between cylinders even if the cylinders are operated to achieve the same opening. , the actual intake air amount differs accordingly, and the influence of the above error occupies a larger proportion of the total intake air amount in the low opening range, for example, a difference of about 2 to 3 in the air-fuel ratio between cylinders occurs at idle. There is a possibility that it will become a problem.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an engine intake system that improves the transient responsiveness of intake air amount to changes in throttle opening and reduces errors in intake air amount between cylinders in a low load range. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the engine intake system of the present invention is provided with a communication path that communicates the intake branch pipes of each cylinder in the middle of the intake branch pipes of each cylinder. An on-off valve that opens and closes depending on the operating condition is provided in the passage, and a throttle valve is installed immediately upstream of the communication passage opening of the intake branch pipe of each cylinder, and the on-off valve is opened in the low load range. It is configured to do so.

(Function) In the above-mentioned intake system, the on-off valve provided in the communication path that communicates the intake branch pipes of each cylinder is opened and closed according to the operating condition.
While increasing the charging amount by obtaining the dynamic effect of intake air at multiple tuning points, the throttle valve is located downstream to reduce the downstream passage volume and reduce transients when the throttle opening changes. In addition to improving responsiveness, in the low load range, the on-off valve in the communication passage immediately downstream of the throttle valve is opened, and the opening of this on-off valve allows the intake branch pipes of each cylinder downstream of the throttle valve to communicate with each other. The intake air flows through the cylinders, averaging out the differences in distribution between cylinders and making sure that the amount of charge is even.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 and FIG. 2 show a schematic configuration of an intake system for a four-cylinder engine in one embodiment.

Four cylinders 2 are installed in the engine body 1, and each cylinder 2
Intake branch pipes 48 to 4d are independently connected to the intake boat 3. Further, an exhaust passage 6 is connected to the exhaust boat 5 of each cylinder 2.

The upstream ends of the intake branch pipes 48 to 4d of each of the cylinders 2 are connected to a surge tank 7, and the intake passage 8 upstream of the surge tank 7 is connected to an air flow meter 9 and an air cleaner 10.

A communication passage 11 that communicates the intake branch pipes 4a to 4d of each cylinder with each other is connected in the middle of the intake branch pipes 48 to 4d of each cylinder. In addition, each intake branch pipe 4a to 4
An on-off valve 12 that opens and closes communication between the two is interposed at the connection between d and the communication passage 11, and the on-off valve 12 is opened and closed synchronously in each cylinder 2 according to the operating state by the operation of an actuator 13. be done.

Furthermore, a throttle valve 14 is interposed immediately upstream of the opening with the communication passage 11 in the intake branch pipes 4a to 4d of each cylinder.
Injector 1 that injects and supplies fuel to the downstream part of d
5 are arranged.

On the other hand, a first bypass passage 17 in which an air valve 16 is inserted to bypass the throttle valve 14 and an IS
A second bypass passage 19 in which a C valve 18 is interposed is connected between the surge tank 7 and the communication passage 11. Further, a blow-by gas passage 21 in which a pressure valve 20 is interposed is connected to the communication passage 11 from the engine body 1 .

The air valve 16 operates to increase the opening degree when it is cold to increase the amount of bypass air, and the ISC valve 18 operates to increase the amount of bypass air.
is feedback-controlled to maintain the idle speed at a predetermined value.

A control signal is output from the controller 22 to the actuator 13, which opens and closes the on-off valve 12, and is driven according to the operating state. Further, fuel injection by the injector 15 is also controlled by a fuel injection pulse from the controller 22. The controller 22 includes, as signals for detecting the operating state, an intake air amount signal from the air flow meter 9, a negative pressure signal from a negative pressure sensor 23 that detects intake negative pressure, and a rotation speed sensor 2 that detects the engine speed.
The engine rotation speed signal etc. from 4 are input.

Regarding the operation control of the on-off valve 12, the controller 22 receives an engine rotation speed signal and an intake negative pressure signal as shown in FIG. 3, and based on the characteristics shown in FIG. The basic region determining means 25 determines whether the operating state is in the open region or the closed region, and the amplifying circuit 26 outputs it as a drive signal for the actuator 13 to drive and control the on-off valve 12 to a predetermined state.

As illustrated in FIG. 4, the opening/closing range of the on-off valve 12 varies depending on the engine speed N and the load B (intake negative pressure).
m) in the low rotation range below and the load B is the predetermined value Bo
A high load range of (for example, -20hdg) or more is set as a full open range, and other low load ranges and high rotation ranges are set as full open range.

In addition, as shown by the broken line, in the low rotation range, the opening degree of the on-off valve 12 is set to a fully closed opening degree of 1 to 3 degrees, which is the opening degree necessary to obtain the distribution function, and The rotation area may be set to be a fully open area. In this case, it is preferable that the number of opening/closing operations is small when a transition is made from a low load region to a high load region and a high rotation state is reached.

Note that the above-mentioned initial opening degree of 1 to 3 degrees is set to an opening degree that does not affect the attenuation of pressure waves due to the inertial effect in the low speed and high load region.

To explain the operation of the above configuration, in a low load state, the on-off valve 12 is substantially open, and intake air flows in according to the opening degree of the throttle valve 14 of the intake branch pipes 4a to 4d of each cylinder. The intake branch pipes 4a to 4d of each cylinder are communicated with each other through a communication passage 11, and the amount of intake air to be filled is equalized. That is, when the opening degree of the throttle valve 14 of a specific cylinder 2 is smaller than that of other cylinders and the amount of intake air is small, the intake negative pressure downstream of the throttle valve 14 in this cylinder 2 becomes larger than that of other cylinders 2, and the communication passage 11 from the intake branch pipes 4a to 4d of the other cylinders 2, the pressure is equalized and the filling amount is equalized. In addition, since the passage volume downstream of the throttle valve 14 is small, even when the throttle is suddenly opened, an increased amount of intake air is quickly supplied to each cylinder 2, improving transient response and providing excellent acceleration performance. It is something.

Furthermore, since bypass air or gas is supplied to the communication passage 11 through the bypass passages 17, 19, the blow-by gas passage 21, etc., these supplies are evenly distributed to each cylinder 2.

On the other hand, in a region where output performance is required by increasing the filling amount by the dynamic effect of intake air in a high load region, in a low engine speed region, the on-off valve 12 of the communication passage 11 is substantially closed. In the closed state, the negative pressure wave generated in each cylinder 2 propagates upstream through the throttle valve 14 that opens each intake branch pipe 4a to 4d, and is reversed to a positive pressure wave at the opening to the surge tank 7. Each cylinder 2 again
Returning to , the filling amount is increased by the pressure rise in the intake port 3 at the end of the intake stroke, and the long intake pipe length synchronizes at low rotational speeds. In addition, in the high rotational speed range of the engine, the on-off valve 12 of the communication passage 11 is fully open, and the negative pressure waves generated in each cylinder 2 propagate upstream through each intake branch pipe 4a to 4d. The pressure wave reverses to a positive pressure wave at the opening of the cylinder 2, returns to each cylinder 2, and increases the filling amount by increasing the pressure of the intake boat 3 at the end of the intake stroke, and synchronizes at high rotational speeds due to the short intake pipe length. . Furthermore, since the intake branches of each cylinder 2 are in communication with each other through the communication passage 11, intake air flows into the cylinder 2 from other cylinders 2 through the communication passage 11 during the intake stroke, resulting in passage resistance. By allowing the intake air to flow in a state where the amount of fuel is small, the filling amount can be increased in the high load, high rotation range.

Next, FIG. 5 shows a modified example, and in this example,
The intake branch pipes 4a to 4d of each cylinder 2 are grouped into cylinders 1-4 and cylinders 2-3 whose intake strokes do not occur continuously, and the collected branch pipes 28a and 28b of each group are connected to the surge tank 7. A communication passage 29 is provided that communicates the intake branch pipes 28a and 28b on the upstream side of the gathering portion with each other, and an on-off valve 30 is provided in the communication passage 29.
A throttle valve 31 is further interposed immediately upstream of the connecting portion of the communication passage 29.

The operation control of the on-off valve 30 and the like are performed in the same manner as described above, and in this example, the passage configuration of the communication passage 29 can be simplified. Other same structures are given the same reference numerals as above.

(Effects of the Invention) According to the present invention as described above, the on-off valve provided in the communication path that communicates the intake branch pipes of each cylinder is opened and closed according to the operating condition, and the dynamic intake air flow at a plurality of tuning points is controlled. The effect can be obtained and the amount of filling can be increased. On the other hand, by locating the throttle valve in the downstream position and reducing the downstream passage volume, it is possible to improve the transient response when the throttle opening changes. By opening the on-off valve in the communication passage immediately downstream of the throttle valve, the intake branch pipes of each cylinder downstream of the throttle valve communicate with each other, allowing intake air to flow between the cylinders. Differences in quantity distribution can be averaged out.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an engine intake system according to an embodiment of the present invention, Fig. 2 is a plan configuration diagram showing the intake passage configuration, Fig. 3 is a functional block diagram of the control system of the on-off valve, and Fig. 4 5 is a characteristic diagram illustrating the opening/closing region of the opening/closing valve, and FIG. 5 is a schematic configuration diagram of the intake passage configuration showing a modified example. 1...Engine body, 2...Cylinder, 4
a~4d. 28a, 28b... Intake branch pipe, 7...
・Surge tank, 11.29...Communication path, 12
．． 30...Opening/closing valve, 13...Actuator, 14.31...Throttle valve, 2
2... Controller.

Claims (1)

[Claims] (1) In an engine intake system in which a communication path is provided midway between the intake branch pipes of each cylinder, and an on-off valve that opens and closes depending on the operating condition is provided in the communication path, each Immediately upstream of the above-mentioned communication passage opening of the intake branch pipe of the cylinder,
An intake system for an engine, characterized in that each valve is provided with a throttle valve, and the opening/closing valve is opened in a low load range.