JPS6296725A - Air intake device for multiple cylinder engine - Google Patents

Abstract

PURPOSE:To enable the intake control to be performed properly all the time by providing an independent intake passage which diverges from a main intake passage and is connected to each cylinder, and then providing, on each of said independent intake passages, both the No.1 communicating passage which connects the upstream and downstream sides of the independent intake passage respectively and the No.2 communicating passage which connects each of the No.1 communicating passage respectively. CONSTITUTION:An independent intake passage 9, which is connected to the intake port 7 of each cylinder in an engine 1, is formed in such a manner that it begins to extend from a cylinder head 5 in the horizontal direction, and then curves upward in nearly a semicircular shape; and it is connected to a branch connection 16a which constitutes a part of a main intake passage 16. In addition, to the curved section of each of the independent intake passages 9 is connected each of the No.1 communicating passages 18 which extends vertically so that the upstream and downstream sides of each of the independent intake passages 9 are connected. And further, each of the No.1 communicating passages 18 is connected each other by each of the No.2 communicating passages 19 which extends horizontally, and moreover, on the downstream side of a connection between each of the No.1 communicating passages 18 and each of the No.2 communicating passages 19 is provided a closing valve 20 for opening and closing each of the No.1 communicating passages 18 respectively, and the valve 20 is caused to open and close in response to the engine load by means of an actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a multi-cylinder engine that utilizes the dynamic effect of intake air to improve the output characteristics of the engine.

(Prior Art) Engines that utilize the dynamic effect of intake air to increase charging efficiency and thereby obtain high output have been known. This type of engine reverses the intake negative pressure wave that occurs in the intake system due to the operation of the intake valve on the upstream side of the intake passage, and introduces it as a positive pressure wave into the combustion chamber in time with the intake timing of the cylinder, thereby pushing the intake air. It is intended to be effective.

Therefore, in order to utilize the dynamic effect of intake air, it is necessary to incorporate a pressure wave oscillation system into the intake device so that the pressure waves are introduced into the combustion chamber at a predetermined timing. but,
Normally, the natural frequency of the pressure wave vibration system is uniformly determined for each intake system, and therefore the timing at which the pressure waves return to the combustion chamber is constant, but the pushing effect of the intake air due to the pressure waves is The desired timing depends on the change in engine speed, so the speed at which the intake dynamic effect is obtained, i.e. the tuning speed, is a relatively narrow rotation at which the pressure wave returns just during the engine's intake stroke. This means that the output improvement effect can only be obtained near the tuned rotation speed. In view of these circumstances,
In the device disclosed in Japanese Patent No. 5-29078, two pressure wave vibration systems having pressure wave propagation paths of different lengths are formed, and the pressure wave vibration systems are switched depending on the rotation speed. It is designed to improve output characteristics over a wide rotational speed range over high rotational speeds.

(Problem to be solved by the invention) In an engine that utilizes the dynamic effect of intake air, if the vibration system is configured so that the propagation path of pressure waves is long, a tuned rotation speed can be obtained in the low rotation range, and the propagation By shortening the path, a synchronized rotation speed can be obtained in the high rotation region. In this case, the pressure wave generated in the intake system due to the operation of the intake valve is a negative pressure wave, so in order to guide this into the combustion chamber as a positive pressure wave that gives a pushing effect on the intake air, a pressure wave vibration system is required. It is necessary to provide an inversion section at the end of the inverter to invert the negative pressure wave into a positive pressure wave.

In order to reverse the negative pressure wave, a certain amount of air is required to compensate for the troughs when the negative pressure waves propagate. As shown in Japanese Patent No. 29078, a volume part having a constant volume such as a surge tank is provided downstream of the throttle valve in the intake passage. However, this increases the intake passage volume downstream of the throttle valve,
There is a problem in that the response to opening and closing of the throttle valve becomes slow, making it impossible to perform proper intake control.

(Means for solving the above problem) The present invention was provided to solve the above problem, and the intake device of the present invention has a cross-sectional area equivalent to that of the main intake passage, and has a cross-sectional area equivalent to that of the main intake passage. a branch part formed at the downstream end of the cylinder and forming a part thereof; an independent intake passage that branches from the branch part and communicates with the combustion chamber of each cylinder; a first communication path that communicates the upstream and downstream;
A second communication passage that communicates with each of the first communication passages, and an on-off valve that opens and closes the first communication passage according to the operating state downstream of the second communication passage connection part of each of the first communication passages. It is characterized by The branch portion of the main intake passage, ie, the intake manifold, of the present invention is formed to have a relatively small cross-sectional area, which is about the same as the cross-sectional area of the main intake passage. Further, in a preferred embodiment of the present invention, - the independent intake passages to each cylinder are branched from a branch portion and curved to communicate with the intake ports of each cylinder. The first communicating passage is provided in each independent intake passage in the form of a bypass passage that vertically communicates with the independent intake passage. Also, in this case, the second
The communication passages are provided as communication pipes that horizontally communicate the first communication passages. The on-off valve is installed near the connection portion of each first communication passage with each independent intake passage on the downstream side of the position where the second communication passage is connected.

In the structure of the present invention, when the on-off valve is closed, the negative pressure wave generated at the start of intake air propagation propagates upstream through the independent intake passage, and then between the independent intake passage and the first communication passage. It propagates downstream in the first communication path from the side connection portion and reaches the second communication path. In the second communication path, the troughs of the negative pressure waves that have propagated are supplemented with air via the intake paths to other cylinders, so that the negative pressure waves are reversed and become positive pressure waves. This inverted positive pressure wave propagates downstream along the propagation path and is introduced into the combustion chamber during the intake stroke, producing an intake air pushing effect. Also, when the on-off valve is open, the negative pressure wave propagates upstream through the independent intake passage,
The air enters the first communicating passage from the downstream side of the first communicating passage and the independent intake passage, propagates through the passage upstream, and reaches the second communicating passage. Then, the negative pressure wave is reversed in the second communication passage and returns to the combustion chamber, providing the same effect of pushing intake air as described above. That is, the negative pressure waves generated in the combustion chamber by the operation of the on-off valve propagate along paths of different lengths, are reversed at the second communication portion, and are introduced into the combustion chamber as positive pressure waves.

(Effects of the Invention) According to the present invention, the negative pressure wave generated in the combustion chamber at the start of intake air propagation travels through two different paths depending on the operation of the on-off valve. Therefore, the effect of pushing the intake air can be obtained in two different rotational speed regions, and the output characteristics can be improved over a wide range. In this case, in the present invention, the second intake passage is configured as a communication pipe that communicates each independent intake passage with each other.
In the communication mode, the negative pressure wave is reversed to obtain a positive pressure wave. With this configuration, the intake air necessary to reverse the negative pressure wave can be secured from the intake passages of other cylinders that are not in the intake process via the second communication section, so the inversion section with the volume of the surge tank or the like can be specially There is no need to provide
The volume of the intake passage downstream of the throttle valve can be kept small. Therefore, highly accurate operational response of the throttle valve can be ensured, and appropriate intake control can be performed.

(Description of Examples) Examples of the present invention will be described below with reference to the drawings.

Referring to FIGS. 1 to 3, the engine 1 of this example is as follows:
It is a four-cylinder engine, and a cylinder block 2 has four cylinder bores 3 formed therein, and a piston 4 is arranged in each cylinder bore 3 so as to be able to reciprocate. cylinder block 2
A cylinder head 5 is connected above, and a space formed by a space above the piston of the cylinder bore 3 and a lower recess of the cylinder head 5 constitutes a combustion chamber 6 .

An intake boat 7 and an exhaust boat 8 are open to the combustion chamber 6, and an independent intake passage 9 and an exhaust passage 10 are formed in the cylinder head 5 so as to communicate with the intake port 7 and the exhaust boat 8, respectively. The intake port 7 is associated with an intake valve 11, and the exhaust boat 8 is associated with an exhaust valve 8a.

A valve mechanism including a camshaft 12, a rocker shaft 13, and a rocker arm 14 is arranged above the cylinder head 5, and this valve mechanism is protected from the outside by a cylinder head cover 15. The independent intake passage 9 of each cylinder first extends horizontally from the cylinder head 5, then curves upward, and then extends horizontally in a folded manner to form a branch that forms part of the main intake passage 16. 16a, respectively.

A fuel injection valve 17 is attached to each independent intake passage 9 near the cylinder head 5 to inject and supply fuel into the independent intake passage 9 at a predetermined timing. Further, each independent intake passage 9 is connected to a first communication passage 18 extending in the vertical direction, and communicates the upstream and downstream sides of the independent intake passage 9 through a shorter route than the above-mentioned curved route. In the first communication passage 18, the upstream connecting part 18a is located at the upstream horizontal part 9a of the independent intake passage 9 downstream of the branching part, and the downstream connecting part 18b is located at the upstream side horizontal part 9a of the independent intake passage 9. It is formed in the downstream horizontal portion 9b upstream of the injection valve 17. Also, the first
A second communication path 19 is connected to each communication path 18 so as to communicate with each communication path 18 in the horizontal direction. Further, on the downstream side of the connection portion 19a of the second communication path 19 of each first communication path 18,
An on-off valve 20 that opens and closes the first communication passage 18 is provided.

As shown in FIG. 2, an actuator 20a is provided to operate the on-off valve 20.
0a is adapted to be activated by intake negative and positive. In this case, the negative pressure for operating the on-off valve 20 is taken out by the negative pressure pipe 21 connected to the curved part 9 of the independent intake passage 9, and is applied to the actuator 20H via the check valve 22, the vacuum tank 23, and the solenoid valve 24. introduced into the working part. The supply and cutoff of this negative pressure is controlled by a solenoid valve 24, which closes the on-off valve 20 in the low engine speed range and opens in the high engine speed range, depending on changes in engine speed. It operates. An air cleaner 25 is installed at the upstream end of the main intake passage 13, an air flow meter 26 for measuring intake airflow is installed downstream of the air cleaner 25, and a throttle valve 27 is installed downstream of the air flow meter 26. In this example, the main intake passage 13, the independent intake passage 9, the first communication passage 18, and the second communication passage 19 are all constructed of tubular members having approximately the same flow passage cross-sectional area.

In the above structure, when the intake valve 11 is opened, a negative pressure wave of intake air is generated in the combustion chamber 6, and this negative pressure wave propagates upstream in the independent intake passage 9. When the on-off valve 20 is closed, the negative pressure wave propagates within the independent intake passage 9 in the order of the downstream horizontal portion 9bS, the curved portion 9c, and the upstream horizontal portion 9a, and the negative pressure wave propagates within the independent intake passage 9 in the order of It enters the first communicating path 18 from the side connecting portion 18a, propagates downward within the first communicating path 18, and reaches the second communicating path 19. In the second communication path 19, the negative pressure wave is reversed to a positive pressure wave. When reversing negative pressure waves and positive pressure waves, a certain amount of intake air is required to supplement the troughs of the negative pressure waves, but in the structure of this example, this intake air is
Mainly from the intake passages of other cylinders that are not taking air,
It is introduced via the second communication path 19. The inverted positive pressure wave generated within the second communication passage reversely follows the propagation path to the upstream second communication passage 12, propagates downstream, and finally reaches the combustion chamber 6. At this time, if the cylinder is in the intake stroke, this inverted positive pressure wave has the effect of increasing the intake air filling amount. The propagation path of the pressure wave when the on-off valve 20 is closed is relatively long, and therefore the time for the pressure wave to return to the combustion chamber is longer. Therefore, the improvement in output due to the effect of increasing the filling efficiency of intake air due to pressure waves is as shown by the broken line a in Fig. 4.
It is given a characteristic that has a peak at relatively low rotation speeds where the valve opening time is long. Further, when the on-off valve 20 is open, the negative pressure wave propagates upstream through the downstream horizontal portion 9b of the independent intake passage 9, and from the downstream connecting portion 18b of the first communicating passage 18 to the first communicating passage. 18 , propagates upstream through the passage 18 and reaches the second communication passage 19 . The negative pressure wave that has reached the second communication passage 19 is reversed in the same manner as described above, follows the propagation path in the opposite direction, and returns to the combustion chamber 6 as a reversed positive pressure wave. In this case, the propagation path of the pressure wave becomes shorter than when the on-off valve 20 is closed. Therefore, the on-off valve 2
When 0 is open, a pushing effect of intake air can be obtained in a relatively high rotation range, and output characteristics can be improved.

As a result, when the on-off valve 20 is open, an output characteristic having a peak on the relatively high rotation side is obtained, as shown by the solid line in FIG. In this example, the opening/closing valve 20 is controlled to be opened when the rotational speed exceeds a point C where the characteristic curves a and b in FIG. 4 intersect. As a result, with the structure of this example, the output characteristics can be improved over a wide range from low rotation to high rotation. In addition, in the structure of this example, the inversion part of the negative pressure wave is not provided with a large volume part, but by providing the second communication passage 19 with a relatively small cross-sectional area that utilizes intake air supply from the intake passage to other cylinders. With this configuration, an increase in the intake passage volume downstream of the throttle valve 27 can be effectively suppressed, and excellent responsiveness of the throttle valve 27 can be ensured.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an engine according to an embodiment of the present invention;
FIG. 2 is a partial sectional view of the engine in FIG. 1, and FIG. 3 is a partial sectional view of the engine in FIG.
Fig. 1 is a perspective view of the engine intake system, and Fig. 4 is a perspective view of the engine intake system.
3 is a graph showing the output characteristics of the engine shown in the figure. 1... Engine, 2... Cylinder block, 4... Piston, 5... Cylinder head, 6... Combustion chamber, 9. ...Independent intake passage, 16...Main intake passage, 18...
...First communication path, 19...Second communication path, 20
・・・・・・Opening/closing valve. Figure 1

Claims (1)

[Claims] A branch part that has the same cross-sectional area as the main intake passage and constitutes a part of the main intake passage, an independent intake passage that branches from the branch part and communicates with the combustion chamber of each cylinder, and each independent intake passage. a first communication passage that communicates the upstream and downstream sides of each independent intake passage; a second communication passage that communicates each first communication passage; and a second communication passage downstream of the second communication passage connection portion of each first communication passage. An intake device for a multi-cylinder engine, comprising an on-off valve provided on the side and opening/closing the first communication passage depending on the operating state.