JPH0543237Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to an intake system for a multi-cylinder internal combustion engine.

[Conventional technology]

A surge tank is installed in the intake manifold of an internal combustion engine, and the inside of this surge tank is divided into two spaces by a control valve, and the equivalent pipe length of the intake system is lengthened by closing this control valve when the engine rotates at low and medium speeds. A so-called variable intake system is already known, which increases the inertial supercharging effect and shortens the equivalent pipe length by opening the control valve during high-speed rotation (JP-A-56-
115818).

On the other hand, in order to enable precise control of the idling speed, a bypass passage is provided that bypasses the throttle valve, and a bypass valve is provided in this bypass passage, and the duty ratio of this bypass valve is controlled during idling when the throttle valve is fully closed. The idle speed control system (Idle speed control system) controls the idling speed by changing the ratio of the valve opening time and valve closing time or by finely adjusting the opening degree of the bypass valve and controlling the amount of intake air in the bypass passage. ISC system) is also well known.

[Problem that the invention attempts to solve]

This invention solves the problems that arise when applying the ISC system to a variable intake system. In other words, if these systems are simply combined, there is a problem that the control valve closes even during startup, preventing combustion in one cylinder group, resulting in poor engine startability. aims to solve this problem.

[Means for solving problems]

The intake system for a multi-cylinder internal combustion engine according to the present invention is as follows:
A bypass passage connects the upstream side of the intake passage from the throttle valve to one of the spaces divided by the control valve of the surge tank, and a bypass valve is provided to open and close this bypass passage, and the control valve is connected at least when the engine is started. At the same time as opening up
It is characterized by being configured so that the bypass valve is also opened.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows a first embodiment of the invention. In this figure, an intake manifold 2 and an exhaust manifold 3 are connected to an engine body 1. The intake manifold 2 includes a surge tank 4 and six branch pipes 5, 6, 7,
The interior of the surge tank 4 is divided into a first space 12 and a second space 13 by a control valve 11. Each cylinder is divided into groups of cylinders whose intake strokes do not overlap, #1 to #3.
It is divided into a cylinder group consisting of cylinders and a cylinder group consisting of #4 to #6 cylinders. The first space 12 includes the branch pipe 5,
The second space 13 communicates with the combustion chambers (not shown) of cylinders #1 to #3 through branch pipes 8, 9, 10.
It communicates with the combustion chambers (not shown) of cylinders #4 to #6 via the cylinder.

The control valve 11 is driven to open and close by an actuator 14, and closes to block the first and second spaces 12 and 13 when the engine is under high load in the low to medium speed rotation range, and opens when the engine rotates at high speed to shut off the first and second spaces 12 and 13. 1 and second space 1
2 and 13 are made conductive. The control valve 11 also opens during startup and under light load. Actuator 14 is a known diaphragm device, and shell 1
5 is partitioned by a diaphragm 16, and negative pressure or atmospheric air is introduced into one chamber 17.The diaphragm 16 has a control valve 11.
A rod 18 connected to is fixed. When negative pressure is introduced into the chamber 17, the diaphragm 16
The rod 18 is displaced and the control valve 1 is displaced.
1 shuts off the inside of the surge tank 4 and the atmosphere is introduced into the chamber 17, the diaphragm 16 is pressed by the spring 35, and the control valve 11 closes the tank 4 via the rod 18.
Open up inside. A negative pressure tank 20 and a switching valve 21 that selectively communicates the inside of this tank 20 with the atmosphere are provided in the middle of the pipe line 19 communicating with the chamber 17, and the negative pressure tank 20 is a surge tank. Connected to 4. The switching valve 21 has a solenoid 22 and a valve body 23. When the solenoid 22 is energized, the valve body 23 opens the opening on the negative pressure tank 20 side of the conduit 19 to communicate the negative pressure tank 20 with the chamber 17, and when the solenoid 22 is demagnetized, the negative pressure in the conduit 19 is opened. The tank 20 side opening is closed to allow the chamber 17 to communicate with the atmosphere. The solenoid 22 is controlled by an electronic control section 24 equipped with a microcomputer.

The intake duct 25 branches into branch pipes 26 and 27 in the middle, the branch pipe 26 connects to the first space 12 of the surge tank 4, and the branch pipe 27 connects to the second space of the surge tank 4.
Connect to space 13. The flow path area of the branch pipes 26 and 27 can be changed by throttle valves 28 and 29, respectively.
8 and 29 are connected to one shaft 30.
It is driven to open and close through. An air cleaner 36 is provided at the upstream opening of the intake duct 25.

The upstream side of the throttle valve 28 of the branch pipe 26 and the first space 12 of the surge tank 4 are connected to a bypass passage 31.
This bypass passage 31 is provided with a bypass valve 32 that opens and closes it. The bypass valve 32 includes a solenoid 33 and a valve body 34, and the valve body 34 closes the passage 3 when the solenoid 33 is energized.
1 and opens the passage 31 when the solenoid 33 is demagnetized. The solenoid 33 is controlled by the electronic control unit 24, and during idling, the duty ratio is controlled or the valve opening is adjusted to an intermediate valve opening so that an amount of air suitable for the idling state at that time passes through the bypass valve 32. Valve body 3
Control 4.

Next, the operation of the first embodiment will be explained with reference to FIGS. 2a and 2b. Figure 2a shows the relationship between the engine speed and shaft torque, and Figure 2b shows the relationship between the engine speed and the opening degrees of the throttle valves 28 and 29 of the control valve 1.
1 shows the opening and closing characteristics.

When the opening degree of the throttle valves 28 and 29, that is, the engine load is above a predetermined value, the control valve 11 controls the
The valve is closed when the engine speed is low or medium speed below a predetermined value. That is, at this time, the switching valve 21 guides the negative pressure in the negative pressure tank 20 to the chamber 17 of the actuator 14, thereby displacing the diaphragm 16 and closing the control valve 11 via the rod 18. Therefore, the inside of the surge tank 4 is separated into the first and second spaces 12 and 13, so the equivalent pipe length of the intake system becomes longer, and the frequency of the intake pulsation of the air column of the intake system and the opening/closing cycle of the intake valve are matched. Then, inertia supercharging is performed, which improves the output in the low and medium speed range (Figure 2 a).
(See dashed line A).

On the other hand, when the opening degree of the throttle valves 28 and 29, that is, the engine load is above a predetermined value, and the engine speed is at a high speed above a predetermined value, the control valve 11 is opened. That is, at this time, the switching valve 21 guides the atmosphere into the chamber 17 of the actuator 14, and the control valve 11 is thereby opened via the diaphragm 16 and the rod 18. Therefore, the first and second spaces 12 and 13 within the surge tank 4 come to communicate with each other. As a result, air is supplied to the combustion chamber of the cylinder in the intake process from both the spaces 12 and 13 of the branch pipes 26 and 27 and the surge tank 4, which reduces ventilation resistance and shortens the equivalent pipe length of the intake system. As a result, the output at high speed is improved (see the dashed line B in FIG. 2a).

Therefore, when the engine load is high, the control valve 11 is closed when the engine speed is below a predetermined value, and the control valve 11 is opened when the engine speed is above the predetermined value.
The shaft torque becomes an envelope of curves A and B (see solid line C in Figure 2a), and it is possible to measure the improvement in output over the entire engine speed range. Note that if the control valve 11 is closed in the entire speed range, the shaft torque will decrease as shown by the dashed line in the high speed range, and if the control valve 11 is opened in the entire speed range, the shaft torque will decrease as shown in the dashed line in the low speed range. becomes smaller.

On the other hand, when starting the engine, the throttle valves 28, 29
is in a fully closed state, but the control valve 11 is opened because the solenoid 22 is demagnetized and the switching valve 21 directs the atmosphere to the chamber 17 of the actuator 14. Moreover, at this time, the bypass valve 32 is also placed in an open state, and the bypass passage 31 is opened. However, it goes without saying that when the bypass valve 32 is subjected to duty ratio control, the bypass passage 31 is opened intermittently. Therefore, the intake air flows into the surge tank 4 through the bypass passage 31 and diffuses throughout the surge tank 4, and then flows through the branch pipes 5, 6, 7, 8,
9 and 10, it is equally guided to each cylinder. Therefore, combustion in all cylinders is performed well, and the engine starts smoothly.

After starting, when the engine load is below a predetermined value, the control valve 11 is similarly open, and when the throttle valves 28 and 29 are almost fully closed, the intake air flows into the surge tank 4 through the bypass passage 31. As the opening degree of the throttle valves 28 and 29 increases, the flow also begins to flow from the branch pipes 26 and 27.

FIG. 3 shows a second embodiment. In this embodiment, the throttle valve 28 is connected to branch pipes 26 and 2 of the intake duct 25.
The bypass passage 3 is provided on the upstream side of the branch part 7.
Reference numeral 1 connects the upstream side of the throttle valve 28 and the first space 12 of the surge tank 4, and the other configurations and functions are the same as in the first embodiment.

[Effect of idea]

As described above, the present invention is configured such that the control valve communicates the first and second spaces of the surge tank when the engine is started, so that the intake air is evenly distributed to each cylinder and the engine is started. can start smoothly.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional plan view showing the first embodiment of the present invention, Fig. 2 a is a graph showing the relationship between engine speed and shaft torque, and Fig. 2 b shows the opening/closing characteristics of the control valve. 3 are partially sectional plan views showing the second embodiment. 4...Surge tank, 5, 6, 7, 8, 9, 1
0... Branch pipe, 11... Control valve, 12... First space, 13... Second space, 31... Bypass passage,
32...Bypass valve.

Claims (1)

[Scope of utility model registration request] An intake passage provided with a throttle valve is connected to a surge tank, and a branch pipe extending from the surge tank is connected to the combustion chamber of each cylinder of a multi-cylinder internal combustion engine, so that the cylinder group of the engine is connected to the first cylinder group. The interior of the surge tank is divided into a second cylinder group, and a first space communicating with the first cylinder group and a second space communicating with the second cylinder group are controlled by a control valve.
In an intake system for a multi-cylinder internal combustion engine that can be divided into a space, a bypass valve connects an upstream side of the intake passage from the throttle valve and a first space of the surge tank through a bypass passage, and opens and closes the bypass passage. and opening the control valve at least when the engine is started,
An intake system for a multi-cylinder internal combustion engine, characterized in that the bypass valve is also opened.