JPH01151764A - Suction unit for engine - Google Patents

Abstract

PURPOSE:To ensure sufficient negative pressure at all times, in an engine provided with first and second throttle valves respectively in a common intake path and an independent intake path, by arranging an intake negative pressure take-in port for each negative pressure utilizing means in an independent intake path in the downstream of the second throttle valve. CONSTITUTION:A surge tank 15 is coupled to the downstream side end section of a common intake path 11 arranged with a first throttle valve 14 interlocked with an accelerator pedal to be opened/closed. An independent intake path 4 coupled with respective intake ports 3 of first to fourth cylinders is branched and coupled with the surge tank 15. Second throttle valve 18 which is controlled to close side in order to prevent counter-flow of exhaust gas into the independent intake path 4 in final stage of exhaust stroke under predetermined light load is arranged in each independent intake path 4. In such engine 1, a negative pressure tank 25 is coupled as a negative pressure source for various negative pressure utilizing means to the surge tank 15 through a first negative pressure lead-in path 26 and to each independent intake path 4 in the downstream of through the second throttle valve 1 through a second negative pressure lead-in path 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for an engine, and in particular, a second throttle valve is provided in an independent intake passage connected to a common intake passage provided with a first throttle valve. This invention relates to a system that prevents exhaust gas from flowing back into the independent intake passage during light loads.

[Prior art] In an engine equipped with a supercharger, the opening period of the intake valve and the opening period of the exhaust valve are overlapped for a relatively long period, and the supercharged intake air is discharged at the end of the exhaust stroke during supercharging. It is well known that the engine scavenges the exhaust gas in the combustion chamber (in the case of a rotary piston engine, the working chamber) to lower the temperature of the intake air before compression, thereby improving the anti-knocking performance. However, when the load is light, the throttle valve is throttled and the intake pressure drops significantly, so at the end of the exhaust stroke, the intake pressure becomes lower than the exhaust pressure, causing the exhaust gas in the combustion chamber (working chamber) or exhaust passage to drop. There was a problem in that gas flowed back into the intake passage, reducing combustion stability.

Therefore, in order to improve this, a first throttle valve is provided in the common intake passage, and a second throttle valve is provided downstream from the first throttle valve in an independent intake passage that communicates with the intake boat of each cylinder, respectively. It has been proposed that the second throttle valve be closed during light loads to prevent exhaust gas from flowing back into the intake passage at the end of the exhaust stroke, thereby improving combustion stability during light loads. There is. In addition, when equipped with a mechanical supercharger, in order to prevent fluctuations in the idle rotation speed due to periodic discharge of intake air from the supercharger during idle,
There is also one in which a second throttle valve is provided in the independent intake passage downstream of the supercharger (see, for example, Japanese Patent Publication No. 10451/1983).

Incidentally, an engine is generally provided with various negative pressure utilization means such as an actuator that uses intake negative pressure as a power source, and the intake negative pressure supplied to each of these negative pressure utilization means is located downstream of the first throttle valve. It is generally provided facing the common intake passage of the first throttle valve or a surge tank (volume section) disposed downstream of the first throttle valve.

However, in the above-mentioned conventional device in which the second throttle valve is provided in the independent intake passage, when the second throttle valve is controlled to the closed side to prevent backflow of exhaust gas into the intake passage during light load, The negative pressure in the combustion chamber (working chamber) during the intake stroke
Since it is difficult for the pressure to propagate to the intake passage upstream of the throttle valve, the pressure in the common intake passage downstream of the first throttle valve or in the surge tank is significantly higher than in the conventional system without a second throttle valve (second throttle valve). (See Figure G). For this reason, it is necessary to provide sufficient negative pressure for negative pressure utilization means that require intake negative pressure during light loads, such as brake vacuum boosters, or for negative pressure utilization means that require negative pressure to be maintained at all times. unable to supply
There has been a problem in that the reliability of these means for utilizing negative pressure is reduced.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and provides an engine in which a second throttle valve is provided in an independent intake passage connected to a common intake passage in which a first throttle valve is provided. , second
It is an object of the present invention to provide an intake device for an engine that can stably supply sufficient negative pressure to each negative pressure utilizing means using intake negative pressure as a power source even when a throttle valve is controlled to the closed side. purpose.

[Structure of the Invention] In order to achieve the above object, the present invention includes a first air intake passage in a common intake passage.
In an engine that is provided with a throttle valve and a second throttle valve is provided in an independent intake passage connected to a common intake passage, the intake negative pressure outlet to each negative pressure utilization means that uses the intake negative pressure as a power source is as described above. There is provided an engine intake device characterized in that it is provided in an independent intake passage downstream of a second throttle valve.

[Effects of the Invention] According to the present invention, the outlet for the intake negative pressure to be supplied to each negative pressure utilizing means using the intake negative pressure as a power source is provided in the independent intake passage downstream of the second throttle valve. Regardless of whether the two throttle valves are opened or closed, the negative pressure generated within the combustion chamber (working chamber) during the intake stroke is taken out from the outlet and supplied to each negative pressure utilization means.

Therefore, even when the second throttle valve is closed, a stable and sufficient negative pressure can be ensured, and the reliability of each negative pressure utilization means can be improved.

In addition, like the conventional one, an intake negative pressure outlet is provided in the common intake passage or the surge tank on the upstream side of the second throttle valve and downstream of the first throttle valve, so that when the second throttle valve is opened, If the intake negative pressure is taken out from this intake negative pressure outlet, the intake air amount between the cylinders will be well balanced.

[Example code] Examples of the present invention will be specifically described below.

As shown in FIG. 1, a four-cylinder engine I equipped with the first to fourth cylinders #l to #4 has, for example, the first cylinder #l, when the intake valve 2 is opened. Intake air (air mixture) is drawn into the combustion chamber 5 from the independent intake passage 4 via the boat 3, this mixture is compressed by a piston (not shown), and ignited and combusted by a spark plug (not shown). The basic configuration is such that combustion gas is discharged to an independent exhaust passage 8 via an exhaust boat 7 when the exhaust valve 6 is opened. In addition, the second
-The fourth cylinders #2 to #4 have a similar configuration, and in Fig. 1, the same numbers as those for the first cylinder #1 are given to the members corresponding to the members of the first cylinder #l. There is.

A common intake passage 11 is provided to supply intake air to the first to fourth cylinders #1 to #4.
! In order from upstream, there are an air cleaner 12 that removes floating dust in the intake air, and an air flow meter 1 that detects the amount of intake air.
3, and a first throttle valve I4 that is opened and closed in conjunction with an accelerator pedal (not shown). The downstream end of the common intake passage 11 is connected to a surge tank 15 that cancels out the pulsation of the intake air and stabilizes the intake air m, while also acting as a pressure reversal section for pressure waves caused by inertial effects.

The surge tank 15 has the first to fourth cylinders #1, respectively.
An independent intake passage 4.4.4.4 communicating with each intake boat 3, 3, 3.3 of ~#4 is connected, and each of these independent intake passages 4, 4, 4.4 will be described in detail later. As explained,
The second throttle valves 1B, 18, 18. are controlled to be closed in order to prevent backflow of exhaust gas at the end of the exhaust stroke into the independent intake passages 4, 4, 4°4 during a predetermined light load. 1
8 are arranged. These second throttle valves 18.18,
18. 18 is attached to one drive shaft 19 and operates the actuator 2 based on a signal from the control unit 20.
1 to be integrally driven to open and close.

Furthermore, the independent intake passages 4 of the first to fourth cylinders #l to #4,
4, 4.4, an injector 22, 22, 2 that injects fuel into intake air near the intake boat 3.3° 3.3, which is slightly downstream of the second throttle valve ts, i8.18.18.
2.22 is provided.

By the way, in order to stably supply intake negative pressure to various negative pressure utilization means that use intake negative pressure as a power source, such as actuators of various control valves and vacuum boosters for brakes, negative pressure with a predetermined volume is used. A tank 25 is provided.

The negative pressure tank 25 communicates with the surge tank 15 via a first negative pressure introduction passage 26, and the pressure inside the surge tank 15 is lower than the pressure inside the negative pressure tank 25. At times, the negative pressure inside the surge tank 15 is introduced into the negative pressure tank 25, while when the pressure inside the surge tank 15 is higher than the pressure inside the negative pressure tank 25, the negative pressure inside the surge tank 15 is introduced into the negative pressure tank 25.
In order to prevent the loss of negative pressure in the first negative pressure introduction passage 2
6, and when the second throttle valves 18.18, 18.18 are controlled to the closing side, as will be explained in detail later, the first check valve 27 receives a signal from the control unit 20 and closes the A first switching valve 28 that closes the first negative pressure introduction passage 26 is provided.

Further, the negative pressure tank 25 is connected to the independent intake passages 4.4. of the first to fourth cylinders #1 to #4 via the second negative pressure introduction passage 31.
4.4 at a position downstream of the second throttle valves ts, ts, t8.18 and upstream of the injectors 22, 22, 22.22. And the second negative pressure introduction passage 3
1 is provided with a second check valve 32 having the same function as the first check valve 27 described above near the connection portion with the independent intake passage 4.4° 4.4. 2nd fish pressure introduction passage 3
1 are gathered into one near the negative pressure tank 25, and second throttle valves 18.1B and 18.18 are opened at a position on the negative pressure tank 25 side from this gathering part, as will be explained later. A second switching valve 33 is provided that closes the second negative pressure introduction passage 31 when the pressure is off.

Hereinafter, the first cylinder #1 system will be explained as an example, but the second to
The same applies to the fourth cylinder #2 to #4 system. In the above configuration, during idle and light load, the actuator 21 receives a signal from the control unit 20.
As a result, the second throttle valve 18 is substantially closed. That is,
As shown in FIG. 2(b), at the end of the exhaust stroke, the opening period of the intake valve 2 shown by curves c, , G and the curves Gs, Gt
During the so-called intake/exhaust overlap, in which the opening period of the exhaust valve overlaps with the opening period of the exhaust valve, the exhaust gas in the combustion chamber 5 tends to flow back into the independent intake passage 4 due to the exhaust pressure. The second throttle valve 18 is substantially closed. This effectively prevents exhaust gas from flowing back into the independent intake passage 4, reduces illusion, and improves combustion stability at idle and under light load. On the other hand, when the load is higher than the above-mentioned idling and light load conditions, the second throttle valve 18 is opened because the combustibility is stabilized and a sufficient amount of intake air is required.

By the way, when the second throttle valve 18 is opened, the control unit 20 opens the first switching valve 28, closes the second switching valve 33, and closes the negative pressure tank 2.
5 is connected to the surge tank 15 through the first negative pressure introduction passage 26.
Negative pressure inside is introduced. That is, when the second throttle valve 18 is open, the negative pressure generated in the combustion chamber 5 during the intake stroke is transmitted to the surge tank 15 as is, so that the first negative pressure introduction passage 26 is surge-free. tank 15
This is because sufficient negative pressure is ensured even when negative pressure is introduced into the negative pressure tank 25 from inside.

In this way, when the second throttle valve 18 is closed, the negative pressure obtained in the negative pressure tank 25 from the independent intake passage 4 downstream of the second throttle valve 18 through the second negative pressure introduction passage 31 is as follows: It will look like the curve G3 in Figure 2(a), and the straight line G,
Compared to the pressure in the surge tank 15 shown by , that is, the negative pressure obtained with a conventional engine equipped with a second throttle valve, a sufficiently strong negative pressure can be obtained, and the reliability of each negative pressure utilization means can be increased. It looks like this. In addition, if the second throttle valve is not provided, a stronger negative pressure (e.g. -500 mmHg) can be obtained as shown by the straight line G4, but such a negative pressure is not necessarily necessary in a normal engine. The negative pressure obtained by this method can sufficiently ensure the reliability of various negative pressure utilization means.

In this embodiment, the first throttle valve 14 disposed in the common intake passage 11 is prevented from interlocking with the accelerator pedal, while the second throttle valve 18 disposed in the independent intake passage 4 is closed at a predetermined light load. I try to control it on the side, but on the contrary,
The second throttle valve installed in the independent intake passage 4! 8 may be operated in conjunction with the accelerator pedal, while the first throttle valve 14 disposed in the common intake passage 11 may be controlled to close when a predetermined light load is applied. In this case as well, the inside of the combustion chamber 5 and the second
Independent intake passage 4 between negative pressure introduction passage 3I and negative pressure outlet
Since there is nothing that impedes the propagation of the negative pressure in the combustion chamber 5, effective negative pressure can be applied through the second negative pressure introduction passage 31 even in an operating state in which the second throttle valve 18 is almost closed. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an engine equipped with an intake device according to the present invention. Figure 2 (a) shows the pressure in the surge tank and the independent intake passage downstream of the second throttle valve when the second throttle valve is closed, and the pressure when the second throttle valve is open or when the second throttle valve is installed. There is a diagram showing the pressure inside the surge tank when there is no surge tank. FIG. 2(b) is a diagram showing the characteristics of the valve openings of the exhaust valve and the intake valve with respect to time. #l to #4...1st to 4th cylinders, 1...engine,
2... Intake valve, 3... Intake boat, 4... Independent intake passage, 5... Combustion chamber, 11... Common intake passage, 14
...First throttle valve, 15...Surge tank, 18...
・Second throttle valve, 20...control unit, 25
...Negative pressure tank, 26...First negative pressure introduction passage, 31
...Second negative pressure introduction passage. Patent applicant Mazda Motor Corporation

Claims (1)

[Claims] (1) In an engine in which a first throttle valve is provided in a common intake passage and a second throttle valve is provided in an independent intake passage connected to the common intake passage, each negative pressure utilization means that uses intake negative pressure as a power source An intake system for an engine, characterized in that an intake port for intake negative pressure is provided in an independent intake passage downstream of the second throttle valve.