JPH0343388Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement in an intake system for an engine provided with an auxiliary intake passage branching from a main intake passage.

(Prior Art) Conventionally, as shown in FIGS. 3 and 4, branch intake passages 3 and 4 are provided which are branched into two from a main intake passage 1 and communicate with the same combustion chamber 2. A throttle valve (second throttle valve) 6 is provided upstream of the branch portion 5 of No. 3 and 4, which closes at light load and opens at high load. An engine intake system has been proposed in which auxiliary intake passages 7 and 8 are provided which communicate with the branch intake passages 3 and 4 (see Japanese Patent Laid-Open No. 55-25511).

Note that 9 is a throttle valve (first throttle valve) provided upstream of the branch portion 5 of the auxiliary intake passages 7 and 8.

In such an intake system, when the throttle valve (second throttle valve) 6 is closed and the engine is under light load, intake air is supplied to the combustion chamber 2 at a high flow velocity exclusively from the auxiliary intake passages 7 and 8, so that the combustion chamber 2 is It has the advantage of generating a swirl that rotates in the circumferential direction, improving combustibility and improving fuel efficiency.

By the way, in the above-mentioned intake system, when the engine load increases due to the operation of the cooler or the rotation of the electric fan for the radiator while the engine is idling, the opening degree of the throttle valve (first throttle valve) 9 of the main intake passage 1 will change. is set so that the intake air increases and the engine speed increases.

Therefore, during such idling, a large amount of intake air is supplied to the combustion chamber 2 from the auxiliary intake passages 7 and 8 at a high flow rate, which causes the swirl to become larger (stronger) than necessary, and vice versa. There were problems with ignition failure and misfires.

(Purpose of the invention) The present invention was made to solve the above-mentioned conventional problems.Especially during idling, the swirl caused by the intake air from the auxiliary intake passage is controlled so that it does not become larger than necessary, thereby achieving stable idling. The purpose is to enable driving.

(Structure of the invention) Therefore, the present invention includes a main intake passage that introduces intake air into the combustion chamber, an auxiliary intake passage that branches at the main intake passage downstream of the first throttle valve and introduces intake air into the combustion chamber, and a main intake passage that introduces intake air into the combustion chamber. In an engine intake system comprising a second throttle valve that is disposed in the main intake passage downstream of a branch part of the auxiliary intake passage from the main intake passage and that opens when the engine is under high load, the auxiliary intake passage a bypass passage whose one end communicates with the main intake passage upstream of the first throttle valve and whose other end communicates with the main intake passage downstream of the second throttle valve, the main intake passage having a passage diameter larger than that of the main intake passage; The external load operating state detecting means detects the operating state of the external load, and a control valve receives the output of the external load operating state detecting means and opens the bypass passage when the operating state of the external load is detected.

(Effect of the invention) According to the invention, one end of the bypass passage communicates with the first throttle valve upstream of the main intake passage whose passage diameter is larger than that of the auxiliary intake passage, and the other end communicates with the second throttle valve. It communicates with the downstream main intake passage, and when an external load operates, the amount of air that increases accordingly is supplied to the combustion chamber from the main intake passage that does not generate swirl. The amount of air from the large main intake passage increases, reducing passage resistance and allowing air to be supplied with good responsiveness. Also, over-swirl is prevented when the amount of air increases, which prevents ignition failure. This allows stable idling operation and prevents a drop in rotation when an external load is applied.

(Example) As shown in FIGS. 1 and 2, the combustion chamber 12 of one cylinder 11 of the engine E has a cylinder block 12 of approximately the same diameter that is approximately symmetrical with respect to the center line l in the width direction of the cylinder block of the engine E. First and second intake ports 1
4 and 15 are opened, and exhaust ports 16 and 17 are opened at positions facing the first and second intake ports 14 and 15 across the longitudinal centerline m.

A main intake passage 18 that supplies intake air to the first and second intake ports 14 and 15 is connected to the cylinder head (see Fig. 2).
40), which are gradually branched out into the first and second
In front (upstream) of the intake ports 14 and 15, the branched intake passages 20 and 21 are branched into two by a partition wall 19 formed to protrude substantially along the width direction center line l. It is connected to first and second intake ports 14 and 15, respectively.

A second throttle valve 22 is provided upstream of the downstream branch point of the intake passage 18. This second throttle valve 2
2 is not specifically shown, but a well-known opening/closing control mechanism (for example, a link mechanism connected to a throttle valve) closes the main intake passage 18 when the load of the engine E is light, and when the load is high, the intake passage 18 is closed according to the load. Its opening and closing are controlled to open the passage 18.

On the other hand, on the upstream side of the second throttle valve 22 of the main intake passage 8, there is a first
The auxiliary intake passage 23 is placed closer to the intake port 14 side.
The upstream opening 23a is opened in the bottom wall of the intake passage 18.

This auxiliary intake passage 23 is connected to the first intake port 14
It has a downstream opening 23b that opens close to the center line, and is gently curved to cross the center line l.
The upstream opening 23a and the downstream opening 23b communicate with each other.

As specifically shown in FIG. 2, the auxiliary intake passage 23 is formed in a bottom wall 24 that forms the bottom of the main intake passage 18, and its downstream opening 23b is located at the upstream end of the partition wall 19. That is, branch intake passage 2
It is set at a position as close as possible to the first intake port 14 which is opened and closed by the intake valve 25 downstream of the branch point 0 and 21. Therefore, the entire amount of intake air flowing down the auxiliary intake passage 23 flows into the combustion chamber 12 from the first intake port 14.
The auxiliary intake passage 23 is connected to the first intake port 1
4, the branch intake passage 20 is curved in the axial direction of the cylinder 11 immediately upstream of the cylinder block 41.
The cylinder head 40 intersects with the mating surface C of the cylinder head 40 at a slight angle of inclination, so that a swirl swirling in the circumferential direction of the combustion chamber 12 is generated.

Slightly downstream of the upstream opening 23a of the auxiliary intake passage 23, a second throttle valve 22 for opening and closing the main intake passage 18 is disposed so as to be inclined obliquely downward toward the downstream. A fuel injection valve 27 is attached to a mounting portion 26a provided in advance on the upper wall 26 of the main intake passage 18 slightly downstream. in this case,
The fuel injection port 28 is connected to the rotation shaft 22b of the second throttle valve 22.
It is set to be located slightly downstream and on the center line of the main intake passage 18.

Note that the intake valve 2 that opens and closes the first intake port 14
5. An intake valve (not shown) that opens and closes the second intake port 15 and an exhaust valve 29 (the other not shown) that opens and closes the exhaust ports 16 and 17 are connected to the engine E by a well-known overhead cam mechanism 30. They are each driven to open and close at a predetermined timing synchronized with the rotation.

Further, as shown in FIG. 1, the spark plug 31
is set in a portion where the first and second intake ports 14 and 15 and exhaust ports 16 and 17 are not provided, more specifically, in a central portion of the combustion chamber 12.

On the other hand, as shown in FIG. 2, a first throttle valve 36 is provided in the main intake passage 18 upstream of the branch portion 43 of the auxiliary intake passage 23, and when the opening of the first throttle valve 36 exceeds a set opening degree, When the second throttle valve 22 is opened, the first throttle valve 36 is operated by an accelerator pedal (not shown).
The opening degree is controlled in conjunction with.

The first and second throttle valves 36, 22 are bypassed from the main intake passage 18 upstream of the first throttle valve 36, and the second throttle valve 36, 22 is bypassed.
A bypass passage 27 communicating with the branch intake passage 20 downstream of the throttle valve 22 is provided, and a control valve 38 for opening and closing the bypass passage 37 is provided in the bypass passage 37.

The control valve 38 is a load means for the engine;
For example, it is controlled by a detection switch 39 that detects the operation of a cooler or the rotation of an electric fan for a radiator, and when the detection switch 39 is turned on due to an increase in engine load, the bypass passage 37 is opened by a control valve 38.

With the above configuration, when the engine is idling, when the second throttle valve 22 is closed, and when a load means such as a cooler is not operating, the bypass passage 37 is closed by the control valve 38. The entire amount of intake air supplied from the main intake passage 18 via the first throttle valve 36 passes through the auxiliary intake passage 23 from the upstream opening 23a, and the flow velocity is accelerated to the downstream opening 2.
3b and enters the combustion chamber 1 from the first intake port 14.
Since the fuel flows into the combustion chamber 12, a swirl is generated that rotates in the circumferential direction of the combustion chamber 12, resulting in good combustibility.

When the engine is idling and the engine load increases due to the operation of the cooler, etc., the detection switch 39 is turned on and the control valve 38 controls the bypass passage 3.
7 is opened, the increased intake air is introduced from the bypass passage 37 to the branch intake passage 20 and flows into the combustion chamber 1.
2 will be supplied.

Therefore, the intake air from the auxiliary intake passage 23 is controlled to a limit that generates the swirl necessary for good combustion, so that ignition failure no longer occurs, and at the same time, the increased intake air is also smoothly supplied to the combustion chamber 12. Therefore, the engine speed will also increase.

Note that the control valve 38 opens even when the engine load increases other than when the engine is idling, but there is no problem because the intake air from the main intake passage 18 simply bypasses the bypass passage 37.

Although the above embodiment was applied to an intake system using the fuel control valve 27, it goes without saying that it can also be applied to an intake system using a carburetor.

[Brief explanation of the drawing]

FIG. 1 is a plan sectional view of an engine intake system according to the present invention, FIG. 2 is a cross-sectional view of FIG. 1, and FIG.
The figure is a longitudinal sectional view of a conventional engine intake system.
This figure is a plan view showing the flow of intake air in FIG. 3. E... Engine, 12... Combustion chamber, 18... Main intake passage, 20, 21... Branch intake passage, 22...
...Second throttle valve, 36...First throttle valve, 37...Bypass passage, 38...Control valve, 39...Detection switch, 43...Branch portion.

Claims (1)

[Claims for Utility Model Registration] A main intake passage that introduces intake air into the combustion chamber, an auxiliary intake passage that branches at the main intake passage downstream of the first throttle valve and introduces intake air into the combustion chamber, and a main intake passage that introduces intake air into the combustion chamber. In an engine intake system that is disposed in the main intake passage downstream of a branch from the main intake passage and is equipped with a second throttle valve that opens when the engine is under high load, the passage diameter is larger than that of the auxiliary intake passage. a bypass passage whose one end communicates with the main intake passage upstream of the first throttle valve and whose other end communicates with the main intake passage downstream of the second throttle valve; and an external load for detecting the operating state of the external load on the engine. An intake system for an engine, comprising: an operating state detecting means; and a control valve that opens the bypass passage when an operating state of an external load is detected in response to an output of the external load operating state detecting means.