JPH0247573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an engine intake system, particularly an intake valve that opens two intake ports into a combustion chamber of the engine, and opens and closes the intake ports for each intake port. This relates to a type of intake device in which a

(Prior art) Conventionally, in a reciprocating engine, two intake ports with approximately equal opening areas are opened for each combustion chamber to ensure a large opening area, and an intake passage formed in the cylinder head is By connecting each intake port at a large angle along the axial direction of the combustion chamber and allowing intake air to flow straight into the combustion chamber, the engine's filling efficiency is maximized and engine output is increased. The intake structure is well known.

Such a two-port intake structure is advantageous in terms of achieving high output during high-load operation, but on the other hand, during low-load operation with a small amount of intake air, the intake flow velocity becomes weaker, resulting in a decrease in combustibility. In terms of fuel efficiency,
There is also a disadvantage in terms of emission.

In order to eliminate this drawback, a low-load intake passage and a high-load intake passage with a shutter valve interposed are connected to the above two intake ports, and the shutter valve is closed when the engine is operating at low load. , a device in which air is taken only from the low-load intake passage is known (for example, Japanese Patent Application Laid-Open No. 1989-1999)
(See Publication No. 44419).

However, such measures are not necessarily effective as low-load measures. In other words, the opening area of the two intake ports was originally designed to be maximized in order to achieve high output, so even if only one intake port is used, during extremely low load operation where the amount of intake air is small, the opening area will be reduced. is still too large to effectively improve the intake flow velocity, and it is not possible to effectively form the swirl that is essential for improving combustibility.

It seems that this problem can be solved by narrowing down the passage area of the low-load intake passage, but for the purpose of achieving high output, the port connection part of the intake passage should be oriented in the axial direction of the combustion chamber, as mentioned above. Because it is formed along the circumferential direction of the combustion chamber, even if a high-velocity flow is generated within the combustion chamber by increasing the intake flow rate, it will not be generated as an effective swirl along the circumferential direction of the combustion chamber. Therefore, there is a problem in that this intake air flow is attenuated early in the compression stroke. However, if you restrict the low-load intake passage too much in an attempt to increase the flow velocity as much as possible, the load range that can be covered will be limited accordingly, and if you open the shutter valve in a relatively low load range, you can also use the high-load intake passage. It becomes necessary to supply intake air.
In that case, since the two intake ports are formed opposite to each other with respect to the horizontal center line of the combustion chamber,
The intake air flow taken in from the low-load intake port and the intake air flow taken in from the high-load intake port collide, and the swirl is further weakened, if not eliminated, ensuring good combustion performance due to the swirl. There are some drawbacks that are difficult to overcome.

(Objective of the Invention) The present invention is effective in improving combustibility within the combustion chamber during low-load operation of the engine without substantially changing the two-intake port system, which aims to increase the output of the engine. Provided is a fuel supply structure that can supply fuel with good responsiveness without being affected by the movement of a control valve that controls the amount of intake air in an engine intake system equipped with an intake structure that can generate a swirl. This is what I am trying to do.

(Structure of the Invention) For this reason, the present invention opens two intake ports into the combustion chamber of the engine, opens and closes each intake port with an intake valve, and connects the two intake ports downstream. A control valve is disposed upstream of the branched common intake passage, and the passage area of the intake passage is controlled to increase or decrease depending on the engine operating condition so that the control valve closes during low load operation and opens during high load operation. On the other hand, an auxiliary intake passage is provided which branches from the intake passage upstream of the on-off valve and is connected to one of the intake ports, and the auxiliary intake passage is connected to the bottom of the intake passage near the branching part of the intake passage. The basic characteristics are that the wall section is formed in a flat shape with a short cross section in the axial direction of the cylinder, and the fuel injection valve is arranged in the range downstream from the control valve and upstream from the branch part of the common intake passage. It is said that

That is, in the intake structure according to the present invention, during low-load operation of the engine when the control valve is closed, the intake air is exclusively taken from the flat auxiliary intake passage passing through the bottom wall through the intake port to which this passage is connected. It is supplied to the combustion chamber of the engine at a flow rate. In that case, the auxiliary intake passage generates a swirl that swirls in the circumferential direction of the combustion chamber.

Furthermore, when the control valve is opened during high-load operation of the engine, intake air is drawn in from the plurality of intake ports with good charging efficiency, thereby ensuring the original high output.

In the above-mentioned intake structure, the present invention disposes a fuel injection valve in the common intake passage downstream of the control valve, and can supply fuel to the combustion chamber through two intake ports regardless of whether the control valve is opened or closed. This is how it was done.

(Effects of the Invention) Therefore, according to the present invention, in addition to the advantages of the intake structure itself, since fuel is injected from downstream of the control valve, it is not affected by the movement of the control valve; The injected fuel does not collide with the control valve, and the fuel can be supplied from a position close to the intake port, thereby improving the responsiveness of fuel supply.

(Example) Hereinafter, an example of the present invention will be described in more detail.

As shown in Fig. 1, the combustion chamber 2 of one cylinder 1 of the engine E is provided with a cylinder of approximately the same diameter, which is approximately symmetrical with respect to the widthwise center line l of the cylinder block of the engine E (see 3 in Fig. 2). The first and second intake ports 4 and 5 are opened, and an exhaust port 6 is opened at a position facing the second intake port 5 across the longitudinal centerline m.

A common intake passage 7 that supplies intake air to the first and second intake ports 4 and 5 is gradually branched within the cylinder head (see 8 in Fig. 2).
In front of the intake ports 4, 5, the branched intake passages 10, 11 are branched into two by a partition wall 9 formed to protrude substantially along the width direction center line l, and these branched intake passages 10, 11 are divided into two branches. They are connected to second intake ports 4 and 5, respectively. As shown in the figure, the center line l' of the common intake passage 7 is slightly eccentric to the first intake port 4 side with respect to the widthwise center line l, and
It is set to be connected straight to the first intake port 4 compared to the intake port 5, and a shutter valve 12 as a control valve is provided on the upstream side thereof. Although this shutter valve 12 is not specifically shown, a well-known opening/closing control mechanism (for example, a link mechanism connected to a throttle valve) closes the common intake passage 7 during low load operation of the engine E, and closes the common intake passage 7 during high load operation. Sometimes its opening and closing is controlled so that it opens depending on the load. On the upstream side of the shutter valve 12 of the common intake passage 7, an upstream opening 13a of the auxiliary intake passage 13 is arranged toward the second intake port 5 side with respect to the center line l' of the common intake passage 7. is opened at the bottom wall of the intake passage 7.
The auxiliary intake passage 13 has a downstream opening 13b that opens close to the first intake port 4, and is gently curved to cross the center line l'. communicate with.
As specifically shown in FIG. 2, this auxiliary intake passage 13 is formed in a bottom wall 14 forming the bottom of the common intake passage 7, and its downstream opening 13b is located at the upstream end of the partition wall 9. , that is, branch intake passage 1
It is set at a position as close as possible to the first intake port 4 which is opened and closed by the intake valve 15 downstream of the branch point 0 and 11. Therefore, the entire amount of intake air flowing down the auxiliary intake passage 13 flows into the combustion chamber 2 from the first intake port 4. The auxiliary intake passage 13 is located at the mating surface A between the cylinder block 3 and the cylinder head 8, whereas the branch intake passage 10 is curved with a large curvature in the axial direction of the cylinder 1 immediately upstream of the first intake port 4. They intersect with each other at a slight angle of inclination with respect to the combustion chamber 2, and thus have directionality in the circumferential direction of the combustion chamber 2.

Slightly downstream of the upstream opening 13a of the auxiliary intake passage 13, a shutter valve 12 for opening and closing the intake passage 7 is provided so as to be inclined obliquely downward toward the downstream. A fuel injection valve 17 is attached to a mounting portion 16a provided in advance on the upper wall 16 of the common intake passage 7. In this case, the fuel injection port 18 is located slightly downstream of the rotating shaft 12a of the shutter valve 12 and on the center line l' of the common intake passage 7 (see FIG. 1). As is well known, the fuel injected by the fuel injection valve 17 travels straight without spreading until a certain distance, and then spreads out in a cone shape. Therefore, as described above, the fuel injection ports 18 are aligned with the center line of the common intake passage 7.
If the center line l' is set on the first intake port 4 side, the distribution ratio of the cone-shaped fuel to the first and second intake ports 4 and 5 is as follows. It increases on the first intake port 4 side.

Therefore, during low-load operation of the engine E when air is taken exclusively from the first intake port 4, more fuel is mixed with the intake air, and the combustibility of the air-fuel mixture is improved.

However, when considering the uniform distribution of fuel to each intake port during high-load operation, the fuel injection valve 17 is aligned with the centerline in the width direction of the cylinder block, which is the line of symmetry with respect to the first and second intake ports 4 and 5. Preferably, it is disposed on top. The key point is which request to prioritize.

Also, the shutter valve 12 is connected to the auxiliary intake passage 1.
It is arranged between the upstream opening 13a of No. 3 and the fuel injection port 18, tilted diagonally downward, and is set to open in the direction of the hour hand from the closed position A shown by the solid line in FIG. 2 to the fully open position B shown by the imaginary line. This allows the intake passage volume downstream of the shutter valve 12 to be minimized when the shutter valve 12 is closed. The installation position of the fuel injection valve 17 is on the upstream side of the partition wall 9 of the first and second intake ports 4 and 5, and it is necessary to distribute the fuel in a cone shape across both branch intake passages 10 and 11. Therefore, if the shutter valve 12, which needs to be installed upstream of the shutter valve 12, cannot be set downstream unnecessarily, but is arranged as described above, it will be closest to the fuel injection valve 17 and will occupy the smallest amount of exclusive use. Since the shutter valve 12 can be installed in the space, the shutter valve 1
The volume of the intake passage downstream of the shutter valve 12, which becomes the dead volume when the shutter valve 2 is closed, can be minimized.

Note that the intake valve 1 that opens and closes the first intake port 4
5. An intake valve (not shown) that opens and closes the second intake port 5 and an exhaust valve 19 that opens and closes the exhaust port 6
By the well-known overhead cam mechanism 20,
They are each driven to open and close at a predetermined timing synchronized with the rotation of the engine E.

Further, as shown in FIG. 1, the spark plug 21
is a part where the first and second intake ports 4 and 5 and the exhaust port 6 are not provided, more specifically,
The auxiliary intake passage 13 is disposed at a position opposite to the first intake port 4 through which the auxiliary intake passage 13 opens, with the longitudinal center line m of the combustion chamber 2 interposed therebetween.

In this plug arrangement, the spark plug 21 is located on the swirl locus formed by the auxiliary intake passage 13, so the spark plug 21
This allows the air-fuel mixture to be ignited with good ignitability.

Next, as shown in FIGS. 3 1 to 9, changes in the cross-sectional shape within the cylinder head 8 of the common intake passage 7 corresponding to cross sections 1 to 9 in FIG. 4 are shown. 7 is a branched intake passage 10, 11 which changes from an elliptical shape to a hooked shape as it goes downstream, and finally has two circular cross sections.
It is branched into.

The auxiliary intake passage 13 has a flat rectangular cross section located below the common intake passage 7 and has a passage cross-sectional area sufficiently smaller than that of the common intake passage 7. Initially, the position is eccentric to the second intake port 5 side (right side in the figure) of the common intake passage 7, and then it gradually shifts to the first intake port 4 side (left side in the figure) and connects to the first intake port 4. It intersects with the bottom surface of the branched intake passage 10 and finally opens immediately upstream of the first intake port 4.

As shown in FIG. 4, by forming the auxiliary intake passage 13 in the bottom wall 14 that forms the bottom surface of the common intake passage 7, the auxiliary intake passage 13 is formed on the mating surface of the cylinder block 3 and the cylinder head 8. The shaft is formed at a relatively small inclination angle with respect to A, and is smoothly curved from the second intake port 5 side to the first intake port 4 side when viewed as a planar shape. During low-load operation of the engine E when the tar valve 12 is fully closed, the intake air flowing down exclusively through the auxiliary intake passage 13 is narrowed down to increase its flow velocity, and is oriented in the circumferential direction of the combustion chamber 2 while being directed to the first intake port 4. From combustion chamber 2
The fuel flows into the combustion chamber 2 and generates a circumferential swirl within the combustion chamber 2.

Since this swirl is formed in the circumferential direction, it is not easily attenuated, and is successfully ignited and burned by the ignition of the spark plug 21 at the end of the compression stroke.

Moreover, the fuel injected from the fuel injection valve 17 is
Even if the shutter valve 12 is closed, fuel can be supplied to the combustion chamber 2 from the first and second intake ports 4 and 5 without being affected by this, and fuel can be injected depending on the operating condition. The fuel is supplied with good response from the fuel injection valve 17 whose amount is accurately controlled.
The responsiveness of this fuel supply is determined by the shutter valve 12.
It is maintained well even during high load operation when the valve is opened.

In the above embodiment, the auxiliary intake passage 13 was formed by crossing from the second intake port 5 side to the first intake port 4 side, but the present invention is not limited to this.

That is, as shown in FIG.
A branch intake passage 1 connected to the first intake port 4
It may be formed straight along the extension line of 0.

In FIG. 5, the same parts as in FIG. 1 are given the same numbers, and further explanation will be omitted.

[Brief explanation of the drawing]

Fig. 1 is an explanatory sectional view of the main parts of an engine showing an embodiment of the present invention, Fig. 2 is a longitudinal sectional view taken in the - line direction of Fig. 1, and Figs. 3 1 to 9 show changes in the cross-sectional shape of the intake passage. Each cross-sectional explanatory diagram, FIG. 4 is a vertical cross-sectional explanatory diagram showing the respective cross-sectional positions of FIGS. 3 1 to 9, and FIG. It is an explanatory diagram. 2... Combustion chamber, 4, 5... First and second intake ports,
7... Common intake passage, 10, 11... Branch intake passage, 12... Shutter valve (control valve), 13...
Auxiliary intake passage, 15...Intake valve, 17...Fuel injection valve, 18...Fuel injection port.

Claims (1)

[Claims] 1 Two intake ports, each opened and closed by an intake valve, are opened to the combustion chamber, and their passage area is variably controlled by a control valve that closes during low-load operation and opens during high-load operation, and is branched downstream of the control valve. an auxiliary intake passage branched from the intake passage upstream of the control valve and connected to any one of the intake ports; The auxiliary intake passage is formed in the bottom wall of the intake passage near the branching part of the intake passage in a flat shape with a cross section that is short in the axial direction of the cylinder, and a fuel injection valve is installed in the intake passage downstream of the control valve. An engine intake system featuring: