JPH0220810B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention includes a plurality of intake ports for introducing intake air into a combustion chamber of an engine, and an intake passage connected to each intake port, The present invention further relates to an engine intake device including an auxiliary intake passage connected to any one intake port.

(Prior art) In order to increase the output of an engine, it is necessary to expand the intake passage area and improve the filling efficiency. An engine intake structure that aims to increase output by introducing intake air from two intake ports for reasons such as the inertial weight of the engine becoming larger and the tracking performance becoming worse, and the strength of the combustion chamber structure being disadvantageous. has been known for a long time.

Such a two-port intake system has the advantage of being able to introduce a large amount of intake air and obtain high output during high-load operation, but the intake air flow rate decreases during low-load operation when the amount of intake air is small. As a result, there arises a problem that ignitability deteriorates and combustibility decreases.
In order to eliminate such disadvantages, it is known to improve the combustibility during low load operation by increasing the intake air flow velocity and forming an intake air swirl during low load operation. For example, JP-A-56-
Publication No. 44419 discloses an intake system in which two intake passages branched from one intake passage are connected to two intake ports opening into a combustion chamber, and a shutter valve that opens at high load is provided in one of the branched intake passages. The structure of the device is disclosed. In this device, since the shutter valve is closed during low-load operation, intake air is introduced only from the other branch intake passage where the shutter valve is not provided. In this device, this prevents a decrease in the flow velocity of intake air and generates a swirl of intake air. In this case, the strength of the swirl is proportional to the amount of intake air passing through the port, but the disclosed device introduces intake air only from one intake port at low loads, and from both ports at high loads. Since it has a simple configuration, it has the disadvantage that the port area is too large in relation to the amount of intake air at extremely low loads, making it impossible to obtain the desired swirl strength. In addition, as mentioned above, as the load increases, the intake air amount also increases and the swirl becomes stronger, but when the shutter valve is opened due to an increase in load, the swirl generated by the intake air introduced from one port is This causes a problem in that combustibility worsens in such a transient operating region because it collides with the flow of intake air introduced from the port and is rapidly weakened.

(Objective of the present invention) An object of the present invention is to minimize the change in swirl strength in view of the above-mentioned disadvantages that occur when the change in swirl strength due to load changes is large. An object of the present invention is to provide an engine intake device that can obtain stable and good combustion performance over a wide operating range.

(Structure and operation of the present invention) The object of the present invention is to provide a plurality of intake ports that open into one combustion chamber, a main intake passage, and a branch intake that branches from the main intake passage and communicates with each of the intake ports. an engine passage, and an on-off valve provided in the main intake passage, which is controlled in a closed direction during low-load operation and controlled in an open direction during high-load operation to increase or decrease the passage area of the main intake passage. In the intake device, the intake passage branches from the main intake passage upstream of the on-off valve, is connected to one of the branch intake passages, and has a passage area smaller than the passage area near the port connection portion of the branch intake passage. An auxiliary intake passage is provided, and the valve body of the on-off valve has a shape in which a portion on the side opposite to the branch intake passage to which the auxiliary intake passage is connected is cut out. This is accomplished by the engine's intake system.

In a preferred embodiment of the invention, the auxiliary intake passage branches off from the bottom of the main intake passage and communicates with one of the branch intake passages through the underside of the branch intake passage. Therefore, the intake air passing through this auxiliary intake passage has a high flow rate and is introduced into the combustion chamber from a relatively low position in the circumferential direction, so that a strong swirl is generated. On the other hand, the valve body of the on-off valve has a part cut out on the side opposite to the branch intake passage to which the auxiliary intake passage is connected, so a part of the intake air is always directed toward the opposite side of the swirl regardless of the opening degree of the on-off valve. It is introduced into the combustion chamber from the side. in this case,
As the load changes, the amount of intake air changes, which in turn changes the strength of the swirl, but at the same time, correspondingly, air is introduced into the combustion chamber from the opposite side of the swirl through the notch in the on-off valve. The amount of air taken in will also change. Then, the two factors suitably cancel each other out within the combustion chamber, and the strength of the resulting swirl does not change significantly. The strength of the swirl obtained is
Passage area of the auxiliary intake passage, direction of introduction of intake air passing through the auxiliary intake passage into the combustion chamber, size of the notch,
It can be changed by appropriately setting the shape, etc. Furthermore, when the load is high, the on-off valve is opened, so a sufficient amount of intake air is introduced into the combustion chamber from the plurality of intake ports.

(Effects of the Present Invention) According to the present invention, it is possible to obtain a swirl of a desired strength and to suppress changes in swirl strength due to changes in load.
Good and stable combustibility can be obtained over a wide load range. Furthermore, sufficient high output can be obtained during high loads.

(Description of Examples) Referring to FIGS. 1 and 2, engine E
is a cylinder block 1 having a cylinder bore 1a.
The engine has a cylinder head 2 attached to the upper part of the cylinder block 1, and a piston 3 is disposed within the cylinder bore 1a so as to be able to reciprocate in the axial direction, thereby forming a combustion chamber 4 within the cylinder bore 1a. The cylinder head 2 has first and second intake ports 5, 6.
and an exhaust port 7 are formed, an intake valve 8 is formed in the first and second intake ports 5 and 6, and an exhaust port 7 is formed in the first and second intake ports 5 and 6, respectively.
An exhaust valve 9 is attached to the. Referring to FIG. 1, the first and second intake ports 5 and 6 have approximately the same diameter;
Cylinder center line l in the width direction of cylinder block 1
The exhaust port 7 is arranged at a position facing the second intake port 6 across the longitudinal centerline m of the cylinder block 1.

The intake system has a main intake passage 11 extending from an air cleaner 10, and a throttle valve 12 is disposed within the main intake passage 11. As shown in FIG. 1, the main intake passage 11 extends into the cylinder head 2.
In the vicinity of the intake ports 5 and 6, the first and second intake ports 5 and 6 are separated by a partition wall 14 formed substantially along the cylinder center line l in the width direction of the cylinder block, and communicate with the first and second intake ports 5 and 6, respectively. It constitutes second branch passages 15 and 16. Exhaust port 7
is connected to the exhaust passage 17 to constitute an exhaust system. This exhaust system may have a normal configuration. In the main intake passage 11, a fuel injection valve 23 is provided on the upstream side of the partition wall 14.
is arranged, and metered fuel is supplied to the combustion chamber 4 based on a signal corresponding to the engine operating conditions. An on-off valve 18 is provided within the main intake passage 11 .

The valve body 18a of this on-off valve 18 is connected to the branch passage 16.
A part of the side part is cut out. Therefore, even when the on-off valve 18 is in a fully closed state, a gap 25 exists between the valve body 18a and the side wall of the main intake passage 11, and therefore a portion of the intake air is The fuel also flows through this gap 25 and is supplied into the combustion chamber. This on-off valve 18
is configured to be closed in a low-load operating range in which the opening of the throttle valve is relatively small, for example, in conjunction with the throttle valve 12, and to be opened when the throttle valve 12 is opened beyond a predetermined opening. An opening 19 is formed at the bottom of the main intake passage 11 slightly upstream of the on-off valve 18, and an auxiliary intake passage 20 is formed extending below the main intake passage 11 from this opening 19. The auxiliary intake passage 20 passes from below the main intake passage 11 to below the first branch passage 15 and extends through the opening 21.
The first branch passage 15 near the first intake port 5
It is connected to the. As shown in Fig. 2, the intake port 5 opens into the combustion chamber 4 at an angle close to the axial direction of the cylinder bore 1a in order to ensure a high filling amount during high-load operation. However, the second intake port 6 also has a similar shape. On the other hand, the auxiliary intake passage 20 is connected from the lower side of the main intake passage 11 and the first branch passage 15 to the first intake port 5.
Since it opens into the nearby first branch passage 15, it is oriented at a relatively shallow angle with respect to the combustion chamber 4. Furthermore, since the first intake port 5 is arranged to be biased to one side with respect to the center line l of the cylinder bore 1a, the intake air jetted into the combustion chamber 4 at a shallow angle from the auxiliary intake passage 20 is directed within the combustion chamber 4. Generates a strong swirl in the horizontal plane.

In order to facilitate the generation of this swirl, it is desirable that the shape of the auxiliary intake passage 20 is formed so as to be oriented substantially tangentially to the peripheral wall of the cylinder bore 1a near the opening 21. In order to obtain such a shape, it is necessary to curve the auxiliary intake passage 20. However, as shown in FIG. 1, the opening 19 of the auxiliary intake passage 20 that branches from the main intake passage 11 has its center located on the opposite side of the first intake port 5 with respect to the center of the main intake passage 11. Since it is arranged closer to the second intake port 6, it is not necessary to give the auxiliary intake passage 20 an extreme bend even when it is shaped along the circumferential direction of the cylinder bore 1a near the opening 21. Gone, the first
As shown in the figure, it is possible to form a relatively gentle flow path with little resistance. During low-load operation, the on-off valve 18 is closed, and therefore, intake air flows through the auxiliary intake passage 20, which opens upstream of the on-off valve 18, and one side of the valve body 18a of the on-off valve 58. A gap 25 between the passage wall of the passage 11 and the valve body 18a, which is formed by having a notch
is introduced into the combustion chamber through the Since the auxiliary intake passage 20 has a smaller cross-sectional area than each of the branch passages 15 and 16, a relatively high flow rate can be maintained even during low-load operation with a small intake air amount. Furthermore, since the auxiliary intake passage 20 is oriented in the circumferential direction of the cylinder bore 1a at a relatively shallow angle as described above, the intake air flow injected from the auxiliary intake passage 20 into the combustion chamber 4 is directed within the combustion chamber 4. to form a strong swirl.

On the other hand, when the on-off valve 18 is in the closed state, the gap 25
When the auxiliary intake passage 20 is connected along the pipe wall of the branch passage 16, the intake air introduced through the second intake port 6 on the opposite side is also introduced in the circumferential direction to the cylinder wall. Ru. In this case, the intake air flowing from the auxiliary intake passage 20 through the intake port 5 and the intake air introduced from the gap 25 through the first intake port 6 have opposite flow directions to form the swirl. Therefore, both intake flows interfere within the combustion chamber 4. As a result, the strength of the intake swirl from the auxiliary intake passage 20 is moderated to some extent, resulting in a swirl of appropriate strength. As shown in FIG. 1, in this embodiment, a portion of the cylinder head 2 where intake and exhaust ports are not formed, that is, a portion facing the first intake port 5 across the longitudinal centerline m of the cylinder block 1. A spark plug 22 is attached to the portion. Therefore, since the ignition plug 22 is located on the swirl locus formed by the intake air flow from the auxiliary intake passage 20, fresh air-fuel mixture is reliably supplied to the vicinity of the ignition plug 22, resulting in a good air-fuel mixture. Combustion occurs with ignitability.
Thereafter, when the load increases within the range where the on-off valve 18 is not opened, the amount of intake air increases, and as a result, the swirl strength of the intake air introduced through the auxiliary intake passage 20 also becomes stronger. Correspondingly, the amount of intake air introduced into the combustion chamber 4 from the intake port 24 through the gap 25 also increases, so that the intake flow counteracting the swirl also increases. Therefore, as a result, the strength of the swirl remaining in the combustion chamber 4 does not change significantly even if the load changes. When the load increases further and the on-off valve 18 is opened,
Intake air is also introduced into the combustion chamber 4 from the intake port 22, but the intake air that passes through the gap 25 is always present, and the balance with the intake air that generates swirl is not impaired, and the strength of the swirl is No major changes will occur. Further, when the opening degree of the on-off valve 18 increases, the force of generating a swirl due to the intake air from the auxiliary intake passage 20 is canceled out and weakened by the intake air from the branched intake passage 16, and the swirl generated within the combustion chamber 4 is weakened. However, since such an operating region is a high-load operating region, combustibility is good, and no problem occurs even if the swirl weakens. Therefore, according to the present invention, it is possible to reduce changes in swirl strength due to load changes in a wide load range from a low load operation region to a medium load operation region,
This makes it possible to obtain stable and good combustibility. Then, during high-load operation, sufficient intake air can be ensured and high output can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of an engine intake system according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of an engine embodying the present invention. 1... Cylinder block, 1a... Cylinder bore, 2... Cylinder head, 3... Piston, 4
... Combustion chamber, 5, 6 ... Intake port, 7 ... Exhaust port, 11 ... Main intake passage, 15, 16 ... Branch intake passage, 18 ... Opening/closing valve, 19 ... Opening, 2
0...Auxiliary intake passage.

Claims (1)

[Claims] 1 A plurality of intake ports opening into one combustion chamber, a main intake passage, a branch intake passage branching from the main intake passage and communicating with each intake port, and a plurality of intake passages provided in the main intake passage to facilitate low-load operation. In an engine intake system equipped with an on-off valve that is sometimes controlled in the closed direction and, during high-load operation, controlled in the open direction to increase or decrease the passage area of the main intake passage, the main intake air upstream of the on-off valve is An auxiliary intake passage is provided which branches from the passage, is connected to any one of the branched intake passages, has a passage area smaller than the passage area near the port connection portion of the branched intake passage, and has a valve body of the on-off valve. An intake device for an engine, characterized in that a portion of the side opposite to the branch intake passage to which the auxiliary intake passage is connected is cut out.