JPH0247574B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a plurality of intake passages leading to a combustion chamber;
The engine is equipped with a mechanism that prevents the mixture from becoming too rich by introducing intake air into the intake passage downstream of the throttle valve during deceleration.

(Prior art) When the accelerator pedal is released in order to decelerate while driving, the throttle valve closes and the negative pressure downstream of the throttle valve increases rapidly, causing the fuel adhering to the intake passage wall to dissipate. Due to the vaporization and the small amount of intake air, the air-fuel mixture introduced into the combustion chamber becomes temporarily rich. This causes problems such as a misfire phenomenon, afterburn, and deterioration of exhaust gas properties. In order to solve this problem, various means are known for introducing intake air downstream of the throttle valve during deceleration to prevent over-enrichment of the air-fuel mixture. For example, Utsukai 53-
No. 131126 describes an anti-afterburn valve (AAV) equipped with a diaphragm device that opens in response to negative pressure downstream of the throttle valve and introduces intake air into the intake manifold.
A valve is provided to communicate the two chambers, and this communication valve is controlled to open and close depending on the degree of negative pressure downstream of the throttle valve.
The valve opening time of the AAV is changed to introduce a mixture with an appropriate air-fuel ratio into the combustion chamber. Also,
JP-A-55-14937 discloses an intake structure that suppresses the adhesion of fuel to the wall surface and supplies an appropriate concentration of air-fuel mixture in an operating region where the amount of intake air is small. In addition, the intake structure is equipped with multiple intake passages that branch out downstream of the throttle valve, and when the load is low, some of the intake passages are closed by on-off valves, the area of the passage is narrowed, and intake air is introduced into the combustion chamber. A device that forms a swirl is known.

In this type of intake system, the on-off valve is closed during deceleration, so even if intake air is introduced into the intake passage downstream of the throttle valve,
Since the intake air is introduced through a passage with a small passage area, there is a problem that the passage resistance is large and sufficient air for dilution cannot be sent into the combustion chamber, and this problem cannot be solved with conventional devices. It is something.

(Objective of the present invention) Therefore, an object of the present invention is to provide a plurality of branch intake passages branching from the main intake passage at least in the vicinity of the combustion chamber, and a plurality of branch intake passages that are provided in the main intake passage and closed during low load operation. an on-off valve that is controlled in the open direction and increases or decreases the passage area of the main intake passage during high-load operation, and a fuel supply means that supplies fuel to the main intake passage downstream of the on-off valve; An intake system for an engine comprising: an intake air amount increasing device that increases the amount of intake air flowing downstream of the throttle valve in the main intake passage and upstream of the opening/closing valve when the throttle valve is suddenly closed; It is an object of the present invention to provide an intake device for an engine that can introduce intake air into the engine and prevent the mixture from becoming over-enriched during deceleration.

(Structure of the Present Invention) This object of the present invention is achieved by an engine intake system characterized by comprising a control device that opens the on-off valve by a predetermined amount while the intake air amount increasing device is in operation. .

(Operation of the present invention) According to the present invention, even when the accelerator pedal is released during deceleration, the intake air amount increasing device increases the amount of intake air flowing downstream of the throttle valve and upstream of the on-off valve. While the booster is in operation, the control device opens the on-off valve by a predetermined amount, which allows intake air to be introduced downstream of the throttle valve during deceleration and prevents the mixture from becoming too rich during deceleration. It becomes possible.

According to the present invention, even if the accelerator pedal is released during deceleration, intake air is introduced to the downstream side of the throttle valve by, for example, not fully closing the throttle valve, and this introduction mechanism When activated, the on-off valve is controlled to be opened.

(Effects of the present invention) According to the present invention, during deceleration, the on-off valve is opened as described above, so the passage area increases and the passage resistance to the intake air introduced downstream of the throttle valve decreases, thereby reducing the flow of air into the combustion chamber. A sufficient amount of intake air can be introduced. Therefore, overconcentration of the air-fuel mixture during deceleration can be reliably prevented.

Moreover, this makes it possible to prevent deterioration of exhaust gas properties.

(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, 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, and is formed in the vicinity of the intake ports 5 and 6 by a partition wall formed substantially along the cylinder center line l in the width direction of the cylinder block. 14, forming first and second branch passages 15 and 16 that communicate with first and second intake ports 5 and 6, respectively. The exhaust port 7 is connected to the exhaust passage 17 to constitute an exhaust system. This exhaust system may have a normal configuration. A fuel injection valve 2 is provided in the main intake passage 11 on the upstream side of the partition wall 14.
3 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 .

This on-off valve 18 is connected to a diaphragm valve 26 equipped with two diaphragm mechanisms via an actuation rod 25.
It is connected to the. The pressure chamber 28 of the first diaphragm device 27 of the diaphragm valve 26 is connected to the downstream side of the throttle valve 12 of the main intake passage 11 by a passage 29, and the pressure chamber 28 of the first diaphragm device 27 of the diaphragm valve 26 is connected to the downstream side of the throttle valve 12 of the main intake passage 11.
The pressure chamber 31 is likewise connected to the main intake passage 11 downstream of the throttle valve 12 by a passage 32 . A diaphragm valve 33 is disposed in the passage 32, and the diaphragm valve controls the connection state of the pressure chamber 31 to the main intake passage 11 downstream of the throttle valve 12, or within the valve 33 which communicates with the atmosphere via a filter 33c. The state of communication with the chamber 33a is switched.

Further, since the link member 27b attached to the first diaphragm 27a and the stopper 30b attached to the second diaphragm 30a can be engaged under certain conditions, the link member 27b can be engaged with the stopper 30b. When in the engaged state, the first diaphragm device 27 and the second diaphragm device 30 are interlocked. That is, the on-off valve 18 can be controlled in the closing direction only by a change in the intake pressure introduced into the first diaphragm device 27. Further, the throttle valve 12 is connected to a diaphragm device 34.
4 is connected to the main intake passage 11 on the downstream side of the throttle valve 12 by a passage 36 via a control valve 35 . The control valve 35 is opened when the intake negative pressure downstream of the throttle valve 12 exceeds a predetermined value, and is closed with a time difference. The passage 36 is connected to the negative pressure chamber 33c of the diaphragm valve 33 via a passage 37, and when the control valve 35 is opened, the intake passage pressure downstream of the throttle valve 12 is introduced into the negative pressure chamber 33c and the valve is closed. 33 is opened and atmospheric pressure is introduced into the passage 32, thereby opening the on-off valve 18.
The on-off valve 18 is designed to be interlocked with the throttle valve 12, and starts to open when the throttle valve 12 is opened to a predetermined opening degree. That is, when the throttle valve 12 is fully closed or the opening degree is extremely small, the pressure chambers 28 and 31 of the first diaphragm device and the second diaphragm device 30 of the diaphragm valve 26 are filled with the throttle valve 12 of the main intake passage 11. Since the downstream intake passage pressure becomes a strong negative pressure, negative pressure is introduced into the pressure chambers 28 and 31 of the first diaphragm device 27 and the second diaphragm device 30 via the passages 29 and 32, thereby, The first spring 28a in the pressure chamber 28, the second spring 31a in the pressure chamber 31
Against this force, the first diaphragm 27a and the second diaphragm 30a hold the rod 25 in the upwardly moved position in the figure, and maintain the on-off valve 18 in the closed state. When the opening degree of the throttle valve 12 exceeds a predetermined value, the intake negative pressure decreases, and the diaphragms 27a and 30a
The spring force of the spring 31a causes the actuating rod 25 to move downward in FIG. 2, and the opening/closing valve 18 begins to open. Furthermore, when negative pressure of a certain value or more occurs downstream of the throttle valve 12, the negative pressure is released through the passage 36.
The control valve 35 is opened through the opening, and the diaphragm 34a of the diaphragm device 34 is moved against the force of the spring 34b to open the throttle valve 12 by a predetermined amount.

The upstream end of the passage 32 is on the downstream side of the throttle valve 12 when the opening degree of the throttle valve 12 is small, and on the upstream side of the throttle valve 12 when the throttle valve 12 is opened beyond a predetermined opening degree. Therefore, when the load is relatively low, the opening of the throttle valve is small, so when the load increases, the throttle opening increases, and the pressure upstream of the valve increases. is introduced into the pressure chamber 31 of the two-diaphragm device 30. 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 extends below the main intake passage 11 from this opening 19 .
is formed. The auxiliary intake passage 20 passes from below the main intake passage 11 to below the first branch passage 15 and is connected to the first intake port 5 through an opening 21 . 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 includes the main intake passage 11 and the first branch passage 1.
Since it opens into the first intake port 5 from the lower side of the intake port 5, 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 from the auxiliary intake passage 20 at a shallow angle is directed within the combustion chamber 4. Generates a strong swirl in the horizontal plane.
When the vehicle is running, if there is an appropriate engine load, the throttle valve 12 has an opening degree that corresponds to the load value. If the load is relatively large,
The opening degree of the throttle valve 12 is large, and therefore the negative pressure generated downstream of the throttle valve 12 is not very large, so a relatively large pressure is introduced into the pressure chambers 28 and 31, and with the help of this pressure. The diaphragm valve 26 pushes the rod 25 downward by the force of the spring, so that the on-off valve 18 is in the open state. In the cranking state, since the opening degree of the throttle valve 12 is large, the pressures introduced into the pressure chambers 28 and 31 are both relatively large. It becomes fully open. In the idling state, the opening degree of the throttle valve 12 is small and the negative pressure in the intake passage is large, so it does not engage with the link 27b and the stopper 30b, and the on-off valve 18 is maintained in a fully closed state. Furthermore, in the low to medium load range (emission mode) where you want to particularly reduce emissions,
That is, when the opening degree of the throttle valve 12 is equal to or greater than a predetermined value, the throttle valve 1 is in the second pressure chamber 31.
2. The upstream intake passage pressure is introduced, but the negative pressure is relatively large. In this case, the ring member 27b
and the stopper 30b are in an engaged state, and the opening degree of the on-off valve 18 is maintained at a predetermined opening degree.

When the throttle valve 12 is suddenly closed, such as during deceleration, a strong negative pressure is generated in the main intake passage 11 downstream of the throttle valve 12, and the on-off valve 18 is controlled in the closing direction. However, if the negative pressure downstream of the throttle valve is higher than a predetermined value, the control valve 35
will be held. Therefore, the strong negative pressure downstream of the throttle valve is transmitted through the passage 36 to the diaphragm device 34.
The throttle valve 12 is opened to introduce a predetermined amount of intake air. Furthermore, when the control valve 35 is opened, the negative pressure introduced into the passage 36 is introduced into the diaphragm valve 33 via the passage 37, thereby opening the valve. As a result, the atmosphere is introduced into the passage 32 via the filter 33c,
This atmospheric air is further led to the pressure chamber 31 of the second diaphragm device 30. Therefore, the negative pressure in the pressure chamber weakens, the spring force overcomes it, and the second spring 31
a expands, pushes down the rod 25, and closes the on-off valve 1.
8 by a predetermined amount. Therefore, the throttle valve 12
When the on-off valve 18 is opened, the passage resistance of the intake air introduced to the downstream side of the combustion chamber 4 is weakened, so that a sufficient amount of dilution air can be ensured within the combustion chamber 4. The pressure change near the intake port 5 during sudden deceleration changes as shown in FIG.

In other words, if a sudden deceleration operation is performed at time A,
That is, when the throttle valve 12 is operated in the closing direction, if the on-off valve 18 remains closed, it changes as shown by the broken line in FIG. When the on-off valve 18 is operated to open, the intake negative pressure changes as shown by the solid line. That is, on-off valve 1
The passage resistance is smaller than when the valve 8 is kept closed, which can effectively prevent the mixture from becoming over-enriched during sudden deceleration, and can prevent deterioration of exhaust gas properties. .

FIG. 4 shows another embodiment of the present invention. In this embodiment, during sudden deceleration, the throttle valve 12 and the on-off valve 18 are kept open to obtain sufficient dilution air. Dash pots 40 and 41 are used to prevent the mixture from becoming overly concentrated.
The dart pot 40 is designed to be able to engage with a rod 12a connected to the operating shaft of the throttle valve 12, and when the throttle valve 12 is closed due to a sudden deceleration operation, the dart pot 40 engages with the rod 12a. Together, the throttle valve 12 is closed with a certain time delay. In addition, the dart pot 41 is operated by a member formed on the rod 25 when the intake negative pressure increases when the throttle valve 12 closes due to a sudden deceleration operation and acts on the rod 25 via the diaphragm device 26. 25a, and acts to prevent the on-off valve 18 from being suddenly closed. In this example as well, the same effects as in the previous example can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of an engine according to an embodiment of the present invention, FIG. 2 is a vertical sectional view of an engine according to an embodiment of the present invention, and FIG. 3 is a graph showing the relationship between intake negative pressure and time. A graph showing the relationship, FIG. 4, is a diagram similar to FIG. 2 showing another embodiment of 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, 20...Auxiliary intake passage, 2
6, 34...Diaphragm device, 33...Diaphragm valve, 35...Control device, 40, 41...Dash pot.

Claims (1)

[Claims] 1 A plurality of branch intake passages branching from the main intake passage at least in the vicinity of the combustion chamber, and a plurality of branch intake passages are provided in the main intake passage, and are controlled in the closed direction during low load operation and in the open direction during high load operation. an on-off valve that increases or decreases the passage area of the main intake passage; a fuel supply means that supplies fuel to the main intake passage downstream of the on-off valve; and when the throttle valve is suddenly closed,
An intake system for an engine including an intake air amount increasing device that increases the amount of intake air flowing downstream of a throttle valve in the main intake passage and upstream of the on-off valve, wherein the on-off valve is in place while the intake air amount increasing device is in operation. An engine intake device characterized by having a control device that opens only a fixed amount.