JPH037016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine equipped with a carburetor having a primary fuel supply system and a secondary fuel supply system.

Modern internal combustion engines are required not only to satisfy exhaust gas purification but also to have low fuel consumption.

By the way, in general, a so-called composite carburetor having a primary side fuel supply system and a secondary side fuel supply system is often used as a mixture generating device, and the mixture generated by one composite carburetor is It is designed to be distributed and supplied to the cylinders.

However, in conventional machines, there is a limit to increasing the air-fuel ratio of the mixture, and even if it is diluted, it is about the current air-fuel ratio. is relatively small (the mixture is rich). In order to prevent the general air-fuel mixture dilution during transients, a separate enricher or leaner is installed to prevent this, but in the former case it is difficult to obtain homogeneous air-fuel mixture formation, and in the latter case, the cylinder This is not necessarily a good idea from the perspective of equalizing the air-fuel mixture distribution between the two.

By the way, it is known that in order to make the air-fuel mixture oriented toward low fuel consumption or to improve the distribution to each cylinder, it is sufficient to sufficiently atomize the air-fuel mixture.
For this reason, recently, communication ports (bypass holes) have been added to the partition walls that define the primary and secondary intake passages to communicate the upstream side of the secondary throttle valve and the downstream side of the primary throttle valve. A device that allows this to be formed is currently being developed. That is, when the secondary throttle valve is closed, the thin air-fuel mixture from the secondary intake passage is sucked into and ejected into the primary intake passage through the communication port, thereby making the mixture lean. This attempts to equalize the pressure within the intake manifold branch between each cylinder. Here, to explain why the air-fuel mixture from the secondary intake passage becomes lean and why this air-fuel mixture can make the air-fuel mixture in the primary intake passage lean, we will first explain why the air-fuel mixture becomes lean at this time. When the load is low, the air flow rate is slow, so there is still less fuel injected from the main nozzle on the secondary side, and more fuel comes from the slow jet and idle port, so the auxiliary air is supplied to the intake passage on the primary side. The air becomes extremely lean (you could almost call it air). This makes it possible to achieve lean. If the secondary throttle valve opens and the flow speed increases,
Since more fuel is drawn into this, the concentration of the air-fuel mixture increases. By the way, if the opening degree of the communication port is determined with the aim of equalizing the pressure within the intake manifold branch, the amount of air sucked from the communication port during idling will become too large, and the idle adjustment of the primary side fuel supply system will become difficult. This causes the problem of becoming too sensitive.

The present invention has been made with the aim of solving the above-mentioned problems, and has a configuration for that purpose, which includes a composite carburetor having a primary side fuel supply system and a secondary side fuel supply system, In an internal combustion engine in which the air-fuel mixture generated by the composite carburetor is distributed and supplied to each cylinder, a partition wall defining a primary intake passage and a secondary intake passage is provided up to a position immediately before the intake valve. to define the primary side intake passage and the secondary side intake passage up to a position just before the intake valve, and the secondary side intake passage and the primary side intake passage upstream of the secondary side throttle valve of the partition wall. A communication port communicating with the downstream primary intake passage is provided for each cylinder, and a secondary throttle valve is provided for each cylinder in the secondary intake passage.

In Fig. 1, 1 is the cylinder head, 2 is the combustion chamber, 3 is the secondary intake port formed in the cylinder head 1, 4 is the primary side intake port that communicates with the middle of the intake port 3, and 5 is the intake port. This is an intake valve that opens and closes the combustion chamber 2 of No. 3.

Further, in FIG. 1, 6 is a carburetor, 7 is an intake manifold, and 8 is an adapter. In the figure, 9 is the primary side intake passage in the intake manifold, 10 is the secondary side intake passage in the intake manifold 7, 11 is the primary side intake passage in the adapter 8, and 12 is the adapter 8.
The primary side intake passage 9 and the secondary side intake passage 10 are partition walls 7a, 8a,
1a defines a position in the cylinder head 1 just in front of the intake valve. 13 is a cooling water passage formed across the intake manifold 7, adapter 8, and cylinder head 1, and 14 is an intake passage 9.
A wall 15 that partitions the cooling water passage 13 and the cooling water passage 13 is a heat absorption fin provided on the wall 14 toward the inside of the cooling water passage 13.

16 is a float chamber of the carburetor 6. This carburetor 6 has a primary side fuel supply system and a secondary side fuel supply system.

The primary side fuel supply system includes a primary side main fuel supply system and a primary side slow fuel supply system. The main fuel supply system on this primary side is the bench lily 17.
A main nozzle 18 disposed within the bench lily 17, a fuel well 19 communicating the main nozzle 18 with the bottom of the flow chamber 16, and a main jet 20 disposed on the float chamber 16 side of the fuel well 19. , a passage 21 that communicates the main nozzle 18 with a passage 6a on the air cleaner side, and a main air jet 22 provided within the passage 21.

In the figure, 23 is a chiyoke valve provided upstream of the main nozzle 18, and 24 is a main nozzle 18.
The downstream intake passage 25 is a primary throttle valve mounted within the intake passage 24.

The slow fuel supply system on the primary side also communicates with a bypass port 26 that opens immediately upstream of the throttle valve 25, an idle boat 27 that opens immediately downstream of the throttle valve 25, the fuel well 19, and the passage 6a. Passage 21 and Passage 2
1. A slow jet 28 provided in the middle, a passage 29 providing communication between the slow air jet 22 and the bypass port 26 provided on the passage 6a side of the passage 21, and the idle port 27 and the package 21, and the passage 29 of the idle port 27. It has a screw 30 for adjusting deployment.

In addition, the intake passages 24, 9, 11 and the intake port 4
The intake passage on the primary side consists of a bench lily 17
and the intake port 3 are communicated with each other.

The secondary fuel supply system also includes a secondary main fuel supply system and a secondary slow fuel supply system.

The main fuel supply system on the secondary side is a bench lily 31
, a main nozzle 32 disposed within the bench lily 31 , a fuel well 33 communicating the main nozzle 32 with the bottom of the float chamber, and the fuel well 3
A main jet 34 provided on the float chamber 16 side of No. 3, and a passage 35 that communicates the main nozzle 32 with the passage 6b upstream of the bench lily,
It has a main air jet 36 provided in a passage 35.

In the figure, 37 is an intake passage downstream of the main nozzle 31, and 38 is a secondary throttle valve installed in the intake passage 12.

The secondary slow fuel supply system also communicates a bypass port 39 that opens immediately upstream of the secondary throttle valve 38 and an idle port 40 that opens immediately downstream of the throttle valve 38, and the passage 6b. the main air jet 42 provided at the end of the passage 41 on the passage 6b side, the fuel well 33 and the passage 41.
It has a passage 43 communicating with the passage 43, and a slow jet 43a provided within the passage 43.

In addition, the intake passage on the secondary side consisting of the intake passages 37, 10, 12 and the intake port 3 is connected to the bench lily 3.
1 and the combustion chamber 2 are communicated with each other.

In the figure, 44 is an exhaust suction port of the adapter 8 that communicates with the idle port 40, 45 is a passage that communicates the port 4 with an exhaust passage (not shown), and 46 is an EGR valve installed in the middle of the passage 45. be. Further, 47 is a throttle shaft that supports the throttle valve 25, 48 is a shaft that supports the throttle valve 38, and 4 is a lever 50 fixed to the throttle shaft 47, which is a lever 49 and an accelerator pedal (not shown). This is the wire that connects the

The throttle valve 38 on the secondary side is opened and closed by a valve operating device that utilizes intake negative pressure, and its opening degree is limited by a link mechanism linked to the throttle valve on the primary side. This valve operating device and link mechanism will be described in detail below.

In this embodiment, an actuator 51 is used as the valve operating device. This actuator 51
, a lid body 53 attached to the main body 52 and the middle body 52
, a diaphragm 54 held between the main body 52 and the lid 53, a rod 55 supported by the diaphragm 54, and a compression coil spring 56 interposed between the diaphragm 54 and the lid 53. In the figure, A indicates a negative pressure introducing chamber formed between the lid body 53 and the diaphragm 54, and B indicates the diaphragm 5.
4 and the main body 52 is an atmosphere open chamber.

The rod 55 of the actuator 51 like this is
It is pivotally connected to the tip of a lever 57 that is integrally fixed to the throttle shaft 48.

Further, 58 is a primary side negative pressure intake opening in the bench lily 17, and 59 is a secondary side negative pressure intake opening in the bench lily 31. This negative pressure intake port 58 communicates with the negative pressure introduction chamber A via passages 60, 61 and orifices 62, 63, and the negative pressure intake port 59 communicates with the negative pressure introduction chamber A via passages 60, 64 and orifices 62, 65. It is connected to A. The actuator 51 is actuated by the pressure acting on the negative pressure intake port 58 when the primary throttle valve 25 is nearly fully open, and opens the secondary throttle valve 38. It is set.

The link mechanism described above is connected to the throttle shaft 4.
The lever 66 attached to the lever 7, the lever part 47a,
47b and rotatably supported by the throttle shaft 48, and a lever portion 67a.
It has a bending part 68 that is integrally provided with the lever 66 and a rod 49 that connects the lever 66 and the lever part 67b.

Reference numeral 70 denotes a limit pin protruding from the end of the lever 57, and the limit pin 70 rotates together with the lever 57 as the lever 57 rotates clockwise, so that it can come into contact with the bent portion 48. is set to .

Furthermore, on the upstream side of the bench lily 31 on the secondary side,
A variable valve 71 is installed that opens and closes depending on the internal intake negative pressure. The variable valve 71 includes a protrusion 72 of the carburetor 6, a lid 73 attached to the protrusion 72, a diaphragm 74 held between the protrusion 72 and the lid 73, and a diaphragm 74 installed in the passage 6b. a piston valve 76 that is supported by the diaphragm 74 and is held so as to be able to move forward and backward with respect to the projection 75, and a compression coil spring 77 that is interposed between the lid body 73 and the diaphragm 74. have An atmosphere open chamber C is formed between the protrusion 75 and the diaphragm 74, and the diaphragm 74
A negative pressure introduction chamber D is formed between and the lid body 73. This atmosphere opening chamber C communicates with the air conditioner through a passage 78 of the carburetor 6, and the negative pressure introducing chamber D communicates with the air conditioner through a hole 79 formed in the piston valve 76. It is connected to Bench Lily 80.

Note that both the primary and secondary intake passages are oriented toward the combustion chamber 2 so as to ultimately generate a swirl of intake air within the combustion chamber 2.

Here, the intake passage 11 on the primary side and the intake passage 12 on the secondary side in the adapter 8 are communicated with each other through a communication port 81 formed in the partition wall 8a that defines both 11 and 12. The communication port 81 is opened and closed by a rotary on-off valve 82. That is, as shown in FIG.
is an annular hollow portion 81a formed in the partition wall 8a;
A communication port 81C that communicates with the secondary passage 12 immediately upstream of the secondary throttle valve 38 and a communication port 81b that communicates between the hollow portion 81a and the primary passage 11 sufficiently downstream of the primary throttle valve 25. It consists of and. Then, an on-off valve 82 is provided in the hollow portion 81a.
A rotary valve body 82a is rotatably fitted, and a communication passage 82b formed in the valve body 82a is appropriately connected to both communication ports 81b and 81c according to its rotational angular position.
It is designed to allow communication and isolation between the two.

In this way, the partition wall 8a constitutes a casing that accommodates the rotary valve body 82a, but the casing portion is formed with the communication port 81b and is connected to the primary passage 11.
A boss portion 8b that bulges inward and a boss portion 8c that bulges into the secondary passage 12 are formed with a communication port 81c formed therein.

A lever 83 is integrated with the rotary valve body 82a on the outside of the adapter 8.
is connected to a diaphragm 86 of an actuator 85 via a rod 84. This actuator 85 has an atmosphere release chamber E and a negative pressure introduction chamber F defined by a diaphragm 86, and the negative pressure introduction chamber F is connected to the primary throttle valve 25 through a piping 87. In the vicinity, the primary passage 2
It opens in 4. The diaphragm 86 is energized by the compression spring 8, and the negative pressure introducing chamber F
When the internal negative pressure does not reach the predetermined negative pressure, the on-off valve 82
(Communication port 81) is closed.

Note that the secondary throttle valve 38 and the on-off valve 82
(ventilation port 81) is arranged near the intake valve 5, and both 38 and 82 (81) are provided for each cylinder on the downstream side of the branch part of the intake manifold 7. .

Next, the operation of the above configuration will be described, first focusing on the operation of the variable bench lily 80.

(1) When idling When the engine is idling, the primary throttle valve 25 and the secondary throttle valve 38 are fully closed. For this reason, during the intake stroke during idling, the idle boat 27,
High intake negative pressure acts only on the section 40.

As a result, during the intake stroke during idling, fuel supplied from the float chamber 10 through the main jet 34 into the fuel well 33 is sucked into the passage 41 through the passage 43 and the slow jet 43a. At the same time, air from the air cleaner side is sucked into the passage 41 via the slow air jet 42. The fuel and air sucked into the passage 41 in this way are mixed and then sprayed from the idle port 40 downstream of the throttle valve 38 on the secondary side. This atomized air-fuel mixture is sucked into the fuel tank 2 via the intake passage 12 and intake port 3 on the secondary side.

On the other hand, fuel supplied into the fuel well 19 from the float chamber 10 via the main jet 20 is sucked into the passage 29 via the passage 21 and the slow jet 28. At the same time, air from the air cleaner is sucked into the passage 29 via the slow air jet 22 and the passage 21. The air and fuel sucked into the passage 29 in this way are mixed and sprayed from the idle port 27 downstream of the throttle valve 25 on the primary side. This atomized air-fuel mixture is transferred to the intake passages 9 and 1 on the primary side.
1. It is injected into the combustion chamber 2 through the intake port 4 in the circumferential direction at high speed.

Due to these, a strong vortex of the air-fuel mixture in the combustion chamber 2 is formed during the intake stroke during idling.

(2) At light load (low load range) Wire 5 is activated by the accelerator pedal (not shown).
0 and rotate the lever 49 clockwise, the primary throttle valve 2
5 opens and its opening degree increases.

As a result, the negative intake pressure during the intake stroke also acts on the primary side bench lily 17, and air from the air cleaner is sucked into the primary side throttle valve 25 via the primary side bench lily 17. As a result, the fuel sucked into the fuel well 19 from the freight chamber 10 via the main jet 20 is sucked into the main nozzle 18, and the air from the air cleaner side passes through the main air jet 22 and the passage 21. and is sucked into the main nozzle 18. The fuel and air thus sucked into the main nozzle 18 are sprayed from the main nozzle 18 into the primary side bench lily 17 and mixed with air from the air cleaner. This air-fuel mixture flows into the intake passage 2
4, 9, 11, combustion chamber 2 via intake port 4
It is ejected inward in the circumferential direction. This combustion chamber 2
The amount and velocity of the air-fuel mixture injected into the engine increase as the opening degree of the throttle valve 25 on the primary side increases.

On the other hand, at this time, the intake negative pressure on the downstream side of the bench lily 17 on the primary side is applied to the negative pressure intake port 58, the passage 61,
It is introduced into the negative pressure introducing chamber A of the actuator 51 via the orifices 63, 62 and the passage 60. This intake negative pressure is applied to the compression coil spring 56.
Since the spring force is sufficiently smaller than the spring force of , the actuator 51 does not operate.

(3) At medium/high load (medium/high load range) (a) When the primary throttle valve 25 is opened from the low load range to the medium load, the fluid flowing inside the bench lily 17 on the primary side is As the speed increases, the negative pressure generated at negative pressure intake 58 increases.

This negative pressure acts on the negative pressure introduction chamber A of the actuator 51 as described above, and since the intake negative pressure in this medium load range is greater than the spring force of the compression coil spring 56 of the actuator 51, When the throttle valve 25 on the primary side is opened to the extent that Displaced. As a result, the lever 57 and the downstream throttle valve 38
The secondary throttle valve 38, which is rotated counterclockwise, is opened.

(b) In this way, the throttle valve 38 on the secondary side
When the throttle valve 38 is opened, the throttle valve 38
The downstream negative intake pressure acts on the intake passages 10, 37 and the variable bench lily 80. The intake negative pressure acting on this variable bench lily 80 is
The diaphragm 74 is introduced into the negative pressure introduction chamber D through the compression coil spring 77, and attempts to displace the diaphragm 74 to the right against the compression coil spring 77.

However, the piston valve 76 of the variable valve 71 does not shift to the right and does not increase its opening unless the pressure within the negative pressure introducing chamber D reaches a predetermined value. Moreover, since the negative pressure is transmitted to the negative pressure introduction chamber D through the narrow passage 79, the pressure in the negative pressure introduction chamber D reaches the predetermined value from the time when a predetermined intake negative pressure acts on the variable vent lily 80. It will take some time to reach this point. Furthermore, in order to displace the piston valve 6 to the right, the intake negative pressure needs to resist the inertial force due to the mass of the piston valve 76. As a result, there is a slight time delay from the time when a predetermined intake negative pressure acts on the variable bench lily 80 until the opening degree of the variable valve 71 (the opening degree of the variable bench lily 80) starts to increase.

On the other hand, until the intake negative pressure in the intake passages 10, 37 reaches a predetermined value, the intake negative pressure on the primary side decreases, the evaporation of fuel is impaired, and the air-fuel mixture on the primary side becomes inappropriate. However, the variable valve 7
1 is very small, the air from the air cleaner is hardly sucked into the bench lily 31 side, and the fuel flows into the main nozzle 32.
The water is sprayed into the bench lily 31 from above. Therefore, even if the air-fuel mixture on the primary side is not optimized at the beginning of the operation of the secondary side, the fuel flow generated on the secondary side will be mixed with the air-fuel mixture on the primary side in the intake port 3, An appropriate amount of air-fuel mixture is sucked into the baking chamber 2.

In this way, when the secondary side begins to operate, a temporary choke effect is obtained, so the mixture ratio (A/F) becomes lean due to a delay in the start of fuel in transient characteristics. ) can be prevented. As a result, the smoothness of operation at the beginning of operation on the secondary side is improved, and stable fuel with improved atomization of the fuel can be obtained.

(c) Further, when the intake negative pressure acting on the variable vent 80 increases as the opening of the throttle valve 38 increases, the opening of the variable vent 80 increases.

Accordingly, an amount of air corresponding to the opening degree of the throttle valve 38 flows through the vent lily 31, so that as the opening degree of the throttle valve 38 increases, an appropriate amount of air-fuel mixture is generated in the vent lily 31.

(d) On the other hand, apart from this effect, when the opening degree of the throttle valve 25 on the primary side increases,
The lever 66 moves clockwise to the throttle valve 2.
Rotates together with 5. This rotation is done by rod 6
9 to the lever 67, and the lever 4
7 is rotated counterclockwise.

Therefore, even if the secondary throttle valve 38 is rotated counterclockwise by the actuator 51, the restriction pin 70 of the lever 57 comes into contact with the bent portion 68 of the lever 67, so that the throttle valve 38 is rotated counterclockwise by the actuator 51. The valve 38 follows the throttle valve 25 on the primary side with a slight delay.

Next, the functions of the communication port 81 and the on-off valve 82 will be explained.

First, during idling, it is located near the primary throttle valve 25, and until idling, it is located upstream of the primary throttle valve 25,
As the primary throttle valve 25 opens, the primary throttle negative pressure at the downstream side is atmospheric pressure, so the negative pressure introduction chamber F of the actuator 85 is also maintained at atmospheric pressure, and the communication port 91 is the opening/closing valve. It is closed by 82. Therefore, the air-fuel mixture is supplied to the combustion chamber 2 with the air-fuel ratio unchanged when it passes through the primary throttle valve 25. In this way, when idling, since the communication port 81 is closed, the air-fuel mixture is supplied to the combustion chamber 2 at the air-fuel ratio set in advance in the primary side fuel supply system, so idling adjustment is not possible. It becomes easier.

When the accelerator is opened and the practical operating range is reached, the throttle valve is located near the first throttle valve 25, upstream of the primary throttle valve 25 until idling, and as the primary throttle valve 25 opens, it is located downstream. The negative pressure generated at the location is transmitted to the negative pressure introduction chamber F of the actuator 85, and the on-off valve 82 is thereby opened. As a result, air from the secondary intake passage is introduced into the primary intake passage through the communication port 81, and the air-fuel mixture supplied to the combustion chamber 2 is
The air-fuel mixture becomes leaner than the air-fuel mixture that has passed through the primary throttle valve 25. In this way, lean combustion is performed in the practical operating range, but the effective opening area of the communication port 81 is set appropriately for each cylinder so that the pressure in the intake branch is uniform. The air-fuel mixture has better distribution and can be leaner overall.

In addition, during a transition in which the accelerator is suddenly depressed from the practical operating range, the primary side throttle negative pressure temporarily approaches atmospheric pressure, and as a result, the on-off valve 82 is closed, and the primary side passage from the communication port 81 is closed. The air supply to the engine is stopped and the air-fuel mixture is temporarily enriched. As a result, temporary combustion instability caused by air-fuel mixture dilution can be prevented.

Here, due to the boss portion 8b, the flow constricts in the primary region in the direction in which the intake valve 5 is seated and toward its valve seat, thereby promoting swirl generation of intake air in the combustion chamber 2, and at the same time, the boss portion 8b
Turbulent flow is generated in part b, promoting atomization of the fuel. Of course, also in the secondary region, the boss portion 8c
The same thing can be said due to the effect of . Furthermore, the boss portions 8b and 8c are connected to the secondary side throttle valve 38.
By arranging them nearby, the generation of turbulent flow at the initial stage of opening of the secondary throttle valve 38 is promoted, and the above-mentioned result becomes even more significant.

As explained above, in the present invention, the primary side intake passage and the secondary side intake passage are separated by a continuous partition up to the position immediately before the intake valve, and the secondary side intake passage and the primary side intake passage are separated by a continuous partition wall. A communication port communicating with the passage is provided for each cylinder, and a throttle valve on the secondary side is provided for each cylinder.
By changing the diameter of the communication port, the pressure within each cylinder can be made uniform, and the air-fuel mixture can be distributed favorably. This improves the lean mixture limit from idling to practical driving, leading to lower fuel consumption. Further, there is an advantage that a stable air-fuel ratio can be obtained during idling, and fuel instability during transients can be prevented.

[Brief explanation of drawings]

Figure 1 is a system diagram showing one embodiment of the present invention, Figure 2 is a system diagram showing an embodiment of the present invention.
The figure is a plan view of the carburetor shown in FIG. 1, and FIG. 3 is an enlarged sectional view of a portion near the on-off valve. 1... Cylinder head, 1a, 7a, 8a...
Partition wall, 5... Intake valve, 6... Carburetor, 25...
... Primary side throttle valve, 38 ... Secondary side throttle valve, 81 ... Communication port, 82 ... Opening/closing valve, 85 ... Actuator, 8b, 8c ... Boss portion.

Claims (1)

[Claims] 1. In an internal combustion engine equipped with one composite carburetor having a primary side fuel supply system and a secondary side fuel supply system, the air-fuel mixture generated by the composite carburetor is distributed and supplied to each cylinder, A partition defining a primary side intake passage and a secondary side intake passage is provided up to a position immediately before the intake valve to define the primary side intake passage and the secondary side intake passage up to a position immediately before the intake valve, and A communication port is provided for each cylinder that communicates the secondary intake passage upstream of the secondary throttle valve of the partition wall with the primary intake passage downstream of the primary throttle valve, and the secondary intake passage is provided for each cylinder. An intake system for an internal combustion engine, characterized in that a secondary throttle valve is provided for each cylinder in a passage.