JPS6213765A - Air-fuel ratio control device in internal combustion engine provided with supercharager - Google Patents

Abstract

PURPOSE:To supply a mixture having an optimum air-fuel ratio in accordance with the operating condition of an engine provided with a supercharger, in a carburettor, by associatingly controlling the amount of air breed and a power valve in accordance with the temperature of the engine and the internal pressure of an intake-air pipe. CONSTITUTION:In a carburetor 19 of an engine 1 provided with a super-charger 4, a temperature sensing change-over valve 26 opens a port 28 to the atmosphere 29 in the low temperature condition of the engine, and therefore, the atmospheric air is introduced into a chamber 45 in a valve 38 to close a hole 42 so that passages 37, 39 for an air bleed 18 are closed to enrich a mixture from an air nozzle 18. In the high temperature condition of the engine, the change-over valve 26 communicates the port 28 with a vacuum port 27 from a hole 31 to introduce a negative pressure into the chamber 45 in the valve 38 so that the hole 42 is opened to introduce air for leaning the mixture. A power valve 19 is opened when a high pressure is effected in the chamber 36 due to operation of the supercharger or when the negative pressure in the hole 31 becomes impossible to draw up a piston 22 even if the pressure in the chamber 36 is negative, and therefore, a rich mixture is fed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a method for controlling the air-fuel ratio of an intake air-fuel mixture in an internal combustion engine equipped with a supercharger such as an exhaust turbo supercharger in the intake system. It is related to the device.

[Conventional technology and its problems]

Modern internal combustion engines are equipped with a supercharger such as an exhaust turbo supercharger in the intake system in order to improve output and reduce fuel consumption. In an engine, the difference between the amount of intake air in the idling operating range and the amount of intake air at maximum output is larger than that in a normal internal combustion engine without a supercharger, making it difficult to control the amount of fuel supplied in the high load range. Since it must be made to increase rapidly, the carburetor of the internal combustion engine with a supercharger is used, for example, in Japanese Utility Model Application Publication No. 57-8329 and No. 59-1484.
As disclosed in Publication No. 57, by using a two-barrel carburetor (double-barrel carburetor) comprising a primary side pen cherry and a secondary side venturi in parallel, the fuel can be improved in a high load range. Usually, efforts are made to increase the supply amount.

However, two-barrel carburetors are significantly more expensive and larger than single-barrel carburetors with only one venturi, and they are also difficult to use in supercharged internal combustion engines. When applied, a large amount of supercharged air whose pressure has increased due to supercharging air flows when the secondary throttle valve begins to open during acceleration, causing the intake air-fuel mixture to the engine to become temporarily lean. The problem is that a so-called secondary shock occurs in which the output of the engine temporarily decreases.

An object of the present invention is to apply a single-barrel carburetor, which is cheaper and smaller than a two-barrel carburetor, as a carburetor in an internal combustion engine with a supercharger.

[Means for solving problems]

For this reason, the present invention provides a supercharged internal combustion engine in which a single barrel carburetor is provided in a supercharging passage on the downstream side of a supercharger, in which air is introduced into the air bleed in the single barrel carburetor. An air bleed switching valve is provided in the passageway to shut off the air introduction passage when the intake negative pressure downstream of the carburetor falls close to atmospheric pressure. A switching valve for the power valve is provided in the negative pressure transmission passage to the power piston chamber of the valve mechanism, and the switching valve is configured to shut off the negative pressure transmission passage when the supercharging pressure on the upstream side of the carburetor increases. It is something.

[Action/effect of the invention]

In areas where the engine load is low, the intake negative pressure on the downstream side of the carburetor is high toward the vacuum side, and the air bleed switching valve in the air introduction passage to the air bleed communicates with the air introduction passage. Air is introduced into the air bleed in the engine, and by introducing air into the air bleed, the amount of fuel supplied from the main nozzle of the carburetor can be regulated to a small amount. The boost pressure on the upstream side is not high, and the power valve switching valve in the negative pressure transmission passage to the power piston chamber is in communication with the negative pressure transmission passage, and the power piston of the power valve mechanism The intake negative pressure downstream of the carburetor acts on the chamber and the power valve mechanism is closed, and the power valve mechanism does not increase the amount of fuel, so the intake air-fuel mixture is The air-fuel ratio can be controlled to the lean side, allowing for fuel savings.

Then, when the supercharging pressure on the upstream side of the carburetor increases in proportion to the increase in engine load, the power valve switching valve in the negative pressure transmission path to the power piston chamber shuts off the negative pressure transmission path. On the other hand, when the intake negative pressure downstream of the carburetor decreases to near atmospheric pressure in proportion to the increase in engine load, the air in the carburetor decreases. The air bleed switching valve in the air introduction passage to the bleed switches to shut off the air introduction passage, cutting off the introduction of air to the air bleed in the carburetor, and increasing the amount of fuel supplied. . In other words, in areas where the engine load is high, the amount of fuel supplied can be increased by both operating the power valve mechanism and cutting the air intake for air bleed. Since the air-fuel ratio of the intake air-fuel mixture can be controlled to the Lynch side, it is possible to ensure high output in a high load range, reduce NOx in a high load range, and suppress the occurrence of non-king in a high load range.

Therefore, according to the present invention, a single-barrel carburetor can be used in a supercharged internal combustion engine, and the single-barrel carburetor can supply substantially the same fuel as a two-barrel carburetor. This has the effect of reliably preventing an increase in the size and cost of the engine due to the conventional use of a two-barrel carburetor in an internal combustion engine with a feeder, as well as the occurrence of a secondary shock during acceleration.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, 1 indicates an intake manifold 2 and an exhaust manifold 3.
4 indicates an exhaust turbo supercharger formed by directly connecting an exhaust turbine 5 and a blower-compressor 6, and the intake manifold 2 includes a single barrel carburetor 7 with a throttle valve 8. A surge tank 9 for eliminating pulsation is connected to the upstream side of the carburetor 7, and the surge tank 9 receives supercharging from the discharge side of the blower-compressor 6 in the exhaust turbo supercharger 4. A passageway 10 is connected. Further, an air cleaner 11 is connected to the suction side of the blower compressor 6, an exhaust passage 12 from the exhaust manifold 3 is connected to the inlet side of the exhaust turbine 5, and an exhaust passage 12 from the exhaust manifold 3 is connected to the inlet side of the exhaust turbine 5, and an exhaust passage 12 to the atmosphere is connected to the outlet side of the exhaust turbine 5. The tubes 13 are connected to each other.

The single barrel carburetor 7 has a float chamber 1.
An air bleed 18 and a power valve mechanism 19 are provided for a main fuel passage 16 with a main jet 17 extending from the float chamber 14 to the main nozzle 15. Power passage 2 connected to bypass the
0, a power piston 22 for operating the power valve 21, and a power spring 24 for urging the power valve 21 in a downward direction, that is, in an opening direction, against a holding spring 23 thereof. The power valve 21 opens when the power piston 22 descends, and the power valve 21 opens when the power piston 22 descends.
When negative pressure below atmospheric pressure acts on the power piston chamber 25, the power piston 22 rises against the power spring 24 due to this negative pressure, and acts on the power piston chamber 25. When the negative pressure is released, the power spring 24 lowers the power spring 24.

In this case, the inner diameter of the main jet 17 in the single barrel carburetor 7 is such that the air-fuel ratio of the intake air mixture when the power valve mechanism 19 is not operating and air is introduced into the air bleed 18 is stoichiometric. The fuel ratio is set to be slightly leaner.

Reference numeral 26 indicates a temperature switching valve that is attached to the cooling water passage, lubricating oil passage, cylinder block, cylinder head, etc. of the engine 1 and is related to the temperature of the engine.
The ports 27, 28, 29 are connected to each other until the engine l warms up to a predetermined temperature, but once the engine l warms up to a predetermined temperature, the ports 27, 28, and
Among the ports, port 27 is connected to an intake pressure port 31 provided downstream of the throttle valve 8, such as in the intake manifold 2, through a passage 30. communicates with the atmosphere.

Reference numeral 32 indicates a diaphragm type switching valve for the power valve mechanism 19, and the power valve switching valve 32 connects the port 27 in the temperature switching valve 26 and the power valve mechanism 19.
Negative pressure transmission passage 3 connecting with power piston chamber 25 in
3, and this power valve switching valve 32
, a spring 35 biases the valve body 34 in the normally open direction.
The pressure chamber 36 is connected to a boost pressure transmission passage 37 from the surge tank 9 upstream of the carburetor 7, so that the boost pressure upstream of the carburetor 7 is equal to or higher than atmospheric pressure. For example, when the supercharging pressure exceeds a value of 280 mmHg, the valve element 34 is pushed down against the spring 35 to block the negative pressure transmission passage 33.

Reference numeral 38 indicates a switching valve for the air bleed 18 in the carburetor 7, and the air bleed switching valve 38 is provided between the supercharging pressure transmission passage 37 and the air introduction passage 39 to the air bleed 18. Inside the valve chamber 40 is a spring 41.
The port 42 to the air introduction passage 39 is held in an open state, and when the port 42 comes into contact with the air introduction passage 39, the air introduction passage 39 is opened.
A plate-shaped valve body 43 is provided to shut off the air.

The air bleed switching valve 38 also includes a diaphragm type operating mechanism 4 for switching and operating the switching valve 38.
4 is provided. That is, this operating mechanism 44 is a rod 4 attached to a diaphragm 46 that constitutes a pressure chamber 45.
7, and a spring 48 that presses and urges the plate-shaped valve body 43 of the air bleed switching valve 38 toward the port 42 via the rod 47, and connects the pressure chamber 45 to the passage 49.
When the negative pressure below atmospheric pressure acting on the pressure chamber 45 is on the vacuum side, for example -250+nHg, the rod 47 is However, when the pressure drops below the above-mentioned value, for example -250 nHg, to the atmospheric pressure side, a spring 48 presses the plate-shaped valve body 43 against the port 42 to block the air introduction passage 39. It is composed of

In this configuration, when the engine 1 has not warmed up to a predetermined temperature, the temperature switching valve 26 communicates the boat 28 with the atmospheric port 29, and the air bleed switching valve 3
The pressure chamber 45 of the diaphragm type actuation mechanism 44 for 8 becomes atmospheric pressure, and the plate-shaped valve body 43 of the air bleed switching valve 38 is closed by the diaphragm type actuation mechanism 44 to cut the introduction of air to the air bleed 18. Therefore, by cutting the air introduction to the air bleed 18, the air-fuel ratio becomes lynch when the temperature of the engine 1 is low.
It is possible to stabilize combustion until the throttle valve 8 warms up to a predetermined temperature, and also to suppress the increase in unburned gas. The boost pressure on the side becomes higher than atmospheric pressure, and this boost pressure reaches 280 mm.
If it exceeds 11g, the valve body 3 in the power valve switching valve 32
4 is closed, the negative pressure transmission passage 3 to the power piston chamber 25
3 is shut off, and the pressure inside the power piston chamber 25 is:
Due to air leakage and inflow from the float chamber 14, the pressure drops to near atmospheric pressure, and the power valve 21 is opened by the power spring 24, so that the amount of fuel supplied increases.
The output in a high load range can be improved by operating the power valve mechanism 19.

When the engine 1 warms up to a predetermined temperature, the temperature switching valve 26 switches the port 27 to communicate with the boat 28. At this time, if the opening degree of the throttle valve 8 is small, the temperature switching valve 26 switches the port 27 to communicate with the boat 28. The intake negative pressure on the side is high on the vacuum side, and this negative pressure acts on the pressure chamber 45 of the diaphragm type operating mechanism 44 for the air bleed switching valve 38, causing the operating mechanism 44 to close the air bleed switching valve 38. Since the holding is released, air is introduced into the air bleed 18 and the air-fuel ratio is made lean.

On the other hand, in the partial load range where the opening degree of the throttle valve 8 is relatively small as described above, the rotation speed of the exhaust turbo supercharger 4 is slow due to the small amount of exhaust gas and the carburetor 7 is slow.
Since the supercharging pressure on the upstream side of
As described above, the intake negative pressure on the downstream side is higher toward the vacuum side, and this intake negative pressure acts on the power piston chamber 25 to keep the power valve 21 closed.

Therefore, when the opening degree of the throttle valve 8 is increased, the intake negative pressure on the downstream side of the throttle valve 8 decreases to approach atmospheric pressure, while the supercharging pressure on the upstream side of the carburetor 7 increases. A value where the intake negative pressure is close to atmospheric pressure, for example -2
When the pressure drops below 5Q mm11g to the atmospheric pressure side, the air bleed actuating mechanism 44 closes the valve body 43 of the air bleed switching valve 38, so the introduction of air to the air bleed 18 is canted and the amount of fuel supplied increases. In addition, if the supercharging pressure upstream of the carburetor 7 rises above atmospheric pressure, for example, 280 m11g, this supercharging pressure causes the power valve switching valve 32 to close to the power piston chamber. Since the negative pressure transmission passage 33 to 25 is shut off, the power valve 21 is opened by its power spring 24, and the amount of fuel supplied is further increased.

In other words, in the low load range of the engine 1, the air-fuel ratio is made lean by introducing air into the air bleed 18 and the power valve mechanism 19 is deactivated, thereby reducing fuel consumption in this load range. On the other hand, in the high load range of the engine 1, the air-fuel ratio is reduced by cutting the air intake to the air bleed 18 and operating the power valve mechanism 19, thereby improving output in the high load range and reducing NOx.
This makes it possible to achieve a reduction in engine speed and suppression of knocking.

[Brief explanation of drawings]

The drawings are diagrams showing embodiments of the invention. 1... Internal combustion engine, 2... Intake manifold, 3...
・Exhaust manifold, 4...Exhaust turbo supercharger, 7.
・・Single barrel carburetor, 8・throttle valve,
18... Air bleed, 19... Power valve mechanism, 2
5... Power piston chamber, 32... Switching valve for power valve, 33... Negative pressure transmission passage, 38... Switching valve for air bleed, 39... Air introduction passage, 44... Operation mechanism.

Claims (1)

[Claims] (1) In a supercharged internal combustion engine in which a single barrel carburetor is provided in a supercharging passage on the downstream side of a supercharger, in an air introduction passage to an air bleed in the single barrel carburetor, An air bleed switching valve is provided that shuts off the air introduction passage when the intake negative pressure downstream of the carburetor falls close to atmospheric pressure. A supercharging system characterized in that a switching valve for a power valve is provided in a negative pressure transmission passage to a piston chamber so as to shut off the negative pressure transmission passage when the supercharging pressure on the upstream side of the carburetor increases. Air-fuel ratio control device for internal combustion engines.