JPH0235146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for a carburetor internal combustion engine.

In a carburetor for an internal combustion engine, multiple air bleeds are installed in the slow system fuel passage of the carburetor, and one air bleed passage is opened and closed by a valve to control the amount of air bleed depending on the altitude. There is (Utility Model Application Publication No. 54-57127). and,
This valve also controls the driving pressure to the enrichment valve. This performs altitude compensation for the air bleed amount and the pressure of the power increase control valve.

In Japanese Patent Publication No. 55-46326, in addition to the normal air bleed passage which is always open to the atmosphere, a second air bleed passage is provided in the slow system fuel passage of the carburetor.
An on-off valve is installed in the air bleed passageway, and this on-off valve is opened and closed according to the altitude of the vehicle equipped with an internal combustion engine.By opening and closing the on-off valve according to changes in altitude, the amount of air bleed can be changed, and the air-fuel ratio can be adjusted. is controlled.

In these conventional technologies, the amount of air bleed is changed so that the air-fuel ratio does not change regardless of the altitude, but it may be possible to apply this technology to control the air-fuel ratio by changing the amount of air bleed by opening and closing the on-off valve. . That is, instead of the air bleed control valve that opens and closes depending on the altitude of the prior art, it is opened so that the air-fuel ratio is close to the stoichiometric ratio when idling, and when the air bleeds from idling to obtain acceleration performance,
A control valve is provided that is closed to enrich the air/fuel ratio.

However, if this control is maintained, the engine will become rich even when the engine stops accelerating and enters steady state, resulting in a disadvantage that the fuel consumption rate will deteriorate. Therefore, there is a demand for controlling the air-fuel ratio in various ways depending on the engine operating state.
That is, when idling, the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio (or slightly leaner than that), when the throttle valve is opened a little from idling, it is controlled to be rich, and when the throttle valve is opened further, it is controlled to be extremely lean. In this case, it would be conceivable to provide another third air bleed passage and provide another on-off valve in this passage. However, this configuration requires two on-off valves, and each on-off valve requires a control device, which increases the number of parts and increases the cost.

An object of the present invention is to reduce the number of parts in a control circuit and to obtain an air-fuel ratio suitable for operating conditions.

According to this invention, an enrichment valve is provided in the main system fuel passage of the carburetor, and the part 1 where the slow system fuel passage of the carburetor is connected to the slow port;
a second part connecting the first part in series with the float chamber; a third part connecting the joint of the first part and the second part to the air bleed means; has a longitudinally extending slow jet which causes the air flowing from the air bleed means to the first part via the third part to be mixed with the fuel from the float chamber, and the air bleed means is provided only in the third part. and the air bleed means is provided in a first atmosphere introduction passage that constantly introduces the atmosphere into the third part, and in the first atmosphere introduction passage,
a first jet that defines the amount of air introduced into the third section from the first atmosphere introduction passage; and a second jet that connects the third section to a sensing port slightly upstream of the idle position of the carburetor throttle valve. an atmosphere introduction passage; a second jet provided in the second atmosphere introduction passage and regulating the amount of air introduced from the second atmosphere introduction passage to the third portion; and a second jet provided in the second atmosphere introduction passage; a check valve that opens when the throttle valve is in the idle position and introduces air into the third portion from the sensing port, but closes by itself when the throttle valve is opened from the sensing port;
a third air introduction passage that connects the part to the air intake port; a larger third jet;
an on-off valve that opens and closes the third atmosphere introduction passage and drives an enrichment valve of the main system fuel passage; and a driving means that drives the on-off valve according to the operating state of the engine, and the driving means The means is to close the third atmosphere introduction passage and operate the on-off valve to operate the enrichment valve in an operating range where the intake air amount is small when the throttle valve is opened compared to idle, and when the intake air amount is large. There is provided an apparatus characterized in that, in the operating range, the third atmosphere introduction passage is opened and the on-off valve is operated to close the enrichment valve.

At idle, the enrichment valve is opened, but the main system hardly works. On the other hand, the on-off valve is closed, the check valve is opened, and air bleed is performed through the first atmosphere introduction passage and the second atmosphere introduction passage, and the air-fuel ratio at this time is slightly leaner than the stoichiometric air-fuel ratio. Become.

When the throttle valve is slightly opened from idle, the check valve is closed, air bleed is performed only from the first atmosphere introduction passage, and the enrichment valve is opened and the air-fuel ratio becomes rich.

When the opening of the throttle valve increases, the enrichment valve closes and the on/off valve remains open, allowing the main system to work, resulting in air bleed. Since the diameter of the jet is larger than that of the jet, the amount of air bleed increases and the degree of lean air-fuel ratio increases.

Referring to the drawings, in FIG. 1, reference numeral 10 denotes a carburetor main body, within which a small bench lily 14 is located inside a large bench lily 12, and a throttle valve 16 is located downstream of the small bench lily 14. A main nozzle 18 is provided in the small bench lily 14, and a main fuel passage 20 and a main jet 22 are provided.
It is connected to the float chamber 24 via. A main air bleed 23 is provided in the main fuel passage 20. Reference numeral 25 designates an enrichment jet, through which fuel from the float chamber 24 is introduced into the main fuel passage 20 when the enrichment valve 26 is in the open state in the lower position. The enrichment valve 26 is connected to a push rod 27 and is driven by the pressure acting on the upper end piston 28 of the push rod 27. That is, when the chamber 30 formed by the piston 28 and the housing 29 is at atmospheric pressure, the enrichment valve 26 is displaced downward by the action of the spring 31 and becomes open. On the other hand, when negative pressure is introduced into the chamber 30, the piston 28 rises against the spring 31, and the enrichment valve 26 rises and becomes closed.
A negative pressure passage 32 introduces operating negative pressure into the chamber 30 and opens into a negative pressure port 33 downstream of the fully closed position of the throttle valve 16.

A slow port 34 is provided near the throttle valve 16 in the idle position, and an idle port 35 is located downstream thereof, and the idle port 35 communicates with the slow port 34 via an idle adjustment screw 36.

The slow fuel passage includes a first portion 38 connected to the slow port 30, a second portion 39 continuous to the float chamber 24, and a third portion extending from the junction of the first portion 38 and the second portion 39. It consists of a portion 40. slow jet 43 in second part 39
is provided. In the present invention, the first part 38 and the second part 38
The portion 39 is not provided with air bleed means, and only the third portion 40 is provided with air bleed means. This air bleed means is provided in a first atmosphere introduction passage 49 that opens upstream of the small bench lily and in the first atmosphere introduction passage 49 for constantly introducing the atmosphere into the third part. The first section defines the amount of air introduced from the passage 49 to the third section 40.
jet 42 and a second atmosphere inlet passage 50 connecting the third portion 40 to a sensing port 52 slightly upstream of the fully closed position of the carburetor throttle valve 16.
, a second jet 44 provided in the second atmosphere introduction passage 50 and regulating the amount of air introduced from the second atmosphere introduction passage 50 to the third portion 40; A throttle valve 16 is provided.
At the idle position, the valve opens and sensing port 5
A check valve 48 which introduces air into the third portion 40 through the air intake port 2 and which closes itself when the throttle valve 16 is opened from the sensing port 52; and a third jet 46 which is provided in the third atmosphere introduction passage 54, defines the amount of air introduced from the third atmosphere introduction passage 54, and whose dimensions are larger than the second jet 44. , the third atmosphere introduction passage 5
4 and drives the enrichment valve of the main system fuel passage, and a driving means that drives the opening and closing valve 56 according to the operating state of the engine, and the driving means is configured to open and close the valve from idle to When the throttle valve 16 is opened, the third atmosphere introduction passage 54, which is composed of a solenoid valve 64 and a control circuit 72, is opened.
At the same time, the on-off valve is operated to operate the enrichment valve 26. The second jet 44 is connected via a passage 47, a check valve 48, and a passage 50 to a sensing port 52 slightly upstream of the throttle valve 16 in the idle position. Check valve 48 is oriented to permit atmospheric flow from passage 50 to passage 47. The third jet 46 communicates with the main air bleed 23 via passages 54 and 55, and at the same time, the passages 53 and
Small bench lily 1 via on-off valve 56 and passage 58
It communicates with the atmosphere upstream of 4. The on-off valve 56 is a negative pressure operated type and has a diaphragm 561.
61 is connected to a valve body 562, which connects an intermediate chamber 564 communicating with the passage 58 to an upper chamber 563 communicating with the passage 53 or a lower chamber 567 communicating with the enrichment valve operating chamber 30 via the passage 59. It functions to selectively switch to. This switching is performed according to the pressure in the negative pressure chamber 565 below the diaphragm 561, but the valve body 562 is pushed upward by the action of the spring 566, and the intermediate chamber 564 is normally switched to the lower chamber 565.
It is biased to communicate with 7. Chamber 565 below diaphragm 561 is selectively communicated via passage 62 with passage 66 or 68 by solenoid valve 64 . The passage 66 is connected to the passage 58, that is, to the atmosphere, and the passage 68 is connected to a negative pressure port 70 which is always downstream of the throttle valve 16. The solenoid valve 64 is connected to the line l
It receives an actuation signal from the control circuit 72 via the control circuit 72. The control circuit 72 forms an actuation signal for the electromagnetic valve 64 in response to operating conditions (for example, intake air amount) detected by the rotation speed sensor and the negative pressure sensor.

Next, the operation will be described. When the throttle valve 16 is idle, the control circuit 72 sets the solenoid valve 64 to the white port position. Therefore, the passage 6 in the chamber 565
Atmosphere is introduced from 2, 66, 58, and the spring 566
pushes the valve body 562 upward in the figure, and the upper chamber 56
3 and the intermediate chamber 564 are cut off, while the lower chamber 567 and the intermediate chamber 564 communicate with each other. Upper chamber 563
Since the third jet 46 and the intermediate chamber 564 are blocked, air bleed from the passage 58 is not performed. Also, the throttle valve 16 at idle is connected to the port 52.
Since the air pressure is below the air pressure, the check valve 48 is opened and air is bled from the second jet 44. Of course, air bleed is also performed from the normally open jet 42. Thus, during idling, air is bled from the two jets 42 and 44, and at this time the air-fuel ratio set by the carburetor is set on the lean side as shown at A in FIG. At this time, air bleed is performed only at section 40 of the slow fuel passage, and at other sections 38 and 39.
Since the bleed air is not mixed with the fuel passing through the slow system, the mixing effect is high, and high idle stability can be maintained even when the air-fuel ratio is on the lean side.

During this idle operation, as mentioned above, the on-off valve 56
Intermediate chamber 54 communicates with lower chamber 567 so that atmospheric air enters enrichment valve chamber 30 via passage 58, chambers 564, 567, and passage 59. Therefore,
Although this chamber 30 is in communication with the port 33 downstream of the throttle valve 16 where negative pressure is generated, the piston 28 is lowered by the action of the spring 31 when the chamber 30 is at atmospheric pressure, and the enrichment valve 26 is opened. It's the location. However, as is well known, the enrichment system hardly works in the idle state, so even if the enrichment valve 26 is open, it does not contribute to fuel supply.

In the region B of FIG. 2 where the throttle valve 16 is rotated from the idle state and the amount of intake air is increased, the throttle valve 16 is located upstream of the port 52, so the port 52 becomes a negative pressure and the check valve 48 is closed. The second jet 44 is thus closed. Also, in this region B, the control circuit 72 keeps the solenoid valve 64 at the white port position as in A, and the third jet 46 is closed. As a result, air is bleed only from the normally open first jet 42, and the amount of air bleed is minimized. Further, the on-off valve 56 maintains the open position in which the atmosphere is introduced into the enrichment valve chamber 30 as in the case of idling, and since the main system is also working, the air-fuel ratio is on the rich side.
In this way, acceleration operation can be performed smoothly from an idle state. Furthermore, since the air-fuel ratio is changed by opening and closing the bleed hole, there is an advantage that it can be done rapidly in steps.

C in Fig. 2, where the throttle valve 16 is further rotated.
In the region , the control circuit 72 switches the solenoid valve 64 to the black port position. Therefore, the negative pressure in the port 70 enters the chamber 566 through the passages 68 and 62, and the diaphragm 561, ie, the valve body 562, is pulled downward in the drawing against the spring 566. Thus, the upper chamber 563 and the intermediate chamber 564 are communicated with each other, and at the same time, the atmosphere enters the third jet 46 via the passage 58, the chambers 564, 563, and the passage 54, and the intermediate chamber 564 is connected to the lower chamber 56.
Passage 5 to disconnection enrichment valve chamber 30 from 7
The introduction of atmospheric air through 9 is stopped, and the chamber 30 is made to have the same negative pressure as the port 33, and the enrichment valve 26 is pulled to the closed position, so that no fuel flows into the enrichment jet 25. At this time, the jet 44 remains closed, but since the third jet 46 is larger in size than the second jet 44, the air-fuel ratio increases significantly and becomes super lean, which helps improve fuel efficiency.
Incidentally, this change to the ultra-lean air-fuel ratio is also done by opening and closing the jet, so it can be done quickly and step-by-step.

As described above, according to the present invention, in a carburetor that bleeds air only to the third portion 40 of the fuel passage, in addition to the normally open jet 42, the second and third jets 44 and 46 are provided, and the operating conditions are adjusted accordingly. By opening and closing synchronously with the enrichment valve according to the engine operating conditions, it is possible to obtain three types of air-fuel ratios depending on the engine operating conditions, even though it has a simple configuration that uses only one electric drive means, improving idle stability. , acceleration performance and fuel consumption requirements can be harmonized.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a carburetor according to the present invention, and FIG. 2 is an air-fuel ratio characteristic diagram according to the present invention. 26...Enrich valve, 38...First part, 39...Second part, 40...Third part,
42...first air bleed jet, 44...
Second air bleed jet, 46...Second air bleed.

Claims (1)

[Claims] 1. An enrichment valve is provided in the main system fuel passage of the carburetor, and a first part where the slow system fuel passage of the carburetor is connected to the slow port, and a second part where the first part is connected in series to the float chamber. and a third part connecting the joint of the first part and the second part to an air bleed means, the second part being connected to the first part from the air bleed means through the third part. It has a longitudinally extending slow jet for mixing fuel from the float chamber with the air flowing toward the float chamber, and air bleed means is provided only in this third section, and the air bleed means is configured to constantly supply atmospheric air to the third section. a first atmosphere introduction passageway for introducing air;
A first jet is provided in the atmosphere introduction passage of the carburetor and defines the amount of air introduced from the first atmosphere introduction passage to the third part, and the third part is provided at a position slightly upstream of the idle position of the throttle valve of the carburetor. a second atmosphere introduction passage connected to the sensing port; and a third atmosphere provided in the second atmosphere introduction passage;
a second jet that defines the amount of air introduced into the third section; and a second jet provided in the second atmosphere introduction passage, which opens when the throttle valve is in the idle position and introduces air into the third section from the sensing port. is provided in a check valve that closes by itself when the throttle valve is opened from the sensing port, a third atmosphere introduction passage that connects the third portion to the atmosphere introduction port, and the third atmosphere introduction passage, It defines the amount of air introduced from the third air introduction passage, opens and closes the third jet whose size is larger than that of the second air introduction passage, and also controls the enrichment of the main system fuel passage. It has an on-off valve that drives the valve, and a drive means that drives the on-off valve according to the operating state of the engine, and the drive means is configured to:
The third atmosphere introduction passage is closed and the on-off valve is operated to open the enrichment valve. In the operating range where the amount of intake air is large, the third atmosphere introduction passage is opened and the enrichment valve is closed. An air-fuel ratio control device for an internal combustion engine, which operates an on-off valve.