JPH0235145B2 - - 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, in addition to a normal air bleed means that 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 provided in the second air bleed passage, the on-off valve is opened and closed according to the altitude of the vehicle equipped with the internal combustion engine, and the amount of air bleed is changed by opening and closing the on-off valve in accordance with changes in altitude. Devices that control the air-fuel ratio are known. For example,
-See No. 46326.

In this conventional technology, the amount of air bleed is changed so that the air-fuel ratio remains unchanged regardless of the altitude, but it may be applied to control the air-fuel ratio by changing the amount of air bleed by opening and closing an on-off valve. That is, when the engine is idling, the on-off valve is opened so that the air-fuel ratio is near the stoichiometric ratio, and when the engine is idling, the on-off valve is closed and the air-fuel ratio is made rich in order to obtain acceleration performance.

However, if this control is used as it is, the engine will become rich even when it stops accelerating and enters steady state, resulting in a disadvantage that the heat consumption rate will deteriorate. Therefore, there is a demand for controlling the air-fuel ratio into three types. That is, when idling, the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio (or slightly leaner), 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 super lean. In this case, in contrast to the prior art, it is conceivable to provide another third air bleed passage and provide an on-off valve in this passage.

However, this configuration requires two on-off valves, and each on-off valve requires a control device.
There is a problem in that the number of parts increases and the cost increases.

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, the slow system fuel passage of the carburetor includes the first part connected to the slow port side, the second part connected in series to the float chamber, and the first part. a third part connecting the joint with the second part to air bleed means;
The second section has a longitudinally extending throw jet which allows the air flowing from the air bleed means to the first section through the third section to mix with the fuel from the float chamber; A bleed means is provided, and the air bleed means is provided in a first atmosphere introduction passage that always introduces the atmosphere into the third part, and in the first atmosphere introduction passage, and is provided in the first atmosphere introduction passage to a third part. a first jet defining the amount of air introduced into the section; a second atmospheric air introduction passage connecting the third section to a sensing port slightly upstream of the idle position of the throttle valve of the carburetor; a second jet provided in the air introduction passage and regulating the amount of air introduced from the second air introduction passage to the third portion; and a second jet provided in the second air introduction passage and provided at the idle position of the throttle valve. Open the valve,
A check valve that introduces air into the third portion from the sensing port and closes itself when the throttle valve is opened from the sensing port, and a third atmospheric air introduction passage that connects the third portion to the atmospheric air inlet. ,
provided in the third atmosphere introduction passage, which defines the amount of air introduced from the third atmosphere introduction passage, and whose dimensions are the second
a third jet larger than the jet of the third jet;
installed in the air intake passageway, and the third
It has an on-off valve that selectively introduces air into the first part through the first part, 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 control the amount of intake air. An air-fuel ratio control device for an internally twisted engine is provided, which is characterized by closing an on-off valve in a small operating range and opening the on-off valve in an operating range where the amount of intake air is large.

At idle, the on-off valve is closed, but the check valve is open, and the first atmosphere introduction passage and the second
Air bleed is performed through the atmospheric air introduction passage, and the air-fuel ratio at this time becomes somewhat leaner than the stoichiometric air-fuel ratio.

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 air-fuel ratio becomes the stoichiometric air-fuel ratio.

When the opening degree of the throttle valve increases, the on-off valve opens and closes to bleed air, but since the diameter of the third jet is larger than the diameter of the second jet, the amount of air bleed increases, resulting in a lean air-fuel ratio. The degree of

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. Note that 26 is an enrichment jet, and 28 is an enrichment valve.

A slow port 30 is provided near the throttle valve 16 in the idle position, and located downstream of the slow port 30 is an idle port 32 that communicates with the slow port 30 via an idle adjustment screw 34.

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. Consists of part 40 and more. A throw jet 43 is provided in the second portion 39. In the present invention, the first part 38 and the second part 39 are not provided with air bleed means, and the third part 38 and the second part 39 are not provided with air bleed means.
Only the section 40 is provided with air bleed means. This air bleed means is provided in the first atmosphere introduction passage 49 that opens upstream of the small bench lily 14 for constantly introducing the atmosphere into the third portion 40, and in the first atmosphere introduction passage 49, and is provided in the first atmosphere introduction passage 49. A first jet 42 that defines the amount of air introduced from the introduction passage 49 to the third section 40 and the third section 40 are connected to a sensing port 52 slightly upstream of the fully closed position of the throttle valve 16 of the carburetor. Provided in the second atmosphere introduction passage 50 and the second atmosphere introduction passage 50,
a second jet 44 that defines the amount of air introduced from the second atmosphere introduction passage 50 to the third portion 40;
The throttle valve 16 is provided in the second atmosphere introduction passage 50 and opens when the throttle valve 16 is in the idle position, introducing air into the third portion 40 from the sensing port 52. However, when the throttle valve 16 is opened from the sensing port 52, A check valve 48 that closes by itself;
A third portion connecting the third portion 40 to the atmosphere inlet 55
the atmosphere introduction passage 54 and the third atmosphere introduction passage 54
The jet 46 is provided in the third atmosphere introduction passage 54 and defines the amount of air introduced from the third atmosphere introduction passage 54 and has a larger dimension than the second jet 44. The driving means has an on-off valve 56 that selectively introduces air into the first part 38 through the third part 40, and a drive means that drives the on-off valve 56 according to the operating state of the engine. is composed of a solenoid valve 64 and a control circuit 72. The direction of the check valve 48 is from the passage 50 to the passage 47.
It is arranged to allow atmospheric flow towards the area. The third jet 46 has a passage 54 and an on-off valve 5.
6 and the atmosphere upstream of the small bench lily 14 via a passage 58 . The on-off valve 56 is a negative pressure operated type and has a diaphragm 561, and the diaphragm 561 is connected to a valve body 562. It is controlled according to the pressure in the chamber 565 below. The spring 566 applies such force to the valve body 562 that the communication between the chambers 563 and 564 is normally cut off. Chamber 565 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. Solenoid valve 64
receives an activation signal from control circuit 72 via line l. The control circuit 72 forms an actuation signal for the electromagnetic valve 64 according to operating conditions (for example, intake air amount) detected by a rotation speed sensor or a negative pressure sensor.

Next, when the throttle valve 16 is idle, the control circuit 72 sets the solenoid valve 64 to the white port position, and the control circuit 72 sets the solenoid valve 64 to the white port position. Therefore, the atmosphere is introduced into the chamber 565 through the passages 62, 66, and 58, and the spring 5
66 pushes the valve body 562 upward in the figure, and the chamber 56
Cut off communication between 3 and 564. Therefore, no air bleed is performed from the third jet 46. Since the throttle valve 16 is located below the port 52, the pressure is at atmospheric 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 in FIG. 2A. At this time, air bleed is performed only in the section 40 of the slow fuel passage and not in the other sections 38 and 39, so the mixing effect of the bleed air and the fuel passing through the slow system is high and the idle is stable even when the air-fuel ratio is on the Lee side. You can maintain a high level of sexuality.

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 bleed is performed only from the normally open first jet 42, the amount of air bleed becomes the minimum, and as a result, the air-fuel ratio becomes rich. In this way, acceleration operation can be performed satisfactorily after idling. 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, rooms 563 and 56
4 are in communication with each other, and the atmosphere is passed through the passage 58 and the chambers 564 and 5.
63 and enters the third jet 46 via passage 54. At this time, the second jet 44 remains closed, but since the dimensions of the third jet 46 are larger than those of the second jet 44, the air-fuel ratio increases significantly and becomes super lean, which helps improve fuel efficiency. .
Incidentally, since this change to the ultra-lean air-fuel ratio is also carried out by opening and closing the jet, it can be carried out quickly and step-by-step.

As described above, according to the present invention, in addition to the normally open jet 42, the second and third jets 44 and 46 are provided in the carburetor that bleeds air only to the third portion 40 of the fuel passage, and these jets are operated. By opening and closing depending on the conditions, three types of air-fuel ratios can be obtained depending on the engine operating conditions despite the simple configuration using only one electric drive means, improving idle stability and acceleration performance. and fuel consumption rate requirements can be harmonized.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a carburetor of the present invention, Fig. 2 is an air-fuel ratio characteristic diagram according to the present invention, 38... first part, 39... second part, 4
0...Third portion, 42...First air bleed jet, 44...Second air bleed jet, 46...Third air bleed jet.

Claims (1)

[Claims] 1. A first part where the slow system fuel passage of the carburetor is connected to the slow port, a second part which connects the first part in series to the float chamber, and a joint between the first part and the second part. a third section connecting the section to the air bleed means, the second section being longitudinally arranged to mix the fuel from the float chamber with the air traveling from the air bleed means through the third section and toward the first section. an extending slow jet, and air bleed means are provided only in this third portion;
The air bleed means is provided with a first atmosphere introduction passage that always introduces the atmosphere into the third part, and is provided in the first atmosphere introduction passage, and is provided with a first atmosphere introduction passage that always introduces the atmosphere into the third part. a first jet that defines the amount of air introduced; a second air introduction passage that connects the third portion to a sensing port slightly upstream of the idle position of the throttle valve of the carburetor; and a second air introduction passage that is provided in the second air introduction passage. a second jet which defines the amount of air introduced from the second atmosphere introduction passageway into the third portion;
A check installed in the second atmosphere introduction passage, which 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 valve, a third atmosphere introduction passage that connects the third portion to the atmosphere introduction port; a third jet which is larger than the second jet; and an on-off valve provided in the third atmosphere introduction passage for selectively introducing air from the atmosphere introduction port through the third part to the first part. and a driving means for driving the on-off valve according to the operating state of the engine, the driving means closes the on-off valve in an operating range where the amount of intake air is small, and closes the on-off valve in an operating range where the amount of intake air is large. An air-fuel ratio control device for an internal combustion engine, characterized in that the air-fuel ratio control device opens the air-fuel ratio.