JPH0370847A - Feedback type evaporator - Google Patents

Abstract

PURPOSE:To prevent the occurrence of back bleed and prevent the interruption of a slow mixed air correcting air in normal engine operating state other than back bleed generating area by interrupting the slow mixed air correcting air in the back bleed generating area during the engine operating state. CONSTITUTION:When engine intake negative pressure and engine rotating speed of a specified area are detected during engine operation, an interruption signal is generated, and on the basis of this signal, an interruption control valve mechanism 22 forcedly interrupts a slow mixed air correcting passage 19. Hence, the transmission of the pressure fluctuation caused by the change of air bleed opening area into a slow fuel system passage 14 is prevented by the drive of a mixing ratio correction control valve 5. Thus, the negative pressure P2 in the slow fuel system passage 14 is regularly made larger than the negative pressure degree of the negative pressure P1 in a main fuel system passage 2, and the difference between the both is increased, whereby the negative pressure P1 is prevented from being larger than the negative pressure P2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a feedback type carburetor for an engine.
More specifically, the present invention relates to a mechanism that prevents backbleed from the slow air passageway to the main fuel passageway.

[Conventional technology]

In recent years, in the field of engine carburetors, so-called feedback systems have been introduced that increase or decrease air in the slow system and control fuel in the main system according to engine operating conditions in order to properly control the air-fuel ratio. vaporizers have been put into practical use.

This type of vaporizer usually has mfj, mfj,
be done. These elements will be explained by referring to the reference numerals of the embodiment of the present invention in the drawing. Main fuel that guides the fuel in the float chamber 1 through the main jet 3 to the main nozzle 11 disposed upstream of the throttle valve 13. An idle hole 21 branched from the main fuel system passage 4 and downstream of the throttle valve 13 via a slow jet 15;
A slow fuel system that guides fuel to a bypass port 20 near the throttle valve 13, a main correction fuel system 8 that guides the fuel in the float chamber 1 to join the passage 4 of the main fuel system, and a A slow system air passage 16 that joins the slow fuel system passage 14 via the slow air bleed 16a, and a throttle mixture correction passage 19 that guides the air upstream of the throttle valve 3 to join the slow system air passage 16. , a mixture ratio correction control valve 5, etc., which opens and closes the slot mixture correction passage 19 by duty control.

During normal running operation other than low-speed operation, the fuel in the float chamber 1 is metered by the main jet 3.

This fuel and the fuel from the main correction fuel system 8, which is introduced under the control of opening and closing by the mixture ratio correction valve 5, join together and are finally ejected from the main nozzle 11.

In addition, in a low-speed operating range where the throttle valve opening is small, such as during idling, the load generated at the tip of the main nozzle 11 is low, so fuel is not ejected from the main nozzle 11, and in this case, the fuel is The air that flows through the slow fuel passage 14 branching from the passage 4, is metered by the slow jet 15, and is then metered by the slow air bleed 16, and the air that passes through the slow compensation system air passage 19 (slow compensation system air passage) 19 is mixed with the air orifice 18 whose opening and closing are controlled by the mixture ratio correction valve 5), and the air is mixed with the bypass hole 20 and the idle hole 2.
It is ejected from the factory.

By the way, in such a feedback type carburetor, for example, when the engine is running at high speed,
In areas such as high-load operation, a so-called back-bleed phenomenon may occur in which air enters the main system fuel passage 4 from the slow system air passage 16 via the slow fuel system passage 14.

The backbleed phenomenon occurs as follows. For example, during engine operation, normally the negative pressure near the main nozzle 11, that is, the negative pressure Pl in the main fuel system passage 4, is compared to the negative pressure near the idle port 21°, that is, the negative pressure near the slow fuel system passage 14. Pressure P2 is larger (back bleed does not occur in this state). However, in the operating range of the engine, when the mixture ratio correction valve 5 is driven by duty control, the influence becomes a pressure fluctuation in the slow system correction air passage 19 and propagates to the slow fuel system passage 14. As a result, a reversed state may occur in which the negative pressure P2 in the passage 14 is smaller than the negative pressure Pl in the main fuel system passage 4. When such a situation occurs, a so-called back bleed phenomenon occurs in which air flows from the slow system air passage 16 into the main fuel system passage 4 via the slow jet 15 and the slow fuel system passage 14.

When this back-bleed phenomenon occurs, too much air is mixed with the fuel flowing through the main fuel passage, and the air-fuel ratio of the air-fuel mixture supplied to the engine becomes lean, resulting in poor engine operability.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 62-294753, conventionally, as a measure to prevent backbleed, the throat mixture correction passage was installed by detecting engine intake negative pressure. Measures have been proposed to block this.

This conventional technology is based on the assumption that the above-mentioned backbleed phenomenon may occur when the engine intake negative pressure reaches a level where the negative pressure in the vicinity of the idle boat or bypass port reaches a level where the engine suction negative pressure reaches a certain level. The correction passage was blocked, and in this way, the pressure fluctuations in the slow mixture correction air passage caused by the air bleed (orifice) control of the mixture ratio correction control valve were prevented from propagating to the slow fuel system. .

That is, as mentioned above, by preventing pressure fluctuations in the slow mixture correction air passage from propagating to the slow fuel system, pressure fluctuations in the negative pressure in the slow fuel line passage are reduced;
The occurrence of back bleed is prevented by making the degree of negative pressure Pa in the slow fuel system passage larger than the negative pressure Pl in the main fuel system passage.

[Problem to be solved by the invention]

By the way, the conventional backbleed prevention technology mentioned above is
A negative pressure diaphragm is used as the drive mechanism for the valve that shuts off the air passage for slow mixture correction, and when the negative pressure diaphragm detects the level of engine intake negative pressure,
The air passage for slow mixture correction was blocked.

However, in such conventional technology, in order to roughly estimate the possibility of back bleed occurrence based on the engine suction negative pressure, the engine operating range where back bleed occurs (
For example, even in a part of the low-load, low-speed range, the air passage for slow mixture correction has been blocked.

As a result, slow system mixture ratio correction control is sacrificed and slow mixture correction air is not supplied to the slow fuel system, resulting in the problem that the air-fuel ratio of the mixture supplied to the engine becomes excessively rich. Ta.

The present invention has been made in view of the above points, and its purpose is to prevent the occurrence of backbleed by cutting off the slow mixture correction air in the region where backbleed occurs under various engine operating conditions. , prevents the slow mixture correction air from being cut off under normal engine operating conditions outside the backbleed region (in other words, prevents slow mixture ratio control from being sacrificed), and is stable under all engine operating conditions. An object of the present invention is to provide a feedback carburetor that can perform air-fuel ratio control with little fluctuation.

[Means to solve the problem]

In order to achieve the above object, the present invention takes the following measures to the feedback type carburetor as described above.

That is, in place of the conventional negative pressure diaphragm shutoff mechanism, a valve mechanism is provided in the throat mixture correction passageway to control the shutoff of the throat mixture correction passageway based on an electric signal, and the shutoff control valve The mechanism has a cutoff signal generating means that generates a cutoff signal by inputting the engine intake negative pressure and the engine rotation speed, and the cutoff signal generating means generates a bank bleed phenomenon in advance during engine operation. The engine suction negative pressure and engine rotational speed in the engine operating range are specified, and the cutoff signal is set to be generated when the specified engine suction negative pressure and engine rotational speed are detected.

[Effect]

All operating conditions of the engine, from low negative pressure and low rotation to high load and high rotation, can be determined from the engine intake negative pressure and engine rotation speed.

In the present invention, focusing on this, the operating range in which bank bleed phenomenon occurs in an engine using a feedback type carburetor is specified in advance in relation to the engine intake negative pressure and the engine speed, and this is used for slow system mixing. This is input as a signal generation condition for the cutoff signal generation means in the air correction passage.

Therefore, when the engine suction negative pressure and engine speed in this specific range are detected during engine operation, a shutoff signal is generated, and based on this signal, the shutoff control valve mechanism is used to correct the throttle mixture. Forcibly block the passage. This prevents pressure fluctuations caused by changes in the air bleed opening area (opening and closing of the orifice of the throat mixture correction passage) due to the drive of the mixture ratio correction control valve from propagating into the slow fuel system passage. Therefore, by always making the negative pressure Pl in the slow fuel system passage higher than the degree of negative pressure Pi in the main fuel system passage and increasing the difference, the negative pressure Pl in the main fuel system passage This prevents the negative pressure P2 from becoming larger than the negative pressure P2 in the slow fuel system passage, thereby preventing the occurrence of back bleed. Therefore, fluctuations in the air-fuel mixture and air-fuel ratio due to bank bleed are prevented, and fluctuations in the engine generated torque are also prevented.
Deterioration of drivability such as so-called surging can be prevented.

In addition, since the cutoff signal is not generated in engine operating conditions other than the backbleed generation region, slow mixture ratio correction control is not sacrificed, for example in low speed and low load areas, and the range of slow mixture correction control is wider than before. It is possible to improve the performance of air-fuel ratio control by expanding the Specifically, it is possible to solve the conventional problem of excessively rich mixture in low speed and low load regions.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIGS. 1 to 3.

FIG. 1 is a structural explanatory diagram of a feedback type carburetor according to the present invention.

In Figure 1, 1 is a float chamber, 2 is a main well,
3 is a main jet, and 4 is a main fuel system passage.

5 is a duty solenoid valve for mixture ratio correction control, and plunger 6 performs reciprocating operation by opening the solenoid.
A main fuel system correction valve 7, a slow air correction valve 17, etc. are provided at both ends of the plunger 6.

The valve 7 is for opening and closing an orifice 8a of a main correction fuel passage 8 that merges with the main fuel system passage 4.
Also.

The valve 17 is used to open and close an orifice 18 of a slow mixture correction passage (hereinafter referred to as a slow system air passage) 19.

The fuel in the float chamber 1 is metered by the main jet 3 and flows through the main fuel passage 4.

In addition, when the valve 7 connected to the plunger 6 is controlled to open or close by the duty solenoid valve 5 for mixture ratio correction, the fuel orifice 8a of the main correction fuel system
The fuel metered by the above merges with the fuel in the main fuel system passage 4 downstream of the main correction fuel passage 8. This combined fuel is introduced into the main well 2, where it is mixed with air metered by the main air bleed 10, and is ejected into the venturi 12 from the main nozzle 11. The venturi 12 is arranged upstream of the throttle valve 13 in the intake passage.

Reference numeral 14 denotes a slow system fuel passage, which branches from the main fuel passage 4 and communicates via a slow jet 15 with a bypass port 20 near the throttle valve 13 and an idle port 2 downstream of the throttle valve 13.

Reference numeral 16 denotes a slow system air passage, one end of which communicates with the upstream side of the venturi 12, and the other end of which communicates with the slow system fuel passage 14 via a slow air bleed 16a.

Reference numeral 19 denotes a slow system correction air passage (throttle mixture correction passage), one end of which communicates upstream of the venturi 12, and the other end of which merges with the slow system air passage 16.

The slow correction air passage 19 is provided with a slow correction air passage blocking mechanism 22, which is the gist of the present invention. The blocking mechanism 22 will be described later.

In low-speed, low-load operating conditions where the opening of the throttle valve 13 is small, the negative pressure generated at the tip of the main nozzle 1 is small.
The fuel is not ejected from the main nozzle 11, but branches from the main fuel passage 4 and flows through the slow fuel passage 14, and is metered by the slow jet 15 during the flow process. This metered fuel is the air metered by the air bleed 16a of the slow system air passage 16, and the air metered by the air orifice 18 when controlling the opening/closing of the valve 17 of the duty solenoid valve 5 for mixing ratio correction This air is mixed with the air (which flows through the slow correction air passage 19) and is ejected from the bypass hole 20 and the idle hole 21.

However, as mentioned in the [Prior Art] section, when the engine is running, such a feedback type carburetor normally reduces the negative pressure near the main nozzle 1, that is, the negative pressure Pl in the main fuel system passage 4. For idle port 21
．． The degree of negative pressure near the bypass port 20, that is, the negative pressure P2 near the slow fuel system passage 14, is greater (in this state, no backbleed occurs). However, in the operating range of the engine, when the valve 7 of the mixture ratio correction valve 5 is driven by duty control, the influence becomes a pressure fluctuation in the slow system correction air passage work 9, and the slow fuel system passage As a result, the negative pressure P2 in the passage 14 becomes the negative pressure P in the main fuel system passage 4.
A reversal situation may occur in which the degree of negative pressure is smaller than i. When such a situation occurs, a so-called back bleed phenomenon occurs in which air flows from the slow system air passage 16 into the main fuel system passage 4 via the slow jet 15 and the slow fuel system passage 14. When this bank bleed phenomenon occurs, too much air is mixed with the fuel flowing through the main fuel passage, and the air-fuel ratio of the air-fuel mixture supplied to the engine becomes lean, resulting in poor engine operability.

In this embodiment, the following measures are taken to deal with this problem.

The slow correction air passage blocking mechanism 22 and the CPU 22 are means for realizing this. The blocking mechanism 22 is.

A plunger 24 driven by a solenoid 23 and a seat 25 open and close the upper slow correction air passage 9. The CPU (computer) 22 has a function of generating a pulse signal to control the energization of the solenoid 23.
Information regarding the engine suction negative pressure detected by the pressure sensor 26 and the engine rotation speed detected by the rotation speed sensor 27 is input.

That is, the plunger 24 is controlled to attract and release the attraction (on/off of the solenoid 23) by a pulse signal transmitted based on the judgment of the CPU 28, and the slow correction air passage 1 is controlled.
Performs opening and closing control of 9.

FIG. 2 shows the control range of the shutoff mechanism 23 according to the present invention. The area A in which the diagonal lines in FIG. 2 are crossed is the engine operating area where the backbleed phenomenon occurs. and,
In this embodiment, the operating range in which actual backbleed occurs is determined in advance, and the engine intake negative pressure and engine speed (because the engine intake air amount is determined by the engine speed) corresponding to this operating range are determined in advance. The combination is set, and the information P of the engine suction negative pressure detected by the pressure sensor 26 is
When the combination of w and the engine speed information Rw detected by the speed sensor 27 matches the above-mentioned combination, C
The PU 28 sends a signal to the solenoid 23 to release the suction of the plunger 24, and the tip of the released plunger 24 comes into contact with the seat 25, thereby blocking the slow correction air passage 19. These operations provide a mechanism in which the slow correction air passage is blocked only in the region where backbleed occurs.

FIG. 3 shows the relationship between the negative pressure P1 in the main fuel line passage and the negative pressure P2 in the slow fuel line passage in the engine operating state near the start point of bank bleed occurrence. As shown in FIG. 3(a), when the slow correction air passage 19 is in the open state, the slow fuel passage 19 is driven by the mixture ratio correction control valve 5.
The range of fluctuation P2 of the negative pressure generated in the main fuel passage 4 is large, and there is a region where the low negative pressure side of this fluctuation is smaller than the negative pressure Pi in the main fuel passage 4, indicating that back bleed is occurring. There is.

On the other hand, as shown in the third [ffl (b), when the slow correction air passage 19 is closed, the negative pressure P2 generated in the slow fuel passageway 4 is generated even under the same conditions as the engine operating state described above.
By blocking the slow correction air passage 19, pressure fluctuations on the correction air passage 9 due to the driving of the mixture ratio correction duty solenoid valve 5 are reduced, and thereby the pressure generated in the slow fuel passage 4 is reduced. Fluctuations are suppressed. As a result, the chance that the low negative pressure side of the fluctuation in negative pressure P2 becomes smaller than the negative pressure in the main fuel passage 4 is reduced.

Therefore, the engine operating range in which bank bleed occurs can be reduced. In addition, by blocking the slow correction air passage 19 only in the engine operating state where back bleed occurs, the opening area equivalent to the air orifice 18 of the air bleed opening to the slow fuel system is reduced. As a result, the negative pressure generated in the slow fuel passage 14 increases, and the negative pressure distribution within the passage can be made such that bank bleed is less likely to occur.

The above has the effect of suppressing the occurrence of backbleed in engine operating conditions where backbleed has conventionally occurred.

Therefore, dilution and fluctuations in the air-fuel ratio of the air-fuel mixture caused by back bleed are prevented, and engine drivability problems such as surging due to fluctuations in the engine generated torque caused by these phenomena can be prevented.

Furthermore, according to this embodiment, the area where the bank bleed phenomenon occurs, as shown in area D in FIG. It is possible to eliminate the blockage of the slow correction air passage 19 in an engine operating region where no lag occurs.

Therefore, slow speed.

Since slow mixture ratio control is appropriately performed over a wide range in the low-load operating range, the air-fuel ratio control performance over the entire engine operating range can be improved.

In other words, under normal operating conditions (an engine in which fuel is supplied only by the slow fuel system) with low engine intake negative pressure and low rotational speed, and when back bleed does not occur, slow The occurrence of back bleed can be prevented without adversely affecting other basic performance, such as over-enrichment of the air-fuel ratio of the supplied air-fuel mixture due to blocking of the mixture correction air.

〔Effect of the invention〕

As described above, according to the present invention, the occurrence of back bleed is prevented by blocking the slow mixture correction air in the region where back bleed occurs under various engine operating conditions, and normal engine operation is achieved in areas other than the region where bank bleed occurs. In this case, the slow mixture correction air is prevented from being cut off, in other words, the slow mixture ratio control is not sacrificed.
Stable air-fuel ratio control with little fluctuation can be performed under all engine operating conditions.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the structure of a feedback carburetor according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the control range of the backbleed prevention mechanism used in the above embodiment, and Fig. 3 is an explanatory diagram of the carburetor according to the above embodiment. FIG. 3 is a diagram showing changes in pressure occurring within a fuel passage. 1...Float chamber, 2...Main well, 3...
Main jet, 4... Main fuel passage, 5... Mixing ratio correction valve, 6... Plunger, 7... Valve, 8... Main correction fuel passage, 10... Main air bleed, 11 ... Main nozzle, (2 ... Venturi, 13 - Throttle valve, 14 - Slow fuel passage, 15 - Slow jet, 16 - Slow system air passage, 17 - Valve, 8... Air orifice, 19... Slow correction air passage, 20... Bypass hole, 21... Idle hole, 22... Slow correction air passage blocking mechanism, 23... Solenoid, 24...
...Plunger, 25...Seat, 26...Pressure sensor, 27...Rotation speed sensor, wet Z daily sheet 30 ((Ll (°-',;,,j"("=::"
]1-1-Float! 1---- %inno enter "1 and 1'l -1-bar 1 and fiber 20-11 by'" and not enter za ---*ltr 48 i a': Lord 4! 'j
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Claims (1)

[Scope of Claims] 1. A main fuel system that guides the fuel in the float chamber via a main jet to a main nozzle located upstream of the throttle valve; A slow fuel system that guides fuel to an idle hole downstream of the valve, a bypass hole near the throttle valve, etc.; a slow air passage that causes air upstream of the throttle valve to join the passage of the slow fuel system via a slow air bleed; and a throttle. A feedback type carburetor comprising a slow air mixture correction passage that guides air upstream of the valve to merge with the slow air mixture passage, and a mixture ratio correction control valve that opens and closes the slow air mixture correction passage by duty control. In the slow mixture correction passage, a valve mechanism is provided for controlling the slow mixture correction passage to shut off based on an electric signal, and the shutoff control valve mechanism receives input of engine intake negative pressure and engine rotation speed. and has a cutoff signal generating means for generating the cutoff signal, and the cutoff signal generating means includes:
A back bleed phenomenon (back bleed is a phenomenon in which air flows from the slow system air passage to the main fuel system passage due to the operation of the mixture ratio correction control valve in the slow mixture correction passage) occurs in advance during engine operation. Feedback characterized in that the engine suction negative pressure and engine rotation speed are specified in an engine operating range in which the engine is operated, and the cutoff signal is generated when the specified engine suction negative pressure and engine rotation speed are detected. formula vaporizer. 2. The feedback type carburetor according to claim 1, wherein the shutoff control valve mechanism is a solenoid valve.