JP3340575B2 - Carburetor control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a carburetor in a feedback control carburetor type engine to prevent a rotation of the carburetor from being reduced due to freezing.

[0002]

2. Description of the Related Art In a carburetor type engine,
When the outside air temperature is low and the humidity is high, the rotation may suddenly drop shortly after the engine is started, leading to engine stall. This is a phenomenon that occurs as a result of cooling the intake air and the inside of the carburetor by the heat of vaporization of the fuel, and the water in the intake air becomes ice, and adheres mainly to the upstream portion of the throttle valve in the carburetor and freezes. is called. Due to this icing, the idle passage of the carburetor is narrowed, the opening area of the throttle valve is reduced and the amount of intake air is reduced, and the over-rich intake causes a decrease in engine speed and a stall. .

Various means for preventing this icing have been proposed. For example, the cooling water is circulated around the throttle to avoid a temperature drop by the heat of the hot water, and is disclosed in Japanese Utility Model Publication No. Sho 62-14364 and Japanese Utility Model Application Laid-Open No. 2-76154. like,
There is known a heater in which the vicinity of a slow air bleed is heated by a heating element attached to the outer surface of a carburetor.

Further, in order to reduce the effects of narrowing of the idle passage and reduction of the opening area of the throttle valve due to the icing, the opening degree of the choke breaker is controlled in two stages so that the air-fuel ratio at the time of icing can be enriched at all. A method for suppressing the occurrence has been proposed, and a method using the above-described means for preventing icing by heating is also known.

[0005]

However, in the case where the icing is prevented by providing the heating means as described above, the structure of the carburetor becomes complicated, processing costs and parts costs increase, and there is a problem in cost. There is a problem that the control by the choke breaker is an indirect countermeasure, and a substantial effect cannot be expected by itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a carburetor control method capable of effectively preventing rotation reduction by icing with simple means.

[0007]

According to the carburetor control method of the present invention, when the cooling water temperature of the engine is equal to or lower than a predetermined value,
After a certain period of time has elapsed after the engine has started, when the engine speed drops from a state where the engine speed has exceeded the predetermined high-band speed to a predetermined low-band speed or less, the opening of the air bleed control valve is adjusted from the set opening. The opening degree is controlled to be increased by a predetermined amount.

[0008]

According to the present invention, when the engine is started at a low temperature where the cooling water temperature is equal to or lower than a predetermined value, the engine speed once increases after the engine is started, and after a while, icing is generated in the carburetor due to heat of vaporization of the fuel. When the idle passage in the engine is narrowed or the passage area of the throttle valve is reduced, the air-fuel ratio of the intake air becomes over-rich and the engine speed starts to decrease, it is determined at that point that the rotation has decreased due to icing, and the air Since the air supply amount is increased by increasing the opening of the bleed control valve by a predetermined amount, it is possible to prevent over-enrichment and prevent a decrease in rotation and an engine stall.

Since the air bleed mixes air in the fuel passage, the air is reliably supplied without being affected by icing, and over-rich air can be prevented. Although the occurrence of icing itself is not prevented as described above, the continuation of normal rotation of the engine warms up the engine and eliminates icing itself.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

First, the overall configuration of the engine will be described with reference to FIG. 1 is a cylinder, 2 is an intake port, 3
Is an exhaust port, intake air is supplied from the air cleaner 4 to the intake port 2 through the intake passage 5, and exhaust gas is exhausted from the exhaust port 3 through the exhaust passage 6. The intake passage 5 is provided with a carburetor 7 for supplying fuel during intake and a throttle valve 8 for controlling the intake amount. 1
Reference numeral 6 denotes a choke valve arranged at the inlet of the carburetor 7, which is opened and closed by a choke breaker (not shown) so as to close the intake passage 5 at the time of starting and to open a predetermined angle immediately after starting. An exhaust gas purifying catalyst 9 is provided in the exhaust passage 6, and an O ₂ sensor 10 for detecting the oxygen concentration in the exhaust gas is provided upstream of the catalyst. This O
_As shown in FIG. 5, the ₂ sensor 10 shows a high output value when the air-fuel ratio is lower (rich) below the stoichiometric air-fuel ratio (λ = 1), and when the air-fuel ratio is high (lean), Relatively inexpensive ones having characteristics such as low output values are used.

The output of the O ₂ sensor 10 is input to an engine control unit (ECU) 11 and an air bleed control valve (ABCV) 12 for controlling the amount of air bleed in the carburetor 7 according to the output value.
And the feedback control is performed so that the fuel supply amount to the intake air becomes the stoichiometric air-fuel ratio. The ABCV 12 is configured to supply air supplied from the air cleaner 4 through the pipe 13 to the main air bleed passage 14a and the slow air bleed passage 14b as shown in FIG. 4, and the position thereof is adjusted by a stepping motor. The supply amount is controlled by the needles 15a and 15b. The main air bleed passage 14a is connected to the main port 17a of the carburetor 7.
The slow air bleed passage 14b is connected to the slow port 17b of the carburetor 7 so as to perform air bleed. In the carburetor 7, 7a is a float chamber, 7b is an air bleed, and 7c is an idle adjustment screw. Also, the ECU 11 has an A / T
A switch ON / OFF signal, an engine speed NE, and a water temperature switch ON / OFF signal are input, and a control signal for a choke breaker is output.

In the engine having the above-described overall configuration, the engine speed is reduced by icing after starting,
In some cases, icing countermeasure control is performed by the ECU 11 in order to eliminate the risk of engine stall.
This will be described below with reference to FIGS.

In FIG. 1, first, it is determined whether or not the cooling water temperature is lower than a predetermined temperature and a water temperature switch is open (step # 1). If the cooling water temperature is higher than the predetermined temperature, icing does not occur. The process returns to step # 6 to determine whether or not the icing countermeasure is being performed. If the icing countermeasure is not being performed, the process returns as it is. If the icing countermeasure is being performed, the process returns to step # 7 to cancel the icing countermeasure and return. If the temperature is equal to or lower than the predetermined temperature, it is determined whether or not the A / T switch is closed in an automatic vehicle (step # 2) for the purpose of eliminating running during the next run, and the neutral (N) or parking (P) is applied. Except when the A / T switch is closed, the process proceeds to step # 6. Next, when T time (for example, about 40 seconds) elapses after the start, the engine speed NE becomes a predetermined high-range speed G1 (for example, 1).
750 rpm) is determined (step # 3). If not, the process proceeds to step # 6. If not, the process proceeds to step # 4, and the current engine speed NE is set to a predetermined value. Is determined to be lower than the low frequency rotation speed G2. If the rotational speed is not lower than the low-pass rotational speed G2, it is determined that there is no rotational decrease due to icing, and the process proceeds to step # 6.
An icing countermeasure is executed (step 5). The countermeasures against icing are as follows.
That is, the opening degree is increased by 0 steps.

By performing the above control, FIG.
As shown in the figure, the engine speed increases after the engine starts, and once the time T has elapsed, the engine speed once exceeds the high-range speed G1. After a while, icing occurs in the carburetor 7 due to heat of vaporization of the fuel, and the carburetor 7 When the idle passage in the engine is narrowed or the passage area of the throttle valve is reduced, the air-fuel ratio of the intake air becomes over-rich, and the engine speed NE starts to decrease, the engine speed NE becomes lower.
At a time point when the IC becomes lower than 2, it is determined that the rotation has decreased due to icing, and the opening of the ABCV 12 is set to 3
The opening is increased by 0 steps. In FIG. 2, since the control is performed while the ABCV 12 is closed after the startup, the opening of the ABCV 12 is controlled to 30 steps at the time of the IC. Of course, if the opening of the ABCV 12 is set to a certain number of steps after startup, the opening is set to 30.
The opening is controlled by adding the step. Then, the air bleed amount increases, and the air supply amount to the intake air increases. At this time, since the air bleed mixes the air in the fuel passage, the air is reliably supplied without being affected by icing. As a result, over-riching due to icing is eliminated, and the decrease in the engine speed NE is recovered thereafter. Thus, a decrease in rotation and an engine stall due to icing are prevented.

Thereafter, the engine is warmed up by continuing the normal rotation of the engine, so that the icing itself is eliminated.

[0017]

According to the carburetor control method of the present invention, as described above, when the engine cooling water temperature is equal to or lower than the predetermined value, and after a certain period of time has elapsed since the start of the engine, the engine speed becomes a predetermined high-range rotation speed. When the number of rotations falls below a predetermined low-range rotation speed from a state where the number of rotations exceeds the number, it is determined that the rotation has decreased due to icing, and the opening of the air bleed control valve is controlled to an opening increased by a predetermined amount from the set opening. Therefore, even if icing occurs when starting at low temperatures, increasing the amount of air supplied from the air bleed control valve can prevent over-rich and prevent rotation reduction and engine stall from occurring. By simply controlling the control valve opening, there is no need to complicate the structure of the carburetor and One at a low cost it is possible to solve the problems caused by icing.

[Brief description of the drawings]

FIG. 1 is a flowchart of a control method for taking measures against icing of a carburetor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an icing countermeasure control method according to the embodiment.

FIG. 3 is an overall schematic configuration diagram of an engine in the embodiment.

FIG. 4 is a schematic configuration diagram of a carburetor and an ABCV in the embodiment.

FIG. 5 is an output characteristic diagram of an O ₂ sensor.

[Explanation of symbols]

 7 Carburetor 11 ECU 12 ABCV

Continuation of the front page (56) References JP-A-57-147851 (JP, A) JP-A 62-78357 (JP, U) JP-A 62-79953 (JP, U) JP-A 60-107350 (JP (U, U) Sho 63-79459 (JP, U) (58) Fields studied (Int. Cl. ⁷ , DB name) F02M 7/24 F02M 7/26 F02M 17/50

Claims (1)

(57) [Claims] When the engine cooling water temperature is equal to or lower than a predetermined value and a predetermined time has elapsed after the engine is started, the engine rotation speed is changed from a state where the engine rotation speed exceeds a predetermined high frequency rotation speed to a predetermined low frequency rotation speed or less. A method for controlling a carburetor, comprising: when the air bleed control valve is lowered, controlling the opening of the air bleed control valve to an opening increased by a predetermined amount from a set opening.