JPS6255448A - Air-fuel ratio controlling device for carburetor - Google Patents

Abstract

PURPOSE:To prevent an engine torque from being abruptly changed by stopping a feedback control of an air-fuel ratio so as to hold a flow rate control valve of a carburetor at the specified position at a time when a secondary throttle vale is started. CONSTITUTION:The opening of a primary throttle control valve 4' in NO. 2 barrel 3 of a carburetor 1 is detected by a throttle opening sensor 6 so as to be inputted into a controlling device 21. When the opening of the primary throttle valve 4' exceeds 45 deg., that is, when the actuation of a secondary throttle valve 5 is detected, the opening of a flow rate control valve 13 which opens and closes an air bleed passages 11 and 12 of the carburetor 1, is held at its position for the specified period of time. With this, an excessive change in the opening of the flow rate control valve is restrained at a time when the secondary throttle valve is started so as to prevent a torque from being changed due to an abrupt change in the air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for a carburetor that is applied to an automatic tri engine as 'E'.

[Conventional technology] Automation these days! 1, three-way catalysts are widely used as one of the first stages of exhaust gas purification f. However, if the air-fuel ratio of the air-fuel mixture is not maintained at a value near the stoichiometric air-fuel ratio, the three-way catalyst will reduce NOx, HC, and
It is not possible to efficiently purify all GO.

Therefore, in engines equipped with a carburetor, an air-fuel ratio control device called a feedback carburetor system is installed to maintain the air-fuel ratio of the air-fuel mixture supplied to the engine at an appropriate value. That is, as a prior art related to such an air-fuel ratio control device, as shown in previously filed Japanese Patent Application No. 148525/1980, a flow control valve (so-called air bleed control valve) is installed in the air bleed passage of a carburetor. By feedback controlling this tit control valve based on the output of the 02 sensor that detects the oxygen concentration in the exhaust gas, the air-fuel ratio of the air-fuel mixture supplied to the engine is kept close to the stoichiometric air-fuel ratio. There are things that can be held.

By the way, few modern automobile engines are equipped with a twin-barrel carburetor that has a primary throttle valve and a secondary throttle valve in order to achieve both fuel economy and drivability. No, this is a carburetor with two barrels arranged side by side through which incoming air passes.

From startup to the normal mid-speed range, only the primary throttle valve installed on the primary side of the body operates.

During high-speed, high-load driving, a secondary throttle valve installed on the secondary side of the body is also operated in conjunction with this primary throttle valve, reducing fuel consumption during normal operation and increasing output during high-speed, high-load driving. The increase in is considered to be 1 power.

[Problems to be Solved by the Invention] However, when the above-mentioned air-fuel ratio control device is combined with such a twin-barrel carburetor, a shock is likely to occur when the secondary throttle valve starts operating. There is a report that.

That is, in such a configuration, the air-fuel ratio instantaneously becomes extremely rich when the secondary throttle valve starts to open, so the feedback control means greatly controls the flow I in the opening direction. (
After that, the flow control valve is returned to the closing side and returns to the normal control state, but if the control valve in the open direction is large, the control is delayed. As a result, the air-fuel ratio temporarily becomes To lean. As a result, there is a disadvantage that large fluctuations occur in the engine torque, causing an unpleasant movement in the longitudinal direction of the vehicle.

The present invention has been developed in view of such circumstances, and an object of the present invention is to effectively prevent the shock that occurs when the secondary throttle valve starts operating.

Means for Solving Problem E] In order to achieve such an object, the present invention is applied to a carburetor'Jh (1) which is provided with a primary throttle valve (4) and a secondary throttle valve (5). mu control valve (13') that opens and closes the air bleed passages (11) and (12) of this carburetor (1).
and an 02 senna (18) that detects the oxygen concentration in the exhaust gas.Based on the signal from this 02 sensor (18), the flow control valve (13) is opened and closed to set the air-fuel ratio of the mixture to be supplied to the engine. Feedback control means (A
), and when the secondary throttle valve (5) starts operating, the feedback control is temporarily +h.
The present invention is characterized in that it comprises a flow control valve holding means (B) for holding the flow control valve (13) at a predetermined position.

[Function] According to such a configuration, when the primary throttle valve (4) installed in the first air inflow path (CI) is installed in the second air inflow path (■) while the opening degree of the primary throttle valve (4) is equal to or more than a predetermined value, When the secondary throttle valve (5) starts operating, the feedback control is temporarily stopped by the function of the flow control valve holding means (B), and the air bleed passage (11) of the carburetor (1), ( 12) Opening and closing flowing water control well (1
3) is held in a predetermined position for a certain period of time. Therefore, a sudden change in the opening degree of the flow control valve (13) is prevented. Then, after a certain period of time, the secondary throttle valve (
5) After the influence of the temporary increase in fuel due to the start of operation has been resolved, the control by the feedper control means (A) starts at 1.
It is granted. As a result, drastic fluctuations in engine torque due to feedback control delays are prevented.

[Example] Hereinafter, an example of the final IJI will be described with reference to FIGS. 2 to 4.

In the figure, l is an effendinizer for automatic ili. This carburetor I is made up of a first body (barrel) 2 that forms a first air inflow path I and a second body (barrel) 3 that forms a second air inflow path (2). The primary throttle valve 4 is of a twin-body type, with a primary throttle valve 4 provided in the first body 2 and a secondary throttle valve 5 provided in the second IH 3. It is configured so that it can be opened in response to a depression operation from the initial stage. On the other hand, the secondary throttle valve 5 is configured to start opening when the primary throttle valve 4 reaches 45 degrees. These interlocking means for the throttle valves 4.5 are well known, so their explanation will be omitted.

Reference numeral 6 denotes a throttle opening sensor for detecting the opening of the primary throttle valve 4. The throttle opening sensor 6 includes a potentiometer 7 that converts the opening of the primary throttle valve 4 into an analog electrical signal, and an A/D converter 8 that converts the output of the potentiometer into a digital electrical signal. It will be done.

11 and 12 are air bleed passages. The air bleed passages 11 and 12 can be opened and closed by a flow control valve 13. The flow rate control valve 13 has a valve seat 15 and a needle valve 16 provided in a valve box 14 whose inlet 13a is open to the atmosphere and whose outlet 113b is connected to the air bleed passage 11.12. The valve 16 is moved forward and backward toward the valve seat 15 by a stepper motor 17 to control the amount of outside air flowing into the air bleed passage 11.12.In this embodiment, the stepper motor 17 The needle valve 16 is set to move from the fully closed position to the fully open position by operating from the O step to the 100th step.

In addition, 18 is 1Q on the one flow side of the three-way catalytic converter 19.
71 exhaust'! ? This is the 02 sensor 18 provided on the 20. This 02 sensor 18 outputs a Low level voltage when the air-fuel ratio of the air-fuel mixture is leaner than the conversion point that exists near the stoichiometric air-fuel ratio and the concentration of Ml and I in the exhaust gas is high. When the air-fuel ratio of the air-fuel mixture is richer than the conversion point F and the oxygen concentration in the exhaust gas is low, the old level voltage is output.

Reference numeral 21 denotes a microcomputer system which serves as the foot control means A and the flow rate control valve holding means B. This microcomputer system 21 includes a central processing bag 2122, a memory 23, and interfaces 24 and 25. The input side interface 24 receives at least a signal from the throttle opening sensor 6 that informs the opening of the primary throttle 7 torque/help 4, a signal from the 02 sensor 18, a signal from the water temperature sensor 26, and a signal from the idle switch 27. The signal J is inputted and fed back from the output side interface 25 to the stepper motor 17; the υ control signal and a signal indicating that the flow rate control valve 13 should be temporarily held at a predetermined position are outputted. It has become. The water temperature sensor 26 is for detecting the engine cooling water temperature, and the water temperature sensor 26 is used to detect the engine cooling water temperature.
The idle switch 27 includes a thermistor (not shown) that converts the output of the thermistor into a digital signal, and an A/D converter (not shown) that converts the output of the thermistor into a digital signal. An ON switch that is ON only when the primary throttle valve 4 has returned to the closed position.
It is an FF switch.

Then, the microcomputer system 21 is a third
It is programmed to operate according to the steps schematically shown in the figure.

First, in step O, 7 lag l is cleared, and the increment counter CM↑ is set to an initial value exceeding 0.48 sec, and the process proceeds to step 50.

In step 50, the signal from the throttle opening sensor 6, the signal from the 02 sensor 18, the signal from the water temperature sensor 26, the signal from the idle switch 27, etc. are input, and the process proceeds to step 51.Step 511? is the primary slow/low speed detected by the throttle opening sensor 6.
It is determined whether the opening degree VTA of the torque valve 4 is less than 45°, and if it is less than 45″, the process proceeds to step 55.
Flag 2 is cleared to indicate that the secondary throttle valve 5 is open, but if it is determined that the angle is 45° or more, the process proceeds to step 52. In step 52, the flag 2 is set. If it is set, the process goes directly to step 56, and if it is not set, the process goes to step 53. In step 53, the increment counter GMT is cleared to start time measurement from zero, and the process goes to step 2. In step 54, the flag 2 is set to 1, and the process advances to step 56. In step 56, it is determined whether the time value of the increment counter CN is less than 0.483+IIC, and if it is less than 0.48 sec, the process proceeds to step 58, where a display indicating that the flow rate control valve 13 should be held is displayed. Set 7 lugs 1 to make 0.
If it exceeds 48 seconds, clear the flag 1 in step 57 and proceed to step 59, step 5.
At step 9, it is determined whether or not the execution conditions for performing normal feedback control are met, and if they are met, the process proceeds to step 6o.

Here, the execution condition for normal feedback control is that "the engine cooling water temperature is 60"0 or higher."
, "the idle switch 27 is OFF", "the fuel is not being cut", and "the flow rate control valve 13
The condition is that "no high load control be carried out." Here, high load control means that when the primary throttle valve 4 exceeds a predetermined high load determination opening degree set to the opening side of 45 degrees, normal feedback control, which will be described later, is interrupted to reduce the flow rate. This refers to control to hold the speed control valve 13 at a predetermined rich side holding position.If it is determined that all of these conditions are satisfied and the process proceeds to step 60, the flag l is set here. Determine whether it is set or not.

If it has not been set, the process advances to step 61; if it has been set, the process advances to step 62. Step 6
1, normal feedback control is performed when the signal of the 02 sensor 18 is Low.
It is determined whether it is a w level signal (lean detection signal) or an old level signal (rich detection signal), and if it is a low level signal, the Rric control valve 13 is operated in the closing direction at a predetermined speed, When the signal from the 02 sensor 18 is the old level signal, the Mtμ control valve 13 is operated in the opening direction at a predetermined speed.

On the other hand, when proceeding to step 62, * trench control valve 1
3 is immediately stopped F and bolded at that position. Then, repeat the above steps while the engine is running.

With such a configuration, in the operating range where the opening degree of the primary throttle valve 4 is less than 45 degrees, the control shown in FIG. 3 proceeds in steps 5o→51→55→56→57. Therefore, if the conditions for executing the normal feedback control are satisfied, the procedure is further changed to steps 59->60-61->50, and the normal feedback control is executed. As a result, the flu
The EA control valve 13 repeats opening and closing operations at a predetermined speed, bringing the air-fuel ratio of the mixture supplied to the engine close to the stoichiometric air-fuel ratio! l
h. When the primary throttle valve 4 is opened from this state, this primary throttle valve 4
When the opening of the secondary throttle valve 5 reaches 45°,
3 begins to open, the control shown in FIG.
→ 52 → 53 → 54 → 56 → 58 → 59, and the increment counter CNT starts counting from zero, and the flag l and flag 2 are set to J(. Then, the normal feedback condition is satisfied. If so, the control further proceeds to steps 59-60-62.
At the 0th moment when the flow rate control valve 13 stops operating at that point +h, the control proceeds again from steps 5o to 51 to 52, but at that time flag 2 is set to 1. , the increment counter GMT is never cleared again, that is, when the mu control valve 13 is bolded to the -U specific position, 0.48 sec from that point
3, the control shown in FIG. 3 is performed in step 5o→
Since the flow progresses in the order of 51→52→56→58→59→6o→62→5o, the flow rate control valve 13 continues to be held at that position. Then, when 0.48 sec has elapsed, the control progresses from step 5o → 51 → 55 → 56 → 57 and the flag l is cleared. Therefore, if the normal feedback execution condition is satisfied, the above-mentioned normal Feedback control will be restarted (see Figure 4).

In this way, the air bleed passages 11.12 of the vaporizer
The flow rate-control valve 13 that opens and closes is controlled, but when the secondary throttle valve 5 starts operating, that is, when the opening degree of the primary throttle valve 4 is 4.
When the angle exceeds 5°, the flow control valve 13 is stopped at that position, and thereafter held at that position for 0.48 seconds.

As a result, it is possible to prevent a significant change in the opening degree of the flow control valve 13 when the secondary throttle valve 5 starts operating.5. Based on the delay in feedback control, excessive changes in the air-fuel ratio can be largely eliminated.

Therefore, sudden fluctuations in engine torque caused by changes in the air-fuel ratio when the secondary throttle valve 5 starts operating can be eliminated.

It is possible to effectively prevent unpleasant shocks from occurring in heavy vehicles.

In addition, in one or more embodiments, a case has been described in which the time point at which the secondary throttle valve starts operating is detected based on a signal from a throttle opening sensor that detects the opening degree of the primary throw and torque valves, but the present invention does not necessarily have to be implemented. Of course, it is not limited to such methods; for example, by measuring the magnitude of negative pressure for operating the secondary throttle valve or by directly mechanically detecting the movement of the secondary throttle valve, It may also be possible to detect the point in time when the secondary throttle valve begins to open.

Further, the time period for which the feedback control is stopped and the flow ψ control valve is held at a specific position is not limited to the above-mentioned A1, but can be modified in various ways without departing from the spirit of the present invention.

Effects of the Invention 1 Since the present invention has the configuration as described above, it is possible to prevent sudden fluctuations in engine torque caused by a delay in feedback M control that occurs immediately after the secondary throttle valve is opened. Therefore, it is possible to provide an air-fuel ratio control device for a carburetor that can effectively suppress unpleasant shocks occurring in a vehicle.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram for clearly explaining the present invention. 2 to 4124 show a first embodiment of the present invention, in which FIG. 2 is an explanatory diagram of the system, FIG. 3 is a flowchart diagram showing the control procedure, and FIG. 4 is an explanatory diagram of the operation. A... Feedback control stage B... Flow rate control valve holding pVit ■... Carburetor 4 - Primary throttle valve S - Secondary throttle valve 11.12 - Metalwork 7 Bleed passage 13... Flow rate Control valve 1B--Red 02 sensor 21--Microcomputer system I-Conflict Φ1
Air inflow path ■φ...Air inflow path of 7A2

Claims (1)

[Claims] A carburetor comprising a primary throttle valve installed in a first air inflow path and a secondary throttle valve installed in a second air inflow path and operates only when the primary throttle valve is opened by a predetermined value or more. The applied air-fuel ratio control device includes a flow control valve that opens and closes the air bleed passage of the carburetor, an O_2 sensor that detects the oxygen concentration in the exhaust gas, and the flow rate control based on the signal from the O_2 sensor. Feedback control means opens and closes a valve to control an air-fuel ratio of the mixture supplied to the engine to a set value, and when the secondary throttle valve starts operating, the feedback control is temporarily stopped and the flow rate control valve is set to the predetermined value. 1. An air-fuel ratio control device for a carburetor, comprising: a flow control valve holding means for holding a flow control valve.