JP3466781B2 - Air-fuel ratio control method for feedback carburetor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an air-fuel ratio of a feedback carburetor mainly applied to an automobile engine. 2. Description of the Related Art Conventionally, in an engine equipped with a feedback carburetor, when the opening of the throttle valve changes, the throttle valve is moved more slowly than in the steady state due to the delay in following the change in the amount of intake air. The air-fuel ratio tends to be lean in the opening direction and rich in the closing direction. In the feedback carburetor, by adjusting the opening degree of the flow control valve by an output signal from the O ₂ sensor (feedback control), but by adjusting the amount of intake air is intended to correct the deviation of the air-fuel ratio, During a transition, the air-fuel ratio may change so quickly that control may not follow. In such a situation, as an air-fuel ratio control method of this kind of feedback carburetor, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-49051, at the time of acceleration or deceleration, in response to an increase in the opening / closing speed of the throttle valve. There is known a feedback carburetor in which at least one of a skip amount and an integration constant in an integral signal with a skip for driving a flow control valve of a feedback carburetor is increased to always perform good air-fuel ratio control. . [0003] In the above-mentioned apparatus, although the skip amount is increased or the integral constant is increased, the air-fuel ratio is feedback-controlled by the increased control amount. However, the control does not follow the air-fuel ratio speed at the time of such a transition, and the control is delayed. That is, even if the skip amount or the integration constant is increased, the control speed is the same as that in the normal operation, and the required intake air amount can be set by increasing the control speed.
At the time when the control is executed according to the set skip amount and the integration constant, the actual air-fuel ratio is further changed, and even if the control is executed, the intake air amount is not sufficient, and a problem occurs. Specifically, the amount of intake air is not sufficient, so that emission may be deteriorated or drivability may be reduced. An object of the present invention is to solve such a problem. [0005] In order to achieve the object, the present invention takes the following measures. That is, the air-fuel ratio control method of the feedback carburetor according to the first aspect of the present invention is based on the output voltage of the O ₂ sensor for detecting the oxygen concentration in the exhaust gas. and adjusting the opening, a feedback carburetor air-fuel ratio control method for maintaining the air-fuel ratio of a mixture supplied to the combustion chamber of the engine to the stoichiometric air-fuel ratio near the throttle valve is opened and closed is
Speed by detecting the change rate of the load of the engine when it is, to set the opening degree of the flow control valve based on the speed of the detected changes, within a predetermined corresponding to the speed of change in the load time controls stretch flow control valve to set the opening, after the control
The predetermined period just before the flow control valve to the control in the same direction
It is characterized in that only the same control as that described above is prohibited. With such a configuration, when the load of the engine changes, the speed of the change in the load of the engine is reduced to the opening of the flow control valve set based on the change amount. The flow control valve is controlled all at once within a predetermined time.
That is, the flow control valve is continuously controlled at once without interruption within a predetermined time, and the amount of air supplied through the flow control valve is controlled at a control speed according to a change in load. . Therefore, even if the fuel does not increase or decrease following a change in the load, the air-fuel ratio is controlled near the stoichiometric air-fuel ratio because the amount of air supplied through the flow control valve is controlled. Will be possible. Therefore, deterioration of emission can be prevented, and reduction in drivability can be suppressed. Moreover, by controlling the flow control valve in this manner, it is possible to control the occurrence of a deviation in the air-fuel ratio due to the fuel flow rate tolerance of the feedback carburetor, and it is possible to increase the fuel flow rate tolerance, Performance can be improved. Further, after controlling the flow control valve, control of the flow control valve in the same direction as the above control is prohibited for a predetermined period set in accordance with the opening degree, so that the same control is repeated. It is possible to suppress the adverse effects of executing. In other words, if the control of the flow rate control valve at a time according to the change in load is repeated in the same control direction, that is, for example, in the control direction of making the air-fuel ratio rich, the opening degree is integrated and the air-fuel ratio is changed from the stoichiometric air-fuel ratio. Although there is a large deviation, the occurrence of such a phenomenon can be prevented by prohibiting the control for a predetermined period. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a feedback carburetor mounted on an intake manifold of an engine, 2 denotes a mixing chamber thereof, 3 denotes a main nozzle, 4 denotes a throttle valve, 5 denotes a float chamber, and 6 denotes an air bleed. , 7 are air bleed passages, and 8 is a flow control valve (Air Bleed Control Valve; ABCV). The flow control valve 8 is provided in the air bleed passage 7 which forms the starting portion of the air bleed 6, and has a suction port 8a open to the atmosphere. This flow control valve 8 is
The pointed valve element 9 is advanced and retracted with respect to the valve seat 10 to
The opening area of an air passage formed between the stepper motor 1 and the valve seat 10 is changed.
It is attached to the tip of one operating rod 12. And
The stepper motor 11 is controlled by the electronic control unit 16,
During the air-fuel ratio feedback control among the fully closed position (0 step) to the fully open position (100 step), the valve body 9 is moved forward and backward around a predetermined position set at a stoichiometric air-fuel ratio, for example, around 14.5. is there. On the other hand, an O ₂ sensor 15 is arranged on the upstream side of the three-way catalytic converter 13 provided in the exhaust system 14. The O ₂ sensor 15 generates only a low output voltage when the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio and the oxygen concentration in the exhaust gas is high. In some cases, it is configured to generate a high output voltage. Reference numeral 16 denotes an electronic control unit mainly composed of a microcomputer system for controlling the flow control valve 8, and includes a central processing unit (CPU) 17, a storage unit 18, an input interface 19, and an output unit. Interface 20. The input interface 19 is proportional to the engine speed that occurs terminal of the O ₂ sensor 15 voltage signal a output from the analog voltage signal b and the ignition coil 22 shows a throttle opening degree output from the throttle sensor 21 The pulse signal c and the like are input, and the opening control signal d and the like are output from the output interface 20 to the flow control valve 8. The microcomputer system 16 includes:
Using the voltage signal a output from the O ₂ sensor 15 and the analog voltage signal b output from the throttle sensor 21 as main information, the step of the stepper motor 11 that drives the valve element 9 of the flow control valve 8 is changed. In addition, a program for selecting and performing the air-fuel ratio feedback control in accordance with the operating condition of the engine so as to obtain the calculated air-fuel ratio is incorporated. This program is based on the output voltage of the O ₂ sensor 15 for detecting the oxygen concentration in the exhaust gas.
The air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is maintained close to the stoichiometric air-fuel ratio by adjusting the opening of the flow control valve 8 of the feedback carburetor 1. The amount of change in the engine load is detected and the detected change is detected. set the opening of the flow control valve 8 based on the amount, Yes and programmed to control the stretch flow control valve 8 to the opening set within a predetermined time corresponding to the rate of change of load, yet the The predetermined period after control
Only the flow control valve 8 is operated in the same direction as the above control.
Are a configuration to prohibit only be controlled to Flip. An outline of the flow rate correction control program is as shown in FIG. In addition, this program
This is executed during the air-fuel ratio feedback control. First, in step S1, the throttle opening, the amount of change in the throttle opening, and the opening / closing direction are detected from the analog voltage signal b output from the throttle sensor 21. The amount of change in the throttle opening is the speed at which the throttle valve 4 is opened and closed, and, for example, increases when the throttle valve 4 is closed instantaneously from the open state. In step S2, it is determined whether or not the amount of change in the throttle opening has changed beyond a predetermined range, and if there has been a change, the process proceeds to step S3.
If not, the process proceeds to step S9. Regarding the amount of change in the throttle opening, the throttle valve 4 is controlled so that normal feedback control is executed with a relatively small change.
Is set to a predetermined range that does not respond to the change of the value, that is, a dead zone. The dead zone only needs to be able to detect the amount of change during rapid acceleration and deceleration, and may be set to a range that includes the amount of change during slow acceleration and deceleration. In step S3, the opening of the flow control valve 8 is set based on the detected change in the throttle opening. In step S4, a predetermined time for controlling the flow control valve 8 at a stroke until the opening of the flow control valve 8 is set based on the change amount is set. In step S5, the control direction of the flow control valve 8 is set based on the detected opening / closing direction of the throttle valve 4. In step S6, the flow control valve 8 is controlled based on the set opening degree, the predetermined time, and the opening / closing direction. Usually, the predetermined time is set to a very short time, for example, a period in which the change in the throttle opening when the throttle valve 4 is operated at that time exceeds the dead zone, and the flow control valve 8 is opened or closed in a substantially step-like manner. This control is hereinafter referred to as pseudo skip control. In step S7, a subsequent control prohibition period is set together with the control prohibition direction based on the control amount of the flow control valve 8. The control prohibition period is set, for example, to a period corresponding to the time required when the executed pseudo skip control is executed by the normal feedback control, and the control prohibition direction is in the same direction as the control direction of the executed pseudo skip control, that is, open. If it is the direction, it may be set to the direction of the opening control. In step S8, the control in the set prohibition direction is prohibited for the control prohibition period, and the pseudo skip control in the direction opposite to the prohibition direction is executed if the condition is satisfied. In step S9, normal feedback control is performed. In such a configuration, as shown in FIG. 3, for example, when the vehicle is running on a mountain road or the like and the engine load changes frequently due to uphill and downhill, that is, throttle opening is performed during feedback control. An operation state in which the degree is periodically opened and closed will be described. First, when the throttle valve 4 is rapidly opened by approaching an uphill, the throttle opening increases in the opening direction,
The change in the throttle opening changes beyond the dead zone. In this case, the control is performed in steps S1 → S2 → S3 → S
The flow proceeds from 4 to S5 to S6, and the pseudo skip control is performed so that the flow control valve 8 has the set throttle opening within a predetermined time. As a result, the flow control valve 8 is closed at a stretch, and the supply of the intake air amount via the air bleed passage 7 is limited to an amount corresponding to the load at that time, that is, a change in the throttle opening. Therefore, even if the throttle valve 4 is opened rapidly, the amount of air supplied from the flow control valve 8 is limited at once, so that the air-fuel ratio does not become lean due to the delay in following the fuel. Thereafter, the control proceeds from step S7 to step S8, in which the pseudo skip control of the flow control valve 8 in the closing direction is prohibited, and the pseudo skip control in the opening direction is enabled. That is, when the throttle opening change is within the range of the dead zone, control is performed in steps S1 → S2 →
S9 and proceeds, by controlling the flow rate control valve 8 based on the output voltage of the O ₂ sensor 15, the feedback control is performed so as to hold the air-fuel ratio to the stoichiometric air-fuel ratio near. On the other hand, when the throttle valve 4 is further opened, even if the change in the throttle opening exceeds the dead zone, the pseudo skip control is not executed within the control prohibition period. Conversely, when the throttle valve 4 is closed, the pseudo skip control is executed even during the control prohibition period as described below. Therefore, since the pseudo skip control is not continuously performed in the same control direction, a problem that the air-fuel ratio deviates greatly from the stoichiometric air-fuel ratio does not occur. In the control prohibition period for prohibiting the pseudo skip control in the closing direction, for example, when the vehicle goes downhill and the throttle valve 4 is closed instantaneously, the control is performed as follows.
Steps S1 to S8 are executed, and the flow control valve 8 is opened to maintain the air-fuel ratio near the stoichiometric air-fuel ratio by the pseudo skip control, as in the case of the uphill. At this time, the fuel is supplied in an amount corresponding to the state in which the throttle valve 4 has been opened due to the slow response, but the air-fuel ratio changes to the rich side by opening the flow control valve 8 at a stretch. Can be prevented. On the other hand, immediately after that, a control prohibition period for prohibiting the pseudo skip control in the opening direction is set, the pseudo skip control in the closing direction is set in a controllable state, and the control is continued until a change in the throttle opening is detected. Step S1 →
The feedback control is performed by executing S2 → S9. As described above, when the throttle valve 4 is opened and closed and the change in the throttle opening changes beyond the range of the dead zone, the flow control valve 8 is pseudo-skip-controlled according to the degree of the change. To supply the required amount of air to the main nozzle 3 through the air bleed passage 7.
In other words, when the throttle valve 4 is opened beyond the dead zone, the flow control valve 8 is closed at a stretch to limit the amount of air to be supplied, and conversely, when the throttle valve 4 is closed,
The flow control valve 8 is opened at a stretch to supply a large amount of air to the main nozzle 3. As a result, the amount of intake air is controlled in accordance with the change in load, and a change in the air-fuel ratio resulting from a fuel delay corresponding to a load change during a transition can be suppressed. In addition, since the pseudo skip control in the same direction as the control is prohibited for a predetermined period immediately after the pseudo skip control is performed, the pseudo skip control is prohibited even if the throttle opening change continuously occurs in the same direction. During this time, normal feedback control is performed, and the opening of the flow control valve 8 is prohibited from unilaterally increasing in the opening or closing direction. Therefore, it is possible to prevent the air-fuel ratio from being deviated to one of the rich side and the lean side and greatly deviating from the stoichiometric air-fuel ratio, thereby deteriorating the emission and drivability. The present invention is not limited to the embodiment described above. In the above-described embodiment, a pseudo skip prohibition period is provided in both the opening and closing directions of the flow control valve 8, but, for example, as shown in FIG. The control prohibition period may be set such that the pseudo skip control is prohibited only when the state is closed. As described above, when the control prohibition period is provided only in one direction, as shown by the arrow A in the figure, the pseudo-skip control is not performed for the throttle opening change that occurs during the control prohibition period, so that the air-fuel ratio changes. However, the change does not adversely affect the operation state because the change is made in the opposite direction to that at the time. In addition, the configuration of each section is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention. According to the present invention, as described in detail above, when the load of the engine changes, the load of the engine changes up to the opening of the flow control valve set based on the change amount. Since the flow control valve is controlled at a stroke within a predetermined time corresponding to the speed of the fuel, the amount of air supplied through the flow control valve is controlled even if the fuel does not increase or decrease following a change in load. Therefore, the air-fuel ratio can be maintained near the stoichiometric air-fuel ratio. Therefore, deterioration of emission can be prevented, and reduction in drivability can be suppressed. Moreover, by controlling the flow control valve in this way, it is possible to control the occurrence of a deviation in the air-fuel ratio due to the fuel flow tolerance of the feedback carburetor,
The fuel flow tolerance can be increased, and the productivity can be improved. Further, after controlling the flow control valve, the control of the flow control valve in the same direction as the above control is prohibited for a predetermined period set in accordance with the opening, so that the same control is repeated. The adverse effects of the execution can be suppressed. In other words, if the control of the flow rate control valve at a time according to the change in load is repeated in the same control direction, that is, for example, in the control direction of making the air-fuel ratio rich, the opening degree is integrated and the air-fuel ratio is changed from the stoichiometric air-fuel ratio. Although there is a large deviation, the occurrence of such a phenomenon can be prevented by prohibiting the control for a predetermined period.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory view schematically showing one embodiment of the present invention. FIG. 2 is a flowchart schematically showing a control procedure of the embodiment. FIG. 3 is an operation explanatory view of the embodiment. FIG. 4 is an operation explanatory view of another embodiment. [Sign Description] 1 ... feedback carburetor 4 ... throttle valve 8 ... flow control valve 14 ... exhaust system 15 ... O ₂ sensor 16 ... electronic control device 17 ... central processing unit 18 ... memory 19 ... input interface 20 ... output interface 21 … Throttle sensor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Fukami 2-1-1 Taoyuan, Ikeda-shi, Osaka Die Inside Hatsugyo Co., Ltd. (72) Inventor Tsutomu Kawamura 2-1-1 Taoyuan, Ikeda-shi, Osaka Die (56) References JP-A-5-215012 (JP, A) JP-A-2-42166 (JP, A) JP-A-2-191856 (JP, A) JP-A-62-17351 ( JP, A) JP-A-59-170450 (JP, A) JP-A-56-148644 (JP, A) JP-A-63-309757 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) F02M 7/12

Claims (1)

(57) [Claim 1] An opening degree of a flow control valve of a feedback carburetor is adjusted based on an output voltage of an O ₂ sensor for detecting an oxygen concentration in exhaust gas, and a combustion chamber of an engine is provided. the air-fuel ratio of a mixture supplied to a air-fuel ratio control method for feedback carburetor to keep the stoichiometric air-fuel ratio near to detect the speed of change in the load of the engine by the speed at which the throttle valve is opened and closed, based on the speed of the detected change and set the opening of the flow control valve to control the stretch flow control valve to the opening degree set within a predetermined time corresponding to the speed of change of the load, said after the control Controls the flow control valve for a predetermined period
Only the same control as above in the same direction is prohibited
A method for controlling an air-fuel ratio of a feedback carburetor.