JPS6388255A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To promote the improvement of the response characteristic and the improvement of fuel consumption, by simultaneously controlling the air amount of an air bleed and the fuel amount of a control jet in a carburetor by a single valve and deciding the fixed speed running from the change rate of an engine speed performing a lean burn control. CONSTITUTION:A carburetor 1 provides a fuel passage 15, bypassing between a float chamber 5 and the side of a main air bleed 8 in a main fuel passage 6, and a control jet 16 halfway the passage 15. While the carburetor 1, in which an air passage 17 communicates with the downstream side of a slow jet 12 in a slow fuel passage 10, provides a control air bleed 18 halfway the passage 17. A valve unit 16a of the control jet 16 is connected to a valve unit 18a of the control air bleed 18 by a common rod 19, and one of these valve units is opened when the other is closed. While a lean burn control is performed by detecting the change rate of an engine speed to decide the time of fixed speed running. In this way, an engine enables the response characteristic of air-fuel ratio control to be enhanced further the fuel consumption to be reduced.

Description

[Detailed description of the invention]

[Fields of Application] The present invention relates to an air-fuel ratio control system that performs feedback control of a mixture air-fuel ratio using a signal from an Ox sensor in a vehicle internal combustion engine.
1! The device is specifically related to lean burn control under constant speed running conditions. This type of air-fuel ratio υ control device has a three-way catalyst in the engine's exhaust system, and determines whether the air-fuel ratio is lean or rich by detecting the 醇'lr and I1w degrees in the exhaust gas with the 01 sensor. Based on this, the air-fuel ratio of the air-fuel mixture generated in the carburetor is maintained near the stoichiometric air-fuel ratio, and purification by the three-way catalyst is effectively performed. On the other hand, feedback control of the air-fuel ratio in such a system is not performed under all engine operating conditions;
Until the sensor and catalyst are activated. It is canceled under certain conditions such as when cold or accelerating. In addition to satisfying the exhaust gas purification performance of the engine, it also aims to make the engine smoother and increase its output. Here, the above-mentioned correction target includes lean burn control to improve fuel efficiency, and the air-fuel ratio is clamped to the lean side under driving conditions such as constant speed.

[Conventional technology]

Conventionally, regarding the lean burn control at the air-fuel ratio υtill, there is a prior art, for example, in Japanese Patent Application Laid-Open No. 58-59324, which describes the overdrive of the transmission or the 4-speed control.
It is shown that the 5th gear position is detected, and as a result, the partial (1 load state) is determined and the air-fuel ratio is corrected to the lean side.

[Problems that the invention attempts to resolve]

By the way, in the above-mentioned conventional system, since the high speed gear lean burn control υ0 method is used, the engine becomes lean not only at a constant speed but also when accelerating in the high speed gear, which tends to cause an output shortage. In addition, in the case of an injector system such as the prior art, the fuel flow rate can be greatly changed by the injector, but in the case of a carburetor, the negative pressure etc. are used as a target, so the small change can be made large. difficult and lacks responsiveness. Therefore, the air-fuel ratio control system of the carburetor is desired to have a configuration that changes the fuel flow rate with good response when lean or ridge t control or t control is released. The present invention has been made in view of these points, and is designed to make the air-fuel ratio control system of the carburetor highly responsive, and to perform lean burn control by accurately determining constant speed running conditions. The purpose of the present invention is to provide an air-fuel ratio device for internal combustion with a -111III ratio.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a control jet for replenishing the fuel system of a carburetor and a control air bleed for replenishing air. The system is configured to feedback-control the air-fuel ratio by changing the air supply so as to reduce one side and increase the other, and to perform lean burn control by determining constant speed running based on the rate of change in engine speed. There is. [Operation] Based on the above configuration, acceleration and constant speed are determined based on the rate of change of the engine U rotation speed, and feedback control is performed during acceleration, etc., and lean burn control is performed during constant speed, etc. During such control, the air-fuel ratio can be quickly and accurately controlled by simultaneously changing the supply of fuel and air in the carburetor. In this manner, the present invention makes it possible to effectively improve fuel efficiency by performing lean burn control during constant speed with little deterioration in running performance. [Examples] Examples of the present invention will be explained below based on the drawings.

[IJl. In FIG. 1, a carburetor and its air-fuel ratio 11w system will be explained. Reference numeral 1 denotes a carburetor main body, which has a venturi 3 upstream of a primary air-fuel mixture passage 2 and a throttle valve 4 downstream. A main fuel passage G from the bottom of the float chamber 5 has a main jet 7 and communicates with a main air bleed 8 , and a main nozzle 9 communicates with the venturi 3 from the main air bleed 8 . A slow fuel passage 10 branching from the middle of the main fuel passage 6 has a slow jet 12 equipped with a slow air bleed 11, and the slow fuel passage 10 further includes a bypass port 13J3 immediately upstream of the throttle valve fully open position and an idle downstream thereof. The float chamber 5 and main fuel passage 6 serve as a 1° air-fuel ratio control system that communicates with the boat 14 and sucks out fuel while warming air in the main and slow systems.
A fuel passage 15 is provided in a bypass manner between the main air bleed 8 side and the main air bleed 8 side, and a control jet 16 is installed in the middle of this fuel passage 15. Further, an air passage 17 communicates with the slow fuel passage 10 on the downstream side of the slow jet 12.
A control air bleed 18 is installed in the middle of this air passage 17. The valve body 16a of the control jet 16 and the valve body 18a of the control air bleed 18 are connected to a common rod 19, and when the solenoid 20 is turned on and off, one of the control jet 1G and the control air bleed 18 is closed and the other is opened. It has become. Here, for example, when the solenoid 20 is turned off, the rod 19 is moved in the -F direction by spring force, the control F bleed 18 is released, and the IT, II control register 16 is opened.
Reduce air and increase fuel to make it richer. on the other hand,
When the solenoid 20 is turned on, it conversely increases the amount of air and decreases the amount of fuel to make it lean, and as a result, the larger the on-duty ratio of the solenoid 20 is, the leaner the air-fuel ratio is set. On the other hand, a three-way catalyst 22 is installed in the exhaust system of the engine body 21, and a 1Δ
Enter 4. In addition, the engine rotation speed from the ignition coil 25, water temperature signals from the water temperature sensor 26, etc. are input to the control unit 24, and the II + control unit 24 UDI signal is input to the solenoid 20. It has become. In FIG. 2, to explain the control unit 24, the air-fuel ratio determination section 3 receives the signal from the Ot sensor 23.
0, and determines whether it is hot or thin from the stoichiometric air-fuel ratio based on the sensor signal and slice level, and based on this, PIe@
The generator 31 generates a PI times signal. This Pl;Q is input to the pulse width converter 32 and is compared with a triangular wave to output a duty signal.In this way, if the air-fuel ratio is narrower than the stoichiometric air-fuel ratio, a lean signal with a larger duty ratio is output, and if it is thinner, a lean signal is output. It becomes a rich signal with a small duty ratio. This duty signal is input to the solenoid 20 via the drive unit 33, forming an air-fuel ratio feedback control system. On the other hand, when the water 1fMT from the water mL lancer 6 is inputted to the cold water supply section 34, it is determined that the water is cold when T<71 with respect to the set water temperature T1, and the fixed duty determination section 35 fixes the rich side. Determine the duty ratio D1. The water 1fiT from the water temperature sensor 26 and the engine rotational speed N from the ignition coil 25 are input to the heating/constant speed determining section 36. The engine speed @, N is input to the engine speed change rate calculation unit 37, and ΔN is calculated for the change rate ΔN1 at each shift position in FIG.
If ΔN1, it is determined that the rotation speed is constant. Then, the constant speed determination unit 36 determines that T>Tt for the set water temperature Tt and the set engine speed N1. When the IIQ machine is running with N>Nl and the rotation speed is the above-mentioned constant speed, a constant speed determination is made, and the fixed duty ratio D2 on the lean side is determined by the fixed duty setting section 38. The fixed duty ratios Dx and Dt are input to a duty clamp section 39 and clamped to these duties. Next, the operation of the air-fuel ratio control device configured as described above will be explained with reference to the flowchart of FIG. 4 and the characteristic diagram of FIG. 5. First, in the partial region where the throttle valve 4 is open for a predetermined period in the carburetor body 1, the fuel in the float chamber 5 passes through the main fuel passage 6, mixes air with the main air bleed 8, and creates a venturi negative pressure through the main nozzle 9. is sucked out. At the same time, the fuel passes through the slow fuel passage 10 and is mixed with air by the slow jet 12.
These fuels are mixed with air in the mixture passage 2 to produce a mixture. Therefore, when the duty ratio of the solenoid 20 is small in the fuel supply described above, there is a large amount of υ1 between the control jets 1G, and the fuel passage 15 supplies excess fuel. On the other hand, the opening rate of the control air bleed 18 is small, and the air supply through the air passage 17 is also reduced, thus making the air-fuel ratio rich. Conversely, when the duty ratio of the solenoid 20 is large, the air supply by the control air bleed 18 becomes greater than the fuel supply by the III control engine jet 16, making the air-fuel ratio lean. The air-fuel ratio changes with good responsiveness through control. On the other hand, when the engine is running, a signal from the 02 sensor 23 enters the control unit 24, and the air-fuel ratio setting section 30 generates a PI multiplication signal 31. The pulse width converter 32 outputs a lean or rich duty signal for rich and lean air-fuel ratios. Further, when the cool state determination section 34 determines the cold state based on the water temperature T, the fixed duty setting section 35 outputs a small fixed duty ratio D1, and the duty clamp section 39 inputs the duty ratio D1 to the solenoid 20. As a result, the air-fuel ratio is fixed in a rich state as shown in FIG. Next, warm I! 412 When N < N t, the rate of change in engine speed ΔN detected at fixed time intervals in the routine of FIG. A fixed duty ratio is not output from any of them. Therefore, the pulse width converter 32
The duty signal t2IIT is input to the solenoid 20, and as a result, the air-fuel ratio is feedback-controlled to near the stoichiometric air-fuel ratio t2IIT as shown in FIG. Further, in the case described above, when a constant speed is determined based on N>N1 and ΔN×ΔN1, a large fixed duty ratio D1 is output from the fixed decoute setting section 38, and this is input to the solenoid 20. Therefore, the air-fuel ratio is fixed at a lean state as shown in FIG. 5, resulting in lean burn. The above feedback, lean burn control, etc. are selected and performed for each driving condition. Note that the fixed air-fuel ratio in the case of constant speed may be changed depending on the engine rotation speed with emphasis on fuel efficiency or output. [Effects of the Invention] As described above, according to the present invention, the air-fuel ratio control system of the carburetor is configured to replenish fuel and air, and when one is decreased by the duty signal, the other is increased. Because of this, responsiveness is good during feedback control and when canceling and returning from feedback control. Since the lean burn control I is performed based on the rate of change in engine speed only at constant speeds where the deterioration of running performance is relatively small, fuel efficiency can be improved without sacrificing running performance. 1 with water temperature and engine speed signals! ! ! Easy to control.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the air-fuel ratio control device of the present invention. Fig. 1 is an overall configuration diagram. Fig. 2 is a block diagram of the control unit. Fig. 3 is a characteristic diagram showing the rate of change in engine speed. Fig. 4 (2),
Φ) is a flowchart diagram, and FIG. 5 is a characteristic diagram of the air-fuel ratio. 1... Carburetor body, 16... Control jet, 17.
...Control air bleed, 20...Solenoid, 23.
...O, sensor, 24...control unit, 36...
BJI machine constant speed determination section, 37... Engine speed change rate pruning section, 38... Fixed duty setting section, 30...
De'-tiklamp section. Patent applicant Fuji Heavy Industries Co., Ltd. Agent Patent attorney Jundo Kobashi Patent attorney Susumu Murai

Claims (1)

[Claims] A control jet for replenishing the fuel system of a carburetor and a control air bleed for replenishing air are provided, and the replenishment amounts of fuel and air are changed to decrease one and increase the other based on a duty signal. Feedback controls the air-fuel ratio and determines whether to drive at a constant speed based on the rate of change in engine speed.
Air-fuel ratio control device for internal combustion engines that controls lean burn.