JPS6198940A - Air/fuel ratio control of engine - Google Patents

Abstract

PURPOSE:To achieve highly accurate control, in economic air/fuel ratio control under light load operation, by calculating the theoretical air/fuel ratio which will be a referential level in economic air/fuel ratio control on the basis of average air/fuel ratio to be obtained when controlling under light load operating region with theoretical air/fuel ratio. CONSTITUTION:When controlling an air-bleed control valve 25 through a step motor 26 thus to control to an economic air/fuel ratio under light load operation, ECU59 will first decide whether the cooling water temperature has exceeded over predetermined level corresponding with completion of warming operation. Upon decision of YES, it is decided whether the car is operating under light load and if the answer of YES, it is decided whether it is within setting cooling water temperature after completion of warming to normal travel. Upon decision of YES, it is feedback controlled to theoretical air/fuel ratio while to learn the average level of moving position of step motor 26 and upon exceeding of said setting cooling water temperature, air/fuel ratio is controlled on the basis of the economic air/fuel ratio to be set on the basis of said average value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine air-fuel ratio control method for controlling the air-fuel ratio of an air-fuel mixture to an economical air-fuel ratio during light load operation of a vehicle.

(Prior Art) Conventionally, when controlling the air-fuel ratio of the air-fuel mixture at an economical air-fuel ratio during light load operation of a vehicle, the economic air-fuel ratio is determined by controlling the air-fuel ratio of the J-arp reed control valve when the engine is controlled at the stoichiometric air-fuel ratio. The actuator movement position is set as a reference, but in this case, the actuator movement position of the air bleed control valve corresponding to the stoichiometric air-fuel ratio [ ; The set value of the economic air-fuel ratio is also constant because it varies greatly depending on the medium load range and high zero load range, as well as due to changes in engine performance, variations in carburetor performance, etc. Therefore, in the case of Figure 2, if the economic air-fuel ratio is set by adding a certain constant to the stoichiometric air-fuel ratio in the high load range, the fuel f1 characteristics will not improve, but on the other hand, it will slightly improve the 1 load range. If the economic air-fuel ratio is set by adding a certain constant to the stoichiometric air-fuel ratio, although the hunched back characteristic is improved, there are drawbacks such as the air-fuel ratio being too lean and the engine stalling.

(Problems to be Solved by the Invention) The present invention makes the air-fuel ratio during light load operation of a vehicle an economical air-fuel ratio that is larger than the stoichiometric air-fuel ratio, and also changes the economic air-fuel ratio from changes over time and from variations in characteristics of the carburetor. The aim is to control with high precision without being influenced by

(Means for Solving the Problems) As shown in FIG. 1, the present invention controls the amount of bleed air by driving an actuator of an air bleed control valve based on signals from various sensors corresponding to engine operating conditions. When controlling the air-fuel ratio of the air-fuel mixture to an economical air-fuel ratio during light load operation of the vehicle, it is determined in step 801 whether the engine cooling water temperature has exceeded, for example, 60° C., which corresponds to the end of warm-up operation; If the temperature exceeds 60°C, it is determined in step SO2 whether the vehicle is operating under a light load or not, and when the vehicle is operating in a medium or high load range other than a light load range, the air-fuel mixture is adjusted to correspond to each load range in step S03. Feedback control is performed using the air-fuel ratio, and it is determined whether the engine is in a stable engine operating state from the end of warm-up operation in step SO4 to normal driving in a light load operating state, for example, whether the engine cooling water temperature is within 75 degrees Celsius. , within 75°C, the engine is feedback-controlled at the stoichiometric air-fuel ratio in step SO5, and the average value of the actuator movement position of the air bleed control valve 1 during light load operation in the middle of feedback control at the stoichiometric air-fuel ratio is calculated. and when the temperature exceeds 75°C, in step S06, the engine sets an economical air-fuel ratio during light load operation based on the average value of the learned actuator movement position, and controls the engine at the economical air-fuel ratio. In the air-fuel ratio control method.

<Embodiment> Next, the configuration of an embodiment of the present invention will be described with reference to FIGS. 3 to 6.

A throttle valve 4 that opens in response to the amount of depression of the accelerator pedal is attached to an intake passage 3 that supplies fuel from the carburetor 2 to the engine, and is biased in the valve closing direction by a spring (not shown). The valve closed position is determined by the actuator 7, in which the operating lever 6 fixed to @If 5 of the throttle valve 4 rotates the threaded rod 10 in the forward and reverse directions via the C motor 8 and the gear train 9, which is capable of reversible operation. The movement in the circumferential direction is determined by contact with the touch head 12 at the tip of the actuator 7 that moves the output l11111, which is fitted with a threaded rod 10 and screwed back and forth, in the circumferential direction, and the operation lever 6 for the touch head 12.
This contact is detected when the idle switch 15 is turned on due to the final gear 14 moving slightly backward together with the output shaft 11 against the biasing force of the spring 13, and the stroke end of the output shaft 110 is detected when the output shaft 110 reaches the top of the output shaft 11. is detected when the dog 16 contacts the lever 18 of the limit switch 17.

This carburetor 2 includes a main cut solenoid valve 22 for cutting the fuel J'F+ supply to the main nozzle 20 formed in the small bench lily 19 of the intake passage 3 at the non-jet 21 position, and A slow solenoid valve 24 for cutting the fuel supply to the squaw boat 23 formed near the throttle valve 4, and an air bleed control valve 25 for adjusting bleed air for the main and slow systems, in this case an electric actuator stepper. By rotating the nut body 27 forward and backward via the motor 26 and moving the needle valve 29 back and forth together with the threaded rod 28 whose movement in the circumferential direction is regulated, the air hole 3 is opened.
The air bleed control valve 25 adjusts the amount of bleed air supplied from 0 through each air passage 31.32 to the main system and slow fuel passage 33.34, etc. The auxiliary fuel pump 35 increases the amount of fuel supplied, in this case, the low 1 of the carburetor 2 by the reciprocating movement of the piston 39 via the plunger 1738 due to the on/off operation of the solenoid coil 36 and the biasing force of the spring 37. -Room 40
-H through the intake side check valve 41.
After suction into the cylinder chamber 42, the discharge side check valve 4
3 to an auxiliary fuel pump 35 that supplies the air to the intake passage 3 through an auxiliary nozzle 45 formed above the large venturi 44.

In the carburetor 2 configured in this way, the DC motor 8 of the actuator 7, each switch 15.17, each fuel cut solenoid valve 22.24, the stepper motor 26 of the air bleed control valve 25, and the auxiliary fuel A solenoid coil 36 of the pump 35, a throttle opening sensor 46 that is attached to the carburetor 2 and generates an output corresponding to the opening of the throttle valve 4, a water temperature sensor 47 that is attached to the water jacket of the engine, and an ignition coil. an engine speed sensor 48 such as the engine speed sensor 48, a vehicle speed sensor 49 that generates an output corresponding to the speed of the vehicle, an O2 sensor 50 that is attached to the exhaust passage and generates an output corresponding to the oxygen concentration, and a clutch off and neutral sensor. A clutch/neutral detection sensor 51 that changes the output when the side lamp is on, a side lamp switch 52 that generates an output when the side lamp is on, an economy/diagnosis lamp 53 that lights up during economy and diagnosis, an air conditioner switch 54, and a starter switch. 55, ignition key switch 56, and alternator control circuit 5
7 are connected to an electric control circuit 59 for engine control, commonly known as an ECU, in which power supply from a battery 58 is controlled on and off by an ignition key switch 56.

Next, FIG. 4 shows a specific example of five electric control circuits, in which the microcomputer CPU, which is controlled according to the program in the storage circuit ROM, receives the engine speed from the engine speed sensor 48 via the waveform shaper 60. In addition to inputting a pulse signal with a corresponding frequency, an analog signal corresponding to the engine cooling water temperature from the water temperature sensor 47 and an analog signal corresponding to the opening degree of the throttle valve 4 from the throttle level sensor 46 are input. The analog signal corresponding to the oxygen concentration from the sensor 50 is inputted via the input port 2 after being converted into a digital signal via the A/D converter 61, and the idle switch 15
On/off signals from the clutch/neutral detection switch 57, air conditioner switch 54, pulse output vehicle speed sensor 49, ignition key switch 56, starter switch 55, and side lamp switch 52 are sent via the input port 3. In addition, the output port 4 of the microcomputer CPU is supplied with the DC motor 8 of the actuator 7, the solenoid coil 36 of the auxiliary fuel pump 35, the main cut valve 22, and the slow cut valve 22 of the auxiliary fuel pump 35 through each drive circuit 65 to 6. In addition to being connected to the solenoid valve 24 and the alternator control circuit 57,
A stepper motor 26 of an air bleed control valve 25 is connected to the output port door 0 via a drive circuit 71.

Next, the operation of this embodiment will be explained.

In the engine control device configured as described above, in this case, in particular, the engine control device for an electronically controlled chokeless carburetor, the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled according to the flowchart shown in FIG.

That is, the actuator of the air bleed control valve 25 is controlled based on the signals from each scale sensor corresponding to the engine operating state, in this case, the bleed F 1B is controlled by the stepper motor 26 during light load operation of the vehicle. When controlling the air-fuel ratio of the air-fuel mixture to an economical air-fuel ratio, it is determined in step 101 whether the engine cooling water temperature has exceeded, for example, 60°C, which corresponds to the end of WAIR operation, and if it has exceeded 60°C, In step 102, it is determined whether or not the vehicle is in a light load operating state, and in step 103, when the vehicle is operating in a medium or high load range other than a light load range, the air-fuel mixture is adjusted to an air-fuel ratio corresponding to each load range, e.g. Feedback control is performed based on the fuel ratio, and it is determined whether or not the engine cooling water temperature is within an arbitrary set temperature, for example, 75°C, from the end of warm-up operation in step 104 to the first running in the light load operating state. death,
Within an arbitrary set temperature range, one engine is feedback-controlled at the stoichiometric air-fuel ratio in step 105, and
In step 106, the average value of the stepper motor 268 dynamic position of the air bleed control valve 25 during light load operation during feedback control at the stoichiometric air-fuel ratio is learned, and if the temperature exceeds an arbitrary set temperature range, in step 107 The economic air-fuel ratio during light load operation is set based on the learned average value of the movement position of the stepper motor 25. For example, as shown in FIG. 6, the economic air-fuel ratio is set by adding a constant α to the learned average value. At the same time, the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled using the economic air-fuel ratio.

In addition, in this example, the engine cooling water temperature was used to detect the stable engine operating state after the warm-up operation was completed.
It can also be detected at a certain time after the warm-up operation is completed.

(Effects of the Invention) The present invention controls the stoichiometric air-fuel ratio, which is a reference for economic air-fuel ratio control, when the air-fuel ratio of the air-fuel mixture is made to be an economical air-fuel ratio that is larger than the stoichiometric air-fuel ratio during light load operation of a vehicle. By increasing the average air-fuel ratio by 1m t' which is obtained when controlling the light-load operating range using the stoichiometric air-fuel ratio, the economic air-fuel ratio can be increased without being affected by changes over time, variations in carburetor characteristics, etc. This has the effect of stably controlling accuracy.

[Brief explanation of the drawing]

Fig. 1 is a flowchart clearly showing the method of the present invention, Fig. 2 is an air-fuel ratio characteristic diagram of a carburetor, Fig. 3 is an explanatory diagram of an embodiment of the present invention, Fig. 4 is an electric circuit diagram thereof, and Fig. 4 is an electric circuit diagram thereof. FIG. 5 is a flowchart 1-diagram, and FIG. 6 is a diagram showing its operating characteristics. S01~806...Step

Claims (1)

[Claims] When controlling the air-fuel ratio of the air-fuel mixture to an economical air-fuel ratio during light load operation of the vehicle by controlling the amount of bleed air by driving the actuator of the air bleed control valve based on signals from various sensors corresponding to the engine operating state, After the machine operation is completed, the engine is feedback-controlled at the stoichiometric air-fuel ratio, and the average value of the actuator movement position of the air bleed control valve during light-load operation during feedback control at the stoichiometric air-fuel ratio is learned, and the learned actuator is The present invention is characterized by setting an economic air-fuel ratio during light load operation based on the average value of the moving positions, and controlling the engine at the economic air-fuel ratio during light load operation after setting the economic air-fuel ratio. Engine air-fuel ratio control method.