JPS6069245A - Fuel cut controlling method for electronically controlled engine - Google Patents

Abstract

PURPOSE:To prevent hunting of engine rotation, by raising the level of engine speed for starting fuel cut in case that an auto-drive mechanism is operated at the time of decelerating an engine when a throttle valve is closed completely and the engine speed is higher than the level of fuel cut starting engine speed. CONSTITUTION:An electronic control unit 56 judges the state that an idle switch 22 is ON and a throttle valve 20 is closed completely. In stopping fuel supply at the time of decelerating an engine when the engine speed detected by a crank- angle sensor 42 is higher than the level of fuel cut starting engine speed, the level of fuel cut starting engine speed is raised if an auto-drive switch 52 is ON and an actuator 54 for controlling an auto-drive mechanism is operated. With such an arrangement, it is enabled to prevent hunting of engine operation due to fuel cut control at the time of driving a vehicle on a long downhill using the auto-drive mechanism. Therefore, uncomfortable feeling of drive is not given to the driver and persons on the vehicle.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fuel cut control method for an electronically controlled engine, and is particularly suitable for use in an automatic small engine equipped with an electronically controlled fuel injection device. On the other hand, the present invention relates to an improvement in a fuel cut control method for an electronically controlled engine in which fuel supply is stopped during deceleration when the throttle valve is fully open and the engine speed exceeds the fuel cut speed.

[Prior Art 1] One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to combustion in an internal combustion engine such as an automobile engine uses an electronically controlled fuel injection device. This is achieved by arranging injectors for injecting fuel into the engine, for example, in several engine cylinders in the intake manifold of the engine, and by controlling the valve opening time of the injectors according to the operating state of the engine. , so that an air-fuel mixture with a predetermined air-fuel ratio is supplied to the engine for combustion. In this electronically controlled fuel injection system, the basic injection rate is normally determined according to the basic operating conditions of the engine, such as the engine load and engine speed detected from the engine intake air amount or intake pipe pressure. , determines the effective injection Q by adding various increases and decreases based on signals input from sensors installed in each part of the engine according to the engine status, etc.
It is designed to perform fuel injection. In addition, in order to reduce hydrocarbons in exhaust gas, improve fuel efficiency, and prevent catalyst heating due to reactions of unburned fuel within the catalyst, the throttle valve is fully open and the engine speed NE is set to a predetermined fuel level. During deceleration exceeding the cut rotation speed NFC, fuel injection is generally stopped to perform a so-called fuel cut. This fuel cut can be done by opening the throttle valve or
The fuel cut is continued until the engine speed NE becomes equal to or less than the predetermined fuel return speed NF1, and the fuel cut is stopped when the throttle valve is opened or when the engine speed NE becomes equal to or less than the fuel return speed NF1. Normally, fuel injection is restarted. In the fuel cut control as described above, during normal driving,
In order to improve exhaust gas purification performance and fuel efficiency by performing sufficient fuel cut frequently, since the fuel return rotation speed NFI is constant, the fuel cut rotation speed NFC and the fuel return rotation speed must be adjusted. Difference in NFI (NFC-NF
It is desirable to reduce the hysteresis NHYS represented by I)=N)-IYs. However, when driving with the constant speed driving mechanism (hereinafter referred to as auto drive mechanism) turned on, which automatically controls the opening of the throttle valve so that the vehicle speed remains constant during long descents when the throttle valve is closed, the vehicle speed may be reduced. In order to keep the speed constant, fuel cut and fuel supply were repeatedly performed during the run, and there was a risk that the engine rotation would hunt. [Object of the Invention] The present invention has been made to solve the above-mentioned conventional problems, and when traveling for a long descent using an auto drive mechanism,
An object of the present invention is to provide a fuel cut control method for an electronically controlled engine that does not cause hunting in engine rotation and therefore does not cause discomfort to vehicle occupants.

[Structure of the invention]

The present invention supplies fuel according to the engine operating state during normal times, but stops fuel supply during deceleration when the throttle valve is fully open and the engine speed exceeds the fuel cut speed 3-. In the fuel cut control method for an electronically controlled engine that is configured to stop, as shown in Figure 1, there are two steps: a procedure for detecting whether the autodrive mechanism is on, and a procedure for detecting whether the autodrive mechanism is on. If , the above objective has been achieved by including the step of increasing the fuel cut rotation speed.

[Action of the invention]

In the present invention, when the autodrive mechanism is on when stopping fuel supply during deceleration when the throttle valve is fully open and the engine speed exceeds the fuel cut speed, the above-mentioned Since the fuel cut-off rotation speed is increased, engine rotation hunting due to fuel cut control will not occur during long downhill travel using the autodrive mechanism.

[Example 1] Referring to the drawings below, an example of an automatic 4-car engine equipped with an intake air amount sensing type electronically controlled fuel injection device in which the fuel cut control method for an electronically controlled engine according to the present invention is adopted. will be explained in detail. As shown in FIG. 2, this embodiment includes an air flow meter 14 for detecting the flow rate of the intake air taken in by the air cleaner 12, and a built-in air flow meter 14 for detecting the temperature of the intake air. a throttle sensor 22 including an idle switch 22A for detecting the opening degree of a throttle valve 20 that rotates in conjunction with the accelerator pedal 18 and controls the flow rate of intake air;
The engine 1 is installed in an intake manifold 26 that distributes intake air flowing in through a surge tank 24 to each cylinder.
The injector 28 intermittently injects pressurized fuel supplied via the fuel tank 30, fuel pump 32, and fuel pipe 34 toward the intake boat of each cylinder of 0, and the ignition coil 36 generates pressurized fuel. Distributor 4 for distributing high voltage secondary ignition signals to the spark plugs 38 of each cylinder
A crank angle sensor 42 built in the engine 0 for detecting the crank angle of the engine 10 from the rotational state of the distributor shaft 40A, and a water temperature sensor 42 disposed in the cylinder block IOA of the engine 10 for detecting the engine cooling water temperature. A sensor 44, a battery 46, a vehicle speed sensor 50 for detecting the traveling speed of the heavy vehicle based on the rotational speed of the output shaft of the transmission 48, and an autodrive switch 52 for turning on and off the autodrive mechanism. , an auto drive control actuator 54 for controlling the opening degree of the throttle valve 20 in place of the driver during auto drive driving, and an intake air amount determined from the output of the air flow meter 12 and the output of the crank angle sensor 42. The basic injection Q4 amount is determined according to the engine rotational speed, and the effective injection amount is determined by correcting the basic injection amount Q4 according to the output of the throttle sensor 22, the output of the landing sensor 44, etc. A valve opening time signal is output to the injector 28 so that the throttle valve 20
is fully open and during deceleration when the engine speed exceeds the fuel cut speed, the valve opening time signal is set to zero to stop fuel supply, and the autodrive switch 52 is turned on. During automatic constant speed driving, the opening degree of the throttle valve 20 is controlled via the auto drive control actuator 54 so that the vehicle speed detected by the vehicle speed sensor 50 is constant, and an electronic control device that increases the fuel cut rotation speed is controlled. Control unit (hereinafter referred to as ECU) 5
It consists of 6. As shown in detail in FIG. 3, the ECU 36 includes a central processing unit (hereinafter referred to as CPU) 56A consisting of, for example, a microprocessor for performing various calculation processes, and a lead for storing control programs, various data, etc. Only memory (hereinafter referred to as ROM) 56B and CPL
A k-th random access memory (hereinafter referred to as RAM) 56 that temporarily stores calculation data etc. in I56A.
C, the air flow meter 14, the intake air temperature sensor 16,
Throttle sensor 22, water temperature sensor 44, battery 46
An analog-to-digital converter (hereinafter referred to as A/D: J converter) 56D, which performs a multiplexer function to convert analog signals input from etc. into digital signals and sequentially capture them, and the idler described in 7. switch 22A1 crank angle sensor 42,
The CPU 56 receives digital signals input from the vehicle speed sensor 50, auto drive switch 52, etc.
According to the calculation result of A, the injector 2 connects the input/output port (hereinafter referred to as I10 boat) 56F for outputting a control signal to the autodrive control actuator 54, etc., and each of the component devices. , and a "Monbus 56F" for transferring data and instructions. The action will be explained below. The fuel cut control in this embodiment is executed according to the flowchart shown in FIG. 4. That is, first step 11
0, it is determined whether the idle switch 22A is on. When the determination result is positive, that is, when it is determined that the throttle valve 20 is in the fully open state,
Proceeding to step 112, the fuel cut execution flag r FC
Determine whether LIT has already been set. If the judgment result is negative, proceed to step 14 and proceed to step 8.
- Determine whether or not the auto drive switch 52 is on. If the determination result is positive, step 116
Proceed to a first fuel cut rotation speed NFCI in which the engine rotation speed NE is higher than the normal fuel cut rotation speed NFC2.
(>NFC2). If the determination result is negative, this routine is skipped as is. On the other hand, if the determination result in step 114 is negative, the process proceeds to step 118, where the engine speed NE is set to the second fuel cut speed NF, which is the normal fuel cut speed.
It is determined whether or not it exceeds C2. If the determination result is negative, the routine exits directly. If the determination result in step 116 or 118 is positive, the process proceeds to step 120, sets the fuel cut execution flag r_FCLIT, causes the fuel cut to be performed, and exits from this routine. On the other hand, if the determination result in step 112 is positive,
That is, when it is determined that the fuel cut is already in progress, the process proceeds to step 122, and it is determined whether the engine rotational speed NE has become equal to or less than the fuel return rotational speed NF1. If the determination result is negative, the routine exits directly. Either the determination result in step 110 is negative and it is determined that the throttle valve is open, or the determination result in step 122 is positive and the engine speed NE is less than or equal to the fuel return rotation speed NF1. When it is determined that
Proceeding to step 124, the fuel cut execution flag f FC
Reset the UT and allow fuel injection to resume,
Exit this routine. In this embodiment, the fuel return rotational speed NFI is kept constant regardless of the on/off state of the autodrive switch 52, so control is simple. Note that it is possible to change not only the fuel cut rotation speed NFC but also the fuel return rotation speed NFI according to the on/off state of the autodrive switch 52. In the above embodiment, the present invention is applied to an automobile engine equipped with an intake air amount sensing type electronically controlled fuel injection device, but the scope of application of the present invention is not limited thereto. Automatic heavy-duty engines equipped with electronically controlled fuel injection systems, or equipped with fuel control systems such as carburetors, etc.
It is clear that the invention can be similarly applied to general electronically controlled engines. [Effects of the Invention] As explained above, according to the present invention, engine rotation does not hunt due to fuel cut control during long downhill driving using the autodrive mechanism, and therefore, it is possible to avoid causing discomfort to vehicle occupants. It has the excellent effect of not causing any damage.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the gist of the fuel cut control method for an electronically controlled engine according to the present invention, and FIG. 2 is a flowchart showing a method for controlling a fuel cut for an electronically controlled engine according to the present invention. A sectional view that does not show the configuration of the engine embodiment but includes a partial block diagram, Figure @3 is a block diagram showing the configuration of the electronic control unit used in the above embodiment, and Figure 4 is a 11 - Same (This is a flowchart showing the fuel cut control routine. NE...Engine speed, NFCl, NFC2...Fuel cut speed, 10...
・Engine, 14...1 Aflow meter, 20...
Throttle valve, 22A...Idle switch, 28.
... Injector, 42 ... Crank angle sensor, 5
0...Vehicle speed sensor, 52...Auto drive switch, 54...Auto drive control actuator, 56
...Electronic control unit (ECU). Agent Takaya Ron (and 1 other person) 12-

Claims (1)

[Claims] (1) Under normal conditions, fuel is supplied according to the engine operating state, but on the other hand, fuel supply is stopped during deceleration when the throttle valve is fully open and the engine speed exceeds the fuel cut speed. The fuel cut control method for an electronically controlled engine described above includes a step of detecting whether or not the auto drive mechanism is on, and a step of increasing the fuel cut rotation speed when the auto drive mechanism is on. A fuel cut control method for an electronically controlled engine, comprising: