JPS5825527A - Control method of fuel cut at deceleration of engine - Google Patents

Abstract

PURPOSE:To avoid an engine stall, by cutting fuel for improvement of fuel consumption and the like through the captioned control device and forming said control device inoperative if rotary speed of an engine decreases exceeding a prescribed reduction rate. CONSTITUTION:In steps 1-4, if a decision is performed for throttle valve to be fully closed further speed of an engine higher than a prescribed value, fuel is cut in a step 5. Then in steps 6, 7, when a revolution period difference DELTAT of the engine is larger than a prescribed value alpha, that is, if a reduction rate of engine speed is decided at least a prescribed value, a fuel cut is stopped in a step 11. Further for the revolution period difference DELTAT smaller than the prescribed value alpha, when speed N is decided lower than a prescribed value B in a step 10, the fuel cut is stopped in the step 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cut control method during deceleration of an engine used in a vehicle such as an automobile.

In recent automobile engines, a so-called fuel cut is generally performed to stop the supply of fuel to the engine during deceleration operation to prevent HC and improve fuel efficiency. This is performed when the system throttle valve is in the fully closed position W (idling open position) and the engine speed is above a predetermined value, that is, the fuel cut return speed, and the engine speed is the fuel cut l1lfllj@
The process ends when the engine speed drops below the engine speed, and fuel supply to the engine is restarted at this time. The fuel cut during deceleration operation has a wide range of fuel cut rotation speeds, in other words, fuel cut I [low scavenging rotation speed is particularly effective for improving fuel efficiency; It is desirable that the cut return rotation speed be set small. but,
If this fuel cut return rotation speed is made too small, there is a risk that the engine speed will drop below the idle rotation speed due to the engine's inherent response delay when fuel supply is resumed after the end of fuel cut during deceleration, and the engine may stall. . This stall tends to occur when the engine load increases due to the cooler compressor operating during fuel cut, or when the rate of decrease in engine speed becomes large, such as when the clutch is disengaged. In order to avoid this, the fuel cut return rotation speed cannot be made too small. Furthermore, in order to set the fuel cut return rotation speed to a small value, it has been considered to detect the operating state of engine auxiliary equipment and the clutch operation, and control the fuel cut return rotation speed accordingly. However, this requires many sensors, complicates the control device, and reduces reliability of control.

The present invention provides a fuel cut control method during deceleration of an engine that effectively cuts fuel in reducing harmful exhaust gas and fuel consumption during deceleration operation without causing engine stall using only sensors originally required for fuel cut control. is intended to provide.

According to the present invention, this purpose is to stop the supply of fuel to the engine when the engine is operating at a deceleration speed, and to prevent the engine speed from decreasing beyond a predetermined value when the fuel supply is stopped, and the engine speed from decreasing to a predetermined value. This is achieved by a fuel cut control method during deceleration of an engine, which is characterized in that the fuel supply to the engine is restarted when at least one of the following occurs.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of a fuel injection type engine in which a method for cutting fuel during deceleration according to the present invention is implemented. In the figure, 1 indicates the engine,
The engine 1 has a cylinder valve 2 and a cylinder head 3.
The cylinder block 2 receives a piston 4 in a cylinder bore formed therein, and a cylinder 11 is provided above the piston 4 in cooperation with the cylinder head.
Grilling chamber 5 is defined.

An intake port 6 and an exhaust port 7 are formed in the cylinder head 3, and these ports are opened and closed by an intake pulp 8 and an exhaust pulp 9, respectively. Further, a spark plug 19 is attached to the cylinder head 3. The spark plug 19 is supplied with current generated by an ignition coil (not shown) via a distributor 27, and generates a spark in the combustion chamber 5 by discharge.

An intake manifold 11, a surge tank 12, a throttle body 13, an intake tube 14, an air flow meter 15, and an air cleaner 16 are connected in this order to the intake port 6, and these constitute an intake system of the engine.

A fuel injection valve 20 is attached near the connection end of the intake manifold 11 to the intake port 6. The fuel injection valve 20 is supplied with liquid fuel such as gasoline stored in a fuel tank 21 by a fuel pump 22 through a fuel supply pipe 23, and is controlled to open when the valve is opened by a pulse signal generated by a control device 50, which will be described later. The fuel injection amount is metered and controlled.

The throttle body 13 has a throttle valve 24 that controls the amount of intake air.
is adapted to be driven in response to depression of the accelerator pedal 25.

Further, the engine intake system is provided with an air bypass passage 1130 that bypasses the throttle body 13 and connects the intake tube 14 and the surge tank 12, and this air bypass passage 11.30 is equipped with an electromagnetic 5-bypass flow rate control The opening/closing and opening degree of the valve 31 are controlled, and the idle speed of the engine is mainly controlled.

The exhaust port 7 has an exhaust manifold 17 and an exhaust pipe 18.
are connected in order.

The control device 50 may be a microcomputer, an example of which is shown in FIG. This microcomputer includes a central processing unit (CPU) 51, a read-only memory (ROM) 52, a random access memory (RAM>53), and another random access memory (RAM) 54 that retains memory even after power is turned off. , an A/D converter 55 having a multiplexer, and an I10 device 56 having a buffer memory, which are interconnected by a common bus 57 .

The A/D converter 55 receives an air flow rate signal generated by the air 70 meter 15, an intake air temperature signal generated by the intake air temperature sensor 58 attached to the air 70 meter 15, and a water temperature sensor 59 attached to the cylinder block 2. It inputs the cooling water concentration signal generated by the CPU 51, converts the data into A/DI, and sends the data to the CPU 51 and the RAM 53 or 54 at a predetermined time according to instructions from the CPU 51.
It is designed to output to. In addition, the 110 equipment 56 is a rotation speed sensor 29 attached to the distributor 27.
The engine speed signal and crank angle signal generated by
A throttle fully closed signal generated by the throttle switch 60 attached to the throttle body 13 is input, and the data is sent to the CPU 51 at a predetermined time according to instructions.
It is configured to output to the PU 51 and RAM 53 or 54.

The CPU 51 calculates the fuel injection amount based on the data detected by each sensor according to the program stored in the ROM 52, and sends a pulse signal based on the fuel injection amount to the I10 unit H.
It is designed to output to the fuel injection valve 20 via 56. That is, the basic fuel amount is calculated based on the air flow rate detected by the CPU 51 line air 70 meter 15 and the engine rotation speed detected by the rotation speed sensor 29, and this is calculated based on the intake air temperature detected by the intake air temperature sensor 58 and the water temperature sensor 59. The fuel amount is corrected in accordance with the engine cooling water concentration detected by the sensor, and a pulse signal having a pulse width corresponding to the corrected fuel amount is generated.

Further, the CPU 51 calculates the amount of bypass air according to the intake air temperature detected by the intake air temperature sensor 58 and the water temperature detected by the water l+in sensor 59 according to the program stored in the ROM 52, and sends a signal corresponding to this. I10 device F
The bypass flow rate 1p is outputted to the JIll valve 31 via 56. Bypass flow control valve 31 is I10@
Its opening/closing and opening degree are controlled according to the bypass air amount signal given from ff56, and mainly controls the idle rotation speed of the engine.

Further, the CPU 51 operates the engine at a reduced speed according to the engine speed detected by the engine speed sensor 29, the throttle opening detected by the throttle switch 60, and the engine rotation period determined from the ignition signal of the engine ignition system. At times, the system controls a so-called fuel cut in which the supply of fuel to the engine is stopped. During the fuel cut period, the CPU 51 stops outputting the fuel injection signal to the fuel injection valve 20. As a result, the fuel injection valve 20 will not open during the fuel cut period.

Next, the manner in which the fuel cut control according to the present invention is implemented will be explained with reference to the flowchart shown in FIG.

In step 1, the data of the throttle signal from the throttle switch 60 and the engine rotational speed signal from the rotational speed sensor 29 are read.

In step 2, it is determined based on the throttle signal whether the throttle valve 24 is in the fully closed position.

When the throttle valve 24 is in the fully closed position, the process proceeds to step 3, and in this step, it is determined whether the fuel cut execution flag is 1 or not. When the fuel cut execution flag is F-1, deceleration operation is already being executed. If the fuel cut has not yet been executed at this time, the process proceeds to step 4, in which it is determined whether the engine speed N is greater than a predetermined value, for example 1300 rpm. be exposed. When N>A is not the case, the process returns to step 1, and when N>A is satisfied, the fuel cut conditions are met and the process proceeds to step 5. Fuel cuts will be implemented at five companies.

That is, at this time, the output of the fuel injection signal to the fuel injection valve 20 is stopped. As a result, the fuel injection valve 20 does not inject fuel, and the engine 1 is not supplied with fuel.

Next, the process advances to step 6, and in this step, the fuel cut execution flag F is set to 1. Next, in step 7, the engine rotation period Tn is measured based on the ignition signal. The rotation period Tn obtained by this measurement is
53.

Next, in step 8, the rotation period Tn calculated in the current control period is subtracted from the rotation period Tts calculated in the previous routine period, and a rotation period difference ΔT is calculated. Note that this rotation period difference ΔT is calculated based on the previous rotation period Tt in the first routine when the fuel cut is executed.
It is executed for the first time in the next routine cycle after the fuel cut is executed from 10- if there is no positive data. Next, in step 9, it is determined whether the rotation period difference ΔT is larger than a predetermined value α. The predetermined value α may be a constant value or may change depending on the cooling water temperature or the like. When the one-rotation period difference ΔT is larger than the predetermined value α, that is, when the rate of decrease in engine speed is greater than or equal to the predetermined value, the process proceeds to step 11, where the fuel cut is stopped and the fuel is immediately supplied to the engine 1. supply will be resumed. When the rotation period difference ΔT is not larger than the predetermined value α, that is, when the reduction rate of the engine rotation speed is less than or equal to the predetermined value, the process proceeds to step 10, and in this step, the engine rotation speed N is set to the predetermined value 8, For example 900
A determination is made as to whether it is smaller than rp-. This predetermined value B is the so-called fuel cut return rotation speed. When the engine speed N is smaller than the predetermined value B, the process proceeds to step 11;
The fuel cut is stopped, and the supply of fuel to the engine 1 is restarted.

If the engine speed N is greater than the predetermined value B in step 10, the process returns to step 1, and new data of the throttle signal and engine speed signal are read.

If it is determined in step 2 that the throttle valve 24 is not in the fully closed position, the process proceeds to step 12, in which it is determined whether the fuel cut execution flag F is 1 or not. -1, that is, when the fuel cut is not being executed, the process returns to step 1. On the other hand, when it is F-1, that is, when the fuel cut is being executed, the process proceeds to step 11, and in this step, the fuel cut is not executed. is stopped, and the supply of fuel to the engine 1 is restarted. Further, if τF-1 in step 3, the process advances to step 7. That is, when a fuel cut is being executed, this routine repeats the cycle of step 1 → step 2 → step 3 → step 7 → step 8 → step 9 → step 10 → step 1, and in step 2, the throttle valve 24 is closed. At least one of the following is determined: the engine is not in the fully closed position, the rotation period difference ΔT is greater than a predetermined value in step 9, and the engine rotation speed N is less than or equal to the fuel cut return rotation speed in step 10. At that time, fuel supply to the engine is resumed.

As described above, according to the present invention, even if the basic fuel cut conditions are met, the throttle valve is in the fully closed position and the engine speed is equal to or higher than the fuel cut return speed, the engine rotation period is reduced. When the amount of fuel, in other words, the rate of decrease in engine speed, decreases beyond a predetermined value, the fuel cut is immediately stopped and the supply of fuel to the engine is restarted. To stall is to be circulated.

It goes without saying that the fuel cut control method during deceleration according to the present invention can also be applied to a carburetor type engine.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a fuel injection type engine suitable for implementing the fuel cut control method during deceleration according to the present invention, and FIG. 2 is a block diagram showing one embodiment of an electronic control device. 3 is a flowchart showing the routine of 13- fuel cut control. 1...Engine, 2...Cylinder block, 3...
・Cylinder head, 4...piston, 5...ill
Chamber, 6... Intake port, 7... Exhaust port, 8...
・Intake pulp, 9... Exhaust pulp, 11... Intake manifold, 12... Surge tank, 13... Throttle body, 14... Intake tube, 15... Air 70 meter, 16... - Air cleaner, 17... Exhaust manifold, 18... Exhaust pipe, 20... Fuel injection valve, 21... Fuel tank, 22... Fuel pump,
23... Fuel supply pipe, 24... Throttle valve,
25... Accelerator pedal, 27-... Distributor, 29... Rotation speed sensor 1.30... Air bypass passage, 31... Bypass flow most control valve, 50...
Control device, 51... central processing unit (CPU)
, 52-IJ-dot > IJ memory lJ (ROM), -
53, 54...Random access memory (RAM),
55...A/D converter, 56...■10 device, 57
...Common bus, 58...Intake temperature sensor, 59...
・Water temperature sensor, 60-...Throttle switch 14-

Claims (1)

[Claims] Stops the supply of fuel to the engine when the engine is decelerating, and prevents the engine speed from decreasing beyond a predetermined value and the engine speed from decreasing beyond a predetermined rate when the fuel supply is stopped. A fuel cut control method during deceleration of an engine, characterized by restarting the supply of fuel to the engine when at least one of them occurs.