JPH059622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fuel cut control method for an internal combustion engine, and in particular, in a vehicle engine, when the engine rotation speed during deceleration when the throttle valve is fully closed is the fuel cut. The present invention relates to a fuel cut control method for an internal combustion engine that stops the supply of fuel to the engine when the rotational speed exceeds an effective rotational speed.

[Prior art]

In order to save fuel in vehicle engines such as automobiles, when the engine rotation speed during deceleration when the throttle valve is fully closed reaches the fuel cut effective rotation speed or more, fuel is supplied to the engine. A fuel cut that stops has traditionally been used. The fuel cut execution speed at which the fuel cut is started is determined based on engine water temperature, etc., so that the engine operating state after the fuel cut is compatible with the operating state taking into account fuel consumption, drivability, etc.

By the way, if the fuel cut is left in a state during deceleration, engine stall will occur, so a fuel cut return rotation speed is determined to stop the fuel cut and suppress the engine stall after the fuel cut. Therefore, in conventional engines, when the engine speed reaches or exceeds the fuel cut execution speed, a fuel cut is performed to suppress fuel consumption, and after the fuel cut, when the engine speed drops to the fuel cut return speed, Control was in place to prevent the engine from stalling by stopping the fuel cut. However, the idle speed may change depending on the age of the engine, the state of use of the engine, etc. For example, in an engine that is not equipped with an idle speed control valve, deposits may accumulate in the bypass passage that determines the idle speed, blocking the passage and causing the engine speed to drop. Additionally, new car engines have large friction and are able to maintain a certain idle speed, but as the mileage increases, engines whose friction decreases will have an increased idle speed due to a decrease in frictional resistance. Furthermore, even in engines equipped with an idle speed control valve, the amount of intake air may increase due to aging of the throttle valve or throttle link, or due to foreign matter getting stuck in the throttle valve, causing the idle speed to rise. , the idle speed may decrease due to an increase in electrical load. Therefore, in engines to which the conventional fuel cut control method is applied, if the fuel cut return rotation speed is set to a too low rotation speed, engine stall may occur if the idle rotation speed is low, or the idle rotation speed may change over time. Taking this into consideration, the fuel cut return rotational speed was set to a somewhat high value. Therefore, conventional methods have not been able to achieve sufficient fuel savings.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an internal combustion engine that can sufficiently save fuel by using a fuel cut that is adapted to the operating condition of the engine without causing engine stall. An object of the present invention is to provide a fuel cut control method for an engine.

[Summary of the invention]

In order to achieve the above object, the present invention starts fuel cut when the throttle valve is fully closed and the engine speed is equal to or higher than the fuel cut execution speed, and when the throttle valve is fully closed and the fuel cut is started. In a fuel cut control method for an internal combustion engine that stops a fuel cut when the subsequent rotation speed decreases below a fuel cut return rotation speed, the rotation speed at an idle time is detected, and the higher the rotation speed at the idle time, the higher the fuel cut return rotation speed. It is characterized by setting the speed low.

[Embodiments of the invention]

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

In FIG. 1, the intake system of an engine 18, which is composed of an intake tube 10, a throttle body 12, a surge tank 14, an intake manifold 16, etc., includes an air flow meter 20, a throttle valve 22, a throttle switch 24, and an injector 2.
6 etc. are provided. Air taken in from the air cleaner 28 is supplied to the intake manifold 16 via the air flow meter 20 and throttle valve 22, and mixed with fuel injected from the injector 26 via the fuel tank 30, fuel pump 32, and fuel supply pipe 34. do. The air-fuel mixture is supplied to the combustion chamber 38 via the intake valve 36, and is then fed to the cylinder head 4.
The fuel is combusted by a spark plug 42 installed at the engine 0, and is discharged to the exhaust system via an exhaust valve 44. The amount of intake air supplied to the intake manifold 16 is controlled according to the opening degree of the throttle valve 22, which is activated in response to depression of the accelerator pedal 46.

Further, the cylinder block 48 is provided with a water temperature sensor 50 for detecting the engine cooling water temperature. Further, a rotation angle sensor 56 for detecting the rotation angle of the crankshaft 54 is built into a distributor 52 that distributes an ignition signal from an igniter (not shown) to each cylinder.

Detection outputs from an air flow meter 20 that detects the amount of intake air, a throttle switch 24 that detects when the throttle valve 22 is fully closed, a water temperature sensor 50, and a rotation angle sensor 56 are supplied to a control device 58.

In addition, the amount of bypass intake air that bypasses the throttle valve 22 in the intake system and is supplied to the surge tank 14 via a bypass pipe 60 that communicates between the upstream side of the throttle valve 22 and the surge tank 14 is It is controlled by a bypass flow control valve 62 provided in the tank 14. That is, this bypass flow control valve 62 is similar to the throttle valve 2.
2 is in a fully closed state at idle, the control device 5
Bypass flow control valve 6 in response to a control signal from 8
2 can be opened and closed to supply the amount of intake air required during idling to the intake manifold 16.

FIG. 2 shows a configuration in which a microcomputer is used as the control device 58.

In FIG. 2, the control device 58 includes a CPU 60,
ROM62, RAM64, 66, A/D converter 6
8, an I/O interface circuit 70, and each part is connected by a bus line 72.

The outputs of the air flow meter 20 and the water temperature sensor 50 are supplied to an A/D converter 68 having a multiplexer. Further, the detection outputs of the rotation angle sensor 56 and the throttle switch 24 are supplied to the I/O interface circuit 70, and the output of the I/O interface circuit 70 is supplied to the bypass flow control valve 62 and the injector 26. ing.

Note that the RAM 66 is configured to retain memory even after power supply is stopped.

The ROM 62 also stores various programs for processing based on the detection outputs of various sensors that detect various operating states of the engine, numerical data of fuel injection time according to the operating states of various engines, and fuel cut during idling. In order to adapt the engine to the idle operating state of the engine, map data is stored that determines the fuel cut execution rotational speed at which the fuel cut is started in relation to the engine water temperature.

The control device 58 configured in this manner controls the fuel injection time per process according to the intake air amount per engine process based on the detected outputs of the air flow meter 20 and the rotation angle sensor 56 at predetermined intervals, for example. The amount of fuel injected from the injector 26 can be controlled by repeatedly detecting it at every predetermined crank angle and supplying a pulse signal with a pulse width corresponding to the fuel injection time to the injector 26.

Further, when it is detected from the detection output of the throttle switch 24 that the throttle valve 22 is fully closed, the control device 58 controls the water temperature sensor 50.
The amount of bypass intake air is calculated according to the detection output output from the , and a control signal corresponding to this calculated value is supplied to the bypass flow rate control valve 62 via the I/O interface circuit 70 to control the amount of bypass intake air. can be controlled. This control determines the idle rotation speed.

The control device 58 also controls the throttle switch 24.
When it is detected by the detection output that the throttle valve 22 is in the fully closed state, and when it is detected by the detection output of the rotation angle sensor 56 that the engine rotation speed has become equal to or higher than the fuel cut execution rotation speed, the injector A so-called fuel cut control is performed in which the supply of a control signal to the injector 26 is stopped, and the injection of fuel from the injector 26 to the intake manifold 16 is stopped.

Further, in this embodiment, since three types of fuel cut return rotational speeds are determined, numerical data of each fuel cut return rotational speed is stored in the ROM 62.

The present embodiment has the above configuration, and its operation will be explained next.

The flowchart in FIG. 3 shows the processing routine of the control device 58 when the present invention is applied to the system shown in FIG.

In FIG. 3, first at step 100,
Based on the detection output of the throttle switch 24, it is determined whether the throttle valve 22 is fully closed. If the determination in this step is NO, the process moves to other processing, and if the determination is YES and the throttle valve 22 is in a fully closed state, the process moves to step 102. In step 102, the rotation angle sensor 56
The detected engine rotation speed is detected by the detection output of
It is determined whether NE is smaller than a set value A of engine rotational speed (for example, 1000 rpm) indicating an idle state. If the determination in this step is NO, the process moves to other processing, and if the determination is YES, the process moves to step 104, assuming that the throttle valve is fully closed and the engine rotational speed is at or below the set value A, idling.

In step 104, the engine rotational speed NE detected in step 102 is stored in register B of the RAM 64, and the process proceeds to step 106. In step 106, it is determined whether the engine speed stored in register B is greater than a set value C (eg, 800 rpm). YES in step 106
If it is determined that
Select the fuel cut return rotational speed X (for example, 850 rpm) stored in the ROM 62.

On the other hand, if the determination in step 106 is NO, the process moves to step 110, and the engine rotation speed stored in register B is set to set value D (for example, 700 rpm).
It is determined whether it is smaller than . If the answer is YES in this step, the process moves to step 112, where the fuel cut return rotational speed Y stored in the ROM 62 is selected, and when the answer is NO, the process moves to step 114, where the fuel cut return rotational speed Y stored in the ROM62 is selected. Z (for example
900rpm).

The magnitude relationship between the return rotational speeds X, Y, and Z selected in steps 108, 112, and 114 is Y>Z>X.

After any one of steps 108, 112, and 114 has been performed, the process moves to step 116, and when the throttle valve is fully closed and the engine rotational speed has exceeded the fuel cut execution rotational speed, A fuel cut is performed, and when the engine rotational speed after the fuel cut is reduced to the selected fuel cut return rotational speed, a control is performed to stop the fuel cut.

In other words, if the fuel cut return rotational speed that is allowed as the rotational speed that suppresses the engine stall after the fuel cutoff due to the stoppage of the fuel cutter is determined in three types, high, medium and low, in correspondence with the idle rotational speed before the fuel cutoff, the idle rotational speed before the fuel cutoff When the speed is in the high speed range, the low speed fuel cut return rotation speed X is selected, and when the idle rotation speed before the fuel cut is in the medium speed range, the medium speed side fuel cut return rotation speed Z is selected, When the speed is in the low speed range, the fuel cut return rotational speed Y on the high speed side is selected. Thereafter, control is performed to stop the fuel cut when the engine rotation speed after the fuel cut has decreased to the selected fuel cut return rotation speed.

As described above, in this embodiment, when the idle rotation speed is low, the fuel cut is stopped at a high fuel cut return rotation speed, and it is possible to prevent the engine from stalling that occurs immediately after the fuel cut is stopped. When the rotation speed is high, the fuel cut is stopped at a low fuel cut return rotation speed to suppress fuel consumption. That is, if the fuel cut return rotation speed is lowered when the rotation speed during idle is high, the rotation speed during fuel cut is high, so the fuel cut time can be lengthened without considering the occurrence of engine stall or reduction in drivability. This allows for improved fuel efficiency. For example, if the idle speed is
If the fuel cut return rotation speed is set low to about 1000 rpm when the fuel cut is about 600 rpm, even if fuel is injected after the fuel cut is stopped, the amount of fuel will be small, so there will not be enough combustion to generate the necessary torque at idle. engine stall may occur. However, if the idle rotation speed is high at around 800 rpm and the fuel cut return rotation speed is set as low as around 1000 rpm, the idle rotation speed will be low during fuel injection.
A larger amount of fuel and air is injected into the combustion chamber than at around 600 rpm, and sufficient torque is generated to suppress the occurrence of engine stall. Note that the air-fuel ratio at idle is constant at A/F 14.7, so the higher the idle speed, the greater the amount of air and fuel.

On the other hand, if the fuel cut return rotational speed is increased when the rotational speed during idle is low, the fuel cutter will stop at a high rotational speed, thereby preventing engine stall from occurring when the fuel cutter returns.

Furthermore, in the embodiment described above, three types of fuel cut return rotational speeds were described, but as long as there are two or more types of fuel cut return rotational speeds, the same operation as in the above embodiment can be performed.

Further, the fuel cut return rotational speed in the above embodiment is determined based on the average value of the idle rotational speeds before the fuel cutoff or the idle rotational speed at a predetermined time before the fuel cutoff.

〔Effect of the invention〕

As described above, according to the present invention, the fuel cut return rotation speed is lowered as the rotation speed during idling is higher, thereby improving fuel efficiency and preventing engine stall from occurring when the fuel cut is returned.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an engine to which the present invention is applied, FIG. 2 is a configuration diagram for explaining the configuration of the control device shown in FIG. 1, and FIG. 3 is a system configuration diagram of an engine to which the present invention is applied. This is a flow chart for explaining the effect when applied. 18... Engine, 20... Air flow meter,
22...throttle valve, 24...throttle switch, 26...injector, 56...rotation angle sensor, 58...control device, 62...bypass flow control valve.

Claims (1)

[Claims] 1. Fuel cut is started when the throttle valve is fully closed and the engine rotation speed is higher than the fuel cut execution rotation speed, and the throttle valve is fully closed and the rotation speed after the fuel cut is In a fuel cut control method for an internal combustion engine that stops the fuel cut when the rotation speed decreases below the fuel cut return rotation speed, the rotation speed at idle is detected, and the higher the rotation speed at idle, the lower the fuel cut return rotation speed is set. A fuel cut control method for an internal combustion engine, characterized in that: