JPH0544549B2 - - Google Patents

Description

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

The present invention relates to a fuel cut control method during deceleration of an electronically controlled engine, and in particular, a method suitable for use in an automobile engine equipped with an electronically controlled fuel injection device.
When the throttle valve is fully closed and the engine speed is above the fuel cutoff speed, the fuel supply is cut off and the throttle valve is opened, or the engine speed becomes below the fuel return speed. The present invention relates to an improvement in a fuel cut control method during deceleration of an electronically controlled engine, in which the fuel supply is restored when the fuel is exhausted.

[Prior art]

One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to the combustion chamber of an internal combustion engine such as an automobile engine uses an electronically controlled fuel injection device. This means that one or two injectors for injecting fuel into the engine are installed in the throttle body (in the case of a single-point injection type), or in several engine cylinders in the intake manifold (in the case of a multi-point injection type). The valve opening time of the injector is controlled in accordance with the operating state of the engine, thereby supplying the air-fuel mixture at a predetermined air-fuel ratio to the engine combustion chamber. In this electronically controlled fuel injection device, normally,
The basic injection amount is 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, and is input from sensors installed in each part of the engine. Based on the signals, various increases and decreases are added to determine the effective injection amount, and fuel injection is executed. Additionally, in order to reduce hydrocarbons in exhaust gas, improve fuel efficiency, and prevent catalyst overheating due to reactions of unburned fuel within the catalyst, fuel injection is generally stopped during deceleration to perform a so-called fuel cut. . Fuel cut during deceleration usually stops fuel injection when the throttle valve is fully closed and the engine speed is equal to or higher than a preset fuel cut speed. The fuel injection is resumed when the fuel cut-off rotation speed is opened or the engine rotation speed becomes equal to or less than the fuel return rotation speed, which is set lower than the fuel cut rotation speed. Although this fuel cut is effective in improving fuel efficiency and reducing harmful exhaust emissions, it has the problem that engine rotation may hunt when combined with an automatic transmission that includes a torque converter. was. That is, as shown in FIG. 1, when the throttle valve is closed while the vehicle is running and deceleration is started, fuel is cut if the engine speed NE is equal to or higher than the fuel cut speed NB. For this reason, the engine speed NE rapidly decreases and eventually reaches the fuel return speed NA. Then, fuel injection is restarted and the engine speed NE increases slightly, but at this time, it may exceed the fuel cut speed NB, and in this case, as shown by the broken line A, the engine speed NE increases slightly. This is repeated repeatedly, causing hunting in the engine speed NE. In particular, if the vehicle speed increases due to a downhill slope during fuel cut, the engine is turned by the torque converter, so the increase in engine speed will be large when the engine returns to normal, and hunting will occur. It is more likely to occur. This hunting phenomenon occurs regardless of the driver's intention, and sometimes gives the driver a very unpleasant feeling. This hunting phenomenon is particularly noticeable in engines in which the amount of fuel is increased by asynchronous injection or the like when the fuel is restored. In order to prevent this hunting phenomenon, it is possible to increase the rotation speed difference (so-called hysteresis) between the fuel cut rotation speed NB and the fuel return rotation speed NA, but in this case, if the fuel return rotation speed NA is too low, engine stall will occur. Because of the risk of There was a possibility that HC would increase and problems such as catalyst overheating would occur. On the other hand, the applicant has already, for example,
When the throttle valve is fully closed during fuel cut, the engine speed NE is equal to the fuel return speed.
It is proposed that the hysteresis width be made larger during a natural return when the pressure drops below NA than during a forced return when the throttle valve is opened during fuel cut. If the hysteresis width was made larger, there was a risk that the fuel cut range, that is, the fuel cut frequency would decrease.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and can effectively prevent engine rotation hunting during natural fuel recovery without substantially reducing the fuel cut range, that is, the fuel cut frequency. Therefore, by expanding the fuel cut range, fuel cut control during deceleration of an electronically controlled engine can improve fuel efficiency, reduce CO and HC harmful exhaust emissions, and prevent catalyst overheating. The purpose is to provide a method.

[Structure of the invention]

According to the present invention, when the throttle valve is fully closed and the engine speed is equal to or higher than the fuel cut speed, the fuel supply is cut off and the throttle valve is opened or the engine speed returns to the fuel cutoff speed. In the fuel cut control method during deceleration of an electronically controlled engine, in which the fuel supply is restored when the engine speed falls below the fuel return speed, as shown in Fig. 2, when the engine speed falls below the fuel return speed. a step of detecting that the fuel supply has been naturally restored; a step of increasing the amount of fuel when the fuel supply has been naturally restored; and a step of increasing the fuel cut rotation speed at least during the fuel increase. By including this, the above objective has been achieved.

[Action of the invention]

In the present invention, when increasing the amount of fuel to quickly stabilize the engine speed when the fuel supply is naturally restored, the fuel cut speed is increased at least during the increase in fuel amount, so that the fuel cut speed is increased. During the increase in fuel amount after recovery, fuel cut is difficult to be performed, and therefore, engine rotation hunting during natural fuel recovery is effectively prevented.

【Example】

Embodiments of an automobile engine equipped with a multi-point injection type intake air amount sensing type electronically controlled fuel injection device employing the fuel cut control method during deceleration of an electronically controlled engine according to the present invention will be described below with reference to the drawings. will be explained in detail. As shown in FIG. 3, this embodiment includes an air flow meter 12 for detecting the flow rate of intake air, an intake temperature sensor 14 built in the air flow meter 12 for detecting the temperature of the intake air, A throttle sensor including an idle contact LL for detecting the opening degree of a throttle valve 18 disposed on the throttle body 16 and opened and closed in conjunction with an accelerator pedal (not shown) disposed on the driver's seat. 20 and arranged in the intake manifold 21,
An injector 22 for intermittently injecting pressurized fuel toward the intake port of each cylinder, and an injector 24 for detecting the rotational state of the engine 10 from the rotational state of a distributor shaft built in the distributor 24. Cylinder discrimination sensor 26, rotation angle sensor 28, and cylinder block 10A of engine 10
A water temperature sensor 30 for detecting the engine cooling water temperature and the air flow meter 12 disposed in the
The fuel injection time is calculated according to the engine load determined from the output and the engine speed determined from the output of the rotation angle sensor 28, and a valve opening time signal is output to the injector 22. According to the invention, the valve opening time signal is turned off and fuel injection is stopped by an electronic control unit (hereinafter referred to as ECU) 32.
In the figure, 36 is a spark plug, 38 is an exhaust manifold, and 40 is an ignition coil with an igniter. The ECU 32, as shown in detail in FIG.
A central processing unit (hereinafter referred to as CPU) 32A consisting of, for example, a microprocessor for performing various arithmetic processing, and a read-only memory (hereinafter referred to as CPU) for storing control programs and various data, etc.
ROM) 32B, and a random access memory (hereinafter referred to as RAM) 32 for temporarily storing calculation data etc. in the CPU 32A.
C, a clock generation circuit 32D for generating various clock signals, the air flow meter 12 output inputted via a buffer 32E, and the water temperature sensor 30 inputted via a buffer 32F.
A multiplexer (hereinafter referred to as MPX) 32H and an analog-to-digital converter (hereinafter referred to as A /D converter)
32J and a first input/output port (hereinafter referred to as I/O port) 32K, the outputs of the cylinder discrimination sensor 26 and rotation angle sensor 28 inputted via the shaping circuit 32L, and the throttle sensor 20. 2nd I/O port 3 for taking in the output of
2M and the calculation result of the CPU 32A,
Output port 32P for outputting a valve opening time signal to the injector 22 via the drive circuit 32N
and a common bus 32Q for connecting the respective component devices and transferring data and instructions. The effects of the embodiment will be explained below. In this example, the fuel cut during deceleration is the fifth
The fuel cut processing routine is executed as shown in the figure. In other words, step
Step 110 is entered to determine whether or not fuel cut is already in progress. If the determination result is positive, the process proceeds to step 112, and since the idle contact LL of the throttle sensor 20 is on, it is determined whether the throttle valve 18 is in a fully closed state. If the judgment result is positive, proceed to step 114;
It is determined whether the current engine rotation speed NE is greater than a preset fuel return rotation speed NA.
If the judgment result is negative, that is, the engine rotation speed
When it is determined that the natural return condition is satisfied when NE becomes less than the fuel return rotation speed NA, the step
The process proceeds to step 116, where flag B indicating natural recovery is set. Note that this flag B is reset in advance at the initial stage, for example, when the engine is started. After step 116 is completed, or when the judgment result in step 112 is negative and it is judged that the throttle valve 18 is opened and the forced return condition is satisfied, the process proceeds to step 118 and restarts fuel injection.Meanwhile, If the judgment result in step 110 is negative, that is, if it is judged that fuel cut is not in progress, the process proceeds to step 120, and the throttle valve 1 is
8 is in a fully closed state. If the determination result is positive, the process proceeds to step 122, where it is determined whether flag B is set. When the determination result is positive, that is, when it is determined that fuel injection has been restarted due to natural recovery,
Proceeding to step 124, the count value of counter A, which is incremented each time by another routine that runs at regular intervals, is longer than the set time required to prevent hunting, that is, the fuel increase time period when fuel supply is restored. It is determined whether the set time is greater than or equal to the value corresponding to the set time β seconds. If the determination result in step 124 is positive or the determination result in step 122 is negative and it is determined that it is okay to use the normal fuel cut rotation speed NB, proceed to step 126, It is determined whether the engine rotation speed NE is greater than the normal fuel cut rotation speed NB. If the determination result in step 126 is negative, or if the determination result in step 114 is positive, the current engine speed NE is equal to the fuel cut speed NB.
When it is determined that the fuel return rotation speed is between NA and NA, or when the determination result in step 120 is negative and it is determined that the throttle valve 18 is open, the fuel is not cut off. , proceed to step 128 and reset flag B. On the other hand, if the judgment result in step 126 is positive, the process proceeds to step 130, where flag B is also
Reset. Further, if the judgment result in step 124 is negative, that is, the elapsed time after the natural recovery is set to the set time β.
If it is determined that it is within seconds, step 132
The engine speed NE is the fuel cut speed.
It is determined whether the value is greater than the sum of NB and an arbitrary value α that is considered good for preventing hunting. If the determination result in step 132 is positive, or after the completion of step 130, that is, if it is determined that the fuel cut condition is satisfied, the process proceeds to step 134, where fuel cut is executed. After completing step 118, 128 or 132, the routine advances to step 136, where counter A is cleared and the routine exits. On the other hand, if the determination result at step 132 is negative, the routine exits directly. In this way, when the engine speed NE becomes lower than the fuel return speed NA and returns naturally from the fuel cut, and the throttle valve 18 is left fully closed, α is added to the fuel cut speed NB. The next fuel cut control is performed using this value as the fuel cut rotation speed. However, when β seconds or more have passed since the previous fuel cut was restored, the fuel cut is again controlled only by the original fuel cut rotation speed NB. In this embodiment, an example of the relationship among the vehicle speed during deceleration, the fuel cut state, the engine speed, and the throttle opening is shown by the solid line B in FIG. 1 mentioned above. As is clear from the figure, engine rotation hunting during natural fuel recovery is effectively prevented. In the above embodiments, the present invention was applied to an automobile engine equipped with a multi-point injection type intake air amount sensing type electronically controlled fuel injection device, but the scope of application of the present invention is not limited to this. It is obvious that the present invention can be similarly applied to automobile engines equipped with a single point injection type intake pipe pressure sensing type electronically controlled fuel injection device, or general electronically controlled engines equipped with other fuel supply devices such as an electronically controlled carburetor. be.

【Effect of the invention】

As described above, according to the present invention, it is possible to effectively prevent engine rotation hunting during fuel natural recovery without substantially reducing the fuel cut range, that is, the fuel cut frequency. Therefore, it is possible to expand the fuel cut range without causing discomfort to the driver, improving fuel efficiency, reducing the amount of harmful exhaust emissions, and preventing catalyst overheating. have an effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram comparing an example of the relationship between vehicle speed during deceleration, fuel cut state, engine speed, and throttle opening in the conventional example and the embodiment of the present invention, and FIG. A flowchart showing the gist of the fuel cut control method during deceleration of the electronically controlled engine,
FIG. 3 is a sectional view including a partial block diagram showing an embodiment of an automobile engine equipped with a multi-point injection type intake air amount sensing type electronically controlled fuel injection device to which the present invention is adopted. FIG. 4 is a block diagram showing the configuration of the electronic control unit used in the above embodiment, and FIG. 5 is a flow chart showing a processing routine for cutting fuel during deceleration. 10... Engine, 12... Air flow meter, 18... Throttle valve, 20... Throttle sensor, LL... Idle contact, 22... Injector, 26... Cylinder discrimination sensor, 28... Rotation angle sensor, NE ...Engine speed, 32...Electronic control unit (ECU), NA...Fuel return speed, NB...Fuel cut speed.

Claims (1)

[Claims] 1. When the throttle valve is in the fully closed state and the engine speed is equal to or higher than the fuel cut speed,
In a fuel cut control method during deceleration of an electronically controlled engine, the fuel supply is cut off and the fuel supply is restored when a throttle valve is opened or when the engine speed falls below the fuel return speed. A procedure for detecting that the fuel supply has been automatically restored when the rotational speed has fallen below the fuel return rotational speed; A procedure for increasing the amount of fuel when the fuel supply has been automatically restored; and at least during the fuel increase. A method for controlling fuel cut during deceleration of an electronically controlled engine, comprising: increasing the fuel cut rotation speed;