JPS60166726A - Fuel cut controlling method in time of deceleration in electronically controlled engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of engine speed hunting, by increasing a cut speed according to the lapse of time after resetting, when an engine speed goes down to less than a reset speed, resetting fuel feed from a fuel cut, and thereby the fuel feed is naturally reset. CONSTITUTION:When a fact that a throttle valve 18 is in a state of being fully closed is detected from output of a throttle sensor 20 and that an engine speed NE is more than a fuel cut speed NB is detected from output of a turning angle sensor 28, fuel feed to an injector 22 is cut off by an ECU32. LIkewise, when the engine speed NE goes down to less than a reset speed NA, the fuel feed is made so as to be rest. And, when the engine speed NE goes down to less than the reset speed NA and thereby the fuel feed is naturally rest, that whether the lapse of time after resetting is within the setting time or not is judged, when YES judgment is the case, the cut speed NB is controlled so as to be raised as much as the specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel cut control method for an electronically controlled engine at slow speed, and is particularly suitable for use in an automobile engine equipped with an electronically controlled fuel injection device. Preferably, when the throttle valve is fully open and the engine speed is above the cut speed, the fuel supply is cut and the throttle valve is opened or the engine speed is below the return speed. This invention relates to an improvement in a fuel cut control method during deceleration of an electronically controlled engine, which restores fuel supply when (Prior Art) One of the methods of supplying an air-fuel mixture with a predetermined air-fuel ratio to the combustion chamber of an internal combustion engine such as an automobile engine is to use an electronic fuel control device. For example, one or two injectors are installed in the throttle body (in the case of a single-point injection type), or several engine cylinders are installed in the intake manifold (in the case of a multi-point injection type), and the injector By controlling the valve opening time according to the operating state of the engine, a mixture having a predetermined air-fuel ratio is supplied to the engine until combustion is reached.In this electronically controlled fuel injection system, normally, The basic injection amount is determined based on 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. The actual injection amount is determined by adding each I increase/decrease amount according to the signal, and fuel injection is executed.In addition, it reduces hydrocarbons in exhaust gas, improves fuel efficiency, and improves the flow of unburned fuel inside the catalyst. For purposes such as preventing catalyst overheating, it is common to stop fuel injection during deceleration and perform a so-called fuel cut.This fuel cut during deceleration is normally performed when the thrower valves 1 to 1 are fully closed. , and when the engine speed is equal to or higher than a preset cut speed, fuel injection is stopped, while the throttle valve is opened or the engine speed is lower than the cut speed beforehand. Fuel injection is restarted when the rotation speed drops below the set return speed.This fuel cut is effective in improving fuel efficiency and reducing harmful exhaust emissions, but automatic transmission including torque converters When used in combination with a motor vehicle, there is a problem in that the engine speed may hunt.In other words, as shown in Figure 1, when the throttle valve is closed and deceleration begins while driving, the engine speed If NE is greater than or equal to the cut rotation speed N8, the fuel is cut.Therefore, the engine rotation speed NE drops rapidly and eventually reaches the return rotation speed NA.Then, fuel injection is restarted and the engine The engine speed NE increases slightly, but at this time, it may exceed the cut engine speed N8. In this case, as shown by the broken line, fuel cut and fuel injection are repeated, and the engine speed NE increases. Hunting may occur.Especially, if the vehicle speed slows down due to a downhill slope during fuel cut, the engine is rotated by the torque converter, so the engine speed when the engine returns to normal speed will be lower. The amount of rise becomes too large, and hunting becomes more likely to occur. This hunting phenomenon occurs regardless of the driver's intention, and may give 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 cut rotation speed NB and the return rotation speed NA, but in this case, the return rotation speed N
If A is made too low, there is a risk of engine stalling, so the only option is to make the cut speed NB higher.As a result, the fuel cut range, that is, the fuel cut frequency, decreases, resulting in poor fuel efficiency. There was a possibility that harmful exhaust gases such as CO and HC would increase and problems such as catalyst overheating would occur. On the other hand, the applicant has already filed, for example, Japanese Patent Application No. 56-126933.
In this case, during a natural return when the engine speed NE becomes lower than the return speed NA with the throttle valve fully open during a fuel cut, the hysteresis width is larger than during a forced return when the throttle valve is opened during a fuel cut. However, if the hysteresis width is always made larger during natural return than during forced return, there is a risk that the fuel cut range, that is, the fuel cut frequency will decrease. OBJECTIVE OF THE INVENTION 1 The present invention has been made to solve the above-mentioned conventional problems, and effectively prevents engine rotation hunting during fuel recovery without substantially reducing the fuel cut range, that is, the fuel cut frequency. Therefore, by expanding the fuel cut range, it is possible to improve fuel efficiency, reduce the amount of harmful exhaust such as Co and HC, and prevent catalyst overheating. The purpose of this paper is to provide a fuel cut control method. (Structure of the Invention) According to the present invention, when the throttle valve is fully open and the engine speed is equal to or higher than the cut speed, the fuel supply is cut and the throttle valve is opened or the engine speed is reduced. A procedure for determining whether or not there is an electron that causes the fuel supply to be restored when the fuel supply becomes lower than the return rotation speed, and when the elapsed time after recovery is within the set time, the cut rotation speed is increased. The above-mentioned object is achieved by including the steps.Furthermore, in the embodiment of the present invention, by setting the set time to be longer than the fuel addition time period at the time of fuel supply restoration,
This is designed to more effectively prevent engine rotation hunting. [Operation between lights] In the present invention, when the fuel supply is automatically restored, if the elapsed time after the restoration is within the set time, the cut rotation speed is increased, so that the setting after the fuel supply is restored. It becomes difficult for the fuel to be cut off for a certain amount of time, and therefore, engine rotation hunting during natural fuel recovery is effectively prevented. (Example 1) Referring to the drawings below, an automobile equipped with a multi-point injection type intake air amount sensing type electronically controlled fuel injection device employing the deceleration fuel cut control method for an electronically controlled engine according to the present invention will be described. An embodiment of the engine will be described in detail.As shown in FIG. The intake air temperature sensor 14 detects the opening degree of the throttle valve 18, which is disposed on the throttle body 16 and opens and closes in conjunction with an accelerator pedal (not shown) disposed on the driver's seat. a throttle sensor 20 including an idle contact LL for the purpose of cylinder discrimination sensor 2G for detecting the rotational state of the engine 10 from the rotational state of the distributor shaft
and a rotation angle sensor 28, a water temperature sensor 30 disposed in the cylinder block 10A of the engine 10 for detecting the engine cooling water temperature, and the engine load determined from the output of the air flow meter 12 and the output of the rotation angle sensor 28. The fuel injection time is measured according to the engine rotation speed, etc., and a valve opening time signal is output to the navigation injector 22, and when decelerating, the invention turns off the valve opening time signal and stops fuel injection. and an electronic control unit (hereinafter referred to as EC'U) 32. In the figure, 36 is a spark plug, 38 is an exhaust manifold, and 40 is an ignition coil with an igniter. - As shown in detail in FIG. 4, the ECU 32 includes a central processing unit (hereinafter referred to as CPtJ) 32A, which includes a microprocessor, for example, for performing various calculation processes.
, a read-only memory (hereinafter referred to as OM) 32B for storing control programs and various data, and a random access memory (hereinafter referred to as RAM) for temporarily storing calculation data, etc. in the C'PU 32A. ) 32C, a clock generation circuit 32D for generating various clock signals, the airflow meter 12 output inputted via a buffer 32E, and a buffer 32
A multiplexer (hereinafter referred to as MPX) for converting analog signals such as the output of the water temperature sensor 30 inputted via F and the output of the intake air temperature sensor 14 inputted via the buffer 32G into digital signals and sequentially fetching the digital signals. )32H
1 analog-to-digital converter (hereinafter referred to as A/D converter) 32J and a first input/output boat (hereinafter referred to as I10 boat) 32 through a shaping circuit 32m, an hθ cylinder discrimination sensor 26 and Rotation angle sensor 28
and a second I10 port 32M for receiving the output of the throttle sensor 20, and the GPU 32.
According to the calculation result of A, the output port 32P for outputting the valve open B# double signal to the injector 22 via the drive circuit 32N is connected between each of the component devices to transfer data and instructions. It consists of a common bus 32Q for The effects of the embodiment will be explained below. The fuel cut during deceleration in this embodiment is executed according to a fuel cut processing routine as shown in FIG. That is, the process enters step 110 every predetermined period of time and determines whether or not a fuel cut is already in progress. If the determination result is positive, the process proceeds to step 112, where it is determined whether or not the throttle valve 18 is fully open since the no fiddle contact LL of the throttle sensor 20 is on. If the determination result is positive, proceed to step 114;
It is determined whether the current engine speed NE is greater than a preset return speed NA. If the determination result is negative, that is, if it is determined that the engine rotational speed NE becomes equal to or less than the recovery rotational speed NA and the natural return condition is satisfied, the process proceeds to step 116, and a 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 116N 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 fuel injection is restarted. On the other hand, if the determination result in step 110 is negative,
That is, when it is determined that the fuel cut is not being executed, the process proceeds to step 120, and it is determined whether or not the throttle valve 18 is fully open. If the determination result is positive, the process proceeds to step 122, where it is determined whether flag B is set. If the determination result is positive, that is, if it is determined that the fuel injection has been restarted due to natural recovery, the process proceeds to step 124, where the counter A, which is incremented each time by another routine that is passed at regular intervals, is counted up. It is determined whether or not the counted value is equal to or greater than a value corresponding to a set time necessary to prevent hunting, for example, a set time β seconds longer than the fuel increase time period when fuel supply is restored. The step 124
If the determination result in step 122 is positive, or if the determination result in step 122 is negative, and it is determined that it is okay to use the normal cutting rotation speed NB, step 126
Proceed to and the engine speed NE becomes the normal cut speed NB.
Determine whether it is greater than or not. If the determination result of step 126 is negative, or the determination result of step 114 is positive, it is determined that the current engine rotation speed NE is between the cut rotation speed NB and the return rotation speed NA. Or, if the determination result in step 120 is negative and it is determined that the throttle valve 1B is open, the process proceeds to step 128 and flag B is reset without performing a fuel cut. On the other hand, if the determination result in step 126 is positive, the process proceeds to step 130, where flag B is also reset. Furthermore, if the determination result in step 124 is negative,
That is, when it is determined that the elapsed time after natural recovery is within the set time β seconds, the process proceeds to step 132, where the engine speed NE is set to an arbitrary value α that is considered to be good for preventing hunting to the cut speed NB. Determine whether the value is greater than the sum of the values. If the determination result in step 132 is positive, or after the aforementioned step 130 is completed, that is, if it is determined that the fuel cut condition is satisfied, the process proceeds to step 134, and a fuel cut is executed. After completing steps 118, 128 or 1321, the process proceeds to step 136, where counter A is cleared and this routine exits. On the other hand, if the determination result at step 132 is negative, the routine exits directly. In this way, the engine speed NE becomes the return speed NA.
If the fuel cut occurs naturally and the throttle valve 18 is left fully open, the next fuel cut control is performed using the cut rotation speed as the cut rotation speed NB. However, if 0 seconds or more have passed since the previous fuel cut was restored, the fuel cut is again controlled only by the original cut rotation speed NB. In this embodiment, the relationship between the vehicle speed during deceleration, the fuel cut state, the engine speed, and the throttle opening degree is effectively prevented. In the above embodiments, the present invention was not 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 can be similarly applied to automobile engines equipped with a single-point injection type intake pipe pressure sensing type electronically controlled fuel @body system, and general electronically controlled engines equipped with other fuel supply devices such as electronically controlled carburetors. it is obvious. [Effects of the Invention] As described above, according to the present invention, engine rotation hunting during natural fuel recovery can be effectively prevented 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, which has excellent effects such as improving fuel efficiency, reducing the amount of harmful exhaust emissions, and preventing catalyst overheating. has.

[Brief explanation of drawings]

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. FIG. 3 is a flowchart showing the gist of the fuel cut control method during deceleration of an electronically controlled engine, which is an automobile engine equipped with a multi-point injection type intake air 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 embodiment, and FIG. 5 is a flowchart showing a processing routine for cutting. 10...Engine, 12...Air 70-meter,
18... Throttle valve, 20... Throttle sensor, LL... Idle contact, 22... Injector, 26... Cylinder discrimination sensor, 28... Rotation angle sensor, NE... Engine rotation speed , 32...Electronic control unit (ECIJ), N A...
・Return rotation speed, NB...Cut rotation speed. Agent Takaya Ron (and 1 other person) Figure 1/l”” TIME Isecl Figure 4 32 Figure 5

Claims (2)

[Claims] (1) When the throttle valve is fully closed and the engine speed is above the cut speed, the fuel supply is cut and the throttle valve is opened, but if the engine speed is below the return speed In a method for controlling fuel cut during deceleration of an electronically controlled engine in which the fuel supply is restored when and, when the elapsed time after recovery is within the set time, the step of increasing the cut rotation speed. (2) The fuel cut control method during deceleration of an electronically controlled engine according to claim 1, wherein the set time is set longer than the fuel increase time period when the fuel supply is restored.