JPH02149739A - Fuel supply stop method and device for engine - Google Patents

Abstract

PURPOSE:To restrain effectively a car body vibration by detecting a timepoint at which a vehicle first starts vibration in a vehicle front direction, or a certain time point which is just before this timepoint, after inspecting the deceleration operation of a vehicle, and stopping the supply of fuel at either of these timings. CONSTITUTION:At a control unit 15, when an engine revolution number becomes less than a predetermined value with an idle switch ON at the time of vehicle travel, a detecting means 20 decides it is a deceleration operation, and as a result, a setting means 21 first sets a time which is from after the materialization of a fuel cut condition to a fuel cut. At the same time, a time in which the differential value of the engine revolution number is changed from a positive one to a negative one, is detected by means of a detecting means 22, and comparison between this value and the time set by the means 21 is done by means of a correcting means 23, and in the case of a deviation being generated, a set time TDLY is corrected, and memorization is made at a memorizing means 24, and at the same time, a corrected time is outputted to an executing means 25 through the means 21, and the stoppage of fuel supply is executed after a set time. Thus, vibration generated at the time of a car body deceleration is effectively restrained, and improvement of operability can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for stopping fuel supply to an engine, which is executed during deceleration of a vehicle.

[Conventional technology]

Traditionally, in the field of automobile engines, in order to improve fuel efficiency and reduce exhaust gas, when a vehicle is decelerating, this deceleration is detected from driving parameters such as the idle switch on and engine speed. A system is adopted in which the fuel supply to the engine is temporarily stopped (hereinafter referred to as fuel cut). As a conventional technique related to fuel cut, there is one disclosed in Japanese Patent Publication No. 16576/1983, for example.

Conventionally, a fuel cut is executed at a timing when a preset time has elapsed after the fuel cut condition is satisfied (start of deceleration operation).

[Problem to be solved by the invention]

By the way, when the vehicle is decelerated, particularly when deceleration is performed in a driving range where the output torque of the first gear or the second gear is relatively large, vibrations are likely to occur in the longitudinal direction of the vehicle.

The reason for this is that when deceleration occurs, the output torque first decreases rapidly and deceleration occurs, but at the same time a force that tries to run forward due to inertia acts on the vehicle, so that energy is transferred from the output shaft of the vehicle onwards. This is caused by accumulation in the elastic body portion of the power transmission system. This energy accumulation manifests itself as displacement, such as twisting of the propeller shaft.

In other words, this accumulated energy is then discharged into the power transmission system, which adds to the engine output as an external force, which temporarily increases the engine output even during deceleration, and this repeats several times until it converges. I'm going to go there,
This phenomenon appears as vehicle longitudinal vibration (vehicle longitudinal acceleration).

The frequency of vibrations in the longitudinal direction of the vehicle that occur during such deceleration driving is a value unique to the vehicle and determined by the vehicle's engine and power transmission system.

By the way, depending on the timing of the fuel cut, as described below, vehicle vibration during deceleration driving can be promoted or suppressed, but in the past, sufficient consideration has not been given to this effect.

Here, the relationship between the fuel cut timing and the longitudinal direction of the vehicle will be explained based on the experimental results shown in FIG. 12.

Figure 12 shows the state of vehicle longitudinal acceleration, injector injection pulse width, and throttle valve opening when transitioning from steady operation to deceleration operation, and To is the point at which fuel cut conditions are met (when deceleration operation begins) , TDLY is T. This is the time from the start to the fuel cut.

A in the figure shows the longitudinal acceleration of the vehicle when the fuel is cut at time TDLY2, when the first forward vibration (forward acceleration) of the vehicle has already progressed to some extent after deceleration driving. Time TDL immediately before forward acceleration occurs
This shows the acceleration in the longitudinal direction of the vehicle when there is a fuel cut at Y1. As shown in Figure 42, when there is deceleration, vehicle longitudinal vibration (longitudinal acceleration) initially becomes negative acceleration (at this time, the inertial energy of the heavy vehicle is accumulated in the spring system of the output transmission system). , the stored energy is then discharged to produce an initial positive acceleration, and these longitudinal accelerations are repeated to gradually converge. And T.D.
In the case of LY2, there is a small amount of fuel supplied in the shaded area, so output torque is generated, and this output torque is added to the vehicle's forward acceleration, causing vehicle longitudinal vibration as shown in A. encouraged.

On the other hand, if the fuel is cut off just before the vehicle's first forward acceleration occurs, as in TDLY 1, the output torque from the fuel supply will not be added to the vehicle's forward acceleration, which will increase vibration. Because there is no vibration, longitudinal vibrations of the vehicle are suppressed.

Conventionally, the timing of such a fuel cut was set independently of longitudinal vibrations of the vehicle during deceleration, and therefore it could not be expected to suppress longitudinal vibrations of the vehicle due to fuel cut during deceleration.

The present invention has been made in view of the above points, and its purpose is to appropriately control the timing of fuel cut during deceleration operation.

The objective is to effectively suppress longitudinal vibrations of a vehicle.

[Problem B that the invention attempts to solve]

Basically, as described above, the present invention was made based on the discovery that if the fuel cut is performed just before the first vehicle forward vibration acceleration occurs, the vibration suppressing effect will work while maintaining the efficiency of the fuel cut. We propose the following problem-solving methods.

The first means of solving the problem is to detect decelerating driving of a vehicle and cut fuel from the engine. Based on driving parameters representative of longitudinal vibrations, the time point at which the vehicle first vibrates in the forward direction of the vehicle or a certain time point immediately before that point is detected, and a fuel cut is executed at one of these detected times.

The second problem-solving means applies a so-called learning function to the fuel cut time setting.

In other words, this problem solving means, when decelerating driving of the vehicle is detected, starts a timer to execute a fuel cut when a preset time TDLY is reached, and at the same time, every time decelerating driving of the vehicle is performed, From driving parameters representative of vibration, detect the time Tn from the start of deceleration driving to the point in time when the vehicle first vibrates in the vehicle forward direction or a certain point immediately before that, and calculate the current time Tn and TDLY.
If a deviation occurs between the two, the time TDLY required for the next fuel cut is corrected based on the deviation.

The third means of solving the problem is to perform a vehicle running test in advance to represent the longitudinal vibration of the vehicle from the start of deceleration driving to the point in time when the vehicle first vibrates in the forward direction of the vehicle or a certain point immediately before that point. The time required from the start of deceleration operation to the fuel cut is set based on the test value detected from the operating parameters.

The fourth problem-solving means is the invention of an apparatus suitable for carrying out the method of the first problem-solving means.

In order to make this easier to understand, this will be explained by referring to the reference numerals in FIG. 11 of the embodiment. Means 3 for detecting the time point at which the first vibration in the forward direction of the vehicle occurs during deceleration driving or the time point immediately before that point based on the differential value of the rotation speed
1, and means 32 for executing fuel cut in real time when any of the above points is detected.

The fifth problem solving means is an apparatus of the second problem solving means, and as shown in FIG. 5, means 20 for detecting deceleration driving of the vehicle.

Time T required from the start of vehicle deceleration operation to fuel cut
A means 21 for setting and storing DLY, a means 25 for executing a fuel cut when the time TDLY is reached after the vehicle has been decelerated by starting the timer, and a driving parameter representing the timer starting and longitudinal vibration of the vehicle (in the embodiment, the engine rotation means 22 for detecting the time Tn from the start of deceleration driving until the first vibration in the forward direction of the vehicle occurs or immediately before that, using the differential value of the number (differential value of the number); The time TDLY is compared with the time Tn from the start of deceleration driving until the first vibration in the vehicle forward direction occurs, and TDLY, Tn
If there is a deviation between the
The device is configured with a means 23 for correcting LY.

[Effect]

According to the first problem-solving means, when deceleration driving of the vehicle is detected, it is determined from the driving parameters representing the longitudinal vibration of the vehicle that the time when the vehicle first vibrates in the forward direction of the vehicle or immediately before that vibration is detected. You can know when to start. If the fuel supply cut is executed at any of these points, the fuel cut will be executed before the vehicle's first forward acceleration (positive acceleration) rises after deceleration, so the output torque based on the fuel will be reduced. This prevents the vehicle from being added to the forward acceleration of the vehicle, eliminates the acceleration of the forward acceleration of the vehicle, and as a result, it is possible to effectively suppress vibrations in the longitudinal direction of the vehicle during deceleration driving.

As will be described later in the example, driving parameters for determining the longitudinal vibration of the vehicle include, for example, the differential value of the engine rotation speed, the differential value of the basic fuel pulse width, the differential value of the intake air amount, and a direct acceleration sensor. It may be detected by

Next, in the second problem-solving means, a fuel cut is initially performed when a preset initial time TDLY is reached. Furthermore, each time the vehicle is decelerated, the time Tn from the start of deceleration to the time when the vehicle first vibrates in the forward direction of the vehicle or a certain time just before that time is detected. Then, the Tn and TDLY times are compared, and if a deviation occurs between the two, the time until the next fuel cut is corrected based on the deviation, so by performing a so-called learning effect, the fuel The cut timing can be executed before the initial acceleration of the vehicle in the forward direction during deceleration driving increases, and similarly to the first means for solving the problem, it is possible to effectively suppress vibrations in the longitudinal direction of the vehicle during deceleration driving.

Next, according to the third problem-solving means, at the stage of a driving test, the time required from the start of vehicle deceleration driving to the point at which the vehicle first vibrates in the vehicle forward direction or a certain point immediately before that point is measured in advance. , based on this test value, the timing of fuel cut during vehicle deceleration operation is set, but in this case as well, the first. Similar to the second problem-solving means, it is possible to execute the fuel cut before the initial forward acceleration rises after deceleration, so it is possible to effectively suppress vibrations in the longitudinal direction of the vehicle during deceleration driving.

Next is the fourth. The fifth problem-solving means relates to a device for executing the fuel cutter 1-, and its operation will be explained in the Examples section below based on the flowcharts in FIGS. 7 and 6, so please refer to it. I want to be

〔Example〕

Embodiments of the present invention will be described based on the drawings.

Figure 3 shows the fuel supply (
Fig. 4 is a block diagram of the injection system and its control system diagram.

In FIG. 3, air enters the air cleaner 1 through the intake section 2, and a hot wire air flow meter 3. Duct 4. It passes through a throttle valve 5 that controls the air flow rate and enters a collector 6. Here, air is distributed to each intake pipe 8 that communicates directly with the engine 7 and sucked into the cylinder. On the other hand, fuel is sucked and pressurized from the fuel tank 9 by a fuel pump 10, passes through a fuel damper 11 and a filter 12, is regulated to a constant pressure by a regulator 14, and is injected into the intake pipe 8 from an injector 13. The output from the air flow meter 3 is input to the control unit 15. control unit 15
The output of a throttle sensor 18 that detects the opening of the throttle valve, a signal from a crank angle sensor built into the distributor 16, and the like are input. As shown in FIG. 4, this control unit 15 includes an MPU, a ROM,
It is composed of a calculation device including a RAM, an A/D converter, an input/output circuit, etc., and performs predetermined calculation processing based on the output signal of the air flow meter 3, the output signal of the distributor, etc., and operates the injector 13 based on the calculation result. , the required amount of fuel is supplied to each intake pipe 8. The ignition timing is controlled by sending a signal to the power transistor of the ignition coil 17.

Furthermore, the control UNILAT 15 in this example is
It has a function to control fuel cut during deceleration operation using the idle switch signal and the engine rotation speed signal from the crank angle sensor.

FIG. 5 shows a block configuration diagram for performing this fuel cut control, and 20 indicates deceleration operation when, for example, the idle switch is turned on while the vehicle is running and the engine speed falls below a predetermined value N8. 21 is a means for setting the time TDLY from when the fuel cut condition is satisfied to the fuel cut; 22 is a means for detecting when the differential value dN/dt of the engine speed has changed from positive to positive after the fuel cut condition is satisfied; The means 23 for detecting the time Tn until it becomes negative inputs the outputs of the means 21 and 22 and calculates the time TDLY from when the fuel cut conditions are satisfied to the differential value dN/dt of the engine speed. Compare the time Tn until TDL changes from positive to negative, and if there is a deviation, TDL
24 is a means for storing the time until fuel cut (including the modified one) TDLY; 25 is a fuel supply execution means for sending a fuel cut command signal to the injector 6 Next The fuel cut operation during deceleration operation of this embodiment will be explained with reference to the flowchart of FIG. 6. code 10
1 to 106 represent steps.

The flowchart in FIG. 6 is part of the engine control program of this embodiment, and this program is repeatedly executed in a short period of time. When the engine operating state enters the deceleration state, the accelerator pedal is released and the idle switch is turned on.
In addition, when the engine speed becomes equal to or lower than the predetermined value N1, in step 101, the detection means 20 of the control unit 15
The start of deceleration operation, which is a condition for establishing a fuel cut, is detected. At this time, the one hour setting means 21 starts the timer,
The time TDLY (TDLY is the time from the start of deceleration operation until the fuel is cut) required for the fuel cut, which was set in advance during the previous deceleration operation, is counted, and when the timer T reaches the time TDLY, the execution means 25 executes the fuel cut. (steps 102 to 104).

Here, TDLY is initially set to an arbitrary initial value,
A plurality of values are set corresponding to the operating range immediately before the start of deceleration, in other words, the stage of the output torque immediately before the start of deceleration.

The reason for this is that the initial phase of the longitudinal vibration of the vehicle that occurs during deceleration varies depending on the operating state of the engine immediately before the start of deceleration, and the appropriate time for TDLY also varies accordingly. That is, the larger the output torque, the larger the change in the initial phase. Therefore, when deceleration operation occurs, an appropriate TDLY is selected from a plurality of set TDLYs. The selection method is used by searching the TDLY table, which has a plurality of data strings, using parameters representative of the operating state immediately before starting deceleration. Furthermore, this T
When DLY is applied during the next deceleration operation, there may be a deviation from the time Tn until the first vehicle forward vibration occurs during actual deceleration operation. Then, in order to eliminate this deviation, the following measures will be taken.

That is, when deceleration occurs, in addition to executing the fuel cut operation based on the aforementioned TDLY, the time detection means 22 determines the time Tn from the start of the current deceleration until the first vibration in the vehicle forward direction occurs, based on the engine rotational speed. It is also determined by differentiating (step 105). Specifically, as shown in FIG. 6, the time at which the engine rotational speed dN/dt turns from negative to positive (dN/dt>O) becomes T''n is the time at which the vehicle forward vibration occurs. Even under the same deceleration driving conditions, each vehicle is different. This is because the longitudinal vibration of the vehicle that occurs during deceleration driving depends on the natural frequency of each vehicle.

Then, the time correction means 23 inputs this Tn and TDLY, and in step 106, the deviation between Tn and TDLY is determined by Tn.
(ΔT=Tn-TDLY), and update TDLY to be used next time using the following formula.

TDLY (new) = TDLY (old) + △T X a...
(1) Here, α is a constant weighting that determines the update rate of TDLY, and is a preset value. Operating conditions that require fuel cut are not rare, and the above equation is repeatedly executed. As a result, TDLY becomes equal to the time Tn after the start of deceleration driving when the first forward acceleration in the longitudinal direction of the vehicle occurs, and fuel cut can be executed at a timing to suppress vibrations as shown in FIG. Note that TDLY is stored even after the engine is stopped, and once the learning of TDLY is converged, an appropriate fuel cut timing can always be obtained.

FIG. 1 and FIG. 2 are one of the experimental results according to this example. Figure 2 shows TD at the timing of the initial fuel cut.
This is an experimental result in which a value TDLY2 is given as an initial value for LY to perform a fuel cut when vibration acceleration in the forward direction of the vehicle has already progressed to a certain extent. At this stage, the forward acceleration of the vehicle overlaps with the output torque due to the fuel supply, so vibrations in the longitudinal direction of the vehicle are promoted and the engine speed also fluctuates greatly.

After that, the deceleration operation in the same operating range is experimentally repeated, and the learning operation shown in the flowchart of FIG. 6 is performed, and when the value of TDLY is sufficiently updated, the experimental results are shown in FIG. 1.

As shown in FIG. 1, TDLY has been updated to a time value TDLY1 at which the fuel cut is performed immediately before the first vibration acceleration in the forward direction of the vehicle begins. As a result, the output torque based on the fuel supply is not added to the forward acceleration of the vehicle during deceleration, so the longitudinal vibration of the vehicle is suppressed.
Both the engine rotational speed and the fluctuation are smaller than the initial state shown in FIG.

FIG. 10 shows changes in TDLY, parameters representing the magnitude of vehicle longitudinal vibration, and vehicle longitudinal acceleration in this process. TDL as shown in Figure 10
Y converges from TDLY2 toward TDLYl, and accordingly, the amount of change in the acceleration in both longitudinal directions of 1p becomes smaller.

FIG. 7 is a flowchart showing another example of fuel cut to which the present invention is applied. This flowchart is executed by the fuel cut control system shown in FIG.

In this embodiment, when there is a deceleration operation, the detection means 30 first determines whether the fuel cut condition is met (step 107) as in the flowchart of FIG. 6, and when the fuel cut condition is met, the timer T is started. Next, the differential value dN/dt of the engine speed is detected by the differential value detection means 31, and first dN/dt is detected.
The point in time when N/dt changes from negative to positive is detected. Then, at the timing when this point is detected, the fuel cut execution means 32
outputs a stop command signal to the injector and immediately cuts fuel (steps 108 to 110). Also,
If the longitudinal vibration of the vehicle is small and dN/dt does not turn positive, fuel cut is performed at a preset time TEND (step 111).

This embodiment also provides the same effect as shown in FIG. 6, and is also simpler since it does not require calculation or storage of TDLY.

An even simpler method is to measure the point at which the vehicle first vibrates in the front direction during the vehicle deceleration operation, or a certain point immediately before that point, during the driving test, and based on this test value, determine whether the vehicle is decelerated or not. The fuel cut timing may be set in advance.

For example, as shown in Figure 9, in the case of car A, TDLY=
For Ti and B cars, set TDLY=T. A flowchart of an embodiment of the method is shown in FIG. That is, as shown in FIG. 8, when deceleration operation is performed and the fuel cut condition is satisfied, timer T is started and steps 111 and 112 are performed.
), the time TDLY (T1.T
,), a fuel cut is executed.

For example, in the case of a single-point fuel injection system, if there is a time lag between when the fuel is cut and when the fuel is actually supplied to the cylinder, the time correction factor in equation (1) should be adjusted to take into account the time lag. This can be solved by changing ΔT as follows.

△T = T n + T I3 F - T D L
Y - (2) Here, TBF is a coefficient when you want to set a time lag between the timing when dN/dt turns positive and the fuel cut timing, and as in the example above, the fuel cut is set to Tn in consideration of the time lag If you want to precede the timing when dN/dt changes from negative to positive, you can set it to a negative value.

In addition, in this example, the differential value of the engine speed was used as a parameter representative of longitudinal vibration of the vehicle, but in addition, the basic fuel pulse width, intake air amount, etc. are also minimized during deceleration operation, so these differential values were used. It may be directly detected using a value, etc., or an acceleration sensor.

Furthermore, the present invention is applicable to all engine fuel systems, including mechanical fuel injectors as well as electronic fuel injection.

〔Effect of the invention〕

According to the present invention as described above, in any of the problem-solving means, the fuel cut is executed at the time when the first forward vibration of the vehicle body occurs during deceleration driving, or at a timing immediately before that, so that the vibration that occurs during deceleration of the vehicle body is reduced. This can be effectively suppressed and improve drivability.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing the operating state of an embodiment of the present invention, FIG. 3 is a configuration diagram showing an example of an engine control system to which the present invention is applied, and FIG. 4 is a diagram showing the above control system. FIG. 5 is a block diagram of a fuel cut control system incorporated in the control unit, FIGS. 6 to 8 are flowcharts showing specific examples of fuel cut, and FIG. The figure is an explanatory diagram showing the appropriate fuel cut timing for each vehicle. FIG. 11 is a block diagram showing another example of the fuel cut control system, and FIG. 12 is an explanatory diagram for explaining the problem to be solved by the present invention. 15... Control unit, 2o... Deceleration operation detection means, 21... Fuel supply stop time setting means. 22... Time detection means for vehicle vibration after deceleration driving. 23... Time correction means, 24... Time storage means, 2
5...Fuel supply stop execution means, 30...Deceleration driving detection means, 31...Vehicle forward direction vibration detection means, 32...
・Fuel supply stop execution means.

Claims (1)

[Claims] 1. In a method of detecting decelerating operation of a vehicle driven by an engine and stopping fuel supply to the engine, when decelerating operation of the vehicle is detected, After deceleration driving is detected, the time when the vehicle first starts to vibrate in the forward direction of the vehicle or a certain time immediately before that is detected from the driving parameters that represent the longitudinal vibration of the vehicle, and the system detects the vibration at any of these detection times. A method for stopping fuel supply to an engine, the method comprising stopping fuel supply. 2. When a vehicle driven by an engine decelerates, this deceleration is detected and the fuel supply to the engine is stopped. When deceleration of the vehicle is detected, a timer is started to trigger a preset signal. At time TDLY, the fuel supply is stopped, and each time the vehicle decelerates, the point at which the vehicle first vibrates in the forward direction from the start of deceleration, based on the driving parameters that represent the longitudinal vibration of the vehicle. Alternatively, detect the time Tn up to a certain point just before that, compare the current time Tn with TDLY, and if a deviation occurs between the two, calculate the time required to stop fuel supply based on that deviation. A method for stopping fuel supply to an engine, characterized by correcting TDLY. 3. When a vehicle driven by an engine is decelerating, this deceleration is detected and the fuel supply to the engine is stopped. The time up to a certain point immediately before that point is detected from driving parameters representative of longitudinal vibration of the vehicle through a vehicle running test in advance, and based on this test value, the time required from the start of deceleration driving to the stop of fuel supply is calculated. A method for stopping fuel supply to an engine, characterized in that: 4. In any one of claims 1 to 3, the fuel for the engine is set such that a plurality of times required from the start of deceleration operation of the vehicle to the stop of fuel supply are set corresponding to the operating range before the start of deceleration operation. How to stop supply. 5. In any one of claims 1 to 4, the operating parameters for determining vehicle longitudinal vibration during deceleration operation include a differential value of engine speed, a differential value of basic fuel injection pulse width, and intake air. Any one of the differential values of the quantity,
Alternatively, a method for stopping fuel supply to an engine that uses the output of an acceleration sensor. 6. means for detecting deceleration of the vehicle; and means for detecting the point in time when the first vibration in the forward direction of the vehicle occurs during deceleration driving, or the point immediately before that, from driving parameters representative of vibration in the longitudinal direction of the vehicle; A fuel supply stop device for an engine, comprising: means for stopping fuel supply in real time upon detecting the above point in time. 7. Means for detecting deceleration of the vehicle; means for setting and storing the time TDLY required from the start of deceleration of the vehicle to the stop of fuel supply; and activation of a timer.
Using a means for stopping fuel supply at time TDLY after decelerating the vehicle, starting a timer, and operating parameters representative of longitudinal vibration of the vehicle, it is possible to stop the fuel supply from the start of decelerating driving until the first vibration in the forward direction of the vehicle occurs, or just before that. TDLY is determined by comparing the time TDLY required to stop the fuel supply during the currently executed vehicle deceleration operation with the time Tn from the start of the deceleration operation until the first vibration in the forward direction of the vehicle occurs. , T
If there is a deviation between n, T
A fuel supply stop device for an engine, comprising: means for correcting DLY;