JPH0216347A - Fuel control device of engine - Google Patents

Abstract

PURPOSE:To prevent a hunting in an original fuel cut control range without loosing the accelerating performance by setting a fuel cut starting engine speed higher than the original set engine speed within the initial determined time in which the engine speed is increased. CONSTITUTION:When the engine speed of an engine A detected by a means B reaches a determined set fuel cut starting engine speed or more, a means C conducts the fuel cut of the engine A. In this fuel control device, the set value of the set fuel cut starting engine speed is changed by a means D. Within the initial determined time in which the engine speed of the engine A is increased, the set fuel cut starting engine speed for operating the means C is set by a means E so that it becomes higher than the original set engine speed. Hence, a hunting in the original fuel cut control range is prevented without loosing the acceleration performance, and a satisfactory drivability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel control device for an engine.

(Prior art) In general, in an engine, if the rotation speed becomes too high due to laning or the like, there is a risk that the reliability of the engine itself will be adversely affected. In order to prevent the engine speed from increasing, that is, to prevent an overspeed condition, a fuel cut control device is provided that suppresses and controls the increase in engine speed by stopping the supply of fuel to the engine. (For example, JP-A-60-14
(See Publication No. 2033).

By the way, in the conventional control of the maximum rotation speed for preventing over-rotation, the control rotation speed for the maximum rotation speed control is as follows:
Normally, from the viewpoint of engine reliability, the instantaneous guaranteed rotation speed Na (for example, 6700 rpm) is allowed only instantaneously.
1) and the continuous guaranteed rotation speed Nb (for example, 6000 r
For example, a switch for instantaneous guaranteed rotational speed that operates when the engine rotational speed reaches the guaranteed instantaneous rotational speed Na, and a switch for continuous guaranteed rotational speed that operates when the guaranteed continuous rotational speed Nb is reached. It consists of two rotational speed responsive ON/OFF switches.

For example, when the actual engine speed NE suddenly increases and exceeds the instantaneous guaranteed rotation speed Na, such as during full-throttle acceleration when the accelerator pedal is kept fully depressed, the instantaneous guaranteed rotation speed rotation speed responsive switch is activated. By activating the fuel cut control device in response to the signal from the engine, the fuel supply to the ennon is cut off and the engine output is suppressed, thereby reducing the engine speed. When the continuous guaranteed rotational speed Nb is reached, the fuel supply is restarted in response to a signal from the continuous guaranteed rotational speed rotation scattering type switch, and the engine output is increased to increase the output and the engine rotational speed. By repeatedly controlling the engine speed to reduce by cutting off the fuel supply, recovering the engine speed by restarting the fuel supply, and increasing the engine speed, the engine speed can be adjusted to the continuous guaranteed speed and the instantaneous guaranteed speed. This is done to prevent over-speeding. That is, by providing a predetermined hysteresis characteristic between the instantaneous guaranteed rotation speed and the continuous guaranteed rotation speed, the maximum rotation speed of the engine is kept within the hysteresis rotation speed range.

(Problem to be Solved by the Invention) However, in the case of the above configuration, the engine speed fluctuates between the hysteresis rotation rlI (700 rpm) within the maximum rotation speed control region (hysteresis region). Since the fluctuation causes hunting, there is a problem in that drivability deteriorates, especially in automobile engines.

On the other hand, if a hysteresis characteristic is provided as described above, there is a problem that the original acceleration performance itself deteriorates due to repeated fuel cuts.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems, and includes an engine rotation speed detection means for detecting the engine rotation speed and a supply of fuel to the engine. and a fuel cut control for cutting the engine speed, and when the engine speed detected by the engine speed detecting means reaches a predetermined set fuel cut start speed or higher, the fuel cut control means is actuated to cut the fuel. In the fuel control device for an engine as described above, a set rotation speed variable means for changing the set value of the set fuel cut start rotation speed is provided, and the fuel cut control means is configured to control the fuel cut control means during an initial predetermined period of time when the engine speed increases. The set fuel cut start rotation speed at which the engine is activated is variably set higher than the original set rotation speed.

(Function) In the configuration of the engine fuel control device of the present invention, when the engine speed detected by the engine speed detecting means exceeds the predetermined set speed at which fuel cut control should be performed, the above-mentioned The fuel cut control means is activated to stop the supply of fuel to the engine to promptly suppress the increase in engine speed and maintain it below the guaranteed speed.

On the other hand, in that case, during the initial predetermined time period when the engine speed increases, the set speed variable means sets the predetermined set speed at which the fuel cut control is to be performed to a higher value than normal. It has become. Therefore, sufficient acceleration performance can be ensured without fuel cut-off during the predetermined period at the beginning of acceleration when the largest torque is required.

(Effects of Each Chamber) Therefore, according to the configuration of the engine fuel control device u of the present invention described above, hunting in the original fuel cut control region can be prevented without impairing equivalent acceleration performance. As a result, it becomes possible to realize good drivability.

(Example) First, Figs. 2 to 4 show a fuel control device for an automobile gasoline engine in which the present invention is applied, and Fig. 2 shows a control system of the above-described embodiment device. The schematic diagram, FIGS. 3 and 4 are flowcharts showing the control functions of the engine control unit in the control system.

First, the outline of the control system of this embodiment will be explained with reference to FIG. 2, and then the control of the main parts will be explained.

In FIG. 1, reference numeral l is the engine body, and intake air is taken in from the outside via an air cleaner 30.
Thereafter, the air is supplied to each cylinder via an air flow meter 2 and a throttle damper 3.

Further, fuel is supplied from the fuel tank 12 to the engine side by the fuel pump 13 and injected by the fuel injector 5. The amount of air taken into the cylinder during running is controlled by a throttle valve 6 provided in the throttle chamber 3. The throttle valve 6 is operated in conjunction with the accelerator pedal 31 via, for example, the engine control unit 9, and is maintained at the minimum opening state in the idling state.

On the other hand, reference numeral 10 indicates an exhaust pipe equipped with a three-way catalytic converter 11. The exhaust pipe TO is provided with a sensor 19 for detecting acid T and a degrees in the exhaust gas.

On the other hand, reference numeral I4 is a spark plug provided in the cylinder head IA of the engine main body l, and the spark plug I4 is provided in the cylinder head IA of the engine body l.
A predetermined ignition voltage is applied to E 4 via a distributor 17 and an igniter 18, and the timing at which this ignition voltage is applied, that is, the ignition timing is the same as E
It is controlled by the ignition timing control signal Igc supplied to the bipedal igniter 18 from the CU9. moreover,
Reference numeral 20 denotes a boost pressure sensor 20, which detects an engine boost pressure B corresponding to the engine load and sends it to the ECU.
Enter 9. Further, reference numeral 16 is a water temperature thermistor provided in the water jacket section of the engine cylinder block section IB.

Above ECU9. For example, a microprocessor (CPt
J), and includes memory (ROM and RAM) and an interface (Ilo) circuit. The interface circuit of this ECU 9 includes, for example, an engine starting signal (ECU trigger) from a starter switch (not shown), an engine rotation speed sensor 1
5, the detection signal NE of the cooling water temperature of the engine body 1 detected by the water temperature thermistor 16, and the detection signal 1w10. Various detection signals such as an oxygen concentration detection signal Vo detected by a sensor (exhaust sensor) 19 and an intake air amount Q detected by an air flow meter are input manually. Then, the ECU 9 controls the exhaust gas of the engine so that the actual air-fuel ratio A/F of the engine converges within a predetermined target air-fuel ratio range (window) centered on the stoichiometric air-fuel ratio (14, 7). The above O provided in the system,
Based on the oxygen concentration detection signal Vo of the sensor 19, the rich state (excessive concentration) or lean state (lean state) of the oxygen concentration in the exhaust gas is determined, and the amount of fuel supplied from the fuel injector 5 is determined according to the determined value. It is configured for highly accurate feedback control. Further, when the operating state of the engine is in a predetermined load range, the feedback control is exceptionally stopped and oven loop control is performed to an air-fuel ratio leaner or richer than the stoichiometric air-fuel ratio.

Next, upper 32 engine control unit (ECU) 9
The engine fuel cut control operation will be described in detail with reference to the flowcharts of FIGS. 3 and 4.

First, in step S, the engine rotational speed Nε is calculated and in step St, the intake air ff1Q is calculated and read.

Then, in the next step S, the basic fuel injection m T p is calculated from the intake air mQ and the engine speed NE. Next, the process proceeds to step S4, where the basic fuel injection amount Tp is
is multiplied by a predetermined current value conversion coefficient β to calculate the fuel injection pulse τi to be applied to the fuel injector 5 shown in FIG.

Next, after inputting the output (T, = 1 or T, = O) of the timer operation shown in the flowchart of Fig. 4, which will be described later, in an interrupt state, the process proceeds to step S, and the relevant timer T is set in the current cycle. Determine whether the value is 0. The setting value of the timer T, as shown in the flowchart of FIG. 4, is set according to the change in the engine speed NE at that time (see FIG. 5) (described later). This is to set the fuel cut start rotation speed NFc during the initial predetermined period of time when the engine speed increases as shown in FIG.

Then, as a result of the determination in "-", if a YES determination is made for T, =O, the process proceeds to step S8 and the value of the fuel cut control starting rotation speed (set rotation speed) NFC is set as normal. 5 is set to N El [normal fuel cut control start rotation speed (instantaneous guaranteed rotation speed)], and then the process proceeds to step Sa for comparison with the actual engine rotation speed NE.

On the other hand, if the result of the determination in step S is No, the process proceeds to step S7 and sets the value of the fuel cup control starting rotation speed Nrc to the so-called instantaneous guaranteed rotation speed in normal conditions as shown in FIG. 5 NEt. Rotation speed NE higher than the specified rotation speed than NEI
t is set, the process proceeds to step S8 in the same way as in the above case (see FIG. 5).

In step S8, the set rotation speed NFC (NFC=NE+, NFc
=NE is compared with the actual engine speed NE detected by the engine speed detection means, and if YES, the actual engine speed NE is equal to or higher than the constant speed of each stage. , both set the value of l to O in the fuel injection pulse of step S4 above to perform fuel cut control.

On the other hand, the actual engine speed NE is
If it is lower than Fc (NE+, NEy), the normal amount of fuel is injected using the fuel injection pulse τl set in step S4.

By the way, the interrupt routine in which an interrupt is applied between steps 84 and S5 is configured as shown in FIG. The flag value of the timer T1 indicating the time (T1=0 when timed out, T=1 during the timer) is set to idle.

That is, first, the actual engine speed NE is set to a predetermined reference speed N E 4 (for example, 5000 rpm).
), and if YES (low), first set the timer flag l in step S, and then set the value of timer T1 in step S3 to T, = To (for example, about 1 second). Set to .

On the other hand, if the determination in step S1 is No (NE
≧N E, ), the process further proceeds to step S4, where it is determined whether the actual engine speed NE is equal to or greater than the continuous guaranteed rotation ¥1NE3, and if YES, the process proceeds to step S6; In this case, proceed to step S. In step S5, it is determined whether or not the timer flag l is set. If YES (flag l), the process proceeds to the above-mentioned step S3 to continue the timer operation, while if NO, the process proceeds to step S7. , after decrementing the set value (1 second) of the timer T1, further step S8
Then, it is determined whether or not the timer 'r has timed out. On the other hand, in the above step S6, the value of the timer flag is reset to 0, and then the above step S6 is performed.
7. Proceed to the operation of Se.

Then, if YES in step S8, the timer T1
2, the set value (T,=O) is generated. On the other hand, in the case of NO, the value of the timer T, which is not 0, is output.

Then, based on this timer value, the operations of steps S to S9 in FIG. 3 described above are performed.

Therefore, according to the configuration of the above embodiment, for example, FIG.
) Even if the engine speed NE temporarily exceeds the instantaneous guaranteed speed NEI, such as during an acceleration shift accompanied by a shift change, as shown by the broken line characteristics, At the initial stage of acceleration, the instantaneous guaranteed rotation speed NEt is higher than the original fuel cut control starting rotation speed (NE).
Since this is temporarily set as a new set rotation speed within a predetermined period of time (T, = 1 second), it is possible to ensure the reliability of the Ennon without impairing acceleration performance.

Further, as a result, vertical fluctuations (hunting) in the engine speed due to repeated "execution-stop" of fuel cut control do not occur, and drivability is therefore improved.

For example, as shown in Fig. 6, the supplied fuel itself is changed stepwise to τi = 0 at the same time as the fuel cut control signal changes based on the above set value, so that the unburned components are in a half-misfired state. Therefore, the reliability of the exhaust gas purification device can be guaranteed.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a schematic diagram showing the system configuration of an engine fuel control device according to an embodiment of the present invention, and Fig. 3 is a diagram showing the basic fuel control system of the embodiment device. Flowchart showing the supply amount control operation, FIG. 4 is a flowchart showing the timer operation based on the control operation in FIG. 3, and FIG. 5 is a time chart corresponding to the operation in the flowchart in FIG. 3. , FIG. 6 is a time chart showing a fuel cut or supply method corresponding to the operation of the flowchart of FIG. 3. 1... Engine body Air flow meter Throttle deflection Fuel injector Throttle valve Ennon control unit Exhaust pipe Three-way catalytic converter 0, sensor

Claims (1)

[Claims] 1. Engine rotation speed detection means for detecting the engine rotation speed and fuel cut control means for cutting fuel supply to the engine, the engine rotation speed detected by the engine rotation speed detection means being a predetermined set fuel. A fuel control device for an engine that operates the fuel cut control means to cut fuel when the rotation speed exceeds the cut start rotation speed, further comprising set rotation speed variable means for changing the set value of the set fuel cut start rotation speed. and variably sets the fuel cut start rotation speed for operating the fuel cut control means during an initial predetermined period of time when the engine rotation speed increases to be higher than the original set rotation speed. Engine fuel control device.