JPH0510492B2 - - Google Patents

Description

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

The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, and is particularly suitable for use in an automobile engine equipped with an electronically controlled fuel injection device. On the other hand, during deceleration when the throttle valve is fully closed and the engine rotation speed is higher than the predetermined fuel cut rotation speed, the throttle valve is opened or the engine rotation speed is reduced. The present invention relates to an improvement in an electronically controlled fuel injection method for an internal combustion engine, in which fuel injection is stopped and fuel cut is performed until the fuel cut-off return rotation reaches a predetermined speed or lower.

[Conventional technology]

2. Description of the Related 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 is achieved by arranging injectors for injecting fuel into the engine, for example, in the intake manifold of the engine for several engine cylinders, and controlling the valve opening time of the injectors according to the operating state of the engine. This allows an air-fuel mixture with a predetermined air-fuel ratio to be supplied to the engine combustion chamber. In this electronically controlled fuel injection, each part of the engine is normally adjusted to the basic injection amount 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. The actual injection amount is determined by adding various increases and decreases based on a signal inputted from a sensor disposed in the engine according to the engine state, etc., and fuel injection is executed. In addition, for the purpose of reducing hydrocarbons in exhaust gas, improving fuel efficiency, and preventing catalyst overheating due to reactions of unburned fuel within the catalyst, the throttle valve is fully closed and the engine rotational speed is set to a predetermined fuel cut rotation. When decelerating, which is higher than the engine speed, it is common to stop fuel injection and perform a so-called fuel cut. This fuel cut continues until the throttle valve is opened or the engine speed becomes below a predetermined fuel cut return rotation, and the throttle valve is opened or the engine rotation speed reaches a predetermined fuel cut return rotation. It was normal to stop fuel cut and restart fuel injection when the speed dropped below that of the engine. According to such a fuel cut, it is possible to obtain effects such as improved fuel efficiency as described above.

[Problem to be achieved by the invention]

However, in the past, in such a fuel cut, when returning from the fuel cut, fuel injection was immediately restarted with the regular fuel injection amount required depending on the engine operating condition, which caused engine combustion to suddenly start. When the fuel was restarted, engine torque was suddenly generated, causing the vehicle in which the engine was installed to shake back and forth, causing a so-called fuel cut recovery shock, which caused discomfort to the driver. Furthermore, even after the fuel cut is restored, if the combustion is unstable, the torque generated by the engine may vary, resulting in a so-called vehicle surge phenomenon (deceleration surge). The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and is an internal combustion engine capable of alleviating vehicle longitudinal vibration when the fuel cut is restored, stabilizing combustion during deceleration, and improving engine operating performance. The purpose is to provide an electronically controlled fuel injection method.

[Means to achieve the task]

The present invention normally performs fuel injection with a fuel injection amount determined according to the engine operating state, while the throttle valve is in a fully closed state and the engine rotational speed is equal to or higher than a predetermined fuel cut rotational speed. An electronically controlled fuel system for an internal combustion engine in which fuel injection is stopped and fuel is cut until the throttle valve is opened or the engine rotation speed falls below a predetermined fuel cut return rotation speed during deceleration. In the injection method, when the engine speed falls below the fuel cut return rotation speed when returning from the fuel cut, first, the fuel injection amount is reduced from the normal injection amount at the time of return, and then,
The reduced fuel injection amount is increased almost continuously, and the fuel injection amount is decelerated rather than increased from the normal injection amount, and when the engine rotation speed becomes less than the predetermined damping start rotation speed, approximately The above objective is achieved by continuously attenuating the injection amount to the normal injection amount. In addition, when returning from the fuel cut, from the time when the engine rotational speed falls below the fuel cut return rotational speed until the fuel injection is performed at the regular fuel injection amount, the engine speed is adjusted according to the oxygen concentration in the exhaust gas. By canceling the air-fuel ratio feedback control, the above-mentioned return reduction and deceleration reduction can be performed without any trouble.

[Effect]

In the present invention, upon recovery from fuel cut, the fuel injection amount is increased almost continuously from an injection amount that is less than the normal injection amount to an injection amount that is greater than the normal injection amount. There is. Thereby, when returning from a fuel cut, the injection amount is not suddenly returned to the normal injection amount, and the shock at the time of returning can be reduced. Also, after increasing the injection amount from the normal injection amount in this way,
After the engine rotational speed falls below a predetermined damping start rotational speed, the fuel injection amount is attenuated almost continuously to the normal injection amount. This reduces the occurrence of torque fluctuations due to an increase in the injection amount. In addition, by starting to attenuate the fuel injection amount, which has been increased from the normal injection amount, after the engine rotational speed falls below the predetermined attenuation start rotational speed, the fuel injection amount is reliably maintained until the engine rotational speed reaches the idle rotational speed. can be reduced to the normal injection amount. In comparison, if the fuel injection amount, which has been increased from the normal injection amount, is set to start attenuating due to the timer time-up, the engine rotational speed will drop to the idle rotational speed in a shorter time than the timer setting time. When the engine stops, idle stability deteriorates.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electronically controlled fuel injection system for an automobile engine that employs the electronically controlled fuel injection method for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, this embodiment includes an air cleaner 12 for taking in atmospheric air, and an air flow meter 14 for detecting the flow rate of intake air taken into an intake pipe 13 by the air cleaner 12.
and an intake temperature sensor 16 built into the air flow meter 14 for detecting the temperature of intake air.
, a throttle valve 20 for controlling the flow rate of intake air, which is disposed on the throttle body 18 and is opened and closed in conjunction with an accelerator pedal (not shown) disposed on the driver's seat; and the throttle valve 20 . Throttle sensor 2 includes an idle switch that is turned off when the throttle valve 20 is opened from a fully closed state, and a power switch that is turned on when the throttle valve is opened beyond a predetermined opening degree.
2, an injector 26 disposed in the intake manifold 24 for injecting fuel toward the intake port of each cylinder of the engine 10, and an injector 26 disposed in the exhaust manifold 28 for injecting fuel from the oxygen concentration in the exhaust gas. An oxygen concentration sensor (referred to as an O ₂ sensor) 30 for detecting the fuel ratio, a three-way catalytic converter 34 disposed in the middle of the exhaust pipe 32, and a three-way catalytic converter 34 disposed in the engine block detect the engine cooling water temperature. and a distributor shaft (not shown) that rotates in conjunction with the rotation of the crankshaft of the engine 10, and generates an ignition primary signal at every predetermined crank angle according to the engine rotation.
A distributor 40 for distributing the high-voltage secondary ignition signal generated by the ignition coil 38 in response to the primary ignition signal to the spark plugs (not shown) of each cylinder, a battery 46, and an output of the air flow meter 14. A basic injection pulse signal T _P having a pulse width corresponding to the basic injection time is generated at every predetermined crank angle according to the intake air amount and the engine rotation speed determined from the primary ignition signal, and the basic injection pulse signal T An analog calculation circuit that applies various corrections to _P and outputs an injector drive pulse signal Ti to the injector 26, and a basic injection pulse signal T _P output from the analog calculation circuit,
A correction signal V _F is formed to make corrections according to the air-fuel ratio output from the O ₂ sensor 30, the output from the throttle sensor 22, etc., and when the throttle valve 20 is in a fully closed state and the engine rotational speed is
During deceleration when N _E is greater than or equal to the predetermined fuel cut rotational speed N _A , the throttle valve 20 is opened or
A four-cylinder automobile engine equipped with a hybrid engine control device 48 including a digital calculation circuit that generates _{a basic injection pulse cut signal T C until} the engine rotation speed N _E becomes equal to or less than a predetermined fuel cut return rotation speed N B. In the intake air amount sensing type electronically controlled fuel injection device of No. 10, in the engine control device 48, upon recovery from fuel cut,
Engine rotation speed N _E is fuel cut return rotation speed
When the fuel injection amount is below N _B , first reduce the fuel injection amount by a predetermined amount from the normal injection amount, then perform a recovery reduction to gradually restore the normal fuel injection amount, and then first reduce the fuel injection amount. When the normal injection amount is gradually increased to a predetermined amount, and then the engine rotational speed N _E falls below the predetermined damping start rotational speed N _R ,
While decelerating and increasing the amount of fuel to be gradually attenuated to the normal fuel injection amount, the engine rotation speed N _E becomes below the fuel cut return rotation speed N _B until fuel injection using the normal fuel injection amount is performed. teeth,
The air-fuel ratio feedback correction according to the output of the O ₂ sensor 30 is not performed. As shown in detail in FIG. 2, the engine control device 48 includes a frequency dividing circuit 50 for dividing the frequency of the primary ignition signal Ig inputted from the distributor 40 into a signal for each predetermined crank angle; A basic injection pulse generation circuit that generates a basic injection pulse signal T _P of a pulse width corresponding to the basic injection time at every predetermined crank angle according to the output of the frequency dividing circuit 50 and the intake air amount signal input from the air flow meter 14. 52 and the basic injection pulse signal T _P inputted via the diode 54, the intake temperature signal of the intake temperature sensor 16 output, the engine cooling water temperature signal of the water temperature sensor 36 output, and the output of the digital control circuit described later. A multiplication correction circuit 56 for performing correction accordingly, an injector drive transistor 60 that is driven by the injector drive pulse signal Ti output from the multiplication correction circuit 56 and for energizing the injector 26, and performs various arithmetic processing. for,
For example, a central processing unit (referred to as CPU) 62a consisting of a microprocessor, a timer 62b for generating various time signals, and a timer 62b for making an interrupt in response to the basic injection pulse signal T _P output from the basic injection pulse generation circuit 52. Interrupt control unit 62c, the
A digital input port 62d for receiving the air-fuel ratio signal output from the O ₂ sensor 30, the output from the throttle sensor 22, etc., an intake air amount signal input from the air flow meter 14, and the water temperature sensor 36.
Analog-to-digital converter (referred to as A/D converter) 6 for converting the engine cooling water temperature signal, etc. input from
2e, a random access memory (referred to as RAM) 62f for temporarily storing calculation data etc. in the CPU 62a, a read-only memory (referred to as ROM) 62g for storing control programs and various constants, etc., calculations in the CPU 62a; Depending on the result, a digital output port 62h for outputting the basic injection pulse cut signal Tc to the input side of the multiplication correction circuit 56;
A digital signal for converting a digital correction signal obtained according to the calculation result of the CPU 62a into an analog correction signal V _F and outputting it to the multiplication correction circuit 56.
An analog converter (referred to as a D/A converter) 62i, a power supply circuit 62j for supplying voltage to each component of the battery 46 applied via the key switch 49, and a voltage directly applied from the battery 46 to the RAM 62f. and a digital control circuit 62 consisting of a power supply circuit 62k for supplying power to the power source. In Figure 2,
64 is a pull-up resistor, and 66 is an injector resistor. The action will be explained below. The fuel cut and return in this example are carried out in the third
It is executed according to the routine shown in the figure. That is, first, in step 101, it is determined based on the output of the throttle sensor 22 whether or not the throttle valve is fully closed. If the judgment result is negative, that is, if the throttle is open,
Proceed to step 102 and connect the digital output port 6.
Basic injection pulse cut signal output from 2h
Tc is set to a high level, the fuel cut is released, and in step 103, both the amount of reduction at the time of return X _F and the amount of deceleration increase D _F are set to 0, and the deceleration increase execution flag F is reset. end. On the other hand, if the judgment result in step 101 is positive, that is, if the throttle valve is fully closed, the process proceeds to step 104, where the engine speed N _E is equal to or higher than the predetermined fuel cut speed N _A. Determine whether it exists or not. If the determination result is positive, the basic injection pulse cut signal Tc output from the digital output port 62h is set to a low level to execute fuel cut, and then in step 106,
The counter CF that counts the number of revolutions after the fuel cut is restored is reset, and the deceleration increase execution flag F is set. After completing step 106, or
If the judgment result in step 104 is negative, the process proceeds to step 107, where the engine rotational speed is
N _E is the specified fuel cut return rotational speed N _B (N _B <
N _A ) Determine whether the following is true. If the determination result is negative, this routine ends. On the other hand, if the judgment result in step 107 is positive, the process proceeds to step 108, where the counter
Determine whether the count value of CF is 0 or not. If the judgment result is positive, that is, if this is the first process after the fuel cut is restored, the process advances to step 109;
-20% is set as an initial value to the return weight loss amount X _F , and the deceleration weight loss amount D _F is set to 0. After step 109, or if the judgment result in step 108 is negative, proceed to step 110, and calculate the amount of weight loss at the time of recovery X _F as shown in the following formula:
The value obtained by adding the amount of deceleration increase D _F is set as the correction signal V _F output from the D/A converter 62i,
Next, in step 111, the fuel cut is released in the same manner as in step 102 above. _{V F =} judge. If the determination result is negative, that is, if the weight loss upon return is being performed, the process proceeds to step 113;
Determine whether or not the rotation number counter should be counted up. If the determination result is positive, that is, if the engine has made one revolution since the previous process,
Proceed to step 114, and as shown in the following formula, add 20/8 to the current amount of weight loss at recovery X _F so that the weight loss at recovery will gradually return from -20% to 0 during 8 engine revolutions.
% is added to the new amount of weight loss upon return X _F. X _F =X _F +20/8% (2) Next, the process proceeds to step 115, and after incrementing the count value of the counter CF by 1, the process returns to step 110. On the other hand, if the determination result in step 113 is negative, this routine ends. If the judgment result in step 112 is positive, that is, if the weight loss at the time of return has been completed, the process proceeds to step 114, where the amount of weight loss at the time of return _XF is set to 0.
shall be. Next, the process proceeds to step 115, where it is determined whether the deceleration/increase execution flag F has been reset. If the judgment result is negative, step
Proceeding to step 116, it is determined whether a predetermined time of 20.48 milliseconds has elapsed since the previous process. If the determination result in step 116 is negative, or if the determination result in step 115 is positive,
Exit this routine. On the other hand, if the determination result in step 116 is positive, the process proceeds to step 117, where the engine rotational speed N _E is changed to the attenuation start rotational speed N _R of the deceleration increase.
It is determined whether the value exceeds (N _R <N _B ). If the determination result is positive, proceed to step 118;
Determine whether the amount of deceleration increase D _F is greater than or equal to the maximum value +10%. If the judgment result is negative, the process proceeds to step 119, and the current amount of deceleration increase D F is changed as shown in the following formula so that the amount of deceleration increase D _F reaches from 0 to +10% over a predetermined time of 1.1 _seconds. 10%/1100/20.4
The value obtained by adding 8 is set as the new amount of deceleration increase D _F. D _F = D _F +10%/1100/20.48...(3) On the other hand, if the judgment result in step 118 is positive, proceed to step 120 and fix the amount of deceleration increase D _F at +10%. . If the judgment result in step 117 is negative, that is, if the engine rotational speed N _E becomes less than or equal to the damping start rotational speed N _R , the process proceeds to step 121 and the amount of deceleration increase D _F is less than or equal to 0. Determine whether or not. If the judgment result is negative, step
Proceed to step 122 and calculate the amount of deceleration increase over a predetermined time of 1.1 seconds D _F
In order to attenuate from +10% to 0, the current deceleration increase amount D _F is increased by 10%/1100/20.4, as shown in the following formula.
The value obtained by subtracting 8 is set as the new amount of deceleration increase D _F. D _F = D _F -10%/1100/20.48... (4) On the other hand, if the judgment result in step 121 is positive, the process proceeds to step 123, where the amount of deceleration increase D _F is set to 0, and , the deceleration/increase execution flag F is reset, and the deceleration/increase is completed. FIG. 4 shows an example of the relationship among the throttle valve opening during deceleration, the engine speed, the correction signal V _F , and the execution state of the air-fuel ratio feedback control in this embodiment. In this embodiment, when returning from fuel cut, after the engine rotation speed N _E becomes equal to or less than the fuel cut return rotation speed N _B , until fuel injection with the normal fuel injection amount is performed,
Since the air-fuel ratio feedback control according to the output of the O ₂ sensor 30 is canceled, it is possible to reliably increase the amount upon return and decrease during deceleration when the fuel is cut off. In the above embodiment, the present invention is applied to an intake air amount sensing type electronically controlled fuel injection device equipped with a hybrid type engine control device, but the scope of application of the present invention is not limited to this, and is not limited to this. The same applies to intake air sensing electronically controlled fuel injection devices equipped with digitalized engine control devices, intake pipe pressure sensing electronically controlled fuel injection devices, and even general electronically controlled fuel injection devices. The applicability is clear.

【Effect of the invention】

As explained above, according to the present invention, since the fuel is gradually increased during fuel re-injection, combustion in the engine starts gradually, the torque change becomes smaller, and the return shock also becomes smaller. In addition, after the fuel cut is restored, the amount of fuel is increased, so the air-fuel ratio becomes rich, and since there is originally a lot of residual gas and the volumetric efficiency is low, combustion is stabilized during deceleration when combustion is poor, and deceleration surges are eliminated. Furthermore, since the fuel is gradually increased and decreased, there is no sudden change in the air-fuel ratio.
Excellent effects such as smooth engine operation performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partial block diagram and cross section showing the structure of an embodiment of an intake air sensing type electronically controlled fuel injection device for an automobile engine, in which the electronically controlled fuel injection method for an internal combustion engine according to the present invention is adopted. FIG. 2 is a block diagram showing the configuration of the engine control device used in the above embodiment, and FIG.
The figure is a flowchart showing the fuel cut/return routine used in the embodiment, and FIG. 4 is the throttle valve opening during deceleration, engine speed, correction signal, and air-fuel ratio feedback control in the embodiment. FIG. 2 is a diagram illustrating an example of the relationship between the execution states of FIG. 10... Engine, 14... Air flow meter, 20... Throttle valve, 22... Throttle sensor, 26... Injector, 30... Oxygen concentration sensor, 40... Distributor, 48...
Engine control device.

Claims (1)

[Claims] 1. In normal times, fuel injection is performed with a fuel injection amount determined according to the engine operating state, while,
During deceleration when the throttle valve is fully closed and the engine rotational speed is higher than the predetermined fuel cut rotational speed, the throttle valve is opened or the engine rotational speed is lower than the predetermined fuel cut return rotational speed. In an electronically controlled fuel injection method for an internal combustion engine that stops fuel injection and performs a fuel cut, when the engine speed falls below the fuel cut return rotation speed when returning from a fuel cut, the first step is to The fuel injection amount is reduced at the time of recovery to be reduced from the normal injection amount, and then the reduced fuel injection amount is increased almost continuously to perform a deceleration increase in which the fuel injection amount is increased from the normal injection amount. . An electronically controlled fuel injection method for an internal combustion engine, characterized in that when the engine rotational speed falls below a predetermined damping start rotational speed, the injection amount is substantially continuously attenuated to a normal injection amount. 2. When returning from the fuel cut, from the time when the engine rotation speed falls below the fuel cut return rotation speed until the fuel injection is performed at the regular fuel injection amount, the engine speed is adjusted according to the oxygen concentration in the exhaust gas. An electronically controlled fuel injection method for an internal combustion engine according to claim 1, wherein air-fuel ratio feedback control is canceled.