JPH0251057B2 - - Google Patents

Description

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

The present invention detects the rotational speed of the internal combustion engine based on a pulse signal indicating the crank angle position of the internal combustion engine, and adds the basic fuel injection amount to the basic fuel injection amount calculated according to the engine rotational speed and the intake air amount. A digitally controlled fuel for an internal combustion engine, in which fuel is synchronously injected in synchronization with the crank angle position with correction according to the engine state of the internal combustion engine, and a predetermined amount of fuel is injected asynchronously when an acceleration signal is detected. Concerning improvement of injection method.

[Conventional technology]

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 (referred to as an engine) is to use a so-called electronically controlled fuel injection device.
In this method, an injector for injecting fuel into the engine is installed in the intake manifold or throttle body of the engine, for example, in several or one engine cylinder, and the valve opening time of the injector is controlled according to the operating state of the engine. By doing so, an air-fuel mixture with a predetermined air-fuel ratio is supplied to the engine combustion chamber. Although there are various types of such electronically controlled fuel injection devices, particularly in recent years, digitally controlled fuel injection devices in which the electronic control circuit is digitalized have been developed. In such a digitally controlled fuel injection device, normally,
The basic fuel injection amount is calculated according to the engine rotational speed detected from the engine intake air amount detected using an air flow meter etc. and the engine rotational speed signal input from the distributor. In order to improve startability or responsiveness immediately after acceleration, synchronous injection, which always injects at the same crank position in synchronization with the engine rotation, with correction based on signals input from the engine status etc. Apart from synchronous injection, asynchronous injection is performed in which a predetermined amount of injection is performed only immediately after a signal from a sensor is received in accordance with the driving condition. The synchronous injection time during which the injector is open corresponding to the synchronous injection is, for example, the basic injection time calculated using the intake air amount from the air flow meter and the rotation signal from the distributor, and the signal from each sensor. Therefore, the injection time is multiplied by a correction coefficient to correct the injection time according to the engine condition at that time, such as when cold or accelerating, and the invalid injection time is added to correct for the injector operation delay due to voltage fluctuation. It has been decided accordingly. For example, in order to improve engine startability, the basic injection time is corrected at the time of engine startup by setting it to a predetermined time regardless of the intake air amount and engine speed when starting the engine. In order to stabilize the engine rotation, the amount is increased for a certain period of time after the engine starts, and the amount is compensated for after the engine starts.Furthermore, when the intake air temperature is low, the air density increases and the amount of air increases. In order to prevent deviations in the air-fuel ratio, the intake air temperature is corrected by increasing the amount when the intake air temperature is low, and
In order to ensure drivability when cold, the amount of cooling water is increased when the temperature is low to compensate for the warm-up increase.Furthermore, to prevent sluggishness immediately after acceleration and improve acceleration performance, the amount of cooling water is increased at a constant level immediately after acceleration. The time is corrected by increasing the amount of acceleration during warm-up by increasing the amount, and in order to increase the engine output at high loads, by increasing the amount at high loads when the throttle valve opening is, for example, 60 degrees or more. In order to bring the air-fuel ratio of the air-fuel mixture to a predetermined air-fuel ratio, for example, near the stoichiometric air-fuel ratio, the air-fuel ratio feedback correction is performed by changing the increase ratio according to the oxygen concentration in the exhaust gas. has been done. Additionally, in order to prevent overheating of the catalytic converter and reduce fuel consumption, or to forcefully suppress the vehicle speed, fuel injection is stopped and fuel is cut when the engine brakes or when the vehicle speed exceeds the specified maximum speed. has been done. On the other hand, the asynchronous injection is controlled independently of the synchronous injection, and for example, when starting the engine, two injections are performed at the same time as an ignition switch signal is detected, in order to improve startability. During acceleration, in order to improve responsiveness immediately after acceleration, 1 is set when the throttle valve fully closed signal switches from on to off.
Once the next time an acceleration signal is input, and then once every time an acceleration signal is input during sudden or medium acceleration when the input interval of the acceleration signal is less than a predetermined time, for example, 200 milliseconds, Alternatively, in order to improve the responsiveness when the fuel cut is restored,
When the fuel is cut off, the throttle valve is opened and the throttle valve fully closed signal is turned off to inject once when the fuel cut is released. Such an electronically controlled fuel injection device, particularly a digitally controlled fuel injection device, is characterized in that it is possible to control the fuel injection amount extremely precisely.

[Problem to be solved by the invention]

However, in such a digitally controlled fuel injection system, conventionally, as seen in Japanese Patent Application Laid-Open No. 102425/1983, the amount of asynchronous injection during acceleration is determined from the interval of occurrence of rotational speed pulses from the distributor. It is only controlled in an on/off manner according to the generation interval of the acceleration signal generated in accordance with the determined engine rotation speed and the change in throttle valve opening, and the engine speed is controlled by the delay corresponding to the generation interval of the rotation speed pulse. This has the disadvantage that it may not be possible to accurately detect the engine rotational speed at low rotational speeds, and that sufficient acceleration performance may not be obtained, especially at low engine rotational speeds when sufficient fuel needs to be supplied. The present invention has been made in order to solve the above-mentioned conventional problems.The present invention grasps the engine rotational state without digitally calculating the current engine rotational speed, and according to this, the engine rotational speed is determined without any delay. It is an object of the present invention to provide a fuel injection method that can reliably increase the amount of asynchronous injection during sudden acceleration at low speed rotation.

[Means to solve the problem]

The present invention detects the rotational speed of the internal combustion engine based on a pulse signal indicating the crank angle position of the internal combustion engine, and adds the basic fuel injection amount to the basic fuel injection amount calculated according to the engine rotational speed and the intake air amount. A digitally controlled fuel for an internal combustion engine, in which fuel is synchronously injected in synchronization with the crank angle position with correction according to the engine state of the internal combustion engine, and a predetermined amount of fuel is injected asynchronously when an acceleration signal is detected. In the injection method, when an acceleration signal is detected again within the predetermined crank angle at which the asynchronous injection is performed, the asynchronous injection amount is increased to achieve the above object.

[Effect]

When the throttle valve is opened, that is, when an acceleration signal is generated from the throttle position sensor attached to the throttle valve, the fuel injection amount is increased and the air-fuel ratio at this time is increased to improve acceleration performance. can be done. Furthermore, by increasing this fuel injection amount as the engine speed decreases, acceleration performance can be further improved. However, an excessive increase in the amount will actually reduce acceleration performance. Further, with the method of determining the engine rotation speed from a pulse signal corresponding to the engine rotation, it is difficult to accurately determine the engine rotation speed with good responsiveness when the engine rotation speed is low. Therefore, in the present invention, when an acceleration signal is detected again within a predetermined crank angle at which asynchronous injection is performed, the current engine rotation speed is digitally calculated by increasing the amount of asynchronous injection. (In other words, without determining the problematic engine rotation speed as described above), the engine rotation state is grasped, and according to this, when the engine is rapidly accelerating at low speed, without any delay,
This makes it possible to reliably increase the amount of asynchronous injection.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. An embodiment of a digitally controlled fuel injection device employing the digitally controlled fuel injection method for an internal combustion engine according to the present invention is, as shown in FIGS. 1 and 2, provided in an intake passage 10 of an engine. An air flow meter 12 that detects the intake air amount of the engine, a distributor 14 that generates a pulse signal according to engine rotation, and a coolant temperature sensor 16 that detects the engine coolant temperature are disposed inside the air flow meter 12. In addition, an intake air temperature sensor 18 that detects the engine intake air temperature, a throttle position sensor 22 that detects the opening of a throttle valve 20 disposed in the intake passage 10 and changes in the throttle valve opening, and a starter switch 24 that generates a starter signal, and an oxygen concentration sensor 2 that detects the oxygen concentration in exhaust gas, which is disposed in the exhaust passage 26.
8, a vehicle speed sensor 32 for detecting the running speed of the vehicle from the rotational speed of the shaft of the transmission 30, an injector 36 for injecting fuel into the intake manifold 34 of the engine, and an intake air amount of the engine. The basic fuel injection time is calculated according to the rotation speed, and corrections are made according to the engine condition, etc.
In addition to outputting the synchronous injection signal to the injector 36, when the acceleration signal is generated after the engine has rotated by a predetermined crank angle since the previous acceleration signal was generated, a predetermined injection time determined according to the engine cooling water temperature, etc. On the other hand, if the current acceleration signal is generated before the engine has rotated by a predetermined crank angle since the previous acceleration signal was generated, the predetermined injection time is increased by 1.5 times. and a digital control circuit 38 which calculates an asynchronous injection signal from the time and outputs it to the injector 36. In FIG. 1, 40 is an air cleaner, 42 is a surge tank, 44 is a spark plug, 46 is a catalytic converter, and in FIG. 2, 48 is a battery. As shown in detail in FIG. 2, the digital control circuit 38 includes an air flow meter 12 (including an intake air temperature sensor 18), a cooling water temperature sensor 16, and
Analog-to-digital converter 50 for converting the analog signal output from the battery 48 into a digital signal
, an input interface circuit 52 for inputting digital signals output from the distributor 14, throttle position sensor 22, starter switch 24, oxygen concentration sensor 28, and vehicle speed sensor 32, and a central processing circuit 54. Read-only memory 56 and random access memory 58
and an output interface circuit 60 that converts the calculation result in the central processing circuit 54 into a fuel injection signal suitable for outputting to the injector 36. As shown in FIG. 3A, the throttle position sensor 22 includes a movable contact 64 that is fixed to the throttle valve shaft 62 and moves in conjunction with changes in the opening of the throttle valve.
, an idle contact 66 which contacts the tip of the movable contact 64 when the throttle valve is fully closed and turns on to detect the fully closed state of the throttle valve; and an idle contact 66 which detects the fully closed state of the throttle valve, and the movable contact 66 when the throttle valve opening reaches 60 degrees or more. A power contact 68 whose tip contacts 64 turns on and detects that the engine is in a high load state, and an idle contact 66.
ACC1 contact 70 and ACC2 contact 7 are arranged at an intermediate position between the movable contact 68 and the power contact 68, and are used to detect the rate of change in the throttle valve opening from the moving speed of the movable contact 68.
2 is provided. Therefore, the idle contact 66
Not only can the opening degree of the throttle valve be detected depending on the on/off state of the power contact 68, but also the off output of the idle contact 66 and, as shown in FIG. 3B,
The rate of change in the throttle valve opening can also be detected from the interval between the pulse outputs of the ACC1 contact 70 and the ACC2 contact 72, that is, the interval at which the acceleration signal is generated. The operation will be explained below. First, digital control circuit 3
8 is the intake air amount Q of the air flow meter 12 output
Based on the engine rotation speed N calculated from the distributor 14 output, the basic injection time T _P is calculated using the following equation. T _P =K・Q/N...(1) Here, K is a coefficient. Furthermore, by correcting the basic injection time T _P using the following formula according to the signals from each sensor,
Calculate the effective synchronous injection time τ ₁ . τ ₁ =T _P・(A/F)・(WL)・(THA) ・{1+(ASE)+(AEW)+(OTP)} {1−(RS)} ……(2) Here, ( A/F) is the air-fuel ratio correction coefficient,
(WL) is the warm-up increase correction coefficient, (THA) is the intake air temperature correction coefficient, (ASE) is the after-start increase correction coefficient, (AEW) is the warm-up acceleration increase correction coefficient,
(OTP) is the overheat (output) increase coefficient,
(RS) is the weight loss coefficient. Effective synchronous injection time τ ₁ obtained in this way
As shown in the following equation, the synchronous injection time τ _S is calculated by adding the invalid injection time τ _V corresponding to the response delay time of the injector 36 when the battery voltage decreases. τ _S = τ ₁ + τ _V ... (3) A fuel injection signal corresponding to this synchronous injection time τ _S is output to the injector 36, and the injector 36 is opened for the synchronous injection time τ _S in synchronization with the engine rotation. , fuel is injected into the intake manifold 34 of the engine. Asynchronous injection during acceleration in this embodiment is performed as follows. That is, the throttle position sensor 22 generates acceleration signals ACC1 and ACC2.
When input, the acceleration interrupt routine is entered as shown in FIG. In this acceleration interrupt routine, first, in accordance with the engine cooling water temperature at the time output from the cooling water temperature sensor 16, engine cooling is performed as shown in FIG. The effective asynchronous injection injection time τACC corresponding to the engine cooling water temperature is read out from the table showing the relationship between the water temperature and the effective asynchronous injection time τACC during acceleration, and is stored in the register A. Next, after the throttle valve fully closed signal output from the idle contact 66 of the throttle position sensor 22 changes from on to off, the generation interval of the second and subsequent acceleration signals ACC1 and ACC2 is a first predetermined time, For example, it is determined whether the time is 200 milliseconds or more, and the acceleration signal ACC1,
When the interval between occurrences of ACC2 is 200 milliseconds or more, asynchronous injection is not performed. On the other hand, the acceleration signal
If the interval between occurrences of ACC1 and ACC2 is less than 200 milliseconds, the effective asynchronous injection time τACC stored in register A is stored in register B. Next, it is determined whether the generation interval of the acceleration signals ACC1 and ACC2 is a second predetermined time, for example, 100 milliseconds or more, and if it is less than 100 milliseconds,
The effective asynchronous injection time τACC stored in register A is doubled and stored in register B. Furthermore, by another routine, the asynchronous injection execution instruction flag fASYNC, which is lowered when the engine rotates through a crank angle of 30 degrees after executing the asynchronous injection, is set to 1.
In other words, it is determined whether the current acceleration signal is generated again within 30 degrees of the crank angle after the previous acceleration signal was generated. When the asynchronous injection execution instruction flag fASYNC is zero,
That is, when an acceleration signal is generated only once within a crank angle of 30 degrees, the value stored in the register B is directly used as the effective asynchronous injection amount τACC during acceleration. On the other hand, when the asynchronous injection execution instruction flag is 1, that is, when the current acceleration signal is generated before 30 degrees of crank angle have passed since the previous acceleration signal, the value stored in register B is multiplied by 1.5. Let the effective asynchronous injection time during acceleration be τACC. Next, the asynchronous injection execution instruction flag
Set fASYNC to 1 and execute asynchronous injection. In actual asynchronous injection, as in the case of synchronous injection, the invalid injection time τ _V is added to the effective asynchronous injection time τACC obtained in this way, as shown in the following formula, to obtain the asynchronous injection time τASYNC. calculate. τASYNC=τACC+ _τV ...(4) In this embodiment, the asynchronous injection amount during acceleration determined according to the engine cooling water temperature is changed to the acceleration determined based on the generation time interval of the acceleration signal with respect to the engine crank angle. Since the acceleration is increased stepwise with good responsiveness according to the speed of the vehicle, fine control is performed and good acceleration performance is obtained.

【Effect of the invention】

As explained above, according to the present invention, the engine rotational state is grasped without digital calculation processing of the current engine rotational speed, and according to this, the asynchronous This has an excellent effect in that the injection amount can be reliably increased, and therefore sufficient acceleration performance can be obtained even when the engine rotates at low speed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view, including a partial block diagram, showing an internal combustion engine equipped with an embodiment of an electronically controlled fuel injection device that employs the digitally controlled fuel injection method for an internal combustion engine according to the present description. , FIG. 2 is a block diagram showing the circuit configuration of the above embodiment, and FIG.
is a front view showing the contact configuration of the throttle position sensor used in the embodiment;
FIG. 3B is a diagram showing an example of the change state of the contact output, FIG. 4 is a flowchart showing the acceleration interrupt routine for asynchronous injection in the embodiment, and FIG. FIG. 3 is a diagram showing the relationship between effective asynchronous injection times during acceleration. 12... Air flow meter, 14... Distributor, 16... Cooling water temperature sensor, 20...
Throttle valve, 22...throttle position sensor,
36...Injector, 38...Digital control circuit.

Claims (1)

[Claims] 1. A basic fuel injection amount calculated according to the engine rotation speed and intake air amount by detecting the rotation speed of the internal combustion engine based on a pulse signal indicating the crank angle position of the internal combustion engine. A digital digital camera for an internal combustion engine that is configured to synchronously inject fuel in synchronization with the crank angle position and asynchronously inject a predetermined amount of fuel when an acceleration signal is detected, by adding correction according to the engine state of the internal combustion engine. In the controlled fuel injection method, when an acceleration signal is detected again within the predetermined crank angle at which the asynchronous injection was performed,
A digitally controlled fuel injection method for an internal combustion engine characterized by increasing an asynchronous injection amount.