JPH10318019A - Fuel injection control method for internal combustion engine and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve startability of an engine by precisely setting a fuel injection rate according to a temperature of a cylinder in the engine. SOLUTION: This device is provided with an engine temperature sensor 9 for detecting a cooling water temperature of an internal combustion engine as an engine temperature TE, and an intake temperature sensor 8 for detecting an intake temperature TA. The engine temperature TE and the intake temperature TA are compared with each other, cooling start control is carried out when the engine temperature TB is lower than the intake temperature TA so as to set an injection rate to a value suited to a time when the temperature of the internal combustion engine is low. When the engine temperature TE is higher than the intake temperature TA, warming-up start control is carried out so as to set the intake rate in start increasing rate control to a value suited to a time when the internal combustion engine is warmed up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control method for an internal combustion engine for controlling an amount of fuel injected from an injector for supplying fuel to the internal combustion engine, and a fuel injection control device used for implementing the method. It is.

[0002]

2. Description of the Related Art A fuel injection device for supplying fuel to an internal combustion engine includes an injector that opens a valve to inject fuel into a throttle body or the like when a predetermined drive current is applied, and a fuel that supplies fuel to the injector. A pump, a sensor for detecting various control conditions such as a throttle valve opening, an atmospheric pressure, an intake air temperature, an engine temperature, etc., and a fuel injection time calculated based on the detected control condition, and a fuel injection time corresponding to the calculated injection time. A control unit for generating an injection command signal having a predetermined time width, and an injector drive circuit for supplying a drive current to the injector while the injection command signal is being supplied. The control unit is usually realized by a microcomputer.

In this type of fuel injection device, the amount of fuel injected from the injector is determined by the product of the fuel injection time (time during which fuel is injected from the injector) and the pressure of the fuel applied to the injector. Generally, the pressure of the fuel supplied from the fuel pump to the injector is controlled to be constant by the regulator, so that the fuel injection amount can be determined by the fuel injection time.

Accordingly, in a fuel injection control device for controlling the amount of fuel injected from an injector, the fuel injection time is calculated with respect to various control conditions such as a throttle valve opening, atmospheric pressure, intake air temperature and engine temperature. Thus, an injection command signal having a time width corresponding to the calculated injection time is generated.

When fuel is injected from the injector into the throttle body of the internal combustion engine, the injected fuel is transported to the cylinder side of the engine while forming a liquid film by attaching to the wall surface of the throttle body. Initially, much of the injected fuel is used to form a liquid film, so only a small portion of the injected fuel reaches the cylinder. For this reason, in an internal combustion engine in which fuel is supplied from an injector, startup increase control is performed to increase the fuel injection amount at the time of starting the internal combustion engine as compared with that during normal operation.

The start increasing control is performed at least at the time of the first fuel injection at the start of the internal combustion engine (usually only at the first injection), and shifts to a steady operation after the initial start increasing control is completed. Until the start transition period.

In the present specification, the increase control performed at least at the time of the first fuel injection at the start of the start of the internal combustion engine is referred to as a start initial increase control, and a start transition period from the end of the start initial increase control to a transition to a steady operation. The increase control performed during (1) is referred to as start transition period increase control. Further, the fuel injection control at the time of steady operation is referred to as steady time injection control.

[0008] In the start-up initial increase control, the fuel is injected at the start-up initial injection amount which is increased by several to several tens times the injection amount in the fuel injection during the steady operation. The starting initial injection amount depends on the amount of fuel forming the liquid film and the initial explosion of the internal combustion engine (first
(The second explosion) is set to a value equal to the sum of the fuel injection amount required for performing the second explosion). The amount of fuel injection required for the first explosion depends on the atmospheric pressure and intake air temperature when the engine is started, and the vaporization rate of the injected fuel (determined by the temperature of the engine). Therefore, the starting initial injection time TF for determining the injection amount at the time of the first injection at the time of starting is the starting initial basic injection time TFO calculated for various control conditions.
The starting initial atmospheric pressure correction coefficient KFP determined according to the starting atmospheric pressure, the starting initial engine temperature correction coefficient KFE determined according to the starting engine temperature, and the intake air temperature determined at the start. It is calculated by multiplying by the initial intake air temperature correction coefficient KFA. As the engine temperature, the temperature of the cooling water of the engine or the temperature of the crankcase of the engine is used.

The fuel having a liquid film formed on the wall surface of the throttle body and the like evaporates as time passes, so that the amount of fuel supplied to the cylinder increases exponentially. Therefore, in order to stabilize the rotation after the start, during the transitional period of the start from the start of the engine to the transition to the steady operation, the injection time is gradually shortened by gradually shortening the injection time to reduce the injection amount. It is necessary to perform a starting transient period increase control approaching the value of (1). The injection time TB in the start transition period increase control is determined by the start transition period basic injection time TBO determined for various control conditions such as the atmospheric pressure and the intake air temperature during the start transition period. The transitional atmospheric pressure correction coefficient KBP determined according to the above, the transitional engine temperature correction coefficient KBE determined according to the engine temperature during the transitional start, and the transitional intake air temperature determined according to the intake air temperature during the transitional start. The calculation is performed by multiplying the correction coefficient KBA by a start transient period elapsed time correction coefficient KBT for gradually decreasing the injection time with time (decreasing with time).

In addition, the injection time Ti in the steady-state injection control
The steady-state basic injection time Tu determined for various control conditions such as atmospheric pressure and intake air temperature during steady-state operation, and a steady-state atmospheric pressure correction coefficient KP determined according to the atmospheric pressure during steady-state operation This is calculated by multiplying a steady-state engine temperature correction coefficient KE determined according to the engine temperature during the steady operation by a steady-state intake temperature correction coefficient KA determined according to the intake air temperature during the steady operation.

Each of the above calculations is performed using an microcomputer provided in the control unit, and the starting initial injection time TF
And the process of calculating the start transition period injection time TB realize the start initial injection time calculation unit and the start transition period injection time calculation unit, respectively.

[0012] The microcomputer constituting the control unit of the fuel injection control device also performs an initial increase control at the start of the internal combustion engine and then shifts to a steady-state injection control through a start transient increase control. When the start of the internal combustion engine is started, the starting initial increase control mode is set, and when the initial start increase control mode is completed, the process is shifted to the start transient period increase control mode. Control mode switching means for switching the control mode so as to always shift to the control mode, and injection having a time width corresponding to the injection time calculated by the start initial injection time calculation means when the control mode is the start initial increase control mode. A starting initial injection command signal generating means for generating a command signal, and starting when the control mode is a starting transient period increasing control mode A starting transient period injection command signal generating means for generating an injection command signal having a time width corresponding to the injection time calculated by the long term injection time calculating means, and a steady-state injection time when the control mode is the steady-state control mode A steady-state injection command signal generating means for generating an injection command signal having a time width corresponding to the injection time calculated by the calculating means.

FIG. 7 shows a drive current Id flowing to the injector through the injector drive circuit in the start increasing control.
Is conceptually shown with respect to the time t. In the figure, Id1 denotes the drive flowing to the injector when the initial increase control is performed (at the time of the first injection at the start of the start). The waveforms of the currents are shown, and Id2 and Id3 show the waveforms of the drive current flowing through the injector at the time of the second and third injections, respectively, in which the starting transient period increase control is performed. In the starting transient period increase control, the injection time gradually decreases with time, and the fuel injection amount Q gradually decreases. FIG. 8 shows how the injection amount Q gradually decreases as time t elapses.

In an internal combustion engine, the amount of fuel required by the engine at the time of starting the engine is determined when the engine is started while the cylinder is cold and when the engine is started when the cylinder is warm. Are different. In a state where the inside of the cylinder is cold, the fuel is hardly vaporized in the cylinder, so that the fuel injection amount required by the engine at the time of starting is increased.
In a state where the inside of the cylinder is warm, the fuel is easily vaporized in the cylinder, so that the amount of fuel required by the engine at the time of starting is reduced.

Therefore, if it is possible to determine whether the temperature in the cylinder of the engine is high or low at the time of starting, it is possible to accurately control the fuel injection amount at the time of starting, and to obtain an engine with good startability. Can be.

[0016]

As described above, in an engine to which fuel is supplied by the fuel injection control device, if it is possible to determine the level of the temperature in the cylinder at the time of starting, the internal combustion engine requires at the time of starting. The fuel can be supplied accurately, and the startability of the engine can be improved.

However, since it is not possible to actually detect the temperature in the cylinder of the engine, conventionally, instead of detecting the temperature in the cylinder, the temperature of the cooling water of the engine or the temperature of the crankcase is detected as the engine temperature. And responded.

However, the temperature of the cooling water of the engine and the temperature of the crankcase are not the same as the temperature in the cylinder, and the temperature of the cooling water (or the crankcase) of the engine and the temperature in the cylinder after the engine is stopped are different. Due to the difference in how the engine cools down, it is often not possible to accurately supply the fuel required by the engine at start-up simply by detecting the coolant temperature of the engine or the temperature of the crankcase and calculating the injection time at start-up. . For example, when the engine is started, the temperature in the cylinder may be high even when the cooling water temperature is low.In such a case, if the fuel injection amount at the start is increased assuming that the engine is cold, the fuel The injection amount becomes larger than the required injection amount of the engine, the air-fuel mixture in the cylinder becomes rich, the spark plug becomes easy to cover, and the rotation speed is hardly increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection control for an internal combustion engine capable of accurately judging the level of a temperature in a cylinder and accurately supplying an amount of fuel required by the engine when the engine is started. It is an object of the present invention to provide a method and a fuel injection control device used for implementing the control method.

[0020]

According to the present invention, a fixed period from the start of the start of the internal combustion engine to the transition to the steady operation is defined as a start increase control period. For an internal combustion engine that performs start-up control to inject fuel that is larger than the amount from the injector, and shifts to steady-state injection control that injects fuel from the injector during normal operation after the start-up control period has elapsed. It relates to a fuel injection control method.

In the present invention, attention has been paid to the relationship between the temperature in the cylinder of the internal combustion engine and the temperature of the cooling water or crankcase of the internal combustion engine and the intake air temperature.

With respect to a two-cycle internal combustion engine in which fuel is injected into the throttle body, the temporal change in the temperature Tc in the cylinder and the temporal change in the coolant temperature TW of the engine detected as the engine temperature TE are examined. Figure 4
Immediately after the engine stops, the temperature in the cylinder TC
Is higher than the temperature TW of the cooling water, and the two temperatures Tc and TW decrease with the lapse of time. However, the two temperatures do not decrease in the same manner, and the temperature TC in the cylinder is lower than the cooling water temperature TW. It turns out that it is harder to fall than that.

In the example shown in FIG. 4, the internal temperature TC of the cylinder is higher than the cooling water temperature Tw for several hours after the engine is stopped at time 0, and several hours have elapsed since the engine was stopped. At the time t1 shown in the figure, TC> TW. If the engine is left for a considerable time after stopping (for example, overnight), the in-cylinder temperature TC and the cooling water temperature TW become equal, as in the state at time t2 in FIG.

On the other hand, the intake air temperature TA shows a value close to the outside air temperature Ta immediately after the stop of the engine, and becomes equal to the outside air temperature several hours after the stop of the engine, but the difference between the temperature TC in the cylinder and the cooling water temperature TW. When there is a difference between the intake air temperatures TA
It can be seen that there is also a difference between the cooling water temperature TW and the intake air temperature TA becomes equal to the cooling water temperature TW when the temperature TC in the cylinder becomes equal to the cooling water temperature TW.

From the above, when the cooling water temperature TW is higher than the intake air temperature TA, the temperature TC in the cylinder is higher than the cooling water temperature TW (the cylinder is still warm). Water temperature TW is intake temperature TA
In the following condition (generally, TW = TA),
It can be seen that it can be determined that the temperature inside the cylinder is equal to the cooling water temperature TW (the state where the inside of the cylinder is cold).

FIG. 5 shows the relationship between the amount of fuel required by the engine at the time of starting and the temperature TW of the cooling water. The curve a in FIG. 5 shows the amount of fuel required by the engine when TW = TA. Is shown. Curve b shows the amount of fuel required by the engine when TW-TA = .DELTA.t is small, and curve c shows TW-TA = .DELTA.t.
This shows the amount of fuel required by the engine when Δt is large. From these curves, the cooling water temperature TW and the intake air temperature TA
It can be seen that as the difference Δt increases, the amount of fuel required by the engine at the time of startup decreases, and by determining the level of the temperature in the cylinder from the magnitude relationship between the cooling water temperature and the intake air temperature, It can be seen that the injection amount at the start can be determined accurately.

Since the cooling water temperature TW of the engine is substantially the same as the temperature of the crankcase of the engine which can be measured from the outside, the same result can be obtained even if the cooling water temperature TW is replaced with the temperature of the crankcase. Can be. Therefore, in the present invention, the coolant temperature or the crankcase temperature is treated as the engine temperature TE.

From the above results, in the present invention, the engine in which the engine temperature TE is higher than the intake air temperature TA and the engine in which the engine temperature TE is lower than the intake air temperature TA are referred to as warm-up and cool-down, respectively. Temperature TE and intake air temperature TA
It is determined whether the engine is in a warm-up state or a cool-down state at the time of starting based on the magnitude relation between the engine and the engine, and the fuel injection amount at the time of starting is determined based on the result of the determination.

That is, in the present invention, the temperature of the cooling water of the internal combustion engine or the temperature of the crankcase of the internal combustion engine is detected as the engine temperature TE, and the intake air temperature TA of the internal combustion engine is detected.
Is detected, the engine temperature TE is compared with the intake air temperature TA, and
When the engine temperature TE is equal to or lower than the intake air temperature, a cold start control is performed to set the injection amount in the start increasing control to an appropriate value when the temperature of the internal combustion engine is low.
When the pressure is higher than A, the warm-up start control for setting the injection amount in the start-up increase control to an appropriate value when the internal combustion engine is warming up is performed.

As the start-up increasing control, at the time of starting the internal combustion engine at least at the first fuel injection, the initial-start-up increasing control for injecting from the injector a fuel which is larger than the injection amount at the time of the steady operation, and the initial-start-up increasing control are completed. After that, during the transition period of the start until the transition to the steady operation, the injection amount increased during the steady operation is gradually decreased from that at the time of the steady operation, and the start transition period increasing control to approach the injection amount at the time of the steady operation is performed. In the case of transition to the steady-state injection control after the end of the transition period increase control, the engine temperature TE and the intake air temperature TA are compared, and when the engine temperature TE is equal to or lower than the intake air temperature, the starting initial increase control and the start transition period are performed. When the engine temperature TE is higher than the intake air temperature TA, the start-up initial increase control and the cold start control are performed to set the injection amount in the boost control to an appropriate value when the temperature of the internal combustion engine is low. A warm-up start control for setting an injection amount in the start transition period increase control to an appropriate value when the internal combustion engine is warming is performed.

In order to carry out the above control method, a fuel injection control device according to the present invention includes an injector for injecting fuel while a predetermined drive current is applied, and a basic fuel for starting the internal combustion engine at the start of operation. Start initial injection time calculating means for calculating an initial start injection time by multiplying an initial start basic injection time, which is an injection time, by a start initial correction coefficient determined according to various control conditions, and shifting to a steady operation after starting the internal combustion engine. In order to gradually decrease the injection time as the time elapses with the start transient period correction coefficient determined according to various control conditions during the start transient period basic injection time, which is the increased basic fuel injection time until the start transient period A start-transition-period injection time calculating means for calculating a start-period-period injection time by multiplying by an elapsed-time correction coefficient; A steady-state injection time calculating means for calculating a steady-state injection time by multiplying by a steady-state correction coefficient determined according to a control condition; and injecting a fuel of an injection amount increased at the start of the internal combustion engine as compared with the steady-state operation. The initial startup increase control mode is entered, and when the initial startup increase control mode is completed, the fuel injection amount is gradually reduced.The transition is made to the startup transient increase control mode, and it is detected that the startup transient increase control mode is completed. Control mode switching means for switching the control mode such that the control mode is shifted to the steady state control mode when the control is performed, and a time corresponding to the injection time calculated by the start initial injection time calculation means when the control mode is the start initial increase control mode. A starting initial injection command signal generating means for generating an injection command signal having a width, and starting over when the control mode is a starting transient period increasing control mode. Starting transient period injection command signal generating means for generating an injection command signal having a time width corresponding to the injection time calculated by the initial injection time calculating means, and the steady-state injection time when the control mode is the steady-state control mode. Steady-state injection command signal generation means for generating an injection command signal having a time width corresponding to the injection time calculated by the calculation means, and an injector drive circuit for applying a drive current to the injector in accordance with the injection command signal In the present invention, the cooling water temperature of the internal combustion engine or the temperature of the crankcase of the internal combustion engine is set to the engine temperature TE.
, An intake temperature detecting means for detecting the intake air temperature TA of the internal combustion engine, and comparing the engine temperature TE detected by the engine temperature detecting means with the intake air temperature TA detected by the intake temperature detecting means. And the engine temperature TE
When the engine temperature is lower than or equal to the intake air temperature, the start-up initial cold start control is performed with the injection time calculated by the start-up initial injection time calculation means as the time width of the injection command signal. When the engine temperature TE is higher than the intake air temperature TA, the start-up initial injection is performed. Initiating initial cooling and warming for performing an initial starting warm-up start control in which the injection time calculated by the time calculating means is corrected to a value suitable when the internal combustion engine is warming up and the corrected injection time is set as a time width of the injection command signal. The engine control means compares the engine temperature TE detected by the engine temperature detecting means with the intake air temperature TA detected by the intake air temperature detecting means. Means for controlling the start of the cooling operation during the transitional period of the start, in which the injection time calculated by the means is set as the time width of the injection command signal. The injection time calculated by the first injection time calculating means is corrected to a value suitable when the internal combustion engine is warming up, and the modified injection time is set to the time width of the injection command signal to perform a startup transient period warm-up start control. And a start-up transition cooling / heating control means. In this case, the starting initial injection time calculating means and the starting transient injection time calculating means are configured to calculate the starting initial injection time (when the engine is cold) and the starting transient injection time when the engine temperature is equal to or lower than the intake air temperature, respectively. Keep it.

As described above, the temperature of the cooling water of the internal combustion engine or the temperature of the crankcase of the internal combustion engine is detected as the engine temperature TE, and the intake air temperature TA of the internal combustion engine is detected. When the engine temperature is higher than the intake air temperature TA, the internal combustion engine performs the cold start control to set the injection amount in the startup increase control to an appropriate value when the temperature of the internal combustion engine is low. If the warm-up start control is set to a value that is appropriate when the engine is warm, the amount of fuel that almost always matches the amount required by the engine when the internal combustion engine is started can be injected. It is possible to prevent the mixture from becoming too rich or too thin, thereby improving the startability of the engine.

FIG. 6 shows the limit width of the fuel injection amount which enables the start of the two-cycle internal combustion engine. The horizontal axis of the figure shows the cooling water temperature TW. The vertical axis indicates the fuel injection amount Q, and 100 [%] of the vertical axis indicates the reference value of the fuel injection amount at the time of starting. In FIG. 6, curve a
1 indicates the lean limit at the time of cold start, and the curve a2
Indicates the lean limit at the time of warm-up start. And curve b
1 indicates the Rich limit at the time of cold start, and the curve b2
Indicates the Rich limit at the start of warm-up.

Here, the lean limit is a lower limit value of the injection amount necessary for facilitating the start of the engine. When the fuel injection amount falls below the lean limit, the lean limit is set to enable the engine to be started. The required number of injections increases, making it difficult to start the engine. Further, the Rich limit is an upper limit of the injection amount necessary for facilitating the start of the engine. If the fuel injection amount exceeds the Rich limit, the mixture becomes too rich and the start of the engine becomes difficult. .

When the fuel injection amount Q at the time of starting is determined from the temperature of the cooling water of the engine as in the conventional fuel injection control, the fuel injection amount at the time of starting is increased to the Rich limit at the time of starting the cold engine. At the start of warm-up, the spark plug becomes wet (covered), making it extremely difficult to start the engine. Since it is necessary to avoid such a situation as much as possible, it is not necessary to determine whether the engine is in a cold state or a warm-up state. In the case of the conventional control method for determining Q, the upper limit of the injection amount is set to the Rich limit (curve b
2) The range of the fuel injection amount that can be started must be limited to the following range, which is limited to the range of W1 in FIG.

On the other hand, as in the present invention, it is determined whether the engine is in a cold state or a warm-up state at the time of starting, and an injection amount at the start corresponding to each state is determined. In this case, the engine can be started even if the injection amount increases to the Rich limit (curve b1) at the time of warm-up start, and the range of the fuel injection amount that can be started is up to the range of W2 in FIG. It is enlarged.

As described above, according to the present invention, since the range of the injection amount that can be started can be expanded, even if the characteristics of the control device and the characteristics of the engine are large to some extent, the startability of the engine is improved. can do.

[0038]

FIG. 1 shows an example of a hardware configuration of a fuel injection control device according to the present invention. In FIG. 1, reference numeral 1 denotes a power generating coil in a magnet generator attached to an internal combustion engine; A DC power supply circuit for converting the output voltage of the power generation coil 1 into a DC constant voltage, 3 is an injector, 4 is an injector drive circuit, and 5 is a control unit that supplies an injection command signal Vj to the injector drive circuit 4.

The injector 3 is provided with an injector body to which fuel is supplied from the fuel pump at a predetermined pressure, a needle valve for opening and closing a fuel injection port provided at a tip of the injector body, and an electromagnet for driving the needle valve. The valve is opened and fuel is injected while a predetermined level of drive current is applied to the drive coil 3a of the electromagnet. The injector 3 is mounted so as to inject fuel into the throttle body of the engine. Since the pressure of the fuel supplied from the fuel pump to the injector 3 is controlled by the regulator and is kept substantially constant, the fuel injection amount becomes higher than the level required for the drive current supplied to the drive coil 3a to open the valve. Time (injection time).

The injector drive circuit 4 comprises a switch circuit using a switching element such as a transistor or an FET which can be controlled on / off. The switching element of the switch circuit is connected in series to the drive coil 3a. A constant drive voltage Vd is applied from the DC power supply circuit 2 to both ends of a series circuit of the drive coil 3a and the switching element.

The control unit 5 comprises a microcomputer having a CPU, a ROM, a RAM, a timer, and the like. By executing a program described later, various calculations for calculating the injection time, the correction coefficient of the injection time, and the like are performed. Means, control mode switching means, and the like.

The control unit 5 includes an output of a throttle sensor 6 for detecting an opening of a throttle valve for adjusting an amount of air flowing into the throttle body, an output of an atmospheric pressure sensor 7 for detecting atmospheric pressure, and an engine. The output of the intake air temperature sensor 8 for detecting the intake air temperature and the output of the engine temperature sensor 9 for detecting the engine temperature are input via an interface (not shown). The engine temperature sensor 9 detects the temperature of the cooling water of the engine or the temperature of the crankcase of the engine as the engine temperature.

The control unit 5 also receives a first signal V at a reference position set at a predetermined rotational angle position of the crankshaft of the engine.
s1 and the output of the signal generator 10 which generates the second signal Vs2 at a position delayed from the reference position is output from the waveform shaping circuit 1.
1 and 12 are input. Waveform shaping circuit 11
Converts the first signal Vs1 output by the signal generator into a signal having a waveform recognizable by the microcomputer and inputs the signal to the microcomputer constituting the control unit 5. Further, the waveform shaping circuit 12 outputs the second signal Vs2 output from the signal generator 10.
Is converted into a signal having a waveform recognizable by the microcomputer and input to the microcomputer.

The control unit 5 calculates the rotation speed of the engine from the generation cycle of the first signal Vs1 and the second signal VS2 given from the signal generator 10, and every time the first signal Vs1 is generated, The fuel injection time is calculated based on the control conditions given by various sensors, and the measured value of the calculated injection time is set in a timer provided in the microcomputer. The timer gives the injection command signal Vj to the injector drive circuit 4 while measuring the measured value of the injection time,
When the measurement of the injection time is completed, the injection command signal Vj is extinguished. As a result, an injection command signal Vj having a time width corresponding to the calculated injection time is given to the injector drive circuit 4.

The injection command signal V is supplied to the injector drive circuit 4.
When j is given, the switching elements constituting the injector drive circuit 4 are turned on, and the injector 3
Drive current Id flows through the drive coil 3a. While the drive current is equal to or higher than the predetermined level, the valve of the injector 3 is opened to inject fuel.

FIG. 2 is a flowchart showing an algorithm of a main part of a program executed by the microcomputer constituting the control unit 5.

The meaning of each symbol shown in the flowchart of FIG. 2 is as follows.

TF: Start initial injection time TFO: Start initial basic injection time KFP: Start initial atmospheric pressure correction coefficient KFE: Start initial engine temperature correction coefficient KFA: Start initial intake air temperature correction coefficient TB: Start transient injection time TBO: Start Transition period basic injection time KBP: Start transition period atmospheric pressure correction coefficient KBE: Start transition period engine temperature correction coefficient KBA: Start transition period intake air temperature correction coefficient KBT: Start transition period elapsed time correction coefficient Ti: Steady state injection time Tu: Constant Constant basic injection time Kp: Steady-state atmospheric pressure correction coefficient KE: Steady-state engine temperature correction coefficient KA: Steady-state intake air temperature correction coefficient Although not shown in FIG. 2, in the main routine of the program executed by the microcomputer, the program starts. Initialization of each part at the time, reading of data from various sensors, calculation of the engine speed, and the like are performed. The flowchart shown in FIG. 2 shows an algorithm of an interrupt routine executed when the signal generator 10 generates the first signal Vs1 during the execution of the main routine. It is determined whether or not the starting initial increase control has been completed (whether or not the first injection has been performed). As a result of this determination, when it is determined that the initial startup increase control has not been completed, then step 2
In step (1), a starting initial basic injection time TFO, which is a basic fuel injection time at the start of starting the internal combustion engine, is calculated for various control conditions. The calculation of the injection time is performed using a map that gives a relationship between the outputs of various sensors and the basic injection time at the start. After calculating the start initial basic injection time TFO, in step 3, a start initial atmospheric pressure correction coefficient KFP to be multiplied by the start initial basic injection time TFO is calculated. The initial atmospheric pressure correction coefficient KFP is calculated using a map that gives a relationship between the atmospheric pressure given by the detection output of the atmospheric pressure sensor 7 and the correction coefficient KFP. Then, in step 4,
Starting initial engine temperature correction coefficient K with respect to engine temperature at startup
FE is map-calculated, and in step S5, a map is calculated for the initial intake air temperature correction coefficient KFA for the intake air temperature detected by the intake air temperature sensor. After calculating the start-up initial intake air temperature correction coefficient KFA, in step 6, a calculation is performed by multiplying the start-up initial basic injection time TFO by the start-up initial correction coefficients KFP, KFE, and KFA to calculate the start-up initial injection time TF. Steps 2 to 6 calculate the initial start-up injection time by multiplying the initial start-up basic injection time, which is the basic fuel injection time at the start of the internal combustion engine, by a start-up initial correction coefficient determined according to various control conditions. An injection time calculation means is realized. The starting initial injection time calculating means is configured to calculate a starting initial injection time suitable when the engine temperature is equal to or lower than the intake air temperature (when the engine is cold).

After calculating the starting initial injection time TF, the engine temperature TE is compared with the intake air temperature TA in step 7, and when the engine temperature TE is lower than the intake air temperature TA,
The start control mode is set as the initial cold start control mode.
The routine proceeds to step 8, where the count value of the cold start initial injection time TF calculated in step 6 is set in a timer.
After setting the count value of the initial injection time TF in the timer, the process returns to the main routine. The control unit 5 outputs the injection command signal Vj while the timer is performing the timekeeping operation, and stops the output of the injection command signal Vj when the timekeeping operation is completed.

If it is determined in step 7 that the engine temperature TE is higher than the intake air temperature TA, the process proceeds to step 9 in which the start control mode is set to the initial warm-up start control mode. In step 9, a calculation is performed by multiplying the initial startup injection time TF calculated in step 6 by the correction coefficient KΔtx to correct the initial startup injection time to a value suitable for warm-up. Next, the count value of the corrected initial injection time TF is set in a timer, and the process returns to the main routine.

In this example, steps 7 to 9
By comparing the engine temperature TE detected by the engine temperature detecting means (sensor 9) with the intake air temperature TA detected by the intake air temperature detecting means (sensor 8), when the engine temperature TE is equal to or lower than the intake temperature, the engine is started. An initial cold start control is performed to set the injection time TF calculated by the initial injection time calculation means (in step 6) to a value suitable when the temperature of the internal combustion engine is low, and the engine temperature TE is higher than the intake air temperature TA. In some cases, a start-up initial cooling / heating control unit for performing a start-up initial warm-up start control for setting the injection time calculated by the start-up initial injection time calculation unit to a value suitable when the internal combustion engine is warming up is realized. Further, in steps 2 to 9, the starting initial increase control is performed. This startup initial increase control is normally performed only at the time of the first injection.

In the interrupt routine shown in FIG.
When it is determined in step 1 that the initial startup increase control has been completed (the first injection has already been performed), the process proceeds to step 10 to determine whether the startup transient period increase control has been completed. judge. As a result, when it is determined that the startup transition period increase control has not been completed, in step 11, the startup transition period basic injection time TBO, which is the basic fuel injection time in the startup transition period of the internal combustion engine, is set for various control conditions. Perform a map operation. After calculating the start transition period basic injection time TBO, in step 12, a map is calculated for a start transition period atmospheric pressure correction coefficient KBP to be multiplied by the start transition period basic injection time TBO. Next, at step 13, a start transition period engine temperature correction coefficient KBE is calculated with respect to the engine transition period engine temperature, and at step 14, the start-up intake air temperature correction coefficient KBA is calculated with respect to the intake air temperature detected by the intake air temperature sensor. Is calculated. Thereafter, in step 15, an elapsed time correction coefficient KBT for gradually decreasing the injection time with the passage of time is calculated, and in step 16, the correction coefficients KBP, KB are added to the basic injection time TBO in the starting transition period.
A calculation for multiplying E, KBA and KBT is performed to calculate a start transition period injection time TB. In steps 11 to 16, the start transition period injection time is calculated by multiplying the start transition period basic injection time, which is the basic fuel injection time in the start transition period of the internal combustion engine, by a start transition period correction coefficient determined according to various control conditions. In this way, the starting transient period injection time calculating means is realized. The start transition period injection time calculation means is configured to calculate a start transition period injection time suitable when the engine temperature is equal to or lower than the intake air temperature (during cold).

After calculating the injection time TB during the transitional period of the start, the engine temperature TE is compared with the intake air temperature TA at step 18, and when the engine temperature TE is equal to or lower than the intake air temperature TA, the start control mode is changed to the start of the transitional period cold start. In the control mode, the process proceeds to step S8, and the count value of the injection period TB during the start transition period calculated in step S16 is set in the timer.
After setting the count value of the injection time TB during the transition period in the timer, the process returns to the main routine. The control unit 5 outputs the injection command signal Vj while the timer is performing the timekeeping operation, and stops the output of the injection command signal Vj when the timekeeping operation is completed.

If it is determined in step 17 that the engine temperature TE is higher than the intake air temperature TA, the process proceeds to step 18 in which the start control mode is set to a transitional start-up warm-up start control mode. In step 18, the start transient period injection time TB calculated in step 16 is multiplied by the start transient period warm-up control correction coefficient KΔtx 'to correct the start transient period injection time to a value suitable for warm-up. Next, the routine proceeds to step 8, where the corrected count value of the injection time TB during the start-up transition period is set in the timer, and then the flow returns to the main routine.

In this example, step 17 and step 1
In step 8 and step 8, the engine temperature TE detected by the engine temperature detecting means (sensor 9) is compared with the intake air temperature TA detected by the intake air temperature detecting means (sensor 8). In the following cases, the engine control device controls the engine during the transitional start-up period to set the injection time TB calculated by the start-up transitional period injection time calculation means (at step 16) to a value suitable when the temperature of the internal combustion engine is low.
When E is higher than the intake air temperature TA, the injection time calculated by the start-time transient injection time calculation means is set to a value suitable when the internal combustion engine is warming. Machine control means is realized. In addition, in steps 10 to 18, the starting transient period increase control is performed. The startup transient period increase control is performed for a fixed time (timed by a timer provided in the microcomputer) after the startup initial stage increase control is completed. It gets shorter as time goes on.

When it is determined in step 10 that the control for increasing the amount during the transition period in the starting period has been completed, the routine proceeds to the steady-state injection control. In this steady-state injection control, in step 19, a steady-state basic injection time Tu, which is a basic fuel injection time during a steady operation of the internal combustion engine, is map-calculated for various control conditions. After calculating the steady-state basic injection time Tu, in step 20, a map calculation is performed on a steady-state atmospheric pressure correction coefficient KP to be multiplied by the steady-state basic injection time Tu. Next, at step 21, a steady-state engine temperature correction coefficient KE is calculated for the steady-state engine temperature, and at step 22, a steady-state intake temperature correction coefficient KA is calculated for the intake air temperature detected by the intake air temperature sensor. I do. afterwards,
In step 23, the steady-state injection time Ti is calculated by multiplying the steady-state basic injection time Tu by the correction coefficients KP, KE, and KA.

In steps 19 to 23, the steady-state injection time is calculated by multiplying the steady-state basic injection time, which is the basic fuel injection time during steady operation of the internal combustion engine, by a steady-state correction coefficient determined according to various control conditions. A steady-state injection time calculating means is realized.

After calculating the steady-state injection time Ti, the routine proceeds to step 8, where the calculated count value of the steady-state injection time Ti is set in a timer, and the process returns to the main routine.

In the example shown in FIG. 2, steps 1 and 10
Thereby, at the start of the start of the internal combustion engine, an initial fuel increase control mode for injecting fuel having an increased fuel injection quantity than at the time of steady operation is performed, and when the initial fuel increase control mode is completed, the fuel injection amount is gradually reduced. Control mode switching means for switching the control mode so as to shift to the start-up transition period increasing control mode and to shift to the steady-state control mode when the completion of the start-up transition period increase control mode is detected.

Also, according to steps 2 to 9, when the control mode is the start-up initial increase control mode, an initial-start-up operation for generating an injection command signal having a time width corresponding to the injection time calculated by the start-up initial injection time calculating means. Injection command signal generating means is realized, and by steps 11 to 18 and step 8, a time width corresponding to the injection time calculated by the starting transient period injection time calculating means when the control mode is the starting transient period increase control mode. A starting transient period injection command signal generating means for generating an injection command signal having the following is realized.

Further, in steps 19 to 23 and step 8, when the control mode is the steady state control mode, an injection command signal having a time width corresponding to the injection time calculated by the steady state injection time calculating means is generated. A steady-state injection command signal generating means is realized.

As described above, the engine temperature TE and the intake air temperature T
By comparing with A, it is determined whether the engine is in a warm-up state or a cold state at the time of starting, and the injection amount at the time of starting is calculated based on the determination result. Since the injection amount can be maintained in an appropriate range, the start of the engine can be facilitated, and an abnormal state in which the engine stops after the engine starts can be prevented.

In the above example, only one correction coefficient is prepared for the warm-up start control. However, the correction coefficient differs depending on the difference Δt (= TE−TA) between the engine temperature TE and the intake air temperature TA. The correction of the injection time may be subdivided by multiplying by a correction coefficient to perform a fine-grained warm-up start control.

In the warm-up start control performed in the initial increase control, the correction of the injection time is subdivided, for example, by replacing the part A enclosed by a broken line in FIG. 2 with the routine shown in FIG. I just need.

In the routine shown in FIG. 3, step 7 is the same as step 7 in FIG. 2, and compares the engine temperature TE with the intake air temperature TA. In step 7,
If it is determined that TE.ltoreq.TA, the control mode is set to the cold start control mode, and the routine proceeds to step 8 in FIG. 2, in which the count value of the initial startup injection time TF is set in the timer of the control unit.

If it is determined in step 7 that TE> TA, the routine proceeds to step 7a, where TE and TA + T
A is compared with that of a (determining whether Δt = TE−TA is less than or equal to a set value Ta). If the result is TE ≦ TA + Ta, step 9a is executed and step 6 in FIG. The correction coefficient KΔt is added to the starting initial injection time TF calculated by
is multiplied by a to calculate a starting initial injection time TF corrected so as to be suitable when the difference between the engine temperature and the intake air temperature is Ta. If it is determined in step 7a that TE> TA + Ta, the routine proceeds to step 7b, where TE.ltoreq.TA + T
Determine if b. As a result, TE ≦ TA + T
b, the routine proceeds to step 9b, where the starting initial injection time T calculated in step 6 of FIG.
F is multiplied by a correction coefficient KΔtb to calculate a starting initial injection time TF suitable when the difference between the engine temperature and the intake air temperature is Tb. In the same manner, the process proceeds to step 7y according to the magnitude of the difference between the engine temperature and the intake air temperature. If it is determined in step 7y that TE ≦ TA + Ty, the process proceeds to step 9y, and proceeds to step 6 in FIG. By multiplying the calculated starting initial injection time TF by the correction coefficient KΔty,
A suitable starting initial injection time TF is calculated when the difference between the engine temperature and the intake air temperature is Ty. When it is determined in step 7y that TE> TA + Ty, the routine proceeds to step 9z, where the engine initial temperature and intake air temperature are calculated by multiplying the initial startup injection time TF calculated in step 6 of FIG. 2 by a correction coefficient KΔtz. Is calculated when the difference between the two is equal to Tz. In FIG. 3, between Ta, Tb,..., Ty, Ta <Tb <.
There is a relationship of Ty.

Similarly, in the warm-up start control performed in the start transient period increase control, in order to subdivide the correction of the injection time, the portion B enclosed by a broken line in FIG.
May be replaced by a routine similar to the routine shown in FIG.

As shown in FIG. 3, when the warm-up state is subdivided and the injection amount in the initial stage and the transition period is finely corrected, the injection amount at the start of the engine is set to a more appropriate value. As a result, the startability of the engine can be further improved.

[0069]

As described above, according to the present invention, the engine temperature TE is compared with the intake air temperature TA to determine whether the engine is warmed up or cold at the time of starting. Since the injection amount at the start is calculated based on the determination result, the injection amount at the start can always be set in an appropriate range to facilitate the start of the engine, and the engine can be started after the engine is started. There is an advantage that it is possible to prevent occurrence of an abnormal state such as stoppage.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a fuel injection control device according to the present invention.

FIG. 2 is a flowchart showing a main part of an algorithm of a program executed by a microcomputer constituting the control unit shown in FIG. 1;

FIG. 3 is a flowchart showing a modification of the main part of the algorithm of the program shown in FIG. 2;

FIG. 4 is a diagram showing temporal changes in a cylinder temperature and a cooling water temperature after the engine stops, together with temporal changes in an intake air temperature and an outside air temperature.

FIG. 5 is a diagram showing a relationship between an injection amount and a cooling water temperature required at the time of starting the engine.

FIG. 6 is a diagram showing a relationship between a range of an injection amount in which the engine can be started and a cooling water temperature in a cold state and a warm-up state.

FIG. 7 is a waveform diagram showing a waveform of a drive current supplied to an injector during startup increasing control.

FIG. 8 is a diagram showing a state in which the fuel injection amount is gradually reduced at the time of start increasing control.

[Explanation of symbols]

 3 Injector 4 Injector drive circuit 5 Control unit 6 Throttle sensor 7 Atmospheric pressure sensor 8 Intake temperature sensor 9 Engine temperature sensor

Claims (3)

[Claims] 1. A fixed period from the start of the start of the internal combustion engine to the transition to the steady operation is defined as a start increase control period. During the start increase control period, the amount of fuel that has been increased from the injection amount during the steady operation is controlled. In the fuel injection control method for an internal combustion engine, which performs start increasing control for injecting from the injector and shifts to steady-state injection control for injecting the fuel of the injection amount during steady operation from the injector after the start increasing control period has elapsed, The temperature of the cooling water of the internal combustion engine or the temperature of the crankcase of the internal combustion engine is detected as an engine temperature (TE), and the intake temperature (TA) of the internal combustion engine is detected. The engine temperature (TE) and the intake temperature (TE) are detected. TA), when the engine temperature (TE) is equal to or lower than the intake air temperature (TA), the injection amount in the start increasing control is set to a value suitable for when the temperature of the internal combustion engine is low. A warm-up start control in which a set cold start control is performed, and when the engine temperature (TE) is higher than an intake air temperature (TA), the injection amount in the start increasing control is set to a value suitable for when the internal combustion engine is warm. And a fuel injection control method for an internal combustion engine. 2. A starting initial increase control for injecting fuel from the injector at a time of at least the first fuel injection at the time of starting the internal combustion engine, which is larger than an injection amount during a steady operation, and terminating the starting initial increase control. After that, during the start transition period until the transition to the steady operation, the start transition period increase control is performed so that the injection amount increased from the steady operation is gradually decreased to approach the injection amount during the steady operation during the transition period. A fuel injection control method for an internal combustion engine which shifts to a steady-state injection control for injecting a fuel of an injection amount during a steady operation after the start transition period increase control is completed, wherein a cooling water temperature of the internal combustion engine or a crankcase of the internal combustion engine is provided. Is detected as an engine temperature (TE), an intake air temperature (TA) of the internal combustion engine is detected, and the engine temperature (TE) and the intake air temperature (TA) are compared. When the temperature (TE) is equal to or lower than the intake air temperature (TA), a cold start control for setting the injection amount in the above-described initial increase control and the increase in the start transition period to an appropriate value when the temperature of the internal combustion engine is low is performed. Engine temperature (TE)
When the temperature of the internal combustion engine is higher than the intake air temperature (TA), a warm-up start control for setting the injection amount in the initial start-up increasing control and the starting transient-time increasing control to an appropriate value when the internal combustion engine is warming up is performed. Fuel injection control method for an internal combustion engine. 3. An injector for injecting fuel while a predetermined drive current is being applied, and a starting initial basic injection time which is a basic fuel injection time when starting the internal combustion engine is determined according to various control conditions. A starting initial injection time calculating means for calculating a starting initial injection time by multiplying by a starting initial correction coefficient;
Starting transient period basic injection time, which is the increased basic fuel injection time during the transition period from the start of the internal combustion engine until transition to steady operation, and the transition coefficient of the starting transient period determined according to various control conditions and the elapsed time of the basic injection time A start transient period injection time calculating means for calculating a start transient period injection time by multiplying by an elapsed time correction coefficient for gradually decreasing the injection time in accordance with the above, and a steady state basic fuel injection time which is a basic fuel injection time of the internal combustion engine. Steady-state injection time calculating means for calculating the steady-state injection time by multiplying the injection time by a steady-state correction coefficient determined in accordance with various control conditions, and an injection increased at a start of the internal combustion engine as compared with a normal operation. The start initial increase control mode for injecting an amount of fuel is performed, and when the start initial increase control mode is completed, a transition is made to a start transient period increase control mode in which the fuel injection amount is gradually reduced, and Control mode switching means for switching the control mode so as to shift to the steady-state control mode when it is detected that the startup transient period increase control mode is completed; and when the control mode is the start initial increase control mode, A starting initial injection command signal generating means for generating an injection command signal having a time width corresponding to the injection time calculated by the injection time calculating means; and a starting transient period when the control mode is a starting transient period increasing control mode. A starting transient period injection command signal generating means for generating an injection command signal having a time width corresponding to the injection time calculated by the injection time calculating means; and the steady-state injection time when the control mode is the steady-state control mode. A steady-state injection command signal generating means for generating an injection command signal having a time width corresponding to the injection time calculated by the calculating means; And an injector drive circuit for applying a drive current to the injector in response to the injection command signal, the fuel injection control device for an internal combustion engine, comprising: determining a coolant temperature of the internal combustion engine or a temperature of a crankcase of the internal combustion engine. Engine temperature detecting means for detecting the temperature (TE); intake temperature detecting means for detecting the intake air temperature (TA) of the internal combustion engine; and engine temperature (TE) detected by the engine temperature detecting means.
) And the intake air temperature (TA) detected by the intake air temperature detecting means.
), The engine temperature (TE) becomes equal to the intake air temperature (TA).
In the following cases, the starting initial cold start control is performed with the injection time calculated by the starting initial injection time calculating means as the time width of the injection command signal, and the engine temperature (TE)
Is higher than the intake air temperature (TA), the injection time calculated by the starting initial injection time calculation means is corrected to a value suitable when the internal combustion engine is warming up, and the corrected injection time is set to the time of the injection command signal. A start-up initial cooling / warm-up control unit for performing a start-up initial warm-up start control having a width; and an engine temperature (TE) detected by the engine temperature detecting unit.
) And the intake air temperature (TA) detected by the intake air temperature detecting means.
When the engine temperature (TE) is equal to or lower than the intake air temperature, cold start control for the start transition period is performed using the injection time calculated by the start transition period injection time calculation means as the duration of the injection command signal. However, when the engine temperature (TE) is higher than the intake air temperature (TA), the injection time calculated by the starting transient injection time calculation means is corrected to a value suitable when the internal combustion engine is warm. A starting transient cooling / heating control means for performing a starting transient warm-up start control in which an injection time is a time width of the injection command signal, wherein the starting initial injection time calculating means and the starting transient period injection time calculating means are provided. A fuel injection control device for an internal combustion engine, which calculates a starting initial injection time and a starting transitional injection time when the engine temperature is equal to or lower than the intake air temperature.