JPH08177552A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To enable the injection of the fuel quantity necessary for the start of an engine even at the time of voltage being lowered so as to secure excellent startability by multiplying the start time effective injection time by correction factors, obtained according to the driving voltage of a fuel pump, to correct the start time effective injection time at the time of starting the engine. CONSTITUTION: In case of reading the output signals of a water temperature sensor 22, an intake air temperature sensor 23, and the like for detecting an engine operating state into a fuel injection control device 19 to control the injection timing of each injector 18, the effective injection time is obtained on the basis of the cooling water temperature at the time of starting an engine. When the cooling water temperature is the specified temperature or lower, individual correction factors are respectively obtained on the basis of battery voltage and intake air temperature, and the effective injection time is multiplied by these correction factors to obtain the corrected effective injection time at the start time. The invalid injection time obtained from the battery voltage is then added to the corrected effective injection time to obtain the fuel injection time at the start time, and each injector 18 is controlled on the basis of this fuel injection time.

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 device for an internal combustion engine, which controls an injector for injecting fuel supplied by a fuel pump into the internal combustion engine (hereinafter referred to as "engine").

[0002]

2. Description of the Related Art Generally, the fuel injection time of an injector at the time of engine start is calculated by the following equation. Fuel injection time at startup = effective injection time + ineffective injection time Here, the invalid injection time is a time that does not contribute to the fuel injection amount due to an actual valve opening / closing operation delay with respect to the electric signal supplied to the injector. . On the other hand, effective injection time (basic injection time)
Is the time when fuel is actually injected, and is the time determined based on the cooling water temperature at the time of starting.

By the way, when the engine is started, the battery voltage is temporarily lowered by the operation of the starter and the voltage applied to the injector is also lowered, so that the invalid injection time is increased due to the delay in the operation of the injector. Further, when the engine is started in a cold state in winter, the vaporization effect of fuel (gasoline) is reduced. Such a decrease in the vaporization effect and an increase in the invalid injection time cause a deterioration in the startability of the engine. Therefore, as shown in JP-A-58-28537, the effective injection time at the start and the intake air temperature are changed. The effective injection time at startup is corrected by multiplying it by the appropriate correction coefficient, and the invalid injection time is set to a time corresponding to the battery voltage, and the fuel injection time at startup is calculated by summing these to obtain the startability. There are things that are designed to improve.

[0004]

In the above-mentioned conventional structure, the deterioration of the startability due to the decrease of the battery voltage at the time of starting the engine is dealt with by increasing the invalid injection time for compensating the operation delay of the injector. However, when the battery voltage decreases, the applied voltage of the fuel pump that supplies the fuel to the injector also decreases, the rotation speed of the fuel pump decreases, and the discharge pressure-discharge flow rate characteristic of the fuel pump decreases as shown in FIG. . In addition, when the temperature of the fuel pump is extremely low, the magnetic field of the magnet of the pump motor that drives the fuel pump becomes strong, and the driving force of the pump motor decreases even with the same applied voltage. The speed decreases, and the discharge pressure-discharge flow rate characteristic decreases. Therefore, at the time of extremely low temperature starting in winter, the pump capacity that has decreased due to the battery voltage decrease will further decrease due to the decrease in the driving force of the pump motor due to low temperature, and the fuel pressure in the fuel pipe (hereinafter referred to as "fuel pressure") will be reduced. It may be less than the set pressure of. In this case, the effective injection time that actually contributes to the fuel injection does not change just by correcting the ineffective injection time according to the battery voltage as in the above-described conventional configuration. Running out,
The engine may not start.

As a method of preventing this, it is conceivable to increase the flow rate of the fuel pump, but in this case, not only the cost of the fuel pump itself is increased but also the fuel consumption of the engine is higher than the fuel consumption of the engine under normal operating conditions. Much more fuel will be discharged from the fuel pump. Therefore, it is necessary to increase the amount of fuel returned from the pressure regulating valve side to the fuel tank, raise the fuel temperature in the fuel tank, thereby increasing the vapor amount, and increasing the capacity of the canister that adsorbs vapor. Problems such as occurrence of fuel odor and leakage of fuel odor will occur.

The present invention has been made in view of the above circumstances, and therefore an object of the present invention is to use a fuel pump having a suitable capacity under normal operating conditions, and at the same time, at a low battery voltage or at a low temperature. An object of the present invention is to provide a fuel injection control device for an internal combustion engine, which is capable of ensuring various startability.

[0007]

To achieve the above object, a fuel injection control device for an internal combustion engine according to claim 1 of the present invention controls an injector for injecting fuel supplied by a fuel pump into the internal combustion engine. In this case, voltage information detecting means for detecting information on the drive voltage of the fuel pump, correction coefficient determining means for obtaining a correction coefficient according to the drive voltage of the fuel pump at the time of starting the internal combustion engine, and starting the correction coefficient. Effective injection time correction means for multiplying the effective injection time at the time to correct the effective injection time at the start, and the invalid injection time added to the corrected effective injection time at the start to obtain the fuel injection time at the start The injection time calculating means is provided.

In this structure, the voltage information detecting means may detect the battery voltage as the information on the driving voltage of the fuel pump. Further, as in claim 3, a pump temperature information detecting means for detecting information on the temperature of the fuel pump is provided,
The correction coefficient determining means may obtain an individual correction coefficient based on the drive voltage of the fuel pump and the temperature of the fuel pump or a correction coefficient that is a combination of both.

In this case, as described in claim 4, the pump temperature information detecting means detects at least one of the fuel temperature, the outside air temperature and the intake air temperature as the information about the temperature of the fuel pump. Is also good.

According to a fifth aspect of the present invention, there is provided water temperature information detecting means for detecting information on the cooling water temperature of the internal combustion engine, and the effective injection time correcting means is the correction coefficient when the cooling water temperature is equal to or higher than a predetermined temperature. The effective injection time may not be corrected by.

[0011]

According to the present invention, when the internal combustion engine (engine) is started, the information about the driving voltage of the fuel pump is detected by the voltage information detecting means, and the correction coefficient is determined by the correction coefficient determining means according to the driving voltage of the fuel pump. Ask for. Next, this correction coefficient is multiplied by the effective injection time at the start to correct the effective injection time at the start by the effective injection time correction means, and the effective injection time at the start after correction by the injection time calculation means is made into the invalid injection time. Is added to obtain the fuel injection time at the start. In this case, since the effective injection time at the start is corrected according to the drive voltage of the fuel pump, it is possible to compensate for the decrease in the pump performance due to the voltage decrease by extending the effective injection time at the start.

By the way, the drive voltage of the fuel pump is obtained by subtracting the voltage drop due to the harness from the battery voltage, and there is a relationship that if the battery voltage decreases, the drive voltage of the fuel pump decreases accordingly. . Therefore, in claim 2, the voltage information detecting means detects the battery voltage as the information about the driving voltage of the fuel pump,
In other words, the drive voltage of the fuel pump is indirectly detected by the battery voltage, and the correction coefficient corresponding to the detected voltage is obtained. Since the battery voltage is supplied to the fuel injection control device as a power supply, detecting the battery voltage is more advantageous in terms of cost than directly detecting the drive voltage of the fuel pump, since the number of parts does not increase.

Further, in the third aspect of the present invention, information relating to the temperature of the fuel pump is detected by the pump temperature information detecting means, and an individual correction coefficient depending on the driving voltage of the fuel pump and the temperature of the fuel pump is obtained or both are combined. The correction coefficient is obtained from a map or the like, and the effective injection time at the start is multiplied by the correction coefficient to correct the effective injection time at the start. As a result, a decrease in pump capacity caused by a decrease in driving force of the pump motor due to a low temperature in winter can be reflected in the effective injection time at startup.

By the way, factors that change the temperature of the fuel pump include the fuel temperature, the outside air temperature, and the intake air temperature.
These are closely related. Therefore, in claim 4, the pump temperature information detecting means detects at least one of the fuel temperature, the outside air temperature, and the intake air temperature as the information about the temperature of the fuel pump. In other words, the temperature of the fuel pump is the fuel temperature. It is indirectly detected from at least one of temperature, outside air temperature, and intake air temperature. These fuel temperature, outside air temperature, and intake air temperature can also be used for other engine controls, so the system configuration does not require an increase in the number of parts compared to directly detecting the temperature of the fuel pump, which is advantageous in terms of cost. is there.

Further, in the present invention, the information about the cooling water temperature of the engine is detected by the water temperature information detecting means, and when the cooling water temperature is equal to or higher than the predetermined temperature, the effective injection time at the start is not corrected by the correction coefficient. To do. That is,
When the cooling water temperature is equal to or higher than the predetermined temperature, such as after warming up the engine, the air-fuel ratio becomes leaner than when the temperature is low, but because the engine friction is small, the engine can be started without the above correction. is there.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, a schematic configuration of the entire fuel injection system will be described based on FIG. In the fuel tank 11,
A fuel pump 12, a filter 13 and a pressure regulating valve 14 are provided, and the fuel discharged from the fuel pump 12 is filtered by the filter 1
3, the pressure regulating valve 14 and the fuel pipe 15 are supplied to the delivery pipe 16, and excess fuel is passed from the pressure regulating valve 14 in the fuel tank 11 through the return pipe 17 to the fuel tank 11
Returned inside. An injector 18 is attached to the delivery pipe 16 corresponding to each cylinder of the engine.

The injection timing of each injector 18 is
It is controlled by the fuel injection control device 19. The fuel injection control device 19 turns on the relay 21 provided between the battery 20 and the fuel pump 12 for a few seconds after the ignition key (not shown) is turned on and during engine operation to turn on the fuel pump 12. Activate. Further, the fuel injection control device 19 includes a water temperature sensor 22 (corresponding to water temperature information detecting means) for detecting the engine cooling water temperature THW, and an intake air temperature THA.
The signals output from various sensors that detect the engine operating state, such as the intake air temperature sensor 23 that detects the
The fuel injection time TSTA is calculated according to the fuel injection time calculation routine shown in FIG. 1, and an injection pulse signal having a pulse width corresponding to this fuel injection time TSTA is output to the injector 18 to inject an optimum amount of fuel into the engine. In the present embodiment, the intake air temperature sensor 23 functions as pump temperature information detecting means for indirectly detecting the temperature of the fuel pump 12.

By the way, the discharge pressure-discharge flow rate characteristic of the fuel pump 12 largely changes depending on the driving voltage, as shown in FIG. For example, when the set fuel pressure is 300 kPa, the discharge pressure becomes lower than the set fuel pressure when the drive voltage is less than 8V. In this case, the pressure regulating valve 14 does not operate, and the discharge pressure = fuel pressure. Further, when the temperature of the fuel pump 12 is low, the magnetic field of the magnet of the pump motor that drives the fuel pump 12 becomes strong and the rotation speed of the fuel pump decreases.
The discharge pressure-discharge flow rate characteristics are further reduced, and the fuel pressure is further reduced.

Even under such a condition, in order to secure the engine startability, the fuel injection time TST at the time of starting the engine is started according to the fuel injection time calculation routine shown in FIG.
Calculate A. In this routine, first, step 10
1, the cooling water temperature THW output from the water temperature sensor 22
Signal is read, and at step 102, this cooling water temperature T
The effective injection time TSTA ₀ at the start is calculated based on HW. In the following step 103, the cooling water temperature THW is compared with a predetermined temperature THW _{0 at} which the increase in friction of the engine becomes remarkable. When the cooling water temperature THW is equal to or lower than the predetermined temperature THW ₀ , the process proceeds to step 104 and the fuel injection control device 19 is supplied with the power supply voltage. The battery voltage V _B applied as
In the following step 105, the battery voltage V _B is used as information regarding the driving voltage of the fuel pump 12, and a correction coefficient FV for compensating for the fuel pressure drop due to the battery voltage drop.
B is calculated based on the battery voltage V _B.

Next, at step 106, the intake air temperature sensor is
Read the signal of intake air temperature THA output from server 23
Then, in the following step 107, this intake air temperature THA is used as fuel.
Substituting as information about the temperature of the pump 12,
The correction coefficient FTHA for compensating the decrease in fuel pressure due to
Calculate based on THA. After this, in step 108,
Effective injection time TS at start-up obtained in step 102
TA₀To the above-mentioned two correction factors FVB and FTHA
Multiply to correct the effective injection time at the start, TSTA '
And On the other hand, in step 103 described above, the cooling water temperature T
HW is the predetermined temperature THW₀When it is determined to be higher
Proceeds to step 109 and is calculated in step 102.
Effective injection time at start₀Without correcting that
Use as it is, TSTA₀Be TSTA '. The reason for this
Is the cooling water temperature THW is the predetermined temperature THW₀ When above,
The air-fuel ratio is leaner than at low temperature and low fuel pressure, but
Since the gin friction is small, the above correction is not necessary.
Even so, the engine can be started.

As described above, step 108 or 10
After finally obtaining the effective injection time TSTA 'at 9 in step 9, the process proceeds to step 110 to calculate the invalid injection time TV from the battery voltage V _B , and at step 111, the effective injection time TSTA' at start is calculated. Is added to the invalid injection time TV to calculate the fuel injection time TSTA at the time of starting. Thereafter, an injection pulse signal having a pulse width corresponding to the fuel injection time TSTA at the time of starting is output to the injector 18 to inject fuel into the engine to start the engine.

In the present embodiment described above, step 10
The process of 4 functions as a voltage information detecting means, and step 1
The processing of 05 and 107 functions as a correction coefficient determination means,
The process of step 108 functions as effective injection time correction means, the process of step 110 functions as invalid injection time setting means, and the process of step 111 functions as injection time calculation means.

In this case, in step 102, the cooling water temperature T
A correction coefficient FVB obtained in steps 105 and 107 according to the battery voltage V _B (driving voltage of the fuel pump 12) and the intake air temperature THA (temperature of the fuel pump 12) at the effective injection time TSTA ₀ at startup obtained from HW. , FTHA are multiplied to correct the effective injection time at the start to TSTA '. Therefore, the effective injection time at the start (actually, the fuel is injected by This can be compensated for by extending the time), and the amount of fuel required for starting the engine can be injected even when the voltage drops or when the temperature is extremely low, and good startability can be secured. Moreover, in step 110, the battery voltage V _B
Since the invalid injection time TV is calculated more, an increase in the operation delay time of the injector 18 due to a decrease in the battery voltage V _B can be dealt with by the increase in the invalid injection time TV, and finally the step The fuel injection time TSTA at the time of starting, which is obtained by 111, can be made substantially ideal in consideration of all of the voltage, temperature, effective injection time and invalid injection time.

FIG. 4 shows the behavior at the time of starting the engine when the fuel injection time is corrected according to the present embodiment described above.
FIG. 4B shows the behavior at the time of starting the engine when the effective injection time is not corrected by the voltage and temperature shown in FIG. In this test, the set fuel pressure of the pressure regulating valve 14 is 300 kP.
a, the cooling water temperature was -20 ° C.
As is clear from the test results, the battery voltage suddenly dropped from 12V to 7 to 8V immediately after the engine was started,
Due to the decrease in the discharge capacity of the fuel pump 12 due to the decrease in the battery voltage, the fuel pressure is also set from the set fuel pressure of 300 kPa to 220 k.
It drops sharply around Pa. Conventionally, the effective injection time that actually contributes to the fuel injection does not change only by correcting the invalid injection time according to the battery voltage. Therefore, the amount of injected fuel is insufficient by the amount that the fuel pressure decreases at the time of engine start, and the amount of injected fuel shown in FIG.
The engine cannot be started as shown in (b).

On the other hand, in this embodiment, the effective injection time at the start is corrected according to the battery voltage (driving voltage of the fuel pump 12) and the intake air temperature (temperature of the fuel pump 12). It is possible to inject the amount of fuel required to start the engine even when the temperature drops or when the temperature is extremely low.
As shown in (4), the engine can be started in a few seconds, and good startability can be secured. For this reason,
It is not necessary to increase the capacity of the fuel pump 12 as in the conventional case, and the cost is not increased, and the fuel temperature and the vapor amount are not increased due to the increase in the amount of fuel returned to the fuel tank 11.

Further, in this embodiment, when the cooling water temperature is equal to or lower than the predetermined temperature, that is, only when the engine is in a high friction mode, the effective injection time at the time of starting is corrected according to the voltage and temperature, and the cooling water temperature is adjusted. When the temperature is higher than the predetermined temperature, that is, when the air-fuel ratio is on the lean side, such as after engine warm-up, has little effect on startability, the lean setting is left without performing the above correction, and It is possible to suppress the occurrence of defects such as plug covering.

In the above embodiment, the pressure regulating valve 14 is provided in the fuel tank 11 so that the return pipe for returning the surplus fuel in the delivery pipe 16 to the fuel tank 11 is eliminated. As in the other embodiment of the present invention shown in FIG. 5, the surplus fuel in the delivery pipe 16 may be returned into the fuel tank 11 through the pressure regulating valve 24 and the return pipe 25 installed near the delivery pipe 16. . When the returnless piping configuration of FIG. 2 and the configuration with the return piping 25 of FIG. 5 are compared, the fuel pressure drop at the time of engine start is larger in the returnless piping configuration of FIG. The effect is great.

In the above embodiment, the battery voltage (driving voltage of the fuel pump 12) and the intake air temperature (fuel pump 12).
Although the effective injection time at the start is corrected in consideration of both the temperature and the temperature), the effective injection time at the start may be corrected by only one of the voltage and the temperature. The engine startability can be improved as compared with the conventional case.

In the above embodiment, the battery voltage is detected as the information about the drive voltage of the fuel pump 12, but the drive voltage of the fuel pump 12 may be directly detected. Further, in the above-described embodiment, the intake air temperature is detected as the information on the temperature of the fuel pump 12, but the fuel temperature in the fuel tank 11 or the outside air temperature is detected, or these detected values are combined to detect the fuel temperature. The temperature of the pump 12 may be judged comprehensively,
Of course, it goes without saying that the temperature of the fuel pump 12 may be directly detected by a temperature sensor.

Further, in the above embodiment, the battery voltage V _B
Correction coefficient FVB based on (driving voltage of fuel pump 12)
And the correction coefficient FTHA based on the intake air temperature THA (temperature of the fuel pump 12) were calculated separately, but a correction coefficient that combines these two is obtained from a two-dimensional map of V _B and THA, and the correction coefficient is started. The effective injection time at the start may be corrected by multiplying the effective injection time at the time.
Further, the processing of step 103 in FIG. 1 is omitted, and the correction coefficient is obtained from the three-dimensional map based on the cooling water temperature THW, the battery voltage V _B (driving voltage of the fuel pump 12) and the intake air temperature THA (temperature of the fuel pump 12). However, even in this case, substantially the same correction as in the present embodiment can be performed.

In the above embodiment, the cooling water temperature THW is used as a signal that substitutes the friction of the engine. However, instead of this, the oil temperature or the cranking rotation speed may be used.

[0032]

As is apparent from the above description, according to the structure of claim 1 of the present invention, the correction coefficient obtained according to the drive voltage of the fuel pump is set as the effective injection time at the start of the engine. Since the effective injection time at the start is multiplied to correct the deterioration of the pump capacity due to the voltage drop, the effective injection time at the start can be compensated for, and the fuel pump with the capacity suitable for normal operating conditions can be used. While using
It is possible to inject the amount of fuel necessary for starting the engine even when the voltage drops, and it is possible to ensure good startability.

Further, according to the second aspect, the drive voltage of the fuel pump is indirectly detected by the battery voltage. Therefore, the number of parts is not increased as compared with the case where the drive voltage of the fuel pump is directly detected. Therefore, the cost can be reduced.

Further, in claim 3, an individual correction coefficient depending on the driving voltage of the fuel pump and the temperature of the fuel pump is calculated, or a correction coefficient which is a combination of both is calculated by a map or the like, and the correction coefficient is effective at the time of starting. Since the effective injection time at the start is corrected by multiplying the injection time, not only the voltage decrease but also the pump performance decrease due to the low temperature can be reflected in the effective injection time at the start, further improving the startability. Can be made.

Further, in the present invention, the temperature of the fuel pump is substituted by at least one of the fuel temperature, the outside air temperature, and the intake air temperature which are temperature information that can be used for other engine control. It is more cost effective than directly detecting the temperature of the fuel pump without increasing the number of parts.

Further, in the present invention, when the cooling water temperature is equal to or higher than the predetermined temperature, the effective injection time at the start is not corrected by the correction coefficient. Therefore, the air-fuel ratio is lean to the lean side as after the engine is warmed up. However, when the startability is hardly affected, the lean setting can be left and the occurrence of problems such as plug fogging due to increased fuel can be suppressed.

[Brief description of drawings]

FIG. 1 is a flowchart showing a processing flow of a fuel injection time calculation routine in an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of the entire fuel injection system.

FIG. 3 is a diagram showing discharge pressure-discharge flow rate characteristics of a fuel pump.

FIG. 4A is a diagram showing changes over time in battery voltage, fuel pressure, and engine speed at the time of starting in one embodiment of the present invention; FIG. 4B is a conventional battery voltage, fuel pressure, and engine speed at starting. Diagram showing changes in number over time

FIG. 5 is a block diagram showing a schematic configuration of the entire fuel injection system in another embodiment of the present invention.

[Explanation of symbols]

11 ... Fuel tank, 12 ... Fuel pump, 13 ... Filter, 14 ... Pressure regulating valve, 16 ... Delivery pipe, 18 ... Injector, 19 ... Fuel injection control device (voltage information detection means, correction coefficient determination means, effective injection time correction means) , Invalid injection time setting means, injection time calculating means), 20 ... battery, 22 ... water temperature sensor (water temperature information detecting means), 23 ... intake air temperature sensor (pump temperature information detecting means), 24 ... pressure regulating valve, 25 ... return piping .

Claims (5)

[Claims] 1. A fuel injection control device for an internal combustion engine, which controls an injector for injecting fuel supplied from a fuel pump into the internal combustion engine, comprising: voltage information detecting means for detecting information about a drive voltage of the fuel pump; A correction coefficient determining means for obtaining a correction coefficient according to the drive voltage of the fuel pump at the time of starting the engine, and an effective injection time correction for correcting the effective injection time at the start by multiplying the effective injection time at the start by the correction coefficient. A fuel injection control device for an internal combustion engine, comprising: means and an injection time calculation means for adding an invalid injection time to a corrected effective injection time at startup to obtain a fuel injection time at startup. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the voltage information detecting means detects a battery voltage as information on a driving voltage of the fuel pump. 3. A pump temperature information detecting means for detecting information on the temperature of the fuel pump, wherein the correction coefficient determining means is an individual correction coefficient depending on a driving voltage of the fuel pump and a temperature of the fuel pump, or both. The fuel injection control device for an internal combustion engine according to claim 1 or 2, wherein a correction coefficient that combines the above is calculated. 4. The pump temperature information detecting means detects at least one of a fuel temperature, an outside air temperature, and an intake air temperature as the information on the temperature of the fuel pump. Fuel injection control device for internal combustion engine. 5. A water temperature information detecting means for detecting information on a cooling water temperature of the internal combustion engine, wherein the effective injection time correcting means corrects the effective injection time by the correction coefficient when the cooling water temperature is equal to or higher than a predetermined temperature. 5. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection control device is not performed.