JP2858285B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly to a device for controlling a fuel supply amount while adjusting a fuel supply pressure by a pressure regulator.

[0002]

2. Description of the Related Art Conventionally, in an electronically controlled fuel injection device for an internal combustion engine, the amount of fuel supplied to the engine is controlled by the valve opening control time of a fuel injection valve. In such a fuel supply device, if the pressure difference between the supply pressure of the fuel to the fuel injection valve and the intake pressure near the injection hole of the fuel injection valve is not constant, the constant fuel corresponding to the valve opening time of the injection valve is generated. It cannot be supplied. Therefore, the suction negative pressure on the downstream side of the throttle valve is led to a reference pressure chamber of a pressure regulator for adjusting a supply pressure (hereinafter, simply referred to as a fuel pressure) of the fuel discharged from the fuel pump to the fuel injection valve, When the pressure difference between the pressure in the reference pressure chamber and the supply pressure from the fuel pump, i.e., the pressure difference between the intake pressure and the fuel pressure of the injection hole portion is equal to or higher than a predetermined value, a return passage for returning fuel to the fuel tank is opened. The differential pressure is kept constant (see Japanese Patent Application Laid-Open No. 60-212634).

Here, since the excess fuel returned from the pressure regulator to the fuel tank is warmed by the heat of the engine, returning the excess fuel to the fuel tank increases the temperature of the fuel in the fuel tank. As a result, fuel vapor may be generated in the fuel tank. For this reason, as a technique for reducing excess fuel as much as possible, a sensor for detecting the fuel pressure regulated by the pressure regulator by detecting the valve lift of the pressure regulator is provided, and the fuel is detected in accordance with the detected fuel pressure. In some cases, the amount of discharge from a pump is controlled.

[0004]

However, there is provided a fuel supply control device having a pressure regulator as described above and configured to control a discharge amount of a fuel pump so as to reduce a surplus fuel amount. Is required to dispose a pressure regulator at a location away from a high-temperature engine for the purpose of keeping fuel temperature at a low temperature and suppressing the generation of fuel vapor. In this case, the pressure regulator and the throttle valve are required. It was inevitable that the pressure introduction pipe connecting the downstream intake pipe would be long.

As described above, the configuration in which the intake negative pressure is guided to the pressure regulator through the long introduction path causes the pressure in the reference pressure chamber of the pressure regulator to change with the intake pressure near the injection hole of the fuel injection valve. Because a large delay occurs in the change, when the intake negative pressure changes, the differential pressure between the injection hole pressure and the fuel supply pressure deviates from a predetermined value, and the pressure difference cannot be adjusted by the pressure regulator itself. Since a similar delay occurs in the fuel pressure detected by the sensor, in the discharge amount control of the fuel pump corresponding to the detected fuel pressure value itself, the differential pressure cannot be adjusted and an error occurs in the fuel supply control. Was sometimes reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is an object of the present invention to accurately control the fuel supply amount during a transient operation while reducing the surplus fuel amount that would cause the temperature inside the fuel tank to rise. It is an object of the present invention to provide a fuel supply control device capable of being provided.

[0007]

Therefore, a fuel supply control device for an internal combustion engine according to the present invention, as shown in FIG. 1, has a pressure of fuel discharged from a fuel tank by a fuel pump and a reference pressure through a pressure introducing pipe. A pressure regulator that adjusts the differential pressure to a constant value by returning surplus fuel to the fuel tank when a differential pressure from an intake pressure of the fuel supply unit guided to the chamber is equal to or more than a predetermined value; Fuel pressure detecting means for detecting a fuel pressure regulated by the pressure regulator while guiding the pressurized fuel to fuel supply means; and a fuel for suppressing the surplus fuel amount to a predetermined value or less according to the detected fuel pressure. In a fuel supply control device for an internal combustion engine comprising discharge amount control means for controlling a discharge amount by a pump, the detected fuel pressure Fuel pressure fluctuation amount calculating means for calculating a dynamic amount; intake pressure transmission response delay amount calculating means for calculating a transmission response delay amount of the intake pressure to the reference pressure chamber based on the calculated fuel pressure fluctuation amount; From the fuel supply means to the engine according to the transmission response delay amount of the intake air pressure
And a fuel supply amount increase / decrease control means for controlling the increase / decrease of the fuel supply amount.

[0008]

When the intake pressure of the fuel supply unit fluctuates, a delay occurs in the intake pressure guided to the reference pressure chamber of the pressure regulator. The amount of the delay is expressed as a function of the fluctuation amount of the fuel pressure regulated by the pressure regulator. Is done. Therefore, the fuel pressure fluctuation detected by the fuel pressure detecting means is calculated by the fuel pressure fluctuation calculating means, and the intake pressure transmission response delay calculating means calculates the transmission delay of the intake pressure based on the calculated value.

The fuel supply amount increase / decrease control means controls the fuel supply amount via the discharge amount control means of the fuel pump or the fuel supply means in accordance with the calculated delay time of the intake pressure, thereby increasing the fuel supply amount. The supply amount can be controlled to a good value without delay, and the transient performance is improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing a fuel supply control device according to one embodiment, air is supplied to an internal combustion engine 1 from an air cleaner 2 via an intake duct 3, a throttle chamber 4, an intake collector 5 and an intake manifold 6.

A fuel injection valve 7 as a fuel supply means is provided for each cylinder in a branch portion of the intake manifold 6. The fuel injection valve 7 is an electromagnetic fuel injection valve that is energized by a solenoid and opens, and is deenergized and closed by a solenoid, and opens according to the pulse width of a drive pulse signal sent from a control unit 16 described later. The fuel that is controlled and adjusted to a predetermined pressure is injected and supplied to each branch of the intake manifold 6.

A fuel pump 9 is provided in the fuel tank 8, and fuel sucked and discharged by the fuel pump 9 passes through a fuel supply pipe 12 provided with a fuel filter 10 and a pressure regulator 11. Then, the fuel is distributed and supplied to each of the fuel injection valves 7. The pressure regulator 11 has an intake collector 5 in its reference pressure chamber 11a.
, An intake negative pressure of the engine 1 (corresponding to the intake pressure of the injection hole of the fuel injection valve 7) is introduced through the pressure introducing pipe 13, and the pressure of the fuel sent from the fuel pump 9 is When the pressure difference from the pressure in the reference pressure chamber 11a exceeds a predetermined value, the fuel supply pressure is adjusted so that the pressure difference becomes constant by opening the return passage 14 and returning the fuel to the fuel tank 8. . If the differential pressure is kept constant, the amount of fuel injected and supplied with respect to the valve opening time of the fuel injection valve 7 has a linear characteristic, so that the injection amount can be controlled as the valve opening time.

The pressure regulator 11 is provided with a fuel pressure sensor 15 as a fuel pressure detecting means for detecting the fuel pressure regulated by the pressure regulator 11 by detecting the valve lift of the valve body. . The fuel pressure _PT detected by the fuel pressure sensor 15 is sent to a control unit 16 for controlling the driving of the fuel pump 9.
In addition to the detection signal from the fuel pressure sensor 6, an intake air flow rate detection signal Q from an air flow meter 17, a rotation speed signal Ne from a crank angle sensor 18, and the like are input to the control unit 16. .

The control unit 16 incorporating a microcomputer calculates a basic injection pulse width Tp (basic valve opening time) corresponding to the required fuel amount of the engine based on the intake air flow rate Q and the rotational speed Ne. on the other hand,
Various correction coefficients COEF are set from information such as the cooling water temperature Tw, and the basic injection pulse width Tp is set to various correction coefficients COE.
The final injection pulse width Ti is set by correcting with F or the like.
By outputting a drive pulse signal having the injection pulse width Ti to the fuel injection valve 4 at a predetermined timing, an amount of fuel corresponding to the demand of the engine is intermittently supplied to the engine by the valve opening control time of the injection valve 4. Injection and supply are performed.

Here, as described above, in order to control the injection amount based on the valve opening time of the fuel injection valve 4, the fuel pressure _PT is set to a target value (in relation to the intake negative pressure) corresponding to the operating condition (intake negative pressure). Therefore, the control unit 16 determines the required discharge amount (control value) of the fuel pump 9 as shown in the flowchart of FIG. Based on the fuel pump 9
Is controlled (or a control value such as a control duty).

In this embodiment, the control unit 16 has functions as a fuel pressure fluctuation amount calculation means, an intake pressure transmission response delay amount calculation means, and a fuel supply amount increase / decrease control means as shown in the flowchart of FIG. I have. In the flowchart of FIG. 3, first, step 1 (S in the figure)
There is one. In the following, the fuel pressure _PT detected by the fuel pressure sensor 15 is read.

In step 2, the fuel pressure P _T detected by the fuel pressure sensor 15 is compared with a target value (a target value of the valve lift of the pressure regulator) P _T0 . Then, in the case of P _T = P _T0, but terminates this routine to maintain the status quo, P _T> proceeds to Step 3 when the P _T0, variation [Delta] P _T (per unit time variation) of P _T Is calculated, and it is determined whether or not the transition state is a predetermined or more transient state by comparing the fluctuation amount ΔP _T with a reference value. The transient state less than the predetermined state is such that the operating condition changes slowly and the discharge amount from the fuel pump 9 is too large relative to the required fuel amount, and as a result, the valve opening lift amount of the pressure regulator 11 decreases. In this case, the transmission delay of the intake pressure by the pressure introducing pipe 13 can be neglected, and the differential pressure is adjusted by increasing the valve opening lift amount, and the fuel supply amount is controlled well. Is too large.

Therefore, if it is determined in step 3 that the transient state is less than the predetermined state, in step 4 both the intake pressure transmission delay correction coefficient K1 and the response delay correction coefficient K2 of the fuel pressure sensor 15, which will be described later, are set to 0. Proceeding to step 7, only the correction amount FPCI (duty value) for reducing the control value FPCON of the discharge amount of the fuel pump 9 to keep the return fuel amount constant is reduced from the current value FPCON _OLD .

On the other hand, if it is determined in step 3 that the transient state is equal to or more than the predetermined transient state, the fluctuation of the intake pressure is large and the transmission delay to the reference pressure chamber 11a via the pressure introducing pipe 13 is large. In that case, go to step 5. In step 5, set by the retrieval or the like from previously experimentally or analytically sought map stored in the ROM of the transmission delay correction coefficient K1 relative transmission delay of the intake air pressure to the change amount [Delta] P _T of the fuel pressure P _T. Here, the delay amount of the pressure transmission is
ΔP _T × (opening area of pressure introducing pipe 8) × (pressure introducing pipe 8
Obligatory in value proportional to the value obtained as the length), the transmission delay correction factor K1 is therefore determined as a function of [Delta] P _T.

Next, the routine proceeds to step 6, where the fuel pressure sensor 15
An operation delay correction coefficient K2 for the operation response delay of is obtained. This is a correction for a response delay after the pressure change is transmitted to the reference pressure chamber 11a until the valve opening lift amount of the pressure regulator 11 changes in response to the pressure change. Load of throttle valve opening T
_VO, basic fuel injection quantity T _P, the amount of change in the intake air flow rate Q delta
Since these parameters increase as TVO _, ΔT _{P, and} ΔQ increase, these parameters are set in advance by experiment or analysis, for example, by searching a map stored in a ROM.

Thereafter, the routine proceeds to step 7, in which the control value FPCON of the discharge amount of the fuel pump 9 is changed from the current value FPCON _OLD to the correction amount FPCI (duty value), the transmission response delay correction coefficient K1 of the intake pressure, the fuel pressure sensor 15 Is controlled to a reduced value. As a result, even when the differential pressure between the intake pressure and the fuel pressure tends to increase due to these response delays, the discharge amount of the fuel pump 9 is corrected to decrease accordingly, thereby preventing the fuel supply amount from excessively increasing. As a result, it is possible to prevent the air-fuel ratio from becoming rich and _the exhaust emission from becoming worse.

The above is the case where the fuel pressure P _T increases from the target value P _T0 and the differential pressure increases. However, the same applies when the fuel pressure P _T is determined to be smaller than the target value P _{T0 in} step 2. Thus, the increase correction control of the fuel discharge amount is performed. That is, it is determined in step 8 whether or not the transient state is equal to or greater than a predetermined state.
The process proceeds to step 12 without performing the correction due to the response delay as 2 = 0, and controls to increase the fuel discharge amount by a predetermined correction amount FPCI while keeping the fuel supply amount constant. This is because the fuel discharge amount is secured so as to obtain a constant return fuel amount, and it is possible to cope with a sudden increase in the required fuel amount thereafter.

If it is determined in step 8 that the transient state is equal to or more than the predetermined transient state, the transmission response delay of the intake pressure via the pressure introducing pipe 13 with respect to the increase of the intake pressure and the fuel pressure sensor
In order to suppress the decrease in the differential pressure due to the delay of the fuel pressure increase due to the operation response delay in step 15, the transmission delay correction coefficient K1 _{and the} operation delay correction coefficient K2 are set in the same manner as described above in steps 10 _and 11, and these correction coefficients K1 _, K2, the control value FPCON of the fuel discharge amount is changed to the current value FPCON _{OLD in} step 12.
Is controlled by adding the correction coefficients K1 and K2 in addition to the correction amount FPCI (duty value).

As a result, even when the pressure difference between the intake pressure and the fuel pressure is about to decrease due to these response delays, the discharge amount of the fuel pump 9 is corrected to increase accordingly, so that a decrease in the fuel supply amount can be prevented. In addition, the air-fuel ratio can be made lean and _the drivability can be prevented from deteriorating. In this embodiment, the fuel pressure sensor 15
The correction of the operation response delay is also performed at the same time, and the air-fuel ratio in the transient state can be stabilized as much as possible.
In addition, besides detecting the valve opening lift amount of the pressure regulator 11 as the fuel pressure sensor, a sensor for directly detecting the fuel pressure can also be used. In this case, if the operation response delay is sufficiently small, such correction is unnecessary. is there.

Further, in this embodiment, the response delay correction of the fuel supply amount is performed by making the differential pressure constant by correcting the increase / decrease of the discharge amount of the fuel pump 9, but the valve opening time of the fuel injection valve 4 is set. The response delay of the fuel supply amount can be corrected by increasing or decreasing the (pulse width). That is, Step _{5, 6, 10,} operation response delay correction coefficients of the transfer response delay correction factor k1 and the fuel pressure sensor 15 of the Likewise intake pressure as a correction coefficient term to be multiplied to the basic fuel injection quantity T _P In 11 of FIG. 3 seeking and k2, in step _6, 11, controlled by setting the fuel injection amount T _I in accordance with respective following formula.

[0026] _{T I = T P · (COEF} -k1-k2) + T S T I = T P · (COEF + k1 + k2) + T S , however, COEF various correction coefficient by the water temperature, T _S is invalid injection caused by the battery voltage is there. If the valve opening time of the fuel injection valve 4 is controlled as described above, the fuel supply amount can be corrected with higher responsiveness, but it is better to correct the discharge amount of the fuel pump 9 in that the differential pressure can be constantly stabilized. Are better.

The correction of the fuel discharge amount by the fuel pump 9 and the correction of the valve opening time of the fuel injection valve 4 may be combined.

[0028]

As described above, according to the present invention, when the intake pressure of the fuel supply unit changes, the response of the fuel pressure regulated by the pressure regulator to the response delay of the pressure transmission via the pressure introducing pipe is reduced. Since the fuel supply amount is increased or decreased based on the fluctuation amount, the fuel supply amount can be appropriately controlled even in a transient state, so that the air-fuel ratio is stabilized and the exhaust emission and drivability are maintained satisfactorily. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a discharge amount control of a fuel pump in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 7 Fuel injection valve 8 Fuel tank 9 Fuel pump 11 Pressure regulator 11a Reference pressure chamber 13 Pressure introduction pipe

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/00-41/40 F02M 37/08 F02M 69/00

Claims (1)

(57) [Claims] When a pressure difference between a pressure of fuel discharged from a fuel tank by a fuel pump and an intake pressure of a fuel supply section led to a reference pressure chamber via a pressure introducing pipe is equal to or higher than a predetermined value, an excess A pressure regulator for adjusting the differential pressure to a constant value by returning fuel to the fuel tank;
Fuel pressure detecting means for guiding the fuel regulated by the pressure regulator to fuel supply means, while detecting fuel pressure regulated by the pressure regulator;
A fuel supply control device for an internal combustion engine, comprising: a discharge amount control unit configured to control a discharge amount of a fuel pump in order to suppress the surplus fuel amount to a predetermined value or less according to the detected fuel pressure. Fuel pressure fluctuation amount calculating means for calculating the fluctuation amount of, and intake pressure transmission response delay amount calculating means for calculating a transmission response delay amount of the intake pressure to the reference pressure chamber based on the calculated fuel pressure fluctuation amount, in response to said transmitted response delay amount of the computed intake pressure
A fuel supply control device for an internal combustion engine, comprising: a fuel supply amount increase / decrease control unit that controls increase / decrease of a fuel supply amount from the fuel supply unit to the engine .