JPH06229280A - Fuel supply control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To control a fuel supply quantity accurately at transient operation time while reducing excess fuel by carrying out operation on a transmission response delay quantity to a reference pressure chamber of intake air pressure according to a changing quantity of fuel pressure regulated by a pressure regulator, and carrying out increasing and decreasing control on the fuel supply quantity. CONSTITUTION:When differential pressure between fuel pressure delivered from a fuel tank 8 by a fuel pump 9 and intake air pressure introduced to a reference pressure chamber 11a through 2 pressure introducing pipe 13 from an intake air collector 5 becomes a specific value or more, a pressure regulator 11 opens a return passage 14, and returns excess fuel to the fuel tank 8, and regulates the differential pressure constant. In this case, in a control unit 16, operation is carried out on a changing quantity of the regulated fuel pressure detected by a fuel pressure sensor 15. Operation is carried out on a transmission response delay quantity to the reference pressure chamber of intake air pressure according to a fuel pressure changing quantity obtained by the operation. Increasing and decreasing control is carried out on a fuel supply quantity according to the transmission response delay quantity obtained by the operation.

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 the fuel supply amount while adjusting the fuel supply pressure with a pressure regulator.

[0002]

2. Description of the Related Art Conventionally, in an electronically controlled fuel injection system for an internal combustion engine, the amount of fuel supplied to the engine has been controlled by the valve opening control time of the fuel injection valve. In such a fuel supply device, if the pressure difference between the fuel supply pressure to the fuel injection valve and the intake pressure in the vicinity of the injection hole of the fuel injection valve is not constant, a constant fuel will be provided corresponding to the valve opening time of the injection valve. You will not be able to supply it. Therefore, the suction negative pressure on the downstream side of the throttle valve is introduced to the reference pressure chamber of the pressure regulator for adjusting the supply pressure (hereinafter, simply referred to as 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, that is, the pressure difference between the intake pressure and the fuel pressure in the injection hole becomes a predetermined value or more, a return passage for returning the fuel to the fuel tank is opened. The differential pressure is kept constant (see Japanese Patent Laid-Open No. 60-212634).

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 raises the fuel temperature in the fuel tank. In some cases, fuel vapor was generated in the fuel tank. Therefore, as a technique for reducing the excess fuel as much as possible, a sensor for detecting the fuel pressure regulated by the pressure regulator by detecting the valve opening lift amount of the pressure regulator is provided, and the fuel is adjusted according to the detected fuel pressure. There is one that controls the discharge amount from the pump.

[0004]

However, there is a fuel supply control device provided with the pressure regulator as described above and configured to control the discharge amount of the fuel pump so as to reduce the surplus fuel amount. In order to keep the fuel temperature at a low temperature and suppress the generation of evaporated fuel, it is required to dispose a pressure regulator at a place distant from the engine that becomes a high temperature. In that case, the pressure regulator and the throttle valve are required. It was inevitable that the pressure introducing pipe connecting to the downstream intake pipe would become long.

As described above, with the structure in which the intake negative pressure is guided to the pressure regulator through the long introduction passage, the pressure in the reference pressure chamber of the pressure regulator is changed with respect to the change in the intake pressure near the injection hole of the fuel injection valve. Since a large delay occurs in the change, the differential pressure between the injection hole pressure and the fuel supply pressure deviates from a predetermined value when the intake negative pressure changes, and the pressure regulator itself cannot adjust the differential pressure. Since a similar delay occurs in the fuel pressure detected by the sensor, in the discharge amount control of the fuel pump according to the fuel pressure detection value itself, the differential pressure adjustment cannot be performed and an error occurs in the fuel supply control, resulting in a transient response. Was sometimes reduced.

The present invention has been made in view of the above problems, and it is possible to accurately control the fuel supply amount during the transient operation while reducing the surplus fuel amount that causes the temperature increase in the fuel tank. It is an object of the present invention to provide a fuel supply control device that is made possible.

[0007]

Therefore, the fuel supply control apparatus 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 via a pressure introducing pipe. When the pressure difference with the intake pressure of the fuel supply section, which is introduced into the chamber, is a predetermined value or more, a pressure regulator is provided for adjusting the pressure difference to a constant value by returning the surplus fuel to the fuel tank. Fuel pressure detection means for detecting the fuel pressure regulated by the pressure regulator while guiding the regulated fuel to the fuel supply means, and 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, which comprises a discharge amount control means for controlling a discharge amount by a fuel pump, the detected fuel pressure A fuel pressure fluctuation amount calculating means for calculating a fluctuation amount; an intake pressure transfer response delay amount calculating means for calculating a transfer response delay amount of the intake pressure to the reference pressure chamber based on the calculated fuel pressure fluctuation amount; And a fuel supply amount increase / decrease control means for increasing / decreasing the fuel supply amount according to the calculated transmission response delay amount of the intake pressure.

[0008]

When the intake pressure of the fuel supply section fluctuates, a delay occurs in the intake pressure introduced into the reference pressure chamber of the pressure regulator. This delay amount is expressed as a function of the fluctuation amount of the fuel pressure regulated by the pressure regulator. To be done. Therefore, the fluctuation amount of the fuel pressure detected by the fuel pressure detection means is calculated by the fuel pressure fluctuation amount calculation means, and the intake pressure transmission response delay amount calculation means calculates the transmission delay amount of the intake pressure based on the calculated value.

Then, the fuel supply amount increase / decrease control means controls the fuel supply amount to increase / decrease through the discharge amount control means of the fuel pump or the fuel supply means in accordance with the calculated intake delay transmission 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. Referring to FIG. 2 showing a fuel supply control device of an embodiment, air is supplied to an internal combustion engine 1 from an air cleaner 2 through an intake duct 3, a throttle chamber 4, an intake collector 5 and an intake manifold 6.

At the branch portion of the intake manifold 6, a fuel injection valve 7 as a fuel supply means is provided for each cylinder. The fuel injection valve 7 is an electromagnetic fuel injection valve that is opened by energizing a solenoid, and is closed by energizing the solenoid, and is opened 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 portion of the intake manifold 6.

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

Further, the pressure regulator 11 is provided with a fuel pressure sensor 15 as fuel pressure detecting means for detecting the fuel pressure regulated by the pressure regulator 11 by detecting the valve opening lift amount of the valve body. . The fuel pressure P _T detected by the fuel pressure sensor 15 is sent to a control unit 16 that drives and controls 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 and a rotation speed signal Ne from a crank angle sensor 18 are input to the control unit 16. .

Then, the control unit 16 incorporating the microcomputer calculates the 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 correction with F or the like.
Then, by outputting the drive pulse signal having the injection pulse width Ti to the fuel injection valve 4 at a predetermined timing, an amount of fuel commensurate with the demand of the engine is intermittently supplied to the engine by the valve opening control time of the injection valve 4. It is designed to be jetted and supplied.

Here, as described above, in order to control the injection amount according to the valve opening time of the fuel injection valve 4, the fuel pressure P _T is set to a target value (with respect to the intake negative pressure) that corresponds to the operating condition (intake negative pressure). It is necessary to control the fuel pressure so that the differential pressure becomes constant. Therefore, the control unit 16 determines the required discharge amount (control value) of the fuel pump 9 as shown in the flowchart of FIG. Fuel pump based on 9
The applied voltage (or control value such as control duty) is controlled.

In this embodiment, the control unit 16 has the functions of the fuel pressure fluctuation amount calculation means, the intake pressure transmission response delay amount calculation means, and the fuel supply amount increase / decrease control means, as shown in the flow chart of FIG. There is. In the flowchart of FIG. 3, first, step 1 (S in the figure)
It is set as 1. The same applies hereinafter), the fuel pressure P _T 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 (target value of valve opening lift amount 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 whether or not the transient state is equal to or larger than a predetermined value is determined by comparing the fluctuation amount ΔP _T with a reference value. A transitional state of less than a predetermined value is such that the operating conditions change gradually and the discharge amount from the fuel pump 9 is too large for the required fuel amount, resulting in a decrease in the valve opening lift amount of the pressure regulator 11. In this case, the transmission delay of the intake pressure through the pressure introducing pipe 13 can be ignored, and the differential pressure is adjusted by the increase of the valve opening lift amount, and the fuel supply amount is controlled well, but the fuel pump 9 The amount discharged from is unnecessarily large.

Therefore, when it is determined in step 3 that the transient state is less than the predetermined value, 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 in step 4. Proceeding to step 7, the control value FPCON of the discharge amount of the fuel pump 9 is reduced and corrected only from the current value FPCON _OLD so that only the correction amount FPCI (duty value) is reduced and corrected to keep the return fuel amount constant.

On the other hand, when it is determined in step 3 that the transient state is not less than the predetermined value, the fluctuation amount of the intake pressure is large and the transmission delay amount to the reference pressure chamber 11a via the pressure introducing pipe 13 is large. In that case, proceed to Step 5. In step 5, the transmission delay correction coefficient K1 for the transmission delay of the intake pressure with respect to the fluctuation amount ΔP _T of the fuel pressure P _T is set by a search from a map stored in the ROM which is experimentally or analytically obtained in advance. Here, the delay amount of pressure transmission is
ΔP _T × (opening area of pressure introducing pipe 8) × (pressure introducing pipe 8
Of the transmission delay correction coefficient K1. Therefore, the transmission delay correction coefficient K1 is obtained as a function of ΔP _T.

Next, in step 6, the fuel pressure sensor 15
The operation delay correction coefficient K2 for the operation response delay of is calculated. This is a correction for the response delay until the valve opening lift amount of the pressure regulator 11 changes in response to the pressure change after the pressure change is transmitted to the reference pressure chamber 11a. Load such as throttle valve opening T
VO _, basic fuel injection amount T _P, intake air flow rate Q variation Δ
Since these values increase as TVO _, ΔT _{P, and} ΔQ increase, these parameters are set experimentally or analytically in advance and set by searching from a map stored in the ROM.

After that, the routine proceeds to step 7, where 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), as well as the transmission response delay correction coefficient K1 of the intake pressure and the fuel pressure sensor 15. The operation response delay correction coefficient K2 is controlled to a reduced value. As a result, even when the differential pressure between the intake pressure and the fuel pressure is about to increase due to these response delays, the discharge amount of the fuel pump 9 is corrected to be reduced accordingly, and the fuel supply amount is prevented from excessively increasing. can, enrichment of the air-fuel _ratio, the deterioration of the exhaust emission can be prevented.

The above is the case where the fuel pressure P _T has increased above the target value P _T0 and the differential pressure has increased, but the same applies when the fuel pressure P _T is judged 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 more than a predetermined value, and if it is determined that the transient state is less than the predetermined value, K1, K
When 2 = 0, the process proceeds to step 12 without performing correction due to response delay, and control is performed to increase the fuel discharge amount by a predetermined correction amount FPCI while the fuel supply amount remains constant. This is because the fuel discharge amount is ensured so as to obtain a constant return fuel amount, and it is possible to cope with a rapid increase in the required fuel amount thereafter.

Further, when it is judged in step 8 that the transient state exceeds the predetermined value, the transmission response delay of the intake pressure through 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 in the increase in fuel pressure due to the delay in the operation response of 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 are set. _, K2 is used to set the control value FPCON of the fuel discharge amount to the current value FPCON _{OLD in} step 12.
Further, in addition to the correction amount FPCI (duty value), the correction coefficients K1 and K2 are added to control the value.

As a result, even when the differential pressure 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 accordingly, and as a result, the decrease in the fuel supply amount can be prevented. , lean air-fuel _ratio, the deterioration of the drivability can be prevented. Further, in this embodiment, the fuel pressure sensor 15
The operation response delay is corrected at the same time, and the air-fuel ratio in the transient state can be stabilized as much as possible.
As the fuel pressure sensor, in addition to detecting the valve lift amount of the pressure regulator 11, a sensor for directly detecting the fuel pressure can be used. In that case, if the operation response delay is sufficiently small, such correction is not necessary. is there.

Further, in this embodiment, the response delay of the fuel supply amount is corrected by making the differential pressure constant by increasing / decreasing the discharge amount of the fuel pump 9, but the valve opening time of the fuel injection valve 4 is changed. It is also possible to correct the response delay of the fuel supply amount by increasing or decreasing (pulse width). That is, in steps 5 _, 6 _, 10 _and 11 of FIG. 3, as a correction coefficient term multiplied by the basic fuel injection amount T _P , the intake pressure transmission response delay correction coefficient k1 and the fuel pressure sensor 15 operation response delay correction coefficient are similarly set as described above. k2 is obtained, and in steps 6 _and 11, the fuel injection amount T _I is set and controlled in accordance with the following equations.

T _I = T _P · (COEF-k1-k2) + T _S T _I = T _P · (COEF + k1 + k2) + T _S where COEF is various correction factors depending on the water temperature and T _S is an invalid injection amount due to 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 better responsiveness, but it is better to correct the discharge amount of the fuel pump 9 in that the differential pressure can always be stabilized. Are better.

Further, the fuel discharge amount correction by the fuel pump 9 and the valve opening time correction of the fuel injection valve 4 may be used together.

[0028]

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

[Brief description of drawings]

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

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

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

[Explanation 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 Inlet Pipe

Claims (1)

[Claims] 1. A differential pressure between a pressure of fuel discharged from a fuel tank by a fuel pump and an intake pressure of a fuel supply section introduced into a reference pressure chamber through a pressure introducing pipe is equal to or more than a predetermined value, A pressure regulator for adjusting the differential pressure to a constant value by returning excess fuel to the fuel tank is provided, and the fuel regulated by the pressure regulator is guided to the fuel supply means, while the fuel pressure regulated by the pressure regulator is regulated. A fuel supply control device for an internal combustion engine, comprising: a fuel pressure detecting means for detecting; and a discharge amount controlling means for controlling a discharge amount by a fuel pump in order to suppress the surplus fuel amount to a predetermined value or less according to the detected fuel pressure. A fuel pressure fluctuation amount calculating means for calculating the detected fluctuation amount of the fuel pressure; and the intake air based on the calculated fuel pressure fluctuation amount. Intake pressure transfer response delay amount calculating means for calculating the transfer response delay amount of force to the reference pressure chamber, and fuel supply amount increase / decrease for controlling increase / decrease of the fuel supply amount according to the calculated intake pressure transfer response delay amount A fuel supply control device for an internal combustion engine, comprising: a control means.