JP3136938B2 - Fuel pressure control device - 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 pressure control device for an internal combustion engine, and more particularly to a fuel pressure control device used for an internal combustion engine that injects fuel directly into a cylinder.

[0002]

2. Description of the Related Art A so-called direct injection type internal combustion engine which injects fuel directly into a cylinder is known as an internal combustion engine for realizing lean combustion for improving the properties of exhaust gas discharged from the internal combustion engine. . In this direct injection type internal combustion engine, a common rail system is used.

That is, fuel is pressurized to a high pressure by a fuel pump, supplied to a pressure accumulating chamber called a common rail, and fuel is injected into a cylinder from a fuel injection valve connected to the common rail. In order to control the fuel injection amount accurately, it is necessary to control the fuel pressure in the common rail accurately.However, the operation amount is determined by performing proportional, integral, and differential calculations on the difference between the target value and the measured value. In addition to the known PID control, a fuel pressure is controlled by controlling the overflow valve opening duty ratio based on a fuel balance control (hereinafter referred to as feedforward control) in a common rail. (See Japanese Patent Application Laid-Open No. 4-365596).

[0004]

However, in PID control or feedforward control, the parameters involved in the control are fixed, so that the discharge efficiency of the fuel pump changes with time, the difference in the fuel pump body and the fuel piping system. The fuel injection amount cannot be accurately controlled according to the capacity difference.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to accurately control fuel pressure irrespective of a change over time in a discharge efficiency of a fuel pump, a difference in body of the fuel pump, and a difference in capacity of a fuel piping system. It is an object of the present invention to provide a fuel pressure control device that can perform the above-described operations.

[0006]

That is, a fuel pressure control device according to a first aspect of the present invention provides a fuel pressure control device capable of controlling a discharge amount.
Fuel pump and pressurized fuel discharged from the fuel pump
Fuel storage chamber and fuel stored in the fuel storage chamber
Fuel pressure detecting means for detecting the pressure of the fuel, and a fuel pressure detecting means
Proportional to the difference between the fuel pressure detected at the stage and the specified target pressure
・ Perform integral / differential (PID) operation to calculate the fuel pump
Control amount determining means for determining the control amount for controlling the discharge amount
And the step, when the integral term deviates from a predetermined range,
Change the proportionality constant used for integration and differentiation (PID) calculation
And adjust the integral term so that it falls within the specified range.
Adjusting means for learning .

[0007] The fuel pressure control apparatus according to the second invention, a fuel pump capable of controlling the discharge amount, the fuel
Fuel storage for storing pressurized fuel discharged from the pump
Detects the pressure of the fuel stored in the storage chamber and the fuel storage chamber
Fuel pressure detecting means and fuel depending on the operating state of the internal combustion engine
Fuel injection amount injected from injection valve and fuel in fuel storage chamber
Pressure should be supplied to maintain the desired target pressure
The amount of fuel supplied and the fuel pressure detected by the fuel pressure detection means
And the amount of fuel stored in the fuel storage chamber
Determine the amount of fuel to be supplied to the fuel storage
The amount of fuel to be supplied is multiplied by the correction coefficient and the fuel pump discharges.
Calculate the amount of fuel to be released and perform integral correction
Control to determine the control amount for controlling the discharge amount of the pump
The amount determining means and the integral correction fuel amount deviate from a predetermined range.
When performing correction learning to change the correction coefficient, the integral correction fuel
Learning means for adjusting the amount to be within a predetermined range.
Be prepared.

[0008]

In the fuel pressure control device according to the first invention , the fuel pressure in the fuel storage chamber is controlled by the control amount determining means. When the integral term deviates from the predetermined range, learning by the learning means is executed, and the integral term is adjusted to be within the predetermined range.

In the fuel pressure control device according to the second invention , the fuel pressure in the fuel storage chamber is controlled by the control amount determining means.
Is controlled, but the fuel pump discharge efficiency changes over time,
Replacement of the fuel storage chamber causes the integrated corrected fuel amount to deviate from the specified range.
If it comes off, learning by the learning means is executed and integration correction
The fuel amount is adjusted so as to be within a predetermined range .

[0010]

FIG. 1 is a block diagram of an embodiment of a fuel pressure control device according to the present invention, and shows a case of a four-cylinder internal combustion engine.
The internal combustion engine 20 has four cylinders 201, 202, 203, and 204, and fuel injection valves 211, 212, 213, and 214 for directly injecting fuel into the cylinders are provided for each cylinder.

[0011] Four fuel injection valves 211, 212, 213
And 214 are connected to the common rail 23 via fuel supply pipes 221, 222, 223 and 224.
The common rail 23 has a fuel pressure P in the common rail.
A pressure sensor 231 for detecting _r is provided. Each cylinder 201, 202, 203 and 204 is supplied with intake air through an intake pipe 24.
Of the internal combustion engine has an intake pressure P
intake air pressure sensor 241 for detecting a _a is provided.

The fuel in the fuel tank 251 is supplied to a fuel pump 253 via a booster pump 252,
Pressurized to megapascal. The pressure and flow rate of the fuel discharged from the fuel pump 253 are controlled by a fuel pressure control unit 254 provided in the fuel pump 253. Some fuel is supplied from the fuel pressure control unit 254 to the fuel tank 25.
Returned to 1.

The fuel pressure controller 254 is operated by the controller 26 which is a microcomputer system.
The control unit 26 has a CPU 26
2, a memory 263, an input interface 264, and an output interface 265. The rotation speed _Ne of the internal combustion engine is detected by a rotation speed sensor 206 built in the distributor 205 of the internal combustion engine 20 and read into the control unit 26 via the input interface 264. Further the fuel pressure P _r and the intake pressure P _a
Is also read into the control unit 26 via the input interface 264.

The first embodiment of the control apparatus for a fuel injection pump according to the present invention is for the case where the fuel pressure control is executed by the well-known PID control, and the PID control is performed when the integral term deviates from a predetermined range. The learning for changing the proportionality constant used in step (1) is executed to adjust the integral term so as to be within a predetermined range. FIG. 2 is a flowchart of a first fuel pressure control routine executed by the control unit. The fuel pressure is controlled by well-known PID control.

The fuel pressure P _r detected by the pressure sensor 231 in step 30 is read to calculate the differential term DPR the following equation at step 31. _{DPR = KPD · (P r -P} rB) where KPD is the fuel pressure at the time derivative constant, P _rB the previous routine execution. Stores currently detected fuel pressure P _r in P _rB in step 32 proceeds to step 33.

In step 33, a proportional term PPR is calculated by the following equation. _{PPR = KPP · (P r -P} T) where KPP is a proportional constant, is P _T is the target pressure. Detected fuel pressure P _r is determined whether greater than the target pressure P _T time in addition step 34, the integral term IPR proceeds to step 35 when a positive determination is made to decrease by the following equation, in step 37 move on.

IPR = IPR-dIP Here, dIP is an integral correction amount and is a constant. Note that d
The IP may be determined by the following equation. _{dIP = KIP · (P r -P} T) Step 3 When here KIP is a negative determination is made in the integration constant step 34
The process proceeds to step S6, where the integral term IPR is increased by the following equation, and the process proceeds to step S37.

IPR = IPR + dIP After performing the first learning process in step 37,
Proceeding to step 38, the operation amount D of the fuel pressure control unit 254 is calculated by the following equation. D = DPR + PPR + IPR In step 39, the manipulated variable D is output, and this routine ends.

FIG. 3 is a flowchart of the first learning process executed in step 37. In step 37a, the number of integrations n is incremented, and in step 37b, the integrated value SI of the integral term is calculated. In step 37c, it is determined whether or not the number of accumulations n is equal to or greater than a predetermined number of times N. If a negative determination is made, it is determined that learning is not necessary, and the process is terminated.

If an affirmative decision is made in step 37c, the operation proceeds to step 37d, in which the integral value SI of the integral term is divided by the number of accumulations n to calculate the integral term average value MI. That is, the integral term average value MI is calculated by the following equation. MI = SI / n Next, in step 37e, the integration number n is calculated in step 3
At step 7f, the integrated value SI of the integral term is reset, and the routine proceeds to step 37g.

In step 37g, the integral term average value MI
Is determined to be greater than or equal to the upper limit value UL. If a negative determination is made, it is determined in step 37h whether or not the integral term average value MI is less than or equal to the lower limit value LL. Step 37h
If a negative determination is made in step, that is, if the integral term average value MI is less than the upper limit value UL and exceeds the lower limit value LL, the routine is terminated without performing learning.

When an affirmative determination is made in step 37g, the process proceeds to step 37i, where the proportional coefficient KPP is increased by a predetermined amount ΔK, and in step 37j, the integral term IPR is reset, and this processing ends. When an affirmative determination is made in step 37h, the process proceeds to step 37k, in which the proportional coefficient KPP is reduced by a predetermined amount ΔK, and in step 37m, the integral term IPR is reset, and this processing ends.

Although the predetermined amount ΔK may be a constant value,
By using the integral term IPR before resetting and determining based on the following equation, it is possible to reduce the error caused by resetting the integral term IPR. _{ΔK = IPR / (P r -P} T) That is, according to the first embodiment controls the fuel pressure in the common rail 23 by the PID control, modifies the proportional constant when the integral term deviates from the predetermined range By performing the learning, a change in the discharge efficiency of the fuel pumps 252 and 253, a difference in the body of the fuel pump, and a capacity of the fuel piping system are performed.
Fuel injection amount can vary is suppressed by the difference.

[0024] If the fuel pressure PID control in the common rail 23, when the time to reach the target pressure P _T is set to a large becomes proportional constant long when set small proportionality constant to the target pressure P _T Excessive or hunting occurs. In order to solve this problem, feed forward control has been proposed. In feed forward control, the fuel pressure is adjusted to the target pressure _PT by supplying the same amount of fuel as the amount of fuel injected from the common rail 23 by the fuel pump. Fuel pump 2 to maintain
There is a possibility that the fuel injection amount may fluctuate more than PID control due to a change in the discharge efficiency of the fuel pump 52 or 253 or a difference in the body of the fuel pump or a difference in the capacity of the fuel piping system.

The second embodiment solves this problem, and uses a combination of feedforward control and a learning function. FIG. 4 shows a second example executed by the control unit 26.
Is a flowchart of a fuel pressure control routine of step S51. In step 51, the fuel pressure _Pr and the internal combustion engine speed _{Ne are determined.}
And read intake pressure P _a.

In step 52, a feedforward control process is executed, and in step 53, a second learning process is executed. In step 54, the fuel pump 2
53 to correct the fuel quantity V _P to be dispensed. _{V P = K · V P +} V SI where K is a correction coefficient.

In step 55, the fuel pressure control unit 25
4 is calculated by the following equation. D = V _p / Q _p where Q _P is the maximum discharge amount of the fuel pump. Then, in step 56, the manipulated variable D is output, and this routine ends. FIG. 5 is a flowchart of the feedforward control process. In step 52a, the fuel injection amount V is determined as _a function of the internal combustion engine speed _Ne and the intake pressure Pa.
_{Determine inj} .

[0028] _{V inj = V inj (N e} , P a) in step 52 b, determines the fuel supply amount V _r12 required by the following equation in order to maintain the fuel pressure in the common rail 23 to the target pressure P _T. V _r12 = V _CR / {1−β · ( _PT− P ₀ )} where V _CR is the volume of the common rail 23 β is the fuel compression ratio P ₀ is the atmospheric pressure In step 52c, the fuel amount V _RI in the common rail 23 Is determined by the following equation.

V _RI = V _CR / {1−β · (P _r −P ₀ )} In step 52d, the fuel amount VS to be supplied to the common rail 23 is determined by the following equation. Considering the ejection efficiency of _{VS = V r12 + V inj -V} RI fuel pump 252 and 253 eta,
Fuel quantity V _P fuel pump 253 is to be dispensed is a VS / eta ejection efficiency eta is changed over time. In addition the volume V _CR of the common rail 23 can not be avoided that changes by the exchange of the common rail.

Therefore, the following integral correction is performed. That is, it is determined the fuel pressure P _r is whether greater than the target pressure P _T at step 52e. When an affirmative determination is made in step 52e, i.e. P _r> if P _T from the integral correction amount of fuel V _SI in step 52f subtracts the predetermined value dV _SI terminates this process.

[0031] If a negative determination is made in step 52e, i.e. P _r <by adding a predetermined value dV _SI to the integral correction amount of fuel V _SI in step 52g, if P _T ends the process. The predetermined value dV _SI may be a fixed value, but the learning effect can be further enhanced by determining the predetermined value dV _SI by the following equation. dV _SI = KI · | P _r −P _T | Here, KI is an integration constant. FIG. 6 is a flowchart of a second learning process. In step 53a, the number of integrations n is incremented. the integrated value SV _{SI SI} of the following formula
Ri is calculated. SV _SI = SV _SI + V _SI

In step 53c, it is determined whether or not the number of times n is equal to or greater than a predetermined number N. If a negative determination is made, the learning is not necessary and the process is terminated.
When a positive determination is made in step 53c, the process proceeds to step 53d, calculates the integral correction fuel quantity average value MV _SI integrated value SV _SI of the integral correction fuel quantity V _SI by dividing the accumulated number n. That is, to calculate the integral correction fuel quantity average value MV _SI by the following equation.

MV _SI = SV _SI / n Next, in step 53e, the number of integrations n is calculated in step 5
To reset the integrated value SV _SI of the integral correction amount of fuel V _SI in 3f goes to step 53 g. In step 53g, it is determined whether or not the integrated correction fuel amount average value MV _SI is equal to or more than the upper limit value UL. If a negative determination is made, step 53h is performed.
In, it is determined whether the integral corrected fuel amount average value MV _SI is equal to or less than the lower limit value LL.

[0034] When a negative determination is made in step 53h, that is, when the integral correction fuel quantity average value MV _SI exceeds the upper limit value is less than UL and lower limit LL ends the routine without learning. If an affirmative determination is made in step 53g, the flow advances to step 53i to set the correction coefficient K to a predetermined amount ΔK
It increased, and resets the integral correction fuel quantity V _SI in step 53j terminates this process.

[0035] The correction coefficient K proceeds to step 53k when an affirmative determination is made in step 53h predetermined amount ΔK decreases, resets the integral correction fuel quantity V _SI in step 53m the processing ends. Incidentally predetermined amount ΔK may be a constant value, but to reduce the error due to reset the integral correction fuel quantity V _SI by using the integral correction fuel quantity V _SI before resetting is determined based on the following equation: Is possible.

ΔK = V _SI / VS That is, according to the second embodiment, not only the fuel pressure can be controlled quickly and without exceeding the target pressure by the feedforward control, but also the fuel pump 25 can be controlled.
Fluctuations in the fuel injection amount due to changes in the discharge efficiency of 2, 253, differences in the body of the fuel pump, and differences in the capacity of the fuel piping system are suppressed.

[0037]

According to the fuel pressure control device of the first invention , the fuel pressure in the fuel storage chamber is controlled to the target pressure by the control amount determining means, while the discharge efficiency of the fuel pump changes over time. If the integral term by the capacitance difference machinery difference and fuel piping system deviates from the predetermined range can be adjusted to the integral term by changing the proportionality constant by the learning means is within a predetermined range, the fuel pressure Control characteristics can be improved.

According to the fuel pressure control device of the second invention , the fuel pressure in the fuel storage chamber is controlled by the control amount determining means.
While controlling to the target pressure, the discharge efficiency of the fuel pump over time
Changes, differences in the body of the fuel pump, and differences in the capacity of the fuel piping system
Learning when the integral correction fuel amount deviates from the specified range
Means to change the correction coefficient by
Can be adjusted to be within a certain range, the fuel pressure
Control characteristics can be improved .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a fuel pressure control device.

FIG. 2 is a flowchart of a first fuel pressure control routine.

FIG. 3 is a flowchart of a first learning process.

FIG. 4 is a flowchart of a second fuel pressure control routine.

FIG. 5 is a flowchart of a feedforward control process.

FIG. 6 is a flowchart of a second learning process.

[Explanation of symbols]

 Reference Signs List 20 internal combustion engine 201, 202, 203, 204 cylinder 211, 212, 213, 214 fuel injection valve 23 common rail 231 pressure sensor 251 fuel tank 252 booster pump 253 fuel pump 254 fuel pressure control unit 26 … Control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02M 55/02 350 F02M 55/02 350E (56) References JP-A-5-106495 (JP, A) JP-A-5-163994 (JP, A) JP-A-4-272446 (JP, A) JP-A-63-266149 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/02 345 F02D 41 / 02 395

Claims (2)

(57) [Claims] 1. A fuel pump capable of controlling a discharge amount, a fuel storage chamber for storing pressurized fuel discharged from the fuel pump, and detecting a pressure of the fuel stored in the fuel storage chamber. and fuel pressure detecting means for the fuel pressure and a predetermined eye detected by said fuel pressure detecting means
Performs proportional / integral / differential (PID) calculations on the difference from the target pressure
Control amount for controlling the discharge amount of the fuel pump.
Control amount determining means for determining the proportional / integral / integral value when the integral term deviates from a predetermined range.
Learning to change the proportionality constant used for differential (PID) calculation
And adjust the integral term to be within the specified range
A fuel pressure control device comprising: a learning unit . 2. A fuel pump capable of controlling a discharge amount.
And a pressurized fuel discharged from the fuel pump.
And a fuel for detecting the pressure of the fuel stored in the fuel storage chamber.
Injected from the fuel injection valve according to the pressure detection means and the operating state of the internal combustion engine
The fuel injection amount and the fuel pressure in the fuel storage chamber are set to predetermined targets.
The amount of fuel to be supplied to maintain pressure and
At the fuel pressure detected by the fuel pressure detecting means,
The fuel storage based on the amount of fuel stored in the fuel storage chamber.
Determine the amount of fuel to be supplied to the storage chamber and supply it to the fuel storage chamber.
By multiplying the amount of fuel to be supplied by the correction coefficient, the fuel pump
Before calculating the amount of fuel to be discharged and performing integral correction
The control amount for controlling the discharge amount of the fuel pump is determined.
Control amount determining means, and the correction when the integrated correction fuel amount deviates from a predetermined range.
Execute the learning to change the coefficient and make the integral correction fuel amount
A fuel pressure control device comprising: learning means for adjusting the pressure to be within the range .