JP2000205018A - Fuel injection apparatus for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of response of fuel pressure control after an integration control input is uselessly stored during a fuel cut, in an apparatus conducting feedback control of a discharge amount of a fuel pump by means of integral action to match fuel pressure with a target value. SOLUTION: In this fuel injection apparatus, as a deviation from target oil pressure (S1) of actual oil pressure sensed by oil pressure (S2), a control error z is calculated (S3). Based on the control error z, a proportional control input P and a derivative control input D is computed (S4, S5). During a fuel cut (S6) and in a case where an actual fuel pressure is higher than a target (S7), update calculation of an integral control input I is prohibited based on the control error z (S9).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an engine, and more particularly, to a device configured to control a fuel pressure by controlling a discharge amount of a fuel pump.

[0002]

2. Description of the Related Art Heretofore, as an apparatus for controlling a fuel pressure by controlling a discharge amount of a fuel pump, there has been the following apparatus (see Japanese Patent Application No. 10-135576).

In other words, a fuel pump (single cylinder pump) is provided for sucking and discharging fuel by a plunger reciprocating by a cam interposed on a cam shaft of an engine, and the fuel discharged from the fuel pump is checked by a check valve. The fuel is supplied to the fuel accumulator through the fuel accumulator, and the fuel is distributed and supplied from the fuel accumulator to the fuel injection valves of the respective cylinders.

On the other hand, an electromagnetic valve which opens and closes in an ON / OFF manner is interposed in a return passage connecting the piston chamber of the fuel pump to the suction side, and the return passage is closed (opened) during the discharge stroke of the fuel pump. ) The discharge amount of the fuel pump can be controlled by controlling the period.

Then, the closed period (discharge amount) of the solenoid valve is feedback-controlled by proportional, integral and differential operations so that the fuel pressure in the fuel storage chamber detected by the fuel pressure sensor coincides with the target pressure.

[0006]

As described above, in a system in which the fuel pressure is controlled to a target value by controlling the discharge amount of a fuel pump, the fuel from the fuel accumulator is supplied only through a fuel injection valve. , The fuel pressure in the fuel storage chamber can be increased by controlling the solenoid valve, but the fuel pressure in the fuel storage chamber cannot be reduced by the solenoid valve alone. The fuel pressure in the fuel accumulator is to be gradually reduced by making the discharge amount from the fuel pump smaller than the fuel amount injected from the valve.

For this reason, if the target fuel pressure decreases and the actual fuel pressure becomes higher than the target, the fuel pressure drops slowly. During this time, the integral operation amount of the feedback control amount becomes useless in the discharge amount decreasing direction. There is a problem that the fuel pressure is accumulated and deteriorates the responsiveness of the subsequent fuel pressure control. In particular, in a fuel cut state in which fuel injection by the fuel injection valve is stopped (all cylinders cut or a partial cylinder cut state), the fuel pressure cannot be reduced, or the fuel pressure descending speed is significantly reduced. There is a problem that the integral operation amount is easily accumulated unnecessarily.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to prevent unnecessary accumulation of an integral operation amount, and thereby maintain a good fuel pressure control responsiveness. The purpose is to provide.

[0009]

According to a first aspect of the present invention, a fuel injection device for an engine supplies fuel from a fuel pump to a fuel accumulator and distributes and supplies fuel from the fuel accumulator to each fuel injection valve. This is a fuel injection device for an engine having the above configuration, which is configured as shown in FIG.

In FIG. 1, a fuel pressure sensor detects a fuel pressure in the fuel accumulator, and a target fuel pressure setting means sets a target value of the fuel pressure. Then, the feedback control means performs feedback control of the discharge amount of the fuel pump by a control operation including at least an integration operation so that the fuel pressure detected by the fuel pressure sensor matches the target value.

Here, the integral manipulated variable clamping means clamps the integral manipulated variable in the integral operation of the feedback control means during the fuel cut. According to such a configuration,
At the time of a fuel cut in which the fuel pressure cannot be lowered (or the descent speed is greatly reduced), the integral manipulated variable is clamped, and even if there is a large deviation between the target value and the actual fuel pressure, the integral manipulated variable is reduced. Prevent accumulation.

In the invention according to claim 2, the integral manipulated variable clamping means clamps the integral manipulated variable when fuel is being cut in one cylinder or a plurality of cylinders. According to this configuration, when the fuel cut is performed in one cylinder or a plurality of cylinders, that is, not limited to the all-cylinder fuel cut, the integral operation amount is clamped when the fuel cut is performed.

Further, according to the third aspect of the present invention, FIG.
The integral manipulated variable clamp means clamps the integral manipulated variable in the integral operation of the feedback control means when the fuel pressure detected by the fuel pressure sensor is higher than a target value.

According to this configuration, when the actual fuel pressure is higher than the target fuel pressure and it is necessary to lower the fuel pressure,
Since it is necessary to wait for a decrease in fuel pressure due to fuel injection from the fuel injection valve, the integral operation amount is clamped.

According to a fourth aspect of the present invention, the integral manipulated variable clamp means is adapted to change the fuel pressure detected by the fuel pressure sensor higher than the target value and decrease the fuel pressure detected by the fuel pressure sensor. In such a case, the integration operation amount in the integration operation of the feedback control means is clamped.

According to this configuration, when the actual fuel pressure is higher than the target value and the actual fuel pressure is not converging to the vicinity of the target value but is gradually decreasing, the integral operation amount is clamped and the fuel injection valve is clamped. The integral manipulated variable is not accumulated during the decrease in fuel pressure due to fuel injection from the engine.

[0017]

According to the first aspect of the present invention, since the integral operation amount is clamped at the time of fuel cut, when the fuel pressure is maintained or when the fuel pressure descending speed is greatly reduced,
Unnecessary accumulation of the integral manipulated variable can be avoided, and
There is an effect that the responsiveness of the fuel pressure control can be favorably maintained.

According to the second aspect of the present invention, the integral operation amount is clamped even when the fuel cut is performed in one cylinder or a plurality of cylinders, so that the unnecessary accumulation of the integral operation amount is accurately avoided. There is an effect that can be.

According to the third aspect of the present invention, the integral operation amount is clamped when the actual fuel pressure is higher than the target and the fuel pressure needs to be reduced. Can be avoided from being accumulated unnecessarily, so that the responsiveness of the fuel pressure control can be favorably maintained.

According to the fourth aspect of the present invention, the integral operation amount is clamped when the actual fuel pressure is higher than the target and is approaching the target. Therefore, for example, the integral operation amount is clamped when the target is overshooted. Therefore, it is possible to prevent the convergence from being delayed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the overall configuration of the engine fuel injection device according to the embodiment.

In FIG. 2, inside the fuel tank 1,
An electric feed pump 2 for pumping the fuel in the tank 1
The fuel discharged from the feed pump 2 is supplied to a single-cylinder fuel pump 7 through a low-pressure side fuel passage 6 provided with a fuel filter 3, a fuel damper 4 and a check valve 5.
Inhaled.

The fuel pump 7 has a structure in which fuel is sucked when a piston that moves up and down by being driven by a pump driving cam provided on a camshaft of an engine moves down, and discharges fuel when moving up.

On the other hand, a return passage 8 is provided for communicating the pump chamber of the fuel pump 7 with the low-pressure fuel passage 6 upstream of the check valve 5, and the return passage 8 is provided in the middle of the return passage 8. The solenoid valve 9 which opens and closes is interposed.

On the other hand, a high pressure side fuel passage 11 in which a check valve 10 is interposed is connected to the discharge port of the fuel pump 7, and the other end of the high pressure side fuel passage 11 is connected to a fuel accumulator (common rail). ) 12 is connected. Then, a branch passage 14 is branched from the fuel pressure accumulating chamber 12 to each of the fuel injection valves 13 mounted on the combustion chamber of each cylinder.

The fuel accumulator 12 is provided with a fuel pressure sensor 15 for detecting the fuel pressure in the fuel accumulator 12.
The solenoid valve 9 is driven and controlled by a control signal from a control unit 16. By controlling the solenoid valve 9, the discharge amount of the fuel pump 7 is controlled. The fuel injection pressure of the valve 13 is controlled.

The control unit 16 receives a fuel pressure signal from the fuel pressure sensor 15 and also receives signals from sensors for detecting various operating states (engine load, engine speed, etc.) of the engine. The solenoid valve 9 is controlled based on the detection result as described later.

Here, an outline of the operation of the solenoid valve 9 will be described. As shown in FIG. 3, the solenoid valve 9 is closed at the piston top dead center (TDC) of the fuel pump 7, and the pump chamber is moved while the piston descends from the top dead center to the bottom dead center (during the suction stroke). Let the fuel inhale. Then, when the piston starts to move upward, fuel is discharged from the fuel pump 7 toward the fuel pressure accumulating chamber 12 while the solenoid valve 9 is closed and the return passage 8 is closed. When the valve is opened, the fuel is returned from the pump chamber of the fuel pump 7 to the low-pressure side fuel passage 6 via the return passage 9, and the discharge of the fuel (supply to the fuel pressure accumulating chamber 12) is stopped.

Therefore, by controlling the valve closing period θop (or the valve opening timing before the piston top dead center) from closing the valve at the piston top dead center to opening the valve in the discharge stroke, the fuel discharge can be performed. The fuel pressure in the fuel pressure accumulating chamber 12, that is, the fuel injection pressure, is controlled.

The solenoid valve 9 is closed during the suction stroke, the solenoid valve 9 is opened once at the piston bottom dead center, and the solenoid valve 9 is closed again in the middle of the discharge stroke. The fuel may be discharged from the valve to the piston top dead center, and the discharge amount may be controlled by the period from the piston bottom dead center to the closing of the solenoid valve 9.

FIG. 4 is a flowchart showing a first embodiment of the control of the solenoid valve 9 by the control unit 16. In S1 (target fuel pressure setting means), a target fuel pressure is set, and in S2, a target fuel pressure is set. The actual fuel pressure detected by the fuel pressure sensor 15 is read.

In S3, a deviation z between the target fuel pressure and the actual fuel pressure is calculated. In S4, a proportional operation amount P is calculated based on the deviation z. In S5, a differential operation amount D is calculated based on the deviation z.

In S6, it is determined whether or not the fuel is being cut. Fuel cut is to temporarily stop fuel injection by the fuel injection valve during deceleration operation or high-speed operation of the engine.The number of cylinders for stopping fuel injection is not limited to all cylinders, but also to some cylinders. Is also good.

When it is determined in S6 that the fuel cut is not being performed, the process proceeds to S9, where the integral operation amount I is updated and calculated based on the deviation z. On the other hand, when it is determined in S6 that the fuel is being cut, the process proceeds to S7, and it is determined whether or not the actual fuel pressure is higher than the target fuel pressure.
And when the actual fuel pressure is lower than the target fuel pressure,
Proceeding to S9, the integral operation amount I is calculated based on the deviation z.
When the actual fuel pressure is higher than the target fuel pressure, the process proceeds to S8 (integral manipulated variable clamping means), where the integral manipulated variable I is clamped to the previous value, and the integral operation based on the deviation z is performed. The update of the quantity I is prohibited.

When the actual fuel pressure is higher than the target fuel pressure, it is necessary to decrease the fuel pressure. However, during fuel cut, fuel injection by the fuel injection valve 13 is not performed at all, or partially. In a state where the fuel pressure is reduced only in the cylinder, the fuel pressure cannot be lowered, or even if the fuel pressure can be lowered, the rate of drop is extremely slow. It will be. Therefore, when the fuel is being cut and the actual fuel pressure is higher than the target, the integral operation amount I is clamped to avoid unnecessary accumulation.

Here, the clamping of the integral manipulated variable I may be performed only on condition that the fuel is being cut. However, when the actual fuel pressure is lower than the target even during the fuel cut, the fuel pressure can be increased by discharging the fuel from the fuel pump 7. It is preferable that the integral manipulated variable I be clamped only when it is higher than the target.

After setting the proportional manipulated variable P, the differential manipulated variable D, and the integral manipulated variable I as described above, in S10 (feedback control means), the proportional manipulated variable P, the differential manipulated variable D, and the integral manipulated variable I are determined. The feedback control amount is determined as the sum of

In step S11, the valve closing period θop is determined from the separately set feedforward control amount and the feedback control amount. In step S12, the electromagnetic valve 9 is determined based on the determined valve closing period θop. Of the fuel pump 7 is controlled.

FIG. 5 shows a second embodiment of the control of the solenoid valve 9 by the control unit 16.
Steps S21 to S25 perform the same processing as steps S1 to S5. In S26, it is determined whether or not the actual fuel pressure is decreasing. If the actual fuel pressure is decreasing, the process proceeds to S27.

In S27, it is determined whether or not the actual fuel pressure is higher than the target fuel pressure. If the actual fuel pressure is higher than the target fuel pressure, the routine proceeds to S28 (integral manipulated variable clamping means), where the integral manipulated variable I is clamped to the previous value.
The update of the integral manipulated variable I based on the deviation z is prohibited.

On the other hand, in S26, it is determined that the actual fuel pressure is not decreasing (in other words, when the fuel pressure is increasing or in a steady state), and in S27, it is determined when the actual fuel pressure is lower than the target. If so, the process proceeds to S29, where the integral manipulated variable I is updated based on the deviation z.

Hereinafter, in S30-S32, the above-mentioned S10-
The same processing as in S12 is performed. When the actual fuel pressure is higher than the target, the feedback control amount is operated to reduce the actual fuel pressure. However, since the decrease in the fuel pressure is realized by the fuel injection from the fuel injection valve 13, However, even if the feedback control amount is changed in a direction to decrease the discharge amount from the fuel pump 7, this does not function effectively, and the integral operation amount is accumulated uselessly.

Therefore, the update calculation of the integral manipulated variable I may be prohibited only by the fact that the actual fuel pressure is higher than the target. However, even when the actual fuel pressure is higher than the target, it converges near the target. When the target value is exceeded due to overshoot of the feedback control, or when the update operation of the integral manipulated variable I is prohibited, it is not preferable to secure the convergence to the target value. The update calculation of the integral manipulated variable I is prohibited when it is higher than the target.

In the present application, in addition to the above-described configuration in which the integral operation amount I is clamped and the update operation of the integral operation amount I is not performed, the clamp of the integral operation amount I is performed. Without reflecting the result to the control of the valve closing period θop, the integral manipulated variable I immediately before entering the clamp condition is used.
Is stored, and the valve closing period θop is
Is included in the configuration. It is also possible to substantially clamp by adjusting the integral gain.Furthermore, when the fuel cut is performed only in a part of the cylinders, the integral gain becomes larger as the number of fuel cut cylinders increases. It may be made smaller so that the update operation of the integral manipulated variable I is performed.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a fuel injection device according to claim 1.

FIG. 2 is a diagram illustrating a system configuration according to the embodiment;

FIG. 3 is a time chart showing a state of discharge amount control of the fuel pump according to the embodiment.

FIG. 4 is a flowchart showing a first embodiment of control contents according to the embodiment;

FIG. 5 is a flowchart showing control contents according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fuel tank 2 feed pump 3 fuel filter 4 fuel damper 5, 10 check valve 6 low pressure side fuel passage 7 fuel pump 8 return passage 9 solenoid valve 11 high pressure side fuel passage 12 fuel accumulator 13 fuel injection valve 14 branch passage 15 fuel pressure Sensor 16 control unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02M 37/00 F02M 37/00 C 51/00 51/00 A 55/02 350 55/02 350E 69/00 340 69 / 00 340T F-term (reference) 3G060 AB01 BC02 CA00 DA00 FA07 GA00 GA03 GA14 3G066 AB02 BA12 BA19 CA01S CA20U CB07U CB12 CB16 CC01 CD25 CD26 CE02 CE22 DA02 DC01 DC09 DC18 3G301 HA01 HA02 HA06 JA03 KA16 KA26 KB03 NB07 LB07 PB08Z PE01Z

Claims (4)

[Claims] 1. A fuel injection device for an engine, wherein a fuel is supplied from a fuel pump to a fuel accumulator and fuel is distributed and supplied from the fuel accumulator to each fuel injection valve. A fuel pressure sensor for detecting the fuel pressure; target fuel pressure setting means for setting a target value of the fuel pressure; and a control operation including at least an integration operation so that the fuel pressure detected by the fuel pressure sensor matches the target value. A fuel injection device for an engine, comprising: feedback control means for performing feedback control of a discharge amount of the fuel supply; and integral operation amount clamping means for clamping an integral operation amount in an integration operation of the feedback control means during a fuel cut. . 2. An engine fuel injection system according to claim 1, wherein said integral manipulated variable clamping means clamps said integral manipulated variable when fuel is being cut in one or more cylinders. . 3. A fuel injection device for an engine having a structure in which fuel is supplied from a fuel pump to a fuel accumulator and fuel is distributed and supplied from the fuel accumulator to each fuel injection valve. A fuel pressure sensor for detecting the fuel pressure; target fuel pressure setting means for setting a target value of the fuel pressure; and a control operation including at least an integration operation so that the fuel pressure detected by the fuel pressure sensor matches the target value. Feedback control means for performing feedback control on the discharge amount of the fuel pressure sensor; and when the fuel pressure detected by the fuel pressure sensor is higher than the target value, integral operation amount clamp means for clamping the integral operation amount in the integration operation of the feedback control means. A fuel injection device for an engine, comprising: 4. The fuel injection control apparatus according to claim 1, wherein the integral operation amount clamping means is configured to output the fuel pressure when the fuel pressure detected by the fuel pressure sensor is higher than the target value and the fuel pressure detected by the fuel pressure sensor is decreasing. 4. The fuel injection device for an engine according to claim 3, wherein an integral operation amount in the integration operation of the feedback control means is clamped.