JPH05163994A - Control device for injection pressure - Google Patents

Abstract

PURPOSE:To prevent engine stop resulting from the under-shoot of common rail pressure by controlling the control quantity of a pump control valve so that the common rail pressure may change near a target value as the controlled state of an engine is monitored through ECU. CONSTITUTION:In ECU 8 to determine and command the supply of fuel to an engine, the opening and closing term of an injection control solenoid valve 2 is computed from the number of engine revolutions N, an engine load alpha and pressure Pc in a common rail serving as accumulating piping through an injection quantity control means 11. The opening term of the injection control solenoid valve 2 is then computed using the above opening term, the number of engine revolutions N, the common rail pressure Pc and a cylinder distinguishing signal G through an injection term control means 12, and an injector 1 is thereby functionally controlled through an injector driving means 13. The turning on pulse of a pump control valve 7 is moreover computed using the computed valve opening term, the number of engine revolutions N, the common rail pressure Pc and the cylinder distinguishing signal G through a common rail pressure control means 14.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an injection pressure control device for an electronically controlled diesel system. Particularly, the present invention refers to common rail pressure control of a high-pressure fuel injection device having a pressure accumulating pipe (common rail) used in a diesel engine or the like.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field, there has been one described in Japanese Patent Laid-Open No. 165858/1984. Here, a so-called common rail fuel injection system has been proposed in recent years as an electronically controlled injection device that is more excellent in controllability, instead of a system including a mechanical fuel injection pump nozzle. This system is an electronically-controlled injection device for gasoline engines (known as "EFI, EGI, etc.") that is currently in practical use and mass-produced as a well-known technique.
The idea is applied to an injection device for a diesel engine, and its control will be described below.

FIG. 11 is a diagram showing the relationship between the pump prestroke amount and the discharge amount, and FIG. 12 is a flow chart for explaining the conventional feedback control. Using the relationship between the pump prestroke amount and the discharge amount as shown in FIG. 11, the target injection pressure PFIN is calculated in step 300, the actual pressure Pc is taken in in step 301, and in step 302, as shown in FIG. ΔPc = P
FIN-Pc is calculated, and ΔP is calculated in step 303.
The proportional term TFBKP for c is calculated, the integral term TFBKI for ΔPc is calculated in step 304, and step 3
In 05, TFBK (i) = TFBK (i-1) + TFBKI + TFBKP
Is calculated. Here, TFBK represents the prestroke amount of the discharge pump. In this way, in the common rail pressure accumulation type injection system, the difference between the target injection pressure obtained from the engine speed and the load and the actual pressure in the common rail is feedback-controlled by controlling the discharge amount of the pressure accumulation pump.

[0004]

As described above, in the conventional fuel injection device, the difference between the target injection pressure and the common rail actual pressure obtained from the rotation speed and the load is fed back by controlling the discharge amount of the accumulator pump. Have control. However, at the time of sudden deceleration such as after racing, even if the discharge amount of the pump is cut off and the pump discharge amount is zero because there is no relief mechanism for the accumulated fuel, the actual pressure does not decrease instantaneously and the deceleration idle Since the target pressure at this time is set to about the nozzle closing pressure for noise reduction, there was a problem that the nozzle was closed and the fuel was cut and engine stall occurred even with a small common rail pressure due to overshoot of control. ..

Therefore, in view of the above problems, it is an object of the present invention to provide an injection pressure control device which controls the actual pump pressure in the vicinity of a target value in a deceleration state and does not cause undershoot leading to engine stall.

[0006]

In order to solve the above problems, the present invention comprises a common rail for injecting fuel into a combustion chamber from an injector, and fuel supplied to the common rail is controlled by a pump control valve to control the common rail. In the injection pressure control device that feedback-controls the fuel pressure to the target value, the valve opening period of the injection control solenoid valve that controls the injection amount from the engine speed (N), the engine load (α), and the common rail pressure (Pc) ( TINT), and the injection timing is controlled from the valve opening period (TINT) corresponding to the injection amount determined by the injection amount control means, the engine speed (N), and the common rail pressure (Pc). In order to open the injection control solenoid valve (TT)
For controlling the injection timing, the injector driving means for driving and controlling the injector by the two control means, the pump control valve based on the valve opening period (TINT), the engine speed (N) and the common rail pressure (Pc). A common rail pressure control means is provided for determining the energizing pulse (TF) of (PCV) and controlling the energizing pulse (TF) during deceleration by using the feedback control learning value of the pump control valve during idling.

[0007]

According to the injection pressure control device of the present invention, the engine is provided with the injector for the combustion chamber of each cylinder.
The fuel injection from the injector to the engine is controlled by turning on and off the injection control solenoid valve by the injection amount control means, the injection timing control means and the injector drive means. The injector is connected to a high-pressure fuel pipe common to all cylinders, a so-called common rail, and fuel in the common rail is injected from the injector to the engine while the injection control solenoid valve is open. Further, high pressure fuel corresponding to the fuel injection pressure is continuously accumulated in the common rail,
The high-pressure fuel is supplied from the feed pump to the high-pressure pump and is boosted in pressure. The pressure of the fuel boosted by the high-pressure pump 5 is detected by the pressure sensor of the common rail, and the pump control valve (PCV) is set so that the pressure of the common rail becomes a predetermined value.
The high pressure fuel is released to the inlet side of the high pressure pump for control.
The injection control solenoid valve and the pump control valve (PCV), which are actuators of the injection pressure control device, control the fuel injection amount, the fuel injection timing, and the fuel pressure of the common rail. Further, these control amounts are determined and commanded by an electronic control computer (ECU) according to engine parameters (engine speed: N, engine load: α, engine water temperature, etc.). The present invention determines the fuel supplied to the engine
The control amount of the pump control valve (PCV) is controlled so that the common rail pressure changes in the vicinity of the target value while monitoring the control state of the engine by the common rail pressure control means of the electronic control computer that issues a command, and the pump control valve (PCV) The control command value of is learned and stored at the time of idling, and the stored learned value is reflected to the pump control command value at the time of deceleration of the engine so that the common rail pressure at the time of deceleration does not become a pressure equal to or lower than the nozzle closing pressure. Prevents engine stalling due to undershoot.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an injection pressure control device according to an embodiment of the present invention. The injection pressure control device shown in this figure is an injector 1 that is arranged in a combustion chamber of each cylinder of an engine to inject fuel, and an injection control that controls ON / OFF of fuel injection from the injector 1 to the combustion chamber. The solenoid valve 2 and the injector 1 are high-pressure fuel pipes connected in common to each cylinder, and the injection control solenoid valve 2
A so-called common rail 3 for injecting fuel therein into the combustion chamber from the injector 1, a feed pump 4 for supplying fuel, and the feed pump 4
From the high pressure pump 5 for supplying fuel to the common rail 3 for continuously accumulating the high pressure corresponding to the fuel injection pressure to the common rail 3 and boosting the pressure, and in the common rail 3 boosted by the high pressure pump 5. The pressure sensor 6 installed on the common rail 3 to detect the fuel pressure of the fuel, and the pressure of the common rail 3 detected by the pressure sensor 6 that escapes to the inlet side of the high-pressure pump 5 is set to a predetermined value. And a pump control valve (PCV) 7 for controlling the fuel pressure of the common rail 3 from the fuel injection amount and the fuel injection timing of the injection control electromagnetic valve 2 which is an actuator according to the engine parameter (engine speed). : N, engine load: α, engine water temperature, etc.) and an electronic control computer (ECU) 8 for determining a command, and an engine on or engaged with the pump shaft. Gin is pulser opposed to arranged the crankshaft including an engine speed sensor 9 for detecting an engine emission speed signal and the cylinder identification signal, respectively, and a cylinder discrimination sensor 10.

The present invention determines the fuel supplied to the engine.
Under control of the common rail pressure by controlling the control amount of the pump control valve (PCV) 7 so that the common rail pressure changes in the vicinity of the target value while monitoring the control state of the engine by the electronic control computer (ECU) 8 which issues a command. It is intended to prevent stalling due to shooting.

FIG. 2 is a diagram showing a control block of an electronic control computer (ECU) according to an embodiment of the present invention.
The electronic control computer (ECU) 8 shown in the figure has an opening period (the valve opening period for the injection control solenoid valve 2 for controlling the injection amount from the engine speed (N), the engine load (α) and the common rail pressure (Pc). TINT) is calculated from the injection amount control means 11, the valve opening period (TINT) corresponding to the injection amount determined by the injection amount control means 11, the engine speed (N), and the Conon rail pressure (Pc). In order to control the injection timing, the cylinder discriminating signal (G) is also used to determine the injection cylinder, and the injection timing control means 12 for calculating and determining the valve opening timing (TT) of the injection controlling solenoid valve 2. , An injector drive means 13 for driving and controlling the injector 1 by the two control means 11 and 12, a valve opening period (TINT) corresponding to an injection amount, and an engine rotation as well as an injection timing. From the number (N) and the common rail pressure (Pc), a cylinder discrimination signal (G) for driving the pump control valve (PCV) 7 corresponding to the injection cylinder.
Common rail pressure control means 1 for calculating and determining the energizing pulse (TF) of the pump control valve (PCV) 7 using
Including 4 and.

FIG. 3 is a block diagram for explaining the common rail pressure control means in FIG. As shown in this figure,
The common rail pressure control means 14 determines the common rail target value (PF) according to the engine condition from the drive pulse (TINT) of the injection control solenoid valve 2 corresponding to the engine speed (N) and the fuel injection amount as described above. A common rail pressure target value calculating means 21 for calculating and a pump control for comparing the actual pressure value (Pc) from the pressure sensor 6 with the target value (PF) and controlling the common rail pressure so that the pressure value becomes the target value. The PCV control command value calculating means 22 for calculating and outputting the command value (TFBK) of the valve (PCV) 7, and the engine accelerator opening degree (α) that determines whether the engine is in a stable state as the basis of the present invention, The pump control valve (PCV) 7 that operates only when the stable state determination means 23 determines from the engine speed (N) or the like and the stable state determination means 23 is in a stable state. Feedback command value (Δ
The learning value updating means 24 for learning / accumulating / updating T) and storing it in a non-volatile memory, the deceleration time judging means 25 for judging the deceleration state from the engine accelerator opening degree (α) and the learning value updating means 24. The stored learning value is taken out after the common rail pressure feedback is stopped when the pressure deviation (ΔP) is less than a predetermined value, and is reflected in the basic control command value of the pump control valve (PCV) 7 as the integrated value ΣΔT so that the common rail pressure during deceleration is the nozzle. The learning value take-out correction means 26 for controlling the command value (TFBK) of the pump control valve (PCV) 7 so that the pressure does not become a pressure equal to or lower than the valve closing pressure to prevent engine stall due to undershoot of the common rail pressure.
Including and

FIG. 4 is an operation timing chart according to this embodiment. As shown in this figure, when the engine state is switched from steady operation to deceleration operation mode, the target value (PF) of the common rail pressure changes to the low pressure side and the actual pressure (P
The following control is performed so that c) becomes the target value (PF).
First, in the conventional control (broken line) before improvement, the pump final command value (TFBK) is determined by the sum of the base command value (TBASE) and the feedback correction value (TFB), and the common rail actual pressure (Pc) is the target value ( Since the feedback control similar to that immediately after the start of deceleration is performed even after the pressure becomes close to PF), the control is over-controlled due to the delay of the control system including the delay of the hydraulic system of the pump, and the pump discharge amount is reduced more than necessary and the common rail is reduced. The actual pressure (Pc) was undershooting and the engine stalled. On the other hand, the control (solid line) after the improvement of the present invention is the common rail actual pressure (P
When c) becomes close to the target value (PF), the learning value (ΣΔT) learned and stored in the idle stable state is used as the feedback correction amount, and feedback is stopped for a predetermined time to prevent overcontrol due to the delay of the control system. It is possible to avoid an undershoot of the common rail actual pressure (Pc) due to an unnecessary reduction of the discharge amount and prevent an engine stall.

5 and 6 are control flow charts (Nos. 1 and 2) according to the present embodiment for realizing the timing chart of FIG. As shown in the figure, step 100
Then, various parameters for engine control are taken in from various sensors that detect the engine operating state. Step 1
In 01, the injection system control amount is determined from the information acquired in step 100. That is, the fuel injection amount (q) is determined from the accelerator opening (α) and the engine speed (Ne), and the fuel injection timing (θ) is determined from the fuel injection amount (q) and the engine speed (Ne).

In step 102, the engine speed (N
The injection pressure target value (PF) is calculated from e) and the injection amount command value (q). In step 103, a pump basic command value (TBASE) for controlling the pump control valve (PCV) 7 corresponding to the target pressure is calculated from the engine speed (Ne) and the injection amount command value (q).

In step 104, the common rail pressure sensor 6 takes in the actual rail pressure (Pc). Step 1
In 05, the actual rail pressure (Pc) and the target rail pressure (Pc)
Calculate the pressure deviation (ΔP) from F). Step 106
Then, the correction amount (TFB) of the pump command value according to the pressure deviation (ΔP) is calculated.

The following steps 107 to 119 relate to the control method according to the present invention and will be described in order. In step 107, it is determined whether or not the engine is in the deceleration state based on the accelerator sensor opening degree and the accelerator fully closed signal (LLON). In step 109, if it is determined in step 107 that the vehicle is not in the deceleration state, the process proceeds to this step, and the pump basic command value (TBAS
E) and pump command value correction amount (TFB) are added to calculate the pump final output (TFBK).

In step 108, the step 107
When it is determined that the vehicle is in the deceleration state, the process proceeds to this step, and it is determined whether the pressure deviation (ΔP) calculated in step 105 is less than or equal to a predetermined value (Ps). The process proceeds to step 110, and if the above-mentioned processing is performed, but is less than or equal to the predetermined value, the process proceeds to step 110. In step 110, in order to detect the control amount in the stable state, it is judged whether or not the duration of the idle state is equal to or longer than a predetermined value.

In step 111, the step 110 is performed.
When the vehicle is in the deceleration state, the process proceeds to this step, and the idle correction learning value (ΣΔT) in the non-volatile memory is taken out without feedback. In step 112, the pump basic command value (TBASE) calculated in step 103 is added to the idle correction learning value (ΣΔT) to obtain the final pump output (TFBK).
).

In step 113, it is judged whether or not there is learning at the time of idling when the idling duration time exceeds the predetermined value in step 110. In step 114, when the learning is performed in step 113, the previous learning value (ΣΔT _i-1 ) is set as the learning value (ΣΔT). On the other hand, in step 115, when there is no learning in step 113, the initial value (ΔTIN) of learning is set as the learning value (ΣΔT).

In step 116, it is determined whether or not the pressure deviation (| ΔP |) resulting from the previous learning correction control result is within a predetermined value (a), and it is further determined whether or not the claw is necessary. In step 117, when learning is required, a pump correction value (TFB) corresponding to the pressure deviation (ΔP) is calculated.

At step 118, the current learning value (ΣΔT _i ) is reflected in the previous pump idle learning value (ΣΔT). In step 119, if the learning is sufficient, the learning value (ΣΔT) is stored in the non-volatile memory. After the above steps 118 and 119 are completed, the process proceeds to the above-mentioned step 112, and the process for reflecting the learning correction value is performed and the step 1
At 20, the output of each command value (q, θ, TFBK) is set, and this control ends.

The contents of the present invention are executed while repeating the control of steps 100 to 120. FIG. 7 is a diagram showing a comparison between the initial value of the idle learning value and that after learning. As shown in the figure, the initial value of the learning according to step 115 of the present embodiment is set to a value on the maximum pump discharge amount side that can prevent undershoot by allowing common rail pressure even in the initial state to allow for deterioration over time and initial variations, and to perform learning. Accordingly, the ejection amount is set to be suppressed.

FIG. 8 is a diagram showing a correction characteristic when the predetermined value (Ps) for discriminating the pressure deviation (ΔP) is operated according to the amount of the learning value. The same effect can be obtained by operating as shown in this figure. Further, in the present embodiment, the pump control command value is operated, but the same effect as the above embodiment can be obtained by increasing or decreasing the common rail pressure target value according to the learned value and setting / operating the guard value in the pump control command value. Needless to say.

FIG. 9 is an operation timing chart according to another embodiment, and FIG. 10 is a control flow chart for realizing the timing chart of the embodiment of FIG. In the present embodiment, the actual injection pressure drop is prevented by providing a guard for the integral correction term for the discharge amount control (PI control) and learning the guard value in the idle state. As shown in FIG. 10, in step 201, the target pressure PFI is calculated from the engine speed (N) and the load.

Next, at step 202, the actual pressure Pc is taken in from the pressure sensor 6 attached to the common rail 3. In step 203, the difference ΔPc from the target is calculated. ΔPc in steps 204 and 205, respectively
A proportional and integral correction amount for is calculated. Up to this point, it is the same as the conventional one.

Next, in step 206, it is determined whether or not the actual Pc has fallen, and if the amount of fall is within the set value (-1 MPa), the routine exits the routine with the current integral amount in step 209. If the value is equal to or larger than the set value in step 207, the integral value TFBKI is judged to be larger or smaller than the learning value TFBKL at idle.

If TFBKI is larger in step 208, a guard is provided rather than setting TFBKI '= TFBKL. Final pre-stroke amount FFB in step 210
Calculate K and exit the feedback routine. According to the present embodiment, as shown in FIG. 9, it is possible to prevent pressure undershoot during deceleration (transition), and prevent problems such as engine stall.

[0028]

As described above, according to the present invention, in the common rail fuel injection system, the electronic control computer that determines and commands the amount of fuel supplied to the engine determines the stable state of the engine and determines the pump control valve (PCV). )
Learning and storing the control command value of, and when the pressure deviation between the common rail actual pressure and the target value during engine deceleration falls below a predetermined value, stop the common rail pressure feedback and reflect the stored learning value in the pump control command value. As a result, it is possible to prevent the common rail pressure during deceleration from becoming equal to or lower than the nozzle closing valve pressure and to prevent engine stall due to undershoot of the common rail pressure. Furthermore, by setting the common rail pressure during idling to a low value close to the nozzle closing pressure, the excellent effect that a comfortable system without engine stall can be realized even if the adaptation with emphasis on combustion noise is performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an injection pressure control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a control block of an electronic control computer (ECU) according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating common rail pressure control means in FIG.

FIG. 4 is an operation timing chart according to the present embodiment.

FIG. 5 is a control flowchart (No. 1) according to the present embodiment for realizing the timing chart of FIG.

FIG. 6 is a control flowchart (No. 2) according to the present embodiment for realizing the timing chart of FIG.

FIG. 7 is a diagram showing a comparison between an initial idle learning value and that after learning.

FIG. 8 is a diagram showing a correction characteristic when a predetermined value (Ps) for discriminating a pressure deviation (ΔP) according to another embodiment is operated according to an amount of a learning value.

FIG. 9 is an operation timing chart according to another embodiment.

FIG. 10 is a control flowchart for realizing the timing chart of the embodiment of FIG.

FIG. 11 is a diagram showing a relationship between a pump prestroke amount and a discharge amount.

FIG. 12 is a flowchart illustrating a conventional feedback control.

[Explanation of symbols]

 1 ... Injector 2 ... Injection control solenoid valve 3 ... Common rail 4 ... Feed pump 5 ... High-pressure pump 6 ... Pressure sensor 7 ... Pump control valve (PCV) 8 ... Electronic control computer (ECU) 9 ... Engine speed sensor 10 ... Cylinder discrimination sensor 11 ... Injection amount control means 12 ... Injection timing control means 13 ... Injector drive means 14 ... Common rail pressure control means 21 ... Common rail pressure target value calculation means 22 ... PCV control command value calculation means 23 ... Stable state discrimination means 24 ... Learning value updating means 25 ... Deceleration time judging means 26 ... Learning value extraction correcting means

Claims (1)

[Claims] 1. An injection pressure control device comprising a common rail for injecting fuel from an injector into a combustion chamber, wherein fuel supplied to the common rail is controlled by a pump control valve to feedback-control the fuel pressure of the common rail to a target value. Injection amount control means for determining the valve opening period (TINT) of the injection control solenoid valve for controlling the injection amount from the engine speed (N), engine load (α) and common rail pressure (Pc), and the injection amount control means In order to control the injection timing from the valve opening period (TINT), the engine speed (N), and the common rail pressure (Pc) corresponding to the injection amount determined in step S1, the valve opening timing (TT) of the injection control solenoid valve is set. An injection timing control means for determining, an injector drive means for driving and controlling the injector by the two control means, the valve opening period (TIN T), engine speed (N) and common rail pressure (Pc) from pump control valve (PC
Common rail pressure control means for determining the energizing pulse (TF) of V) and controlling the energizing pulse (TF) during deceleration by using the feedback control learning value of the pump control valve during idling. Injection pressure control device.