JPH05187301A - Accumulator fuel injection device of diesel engine - Google Patents

Abstract

PURPOSE:To maintain good exhaust gas performance even during transient time, and also prevent the increase of smoke generated at the time of acceleration driving, the increase of NOX generated at the time of deceleration driving, and generation of noise, in a common rail type unit injector. CONSTITUTION:After a target injection amount QFIN and a target pressure value PFIN are calculated (S1 to S4), averaging according to change condition of the target pressure value PFIN is carried out (S5). This averaging is treated in such order that the maximum changable amount is regulated beforehand per one injection cycle, and then the target pressure value PFIN is corrected when change of the regulated value or more is generated so as to carry out moderate change. Common rail pressure feed back control is carried out by a command pressure value PFIN'' corrected by averaging process, and also an injection timing correction amount T is calculated (S6, S7) referring to an injection timing correction map in which the differrence value P between the target pressure value and the demmand pressure value is set as a parameter. The injection timing correction amount T is added to a reference injection timing TFIN calculated on the basis of the target pressure value PFIN to obtain a command injection timing TFIN'' (S9) so as to drive an injector (S10).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention calculates fuel injection conditions such as fuel injection amount and fuel injection timing according to operating conditions,
The present invention relates to a pressure-accumulation fuel injection device for a diesel engine, which injects high-pressure fuel once stored in a pressure accumulator according to these fuel injection conditions.

[0002]

2. Description of the Related Art Conventionally, as described in Japanese Patent Publication No. 6060020, a common rail type unit injector is
The common rail pressure is controlled to a target value according to the operating conditions, and the fuel injection amount and the fuel injection timing according to the operating conditions are calculated to control the valve opening of the injector, so that the fuel injection corresponding to the operating conditions is performed. It was configured to do.

[0003]

DISCLOSURE OF THE INVENTION Under normal operating conditions,
Since the common rail pressure is maintained at the target value according to the operating condition, the fuel injection to the engine is according to the operating condition. However, at the time of acceleration or load increase, the actual rise of the common rail pressure is delayed although the target value of the common rail pressure sharply rises. Therefore, fuel injection is performed at a pressure lower than the target value.
As shown in (A), the injection rate decreases and the ignition timing is delayed, resulting in an increase in smoke, an increase in unburned HC gas, and a C
There is a problem that the exhaust gas performance is deteriorated such that the amount of O 2 gas is increased.

On the other hand, when there is a change in the operating condition such as a sudden deceleration from high speed running, the common rail pressure remains higher than the target value. In this situation,
Since the injection rate is high and the fuel is easily atomized, the ignition timing is shortened as a result (FIG. 14 (B)), noise is generated, and NOx is increased, which causes deterioration of exhaust gas performance. was there.

The present invention can maintain good exhaust gas performance even during a transitional period as seen in such a sudden change in operating conditions, increase smoke during acceleration, and increase NO during deceleration.
It was completed for the purpose of providing a pressure-accumulation fuel injection device for a diesel engine capable of preventing the increase of x and the generation of noise.

[0006]

The pressure-accumulation fuel injection device for a diesel engine according to the present invention, which has been made to achieve the above object, has a pressure-accumulation chamber for temporarily storing the fuel to be supplied to the diesel engine in a high pressure state. A fuel pressure feeding means for feeding fuel to the pressure accumulating chamber, a pressure detecting means for detecting a fuel pressure in the pressure accumulating chamber, an operating condition detecting means for detecting an operating condition of the diesel engine, and an operating condition detecting means for detecting the operating condition. Target pressure instructing means for instructing the target pressure of the fuel in the pressure accumulating chamber based on the operating condition, and comparing the target pressure with the pressure detected by the pressure detecting means, and setting the fuel pressure in the accumulating chamber as the target pressure. Feedback control means for driving and controlling the fuel pressure feeding means, and injection timing instructing means for instructing the fuel injection timing corresponding to the operating condition detected by the operating condition detecting means. In a pressure-accumulation fuel injection device for a diesel engine, comprising: a fuel injection means for injecting a high-pressure fuel stored in the pressure accumulator into the diesel engine based on the instructed fuel injection timing, the target pressure is changed more than a predetermined value. If it is determined that the target pressure has been changed by a predetermined amount or more, the change of the target pressure takes a predetermined amount of time or more. A sudden change target pressure changing means that is executed gently; and a sudden change injection timing correcting means that reflects a gradual change in the target pressure when the fuel injection timing is instructed when the sudden change target pressure changing means operates. It is characterized by having.

As a result of adopting this configuration, even if the target pressure calculation value of the fuel in the pressure accumulating chamber suddenly rises, for example, at the time of sudden acceleration, the target pressure changing means for sudden change gradually changes the target pressure over a certain period of time. Is executed. That is, the target pressure is not changed stepwise at the time of sudden acceleration, but is gradually changed to the target pressure by calculation by gradually increasing it. As a result, the actual fuel pressure in the accumulator does not fall significantly below the command value, and gradually increases in a state of being in agreement with the command. At this time, the sudden change injection timing correction means,
Since the fuel injection timing that reflects the gradual change of the target pressure is realized, ignition is not too late. As a result, a large amount of smoke is generated during sudden acceleration, unburned HC, CO
Problems such as worsening emission do not occur.

On the contrary, when the speed is suddenly decelerated, the target pressure changing means for sudden change gradually reduces the target pressure. Therefore, the actual fuel pressure in the accumulator also agrees well with the command value in this case.
Moreover, the fuel injection timing is also changed gradually by the sudden change injection timing correction means, not at once, and there is no problem that the ignition timing is too early and NOx is generated or noise is generated. ..

Moreover, since the injection pressure is not simply corrected, but the target pressure is gradually decreased or gradually increased, an unpredictable state such as an overshoot phenomenon of the fuel pressure in the accumulator can occur. In addition, since the feedback control is not unreasonable, the pressure controllability is good, and from this point as well, it is possible to accurately prevent the conventional problems such as the generation of noise and the acceleration of emission deterioration.

In addition, if it is attempted to use the fuel pressure actually detected in the calculation of the injection timing correction amount, in the case of sudden acceleration / deceleration, there is no choice but to rely on the past detected value.
It was extremely difficult to eliminate that amount of error,
According to the configuration of the present invention, since the actual fuel pressure follows the command of the target pressure without difficulty, the correction amount is calculated using this target pressure, so that the detection delay Problems can be solved easily. That is, it is possible to improve the accuracy of various controls related to the pressure of the accumulator as well as the control of the pressure of the accumulator.

[0011]

The present invention will now be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a configuration explanatory view of a common rail fuel injection control device including a variable discharge high pressure pump.

This common rail type fuel injection control device 1
Is a 6-cylinder diesel engine 2, an injector 3 for injecting fuel into each cylinder of the diesel engine 2, a common rail 4 for accumulating high-pressure fuel supplied to the injector 3, and a variable discharge for pumping high-pressure fuel to the common rail 4. A high-pressure pump 5 and an electronic control unit (ECU) 6 that controls these pumps.

The ECU 6 controls the state of the diesel engine 2, for example, the detection value of the rotation speed sensor 7 and the accelerator sensor 8.
The target common rail pressure PFIN for realizing the fuel injection pressure that optimizes the combustion state of the diesel engine 2 is calculated by taking in the operating conditions such as the detected value of, and the detection value of the common rail pressure sensor 9 provided in the common rail 4 is calculated. The actual common rail pressure PC based on the target common rail pressure PFI
Common rail pressure feedback control is performed to drive and control the variable discharge high pressure pump 5 so as to maintain N.

The variable discharge high-pressure pump 5 sucks the fuel stored in the fuel tank 10 through the low-pressure supply pump 11 and pressurizes it to a high pressure inside itself according to the control command from the ECU, and pressurizes this. Supplying high pressure fuel 12
To the common rail 4 by pressure.

Each injector 3 is connected by a pipe 13 to
It is connected to a common rail 4 that stores high-pressure fuel.
Then, by opening / closing the control valve 14 arranged in each injector 3, the high pressure fuel accumulated in the common rail 4 to become the target common rail pressure PFIN is injected into the combustion chamber of each cylinder of the diesel engine 2. To be done. The opening / closing operation of the control valve 14 of the injector 3 is executed based on an injector control command from the ECU 6. This injector control command is for adjusting the fuel injection amount and the fuel injection timing, is calculated based on the detection values from the operating condition detecting means such as the rotation speed sensor 7 and the accelerator sensor 8, and the crank angle sensor 15 is used. It is output from the ECU 6 at a predetermined timing based on the detection value of the cylinder discrimination sensor 16 or the like. The control command for the variable discharge high-pressure pump 5 is also output at a predetermined timing based on the detected values from the crank angle sensor 15, the cam angle sensor 38 described later, and the like.

Next, the structure of the variable discharge high pressure pump 5 will be described with reference to FIGS. Variable discharge high pressure pump 5
Is connected to the housing 20, the cam chamber 30 arranged at the lower end thereof, the pump cylinder 21 arranged in the housing 20, and the pump cylinder 21, and supplies low-pressure fuel from the low-pressure supply pump 11. The receiving pipe 22 for receiving and the solenoid valve 60 screwed to the upper end of the pump cylinder 21 are provided.

A plunger 23 is slidably fitted in the pump cylinder 21 while maintaining liquid tightness. The plunger 23 has a cylindrical shape, and an upper end surface thereof cooperates with an inner peripheral surface of the pump cylinder 21 to form a pump chamber 24. In the pump cylinder 21, the supply pipe 1 to the common rail 4
A discharge hole 41 for connecting the two is provided.

Further, the pump cylinder 21 and the housing 2
A fuel reservoir 26 is formed between the fuel tank 26 and the fuel tank 0, and the low-pressure fuel introduced into the housing 20 from the introduction pipe 22 accumulates therein. The fuel reservoir 26 also functions as a relief of the fuel overflowing from the pump chamber 24.

The discharge hole 41 communicates with the discharge port 45 via a check valve 42. The fuel pressurized in the pump chamber 24 pushes the valve body 43 of the check valve 42 open against the urging force of the return spring 44 and the common rail pressure, and passes from the discharge port 45 through the supply pipe 12 to It is pumped to the common rail 4.

The lower end of the plunger 23 is connected to a valve seat 35, and the valve seat 35 is pressed by a plunger spring 27 against a tappet 34 having a cam roller 33. In the cam chamber 30, the rotation speed of the diesel engine 2 is 1
A cam shaft 31 that rotates at / 2 is inserted, and a cam 32 that contacts the cam roller 33 is fixed to the cam shaft 31.
The rotation of the cam shaft 31 causes the plunger 23 to reciprocate up and down along the cam profile of the cam 32 via the cam roller 33 and the tappet 34.

If the bottom dead center of the plunger 23 of the cam profile is 0 °, the cam 32 has a circle of curvature R ₁ centered outside the cam 32 from about 0 ° to about 30 °. It is composed of an arcuate concave curved surface 32c and a curved surface 32d having a center of curvature inside the cam 32, and has a substantially elliptical shape having a cam profile such that the plunger 23 reaches the top dead center at a cam angle of 90 degrees.

The solenoid valve 60 screwed to the upper end of the pump cylinder 21 has a valve body 62 for opening and closing the low pressure passage 61 opening to the pump chamber 24. The valve body 62 is a so-called open valve. Therefore, the valve body 62 is usually the spring 6
5 is opened into the pump chamber 24 by 5 to open the low-pressure passage 61.
5 against the urging force of the low pressure passage 61 and the pump chamber 2
4 is cut off. Further, since the valve body 62 receives the fuel pressure inside the pump chamber 24 as the pressure in the valve closing direction, the higher the fuel pressure is, the better the sealing performance at the time of valve closing becomes.

The low pressure passage 61 opened and closed by the valve body 62 communicates with the fuel reservoir 26 via the gallery 63 and the passage 64. On the other hand, the plunger 23 moves up and down in the pump cylinder 21 as the cam shaft 31 rotates. The plunger 23 is lowered by the returning force of the plunger spring 27.

When the plunger 23 descends, the low pressure fuel is transferred to the fuel reservoir 26 through the solenoid valve 60 which is normally open.
Is sucked into the pump chamber 24. The fuel sucked into the pump chamber 24 tends to pressurize as the plunger 23 rises, but when the solenoid valve 60 is not energized, it passes through the low pressure passage 61, the gallery 63 and the passage 64 and enters the fuel reservoir 26. Overflow does not substantially pressurize the fuel in the pump chamber 24.

On the other hand, when the solenoid valve 60 is energized while the plunger 23 is rising, the valve body 62 causes the low pressure passage 61 to move.
Therefore, the fuel in the pump chamber 24 cannot overflow and begins to be pressurized. And the pump room 2
When the fuel pressure in 4 rises and overcomes the biasing force of the return spring 44 of the check valve 42 and the pressure of the common rail 4 applied to the valve body 43, the check valve 42 is pushed open and the high pressure fuel is discharged. It is pressure-fed to the common rail 4 through the hole 41, the discharge port 45, and the supply pipe 12.

As shown in FIG. 3, one timing gear 36 is provided on the cam shaft 31, and a variable discharge high pressure pump 5 (in this embodiment, 3) in the number of cylinders of the engine 2 is used.
Individual pieces) are provided. In the figure, for convenience, one of the variable discharge high-pressure pumps is omitted, and only two variable discharge high-pressure pumps 5a and 5b are shown. Further, since the same configurations as those shown in FIG. 2 are respectively attached with subscripts a and b, refer to FIG. 2 for the detailed structure and the like of the configurations with those subscripts a and b.

The timing gear 36 is provided with a total of six protrusions 37. Further, a cam angle sensor 38 including an electromagnetic pickup is provided in close proximity to the timing gear 36. The projection 37 provided on the timing gear 36 is provided on each cam 32 during one rotation of the cam shaft 31.
By the action of a, 32b, ...
The cam angle sensor 38 detects the start timing of the ascending stroke of the plungers 23a, 23b, ... The timing signal detected by the cam angle sensor 38 is E
Input to CU6.

Based on the timing signal from the cam angle sensor 38, the ECU 6 controls the solenoid valves 60a, 60b, ...
Drive pulse is output to. As shown in FIG. 4, the drive pulse is output with a delay of a period TF (hereinafter, referred to as an output waiting period TF) using the timing signal detected at the bottom dead center position of the plunger 23 as a reference pulse. Due to this drive pulse, energization of the solenoid valve 60 is started, and the valve body 62 is closed with a delay of a period TC (hereinafter referred to as a valve closing delay TC) due to the rising of the current. After that, the closed state of the valve body 62 is maintained due to the rise in pressure of the pump chamber 24 accompanying the rise of the plunger 23, so that the drive pulse is turned off after a short period TON, and power consumption is saved. . This is an advantage because the valve is open.

After the valve body 62 is closed in this way, the period until the plunger 23 reaches the top dead center is the fuel pressurization period in the pump chamber 24, and the amount of fuel proportional to the area of the hatched portion in the figure is common rail. It will be pumped to No. 4. Therefore, in this figure, if the driving pulse output timing is advanced so that the hatching area becomes large, more fuel is pumped to the common rail 4, and conversely if the output timing is delayed, the fuel pumping amount to the common rail 4 is increased. Decrease.
That is, the pressure of the common rail 4 can be adjusted by the output timing of the drive pulse (output waiting period TF).

Next, the main routine for feedback controlling the pressure of the common rail 4 will be described. E
In the CU 6, as shown in FIG. 5, the engine rotation speed Ne is calculated based on the detection value of the rotation speed sensor 7 (S1), and the detection value of the accelerator sensor 8 is A / D converted to obtain the accelerator opening A.
ccp is calculated (S2).

Next, referring to the target fuel injection amount calculation map as shown in FIG. 6 based on the engine speed Ne and the accelerator opening degree Accp, the target fuel injection amount QFIN is obtained.
Is calculated (S3). Then, this target fuel injection amount QF
Based on the IN and the engine speed Ne, the target common rail pressure calculation map as shown in FIG. 7 is referred to, and the target common rail pressure PFIN is calculated (S4). Each map is stored in the built-in ROM of the ECU 6, and the calculation results QFIN, PFIN, etc. are stored in the built-in RAM.

Next, a smoothing process is executed according to the state of change of the command value of the target common rail pressure PFIN (S).
5). In this process, the maximum change amount of the target common rail pressure PFIN for each cycle by the high-pressure pump 5 is specified, and when it exceeds the maximum amount, the target common rail pressure PFIN is corrected to suppress the change within a predetermined range. ..

The details of this smoothing process are shown in FIG. Note that subscripts such as i-1, i in the figure correspond to the number of cycles of the engine, i represents the current cycle, and i-1 represents the immediately preceding cycle. That is, the variable with this subscript is updated every 120 ° crank angle in the case of the 6-cylinder engine as in the present embodiment, and every 180 ° crank angle in the case of the 4-cycle 4-cylinder engine.

In step S4, when the target common rail pressure PFINI is calculated this time, the difference (target pressure change amount) ΔPFINI from the pressure command value PFIN "i-1 stored as the previous result is calculated ( SS1). The pressure command value PFIN "i-1 is the value of the target common rail pressure PFIN as it is when it is determined that the target common rail pressure PFIN is not significantly changed by a predetermined value or more as a result of performing the following processing in the previous cycle. If it is determined that the change is greater than the predetermined value, the change amount is smaller than the target common rail pressure PFIN. In the following processing, the pressure command value PFIN "is determined within a range in which the command can be quickly and reasonably followed in the feedback control of the common rail pressure. Therefore, the value is in good agreement with the actual common rail pressure PC. It can be said that it is a value that accurately represents the actual common rail pressure PC at the present time.

Thus, first, the target pressure change amount ΔPFI of this time
When Ni is calculated, next, the target pressure change amount ΔPFINI
Is positive or negative, that is, whether the pressure reduction command or the pressure increase command is in progress (SS2). If ΔPFINi ≧ 0, that is, if the pressure increase command is in progress, the process proceeds to step SS3-1. This step S
In S3-1, it is determined whether the target pressure change amount ΔPFINI is larger or smaller than the maximum pressure increase amount ΔPMAXU of the actual common rail pressure PC. It should be noted that the maximum change amount ΔPMAXU during pressure increase can be maximized for one injection cycle from the fuel injection for any cylinder to the fuel injection for any other cylinder during pressure increase. It is a value set below the pressure change amount, and the high pressure pump 5
Is prescribed in advance from the relationship of the ejection capacity of

When it is determined to be "NO" in step SS3-1, the target common rail pressure PFINi calculated in step S4 is directly output as the pressure command value PFIN "i (SS4-1, SS5). −
If it is determined to be "YES" in step 1, the pressure command value PFIN "i-1 in the previous cycle is increased to the maximum change amount during pressure increase ΔPMA.
The pressure command value PF in this cycle is calculated by adding XU
It is output as IN "i (SS4-2, SS5).

On the other hand, if it is determined in SS2 that the pressure is being reduced, the process proceeds to step SS3-2. Here, the absolute value of the target pressure change amount ΔPFINi is the maximum change amount during depressurization ΔPMAX.
It is determined whether it is larger or smaller than D. The maximum change amount ΔPMAXD during depressurization is the amount of pressure change that can be maximally reduced for one injection cycle during depressurization, and is defined from the relationship of leak conditions of each part. The system as in the embodiment does not include a means for actively reducing the common rail pressure, and the pressure is reduced by relying on a leak in a device such as a plunger or an injector in a state where the high pressure pump 5 does not discharge the pressure. This is because it is configured to be.

In step SS3-2, "NO"
If it is determined that the target common rail pressure PFINI in this cycle is the pressure command value PFIN "
output as i (SS4-4, SS5), and step SS
When it is determined to be “YES” in 3-2, the maximum change amount Δ when decreasing from the pressure command value PFIN ″ i−1 in the previous cycle Δ
The value obtained by subtracting PMAXD is output as the pressure command value PFIN "i in this cycle (SS4-3, SS
5).

Thus, the feedback control of the common rail pressure is executed according to the pressure command value PFIN "i corrected based on the follow-up performance at the time of pressure increase and pressure reduction of the system. Therefore, the pressure command value PFIN" and the actual common rail The state is in good agreement with the pressure PC, and it can be considered that PFIN ″ = PC.

When this smoothing processing is completed, the main routine proceeds to the processing of step S6 and subsequent steps in FIG. Before explaining the following processing, the reason why the following processing is necessary will be described in detail with reference to FIG. In general, when the injection pressure is high and the same injection amount as when the injection pressure is low is injected at the same injection timing, the injection rate becomes high and the ignition delay becomes short, as shown in FIG. As a result, the center of gravity of the heat release rate shifts to the advance side, and the overall height increases. This leads to a large rise in NOx. Such a state is
It appears when the injection timing is advanced more than necessary.

On the contrary, when the fuel injection is executed at a low pressure with the intention of sufficiently high pressure, as shown in FIG.
As described above, the center of gravity of the heat release rate shifts to the retard side and the whole becomes low, resulting in the discharge of smoke, particulates, and the like. Such a state appears when the injection timing is retarded more than necessary.

Therefore, if the injection timing is delayed in the fuel injection when the pressure does not fall as planned and the injection timing is advanced in the fuel injection when the pressure does not rise as planned, these problems are solved. can do. From these, in step S6, the pressure difference ΔP between the initially set target common rail PFIN and the pressure command value PFIN ″ calculated in step S5 is calculated. This pressure command value PFIN ″ is calculated by the system. Maximum amount of change considering control capability △ PMAXU, △
Since it has been corrected by PMAXD, it may be considered that it eventually matches the current actual common rail pressure PC. That is, it is extremely difficult to detect the current actual common rail pressure in a timely manner. However, by using the pressure command value PFIN ″ corrected according to the capacity of the high-pressure pump 5 or the like, the target common rail pressure PFIN and the actual common rail pressure can be obtained. An accurate pressure difference with the pressure PC at the present time will be obtained.

That is, in the present embodiment, in order to easily give an accurate reference as to how much the correction should be performed, in step S6, the pressure difference is calculated using the pressure command value PFIN "instead of the actual common rail pressure PC. ΔP was obtained, and in order to correct the injection timing according to this pressure difference ΔP, the engine speed N as shown in FIG.
The injection timing correction amount ΔT is calculated with reference to the injection timing correction map using e and the pressure difference ΔP as parameters (S
7).

In a succeeding step S8, the reference injection timing TFIN is obtained from a map composed of the engine speed Ne and the injection amount QFIN, as is normally done. This injection timing TFIN is the actual common rail pressure PC
Is an effective value when is equal to the target common rail pressure PFIN. Therefore, a value obtained by adding the injection timing correction amount ΔT obtained in step S7 to this is set as the command injection timing TFIN "(S9), and the injector is driven using this command injection timing TFIN" (S10).

The operation of the above processing is shown in FIGS.
Shown in. FIG. 10 shows a case where the target common rail pressure PFIN suddenly rises, and the change in the target common rail pressure from P0 to P1 is large and exceeds the maximum change amount ΔPMAXU during pressure increase. Therefore, the target common rail pressure PFIN is not used as the command value as it is, but in Step SS3.
-1, SS4-2 processing is executed and pressure P0 before change
In addition, the maximum change amount ΔPMAXU during pressure increase is added for each injection cycle, and the gradually increased pressure command value PFIN ″ is used as a command value for control.

FIG. 11 shows a case in which the target common rail pressure PFIN suddenly drops, and the change amount of the target common rail pressure from P0 to P1 is equal to or more than the maximum change amount ΔPMAXD of the pressure command value at the time of pressure reduction. .. Therefore, the target common rail pressure PFIN is not used as it is as the command value, but the processing of steps SS3-2 and SS4-3 is executed and the maximum change amount ΔPMA from the pressure P0 before the change is reduced.
XD is subtracted for each injection cycle, and the gradually decreased pressure command value PFIN ″ is used as the command value for control.

The processing shown in FIG. 10 is executed by the accelerator opening Acc.
This is executed when p is changed from 0 (fully closed) to 1 (fully opened). This example is shown in FIG. As illustrated, when the accelerator opening Accp changes from fully closed to fully open, the target fuel injection amount QFIN increases. Then, the target common rail pressure PF
IN also increases. However, in the feedback control of the common rail pressure, the pressure command value PFI modified as described above is used.
N "is used. Therefore, the actual common rail pressure PC has a relationship that is in good agreement with the pressure command value PFIN". Since the control is easy, the actual common rail pressure PC is
It gradually rises without overshooting and converges to the original target common rail pressure.

During this time, the corrected command injection timing TFIN "is used for the actual fuel injection. The command injection timing TFIN" is corrected by using the pressure command value PFIN ", but in the end, the actual common rail pressure PC. When using the detected value of the actual common rail pressure PC, only the value a few cycles before can be used, but according to the present embodiment, it is possible to accurately use a timely value. Therefore, the ignition delay time can be controlled extremely accurately even during the transition.

On the other hand, FIG. 13 shows a conventional example. In this conventional example, the command values QFIN, PFIN, and TFIN of the injection amount, the common rail pressure, and the injection timing all change stepwise at the same time as the stepwise change of the accelerator opening Accp. Of these, the injection amount and the injection timing can immediately follow the command values QFIN and TFIN, but the actual common rail pressure PC cannot immediately follow the command value PFIN. Therefore, if the injector 3 is driven in this state, the generation of smoke, particulates and the like will increase, which causes a serious problem in emission.

Even during deceleration, in this embodiment, the pressure command value PFIN "that matches the actual common rail pressure PC is used, and the fuel injection timing is gradually changed, so that the ignition delay timing can be accurately controlled. The problem of noise generation and NOx increase unlike the conventional control does not occur.

Further, as can be seen by comparing FIG. 12 and FIG. 13, the pressure controllability of the embodiment is superior to that of the conventional example, and there is an effect that overshoot does not occur. Poor pressure controllability may lead to noise and worse emulation. Therefore, according to the present embodiment, even if the pressure controllability is improved, there is an effect of preventing noise generation and emission deterioration.

As described above, according to the present embodiment, it is possible to control the injection timing at the time of transition in which the common rail pressure changes, such as sudden acceleration or sudden deceleration, to an ideal state, and NOx and smoke at the time of transition are controlled. The generation of particulates can be suppressed. In addition, it is possible to suppress the occurrence of noise.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modes can be adopted without departing from the scope of the invention. For example, in the embodiment, the command values PFIN "and TFIN" are gradually increased / decreased stepwise, but a smoother linear increase / decrease may be adopted.

[0054]

As described above, according to the pressure-accumulation type fuel injection device for a diesel engine of the present invention, it is possible to maintain a good exhaust gas performance even during a transient state such as a sudden change in operating conditions, and to accelerate the vehicle during acceleration. It is possible to prevent the increase of smoke, the increase of NOx during deceleration, and the generation of noise.

Moreover, since not only the injection timing is corrected but also the target pressure is gradually decreased or gradually increased, an unpredictable state such as an overshoot phenomenon of the fuel pressure in the accumulator does not occur. Since the feedback control can be performed comfortably, the pressure controllability is good,
From this point as well, it is possible to accurately prevent the conventional problems such as generation of noise and promotion of deterioration of emission.

In addition, if it is attempted to use the fuel pressure actually detected in the calculation of the injection timing correction amount, in the case of rapid acceleration / deceleration, there is no choice but to rely on the past detected value.
It was extremely difficult to eliminate that amount of error,
According to the configuration of the present invention, the commanded target pressure is always substantially equal to the actual fuel pressure. Therefore, by using this target pressure to calculate the correction amount, the detection delay Problems can be solved easily. That is,
The controllability of various controls related to the pressure of the pressure accumulating chamber as well as the control of the pressure of the pressure accumulating chamber can be improved, and the accuracy thereof can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a system of an embodiment.

FIG. 2 is a cross-sectional view showing the configuration of a variable discharge high pressure pump.

FIG. 3 is a schematic diagram schematically showing the configuration of a variable discharge high pressure pump.

FIG. 4 is a timing chart for explaining the operation of the variable discharge high pressure pump.

FIG. 5 is a flowchart of a main routine of fuel injection control executed by the ECU.

FIG. 6 is a map for calculating a target fuel injection amount.

FIG. 7 is a map for calculating a target common rail pressure.

FIG. 8 is a detailed flowchart of a command value smoothing process in the fuel injection control executed by the ECU.

FIG. 9 is a map for injection timing correction.

FIG. 10 is an explanatory diagram showing how the target common rail pressure changes and the command value changes during sudden acceleration.

FIG. 11 is an explanatory diagram showing how the target common rail pressure changes and the command value changes during sudden deceleration.

FIG. 12 is a timing chart of a control state at the time of sudden acceleration.

FIG. 13 is a timing chart of a control state at the time of sudden acceleration in the conventional example.

FIG. 14 is an explanatory diagram showing the problems of the conventional example.

[Explanation of symbols]

1 ... Common rail fuel injection control device, 2 ... Diesel engine, 3 ... Injector, 4 ... Common rail, 5 ... Variable discharge high-pressure pump, 6 ...
Electronic control unit (ECU), 7 ... Rotation speed sensor, 8 ...
..Accelerator sensors, 9 ... Common rail pressure sensors,
10 ... Fuel tank, 11 ... Low-pressure supply pump, 1
2 ... Supply pipe, 13 ... Pipe, 14 ... Control valve, 15 ... Crank angle sensor, 16 ... Cylinder discrimination sensor, 23 ... Plunger, 24 ... Pump chamber, 26 ... Fuel reservoir, 32 ... Cam, 38 ...
Cam angle sensor, 42 ... Check valve, 45 ... Discharge port, 60 ... Electromagnetic valve, 61 ... Low pressure passage, 62 ...
・ Valve.

Claims (1)

[Claims] 1. A pressure accumulating chamber for temporarily accumulating fuel to be supplied to a diesel engine in a high pressure state, fuel pressure feeding means for feeding fuel to the pressure accumulating chamber, and pressure detecting means for detecting fuel pressure in the pressure accumulating chamber. Operating condition detecting means for detecting an operating condition of the diesel engine; target pressure instructing means for instructing a target pressure of the fuel in the pressure accumulating chamber based on the operating condition detected by the operating condition detecting means; Compare the detected pressure by the pressure detection means,
Feedback control means for driving and controlling the fuel pressure feeding means so that the fuel pressure in the pressure accumulating chamber becomes the target pressure, and an injection timing instruction for instructing a fuel injection timing corresponding to the operating condition detected by the operating condition detecting means. And a fuel injection device for injecting high-pressure fuel stored in the pressure accumulating chamber to a diesel engine based on the instructed fuel injection timing. When it is determined by the determining means that the target pressure should be changed by a predetermined amount or more, the target pressure is changed for a predetermined time or more. When the sudden change target pressure changing means for gradually executing the fuel injection and the sudden change target pressure changing means operate, the target is changed by instructing the fuel injection timing. Accumulator fuel injection system for a diesel engine, characterized in that a sudden change time injection timing correction means for reflecting a gradual change.