JP2000282929A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device of suction amount adjustable type, capable of enhancing the controllability when feedback controlling a common rail pressure. SOLUTION: The actual fuel pressure on a common rail 1, where the pressure of a high pressure fuel to be injected into a cylinder of an internal combustion engine from an injection valve 2 is accumulated, is sensed by a fuel pressure sensor S, and on the basis of the obtained value, the amount of the fuel sucked into the pressurizing chamber of a fuel supply pump 4 is controlled by an ECU 3. The ECU 3 includes an unfed amount calculating means for calculating the amount of the fuel sucked into the pressurizing chamber in conformity to the suction command, before the foregoing time and left in the condition not fed by pressure to a pressure accumulating chamber and a suction amount calculating means to calculate the suction amount according to the suction command at this time, on the basis of the increment of the fuel pressure predicted from the obtained unfed amount and calculates the suction amount from the difference of the actual fuel pressure upon predicting the fuel pressure on the common rail 1 at pressure feeding of fuel. Accordingly, a suction command output means outputs a suction command signal to a suction amount adjusting valve of the fuel supply pump 4, so that it is made practicable to enhance the followup performance after the target pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common rail type fuel injection system for an internal combustion engine, and more particularly to control of common rail pressure in a fuel injection system using a suction metering type fuel supply pump.

[0002]

2. Description of the Related Art In a common rail fuel injection device known as a fuel injection system for a diesel engine, high pressure fuel is stored in a pressure storage chamber (common rail) common to each cylinder, and at a predetermined timing from an injection valve communicating with the common rail. Fuel is injected into each cylinder. High-pressure fuel is pressure-fed to the common rail from a fuel supply pump having a variable discharge amount, and the pressure of the high-pressure fuel is controlled to feedback-control the fuel pressure in the common rail. As such a fuel supply pump, a pump having a pressurizing chamber for pressurizing the fuel by reciprocating movement of a plunger and an electromagnetic valve for opening and closing a flow path to the pressurizing chamber has been conventionally used. , That is, so-called pre-stroke control. This is because, after the fuel is sucked into the pressurizing chamber, the solenoid valve is not closed immediately even if the plunger moves to the pumping stroke, and the valve is kept open until the fuel in the pressurizing chamber reaches a predetermined amount, and the excess fuel is discharged. The amount of pumping is controlled by controlling the valve closing timing of the solenoid valve.

[0003] However, in the fuel supply pump having the above-described configuration for performing the metering at the time of discharge, since the solenoid valve is configured to directly receive the fuel pressure in the pressure chamber, high pressure resistance is required. It is easy to be. Therefore, in recent years, attention has been paid to a suction metering-type fuel supply pump that determines a pumping amount at the time of suction. This pump is provided with a suction metering valve for controlling the amount of fuel sucked into the pressurizing chamber, and a check valve is disposed in a flow path from the suction metering valve to the pressurizing chamber. When a necessary amount of fuel is supplied into the pressurizing chamber in advance by a solenoid valve serving as a valve, the flow path to the pressure chamber is closed by the check valve from the start of pressurizing the fuel to the end of pumping. In this method, the fuel pressure when passing through the suction metering valve is at most several hundred Pa, so that the size and cost can be reduced.

[0004]

However, the suction metering type fuel supply pump has a problem in that since it takes a long time until the sucked fuel is pumped, this becomes a delay amount and controllability deteriorates. is there. For example, in the conventional control method, the feedback amount is calculated from the differential pressure between the actual fuel pressure of the common rail and the target pressure. However, when unpressurized fuel is present in the pressurized chamber when calculating the suction amount, the unpressurized fuel is transmitted. The pumping of fuel causes excessive pumping, the common rail pressure rises above the target, and the amount of feedback required for the target pressure changes. A decrease in the controllability of the fuel pressure affects the combustion and deteriorates the emission.

[0005] On the other hand, there is a demand that the same fuel supply pump can be applied to various engines having different numbers of injections and pumping times, and that the cost be reduced by using common parts. In particular, from the viewpoint of the pump rotation speed, there is a great demand for a combination in which the number of times of injection is greater than the number of times of pumping. However, in the suction metering type fuel supply pump, the fuel is injected before the sucked fuel is pumped. And the controllability deteriorates due to the pumping delay. In particular, when the target pressure changes abruptly, such as during rapid acceleration, the pumping delay increases and the ability to follow the target pressure decreases,
There was a problem that the overshoot amount became large.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection device of a suction metering type.
The purpose of this is to improve controllability in feedback control of the common rail pressure.Especially, even when the number of injections and the number of times of pumping are different or when the target pressure changes suddenly, the followability to the target pressure and the overshoot amount are improved. An object of the present invention is to realize a fuel injection device that can be reduced.

[0007]

According to a first aspect of the present invention, there is provided a fuel injection device, comprising: a pressure accumulating chamber for accumulating high pressure fuel; an injection valve for injecting the high pressure fuel in the pressure accumulating chamber to a cylinder of an internal combustion engine; A fuel supply pump that pressurizes the fuel sucked into the pressurizing chamber through the fuel supply pump and pressurizes the fuel into the accumulator, a pressure detector that detects the fuel pressure in the accumulator, and an actual fuel pressure that is detected by the pressure detector. A control unit that controls the fuel pressure in the accumulator by controlling the amount of fuel sucked into the pressurizing chamber based on the pressure. Further, the control unit includes an unpressurized feed amount calculating unit that calculates an amount of fuel that is sucked into the pressurized chamber by the previous suction command and that is not pumped into the accumulator, and Suction amount calculating means for calculating the suction amount based on the current suction command based on the predicted increment of the fuel pressure, and a suction command output for outputting a suction command signal to the suction metering valve according to the calculated suction amount. Means.

The control unit calculates the amount of fuel that has already been sucked into the pressurizing chamber and is in a non-pumped state at the time of calculation of the suction amount. Is added to the actual fuel pressure to predict the fuel pressure in the accumulator at the time of pumping. Since the predicted pressure is a value that takes into account the amount of unpressurized pumping that is pumped during the delay time from suction to pumping, the pumping amount, that is, the suctioning amount, is calculated from the difference between this and the target fuel pressure. In addition, the influence of the pumping delay can be reduced. Therefore, the followability to the target pressure can be improved, and the controllability of the fuel pressure can be improved.

According to a second aspect of the present invention, the control unit includes an injection amount calculating means for calculating a fuel injection amount to be injected into a cylinder of the internal combustion engine until the pumping of the unpressurized fuel is completed. The suction amount calculation means calculates the suction amount based on the calculated injection amount and the increment of the fuel pressure predicted from the unpressurized feed amount.

When fuel is injected into the cylinder of the internal combustion engine during the delay time from the suction to the pumping, the fuel pressure in the accumulator also fluctuates depending on the injection amount. Therefore, the control unit sets the amount of injection to be injected into the internal combustion engine by the end of the non-pumped amount to the fuel pressure increment as the amount subtracted from the unpumped amount. Thereby, the controllability of the fuel pressure can be further improved.

According to a third aspect of the present invention, the control unit has a leak amount calculating means for calculating an amount of fuel leaking until the pressure feeding of the unpressurized fuel is completed. The means calculates the suction amount based on the calculated leak amount, the injection amount, and the fuel pressure increase amount predicted from the unpressurized feed amount.

[0012] The fuel pressure in the accumulator also fluctuates due to fuel leaks from various parts of the fuel injection device. Therefore, the control unit calculates the amount of fuel leaking from each part by the end of the pumping of the unpumped amount, and increases the fuel pressure by the amount obtained by subtracting the leak amount and the injection amount from the unpumped amount. Assume quantity. Thereby, the controllability of the fuel pressure can be further improved.

According to a fourth aspect of the present invention, the suction amount calculating means adds the increment of the fuel pressure according to any one of the first to third aspects to the actual fuel pressure to determine when the non-pumped fuel has been pumped. As the predicted value of the fuel pressure at
The suction amount is calculated from the pressure difference between the predicted value and the target value of the fuel pressure.

Specifically, a value obtained by adding the increment of the fuel pressure calculated in each claim to the actual fuel pressure is set as a predicted value of the fuel pressure after the pumping delay time. Then, by comparing this with the target value of the fuel pressure set according to the operating state, the amount of the differential pressure with respect to the target pressure is known, and the intake amount can be calculated based on this.

According to a fifth aspect of the present invention, the control unit includes: an injection valve driving unit that drives the fuel injection valve to inject fuel into the cylinder of the internal combustion engine with a predetermined injection amount command value; On the other hand, there is provided an injection command timing delay means for delaying an injection command based on the injection amount command value for a time corresponding to a delay time until the unpressurized fuel is fed under pressure.

When the control unit outputs a drive signal to the injection valve driving means, the injection valve injects fuel to each cylinder at a predetermined injection amount command value. Here, if the injection command timing is delayed by the predetermined delay time after calculating the injection quantity command value, the injection quantity calculated by the injection quantity calculation means of the second aspect is not the predicted value but the actual injection quantity. Since the calculation can be performed based on the injection amount, the fuel pressure after the delay time can be accurately detected.

According to a sixth aspect of the present invention, in the response delay time from the suction command by the suction command output means to the operation of the suction metering valve, the uncompressed feed amount calculating means is based on the suction amount in the previous two previous suction commands. Then, in the time after the response delay time, the amount of the fuel in the unpressurized state is calculated based on the suction amount in the previous suction command.

If there is a response delay from the output of the suction command signal by the suction command output means to the activation of the suction metering valve, the suction amount within the response delay time is determined by the suction amount in the previous suction command. It is based on Therefore, in the calculation of the unpumped amount, the unpumped amount can be accurately detected by calculating the suction amount separately for the response delay time and thereafter.

In the present invention, it is assumed that the number of times of pumping per one revolution of the fuel supply pump and the number of times of injection into the cylinder of the internal combustion engine are different. The present invention has a great effect when applied to a system in which the number of times of pumping and the number of times of injection differ from each other, in which the effect of the pumping delay is remarkable.

According to claim 8, the internal combustion engine is a diesel engine. The present invention is highly effective when applied to a diesel engine that requires high controllability of fuel pressure.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is an overall configuration diagram of a common rail type fuel injection device for a diesel engine. A common rail 1 as a pressure storage chamber in which high-pressure fuel corresponding to the fuel injection pressure is stored.
And a plurality of fuel injection valves 2 connected to the common rail 1 to inject fuel into each cylinder of a diesel engine (not shown). Here, only the fuel injection valve 2 corresponding to one of the four-cylinder engines is shown, and illustration of the other cylinders is omitted. ECU3 that is a control unit
Determines the optimal injection timing and injection amount (injection period) according to the engine state, and drives each fuel injection valve 2 via the EDU 31 serving as injection valve driving means.

The high-pressure fuel stored in the common rail 1 is
The fuel is supplied from the fuel supply pump 4 through the high-pressure channel 11. The fuel supply pump 4 is connected to the filter F from the fuel tank T.
The low-pressure fuel sucked through the high pressure is pressurized to a high pressure and sent to the high-pressure channel 11 by pressure. The ECU 3 determines the discharge amount to the common rail 1 based on a signal from the fuel pressure sensor S provided on the common rail 1 and outputs a control signal to the fuel supply pump 4 to control the common rail pressure. The method of controlling the amount of pressure supplied by the fuel supply pump 4 will be described later.

The common rail 1 has a pressure reducing valve 14 for opening and closing a flow path 13 to a low pressure flow path 12 communicating with the fuel tank T. For example, the common rail pressure can be rapidly reduced at the time of deceleration or the like. Further, a pressure limiter 17 is provided in the middle of the high-pressure flow path 11 and functions as a safety valve for preventing the common rail pressure from becoming abnormally high. Further, the leaked fuel from the fuel injection valve 2 and the leaked fuel from the fuel supply pump 4 also flow through the flow path 15,
The fuel is returned from the fuel tank 16 to the fuel tank T through the low-pressure passage 12.

Next, the details of the fuel supply pump 4 will be described with reference to FIGS. In the figure, cylinder heads 5 and 6 are fixed to upper and lower surfaces of a pump housing 41, respectively.
Plungers 51 and 61 are supported in each of the cylinder heads 5 and 6 so as to be slidable back and forth. Above the plunger 51 and below the plunger 61, there are provided fuel pressurizing chambers 52 and 62 formed by end faces of the plungers 51 and 61 and inner wall surfaces of the cylinder heads 5 and 6, and check valves 53 and 63. Through which low-pressure fuel flows.

As shown in FIG. 2, a drive shaft 42, which is driven to rotate in synchronization with half the rotation of the engine, is inserted into the pump housing 41, and is rotatably supported via a journal 43. . Drive shaft 4
A cam 44 is formed integrally on the outer periphery of the intermediate portion of
The plungers 51 and 61 are disposed at vertically symmetric positions with respect to the cam 44.

As shown in FIG. 3, a cam 44 having a circular cross section is provided eccentrically with respect to the drive shaft 42, and a shoe 45 having a rectangular outer shape is slidably held on the outer periphery thereof via a bush 46. . Plate members 55 integral with the plungers 51 and 61 are provided on upper and lower end surfaces of the shoe 45,
65 is pressed by the biasing force of the springs 56 and 66. When the cam 44 integrated with the drive shaft 42 rotates, the shoe 46 revolves along a predetermined circular path, and the plate members 55 and 65
Reciprocatingly slides on the upper and lower end surfaces. Accordingly, the plungers 51 and 61 move up and down to pressurize the fuel in the pressurizing chambers 52 and 62.

FIG. 4 is a schematic diagram showing a fuel intake and pressure feeding path. Here, for convenience, only a path to the pressurizing chamber 52 is shown, but the same applies to the pressurizing chamber 62. The fuel supply pump 4 has a built-in inner gear type feed pump 71. The feed pump 71 pressurizes fuel sucked from a fuel introduction path 72 communicating with a fuel tank T (see FIG. 1) to a predetermined low pressure to increase the fuel. The fuel is sent to the fuel reservoir 74 from the flow path 73. The feed pump 71 is provided with a pressure regulating valve 75 so that the discharge pressure does not exceed a predetermined pressure.

The fuel in the fuel pool 74 is supplied to the intake metering valve 8.
Then, it is sucked into the pressurized chamber via the check valve 53. The suction metering valve 8 provided between the fuel reservoir 74 and the fuel flow path 76 leading to the check valve 53 drives a valve element 82 slidably held in a housing 81 and the valve element 82. Coil 8
The lift amount of the valve element 82, that is, the opening area of the flow path communicating with the fuel flow path 76 is adjusted by controlling the amount of electricity supplied to the coil 83 by the ECU 3, and the pressurizing chamber 5 is controlled.
It is possible to control the amount of fuel sucked into the fuel cell 2. The valve element 82 closes with the spring force of the spring 84 when the coil 83 is not energized, and opens when the coil 83 is energized against the spring force.

The check valve 53 is provided between the fuel passage 76 and the pressurizing chamber 52.
It is arranged between. Tapered valve body 53a of check valve 53
Is normally urged upward by a spring 53b, is seated on the seat surface 53c, and is closed. When low-pressure fuel flows from the suction metering valve 8 via the fuel flow path 76 and the flow path 53d, the valve 53a is opened by the pressure of the fuel, and the fuel is sucked into the pressurizing chamber 52. When the pressurization is started, the valve body 53a closes with the pressure of the fuel and holds it until the fuel is pumped.

The pressurized fuel is discharged from the discharge valve 77 through the pressure feed passage 57. The suction metering valve 8 communicates with the pressurizing chamber 62 in FIG. 2 by a fuel flow path (not shown), and supplies fuel to the pressurizing chamber 62 via a check valve 63. The fuel pressurized in the pressurizing chamber 62 is similarly discharged from the discharge valve 78 through the pressure feed passage 67. Discharge valve 7
The ball valves 7 and 78 function as check valves.
7a and 78a to prevent backflow of fuel from the discharge holes 77b and 78b toward the pressure feed passages 57 and 67. The high-pressure fuel discharged from the discharge holes 77b and 78b merges on the way, and is supplied from the high-pressure channel 11 to the common rail 1 (see FIG. 1).

Next, the operation of the fuel supply pump 4 having the above configuration will be described. In FIG. 3, the drive shaft 4
When the cam 44 rotates with the rotation of 2, the shoe 45 revolves accordingly. At this time, the plate members 55, 65 of the plungers 51, 61 with respect to the upper and lower end surfaces of the shoe 45.
Slides back and forth, the plungers 51 and 61 move up and down in the cylinder heads 5 and 6. As the shoe 45 revolves, the plungers 51 and 61 are alternately lifted, and the plunger 51 is at the top dead center and the plunger 61 is at the bottom dead center in the illustrated state. When the plunger 51 at the top dead center is lowered, the pressure in the pressurizing chamber 52 decreases, and the check valve 53 is opened by the pressure of the fuel, and the fuel is sucked into the pressurizing chamber 52 from the flow path 53d. After the plunger 51 has reached the bottom dead center (the state of the plunger 61 in the figure), the ascent is started again.
3 closes, the fuel pressure rises, the discharge valve 77 is opened, and high-pressure fuel is pumped to the common rail 1.

As described above, the fuel supply pump 4 performs two suction and pressure strokes per one rotation of the drive shaft 42.
It is configured to be cycled. The amount of pumping is controlled by the amount of fuel sucked into the pressurizing chambers 52 and 62, and the amount of suction can be controlled by controlling the valve opening of the suction metering valve 8. This method has an advantage that the suction metering valve 8 can be reduced in size and weight, but there is a problem in that the controllability is reduced in the conventional PID (proportional-integral-derivative) control because a pumping delay occurs. This will be described with reference to a time chart shown in FIG. Here, 4 rotations per pump revolution
The case where four injections are performed (four injections and two pressure feeds) is taken as an example. The figure shows an engine crank angle signal, an injection amount calculation time, an injection period of each of the cylinders # 1 to # 4, an intake amount calculation time, an opening of the intake metering valve 8, a plunger 51, 61 of the fuel supply pump 4 ( The lift amounts (shown as # 1 and # 2 in the figure) and the actual fuel pressure of the common rail 1 are shown in comparison.

First, the pumping delay in the suction metering method will be described. In FIG. 5, the calculation of the suction amount is performed at the timing when the pumping of the plungers # 1 and # 2 is completed. For example, in the drawing, when the actual fuel pressure is detected by the fuel pressure sensor S at the time (a) at which the plunger # 1 is at the top dead center, the feedback amount is calculated from the pressure difference from the target fuel pressure, and at the time (b) Command the suction amount Qin (I). As a result, fuel sucked according to the opening of the suction metering valve 8 during the suction period of the plunger # 1 is pressurized during the next pumping period,
Pumped. That is, a pumping delay represented by the pumping delay time Tdelay2 occurs from the suction command at the point (b) to the point (c) at which the pumping ends, during which four fuel injections are performed. On the other hand, at the time point (a), the other plunger # 2 contains fuel that has already been sucked in by the previous suction command and has not been pumped, and is pumped within the pumping delay time Tdelay2. In the conventional PID (proportional-integral-derivative) control, controllability deteriorates because fuel pumping and injection during the pumping delay time are not expected, and when the proportional gain is reduced, for example, during rapid acceleration, the tracking performance deteriorates. However, when the proportional gain is increased, the amount of overshoot increases.

Therefore, in the present invention, the actual fuel pressure at the time of pumping is predicted by using the pumping amount, the injection amount, and the leak amount of the fuel within the pumping delay time, and the suction command amount is calculated based on this. FIG. 6 shows a control logic of the ECU 3 in the present embodiment. The ECU 3 is configured to control the amount of fuel (not yet pumped) to the common rail 1 by suction from the suction metering valve 8 into the fuel supply pump 4. Pumping amount), and the pumping amount / fuel pressure converting means multiplies the calculated pumping amount by the bulk modulus and divides by the volume of the common rail 1 to reduce the pressure increment. calculate.
The sum of the pressure increment and the current fuel pressure of the common rail 1 is used to derive the fuel pressure after the pumping delay time, and the suction amount calculating means calculates the difference between the fuel pressure after the pumping delay time and the target fuel pressure. Calculate the inhalation volume. Based on this, a suction command signal is output to the suction metering valve 8 by suction command output means (not shown). As a result, the amount of overshoot due to the pumping delay can be reduced, and the proportional gain can be set close to 1, so that the followability is also improved.

The ECU 3 further calculates an injection amount calculating means for calculating an injection amount to be injected within a time (a pumping delay time) until the unpressurized amount is pressure-fed to the common rail 1, a fuel supply pump 4 and a fuel injection valve. If the leak amount calculating means for calculating the leak amount from the fuel cell 2 is provided, the fuel pressure of the common rail 1 after the pumping delay time can be detected more accurately. In this case, the amount obtained by adding the injection amount and the leak amount is subtracted from the unpressurized feed amount, a pressure increase is calculated by the pumped amount / fuel pressure conversion means, and the sum of the pressure increase and the actual fuel pressure is calculated. The fuel pressure after the pumping delay time. Thereby, controllability is further improved.

FIG. 7 is a flowchart showing an example of the suction amount control based on FIG. In addition to the actual fuel pressure of the common rail 1 detected by the fuel pressure sensor S, the ECU 3
Various information, such as the engine speed and the accelerator opening, is input from various sensors (not shown) as needed.
In step 101, first, the actual fuel pressure Pcr of the common rail 1 detected by the fuel pressure sensor S is detected,
In step 102, the unpressurized feed amount Q1 is calculated. Not pumped Q
As shown in FIG. 8, reference numeral 1 denotes the amount of fuel that has been sucked but not yet pumped, and is represented by the following equation. Q1 = Amount of fuel that has been sucked but not yet pumped ≒ Pumped amount Qout (I-2) based on the previous suction command amount Qin (I-2) ≒ Qin (I-2) In FIG. Command amount Q
in (I-2), the suction period based on the suction valve opening Qopen (I-2), and the suction period based on the suction valve opening Qopen (I) determined based on the current suction command amount Qin (I). Refers to the amount of fuel inhaled. However, is small, and the calculation is performed considering only for simplicity. In addition, the pumping amount Qout (I-
2) is difficult to actually measure, and the suction command amount Qin (I
-2), which can be used instead.

In step 103, the fuel injection amount Qinj1 from the present to the time after Tdelay1 time is calculated. From FIG. 5, Qinj1 is represented by the sum of the injection amount command value Q (I) and the injection amount command value Q (I + 1), and the injection amount command value Q (I + 1) is calculated at the time (b). Therefore, the current injection amount command value Q (I) may be used instead. In step 104, a fuel leak amount Qleak1 from the present time to Tdelay1 hour later is calculated. Tdelay1
Is the pumping delay time until the end of the pumping of the unpumped amount Q1,
leak1 may be substituted with the current leak amount. The current leak amount is determined by the injection amount command value Q, the injection period, the actual fuel pressure Pcr,
Accurate calculation can be performed using a control map or function using the engine speed as a parameter.

In step 105, the fuel pressure Ppre of the common rail 1 after the unpressurized feed amount Q1 has been fed is calculated. Ppre is calculated based on the following equation (1) using the values measured or calculated in steps 101 to 104. Ppre = Pcr + (Q1-Qinj1-Qleak1) * (Kα / V) (1) where Kα is the bulk modulus of the fuel in the common rail 1,
V is the internal volume of the common rail, which is used to convert the amount of fuel into pressure. Thus, the fuel pressure Ppre to which the pressure increment one hour after Tdelay is added is known. Step 106
Then, the differential pressure ΔP between the fuel pressure Ppre after the unpressurized feed amount Q1 has been fed and the current target fuel pressure Ptarget is calculated.
The target fuel pressure Ptarget is calculated from an engine speed, an accelerator opening, an injection amount, and the like, based on a control map (not shown). In step 107, the Δ calculated in step 106
Using P, the feedback pressure amount PFB is calculated by known PID control. This calculation formula is shown in the following formula (2). PFB = Kp ΔP + Ki ∫ΔP + Kdd / dtΔP (2)

In step 108, the feedback fuel amount QFB is calculated by multiplying the PFB calculated in step 107 by the value obtained by dividing the bulk modulus Kα by the common rail inner volume V.
Is calculated. In step 109, the fuel injection amount Qinj2 from one hour after Tdelay to two hours after Tdelay is calculated. Q
inj2 is the injection amount command value Q (I + 2) and the injection amount command value Q shown in FIG.
It is expressed by the sum of (I + 3), but it is difficult to predict, so the current injection amount command value Q (I) may be used instead. In step 110, the fuel leak amount Qleak2 from one hour after Tdelay to two hours after Tdelay is calculated. Tdelay2 is a pumping delay time until the pumping of the fuel to be sucked is completed, and Qleak2 may be substituted by the current leak amount. In step 111,
QFB and Qin calculated in these steps 108 to 110
Calculate the pumping command amount Qout (I) from the sum of j2 and Qleak2,
Further, at step 112, a predetermined conversion coefficient Kx is added to Qout.
To calculate the suction command amount Qin (I).

At the time point (b) in FIG. 6, an intake command is issued based on the intake command amount Qin (I) calculated in this way, and when the intake valve opening is set, the amount of fuel corresponding to this is set. Is sucked into the plunger # 1 and pumped after Tdelay 2 hours. At this time, the pumping amount Qout (I) is based on the unpressurized pumping amount Q1 sucked into the plunger # 2 based on the previous suction command amount Qin (I-2) and the fuel injection amount Qinj up to two hours after Tdelay.
Since the amount of increase and decrease of the fuel pressure due to the fuel leak amount Qleak is taken into account, it is possible to prevent a decrease in controllability due to a delay in pumping and improve the followability to the target pressure.

FIG. 9 shows a simulation result of control based on the present embodiment. FIG. 9 shows the target pressure and the fuel injection amount of the common rail 1 with respect to the pump rotation speed.
FIG. 9B shows a case where the suction amount control based on the flowchart of FIG. 7 is performed as shown in FIG. 9A, and FIG. 9C shows a case where the conventional PI (proportional integration) control is performed. The comparison is shown. As is apparent from the figure, in the conventional PI control, the responsiveness to the target fuel pressure is poor, and the difference in the pressure difference from the actual fuel pressure is large. However, in the control of the present embodiment, the responsiveness is good, The characteristics of the period are also excellent.

FIG. 10 shows a control logic according to a second embodiment of the present invention. In addition to the control logic of FIG. 6, an injection command timing delay means and a target fuel pressure delay means are provided. In the first embodiment, in order to calculate the injection amount within the pumping delay time Tdelay2, it is necessary to predict the injection amount command value until after the pumping delay time Tdelay2 or substitute the current injection amount command value. However, as shown in FIG. 11, the injection amount command value Q (I) calculated at the time point (a) is delayed at the time point (d) delayed by a time corresponding to the pumping delay time Tdelay2. By delaying the injection command by each injection amount command value, the injection amount command value within the pumping delay time Tdelay2 becomes known. Therefore, it is possible to reduce an error caused by a difference between the injection amount command value at the time of inhalation and the actual injection amount.

In the first embodiment, the suction command amount Qin (I) is calculated based on the pressure difference ΔP between the fuel pressure Ppre after the pumping delay time Tdelay2 and the current target fuel pressure Ptarget. Since the injection amount command value within the pumping delay time Tdelay2 is known, it is relatively easy to predict the target fuel pressure Ptarget in consideration of the injection amount command value within the pumping delay time Tdelay2. Therefore, the target fuel pressure Ptarget calculated in this way is delayed by the pumping delay time Tdelay2 by the target fuel pressure delay means to obtain a target fuel pressure Ptarget after the pumping delay time Tdelay2. The suction amount calculating means calculates the suction command amount Qin (I) from the target fuel pressure Ptarget after the pumping delay time and the fuel pressure Ppre after the pumping delay time. Therefore, since the target fuel pressure after the pumping delay time is known, it is possible to reduce an error due to a change in the target fuel pressure value that may occur within the pumping delay time Tdelay2, and to improve the followability to the target fuel pressure. it can.

FIG. 12 is a flowchart of the control of the ECU 3 in the present embodiment. The difference from the flowchart of the first embodiment is that step 203 and step 20 are different.
9, in step 103 of FIG. 7, the fuel injection amount Qinj1 from the current time to one hour after Tdelay = injection amount command value Q (I) + injection amount command value Q (I + 1) is set. Injection amount Qinj1 = injection amount command value Q (I-3) + injection amount command value Q (I-2). In step 109 of FIG.
delay Fuel injection quantity Q from 1 hour to Tdelay 2 hours
inj2 = injection amount command value Q (I + 2) + injection amount command value Q (I + 3). In step 209, fuel injection amount Qinj2 = injection amount command value Q (I-1) + injection amount command The value may be Q (I).
Also, the target fuel pressure Ptarget in step 206
Uses the target fuel pressure Ptarget after Tdelay2 hours delayed by the target fuel pressure delay means.

FIGS. 13 to 15 show a third embodiment of the present invention. In the present embodiment, as shown in FIG.
Shows a control in the case where there is a response delay T2 from the output of the suction command signal to the suction metering valve 8 to the actuation of the suction valve drive driver until the suction valve opening reaches the set value. This is effective when the response delay T2 of the suction metering valve 8 cannot be ignored with respect to the suction valve command cycle T1. Thus, when there is a response delay T2 of the suction metering valve 8, Qin (I)
Since the suction valve opening Qopen (I) corresponding to the above is achieved with a delay of T2 time from the suction command, if the unpressurized feed amount Q1 is simply taken as the previous suction command amount Qin (I-2), an error will occur and stable Worse.

In the present embodiment, the unpressurized feed amount Q1 is calculated in consideration of the response delay T2 of the suction valve. As shown in FIG. 14, in consideration of the response delay T2 of the suction valve, the unpressurized feed amount Q1 in the present embodiment is different from the previous suction command amount Qin.
The amount of fuel sucked during the suction period ΔT1 based on the suction valve opening Qopen (I-2) determined by (I-2) and the suction valve opening determined by the previous two-time suction command amount Qin (I-4) Qopen (I
-4) is the sum of the amounts of fuel sucked during the suction period ΔT2. Therefore, paying attention to the ratios of the inhalation periods ΔT1 and ΔT2, it is calculated from the following equation using T1 and T2. Q1 = inhaled but not pumped fuel amount = amount inhaled during ΔT2 period + amount inhaled during ΔT1 period ≒ Qin (I-4) ΔT2 / (ΔT1 + ΔT2) + Qin (I-2) ΔT1 / (ΔT1 + ΔT2) here Since ΔT1: ΔT2 ≒ T2: (T1-T2), Q1 ≒ Qin (I-4) T2 / T1 + Qin (I-2) (T1-T2
2) / T1

FIG. 15 is a flowchart showing a method of calculating the unpressurized feed amount Q1. In step 301, the response delay time T2 of the suction valve is calculated, and then in step 302, the command cycle T1 of the suction valve is calculated. At 303, the unpressurized feed amount is calculated based on the above-described formula for calculating Q1. By doing so, the unpressurized feed amount Q1 can be accurately calculated, and the error is reduced, so that the control stability is improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a common rail fuel injection device showing a first embodiment of the present invention.

FIG. 2 is an overall sectional view of a fuel supply pump.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view showing a fuel flow path of a fuel supply pump.

FIG. 5 is a diagram showing a time chart of suction amount control in the first embodiment.

FIG. 6 is a diagram illustrating control logic according to the first embodiment.

FIG. 7 is a diagram showing a time chart for explaining a method of calculating an unpressurized feed amount in the first embodiment.

FIG. 8 is a diagram showing a flowchart of control in the first embodiment.

9A shows calculation conditions for simulating control based on the first embodiment, FIG. 9B shows a simulation result by the control of the present invention, and FIG. 9C shows a simulation result by conventional control; FIG.

FIG. 10 is a diagram illustrating control logic according to the second embodiment.

FIG. 11 is a diagram showing a time chart of suction amount control in the second embodiment.

FIG. 12 is a diagram illustrating a flowchart of control according to the second embodiment.

FIG. 13 is a diagram showing a time chart of suction amount control in the third embodiment.

FIG. 14 is a diagram showing a time chart for explaining a method of calculating an unpressurized feed amount according to the third embodiment.

FIG. 15 is a diagram illustrating a flowchart of control according to the third embodiment.

[Explanation of symbols]

 Reference Signs List 1 common rail (accumulation chamber) 2 fuel injection valve (injection valve) 3 ECU (control unit) 31 EDU (injection valve driving means) 4 fuel supply pump 52, 62 pressurization chamber 8 suction metering valve S fuel pressure sensor (pressure detection) Part)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 59/20 F02M 59/20 DF Term (Reference) 3G066 AA07 AB02 AC09 AD02 BA19 BA51 CA01S CA04U CA08 CA09 CA34 CA35 CC01 CD02 CE02 CE22 DA01 DB15 DC18 3G084 AA01 BA13 BA14 DA08 DA25 EA04 EA08 EA11 EB08 EB11 EC03 FA00 FA10 FA13 FA33 3G301 HA02 JA07 JA12 LB13 MA11 NA08 NC02 ND01 NE22 PB03Z PB08A PB08Z PE01Z PF03Z

Claims (8)

[Claims] 1. An accumulator for accumulating high-pressure fuel, an injection valve for injecting the high-pressure fuel in the accumulator into a cylinder of an internal combustion engine,
A fuel supply pump for pressurizing the fuel sucked into the pressurized chamber via the suction metering valve and forcing the fuel into the accumulator, a pressure detector for detecting the fuel pressure in the accumulator, and a pressure detected by the pressure detector. A fuel injection device having a control unit for controlling the fuel pressure in the accumulator by controlling the amount of fuel sucked into the pressurization chamber based on the actual fuel pressure. An unpressurized feed amount calculating means for calculating an amount of fuel sucked into the pressurized chamber by the command and in a non-pressurized state to the accumulator, based on an increment of the fuel pressure predicted from the calculated unpressurized amount; It has a suction amount calculating means for calculating a suction amount according to the current suction command, and a suction command output means for outputting a suction command signal to the suction metering valve according to the calculated suction amount. Fuel injection device. 2. An injection amount calculation means for calculating a fuel injection amount injected into a cylinder of the internal combustion engine until the pumping of the unpressurized fuel is completed, the control unit comprising: 2. The fuel injection device according to claim 1, wherein the suction amount calculating means calculates the suction amount based on an amount of increase in fuel pressure predicted from the calculated injection amount and the unpressurized feed amount. 3. The control unit has a leak amount calculating unit that calculates an amount of fuel leaking until the pumping of the unpressurized fuel is completed, and the suction amount calculating unit includes: The fuel injection device according to claim 2, wherein the suction amount is calculated based on a calculated leak amount, an increment of the fuel pressure predicted from the injection amount, and the unpressurized delivery amount. 4. The suction amount calculating means adds the increment of the fuel pressure to the actual fuel pressure to obtain a predicted value of the fuel pressure at the end of the non-pumped fuel pressure feeding, and The fuel injection device according to any one of claims 1 to 3, wherein the suction amount is calculated from a pressure difference between the value and a target value of the fuel pressure. 5. The injector according to claim 1, wherein the control unit drives the fuel injection valve to inject fuel into the cylinder of the internal combustion engine with a predetermined injection amount command value. 5. An injection command timing delay means for delaying an injection command based on the injection amount command value for a time corresponding to a delay time until the unpressurized fuel is fed under pressure. Fuel injector. 6. The uncompressed feed amount calculating means determines a response delay time from the suction command by the suction command output means to the operation of the suction metering valve, based on the suction amount in the last two suction commands. The fuel injection device according to any one of claims 1 to 5, wherein in a time period after the response delay time, the amount of the fuel in the unpressurized state is calculated based on the suction amount in the previous suction command. 7. The fuel injection device according to claim 1, wherein the number of times of pumping per revolution of the fuel supply pump is different from the number of times of injection into a cylinder of the internal combustion engine. 8. The fuel injection device according to claim 1, wherein the internal combustion engine is a diesel engine.