Fuel injection device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a common rail fuel injection device for an internal combustion engine, and more particularly to control of a common rail pressure in a fuel injection device using a suction metering type fuel supply pump.

【0002】

[Conventional technology]

In a common rail fuel injection system known as a fuel injection system for diesel engines, high-pressure fuel is accumulated in a pressure accumulator chamber (common rail) common to each cylinder, and fuel is supplied to each cylinder at a predetermined timing from an injection valve communicating with the common rail. It is designed to be injected. High-pressure fuel is pumped to the common rail from a fuel supply pump with a variable discharge amount, and by controlling this pumping amount, the fuel pressure in the common rail is feedback-controlled. Conventionally, as such a fuel supply pump, a pressurizing chamber for pressurizing fuel by reciprocating movement of a plunger and a pump equipped with a solenoid valve for opening and closing a flow path to the pressurizing chamber have been used, and the pumping amount is adjusted at the time of discharge. So-called pre-stroke control is performed. 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, resulting in excess fuel. The pumping amount is controlled by controlling the closing timing of the solenoid valve.

【0003】

However, in the fuel supply pump having the above configuration for adjusting the amount 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, and the solenoid valve tends to be large and costly. Therefore, in recent years, attention has been paid to a suction metering type fuel supply pump that determines the pumping amount at the time of suction. This pump is provided with a suction metering valve that controls the amount of fuel sucked into the pressurizing chamber, and a check valve is arranged in the flow path from the suction metering valve to the pressurizing chamber. When a required amount of fuel is supplied to the pressurizing chamber in advance by the electromagnetic valve serving as a valve, the check valve closes the flow path to the pressure chamber from the start of pressurization of 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 it is possible to reduce the size and cost.

【0004】

[Problems to be Solved by the Invention]

However, the suction metering type fuel supply pump has a problem that it takes time for the sucked fuel to be pumped, which causes a delay amount and lowers controllability. For example, in the conventional control method, the feedback amount is calculated from the difference pressure between the actual fuel pressure of the common rail and the target pressure, but if there is unpressurized fuel in the pressurizing chamber when calculating the suction amount, this unpressurized fuel is calculated. When the fuel is pumped, it becomes excessively pumped, the common rail pressure rises above the target, and the amount of feedback required for the target pressure changes. A decrease in fuel pressure controllability affects combustion and deteriorates emissions, so improving controllability has become a major issue.

【0005】

On the other hand, there is a demand that the same fuel supply pump can be applied to various engines having different injection times and pumping times, and cost reduction can be achieved by standardizing parts. In particular, from the viewpoint of the endurance rotation speed of the pump, there is a great demand for a combination in which the number of injections> the number of pumping times. There is a problem that the controllability is deteriorated due to the pumping delay. In particular, when the target pressure changes abruptly, such as during sudden acceleration, there is a problem that the pumping delay becomes large, the followability to the target pressure decreases, and the overshoot amount increases.

【0006】

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve controllability when feedback-controlling common rail pressure in a suction metering type fuel injection device, and in particular, the number of injections and pressure feeding. It is an object of the present invention to realize a fuel injection device capable of improving the followability to the target pressure and reducing the amount of overshoot even when the number of times is different or the target pressure changes suddenly.

【0007】

[Means for solving problems]

The fuel injection device according to claim 1 is sucked into the pressurizing chamber via a pressure accumulating chamber in which the high-pressure fuel is accumulated, an injection valve for injecting the high-pressure fuel in the accumulating chamber into the cylinder of the internal combustion engine, and a suction metering valve. A fuel supply pump that pressurizes fuel and pumps it to the accumulator chamber, a pressure detection unit that detects the fuel pressure in the accumulator chamber, and an actual fuel pressure detected by the pressure detection unit, and sucks the fuel into the pressurization chamber. It is provided with a control unit that controls the fuel pressure in the accumulator chamber by controlling the amount of fuel to be produced. Further, the control unit is based on the unpressurized feed amount calculating means for calculating the amount of fuel sucked into the pressurizing chamber and unpressurized to the accumulator chamber according to the suction command before the previous time, and the calculated unpressurized feed amount. An intake amount calculation means that calculates the intake amount according to the current intake command based on the predicted increment of the fuel pressure, and an intake command output that outputs an intake command signal to the intake adjustment valve according to the calculated intake amount. Have the means.

【0008】

The control unit calculates the amount of fuel that has already been sucked into the pressurizing chamber and is in the unpressurized state at the time of calculating the suction amount, and the increment amount of the fuel pressure based on the unpressurized amount is the actual fuel. In addition to the pressure, the fuel pressure in the accumulator chamber at the time of pumping is predicted. This predicted pressure is a value that allows for the amount of unpressed feed that is pumped during the delay time from suction to pumping. Therefore, if the pumping amount, that is, the suction amount is calculated from the difference between this and the target fuel pressure. , The influence of pumping delay can be reduced. Therefore, it is possible to improve the followability to the target pressure and improve the controllability of the fuel pressure.

【0009】

In claim 2, the control unit has an injection amount calculating means for calculating the fuel injection amount to be injected into the cylinder of the internal combustion engine until the pumping of the fuel in the unpressurized state is completed. The suction amount calculating means calculates the suction amount based on the calculated injection amount and the increment amount of the fuel pressure predicted from the unpressurized feed amount.

【0010】

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

【0011】

In claim 3, the control unit has a leak amount calculating means for calculating the amount of fuel leaking until the pumping of the fuel in the unpumped state is completed, and the suction amount calculating means is The intake amount is calculated based on the calculated leak amount, the injection amount, and the increment amount of the fuel pressure predicted from the unpressurized amount.

【0012】

The fuel pressure in the accumulator chamber also fluctuates due to fuel leaks from each part of the fuel injection device. Therefore, the control unit calculates the amount of fuel leaking from each part by the end of pumping of the unpressurized amount, and increases the fuel pressure by subtracting the leak amount and the injection amount from the unpressurized amount. It is a quantity. Thereby, the controllability of the fuel pressure can be further improved.

【0013】

In claim 4, the suction amount calculating means adds the increment amount of the fuel pressure in claims 1 to 3 to the actual fuel pressure, and the fuel pressure at the end of pumping of the fuel in the unpumped state. The suction amount is calculated from the difference pressure between the predicted value and the target value of the fuel pressure.

【0014】

Specifically, the value obtained by adding the increment amount of the fuel pressure calculated in each claim to the actual fuel pressure is used as the 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 differential pressure with respect to the target pressure can be known, and the intake amount can be calculated based on this.

【0015】

In claim 5, the control unit refers to the injection valve driving means for driving the fuel injection valve and the injection valve driving means for injecting fuel into the cylinder of the internal combustion engine at a predetermined injection amount command value. It has 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 fuel in the unpumped state is pumped.

【0016】

When a drive signal is output from the control unit to the injection valve driving means, the injection valve injects fuel into 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 amount command value, the injection amount calculated by the injection amount calculation means according to claim 2 is not the predicted value but the actual injection amount. Since it can be calculated by the injection amount, the fuel pressure after the delay time can be detected accurately.

【0017】

In claim 6, the unpressured feed amount calculating means is based on the suction amount in the previous suction command in the response delay time from the suction command by the suction command output means to the operation of the suction metering valve. In the time after the response delay time, the amount of fuel in the unpumped state is calculated based on the intake amount in the previous intake command.

【0018】

If there is a response delay before the suction metering valve operates after the suction command signal is output by the suction command output means, the suction amount within the response delay time is based on the suction amount in the previous suction command. It becomes. Therefore, in the calculation of the unpressurized feed amount, the unpressurized feed amount can be detected accurately by calculating each inhalation amount separately within the response delay time and after that.

【0019】

In claim 7, it is assumed that the number of times of pumping per rotation 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 is highly effective when applied to a system in which the number of pumping times and the number of injections are different, in which the influence of the pumping delay becomes significant.

【0020】

In 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】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described. FIG. 1 is an overall configuration diagram of a common rail fuel injection device for a diesel engine. A common rail 1 as an accumulator chamber in which high-pressure fuel corresponding to the fuel injection pressure is accumulated and a diesel engine connected to the common rail 1 (not shown). ) Has a plurality of fuel injection valves 2 for injecting fuel into each cylinder. Here, only the fuel injection valve 2 corresponding to one of the 4-cylinder engines is shown, and the illustration of the other cylinders is omitted. The ECU 3, which is a control unit, determines the optimum injection timing and injection amount (injection period) according to the engine state, and drives each fuel injection valve 2 via the EDU 31 which is an injection valve driving means.

【0022】

The high-pressure fuel accumulated in the common rail 1 is supplied from the fuel supply pump 4 via the high-pressure flow path 11. The fuel supply pump 4 pressurizes the low-pressure fuel sucked from the fuel tank T through the filter F to a high pressure and pumps it to the high-pressure flow path 11. Based on the signal from the fuel pressure sensor S provided on the common rail 1, the ECU 3 determines the discharge amount to 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 pumping amount of the fuel supply pump 4 will be described later.

【0023】

The common rail 1 has a pressure reducing valve 14 for opening and closing the flow path 13 to the low pressure flow path 12 communicating with the fuel tank T, and for example, the common rail pressure can be quickly reduced during deceleration or the like. Further, a pressure limiter 17 is arranged in the middle of the high pressure flow path 11 to function 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 are also returned to the fuel tank T from the flow paths 15 and 16 via the low pressure flow path 12, respectively.

【0024】

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 the upper and lower surfaces of the pump housing 41, respectively, and the plungers 51 and 61 are slidably supported in the cylinder heads 5 and 6, respectively. Above the plunger 51 and below the plunger 61, fuel pressurizing chambers 52 and 62 formed by the end faces of the plungers 51 and 61 and the inner wall surfaces of the cylinder heads 5 and 6 are provided, and check valves 53 and 63 are provided. The low-pressure fuel flows in through the above.

【0025】

As shown in FIG. 2, a drive shaft 42 that is rotationally driven in synchronization with half the rotation of the engine is inserted and arranged in the pump housing 41, and is rotatably supported via the journal 43. A cam 44 is integrally formed on the outer periphery of the middle portion of the drive shaft 42, and the plungers 51 and 61 are arranged at symmetrical positions above and below the cam 44.

【0026】

As shown in FIG. 3, the cam 44 having a circular cross section is provided eccentrically with respect to the drive shaft 42, and a shoe 45 having a quadrangular outer shape is slidably held on the outer periphery thereof via a bush 46. Plate members 55 and 65 integrated with the plungers 51 and 61 are pressed against the upper and lower end surfaces of the shoe 45 by the urging force of the springs 56 and 66. Then, 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 reciprocate on the upper and lower end surfaces of the shoe 45. Along with this, the plungers 51 and 61 move up and down to pressurize the fuel in the pressurizing chambers 52 and 62.

【0027】

FIG. 4 is a schematic diagram showing a fuel intake and pumping route, and here, for convenience, only the route 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, and the feed pump 71 pressurizes the fuel sucked from the fuel introduction path 72 communicating with the fuel tank T (see FIG. 1) to a predetermined low pressure to fuel the fuel. It is sent from the flow path 73 to the fuel reservoir 74. The feed pump 71 is provided with a pressure regulating valve 75 to prevent the discharge pressure from exceeding a predetermined pressure.

【0028】

The fuel in the fuel reservoir 74 is sucked into the pressurizing chamber via the suction metering valve 8 and 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 the valve body 82 slidably held in the housing 81 and the valve body 82. It has a coil 83, and by controlling the amount of electricity supplied to the coil 83 by the ECU 3, the lift amount of the valve body 82, that is, the opening area of the flow path communicating with the fuel flow path 76 is adjusted into the pressurizing chamber 52. It is possible to control the amount of fuel inhaled. The valve body 82 is closed by the spring force of the spring 84 when the coil 83 is not energized, and opens against the spring force when the coil 83 is energized.

【0029】

The check valve 53 is arranged between the fuel flow path 76 and the pressurizing chamber 52. Under normal conditions, the tapered valve body 53a of the check valve 53 is urged upward by the spring 53b, seated on the seat surface 53c, and closed. When low-pressure fuel flows in from the suction metering valve 8 through the fuel flow path 76 and the flow path 53d, the valve body 53a is opened by the pressure of the fuel, and the fuel is sucked into the pressurizing chamber 52. When pressurization is started, the valve body 53a closes at the pressure of the fuel and holds it until the fuel is pumped.

【0030】

The pressurized fuel is discharged from the discharge valve 77 via the pressure feed passage 57. The suction metering valve 8 is also communicated to the pressurizing chamber 62 side in FIG. 2 by a fuel flow path (not shown), and fuel is supplied to the pressurizing chamber 62 via the check valve 63. Similarly, the fuel pressurized in the pressurizing chamber 62 is discharged from the discharge valve 78 through the pressure feeding passage 67. The discharge valves 77 and 78 function as check valves and have ball valves 77a and 78a to prevent backflow of fuel from the discharge holes 77b and 78b in the pressure feed passages 57 and 67. The high-pressure fuels discharged from the discharge holes 77b and 78b merge in the middle and are supplied to the common rail 1 from the high-pressure flow path 11 (see FIG. 1).

【0031】

Next, the operation of the fuel supply pump 4 having the above configuration will be described. In FIG. 3, when the cam 44 rotates with the rotation of the drive shaft 42, the shoe 45 revolves accordingly. At this time, the plate members 55 and 65 of the plungers 51 and 61 slide back and forth with respect to the upper and lower end surfaces of the shoe 45, so that the plungers 51 and 61 move up and down in the cylinder heads 5 and 6. Plungers 51 and 61 are alternately lifted as the shoe 45 revolves, with the plunger 51 at top dead center and the plunger 61 at bottom dead center as shown. When the plunger 51 at the top dead center is lowered, the pressure in the pressurizing chamber 52 is lowered, 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 reaches bottom dead center (the state of the plunger 61 in the figure), when it starts to rise again, the check valve 53 closes, the fuel pressure rises, the discharge valve 77 opens, and the common rail High pressure fuel is pumped to 1.

【0032】

As described above, the fuel supply pump 4 is configured so that the suction and pumping strokes are performed for two cycles per rotation of the drive shaft 42. The pumping amount is controlled by the amount of fuel sucked into the pressurizing chambers 52 and 62, and the suction amount can be controlled by controlling the valve opening degree of the suction metering valve 8. This method has the advantage that the suction metering valve 8 can be made smaller and lighter, but there is a problem that the controllability is lowered in the conventional PID (proportional integral differential) control because the pumping delay occurs. This will be described using the time chart shown in FIG. Here, the case where four injections are performed per one rotation of the pump (4 injections, 2 pumps) is taken as an example. The figure shows the engine crank angle signal, injection amount calculation timing, injection period of each cylinder # 1 to # 4, suction amount calculation timing, opening of intake metering valve 8, and plungers 51 and 61 of fuel supply pump 4 ( In the figure, the lift amount (shown as # 1 and # 2) and the actual fuel pressure of the common rail 1 are shown in comparison.

【0033】

First, the pumping delay in the suction metering method will be described. In FIG. 5, the inhalation amount is calculated at the timing when the pumping of the plungers # 1 and # 2 is completed. For example, in the figure, when the actual fuel pressure is detected by the fuel pressure sensor S at the time when plunger # 1 is at top dead center (a), the feedback amount is calculated from the pressure difference from the target fuel pressure at the time (b). Inhalation amount Qin (I) To command. As a result, the fuel sucked according to the opening degree of the suction metering valve 8 during the suction period of the plunger # 1 is pressurized and pumped during the next pumping period. That is, a pumping delay represented by the pumping delay time Tdelay2 occurs from the suction command at the time (b) to the time (c) when the pumping ends, and four fuel injections are performed during this period. On the other hand, at the time (a), there is fuel in the other plunger # 2 that has already been sucked and has not been pumped by the previous suction command, and is pumped into the pumping delay time Tdelay2. In the conventional PID (proportional integral differential) control, the controllability deteriorates because the pumping and injection of fuel during this pumping delay time are not expected, and the followability deteriorates when the proportional gain is made small at the time of sudden acceleration. However, there is a problem that the amount of overshoot increases when the proportional gain is increased.

【0034】

Therefore, in the present invention, the actual fuel pressure at the time of pumping is predicted by using the fuel pumping amount within the pumping delay time, the injection amount, and the leak amount, and the suction command amount is calculated based on this. FIG. 6 shows the control logic of the ECU 3 in the present embodiment. The ECU 3 is the amount of fuel sucked into the fuel supply pump 4 from the suction metering valve 8 and not pumped to the common rail 1 (not yet). It has an unpumped amount calculation means for calculating the pumped amount), and the pumped amount / fuel pressure conversion means multiplies the calculated unpressed amount by the volume elastic coefficient and divides by the volume of the common rail 1 to increase the pressure. calculate. By summing this pressure increment and the current fuel pressure of the common rail 1, the fuel pressure after the pumping delay time is derived, and the suction amount calculation means is used to calculate the difference between the fuel pressure after the pumping delay time and the target fuel pressure. Calculate the inhalation amount. Based on this, a suction command signal is output to the suction metering valve 8 by a 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 taken close to 1, so that the followability is also improved.

【0035】

The injection amount calculation means for calculating the injection amount injected into the ECU 3 within the time until the unpumped amount is pumped to the common rail 1 (pumping delay time), and the fuel supply pump 4 and the fuel injection valve 2 If a leak amount calculation means for calculating the leak amount is provided, the fuel pressure of the common rail 1 after the pumping delay time can be detected more accurately. In this case, the sum of the injection amount and the leak amount is subtracted from the unpressured amount, the pressure increment is calculated by the pressure feed amount / fuel pressure conversion means, and the sum of this pressure increment and the actual fuel pressure is taken. It is the fuel pressure after the pumping delay time. This further improves controllability.

【0036】

FIG. 7 is a flowchart showing an example of inhalation amount control based on FIG. In addition to the actual fuel pressure of the common rail 1 detected by the fuel pressure sensor S, various information such as the engine speed and the accelerator opening are input to the ECU 3 from various sensors (not shown) at any time. In step 101, first, the actual fuel pressure Pcr of the common rail 1 detected by the fuel pressure sensor S is detected, and in step 102, the unpressurized feed amount Q1 is calculated. As shown in FIG. 8, the unpumped amount Q1 is the amount of fuel that has been inhaled but has not been pumped, and is represented by the following formula. Q1 = Amount of fuel that has been inhaled but has not been pumped Pumping amount Qout (I-2) by the previous inhalation command amount Qin (I-2) Qin (I-2) In FIG. 8, the unpressured feed amount Q1 is determined by the suction period according to the suction valve opening Qopen (I-2) determined by the previous suction command amount Qin (I-2) and the current suction command amount Qin (I). Refers to the amount of fuel sucked during the suction period according to the specified suction valve opening Qopen (I). However, is a very small amount, and the calculation is performed considering only for simplicity. In addition, it is difficult to actually measure the pumping amount Qout (I-2), and the inhalation command amount Qin (I-2) Since it is almost equal to, this can be used as a substitute.

【0037】

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

【0038】

In step 105, the fuel pressure Ppre of the common rail 1 after the unpressured amount Q1 is pumped 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) Here, Kα is the volume elastic modulus of the fuel in the common rail 1, and V is the volume in the common rail, which is used to convert the amount of fuel into pressure. As a result, the fuel pressure Ppre with the pressure increment after 1 hour of Tdelay is known. In step 106, the differential pressure ΔP between the fuel pressure Ppre and the current target fuel pressure Ptarget after the unpressured amount Q1 is pumped is calculated. The target fuel pressure Ptarget is calculated from the engine speed, accelerator opening, injection amount, etc. based on a control map (not shown). In step 107, the feedback pressure amount PFB is calculated by the known PID control using the ΔP calculated in step 106. This calculation formula is shown in the following formula (2). PFB = Kp ΔP + Ki ΔP + Kd d / dt ΔP (2) [0039]

In step 108, the feedback fuel amount QFB is calculated by multiplying the PFB calculated in step 107 by the volume elastic modulus Kα divided by the volume V in the common rail. In step 109, the fuel injection amount Qinj2 from 1 hour after Tdelay to 2 hours after Tdelay is calculated. Qinj2 is represented by the sum of the injection amount command value Q (I + 2) and the injection amount command value Q (I + 3) in Fig. 5, but since it is difficult to predict, the current injection amount command value Q (I) May be substituted. In step 110, the fuel leak amount Qleak2 from 1 hour after Tdelay to 2 hours after Tdelay is calculated. Tdelay2 is the pumping delay time until the end of pumping of the fuel to be sucked, and Qleak2 may be replaced by the current leak amount. In step 111, the pumping command amount Qout (I) is calculated from the sum of QFB, Qinj2, and Qleak2 calculated in steps 108 to 110, and further, in step 112, Qout is multiplied by a predetermined conversion coefficient Kx to obtain the inhalation command amount Qin. Calculate (I).

【0040】

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

【0041】

FIG. 9 shows the simulation result of the control based on the present embodiment. The conventional case where the target pressure and fuel injection amount of the common rail 1 with respect to the pump rotation speed are set as shown in FIG. 9 (a) and the intake amount is controlled based on the flowchart of FIG. 7 above is shown in FIG. 9 (b). The case where PI (proportional integration) control is performed is shown in comparison with Fig. 9 (c). As is clear from the figure, in the conventional PI control, the followability to the target fuel pressure is poor and the variation of the differential pressure from the actual fuel pressure is large, but in the control of the present embodiment, the followability is good and the transient The characteristics of the period are also excellent.

【0042】

FIG. 10 shows the control logic according to the second embodiment of the present invention, and in addition to the control logic of FIG. 6, injection command timing delay means and target fuel pressure delay means are provided. In the first embodiment described above, 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 (a) is delayed by the time corresponding to the pumping delay time Tdelay2, so that it is injected at the time (d). By delaying the injection command according to each injection amount command value, the injection amount command value in the pumping delay time Tdelay2 becomes known. Therefore, it is possible to reduce an error due to a difference between the injection amount command value at the time of suction and the actual injection amount.

【0043】

Further, in the first embodiment described above, the suction command amount Qin (I) was calculated based on the differential pressure ΔP between the fuel pressure Ppre after the pumping delay time Tdelay2 and the current target fuel pressure Ptarget, but the pumping delay time Since the injection amount command value in Tdelay2 is known, it becomes relatively easy to predict the target fuel pressure Ptarget in consideration of the injection amount command value in 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 the target fuel pressure Ptarget after the pumping delay time Tdelay2. The suction amount calculation 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 becomes known, the error due to the fluctuation of the target fuel pressure value that may occur within the pumping delay time Tdelay2 can be reduced, and the followability to the target fuel pressure can be improved. it can.

【0044】

FIG. 12 is a flowchart of ECU 3 control in the present embodiment. The difference from the flowchart of the first embodiment is in step 203 and step 209. In step 103 of FIG. 7, the fuel injection amount from the present to 1 hour after Tdelay Qinj1 = injection amount command value Q (I) + injection amount Although the command value Q (I + 1) is set, in step 203, the fuel injection amount Qinj1 = injection amount command value Q (I-3) + injection amount command value Q (I-2). Further, in step 109 of FIG. 7, the fuel injection amount Qinj2 from 1 hour after Tdelay to 2 hours after Tdelay = injection amount command value Q (I + 2) + injection amount command value Q (I + 3) was set. In 209, the fuel injection amount Qinj2 = injection amount command value Q (I-1) + injection amount command value Q (I) may be set. Further, as the target fuel pressure Ptarget in step 206, the target fuel pressure Ptarget 2 hours after the T delay delayed by the target fuel pressure delay means is used.

【0045】

FIGS. 13 to 15 show a third embodiment of the present invention. In the present embodiment, as shown in FIG. 13, the response delay from when the ECU 3 outputs the intake command signal to the intake metering valve 8 until the intake valve drive driver operates and the intake valve opening reaches the set value. It shows the control when there is T2, and is effective when the response delay T2 of the intake metering valve 8 cannot be ignored with respect to the intake valve command cycle T1, for example, at high speed. In this way, when there is a response delay T2 of the suction metering valve 8, the suction valve opening Qopen (I) corresponding to Qin (I) is achieved with a delay of T2 hours from the suction command. If the previous inhalation command amount Qin (I-2) is simply used, an error will occur and the stability will deteriorate.

【0046】

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, considering the response delay T2 of the intake valve, the unpressured feed amount Q1 in the present embodiment is the intake valve opening Qopen (I) determined by the previous intake command amount Qin (I-2). The amount of fuel sucked in the suction period ΔT1 according to -2) and the amount of fuel sucked in the suction period ΔT2 by the suction valve opening Qopen (I-4) determined by the suction command amount Qin (I-4) two times before. Is the sum of. Therefore, paying attention to the ratio of these inhalation periods ΔT1 and ΔT2, it is calculated from the following formula using T1 and T2. Q1 = Amount of fuel that has been inhaled but has not been pumped = Amount inhaled during the ΔT2 period + Amount inhaled during the 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) / T1 [0047]

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

[Simple explanation of drawings]

[Figure 1]

It is an overall block diagram of the common rail type fuel injection apparatus which shows the 1st Embodiment of this invention.

[Figure 2]

It is an overall sectional view of a fuel supply pump.

[Fig. 3]

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

[Fig. 4]

It is sectional drawing which shows the fuel flow path of a fuel supply pump.

[Fig. 5]

It is a figure which shows the time chart of the inhalation amount control in 1st Embodiment.

[Fig. 6]

It is a figure which shows the control logic in 1st Embodiment.

[Fig. 7]

It is a figure which shows the time chart for demonstrating the calculation method of the unpumping amount in 1st Embodiment.

[Fig. 8]

It is a figure which shows the flowchart of the control in 1st Embodiment.

[Fig. 9]

(a) is a calculation condition for simulating the control based on the first embodiment, (b) is a diagram showing the simulation result by the control of the present invention, and (c) is a diagram showing the simulation result by the conventional control.

[Fig. 10]

It is a figure which shows the control logic in the 2nd Embodiment.

[Fig. 11]

It is a figure which shows the time chart of the inhalation amount control in 2nd Embodiment.

[Fig. 12]

It is a figure which shows the flowchart of the control in 2nd Embodiment.

[Fig. 13]

It is a figure which shows the time chart of the inhalation amount control in 3rd Embodiment.

[Fig. 14]

It is a figure which shows the time chart for demonstrating the calculation method of the unpumping amount in 3rd Embodiment.

[Fig. 15]

It is a figure which shows the flowchart of the control in 3rd Embodiment.

[Explanation of symbols]

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 Inhalation metering valve S Fuel pressure sensor (pressure detector)