Control device for fuel injection system

Abstract

Control device (90) for a fuel injection system (10), wherein the fuel injection system comprises: a low-pressure pump (20) configured to compress a fuel in a fuel tank (18) and deliver the fuel; a high-pressure pump (30) configured to increase the pressure of the fuel delivered by the low-pressure pump and to deliver high-pressure fuel; a storage tank (60) configured to store the high-pressure fuel delivered by the high-pressure pump; a fuel injector (62) configured to inject the high-pressure fuel contained in the reservoir; a relief valve (80) provided in a high-pressure section (44, 60) downstream of the high-pressure pump and configured to open when a high-pressure anomaly occurs in the high-pressure section; and a return line (45) which is configured such that it returns the high-pressure fuel in the high-pressure section to a low-pressure section provided downstream of the low-pressure pump by opening the relief valve, wherein the control device is configured to control the high-pressure fuel in the storage tank within a predetermined pressure range, wherein the control device comprises: a fuel pressure determining unit configured to determine whether the pressure in the high-pressure section rises to a predetermined determining pressure that is higher than the pressure range and lower than a valve opening pressure for opening the relief valve; and a restriction unit configured to cause the low-pressure pump to implement a fuel delivery restriction when the fuel pressure determination unit determines that the pressure in the high-pressure section is rising to the determination pressure.

Description

Technical field

[0001] The present disclosure relates to a control device for a fuel injection system. General state of the art

[0002] JP 2015 - 55 230 A discloses a fuel injection system. The fuel injection system comprises a low-pressure pump that compresses and delivers fuel in a fuel reservoir, a high-pressure pump that compresses and delivers the fuel compressed by the low-pressure pump, and a fuel rail, which corresponds to a reservoir that stores the high-pressure fuel delivered by the high-pressure pump. In the fuel injection system, a relief valve opens to reduce the pressure in the reservoir in an abnormal condition in which the pressure of a high-pressure section on the downstream side of the high-pressure pump becomes higher than a predetermined valve opening pressure. Literature on the state of the art, patent literature JP 2015 - 55 230 A JP 2010 - 31 816 A DE 10 2011 005 286 A1 Summary of the invention

[0003] Some fuel injection systems include a return line that returns fuel from a high-pressure section to a low-pressure section downstream of a low-pressure pump by opening a relief valve. In a fuel injection system equipped with such a return line, when the relief valve opens, high-pressure fuel from the high-pressure section flows all at once into the low-pressure section. This creates a fuel pressure spike in the low-pressure section, which can be higher than the pressure assumed in the low-pressure section. In this case, there is a concern that deterioration of the low-pressure section may be promoted.

[0004] In view of the aforementioned difficulties, it is an object of the present disclosure to provide a control device for a fuel injection system which is capable of reducing a fuel peak pressure generated in a low-pressure section due to the opening of a relief valve.

[0005] According to one aspect of the present disclosure, a control device for a fuel injection system is used. The fuel injection system comprises a low-pressure pump, a high-pressure pump, a reservoir or accumulator, a fuel injector, a relief valve, and a return line. The low-pressure pump compresses fuel in a fuel reservoir and delivers the fuel. The high-pressure pump increases the pressure of the fuel delivered by the low-pressure pump and delivers high-pressure fuel. The accumulator stores the high-pressure fuel delivered by the high-pressure pump. The fuel injector injects the high-pressure fuel into the accumulator. The relief valve is provided in a high-pressure section downstream of the high-pressure pump and opens when a high-pressure anomaly occurs in the high-pressure section.The return line returns the high-pressure fuel in the high-pressure section to a low-pressure section located downstream of the low-pressure pump by opening the relief valve. The control device regulates the high-pressure fuel in the accumulator within a predetermined pressure range. The control device comprises a fuel pressure sensing unit and a limiting unit.

[0006] The fuel pressure sensing unit determines whether the pressure in the high-pressure section rises to a predetermined setpoint pressure that is higher than the predetermined pressure range and lower than the valve opening pressure required to open the relief valve. The limiting unit causes the low-pressure pump to implement a fuel delivery limiter when the fuel pressure sensing unit determines that the pressure in the high-pressure section is rising to the setpoint pressure.

[0007] When the high-pressure fuel flows from the high-pressure section to the low-pressure section upon opening of the relief valve, the fuel peak pressure, which changes the pressure in a peak shape, is generated at the low-pressure section. In this case, it is assumed that the fuel peak pressure depends on the fuel supply pressure and the supply rate from the low-pressure pump to the high-pressure pump, and can be defined by the following equation. Fuel peak pressure = Pf + (K⋅ΔVlp + K⋅ΔVrel − K⋅ΔVhp) / Vin − Fpd

[0008] Pf corresponds to the fuel supply pressure to the high-pressure pump, K corresponds to the volume-elastic coefficient, ΔVlp corresponds to the fuel quantity supplied to the high-pressure pump, ΔVrel corresponds to the discharge fuel quantity, which is the amount of fuel returning to the low-pressure side when the discharge valve is open, ΔVhp corresponds to the fuel intake quantity of the high-pressure pump, Vin corresponds to the volume of the low-pressure side, and Fpd corresponds to the damping factor of the built-in pulsation damper. According to the above configuration, the pressure of the high-pressure side is determined to have risen to the predetermined setpoint pressure, which is higher than the pressure range assumed in the accumulator and lower than a predetermined valve opening pressure for opening the discharge valve. In this case, the fuel delivery restriction to the low-pressure pump is implemented.Consequently, the pressure in the low-pressure section is reduced as the likelihood of the relief valve opening increases with rising pressure in the high-pressure section. Thus, even with the relief valve open, this configuration can reduce peak fuel pressure and suppress deterioration in the low-pressure section. Brief description of the illustrations

[0009] The foregoing and further objects, features and advantages of the present invention will become more apparent from the following detailed description, which is carried out with reference to the accompanying figures. The figures show: Fig. 1 a figure showing a fuel supply system; Fig. 2 a time diagram showing a pressure change in a supply line; Fig. 3 a flowchart showing a fuel dispensing restriction; Fig. 4 a time diagram showing the operation of an ECU when a high-pressure anomaly occurs; Fig. 5 a flowchart showing a fuel dispensing restriction according to a second embodiment; and Fig. 6 a time diagram showing the operation of an ECU when a high-pressure anomaly occurs. Embodiments for carrying out the invention (First embodiment)

[0010] First, a configuration of a fuel injection system 100 according to the first embodiment is described with reference to the figures. A in Fig. 1 The fuel injection system 10 shown is mounted on a vehicle and injects fuel into a cylinder of a machine 100 as an internal combustion engine.

[0011] Each cylinder of a cylinder block 110 of the machine 100 houses a piston which is connected to a crankshaft 12 as an output shaft. Furthermore, each cylinder is connected to an intake manifold, through which incoming air flows through an intake port, and to an exhaust manifold, through which exhaust gas is expelled through an exhaust port.

[0012] In the present embodiment, the machine 100 is a cylinder injection type (direct injection type) in which fuel is injected directly into the cylinder, and an injector 62 is provided as a fuel injection valve for each cylinder. A spark plug is attached to each cylinder of the cylinder head of the machine 100, and the air-fuel mixture in the cylinder is ignited by the spark discharge of the spark plug.

[0013] A rotation angle sensor 13 is mounted on the outer circumferential side of the crankshaft 12. Each time the crankshaft 12 rotates by a predetermined crank angle, this sensor outputs a crank angle signal with a pulse shape. The crank angle and the engine speed Ne are determined based on the crank angle signal output by the rotation angle sensor 13.

[0014] In addition to the injector 62, the fuel injection system 10 includes a fuel reservoir 18, a low-pressure pump 20, a high-pressure pump 30 and a supply line 60, which corresponds to a collector or storage tank.

[0015] The low-pressure pump 20 is located inside the fuel tank 18, draws in the fuel from the fuel tank 18, compresses the fuel, and then discharges it. In the present embodiment, the low-pressure pump 20 is a variable-displacement pump in which the fuel delivery pressure Pf (supply pressure) to the high-pressure pump 30 is variable. The low-pressure pump 20 is, in particular, an electric pump that operates by driving an impeller in the pump housing with an electric motor. The low-pressure pump 20 adjusts the delivery by changing the rotational speed of the impeller according to the setpoint delivery pressure F*, which corresponds to the setpoint delivery pressure Pf. The setpoint delivery pressure F* is, for example, variably set in the range of 300 to 500 kPa.

[0016] The outlet of the low-pressure pump 20 is connected to the high-pressure pump 30 via the low-pressure line 22. The high-pressure pump 30 increases the pressure of the fuel supplied by the low-pressure line 22 and delivers the fuel to the high-pressure line 44. The cylinder body 32 of the high-pressure pump 30 defines a low-pressure chamber 40 and a compression chamber 42. The low-pressure chamber 40 is connected to the low-pressure line 22 and stores the fuel supplied via this line. A metering valve 36 is provided in the passage where the low-pressure chamber 40 and the compression chamber 42 are connected. The metering valve 36 controls the amount of fuel supplied from the low-pressure chamber 40 to the compression chamber 42.

[0017] The compression chamber 42 is equipped with a piston 34, which changes the pressure in the compression chamber 42 by a reciprocating motion. The end of the piston 34 opposite the end on the side of the compression chamber 42 is connected to a cam 14. The cam 14 is connected to the crankshaft 12 of the machine 100. When the cam 14 rotates with the rotation of the crankshaft 12, the piston 34 moves back and forth between top dead center and bottom dead center. Furthermore, the greater the engine speed Ne, the more pronounced the reciprocating motion of the piston 34.

[0018] The compression chamber 42 is equipped with a discharge valve 38 for dispensing the fuel compressed in the compression chamber 42. The discharge opening of the discharge valve 38 is connected to the high-pressure line 44, which is connected to the supply line 60. The discharge valve 38 acts as a shut-off valve, allowing fuel flow from the compression chamber 42 to the high-pressure line 44 and opening when the fuel pressure in the compression chamber 42 exceeds a predetermined discharge pressure.

[0019] When the metering valve 36 opens and the piston 34 descends from top dead center to bottom dead center, the fuel in the low-pressure chamber 40 is drawn into the compression chamber 42. When the metering valve 36 opens and the piston 34 rises from bottom dead center to top dead center, the fuel in the compression chamber 42 is returned to the low-pressure chamber 40 via the metering valve 36. The metering valve 36 then closes, and the piston 34 continues to rise, compressing the fuel in the compression chamber 42. When the pressure in the compression chamber 42 becomes equal to or greater than the discharge pressure, the fuel is discharged by the discharge valve 38.

[0020] The supply line 60, which is connected to the high-pressure line 44, stores the fuel delivered by the high-pressure pump 30 at a high pressure. The supply line 60 is connected to the injector 62.

[0021] The high-pressure line 44 is equipped with a pressure relief valve 80. The pressure relief valve 80 opens when the pressure rises to a predetermined valve opening pressure and closes when the pressure in the open state drops to a predetermined valve closing pressure, which is lower than the valve opening pressure. The inlet of the pressure relief valve 80 is connected to the high-pressure line 44, and the outlet of the pressure relief valve 80 is connected to the low-pressure chamber 40 via the return line 45. When the pressure relief valve 80 is open, the fuel in the high-pressure line 44 returns through the pressure relief valve 80 to the low-pressure chamber 40, and the pressure increase in the high-pressure line 44 and the supply line 60 is prevented.The valve opening pressure for opening the relief valve 80 is set so that it is lower than, for example, the pressure resistance before the supply line 60 deteriorates.

[0022] In the present embodiment, the low-pressure chamber 40 and the low-pressure-side line 22 correspond to a low-pressure section to which the fuel returns via the return line 45 when the relief valve 80 is open. The return line 45 can return the fuel to the low-pressure-side line 22. Furthermore, the high-pressure-side line 44 corresponds to a high-pressure section.

[0023] The supply line 60 is equipped with a rail pressure sensor 82, which detects the rail pressure Pr, i.e., the pressure within the supply line 60. The low-pressure side line 22 is equipped with a delivery pressure sensor 83, which detects the delivery pressure Pf, corresponding to the pressure of the fuel supplied to the high-pressure pump 30. Inside the fuel tank 18, a fuel temperature sensor 84 is provided, which detects the fuel temperature Tf.

[0024] The fuel injection system 10 includes an ECU 90. The ECU 90 is a microcomputer comprising a CPU, ROM, RAM, control circuitry, an input / output interface, and the like. The values ​​acquired by sensors 82 to 84 are entered into the ECU 90.

[0025] The ECU 90 adjusts the fuel injection of the low-pressure pump 20 according to the target delivery pressure F*. For example, the ECU 90 performs feedback control for the fuel delivery of the low-pressure pump 20 based on the deviation between the delivery pressure Pf detected by the delivery pressure sensor 83 and the target delivery pressure F*. The ECU 90 can perform open-loop control for the delivery pressure. Furthermore, the ECU 90 performs feedback control for the delivery quantity of the high-pressure pump 30 based on the deviation between the target rail pressure R*, which corresponds to the target rail pressure Pr, and the rail pressure Pr detected by the rail pressure sensor 82. Consequently, the rail pressure Pr is appropriately controlled within a predetermined pressure range.

[0026] Fig. Figure 2 shows the transition of the rail pressure Pr when a high-pressure anomaly occurs on the high-pressure section side of the fuel injection system 10. Fig. 2. Before time t1, the high-pressure pump 30 does not fail. The injection quantity of the high-pressure pump 30 is adjusted so that the fuel pressure of the supply line 60 is controlled by the rail pressure setpoint R*. Immediately before time t2, the high-pressure pump 30 fails. The rail pressure Pr increases, resulting in a full-throttle discharge anomaly, during which the high-pressure pump 30 delivers fuel at the maximum delivery rate. At time t3, the rail pressure Pr reaches the valve opening pressure TH1 of the relief valve 80, and the relief valve 80 opens. With the opening of the relief valve 80, the fuel in the high-pressure line 44 returns through the return line 45 to the low-pressure chamber 40, and the rail pressure Pr decreases after time t3.

[0027] When the high-pressure fuel flows from the high-pressure line 44 through the return line 45 into the low-pressure chamber 40 via the opening of the relief valve 80, a fuel peak pressure is generated on the low-pressure side, which changes the pressure in a peak shape. The fuel peak pressure is considered to depend on the fuel supply pressure and the supply quantity to the high-pressure pump 30 and can be defined by the following equation (1). Fuel peak pressure = Pf + (K⋅ΔVlp + K⋅ΔVrel − K⋅ΔVhp) / Vin − Fpd

[0028] Pf corresponds to the delivery pressure, K corresponds to the volume elastic coefficient, ΔVlp corresponds to the amount of fuel supplied to the high-pressure pump 30, ΔVrel corresponds to the relief fuel quantity, which corresponds to the amount of fuel returning to the side of the low-pressure section when the relief valve 80 is open, ΔVhp corresponds to the fuel intake quantity of the high-pressure pump 30, Vin corresponds to the volume of the low-pressure chamber 40 and the low-pressure side line 22, and Fpd corresponds to the damping amount of the built-in pulsation damper.

[0029] In the preceding equation (1), by limiting the output of the low-pressure pump 20, each term of the delivery pressure Pf and the delivery quantity ΔVlp becomes small, and the peak fuel pressure can be reduced. If the rail pressure Pr is higher than the pressure range controlled by the ECU 90, it is predicted here that the rail pressure Pr will rise to the valve opening pressure TH1 of the relief valve 80 due to a pump anomaly or the like. If the ECU 90 determines that the rail pressure Pr will rise to a predetermined set pressure TH2, which is higher than the assumed pressure range in the supply line 60 and lower than the valve opening pressure TH1, the ECU 90 limits the fuel output of the low-pressure pump 20. In the present embodiment, the ECU 90 corresponds to a fuel pressure set unit.

[0030] In the present embodiment, the ECU 90, acting as a fuel delivery limiter, reduces the setpoint delivery pressure F* in the low-pressure pump 20 compared to the case where the rail pressure Pr does not rise to the target pressure TH2. Since the delivery pressure Pf is reduced, the rise in peak fuel pressure is consequently suppressed. In the present embodiment, the ECU 90 corresponds to a limiting unit.

[0031] The ECU 90 sets the delivery pressure setpoint F* to the higher of the fuel's saturation vapor pressure and the lower limit of the fuel intake pressure at the high-pressure pump 30. The saturation vapor pressure corresponds to the pressure at which bubbles can form in the fuel. The intake pressure corresponds to the delivery pressure Pf at which fuel can be drawn from the low-pressure line 22 into the high-pressure pump 30. Since the fuel's saturation vapor pressure increases with rising fuel temperature Tf, the ECU 90 can calculate the fuel's saturation vapor pressure based on the fuel temperature Tf.

[0032] Once the fuel peak pressure has been generated, it is not necessary to continue the fuel delivery restriction of the low-pressure pump 20. The ECU 90 determines whether the relief valve 80 is open after the fuel delivery restriction is imposed. If the ECU 90 determines that the relief valve 80 is open, the ECU 90 releases or lifts the fuel delivery restriction at the low-pressure pump 20. When the relief valve 80 is open, the rail pressure Pr is reduced. Therefore, in the present embodiment, the ECU 90 lifts the fuel delivery restriction when it is determined that the rail pressure Pr drops to a predetermined release pressure TH3, which is assumed to occur due to the opening of the relief valve 80.

[0033] In the full-discharge state of the high-pressure pump 30, the number of discharges by the high-pressure pump 30 per unit of time increases more sharply as the engine speed Ne increases, thus increasing the discharge quantity from the high-pressure pump 30 per unit of time. Consequently, the rail pressure Pr converges to a high value after the relief valve 80 has been opened. Since the volumetric elasticity modulus of the fuel changes according to the fuel temperature Tf, the rate of decrease of the rail pressure Pr after opening the relief valve 80 and the pressure at the time of convergence also change. In the present embodiment, the ECU 90 calculates the release pressure TH3 based on the engine speed Ne and the fuel temperature Tf. The ECU 90 corresponds to a valve opening determination unit.

[0034] The pressure contributing to the opening of the relief valve 80 corresponds to the pressure in the high-pressure-side line 44. Since the high-pressure-side line 44 has a smaller inner diameter and a smaller volume than the supply line 60, the pressure pulsation is greater than the rail pressure Pr. The higher the machine speed Ne, the greater the pressure pulsation in the high-pressure-side line 44. When the machine speed Ne is low, the maximum value of the pressure pulsation is approximately 1 to 2 MPa greater than the rail pressure Pr. However, when the machine speed Ne is high, the maximum value of the pressure pulsation is approximately 10 to 15 MPa greater than the rail pressure Pr. Therefore, when the machine speed Ne is high, the rail pressure Pr at the time the relief valve 80 opens is approximately 10 to 15 MPa lower than the valve opening pressure TH1 of the relief valve 80.As a result, the differential pressure between the rail pressure Pr and the low-pressure side pressure (corresponding to the delivery pressure) becomes small. Therefore, the amount of fuel returned when the relief valve 80 opens is small, and the peak fuel pressure becomes lower than the value when the engine speed Ne is at a low speed. Provided the peak fuel pressure is not a value that causes deterioration on the low-pressure side, it is not necessary to limit the fuel delivery of the low-pressure pump 20. Therefore, in the present embodiment, the ECU 90 limits the fuel delivery by the low-pressure pump 20 when the rail pressure Pr is higher than the set pressure TH2, in the case where the engine speed Ne is lower than the speed set value TH4, which corresponds to the predetermined speed.

[0035] The following describes the fuel delivery restriction to reduce peak fuel pressure with reference to Fig. 3 described. The in Fig. The processing shown in step 3 is performed repeatedly by the ECU 90 within a predetermined control cycle period.

[0036] In step S10, the current rail pressure Pr, the engine speed Ne and the fuel temperature Tf are obtained.

[0037] Step S11 determines whether the restriction execution flag G is off. The restriction execution flag is set to on if the fuel delivery restriction for low-pressure pump 20 is executed, and to off if the fuel delivery restriction is not executed. If the restriction execution flag G is off, processing continues with step S12.

[0038] In step S12, it is determined whether the current engine speed Ne obtained in step S10 is lower than the speed determination value TH4. If it is determined that the engine speed Ne is equal to or higher than the speed determination value TH4, it is not necessary to reduce the peak fuel pressure. Thus, the processing of Fig. 3 temporarily terminated.

[0039] If it is determined that the machine speed Ne is lower than the speed determination value TH4, processing continues with step S13. In step S13, it is determined whether the rail pressure Pr obtained in step S10 is higher than the determination pressure TH2. If it is determined that the rail pressure Pr is equal to or less than the determination pressure TH2, it is unlikely that the rail pressure Pr will subsequently rise to the valve opening pressure TH1. Therefore, processing of Fig. 3 temporarily terminated.

[0040] If, in step S13, it is determined that the rail pressure Pr is higher than the set pressure TH2, processing continues with step S14. In step S14, the delivery pressure setpoint F* is changed to the higher of the lower limit of the intake pressure limit of the high-pressure pump 30 and the saturation vapor pressure of the fuel. The saturation vapor pressure of the fuel is calculated from the fuel temperature Tf obtained in step S10. Consequently, the fuel delivery of the low-pressure pump 20 is limited.

[0041] In step S15, the restriction execution flag G is switched to On. The in Fig. The processing shown in step 3 will be completed.

[0042] If, in the subsequent control cycle, step S11 determines that the restriction execution flag G is switched to "On", processing continues with step S16. In step S16, the restriction continuation counter CT, which measures the duration of the fuel dispensing restriction, is incremented.

[0043] In step S17, it is determined whether the rail pressure Pr is lower than the predetermined release pressure TH3, which accompanies the opening of the relief valve 80. If the rail pressure Pr is equal to or greater than the release pressure TH3, the fuel peak pressure is not generated, and the process continues with step S18.

[0044] Since the setpoint delivery pressure F* with respect to the low-pressure pump 20 is reduced, the rail pressure Pr does not rise to the valve opening pressure TH1 and the relief valve 80 does not open. In the present embodiment, the fuel delivery restriction is lifted either when it is determined that the relief valve 80 is open after the fuel delivery restriction has been applied, or when the lift-off time TH5 has elapsed, whichever occurs first.

[0045] In step S18, it is determined whether the restriction continuation counter CT exceeds the cancellation time TH5. The cancellation time TH5 is set to a time longer than the assumed time when the relief valve 80 opens and the generation of the fuel peak pressure ends. If the determination in step S18 is negative, the processing of Fig. 3 completed.

[0046] If, in the subsequent control cycle in step S17, it is determined that the relief valve 80 is open, or if the restriction continuation counter CT exceeds the release time TH5 in step S18, processing continues with step S19. In step S19, the delivery pressure setpoint F*, which was changed in step S14, is reset to its original value. Consequently, the fuel delivery restriction for the low-pressure pump 20 is lifted.

[0047] In step S20, the restriction execution flag G is switched to off and the restriction continuation counter CT is initialized to zero. The in Fig. The processing shown in step 3 will be completed.

[0048] The following describes the operation of the ECU 90 during a high-pressure anomaly. Fig. 4(a) shows the transition of the rail pressure Pr, and Fig. 4(b) shows the transition between the setpoint discharge pressure F* and the discharge pressure Pf. Fig. Figure 4(c) shows the transition of the restriction continuation counter CT.

[0049] Before time t11, the high-pressure pump 30 does not fail. The fuel delivery of the high-pressure pump 30 is adjusted so that the rail pressure of the supply line 60 is controlled by the rail pressure setpoint R*. Immediately before time t11, the high-pressure pump 30 fails, and the full-delivery anomaly occurs, in which the high-pressure pump 30 delivers at its maximum delivery rate. The single delivery rate from the high-pressure pump 30 exceeds the single injection rate of the injector 62, and the rail pressure Pr increases with each delivery by the high-pressure pump 30.

[0050] Since the rail pressure Pr becomes higher than the setpoint pressure TH2 at time t12, the delivery pressure setpoint F* of the low-pressure pump 20 is reduced. The fuel delivery of the low-pressure pump 20 is restricted, so that the delivery pressure Pf is controlled by the changed delivery pressure setpoint F*. At time t12, the restriction continuation counter CT begins to increase.

[0051] At time t13, the rail pressure Pr reaches the valve opening pressure TH1, and the relief valve 80 changes from the closed to the open state. With the opening of the relief valve 80, the fuel in the high-pressure line 44 returns through the return line 45 to the low-pressure chamber 40, thus generating a fuel peak pressure at which the delivery pressure Pf changes peak-like. Fig. Figure 4(b) serves as a comparative example: a discharge pressure Pf with an unchanged discharge pressure setpoint F* is represented by a dashed line. If the discharge pressure setpoint F* is not reduced, the discharge pressure Pf changes to a higher value between time t12 and time t13 than if the discharge pressure setpoint F* were changed.

[0052] In the present embodiment, the delivery pressure Pf is reduced during the period from when the rail pressure Pr exceeds the set pressure TH2 until the relief valve 80 opens. Therefore, after the relief valve 80 opens, the peak fuel pressure is reduced compared to the case where the delivery pressure Pf is not reduced.

[0053] At the subsequent time t14, the rail pressure Pr is reduced to the cancellation setpoint pressure TH3 before the restriction continuation counter CT reaches the cancellation time TH5. Consequently, the fuel delivery restriction for the low-pressure pump 20 is lifted, the delivery pressure setpoint F* is restored, and the delivery pressure Pf rises to the delivery pressure setpoint F*.

[0054] According to the first embodiment described above, the following effects can be achieved.

[0055] If the ECU 90 determines that the rail pressure Pr is rising to the setpoint pressure TH2, which is higher than the assumed pressure range in the supply line 60 and lower than the valve opening pressure TH1, the ECU 90 reduces the setpoint delivery pressure F* of the low-pressure pump 20. Consequently, the pressure on the low-pressure side can be reduced if the likelihood of the relief valve 80 opening increases with the pressure increase when the relief valve 80 closes. Even when the relief valve 80 is open, the configuration can cause the peak fuel pressure to be reduced. Therefore, deterioration of the low-pressure side can be suppressed.

[0056] The ECU 90 lifts the fuel delivery restriction when it determines that the relief valve 80 is open. Therefore, a continuation of the fuel delivery restriction, even after peak fuel pressure has been reached, is prevented by the opening of the relief valve 80. Consequently, it is possible to prevent an excessive drop in the low-pressure section pressure, thus preventing a delivery malfunction of the high-pressure pump 30 and a fuel malfunction due to a drop in fuel pressure to the saturation vapor pressure.

[0057] The ECU 90 lifts the fuel delivery restriction at the time it is determined that the relief valve 80 is open after the fuel delivery restriction has been implemented, or at the time the lift-off time TH5 is reached, whichever occurs first. This prevents the delivery pressure Pf from being reduced too much, even if the relief valve 80 is not open.

[0058] If it is determined that the rail pressure Pr has risen to the set pressure TH2, the ECU 90 limits the fuel delivery at the low-pressure pump 20, provided that the engine speed Ne is lower than the speed set value TH4. Consequently, an excessive reduction in the delivery pressure Pf can be prevented if the peak fuel pressure is not likely to increase. (Modification of the first embodiment)

[0059] As a fuel delivery restriction for the low-pressure pump 20, the fuel delivery of the low-pressure pump 20 can be stopped. In this case, the fuel delivery of the low-pressure pump 20 can be stopped instead of the delivery pressure setpoint F* in step S14 of Fig. 3. To reduce. For example, the fuel delivery of the low-pressure pump 20 is stopped by withholding electrical power from the low-pressure pump 20. Furthermore, if the process is successful in step S17 or step S18, it continues with step S19, and the fuel delivery of the low-pressure pump 20 can be restarted. This modification also provides similar effects to the first embodiment.

[0060] Based on the estimated behavior of the rail pressure Pr during the pressure drop time interval, assuming the relief valve 80 is closed, it can be determined whether the relief valve 80 is open. Specifically, in step S17, the ECU 90 can determine that the relief valve 80 is open if the rate of reduction of the rail pressure Pr is higher than the predetermined rate of reduction after the fuel delivery restriction is applied to the low-pressure pump 20.

[0061] If it is determined that the saturation vapor pressure of the fuel is higher than the lower limit of the intake pressure of the fuel in the high-pressure pump 30, the ECU 90 sets in step S14 of Fig. 3. The delivery pressure setpoint F* is adjusted to the fuel saturation. If it is determined that the lower limit of the fuel intake pressure in the high-pressure pump 30 is higher than the saturation vapor pressure of the fuel, the ECU 90 adjusts in step S14 of Fig. 3 sets the delivery pressure setpoint F* to the lower limit of the fuel suction limit pressure in pump 30. (Second embodiment)

[0062] A second embodiment differs from the first embodiment, as described below. The parts with the same reference numerals denote the same parts, and their descriptions are not repeated.

[0063] If the high-pressure pump 30 exhibits a high-pressure anomaly, the rail pressure Pr rises from the set pressure TH2 to the valve opening pressure TH1, and the delivery pressure Pf must be reduced sufficiently until the relief valve 80 opens. Therefore, in the present embodiment, the fuel delivery limitation of the low-pressure pump 20 is achieved by both stopping the fuel delivery by the low-pressure pump 20 and reducing the setpoint delivery pressure F*.

[0064] The following describes the fuel delivery restriction for reducing peak fuel pressure according to the present embodiment with reference to Fig. 5 described. The in Fig. The processing shown in section 5 is performed repeatedly by the ECU 90 within a predetermined control cycle period.

[0065] In step S30, the fuel delivery restriction is determined by whether the first restriction execution flag G11, which indicates that the fuel delivery of the low-pressure pump 20 is stopped, and the second restriction execution flag G12, which indicates that the setpoint delivery pressure F* of the low-pressure pump 20 is reduced, are off. If a negative determination occurs in step S30, the process continues with step S12.

[0066] After an affirmative determination is made in step S12, processing continues with step S31 if step S13 determines that the rail pressure Pr is higher than the target pressure TH2. In S31, the fuel delivery of the low-pressure pump 20 is stopped. The fuel delivery of the low-pressure pump 20 is stopped, for example, by switching the control signal GS, which supplies the low-pressure pump 20 with electrical power, from the on-command to the off-command.

[0067] In step S14, with fuel delivery from the low-pressure pump 20 stopped, the delivery pressure setpoint F* of the low-pressure pump 20 is set to the higher value from the saturation vapor pressure of the fuel and the lower limit of the intake limit pressure of the high-pressure pump 30.

[0068] In step S32, both the first restriction execution flag G11 and the second restriction execution flag G12 are switched to On. The in Fig. The processing shown in step 5 will be completed.

[0069] Since both the first constraint execution flag G11 and the second constraint execution flag G12 are set to "On", step S30 in the subsequent control cycle is determined to be negative, and processing proceeds to step S33. Because the first constraint execution flag G11 is set to "On" in step S33, processing continues with step S16 to increment the constraint continuation counter CT.

[0070] In step S34, it is determined whether the delivery restart condition for restarting the fuel delivery of the low-pressure pump 20 is met. In the present embodiment, the restart condition is defined such that the delivery pressure Pf is equal to or less than the delivery restart pressure TH6, which is obtained by adding a predetermined margin pressure to the delivery pressure setpoint F* set in step S14.

[0071] If it is determined that the submission restart condition is not met, the processing of Fig. 5 temporarily terminated. If, on the other hand, it is determined that the delivery restart condition is met, processing proceeds to step S35. In step S35, fuel delivery is restarted by the low-pressure pump 20. In step S36, the restriction execution flag G11 is switched to Off. The in Fig. The processing shown in step 5 is terminated.

[0072] After the fuel delivery restarts, the low-pressure pump 20 adjusts the fuel delivery according to the setpoint delivery pressure F* set in step S13. Therefore, the fuel delivery of the low-pressure pump 20 is limited even after the fuel delivery restarts.

[0073] Since the second restriction execution flag G12 is switched on, the negative determination is then carried out in step S30, and processing continues with step S33. Since the first restriction execution flag G11 is switched off, the negative determination is carried out in step S33, and processing continues with step S17. If an affirmative determination is made in step S17 or S18, processing continues with step S19 to restore the setpoint delivery pressure F*. In step S37, the second restriction execution flag G12 is switched off, and the restriction continuation counter CT is initialized to zero.

[0074] The operation of the ECU 90 during a high-pressure anomaly according to the second embodiment is described below. Fig. 6(a) shows the transition of the rail pressure Pr, and Fig. 6(b) shows the transition between the setpoint discharge pressure F* and the discharge pressure Pf. Fig. Figure 6(c) shows the transition of the control signal GS of the low-pressure pump 20.

[0075] Before time t21, the high-pressure pump 30 does not fail. The fuel delivery of the high-pressure pump 30 is adjusted so that the rail pressure of the supply line 60 is controlled by the rail pressure setpoint R*. Immediately before time t21, the high-pressure pump 30 malfunctions and the full-delivery anomaly occurs, in which the high-pressure pump 30 delivers at the maximum delivery rate.

[0076] At time t22, when the rail pressure Pr exceeds the setpoint pressure TH2, the control signal GS switches from the on-command to the off-command, and the fuel delivery of the low-pressure pump 20 is stopped. Consequently, the delivery pressure Pf is rapidly reduced in the early phase after the rail pressure Pr rises above the setpoint pressure TH2. Furthermore, the delivery pressure setpoint F* of the low-pressure pump 20 is changed to a low value.

[0077] At time t23, when the delivery pressure Pf becomes equal to or less than the delivery restart pressure TH6, the control signal GS is switched from the off-operation command to the on-operation command, and the fuel delivery of the low-pressure pump 20 is restarted. After time t23, the fuel delivery of the low-pressure pump 20 is adjusted so that the delivery pressure Pf becomes the setpoint delivery pressure F* that was changed at time t22. Therefore, the rate at which the delivery pressure Pf decreases is lower than the rate at which it decreases between times t22 and t23.

[0078] At time t24, the rail pressure Pr reaches the valve opening pressure TH1, and the relief valve 80 changes from the closed to the open state. The opening of the relief valve 80 generates the peak fuel pressure. Fig.Figure 6(b) shows, as a comparative example, a delivery pressure Pf with a dashed line when the fuel delivery of the low-pressure pump 20 is not restricted. In the present embodiment, the delivery pressure Pf decreases rapidly due to the cessation of fuel delivery by the low-pressure pump 20 between the time when the rail pressure Pr becomes higher than the setpoint pressure TH2 and the time when the relief valve 80 is opened. Thus, the subsequent reduction of the setpoint delivery pressure F* causes the delivery pressure Pf to decrease further. Therefore, after the relief valve 80 opens, the peak value of the fuel pressure is reduced compared to the case where the fuel delivery is not restricted.

[0079] At time t25, the rail pressure Pr is reduced to the cancellation pressure TH3, and the fuel delivery restriction at the low-pressure pump 20 is lifted. Therefore, the target delivery pressure F* is restored, and the delivery pressure Pf increases.

[0080] In the embodiment described above, the ECU 90 stops the fuel delivery by the low-pressure pump 20 as the fuel delivery limit and then reduces the delivery pressure Pf compared to the case where it is not determined that the rail pressure Pr has risen to the target pressure TH2. Consequently, if the rail pressure Pr rises to the target pressure TH2, the delivery pressure Pf can be reduced rapidly. Therefore, even if the time required for the rail pressure Pr to reach the valve opening pressure TH1 after exceeding the target pressure TH2 is short, the peak fuel pressure can be sufficiently reduced. (Other embodiments)

[0081] The convergence value of the rail pressure Pr after opening the relief valve 80 changes according to the engine speed Ne and the fuel temperature Tf. Therefore, the ECU 90 can calculate the release pressure TH3 to remove the fuel delivery restriction based on the engine speed Ne and the fuel temperature Tf. In particular, when the engine speed Ne is high, the rail pressure Pr converges at a higher value. Therefore, when the engine speed Ne is high, the release pressure can be calculated to a higher value. Furthermore, the higher the fuel temperature Tf, the lower the volumetric elastic modulus of the fuel, so the rail pressure Pr is less likely to decrease. Therefore, the higher the fuel temperature Tf, the higher the release pressure can be calculated.In this case too, the ECU 90 can lift the fuel delivery restriction if the rail pressure Pr is reduced to the lift-determination pressure TH3 or if the predetermined lift-determination time TH5 has elapsed, whichever occurs first.

[0082] The relief valve 80 can be located in the supply line 60. In this case, when the relief valve 80 opens, the fuel in the supply line 60 returns to the low-pressure section via the return line 45.

[0083] Instead of using the rail pressure Pr, the pressure in the high-pressure side line 44 or the pressure in the injector 62 can be used as the pressure of the high-pressure section.

[0084] The control device and the technology according to the present disclosure can be achieved by a dedicated computer provided by forming a processor and a memory, which are programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and the method described in the present disclosure can be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits.Alternatively, the controller and the method, as described in the present disclosure, can be implemented by one or more specialized computers configured as a combination of a processor and a memory programmed to perform one or more functions, and a processor configured with one or more hardware logic circuits. Furthermore, the computer program can be stored on a computer-readable, non-transient, physical recording medium as an instruction to be executed by the computer.

[0085] Although the present revelation has been described according to the examples, it is clear that the present revelation is not limited to such examples or structures. The present revelation includes various modifications and variations within the range of equivalence. Furthermore, various combinations and formations, as well as other combinations and formations involving one, more than one, or fewer than one element, can be found in the present revelation.

Claims

[1] Control device (90) for a fuel injection system (10), the fuel injection system comprising: a low-pressure pump (20) configured to compress a fuel in a fuel tank (18) and deliver the fuel; a high-pressure pump (30) configured to increase the pressure of the fuel delivered by the low-pressure pump and to deliver high-pressure fuel; a storage tank (60) configured to store the high-pressure fuel delivered by the high-pressure pump; a fuel injector (62) configured to inject the high-pressure fuel contained in the reservoir; a relief valve (80) provided in a high-pressure section (44, 60) downstream of the high-pressure pump and configured to open when a high-pressure anomaly occurs in the high-pressure section; and a return line (45) which is configured such that it returns the high-pressure fuel in the high-pressure section to a low-pressure section provided downstream of the low-pressure pump by opening the relief valve, wherein the control device is configured to control the high-pressure fuel in the storage tank within a predetermined pressure range, wherein the control device comprises: a fuel pressure determining unit configured to determine whether the pressure in the high-pressure section rises to a predetermined determining pressure that is higher than the pressure range and lower than a valve opening pressure for opening the relief valve; and a restriction unit configured to cause the low-pressure pump to implement a fuel delivery restriction when the fuel pressure determination unit determines that the pressure in the high-pressure section is rising to the determination pressure. [2] Control device for the fuel injection system according to claim 1, wherein a pressure in the low-pressure section is configured such that it is changed by adjusting the output of the low-pressure pump, and The restriction unit, as the fuel delivery restriction, reduces the pressure in the low-pressure section so that it is lower than a pressure in a case where the fuel pressure determination unit does not determine that the pressure in the high-pressure section rises to the determination pressure. [3] Control device for the fuel injection system according to claim 2, wherein the restriction unit, as the fuel delivery restriction, causes the low-pressure pump to stop delivering fuel and then reduces the pressure in the low-pressure section so that it is lower than the pressure in the case where the fuel pressure determination unit does not determine that the pressure in the high-pressure section rises to the determination pressure. [4] Control device for the fuel injection system according to one of claims 1 to 3, further comprising a valve opening determination unit configured to determine whether the relief valve is opened after the start of the fuel delivery restriction, wherein The restriction unit lifts the fuel delivery restriction when the valve opening determination unit determines that the relief valve is open. [5] Control device for the fuel injection system according to claim 4, wherein the restriction unit removes the fuel delivery restriction when the valve opening determination unit determines that the relief valve is open, or a predetermined removal time elapses, whichever occurs first. [6] Control device for the fuel injection system according to any one of claims 1 to 3, wherein the restriction unit removes the fuel delivery restriction when the pressure of the high-pressure section is reduced to a predetermined removal determination pressure which is lower than the determination pressure, or a predetermined removal time elapses, whichever occurs first. [7] Control device for the fuel injection system according to any one of claims 1 to 6, wherein The high-pressure pump increases the pressure of the fuel by rotating an output shaft of an internal combustion engine, and When the fuel pressure determination unit determines that the pressure of the high-pressure section is rising to the determination pressure, the restriction unit performs the fuel delivery restriction under a condition that the rotational speed of the output shaft of the internal combustion engine is lower than a predetermined rotational speed.

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