JP5630462B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device that determines a pumping abnormality of a high-pressure pump that pressurizes and feeds fuel supplied from an electric low-pressure pump, and a fuel injection system using the same.

  Conventionally, a high-pressure pump that pressurizes and feeds fuel supplied from an electric low-pressure pump is metered by a metering valve, and fuel pressurized by a high-pressure pump is accumulated in a pressure accumulating chamber and then fed from a fuel injection valve. In a fuel injection system for injection, a fuel pressure in a pressure accumulating chamber is detected by a pressure sensor, and a pumping amount of a high-pressure pump is metered by a metering valve so that the detected actual pressure becomes a target pressure ( For example, see Patent Document 1.)

  In Patent Document 1, based on the detection result of the fuel pressure in the accumulator, the actual pressure in the accumulator is excessively higher than the target pressure because the pumping amount of the high-pressure pump is excessive due to malfunction of the metering valve. If it is determined that the voltage is increased, the voltage applied to the electric low-pressure pump is decreased. Accordingly, in Patent Document 1, the actual pressure in the pressure accumulating chamber rises excessively from the target pressure by reducing the amount of fuel supplied from the low pressure pump to the high pressure pump and reducing the pumping amount of the high pressure pump. Trying to prevent.

JP 2010-255544 A

  However, in the method of determining that the fuel pressure of the high-pressure system has risen excessively by detecting the fuel pressure in the pressure accumulating chamber that accumulates high-pressure fuel, the amount of high-pressure pump is excessive, so The fuel pressure has already increased excessively. Even if the voltage applied to the electric low-pressure pump is reduced, the amount of fuel supplied to the high-pressure pump is reduced after the voltage applied to the low-pressure pump is reduced, and the pumping amount of the high-pressure pump is reduced. There is a response delay before the fuel pressure drops.

  Therefore, the fuel pressure rises excessively in the high pressure system from when it is determined that the fuel pressure of the high pressure system is excessively increased until the pumping amount of the high pressure pump decreases and the fuel pressure of the high pressure system decreases. There is a problem that the state continues.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control device that detects an abnormal pumping of a high-pressure pump at an early stage and a fuel injection system using the same.

  While the metering valve is open during the pumping stroke of the high-pressure pump, the fuel in the pressurizing chamber is returned to the low pressure side. When the metering valve is closed, the pressurization of the fuel is started in the pressurizing chamber. In a configuration in which the metering valve regulates the pumping amount of the pump, the fuel pressure on the low pressure side rises while the metering valve opens in the pumping stroke and the fuel in the pressurizing chamber is returned to the low pressure side. During the stroke, the fuel pressure on the low pressure side decreases while the metering valve is closed and the pressurized fuel is being pumped to the high pressure side.

  Since the pumping amount of the high-pressure pump is determined by the pressurization period during which the metering valve is closed during the pumping stroke, if a change in the fuel pressure in the low-pressure system is detected, whether or not the high-pressure pump is abnormal in pumping is determined. Can be judged.

Therefore, according to the fuel injection control device of the present invention, the high-pressure pump is abnormally pumped based on the detected value of either the low-pressure fuel pressure between the electric low-pressure pump and the high-pressure pump or the physical quantity related to the fuel pressure. It is determined whether or not there is.
When determining whether the high-pressure pump is abnormal in pumping, the pumping amount of the high-pressure pump is estimated based on the detected value, and the estimated pumping amount and the high-pressure system from the high-pressure pump to the fuel injection valve are consumed. Compared with the fuel consumption, if the estimated pumping amount is more than the predetermined amount with respect to the fuel consumption, it is determined that the high-pressure pump is overpressured, and the estimated pumping amount is the predetermined amount with respect to the fuel consumption. In the following cases, it is determined that the high pressure pump is insufficiently pumped.
Alternatively, when the detected value does not change at a predetermined timing, it is determined that the high pressure pump is abnormally pumped.

  In this way, whether or not the high-pressure pump is abnormally pumped is determined based on the detected value of the low-pressure fuel pressure itself or the detected value of the physical quantity that changes in accordance with the fuel pressure in relation to the low-pressure fuel pressure. Since the determination is made, it is possible to detect the abnormal pressure feeding of the high pressure pump at an early stage before the fuel pressure of the high pressure system becomes abnormal due to the abnormal pressure feeding of the high pressure pump.

  As a result, when an overpressure that causes an excessive increase in the amount of pumping occurs as an abnormal pumping of the high-pressure pump, for example, appropriate processing such as stopping the fuel supply from the electric low-pressure pump to the high-pressure pump can be quickly executed. As a result, it is possible to quickly eliminate the overpressure of the high pressure pump and to prevent the fuel pressure from rising excessively in the high pressure system.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

The block diagram which shows the fuel-injection system by this embodiment. The schematic diagram which shows the structure of a high pressure pump. The time chart which shows the relationship between metering valve current, low pressure pump drive current, low pressure fuel pressure, and cam lift. The flowchart which shows the pumping abnormality determination process 1 of a high pressure pump. The flowchart which shows the pumping abnormality determination process 2 of a high pressure pump.

(Fuel injection system)
A fuel injection system 2 shown in FIG. 1 is for injecting fuel into, for example, a multi-cylinder diesel engine for automobiles (hereinafter also simply referred to as “engine”). The fuel injection system 2 is mainly composed of a feed pump (FP) 12, a high-pressure pump 20, a common rail 40, a fuel injection valve 50, and an electronic control unit (ECU) 60. Yes. In FIG. 1, only the fuel injection valve 50 corresponding to one cylinder among the plurality of cylinders is illustrated, and illustration of the fuel injection valves 50 of other cylinders is omitted.

  The FP 12 is an electric pump that rotates, by a motor, an impeller having a plurality of blades formed on the outer periphery of a disk-shaped rotating body. The FP 12 sucks the fuel in the fuel tank 10 and supplies it to the high-pressure pump 20 side as the impeller rotates. The FP 12 is directly connected to the battery and supplied with a drive current. Therefore, if the rotation speed of the FP 12 is constant, the drive current of the FP 12 is substantially constant.

  As shown in FIG. 2, the high-pressure pump 20 sucks fuel supplied from the FP 12 through the low-pressure pipe 100 into the pressurizing chamber 200 by reciprocating the plunger 22 as the camshaft cam rotates. This is a known pump for pressurization.

  When the energization is turned off, the metering valve 24 is opened and the fuel inlet 26 is opened. As a result, the low pressure pipe 100 and the pressurizing chamber 200 communicate with each other in the suction stroke in which the plunger 22 descends from the top dead center toward the bottom dead center, and fuel is sucked into the pressurizing chamber 200.

  When the energization is turned on, the metering valve 24 is closed and the fuel inlet 26 is closed. In the pressure feed stroke in which the plunger 22 rises from the bottom dead center toward the top dead center, the metering valve 24 closes, the fuel inlet 26 is closed, and the communication between the low pressure pipe 100 and the pressurizing chamber 200 is shut off. Pressurization of the fuel in the pressurizing chamber 200 is started.

The discharge valve 28 is opened when the fuel in the pressurizing chamber 200 is pressurized and exceeds a predetermined valve opening pressure, and the fuel in the pressurizing chamber 200 is pumped to the high-pressure pipe 104.
The regulating valve 30 shown in FIG. 1 is installed in a pipe connecting a low-pressure pipe 100 that supplies fuel from the FP 12 to the high-pressure pump 20 and a return pipe 102 that returns surplus fuel from the high-pressure pump 20 to the fuel tank 10. Yes. The regulator valve 30 is opened at a predetermined valve opening pressure, whereby excess fuel in the low pressure pipe 100 is returned from the return pipe 102 to the fuel tank 10. Thereby, the fluctuation | variation of the fuel pressure of the low pressure piping 100 between the regulator valve 30 and the high pressure pump 20 is suppressed.

  In the configuration using the discharge metering type metering valve 24 that determines the pressurization start timing by metering the metering valve 24 as in the present embodiment and metering the pumping amount of the high pressure pump 20, the high pressure The fuel pressure of the low pressure system upstream of the pump 20 only needs to be equal to or higher than the pressure at which the fuel corresponding to the capacity of the pressurizing chamber 200 can be sucked in the suction stroke, and therefore, compared with a configuration using a suction metering type metering valve. The valve opening pressure of the regulating valve 30 may be high, the flow rate may be small, and the opening / closing response may be slow.

  The pressure sensor 32 is installed in the low pressure pipe 100 between the regulating valve 30 and the high pressure pump 20. By installing a pressure sensor 32 between the regulating valve 30 and the high-pressure pump 20 in the immediate vicinity of the upstream side of the high-pressure pump 20, the fluctuation of the pressure due to the fuel supplied from the FP 12 is eliminated and the operation of the high-pressure pump 20 is performed. The accompanying change in fuel pressure in the low-pressure system can be detected with high accuracy by eliminating the influence of pressure attenuation as much as possible.

  The common rail 40 is a hollow member that forms a pressure accumulating chamber that accumulates fuel pumped from the high-pressure pump 20. The common rail 40 is provided with a high pressure sensor 42 for detecting the fuel pressure in the common rail.

  The ECU 60 is mainly configured by a microcomputer centering on a CPU, RAM, ROM, flash memory and the like. The ECU 60 executes the control program stored in the ROM or the flash memory, and inputs various information representing the engine operating state such as the current value of the driving current of the FP 12 and the pressure sensors 32 and 42, and the fuel injection. Various controls of the system 2 are executed.

For example, the ECU 60 controls the valve closing timing of the metering valve 24 so that the common rail pressure detected by the pressure sensor 42 becomes the target pressure, and meteres the pumping amount of the high-pressure pump 20.
Further, the ECU 60 controls the injection amount of the fuel injection valve 50, the injection timing, and the pattern of multi-stage injection that performs pilot injection, pre-injection, after-injection, post-injection after the pilot injection, and the like.

  The ECU 60 stores a so-called TQ map indicating the correlation between the pulse width (T) of the injection command signal that commands the fuel injection valve 50 and the injection amount (Q) in a ROM or flash memory for each predetermined pressure region of the common rail pressure. I remember it. Then, when the target injection amount of the fuel injection valve 50 is determined based on the engine speed and the accelerator opening, the ECU 60 refers to the TQ map of the corresponding pressure region according to the common rail pressure detected by the pressure sensor 42. The pulse width of the injection command signal for commanding the target injection amount to the fuel injection valve 50 is acquired from the TQ map.

(Operation of high-pressure pump 20)
Next, the operation of the high-pressure pump 20 and changes in the driving current of the FP 12 and the low-pressure fuel pressure accompanying the operation of the high-pressure pump 20 will be described.

  As shown in FIG. 3, the ECU 60 turns off the power supply to the metering valve 24 in the intake stroke in which the plunger 22 of the high-pressure pump 20 descends from the top dead center to the bottom dead center according to the cam profile. As a result, the fuel inlet 26 is opened, and the low-pressure fuel in the low-pressure pipe 100 is sucked into the pressurizing chamber 200 through the fuel inlet 26. At this time, the low-pressure fuel pressure detected by the pressure sensor 32 decreases.

  When the fuel pressure in the low-pressure system decreases, the force that hinders the rotation of the FP 12 decreases, so the rotation speed of the FP 12 increases and the back electromotive force generated in the motor of the FP 12 increases. As a result, the drive current flowing through the FP 12 decreases.

  In the pumping stroke in which the plunger 22 rises from the bottom dead center toward the top dead center, the ECU 60 turns off the energization to the metering valve 24 halfway. Then, the fuel in the pressurizing chamber 200 is returned from the fuel inlet 26 to the low pressure pipe 100 by the raising of the plunger 22. At this time, the low-pressure fuel pressure detected by the pressure sensor 32 increases.

  When the fuel pressure in the low-pressure system increases, the force that hinders the rotation of the FP 12 increases, so the rotation speed of the FP 12 decreases and the counter electromotive force generated in the motor of the FP 12 decreases. As a result, the drive current increases.

  When the energization of the metering valve 24 is turned on during the pumping stroke and the metering valve 24 is closed, the fuel inlet 26 is closed, so that the fuel in the pressurizing chamber 200 is pressurized as the plunger 22 moves up. When the metering valve 24 is closed, the fuel in the pressurizing chamber 200 is not returned to the low-pressure pipe 100, so that the low-pressure fuel pressure detected by the pressure sensor 32 rapidly decreases.

When the fuel pressure in the low-pressure system decreases, the rotation speed of the FP 12 increases and the back electromotive force generated in the motor of the FP 12 increases. As a result, the drive current decreases.
When the fuel pressure in the pressurizing chamber 200 becomes equal to or higher than the opening pressure of the discharge valve 28, the discharge valve 28 is opened, and the fuel in the pressurizing chamber 200 is pumped to the common rail 40 through the high-pressure pipe 104.

  The ECU 60 turns off the energization of the metering valve 24 before the plunger 22 reaches the top dead center of the pumping stroke when a predetermined time has elapsed after the energization of the metering valve 24 is turned on. In this case, the valve member of the metering valve 24 receives a force in the valve closing direction that closes the fuel inlet 26 due to the fuel pressure in the pressurizing chamber 200, so that the metering valve 24 maintains the closed state.

  When the plunger 22 reaches the top dead center in a state where the energization to the metering valve 24 is turned off, the pumping stroke is finished. When the plunger 22 starts to descend from the top dead center, the metering valve 24 that is turned off is opened and the suction stroke is started, so that fuel is sucked into the pressurizing chamber 200.

  Here, for example, when the metering valve 24 malfunctions and a pumping abnormality that prevents the pumping amount of the high-pressure pump 20 from being properly metered in response to a command from the ECU 60 occurs, the fuel pressure of the common rail 40 with respect to the target pressure. May rise or fall excessively.

  Therefore, in the present embodiment, as described below, in order to detect an abnormal pumping of the high-pressure pump 20 at an early stage, a change in a physical quantity related to a low-pressure fuel pressure or a low-pressure fuel pressure is detected to detect high pressure. The pumping amount of the pump 20 is estimated, and it is determined whether or not the high-pressure pump 20 has a pumping abnormality.

(Pumping amount estimation)
The pumping amount of the high-pressure pump 20 is such that the plunger 22 reaches the top dead center after the metering valve 24 is closed and the pressurization of the fuel in the pressurizing chamber 200 is started and the discharge valve 28 is opened. Thus, it is determined by the pressurizing period until the pumping is completed.

  As described above, in the pumping stroke, when the plunger 22 starts to rise from the bottom dead center to the top dead center, the low-pressure fuel pressure rises, and when the metering valve 24 is closed and fuel pumping starts, the low pressure is started. The fuel pressure of the system drops rapidly. Accordingly, in the pumping stroke, when the period from when the low-pressure fuel pressure starts to rise to when it suddenly drops is the pressure rising period, the pressurizing period is from the pumping stroke period to the pressure rising period representing the pumping stroke period. Is a value obtained by subtracting.

  Judging from the crank angle that represents the rotation angle of the crankshaft that drives the camshaft, the pressure rise period varies depending on the valve closing timing of the metering valve 24, but the pumping stroke period is a fixed value regardless of the engine speed. is there. Therefore, if the pressure increase period is known, the pressurization period is determined, and the pumping amount of the high-pressure pump 20 can be estimated from the pressurization period. Since the pumping stroke period is a fixed value, the pumping amount of the high-pressure pump 20 can be estimated from the pressure rising period.

The pumping amount can be estimated as follows from (1) the detected pressure of the pressure sensor 32 or (2) the driving current of the FP 12.
(1) Pressure detected by the pressure sensor 32 When the pressure sensor 32 detects the low-pressure fuel pressure, the pressure increase period Tp from when the low-pressure fuel pressure starts to rise until the rise ends and rapidly decreases. Can be obtained directly. The rise start timing and the rise end timing of the low-pressure fuel pressure are detected by the time when the ECU 60 performs sampling, and the pressure rise period Tp is also obtained by time.

Specifically, the pumping amount Q of the high-pressure pump 20 is obtained from the following equation (1), where TG is the fuel pressure rising start timing and TR is the rising end timing.
Q = F (TG-TR) (1)
(TG-TR) is a parameter representing the pressure increase period Tp. As described above, if the pressure increase period is known, the pressurization period is determined. The function F is a mathematical expression or map data for obtaining a pumping amount determined by the cam profile using (TG-TR) as a parameter.

  However, since the pumping amount cannot be obtained with the pressure increase period Tp expressed in time, the pressure increase period Tp expressed in time is converted into a crank angle based on the engine speed, and expressed in angle. The pumping amount is obtained from the passed pressure increase period Tp.

  Here, if there is an error in the mounting angle of the high-pressure pump 20, the rising start timing TG and the rising end timing TR may be different from the crank angle when the high-pressure pump 20 is normally mounted. Further, the detected rise start timing TG and rise end timing TR may deviate from the actual rise start timing TG and rise end timing TR due to the propagation delay of the fuel pressure detected by the pressure sensor 32.

  However, the attachment of the high-pressure pump 20 is obtained by obtaining the pumping amount of the high-pressure pump 20 by using the difference (TG-TR) between the rising start timing TG and the rising end timing TR as a parameter representing the pressure rising period as in the equation (1). The pumping amount can be estimated with high accuracy by offsetting the angle error and the pressure propagation delay.

  If the error in the mounting angle of the high-pressure pump 20 and the propagation delay of the fuel pressure detected by the pressure sensor 32 are negligible, the period from the rising end timing TR to the top dead center of the pumping stroke is the pressurizing period. Therefore, the pumping amount of the high-pressure pump 20 may be estimated only from the rising end timing TR.

(2) Drive Current The drive current of the FP 12 changes according to the low-pressure fuel pressure as described above, although there is a time delay with respect to the low-pressure fuel pressure detected by the pressure sensor 32. The current increase period Ti, which is a period between the increase start timing TG at which the drive current starts increasing and the increase end timing TR at which the increase ends, is the same length as the pressure increase period Tp. Accordingly, by obtaining the current rise period Ti from the rise start timing and the rise end timing of the drive current, the high pressure pump 20 is pumped from the equation (1) in the same manner as when the pressure sensor 32 detects the low pressure fuel pressure. The quantity Q can be determined.

  Note that the change in the low-pressure fuel pressure caused by the operation of the high-pressure pump 20 attenuates due to the piping length while propagating from the high-pressure pump 20 to the FP 12. If this attenuation is large, it becomes difficult to obtain the current rising period Ti with high accuracy from the change in the driving current of the FP 12. Therefore, in order to reduce the attenuation of the fuel pressure propagating to the FP 12 as much as possible, it is desirable to use a material having a high elastic coefficient for the low-pressure pipe 100.

  Further, the value of the low-pressure fuel pressure detected by the pressure sensor 32 is the difference between the regulator valve 30, the rotation speed of the high-pressure pump 20, the injection amount of the fuel injection valve 50, and the foreign matter of the fuel filter installed in the low-pressure system. It varies depending on the degree of pressure loss due to collection, fuel properties, fuel temperature, and the like. Therefore, even if the fuel pressure value detected by the pressure sensor 32 is compared with a fixed threshold value, the fuel pressure rise start timing and rise end timing cannot be obtained with high accuracy.

  Therefore, the pressure rise period Tp can be obtained with high accuracy by obtaining the rise start timing and the rise end timing using a differential value, a slope, a change width, or the like of the low-pressure fuel pressure.

  Similarly, when obtaining the rise start timing and rise end timing of the drive current of the FP 12, by obtaining the rise start timing and the rise end timing with a differential value, slope, change width, etc. of the drive current, or a combination thereof, The current rising period Ti can be obtained with high accuracy.

  In the case of the driving current of the FP 12, noise is generated as shown in FIG. 3 due to pressure pulsation generated by blades formed on the outer periphery of the impeller when the FP 12 pumps fuel, and rotational speed unevenness caused by magnetic unevenness in the circumferential direction of the motor. Occurs. Therefore, it is desirable to obtain the rise start timing and rise end timing of the drive current after removing this noise by the band pass filter.

  Next, the pumping abnormality determination processes 1 and 2 of the high-pressure pump 20 executed by the control program stored in the ROM or the like by the ECU 60 will be described. In the flowcharts of FIGS. 4 and 5, “S” represents a step.

(Pressure abnormality determination process 1)
In the pumping abnormality determination process 1 shown in FIG. 4, the pumping abnormality of the high-pressure pump 20 is determined based on the driving current of the FP 12.

  The ECU 60 samples the drive current of the FP 12 at a predetermined time interval and performs AD conversion (S400), and performs AD conversion in a noise frequency band determined by the number of rotations of the FP 12 and the number of impeller blades and the magnetic unevenness of the FP 12 motor. A band pass filter is applied to the converted value (S402).

  It is determined that the drive current rise start timing TG is reached when both the forward and backward inclination and the rise width of the drive current after passing through the filter are in a predetermined rise range (S404). When both the forward and backward inclination and the decrease range are within the predetermined decrease ranges, it is determined that the drive current increase end timing TR is reached (S406).

In S408, the ECU 60 calculates the estimated pumping amount of the high-pressure pump 20 from the equation (1) based on the rising start timing TG and the rising end timing TR.
If the estimated pumping amount is overpressure (system consumption + maximum system variation) or more, or if the estimated pumping amount is (system consumption-maximum system variation) or less (S410: Yes), the process proceeds to S412. If the process is shifted to neither over-pressure feeding nor under-pumping (S410: No), this process is terminated.

  The system consumption used in the determination of S410 is the amount of leakage of the high-pressure system from the high-pressure pump 20 to the fuel injection valve 50 measured in advance in the fuel injection system 2 of FIG. The reference fuel consumption amount in the high-pressure system expressed by the injection amount of the fuel injection valve 50 is shown. Then, in consideration of the maximum system variation including the difference in fuel injection system and the change over time in the system consumption, it is determined whether the high-pressure pump 20 is over-pressured or insufficiently pumped.

  In S412, if overpressurization has not occurred continuously n times (S412: No), the ECU 60 ends this process. If overpressure feeding has occurred n times continuously (S412: Yes), the ECU 60 stops the power supply to the FP 12 and stops the FP 12 (S414).

  By determining that the high pressure pump 20 is overpressure based on the driving current of the FP 12 and stopping the FP 12, the fuel supply from the FP 12 to the high pressure pump 20 is stopped before the common rail pressure rises excessively, and the high pressure pump 20 The pumping of fuel from the pump can be stopped to prevent the common rail pressure from rising.

  When it is determined that the pressure feeding is insufficient in the determination of S410, the valve closing start timing of the metering valve 24 may be advanced. If the valve closing start timing of the metering valve 24 is advanced and the insufficient pumping is resolved for a predetermined number of times, it can be determined that insufficient pumping has occurred because the valve closing response of the metering valve 24 has decreased due to changes over time. .

In the case of determining an abnormal pumping of the high-pressure pump 20 based on the driving current of the FP 12, the pressure sensor 32 installed in the low-pressure pipe 100 can be omitted.
(Pressure feed abnormality determination process 2)
In the pumping abnormality determination process 2 shown in FIG. 5, the pumping abnormality of the high-pressure pump 20 is determined based on the low-pressure fuel pressure detected by the pressure sensor 32.

  The ECU 60 samples the output signal of the pressure sensor 32 that detects the low-pressure fuel pressure at predetermined time intervals and performs AD conversion (S420). Then, it is determined that it is the start timing TG of the low pressure fuel pressure when both the forward and backward inclination and the increase range of the low pressure fuel pressure are within a predetermined increase range (S422). It is determined that the low-pressure fuel pressure rise end timing TR is reached when both the fuel pressure gradient before and after and the reduction range are within the predetermined reduction ranges (S424). The processing after S426 is substantially the same as the processing after S408 in FIG.

  In the pumping abnormality determination process 2 of FIG. 5, the pumping abnormality of the high-pressure pump 20 is determined based on the low-pressure fuel pressure detected by the pressure sensor 32. Therefore, the pumping abnormality of the high-pressure pump 20 can be determined with higher accuracy.

  According to the present embodiment described above, since the pumping abnormality of the high-pressure pump 20 is determined based on the driving current of the FP 12 that changes in relation to the low-pressure fuel pressure or the low-pressure fuel pressure itself, the high-pressure common rail pressure is excessive. Before the pressure rises, it is possible to detect an abnormal pumping of the high-pressure pump 20 at an early stage based on a change in the fuel pressure of the low-pressure system. Thereby, when it determines with the high pressure pump 20 being overpressure feeding, it can prevent that a common rail pressure rises excessively by stopping the drive of FP12.

  Further, by determining the abnormal pressure feeding of the high-pressure pump 20 based on the change in the low-pressure fuel pressure, appropriate processing such as stopping the driving of the FP 12 is executed to prevent the common rail pressure from excessively rising. Therefore, the structure which does not install a pressure regulator in the common rail 40 is employable.

[Other Embodiments]
In the above embodiment, the driving current of the FP 12 is detected as a physical quantity related to the low-pressure fuel pressure. In addition to this, as long as the rotation speed of the FP 12 or the flow rate of the low-pressure pipe 100 can be detected, these may be detected as physical quantities related to the fuel pressure of the low-pressure system.

  In the above-described embodiment, the abnormality in pumping of the high-pressure pump 20 is determined from the start timing and the end timing of the increase in the low-pressure fuel pressure or the driving current of the FP 12. On the other hand, when the low-pressure fuel pressure or the driving current of the FP 12 does not change at a predetermined timing, it may be determined that the high-pressure pump 20 is abnormally pumped.

  For example, when the rising end timing of the low pressure fuel pressure or the driving current of the FP 12 is earlier than a predetermined timing determined by the ECU 60, it is determined that the high pressure pump 20 is overpressure fed, and when it is later than the predetermined timing, the high pressure is increased. It can be determined that the pump 20 is insufficiently pumped.

  In the above embodiment, the rise start timing and the rise end timing are detected based on both the drive current or the slope of the low-pressure fuel pressure and the change width represented by the rise or fall width. On the other hand, the rise start timing and the rise end timing may be detected based only on the gradient or change width of the drive current or the low-pressure fuel pressure. Further, a differential value may be used instead of the slope.

  In the above embodiment, the driving current of the FP 12 or the fuel pressure of the low pressure system is sampled at predetermined time intervals, and the rising start timing and the rising end timing are detected. On the other hand, the driving current of the FP 12 or the low-pressure fuel pressure may be sampled in synchronization with the crank angle to detect the rising start timing and the rising end timing.

  In the above embodiment, the FP 12 is stopped when it is determined that the high-pressure pump 20 is overpressure-feeding. However, if the drive current supplied to the FP12 can be variably controlled, the drive current is reduced according to the degree of overpressure-feeding. May be.

Further, in order to prevent an excessive increase in the fuel pressure of the high pressure system, a pressure regulator may be installed on the common rail 40 in addition to the processing of the above embodiment.
The present invention is not limited to a common rail system for a diesel engine, and may be applied to a fuel injection system of a direct injection gasoline engine that accumulates fuel in a pressure accumulating chamber formed by a delivery pipe.

  In the above embodiment, the functions of the detection value acquisition unit, the determination unit, and the pumping amount estimation unit are realized by the ECU 60 whose functions are specified by the control program. On the other hand, at least some of the functions of the plurality of means may be realized by hardware whose functions are specified by the circuit configuration itself.

  As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

2: fuel injection system, 12: FP (low pressure pump), 20: high pressure pump, 24: metering valve, 32: pressure sensor, 40: common rail, 50: fuel injection valve, 60: ECU (fuel injection control device, detection) Value acquisition means, determination means, pumping amount estimation means)

Claims (5)

The pressurization start timing for pressurizing the fuel supplied from the electric low-pressure pump (12) by the high-pressure pump (20) is controlled by the metering valve (24) to meter the pumping amount of the high-pressure pump, and the high-pressure pump A fuel injection control device (60) applied to a fuel injection system (2) for accumulating the fuel pressurized in the pressure accumulation chamber (40) and injecting the fuel from the fuel injection valve (50),
Detection value acquisition means (S400, S420) for acquiring a detection value of either a low-pressure fuel pressure between the low-pressure pump and the high-pressure pump or a physical quantity related to the fuel pressure;
Pumping amount estimating means (S408, S426) for estimating the pumping amount of the high-pressure pump based on the detection value acquired by the detection value acquiring means;
The pumping amount estimated by the pumping amount estimating means is compared with the fuel consumption consumed in the high pressure system from the high pressure pump to the fuel injection valve, and the pumping amount is a predetermined amount with respect to the fuel consumption. If it is above, it is determined that the high-pressure pump is over-pressured, and if the pressure-feeding amount is less than a predetermined amount with respect to the fuel consumption, determination means (S410, S428) that determines that the high-pressure pump is insufficiently pumped ,
A fuel injection control device comprising: The pressurization start timing for pressurizing the fuel supplied from the electric low-pressure pump (12) by the high-pressure pump (20) is controlled by the metering valve (24) to meter the pumping amount of the high-pressure pump, and the high-pressure pump A fuel injection control device (60) applied to a fuel injection system (2) for accumulating the fuel pressurized in the pressure accumulation chamber (40) and injecting the fuel from the fuel injection valve (50),
Detection value acquisition means (S400, S420) for acquiring a detection value of either a low-pressure fuel pressure between the low-pressure pump and the high-pressure pump or a physical quantity related to the fuel pressure;
When the detection value acquired by the detection value acquisition means does not change at a predetermined timing, determination means (S410, S428) for determining that the high-pressure pump is abnormally pumped ,
A fuel injection control device comprising: The fuel injection control device according to claim 1 or 2 , wherein the detection value acquisition means (S400) acquires a detection value of a driving current of the low-pressure pump as a detection value of the physical quantity. The fuel injection control device according to claim 1 or 2 , wherein the detection value acquisition means (S420) acquires a detection value of the fuel pressure of the low pressure system from a pressure sensor installed in the low pressure system. . An electric low-pressure pump;
A high-pressure pump that controls the pressurization start timing for pressurizing the fuel supplied from the low-pressure pump with a metering valve to meter the pumping amount;
A common rail for accumulating fuel supplied from the high-pressure pump;
A fuel injection valve for injecting fuel accumulated in the common rail;
A fuel injection control device according to any one of claims 1 to 4 ,
A fuel injection system comprising:

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