JP2011132872A - Fuel pressure control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel pressure control device capable of quickly restarting an internal combustion engine from idle stop. <P>SOLUTION: The fuel pressure control device makes a fuel feed pump take in fuel and pressure-feed the fuel to a common rail, if an idle stop request flag is ON (S400:Yes) and if a timing is right for a temporal synchronization of performing an intake control during lowering of an engine rotation number (S404:Yes). Then, if the pressure difference ΔPc between the actual pressure of a common rail pressure and a target pressure set according to either during idle stop or at engine start-up is larger than a drive permission determination value at which it is necessary to open a decompression valve and reduce the common rail pressure and if the drive permission flag is ON (S424:Yes), the fuel pressure control device calculates final current apply time at which currents are fed to the decompression valve (S428 to S436) and reduces the common rail pressure by opening or closing the decompression valve based on the final current feed time (S438). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel pressure control device that is applied to a fuel injection system that injects fuel supplied from a fuel supply pump and accumulated in a common rail into each cylinder of an internal combustion engine from a fuel injection valve, and controls the fuel pressure in the common rail.

  Conventionally, there is known a fuel injection system that injects fuel supplied from a fuel supply pump and accumulated in a common rail into each cylinder of an internal combustion engine from a fuel injection valve (see, for example, Patent Documents 1 and 2).

  Here, in Patent Document 2, in order to shorten the starting time when starting the internal combustion engine from the stopped state, when the internal combustion engine stops, fuel is sucked into the fuel supply pump, and the internal combustion engine starts. Discloses a technology for pumping fuel sucked into a fuel supply pump to a common rail. As a result, the fuel is quickly pumped from the fuel supply pump at the start, and the fuel pressure necessary for the start is obtained in a short time.

  In particular, in a fuel injection system that performs idle stop by stopping fuel injection from the fuel injection valve when the vehicle stops for a predetermined time or longer due to a signal or the like, the vehicle is idle when the driver performs an operation to resume traveling. It is desirable not to give the driver discomfort by quickly starting the internal combustion engine from the stop.

JP 2008-128163 A JP 2002-371873 A

  However, in Patent Document 2, the fuel is sucked into the fuel supply pump until the engine speed is reduced to a speed at which the fuel can be sucked into the fuel supply pump but before the internal combustion engine is stopped after the ignition switch is turned off. stand by. That is, when fuel injection from the fuel injection valve is stopped, the fuel supply pump does not pump fuel.

  In this state, the common rail pressure decreases due to fuel leaking from the fuel injection system during the idle stop. Therefore, when releasing the idle stop and restarting the internal combustion engine, the fuel pressure required for the restart, that is, the fuel injection The common rail pressure may not reach the fuel pressure at which fuel can be injected from the valve. As a result, even if the fuel supply pump quickly pumps fuel that has been sucked in advance, there is a problem that restart is delayed until the common rail pressure reaches the fuel pressure required for restart.

  The present invention has been made to solve the above problem, and an object of the present invention is to provide a fuel pressure control device that can quickly restart an internal combustion engine from an idle stop.

  According to the first to sixth aspects of the present invention, when the idling stop is started, the pressure control means commands the pressure feed control means to command the fuel supply pump while the rotation speed of the internal combustion engine is decreasing until the internal combustion engine stops. Then, the fuel is pumped and the common rail pressure detected by the pressure detecting means is adjusted to a predetermined pressure.

  As described above, when the idling stop is started, the fuel is pumped from the fuel supply pump while the rotational speed of the internal combustion engine is decreasing. Therefore, the common rail pressure can be increased and regulated to a predetermined pressure. As a result, even when fuel leaks from the fuel injection system during idle stop and the common rail pressure decreases, the common rail pressure at the time of restart can be increased compared to the case where fuel is not pumped from the fuel supply pump. As a result, fuel injection from the fuel injection valve can be resumed, and the internal combustion engine can be restarted quickly from the idle stop.

According to the second aspect of the present invention, the predetermined pressure is set higher than the starting pressure for starting the internal combustion engine from the idle stop.
As a result, even if fuel leaks from the fuel injection system during idling stop and the common rail pressure drops from the predetermined pressure, the common rail pressure is prevented from dropping as much as possible when the internal combustion engine is restarted. it can. As a result, the internal combustion engine can be promptly restarted from the idle stop.

  By the way, it is difficult to control the pumping amount of the fuel supply pump with high accuracy during the decrease in the rotational speed of the internal combustion engine when shifting to the idle stop. Therefore, it is difficult to adjust the common rail pressure to a predetermined pressure only by controlling the pumping amount of the fuel supply pump.

  Therefore, according to the third aspect of the present invention, the pressure control means is configured such that the common rail pressure exceeds the predetermined pressure from when the idle stop is started until the idle stop is released and fuel injection from the fuel injection valve is started. If it is too high, the common rail pressure is reduced by controlling the pressure reducing valve.

  As a result, during a decrease in the rotational speed of the internal combustion engine when shifting to the idle stop, the fuel is pumped from the fuel supply pump so that the common rail pressure is once higher than a predetermined pressure, and then the common valve pressure is controlled by controlling the pressure reducing valve. The pressure can be adjusted to a predetermined pressure. As a result, high-precision control of the fuel pumping amount for adjusting the commonley pressure to a predetermined pressure is unnecessary. Then, the commonley pressure can be adjusted to a predetermined pressure with high accuracy by the pressure reducing valve.

  By the way, while the rotational speed of the internal combustion engine is decreasing, the rotation angle synchronization period of the internal combustion engine is gradually increased, so that the control interval of the pressure reducing valve is also gradually increased. Therefore, the frequency at which the common rail pressure is regulated by controlling the pressure reducing valve decreases. As a result, it becomes difficult to control the pressure reducing valve to adjust the common rail pressure to a predetermined pressure.

  Therefore, according to the invention described in claim 4, when the fuel injection from the fuel injection valve is stopped and the operation state of the internal combustion engine shifts from the idle operation state to the idle stop state, the pressure control means synchronizes the rotation angle of the internal combustion engine. The pressure reducing valve is controlled at a predetermined driving cycle based on time synchronization by switching from time synchronization to time synchronization.

As a result, even if the period of rotation angle synchronization of the internal combustion engine becomes longer while the rotational speed of the internal combustion engine is decreasing, the pressure reducing valve can be controlled at a constant drive period to adjust the common rail pressure to a predetermined pressure.
According to the fifth aspect of the present invention, the plurality of time-synchronized cycles are set to one cycle of the drive cycle, and the pressure control means opens the pressure reducing valve once in one drive cycle to increase the common rail pressure. Reduce pressure.

  In this way, the pressure reducing valve is not opened at every time synchronization timing, but is opened once in one driving cycle with a plurality of time synchronization cycles as one cycle by thinning out the time synchronization timing. As a result, the frequency of opening and closing the pressure reducing valve decreases. As a result, the operating noise when the pressure reducing valve opens and closes can be reduced.

Further, since the frequency of driving the pressure reducing valve is lower than when the pressure reducing valve is driven at each time synchronization timing, the life of the pressure reducing valve can be extended.
By the way, the energization time for determining the valve opening time of the pressure reducing valve is calculated from the differential pressure between the predetermined pressure that is the target pressure during idling stop and the common rail pressure detected by the pressure detecting means.

However, since the temperature increase of the pressure reducing valve increases as the energization time per time for the pressure reducing valve becomes longer, the maximum value of the time of energization per time for the pressure reducing valve is set.
In addition, even if the energization time per cycle is short, when energizing the pressure reducing valve continuously in a plurality of drive cycles, if the ratio of the energization time to the drive cycle (duty) exceeds a predetermined value, the temperature of the pressure reducing valve The rise is greater. Therefore, the upper limit value of the energization duty is set in one driving cycle.

  Therefore, according to the invention described in claim 6, the pressure control means permits the energization time for the pressure reducing valve calculated based on the differential pressure between the predetermined pressure and the common rail pressure, and the energization of the pressure reducing valve once. The minimum energizing time is energized to the pressure reducing valve in one driving cycle among the maximum energizing time to be performed and the upper limit energizing time calculated from the energizing duty permitted in one driving cycle for the pressure reducing valve. The energization time.

Accordingly, the common rail pressure can be adjusted to a predetermined pressure with high accuracy by opening the pressure reducing valve while suppressing temperature rise of the pressure reducing valve as much as possible.
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. Sectional drawing which shows a pressure-reduction valve. The time chart which shows the change of the fuel pressure at the time of idle stop control. (A) is a time chart showing decimation control of the pressure reducing valve, (B) is a characteristic diagram showing the relationship between ΔPc and energization time according to the level of the common rail pressure, and (C) is a guard process for the energization time in the drive cycle. A time chart showing. The flowchart which shows the control routine of the common rail pressure after changing to idle stop until restarting an internal combustion engine.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a fuel injection system 10 of the present embodiment.
(Fuel injection system 10)
The accumulator fuel injection system 10 includes a fuel supply pump 16, a common rail 20, a pressure sensor 22, a pressure reducing valve 30, a fuel injection valve 60, an electronic control unit (ECU) 70, and an electronic driving unit (EDU). Unit) 72 and the like, and fuel is injected into each cylinder of a four-cylinder diesel engine (hereinafter also simply referred to as an engine) (not shown) as an internal combustion engine. In order to avoid the complexity of the figure, only the control signal line from the EDU 72 to one fuel injection valve 60 is shown in FIG.

  The fuel filter 14 removes foreign matters in the fuel sucked by the fuel supply pump 16 from the fuel tank 12. The fuel supply pump 16 incorporates a feed pump that sucks fuel from the fuel tank 12, pressurizes the sucked fuel, and pumps it to the common rail 20 through the supply pipe 200.

  The fuel supply pump 16 is a known pump that pressurizes the fuel sucked into the pressurizing chamber when the plunger reciprocates as the cam of the camshaft rotates. By controlling the current value supplied to the metering valve (not shown) of the fuel supply pump 16 by the ECU 70, the fuel suction amount sucked in the suction stroke by the fuel supply pump 16 is metered. Then, by adjusting the fuel intake amount, the fuel pumping amount of the fuel supply pump 16 is adjusted. Note that a metering valve may be installed on the discharge side of the fuel supply pump 16 to meter the fuel pumping amount.

  The common rail 20 accumulates the fuel pumped by the fuel supply pump 16, maintains the fuel pressure at a predetermined high pressure corresponding to the engine operating state, and supplies the fuel to the fuel injection valve 60 through the injection pipe 202. The pressure sensor 22 outputs a signal corresponding to the fuel pressure (common rail pressure) inside the common rail 20.

When the pressure reducing valve 30 is opened, the fuel inside the common rail 20 is discharged to the return pipe 204 on the low pressure side.
As shown in FIG. 2, the valve body 32 of the pressure reducing valve 30 is screwed to the common rail 20. The valve member 38 is supported by the cylinder 36 so as to be reciprocally movable, and is urged against the flat valve seat member 34 by the load of the spring 42. A ball 40 is fitted in a recess formed on the valve seat member 34 side of the valve member 38. When the ball 40 is seated on the valve seat member 34, the communication between the common rail 20 and the low-pressure side is blocked.

  The coil 44 is wound around the stator core 46. When the coil 44 is energized from the EDU 72 via the connector terminal 50, the valve member 38 is attracted toward the stator core 46 against the load of the spring 42, and accordingly the ball 40 is separated from the valve seat member 34. .

  Then, the fuel in the common rail 20 passes through the fuel passages 100, 102, 104, 106, 108, 110 formed in the valve body 32, the valve seat member 34, the cylinder 36, the stator core 46, the screw nut 48, and the like, and the fuel in the common rail 20 is returned to the return pipe 204. And is discharged to the fuel tank 12.

  A fuel injection valve 60 shown in FIG. 1 is mounted on each cylinder of a four-cylinder diesel engine, and injects fuel accumulated in the common rail 20 into the cylinder. The fuel injection valve 60 performs multi-stage injection including pilot injection and post injection before and after the main injection in one combustion cycle based on the operating state of the engine. The fuel injection valve 60 and the common rail 20 are connected by an injection pipe 202.

  The fuel injection valve 60 is a known electromagnetically driven injection valve that controls the fuel injection amount by controlling the pressure in the back pressure chamber that applies fuel pressure to the nozzle needle in the valve closing direction. The electromagnetic drive part of the fuel injection valve 60 is composed of a piezo actuator or an electromagnetic coil.

  The back pressure control valve 62 opens when the pressure in the back pressure chamber of the fuel injection valve 60 exceeds a predetermined pressure, and discharges the fuel in the back pressure chamber to the return pipe 204. This prevents the pressure in the back pressure chamber of the fuel injection valve 60 from exceeding a predetermined pressure.

  The ECU 70 is mainly composed of a microcomputer (microcomputer) mainly including a rewritable nonvolatile memory such as a CPU, a ROM, a RAM, and a flash memory, an input / output interface, and the like.

  The ECU 70 acquires the engine operating state from the output signals of various sensors such as the pressure sensor 22, the crank angle sensor 80, the cam angle sensor 82, the accelerator sensor 84 that detects the opening (ACC) of the accelerator pedal, and the water temperature sensor. And ECU70 takes in an output signal from various sensors, and controls an engine operating state.

  The crank angle sensor 80 outputs a pulse signal every time the crankshaft of the engine rotates by a predetermined angle. The ECU 70 detects the engine speed from the number of pulse signals output from the crank angle sensor 80 per unit time.

  The cam angle sensor 82 is a sensor that determines the cylinder positions of the four cylinders of the diesel engine. For example, the cam angle sensor 82 outputs a pulse signal that determines a specific cylinder position while the camshaft rotates once. Based on the pulse signals output from the crank angle sensor 80 and the cam angle sensor 82, the ECU 70 detects the crank angle position of the engine and discriminates the cylinder.

  The ECU 70 executes various controls of the fuel injection system 10 by executing a control program stored in the ROM or the flash memory. For example, the ECU 70 controls the discharge amount of the fuel supply pump 16 and the opening / closing of the pressure reducing valve 24 to detect the common rail pressure detected from the output signal of the pressure sensor 22 and the common rail pressure set based on the engine operating state. F / B control is performed to cause the common rail pressure to follow the target pressure based on the differential pressure from the target pressure.

Further, the ECU 70 controls the injection amount of the fuel injection valve 60, the injection timing, and the multi-stage injection pattern when pilot injection, post injection, etc. are performed before and after the main injection.
The ECU 70 outputs a pulse signal to the EDU 72 as an injection control signal for controlling the injection timing and the injection amount of the fuel injection valve 60.

The EDU 72 is a driving device for supplying a driving current or a driving voltage to the pressure reducing valve 24 and the fuel injection valve 60 based on a control signal output from the ECU 70.
(Common rail pressure control)
As shown in FIG. 3, the fuel injection system 10 of the present embodiment stops the fuel injection from the fuel injection valve 60 and rotates the engine when a predetermined idle stop condition such as the engine operating state is in an idle state is satisfied. Idle stop to stop.

  The ECU 70 performs common rail pressure control described below in order to quickly restart the engine from when the idle stop is started until the idle stop is released and fuel injection from the fuel injection valve 60 is started. Execute.

(1) While the engine is stopped The ECU 70 turns on the idle stop request flag when the idle stop condition is satisfied, and the residual pressure control pressure, which is the target pressure of the common rail pressure during the idle stop, is the target pressure (also referred to as idle pressure) during idle operation. .) Is set higher.

  When the idle stop request flag is turned on, the normal F / B control for the fuel supply pump 16 is stopped, the metering valve is closed, and the stop control for temporarily reducing the intake amount of the fuel supply pump 16 to 0 is executed. . That is, the fuel pumping from the fuel supply pump 16 is stopped and the pumping amount is set to zero.

When the idle stop request flag is turned on, the ECU 70 changes the control for the pressure reducing valve 30 from crank angle synchronization to time synchronization by timer interruption.
Then, the ECU 70 stops fuel injection from the fuel injection valve 60, and when the engine speed decreases to a predetermined speed, the ECU 70 opens the metering valve and sucks fuel into the fuel supply pump 16, and the fuel supply pump 16 The fuel is pumped from the common rail 20 to the common rail 20. In this case, the intake amount of the fuel supply pump 16, that is, the pumping amount is set to a fixed value by the metering valve.

  When the fuel is pumped from the fuel supply pump 16, the common rail pressure increases. If the actual pressure exceeds the target residual pressure control pressure during the suction control with the suction amount fixed by the metering valve, the pressure reducing valve 30 is opened based on the magnitude of the differential pressure between the actual pressure and the target pressure. The

  At this time, the pressure reducing valve 30 is controlled at the timing of time synchronization. For example, as shown in FIG. 4A, the opening / closing drive of the pressure reducing valve 30 is executed once in one driving cycle in which three cycles of time synchronization are defined as one cycle.

  As described above, the control for the pressure reducing valve 30 is started by interrupting at the timing of the time synchronization, but the time synchronization timing when the driving of the pressure reducing valve 30 is not permitted is thinned to open and close the time to open and close the time. Compared to the case where the pressure reducing valve 30 is driven to open and close at each synchronization timing, the operation noise caused by opening and closing the pressure reducing valve 30 can be reduced. Moreover, since the opening / closing drive frequency with respect to the pressure reducing valve 30 is reduced, there is an effect that the life of the pressure reducing valve 30 is extended.

  In FIG. 4A, the driving of the pressure reducing valve 30 is permitted only in one period out of the three time synchronization periods. However, the number of time synchronization periods permitting the driving is reduced pressure described later. As long as it is within the last energization time for one time with respect to the valve 30, you may straddle a several period of time synchronization within a drive period.

  As shown in FIG. 4B, the length of time for energizing the pressure reducing valve 30 is determined by the differential pressure ΔPc between the actual pressure and the target pressure and the common rail pressure at that time. Hereinafter, for pressure regulation control to reduce the common rail pressure, the energization time for the pressure reducing valve 30 determined by the differential pressure ΔPc between the actual pressure and the target pressure and the common rail pressure at that time is also referred to as “initial energization time”. . As the differential pressure ΔPc increases and the common rail pressure decreases, the initial energization time increases.

  However, the energization time for the pressure reducing valve 30 that is finally permitted in one driving cycle is the upper limit energization calculated from the maximum energizing time for the pressure reducing valve 30 and the energization duty that is the ratio of the energization on time within the driving cycle. Limited based on time.

  The maximum energization time is a time set so that the temperature increase amount of the pressure reducing valve 30 by one energization does not exceed a predetermined value. The energization duty is the duty of the energization time with respect to the drive cycle, which is set so that the temperature rise amount of the pressure reducing valve 30 does not exceed a predetermined value when the pressure reducing valve 30 is continuously opened and closed with a plurality of drive cycles. This is the upper limit.

  In FIG. 4A, driving of the pressure reducing valve 30 is not permitted in two of the three time-synchronized cycles, but the duty upper limit value is one time with three time-synchronized cycles as one cycle. It is set for the drive cycle. In addition, as shown in FIG. 4A, when the drive permission is given only in one cycle among the plurality of time synchronization cycles, the duty upper limit of the energization time for one permitted time synchronization cycle. A value may be set.

The energization time during which the pressure reducing valve 30 can be energized in one driving cycle is set to the minimum energization time among the initial energization time, the maximum energization time, and the upper limit energization time.
For example, as shown in FIG. 4C, consider a case where initial energization times t1 and t2 are calculated based on the differential pressure ΔPc and the common rail pressure at each driving cycle.

Since the initial energization time t1 is equal to or shorter than the maximum energization time and the ratio to the drive cycle is also equal to or less than the energization duty, the pressure reducing valve 30 is energized as it is with the length of the initial energization time t1.
On the other hand, the initial energization time t2 is longer than the initial energization time t1 because the differential pressure ΔPc is large. Then, although the initial energization time t2 is shorter than the maximum energization time, the ratio to the driving cycle exceeds the energization duty, so the guard process is executed. The guarded time is used as the energization time for the pressure reducing valve 30.

(2) Engine stop As shown in FIG. 3, when the engine is stopped, the fuel is not pumped from the fuel supply pump 16, so the increase in the common rail pressure is stopped. At this time, the ECU 70 executes stop control for closing the metering valve of the fuel supply pump 16 to reduce the amount of fuel leak from the fuel supply pump 16 as much as possible. Further, when the fuel injection valve 60 is a piezo actuator drive type, the amount of fuel leakage from the fuel injection valve 60 can be made almost zero.

Note that the above-described pressure regulation control of the common rail pressure by the pressure reducing valve 30 is continuously executed based on the differential pressure ΔPc between the actual pressure and the target pressure.
(3) Engine restart (3-1) Before discrimination of starting cylinder When the idle stop condition is not satisfied due to release of depression of the brake pedal or the like, the ECU 70 rotates the starter. Then, the intake amount of the fuel supply pump 16, that is, the pumping amount, is set to a fixed value for restart by the metering valve.

  Even if the starter is rotated, fuel is not injected from the fuel injection valve 60 until the determination of the start cylinder of the engine is completed. The ECU 70 opens and closes the pressure reducing valve 30 to leave the target pressure of the common rail pressure so that the fuel can be properly burned and the engine can be started when the determination of the starting cylinder is completed and the fuel injection valve 60 injects the fuel. Decrease pressure control pressure to starting pressure.

Until the determination of the starting cylinder is completed, the pressure regulation control by the time-synchronization of the common rail pressure by the pressure reducing valve 30 is continuously performed based on the differential pressure between the actual pressure and the starting pressure that is the target pressure. Is done.
(3-2) After discriminating the starting cylinder When the crankshaft and the camshaft rotate and the starting cylinder is discriminated from the output signals of the crank angle sensor 80 and the cam angle sensor 82, the ECU 70 sets the fuel injection valve 60 from the starting cylinder. Command fuel injection. In accordance with this, the idle stop request flag is turned off. As a result, the ECU 70 ends the control for adjusting the common rail pressure for idling stop based on time synchronization by the pressure reducing valve 30, and executes the F / B control based on the differential pressure between the actual pressure and the target pressure.

  When fuel is injected from the fuel injection valve 60 and the engine speed reaches a predetermined speed, the ECU 70 sets the target pressure of the common rail pressure from the start pressure to the idle pressure. Thereafter, the engine speed increases and reaches the target idle speed.

(Common rail pressure control routine)
Next, a common rail pressure control routine executed by the ECU 70 during idle stop will be described with reference to FIG. The routine of FIG. 5 is executed at a predetermined time period by a time interrupt. In FIG. 5, “S” represents a step.

  In S400, the ECU 70 determines whether or not an idle stop request is being made. This determination is made based on whether the idle stop request flag is on or off. As described above, the idle stop request flag is set to ON after the idle stop condition is satisfied and the fuel injection from the fuel injection valve 60 is stopped until the idle stop is released and the starting cylinder is determined. Otherwise, it is set to off.

  When the idle stop request flag is off (S400: No), the ECU 70 executes the F / B control of the common rail pressure by the normal metering valve and the pressure reducing valve 30 (S402), and ends this routine.

  When the idle stop request flag is on (S400: Yes), in S404, the ECU 70 opens or closes the metering valve to determine whether to perform the intake control or the stop control for the fuel supply pump 16.

  After executing the suction control (S404: Yes, S406) or the stop control (S404: No, S408), in S410, the ECU 70 determines whether it is time synchronization timing for executing the drive control on the pressure reducing valve 30 or not. To do. In the routine of FIG. 5, drive control for the pressure reducing valve 30 is permitted only once every three times of time synchronization, not across a plurality of time synchronization cycles.

  If it is time synchronization timing for executing the drive control and the drive condition is satisfied (S410: Yes), the ECU 70 turns on the drive permission flag in S412 and the drive condition must be satisfied instead of the timing for executing the drive control. If (S410: No), in S414, the ECU 70 turns off the drive permission flag.

Next, in S416, the ECU 70 determines whether or not the engine is in the engine start state before the start cylinder is determined in a state where the idle stop is released and the starter is driven.
If the engine is in the engine start state (S416: Yes), the ECU 70 sets the common rail pressure target pressure to the start pressure in S418. If the engine is not in the engine start state (S416: No), the ECU 70 sets the common rail pressure target pressure in S420. Set to residual pressure control pressure during idling stop.

  Next, in S422, the ECU 70 calculates a differential pressure ΔPc between the actual common rail pressure and the target pressure. In S424, the ECU 70 determines whether or not ΔPc is larger than a drive permission determination value that requires opening the pressure reducing valve 30 to reduce the common rail pressure, and whether or not the drive permission flag is ON. When the differential pressure ΔPc is equal to or smaller than the drive permission determination value, it is determined that the actual pressure is sufficiently close to the target pressure and it is not necessary to open the pressure reducing valve 30 to reduce the common rail pressure.

  If ΔPc is equal to or smaller than the drive permission determination value or the drive permission flag is OFF (S424: No), in S426, the ECU 70 sets the energization time to the pressure reducing valve 30 to 0 and does not open the pressure reducing valve 30. This routine ends.

  If ΔPc is larger than the drive permission determination value and the drive permission flag is ON (S424: Yes), in S428, the ECU 70 determines the initial energization time Ta from the common rail pressure and the differential pressure ΔPc based on FIG. Is calculated.

  In S430, the ECU 70 sets the smaller one of the aforementioned maximum energization time and upper limit energization time as the energization guard time Tb in which the pressure reducing valve 30 can be energized in one time synchronization period.

  If Ta <Tb (S432: Yes), the energization time for the pressure reducing valve 30 is set to the initial energization time Ta in this time synchronization period (S434). If Ta ≧ Tb (S432: No), the energization time for the pressure reducing valve 30 is set to the energization guard time Tb in the current time synchronization cycle (S436).

In S438, the ECU 70 opens and closes the pressure reducing valve 30 based on the final energization time set in S434 or S436, and ends this routine.
In the above-described embodiment, when the idle stop condition is satisfied, the fuel is pumped from the fuel supply pump 16 to the common rail 20 during the decrease in the engine speed until the fuel injection from the fuel injection valve 60 is stopped and the engine is stopped. Therefore, the common rail pressure can be increased and adjusted to a predetermined pressure.

  Thereby, even if fuel leaks from the fuel injection system 10 during the idle stop and the common rail pressure decreases, the fuel pressure required when restarting the engine from the idle stop can be maintained.

  In addition, when the idle stop condition is satisfied, the opening / closing drive for the pressure reducing valve 30 is controlled by switching from the angle synchronization by the crank angle to the time synchronization. The common rail pressure can be adjusted to a predetermined pressure by controlling the pressure reducing valve 30 at a certain time synchronized timing.

In the above embodiment, the ECU 70 corresponds to the fuel pressure control device of the present invention.
5 corresponds to the function executed by the pressure feed control means of the present invention, and the process of S422 corresponds to the function executed by the pressure detection means of the present invention, S406, S408, S408. 426 and S434 to S438 correspond to functions executed by the pressure control means of the present invention.

[Other Embodiments]
In the above-described embodiment, when the idle stop condition is satisfied, the fuel is pumped from the fuel supply pump 16 to the common rail 20 during the decrease in the engine speed until the fuel injection from the fuel injection valve 60 is stopped and the engine stops. The pressure was increased, and the pressure reducing valve 30 was driven to open and close to adjust the common rail pressure to a predetermined residual pressure control pressure. On the other hand, the common rail pressure may be adjusted to a predetermined residual pressure control pressure only by controlling the pumping amount from the fuel supply pump 16 by the metering valve.

Alternatively, the opening / closing drive for the pressure reducing valve 30 may be executed at each time synchronization timing without thinning out the time synchronization timing.
In the above embodiment, the functions of the pressure feed control means, the pressure detection means, and the pressure control means are realized by the ECU 70 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.

10: fuel injection system, 16: fuel supply pump, 20 common rail, 30: pressure reducing valve, 60: fuel injection valve, 70: ECU (fuel pressure control device, pressure feed control means, pressure detection means, pressure control means)

Claims (6)

A common rail that accumulates fuel,
A fuel supply pump for pumping fuel to the common rail;
A fuel injection valve that injects fuel accumulated in the common rail into each cylinder of the internal combustion engine;
A fuel pressure control device that is applied to a fuel injection system that controls a common rail pressure that is a fuel pressure in the common rail.
A pumping control means for controlling fuel pumping of the fuel supply pump;
Pressure detecting means for detecting the common rail pressure;
When the idling stop is started, the pressure detection unit detects the pressure from the fuel supply pump by instructing the pressure control unit during a decrease in the rotational speed of the internal combustion engine until the internal combustion engine stops. Pressure control means for adjusting the common rail pressure to a predetermined pressure;
A fuel pressure control device comprising:   The fuel pressure control device according to claim 1, wherein the predetermined pressure is set higher than a starting pressure for starting the internal combustion engine from an idle stop. The fuel injection system includes a pressure reducing valve that opens by energization control and discharges the fuel in the common rail to reduce the common rail pressure,
The pressure control means controls the pressure reducing valve when the common rail pressure is higher than the predetermined pressure from when the idle stop is started to when the idle stop is released and fuel injection from the fuel injection valve is started. And reducing the common rail pressure,
The fuel pressure control device according to claim 1, wherein the fuel pressure control device is a fuel pressure control device.   When the fuel injection from the fuel injection valve is stopped and the operation state of the internal combustion engine shifts from the idle operation state to the idle stop state, the pressure control means switches the rotation angle synchronization of the internal combustion engine from time synchronization to the pressure reduction. The fuel pressure control device according to claim 3, wherein the valve is controlled. A plurality of periods of the time synchronization are set to one period of the driving period;
The pressure control means opens the pressure reducing valve once in one driving cycle with a plurality of time-synchronized cycles as one cycle, thereby reducing the common rail pressure.
The fuel pressure control device according to claim 4.   The pressure control means includes an energization time for the pressure reducing valve that is calculated based on a differential pressure between the predetermined pressure and the common rail pressure, and a maximum energization time that is permitted by one energization of the pressure reducing valve; The minimum energization time out of the upper energization time calculated from the energization duty allowed for the pressure reducing valve in the drive cycle having one cycle or a plurality of cycles as time synchronization is one drive cycle. The fuel pressure control device according to claim 4, wherein an energization time for energizing the pressure reducing valve is set.

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