JP2010019088A - Idling stop control device and fuel injection system using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an idling stop control device quickly re-starting an internal combustion engine from an idling stop state and a fuel injection system using the same. <P>SOLUTION: When idling stop execution conditions are satisfied, the idling stop control device calculates the target pressure PcS of common rail pressure optimum for restarting an engine based on an intake air temperature and a water temperature (S300), and regulates common rail pressure to the target pressure (S302). If a difference between the calculated target pressure PcS and the current common rail pressure Pc is not smaller than a prescribed value ΔPc or a difference between a current water temperature TENG-C and a water temperature TENG-P at a time of the last common rail pressure regulation is not lower than prescribed value ΔTENG during the idling stop (S304:No), the idling stop control device recalculates optimum common rail pressure for restarting the engine (S308), and regulates common rail pressure to the target pressure (S310). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an idle stop control device that controls the pressure in a common rail when performing idle stop, and a fuel injection system using the idle stop control device.

  2. Description of the Related Art Conventionally, in a common rail type fuel injection system in which fuel pumped from a fuel supply pump and accumulated in a common rail is injected into each cylinder of an internal combustion engine from a fuel injection valve, when the internal combustion engine is stopped, , Also referred to as common rail pressure). This is because it is not necessary to maintain the common rail pressure when the internal combustion engine is stopped, and the high pressure fuel is prevented from being ejected during maintenance work.

  In particular, as disclosed in Patent Document 1, when using a fuel injection valve with a small amount of static leakage from the high pressure side to the low pressure side when power is off, the internal combustion engine is stopped and the fuel is Since the amount of fuel leaking with the energization to the injection valve turned off is small, the common rail pressure is hardly reduced from the pressure when the internal combustion engine is stopped. Therefore, when using such a fuel injection valve with a small static leak amount, the common rail pressure is reduced when the internal combustion engine is stopped in consideration of maintenance work and the like as described above. .

Further, in the common rail fuel injection system, a technique for controlling the common rail pressure based on the intake air temperature at the time of starting is known in order to improve the startability of the internal combustion engine (see, for example, Patent Document 2).
JP 2000-45902 A JP 2007-321623 A

  By the way, when waiting for a signal or stopping and stopping for a short time, in order to reduce fuel consumption and exhaust gas, an idle stop that automatically stops the internal combustion engine by stopping fuel injection to the internal combustion engine is performed. Yes.

  When the idling stop is performed, it is desirable that when the internal combustion engine is restarted by releasing the brake pedal and then depressing the accelerator pedal, the engine can be restarted quickly.

  However, as described above, when the common rail pressure is reduced when the internal combustion engine is stopped, when the idle stop state is released and the internal combustion engine is restarted, a time delay occurs until the common rail pressure is increased to the restart required. There is a problem that it takes a long time to restart.

  On the other hand, if the internal combustion engine is stopped without reducing the common rail pressure, it cannot be predicted whether the common rail pressure at that time is suitable for restarting the internal combustion engine after the release of the idle stop state. When deviating from the pressure suitable for restarting the internal combustion engine after canceling the idle stop state, a time delay occurs until the pressure is adjusted to the common rail pressure required for restart, and the time until restart can be increased. There is a problem.

  Also, as in Patent Document 2, even when the common rail pressure is controlled based on the intake air temperature at the time of starting, a time delay occurs until the common rail pressure required for restarting is increased, and the time until restarting is possible. There is a problem of becoming longer.

  The present invention has been made to solve the above problems, and an object thereof is to provide an idle stop control device that quickly restarts an internal combustion engine from an idle stop state and a fuel injection system using the idle stop control device.

  In many cases, the interval from the idling stop to the release of the idling stop state to the restarting of the internal combustion engine is considered to be about several seconds to several tens of seconds. Therefore, it is considered that the stop environment of the internal combustion engine, such as the intake air temperature and the water temperature when restarting the internal combustion engine from the idle stop state, has hardly changed from the stop environment of the internal combustion engine when performing the idle stop.

  Therefore, according to the first to sixth aspects of the present invention, the target pressure calculation means is a target pressure suitable for restarting the internal combustion engine as the pressure in the common rail when the internal combustion engine is stopped and the idle stop is performed. The pressure control means adjusts the pressure in the common rail to the target pressure calculated by the target pressure calculation means.

  Thus, when the internal combustion engine is restarted after releasing the idle stop state, the pressure in the common rail is maintained at a pressure suitable for restarting. As a result, when the internal combustion engine is restarted, fuel can be injected from the fuel injection valve into each cylinder of the internal combustion engine at a fuel pressure suitable for restarting, so that the internal combustion engine can be restarted quickly from the idle stop state.

According to the second aspect of the present invention, the target pressure calculated by the target pressure calculating means is higher than a pressure suitable for restarting the internal combustion engine.
Thereby, even if the pressure in the common rail when releasing the idle stop state and restarting the internal combustion engine due to the fuel leak during the idle stop is lower than the target pressure regulated when performing the idle stop, When restarting the internal combustion engine, the pressure in the common rail can be set to a pressure suitable for restarting.

  According to the third aspect of the present invention, when the recalculation determination means determines that the target pressure needs to be recalculated based on the stop environment of the internal combustion engine or the pressure in the common rail, the target pressure calculation means The target pressure is recalculated based on the environment or the pressure in the common rail, and the pressure control means adjusts the pressure in the common rail to the target pressure recalculated by the target pressure calculation means.

  As a result, even if a change occurs in the stop environment of the internal combustion engine or the pressure in the common rail during the idle stop, the target pressure suitable for restarting the internal combustion engine is set based on the change in the pressure in the stop environment or the common rail. The pressure in the common rail can be adjusted. As a result, even if a change occurs in the stop environment of the internal combustion engine or the pressure in the common rail during the idle stop, the internal combustion engine can be promptly restarted from the idle stop state.

  In addition, as described in claim 4, as a stop environment of the internal combustion engine, whether the difference between the water temperature when the pressure in the common rail is finally adjusted to the target pressure and the current water temperature is a predetermined value or more Alternatively, when the difference between the target pressure and the current pressure in the common rail is equal to or greater than a predetermined value, it is desirable to determine that the target pressure needs to be recalculated.

According to the fifth aspect of the present invention, the fuel injection valve has a small amount of static leakage when energization is turned off.
Thereby, since the pressure drop in the common rail during idle stop can be reduced, the internal combustion engine can be restarted in the state of the target pressure adjusted when the idling stop is performed.

  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.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
A fuel injection system according to a first embodiment of the present invention is shown in FIG.

(Fuel injection system 10)
The fuel injection system 10 of the present embodiment is for supplying fuel to, for example, a four-cylinder diesel engine (hereinafter also simply referred to as “engine”) 2 for an automobile, and supplies fuel to the common rail 20. A high-pressure pump 14, an electric pump 18, a common rail 20 that stores high-pressure fuel, a fuel injection valve 30 that injects high-pressure fuel supplied from the common rail 20 into each cylinder of the engine 2, and an electronic control device that controls this system ( ECU: Electronic Control Unit) 40. The high-pressure pump 14 incorporates a feed pump that pumps fuel from the fuel tank 12.

  The high-pressure pump 14 as a fuel supply pump is a known pump that pressurizes the fuel sucked into the pressurizing chamber from the feed pump by reciprocating the plunger as the cam of the camshaft rotates. Plural plungers of the high pressure pump 14 are installed around one cam.

  The metering valve 16 serving as a metering actuator is installed on the suction side of the high-pressure pump 14 and regulates the amount of fuel sucked by the high-pressure pump 14 during the suction stroke by current control. Then, by adjusting the fuel intake amount, the fuel discharge amount of the high-pressure pump 14 is adjusted.

  The electric pump 18 is a separate system from the high-pressure pump 14 and directly pumps the fuel in the fuel tank 12 to the common rail 20 via the check valve 26. As will be described later, the electric pump 18 is a dedicated pump for increasing the common rail pressure during idling stop, and it is sufficient that the common rail pressure during idling stop can be increased by pumping fuel to the common rail 20. Therefore, the discharge amount of the electric pump 18 is smaller than that of the feed pump built in the high-pressure pump 14.

  The common rail 20 is provided with a pressure sensor 22 that detects internal fuel pressure (common rail pressure). The pressure reducing valve 24 reduces the common rail pressure by discharging the fuel inside the common rail 20 to the fuel tank 12 side. The pressure reducing valve 24 is an electromagnetic valve that opens and closes according to a command from the ECU 40. The check valve 26 allows fuel flow from the electric pump 18 to the common rail 20 and prohibits fuel flow from the common rail 20 to the electric pump 18.

The engine 2 is provided with a rotational speed sensor 28 that detects the rotational speed of the engine 2 as a sensor that detects the operating state.
Further, as other sensors for detecting the driving state, an accelerator sensor for detecting an accelerator opening that is an operation amount of an accelerator pedal, a temperature sensor for detecting a temperature of intake air (intake air temperature), and a temperature of coolant (water temperature), respectively. Etc. are provided in the fuel injection system 10.

  The fuel injection valve 30 is, for example, a known injection valve that controls the lift of the nozzle needle that opens and closes the nozzle hole with the pressure in the control chamber, as disclosed in Patent Document 1. In the fuel injection valve disclosed in Patent Document 1, the movable member abuts against the seat portion to cut off the communication between the high pressure control chamber and the low pressure side, and the nozzle is injected by holding the control chamber at a high pressure. The hole is closed to block fuel injection. Accordingly, in the fuel injection valve 30 adopting this configuration, the static leak amount from the high pressure control chamber to the low pressure side is reduced in a state where the engine 2 is stopped and the power supply to the fuel injection valve 30 is turned off. It is very small. As a result, since the amount of fuel leakage from the fuel injection system 10 can be reduced during the idle stop, the common rail pressure can be maintained at a predetermined pressure during the idle stop.

  The ECU 40 constituting the idle stop control device is constituted by a microcomputer having a CPU, a ROM, a RAM, a flash memory, an input / output interface, and the like. The ECU 40 takes in detection signals from various sensors including the pressure sensor 22 and the rotation speed sensor 28, and controls the engine operating state. For example, the ECU 40 controls the discharge amount of the high-pressure pump 14, the fuel injection amount of the fuel injection valve 30, the fuel injection timing, and the multistage injection pattern when pilot injection, post injection, etc. are performed before and after the main injection.

Next, each means of the ECU 40 that functions by a control program stored in a storage device such as a ROM or a flash memory of the ECU 40 will be described.
(Idle state determination means)
The ECU 40 determines that the idle stop execution condition is satisfied when the vehicle stops, the vehicle speed is 0, the accelerator opening is 0, and the brake is turned on. The ECU 40 may determine that the idle stop execution condition is satisfied when a predetermined time elapses after the vehicle speed becomes zero. On the other hand, when the brake is turned off during the idle stop, the ECU 40 determines that the idle stop state is released.

(Target pressure calculation means)
When the idling stop execution condition is satisfied, the ECU 40 calculates the target pressure of the optimum common rail pressure for restarting the engine 2 when the idling stop state is released based on the stop environment when the engine 2 stops. To do. As the stop environment of the engine 2, intake air temperature, water temperature, and the like are conceivable.

  The ECU 40 may calculate the target pressure higher than the optimum common rail pressure when the engine 2 is restarted, taking into account that fuel leaks from the fuel injection valve 30 and the like during idle stop and the common rail pressure decreases.

  In addition, when the recalculation determination unit described later determines that the target pressure needs to be recalculated during the idling stop, the ECU 40 recalculates the target pressure based on the stop environment of the engine 2 or the common rail pressure.

(Recalculation judgment means)
If the stop environment of the engine 2 changes during the idling stop, the ECU 40 includes an optimum common rail pressure when the idling stop state is released and the engine 2 is restarted, including the target pressure calculated when the idling stop execution condition is satisfied. May change from the last calculated target pressure. As the stop environment of the engine 2, the intake air temperature and the water temperature can be considered as described above.

  Thus, if the target pressure suitable for restarting changes during idle stop, the engine 2 may not be able to be restarted quickly when the idle stop state is canceled with the adjusted common rail pressure maintained. . Therefore, the ECU 40 determines whether to recalculate the target pressure based on a change in the stop environment of the engine 2.

In addition, during idle stop, the common rail pressure adjusted to the target pressure may decrease from the target pressure due to fuel leakage.
In such a case, the ECU 40 determines that the engine 2 cannot be restarted promptly when the idle stop state is canceled with the common rail pressure lowered from the target pressure. Therefore, the ECU 40 determines whether to recalculate the target pressure based on the difference between the last calculated target pressure and the current commonlay pressure.

  Further, when the engine 2 is started to operate the air conditioner during idle stop, the pressure is too high with the common rail pressure adjusted to the last calculated target pressure, and the noise and vibration of the engine 2 are large. If it judges that it will become, ECU40 will judge that it is necessary to recalculate and reduce the target pressure of common rail pressure at the time of starting engine 2 in order to operate an air conditioner.

(Pressure control means)
If the common rail pressure detected by the pressure sensor 22 is lower than the target pressure until the engine 2 is stopped when the idle stop execution condition is satisfied and the target pressure calculation means calculates the target pressure, the ECU 40 adjusts. By controlling the amount valve 16 and increasing the amount of fuel that the high-pressure pump 14 pumps to the common rail 20, the common rail pressure is increased and adjusted to the target pressure.

  On the other hand, when the common rail pressure detected by the pressure sensor 22 is higher than the target pressure, the ECU 40 opens the pressure reducing valve 24 and discharges fuel from the common rail 20 to reduce the common rail pressure and adjust it to the target pressure. Alternatively, the amount of fuel pumped by the high-pressure pump 14 to the common rail 20 may be reduced by controlling the metering valve 16 so as to reduce the common rail pressure to adjust the target pressure.

  The ECU 40 gradually cuts the fuel injection from the fuel injection valve 30 while adjusting the common rail pressure to the target pressure, and stops the engine 2. Therefore, when the engine 2 stops, the common rail pressure is adjusted to the target pressure.

  Further, when the recalculation determination unit determines that the target pressure needs to be recalculated during the idling stop and the target pressure calculation unit recalculates the target pressure, the ECU 40 controls the electric pump 18 or the pressure reducing valve 24. Adjust the common rail pressure to the recalculated target pressure.

  For example, when the common rail pressure detected by the pressure sensor 22 is lower than the recalculated target pressure, the ECU 40 increases the common rail pressure to the target pressure by driving the electric pump 18 and pumping fuel to the common rail 20. .

  On the other hand, when the common rail pressure detected by the pressure sensor 22 is higher than the recalculated target pressure, the ECU 40 opens the pressure reducing valve 24 and discharges fuel from the common rail 20 to reduce the common rail pressure to the target pressure. To do. When reducing the common rail pressure, the ECU 40 controls the energization of the fuel injection valve 30 to discharge the fuel in the control chamber to the low pressure side so that the nozzle needle 32 is lifted and fuel is not injected from the injection hole 200. May be.

(Common rail pressure control)
FIG. 2 shows a pressure control routine for controlling the common rail pressure suitable for restarting the engine 2 during the idling stop or during the idling stop. The routine shown in FIG. 2 is executed when the idle stop execution condition is satisfied and the idle stop flag (flag _IS ) is turned on. The idle stop flag (flag _IS ) is set to OFF when the condition for canceling the idle stop state is satisfied. In FIG. 2, “S” represents a step.

In S300, the ECU 40 calculates the target pressure (Pc _S ) of the optimum common rail pressure for releasing the idle stop state and restarting the engine 2 based on the intake air temperature and the water temperature that are the current stop environment of the engine 2. . At this time, as described above, the target pressure may be calculated to be higher than the optimum common rail pressure when the engine 2 is restarted in consideration of fuel leak during idling stop.

  In S302, the ECU 40 adjusts the common rail pressure to the target pressure by controlling the discharge amount of the high-pressure pump 14 or the fuel discharge amount from the pressure reducing valve 24 while gradually cutting the injection amount of the fuel injection valve 30.

In S304, the ECU 40 determines whether the idle stop flag (flag _IS ) is 0 (off) and the release condition for the idle stop state is satisfied. If the idle stop flag (flag _IS ) is 0 and the conditions for canceling the idle stop state are satisfied (S304: Yes), the ECU 40 ends this routine and shifts to restart control of the engine 2.

When the idling stop flag (flag _IS ) is 1 (on) and the idling stop execution condition is satisfied (S304: No), in S306, the ECU 40 performs one of the following formulas (1) and (2). Is determined. Equation (1) represents that the difference between the calculated target pressure (Pc _S ) and the current common rail pressure (Pc) is equal to or greater than a predetermined value (ΔPc). Equation (2) indicates that the difference between the current water temperature (T _ENG - _C ) and the water temperature (T _ENG - _P ) when the common rail pressure was last adjusted is greater than or equal to a predetermined value (ΔT _ENG ). Yes.

| Pc _S −Pc | ≧ ΔPc (1)
| T _{ENG -C} -T _{ENG -P} | ≧ ΔT _ENG (2)
When both of the formula (1) and the formula (2) are not satisfied (S306: No), the ECU 40 proceeds to S304 without recalculating the target pressure.

When Expression (1) is satisfied (S306: Yes), in S308, the ECU 40 recalculates the optimum common rail pressure for restarting the engine 2 based on the current intake air temperature and water temperature. Note that if the formula (1) is satisfied because the current common rail pressure (Pc) is lower than the target pressure (Pc _S ), the ECU 40 determines that the common rail pressure has decreased due to fuel leak, and the engine 40 The target pressure may be calculated higher than the optimum common rail pressure for restarting 2.

  When Expression (2) is satisfied (S306: Yes), in S308, the ECU 40 calculates the target pressure of the optimum common rail pressure for restarting the engine 2 based on the current intake air temperature and water temperature.

  When the target pressure is calculated in S308, the ECU 40 controls the electric pump 18 or the pressure reducing valve 24 to adjust the common rail pressure to the target pressure in S310, and the process proceeds to S304.

  In the first embodiment described above, the target pressure suitable for restarting the engine 2 is calculated when the idling stop is performed, and the common rail pressure is adjusted to the calculated target pressure. Thus, when the engine 2 is restarted, fuel can be injected from the fuel injection valve 30 to each cylinder of the engine 2 at a common rail pressure suitable for restarting. As a result, the engine 2 can be restarted quickly.

  In addition, if a change occurs in the stop environment of the engine 2 or the common rail pressure during the idle stop, the target pressure is recalculated and the common rail pressure is readjusted. Thereby, even if a change occurs in the stop environment of the engine 2 or the common rail pressure, the engine 2 can be restarted quickly.

[Second Embodiment]
A fuel injection system according to a second embodiment of the present invention is shown in FIG. In addition, the same code | symbol is attached | subjected to the substantially same component as 1st Embodiment.

  In the fuel injection system 50 of the second embodiment, the high-pressure pump 60 that is a fuel supply pump is supplied with the fuel in the fuel tank 12 from the electric pump 62. The electric pump 62 supplies fuel to the high-pressure pump 60 during engine operation, and in the case of increasing the common rail pressure during idle stop, the electric pump 62 pumps fuel to the common rail 20 via the high-pressure pump 60 according to a command from the ECU 40. To increase the common rail pressure.

[Other Embodiments]
In the above embodiment, during the idle stop, the difference between the target pressure and the current common rail pressure becomes a predetermined value or more, or the difference between the water temperature when the common rail pressure is finally adjusted and the current water temperature is the predetermined value or more. Then, the target pressure was recalculated, and the common rail pressure was adjusted to the recalculated target pressure. On the other hand, if the target pressure is calculated and the common rail pressure is adjusted to the target pressure at the time of idling stop, the common rail pressure is adjusted first without recalculating the target pressure until the idle stop state is released. Then, the engine 2 may be restarted. This is because the period of the idling stop state is often about several seconds to several tens of seconds, and it is estimated that the stop environment of the engine 2 and the common rail pressure hardly change during that period. In particular, when the fuel injection valve 30 having a small static leak amount when the energization is turned off is used as in the present embodiment, the common rail pressure is considered to hardly decrease during the idle stop.

  In the above embodiment, the pressure reducing valve 24 is provided on the common rail 20 in order to reduce the common rail pressure. In contrast, if the common rail pressure is reduced by discharging the fuel in the control chamber to the low pressure side to the extent that fuel is not injected from the fuel injection valve 30, the present invention is also applied to a fuel injection system that does not use the pressure reducing valve 24. Applicable.

  Further, as in the above-described embodiment, if the fuel injection valve has a small static leak amount by blocking the communication between the control chamber and the low pressure side by the movable member coming into contact with the seat portion, the control chamber of the fuel injection valve The opening / closing control may be either a solenoid type or a piezo actuator type.

  On the other hand, you may employ | adopt the fuel injection valve of the structure which interrupts | blocks a fuel injection by interrupting | blocking communication with a control chamber and a low voltage | pressure side at a sliding location. In the fuel injection valve having this configuration, the static leak amount is increased as compared with the fuel injection valve 30 of the above embodiment. However, considering that the period of the idle stop state is a short period of about several seconds to several tens of seconds and the decrease in the common rail pressure during the idle stop is not so large, the common rail pressure is reduced when releasing the idle stop state. Even if the pressure drops from the target pressure, the common rail pressure can be adjusted to the target pressure in a short time.

  In the above embodiment, the functions of the target pressure calculation means, the pressure control means, and the recalculation determination means are realized by the ECU 40 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.

The block diagram which shows the fuel-injection system by 1st Embodiment. The flowchart which shows the control routine of a common rail pressure. The block diagram which shows the fuel-injection system by 2nd Embodiment.

Explanation of symbols

2: diesel engine (internal combustion engine), 10, 50: fuel injection system, 14, 60: high pressure pump (fuel supply pump), 18, 62: electric pump, 20: common rail, 24: pressure reducing valve, 30: fuel injection valve , 40: ECU (idle stop control device, target pressure calculation means, pressure control means, recalculation determination means)

Claims (6)

In an idle stop control device applied to a fuel injection system that injects fuel, which is pumped from a fuel supply pump and accumulated in a common rail, into each cylinder of an internal combustion engine from a fuel injection valve,
Target pressure calculating means for calculating a target pressure suitable for restarting the internal combustion engine as the pressure in the common rail when the internal combustion engine is stopped and idle stop is performed;
Pressure control means for adjusting the pressure in the common rail to the target pressure calculated by the target pressure calculation means when performing idle stop;
An idle stop control device comprising:   2. The idle stop control device according to claim 1, wherein the target pressure calculated by the target pressure calculating means is higher than a pressure suitable for restarting the internal combustion engine. Re-calculation determining means for determining whether the target pressure needs to be recalculated based on the stop environment in which the internal combustion engine is stopped or the pressure in the common rail during idle stop,
When the recalculation determination unit determines that the target pressure needs to be recalculated, the target pressure calculation unit recalculates the target pressure based on the stop environment of the internal combustion engine or the pressure in the common rail, 3. The idle stop control device according to claim 1, wherein the pressure control unit adjusts the pressure in the common rail to the target pressure recalculated by the target pressure calculation unit.   The recalculation determination means is configured such that the difference between the water temperature when the pressure in the common rail is finally adjusted to the target pressure and the current water temperature is a predetermined value or more, or the target pressure and the current common rail The idle stop control device according to claim 3, wherein when the difference from the pressure is greater than or equal to a predetermined value, it is determined that recalculation of the target pressure is necessary.   The idle stop control device according to any one of claims 1 to 4, wherein the fuel injection valve has a small amount of static leakage when energization is turned off. A fuel injection valve for injecting fuel into each cylinder of the internal combustion engine;
A common rail for accumulating fuel to be supplied to the fuel injection valve;
A fuel supply pump for pumping fuel to the common rail;
Idle stop control device according to any one of claims 1 to 5,
A fuel injection system comprising:

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