JP2005147019A - Fuel pressure control device for cylinder injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fuel pressure control device for a cylinder injection type internal combustion engine increasing fuel pressure inside a fuel rail immediately before engine stop to improve restartability, and suppressing HC amount in exhaust gas at the time of restart. <P>SOLUTION: This fuel pressure control device for the cylinder injection type internal combustion engine is provided with a fuel pressure sensor 19 for detecting fuel pressure PF supplied to an injector 15, fuel pressure control means 18, 30 for variably setting the detected fuel pressure PF as feedback information, and a state-immediately-before-stop determining means for determining a state of the internal combustion engine immediately before stop. The fuel pressure control means 18, 30 increase the fuel pressure PF after the state immediately before stop is determined. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel pressure control apparatus in a direct-injection and spark-ignition in-cylinder injection internal combustion engine that directly injects and burns fuel supplied from a fuel pump into combustion chambers of a plurality of cylinders. To an internal combustion engine that can be started by injecting and igniting a specific cylinder in an expansion stroke in a stopped state (no cranking motor is required or a cranking assisting starter is provided) On the other hand, the present invention relates to a fuel pressure control device for a direct injection internal combustion engine provided with a fuel pressure control means for improving startability.

Conventionally, direct-injection and spark-ignition in-cylinder injection internal combustion engines in which fuel supplied from a fuel pump is directly injected into combustion chambers of a plurality of cylinders via fuel rails and burned by spark ignition of a spark plug Is well known.
As a starting device for this type of in-cylinder injection internal combustion engine, an expansion stroke cylinder detecting means for detecting a cylinder in an expansion stroke when the operation of the internal combustion engine is stopped, and an expansion according to a predetermined start signal for the internal combustion engine Proposed is provided with an injection control means for injecting fuel into the stroke cylinder, and an ignition control means for igniting the expansion stroke cylinder when a predetermined delay time has elapsed after the fuel injection by the injection control means. (For example, refer to Patent Document 1).

Patent Document 1 aims to improve the startability by sufficiently vaporizing the fuel by performing ignition after a predetermined delay time has elapsed.
In addition, the conventional fuel pressure control device for a direct injection internal combustion engine related to Patent Document 1 includes so-called variable fuel pressure control means for variably setting the pressure of fuel supplied to the injector (fuel pressure in the fuel rail). Is provided.

  In a conventional fuel pressure control device for a direct injection internal combustion engine, the target fuel pressure is generally set lower than usual in order to weaken the spray penetration force in the low rotation range. Further, before the internal combustion engine is stopped, for example, the engine speed is often as low as the idle engine speed, and the fuel pressure is often low. In some cases, the fuel pressure is lowered before the internal combustion engine is stopped in consideration of the problem of sealing of the fuel system piping.

That is, in order to start without using a starter motor and inject a fuel into a specific cylinder that is stopped in the expansion stroke and ignite, in order to improve startability, it is sufficient to facilitate ignition. It is necessary to inject the atomized fuel.
At this time, if the fuel is injected at a high pressure, the atomization is promoted. However, in general, the fuel pressure when the engine is stopped or after the stop is controlled to decrease before the stop due to the sealing problem, and the control is not performed. However, there is a phenomenon that naturally decreases with time.

JP 2002-004929 A

  According to a conventional fuel pressure control device for a direct injection internal combustion engine, the target fuel pressure is set to a low value when the internal combustion engine is running at a low speed, and the fuel pressure is low before the stop and the fuel pressure is lowered before the stop. Therefore, since the fuel pressure at the time of restart after the stop is lowered, the atomization of the fuel is not promoted, and the startability is deteriorated and the amount of HC (Hydro-Carbon) in the exhaust gas increases. there were.

  Further, in an internal combustion engine that performs automatic processing such as automatic stop and automatic start, a determination unit that determines an expansion stroke cylinder is provided, and ignition is performed after injecting fuel into the expansion stroke cylinder in a stopped state, thereby igniting the internal combustion engine. Enables start-up and eliminates the need for a cranking motor (or has a start-up device for cranking assistance), but after stopping the internal combustion engine, the fuel pressure in the fuel rails is due to the tightness of the fuel system piping. Since the fuel pressure gradually decreases with time, if the period from the stop to the restart is long, the fuel pressure decreases significantly, and the fuel is injected into the expansion stroke cylinder (the cylinder pressure is relatively high). There is a problem that the restartability is deteriorated, and restarting may be impossible.

  The present invention has been made in order to solve the above-described problem. In the case of a stop state in which the next restart is known in advance, the fuel pressure is increased and the opportunity to start without using a starter motor is possible. It is an object of the present invention to obtain a fuel pressure control device for a direct injection internal combustion engine that improves the restartability after stopping the internal combustion engine and suppresses the amount of HC in the exhaust gas at the time of restart.

  A fuel pressure control apparatus for a direct injection internal combustion engine according to the present invention is supplied to an injector for directly injecting fuel into a plurality of cylinders, an ignition plug for igniting fuel in each cylinder, and an injector. A fuel pressure sensor for detecting the fuel pressure as a fuel pressure, a fuel pressure control means for variably setting the fuel pressure using the fuel pressure detected by the fuel pressure sensor as feedback information, and a state immediately before stopping determining means for determining a state immediately before stopping the internal combustion engine. The fuel pressure control means increases the fuel pressure after the state immediately before stop is determined by the state determination means immediately before stop.

  According to the present invention, a high fuel pressure can be maintained when the engine is stopped, fuel can be atomized at the time of restart, the restartability can be improved, and the amount of HC in the exhaust gas can be reduced.

Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram schematically showing a fuel pressure control apparatus for a direct injection internal combustion engine according to Embodiment 1 of the present invention. For example, FIG. 1 shows a case where the control apparatus is configured by a control apparatus for an internal combustion engine mounted on a vehicle. .
FIG. 2 is a block diagram showing the fuel system of the fuel pressure control apparatus for a direct injection internal combustion engine according to Embodiment 1 of the present invention.

  In FIG. 1, an engine 10 constituting a cylinder injection type internal combustion engine has a plurality of cylinders, and high pressure fuel is directly injected into a combustion chamber 11 of each cylinder via a fuel rail 12. It is configured. Here, in order to avoid the complexity of the drawings, a configuration related to only one cylinder is typically shown.

A crank angle sensor 13 is provided on the crankshaft of the engine 10, and a cam angle sensor 14 is provided on the camshaft.
The crank angle sensor 13 outputs a pulse signal corresponding to the rotational speed Ne of the engine 10.

In each combustion chamber 11 for each cylinder, an injector 15 for directly injecting fuel and an ignition plug 16 for generating a spark for burning the fuel are provided.
Further, a camshaft for the exhaust valve (or intake valve) of the engine 10 is provided with a pump cam 17 that rotates integrally with the camshaft.

The fuel pressure control means 18 provided in association with the pump cam 17 is a high pressure pump whose output port communicates with the fuel rail 12, and is driven so that the fuel pressure PF in the fuel rail 12 matches the target fuel pressure PFo (described later). To do).
The target fuel pressure PFo is variably set based on, for example, the rotational speed Ne of the engine 10 or load information.
The fuel rail 12 is provided with a fuel pressure sensor 19 for outputting the fuel pressure PF in the fuel rail 12 as feedback information.

A fuel tank 20 is communicated with the input port of the fuel pressure control means 18.
A feed pump 21 for pumping up fuel is provided in the fuel tank 20. On the output side of the feed pump 21, a filter 22 for purifying the fuel and a regulator 23 for adjusting the pressure of fuel supplied to the fuel pressure control means 18 are provided.

In FIG. 2, a specific configuration of the fuel pressure control means 18 and the fuel rail 12 is shown in relation to the fuel system from the fuel tank 20.
The injector 15, the fuel pressure control means 18, and the feed pump 21 in the fuel tank 20 are driven and controlled by an electronic control unit (hereinafter referred to as “ECU”) 30.

  In FIG. 2, the ECU 30 detects the engine rotation speed Ne based on output information from the crank angle sensor 13 and discriminates each cylinder based on output information from the cam angle sensor 14.

  Further, the ECU 30 determines the stroke of each cylinder (at least one of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke), calculates the fuel injection and ignition timing of each cylinder, and drives and controls various actuators. To do. Further, the ECU 30 feedback-controls the fuel pressure PF in the fuel rail 12 to the target fuel pressure based on the output information (fuel pressure PF) from the fuel pressure sensor 19.

The fuel pressure control means 18 includes a piston 31 that moves up and down by the pump cam 17, a pressure increasing chamber 32 that works in conjunction with the piston 31, and a spill valve 33 that adjusts the amount of fuel introduced into the fuel rail 12.
The spill valve 33 includes a coil 34 that moves upward when energized, a spring 35 that biases the coil 34 downward, and a valve body 36 that is provided at the lower end of the coil 34.

A check valve 37 is inserted on the input port side of the pressure increasing chamber 32 and the output port side to the fuel rail 12.
The fuel rail 12 is provided with a relief valve 38. The relief valve 38 is opened when the fuel pressure PF in the fuel rail 12 reaches the opening pressure of the relief valve 38, and the fuel in the fuel rail 12 is fueled. It is configured to return to the tank 20.

1 and 2, the ECU 30 sets the target fuel pressure PFo based on the engine rotational speed Ne, the load information, and the like, and drives and controls the fuel pressure control means 18 so that the fuel pressure PF in the fuel rail 12 is equal to the target fuel pressure PFo. Control to be.
Further, the ECU 30 individually controls the injector 15 and the spark plug 16 for each cylinder, and controls the fuel injection and ignition timing of each cylinder. At this time, each injector 15 and each spark plug 16 are driven by an injector drive signal and an ignition signal output from the ECU 30.

Next, the normal fuel pressure feedback control operation (the pressure setting operation of the fuel supplied to the injector 15) by the ECU 30 and the fuel pressure control means 18 will be described with reference to FIGS.
First, the fuel pumped up from the fuel tank 20 by the feed pump 21 passes through the filter 22, is adjusted in fuel pressure by the regulator 23, and is introduced into the fuel pressure control means 18.

The piston 31 in the fuel pressure control means 18 is moved up and down by the pump cam 17 that rotates integrally with the camshaft. As a result, the volume of the pressure increasing chamber 32 changes, and the fuel compressed by the pressure increasing chamber 32 is reversed. It is configured to be introduced into the fuel rail 12 via the stop valve 37.
However, the amount of fuel introduced into the fuel rail 12 is adjusted by a valve body 36 of the spill valve 33 (hereinafter simply referred to as “spill valve 33”).

The coil 34 in the spill valve 33 moves upward by an energization signal from the ECU 30, overcomes the urging force of the spring 35, and opens the valve body 36 at the lower end related to the pressure increasing chamber 32.
When the valve body 36 is opened, the pressure increasing chamber 32 communicates with the suction port side, and the fuel in the pressure increasing chamber 32 returns to the suction port side, so that fuel is not sent to the fuel rail 12. Therefore, the high pressure fuel is not discharged from the fuel pressure control means 18 (high pressure pump) to the fuel rail 12.

On the other hand, when the energization of the coil 34 is interrupted, the coil 34 moves downward by the urging force of the spring 35 and closes the valve body 36, so that the high pressure fuel is discharged from the fuel pressure control means 18 to the fuel rail 12.
At this time, the relief valve 38 opens when the fuel pressure PF reaches the valve opening pressure, and returns the fuel in the fuel rail to the fuel tank 20.
Further, the fuel pressure sensor 19 detects the fuel pressure PF in the fuel rail 12 and transmits it to the ECU 30 to contribute to fuel pressure feedback control by the ECU 30.
The high pressure fuel in the fuel rail 12 thus controlled in fuel pressure is directly injected into the combustion chamber 11 from the injector 15.

The above fuel pressure control is a processing operation (so-called low pressure spill variable fuel pressure control) for adjusting the fuel introduction amount to the fuel rail 12 so that the fuel pressure PF becomes the target fuel pressure PFo.
In the first embodiment of the present invention, a process (so-called high-pressure spill type variable fuel pressure control) of spilling the fuel introduced into the fuel pressure control means 18 and adjusting to the target fuel pressure PFo may be applied. .

In this case, the ECU 30 includes a state immediately before stop determination unit that determines a state immediately before the engine 10 is stopped.
Further, the fuel pressure control means 18 that functions in association with the ECU 30 increases the fuel pressure PF after the state immediately before stop is determined by the state determination means immediately before stop.

The control operation of the spill valve 33 according to Embodiment 1 of the present invention will be described below with reference to the flowchart of FIG.
First, the state determination means immediately before stop in the ECU 30 determines whether or not the state immediately before the engine 10 stops based on the operation state information from various sensors (step S31).

In step S31, if it is determined that the engine 10 is in a state immediately before stopping (that is, YES), the spill valve 33 is normally closed, and all the fuel in the pressure increasing chamber 32 is supplied to the fuel rail 12. It is set (step S32), the fuel pressure PF is increased, and the processing routine of FIG. 3 is exited.
On the other hand, if it is determined in step S31 that the state is not immediately before stopping (that is, NO), the process routine of FIG. 3 is exited without executing step S32.

  As described above, after the state determination means immediately before stopping determines that the engine 10 is immediately before stopping, the fuel pressure control means 18 is activated to increase the fuel pressure PF, so that the high fuel pressure can be maintained when the engine 10 is stopped. It is possible to atomize the fuel at the time of starting, improving the restartability and reducing the amount of HC in the exhaust gas.

Embodiment 2. FIG.
In the first embodiment, when the state immediately before the stop of the engine 10 is determined, the spill valve 33 is normally closed and the fuel pressure PF is increased unconditionally. However, after the state immediately before the stop is determined, Alternatively, the fuel pressure PF may be increased over a certain period until the engine 10 stops.

The second embodiment of the present invention in which the fuel pressure PF is raised over a certain period will be described below.
FIG. 4 is a flowchart showing the control operation (fuel pressure control process) of the spill valve 33 according to the second embodiment of the present invention. Steps S41 and S44 are the above-described steps S31 and S32 (see FIG. 3), respectively. Is the same process.

In FIG. 4, first, the state determination means immediately before stop in the ECU 30 determines whether or not the state is immediately before the engine 10 stops (step S41).
If it is determined in step S41 that the engine 10 is in a state just before stopping (that is, YES), the timer counter TM is incremented by “1” (step S42), and then the value of the timer counter TM is set to a predetermined period. It is determined whether it is smaller than the corresponding set value (step S43).

  If it is determined in step S43 that TM <set value (that is, YES), the spill valve 33 is normally closed since the fixed period has not elapsed (the engine 10 has stopped) since the state immediately before the stop was determined. (All discharge state) is set (step S44), the fuel pressure PF is increased, and the process routine of FIG. 4 is exited.

On the other hand, if it is determined in the first determination step S41 that the engine 10 is not in a state immediately before stopping (that is, NO), the timer counter TM is cleared to 0 and initialized (step S45), and the processing routine of FIG. 4 is exited.
Further, if it is determined in step S43 that TM ≧ set value (that is, NO), a certain period of time has elapsed (the engine 10 is stopped) from the time point when the state immediately before stop is determined, so that the fuel pressure increase process (step The process routine of FIG. 4 is immediately exited without executing S44).

  As described above, the engine 10 is stopped by enabling the fuel pressure control means 104 and increasing the fuel pressure PF for a certain period of time until the internal combustion engine is actually stopped after the state determination means immediately before stop is determined to be immediately before stop. Sometimes a high fuel pressure can be maintained, fuel can be atomized at the time of restart, restartability can be improved, and the amount of HC in the exhaust gas can be reduced.

Embodiment 3 FIG.
In the first and second embodiments, the boost value of the fuel pressure PF after the determination of the state immediately before the stop is not mentioned, but the fuel pressure PF is set to a predetermined pressure or higher that can ensure the restartability of the engine 10. May be.
The operation according to the third embodiment of the present invention will be described below with reference to FIGS. 1 and 2 and FIG.

In this case, the fuel pressure control means 18 that functions in association with the state determination means immediately before stop in the ECU 30 sets the fuel pressure PF to be equal to or higher than a predetermined pressure after the state determination means immediately before stop determines the state immediately before stop. Yes.
Here, the predetermined pressure is set to a fuel pressure that can sufficiently ensure restartability when the engine 10 is restarted after being stopped.

FIG. 5 is a flowchart showing an operation according to Embodiment 3 of the present invention, and shows a process for setting the fuel pressure PF after the determination of the state immediately before stopping to a predetermined pressure or higher.
In FIG. 5, it is first determined whether or not the engine 10 is just before stopping (step S51). If it is determined that the engine 10 is just before stopping (ie, YES), a predetermined pressure is set as the target fuel pressure PFo. (Step S52).

Subsequently, the ECU 30 determines whether or not the actual fuel pressure PF detected by the fuel pressure sensor 19 is lower than the target fuel pressure PFo (step S53).
If it is determined in step S53 that PF <PFo (that is, YES), the spill valve 33 is normally closed (full discharge state), the fuel pressure PF is increased (step S54), and the process routine of FIG. 5 is exited.

  On the other hand, if it is determined in step S53 that PF ≧ PFo (that is, NO), fuel pressure feedback control is executed so that the fuel pressure PF matches the target fuel pressure PFo (step S55), and the process routine of FIG. 5 is exited.

  Further, in the first determination step S51, if it is determined that the state is not immediately before the stop (that is, NO), it is determined whether or not a feedback (F / B) control condition to the target fuel pressure PFo is satisfied (step S56). ).

  If it is determined in step S56 that the F / B control condition is satisfied (that is, YES), the process proceeds to the fuel pressure feedback control in step S55, and the F / B control condition is not satisfied (that is, NO). If it is determined, step S55 is not executed, and the process routine of FIG. 5 is immediately exited.

As described above, the fuel pressure control means 18 sets the fuel pressure PF to be equal to or higher than the predetermined pressure by the fuel pressure control means 18 until the engine 10 is stopped after the state immediately before the stop is determined. It is possible to maintain a high fuel pressure that allows a good restart at the start.
Therefore, similarly to the above, the fuel can be atomized when the engine 10 is restarted, the restartability can be improved, and the amount of HC in the exhaust gas can be reduced.

Embodiment 4 FIG.
In the first to third embodiments, the determination condition in the state immediately before the stop is not particularly mentioned. However, after the elapsed time Ts after the engine starts reaches a predetermined period or more, the engine rotation speed Ne is equal to or lower than the predetermined speed. In this case, the state immediately before stopping may be determined.

In this case, the ECU 30 includes a starting state determining unit that determines a starting state of the engine 10, an elapsed time measuring unit that measures an elapsed time after starting the engine 10 as an elapsed time Ts after starting, and an elapsed time Ts after starting. And a state immediately before stop determination means for determining a state immediately before stop from the engine speed Ne.
The state determining means immediately before stopping determines the state immediately before stopping when the engine rotation speed Ne becomes equal to or lower than a predetermined speed after the elapsed time Ts after starting of the engine 10 reaches a predetermined period or more.

Hereinafter, the state determination process immediately before stopping according to the fourth embodiment of the present invention will be described with reference to the flowchart of FIG.
In FIG. 6, first, the state determination means immediately before stopping determines whether or not the elapsed time Ts after start has elapsed for a predetermined period or longer (step S61).

At this time, the predetermined period compared with the elapsed time Ts after starting is set to, for example, about 10 to 60 [sec] in order to satisfy the following conditions (A) and (B) simultaneously.
(A) Exclude the case of starting failure or engine stall immediately after starting.
(B) When starting from a low fuel pressure (about 0.5 MPa), the time when the fuel pressure is sufficiently high is reached.

If it is determined in step S61 that Ts ≧ predetermined period (that is, YES), then whether or not the actual engine rotational speed Ne detected by the crank angle sensor 13 is equal to or lower than the predetermined rotational speed for determining the state immediately before stopping. It is determined whether or not (step S62).
At this time, the predetermined rotational speed is a rotational speed smaller than the idle rotational speed (for example, 600 rpm), and is set to, for example, a start determination rotational speed (about 500 rpm).

  In step S62, if it is determined that Ne ≦ predetermined speed (that is, YES), the condition immediately before the stop of the engine 10 is satisfied, so “1” is set to the immediately before stop determination flag (step S63), the process routine of FIG. 6 is exited.

  On the other hand, if Ts <predetermined period (that is, NO) is determined in step S61, or if Ne> predetermined rotational speed (that is, NO) is determined in step S62, the condition immediately before the stop is satisfied. Therefore, the state determination flag immediately before stopping is cleared to “0” (step S64), and the process routine of FIG. 6 is exited.

  Thus, by using the post-start elapsed time Ts and the engine speed Ne as the determination conditions for the state immediately before the stop of the engine 10, the state immediately before the stop can be accurately determined, and unnecessary fuel pressure PF due to erroneous determination Ascending control can be avoided.

Embodiment 5 FIG.
In the first to fourth embodiments, the automatic stop and the automatic start of the engine 10 are not specifically mentioned. For example, when the automatic stop is determined, the engine 10 is started after the fuel pressure PF is increased. You may stop automatically.

In general, a vehicle having an automatic stop function is a vehicle having a so-called idle stop function.
In an internal combustion engine that performs automatic processing (idle stop), for example, when the vehicle stops, the engine 10 automatically stops, and when the vehicle restarts (the driver depresses the accelerator pedal again), the engine 10 automatically Start.

Hereinafter, Embodiment 5 of the present invention configured to execute the automatic stop after raising the fuel pressure PF after the automatic stop determination of the engine 10 that performs the automatic processing will be described.
In this case, in addition to the above-described configuration, the ECU 30 includes an automatic processing unit that performs automatic processing including automatic stop and automatic start of the engine 10, an automatic stop determination unit that determines whether or not to execute the automatic stop, Automatic stop execution means for executing stop.

  The fuel pressure control means 18 increases the fuel pressure PF under the control of the ECU 30 after the execution of the automatic stop is determined by the automatic stop determination means in the ECU 30, and the automatic stop execution means in the ECU 30 increases the fuel pressure PF. The engine 10 is automatically stopped.

FIG. 7 is a flowchart showing automatic stop processing according to Embodiment 5 of the present invention.
In FIG. 7, first, the automatic stop determination means in the ECU 30 determines whether or not an idle stop condition (automatic stop condition) is satisfied (step S71).

At this time, the idle stop generally assumes an idle stop state such as a signal stop, and examples of the automatic stop condition include a case where all of the following conditions (1) to (3) are satisfied.
(1) The vehicle speed is “0 km / h”.
(2) The throttle valve is “fully closed”
(3) The brake pedal is being operated.

If it is determined in step S71 that the idle stop condition is satisfied (that is, YES), the fuel pressure control means 18 always closes the spill valve 33 (full discharge state) (step S72), and the pressure increasing chamber 32 is reached. Is supplied to the fuel rail 12 to increase the fuel pressure PF.
Thus, after the fuel pressure PF rises, the automatic stop execution means executes idle stop (automatic stop) (step S73), and exits the processing routine of FIG.

  On the other hand, if it is determined in step S71 that the idle stop condition is not satisfied (that is, NO), the process routine of FIG. 7 is exited without executing the automatic stop process (steps S72 and S73).

  In this way, in an internal combustion engine that performs automatic processing, when automatic stop is determined by the automatic stop determination means, the engine 10 is automatically stopped after increasing the fuel pressure PF, so that a good restart is possible at the next start. The engine 10 can be automatically stopped by securing a sufficient fuel pressure PF for obtaining the performance. Therefore, good restartability can be realized.

Embodiment 6 FIG.
In the fifth embodiment, the period (pressure increase period) for increasing the fuel pressure PF after the automatic stop determination is not particularly mentioned, but the fuel pressure PF may be increased over a predetermined pressure increase period after the automatic stop determination.

  In this case, the fuel pressure control means 18 increases the fuel pressure PF over a predetermined pressure increase period after the execution of the automatic stop is determined by the automatic stop determination means, and the automatic stop execution means determines that the engine 10 Is to stop automatically.

Hereinafter, the automatic stop process according to the sixth embodiment of the present invention in which the fuel pressure PF is increased over a predetermined pressure increase period will be described with reference to the flowchart of FIG.
In FIG. 8, step S81 is a determination process similar to step S71 described above (see FIG. 7).

  First, the automatic stop determination means in the ECU 30 determines whether or not the idle stop condition is satisfied (step S81), and if it is determined that the idle stop condition is satisfied (that is, YES), the timer counter TMi is incremented by “1” (step S82).

Subsequently, the automatic stop execution means in the ECU 30 determines whether or not the value of the timer counter TMi is smaller than a set value corresponding to the predetermined boosting period (step S83).
If it is determined in step S83 that TMi <set value (that is, YES), the predetermined pressure increase period has not elapsed, so the fuel pressure control means 18 causes the spill valve 33 to be normally closed (full discharge state) (step S84). Then, the fuel pressure PF is increased and the processing routine of FIG. 8 is exited.

  On the other hand, if it is determined in step S83 that TMi ≧ set value (that is, NO), since the predetermined pressure increase period has elapsed from the time when the automatic stop condition is satisfied, the automatic stop execution means performs idle stop (automatic stop). Is executed (step S85), and the process routine of FIG. 8 is exited.

  If it is determined in the first determination step S81 that the idle stop condition is not satisfied (that is, NO), the timer counter TMi is cleared to 0 and initialized (step S86), and the processing routine of FIG. Get out.

  Thus, in an internal combustion engine that performs automatic processing, when automatic stop is determined, the engine 10 is automatically stopped after increasing the fuel pressure PF over a predetermined pressure increase period, thereby obtaining the next good restartability. Only sufficient fuel pressure PF can be secured and the engine 10 can be stopped. Therefore, the restartability of the engine 10 can be further improved.

Embodiment 7 FIG.
In the fifth and sixth embodiments, the boost value of the fuel pressure PF after the automatic stop condition is satisfied is not mentioned, but the fuel pressure PF is set to a predetermined pressure or higher that can ensure the restartability of the engine 10. May be.

In this case, the fuel pressure control means 18 sets the fuel pressure to a predetermined pressure or higher by the fuel pressure control means after determining the automatic stop of the internal combustion engine by the automatic stop determination means.
Here, the predetermined pressure is set to a fuel pressure that can sufficiently ensure restartability when the engine 10 is restarted after being stopped, as described above.

Hereinafter, the automatic stop process according to the seventh embodiment of the present invention in which the fuel pressure PF after the automatic stop determination is set to a predetermined pressure or higher will be described with reference to the flowchart of FIG.
In FIG. 9, steps S91, S94 and S95 are the same processes as steps S81, S84 and S85 described above (see FIG. 8), respectively.

First, it is determined whether or not the idle stop condition is satisfied (step S91). If it is determined that the idle stop condition is not satisfied (that is, NO), the process routine of FIG. 9 is immediately exited.
On the other hand, if it is determined in step S91 that the idle stop condition is satisfied (that is, YES), the ECU 30 sets a predetermined pressure as the target fuel pressure PFo (step S92), and the actual fuel pressure PF becomes the target fuel pressure PFo. It is determined whether it is lower than (step S93).

If it is determined in step S93 that PF <PFo (that is, YES), the spill valve 33 in the fuel pressure control means 18 is normally closed (full discharge state) (step S94), the fuel pressure PF is increased, and FIG. Exit the processing routine.
On the other hand, if it is determined in step S93 that PF ≧ PFo (that is, NO), idle stop (automatic stop) is executed (step S95), and the process routine of FIG. 9 is exited.

  As described above, after the automatic stop is determined, the fuel pressure PF is increased to a predetermined pressure or higher, and then the engine 10 is automatically stopped, so that the engine 10 is stopped after securing the fuel pressure to the extent that the next good restartability can be obtained. And restartability can be improved.

Embodiment 8 FIG.
Although not particularly mentioned in the first to seventh embodiments, the present invention may be applied to an internal combustion engine in which fuel is injected into a specific cylinder (expansion stroke cylinder) in an expansion stroke when the engine is stopped to enable ignition. .

In this case, the ECU 30 includes an expansion stroke cylinder determining unit that determines an expansion stroke cylinder among the plurality of cylinders. When the engine 10 is stopped, the ECU 30 performs ignition after injecting fuel into the expansion stroke cylinder. It is configured to start.
Thereby, the electric motor for cranking can be made unnecessary. Alternatively, a starter for cranking assistance may be provided.
Here, the fuel pressure control means 18 controls the fuel pressure PF immediately before the engine 10 is stopped.

The operation according to the eighth embodiment of the present invention applied to an internal combustion engine configured to be able to ignite by injecting fuel into the expansion stroke cylinder at the time of stop will be described below with reference to the flowchart of FIG.
Here, a case where the present invention is applied to a vehicle having an automatic stop processing function is taken as an example, and in FIG. 10, steps S101 to S105 are the same as steps S91 to S95 described above (see FIG. 9), respectively.

First, it is determined whether or not the idle stop condition is satisfied (step S101). If it is determined that the idle stop condition is not satisfied (that is, NO), the process routine of FIG. 10 is immediately exited.
On the other hand, if it is determined in step S101 that the idling stop condition is satisfied (that is, YES), the aforementioned predetermined pressure is set as the target fuel pressure PFo (step S102), and then the actual fuel pressure PF is greater than the target fuel pressure PFo. It is also determined whether or not the value is lower (step S103).

If it is determined in step S103 that PF <PFo (that is, YES), the spill valve 33 is normally closed (full discharge state) (step S104), the fuel pressure PF is increased, and the process routine of FIG. 10 is exited.
On the other hand, if it is determined in step S103 that PF ≧ PFo (that is, NO), idle stop (automatic stop) is executed (step S105), and then it is determined whether or not a start request has been made (step S106). .

Here, the start request is, for example, a restart request after an idle stop, and the determination condition of the start request is triggered by “the brake is released”.
A specific example of a general idle stop will not be described in detail here, but can be referred to, for example, “automatic vehicle engine stop and restart device” described in Japanese Patent Application Laid-Open No. 8-291725.

If it is determined in step S106 that there is no start request (ie, NO), the process routine of FIG. 10 is immediately exited.
On the other hand, if it is determined in step S106 that a start request has been made (that is, YES), the cranking motor is required in consideration of, for example, the elapsed time after the engine 10 is stopped (post-stop elapsed time Tp). It is determined whether or not restarting is possible without using a cranking motor (step S107).

If it is determined in step S107 that the elapsed time Tp after the stop is equal to or longer than the predetermined stop period and the cranking motor is necessary (that is, YES), the cranking motor is started (step S108). Then, the process routine of FIG. 10 is exited.
On the other hand, if it is determined in step S107 that the post-stop elapsed time Tp has not reached the predetermined stop period and the cranking motor is unnecessary (ie, NO), the engine is started without the cranking motor. (Step S109), the process routine of FIG. 10 is exited.

As described above, in an internal combustion engine that can be started by ignition after fuel injection to the expansion stroke cylinder in a stopped state and that does not require a cranking motor (or includes an auxiliary starter for cranking assistance), the engine By increasing the fuel pressure PF before 10 stops, the fuel pressure PF after the stop can be maintained at a high pressure for a relatively long period (a predetermined stop period).
Therefore, if the elapsed time after the stop is less than the predetermined stop period, the restart can be performed without using the cranking motor, and the restartable period can be set longer without using the cranking motor.

  In the first to eighth embodiments, the spill valve 33 is set to be normally closed (full discharge state) in order to increase the fuel pressure PF. However, while opening / closing control of the spill valve 33 is performed by fuel pressure feedback control or the like. The fuel pressure PF may be increased.

1 is a configuration diagram schematically showing a fuel pressure control apparatus for a direct injection internal combustion engine according to Embodiment 1 of the present invention. FIG. 1 is a block configuration diagram showing a fuel system of a fuel pressure control device for a direct injection internal combustion engine according to Embodiment 1 of the present invention. FIG. It is a flowchart which shows the operation | movement by Embodiment 1 of this invention. It is a flowchart which shows the operation | movement by Embodiment 2 of this invention. It is a flowchart which shows the operation | movement by Embodiment 3 of this invention. It is a flowchart which shows the operation | movement by Embodiment 4 of this invention. It is a flowchart which shows the operation | movement by Embodiment 5 of this invention. It is a flowchart which shows the operation | movement by Embodiment 6 of this invention. It is a flowchart which shows the operation | movement by Embodiment 7 of this invention. It is a flowchart which shows the operation | movement by Embodiment 8 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Engine (cylinder injection type internal combustion engine), 11 Combustion chamber, 12 Fuel rail, 13 Crank angle sensor, 14 Cam angle sensor, 15 Injector, 16 Spark plug, 17 Pump cam, 18 Fuel pressure control means (high pressure fuel pump), 19 Fuel pressure sensor, 20 fuel tank, 30 ECU, 33 spill valve, 36 valve body.

Claims (9)

An injector for directly injecting fuel into each of a plurality of cylinders;
A spark plug for igniting fuel in each cylinder;
A fuel pressure sensor that detects a fuel pressure supplied to the injector as a fuel pressure;
Fuel pressure control means for variably setting the fuel pressure using the fuel pressure detected by the fuel pressure sensor as feedback information;
Comprising a state immediately before stop determining means for determining a state immediately before stop of the internal combustion engine,
The fuel pressure control device for a direct injection internal combustion engine, wherein the fuel pressure control means increases the fuel pressure after the state immediately before stop is determined by the state determination means immediately before stop.   2. The fuel pressure control unit according to claim 1, wherein the fuel pressure control unit increases the fuel pressure over a certain period until the internal combustion engine stops after the state just before stopping is determined by the state determining unit immediately before stopping. A fuel pressure control device for a direct injection internal combustion engine.   The fuel pressure control means sets the fuel pressure to be equal to or higher than a predetermined pressure at which restartability of the engine can be secured after the state immediately before stop is determined by the state determination means immediately before stop. The fuel pressure control device for a cylinder injection internal combustion engine according to claim 1 or 2. Starting state determining means for determining a starting state of the internal combustion engine;
A post-startup elapsed time measuring means for measuring an elapsed time after start-up of the internal combustion engine as post-startup elapsed time;
The state immediately before stop determining means determines the state immediately before stop when the rotation speed of the internal combustion engine indicates a predetermined speed or less after the elapsed time after start reaches a predetermined period or more. The fuel pressure control device for a cylinder injection internal combustion engine according to any one of claims 1 to 3. An injector for directly injecting fuel into each of a plurality of cylinders;
A spark plug for igniting fuel in each cylinder;
A fuel pressure sensor that detects a fuel pressure supplied to the injector as a fuel pressure;
Fuel pressure control means for variably setting the fuel pressure using the fuel pressure detected by the fuel pressure sensor as feedback information;
Automatic processing means for performing automatic processing including automatic stop and automatic start of the internal combustion engine;
Automatic stop determining means for determining whether to execute the automatic stop;
Automatic stop execution means for executing automatic stop,
The fuel pressure control means increases the fuel pressure after execution of the automatic stop is determined by the automatic stop determination means,
The fuel pressure control device for a direct injection internal combustion engine, wherein the automatic stop execution means automatically stops the internal combustion engine after the fuel pressure increases. The fuel pressure control means increases the fuel pressure over a predetermined pressure increase period after the execution of the automatic stop is determined by the automatic stop determination means,
The fuel pressure control device for a direct injection internal combustion engine according to claim 5, wherein the automatic stop execution means automatically stops the internal combustion engine after the predetermined pressure increase period has elapsed.   The in-cylinder injection according to claim 5 or 6, wherein the fuel pressure control means sets the fuel pressure to a predetermined pressure or higher after the execution of the automatic stop is determined by the automatic stop determination means. Type internal combustion engine fuel pressure control device. An expansion stroke cylinder discriminating means for discriminating a cylinder in the expansion stroke among the plurality of cylinders as an expansion stroke cylinder;
The internal combustion engine is configured to be able to start by performing ignition after injecting fuel into the expansion stroke cylinder in a stopped state,
The fuel pressure control device for a direct injection internal combustion engine according to any one of claims 1 to 7, wherein the fuel pressure control means controls the fuel pressure immediately before the internal combustion engine is stopped.   The fuel pressure control device for a direct injection internal combustion engine according to claim 8, further comprising an auxiliary starter device for assisting cranking of the internal combustion engine.

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