JP2010031815A - Fuel injection system and internal combustion engine system with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure capable of suitably changing a ratio between in-cylinder injection and in-passage injection in accordance with an engine operation state while suppressing adhesion of deposit in an in-cylinder injection valve to the minimum. <P>SOLUTION: A fuel injection system is provided with the in-cylinder injection valve (28C), an in-passage injection valve (28P), and a pressure adjusting means (47). The in-cylinder injection valve (28C) directly injects fuel (F) into a combustion chamber (CC) of an internal combustion engine (2). The in-passage injection valve (28P) injects the fuel (F) into an intake passage (25) communicated with the combustion chamber (CC). The pressure adjusting means (47) decreases a fuel supply pressure with respect to the in-cylinder injection valve (28C) during stopping of injection of the fuel (F) from the in-cylinder injection valve (28C). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a fuel injection system comprising: an in-cylinder injection valve that directly injects fuel into a combustion chamber of an internal combustion engine; and an in-passage injection valve that injects the fuel into an intake passage communicating with the combustion chamber; The present invention relates to an internal combustion engine system provided with this fuel injection system.

  In general, this type of device switches the ratio between in-cylinder injection and in-passage injection (ex-cylinder injection) according to the load region of the internal combustion engine (for example, Japanese Patent Application Laid-Open No. 2005-171821, (See JP 2006-132517 A, JP 2007-9815 A, etc.).

  As disclosed in JP-A-2005-171821, in-cylinder injection valves, it is necessary to inject fuel in the form of a mist against the pressure in the combustion chamber. Therefore, the in-cylinder injection valve is supplied with fuel having a pressure higher than that of the out-cylinder injection valve (the intake system injection valve, that is, the port injection valve). For this reason, in this in-cylinder injection valve, the allowable minimum in-cylinder fuel injection amount, which is a lower limit value capable of stably performing fuel injection, is larger than that of the out-of-cylinder injection valve.

Therefore, in the configuration disclosed in Japanese Patent Laid-Open No. 2005-171821, the ratio between in-cylinder injection and out-cylinder injection is switched as follows: (1) In-cylinder injection only in the high load region (2 ) In-cylinder injection only in the low load region, and (3) In-cylinder injection and out-cylinder injection in the intermediate load region. In such a configuration, even when in-cylinder injection is attempted, in-cylinder injection is switched to out-of-cylinder injection when the injection amount is smaller than the allowable minimum in-cylinder fuel injection amount.
JP 2005-171821 A JP 2006-132517 A Japanese Patent Laid-Open No. 2007-9815

  As described above, in this type of conventional apparatus, in-cylinder injection may be stopped in a low load region or the like. While the in-cylinder injection is stopped, a so-called deposit may be deposited inside or around the injection hole of the in-cylinder injection valve due to the temperature rise of the in-cylinder injection valve. Here, the deposit is typically a bowl-shaped foreign matter generated by heating the fuel. Such deposit adhesion causes a decrease in the flow rate of the fuel, deformation of the spray shape, and the like, and fuel injection control is not performed well. Therefore, it is desirable to restart the in-cylinder injection as quickly as possible from the viewpoint of suppressing deposit adhesion.

  However, since the fuel pressure is maintained at a high level while the in-cylinder injection is stopped, the above-described allowable minimum in-cylinder fuel injection amount is relatively large. Therefore, in-cylinder injection may not be easily resumed in an operation region where the fuel injection amount is relatively small, such as a transition region from low load operation to medium load operation. On the other hand, if the in-cylinder injection is forcibly restarted in such a case, fuel injection in the in-cylinder injection valve is not performed satisfactorily, which may cause a malfunction such as misfire.

  The present invention has been made to cope with such a problem. That is, an object of the present invention is to provide a configuration in which the ratio of in-cylinder injection and in-passage injection can be appropriately switched according to the engine operating state while suppressing deposit adhesion on the in-cylinder injection valve as much as possible. It is to provide.

<Configuration>
The fuel injection system of the present invention includes a cylinder injection valve and a passage injection valve. The in-cylinder injection valve directly injects fuel into the combustion chamber of the internal combustion engine. The in-passage injection valve is configured to inject the fuel into an intake passage that communicates with the combustion chamber.

  The fuel injection system may be provided with a high pressure fuel supply passage, a high pressure fuel pump, and a relief valve. The high pressure fuel supply passage is connected to the in-cylinder injection valve. The high-pressure fuel pump is provided to deliver the fuel to the high-pressure fuel supply passage. The relief valve is interposed in the high pressure fuel supply passage so as to open when the fuel supply pressure in the high pressure fuel supply passage reaches a predetermined relief pressure and discharge the fuel from the high pressure fuel supply passage. It is disguised.

  The internal combustion engine system of the present invention includes an EGR passage (exhaust gas recirculation passage) and the fuel injection system of the present invention. Here, “EGR” is an abbreviation for “Exhaust Gas Recirculation”. The EGR passage is provided so as to connect an exhaust passage communicating with the combustion chamber and the intake passage. The internal combustion engine system may further include an EGR cooler that cools EGR gas (exhaust gas passing through the EGR passage). The EGR cooler is interposed in the EGR passage.

  The fuel injection system according to the present invention is characterized in that the fuel supply pressure (hereinafter referred to as “fuel pressure”) to the in-cylinder injection valve during operation of the internal combustion engine and stop of the fuel injection from the in-cylinder injection valve. The pressure adjusting means is provided. For example, the pressure adjusting means adjusts the fuel pressure while the fuel injection from the in-cylinder injection valve is stopped during low-load operation of the internal combustion engine (including idling during deceleration or fuel cut). It is supposed to decrease.

  The pressure regulating means may include at least the relief valve. As this relief valve, for example, a so-called electromagnetic valve that opens and closes electromagnetically can be used. Alternatively, as the relief valve, a valve that is mechanically operated by a fuel pressure in the high-pressure fuel supply passage (so-called mechanical valve) can be used. In the latter case, the pressure adjusting means may also include the high pressure fuel pump.

  The fuel injection system of the present invention may further include injection control means. The injection control means controls the fuel injection state in the in-cylinder injection valve and the in-passage injection valve.

  Here, the injection control means stops the injection of the fuel from the in-cylinder injection valve when the fuel pressure during a low load operation exceeds a predetermined pressure, and only the fuel from the in-passage injection valve. May be sprayed.

  Alternatively, the injection control means stops the injection of the fuel from the in-cylinder injection valve when the in-cylinder injection required amount during low load operation is smaller than a predetermined allowable minimum in-cylinder fuel injection amount, and The fuel may be injected only from the inner injection valve. Here, the in-cylinder injection request amount is calculated as a quantity to be injected from the in-cylinder injection valve by the fuel injection amount calculation means according to the operating state. The allowable minimum in-cylinder fuel injection amount is a lower limit value at which stable injection can be performed from the in-cylinder injection valve, and is an amount determined according to the fuel pressure.

<Action and effect>
For example, in-cylinder injection is stopped during low load operation such as during deceleration. In particular, in the case of the internal combustion engine system provided with the EGR passage, the in-cylinder injection rate is set to be relatively low for the following reason, and therefore the ratio at which in-cylinder injection is stopped can be high.

  When the fuel injected from the in-cylinder injection valve adheres to the top surface of the piston, particulate matter (hereinafter referred to as “PM”: PM is an abbreviation of Particulate Matter) may be generated in the exhaust gas. . This PM is soot or the like, and is generated when the fuel adhering to the piston is exposed to a high temperature without being completely burned without being vaporized.

  When exhaust gas recirculation (EGR) is performed, the combustion temperature is lowered, and therefore PM is likely to be generated. When a large amount of PM is generated, PM adheres in the EGR cooler, thereby disturbing the control of the EGR rate or reducing the cooling performance of the EGR gas. For this reason, when the EGR passage is provided in the internal combustion engine system, the in-cylinder injection rate is set low for PM countermeasures.

  In the configuration of the present invention, the pressure adjusting means operates while in-cylinder injection is stopped (for example, during low load operation such as during deceleration). Specifically, for example, the relief valve is electromagnetically opened. Alternatively, for example, when the high-pressure fuel pump is driven at a high output (a high delivery amount), the fuel pressure is once increased to reach the relief pressure, and the relief valve is opened by the fuel pressure.

  By the operation of the pressure adjusting means as described above, the fuel supply pressure is lowered, and the allowable minimum in-cylinder fuel injection amount is reduced. Thereby, in-cylinder injection can be restarted as early as possible, and the generation of deposits in the in-cylinder injection valve can be suppressed as much as possible. Therefore, according to the present invention, it is possible to appropriately switch the ratio between the in-cylinder injection and the in-passage injection in accordance with the engine operating state while suppressing the deposit adhesion on the in-cylinder injection valve as much as possible. Become.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings. In addition, the description about the following embodiment is specific to the extent possible, merely an example of the embodiment of the present invention in order to satisfy the description requirement (description requirement / practicability requirement) of the specification required by law. It is only what is described in. Therefore, as will be described later, it is quite natural that the present invention is not limited to the specific configurations of the embodiments described below. Examples of modifications to an embodiment are listed together at the end, as they are inserted during the description of the embodiment, preventing understanding of a consistent description of the embodiment.

<Configuration of internal combustion engine system>
FIG. 1 is a diagram schematically showing an overall configuration of an internal combustion engine system 1 (vehicle) according to an embodiment of the present invention. The internal combustion engine system 1 includes an in-line multi-cylinder internal combustion engine 2, an intake / exhaust system 3, a fuel supply system 4, and a control device 5 (in FIG. 1, a plane orthogonal to the cylinder arrangement direction). A cross-sectional view of the internal combustion engine 2 is shown. Hereinafter, the configuration of each part of the internal combustion engine system 1 will be described in more detail.

<< Internal combustion engine >>
A cylinder block 20a including a lower case, an oil pan, and the like is a member that constitutes a main body portion (engine block) of the internal combustion engine 2 together with the cylinder head 20b. A cylinder head 20b is fixed to the upper end of the cylinder block 20a.

  A plurality of cylinders 21 are formed in the cylinder block 20a. A piston 22 is accommodated in the cylinder 21 so as to be reciprocally movable. Below the cylinder 21 and the piston 22, a crankshaft 23 is rotatably supported and accommodated. The crankshaft 23 is connected to the crankshaft 23 via a connecting rod 24 so as to be rotationally driven based on the reciprocating movement of the piston 22.

  A recess is formed in the lower end surface of the cylinder head 20b (the surface facing the cylinder block 20a). This concave portion is provided at a position corresponding to the upper end portion of the cylinder 21. A combustion chamber CC is formed by the space inside the recess and the space inside the cylinder 21 above the top surface of the piston 22.

  The cylinder head 20b is formed with an intake port 25 and an exhaust port 26 that are gas passages communicating with the combustion chamber CC. The cylinder head 20b is provided with a valve operating mechanism 27 for opening and closing the intake port 25 and the exhaust port 26. The valve mechanism 27 includes an intake valve 27a for opening and closing the intake port 25, an exhaust valve 27b for opening and closing the exhaust port 26, and a mechanism for opening and closing the intake valve 27a and the exhaust valve 27b at a predetermined timing. Yes.

  Further, the internal combustion engine 2 is provided with one in-cylinder injector 28C and one port injector 28P for each cylinder 21. The in-cylinder injector 28C corresponding to the in-cylinder injection valve of the present invention directly injects fuel F into the combustion chamber CC. The port injector 28P corresponding to the in-passage injection valve of the present invention injects fuel F into the intake port 25 communicating with the combustion chamber CC.

<< Intake and exhaust system >>
An intake pipe 31 including an intake manifold and a surge tank is connected to the intake port 25. Auxiliary equipment such as an air filter 32 and a throttle valve 33 is interposed in the intake pipe 31 that constitutes the intake passage of the present invention together with the intake port 25. The throttle valve 33 is provided so that the opening cross-sectional area of the intake passage is variable, and is driven by a throttle valve actuator 33a.

  On the other hand, an exhaust pipe 34 including an exhaust manifold is connected to the exhaust port 26. Auxiliary equipment such as an exhaust gas purifying catalyst 35 is interposed in the exhaust pipe 34 that constitutes the exhaust passage of the present invention together with the exhaust port 26.

  EGR, which is a passage of EGR gas, connects the downstream side of the intake pipe 31 in the direction of intake air flow with respect to the throttle valve 33 and the upstream side of the exhaust pipe 34 in the direction of exhaust gas flow with respect to the exhaust gas purification catalyst 35. A passage 36 is provided. An EGR control valve 37 and an EGR cooler 38 are interposed in the EGR passage 36.

  The EGR control valve 37 is configured and arranged so as to control the supply amount of EGR gas to the intake pipe 31. The EGR cooler 38 can cool the EGR gas by heat exchange between the cooling water and the exhaust gas when a part of the cooling water used for cooling the cylinder block 20a and the cylinder head 20b is introduced. It is configured.

<< Fuel supply system >>
The fuel supply system 4 that constitutes the fuel injection system of the present invention together with the in-cylinder injector 28C, the port injector 28P, and the control device 5 to be described later uses the fuel F stored in the fuel tank 41 as the in-cylinder injector 28C and the port. It is configured as follows so as to be supplied to the injector 28P.

  The fuel tank 41, the in-cylinder injector 28C, and the port injector 28P are connected to the fuel supply passage 42. The fuel supply passage 42 is a passage for the fuel F for supplying the fuel F from the fuel tank 41 to the in-cylinder injector 28C and the port injector 28P. The main fuel supply passage 42a, the low-pressure fuel supply passage 42b, and the high-pressure fuel A supply passage 42c, a main return passage 42d, and a relief passage 42e are provided.

  An upstream end (hereinafter simply referred to as “upstream side”) of the main fuel supply passage 42 a in the fuel supply direction is inserted into the bottom of the fuel tank 41. Low-pressure fuel supply so as to branch from the main fuel supply passage 42a slightly downstream from the downstream end (hereinafter simply referred to as “downstream”) of the main fuel supply passage 42a in the fuel supply direction. A passage 42b is provided. The low pressure fuel supply passage 42b is connected to the port injector 28P. A high pressure fuel supply passage 42c is connected to the downstream end of the main fuel supply passage 42a. The high pressure fuel supply passage 42c is connected to the in-cylinder injector 28C.

  The main return passage 42d is provided on the upstream side of the low-pressure fuel supply passage 42b so as to branch from the main fuel supply passage 42a. A downstream end (lower end in the figure) of the main return passage 42d is connected to the fuel tank 41. The upstream end of the relief passage 42e is connected to the upstream end of the high-pressure fuel supply passage 42c. The downstream end (lower end in the figure) of the relief passage 42e is connected to the fuel tank 41.

  A fuel filter 43, a main fuel pump 44, and a main regulator 45 are interposed in the main fuel supply passage 42a. The fuel filter 43 and the main fuel pump 44 are provided upstream of the position where the main return passage 42d branches from the main fuel supply passage 42a. The fuel filter 43 is provided on the upstream side of the main fuel pump 44. The main fuel pump 44 is a so-called low pressure fuel pump, and sends the fuel F in the fuel tank 41 toward the low pressure fuel supply passage 42b and the high pressure fuel supply passage 42c.

  The main regulator 45 is provided at a position where the main return passage 42d branches from the main fuel supply passage 42a. The main regulator 45 is configured to adjust the pressure of the fuel F in the main fuel supply passage 42a (hereinafter, the pressure of the fuel F may be referred to as “fuel pressure”) to a predetermined pressure. Specifically, the main regulator 45 opens the valve when the fuel pressure in the main fuel supply passage 42a reaches a predetermined pressure (for example, 0.3 MPa), thereby discharging the fuel F from the main fuel supply passage 42a. Thus, the fuel tank 41 is returned to the fuel tank 41 through the main return passage 42d.

  In the main fuel supply passage 42a, a high-pressure fuel pump 46 constituting the pressure adjusting means of the present invention is interposed downstream of the position where the low-pressure fuel supply passage 42b branches. The high-pressure fuel pump 46 has a known configuration with variable output (delivery amount), and sends the fuel F to the high-pressure fuel supply passage 42c at an arbitrary pressure according to the pump duty. The configuration of the high-pressure fuel pump 46 is well known as will be described later. Therefore, illustration and description of a more detailed configuration of the high-pressure fuel pump 46 are omitted in the present application.

  A relief valve 47 is interposed at a connection portion between the high-pressure fuel supply passage 42c and the relief passage 42e. The relief valve 47 is a so-called mechanical relief valve that is operated by the fuel pressure in the high-pressure fuel supply passage 42c. That is, the relief valve 47 opens when the fuel pressure in the high-pressure fuel supply passage 42c reaches a predetermined relief pressure (for example, 22 MPa), thereby discharging the fuel F from the high-pressure fuel supply passage 42c and releasing the relief passage 42e. It is designed to return to the fuel tank 41 via

<< Control device >>
The control device 5 constituting the injection control means of the present invention is configured as follows so as to control the fuel injection state from the in-cylinder injector 28C and the port injector 28P in accordance with the operating state of the internal combustion engine 2. ing.

  The control device 5 includes an engine electronic control unit (ECU) 50. The ECU 50 includes a CPU 50a, a ROM 50b, a RAM 50c, a backup RAM 50d, an interface 50e, and a bidirectional bus 50f. The CPU 50a, ROM 50b, RAM 50c, backup RAM 50d, and interface 50e are connected to each other by a bidirectional bus 50f.

  In addition to the routine (program) executed by the CPU 50a, the ROM 50b stores in advance a table (map), parameters, and the like used when executing this routine. The RAM 50c can temporarily store data as necessary when a routine is executed by the CPU 50a. The backup RAM 50d stores data when the routine is executed by the CPU 50a with the power turned on, and can retain the stored data even after the power is turned off.

  The interface 50e is electrically connected to various sensors described later, and can transmit signals from these to the CPU 50a. The interface 50e is electrically connected to operation units such as the in-cylinder injector 28C, the port injector 28P, and the high-pressure fuel pump 46, and a control signal for operating these operation units is sent from the CPU 50a to these operations. It can be transmitted to the part. That is, the ECU 50 is configured to receive signals from the above-described various sensors and the like, and to send out the above-described control signals to each operation unit based on the calculation result of the CPU 50a corresponding to the signals.

<<< various sensors >>>
The internal combustion engine system 1 of the present embodiment includes an air flow meter 51, a throttle position sensor 52, a crank position sensor 53, a coolant temperature sensor 54, an air-fuel ratio sensor 55, a high-pressure side fuel pressure sensor 56, an accelerator opening. Sensor 57 is provided.

  The air flow meter 51 is interposed in the intake pipe 31 at a position downstream of the air filter 32. The air flow meter 51 is configured to output a signal corresponding to an intake air flow rate Ga that is a mass flow rate of intake air flowing through the intake pipe 31 per unit time.

  The throttle position sensor 52 is attached to the intake pipe 31 at a position corresponding to the throttle valve 33. The throttle position sensor 52 is configured to output a signal corresponding to the throttle valve opening degree TA which is the rotational phase of the throttle valve 33.

  The crank position sensor 53 is disposed so as to face the crankshaft 23. The crank position sensor 53 is configured to output a waveform signal having a pulse corresponding to the rotation angle of the crankshaft 23 (a signal corresponding to the engine speed Ne).

  The coolant temperature sensor 54 is mounted on the cylinder block 20a. The cooling water temperature sensor 54 is configured to output a signal corresponding to the temperature of the cooling water in the water jacket provided in the cylinder block 20a (cooling water temperature THW).

  The air-fuel ratio sensor 55 is mounted in an exhaust passage (specifically, an exhaust manifold) upstream of the exhaust gas purification catalyst 35. The air-fuel ratio sensor 55 is configured to output a voltage corresponding to the oxygen concentration of the exhaust gas discharged from the combustion chamber CC via the exhaust port 26.

  The high-pressure side fuel pressure sensor 56 is attached to the high-pressure fuel supply passage 42c. The high-pressure side fuel pressure sensor 56 is configured to generate an output corresponding to the fuel pressure in the high-pressure fuel supply passage 42c.

  The accelerator opening sensor 57 outputs a signal (accelerator pedal operation amount Accp) representing the amount of operation of the accelerator pedal 58 operated by the driver.

<Specific Example of Operation of Embodiment>
Next, a specific example of the operation of the internal combustion engine system 1 of the present embodiment having the above-described configuration will be described using a flowchart. In the following description of the flowchart and the drawings showing the flowchart, “step” is abbreviated as “S”.

<< Injection ratio determination >>
FIG. 2 is a flowchart showing one specific example of the injection ratio determination operation executed by the CPU 50a shown in FIG. The CPU 50a repeatedly executes the injection ratio determination routine 200 shown in FIG. 2 every time the crank angle reaches a predetermined value.

  When this routine is executed, first, in S210, based on parameters such as the load factor KL and the engine speed Ne and a predetermined map stored in advance in the ROM 50b, the in-cylinder direct injection ratio RDI (current time) The ratio of the fuel injection amount from the in-cylinder injector 28C to the total fuel injection amount) is determined. The port injection ratio RIP (the ratio of the fuel injection amount from the port injector 28P in the current fuel injection to the total fuel injection amount) is a value obtained by subtracting the in-cylinder direct injection ratio RDI from 1.

  Next, in S220, the in-cylinder injection request amount QDIreq is obtained by the product of the current total fuel injection amount (command fuel injection amount) Q and the in-cylinder direct injection ratio RDI. The command fuel injection amount Q is calculated at predetermined timings by the CPU 50a based on the operating state of the internal combustion engine 2 acquired from the outputs of the various sensors described above.

  Subsequently, in S230, the current fuel pressure Pf in the high-pressure fuel supply passage 42c is acquired based on the output of the high-pressure side fuel pressure sensor 56. Based on the fuel pressure Pf and a predetermined map stored in advance in the ROM 50b, in the subsequent S240, the allowable minimum in-cylinder fuel injection amount QDImin in the in-cylinder injector 28C is acquired.

  Thereafter, the process proceeds to S250, and it is determined whether or not the idle determination flag Xidol is OFF. When the engine is idle ON (S250 = No), the process proceeds to S260, and it is determined whether or not the current fuel pressure Pf is higher than a predetermined value Pf0 (for example, 10 MPa).

  When the current fuel pressure Pf during idling is higher than the predetermined value Pf0 (S260 = Yes) and the current in-cylinder direct injection ratio RDI is not 0, the in-cylinder injection request amount QDIreq is a small amount that is not 0, It is assumed that the fuel pressure Pf is too high and the in-cylinder injection request amount QDIreq is difficult to be stably injected. Therefore, the process proceeds to S270, the in-cylinder direct injection ratio RDI is corrected to 0, and this routine is temporarily ended.

  On the other hand, if the current fuel pressure Pf is equal to or less than the predetermined value Pf0 even during idling (S260 = No), the fuel pressure Pf is not so high even if the current in-cylinder injection request amount QDIreq is a small amount that is not zero. Therefore, the in-cylinder injection request amount QDIreq can be stably injected. Therefore, the process of S270 is skipped, and this routine is temporarily terminated while the injection ratio set in S210 is maintained.

  If the engine is idling off (S250 = Yes), the process proceeds to S280, whether the idling was off at the time of the previous execution of this routine, that is, whether idling was canceled by the driver's depressing operation of the accelerator pedal 58. Is determined. If the idling is OFF at the time of the previous execution of this routine (S280 = Yes), the current execution of this routine is during normal operation, so the process of S290 is performed while the injection ratio set in S210 is maintained. It is skipped and this routine is finished once.

  When the idling is canceled by the driver depressing the accelerator pedal 58 (S280 = No), the process proceeds to S290, and whether the in-cylinder injection request amount QDIreq is equal to or larger than the allowable minimum in-cylinder fuel injection amount QDImin. Determined. If the in-cylinder injection request amount QDIreq is smaller than the allowable minimum in-cylinder fuel injection amount QDImin (S290 = No), the fuel pressure Pf is too high this time, and the in-cylinder injection request amount QDIreq is stably injected by the in-cylinder injector 28C. Since it is assumed that it is difficult to do this, the process proceeds to S270, the in-cylinder direct injection ratio RDI is corrected to 0, and this routine is once ended. On the other hand, when the in-cylinder injection request amount QDIreq is equal to or larger than the allowable minimum in-cylinder fuel injection amount QDImin (S290 = Yes), this time, the in-cylinder injection request amount QDIreq can be stably injected by the in-cylinder injector 28C. The process does not proceed to S270, and this routine is temporarily terminated.

<< Pump control >>
FIG. 3 is a flowchart showing one specific example of the control operation of the high-pressure fuel pump 46, which is executed by the CPU 50a shown in FIG. The CPU 50a repeatedly executes the pump control routine 300 shown in FIG. 3 every time the crank angle reaches a predetermined value.

  When this routine is executed, first, the load factor KL is acquired in S310. The load factor KL can be acquired based on, for example, the output of the accelerator opening sensor 57 (accelerator pedal operation amount Accp).

  Next, in S320, it is determined whether or not the idle determination flag Xidol is ON. When the engine is idle OFF (S320 = No), the process proceeds to S330, and the pump duty HPPduty of the high-pressure fuel pump 46 is set based on the load factor KL and a predetermined map stored in advance in the ROM 50b. This routine ends once. If it is idle ON (S320 = Yes), the process does not proceed to S330 but proceeds from S340 onward.

  In S340, it is determined whether or not the fuel injection from the in-cylinder injector 28C is stopped. When the direct injection is not stopped (S340 = No), the process proceeds to S350, the pump duty HPPduty is set to the predetermined value HPPduty1, and this routine is temporarily ended. Here, the predetermined value HPPduty1 is a value corresponding to a minimum fuel pressure Pf1 (for example, 4 MPa) that can be set in order to stably inject fuel with the in-cylinder injector 28C. If the direct injection is stopped (S340 = Yes), the process proceeds to S360 and subsequent steps in order to set the fuel pressure Pf in the high-pressure fuel supply passage 42c to a low value for early resumption of direct injection.

  In S360, the fuel pressure Pf in the high-pressure fuel supply passage 42c is acquired. Next, in S370, it is determined whether or not the fuel pressure Pf is higher than the predetermined value Pf0. When the current fuel pressure Pf is higher than the predetermined value Pf0 (S370 = Yes), the process proceeds to S380, the pump duty HPPduty is set to the maximum value HPPduty_max, and this routine is temporarily ended. On the other hand, when the current fuel pressure Pf is equal to or less than the predetermined value Pf0 (S370 = No), the process proceeds to S350, the pump duty HPPduty is set to the above-mentioned predetermined value HPPduty1, and this routine is temporarily ended.

  Here, when the current fuel pressure Pf is higher than the predetermined value Pf0 (S370 = Yes), the pump duty HPPduty is set to the maximum value HPPduty_max as described above (S380), whereby the fuel pressure in the high-pressure fuel supply passage 42c is set. Pf once reaches the relief pressure in the relief valve 47. Then, the relief valve 47 opens and the fuel pressure Pf decreases. Thereafter, by setting the pump duty HPPduty to the predetermined value HPPduty1, the allowable minimum in-cylinder fuel injection amount QDImin becomes as small as possible and early direct injection restart is realized, so that the early high-pressure fuel supply passage 42c is realized. The fuel pressure Pf is kept low.

<< Injection ratio determination >>
FIG. 4 is a flowchart showing another specific example of the injection ratio determination operation executed by the CPU 50a shown in FIG. The CPU 50a repeatedly executes the injection ratio determination routine 200 shown in FIG. 4 every time the crank angle reaches a predetermined value.

  When this routine is executed, first, the load factor KL is acquired in S410. Next, in S420, the in-cylinder direct injection ratio RDI is determined based on parameters such as the load factor KL and the engine speed Ne and a predetermined map stored in advance in the ROM 50b.

  Subsequently, the process proceeds to S430, and it is determined whether or not the load factor KL is smaller than a predetermined small value KL0. When the load factor KL is equal to or greater than the predetermined value KL0 (S430 = No), the in-cylinder injection request amount QDIreq is relatively large and stable at the injection ratio determined in the above-described S420. It is assumed that fuel injection is possible. Therefore, in this case, the processing after S440 is skipped, and this routine is once ended.

  When the load factor KL is smaller than the predetermined value KL0 (S430 = Yes), it is assumed that the in-cylinder injection request amount QDIreq is small in idling or a low load operation equivalent to this (during vehicle deceleration, etc.) (vehicles) Even during fuel cut during deceleration, the determination in S430 is Yes.) Therefore, in this case, the process proceeds after S440.

  In S440, it is determined whether or not the in-cylinder direct injection ratio RDI determined in S420 is greater than zero. When the in-cylinder direct injection ratio RDI determined in S420 is 0 (S440 = No), the processing after S450 is skipped, and this routine is once ended. If the in-cylinder direct injection ratio RDI determined in S420 is greater than 0 (S440 = Yes), the process proceeds from S450 onward.

  In S450, the in-cylinder injection request amount QDIreq is obtained by the product of the current total fuel injection amount (command fuel injection amount) Q and the in-cylinder direct injection ratio RDI. Next, in S460, the current fuel pressure Pf in the high-pressure fuel supply passage 42c is acquired based on the output of the high-pressure side fuel pressure sensor 56. Based on this fuel pressure Pf and a predetermined map stored in advance in the ROM 50b, the current allowable minimum in-cylinder fuel injection amount QDImin in the in-cylinder injector 28C is acquired in S470.

  Subsequently, the process proceeds to S480, and it is determined whether the in-cylinder injection request amount QDIreq is smaller than the allowable minimum in-cylinder fuel injection amount QDImin. If the in-cylinder injection request amount QDIreq is smaller than the allowable minimum in-cylinder fuel injection amount QDImin (S480 = Yes), the fuel pressure is too high this time, and the in-cylinder injection request amount QDIreq is stably injected by the in-cylinder injector 28C. Since it is assumed that it is difficult, the process proceeds to S490, and the in-cylinder direct injection ratio RDI is corrected to zero. On the other hand, if the in-cylinder injection request amount QDIreq is equal to or larger than the allowable minimum in-cylinder fuel injection amount QDImin (S480 = No), this time, the in-cylinder injection request amount QDIreq can be stably injected by the in-cylinder injector 28C. The process of S490 is skipped. After these processes of S480 and S490, this routine is once ended.

<< Pump control >>
FIG. 5 is a flowchart showing a specific example of the control operation of the high-pressure fuel pump 46, which is executed by the CPU 50a shown in FIG. The CPU 50a repeatedly executes the pump control routine 300 shown in FIG. 5 every time the crank angle reaches a predetermined value.

  When this routine is executed, first, the load factor KL is acquired in S510. Next, in S520, it is determined whether the load factor KL is smaller than a predetermined small value KL0.

  When the load factor KL is equal to or greater than the predetermined value KL0 (S520 = No), the process proceeds to S530, where the pump duty HPPduty of the high-pressure fuel pump 46 is the load factor KL and a predetermined map stored in the ROM 50b in advance. The routine is temporarily ended.

  On the other hand, when the load factor KL is smaller than the predetermined value KL0 (S520 = Yes), the process proceeds to S540, and it is determined whether or not the fuel injection from the in-cylinder injector 28C is stopped. When the direct injection is not stopped (S540 = No), the process proceeds to S530, the pump duty HPPduty of the high-pressure fuel pump 46 is set, and this routine is temporarily ended. When the direct injection is stopped (S540 = Yes), the process proceeds to S550 and subsequent steps in order to set the fuel pressure Pf in the high-pressure fuel supply passage 42c to a low level for early resumption of direct injection.

  In S550, the fuel pressure Pf in the high-pressure fuel supply passage 42c is acquired. Next, it is determined whether or not the fuel pressure Pf is higher than a predetermined value Pf1. As described above, the predetermined value Pf1 is a value corresponding to the minimum fuel pressure that can be set in order to stably inject fuel with the in-cylinder injector 28C.

  When the current fuel pressure Pf is higher than the predetermined value Pf1 (S560 = Yes), the process proceeds to S570, the pump duty HPPduty is set to the maximum value HPPduty_max, and this routine is temporarily ended. On the other hand, when the current fuel pressure Pf is equal to or less than the predetermined value Pf1 (S560 = No), the process proceeds to S580, the pump duty HPPduty is set to the predetermined value HPPduty1, and this routine is temporarily ended.

  Here, when the current fuel pressure Pf is higher than the predetermined value Pf1, the pump duty HPPduty is set to the maximum value HPPduty_max as described above. Reach pressure. Then, the relief valve 47 opens and the fuel pressure Pf decreases. Thereafter, by setting the pump duty HPPduty to the predetermined value HPPduty1, the allowable minimum in-cylinder fuel injection amount QDImin becomes as small as possible and early direct injection restart is realized, so that the early high-pressure fuel supply passage 42c is realized. The fuel pressure Pf is kept low.

<Effect by embodiment>
During low load operation such as during deceleration (especially when the in-cylinder injection request amount QDIreq is smaller than the allowable minimum in-cylinder fuel injection amount QDImin), in-cylinder injection is stopped.

  Here, in the prior art, for example, when the vehicle enters an idle state for vehicle deceleration from a high load operation, the fuel pressure in the high pressure fuel supply passage 42c remains in a high state (for example, 20 MPa) corresponding to the high load operation. Fuel injection from the inner injector 28C is stopped. For this reason, while the fuel injection from the in-cylinder injector 28C is stopped, the allowable minimum in-cylinder fuel injection amount QDImin in the in-cylinder injector 28C is large.

  Therefore, in this state, fuel injection from the in-cylinder injector 28C is not performed until the in-cylinder injection request amount QDIreq becomes sufficiently large, and the resumption of fuel injection from the in-cylinder injector 28C is delayed. Therefore, there is a concern that deposits are generated and adhered due to the temperature rise of the in-cylinder injector 28C.

  In particular, in the internal combustion engine system 1 in which the EGR passage 36 is provided, the in-cylinder direct injection ratio RDI is set to be relatively low for the following reasons, so that the ratio at which in-cylinder injection is stopped can be high. Therefore, in such an internal combustion engine system 1, there is a further concern about the generation and adhesion of deposits in the in-cylinder injector 28C.

  That is, if the fuel F injected from the in-cylinder injector 28C adheres to the top surface of the piston 22, PM may be generated in the exhaust gas. In this regard, in the internal combustion engine system 1 in which the EGR passage 36 is provided, when the EGR is performed, the combustion temperature decreases, so that PM is easily generated. Further, when a large amount of PM is generated, PM adheres to the EGR cooler 38, thereby disturbing control of the EGR rate or reducing the cooling performance of the EGR gas. For this reason, in-cylinder direct injection ratio RDI is set low for PM measures.

  In contrast, in the present embodiment, the high pressure fuel pump 46 is driven at a high output (high duty) while the in-cylinder injection is stopped, so that the fuel pressure Pf is once increased to reach the relief pressure, and the relief pressure is reached. The valve 47 is opened by hydraulic pressure.

  By such operations of the high pressure fuel pump 46 and the relief valve 47, the fuel pressure in the high pressure fuel supply passage 42c (fuel supply pressure to the in-cylinder injector 28C) is reduced while the fuel injection from the in-cylinder injector 28C is stopped. The allowable minimum in-cylinder fuel injection amount QDImin in the in-cylinder injector 28C is reduced. Therefore, according to this embodiment, the resumption of fuel injection from the in-cylinder injector 28C can be accelerated (particularly also in the internal combustion engine system 1 provided with the EGR passage 36), and deposit generation and adhesion are suppressed. The

<List of examples of modification>
It should be noted that the above-described embodiments and specific examples thereof are merely examples of embodiments of the present invention that the applicant considered to be the best at the time of filing of the present application, as described above, The invention should not be limited by the above-described embodiment or the like. Therefore, it goes without saying that various modifications can be made to the above-described embodiments and the like within a range that does not change the essential part of the present invention.

  Hereinafter, some modifications will be exemplified. Here, in the following description of the modified example, components having the same configurations and functions as the components in the above-described embodiment are given the same name and the same reference numerals in the modified example. And And about description of the said component, description in the above-mentioned embodiment shall be used suitably in the range which is not inconsistent.

  However, it goes without saying that the modified examples are not limited to the following. The limited interpretation of the present invention based on the description of the above-described embodiment and the following modifications unfairly harms the interests of the applicant (especially rushing the application under the principle of prior application), but improperly imitates the imitator. It is beneficial and not allowed.

  Further, it goes without saying that the matters described in the above-described embodiments (including specific examples) and the following modifications can be applied in appropriate combination within a technically consistent range.

  (1) The present invention is not limited to the specific device configuration disclosed in the above-described embodiment. For example, the application target of the present invention is not limited to a vehicle. There is no particular limitation on the number of cylinders, the cylinder arrangement method (in-line, V-type, horizontally opposed), and the like.

  As the high-pressure fuel pump 46, for example, a mechanical pump provided with a fuel pressure control valve (electromagnetic spill valve) electromagnetically controlled by the ECU 50 (JP-A-4-50462, JP-A-10-288107, JP-A-2001). -263144, JP-A-2007-23801, etc.) can be used. In this case, the fuel pressure is controlled according to the valve closing time (duty ratio) of the fuel pressure control valve described above. Alternatively, as the high-pressure fuel pump 46, for example, an electric pump can be used. In this case, the fuel pressure is controlled according to the input current or voltage (duty ratio with respect to the maximum value) to the electric pump.

  The relief valve 47 may be a solenoid valve. In this case, the high-pressure fuel pump 46 is not included in the pressure adjusting means of the present invention, and the relief valve 47 and the control device 5 may be included.

  (2) The present invention is not limited to the specific operation as shown in the specific examples described above. That is, each process in the above-described specific example can be appropriately changed within the scope of the present invention. For example, the order of the steps in the flowcharts described above can be changed as appropriate.

  Further, as described above, “fuel injection cut” in which processing for reducing the fuel pressure in the high-pressure fuel supply passage 42c is performed may include fuel cut.

  When an electromagnetic valve is used as the relief valve 47, it is not necessary to temporarily increase the pressure by the high-pressure fuel pump 46 as a process for reducing the fuel pressure in the high-pressure fuel supply passage 42c. The “relief pressure” in this case is a valve opening pressure set by the ECU 50 (for example, according to the operating state). When the fuel pressure Pf acquired based on the output of the high-pressure side fuel pressure sensor 56 exceeds the valve opening pressure, the relief valve 47 is opened by a control signal from the ECU 50. From this point of view, the “relief pressure” can also be referred to as “control pressure”.

  When acquiring the load factor KL in S310 and the like, the output of the throttle position sensor 52 (throttle valve opening TA) can be used instead of the output of the accelerator opening sensor 57 (accelerator pedal operation amount Accp). Alternatively, instead of the load factor KL, other parameters (intake air flow rate Ga, in-cylinder intake air amount Mc calculated based on this, etc.) can be used.

  (3) Other modifications not specifically mentioned are naturally included in the technical scope of the present invention within the scope not changing the essential part of the present invention.

  Further, in each element constituting the means for solving the problems of the present invention, what is expressed in terms of function and function is the specific structure disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function.

1 is a diagram schematically showing an overall configuration of an internal combustion engine system (vehicle) that is an embodiment of the present invention. FIG. It is a flowchart which shows one specific example of the injection ratio determination operation | movement performed by CPU shown by FIG. It is a flowchart which shows one specific example of control operation | movement of a high pressure fuel pump performed by CPU shown in FIG. 7 is a flowchart showing another specific example of the injection ratio determination operation executed by the CPU shown in FIG. 1. It is a flowchart which shows the specific example of control operation of the high pressure fuel pump performed by CPU shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine system 2 ... Internal combustion engine 22 ... Piston 25 ... Intake port 28C ... In-cylinder injector 28P ... Port injector 3 ... Intake / exhaust system 36 ... EGR passage 38 ... EGR cooler 4 ... Fuel supply system 41 ... Fuel tank 42 ... Fuel Supply passage 42a ... Main fuel supply passage 42b ... Low pressure fuel supply passage 42c ... High pressure fuel supply passage 42d ... Main return passage 42e ... Relief passage 43 ... Fuel filter 44 ... Main fuel pump 46 ... High pressure fuel pump 47 ... Relief valve 5 ... Control Device 50 ... ECU 50a ... CPU
56 ... High-pressure side fuel pressure sensor 57 ... Accelerator opening sensor CC ... Combustion chamber

Claims (9)

An in-cylinder injection valve that directly injects fuel into the combustion chamber of the internal combustion engine;
An in-passage injection valve that injects the fuel into an intake passage that communicates with the combustion chamber;
Pressure regulating means for lowering the fuel supply pressure to the in-cylinder injection valve during operation of the internal combustion engine and stopping the fuel injection from the in-cylinder injection valve;
A fuel injection system comprising: The fuel injection system of claim 1, wherein
A high pressure fuel supply passage connected to the in-cylinder injection valve;
The pressure adjusting means is
A relief interposed in the high-pressure fuel supply passage so as to open when the fuel supply pressure in the high-pressure fuel supply passage reaches a predetermined relief pressure and discharge the fuel from the high-pressure fuel supply passage. A fuel injection system comprising a valve. A fuel injection system according to claim 2,
The relief valve is configured to be mechanically operated by the fuel supply pressure in the high-pressure fuel supply passage,
The pressure adjusting means is
The relief valve;
A high-pressure fuel pump provided to deliver the fuel to the high-pressure fuel supply passage;
A fuel injection system comprising: The fuel injection system according to any one of claims 1 to 3,
The fuel injection system further comprising injection control means for controlling an injection state of the fuel in the in-cylinder injection valve and the in-passage injection valve. A fuel injection system according to claim 4, comprising:
The injection control means stops the injection of the fuel from the in-cylinder injection valve and only the in-passage injection valve when the fuel supply pressure during low load operation of the internal combustion engine exceeds a predetermined pressure. The fuel injection system characterized by injecting the said fuel from. A fuel injection system according to claim 4 or claim 5, wherein
When the in-cylinder injection request amount calculated as an amount to be injected from the in-cylinder injection valve during low load operation of the internal combustion engine is smaller than a predetermined allowable minimum in-cylinder fuel injection amount, A fuel injection system, wherein the fuel injection from the cylinder injection valve is stopped and the fuel is injected only from the injection valve in the passage. A fuel injection system according to any one of claims 1 to 6,
The fuel injection system according to claim 1, wherein the pressure adjusting means reduces the fuel supply pressure while the fuel injection from the in-cylinder injection valve is stopped during low-load operation of the internal combustion engine. An internal combustion engine system comprising the fuel injection system according to any one of claims 1 to 7,
An internal combustion engine system comprising an exhaust gas recirculation passage that connects an exhaust passage communicating with the combustion chamber and the intake passage. The internal combustion engine system according to claim 8,
An internal combustion engine system further comprising an EGR cooler that is interposed in the exhaust gas recirculation passage and cools EGR gas that passes through the EGR passage.

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