JP5870959B2 - Fuel injection control device and fuel injection system - Google Patents

Description

  The present invention relates to a fuel injection control device and a fuel injection system applied to a fuel injection system that injects fuel boosted by a high-pressure pump from an injector.

  A general injector of this type includes a fixed core that generates an electromagnetic attraction force when the coil is energized, and a movable core that is attracted to the fixed core and moves together with the valve body. Then, by controlling the energization time Ti to the coil, the valve opening time of the valve element is controlled, and the fuel injection period, that is, the injection amount Q is controlled.

  The conventional general control is based on the premise that injection (full lift injection) is performed so that the valve closing operation is started after the valve body reaches the full lift position. Therefore, when a small amount of fuel is injected, the minimum energization time Ti (full lift minimum time) that allows full lift injection is set, and the pressure of the fuel supplied to the injector is reduced.

  On the other hand, Patent Document 1 discloses a control for injecting (partial injection) so as to start the valve closing operation before the valve element reaches the full lift position by making the energization time Ti shorter than the full lift minimum time. Yes. This control can also inject a small amount of fuel.

JP 2013-2400 A

  Here, the higher the fuel pressure (suck fuel pressure) in the portion (sack chamber) downstream of the seat part of the valve body in the fuel passage inside the injector, the smaller the spray particle size of the fuel injected from the nozzle hole. The resulting combustion energy is increased. Therefore, increasing the pressure of the fuel supplied to the injector (supply fuel pressure) is desirable in that the spray particle size can be reduced.

  However, immediately after the valve element is opened, the fuel is highly throttled in the seat portion, so that the sac fuel pressure does not increase immediately when the supply fuel pressure is increased. For this reason, when the partial injection described above is performed, the injection is terminated without sufficiently increasing the sac fuel pressure, so that it is not possible to inject fuel with a small spray particle size.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel injection control device and a fuel injection system that enable a small amount of fuel injection while reducing the spray particle size.

  One disclosed invention employs the following technical means to achieve the above object. In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of the disclosed invention is limited Not what you want.

  One of the disclosed inventions includes an injector (10) that opens the valve body (12) to inject fuel from the nozzle hole (17a), and a high-pressure pump (40) that boosts the fuel and supplies the fuel to the injector. It is assumed that the fuel injection control device (20) is applied to the fuel injection system provided.

And 1st invention is equipped with the following structures, It is characterized by the above-mentioned. That is, the full lift injection that starts the valve closing operation after the valve body that has started the valve opening operation reaches the full lift position, and the partial injection that the valve body that has started the valve opening operation starts the valve closing operation without reaching the full lift position Selection means (S10, S11) is provided for selecting which of the two to inject. Pump control means (S23) for controlling the operation of the high-pressure pump is provided so that the pressure of the fuel supplied to the injector becomes the target pressure (Ptrg). Target pressure setting that sets the target pressure according to the operating state of the internal combustion engine when full lift injection is selected, and sets the target pressure to a value that is greater than or equal to the preset lower limit pressure when partial injection is selected Means (S21, S22) are provided , and the characteristic line representing the relationship between the pressure of the fuel supplied to the injector and the spray particle diameter of the fuel injected from the injection hole has a maximum second-order differential value. there exists a point (P), the lower limit pressure that is set to a pressure value at the change point (Pa).
The second invention includes the selection means (S10, S11) and the pump control means (S23) described above, and sets the target pressure according to the operating state of the internal combustion engine when full lift injection is selected, Target pressure setting means for setting the target pressure to the maximum value (Pmax) of the target pressure that the fuel injection system can take when partial injection is selected.
The third invention includes the selection means (S10, S11) and the pump control means (S23) described above, and sets the target pressure according to the operating state of the internal combustion engine when full lift injection is selected, Target pressure setting means for setting the target pressure to a value of 10 MPa or more when partial injection is selected.

Here, contrary to the first, second, and third inventions, if the target pressure is set according to the operating state of the internal combustion engine even during partial injection, the target injection amount is very small and the target In some cases, the pressure becomes small, and injection cannot be performed with a small spray particle size. On the other hand, in the first, second, and third inventions, the target pressure is set to a value that is equal to or greater than the preset lower limit pressure during partial injection. Therefore, since the injection is performed with a sufficiently high supply fuel pressure during the partial injection, the spray particle size is small even with the partial injection. Therefore, it is possible to inject a small amount of fuel while reducing the spray particle size. In addition, since the target pressure is set according to the operating state of the internal combustion engine at the time of full lift injection, it is possible to avoid an unnecessarily high supply fuel pressure at the time of full lift injection, and the energy required for driving the high pressure pump becomes unnecessarily large. Can be avoided.

1 is an overall view showing a fuel injection system according to a first embodiment of the present invention. Sectional drawing explaining the whole structure of the injector shown in FIG. FIG. 3 is an enlarged view of FIG. 2 showing a shape of a nozzle hole. FIG. 3 is an enlarged view of FIG. 2 showing a magnetic circuit. The schematic diagram explaining the whole high-pressure pump structure shown in FIG. The figure which shows the change which arises with the passage of time of the applied voltage to a coil, coil current, and electromagnetic attraction force when ECU shown in FIG. 1 implements injection control. The figure which shows the Ti-Q characteristic of the injector shown in FIG. The flowchart which shows the process sequence of the injection control by the microcomputer shown in FIG. The flowchart which shows the process sequence of the pump control by the microcomputer shown in FIG. The flowchart which shows the procedure of the map update process by the microcomputer shown in FIG. It is a graph explaining the effect by 2nd Embodiment of this invention, and the test result which shows the relationship between a spray particle size and supply fuel pressure. It is a graph explaining the effect by 3rd Embodiment of this invention, and the numerical-analysis result which shows the relationship between the spray particle diameter deterioration degree and supply fuel pressure. The test result which shows the relationship between a spray particle size deterioration degree and a sheet | seat drawing rate.

  Hereinafter, embodiments of a fuel injection control device according to the present invention and a fuel injection system including the device will be described with reference to the drawings.

(First embodiment)
An injector 10 shown in FIG. 1 is mounted on an ignition type internal combustion engine (gasoline engine), and directly injects fuel into a combustion chamber 2 of the internal combustion engine. Specifically, a mounting hole 4 for inserting the injector 10 is formed at a position that coincides with the cylinder axis C in the cylinder head 3 that forms the combustion chamber 2.

  The fuel supplied to the injector 10 is stored in a fuel tank (not shown). The fuel in the fuel tank is pumped up by a low-pressure pump, pressurized by the high-pressure pump 40 and pumped to the delivery pipe 30. The high-pressure fuel in the delivery pipe 30 is distributed and supplied to the injectors 10 of each cylinder. The structure of the high-pressure pump 40 will be described in detail later with reference to FIG.

  A spark plug 6 is attached to the cylinder head 3. The spark plug 6 and the injector 10 are arranged side by side in a portion of the cylinder head 3 opposite to the piston with respect to the combustion chamber 2.

  As shown in FIG. 2, the injector 10 includes a body 11, a valve body 12, a coil 13, a fixed core 14, a movable core 15, a housing 16, and the like. The body 11 is made of a magnetic material so that the fuel passage 11a is formed inside. The body 11 forms a seating surface 17b on which the valve body 12 is seated and seated, and an injection hole 17a for injecting fuel.

  If it demonstrates in detail using FIG. 3, the nozzle hole body 17 in which the seating surface 17b was formed will be attached to the body 11. FIG. A nozzle hole plate 17p in which a nozzle hole 17a is formed is attached to the nozzle hole body 17. A portion of the valve body 12 that is seated on the seating surface 17b is a seat portion 12a. Specifically, the boundary line between the main body portion 12b and the tip end portion 12c of the valve body 12 functions as the seat portion 12a seated on the seating surface 17b. The main body portion 12b has a cylindrical shape extending in the direction of the axis C, and the tip portion 12c has a conical shape extending from the tip on the nozzle hole side of the main body portion 12b toward the nozzle hole 17a. In short, the corner portion that is the boundary line between the cylinder and the cone corresponds to the annular sheet portion 12a extending around the axis C.

  When the valve body 12 is closed so that the seat portion 12a is seated on the seating surface 17b, fuel injection from the injection hole 17a is stopped. When the valve body 12 is opened (lifted up) so as to separate the seat portion 12a from the seating surface 17b, fuel is injected from the injection hole 17a. A portion of the fuel passage 11a downstream from the seat portion 12a of the valve body 12 and upstream of the nozzle hole 17a is a sac chamber 17s. The higher the fuel pressure in the sac chamber 17s (sack fuel pressure), the smaller the spray particle size of the fuel injected from the nozzle hole 17a.

  The flow path length L of the nozzle hole 17a is smaller than the inlet diameter D of the nozzle hole 17a. The injection hole 17a is formed in the injection hole plate 17p so that the flow path direction of the injection hole 17a is inclined with respect to the direction perpendicular to the plate surface of the injection hole plate 17p. The cross-sectional shape of the nozzle hole 17a is circular. Therefore, the inlet shape of the nozzle hole 17a is an ellipse, and strictly speaking, the inlet diameter D is the major axis of the ellipse.

  Returning to the description of FIG. 2, the coil 13 is wound around a resin bobbin 13a and sealed with the bobbin 13a and the resin material 13b. That is, the coil 13, the bobbin 13a, and the resin material 13b constitute a cylindrical coil body.

  The fixed core 14 is made of a magnetic material in a cylindrical shape, and forms a fuel passage 14a inside the cylinder. A fixed core 14 is inserted into the inner peripheral surface of the body 11, and a bobbin 13 a is inserted into the outer peripheral surface of the body 11. Further, the outer peripheral surface of the resin material 13 b that seals the coil 16 is covered with the housing 16. The housing 16 is formed of a magnetic material in a cylindrical shape. A lid member 18 made of a magnetic material is attached to the opening end of the housing 16. As a result, the coil body is surrounded by the body 11, the housing 16 and the lid member 18.

  The movable core 15 is formed in a disk shape from a magnetic material, and is inserted and disposed on the inner peripheral surface of the body 11. The body 11, the valve body 12, the coil body, the fixed core 14, the movable core 15, and the housing 16 are arranged so that their center lines coincide with each other. The movable core 15 is disposed on the side of the injection hole 17a with respect to the fixed core 14, and is disposed opposite to the fixed core 14 so as to have a predetermined gap with the fixed core 14 when the coil 13 is not energized. Yes.

  When the coil 13 is energized to generate an electromagnetic attractive force on the fixed core 14, the movable core 15 is attracted to the fixed core 14 by this electromagnetic attractive force. As a result, the valve body 12 connected to the movable core 15 is lifted up (opening operation) against the elastic force of the main spring SP1 and the fuel pressure closing force. The fuel pressure closing force is a force by which the fuel pressure in the fuel passage 11a pushes the valve body 12 to the valve closing side. On the other hand, when energization of the coil 13 is stopped, the valve body 12 is closed together with the movable core 15 by the elastic force of the main spring SP1.

  FIG. 4 is an enlarged view of FIG. 2 and shows a state where the injector 10 is inserted into the mounting hole 4 of the cylinder head 3 and attached. Since the body 11, the housing 16, the lid member 18 and the fixed core 14 surrounding the coil body are formed of a magnetic material as described above, a magnetic circuit serving as a path for magnetic flux generated by energization of the coil 13 is formed. Become. That is, magnetic flux flows through the magnetic circuit as indicated by the arrows in the figure.

  In addition, the part of the area | region which accommodates the coil 13 among the housings 16 is called the coil area | region part 16a. A portion of the housing 16 where the magnetic circuit is formed is referred to as a magnetic circuit region portion 16b. In other words, in the insertion direction (vertical direction in FIG. 4), the end surface position of the lid member 18 on the side opposite to the injection hole (upper side in FIG. 4) is the region boundary on the side opposite to the injection hole of the magnetic circuit region portion 16b. . In the example of FIG. 4, the entire insertion direction (vertical direction in FIG. 4) of the magnetic circuit region portion 16 b is surrounded by the inner peripheral surface 4 a of the mounting hole 4 over the entire circumference. A portion of the cylinder head 3 surrounding the magnetic circuit over the entire circumference corresponds to the “annular conductive portion 3a (a predetermined portion of the internal combustion engine)”.

  An outer peripheral surface of a portion of the body 11 located closer to the nozzle hole than the housing 16 is in contact with the inner peripheral surface 4b of the mounting hole 4 (see FIG. 1). On the other hand, a clearance CL is formed between the outer peripheral surface of the housing 16 and the inner peripheral surface 4a of the mounting hole 4 (see FIG. 4). In other words, the outer peripheral surface of the magnetic circuit region portion 16b and the inner peripheral surface 4a of the mounting hole 4 face each other with a gap CL therebetween.

  As described above, since the magnetic circuit is surrounded by the annular conductive portion 3a, when an electric current is passed through the coil 13 and a magnetic flux change occurs in the magnetic circuit (see the arrow in FIG. 4), the annular conductive portion is accompanied by the magnetic flux change. An eddy current is generated in 3a. This eddy current flows in the direction perpendicular to the paper surface of FIG.

  Returning to the description of FIG. 2, a through hole 15 a is formed in the movable core 15, and the valve body 12 slides with respect to the movable core 15 by inserting the valve body 12 into the through hole 15 a. It is assembled so that relative movement is possible. A locking portion 12 d is formed at the end of the valve body 12 on the side opposite to the injection hole. When the movable core 15 is attracted to the fixed core 14 and moved, the locking portion 12d moves in a state of being locked to the movable core 15, so that the valve body 12 also moves simultaneously with the start of movement of the movable core 15 ( Valve opening operation). However, even when the movable core 15 is in contact with the fixed core 14, the valve element 12 can move relative to the movable core 15 and lift up.

  A main spring SP1 is disposed on the side opposite to the injection hole of the valve body 12, and a sub spring SP2 is disposed on the injection hole side of the movable core 15. These springs SP1 and SP2 are coiled and deformed in the direction of the axis C to be elastically deformed. The elastic force (main elastic force Fs1) of the main spring SP1 is applied to the valve body 12 in the valve closing direction as a reaction force from the adjustment pipe 101. The elastic force (sub elastic force Fs2) of the sub spring SP2 is applied to the movable core 15 in the suction direction as a reaction force from the recess 11b of the body 11.

  In short, the valve body 12 is sandwiched between the main spring SP1 and the seating surface 17b, and the movable core 15 is sandwiched between the sub spring SP2 and the locking portion 12d. Then, the sub elastic force Fs2 is transmitted to the locking portion 12d via the movable core 15, and is given to the valve body 12 in the valve opening direction. Therefore, it can be said that the elastic force Fs obtained by subtracting the sub elastic force Fs2 from the main elastic force Fs1 is applied to the valve body 12 in the valve closing direction.

  Specifically, when the valve body 12 is lifted up, the main spring force Fs1 increases because the compression amount (elastic deformation amount) of the main spring SP1 increases. On the other hand, with respect to the sub spring SP2, when the valve body 12 is lifted up, the compression amount (elastic deformation amount) decreases, so the sub elastic force Fs2 decreases. These combined elastic forces Fs (= Fs1 + Fs2) increase with lift-up.

  The main elastic force Fs1 (set load Fset1) when the valve is closed (stroke = 0) is larger than the sub elastic force Fs2 (set load Fset2) when the valve is closed. Therefore, the combined elastic force Fs when the valve is closed is smaller than the set load Fset1. As shown in FIG. 2, the set load Fset1 of the main spring SP1 can be adjusted by adjusting the attachment position of the adjustment pipe 101 with respect to the inside of the cylinder of the fixed core 14.

  Next, the high-pressure pump 40 will be described with reference to FIG. The high-pressure pump 40 is a piston pump that sucks and discharges fuel by reciprocating movement of the plunger 45. Specifically, the drive shaft 5 of the high-pressure pump 40 is rotationally driven by the crankshaft of the internal combustion engine. That is, the high-pressure pump 40 is a mechanical pump that is driven by the rotational torque of the internal combustion engine. The cam mechanism 46 converts the rotational movement of the drive shaft 5 into the reciprocating movement of the plunger 45. The plunger 45 reciprocates in a pump chamber 44 disposed in the middle of the fuel passage 48. As a result, the fuel supplied from the low pressure pump to the high pressure pump 40 is sucked into the pump chamber 44, compressed by the plunger 45, and then discharged from the pump chamber 44 to the delivery pipe 30.

  On the fuel suction side of the high-pressure pump 40, a normally-opening type metering valve 43 that closes when energized is provided. By controlling the valve closing time of the metering valve 43, the fuel discharge of the high-pressure pump 40 is performed. The amount is adjusted. That is, when the plunger 45 is lowered, fuel is sucked into the pump chamber 44. Thereafter, when the metering valve 43 is not energized when the plunger 45 starts to rise, the metering valve 43 is kept open to return the fuel in the pump chamber 44 to the upstream side. On the other hand, when the metering valve 43 is closed as the metering valve 43 is energized, the fuel pressure in the pump chamber 44 rises, and the high-pressure fuel is pumped to the delivery pipe 30. In such a case, as the valve closing timing (energization timing) of the metering valve 43 is retarded, the fuel pumping period becomes shorter, and consequently the fuel pumping amount decreases. The metering valve 43 may be a normally closed type instead of the normally open type.

  A relief valve 47 as a pressure release valve for limiting the fuel discharge pressure is provided on the downstream side of the check valve 42. The relief valve 47 opens when the fuel discharge pressure of the high-pressure pump 40 is equal to or higher than a predetermined relief pressure (for example, 25 MPa). When the valve is opened, the fuel discharged from the high-pressure pump 40 is supplied to the fuel tank via the fuel return pipe 49. Return to 25. This prevents the fuel pressure in the delivery pipe 30 from exceeding the relief pressure. Note that the relief valve 47 may be provided in the delivery pipe 30 instead of being provided in the high-pressure pump 40.

  Returning to the description of FIG. 1, the electronic control unit (ECU 20) corresponds to the “fuel injection control unit” recited in the claims, and includes a microcomputer (microcomputer 21), an integrated IC 22, a booster circuit 23, a switching unit. Elements SW2, SW3, SW4 and the like are provided.

  The microcomputer 21 includes a central processing unit, a nonvolatile memory (ROM), a volatile memory (RAM), and the like. Based on the load of the internal combustion engine and the engine speed, the required fuel injection amount Qreq and the target injection start Calculate the time. A characteristic line (see FIG. 7) showing the relationship between the energization time Ti and the injection amount Q is obtained by testing in advance, and the energization time Ti to the coil 13 is controlled according to the characteristic line, thereby Control the quantity Q.

  For example, a map (Ti-Q map) showing the relationship between the energization time Ti and the injection amount Q is created based on the characteristic line, and the Ti-Q map is stored in the memory. Then, the energization time Ti suitable for the required injection amount (required injection amount Qreq) is set in consideration of the Ti-Q map. The higher the fuel pressure supplied to the injector 10 (that is, the fuel pressure in the delivery pipe 30), the shorter the energization time Ti. Therefore, a Ti-Q map is created and stored for each supply fuel pressure, and the Ti-Q map to be considered is switched according to the supply fuel pressure at the time of injection.

  The integrated IC 22 includes an injection drive circuit 22a that controls the operation of the switching elements SW2, SW3, and SW4, and a charging circuit 22b that controls the operation of the booster circuit 23. These circuits 22 a and 22 b operate based on the injection command signal output from the microcomputer 21. The injection command signal is a signal for instructing the energization state of the coil 13 of the injector 10 and is set by the microcomputer 21 based on the above-described required injection amount Qreq and the target injection start timing and the coil current detection value I described later. The The injection command signal includes an injection signal, a boost signal, and a battery signal, which will be described later.

  The booster circuit 23 includes a coil 23a, a capacitor 23b, a diode 23c, and a switching element SW1. When the charging circuit 22b controls the switching element SW1 so that the switching element SW1 is repeatedly turned on and off, the battery voltage applied from the battery terminal Batt is boosted (boosted) by the coil 23a and stored in the capacitor 23b. . The voltage of the electric power boosted and stored in this way corresponds to the “boost voltage”.

  When the injection drive circuit 22a turns on both the switching elements SW2 and SW4, a boost voltage is applied to the coil 13 of the injector 10. On the other hand, when the switching element SW2 is turned off and the switching element SW3 is turned on, the battery voltage is applied to the coil 13 of the injector 10. Note that when the voltage application to the coil 13 is stopped, the switching elements SW2, SW3, and SW4 are turned off. The diode 24 is for preventing the boost voltage from being applied to the switching element SW3 when the switching element SW2 is turned on.

  The shunt resistor 25 is for detecting the current flowing through the switching element SW4, that is, the current flowing through the coil 13 (coil current). The microcomputer 21 is based on the amount of voltage drop generated in the shunt resistor 25 and the coil described above. A current detection value I is detected.

  Next, the electromagnetic attractive force (valve opening force) generated by flowing the coil current will be described in detail.

  The greater the magnetomotive force (ampere turn AT) generated by the fixed core 14, the greater the electromagnetic attractive force. That is, if the number of turns of the coil 13 is the same, the electromagnetic attraction force increases as the coil current is increased and the ampere turn AT is increased. However, it takes time for the suction force to reach a maximum value after energization is started. In the present embodiment, the electromagnetic attractive force when saturated and reaches the maximum value is referred to as a static attractive force Fb.

  Further, the electromagnetic attractive force necessary for the valve body 12 to start the valve opening operation is referred to as a required valve opening force Fa. The higher the fuel pressure supplied to the injector 10, the greater the electromagnetic suction force (valve opening start suction force) required for the valve body 12 to start the valve opening operation. Further, the valve opening start suction force increases according to various situations such as when the viscosity of the fuel is large. Therefore, the valve opening start suction force when the situation in which the valve opening start suction force is maximized is assumed is defined as the required valve opening force Fa.

  FIG. 6A shows a voltage waveform applied to the coil 13 when the fuel injection is performed once. As shown in the figure, the energization is started by applying the boost voltage at the voltage application start timing t1 (that is, the start timing of the energization time Ti) commanded by the injection command signal. Then, with the start of energization, the coil current increases to the first target value I1 (see FIG. 6B). The energization is turned off at time t1 when the above-described coil current detection value I reaches the first target value I1. In short, control is performed so that the coil current is increased to the first target value I1 by applying the boost voltage by the first energization.

  Thereafter, the energization by the battery voltage is controlled so that the coil current is maintained at the second target value I2 set to a value lower than the first target value I1. Specifically, the average value of the fluctuating coil current is changed to the second target value I2 by repeatedly turning on and off the battery voltage so that the deviation between the coil current detection value I and the second target value I2 is within a predetermined range. The duty is controlled so that The second target value I2 is set to a value such that the static suction force Fb is greater than or equal to the required valve opening force Fa.

  Thereafter, the energization by the battery voltage is controlled so that the coil current is maintained at the third target value I3 set to a value lower than the second target value I2. Specifically, the average value of the fluctuating coil current is changed to the third target value I3 by repeatedly turning on and off the battery voltage so that the deviation between the coil current detection value I and the third target value I3 is within a predetermined range. The duty is controlled so that

  As shown in FIG. 6C, the electromagnetic attractive force continues to increase during a period from the start of energization, that is, the increase control start time (t0) to the pickup control end time (t3). Note that the rate of increase of the electromagnetic attractive force is slower in the pickup control period than in the increase control period. The first target value I1, the second target value I2, and the pickup control period are set so that the suction force exceeds the required valve opening force Fa during the period (t0 to t3) during which the suction force increases. Yes.

  In the hold control period (t4 to t5), the suction force is held at a predetermined value. The third target value I3 is set so that the predetermined value is higher than the valve opening holding force Fc required to hold the valve open state. The valve opening holding force Fc is smaller than the required valve opening force Fa.

  The injection signal included in the injection command signal is a pulse signal for instructing the energization time Ti, and the pulse-on time is set at a time t0 that is earlier than the target injection start time by a predetermined injection delay time. Then, the pulse-off time is set at the time t5 (that is, the end time of the energization time Ti) when the time corresponding to the energization time Ti has elapsed since the pulse was turned on. The switching element SW4 operates according to this injection signal.

  The boost signal included in the injection command signal is a pulse signal for instructing on / off of energization by the boost voltage, and the pulse is turned on simultaneously with the pulse on of the injection signal. Thereafter, the boost signal is repeatedly turned on and off until the coil current detection value I reaches the first target value I1. The switching element SW2 operates according to the on / off of the boost signal. Thereby, the boost voltage is applied in the increase control period.

  The battery signal included in the injection command signal is turned on at the pickup control start time t2. Thereafter, the battery signal is repeatedly turned on and off so as to perform feedback control so that the coil current detection value I is held at the second target value I2 until the elapsed time from the start of energization reaches a predetermined time. Thereafter, the battery signal is repeatedly turned on and off so as to perform feedback control so that the coil current detection value I is held at the third target value I3 during the period until the pulse of the injection signal is turned off. The switching element SW3 operates according to this battery signal.

  The fuel pressure supplied to the injector 10 is detected by a fuel pressure sensor 31 (see FIG. 1) attached to the delivery pipe 30. The ECU 20 determines whether or not to perform the above-described pickup control according to the supply fuel pressure detected by the fuel pressure sensor 31. For example, when the supply fuel pressure is equal to or higher than a predetermined value, the pickup control is permitted, but when it is lower than the predetermined value, the pickup control is not performed, and the hold control is performed after the ascent control.

  FIG. 7 shows a characteristic line representing the relationship between the energization time Ti and the injection amount Q. The solid line in the figure is the characteristic line when the supply fuel pressure is 10 MPa, and the dotted line is the characteristic line when the supply fuel pressure is 20 MPa. In this embodiment, the maximum value of the target pressure that can be taken by the fuel injection system (system maximum fuel pressure Pmax) is 10 MPa. The system maximum fuel pressure Pmax is set to a value lower than the maximum discharge pressure of the high-pressure pump 40, and is set to a maximum value that can stably hold the fuel pressure (supply fuel pressure) in the delivery pipe 30.

  Of the characteristic lines, the area indicated by reference numeral A1 is referred to as a partial area, and the area indicated by reference numeral A2 is referred to as a full lift area. When fuel is injected during the energization time Ti in the partial region A1 (partial injection), the valve closing operation is started before the movable core 15 collides with the fixed core 14, that is, before the valve body 12 reaches the full lift position. A small amount of fuel is injected. The full lift position is the lift position of the valve body 12 when the movable core 15 collides with the fixed core 14. On the other hand, when the fuel is injected during the energization time Ti in the full lift region A2 (full lift injection), the valve body 12 starts the valve closing operation after reaching the full lift position, so that compared with the case where the fuel is injected in the partial region A1. The injection amount increases.

  The maximum injection amount B that can be injected in the partial region A1 increases as the supply fuel pressure increases. Therefore, for example, when the injection amount indicated by the symbol Q1 in FIG. 7 is injected at the supply fuel pressure of 10 MPa, the injection is performed in the full lift region A2, but when this injection amount Q1 is injected at 20 MPa, the partial region A1. Will be injected.

  The ratio of the sheet throttle degree to the total value of the pressure loss (sheet throttle degree) due to the flow restrictor at the seat portion 12a of the valve body 12 and the pressure loss due to the flow restrictor (nozzle restrictor degree) at the nozzle hole 17a, This is called the sheet drawing ratio. Immediately after the start of injection, the degree of sheet restriction is greater than the degree of restriction of the injection hole, and the sheet restriction ratio decreases as the valve body 12 is lifted up. In addition, the code | symbol C in FIG. 7 shows the electricity supply time Ti used as the sheet | seat drawing rate 50% in the characteristic line in case supply fuel pressure is 10 Mpa.

  Next, processing procedures for various controls performed by the microcomputer 21 will be described with reference to FIGS. 8, 9, and 10. These controls are repeatedly executed at a predetermined cycle (for example, a calculation cycle of the CPU) during the operation period of the internal combustion engine.

  First, the procedure for controlling the injector 10 will be described with reference to FIG. First, in step S10 (selecting means) in FIG. 8, it is determined whether or not the above-mentioned required injection amount Qreq is equal to or less than the partial maximum injection amount Qplmax at the system maximum fuel pressure Pmax. If it is determined that Qreq ≦ Qplmax, it means that injection in the partial region A1 becomes possible if the supply fuel pressure is set to the system maximum fuel pressure Pmax. In the case of an affirmative determination in this way, in the next step S11 (selecting means), the “output improvement amount” and “pump loss amount” described below are compared in magnitude.

  For example, in the case where injection is possible in both the partial region A1 and the full lift region A2 as in the micro injection indicated by the symbol Q1 in FIG. 7, the supply fuel pressure is set to the system maximum fuel pressure Pmax and the injection is selected in the partial region A1. In this case, since the injection is performed at a higher pressure than in the case of the injection in the full lift region A2, the spray particle size becomes small. Therefore, the output torque of the internal combustion engine with respect to the fuel injection amount, that is, the output efficiency of the internal combustion engine is improved. Note that the torque required for driving the high-pressure pump 40 is excluded from the output torque referred to here.

  However, as a contradiction, when partial injection is selected and the supply fuel pressure is set to the system maximum fuel pressure Pmax, the rotational load of the drive shaft 5 increases as the discharge amount of the high-pressure pump 40 increases, and the output torque with respect to the fuel injection amount described above (Output efficiency) decreases.

  Thus, compared with the case where full lift injection is selected, the amount by which partial injection is selected and the spray particle size is reduced to improve the output efficiency of the internal combustion engine is referred to as “output improvement amount”. The amount by which the output efficiency of the internal combustion engine is reduced due to the increase in the load of the high-pressure pump 40 when partial injection is selected as compared with the case where full lift injection is selected is referred to as “pump loss amount”.

  These pump loss amount and output improvement amount differ depending on the operating state of the internal combustion engine at that time. Specific examples of the operating state include the load of the internal combustion engine, the rotational speed, the temperature, the load when the internal combustion engine drives the auxiliary machine, and the like. Therefore, in step S11, the magnitude of the output improvement amount and the pump loss amount is compared according to these operating states.

  When it is determined in step S11 that the output improvement amount is greater than the pump loss amount, in the subsequent steps S12 and S13, the injector 10 is set so that the supply fuel pressure is set to the system maximum fuel pressure Pmax and the required injection amount Qreq is injected in the partial region A1. Control the operation of

  Specifically, first, in step S12 (injection command period setting means), the energization time Ti corresponding to the required injection amount Qreq is set in consideration of the Ti-Q map created based on the characteristic line corresponding to Pmax. . Then, by outputting an injection command signal including the energization time Ti (injection signal) set in this way to the integrated IC 22, the injector 10 injects the required injection amount Qreq in the partial region A1 on the characteristic line corresponding to Pmax. To do. In the next step S13, the forcible command flag is set to ON so that a target supply fuel pressure Ptrg (target pressure), which will be described later, is set to the system maximum fuel pressure Pmax.

  On the other hand, when it is determined in step S10 that Qreq> Qplmax (S10: YES), the partial maximum injection amount Qplmax is insufficient with respect to the required injection amount Qreq. Therefore, in this case, in step S14 (injection command period setting means), the operation of the injector 10 is controlled so that the required injection amount Qreq is injected in the full lift region A2.

  If it is determined in step S11 that the output improvement amount is equal to or less than the pump loss amount (S10: NO), the above shortage does not occur and the injection in the partial area A1 is possible, but the injection is performed in the partial area A1. The demerit (pump loss amount) is larger than the merit (output improvement amount). Therefore, also in this case, in step S14, the operation of the injector 10 is controlled so that the required injection amount Qreq is injected in the full lift region A2. After executing the process of step S14, the forcible command flag is set to OFF in the subsequent step S15.

  Next, the procedure for controlling the high-pressure pump 40 will be described with reference to FIG. First, in step S20 of FIG. 9, it is determined whether or not the forced command flag is set to ON in the process of FIG. If it is set to ON (S20: YES), the target supply fuel pressure Ptrg is set to the system maximum fuel pressure Pmax in the subsequent step S21 (target pressure setting means). On the other hand, when it is set to OFF (S20: NO), in the subsequent step S22 (target pressure setting means), the target supply is performed based on the load of the internal combustion engine and the engine speed using the fuel pressure map described below. The fuel pressure Ptrg is set.

  Specifically, the relationship between the target injection amount Qreq corresponding to the load and the engine speed and the optimum value of the supplied fuel pressure is obtained by testing in advance, and a fuel pressure map indicating the relationship is stored in the memory. . This fuel pressure map is created based on the test results when the fuel is injected in the full lift region A2. Then, based on the target injection amount Qreq and the engine speed, the target supply fuel pressure Ptrg is set in consideration of the fuel pressure map.

  In the subsequent step S23 (pump control means), the high pressure pump 40 is feedback-controlled so that the actual fuel pressure Pact detected by the fuel pressure sensor 31 matches the target supply fuel pressure Ptrg set in steps S21 and S22. Specifically, the operation of the metering valve 43 is controlled based on the deviation between the target supply fuel pressure Ptrg and the actual fuel pressure Pact, and the fuel pumping amount by the plunger 45 is feedback-controlled.

  Next, the procedure for updating and learning the fuel pressure map will be described with reference to FIG. First, in step S30 (detection means) in FIG. 10, the waveform of the current flowing through the coil 13 when the coil 13 is energized (see FIG. 6B) or the waveform of the voltage applied to the coil 13 is acquired. In the subsequent step S31 (detection means), the valve closing timing at which the valve body 12 is seated on the seating surface 17b and the injection is terminated is estimated based on the waveform acquired in step S30. For example, since a unique pulsation appears in the waveform with the seating, the valve closing timing is estimated based on the pulsation appearance timing.

  In subsequent step S32 (injection data acquisition means), the actual injection amount is estimated based on the valve closing timing estimated in step S31. Specifically, first, the injection start timing (valve opening timing) is estimated based on the timing when the injection command signal commands the start of energization of the coil 13. For example, a timing obtained by adding a predetermined delay time from the command timing for starting energization may be estimated as the valve opening timing. Then, the injection period is calculated based on the estimated valve opening timing and valve closing timing. Next, the actual injection amount is calculated based on the supply fuel pressure at the time of injection and the calculated injection period.

  In the subsequent step S33 (injection data acquisition means), the injection amount Q stored in the Ti-Q map used in the control of FIG. 8 based on the actual injection amount estimated in step S32 and the energization time Ti at the time of injection. Update and rewrite. Thereby, the value of the Ti-Q map is learned based on the actual injection amount. The Ti-Q map learned in this way corresponds to injection data representing the relationship between the valve opening command period and the actual injection amount.

  In short, the present embodiment described above has the characteristics listed below. And the effect demonstrated below is exhibited by each of those characteristics.

<Feature 1>
In controlling the high pressure pump 40 so that the supply fuel pressure becomes the target pressure Ptrg, the target pressure Ptrg is set to the system maximum fuel pressure Pmax (a value equal to or higher than a preset lower limit pressure) during partial injection. Therefore, at the time of partial injection, injection is performed with a sufficiently high supply fuel pressure to obtain a small spray particle size. Therefore, it is possible to inject a small amount of fuel while reducing the spray particle size.

  On the other hand, at the time of full lift injection, the target pressure Ptrg is set according to the operating state of the internal combustion engine. Therefore, it is possible to avoid an unnecessarily high supply fuel pressure at the time of full lift injection, and to avoid an unnecessary increase in energy required for driving the high-pressure pump 40, that is, a load on the internal combustion engine that rotates the drive shaft 5.

<Feature 2>
Since the ECU 20 sets the target pressure Ptrg at the time of partial injection to the system maximum fuel pressure Pmax, the increase in the spray particle size at the time of partial injection can be suppressed to the maximum. Therefore, the combustion energy obtained per unit injection amount can be increased.

<Feature 3>
The ECU 20 compares the output improvement amount caused by selecting the partial injection to reduce the spray particle size and the pump loss amount caused by selecting the partial injection and increasing the load of the high-pressure pump 40. Then, partial injection is selected on the condition that output improvement amount> pump loss amount (S11: YES). For this reason, it is possible to avoid a situation in which the output of the internal combustion engine obtained with respect to the injection amount is reduced even though the spray particle size is reduced by partial injection.

<Feature 4>
The ECU 20 includes detection means S30 and S31, injection data acquisition means S32 and S33, and injection command period setting means S12 and S14. The detecting means S30 and S31 detect the valve closing timing of the valve body 12. The injection data acquisition means S32 and S33 calculate the actual injection amount by the partial injection based on the valve closing timing detected at the time of partial injection. The injection data acquisition means S32 and S33 acquire injection data representing the relationship between the valve opening command period of the valve body 12 and the actual injection amount. The injection command period setting means S12 and S14 set a period (injection command signal) for instructing the injector 10 to open the valve based on the requested injection amount and the injection data.

  When the actual injection amount is calculated by detecting the valve closing timing in this way, the calculation accuracy of the actual injection amount is deteriorated if the sac fuel pressure is low. Therefore, if the injection command signal is set based on the injection data based on the calculation result, there is a concern that the injection accuracy may deteriorate. On the other hand, in the present embodiment, the target pressure is set to a value equal to or higher than the lower limit pressure during partial injection, so that the sac fuel pressure during partial injection increases. Therefore, the calculation accuracy deterioration of the actual injection amount can be suppressed, and the injection accuracy deterioration can be suppressed.

<Feature 5>
Here, contrary to the present embodiment, in the case of an injector having a configuration in which the valve body is engaged with the movable core after the movable core has moved by a predetermined amount and the valve opening operation is started, the valve body is opened with force. That is, the initial speed of the valve element that opens is fast. As a result, the rate of increase of the sac fuel pressure is increased, so that a problem such as “injection is terminated without sufficiently increasing the sac fuel pressure during partial injection, so that fuel with a small spray particle size cannot be injected” does not appear remarkably.

  On the other hand, the injector 10 according to the present embodiment is configured such that the valve body 12 also starts moving (valve opening operation) simultaneously with the start of movement of the movable core 15. Therefore, the effect of “the spray particle size can be reduced” by the configuration of “setting the target pressure to a value equal to or higher than the lower limit pressure at the time of partial injection” is remarkably exhibited.

<Feature 6>
Regarding the shape of the nozzle hole 17a, there are the following two design philosophies in order to promote atomization of the fuel spray. One is that by increasing the flow path length L of the nozzle hole 17a, the fuel is torn in the nozzle hole 17a by the shearing force of the fuel and air, thereby achieving atomization. It is an idea. The other is to reduce the pressure loss in the nozzle hole 17a by shortening the flow path length L of the nozzle hole 17a, and the fuel is torn by the shear force of the fuel and air immediately after being injected from the nozzle hole 17a. This is the idea of shearing outside the nozzle hole that promotes atomization and promotes atomization. In this embodiment, L <D is set as shown in FIG. 3, and the structure is based on the concept of shear after injection.

  Contrary to this embodiment, in the case of the structure by the shear in the nozzle hole (L> D), the degree of contribution of the sac fuel pressure to the atomization of the spray is smaller than in the case of the shear outside the nozzle hole. Therefore, the problem that “the fuel in the small spray particle size cannot be injected because the injection ends without sufficiently increasing the sac fuel pressure during the partial injection” does not appear remarkably.

  On the other hand, the injector 10 according to the present embodiment has a structure (L <D) based on the idea of shear outside the nozzle hole. Therefore, the effect of “the spray particle size can be reduced” by the configuration of “setting the target pressure to a value equal to or higher than the lower limit pressure at the time of partial injection” is remarkably exhibited.

<Feature 7>
In the injector 10 according to this embodiment, at least a part of the outer peripheral surface of the coil region portion 16a of the housing 16 is surrounded by the inner peripheral surface 4a of the mounting hole 4 over the entire periphery. Here, since the cylinder head 3 constituting the combustion chamber 2 becomes high temperature, if the coil region portion 16a is surrounded by the attachment hole 4, the temperature of the coil 13 tends to become high temperature. Then, since the electrical resistance of the coil 13 increases, the value of the current flowing through the coil 13 decreases with the start of energization, and the increase rate of the magnetic attractive force decreases. That is, the suction force increase speed from t0 to t1 in FIG. As a result, the period during which the sac fuel pressure is low immediately after the valve opening becomes longer, so that the demand for atomization of the spray during this period increases.

  Accordingly, the injector 10 in which the coil region 16a is surrounded by the inner peripheral surface 4a over the entire circumference as in the present embodiment is configured to “set the target pressure to a value equal to or higher than the lower limit pressure during partial injection”. If it is adopted, an effect such as “the spray particle size can be reduced” is remarkably exhibited.

<Feature 8>
The injector 10 is disposed in the vicinity of the spark plug 6 because it is disposed at a position where fuel is directly injected into the combustion chamber 2. For this reason, it is important to reduce the spray particle size in order to reduce the fuel injected from the injector 10 from adhering to the spark plug 6. For this reason, if the configuration in which the target pressure is set to a value equal to or higher than the lower limit pressure at the time of partial injection is adopted for the injector 10 of the direct injection arrangement as in the present embodiment, an effect of “the spray particle size can be reduced” is obtained. It comes to be demonstrated remarkably.

<Feature 9>
In step S10 of FIG. 8, it is determined whether or not the required injection amount Qreq is equal to or less than the partial maximum injection amount Qplmax, and partial injection is selected on the condition that Qreq ≦ Qplmax. According to this, as shown by the symbol Q1 in FIG. 7, when both the partial injection and the full lift injection are possible depending on the supply fuel pressure, the partial injection is selected. Therefore, even when a very small amount of fuel is injected, the fuel spray is injected at a higher pressure than full lift injection, and atomization of fuel spray can be sufficiently promoted.

(Second Embodiment)
In the first embodiment, the target supply fuel pressure Ptrg at the time of partial injection is set to the system maximum fuel pressure Pmax (for example, 20 MPa). On the other hand, in this embodiment, the target supply fuel pressure Ptrg at the time of partial injection is set to a value lower than the system maximum fuel pressure Pmax and higher than the lower limit pressure. Hereinafter, the technical meaning of the lower limit pressure will be described.

  FIG. 11 is a test result showing the relationship between the spray particle size and the supply fuel pressure, and is a result of testing at three points of 5 MPa, 10 MPa, and 20 MPa. The solid line in the figure indicates the test result when 1 mg of fuel is partially injected, the dotted line indicates the test result when 3 mg of fuel is partially injected, and the alternate long and short dash line indicates the full lift injection with the minimum injection amount Qmin. The hardware configuration of the fuel injection system used for this test is the same as that of the fuel injection system according to the first embodiment.

  As shown in FIG. 11, basically, in the case of partial injection, the spray particle size is larger than in the case of full lift injection. In particular, when the pressure is 5 MPa, the spray particle diameter becomes as large as about 5 μm, and the degree of increase is referred to as a spray particle diameter deterioration degree ΔSMD. However, when the pressure was 10 MPa, the spray particle size deterioration degree ΔSMD was small, and it was found that a spray particle size equivalent to that of full lift injection can be achieved even with partial injection. And even if the supply fuel pressure is 10 MPa or more, the degree of deterioration of the spray particle size is hardly improved, and there is no room for improvement of the spray particle size after 10 MPa.

  Thus, of the supply fuel pressure, the boundary value that can greatly improve the degree of deterioration of the spray particle diameter, and the boundary value that hardly increases the degree of deterioration of the spray particle diameter even if the supply fuel pressure is further increased is the lower limit pressure Pa described above. It is. According to the test result of FIG. 11, it can be seen that the value of the supply fuel pressure of 10 MPa is higher than the lower limit pressure and lower than the system maximum fuel pressure Pmax.

  In this embodiment in view of this point, the target supply fuel pressure Ptrg at the time of partial injection is set to 10 MPa. Therefore, the ratio of the “output improvement amount” by increasing the supply fuel pressure at the time of partial injection and reducing the spray particle size to the “pump loss amount” by increasing the load of the high-pressure pump 40 by increasing the supply fuel pressure. (Output improvement efficiency) can be increased. That is, it is possible to improve the output improvement amount while keeping the pump loss amount low.

(Third embodiment)
In the second embodiment, the target supply fuel pressure Ptrg at the time of partial injection is set to 10 MPa. However, in this embodiment, the target supply fuel pressure Ptrg at the time of partial injection is set to the lower limit pressure Pa. The supply fuel pressure corresponding to the change point P of the characteristic line shown in FIG. 12 indicates the lower limit pressure Pa. Hereinafter, the technical meaning of the change point P will be described.

  FIG. 11 shows characteristic lines representing the relationship between the supply fuel pressure and the spray particle size at three points of 5 MPa, 10 MPa, and 20 MPa. If the number of test points is increased, the present inventors have implemented that there is a change point where the second-order differential value of the characteristic line is maximized in a portion between 5 MPa and 10 MPa in the characteristic line. It became clear by numerical analysis. FIG. 12 shows the result of the numerical analysis. The vertical axis of FIG. 12 indicates the spray particle size deterioration degree ΔSMD, and the horizontal axis indicates the supply fuel pressure. A change point P in FIG. 12 corresponds to a change point at which the second-order differential value of the characteristic line is maximized.

  In short, the slope of the characteristic line representing the relationship between the supply fuel pressure and the spray particle size increases as the supply fuel pressure decreases, but does not increase in proportion to the supply fuel pressure, but is an exponential function with respect to the decrease in the supply fuel pressure. Will increase. The point at which the increase speed is maximum is the change point P described above. That is, the point at which the second-order differential value of the characteristic line becomes the maximum is the changing point P, and the inclination increasing speed of the characteristic line is the fastest, so that the spray particle size suddenly increases (the degree of deterioration increases). It can be said that this is a point that changes.

  In this embodiment in view of this point, the fuel pressure at the change point P is regarded as the lower limit pressure Pa, and the target supply fuel pressure Ptrg at the time of partial injection is set to the lower limit pressure Pa. Therefore, the ratio of the “output improvement amount” by increasing the supply fuel pressure at the time of partial injection and reducing the spray particle size to the “pump loss amount” by increasing the load of the high-pressure pump 40 by increasing the supply fuel pressure. (Output improvement efficiency) can be increased. That is, it is possible to improve the output improvement amount while keeping the pump loss amount low.

(Fourth embodiment)
In the first embodiment, in step S11 of FIG. 8, the output improvement amount and the pump loss amount are calculated, and it is determined based on the calculation results whether the output improvement amount> the pump loss amount. In contrast, in the present embodiment, when the internal combustion engine is started, full lift injection is selected on the assumption that the output improvement amount is smaller than the pump loss amount without calculating the output improvement amount and the pump loss amount.

  The “starting time” here means when the internal combustion engine is driven by a starter motor. At the time of such starting, there is a high probability that the output improvement amount is larger than the pump loss amount. Therefore, according to the present embodiment, it is possible to realize the control for full lift injection when the output improvement amount <the pump loss amount, while reducing the processing load of the microcomputer 21 that calculates the output improvement amount and the pump loss amount.

(Fifth embodiment)
In the first embodiment, in step S10 of FIG. 8, the partial maximum injection amount Qplmax and the required injection amount Qreq are compared in magnitude, and it is determined whether or not to perform partial injection based on the comparison result. On the other hand, in the present embodiment, when the internal combustion engine is idling, it is assumed that the required injection amount Qreq is equal to or less than the partial maximum injection amount Qplmax without comparing the magnitudes of Qplmax and Qreq, and partial injection is selected. To do.

  During such idle operation, there is a high probability that the required injection amount Qreq is equal to or less than the partial maximum injection amount Qplmax. Therefore, according to the present embodiment, it is possible to control to perform partial injection when Qreq ≦ Qplmax while reducing the processing load of the microcomputer 21 that compares Qplmax and Qreq.

(Sixth embodiment)
In the present embodiment, the present invention relates to a case where divided injection is performed in which the required injection amount Qreq is divided into a plurality of times during one combustion cycle. In controlling the fuel discharge amount of the high-pressure pump 40 to control the supply fuel pressure to the target fuel pressure Ptrg, there is a control response delay. Therefore, even if the target fuel pressure Ptrg is changed for each of a plurality of injections in one combustion cycle, the actual supply fuel pressure cannot accurately follow the change in the target fuel pressure Ptrg.

  In this embodiment in view of this point, all of the multiple injections are satisfied when the condition (S10: YES, S11: YES) for selecting the partial injection among the multiple injections in one combustion cycle is satisfied. The target pressure Ptrg is set to the system maximum fuel pressure Pmax. For this reason, even partial injection related to split injection can be injected with a sufficiently high supply fuel pressure to have a small spray particle size.

  Further, in the case of divided injection, the amount injected at one time is very small. Therefore, according to the present embodiment in which the configuration in which the target fuel pressure Ptrg is set to the lower limit pressure or higher during partial injection is applied to the fuel injection system configured to allow split injection, the effect of atomization of spray during the partial injection is remarkable. Demonstrated.

(Seventh embodiment)
In the sixth embodiment, the target pressure Ptrg is set to the system maximum fuel pressure Pmax for all of the plurality of injections on condition that the partial injection selection condition is satisfied even once among the plurality of injections related to the divided injection. Is set. On the other hand, in the present embodiment, the target pressure Ptrg is set to the system maximum fuel pressure Pmax for all of the plurality of injections on condition that all of the plurality of injections related to the divided injection satisfy the condition for selecting the partial injection. To do.

  In this way, when partial injection is performed for all of the multiple injections, the spray atomization effect is exhibited multiple times during one combustion cycle, so the spray atomization effect is significant. Demonstrated.

(Eighth embodiment)
FIG. 13 is a numerical analysis result showing the relationship between the sheet squeezing ratio and the spray particle size. The vertical axis in FIG. 13 shows the degree of deterioration of the spray particle size when full lift injection is performed, and the horizontal axis in FIG. Indicates the sheet drawing ratio. The analysis result shown in FIG. 13 shows that the larger the sheet squeezing rate, the greater the degree of spray particle size deterioration.

  However, the slope of the characteristic line shown in FIG. 13 increases as the sheet aperture ratio increases, but does not increase in proportion to the sheet aperture ratio, but increases exponentially with the increase in the sheet aperture ratio. Go. And the point where the increase rate is the maximum is the changing point indicated by reference sign P1 in the figure. That is, the point where the second-order differential value of the characteristic line shown in FIG. 13 is the maximum is the changing point P1, the inclination increasing speed of the characteristic line is the fastest, and the spray particle size deterioration degree increases rapidly. It can be said that this is a changing point.

  In the present embodiment in view of this point, a configuration in which the target fuel pressure Ptrg is set to be equal to or higher than the lower limit pressure at the time of partial injection is applied to the injector 10 configured to have a sheet squeezing rate Ra (for example, 30%) or more at the change point P1. Apply. Therefore, the effect of atomization of spray is remarkably exhibited.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  -The selection means which concerns on this invention is not limited to the method of step S10, S11 shown in FIG. For example, in the flowchart of FIG. 8, the determination process in step S10 or step S11 may be abolished. In step S10, the required injection amount Qreq is compared with the partial maximum injection amount Qplmax. However, the required injection amount Qreq is compared with the determination value set to a value different from the partial maximum injection amount Qplmax. You may compare.

  -In the case of split injection, there is a high probability that one required injection amount Qreq will be equal to or less than the partial maximum injection amount Qplmax. Therefore, when divided injection is requested, it is assumed that Qreq ≦ Qplmax (S10: YES) and partial injection is selected without performing the process of step S10 in FIG. 8 that compares Qplmax and Qreq in magnitude. Also good.

  In the pump control shown in FIG. 9, the operation of the metering valve 43 is feedback controlled based on the deviation between the target supply fuel pressure Ptrg and the actual fuel pressure Pact. However, the pump control means according to the present invention is not limited to the feedback control. For example, the operation of the metering valve 43 with respect to the target supply fuel pressure Ptrg is set in advance, and the operation of the metering valve 43 is performed according to the setting. You may control.

  In the first embodiment, the flow path length L of the injection hole 17a is shorter than the inlet diameter D of the injection hole 17a based on the idea of shear after injection. And when the inlet shape of the nozzle hole 17a is an ellipse, in the said 1st Embodiment, although the major axis dimension of an ellipse is used for the inlet diameter D, you may use a minor axis dimension. Further, the flow path length L may be smaller than the diameter dimension of the cross section of the nozzle hole 17a.

  The injector 10 according to the first embodiment is configured so that the valve body 12 also starts moving (valve opening operation) simultaneously with the start of movement of the movable core 15. On the other hand, even if the movement of the movable core 15 is started, the valve body 12 does not start to open, and when the movable core 15 moves by a predetermined amount, the movable core 15 engages with the valve body 12 and opens the valve. It may be configured to start.

  -In the said 1st Embodiment, the whole magnetic circuit area | region part 16b is surrounded by the internal peripheral surface 4a of the attachment hole 4 over the perimeter. On the other hand, a part of the magnetic circuit region portion 16b may be configured to be surrounded by the inner peripheral surface 4a over the entire circumference. Moreover, the whole coil area | region part 16a may be surrounded by the inner peripheral surface 4a of the attachment hole 4 over the perimeter, and a part of coil region part 16a is an inner peripheral surface over the perimeter. You may be comprised so that it may be enclosed by 4a.

  -Although the injector 10 which concerns on the said 1st Embodiment is attached to the cylinder head 3 as shown in FIG. 1, the injector attached to the cylinder block which forms a sliding wall surface with a cylinder may be sufficient. Moreover, in the said embodiment, although the injector which injects a fuel directly into the combustion chamber 10a is made into a control object, it is good also considering the injector which injects a fuel into an intake pipe as a control object.

  In the first embodiment, the injector 10 mounted on the ignition type internal combustion engine (gasoline engine) is applied. However, the injector mounted on the compression ignition type internal combustion engine (diesel engine) is applied. Also good.

  Here, the target pressure Ptrg in the case of a gasoline engine is orders of magnitude lower than that in the case of a diesel engine. Therefore, the concern that the spray particle size at the time of partial injection increases due to the fact that the sac fuel pressure does not increase immediately after the valve is opened becomes significant in the case of a gasoline engine. Therefore, when the configuration of “setting the target pressure to a value equal to or higher than the lower limit pressure during partial injection” is applied to the injector of a gasoline engine, the effect that “the spray particle size can be reduced” is remarkably exhibited. Become.

  DESCRIPTION OF SYMBOLS 10 ... Injector, 12 ... Valve body, 17a ... Injection hole, 20 ... ECU (fuel injection control apparatus), 40 ... High pressure pump, S10, S11 ... Selection means, S21, S22 ... Target pressure setting means, S23 ... Pump control means

Claims (18)

The present invention is applied to a fuel injection system including an injector (10) for injecting fuel from an injection hole (17a) by opening the valve body (12) and a high-pressure pump (40) for increasing the pressure of the fuel and supplying the fuel to the injector. In the fuel injection control device (20),
Full lift injection that starts the valve closing operation after the valve body that has started the valve opening operation reaches the full lift position, and partial injection that starts the valve closing operation without the valve body that has started the valve opening operation reaching the full lift position Selection means (S10, S11) for selecting which of the injection is performed,
Pump control means (S23) for controlling the operation of the high-pressure pump so that the pressure of the fuel supplied to the injector becomes a target pressure (Ptrg);
When the full lift injection is selected, the target pressure is set according to the operating state of the internal combustion engine, and when the partial injection is selected, the target pressure is set to a value equal to or higher than a preset lower limit pressure. Target pressure setting means (S21, S22),
Equipped with a,
The characteristic line representing the relationship between the pressure of the fuel supplied to the injector and the spray particle size of the fuel injected from the injection hole has a change point (P) at which the second-order differential value becomes maximum. And
The fuel injection control apparatus , wherein the lower limit pressure is set to a pressure value (Pa) at the change point . 2. The fuel injection control device according to claim 1 , wherein the value equal to or higher than the lower limit pressure is set to a maximum value (Pmax) of the target pressure that the fuel injection system can take . The fuel injection control device according to claim 1 , wherein a value equal to or higher than the lower limit pressure is set to 10 MPa or more . In the case of performing divided injection in which the required injection amount is divided into a plurality of times during one combustion cycle, the target is satisfied when the condition for selecting the partial injection is satisfied even once among the plurality of injections. The fuel injection control device according to any one of claims 1 to 3 , wherein the pressure setting means sets the target pressure to a value equal to or higher than the lower limit pressure for all of the plurality of injections. . In the case of performing divided injection in which the required injection amount is divided into a plurality of times during one combustion cycle, the target pressure setting is performed when the condition for selecting the partial injection is satisfied for all of the plurality of injections. The fuel injection control device according to any one of claims 1 to 3 , wherein the means sets the target pressure to a value equal to or higher than the lower limit pressure for all of the plurality of injections . The present invention is applied to a fuel injection system including an injector (10) for injecting fuel from an injection hole (17a) by opening the valve body (12) and a high-pressure pump (40) for increasing the pressure of the fuel and supplying the fuel to the injector. In the fuel injection control device (20),
Full lift injection that starts the valve closing operation after the valve body that has started the valve opening operation reaches the full lift position, and partial injection that starts the valve closing operation without the valve body that has started the valve opening operation reaching the full lift position Selection means (S10, S11) for selecting which of the injection is performed,
Pump control means (S23) for controlling the operation of the high-pressure pump so that the pressure of the fuel supplied to the injector becomes a target pressure (Ptrg);
When the full lift injection is selected, the target pressure is set according to the operating state of the internal combustion engine, and when the partial injection is selected, the maximum value (Pmax) of the target pressure that the fuel injection system can take Target pressure setting means for setting the target pressure to,
Fuel injection control apparatus comprising: a. The present invention is applied to a fuel injection system including an injector (10) for injecting fuel from an injection hole (17a) by opening the valve body (12) and a high-pressure pump (40) for increasing the pressure of the fuel and supplying the fuel to the injector. In the fuel injection control device (20),
Full lift injection that starts the valve closing operation after the valve body that has started the valve opening operation reaches the full lift position, and partial injection that starts the valve closing operation without the valve body that has started the valve opening operation reaching the full lift position Selection means (S10, S11) for selecting which of the injection is performed,
Pump control means (S23) for controlling the operation of the high-pressure pump so that the pressure of the fuel supplied to the injector becomes a target pressure (Ptrg);
Target pressure setting means for setting the target pressure according to the operating state of the internal combustion engine when the full lift injection is selected, and for setting the target pressure to a value of 10 MPa or more when the partial injection is selected;
Fuel injection control apparatus comprising: a. The high-pressure pump is a mechanical pump that is driven by the rotational torque of the internal combustion engine,
The amount by which the output efficiency of the internal combustion engine is improved due to the reduction of the spray particle size by selecting the partial injection is called an output improvement amount, and the load of the high-pressure pump is increased by selecting the partial injection. In the case where the amount by which the output efficiency of the internal combustion engine decreases due to that is called the pump loss amount,
The fuel injection according to any one of claims 1 to 7, wherein the selection means (S11) selects the partial injection on the condition that the output improvement amount is larger than the pump loss amount. Control device. 9. The fuel injection control device according to claim 8 , wherein the selection means considers that the pump loss amount is larger than the output improvement amount when the internal combustion engine is started . Detection means (S30, S31) for detecting the valve closing timing of the valve body;
Based on the valve closing timing detected when the partial injection is performed, the actual injection amount by the partial injection is calculated, and the injection data representing the relationship between the valve opening command period of the valve body and the actual injection amount is obtained. Injection data acquisition means (S32, S33) to perform,
Injection command period setting means (S12, S14) for setting a period for instructing the injector to open the valve based on the required injection amount and the injection data;
The fuel injection control device according to any one of claims 1 to 9, characterized in that it comprises a. The injector is
A fixed core (14) that generates an electromagnetic attraction force when energized to the coil (13), and a movable core (15) that is attracted to the fixed core and moves together with the valve body;
The fuel injection control device according to any one of claims 1 to 10, wherein the valve body is also configured to start a valve opening operation simultaneously with the start of movement of the movable core . The injector is
A fixed core (14) that generates an electromagnetic attraction force when energized to the coil (13), and a movable core (15) that is attracted to the fixed core and moves together with the valve body;
The valve body engages with the movable core after the movable core moves by a predetermined amount, and is configured to start a valve opening operation. Fuel injection control device. The fuel according to any one of claims 1 to 12, wherein the injector has a structure in which a flow path length (L) of the nozzle hole is smaller than an inlet diameter (D) of the nozzle hole. Injection control device. In the case where the maximum injection amount when the partial injection is performed at the maximum value (Pmax) of the target pressure that can be taken by the fuel injection system is called a partial maximum injection amount (Qplmax),
The said selection means (S10) selects the said partial injection on condition that the request | requirement injection quantity (Qreq) is below the said partial maximum injection quantity, It is any one of Claims 1-13 characterized by the above-mentioned. The fuel injection control device described. 15. The fuel injection control device according to claim 14, wherein the selection means considers that the required injection amount is equal to or less than a partial maximum injection amount when the internal combustion engine is idling . The injector is
A fixed core (14) for forming an electromagnetic force by forming a part of a magnetic circuit serving as a path of magnetic flux generated by energizing the coil (13);
A movable core (15) that is attracted by the electromagnetic force and moves together with the valve body;
A housing (16) that is inserted into and attached to a mounting hole (4) formed at a predetermined location (3a) of the internal combustion engine, and that houses the coil therein;
The housing has a cylindrical shape forming a part of a magnetic circuit constituting a path of magnetic flux generated by energization of the coil,
When the portion of the housing that accommodates the coil is referred to as a coil region portion (16a), at least a part of the outer peripheral surface of the coil region portion extends over the entire inner peripheral surface of the mounting hole. The fuel injection control device according to any one of claims 1 to 15, wherein the fuel injection control device is surrounded by (4a). The injector is arranged at a position for directly injecting fuel into the combustion chamber (2) of the internal combustion engine,
The fuel injection control device according to any one of claims 1 to 16, wherein the internal combustion engine is an ignition internal combustion engine that is ignited and burned by a spark of a spark plug (6). A fuel injection control device according to any one of claims 1 to 17,
The injector;
The high pressure pump;
A fuel injection system comprising:

Images