JP6187663B2 - 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 that control energization to a coil of a fuel injection valve to control an injection state such as a fuel injection start timing and an injection amount.

  The control device described in Patent Literature 1 relates to a fuel injection valve having a structure in which fuel is injected by lifting up (opening operation) a valve body by electromagnetic attraction generated by energizing a coil. In addition, the valve opening timing and the valve opening period of the valve body are controlled by controlling the energization time thereof, and the fuel injection start timing and the injection amount are controlled.

  In this control device, as shown in FIG. 7, after energization of the coil is started, voltage application to the coil is continued and the coil current is increased until the coil current reaches the target peak value Ipeak. The target peak value is set to a value necessary for the valve body to reach the maximum lift position.

  Here, the current required to hold the valve body that has reached the maximum lift position at that position may be less than the target peak value. One reason for this is that when the attractive force is increased, the change in the magnetic field is large, so that it is greatly affected by the inductance. However, when the attractive force is held at a constant value, there is almost no influence of the inductance.

  Therefore, in the above control device, when the coil current increases and reaches the target peak value, the coil current is decreased, and the voltage to the coil is set so that the holding value Ihold is set to a value lower than the target peak value. The application is duty controlled.

JP 2012-177303 A

  Here, when the coil becomes hot, the electrical resistance of the coil increases. Then, as shown by the dotted lines in FIGS. 7A and 7B, the time t10 to t20 required for the coil current to reach the target peak value Ipeak from the start of voltage application becomes longer. As a result, the increase gradient ΔF of the suction force becomes gentle (see the dotted line in FIG. 7C), so that the valve opening start timing ta is delayed and the valve opening period Tact is shortened.

  In short, the current increase gradient ΔI changes due to the temperature characteristics of the coil current, and as a result, the increase gradient ΔF of the attractive force changes, and the valve opening start timing ta and the valve opening period Tact (injection amount). ) Changes. That is, because the injection start timing ta and the injection amount are affected by the temperature characteristics, the accuracy of the injection state with respect to the energization start timing t10 and the energization period Ti is deteriorated.

  In particular, when performing multi-stage injection in which fuel is injected a plurality of times during one combustion cycle, it is required to inject a minute amount of fuel with high accuracy. During such minute injection, the deviation of the injection start timing ta is required. Has a large influence on the deviation of the injection amount, and the deterioration of the injection amount accuracy due to the temperature characteristic becomes remarkable.

  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 improve control robustness with respect to temperature characteristics when controlling an injection state. is there.

  The 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.

  The disclosed invention is applied to a fuel injection valve (10) that opens a valve element (12) by an electromagnetic attractive force generated by energizing a coil (14) to inject fuel, and a coil current flowing through the coil It is assumed that the fuel injection control device controls the fuel injection state from the fuel injection valve by controlling the above.

  Then, a booster circuit (23) for boosting the battery voltage, and a rise control means (S11, S14) for applying the boost voltage boosted by the booster circuit to the coil so that the coil current rises to the first target value (Ihold1). And a hold control means (S11, S14, S15, S17) for applying a boost voltage to the coil and a control by the hold control means so that the coil current raised by the rise control means is held at the first target value. And a battery hold control means (S22, S25, S26, S28) for applying a battery voltage to the coil so that the coil current is held at the second target value (Ihold2).

  The variation frequency of the coil current during the control period by the hold control unit is larger than the variation frequency of the coil current during the control period by the battery hold control unit.

  According to the present invention, as illustrated in FIG. 5, the rising period t10 to t11 in which the coil current is increased to the first target value Ihold1 by the increase control unit, and then the first target value Ihold1 is held by the hold control unit. The electromagnetic attraction force can be increased over both periods t10 to t13 of the hold periods t11 to t13. Then, the ratio of the rising periods t10 to t11 occupying the period from when the energization starts until the electromagnetic attractive force reaches the required valve opening force Fa (attractive force increasing periods t10 to ta) can be reduced.

  Here, as described above, the slope ΔI of the current rise changes due to the temperature characteristics. Therefore, during the rise periods t10 to t11, the rise slope ΔF of the attractive force affects the influence of the temperature characteristics. It can be said that it is a period to receive greatly. On the other hand, since the coil current is held at the first target value in the hold periods t11 to t13, it can be said that the hold periods t11 to t13 are periods in which the suction force increase gradient ΔF is hardly affected by the temperature characteristics.

  On the other hand, according to the present invention, as described above, the ratio of the rising periods t10 to t11 occupying the attractive force increasing periods t10 to ta can be reduced. It can be made smaller (see the dotted line in FIG. 5C). In the conventional control device shown in FIG. 7, when the coil current reaches the target peak value Ipeak, the holding value Ihold is lowered. Therefore, as shown in FIG. 7, the current increase periods t10 to t20 and the attractive force increase period It is in agreement with t10 to t20 (the above ratio = 100%). For this reason, the degree of increase in the suction force gradient ΔF is influenced by the temperature characteristics (see the dotted line in FIG. 7C).

  Therefore, according to the present invention, it is possible to reduce the change in the suction force increase slope ΔF due to the temperature characteristics, and thus it is possible to suppress the valve opening start timing ta and the valve opening period Tact (injection amount) from changing depending on the temperature characteristics. (Refer to the dotted line in FIG. 5D). Therefore, deterioration of the accuracy of the injection state with respect to the energization start timing t1 and the energization period Ti can be suppressed, and the robustness of the control over the temperature characteristics can be improved.

The block diagram which shows the fuel-injection control apparatus concerning one Embodiment of this invention. The figure which shows the injection characteristic showing the relationship between the electricity supply period Ti and the injection quantity q. The figure which shows the magnetic circuit characteristic showing the relationship between the ampere turn AT and the electromagnetic attraction force F. The figure which shows a mode that an electromagnetic attracting force rises with progress of time, is saturated, and becomes a static attracting force. The figure which shows the change which arises with time passage of the applied voltage to a coil, coil current, electromagnetic attraction force, and lift amount when injection control by the fuel injection control device shown in FIG. 1 is performed. The flowchart which shows the procedure of the injection control implemented by the microcomputer of the fuel-injection control apparatus shown in FIG. The figure which shows the change which arises with the passage of time of the voltage by the conventional control apparatus, an electric current, attraction | suction force, and lift amount.

  Hereinafter, an embodiment of a fuel injection control device according to the present invention will be described with reference to the drawings.

  A fuel injection valve 10 shown in FIG. 1 is mounted on an ignition internal combustion engine (gasoline engine), and directly injects fuel into a combustion chamber of the internal combustion engine. The fuel injection valve 10 includes a body 11 having a fuel passage and an injection hole 11a for injecting fuel. In the body 11, a valve body 12, a movable core (not shown), a fixed core 13 and the like are accommodated. The valve body 12 has a seat surface 12 a that is separated from and seated on the seating surface 11 b of the body 11. When the valve body 12 is closed so that the seat surface 12a is seated on the seating surface 11b, fuel injection from the nozzle hole 11a is stopped. When the valve body 12 is opened (lifted up) so as to separate the seat surface 12a from the seating surface 11b, fuel is injected from the injection hole 11a.

  The fixed core 13 is configured by winding a coil 14 around an iron core. When the coil 14 is energized, the fixed core 13 generates a magnetic attractive force, and the movable core is attracted to the fixed core 13 by this magnetic attractive force and lifts up. . The valve body 12 coupled to the movable core lifts up (valve opening operation) together with the movable core. On the other hand, when energization of the coil 14 is stopped, the valve body 12 is closed together with the movable core by the elastic force of a spring (not shown).

  The electronic control unit (ECU 20) includes a microcomputer (microcomputer 21), an integrated IC 22, a booster circuit 23, switching elements SW2, SW3, SW4, and the like. The ECU 20 corresponds to a fuel injection control device, and the fuel injection system includes the fuel injection valve 10 and the ECU 20. The microcomputer 21 includes a central processing unit, a non-volatile memory (ROM), a volatile memory (RAM), and the like, and based on the load of the internal combustion engine and the engine speed, the target fuel injection amount and the target injection start timing. Is calculated. The injection amount q is controlled by controlling the energization time Ti to the coil 14 according to the injection characteristics shown in FIG. A symbol t10 in the figure indicates the energization start time. In addition, the symbol t10b in the figure indicates a time when the opening of the nozzle hole 11a is maximized. At this time, the movable core comes into contact with the fixed core 13 and the lift amount of the valve body 12 is maximized. It is around the time.

  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 14 of the fuel injection valve 10 and is set by the microcomputer 21 based on the above-described target injection amount and target injection start timing and the coil current detection value I described later. Is done. 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 14 of the fuel injection valve 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 14 of the fuel injection valve 10. When the voltage application to the coil 14 is stopped, the switching elements SW2, SW3, 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 (coil current) flowing through the coil 14, and the microcomputer 21 uses the coil drop described above based on the amount of voltage drop generated in the shunt resistor 25. A current detection value I is detected.

  Next, the force (electromagnetic attractive force F) by which the movable core is attracted by flowing a coil current will be described in detail. As shown in FIG. 3, the attractive force F increases as the magnetomotive force (ampere turn AT) generated in the fixed core 13 increases. That is, if the number of turns of the coil 14 is the same, the attractive force F increases (F2> F1) as the coil current increases and the ampere turn AT increases (AT2> AT1). However, it takes time as shown in FIG. 4 until the suction force F reaches the maximum value after the energization is started. In the present embodiment, the suction force F when saturated and reaches the maximum value is referred to as a static suction force Fb.

  Further, the electromagnetic attractive force F necessary for the valve body 12 to start the valve opening operation is referred to as a necessary valve opening force. Note that the higher the pressure of the fuel supplied to the fuel injection valve 10, the greater the electromagnetic attraction force (required valve opening force) required for the valve body 12 to start the valve opening operation. Further, the required valve opening force increases according to various situations such as when the viscosity of the fuel is high. Therefore, the maximum value of the required valve opening force when the situation where the required valve opening force is maximized is defined as the required valve opening force Fa.

  FIG. 5A shows a voltage waveform applied to the coil 14 when the fuel injection is performed once. As illustrated, the boost voltage is applied to start energization at the voltage application start time t10 commanded by the injection command signal. Then, with the start of energization, the coil current increases to the first target value Ihold1 (see FIG. 5B). Thereafter, energization is turned off at time t11 when the coil current reaches the first upper limit value IH1 set to a value higher than the first target value.

  In short, control (increase control) is performed to increase the coil current to the first target value Ihold1 by applying the boost voltage by the first energization in steps S11 and S14 (increase control means). The initial energization period by this ascent control is referred to as ascending periods t10 to t11. The first target value Ihold1 is set to a value such that the static suction force Fb is equal to or greater than the required valve opening force Fa.

  Thereafter, at time t12 when the coil current reaches the first lower limit value IL1 set to a value lower than the first target value Ihold1, the boost voltage is applied again to turn on the current. Thereafter, energization is turned off when the coil current rises to the first upper limit value IH1, and energization is turned on when the coil current falls to the first lower limit value IL1.

  In short, the duty is set so that the average value of the fluctuating coil current is held at the first target value Ihold1 by repeating energization on and off with the boost voltage for the second and subsequent times in steps S11, S14, S15, and S17 (hold control means). Control (hold control). This hold control ends at time t13 when the elapsed time Tboost from the start of energization reaches the predetermined time T1. The energization on / off period by the hold control is referred to as hold periods t11 to t13.

  Thereafter, at time t14 when the coil current reaches the second lower limit value IL2 set to a value lower than the second target value Ihold2, the battery voltage is applied to turn on the power. Thereafter, energization is turned off when the coil current rises to the second upper limit value IH2 set to a value higher than the second target value Ihold2, and energization is turned on when the coil current falls to the second lower limit value IL2.

  In short, duty control (battery hold) is performed so that the average value of the fluctuating coil current is held at the second target value Ihold2 by repeating energization on and off by the battery voltage by S22, S25, S26, and S28 (battery hold control means). Control. This battery hold control ends at time t20 when the elapsed time Tpickup from the start of energization reaches the predetermined time T2. The energization on / off period by this battery hold control is referred to as battery hold periods t14 to t20. The second target value Ihold2 is set to a value that maintains the electromagnetic attractive force that has been increased by the increase control and the hold control.

  In the example of FIG. 5, the second target value Ihold2 is set to a value lower than the first target value Ihold1, but the second target value Ihold2 may be set to the same value as the first target value Ihold1.

  Further, the values of the first upper limit value IH1, the first lower limit value IL1, the second upper limit value IH2, and the second lower limit value IL2 are the same as the coil current fluctuation frequency during the hold period and the coil current fluctuation during the battery hold period. It is set to be larger than the frequency.

  Here, the rising slope of the coil current when the boost voltage is applied is larger than the rising slope of the coil current when the battery voltage is applied. Therefore, as shown in FIG. 5, the width ΔI1 of the first upper limit value IH1 and the first lower limit value IL1, and the width ΔI2 of the second upper limit value IH2 and the second lower limit value IL2 are the same value. If thresholds IH1, IL1, IH2, and IL2 are set, the fluctuation frequency in the hold period becomes larger than the fluctuation frequency in the battery hold period. Therefore, when the second target value Ihold2 is set to the same value as the first target value Ihold1, if IH1 = IH2 and IL1 = IL2, ΔI1 = ΔI2.

  After the battery hold period t14 to t20 ends, at time t30 when the coil current reaches the third lower limit value IL3 set to a value lower than the third target value Ihold3, the battery voltage is applied again to turn on the power. Yes. Thereafter, energization is turned off when the coil current rises to the third upper limit value IH3 set to a value higher than the third target value Ihold3, and energization is turned on when the coil current falls to the third lower limit value IL3.

  In short, the duty control (lift maintenance control) is performed so that the average value of the fluctuating coil current is held at the third target value Ihold3 by repeatedly turning on and off the battery voltage. This lift maintenance control is ended by turning off the energization at the voltage application end time t40 commanded by the injection command signal.

  The injection signal included in the injection command signal is a pulse signal for instructing the energization time Ti, and the pulse-on timing is set at a timing t10 that is earlier by a predetermined injection delay time t10 to ta than the target injection start timing. The pulse-off time is set at time t40 when the time corresponding to the energization time Ti has elapsed since the pulse-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 so that feedback control is performed so that the coil current detection value I is held at the first target value Ihold1 until the elapsed time Tboost from the start of energization reaches the predetermined time T1. The switching element SW2 operates according to the boost signal.

  The battery signal included in the injection command signal is turned on when the elapsed time Tboost reaches the predetermined time T1. Thereafter, the battery signal is repeatedly turned on and off so that feedback control is performed so that the coil current detection value I is held at the second target value Ihold2 until the elapsed time Tpickup from the start of energization reaches the predetermined time T2. Thereafter, the battery signal is repeatedly turned on and off so that the feedback control is performed so that the coil current detection value I is held at the third target value Ihold3 until the pulse of the injection signal is turned off. The switching element SW3 operates according to this battery signal.

  The boost signal and battery signal described above are output by the microcomputer 21 in accordance with the procedure of FIG. Note that the processing in FIG. 6 is repeatedly executed at a predetermined cycle, triggered by the command to start injection by the injection signal. Then, the above-described ascent control and hold control are realized by the process of step S10 indicated by the one-dot chain line in FIG. 6, and the above-described battery hold control is realized by the process of step S20 indicated by the one-dot chain line, and the process of step S30. Thus, the above-described lift maintenance control is realized.

  First, in step S11 of FIG. 6, the boost signal pulse is turned on to start application of the boost voltage Uboost. Thereafter, until it is determined that the coil current detection value I has reached the first upper limit value IH1 (S14: NO), the boost signal pulse-on is continued and the application of the boost voltage Uboost is continued. The first upper limit value IH1 is set to a value that is larger than the first target value Ihold1 by a predetermined amount. Therefore, the coil current increases to the first target value Ihold1 by the first boost voltage application, and the above-described increase control is realized.

  If the elapsed time Tboost from the start of application reaches the predetermined time T1 before the coil current detection value I reaches the first upper limit value IH1 due to some abnormality (S12: NO), the boost signal The pulse is turned off to stop applying the boost voltage Uboost. If it is determined that I ≧ IH1 has been reached during the increase control (S14: NO), the application of the boost voltage Uboost is stopped in the subsequent step S15. Thereby, ascent control is complete | finished.

  Next, on the condition that Tboost <T1 (S16: YES), the boost signal pulse-off is continued until it is determined that the coil current detection value I has decreased to the first lower limit value IL1 (S17: NO). To stop the application. The first lower limit value IL1 is set to a value smaller than the first target value Ihold1 by a predetermined amount.

  Thereafter, if it is determined that I ≦ IL1 (S17: NO), the process proceeds to step S11, where the boost signal pulse is turned on to restart the application of the boost voltage Uboost. Therefore, during the period from when the ascent control is finished until it is determined that Tboost ≧ T1 (S12: NO, S16: NO), the boost signal is turned on / off using the first upper limit value IH1 and the first lower limit value IL1 as threshold values. Can be switched. As a result, the average value of the coil current is held at the first target value Ihold1, and the hold control described above is realized.

  Next, when it is determined that Tboost ≧ T1 (S12: NO, S16: NO), voltage application is stopped until it is determined that the coil current detection value I has decreased to the second lower limit value IL2 (S21: NO). Continue. The second lower limit value IL2 is set to a value that is smaller than the second target value Ihold2 by a predetermined amount. In the example shown in FIG. 5, the second target value Ihold2 is set to a value smaller than the first target value Ihold1, but even if the second target value Ihold2 is set to the same value as the first target value Ihold1. Good.

  If it is determined that I ≦ IL2 (S21: NO), the process proceeds to step S22, where the pulse of the battery signal is turned on to start application by the battery voltage Ubatt. Thereafter, the battery voltage pulse is turned on and the battery voltage Ubatt is applied until it is determined that the coil current detection value I has reached the second upper limit value IH2 (S25: NO). The second upper limit value IH2 is set to a value larger by a predetermined amount than the second target value Ihold2.

  Thereafter, when it is determined that I ≧ IH2 is reached during the application of the battery voltage (S25: NO), in the subsequent step S26, the pulse of the battery signal is turned off to stop the application of the battery voltage Ubatt. Thereafter, when it is determined that I ≦ IL2 (S28: NO), the process proceeds to step S22, where the pulse of the battery signal is turned on, and application by the battery voltage Ubatt is resumed. Therefore, the period from the end of the hold control to the determination that the elapsed time Tpickup from the start of energization has reached the predetermined time T2 (S23: NO, S27: NO) is the second upper limit value IH2 and the second upper limit value IH2. The battery signal is switched on and off using the lower limit value IL2 as a threshold value. As a result, the average value of the coil current is held at the second target value Ihold2, and the battery hold control described above is realized.

  Next, when it is determined that Tpickup ≧ T2 (S23: NO, S27: NO), the battery hold control is terminated, and the battery signal pulse is turned off in steps S24 and S26, and the next step S30 is performed. move on. In step S30, the battery signal is switched on and off using the third upper limit value IH3 and the third lower limit value IL3 as threshold values. Thereby, the average value of coil current is hold | maintained at 3rd target value Ihold3, and the lift maintenance control mentioned above is implement | achieved.

  The third upper limit value IH3 is set to a value larger than the third target value Ihold3 by a predetermined amount, and the third lower limit value IL3 is set to a value smaller than the third target value Ihold3 by a predetermined amount. The third target value Ihold3 is set to a value smaller than the second target value Ihold2.

  Next, the operation of the fuel injection valve 10 by performing the various controls described above will be described with reference to FIGS. FIG. 5C shows a time change of the electromagnetic attractive force F, and FIG. 5D shows a time change of the lift amount of the valve body 12.

  As shown in FIG. 5 (c), the electromagnetic attractive force F starts to increase with the start of the increase control. The electromagnetic attraction force F continues to increase after the end of the increase control, and the electromagnetic attraction force F reaches the required valve opening force Fa during the hold periods t11 to t13 in which the hold control is performed. Then, at the time ta when F = Fa as described above, the seat surface 12a of the valve body 12 is separated from the seating surface 11b, and the valve opening operation (lift-up) is started (see FIG. 5D).

  Thereafter, when the coil current is held at the first target value Ihold1 by hold control, the electromagnetic attractive force F rises to the static attractive force Fb. That is, the predetermined time T1 related to Tboost is set so that the electromagnetic attractive force F becomes the static attractive force Fb during the hold periods t11 to t13. Since this first target value Ihold1 is set to a value such that the static attractive force Fb is equal to or greater than the required valve opening force Fa, the electromagnetic attractive force F rises to the static attractive force Fb and becomes saturated. During the period, the electromagnetic attractive force F reaches the required valve opening force Fa.

  Thereafter, after t14 when the boost voltage is switched to the battery voltage, the coil current is held at the second target value Ihold2 by the battery hold control. The second target value Ihold2 is set to a value that maintains the electromagnetic attractive force (that is, the static attractive force Fb) increased by the ascent control and the hold control. Therefore, in the battery hold period t14 to t20, the electromagnetic attractive force F is held at the static attractive force Fb. A predetermined time T2 related to Tpickup is set so that the lift amount becomes the maximum value Lmax during the battery hold period t14 to t20.

  Thereafter, the electromagnetic attraction force F decreases to a predetermined value during a period from the end time t20 of the battery hold control to the start time t30 of the lift maintenance control, and then maintained at the predetermined value by the lift maintenance control. The lift position is maintained at the maximum value Lmax during a period from the end time t20 of the battery hold control to the end time t40 of the lift maintenance control.

  After that, when the lift maintenance control is finished, the valve body 12 starts the valve closing operation and the lift amount decreases as the electromagnetic attractive force F starts to decrease. At time td when the lift amount becomes zero, the seat surface 12a of the valve body 12 is seated on the seating surface 11b and is closed. Note that, from the time point t40 to the time point t41 when the energization ends, a voltage having an opposite phase is applied to the coil 14 to accelerate the fall of the current and improve the valve closing response of the valve body 12.

  As described above, according to the present embodiment, the electromagnetic attraction force is increased to the static attraction force Fb over both the increase periods t10 to t11 and the hold periods t11 to t13. Therefore, the ratio of the rising periods t10 to t11 in the period from when the energization starts until the electromagnetic attractive force reaches the required valve opening force Fa (attractive force increasing periods t10 to ta) decreases. Therefore, since the upward gradient ΔF of the suction force is hardly affected by the temperature characteristic (see the dotted line in FIG. 5C), the valve opening start timing ta and the valve opening period Tact (injection amount) depend on the temperature characteristics. (See the dotted line in FIG. 5D). Therefore, deterioration of the accuracy of the injection state with respect to the energization start timing t1 and the energization period Ti can be suppressed, and the robustness of the control over the temperature characteristics can be improved.

  Furthermore, according to the present embodiment, the electromagnetic attraction force is increased to the static attraction force Fb by performing the hold control after the ascent control, so that the electromagnetic attraction force is required to be opened without performing the hold control. The maximum value of the coil current can be reduced as compared with the case of the conventional control in which the temperature is increased to Fa or higher. Therefore, the energy required for fuel injection can be reduced.

  Furthermore, according to the present embodiment having the characteristics listed below, the functions and effects described below are exhibited by the respective characteristics.

<Feature 1>
In the ascending control and the hold control, the voltage application to the coil 14 is controlled so that the valve opening is started during the period in which the coil current is held at the first target value. In other words, the voltage and the voltage application time during the raising control are controlled so that the valve opening does not start during the raising control. Then, the duty ratio and hold control time during the hold control are controlled so that the valve opening is started during the hold control.

  For this reason, it is possible to avoid the start of valve opening during the raising control, and to ensure that the above-described effects such as “the ratio of the rising periods t10 to t11 occupying the suction force increasing periods t10 to ta is small” are exhibited. Become.

<Feature 2>
In the increase control and hold control, the boost voltage boosted by the booster circuit 23 is applied to the coil 14, and after the hold control is performed, the battery voltage is applied to the coil 14 so that the coil current is held at the second target value Ihold2. The battery hold control to be applied is performed. The second target value Ihold2 is set to a value that maintains the electromagnetic attractive force (static attractive force Fb) increased by the ascent control and the hold control.

  Here, if the holding control period is made longer than necessary, the period using the boost voltage (the rising period + the holding period) becomes longer, so there is a concern that the energy consumption required for one injection increases. become. That is, it is necessary to increase the capacity of the capacitor 23b.

  In this embodiment in view of this point, the battery control is switched to the battery hold control after the hold control. That is, after the coil current reaches the second target value Ihold2, paying attention to the fact that the battery voltage can be maintained at the second target value Ihold2, and the boost voltage is switched to the battery voltage and increased by hold control. The coil current is held at the second target value Ihold2 so that the electromagnetic attraction force (static attraction force Fb) is maintained. Therefore, according to the present embodiment, an increase in energy consumption can be suppressed, and the capacity of the capacitor 23b can be reduced.

<Feature 3>
The first upper limit value IH1, the first lower limit value IL1, the first lower limit value IL1, and the second lower limit value IL1 so that the coil current fluctuation frequency (first frequency) during the hold period is greater than the coil current fluctuation frequency (second frequency) during the battery hold period. The second upper limit value IH2 and the second lower limit value IL2 are set.

  Here, if the first frequency is made the same as the second frequency, contrary to the present embodiment, the current rise slope at the time of applying the boost voltage is larger than that at the time of applying the battery voltage. The fluctuation range becomes larger and the energy efficiency becomes worse. On the other hand, in the present embodiment, since the threshold values IH1, IL1, IH2, and IL2 are set so that the first frequency is higher than the second frequency, the fluctuation range of the coil current during the hold period can be reduced. Deterioration of energy efficiency can be suppressed.

(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.

  In the above embodiment, the battery hold control is performed after the hold control is performed, and the static suction force Fb is maintained by the battery hold control. On the other hand, after the battery hold control is abolished and the attraction force reaches the static attraction force Fb, the boost voltage application by the hold control may be continued to maintain the static attraction force Fb. .

  In the above embodiment, the second target value Ihold2 used for battery hold control is set to a value smaller than the first target value Ihold1, but the second target value Ihold2 is set to the same value as the first target value Ihold1. May be.

  In the above embodiment, the width of the first upper limit value IH1 and the first lower limit value IL1 used for holding the first target value Ihold1 is set to be the same as the width of the second upper limit value IH2 and the second lower limit value IL2. However, different widths may be set.

  In the above embodiment, the fuel injection valve 10 mounted on the ignition type internal combustion engine (gasoline engine) is the control target of the fuel injection control device, but is mounted on the compression self-ignition internal combustion engine (diesel engine). The fuel injection valve may be controlled. Furthermore, in the above-described embodiment, the fuel injection valve that directly injects fuel into the combustion chamber is the control target. However, the fuel injection valve that injects fuel into the intake pipe may be the control target.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 12 ... Valve body, 14 ... Coil, 23 ... Booster circuit, Ihold1 ... 1st target value, Ihold2 ... 2nd target value, S11, S14 ... Ascent control means, S11, S14, S15, S17 ... Hold control means, S22, S25, S26, S28 ... battery hold control means.

Claims (7)

This is applied to the fuel injection valve (10) for injecting fuel by opening the valve element (12) by electromagnetic attraction generated by energizing the coil (14), and by controlling the coil current flowing through the coil. A fuel injection control device for controlling a fuel injection state from the fuel injection valve,
A booster circuit (23) for boosting the battery voltage;
Ascending control means (S11, S14) for applying a boost voltage boosted by the boosting circuit to the coil so that the coil current rises to a first target value (Ihold1);
Hold control means (S11, S14, S15, S17) for applying the boost voltage to the coil so that the coil current raised by the rise control means is held at the first target value;
After the control by the hold control means, battery hold control means (S22, S25, S26, S28) for applying the battery voltage to the coil so that the coil current is held at the second target value (Ihold2). When,
With
The fuel injection control device characterized in that a fluctuation frequency of the coil current during a control period by the hold control means is larger than a fluctuation frequency of the coil current during a control period by the battery hold control means. The maximum value of the electromagnetic attraction force necessary for the valve body to start the valve opening operation is called a necessary valve opening force (Fa), and the electromagnetic attraction force saturated by continuing to flow the coil current of the first target value. In the case of calling the static suction force (Fb),
2. The fuel injection control device according to claim 1, wherein the first target value is set to a value such that the static suction force is greater than or equal to the required valve opening force.   3. The fuel according to claim 1, wherein the second target value is set to a value at which the electromagnetic attractive force raised by the ascent control means and the hold control means is maintained. Injection control device.   The fuel injection control device according to any one of claims 1 to 3, which is applied to the fuel injection valve that directly injects fuel into a combustion chamber of an internal combustion engine.   The fuel injection control device according to any one of claims 1 to 4, which is applied to the fuel injection valve that injects fuel a plurality of times during one combustion cycle. The hold control means turns off the energization when the coil current reaches the first upper limit value (IH1) set to a value higher than the first target value, and sets the value to a value lower than the first target value. When the coil current reaches the first lower limit value (IL1), the energization is turned on to control the average value of the fluctuating coil current to be the first target value,
The battery hold control means turns off the energization when the coil current reaches the second upper limit value (IH2) set to a value higher than the second target value, and sets the value to a value lower than the second target value. When the coil current reaches the set second lower limit value (IL2), the energization is turned on to control the average value of the fluctuating coil current to be the second target value,
The first upper limit value and the first lower limit value so that the fluctuation frequency of the coil current during the control period by the hold control means is larger than the fluctuation frequency of the coil current during the control period by the battery hold control means. The fuel injection control device according to any one of claims 1 to 5, wherein the second upper limit value and the second lower limit value are set. A fuel injection control device according to any one of claims 1 to 6,
The fuel injection valve;
A fuel injection system comprising:

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