Patent Publication Number: US-11649781-B2

Title: Injection control device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of priority from Japanese Patent Application No. 2020-157466 filed on Sep. 18, 2020. The entire disclosure of the above application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an injection control device that opens and closes a fuel injection valve by driving the valve with a current to control fuel injection to an internal combustion engine. 
     BACKGROUND 
     An injection control device opens and closes a fuel injection valve called an injector by driving the valve with a current to control fuel injection to an internal combustion engine such as a gasoline engine of an automobile. The injection control device applies a high voltage to the fuel injection valve to control the valve opening. That is, the injection control device includes a booster circuit for boosting a battery voltage to be a reference power supply voltage of a power supply circuit and a boosting control unit for boosting and controlling the booster circuit. The injection control device boosts the battery voltage with the booster circuit to generate a boosting voltage and apply the generated boosting voltage to the fuel injection valve to control the valve opening. The injection control device detects an inflection point of a waveform of the current or voltage with which the fuel injection valve is energized to detect a valve-closing timing of the fuel injection valve. The injection control device detects a time from an on-to-off switching timing of an energization to a valve-closing timing as a valve-closing detection time and learns the detected valve-closing detection time to improve the injection accuracy. 
     It has been found that in the injection control device, charge noise may be generated by boosting control, and at the time of controlling the opening and closing of the valves by monitoring the energization current of the fuel injection valve, when the charge noise generated by the boosting control is transmitted in a wiring board or a power supply system path, the current monitoring accuracy deteriorates. When the current monitoring accuracy deteriorates, the injection amount varies, the exhaust emission deteriorates, and the fuel consumption deteriorates. Under such circumstances, in a comparative configuration, the boosting control is prohibited for a certain time so that the valve-closing detection learning is not adversely affected by the generation of the charge noise. 
     SUMMARY 
     An injection control device includes: a booster circuit that boosts a battery voltage; a boosting control unit that performs boosting control on the booster circuit; a charge control setting unit that sets a charge prohibition time of the booster circuit for the boosting control unit; and a maximum time specification unit that specifies a maximum valve-closing detection time based on a valve-closing detection time. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other features and advantages of the present disclosure will be more clearly understood from the following detailed description with reference to the accompanying drawings. In the accompanying drawings, 
         FIG.  1    is a block diagram illustrating an embodiment and illustrating an electrical configuration; 
         FIG.  2    is a timing chart; 
         FIG.  3    is a flowchart (first part); 
         FIG.  4    is a flowchart (second part); and 
         FIG.  5    is a flowchart (third part). 
     
    
    
     DETAILED DESCRIPTION 
     In the configuration in which the boosting control is prohibited for a certain period of time, a difficulty occurs in which the charge possible time per cycle of the internal combustion engine is reduced, and the charge possible time cannot be ensured sufficiently. In order to solve such a difficulty, it is conceivable to form a booster circuit to be a circuit chargeable at high speed, but in a configuration in which the circuit chargeable at high speed is provided, new difficulties occur, such as an increase in the size of the circuit and a cost increase. 
     One example of the present disclosure provides an injection control device that can appropriately enhance the injection accuracy by appropriately learning a valve-closing detection time and appropriately ensure the charge possible time. 
     According to one example, an injection control device opens and closes a fuel injection valve by driving the fuel injection valve with a current to control fuel injection to an internal combustion engine. The injection control device includes: a booster circuit that boosts a battery voltage; a boosting control unit that performs boosting control on the booster circuit; a charge control setting unit that sets a charge prohibition time of the booster circuit for the boosting control unit; and a maximum time specification unit that specifies a maximum valve-closing detection time based on a valve-closing detection time. The charge control setting unit sets the maximum valve-closing detection time as the charge prohibition time for the boosting control unit. 
     According to the configuration described above, the maximum valve-closing detection time is specified from the valve-closing detection time, the specified maximum valve-closing detection time is set as the charge prohibition time to the boosting control unit, the charge of the booster circuit is prohibited in the maximum valve-closing detection time, and the charge of the booster circuit is permitted in a time except for the maximum valve-closing detection time. That is, by prohibiting the charge of the booster circuit in the maximum valve-closing detection time, it is possible to appropriately enhance the injection accuracy by appropriately learning the valve-closing detection time and to appropriately ensure the chargeable time. On the other hand, by permitting the charge of the booster circuit at a time except for the maximum valve-closing detection time, the charge possible time can be ensured appropriately. This eliminates the need for the booster circuit to be a circuit chargeable at high speed, and it is possible to appropriately enhance the injection accuracy by appropriately learning the valve-closing detection time and to appropriately ensure the charge possible time. 
     Hereinafter, an embodiment applied to direct injection control of a gasoline engine of an automobile as an internal combustion engine will be described with reference to the drawings. An electronic control unit  1  as an injection control device according to the present embodiment is referred to as an ECU and controls fuel injection of a fuel injection valve  2  provided in each cylinder of an engine, as illustrated in  FIG.  1   . The fuel injection valve  2 , also referred to as an injector, energizes a solenoid coil  2   a  to drive a needle valve, thereby directly injecting fuel into each cylinder of the engine. Although  FIG.  1    illustrates a four-cylinder engine, a three-cylinder engine, a six-cylinder engine, an eight-cylinder engine, and the like can be also used. Further, an injection control device for a diesel engine can be also used. 
     The electronic control unit  1  includes a booster circuit  3 , a microcomputer  4 , a control integrated circuit (IC)  5 , a drive circuit  6 , and a current detection unit  7 . The microcomputer  4  includes one or more cores  10 , a memory  11  such as read-only memory (ROM) and random-access memory (RAM), and a peripheral circuit  12  such as an analog-to-digital (A/D) converter. The microcomputer  4  receives input of sensor signals S from various sensors  8  for detecting the operating state of the engine. The microcomputer  4  calculates an energization instruction TQ on the basis of the program stored in the memory  11  and the sensor signals S input from the various sensors  8 , as described later. In the drawings, the microcomputer  4  may be also referred to as COMP, and the current detection unit may be also referred to as CURRENT DETECT. 
     The various sensors  8  include a water temperature sensor  9  that detects the temperature of the cooling water of the engine. Although not illustrated, in addition to the water temperature sensor  9  described above, the various sensors  8  also include an air-fuel ratio (A/F) sensor that detects an air-fuel ratio of exhaust gas, a crank angle sensor that detects the crank angle of the engine, an airflow meter that detects the intake air amount of the engine, a fuel pressure sensor that detects the fuel pressure when the fuel is injected, a throttle opening sensor that detects a throttle opening, and the like. In  FIG.  1   , the various sensors  8  are illustrated in a simplified manner. In the drawings, the water temperature sensor  9  may be also referred to as WATER TEMP. 
     In the microcomputer  4 , the core  10  grasps the load of the engine from the sensor signals S input from the various sensors  8  and calculates the required fuel injection amount of the fuel injection valve  2  on the basis of the engine load. When calculating the required fuel injection amount of the fuel injection valve  2 , the core  10  then calculates an energization instruction time Ti for the energization instruction TQ on the basis of the calculated fuel injection amount and the fuel pressure at the time of injecting the fuel detected by the fuel pressure sensor. The core  10  calculates the injection command timing for each cylinder from the sensor signals S input from the various sensors  8  and outputs the energization instruction TQ to the control IC  5  at the calculated injection command timing. In this case, although a detailed description is omitted, the core  10  calculates an A/F correction amount so as to become a target air-fuel ratio on the basis of the air-fuel ratio detected by the A/F sensor, and performs air-fuel ratio feedback control. Further, the core  10  performs A/F learning on the basis of the history of A/F correction and adds the learning correction value to the calculation of the A/F correction amount. 
     The control IC  5  is, for example, an integrated circuit device using an application-specific integrated circuit (ASIC) and, although not illustrated, the control IC  5  includes a control body such as a logic circuit and a central processing unit (CPU), a storage unit such as RAM, ROM, an erasable programmable read-only memory (EEPROM), comparator equipment using a comparator, and the like, for example. The control IC  5  performs the current control of the fuel injection valve  2  via the drive circuit  6  in accordance with the hardware and software configuration of the control IC  5 . The control IC  5  has functions as a boosting control unit  5   a , an energization control unit  5   b , a current monitoring unit  5   c , and an area correction amount calculation unit  5   d . In the drawings, the boosting control unit  5   a  may be also referred to as BOOSTING CONT, the energization control unit  5   b  may be also referred to as ENERGIZATION CONT, the current monitoring unit  5   c  may be also referred to as CURRENT MONITORING, and the area correction amount calculation unit  5   d  may be also referred to as AMOUNT CAL. 
     Although not illustrated, the booster circuit  3  is configured to receive input of a battery voltage VB, boost the input battery voltage VB, and charge the booster capacitor  3   a  serving as a charge unit with a boosting voltage Vboost to a fully charged voltage. The battery voltage VB is, for example, 12 volts, and the boosting voltage Vboost is, for example, 65 volts. The boosting voltage Vboost is supplied to the drive circuit  6  as power for driving the fuel injection valve  2 . The boosting control unit  5   a  performs the boosting control of the booster circuit  3  and controls the charge of the booster circuit  3 . 
     The drive circuit  6  receives the input of the battery voltage VB and the boosting voltage Vboost. 
     Although not illustrated, the drive circuit  6  includes a transistor for applying the boosting voltage Vboost to the solenoid coil  2   a  of the fuel injection valve  2  in each cylinder, a transistor for applying the battery voltage VB, a transistor for selecting a cylinder to be energized, and the like. Each transistor of the drive circuit  6  is turned on and off by the energization control unit  5   b . The drive circuit  6  applies a voltage to the solenoid coil  2   a  to drive the fuel injection valve  2  on the basis of the energization control of the energization control unit  5   b.    
     The current detection unit  7  includes a current detection resistor (not illustrated) or the like and detects a current flowing through the solenoid coil  2   a . The current monitoring unit  5   c  includes, for example, a comparator (not illustrated), an A/D converter, or the like and monitors, through the current detection unit  7 , an energization current value EI actually flowing through the solenoid coil  2   a  of the fuel injection valve  2  in each cylinder. 
     The control IC  5  stores an energization current profile PI showing an ideal relationship between an energization time Ti and an energization current value EI so as to obtain an integrated energization current value of the fuel injection valve  2  corresponding to the energization instruction TQ input from the microcomputer  4 . The energization control unit  5   b  performs current control on the fuel injection valve  2  via the drive circuit  6  on the basis of the energization current profile PI. In the control of the fuel injection valve  2 , the gradient of the energization current of the fuel injection valve  2  is lower than the energization current profile PI due to various factors such as ambient temperature environment and aging deterioration, and the actual injection amount is lower than the commanded injection amount. On the other hand, at the time of controlling the energization of the fuel injection valve  2 , a fuel injection amount proportional to the integrated value of the energization current is obtained. 
     The area correction amount calculation unit  5   d  calculates an energization time correction amount ΔTi by calculating the area correction amount on the basis of the difference between the integrated current of the energization current profile PI and the integrated current of the energization current value EI of the current that actually flows in the fuel injection valve  2  and is detected by the current detection unit  7  so that the current values become equivalent. In this case, for example, the area correction amount calculation unit  5   d  calculates a time for reaching a first current threshold and calculates a time for reaching a second current threshold for each of the energization current profile PI and the energization current value EI. The area correction amount calculation unit  5   d  then estimates an area difference from the calculated times, calculates an area correction amount so as to obtain an area equivalent to the estimated area difference, and calculates the energization time correction amount ΔTi. The area correction amount calculation unit  5   d  may adopt a method other than the method described above and calculate the area correction amount to calculate the energization time correction amount ΔTi. It is possible to obtain the required appropriate fuel injection amount of the fuel injection valve  2  by the corrected energization instruction TQ, obtained by the area correction amount calculation unit  5   d  correcting the current area, correcting the energization time of the energization instruction TQ in accordance with the energization time correction amount ΔTi, and correcting the energization time. Note that the area correction amount calculation unit  5   d  outputs the energization time correction amount ΔTi calculated in this manner to the microcomputer  4 . 
     The microcomputer  4  has a function of performing valve-closing detection learning in order to enhance injection accuracy. That is, the microcomputer  4  detects the inflection point of the waveform of the current or voltage with which the fuel injection valve  2  is energized, detects the valve-closing timing of the fuel injection valve  2 , detects a time from the on-to-off switching timing of the corrected energization instruction TQ to the valve-closing timing as a valve-closing detection time, and learns the detected valve-closing detection time. 
     It has been found that in the injection control device  1 , charge noise may be generated by boosting control, and the current monitoring accuracy deteriorates when the charge noise generated by the boosting control is transmitted in a wiring board or a power supply system path at the time of controlling the opening and closing of the valves by monitoring the energization current of the fuel injection valve  2 . Therefore, there is a configuration in which the boosting control is prohibited fora certain period of time so that the valve-closing detection learning is not adversely affected by the generation of the charge noise. However, in such a configuration, the charge possible time per cycle of the internal combustion engine is reduced, and the charge possible time cannot be ensured sufficiently. Further, it is conceivable to form a booster circuit  3  to be a circuit chargeable at high speed, but in a configuration in which the circuit chargeable at high speed is provided, new problems occur, such as an increase in the size of the circuit and a cost increase. 
     Therefore, in the present embodiment, the following configuration is adopted. The core  10  has functions as a charge control setting unit  10   a , a maximum time specification unit  10   b , a learning time acquisition unit  10   c , a maximum value storage unit  10   d , and a maximum value update unit  10   e . In the drawings, the charge control setting unit  10   a  may be also referred to as may be also referred to as CHARGE CONTROL SET, the maximum time specification unit  10   b  may be also referred to as MAX TIME SPEC, the learning time acquisition unit  10   c  may be also referred to as LEARNING TIME ACQ, the maximum value storage unit  10   d  may be also referred to as MAX VALUE STORAGE, and the maximum value update unit  10   e  may be also referred to as MAX VALUE UPDATE. 
     The charge control setting unit  10   a  outputs a charge permission command to the boosting control unit  5   a  and sets charge permission for driving the booster circuit  3  to the boosting control unit  5   a . The boosting control unit  5   a  receives the input of the charge permission command from the charge control setting unit  10   a , and when the charge permission is set by the charge control setting unit  10   a , the boosting control unit  5   a  drives the booster circuit  3  to charge the booster capacitor  3   a  with the boosting voltage Vboost to a fully charged voltage. 
     On the other hand, the charge control setting unit  10   a  outputs a charge prohibition command to the boosting control unit  5   a  and sets charge prohibition against the booster circuit  3  to the boosting control unit  5   a . The boosting control unit  5   a  receives the input of the charge prohibition command from the charge control setting unit  10   a , and when the charge prohibition is set by the charge control setting unit  10   a , the boosting control unit  5   a  stops the booster circuit  3  in a charge prohibition band designated by the input charge prohibition command. In this case, by the booster circuit  3  being stopped in the charge prohibition band, charge noise due to the boosting control is not generated, and the current monitoring accuracy does not deteriorate. 
     Here, a mode of detecting the valve-closing detection time will be described. As illustrated in  FIG.  2   , at the injection command timing, the injection control device  1  switches the energization instruction TQ from off to on and starts supplying the energization current to the fuel injection valve  2 . When the supply of the energization current to the fuel injection valve  2  is started, the fuel injection valve  2  is opened, the lift amount of the needle valve increases, and fuel is injected into the cylinder of the engine. Thereafter, the injection control device  1  switches the corrected energization instruction TQ by the current area correction from off to on and stops the supply of the energization current to the fuel injection valve  2 . When the supply of the energization current to the fuel injection valve  2  is stopped, the downstream voltage of the fuel injection valve  2  is generated. Then, when the lift amount of the needle valve decreases, and the fuel injection valve  2  is closed, an electromotive force is generated by a magnetic flux change due to the sitting at the lift position, and an inflection point occurs in the downstream voltage of the fuel injection valve  2 . The core  10  detects the timing at which the inflection point occurs as the valve-closing timing of the fuel injection valve  2  and detects the time from the on-off switching timing of the corrected energization instruction TQ to the valve-closing timing as the valve-closing detection time. 
     The charge control setting unit  10   a  outputs the charge prohibition command to the boosting control unit  5   a  in the following manner during the period in which the valve-closing detection time is detected, and stops the booster circuit  3  in the charge prohibition band designated by the charge prohibition command. In this case, the charge control setting unit  10   a  sets the charge prohibition band by either a fixed charge prohibition band setting method which sets a period from TQ-off until the lapse of a predetermined time as the charge prohibition band, or a selective charge prohibition band setting method which selects and determines the charge prohibition band. 
     In the fixed charge prohibition band setting method, the charge control setting unit  10   a  notifies the boosting control unit  5   a  of a predetermined time and sets as the charge prohibition band a period from the on-to-off switching timing of the corrected energization instruction TQ to the timing at which the predetermined time elapses. Here, the predetermined time is sufficiently long with respect to the valve-closing detection time, and the charge control setting unit  10   a  sets the entire period of the valve-closing detection time as the charge prohibition band. 
     In the selective charge prohibition band setting method, the charge control setting unit  10   a  selects one of several patterns and sets a partial or entire period of the valve-closing detection time as the charge prohibition band. For example, as a first pattern, the charge control setting unit  10   a  does not set as the charge prohibition band a period from the on-to-off switching timing of the corrected energization instruction TQ to a timing at which the downstream voltage of the fuel injection valve  2  decreases to a second voltage value (e.g., 30 volts) in the valve-closing detection time, but sets as the charge prohibition band a period from a timing at which the downstream voltage of the fuel injection valve  2  decreases to a second voltage value to the valve-closing timing. 
     For example, as a second pattern, the charge control setting unit  10   a  does not set as the charge prohibition band a period from the on-to-off switching timing of the corrected energization instruction TQ to a timing at which the downstream voltage of the fuel injection valve  2  decreases to a first voltage value (e.g., 60 volts) in the valve-closing detection time, but sets as the charge prohibition band a period from a timing at which the downstream voltage of the fuel injection valve  2  decreases to a first voltage value to the valve-closing timing. 
     For example, as a third pattern, the charge control setting unit  10   a  sets as the charge prohibition band a period from the on-to-off switching timing of the corrected energization instruction TQ to the valve-closing timing, that is, the entire period of the valve-closing detection time, in the valve-closing detection time. In some cases, the charge control setting unit  10   a  does not set the entire period of the valve-closing detection time as the charge prohibition band. In the present embodiment, the three patterns have been exemplified as patterns for arbitrarily setting the charge prohibition band, but the charge prohibition band may be set by a pattern other than the exemplified patterns. 
     Further, the charge control setting unit  10   a  sets a forcible cancel time starting from the on-to-off switching timing of the corrected energization instruction TQ on the chance that the valve closing may not be detected. The forcible cancel time is a time for forcibly canceling the charge prohibition band. In this case, the charge control setting unit  10   a  can variably set the forcible cancel time and sets a time longer than the valve-closing detection time as the forcible cancel time. 
     When detecting the valve-closing detection time, the maximum time specification unit  10   b  specifies the maximum valve-closing detection time from the detected valve-closing detection time. When the maximum valve-closing detection time is specified by the maximum time specification unit  10   b , the charge control setting unit  10   a  sets the specified maximum valve-closing detection time as the charge prohibition time to the boosting control unit  5   a . The learning time acquisition unit  10   c  learns the valve-closing detection time when minute injection for learning is performed in a period in which the maximum valve-closing detection time is set, to acquire the valve-closing detection learning time. 
     When the valve-closing detection learning time is acquired by the learning time acquisition unit  10   c , the maximum value storage unit  10   d  specifies the maximum value of the acquired valve-closing detection learning time as the learned maximum time and stores the specified learned maximum time. When the learned maximum time is stored into the maximum value storage unit  10   d , the charge control setting unit  10   a  calculates a time obtained by adding a margin time to the learned maximum time stored in the maximum value storage unit  10   d  as a learned valve-closing detection time. 
     In and after the next trip, the charge control setting unit  10   a  sets the calculated learned valve-closing detection time as the charge prohibition time for the boosting control unit  5   a.    
     The maximum value update unit  10   e  updates the learned maximum time stored in the maximum value storage unit  10   d . When the learned maximum time stored in the maximum value storage unit  10   d  is updated, the charge control setting unit  10   a  calculates a time obtained by adding the margin time to the valve-closing detection learning time after the update as a learned valve-closing detection time after the update, and sets the calculated learned valve-closing detection time after the update as the charge prohibition time for the boosting control unit  5   a.    
     Next, the operation of the above-described configuration will be described with reference to  FIGS.  3  to  5   . Here, a description will be given of maximum time setting processing for setting the maximum valve-closing detection time, first learning processing for learning a first valve-closing detection time, and second learning processing for learning a valve-closing detection time after the first learning processing. 
     (1) Maximum Time Setting Processing 
     In the microcomputer  4 , the core  10  starts the maximum time setting processing each time the start event of the maximum time setting processing occurs. As illustrated in  FIG.  3   , when the maximum time setting processing is started, the core  10  acquires the maximum valve-closing detection time from the past valve-closing detection time (S 1 ). The core  10  notifies the boosting control unit  5   a  of the acquired maximum valve-closing detection time, thereby setting the maximum valve-closing detection time to the boosting control unit  5   a  (S 2 ), terminating the maximum time setting processing, and waits for the occurrence of the next start event. That is, the core  10  sets as the charge prohibition band a period from the on-to-off switching timing of the corrected energization instruction TQ to the timing at which the maximum valve-closing detection time elapses. 
     (2) First Learning Processing 
     In the microcomputer  4 , the core  10  starts the first learning processing each time the start event of the first learning processing occurs. As illustrated in  FIG.  4   , when the first learning processing is started, the core  10  learns the valve-closing detection time when the minute injection for learning is performed, to acquire the valve-closing detection learning time (S 11 ). Upon learning the valve-closing detection time when the minute injection for learning is performed, the core  10  counts up the number of times of valve-closing detection learning (S 12 ). 
     The core  10  compares the number of times of valve-closing detection learning after the number of times of valve-closing detection learning is counted up with a prescribed number of times prescribed in advance and determines whether the prescribed number of times of valve-closing detection learning has been completed (S 13 ). When determining that the number of times of valve-closing detection learning has not reached the prescribed number of times and the prescribed number of times of valve-closing detection learning has not been completed (S 13 : NO), the core  10  terminates the first learning processing and waits for the occurrence of the next start event. That is, until the prescribed number of times of valve-closing detection learning is completed, the core  10  learns the valve-closing detection time when the minute injection for learning is performed, to acquire the valve-closing detection learning time. 
     When determining that the number of times of valve-closing detection learning has reached the prescribed number of times and the prescribed number of times of valve-closing detection learning has been completed (S 13 : YES), the core  10  specifies the maximum value of the valve-closing detection learning time acquired by the prescribed number of times of valve-closing detection learning as the learned maximum time (S 14 ). When specifying the learned maximum time, the core  10  adds the margin time to the specified learned maximum time to calculate the learned valve-closing detection time (S 15 ), terminates the first learning processing, and waits for the occurrence of the next start event. In and after the next trip, the core  10  notifies the boosting control unit  5   a  of the learned valve-closing detection time calculated in this manner, thereby setting the learned valve-closing detection time to the boosting control unit  5   a  and setting, as a new charge prohibition band, a period from the on-to-off switching timing of the corrected energization instruction TQ to the timing at which the learned valve-closing detection time elapses. 
     (3) Second Learning Processing 
     In the microcomputer  4 , the core  10  starts the second learning processing each time the start event of the second learning processing occurs. As illustrated in  FIG.  5   , when the second learning processing is started, the core  10  learns the valve-closing detection time when the minute injection for learning is performed, to acquire the valve-closing detection learning time (S 21 ). Each time of learning of the valve-closing detection time when the minute injection for learning is performed, the core  10  counts up the number of times of valve-closing detection learning (S 22 ). 
     The core  10  compares the number of times of valve-closing detection learning after the count-up with a prescribed number of times prescribed in advance and determines whether the prescribed number of times of valve-closing detection learning has been completed (S 23 ). When determining that the number of times of valve-closing detection learning has not reached the prescribed number of times and the prescribed number of times of valve-closing detection learning has not been completed (S 23 : NO), the core  10  terminates the second learning processing and waits for the occurrence of the next start event. 
     When the number of times of valve-closing detection learning reaches a prescribed number, and the prescribed number of times of valve-closing detection learning is completed (S 23 : YES), the core  10  compares the maximum value of the valve-closing detection learning time acquired by the prescribed number of times of valve-closing detection learning with the present learned maximum time and determines whether the maximum value of the valve-closing detection learning time exceeds the present learned maximum time (S 24 ). When it is determined that the maximum value of the valve-closing detection learning time does not exceed the present learned maximum time (S 24 : NO), the core  10  terminates the second learning processing and waits for the occurrence of the next start event. 
     When determining that the maximum value of the valve-closing detection learning time exceeds the present learned maximum time (S 24 : YES), the core  10  specifies the maximum value of the valve-closing detection learning time exceeding the present learned maximum time as a new learned maximum time and updates the learned maximum time (S 25 ). When updating the learned maximum time, the core  10  adds the margin time to the learned maximum time after the update to calculate a new learned valve-closing detection time, updates the learned valve-closing detection time (S 26 ), terminates the second learning processing, and waits for the occurrence of the next start event. 
     In and after the next trip, the core  10  notifies the boosting control unit  5   a  of the learned valve-closing detection time updated in this manner, thereby setting the learned valve-closing detection time after the update to the boosting control unit  5   a  and setting, as a new charge prohibition band, a period from the on-to-off switching timing of the corrected energization instruction TQ to the timing at which the learned valve-closing detection time after the update elapses. 
     As described above, according to the present embodiment, the following effects can be obtained. In the injection control device  1 , the maximum valve-closing detection time is specified from the valve-closing detection time, the specified maximum valve-closing detection time is set as the charge prohibition time to the boosting control unit  5   a , the charge of the booster circuit  3  is prohibited in the maximum valve-closing detection time, and the charge of the booster circuit  3  is permitted in a time except for the maximum valve-closing detection time. That is, by prohibiting the charge of the booster circuit  3  in the maximum valve-closing detection time, it is possible to appropriately learn the valve-closing detection time to appropriately improve the injection accuracy. On the other hand, by permitting the charge of the booster circuit  3  at a time except for the maximum valve-closing detection time, the charge possible time can be ensured appropriately. This eliminates the need for the booster circuit  3  to be a circuit chargeable at high speed, and it is possible to appropriately improve the injection accuracy by appropriately learning the valve-closing detection time and appropriately ensure the charge possible time, while avoiding concerns such as an increase in the size of the circuit and a cost increase. 
     An appropriate charge prohibition time can be set by learning the valve-closing detection time when the minute injection for learning is performed in a period in which the maximum valve-closing detection time is set, storing the maximum value of the valve-closing detection learning time acquired by the learning as the learned maximum time, and setting the learned valve-closing detection time obtained by adding the margin time to the learned maximum time as the charge prohibition time to the boosting control unit  5   a  in the next trip and a subsequent step. 
     Further, an appropriate charge prohibition time can always be set by updating the learned maximum time and setting the learned valve-closing detection time after the update, obtained by adding the margin time to the learned maximum time after the update, as the charge prohibition time to the boosting control unit  5   a.    
     By setting the charge prohibition time to the boosting control unit  5   a  at the upper limit value or less, it is possible to appropriately cope with a case where the closing of the valve becomes undetectable due to, for example, a failure, disconnection of a circuit that detects the valve closing, or the like. That is, once the charge prohibition time is set beyond the upper limit value, there is a possibility that the charge prohibition cannot be stopped when the valve closing cannot be detected due to, for example, a failure, disconnection of a circuit that detects the valve closing, or the like, but the charge prohibition can be stopped by setting the charge prohibition time at the upper limit value or less, and appropriate measures can be taken. 
     The microcomputer  4  and the control IC  5  described above may be integrated, and in this case, it is desirable to use an arithmetic processing device capable of high-speed computing. The means and functions provided by the microcomputer  4  and the control IC  5  can be provided by software recorded in a substantial memory device and a computer, software, hardware, or a combination thereof for performing the software. For example, when the controller is provided by an electronic circuit that is hardware, the control device can include a digital circuit including one or more logic circuits, or an analog circuit. Further, for example, when the controller performs various kinds of control by software, a program is stored in the storage unit, and a method corresponding to the program is performed by the control body performing the program. 
     In addition, various changes can be made on the hardware configuration of the fuel injection valve, the booster circuit, the drive circuit, the current detection unit, and the like. While the present disclosure has been described in accordance with the embodiment, it is understood that the present disclosure is not limited to such embodiments or structures. The present disclosure also encompasses various modified examples and modifications within a uniform range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than that, or less than that, are also within the scope and idea of the present disclosure. 
     The control unit and the method according to the present disclosure may be achieved by a dedicated computer provided by constituting a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and the method according to the present disclosure may be achieved by a dedicated computer provided by constituting a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method according to the present disclosure may be achieved using one or more dedicated computers constituted by a combination of the processor and the memory programmed to execute one or more functions and the processor with one or more hardware logic circuits. The computer program may be stored in a computer-readable non-transitory tangible storage medium as an instruction to be executed by the computer. 
     Here, the process of the flowchart or the flowchart described in this application includes a plurality of sections (or steps), and each section is expressed as, for example, S 1 . Further, each section may be divided into several subsections, while several sections may be combined into one section. Furthermore, each section thus configured may be referred to as a device, module, or means.