Patent Publication Number: US-11384704-B2

Title: Injection control device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2020-093308, filed on May 28, 2020, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure generally relates to an injection control device that controls valve opening/closing of a fuel injection valve. 
     BACKGROUND INFORMATION 
     The injection control device is used to inject fuel into an internal combustion engine by opening and closing a fuel injection valve. The injection control device controls valve opening by energizing an electrically driveable fuel injection valve with an electric current. In recent years, an ideal current profile of an energization current based on an instruction injection amount has been defined, and an injection control device controls valve opening by applying an electric current to a fuel injection valve based on the ideal current profile. 
     SUMMARY 
     It is an object of the present disclosure to provide an injection control device capable of performing injection control without steeply changing an injection amount with respect to a small change in the energization instruction time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Objects, features, and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings, in which: 
         FIG. 1  is an electrical configuration diagram of an injection control device in a first embodiment of the present disclosure; 
         FIG. 2  is an explanatory diagram of information communicated between a microcontroller and a control IC; 
         FIG. 3  is an explanatory diagram of a map; 
         FIG. 4  is an explanatory diagram of a method of calculating an integrated current difference; 
         FIG. 5  is an explanatory diagram of a method of calculating an estimated peak current value; 
         FIG. 6  is an explanatory diagram of a step region of an injection amount; 
         FIG. 7  is a flowchart showing a correction coefficient setting process and an energization time correction amount calculation process in a second embodiment; 
         FIG. 8  is an explanatory diagram of a map for a normal region; 
         FIG. 9  is an explanatory diagram of a map for a step area; and 
         FIG. 10  is an explanatory diagram of a step region of an injection amount. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described with reference to the attached drawings. As shown in  FIG. 1 , an electronic control unit  1  (ECU) is configured as an injection control device that drives and controls a solenoid-type fuel injection valve  2  (also called an injector) which injects and supplies fuel directly to a plurality of cylinders of an internal combustion engine mounted on a vehicle such as an automobile. Here, the fuel injection valve  2  for 4 cylinders is shown, but it is also applicable to 2 cylinders, 3 cylinders, 6 cylinders, and 8 cylinders. Hereinafter, an example of such device applied as the electronic control unit  1  for controlling a gasoline engine will be described, but it may also be applied to an electronic control device for controlling a diesel engine. 
     The electronic control device  1  includes an electrical configuration as a booster circuit  3 , a microcontroller  4 , a control IC  5 , a drive circuit  6 , and a current detector  7 , and is used as an injection control device that controls fuel injection. The microcontroller  4  is configured to include one or more cores  4   a , a memory  4   b  such as ROM and RAM, and a peripheral circuit  4   c  such as an A/D converter, and performs various controls based on a program stored in the memory  4   b  and a sensor signal S acquired from various sensors  8 . 
     For example, the sensors  8  for a gasoline engine may include: (i) a crank angle sensor that outputs a pulse signal each time a crank shaft rotates by a predetermined angle, (ii) a water temperature sensor that is arranged in a cylinder block of an internal combustion engine to detect a cooling water temperature, (iii) an intake amount sensor that detects an air intake amount, (iv) a fuel pressure sensor  9  that detects a fuel pressure at the time of fuel injection from the fuel injection valve  2 , (v) an A/F sensor that detects the air-fuel ratio of the internal combustion engine, that is, the A/F value, and the like. Further, the microcontroller  4  can acquire the fuel pressure at the time of injecting fuel into the internal combustion engine from the fuel pressure sensor  9  through the peripheral circuit  4   c .  FIG. 1  shows the sensors  8  in a simplified manner. 
     The microcontroller  4  calculates an engine speed (i.e., engine rotation number) from a pulse signal of the crank angle sensor, and acquires an accelerator opening degree from an accelerator signal. The microcontroller  4  calculates a target torque required for the internal combustion engine based on: (i) the accelerator opening degree, (iii) an estimated temperature of the fuel injection valve  2  from the cooling water temperature detected by the water temperature sensor, (iii) a hydraulic pressure, and (iv) the A/F value, and then calculates a required injection amount, which serves as a target injection amount, based on the target torque. 
     Further, the microcontroller  4  calculates an energization instruction time Ti of an instruction TQ (also known as an injection instruction) based on at least: (i) the required/target injection amount, and (ii) the fuel pressure detected by the fuel pressure sensor  9 . The microcontroller  4  calculates an injection instruction timing (such as start time t 0  in  FIG. 3 ) for each cylinder based on the sensor signal S input from the various sensors  8  described above, and outputs the instruction TQ for injecting fuel to the control IC  5  at the calculated injection instruction timing. 
     Note that the microcontroller  4  can calculate an injection start time for each cylinder based at least partly on the engine speed calculated by the pulse signal of the crank angle sensor. 
     The control IC  5  is, for example, an integrated circuit device using an ASIC, and includes, for example, a logic circuit, a control main body such as a CPU, a storage unit such as a RAM, a ROM, or an EEPROM, and a comparator using a comparator (none of which is shown), configured to perform various controls based on hardware and software. The control IC  5  has functions as a boost controller  5   a , an energization controller  5   b , and a current monitor  5   c.    
     The booster circuit  3  is composed of a booster type DC/DC converter, and operates by receiving an input of a battery voltage VB. The boost controller  5   a  boost-controls the battery voltage VB input to the booster circuit  3 , and supplies the boost voltage Vboost from the booster circuit  3  to the drive circuit  6 . 
     The drive circuit  6  is configured as receiving an input of the battery voltage VB and the boost voltage Vboost, and injects fuel by driving the fuel injection valve  2  according to energization control by an energization controller  5   b  of the control IC  5 , which applies voltage to a solenoid coil of the fuel injection valve  2  in each cylinder, i.e., by applying the boost voltage Vboost or the boost voltage Vboost or the battery voltage VB. 
     The current detector  7  is composed of a current detection resistor. The current monitor  5   c  of the control IC  5  is configured by using, for example, a comparison unit using a comparator, an A/D converter and the like (neither shown), and monitors the electric current flowing through the solenoid coil  2   a  of the fuel injection valve  2  via the current detector  7 . 
     Further,  FIG. 2  schematically shows a part of the functional configurations of the microcontroller  4  and the control IC  5 . The microcontroller  4  functions as an energization instruction time calculator  10 , and a conversion coefficient setter  11  by executing a program stored in the memory  4   b  by the core  4   a . The control IC  5  also has functions of the boost controller  5   a , of the energization controller  5   b , and of the current monitor  5   c  described above, as well as a function of an energization time correction amount calculator  5   d  serving as an area correction unit. 
     The energization instruction time calculator  10  calculates the required injection amount at the start of injection control based on the sensor signal S of the various sensors  8  related to the internal combustion engine, and calculates an energization instruction time Ti of the instruction TQ. The energization instruction time Ti of the instruction TQ indicates a duration/length of instruction time for applying a voltage, for example, a boost voltage Vboost to the fuel injection valve  2  during injection control. 
     The conversion coefficient setter  11  sets correction coefficients α and β. The correction coefficient α is a coefficient used for estimating an integrated current difference between a normal (or “ideal”) current profile PI flowing electric current through the fuel injection valve  2  and an actual energization current EI. The correction coefficient α is a coefficient set to a value of zero or more calculated in advance based on the load characteristics of the fuel injection valve  2 , etc., and is recorded in advance in the memory  4   b  by an α map  12  (see  FIG. 3 ). The α map  12  is a map in which the correction coefficients α are arranged in a matrix. The conversion coefficient setter  11  sets the correction coefficient α with reference to fuel pressure information of the fuel pressure sensor  9  and the α map  12 . 
     As illustrated in  FIG. 3 , the α map  12  serves as a map for deriving the correction coefficient α from the energization instruction time Ti of the instruction TQ and the fuel pressure detected by the fuel pressure sensor  9  at the time of injection, and the α map  12  is provided for setting the correction coefficient α for a certain range, i.e., from a peak current not yet reached timing to a peak current already reached timing. The correction coefficient α is provided to calculate an energization time correction amount ΔTi in equations (1) to (4) described later. The conversion coefficient setter  11  can increase the energization time correction amount ΔTi by setting the correction coefficient α to a large value, or can also set the energization time correction amount ΔTi to zero by setting the correction coefficient α to zero. Note that times T 1  to T 8  indicate values that satisfy a relation of T 1 &lt;T 2 &lt; . . . &lt;T 8 , and fuel pressures P 1  to P 6  also indicate pressure values that satisfy a relation of P 1 &lt;P 2 &lt; . . . &lt;P 6 . 
     In a column of time T 1  of the α map  12 , correction coefficients α 11  to α 61  corresponding to the fuel pressures P 1  to P 6  are stored. In the column of time T 1 , the correction coefficients α 11  to α 61  are set to increase as the fuel pressures P 1  to P 6  increase. The correction coefficients α 12  to α 62  corresponding to the fuel pressures P 1  to P 6  are also stored in a column of time T 2  of the α map  12 . Similarly, in the column of time T 2 , the correction coefficients α 12  to α 62  are set to increase as the fuel pressures P 1  to P 6  increase. 
     The correction coefficients α 13  to α 63  corresponding to the fuel pressures P 1  to P 6  are also stored in a column of time T 3  of the α map  12 . In the column of time T 3 , the correction coefficients α 13  to α 63  are set to increase as the fuel pressures P 1  to P 6  increase. The correction coefficients α 14  to α 64  corresponding to the fuel pressures P 1  to P 6  are also stored in a column of time T 4  of the α map  12 . In the column of time T 4 , the correction coefficients α 14  to α 64  are set to increase as the fuel pressures P 1  to P 6  increase. 
     The correction coefficients α 15  to α 65  corresponding to the fuel pressures P 1  to P 6  are also stored in a column of time T 5  column of the α map  12 . In the column of time T 5 , the correction coefficients α 15  to α 65  are set to increase as the fuel pressures P 1  to P 6  increase. The correction coefficients α 16  to α 66  corresponding to the fuel pressures P 1  to P 6  are also stored in a column of time T 6  of the α map  12 . In the column of time T 6 , the correction coefficients α 15  to α 66  are set to increase as the fuel pressures P 1  to P 6  increase. 
     The correction coefficients α 17  to α 67  corresponding to the fuel pressures P 1  to P 6  are also stored in a column of time T 7  of the α map  12 . In the column of time T 7 , the correction coefficients α 17  to α 67  are set to be equal even if the fuel pressures P 1  to P 6  increase. The correction coefficients α 18  to α 68  corresponding to the fuel pressures P 1  to P 6  are stored in a column of time T 8  of the α map  12 . The energizing time to reach (i.e., achieve) the target peak current during the partial lift injection is set between time T 7  and time T 8 . However, the correction coefficients α 18  to α 68  for time T 8  are all set to zero corresponding to all of the fuel pressure P 1  to P 6 . 
     In one embodiment of the α map  12  in  FIG. 3 , there are 3 general cases: 
     case (i) the correction coefficient α increases as the fuel pressure increases in columns T 1  to T 6 ; 
     case (ii) the correction coefficient α remains constant as the fuel pressure increases in column T 7 ; and 
     case (iii) the correction coefficient α remains zero as the fuel pressure increases in column T 8 . 
     For example, if the energization time of the fuel injection valve  2  is about time T 8 , for a guarantee that the target peak current Ipk is always reached (i.e., achieved) during the partial lift injection, it is configured that the energization time correction amount ΔTi, i.e., an extension of time (ΔTi), calculated by multiplying one of the correction coefficients α 18  to α 68  always results in zero. Although a simplified example has been described here, the correction coefficient α is recorded in the α map  12  corresponding to all the energization times that can be set. 
     In  FIG. 3 , the correction coefficient β is a coefficient used for estimating an estimated peak current value Ipa 1  of the injection control, and is a coefficient calculated in advance based on the load characteristics of the fuel injection valve  2  and the like. In one embodiment, the correction coefficient β is an intercept of the vertical axis and has a negative value. 
     The energization controller  5   b  of the control IC  5  inputs the energization instruction time Ti of the instruction TQ, and the energization time correction amount calculator  5   d  inputs the correction coefficients α and β. When the energization instruction time Ti of the instruction TQ is input, the energization controller  5   b  of the control IC  5  performs energization control for supplying electric power from the drive circuit  6  to the fuel injection valve  2  (for example, for supplying the boost voltage Vboost). On the other hand, when the fuel injection valve  2  is driven with electric current by the energization controller  5   b  to inject fuel therefrom, the energization time correction amount calculator  5   d  of the control IC  5  calculates the energization time correction amount ΔTi by acquiring the electric current flowing through the fuel injection valve  2  and by performing area correction of the electric current. 
     When the energization time correction amount calculator  5   d  calculates the energization time correction amount ΔTi, the energization time correction amount calculator  5   d  feeds it back to the energization controller  5   b . The energization controller  5   b  performs energization control of the fuel injection valve  2  by reflecting the energization time correction amount ΔTi in real time to the energization instruction time Ti of the instruction TQ that is input corresponding to a certain injection. 
     Hereinafter, details of operation in case of multi-stage in-cylinder injection from the fuel injection valve  2  will be described. In the partial lift injection, an injection process of closing the fuel injection valve  2  before completely opening the valve  2  is performed. 
     When the battery voltage VB is applied to the electronic control device  1 , the microcontroller  4  and the control IC  5  are activated. The boost controller  5   a  of the control IC  5  boosts the output voltage of the booster circuit  3  by outputting a boost control pulse to the booster circuit  3 . The boost voltage Vboost is charged up to a full charge voltage Vfull that exceeds the battery voltage VB. 
     The microcontroller  4  calculates the required injection amount by the energization instruction time calculator  10  at the start of energization of peak current control, i.e., at on-timing t 0  of when outputting the energization instruction, and simultaneously calculates the energization instruction time Ti of the instruction TQ, and outputs the calculation results to the energization controller  5   b  of the control IC  5 . As a result, the microcontroller  4  instructs the control IC  5  with the energization instruction time Ti of the instruction TQ. 
     On the other hand, while acquiring, from the fuel pressure sensor  9  of the fuel injection valve  2 , the fuel pressure information immediately before on-timing t 0  for issuing the energization instruction, the microcontroller  4  refers to the α map  12  to set the correction coefficient α by the conversion coefficient setter  11 . Further, the microcontroller  4  outputs the correction coefficients α and β to the energization time correction amount calculator  5   d  by the conversion coefficient setter  11 . 
     The control IC  5  stores, in an internal memory, the normal current profile PI which is a target current for energizing the fuel injection valve  2 , and, based on the normal current profile PI, performs the peak current control to attempt to achieve the target peak current Ipk by applying the boost voltage Vboost to the fuel injection valve  2   a  under the control of the energization controller  5   b.    
     The control IC  5  continues to apply the boost voltage Vboost between the terminals of the fuel injection valve  2   a  until the target peak current Ipk indicated by the normal current profile PI is reached based on the energization instruction time Ti of the instruction TQ. The energization current EI of the fuel injection valve  2   a  then rises sharply and opens the valve  2 . As shown in  FIG. 4 , the energization current EI of the fuel injection valve  2   a  changes non-linearly based on the structure of the fuel injection valve  2   a.    
     The energization time correction amount calculator  5   d  calculates an integrated current difference ΣΔI between the normal current profile PI and the energization current EI that energizes the fuel injection valve  2 . Since the integrated current difference ΣΔI is an area surrounded by a non-linear current curve, a calculation load tends to be large for detailed calculation. Therefore, as shown in  FIG. 10  and an equation (1), an area size of a trapezoid having (t, I)=(t 1   n , It 1 ), (t 1 , It 1 ), (t 2   n , It 2 ), (t 2 , It 2 ) as vertices may be calculated for approximation of the integrated current difference ΣΔI. In one embodiment, the calculated trapezoid area is associated with and may be approximately proportional to a difference between the integrated current PI minus the integrated current EI.
 
(Equation 1)
 
ΣΔ I ={( t   t   −t   1n )+( t   2   −t   2n )}×( I   2   −I   1 )+2  (1)
 
     The energization time correction amount calculator  5   d  calculates the integrated current difference ΣΔI between (i) the normal current profile PI from an ideal reach time tin reaching a current threshold value It 1  to an ideal reach time t 2   n  reaching a current threshold value It 2 , and (ii) the energization current EI of the fuel injection valve  2  from a reach time t 1  actually reaching the current threshold value It 1  to a reach time t 2  actually reaching a current threshold value It 2 . In such manner, the energization time correction amount calculator  5   d  can easily calculate the integrated current difference ΣΔI by detecting the reach times t 1  and t 2  at which the current threshold values It 1  and It 2  are reached. 
     Further, the energization time correction amount calculator  5   d  calculates a shortage energy Ei (i.e., an amount of energy/electric power insufficiency) by multiplying a correction coefficient α by the integrated current difference ΣΔI as shown in an equation (2). In one embodiment, equation 2 calculates an estimated charge difference between the integrated real/ideal current PI minus the integrated real/measured current EI. 
     In another embodiment, an estimated charge difference is associated with a true energy difference/shortage, and is proportional to the true energy difference/shortage when the boost voltage is approximately constant. In this case, the correction coefficient α in equation (2) below may have units of energy/charge, or of Joules/Coulombs. 
     In another embodiment (not shown), a power (current times voltage) may be measured, and a true energy difference/shortage may be more directly calculated.
 
(Equation 2)
 
 Ei=ΣΔI ×α={( t   1   −t   1n )+( t   2   −t   2n )}×( I   2   −I   1 )+2×α  (2)
 
     As shown in  FIG. 5 , the energization time correction amount calculator  5   d  calculates the current gradient from on-timing t 0  of an injection instruction signal to reach time t 1  at which the electric current reaches the current threshold value It 1 , calculates the correction coefficient β as an intercept, and calculates an estimated peak current value Ipa 1  at the time when the energization instruction time Ti indicated by the instruction TQ has elapsed from t 0 . At such timing, the estimated peak current value Ipa 1  may preferably be calculated based on an equation (3). 
     
       
         
           
             
               
                 
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     The correction coefficient β indicates an offset term for accurately estimating the estimated peak current value Ipa 1  at an application off timing. Further, here, the current gradient from on-timing t 0  of the injection instruction signal to the reach time t 1  at which the energization current reaches the current threshold value It 1  is used as the first term of the equation (3). However, a current gradient from on-timing t 0  of the injection instruction signal to the reach time t 2  at which the energization current reaches the current threshold value It 2  may also be used as the first term of the equation (3). 
     In one embodiment, a slope is calculated based on a measured time (t 1 ) at which a first current threshold value It 1  is reached. Then an intercept is calculated based on a measured time t 2  at which a second current threshold value It 2  is reached, and based upon the calculated slope. Using the intercept and the slope, a peak current Ipa 1  is estimated at tb (at the end of the instruction TQ). This embodiment assumes that the EI profile is substantially linear (with a constant slope) at an early phase (t 0  to t 1 ) and at a late phase (t 2  to tb), and may have a curved portion in a center phase (t 1  to t 2 ). In  FIG. 5 , this curved portion causes an non-zero correction coefficient β as an intercept. 
     Next, the energization time correction amount calculator  5   d  calculates the energization time correction amount ΔTi for compensating for the shortage energy Ei, as illustrated in  FIG. 4 . Specifically, as shown in an equation (4), the energization time correction amount calculator  5   d  calculates the energization time correction amount ΔTi by dividing the calculated shortage energy Ei by the estimated peak current value Ipa 1 . 
     
       
         
           
             
               
                 
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     The denominator and numerator 1/(1024×0.03) in the equation (4) represent a gain for converting the A/D conversion value of the detection current I into a physical quantity. Further, α2=α/2. By deriving the energization time correction amount ΔTi using the equation (4), which depends on the shortage energy Ei and the estimated peak current value Ipa 1  the extension time to compensate for the shortage energy Ei can be easily calculated with dramatically reduced calculation amount. 
     When the energization time correction amount calculator  5   d  outputs the calculated energization time correction amount ΔTi to the energization controller  5   b , the energization controller  5   b  corrects the energization instruction time Ti during a period before a timing of when the detected current I detected by the current monitor  5   c  reaches the estimated peak current value Ipa 1 , by using the energization instruction calculated value of the instruction TQ+the energization time correction amount ΔTi as the effective energization instruction time of the instruction TQ. As a result, the energization instruction time Ti of the instruction TQ can be easily corrected, and the energization time can be extended. By using such a method, it is not necessary to adjust the energization instruction time Ti in anticipation of variation thereof in order to prevent misfire, and misfire countermeasures can be taken without deteriorating fuel consumption as much as possible. 
     The energization time correction amount calculator  5   d  calculates the energization time correction amount ΔTi during a period between the time when the current threshold value It 2  is reached and before the timing tb when the estimated peak current value Ipa 1  is reached (see  FIG. 5 ). Therefore, the energization instruction time Ti can be corrected with a margin (i.e., well in advance/correction of Ti appropriately performable with sufficient calculation time). Although an example of calculating the energization time correction amount ΔTi based on the equations (1) to (4) is shown, these equations show an example only and the correction method is not limited to such method. 
     As described above, the correction coefficient α is recorded in the α map  12  corresponding to all the settable energization times, and the energization time correction amount calculator  5   d  calculates the energization time correction amount ΔTi by constantly/always performing the area correction using the conversion coefficients α and β for each injection regardless of whether or not the drive current of the fuel injection valve  2  reaches the target peak current Ipk. Since the conversion coefficient setter  11  sets the conversion coefficient α each time the area correction is performed, the energization time correction amount calculator  5   d  can set the energization instruction time correction amount ΔTi in which the conversion coefficient α is changed for each injection. 
       FIG. 6  schematically shows an example of a change in the injection amount which is under logic control by the control IC  5  with respect to a change in the energization instruction time Ti that is output as an instruction by the microcontroller  4 . In  FIG. 6 , an ideal injection amount is represented by a broken line, and an actual injection amount is represented by a solid line. 
     As shown in  FIG. 6 , even if a change in the energization time is continuous, the injection amount does not change smoothly and continuously, i.e., the injection amount is rather changing stepwise. The graph in  FIG. 6  shows a stepwise change in the injection amount due to the calculation process of the energization time correction amount ΔTi. That is, whether or not to perform the calculation process of the energization time correction amount ΔTi is changed depending on whether or not the target peak current Ipk is reached for each injection. Therefore, the energization time is corrected by a certain amount, i.e., by the energization time correction amount ΔTi, in one case, and is not corrected in another case, thereby causing a big change in the actual energization time and making a stepwise graph of the injection amount 
     Therefore, in the present embodiment, the conversion coefficient setter  12  sets the conversion coefficient each time the fuel is injected from the fuel injection valve  2 , and the energization time correction amount calculator  5   d  calculates the energization time correction amount ΔTi by performing the area correction using the conversion coefficient α each time the injection is performed regardless of whether or not the drive current of the fuel injection valve  2  has reached the target peak current Ipk. 
     Regardless of whether the energization current of the fuel injection valve  2  reaches the target peak current Ipk, the control IC  5  constantly performs area correction for each injection, so that the microcontroller  4  appropriately sets the correction coefficient α according to the α map  12 , it is possible to eliminate as much as possible a phenomenon that the injection amount steeply/rapidly changes with respect to a minute change in the energization time. As a result, the injection amount can be continuously changed even with a small change in the energization instruction time Ti. In such a control scheme, the A/F value can be controlled to a desired target A/F value. Note that the correction coefficient setter  11  described above sets the correction coefficient α by the α map  12 . However, if the correction coefficient α can be converted into a mathematical formula, the α map  12  may be provided as needed. 
     Second Embodiment 
       FIGS. 7 to 10  show explanatory views of the second embodiment. The microcontroller  4  stores various information such as a program in the internal memory  4   b . Therefore, a constraint condition may be put regarding the storage capacity of the memory  4   b , and the number of recorded items of the correction coefficient α of the α map  12  may be limited. In such a case, it may be preferable to switch α maps  12   a  and  12   b  between a normal region (hereinafter, the normal region) and a region where the injection amount has a step (hereinafter, referred to as the step region). 
     The α map  12   a  as the second map is a map showing the correspondence between (i) the energization instruction time Ti applied to a time region other than the one in which the injection amount has a step and (ii) the conversion coefficient α. The α map  12   b  as the first map is a map showing the correspondence between the energization instruction time Ti applied to the time region where a step is generated in the injection amount and the conversion coefficient α.  FIG. 8  schematically shows the α map  12   a  used in the normal region, and  FIG. 9  schematically shows the α map  12   b  used in the step region. 
     As illustrated in  FIG. 8 , the α map  12   a  used in the normal region records the correction coefficient α corresponding to the energization times T 1 , T 2 , and T 5 . The energizing times T 1  and T 2  are times during which the energization current of the fuel injection valve  2  does not reach the target peak current Ipk, as illustrated in  FIG. 10 . The energization time T 5  is a time during which the energization current of the fuel injection valve  2  always/securely reaches the target peak current Ipk. Although shown in a simplified manner here, the α map  12   a  provides a correction coefficient α corresponding to any normal regions (i.e., exhaustively). 
     The correction coefficients α 11 , α 31 , and α 61  corresponding to the fuel pressures P 1 , P 3 , and P 6  are stored in a time T 1  column of the α map  12   a . The time T 1  column is set so that the correction coefficients α 11 , α 31 , and α 61  increase as the fuel pressures P 1 , P 3 , and P 6  increase. 
     The correction coefficients α 12 , α 32 , and α 62  corresponding to the fuel pressures P 1 , P 3 , and P 6  are stored in a time T 2  column of the α map  12   a . In the column of time T 2 , the correction coefficients α 12 , α 32 , and α 62  are set to increase as the fuel pressures P 1 , P 3 , and P 6  increase. 
     The correction coefficients α 15 , α 35 , and α 65  corresponding to the fuel pressures P 1 , P 3 , and P 6  are stored in a time T 5  column of the α map  12   a . However, the correction coefficients α 15 , α 35 , and α 65  for the time T 5  column are all set to zero for the fuel pressures P 1 , P 3 , and P 6 . 
     In the present embodiment, for example, if the energization time of the fuel injection valve  2  is about time T 5 , the target peak current Ipk always reaches the target peak current Ipk during the partial lift injection, thereby the energization time correction amount ΔTi calculated by the energization time correction amount calculator  5   d  using the correction coefficients α 15 , α 35 , and α 65  is set/configured to result in zero (i.e., the extension of time is set to zero). Here, although a simplified example has been described, the correction coefficient α is recorded in the α map  12   a  corresponding to all the settable energization times. 
     In the α map  12   b  used in the step region, the correction coefficients α corresponding to the energization times T 4   a  to T 4   d  are recorded, for the vicinity of the boundary of whether or not the target peak current Ipk is reached during the partial lift injection. The energizing times T 4   a  to T 4   d  indicate the times when the step region is finely divided as illustrated in  FIG. 10 . That is, in the step region, the injection amount steeply changes even if the energization time changes by a small amount, so the correction coefficient α is recorded in small steps. 
     The correction coefficients α 14   a  to α 54   a , α 14   b  to α 54   b , α 14   c  to α 54   c , and α 14   d  to α 54   d  corresponding to the fuel pressures P 1  and P 3  to P 5  are stored in columns of time T 4   a  to time T 4   d  of the α map  12   b , respectively. In the columns of time T 4   a  to time T 4   d , the correction coefficients α 14   a  to α 54   a , α 14   b  to α 54   b,  α 14   c  to α 54   c , and α 14   d  to α 54   d  are set to increase as the fuel pressures P 1  and P 3  to P 5  increase. 
     In the column of time T 5  of the α map  12   b , the correction coefficients α 15  to α 55  corresponding to the fuel pressures P 1  and P 3  to P 5  are stored. Zeroes are set in the time T 5  column. 
     As illustrated in  FIG. 7 , when the energization instruction time Ti of the instruction TQ is calculated by the energization instruction time calculator  10  at the start of injection, the microcontroller  4  determines, in S 1 , whether or not the energization instruction time Ti is the time in a step region of the injection amount. If the energization instruction time Ti belongs to the step region, the conversion coefficient setter  11  selects the α map  12   b  for the step region in S 2 , sets the correction coefficient α, and outputs the selection/setting result to the energization time correction amount calculator  5   d . Then, the energization time correction amount calculator  5   d  of the control IC  5  calculates the energization time correction amount ΔTi using the set correction coefficient α. 
     On the other hand, as a result of determination in S 1  regarding whether or not the energization instruction time Ti is the time in the step region of the injection amount, if the energization instruction time Ti belongs to the normal region, the conversion coefficient setter  11  selects the α map  12   a  for the normal region in S 4 , sets the correction coefficient α, and outputs the selection/setting result to the energization time correction amount calculator  5   d . Then, the energization time correction amount calculator  5   d  of the control IC  5  calculates the energization time correction amount ΔTi using the set correction coefficient α. Since the operations other than the above are the same as those in the first embodiment, the description thereof is omitted. 
     According to the present embodiment, the conversion coefficient setter  11  switches the α maps  12   a  and  12   b  according to the energization instruction time to set the conversion coefficient α. The matrix (i.e., size) of each of the α maps  12   a  and  12   b  used in the normal region and the step region is reducible, and the storage capacity of the memory  4   b  can thus be reducible. Moreover, the conversion coefficient setter  11  can set the correction coefficient α corresponding to the energization instruction time Ti in a fine-tuned manner by using the α map  12   b  for the step region, and can improve the accuracy of the injection control amount. 
     Other Embodiments 
     The present disclosure should not be limited to the embodiments described above, and various modifications may further be encompassed without departing from the gist of the present disclosure. For example, the following modifications or extensions are possible. The plurality of embodiments described above may be combined as required. 
     In the above-described embodiments, the present disclosure is applied to an in-cylinder injection that injects fuel directly into the combustion chamber of an internal combustion engine. However, the present disclosure is not limited to such form, and is applicable to well-known port injection that injects fuel in front of (i.e., to an upstream of) an intake valve. 
     In the above-described embodiments, the integrated current difference ΣΔI 1  is simply calculated by calculating the area size of the trapezoid, but the present disclosure is not limited to such form. 
     The energization current EI of the fuel injection valve  2   a  changes non-linearly before reaching the peak current Ipk and after reaching the peak current Ipk. Therefore, it may be preferable to calculate the integrated current difference by approximating the integrated current using a polygon such as a triangle, a rectangle, or a trapezoid. Such an approximation can dramatically reduce the amount of calculation. 
     Although the embodiment in which the microcontroller  4  and the control IC  5  are configured/implemented as separate integrated circuits has been described, they may be integrally configured/implemented. In case of having an integrated configuration, it may be preferable to use an arithmetic processor or the like capable of high-speed processing/calculation. 
     The means and/or functions provided by the microcontroller  4  and the control IC  5  can be provided by software recorded in a substantive memory device and a computer that executes the software, or by software, or by hardware, or by a combination thereof. For example, when a control device is provided by an electronic circuit that is hardware, it can be configured by a digital circuit or an analog circuit including one or more logic circuits. Further, for example, when the control device executes various controls by software, a program is stored in a storage unit, and a control entity executing the program implements a method corresponding to the program. 
     Embodiments described above may be combined to implement the control of the present disclosure. In addition, the reference numerals in parentheses described in the claims simply indicate correspondence to the concrete means described in the embodiments, which is an example of the present disclosure. That is, the technical scope of the present disclosure is not necessarily limited thereto. A part of the above-described embodiment may be dispensed/dropped as long as the problem identified in the background is resolvable. In addition, various modifications from the present disclosure in the claims are considered also as an embodiment thereof as long as such modification pertains to the gist of the present disclosure. 
     Although the present disclosure has been described in accordance with the above-described embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure encompasses various modifications and variations within the scope of equivalents. In addition, various modes/combinations, one or more elements added/subtracted thereto/therefrom, may also be considered as the present disclosure and understood as the technical thought thereof.