Abstract:
The purpose of the present invention is to provide a fuel injection valve control device with which. variability in the injection amount with respect to drive pulse width can be kept to a satisfactory level in each of a plurality of fuel injection devices. The present invention provides a fuel injection valve control device for controlling a plurality of fuel injection devices each equipped with a valve body and a solenoid for opening the valve body, characterized in that the device is configured such that, a prescribed time after voltage has been applied to the solenoid, a holding current is applied, the prescribed time and the holding current being corrected for each of the fuel injection devices, on the basis of the operating characteristics of the fuel injection device.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a fuel injection valve control device. 
       BACKGROUND ART 
       [0002]    Generally, a fuel injection valve control device is proposed in which variability in injection amount characteristics for each of the fuel injection devices can be suppressed (refer to, for example, PTL 1). 
         [0003]    According to PTL 1, a characteristic curve of an injection amount characteristic of a fuel injection valve control device is divided into three regions including a partial stroke region, a transition region, and a full stroke region. Then, in PTL 1, although the partial stroke region and the full stroke region are linear, in particular, control accuracy in the transition region is reduced, and variability between various samples of injection valves having the same structure is significantly increased. 
         [0004]    To solve this issue, in the fuel injection valve control device disclosed in PTL 1, it is proposed that the partial stroke region and the full stroke region are used by masking the transition range of the characteristic curve. 
       CITATION LIST 
     Patent Literature 
       [0005]    PTL 1: JP 2012-527564 W 
         [0006]    PTL 2: WO 2013/191267 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    However, in fact, variability is generated also in other regions in addition to the transition region described in PTL 1, and also in a region from the transition region to the full stroke region, variability in injection amount characteristics is generated by such as a bounce when a valve body reaches full stroke. 
         [0008]    As described above, variability which can be caused by a bounce in a region from the transition region to the full stroke region is not considered in PTL 1. Therefore, it is difficult that the fuel injection valve control device disclosed in PTL 1 reduces variability in injection amount characteristics for each of a plurality of fuel injection devices in a wide range. 
         [0009]    The purpose of the present invention is to provide a fuel injection valve control device with which variability in the injection amount with respect to drive pulse width can be kept to a satisfactory level in each of a plurality of fuel injection devices. 
       Solution to Problem 
       [0010]    In the present invention, a fuel injection valve control device controls a plurality of fuel injection devices, each including a valve body, and a solenoid to open the valve body. The fuel injection valve control device applies a boosting voltage to the solenoid to stop the solenoid and, after a prescribed time, applies a holding current. The prescribed time and the holding current are corrected for each of the fuel injection devices, on the basis of operating characteristics of the fuel injection device. 
       Advantageous Effects of Invention 
       [0011]    According to the present invention, variability in an injection amount with respect to a drive pulse width can be kept to a wide level in each of a plurality of fuel injection devices. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a view illustrating an internal combustion engine in which a fuel injection device provided. 
           [0013]      FIG. 2  is a view illustrating a fuel injection device. 
           [0014]      FIG. 3  is a diagram indicating a fuel injection valve control device according to a first embodiment. 
           [0015]      FIG. 4  indicates a control time chart of a fuel injection device by a fuel injection valve control device and indicates injection amount characteristics of the fuel injection device. 
           [0016]      FIG. 5  indicates a time chart to correct a boosting voltage application time and indicates injection amount characteristics of a fuel injection device. 
           [0017]      FIG. 6  indicates a time chart to correct a boosting voltage application time and a gap time and indicates injection amount characteristics of a fuel injection device. 
           [0018]      FIG. 7  indicates a time chart to correct a boosting voltage application time, a gap time, and a holding current and indicates injection amount characteristics of a fuel injection device according to a first embodiment. 
           [0019]      FIG. 8  indicates a fuel injection valve control device according to a second embodiment. 
           [0020]      FIG. 9  indicates a control time chart by a fuel injection valve control device and indicates injection amount characteristics of a fuel injection device. 
           [0021]      FIG. 10  indicates a time chart to correct a gap time and indicates injection amount characteristics of a fuel injection device. 
           [0022]      FIG. 11  indicates a time chart to correct a gap time and a holding current according to a third embodiment and indicates injection amount characteristics of a fuel injection device. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0023]    A fuel injection valve control device according to an embodiment of the present invention will be described below with reference to the drawings. 
       First Embodiment 
       [0024]      FIG. 1  illustrates an internal combustion engine including a fuel injection device controlled by a fuel injection valve control device according to a first embodiment. 
         [0025]    The internal combustion engine takes air and fuel in a cylinder  106 , explodes the mixture by igniting by an ignition plug  121 , and reciprocates a piston  122 . This reciprocating motion is converted into a rotary motion of a crank shaft in a link mechanism including such as a connecting rod  123  and becomes a driving force to move a vehicle. 
         [0026]    Air is filtered by an air cleaner  101 , and a flow rate is adjusted by a throttle  103 . Then, the air flows into the cylinder  106  through a collector  104  and an intake port  105 . An air flow sensor  102  is provided between the air cleaner  101  and the throttle  103  and measures the amount of air taken into the internal combustion engine. 
         [0027]    On the other hand, fuel in a fuel tank  111  is sent to a low pressure pipe  113  by a low pressure pump  112 , fuel in the low pressure pipe  113  is sent to a high pressure pipe  115  by a high pressure pump  114 , and fuel in the high pressure pipe  115  is kept at a high pressure. The high pressure pipe  115  includes a fuel injection device  116 , and a valve body opens when current flows to a solenoid in the fuel injection device  116 . While the valve body is opened, fuel is injected. 
         [0028]      FIG. 2  illustrates a structure of a fuel injection device. A member forming an outer side of the fuel injection device is a housing  201 . A core  202  is fixed to the housing  201 , and also a solenoid  203  is disposed so as to surround a central axis of the fuel injection device. The fuel injection device includes a vertically movable valve body  204 . An anchor  205  is disposed so as to surround a periphery of the valve body  204 . A set spring  207  to press the valve body  204  toward a valve seat  206  is disposed in an upper portion of the valve body  204 . A spring adjuster  208  is fixed to the housing  201  in the upper portion of the set spring  207 , and a spring force is adjusted according to a vertical position of the spring adjuster  208 . During operation, the inside of the housing  201  is filled with fuel. When current flows in the solenoid  203 , the anchor  205  is attracted to the solenoid  203 , a lower end of the valve body  204  is separated from the valve seat  206 . Then, fuel is injected from a nozzle hole  209  provided on the valve seat  206  which has been closed by the valve body  204 . Further, a zero spring  210  is provided between the anchor  205  and the housing  201 , and after fuel injection, the anchor  205  is returned to an initial position by a spring balance. 
         [0029]    The fuel injection device having the above-described configuration is controlled by a fuel injection valve control device illustrated in  FIG. 3 . The fuel injection valve control device drives the solenoid  203  by using electric power sent from a battery  311 . The fuel injection valve control device includes a boosting circuit  310 , a capacitor  309 , switches  301 ,  302 , and  303 , a shunt resistor  304 , and diodes  308  and  305 . The boosting circuit  310  boosts a voltage of a battery  311 . The capacitor  309  stores the boosted voltage. The switch  301  turns on and off between a boosted voltage Vboost and a VH terminal  350  of a solenoid. The switch  302  turns on and off between a battery voltage Vbat and the VH terminal  350  of the solenoid. The switch  303  turns on and off between a VL terminal  351  of the solenoid and a grounding voltage GND. The shunt resistor  304  is disposed between the switch and the GND and generates a voltage proportional to current. The diode  308  flows current from the VL terminal toward between the capacitor  309  and the boosting circuit  310 . The diode  305  flows current from the GND to the VH terminal. A zener diode (not illustrated) is disposed between the VL terminal  351  and the diode  308 , and circulation easily occurs to the capacitor  309  by increasing voltage of a circulating current. 
         [0030]    The boosting circuit  310  increases the battery voltage Vbat, which is generally 12 to 14 V, to the boosting voltage Vboost. The boosting voltage Vboost is, for example, 65 V. The boosting voltage Vboost is set to a higher voltage than the battery voltage Vbat since the valve body  204  overcomes a pressing force by the set spring  207  and rapidly opens. Further, the battery voltage Vbat may be lower than the boosting voltage Vboost as long as the battery voltage Vbat maintains a valve opening state. 
         [0031]    Further, the fuel injection valve control device includes reference memories  321 ,  322 , and  323  and a switch control unit  312 . The reference memories  321 ,  322 , and  323  store a parameter to control solenoid drive current. The switch control unit  312  turns on and off the three switches based on current measured by a resistor. The reference memory  321  stores a time Tp to apply the boosting voltage Vboost. The reference memory  322  stores a gap time T 2  from stopping the boosting voltage Vboost to applying a battery voltage. The reference memory  323  stores a holding current Ih which flows by switching the battery voltage. 
         [0032]    Next, the outline of control of a fuel injection device using a fuel injection valve control device will be described with reference to  FIG. 4 . The lower diagram of  FIG. 4  indicates injection amount characteristics of the fuel injection device by a relation between a drive pulse width Ti and a flow rate. 
         [0033]    When the drive pulse Ti is sent to a fuel injection valve control device  3  from an ECU (not illustrated), the switch control unit  312  turns on the switches  303  and  301  by synchronizing the rising (Time t 1 ). Then, the voltage Vboost boosted by the boosting circuit  310  is applied between terminals of the solenoid  203 , and current gradually starts to flow in the solenoid  203 . The current gradually increases, and also a magnetic field generated by the solenoid  203  increases. 
         [0034]    As a magnetic attraction force attracting the anchor  205  illustrated in  FIG. 2  to the core  202  by the magnetic field increases, the anchor  205  starts to move toward the core  202  (Time t 2 ). A slight gap is formed from an initial position of the anchor  205  balanced by a force of the zero spring  210  to a projection of the valve body  204 . When the anchor  205  moves in the gap and collides with the projection of the valve body  204 , the valve body  204  starts to be lifted by the anchor  205 . At this time, fuel starts to flow out from the nozzle hole  209  (Time t 3 ). 
         [0035]    When the boosting voltage application time Tp to apply the boosting voltage Vboost elapses (Time t 4 ), the switches  303  and  301  are turned off. The voltage application time Tp is generally set shorter than the time until when the anchor  205  arrives at the core  202 . This is not to unnecessarily increase the power generated when the anchor  205  collides with the core  202 . 
         [0036]    When the switches  303  and  301  are turned off at the time t 4 , the current flowing into the GND through the switch  303  flows into the capacitor  309  through the diode  308 , and a voltage VL of the LOW-side terminal  351  of the solenoid  203  becomes higher than the voltage VH of the HI-side terminal  350 . As a result, a reverse voltage is applied to the solenoid  203 . By applying a reverse voltage in this manner, the anchor  205  receives a repulsive force from the core  202 . Therefore, the valve body  204  can brake further quickly. This state is maintained until a time t 5  after lapse of the gap time T 2  from the time t 4 . However, a reverse voltage is not necessarily applied. Voltage may come to zero by keeping the switch  301  in an OFF state and the switch  303  in an ON state. In addition, a reverse voltage is not necessarily applied in the entire range of the times t 4  to t 5 . For example, a reverse voltage is applied at the time t 4  once, and the voltage may be zero after that until the time t 5 . 
         [0037]    At the time t 5 , the switches  302  and  303  are turned on, and the holding current Ih is flowed by applying the battery voltage Vbat to the solenoid  203 . As a result, the valve body  204  and the anchor  205  are continuously in contact with the core  202 . At this time, such that a value of the holding current Ih becomes a constant current value on an average, current flowing into the solenoid  203  is calculated from voltage generated to the shunt resistor  304 , and the switch  302  is turned on and off. 
         [0038]    The switches  302  and  303  are turned off by synchronizing with falling of a drive pulse (Time t 6 ). Then, the current is rapidly damped, and a magnetic attraction force is damped. Consequently, the valve body  204  and the anchor  205  are pressed by a force of the set spring  207  and moved toward the valve seat  206 . At this time, while the current is damped, the current flows into the capacitor  309 . Therefore, a reverse voltage is applied to the solenoid  203 , and when the current is converted to zero, the voltage comes close to zero. Consequently, the valve body  204  reaches to the valve seat  206 , and outflow of fuel from a nozzle hole stops (Time t 7 ). 
         [0039]    The valve body  204  and the valve seat  206  have slight elasticity. Therefore, the valve body  204  continuously moves toward the valve seat  206  even after the valve body  204  reaches the valve seat  206 , and then the valve body  204  and the valve seat  206  start to restore. At this time, the anchor  205  separates from the valve body  204  and continuously moves toward the valve seat  206  by inertia (Time t 8 ). Until the time t 8 , the set spring  207  force and a fuel pressure are applied to the anchor  205  through the valve body  204 . After the time t 8 , the anchor  205  and the valve body  204  are separated, and these forces are not applied to the anchor  205 . Therefore, acceleration of the anchor  205  rapidly decreases. When the acceleration of the anchor  205  changes, a counter-electromotive force generated to the solenoid  203  is changed by a motion of the anchor  205 , and a voltage of the solenoid  203  has an inflexion point. After the anchor  205  separates from the valve body  204 , the anchor  205  continuously moves toward the valve seat  206  by inertia. However, the zero spring  210  is gradually compressed and then starts to extend. Then, the anchor  205  starts to move toward the core  202 , the zero spring  210  extends, and the anchor  205  is returned to an initial position. 
         [0040]    With this mechanism, a fuel injection device is controlled and injects fuel of the amount corresponding to the provided drive pulse width Ti. Desirably, air and fuel are taken into an internal combustion engine at a constant ratio to efficiently utilize an exhaust catalyst. Therefore, the drive pulse width Ti is set to a value proportional to a value Qa/Neng/λ obtained by dividing, by a target air fuel ratio λ, a value Qa/Neng obtained by dividing an air quantity Qa measured by an air flow sensor by an engine speed Neng. 
         [0041]    By the way, a plurality of fuel injection devices included in one engine has variability in an individual device and has different operating characteristics. Therefore, even if the same drive pulse width Ti is applied to the devices, the amounts of fuel injected from the fuel injection devices disposed to each cylinder are varied. Consequently, fuel with a high air fuel ratio is injected from some cylinders, and fuel with a low air fuel ratio is injected from the other cylinders. It is considered that such variability is caused by various factors including tolerance of parts, a change in the environment where each of the fuel injection devices is disposed, and a difference in elasticity of set springs, and the major factor therein is that a valve behavior is varied by the difference in elasticity of the set springs. 
         [0042]      FIG. 4  indicates examples of three fuel injection devices INJ A, B, and C which have different injection amount characteristics. Elastic forces of the set springs  207  of the fuel injection devices A, B, and C are strong, normal, and weak, respectively. In the case where the same boosting voltage and holding current are applied to these three fuel injection valves A, B, and C without considering the variability in particular, valve lifts and injection amount characteristics of the fuel injection devices INJ A, B, and C are indicated in  FIG. 4  by solid lines, long dashed lines, and short dashed lines. 
         [0043]    When a boosting voltage is applied, a valve body is rapidly lifted by a strong cinematic force. Therefore, the difference in elasticity of set springs is not significantly affected to a lift amount of the valve body. On the other hand, after the boosting voltage is applied, the magnetic force lifting the valve body is not much strong in comparison with during applying the boosting voltage. Therefore, the difference in elasticity of set springs remarkably affects the lift amount of the valve body. 
         [0044]    Next, in particular, the time t 4  and thereafter which is one of the scenes in which the variability is generated will be described. At this time, the magnetic attraction force Fmag generated by the solenoid  203  is gradually reduced. When the Fmag is smaller than a total of a force Fsp of the set spring  207  and a fuel pressure Fpf acting toward the valve seat  206 , a valve is changed from rising to falling. This timing depends on the magnitude of the set spring force Fsp and the fuel pressure Fpf. If the set spring force Fsp is large, the valve is rapidly changed from rising to falling (t 10 A), and if the Fsp is small, the valve is slowly changed from rising to falling (t 10 C). By stopping drive current, the valve changed from rising to falling is continued to fall until the current is applied again in time t 5 . 
         [0045]    After T 2 , in other words, at the time t 5 , the holding current Ih is made to flow. Consequently, a magnetic attraction force exceeds a set spring force Fsp+Fpf again at certain times t 12  A, B, and C. This timing becomes slow when the set spring force Fsp of each of the fuel injection devices A, B, and C is large (Time t 12 A), and the timing becomes fast when the set spring force Fsp is small (Time t 12 C). The valve body  204  rises again at each of the times t 12  A, B, and C. 
         [0046]    In addition, a rising speed of a valve increases as a magnetic attraction force by the Ih overcomes the Fsp+Fpf. Therefore, if the Ih is same, the rising speed becomes fast as the set spring force Fsp decreases, and the rising speed becomes slow as the set spring force Fsp increases. 
         [0047]    Next, injection amount characteristics of each of the fuel injection devices INJ A, B, and C will be described with reference to the bottom diagram of  FIG. 4 . 
         [0048]    Here, a graph of an injection amount characteristic of a fuel injection device will be described. A horizontal axis indicates a drive pulse width of the injection amount characteristic of the fuel injection device, and a longitudinal axis indicates an injection amount. The drive pulse width corresponds to a drive pulse application time. This injection amount indicates an integral flow rate of all of the period from valve opening to valve closing in the case where the drive pulse is applied over a certain time. Therefore, for example, if a drive pulse is applied over a time period Ty which is from a time tx to a time ty, the injection amount includes a rate of flow flowing until a valve is actually closed after application of the drive pulse is finished at the time ty in addition to a total rate of flow flowing from valve closing to the time ty. Therefore, lift amounts of valve bodies are not significantly varied during the boosting voltage application period Tp. However, injection amounts are varied in reflection of the lift amounts of the valve bodies during the gap time T 2  after the application period Tp. Further, during the gap time T 2 , all of the switches  301  to  303  are turned off even if application of a drive pulse is finished. Therefore, the injection amount is not affected, and a horizontal part appears. 
         [0049]    When a lift amount of the valve body  204  is large after the elapse of the voltage application time Tp, the horizontal part of an injection amount characteristic becomes high, and when a slope of the increase of a valve lift from the time t 5  to t 13  is steep, a slope of the injection amount characteristic until the valve body is fully lifted (time t 13  A, B, and C) becomes steep. As described above, it is confirmed that even if the same boosting voltage and holding current are applied, injection amount characteristics of fuel injection devices A, B, and C are significantly varied. 
         [0050]    Next, a method for matching the injection amount characteristics by the fuel injection valve control devices according to the embodiment will be described. Specifically, in the fuel injection valve control device, the boosting voltage application time Tp, the gap time T 2 , and the holding current Ih are corrected. The voltage application time Tp, the gap time T 2 , the holding current Ih are set according to the set spring force Fsp. In the case where the set spring force Fsp is determined, the set spring force Fsp is input to the fuel injection valve control device in advance. 
         [0051]    &lt;Correction of Voltage Application Time Tp&gt; 
         [0052]    A fuel injection valve control device according to the embodiment includes a voltage application time correction unit  341  as indicated in  FIG. 3 . Effects of correction by the voltage application time correction unit  341  will be described based on.  FIG. 5 .  FIG. 5  describes the case where the voltage application time Tp is changed for each of the fuel injection devices A, B, and C. As indicated in the upper diagram of  FIG. 5 , the boosting voltage application time correction unit  341  corrects the voltage application time Tp to a voltage application time TpC which is shorter than a standard in a fuel injection valve C in which the set spring force Fsp is small. Further, a voltage application time with respect to the fuel injection device A in which the spring force Fsp is large is corrected to a voltage application time TpA which is larger than the standard. Peak times of a valve lift are matched as indicated in the central diagram of  FIG. 5  by the voltage application time correction unit  341 . Further, injection amount characteristics with respect to the drive pulse width Ti are as indicated in the bottom diagram of  FIG. 5 , and horizontal parts of the injection amount characteristics are matched. 
       &lt;Correction of Gap Time T 2 &gt; 
       [0053]    As illustrated in  FIG. 3 , the fuel injection valve control device according to the embodiment includes a gap time correction unit  342  which corrects the gap time T 2  from stopping the voltage Vboost to applying a next battery voltage. Effects of the correction by the gap time correction unit  342  will be described with reference to  FIG. 6 .  FIG. 6  describes the case where the gap time T 2  is further changed for each of the fuel injection devices A, B, and C in a state in which the voltage application time Tp is already corrected by the above-describe voltage application time correction unit  341 . 
         [0054]    As indicated in the upper diagram of  FIG. 6 , the fuel injection valve control device retards the holding current application time t 5  to the time t 5 C with respect to the fuel injection valve C in which the set spring force Fsp is weak (specifically, the gap time T 2  from the boosting voltage application end time t 4  to the holding current application time t 5  is denoted by T 2 C) As a result, the fuel injection valve control device retards rising of a magnetic attraction force and a timing when the valve rift starts to rise again. 
         [0055]    Further, the fuel injection valve control device, also as indicated in the upper diagram of  FIG. 6 , advances the holding current application time t 5  to the time t 5 A with respect to the fuel injection valve A with the strong set spring force Fsp (specifically, the gap time T 2  is denoted by T 2 A). As a result, the fuel injection valve control device advances rising of a magnetic attraction force and advances a timing when the valve body  204  starts to rise again. 
         [0056]    By the gap time correction unit  342 , the timings when all of the valve bodies  204  of the fuel injection devices A, B, and C start to rise again are matched as indicated in the central diagram of  FIG. 6 . Further, injection amount characteristics with respect to the drive pulse width Ti are as indicated in the bottom diagram of  FIG. 6 , and the injection amount characteristics from a horizontal part to a range in which a flow rate increases are matched. 
       &lt;Correction of Holding Current Ih&gt; 
       [0057]    The fuel injection valve control device according to the embodiment includes a holding current correction unit  343  which corrects the holding current Ih as indicated in  FIG. 3 . Effects of the correction by the holding current correction unit  343  will be described with reference to  FIG. 7 .  FIG. 7  describes the case where the holding current Ih is further changed for each of the fuel injection devices A, B, and C in a state which the boosting voltage application time Tp and the gap time  12  are already corrected by the voltage application time correction unit  341  and the gap time correction unit  342 . 
         [0058]    As indicated in the upper diagram of  FIG. 7 , the fuel injection valve control device corrects the holding current Ih of the fuel injection valve A in which the set spring force Fsp is large to a large holding current value IhA and corrects the holding current Ih of the fuel injection valve C in which the set spring force is small to a small holding current value IhC. Accordingly, as indicated in the middle diagram of  FIG. 7 , rising speeds (specifically, slope) of the valve bodies  204  from the time when the valve bodies  204  start to rise until the valve bodies are fully lifted are matched. Further, injection amount characteristics with respect to the drive pulse width Ti are as indicated in the bottom diagram of  FIG. 7 , and shapes of the characteristics are matched. Furthermore, the shapes of the injection amount characteristics are almost straight lines, and slopes of the straight lines can be recognized to match. 
         [0059]    As described above, in the fuel injection valve control device, valve behaviors are matched by correcting the voltage application time Tp, the gap time  12 , the holding current Ih, and as a result, injection amount characteristics can be matched. In the case of comparing  FIGS. 4 and 7 , the heights of peaks of the valve behaviors, and timings of temporary falling, and slopes in the case where the values are lifted again after falling temporarily are matched. 
         [0060]    According to the fuel injection valve control device according to the embodiment, as indicated in the bottom diagram of  FIG. 7 , a range available for a fuel injection device can be expanded to the lower limit Qmin line of the injection amount characteristics. 
       Second Embodiment 
       [0061]    When the fuel injection valve control device according to the first embodiment corrects the voltage application time Tp, the gap time  12 , the holding current Ih, a set spring force is previously input. A fuel injection valve control device according to a second embodiment corrects them based on a valve behavior in the case where a fuel injection device is actually operated. 
         [0062]    As indicated in  FIG. 8 , the fuel injection valve control device according to the second embodiment includes a drive voltage second order differential unit  331 , a current second order differential unit  332 , and peak detection units  333  and  334 . The drive voltage second order differential unit  331  and the current second order differential unit  332  second-order differentiate drive voltage and current of a solenoid  203 , respectively. The peak detection units  333  and  334  search a timing and a value for taking extreme values of second-order differential values of the current and the voltage. 
         [0063]    In the case where the fuel injection device is driven at the current indicated in the upper diagram of  FIG. 9  and the drive voltage indicated in the middle diagram of  FIG. 9 , a valve behavior of the fuel injection device is as indicated in the bottom diagram of  FIG. 9 . Further, a waveform obtained by second-order differentiating the drive current is as indicated by a broken line in the upper diagram of  FIG. 9 , and it is found that a peak of the second-order differential value corresponds to a valve opening completion timing. Further, a waveform obtained by second-order differentiating the drive voltage is as indicated by a broken line in the middle diagram of  FIG. 9 , and it is found that a peak of the second-order differential value corresponds to a valve closing completion timing. 
         [0064]    In an example of  FIG. 9 , the anchor  205  is intentionally collided with the core  202  during valve opening, and therefore, a waveform or a valve lift differs from the waveform in such as  FIG. 4 . This is because a large counter-electromotive force is generated by the intentional collision at a valve closing completion timing, and a second-order differential value can be easily detected. 
         [0065]    In general, in a fuel injection device, valve closing is completed fast, and valve opening is completed slowly, in the case where a set spring force is strong. Therefore, the set spring force can be estimated from a valve closing completion timing or a valve opening completion timing. Therefore, the correction unit may store a spring force in advance in some storage unit and may calculate a correction value from a detection result by detecting a valve closing completion timing and a valve opening completion timing. 
         [0066]    Further, extreme values of the second-order differential values of voltage and current are proportional to a speed of a valve colliding with a valve seat during valve closing and a speed of an anchor colliding with a stopper at a valve opening completion timing. Therefore, when the extreme value of the second-order differential value of voltage is large, a spring force can be estimated to be large, and when the extreme value of the second-order differential of current is large, the spring force can be estimated to be small. 
         [0067]    Therefore, the fuel injection valve control device according to the embodiment corrects the voltage application time Tp, the gap time T 2 , and the holding current Ih based on detection results of the peak detection units  333  and  334 . 
       Third Embodiment 
       [0068]    The fuel injection valve control device according to the above-described embodiment corrects the voltage application time Tp, the gap time T 2 , and the holding current Ih. However, in a third embodiment, a gap time  12  and a holding current Ih are corrected. 
         [0069]    First, in the embodiment, a voltage application time Tp is not corrected. Therefore, flow rates with respect to a drive pulse width Ti are not matched. However, by correcting the gap time  12 , as indicated in  FIG. 10 , timings when valve bodies  204  start to rise again are matched to a time t 12 . As a result, as indicated in the bottom diagram of  FIG. 10 , ranges from a horizontal part of an injection amount characteristic to a timing when a flow rate increases again are matched. Further, by correcting the holding current Ih, as indicated in  FIG. 11 , rising speeds (specifically, slopes) of the valve bodies  204  from the timing when the valve body  204  rises again to the timing when the valve body  204  is fully lifted are matched. In this manner, trends of a flow rate change with respect to the drive pulse width Ti of each fuel injection device can be matched. 
         [0070]    In a part in which an injection amount is larger than the Qmin, flow rate characteristics of the INJ B and C are in parallel with a flow rate characteristic of the INJ A. At this time, when a drive pulse of the INJ C is extended for ΔTc, and a drive pulse of the INJ B is extended for ΔTb, a minimum flow rate can be reduced to the Qmin from a full lift. 
         [0071]    The fuel injection valve control device according to the present invention is not limited to the above-described embodiments, and configurations thereof can be appropriately changed in a range not deviating from the gist of the present invention. 
         [0072]    For example, in the above embodiments, when characteristics of the fuel injection device are determined, a set spring force is used. However, the set spring force is not necessarily used, and the characteristics of the fuel injection device may be determined on the basis of variability in operation times of valve bodies in the case where the same operation is performed. An example of an operation time of a valve body is a valve opening time from open to close. In this case, after a valve body is opened, without being fully lifted, the valve opening time in the case where the valve body is closed from a state of intermediate lift is preferably used. In this manner, in particular, variability caused by an elastic force of a set spring can be detected without considering tolerance of a housing. Further, as the other example of an operation time of a valve body, there is a method using a valve closing time. In this case, after drive voltage or drive current is turned off, a time until a valve body is actually seated is detected. This is because an elastic force of a set spring is most affected when a valve body is closed, and therefore it is suitable to detect a valve closing time to detect variability in the elastic force of a set spring. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           101  air cleaner 
           102  airflow sensor 
           103  throttle 
           104  collector 
           105  intake port 
           106  cylinder 
           111  fuel tank 
           112  low pressure pump 
           113  low pressure pipe 
           114  high pressure pump 
           115  high pressure pipe 
           116  fuel injection device 
           121  ignition plug 
           122  piston 
           123  connecting rod 
           201  housing 
           202  core 
           203  solenoid 
           204  valve body 
           205  anchor 
           206  valve seat 
           207  set spring 
           208  spring adjuster 
           209  nozzle hole 
           301  switch 
           302  switch 
           303  switch 
           304  shunt resistor 
           305  diode 
           306  diode 
           307  diode 
           308  diode 
           309  capacitor 
           310  boosting circuit 
           311  battery 
           312  switch control unit 
           321  reference memory 
           322  reference memory 
           323  reference memory 
           341  correction unit 
           342  correction unit 
           343  correction unit 
           331  differential unit 
           332  differential unit 
           333  peak search unit 
           334  peak search unit