JP2013142347A - Injector drive control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injector drive control device capable of suppressing a large reduction of a boost voltage even when an energy necessary for a valve-opening operation of an injector increases, and capable of maintaining an appropriate boost voltage for passing a valve-opening current.SOLUTION: When a control device controls a boost circuit part 30 to boost a voltage while a valve-opening current is applied from a charge capacitor 33 to a direct injection injector 50, the device increases a charge amount per unit time when charging the charge capacitor 33 with an increase of fuel pressure. Thereby, when a valve opening current is supplied from the charge capacitor 33, a charge amount corresponding to the amount of the valve opening current is supplied to the charge capacitor 33.

Description

  The present invention relates to an injector drive control device for driving an injector (direct injection injector) that directly injects fuel into a cylinder of an internal combustion engine.

  In an internal combustion engine using gasoline or light oil as a fuel, it is known to use a so-called direct injection injector that directly injects fuel into a cylinder of the internal combustion engine for the purpose of improving the combustion efficiency of the fuel. Yes.

  The injection of fuel into the cylinder by the direct injection injector is executed in the compression process of the internal combustion engine during stratified combustion. At this time, in order to inject fuel with an appropriate fuel particle size and injection shape into the cylinder that has become high pressure by the compression process, it is necessary to increase the pressure of the fuel injected from the direct injection injector to a corresponding pressure. Therefore, a fuel supply system including a direct injection injector is provided with a fuel pump that can increase the fuel pressure to a required pressure, a relief valve that defines an upper limit value of the fuel pressure, and the like.

  On the other hand, with the increase in fuel pressure, the direct injection injector must overcome the high fuel pressure to perform the valve opening operation, and the valve opening operation requires a large amount of energy. Therefore, as described in Patent Document 1, for example, a drive control device that drives a direct injection injector is provided with a booster circuit that boosts a voltage from an in-vehicle battery, and the boosted voltage generated by the booster circuit is used. The energization current to the direct injection injector can be increased to a current value necessary for the valve opening operation.

  In the booster circuit in Patent Document 1, when the boosted voltage charged in the booster capacitor falls below the boost stop voltage due to energization to the direct injection injector, the boost control is started. End control. And in the first half and the second half of the boost control, the magnitude of the energization current from the in-vehicle battery to the boost coil is changed, or the cycle for switching between energization and de-energization from the in-vehicle battery to the boost coil is changed. Yes.

JP 2010-229877 A

  The fuel pump described above generally uses an internal combustion engine as a drive source in order to discharge high-pressure fuel. The fuel pump is provided with an electromagnetic valve for adjusting the discharge amount of the pump, and the fuel pressure discharged from the fuel pump is controlled to the target fuel pressure by using the electromagnetic valve. This target fuel pressure may be changed according to the operating state or operating load of the internal combustion engine.

  When the target fuel pressure of the fuel pump is changed, the fuel pressure actually discharged from the fuel pump also changes so as to follow the target fuel pressure. Then, since the fuel pressure introduced into the direct injection injector also changes, the energy required for causing the direct injection injector to perform the valve opening operation also changes.

  However, in the conventional device, the boosting operation is simply started when the booster circuit detects that the boosted voltage has fallen below the predetermined boosting start voltage value. When it is detected that the voltage value has been reached, the boosting operation is only stopped. That is, in the conventional device, the content of the boosting operation is not changed according to the required energy change. For this reason, when the energy required for the valve opening operation is large, the boosted voltage is greatly reduced, and it takes a relatively long time to restore the boosted voltage to a level at which the valve opening current can be supplied. In addition, for example, when an abnormality occurs in the fuel pump and the fuel pressure reaches the upper limit defined by the relief valve, there is a possibility that the boosted voltage is insufficient to pass the valve opening current. .

  The present invention has been made in view of the above-described points. Even when the energy required for causing the injector to perform the valve opening operation is increased, it is possible to prevent the boost voltage from being greatly reduced and to be opened. It is an object of the present invention to provide an injector drive control device capable of ensuring an appropriate boosted voltage for energizing a valve current.

In order to achieve the above object, an injector drive control device according to claim 1,
In order to drive an injector that directly injects fuel into a cylinder of an internal combustion engine,
A pressure sensor for detecting the pressure of fuel introduced into the injector for injection into the cylinder of the internal combustion engine;
A boosting circuit that includes a charge capacitor and generates a boosted voltage by charging the charge capacitor using the voltage of the in-vehicle battery;
An energization circuit for injecting fuel from the injector by energizing a valve opening current according to the fuel pressure using the boosted voltage charged in the charge capacitor in order to cause the injector to perform a valve opening operation;
Boost control that increases the amount of charge per unit of time when charging the charge capacitor as the fuel pressure increases when the booster circuit performs boost operation while the valve opening current flows from the charge capacitor to the injector And means.

  The valve opening current for opening the closed injector needs to cause the injector to open against the fuel pressure introduced into the injector, so the boost voltage charged in the charge capacitor It is energized using. At this time, the current value of the valve opening current is adjusted according to the fuel pressure, so that the injector can perform the valve opening operation regardless of the fuel pressure.

  When such a valve opening current is applied to the injector from the charge capacitor, when the booster circuit performs a boost operation, the higher the fuel pressure, the less the charge amount per unit time for charging the charge capacitor. increase. Thus, when a valve opening current is supplied from the charge capacitor, a charge amount corresponding to the magnitude of the valve opening current is charged in the charge capacitor. For this reason, it is possible to suppress a significant decrease in the boost voltage of the charge capacitor. In addition, even when the fuel pressure discharged from the fuel pump reaches the upper limit, the boost voltage charged in the charge capacitor is supplemented to supply a valve opening current that can cause the injector to perform the valve opening operation. Will be able to.

  In order to increase the charge amount per unit time, the configuration described in claim 2 or claim 3 may be employed. That is, according to claim 2, the booster circuit includes a charge coil and a switching element, and magnetic energy stored in the charge coil is periodically turned on and off by the switching element. Is generated as electric energy, and the charge capacitor is charged to generate a boosted voltage. The boost control means changes the energization current value of the charge coil when the switching element is turned off, thereby changing the unit time. Control the amount of charge per hit. Alternatively, the boost control unit may control the charge amount per unit time by changing a period during which the energization to the charge coil is turned off.

  Here, in the booster circuit configured as described above, when the switching element is turned on, current is supplied from the in-vehicle battery to the charge coil, and when the switching element is turned off, the charge coil is charged to the charge capacitor. Current flows. When the valve opening current is not supplied from the charge capacitor to the injector, only the charging current flows through the charge capacitor, so that the magnitude of the charging current can be detected. If the magnitude of the charging current can be detected, the switching element can be switched from OFF to ON when the charging current falls below a predetermined value. By controlling the switching of the switching element as described above, The charge capacitor can be charged efficiently.

  However, during the period in which the valve opening current is passed from the charge capacitor to the injector, the discharge from the charge capacitor (that is, the energization of the valve opening current) and the charging of the charge capacitor (that is, the energization of the charging current) are performed simultaneously. Done. Therefore, the magnitude of the charging current of the charge capacitor cannot be detected during that period. Therefore, in this case, the switching element off period must be managed by time. That is, an off period of the switching element is determined in consideration of variation in time until the charging current sufficiently decreases, and the switching element is switched from off to on when the off period elapses. As a result, the charging current is inevitably lowered, and there is a play period in which the switching element remains off, although the switching element should be switched from off to on, and the charging efficiency deteriorates. Resulting in.

  In that respect, at least such a play period is shortened by adopting the configuration described in claim 2 or claim 3 and increasing the energization current value or shortening the OFF period of the switching element. It becomes possible. Therefore, the charging efficiency to the charge capacitor is improved, and the amount of charge per unit time can be increased.

  According to a fourth aspect of the present invention, the boost control means compares the fuel pressure detected by the pressure sensor with a predetermined threshold value to determine the level of the fuel pressure in at least two stages, and determines it as a high fuel pressure. When this is done, the charge amount per unit time may be increased compared to when it is determined that the fuel pressure is low. That is, the charge charge amount per unit time may be continuously increased according to the fuel pressure. However, as described in claim 4, the range of the fuel pressure is determined in a plurality of stages, and the unit time is determined. The hit charge amount may be set to a size according to the determined range.

  According to a fifth aspect of the present invention, when the fuel pressure rises and the high-pressure abnormality occurs, the internal combustion engine shifts to the retreat travel mode that is an operation state in which the engine speed is limited. It is preferably equal to a threshold value for determining a high pressure abnormality. When an abnormality occurs in the fuel pump and the operating state of the internal combustion engine enters the retreat traveling mode, the engine speed is limited, so the load on the control device for the internal combustion engine, including the injector drive control device, is reduced, and the heat generation The degree of is also suppressed. Therefore, if the thermal environment is relatively good in this way, even if the charge charge amount per unit time to the charge capacitor is increased, a special heat dissipation structure is adopted for the heat generation. This is because there is no need to do so, and the cost does not increase.

  According to a sixth aspect of the present invention, the temperature sensor for detecting the temperature in the injector drive control device is provided, and the step-up control means has a temperature per unit time when the temperature detected by the temperature sensor is equal to or higher than a predetermined threshold temperature. The control for increasing the charge amount may not be performed. In this way, it is possible to more reliably suppress an increase in the temperature inside the apparatus due to the heat generated by the element.

It is a block diagram which shows the structure containing the injector drive control apparatus by embodiment. It is a flowchart which shows the process for changing a pressure | voltage rise control method in an injector drive control apparatus. FIG. 10 is an operation waveform diagram for explaining a boosting operation in a normal boosting control method before change in the present embodiment. It is an operation | movement waveform diagram for demonstrating an example of the pressure | voltage rise control method after a change. It is an operation | movement waveform diagram for demonstrating another example of the pressure | voltage rise control method after a change. It is a graph which shows the fuel pressure range which can make a direct injection injector perform valve opening operation | movement by the pressure | voltage rise control method before and behind a change.

  Hereinafter, an injector drive control device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram showing a configuration including an injector drive control device 10 according to the present embodiment. In FIG. 1, a direct injection injector 50 is attached to the upper part of each cylinder (cylinder) of an internal combustion engine (engine) (not shown) and directly injects fuel into the cylinder.

  Although not shown, the engine has an air flow meter that detects the intake air amount, a throttle opening sensor that detects the opening of the throttle valve, and a crank angle sensor that outputs a pulse signal each time the crankshaft rotates a predetermined crank angle. Various sensors such as an intake pipe pressure sensor for detecting the pressure in the intake pipe, a cooling water temperature sensor for detecting the cooling water temperature, and an air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas are provided.

  The outputs of these various sensors are input to the engine control microcomputer 1. The engine control microcomputer 1 executes various engine control programs stored in a built-in ROM, so that the fuel injection amount of the direct injection injector 50 is determined according to the engine operating state grasped from the various sensor outputs described above. The fuel injection timing, the ignition timing of a spark plug (not shown), and the like are controlled.

  In order to control the fuel injection amount and fuel injection timing of the direct injection injector 50, the engine control microcomputer 1 outputs an injector energization signal to the injector drive control device 10 at an appropriate timing. When the injector drive control device 10 receives the injector energization signal, first, the injector drive control device 10 energizes the valve opening current so that the closed direct injection injector 50 performs the valve opening operation. After the energization of the valve opening current, the injector drive control device 10 further energizes the direct injection injector 50 so that the direct injection injector 50 keeps the valve open state while the injector energization signal is output. To do. Therefore, the fuel injection amount and fuel injection timing of the direct injection injector 50 can be controlled by the period and timing when the injector energization signal is output.

  The engine control microcomputer 1 and the injector drive control device 10 are arranged in a common casing as an engine control device.

  The engine control microcomputer 1 receives a temperature detection signal from a thermistor 2 as a temperature sensor for detecting the temperature in the common casing. Further, a pressure detection signal from a fuel pressure sensor 3 that detects fuel pressure supplied to the direct injection injector 50 is also input to the engine control microcomputer 1 from a high pressure fuel pump 5 that is driven by the engine and discharges high pressure fuel. The As shown in FIG. 1, the fuel pressure sensor 3 is disposed in a fuel supply pipe that guides the high-pressure fuel discharged from the high-pressure fuel pump 5 to the direct injection injector 50.

  Although not shown, the fuel supply pipe from the high-pressure fuel pump 5 to the direct injection injector 50 is opened when an abnormality occurs in the high-pressure fuel pump 5 and the fuel pressure in the fuel supply pipe rises. A relief valve for returning the fuel to the fuel tank is provided. Accordingly, the upper limit value of the pressure of the fuel supplied by the high pressure fuel pump 5 is defined by the relief pressure by the relief valve.

  The injector drive control device 10 mainly charges the charge capacitor 33 using the voltage of the energization circuit unit 20 for controlling the drive current energized to the direct injection injector 50 and the battery (not shown) mounted on the vehicle. And a booster circuit unit 30 for generating a boosted voltage by charging. Note that the control unit in the energization circuit unit 20 and the control unit in the boost circuit unit 30 are integrated by an integrated IC 21.

  The energization circuit unit 20 includes switching elements 24 and 25 for energizing the direct injection injector 50 with a valve opening current for opening the closed direct injection injector 50. These switching elements 24 and 25 are connected in series to the charge capacitor 33 and the direct injection injector 50, and are simultaneously turned on by a valve opening current control signal when the valve opening current should be energized. Then, a valve opening current capable of opening the closed direct injection injector 50 via the switching elements 24 and 25 by the boosted voltage charged in the charge capacitor 33 is supplied to the direct injection injector 50. Energized (valve opening current control). In the direct injection injector 50, a valve body and a solenoid coil for generating a magnetic force for moving the valve body are provided. For this reason, as shown in FIG. 2, the drive current supplied to the direct injection injector 50 gradually increases to the valve opening current value (Ipeak) due to the inductance of the solenoid coil.

  Here, the valve opening current value (Ipeak) required for opening the direct injection injector 50 changes according to the pressure of the fuel introduced into the direct injection injector 50. Therefore, the engine control microcomputer 1 stores the correspondence relationship between the fuel pressure introduced into the direct injection injector 50 and the valve opening current value (Ipeak) as a control map. And the valve opening current value (Ipeak) corresponding to the fuel pressure detected by the fuel pressure sensor 3 is instructed to the control unit of the energization circuit unit 20. The control unit of the energization circuit unit 20 calculates the value of the drive current that is actually energized in the direct injection injector 50 as the valve opening current based on the terminal voltage of the resistor 26. Then, the control unit of the energization circuit unit 20 outputs the valve opening current control signal to the two switching elements until a drive current corresponding to the instructed valve opening current value (Ipeak) is supplied to the direct injection injector 50. 24 and 25. In principle, the switching element 25 connected to the downstream side of the energization path of the direct injection injector 50 is always turned on.

  When the drive current of the direct injection injector 50 reaches the valve opening current value (Ipeak), the control unit of the energizing circuit unit 20 stops outputting the valve opening current control signal to the switching element 24 and ends the valve opening current control. To do. At this time, the direct injection injector 50 is already in a valve-opened state, and a drive current as large as the valve-opening current value (Ipeak) is not necessary only to maintain the valve-opened state. It is.

  After the valve opening current control is completed, the controller of the energization circuit unit 20 holds the drive current energized in the direct injection injector 50 for maintaining the valve open state until the injector energization signal is turned off. The drive current supplied to the direct injection injector 50 is controlled so as to be the current value (Ihold) (holding current control). The holding current value (Ihold) is set to a constant value regardless of the fuel pressure.

  In the holding current control, since a large drive current is not required, the boosted voltage charged in the charge capacitor 33 is not used but is performed using the battery voltage. That is, by outputting a holding current control signal to the switching element 22 connected to the in-vehicle battery based on the value of the driving current energized in the direct injection injector 50, the driving current is maintained at the holding current value (Ihold). To control the conduction state of the switching element 22.

  Thus, in the holding current control, the holding current is supplied to the direct injection injector 50 using the battery voltage. For this reason, as shown in FIG. 2, when the valve opening current control is completed, the decrease of the boost voltage of the charge capacitor 33 is finished, and thereafter, the boost voltage of the charge capacitor 33 increases with the start of the holding current control. start.

  The holding current is applied to the direct injection injector 50 via the diode 23. Needless to say, the switching element 25 is always on even during the holding current control in which the switching element 22 is turned on by the holding current control signal.

  Next, the booster circuit unit 30 will be described. As shown in FIG. 1, the booster circuit unit 30 includes a charge coil 31, a switching element 32, a rectifier diode 34, a charge capacitor 33, and the like. Hereinafter, the boosting operation by the normal boosting control of the boosting circuit unit 30 by these components will be described. In FIG. 2, when the boosted voltage charged in the charge capacitor 33 drops below the boost start voltage value V1, the boost operation is started, and when the boost voltage rises above the boost stop voltage value V2, An example in which the operation is stopped is shown.

  When executing the boosting operation, first, the logic circuit unit 44 as the control unit of the boosting circuit unit 30 turns on the switching element 32. Thereby, a current flows from the in-vehicle battery via the charge coil 31, the switching element 32, and the resistor 37. At this time, the terminal voltage of the resistor 37 is taken into the control unit of the booster circuit unit 30, amplified by the amplifier 42, and then compared with a predetermined threshold value (Vth_coil) by the comparator 43. When it is determined that the terminal voltage of the resistor 37 exceeds the threshold value (Vth_coil) and the current flowing through the resistor 37, that is, the current value of the current flowing through the charge coil 31, has reached a predetermined value (Icoil_A), the logic circuit The unit 44 turns off the switching element 32. Then, the magnetic energy stored in the charge coil 31 is discharged as electric energy by the current that has been applied until the switching element 32 is turned off, and charging of the charge capacitor 33 is started via the rectifier diode 34.

  The conditions for switching the switching element 32 from OFF to ON are different during valve opening current control and during holding current control. During the holding current control, the holding current is supplied to the direct injection injector 50 using the battery voltage as described above. For this reason, since the valve opening current is not supplied from the charge capacitor 33 to the direct injection injector 50, only the charge current from the charge coil 31 flows through the charge capacitor 33. Thus, in the situation where only the charging current flows through the charge capacitor 33, the magnitude of the capacitor charging current (Ico) can be detected from the terminal voltage of the resistor 38 connected in series with the charge capacitor 33.

  Therefore, during the holding current control, the control unit of the booster circuit unit 30 takes in the terminal voltage of the resistor 38 and amplifies it by the amplifier 40, and then compares it with a predetermined threshold value (Vth_co) in the comparator 41. Then, as shown in FIG. 2, when the terminal voltage corresponding to the capacitor charging current (Ico) drops below a predetermined threshold (Vth_co), the charging of the charge capacitor 33 is completed by the charging current from the charging coil 31. The switching element 32 is switched from OFF to ON. As described above, by controlling the switching of the switching element 32 from OFF to ON based on the magnitude of the capacitor charging current (Ico), the charge capacitor 33 can be efficiently charged.

  On the other hand, during the valve opening current control, the valve opening current flows from the charge capacitor 33 to the direct injection injector 50. Therefore, when the boosting operation is performed during the valve opening current control, discharging from the charge capacitor 33 for energizing the valve opening current and charging to the charge capacitor 33 due to energization of the charging current from the charge coil 31 are performed simultaneously. Will be done. For this reason, the magnitude of the charging current (Ico) of the charge capacitor 33 cannot be accurately detected from the terminal voltage of the resistor 38 while the boosting operation is being performed during the valve opening current control.

  Therefore, in the present embodiment, when the boosting operation is performed during the valve opening current control, the period during which the switching element 32 is turned off is managed by time. That is, as shown in FIG. 2, the off-period (T_A) of the switching element 32 is determined in consideration of variations in time until the capacitor charging current (Ico) sufficiently decreases, and the off-period (T_A) has elapsed. At that time, the switching element 32 is switched from OFF to ON. For this reason, the capacitor charging current (Ico) is sufficiently reduced, and there is a play period in which the switching element 32 remains off even though the switching element 32 should be switched from off to on. Therefore, it is inevitable that the charging efficiency is somewhat deteriorated.

  In the booster circuit unit 30, resistors 35 and 36 connected in series are connected in parallel with the charge capacitor 33, and the control unit of the booster circuit unit 30 outputs the voltage divided by the resistors 35 and 36. take in. This divided voltage correlates with the boosted voltage charged in the charge capacitor 33, and is amplified by the amplifier 39 and then input to the logic circuit unit 44. In this way, the logic circuit unit 44 monitors the boosted voltage of the charge capacitor 33. When the boosted voltage falls below the boosting start voltage value V1, the logic circuit unit 44 starts the boosting operation and exceeds the boosting stop voltage value V2. When switching occurs, the switching element 32 is controlled to stop the boosting operation.

  In addition, an off timer 45 is connected to the logic circuit unit 44. The off timer 45 is for counting the off period (T_A) of the switching element 32 when the booster circuit unit 30 performs a boost operation during the valve opening current control.

  As described above, when the boosting operation is performed by the normal boosting control in the boosting circuit unit 30 during the valve opening current control, the charging efficiency is worse than when the boosting operation is performed during the holding current control. There is a tendency.

  On the other hand, as shown in FIG. 2, the boosted voltage of the charge capacitor 33 decreases during the valve opening current control, but coupled with the low charging efficiency of the charge capacitor 33 in the meantime, the degree of decrease in the boosted voltage is further increased. It gets bigger. Further, during the valve opening current control, the valve opening current value (Ipeak) corresponding to the fuel pressure is supplied to the direct injection injector 50 as described above. For this reason, as the fuel pressure increases and the energy required for the valve opening operation increases, the degree of decrease in the boost voltage of the charge capacitor 33 increases.

  If the boosted voltage of the charge capacitor 33 greatly decreases due to such a cause, it takes a relatively long time to recover the decreased boosted voltage to a level at which the valve opening current can be energized. Then, for example, when the engine speed increases, there is a possibility that a sufficient boosted voltage cannot be charged in the charge capacitor 33 by the time when the valve opening current should be supplied to the direct injection injector 50.

  In addition, when an abnormality occurs in the high-pressure fuel pump 5 and the fuel pressure reaches the upper limit value defined by the relief valve, it is necessary to increase the valve opening current value (Ipeak) to the maximum value. When such valve opening current is applied, the boosted voltage of the charge capacitor 33 may be insufficient regardless of the engine speed.

  Therefore, in the present embodiment, the boost control method when the boost operation is performed in the boost circuit unit 30 during the valve opening current control is changed according to the fuel pressure. Specifically, when the fuel pressure is higher than a predetermined pressure, the amount of charge charged per unit time when charging the charge capacitor 33 is increased compared to the case where the fuel pressure is lower than that. Thus, the boost control method was changed. Thereby, when a valve opening current is supplied from the charge capacitor 33 to the direct injection injector 50, the charge capacitor is charged with an amount of charge corresponding to the magnitude of the valve opening current that changes according to the fuel pressure. Therefore, it is possible to suppress the boosted voltage of the charge capacitor 33 from greatly decreasing. In addition, even when the fuel pressure is high, the boosted voltage charged in the charge capacitor 33 is supplemented and a valve opening current that can cause the direct injection injector 50 to perform the valve opening operation is supplied. Can do.

  FIG. 3 is a flowchart showing a process for changing the pressure increase control method. First, in step S100, it is determined whether or not the fuel pressure is equal to or higher than a predetermined pressure (for example, 20 Mpa). If the fuel pressure is equal to or higher than the predetermined pressure, it is necessary to change the pressure increase control method, and the process proceeds to step S110. In step S110, it is determined whether or not the temperature in the control device detected by the thermistor 2 is equal to or lower than a first predetermined temperature (for example, 90 ° C.). In this way, the temperature in the control device is determined by changing the boost control method so as to increase the amount of charge per unit time, in particular, because the load on the boost circuit unit 30 increases. This is to determine whether or not there is a possibility that the element temperature and the ambient temperature will rise to the extent that there is a possibility of adversely affecting the device.

  If it is determined that the temperature in the control device is equal to or lower than the first predetermined temperature, even if the boost control method is changed so as to increase the amount of charge per unit time when charging the charge capacitor 33, It is thought that the temperature will not rise to such an extent that it has an adverse effect. For this reason, the process proceeds to step S120, and the boost control method is changed from the normal boost control to the boost control at high pressure. Note that boost control at high pressure will be described in detail later. On the other hand, if it is determined that the temperature inside the control device is higher than the first predetermined temperature, the boost control method is not changed, and the process returns to step S100.

  In this embodiment, the boost control method is changed only when the thermal environment in the control device is good. For this reason, there is a merit that it is not necessary to cost the heat dissipation design and the heat dissipation structure in the control device.

  If the control device internal temperature is the first predetermined temperature and the boost control method is not changed, the boost voltage is insufficient in normal boost control, and fuel is injected from the direct injection injector 50. There is a possibility that it will not be possible. However, when the fuel cannot be injected, the engine speed decreases. As a result, the pressure of the fuel discharged from the high-pressure fuel pump 5 decreases, or the fuel injection interval from the direct injection injector 50 increases. It becomes. Therefore, fuel can be injected from the direct-injection injector 50 and the engine can be maintained in a rotating state even under normal boost control.

  In subsequent step S130, it is determined whether or not the temperature inside the control device has risen to a second predetermined temperature (for example, 100 ° C.) or more. When the temperature inside the control device rises to the second predetermined temperature or more due to the change in the boost control method, it is considered that there is a possibility of adversely affecting each element, and the process proceeds to step S150 and the boost control method is Return to the original normal boost control. On the other hand, if it is determined in step S130 that the temperature in the control device is lower than the second predetermined temperature, the process proceeds to step S140, and it is determined whether or not the fuel pressure has decreased below the predetermined pressure. If the fuel pressure drops below the predetermined pressure, there is no need to adopt the high pressure control method, so the process proceeds to step S150, and the boost control method is restored.

  Next, boost control at high pressure will be described with reference to FIGS. There are two patterns of boost control at high pressure, and FIG. 4 shows a first pattern of boost control at high pressure. That is, in the example shown in FIG. 4, when the boosting operation is performed during the valve opening current control, the period during which the switching element 32 is turned off is the same as the normal boosting control, and the current flowing through the charge coil 31 is changed to the normal level. It is increased to a current value (Icoil_B) higher than the current value (Icoil_A) during the boost control. As a result, more energy is accumulated in the charge coil 31 during the period when the switching element 32 is on. Therefore, when the switching element 32 is turned off, the maximum value (Ico_B) of the charging current flowing from the charge coil 31 to the charge capacitor 33 becomes larger than the maximum value (Ico_A) of the charging current by the normal boost control.

  In the example shown in FIG. 4, the energizing current value of the charge coil 31 is kept at a high value (Icoil_B) even after the valve opening current control is finished and the control is shifted to the holding current control. You may return to the same value as control. During the holding current control, the charge capacitor 33 is charged based on the capacitor charging current (Ico) so as to improve the efficiency. Therefore, the charge amount per unit time of the charge capacitor 33 does not substantially change regardless of whether the energization current value of the charge coil 31 is Ico_A or Ico_B.

  Further, in the example of the second pattern shown in FIG. 5, when the boosting operation is performed during the valve opening current control, the current flowing through the charge coil 31 is the same as the current value (Icoil_A) during the normal boosting control. However, the period during which the switching element 32 is turned off is set to a period (T_B) that is shorter than the off period (T_A) of normal boost control. As a result, as shown in FIG. 5, the number of times the switching element 32 is turned on and off during the valve opening current control can be increased.

  Here, as described above, in the boosting operation by the normal boosting control during the valve closing current control, there is an idle period in the OFF period of the switching element 32. In any of the patterns of FIGS. 4 and 5, such a play period can be shortened. Therefore, according to any pattern, the charging efficiency to the charge capacitor 33 is improved, and the charge amount per unit time can be increased.

  FIG. 6 shows a range in which the valve opening operation can be performed by the normal pressure increase control with respect to the fuel pressure and the valve opening current value, and a range in which the valve opening operation can be performed by the pressure increase control at the time of high pressure. An example is shown. As shown in FIG. 6, when the fuel pressure is increased or the valve opening current value is increased, the boost voltage required for causing the direct injection injector 50 to perform the valve opening operation in the normal boost control. May not be able to charge the charge capacitor 33.

  In this respect, in this embodiment, when the fuel pressure rises, the control is changed to the boost control at the time of high pressure. Therefore, even in such a situation, the charge capacitor 33 is charged with a boost voltage sufficient to perform the valve opening operation. can do.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. It is.

  For example, in the above-described embodiment, when the pressure of the fuel discharged from the high-pressure fuel pump 5 exceeds a predetermined pressure, the boost control method is changed from normal boost control to boost control at high pressure. Met. However, the switching of the boost control method is not limited to two steps, and may be switched to three or more steps according to the fuel pressure. Furthermore, the boost control content may be changed by continuously changing the value of the current supplied to the charge coil 31 and the OFF period of the switching element 32 in accordance with the fuel pressure.

  In the above-described embodiment, the thermistor (temperature sensor) 2 detects the temperature in the control device and determines whether or not to change the boost control method. However, for example, when the pressure of the fuel discharged from the high-pressure fuel pump 5 becomes a high pressure equal to or higher than a predetermined pressure (which is a reference for determining whether or not to change the boost control method), it is regarded as a high fuel pressure abnormality, and engine control is performed. In the case where the device performs control such that the engine speed is shifted to the retreat travel mode in which the engine speed is limited to a predetermined speed or less, the temperature sensor is not necessarily provided. That is, because the engine speed is limited, the load on the control device including the injector drive control device 10 is reduced, and the degree of heat generation is also suppressed.

  Further, in the above-described embodiment, the boosting operation is started in the booster circuit unit 30 when the boosted voltage of the charge capacitor 33 is lowered to the boosting start voltage V1 or less due to the energization of the valve opening current. However, the boosting operation may be started in synchronization with the start of energization of the valve opening current.

DESCRIPTION OF SYMBOLS 1 Engine control microcomputer 2 Thermistor 3 Fuel pressure sensor 5 High pressure fuel pump 10 Injector drive control apparatus 20 Energization circuit part 30 Boosting circuit part 33 Charge capacitor 50 Direct injection injector

Claims (6)

An injector drive control device for driving an injector that directly injects fuel into a cylinder of an internal combustion engine,
A pressure sensor for detecting the pressure of fuel introduced into the injector for injection into the cylinder of the internal combustion engine;
A boosting circuit that includes a charge capacitor and generates a boosted voltage by charging the charge capacitor using the voltage of the in-vehicle battery;
An energization circuit for injecting fuel from the injector by energizing a valve opening current corresponding to the fuel pressure using a boosted voltage charged in the charge capacitor in order to cause the injector to perform a valve opening operation; When a boosting operation is performed by the booster circuit while a valve opening current is supplied from the capacitor to the injector, the amount of charge per unit time when charging the charge capacitor increases as the fuel pressure increases. An injector drive control device comprising: a step-up control unit that causes The booster circuit includes a charge coil and a switching element, and the switching element periodically turns on and off the energization from the in-vehicle battery to the charge coil, thereby using the magnetic energy accumulated in the charge coil as electric energy. Discharging and charging the boost voltage to the charge capacitor,
2. The injector according to claim 1, wherein the boosting control unit controls a charge amount per unit time by changing an energization current value of the charge coil when the switching element is turned off. Drive control device. The booster circuit includes a charge coil and a switching element, and the switching element periodically turns on and off the energization from the in-vehicle battery to the charge coil, thereby using the magnetic energy accumulated in the charge coil as electric energy. Discharging and charging the boost voltage to the charge capacitor,
2. The injector drive control device according to claim 1, wherein the boosting control unit controls a charge amount per unit time by changing a period during which the energization to the charge coil is turned off.   The boost control means compares the fuel pressure detected by the pressure sensor with a predetermined threshold to determine the level of the fuel pressure in at least two stages. When the fuel pressure is determined to be high, the low fuel pressure 4. The injector drive control device according to claim 1, wherein the charge charge amount per unit time is increased as compared with the case where it is determined that. The internal combustion engine, when the fuel pressure rises and becomes a high pressure abnormality, shifts to a retreat travel mode that is an operation state in which the engine speed is limited,
5. The injector drive control device according to claim 4, wherein the threshold value is equal to a threshold value for determining a high pressure abnormality of the fuel pressure. It has a temperature sensor that detects the temperature in the injector drive control device,
6. The boost control unit according to claim 1, wherein when the temperature detected by the temperature sensor is equal to or higher than a predetermined threshold temperature, the boost control unit does not perform control to increase the charge amount per unit time. The injector drive control device according to any one of the above.

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