JP5979104B2 - Boost power supply - Google Patents

Description

  The present invention relates to a boosting power supply device provided in a control device that drives an injector.

  A control device that drives an injector that injects fuel into an engine of a vehicle has a booster circuit that boosts the battery voltage of the vehicle and charges the capacitor so that the charging voltage of the capacitor becomes a target voltage higher than the battery voltage. Provided. In this type of control device, the valve opening of the injector is accelerated by discharging from the capacitor of the booster circuit to the coil of the injector at the start of driving of the injector (see, for example, Patent Document 1).

  In addition, in an engine mounted on a vehicle, fuel injection by an injector is performed a plurality of times during a single fuel injection period (for example, compression to combustion stroke) of a cylinder in order to achieve highly efficient combustion for the purpose of reducing exhaust gas. There is technology to do. The technique is called, for example, multistage injection, and is sometimes called proximity injection.

  In such a control device that performs multi-stage injection, it is necessary to supply (release) a plurality of times of energy to the coil of the injector in a short time. For this reason, the capacitance of the capacitor of the booster circuit (hereinafter, also simply referred to as “capacitance”) is large so that, for example, a predetermined number of times of fuel injection can be reliably performed within a predetermined time for design even without charging. Set to a value.

JP 2009-22139 A

  In the booster circuit, the larger the capacity of the capacitor, the longer the charging time (hereinafter referred to as the necessary charging time) required for setting the charging voltage of the capacitor to the target voltage. For this reason, if the capacity of the capacitor is always large, the charging voltage of the capacitor is insufficient in some cases.

  For example, the required charging time becomes long even when the battery voltage is low. For this reason, if the capacity of the capacitor is large, for example, when the battery voltage decreases, such as at the start of the engine, the required charging time will be further increased, and as a result, the charging voltage at the start of fuel injection will not be in time for charging. There may be a situation where the target voltage is not reached. If such a condition occurs, the target voltage cannot be applied to the coil of the injector, the injector opening timing is delayed, and the control accuracy of the fuel injection is lowered (specifically, the fuel injection amount is reduced). Will be invited).

  In view of the above, an object of the present invention is to prevent the valve opening delay of the injector from occurring in time for charging the capacitor to the target voltage.

The step-up power supply device according to the first aspect of the present invention is provided in a control device that drives an injector that injects fuel into an engine of a vehicle.
The boosting power supply device includes an output capacitor for storing electrical energy discharged to the valve opening electric load for opening the injector, and an output capacitor for boosting the battery voltage of the vehicle. A charging circuit for charging, and a charging control circuit for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage.

  In particular, in this step-up power supply device, the output capacitor is composed of a plurality of capacitors in parallel, and a capacitor for adjusting the capacitance is connected in series to capacitors other than the specific capacitor among the plurality of capacitors. When the switching means turns on the capacitance adjusting switch, a capacitor in series with the switch is connected in parallel with the specific capacitor, and when the switching means turns off the capacitance adjusting switch, the capacitor in series with the switch is changed. When disabled (in other words, disconnected from the charge / discharge path of the output capacitor), the capacitance of the output capacitor decreases.

  In this step-up power supply device, the switching means turns off the capacitance adjustment switch, thereby reducing the capacitance of the output capacitor and shortening the charging time until the charging voltage of the output capacitor reaches the target voltage. Can do. Therefore, it is possible to prevent a delay in valve opening of the injector due to insufficient charging of the output capacitor to the target voltage.

It is a block diagram showing the fuel-injection control apparatus of 1st Embodiment. It is explanatory drawing explaining operation | movement of a drive control circuit. It is a flowchart showing the 1st determination process of 1st Embodiment. It is a flowchart showing the 2nd determination process of 1st Embodiment. It is a flowchart showing the 3rd determination process of 1st Embodiment. It is a flowchart showing the 4th determination process of 1st Embodiment. It is a flowchart showing the 5th determination process of 1st Embodiment. It is a flowchart showing the capacity | capacitance return process of 1st Embodiment. It is explanatory drawing for demonstrating a subject. It is a flowchart showing the capacity | capacitance return process of 2nd Embodiment.

A fuel injection control device according to an embodiment will be described with reference to the drawings.
The fuel injection control device of this embodiment includes four solenoid injectors that inject and supply fuel to each cylinder # 1 to # 4 of a multi-cylinder (four cylinders in this example) engine mounted on a vehicle (automobile). By driving the energization start timing and energization time to the coil of each injector, the fuel injection timing and the fuel injection amount to each cylinder # 1 to # 4 are controlled. In the present embodiment, the transistor as the switching element is, for example, a MOSFET, but may be another type of transistor such as a bipolar transistor or IGBT (insulated gate bipolar transistor).

[First Embodiment]
As shown in FIG. 1, an electronic control unit (hereinafter referred to as ECU) 31 that is a fuel injection control unit includes a terminal CM to which one end (upstream side) of a coil 41a of an injector 41 that is a drive target is connected, and a coil 41a. Terminal INJ to which the other end (downstream side) is connected, transistor T10 having one output terminal connected to terminal INJ, and current detection connected between the other output terminal of transistor T10 and the ground line Resistor R10.

  In the injector 41, when a coil 41a serving as an electric valve for valve opening is energized, a valve body (so-called nozzle needle) (not shown) moves to the valve opening position (in other words, lifts), and fuel injection is performed. When the energization of the coil 41a is interrupted, the valve body returns to the original valve closing position, and fuel injection is stopped.

  In FIG. 1, only one injector 41 corresponding to the nth cylinder #n (n is any one of 1 to 4) among the four injectors 41 is shown. The driving will be described. Actually, the terminal CM is a common terminal for the injector 41 of each cylinder, and the coil 41a of each injector 41 is connected to the terminal CM. The terminal INJ and the transistor T10 are provided for each injector 41 (in other words, for each cylinder). The transistor T10 is a switching element for selecting the injector 41 to be driven (in other words, the cylinder to be injected), and is called a cylinder selection switch.

  The ECU 31 then includes a transistor T11 as a constant current switching element having one output terminal connected to a power supply line Lp to which a battery voltage (vehicle battery voltage) VB as a power supply voltage is supplied, and the other of the transistors T11. A backflow preventing diode D11 having an anode connected to the output terminal and a cathode connected to the terminal CM, a current return diode D12 having an anode connected to the ground line and a cathode connected to the terminal CM, and a booster A circuit 33.

  The battery voltage VB is supplied to the power supply line Lp when the vehicle user performs a predetermined ignition-on operation. Examples of the ignition-on operation include an operation of moving a key inserted into the ignition key cylinder to an ignition-on position and an operation of pushing a push start button.

The diode D12 causes a current to flow back to the coil 41a when the transistor T11 is turned off from the on state while the transistor T10 is turned on.
The step-up circuit 33 is a step-up DC / DC converter, and serves as an output capacitor 34 in which electrical energy discharged to the coil 41a is stored, and a capacitance adjustment switch for adjusting the capacitance of the output capacitor 34. Transistor T1, a charging circuit 35 that boosts the battery voltage VB to charge the output capacitor 34, and a charging control circuit 36 that operates the charging circuit 35 so that the charging voltage of the output capacitor 34 becomes the target voltage. Prepare.

The charging circuit 35 includes an inductor L0, a boosting transistor T0, a backflow preventing diode D0, and a current detecting resistor R0.
The inductor L0 has one end connected to the power supply line Lp and the other end connected to one output terminal (drain) of the transistor T0. The resistor R0 is connected between the other output terminal (source) of the transistor T0 and the ground line. The anode of the diode D0 is connected to the connection point between the inductor L0 and the transistor T0.

  The output capacitor 34 is composed of a plurality (two in this example) of capacitors C0 and C1 in parallel with each other, and one end (positive electrode side) of the capacitors C0 and C1 is connected to the cathode of the diode D0. The capacitors C0 and C1 are, for example, aluminum electrolytic capacitors, but may be other types of capacitors.

  The other end (negative electrode side) of the capacitor C0 is connected to a connection point between the transistor T0 and the resistor R0. Further, the transistor T1 is connected in series to the other end (negative electrode side) of the capacitor C1, and the output terminal (source) opposite to the capacitor C1 side of the transistor T1 is a connection point between the transistor T0 and the resistor R0. It is connected to the.

  Therefore, the capacitor C1 is connected in parallel with the capacitor C0 when the transistor T1 is turned on. When the transistor T1 is turned off, the capacitor C1 is disconnected from the charge / discharge path and invalidated. Therefore, if the capacitance of the capacitor C0 is “Cap0” and the capacitance of the capacitor C1 is “Cap1”, the capacitance of the output capacitor 34 is “Cap0 + Cap1” when the transistor T1 is turned on. When the transistor T1 is turned off, the capacitance of the output capacitor 34 is reduced to “Cap0”.

  In the booster circuit 33, when the transistor T0 is turned on / off, a flyback voltage (back electromotive voltage) higher than the battery voltage VB is generated at the connection point between the inductor L0 and the transistor T0. The output capacitor 34 (specifically, both or one of C0 and C1) is charged through the diode D0. For this reason, the output capacitor 34 is charged with a voltage higher than the battery voltage VB.

  The charge control circuit 36 operates when the charge permission signal supplied to the circuit 36 is at an active level, and is the voltage on the positive side of the output capacitor 34 (C0, C1) (also the charge voltage of the output capacitor 34). The transistor T0 is turned on / off so that VC (hereinafter referred to as capacitor voltage) becomes a preset target voltage (> VB).

  The charge control circuit 36 monitors the capacitor voltage VC and also monitors the charging current of the output capacitor 34 by the voltage generated in the resistor R0, so that the transistor T0 is charged so that the output capacitor 34 is charged with an efficient cycle. Turn on / off. Then, when the capacitor voltage VC reaches the target voltage, the charging control circuit 36 keeps the transistor T0 off and stops charging the output capacitor 34. For this reason, the output capacitor 34 is charged such that the capacitor voltage VC, which is the charging voltage thereof, becomes the target voltage.

  Further, the ECU 31 uses the transistor T12 as a discharge switching element for connecting the positive electrode side of the output capacitor 34 to the terminal CM, the energy recovery device having the anode connected to the terminal INJ and the cathode connected to the positive electrode side of the capacitor C0. The drive control circuit 37 which controls the electric current sent through the coil 41a by controlling the diode D13 of this, and transistors T10, T11, T12, the microcomputer (microcomputer) 38, and the power supply circuit 39 are provided.

  The power supply circuit 39 is supplied with the battery voltage VB from the power supply line Lp, and generates and outputs a constant power supply voltage Vcc (for example, 5 V) from the supplied battery voltage VB. The microcomputer 38 operates with the power supply voltage Vcc from the power supply voltage 39. The power supply circuit 39 also has a power-on reset function that keeps resetting the microcomputer 38 for a fixed time after the output of the power supply voltage Vcc is started.

  The microcomputer 38 includes a CPU 51 that executes a program, a ROM 52 that stores programs and fixed data, a RAM 53 that stores calculation results by the CPU 51, an A / D converter (ADC) 54, and the like.

  The microcomputer 38 generates an injection command signal for each cylinder based on engine operation information detected by various sensors (not shown) such as the engine speed NE, the accelerator opening ACC, and the engine coolant temperature THW. Output to the drive control circuit 37. The injection command signal has a meaning that the coil 41a of the injector 41 is energized (in other words, the injector 41 is opened) only when the level of the signal is the active level (for example, high in the present embodiment). .

  Further, the microcomputer 38 sets the charge permission signal to the charge control circuit 36 to an active level and sets the capacitor voltage when all the injection command signals for each cylinder are low (that is, when fuel injection is not performed). VC is set to the target voltage.

  The active level of the charge permission signal is, for example, low, and the microcomputer 38 sets the charge permission signal to the active level (low) from the power-on reset described above. In addition to the microcomputer 38, the charge control circuit 36 and the drive control circuit 37 operate using the battery voltage VB from the power supply line Lp as a power supply. For this reason, from the time when the battery voltage VB is supplied to the power supply line Lp and the ECU 31 is activated, the booster circuit 33 charges the output capacitor 34 so that the capacitor voltage VC becomes the target voltage.

Next, the operation of the drive control circuit 37 will be described with reference to FIG.
As shown in FIG. 2, when the injection command signal S # n of the n-th cylinder #n output from the microcomputer 38 becomes high, the drive control circuit 37 is in a state where the injection command signal S # n is high. Then, the transistor T10 corresponding to the injector 41 of the nth cylinder #n is turned on. Further, when the injection command signal S # n becomes high, the drive control circuit 37 also turns on the transistor T12.

  Then, the positive electrode side terminal of the output capacitor 34 is connected to the terminal CM and discharged from the output capacitor 34 to the coil 41a. By this discharge, energization to the coil 41a is started.

  Then, after the transistor T12 is turned on, the drive control circuit 37 detects a current flowing through the coil 41a (which is also a drive current of the injector 41, hereinafter also referred to as a coil current) from a voltage generated in the resistor R10. When it is detected that the target maximum value IthP of the discharge current is reached, the transistor T12 is turned off.

  In this way, at the start of energization of the coil 41a, the electrical energy accumulated in the output capacitor 34 is discharged to the coil 41a, thereby speeding up the valve opening response of the injector 41.

  Then, after turning off the transistor T12, the drive control circuit 37 turns on / off the transistor T11 so that the coil current detected by the voltage generated in the resistor R10 becomes a constant current smaller than the target maximum value IthP. Constant current control is performed.

  More specifically, when the injection command signal S # n is high, the drive control circuit 37 turns on the transistor T11 when detecting that the coil current is lower than the lower threshold value IthL as constant current control. When the coil current is detected to be equal to or higher than the upper threshold value IthH, control is performed to turn off the transistor T11. The relationship between the lower threshold value IthL, the upper threshold value IthH, and the target maximum value IthP is “IthL <IthH <IthP”.

  For this reason, when the coil current decreases from the target maximum value IthP and falls below the lower threshold value IthL, thereafter, the transistor T11 is repeatedly turned on / off, and the average value of the coil current becomes the upper threshold value IthH and the lower threshold value. It is controlled to a current between IthL.

  By such constant current control, after the transistor T12 is turned off, a constant current is supplied from the power supply line Lp to the coil 41a via the transistor T11, and the injector 41 is held open by the constant current. When the transistor T11 is turned from on to off, a current flows back to the coil 41a through the diode D12. Further, as shown in the second stage in FIG. 2, the transistor T11 is turned on for a short time after the injection command signal S # n becomes high because of constant current control.

  Thereafter, when the injection command signal S # n from the microcomputer 38 changes from high to low, the drive control circuit 37 turns off the transistor T10, ends constant current control, and keeps the transistor T11 in the off state. Then, energization of the coil 41a is stopped, the injector 41 is closed, and fuel injection by the injector 41 is completed. The injectors 41 other than the nth cylinder #n are also driven in the same procedure as described above.

  Returning to FIG. 1, the ECU 31 also includes two resistors 57 and 58 that divide the battery voltage VB into a voltage that can be input by the microcomputer 38. A voltage generated at a connection point between the resistors 57 and 58 and divided from the battery voltage VB (hereinafter referred to as a divided voltage) is input to the microcomputer 38. The microcomputer 38 A / D-converts the voltage divided by the resistors 57 and 58 by the A / D converter 54 and detects the battery voltage VB from the A / D conversion value.

  The ECU 31 further includes a thermistor 59 having one end connected to the ground line, and a pull-up resistor 60 having one end connected to the other end of the thermistor 59 and the other end applied with the power supply voltage Vcc.

  The thermistor 59 is a resistor whose resistance value changes according to temperature, and is mounted in the ECU 31 near the output capacitor 34 (for example, a position adjacent to the output capacitor 34). For this reason, the resistance value of the thermistor 59 changes according to the internal temperature of the ECU 31 (hereinafter also referred to as the ECU internal temperature). The ECU internal temperature is also the ambient temperature of the output capacitor 34.

  A voltage generated at the connection point between the thermistor 59 and the resistor 60 (hereinafter referred to as a temperature monitor voltage) changes according to the ECU internal temperature, and the temperature monitor voltage is input to the microcomputer 38. The microcomputer 38 A / D converts the temperature monitor voltage by the A / D converter 54 and detects the ECU internal temperature from the A / D conversion value. For example, the microcomputer 38 converts the A / D conversion value of the temperature monitor voltage into the ECU internal temperature using a data map or a calculation formula prepared in advance in the ROM 52.

  In addition, the microcomputer 38 receives a starter signal STA that becomes an active level (for example, high) when a starter that cranks the engine for starting is operating. The microcomputer 38 determines whether or not the starter is operating based on the starter signal STA.

Next, specific contents in the ECU 31 will be described.
In this embodiment, the transistor T1 in series with the capacitor C1 is turned off when the drive signal from the microcomputer 38 is low, and turned on when the drive signal is high. Further, the microcomputer 38 sets the drive signal of the transistor T1 to low from the above power-on reset (also when the ECU 31 is activated). Then, the microcomputer 38 switches each of the transistors T1 on and off by performing each of the first to fifth determination processes described below and the capacity recovery process. These processes are executed, for example, at regular intervals.

  As shown in FIG. 3, in the first determination process, the microcomputer 38 determines whether or not the battery voltage VB is equal to or lower than a predetermined voltage (6V in this example) (S110), and determines that the battery voltage VB is equal to or lower than the predetermined voltage. If determined (S110: YES), the transistor T1 is turned off (S120). Specifically, the drive signal for the transistor T1 is set to low. The predetermined voltage is set to a value of the battery voltage VB that is considered to be likely to decrease to the voltage value when the starter is operated, for example.

  As shown in FIG. 4, in the second determination process, the microcomputer 38 determines whether or not the starter is operating (S130). If the microcomputer 38 determines that the starter is operating (S130: YES), The transistor T1 is turned off (S140).

  As shown in FIG. 5, in the third determination process, the microcomputer 38 determines whether or not the engine speed NE is equal to or lower than a predetermined speed (800 rpm in this example) (S150). If it is determined that the rotation speed is equal to or lower than the predetermined rotation speed (S150: YES), the transistor T1 is turned off (S160). The predetermined rotational speed is set to, for example, an idle rotational speed or a value slightly larger than the idle rotational speed.

  As shown in FIG. 6, in the fourth determination process, the microcomputer 38 determines whether or not the number of continuous injections is equal to or less than a predetermined number (2 times in this example) (S170), and the number of continuous injections is equal to or less than the predetermined number. (S170: YES), the transistor T1 is turned off (S180). The number of continuous injections is the number of fuel injections to be performed by the injector 41 during a single fuel injection period of the cylinder. Further, as the fuel injection possible period, for example, a period from the start of the compression stroke to the end of the combustion stroke can be considered, but a part of the intake stroke may be included, and conversely, for example, the period of the combustion stroke May be just.

  As shown in FIG. 7, in the fifth determination process, the microcomputer 38 determines whether or not the ECU internal temperature is equal to or lower than a predetermined temperature (0 ° C. in this example) (S190), and the ECU internal temperature is equal to or lower than the predetermined temperature. (S190: YES), the transistor T1 is turned off (S200).

  On the other hand, as shown in FIG. 8, in the capacity recovery process, the microcomputer 38 determines whether or not the transistor T1 is turned off in the first S210, and if the transistor T1 is not turned off (that is, turned on). If so, the capacity restoration process is terminated.

  If the microcomputer 38 determines in S210 that the transistor T1 is turned off, in S220, the microcomputer 38 determines that the battery voltage VB is greater than the predetermined voltage determined in S110 of the first determination process (this voltage). In the example, it is determined whether or not it is 8V) or higher. When the microcomputer 38 determines that the battery voltage VB is not equal to or higher than the return voltage (S220: NO), the capacity recovery process is terminated as it is, but when the battery voltage VB is determined to be equal to or higher than the return voltage. (S220: YES), go to S230.

  In S230, the microcomputer 38 determines whether or not the starter is not operating (stopping operation). If the microcomputer 38 determines that the starter is operating (S230: NO), the microcomputer 38 terminates the capacity restoration process as it is, but if it determines that the starter is not operating (S230: YES), the process proceeds to S240.

  In S240, the microcomputer 38 determines whether or not the engine rotational speed NE is equal to or higher than a return rotational speed (1000 rpm in this example) larger than the predetermined rotational speed determined in S150 of the third determination process. If the microcomputer 38 determines that the engine speed NE is not equal to or higher than the return speed (S240: NO), the microcomputer 38 ends the capacity recovery process as it is, but the engine speed NE is equal to or higher than the return speed. (S240: YES), the process proceeds to S250.

  In S250, the microcomputer 38 determines whether or not the number of continuous injections is equal to or greater than the number of return times (three times in this example) that is greater than the predetermined number determined in S170 of the fourth determination process. If the microcomputer 38 determines that the continuous injection number is not equal to or greater than the return number (S250: NO), the microcomputer 38 terminates the capacity return process as it is, but determines that the continuous injection number is equal to or greater than the return number. (S250: YES), the process proceeds to S260.

  In S260, the microcomputer 38 determines whether or not the ECU internal temperature is equal to or higher than a return temperature (20 ° C. in this example) that is higher than the predetermined temperature determined in S190 of the fifth determination process. If the microcomputer 38 determines that the ECU internal temperature is not equal to or higher than the return temperature (S260: NO), the microcomputer 38 ends the capacity recovery process as it is, but determines that the ECU internal temperature is equal to or higher than the return temperature. (S260: YES), the process proceeds to S270.

  In S270, the microcomputer 38 turns on the transistor T1. Specifically, the drive signal for the transistor T1 is set high. Then, the capacitance of the output capacitor 34 returns from “Cap0” to “Cap0 + Cap1”. Thereafter, the microcomputer 38 ends the capacity restoration process.

  In other words, the microcomputer 38 turns off the transistor T1 when the ECU 31 is activated, thereby reducing the capacitance of the output capacitor 34 from the maximum value (Cap0 + Cap1). Then, the microcomputer 38 turns on the transistor T1 to return the electrostatic capacitance of the output capacitor 34 to the maximum value when all the conditions determined in each of S220 to S260 in the capacitance return processing are satisfied. The microcomputer 38 turns off the transistor T1 and turns off the output capacitor 34 when any of the conditions determined in each of S110, S130, S150, S170, and S190 in the first to fifth determination processes is satisfied. The capacitance is reduced from the maximum value. After that, the microcomputer 38 turns on the transistor T1 again to return the electrostatic capacitance of the output capacitor 34 to the maximum value when all the conditions determined in each of S220 to S260 in the capacitance return processing are satisfied. I am letting. Among S220 to S260, the determination content of S220 corresponds to the return condition when the transistor T1 is turned off in the first determination processing, and the determination content of S230 is the case where the transistor T1 is turned off in the second determination processing. Corresponding to the return condition, the determination content in S240 corresponds to the return condition when the transistor T1 is turned off in the third determination process, and the determination content in S250 is the result in the case where the transistor T1 is turned off in the fourth determination process. Corresponding to the return condition, the determination content of S260 corresponds to the return condition when the transistor T1 is turned off in the fifth determination process.

In the ECU 31 of the present embodiment, a boosting power supply device is configured by the boosting circuit 33 and the microcomputer 38.
In the ECU 31, when the fuel injection is started (that is, when energization of the coil 41a of the injector 41 is started), the output capacitor 34 is not charged to the target voltage in time, and the capacitor voltage VC has not reached the target voltage. Suppose that a situation occurs. In this case, as indicated by the dotted waveform in the first stage of FIG. 9, the time from the start of energization to the coil 41a until the coil current reaches the target maximum value IthP is increased. Then, as shown by the dotted line in the second stage of FIG. 9, the valve opening timing of the injector 41 is delayed, and the control accuracy of the fuel injection is lowered (specifically, the fuel injection amount is reduced). .

  However, in the ECU 31, the microcomputer 38 can turn off the transistor T <b> 1 to reduce the capacitance of the output capacitor 34, which is necessary for setting the capacitor voltage VC to the target voltage. Charging time (hereinafter referred to as necessary charging time) can be shortened. Therefore, it is possible to prevent the delay in opening the injector 41 from charging the output capacitor 34 to the target voltage in time (hereinafter also referred to as “injector opening delay due to charging delay”). be able to.

For example, the required charging time increases as the battery voltage VB decreases.
For this reason, in the ECU 31, the microcomputer 38 turns off the transistor T1 when the battery voltage VB is equal to or lower than the predetermined voltage (S110: YES → S120). Therefore, the increase in the required charging time due to the decrease in the battery voltage VB can be offset by reducing the capacitance of the output capacitor 34, and as a result, the delay in opening the injector due to the charging delay can be prevented. Can do.

Further, when the engine in which the starter operates is started, the battery voltage VB is lower than when the engine is operating.
Therefore, the microcomputer 38 turns off the transistor T1 when the starter is operating (S130: YES → S140). Therefore, it is possible to cancel the decrease in the capacitance of the output capacitor 34 from the decrease in the battery voltage VB due to the operation of the starter and the increase in the required charging time. As a result, the injector valve opening due to the charging delay Delay can be prevented.

  Even during the operation of the engine, when the engine speed NE is low, multistage injection is not performed. Therefore, the capacitance of the output capacitor 34 may be smaller than the maximum “Cap0 + Cap1”.

  Therefore, the microcomputer 38 turns off the transistor T1 when the engine speed NE is equal to or lower than the predetermined speed (S150: YES → 160). Therefore, at the time of engine low speed where the engine speed NE is equal to or lower than the predetermined speed, for example, even if the battery voltage VB decreases, it is possible to prevent the required charging time from becoming long. As a result, the injector due to charging delay The valve opening delay can be prevented.

  Further, when the multistage injection is not performed or when the number of continuous injections is small even when the multistage injection is performed, the capacitance of the output capacitor 34 may be smaller than the maximum “Cap0 + Cap1”.

  For this reason, the microcomputer 38 turns off the transistor T1 when the number of continuous injections is equal to or less than the predetermined number (S170: YES → 180). Therefore, when the number of continuous injections is less than the predetermined number and the capacitance of the output capacitor 34 may be smaller than “Cap0 + Cap1”, for example, even if the battery voltage VB decreases, the required charging time is prevented from becoming long. As a result, the injector valve opening delay due to the charging delay can be prevented.

Further, the output capacitor 34 has a higher ESR (equivalent series resistance) as the ambient temperature thereof becomes lower, so that the required charging time becomes longer.
Therefore, the microcomputer 38 detects the ECU internal temperature as the ambient temperature of the output capacitor 34 and determines that the detected ECU internal temperature is equal to or lower than the predetermined temperature (that is, the ambient temperature of the output capacitor 34 is the predetermined temperature). The transistor T1 is turned off (when it is determined as follows) (S190: YES → S200). Therefore, the increase in the required charging time due to the decrease in the ambient temperature of the output capacitor 34 can be offset by reducing the capacitance of the output capacitor 34. As a result, the injector valve opening delay due to the charging delay Can be prevented.

  The ambient temperature of the output capacitor 34 can also be detected by, for example, a method in which a temperature sensor is provided on one of the outer wall surfaces of the capacitors C0 and C1 constituting the output capacitor 34. On the other hand, since the microcomputer 38 detects the ECU internal temperature as the ambient temperature of the output capacitor 34, the ambient temperature of the output capacitor 34 can be easily detected.

  On the other hand, when the ECU 31 is provided in the engine room 61 (see FIG. 1) in which the engine is stored in the vehicle, the microcomputer 38 detects the temperature of the engine room 61 as the ambient temperature of the output capacitor 34. Also good. This is because there is a correlation between the temperature of the engine room 61 and the internal temperature of the ECU (and thus the ambient temperature of the output capacitor 34). For example, if there is a temperature sensor that detects the temperature of the engine room 61, the microcomputer 38 can detect the temperature of the engine room 61 from the output of the temperature sensor.

  The microcomputer 38 is a specific object whose temperature correlates with the temperature of the engine room 61 as the temperature of the engine room 61 (and thus the ambient temperature of the output capacitor 34). ) It may be detected. As the specific thing, the fuel supplied to an engine, the engine oil of an engine, the cooling water of an engine, etc. can be considered, for example. Among them, the highest correlation with the temperature of the engine room 61 is considered to be the temperature of the fuel. Further, in the vehicle, the temperature of the fuel, the engine oil, and the cooling water is usually detected for other purposes by the fuel temperature sensor 63, the oil temperature sensor 65, and the water temperature sensor 67 (see FIG. 1). By inputting the signals from .about.67 to the microcomputer 38, it can be detected without adding a separate sensor.

  It should be noted that no matter what temperature is detected as the ambient temperature of the output capacitor 34, in S190 of FIG. This also applies to S260 in FIG.

[Second Embodiment]
Next, the ECU of the second embodiment will be described. As the ECU, the same reference numeral “31” as that of the first embodiment is used. The same reference numerals as those in the first embodiment are used for the same components and processes as those in the first embodiment. This also applies to other embodiments described later.

  The ECU 31 of the second embodiment is different from the first embodiment in that the microcomputer 38 performs the capacity restoration process of FIG. 10 instead of the processes of FIGS. The capacity restoration process in FIG. 10 is executed at regular intervals, for example.

  As shown in FIG. 10, in the capacity restoration process, the microcomputer 38 determines whether or not the starter is not operating in the first S310. If the microcomputer 38 determines that the starter is operating (S310: NO), the microcomputer 38 ends the capacity restoration process as it is, but determines that the starter is not operating (ie, not operating). If so (S310: YES), the process proceeds to S320.

  In S320, the microcomputer 38 determines whether or not the battery voltage VB is equal to or higher than a predetermined normal determination value (8 V in this example). If the microcomputer 38 determines that the battery voltage VB is not equal to or higher than the normal determination value (S320: NO), the microcomputer 38 terminates the capacity recovery process as it is, but determines that the battery voltage VB is equal to or higher than the normal determination value. (S320: YES), the process proceeds to S330.

  In S330, the microcomputer 38 determines whether or not the engine speed NE is equal to or higher than an operation determination value (1000 rpm in this example) equal to or higher than the idle speed. If the microcomputer 38 determines that the engine speed NE is not equal to or greater than the operation determination value (S330: NO), the microcomputer 38 ends the capacity recovery process as it is, but the engine speed NE is equal to or greater than the operation determination value. (S330: YES), the process proceeds to S340.

In step S340, the microcomputer 38 turns on the transistor T1, and then ends the capacitance restoration process.
In other words, when the battery voltage VB is supplied to the ECU 31 and the ECU 31 is activated, the microcomputer 38 turns off the transistor T1 as described above, and then determines "YES" in all of S310 to S330. Thus, the transistor T1 is turned on from the off state. At that time, the capacitance of the output capacitor 34 is switched from “Cap0” to the normal value “Cap0 + Cap1”.

  According to such an ECU 31, it is possible to make the capacitance of the output capacitor 34 “Cap0” smaller than the normal value “Cap0 + Cap1” from when the ECU 31 is started until the start of the engine is completed.

  For this reason, even if the battery voltage VB decreases due to the starter operation at the start of the engine, the capacitance of the output capacitor 34 is reduced until the start of the engine is completed. As a result, the injector valve opening delay due to the charging delay can be prevented. Therefore, at the time of starting the engine, the fuel injection amount does not decrease, and good startability of the engine can be ensured.

  Further, the microcomputer 38 indicates that “the starter is not operating (S310: YES), the battery voltage VB is equal to or higher than the normal determination value (S320: YES), and the engine speed is equal to or higher than the operation determination value. (S330: YES) ”is determined to be satisfied, and it is possible to correctly determine the completion of engine start.

[Third Embodiment]
In the ECU 31 of the third embodiment, compared with the second embodiment, the microcomputer 38 does not execute the process of FIG. 10 after turning on the transistor T1 in the capacity recovery process of FIG. Similarly to the above, each process in FIGS. 3 to 8 is executed at regular intervals, for example.

  According to this ECU 31, since the transistor T1 is switched on and off in the same way as the ECU 31 of the first embodiment even after the start of the engine is completed and the transistor T1 is turned on, the first embodiment The same effect as the ECU 31 can be obtained.

[Modification 1]
In the first embodiment and the third embodiment, the microcomputer 38 may be configured not to execute one to four of the first to fifth determination processes. In that case, among the steps S220 to S260 in the capacity restoration process of FIG. 8, the steps corresponding to the determination process that is not executed can be deleted.

[Modification 2]
In the second embodiment and the third embodiment, the microcomputer 38 determines that the start of the engine is completed when it determines “YES” in one or two of S310 to S330 in FIG. The transistor T1 may be turned on.

  Further, for example, when the microcomputer 38 determines “YES” in all of S310 to S330 and further determines that other conditions are satisfied, the microcomputer 38 determines that the start of the engine is completed and turns on the transistor T1. Also good. As another condition, for example, a condition that the vehicle speed is equal to or higher than a predetermined value can be considered.

[Modification 3]
In each of the above embodiments and modifications, the number of capacitors constituting the output capacitor 34 may be three or more. In that case, a transistor (same as T1 in FIG. 1) is provided in series with each capacitor other than one capacitor C0, and each transistor is switched on and off depending on the situation. Just do it.

As mentioned above, although embodiment of this invention was described, this invention can take a various form, without being limited to the said embodiment. Moreover, the numerical value mentioned above is also an example.
For example, the functions of one constituent element in the above embodiment may be distributed as a plurality of constituent elements, or the functions of a plurality of constituent elements may be integrated into one constituent element. In addition, at least a part of the configuration of the above embodiment may be replaced with a known configuration having a similar function. Moreover, you may abbreviate | omit a part of structure of the said embodiment as long as a subject can be solved. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment.

  In addition, all the aspects included in the technical idea specified by the wording described in the claims are embodiments of the present invention. For example, the injector 41 is not a solenoid type, and may be a type of injector that includes a piezo element as an electric load for valve opening, and that opens when the piezo element expands by charging. In addition to the boosting power supply device described above, the present invention can be implemented in various forms such as a system including the boosting power supply device as a constituent element, a program for causing a computer to function as the boosting power supply device, a medium storing the program, and a boosting method. The invention can also be realized.

  DESCRIPTION OF SYMBOLS 31 ... Control apparatus, 34 ... Output capacitor, C0, C1 ... A plurality of capacitors forming an output capacitor, 35 ... Charging circuit, 36 ... Charge control circuit, T1 ... Transistor as a capacity adjustment switch, 38 ... Microcomputer, 41 ... Injector, 41a ... Electric load for valve opening

Claims (11)

Provided in a control device (31) for driving an injector (41) for injecting fuel into a vehicle engine,
An output capacitor (34) in which electric energy discharged to the valve opening electric load (41a) of the injector to open the injector is stored;
A charging circuit (35) for boosting the battery voltage of the vehicle and charging the output capacitor;
A charge control circuit (36) for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage;
A step-up power supply device comprising:
The output capacitor comprises a plurality of capacitors (C0, C1) in parallel,
The boost power supply device
Among the plurality of capacitors, a switch connected in series to a capacitor (C1) other than the specific capacitor (C0), and when turned on, a capacitor in series with the switch is connected in parallel with the specific capacitor, Capacitance adjustment switch (T1) that disables the capacitor in series with the switch by turning off and decreases the capacitance of the output capacitor;
Switching means for switching on and off the capacity adjustment switch ,
The switching means (38, S110, S120) turns off the capacity adjustment switch when the battery voltage is equal to or lower than a predetermined voltage.
Boost switching control in accordance with. Provided in a control device (31) for driving an injector (41) for injecting fuel into a vehicle engine,
An output capacitor (34) in which electric energy discharged to the valve opening electric load (41a) of the injector to open the injector is stored;
A charging circuit (35) for boosting the battery voltage of the vehicle and charging the output capacitor;
A charge control circuit (36) for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage;
A step-up power supply device comprising:
The output capacitor comprises a plurality of capacitors (C0, C1) in parallel,
The boost power supply device
Among the plurality of capacitors, a switch connected in series to a capacitor (C1) other than the specific capacitor (C0), and when turned on, a capacitor in series with the switch is connected in parallel with the specific capacitor, Capacitance adjustment switch (T1) that disables the capacitor in series with the switch by turning off and decreases the capacitance of the output capacitor;
Switching means for switching on and off the capacity adjustment switch,
The switching means (38, S130, S140) turns off the capacity adjustment switch when a starter for cranking the engine to start is operating.
A step-up power supply device. Provided in a control device (31) for driving an injector (41) for injecting fuel into a vehicle engine,
An output capacitor (34) in which electric energy discharged to the valve opening electric load (41a) of the injector to open the injector is stored;
A charging circuit (35) for boosting the battery voltage of the vehicle and charging the output capacitor;
A charge control circuit (36) for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage;
A step-up power supply device comprising:
The output capacitor comprises a plurality of capacitors (C0, C1) in parallel,
The boost power supply device
Among the plurality of capacitors, a switch connected in series to a capacitor (C1) other than the specific capacitor (C0), and when turned on, a capacitor in series with the switch is connected in parallel with the specific capacitor, Capacitance adjustment switch (T1) that disables the capacitor in series with the switch by turning off and decreases the capacitance of the output capacitor;
Switching means for switching on and off the capacity adjustment switch,
The switching means (38, S150, S160) turns off the capacity adjusting switch when the engine speed is equal to or lower than a predetermined speed.
A step-up power supply device. Provided in a control device (31) for driving an injector (41) for injecting fuel into a vehicle engine,
An output capacitor (34) in which electric energy discharged to the valve opening electric load (41a) of the injector to open the injector is stored;
A charging circuit (35) for boosting the battery voltage of the vehicle and charging the output capacitor;
A charge control circuit (36) for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage;
A step-up power supply device comprising:
The output capacitor comprises a plurality of capacitors (C0, C1) in parallel,
The boost power supply device
Among the plurality of capacitors, a switch connected in series to a capacitor (C1) other than the specific capacitor (C0), and when turned on, a capacitor in series with the switch is connected in parallel with the specific capacitor, Capacitance adjustment switch (T1) that disables the capacitor in series with the switch by turning off and decreases the capacitance of the output capacitor;
Switching means for switching on and off the capacity adjustment switch,
The injector is for injecting fuel into a cylinder of the engine,
The switching means (38, S170, S180) turns off the capacity adjusting switch when the number of fuel injections to be performed by the injector is less than or equal to a predetermined number in a single fuel injection possible period of the cylinder. ,
A step-up power supply device. Provided in a control device (31) for driving an injector (41) for injecting fuel into a vehicle engine,
An output capacitor (34) in which electric energy discharged to the valve opening electric load (41a) of the injector to open the injector is stored;
A charging circuit (35) for boosting the battery voltage of the vehicle and charging the output capacitor;
A charge control circuit (36) for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage;
A step-up power supply device comprising:
The output capacitor comprises a plurality of capacitors (C0, C1) in parallel,
The boost power supply device
Among the plurality of capacitors, a switch connected in series to a capacitor (C1) other than the specific capacitor (C0), and when turned on, a capacitor in series with the switch is connected in parallel with the specific capacitor, Capacitance adjustment switch (T1) that disables the capacitor in series with the switch by turning off and decreases the capacitance of the output capacitor;
Switching means for switching on and off the capacity adjustment switch,
The switching means (38, S190, S200) turns off the capacitance adjustment switch when it is determined that the ambient temperature of the output capacitor is equal to or lower than a predetermined temperature.
A step-up power supply device. The step-up power supply device according to claim 5 .
The switching means detects the internal temperature of the control device as the ambient temperature of the output capacitor;
A step-up power supply device. The step-up power supply device according to claim 5 .
The control device is provided in an engine room (61) in which the engine is stored in the vehicle.
The switching means detects the temperature of the engine room as the ambient temperature of the output capacitor;
A step-up power supply device. The step-up power supply device according to claim 7 .
The switching means detects the temperature of an object having a correlation with the temperature of the engine room as the temperature of the engine room;
A step-up power supply device. The step-up power supply device according to claim 8 ,
The object is a fuel supplied to the engine;
A step-up power supply device. Provided in a control device (31) for driving an injector (41) for injecting fuel into a vehicle engine,
An output capacitor (34) in which electric energy discharged to the valve opening electric load (41a) of the injector to open the injector is stored;
A charging circuit (35) for boosting the battery voltage of the vehicle and charging the output capacitor;
A charge control circuit (36) for operating the charging circuit so that a charging voltage of the output capacitor becomes a target voltage;
A step-up power supply device comprising:
The output capacitor comprises a plurality of capacitors (C0, C1) in parallel,
The boost power supply device
Among the plurality of capacitors, a switch connected in series to a capacitor (C1) other than the specific capacitor (C0), and when turned on, a capacitor in series with the switch is connected in parallel with the specific capacitor, Capacitance adjustment switch (T1) that disables the capacitor in series with the switch by turning off and decreases the capacitance of the output capacitor;
Switching means for switching on and off the capacity adjustment switch,
The control device and the boost power supply device operate by supplying the battery voltage as a power source to the control device,
The switching means (38, S310 to S340)
When the battery voltage is supplied to the control device and the control device starts to operate, the capacity adjustment switch is turned off, and then the capacity adjustment switch is determined when it is determined that the engine has been started. Turning on from off,
A step-up power supply device. The step-up power supply device according to claim 10 .
The switching means is
The starter for cranking the engine for starting is not operating, the battery voltage is equal to or higher than a predetermined normal determination value, and the engine speed is equal to or higher than an operation determination value equal to or higher than the idle speed. Determining that the engine has been started,
A step-up power supply device.

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