JP6133627B2 - Booster circuit - Google Patents

Description

  The present invention relates to a booster circuit, and more particularly to control of a booster circuit that keeps a boost recovery time constant.

  In recent years, an in-cylinder direct injection engine system including an injector that directly injects fuel into a cylinder has been attracting attention for the purpose of reducing fuel consumption and exhaust gas.

  As shown in FIG. 1, the in-cylinder direct injection engine system includes an in-cylinder direct injection type injector 106, and the injector 106 injects fuel pressurized to a high pressure into the cylinder. Requires a large current to flow. For this reason, the in-cylinder direct injection engine control unit generates a boosted voltage by a booster circuit. When the engine is driven, a large current is supplied to the injector 106 using the boosted voltage, and the injector 106 is opened to inject high-pressure fuel into the cylinder.

  Further, in order to meet market demands such as PM suppression and fuel efficiency improvement, it is required to add a multi-stage injection function for performing continuous injection multiple times in one cylinder. By adopting the multi-stage injection function, it is possible to prevent fuel adhesion in the cylinder and to cool the cylinder with the fuel, thereby preventing oil dilution, suppressing PM, and improving fuel efficiency.

JP 2012-145119 A

  In the in-cylinder direct injection engine system, the boosted voltage decreases due to the energization of the injector. Therefore, it is necessary to restore the boosted voltage that has been reduced until the next injector energization to a specified voltage value by the boosting operation. The time required to restore the boosted voltage is referred to as the boosting recovery time, and the boosting recovery time depends on the battery power supply voltage (DC voltage source voltage). When the battery power supply voltage increases, the boost recovery time becomes shorter, and when the battery power supply voltage decreases, the boost recovery time becomes longer.

  When driving at high speed or using multi-stage injection, the energization interval of the injector 106 is shortened. Therefore, when the battery power supply voltage decreases and the time until the boost voltage is restored increases, the boost voltage is restored to the specified voltage when the next injector is energized. Things that can't be done can happen. If the injector is energized at a voltage lower than the specified boost voltage, the time required for opening the injector will increase, causing variations in the fuel injection amount. For this reason, it is important to stabilize the boosting return time when driving at a high speed or adopting multistage injection.

  As described above, in the booster circuit, even if the voltage of the DC voltage source decreases, it is a problem to keep the boost recovery time constant.

The booster circuit of the present invention is connected to a DC voltage source, boosts the voltage of the DC voltage source, a switching element for passing a boost current to the boost coil, and stores energy generated by the boost coil. A boost capacitor, a current detector for detecting a boost current of the boost coil, and after the boost current of the boost coil reaches the upper limit threshold, the switching element is turned off until the boost current reaches the lower limit threshold, thereby blocking the boost current A booster circuit comprising: a booster circuit controller that generates boosted voltage by repeatedly performing booster control to charge the booster capacitor with energy stored in the booster coil; and a voltage detector that detects the boosted voltage. When the voltage of the DC voltage source fluctuates, the booster circuit control unit waits until the boosted voltage returns to the original boosted voltage. As the pressure recovery time constant, and changes the average voltage boosting current value of the boost current in accordance with a variation in the voltage of the DC voltage source.

  In the present invention, the voltage of the DC voltage source is observed, and when the voltage of the DC voltage source fluctuates, the boosting recovery time is stabilized by changing the average boosted current value accordingly.

  According to the present invention, in the booster circuit, the boost recovery time can be kept constant even when the voltage of the DC voltage source fluctuates.

1 is a schematic diagram showing an example of an in-cylinder direct injection engine system. 1 is a block diagram showing an internal combustion engine control device in Embodiment 1. FIG. 1 is a circuit diagram showing an internal combustion engine control device of an in-cylinder direct injection engine system in Embodiment 1. FIG. It is a time chart which shows an injector electric current and pressure | voltage rise operation | movement. It is a time chart which shows the step-up current at the time of step-up operation. 3 is a time chart showing a voltage of a DC voltage source and a boost current in the first embodiment.

  FIG. 1 is a schematic diagram illustrating an example of an in-cylinder direct injection engine system according to the first embodiment. The schematic diagram of FIG. 1 is an example, and the present invention is not limited to this.

  The intake air passes through the air flow sensor 1 and is introduced into the combustion chamber 4 through the intake pipe 3 via the throttle valve 2 that controls the intake air flow rate.

  The fuel in the fuel tank 5 is pressurized to a high pressure by the high-pressure pump 6 and injected from the injector 106 into the combustion chamber 4. The fuel injected into the combustion chamber 4 generates an air-fuel mixture with intake air, is ignited by the ignition 7, and burns in the combustion chamber 4.

  The exhaust gas after combustion in the combustion chamber 4 is discharged to the exhaust pipe 8, and an EGR valve 9 is formed in the middle of the exhaust pipe 8. Part of the exhaust gas (EGR gas) flowing through the exhaust pipe 8 is recirculated into the intake pipe 3 from the EGR valve 9 through the EGR pipe 10. The EGR gas flow rate is adjusted by the EGR valve 9.

  The exhaust gas discharged to the exhaust pipe 8 is discharged into the atmosphere after the harmful exhaust components are purified by the three-way catalyst 11.

  FIG. 2 shows an in-cylinder direct injection type internal combustion engine control apparatus. As shown in FIG. 2, in the internal combustion engine control apparatus, an input signal 100 from each sensor is taken into the control unit 101, and the control unit 101 controls the booster circuit control unit 102 and the injector circuit control unit 103. The booster circuit control unit 102 operates the booster circuit 104, the injector circuit control unit 103 operates the injector drive circuit 105, and the injector drive circuit 105 drives the injector 106.

  The control unit 101 is implemented by, for example, a microcomputer. Also, depending on the situation, operation information in the booster circuit 104 and the injector drive circuit 105 is fed back to the booster circuit control unit 102, the injector circuit control unit 103, and the control unit 101, and a function for performing an operation based on the information is added. May be.

  FIG. 3 shows details of the booster circuit 104 and the injector drive circuit 105.

  The booster circuit 104 generates a high voltage necessary for opening the injector from an on-vehicle DC voltage source (for example, a battery power supply voltage: hereinafter referred to as a battery power supply voltage). The booster circuit 104 includes a booster coil 201, a switching element (for example, FET) 202, a current detection resistor 203, a booster capacitor 204, a backflow prevention diode 208, and a booster circuit control unit 102.

  The injector driving circuit 105 for driving the injector 106 includes an injector driving circuit control unit 103. The injector driving circuit control unit 103 displays the state of the booster circuit output from the boosting control unit 205 and the state of the coil of the injector 106. Monitoring and controlling the injector drive circuit 105.

  The boosting circuit control unit 102 controls the boosting operation. The step-up circuit control unit 102 includes a step-up control unit 205 that controls driving of the switching element 202, a voltage detection unit 206 that detects a charging voltage accumulated in the step-up capacitor 204, and a current detection unit that detects a current flowing through the switching element 202. For example, these functions are collectively implemented in a custom IC.

  FIG. 4 is a graph showing an example of the injector current waveform and the boosting operation. (A) is an injector drive signal sent from the control unit 101 to the injector drive circuit control unit 103, and the injector 106 is energized during a period 300 in which the injector drive signal is Hi output. When the injector drive signal becomes Lo output, energization to the injector 106 is terminated.

  (B) is an example of a current waveform flowing through the injector 106. A period 301 is a period during which the injector is opened, and the injector 106 is energized using the boosted voltage. A period 302 is a period during which the valve open state of the injector 106 is maintained, and the retention time 302 is determined by an injector current energization period corresponding to the magnetic circuit characteristics, fuel pressure, and supplied fuel amount.

  (C) represents the boosted voltage. When the injector 106 is opened while the voltage of 303 is stored in the boosting capacitor 204 by the boosting operation in the boosting circuit 104, the booster voltage is used to energize the injector 106. Decline. When the boosted voltage decreases by a certain value 304 or more, the voltage detection unit 206 of the booster circuit control unit 102 detects a voltage drop and starts a boosting operation. The boosting operation continues until the voltage value of 303 is recovered.

  (D) is a boost control signal for controlling the switching on and off of the switching element 202 by the boost controller 205, and (e) is a boost current flowing through the boost coil 201.

  As shown in FIGS. 4D and 4E, when the boosted voltage drops by a certain value 304 or more, the boost control signal is turned on by the input from the control unit 101 to start the boosting operation, and the boosted current rises. When the boosted current reaches the upper limit threshold value 305, the current detection unit 207 of the booster circuit control unit 102 detects the current value and turns off the switching element 202. The energy stored in the booster coil 201 during the period when the switching element 202 is off is charged in the booster capacitor 204, and the boosted voltage slightly increases. While the switching element 202 is off, the boost current decreases, and when the lower limit threshold 306 is reached, the boost switching element 202 is turned on again. By repeating the series of switching operations of the switching element 202, the boosted voltage is restored to the original voltage 303 as shown in FIG. The average value of the upper limit threshold value 305 and the lower limit threshold value 306 of the boost current is referred to as an average boost current value 307, and the time 308 required to return the boosted voltage reduced by the energization of the injector to the original voltage value 303 is referred to as a boost recovery time.

  FIG. 5 is a graph showing an enlarged waveform of the boost current during the boost operation. The boosting current increases during the ON period 400 of the switching element 202. When the boosting current reaches the upper limit threshold 305, the switching element 202 is turned off, and the boosting current is increased during the OFF period 401 until the boosting current reaches the lower limit threshold 306. Reduce current.

  Assuming that the inductance of the boosting coil 201 is L and the battery power supply voltage 200 is V, the slope of the boosting current during the ON period 400 in which the boosting current is raised to the upper threshold 305 is proportional to V / L. Therefore, the ON period 400 is shortened as the battery power supply voltage 200 is large, and the boosting recovery time 308 is also shortened. On the other hand, if the battery power supply voltage 200 is small, the ON period 400 is lengthened and the boosting recovery time 308 is also lengthened.

  Further, when restoring the boosted voltage, the amount of energy stored in the boost capacitor 204 by the boosting operation is proportional to the vertical line area 402. Therefore, if the average boost current value 307 increases, the vertical line area 402 increases, so the boost recovery time 308 decreases. If the average boost current value 307 decreases, the vertical line area 402 decreases, and the boost recovery time 308 decreases. become longer.

  Conventionally, when performing a boost operation, the upper limit threshold value 305 and the lower limit threshold value 306 of the boost current are constant, and the average boost current value 307 is always constant. This method has an advantage that control is easy because there is no need to change the upper limit threshold value 305 and the lower limit threshold value 306 of the boost current from the initial setting. However, when the battery power supply voltage 200 fluctuates, there is a problem that the boost recovery time 308 fluctuates accordingly.

  Hereinafter, Embodiments 1-4 of the present invention will be specifically described.

[Embodiment 1]
FIG. 6 shows the behavior of the battery power supply voltage 200 and the boosted current when the battery power supply voltage 200 varies from the reference voltage value 500 by the voltage value 501 when the internal combustion engine control apparatus according to the first embodiment is driven.

  As shown in Table 1, a table of combinations of the battery power supply voltage 200 and the upper limit threshold value 305 and the lower limit threshold value 306 of the boost current that makes the boost recovery time constant is set in the control unit 101 in advance.

  When the internal combustion engine control device is driven, the control unit 101 periodically observes the battery power supply voltage 200. The observed battery power supply voltage 200 is compared with Table in Table 1 to derive the upper limit threshold value 502 and the lower limit threshold value 503 of the boost current necessary to achieve the specified boost recovery time 308.

  The upper limit threshold value 502 and the lower limit threshold value 503 of the boost current derived from the control unit 101 are sent to the booster circuit control unit 102, and the booster circuit 104 is driven by the specified upper limit threshold value 502 and lower limit threshold value 503 of the specified boost current. As a result, the average boosted current value also varies from the current value 307 to the current value 504 as shown in FIG. By changing the average boost current value in this way, it is possible to cancel the boost recovery time fluctuation due to the power supply voltage fluctuation and keep the boost recovery time 308 constant. In addition, fuel injection can be performed stably even at high speeds and multistage injection.

[Embodiment 2]
Next, an internal combustion engine control apparatus according to Embodiment 2 will be described. In the first embodiment, the battery power supply voltage 200 is regularly observed, and the upper limit threshold and the lower limit threshold of the boost current are derived according to the battery power supply voltage each time. On the other hand, in the second embodiment, as a method for detecting the battery power supply voltage 200, the power supply voltage value is not regularly observed, but the battery power supply voltage 200 changes from a specified voltage value to a certain level or more. If it continues for more than the time, the control unit 101 changes the upper limit threshold value 305 and the lower limit threshold value 306 of the boost current. Other configurations are the same as those of the first embodiment.

  Thereby, in addition to the effect of Embodiment 1, it becomes possible to reduce a calculation load.

[Embodiment 3]
Next, an internal combustion engine control apparatus according to Embodiment 3 will be described.

  In the first embodiment, the upper limit threshold and the lower limit threshold of the boost current are derived from the table of Table 1, but in the third embodiment, the upper limit threshold and the lower limit threshold of the boost current set by the control unit 101 are calculated each time. ,calculate.

  Specifically, the difference between the observed battery power supply voltage 200 and the specified voltage value is taken, and the change in the slope of the boost current during the ON period 400 (when the boost current rises) is determined from the difference between the voltage values. calculate. Here, the slope of the boost current is proportional to V / L (where V: battery power supply voltage, L: inductance). Therefore, it is possible to obtain a change in inclination from the difference between the voltage values.

  Since the time required for the boost current to reach from the lower limit threshold value to the upper limit threshold value is obtained from the slope of the boost current, the change amount of the boost return time can be calculated from the change amount of the boost current slope.

Next, the amount of energy stored in the boost capacitor 204 by one on / off switching of the switching element 202 is obtained so that the calculated boost recovery time fluctuation can be eliminated. Since I = ΔQ / Δt (where I: boost current, dQ: charge, dt: time difference), the charge ΔQ stored in the boost capacitor is obtained from the boost current by switching the switching element 202 on and off once. The amount of energy (∝Q ² / C (where C is the capacitance of the boost capacitor 204)) can be obtained from the electric charge. Based on this value, an average boost current value that can eliminate the boost recovery time fluctuation is calculated, and an upper limit threshold and a lower limit threshold of the boost current to be set are obtained.

  In this method, the control unit 101 needs to perform the calculation as described above, so that control becomes difficult as compared with the first embodiment. However, since it is possible to cope with small fluctuations in the battery power supply voltage value, the boost recovery time 308 can be further stabilized in the third embodiment.

[Embodiment 4]
In the first to third embodiments, when the average boost current is changed, the average boost current 307 is changed by changing the boost current upper limit threshold 305 and the boost current lower limit threshold 306 together. A method may be used in which one of 305 and the lower threshold 306 is changed to change the average boost current value 307. Further, a method of greatly changing the upper limit threshold of the boost current to reduce the change of the lower limit threshold and vice versa may be used.

  For example, when only the upper limit threshold value of the boost current is increased, the power consumption of the booster coil increases due to the AC component, but by increasing only the lower limit threshold value, the power consumption due to the AC component of the booster coil decreases. On the other hand, when only the lower limit threshold value is increased, the switching frequency of the switching element 202 is increased, and the switching loss is increased.

  According to the fourth embodiment, the degree of freedom in setting the upper limit threshold and the lower limit threshold is improved, and it is possible to set the upper limit threshold and the lower limit threshold in consideration of the influence of each element as described above.

DESCRIPTION OF SYMBOLS 101 ... Control part 102 ... Booster circuit control part 106 ... Injector 200 ... DC voltage source (battery power supply voltage)
201 ... Boosting coil 202 ... Switching element (FET)
DESCRIPTION OF SYMBOLS 203 ... Current detection part 204 ... Boost capacitor 206 ... Boost voltage detection part 307,504 ... Average step-up current value 305, 502 ... Upper limit threshold value 306, 503 ... Lower limit threshold value

Claims (7)

A boosting coil connected to a DC voltage source and boosting the voltage of the DC voltage source;
A switching element for passing a boost current to the boost coil;
A boost capacitor for storing energy generated by the boost coil;
A current detector for detecting a boost current of the boost coil;
After reaching the boost current limit threshold of the boosting coil, and turns off the switching element until it reaches the lower threshold to cut off the boost current, the step-up control for charging the energy stored in the boost coil to said boost capacitor A booster circuit controller that repeatedly generates a boosted voltage;
In a booster circuit comprising a voltage detector that detects the boosted voltage,
The booster circuit control unit includes:
When the voltage of the DC voltage source is varied, the so boosted voltage to a constant boost voltage recovery time to return to the voltage of the original boost state, the boost in accordance with a variation in the voltage of the DC voltage source boosting circuit characterized that you change the average voltage boosting current value of the current. The booster circuit control unit includes:
2. The booster circuit according to claim 1, wherein the average boost current value is changed by changing an upper limit threshold and a lower limit threshold of the boost current. The booster circuit control unit includes:
2. The booster circuit according to claim 1, wherein the average boost current value is changed by changing one of an upper limit threshold and a lower limit threshold of the boost current. The booster circuit control unit includes:
4. The average boosted current value is changed when it is detected that the voltage value detected by the voltage detector has fluctuated more than a predetermined value from a specified voltage value, or periodically. The booster circuit according to any one of the above. The booster circuit control unit includes:
Based on the voltage detected by the voltage detecting section, each time the step-up circuit according to any one of claims 1 to 4, characterized in that to calculate the average boost current. The booster circuit control unit includes:
5. The boosted current is derived based on the voltage of the DC voltage source from a table of the voltage of the DC voltage source and the boosted current stored in advance in the control unit. 2. The booster circuit according to item 1. The booster circuit is provided in a control device for an internal combustion engine,
The booster circuit according to any one of claims 1 to 6, wherein the booster voltage generated by the booster circuit is used to open an injector that injects fuel into an engine cylinder.

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