JP6493108B2 - Injection control device - Google Patents

Description

  The present invention relates to an injection control device.

  As an injection control device, for example, a driving device for performing injection control by a piezo injector uses a charge charged in a capacitor by a voltage boosted from a power supply voltage. Control is performed to open the injector by connecting to the piezo injector and charging, to release the connection from the capacitor, and to connect the piezo injector to the ground and to discharge the charge to close the injector. In this case, in order to charge and discharge the piezo injector, each injection valve drive circuit includes switching elements such as a charging MOSFET and a discharging MOSFET. A plurality of the injection valve drive circuits are provided, and a fuse is provided between the common parts.

  Under normal operating conditions, the charging MOSFET and the discharging MOSFET are not turned on at the same time. However, if one of them is short-circuited, the two MOSFETs become conductive at the timing of charging or discharging. To form a short state. At this time, initially, the charge of the capacitor flows through the two MOSFETs, and when the voltage of the capacitor becomes lower than the power supply voltage, a through current directly flows from the power supply side through a common component such as a booster circuit.

  There is no problem if the fuse on the circuit where the short circuit failure occurs before the through current flows, but if the fuse does not melt reliably, the common circuit elements that make up the booster circuit when the through current flows May be destroyed. In a configuration in which a plurality of piezo injectors are driven, if the injection valve drive circuit of one piezo injector fails, the elements of the common circuit are destroyed, and the injection valve drive circuit of the other piezo injector cannot be driven.

JP 2002-199748 A

  The present invention has been made in consideration of the above circumstances, and an object thereof is to drive a plurality of capacitive loads, and to share common components when a short circuit failure occurs in a circuit that drives one capacitive load. It is an object of the present invention to provide an injection control device capable of preventing the destruction of the fuel.

The injection control device according to claim 1 controls the drive of a plurality of capacitive loads that drive the injection valve, and boosts the power supply voltage to a predetermined voltage to charge the capacitive element via a common component diode. A booster circuit, a resistor provided in the booster circuit and connected in series with the capacitive element, and a power supply from the capacitive element to each of the plurality of capacitive loads. A plurality of injection valve drive circuits including MOSFETs, and a plurality of fuse circuits provided in energization paths from the capacitive element to each of the plurality of injection valve drive circuits. When an overcurrent flows through any of the injection valve drive circuits, a discharge capability is provided to blow the corresponding fuse element of the fuse circuit by discharging the charge.

  By adopting the above configuration, electric charges are accumulated in a state where the capacitance element is boosted to a predetermined voltage by the boosting operation of the boosting circuit. When the capacitive load is driven by the injector driving circuit, the charging MOSFET of the corresponding injector driving circuit is driven to charge the capacitive element to the capacitive load. Thereby, the capacitive load is driven and the injection valve is driven. Thereafter, when the discharging MOSFET is driven, the charge of the capacitive load is discharged and the injection valve returns to the original state.

  In the above case, when a short-circuit failure occurs in the charging MOSFET or discharging MOSFET of the injection valve driving circuit that drives each capacitive load, the operation is as follows. When either one of the charging MOSFET and the discharging MOSFET causes a short circuit failure, it becomes a conductive state with a small resistance, which is almost the same as the on-operation state. In this state, when the other MOSFET is turned on, the two MOSFETs are both turned on, and a current flows due to discharge of the charge of the capacitive element. At this time, the capacitor element is configured to increase the charge charging and discharging ability and thereby increase the amount of current, so that the fuse of the fuse circuit connected to the energization path to the target injector driving circuit The element can be blown only by the electric charge charged in the capacitor element.

  As a result, the injection valve drive circuit in which the short circuit failure has occurred can be separated from the booster circuit before the current due to the charge of the capacitive element decreases and the through current flows from the power supply side. As a result, it is possible to prevent the breakdown of common components such as a booster circuit due to the flow of through current.

  In this case, the amount of current corresponding to the discharge capability of the capacitive element can be increased by increasing the capacitance value, and can also be increased by decreasing the equivalent series resistance, or increasing the capacitance and It can be increased by reducing the equivalent series resistance. Therefore, connecting a plurality of capacitive elements in parallel satisfies either of these, and the discharge capacity, that is, the amount of current can be increased.

Electrical configuration diagram showing the first embodiment (A) Action explanatory diagram at the time of charge charge to the piezo injector, (b) Action explanatory diagram at the time of charge discharge from the piezo injector (A) Operation explanatory diagram when the injection valve drive circuit 4a is abnormal, (b) Operation explanatory diagram when the injection valve drive circuit 4b is abnormal Equivalent circuit diagram for explaining the operating principle Fuse characteristics of chip fuse

Hereinafter, an embodiment will be described with reference to FIGS.
In this embodiment, a case where a piezo injector is driven as a fuel injection device will be described. FIG. 1 shows a circuit configuration of the injection control device 1. The injection control device 1 includes a booster circuit 2 and two injection valve drive circuits 4a and 4b for driving and controlling two piezo injectors 3a and 3b as a plurality of capacitive loads.

  The piezo injectors 3a and 3b are, for example, a stack of a plurality of piezo elements. For example, when a voltage is applied to a piezo element sandwiched between two electrodes and a charging operation is performed, the piezo injectors 3a and 3b contract due to the piezoelectric effect. By utilizing the contraction operation by the plurality of piezo elements, the piezo injectors 3a and 3b arranged in the inserted state at the tip of the nozzle are contracted to open the nozzle. On the other hand, in the piezoelectric injectors 3a and 3b, when the charged electric charges are discharged, each piezoelectric element returns from the contracted state to the original extended state. As a result, the piezo injectors 3a and 3b extend to close the nozzle. In this way, the fuel injection from the nozzle can be controlled by causing the piezo injectors 3a and 3b to operate to contract and extend.

  The booster circuit 2 boosts and outputs the voltage of the DC power supply VD, and is composed of a booster coil 5, a switching element 6, a current limiting resistor 7, and a diode 8. A series circuit of a booster coil 5, a switching element 6, and a resistor 7 is connected between the DC power supply VD and the ground. A common connection point between the booster coil 5 and the switching element 6 is connected to capacitors 9, 10 and 11 as capacitive elements via a diode 8 in the forward direction. The other terminal of the capacitor 9 is connected to the ground via the resistor 7. The other terminals of the capacitors 10 and 11 are connected to the ground.

  A common connection point between the diode 8 and the capacitor 9 is branched into an energization path that reaches the two injection valve drive circuits 4a and 4b. These energization paths are provided with fuse circuits 12a and 12b, respectively. Each of the fuse circuits 12a and 12b is a circuit in which chip fuses 13 which are two fuse elements are connected in series, and are provided so as to be blown when an overcurrent flows.

  In addition, in the injection valve drive circuits 4a and 4b in the present embodiment, a driving method is used in which a current is supplied in a pulse manner to the piezo injectors 3a and 3b. If it repeats, there is a possibility of expansion and contraction and fusing by stress. In addition, since the three chip fuses 13 are connected in series here, it is preferable to melt them at the same time. From these points, the two chip fuses 13 used in the fuse circuits 12a and 12b are preferable in that they have little variation in fusing characteristics and are resistant to stress due to metal fatigue.

  The fuse circuit 12a is connected to the injection valve drive circuit 4a, and the fuse circuit 12b is connected to the injection valve drive circuit 4b. Each of the injection valve drive circuits 4a and 4b includes a charging MOSFET 14a, a discharging MOSFET 14b, and a coil 15. The charging MOSFET 14a and the discharging MOSFET 14b are connected to the ground in a state of being connected in series. The MOSFETs 14a and 14b are n-channel type and both have a configuration in which a feedback diode is added. A parallel circuit of the coil 15 and the piezo injector 3a or the coil 15 and the piezo injector 3b is connected to each discharging MOSFET 14b in parallel. The coil 15 is for limiting the current during charging and discharging of the piezo injectors 3a and 3b, and also functions for energy recovery.

Next, the operation of the above configuration will be described with reference to FIGS.
In the booster circuit 2, the switching element 6 is controlled to be turned on / off by a control circuit (not shown), whereby the capacitors 9 to 11 are charged via the diode 8 by the induced voltage generated in the booster coil 5 to a predetermined high voltage. Become. This step-up control is performed at an appropriate timing and is maintained so that the voltages of the capacitors 9 to 11 become a predetermined high voltage.

  On the other hand, when the injection valve is driven by the piezo injectors 3a and 3b, when the fuel injection timing is reached by the control circuit, a drive signal is sent to the injection valve drive circuit 4a or 4b of the target piezo injector 3a or 3b. Is output. Here, a case where the piezo injector 3a is driven will be described.

  In this case, the control circuit gives a pulse-like drive signal to the charging MOSFET 14a of the injection valve drive circuit 4a a plurality of times. At this time, the discharging MOSFET 14b is held in the off state. During the period when the charging MOSFET 14a is on, the charging current I flows from the capacitor 9 through the fuse circuit 12a as shown by the arrow A in FIG. 2A, and further charging is performed as shown by the arrows B and C. The battery 14a is charged from the MOSFET 14a through the coil 15 to the piezo injector 3a. When a voltage is applied by charging, the piezo injector 3a enters a contracted state and opens the injection nozzle. The piezo injector 3a is driven to a predetermined opening by a plurality of ON operations of the charging MOSFET 14a, and a predetermined injection is performed.

  Thereafter, when it is time to close the injection valve, the control circuit gives a pulsed drive signal to the discharge MOSFET 14b of the injection valve drive circuit 4a multiple times. At this time, the charging MOSFET 14a is held in the off state. As a result, as indicated by arrows D and E in FIG. 2B, when the discharging MOSFET 14b is turned on, the charge of the piezo injector 3a is discharged to the ground via the coil 15 and the discharging MOSFET 14b. When the voltage drops due to discharge, the piezo injector 3a shifts from the contracted state to the extended state and closes the injection nozzle. The piezo injector 3a returns to a predetermined original state by a plurality of ON operations of the discharge MOSFET 14b, and one injection operation is completed.

Although the description is omitted, the same applies to the case of driving the piezo injector 3b.
In the normal operation described above, the current that flows when driving the piezo injectors 3a and 3b does not blow the chip fuse 13 of the fuse circuits 12a and 12b. In other words, it blows in the normal use state. There is a current capacity that does not.

  Next, the operation in the case where the charging MOSFET 14a or the discharging MOSFET 14b has caused a short failure in the configuration of the injection valve driving circuit 4a or 4b will be described. In any of the injection valve drive circuits 4a and 4b, when one MOSFET 14a or 14b is short-circuited, when the other is turned on, the terminal of the capacitor 9 is shorted to the ground, and the charge is rapidly discharged. An abnormal condition occurs.

  FIG. 3A shows the operation of the injection valve drive circuit 4a in an abnormal state, and FIG. 3B shows the operation of the injection valve drive tail r4b in an abnormal state. In either case, the chip fuses 13 of the fuse circuits 12a and 12b are fused together by the same operation. Here, the operation in the abnormal state of the injection valve drive circuit 4a will be described with reference to FIG.

  For example, a case where a short-circuit failure has occurred in the charging MOSFET 14a of the injection valve drive circuit 4a will be described. In this case, the piezo injector 3a is charged without driving the charging MOSFET 14a. However, since the pulsed on / off signal is not given by the drive signal, the piezo injector 3a is energized continuously. Further, after the piezo injector 3a is charged, the charging path is maintained and the injection nozzle is fully opened.

  On the other hand, in the operation in which the discharging MOSFET 14b is operated to discharge the electric charge of the piezo injector 3a, when the discharging MOSFET 14b is turned on, the charging path from the capacitor 9 is shorted to the ground via the charging MOSFET 14a in a short state. It will be in the state. As a result, as indicated by arrows F, G, H, and J in FIG. 3A, the capacitors 9, 10, and 11 are discharged in a short time, and a large current flows through the fuse circuit 12a. . As a result, the two chip fuses 13 of the fuse circuit 12a are melted together by the energy of the discharge currents of the capacitors 9, 10, 11 and the current is cut off.

  Incidentally, in the conventional equivalent in which the capacitors 10 and 11 are not provided, the chip fuse 13 is blown using only the electric charge of the capacitor 9, but in this case, variations in circuit constants of elements constituting the circuit are caused. In consideration of the above, it has been difficult to blow out reliably. On the other hand, in this embodiment, since the capacitors 10 and 11 are added, the corresponding capacity is added to the capacity of the capacitor 9, and the equivalent series resistance component of the capacitor is added in parallel. Thus, the resistance component can be reduced. As a result, the chip fuse 13 can be surely blown when a short circuit failure occurs.

  As described above, the two chip fuses 13 of the fuse circuit 12a are blown, whereby the injection valve drive circuit 4a is disconnected from the booster circuit 2. As a result, the piezo injector 3a driven by the injection valve drive circuit 4a cannot be driven, but the piezo injector 3b driven by the injection valve drive circuit 4b is held in a drivable state.

  After the two chip fuses 13 are blown, a high potential difference is generated between the terminals of the two chip fuses 13 due to the terminal voltage of the capacitor 9. At this time, if the distance between the terminals after fusing is short, there is a concern about the generation of an arc. In this embodiment, since the fuse circuit 12a in which two or more chip fuses 13 are mounted in series is provided, the distance between the terminals after fusing can be increased. Thereby, the injection valve drive circuit 4a can be reliably disconnected.

  Further, since the chip fuse 13 can be blown by discharging the electric charges of the capacitors 9 to 11, no through current flows directly from the power source VD side after the discharging by the capacitors 9 to 11, and the booster circuit 2 is configured. It is possible to avoid the circuit element from being destroyed by the through current.

  When the discharging MOSFET 14b is short-circuited, when the charging operation to the piezo injectors 3a and 3b is performed, when the charging MOSFET 14a is turned on, a short circuit to the ground is caused via the short-circuiting discharging MOSFET 14b. Occur. As a result, the charges of the capacitors 9 to 11 are similarly discharged to the fuse circuit 12a. As a result, the two chip fuses 13 of the fuse circuit 12a are melted together by the energy of the discharge currents of the capacitors 9, 10, 11 and the current is cut off.

  Therefore, when the two chip fuses 13 of the fuse circuit 12a are blown in the same manner as described above, the injection valve drive circuit 4a is disconnected from the booster circuit 2, and the circuit elements constituting the booster circuit 2 pass through current. Can be avoided.

  Although detailed description is omitted, in the case of the injection valve drive circuit 4b, if the charging MOSFET 14a or the discharging MOSFET 14b causes a short-circuit failure, the arrows K, L, M, As indicated by N, a large current flows through the fuse circuit 12b. As a result, the two chip fuses 13 of the fuse circuit 12b are melted together by the energy of the discharge currents of the capacitors 9, 10, and 11, and the current is cut off.

  Therefore, when the two chip fuses 13 of the fuse circuit 12b are blown in the same manner as described above, the injection valve drive circuit 4b is disconnected from the booster circuit 2, and the circuit elements constituting the booster circuit 2 pass through current. Can be avoided.

  Next, the configuration adopted in this embodiment and the principle thereof will be described in order to ensure the above-described operation. FIG. 4 shows an equivalent circuit diagram when the chip fuse 13 provided in the fuse circuit 12a of the injection valve drive circuit 4a is blown. Here, three capacitors 9, 10, 11 connected in parallel are shown side by side.

  When the energy due to the discharge of the capacitor is taken into consideration, a capacitance value C of the capacitor and an equivalent series resistance (ESR) Rc are assumed. In this case, the capacitances of the capacitors 9, 10, and 11 are C9, C10, and C11, the equivalent series resistances are R9, R10, and R11, and the resistance values are Rc9, Rc10, and Rc11. In general, in discharging a capacitor, when a capacitor is discharged, a time constant element is added by an equivalent series resistance, so that the current is reduced. The following verification takes these components into account.

  In the circuit of FIG. 4, the resistance value of the resistor 7 is R7, the resistance value of the chip fuse 13 is Rh, and the resistance value of the charging MOSFET 14a in which a short circuit failure has occurred is Rmos. The resistance value Rmos is assumed to be equal to the on-resistance as a maximum value. The resistance value of the discharge MOSFET 14b is Rmos because it is an on-resistance. Assume that a resistor R1 is interposed in series with the discharging MOSFET 14b, and the resistance value is R1.

FIG. 5 shows the fusing characteristics of the chip fuse 13. The horizontal axis represents the fusing time T (s), and the vertical axis represents the amount of current I ² t [A ² s] flowing through the chip fuse 13. A solid line Q indicates a boundary, and the upper X region is a region of “stress that melts even if applied once”. The area below the solid line Q is an area that does not melt, but in reality, the SA area below it shows the area of “stress that does not blow even if applied for 20 years” with the solid line R with the load factor lowered by 5% as a boundary. ing.

  Under normal operating conditions, the injection valve drive circuits 4a and 4b can be driven without the chip fuse 13 being blown under the operating conditions that fall into the SA region of "stress that does not blow even after 20 years". . Further, when an abnormal state such as a short circuit failure occurs, the chip fuse 13 can be surely blown if the operating condition is in the X region of “stress that melts even if applied once”.

  Under normal operating conditions, the injector drive circuits 4a and 4b drive the piezo injectors 3a and 3b with a pulsed drive signal for a plurality of injection nozzles, and further drive them alternately. The two chip fuses 13 are energized at time intervals. Thereby, in normal time, the piezo injectors 3a and 3b can be operated without the chip fuse 13 being blown.

  On the other hand, when a short-circuit failure occurs in the charging MOSFET 14a or the discharging MOSFET 14b, the two MOSFETs 14a and 14b are in the same state as when the MOSFETs 14a and 14b are turned on at the same time. . The situation at this time will be verified with reference to FIG. In this situation, it is necessary to surely blow the chip fuse 13 by discharging the electric charges of the capacitors 9, 10 and 11.

  Here, the minimum value of the current amount due to the discharge of the capacitors 9, 10, 11 is estimated. That is, if the chip fuse 13 can be blown even with the minimum amount of current due to discharge, it can be blown reliably even if there is a variation.

When the synthetic capacitor of the capacitors 9, 10, and 11 is C, the capacitance value C is
C = C9 + C10 + C11 (1)
It is. The amount of current that can be generated by the charge of the composite capacitor C can be expressed by the following equation (2).
1/2 × (Imax) ² × τ (2)

In the formula (2), the current Imax is (voltage V) / (resistance R), and the time τ is a time constant CR. From these, the expression (2) can be rewritten as the following expression (3).
1/2 × (Imax) ² × τ
= 1/2 × (V / R) ² × CR
= 1/2 × V ² / R × C (3)

  The amount of current required for fusing obtained by Equation (3) needs to be ensured even under the smallest conditions in consideration of variations in the composite capacitor C and each resistance. Therefore, in consideration of the upper and lower limits of variation, the capacitor terminal voltage V adopts the minimum value Vmin, the composite capacitor capacitance C adopts the minimum value Cmin, and the resistance value R of the resistance of the entire discharge circuit is the maximum value. Rmax is adopted. The amount of current thus obtained is a condition for reliably fusing.

Here, the voltage V in the above equation (3) is expressed as the following equation (4).
V = √ (2W / C) (4)
In the above formula (4), W = (charge amount before injection (1/2 CV ² ) −injection energy).
As can be seen from the above equation (3), the amount of current necessary for fusing the chip fuse 13 is such that the capacitance value C of the composite capacitor C is increased, the resistance value R is decreased, or both are satisfied. It can be improved by doing.

  In this embodiment, since the capacitors 10 and 11 are added in parallel in addition to the capacitor 9 of the conventional configuration, the amount of current can be increased by, for example, doubling the capacitance value. Further, as in this embodiment, the components of the equivalent series resistance R9 inherent in the capacitor 9 are configured to connect the capacitors 10 and 11 in parallel with the capacitor 9, so that the equivalent series resistances are connected in parallel. This contributes to reducing the equivalent series resistance as a whole. Therefore, connecting the capacitors 10 and 11 in parallel with the capacitor 9 has an effect of lowering the equivalent series resistance, and this can also increase the amount of current.

  According to the present embodiment, since the capacitors 10 and 11 are connected in parallel to the capacitor 9 of the booster circuit 2, the capacity can be increased as a whole. Since the equivalent series resistances 10 and 11 are connected in parallel, the combined equivalent series resistance can also be reduced. As a result, the amount of current flowing from the capacitors 9, 10, 11 to the chip fuse 13 of the fuse circuits 12 a, 12 b can be increased and can be surely blown. As a result, even when one MOSFET 14a or 14b of the injection valve drive circuits 4a and 4b has a short circuit failure, the circuit can be disconnected by the discharge current of the capacitors 9 to 11. As a result, it is possible to prevent a through current from flowing through the booster circuit 2 and prevent the common component from being destroyed.

  Further, since the chip fuse 13 is used in the fuse circuits 12a and 12b, the mechanical strength against the repeated stress caused by the thermal expansion and contraction of the fuse wire is increased because the voltage applied to the piezo injectors 3a and 3b is a pulse voltage. Reliability can be increased. Moreover, the insulation distance can be ensured by connecting the two chip fuses 13 in series.

  In the above configuration, the capacitors 10 and 11 are connected to the capacitor 9 in parallel, so that the total capacity is set to about twice the capacity of the capacitor 9. However, the capacitance values of a plurality of capacitors are combined. As a result, even if it is configured to have a capacity equivalent to that of the capacitor 9, the combined value of the equivalent series resistance at this time can be reduced, so that the amount of current can be increased.

(Other embodiments)
In addition, this invention is not limited only to one embodiment mentioned above, It can apply to various embodiment in the range which does not deviate from the summary, For example, it can deform | transform or expand as follows. .

  In the above-described embodiment, the case where two injection valve drive circuits are provided has been described. However, the present invention can be applied to a structure in which three or more piezo injectors are provided and three or more injection valve drive circuits are provided.

  In the above-described embodiment, the two chip fuses 13 are provided in series as the fuse circuits 12a and 12b. However, a single structure or three or more pieces may be provided in series. it can.

Although the case where the chip fuse 13 is used as the fuse element has been described, other fuse elements can also be used.
The capacitive load has been described in the case of using a piezo injector, but it can also be applied to those using other capacitive loads.

  Capacitors as capacitors include capacitors 9 in the booster circuit 2 and capacitors 10 and 11 corresponding to the injection valve drive circuits 4a and 4b. However, the present invention is not limited to this, and a larger number of capacitors are connected in parallel. It can also be set as the structure to do.

  In the drawings, 1 is an injection control circuit, 2 is a booster circuit, 3a and 3b are piezo injectors (capacitive load), 4a and 4b are injection valve drive circuits, 9, 10 and 11 are capacitors (capacitive elements), 12a and 12b. Is a fuse circuit, 13 is a chip fuse (fuse element), 14a is a charging MOSFET, and 14b is a discharging MOSFET.

Claims (4)

Drive control of a plurality of capacitive loads (3a, 3b) for driving the injection valve,
A booster circuit (2) that boosts the power supply voltage to a predetermined voltage and charges the capacitive elements (9, 10, 11) via the common component diode (8) ;
A resistor (7) provided in the booster circuit and connected in series with the capacitive element;
A plurality of injection valve drive circuits (4a, 4b) each provided with power supplied from the capacitive element to each of the plurality of capacitive loads and provided with a charging MOSFET (14a) and a discharging MOSFET (14b); ,
A plurality of fuse circuits (12a, 12b) provided in energization paths from the capacitive element to each of the plurality of injection valve drive circuits,
The capacitive control device has a discharge capability for fusing the fuse element (13) of the corresponding fuse circuit by discharging charged charge when an overcurrent flows through any of the plurality of injection valve drive circuits. . The injection control device according to claim 1,
The above-mentioned capacitive element is configured to have a discharge capability for fusing the fuse element by increasing the capacitance value by reducing the equivalent series resistance by connecting a plurality of capacitors (9, 10, 11) in parallel. Control device. In the injection control device according to claim 1 or 2,
The fuse circuit (12a, 12b) is an injection control device including a plurality of fuse elements (13) connected in series. In the injection control device according to any one of claims 1 to 3,
The said fuse element is an injection control apparatus which is a chip fuse (13).

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