JP7207196B2 - injector drive circuit - Google Patents

Description

The present invention relates to an injector drive circuit.

When a drive signal is given from the microcomputer, the injector drive circuit selects a corresponding injector by a cylinder selection transistor and performs drive control so as to perform injection at a predetermined opening for a specified time. I do. Specifically, the injector drive circuit is driven to a predetermined opening by first energizing a high-voltage power supply with a discharging transistor, and then a constant current is applied to maintain the opening by a constant-current transistor. energize.

In this case, when one of the injectors has a coil short failure, the injector drive circuit receives a drive signal from the microcomputer and starts energizing the failed injector. Since the current detection circuit detects the overcurrent state, the transistor for cylinder selection is immediately turned off accordingly.

At this time, the ON state of the constant current transistor continues as long as the drive signal remains high, so the potential of the INJ+ node, which is the positive terminal of the faulty injector, is fixed at the power supply voltage. Become. After that, when the driving signal becomes low level, the constant current transistor is turned off, and the potential of the INJ+ node is lowered.

However, in a malfunctioning injector, there is no flyback or return current caused by the coil component, unlike in normal operation, so the potential of the INJ+ node slows down according to the time constant of the resistance and capacitance components connected to the INJ+ node. decreases to

On the other hand, in the injector driving circuit, the potential of the INJ+ node is changed to a steady voltage (for example, 2.5V) in order to perform a detection operation such as a power supply short-circuit after the predetermined mask time and filter time have elapsed after the supply of electricity to the injector is stopped. 5V). However, if the potential drop of the INJ+ node is slow as described above, the potential may not settle down to a steady voltage within the predetermined mask time and filter time.

Therefore, the injector drive circuit may erroneously detect a power supply short-circuit state because the potential of the INJ+ node has not decreased after the mask time and filter time have elapsed. However, the power supply short detection is treated as a common failure, so even though only one cylinder has a coil short, the injectors of other cylinders driven by the common circuit are also judged to have a failure. There is a problem. As a result, other injectors that are not malfunctioning cannot be used either.

However, in order to avoid this, it is conceivable to set the mask time and the filter time longer, for example, so that the power supply short detection is performed in a state where the potential of the INJ+ node is lowered. However, in this case, the longer interval makes it impossible to carry out multi-stage/proximity injection.

Also, in order to speed up the potential convergence of the INJ+ node, it is possible to reduce the resistance component and the capacitance component connected to the INJ+ node. This imposes significant restrictions on characteristics such as the energization duration, and the trade-off relationship is severe, making it not an effective measure.

Japanese Patent No. 3825235

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an injector driving circuit capable of quickly lowering the potential of the positive terminal of the injector.

The injector drive circuit according to claim 1 is an injector drive circuit that selects a plurality of injectors with a selection switch and controls driving by energizing with an energization switch, wherein the control circuit drives and controls the selection switch and the energization switch. (21), an overcurrent detection circuit (27) that outputs a detection signal when an overcurrent flows through the energized injectors (27), and is connected to one of terminals connected to the plurality of injectors. and a charge extraction circuit (35, 40, 50, 60, 70, 80, 90) for extracting the charge from the connected terminal.

By adopting the above configuration, when the drive signal is applied, the control circuit turns on the selection switch and the energization switch to energize the selected injector among the plurality of injectors. As a result, a predetermined current flows through the injector and normal operation is performed.

When a short-circuited injector occurs among the plurality of injectors, the control circuit receives a drive signal to energize the short-circuited injector, and the overcurrent detection circuit outputs a detection signal. As a result, the control circuit turns off the selection switch to stop the supply of electricity to the short-circuited injector.

In this case, the control circuit keeps the energizing switch in the ON state while the drive signal is being applied, so voltage is applied to the positive terminal of the injector. After that, when the drive signal is turned off, the control circuit turns off the energization switch, but since the selection switch was turned off first, a voltage was applied to the positive terminal of the injector by the capacitive component provided in the circuit. condition continues.

At this time, when the energization switch is turned off, the control circuit drives the charge extracting circuit to extract the charge from the positive electrode terminal of the injector, thereby quickly returning it to the level of the off state. As a result, when an injector has a short-circuit failure, only the failed injector can be accurately detected, and by stopping the corresponding injector, only that cylinder can be stopped.

Electrical configuration diagram showing the first embodiment Time chart 1 Time chart 2 Electrical configuration diagram showing the second embodiment Electrical configuration diagram showing the third embodiment Electrical configuration diagram showing the fourth embodiment Electrical configuration diagram showing the fifth embodiment Electrical configuration diagram showing the sixth embodiment Electrical configuration diagram of logic circuit Electrical configuration diagram showing the seventh embodiment

(First embodiment)
A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. In addition, in this embodiment, a plurality of injectors are provided corresponding to each cylinder of the engine. Of the plurality of injectors, two injectors 1 and 2 will be illustrated and explained, but a configuration in which more injectors are connected is also applicable.

In FIG. 1 showing the overall electrical configuration, two injectors 1 and 2 are inductive and each drive a fuel injection valve to inject fuel into each cylinder of the engine. The injectors 1 and 2 are energized by an energizing circuit, and the energizing circuit is driven and controlled by an injector drive circuit 20 .

Positive terminals INJ+ of injectors 1 and 2 are commonly connected to a high voltage power supply VH via a discharge MOS transistor (hereinafter simply referred to as a discharge MOS) 5 as an energization switch. A negative terminal INJ- of the injector 1 is connected to ground through a cylinder selection MOS transistor (hereinafter simply referred to as selection MOS) 3 as a selection switch and a current detection resistor 6 . A negative terminal INJ- of the injector 2 is connected to the ground via a selection MOS transistor 4 and a current detection resistor 6. FIG.

The positive terminal INJ+ is connected to the DC power supply VD through a backflow prevention diode 8 in the reverse direction and through a constant current MOS transistor (hereinafter simply referred to as a constant current MOS) 7 as an energization switch. A freewheeling diode 9 is forwardly connected to the positive terminal INJ+ from the ground. A resistor 10 and a capacitor 11 are connected in parallel with the freewheeling diode 9 .

The injector drive circuit 20 has terminals A to I, and is mainly composed of a control circuit 21 as follows. Drivers 22 and 23 are connected to the gates of selection MOSs 3 and 4 via terminals A and B, respectively, and receive cylinder selection signals Ss1 and Ss2 from control circuit 21 to corresponding ones to output gate drive signals.

The driver 24 has an output terminal connected to the gate of the discharge MOS 5 via a terminal C, and positive and negative power supply terminals connected to terminals D and E, respectively. An external bootstrap capacitor 12 is connected between the terminals DE. Terminal E is also connected to the drain of discharge MOS 5 and takes in the voltage of positive terminal INJ+ of injectors 1 and 2 as Vinj. The driver 24 gives a gate drive voltage to the discharge MOS 5 when a drive signal is given from the control circuit 21 .

The driver 25 has an output terminal connected to the gate of the constant current MOS 7 via a terminal F, and positive and negative power supply terminals connected to terminals G and H, respectively. A bootstrap capacitor 13 is externally connected between the terminals GH. The terminal H is also connected to the drain of the constant current MOS7. The driver 25 gives a gate drive voltage to the discharge MOS 5 when a drive signal is given from the control circuit 21 .

Both the current detection circuit 26 and the overcurrent detection circuit 27 have non-inverting input terminals connected between the terminals I and J, and take in the terminal voltage of the current detection resistor 6 connected between the terminals I and J. A reference voltage Vref1 is input to the inverting input terminal of the current detection circuit 26 . The reference voltage Vref1 can be changed and set by the control circuit 21, and the current detection level can be changed. A reference voltage Verf<b>2 is input to the inverting input terminal of the overcurrent detection circuit 27 . The reference voltage Vref2 is set to the overcurrent detection level.

Current detection circuit 26 and overcurrent detection circuit 27 output a high-level detection signal to control circuit 21 when voltage drops caused by currents Iinj1 and Iinj2 flowing through current detection resistor 6 exceed reference voltage Vref1 or Vref2, respectively. . Based on the high-level detection signal from the current detection circuit 26, the control circuit 21 determines that a current of a predetermined level or more is flowing through the injector 1 or 2 that is energized. Further, the control circuit 21 determines from the high-level detection signal from the overcurrent detection circuit 27 that an overcurrent is flowing through the energized injector 1 or 2 .

The terminal E is connected to a circuit that applies a predetermined potential for diagnosis and detects the potential of the positive terminal INJ+ when the injectors 1 and 2 are not energized. A series circuit of a P-channel MOS transistor 28, a diode 29 and resistors 30 and 31 is connected between a DC power supply VB and the ground. A common connection point between the diode 29 and the resistor 30 is connected to the terminal E. The differential amplifier 32 has an inverting input terminal connected to a common connection point between the resistors 30 and 31, and a non-inverting input terminal to which the reference voltage Vref3 is input.

The differential amplifier 32 drives the MOS transistor 28 to apply a constant voltage to the terminal E, ie, the positive terminals INJ+ of the injectors 1 and 2, in a non-energized state. The injectors 1 and 2 are set to a voltage so low that they do not operate, and if this voltage is detected, the positive terminal INJ+ is in a normal state.

A comparator 33 for power supply short detection detects a power short circuit from the voltage of the positive terminal INJ+ of the injectors 1 and 2. The common connection point of the resistors 30 and 31 is connected to the inverting input terminal, and the power short detection is detected to the non-inverting input terminal. A reference voltage Vref4 for is input. A ground short detection comparator 34 for detecting a ground short from the voltage of the positive terminals INJ+ of the injectors 1 and 2 has an inverting input terminal connected to a common connection point between the resistors 30 and 31, and a non-inverting input terminal connected to the ground. A reference voltage Vref5 for short detection is input.

As described above, when the voltage at the terminal E becomes abnormally high or becomes zero while a constant voltage is applied to the terminal E by the MOS transistor 28, the comparator 33 or 34 detects this state. is detected, a detection signal is input to the control circuit 21, and an abnormal state is determined.

Further, the positive terminals INJ+ of the injectors 1 and 2 are connected to a charge extracting circuit 35 for extracting charges in the event of a failure. The charge extraction circuit 35 has a configuration in which a series circuit of a switch 37 and a constant current source 38 is connected between the positive terminal INJ+ and the ground. The switch 37 is configured using, for example, a MOS transistor or the like, and is provided so as to be turned on when a high level signal is given from the AND circuit 36 .

One input terminal of the AND circuit 36 is connected to the output terminal of the overcurrent detection circuit 27, and the other input terminal receives the inverted drive signal Sd. Therefore, the AND circuit 36 turns on the switch 37 when the driving signal Sd is in the low level off state and the overcurrent detection signal is in the high level.

Next, the operation of the above configuration will be described with reference to FIGS. 2 and 3 as well. FIG. 2 is a timing chart corresponding to normal operation in which short-circuit failure does not occur in injector 1 or 2, and FIG. 3 is a timing chart when short-circuit failure occurs.

First, normal energization operation will be described. In the control circuit 21 of the injector driving circuit 20, when the injector 1 or 2 is not energized, the MOS transistor 28 is driven by the differential amplifier 32 to connect the positive terminals INJ+ of the injectors 1 and 2 to the injector current. A predetermined voltage for diagnosis is applied to such an extent that it does not operate as a In this state, if an abnormality such as a power short circuit or ground short circuit occurs, the comparator 33 or 34 detects it.

At time t0, when a drive signal Sd is given from a microcomputer (not shown), the control circuit 21 outputs a selection signal Ss1 to the driver 22 corresponding to, for example, the injector 1 to be energized, and the driver 22 applies the gate voltage Vgs to the selection MOS3. give. Also, at this time, the control circuit 21 outputs a drive signal to the driver 24 to drive the discharge MOS 5 .

As a result, the discharge MOS 5 is turned on, the high voltage VH is applied to the positive terminal INJ+ of the injector 1, and the injector current Iinj begins to flow. The injector 1 drives the valve to a predetermined degree of opening, and fuel injection into the cylinder is started. The control circuit 21 turns off the discharge MOS 5 after energizing the discharge MOS 5 for a predetermined time. At this time, a flyback voltage is generated in the injector 1 due to the cutoff of the current from the high voltage VH, and the injector current Iinj does not immediately become zero, and the current continues from the ground through the free wheel diode 9. gradually decreases.

Subsequently, the control circuit 21 outputs a drive signal to the driver 25 to intermittently turn on and off the constant current MOS 7 to apply the DC voltage VD to the injector 1 . At this time, when the constant current MOS 7 is turned off, the flyback voltage is generated in the same manner as described above, causing the injector 1 to gradually decrease in return current. be done. As a result, the injector 1 is in a state in which the opening degree of the valve is maintained.

After that, when the driving signal Sd is turned off at time t1, the control circuit 21 turns off the selection MOS 3 and waits until the next driving signal Sd is applied. Also, when the injector 1 is de-energized, a flyback voltage is generated and a return current flows, so the injector current Iinj gradually decreases.

Also, the potential of the positive terminal INJ+ of the injector 1 abruptly changes to the negative side due to the flyback voltage. After that, when the return current from the injector 1 disappears, the MOS transistor 28 is driven by the differential amplifier 32, and a predetermined voltage for diagnosis is applied to the positive terminal INJ+.

In FIG. 2, of the positive electrode terminal voltage Vinj, during the time tb from time ta at which the constant current MOS 7 is energized before time t1 to time t1 until the voltage Vinj of the positive electrode terminal INJ+ reaches a predetermined voltage. A separate time chart at the bottom shows the details of the transition of .

When the final energization by the constant current MOS 7 is completed, the voltage Vinj is abruptly lowered to zero level by the action of the flyback voltage, and thereafter, by the energization by the MOS transistor 28, it gradually rises to a predetermined voltage from time t1 to t2. ing. In this case, the predetermined voltage is set to a low level voltage of about 2.5V, for example.

The period from time t1 to t2 is set as mask time Tm until the voltage settles down, and the time from time t2 to time t3 after a certain period of time has passed is set as filter time Tf. It should be noted that the mask time Tm and the filter time Tf can be combined as the mask time. After the mask time Tm and filter time Tf have passed, the voltage of the positive terminal INJ+ is stabilized, and the power short circuit or ground short circuit diagnosis operation is performed at the timing after this.

Next, with reference to FIG. 3, the operation when the drive signal Sd is input to the control circuit 21 when one of the injectors 1 and 2 is short-circuited will be described. Here, it is assumed that the injector 1 is short-circuited, for example. That is, the injector 1 is in a state where the resistance is zero and the inductor is also zero.

In this situation, when the drive signal Sd is applied at time t10, the control circuit 21 turns on the selection MOS3 and turns on the discharge MOS5 in the same manner as described above. As a result, the high voltage VH is applied to the positive terminal INJ+ of the injector 1, and the injector current Iinj begins to flow.

However, in this case, since the injector 1 has a short-circuit failure, the injector current Iinj abruptly exceeds the predetermined current Im. The injector current Iinj also increases when the constant current MOS7 is turned on after the discharge MOS5 is turned off at time t11. At time t12, when injector current Iinj exceeds threshold current Ith for determining overcurrent, overcurrent detection circuit 27 detects this and outputs overcurrent detection signal Sx to control circuit 21. FIG.

When receiving the overcurrent detection signal Sx, the control circuit 21 determines that the injector 1 is short-circuited, and turns off the selection MOS 3 at time t13. In addition, the control circuit 21 turns off the selection MOS 3, but the constant current MOS 7 maintains the ON/OFF control state when the drive signal Sd is applied. It is in a state in which it is effectively applied.

As a result, the injector current Iinj becomes zero because there is no conduction path. However, since the injector 1 is short-circuited, no flyback voltage is generated, so the voltage Vinj at the positive terminal INJ+ does not invert to negative. , the state in which the DC voltage VD is applied continues.

As a result, the positive electrode terminal INJ+ is in a state in which the electric charge charged in the capacitor 11 is accumulated, so that the DC voltage VD is held. Here, the charge of the capacitor 11 is gradually discharged via the resistor 10, but is also charged when the DC voltage VD is intermittently applied. Therefore, the terminal voltage of the capacitor 11 is maintained at the voltage VD with almost no drop.

After that, when the drive signal Sd is turned off at time t14, the constant current MOS 7 is turned off by the control circuit 21, so that the potential of the positive terminal INJ+ is changed from the charge of the capacitor 11 to the discharge through the resistor 10. As a result, it will gradually decrease.

Here, the time constant of the discharge by the resistor 10 and the capacitor 11 is generally set to a relatively large value based on the design data required for energizing the injectors 1 and 2. Therefore, the terminal voltage of the capacitor 11 is It takes a predetermined time to drop. If this time is lengthened, the mask time Tm and the filter time Tf after the drive signal Sd is turned off are shortened, for example, as indicated by the dashed line in FIG. There are cases where the potential of the positive terminal INJ+ does not drop below the predetermined level even after the time has elapsed.

In the present embodiment, in response to such a situation, when the overcurrent detection signal Sx is input, the control circuit 21 drives the charge extraction circuit 37 so that the charge of the capacitor 11 can be extracted. It is configured.

That is, when the overcurrent detection circuit 27 outputs the high-level detection signal Sx, the AND circuit 36 outputs a high-level signal in response to the low-level drive signal Sd. switch 37 is turned on. When the switch 37 is turned on, the charge in the capacitor 11 is drawn out by the constant current circuit 38 from the positive terminal INJ+ through the terminal E, and the level of the capacitor 11 rapidly decreases.

As a result, the voltage Vinj of the positive terminal INJ+ reaches a predetermined level Vth or less by time t15 when the mask time Tm elapses, and finally can be lowered to zero volts at time t16. In this state, it becomes possible to reliably detect other failure states and drive the injectors 2 that are not in the short-circuited state at time t17 when the next injector is driven.

In the above description, the injector 1 is short-circuited, but the same operation can be performed when the injector 2 is short-circuited.

According to the first embodiment as described above, since the electric charge extracting circuit 35 is provided in response to the short failure of the injector 1 or 2, the control circuit 21 receives the driving signal Sd and energizes the injector 1 or 2. Sometimes, in the case of a short-circuit failure, the voltage Vinj of the positive terminal INJ+ can be quickly pulled out by the charge extraction circuit 35 to be reduced to a low potential after the energization is turned off.

Thus, regardless of the time constants of the resistor 10 and the capacitor 11 connected to the positive terminal INJ+, when the mask time Tm and the filter time Tf have elapsed, the detection operation can be reliably performed without erroneous detection, and It can be used without any restrictions such as lengthening the time until the next injector is driven.

In other words, by accelerating the potential drop of the positive terminal INJ+, it is not necessary to take a long time when the injector 1 or 2 is shorted, and the mask time Tm and filter time Tf for diagnosis can be set short. . As a result, it is possible to accurately determine the malfunctioning cylinder even when the proximity injection is performed.

In the above embodiment, the overcurrent detection circuit 27 detects an overcurrent and inputs the detection signal Sx to the control circuit 21. However, the voltage across the current detection resistor 6 is taken into the control circuit 21, The current value may be converted to a digital value inside the control circuit 21 and detected internally to detect an overcurrent.

(Second embodiment)
FIG. 4 shows a second embodiment, and portions different from the first embodiment will be described below. In this embodiment, the injector drive circuit 20 a is configured to have a charge extraction circuit 40 instead of the charge extraction circuit 35 . In FIG. 4, the electric charge extraction circuit 40 has a configuration in which a resistor 41 is provided in place of the constant current circuit 38 .

According to the second embodiment, similarly to the first embodiment, the voltage Vinj of the positive terminal INJ+ is reduced by the charge extracting circuit 40 after the constant current MOS 7 is turned off in response to a short-circuit failure of the injector 1 or 2. Through switch 37 and resistor 41, the charge can be rapidly drawn to a low potential.

(Third embodiment)
FIG. 5 shows a third embodiment, and portions different from the first embodiment will be described below. In this embodiment, the injector driving circuit 20b is configured to have a charge extraction circuit 50 instead of the charge extraction circuit 35. As shown in FIG. In FIG. 5, the electric charge extraction circuit 50 is provided with a differential amplifier 51 and a reference power source 52 instead of the switch 37 and the constant current circuit 38 .

According to the third embodiment, similarly to the first embodiment, the voltage Vinj of the positive terminal INJ+ is reduced by the charge extracting circuit 50 after the constant current MOS 7 is turned off in response to the short-circuit failure of the injector 1 or 2. By the operation of the differential amplifier 51, the charge can be quickly drawn out at a constant voltage and the potential can be lowered.

(Fourth embodiment)
FIG. 6 shows a fourth embodiment, and portions different from the first embodiment will be described below. In this embodiment, the injector driving circuit 20c is provided with a charge extraction circuit 60 in place of the charge extraction circuit 35, and a comparator 39 is newly provided.

In FIG. 6, the electric charge extracting circuit 60 is provided with a 3-input AND circuit 61 in place of the AND circuit 36 . In addition to the overcurrent detection signal Sx and the drive signal Sd, the AND circuit 36 is configured to receive the electric charge extraction stop signal Sy.

A charge drawing stop comparator 39 for detecting that the voltage of the positive terminal INJ+ of the injectors 1 and 2 has dropped to the charge drawing stop level has a non-inverting input terminal connected to a common connection point between the resistors 30 and 31, A reference voltage Vref6 for detecting stoppage of charge extraction is input to the inverting input terminal. When the potential of the positive terminal INJ+ is high, the comparator 39 is at high level, and when the potential of the positive terminal INJ+ becomes lower than the reference voltage Vref6, the comparator 39 outputs a low level charge extraction stop signal Sy.

With the configuration as described above, the charge extracting circuit 60, when the overcurrent detection circuit 27 outputs a high-level detection signal Sx and the comparator 39 outputs a high-level signal, the AND circuit 61: When the driving signal Sd becomes low level, a high level signal is output, thereby turning on the switch 37 . When the switch 37 is turned on, the charge in the capacitor 11 is drawn out by the constant current circuit 38 from the positive terminal INJ+ through the terminal E, and the level of the capacitor 11 rapidly decreases.

Then, when the charge extraction progresses and the potential of the positive terminal INJ+ drops and the comparator 39 outputs a low level charge extraction stop signal Sy, the AND circuit 61 inverts the output to low level and turns off the switch 37 . As a result, the charge extraction operation is stopped.

According to the fourth embodiment, in addition to the effects of the first embodiment, the operation of the charge extraction circuit 60 can be stopped by setting the reference voltage Vref6 near zero volts. Power consumption can be reduced.

(Fifth embodiment)
FIG. 7 shows a fifth embodiment, and portions different from the first embodiment will be described below. In this embodiment, the injector drive circuit 20 d is configured to have a charge extraction circuit 70 instead of the charge extraction circuit 35 .

In FIG. 7, the charge extraction circuit 70 does not extract the charge from the positive terminal INJ+ side of the injectors 1 and 2, but from the negative terminal INJ-1 or INJ-2 side of the injector 1 or 2 in the ground short state. This is a configuration for extracting electric charges.

That is, a circuit for extracting charges from the negative terminal INJ-1 of the injector 1 and a circuit for extracting charges from the negative terminal INJ-2 of the injector 2 are configured in the same manner as the charge extracting circuit . Specifically, an AND circuit 71 , a switch 72 and a constant current circuit 73 are provided, and an AND circuit 74 , a switch 75 and a constant current circuit 76 are provided.

Moreover, the AND circuits 71 and 74 are configured such that the overcurrent detection signal Sx is inputted to one input terminal thereof. Further, the other input terminals of the AND circuits 71 and 74 are configured such that the drive signal Sd1 for the injector 1 and the drive signal Sd2 for the injector 2 are respectively inverted and inputted.

In the above configuration, it is assumed that the injector 1 is in a ground short state, for example, and the drive signal Sd1 for the injector 1 is output from the control circuit 21. A description will be given. In order to drive the injector 1, the control circuit 21 supplies the selection signal Ss1 to drive the selection MOS3 and supplies the drive signal Sd1 to turn on the discharge MOS5.

As a result, when a high voltage VH is applied to the positive terminal INJ+ of the injector 1, the injector current Iinj increases to the overcurrent level because the injector 1 is short-circuited, and the overcurrent detection circuit 27 detects overcurrent. A signal Sx is output to the control circuit 21 . The control circuit 21 turns off the selection MOS 3 according to the input of the overcurrent detection signal Sx.

When the overcurrent detection circuit 27 outputs the high-level detection signal Sx, the AND circuit 71 turns the drive signal Sd1 to low level, and the switch 72 is turned on. When the switch 72 is turned on, the charge in the capacitor 11 is drawn out at a constant current from the negative terminal INJ-1 of the injector 1 through the terminal K by the constant current circuit 73, so that the charge can be quickly reduced to near zero volts. become.

In the above description, the case where the injector 1 is short-circuited has been described, but even when the injector 2 is short-circuited, the AND circuit 74 operates by the detection signal Sx and the drive signal Sd2 in the same manner as described above. , and the constant current circuit 76 can extract the charge from the negative terminal INJ-2 side of the injector 2 .
Therefore, the same effects as those of the first embodiment can be obtained by the fifth embodiment as well.

(Sixth embodiment)
FIGS. 8 and 9 show a sixth embodiment, and the differences from the first embodiment will be explained below. In this embodiment, the injector drive circuit 20 e is configured to have a charge extraction circuit 80 instead of the charge extraction circuit 35 .

In FIG. 8, the charge extraction circuit 80 is provided with a logic circuit 81 instead of the AND circuit 36. In the logic circuit 81, drive signals Sd1 and Sd2 of the injectors 1 and 2 are input, and the detection signal Sx is Instead, the selection signals Ss1 and Ss2 are input.

As shown in FIG. 9, the logic circuit 81 of the charge extraction circuit 80 is provided corresponding to the injector 1 with an AND circuit 81a, a delay buffer 81b, a D flip-flop 81c, and an exclusive OR 81d. Similarly, a circuit composed of an AND circuit 81e, a delay buffer 81f, a D flip-flop 81g, and an exclusive OR 81h is provided corresponding to the injector 2. FIG. The outputs of the two circuits are input to an OR circuit 81i, which outputs an instruction signal for charge extraction to the switch 37 from the output terminal So.

In this embodiment, the overcurrent detection signal Sx output by the overcurrent detection circuit 27 is not used. A low-level selection signal Ss1 or Ss2 for turning off the selection MOS 3 or 4 is output to stop energization. Therefore, in the charge extraction circuit 80, the low-level selection signal Ss1 or Ss2 can be used as a signal output under substantially the same conditions as the detection signal Sx.

In the above configuration, assuming that the injector 1 is short-circuited to ground, for example, and the injector 1 is driven by the control circuit 21, the injector current Iinj increases to the overcurrent level. When the overcurrent detection signal Sx is output from the overcurrent detection circuit 27, the control circuit 21 outputs a low-level selection signal Ss1 for turning off the selection MOS 3 according to the input of the overcurrent detection signal Sx.

As a result, the charge extraction circuit 80 outputs a signal for driving the switch 37 to ON when the low-level selection signal Ss1 is input to the logic circuit 81 . When the switch 37 is turned on, the charge of the capacitor 11 is drawn out from the positive terminal INJ+ by the constant current circuit 38 at a constant current, and the charge can be quickly lowered to near zero volts.

In the above explanation, the case where the injector 1 is short-circuited has been explained, but even when the injector 2 is short-circuited, the logic circuit Since a signal for turning on the switch 37 is output from 81, electric charge can be extracted from the positive terminal INJ+ by the constant current circuit .

Therefore, even in such a sixth embodiment, the same effect as in the first embodiment can be obtained. Further, according to the present embodiment, the selection signals Ss1 and Ss2 can be used as signals other than the detection signal of the overcurrent detection circuit 27 to trigger extraction of electric charges. In other words, it is also possible to adopt a configuration in which the control circuit 21 outputs the selection signals Ss1 and Ss2 based on the detection signal Sx and does not use the detection signal Sx of the overcurrent detection circuit 27 .

(Seventh embodiment)
FIG. 10 shows a seventh embodiment, and the parts different from the first embodiment will be explained below. In this embodiment, the injector drive circuit 20f is configured to have a charge extraction circuit 90 instead of the charge extraction circuit 35. FIG. In FIG. 10, a charge extracting circuit 90 has an n-channel MOS transistor 91 instead of the switch 37 and the constant current circuit 38 .

According to the seventh embodiment, similarly to the first embodiment, the voltage Vinj of the positive terminal INJ+ is reduced by the charge extracting circuit 90 after the constant current MOS 7 is turned off in response to a short failure of the injector 1 or 2. , the charge can be rapidly drawn out via the MOS transistor 91 to bring it to a low potential.

In this case, electric charges are extracted only through the on-resistance of the MOS transistor 91, so the potential of the positive terminal INJ+ can be lowered more quickly than in the first or second embodiment.
(Other embodiments)

The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the scope of the invention. For example, the following modifications or extensions can be made.

The fourth embodiment shows the case where the charge extraction circuit 60 and the charge extraction stop circuit 39 using the configuration of the charge extraction circuit 35 of the first embodiment are provided, but it can also be applied to other embodiments.

In the fifth embodiment, the configuration of the charge extraction circuit 35 of the first embodiment is provided as the charge extraction circuit 70, but the charge extraction circuits 40, 50, 60, 80, and 90 shown in the other embodiments are used. can also be applied.

Although the present disclosure has been described with reference to examples, it is understood that the present disclosure is not limited to such examples or structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and configurations, as well as other combinations and configurations, including single elements, more, or less, are within the scope and spirit of this disclosure.

In the drawings, 1 and 2 are injectors, 3 and 4 are selection MOS transistors (selection switches), 5 is a discharge MOS transistor (energization switch), 6 is a current detection resistor, 7 is a constant current MOS transistor (energization switch), and 9 is 10 is a resistor; 11 is a capacitor; 20, 20a, 20b, 20c, 20d, 20e, and 20f are injector drive circuits; 21 is a control circuit; , 39 is a comparator, 35, 40, 50, 60, 70, 80 and 90 are charge drawing circuits, 36 and 61 are AND circuits, 37 is a switch, 38 is a constant current circuit, 41 is a resistor, and 51 is a differential amplifier. be.

Claims (9)

An injector drive circuit that selects a plurality of injectors with a selection switch and controls driving by energizing with an energization switch,
a control circuit (21) for driving and controlling the selection switch and the energization switch;
an overcurrent detection circuit (27) for outputting a detection signal when an overcurrent flows through the energized injectors;
an injector drive circuit (35, 40, 50, 60, 70, 80, 90) connected to one of the terminals connected to the plurality of injectors and extracting electric charge from the connected terminal. 2. The charge drawing circuit according to claim 1, wherein when a short circuit fault in one of the plurality of injectors is detected from the current detected by the overcurrent detection circuit, the charge drawing circuit draws the charge from one terminal side of the short-circuited injector. injector drive circuit. a stop detection circuit (39) for detecting a stop voltage during the charge extraction operation by the charge extraction circuit;
3. The injector drive circuit according to claim 1, wherein the charge extraction circuit (60) stops the charge extraction operation when the stop detection circuit detects a stop voltage. 4. An injector drive circuit as claimed in any preceding claim, wherein the charge extraction circuit (35, 40, 50, 60, 80, 90) is connected to a common positive terminal of the plurality of injectors. The injector drive circuit according to any one of claims 1 to 3, wherein the charge extraction circuit (70) is connected to negative terminals of the plurality of injectors. 6. The charge extraction circuit (80) according to any one of claims 1 to 5, wherein the charge extraction circuit (80) extracts the charge based on a signal for turning on the energization switch and a signal for turning off the selection switch by the control circuit. Injector drive circuit. 7. An injector drive circuit according to any one of the preceding claims, wherein the charge extraction circuit (35, 60, 70, 80) performs charge extraction with constant current. 7. An injector drive circuit as claimed in any preceding claim, wherein the charge extraction circuit (40) implements charge extraction via a resistor. The injector drive circuit according to any one of claims 1 to 6, wherein the charge extraction circuit (50) performs charge extraction at a constant voltage.

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