JP2012026359A - Fuel pump control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pump control device, capable of performing the adequate control according to the cause of an overcurrent by determining the cause of the overcurrent when generating the overcurrent in a driving circuit of a motor M1.SOLUTION: When a load current becomes the overcurrent and exceeds the lock determination threshold, the motor M1 is once turned off, and then, the state determination processing is executed for the ON period, in which the motor M1 is turned on, and the OFF period, in which the motor M1 is turned off. Then, based on the VIS signal and VMS signal in the OFF period and the VIS signal and VMS signal in the ON period, it is determined whether the cause of occurrence of the overcurrent is attributable to the lock failure of the motor M1 or is attributable to a short circuit failure. If the lock failure is determined, any foreign matters are removed by intermittently driving the motor M1. If the short circuit failure is determined, an FET (T1) is shut off, and the motor M1 is stopped. Thus, an adequate countermeasure can be taken according to the cause of the overcurrent, and the reliability of the control of a fuel pump can be enhanced.

Description

  The present invention relates to a control device that controls a fuel pump mounted on a vehicle or the like, and more particularly to a technique for detecting an abnormality in a drive motor and performing appropriate control.

  For example, a motor for driving a fuel pump mounted on a vehicle is connected to a DC power source via a semiconductor switch such as a MOSFET and is controlled to rotate at a desired speed by PWM control of the semiconductor switch. . In addition, foreign matter may be clogged in the fuel pump or fuel piping. In this case, the fuel pump locks and the fuel supply stops, causing trouble. The semiconductor switch is intermittently operated (repeatedly conducting and stopping repeatedly). The method of avoiding the lock of the fuel pump by being driven in the operation) is adopted. That is, when the current flowing through the motor for driving the fuel pump becomes an overcurrent, the semiconductor switch is intermittently fully conducted to add vibration to the foreign matter to remove the clogging of the foreign matter (for example, Patent Documents). 1).

JP-A-5-332215

  However, in the conventional fuel pump control device, when an overcurrent is detected, the semiconductor switch is fully turned on. Therefore, when the cause of the overcurrent is a fuel pump lock, clogging of foreign matters can be removed. In the case of an overcurrent due to a short circuit accident or the like, an unnecessary current continues to flow through the semiconductor switch. Therefore, by installing a temperature sensor and measuring the temperature of the semiconductor switch, overheating of the semiconductor switch and the electric wire is prevented. For this reason, there exists a fault that an apparatus structure becomes large and the cost becomes high.

  The present invention has been made to solve such a conventional problem, and the object of the present invention is to determine the cause of an overcurrent when an overcurrent occurs in a motor drive circuit, and An object of the present invention is to provide a fuel pump control device capable of appropriate control according to the cause.

  In order to achieve the above object, the invention according to claim 1 of the present application is a fuel pump control device for controlling a motor for driving a fuel pump using a semiconductor switch, and a current detecting means for detecting a load current flowing through the motor. When the overcurrent (for example, lock determination current) is detected by the current detection means, the semiconductor switch (T1) is turned off, and then the semiconductor switch is turned on, and the semiconductor switch is turned off. Based on the voltage between the terminals of the motor (for example, VMS signal) and the load current (for example, VIS signal) in the off period, the cause of the overcurrent is With a state determination unit (for example, the state determination unit 12) that determines whether it is due to a lock failure or a short-circuit failure, and the state determination unit, When it is determined that the cause of the current is a lock failure, the semiconductor switch is controlled to intermittently drive the motor, and when the cause of the overcurrent is determined to be a short-circuit failure, the semiconductor And a control means (for example, the output control unit 11) for performing control to shut off the switch.

  According to a second aspect of the present invention, the state determination unit is configured such that the voltage between the terminals in the off period is less than a preset first threshold (for example, a threshold set between GND and VB) and the load. When the current is less than a preset second threshold value (for example, a threshold value set by the voltage V1), it is determined that the cause of the overcurrent is a lock failure, and the control means is determined to be a lock failure. In this case, the semiconductor switch is intermittently driven after the off period.

  According to a third aspect of the present invention, when the load current is equal to or higher than a preset third threshold value (for example, a threshold value set by the voltage V3), the control means always supplies the load current to the first threshold value. The logic switch is fixed to “Logic_H” which is equal to or greater than two thresholds, and the semiconductor switch is PWM-controlled during the on period, and the state determination unit is configured such that the voltage between the terminals during the off period is less than the first threshold value. When the load current is greater than or equal to the second threshold value, it is determined that a short circuit failure has occurred, and when the control means determines that a short circuit failure has occurred, the control means shuts off the semiconductor switch after the off period. And

  According to a fourth aspect of the present invention, the state determination means is based on the voltage between the terminals in the off period and the load current, and causes the overcurrent in addition to the lock failure and the short-circuit failure. The control means drives the semiconductor switch with a full duty when it is determined that the cause of the overcurrent is an overvoltage.

  In the fuel pump control device according to the present invention, when the load current becomes an overcurrent, the semiconductor switch is once shut off, and then the on period and the off period are set. Among these, the load current in the off period, and Based on the state of the voltage between the terminals of the motor, it is determined whether the cause of the overcurrent is a lock failure or a short-circuit failure. Based on the determination result, the motor is intermittently driven when the cause of the overcurrent is a lock failure, and the semiconductor switch is cut off when the cause is an overcurrent. Therefore, it is possible to take an appropriate measure according to the cause of the overcurrent and improve the reliability of the fuel pump control.

It is a circuit diagram which shows the structure of the fuel pump control apparatus which concerns on one Embodiment of this invention. It is a circuit diagram which shows the detailed structure of the output control part provided in the fuel pump control apparatus which concerns on one Embodiment of this invention. 6 is a timing chart showing changes in signals when an overcurrent caused by a motor lock failure flows in the fuel pump control device according to the embodiment of the present invention. It is a timing chart which shows change of each signal when overcurrent resulting from a short circuit failure flows in a fuel pump control device concerning one embodiment of the present invention. It is explanatory drawing which shows the state determination corresponding table set to the state determination part of the fuel pump control apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the correspondence of the determination result of abnormality cause, fail safe control, and return conditions in the fuel pump control apparatus which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a fuel pump control apparatus according to an embodiment of the present invention. As shown in FIG. 1, this fuel pump control device 100 is mainly connected to an output control unit 11, a state determination unit 12, a fail safe control unit 13, an on / off control unit 14, and each other in series. Two FETs (T1; semiconductor switch) and (T2) are provided. Further, the fuel pump control device 100 is connected to the engine control unit 21.

  Of the two FETs, the FET (T1) is a P-type MOSFET and the FET (T2) is an N-type MOSFET, and these connection points are connected to one end of a motor M1 for driving the fuel pump. The other end is grounded. Further, one end of the FET (T1) is connected to a plus terminal of a DC power source VB (the output voltage is also indicated by the same symbol VB) via a resistor Ra and a switch SW1, and one end of the FET (T2) is grounded to the ground. Yes. The FETs (T1) and (T2) are PWM-controlled by the pulse signals PB1 and PB2 output from the output control unit 11 to drive the motor M1. The current flowing through the motor M1 is referred to as a load current IL.

  The output control unit 11 outputs the pulse signals PB1 and PB2 based on the output voltage VIL of the amplifier AMP1 and the pulse signal PB supplied from the switch SW4 side, and the DC power source VB becomes an overvoltage, and When the load current IL flowing through the motor M1 becomes an overcurrent, the signal VIover is output. Details will be described later with reference to FIG.

  Based on the output signal VIS of the comparator CMP1 and the voltage VMS generated at both ends of the motor M1, the state determination unit 12 detects an abnormality that occurs in the drive circuit of the motor M1 (a circuit including an electric wire, FET, and load). Furthermore, the process which determines the cause of this abnormality is performed. Specifically, based on a state determination correspondence table (see FIG. 5) described later, whether the cause of the abnormality is a lock failure of the motor M1, a short-circuit failure (including an overheat abnormality), or an overvoltage abnormality. judge. When the abnormality cause determination process is in progress, a signal indicating that the abnormality is in process is output to the switch SW4. When the abnormality cause is specified, an abnormality signal indicating the cause of the abnormality is output to the switch SW3. In addition, this abnormality signal is output to the engine control unit 21 as a DIAG signal.

  The engine control unit 21 outputs a driving pulse signal to the fuel pump control device 100. This pulse signal is supplied to the output controller 11 as a PB signal via the switches SW3 and SW4. Thereafter, the PB signal is amplified under the control of the output control unit 11, and is output to the gates of the FETs (T1) and (T2) as pulse signals PB1 and PB2, thereby controlling the FETs (T1) and (T2). The Further, when it is determined that an abnormality has occurred in the motor M1 based on the DIAG signal supplied from the state determination unit 12, the engine control unit 21 detects an abnormality by an alarm means (not shown) or the like. Control is performed to notify the occupant of the vehicle that this has occurred.

  The fail safe control unit 13 is connected to the switch SW3, and when the abnormality is detected by the state determination unit 12 and the switch SW3 is connected to the “abnormal” side, the cause of the abnormality is a lock failure of the motor M1. The drive signals of the FETs (T1) and (T2) corresponding to the respective cases of short circuit failure or overvoltage abnormality are output. Details will be described later.

  The on / off control unit 14 is connected to the switch SW4. When the signal indicating that the determination is in progress is output from the state determination unit 12, and the switch SW4 is connected to the “state determination” side, the state determination unit 14 A drive signal is output. Details will be described later.

  Two terminals of the resistor Ra are respectively connected to two input terminals of the amplifier AMP1, and an output terminal of the amplifier AMP1 is connected to both the output control unit 11 and the current source Ia. One end of the current source Ia is connected to the plus terminal of the DC power supply VB via the switch SW1, and the other end is grounded to the ground via the switch SW2 and the resistor Ris. The current source Ia operates so as to flow a current proportional to the output voltage VIL of the amplifier AMP1. Since the output voltage VIL is a voltage proportional to the load current IL (current flowing to the motor M1), the current flowing to the current source Ia has a magnitude proportional to the load current IL, and there is a load at both ends of the resistor Ris. A voltage having a magnitude proportional to the current IL is generated.

  A current source Ib is provided in parallel to the current source Ia. That is, one end of the current source Ib is connected to the plus terminal of the DC power source VB via the switch SW1, and the other end is connected to the switch SW2. Therefore, depending on the switching state of the switch SW2, either the current source Ia or the current source Ib flows through the resistor Ris. The current source Ib passes a current for generating “Logic_H” to be described later.

  One end of the resistor Ris is connected to the plus side input terminal of the comparator CMP1, and the minus side input terminal of the comparator CMP1 has a threshold voltage V1 (corresponding to the second threshold value) for determining the locked state of the motor M1. Power supply is connected. A capacitor C1 is provided in parallel with the resistor Ris. The output terminal of the comparator CMP1 is connected to the state determination unit 12. Therefore, when the voltage VIS ′ generated in the resistor Ris exceeds the threshold voltage V1, the output signal VIS of the comparator CMP1 becomes “H”, and when the voltage VIS ′ falls below the threshold voltage V1, the comparator CMP1. The output signal VIS becomes “L” and is supplied to the state determination unit 12.

  In addition, the state determination unit 12 is connected to one end of the motor M1 via the resistor R1. Therefore, the voltage VMS generated at both ends of the motor M1 is supplied to the state determination unit 12. The VMS signal is “H” when the voltage generated in the motor M1 is the output voltage VB of the power supply voltage, and “L” when the voltage is the ground level. That is, a threshold voltage (voltage corresponding to the first threshold) is set between ground and VB, and when this voltage is exceeded, the VMS signal is set to “H”, and when it is below, the VMS signal is set. Let it be “L”.

  Next, a detailed configuration of the output control unit 11 will be described with reference to FIG. As shown in FIG. 2, the output control unit 11 includes a switch SW5 connected to the switch SW4 shown in FIG. 1, a switch SW6 provided on the subsequent stage side of the switch SW5, and an amplifier provided on the subsequent stage of the switch SW6. AMP2 and AMP3 are provided. An overcurrent control unit 31 is connected to one terminal of the switch SW5, and an overvoltage control unit 32 is connected to one terminal of the switch SW6. The output terminal of the amplifier AMP2 is connected to the gate of the FET (T1) shown in FIG. 1, and the output terminal of the amplifier AMP3 is connected to the gate of the FET (T2).

  Furthermore, the output control unit 11 compares the output voltage VB of the DC power supply with a preset threshold voltage V2, a voltage VIL (output voltage of the amplifier AMP1 in FIG. 1), and a preset threshold voltage V3 ( And a comparator CMP3 for comparing with a voltage corresponding to the third threshold).

  The output terminal of the comparator CMP2 is branched into two systems, one of which is connected to the input terminal of the OR circuit OR1, and the other branch line is connected to the switch SW6. The output terminal of the comparator CMP3 is connected to the one-shot pulse generator 33. The output terminal of the one-shot pulse generator 33 is branched into two systems, and one of these branch lines is connected to the input terminal of the OR circuit OR1. The other branch line is connected to the switch SW5. When the output signal of the comparator CMP2 is “L”, the switch SW6 is connected to the “normal” side, and when the output signal is “H”, the switch SW6 is connected to the “overvoltage” side. .

  When the output signal of the comparator CMP3 is “L”, the switch SW5 is connected to the “normal” side, and when the voltage VIL rises and the output signal of the comparator CMP3 becomes “H”. The switch SW6 is connected to the “overcurrent” side for the on-time Tov of the one-shot pulse output from the one-shot pulse generator 33.

  The output terminal of the OR circuit OR1 is connected to the switch SW2 shown in FIG. That is, the switch SW2 is switched by VIover which is an output signal of the OR circuit OR1. Specifically, when VIover is set to “H”, the switch SW2 is switched to be connected to the current source Ib side.

  Next, the state determination correspondence table set in the state determination unit 12 illustrated in FIG. 1 will be described with reference to FIG. When the load current IL reaches the lock determination threshold value (corresponding to the voltage V1 in FIG. 1), the state determination unit 12 temporarily shuts off the motor M1, and then turns on the motor M1, and the motor An off period in which M1 is turned off is set, and the state of the motor drive circuit is determined based on the relationship between the VIS signal and the VMS signal in the on period and the relationship between the VIS signal and the VMS signal in the off period.

  That is, as shown in FIG. 5, when the VIS signal when the motor is on is “L”, the VMS signal is “H”, the VIS signal when the motor is off is “L”, and the VMS signal is “L”, The drive circuit is determined to be normal. Hereinafter, in the same order, when “H, H, L, L”, it is determined that the motor M1 has a lock failure, and when “H, H, H, L”, the motor M1 is short-circuited. It is determined that there is a failure (or abnormal overheating), and in the case of “H, H, H, H”, it is determined that there is an abnormal overvoltage of the DC power supply VB.

  Next, the operation of the fuel pump control device 100 of the present embodiment configured as described above will be described with reference to the timing charts shown in FIGS.

  FIG. 3 shows a case where a lock failure occurs in the motor M1 (failure in which the motor M1 stops due to foreign matter clogging) and the load current IL flowing in the drive circuit of the motor M1 exceeds the lock determination threshold value. 5 is a timing chart showing changes in signals, where (a) shows changes in PB signals (PB1, PB2), (b) shows VMS signals, and (c) shows voltage VIS ′.

  In FIG. 3, a period from time t1 to t2 indicates a period during which the motor M1 is normally driven. At this time, the switch SW3 shown in FIG. 1 is connected to the “normal” side, and the switch SW4 is also connected to the “normal” side. Therefore, a driving pulse signal (PB signal) output from the engine control unit 21 is used. ) Is supplied to the output control unit 11. Further, since the switch SW5 shown in FIG. 2 is connected to the “normal” side, and the switch SW6 is also connected to the “normal” side, the PB signal (see FIG. 3A) is sent to the two amplifiers AMP1 and AMP2. Supplied. Therefore, PB1 obtained by amplifying the PB signal is supplied to the gate of the FET (T1), and PB2 is supplied to the gate of the FET (T2).

  When the PB signal is “H”, the P-type MOSFET (T1) shown in FIG. 1 is turned off and the N-type MOSFET (T2) is turned on. Therefore, no voltage is applied to the motor M1, and the PB signal is “L”. ", The FET (T1) is turned on and the FET (T2) is turned off, so that a voltage is applied to the motor M1. Therefore, by changing the duty ratio of the PB signal, the number of revolutions of the motor M1 can be changed, and thus the amount of fuel supplied by the fuel pump can be controlled.

  The load current IL flowing through the motor M1 changes such that it rises when the PB signal becomes “L” and falls when it becomes “H”.

  The VMS signal indicating the voltage generated at both ends of the motor M1 is “H” when the motor M1 is on. That is, as shown in FIG. 3B, when the PB signal is “L”, the VMS signal is “H”. On the other hand, when the PB signal is “H”, the VMS signal is “L”.

  When the load current IL flows, a voltage having a magnitude proportional to the load current IL is generated across the resistor Ra. This voltage is amplified by the amplifier AMP1, and the amplified voltage VIL is supplied to the current source Ia, and the switch SW2 is connected to the Ia side, so that the current source Ia has a current corresponding to the voltage VIL. Works to flow. That is, a current IS having a magnitude proportional to the load current IL is passed through the resistor Ris.

  When the current IS flows through the resistor Ris, a voltage having a magnitude proportional to the current IS, that is, a voltage VIS 'having a magnitude proportional to the load current IL is generated at both ends of the resistor Ris. Therefore, as shown in FIG. 3C, the voltage VIS 'changes substantially in accordance with the load current IL. Then, the voltage VIS 'is supplied to the plus side input terminal of the comparator CMP1. The comparator CMP1 compares the voltage VIS ′ with a threshold voltage V1 (voltage corresponding to the lock determination threshold), and outputs a signal “L” when VIS ′ ≦ V1, and an “H” signal when VIS ′> V1. Output as VIS signal.

  The example shown in FIG. 3C shows a case where the load current IL reaches the lock determination threshold at time t2 and the voltage VIS ′ exceeds the threshold voltage V1, and at this time t2, the VIS signal is “L”. Will be reversed from “H” to “H”. If an overcurrent occurs due to a lock failure of the motor M1, the output voltage VIL of the amplifier AMP1 shown in FIG. 1 increases, but does not exceed the threshold voltage V3 (see FIG. 2), and a one-shot pulse is generated. The one-shot pulse signal is not output from the device 33.

  When the VIS signal becomes “H” at time t <b> 2, the state determination unit 12 thereafter executes state determination processing. That is, a signal indicating that the state is being determined at time t3 is output to the switch SW4. Accordingly, the switch SW4 is switched from the “normal” side to the “state determination” side. As a result, the pulse signals output from the on / off control unit 14 are output to the gates of the FETs (T1) and (T2) as PB1 and PB2. The PB signals (PB1, PB2) are pulse signals that once become “H” at time t3, then become “L” at time t4, “H” at time t5, and “L” at time t6. This is a pulse signal of 1.5 [KHz] and a duty ratio of 25%. Since the motor M1 is turned off when the PB signal is “H” and the motor M1 is turned on when the PB signal is “L”, the VMS signal has a duty ratio of 75 as shown in FIG. % Pulse signal.

  Then, the state determination unit 12 is based on the VIS signal and VMS signal when the motor M1 is turned on (on period), and the VIS signal and VMS signal when the motor M1 is turned off (off period). Then, the state of the motor M1 drive circuit is determined based on the state determination correspondence table shown in FIG.

  When the motor M1 has a lock failure, a load current exceeding the lock determination threshold flows when the motor M1 is turned on. Therefore, the VIS signal becomes “H”, and the voltage generated at both ends of the motor M1 is almost equal to the output of the DC power supply. Since the voltage is VB, the VMS signal is “H”. Further, when the motor M1 is off, the VIS signal is “L”, the VMS signal is “L”, and “H, H, L, L”. Therefore, based on the state determination correspondence table of FIG. It is recognized that the cause of the occurrence is a lock failure of the motor M1.

  If the state determination unit 12 determines that the motor M1 has a lock failure, the state determination unit 12 outputs an abnormality detection signal to the engine control unit 21 as a DIAG signal. As a result, the engine control unit 21 issues an alarm with an alarm device (not shown). Further, the abnormality detection signal is output to the switch SW3 and the switch SW3 is switched from the “normal” side to the “abnormal” side, so that the pulse signal is output as a PB signal from the fail safe control unit 13. The fail safe control unit 13 outputs a pulse signal for intermittently operating the motor M1. Specifically, after the time t6 when the state determination process ends, the motor M1 is driven intermittently by repeating full conduction and stoppage.

  As a result, when the motor M1 is locked due to the foreign matter being clogged in the fuel pump, the foreign matter can be removed by the intermittent operation of the motor M1, avoiding the cause of the lock failure, It can be driven normally.

  Next, an operation when a short circuit failure occurs in the drive circuit of the motor M1 will be described with reference to a timing chart shown in FIG. 4A shows changes in the PB signals (PB1, PB2), (b) shows changes in the VMS signal, (c) shows changes in the voltage VIS ′, and (d) shows changes in the load current IL. Indicates.

  When the motor M1 operates normally in the period of time t11 to t12 shown in FIG. 4 and a short circuit failure (dead short etc.) occurs in the drive circuit of the motor M1 at time t12, as shown in FIG. The current IL increases rapidly. As a result, the output voltage VIL (voltage having a magnitude proportional to the load current IL) of the amplifier AMP1 shown in FIG. 1 exceeds the threshold voltage V3 (see FIG. 2), so the output signal of the comparator CMP3 is changed from “L”. The signal is inverted to “H”, and this “H” signal is output to the one-shot pulse generator 33. As a result, the one-shot pulse generator 33 outputs a one-shot pulse that becomes “H” for the time Tov.

  As a result, the switch SW5 is switched from the “normal” side to the “overcurrent” side, and the VIover signal is output from the OR circuit OR1.

  By outputting the VIover signal, the switch SW2 shown in FIG. 1 is switched from the “Ia” side to the “Ib” side. Since the current source Ib passes a constant current corresponding to the lock current of the motor M1, the voltage VIS ′ exceeds the threshold voltage V1 regardless of the subsequent change in the load current IL, and the comparator CMP1. The VIS signal which is the output signal of “H” is “H”. Hereinafter, this state is referred to as “Logic_H”.

  Further, since the VIS signal becomes “H”, the state determination unit 12 outputs a signal indicating that determination is in progress to the switch SW4, so that the switch SW4 is switched from the “normal” side to the “state determination” side, At time t13, control is performed to turn off the motor M1, and then turn on the motor M1 at time t14. That is, a PB signal that is “H” during the period of time t13 to t14, “L” during the period of time t14 to t15, and “H” during the period of time t15 to t16 is output. As described above, the VIS signal is set to “Logic_H” in the period from time t13 to time t16.

  On the other hand, since the switch SW5 shown in FIG. 2 is switched to the “overcurrent” side, the period shorter than the on-time Tov of the one-shot pulse from the overcurrent control unit 31 during the period when the PB signal is “L”. Is output by the amplifiers AMP2 and AMP3 and supplied to the gates of the FETs (T1) and (T2). Since the FETs (T1) and (T2) are controlled by this pulse signal, the load current IL is set to the on-time Tov of the one-shot pulse as shown in the period from time t14 to t15 in FIG. A load current IL that fluctuates with a shorter cycle T1 flows. Since the ON time at this time is set to an extremely short time, the problem that the drive circuit of the motor M1 is overheated does not occur even when a short circuit failure occurs. When the load current IL flows, the VMS signal becomes “H”.

  Then, the state determination unit 12 determines the state of the motor M1 drive circuit based on the VIS signal and VMS signal when the motor M1 is turned on, and the VIS signal and VMS signal when the motor M1 is turned off. Is determined based on the state determination correspondence table shown in FIG.

  When the short circuit failure shown in FIG. 4 occurs, since the VIS signal is “Logic_H”, the motor M1 is both “H” when the motor M1 is on and off, and the VMS signal is when the motor M1 is off (t13 to t14). Is “L”, and is “H” when on (t14 to t15), so that the state determination unit 12 is supplied with signals “H, H, H, L”. Therefore, based on the state determination correspondence table of FIG. 5, it is recognized that the cause of the overcurrent is a short circuit failure or an overheat abnormality in the drive circuit of the motor M1.

  Therefore, the state determination unit 12 determines that a short circuit failure or an overheat abnormality has occurred in the drive circuit of the motor M1, and outputs an abnormality signal. When this abnormality signal is supplied, the engine control unit 21 issues an alarm with an alarm device (not shown), so that the operator can recognize that a short circuit fault or an overheat abnormality has occurred. Can do.

  Further, the abnormality detection signal is output to the switch SW3, and the switch SW3 is switched from the “normal” side to the “abnormal” side. Therefore, the fail safe control unit 13 fixes the PB signal to “H” and the motor M1. Turn off. Therefore, when a short circuit failure or an overheat abnormality occurs in the drive circuit of the motor M1, the drive circuit of the motor M1 can be protected from overheating by forcibly turning off the motor M1.

  Next, an operation when the output voltage VB of the DC power supply becomes an overvoltage will be described. When the output voltage VB becomes an overvoltage and exceeds the threshold voltage V2 shown in FIG. 2, the comparator CMP2 is inverted from “L” to “H”. As a result, the output signal VIover of the OR circuit OR1 becomes “H”, and the switch SW2 is switched from the “Ia” side to the “Ib” side. Accordingly, the output current of the current source Ib flows through the resistor Ris, and the voltage VIS ′ exceeds the threshold voltage V1, so the VIS signal is fixed to “Logic_H”.

  Further, when the output signal of the comparator CMP2 is switched to “H”, the switch SW6 is switched from the “normal” side to the “overvoltage” side. As a result, the output signal of the overvoltage control unit 32 is output to the amplifiers AMP2 and AMP3. This output signal is set to a signal with a duty ratio of 100% (full duty), amplified by the amplifiers AMP1 and AMP2, and then supplied to the gates of the FETs (T1) and (T2). Accordingly, the FET (T1) is always on, the FET (T2) is always off, and the motor M1 is DC driven.

  Since the motor M1 is DC driven, the FETs (T1) and (T2) do not perform the switching operation, so that the heat generation of the FETs (T1) and (T2) can be suppressed, and the temperature rise of the entire device can be suppressed. Can be suppressed.

  The above contents are summarized as shown in FIG. That is, when the state determination unit 12 determines that the lock failure of the motor M1 has occurred, the foreign matter causing the lock failure is removed by driving the motor M1 intermittently. Then, when the voltage VIS 'falls below the threshold voltage V1, the lock failure is released and the motor M1 is driven normally.

  If it is determined that a short circuit failure (or overheating abnormality) has occurred in the drive circuit of the motor M1, the motor M1 is stopped and the DC power supply VB is turned off. Thereafter, when the cause of the short circuit is investigated and the faulty part is recovered, normal driving is possible.

  Further, when it is determined that the output voltage VB is an overvoltage, the motor M1 is DC driven. Thereafter, when the output voltage VB falls below the threshold voltage V2, the motor M1 is driven normally.

  Thus, in the fuel pump control device 100 according to the present embodiment, the state determination process is executed when the load current IL exceeds the lock determination threshold value (current corresponding to V1). In the state determination process, the motor M1 is turned on for a predetermined time and turned off for a predetermined time, and the VIS signal and VMS in each of these time zones are acquired. Based on the VIS signal and VMS signal when the motor M1 is on, and the VIS signal and VMS signal when the motor M1 is off, the load current IL exceeds the lock determination threshold with reference to the state determination correspondence table shown in FIG. It is determined whether the cause is a lock failure of the motor M1, a short circuit failure of the drive circuit or an overheat abnormality, or an overvoltage abnormality of the DC power supply VB, and the motor M1 is determined according to the determination result. The drive circuit is controlled.

  Specifically, in the order of “L, H, L, L” in the order of the VIS signal, the VMS signal, the VIS signal, and the VMS signal when the motor M1 is on, “H, H, L” , L ”, it is determined that there is a lock failure,“ H, H, H, L ”is a short circuit failure or overheat abnormality, and“ H, H, H, H ”is an overvoltage abnormality.

  In the case of “lock failure”, the motor M1 is intermittently driven to remove foreign matter. In the case of “short circuit failure or overheating abnormality”, the motor M1 is stopped to protect the circuit. In the case of “overvoltage abnormality”. First, the motor M1 is DC driven to suppress the amount of heat generation. Therefore, it is possible to take an appropriate measure according to the cause of the increase in the load current IL, and to improve the reliability of the fuel pump control. Further, it is not necessary to provide a temperature sensor for preventing overheating at the time of a short circuit failure as in the prior art, and the apparatus configuration can be simplified and the cost can be reduced.

  In addition, since an abnormal state can be output as a DIAG signal from the state determination unit 12 to the engine control unit 21, when an overcurrent occurs, information on the cause can be notified to the operator. It becomes possible to respond quickly when a current abnormality occurs.

  In the above-described embodiment, as shown in the state determination correspondence table of FIG. 5, the state determination process is performed using the VIS signal and VMS signal when the motor M1 is on, and the VIS signal and VMS signal when the motor M1 is off. As described above with reference to FIG. 5, the VIS and VMS when the motor M1 is on are all “H” when the motor M1 is on. The cause of the failure can be determined only by the state. Therefore, if it is assumed that an abnormality has occurred when the VIS signal exceeds the lock determination threshold, it is possible to determine the cause of the abnormality only by determining the state when the motor M1 is off. According to such a configuration, there is an advantage that the calculation load in the state determination unit 12 can be reduced.

  Although the fuel pump control device of the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. be able to.

  INDUSTRIAL APPLICABILITY The present invention can be used for determining a subsequent response when an overcurrent occurs in a fuel pump mounted on a vehicle.

DESCRIPTION OF SYMBOLS 11 Output control part 12 State determination part 13 Fail safe control part 14 On / off control part 21 Engine control unit 31 Overcurrent control part 32 Overvoltage control part 33 One shot pulse generator 100 Fuel pump control apparatus

Claims (4)

In a fuel pump control apparatus that controls a motor for driving a fuel pump using a semiconductor switch,
Current detecting means for detecting a load current flowing through the motor;
When an overcurrent is detected by the current detection means, the semiconductor switch is turned off, and thereafter, an on period for turning on the semiconductor switch and an off period for turning off the semiconductor switch are controlled, State determination means for determining whether the cause of the overcurrent is due to a lock failure of the motor or a short-circuit failure based on the voltage between the terminals of the motor in the off period and the load current;
When the state determination means determines that the cause of the overcurrent is a lock failure, the semiconductor switch is controlled to intermittently drive the motor, and the cause of the overcurrent is determined to be a short-circuit failure. A control means for performing control to shut off the semiconductor switch,
A fuel pump control device comprising: The state determination means includes
When the voltage between the terminals in the off period is less than a preset first threshold and the load current is less than a preset second threshold, it is determined that the cause of the overcurrent is a lock failure,
2. The fuel pump control device according to claim 1, wherein the control unit intermittently drives the semiconductor switch after the off period when it is determined that a lock failure occurs. When the load current is equal to or greater than a preset third threshold, the control means fixes the load current to “Logic_H” that is always equal to or greater than the second threshold, and in the ON period, PWM control of the semiconductor switch,
The state determination means determines a short-circuit failure when the voltage between the terminals in the off period is less than the first threshold and the load current is greater than or equal to the second threshold.
3. The fuel pump control device according to claim 2, wherein, when it is determined that a short circuit failure has occurred, the control unit shuts off the semiconductor switch after the off period. The state determination means determines whether the cause of the overcurrent is due to the overvoltage of the DC power source in addition to the lock failure and the short-circuit failure based on the voltage between the terminals in the off period and the load current. And
2. The fuel pump control device according to claim 1, wherein when it is determined that the cause of an overcurrent is an overvoltage, the control unit drives the semiconductor switch with a full duty.

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