JPH03118486A - Load fault detector - Google Patents

Abstract

PURPOSE:To detect the wire breakdowns and the like of a plurality of loads by providing a decision mean which compares the output of a time measuring means with the output of a reference-time storage means based on an inverted signal and decides the faults of the loads. CONSTITUTION:When a driving signal S from a load control circuit 3 is switched to ON from OFF, a comparing signal C from a comparator 14 is inputted into a decision circuit 15 when a detected voltage Vs exceeds a reference voltage Vref after the specified measuring time has elapsed from the switching. A trigger signal is applied to a timer 6 at the switching timing of the signal S outputted from the circuit 13, and time counting is started. The measured time is imparted to the circuit 15 at any time. A preset reference time is imparted in the circuit 15 from a reference time storage circuit 17. The circuit 15 decides the relationship between the received measured time and the reference time, and decides whether the load has fault due to the wire breakdown or the short circuits of driving coils L1 and L2 or it is normal.

Description

[Detailed Description of the Invention] Overview In recent years, with the enhancement of diagnostic functions, it has become necessary to perform failure detection, which has not been performed in the past. The failure detection may include, for example, failure detection of a plurality of solenoid loads such as a drive coil of a fuel injection valve.6 In the present invention, the amount of current that flows through the plurality of solenoid loads and changes over time is determined in advance by a standard. By comparing the values with the values and determining what ratio they have, it is detected whether the plurality of solenoid loads are normal or in failure, and whether the failure is due to a disconnection or a short circuit. can be detected up to Further, since the timing at which failure detection is performed is set according to the time change in the amount of current, failure to detect or false detection can be avoided.

INDUSTRIAL APPLICATION FIELD The present invention relates to a load failure detection device that can accurately detect failures such as short circuits and disconnections in loads such as a plurality of solenoids driven based on drive signals.

Conventional technology In recent years, vehicle failures have been detected using the ECU (Electronic Unit) mounted on the vehicle.
The diagnostic function, the so-called diagnosis function, has been enhanced using the Ctronic Control Unit. Therefore, in conjunction with the diagnosis function, it has become necessary to perform failure detection, which has not been performed in the past. An example of the need for failure detection is a failure due to a short circuit or disconnection in a plurality of solenoid loads, such as a drive coil for a fuel injection valve or a lock control coil for a keyless entry system.

FIG. 4 shows a configuration conventionally considered as a failure detection device for a plurality of solenoid loads. The driving coils LIOL20 of a plurality of (two in FIG. 4) fuel injection valves, which are solenoid loads, are connected in parallel, and each end is connected to a power supply line connected from a battery and a switching means consisting of a transistor TRO. Connected.

A fuel injection control port n is connected to the base of the transistor TRO.
When a drive signal consisting of a pulse signal is applied from the load control circuit 3 provided in the transistor TRO
conducts, and the drive coils LIO and L20 are excited. A resistor RsO is connected between the emitter of the transistor TRO and the ground potential, and the amount of current flowing through the drive coil L20 is converted into a detection voltage VsO by the resistor RsO, and the negative voltage of the comparator 4 is converted to a detection voltage VsO. given to the input terminal. Further, resistors RIO and R20 connected in series from the power supply line are connected to the positive input terminal of the comparator 4.
A reference voltage Vre fO is applied from the connection point.

The output of the comparator 4 is given to a determination circuit 5 provided in the fuel injection control circuit 2. Further, a timer 6 is provided in association with the determination circuit 5.

The timer 6 starts counting the time when the drive signal output from the load control circuit 3 switches from a low level that shuts off the switching means to a high level that makes it conductive, and after a predetermined reference time, the determination circuit 5 The 0 judgment circuit 5 which outputs the judgment start signal to the 0 judgment circuit 5 outputs the judgment start signal from the output from the comparator 4 when the judgment start signal is input.
The states of the drive coils LIO and L20 are determined.

FIG. 5 is a diagram showing the characteristics of the detection voltage VsO accompanying the drive signal. The solid line 11 in FIG. 5 indicates the drive coil LIO,L.
The detection voltage VsO when 20 is normal is shown, and when the transistor TRO is turned on, the electromotive force VB of the battery causes each of the coils LIO and L20 to be turned on.
is excited, and the detection voltage VsO rises rapidly. On the other hand, the solid line 12 indicates the detected voltage VsO when one of the drive coils LIO and L20 is disconnected.
characteristics are shown. That is, since one of the drive coils is disconnected, the detection voltage VsO is equal to the solid line 11.
The amount of change over time is approximately 1/ compared to the normal state shown by
It becomes 2. However, it is assumed that the drive coils LIO and L20 have the same solenoid load.

The reference voltage VrefO is set between the attained power shortage after measuring the reference time and the attained voltage when one coil is disconnected in the characteristics of the detected voltage VsO in the normal state. In this way, in the determination made after the reference time, if each drive coil LIO, L20 is normal, the output from the comparator 4 becomes high level, and on the other hand, one of the drive coils is disconnected. At times, the output of the comparator 4 is at a low level.

FIG. 6 is a flowchart for explaining the determination process. In step s1, it is determined whether the drive signal output from the load control circuit 3 has been switched to a high level. If the judgment is negative, the process proceeds to other processes without performing failure detection.On the other hand, if the judgment is positive, step S after measuring the reference time is performed.
At step 2, it is determined whether the output of the comparator 4 is at a high level. If the determination is affirmative, as described above, it is determined that the drive coils LIO, L20 are not disconnected and are normal, and the process returns to step s1 again. On the other hand, if the output of the comparator 4 is at a low level, it is determined that one of the drive coils is disconnected, as described above, and in step s3, an indicator lamp or the like is used to indicate the disconnection. A warning is issued and processing proceeds to other processing.

Problems to be Solved by the Invention In this conventional configuration, the solenoid load is turned off after a predetermined reference time has elapsed after the drive signal switches from low level, which is an off signal, to high level, which is an on signal. By comparing a detection voltage VsO based on the amount of current flowing through the solenoid with a predetermined reference voltage, it is detected whether or not the solenoid load is malfunctioning.

By the way, the characteristics in FIG. 5 show the time characteristics of the detection voltage VsO after the drive signal is switched from low level to high level, and the reference voltage Vrefo has changed from the time of switching of the drive signal to the reference voltage VsO. It is set based on the relationship between the reached voltage of the detection voltage VsO after a certain period of time has elapsed. Therefore, for example, when driving at high speed, the pulse width of the drive signal for driving the drive coil of the fuel injector becomes shorter in time, and the duration time t1 of the ON signal becomes shorter than the reference time t.
Even if the drive coil LIO, L2 is shorter than
0 is normal, the detection voltage VsO is equal to the reference voltage V
It may happen that the drive signal switches to an off signal before reaching refO. In this case, even after the reference time has elapsed, the detection voltage V s O has not exceeded the reference voltage VrefO, so even if the solenoid load is normal, it cannot be determined to be normal and cannot be detected. Furthermore, it may be mistakenly detected as a failure due to disconnection.

Further, FIG. 5 shows the detected voltage V s when either one of the driving coils LIO and L20 is short-circuited inside the conductor.
The properties of O are also shown by the dashed line 13. If one of the driving coils is short-circuited, the amount of current flowing into the transistor TR10 is sufficiently large compared to the normal state. Therefore, the rise of the time characteristic of the detection voltage VsO is also sufficiently fast compared to the normal state. become. Therefore, when making a determination after the reference time has elapsed,
When the short circuit occurs, the output from the comparator 4 becomes high level, and as a result, the determination circuit 5 determines that it is normal, that is, although it can be determined that the failure is not due to a disconnection, it is a failure due to a short circuit. It cannot be determined.

In this conventional configuration of the failure detection device 1, problems arise such as inability to detect or false detection caused by a change in the ON duration of the drive signal, and inability to detect a failure due to an internal short circuit in the load.

Therefore, an object of the present invention is to be able to reliably detect failures due to disconnection of multiple loads as well as failures due to short circuits of multiple loads, and further to detect a change in the ON duration of a drive signal for driving the loads. It is an object of the present invention to provide a load failure detection device that can reliably detect failures regardless of the situation.

Means for Solving the Problems The present invention provides a device for detecting failures in a plurality of loads driven by switching means to which a drive signal is input, which compares the amount of current flowing through the loads with a predetermined reference level, and compares the amount of current flowing through the loads with a predetermined reference level. an inverting device that outputs an inverted signal when the level of the drive signal is inverted; a clocking device that performs a timing operation based on the drive signal; a reference time storage device that stores a predetermined reference time; and based on the inverted signal, The load failure detection device is characterized in that it includes determination means for comparing the output of the timer and the output of the reference time storage means to determine a failure of the load.

Operation According to the load failure detection device of the present invention, failures in a plurality of loads driven by a switching means to which a drive signal is input can be detected. A value based on the amount of current flowing to the load is provided to the inverting means.

The inverting means compares the value with a predetermined reference level, and outputs an inverted signal when the mutual levels are inverted. Further, the timekeeping means performs a timekeeping operation based on the drive signal. The determination means compares the time measured by the timer with a reference time stored in advance by the reference time storage means, based on the inverted signal, and determines a failure of the load.

In this way, by determining the relationship between the measured time and the reference time, it is possible to determine whether the plurality of loads are in a normal state or a faulty state, and if the plurality of loads are in a faulty state, whether the fault is caused by a disconnection in any of the loads or by an internal short circuit in the load. can be determined. Furthermore, since a failure is determined when the inverted signal is output, a load failure can be reliably determined regardless of the displacement of the on-Iln period of the drive signal, and undetectable or erroneous detection will not occur.

Embodiment FIG. 1 is a block diagram showing a simplified electrical configuration of a fault detection device 11 which is an embodiment of the present invention.
The failure may be due to disconnection of one of the solenoid loads, or
It is possible to detect either a failure due to a short circuit or if everything is normal.

Solenoid loads, such as drive coils LL and L2 for fuel injection valves, are connected in parallel, one of the parallel wires is connected to a line s11 of an electromotive voltage VB of a battery (not shown), and the other of the parallel wires is connected in common. It is connected to the collector of a transistor TR which is a switching means. The emitter of the transistor TR is grounded via a resistor Rs, and by inputting a control signal S to the base of the transistor TR, the drive coils LL and L2 are excited by the electromotive voltage VB, and the fuel Injection control is performed.

The drive signal S is output from a load control circuit 13 provided within the fuel injection control circuit 12, which is comprised of, for example, a microcomputer. The drive signal S is, for example, a pulse signal whose period can be adjusted and set, and when it is at a high level, it indicates an on signal for injecting fuel.
R is made conductive, and the respective driving coils Ll and L2 are excited. - When the level is low, an off signal is displayed to stop fuel injection, the transistor TR is cut off, and the drive coils Ll and L2 are demagnetized.

Based on the drive signal S, the total amount of current flowing through each drive coil 1°L2 flows into the resistor Rs. The resistor Rs converts the amount of current into a voltage and supplies it to the negative input terminal of the comparator 14 as a detection voltage Vs. The positive input terminal of the comparator 14 is supplied with the potential at the connection point of the resistors R1 and R2 connected in series from the line S11 as a reference voltage Vref. In the comparator 14, the detection voltage V
s and a reference voltage Vref, and outputs a comparison signal C. That is, between the detection voltage Vs and the reference voltage Vref, Vref>Vs 0. -(1)
When the relationship is satisfied, the comparator 14 outputs a high-level comparison signal C, while Vref≦Vs
=, when the relationship (2) is satisfied, a low level comparison signal C is output. therefore,
After the drive signal S from the load control circuit 13 is switched from an OFF signal to an ON signal, the amount of current flowing into the solenoid load rapidly increases, and after a measurement time T, which will be described later, has elapsed since the switching time, the detected voltage Vs increases. The reference voltage Vref is exceeded, and thus the comparison signal C of the comparator 14 switches from high level to low level.

The comparison signal C from the comparator 14 is input to a determination circuit 15 provided within the fuel injection control circuit 12. Incidentally, a timer 16 is provided in conjunction with the determination circuit 15. The timer 16 is triggered at the timing when the drive signal S output from the load control circuit 13 switches from an OFF signal to an ON signal, that is, at the timing when the drive signal S rises from a low level to a high level, and starts a timing operation.

In this way, the measured time T measured by the timer 16 is given to the judgment circuit 15 at any time.
In response to the input comparison signal C, the measurement time T at the time when the comparison signal C switches from high level to low level is acquired. In other words, the captured measurement time T is a period when the detected voltage Vs is the reference voltage V r e f after the drive signal S is switched from an OFF signal to an ON signal.
It shows the time elapsed until the comparison signal C switches from high level to low level. Note that the timing signal at which the comparison signal C switches from high level to low level is an inverted signal.

The determination circuit 15 is further supplied with a preset reference time to from a reference time storage circuit 17. The reference time storage circuit 17 is constituted by, for example, a read-only memory. The determination circuit 15 determines the relationship between the measured time T taken in as described above and the reference time 0, and thus determines the relationship between the drive coils LL and L as described later.
2. Detects whether there is a failure due to disconnection or short circuit, or whether it is normal.

FIG. 2 is a diagram showing the time characteristics of the detection voltage Vs and the comparison signal C. FIG. 2(1) shows the time characteristics of the detected voltage Vs. In FIG. 1, the drive coil LL
, L2 are normal without failure, the detection voltage Vs suddenly rises as the drive No. 13 S is switched from the OFF signal to the ON signal, as shown by a solid line 111. On the other hand, when either one of the driving coils Ll and L2 is disconnected, the amount of current flowing into the resistor Rs decreases compared to the normal value, and the detection voltage Vs
As shown by the solid line N12, with the switching of the drive signal S, the amount of change with respect to time in the normal state is approximately 1/1
It rises at a rate of 2. Here, it is assumed that the drive coils LL and L2 are the same solenoid load.

On the other hand, if one or both of the drive coils LL and L2 is short-circuited inside the conductor, the amount of current flowing into the resistor Rs is sufficiently large compared to the normal state, and therefore the detection voltage S is also the drive signal S
At the same time as switching, the signal suddenly rises as shown by a broken line 113.

The reference voltage Vref input to the comparator 14 is the detection voltage
That is, the detection voltage Vs indicated by the solid line 112 is selected to be smaller than the voltage reached in the minimum setting period of the ON duration period t2 of the drive signal S whose cycle is adjusted.

FIG. 2(2) shows the relationship between the measurement time T in the normal state or failure state of the drive coil.

As mentioned above, the measurement time T is the time measured from when the drive signal S switches from an OFF signal to an ON signal until the comparison signal C, which is the output of the comparator 14, switches from a high level to a low level. It is. The origin in FIGS. 2 (1) and (2) is assumed to be when the drive signal S is switched from the OFF signal to the ON signal, so the point of origin in FIG. The time shown in FIG. 2 indicates the measurement time T in the normal and faulty states of the respective drive coils LL and L2. That is, the reference mark T1 is the measured time when each drive coil Ll, L2 is normal, the reference mark T2 is the measured time when one of the drive coils is disconnected, and the reference mark T3 is the measured time when one of the drive coils is disconnected. This is the measurement time when the coil is short.

These measured times T are compared with a reference time 10 outputted from the reference time storage circuit 17. The reference time to
is selected to be the same as the measurement time T1 in the normal state.

Therefore, when the measurement time T is equal to the reference time to, the drive coil is normal. On the other hand, when the measurement time T is longer than the reference time to, one of the drive coils is I! If the failure is due to an Ir line, and the measured time T is less than the reference time to, it can be determined that the failure is due to a short circuit in the drive coil.

-m, due to accuracy problems, it may not be possible to detect coincidence between the measurement time T1 and the reference time to even under normal conditions. Therefore, in this embodiment, determination areas W1 to W3 are set in advance based on the reference time to.

For example, the region that satisfies the relationship 0.5tO≦T≦1.5tO (3) between the measurement time T and the reference time 10 is defined as the normal region W1, and 1.5tO≦T
...The area that satisfies the relationship (4) is 1
! 7r&l region W2, and a region satisfying the relationship Too, 5tO...(5) is defined as a short circuit region W3. In this way, by determining in which region the measured time T falls, it is possible to detect whether the drive coils Ll, L2 are in a normal or faulty state. Note that when determining the determination area, the values of 0, 5, and 1.5, which are the counts multiplied by the reference time rrr1tO, are arbitrarily selected in consideration of the accuracy of the apparatus and the like.

FIG. 3 is a flowchart for explaining the determination process. In step m1, it is determined whether the drive signal S has been switched from an off signal to an on signal. The drive signal S
When the signal changes from the off signal to the on signal, the process proceeds to step m2, starts the timer 16, and determines in step m3 whether or not the comparison signal C of the comparator 14 has changed from the high level to the low level. . When the comparison signal C switches from high level to low level, the time T measured by the timer 16 up to that point is read into the determination circuit 15, and the process proceeds to step m5.

In step m5, it is determined whether the measured time T satisfies the third equation. If the judgment is affirmative, in step m6, the measurement time T is within the normal region W.
1, that is, the drive coils LL and L2 are determined to be normal without failure, and the process proceeds to other processes.

On the other hand, if it is determined in step m5 that the measured time T does not satisfy the third equation, the process proceeds to step m7, where it is determined whether the measured time T satisfies the fifth equation. be judged. If the above judgment is affirmative,
In step m8, it is determined that the measured time T is included in the short-circuit region W3, that is, one of the drive coils Ll and L2 is short-circuited inside the conductor, and a warning is issued, for example, with an indicator lamp, and other processing is performed. Proceed to processing.

Further, in the step m7, the measurement time T is
If it is determined that the formula is not satisfied, the process proceeds to step m
Proceed to 9. In step m9, the measurement time T is included in the disconnection area W2, that is, the drive coils Ll, L
2 is determined to be disconnected, a warning is given with a display lamp, etc., and the process proceeds to other processes.

Therefore, according to this embodiment, each drive coil Ll, L
Focusing on the difference in the amount of current flowing depending on the normality or failure of No. 2, the normality or failure state of each drive coil is determined by the time measured until the detected voltage based on the current amount exceeds a predetermined reference voltage. Detected. Therefore, depending on each measurement time, it is possible to detect whether the drive coils LL and L2 are normal or malfunctioning, and if they are malfunctioning, whether the failure is due to a disconnection or a short circuit, Very high performance in detecting solenoid load failures.

Further, the failure detection is performed after a measured time has elapsed since the drive signal S was switched. Therefore, the reference voltage Vref is set during the on-continuation period t2 of the drive signal S as described above.
By selecting the voltage to be smaller than the minimum attainable voltage in the minimum set period of
2 changes as the vehicle travels, it is possible to accurately detect the normal or faulty state of the solenoid load. Never.

Furthermore, in the failure detection device 11 according to this embodiment, the drive coil L1. Detection voltage Vs when L2 is normal
and reference voltage Vref satisfy the following relationships.

...(7) RL: Internal resistance of Ll, L2 L: Inductance of Ll, L2 Therefore, when calculating the measurement time T1 during which the detection voltage Vs and the reference voltage Vrf match, the relationship of (8) is obtained. is satisfied, and the measurement time T1 becomes a constant.

That is, the measurement time T1 does not depend on the supplied electromotive voltage VB. Therefore, even if the electromotive voltage VB fluctuates depending on usage conditions, the detected voltage VB
The measurement time T1 until s matches the reference voltage Vref is constant. Similarly, other measurement time T2. T3 also remains constant. Since the reference time to mentioned above is selected to be the same as the measurement time T1, once the reference time to is set at the manufacturing stage in this way, even if the electromotive voltage VB changes, the reference time 10 can be corrected, etc. does not require reconfiguration. In this way, regardless of fluctuations in the electromotive voltage VB, the previously set reference time 10 can be utilized and accurate failure detection can be performed, resulting in very high performance as a failure detection device.

Although the present embodiment is described in relation to a failure detection device for two solenoid loads (2), the number of solenoid loads is not limited.

In other words, in the detected voltage when only one of the plurality of solenoid loads is normal, the reference voltage V is lower than the voltage reached in the minimum setting period of the on-continuation period of the drive signal.
ref is set, and based on the reference voltage Vref,
As in this embodiment, a reference time and a determination area may be set, and it may be determined in which determination area the measurement time falls each time the measurement time elapses.

In addition, in this embodiment, the solenoid load is applied to the driving coil of the fuel injection valve.
This is not limited to this example, but
For example, it may be a coil for controlling door locking in a keyless entry system or the like. Further, the load is not limited to a solenoid in this embodiment, and any load may be used as long as the amount of current flowing therein changes with time.

Therefore, according to this embodiment, it is possible to detect not only a load failure but also whether the failure is due to a disconnection or a short circuit. Also, drive the load.
Effects of the Invention According to the present invention, even if the ON duration of the drive signal changes, detection failure or false detection does not occur. state can be detected. Therefore, it is possible to detect whether the circuit is normal or a failure, and it is also possible to detect whether the failure is due to a disconnection or a short circuit.

In addition, since the reference level caused by the inverted signal is set below a predetermined level, no detection failure or erroneous detection occurs regardless of fluctuations in the drive signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a simplified configuration of a failure detection device 11 which is an embodiment of the present invention, and FIG.
and ratio F! 3 is a diagram showing the time characteristics of signal C, and FIG. 3 is a flowchart 1 for explaining the determination process. FIG. 4 is a block diagram showing a simplified configuration of a conventional failure detection device 1, and FIG. is a diagram showing the time characteristics of the conventional detection voltage VsO, and FIG. 6 is a flowchart for explaining the conventional determination process. DESCRIPTION OF SYMBOLS 11... Failure detection device, 12... Fuel injection control circuit, 13... Load control circuit, 14... Comparator, 15.
... Judgment circuit, 16... Timer, 17... Reference time storage circuit, C... Comparison signal, LL, L2... Fuel injection valve drive coil, S... Drive signal, to river Standard time, T...Measurement time, TR...Transistor, V
r e f...Reference voltage, ■s...Detection voltage, Wl
...normal area, W2...disconnection area, W3...short circuit area,

Claims (1)

[Claims] A device for detecting a failure in a plurality of loads driven by switching means to which a drive signal is input, comprising: comparing the amount of current flowing through the loads with a predetermined reference level, and determining whether the mutual levels are the same; a reversing means that outputs an inverted signal when reversed; a time measuring means that performs a time measuring operation based on the drive signal; a reference time storage means that stores a predetermined reference time; A failure detection device for a load, comprising: determination means for comparing the output with the output of the reference time storage means and determining a failure of the load.