JPH066927B2 - Abnormality detection device for pulse output type sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pulse output type sensor abnormality detection device, and in particular, is an air amount sensor that outputs a detected value of an intake air amount of an engine pulsed normally? The present invention relates to an abnormality detection device that determines whether or not it is.

[Conventional technology]

In order to electronically control an engine, a sensor that accurately grasps the operating state of the engine, a memory that stores programs and data necessary for calculation, a computer that uses these information to calculate optimum conditions for controlling the engine, and An actuator that directly operates the engine is required.

Of these, the sensor plays an important role not only in the state of the engine itself, but also in converting it into an electrical signal of information related to the operating environment of the engine, such as physical quantity, electricity quantity, and chemical quantity, and transmitting it to the computer. Early detection is very important for safety.

Therefore, in recent years, various self-diagnosis devices have been proposed for determining whether a sensor attached to an automobile is normal or abnormal.

A conventional parameter for knowing the operating state of the engine, particularly a sensor for detecting the load state of the engine, generally outputs an analog voltage. Therefore, in this type of sensor, a diagnostic method is generally used to determine that the sensor is abnormal when the output becomes 0 V (CND voltage) or when it becomes the same voltage as the power supply voltage Vcc (5 V, for example). Met.

[Problems to be solved by the invention]

However, for a sensor that outputs the number of vortices generated in a unit time by an ultrasonically modulated pulse train, such as a Karman vortex sensor that measures the air flow rate to the engine, the output voltage of the sensor is always 0V ( GND) or 5V (Vc
Since it is in c), the conventional abnormality diagnosis method as described above cannot be applied.

Therefore, the present inventors have already determined whether the sensor that outputs the detected value of the operating state of the engine as a pulse train signal is operating normally, and whether it is stored in the memory or whether it is normal in the display device. An abnormality detection device for a pulse output type sensor that can display and provide effective information for accurate repair work has been proposed (Japanese Patent Laid-Open No. 62-038856).

However, the proposed pulse output type sensor abnormality detection device has a problem that the sensor is erroneously diagnosed as abnormal when the sensor power supply voltage drops. That is, for example, when the engine is started, the battery voltage drops significantly immediately after the starter motor starts, and the battery voltage rises again after the starter motor stops operating, but when the battery voltage drops, the sensor power supply voltage falls below the operating voltage. In this case, since the sensor does not operate normally during this period, there is a problem that if the diagnosis of the sensor is executed at this time, an erroneous diagnosis that the sensor is abnormal is made.

An object of the present invention is, when the battery voltage or the power supply voltage of the sensor is temporarily lowered, without erroneously diagnosing the abnormality of the sensor that outputs the detected value of the operating state of the engine as a pulse train signal, to the battery voltage or the sensor If the power supply voltage is normal, it is judged whether the sensor is operating normally, and it is stored in the memory or is displayed on the display device to indicate whether it is normal or not. It is an object of the present invention to provide an excellent pulse output type sensor abnormality detecting device that can bring about the above.

[Means for solving problems]

The structure of the present invention for achieving the above object is shown in FIG.
The abnormality detection device for the pulse output type sensor in FIG.
A pulse output type sensor that outputs a detected value of the operating state of the engine as a pulse train signal, a rotation speed detection means that detects the rotation speed of the engine, a detection means of a battery voltage or a power supply voltage of the sensor, and a detection means of the voltage. Counting means for counting time when the detected voltage value is equal to or higher than a normal operating voltage of the sensor and when the engine speed is equal to or higher than the predetermined value, and is reset each time the pulse from the sensor rises or falls. , And signal generating means for generating an abnormal state signal of the sensor when the count value of the counting means exceeds a predetermined value.

[Work]

According to the present invention, the set value of the engine speed at which the counting means starts counting is set to be less than the idling speed, and the lower limit value of the power supply voltage at which the pulse output type sensor operates normally is set to the abnormal signal generation means. By setting, even if the engine idling speed obtained by the rotation of the cranking motor or less, if the power supply voltage of the sensor and the engine speed exceeds the set value, the pulse train from the pulse output type sensor is detected. When the sensor is operating normally, the counting means is cleared every pulse and the counting is repeated. At this time, the abnormal signal of the sensor is not output from the counting means, but when the operation of the pulse output type sensor is abnormal, the counted value of the counting means is not cleared, so when the counted value exceeds the predetermined value. Then, the abnormal state signal of the sensor is output from the counting means.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is an overall schematic diagram showing the configuration of an embodiment of a pulse output type sensor abnormality detection device of the present invention. In FIG. 2, an air flow sensor 3 is provided in the intake passage 2 of the engine 1 downstream of a rectifier 9 made of aluminum honeycomb. The airflow sensor 3 is a Karman vortex sensor that generates a Karman vortex K in the intake passage 2 and detects the intake air amount by ultrasonic modulation of the vortex generated in a unit time, and is, for example, a vortex generator. 3a, an ultrasonic transmitter 3b and an ultrasonic receiver 3c.

As the air flow sensor 3, other than the ultrasonic type, a type such as a mirror vibration reflection type can be used.

The air flow sensor 3 is a pulse output type sensor,
The output characteristic of the intake air amount of the engine 1 outputs a frequency as shown in FIG. This output signal is composed of a pulse train of low level L (0V) -high level H (5V). For example, the waveform C at the time of engine starting is shown in FIG. 4 together with the starter motor signal waveform A and the engine crank angle signal waveform T. It is shown.

The ultrasonic receiver 3c of the air flow sensor 3 is connected to the input / output interface 11 of the control circuit 10. The control circuit 10 is configured as, for example, a microcomputer, and is provided with a reference time generator 12, a CPU 13, and a memory 14 such as a RAM and a ROM in addition to the input / output interface 11 described above. Alternatively, they are connected by a dedicated line 16.

Further, the input / output interface 11 includes an engine 1
The rotation speed detection sensor 5 and the alarm 6 attached to the distributor 4 are connected. Further, the battery 8 is connected to the A / D converter 17 via the ignition switch 7. The rotation speed detection sensor 5 inputs the rotation speed of the engine 1 to the control circuit 10, and the A / D converter 1
Reference numeral 7 supplies the battery voltage, that is, the power supply voltage of the air flow sensor 3 to the bus line 15, and the alarm 6 is supplied with a signal from the control circuit 10 when the air flow sensor 3 is abnormal, and informs the abnormality of the air flow sensor 3 by, for example, sound or light. .

In the pulse output type sensor abnormality detecting device of the present invention configured as described above, the battery voltage B becomes the predetermined voltage value V ₀ (for example, 6 V) in step 100 by the time interruption routine shown in FIG. 5 every predetermined time. When it exceeds (YES), the process proceeds to step 101, and when the engine speed N exceeds a predetermined value (for example, 200 rpm) in this step 101 (YES),
The count value TC of the time count counter in the CPU 13 is incremented by 1 (step 102), and the time count value TR of the normality determination timer counter is also incremented by 1 (step 102).
103). In this embodiment, when the battery voltage B <6 V or the rotation speed N <200 rpm, the count value TC is cleared to 0 in step 104, but in this case, the count value TC is held without being cleared. I sometimes do it.

Further, the CPU 13 receives a pulse from the air flow sensor 3 whose noise component is removed by a noise filter (not shown) in the input / output interface 11 through an interrupt input port (not shown). , CPU 13 performs a falling edge interrupt routine shown in FIG. 6 at each falling edge of this pulse. In this routine, in step 201, the air flow rate is calculated using the count value TC of the time counter (K is a constant), and in step 202 the value is stored in the memory 14 of FIG. Then, in step 203, the count value TC is reset to 0, and in step 204 C
It is determined whether or not there is an alarm output from PU13.

When there is an alarm output (YES), the routine proceeds to step 205, where the value of the pulse count value PN output from the air flow sensor 3 of the above-described normality determination timer counter is increased by 1, and when there is no alarm output (NO In step 206, the time count value TR and the pulse count value PN of the timer counter are reset to zero.

Next, the operation of the abnormality detecting device for a pulse output type sensor according to the present invention after the engine is started will be described with reference to the routine of FIG. 7 and the waveform diagrams of FIGS.

(1) Normal state (waveform diagram is FIG. 8) When the starter motor is switched from the OFF state to the ON state and the engine is started, the engine speed N starts to increase (waveforms A and B). Along with this, air is introduced into the engine combustion chamber, but the pulse output from the air flow sensor drops from 5V to 0V when the starter motor signal STA changes from OFF to ON, and then decreases due to the starter motor startup. battery voltage B (waveform G) is not output until a normal operating voltage V _R of the air flow sensor. When the battery voltage B reaches the voltage V _R, an air flow sensor in a normal state sends a pulse output proportional to the amount of air (waveform c).

In this embodiment Aru select the setting value V _O of the battery voltage B to operate the time number counter as V _O> V _R.
Further, in the device of the present invention, the time counting counter does not operate as described above until the engine speed N reaches the predetermined value N _O , for example, 200 rpm, and the count value TC is 0 (waveform D). eventually, the battery voltage B ≧ V _O, until the engine speed N ≧ N _O a satisfying both time Z, the count value TC of the time number counter remains zero.

In this manner, when a controlled counting of the count value TC of the time count counter by the value of the engine rotational speed N, the time counting as indicated engine speed N by the dashed line switch at the time exceeds a predetermined value N _O X count TC is started to make the counter, in front of the time Y to the battery voltage B reaches the normal operating voltage V _R of the air flow sensor, so that the count value TC reaches the abnormality determination value TC _O, air flow sensor is abnormal Because it will be diagnosed as being present.

The above steps are steps in the flowchart of FIG.
After NO in 300 (battery voltage B <6V) or YES in step 300 (battery voltage B ≧ 6V), NO in step 301 (alarm output = 0), and the process proceeds to step 302. Is NO (engine speed N <200 rpm). At this time, every time the pulse from the air flow sensor falls, the above-described fall interrupt routine (FIG. 6) is executed, and the step
205 is not done.

When the battery voltage B becomes equal to or higher than the predetermined value V _O and the engine speed N becomes equal to or higher than the predetermined value N _O , the time counting counter starts counting (waveform D in FIG. 8), and the count value TC is obtained from the air flow sensor. It is cleared and becomes 0 at each falling edge of the pulse. Then, if the count value TC is cleared at each falling edge of the pulse, the value does not increase and it is considered that the air flow sensor is operating normally. Therefore, an alarm signal is not output from the CPU. , The abnormal flag D as shown by the waveform E in FIG.
F does not stand.

The above process shifts from step 301 to step 302 in the flowchart of FIG.
S (engine speed N ≧ N _O ) is reached and the routine proceeds to step 303, but at this step 303 NO (time count value TC ≦ T
Co) and the routine proceeds to step 306.
Further, the step of timer interrupt routine described above when the engine rotational speed N is equal to or greater than a predetermined value N _O (FIG. 5) 102,10
3 is executed, and thereafter, the steps 102 and 103 are the number of revolutions N.
But unless not rotate under the predetermined value N _O, it is executed at predetermined time intervals, if it falls below the count value TC = 0 in step 104 is executed.

(2) In case of abnormality (waveform diagram is FIG. 9) When the starter motor is switched from the OFF state to the ON state and the engine is started, the battery voltage B decreases and the engine speed N starts to increase (waveform I , Ro, to). Although the air in the room engine combustion with which is introduced, when there is abnormality in the air flow sensor, and thereafter the engine speed N exceeds a predetermined value N _O, and the battery voltage B is a predetermined value V
_No pulse is sent from this sensor even when the time Z exceeds _O (as indicated by waveform C, and at this time, the output GND voltage or Vcc voltage).

When the battery voltage B becomes equal to or higher than the predetermined value V _O (6V) and the engine speed N becomes equal to or higher than the predetermined value N _O (200 rpm) at time Z, the count value TC of the time counting counter increases with time (FIG. 5). However, since there is no output pulse from the air flow sensor as described above, the falling interrupt routine is not executed and this count value TC is not cleared. As a result, the count value TC continues to increase, eventually exceeds the abnormality determination value TC _O at time W (waveform d).

At this point, the CPU makes an abnormality determination, sets an abnormality flag DF (waveform E), and outputs an alarm signal. In the configuration shown in FIG. 2, this alarm signal activates an alarm 6 for notifying an abnormality of the airflow sensor 3 by light or sound.

The above-described abnormality determination is the same not only when the engine is started, but also when an abnormality occurs in the airflow sensor during engine operation.

In this way, the abnormality of the air flow sensor 3 is detected,
After the alarm signal is output, the normality determination timer counter operates, and thereafter, the alarm signal continues to be output until the timer counter determines that the airflow sensor 3 has returned to normal.

The above process will be described with reference to FIG. When the pulse is no longer output from the air flow sensor, T
If C> TC _O (YES), the process proceeds to step 304. In step 304, alarm output = 1 and an alarm signal is output. Then, in step 305, the time count value TR of the timer counter is reset to 0. When the process returns to step 301 again, there is an alarm output, so YES is obtained and the process proceeds to step 307.

Step 307 is a step of determining the count value of the pulse number PN from the air flow sensor 3 at the time of returning to normal. At this point, the pulse number PN from the air flow sensor 3 is PN = 0, so the result is NO, and the routine proceeds to step 308. Steps 308 and 309 are steps to clear the above-mentioned timer counter at every predetermined time, and the time count value T of the timer counter which is incremented at every predetermined time at step 103 in FIG.
When R does not reach the predetermined value TR _O (e.g. 1000 ms) (YE
S) is increased as it counts TR, when the count value TR is equal to or greater than the predetermined value TR _O is 0 to clear the pulse count PN of the count value TR and the timer counter. In the above process, no pulse is output from the air flow sensor, so the falling interrupt routine is not executed.

(3) When returning to normal (waveform diagram is FIG. 10) After the abnormality is determined, the engine speed N is the predetermined value N.
A case where the air flow sensor is restored so as to function normally when _O is exceeded will be described.

When the air flow sensor is abnormal, the normality determination timer counter is set to a predetermined cycle TR as shown by the waveform in FIG.
_O (for example, 1000 ms) repeats counting time and resetting. The apparatus of the present invention, during the counting period TR _O of the timer counter, have when the output pulse from the air flow sensor is input to a predetermined value CK O _(for example, 15) or more control circuits, air flow sensor is restored successfully Is determined (waveform c, e).

This will be described with reference to the flowchart of FIG. If there is an alarm output, step 301 →
After going through step 307 → step 308 → step 301 or step 309, the routine of step 301 is executed. During this process, no pulse was output from the airflow sensor, so the falling interrupt routine was not executed.

When the sign of demodulation appears in the air flow sensor and a pulse starts to be output, the falling interrupt routine of FIG. 6 is executed at the falling edge of the pulse, and after the determination at step 204, the routine proceeds to step 205 and the timer counter is started. Thus, the pulse number PN is counted. Pulse number PN from such an air flow sensor which is counted in the, if less than the predetermined value CK O ₍₁₅ pieces) in the counting period TR _O of the aforementioned timer counter, and NO in step 307 of FIG. 7 Since the determination is made, the alarm output = 1 remains, and it is not considered that the air flow sensor has returned to normal.

However, the timer counter counting period TR _O pulse count PN of the timer counter is a predetermined value in the _CK O (15 pieces)
When it reaches 0, it is judged as YES in Step 307 and the process proceeds to Step 310, and the alarm output is reset to 0.
The alarm signal output stops.

As a result, the next time it is determined to be NO in step 301, and thereafter step 301 → step 302 → step 30
3 → The normal routine of step 306 is repeated.

As described above, in the device of the present invention, the normal or abnormal state of the output of the pulse output type sensor and the return state from the abnormal state to the normal state can be accurately determined, and the abnormal state of the sensor can be displayed by means such as an alarm. it can.

In the above embodiment, one abnormality flag DF is used as an alarm signal to display the determination of the abnormal state, but two abnormality flags DF are used for service maintenance.
Use of 1, DF2 further improves serviceability.

That is, after the first abnormality flag DF1 is cleared by the service factory by removing the battery or the like, once the abnormality determination is made and DF1 = 1, even if the normal determination is made thereafter, the first abnormality flag DF1 is not cleared. If the information indicating whether the air flow sensor is normal or abnormal is expressed by using the second abnormality flag DF2, even if the air flow sensor is temporarily in an abnormal state but returns to the normal state thereafter, a temporary abnormality is generated. The state history remains in the first abnormality flag DF1 and can be used for early detection of a defect in the air flow sensor.

〔The invention's effect〕

As described above, according to the present invention, when the power supply voltage of the pulse output type sensor temporarily falls outside the normal operating range of this sensor, the sensor power supply is not erroneously diagnosed as abnormal. When the voltage is within the normal operating range of the sensor, the time between the rising and falling edges of the pulse from the pulse output type sensor is counted, and when this count value exceeds a specified value, the pulse generation source is abnormal. Since it is determined that the pulse output type sensor is normal or abnormal, the pulse output type sensor can be accurately diagnosed.

[Brief description of drawings]

FIG. 1 is an overall block diagram for explaining the configuration of the present invention, FIG. 2 is an overall schematic diagram showing an embodiment of an abnormality detecting device for a pulse output type sensor according to the present invention, and FIG. 3 is FIG. 2 is a diagram showing the output frequency characteristic of the air flow sensor with respect to the air flow rate, and FIG. 4 is a waveform diagram showing the output signal at the time of engine start of the air flow sensor of FIG. 2 together with the starter motor signal and the crank angle signal, FIG. 5, FIG. 6 and 7 are the second
A flow chart for explaining the operation of the control circuit in the figure,
FIG. 8 is a waveform diagram showing the output waveform of each part when the air flow sensor is normal with time from engine start, FIG. 9 is a waveform diagram corresponding to FIG. 8 when the air flow sensor is abnormal, and FIG. 10 is an air flow sensor. FIG. 6 is a waveform diagram showing the waveform of each part when the normal state returns from the abnormal state with time. 1 ... Engine, 2 ... Intake passage, 3 ... Air flow sensor, 5 ... Rotation speed detection sensor, 8 ... Battery, 10 ... Control circuit, K ... Karman vortex.

Claims (4)

[Claims] 1. A pulse output type sensor (3) for outputting a detected value of an operating state of the engine (1) as a pulse train signal, a rotational speed detecting means (5) for detecting the rotational speed of the engine (1), a battery voltage or The sensor power supply voltage detecting means (10), the detection voltage value of the voltage detecting means is a predetermined value (V _O ) or more that is the normal operating voltage (V _R ) or more of the sensor, and the engine speed is a predetermined value ( N _O ), the time is counted, and the counting means (TC) is reset each time the pulse from the sensor rises or falls, and when the count value of the counting means exceeds a predetermined value, the sensor An abnormality detecting device for a pulse output type sensor, comprising: a signal generating means (13) for generating an abnormal state signal. 2. The method according to claim 1, wherein said counting means has means for holding the count value up to that time when the engine speed falls below a predetermined value until the engine speed rises above a predetermined value. The described device. 3. The apparatus according to claim 1, wherein said counting means has means for clearing the count value when the engine speed becomes equal to or lower than a predetermined value. 4. When a predetermined number of pulses are input from the sensor to the counting means within a predetermined time after the abnormal state signal is generated from the signal generating means, the signal generating means causes the sensor to operate normally. Claim 1 for generating a status signal
The apparatus according to any one of items 1 to 3.