JP4700350B2 - Sensor diagnostic method - Google Patents

Description

  The present invention relates to a diagnostic method for a sensor in an automobile having an internal combustion engine, for example. Such a sensor to be diagnosed is, for example, a phase sensor of a car camshaft. This type of sensor provides a corresponding output signal depending on whether the detected quantity is above or below a certain threshold.

  This type of sensor is, for example, a sensor that reacts to a magnetic field, and the rotational speed and / or position of the transmitter wheel provided with the teeth is determined by such a sensor. In this type of sensor, the transmitter wheel (its position and rotational speed should be detected) passes between the sensor and the magnet, so that the teeth of the transmitter wheel are just opposite the magnetic field. The sensor will register a weak magnetic field when it comes, and just register the strong magnetic field (or vice versa) when the transmitter wheel teeth are in a position that does not oppose the magnetic field (when the gap part is in a position facing the magnetic field) Configured and arranged. Such sensors operate in a dielectric manner or are based on Hall technology or XMR technology.

  FIG. 2 schematically shows such a device having a transmitter. Here, R represents a transmitter wheel, G represents a transmitter including a magnet and a sensor, and W represents an element to which the transmitter wheel R is attached. The rotational speed and / or position of this element should be determined; this element W is for example the crankshaft or camshaft of an internal combustion engine.

  As a reminder, it is suggested that the device shown in FIG. 2 is very schematically shown. In particular, the transmitter wheel R may actually have more teeth or other shaped teeth.

  The magnetic field registered by the sensor is now converted into current or voltage. This amount of current or voltage is directly or indirectly proportional to the magnitude of the magnetic field.

  The sensor which is the basis of the diagnostic method according to the present invention transmits a digital signal. For this purpose, the sensor compares the electrical quantity, which is a change in the registered magnetic field, with a threshold and sends a high level signal when and when this electrical quantity is greater than the threshold, A low level signal is sent when the amount is less than the threshold and during that time (or vice versa).

  It is clear that this type of sensor will only output the expected output signal if the threshold is correctly defined and will not require detailed explanation.

  However, in practice, the amount of magnetic field registered by the sensor and the electrical amount that is the amount of the magnetic field changed can vary from one element to another (eg temperature, sensor placement, degree of contamination, age, etc.) It is known to depend. This suddenly makes the threshold that was originally optimally no longer optimal or completely unusable.

  For this reason, self-calibrating sensors are often used. Such a self-calibrating sensor can adjust the threshold by itself to a given state. This is done for example by: That is, during normal operation of the sensor, it is determined by determining in which region the amount to be compared with the threshold has changed, and then changing the threshold, for example, to be located exactly in the center of this region.

  However, such self-calibration does not always give results. That is, self-calibration can only be performed when the transmitter wheel is rotating. This is because only here can be obtained a region in which the amount to be compared with the threshold value changes.

  On the other hand, however, the following is often important: That is, it is important to obtain information on the position or rotational speed of the element to be monitored immediately after the start of operation of the sensor and / or the device comprising the sensor, ie when the transmitter wheel is still stopped.

  This is the case, for example, when the sensor is used to monitor the position and / or rotational speed of the camshaft of an internal combustion engine. In this case, it is desirable that information on the position of the camshaft is already obtained before the internal combustion engine is started. Such information (more precisely, information on whether the sensor is just the teeth or gaps of the transmitter wheel facing the sensor) is necessary to optimally start the internal combustion engine.

  However, since the sensor is not calibrated when and during the camshaft is stopped, it cannot reliably start with the information that the sensor supplies about camshaft position is correct.

  There is a corresponding problem with all other sensors where the output signal depends on whether the detected amount is above or below a threshold value.

  Accordingly, it is an object of the present invention to provide a method for diagnosing a sensor in a motor vehicle having an internal combustion engine in which the output signal of the sensor not reflecting the occupied state (herrschenden Verhaeltnisse) is prevented from being used. . Another object of the present invention is to provide a sensor having a function corresponding to this.

  The above problem is solved by a method for diagnosing a sensor in a motor vehicle having an internal combustion engine. Furthermore, the above-mentioned problem is solved by a sensor whose output signal depends on whether the detected quantity is above or below a certain threshold value, where the sensor is activated during operation. If the threshold used at the start checks whether the correct determination of the signal to be output is guaranteed and if not, the sensor outputs information representing such a situation.

  When the sensor according to the invention is in operation, it is checked whether the threshold used at the start of operation of the sensor guarantees the correct determination of the signal to be output, and if not, the sensor It is characterized by the output of information representing a specific situation.

  This allows the sensor to use the signal output by the sensor, and the signal output by the sensor at the start of the next operation may or may not reflect the occupied state reliably. Communicate that. This prevents the device using the sensor output signal from operating in dependence on information that does not reflect the occupied state.

  Advantageous developments of the invention are described in the dependent claims, the following description and the drawings.

The invention is explained in more detail below on the basis of examples with reference to the drawings.
FIG. 1A shows the time course of the amount detected by the sensor described below,
FIG. 1B shows an output signal that is normally output by the sensor when it detects the course characteristic shown in FIG.
FIG. 1C shows an output signal output by the sensor when it is confirmed that the sensor output signal does not guarantee to reflect the occupied state when the threshold value used at the start of operation is used.
FIG. 2 shows a device including the sensor described below,
FIG. 3 shows a test for whether the threshold is exceeded,
FIG. 4 shows an embodiment of the method according to the invention for diagnosing a sensor in a motor vehicle having an internal combustion engine.

  The sensor described below is a rotation speed sensor that detects the rotation speed or position of a camshaft of an internal combustion engine. Here, a so-called phase sensor is meant by the position of the camshaft. This phase sensor determines in which phase the crankshaft of the internal combustion engine is present. This sensor is precisely a sensor that reacts to a magnetic field. The rotational speed and / or position of the toothed transmitter wheel attached to the camshaft by this sensor and thus the position of the camshaft carrying the transmitter wheel is also determined. This sensor is configured and arranged as follows. That is, the transmitter wheel passes between the sensor and the magnet so that if the transmitter wheel teeth are just facing the sensor, the sensor will register a weak magnetic field and the transmitter wheel teeth will just be facing the sensor. Otherwise, the sensor is configured and arranged to register a strong magnetic field (or vice versa) (if the gap portion faces the sensor).

  The magnetic field registered by the sensor is now converted into current or voltage. The amount of current or voltage is directly or indirectly proportional to the magnitude of the magnetic field. For further observation, we start with the fact that the magnetic field is converted into a voltage. However, the following embodiments are correspondingly effective for converting to current.

  The time course of the voltage resulting from the conversion is shown, for example, in FIG. 1a. The illustrated voltage characteristics are shown normalized. Here, the value 0 is assigned to the minimum voltage, and the value 1 is assigned to the maximum voltage.

  The sensor under consideration outputs a digital sensor. For this purpose, the sensor compares the electrical quantity, which is a change of the registered magnetic field, with a threshold value, and sends a high level signal when and when the electrical quantity is greater than the threshold value. A low level signal is sent when the amount is less than the threshold and during that time (or vice versa).

  The threshold value, indicated by S in FIG. 1A, located exactly in the middle of the maximum and minimum voltages is used to convert the voltage shown in FIG. 1A into the signal to be output by the sensor as described above. In this case, the voltage course characteristic shown in FIG. 1B is obtained.

  The signal shown in FIG. 1B is output by the sensor and evaluated by the device to which the sensor is connected. In this example, it is assumed that only each forward edge of the pulse is considered here. The device for evaluating the signal of the sensor is usually an evaluation circuit that is directly integrated into the sensor. Alternatively, it is a control device that controls the operation of the internal combustion engine (engine control device).

  As already described at the outset, the voltage course characteristics shown in FIG. 1A can vary depending on different factors (eg, temperature, sensor placement, degree of contamination, age, etc.). In particular, it can occur that the minimum voltage increases and / or the maximum voltage decreases or that both the minimum and maximum voltages increase or decrease. As a result, if the threshold suddenly no longer lies in the middle between the minimum and maximum voltages, this can be slowed down and otherwise the condition is the same, the changed analog signal is converted into a digital signal. May result in different results than the signal shown in FIG. 1B.

  Such a situation is considered in this embodiment by: That is, it is taken into account that the sensor used is configured as a self-calibrating sensor. This sensor uses the threshold stored in the sensor only immediately after the system is started, determines a more appropriate threshold as quickly as possible, and uses this instead of the threshold stored in the sensor.

  Theoretically, it would be possible to provide a non-volatile memory in the sensor. In this non-volatile memory, a threshold value that is present last immediately before the end of the operation of the internal combustion engine is stored, and this threshold value is used at the start of the next operation. However, such variations are almost impossible to achieve economically for technical and cost reasons. Therefore, the operation must generally be performed with a threshold stored in the sensor, which is fixedly set.

  The optimum threshold value is determined during operation of the internal combustion engine, for example, by the following. That is, it is performed by obtaining an intermediate value between the maximum voltage and the minimum voltage of the voltage characteristic shown in FIG. 1A or changed with respect to this, and using this intermediate value as a threshold value.

  The sensor considered here has further special points. That is, while the sensor is in operation, the threshold used at the start of operation of the sensor is checked to ensure that the correct determination of the output signal is ensured. It has the special advantage of notifying the device connected to the sensor. That is, in this case, a corresponding signal is transmitted to the engine control device. This transmission is performed by superimposing such additional information on the information to be transmitted first without any loss. This is done by superimposing the main information on the falling edge with respect to the signal that occurs at the temporal position of the rising edge. The rising edge is transmitted as in normal operation, thereby ensuring the system's running function.

  This prevents devices that operate depending on the sensor from operating with sensor signals that may be erroneous at the start of the next activation of the sensor. In other words: if the deviation between the threshold stored in the sensor and the threshold corrected during operation is too great, a signal is transmitted to the engine controller and in a fixed storage in the engine controller Remembered. Based on this stored information, the engine control device suggests that the corresponding sensor (eg the internal combustion engine camshaft phase sensor) is not available at restart or can only be used with limitations. Furthermore, the engine control device can start the internal combustion engine based on an alternative sensor amount or based on a stored characteristic amount. This is usually a so-called emergency function, which in this case is used to carry out the starting of the internal combustion engine. When the internal combustion engine is started and the camshaft begins to move, the sensor calibration process begins, and after the sensor calibration is complete, the output signal supplied by the sensor is used for engine control.

  The sensor considered here signals via the connection that the threshold used at the start of the operation of the sensor does not guarantee the correct determination of the sensor output signal. Through this connection, the sensor sends a signal representing the detected quantity, for example shown in FIG. 1B. In other words, in the present invention, no additional drive control line is required to transmit the error signal, and the connection line of the sensor used in any way in the following manner is used for signal transmission to the engine controller. To do.

  In the present embodiment, this is performed by the following. That is, the duration of the signal to be output for a given pulse (see the signal in FIG. 1B) is shortened, which is the tooth of the transmitter wheel passing through the sensor or the gap portion of the transmitter wheel passing through the sensor ( This is done by not originating from Luecke). This is done in the controller by easy validation.

  The time course of such a course characteristic is shown in FIG. 1C. The signal shown in FIG. 1C is the signal shown in FIG. 1B in the following case. That is, the signal shown in FIG. 1B when the sensor confirms that the correct determination of the sensor output signal is not guaranteed by the threshold used at the start of sensor operation.

  The pulses contained in the signals shown in FIGS. 1B and 1C have rising edges at exactly the same location and are not different in this respect.

  Since the device for evaluating the sensor signal (engine control device) operates in this example only depending on the rising edge of the pulse contained in the sensor signal, this is the case when the signal shown in FIG. 1C is received. It operates in the same way as when the signal shown in FIG. 1B is supplied.

  However, the pulses contained in the signal shown in FIG. 1C are much shorter than in the case of the signal shown in FIG. 1B. This is so short that it does not result from sensor passage through the transmitter wheel teeth or transmitter wheel gap portion. With the unusual length of the pulse, the evaluator identifies: That is, it identifies that the correct determination of the sensor output signal is not guaranteed by the threshold used at the start of sensor operation. The signaling used in FIG. 1C is actually the encoding of the signal shown in FIG. 1B.

  As an alternative to the encoding shown in FIG. 1C, for example, the following two encoded versions can be used.

  In any case, a special pulse width is used when using a pulse width modulated protocol that already conveys additional information.

  In the case of the Manchester coding three-level protocol, encoding is performed by, for example, specific bits.

  How the evaluation device reacts to the correspondingly encoded signal depends on the individual case. It is clear that there are different means for this. In this example under consideration, the evaluation device reacts by: That is, the situation transmitted to the evaluation device is stored in the nonvolatile memory, and the reaction is performed by ignoring the signal supplied from the sensor to the evaluation device at the start of the next operation. This is possible without a major problem in this embodiment. This is because the position of the crankshaft is also obtained, and the position of the camshaft is also obtained from the position of the crankshaft. Such a camshaft position calculation is not as accurate as a camshaft calculation by a sensor provided on the camshaft, but is sufficiently accurate to start the engine. This is a so-called emergency function.

  The camshaft rotates after the engine starts, so the sensor that detects the camshaft position calibrates itself to determine and use the optimum threshold. As long as this is done, the sensor output signal is used without limitation.

  Note that the following is just in case. That is, it should be noted that this sensor may be another sensor whose output signal depends on whether the detected amount is above or below the threshold. The measurement signal determined during operation is used to predict future conditions by comparison with a target value, which is already transmitted during operation by output of additional information.

  The special features of the sensors described above have proven advantageous with non-self-calibrating sensors.

  Also note that the optimal threshold does not have to be centered between the maximum and minimum input quantities; in some use cases the threshold is more or less well above the median, or It may be required to be below.

  Ultimately, the threshold used at the start of sensor start-up does not necessarily have to be stored in the sensor; this threshold may be supplied to the sensor from somewhere else at the start of operation.

  The sensor described above prevents the possibility of using sensor output signals that do not reflect the occupancy state without depending on the details of the actual implementation.

  FIG. 3 shows the vibration of the sensor output signal 31 in a so-called drift situation. Here, the maximum output value and the minimum output value of the sensor drift over time and deviate from the original values. In FIG. 3, the time axis is shown on the horizontal line, and the amplitude of the sensor signal is shown on the vertical line. The threshold value stored in the sensor in a fixed manner by the broken line 32 is shown. The vertical line 33 reliably confirms that the minimum value of the sensor output signal 31 has exceeded the threshold, and thus indicates when reliable function is no longer guaranteed when the sensor is switched on. At this point, the present invention informs the engine controller or general controller that the sensor may supply inaccurate data when the vehicle is restarted. This is also the case for example as follows. That is, even when the sensor signal falls and the maximum value of the sensor signal falls below the threshold value. In general, two different thresholds may be defined for the minimum and maximum values of the sensor signal.

  In other words: if the minimum or maximum value of the sensor signal drifts away and exceeds or falls below the threshold, the sensor does not provide a reliable output signal with a high probability when the car is restarted and after calibration is performed You have to start from being able to use it for the first time. Corresponding information is stored in the non-volatile memory of the engine controller and is queried from the controller in a new restart situation.

  During further operation of the internal combustion engine or sensor, if it becomes clear that the output signal of the sensor is again within the area allowing evaluation after restart, the entry made in the engine controller memory is reset. The

  In the context of the present invention, the threshold value stored in the sensor, which is used immediately after starting the internal combustion engine, and the threshold value resulting from calibration performed during operation of the internal combustion engine must be clearly distinguished. . The threshold value resulting from calibration performed during operation of the internal combustion engine is stored, for example, in the volatile memory of the sensor.

  FIG. 4 shows a method according to the invention for diagnosing a sensor in a motor vehicle having an internal combustion engine. The method starts at step 41 with a start request, for example, by a driver of the car operating an ignition key. Subsequently, in step 42, it is checked whether this sensor can be used to control the internal combustion engine. This is done by reading the corresponding information from the non-volatile memory of the engine controller. If it is determined that the sensor or sensor output signal is available, a normal start of the internal combustion engine is performed at step 43 using the sensor data. When it is determined that the sensor data is not used, the process proceeds to step 44. In step 44, the emergency function is activated. For example, as described above, a crankshaft angle sensor is used to locate the camshaft. In step 45, which leads to both step 43 and step 44, the sensor is calibrated. Here, the minimum value and the maximum value are detected, and the threshold value is set to an intermediate value. In step 46, the measured minimum and maximum values are checked for violating the threshold criteria described above. If so, in step 47, an error signal is transmitted to the engine controller in accordance with the present invention. This information is stored in non-volatile memory in the engine controller and is used for the next starting process. If it is determined in step 56 that the threshold criteria is not violated, then in step 48 the error entry, possibly present in the non-volatile memory of the controller, is erased. After steps 47 and 48, the method continues to step 45. This loop is performed until the internal combustion engine is deactivated.

FIG. 1A is a diagram showing a temporal characteristic of an amount detected by a sensor, and FIG. 1B is a diagram showing an output signal normally output by the sensor when the characteristic shown in FIG. 1a is detected. FIG. 1C is a diagram showing an output signal output by the sensor when it is confirmed that the sensor output signal does not guarantee the occupied state when the threshold value used at the start of operation is used. It is a figure showing the apparatus containing a sensor. It is a figure showing the test | inspection about whether it exceeded the threshold value. 1 represents an embodiment of a method according to the invention for diagnosing a sensor in a motor vehicle having an internal combustion engine. FIG.

Claims (7)

A method of diagnosing a phase sensor of a camshaft of an automobile having an internal combustion engine,
During operation of the motor vehicle, the output signal of the phase sensor of the cam shaft, the minimum value of whether the maximum value is below the threshold value stored in the phase sensor of the cam shaft or the output signal of the output signal the Inspect whether the threshold value stored in the camshaft phase sensor has been exceeded,
When the maximum value falls below the threshold value stored in the camshaft phase sensor or the minimum value exceeds the threshold value stored in the camshaft phase sensor, Transmitting a signal to the control device that informs the control device that the phase sensor of the camshaft may supply incorrect data upon restart;
When the maximum value exceeds the threshold value the minimum value or falls below the threshold value stored in the phase sensor of the cam shaft is stored in a phase sensor of the cam shaft, first crank The output signal of the shaft sensor is used to control and / or adjust the vehicle when the vehicle is restarted, and the camshaft phase sensor is again controlled and / or adjusted after the camshaft phase sensor is self- calibrated. Or used for adjustment,
A method of diagnosing a phase sensor of a camshaft of an automobile having an internal combustion engine. The method of claim 1, wherein the calibration is performed by learning a maximum output value and a minimum output value of a phase sensor of the camshaft . The signal is stored in a non-volatile memory in the control device, whereby the signal that informs the control device that the camshaft phase sensor may supply incorrect data when the vehicle is restarted is an internal combustion engine. The method according to claim 1, wherein the method is used directly upon restarting. The start of the internal combustion engine, in emergency, performed without using a phase sensor of the cam shaft, the method of claim 1. The method of claim 1, wherein the threshold is stored in a fixed storage of a phase sensor of the camshaft . 6. The method of claim 5 , wherein the threshold is adjusted by calibration of the camshaft phase sensor. The method of claim 1, wherein the signal is encoded and transmitted to inform a controller that the camshaft phase sensor may supply incorrect data when the vehicle is restarted.

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