Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups
  • G01P21/02—Testing or calibrating of apparatus or devices covered by the preceding groups of speedometers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
  • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
  • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
  • G01D5/2006—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
  • G01D5/2013—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils by a movable ferromagnetic element, e.g. a core
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/42—Devices characterised by the use of electric or magnetic means
  • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
  • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
  • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
  • G01P3/489—Digital circuits therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/009—Electrical control of supply of combustible mixture or its constituents using means for generating position or synchronisation signals

Definitions

• the present invention relates to a device according to the preamble of claim 1, i.e. a sensor whose output signal depends on whether a detected variable is above or below a certain threshold.
• Such a sensor is, for example, a sensor which reacts to magnetic fields and by means of which the rotational speed and / or the position of a sensor wheel provided with teeth
• Sensor of this type is constructed and arranged in such a way that the sensor wheel, the position or rotational speed of which is to be determined, passes between the sensor and a magnet, as a result of which the sensor registers a weak magnetic field when it is currently facing a sensor wheel tooth, and as a result of which the Sensor registers a strong magnetic field when it is not currently facing a sensor wheel tooth (a gap) (or vice versa).
• FIG. R denotes the sensor wheel, G a sensor containing the magnet and the sensor, and W the element on which the sensor wheel R is mounted and whose speed of rotation and / or position is to be determined; is the element W.
• the element W for example the crankshaft or the camshaft of an internal combustion engine.
• FIG. 2 For the sake of completeness, it should be pointed out that the arrangement shown in FIG. 2 is shown in a highly schematic manner. In particular, the encoder wheel R will have more teeth in practice.
• Size is directly or indirectly proportional to the size of the magnetic field.
• the sensor considered here outputs a digital signal. For this purpose, it compares the electrical variable into which the registered magnetic field has been converted with a threshold value, and outputs a signal with a high level if and as long as the electrical variable is larger than the threshold value, or outputs a signal with a low level Level off if and as long as the electrical quantity is smaller than the threshold value (or vice versa).
• Factors such as the temperature, the arrangement of the sensor, the degree of contamination, the age etc. depend on, whereby an originally optimally defined threshold value is suddenly no longer optimal or completely unusable. For this reason, self-calibrating sensors are often used, which can independently adapt the threshold value to the given conditions. This can be done, for example, by the sensors determining during normal operation in which area the variable to be compared with the threshold value varies, and then changing the threshold value so that it lies exactly in the middle of this area.
• the present invention is therefore based on the object of developing the sensor according to the preamble of claim 1 in such a way that the use of output signals of the sensor which do not reflect the prevailing conditions can be prevented.
• the sensor according to the invention is characterized in that it checks during operation whether a correct determination of the signal to be output can be ensured by a threshold value used when the sensor is started up, and that the sensor then detects that this is not the case outputs information representing this fact.
• the sensor can thereby inform the device which uses the signals it outputs that the signal which it outputs the next time it is started up may or may not reflect the prevailing conditions. This can prevent the device using the sensor output signals from operating depending on information that does not reflect the prevailing conditions.
• FIG. 1A shows the time course of a variable detected by the sensor described below
• FIG. 1B shows the output signal which the sensor normally outputs when the course shown in FIG. 1A is recorded
• Figure IC shows the output signal that the sensor outputs when it has determined that the use of a threshold value used during commissioning cannot guarantee that the sensor output signal reflects the prevailing conditions
• Figure 2 shows an arrangement containing the sensor described below.
• the sensor described below is a speed sensor for detecting the speed or the position of the camshaft of an internal combustion engine. More precisely, it is a sensor that reacts to magnetic fields, by means of which the rotational speed and / or the position of a toothed sensor wheel attached to the camshaft, and thus also the position of the camshaft carrying the sensor wheel, can be determined.
• This sensor is constructed and arranged in such a way that the sensor wheel passes between the sensor and a magnet, whereby the sensor registers a weak magnetic field if it is currently facing a sensor wheel tooth, and the sensor registers a strong magnetic field if it is not currently using a sensor wheel —Tooth (a gap) faces (or vice versa).
• the magnetic field registered by the sensor is converted into a current or a voltage, the size of which is directly or indirectly proportional to the size of the magnetic field. For the further considerations it is assumed that the magnetic field is converted into a voltage.
• the time course of the voltage resulting from the conversion is shown by way of example in FIG. 1A.
• the voltage curve shown is shown standardized, with the minimum voltage being assigned the value 0 and the maximum voltage being assigned the value 1.
• the sensor considered here outputs a digital signal. For this purpose, it compares the electrical variable into which the registered magnetic field has been converted with a threshold value, and outputs a signal with a high level if and as long as the electrical variable is larger than the threshold value, or outputs a signal with a low level Level off if and as long as the electrical quantity is smaller than the threshold value (or vice versa).
• the signal shown in FIG. 1B is output by the sensor and evaluated by the device to which the sensor is connected. In the example considered, it is assumed that only the leading edge of the pulse is of interest here.
• the voltage curve shown in FIG. 1A can change depending on various factors such as, for example, the temperature, the arrangement of the sensor, the degree of contamination, the age, etc. In particular, it can happen that the minimum voltage increases and / or the maximum voltage decreases, or both the minimum voltage and the maximum voltage increase or decrease.
• the sensor used is designed as a self-calibrating sensor which only uses the threshold value stored in the sensor immediately after the system has been started up and as quickly as possible determines a more suitable threshold value and this instead of the threshold value stored in the sensor used.
• the optimum threshold value can be determined, for example, by determining the mean value between the maximum voltage and the minimum voltage of the voltage curve shown in FIG. 1A or modified in comparison thereto, and using this mean value as the threshold value.
• the sensor considered here also has the
• this is done by making the duration of the pulses present in the signal to be output (signal according to FIG. IB) so short that they cannot originate from a tooth of the sensor wheel running past the sensor or from a gap of the sensor wheel running past the sensor.
• FIG. 1C The time course of such a signal is illustrated in Figure IC.
• the signal shown in FIG. 1C is the signal shown in FIG. 1B in the case where the sensor has determined that the sensor output signal cannot be properly determined by the threshold value used when the sensor was started up.
• the pulses contained in the signals according to FIGS. IB and IC have the rising edges at exactly the same points and do not differ in this point.
• the device evaluating the sensor signals in the example under consideration only works depending on the rising edges of the pulses contained in the sensor signals, it can when receiving the signal shown in FIG. IC, work exactly as if it were to be supplied with the signal shown in FIG. IB.
• the pulses contained in the signal according to FIG. IC are much shorter than is the case with the signal according to FIG. IB. They are so short that they cannot result from a sensor wheel tooth or a sensor wheel gap passing the sensor.
• the evaluation device can recognize from the extraordinary length of the pulses that the threshold value used when the sensor is started up cannot ensure that the sensor output signal is properly determined.
• the evaluation device reacts to this depends on the individual case. It should be clear that there are many different possibilities for this. In the example under consideration, the evaluation device reacts by storing the fact communicated to it in a non-volatile memory and by the next time it is started up
• the camshaft rotates so that the sensor that detects the camshaft position can now calibrate itself and determine and use an optimal threshold value.
• the sensor output signals can be used without restrictions.
• the sensor can also be any other sensor whose output signal depends on whether a detected variable is above or below a threshold value.
• the optimal threshold does not have to be midway between the maximum and minimum inputs; depending on the application, it may be necessary that the threshold is more or less far above or below the mean.
• the threshold value used when starting up the sensor is stored in the sensor; this threshold value can also be supplied to the sensor from elsewhere during commissioning.
• the senor described can prevent the sensor output signals that do not reflect the prevailing conditions from being used.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (2)

Families Citing this family (7)

• 2001
  • 2001-08-09 DE DE2001139149 patent/DE10139149A1/de not_active Withdrawn
• 2002
  • 2002-07-18 WO PCT/DE2002/002631 patent/WO2003016921A2/fr not_active Application Discontinuation

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