FR2797303A1 - GEODESTIC ALTIMETRIC DETECTION FROM PRESSURE IN THE SUCTION TUBING OF A MOTOR VEHICLE ENGINE - Google Patents

Abstract

Geodetic altimetric detection from the pressure in the suction pipe of a motor vehicle engine. Means (10) capture the pressure in the suction pipe as well as other operating parameters such as the speed of rotation and the temperature of the engine. The measured values of the pressure in the suction pipe are filtered by a filter (13), the time constant of which depends on the operating parameters. The altimetric detection is used in particular to cut or restart on-board diagnostic functions.

Description

I

State of the art.

  The present invention relates to an al-

  timetric geodesic from the pressure in the tubu-

  suction lure of a motor vehicle engine with means for sensing the pressure in the suction manifold and other operating variables such as the speed

and the engine temperature.

  Knowledge of atmospheric height ins-

  of operation of a motor vehicle is im-

  particularly for correctly dosing the fuel because

  this presupposes precise knowledge of the air mass aspirated

  dream. Due to the difference in air density at different altitudes of the vehicle, the precise capture of the mass of aspirated air can become difficult. This is why various solutions have been proposed for correcting the influence of the altitude on the signal of the quantity of air or of the mass of air sucked in per suction phase, generally called the load signal. By way of example, reference is made to document DE 44 34 265 Ai which relates to a

  "load entry system with altimeter adaptation

  trique ". This document describes an installation for entering the

  load with altimetric adaptation, according to which

  mines the charge from a main charge signal

  during altitude and an auxiliary load signal

  independent of altitude. In some operating states

  by comparison of the main load signal and the

  general auxiliary load, we can evaluate a current geodetic height. By a specific calculation, we form a

  adaptation coefficient to minimize the altitude error.

  The document US Pat. No. 5,226,393 relates to an altitude detection system for an internal combustion engine, to ensure control, as a function of the altitude, of the fuel supply, of the quantity of air drawn in and

from the ignition point.

  Taking into account the on-board diagnostic (OBD) required by American regulations, to determine

  the instantaneous altitude of the vehicle position, it was born

  stop being able to cut off the on-board diagnostic above a certain altitude. The altitude signal can

  thus be grasped in principle with an absolute pressure sensor

  read whose output signal can be corrected depending on the temperature if necessary. Such pressure sensors

  absolute however necessarily increase the cost of the vehicle

  runs so the tendency is to grab the pressure

  absolute and thus the atmospheric height using the large

  measuring instruments already existing in the motor vehicle.

  Thus, the object of the present invention is to

  set, with simple and reliable means, starting from the cap-

  pressure gauge of the suction manifold, to determine a value of the atmospheric height among others to provide a cut-off signal from the on-board diagnostic

  of a defined altitude, in order to eliminate the diagnostic states

  tic critical for error detection.

Advantages of the invention.

  To this end, the invention relates to an altimetric detection characterized in that the measurement values of the pressure in the suction pipe are calculated continuously and according to the operating point relative to the ambient pressure, then these values are

  subject to filtering, the time constant of the filter

  during operating parameters.

  The system according to the invention allows a measurement

  sure / combined simulation of the atmospheric height from a signal from the pressure sensor in the suction pipe and, finally, a cut signal is obtained

  and reliable connection for on-board diagnostics.

  According to other advantageous characteristics of the invention: * the time constant of the filter depends at least on the

  operating quantity under load (range) and one cry-

  quality gauge dependent on the operating point for the calculation, in particular the engine temperature; * altimetric detection is used to cut functions

OBDII.

  * the interruption of the OBDII functions takes into account a pressure or altitude tolerance value; * the interruption of the OBDII functions takes into account a waiting time; e a pressure in the suction pipe, obtained during the initialization and / or shutdown phase (engine speed substantially zero), is used directly for assigning the altitude; * in pushing mode, at least one replacement value for the pressure in the tubing is taken into account

  of suction, and the calculation is made in the direction of an al-

lower titude.

  * the pressure tolerance value for cutting the

  OBDII functions depend on at least one of the following quantities

  values: tolerance of the pressure sensor, value of

  persion of the internal combustion engine or vehicle,

meteorological variation.

  Drawings. A geodetic altitude detection from the pressure in the suction pipe, according to the invention, in the case of a motor vehicle, is shown by way of example in the appended drawings in which:

  * Figures 1a and 1b show measurements or simulations

  characteristic values of pressure values giving the atmospheric height, and

  * Figure 2 shows a very simplified block diagram.

  Description of the exemplary embodiment.

  Figures la, lb show an "elevated profile

  trunk ", plotted against time, traveled for a certain

  tain journey of a vehicle and for different operating conditions. In Figure 1 the X axis represents time and the Y axis atmospheric pressure; a higher value of

  1013 mbar represents zero normal pressure (NN); a va-

  their 740 mbar, located in the lower third, represents a relatively large altitude and, finally, the reference B-nobd represents a lower signal value of 740 mbar. This value B-nobd constitutes the important altitude mark for switching off or restarting the functions

  on-board diagnostic. Between the values of 740 mbar and B-

  nobd, we have a PTOL pressure tolerance band.

  The pressure values, shown in the figure

  1, are entered using a pressure sensor in the tube

  suction bulb; they are partially simulated and are

  provided, as part of an appraisal process

  falling in FIG. 2, as a value puf supplied by a low-pass filter. The bottom line of Figure 1 shows

  the operating conditions during this shift cycle

thus registered.

  To better understand the pressure curve puf

  shown in Figure 1, refer to Figure 2.

  This figure shows a suction pressure sensor 10, a block 11 providing different replacement values

  depending on the operating state or the operating condition-

  internal combustion engine or vehicle. These operating conditions are determined in a block 12 which makes them available. Reference 13 relates to a low-pass filter which receives as input quantities both the output signal calculated in return from the suction pressure sensor 10 as well as various replacement values of block 11, applied via 'a switch

14 represented symbolically.

  The return calculation mentioned above applies the correlation of the instantaneous pressure in the tubing

  suction to the surrounding pressure; we hold in part

  especially account for pressure losses. The time constant of

  filter 13 can also be ordered and depends on the conditions

  operating conditions which must be determined in block 12. To supply the filter time constants depending on the operating conditions, there is a switch 13 which can supply, according to different operating conditions, different values of a block 16, for example depending on

  initialization, of the maximum load, of the load per-

  tial or lower load range. It is interesting-

  as long as the filter time constant depends at least on operating characteristics such as the load or the load range, and on a quality criterion depending on the

  operating point, for the calculation, in particular the temperature

engine erasure.

  The output signal of the filter 13 carries the reference

  rence puf (environmental pressure, filtering). Then there is a threshold switch 18 which receives the output signal from the filter 13 as the first input quantity x whereas at the output it provides, for the threshold, directly a signal y of a limit value block 19 When the puf signal applied to the input x of the threshold switch 18 passes below the threshold y, in a practical case, there is emission of a positive signal which, at the end of a waiting time in the wait time block 20, finally provides the signal B-nobd for

cut the OBD function.

  In an operating cycle, at the instant TO (FIG. 1a) begins an initialization phase of the motor vehicle control unit, for example by actuation of the ignition switch. With the engine still at rest, the value of

  pressure supplied by the pressure sensor 10 in the tubu-

  suction lure. Block 12 of operating conditions

  in Figure 2 recognizes this initialization phase and as-

  on a corresponding actuation of switches 14 and 15

  so that the value of the signal from sensor 10 is transmitted directly

  directly to filter 13 with a sufficient filter time constant for the initialization phase but sufficient

  weak so that ultimately the output signal puf of the wire-

  tre 13 largely corresponds to the measured value ac-

  during the initialization phase.

  If, at time tl, the engine is started with

  internal bustion, according to the example in FIG. 1a, there is a partial load (TL) operating mode; according to this operating mode there is first an ascent then a descent. This is expressed by an initial pressure drop

  followed by an increase in pressure until time t2 which in-

  indicates a certain end of the partial charge phase. Pen-

  During this partial charge phase TL, the values of the signals from the suction pressure sensor 13 are continuously entered and are processed in the filter 13 according to FIG. 2, with a filter time constant corresponding to this.

  operating mode. Between times t2 and t3, we suppress

  poses that there is a pushing mode with a throttle flap closed or practically closed. In this case, the strong suction effect of the internal combustion engine gives a very low absolute pressure in the manifold

  with the risk that the result of the calculation could

  could be falsified for altitude, for the given measurement values of the pressure sensor. For this reason, in

  pressure, an increase in pressure is signaled and thus a decrease

  nution of the atmospheric height because a prolonged thrust mode can only correspond to a descent. The filter 13 of FIG. 2 is thus assigned a replacement value for a filter time constant then fixed empirically; this constant is predetermined in block 16. The pushing mode ends at time t3 and there will finally be a relatively short journey time until time t4 on a horizontal roadway. After time t4 we go to maximum load; the maximum load mode is frequently synonymous with a rise, so that the atmospheric pressure decreases again. This operating mode is taken into account with a pressure signal

only weakly filtered.

  The path between instants t5 and t6 corresponds to

  lays at a slight increase in height, symbolized, re-

  presented by the lower charge and so by filtering

stronger.

  Beyond t6 we assume that we are

  again in partial charge mode as part of a new

  velle rise (with a small part of descent) so that at time t7 we are at the limit pressure PGlim equal by

example at 740 mbar.

  To ensure that this function is not prematurely disabled for diagnostic functions in practical situations, a strip of

  tolerance for the pressure value (PTOL) whose meaning

  cation is explained by the shape of the signal in Figure lb. When the puf pressure decreases again after a rise

  provisional, it reaches at time t8 a characteristic limit

  sed by PGlim minus PTOL. This PTOL tolerance band must be chosen independently of the tolerances of the sensors, the dispersion of the engine and / or the maximum atmospheric variations evaluated, which are perceptible for example in the form of the temperature of the air drawn in. If the signal

  the output of the threshold switch 18 according to FIG. 2 is

  passed down for the first time at time t8, then the signal block "waiting time" is triggered for the time delay at connection 20. For the continuation of the signal form after time t8, we assume that there is a variation

  relatively fast pressure value puf applica-

  ble then around this threshold PGlim minus PTOL, with the consequence that we will not immediately have the necessary residence time of the signal below this limit because the waiting time must start again with the new

  exceeding the limit but ends all-

  times if, during the waiting time, the pressure exceeds by

again this threshold.

  It is assumed that at time t9 begins a prolonged phase of pressure drop so that at time t10,

  the waiting time to guarantee detection of this high

  teur, is finished; this results in the signal B-nobd which if-

  general possibility of cutting diagnostic operations. At time t11, it is assumed that the value of the pressure PGlim reduced by PTOL is again exceeded upwards. As there is no waiting time in this case, the B-nobd signal ends at the same time. Thus, the diagnostic functions when the value is exceeded

  are activated again immediately.

  In the geodetic altitude detection from the suction pipe described above, the important thing is to subject to a filtering the measurement values of the pressure in the suction pipe, and that the constant

  of the filter depends on the characteristic operating variables -

  ment. In addition, depending on the operating conditions, replacement values of the measurement signal of the

  pressure sensor in the suction pipe. By in-

  straight, in particular for prolonged pushing phases, a corresponding rise in the pressure signal is thus simulated by the greatest deviation between the pressure in the suction pipe and the ambient pressure existing in the pushing mode.

  It is particularly advantageous to also introduce a pressure tolerance band PTOL which is adjacent to the lower limit pressure PGlim. This allows

  to have a pressure tolerance band depending on the different operating parameters.

Claims (6)

R E V E N D I C A T I ON S   1) Geodetic altimetric detection from pressure   in the intake manifold of a motor vehicle engine   bile with means for capturing the pressure in the tubu-   suction and other operating variables such as engine speed and temperature, characterized in that * the measured values of the pressure in the manifold   are continuously calculated and followed   before the operating point relative to the ambient pressure, then these values are subject to filtering, * the time constant of the filter depending on the parameters Operating.   2) Detection according to claim 1, characterized in that   the filter time constant depends at least on the large   operating time under load (range) and a quality criterion depending on the operating point for the start of the   calculation, including engine temperature.   3) Detection according to claim 1, characterized in that   altimetric detection is used to cut OBDII functions.   4) Detection according to claim 3, characterized in that the cut-off of the OBDII functions takes account of a value of   pressure or altitude tolerance.    ) Detection according to claim 3, characterized in that the interruption of the OBDII functions takes account of a waiting time. 6) Detection according to claim 1, characterized in that a pressure in the suction pipe, obtained during the initialization and / or shutdown phase (engine speed substantially zero), directly serves for the allocation of the 'altitude.   7) Detection according to any one of claims 1 to   6, characterized in that in pushing mode, account is taken of at least one replacement value of the pressure in the suction pipe and   the calculation is made in the direction of a lower altitude.   8) Detection according to claim 4, characterized in that   the pressure tolerance value for switching off the functions   OBDII depends on at least one of the following quantities:   tolerance of the pressure sensor, dispersion value of the mo-   internal combustion engine or vehicle, weather variation loqique.