JP2001082241A - Geodetic level detecting circuit derived from vehicular intake pipe pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a state determined critical s an error by filtering to set the time constant of a filter thereof according to a movement property amount, after return calculating the measurement value of intake pipe pressure to an ambient pressure depending on an operating point. SOLUTION: An output signal of an intake pipe pressure sensor 10 return calculated as an input value of a low pass filter(LPF) 13, and each substitution value from a block 11 are supplied through a switch 14, and a switch 15 is provided for adjusting a filter time constant depending on an operating condition of the LPF 13. The switch 15 sent out various values from a block 16 by depending on an initialization circuit, all loads, a partial load and the like. The output signal of the LPF 13 is supplied to a threshold value switch 18 as a first input amount (x), and compared with a threshold value (y) from a limit value block 19. According to a deviation signal, a signal for shutting down an on-board diagnosing function is sent out through a delay circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a geodesic level detection derived from an intake pipe pressure of a vehicle equipped with means for detecting the intake pipe pressure and other operating characteristics, for example, the rotational speed and the engine temperature. Circuit.

[0002]

BACKGROUND OF THE INVENTION It is important to know the instantaneous atmospheric level during operation of a vehicle, especially from the viewpoint of accurate fuel metering. This is because accurate fuel metering is based on accurate knowledge of the amount of intake air. When the height of the location point of the vehicle is variously different, the air concentration is different, so that it is difficult to accurately detect the amount of inhaled air. Thus, several proposals have already been made for correcting the effect of height on the signal of the amount of air taken or the signal of the amount of air per suction stroke (generally represented by the load signal). For example, German Patent Application Publication No. 44
No. 34265 describes "Einrichtung zur Lasterfassu
ng mit Hoehenadaptation ". This shows a device that performs load detection with level adaptation, where the load is a height dependent main load signal and a height independent sub load signal. And is determined based on
By comparing the main load signal and the sub load signal in a predetermined running state, the geodetic height at that time can be evaluated. Subsequently, by using a special formula, an adaptive coefficient for reducing the height error is formed.

[0003] US Pat. No. 5,226,393 discloses that
A level detection system of an internal combustion engine for controlling the fuel supply, the intake air quantity and the ignition timing as a function of height is shown.

Considering the on-board diagnosis OBD related to the above-mentioned patent specification, it is necessary to shut off the on-board diagnosis at a predetermined level or more in order to detect the height of the vehicle position at that time. The signal relating to the level here is basically detected by an absolute pressure sensor, the output signal of which must be corrected, possibly depending on the temperature. Moreover, this type of absolute pressure sensor necessarily increases the cost of the vehicle. For this purpose, efforts are being made to detect the absolute pressure and thus the atmospheric level by means of existing measured quantities of the vehicle.

[0005]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a simple and reliable means for detecting an atmospheric level value based on an intake pipe pressure sensor. The purpose is to provide a shut-off signal so that a condition diagnosed as critical can be excluded as an error.

[0006]

SUMMARY OF THE INVENTION This object is achieved by a method in which the measured intake pipe pressure is calculated back to ambient pressure in a continuous and operating point-dependent manner, and then the measured intake pipe pressure is filtered. Is solved by a configuration that depends on the operation characteristic amount.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS With the device according to the invention, a combination of atmospheric level measurement and simulation is performed based on the signal of the intake pipe pressure sensor, and furthermore a reliable switch-off signal for on-board diagnosis and re-switching. An ON signal is supplied.

[0008] Further advantages of the invention result from the following description of embodiments in connection with the dependent claims.

[0009]

1 and 2 show a "level profile" with respect to time. This represents the level detected when assuming that the vehicle runs under various operating conditions for a predetermined time. 1 and 2, the X axis represents time, and the Y axis represents the atmospheric pressure value. Here, the upper value of 1013 hPa indicates a normal zero pressure value NN, and the lower 7
The value of 40 hPa reflects a relatively large height. Further, the value B-nobd is a signal value representing 740 hPa or less. This value B-nobd is an important value for shutting off the on-board diagnostic function and switching on again. There is a so-called pressure tolerance zone PTOL between the value 740 hPa and B-nobd.

The pressure values read from FIGS. 1 and 2 are detected by an intake pipe pressure sensor and simulated for each section, and are prepared as low-pass filtered values puf in the range of the detection method read from FIG. . The operating conditions during the assumed driving cycle are shown in the lower rows of FIGS.

The pressure characteristics puf which can be read from FIGS.
FIG. 3 is provided for a better understanding of.
Here, reference numeral 10 designates an intake pipe pressure sensor, and reference numeral 11 designates a block for adjusting various replacement values depending on the operating state of the vehicle or the operating conditions of the internal combustion engine. These operating conditions are detected and adjusted at block 12. A low-pass filter is indicated by the reference numeral 13, in which the output signal of the intake pipe pressure sensor 10 and the individual replacement values from the block 11 are symbolically indicated by a switch 14 as input values. Supplied. The above-mentioned back calculation includes the correlation between the current intake pipe pressure and the ambient pressure, in which the flow-induced pressure losses are taken into account in particular. The filter time constant of the filter 13 can be controlled in a similar manner.
It depends on the operating condition obtained in. The switch 15 is used to adjust the filter time constant depending on the operating conditions. This switch provides different values from block 16 for different operating conditions, such as initialization circuitry, full load,
Deliver depending on the partial load or the lower load area.
In this case, the filter time constant preferably depends at least on the load or load area and on the operating point-dependent quality criterion for the calculation formula, in particular on the operating parameters such as the engine temperature.

The output signal of the filter 13 is represented by puf (filtered by pressure and environment). Subsequently, the output signal of the filter 13 is supplied as a first input quantity x to a threshold switch 18, on the input side of which the threshold value itself is adjusted by a limit value block 19. If the signal value puf falls below the threshold value y at the input x of the threshold switch 18, a positive signal is actually sent out. This signal sends out a signal B_nobd for cutting off the OBD function after the waiting time has elapsed in the waiting time block 20.

At time t0 (FIG. 1) during the driving cycle, the initialization phase of the control unit of the vehicle is started, for example, by operating an ignition switch. The pressure value of the intake pipe pressure sensor 10 is read and stored while the engine is still stopped. The operating condition block 12 of FIG. 3 detects this initialization phase by operating the corresponding switches 14, 15 and conducts the signal value of the sensor 10 directly to the filter 13. The filter time constant, which is sufficient for the initialization phase but is very small, will ultimately
Output signal puf approximately corresponds to the instantaneous measured value during the initialization phase.

When the time point t1 of the internal combustion engine starts, FIG.
According to the embodiment, the partial load operation TL is started. Here, the ascending traveling on the slope is performed first, and then the descending traveling on the slope is performed. This initially results in a pressure drop, followed by a pressure rise until time t2, at which point a predetermined end of the partial load phase is indicated. Partial load phase TL
During the operation, the signal value from the intake pipe pressure sensor 13 is continuously detected, and a predetermined filter time constant provided for this operation is processed by the filter 13 in FIG. From time t2 to t3, an engine braking operation or overrun occurs due to the closing or rapid closing of the throttle valve. In this case, due to the strong intake effect of the internal combustion engine, very low absolute pressures occur in the intake pipe, which leads to a risk of misleading the calculation at a given measured value of the pressure sensor for the level. For this purpose, an increase in pressure, i.e. a decrease in atmospheric level, is signaled during engine braking.
This is because a relatively long engine braking operation occurs only when traveling downhill. Thus, the filter 13 of FIG. 3 is supplied with a replacement value for an empirically determined filter time constant preset in block 16.

[0015] The engine braking operation ends at time t3, and in a flat section, at a relatively short running time at time t4.
Ends by After time t4, the case of full load is shown, where full load is often synonymous with climbing up a hill and the atmospheric pressure drops again. In this operating state, pressure signals with only weak filtering are taken into account.

From t5 to t6, a slight level increase is shown, which is indicated by the lower load and the strong filtering.

After t6, the partial load operation is again shown in the range of ascending traveling on another slope (with a small descending component). Thereby, at time point t7, a limit pressure PGrenz of, for example, 740 hPa is achieved.

To ensure that existing functions in specific situations are deactivated at the appropriate time and diagnostic functions are used, a tolerance band PTOL for pressure values is used. The significance of this band is clear from the signal characteristics following FIG. If the pressure value puf is newly reduced after a temporary rise, this pressure value is reduced at time t8 by PGrenz-
The limit value represented by PTOL is reached. In this case, the tolerance band PTOL must be selected as a function of the tolerance of the sensor, the variance of the engine and / or the maximum climate change recognized and evaluated, for example, via the intake air temperature. If the output signal of the threshold switch 18 of FIG. 3 is only exceeded below at time t8, the signal block triggers a waiting time for the switch-on delay 20. A further signal characteristic after time t8 is shown, in which it can be seen that the pressure value puf deviates relatively quickly around the threshold value PGrenz-PTOL. As a result, the required dwell time for signals below this threshold is not achieved immediately. This is because the waiting time is started anew whenever there is a new lower limit is exceeded, and ends when the pressure rises again above this threshold during the waiting time.

At time t9, a relatively long phase of pressure drop is started, and at time t10, a waiting time elapses to reliably detect the level. This results in the formation of a signal B-nobd, which signals a possible interruption to the diagnostic process. At time t11, the pressure value PGrenz-PT
OL is exceeded again. In this case, since no waiting time is provided, the signal B-nobd also ends at the same time. The diagnostic function is thereby activated again as soon as the pressure value is exceeded.

An important point in the detection of the geodesic level derived from the above-mentioned intake pipe is that the measured value of the intake pipe pressure is subjected to filtering, and the filter time constant depends on the operation characteristic amount. Further, a substitute value for the measurement signal from the intake pipe pressure sensor is prepared according to the operating condition. In each section, the rise of the pressure signal that appears together, especially during relatively long engine braking operations, is simulated. This is because there is a large difference between the pressure in the intake pipe and the ambient pressure in the case of engine braking operation. Particular preference is given, as mentioned, to the pressure tolerance zone PTOL, which approaches the lower limit value PGrenz. In this case, the pressure tolerance zone is formed depending on various operating conditions.

[Brief description of the drawings]

FIG. 1 shows the measurement and simulation of a pressure value representing the level of the atmosphere.

FIG. 2 shows the measurement and simulation of a pressure value representing the level of the atmosphere.

FIG. 3 is a schematic block circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Intake pressure sensor 11 Replacement value preparation block 12 Operating condition block 13 Filter 14, 15 Switch 16 Block 18 Threshold switch 19 Limit value block 20 Switch-on delay circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jurgen Stock, Germany Eberdingen Haakstrasse 43 (72) Inventor Joachim Var, Germany Birkenheide Peter-Paul-Rubensstrasse 6 (72) Inventor Tar John Gwong South Korea Yong-si Xang-sang-Mun-Sanghari-in-Yung Apartment 1133-1503

Claims (8)

[Claims] 1. A geodesic level detection circuit derived from an intake pipe pressure of a vehicle having means for detecting an intake pipe pressure and another operating characteristic quantity, for example, a rotational speed and an engine temperature, comprising: Is continuously and dependent on the operating point calculated back to ambient pressure, and then the measured intake pipe pressure is filtered, where the time constant of the filter depends on the operating characteristic quantity,
A geodetic level detection circuit derived from an intake pipe pressure of a vehicle. 2. The level detection circuit according to claim 1, wherein the time constant of the filter depends on at least an operation characteristic amount of a load (region) and a quality criterion of operating point dependency on a calculation formula, for example, an engine temperature. . 3. The level detection circuit according to claim 1, wherein the level detection circuit is used to shut off an OBDII function unit. 4. The level detection circuit according to claim 3, wherein the interruption of the OBDII function section is performed in consideration of a pressure tolerance value or a level tolerance value. 5. The level detection circuit according to claim 3, wherein the interruption of the OBDII function section is performed in consideration of a standby time. 6. The intake pipe pressure detected during an initialization phase and / or a stop phase (a phase in which the engine speed is substantially zero) is directly used for level assignment. 2. The level detection circuit according to claim 1. 7. The level detection circuit according to claim 1, wherein at least one replacement value for the intake pipe pressure is taken into account during engine braking and the calculation is performed in a direction of decreasing level. . 8. The method according to claim 4, wherein the pressure tolerance value for shutting off the OBDII function depends on at least one of pressure sensor tolerance, internal combustion engine or vehicle variance, and climate change. Level detection circuit.