Load measuring device with a altitude adaption

Details Load measuring device with a altitude adaption Load measuring device with a altitude adaption

1996-04-26

1998-01-13

Argenbright, Tony M.

Internal-combustion engines

Charge forming device

Crankcase vapor used with combustible mixture

731181, 731182, 123488, F02D 4118, F02D 4104, F02D 4132

Patent

active

057067910

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a device for load detection with an altitude adaptation.
Normally the aspirated air flow is determined with the aid of a heating wire or hot film air-flow sensor to detect the load on an internal combustion engine.
Pulsations of the aspirated air occur within certain operational ranges of the internal combustion engine, which can lead to a distortion of the measured values supplied by the air-flow sensor. This is the case in particular when there is a reverse flow in the range close to full load and the air-flow sensor cannot distinguish between the flow directions and falsely registers the outflowing air as aspirated air.
So that a dependable load determination becomes possible also when a reverse flow occurs, a second load signal, the so-called collateral load signal, could be determined based, for example, on the rpm of the internal combustion engine and the throttle angle. If the control device determines that an operational state exists in which reverse flow could occur, the collateral load signal, instead of the main signal, is used for controlling the internal combustion engine. However, the collateral load signal must be subjected to an altitude adaptation because, in contrast to the main signal, it is not a function of the density of the aspirated air and therefore not of the altitude.
If such an altitude adaptation of the collateral load signal were not performed, load jumps would occur in the course of switch-over between the main and the collateral load signals as soon as the internal combustion engine or the vehicle driven by it is at an altitude not corresponding to a standard altitude.
With presently employed systems the main load signal is limited by an rpm-dependent characteristic curve in the reverse flow range, this limit is also additionally altitude-corrected.
With devices for load determination in connection with internal combustion engines, such as described in the published patent applications DE-P 43 22 281 or DE-P 43 36 813, for example, it is proposed to perform an altitude adaptation for the collateral load signal by forming the difference between the main load signal and the collateral load signal under operational conditions in which a reverse flow can assuredly take place and to perform the altitude adaptation, starting with this difference, which can only be a function of the altitude or the density. As described in DE-P 43 22 281, the filtered collateral signal is subtracted from the also filtered main signal for this purpose, the difference leads to an adaptation value which represents a measurement of the changed density. Under certain operational conditions the comparison result is passed on to an integrator and is integrated in this integrator.
This integrator operates with two different time constants. In the characteristic fields in which an adaptation and therefore the learning of the altitude factor is possible, this learning process mainly proceeds with a relatively slow time constant of the integrator. A compromise between a sufficiently rapid learning speed and signal rest is sought. However, if a departure from the adaptation range is made, there is the danger that a large altitude difference could be traversed without the altitude having been learned. In order to make possible relatively fast learning upon renewed learning operations, i.e. upon reentering the adaptation range, a short switch-over to the rapid adaptation time constant of the integrator is performed. The switch-over criteria between the two time constants are controlled, for example, by means of the length of a performed overrun phase. Following renewed learning, the rapid time constant is allowed for an applicable time and subsequently a switch-over to the Slow time constant is made.
This switch-over between two fixed integrator time constants for the adaptation, known from DE-P 43 22 281, can be unfavorable under certain circumstances. The known system also has the disadvantage that there is no check whether the learned altitude actually is

REFERENCES:
patent: 4718388 (1988-01-01), Kiuchi
patent: 4773375 (1988-09-01), Okino et al.
patent: 5226393 (1993-07-01), Nagano et al.
patent: 5241857 (1993-09-01), Schnaibel et al.
patent: 5481462 (1996-01-01), Nagai

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