Measuring and testing – Simulating operating condition – Marine
Patent
1990-07-11
1991-12-03
Myracle, Jerry W.
Measuring and testing
Simulating operating condition
Marine
731173, G01M 1500
Patent
active
050690639
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device for detecting a pulsating variable in an internal combustion engine by sampling a measurement value in synchronization with a crankshaft angle every half-period of the pulsating variable.
It is known that significant variables in internal combustion engines such as, for example, the vacuum in the intake pipe are quasi-continuous variables which pulsate or periodically fluctuate with the power cycle of the internal combustion engine. However, it is the mean value of these variables which is needed for regulating the internal combustion engine.
Devices for detecting a periodically fluctuating variable, for example the vacuum in the intake pipe, and for determining the mean value of this variable are already known. Thus, in German Offenlegungsschrift 3,223,328, the pressure is measured ignition-synchronously once per ignition interval and from the instantaneous value of the pressure thus obtained the mean value is calculated. In case of a phase shift of the pressure signal which is caused, for example, by fuel condensates which can become deposited in the hose between the intake pipe and pressure transducer, however, the solution proposed in German Offenlegungsschrift 3,223,328 leads to errors in the averaging.
In German Offenlegungsschrift 3,212,561, the intake pipe pressure is determined by fixed-angle dual sampling per ignition interval. If only the fundamental oscillation is present, the dual sampling of the intake pipe pressure per ignition interval would be sufficient for determining the exact mean value of the intake pipe pressure. At certain rotational speeds, however, higher-frequency components are superimposed on the periodic intake pipe pressure variation which could lead to errors occurring in the averaging even with dual sampling.
SUMMARY OF THE INVENTION
The object of the invention is a device in which a signal variation is almost sinusoidal or quasi-sinusoidal with the duration of the period of the ignition interval for all rotational speeds being obtained by damping of either the pulsating variable itself or the output signal of a sensor which detects a pulsating variable. Thus, an error-free mean value can be formed from this signal variation in any speed range and in any phase relationship by dual sampling per ignition interval or duration of the period of the pulsating variable. The object of the invention is achieved by providing a sensor associated with a filtering device and/or a damping device. The means value is formed from two measurement values per period.
If the pulsating variable is the intake pipe pressure, an almost sinusoidal pressure variation can be obtained for all rotational speeds at the pressure sensor by filtering the intake pipe pressure by a pneumatic filter.
By suitably designing the pneumatic filter, it can be prevented that condensate reaches the pressure sensor and leads to a destruction of the pressure sensor. It is a further advantage that the maximum pressure controlled by the pressure sensor or the controllable pressure range does not need to be unnecessarily large since the pulsations are damped when they reach the sensor.
If it is intended to arrange the pressure sensor in the control device, the pneumatic filter is connected to the intake pipe with an additional variable-length hose. As a result, the control device can be installed at any point without having to change the dimensioning of the pneumatic filter.
In the case of pressure sensors which are arranged outside the control device, a particularly simple pneumatic filter can be used which only consists of a throttle and a short hose.
Instead of a pneumatic filter for smoothing the intake pipe pressure at the input to the pressure sensor, an electric or electronic filter can also be used for smoothing the sensor output signal.
It is particularly advantageous that other pulsating variables can also be damped by an electric or electronic filter following the respective sensor, in such a manner that a quasi-sinusoidal signal is produced. A su
REFERENCES:
patent: 4311042 (1982-01-01), Hosoya et al.
Chrobaczek Martin
Denz Helmut
Heim Hans
Roth Andreas
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