Measuring and testing – Simulating operating condition – Marine
Patent
1981-09-09
1983-09-20
Goldstein, Herbert
Measuring and testing
Simulating operating condition
Marine
73204, 123494, 123478, G01F 168
Patent
active
044048467
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an air flow rate measuring device and, more particularly, to an air flow rate measuring device incorporating a hot wire type air flow meter suitable for use in automobiles.
BACKGROUND ART
A device for measuring the flow rate of intake air in an automobile engine, of the type having a resistance element having a resistance temperature coefficient and disposed in the intake air passage and adapted to measure the intake air flow rate using the change in the resistance, is known by, for example, U.S. Pat. No. 3,747,577. This resistance element is heated within the intake air passage of the engine by electric current supplied thereto, and the resistance value thereof is changed in accordance with the flow rate of the intake air in the intake passage.
In automobile engines, the air-fuel ratio is controlled upon detection of the intake air flow rate per one suction stroke of the engine by accumulating the intake air flow rate. It is, therefore, very important to precisely detect the flow rate of the intake air. An inaccurate measurement leads to an incorrect control of the air-fuel ratio.
The size of the hot wire type air flow meter is advantageously small but this type of flow meter has a drawback that it cannot detect the direction of flow of the air. Therefore, it is not possible to measure the correct or true intake air flow rate by a mere accumulation of the output of the hot wire type air flow meter, particularly in the low speed region of operation of a 4-cylinder internal combustion engine.
DISCLOSURE OF INVENTION
Accordingly, an object of the invention is to provide an air flow rate measuring device having a hot wire type air flow meter improved for use in automobile engines.
Another object of the invention is to provide an air flow rate measuring device incorporating a hot wire type air flow meter capable of measuring the true intake air flow rate in automobile engines.
When a 4-cylinder engine is operating at a low speed, the intake air flow rate (instantaneous value) of the engine fluctuates largely. In addition, in the region near the top dead center, the intake valve and the exhaust valve are opened simultaneously so that the intake air is forced back by the pressure which acts to reverse the flow of gas from the exhaust valve toward the intake valve. This reversing of the gas does not take place when the intake valve solely is kept opened.
The reversing of the gas takes place in the low speed region of 600 to 3000 R.P.M. and in the region of low intake vacuum of below -100 mmHg. The hot air type flow meter produces the detection signal irrespective of the flowing direction of the air.
Representing the apparent intake air amount obtained by an integration or accumulation of the hot wire type flow meter by Q.sub.a (m.sup.3), the air amount flowing in the reverse direction by Q.sub.1 (m.sup.3), the air amount in the forward direction by Q.sub.2 (m.sup.3) and the true air amount by Q.sub.0 (m.sup.3), the following equations (1) and (2) are established.
Thus, the true air flow rate Q.sub.0 is given as the difference between the flow rate Q.sub.2 in the forward direction and the flow rate Q.sub.1 in the backward direction.
According to the invention, the apparent air flow rate Q.sub.a is measured by integrating or accumulating the output of the hot wire type air flow meter disposed in the intake air passage, and a signal representing the period of reversing flow is generated to divide the apparent air flow rate Q.sub.a into the flow rate Q.sub.1 in the backward direction and the flow rate Q.sub.2 in the forward direction. Then, the difference Q.sub.2 -Q.sub.1 is calculated by an operation unit to determine the true air flow rate Q.sub.0.
According to an embodiment of the invention, there is provided a memory device adapted to memorize the crank angle corresponding to engine speed, and a crank angle sensor adapted to produce a signal corresponding to the crank angle of the engine. The period of the backward flow of intake air is read out from the mem
REFERENCES:
patent: 4322970 (1982-04-01), Peter
Fujieda Mamoru
Kirisawa Tadashi
Kuroiwa Hiroshi
Ohyama Yoshishige
Yamauchi Teruo
Goldstein Herbert
Hitachi , Ltd.
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