Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1981-01-14
1983-02-15
Lall, P. S.
Internal-combustion engines
Charge forming device
Fuel injection system
123446, F02D 300
Patent
active
043734901
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fuel injection apparatus of the type which maintains at a predetermined value the pressure difference across a throttle valve (air flow rate detecting valve) disposed in a suction pipe to thereby detect the flow rate of air being sucked into an engine from the degree of opening of said throttle valve, while uniquely establishing correspondence between the degree of opening of said throttle valve and the area of opening of a fuel measuring gate, and maintaining the pressure difference across said fuel measuring gate at a predetermined value, and which adjusts said predetermined value by the on-off action of a solenoid valve, thereby compensating the air-fuel ratio.
BACKGROUND TECHNIQUE
Recently, a variety of apparatuses of this type have been developed and the present application also has already proposed one such apparatus. These apparatuses are designed so that signals from sensors which detect the operating conditions of an engine cause the on-off operation of a solenoid valve disposed in a fuel pressure control circuit, thereby changing the pressure difference across a fuel measuring gate to compensate the air-fuel ratio according to the operating conditions of the engine. If the output time ratio between rich and lean signals from said sensors (which corresponds to the on-off time ratio of the solenoid valve) deviates from a predetermined value, the pressure in the bellows of a servomechanism which detects the air flow rate is changed by a heater so as to correct the basic air-fuel ratio, which is set by said servomechanism, to maintain said time ratio at a predetermined value, thereby maintaining said air-fuel ratio at a desired constant value while reducing the time required to effect said compensation of the air-fuel ratio to suit it to the operating conditions of the engine and improving the response characteristic of the engine.
However, there are cases where the bellows of the servomechanism has to be reduced in size depending upon the design conditions thereof, and the operation of installing said heater in such bellows is not easy. Further, it requires a high degree of skill to insulate the heater and bellows from each other and at the same time seal the bellows to prevent leakage of the gas contained therein. Thus, it has been desired to improve said arrangement.
Accordingly, in view of the above described drawbacks of the apparatus previously proposed by the present applicant, it is an object of the present invention to provide an improved apparatus.
DISCLOSURE OF THE INVENTION
According to the present invention, the heater disposed in the bellows of the servomechanism of the conventional apparatus described above is replaced by a second solenoid valve placed in the fuel pressure control circuit in parallel with said first solenoid valve so that the on-off operation of said second solenoid valve corrects the basic air-fuel ratio. With such arrangement, it is possible to eliminate the drawbacks inherent in the conventional apparatus without losing the merits thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing the present inventive apparatus in its entirety;
FIG. 2 is a circuit diagram of an electronic control unit of the present inventive apparatus;
FIG. 3 is a view showing a control voltage in a comparing unit 57 included in the circuit shown in FIG. 2;
FIG. 4 is a view showing the time ratio of rich and lean signals from an oxygen sensor of the present inventive apparatus;
FIG. 5 is a view showing basic air-fuel ratio versus after-control air-fuel ratio characteristics; and
FIG. 6 is a view showing basic air-fuel ratio versus O.sub.2 sensor .lambda. signal characteristics.
OPTIMUM FOR EMBODYING THE INVENTION
The arrangement of the present invention will now be described in more detail with reference to the drawings showing an embodiment thereof.
In FIG. 1, the numeral 1 denotes an air flow rate measuring unit comprising a servomechanism A and a valve opening mechanism B; 2 denotes a fuel flow rate measuring unit;
REFERENCES:
patent: 2493582 (1950-01-01), Hunt
patent: 2493587 (1950-01-01), Lee
patent: 3993034 (1976-11-01), Passera et al.
Kimata Kei
Nakazeki Tsugito
Lall P. S.
NTN Toyo Bearing Company Limited
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