Internal-combustion engines – Charge forming device – Gaseous fuel and air mixer
Reexamination Certificate
2000-01-28
2001-06-05
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Gaseous fuel and air mixer
C123S690000, C123S1980DA, C123S1980DB
Reexamination Certificate
active
06240910
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection control system for a compressed natural gas-fueled automotive vehicle using compressed natural gas (CNG) as a fuel.
2. Description of the Related Art
A compressed natural gas-fueled vehicle uses compressed natural gas instead of the gasoline as a fuel. The compressed natural gas is mixed with air in an intake manifold and supplied to the engine. In the compressed natural gas-fueled vehicle, high-pressure natural gas is stored in a tank. For this reason, a sensor for detecting the gas pressure is included for fail-safe control such as closing a gas shutoff valve when the gas leaks. This fail-safe control operation is not performed in the case where the gas is consumed to such an extent that the residual gas amount has been reduced to a very small level.
In the case where the residual amount of gas has reached to a very small level, however, a misfire may occur due to the fuel shortage in the engine. If a high load operation (high-speed run, for example) of the vehicle is continued under this condition, the uncombusted gas which may be discharged from the engine into a catalyst unit is burnt by a catalyst already very high in temperature. Thus, the catalyst is heated to an abnormal temperature and thus may give rise to a breakdown of the catalyst unit or another problem may result.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a compressed natural gas-fueled automotive vehicle in which the fail-safe control operation is performed when the gas pressure is reduced to thereby secure the safety of the vehicle.
The present invention has been developed to achieve the object described above.
According to a first aspect of the invention, there is provided a fuel injection control system, for a compressed natural gas-fueled vehicle using compressed natural gas as a fuel, comprising a gas pressure sensor for detecting the gas pressure in the fuel supply path and a drive sensor for detecting the vehicle moving condition, wherein the fuel injection control unit for controlling the fuel injection apparatus stops supplying the fuel when the gas pressure sensor detects a reduction in gas pressure and the drive sensor detects that the vehicle is running.
In a compressed natural gas-fueled vehicle, when the gas is consumed to such an extent that the residual amount of the gas in the tank reaches a very low level, the gas pressure in the fuel supply route is reduced and a misfire occurs in the engine. Also, when the vehicle is moving, the catalyst temperature becomes so high that the uncombusted gas comes into contact with the high-temperature catalyst in the catalyst unit and begins to burn. In the case where the fuel supply is stopped upon detection of the vehicle moving and a low gas pressure, in contrast, uncombusted gas is not discharged into the catalyst unit. As a result, the catalyst unit is prevented from being broken down due to the abnormal heating of the catalyst.
According to a second aspect of the invention, there is provided a fuel injection control system, of a compressed natural gas-fueled vehicle using the compressed natural gas a fuel, comprising a gas pressure sensor for detecting the gas pressure in a fuel supply path and catalyst temperature detecting means for detecting the temperature of the catalyst arranged downstream of the internal combustion engine, wherein the fuel injection control unit for controlling the fuel injection control apparatus stops supplying fuel when the gas pressure sensor detects a reduction in gas pressure and the catalyst temperature detecting means detects a catalyst temperature not lower than a predetermined value.
In the second aspect of the invention, when the gas pressure is reduced, the fuel supply is stopped upon detection of a catalyst temperature not lower than a predetermined value, and therefore uncombusted gas is not discharged into the catalyst unit, thereby preventing the catalyst unit from being broken down due to abnormal heating of the catalyst.
In the first and second aspects of the invention, the uncombusted gas is prevented from burning in the catalyst unit by stopping the fuel supply.
According to third and fourth aspects of the invention, in contrast, there is provided a fuel injection control system, for a compressed natural gas-fueled vehicle, in which the vehicle speed is reduced instead of stopping the fuel supply.
Specifically, according to the third aspect of the invention, the vehicle speed is reduced when a gas pressure sensor detects a reduction in gas pressure and when the drive sensor detects that the vehicle is moving.
According to the fourth aspect of the invention, on the other hand, the vehicle speed is reduced when the gas pressure sensor detects a reduction in gas pressure and when the catalyst temperature detecting unit detects a catalyst temperature not lower than a predetermined value. With the reduction in vehicle speed, the catalyst temperature drops so that the uncombusted gas, even if it is discharged into the catalyst unit, is not burned.
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Igarashi Kohei
Maekawa Masahiro
Matsuoka Hiroki
Viggers John Stephen
Fujitsu Ten Limited
Oliff & Berridg,e PLC
Solis Erick
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