Long fuel distance internal combustion engine, having a methane feeding system

Abstract: A motor-vehicle internal combustion engine, provided with a methane feeding system, comprises a compressor (8) for increasing the pressure of methane which is fed to the engine, when the pressure within the methane reservoir (4) decreases below a predetermined threshold value.

Description: The present invention relates to the field of internal combustion engines having a methane feeding system, of the type comprising: a plurality of methane injector devices, respectively associated with the cylinders of the engine, a methane feeding manifold for feeding methane to the injectors, a high pressure methane reservoir connected to said manifold, a methane pressure regulator device, interposed in the connection between the reservoir and the manifold, to decrease the pressure of methane from the value at which it is accumulated in the reservoir down to a value adapted for the proper operation of the injector devices, and an electronic control unit for controlling the injector devices, adapted to control the injector devices as a function of a number of engine operating parameters. An engine of the above indicated type is disclosed for example in European Patent Application EP-A-0 801 223, which has been published after the priority date of the present application. A drawback which is encountered sometimes by users of motor-vehicles provided with methane operated engines lies in that, for instance in Italy, the service stations where it is possible to fill up with methane are not yet distributed extensively on the whole territory. Therefore, it would be desirable to have engines capable of having a long fuel distance. The object of the present invention is therefore that of providing an engine having a methane feeding system which, for a given volume of the reservoir, is able to have a greater fuel distance. In view of achieving this object, the invention provides an engine of the type indicated at the beginning, characterized in that said engine comprises a compressor interposed in the connection between the reservoir and the pressure regulator device, sensor means for sensing the pressure of the methane in the reservoir and in that said electronic control unit attends to activating said compressor when the pressure of the methane within the reservoir decreases below a first predetermined threshold value and as long as this pressure does not decrease further until it becomes lower than a second predetermined threshold value, lower than said first threshold value. Due to these features, the engine according to the invention is able of having a longer fuel distance with respect to an engine according to the prior art provided with a reservoir having identical volume. In the engines of the above indicated type, the pressure at which the methane is accumulated within the reservoir typically is relatively high, in the order of 200 bars. The pressure at which the injector devices operate is instead in the order of 7 bars. The pressure regulator device interposed between the reservoir and the methane feeding manifold or rail is used just for decreasing the pressure of the gas from the high value at which it is accumulated within the reservoir down to the value at which the injector devices are able to operate properly. Therefore, in conventional engines, when the pressure within the reservoir decreases below a value in the order of 15 bars, the methane left within the reservoir cannot be used in practice, since it is not able to reach the injectors at a pressure sufficient for the proper operation thereof. In the engine according to the invention, when the pressure within the methane reservoir decreases below the above mentioned threshold value, such as approximately 15 bars, the electronic control unit attends to activating a compressor which is arranged in the connection between the reservoir and the pressure regulator. This compressor brings the gas pressure again to a sufficiently high value, such as approximately 20 bars to enable the engine to keep on operating properly, until the pressure within the reservoir decreases below a minimum value, such as approximately 9 bars, which is admissible for the proper operation of the engine. The engine according to the invention is provided therefore with a kind of fuel reserve which is exploited by activating the above mentioned compressor when the methane pressure within the reservoir decreases below the above mentioned threshold value in the order of 15 bars. The invention will be now described in detail with reference to the annexed drawing, given purely by way of non limiting example, which shows a diagram of an engine according to the invention. With reference to the drawing, numeral 1 generally designates a motor-vehicle internal combustion engine provided with a methane feeding system. According to a conventional art, the methane feeding system is provided in addition to a conventional gasoline feeding system with which the engine is also provided. The drawing only shows the details of the methane feeding system, the gasoline feeding system being absolutely conventional. Reference numeral 2 generally designates four injector devices, for injecting methane into respective cylinders of engine 1. Injectors 2 receive methane from a feeding manifold or rail 3, whose inlet is connected to a reservoir 4 in which the methane is accumulated at high pressure, such as in the order of 200 bars. Reservoir 4 is connected to manifold 3 through a line 5 in which there is interposed a pressure regulator device 6, which can be made in any known way, but preferably being of the type disclosed in European Patent application EP-A-0 685 639 of the same applicant. Yet according the prior art, the injector devices 2 are controlled by an electronic control unit 7 which receives a number of signals indicative of various engine operating parameters. The sensor means provided for feeding these signals to the control unit and the associated connections are not described herein, since they can be made in any known way and do not fall within the scope of the present invention. According to the invention, in the connection between the reservoir 4 and the pressure regulator device 6 there is interposed a compressor 8 of any known type which is activated by the electronic control unit 7 when a pressure sensor 9 associated with reservoir 4 indicates a decrease of the pressure within reservoir 4 below a predetermined threshold value, such as in the order of 15 bars and as long as this pressure does not decrease further until it becomes lower than a minimum value which is admissible for the proper operation of the engine, such as in the order of 9 bars. As already indicated above, due to the above described features, the engine according to the invention, contrary to the engines according to the prior art, is able of keeping on operating even when the pressure within reservoir 4 decreases below the above mentioned first threshold value of the order of 15 bars. In this condition, indeed, compressor 8 attends to increase the methane pressure up to a value sufficient for enabling the engine to operate properly, such as in the order of 20 bars. The engine according to the invention is therefore able to exploit a fuel reserve as long as the pressure within the reservoir does not decrease below the above mentioned second minimum threshold value, in the order of 9 bars. For a given volume of the reservoir, the engine according to the invention is therefore able to have a longer fuel distance. Naturally, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and illustrated purely by way of example, without departing from the scope of the present invention.

Claims: Internal combustion engine having a methane feeding system, comprising: a plurality of methane injector devices (2), respectively associated with the cylinders of the engine, a methane feeding manifold (3) for feeding methane to the injectors (2), a high pressure methane reservoir (4) connected to said manifold (3), a methane pressure regulator device (6), interposed in the connection between the reservoir (4) and the manifold (3), for decreasing the methane pressure from the value at which it is accumulated within the reservoir (4) down to a value adapted for the proper operation of the injector devices (2), and an electronic control unit (7) for controlling the injector devices (2), which controls the injector devices (2) as a function of a number of engine operating parameters, characterized in that said engine further comprises: a compressor (8) interposed in the connection between the reservoir (4) and the pressure regulator device (6), sensor means for sensing the pressure of methane within the reservoir (4); said electronic control unit (7) being adapted to activate said compressor (8) when the pressure of the methane within the reservoir (4) decreases below a first predetermined threshold value and as long as this pressure does not further decrease until it becomes lower than a second predetermined threshold value, lower than said first threshold value. Engine according to claim 1, characterized in that said first threshold value is in the order of 15 bars. Engine according to claim 1, characterized in that said second threshold value is in the order of 9 bars.

Inventors: BARBIERO ROBERTO, FERRERA MASSIMO, GOZZELINO RICCARDO, BARBIERO, ROBERTO, FERRERA, MASSIMO, GOZZELINO, RICCARDO
Applicants: FIAT RICERCHE, C.R.F. SOCIETA' CONSORTILE PER AZIONI
Application year: 1997
Main classification: F02B43
IPC codes: F02B43