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A fuel supply apparatus is provided which works to supply fuel such as a dimethly ether used as an alternative to a typical fuel for an internal combustion engine. The fuel supply apparatus includes a high-pressure pump working to feed the to injectors from a fuel tank through a common rail, a fuel

A fuel supply apparatus is provided which works to supply fuel such as a dimethly ether used as an alternative to a typical fuel for an internal combustion engine. The fuel supply apparatus includes a high-pressure pump working to feed the to injectors from a fuel tank through a common rail, a fuel return line, and a compressor working to add to a back pressure higher than a vapor pressure of the fuel to the return line. The addition of the back pressure higher than the vapor pressure of the fuel facilitates liquidizing of the fuel. This results in a decrease in leakage of the fuel, which improves the efficiency of burning of the fuel and ensures the startability and drivability of the engine.

대표청구항 ▼

1. An alternative fuel supply apparatus for an internal combustion engine comprising:a high-pressure pump working to feed a fuel which is susceptible to vaporization to injectors from a fuel tank through a common rail under a given high pressure;a return line including a first line and a second line

1. An alternative fuel supply apparatus for an internal combustion engine comprising:a high-pressure pump working to feed a fuel which is susceptible to vaporization to injectors from a fuel tank through a common rail under a given high pressure;a return line including a first line and a second line which extend from said high-pressure pump to the fuel tank;a pressurizing mechanism disposed in the first line of said return line to add a back pressure higher than a vapor pressure of the fuel to the first line; anda selector to selectively communicate one of (1) the fuel tank and the first line through said pressurizing mechanism (2) the fuel tank and second line, based on a pressure of the fuel within said return line. 2. An alternative fuel supply apparatus as set forth in claim 1, wherein said high-pressure pump includes a pump chamber to which the fuel from the feed pump is inputted through a fuel gallery at a feed pressure, a plunger reciprocating within a plunger chamber formed within a cylinder to pressurize the fuel within the pump chamber and inject the pressurized fuel into the engine through a discharge valve and each of the injectors, a higher-pressure leakage line, and a lower-pressure leakage line, the higher-pressure and lower-pressure leakage lines working to withdraw the fuel leaking out of the pump chamber through a gap between the plunger and the plunger chamber following reciprocating motion of the plunger. 3. An alternative fuel supply apparatus as set forth in claim 2, wherein the higher-pressure leakage line communicates with the fuel gallery through a feed line, and the lower-pressure leakage line communicates with a sealed chamber formed beneath the plunger. 4. An alternative fuel supply apparatus as set forth in claim 2, wherein the fuel flowing through the lower-pressure leakage line is withdrawn through a withdrawing means provided in said cylinder. 5. An alternative fuel supply apparatus as set forth in claim 4, wherein said withdrawing means is implemented by a leakage path formed in a side wall of the cylinder. 6. An alternative fuel supply apparatus as set forth in claim 2, further comprising a solenoid valve which is disposed within an upper end portion of the cylinder and includes a valve member, a valve body, a non-magnetic member, and a plurality of cores, the valve member working to selectively open and close a line connecting between said pump chamber and said fuel gallery to control an amount of the fuel flowing out of said discharge valve, the valve body being disposed within the upper end portion of the cylinder in a fluid-tight fashion, the cores being arranged coaxially with each other through the non-magnetic member and welded rigidly in a fluid-tight fashion inside said solenoid valve. 7. An alternative fuel supply apparatus as set forth in claim 2, wherein said discharge valve is opened in response to a pressure which acts thereon and is lower than said feed pressure. 8. An alternative fuel supply apparatus as set forth in claim 2, further comprising a pressure regulator connected to the fuel gallery, said pressure regulator including a valve which is urged by a spring into a closed state, the valve of said pressure regulator being moved by a back pressure arising from a vapor pressure of the fuel against a mechanical pressure produced by the spring so that the valve is opened to discharge the fuel flowing from the fuel gallery. 9. An alternative fuel supply apparatus as set forth in claim 1, further comprising a pressure sensor and a temperature sensor which measure a pressure and a temperature of the fuel whose bulk modulus of elasticity and density are sensitive to changes in pressure and temperature of the fuel and a control circuit which works to correct a discharged amount of the fuel from said high-pressure pump as functions of the pressure and temperature measured by said pressure and temperature sensors to modify a pressure of the fuel stored in said common rail to a given level and to control a quantity of the fuel injected to the engine through the injectors to a give value as a function of an operating condition of the engine. 10. An alternative fuel supply apparatus as set forth in claim 1, wherein said pressurizing mechanism is implemented by a compressor which works to pressurize the fuel being returned to the fuel tank. 11. An alternative fuel supply apparatus for an internal combustion engine comprising:a high-pressure pump connected to a fuel tank through a feed pump, a fuel cooler, and a fuel filter, the fuel tank storing therein a vaporable fuel under pressure higher than a vapor pressure of the fuel;a common rail within which the fuel supplied from the fuel tank through said high-pressure pump is stored at a given high pressure, said common rail being connected to injectors working to inject the fuel into the engine;a pressure limiter installed in said common rail to set a maximum pressure within said common rail;a fuel return line returning fuel relieved from said common rail through said pressure limiter and fuel flowing out of said high-pressure pump to the fuel tank; anda fuel selector valve, a purge tank, a compressor, and a fuel cooler installed in said fuel return line in this order. 12. An alternative fuel supply apparatus as set forth in claim 11, wherein said high-pressure pump includes a pump chamber to which the fuel from the feed pump is inputted through a fuel gallery at a feed pressure, a plunger reciprocating within a plunger chamber formed within a cylinder to pressurize the fuel within the pump chamber and inject the pressurized fuel into the engine through a discharge valve and each of the injectors, a higher-pressure leakage line, and a lower-pressure leakage line, the higher-pressure and lower-pressure leakage lines working to withdraw the fuel leaking out of the pump chamber through a gap between the plunger and the plunger chamber following reciprocating motion of the plunger. 13. An alternative fuel supply apparatus as set forth in claim 12, wherein the higher-pressure leakage line communicates with the fuel gallery through a feed line, and the lower-pressure leakage line communicates with a sealed chamber formed beneath the plunger. 14. An alternative fuel supply apparatus as set forth in claim 12, wherein the fuel flowing through the lower-pressure leakage line is withdrawn through a withdrawing means provided in said cylinder. 15. An alternative fuel supply apparatus as set forth in claim 14, wherein said withdrawing means is implemented by a leakage path formed in a side wall of the cylinder. 16. An alternative fuel supply apparatus as set forth in claim 12, further comprising a solenoid valve which is disposed within an upper end portion of the cylinder and includes a valve member, a valve body, a non-magnetic member, and a plurality of cores, the valve member working to selectively open and close a line connecting between said pump chamber and said fuel gallery to control an amount of the fuel flowing out of said discharge valve, the valve body being disposed within the upper end portion of the cylinder In a fluid-tight fashion, the cores being arranged coaxially with each other through the non-magnetic member and welded rigidly in a fluid-tight fashion inside said solenoid valve. 17. An alternative fuel supply apparatus as set forth in claim 12 wherein said discharge valve is opened in response to a pressure which acts thereon and is lower than said feed pressure. 18. An alternative fuel supply apparatus as set forth in claim 12, further comprising a pressure regulator connected to the fuel gallery, said pressure regulator including a valve which is urged by a spring into a closed state, the valve of said pressure regulator being moved by a back pressure arising from a vapor pressure of the fuel against a mechanical pressure produced by the spring so that the valve is opened to discharge the fuel flowing from the fuel gallery. 19. An alternative fuel su pply apparatus as set forth in claim 11, wherein said pressure limiter sets a maximum pressure within said common rail and is controlled in a fluid-tight fashion by opening and closing a solenoid valve. 20. An alternative fuel supply apparatus as set forth in claim 11, wherein said feed pump is installed in the fuel tank which is kept at a vapor pressure of the fuel, and wherein the vapor pressure of the fuel is added to a feed pressure of the feed pump. 21. An alternative fuel supply apparatus as set forth in claim 11, wherein said fuel selector valve is implemented by a three-way valve, when the fuel returning from each of said high-pressure pump and said pressure limiter is in a gaseous state, said fuel selector valve feeding it to said purge tank, when the fuel returning from each of said high-pressure pump and said pressure limiter is in a liquid state, said fuel selector feeding it to the fuel tank. 22. An alternative fuel supply apparatus as set forth in claim 11, wherein said compressor works to pressurize the fuel which is stored within said purge tank in a gaseous state and bring it into a liquid state through said fuel cooler which is, in turn, returned back to the fuel tank. 23. An alternative fuel supply apparatus as set forth in claim 11, wherein said high-pressure pump has a discharge valve which is opened in response to a pressure lower than or equal to the sum of a feed pressure of the feed pump and a vapor pressure of the fuel within the fuel tank, and wherein at start-up of the engine, a vaporized fuel is withdrawn from said discharge valve to the fuel tank in a liquid state through said common rail, said pressure limiter, said fuel selector valve, and said purge tank. 24. An alternative fuel supply apparatus as set forth in claim 11, further comprising a pressure sensor and a temperature sensor which measure a pressure and a temperature of the fuel whose bulk modulus of elasticity and density are sensitive to changes in pressure and temperature of the fuel and a control circuit which works to correct a discharged amount of the fuel from said high-pressure pump as functions of the pressure and temperature measured by said pressure and temperature sensors to modify a pressure of the fuel stored in said common rail to a given level and to control a quantity of the fuel injected to the engine through the injectors to a give value as a function of an operating condition of the engine. 25. An alternative fuel supply apparatus for an internal combustion engine comprising:a high-pressure pump working to feed a fuel which is susceptible to vaporization to injectors from a fuel tank through a common rail under a given high pressure;a return line extending from said high-pressure pump to the fuel tank; anda pressurizing mechanism working to add to said return line a back pressure higher than a vapor pressure of the fuel,wherein said high-pressure pump includes a pump chamber to which the fuel from the feed pump is inputted through a fuel gallery at a feed pressure, a plunger reciprocating within a plunger chamber formed within a cylinder to pressurize the fuel within the pump chamber and inject the pressurized fuel into the engine through a discharge valve and each of the injectors, a higher-pressure leakage line, and a lower-pressure leakage line, the higher-pressure and lower-pressure leakage lines working to withdraw the fuel leaking out of the pump chamber through a gap between the plunger and the plunger chamber following reciprocating motion of the plunger.