Patent Application
20080017170
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
The following will describe a fuel supply system for a DME engine of a first preferred embodiment according to the present invention with reference to
The feed pump 3 is an electric type gear pump in which a motor is installed. The feed pump 3 is connected to a power energy, which is not shown, by a motor power energy cable 20. The cable 20 has a switch 21 to shift connection of U-phase, V-phase, and W-phase. The feed pump 3 rotates in a normal direction, or rotates in a reverse direction by switching the switch 21. The switch 21 is electrically connected to an electronic computer unit (hereinafter referred to ECU) 22. The switch 21 is switched by the ECU 22, thereby the feed pump 3 rotates in the normal direction when the engine is operated, and rotates in the reverse direction when the engine is stopped.
A high-pressure supply pump 7 as a high-pressure pump is connected to the feed pump 3 at a discharge port 3a through a low-pressure fuel supply passage 4. The low-pressure fuel supply passage 4 is located at the upstream side of the high-pressure supply pump 7. A solenoid valve 6 as a third solenoid valve is located in the low-pressure fuel supply passage 4 to open and close the low-pressure fuel supply passage 4. The third solenoid valve 6 is electrically connected to the ECU 22. The ECU 22 controls the operation of the third solenoid valve 6, and the third solenoid valve 6 is opened when the engine is operated, and is closed when the engine is stopped. The high-pressure supply pump 7 is operated by the engine which is not shown, and the drive power of the high-pressure supply pump 7 is transmitted from the engine. The DME fuel is supplied from the low-pressure fuel supply passage 4 to the high-pressure supply pump 7, and is pressurized and discharged from the pump 7.
A common rail 9 is connected to the high-pressure supply pump 7 by a first high-pressure supply passage 8. The common rail 9 is connected to a fuel injector 11 through a second high-pressure fuel supply passage 10. Each cylinder of the engine has a corresponding fuel injector 11. The fuel injector 11 has a nozzle 11a and a leakage port 11b. The excess DME fuel is discharged through the leakage port 11b to the outside of the system 1. The DME fuel with high pressure is distributed from the common rail 9, and is injected into a combustion chamber (not shown) through the nozzle 11a. A high-pressure fuel supply passage is constituted by the first high-pressure fuel supply passage 8 located downstream side of the high-pressure supply pump 7, the common rail 9, and the second high-pressure fuel supply passage 10.
The fuel supply system 1 includes a fuel recovery passage 12. The fuel recovery passage 12 includes a confluence passage 12g. One end of the confluence passage 12g is connected to the upstream side of the excess flow stop valve 5 of the low-pressure fuel supply passage 4. The other end of the confluence passage 12g is connected to a first branch passage 12a and a third branch passage 12c at a branch point 12d. The confluence passage 12g is connected to a second branch passage 12b at a branch point 12e. A first fuel recovery passage is constituted by the confluence passage 12g, the first branch passage 12a, and the second branch passage 12b. The branch passages 12a, 12b, 12c merge into the confluence passage 12g of the fuel recovery passage 12, and the confluence passage 12g has a solenoid valve 15 to open and close the confluence passage 12g. The first branch passage 12a is connected to the common rail 9, and has a solenoid valve 13 to open and close the branch passage 12a. The second branch passage 12b is connected to the first high-pressure fuel supply passage 8 and has a solenoid valve 14 to open and close the second branch passage 12b. The solenoid valves 13, 14, 15 are electrically connected to the ECU 22. The ECU 22 controls the operation of the solenoid valves 13, 14, 15, and the solenoid valves 13, 14, 15 are closed when the engine is operated, and the valves 13, 14, 15 are opened when the engine is stopped. The solenoid valves 13, 14, 15 function respectively as a first solenoid valve to open and close the first fuel recovery passage 12a, 12b, 12g.
The third branch passage 12c is connected to the leakage port 11b of the fuel injector 11. One end of a fourth branch passage 12h is connected to the fuel recovery passage 12 at a connection point 12f which is located between the branch point 12e and the first solenoid valve 15. The other end of the fourth branch passage 12h is connected to the gas phase part 2a in the fuel tank 2. The fourth branch passage 12h has a second solenoid valve 16 to open and close the fourth branch passage 12h. The second solenoid valve 16 is electrically connected to the ECU 22. The second solenoid valve 16 is opened when the engine is operated, and is closed when the engine is stopped. A second fuel recovery passage is constituted by the third branch passage 12c, part of the confluence passage 12g (between the branch point 12d and the connection point 12f, and the fourth branch passage 12h.
The following will describe operation of the fuel supply system for the DME engine of the first preferred embodiment. As shown in
The DME fuel with low pressure, which is supplied from the low-pressure fuel supply passage 4, is pressurized in the high-pressure supply pump 7 and is discharged from the pump 7 to the first high-pressure fuel supply passage 8 to be supplied to the common rail 9. Then the DME fuel is distributed to each of the fuel injector 11 through the second high-pressure fuel supply passage 10. The fuel injector 11 injects the highly-pressurized DME fuel through the nozzle 11a to the combustion chamber. The DME fuel injected into the combustion chamber is applied compression ignition, and combusted, similar to a normal diesel engine.
While the DME fuel is supplied to the combustion chamber from the fuel tank 2, the DME fuel flows into the first branch passage 12a and the second branch passage 12b. The solenoid valves 13, 14 are closed when the engine is operated, thereby the DME fuel in the first high-pressure fuel supply passage 8 and the common rail 9 is prevented from flowing into the fuel tank 2 through the first branch passage 12a, the second branch passage 12b, and the confluence passage 12g. The second solenoid valve 16 is opened when the engine is operated, thereby the DME fuel discharged from the leakage port 11b of the fuel injector 11 is recovered into the fuel tank 2 through the third branch passage 12c, the confluence passage 12g, and the fourth branch passage 12h. The solenoid valve 15 is closed when the engine is operated, thereby the DME fuel discharged from the leakage port 11b of the fuel injector 11 is prevented from flowing into the low-pressure fuel supply passage 4.
When the engine is stopped, the injection of the DME fuel from the fuel injector 11 to the combustion chamber is stopped, and the flow of the DME fuel in the fuel supply system 1 is stopped. Thus, the DME fuel with high pressure is remained on the downstream side of the high-pressure supply pump 7, and the DME fuel with low pressure is remained on the upstream side of the pump 7. The DME fuel with high pressure is remained in the part of the first branch passage 12a which is nearer to the common rail 9 than the solenoid valve 13, and in the part of the second branch passage 12b which is nearer to the first high-pressure supply passage 8 than the solenoid valve 14.
The solenoid valves 13, 14 are opened when the engine is stopped. The first high-pressure fuel supply passage 8 and the common rail 9, and the confluence passage 12g communicate through the first branch passage 12a and the second branch passage 12b. When the engine is stopped, the solenoid valve 15 is opened, and the low-pressure fuel supply passage 4 is connected to the confluence passage 12g. When the engine is stopped, the ECU 22 shifts the switch 21 to rotate the feed pump 3 in a reverse direction. Thus, the DME fuel remained at the downstream side of the high-pressure supply pump 7 is sucked into the feed pump 3 through the first branch passage 12a or the second branch passage 12b, the confluence passage 12g, and the low-pressure supply passage 4, and is recovered into the fuel tank 2. The confluence passage 12g is connected to the low-pressure supply passage 4 at the upstream side of the excess flow stop valve 5, and the excess flow stop valve 5 does not interfere the recovery of the DME fuel into the fuel tank 2.
The DME fuel with low pressure is remained in the low-pressure fuel supply passage 4, and is also sucked into the feed pump 3. Thus, the DME fuel remained at the upstream side of the high-pressure supply pump 7 is recovered into the fuel tank 2. The third solenoid valve 6 is closed when the engine is stopped, and the DME fuel remained in the low-pressure fuel supply passage 4 does not flow to the downstream side of the high-pressure supply pump 7. The second solenoid valve 16 is closed when the engine is stopped, and the DME fuel in the fuel tank 2 does not flow into the confluence passage 12g through the fourth branch passage 12h. It is presumed that the recovered DME fuel in the fuel tank 2 is in the state which gas phase and liquid phase is mixed. The DME fuel in gas phase, which is recovered into the fuel tank 2, is cooled in the fuel tank 2 and tends to change into liquid phase, because the fuel tank 2 has more radiation effect than the low-pressure fuel supply passage 4, the first high-pressure fuel supply passage 8, and the second high-pressure fuel supply passage 10.
As described above, the upstream side and downstream side of the high-pressure supply pump 7 is connected through the confluence passage 12g, the first and second branch passages 12a, 12b (the first fuel recovery passage). The first fuel recovery passage includes solenoid valves 13, 14, 15 (the first solenoid valves) to open and close the first fuel recovery passage. When the engine is operated, the first solenoid valves are closed. When the engine is stopped, the first solenoid valves are opened and the feed pump 3 rotates in the reverse direction so as to recover the DME fuel remained in the first high-pressure fuel supply passage 8, the common rail 9, and the second high-pressure fuel supply passages 10 (high-pressure fuel supply passage), and the low-pressure fuel supply passage 4 into the fuel tank 2. Accordingly, the DME fuel remained in the high-pressure fuel supply passages and the low-pressure fuel supply passage 4 does not leak from the fuel injector 11 into the combustion chamber when the engine is stopped. Further, the fuel supply system of this embodiment is installable to vehicles, because the fuel supply system does not have a purge tank and a reliquefaction compressor.
The common rail 9 constitutes part of the high-pressure fuel supply passage. The common rail 9 is connected to the first branch passage 12a, and the DME fuel remained in the common rail 9 is recovered reliably. Further, one end of the confluence passage 12g is connected to the low-pressure fuel supply passage 4 at the upstream side of the excess flow stop valve 5 so that the DME fuel remained in the high-pressure fuel supply passages is recovered effectively into the fuel tank 2 when the engine is stopped, without the resistance of the excess flow stop valve 5. The fuel injector 11 is connected to the gas phase part 2a in the fuel tank 2 through the third branch passage 12c, the confluence passage 12g, and the fourth branch passage 12h (the second fuel recovery passage), and the second solenoid valve 16 is located in the fourth branch passage 12h to open and close the second fuel recovery passage. The second solenoid valve 16 is opened when the engine is operated. Accordingly, the excess DME fuel, which is discharged from the fuel injector 11 when the engine is operated, is recovered into the fuel tank 2. When the engine is stopped, the second solenoid valve 16 is closed, and the DME fuel in the fuel tank 2 does not flow into the confluence passage 12g through the fourth branch passage 12h.
Additionally, the third solenoid valve 6 is located in the low-pressure fuel supply passage 4. The third solenoid valve 6 is closed when the engine is stopped so that the DME fuel remained in the low-pressure fuel supply passage 4 does not flow to the downstream side of the high-pressure supply pump 7.
The following will describe a fuel supply system for a DME engine of a second preferred embodiment with reference to
The gas phase part 2a of the fuel tank 2 is connected to the high-pressure side of the high-pressure supply pump 7. Thus, the fuel supply system 30 equalizes the pressure of the DME fuel which is remained in high-pressure state at the downstream side of the high-pressure supply pump 7, and the pressure in the fuel tank 2 (saturated vapor pressure). That is, the pressure of the DME fuel remained at the downstream side of the high-pressure supply pump 7 is decreased at an early stage, and the DME fuel does not easily leak from the fuel injector 11 into the combustion chamber.
The following will describe a fuel supply system for a DME engine of a third preferred embodiment with reference to
The supply port 44a of ejector 44 is connected to one end of a flow supply passage 42 for driving the ejector 44. The other end of the flow supply passage 42 is connected to the low-pressure supply passage 4 at a connection point 4a located between the excess flow stop valve 5 and the third solenoid valve 6. The flow supply passage 42 includes a sixth solenoid valve 43 to open and close the flow supply passage 42. The sixth solenoid valve 43 is electrically connected to an ECU 48. The ECU 48 controls the sixth solenoid valve 43. The sixth solenoid valve 43 is closed when the engine is operated. When the engine is stopped and until the predetermined time t has passed, the sixth solenoid valve 43 is closed, and when the predetermined time t has passed after the stop of the engine, the valve 43 is opened, by the control of the ECU 48. The exhaust port 44b of the ejector 44 is connected to one end of an exhaust passage 45. The other end of the exhaust passage 45 is connected to the gas phase part 2a of the fuel tank 2.
Accordingly, at the time when the predetermined time t has passed after the stop of the engine, the feed pump 3 is operated, and the DME fuel in the fuel tank 2 is supplied to the supply port 44a through the flow supply passage 42, and then the DME fuel is returned back to the fuel tank 2 through the exhaust port 44b and the exhaust passage 45.
The suction port 44c of the ejector 44 is connected to one end of a suction passage 46. The other end of the suction passage 46 is connected to the confluence passage 12g of the fuel recovery passage 12 at a connection point 12j which is located between the branch point 12e and the connection point 12f. The suction passage 46 includes a fifth solenoid valve 47 to open and close the suction passage 46. The fifth solenoid valve 47 is electrically connected to the ECU 48. The fifth solenoid valve 47 is controlled by the ECU 48. Similar to the sixth solenoid valve 43, the fifth solenoid valve 47 is closed when the engine is operated. The fifth solenoid valve 47 is also closed until a predetermined time t has passed after the stop of the engine. The fifth solenoid valve 47 is opened when the predetermined time t has passed after the stop of the engine.
The ECU 48 controls the operation of the sixth solenoid valve 43 and the fifth solenoid valve 47. When the engine is operated and until the predetermined time t has passed after the stop of the engine, the ECU 48 controls also the operation of the solenoid valves 6, 13, 14, 15, and 16, and the switch 21 similar to the ECU 22 in the first embodiment. When the predetermined time t has passed after the stop of the engine, the ECU 48 closes the solenoid valve 15, and shifts the switch 21 to rotate the feed pump 3 in a normal direction. Other structures are similar to the first embodiment. A table 1 indicates the operation of the feed pump 3, the third solenoid valve 6, the first solenoid valves 13, 14, 15, the second solenoid valve 16, the sixth solenoid valve 43, and the fifth solenoid valve 47.
The operation of the fuel supply system 41 for the DME engine of the third preferred embodiment with reference to
As indicated in the table 1, when the predetermined time t has passed after the stop of the engine, the sixth solenoid valve 43 and the fifth solenoid valve 47 are opened. As shown in
When the predetermined time t has passed after the stop of the engine, the feed pump 3 rotates in the normal direction, and discharges the DME fuel in liquid phase in the fuel tank 2 into the low-pressure fuel supply passage 4. Because the third solenoid valve 6 is closed when the engine is stopped, the DME fuel which is discharged to the low-pressure fuel supply passage 4 does not flow into the high-pressure supply pump 7, but flows through the connection point 4a and the flow supply passage 42 in this order to be supplied to the supply port 44a of the ejector 44. The DME fuel supplied to the supply port 44a of the ejector 44 is ejected inside the ejector 44 at high speed. Utilizing the pressure decrease at the suction port 44c at ejection, the ejector 44 sucks the DME fuel remained at the downstream side of the high-pressure supply pump 7 through the confluence passage 12g, the suction passage 46, and the suction port 44c. The second solenoid valve 16 is closed when the engine is stopped, and the DME fuel in gas phase in the fuel tank 2 does not flow into the confluence passage 12g through the fourth branch passage 12h. The ejector 44 mixes therein the DME fuel which is supplied through the supply port 44a and the DME fuel which is sucked through the suction port 44c, and the mixed DME fuel is discharged to the exhaust passage 45 through the exhaust port 44b, and is returned back to the fuel tank 2.
Thus, the DME fuel in the fuel tank 2 is supplied to the supply port 44a of the ejector 44. The DME fuel remained at the downstream side of the high-pressure supply pump 7 is sucked into the ejector 44 through the suction passage 46 and the suction port 44c. The DME fuel is recovered into the fuel tank 2 through the exhaust port 44b and the exhaust passage 45. When the predetermined time t has passed after the stop of the engine, the DME fuel in gas phase is remained at the downstream side of the high-pressure supply pump 7. The feed pump 3 rotates in the normal direction and discharges the DME fuel in liquid phase in the fuel tank 2. Thus, it is prevented that only the DME fuel in gas phase may circulate in the feed pump 3 and that non-lubrication state may occur. Accordingly durability of the feed pump 3 is improved, and the reliability of the fuel supply system 41 for the DME engine is improved. The flow supply passage 42 is connected to the flow-pressure fuel supply passage 4, and the flow supply passage 42 has the sixth solenoid valve 43 which is opened when the predetermined time t has passed after the stop of the engine. Thus, part of the low-pressure fuel supply passage 4 is utilized to supply the DME fuel to the ejector 44, and the piping of the fuel supply system 41 for the DME engine is simplified and the fuel supply system 41 is downsized.
The following will describe a fuel supply system for a DME engine of a fourth preferred embodiment with reference to
The feed pump 52 has a solenoid switching valve 52c. By shifting the solenoid switching valve 52c, a compression chamber (not shown) of the feed pump 52 is connected to either the discharge port 52a or the discharge port 52b. The solenoid switching valve 52c is electrically connected to an ECU 54 and is controlled to switch the connection between the compression chamber and the discharge ports 52a, 52b. The compression chamber is connected to the discharge port 52a when the engine is operated or until when the predetermined time t has passed after the stop of the engine The compression chamber is connected to the discharge port 52b after the predetermined time t has passed after the stop of the engine. The ECU 54 shifts the solenoid switching valve 52c and controls the operation of the solenoid valves 6, 13, 14, 15, 16, 47, and the shift of the switch 21, similar to the ECU 48 of the third embodiment. A table 2 indicates the operation of the third solenoid valve 6, the solenoid valves 13, 14, 15 and the second solenoid valve 16, and the fifth solenoid valve 47, the feed pump 52, and the solenoid switching valve 52c. Other structures are similar to the third embodiment.
The operation of the fuel supply system 51 for the DME engine will be described with reference to
When the predetermined time t has passed after the stop of the engine, the feed pump 3 rotates in the normal direction, and the compression chamber of the feed pump 3 is connected to the discharge port 52b though the solenoid switching valve 52c. Thus, the DME fuel in the fuel tank 2 is discharged to the flow supply passage 53, and is supplied to the supply port 44a of the ejector 44. When the predetermined time t has passed after the stop of the engine, the fifth solenoid valve 47 is opened. Accordingly, by the flow of the DME fuel supplied to the ejector 44 through the flow supply passage 53, the DME fuel in gas phase, which is remained at the downstream side of the high-pressure supply pump 7, is sucked into the ejector 44 through the suction passage 46.
As described above, the discharge port 52a is connected to the low-pressure fuel supply passage 4, and the discharge port 52b is connected to the flow supply passage 53. The connection between the discharge ports 52a, 52b and the compression chamber is switched by the solenoid switching valve 52c of the feed pump 52. That is, when the engine is operated or until the predetermined time t has passed after the stop of the engine, the discharge port 52a is connected to the compression chamber of the feed pump 52, and after the predetermined time t has passed, the discharge port 52b is connected to the compression chamber of the feed pump 52. Thus, the fourth embodiment has the same effect as the third embodiment.
Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2006-198252 | Jul 2006 | JP | national |
| P2007-002471 | Jan 2007 | JP | national |
