JP2008298042A - Fuel supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply system which can sweep away the fuel in all tanks by a feed pump eve if a plurality of tanks is provided, requires no complicated control system, has a simple structure and is cheap in the fuel supply device for supplying liquid fuel from a fuel tank to an internal combustion engine and returning excess liquid fuel among the liquid fuel supplied to the internal combustion engine to the fuel tank. <P>SOLUTION: The fuel supply system comprises a fuel return tank 7 connected to a fuel return passage 5 to get an in flow of the excess fuel warmed on the internal combustion engine 3 side, and a fuel supply tank 8 connected to a fuel supply passage 4 to accommodate the liquid fuel to be supplied to the internal combustion engine 3 wherein the liquid fuel in the fuel return tank 7 is conveyed to the fuel supply tank 8 via the passage 9 between tanks with a difference between a vapor pressure Pr of the liquid fuel in the fuel return tank 7 and a vapor pressure Pi of the liquid fuel in the fuel supply tank 8, and the liquid fuel in the fuel supply tank 8 is pressurized by the feed pump 10 to be supplied to the internal combustion engine 3 via the fuel supply passage 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel supply device that supplies liquefied fuel (dimethyl ether or the like) from a fuel tank to an internal combustion engine and returns surplus liquefied fuel from the liquefied fuel supplied to the internal combustion engine to the fuel tank.

  FIG. 3 shows a general fuel supply device 1x for a vehicle using light oil as the fuel. As shown in the figure, a large vehicle of light oil fuel such as a truck often includes a sub tank 8a in addition to the main tank 7a in order to increase the cruising distance. The fuel in the main tank 7 a is supplied to the engine supply pump 6 of the diesel engine 3 through the fuel supply passage 4, and surplus fuel out of the fuel supplied to the engine 3 side passes through the fuel return passage 5. 7a is returned. A sub tank 8a is connected to the main tank 7a in a liquid phase, and the internal pressures of both tanks 7a, 8a are equivalent to atmospheric pressure and are equal. In FIG. 3, the sub tank 8a is drawn below the main tank 7a. However, the sub tank 8a is drawn as such for convenience of drawing, and the main tank 7a and the sub tank 8a are actually arranged at the same height. Yes. According to this configuration, when the fuel in the main tank 7a flows toward the engine 3 and the liquid level of the main tank 7a is lowered, the liquid level of the sub tank 8a communicated with the main tank 7a is also lowered, and both liquid levels are equal. . Therefore, substantially all of the fuel in both tanks 7a and 8a can be dispensed.

  FIG. 4 shows a fuel supply device 1x shown in FIG. 3 that is diverted to a vehicle fuel supply device 1y using dimethyl ether (hereinafter DME) as a fuel. DME is a liquefied fuel that is liquefied by applying pressure to what is in a gaseous state at normal temperature and pressure, and is much easier to vaporize than light oil. For this reason, in the fuel supply device 1y using DME as fuel, the DME supplied from the main tank 7a to the engine 3 side is supplied to the engine 3 in the engine supply pump 6 attached to the engine 3 as shown in FIG. In order to prevent vaporization when receiving heat from the main tank 7a, the main pump 7a is pressurized by the feed pump 10 and pumped to the engine 3 side. With this configuration, the surplus DME that is returned from the engine 3 side through the fuel return passage 5 to the main tank 7a receives the heat of the engine 3 in the vicinity of the engine supply pump 6, and therefore passes through the fuel supply passage 4 and the engine. The temperature becomes higher than the temperature of DME toward the third side and returns to the main tank 7a. Therefore, the vapor pressure Pm of DME in the main tank 7a becomes higher than the vapor pressure Ps in the sub tank 8a, and the DME in the sub tank 8a flows out to the main tank 7a even if the liquid level in the main tank 7a falls. Conversely, DME in the main tank 7a flows out to the sub tank 8a. Thus, even if the two tanks 7a and 8a are mounted on the vehicle, DME that cannot be paid out remains in the sub-tank 8a, so that the cruising distance cannot be extended.

  FIG. 5 shows a fuel return passage 5 through which excess DME from the engine 3 flows. A bifurcated return passage 5a is connected to each tip portion of the return passage 5a so that gas phase portions of two tanks 7a and 8a are connected. To the liquid phase portions of the tanks 7a and 8a, respectively, and the collecting passage 4a is connected to the fuel supply passage 4 for supplying DME to the engine 3 side. 1z (see Patent Document 1). In each tank 7a, 8a, DME is accommodated and a feed pump 10 (in-tank pump) connected to the take-out passage 4a is accommodated. In this configuration, since the tanks 7a and 8a are in parallel, there is no distinction between main and sub. For each of the tanks 7a and 8a, a pressure-resistant tank for LPG or the like is used. Since the fuel supply apparatus 1z is of the tank parallel type, there is no problem in the main / sub tank type fuel supply apparatus 1y described with reference to FIG. And the return of DME from the engine 3 side to the tanks 7a and 8a are two systems. The vapor pressure of DME in the tanks 7a and 8a can be different. If the vapor pressures in the tanks 7a and 8a are different, the amount of DME returning to the tanks 7a and 8a differs depending on the tanks 7a and 8a. For this reason, even if the two tanks 7a and 8a are mounted on the vehicle, it is difficult to completely discharge the DME in the tanks 7a and 8a. The distance cannot be secured.

  If the DME liquid level in each of the tanks 7a and 8a is to be made equal, the DME liquid level in each of the tanks 7a and 8a is detected by a sensor to control the pumping amount of the feed pump 10 in each of the tanks 7a and 8a. The control system becomes complicated. In this case, since the feed pump 10, the sensor, and the feed pump control system are required for each of the tanks 7a and 8a, an increase in cost is inevitable.

International Publication No. 2004/016934 Pamphlet JP 2004-108175 A Japanese Patent Laid-Open No. 3-153419

  By the way, since DME has a smaller calorific value than light oil, it is necessary to mount a DME having a capacity about twice that of light oil on the vehicle in order to obtain the same cruising distance as light oil. For example, in a vehicle on which 100 L of light oil is mounted, about 200 L is required for DME. In other words, when DME is used as a fuel, a fuel tank having a capacity approximately twice that of light oil is required. Even if such a large-capacity fuel tank is mounted on the vehicle as a single tank, the vehicle wheel This is difficult due to restrictions on the base and restrictions on other bodywork. In reality, a plurality of small-capacity fuel tanks (DME tanks) are mounted on the vehicle.

  Here, in the case where a plurality of DME tanks are mounted on a vehicle, this is developed based on the technology of the light oil fuel supply apparatus 1x having two light oil tanks shown in FIG. The DME fuel supply devices 1y and 1z having two DME tanks to be shown are conceivable. The problems thereof are as described above.

  An object of the present invention, which was created in view of the above circumstances, is a fuel supply device that supplies liquefied fuel from a fuel tank to an internal combustion engine, and returns excess liquefied fuel from the liquefied fuel supplied to the internal combustion engine to the fuel tank. To provide an inexpensive fuel supply device that can dispense fuel in all tanks with a single feed pump even if a plurality of tanks are provided, does not require a complicated control system, and has a simple structure. It is in.

  In order to achieve the above object, the present invention provides a fuel tank containing liquefied fuel, a fuel supply passage for supplying liquefied fuel from the fuel tank to the internal combustion engine, and an excess of the liquefied fuel supplied to the internal combustion engine. A fuel supply device comprising a fuel return passage for returning the liquefied fuel to the fuel tank, wherein the fuel tank is connected to the fuel return passage and into which the surplus fuel flows, and the fuel supply A fuel supply tank connected to a passage and containing liquefied fuel to be supplied to the internal combustion engine, and between the fuel return tank and the fuel supply tank, the vapor pressure and fuel of the liquefied fuel in the fuel return tank Due to the difference in vapor pressure of the liquefied fuel in the supply tank, an inter-tank passage is provided to transfer the liquefied fuel in the fuel return tank to the fuel supply tank, and the liquefied fuel in the fuel supply tank is added. And, those having a feed pump supplied to the internal combustion engine through the fuel supply passage.

  A pressure-feed pump that pumps the liquefied fuel in the fuel return tank to the fuel supply tank may be provided in the inter-tank passage.

  The inter-tank passage may connect a liquid phase portion of the fuel return tank and a gas phase portion of the fuel supply tank.

  The liquefied fuel may be dimethyl ether.

  According to the present invention, a fuel supply device that supplies liquefied fuel from a fuel tank to an internal combustion engine and returns surplus liquefied fuel out of the liquefied fuel supplied to the internal combustion engine to the fuel tank may include a plurality of tanks. The fuel in all the tanks can be dispensed with one feed pump, and an inexpensive fuel supply device with a simple structure that does not require a complicated control system can be provided.

  A preferred embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, a fuel supply device 1 according to this embodiment includes a fuel tank 2 in which DME as liquefied fuel is accommodated, and DME from the fuel tank 2 to an internal combustion engine 3 (diesel engine, hereinafter referred to as an engine). A fuel supply passage 4 to be supplied and a fuel return passage 5 for returning surplus DME of the DME supplied to the engine 3 to the fuel tank 2 are mounted on a vehicle (a truck or the like).

  The engine 3 is provided with an engine supply pump 6, and a fuel supply passage 4 and a fuel return passage 5 are connected to the engine supply pump 6. The DME in the fuel supply passage 4 is supplied to the engine 3 via the engine supply pump 6, and surplus DME among the supplied DME is returned to the fuel return passage 5 through the engine supply pump 6.

  The fuel tank 2 is connected to a fuel return passage 5 and a fuel return tank 7 (pressure tank) into which the above-mentioned surplus DME flows, and a fuel supply tank in which a DME connected to the fuel supply passage 4 and supplied to the engine 3 is accommodated. 8 (pressure tank). The fuel return passage 5 is connected to the DME gas phase portion (hereinafter referred to as gas phase portion) in the upper portion of the fuel return tank 7, and the fuel supply passage 4 is connected to the DME liquid phase portion (hereinafter referred to as liquid phase portion) in the lower portion of the fuel supply tank 8. It is connected to the.

  Between the fuel return tank 7 and the fuel supply tank 8, there is a difference between the DME vapor pressure Pr in the fuel return tank 7 and the DME vapor pressure Pi in the fuel supply tank 8. Between the tanks 9 for transferring the fuel to the fuel supply tank 8. One end of the inter-tank passage 9 is connected to the liquid phase portion below the fuel return tank 7, and the other end is connected to the gas phase portion above the fuel supply tank 8.

  Inside the fuel supply tank 8 is housed a feed pump 10 (in-tank pump) that pressurizes DME in the fuel supply tank 8 and supplies it to the engine 3 (engine supply pump 6) via the fuel supply passage 4. Yes. The in-tank pump 10 is immersed in DME (liquid) in the fuel supply tank 8, takes in the DME, pressurizes it, and discharges it to the fuel supply passage 4.

  In FIG. 1, 11 is a valve that opens and closes the fuel return passage 5 and is opened at least when the engine 3 is in operation. The discharge pipe 13 bent to the right is a relief mechanism that opens when the internal pressure (gas phase portion) of the fuel return tank 7 exceeds a predetermined pressure. Reference numeral 14 denotes a supply port mechanism for supplying DME to the fuel return tank 7. The replenishing port mechanism 14 is configured by connecting a check valve 15, an opening / closing valve 16 and a replenishment pipe 17 in series, and the replenishment pipe 17 flows out DME to be replenished to a gas phase portion in the fuel return tank 7. , Bent upward and extended. The on-off valve 16 is normally closed and is opened only when DME is replenished.

  Further, 18 is a valve for opening and closing the fuel return tank 7 side of the inter-tank passage 9, and 19 is a valve for opening and closing the fuel supply tank 8 side of the inter-tank passage 9. These valves 18 and 19 are opened at least during operation of the engine 3. 20 indicates that the DME in the inter-tank passage 9 flows out to the gas phase portion in the fuel supply tank 8, so that the discharge pipe is bent upward, and 21 indicates that the internal pressure (gas phase portion) of the fuel supply tank 8 exceeds the predetermined pressure. A relief mechanism 22 that opens when the fuel supply tank 8 is supplied is a supply port mechanism (same configuration as the supply port mechanism 14) for supplying DME to the fuel supply tank 8. A valve 23 opens and closes the fuel supply passage 4 and is opened at least during operation of the engine 3.

  The operation of this embodiment will be described.

  The DME (liquid) in the fuel supply tank 8 shown in FIG. 1 is pressurized (for example, about 3 MPa) by the in-tank pump 10 and discharged to the fuel supply passage 4. It is supplied to the pump 6.

  Here, the vapor pressure of DME is about 0.5 MPa at 20 ° C., and the vapor pressure increases as the temperature increases. However, in the engine supply pump 6 on the engine 3 side, the temperature of DME is the engine 3 (engine block). Etc.) and rises to about 80 ° C. (vapor pressure 2.2 MPa). For this reason, the DME in the fuel supply tank 8 is pressurized to about 3 MPa by the in-tank pump 10 so that the pressure of the DME in the engine supply pump 6 becomes 2.2 MPa or more which is the vapor pressure there. The DME that is supplied to the engine 6 and heated by the engine supply pump 6 by receiving heat from the engine 3 is prevented.

  Thus, of the DME supplied to the engine 3 in a liquid state with evaporation prevented, excess DME is returned from the engine supply pump 6 to the fuel return tank 7 through the fuel return passage 5. Here, the DME returned from the engine supply pump 6 to the fuel return tank 7 is warmed by receiving heat from the engine 3 in the vicinity of the engine supply pump 6. The temperature is higher than the DME in the fuel supply tank 8 and returns to the fuel return tank 7. Therefore, the vapor pressure Pr of DME in the fuel return tank 7 becomes higher than the vapor pressure Pi of DME in the fuel supply tank 8.

  When the vapor pressure Pr> the vapor pressure Pi, the DME in the fuel return tank 7 is transferred to the fuel supply tank 8 through the inter-tank passage 9 due to the difference between the vapor pressures Pr and Pi. That is, the inter-tank passage 9 interposed between the fuel return tank 7 and the fuel supply tank 8 is formed between the vapor pressure Pr of DME in the fuel return tank 7 and the vapor pressure Pi of DME in the fuel supply tank 8. Due to the difference, the DME in the fuel return tank 7 is transferred to the fuel supply tank 8 without using a pumping means such as a pump.

  The DME in the fuel supply tank 8 thus transferred is pressurized (about 3 MPa) by the in-tank pump 10 as described above, discharged to the fuel supply passage 4, passes through the fuel supply passage 4, and is supplied to the engine supply of the engine 3. Excess DME supplied to the pump 6 and not consumed by the engine 3 is returned from the engine supply pump 6 to the fuel return tank 7 and circulated again.

  As described above, according to the fuel supply device 1 according to the present embodiment, the DME that is returned from the engine supply pump 6 to the fuel return tank 7 through the fuel return passage 5 is supplied to the engine supply pump 6 during the operation of the engine 3. Since it is warmed by receiving heat from the engine 3 in the vicinity, it is returned to the fuel return tank 7, so that the DME in the fuel return tank 7 becomes hotter than the DME in the fuel supply tank 8, The state in which the vapor pressure Pr of DME is higher than the vapor pressure Pi of DME in the fuel supply tank 8 is maintained, and all the DME in the fuel return tank 7 is discharged to the fuel supply tank 8 due to the difference between the vapor pressures Pr and Pi. . Then, all the DME in the fuel supply tank 8 can be discharged by the in-tank pump 10 and supplied to the engine 3 (engine supply pump 6). As a result, all of the DME in the fuel return tank 7 and the fuel supply tank 8 are obtained. The cruising distance for DME capacity can be secured.

  The DME is transferred from the fuel return tank 7 to the fuel supply tank 8 between the vapor pressure Pr in the fuel return tank 7 and the vapor pressure Pi in the fuel supply tank 8 generated by the operating heat of the engine 3 as described above. Since the difference is utilized, the fuel supply tank is used as the feed pump 10 for supplying DME from the fuel tank 2 side including the fuel return tank 7 and the fuel supply tank 8 to the engine 3 side (engine supply pump 6). Only the in-tank pump 10 in 8 is sufficient. That is, all the DME in the two tanks 7 and 8 can be dispensed by one in-tank pump 10 and supplied to the engine 3 side. Therefore, in this embodiment, the number of feed pumps 10 (in-tank pumps) is reduced from two to one compared to the type shown in FIG. 5, and in the type shown in FIG. 5, all DMEs in the tanks 7a and 8a are paid out. In addition, the liquid level sensors of the tanks 7a and 8a, which were necessary to take out, become unnecessary, and in addition, the outputs of these liquid level sensors are linked with the in-tank pump 10 of the tanks 7a and 8a. Since a control system for aligning the liquid level is not required, the structure is simplified and a significant cost reduction can be promoted.

  By the way, during the warm-up operation of the engine 3 immediately after the start of the engine 3 in a cold district or the like, the engine 3 has not yet been warmed, so that the DME returning from the engine supply pump 6 to the fuel return tank 7 through the fuel return passage 5 is In the vicinity of the engine supply pump 6, the fuel returns to the fuel return tank 7 without being sufficiently warmed by the heat of the engine 3. For this reason, the vapor pressure Pr of the DME in the fuel return tank 7 is not sufficiently higher than the vapor pressure Pi of the DME in the fuel supply tank 8, and the DME is pumped from the fuel return tank 7 to the fuel supply tank 8. Unexpected cases can occur.

  Therefore, as shown in FIG. 2, a pressure feed pump 24 for pressure-feeding the DME in the fuel return tank 7 to the fuel supply tank 8 may be provided in the inter-tank passage 9 connecting the fuel return tank 7 and the fuel supply tank 8. Good. The embodiment of FIG. 2 has the same configuration as that of the embodiment of FIG. The pressure pump 24 is composed of an intake pump accommodated in the fuel return tank 7, and has a pressurizing capacity (about 0.2 MPa) capable of transferring DME in the fuel return tank 7 to the fuel supply tank 8 having substantially the same tank internal pressure. ) Is sufficient, and an inexpensive one whose pressure performance is significantly lower than that of the feed pump 10 (in-tank pump: about 3 MPa) provided in the fuel supply tank 8 can be used.

  In the fuel supply device 1a according to the embodiment of FIG. 2, it is necessary to add a pressure pump 24 as compared with the fuel supply device 1 according to the embodiment of FIG. Since a low (about 0.2 MPa) and inexpensive one is sufficient, the cost is only slightly increased, the above-mentioned problem at the time of cold start can be solved, and the same effects as the embodiment of FIG. 1 can be achieved. Further, the embodiment of FIG. 2 is low in cost as compared with the one that requires two expensive feed pumps 10 having high pressurization capability (about 3 MPa) as in the type of FIG.

  The feed pump 10 in FIGS. 1 and 2 is not limited to the in-tank pump housed in the fuel supply tank 8, and may be a line pump provided outside the fuel supply tank 8 or in the fuel supply passage 4. 2 is not limited to the in-tank pump housed in the fuel return tank 7, but may be a line pump provided outside the fuel return tank 7 or in the inter-tank passage 9.

1 is an explanatory diagram showing an outline of a fuel supply device according to an embodiment of the present invention. It is explanatory drawing by which the outline of the fuel supply apparatus which concerns on modification embodiment of this invention was represented. It is explanatory drawing by which the outline of the conventional fuel supply apparatus of light oil fuel was represented. It is explanatory drawing of what diverted the fuel supply apparatus of FIG. 3 to the fuel supply apparatus of the vehicle which used DME for the fuel. It is explanatory drawing by which the outline of the fuel supply apparatus of the vehicle which used the conventional DME for the fuel was represented.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel supply apparatus 1a Fuel supply apparatus 2 Fuel tank 3 Diesel engine (internal combustion engine)
4 Fuel supply passage 5 Fuel return passage 7 Fuel return tank 8 Fuel supply tank 9 Inter-tank passage 10 Feed pump (in-tank pump)
24 Pressure feed pump Pr Vapor pressure of liquefied fuel (DME) in fuel return tank 7 Pi Vapor pressure of liquefied fuel (DME) in fuel supply tank 8

Claims (4)

A fuel tank containing liquefied fuel, a fuel supply passage for supplying liquefied fuel from the fuel tank to the internal combustion engine, and a fuel return for returning surplus liquefied fuel from the liquefied fuel supplied to the internal combustion engine to the fuel tank A fuel supply device comprising a passage,
The fuel tank includes a fuel return tank connected to the fuel return passage and into which the surplus fuel flows, and a fuel supply tank connected to the fuel supply passage and containing liquefied fuel supplied to the internal combustion engine. ,
The liquefied fuel in the fuel return tank is supplied between the fuel return tank and the fuel supply tank by the difference between the vapor pressure of the liquefied fuel in the fuel return tank and the vapor pressure of the liquefied fuel in the fuel supply tank. An inter-tank passage to be transferred to the tank,
A fuel supply apparatus comprising a feed pump for pressurizing the liquefied fuel in the fuel supply tank and supplying the liquefied fuel to the internal combustion engine through the fuel supply passage.   The fuel supply device according to claim 1, wherein a pressure-feed pump that pressure-feeds the liquefied fuel in the fuel return tank to the fuel supply tank is provided in the inter-tank passage.   The fuel supply apparatus according to claim 1 or 2, wherein the inter-tank passage connects a liquid phase portion of the fuel return tank and a gas phase portion of the fuel supply tank.   The fuel supply apparatus according to any one of claims 1 to 3, wherein the liquefied fuel is dimethyl ether.

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