JP2010163909A - On-vehicle fuel separation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply device, capable of preventing excessive heat of fuel by a fuel heating device even when operation of an internal combustion engine is stopped. <P>SOLUTION: The fuel supply device 24 for an internal combustion engine includes: the fuel heating device 56 for heating raw material fuel; a fuel pump 60 for feeding fuel in a fuel tank 23 to the fuel heating device; and a fuel distribution passage 62 for feeding the fuel from the fuel heating device to fuel injection valves 11a and 11b. When the operation of the internal combustion engine is stopped, the fuel in the fuel heating device is forcedly returned to the fuel tank by reversely rotating the fuel pump. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an on-vehicle fuel separator.

  2. Description of the Related Art There is known a fuel separation device that separates fuel supplied as a raw material (that is, raw material fuel) and generates a fuel having properties different from those of the raw material fuel. As such a fuel separation device, for example, there is a device equipped with a separation membrane that selectively permeates a high octane component in the fuel (for example, Patent Document 1). In this fuel separator, a high octane fuel having a higher octane number than that of the raw material fuel is generated on one side of the separation membrane, and a low octane fuel having a lower octane number than that of the raw material fuel is generated on the other side of the separation membrane.

  In particular, in the fuel separation device described in Patent Document 1, by heating the raw material fuel supplied to the separation membrane with a heat exchanger, the high octane number that permeates the separation membrane out of the amount of the high octane component contained in the fuel. Increasing the proportion of the amount of ingredients. Thereby, the separation efficiency of the raw material fuel in the fuel separator can be increased.

JP 2004-232624 A JP 2003-176766 A JP 2004-162655 A JP 2004-360645 A

  By the way, as described above, in the fuel separator, it is necessary to raise the temperature of the raw material fuel supplied to the separation membrane in order to increase the separation efficiency of the raw material fuel. For this reason, in many cases, the fuel separator is provided with a fuel heating device, particularly a heat exchanger, for heating the raw material fuel.

  Here, when the internal combustion engine is stopped, the supply of fuel to the internal combustion engine is normally stopped. When the supply of fuel to the internal combustion engine is stopped, the fuel in the fuel supply passage remains at that position. Therefore, the fuel that was in the heat exchanger when the internal combustion engine was stopped remains in the heat exchanger as it is.

  However, in general, the heat exchanger supplies heat to the raw material fuel in the heat exchanger for a certain period even after the internal combustion engine is stopped. For this reason, the fuel remaining in the heat exchanger after the internal combustion engine is stopped may be excessively heated. If the fuel is excessively heated in this manner, the fuel may be deteriorated or the circulation efficiency of the fuel may be reduced due to the generation of bubbles in the fuel supply passage.

  Therefore, an object of the present invention is to provide a fuel supply device that prevents the fuel from being excessively heated by the fuel heating device even when the operation of the internal combustion engine is stopped.

  In order to solve the above problems, in the first invention, a fuel heating device that heats fuel, a fuel pump that sends fuel in a fuel tank to the fuel heating device, and a fuel injection valve that sends fuel from the fuel heating device In the fuel supply device for an internal combustion engine, comprising the fuel flow passage for feeding to the fuel tank, when the operation of the internal combustion engine is stopped, the fuel pump is forcibly rotated to reversely rotate the fuel in the fuel heating device. Returned to

  According to a second invention, in the first invention, a bypass passage communicating with the fuel flow passage and the fuel tank is further provided, and fluid flow from the fuel tank to the fuel flow passage is permitted in the bypass passage. A check valve is provided to prohibit the flow of fluid from the fuel flow passage to the fuel tank.

  According to a third invention, in the first invention, a bypass passage communicating with the fuel flow passage and the fuel tank is further provided, and an on-off valve is provided in the bypass passage, and the on-off valve stops the operation of the internal combustion engine. Sometimes it is opened.

  According to a fourth invention, in the third invention, the on-off valve is opened even when the temperature of the fuel in the fuel heating device becomes equal to or higher than a reference temperature, and the fuel pump is operated when the operation of the internal combustion engine is stopped. In addition, even when the temperature of the fuel in the fuel heating device becomes equal to or higher than the reference temperature, after the opening / closing valve is opened, the fuel in the fuel heating device is forced into the fuel tank by reverse rotation. return.

  In a fifth invention, in any one of the first to fourth inventions, the fuel heating device is a heat exchanger using heat generated by combustion of an air-fuel mixture in an internal combustion engine.

  In a sixth invention, in any one of the first to fourth inventions, the fuel heating device heats fuel using heat generated by electric power.

  According to a seventh invention, in any one of the first to sixth inventions, the apparatus further comprises a separator for separating the raw material fuel heated by the fuel heating device into a plurality of types of fuel, And a high octane fuel having a higher octane number than that of the raw material fuel and a low octane fuel having a lower octane number than that of the raw material fuel.

  According to the present invention, when the operation of the internal combustion engine is stopped, the fuel is forcibly discharged from the fuel heating device by reversely rotating the fuel pump, so that the fuel is prevented from being excessively heated by the fuel heating device. .

  Hereinafter, a fuel supply device according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a side sectional view of a spark ignition type internal combustion engine on which the fuel supply device of the present invention is mounted.

  Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is a spark plug disposed at the center of the top surface of the combustion chamber 5, and 7 is intake air. 8 is an intake port, 9 is an exhaust valve, and 10 is an exhaust port. A fuel injection valve (hereinafter referred to as “in-cylinder injection fuel injection valve”) 11 a that directly injects fuel into the combustion chamber 5 is disposed around the cylinder inner wall surface of the cylinder head 4. The intake port 8 is connected to a surge tank 13 via an intake branch pipe 12, and a fuel injection valve (hereinafter referred to as “port injection”) for injecting fuel into each intake branch pipe 12 into the corresponding intake port 8. 11b) (referred to as “fuel injection valve”).

  The surge tank 13 is connected to an air cleaner 15 via an intake duct 14, and a throttle valve 17 and an air flow meter 18 driven by an actuator 16 are disposed in the intake duct 14. On the other hand, the exhaust port 10 is connected through an exhaust manifold 19 to a catalytic converter 20 containing an exhaust purification catalyst (for example, a three-way catalyst). Catalytic converter 20 is connected to exhaust pipe 21.

  The fuel injection valves 11 a and 11 b are connected to the fuel supply device 24. Further, the exhaust manifold 19 or the exhaust pipe 21 is provided with an exhaust heat recovery device 25 that recovers heat from the exhaust gas flowing in the exhaust manifold 19 or the exhaust pipe 21 and transfers the heat to the object to be heated.

  Next, the configuration of the fuel supply device 24 of the present embodiment will be described with reference to FIG. FIG. 2 is a diagram schematically showing a schematic configuration of the fuel supply apparatus.

  The fuel supply device 24 shown in FIG. 2 includes a raw material fuel tank 23, a fuel separator 50, a high octane fuel tank 51 and a low octane fuel tank 52. The raw material fuel tank 23 is supplied with raw material fuel (for example, normal (commercially available) gasoline) and stored. The fuel stored in the raw material fuel tank 23 is separated by the fuel separator 50 into a high octane fuel having a higher octane number than that of the raw material fuel and a low octane fuel having a lower octane number than that of the raw material fuel. It is stored in a high octane fuel tank 51 and a low octane fuel tank 52.

  The high-octane fuel in the high-octane fuel tank 51 is supplied to the port injection fuel injection valve 11b by the feed pump 53 and injected into the intake port 8 of each cylinder. On the other hand, the low octane fuel in the low octane fuel tank 52 is supplied by the feed pump 54 to the in-cylinder fuel injection valve 11a and directly injected into the combustion chamber 5 of each cylinder.

  Thus, in this embodiment, since the fuel injection valves 11a and 11b that are independent from each other are used for the low-octane fuel and the high-octane fuel, the low-octane fuel and the high-octane fuel are used according to the engine operating state. One of them can be selectively supplied to the combustion chamber 5 of each cylinder of the engine body 1 at a predetermined ratio.

  Next, the fuel separator 50 of this embodiment will be briefly described with reference to FIG. The fuel separation device 50 includes a heat exchanger (fuel heating device) 56, a separation unit 57 using a separation membrane, a gas-liquid separator 58, and the like.

  The separation unit 57 is configured such that a housing 57a made of a heat-resistant container is divided into two compartments 57c and 57d by an aroma separation membrane 57b. As the aroma separation membrane 57b, one having a property of selectively permeating aromatic components in gasoline is used. That is, in the aroma separation membrane 57b, the raw fuel is supplied to one side (for example, the section 57c side, that is, the low octane number fuel side) at a relatively high pressure, and the other side (for example, the section 57d side, that is, the high octane number). When the fuel side is kept at a relatively low pressure, aromatic components in the raw material fuel mainly permeate the separation membrane 57b and leached out to the surface of the separation membrane 57b on the low pressure side (section 57d side, that is, high octane number side) The surface of the separation membrane 57b facing the low pressure side is covered.

  By removing the liquid leached fuel that covers the surface of the low-pressure side separation membrane 57b, aromatic components are leached from the high-pressure compartment 57c side to the low-pressure compartment 57d side through the separation membrane 57b. In the present embodiment, by maintaining the pressure on the low pressure side (compartment 57d side) at a pressure lower than the vapor pressure of the brewed aromatic component, the leached fuel containing a large amount of aromatic component covering the surface of the separation membrane 57b on the low pressure side. Is evaporated and continuously removed from the surface and recovered in the form of fuel vapor.

  The fuel vapor recovered from the low pressure side section 57d of the separation unit 57 is sent to the gas-liquid separator 58 where it is cooled. As a result, the aromatic component having a relatively high boiling point is liquefied, and a liquid high-octane fuel containing a large amount of the aromatic component is generated below the gas-liquid separator 58. The high-octane fuel produced in this way is supplied to the high-octane fuel tank 51.

  On the other hand, the fuel remaining in the high pressure side section 57c of the separation unit 57 has a high octane component content reduced by removing a part of the aromatic component. Therefore, a low octane fuel with a low content of aromatic components is generated in the high pressure side compartment 57c of the separation unit 57. The low-octane fuel produced in this way is supplied to the low-octane fuel tank 52.

  Here, the separation efficiency of the separation membrane 57b varies greatly depending on the operating conditions of the separation membrane 57b. Therefore, in order to increase the separation efficiency by the separation membrane 57b, it is necessary to appropriately control the operating conditions of the separation membrane 57b. An operating condition that affects the separation efficiency of the separation membrane 57b includes the temperature of the raw material fuel supplied to the separation membrane 57b.

  The ratio (permeability) of the aromatic component in the raw material fuel that permeates the separation membrane 57b increases as the temperature of the raw material fuel increases until the temperature reaches a certain temperature from the atmospheric temperature. This certain temperature is a temperature at which the temperature on the low pressure side (section 57d) of the separation membrane 57b reaches a certain lower limit temperature. This lower limit temperature is a function of the pressure on the low pressure side of the separation membrane 57b. For example, the pressure on the low pressure side is about 353 ° K (80 ° C.) at 5 kPa.

  On the other hand, if the temperature on the low pressure side continues to rise above the lower limit temperature, the transmittance will decrease above a certain temperature. That is, there exists an optimum temperature range in which the temperature on the low pressure side should be maintained, and this optimum temperature range is, for example, about 348 K to 398 K (about 75 ° C. to 125 ° C.) when the low pressure side pressure is in the range of 5 to 20 kPa. Become.

  Therefore, in order to maximize the separation efficiency of the separation membrane 57b, it is necessary to maintain the temperature of the raw material fuel so that the low-pressure side temperature of the separation membrane 57b is in the optimum temperature range. For this reason, in this embodiment, before supplying the raw material fuel to the separation unit 57, the raw material fuel is heated using the heat exchanger 56 so as to maintain the temperature at which the separation efficiency by the separation membrane 57b becomes the highest. I have to.

  In the embodiment of the present invention, an exhaust heat recovery device 25 that recovers heat from the exhaust gas and transfers the recovered heat to a heating target (raw material fuel in the present embodiment) is used as the heat exchanger 56. The However, the heat exchanger 56 may have other configurations, such as a heat exchanger that performs heat exchange between the engine body and the cooling water and the raw material fuel. Or if it is a fuel heating apparatus which heats raw material fuel, it may not be a heat exchanger, for example, an electric heater (namely, apparatus which heats raw material fuel using the heat generated by electric power) etc. may be used. Is possible.

  The configuration of the fuel supply device 24 described above is an example. As long as a fuel separation device that requires a heat exchanger is provided, the fuel supply device 24 of any configuration may be used. Therefore, for example, a separator different from the separation unit 57 may be used to separate the raw fuel into a high octane fuel and a low octane fuel.

  Next, with reference to FIG. 3, the structure of the fuel supply apparatus 24 of 1st embodiment of this invention is demonstrated in detail. FIG. 3 is a conceptual diagram showing in detail a portion surrounded by A in FIG.

  As shown in FIG. 3, the fuel pump 60 in the raw material fuel tank 23 is connected to the heat exchanger 56 via an upstream fuel circulation pipe (upstream fuel flow passage) 61. The heat exchanger 56 is connected to a regulator 63 via a downstream fuel flow pipe (downstream fuel flow passage) 62. The regulator 63 is connected to the high pressure section 57c of the separation unit 57 as shown in FIG. When the fuel pump 60 is rotated forward, the fuel in the raw material fuel tank 23 is discharged toward the heat exchanger 56, and when rotated reversely, the fuel in the heat exchanger 56 is sucked into the raw material fuel tank 23.

  A bypass pipe (bypass passage) 64 for bypassing the heat exchanger 56 is branched from the upstream fuel circulation pipe 62, and the bypass pipe 64 is communicated with the raw fuel tank 23. The end of the bypass pipe 64 on the raw material fuel tank 23 side is disposed on the upper part of the raw material fuel tank 23. Therefore, the bypass pipe 64 is communicated with the gas phase portion of the raw material fuel tank 23.

  The downstream fuel flow pipe 62 is provided with a check valve 65 on the downstream side of the connection portion of the bypass pipe 64. The check valve 65 allows fuel to flow from the heat exchanger 56 toward the regulator 63, but prohibits fuel from flowing from the regulator 63 toward the heat exchanger 56.

  The bypass pipe 64 is also provided with a check valve 66. The check valve 66 allows fuel to flow from the raw fuel tank 23 toward the downstream fuel circulation pipe 62, but prohibits fuel from flowing from the downstream fuel circulation pipe 62 toward the raw fuel tank 23. To do.

  A branch pipe (branch passage) 67 branches off from the upstream fuel flow pipe 61, and a regulator 68 is provided in the branch pipe 67. Therefore, the pressure of the fuel flowing through the upstream side fuel flow pipe 61 is maintained at a substantially constant pressure by the regulator 68.

  Next, the flow of fuel in the fuel supply device 24 configured as described above will be described. FIG. 4 is a diagram showing the flow of fuel during normal operation. The arrows in the figure indicate the flow of fuel.

  During normal operation, the fuel pump 60 is rotated forward. Therefore, as indicated by arrows in FIG. 4, the raw fuel whose pressure has been increased by the fuel pump 60 flows into the heat exchanger 56 through the upstream fuel flow pipe 61. Thereafter, the raw material fuel flows from the heat exchanger 56 through the check valve 65 and the regulator 63 into the separation unit 57. In particular, since the check valve 65 permits fuel to flow from the heat exchanger 56 side to the regulator 63 side, the flow of fuel in the downstream side fuel circulation pipe 61 is not blocked by the check valve 65. The raw material fuel is heated to an appropriate temperature when passing through the heat exchanger 56. For this reason, the temperature of the raw material fuel flowing into the separation unit 57 is a temperature within the optimum temperature range.

  When the pressure in the downstream fuel circulation pipe 62 is increased by rotating the fuel pump 60 forward, the pressure in the downstream fuel circulation pipe 62 becomes higher than the pressure in the gas phase portion of the raw material fuel tank 23. As a result, a pressure difference is generated on both sides of the bypass pipe 64, and fuel tends to flow from the downstream fuel circulation pipe 62 toward the raw fuel tank 23. However, since the check valve 66 prohibits fuel from flowing through the bypass passage 64 from the downstream fuel flow pipe 62 toward the raw fuel tank 23, fuel does not flow through the bypass passage 64.

  By the way, when the operation of the internal combustion engine is stopped, even if the fuel in the heat exchanger 56 is not excessively heated immediately after the operation of the internal combustion engine is stopped, a certain amount of time passes after that, and then the heat exchanger 56. The fuel inside is often overheated.

  That is, when the operation of the internal combustion engine is stopped, the supply of fuel to the fuel injection valves 11a and 11b is stopped. For this reason, the flow rate of the fuel flowing through the heat exchanger 56 is also almost zero. Therefore, fuel stays in the heat exchanger 56. On the other hand, in the heat exchanger 56, even if the operation of the internal combustion engine is stopped, the supply of heat to the fuel is not stopped immediately, and the heat is continuously supplied to the fuel due to residual heat remaining in the heat exchanger 56 and the like. . For this reason, even after the operation of the internal combustion engine is stopped, heat continues to be supplied to the fuel remaining in the heat exchanger 56, and the fuel in the heat exchanger 56 is excessively heated.

  If the fuel is excessively heated in the heat exchanger 56, the fuel may be deteriorated or the circulation efficiency of the fuel may be reduced due to the generation of bubbles. When such a problem occurs, the combustion state in the internal combustion engine is deteriorated.

  Therefore, in the embodiment of the present invention, when the operation of the internal combustion engine is stopped, the fuel in the heat exchanger 56 is forcibly returned from the heat exchanger 56 into the raw material fuel tank 23 by reversely rotating the fuel pump 60. I have to.

  FIG. 5 is a diagram showing the flow of fuel when the operation of the internal combustion engine is stopped. When the operation of the internal combustion engine is stopped, the fuel pump 60 is rotated in the reverse direction. Thereby, the fuel in the downstream fuel flow pipe 62, the heat exchanger 56, and the upstream fuel flow pipe 61 on the heat exchanger 56 side (that is, the upstream side) from the check valve 65 is sucked into the raw material fuel tank 23. It is swallowed and returned to the raw material fuel tank 23. However, the presence of the check valve 65 causes the fuel in the downstream fuel flow pipe 62 on the regulator 63 side (that is, downstream) from the check valve 65 to flow to the heat exchanger 56 side through the check valve 65. Is prohibited, and therefore, it is not sucked into the raw fuel tank 23.

  On the other hand, when negative pressure is generated in the downstream fuel circulation pipe 62 by rotating the fuel pump 60 in the reverse direction, the pressure in the downstream fuel circulation pipe 62 becomes lower than the pressure in the raw material fuel tank 23, thereby bypassing A pressure difference is generated on both sides of the pipe 64, and fluid tends to flow from the raw fuel tank 23 toward the downstream fuel circulation pipe 62. The check valve 66 allows the fuel to flow through the bypass passage 64 from the raw fuel tank 23 toward the downstream fuel flow pipe 62, and thus the fluid flows through the bypass passage 64. Here, since the end of the bypass pipe 64 communicates with the gas phase portion of the raw fuel tank 23, the gas in the raw fuel tank 23 flows through the bypass passage 64.

  Thus, when the fuel pump 60 is rotated in the reverse direction, a circulation path is formed by the upstream fuel circulation pipe 61, the heat exchanger 56, the downstream fuel circulation pipe 62, and the bypass pipe 64. The fuel that has been present in the fuel is allowed to flow out into the raw material fuel tank, and gas is allowed to flow into the circulation path from the raw material fuel tank 23. Accordingly, eventually, the circulation path is filled with gas, and the fuel in the heat exchanger 56 is almost completely eliminated, so that the fuel is not further heated by the heat exchanger 56. The As described above, in the fuel supply device 24 of the present invention, when the operation of the internal combustion engine is stopped, the fuel in the heat exchanger 56 is forcibly transferred from the heat exchanger to the raw fuel tank 23 by rotating the fuel pump 60 in the reverse direction. By returning, the fuel is prevented from being excessively heated in the heat exchanger 56. The reverse rotation of the fuel pump 60 is stopped after a predetermined time has elapsed after the reverse rotation of the fuel pump 60 is started, and the fuel remaining in the heat exchanger 56 is completely or almost disappeared.

  Here, in order to suck the fuel in the heat exchanger 56 and the like, it is conceivable to provide a small pump or the like in addition to the fuel pump 60. On the other hand, according to the above embodiment, the fuel in the heat exchanger 56 and the like is sucked by rotating the fuel pump 60 in reverse, and the suction force of the fuel pump 60 is larger than that of a small pump or the like. Therefore, the fuel can be removed from the heat exchanger 56 quickly and efficiently.

  When a small pump or the like is provided in addition to the fuel pump 60, piping and valves for the small pump must be provided in addition to the small pump itself. On the other hand, according to the above-described embodiment, it is not necessary to newly provide a pump or the like other than the fuel pump 60 for pumping the fuel, and thus the number of parts can be reduced.

  Further, when the fuel in the heat exchanger 56 is sucked into the raw fuel tank 23, if the gas in the gas phase portion of the raw fuel tank 23 does not flow into the heat exchanger 56 or the like via the bypass pipe 64, heat exchange is performed. There is a possibility that the negative pressure generated in the heat exchanger 56 or the like becomes too large and the heat exchanger 56 itself or the piping is damaged. On the other hand, according to the above embodiment, when the fuel in the heat exchanger 56 is sucked into the raw fuel tank 23, the gas in the gas phase portion of the raw fuel tank 23 is converted into the heat exchanger via the bypass pipe 64. Therefore, the negative pressure generated in the heat exchanger 56 by the fuel pump 60 is prevented from becoming too large.

  Next, the configuration of the fuel supply device 24 ′ according to the second embodiment of the present invention will be described in detail with reference to FIG. 6. FIG. 6 is a conceptual diagram showing a portion surrounded by A in FIG. 2 as in FIG. In FIG. 6, the same reference numerals are assigned to the same components as those of the fuel supply device 24 of the first embodiment shown in FIG.

  As shown in FIG. 6, the configuration of the fuel supply device 24 'of the second embodiment is basically the same as the configuration of the fuel supply device 24 of the first embodiment shown in FIG. However, the check valve 66 is provided in the bypass passage 64 in the fuel supply device 24 of the first embodiment, whereas the two-way valve 70 is provided in the bypass passage 64 in the fuel supply device 24 ′ of the second embodiment. Is provided.

  Next, the fuel flow in the fuel supply device 24 ′ configured as described above will be described. FIG. 7 is a diagram showing the flow of fuel during normal operation. The arrows in the figure indicate the flow of fuel.

  During normal operation, the fuel pump 60 is rotated forward. Therefore, as indicated by arrows in FIG. 7, the raw fuel whose pressure has been increased by the fuel pump 60 flows in the order of the upstream side fuel circulation pipe 61, the heat exchanger 56, the downstream side fuel circulation pipe 62, and the regulator 63. It flows into the separation unit 57. The raw material fuel is heated to an appropriate temperature when passing through the heat exchanger 56. For this reason, the temperature of the raw material fuel flowing into the separation unit 57 is a temperature within the optimum temperature range.

  In the present embodiment, when the operation of the internal combustion engine is stopped, the fuel pump 60 is reversely rotated to force the fuel in the heat exchanger 56 in order to suppress excessive heating of the fuel in the heat exchanger 56. While returning from the heat exchanger 56 into the raw material fuel tank 23, the two-way valve 70 is opened.

  FIG. 8 is a diagram showing the flow of fuel when the operation of the internal combustion engine is stopped. When the operation of the internal combustion engine is stopped, the fuel pump 60 is reversely rotated. Therefore, the fuel in the downstream fuel flow pipe 62, the heat exchanger 56, and the upstream fuel flow pipe 61 on the heat exchanger 56 side of the check valve 65 is reduced. The fuel is sucked into the raw fuel tank 23 and returned to the raw fuel tank 23.

  Further, the two-way valve 70 is opened when the operation of the internal combustion engine is stopped. By rotating the fuel pump 60 in the reverse direction, a negative pressure is generated in the downstream fuel circulation pipe 62, so that the pressure in the downstream fuel circulation pipe 62 is lower than the pressure in the gas phase portion of the raw fuel tank 23. Therefore, the gas in the raw material fuel tank 23 flows toward the downstream fuel circulation pipe 62.

  Therefore, also in this embodiment, as in the case shown in FIG. 5, when the operation of the internal combustion engine is stopped, the upstream fuel circulation pipe 61, the heat exchanger 56, the downstream fuel circulation pipe 62, and the bypass pipe 64 provide a circulation path. Over time, the fuel in the heat exchanger 56 is almost completely eliminated. The reverse rotation of the fuel pump 60 is stopped after a predetermined time has elapsed after the reverse rotation of the fuel pump 60 is started, and the fuel remaining in the heat exchanger 56 is completely or almost disappeared. At the same time, the two-way valve 70 is also closed.

  By the way, depending on the operation state of the internal combustion engine, the amount of fuel injected from the fuel injection valves 11a and 11b is small. Therefore, in such a case, the fuel flows through the upstream fuel circulation pipe 61, the heat exchanger 56, and the downstream fuel circulation pipe 62. The flow rate of flowing fuel is small. In such a case, if the amount of heat supplied to the fuel in the heat exchanger 56 remains large, the raw material fuel in the heat exchanger 56 will be excessively heated. In particular, when the temperature of the raw material fuel is raised using the heat of the exhaust gas discharged from the internal combustion engine, the amount of heat transferred to the raw material fuel in the heat exchanger 56 is determined according to the temperature and flow rate of the exhaust gas. When the temperature of the exhaust gas discharged from the internal combustion engine is high and the flow rate is high, the amount of heat transferred to the raw material fuel is large. Conversely, when the temperature of the exhaust gas is low and the flow rate is low, the amount of heat transferred to the raw material fuel is Few. Therefore, it is difficult to optimally control the amount of heat transferred to the raw material fuel, and a situation occurs in which the raw material fuel is excessively heated.

  Therefore, in the present embodiment, when the raw material fuel is excessively heated in the heat exchanger 56 or when the raw material fuel is expected to be excessively heated in the heat exchanger 56, The raw material fuel is forcibly discharged.

  9 and 8 show that when it is determined that the raw material fuel is excessively heated in the heat exchanger 56, or when it is predicted that the raw material fuel is excessively heated in the heat exchanger 56 (hereinafter, “ It is a figure which shows the flow of the fuel in "when overheating".

  When the raw material fuel in the heat exchanger 56 is overheated, first, the operation of the fuel pump 60 is stopped and the two-way valve 70 is opened. At this time, the pressure of the fuel in the heat exchanger 56 and the downstream fuel flow pipe 62 is higher than the pressure in the raw fuel tank 23. Accordingly, the excessively heated heat exchanger 56 and the raw fuel in the downstream fuel circulation pipe 62 are returned to the raw fuel tank 23 via the two-way valve 70 as indicated by arrows in FIG. . Thereby, a part of the raw material fuel in the heat exchanger 56 and the downstream side fuel circulation pipe 62 is returned to the raw material fuel tank 23. In particular, during overheating, vaporized high-pressure fuel exists in the heat exchanger 56 and the downstream fuel flow pipe 62, but the gas portion of this fuel flows to the gas phase portion in the raw fuel tank 23. become.

  When the two-way valve 70 is thus opened, the fuel in the heat exchanger 56 is returned to the raw material fuel tank 23 to some extent, and the fuel pressure in the heat exchanger 56 is reduced to some extent. Next, the fuel pump 60 is rotated in the reverse direction. Therefore, as shown by the arrows in FIG. 8, the fuel in the downstream fuel flow pipe 62, the heat exchanger 56, and the upstream fuel flow pipe 61 on the heat exchanger 56 side of the check valve 65 is fed to the raw fuel tank 23. It is sucked in and returned to the raw material fuel tank 23. Even if the fuel pump 60 starts reverse rotation, the two-way valve 70 is kept open. Accordingly, as shown in FIG. 8, the gas in the raw material fuel tank 23 flows toward the downstream fuel flow pipe 62.

  Therefore, in the present embodiment, even when the raw material fuel is excessively heated, a circulation path is formed by the upstream fuel circulation pipe 61, the heat exchanger 56, the downstream fuel circulation pipe 62, and the bypass pipe 64, and the heat exchanger 56 is eventually added. The fuel inside is almost completely eliminated. The reverse rotation of the fuel pump 60 causes the fuel remaining in the heat exchanger 56 or the like to be completely or almost eliminated, or the amount of fuel injected from the fuel injection valves 11a and 11b increases and the fuel passing through the heat exchanger 56 passes. When the flow rate increases or the amount of heat supplied to the heat exchanger 56 decreases, the heat exchanger 56 is stopped. At the same time, the two-way valve 70 is also closed.

  In the present embodiment, whether the raw material fuel is excessively heated in the heat exchanger 56 is determined by a temperature sensor (not shown) provided in the heat exchanger 56 or on the downstream side of the heat exchanger 56. Judgment is made based on the detected fuel temperature. For example, when the fuel temperature detected by the temperature sensor is lower than a predetermined reference temperature, it is determined that the raw material fuel is not heated excessively in the heat exchanger 56. On the other hand, when the fuel temperature detected by the temperature sensor is equal to or higher than a predetermined reference temperature, it is determined that the raw material fuel is excessively heated in the heat exchanger 56, and the fuel from the heat exchanger 56 as described above. Is discharged. Here, the reference temperature is, for example, a temperature at which if the fuel temperature rises further, there is a possibility that deterioration of the fuel properties or reduction of the circulation efficiency of the raw material fuel due to the generation of bubbles, etc. may occur. It is obtained by calculation.

  Alternatively, whether the raw material fuel is excessively heated in the heat exchanger 56, or whether the raw material fuel is expected to be excessively heated in the heat exchanger 56, is the raw material flowing in the heat exchanger 56 The determination may be based on the fuel temperature calculated based on the flow rate of the fuel and the amount of heat applied to the raw fuel from the heat exchanger. In this case, when the exhaust heat recovery device 25 is used as the heat exchanger 56, the amount of heat applied from the heat exchanger 56 to the raw material fuel can be calculated based on the exhaust gas temperature and the exhaust gas flow rate.

  In the first embodiment described above, the fuel pump 60 may be rotated in the reverse direction when the raw material fuel is overheated to return the fuel in the heat exchanger 56 and the like into the raw material fuel tank 23. However, in this case, the high-temperature and high-pressure raw fuel cannot return to the raw fuel tank 23 through the bypass pipe 64, but returns to the raw fuel tank 23 through the fuel pump 60. It is necessary to make 60 highly durable.

It is a figure which shows side surface sectional drawing of a spark ignition type internal combustion engine. It is a figure which shows typically schematic structure of a fuel supply apparatus. It is a conceptual diagram which shows the part enclosed by A in FIG. 2 in detail. It is a figure which shows the flow of the raw material fuel in the normal time. It is a figure which shows the flow of the raw material fuel at the time of the operation stop of an internal combustion engine. It is a conceptual diagram similar to FIG. 3 of the fuel supply apparatus of 2nd embodiment of this invention. It is a figure which shows the flow of the raw material fuel in the normal time. It is a figure which shows the flow of the raw material fuel at the time of the operation stop of an internal combustion engine. It is a figure which shows the flow of the raw material fuel at the time of the overheating of the fuel in a heat exchanger.

DESCRIPTION OF SYMBOLS 1 Engine main body 23 Raw material fuel tank 24 Fuel supply apparatus 25 Exhaust heat recovery apparatus 60 Fuel pump 61 Upstream fuel supply pipe 62 Downstream fuel supply pipe 63 Regulator 64 Bypass pipe 65, 66 Check valve 67 Branch pipe 68 Regulator 70 Two-way valve

Claims (7)

An internal combustion engine comprising: a fuel heating device that heats fuel; a fuel pump that sends fuel in a fuel tank to the fuel heating device; and a fuel flow passage that sends fuel from the fuel heating device to a fuel injection valve. In the fuel supply device,
A fuel supply device configured to forcibly return the fuel in the fuel heating device into the fuel tank by reversely rotating the fuel pump when the operation of the internal combustion engine is stopped.   A bypass passage communicating with the fuel flow passage and the fuel tank is further provided, and fluid flow from the fuel tank to the fuel flow passage is permitted in the bypass passage, but fluid flow from the fuel flow passage to the fuel tank is The fuel supply apparatus according to claim 1, wherein a check valve for prohibiting is provided.   2. The bypass passage according to claim 1, further comprising a bypass passage communicating with the fuel flow passage and the fuel tank, wherein the bypass passage is provided with an on-off valve, and the on-off valve is opened when the operation of the internal combustion engine is stopped. Fuel supply device.   The on-off valve is also opened when the temperature of the fuel in the fuel heating device becomes equal to or higher than the reference temperature, and the fuel pump has a reference temperature of the fuel in the fuel heating device in addition to when the internal combustion engine is stopped. The fuel supply device according to claim 3, wherein the fuel supply device according to claim 3, wherein the fuel in the fuel heating device is forcibly returned to the fuel tank by being reversely rotated after the on-off valve is opened even when the temperature becomes higher than the temperature.   The fuel supply device according to any one of claims 1 to 4, wherein the fuel heating device is a heat exchanger using heat generated by combustion of an air-fuel mixture in an internal combustion engine.   The fuel supply device according to any one of claims 1 to 4, wherein the fuel heating device heats the fuel using heat generated by electric power.   The separator further includes a separator that separates the raw material fuel heated by the fuel heating device into a plurality of types of fuel, the plurality of types of fuel having a high octane number higher than that of the raw material fuel and a lower octane number than that of the raw material fuel. The fuel supply device according to any one of claims 1 to 6, comprising a low octane fuel.

Images