JP5945824B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine for vaporizing liquefied fuel and supplying it to an internal combustion engine.

  As a fuel for an internal combustion engine, it is known to use a gaseous fuel at room temperature and normal pressure such as LPG. Such gaseous fuel is liquefied by cooling and stored in the fuel tank. The liquefied fuel in the fuel tank is generally vaporized and supplied into the cylinder of the internal combustion engine.

  A fuel supply device for an internal combustion engine that injects liquefied fuel from a fuel injection valve in a liquid state has been proposed (see Patent Document 1). In this fuel supply apparatus, when the engine is stopped, the liquid fuel in the fuel pipe communicating with the fuel injection valve and the fuel tank is vaporized when the engine is stopped in order to prevent the liquid fuel in the fuel pipe from being vaporized and the pressure inside the fuel pipe from becoming high. A vaporized fuel storage tank for storing fuel at a low pressure is communicated with the fuel pipe.

JP 2010-163908 A JP 2010-203712 A JP 2012-007767 A

  However, it is described that the volume of the vaporized fuel storage tank needs to be approximately 1000 times the volume of the fuel pipe in order to sufficiently suppress the high pressure in the fuel pipe by such a vaporized fuel storage tank. It is not easy to mount on the vehicle.

  Accordingly, an object of the present invention is to provide a vaporizer that vaporizes liquefied fuel to vaporize the liquefied fuel and supply it to the cylinder, a vaporized fuel injection valve for injecting the vaporized fuel, a vaporizer, and a vaporized fuel. In a fuel supply device for an internal combustion engine having a vaporized fuel supply system having a vaporized fuel pipe between an injection valve and a vaporized fuel supply system, the liquid fuel in the vaporized fuel supply system is vaporized while the engine is stopped without providing a vaporized fuel storage tank. In order to prevent the inside of the vaporized fuel supply system from exceeding the set pressure, the amount of liquid fuel in the vaporized fuel supply system is estimated.

  According to a first aspect of the present invention, there is provided a fuel supply device for an internal combustion engine, comprising: a vaporizer for vaporizing the liquefied fuel to vaporize the liquefied fuel and supplying the vaporized fuel; and a vaporized fuel for injecting the vaporized fuel In a fuel supply device for an internal combustion engine comprising an injection valve and a vaporized fuel supply system having a vaporized fuel pipe between the vaporizer and the vaporized fuel injection valve, the vaporization from the current engine start to the current engine stop From the liquefied fuel weight supplied to the fuel supply system, the vaporized fuel weight injected from the vaporized fuel injection valve from the current engine start to the current engine stop, and the vaporized fuel supply system at the time of the current engine stop. The weight of the liquid fuel in the vaporized fuel supply system when the engine is stopped this time is estimated by subtracting the vaporized fuel weight remaining in the engine.

  According to a second aspect of the present invention, there is provided the fuel supply apparatus for an internal combustion engine according to the first aspect, wherein the carburetor has a double pipe structure having an inner pipe and an outer pipe. The liquefied fuel passing through the inner pipe is vaporized by receiving heat from a heat medium passing between the inner pipe and the outer pipe, and the heat medium between the inner pipe and the outer pipe. The passage is such that the heat medium that has passed through the lower side of the inner pipe passes through the upper side of the inner pipe, and the heat medium that has passed through the upper side of the inner pipe then passes through the lower side of the inner pipe. It has the spiral channel | path part which passes through, It is characterized by the above-mentioned.

  According to the fuel supply device for an internal combustion engine according to claim 1 of the present invention, a vaporizer for vaporizing the liquefied fuel to vaporize the liquefied fuel and supplying it to the cylinder, and for injecting the vaporized fuel In a fuel supply device for an internal combustion engine comprising a vaporized fuel injection valve and a vaporized fuel supply system having a vaporized fuel pipe between the vaporizer and the vaporized fuel injection valve, the vaporized fuel from the current engine start to the current engine stop From the known liquefied fuel weight supplied to the supply system, from the known current engine start to the current engine stop based on the valve opening time of the vaporized fuel injection valve and the vaporized fuel pressure and temperature in the vaporized fuel supply system Based on the weight of the vaporized fuel injected from the vaporized fuel injection valve, the volume of the vaporized fuel supply system, and the pressure and temperature of the vaporized fuel in the vaporized fuel supply system, the vaporized fuel supply system is Remaining mind By subtracting the fuel weight, the liquid fuel weight in the vaporized fuel supply system at the time of the engine stop this time is estimated. Depending on the liquid fuel weight thus estimated, it was vaporized while the engine was stopped. In some cases, the inside of the vaporized fuel supply system may exceed the set pressure, and therefore measures can be taken to prevent this.

  According to the fuel supply device for an internal combustion engine according to claim 2 of the present invention, in the fuel supply device for an internal combustion engine according to claim 1, the carburetor has a double-tube structure having an inner tube and an outer tube. The liquefied fuel passing through the inner pipe is vaporized by receiving heat from the heat medium passing between the inner pipe and the outer pipe, and the heat medium passage between the inner pipe and the outer pipe A spiral passage portion in which the heat medium that has passed through the lower side of the pipe passes through the upper side of the inner pipe, and the heat medium that has passed through the upper side of the inner pipe passes through the lower side of the inner pipe. Therefore, the heat medium can efficiently vaporize the liquefied fuel that passes mainly along the lower side of the inner tube.

1 is a schematic view showing an internal combustion engine equipped with a fuel supply device according to the present invention. It is a longitudinal cross-sectional view perpendicular | vertical to the axis line which shows the double tube | pipe type vaporizer as another Example of a vaporizer. It is XX sectional drawing of FIG. It is BB and FF sectional drawing of FIG. It is CC sectional drawing of FIG. It is DD sectional drawing of FIG. It is EE sectional drawing of FIG.

  FIG. 1 is a schematic view showing an internal combustion engine equipped with a fuel supply apparatus according to the present invention. Control of each member of the internal combustion engine described below is performed by an electronic control device (not shown). In the figure, 10 is an engine body, 20 is an engine intake system, and 30 is an engine exhaust system. In the engine intake system 20, reference numeral 21 is a surge tank common to each cylinder, and 22 is an intake branch pipe that is located downstream of the surge tank 21 and connected to the intake port 11 of each cylinder. Each intake branch pipe 22 is provided with a vaporized fuel injection valve 26 for metering and supplying vaporized fuel obtained by vaporizing liquefied fuel into the cylinder. Reference numeral 23 denotes an intake passage located on the upstream side of the surge tank 21, and an air cleaner 24 is disposed at the upstream end. A throttle valve 25 is disposed immediately upstream of the surge tank 21 in the intake passage 23.

  The engine exhaust system 30 is connected to the exhaust port 12 of each cylinder. Reference numeral 31 denotes a catalyst device (for example, a three-way catalyst device) located downstream of the exhaust merging portion of each cylinder of the engine exhaust system 30. In the engine body 10, 13 is an intake valve, 14 is an exhaust valve, 15 is an ignition plug, preferably a plasma jet type ignition plug, and a cylinder is formed by injecting a plasma jet at an ignition timing at the end of the compression stroke. The mixture is ignited and burned. 16 is a piston.

  Reference numeral 40 denotes a liquefied fuel tank, which stores LPG having a predetermined pressure and a predetermined temperature mainly composed of propane (boiling point −42.09 ° C.) and butane (boiling point −0.5 ° C.). Of course, the liquefied fuel targeted by the fuel supply apparatus according to the present invention is not limited to LPG, and can be any combustible substance that is gaseous at normal temperature and pressure. For example, a flammable substance having a boiling point similar to that of propane, a flammable substance having a boiling point comparable to that of butane, and a flammable substance having a boiling point between that of propane and that of butane can be used.

  A vaporizer 60 includes a heating device 61 for vaporizing the liquefied fuel, and 62 is a liquefied fuel injection valve for metering and injecting the liquefied fuel into the vaporizer 60. The heating device 61 may be an electric heater or may utilize exhaust gas heat or cooling water heat before being cooled by a radiator.

  A fuel pump 41 is disposed in the liquefied fuel tank 40 and pumps the liquefied fuel to the liquefied fuel injection valve 62 through the liquefied fuel pipe 42. A normally open closing valve 43 is arranged in the liquefied fuel pipe 42. The vaporized fuel vaporized from the liquefied fuel in the vaporizer 60 passes through the vaporized fuel pipe 63 and is supplied to the vaporized fuel injection valve 26.

  The vaporizer 60 is provided with a pressure sensor 64 for detecting the pressure of the vaporized fuel vaporized in the vaporizer 60 and a temperature sensor 65 for detecting the temperature of the vaporized fuel, and the vaporized fuel in the vaporizer 60 is set. The liquefied fuel pumped by the fuel pump 41 is metered from the liquefied fuel injection valve 62 and supplied into the carburetor 60 so that the pressure and the set temperature are maintained. The required amount (weight) of vaporized fuel in the carburetor 60 supplied into the cylinder is determined for each engine operating state (engine load and engine speed), and the current pressure of vaporized fuel in the carburetor 60 is determined. In addition, the vaporized fuel injection valve 26 is supplied by controlling the valve opening time in consideration of the temperature.

  Thus, in the fuel supply device including the vaporized fuel supply system having the vaporizer 60, the vaporized fuel injection valve 26, and the vaporized fuel pipe 63 between the vaporizer 60 and the vaporized fuel injection valve 26, the engine is stopped. In addition, if the liquid fuel in the vaporized fuel supply system is vaporized and the vaporized fuel supply system exceeds a set pressure (for example, 0.5 MPa), the vaporized fuel supply system may be damaged. (For example, the vaporizer 60) is provided with a safety valve (not shown) that opens at a set pressure. When the vaporized fuel supply system exceeds the set pressure, the vaporized fuel of the vaporized fuel supply system is passed through the safety valve. Is released into the atmosphere to prevent damage to the vaporized fuel supply system.

  However, since it is not preferable to release the vaporized fuel to the atmosphere in this way, even if the liquid fuel in the vaporized fuel supply system vaporizes while the engine is stopped, the vaporized fuel supply system does not exceed the set pressure. It is preferable to make it.

  Reference numeral 66 denotes a return pipe that communicates the bottom surface of the vaporizer 60 and the liquefied fuel tank 40, for returning only the liquid fuel separated by the gas-liquid separator 67 and the gas-liquid separator 67 to the liquefied fuel tank 40. A liquid fuel pump 68 is arranged.

  When the engine is stopped, the liquid fuel pump 68 may be always operated to return the liquid fuel in the vaporizer 60 to the liquefied fuel tank 40. However, in this case, the liquid fuel pump 68 is operated unnecessarily. There are things to do.

  In the fuel supply apparatus of this embodiment, in the electronic control unit, first, the liquefied fuel weight M1 supplied to the vaporized fuel supply system from the current engine start to the current engine stop, specifically, the current engine start. The weight M1 of the liquefied fuel supplied from the liquefied fuel injection valve 62 to the carburetor 60 from the time when the engine is stopped to the pressure and temperature of the liquefied fuel injected from the liquefied fuel injection valve 62 (if it fluctuates), Calculation is based on the valve opening time (injection liquid volume) of the liquefied fuel injection valve 62.

  Next, the vaporized fuel weight M2 injected from the vaporized fuel injection valves 26 of all cylinders from the current engine start to the current engine stop, the valve opening time (injection gas volume) of each vaporized fuel injection valve 26, and each vaporization. Calculation is performed based on the pressure and temperature of the vaporized fuel in the carburetor 60 during the opening of the fuel injection valve 26 (Boil Charles' law). The pressure and temperature of the vaporized fuel can be detected by the pressure sensor 64 and the temperature sensor 65.

  Next, when the engine is stopped this time, the vaporized fuel weight M3 remaining in the vaporized fuel supply system is changed to the total volume of the vaporizer 60 and the vaporized fuel pipe 63, and the pressure and temperature of the vaporized fuel in the vaporizer 60. Calculate based on (Boyle Charles' law). The pressure and temperature of the vaporized fuel can be detected by the pressure sensor 64 and the temperature sensor 65.

  Thus, the liquefied fuel weight M1 supplied to the vaporized fuel supply system from the current engine start to the current engine stop, and the vaporized fuel weight M2 consumed from the vaporized fuel supply system from the current engine start to the current engine stop. And the vaporized fuel weight M3 remaining in the vaporized fuel supply system at the time of the current engine stop, respectively, the vaporized fuel weights M2 and M3 are subtracted from the liquefied fuel weight M1, thereby Sometimes the liquid fuel weight M (= M1-M2-M3) remaining in the vaporized fuel supply system can be estimated.

  Thus, if the liquid fuel weight M remaining in the vaporized fuel supply system at the time of the current engine stop is estimated, the engine stop is performed based on the pressure and temperature of the vaporized fuel in the vaporized fuel supply system at the time of the current engine stop. It can be easily determined whether or not the inside of the vaporized fuel supply system exceeds the set pressure when the liquid fuel weight M is completely vaporized due to the outside air temperature, and the inside of the vaporized fuel supply system is judged to exceed the set pressure. In this case, the liquid fuel pump 68 may be operated to return the liquid fuel in the vaporizer 60 to the liquefied fuel tank 40. Thus, all of the liquid fuel in the vaporized fuel supply system is vaporized while the engine is stopped, but the vaporized fuel supply system is kept from exceeding the set pressure.

  In order to make it difficult for the inside of the vaporized fuel supply system to exceed the set pressure when the liquid fuel weight M is completely vaporized, a volume portion is provided in the middle of the vaporized fuel pipe 63 to increase the volume of the vaporized fuel pipe 63. Also good.

  If the return pipe 66 is not provided, the liquid fuel weight M remaining in the vaporized fuel supply system is estimated when the driver's ignition-off signal is issued, and the outside air temperature is determined while the engine is stopped. When it is determined that the inside of the vaporized fuel supply system when the liquid fuel weight M is completely vaporized exceeds the set pressure, the idle operation is continued without stopping the engine, and the vaporized fuel is consumed from the vaporized fuel supply system. Lowering the pressure of the vaporized fuel in the vaporized fuel supply system until it is determined that the inside of the vaporized fuel supply system does not exceed the set pressure when the liquid fuel weight M is completely vaporized by the outside air temperature while the engine is stopped, A part (or all) of the liquid fuel may be vaporized so as to reduce the liquid fuel weight M. Thus, all of the liquid fuel in the vaporized fuel supply system is vaporized while the engine is stopped, but the vaporized fuel supply system is kept from exceeding the set pressure.

  In such idle operation, it is preferable to increase fuel consumption by increasing the idle speed or retarding the ignition timing.

  FIG. 2 is a longitudinal sectional view perpendicular to an axis showing a double tube type vaporizer as another embodiment of the vaporizer. The double-tube carburetor 70 has an inner pipe 71 and an outer pipe 72 to which liquefied fuel is supplied, and for example, engine cooling water before being cooled by a radiator is used as a heat medium. 71 to pass through.

  As shown in FIG. 2, in the inner pipe 71, the liquefied fuel has the liquid fuel LI before vaporization positioned on the lower side and the vaporized fuel GA positioned on the upper side. On the other hand, the heat medium TM fills and passes between the inner pipe 71 and the outer pipe 72.

  As a result, the heat medium passing through the lower side of the inner pipe 71 in the outer pipe 72 is greatly deprived of heat by the liquid fuel LI, while passing through the upper side of the inner pipe 71 in the outer pipe 72. Since the heat medium does not take much heat to the vaporized fuel GA, the temperature does not decrease so much. Thus, in a common double tube type vaporizer, the liquefied fuel cannot be efficiently vaporized by the entire heat medium.

  The double tube type vaporizer 70 of the present embodiment is a cross section taken along line XX in FIG. 2, FIG. 4 is a cross section taken along lines BB and FF in FIG. 3, and is a cross section taken along line CC in FIG. 5 and FIG. 6 which is a DD cross section of FIG. 3 and FIG. 7 which is an EE cross section of FIG. 3, the outer tube 72 is partially elliptical or oval in contact with the inner tube 71. Has a cross section. FIG. 2 corresponds to the AA and GG cross sections of FIG.

  Thus, the heat medium that has passed through the lower side of the inner pipe 71 in the outer pipe 72 in the AA cross section and the BB cross section in FIG. 3 is obliquely below the inner pipe 71 in the outer pipe 72 in the CC cross section. Passes through the lateral side of the inner tube 71 in the outer tube 72 in the DD cross section, passes obliquely above the inner tube 71 in the outer tube 72 in the EE cross section, and passes through the FF cross section and G It passes above the inner tube 71 in the outer tube 72 in the -G cross section.

  On the other hand, the heat medium that has passed through the upper side of the inner pipe 71 in the outer pipe 72 in the AA cross section and the BB cross section in FIG. 3 passes through the oblique upper side of the inner pipe 71 in the outer pipe 72 in the CC cross section. In the DD section, it passes through the lateral side of the inner pipe 71 in the outer pipe 72, and in the EE section, it passes through the diagonally lower side of the inner pipe 71 in the outer pipe 72, and the FF section and G- It passes below the inner tube 71 in the outer tube 72 in the G cross section.

  In this way, the heat medium passage between the inner pipe 71 and the outer pipe 72 passes through the lower side of the inner pipe 71, and then the heat medium whose temperature has decreased passes through the upper side of the inner pipe 71 and the inner pipe. Since the heat medium that has passed the upper side of 71 and has not decreased in temperature so much has a spiral passage portion that subsequently passes the lower side of the inner pipe 71, the heat medium is The liquefied fuel LI that mainly passes along the lower side can be efficiently vaporized.

DESCRIPTION OF SYMBOLS 10 Engine main body 20 Engine intake system 26 Vaporized fuel injection valve 40 Liquefied fuel tank 60 Vaporizer 63 Liquefied fuel piping 66 Return path 70 Vaporizer 71 Inner pipe 72 Outer pipe

Claims (2)

  A vaporizer for vaporizing the liquefied fuel to vaporize the liquefied fuel and supplying it to the cylinder, a vaporized fuel injection valve for injecting the vaporized fuel, and between the vaporizer and the vaporized fuel injection valve In a fuel supply device for an internal combustion engine having a vaporized fuel supply system having a vaporized fuel pipe, from the weight of the liquefied fuel supplied to the vaporized fuel supply system from the current engine start to the current engine stop, from the current engine start By subtracting the vaporized fuel weight injected from the vaporized fuel injection valve until the current engine stop and the vaporized fuel weight remaining in the vaporized fuel supply system at the time of the current engine stop, the current engine stop A fuel supply device for an internal combustion engine, wherein the weight of liquid fuel in the vaporized fuel supply system at the time is estimated.   The vaporizer has a double tube structure having an inner tube and an outer tube, and the liquefied fuel passing through the inner tube receives heat from a heat medium passing between the inner tube and the outer tube. The heat medium passage between the inner tube and the outer tube has a heat medium passage that passes through the lower side of the inner tube and then passes through the upper side of the inner tube. 2. The fuel supply apparatus for an internal combustion engine according to claim 1, wherein the heat medium that has passed through the upper side of the pipe has a spiral passage portion that subsequently passes through the lower side of the inner pipe.

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