JP3799520B2 - Diesel engine fuel supply device and diesel engine using the fuel supply device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply device for a diesel engine using a liquefied low-boiling point fuel used for driving a vehicle, a ship, a generator, etc. as a main fuel, and a diesel engine using the fuel supply device.
[0002]
[Prior art]
Conventionally, diesel oil is generally used as fuel for diesel engines, but recently, it has been studied to use dimethyl ether (hereinafter referred to as DME) as fuel instead of diesel oil. When DME is used as a fuel in a diesel engine, it not only has the same cetane value as light oil, but also has a lower NOx concentration in the exhaust gas than light oil and has very little flue gas in the entire output range. Expected.
[0003]
However, since the DME fuel has a boiling point as low as −25 ° C., it is a gas at normal temperature. When such a low boiling point fuel is used in a diesel engine, the discharge pressure of the fuel supply pump, that is, the fuel supply pressure to the fuel injection pump. Needs to be pressurized and supplied to a pressure (e.g., about 1.5 to 2.5 MPa) or higher than the saturated vapor pressure (e.g., about 0.5 to 1.0 MPs) of the fuel in the combustion container.
[0004]
As a technique for solving such a problem, for example, there is a low-boiling point fuel supply device for a diesel engine described in Japanese Patent Application Laid-Open No. 2000-11687. This device includes a pressure vessel for storing liquefied low-boiling point fuel, a fuel feed pump connected to the pressure vessel and driven by suction and discharge of compressed gas, and a fuel engine body in conjunction with starting and stopping of a diesel engine. With a valve mechanism that opens and closes the supply line to the fuel chamber, and increases the fuel pressure on the fuel chamber side relative to the operating gas pressure by the piston area ratio of the suction and discharge chambers of the fuel feed pump. It is.
[0005]
[Problems to be solved by the invention]
The fuel supply device as described above can stably supply the liquefied low boiling point fuel to the combustion injection pump. However, in a vehicle that does not include an air compressor for driving the fuel feed pump, a nitrogen gas cylinder or the like is used. Since a compressed gas cylinder must be installed, problems such as an increase in installation space and weight arise.
[0006]
For this reason, it is driven by an electric motor such as a gear pump, a trochoid pump, or a piston pump that is commercially available as a pump for boosting liquefied low-boiling point fuel such as LPG instead of a gas-driven compression-driven fuel feed pump. It is also possible to increase the pressure of the liquefied low-boiling point fuel using a mechanical pump. However, as described above, it is necessary to pressurize the DME fuel to a pressure equal to or higher than the saturated vapor pressure and supply it to the fuel injection pump. A small-sized low-boiling point mechanical pump for obtaining such pressure is generally used. The mechanical pump that meets the specifications is very large and cannot be used for in-vehicle use.
Further, if a single mechanical pump is used to obtain the supply pressure to the fuel injection pump, very large power is required, and it is difficult to drive with a vehicle-mounted battery.
[0007]
The present invention has been made to solve the above-described problems, and is small and lightweight, and can be easily used even when an air compressor is not provided. It is an object of the present invention to provide a fuel supply device for a diesel engine that can be supplied to a pump and a diesel engine using the same.
[0008]
[Means for Solving the Problems]
A fuel supply apparatus for a diesel engine according to the present invention includes a combustion container for storing a liquefied low-boiling point fuel, and a fuel supply apparatus that is provided between the fuel container and a fuel injection pump and pressurizes the liquefied low-boiling point fuel. The fuel supply device is provided with fuel boosting means in which a plurality of booster pump units each having a booster pump immersed in the fuel are connected in series.
[0009]
In the fuel supply device for a diesel engine described above, a differential pressure adjusting valve is provided between the fuel return pipe on the engine side and the fuel return pipe on the fuel container side to adjust the differential pressure between the two to a predetermined pressure difference.
[0010]
In any of the above diesel engine fuel supply apparatuses, an accumulator is provided between the boost pump unit at the final stage of the fuel booster and the fuel injection pump.
[0011]
A diesel engine according to the present invention includes any one of the above fuel supply devices.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram of an embodiment of the present invention. In the figure, reference numeral 1 denotes a fuel container in which a liquefied low-boiling point fuel such as DME (hereinafter simply referred to as fuel) is placed. The fuel in the fuel container 1 usually has a pressure P = 0.5 to 1.0 MPa. The temperature T is maintained at about 20 to 50 ° C.
A fuel supply device 4 is provided between the fuel container 1 and a fuel injection pump 25 described later, and includes a fuel boosting means 5 that boosts the fuel in the fuel container 1. This fuel boosting means 5 is composed of a plurality of booster pump units 6a, 6b, 6c connected in series, and the lower part of the first-stage booster pump unit 6a and the bottom of the fuel container 1 are always open by the pipe line 2. It is connected via the on-off valve 3. Although the figure shows a case where the booster pump units 6 are connected in series in three stages, it may be two or more stages.
[0013]
FIG. 2 is a cross-sectional view showing an example of the booster pump unit 6 in which the booster pump 8 is built in the pressure vessel 7. As shown in FIG. 3, an example of the booster pump 8 is a drive motor 10 in a cylindrical container 9, and a mechanical pump 11 such as a trochoid type or a gear type that is rotationally driven by the drive motor 10. It is constituted by. In addition, 12 is a discharge port provided in the upper part of the container 9, and 13 is a connector to which electrical wiring for supplying power to the drive motor 10 is connected.
[0014]
In FIG. 2 again, the pressure vessel 7 has a cylindrical structure whose upper and lower sides are closed, and a low pressure chamber 15 connected to the fuel vessel 1 via the fuel inlet 14 is provided at the lower portion. Reference numeral 16 denotes a high-pressure chamber provided in the upper portion of the low-pressure chamber 15. The booster pump 8 is inserted and fixed in the high-pressure chamber 16, and the low-pressure chamber 15 and the high-pressure chamber 16 are attached to the lower portion of the booster pump 8 ( Registered trademark), and is kept secret via a packing 17 made of a material such as copper.
[0015]
Reference numeral 18 denotes a high-pressure fuel outlet provided on the upper wall of the pressure vessel 7, which is connected to the fuel inlet 14 of the next-stage booster pump units 6b and 6c. Reference numeral 19a denotes a terminal provided on the upper wall, to which the connector 13 and, for example, a vehicle-mounted battery 19 are connected.
In the booster pump unit 6 as described above, the high pressure chamber 16 is filled with fuel, and the booster pump 8 is immersed in this fuel. The drive motor 10 of the booster pump units 6a, 6b, 6c is connected to, for example, an in-vehicle battery (DC 24V or 12V) 19 in series and driven, and Δp per unit, that is, suction pressure And the discharge pressure is about 0.5 MPa.
[0016]
In the booster pump unit 6, when the booster pump 8 is driven, the fuel in the low pressure chamber 15 having the same pressure as that in the fuel container 1 is boosted by about 0.5 MPa by the booster pump 8, and is discharged from the discharge port 12 to the high pressure chamber 16. The pressure is discharged to the inside of the booster pump 8 and maintained at the same pressure as the pressure in the booster pump 8, and is sent from the high-pressure fuel outlet 18 to the next-stage booster pump units 6 b and 6 c, and similarly boosted by about 0.5 MPa.
[0017]
According to the embodiment of FIG. 1, since the three booster pump units 6a to 6c are connected in series, the pressure increase amount of the fuel is about 1.5 MPa, and the self-pressure in the fuel container 1, that is, the case of DME fuel Assuming that the saturated vapor pressure in the fuel container 1 is about 0.6 MPa, a fuel supply pressure of 2.0 MPa or more can be obtained by the fuel boosting means.
Further, since the drive motor 10 of the booster pump units 6a to 6c is connected in series to the battery 19, if the battery 19 is 24V, the load (Δp) distribution of the three booster pump units 6a to 6c is balanced, The load voltage of each booster pump unit 6a to 6c is balanced at 8V, and the total current is 24V, so that the current consumption can be reduced to about 8 to 10A.
[0018]
In FIG. 1 again, 20 is a diesel engine (hereinafter simply referred to as an engine), 21 is a cylinder, 22 is a piston, 23 is an intake port, and 24 is an exhaust port. A fuel injection pump 25 is attached to the engine 20, and an injection nozzle 26 is attached to the cylinder head of each cylinder 21 and injects fuel supplied from the fuel injection pump 25 into the cylinder 21.
[0019]
A fuel supply pipe 30 connects the high-pressure fuel outlet 18 of the booster pump unit 6c in the final stage of the fuel booster 5 and the fuel injection pump 25. An electromagnetic on-off valve 31 is provided on the outlet side of the booster pump unit 6c. An air release solenoid valve 32 for releasing the pressure in the fuel supply pipe 30 to the atmosphere when the engine is stopped is provided on the downstream side. Reference numeral 33 denotes an accumulator provided on a branch pipe 34 branched from the fuel supply pipe 30 on the upstream side (the boost pump unit 6 c side) of the electromagnetic on-off valve 31. Reference numeral 35 denotes a relief valve that relieves the pressure in the fuel container 1 when the pressure in the boost pump unit 6c, the electromagnetic on-off valve 31, the accumulator 33, and the branch pipe 34 becomes abnormally high.
A fuel return pipe 36 is provided between the fuel injection pump 25 and the injection nozzle 26 and the fuel container 1, and returns a fuel surplus from the fuel injection pump 25 and a leak from the injection nozzle 26 to the fuel container 1. A differential pressure regulating valve 38 is provided between the fuel return pipe 35 on the 20 side and the fuel return pipe 37 on the fuel container 1 side.
[0020]
Next, the operation of the present invention configured as described above will be described. Among the components constituting the fuel boosting means 5, the low pressure chamber 15 and the high pressure chamber 16 of the boost pump units 6a, 6b, 6c, the upstream side of the closed electromagnetic switching valve 31, the branch pipe 34, the accumulator 33, the differential pressure It is assumed that the system formed by the fuel return pipe 37 between the regulating valve 38 and the fuel container 1 is filled with fuel having substantially the same pressure as the saturated vapor pressure in the fuel container 1, for example.
[0021]
The differential pressure regulating valve 38 has a predetermined pressure difference between the upstream side, that is, in FIG. 1, the fuel return pipe 36 on the engine side and the downstream side, that is, the fuel return pipe 37 on the fuel container 1 side. The pressure is always adjusted mechanically, and the pressure is adjusted so that the pressure on the upstream side is adjusted based on the pressure on the downstream side, and the pressure on the upstream side becomes higher.
The differential pressure adjusting valve 38 is closed until a predetermined differential pressure is reached. When the engine 20 is stopped, that is, when the booster pump units 6a to 6c are stopped, the differential pressure adjusting valve 38 is closed. ing.
[0022]
The switch 19b of the battery 19 is interlocked with the engine key. When the engine key is turned and the switch 19b is first turned on to drive the drive motor 10 of each booster pump unit 6a-6c, the electromagnetic on-off valve 31 is interlocked with this. Is opened, and the open air solenoid valve 32 is closed.
As described above, the fuel in the fuel container 1 having a saturated vapor pressure of, for example, about 0.6 MPa is boosted by 0.5 MPa in each of the booster pump units 6a to 6c as described above. Therefore, in the first-stage booster pump unit 6a, about 1.1 MPa The pressure is about 1.6 MPa at the middle boost pump unit 6 b and about 2.1 MPa at the high pressure fuel outlet 18 of the final boost pump unit 6 c, and is sent from the fuel supply pipe 30 to the fuel injection pump 25. Note that low boiling point and low viscosity fuel, such as DME fuel, often leaks from the booster pump seal mechanism, but according to the booster pump unit 6 of the present invention, the booster pump 8 is immersed in the fuel. Therefore, it is not necessary to consider the processing of leaks.
[0023]
Then, fuel is sent from the fuel injection pump 25 to the injection nozzles 26 provided in the respective cylinders 21 and sequentially injected into the cylinders 21 to drive the engine 20. The fuel leaking from the injection nozzle 26 is returned to the fuel container 1 from the return pipes 36 and 37.
[0024]
As described above, the fuel supply pipe 30, the fuel injection pump 25 and the injection nozzle 26, and the fuel return pipe 35 on the engine 20 side from the high-pressure fuel outlet 18 to the fuel injection pump 25 of the booster pump unit 6c in the final stage of the fuel booster 5 are provided. By forming a fuel pipe path including the differential pressure adjusting valve 38 and the fuel return pipe 37 on the fuel container 1 side, the load of the final boost pump unit 6c is adjusted by adjusting the opening of the differential pressure adjusting valve 38. That is, the outlet pressure, that is, the fuel supply pressure to the injection pump 26 can be adjusted.
[0025]
For example, when the engine 20 is used in a situation immediately after starting or in a cold region, when the temperature of the fuel in the fuel container 1 is low and the saturated vapor pressure in the fuel container 1 is low, the fuel supply pressure is adjusted. If a constant pressure control is performed using a pressure regulating valve whose absolute pressure value is always constant and the discharge pressure of the booster pump unit 6 is an absolute value, the boosted pressure per stage of the booster pump unit 6 increases. Although an excessive load is applied to the booster pump unit 6, the discharge pressure is relatively determined by using the differential pressure adjustment valve 38 that adjusts the pressure as a relative value to the pressure in the fuel container 1. The load on the booster pump unit 6 can be made constant without being affected by the saturated vapor pressure in the fuel container 1.
[0026]
In addition, when the engine 20 is operated for a long time or when the engine 20 operates under a high air temperature, the fuel returning from the fuel injection pump 25 to the fuel container 1 passes through the fuel injection pump 25. Since the temperature is high and the temperature of the fuel leaking from the injection nozzle 26 and returning to the fuel container 1 is also high, the temperature of the fuel returning from the fuel injection pump 25 and the injection nozzle 26 is about 60 ° C., for example. For this reason, the fuel temperature in the fuel container 1 is increased by the returned fuel, and as a result, the saturated vapor pressure in the fuel container 1 is increased.
[0027]
Even in such a case, since the pressure adjustment valve 38 adjusts so that the difference between the saturated vapor pressure in the fuel container 1 and the pressure of the fuel delivered from the booster pump unit 6 is substantially constant, the booster pump unit The load of 6 becomes almost constant.
As described above, by providing the differential pressure adjusting valve 38, the load of the booster pump unit 6, that is, the work amount becomes substantially constant even when the usage state changes, so that a stable operation can be obtained.
[0028]
The fuel injection pump 25 is usually a multi-cylinder jerk-type pump. In this case, however, the fuel supply pipe 30 is pulsated violently, and the final booster pump unit 6c has an excessive load ( Torque) fluctuations are generated. By absorbing such pulsation by the accumulator 33 provided on the outlet side of the booster pump unit 6c in the final stage, the pulsation on the outlet side of the booster pump unit 6c is eliminated, and the load fluctuation of the booster pump unit 6c can be reduced. it can.
[0029]
The operation when the engine 20 is stopped is as follows. While the engine 20 is stopped, the electromagnetic on-off valve 31 is closed, and the booster pump units 6a to 6c are stopped. At this time, since there is no pressure difference between the inlet and the outlet of the differential pressure regulating valve 38, the differential pressure regulating valve 38 is closed. Thereafter, the atmospheric release solenoid valve 32 is opened, and the pressure in the fuel supply pipe 30, the fuel injection pump 25, the injection nozzle 26, and the fuel return pipe 36 is released to the atmosphere.
[0030]
In the above description, the fuel supply device according to the present invention is mainly applied to a diesel engine for a vehicle. However, the present invention is not limited to this, and the operation is applied to a diesel engine for operation such as a ship or a generator. Can also be implemented.
Moreover, although the case where this invention was implemented to the diesel engine which uses DME fuel was shown, this invention can be implemented also to the diesel engine which uses liquefied low boiling point fuel like LPG, for example.
[0031]
As is apparent from the above description, the present invention comprises a plurality of booster pump units 6 connected in series as the booster 5 for liquefied low-boiling point fuel used to drive the engine 20, and with a small amount of power from the battery 19. Since the fuel supply device 4 that can be operated is provided, the fuel pressure-increasing means can be greatly reduced in size and weight, so that it can be easily mounted on a vehicle without an air compressor. .
Further, in the present invention, since the fuel boosting means 5 including the boosting pump unit 6 is provided separately from the fuel container 1 in which the liquefied low boiling point fuel is placed, an in-vehicle liquefied low boiling point fuel tank for LPG vehicles is provided in the fuel container 1. Since it can be used, cost can be reduced.
[0032]
【The invention's effect】
A fuel supply apparatus for a diesel engine according to the present invention includes a combustion container for storing a liquefied low boiling point fuel, and a fuel supply apparatus provided between the fuel container and a fuel injection pump for boosting the liquefied low boiling point fuel. Since this fuel supply device is provided with fuel boosting means in which a plurality of booster pump units in which a booster pump is immersed in the fuel is connected in series and is driven by a battery, the fuel boosting means is greatly reduced in size. And it can be reduced in weight, can be used easily even if it does not have an air compressor, and can supply fuel to a fuel injection pump stably.
[0033]
In addition, a differential pressure adjustment valve is provided between the fuel return pipe on the engine side and the fuel return pipe on the fuel container side to adjust the differential pressure between the two to a predetermined pressure difference. The load of the booster pump unit is kept almost constant.
[0034]
Further, since the accumulator is provided between the boost pump unit at the final stage of the fuel booster and the fuel injection pump, the pulsation generated from the fuel injection pump is absorbed by the accumulator, so that the discharge side of the boost pump unit is The pulsation is eliminated, and the load fluctuation of the booster pump unit can be reduced.
[0035]
In addition, since the diesel engine according to the present invention includes any one of the fuel supply devices described above, the fuel at a pressure necessary to send the liquefied low-boiling point fuel to the fuel injection pump is supplied, and stable operation can be performed. it can.
[Brief description of the drawings]
FIG. 1 is a system diagram of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of the booster pump unit of FIG.
FIG. 3 is an explanatory diagram of a booster pump built in the booster pump unit of FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel container 4 Fuel supply apparatus 5 Fuel pressure | voltage rise means 6 Pressure | voltage rise pump unit 7 Pressure vessel 8 Boost pressure pump 12 Fuel discharge port 15 Low pressure chamber 16 High pressure chamber 18 High pressure fuel outlet 19 Battery 20 Diesel engine (engine)
25 Fuel injection pump 26 Injection nozzle 30 Fuel supply piping 31 Electromagnetic on-off valve 32 Atmospheric release electromagnetic valve 33 Accumulator 35 Relief valves 36, 37 Fuel return piping 38 Differential pressure adjustment valve

Claims (4)

A fuel container for containing liquefied low-boiling point fuel, and a fuel supply device that is provided between the fuel container and a fuel injection pump and pressurizes the liquefied low-boiling point fuel,
A fuel supply device for a diesel engine, characterized in that fuel boosting means comprising a plurality of booster pump units in which a booster pump is immersed in fuel is connected in series to the fuel supply device. 2. The diesel engine according to claim 1, wherein a differential pressure adjusting valve is provided between the fuel return pipe on the engine side and the fuel return pipe on the fuel container side to adjust the differential pressure between the two to a predetermined pressure difference. Engine fuel supply device. 3. The fuel supply apparatus for a diesel engine according to claim 1, wherein an accumulator is provided between the boost pump unit at the final stage of the fuel booster and the fuel injection pump. A diesel engine comprising the fuel supply device according to claim 1.

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