Compressed natural gas (CNG) fueling system for CNG vehicles

A CNG fueling system includes a plurality of CNG tanks for storing compressed natural gas, a supply pipe for connecting the tanks to a combustion chamber of a internal combustion engine, valves provided in the supply pipe, a low pressure regulator for regulating low pressure, and a gas mass sensor for sensing the mass of the gas. The CNG fueling system further includes a lubricant drainage device connected with the low pressure regulator for draining lubricant that has infiltrated into the system.

BACKGROUND OF THE INVENTION
 (a) Field of the Invention
 The present invention relates to fueling systems for vehicles, and, more
 particularly, to a CNG-vehicle fueling system having a lubricant drainage
 device for preventing infiltrated lubricant from causing system elements
 not to function properly.
 (b) Description of the Related Art
 The use of natural gas as an alternative fuel for motor vehicles has
 economical and ecological advantages because natural gas is less costly
 and cleaner burning than gasoline or diesel. However, use natural gas as a
 fuel for a motor vehicle, a CNG fueling system must be provided for the
 vehicle.
 FIG. 5, shows a conventional CNG fueling system. As shown in FIG. 5, the
 conventional CNG fueling system including a CNG tank 102 and a flow line
 104 which connects the CNG tank 102 and an internal combustion engine (not
 shown in the drawing), along which a high-pressure regulator 106 for
 regulating high-pressure gas from CNG tank 102, a solenoid valve 108 which
 is opened or closed according to signals from a electronic control unit
 (ECU), a low-pressure regulator 110 for regulating low-pressure gas, a gas
 mass sensor 112 for detecting the amount of the gas flow, and a flow
 controller 114 for adjusting the gas introducing into the engine. The CNG
 tank 102 is also provided with a connector 116 to be connected with a gas
 charger.
 However, the CNG fueling system has drawbacks in that when charging the
 CNG, lubricant infiltrates into system elements such as the low-pressure
 regulator 110, the gas mass sensor 112, the flow controller 114, and even
 into a combustion chamber of a vehicle engine due to the high charging
 pressure. This lubricant infiltration can cause system elements not to
 function properly. Accordingly, engine performance deteriorates,
 especially related to the generation of toxic has due to the combustion of
 these infiltrated lubricants in the engine.
 SUMMARY OF THE INVENTION
 The present invention has been made in an effort to solve the above
 problems of the prior art.
 It is an object of the present invention to provide a CNG fueling system
 for preventing lubricant from infiltrating into system elements and
 combustion chamber so as to avoid the malfunction of other devices which
 deteriorate engine performance and in order to reduce toxic gases causing
 by burning lubricant.
 To achieve the above object, the CNG fueling system of the present
 invention comprising a plurality of CNG tanks for storing compressed
 natural gas, a supply pipe for connecting the tanks to a combustion
 chamber of a internal combustion engine, valves provided with the supply
 pipe, a low pressure regulator for regulating low pressure, and a gas mass
 sensor for sensing the mass of the gas. The CNG fueling system further
 comprises a lubricant drainage device connected with the low pressure
 regulator for draining lubricant that has infiltrated into the system, the
 lubricant drainage device comprising a lubricant separator provided in the
 low pressure regulator for separating the lubricant from the gas by
 generating a vortex, a drainage tank for storing the lubricant from the
 low pressure regulator, a drainage pipe connecting the low pressure
 regulator at its bottom surface with the drainage tank so as the lubricant
 drain to the drainage tank, and a lubricant discharge means for
 discharging the lubricant in the drainage tank, if the lubricant reaches a
 predetermined level.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A preferred embodiment of the present invention will be described
 hereinafter with reference to the accompanying drawings.
 FIG. 1 shows the CNG fueling system according to the preferred embodiment
 of the present invention.
 As shown in FIG. 1, the CNG fueling system comprises a plurality of CNG
 tanks, a supply pipe 4, a manual valve 6, a high pressure regulator 8, a
 solenoid valve 10, a low pressure regulator 12, a gas mass sensor 14, and
 a flow controller 16. The CNG tanks are connected with a combustion
 chamber of internal combustion engine 1 via supply pipe 4. The manual
 valve 6, the high-pressure regulator 8, the solenoid valve 10, the low
 pressure regulator 12, the gas mass sensor 14, and the flow controller 16
 are provided in the supply pipe 4. The CNG tanks 2 have a connector 18 in
 common which is used to connect with a gas charger.
 The high-pressure regulator 8 is positioned downstream of the manual valve
 6 for adjusting the high pressure of the gas from the CNG tanks 2. The
 low-pressure regulator 12 for adjusting the low pressure of the gas is
 positioned downstream of the high-pressure regulator 8, and the solenoid
 valve 10 which is opened or closed according to signals from an ECU (not
 shown) is positioned between the high and low pressure regulators 8 and
 12. Downstream of the low-pressure regulator 12, the gas mass sensor 14
 for detecting a flow amount and sending signals to the ECU and the flow
 amount controller 16 for adjusting the flow amount are positioned one
 after the other. The low pressure regulator 12 is provided with lubricant
 drainage device 20 for draining lubricant infiltrating from a gas charger
 through the supply pipe 4. The lubricant infiltration is caused by high
 charging pressure.
 As shown in FIG. 2, the lubricant drainage device 20 comprises a lubricant
 separator 24 for separating lubricant from the gas, a drainage pipe 22
 connected to the low pressure regulator 12, and a drainage tank 34 for
 storing the lubricant coming from the low pressure regulator 12 through
 drainage pipe 22.
 The lubricant separator 24 is a rotary fan having a plurality of blades and
 rotatably mounted on its axle 26, one end of which is fixed on an inner
 wall of the low-pressure regulator 12 such that when a mixture of the gas
 and the lubricant is introduced into the low-pressure regulator 12 through
 the opening 30, the fan 24 generates a vortex by rotating under the
 pressure of the gas, resulting in that the lubricant goes to the bottom of
 the low pressure regulator 12 due to gravity and the gas is sent out
 through a pressure control valve 32.
 The drainage pipe 22 is connected at one end to the bottom of the low
 pressure regulator 12 and its other end is deeply inserted near to the
 bottom of the drainage tank 34 for guiding the lubricant to the drainage
 tank 34. In the drainage tank, a buoy 36 is provided circumferencially
 around the part of the drainage pipe 22 that is inserted into the drainage
 tank 34. On the upper surface of the buoy 36, a lubricant level sensor 38
 is mounted for detecting the lubricant level, and a stopper 40 is formed
 to catch the lower surface of the buoy 36 so as to keep the buoy 36 at a
 set distance from the bottom of the drainage tank 34 even when the
 lubricant level is the lowest point. That is, by maintaining at least a
 minimum amount of lubricant in the bottom of the drainage tank 34 and
 always keeping the end of the drainage pipe 22 dipped into the lubricant,
 the gas in the low pressure regulator 12 is prevented from being
 introduced into the drainage tank 34 via the drainage pipe 22.
 As lubricant flows into the drainage tank 34, the buoy 36 floats up and if
 the lubricant is over a predetermined level, the lubricant is discharged
 out through a discharge pipe 42. That is, as shown in FIG. 4, if the buoy
 36 floats up to the predetermined level, the lubricant level sensor 38
 mounted on the upper surface of the buoy 36 detects the lubricant level
 and sends a signal to the ECU. Then, the ECU permits a solenoid valve 44
 to be electrically energized so that the solenoid valve 44 can be opened
 to discharge the lubricant outside the system.
 As shown in the preferred embodiment according to the present invention,
 the CNG fueling system is provided with a lubricant drainage device which
 is connected with the low pressure regulator such that if the lubricant
 infiltrates into the system through the supply pipe, the infiltrated
 lubricant can be drained to the drainage tank and discharged out of the
 system. Accordingly, malfunctions caused by infiltrated lubricant in the
 gas mass sensor and the flow controller can be prevented so that the
 engine performance improves. Also, since the lubricant can not reach the
 combustion chamber of the engine, toxic gas in exhaust can be drastically
 reduced.
 Although preferred embodiments of the present invention have been described
 in detail hereinabove, it should be clearly understood that many
 variations and/or modifications of the basic inventive concepts herein
 taught which may appear to those skilled in the present art will still
 fall within the spirit and scope of the present invention, as defined in
 the appended claims.