AU2006201760B2

AU2006201760B2 - Fuel Supply System of LPI Engine and Method for Forcibly Returning Fuel Thereby

Info

Publication number: AU2006201760B2
Application number: AU2006201760A
Authority: AU
Inventors: Deok Ryol Kim
Original assignee: Hyundai Motor Co
Current assignee: Hyundai Motor Co
Priority date: 2006-04-12
Filing date: 2006-04-27
Publication date: 2008-06-26
Anticipated expiration: 2026-04-27
Also published as: KR100802930B1; JP4324601B2; KR20070101687A; NL1031682A1; CN101054925A; CN101054925B; ITMI20060791A1; AU2006201760A1; NL1031682C2; JP2007285285A

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventor: Address for Service: Invention Title: Hyundai Motor Company Deok Ryol Kim HODGKINSON McINNES PAPPAS Patent Trade Mark Attorneys Levels 3, 20 Alfred Street MILSONS POINT NSW 2061 "Fuel Supply System of LPI Engine and Method for Forcibly Returning Fuel Thereby" Details of Basic Application: Korea Patent Application No. 10-2006-0033083 Filed 12 April 2006 The following statement is a full description of this invention, including the best method of performing it known to us: P20494AU00 00 O TITLE OF THE INVENTION FUEL SUPPLY SYSTEM OF LPI ENGINE AND METHOD FOR FORCIBLY RETURNING FUEL THEREBY CROSS-REFERENCE TO RELATED APPLICATION S 5 This application claims priority to and the benefit of Korean Patent Application No. 10-2006-0033083 filed in the Korean Intellectual Property Office

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0on April 12, 2006, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a fuel supply system of an LPI engine and a method for forcibly returning fuel thereby. More particularly, the present invention relates to a fuel supply system of an LPI engine and a method for forcibly retuming fuel thereby having an advantage of preventing fuel leakage caused by a temperature and pressure rise of a remaining fuel in a fuel supply line and a fuel retum line when an ignition switch turns off.

Description of the Related Art Generally, an LPI engine refers to an engine where a fuel pump is mounted in a tank and LPG fuel is injected to the engine through an injector by supplying the LPG fuel to the injector in a liquid state. The LPI engine may meet exhaust regulations, and may solve various problems of a conventional LPG system, such as bad starting in winter and deterioration of an output power.

As shown in FIG. 6, a conventional LPI fuel supply system includes a 00

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tank 10 having a fuel pump 12 for supplying a liquefied fuel to an engine ;compartment 20, a fuel supply line 30 having one end connected to the fuel _pump 12 and the other end connected to the engine compartment 20, and a fuel return line 40 having one end connected to the engine compartment 20 and the other end connected to the tank OTherefore, the fuel supplied from the fuel pump 12 is carried successively

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athrough the fuel supply line 30 and an injector, and injected to a combustion chamber. Then, a remaining fuel is returned to the tank 10 through the fuel return line Meanwhile, the fuel supply line 30 is provided with a cut-off valve 32 for cutting off a fuel supply when the engine stops, and a temperature sensor 34 for measuring fuel temperature.

In addition, the fuel return line 40 is provided with a pressure sensor 49 for measuring fuel pressure and a pressure regulator 48 for maintaining the fuel pressure within a predetermined range.

According to the conventional fuel supply system, fuel may remain in the fuel supply line and the fuel return line near the injector when the engine is stopped, and the remaining fuel may leak into the combustion chamber while the engine is cooled to room temperature.

Such a fuel leakage causes a fuel concentration in a cylinder to be very rich, so many problems may occur such that starting is delayed and HC exhaust amount increases.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore 00

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it may contain information that does not form the prior art that is already known ;in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a fuel supply system of an LPI engine and a method for forcibly retumrning fuel thereby having Nadvantages of preventing rise of an engine fuel pressure by returning a

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Oremaining fuel in a fuel supply line and a fuel return line.

In addition, the present invention has advantages of preventing fuel leakage through an injector so as to meet reinforced exhaust gas regulations.

An exemplary fuel supply system for an LPI engine according to an embodiment of the present invention includes: a tank having a fuel pump for supplying a fuel and a fuel return pump for forcibly returning the fuel; an engine compartment having a plurality of injectors that inject the fuel; a fuel supply line having one end connected to the fuel pump and the other end connected to the engine compartment, the fuel supply line having a cut-off valve and a temperature sensor; and a fuel return line having one end connected to the engine compartment and the other end bifurcated into a forcible return line and a normal return line so as to return a remaining fuel to the tank, the fuel return line having a pressure sensor and a pressure regulator, wherein the forcible retumrn line is connected to the fuel return pump of the tank.

The normal return line may have a cut-off valve so as to cut off the normal retumrn line when the fuel is returned forcibly.

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The fuel return pump includes: a pump case; a motor for supplying energy so as to rotate a shaft and pump the fuel, the motor being mounted on an _upper portion of the pump case; a shaft cam mounted on a lower end of the shaft of the motor, the shaft cam rotating with the shaft; a plunger for converting a S 5 rotary motion of the shaft into a reciprocal rectilinear motion, the plunger Sextemrnally jointed to the shaft cam; and a diaphragm for pumping the fuel, the

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adiaphragm interlocked to the plunger.

A lubrication oil supply pipe for supplying lubrication oil and a fuel exhaust pipe for exhausting the retumrned fuel into the tank may be connected to an upper end of the pump case.

A lubrication oil pathway that encloses the shaft may be formed vertically at a middle portion of the motor, and an oil screw for pulling up the lubrication oil may be mounted on a lower portion of an exterior circumference of the shaft such that the lubrication oil is pulled up to an upper end of the motor and scattered.

An exemplary fuel supply system for an LPI engine according to a second embodiment of the present invention includes: a tank having a fuel pump for supplying a fuel and a fuel return pump for forcibly returning the fuel; an engine compartment having a plurality of injectors that inject the fuel; a fuel supply line having one end connected to the fuel pump and the other end connected to the engine compartment, the fuel supply line having a cut-off valve and a temperature sensor; and a fuel retumrn line having one end connected to the engine compartment and the other end bifurcated into a forcible return line and a normal return line so as to return a remaining fuel to the tank, the fuel 00 return line having a pressure sensor and a pressure regulator, wherein the ;forcible return line is connected to the fuel return pump of the tank and has a cut-off valve so as to open the forcible retumrn line by opening the cut-off valve when the fuel is returned forcibly.

C: 5 The fuel retumrn pump includes: a pump case; a motor for supplying Oenergy so as to rotate a shaft and pump the fuel, the motor being mounted on an

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Cupper portion of the pump case; a shaft cam mounted on a lower end of the shaft of the motor, the shaft cam rotating with the shaft; a plunger for converting a rotary motion of the shaft into a reciprocal rectilinear motion, the plunger externally jointed to the shaft cam; and a diaphragm for pumping the fuel, the diaphragm interlocked to the plunger.

A lubrication oil supply pipe for supplying lubrication oil and a fuel exhaust pipe for exhausting the returned fuel into the tank may be connected to an upper end of the pump case.

An exemplary method for forcibly returning fuel which remains in a fuel supply line and a fuel return line of an LPI engine according to a third embodiment of the present invention includes: determining whether an ignition switch is turned on; turning on a main relay and a fuel pump relay if the ignition switch is turned on; returning the fuel through the normal return line; determining 00

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whether the ignition switch is turned off; comparing engine fuel pressure with a ;reference pressure if the ignition switch is turned off; forcibly returning the fuel by _an operation of a cut-off valve and a fuel return pump if the engine fuel pressure is larger than the reference pressure; and tumrning off the main relay and the fuel pump relay.

OThe step of returning the fuel through the normal return line includes

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Sopening the normal return line by opening the cut-off valve mounted thereon, and maintaining the fuel return pump to be turned off.

The step of forcibly retumrning the fuel by operation of the cut-off valve and the fuel return pump includes: cutting off the normal return line by closing the cut-off valve mounted thereon; forcibly returning the fuel by turning on the fuel return pump; comparing the engine fuel pressure with the reference pressure; and opening the cut-off valve and tumrning off the fuel return pump if the engine fuel pressure is smaller than the reference pressure.

An exemplary method for forcibly returning fuel which remains in a fuel supply line and a fuel return line of an LPI engine according to a fourth embodiment of the present invention is the same as the third embodiment except for the forcible return line having the cut-off valve and the controlling method for opening and closing the normal return line and the forcible return line by an operation of the cut-off valve. Thus, only the differences from the third embodiment will hereinafter be described.

The step of returning the fuel through the normal return line includes cutting off the forcible return line by closing the cut-off valve mounted thereon and maintaining the fuel return pump to be turned off in a method according to 00 O the fourth embodiment of the present invention for forcibly returning a fuel which ;remains in a fuel supply line and a fuel return line of an LPI engine.

SIn addition, the step of forcibly returning the fuel by operation of the cut-off valve and the fuel return pump includes: opening the forcible return line by opening the cut-off valve mounted thereon; forcibly returning the fuel by 0tumrning on the fuel return pump; comparing the engine fuel pressure with the

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reference pressure; and closing the cut-off valve and turning off the fuel return pump if the engine fuel pressure is smaller than the reference pressure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a fuel supply system of an LPI engine according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a fuel return pump for a fuel supply system of an LPI engine according to the exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of a fuel return pump for a fuel supply system of an LPI engine according to another exemplary embodiment of the present invention.

FIG. 4 is a flowchart of a method for forcibly retumrning a fuel of an LPI engine according to an exemplary embodiment of the present invention.

FIG. 5 is a flowchart of a method for forcibly returning a fuel of an LPI engine according to another exemplary embodiment of the present invention.

FIG. 6 is a schematic diagram of a fuel supply system of a conventional LPI engine.

00 O DETAILED DESCRIPTION OF THE EMBODIMENTS Exemplary embodiments of a fuel supply system of an LPI engine of the Spresent invention will hereinafter be described in detail with reference to the accompanying drawings.

C 5 FIG. 1 is a schematic diagram of a fuel supply system of an LPI engine 0according to an exemplary embodiment of the present invention.

As shown in FIG. 1, an exemplary fuel supply system of an LPI engine according to an embodiment of the present invention includes a tank 10 filled with a fuel, an engine compartment 20 wherein the fuel is bumrned, a fuel supply line 30 wherein the fuel is supplied to the engine compartment 20, and a fuel return line 40 wherein a remaining fuel after combustion is returned to the tank A fuel pump 12 and a fuel retumrn pump 14 are mounted in the tank The fuel pump 12 pumps the fuel in order to supply the fuel to the engine compartment 20. The fuel return pump 14 returns the remaining fuel in the fuel supply line 30 and the fuel return line 40 into the tank 10 when an engine stops.

As shown in FIG. 2, the fuel return pump 14 includes a pump case 52, a motor 50 for supplying energy in order to forcibly return the fuel, a shaft cam 54 mounted on a shaft 64 of the motor 50, a plunger 56 externally jointed to the shaft cam 54, and a diaphragm 58 interlocked to the plunger 56.

The pump case 52 is made of a material, such as a plastic, which has a small heat transfer coefficient so as to minimize heat transfer from the motor to the tank 10. In addition, a lubrication oil supply pipe 60 for supplying lubrication oil and a fuel exhaust pipe 62 for exhausting a returned fuel into the 00 O tank 10 are connected to an upper end of the pump case 52.

The motor 50 is mounted in an upper portion of the pump case 52. The shaft 64 is mounted in the motor 50. The shaft 64 rotates and supplies energy so as to pump the fuel.

O 5 Meanwhile, a lubrication oil pathway 68 which encloses the shaft 64 is 0formed vertically at a middle portion of the motor 50. An oil screw 66 for pulling

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up the lubrication oil is mounted on a lower portion of an exterior circumference Sof the shaft 64. The oil screw 66 mounted on the shaft 64 rotates and pulls up the lubrication oil so that the lubrication oil is scattered. Then, the scattered lubrication oil flows through an exterior circumference of the motor 50 so as to cool and lubricate the motor 50. After that, the lubrication oil falls down and circulates. In addition, the lubrication oil supply pipe 60 is connected to the lubrication oil pathway 68 so as to supply the lubrication oil.

The shaft cam 54 is eccentrically mounted on a lower end of the shaft 64 of the motor 50 and rotates with the shaft 64.

The plunger 56 is externally jointed to the shaft cam 54. The plunger 56 converts an eccentric rotary motion of the shaft cam 54 into a reciprocal rectilinear motion.

The diaphragm 58 is interlocked to the plunger 56 and performs a reciprocal rectilinear motion so as to pump the fuel. The diaphragm 58 is elastically supported by a spring The engine compartment 20 has a plurality of injectors for injecting the fuel to a combustion chamber.

The fuel supply line 30 connects the fuel pump 12 to the injectors of the 00 engine compartment 20 so as to supply the fuel from the tank 10 to the injectors.

;A cut-off valve 32 and a temperature sensor 34 are mounted on the fuel supply line 30. The fuel supply to the engine compartment 20 is cut off by the cut-off valve 32 when the engine stops, and fuel temperature is measured by the 0 5 temperature sensor 34. The fuel supply and engine operation are controlled 0 according to the fuel temperature.

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OThe fuel retumrn line 40 for returning a surplus fuel to the tank 10 has one end connected to the engine compartment 20 and the other end bifurcated into a forcible return line 42 and a normal return line 44. The forcible return line 42 is connected to the fuel return pump 14 of the tank 10. The remaining fuel in the fuel supply line 30 and the fuel retumrn line 40 is forcibly returned to the tank through the forcible return line 42 when the engine stops. In addition, the surplus fuel that remains unburned in a combustion process is returned to the tank 10 through the normal retumrn line 44 when the engine operates, not by operation of the fuel retumrn pump 14.

In addition, as shown in FIG. 2, the normal retumrn line 44 has a cut-off valve 46. When the engine operates, the cut-off valve 46 is opened and the surplus fuel is returned to the tank 10 through the normal return line 44.

However, in a case that the remaining fuel in the fuel supply line 30 and the fuel return line 40 is forcibly retumrned since an engine fuel pressure is larger than a predetermined pressure when the engine stops, the cut-off valve 46 on the normal return line 44 is closed and the remaining fuel is returned to the tank through the forcible return line 42.

Meanwhile, as shown in FIG. 3, the cut-off valve 46 may be mounted on 00 O the forcible return line 42. In this case, the cut-off valve 46 is closed and the surplus fuel is returned to the tank 10 through the normal return line 44 when the Sengine operates. However, in a case that the remaining fuel in the fuel supply line 30 and the fuel return line 40 is forcibly returned since the engine fuel O 5 pressure is larger than the predetermined pressure when the engine stops, the cut-off valve 46 on the forcible return line 42 is opened and the remaining fuel is

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returned to the tank 10 through the forcible return line 42.

SA pressure sensor 49 and a pressure regulator 48 are mounted on the fuel return line 40. Fuel pressure is measured by the pressure sensor 49, and is maintained within a predetermined range by the pressure regulator 48.

Meanwhile, an exemplary fuel supply system of an LPI engine according to an embodiment of the present invention is controlled by an electronic signal of an ECU (not shown). Such control method is obvious to a person of an ordinary skilled in the art and thus will not be described in further detail.

With reference to the accompanying drawings, an exemplary method for forcibly returning a fuel of an LPI engine according to an embodiment of the present invention will hereinafter be described in detail.

As shown in FIG. 4 and FIG. 5, exemplary methods for forcibly returning fuel of an LPI engine according to an embodiment of the present invention starts with determining whether an ignition switch is turned on at step S100. If the ignition switch is turned on, an ECU turns on a main relay and a fuel pump relay at step S110. Fuel is returned through the normal return line 44 when the engine operates normally at steps S120 and S120'.

After that, the ECU determines whether the ignition switch is tumrned off at 00 O step S130. If the ignition switch is turned on, the fuel is continuously returned ;through the normal return line 44. If the ignition switch is turned off, the ECU compares engine fuel pressure with a predetermined reference pressure at step S140.

C 5 In this case, if the engine fuel pressure is larger than the reference 0 pressure, the fuel is forcibly returned by operation of the cut-off valve 46 and the fuel return pump 14 at steps S150 and S150'. If the engine fuel pressure is smaller than the reference pressure, the fuel is not forcibly returned.

Finally, the main relay and the fuel pump relay are turned off, and the engine is maintained to stop at step S160.

Meanwhile, the steps S120 and S120' of returning the fuel through the normal retumrn line 44 and the steps S150 and S150' of forcibly returning the fuel by the operation of the fuel retumrn pump 14 will hereinafter be described in detail for the separate instances where the cut-off valve 46 is mounted on the normal return line 44 and the cut-off valve 46 is mounted on the forcible return line 42.

As shown in FIG. 4, if the cut-off valve 46 is mounted on the normal return line 44, at the step S120 of returning the fuel through the normal return line 44, the cut-off valve 46 is maintained to be opened so as to open the normal return line 44. Then, the fuel return pump 14 is maintained to be turned off and a surplus fuel is returned to the tank 10 through the normal return line 44.

In addition, at the step S150 of forcibly retumrning the fuel by operation of the fuel return pump 14, the cut-off valve 46 mounted on the normal return line 44 is closed so as to cut off the normal retumrn line 44 at step S210, and the fuel return pump 14 is turned on so as to forcibly return the fuel to the tank 10 at step 00 O S220.

After that, the engine fuel pressure is compared with the reference

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pressure again at step S230. If the engine fuel pressure is larger than the reference pressure, the fuel is forcibly returned by the operation of the fuel return C 5 pump 14. If the engine fuel pressure is smaller than the reference pressure, the 0cut-off valve 46 is opened and the fuel return pump 14 is turned off so as not to forcibly return the fuel at step S240.

However, as shown in FIG. 5, if the cut-off valve 46 is mounted on the forcible return line 42, at the step S120' of returning the fuel through the normal return line 44, the cut-off valve 46 mounted on the forcible return line 42 is closed so as to cut off the forcible return line 42. Then, the fuel return pump 14 is maintained to be turned off.

In addition, at the step S150' of forcibly returning the fuel by operation of the fuel return pump 14, the cut-off valve 46 mounted on the forcible return line 42 is opened so as to open the forcible retumrn line 42 at step S210', and the fuel return pump 14 is tumrned on so as to forcibly return the fuel to the tank 10 at step S220'.

After that, the engine fuel pressure is compared with the reference pressure again at step S230'. If the engine fuel pressure is larger than the reference pressure, the fuel is forcibly returned by the operation of the fuel return pump 14. If the engine fuel pressure is smaller than the reference pressure, the cut-off valve 46 is closed and the fuel return pump 14 is turned off so as not to forcibly return the fuel at step S240'.

While this invention has been described in connection with what is 00

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presently considered to be practical exemplary embodiments, it is to be ;understood that the invention is not limited to the disclosed embodiments, but, _on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

C 5 As described above, the remaining fuel in the fuel supply line and the fuel Oreturn line is returned when the engine stops according to the present invention.

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OTherefore, a fuel pressure rise is prevented.

In addition, fuel leakage caused by a fuel pressure rise is prevented according to the present invention. The problems that starting is delayed and a HC exhaust amount increases may be solved.

Claims

2. The system of claim 1, wherein the normal return line has a cut-off valve so as to cut off the normal retumrn line when the fuel is returned forcibly.
3. The system of claim 1, wherein the forcible return line has a cut-off valve so as to open the forcible return line by opening the cut-off valve when the fuel is returned forcibly.
4. The system of claim 2 or claim 3, wherein the fuel return pump comprises: 00 a pump case; ;a motor for supplying energy so as to rotate a shaft and pump the fuel, the motor being mounted in an upper portion of the pump case; a shaft cam mounted on a lower end of the shaft of the motor, the shaft NO 5 cam rotating with the shaft; a plunger for converting a rotary motion of the shaft into a reciprocal IND rectilinear motion, the plunger being externally jointed to the shaft cam; and a diaphragm for pumping the fuel, the diaphragm being interlocked to the plunger.
5. The system of claim 4, wherein a lubrication oil supply pipe for supplying lubrication oil and a fuel exhaust pipe for exhausting the returned fuel into the tank are connected to an upper end of the pump case.
6. The system of claim 5, wherein a lubrication oil pathway that encloses the shaft is formed vertically at a middle portion of the motor, and an oil screw for pulling up the lubrication oil is mounted on a lower portion of an exterior circumference of the shaft such that the lubrication oil is pulled up to an upper end of the motor and scattered.
7. A method for forcibly returning fuel which remains in a fuel supply line and a fuel return line of an LPI engine, comprising: determining whether an ignition switch is turned on; turning on a main relay and a fuel pump relay if the ignition switch is turned on; returning the fuel through the normal retumrn line; 16 00 O determining whether the ignition switch is turned off; comparing engine fuel pressure with a reference pressure if the ignition 0switch is turned off; forcibly returning the fuel by operation of a cut-off valve and a fuel return .O 5 pump if the engine fuel pressure is larger than the reference pressure; and turning off the main relay and the fuel pump relay. IND \O
8. The method of claim 7, wherein the step of returning the fuel through the normal retum line comprises: opening the normal return line by opening the cut-off valve mounted thereon; and maintaining the fuel return pump to be turned off.
9. The method of claim 8, wherein the step of forcibly returning the fuel by operation of the cut-off valve and the fuel retum pump comprises: cutting off the normal return line by closing the cut-off valve mounted thereon; forcibly returning the fuel by turning on the fuel return pump; comparing the engine fuel pressure with the reference pressure; and opening the cut-off valve and turning off the fuel return pump if the engine fuel pressure is smaller than the reference pressure.
10. The method of claim 7, wherein the step of returning the fuel through the normal return line comprises: cutting off the forcible return line by closing the cut-off valve mounted thereon; and 00 O maintaining the fuel return pump to be turned off. ;Z
11. The method of claim 10, wherein the step of forcibly returning the fuel by operation of the cut-off valve and the fuel return pump comprises: 0opening the forcible return line by opening the cut-off valve mounted S 5 thereon; forcibly returning the fuel by turning on the fuel return pump; comparing the engine fuel pressure with the reference pressure; and closing the cut-off valve and turning off the fuel retumrn pump if the engine fuel pressure is smaller than the reference pressure.
12. A fuel supply system for an LPI engine as substantially hereinbefore described and with reference to Figures
13. A method for forcibly returning fuel which remains in a fuel supply line and a fuel return line of an LPI engine as substantially hereinbefore described and with reference to Figures