JP2009228583A - Liquefied gas fuel supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefied gas fuel supply system which can remove the air mixed into a fuel tank without bringing a vehicle into a maintenance shop when air has been mixed into the fuel tank. <P>SOLUTION: The fuel supply system 10 includes a canister 31, vapor piping 30, an air-removing solenoid valve 33, and an ECU 20. The canister 31 absorbs a vapor fuel in the fuel tank 11, and the vapor piping 30 connects between the fuel tank 11 and the canister 31. The air-removing solenoid valve 33 is provided at the midpoint of the vapor piping 30. When the ECU 20 determines that the air has been mixed into the fuel tank 11 based on the rate of change of a propane rate in the fuel tank 11, it opens the air-removing solenoid valve 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquefied gas fuel supply device that supplies liquefied gas fuel to an engine. More specifically, the present invention relates to a liquefied gas fuel supply apparatus that can process air mixed in a fuel tank.

  In recent years, vehicles equipped with engines using liquefied gas as fuel have been put into practical use. In a liquefied gas fuel supply device that supplies liquefied gas to an engine that uses liquefied gas as a fuel, if air or the like is mixed in the fuel tank, the fuel composition in the fuel tank cannot be accurately detected. The injection controllability is deteriorated. Further, since the fuel tank is required to have pressure resistance, a metal tank is used. However, if the state in which air is mixed in the fuel tank continues for a long time, there is a risk that rust will be generated in the fuel tank. When rust is generated in the fuel tank, the rust is supplied to the engine together with the fuel, which may cause a failure of the injector or the like, and the pressure resistance of the fuel tank may be reduced.

Therefore, in the liquefied gas fuel supply device, it is necessary to detect that air is mixed in the fuel tank and to quickly remove the mixed air from the fuel tank. Therefore, for example, in the liquefied gas fuel supply device disclosed in Patent Document 1, when detecting the mixing of air into the fuel tank, and detecting means for detecting the mixing of air into the fuel tank, this is used. Informing means for informing the person is provided. As a result, the detection means detects the entry of air into the fuel tank, informs the user through the notification means, and prompts maintenance of air removal.
JP 2006-77584 A

  However, the above-described liquefied gas fuel supply apparatus can know the mixing of air into the fuel tank, but there is a problem that it is necessary to go to a maintenance factory to remove the mixed air. For this reason, the fuel controllability remains deteriorated until the vehicle is brought into the maintenance shop. Even if air is mixed into the fuel tank, the fuel controllability is deteriorated and drivability is deteriorated. However, the vehicle is not disabled, so that the vehicle may not be brought into the maintenance shop. Furthermore, since the complicated work is required to remove the air mixed in the fuel tank, the maintenance cost for removing the air is high. This also increases the possibility that the vehicle will not be brought into the maintenance shop.

  And, even if air mixing into the fuel tank is detected, if the mixed air is not removed without bringing the vehicle into the maintenance shop, as described above, rust is generated in the fuel tank, This may cause a failure of the injector or the like and a decrease in pressure resistance of the fuel tank.

  Therefore, the present invention has been made to solve the above-described problems, and when air is mixed into the fuel tank, the air mixed in the fuel tank is removed without bringing the vehicle to the maintenance shop. It is an object of the present invention to provide a liquefied gas fuel supply device capable of performing

  The liquefied gas fuel supply device according to the present invention made to solve the above problems supplies liquefied gas fuel pumped out by a fuel pump from a fuel tank containing liquefied gas fuel to an injector via a branch pipe. However, in the liquefied gas fuel supply apparatus for supplying the fuel to the engine from the injector, the air mixing determination means for determining whether or not air is mixed in the fuel tank, and the gas phase fuel in the fuel tank are adsorbed. An adsorbing means, a connecting pipe connecting the fuel tank and the adsorbing means, an on-off valve provided in the middle of the connecting pipe, and a control means for controlling the operation of the on-off valve. The means opens the on-off valve when it is determined by the air mixing means that air is mixed into the fuel tank.

  In this liquefied gas fuel supply device, it is determined whether or not air is mixed in the fuel tank by the air mixing determination means, and when it is determined that air is mixed in the fuel tank, the control means An on-off valve provided in the middle of the connecting pipe connecting the fuel tank and the adsorbing means is opened. Then, the air mixed in the fuel tank is discharged from the fuel tank to the connection pipe together with the vapor phase fuel. And the air discharged | emitted in connection piping passes an adsorption | suction means, and is discharge | released in air | atmosphere. On the other hand, the gas-phase fuel discharged into the connecting pipe together with the air mixed in the fuel tank is not adsorbed by the adsorbing means and released into the atmosphere. The vapor phase fuel adsorbed and accumulated by the adsorbing means may be returned to the intake passage of the engine under a predetermined condition.

  Thus, in this liquefied gas fuel supply apparatus, when air is mixed into the fuel tank, the mixed air is released into the atmosphere via the connecting pipe and the adsorbing means. That is, it is removed from the fuel tank. Therefore, when air enters the fuel tank, the air can be removed from the fuel tank without bringing the vehicle to the maintenance shop. As a result, since air can be removed from the fuel tank in a short time after the air is mixed into the fuel tank, deterioration of the fuel controllability can be prevented. Further, since the state in which air is mixed into the fuel tank does not last for a long time, the occurrence of rust in the fuel tank can be prevented, and the reliability of the fuel supply device can be improved.

  In the liquefied gas fuel supply apparatus according to the present invention, the liquefied gas fuel supply device further includes an in-tank fuel composition detecting means for detecting a composition of the liquefied gas fuel in the fuel tank, and the aeration determination means is configured to include the fuel composition in the tank When the change rate of the composition of the liquefied gas fuel detected by the detection means has changed by a predetermined ratio or more, it may be determined that air has entered the fuel tank. The change rate of the composition of the liquefied gas fuel is a change rate of the fuel composition per unit fuel consumption.

  In this liquefied gas fuel supply apparatus, the composition of the liquefied gas fuel in the fuel tank is detected by the fuel composition detecting means in the tank. Specifically, the fuel composition is detected from the pressure and temperature in the fuel tank using the saturated vapor pressure curve of the liquefied gas fuel.

  Here, if air is not mixed in the fuel tank, the fuel composition in the fuel tank does not change even if the fuel is consumed. On the other hand, if air is mixed in the fuel tank, the volume ratio of the air in the fuel tank increases as the fuel is consumed. That is, since the partial pressure of air becomes small, the fuel composition changes greatly. Therefore, in this liquefied gas fuel supply device, it is determined that air is mixed in the fuel tank when the change rate of the composition of the liquefied gas fuel in the fuel tank changes by a predetermined ratio or more. As a result, it is possible to accurately detect the entry of air into the fuel tank, and when the air enters the fuel tank, the open / close valve is opened, so that the air mixed into the fuel tank can be quickly removed. can do.

  In the liquefied gas fuel supply apparatus according to the present invention, the control means may close the on-off valve when the composition of the liquefied gas fuel detected by the in-tank fuel composition detecting means becomes constant. desirable.

  When the air mixed in the fuel tank is removed, the composition of the liquefied gas fuel in the fuel tank becomes constant without changing. Then, when the composition of the liquefied gas fuel detected by the fuel composition detection means in the tank becomes constant, it is considered that the air mixed in the fuel tank has been completely removed. For this reason, in this liquefied gas fuel supply device, when the composition of the liquefied gas fuel detected by the in-tank fuel composition detecting means becomes constant, the control means closes the on-off valve. As a result, the air mixed in the fuel tank can be completely removed, and the amount of gas phase fuel discharged from the fuel tank can be reduced as much as possible by shortening the time during which the on-off valve is opened.

  According to the liquefied gas fuel supply apparatus according to the present invention, as described above, when air is mixed into the fuel tank, the air is completely removed from the fuel tank quickly and reliably without bringing the vehicle into the maintenance shop. can do.

  Hereinafter, a most preferred embodiment in which the liquefied gas fuel supply device of the present invention is embodied will be described in detail with reference to the drawings. In the present embodiment, the liquefied gas fuel supply apparatus of the present invention is applied to an apparatus for supplying LPG fuel to a liquefied petroleum gas (LPG) engine. A schematic configuration of the liquefied gas fuel supply apparatus according to the embodiment is shown in FIG. FIG. 1 is a diagram showing a schematic configuration of a liquefied gas fuel supply apparatus.

  As shown in FIG. 1, the fuel supply apparatus 10 according to the present embodiment includes a fuel tank 11, a fuel pump 12, a fuel pipe 13, a branch pipe 14, four injectors 16, and a return pipe 15. And an electronic control unit (ECU) 20. The liquid phase fuel in the fuel tank 11 is supplied to the injector 16, and the fuel is injected from the injector 16 to an engine (not shown).

  The fuel tank 11 contains LPG fuel. Since the fuel tank 11 is required to have pressure resistance, a metal tank having a cylinder shape is used. A fuel temperature sensor 21 and a fuel pressure sensor 22 are attached to the fuel tank 11. The fuel temperature sensor 21 detects the temperature of the LPG fuel in the fuel tank 11 and outputs an electrical signal corresponding to the detection result. The fuel pressure sensor 22 detects the pressure of the LPG fuel in the fuel tank 11 and outputs an electrical signal corresponding to the detection result. The fuel temperature sensor 21 and the fuel pressure sensor 22 are connected to the ECU 20. Both electrical signals output from the fuel temperature sensor 21 and the fuel pressure sensor 22 are input to the ECU 20.

  The fuel pipe 13 connects the fuel pump 12 and the branch pipe 14. The fuel pump 12 pumps out the liquid phase fuel from the fuel tank 11 and pumps it to each injector 16 via the fuel pipe 13 and the branch pipe 14.

  Each injector 16 injects the LPG fuel stored in the fuel tank 11 into the intake passage (not shown) of the engine in a mist state in a liquefied state. The injector 16 is an electromagnetic injection valve, which is normally closed and is electrically opened. The injector 16 receives and injects liquid-phase fuel stored at the bottom of the fuel tank 11 for injection. For this purpose, the fuel pump 12 installed at the bottom of the fuel tank 11 pumps the liquid phase fuel from the bottom of the fuel tank 11 and guides the pumped liquid phase fuel to each injector 16 via the branch pipe 14. It has become.

  One end of the branch pipe 14 is connected to the fuel pipe 13, and the other end is connected to the return pipe 15. The return pipe 15 is for returning all or a part of the liquid-phase fuel pressure-fed to each injector 16 through the fuel pipe 13 and the branch pipe 14 to the fuel tank 11. As a result, when each injector 16 is operating, the liquid phase fuel that has been pumped to each injector 16 and not injected passes through each injector 16 and then returns to the fuel tank 11 via the return pipe 15. It is supposed to be. Thus, when liquid phase fuel is pumped to the injector 16, the injector 16 is cooled by the passage of the fuel. The return pipe 15 is provided with a pressure regulator 17. Thereby, the fuel pressure in the fuel pipe 13 and the branch pipe 14, that is, the fuel pressure between the outlet of the fuel pump 12 and the pressure regulator 17 is adjusted to a constant pressure.

  Further, the fuel supply device 10 is provided with an air removal system for removing air mixed in the fuel tank 11 separately from the fuel supply system. Specifically, a vapor pipe 30 having one end disposed in the upper part (gas phase region) of the fuel tank 11, a canister 31 to which the other end of the vapor pipe 30 is connected, and a purge that connects the canister 31 and the intake passage. A pipe 32 is provided, and an air removal system is configured between the fuel tank 11 and the intake passage. An air removal electromagnetic valve 33 is provided in the vapor pipe 30 that connects the fuel tank 11 and the canister 31. The electromagnetic valve 33 is connected to the ECU 20 and is opened and closed at a predetermined timing according to a command from the ECU 20. In the present embodiment, the air removal electromagnetic valve 33 corresponds to the “open / close valve” of the present invention, and the ECU 20 corresponds to the “control unit” of the present invention.

  The canister 31 has a built-in adsorbent made of activated carbon so that when the air mixed in the fuel tank 11 is removed, the vapor phase fuel discharged together with the air from the fuel tank 11 is temporarily collected. It has become. The canister 31 is provided with an atmospheric port 35 opened to the atmosphere, and air removed from the fuel tank 11 from the atmospheric port 35 is released into the atmosphere.

  Here, the gas phase fuel collected in the canister 31 is opened to the intake passage through the purge pipe 32 due to the negative pressure of the intake passage when the purge electromagnetic valve 34 provided in the purge pipe 32 is opened by a command from the ECU 20. Purged. In this way, when the air mixed into the fuel tank 11 is removed, the vapor phase fuel discharged from the fuel tank 11 is prevented from being released into the atmosphere. This purge is performed at a timing generally performed in a gasoline engine.

  The ECU 20 comprehensively controls the above-described fuel supply device 10 including opening / closing control of the electromagnetic valves 33 and 34. Therefore, an output signal from the fuel temperature sensor 21, an output signal from the fuel pressure sensor 22, and output signals from various sensors that detect the operating state of the engine are input to the ECU 20. The ECU 20 has a known configuration including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, and the like. The ROM stores in advance a predetermined control program related to various controls. The CPU executes various controls in accordance with programs stored in the ROM.

  Next, the operation of the fuel supply device 10 will be briefly described. When the fuel pump 12 is driven, the liquid phase fuel in the fuel tank 11 is pumped up and supplied to the fuel pipe 13 and the branch pipe 14. Then, the LPG fuel is injected and supplied to the engine by operating each injector 16 according to a command from the ECU 20. At this time, part of the fuel in the branch pipe 14 is returned to the fuel tank 11 via the return pipe 15.

  Here, if maintenance of the fuel system parts or the like is performed, air remains in the fuel pipes 13, 14, 15. Then, the air remaining in the fuel pipes 13, 14, 15 is directly carried to the fuel tank 11 by the circulation of the LPG fuel in the fuel pipes 13, 14, 15. In this way, air is mixed into the fuel tank 11, and the mixed air is mixed with the vapor phase fuel in the fuel tank 11.

  And if air mixes in the fuel tank 11, the fuel composition in the fuel tank 11 cannot be detected accurately, and the fuel injection controllability deteriorates. Further, if the state where air is mixed in the fuel tank 11 continues for a long time, rust may be generated in the fuel tank. And when rust generate | occur | produces in the fuel tank 11, there existed a possibility that the rust might be supplied to an engine with a fuel and failure | failure of the injector 16 etc. may generate | occur | produce, and there existed a possibility that the pressure resistance of the fuel tank 11 might fall.

  For this reason, the fuel supply apparatus 10 according to the present embodiment detects the entry of air into the fuel tank 11 and removes the mixed air from the fuel tank 11 by the air removal system described above. Therefore, the mixed air removal process in the fuel supply apparatus 10 will be described with reference to FIG. FIG. 2 is a flowchart showing the contents of the mixed air removal process.

  In the fuel supply device 10, first, the air removal electromagnetic valve 33 is opened when air mixing into the fuel tank 11 is detected. After that, when it is determined that the mixed air has been removed from the fuel tank 11, the air removal electromagnetic valve. The valve 33 is closed. Specifically, as shown in FIG. 2, the ECU 20 detects the fuel pressure (tank pressure) and the fuel temperature (tank temperature) in the fuel tank 11 based on output signals from the fuel pressure sensor 22 and the fuel temperature sensor 21 ( Step 1). Then, the propane rate of the LPG fuel in the fuel tank 11 is calculated from the detected tank pressure and tank temperature (step 2). The propane rate can be calculated using a saturated vapor pressure curve based on the fuel pressure (tank pressure) and the fuel temperature (tank temperature).

  Next, the ECU 20 determines whether the change rate of the propane rate is smaller than the determination value A and whether a predetermined time has elapsed since the start of engine operation (step 3). By the processing in step 3, it is determined whether or not air is mixed in the fuel tank 11. Note that the elapse determination of the predetermined time in step 3 is performed based on whether or not the value of the counter counted up from the start of engine operation has reached the predetermined value C.

  Here, the change rate (% / L) of the propane rate means a change in the propane rate per unit fuel consumption, and is indicated by a negative value. For this reason, when the air is not mixed in the fuel tank 11, even if the LPG fuel is consumed, the rate of change of the propane rate is constant (“0% / L”). On the other hand, when air is mixed in the fuel tank 11, the volume ratio of the air increases as the LPG fuel is consumed, and the partial pressure of the air decreases, so the propane rate changes (decreases). The rate of change of the propane rate also changes (decreases: increases to the minus side). Accordingly, when the rate of change of the propane rate has changed by a predetermined rate or more, that is, when the rate has fallen below the determination value A, it can be determined that air is mixed in the fuel tank 11. However, since the fuel consumption is small in a short time, there is a possibility that the air mixing into the fuel tank 11 may not be accurately detected, and therefore the passage of a predetermined time is added to the determination requirement. For example, the predetermined time may be set to about 1 hour. Note that the method of detecting air mixing into the fuel tank 11 is not limited to this, and other methods (for example, see JP-A-2006-77584) may be used.

  In step 3, when the change rate of the propane rate is lower than the determination value A and a predetermined time has elapsed since the start of engine operation, that is, when air is mixed in the fuel tank 11 (S3: YES), the ECU 20 opens the air removal electromagnetic valve 33. Then, the air mixed in the fuel tank 11 reaches the canister 31 through the vapor pipe 30 and is discharged from the atmospheric port 35 of the canister 31. Thereby, the air mixed in the fuel tank 11 is removed. Note that, as the determination value A, for example, about “−10% / L” may be set.

  Here, when the air removal electromagnetic valve 33 is opened, the vapor phase fuel in the fuel tank 11 is also discharged from the fuel tank 11 in addition to the mixed air. This vapor phase fuel is collected in the canister 31. Is done. The vapor phase fuel collected in the canister 31 is opened to the intake passage through the purge pipe 32 by the negative pressure of the intake passage when the purge electromagnetic valve 34 provided in the purge pipe 32 is opened by a command from the ECU 20. Purged. For this reason, when the air mixed in the fuel tank 11 is removed, the vapor phase fuel discharged from the fuel tank 11 is not released into the atmosphere.

  Thereafter, the ECU 20 determines whether or not the rate of change of the propane rate exceeds the determination value B (step 5). This determination value B is a value (determination value B> determination value A) that is larger than the determination value used in the process of step 3 and is a value for determining that air has been completely removed from the fuel tank 11. is there. As the determination value B, for example, about “−3% / L” may be set. That is, when the mixed air is removed, the propane rate becomes constant, so the rate of change of the propane rate approaches “0% / L”. By setting the determination value to such a value, the fuel tank 11 can be accurately and quickly determined that the air has been completely removed from the air.

  When the change rate of the propane rate exceeds the determination value B, that is, when the air is completely removed from the fuel tank 11 (S5: YES), the ECU 20 closes the air removal electromagnetic valve 33 (step 6). As described above, after the air is completely removed from the fuel tank 11, the air removal electromagnetic valve 33 is immediately closed, so that the discharge of the gas phase fuel from the fuel tank 11 can be minimized.

  Next, the state of each part of the fuel supply apparatus 10 when the above-described mixed air removal process is performed will be described with reference to FIG. FIG. 3 is a timing chart showing the state of each part of the fuel supply device during the process of removing the mixed air. Here, a case where maintenance is performed between time t1 and t2 and air is mixed into the fuel tank will be described as an example. First, before the time t1, since the air is not mixed in the fuel tank 11, the air mixing flag is OFF. The tank pressure and the propane ratio are constant, and the rate of change of the propane ratio is constant at “0% / L”. Since the engine is in operation, the remaining amount of fuel is gradually decreasing.

  Then, the engine is stopped at time t1, and the engine is operated at time t2. Here, as described above, it is assumed that maintenance is performed between times t1 and t2 and air is mixed into the fuel tank 11. Then, when the engine is operated at time t2, since the air is mixed in the fuel tank 11, the tank pressure and the propane rate are increased. Along with this, the rate of change of the propane rate changes rapidly and falls below the judgment value A. Then, the time counter starts counting up. At this time, since the time counter, which is one of the air mixing determination conditions, has not reached the predetermined value C, it is determined “NO” in Step 3 of FIG. 2, so the air mixing flag remains OFF. Thereafter, as the fuel is consumed, the tank pressure, the propane rate, and the propane rate gradually change (decrease).

  Thereafter, at time t3 when the time counter reaches the predetermined value C after a lapse of time, “YES” is determined in the step 3 of FIG. At this time, the air removal electromagnetic valve 33 is opened by the ECU 20. Note that the air removal electromagnetic valve 33 actually opens slightly after time t3. And if the air removal solenoid valve 33 opens, a tank pressure and a propane rate will fall rapidly. For this reason, the rate of change of the propane rate also changes abruptly.

  Then, just before time t4, the air is completely removed from the fuel tank 11 and the propane ratio becomes constant. Then, the change rate of the propane rate returns to “0% / L”. At time t4, the change rate of the propane rate becomes larger than the determination value B. At this time, since it is determined as “YES” in Step 5 of FIG. 2, the air removal electromagnetic valve 33 is closed. Also, the aeration flag is turned off.

  As described above, in the fuel supply device 10 according to the present embodiment, when it is detected that air is mixed in the fuel tank 11 during engine operation (S3: YES), air removal is performed. The electromagnetic valve 33 is opened. Thereby, the air mixed in the fuel tank 11 is released into the atmosphere through the vapor pipe 30 and the canister 31. Therefore, when air enters the fuel tank 11, the air can be removed from the fuel tank 11 without bothering to bring the vehicle to the maintenance shop. As a result, since the air can be removed from the fuel tank 11 in a short time after the air is mixed into the fuel tank 11, the deterioration of the fuel controllability can be prevented. Further, since the state in which air is mixed into the fuel tank 11 does not last for a long time, the occurrence of rust in the fuel tank 11 can be prevented, and the reliability of the fuel supply device 10 can be improved. .

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the example in which the present invention is applied to the fuel supply device that supplies the LPG fuel to the engine has been described. However, the present invention is not limited to the LPG fuel, but the liquefied gas fuel (for example, liquefied natural gas (LNG) ) Etc.) can also be applied to a fuel supply device that supplies the engine.

It is a figure which shows schematic structure of the liquefied gas fuel supply apparatus which concerns on embodiment. It is a flowchart which shows the content of the removal process of mixed air. It is a timing chart which shows the state of each part of a fuel supply device at the time of removal processing of mixed air.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel supply apparatus 11 Fuel tank 12 Fuel pump 13 Fuel piping 14 Branch piping 15 Return piping 16 Injector 17 Pressure regulator 20 ECU
21 Fuel temperature sensor 22 Fuel pressure sensor 30 Vapor piping (connection piping)
31 Canister (Adsorption means)
32 Purge piping 33 Air removal solenoid valve (open / close valve)
34 Purge solenoid valve 35 Air port

Claims (3)

In the liquefied gas fuel supply device for supplying the liquefied gas fuel pumped from the fuel tank in which the liquefied gas fuel is pumped by the fuel pump to the injector through the branch pipe,
Air mixing judgment means for judging whether air is mixed in the fuel tank;
Adsorbing means for adsorbing gas-phase fuel in the fuel tank;
A connection pipe connecting the fuel tank and the adsorption means;
An on-off valve provided in the middle of the connecting pipe;
Control means for controlling the operation of the on-off valve,
The liquefied gas fuel supply device, wherein the control means opens the on-off valve when it is determined by the air mixing means that air is mixed into the fuel tank. In the liquefied gas fuel supply device according to claim 1,
A tank fuel composition detecting means for detecting the composition of the liquefied gas fuel in the fuel tank;
The aeration determination unit determines that air has entered the fuel tank when the change rate of the composition of the liquefied gas fuel detected by the in-tank fuel composition detection unit changes by a predetermined ratio or more. A liquefied gas fuel supply device. In the liquefied gas fuel supply device according to claim 2,
The liquefied gas fuel supply device, wherein the control means closes the on-off valve when the composition of the liquefied gas fuel detected by the in-tank fuel composition detecting means becomes constant.

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