KR20060048052A - Fuel supplying device of an engine - Google Patents

Abstract

(Problem) To predict the vapor mixing in the fuel in the liquid state and to control the fuel supply amount to the engine with good precision.

(Solution means) The fuel supply apparatus pumps LPG stored in the liquid state in the fuel tank 1 to the delivery pipe 6 and each injector 4, and in the fuel state detected by the various sensors 48 to 51. On the basis of this, the fuel injection amount supplied from each injector 4 to the engine 3 is corrected. The electronic controller 40 adjusts the fuel composition Fc at the tank temperature Tt and the tank pressure Pt detected by the tank fuel temperature sensor 48 and the tank fuel pressure sensor 49. The fuel liquid density and vapor mixing ratio in the delivery pipe 6 are estimated from the fuel composition Fc and the delivery fuel temperature Td detected by the delivery fuel temperature sensor 50, and those fuel liquids are estimated. The fuel injection amount supplied to the engine 3 is corrected in accordance with the density and the steam mixing ratio.

Fuel supply

Description

FUEL SUPPLYING DEVICE OF AN ENGINE}

1 is a schematic configuration diagram showing an LPG engine system.

2 is a flowchart showing the contents of LPG fuel injection control.

3 is a graph showing a correction map.

* Description of Symbols for Major Symbols in Drawings *

1 fuel tank

3 engine for LPG

4 Injectors (fuel injection equipment)

6 Delivery pipes (fuel injection equipment)

40 ECU (Steam Compensation Means)

48 Fuel temperature sensor for tank (detecting means, first fuel temperature detecting means)

49 Fuel pressure sensor for tank (detection means, fuel pressure detection means)

50 Fuel temperature sensor for delivery (detection means, second fuel temperature detection means)

Fuel temperature in Tt tank

Fuel pressure in Pt tank

Fuel temperature in Td delivery

Fc fuel composition

Basic injection volume at Ts start

Injection volume at TAUs start

Basic injection volume after starting Tas

Injection volume after starting TAUas

[Patent Document 1] Japanese Patent Application Laid-Open No. 59-43659 (No. 1 to 5 pages, Fig. 1)

[Patent Document 2] Japanese Patent Application Laid-Open No. 11-210557 (pages 2 to 8, FIGS. 1 and 2)

[Patent Document 3] Japanese Unexamined Patent Publication No. 2003-90237 (2-10 pages, FIGS. 1 and 2)

The present invention relates to a fuel supply device for supplying fuel to an engine. Specifically, the present invention relates to a fuel supply device for an engine using a fuel that is easily changed in composition and properties, such as liquefied petroleum gas (LPG) and liquefied natural gas (LNG).

In general, LPG and LNG used as fuel in engines tend to change greatly in composition and properties due to differences in seasons and regions. For this reason, in order to use LPG and LNG in an engine, it is necessary to correct fuel supply amount according to a difference in a composition and a property. Therefore, the above patent documents 1 to 3 describe a fuel supply device in which the LPG is supplied to the engine in accordance with the difference in the composition and properties of the LPG.

The fuel supply apparatus of patent document 1 measures the vapor pressure and temperature of LPG, calculates the composition and liquid specific gravity, and corrects and controls the valve opening time of a fuel injection valve by steam pressure, liquid specific gravity, and composition. . As a result, the fuel flow rate is controlled to be a constant excess air ratio.

Patent document 2 describes a fuel supply device in which gaseous fuel and liquid fuel are selectively supplied to an engine. When the state of the liquefied gas supplied from the bomb to the liquid fuel supply means is liquid, the fuel supply device controls the liquid fuel supply means to supply the liquid fuel to the engine, and the supplied liquefied gas is gaseous. In this case, gaseous fuel supply means is controlled to supply gaseous fuel to the engine. As a result, engine starting at low temperatures and idling stability after starting can be ensured to ensure controllability and responsiveness.

The fuel supply device described in Patent Document 3 has a fuel temperature and fuel pressure in the fuel tank and a fuel injection mechanism (delivery pipe and fuel injection valve) in order to perform a more appropriate fuel injection corresponding thereto even if the composition or state of the fuel changes. The fuel state in the fuel injection mechanism is estimated based on the fuel temperature and the fuel pressure, and the fuel injection amount is controlled according to the estimated fuel state. In detail, a fuel composition is estimated based on the fuel temperature and fuel pressure in a fuel tank, and the saturated steam characteristic of the fuel is calculated | required. In addition, one of the saturated steam pressure and the saturated steam temperature of the fuel in the fuel injection mechanism is obtained from one of the obtained saturated steam characteristics and the fuel temperature and the fuel pressure of the fuel injection mechanism. The fuel state in the fuel injection mechanism is estimated based on one of the relationship between the obtained saturated vapor pressure and the fuel pressure of the fuel injection mechanism, and the relationship between the saturated steam temperature and the fuel temperature in the fuel injection mechanism.

By the way, each fuel supply apparatus described in patent documents 1-3 basically estimates the composition and property of a fuel based on fuel temperature and fuel pressure. That is, the fuel composition is estimated, and it is estimated whether the fuel is in a gaseous state or a liquid state according to the estimation result. The fuel injection amount to the engine is controlled according to the fuel state. Therefore, in the control of the fuel injection amount, the fuel injection amount is corrected according to the saturation vapor curve obtained from the relationship between the fuel temperature and the fuel pressure after estimating whether the fuel is in the liquid state or the gaseous state.

However, the Applicant has confirmed that an error occurs in the fuel injection amount, even though the fuel injection amount is controlled while assuming that the fuel supply control as described above is in a completely liquid state. This is because the vapor in the bubble state is mixed in the liquid fuel present in the fuel injection mechanism (delivery pipe and the fuel injection valve), so that an error equal to the amount of steam mixed in the fuel injection amount corrected as a completely liquid state is generated. I think it is by thing. As the cause, for example, it is considered that the heat that the component parts of the delivery pipe or the fuel injection valve receive from the engine body is transmitted from the component parts to the liquid fuel and a part of the liquid fuel evaporates. . In the fuel supply apparatuses described in Patent Documents 1 to 3 described above, the fuel injection amount is only corrected according to the state of the fuel that is uniquely estimated, that is, the liquid state or the gaseous state, and the vapor mixing content as described above is expected. No correction is made at all. For this reason, there exists a possibility that an error may arise in fuel injection quantity only by steam mixing content, and the air-fuel ratio in an engine may arise.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel supply apparatus for an engine that makes it possible to predict the amount of mixing of steam in a fuel in a liquid state and to control the fuel supply amount to the engine with high precision. It is to offer.

(Means to solve the task)

In order to achieve the above object, the invention according to claim 1 is a fuel injection device based on the fuel state detected by the detection means, by the fuel injection device stored in the liquid state in the fuel tank in the fuel injection device In a fuel supply apparatus for an engine configured to correct a fuel injection amount supplied to an engine from the engine, the mixing ratio of steam in the liquid state fuel is estimated based on the fuel state detected by the detection means as the fuel injection device, and It is intended to have a vapor correction means for correcting the fuel injection amount from the fuel injection device in accordance with the estimated mixing ratio.

According to the structure of the said invention, the fuel injection amount correct | amended in the liquid state fuel conveyed from a fuel tank to the fuel injection device according to the fuel state in the said fuel injection device, and the fuel injection device as much as the fuel injection amount after the correction | amendment Fuel is supplied to the engine. Here, in some cases, the fuel in the device evaporates and vapor is mixed into the fuel in the liquid state by the heat received by the fuel injection device from the engine. According to the configuration of the present invention, the steam correction means estimates the mixing ratio of steam in the fuel in the liquid state on the basis of the fuel state detected by the fuel injection device, and adjusts the fuel injection amount according to the estimated mixing ratio. Correcting. Therefore, the fuel is supplied to the engine in the amount of the steam content mixed with the fuel in the liquid state.

In order to achieve the above object, the invention according to claim 2 is, in the invention according to claim 1, the detection means includes a first fuel temperature detection means for detecting a fuel temperature in the fuel tank, and a fuel tank. Fuel pressure detecting means for detecting fuel pressure in the fuel cell and second fuel temperature detecting means for detecting fuel temperature in the fuel injection device, wherein the steam correction means includes: a fuel temperature in the detected fuel tank; Estimate the fuel composition from the fuel pressure, estimate the fuel liquid density and mixing ratio in the fuel injection apparatus from the estimated fuel composition and the fuel temperature in the detected fuel injection apparatus, and estimate the fuel liquid density and mixing ratio The purpose of this is to correct the fuel injection amount from the fuel injection device.

According to the configuration of the invention, with respect to the action of the invention according to claim 1, the steam correction means estimates the fuel composition from the fuel temperature and the fuel pressure in the fuel tank, and the estimated fuel composition and the fuel injection device Since the fuel liquid density and the mixing ratio in the fuel injection device are estimated from the fuel temperature, the mixing ratio of the vapor in the fuel in the liquid state is more accurately estimated. In addition, since the fuel injection amount is corrected according to the estimated fuel liquid density and the mixing ratio of steam, a more accurate amount of fuel is supplied to the engine.

(The best mode for carrying out the invention)

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment which actualized the fuel supply apparatus of the engine in this invention with the liquefied fuel gas (LPG) engine is described in detail with reference to drawings.

The LPG engine system of this embodiment is shown by a schematic block diagram in FIG. The engine system mounted on the vehicle includes a fuel tank 1 for storing LPG in a liquid state. The fuel pump 2 built in the fuel tank 1 discharges LPG in a liquid state stored in the tank 1. In this embodiment, the engine 3 for LPG is a four-cylinder reciprocating type, cylinder # 1, cylinder # 2, cylinder # 3 and cylinder # 4. ). In each cylinder # 1-# 4, the injector 4 for injection-injecting and supplying LPG of a liquid state is provided. LPG in the liquid state discharged from the fuel pump 2 is supplied to each injector 4 via the fuel line 5 and the delivery pipe 6. The injected liquid LPG is injected in the liquid state to the intake ports of the cylinders # 1 to # 4 leading to the intake passage 7 by operating the injector 4. Intake path 7 receives air from the outside via air cleaner 8. Air taken into the intake passage 7 and LPG in the liquid state injected from each injector 4 are sucked into the combustion chamber of each cylinder # 1 to # 4 as a combustible mixer. LPG in the liquid state remaining in the delivery pipe 6 is returned to the fuel tank 1 via the return line 9. In this embodiment, the fuel injection device of this invention is comprised by each injector 4 and the delivery pipe 6.

A throttle valve 10 is formed in the intake passage 7. This throttle valve 10 is opened and closed in conjunction with the operation of the accelerator pedal 11 formed in the driver's seat. By this opening and closing, the air amount (intake amount) suctioned into each cylinder # 1-# 4 from the intake passage 7 is adjusted.

The spark plug 12 formed in the combustion chamber of each cylinder # 1-# 4, respectively, receives the ignition signal output through the ignition coil 14 with the igniter built in arrange | positioned in each cylinder # 1-# 4. Receive ignition operation. Each spark plug 12 and each ignition coil 14 constitute an ignition device that ignites a combustible mixer sucked into the combustion chamber of each cylinder # 1 to # 4. In each cylinder # 1-# 4, the combustible mixer sucked into a combustion chamber in an intake stroke is compressed by a compression stroke, and the spark plug 12 sparks and expands | expands and expands by a spark operation in an expansion stroke. The exhaust gas after combustion is discharged from the combustion chamber to the outside through the exhaust passage 15 in the subsequent exhaust stroke. Then, in response to the combustion of the combustible mixer in the combustion chambers of the cylinders # 1 to # 4, a piston (not shown) is operated to rotate the crankshaft 16, thereby driving the vehicle to drive the vehicle by the engine 3. Is obtained. The starter 17 formed in the engine 3 is used for cranking at the start of the engine 3.

In the fuel line 5 between the fuel tank 1 and the delivery pipe 6, a first shutoff valve 18, a fuel filter 19, and a second shutoff valve 20 are formed in series. The fuel filter 19 is used to remove foreign substances mixed in the LPG in the liquid state. The first and second shut-off valves 18 and 20 are closed to forcibly shut off the LPG from the fuel tank 1 to the delivery pipe 6 at the time of shutting off the fuel of the engine 3 or in an emergency.

In the return line 9 from the delivery pipe 6 to the fuel tank 1, the first regulator 21 and the second regulator 22 are formed in series. In addition, a third shut-off valve 24 is formed in the bypass passage 23 bypassing the second regulator 22. The third shut-off valve 24 is normally open. In this normally open state, LPG returned from the delivery pipe 6 to the fuel tank 1 via the return line 9 does not pass through the second regulator 22 after passing through the first regulator 21. Flows into the fuel tank 1 without passing through the bypass passage 23. As a result, the fuel pressure of the LPG in the delivery pipe 6 is maintained at a constant pressure for one regulator. On the other hand, the LPG returned from the delivery pipe 6 to the fuel tank 1 via the return line 9 by closing the third shut-off valve 24 is the first regulator 21 and the second regulator 22. ) And flow into the fuel tank (1). Thereby, the fuel pressure of LPG in the delivery pipe 6 is maintained at the constant pressure for two regulators. In other words, when the third shut-off valve 24 is closed, the fuel pressure of the LPG in the delivery pipe 6 is raised from the normal state. The end of the return line 9 is disposed in the fuel tank 1, and a check valve 25 is formed to prevent backflow of the LPG.

Each injector 4 described above and each ignition coil 14 incorporating an igniter are connected to each electronic control unit (ECU) 40. The various sensors 41 to 47 provided on the engine 3 and the like correspond to driving state detection means for detecting the driving state of the engine 3, and are connected to the ECU 40, respectively. That is, the throttle sensor 41 formed in the throttle valve 10 detects the opening degree (throttle opening degree TA) of the throttle valve 10, and outputs the electric signal according to the detected value. The air flow meter 42 formed in the intake passage 7 detects the air flow rate Qa flowing through the intake passage 7 and outputs an electric signal corresponding to the detected value. The water temperature sensor 43 formed in the engine 3 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 3, and outputs an electric signal corresponding to the detected value. The rotational speed sensor 44 formed in the engine 3 detects the rotational speed (engine rotational speed) NE of the crankshaft 16 and outputs an electric signal in accordance with the detected value. The oxygen sensor 45 formed in the exhaust passage 15 detects the oxygen concentration (output voltage; Ox) in the exhaust gas discharged to the exhaust passage 15, and outputs an electric signal in accordance with the detected value. The ignition switch (IG · SW) 46 formed in the driver's seat is turned ON at the start of the engine 3 to supply electric power from the battery 31 to the ECU 40. The starter switch 47 formed in the starter 17 outputs a starter signal in accordance with the start of the starter 17, that is, during cranking.

 In this embodiment, the ECU 40 inputs various signals output from the various sensors 41 to 47 described above. The ECU 40 outputs an injection signal to each injector 4 and performs an igniter of each ignition coil 14 on the basis of these input signals to output LPG injection control, ignition timing control, and the like. Output an ignition signal.

Here, LPG injection control controls LPG injection amount by the injector 4 formed in each cylinder # 1-# 4, and its injection time based on the operating state of the engine 3. Therefore, in the ECU 40, the LPG injection amount corresponding to the operating state of the engine 3 is calculated. With the ignition timing control, the ignition plug 12 of each cylinder # 1-# 4 is controlled by controlling the igniter of the ignition coil 14 in each cylinder # 1-# 4 according to the operation state of the engine 3. ) To control the ignition timing.

Here, since LPG has a large change in properties with respect to temperature and pressure compared with gasoline, the amount of injection in accordance with the temperature and pressure of the LPG in order to accurately calculate the fuel amount of the LPG in the liquid state injected from each injector 4. Needs to be corrected. Therefore, in this embodiment, in order to detect the temperature state and the pressure state of LPG of a liquid state, the tank fuel temperature sensor 48 and the tank fuel pressure sensor 49 are formed in the fuel tank 1. The tank fuel temperature sensor 48 detects the temperature (in-tank fuel temperature; Tt) of LPG in the liquid state stored in the fuel tank 1, and outputs an electric signal in accordance with the detected value. The tank fuel temperature sensor 48 corresponds to the first fuel temperature detecting means of the present invention. The tank fuel pressure sensor 49 detects the pressure (in-tank fuel pressure; Pt) of the LPG in the liquid state stored in the fuel tank 1, and outputs an electric signal in accordance with the detected value. The tank fuel pressure sensor 49 corresponds to the fuel pressure detecting means of the present invention. Moreover, the delivery fuel temperature sensor 50 and the delivery fuel pressure sensor 51 are provided in the delivery pipe 6. The delivery fuel temperature sensor 50 detects the temperature of the liquid phase LPG (delivery fuel temperature; Td) in the delivery pump 6, and outputs an electric signal corresponding to the detected value. The delivery fuel pressure sensor 51 detects the pressure (LPD in delivery) Pd of the liquid phase state in the delivery pipe 6, and outputs an electric signal according to the detected value. The delivery fuel temperature sensor 50 is corresponded to the 2nd fuel temperature detection means of this invention. These sensors 48 to 51 are connected to the ECU 40, respectively. In addition, the fuel pump 2 and the first to third shut-off valves 18, 20, and 24 described above are connected to the ECU 40, respectively. In the LPG injection control, the ECU 40 executes a process of correcting the fuel injection amount according to the composition, the properties, and the like of the LPG, based on various signals output from these sensors 48 to 51. In particular, in this embodiment, the ECU 40 includes the vapor in the liquid phase LPG based on the fuel state detected by the sensors 48 to 51 formed in the fuel tank 1 and the delivery pipe 6. The mixing ratio of vapor) is estimated, and the amount of fuel injected from the fuel injection device, that is, the delivery pipe 6 and each injector 4, is corrected according to the estimated mixing ratio. ECU 40 which performs this correction is corresponded to the steam correction means of this invention.

The ECU 40 includes a central processing unit (CPU), a read output dedicated memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit, an external output circuit, and the like, respectively. The ECU 40 constitutes a logic arithmetic circuit formed by connecting a CPU, a ROM, a RAM, a backup RAM, an external input circuit, an external output circuit, and the like by a bus. Each ROM memorize | stores predetermined control programs concerning various control in advance. Each RAM temporarily stores the calculation result of each CPU. Each backup RAM stores data stored in advance. Each CPU executes the above-described various control and the like according to a predetermined control program based on signals from various sensors 41 to 51 inputted through the input circuit.

Here, the LPG fuel injection control executed by the ECU 40 will be described in detail. 2 shows the contents of the LPG fuel injection control in a flowchart.

First, ECU 40 waits for IG.SW46 to be turned ON in step 100, and determines whether cranking is started based on the presence or absence of a starter signal from starter switch 47 in step 110. FIG. And when it is not cranking start, ECU 40 returns a process to step 100. FIG. In the case of cranking start, the ECU 40 proceeds to step 120.

In step 120 the ECU 40 estimates the fuel composition Fc from the in-tank fuel pressure Pt and the in-tank fuel temperature Tt detected by each sensor 48, 49. The ECU 40 estimates the fuel composition Fc according to the values of the in-tank fuel pressure Pt and the in-tank fuel temperature Tt by referring to the fuel composition map (not shown) obtained experimentally in advance.

Next, in step 130, the ECU 40 performs a liquid phase in the delivery pipe 6 from the delivery fuel temperature Td detected by the delivery fuel temperature sensor 50 and the estimated fuel composition Fc. Regarding the LPG in the state, the fuel liquid density correction coefficient σd is calculated. This fuel liquid density correction coefficient (σd) reflects the value which estimated the fuel liquid density of LPG of the liquid state in the delivery pipe 6.

Next, in step 140, the ECU 40 selects a vapor in the delivery pipe 6 from the delivery fuel temperature Td detected by the delivery fuel temperature sensor 50 and the estimated fuel composition Fc. The correction coefficient Kv is calculated. In this embodiment, the ECU 40 calculates the vapor correction coefficient Kv in accordance with the values of the in-delivery fuel temperature Td and the fuel composition Fc by referring to the correction map shown in FIG. 3. In the correction map of FIG. 3, a large number of curves show a difference in fuel composition Fc, and the larger the curve located above each curve, the larger the propane ratio. In addition, it can be seen that the fuel composition Fc represented by each curve also decreases in vapor delivery correction coefficient Kv as the delivery fuel temperature Td is lower, making it difficult to generate vapor. Therefore, the vapor correction coefficient Kv obtained from this correction map suitably reflects the estimation of the vapor mixing ratio with respect to the LPG in the liquid state in the delivery pipe 6.

Next, in step 150, the ECU 40 calculates the starting injection amount Ts at start-up reflecting the cooling water temperature THW from the cooling water temperature THW detected by the water temperature sensor 43. The ECU 40 calculates the starting basic injection amount Ts according to the value of the cooling water temperature THW by referring to the starting basic injection amount map (not shown) obtained in advance experimentally. For example, at the time of cold start-up, the basic injection amount at the time of start-up is computed from the necessity of warming-up. In addition, at the time of restarting after a warm air, the starting basic injection amount less than cold starting is calculated.

Next, in step 160, the ECU 40 calculates the starting injection amount TAUs by multiplying the calculated starting initial injection amount Ts, the fuel liquid density correction coefficient σd, and the vapor correction correction coefficient Kv. do. That is, the starting injection amount TAUs is obtained by correcting the starting basic injection amount Ts determined according to the cooling water temperature THW by the liquid density correction coefficient σd and the vapor correction correction coefficient Kv.

And in step 170, ECU 40 controls each injector 4 based on the calculated start-up injection amount TAUs, so as to start engine 3 from each injector 4, engine 3 Injection amount of the fuel required for each of the cylinders (# 1 to # 4).

Thereafter, the ECU 40 determines whether the engine rotational speed NE detected by the rotational speed sensor 44 has exceeded the predetermined reference rotational speed NE1 in step 180. And if this determination is negative, it is assumed that the start of the engine 3 is not completed, and the ECU 40 returns the process to step 110. If the result of the determination is affirmative, it is assumed that the start of the engine 3 is completed, and the ECU 40 proceeds to step 190.

In step 190, the ECU 40 estimates the fuel composition Fc from the in-tank fuel pressure Pt and the in-tank fuel temperature Tt detected by the respective sensors 48 and 49 again.

Next, in step 200, the ECU 40 performs a liquid phase in the delivery pipe 6 from the delivery fuel temperature Td detected by the delivery fuel temperature sensor 50 and the estimated fuel composition Fc. Regarding the LPG in the state, the fuel liquid density correction coefficient σd is calculated. This fuel liquid density correction coefficient (σd) also reflects the value which estimated the fuel liquid density of LPG of the liquid state in the delivery pipe 6.

Next, in step 210, the ECU 40 receives a vapor in the delivery pipe 6 from the delivery fuel temperature Td detected by the delivery fuel temperature sensor 50 and the estimated fuel composition Fc. The correction coefficient Kv is calculated. This vapor correction coefficient Kv also reflects the value which estimated the vapor mixing ratio of LPG of the liquid state in the delivery pipe 6.

Next, in step 220, ECU 40 calculates the basic injection amount Ta after starting from the intake amount Qa detected by air flow meter 42 according to the intake amount Oa. The ECU 40 calculates the post-start basic injection amount Tas according to the value of the intake air amount Qa by referring to the post-start basic injection amount map (not shown) experimentally obtained in advance. For example, when the amount of intake air Qa is large, a large amount of basic injection amount Ta after starting is calculated as compared with when the amount of intake air Qa is small.

Next, in step 230, the ECU 40 calculates the post-start injection amount TAUas by multiplying the calculated post-start basic injection amount Tas, fuel liquid density correction coefficient σd and vapor correction coefficient Kv. do. That is, the post-starting injection amount TAUsa is obtained by correcting the post-start basic injection amount Tas determined according to the intake air amount Qa by the liquid density correction coefficient sigma d and the vapor correction correction coefficient Kv.

In step 240, the ECU 40 controls the injectors 4 based on the calculated post-start injection amount TAUas, so as to drive the engine 3 after starting, from the injectors 4 to the engines. The amount of fuel required for each of the cylinders # 1 to # 4 of (3) is injected and supplied.

Thereafter, the ECU 40 returns the processing to step 210 and repeats the processing of steps 190 to 240.

According to the fuel supply apparatus of the engine in this embodiment described above, LPG in the liquid state conveyed from the fuel tank 1 to the delivery pipe 6 and each injector 4 is the fuel in the delivery pipe 6. According to the condition, the basic injection amount Ts at start-up and the basic injection amount Tas after start-up are corrected, and from each injector 4 to the engine 3 by the starting injection amount TAUs and post-starting injection amount TAUas after the correction. Fuel is injected and supplied.

Here, during operation of the engine 1, a portion of the LPG in the pipe 6 may evaporate and vapor may be mixed into the liquid phase LPG by the heat received by the delivery pipe 6 from the engine 3. . According to the fuel supply device of this embodiment, the ECU 40 estimates the vapor mixing ratio in LPG in the liquid state based on the fuel state detected by the delivery pipe 6, and estimates the vapor mixing ratio in the estimated vapor mixing ratio. Therefore, the basic injection amount Ts at the start and the basic injection amount Ta after the start are corrected. Therefore, the fuel 3 is supplied to the engine 3 in the amount of the vapor powder mixed in the LPG in the liquid state (fuel injection amount TAUs at start-up and fuel injection amount TAUas after start-up). For this reason, the vapor mixing content in LPG of a liquid state can be anticipated, and the fuel supply amount to the engine 3 can be controlled with high precision. Thereby, the dispersion | variation in the air fuel ratio in the engine 3 can be suppressed. On the other hand, in the fuel supply apparatus of the prior art, since the correction which anticipated the above-mentioned vapor mixing content was not performed at all, but the fuel injection amount was corrected on the premise of a completely liquid state, the fuel injection amount was only changed by the vapor mixing amount. Is inevitable, and variations in the air-fuel ratio in the engine 3 could not be avoided. In the fuel supply device of this embodiment, the point can be improved.

In particular in this embodiment, the ECU 40 estimates the fuel composition Fc from the in-tank fuel temperature Tt and the in-tank fuel pressure Pt and estimates the estimated fuel composition Fc and the in-delivery fuel temperature. Since the fuel liquid density and vapor mixing ratio in the delivery pipe 6 are estimated from the fuel liquid density correction coefficient σd and the vapor correction coefficient Kv calculated from (Td), vapor in the liquid phase LPG The mixing ratio is more accurately estimated. In addition, since the basic injection amount Ts at startup and the basic injection amount Ta after startup are corrected according to their estimated fuel liquid density and vapor mixing ratio, a more accurate amount of fuel is supplied to the engine 3. In this sense, the control accuracy of the fuel supply amount to the engine 3 can be further increased, and the variation in the air-fuel ratio in the engine 3 can be suppressed.

In addition, this invention is not limited to the said embodiment, It can implement as follows in the range which does not deviate from the meaning of invention.

(1) In the above embodiment, the present invention is embodied as a four-cylinder engine 3, but can also be embodied by an engine having a number of cylinders other than four-cylinder.

(2) Although LPG was used as the fuel in the above embodiment, LNG can also be used as the fuel.

According to the invention described in claim 1, the amount of fuel supplied to the engine can be controlled with high precision in anticipation of the vapor mixing content in the fuel in the liquid state.

According to the invention described in claim 2, the control accuracy of the fuel supply amount to the engine can be further improved with respect to the effect of the invention according to claim 1.

Claims (2)

A fuel supply device for an engine configured to pressurize fuel stored in a liquid state in a fuel tank to a fuel injection device and to correct a fuel injection amount supplied from the fuel injection device to an engine based on the fuel state detected by the detection means. To The fuel injection device estimates the mixing ratio of steam in the fuel in the liquid state based on the fuel state detected by the detecting means as the fuel injection device, and corrects the fuel injection amount from the fuel injection device according to the estimated mixing ratio. A fuel supply device for an engine, characterized by comprising a steam compensating means. The fuel tank according to claim 1, wherein the detecting means comprises: first fuel temperature detecting means for detecting fuel temperature in the fuel tank, fuel pressure detecting means for detecting fuel pressure in the fuel tank, and the fuel powder. Second fuel temperature detecting means for detecting fuel temperature in the using device, The steam correction means estimates the fuel composition from the fuel temperature and the fuel pressure in the detected fuel tank, and the fuel in the fuel injection device from the estimated fuel composition and the fuel temperature in the detected fuel injection device. And a fuel injection amount from the fuel injection device is corrected according to the estimated fuel liquid density and the mixing ratio.

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