JP2009250206A - Liquefied gas fuel supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefied gas fuel supply device capable of accurately calculating and updating a fuel composition of liquefied gas fuel in a fuel tank. <P>SOLUTION: This fuel supply device 10 is provided with a fuel temperature sensor 21 for detecting the temperature of LPG fuel in the fuel tank 11, a fuel pressure sensor 22 for detecting pressure of the LPG fuel in the fuel tank 11 and an ECU 20 for calculating and updating a propane rate of the LPG fuel in the fuel tank 11 based on each detection value of the fuel temperature sensor 21 and the fuel pressure sensor 22. The ECU 20 inhibits the update of the propane rate till the lapse of a prescribed period after starting an engine and updates the propane rate when the prescribed period elapses. <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 accurately calculate and update the composition of liquefied gas fuel.

In recent years, vehicles equipped with engines using liquefied gas as fuel have been put into practical use. An example of a liquefied gas fuel supply device that supplies liquefied gas to an engine using liquefied gas as a fuel is disclosed in Patent Document 1. In the liquefied gas fuel supply device disclosed here, every time the ignition switch (IG) is turned ON, the fuel temperature and fuel pressure in the fuel tank are detected, and the fuel composition (propane rate in the case of LPG fuel) is detected therefrom. Is calculated and updated, and fuel injection is controlled based on the updated fuel composition. Here, the LPG fuel is a mixed fuel of propane and butane, and the propane ratio in the LPG fuel refers to a molar ratio of propane fuel. Thereby, in this liquefied gas fuel supply device, even when the fuel composition changes, it is possible to perform appropriate fuel injection commensurate with it.
JP 2001-107805 A

  However, in the above-described liquefied gas fuel supply device, there is a case where the composition of the liquefied gas fuel cannot be accurately calculated and updated. For example, when the fuel temperature in the fuel tank becomes uneven, the fuel temperature in the fuel tank cannot be accurately detected (detection error becomes large), and the fuel temperature having a large error is used. Since the fuel composition is calculated, the composition of the liquefied gas fuel cannot be calculated with high accuracy. That is, an error between the calculated fuel composition and the actual fuel composition increases.

  Here, as the case where the fuel temperature in the fuel tank becomes non-uniform, it can be considered that the fuel is replenished, the return fuel is mixed in the fuel tank, or the influence of the outside air. In such a case, the fuel temperature is locally high or low only in the vicinity of the fuel temperature detection unit with respect to the average fuel temperature in the fuel tank (fuel temperature when the temperature distribution is uniform), Until the liquefied gas fuel is sufficiently stirred in the fuel tank, the fuel temperature is not uniform. Therefore, it becomes impossible to accurately detect the fuel temperature in the fuel tank.

  As a result of not being able to accurately detect the fuel temperature in the fuel tank, if the composition of the liquefied gas fuel cannot be accurately calculated and updated, appropriate fuel injection cannot be performed, and fuel injection control Sexuality will deteriorate. As a result, the startability of the engine may be deteriorated or rough idle may occur.

  Accordingly, the present invention has been made to solve the above-described problems, and provides a liquefied gas fuel supply device capable of accurately calculating and updating the fuel composition of the liquefied gas fuel in the fuel tank. Is an issue.

  The liquefied gas fuel supply apparatus according to the present invention, which has been made to solve the above problems, is configured to supply the liquefied gas fuel pumped out by a fuel pump from a fuel tank in which the liquefied gas fuel is stored, to the injector. In the liquefied gas fuel supply device for injecting and supplying from the fuel to the engine, fuel temperature detecting means for detecting the temperature of the liquefied gas fuel in the fuel tank, and fuel pressure detecting means for detecting the pressure of the liquefied gas fuel in the fuel tank; The fuel composition calculating means for calculating the composition of the liquefied gas fuel in the fuel tank based on the detected values of the fuel temperature detecting means and the fuel pressure detecting means, and the fuel composition newly calculated by the fuel composition calculating means. Fuel composition update means for updating the previously calculated fuel composition to the currently calculated fuel composition when calculated, and updating the fuel composition Stage, and performs updating of the fuel composition when the predetermined time period after the engine start has elapsed.

  In this liquefied gas fuel supply device, the temperature of the liquefied gas fuel in the fuel tank is detected by the fuel temperature detecting means, and the pressure of the liquefied gas fuel in the fuel tank is detected by the fuel pressure detecting means. Then, the composition of the liquefied gas fuel in the fuel tank is calculated by the fuel composition calculating means based on the detected values of the fuel temperature detecting means and the fuel pressure detecting means. This fuel composition is calculated using the saturated vapor pressure curve of the liquefied gas fuel. The calculation of the fuel composition by the fuel composition calculation means is performed at least every time the engine is started (each time the ignition switch is turned on).

  The fuel composition update means updates the fuel composition previously calculated by the fuel composition calculation means to the fuel composition calculated this time when a predetermined period has elapsed after engine startup. Thus, after the engine is started, the fuel composition can be updated after the liquefied gas fuel in the fuel tank is stirred by the fuel pump or the like and the fuel temperature becomes uniform. As a result, it is possible to prevent the fuel composition from being calculated and updated when the fuel temperature in the fuel tank is not uniform. In addition, since the fuel composition is updated when a predetermined period has elapsed after the engine is started, the fuel composition is not updated when the engine is started, and the fuel composition updated at the previous engine start (during operation) remains unchanged. Used for fuel injection control at engine startup. Since the fuel composition in the fuel tank hardly changes unless refueling is performed, the fuel composition updated during the previous engine operation (starting) is used for fuel injection control during the current engine starting. However, controllability does not deteriorate. For these reasons, the composition of the liquefied gas fuel in the fuel tank can always be calculated and updated with high accuracy. As a result, deterioration of the fuel injection controllability can be prevented.

  Here, in the liquefied gas fuel supply apparatus according to the present invention, the predetermined period may be a period until the fuel temperature distribution in the fuel tank becomes substantially uniform after the engine is started.

  By determining the predetermined period as described above, the fuel composition can be calculated and updated after the fuel temperature in the fuel tank becomes uniform after the engine is started. As a result, it is possible to reliably prevent the fuel composition from being calculated and updated when the fuel temperature in the fuel tank is not uniform. Therefore, the composition of the liquefied gas fuel in the fuel tank can always be calculated and updated with high accuracy.

  Another type of liquefied gas fuel supply device according to the present invention, which has been 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. In the liquefied gas fuel supply apparatus for injecting and supplying the engine from the injector, fuel temperature detecting means for detecting the temperature of the liquefied gas fuel in the fuel tank, and fuel pressure for detecting the pressure of the liquefied gas fuel in the fuel tank A fuel composition calculation means for calculating the composition of the liquefied gas fuel in the fuel tank based on the detection values of the detection means, the fuel temperature detection means and the fuel pressure detection means; and the fuel composition calculation means. Fuel composition updating means for updating the previously calculated fuel composition to the currently calculated fuel composition when the fuel composition is calculated, Formed updating means, and performs updating of the fuel composition when it reaches a predetermined vehicle speed after the engine is started.

  Also in this liquefied gas fuel supply device, the temperature of the liquefied gas fuel in the fuel tank is detected by the fuel temperature detecting means, and the pressure of the liquefied gas fuel in the fuel tank is detected by the fuel pressure detecting means. Then, the composition of the liquefied gas fuel in the fuel tank is calculated by the fuel composition calculating means based on the detected values of the fuel temperature detecting means and the fuel pressure detecting means.

  Thereafter, when the vehicle speed reaches a predetermined speed after the engine is started by the fuel composition update means, the fuel composition is newly calculated and updated by the fuel composition calculation means. Thus, after the engine is started, the fuel composition can be updated after the liquefied gas fuel in the fuel tank is agitated by the swing of the vehicle and the fuel temperature becomes uniform. As a result, it is possible to prevent the fuel composition from being calculated and updated when the fuel temperature in the fuel tank is not uniform. In addition, since the fuel composition is updated when the predetermined vehicle speed is reached after the engine is started, the fuel composition is not updated when the engine is started, and the fuel composition updated during the previous engine operation (starting) is not changed. Used for fuel injection control at start-up. Since the fuel composition in the fuel tank hardly changes unless refueling is performed, the fuel composition updated during the previous engine operation (starting) is used for fuel injection control during the current engine starting. However, controllability does not deteriorate. For these reasons, the composition of the liquefied gas fuel in the fuel tank can always be calculated and updated with high accuracy. As a result, deterioration of the fuel injection controllability can be prevented.

  In the above-described liquefied gas fuel supply apparatus, the fuel composition update unit is configured such that the difference between the fuel composition calculated this time by the fuel composition calculation unit and the fuel composition calculated last time is equal to or greater than a predetermined value. It is desirable to update the fuel composition when starting the engine.

  If the fuel composition changes greatly due to fuel replenishment while the engine is stopped, the fuel composition error will become large if the fuel composition is not newly calculated and updated at the next engine start. The injection controllability deteriorates. A case where the fuel composition is largely changed by refueling may be, for example, a case where a liquefied gas fuel of a cold district specification is replenished with normal liquefied gas fuel in the fuel tank. It is done.

  Therefore, when the difference between the fuel composition calculated this time by the fuel composition calculation means and the fuel composition calculated last time (updated) is equal to or greater than a predetermined value, the fuel composition is updated at the time of engine start by the fuel composition update means. Thus, an error from the actual fuel composition can be eliminated. That is, the fuel composition can be accurately calculated and updated. As a result, even when the fuel is replenished and the fuel composition changes greatly, the fuel injection controllability at the start of the engine and thereafter does not deteriorate.

  According to the liquefied gas fuel supply apparatus according to the present invention, as described above, the fuel composition of the liquefied gas fuel in the fuel tank can be accurately calculated and updated, and the fuel injection controllability is deteriorated at the time of engine start. Can be prevented.

  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.

(First embodiment)
First, the first embodiment will be described. Therefore, the configuration of the LPG fuel supply apparatus according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing a schematic configuration of an LPG fuel supply apparatus according to the first embodiment. FIG. 2 is a diagram showing the arrangement positions of the fuel pump, the fuel temperature sensor, and the fuel pressure sensor in the fuel tank.

  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 LPG 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 temperature sensor 21 and the fuel pressure sensor 22 are installed at the bottom of the fuel tank 11 as shown in FIG. This is because even when the LPG fuel in the fuel tank 11 is reduced, it is necessary to always be submerged so that the temperature and pressure of the LPG fuel can be detected.

  The fuel pipe 13 connects the fuel pump 12 and the branch pipe 14. The fuel pump 12 pumps out the LPG fuel from the fuel tank 11 and pumps it to each injector 16 via the fuel pipe 13 and the branch pipe 14. The fuel pump 12 is installed at the bottom of the fuel tank 11 as shown in FIG. Thereby, even when the LPG fuel in the fuel tank decreases, the LPG fuel can be surely pumped out.

  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 the LPG fuel stored in the fuel tank 11 and injects it. For this purpose, the fuel pump 12 installed at the bottom of the fuel tank 11 pumps LPG fuel from the bottom of the fuel tank 11 and guides the pumped LPG fuel to each injector 16 via the branch pipe 14. ing.

  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 other end of the return pipe 15 is opened at the upper part in the fuel tank 11. Thereby, the return pipe 15 is configured to return all or part of the LPG fuel pressure-fed to each injector 16 through the fuel pipe 13 and the branch pipe 14 to the fuel tank 11. For this reason, when each injector 16 is operating, the LPG fuel that has been pumped to each injector 16 and has not been injected passes through each injector 16 and then returns to the fuel tank 11 via the return pipe 15. It is like that. Thus, when LPG 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.

  The ECU 20 comprehensively controls the fuel supply device 10 described above. Therefore, the ECU 20 receives 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 (including the vehicle speed signal). It has become. 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.

  The ECU 20 receives the output signal from the fuel temperature sensor 21 and the output signal from the fuel pressure sensor 22 and calculates the propane rate (fuel composition) of the LPG fuel in the fuel tank 11 based on these signals. That is, the ECU 20 corresponds to the “fuel composition calculating means” of the present invention. Further, the ECU 20 also updates the calculated propane rate (including determination of the update time). That is, the ECU 20 corresponds to the “fuel composition update means” of the present invention.

  Subsequently, the operation of the fuel supply apparatus 10 having the above-described configuration will be briefly described. When the ignition switch (IG) is turned on, the ECU 20 inputs detection signals from the fuel temperature sensor 21 and the fuel pressure sensor 22 and uses the saturated vapor pressure curve of the LPG based on the detection signals to enter the fuel tank 11. The propane rate of the LPG fuel is calculated and stored (updated). Thereafter, when the fuel pump 12 is driven, the LPG fuel in the fuel tank 11 is pumped up and supplied to the fuel pipe 13 and the branch pipe 14. Then, the ECU 20 outputs a command to each injector 16 in consideration of the updated propane rate. When the injector 16 is operated based on a command from the ECU 20, LPG fuel is injected and supplied to the engine to drive the engine. During engine operation, part of the fuel in the branch pipe 14 is returned to the fuel tank 11 via the return pipe 15.

  Here, when the idling operation is performed for a long time, the return fuel warmed by heat generated from the engine or the like is returned into the fuel tank 11. On the other hand, a relatively low temperature LPG fuel in the fuel tank 11 is supplied to the injector 16. Therefore, when the engine is restarted after idling for a long period of time, the temperature of the LPG fuel in the fuel tank 11 becomes non-uniform (a temperature difference occurs between the upper part and the lower part). Further, even when the fuel is replenished, the temperature of the LPG fuel in the fuel tank 11 becomes non-uniform.

  In this way, the composition of the LPG fuel has not changed, but the ECU 20 calculates the propane rate of the LPG fuel in the fuel tank 11 at the next engine start when the temperature of the LPG fuel in the fuel tank 11 is not uniform. If updated, a large error may occur with respect to the actual fuel composition. As a result, there is a possibility that the controllability of fuel injection by the fuel supply device 10 at the time of engine start is deteriorated.

  On the other hand, when fuels with different fuel properties are replenished, the fuel composition of LPG changes greatly. In such a case, if the ECU 20 does not calculate and update the propane rate of the LPG fuel in the fuel tank 11 at the next engine start, a large error occurs with respect to the actual fuel composition, and the engine start There is a possibility that the controllability of fuel injection by the fuel supply device 10 will deteriorate.

  For this reason, the fuel supply apparatus 10 according to the present embodiment controls the update timing of the propane rate used by the ECU 20 for fuel injection control so that the controllability of fuel injection by the fuel supply apparatus 10 does not deteriorate. . Therefore, the propane rate update control in the fuel supply device 10 will be described with reference to FIG. FIG. 3 is a flowchart showing the content of the propane rate update control.

  As shown in FIG. 3, in the fuel supply device 10, when the IG is turned on (step 1), the ECU 20 determines the LPG fuel in the fuel tank 11 based on the output signals from the fuel temperature sensor 21 and the fuel pressure sensor 22. Obtain temperature and pressure (step 2). Then, the ECU 20 calculates and stores the propane rate of the LPG fuel in the fuel tank 11 based on the fuel temperature and fuel pressure acquired in step 2 (step 3).

  Next, the ECU 20 compares the propane rate calculated this time with the propane rate at the previous update, and determines whether or not the difference is less than a predetermined value Pc (for example, about 30%) (step 4). In the process of step 4, the presence or absence of refueling of LPG fuel having greatly different fuel properties is determined. At this time, if the difference in the propane rate is less than the predetermined value Pc, that is, if LPG fuel is not significantly different in fuel properties (S4: YES), the ECU 20 uses the propane rate used for fuel injection control. Is prohibited (step 5), and the next processing is executed. In other words, the propane rate that was used during the previous engine operation (if updated during engine operation, the updated propane rate), in other words, the propane rate that was used immediately before the engine stopped is used as is, and the engine is started. Fuel injection control at the time is performed, and the engine is started.

  On the other hand, when the difference between the propane rates is equal to or greater than the predetermined value Pc, that is, when the LPG fuel having greatly different fuel properties is supplied (S4: NO), the ECU 20 updates the propane rate used for fuel injection control. Then (step 6), the following processing is executed. That is, the updated propane rate, in other words, the propane rate calculated in step 3 is used to perform fuel injection control at the time of engine start, and the engine is started.

  Then, after the engine is started, the ECU 20 determines whether or not a predetermined time has elapsed (step 7). Here, as the predetermined time, a time required for the temperature of the LPG fuel in the fuel tank 11 to be uniform may be set. Further, the predetermined time may be changed in consideration of the operating state of the engine. In the present embodiment, it is determined that a predetermined time has elapsed when about 1 minute has elapsed since the engine was started.

  Thereafter, when a predetermined time has elapsed (S7: YES), the ECU 20 acquires the temperature and pressure of the LPG fuel in the fuel tank 11 based on the output signals from the fuel temperature sensor 21 and the fuel pressure sensor 22 (step 8). Next, the ECU 20 calculates and stores the propane rate of the LPG fuel in the fuel tank 11 based on the fuel temperature and fuel pressure acquired in step 8 (step 9). Then, the ECU 20 updates the propane rate (step 10). Thus, the updated propane rate, in other words, the propane rate calculated in step 9 is used, and the subsequent fuel injection control is performed.

  Here, changes in various signals and a propane rate when the above-described control is performed will be described with reference to FIGS. 4 and 5. FIG. 4 is a timing chart showing various signals and changes in the propane rate when the temperature of the LPG fuel in the fuel tank becomes uneven. FIG. 5 is a timing chart showing changes in various signals and a propane rate when LPG fuels having different fuel properties are replenished.

  First, with reference to FIG. 4, a description will be given of a case where LPG fuel is not replenished during IG-OFF and the temperature of the LPG fuel in the fuel tank becomes uneven. In such a case, before IG is turned OFF at time t0, the fuel injection control is performed using the propane rate updated during engine operation. At this time, the temperature of the LPG fuel in the fuel tank 11 is uniform, and the average fuel temperature (fuel temperature when the temperature distribution is uniform) Ta of the LPG fuel and the fuel temperature Ts detected by the fuel temperature sensor 21 are equal. . While the engine is stopped (between times t0 and t1), the temperature of the LPG fuel near the fuel temperature sensor 21, that is, near the lower portion of the fuel tank 11, rises (for example, about 3 to 5 ° C.). As such a situation, for example, a case where the lower part of the fuel tank 11 is warmed by geothermal heat (radiant heat from asphalt, etc.) in summer can be considered. In such a case, the average fuel temperature Ta of the LPG fuel in the fuel tank 11 hardly changes, but the fuel temperature Ts detected by the fuel temperature sensor 21 rises, and the fuel temperature in the fuel tank 11 is reduced. It cannot be detected accurately.

  When the IG is turned on at time t1, the propane rate is calculated by the ECU 20 (S1 to S3 in FIG. 3). At this time, the fuel temperature Ts detected by the fuel temperature sensor 21 at the time of IG-ON is higher than the average fuel temperature Ta of the LPG fuel in the fuel tank 11. For this reason, the propane rate calculated by the ECU 20 at the time of IG-ON has an error (about 10 to 20%) with respect to the actual propane rate (see white circles and broken lines shown in FIG. 4). Therefore, if the propane rate is updated at time t2 (when IG-ON) as in the prior art (see the white circles shown in FIG. 4), the controllability of fuel injection is deteriorated.

  On the other hand, since the fuel supply apparatus 10 is not refueled, the propane rate at time t1 (IG-ON) and the propane rate at the previous update (propane rate at the previous IG-OFF) ) Is less than a predetermined value Pc (for example, 30%), the update of the propane rate is prohibited (S4 in FIG. 3: YES, S5). As a result, the fuel injection control is executed using the propane rate updated last time as it is. As a result, the propane rate used for fuel injection control hardly causes an error with respect to the actual propane rate Pr (see the solid line between times t1 and t2 shown in FIG. 4). It is possible to prevent the controllability from deteriorating. Therefore, stable engine start and idling operation can be performed without deteriorating engine startability or generating rough idle.

  Thereafter, the LPG fuel in the fuel tank 11 is agitated by the operation of the fuel pump 12 and the like by operating the engine. For this reason, the fuel temperature of the LPG fuel in the fuel tank 11 becomes uniform. Then, the fuel temperature Ts detected by the fuel temperature sensor 21 at time t2 is substantially the same as the average temperature Ta of the LPG fuel in the fuel tank 11. That is, it can be said that the fuel temperature of the LPG fuel in the fuel tank 11 becomes uniform after a predetermined time has elapsed since the engine was started (S7 in FIG. 3: YES).

  Then, in a state where the fuel temperature of the LPG fuel in the fuel tank 11 is uniform, the ECU 20 calculates the propane rate and updates the propane rate (see S8 to S10 in FIG. 3 and the black circles shown in FIG. 4). . As a result, after time t2, the fuel injection control is executed using the updated propane rate. As a result, there is almost no error with respect to the actual propane rate Pr even after time t2 (see the black circle shown in FIG. 4 and the solid line after time t2), so the controllability of fuel injection does not deteriorate. Stable operation of the engine can be ensured.

  As described above, the fuel supply device 10 calculates and updates the propane rate of the LPG fuel in the fuel tank 11 in a state where the temperature of the LPG fuel in the fuel tank 11 becomes uniform. Therefore, the propane rate of the LPG fuel in the fuel tank 11 can be accurately calculated and updated. As a result, deterioration of the fuel injection controllability can be prevented.

  Here, if refueling is performed while the engine is stopped and the propane rate changes greatly, the propane rate will not be updated at the next engine start (see the white circle shown in FIG. 5), and an error from the actual propane rate Pr. As a result, the fuel injection controllability deteriorates. In addition, when fuel is replenished and the propane rate changes greatly, for example, LPG fuel for cold regions (fuel with a high propane rate) is replenished with normal LPG fuel in the fuel tank. The case may be considered.

  Then, the case where the LPG fuel from which a fuel property greatly differs is replenished during IG-OFF is demonstrated referring FIG. In such a case, before IG is turned OFF at time t0, the fuel injection control is performed using the propane rate updated during engine operation. When fuel supply is started from time t1 when the engine is stopped, the temperature and pressure of the LPG fuel in the fuel tank 11 both start to rise. In addition, the actual propane rate Pr of the LPG fuel in the fuel tank also increases. Thereafter, when refueling is completed at time t2, the fuel temperature, fuel pressure, and propane rate become constant thereafter.

  When IG is turned on at time t3, the propane rate is calculated by the ECU 20 (S1 to S3 in FIG. 3). The propane rate calculated at this time has a difference from the propane rate at the previous update (the propane rate at the previous IG-OFF) is a predetermined value Pc (for example, 30%) or more, so the propane rate is updated. (S4 in FIG. 3: NO, S6, see the black circle shown in FIG. 5). As a result, after time t3, the updated propane rate is used and fuel injection control is executed. Thereby, it can prevent that the controllability of the fuel injection at the time of engine starting deteriorates. Therefore, stable engine start and idling operation can be performed without deteriorating engine startability or generating rough idle.

  After that, as described above, the ECU 20 calculates the propane rate and updates the propane rate in the state where the engine is operated and the fuel temperature of the LPG fuel in the fuel tank 11 becomes uniform (in FIG. 3). S8 to S10) Since the controllability of fuel injection is not deteriorated, stable operation of the engine can be ensured.

  As described above, in the fuel supply device 10, when LPG fuel having greatly different fuel properties is supplied, the fuel supply device 10 is updated to the propane rate calculated at the time of IG-ON. Therefore, the propane rate of the LPG fuel in the fuel tank 11 can be accurately calculated and updated. As a result, deterioration of the fuel injection controllability can be prevented.

  As described above in detail, the fuel supply apparatus 10 according to the first embodiment is configured when the difference between the propane rate calculated at the time of IG-ON and the propane rate at the previous update is less than the predetermined value Pc. Prohibits renewal of the propane rate until the LPG fuel temperature in the fuel tank 11 becomes uniform after a predetermined time has elapsed after the engine is started, and a new state is established when the temperature of the LPG fuel in the fuel tank 11 becomes uniform. The propane rate is calculated and updated. Thereby, the propane rate of the LPG fuel in the fuel tank 11 can be always calculated and updated with high accuracy. As a result, even when the temperature of the LPG fuel in the fuel tank 11 becomes uneven, it is possible to prevent deterioration of the fuel injection controllability at the time of starting the engine and thereafter.

  On the other hand, when the difference between the propane rate calculated at the time of IG-ON and the propane rate at the time of the previous update is equal to or greater than the predetermined value Pc, the fuel supply device 10 updates to the propane rate calculated at the time of IG-ON. . Thereby, the propane rate of the LPG fuel in the fuel tank 11 can be accurately calculated and updated. As a result, even when the fuel is replenished and the propane rate of the LPG fuel in the fuel tank 11 is greatly changed, it is possible to prevent the fuel injection controllability from deteriorating at the time of starting the engine.

(Second Embodiment)
Next, a second embodiment will be described. The basic configuration of the second embodiment is substantially the same as that of the first embodiment, but the content of update control of the propane rate is different. For this reason, in the following, the same components as those in the first embodiment will be denoted by the same reference numerals, description thereof will be omitted as appropriate, and differences will be mainly described.

  First, the update control of the propane rate in the fuel supply apparatus according to the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing the content of update control of the propane rate in the second embodiment.

  In the fuel supply apparatus according to the second embodiment, as shown in FIG. 6, when the IG is turned on (step 21), the ECU 20 determines the fuel based on the output signals from the fuel temperature sensor 21 and the fuel pressure sensor 22. The temperature and pressure of the LPG fuel in the tank 11 are acquired (step 22). Then, the ECU 20 calculates and stores the propane rate of the LPG fuel in the fuel tank 11 based on the fuel temperature and fuel pressure acquired in step 2 (step 23).

  Next, the ECU 20 compares the propane rate calculated this time with the propane rate at the previous update, and determines whether or not the difference is less than a predetermined value Pc (for example, about 30%) (step 24). In the process of step 24, the presence or absence of refueling of LPG fuel having greatly different fuel properties is determined. At this time, if the difference in the propane rate is less than the predetermined value Pc (S24: YES), the ECU 20 prohibits the update of the propane rate used for fuel injection control (step 25) and executes the next process. To do. In other words, the propane rate that was used during the previous engine operation (if updated during engine operation, the updated propane rate), in other words, the propane rate that was used immediately before the engine stopped is used as is, and the engine is started. Fuel injection control at the time is performed, and the engine is started.

  On the other hand, when the difference between the propane rates is equal to or greater than the predetermined value Pc (S24: NO), the ECU 20 updates the propane rate used for the fuel injection control (step 26) and executes the following process. That is, the updated propane rate, in other words, the propane rate calculated in step 3 is used to perform fuel injection control at the time of engine start, and the engine is started.

  Then, after the engine is started, the ECU 20 determines whether or not the vehicle speed is equal to or higher than the predetermined speed Vc (step 27). Here, as the predetermined speed Vc, for example, about 10 to 20 km / h may be set. If the vehicle speed becomes equal to or higher than the predetermined speed Vc, the LPG fuel in the fuel tank 11 is sufficiently agitated not only by the action of the fuel pump 12 but also by the swing of the vehicle, that is, the fuel tank 11, and the temperature of the LPG fuel becomes uniform. It is thought that.

  Thereafter, when the vehicle speed becomes equal to or higher than the predetermined speed Vc (S27: YES), the ECU 20 acquires the temperature and pressure of the LPG fuel in the fuel tank 11 based on the output signals from the fuel temperature sensor 21 and the fuel pressure sensor 22 (step). 28). Next, the ECU 20 calculates and stores the propane rate of the LPG fuel in the fuel tank 11 based on the fuel temperature and fuel pressure acquired in step 28 (step 29). Then, the ECU 20 updates the propane rate (step 30). Thus, the updated propane rate, in other words, the propane rate calculated in step 29 is used, and the subsequent fuel injection control is performed.

  Here, changes in various signals and propane ratio when the above-described control is performed will be described with reference to FIG. FIG. 7 is a timing chart showing various signals and changes in the propane rate when the temperature of the LPG fuel in the fuel tank becomes uneven.

  The IG is turned on at time t1, but at this time, the fuel temperature Ts detected by the fuel temperature sensor 21 is lower than the average fuel temperature Ta of the LPG fuel in the fuel tank 11, The fuel temperature in the fuel tank 11 cannot be detected accurately. Such a situation can be considered, for example, when the engine is stopped after idling for a long time and then the engine is started.

  Then, the propane rate is calculated by the ECU 20 (S1 to S3 in FIG. 3). At this time, since the fuel temperature Ts detected by the fuel temperature sensor 21 at the time of IG-ON is lower than the average fuel temperature Ta of the LPG fuel in the fuel tank 11, it is calculated by the ECU 20 at the time of IG-ON. The produced propane rate has an error (about 10 to 20%) with respect to the actual propane rate Pr (see white circles and broken lines shown in FIG. 7). Therefore, if the propane rate is updated at time t1 (during IG-ON) as in the prior art (see the white circles shown in FIG. 7), the controllability of fuel injection deteriorates.

  On the other hand, in the fuel supply device according to the present embodiment, since refueling is not performed during the previous engine stop, the propane rate at time t1 (IG-ON) and the propane rate at the previous update time Since the difference from the propane rate at the time of the previous IG-OFF is less than a predetermined value Pc (for example, 30%), updating of the propane rate is prohibited (S4 in FIG. 3: YES, S5). As a result, the fuel injection control is executed using the propane rate updated last time as it is. As a result, the propane rate used for fuel injection control hardly causes an error with respect to the actual propane rate Pr (see the solid line between times t1 and t3 shown in FIG. 7). It is possible to prevent the controllability from deteriorating. Therefore, stable engine start and idling operation can be performed without deteriorating engine startability or generating rough idle.

  Thereafter, when the engine is operated, the LPG fuel in the fuel tank 11 is agitated by the action of the fuel pump 12 or the like or the traveling of the vehicle. For this reason, the fuel temperature of the LPG fuel in the fuel tank 11 becomes uniform. First, the vehicle starts to travel at time t2, and reaches a predetermined speed Vc at time t3. As a result, the LPG fuel in the fuel tank 11 is sufficiently agitated and the fuel temperature becomes uniform due to the action of the fuel pump 12 and the like and the swinging of the fuel tank 11 due to the traveling of the vehicle. That is, at time t2, the average fuel temperature Ta of the LPG fuel in the fuel tank 11 and the fuel temperature Ts detected by the fuel temperature sensor 21 are substantially the same.

  Then, at time t3, that is, in a state where the fuel temperature of the LPG fuel in the fuel tank 11 becomes uniform, the propane rate is calculated by the ECU 20, and the propane rate is updated (S8 to S10 in FIG. 3, FIG. 7). (See the black circle shown). As a result, after time t3, the updated propane rate is used and fuel injection control is executed. Thereby, since there is almost no error with respect to the actual propane rate Pr even after time t3 (see the black circle and solid line after time t3 shown in FIG. 4), the controllability of fuel injection does not deteriorate. Stable operation of the engine can be ensured.

  Thus, in the fuel supply device according to the second embodiment, the propane rate of the LPG fuel in the fuel tank 11 is calculated and updated in a state where the temperature of the LPG fuel in the fuel tank 11 becomes uniform. . Therefore, the propane rate of the LPG fuel in the fuel tank 11 can be accurately calculated and updated. As a result, deterioration of the fuel injection controllability can be prevented.

  Note that, when fuel is replenished while the engine is stopped and the propane rate changes greatly, the same control as in the first embodiment is performed. Therefore, even in the fuel supply device according to the second embodiment, when the LPG fuel with greatly different fuel properties is replenished, the propane rate calculated at the time of IG-ON is updated, so The propane rate of the LPG fuel can be accurately calculated and updated. As a result, deterioration of the fuel injection controllability can be prevented.

  As described above in detail, the fuel supply apparatus according to the second embodiment is configured so that the difference between the propane rate calculated at the time of IG-ON and the propane rate at the previous update is less than the predetermined value Pc. The propane rate is prohibited from being updated until the vehicle speed reaches the predetermined speed Vc and the temperature of the LPG fuel in the fuel tank 11 becomes uniform, and the vehicle speed reaches the predetermined speed Vc and the temperature of the LPG fuel in the fuel tank 11 is ensured. The propane rate is newly calculated and updated in a state in which it becomes uniform. Thereby, the propane rate of the LPG fuel in the fuel tank 11 can be always calculated and updated with high accuracy. As a result, even when the temperature of the LPG fuel in the fuel tank 11 becomes uneven, it is possible to prevent deterioration of the fuel injection controllability at the time of starting the engine and thereafter.

  On the other hand, when the difference between the propane rate calculated at the time of IG-ON and the propane rate at the previous update is equal to or greater than the predetermined value Pc, the fuel supply device according to the second embodiment is calculated at the time of IG-ON. Update to propane rate. Thereby, the propane rate of the LPG fuel in the fuel tank 11 can be accurately calculated and updated. As a result, even when the fuel is replenished and the propane rate of the LPG fuel in the fuel tank 11 is greatly changed, it is possible to prevent the fuel injection controllability from deteriorating at the time of starting the engine.

  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 first embodiment described above, it is determined that a predetermined time has elapsed when about 1 minute has elapsed since the engine was started. However, the determination of the elapse of the predetermined time is not limited to this. For example, the temperature of the LPG fuel in the fuel tank 11 is almost the same as the fuel temperature at the previous engine stop (the difference is within 2 ° C.). Sometimes it can be determined that a predetermined time has passed. This is because at time t0 (IG-OFF time), the LPG fuel is sufficiently agitated in the fuel tank 11, and the temperature of the LPG fuel is uniform. Therefore, if the fuel temperature Ts detected by the fuel temperature sensor 21 at time t2 is substantially the same as the fuel temperature detected by the fuel temperature sensor 21 at time t0, the LPG fuel is sufficient in the fuel tank 11. This is because the temperature of the LPG fuel is considered to be uniform.

  In the second embodiment described above, the propane rate update control subroutine is terminated when the propane rate is updated when the predetermined speed Vc is reached after the engine is started. However, even after the propane rate is updated when the predetermined speed Vc is reached, the processing after step 27 may be repeated. By doing so, even when the idling operation is performed for a long time and the temperature of the LPG fuel in the fuel tank 11 becomes uneven during the idling operation, it is possible to prevent the fuel injection controllability from being deteriorated.

  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 LPG fuel supply apparatus which concerns on 1st Embodiment. It is a figure which shows the arrangement position of the fuel pump in a fuel tank, a fuel temperature sensor, and a fuel pressure sensor. It is a flowchart which shows the content of update control of a propane rate. It is a timing chart which shows the change of various signals and the propane rate when the temperature of the LPG fuel in the fuel tank becomes non-uniform. It is a timing chart which shows the change of various signals when the LPG fuel from which a fuel property differs differs, and a propane rate. It is a flowchart which shows the content of the update control of the propane rate in 2nd Embodiment. It is a timing chart which shows the change of various signals and the propane rate when the temperature of the LPG fuel in the fuel tank becomes non-uniform.

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 Pc Predetermined value Pr Actual propane rate Ta Average fuel temperature Ts in fuel tank Detected value Vc of fuel temperature sensor Predetermined speed

Claims (4)

In the liquefied gas fuel supply device that supplies the liquefied gas fuel pumped out from the fuel tank in which the liquefied gas fuel is stored by the fuel pump to the injector, and supplies the injector to the engine,
Fuel temperature detecting means for detecting the temperature of the liquefied gas fuel in the fuel tank;
Fuel pressure detection means for detecting the pressure of the liquefied gas fuel in the fuel tank;
Fuel composition calculating means for calculating the composition of the liquefied gas fuel in the fuel tank based on the detected values of the fuel temperature detecting means and the fuel pressure detecting means;
Fuel composition update means for updating the fuel composition calculated last time to the fuel composition calculated this time when the fuel composition is newly calculated by the fuel composition calculation means,
The liquefied gas fuel supply device, wherein the fuel composition update means updates the fuel composition when a predetermined period has elapsed after the engine is started. In the liquefied gas fuel supply device according to claim 1,
The liquefied gas fuel supply apparatus, wherein the predetermined period is a period until the fuel temperature distribution in the fuel tank becomes substantially uniform after the engine is started. In the liquefied gas fuel supply device that supplies the liquefied gas fuel pumped out from the fuel tank in which the liquefied gas fuel is stored by the fuel pump to the injector, and supplies the injector to the engine,
Fuel temperature detecting means for detecting the temperature of the liquefied gas fuel in the fuel tank;
Fuel pressure detection means for detecting the pressure of the liquefied gas fuel in the fuel tank;
Fuel composition calculating means for calculating the composition of the liquefied gas fuel in the fuel tank based on the detected values of the fuel temperature detecting means and the fuel pressure detecting means;
Fuel composition update means for updating the fuel composition calculated last time to the fuel composition calculated this time when the fuel composition is newly calculated by the fuel composition calculation means,
The liquefied gas fuel supply device, wherein the fuel composition update means updates the fuel composition when a predetermined vehicle speed is reached after the engine is started. The liquefied gas fuel supply device according to any one of claims 1 to 3,
The fuel composition update means updates the fuel composition when starting the engine when the difference between the fuel composition calculated this time by the fuel composition calculation means and the fuel composition calculated last time is a predetermined value or more. A liquefied gas fuel supply device.

Images