JP2010024886A - Fuel supply system for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply system for an engine capable of improving the startability of the engine. <P>SOLUTION: The fuel supply system is provided with a delivery pipe 130 to which an injector 120 is connected, and a changeover valve 180 having a function changing over fuel channels to stop delivery of fuel from a second end part 132 of the delivery pipe 130 under a condition where water temperature THW is not lower than a threshold THW2 and to increase fuel pressure to high pressure P1 and deliver fuel from the second end part 132 of the delivery pipe 130 under a condition where the water temperature THW is in a range lower than the threshold THW2 when it is determined that fuel is refilled to a fuel tank. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply system for an engine, and more particularly, to a technique for switching between a state in which fuel discharge from a pike connected to an injector is stopped and a state in which fuel pressure is increased and fuel is discharged from a delivery pipe. .

  Conventionally, an FFV (Flexible Fuel Vehicle) using a fuel in which alcohol (for example, ethanol) is mixed with gasoline or a fuel composed only of alcohol (hereinafter also referred to as alcohol fuel) is known. Alcohol fuel has different characteristics from gasoline. For example, alcohol fuel is less ignitable than gasoline. Therefore, when alcohol fuel is used, for example, engine startability deteriorates. Thus, a technique has been proposed for improving startability by injecting alcohol fuel maintained at a high pressure from an injector when the engine is started.

  Japanese Patent Application Laid-Open No. 62-186061 (Patent Document 1) discloses a main fuel pressure regulator that pumps an alcohol-mixed fuel of a predetermined pressure to a main injection valve that injects fuel into an internal combustion engine, and an auxiliary injection valve that performs fuel injection during guidance. Disclosed is a fuel injection device for an internal combustion engine, which includes a starting fuel pressure regulator that pumps an alcohol-mixed fuel having a predetermined pressure higher than a predetermined pressure.

According to the fuel injection device described in this publication, at the time of start-up, the alcohol-mixed fuel maintained at a higher pressure by the start fuel pressure regulator than the alcohol-mixed fuel pumped by the main fuel pressure regulator to the main injection valve It is injected into the engine. As a result, alcohol fuel pressurized to a high pressure is injected from the start injection valve. Therefore, the injected alcohol is vaporized by boiling due to rapid decompression. As a result, the startability of the internal combustion engine is improved.
JP-A-62-186061

  However, the optimum fuel injection amount can vary depending on the alcohol concentration of the fuel depending on the operation of the engine. Therefore, even if the fuel pressure is increased at the time of starting as in the fuel injection device described in Japanese Patent Application Laid-Open No. 62-186061, the amount of fuel injected at the start is excessive after the alcohol fuel is replenished and the alcohol concentration changes. Startability may deteriorate due to lack or shortage. In particular, in an engine in which an alcohol concentration is estimated from an air-fuel ratio or the like because no sensor for detecting the alcohol concentration is provided, it is difficult to detect the alcohol concentration after refueling. obtain.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an engine fuel supply system that can improve startability.

  An engine fuel supply system according to a first aspect of the present invention is an engine fuel supply system in which a fuel tank for storing fuel and an injector for injecting fuel are provided, and an alcohol concentration is estimated from an air-fuel ratio. This fuel supply system is provided with a determination unit for determining whether or not fuel has been supplied to the fuel tank, a first end for supplying fuel from the fuel tank, and a second end for discharging the fuel. And the delivery pipe to which the injector is connected and the fuel tank, if it is determined that the fuel has been replenished, the engine temperature is within a predetermined first range from the second end of the delivery pipe. So that the fuel pressure increases and the fuel is discharged from the second end of the delivery pipe when the engine temperature is in the second range lower than the first range. And a switching mechanism for switching the fuel flow path.

  According to this configuration, when it is determined that fuel has been replenished to the fuel tank, the second end of the delivery pipe to which the injector is connected in a state where the engine temperature is in the first predetermined range. The fuel discharge is stopped. Thereby, for example, after the alcohol concentration has changed due to replenishment of alcohol fuel, it is possible to make it difficult for a fuel whose alcohol concentration is unknown to be newly supplied into the delivery pipe. Therefore, the fuel that remains in the delivery pipe and whose alcohol concentration is known can be injected from the injector. As a result, the startability of the engine can be improved by controlling the fuel injection amount at the start of the engine according to the alcohol concentration so that there is no excess or deficiency. On the other hand, when the engine temperature is low, the fuel pressure is increased and the fuel is discharged from the second end of the delivery pipe. Thereby, at the low temperature when the volatility of the alcohol fuel deteriorates, the alcohol concentration of the fuel is unknown, but the fuel injection amount can be increased. In other words, by using a fuel whose alcohol concentration is known, it is possible to prevent a fuel shortage by sufficiently increasing the fuel injection amount rather than preventing an excessive fuel injection. be able to. Therefore, the startability of the engine can be ensured. As a result, it is possible to provide an engine fuel supply system capable of improving startability.

  In the fuel supply system for an engine according to the second invention, in addition to the configuration of the first invention, the switching mechanism is configured such that the alcohol concentration of the fuel is a predetermined concentration when the engine temperature is in the second range. When the following is true, fuel discharge from the second end of the delivery pipe is stopped, and when the alcohol concentration of the fuel is greater than a predetermined concentration, the fuel pressure increases and the second of the delivery pipe The fuel flow path is switched so that the fuel is discharged from the end.

  According to this configuration, even when the temperature of the engine is low, when the alcohol concentration already estimated, that is, the alcohol concentration of the fuel remaining in the delivery pipe is equal to or lower than a predetermined concentration, the injector The fuel discharge from the second end of the delivery pipe to which is connected is stopped. As a result, if the alcohol concentration is low, that is, the gasoline concentration is high, and there is little need to increase the fuel injection amount, the fuel with known alcohol concentration is used. It is possible to control the fuel injection amount so that there is no occurrence. On the other hand, when the alcohol concentration is high, it is possible to increase the fuel pressure and increase the fuel injection amount in a state where it is highly necessary to inject more fuel to start the engine. Therefore, the startability of the engine can be improved.

  In the engine fuel supply system according to the third aspect of the invention, in addition to the configuration of the first or second aspect of the invention, the switching mechanism increases the fuel pressure in a state where the switching mechanism is in the third range at a higher temperature than the first range. In addition, the flow path of the fuel is switched so that the fuel is discharged from the second end of the delivery pipe.

  According to this configuration, the fuel pressure can be increased in a state where the volatility of the fuel is good regardless of the alcohol concentration, that is, in a state where the startability of the engine is good, due to the high temperature of the engine. Therefore, vaporization of alcohol fuel can be further promoted.

  In the fuel supply system for an engine according to the fourth aspect of the present invention, in addition to the configuration of any one of the first to third aspects, the switching mechanism is configured such that the second pressure of the delivery pipe is increased when the fuel pressure is higher than the first pressure. A first regulator provided at the second end of the delivery pipe to discharge the fuel from the end, and to discharge the fuel when the fuel pressure is higher than a second pressure lower than the first pressure A second regulator connected to the first end of the delivery pipe, and a second end of the delivery pipe provided between the first end and the second regulator of the delivery pipe. And a switching valve for switching the fuel flow path so as to increase the fuel pressure by stopping and closing the fuel and to discharge the fuel from the second end of the delivery pipe.

  According to this configuration, the state in which the discharge of fuel from the second end of the delivery pipe to which the injector is connected is stopped by the two regulators and the switching valve that are set to maintain different pressures and the pressure of the fuel. And the state in which fuel is discharged from the second end of the delivery pipe can be switched.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  An engine system having a fuel supply system according to an embodiment of the present invention will be described with reference to FIG. Although FIG. 1 shows a V-type 8-cylinder gasoline engine as an engine, the present invention is not limited to such an engine, and various types such as a V-type 6-cylinder engine and an in-line 4-cylinder engine are available. Applicable to engine.

  The engine 10 is an internal combustion engine that is driven by an alcohol fuel containing alcohol (for example, ethanol) in addition to gasoline. As shown in FIG. 1, the engine 10 includes eight cylinders 112, and each cylinder 112 is connected to a common surge tank 30 via an intake manifold 20. The surge tank 30 is connected to the air cleaner 50 via the intake duct 40.

  A throttle valve 70 driven by an electric motor 60 is disposed in the intake duct 40. The throttle valve 70 is controlled so that the throttle opening degree TA changes according to the accelerator opening degree. When the engine 10 is in an idle state, the throttle opening is controlled by ISC (Idle Speed Control) so that the engine speed becomes the target idle speed.

  Each cylinder 112 is connected to a common exhaust manifold 80, and this exhaust manifold 80 is connected to a three-way catalytic converter 90. Each cylinder 112 is provided with a spark plug 110, an intake port or / and an injector 120 that injects fuel into the intake passage. The spark plug 110 and the injector 120 are controlled based on an output signal from an EFI (Electronic Fuel Injection) -ECU (Electronic Control Unit) 300. Each injector 120 is connected to a delivery pipe 130.

  The EFI-ECU 300 is composed of a digital computer and includes a clock, a ROM (Read Only Memory), a RAM (Random Access Memory), a CPU (Central Processing Unit), and the like.

  In the present embodiment, electric power is supplied from battery 302 to EFI-ECU 300. When the ignition switch 304 is turned on, the EFI-ECU 300 is activated. On the other hand, when the ignition switch 304 is turned off, the EFI-ECU 300 enters a dormant state.

  Further, when the ignition switch 304 is switched from on to off, the engine 10 is stopped. When the ignition switch 304 is switched from OFF to ON, the engine 10 is controlled to start. Note that, instead of the ignition switch 304, the engine 10 may be controlled to start when the start switch is operated from OFF to ON.

The output voltage of the air-fuel ratio sensor 350 is input to the EFI-ECU 300. The air-fuel ratio sensor 350 is a global air-fuel ratio sensor (linear air-fuel ratio sensor) that generates an output voltage proportional to the air-fuel ratio of the air-fuel mixture burned by the engine 10. The air-fuel ratio sensor 350 detects whether the air-fuel ratio of the air-fuel mixture combusted in the engine 10 is rich (small) or lean (large) relative to the stoichiometric air-fuel ratio. An O ₂ sensor may be used.

  In the present embodiment, EFI-ECU 300 calculates feedback correction amount FAF of the fuel injection amount based on the output voltage of air-fuel ratio sensor 350. For example, when the air-fuel ratio is larger (lean) than the target air-fuel ratio (theoretical air-fuel ratio or the like), the feedback correction amount FAF is calculated to be large. On the other hand, when the air-fuel ratio is smaller (rich) than the target air-fuel ratio, the feedback correction amount FAF is calculated to be small.

  Further, when a predetermined learning condition is satisfied, a learning value (a value representing a constant deviation amount of the fuel injection amount) KG of the feedback correction amount FAF is calculated. For example, when the feedback correction amount FAF is larger than the threshold value FAF1, the learning value KG is increased by a predetermined value, or when the feedback correction amount FAF is smaller than the threshold value FAF2, the predetermined value is predetermined. The learning value KG is calculated by reducing the learning value KG by the value. Therefore, the larger the air-fuel ratio (lean), the larger the learning value KG of the feedback correction amount FAF. As the air-fuel ratio is smaller (rich), the learning value KG of the feedback correction amount FAF becomes smaller.

  The correction amount of the fuel injection amount is the sum of the feedback correction amount FAF and the learning value KG. Note that the method for calculating the feedback correction amount FAF and its learning value KG may be any known general technique, and therefore detailed description thereof will not be repeated here.

  By the way, the higher the alcohol concentration DEN of the fuel, the smaller the amount of gasoline injected from the injector 120. Therefore, the air-fuel ratio becomes lean with respect to the target air-fuel ratio. In this case, the feedback correction amount FAF is calculated so as to increase the fuel injection amount. Therefore, in the present embodiment, the alcohol concentration DEN is learned according to the learning value KG of the air-fuel ratio feedback correction amount FAF.

  For example, the learning value DENG of the alcohol concentration DEN is calculated using the following formula 1. Note that, as the initial value DENGI of the learning value DENG of the alcohol concentration DEN, a value determined in advance through experiments and simulations is used.

DENG (i) ＝ DENG (i-1) + G × (KG (i) −KG (i-1))… (1)
“DENG (i)” in Equation 1 represents the current value of the learning value DENG of the alcohol concentration DEN. “DENG (i−1)” indicates the previous value of the learning value DENG of the alcohol concentration DEN. “G” is a gain, for example, a positive value. By changing the gain G, the change amount of the learning value DENG of the alcohol concentration DEN, that is, the learning speed can be changed. “KG (i)” indicates the current value of the learning value KG of the feedback correction amount FAF. “KG (i−1)” indicates the previous value of the learning value KG of the feedback correction amount FAF.

  As is apparent from Equation 1, the larger the learned value KG of the feedback correction amount FAF, the larger the alcohol concentration DEN is learned. The smaller the learning value KG of the feedback correction amount FAF, the smaller the alcohol concentration DEN is learned. In other words, it is learned that the alcohol concentration DEN increases as the air-fuel ratio increases (lean). It is learned that the alcohol concentration DEN becomes smaller as the air-fuel ratio becomes smaller (richer).

  Note that the calculation method of the learning value DENG of the alcohol concentration DEN is not limited to these, and the learning value DENG of the alcohol concentration DEN may be calculated using other methods.

  Further, the EFI-ECU 300 receives from the water temperature sensor 360 a signal representing the temperature THW of the cooling water for the engine 10 (hereinafter also referred to as water temperature) THW. The EFI-ECU 300 indirectly detects the temperature of the engine 10 from the water temperature THW.

  The fuel supply system according to the present embodiment will be further described with reference to FIG. A main pipe 140 is connected to the delivery pipe 130 to which the injector 120 is connected. That is, the main pipe 140 is connected to the injector 120 via the delivery pipe 130. The delivery pipe 130 is supplied with fuel from the first end 131 and discharged from the second end 132.

  Alcohol fuel in the fuel tank 152 is supplied from the fuel pump 150 to the main pipe 140. The fuel pump 150 is driven by the engine 10. The higher the rotation speed of the fuel pump 150, the more alcohol fuel is discharged from the fuel pump 150.

  A first pressure regulator 161 that maintains the pressure of the delivery pipe 130 and the main pipe 140 at “P1” is provided at the second end 132 in the delivery pipe 130. The second end portion 132 is provided on the opposite side of the first end portion 131. The first pressure regulator 161 is configured to return a part of the fuel in the delivery pipe 130 to the fuel tank 152 via the return pipe 170 when the pressure of the delivery pipe 130 and the main pipe 140 becomes higher than “P1”. The

  Further, the main piping 140 is provided with a second pressure regulator 162 and a switching valve 180 on the side opposite to the portion connected to the delivery pipe 130. That is, the second pressure regulator 162 is connected to the first end 131 of the delivery pipe 130. A switching valve 180 is provided between the first end 131 of the delivery pipe 130 and the second pressure regulator 162.

  The second pressure regulator 162 is configured to maintain the pressure of the delivery pipe 130 and the main pipe 140 at “P2” in a state where the switching valve 180 is open. That is, when the pressure in the delivery pipe 130 and the main pipe 140 becomes higher than “P2” in a state where the switching valve 180 is open, the second pressure regulator 162 transfers a part of the fuel in the main pipe 140 to the fuel tank 152. Configured to return.

  Therefore, when the switching valve 180 is opened, the fuel pressure is set to “P2”. On the other hand, when the switching valve 180 is closed, the fuel pressure is set to “P1”. “P1” is set as a pressure higher than “P2”. That is, “P2” is set as a pressure lower than “P1”. Therefore, when the switching valve 180 is switched from the closed state to the opened state, as shown in FIG. 3, the fuel discharged from the fuel pump 150 does not pass through the first pressure regulator 161 and does not pass through the switching valve 180 and the first one. It is returned to the fuel tank 152 via the two-pressure regulator 162. That is, the discharge of fuel from the second end 132 of the delivery pipe 130 is stopped.

  On the other hand, when the switching valve 180 is closed, the fuel discharged from the fuel pump 150 is supplied to the main pipe 140 and the delivery pipe 130 as shown in FIG. When the pressure in the delivery pipe 130 and the main pipe 140 becomes higher than “P1”, a part of the fuel in the delivery pipe 130 is discharged from the first pressure regulator 161, that is, from the second end 132 of the delivery pipe 130. The discharged fuel is returned to the fuel tank 152 through the return pipe 170.

  Therefore, the switching valve 180 stops discharging fuel from the second end 132 of the delivery pipe 130, and increases the fuel pressure and discharges fuel from the second end 132 of the delivery pipe 130. In addition, it has a function of switching the fuel flow path. The switching valve 180 is an electromagnetically driven valve, for example, and is controlled by the EFI-ECU 300.

  The remaining amount MASS of the alcohol fuel in the fuel tank 152 is detected by a sender gauge (fuel remaining amount meter) 360, and a signal indicating the detection result is input to the EFI-ECU 300. The EFI-ECU 300 determines that the alcohol fuel has been replenished, for example, when the remaining amount MASS of the alcohol fuel increases.

  The function of the EFI-ECU 300 will be described with reference to FIG. Note that the functions described below may be realized by hardware or may be realized by software.

The EFI-ECU 300 includes a detection unit 400, a learning unit 402, a determination unit 404, an injection control unit 410, a start unit 420, and a fuel pressure control unit 430. The detection unit 400 outputs the output voltage of the air-fuel ratio sensor 350. Based on this, the air-fuel ratio of the engine 10 is detected.

  The learning unit 402 learns the alcohol concentration DEN according to Equation 1 described above. That is, the learning unit 402 learns that the alcohol concentration DEN increases as the air-fuel ratio increases (lean), and learns so that the alcohol concentration DEN decreases as the air-fuel ratio decreases (rich). .

  The determination unit 404 determines whether alcohol fuel has been supplied to the fuel tank 152. For example, when the remaining amount MASS of alcohol fuel increases, it is determined that the alcohol fuel has been replenished. The method for determining whether or not alcohol fuel has been replenished is not limited to this.

  As shown in FIG. 6, the injection control unit 410 controls the injector 120 so that the fuel injection amount TAU increases as the learning value DENG of the alcohol concentration DEN increases. Further, the injector 120 is controlled such that the fuel injection amount TAU increases as the water temperature THW decreases. The fuel injection amount TAU is determined in consideration of the intake air amount, the water temperature THW feedback correction amount FAF, the learning value KG, and the like in addition to the learning value DENG and the water temperature THW of the alcohol concentration DEN.

  Returning to FIG. 5, the starter 420 controls the engine 10 to start when the ignition switch 304 is operated from OFF to ON while the engine 10 is stopped.

  The fuel pressure control unit 430 controls the pressure of the fuel in the delivery pipe 130 and the main pipe 140 by controlling opening and closing of the switching valve 180. More specifically, as shown in FIG. 7, when the engine 10 is started, if it is not determined that the alcohol fuel has been replenished, the fuel pressure increases to “P1”, which is a high pressure, and the second of the delivery pipe 130. The switching valve 180 is closed so that the fuel is discharged from the end portion 132.

  On the other hand, when it is determined that the alcohol fuel is replenished when the engine 10 is started, the switching valve 180 is controlled according to the water temperature THW.

  In a state where the water temperature THW is in a range equal to or higher than the threshold value THW1, the switching valve 180 is closed so that the fuel pressure increases to “P1”, which is a high pressure, and the fuel is discharged from the second end 132 of the delivery pipe 130. . The threshold value THW1 is a positive value, for example.

  In a state where the water temperature THW is equal to or higher than the threshold value THW2 (THW2 <THW1) and smaller than the threshold value THW1, the discharge of fuel from the second end 132 of the delivery pipe 130 is stopped and the fuel pressure is reduced. The switching valve 180 is opened so as to set to “P2”. The threshold value THW2 is a negative value, for example.

  In a state where the water temperature THW is smaller than the threshold value THW2, the switching valve 180 is closed so that the fuel pressure increases to the high pressure “P1” and the fuel is discharged from the second end 132 of the delivery pipe 130. To be controlled.

  Further, fuel pressure control unit 430 controls switching valve 180 according to alcohol concentration DEN in a state where water temperature THW is in a range smaller than threshold value THW2. More specifically, the fuel pressure control unit 430 controls the switching valve 180 to open when the fuel injection amount TAU is equal to or less than the threshold value TAU1 in a state where the water temperature THW is in a range smaller than the threshold value THW2. When the fuel injection amount TAU is larger than the threshold value TAU1, the switching valve 180 is controlled to close.

  As described above, the injector 120 is controlled so that the fuel injection amount TAU increases as the learning value DENG of the alcohol concentration DEN increases. Therefore, when the fuel injection amount TAU is equal to or less than the threshold value TAU1, the learned value DENG of the alcohol concentration DEN is equal to or less than the threshold value DENG1. Therefore, by controlling the switching valve 180 according to the fuel injection amount TAU, the switching valve 180 is indirectly controlled according to the alcohol concentration DEN.

  Further, the injector 120 is controlled such that the fuel injection amount TAU increases as the water temperature THW decreases. Therefore, as shown in FIG. 8, even if the threshold value TAU1 of the injection amount TAU is constant, the threshold value DENG1 of the learning value DENG of the alcohol concentration DEN is smaller as the water temperature THW is lower.

  In other words, as shown in FIG. 9, the threshold value THW2 of the water temperature THW is set to be lower as the alcohol concentration DEN is smaller.

  A control structure of a program executed by EFI-ECU 300 will be described with reference to FIG. A program described below is recorded in, for example, a ROM. The program executed by the EFI-ECU 300 may be recorded on a recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) and distributed to the market.

  In step (hereinafter, step is abbreviated as S) 100, EFI-ECU 300 determines whether or not ignition switch 304 is operated from OFF to ON in a state where engine 10 is stopped. If the ignition switch 304 is operated from OFF to ON while the engine 10 is stopped (YES in S100), the process proceeds to S102. If not (NO in S100), the process returns to S100.

  In S102, EFI-ECU 300 determines whether or not water temperature THW is in a range equal to or higher than threshold value THW1. If water temperature THW is in a range equal to or higher than threshold value THW1 (YES in S102), the process proceeds to S122. If not (NO in S102), the process proceeds to S104.

  In S104, EFI-ECU 300 determines whether or not alcohol fuel has been replenished, that is, whether or not the remaining amount MASS of alcohol fuel has increased. If the alcohol fuel is replenished (YES in S104), the process proceeds to S110. If not (NO in S104), the process proceeds to S122.

  In S110, EFI-ECU 300 reads learning value DENG of alcohol concentration DEN from RAM.

  In S112, EFI-ECU 300 determines whether or not water temperature THW is in a range smaller than threshold value THW2. If water temperature THW is in a range smaller than threshold value THW2 (YES in S112), the process proceeds to S114. If not (NO in S112), the process proceeds to S120.

  In S114, EFI-ECU 300 sets fuel injection amount TAU when engine 10 is started with fuel pressure set to a low pressure "P2" based on learned value DENG of alcohol concentration DEN and water temperature THW. . The injection amount TAU is set so that the fuel injection amount TAU increases as the learning value DENG of the alcohol concentration DEN increases. Further, the fuel injection amount TAU is set so as to increase as the water temperature THW decreases.

  In S116, EFI-ECU 300 determines whether or not the fuel injection amount TAU at the start of engine 10 with the fuel pressure set to the low pressure “P2” is equal to or less than threshold value TAU1. If fuel injection amount TAU is equal to or smaller than threshold value TAU1 (YES in S116), the process proceeds to S120. If not (NO in S116), the process proceeds to S122.

  In S120, EFI-ECU 300 controls switching valve 180 to open. In S122, EFI-ECU 300 controls switching valve 180 to close. In S124, EFI-ECU 300 controls engine 10 to start.

  The operation of the fuel supply system according to the present embodiment based on the above-described structure and flowchart will be described.

  If the ignition switch 304 is operated from OFF to ON while the engine 10 is stopped (YES in S100), it is determined whether or not the water temperature THW is in a range equal to or higher than the threshold value THW1. (S102).

  When water temperature THW is in a range equal to or higher than threshold value THW1 (YES in S102), switching valve 180 is controlled to close (S122). Thereby, the fuel pressure can be set to a high pressure “P1” in a state where the volatility of the fuel is good regardless of the alcohol concentration DEN, that is, in a state where the startability of the engine 10 is good, due to the high temperature of the engine 10. . Therefore, vaporization of alcohol fuel can be further promoted. In this state, the engine 10 is controlled to start (S124). Thereby, the startability of the engine 10 can be improved.

  If water temperature THW is in a range smaller than threshold value THW1 (NO in S102), it is determined whether alcohol fuel has been replenished (YES in S104). If the alcohol fuel is not replenished (NO in S104), the switching valve 180 is controlled to close (S122). As a result, the fuel whose alcohol concentration DEN is known can be supplied to the delivery pipe 130, and the fuel pressure can be set to the high pressure “P1”. Therefore, it is possible to control the fuel injection amount TAU at the start of the engine 10 according to the alcohol concentration DEN so as to promote the vaporization of the alcohol fuel and to prevent excess or deficiency. In this state, the engine 10 is controlled to start (S124). Therefore, the startability of the engine 10 can be improved.

  When alcohol fuel is supplied (YES in S104), learning value DENG of alcohol concentration DEN is read from RAM (S110). Further, it is determined whether or not the water temperature THW is in a range smaller than the threshold value THW2 (S112).

  When the engine 10 is started immediately after the alcohol fuel is supplied, learning of the alcohol concentration DEN of the supplied fuel is not completed. Therefore, when starting the engine 10 using the replenished fuel, it is difficult to set an optimal injection amount TAU that is not excessive or insufficient.

  Therefore, when water temperature THW is equal to or higher than threshold value THW2 and in a range smaller than threshold value THW1 (NO in S112), control is performed so that switching valve 180 is opened (S120). Thereby, although the fuel pressure is reduced, the discharge of the fuel from the second end portion 132 of the delivery pipe 130 can be stopped so that the fuel is hardly supplied from the fuel pump 150 to the delivery pipe 130. Therefore, it is possible to make it difficult for a fuel whose alcohol concentration DEN is unknown to be newly supplied to the delivery pipe 130. In this state, the engine 10 is controlled to start (S124). As a result, the engine 10 can be started using the fuel that remains in the delivery pipe 130 and whose alcohol concentration DEN is known when the engine 10 was last operated. Therefore, the startability of the engine 10 can be improved by controlling the fuel injection amount TAU at the start of the engine 10 according to the alcohol concentration DEN so that there is no excess or deficiency.

  On the other hand, when water temperature THW is in a range smaller than threshold value THW2 (YES in S112), fuel pressure is set to low pressure “P2” based on learning value DENG of alcohol concentration DEN and water temperature THW. The fuel injection amount TAU at the time of starting the engine 10 is set (S114).

  When fuel injection amount TAU is larger than threshold value TAU1 (NO in S116), that is, when learning value DENG of alcohol concentration DEN is larger than threshold value DENG1, switching valve 180 is controlled to close (S122). . Thus, when the engine 10 is at a low temperature and the alcohol concentration DEN is high, the fuel discharged from the fuel pump 150 can be supplied to the delivery pipe 130 and the fuel pressure can be set to the high pressure “P1”. Therefore, in a state where the volatility of alcohol fuel deteriorates and it is highly necessary to inject more fuel to start the engine, the fuel pressure is increased to promote vaporization of the alcohol fuel, and the fuel injection amount TAU is reduced. Can do a lot. In other words, the fuel injection amount TAU does not become insufficient by preventing the fuel from being injected excessively by using the fuel whose alcohol concentration DEN is known. Can be. In this state, the engine 10 is controlled to start (S124). Therefore, the startability of the engine can be ensured. As a result, startability can be improved.

  When fuel injection amount TAU is equal to or smaller than threshold value TAU1 (YES in S116), that is, when learning value DENG of alcohol concentration DEN is equal to or smaller than threshold value DENG1, control is performed to open switching valve 180 ( S120). Therefore, the fuel discharge from the second end portion 132 of the delivery pipe 130 can be stopped so that the delivery pipe 130 fuel is hardly supplied from the fuel pump 150. Thereby, although the fuel pressure is lowered, it is possible to make it difficult for the fuel whose alcohol concentration DEN is unknown to be newly supplied to the delivery pipe 130. In this state, the engine 10 is controlled to start (S124). Therefore, if the alcohol concentration DEN is low, that is, the gasoline concentration is high, and there is little need to increase the fuel injection amount TAU, it remains in the delivery pipe 130 and the alcohol concentration DEN is found. The engine 10 can be started using the fuel that is being used. Therefore, the startability of the engine 10 can be improved by controlling the fuel injection amount TAU at the start of the engine 10 according to the alcohol concentration DEN so that there is no excess or deficiency.

  As described above, according to the fuel supply system according to the present embodiment, when the water temperature THW is equal to or higher than the threshold value THW2 and is in a range smaller than the threshold value THW1, the second end portion of the delivery pipe. The fuel discharge from is stopped. Thereby, it is possible to make it difficult for a fuel whose alcohol concentration DEN is unknown to be newly supplied to the delivery pipe. Therefore, the engine can be started using the fuel that remains in the delivery pipe and whose alcohol concentration DEN is known when the engine is operated last time. As a result, the startability of the engine can be improved by controlling the fuel injection amount TAU at the start of the engine according to the alcohol concentration DEN so that there is no excess or deficiency. On the other hand, when the water temperature THW is in a range smaller than the threshold value THW2, the fuel pressure is set to “P1”, which is a high pressure, and the fuel from the second end of the delivery pipe is discharged. Therefore, at low temperatures when the volatility of the alcohol fuel deteriorates, the alcohol concentration is unknown, but it is possible to promote the vaporization of the alcohol fuel and increase the fuel injection amount TAU. In other words, the fuel injection amount TAU does not become insufficient by preventing the fuel from being injected excessively by using the fuel whose alcohol concentration DEN is known. Can be. Therefore, the startability of the engine can be ensured. As a result, startability can be improved.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of an engine system. It is a figure which shows a fuel supply system. It is a figure which shows the flow path of the fuel in the state which the switching valve opened. It is a figure which shows the flow path of the fuel in the state which the switching valve closed. It is a functional block diagram of EFI-ECU. It is a figure which shows the relationship between the learning value DENG of alcohol concentration DEN, and the fuel injection quantity TAU. It is a figure which shows the conditions for opening and closing a switching valve. FIG. 6 is a diagram showing threshold values DENG1 of threshold values THW1 and THW2 for water temperature THW and learning value DENG for alcohol concentration DEN. It is a figure which shows threshold value THW1, THW2 of water temperature THW. It is a flowchart which shows the control structure of the program which EFI-ECU performs.

Explanation of symbols

  10 engine, 20 intake manifold, 30 surge tank, 40 intake duct, 42 air flow meter, 50 air cleaner, 60 electric motor, 70 throttle valve, 80 exhaust manifold, 90 three-way catalytic converter, 110 spark plug, 112 cylinder, 120 injector, 130 delivery pipe, 140 main pipe, 150 fuel pump, 152 fuel tank, 161 first pressure regulator, 162 second pressure regulator, 170 return pipe, 180 switching valve, 300 EFI-ECU, 302 battery, 304 ignition switch, 350 empty Fuel ratio sensor, 360 Water temperature sensor, 400 detection unit, 402 learning unit, 404 determination unit, 410 injection control unit, 420 start unit, 430 fuel Pressure control unit.

Claims (4)

A fuel supply system for an engine, in which a fuel tank for storing fuel and an injector for injecting fuel are provided, and an alcohol concentration is estimated from an air-fuel ratio,
A determination unit for determining whether or not fuel is supplied to the fuel tank;
A delivery pipe to which a first end portion for supplying fuel from the fuel tank and a second end portion for discharging fuel are provided and to which the injector is connected;
When it is determined that the fuel tank has been refueled, the fuel discharge from the second end of the delivery pipe is stopped in a state where the temperature of the engine is in a predetermined first range. The fuel pressure is increased and the fuel is discharged from the second end of the delivery pipe while the temperature of the engine is in a second range lower than the first range. An engine fuel supply system comprising a switching mechanism for switching a flow path.   The switching mechanism discharges fuel from the second end of the delivery pipe when the alcohol concentration of the fuel is equal to or lower than a predetermined concentration in a state where the temperature of the engine is in the second range. The fuel flow path so that the fuel pressure increases and the fuel is discharged from the second end of the delivery pipe when the alcohol concentration of the fuel is greater than the predetermined concentration. The engine fuel supply system according to claim 1, wherein the engine fuel supply system is switched.   The switching mechanism is configured to allow fuel flow so that the fuel pressure increases and the fuel is discharged from the second end of the delivery pipe in a state where the temperature is in a third range that is higher than the first range. The fuel supply system for an engine according to claim 1 or 2, wherein the path is switched. The switching mechanism is
A first regulator provided at the second end of the delivery pipe to discharge fuel from the second end of the delivery pipe when the fuel pressure is higher than the first pressure;
A second regulator coupled to the first end of the delivery pipe to discharge the fuel when the pressure of the fuel is higher than a second pressure lower than the first pressure;
Provided between the first end of the delivery pipe and the second regulator, and stops the discharge of the fuel from the second end of the delivery pipe by opening, and the pressure of the fuel by closing. A fuel supply system for an engine according to any one of claims 1 to 3, further comprising a switching valve that switches a fuel flow path so that fuel is discharged from the second end of the delivery pipe as the fuel flow increases. .

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