JP2006322401A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent vaporization of fuel during the engine stop period and surely preventing poor start caused by the same in an FFV engine capable of using alcohol fuel. <P>SOLUTION: It is estimated according to predetermined conditions (step S102-104) whether fuel in a fuel supply passage is vaporized during the engine stop period at a time of engine stop, pressure of fuel in the fuel supply passage is raised (step S105) when vaporization of fuel is estimated. Possibility of vaporization of fuel during the stop period is estimated at a time of engine stop, not at a time of start, pressure of fuel in the fuel supply passage is raised if vaporization is estimated. Consequently, vaporization of fuel during the engine stop period is surely prevented and poor start at a time of next start can be surely prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine control device, and more particularly to an engine control device that can use alcohol and gasoline as fuels alone or in combination.

  In recent years, a system that can simultaneously use alcohol as an alternative fuel in addition to gasoline fuel has been put into practical use. In vehicles such as automobiles (FFV) equipped with this system, not only gasoline, The vehicle can be run only with a mixed fuel of alcohol and gasoline, or alcohol. The alcohol concentration (content rate) of the fuel used in the FFV varies between 0% (gasoline only) and 100% (alcohol only) depending on the user circumstances at the time of refueling.

  On the other hand, even in a normal engine, there is a problem that the temperature in the fuel passage such as the delivery pipe rises due to the radiant heat or radiant heat received from the engine after the engine is stopped, and the fuel vaporizes to cause a start failure at the next start. For example, in the case of an engine mounted on a vehicle, this is likely to occur when the engine is stopped after traveling in a high temperature environment and the engine is started again within a short time. Moreover, in FFV, alcohol has a lower boiling point than gasoline and is likely to vaporize. Therefore, the higher the alcohol concentration of the fuel, the more likely this problem occurs.

  As a technique for preventing fuel vaporization, for example, an LPG fuel engine disclosed in Patent Document 1 is known. In this LPG fuel engine, based on the properties of the LPG fuel and the temperature of the LPG fuel at a predetermined location on the flow path between the LPG fuel pump and the injector, the target pressure is set so that the LPG fuel does not vaporize at the predetermined location. And a control means for controlling the pump so that the LPG fuel pressure at the predetermined location matches the target pressure.

JP 2004-346813 A

  However, the LPG fuel engine disclosed in Patent Document 1 drives the pump using the non-vapor generated pressure as a target pressure when the generation of vapor is estimated at the time of starting the engine. In other words, the generation of vapor during the engine stop period is allowed. Therefore, it is hard to say that the starting failure at the time of engine restart can be surely prevented. Even if the fuel of FFV is 100% alcohol, the possibility that the fuel vaporizes while the engine is stopped is much lower than the LPG fuel that is a gas at normal temperature and pressure. Actually, starting failure due to vaporization occurs in FFV only in a very limited situation. In consideration of this, it is not always appropriate to apply the technology of the LPG fuel engine to the FFV engine as it is.

  The present invention has been made in view of such circumstances, and an object of the present invention is to ensure fuel vaporization during the engine stop period and start failure due to this in an FFV engine that can use alcohol fuel. It is an object of the present invention to provide an engine control device that can prevent the above.

  In order to achieve the above object, a first aspect of the present invention is an engine control device capable of using alcohol and gasoline as fuels alone or in combination, and an injector for injecting fuel, A fuel supply passage for supplying fuel to the injector; a prediction means for predicting whether or not the fuel in the fuel supply passage is vaporized during the engine stop period when the engine is stopped; And a boosting means for boosting the fuel in the fuel supply passage when the fuel is predicted to vaporize by the means.

  According to this aspect of the present invention, whether or not fuel vaporization during the stop period is predicted when the engine is not started but when the engine is stopped. The fuel is boosted. Therefore, the fuel vaporization during the engine stop period is reliably prevented, and the starting failure at the next restart can be surely prevented.

  Preferably, the outside air temperature detecting means for detecting the outside air temperature, the alcohol concentration detecting means for detecting the alcohol concentration of the fuel, and the warming up end detecting means for detecting the end of warming up of the engine, The outside air temperature detected by the outside air temperature detecting means is not less than a predetermined temperature, the alcohol concentration detected by the alcohol concentration detecting means is not less than a predetermined concentration, and the warm-up completion detecting means When the end of warm-up is detected, the predicting means predicts that the fuel vaporizes. With this condition setting, fuel vaporization can be accurately predicted.

  Preferably, based on the fuel pressure detecting means for detecting the fuel pressure in the fuel supply passage, the alcohol concentration detecting means for detecting the alcohol concentration of the fuel, and the alcohol concentration detected by the alcohol concentration detecting means. And a target fuel pressure determining means for determining a target fuel pressure that does not cause fuel vaporization during the engine stop period, wherein the boosting means detects the fuel pressure detected by the fuel pressure detecting means. The fuel is boosted to match the target fuel pressure.

  The fuel pressure that does not cause fuel vaporization during the engine stop period depends on the alcohol concentration. Therefore, by determining the target fuel pressure based on the alcohol concentration of the fuel and increasing the fuel so as to match the target fuel pressure, fuel vaporization during the engine stop period can be reliably prevented.

  Preferably, the fuel supply passage is provided with a valve for preventing a back flow of the pressurized fuel. As a result, the pressurized fuel can be reliably confined in the fuel supply passage until the next start.

  Preferably, alcohol concentration detection means for detecting the alcohol concentration of the fuel, limit fuel temperature determination means for determining a predetermined limit fuel temperature based on the alcohol concentration of the fuel detected by the alcohol concentration detection means, Fuel temperature detection means for detecting the fuel temperature in the fuel supply passage, determination means for determining whether or not the fuel temperature detected by the fuel temperature detection means is lower than the limit fuel temperature when the engine is started, When the determination means determines that the fuel temperature is lower than the limit fuel temperature, the fuel supply passage further includes a pressure reduction means for reducing the fuel pressure in the fuel supply passage to a predetermined value.

  According to this, since the fuel boosted at the time of stop is decompressed at the time of start-up, fuel pressure correction during the injection period is unnecessary, and control can be simplified. Here, even if the fuel is kept in a pressure-rising state so that the fuel does not vaporize during the engine stop period, the fuel temperature rises during the stop period and may vaporize when the pressure is reduced during start-up. According to such a configuration, the pressure is reduced only when the fuel temperature at the start is lower than the predetermined limit fuel temperature, so that vaporization after the pressure reduction can be surely prevented and a start failure can be prevented.

  The second aspect of the present invention is an engine control device that can use alcohol and gasoline as fuels individually or in combination, and an injector for injecting fuel, and supplying the fuel to the injector A fuel supply passage for carrying out the operation, a prediction means for predicting whether the fuel in the fuel supply passage is vaporized during the engine stop period when the engine is stopped, and a fuel supplied by the prediction means. And a recovery means for recovering the fuel in the fuel supply passage to a fuel tank when it is predicted that the fuel is to be converted into a fuel.

  According to the second aspect of the present invention, the fuel in the fuel supply passage is collected in the fuel tank when it is predicted that the fuel will be vaporized when the engine is stopped. Thereby, the next start by the fuel mixed with vapor is avoided, and a start failure can be prevented. At the time of restart, the fuel is newly replenished into the fuel supply passage.

  Preferably, an outside air temperature detecting means for detecting the outside air temperature, an alcohol concentration detecting means for detecting the alcohol concentration of the fuel, and a warming up end detecting means for detecting the end of warming up of the engine. In addition, the outside air temperature detected by the outside air temperature detecting means is not less than a predetermined temperature, the alcohol concentration detected by the alcohol concentration detecting means is not less than the predetermined concentration, and the warm-up completion detecting means is used to warm the engine. When the end of the aircraft is detected, the prediction means predicts that the fuel will be vaporized.

  The third aspect of the present invention is an engine control apparatus that can use alcohol and gasoline as fuels alone or in combination, respectively, an injector for injecting fuel, and supplying fuel to the injector A fuel supply passage for detecting the fuel temperature, a fuel temperature detection means for detecting the fuel temperature in the fuel supply passage, an alcohol concentration detection means for detecting the alcohol concentration of the fuel, and detected by the alcohol concentration detection means Based on the alcohol concentration of the fuel, limit fuel temperature determining means for determining a predetermined limit fuel temperature, and determining whether the fuel temperature detected by the fuel temperature detecting means at the time of starting the engine is equal to or higher than the limit fuel temperature A start prohibition means for prohibiting start of the engine when the fuel temperature is determined to be equal to or higher than the limit fuel temperature by the start time determination means and the start time determination means; Characterized by comprising a means.

  When the engine start is prohibited in this way, the user is forced to wait for a while until the fuel temperature falls. However, when the time elapses, the fuel temperature is eventually lowered to a temperature at which the fuel can be started, so that the start is possible. According to such a configuration, means for boosting, depressurizing, or collecting the fuel in the fuel tank is not necessary, so that the device configuration can be simplified and the cost of the device can be reduced.

  Preferably, warning means for issuing a predetermined warning when the start prohibiting means prohibits starting of the engine is further provided.

  According to a fourth aspect of the present invention, there is provided an engine start control device capable of using alcohol and gasoline as fuels alone or in combination, the injector for injecting fuel, and the injector from a fuel tank. A fuel supply passage for supplying fuel to the fuel, a fuel recovery passage for recovering fuel from the fuel supply passage to the fuel tank, an electromagnetic valve provided in the fuel recovery passage, and a fuel in the fuel supply passage A fuel temperature sensor for detecting the temperature, an alcohol concentration sensor for detecting the alcohol concentration of the fuel, and a predetermined limit fuel temperature is determined based on the alcohol concentration of the fuel detected by the alcohol concentration sensor When it is determined that the fuel temperature detected by the fuel temperature sensor is higher than the limit fuel temperature when the engine is stopped, the electromagnetic The open, characterized in that the fuel of the fuel supply passage and a electronic control unit for recovering the fuel tank through the fuel return passage.

  In the fourth embodiment of the present invention, utilizing the characteristic of the rise and fall of the fuel temperature during the engine stop period, the fuel temperature is monitored during the stop period and compared with a predetermined limit fuel temperature, When the fuel temperature becomes higher than the critical fuel temperature, it is predicted that the fuel will be vaporized in the subsequent stages, and the fuel in the fuel supply passage is recovered in the fuel tank as in the second embodiment of the present invention. Since vaporization is predicted while monitoring the fuel temperature during the engine stop period, more accurate control is possible, and vaporization and restart failure can be reliably prevented.

  Preferably, the electronic control unit updates and stores the maximum value of the fuel temperature detected by the fuel temperature sensor, and when the fuel temperature is determined to be equal to or lower than the limit fuel temperature, the fuel temperature is equal to the fuel temperature. It is determined whether or not it is lower than a value obtained by subtracting a predetermined value from the maximum value, and when it is determined that the fuel temperature is lower than the value, it stops itself.

If the fuel temperature is lower than the above value, it means that the fuel temperature has started to drop beyond the peak. Therefore, the monitoring can be terminated if this happens, and the electronic control unit can be stopped to bring the engine into a completely stopped state.
Preferably, the limit fuel temperature is a lower limit value of the fuel temperature that causes fuel vaporization when the fuel is at a predetermined pressure.

  According to the present invention, in an FFV engine that can use alcohol fuel, an excellent effect is achieved that fuel vaporization during an engine stop period and start-up failure caused by this can be reliably prevented. .

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an engine control apparatus according to the present embodiment. The illustrated engine 1 is an FFV engine and has four cylinders in the present embodiment, but the number of cylinders is not particularly limited. The engine 1 in this embodiment is an intake passage injection type that injects fuel into the intake passage (especially in the intake port), but has an in-cylinder injection type that directly injects fuel into the cylinder, or both injection methods. A dual injection type may be used.

  Air sucked from the air cleaner 2 is distributed and supplied to the combustion chambers of the respective cylinders via the intake passage 5. The intake passage 5 is defined by an intake pipe 51, an intake manifold 52, and intake ports (not shown) formed in the cylinder head of each cylinder, which are sequentially arranged from the upstream side. The intake manifold 52 includes a surge tank 4 as a collecting portion located on the upstream side, and a branch pipe 53 for each cylinder connected to an intake port of each cylinder. The intake pipe 51 is provided with an electronically controlled throttle valve 3. The injector 11 is provided for each cylinder and injects fuel toward the intake passage of each cylinder, particularly toward the outlet of the intake port. The fuel injected from the injector 11 is mixed with air to form a relatively homogeneous mixture in the in-cylinder combustion chamber. The injector 11 is opened by an on signal output from an electronic control unit (hereinafter referred to as ECU) 100 as control means, injects fuel, is closed by an off signal output from the ECU 100, and performs fuel injection. Stop.

  The air-fuel mixture formed in the combustion chamber is ignited by the spark plug 7 based on the ignition signal from the ECU 100 and combusts. Exhaust gas from the engine 1 is exhausted through an exhaust passage 8. The exhaust passage 8 includes an exhaust port formed for each cylinder in the cylinder head of the engine 1 and an internal passage of an exhaust manifold that communicates with the exhaust port and is attached to the cylinder head. An exhaust purification catalyst 9 is disposed on the downstream side of the exhaust manifold, and an exhaust pipe is connected to the downstream side of the catalyst 9. The outlet of the intake port and the inlet of the exhaust port are opened and closed by an intake valve and an exhaust valve (not shown), respectively.

  The fuel stored in the fuel tank 10 is supplied to each injector 11 via the fuel supply passage 12. Here, the engine 1 of the present embodiment can use alcohol and gasoline as fuels alone or in combination, and the fuel tank 10 stores fuel having an arbitrary alcohol concentration. This fuel may be 100% gasoline, may be a mixed fuel in which alcohol such as methanol or ethanol is mixed with gasoline, or may be 100% alcohol. In many cases, what kind of fuel is supplied to the fuel tank 10 depends on the use environment of the user such as what kind of gas station the user can use.

  The fuel supply passage 12 includes a delivery pipe 13 commonly connected to the injectors 11 and a fuel supply pipe 16 that connects the delivery pipe 13 and the fuel tank 10 to each other. A feed pump 14 is provided in a fuel supply pipe 16 near the fuel tank 10. The feed pump 14 is a variable type whose discharge flow rate is controlled by the ECU 100. By controlling the discharge flow rate, the fuel pressure in the delivery pipe 13, that is, the injection pressure from the injector 11 is controlled. The fuel supply pipe 16 is provided with a supply-side electromagnetic valve 6 that is controlled to be opened and closed by the ECU 100. The supply-side solenoid valve 6 is normally opened, but is closed after the fuel pressure in the delivery pipe 13 is increased, as will be understood later, to prevent back flow of fuel.

  In order to allow the fuel in the delivery pipe 13 to be collected in the fuel tank 10, the delivery pipe 13 and the fuel tank 10 are connected to each other by a fuel collection passage 18. A recovery-side electromagnetic valve 20 is provided in the fuel recovery passage 18. The collection-side solenoid valve 20 here is a variable type whose opening is controlled by the ECU 100 from fully open to fully closed. As will be described later, the opening is appropriately controlled when the engine is started, and the fuel pressure in the delivery pipe 13 is controlled. Is matched with a predetermined target pressure. It is fully closed except during fuel recovery. In order to actively recover the fuel, a fuel recovery pump 17 is preferably provided in the fuel recovery passage 18.

  An alcohol concentration sensor 21 is provided to detect the alcohol concentration of the fuel. The alcohol concentration sensor 21 of the present embodiment is installed in the fuel tank 10 and uses a capacitance type sensor that detects the alcohol concentration based on the dielectric constant of the fuel. However, an optical alcohol concentration sensor that detects the alcohol concentration based on the refractive index of the fuel can also be used. The alcohol concentration sensor 21 may be installed in the fuel supply pipe 16 or the delivery pipe 13. The delivery pipe 13 is provided with a fuel pressure sensor 23 and a fuel temperature sensor 15 for detecting the pressure and temperature of the fuel inside the delivery pipe 13. Hereinafter, “fuel pressure” and “fuel temperature” are abbreviated as “fuel pressure” and “fuel temperature” as appropriate.

  The ECU 100 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, and uses various maps stored in the ROM to obtain detection values of various sensors. On the basis of this, predetermined calculation processing is appropriately performed, and the injector 11, the spark plug 7, the drive motor 19 for the electric throttle valve 3, the feed pump 14, the supply side electromagnetic valve 6, the recovery side electromagnetic valve 20, the fuel recovery pump 17, etc. Control.

  In addition to the alcohol concentration sensor 21, the fuel pressure sensor 23, and the fuel temperature sensor 15, the sensors include the following. That is, the engine 1 is provided with a crank sensor 24 for detecting the crank angle. The crank sensor 24 outputs a pulse signal at predetermined crank angle intervals. Based on this pulse signal, ECU 100 detects the crank angle of engine 1 and calculates the rotational speed.

  In addition, an intake air temperature sensor 26 that detects the intake air temperature, that is, an atmospheric temperature, an accelerator opening sensor 27 that detects the amount of depression of the accelerator pedal (accelerator opening), a throttle position sensor 28 that detects the opening of the throttle valve 3, and the engine 1 The sensors include a water temperature sensor 29 for detecting the cooling water temperature and an intake pressure sensor 25 for detecting the pressure in the intake passage 5 downstream of the throttle valve 3. The ECU 100 basically controls the drive motor 19 so that the output value of the throttle position sensor 28 becomes a value corresponding to the output value of the accelerator opening sensor 27 and controls the opening of the throttle valve 3. Further, the ECU 100 calculates the engine load based on the output value of the intake pressure sensor 25. The engine load may be calculated based on the output values of the accelerator opening sensor 27 and the throttle position sensor 28, or the engine load may be calculated based on the output value by providing an air amount sensor.

  A manually operated ignition switch (IG) 30 and a warning lamp 31 are connected to the ECU 100. The user operates the ignition switch 30 to start or stop the engine.

  Next, stop control and start control in the engine 1 will be described. In the following description, the flowcharts shown in the drawings are executed by the ECU 100, and each map is created in advance based on a test or the like and stored in a memory (ROM) of the ECU 100. Each step in the control is represented by “S”.

  FIG. 2 shows a first form of stop control. The stop control is started when the ignition switch 30 is turned off by the user. The ECU 100 first turns off the injector 11 and the spark plug 7 to stop fuel injection and ignition, and stops the engine 1 (S101). Next, the ECU 100 determines whether or not the outside air temperature Ta detected by the intake air temperature sensor 26 is equal to or higher than a predetermined temperature Ta1 (for example, 30 ° C.) that can be regarded as a sufficiently high temperature (S102). When the outside air temperature Ta is equal to or higher than the predetermined temperature Ta1, the ECU 100 determines whether the alcohol concentration L detected by the alcohol concentration sensor 21 is equal to or higher than a predetermined concentration L1 (for example, 70%) that can be regarded as a sufficiently high alcohol concentration (S103). ). When the alcohol concentration L is equal to or higher than the predetermined concentration L1, the ECU 100 determines whether or not the engine has been warmed up (S104). Specifically, this is performed by the ECU 100 determining whether or not the engine water temperature Tw detected by the water temperature sensor 29 is equal to or higher than a predetermined temperature Tw1 that can be regarded as after warm-up. This determination may be made using the oil temperature or the engine block temperature instead of the water temperature. When the engine water temperature Tw is equal to or higher than the predetermined temperature Tw1, it is determined that the engine has been warmed up, and the process proceeds to the next step S105.

  In these steps S102 to S104, prediction is made as to whether or not the fuel in the fuel supply passage 12 is vaporized during the engine stop period. In other words, the higher the outside air temperature and the higher the alcohol concentration of the fuel, the more easily the fuel vaporizes, and the vaporization means that the engine body has been warmed up and the engine body has become sufficiently hot. It is easy to occur when is large. Here, in the fuel supply passage 12, vaporization is most likely to occur in the delivery pipe 13. This is because the delivery pipe 13 is disposed close to the engine body and across all cylinders. Note that vaporization is likely to occur in the intake passage injection engine as in this embodiment rather than in-cylinder injection engine. This is because the intake passage injection engine has a lower injection pressure, that is, a fuel pressure, than the in-cylinder injection engine. However, the present invention can also be applied to a cylinder injection engine or a dual injection engine as described above.

  The ECU 100 predicts that the fuel vaporizes when any of the determinations in steps S102 to S104 is right, and executes the following pressure increase control of the fuel in the fuel supply passage 12 in step S105. That is, the feed pump 14 is operated to increase the fuel pressure so that the detected value (actual fuel pressure) of the fuel pressure sensor 23 matches a predetermined target pressure. When the actual fuel pressure matches the target pressure, the supply-side electromagnetic The valve 6 is closed to confine the boosted fuel in the fuel supply passage 12 (particularly the delivery pipe 13) on the downstream side of the supply-side electromagnetic valve 6. The pressure increase is performed only in a predetermined section of the fuel supply passage 12 including the delivery pipe 13.

  Here, the actual fuel pressure before the pressure increase substantially coincides with the basic target pressure. The basic target pressure is set to a constant value (for example, 0.4 MPa) under the assumption that the fuel is 100% gasoline. Normally, the actual fuel pressure is controlled to this basic target pressure regardless of the alcohol concentration of the fuel. Is done. Normally, even if alcohol mixed fuel is used, if the actual fuel pressure is equal to the basic target pressure, vaporization will not occur during the engine stop period, but as described above, the outside air temperature is high, the alcohol concentration is high, etc. If bad conditions overlap, vaporization may occur. Therefore, if it is predicted that the fuel will be vaporized, the value higher than the basic target pressure is set as the target pressure, and the actual fuel pressure is once increased and maintained in the increased state until the next start, as executed in step S105. Like to do.

  The target pressure during pressure increase is calculated from the target pressure map during pressure increase shown in FIG. 3 based on the alcohol concentration L of the fuel. As can be seen, the higher the alcohol concentration L of the fuel, the higher the target pressure. Even when the predetermined concentration L1 = 70%, the target pressure is higher than the basic target pressure (0.4 MPa) (0.5 MPa). . This target pressure map for boosting is created as follows. As shown in FIG. 4, a vapor pressure diagram for each alcohol concentration of the fuel is first considered. The figure illustrates the case where the alcohol concentration is 0% and 70%. As can be seen, the higher the alcohol concentration of the fuel, the higher the saturated vapor pressure of the fuel, and the fuel must be kept at a higher pressure when attempting to keep the fuel in a liquid state. When the fuel is left during the engine stop period (this is referred to as soak), as shown in FIG. 5, the fuel temperature Tf once rises as the soak time t elapses and then falls later.

  In order to reliably prevent vaporization so as to cause a start failure in the soak of the fuel accompanying such a temperature change, as shown in FIG. 4, a higher pressure side than the vapor pressure curve (solid line) of the fuel with a predetermined alcohol concentration The curve (referred to as a vapor generation prediction line, indicated by a broken line) is hypothesized, and the maximum predicted fuel temperature Tmax (for example, 100 ° C.) in the soak is obtained from experiments. Then, the pressure corresponding to the maximum predicted temperature Tmax on the vapor generation prediction line is set as the value Pt of the target pressure map during pressure increase. Such a diagram creation and operation is performed for each alcohol concentration, and each value in the pressure increase target pressure map is set.

  Returning to FIG. 2, the ECU 100 thus pressurizes the fuel, stops the feed pump 14 (S106), and then stops itself (S107). The same applies when the determination in any of steps S102 to S104 is negative.

  As described above, according to the stop control, the fuel is boosted and held when the engine is stopped, so that fuel vaporization during the engine stop period (during soak) is surely prevented, and the start failure at the next start is started. Can be prevented.

  In addition, supplementing the vaporization prediction during the engine stop period, the set value Ta1 in step S102 is the worst state in which the fuel is 100% alcohol, and the restart failure is caused by the increase in the fuel temperature in the soak. The minimum outside air temperature that can cause the generation of vapor is determined through experiments. The alcohol concentration set value L1 in step S103 is the minimum alcohol concentration that may cause vapor generation to the extent that restart failure occurs due to the increase in the fuel temperature in the soak under such an outside air temperature Ta1. Is determined by experimentation. In step S104, if the engine has not been warmed up, even if the outside air temperature is high, the influence of the radiant heat from the engine is small, and the increase in the fuel temperature in the soak is small. Therefore, such boost control is not executed.

  As shown in FIG. 5, the fuel temperature Tf rises at the early stage of the soak mainly because the fuel flow is lost when the delivery pipe 13 receives the radiant heat from the engine. After this rise, the fuel temperature Tf falls due to cooling by outside air or the like. In general, a gasoline engine is hard designed so that vapor does not occur even when the fuel temperature rises. However, in a special situation where the fuel is made to have a high alcohol concentration with the same specifications and restarted immediately after stopping at high temperatures (short-time soak), such vaporization and restart failure may occur. In addition, there have been few countermeasures for such special cases. The present invention proposes a suitable proposal for such measures, and proposes a method for dealing with such a special case without changing the existing apparatus configuration as much as possible.

  Next, a first form of start control combined with such a first form of stop control will be described with reference to FIG. The outline of the start control here is to start the operation by reducing the pressure-increased fuel to the basic pressure (the aforementioned basic target pressure = 0.4 MPa). Since the fuel injection timing, fuel injection amount, etc. are set based on the basic pressure, it is not necessary to perform fuel pressure correction of the fuel injection amount, etc. by returning to the basic pressure in this way and simplifying the control There is an advantage that can be

  The start control is started when the ignition switch 30 is turned on by the user. The ECU 100 first acquires the fuel temperature Tf and the alcohol concentration L detected by the fuel temperature sensor 15 and the alcohol concentration sensor 21, respectively (S201). Next, the ECU 100 determines whether or not the acquired fuel temperature Tf is lower than a predetermined limit fuel temperature Tflim (S202). This limit fuel temperature Tflim is obtained from the limit fuel temperature map of FIG. 7 based on the acquired alcohol concentration L. As can be seen, the lower limit fuel temperature Tflim is set as the alcohol concentration L becomes higher. The limit fuel temperature Tflim is a lower limit value of the fuel temperature that causes fuel vaporization when the boosted fuel has a predetermined value, that is, a basic pressure. That is, after the fuel pressure is increased, the fuel temperature rises as the soak time elapses. In this state, as described above, since the target pressure during pressure increase is set to a value that can prevent vaporization, vaporization does not occur. However, if the fuel pressure is reduced to the basic pressure during restart, vaporization may occur as a result of the increase in fuel temperature. The lower limit value of the fuel temperature that causes vaporization after this pressure reduction is the limit fuel temperature Tflim. More simply, referring to FIG. 5, vaporization occurs when the fuel pressure is lowered to the basic pressure when the fuel temperature Tf is equal to or higher than the limit fuel temperature Tflim, and the fuel pressure when the fuel temperature Tf is lower than the limit fuel temperature Tflim. Vaporization does not occur when the pressure is lowered to the basic pressure.

  Returning to FIG. 6, when the ECU 100 determines in step S202 that the fuel temperature Tf is lower than the limit fuel temperature Tflim, the ECU 100 controls the opening of the recovery-side solenoid valve 20 while monitoring the fuel pressure value by the fuel pressure sensor 23 to deliver the fuel. A part of the fuel in the pipe 13 is recovered (relieved) in the fuel tank 10 and depressurized to match (regulate) the basic target pressure (S203). At this time, if there is a fuel recovery pump 17, the fuel recovery pump 17 is operated. Then, normal start control is executed (S204). That is, the feed pump 14 is operated, the supply-side solenoid valve 6 is opened, the starter is operated, and fuel injection and ignition are executed.

  On the other hand, when ECU 100 determines in step S202 that the fuel temperature Tf is equal to or greater than the limit fuel temperature Tflim, the ECU 11 sets the energization period of the injector 11 (this corresponds to the fuel injection amount) to the fuel pressure value Pf detected by the fuel pressure sensor 23. Correction is made accordingly and start control is executed (step S205). That is, in this case, vaporization occurs when the fuel pressure is reduced to the basic pressure, so the fuel pressure is kept higher than the basic pressure and the fuel injection pressure is corrected to be shorter than the predetermined basic injection period by adjusting the difference in pressure. Perform injection.

  According to this starting control, the fuel pressure is reduced to the basic pressure only when the starting fuel temperature Tf is lower than the limit fuel temperature Tflim. Therefore, it is not necessary to correct the fuel injection amount while preventing vaporization due to the reduced pressure. As a result, control can be simplified. Further, when the fuel temperature Tf at the start is equal to or higher than the limit fuel temperature Tflim, the fuel injection amount is corrected while the fuel pressure is higher than the basic pressure, so that a good start can be performed while preventing vaporization.

  By the way, in order to perform this starting control, the fuel temperature sensor 15, the fuel pressure sensor 23, the recovery side electromagnetic valve 20, and the fuel recovery passage 18 (and the fuel recovery pump 17) are necessary. In the case of a control device without such elements, as in the second form of start control shown in FIG. 7, step S201 ′, that is, acquisition of fuel pressure Pf and alcohol concentration L, and step S205, start with fuel pressure correction during the fuel injection period. If only control is performed, the engine can be started.

  Steps S204 and S205 in FIG. 6 are the same, but the value of alcohol concentration L is necessary on the premise that the basic fuel injection amount is 100% gasoline. This is because it is necessary to perform density correction. That is, ECU 100 determines a basic injection amount from a predetermined map or the like, and multiplies the basic injection amount by an alcohol concentration correction coefficient (may be added) to determine a fuel injection amount after alcohol concentration correction. The alcohol concentration correction coefficient is set to a value of 1 or more that increases as the alcohol concentration L of the fuel increases. That is, the amount of fuel injected increases as the alcohol concentration L increases. The fuel pressure correction is executed for the fuel injection amount after the alcohol concentration correction. This is the same for the starting control described later.

  Next, a second form of stop control will be described based on FIG. The second form of the stop control is generally the same as the first form, and will be described below focusing on the differences. As an outline, when the ECU 100 predicts that the fuel is vaporized, the recovery control for recovering (returning) the fuel in the fuel supply passage 12 to the fuel tank 10 is executed.

  Steps S401 to 404 are the same as Steps S101 to S104. The ECU 100 predicts that the fuel is vaporized when the determinations in steps S402 to 404 are correct, stops the feed pump 14 (S405), and returns the fuel to the fuel tank 10 (S406). At this time, the ECU 100 closes the supply-side electromagnetic valve 6, opens the recovery-side electromagnetic valve 20, and activates the fuel recovery pump 17, if there is, so that the fuel supply passage on the downstream side of the supply-side electromagnetic valve 6 The fuel in the fuel tank 10 is recovered in the fuel tank 10 (particularly the delivery pipe 13). Then, the ECU itself is stopped (S407), and this control is terminated. When the determination in any of steps S402 to 404 is negative, the ECU 100 stops the feed pump 14 (S408), stops itself (S407), and ends this control.

  FIG. 10 shows a third form of start control combined with the second form of stop control. The start control is started at the same time when the ignition switch 30 is turned on. The ECU 100 first operates the feed pump 14 and opens the supply-side electromagnetic valve 6 (S501), and supplies fuel to the delivery pipe 13. This supply is continued until the detected value of the fuel pressure sensor 23 becomes equal to the basic target pressure (S502). When the two values are equal to each other, normal start control is executed (S503) as in step S204 of FIG. That is, the starter is operated to execute fuel injection and ignition.

  According to these stop control and start control, since all the fuel in the delivery pipe 13 is recovered at the time of stop, naturally, fuel vaporization in the soak does not occur there. Further, since the boosting at the time of stopping as described above is not executed, it is not necessary to specially strengthen the pressure-resistant structure of the fuel injection system. And the fuel temperature sensor 15 becomes unnecessary and the collection | recovery side solenoid valve 20 does not need to be variable. The maps shown in FIGS. 3 and 7 are also unnecessary. Therefore, there exists an advantage which can simplify an apparatus structure and control.

  Next, a fourth form of start control will be described based on FIG. The fourth form of the start control can be widely used in combination with a normal fuel injection device. As an outline, when it is estimated that the fuel is already vaporized at the start, the start is prohibited.

  Step S601 is the same as step S201 of the first form of start control shown in FIG. When the ECU 100 determines that the fuel temperature Tf is equal to or higher than the limit fuel temperature Tflim in step S602, the ECU 100 estimates that the fuel has vaporized, turns on the warning lamp 31 to warn that the engine cannot be started (S603), and ignition. Even if the switch 30 is operated to the starter position, the start prohibition control is executed to deactivate the starter (S604). The warning may simply prompt the user to wait, or may display a waiting time simply inferred from the fuel temperature and the atmospheric temperature. This forces the user to turn off the ignition switch 30 and wait for a while until the fuel temperature drops. If the fuel temperature Tf becomes lower than the limit fuel temperature Tflim after a lapse of time, step S602 becomes negative due to the user's re-operation of the ignition switch 30, and normal start control is executed (S605). At this time, the fuel temperature has already dropped sufficiently, and it is considered that the vaporized fuel has returned to the liquid state again, and a normal start is possible.

  Here, it is characteristic that the limit fuel temperature Tflim shown in the map of FIG. 7 is used for the determination of fuel vaporization at the time of start (S602). That is, in the case of a normal engine stop, the fuel at the basic pressure (= 0.4 MPa) remains in the delivery pipe 13. If soak is started in this state and the fuel temperature rises, the fuel may be vaporized. The presence or absence of this vaporization is determined by comparison with the limit fuel temperature Tflim at the time of restart. As the limit fuel temperature Tflim, values corresponding to all alcohol concentrations L can be acquired as shown in FIG.

  According to the fourth form of the start control, the supply-side electromagnetic valve 6 and the recovery-side elements, that is, the recovery-side electromagnetic valve 20 and the fuel recovery passage 18 (and also the fuel recovery pump 17) are not required, and the apparatus configuration is greatly reduced. There is an advantage that it can be simplified and is versatile. Note that the fourth form of the start control can be combined with the first form of the stop control shown in FIG. 2. In this case, the normal start control in step S605 is performed, and the fuel pressure correction in step S205 is performed. What is necessary is just to replace with the accompanying start control. The warning in step S603 may be a voice warning or the like.

  Next, a third form of stop control will be described based on FIG. When the ignition switch 30 is turned off and stop control is started, the ECU 100 first acquires the fuel temperature Tf and the alcohol concentration L detected by the fuel temperature sensor 15 and the alcohol concentration sensor 21, respectively, and the acquired fuel temperature. Tf is stored as an initial value of the maximum fuel temperature Tfmax (S701). Next, the ECU 100 stops fuel injection and ignition, and stops the engine, but does not stop itself to execute the following fuel temperature monitoring (S702). The ECU 100 acquires the fuel temperature Tf detected by the fuel temperature sensor 15 every predetermined time (for example, 10 s), compares it with the stored maximum fuel temperature Tfmax, and sets the larger one as the maximum fuel temperature Tfmax. Update memorize. That is, as shown in FIG. 5, since the fuel temperature Tf in the soak once rises and then decreases, the maximum fuel temperature Tfmax is sequentially updated before reaching the peak, and the peak value reaches the maximum after reaching the peak. It is held as the fuel temperature Tfmax.

  Next, the ECU 100 compares the acquired fuel temperature Tf with the limit fuel temperature Tflim obtained from the map of FIG. 7 at each predetermined time, and determines whether or not the fuel temperature Tf is higher than the limit fuel temperature Tflim.

  When the fuel temperature Tf is higher than the limit fuel temperature Tflim, recovery control for returning the fuel in the delivery pipe 13 to the fuel tank 10 is performed as in steps S405 and 406 in FIG. 8 (step S705). In this case, as shown in FIG. 13, the limit fuel temperature Tflim is lower than the fuel temperature peak in the soak, and the fuel temperature Tf exceeds the limit fuel temperature Tflim while the fuel temperature rises. Since the fuel pressure is a basic pressure, when the fuel temperature Tf exceeds the limit fuel temperature Tflim, the fuel is likely to vaporize. Therefore, in this case, the fuel is collected and replenished at the next start (this will be described later). When the fuel return is completed, the ECU 100 is stopped (step S706), and this control is completed.

  On the other hand, when the fuel temperature Tf is equal to or lower than the limit fuel temperature Tflim, the fuel temperature Tf is compared with a value obtained by subtracting a predetermined temperature A (for example, 10 ° C.) from the maximum fuel temperature Tfmax, and the fuel temperature Tf is lower than that value. Determine whether or not. If it is not lower, the process returns to S703 and the fuel temperature monitoring is continued. If it is lower, the ECU 100 is stopped (step S706), and this control is finished. In this case, as shown in FIG. 14, the limit fuel temperature Tflim is higher than the fuel temperature peak in the soak. If the fuel temperature rises and exceeds the peak, the fuel temperature at this fuel temperature peak is stored as the maximum value Tfmax. Thereafter, when the fuel temperature is greatly lowered from the fuel temperature Tfmax at the peak than the predetermined temperature A (see point B), the ECU 100 is the first time that the limit fuel temperature Tflim is higher than the fuel temperature peak for the first time. In addition, it is determined that there is no longer a risk of fuel vaporization. Therefore, at this time, ECU 100 stops itself and ends monitoring.

  According to this stop control, the fuel recovery control is executed only when it is surely required, as compared with the stop control shown in FIGS. In place of the fuel recovery control in step S705, it is also possible to execute fuel boost control as in step S105 in FIG.

  Next, a fifth form of start control combined with the third form of stop control will be described with reference to FIG. This start control is substantially the same as the third form of start control shown in FIG. 10, except that step S801 is added. The start control is started at the same time when the ignition switch 30 is turned on, and the ECU 100 determines whether or not the fuel pressure Pf detected by the fuel pressure sensor 23 is lower than the basic target pressure (= 0.4 MPa). That is, here, it is substantially determined whether or not fuel recovery is executed in the start-up control. If fuel recovery is not executed, the fuel pressure Pf is equal to the basic target pressure, and normal start control is executed (S804). On the other hand, if fuel recovery is being performed, the fuel pressure Pf is lower than the basic target pressure, so the feed pump 14 is operated and the supply-side solenoid valve 6 is opened (S802) until the fuel pressure Pf becomes equal to the basic target pressure. The delivery pipe 13 is replenished with fuel (S803: NO). When the fuel pressure Pf becomes equal to the basic target pressure (S803: YES), normal start control is executed (S804). When fuel boost control is executed during stop control, fuel relief / regulation may be executed as in step S203 of FIG.

  In the present embodiment, the predicting means, the target fuel pressure determining means, the starting time determining means, and the starting prohibiting means are constituted by the ECU 100, the boosting means is constituted by the ECU 100 and the feed pump 14, and the outside air temperature detecting means is absorbed. Consists of an air temperature sensor 26, an alcohol concentration detecting means is constituted of an alcohol concentration sensor 21, a warm-up completion detecting means is constituted of an ECU 100 and a water temperature sensor 29, a fuel pressure detecting means is constituted of a fuel pressure sensor 23, and a valve is supplied. The fuel temperature detecting means is constituted by the fuel temperature sensor 15, and the pressure reducing means is constituted by the ECU 100, the fuel pressure sensor 23, the fuel recovery passage 18, the recovery side electromagnetic valve 20, and the fuel recovery pump 17 as necessary. The recovery means includes a fuel recovery passage 18, a recovery side solenoid valve 20, and a required Fuel by the recovery pump 17 is configured, and a warning means by the warning lamp 31 in accordance with the.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

It is a system top view which shows the control apparatus of the engine which concerns on one Embodiment of this invention. It is a flowchart which shows the 1st form of the stop control which concerns on this embodiment. It is a figure which shows a target pressure map. It is a saturated vapor pressure diagram of the fuel used for preparation of a target pressure map. It is a graph which shows the relationship between the soak time of fuel, and fuel temperature. It is a flowchart which shows the 1st form of the starting control which concerns on this embodiment. It is a figure which shows a limit fuel temperature map. It is a flowchart which shows the 2nd form of the starting control which concerns on this embodiment. It is a flowchart which shows the 2nd form of the stop control which concerns on this embodiment. It is a flowchart which shows the 3rd form of the starting control which concerns on this embodiment. It is a flowchart which shows the 4th form of the starting control which concerns on this embodiment. It is a flowchart which shows the 3rd form of the stop control which concerns on this embodiment. It is a graph which shows the relationship between fuel temperature change and limit fuel temperature. It is a graph which shows the relationship between fuel temperature change and limit fuel temperature. It is a flowchart which shows the 5th form of the starting control which concerns on this embodiment.

Explanation of symbols

1 Engine 6 Supply Side Solenoid Valve 10 Fuel Tank 11 Injector 12 Fuel Supply Passage 13 Delivery Pipe 14 Feed Pump 15 Fuel Temperature Sensor 16 Fuel Supply Pipe 17 Fuel Recovery Pump 18 Fuel Recovery Passage 20 Recovery Side Electromagnetic Valve 21 Alcohol Concentration Sensor 23 Fuel Pressure Sensor 25 Intake pressure sensor 26 Intake temperature sensor 30 Ignition switch 31 Warning lamp 100 Electronic control unit (ECU)
Ta outside temperature Tw engine water temperature Tf fuel temperature Tflim limit fuel temperature Tfmax maximum fuel temperature Pf fuel pressure L alcohol concentration

Claims (12)

An engine control device that can use alcohol and gasoline as fuels individually or in combination,
An injector for injecting fuel;
A fuel supply passage for supplying fuel to the injector;
Predicting means for predicting according to a predetermined condition whether or not the fuel in the fuel supply passage is vaporized during the engine stop period when the engine is stopped;
An engine control device, comprising: a boosting unit that boosts the fuel in the fuel supply passage when the prediction unit predicts that the fuel is vaporized. Outside air temperature detecting means for detecting outside air temperature,
Alcohol concentration detection means for detecting the alcohol concentration of the fuel;
Further comprising a warm-up completion detecting means for detecting the warm-up completion of the engine,
The outside air temperature detected by the outside air temperature detecting means is equal to or higher than a predetermined temperature, the alcohol concentration detected by the alcohol concentration detecting means is equal to or higher than a predetermined concentration, and the warm-up completion detecting means stops the engine warm-up. 2. The engine control apparatus according to claim 1, wherein, when detected, the prediction means predicts that the fuel is vaporized. Fuel pressure detection means for detecting fuel pressure in the fuel supply passage;
Alcohol concentration detection means for detecting the alcohol concentration of the fuel;
A target fuel pressure determining means for determining a target fuel pressure that does not cause fuel vaporization during the engine stop period based on the alcohol concentration detected by the alcohol concentration detecting means;
2. The engine control apparatus according to claim 1, wherein the boosting means boosts the fuel so that a fuel pressure detected by the fuel pressure detecting means matches the target fuel pressure.   The engine control device according to any one of claims 1 to 3, wherein a valve for preventing a back flow of the pressurized fuel is provided in the fuel supply passage. Alcohol concentration detection means for detecting the alcohol concentration of the fuel;
Limit fuel temperature determining means for determining a predetermined limit fuel temperature based on the alcohol concentration of the fuel detected by the alcohol concentration detecting means;
Fuel temperature detection means for detecting the fuel temperature in the fuel supply passage;
Determination means for determining whether or not the fuel temperature detected by the fuel temperature detection means is lower than the limit fuel temperature at the time of engine start;
The pressure reducing means for reducing the fuel pressure in the fuel supply passage to a predetermined value when the determining means determines that the fuel temperature is lower than the limit fuel temperature. Engine control device. An engine control device that can use alcohol and gasoline as fuels individually or in combination,
An injector for injecting fuel;
A fuel supply passage for supplying fuel to the injector;
Predicting means for predicting according to a predetermined condition whether or not the fuel in the fuel supply passage is vaporized during the engine stop period when the engine is stopped;
An engine control device comprising: a recovery means for recovering the fuel in the fuel supply passage to a fuel tank when the prediction means predicts that the fuel is vaporized. Outside air temperature detecting means for detecting outside air temperature,
Alcohol concentration detection means for detecting the alcohol concentration of the fuel;
Further comprising a warm-up completion detecting means for detecting the warm-up completion of the engine,
The outside air temperature detected by the outside air temperature detecting means is equal to or higher than a predetermined temperature, the alcohol concentration detected by the alcohol concentration detecting means is equal to or higher than a predetermined concentration, and the warm-up completion detecting means stops the engine warm-up. 7. The engine control apparatus according to claim 6, wherein, when detected, the prediction means predicts that the fuel is vaporized. An engine control device that can use alcohol and gasoline as fuels individually or in combination,
An injector for injecting fuel;
A fuel supply passage for supplying fuel to the injector;
Fuel temperature detection means for detecting the fuel temperature in the fuel supply passage;
Alcohol concentration detection means for detecting the alcohol concentration of the fuel;
Limit fuel temperature determining means for determining a predetermined limit fuel temperature based on the alcohol concentration of the fuel detected by the alcohol concentration detection means;
A start time determination means for determining whether or not the fuel temperature detected by the fuel temperature detection means is equal to or higher than the limit fuel temperature when the engine is started;
An engine control device comprising start prohibiting means for prohibiting engine start when the fuel temperature is determined to be equal to or higher than the limit fuel temperature by the start time determining means.   9. The engine control apparatus according to claim 8, further comprising warning means for issuing a predetermined warning when the start prohibiting means prohibits starting of the engine. An engine start control device that can use alcohol and gasoline as fuels individually or in combination,
An injector for injecting fuel;
A fuel supply passage for supplying fuel from a fuel tank to the injector;
A fuel recovery passage for recovering fuel from the fuel supply passage to the fuel tank;
An electromagnetic valve provided in the fuel recovery passage;
A fuel temperature sensor for detecting a fuel temperature in the fuel supply passage;
An alcohol concentration sensor for detecting the alcohol concentration of the fuel;
Based on the alcohol concentration of the fuel detected by the alcohol concentration sensor, a predetermined limit fuel temperature is determined, and when the engine is stopped, it is determined that the fuel temperature detected by the fuel temperature sensor is higher than the limit fuel temperature. And an electronic control unit that opens the solenoid valve and recovers the fuel in the fuel supply passage to the fuel tank through the fuel recovery passage.   The electronic control unit updates and stores the maximum value of the fuel temperature detected by the fuel temperature sensor, and when the fuel temperature is determined to be equal to or lower than the limit fuel temperature, the fuel temperature is calculated from the maximum value of the fuel temperature. 11. The engine control device according to claim 10, wherein it is determined whether or not the fuel temperature is lower than the value obtained by subtracting a predetermined value, and when the fuel temperature is determined to be lower than the value, the engine is stopped.   12. The engine according to claim 5, 8, 10, or 11, wherein the critical fuel temperature is a lower limit value of a fuel temperature that causes fuel vaporization when the fuel is at a predetermined pressure. Control device.

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