JP2005248737A - Diagnostic device for fuel supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect opening sticking failure of a flow passage switching means by existing equipment without adding new components. <P>SOLUTION: A switching valve 15 arranged in a fuel return line 3b is normally in a closing state. Excessive fuel is returned to a fuel tank 4 through a fuel by-pass line 3c. The opening sticking failure diagnosis of the switching valve 15 is executed by comparing a fuel temperature integral value CFTMP calculated on the basis of the fuel temperature FTMP in the fuel tank 4 detected by a fuel temperature sensor 6 and an integral value CFTCAL of an estimated fuel temperature FTCAL calculated on the basis of parameters expressing operating states of a vehicle such as an intake air quantity GA detected by an intake air quantity sensor 10, engine rotation speed NE detected by an engine rotation speed sensor 12 and vehicle speed VSP detected by a vehicle speed sensor 17. When the difference therebetween is a predetermined value or more, the device estimates that excessive fuel passes through a fuel delivery line 3a to be returned to the fuel tank 4 with its temperature increased, and diagnoses the switching valve 15 as opening failure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a diagnostic device for a fuel supply device that determines whether or not there is an open sticking failure of a flow path switching means provided in a fuel return line that returns a surplus of fuel supplied to an injector to a fuel tank.

  Conventionally, as a fuel supply device that supplies fuel to an engine injector, the fuel discharged from the fuel pump is supplied to the injector through the fuel delivery line in excess of the amount that is actually injected. A return type fuel supply and supply device that returns the fuel to the fuel tank through the fuel return line is often used.

  In this type of fuel supply device, the discharge amount of the fuel pump is always substantially constant. Therefore, when the amount of fuel injected from the injector is small, surplus fuel returned to the fuel tank (hereinafter referred to as “surplus fuel”). ) Will increase. When surplus fuel passes through the fuel piping in the engine room, the radiant heat of the engine and the like is received. Therefore, when this surplus fuel increases, the fuel temperature in the fuel tank rises and fuel evaporative gas (hereinafter referred to as “ The amount of generated “evaporative gas” is increased, which causes inconveniences such as the need to enlarge the canister for adsorbing the evaporated gas.

  As countermeasures, for example, in Japanese Patent Application Laid-Open No. 2003-97374, a pressure regulator for adjusting fuel pressure is installed in the fuel delivery line, and the fuel delivery line and the downstream side of the fuel return line are connected via the fuel bypass line. Connected, and further, a flow path switching valve is installed upstream of the fuel return line, and the fuel return line is opened with the flow path switching valve until the time corresponding to the cooling water temperature has elapsed since the start of the engine, A technique is disclosed in which, after a predetermined time has elapsed after the engine is started, the flow path switching valve is switched to close the fuel return line.

  According to this prior art, at the time of restart (hot start) immediately after the engine is stopped, the flow path switching valve opens the fuel return line, so that the fuel retained in the fuel pipe and heated to the fuel tank Since it is discharged, vapor can be removed from the fuel pipe. Also, after the set time has elapsed, the fuel return line is blocked by the flow path switching valve, so that surplus fuel is returned directly to the fuel tank through the fuel bypass line, as in the so-called returnless type fuel supply device. The fuel temperature in the fuel tank is not increased more than necessary, and the generation of evaporation gas can be suppressed.

  By the way, when the flow path switching valve is fixed (open fixed) with the fuel return line open, the surplus fuel is returned to the fuel tank in a state of receiving heat through the fuel pipe disposed in the engine room. Therefore, there is a disadvantage that the fuel temperature in the fuel tank rises and the amount of evaporated gas increases.

Therefore, in the above-mentioned Japanese Patent Application Laid-Open No. 2003-97374, a first fuel temperature sensor is disposed at the inlet of a fuel distribution pipe to which an injector is connected, and a second fuel temperature sensor is disposed downstream of the flow path switching valve. In order to close the fuel return line, the control unit outputs a valve closing signal to the flow path switching valve, and then the fuel temperature detected by the first fuel temperature sensor and the fuel temperature detected by the second fuel temperature sensor. When the deviation is less than or equal to a predetermined value, a diagnostic device is provided that determines that the flow path switching valve is stuck open.
JP 2003-97374 A

  However, the technique disclosed in Japanese Patent Application Laid-Open No. 2003-97374 requires two temperature sensors, a first fuel temperature sensor and a second fuel temperature sensor, to detect the sticking of the flow path switching valve. For this reason, the number of parts is increased, and the accompanying wiring and connection connectors are required. Further, since it is necessary to add an interface circuit for connection to the control unit, there is a problem that the product cost increases. is there.

  Furthermore, since two fuel temperature sensors are required, the fuel temperature cannot be applied to an existing fuel supply device in which the fuel temperature is detected by a single fuel temperature sensor disposed in the fuel tank. There is a missing problem.

  In view of the above circumstances, the present invention can detect an open fixing failure of the flow path switching means with existing equipment without adding new parts, and suppresses a significant increase in product cost. An object of the present invention is to provide a diagnostic device for a fuel supply device that is excellent in performance.

  In order to achieve the above object, a fuel supply device diagnostic apparatus according to the present invention comprises a fuel delivery line for supplying fuel from a fuel pump to an injector, and a fuel return line for returning surplus fuel supplied to the injector to a fuel tank. A fuel bypass line that bypasses the fuel delivery line and the fuel return line, a fuel pressure adjusting means that is interposed in the bypass line and that regulates the pressure of fuel supplied to the injector, and the fuel return line In the fuel supply device that has a flow path switching means interposed upstream of the connection part of the fuel bypass line and switches the flow path of the surplus fuel by switching the flow path switching means based on the operating state, A signal for closing the fuel return line is output to the flow path switching means. Diagnosis condition determining means for determining that the diagnosis condition is satisfied, fuel temperature detecting means for detecting the actual fuel temperature in the fuel tank, and estimated fuel for setting the estimated fuel temperature in the fuel tank based on the operating state A temperature determining means, and a failure determining means for determining whether or not there is an open sticking failure of the flow path switching means based on the actual fuel temperature and the estimated fuel temperature when the diagnosis condition determining means determines that the diagnosis condition is satisfied. It is characterized by providing.

  According to the present invention, it is possible to detect an open fixing failure of the flow path switching means with existing equipment without adding new parts, suppress a significant increase in product cost, and excellent versatility. An excellent effect is exhibited.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of the fuel supply apparatus.

  Reference numeral 1 in FIG. 1 denotes an engine. In this embodiment, a horizontally opposed four-cylinder engine is shown. An injector 2 is disposed in each cylinder of the engine 1. The injectors 2 are in communication with each other via a fuel line 3. The fuel line 3 constitutes a so-called line pressure maintaining fuel injection system, and communicates with the fuel delivery line 3a extending from the upstream side through the injectors 2 and downstream of the fuel delivery line 3a. It has a fuel return line 3 b that faces the fuel tank 4 on the downstream side. Further, the upstream side of the fuel delivery line 3a and the downstream side of the fuel return line 3b are bypass-connected via the fuel bypass line 3c.

  An in-tank type fuel pump 5 facing the fuel tank 4 is connected upstream of the fuel delivery line 3a. The fuel pump 5 is provided with a fuel temperature sensor 6 as fuel temperature detecting means for detecting the fuel temperature FTMP. Further, a fuel level sensor 7 is disposed in the fuel tank 4 as fuel level detecting means for detecting the fuel level FLVL.

  An air cleaner 9 is disposed upstream of an intake passage 8 communicating with each cylinder of the engine 1 via an intake manifold (not shown), and an intake air amount GA [g / An intake air amount sensor 10 for detecting sec] is disposed, and a throttle valve 11 is disposed downstream thereof. The engine 1 is also provided with an engine speed sensor 12 that detects the engine speed NE from the rotation of the crankshaft 1a.

  A pressure regulator 14 for adjusting fuel pressure is interposed in the fuel bypass line 3c. The pressure regulator 14 is a well-known regulator that adjusts the fuel pressure (relative pressure) applied to the injector 2 to be always constant with respect to the intake pipe pressure downstream of the throttle valve 11 that is the injection atmosphere of the injector 2. The surplus fuel at the time of pressure adjustment is returned to the fuel tank 4 through the fuel return line 3b.

  Further, a flow path switching valve 15 as a flow path switching means is interposed upstream of a portion of the fuel delivery line 3a to which the fuel bypass line 3c is connected, and an orifice 16 is interposed upstream thereof. . The flow path switching valve 15 is a normally-closed solenoid valve, and is opened by a closing signal from an engine control unit (ECU) 21 described later.

  The above-described sensors 6, 7, 10, and 12 are connected to the ECU 21, and the outside air temperature sensor 13 that detects the outside air temperature TAMB, and the vehicle speed VSP is detected from the rotation of the output shaft of the transmission (not shown). A vehicle speed sensor 17 is connected. The outside air temperature sensor 13 may be substituted with the intake air temperature detected by the intake air temperature sensor provided in the intake air amount sensor 10.

  The ECU 21 outputs a close signal to the flow path switching valve 15 for a set time (for example, a time set based on the cooling water temperature when the ignition switch is turned on) from when the ignition switch is turned on, and switches the flow path. The valve 15 is opened.

  On the other hand, when the ignition switch is turned on, the fuel pump 5 is driven, and the fuel stored in the fuel tank 4 is discharged to the fuel delivery line 3a via the fuel pump 5. The fuel discharged to the fuel delivery line 3a side is distributed to the fuel bypass line 3c and the fuel delivery line 3a side on the upstream side.

  The fuel distributed to the fuel bypass line 3c is returned to the fuel tank 4 from the downstream side of the fuel return line 3b. On the other hand, the fuel distributed to the fuel delivery line 3a passes through each injector 2 and injects fuel from the injector 2 in a predetermined manner, and surplus fuel passes through the fuel return line 3b communicated downstream of the fuel delivery line 3a. After that, it is returned to the fuel tank 4. The fuel pressure in the fuel line 3 is regulated by the orifice 16 and the pressure regulator 14 interposed in the fuel return line 3b.

  Since the fuel staying in the fuel delivery line 3a is pushed out to the fuel return line 3b by the fuel sent from the fuel tank 4, vapor generated in the fuel delivery line 3a can be discharged to the fuel tank 4. In addition, the fuel in the fuel delivery line 3a can be cooled.

  Thereafter, when the set time elapses, the closing signal output from the ECU 21 to the flow path switching valve 15 is stopped, and the flow path switching valve 15 is closed to shut off the fuel return line 3b. As a result, the fuel pressure in the fuel line 3 rises due to the discharge pressure from the fuel pump 5, the fuel pressure is regulated by the pressure regulator 14, and surplus fuel passes through the fuel return line 3b from the fuel bypass line 3c. Returned to

  At this time, since the surplus fuel is returned to the fuel tank 4 side from the fuel bypass line 3c connected to the fuel delivery line 3a, there is almost no heat received from the engine 1, and even if it is returned to the fuel tank 4, the fuel tank 4 There is almost no increase in fuel temperature.

  By the way, when an open fixing failure occurs in the flow path switching valve 15, the fuel return line 3b does not close even after a predetermined time has elapsed after turning on the ignition switch, so that the fuel is supplied from the fuel delivery line 3a to the fuel return line 3b. After that, it is returned to the fuel tank 4. The temperature of the fuel passing through the fuel line 3 is increased by heat received from the engine 1, and the amount of evaporated gas is easily increased.

  Therefore, the ECU 21 is provided with a diagnostic function for detecting an open sticking failure of the flow path switching valve 15. Specifically, the open-fixation failure diagnosis executed by the ECU 21 is processed according to the flowcharts shown in FIGS.

  The flowchart of FIG. 2 shows an execution condition determination processing routine for determining the execution condition of the open fixation failure diagnosis. As will be described later, in the open fixing failure diagnosis, the actual fuel temperature (hereinafter referred to as “actual fuel temperature”) FTMP detected by the fuel temperature sensor 6 and the estimated fuel temperature FTCAL of the fuel stored in the fuel tank 4 are determined. Based on this, it is determined whether or not the flow path switching valve 15 is stuck open. However, since the estimated fuel temperature FTCAL is set based on the engine speed NE, the intake air amount GA, and the vehicle speed VSP, the driving state of the vehicle changes greatly. There is a possibility that the accurate estimated fuel temperature FTCAL cannot be set in the region where it is easy to do. Therefore, in the execution condition determination processing routine, an execution condition is determined as to whether or not the driving state of the vehicle can be diagnosed.

  This routine is executed every predetermined calculation cycle (for example, 1000 ms). In steps S21 to S25, diagnosis execution conditions are determined. If all the diagnosis execution conditions are satisfied, the process proceeds to step S26. On the other hand, if any one of the diagnosis execution conditions is not satisfied, the process proceeds to step S30, the execution condition determination flag xFRTRNEX is cleared (xFRTRNEX = 0), and the routine is exited.

  That is, in step S21, step S22, and step S25, it is checked whether or not the vehicle is in a steady operation state based on the intake air amount GA, the vehicle speed VSP, and the engine speed NE. In step S23 and step S24, it is checked whether or not the fuel temperature is likely to change significantly based on the outside air temperature TAMB and the fuel level FLVL in the fuel tank 4.

  Specifically, first, in step S21, the intake air amount GA is compared with the lower limit value kGAL and the upper limit value kGAH. When GA <kGAL or kGAH ≦ GA, it is determined that the diagnosis execution condition is not satisfied, and the process jumps to step S30. If kGAL ≦ GA <kGAH, it is determined that the diagnosis execution condition is satisfied, and the process proceeds to step S22.

  When the intake air amount GA is too small (GA <kGAL) or too large (kGAH ≦ GA), the intake air amount GA is likely to fluctuate greatly, and the estimated fuel temperature FTCAL is accurately set based on the intake air amount GA. It becomes difficult. Therefore, in such a case, the diagnosis execution condition is not satisfied. The lower limit value kGAL and the upper limit value kGAH are fixed values obtained in advance from experiments, simulations, and the like.

  In step S22, the vehicle speed VSP is compared with the lower limit value kVSPL and the upper limit value kVSPH. When VSP <kVSPL or kVSPH ≦ VSP, it is determined that the diagnosis execution condition is not satisfied, and the process jumps to step S30. When kVSPL ≦ VSP <kVSPH, it is determined that the diagnosis execution condition is satisfied, and the process proceeds to step S23.

  Since the vehicle speed VSP is read as a parameter for setting the estimated fuel temperature heat radiation rate coefficient TFTVSP in the open-fixation failure diagnosis described later, as in low speed running (VSP <kVSPL) or high speed running (kVSPH ≦ VSP) In a region where the vehicle speed VSP is relatively large and easily fluctuates, there is a possibility that the estimated fuel temperature heat release rate coefficient TFTVSP cannot be set accurately.

  Therefore, in such an engine operating state, the diagnosis execution condition is not satisfied. Note that the lower limit value kGAL and the upper limit value kGAH are fixed values obtained in advance from experiments, simulations, and the like. For example, kGAL = 30 [km / h] and kGAH = 110 [km / h].

  In step S23, the outside air temperature TAMB is compared with the lower limit value kTAMBL and the upper limit value kTAMBH. If TAMB <kTAMBL or kTAMBH ≦ TAMB, it is determined that the diagnosis execution condition is not satisfied, and the process jumps to step S30. If kTAMBL ≦ TAMB <kTAMBH, it is determined that the diagnosis execution condition is satisfied, and the process proceeds to step S24.

  The outside temperature TAMB tends to have a great influence on the fuel temperature. Accordingly, the diagnosis execution condition is not satisfied under an environmental condition in which the outside air temperature TAMB is a disturbance with respect to the fuel temperature. The lower limit value kTAMBL and the upper limit value kTAMBH are fixed values obtained in advance from experiments, simulations, and the like. For example, kTAMBL = 10 [° C.] and kTAMBH = 50 [° C.].

  In step S24, the fuel level FLVL is compared with the lower limit value kFLL and the upper limit value kFLH. When FLVL <kFLL or kFLH ≦ FLVL, it is determined that the diagnosis execution condition is not satisfied, and the process jumps to step S30. If kFLL ≦ FLVL <kFLH, it is determined that the diagnosis execution condition is satisfied, and the process proceeds to step S25.

  When the fuel level FLVL stored in the fuel tank 4 is too low (FLVL <kFLL) or nearly full (kFLH ≦ FLVL), the fuel temperature is likely to fluctuate greatly. The diagnosis execution condition is not satisfied. The lower limit value kFLL and the upper limit value kFLH are fixed values determined by the capacity of the target fuel tank 4, etc. For example, the lower limit value kFLL is about 10% of the full tank, and the upper limit value kFH is 90% of the full tank. Degree.

  In step S25, the engine speed NE is compared with the lower limit value kNEL and the upper limit value kNEH. When NE <kNEL or kNEH ≦ NE, it is determined that the diagnosis execution condition is not satisfied, and the process jumps to step S30. If kNEL ≦ NE <kNEH, it is determined that the diagnosis execution condition is satisfied, and the process proceeds to step S26.

  Since the engine speed NE is read as a parameter when setting the estimated fuel temperature heating amount MFTCAL in the open sticking failure diagnosis described later, the engine speed NE is low (NE <kNEL) or high (kNEH ≦ NE). Thus, there is a possibility that the estimated fuel temperature heating amount MFTCAL cannot be set accurately in a region where the engine speed NE fluctuates relatively large. Therefore, the diagnosis execution condition is not satisfied in such an operating state. Note that the lower limit value kNEL and the upper limit value kNEH are fixed values obtained in advance from experiments, simulations, and the like, for example, kGAL = 1000 [rpm] and kGAH = 6000 [rpm].

  In step S26, it is checked whether or not a close signal is output to the flow path switching valve 15. If the close signal is output, the process proceeds to step S27. If the close signal is not output, the process jumps to step S30. On the other hand, if the close signal is output, the process proceeds to step S27.

  When proceeding to step S27, it is checked whether or not a failure is detected in another failure diagnosis (for example, failure diagnosis of an evaporation purge system in which the evaporated fuel (evaporation) in the fuel tank 4 is supplied to the intake system for combustion). If detected, the process branches to step S30. On the other hand, if no failure is detected, the process proceeds to step S28.

  In step S28, the value of the diagnosis end flag xDIAGEND is referred to. When xDIAGEND = 0, the process proceeds to step S29, the execution condition determination flag xFRTRNEX is set (xFRTRNEX ← 1), and the routine is exited. On the other hand, when xDIAGEND = 1, the process branches to step S30.

  The initial value of the diagnosis end flag xDIAGEND is 0, and is set in step S54 or S55 of the normal / abnormality determination processing routine described later. The diagnosis end flag xDIAGEND is set to an initial value when the ignition switch is turned on (xDIAGEND ← 0). Therefore, once the diagnosis end flag xDIAGEND is set, the diagnosis is not executed until the ignition switch is turned on after the engine is stopped.

  Further, in the estimated fuel temperature calculation processing routine shown in FIG. 3, the estimated fuel temperature FTCAL and the estimated fuel temperature integrated value CFTCAL are calculated.

  By the way, as shown by a solid line in FIG. 8, in a normal state in which the flow path switching valve 15 is closed and excess fuel is returned from the fuel bypass line 3c to the fuel tank 4 via the fuel return line 3b, The change in the actual fuel temperature integrated value under the conditions of the air amount GA, the predetermined vehicle speed VSP, the predetermined fuel level FLVL, and the predetermined outside air temperature TAMB is regarded as normal. On the other hand, when the flow path switching valve 15 is stuck open and malfunctions under the same conditions, the surplus fuel receives a higher temperature than the normal time due to heat received from the engine 1, and the integrated value of the actual fuel temperature is: As shown by the broken line in FIG. In this routine, the fuel temperature in the fuel tank 4 is estimated in a predetermined operation state, the estimated fuel temperature is compared with the actual fuel temperature, and the presence / absence of an open sticking failure of the flow path switching valve 15 is diagnosed.

  This routine is executed every predetermined calculation cycle (for example, 1000 ms). First, in step S31, the value of the execution condition determination flag xFRTRNEX is referred to. If xFRTRNEX = 1, the diagnosis execution condition is satisfied, the process proceeds to step S32. If xFRTRNEX = 0 and the diagnosis execution condition is not satisfied, the process branches to step S40.

  In step S32, the fuel level FLVL is determined in steps S32 to S34, and in the subsequent steps S35 to S37, the estimated fuel temperature heating amount MFTCAL and the estimated fuel temperature heat release rate coefficient TFTVSP corresponding to the fuel level FLVL are set. To do. Since the change characteristic of the fuel temperature in the fuel tank 4 differs depending on the fuel level FLVL, the estimated fuel temperature heating amount MFTCAL and the estimated fuel temperature heat radiation rate coefficient TFTVSP are set to different values according to the fuel level FLVL.

  In step S32, it is checked whether or not the fuel level FLVL is equal to or lower than a low level determination value kFLVL10 (for example, 10 [L]). If FLVL <kFLVL10, the process proceeds to step S35, and if FLVL ≧ kFLVL10, step S35 is performed. Proceed to S33.

  When the process proceeds to step S35, the estimated fuel temperature heating amount calculation map mDFTMAP10 shown in FIG. 6A is referred to with interpolation calculation using the intake air amount GA [g / sec] and the engine speed NE [rpm] as parameters. To set the estimated fuel temperature heating amount MFTCAL. Further, with the vehicle speed VSP as a parameter, the estimated fuel temperature heat radiation rate coefficient calculation table tFTVSP10 shown in FIG. 7A is referred to with interpolation calculation to set the estimated fuel temperature heat radiation speed coefficient TFTVSP.

  In step S33, it is checked whether or not the fuel level FLVL is lower than the medium / low level determination value kFLVL20 (for example, 20 [L]). If FLVL <kFLVL20, that is, kFLVL10 ≦ FLVL <kFLVL20, the process proceeds to step S36. Further, when FLVL ≧ kFLVL20, the process proceeds to step S34.

  When the process proceeds to step S36, the estimated fuel temperature heating amount calculation map mDFTMAP20 shown in FIG. 6B is referred to with interpolation calculation using the intake air amount GA [g / sec] and the engine speed NE [rpm] as parameters. To set the estimated fuel temperature heating amount MFTCAL. Further, with the vehicle speed VSP as a parameter, the estimated fuel temperature heat radiation rate coefficient calculation table tFTVSP20 shown in FIG. 7B is referenced with interpolation calculation to set the estimated fuel temperature heat radiation speed coefficient TFTVSP.

  In step S34, it is checked whether or not the fuel level FLVL is equal to or lower than the intermediate level determination value kFLVL30 (for example, 30 [L]). If FLVL <kFLVL30, that is, kFLVL20 ≦ FLVL <kFLVL30, the process proceeds to step S37. If FLVL ≧ kFLVL30, the process branches to step S40. Therefore, this routine is not executed until the fuel level FLVL becomes less than the medium level determination value kFLVL30, for example, when the fuel tank 4 is fully filled with fuel.

  When the process proceeds to step S37, the estimated fuel temperature heating amount calculation map mDFTMAP30 shown in FIG. 6C is referenced with interpolation calculation using the intake air amount GA [g / sec] and the engine speed NE [rpm] as parameters. To set the estimated fuel temperature heating amount MFTCAL. Further, using the vehicle speed VSP as a parameter, the estimated fuel temperature heat release rate coefficient calculation table tFTVSP30 shown in FIG. 7C is referred to with interpolation calculation to set the estimated fuel temperature heat release rate coefficient TFTVSP.

  The estimated fuel temperature heating amount MFTCAL stored in each estimated fuel temperature heating amount calculation map mDFTMAP10, mDFTMAP20, mDTMMAP30 is the current temperature increase amount with respect to the estimated fuel temperature FTCAL calculated during the previous routine execution, and the intake air amount GA and Expressed as a function of engine speed NE. Further, the estimated fuel temperature heating amount MFTCAL is set to a lower value as the fuel level FLVL becomes higher.

  Each estimated fuel temperature heat release rate coefficient calculation table tFTVSP10, tFTVSP20, tFTVSP30 is the current temperature heat release with respect to the estimated fuel temperature FTCAL calculated during the previous routine execution, and is expressed as a function of the vehicle speed VSP, and the fuel level FLVL is The lower the value, the higher the value.

  Then, when the process proceeds from any one of steps S35 to S37 to step S38, the estimated fuel temperature FTCAL is calculated according to the following equation.

FTCAL = FTCALn−1 + MFTCAL− (TFTVSP · (FTCALn−1−TAMB)) (1)
Note that FTCALn-1 is the estimated fuel temperature calculated in the previous routine execution.

  Equation (1) is obtained by adding the estimated fuel temperature heating amount MFTCAL to the previous estimated fuel temperature FTCAL, and subtracting the heat radiation amount (TFTVSP · (FTCALn−1−TAMB)) from the previous estimated fuel temperature FTCAL to obtain the current estimated fuel temperature FTCAL. Is to be calculated.

  Next, when the routine proceeds to step S39, the estimated fuel temperature FTCAL calculated in step S38 is added to the estimated fuel temperature integrated value CFTCALn-1 calculated at the time of the previous routine execution (FTCAL ← FTCALn-1 + FTCAL), and the routine is exited.

  If it is determined in step S31 that the diagnosis execution condition xFRTRNEX = 0 is not satisfied, or if it is determined in step S34 that FLVL ≧ kFLVL30 and branching to step S40, the estimated fuel temperature FTCALn−1 stored in a memory (not shown) is used. Is set at the actual fuel temperature FTMP (FTCALn-1 ← FTMP), the estimated fuel temperature integrated value CFTCALn-1 is cleared (CFTCALn-1 ← 0), and the routine is exited.

  When the ignition switch is turned on, the system is initialized and the estimated fuel temperature integrated value CFTCALn-1 is cleared (CFTCALn-1 ← 0). Further, immediately after the initialization process, the estimated fuel temperature FTCALn-1 is set to the actual fuel temperature FTMP read first (FTCALn-1 ← FTMP).

  In the actual fuel temperature integrated value calculation processing routine shown in FIG. 4, the integrated value CFTMP of the actual fuel temperature FTMP is set.

  This routine is executed every predetermined calculation cycle (for example, 1000 ms). First, in step S41, the value of the execution condition determination flag xFRTRNEX is referred to. If xFRTRNEX = 1, the diagnosis execution condition is satisfied, the process proceeds to step S42. The actual fuel temperature integrated value CFTMP is set by adding the actual fuel temperature FTMP detected by the fuel temperature sensor 6 to the actual fuel temperature integrated value CFTMPn-1 set at the time of executing the routine (CFTMP ← CFTMPn-1 + FTMP). Exit.

  On the other hand, if it is determined in step S41 that the diagnosis execution condition xFRTRNEX = 0 is not satisfied, the process branches to step S43, and the actual fuel temperature integrated value CFTMPn-1 set in the previous routine stored in a memory (not shown) is cleared. (CFTMPn-1 ← 0) and exit the routine.

  Further, in the normality / abnormality determination processing routine shown in FIG. 5, the presence / absence of an open sticking failure of the flow path switching valve 15 is checked based on the actual fuel temperature integrated value CFTMP and the estimated fuel temperature integrated value CFTCAL.

  This routine is executed every predetermined calculation cycle (for example, 1000 ms). First, in step S51, the value of the execution condition determination flag xFRTRNEX is referred to, and when xFRTRNEX = 1, the diagnosis execution condition is satisfied, the process proceeds to step S52. If xFRTRNEX = 0 and the diagnosis execution condition is not satisfied, the routine is exited.

  In step S52, the actual fuel temperature integrated value CFTMP is compared with the determination start reference value kCFTMP. The determination start reference value kCFTMP is determined whether or not the actual fuel temperature FTMP has been stabilized to some extent, that is, whether or not the difference between the normal value and the normal value of the actual fuel temperature integrated value CFTMP has been opened to allow diagnosis. This value is set by experiment or simulation.

  When CFTMP <kCFTMP, the routine is exited as it is. On the other hand, when CFTMP ≧ kCFTMP, the process proceeds to step S53.

  In step S53, the actual fuel temperature integrated value CFTMP is compared with the estimated fuel temperature integrated value CFTCAL plus the diagnostic adjustment coefficient kFTTUNE (CFTCAL + kFTTUNE) to diagnose the presence or absence of an open sticking failure of the flow path switching valve 15. .

  The diagnostic adjustment coefficient kFTTUNE is a value for absorbing a diagnostic error, and is a variable value set based on at least one parameter of the fuel level FLVL, the outside air temperature TAMB, and the actual fuel temperature FTMP at the start. That is, when the fuel level FLVL is high and low, when the outside air temperature TAMB is high, or low, or when the actual fuel temperature FTMP at the time of start is high, the actual fuel temperature integrated value CFTMP and the estimated fuel temperature integrated value CFTCAL Therefore, the accuracy of diagnosis is increased by adding the diagnostic adjustment coefficient kFTTUNE to the estimated fuel temperature integrated value CFTCAL.

  When CFTCAL> CFTCAL + kFTTUNE, the flow path switching valve 15 is open and stuck, so the fuel passes through the fuel delivery line 3a and returns to the fuel tank 4 through the fuel return line 3b. Therefore, the actual fuel temperature FTMP Therefore, the actual fuel temperature integrated value CFTMP, which is the integrated value, exceeds the estimated fuel temperature integrated value CFTCAL.

  Therefore, in such a case, it is determined that the flow path switching valve 15 is in an open fixing failure, and the process proceeds to step S54 where the failure diagnosis determination flag kFRTRNNNG is set (kFRTRNNG ← 1) and the diagnosis end flag xDIAGEND is set ( xDIAGEND ← 1), exit the routine.

  When CFTCAL ≦ CFTCAL + kFTTUNE, it is determined that the flow path switching valve 15 is normally closed, and the process branches to step S55 to clear the failure diagnosis determination flag kFRTRNG (kFRTRNNG ← 0), and the diagnosis ends. The flag xDIAGEND is set (xDIAGEND ← 1), and the routine is exited.

  Once the diagnosis end flag xDIAGEND is set, after the engine is stopped, the diagnosis is not executed until the next ignition switch is turned on.

  When the failure diagnosis determination flag kFRTRNNG is set, the ECU 21 drives a warning means such as a warning lamp provided on an instrument panel or the like (not shown) to open and fix the flow path switching valve 15 to the driver. In addition to notifying the failure, the corresponding trouble code is stored in the memory.

  As described above, in this embodiment, the change in the actual fuel temperature FTMP in the fuel tank 4 is detected based on the estimated fuel temperature FTCAL set based on the parameter indicating the driving state of the vehicle, and the integrated value CFTCAL is By comparing the integrated value CFTMP of the fuel temperature FTMP to detect an open fixing failure of the flow path switching valve 15, only one fuel temperature sensor is required, and there is no need to add a new one. It can be adopted immediately in existing vehicles, and excellent versatility can be obtained.

  In addition, since the actual fuel temperature integrated value CFTMP and the estimated fuel temperature integrated value CFTCAL are compared, the deviation between the normal state and the failure of the flow path switching valve 15 becomes large, and the flow path switching valve 15 is stuck open. Faults can be detected accurately. Furthermore, since the diagnostic adjustment coefficient kFTUNE is added to the estimated fuel temperature integrated value CFTCAL, higher diagnostic accuracy can be obtained.

  In addition, since the estimated fuel temperature FTCAL is set according to the fuel level FLVL, higher diagnostic accuracy can be obtained.

Schematic configuration diagram of fuel supply system Flow chart showing execution condition determination processing routine Flowchart showing estimated fuel temperature calculation processing routine Flowchart showing actual fuel temperature integrated value calculation processing routine Flow chart showing normality / abnormality determination processing routine Explanatory drawing of estimated fuel temperature heating amount calculation map for each fuel level Explanatory diagram of the estimated fuel temperature heat release rate coefficient calculation table for each fuel level Explanatory drawing comparing fuel temperature integrated value when switching valve is normal and when stuck open

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 3 Fuel line 3a Fuel delivery line 3b Fuel return line 3c Fuel bypass line 4 Fuel tank 6 Fuel temperature sensor 7 Fuel level sensor 10 Intake air amount sensor 12 Engine speed sensor 13 Outside air temperature sensor 14 Pressure regulator 15 Flow path switching valve 17 Vehicle speed sensor CFTMP Actual fuel temperature integrated value CFTCAL Estimated fuel temperature integrated value FLVL Fuel level FTCAL Estimated fuel temperature FTMP Actual fuel temperature GA Intake air amount kFLVL10, kFLVL20, kFLVL30 Level judgment value kFTTUNE Diagnostic adjustment coefficient MFTCAL N Estimated fuel temperature Number of revolutions TAMB outside temperature TFTVSP Estimated fuel temperature heat release speed factor VSP Vehicle speed

Agent Patent Attorney Susumu Ito

Claims (5)

A fuel delivery line for supplying fuel from the fuel pump to the injector;
A fuel return line for returning the surplus fuel supplied to the injector to the fuel tank;
A fuel bypass line that bypasses the fuel delivery line and the fuel return line;
A fuel pressure adjusting means for adjusting the pressure of fuel to be supplied to the injector while being interposed in the bypass line;
Flow path switching means interposed upstream of the fuel bypass line connection portion of the fuel return line, and switching the flow path switching means based on the operating state to flow the excess fuel. In the fuel supply device that switches the path,
Diagnostic condition determination means for determining that a diagnostic condition is satisfied when a signal for closing the fuel return line is output to the flow path switching means;
Fuel temperature detecting means for detecting the actual fuel temperature in the fuel tank;
Estimated fuel temperature setting means for setting an estimated fuel temperature in the fuel tank based on the operating state;
And a failure determination means for determining whether or not there is an open sticking failure of the flow path switching means based on the actual fuel temperature and the estimated fuel temperature when the diagnosis condition determination means determines that the diagnosis condition is satisfied. A fuel supply device diagnostic device. Actual fuel temperature integrating means for integrating the actual fuel temperature for a set time;
Estimated fuel temperature integrating means for integrating the estimated fuel temperature for a set time;
The failure determination means compares the actual fuel temperature integrated value with the estimated fuel temperature integrated value when a diagnosis condition is satisfied, and if the actual fuel temperature integrated value is larger than the estimated fuel temperature integrated value, the flow path switching means 2. The fuel supply apparatus diagnosis apparatus according to claim 1, wherein the fuel supply apparatus diagnosis apparatus determines that there is an open fixation failure. The estimated fuel temperature detecting means sets an estimated fuel temperature heating amount and an estimated fuel temperature heat radiation amount based on the operating state and the fuel level of the fuel tank, respectively.
3. The fuel supply device according to claim 1, wherein the current estimated fuel temperature is set based on the estimated fuel temperature heating amount, the estimated fuel temperature heat radiation amount, and the estimated fuel temperature set at the previous calculation. Diagnostic device.   The estimated fuel temperature detection means calculates an estimated fuel temperature heating amount based on the intake air amount and the engine speed, and estimates the estimated fuel temperature based on the vehicle speed, the outside air temperature, and the estimated fuel temperature calculated at the previous calculation. Calculating the estimated fuel temperature by calculating a heat radiation amount and adding the estimated fuel temperature heating amount to the estimated fuel temperature set at the previous calculation and subtracting the estimated fuel temperature heat radiation amount The fuel supply apparatus diagnostic apparatus according to claim 1 or 2.   5. The diagnostic apparatus for a fuel supply apparatus according to claim 4, wherein the estimated fuel temperature heating component and the estimated fuel temperature heat radiation component have different characteristics for each fuel level.

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