JP2006104986A - Evaporated fuel purge system of engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To diagnose failure, even when suction pipe pressure downstream of a throttle valve becomes positive pressure, when a supercharger operates. <P>SOLUTION: Purge passages 12 and 13 are respectively communicated with an air chamber 2 and the upstream side of the supercharger 5 of an intake passage 3, and a purge passage 11 for collecting both purge passages 12 and 13 is communicated with a canister 10. The canister 10 and a fuel tank 7 are communicated via an evaporation passage 9, and purge valves 14 and 15 are interposed in the respective purge passages 12 and 13. When a diagnostic condition is realized, the respective valves 14 and 15 are closed, and after holding internal pressure of an evaporation purge system reaching the fuel tank 7 from the respective valves 14 and 15, negative pressure is introduced from an air chamber 2 by opening the valve 14 when the suction pipe pressure Pa in the air chamber 2 is negative pressure, and the negative pressure is introduced from an upstream side intake passage 3 by opening the valve 15 in positive pressure. Afterwards, when tank internal pressure Pt reaches target negative pressure Pm, the existence of failure is diagnosed by detecting an internal pressure increase by evaporation fuel by closing both valves 14 and 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention introduces a negative pressure from the intake passage on the downstream side of the supercharger when the suction pipe pressure is negative, and introduces the intake air on the upstream side of the supercharger when positive pressure is introduced. The present invention relates to an evaporated fuel purge system for a supercharged engine in which negative pressure is introduced from a passage.

  2. Description of the Related Art Conventionally, vehicles such as automobiles have an evaporative fuel purge system in order to prevent the fuel evaporating gas generated in the fuel tank from being discharged into the atmosphere. This evaporative fuel purge system stores evaporative fuel in a canister, and purges and burns the intake system as a mixture of fresh air and evaporative fuel (evaporative gas) when a predetermined purge execution condition is satisfied.

  In this case, in the naturally aspirated engine, an air introduction port is provided on the canister side, and the evaporation gas is purged to the intake system by the differential pressure between the atmospheric pressure at the air introduction port and the negative pressure on the engine side. On the other hand, in an engine with a supercharger, because the supercharging pressure of the supercharger causes the pressure downstream of the compressor to become positive pressure and evaporation purge cannot be performed, the evaporation gas is purged upstream of the compressor.

  As a means for switching the barge passage in accordance with the pressure downstream of the throttle valve, there are a mechanical type and an electronic control type. As the mechanical evaporator system, for example, a pressure sensitive system as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 5-1631) is often used.

  That is, in the technique disclosed in the publication, the canister communicates with the upstream side of the compressor via the first purge passage, and further communicates with the downstream side of the throttle valve via the second purge passage. A pressure sensitive control valve is installed in When the intake air amount is in the low and middle range, the control valve interposed in the second purge passage is opened. At this time, when the downstream side of the throttle valve is in a negative pressure state, the second purge passage is opened. The evaporative gas is purged downstream of the throttle valve. On the other hand, when the engine speed increases and the intake air amount increases, the control valve provided in the first purge passage is opened, and the evaporation gas is purged from both purge passages.

An electronically controlled evaporative fuel purge system is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-287162. That is, in the publication, a first purge passage communicating with the canister on the downstream side of the throttle valve and a second purge passage communicating with the upstream side of the compressor are connected, and the first and second purge passages are connected to both purge passages. When each of the purge valves is installed and the downstream pressure of the throttle valve is negative, the second purge valve is closed to purge the vapor from the first purge passage to the downstream side of the throttle valve, while when the downstream pressure of the throttle valve is positive. Discloses a technique for purging the evaporation gas from the second purge passage to the compressor upstream side by closing the first purge valve and opening the second purge valve.
JP-A-5-1631 JP-A-11-287162

  By the way, in such an evaporative fuel purge system, if an abnormality such as a leakage failure occurs in the evaporative purge system including the fuel tank and canister, not only will air pollution occur, but exhaust emissions and fuel consumption will deteriorate. The fuel purge system is provided with a diagnostic function for checking whether there is a failure.

  Generally, in the failure diagnosis of the evaporated fuel purge system, the internal pressure of the evaporative purge system is set to a predetermined negative pressure state, and then the CCV (Canister Closed) installed in the purge valve and the air inlet of the canister are installed in the purge passage. (Valve) is closed, the inside of the evaporation purge system from the fuel tank to the purge valve to the purge valve is sealed to maintain a negative pressure state, and the pressure change at that time is measured to determine whether there is a failure, so-called negative Many pressure type fault diagnosis systems are used.

  However, when the negative pressure type fault diagnosis system is applied to the pressure-sensitive evaporative fuel purge system disclosed in Patent Document 1, in this system, when the engine speed increases, the second purge passage communicated with the upstream side of the compressor. As a result, the pressure-sensitive control valve provided in the valve is opened, making it impossible to detect pressure fluctuations in the evaporation purge system.

  Therefore, the failure diagnosis is limited only when the intake air amount is low or middle, that is, when the control valve interposed in the second purge passage is closed, and there are few opportunities for failure diagnosis. There is a limit to increasing accuracy.

  On the other hand, when a negative pressure type fault diagnosis system is applied to an electronically controlled evaporative fuel purge system as disclosed in Patent Document 2, in this system, when fault diagnosis is performed, the influence of pressure fluctuations in the intake system is affected. The purge valve does not open in response to this, but for example when a negative pressure is introduced into the evaporation purge system to start failure diagnosis, the turbocharger operates and the downstream pressure of the throttle valve becomes positive. The negative pressure cannot be introduced, and the failure diagnosis is cancelled. If the failure diagnosis is cancelled, the diagnosis opportunities are reduced accordingly, and thus there is a limit to further improving the diagnosis accuracy in this case.

  In view of the above circumstances, the present invention does not cancel the failure diagnosis even when the supercharger operates and the suction pipe pressure in the intake passage downstream of the supercharger becomes positive. An object of the present invention is to provide an evaporative fuel purge system for an engine with a supercharger capable of ensuring sufficient diagnostic opportunities and obtaining higher diagnostic accuracy.

  In order to achieve the above object, the present invention provides a purge passage having an intake passage having a supercharger, and first and second purge passages respectively communicating with a downstream intake passage and an upstream intake passage of the supercharger. And a canister communicating with the upstream side of the purge passage, an evaporation passage communicating the canister and the fuel tank, a purge valve interposed in the purge passage, and a fresh air inlet provided in the canister. An air release valve provided, an internal pressure detecting means for detecting the internal pressure of the evaporation purge system from the fuel tank to the purge valve, an intake pipe pressure detecting means for detecting the intake pipe pressure in the downstream intake passage, and the valves And an evaporative fuel purge system for a supercharged engine having a control means for controlling an open / close state of the engine, wherein the control means is configured to detect the purge valve when a diagnosis condition is satisfied. After closing the atmosphere release valve and holding the internal pressure of the evaporation purge system, negative pressure introduction means for introducing a negative pressure into the evaporation purge system, holding the internal pressure of the evaporation purge system after introducing the negative pressure, A diagnostic means for diagnosing the presence or absence of a failure by detecting an increase in internal pressure of the evaporation purge system due to the evaporated fuel generated in the fuel tank by an internal pressure detecting means, and the negative pressure introducing means includes a suction pipe pressure detecting means The purge valve is operated based on the detected suction pipe pressure. When the suction pipe pressure is negative, the first purge passage is opened and the second purge passage is closed. When the suction pipe pressure is positive, The first purge passage is closed and the second purge passage is opened to introduce a negative pressure into the evaporation purge system.

  According to the present invention, when the supercharger is activated and the intake pipe pressure in the downstream intake passage of the supercharger becomes positive, negative pressure is introduced from the upstream intake passage of the supercharger. As a result, failure diagnosis is not canceled, a sufficient opportunity for diagnosis can be secured, and higher diagnosis accuracy can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 4 show a first embodiment of the present invention. FIG. 1 shows a schematic configuration diagram of an evaporative fuel purge system provided in an engine with a supercharger.

  Reference numeral 1 in FIG. 1 denotes an intake system of the engine. The upstream side of an intake manifold 1a connected to an intake port of an engine (not shown) is gathered and communicated with the air chamber 2. Further, an intake passage 3 communicates with the upstream side of the air chamber 2. The intake passage 3 is provided with a throttle valve 4 and a compressor 5b of the turbocharger 5 from the downstream side. Further, an air cleaner 6 is attached to the intake intake port side of the intake passage 3.

  Further, the turbine 5a of the turbocharger 5 is interposed in the exhaust passage. When the turbine 5a is rotated by the exhaust pressure, the compressor 5b that rotates integrally with the turbine 5a supercharges the intake air. And the optimal supercharging pressure is set by controlling the exhaust pressure supplied to the turbine 5a according to an engine operating state by a wastegate valve (not shown) or the like.

  On the other hand, reference numeral 7 denotes a fuel tank, and an upper portion of the fuel tank 7 communicates with an upstream side of an evaporation passage 9 constituting an evaporation purge system. The evaporation passage 9 discharges the evaporated fuel generated in the fuel tank 7, and the downstream side of the evaporation passage 9 communicates with the upper portion of the canister 10 having an adsorption portion such as activated carbon.

  The canister 10 is provided with a fresh air inlet 10a communicating with the atmosphere at the lower part, and an upper part of the canister 10 is a mixture of fresh air from the fresh air inlet 10a and the evaporated fuel stored in the adsorption part (evaporative gas). An upstream side of the upstream purge passage 11 leading to 1 is connected.

  The downstream side of the upstream purge passage 11 is branched into a first purge passage 12 and a second purge passage 13 along the way, the first purge passage 12 communicates with the air chamber 2, and the second purge passage 13 communicates with the intake passage 3 on the upstream side of the compressor 5b.

  A first purge valve 14 is interposed in the middle of the first purge passage 12, and a second purge valve 15 is interposed in the middle of the second purge passage 13. These purge valves 14 and 15 constitute a passage opening / closing means. In this embodiment, as the purge valves 14 and 15, a duty solenoid valve that is fully closed at 0% and fully opened at 100% is employed.

  Furthermore, CCV16 as an air release valve is interposed in the fresh air inlet 10a. Each of these valves 14 to 16 is an electromagnetically driven valve that is controlled by a drive signal from an ECU 21 described later.

  The air chamber 2 is exposed to a suction pipe pressure sensor 23 as pressure detection means, and the fuel tank 7 is exposed to an internal pressure sensor 8 as internal pressure detection means. The suction pipe pressure sensor 23 detects the suction pipe pressure as an absolute pressure, while the internal pressure sensor 8 detects the pressure (tank pressure) Pt in the upper space of the fuel tank 7 as a relative pressure based on the atmospheric pressure. .

  On the other hand, reference numeral 21 denotes an electronic control unit (ECU) comprising a microcomputer or the like as a control means. An internal pressure sensor 8 and a suction pipe pressure sensor 23 are connected to the input side of the ECU 21 and engine rotation is performed. Sensors for detecting engine operating state parameters, such as an engine speed sensor 22 for detecting the number Ne, are connected.

  The first and second purge valves 14 and 15 and the CCV 16 are connected to the output side of the ECU 21, and actuators such as an injector (not shown) for controlling the engine operating state are connected.

  The ECU 21 performs normal engine control such as a fuel injection amount for the injector and the like and an evaporation purge control based on the engine operating state parameter. The evaporation purge control is executed when it is determined whether or not the evaporation purge condition is satisfied based on the operation condition, and the evaporation purge condition is satisfied. When the evaporation purge condition is satisfied, the opening degree of both purge valves 14 and 15 is controlled so that the influence on the air-fuel ratio of the evaporation gas purged to the intake system becomes a substantially constant rate.

  That is, the ECU 21 opens the first purge valve 14 when the suction pipe pressure Pa is lower than the atmospheric pressure Pat (negative pressure) based on the suction pipe pressure Pa downstream of the throttle valve 4 detected by the suction pipe pressure sensor 23. Then, the second purge valve 15 is closed and the opening degree of the first purge valve 14 is adjusted to control the purge ratio of the evaporation gas purged from the first purge passage 12 to the air chamber 2 by negative pressure with respect to the intake air. . When the suction pipe pressure Pa is higher than the atmospheric pressure Pat (positive pressure), that is, when the turbocharger 5 is operating, the first purge valve 14 is closed, the second purge valve 15 is opened, The opening degree of the second purge valve 14 is adjusted, and the purge ratio of the evaporation gas purged by the negative pressure from the second purge passage 13 to the upstream side of the compressor 5b is controlled. The CCV 16 is closed only when performing an evaporative purge failure diagnosis, which will be described later, and is normally open.

  Further, the ECU 21 performs failure diagnosis of the evaporation purge system at a predetermined timing after the engine is started in order to maintain the reliability of the evaporation purge control. Specifically, the failure diagnosis of the evaporation purge system executed by the ECU 21 is processed in accordance with the failure diagnosis routine shown in FIGS.

  The failure diagnosis routines shown in FIGS. 2 and 3 will be described below with reference to the time chart shown in FIG.

  This routine is executed once or every predetermined cycle after the engine is started. First, in step S1, engine operating state parameters (engine speed Ne, suction pipe pressure Pa, etc.) necessary for failure diagnosis are read.

  Subsequently, it progresses to step S2 and a diagnosis start condition is determined. The diagnosis start condition is, for example, when the engine speed Ne is within a predetermined range (for example, about 1000 to 2000 rpm) and the suction pipe pressure Pa is negative (Pa <Pat), that is, when the turbocharger 5 is in an inoperative state. Then, it is determined that the diagnosis start condition is satisfied, and the process proceeds to step S3. If the engine speed Ne is out of the set range or the suction pipe pressure Pa is equal to or higher than the atmospheric pressure Pat, it is determined that the diagnosis start condition is not satisfied, the process jumps to step S19, and the diagnosis history is stored. After performing the diagnosis end processing such as making the routine exit, the routine is exited and the routine proceeds to normal control.

  On the other hand, when it is determined that the diagnosis start condition is satisfied and the process proceeds to step S3, failure diagnosis is started in step S3 and subsequent steps. When the failure diagnosis is started, the evaporation generation amount measurement mode is executed in steps S3 to S5.

  In step S3, a valve closing signal is output to the first purge valve 14, the second purge valve 15, and the CCV 16, and the valves 14 to 16 are closed to maintain the internal pressure of the evaporation purge system. Then, as shown in FIG. 4, the internal pressure of the evaporation purge system gradually increases as time elapses due to the evaporation of the fuel stored in the fuel tank 7.

  Next, the process proceeds to step S4, the tank internal pressure Pt detected by the internal pressure sensor 8 is measured, and the process proceeds to step S5 to check whether the tank internal pressure Pt has reached the set pressure Po. When the tank internal pressure Pt has not reached the set pressure Po (Pt <Po), step S4 is repeatedly executed to wait until the tank internal pressure Pt reaches the set pressure Po. When the tank internal pressure Pt reaches the set pressure Po (Pt ≧ Po), the process proceeds to step S6. In steps S4 and S5, it is determined whether or not the tank internal pressure Pt has reached the set pressure Po due to the increase in the tank internal pressure Pt. Instead of this step, the elapsed time is measured and the elapsed time is calculated. The tank internal pressure may be estimated. In this case, the set time is set by estimating the time to reach the set pressure Po based on the remaining amount of fuel stored in the fuel tank 7 and the outside air temperature, for example.

  Then, when the process proceeds from step S5 to step S6, the negative pressure introduction mode is executed in steps S6 to S13. In step S6, the suction pipe pressure Pa detected by the suction pipe pressure sensor 23 facing the air chamber 2 is read, and the process proceeds to step S7. In steps S7 and S8, it is checked whether the suction pipe pressure Pa is on the negative pressure side or the positive pressure side. First, in step S7, the suction pipe pressure Pa is compared with the first set pressure P1. The first set pressure P1 is a preset value lower than the atmospheric pressure Pat (for example, 700 mmHg, where Pat = 760 mmHg). When Pa ≦ P1, it is determined that the pressure is on the negative pressure side, and the process proceeds to step S9. While opening the 1st purge valve 14, the valve opening degree is controlled based on an engine operating state. At this time, the second purge valve 15 is kept closed. Since the first purge valve 14 is interposed in the first purge passage 12 communicating with the air chamber 2 and the air chamber 2 is in a negative pressure state, the first purge valve 14 is opened so that a negative pressure is applied to the evaporation purge system. Therefore, the tank internal pressure Pt gradually decreases.

  If it is determined in step S7 that Pa> P1, the process proceeds to step S8, and the suction pipe pressure Pa is compared with the first set pressure P1 and the second set pressure P2. The second set pressure P2 is a preset value (for example, 1000 mmHg, where Pat = 760 mmHg) higher than the atmospheric pressure Pat, and the suction pipe pressure Pa is between the first set pressure P1 and the second set pressure P2. (P1 <Pa ≦ P2), it is determined that the suction pipe pressure Pa is in the dead zone, the process proceeds to step S10, and both purge valves 14 and 15 are closed. As a result, the evaporation purge system is closed and the internal pressure is maintained.

  When it is determined in step S8 that Pa> P2, that is, when the turbocharger 5 is operated and the downstream side of the compressor 5b is in the positive pressure state, the process proceeds to step S11, and the second purge valve 15 Open the valve. At this time, the first purge valve 14 is kept closed. The second purge valve 15 faces the intake passage 3 on the upstream side of the compressor 5b of the turbocharger 5. Since the negative pressure is introduced into the evaporation purge system by opening the second purge valve 15, the tank internal pressure Pt gradually decreases.

  Then, when the process proceeds from step S9, S10 or S11 to step S12, the tank internal pressure Pt is rapidly increased, or the closing time of both purge valves 14, 15 in the negative pressure introduction mode is a predetermined time (for example, 3 seconds) or more. Check if it has passed. In the failure diagnosis according to this embodiment, the tank internal pressure Pt is once reduced to a predetermined pressure, and the presence / absence of the failure is determined from the subsequent increase rate of the tank internal pressure Pt. If the valve suddenly rises or if the closing time of both purge valves 14 and 15 has exceeded a predetermined time and the negative pressure cannot be introduced, the process jumps to step S19 to store the diagnosis history. After exiting, the routine exits and shifts to normal control.

  In step S12, if the tank internal pressure Pt is not increased or the closing time of both purge valves 14 and 15 is within a predetermined time, the process proceeds to step S13, and the tank internal pressure Pt is reduced to the target negative pressure Pm. Check whether or not. And when it has not fallen to the target negative pressure Pm (Pa> Pm), it returns to step S6 and performs negative pressure introduction mode again.

  As described above, in the present embodiment, in the negative pressure introduction mode, the suction pipe pressure Pa is measured, and when the suction pipe pressure Pa is equal to or higher than the atmospheric pressure at, the intake passage 3 on the upstream side of the compressor 5b of the turbocharger 5 is Since the negative pressure is introduced, it is possible to introduce the negative pressure into the evaporation purge system even when the turbocharger 5 is supercharged. Therefore, the opportunity for introducing the negative pressure increases, and the tank internal pressure Pt is reduced. It can be reduced to the target negative pressure Pm in a relatively short time. In addition, since the dead zone is set, the opening and closing of the first purge valve 14 and the second purge valve 15 are not frequently switched in a short time, and the negative pressure can be introduced satisfactorily.

  On the other hand, when the suction pipe pressure Pa decreases to the target negative pressure Pm (Pa ≦ Pm), the process proceeds from step S13 to step S14. In steps S14 and S15, the negative pressure holding mode is executed. That is, in step S14, both purge valves 14 and 15 are closed and the internal pressure of the evaporation purge system is maintained. Then, the internal pressure of the evaporation purge system rises with time due to the evaporation of the fuel stored in the fuel tank 7.

  Subsequently, it progresses to step S15 and elapsed time is measured. When the elapsed time reaches the set time, the process proceeds to step S16, and the negative pressure change amount measurement mode is executed in steps S16 to S18. In step S16, the amount of change in the tank internal pressure Pt over a predetermined time, that is, the amount of change in the negative pressure of the evaporation purge system is measured.

  Then, the process proceeds to step S17, where the change amount is compared with a preset failure determination change amount. When the measured change amount is larger than the failure determination change amount, that is, the tank internal pressure Pt is rapidly increased. If it is determined that there is an abnormality, the process proceeds to step S18, where warning means such as a warning lamp provided on an instrument panel (not shown) is driven to display an abnormality and store a trouble code indicating the content of the failure. The process proceeds to step S19. If the measured change amount is smaller than the failure determination change amount, it is determined as normal and the process proceeds to step S19.

  When the process proceeds from step S17 or step S18 to step S19, a diagnosis end process such as storing the current diagnosis history is performed, the routine is exited, and the normal control is started.

  5 to 7 show a second embodiment of the present invention. In addition, about the component same as a 1st form, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the first embodiment described above, the case where the failure diagnosis according to the present invention is applied to the evaporated fuel purge system that employs an electromagnetically driven valve as the second purge valve 15 has been described. The fault diagnosis according to the present invention is applied to an evaporative fuel purge system employing a mechanically driven valve.

  That is, as shown in FIG. 5, the second purge valve 15 employs, for example, a diaphragm as a driving method, introduces an atmospheric pressure Pat into a reference pressure chamber disposed with the diaphragm interposed therebetween, The chamber 2 is communicated with the pressure introduction passage 15a, and the suction pipe pressure Pa is introduced into the air chamber 2 into the operation chamber. As a result, the second purge valve 15 opens when the suction pipe pressure Pa is higher than the atmospheric pressure Pat and closes when it is lower due to the differential pressure between the atmospheric pressure Pat and the suction pipe pressure Pa. Further, a diagnosis switching valve 24 that is normally opened and opens and closes during failure diagnosis is interposed in the pressure introduction passage 15a.

  Accordingly, in normal evaporation purge control, when the suction pipe pressure Pa is negative, the first purge valve 14 is opened and the second purge valve 15 is closed. On the other hand, when the suction pipe pressure Pa is positive, the first purge valve 14 is closed and the second purge valve 15 is opened. As a result, when the suction pipe pressure Pa is negative, the evaporated gas is purged into the air chamber 2 through the first purge passage 12. On the other hand, when the suction pipe pressure Pa becomes positive, the evaporated gas is purged through the second purge passage 13 to the upstream side of the intake passage 3 where the compressor 5b of the turbocharger 5 is disposed.

  Hereinafter, the failure diagnosis of the evaporated fuel purge system executed by the ECU 21 will be described according to the failure diagnosis routine shown in FIGS. 6 and 7 with reference to the time chart shown in FIG. This routine is executed once or every predetermined cycle after the engine is started, as in the first embodiment.

  First, in step S21, engine operating state parameters (engine speed Ne, suction pipe pressure Pa, etc.) necessary for failure diagnosis are read in the same manner as in the first embodiment, and diagnosis start conditions are determined in step S22. The diagnosis start condition is the same as in the first embodiment. For example, the engine speed Ne is within a predetermined range (for example, about 1000 to 2000 rpm), and the suction pipe pressure Pa is negative (Pa <Pat), that is, a turbocharger. When 5 is in the non-operating state, it is determined that the diagnosis start condition is satisfied, and the process proceeds to step S23. If the engine speed Ne is out of the set range or the suction pipe pressure Pa is equal to or higher than the atmospheric pressure Pat, it is determined that the diagnosis start condition is not satisfied, the process jumps to step S39, and the diagnosis history is stored. After performing the diagnosis end processing such as making the routine exit, the routine is exited and the routine proceeds to normal control.

  On the other hand, when it is determined that the diagnosis start condition is satisfied and the process proceeds to step S23, failure diagnosis is started in step S23 and subsequent steps. When the failure diagnosis is started, the evaporation generation amount measurement mode is executed in steps S23 to S25.

  In step S23, a valve closing signal is output to the first purge valve 14, the diagnosis switching valve 24, and the CCV 16, and the valves 14, 24, and 16 are closed. Since the suction pipe pressure Pa at the start of diagnosis is on the negative pressure side, the second purge valve 14 is in a closed state. Therefore, when the diagnosis is started, the second purge valve 14 is kept closed even if the diagnosis switching valve 24 is closed. As a result, the purge valves 14 to 16 are closed, and the internal pressure of the evaporation purge system is maintained. Then, as shown in FIG. 8, the internal pressure of the evaporation purge system gradually increases with the elapse of time due to the evaporation of the fuel stored in the fuel tank 7.

  Next, the process proceeds to step S24. Steps S24 to S28 correspond to steps S4 to S8 of the first form.

  That is, the tank internal pressure Pt is measured in step S24, the tank internal pressure Pt is compared with the set pressure Po in step S25, and if Pt <Po, step S24 is repeatedly executed, and if Pt ≧ Po, step S26 is performed. Proceed to In steps S24 and S25, the elapsed time may be measured, and the tank internal pressure may be estimated based on the elapsed time.

  When the process proceeds to step S26, the negative pressure introduction mode is executed in steps S26 to S33. Steps S26 to S28 correspond to steps S6 to S8 of the first form.

  That is, in step S26, the suction pipe pressure Pa detected by the suction pipe pressure sensor 23 is read. Subsequently, in steps S27 and S28, the suction pipe pressure Pa is compared with the first set pressure P1 and the second set pressure P2. It is checked whether the suction pipe pressure Pa is on the negative pressure side or the positive pressure side.

  When Pa ≦ P1, it is determined that the pressure is on the negative pressure side, and the process proceeds to step S29. If P1 <Pa ≦ P2, it is determined that the band is in the dead band, and the process proceeds to step S30. On the other hand, when Pa> P2, it is determined that the pressure is on the positive pressure side, and the process proceeds to step S31.

  In step S29, the first purge valve 14 is opened and the valve opening degree is controlled based on the engine operating state. At this time, since the diagnosis switching valve 24 is closed, the second purge valve 15 is kept closed. As a result, since only the first purge valve 14 is opened, negative pressure is introduced from the first purge passage 12 to the evaporation purge system, and the tank internal pressure Pt gradually decreases.

  In step S30, since the suction pipe pressure Pa is in the dead zone, both the first purge valve 14 and the diagnostic switching valve 24 are closed. Then, the first purge passage 12 is closed. Further, when the suction pipe pressure Pa immediately before the diagnosis switching valve 24 is closed is on the negative pressure side, a negative pressure is sealed in the pressure introduction passage 15a by the valve closing operation of the diagnosis switching valve 24. Therefore, the second purge valve 15 The valve closed state is maintained. As a result, the second purge passage 13 is blocked and the internal pressure of the evaporation purge system is maintained.

  On the other hand, when the suction pipe pressure Pa immediately before the diagnosis switching valve 24 is closed is on the positive pressure side, the positive pressure is enclosed in the pressure introduction passage 15a by the valve closing operation of the diagnosis switching valve 24. Is kept open. As a result, the second purge passage 13 communicates with the intake passage 3 upstream of the compressor 5b, but the intake passage 3 upstream of the compressor 5b tends to have a negative pressure due to the flow of intake air. Is not introduced into the evaporation purge system at atmospheric pressure.

  On the other hand, in step S31, the diagnosis switching valve 24 is opened, so that the positive pressure in the air chamber 2 is introduced into the diagnosis switching valve 24 via the pressure introduction passage 15a and opened. As a result, negative pressure is introduced into the evaporation purge system from the intake passage 3 upstream of the compressor 5b of the turbocharger 5, and the tank internal pressure Pt gradually decreases.

  Then, when the process proceeds from step S29, S30 or S31 to step S32, the tank internal pressure Pt is rapidly increased, or the valve closing time of the diagnosis switching valve 24 in the negative pressure introduction mode has exceeded a predetermined time (for example, 3 seconds). Find out if you are doing. When the tank internal pressure Pt has risen rapidly or when the valve closing time of the diagnosis switching valve 24 has exceeded a predetermined time, the process jumps to step S39 to perform diagnosis end processing such as storing the diagnosis history. After that, exit the routine and shift to normal control.

  In step S32, if the tank internal pressure Pt has not increased or if the valve closing time of the diagnosis switching valve 24 is within a predetermined time, the process proceeds to step S33, where has the tank internal pressure Pt decreased to the target negative pressure Pm? Check for no. And when it has not fallen to the target negative pressure Pm (Pa> Pm), it returns to step S26 and performs negative pressure introduction mode again.

  Thus, in the present embodiment, in the negative pressure introduction mode, the suction pipe pressure Pa is measured, and when the suction pipe pressure Pa is equal to or higher than the atmospheric pressure, the negative pressure is introduced from the intake passage 3 upstream of the compressor 5b of the turbocharger 5. Since the pressure is introduced, it is possible to introduce a negative pressure into the evaporation purge system even when the turbocharger 5 is supercharging. Therefore, the opportunity for introducing the negative pressure is increased, and the tank internal pressure Pt is compared. The target negative pressure Pm can be reduced in a short time. In addition, since the dead zone is set, the opening and closing of the first purge valve 14 and the second purge valve 15 are not frequently switched in a short time, and the negative pressure can be introduced satisfactorily.

  Further, a mechanically driven valve is employed as the second purge valve 15, and a diagnostic switching valve 24 is interposed in the pressure introduction passage 15 a, and the second purge valve 15 is switched by opening / closing control of the diagnostic switching valve 24. Therefore, the present invention can be easily applied to the existing second purge valve 15 that employs a mechanically driven valve, and high versatility can be obtained.

  On the other hand, when the suction pipe pressure Pa decreases to the target negative pressure Pm (Pa ≦ Pm), the process proceeds from step S33 to step S34. In steps S34 and S35, the negative pressure holding mode is executed as in the first embodiment. That is, in step S34, the first purge valve 14 is closed and the diagnosis switching valve 24 is closed. When the diagnosis switching valve 24 is closed, negative pressure is sealed in the pressure introduction passage 15a, so that the second purge valve 15 is kept closed. As a result, the internal pressure of the evaporation purge system is maintained. Then, the internal pressure of the evaporation purge system rises with time due to the evaporation of the fuel stored in the fuel tank 7.

  Subsequently, it progresses to step S35 and elapsed time is measured. When the elapsed time reaches the set time, the process proceeds to step S36, and the negative pressure change amount measurement mode is executed in steps S36 to S38. Steps S36 to S38 correspond to steps S16 to S18 of the first form.

  That is, in step S36, a negative pressure change amount of the evaporation purge system that is a change amount of the tank internal pressure Pt in a predetermined time is measured, and in step S37, the change amount is compared with a preset failure determination change amount. If the measured change amount is larger than the failure determination change amount, it is determined that there is an abnormality, and the process proceeds to step S38, where warning means such as a warning lamp is driven to display an abnormality, and a trouble code indicating the failure content is stored. Then, the process proceeds to step S39. On the other hand, when the measured change amount is smaller than the failure determination change amount, it is determined as normal and the process proceeds to step S39 as it is.

  When the process proceeds to step S39, a diagnosis end process such as storing the current diagnosis history is performed, the routine is exited, and the normal control is started.

  9 to 12 show a third embodiment of the present invention. In addition, about the component same as a 1st form, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the first and second embodiments described above, the failure diagnosis of the evaporated fuel purge system in which the purge valves 14 and 15 are individually provided in the first purge passage 12 and the second purge passage 13 has been described. The failure diagnosis according to the present invention is applied to an evaporative fuel purge system in which a three-way valve type purge switching valve 25 as a passage opening / closing means is interposed at a branch portion of both purge passages 12 and 13.

  The purge switching valve 25 is switched by a switching signal from the ECU 21. An evaporation purge valve 26 is interposed in the upstream purge passage 11 connected to the upstream side of the purge switching valve 25. The evaporation purge valve 26 is opened / closed only at the time of failure diagnosis, and is kept open during normal control.

  In normal evaporation purge control, when the suction pipe pressure Pa is negative, the purge switching valve 25 is opened to the first purge passage 12 side, and when the suction pipe pressure Pa is positive pressure, the purge switching valve 25 is brought to the second purge passage 13 side. be opened. Therefore, when the suction pipe pressure Pa is negative, the evaporation gas is purged into the air chamber 2 through the first purge passage 12, and when the suction pipe pressure Pa is positive, the evaporation gas is passed through the second purge passage 13. The air is purged upstream of the intake passage 3 where the compressor 5b of the turbocharger 5 is disposed.

  Hereinafter, the failure diagnosis of the evaporated fuel purge system executed by the ECU 21 will be described according to the failure diagnosis routines shown in FIGS. 10 and 11 with reference to the time chart shown in FIG. This routine is executed once or every predetermined cycle after the engine is started, as in the first embodiment.

  First, in step S41, as in the first embodiment, engine operating state parameters (engine speed Ne, suction pipe pressure Pa, etc.) necessary for failure diagnosis are read, and in step S42, diagnosis start conditions are determined. The diagnosis start condition is the same as in the first embodiment. For example, the engine speed Ne is within a predetermined range (for example, about 1000 to 2000 rpm), and the suction pipe pressure Pa is negative (Pa <Pat), that is, a turbocharger. When 5 is in the non-operating state, it is determined that the diagnosis start condition is satisfied, and the process proceeds to step S43. If the engine speed Ne is out of the set range or the suction pipe pressure Pa is equal to or higher than the atmospheric pressure Pat, it is determined that the diagnosis start condition is not satisfied, and the process jumps to step S49 to store the diagnosis history. After performing the diagnosis end processing such as making the routine exit, the routine is exited and the routine proceeds to normal control.

  On the other hand, when it is determined that the diagnosis start condition is satisfied and the process proceeds to step S43, failure diagnosis is started in step S43 and subsequent steps. When the failure diagnosis is started, the evaporation generation amount measurement mode is executed in steps S43 to S45.

  In step S43, a valve closing signal is output to the evaporation purge valve 26 and the CCV 16, and both the valves 26 and 16 are closed. Since the suction pipe pressure Pa at the start of diagnosis is on the negative pressure side, the internal pressure of the evaporation purge system upstream of the evaporation purge valve 26 is maintained in a negative pressure state by closing both valves 26 and 16. Then, as shown in FIG. 12, the internal pressure of the evaporation purge system gradually rises with time due to the evaporation of the fuel stored in the fuel tank 7.

  Next, the process proceeds to step S44. Steps S44 to S48 correspond to steps S4 to S8 of the first form.

  That is, the tank internal pressure Pt is measured in step S44, the tank internal pressure Pt is compared with the set pressure Po in step S45, and if Pt <Po, step S44 is repeatedly executed, and if Pt ≧ Po, step S46 is performed. Proceed to In steps S44 and S45, the elapsed time may be measured and the tank internal pressure may be estimated based on the elapsed time.

  Then, when the process proceeds to step S46, the negative pressure introduction mode is executed in steps S46 to S53. Steps S46 to S48 correspond to steps S6 to S8 of the first form.

  That is, the suction pipe pressure Pa detected by the suction pipe pressure sensor 23 is read in step S46, and subsequently, in steps S47 and S48, the suction pipe pressure Pa is compared with the first set pressure P1 and the second set pressure P2, and the suction is performed. It is checked whether the tube pressure Pa is on the negative pressure side or the positive pressure side.

  When Pa ≦ P1, it is determined that the pressure is on the negative pressure side, and the process proceeds to step S49. If P1 <Pa ≦ P2, it is determined that it is in the dead band, and the process proceeds to step S50. On the other hand, when Pa> P2, it is determined that the pressure is on the positive pressure side, and the process proceeds to step S51.

  In step S49, since the suction pipe pressure Pa is on the negative pressure side, the evaporation purge valve 26 is opened, and the purge switching valve 25 is opened to the first purge passage 12 side. Then, a negative pressure is introduced from the first purge passage 12 to the evaporation purge system, and the tank internal pressure Pt gradually decreases.

  In step S50, since the suction pipe pressure Pa is in the dead zone, the evaporation purge valve 26 is closed. Then, the internal pressure of the evaporation purge system upstream from the evaporation purge valve 26 is maintained.

  On the other hand, in step S51, since the suction pipe pressure Pa is on the positive pressure side, the evaporation purge valve 26 is opened and the purge switching valve 25 is opened to the second purge passage 13 side. Then, a negative pressure is introduced from the second purge passage 13 into the evaporation purge system, and the tank internal pressure Pt further decreases.

  Then, when the process proceeds from step S49, S50 or S51 to step S52, the tank internal pressure Pt is rapidly increased, or the closing time of the evaporation purge valve 26 in the negative pressure introduction mode has elapsed for a predetermined time (for example, 3 seconds) or more. Check whether there is any. When the tank internal pressure Pt has risen rapidly or when the evaporative purge valve 26 has been closed for a predetermined time or longer, the routine jumps to step S59 to perform diagnosis end processing such as storing the diagnosis history. After that, the routine is exited and the normal control is started.

  If the tank internal pressure Pt has not increased in step S52 or if the evaporative purge valve 26 is closed within the predetermined time, the process proceeds to step S53, and whether the tank internal pressure Pt has decreased to the target negative pressure Pm. Find out. And when it has not fallen to the target negative pressure Pm (Pa> Pm), it returns to step S46 and performs negative pressure introduction mode again.

  Thus, in the present embodiment, in the negative pressure introduction mode, the suction pipe pressure Pa is measured, and when the suction pipe pressure Pa is equal to or higher than the atmospheric pressure, the negative pressure is introduced from the intake passage 3 upstream of the compressor 5b of the turbocharger 5. Since the pressure is introduced, it is possible to introduce a negative pressure into the evaporation purge system even when the turbocharger 5 is supercharging. Therefore, the opportunity for introducing the negative pressure is increased, and the tank internal pressure Pt is compared. The target negative pressure Pm can be reduced in a short time. In addition, since the dead zone is set, the opening and closing of the first purge valve 14 and the second purge valve 15 are not frequently switched in a short time, and the negative pressure can be introduced satisfactorily.

  In addition, since the evaporation purge valve 26 is arranged upstream of the purge switching valve 25, the internal pressure of the evaporation purge system can be easily maintained by closing the purge switching valve 25 and the CCV 16, and good control is achieved. Sex can be obtained.

  On the other hand, when the suction pipe pressure Pa decreases to the target negative pressure Pm (Pa ≦ Pm), the process proceeds from step S53 to step S54. In steps S54 and S55, the negative pressure holding mode is executed. That is, in step S54, the evaporation purge valve 26 is closed to maintain the internal pressure of the evaporation purge system. Then, the internal pressure of the evaporation purge system rises with time due to the evaporation of the fuel stored in the fuel tank 7.

  Subsequently, it progresses to step S55 and elapsed time is measured. When the elapsed time reaches the set time, the process proceeds to step S56, and the negative pressure change amount measurement mode is executed in steps S56 to S58. Steps S56 to S58 correspond to steps S16 to S18 of the first form.

  That is, in step S56, a negative pressure change amount of the evaporation purge system, which is a change amount of the tank internal pressure Pt in a predetermined time, is measured, and in step S57, the change amount is compared with a preset failure determination change amount. If the measured change amount is larger than the failure determination change amount, it is determined that there is an abnormality, and the process proceeds to step S58 where warning means such as a warning lamp is driven to display an abnormality, and a trouble code indicating the failure content is stored. Then, the process proceeds to step S59. On the other hand, if the measured change amount is smaller than the failure determination change amount, it is determined as normal and the process proceeds to step S59.

  When the process proceeds to step S59, a diagnosis end process such as storing the current diagnosis history is performed, and then the routine is exited to shift to normal control.

  FIGS. 13 to 16 show a fourth embodiment of the present invention. In addition, about the component same as a 1st form, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  This embodiment is a modification of the above-described second embodiment. In other words, the first purge valve 14 employed in the second embodiment performs open / close control according to the suction pipe pressure Pa even in normal evaporation purge control, but the first purge valve 14 of this embodiment is normally opened. Opening / closing operation is performed only at the time of failure diagnosis. In the second embodiment, the pressure introduction passage 15a of the second purge valve 15 employing a mechanically driven valve is communicated with the air chamber 2. In this embodiment, the first purge passage upstream of the first purge valve 14 is connected. 12 communicates. Further, a check valve 27 is interposed further upstream of the portion of the first purge passage 12 where the pressure introduction passage 15a communicates. This check valve 27 prevents the backflow of the evaporation gas. The flow of the evaporation gas is allowed only when the pressure on the upstream side of the check valve 27 is higher than the pressure on the downstream side, and the pressure on the upstream side is the pressure on the downstream side. Evaporative gas flow is blocked at lower temperatures.

  In the normal evaporation purge control, when the suction pipe pressure Pa is negative, the second purge valve 15 is closed by the negative pressure introduced through the pressure introduction passage 15a. As a result, the evaporated gas is purged into the air chamber 2 via the upstream purge passage 11 and the first purge passage 12. On the other hand, when the suction pipe pressure Pa is positive, the second purge valve 15 is opened by the positive pressure introduced through the pressure introduction passage 15a. As a result, the evaporative gas is purged to the upstream side of the intake passage 3 where the compressor 5b of the turbocharger 5 is disposed via the upstream purge passage 11 and the second purge passage 13. At that time, since the check valve 27 is interposed in the first purge passage 12, the evaporated gas does not flow.

  Hereinafter, the failure diagnosis of the evaporated fuel purge system executed by the ECU 21 will be described in accordance with the failure diagnosis routine shown in FIGS. 14 and 15 with reference to the time chart shown in FIG. This routine is executed once or every predetermined cycle after the engine is started, as in the first embodiment.

  First, in step S61, engine operating state parameters (engine speed Ne, suction pipe pressure Pa, etc.) necessary for failure diagnosis are read in the same manner as in the first embodiment, and diagnosis start conditions are determined in step S62. As in the first embodiment, the diagnosis start condition is, for example, that the engine speed Ne is within a predetermined range (for example, about 1000 to 2000 rpm) and the suction pipe pressure Pa is negative (Pa <Pat), that is, the turbocharger 5 is When in the inoperative state, it is determined that the diagnosis start condition is satisfied, and the process proceeds to step S63. If the engine speed Ne is out of the set range or the suction pipe pressure Pa is equal to or higher than the atmospheric pressure Pat, it is determined that the diagnosis start condition is not satisfied, the process jumps to step S79, and the diagnosis history is stored. After performing the diagnosis end processing such as making the routine exit, the routine is exited and the routine proceeds to normal control.

  On the other hand, when it is determined that the diagnosis start condition is satisfied and the process proceeds to step S63, failure diagnosis is started in step S63 and subsequent steps. When the failure diagnosis is started, the evaporation generation amount measurement mode is executed in steps S63 to S65.

  In step S63, a valve closing signal is output to the first purge valve 14 and the CCV 16, and both the valves 14 and 16 are closed. Since the suction pipe pressure Pa at the start of diagnosis is on the negative pressure side, this negative pressure is introduced into the second purge valve 15 via the pressure introduction passage 15a, so that the second purge valve 15 is kept closed. As a result, the internal pressure of the evaporation purge system is maintained, and as shown in FIG. 16, the internal pressure of the evaporation purge system gradually increases as time elapses due to evaporation of the fuel stored in the fuel tank 7.

  Next, the process proceeds to step S64. Steps S64 to S68 correspond to steps S4 to S8 of the first form. That is, the tank internal pressure Pt is measured in step S64, the tank internal pressure Pt is compared with the set pressure Po in step S65, and if Pt <Po, step S64 is repeatedly executed, and if Pt ≧ Po, step S66 is performed. Proceed to In steps S64 and S65, the elapsed time may be measured, and the tank internal pressure may be estimated based on the elapsed time.

  When the process proceeds to step S66, the negative pressure introduction mode is executed in steps S66 to S73. Steps S66 to S68 correspond to steps S6 to S8 of the first form.

  That is, in step S66, the suction pipe pressure Pa detected by the suction pipe pressure sensor 23 is read, and in steps S67 and S68, the suction pipe pressure Pa is compared with the first set pressure P1 and the second set pressure P2, and the suction is performed. It is checked whether the tube pressure Pa is on the negative pressure side or the positive pressure side.

  When Pa ≦ P1, it is determined that the pressure is on the negative pressure side, and the process proceeds to step S69. If P1 <Pa ≦ P2, it is determined that it is in the dead band, and the process proceeds to step S70. On the other hand, when Pa> P2, it is determined that the pressure is on the positive pressure side, and the process proceeds to step S71.

  In step S69, since the suction pipe pressure Pa is on the negative pressure side, the first purge valve 14 is opened and the valve opening degree is controlled based on the engine operating state. When the first purge valve 14 is opened, the negative pressure in the air chamber 2 is introduced into the second purge valve 15 via the pressure introduction passage 15a, so that the valve closed state is maintained. As a result, a negative pressure is introduced from the first purge passage 12 to the evaporation purge system, and the tank internal pressure Pt gradually decreases.

  In step S70, since the suction pipe pressure Pa is in the dead zone, the first purge valve 14 is closed. Further, when the suction pipe pressure Pa immediately before the first purge valve 14 is closed is on the negative pressure side, since the negative pressure is introduced into the pressure introduction passage 15a, the second purge valve 15 is maintained in the closed state. . As a result, the internal pressure of the evaporation purge system is maintained. On the other hand, when the suction pipe pressure Pa immediately before the first purge valve 14 is closed is on the positive pressure side, since the positive pressure is introduced into the pressure introduction passage 15a, the second purge valve 15 is kept open. . As a result, the second purge passage 13 communicates with the intake passage 3 upstream of the compressor 5b, but the intake passage 3 upstream of the compressor 5b tends to have a negative pressure due to the flow of intake air. No air is introduced into the evaporation purge system.

  On the other hand, in step S71, since the suction pipe pressure Pa is positive, the first purge valve 14 is closed. At that time, since the suction pipe pressure Pa immediately before the first purge valve 14 is closed is on the positive pressure side, a positive pressure is introduced into the second purge valve 15 via the pressure introduction passage 15a. Accordingly, the second purge valve 15 is opened, a negative pressure is introduced from the intake passage 3 upstream of the compressor 5b of the turbocharger 5 to the evaporation purge system, and the tank internal pressure Pt gradually decreases.

  Then, when the process proceeds from step S69, S70 or S71 to step S72, the tank internal pressure Pt is rapidly increased or the closing time of the first purge valve 14 in the negative pressure introduction mode has exceeded a predetermined time (for example, 3 seconds). Find out if you are doing. Then, when the tank internal pressure Pt has risen rapidly or when the closing time of the first purge valve 14 has exceeded a predetermined time, the process jumps to step S79 to perform diagnosis end processing such as storing the diagnosis history. After that, exit the routine and shift to normal control.

  In step S72, if the tank internal pressure Pt has not increased or if the closing time of the first purge valve 14 is within the predetermined time, the process proceeds to step S73, and whether the tank internal pressure Pt has decreased to the target negative pressure Pm. Check for no. If the pressure does not drop to the target negative pressure Pm (Pa> Pm), the process returns to step S66 and the negative pressure introduction mode is executed again.

  Thus, in the present embodiment, in the negative pressure introduction mode, the suction pipe pressure Pa is measured, and when the suction pipe pressure Pa is equal to or higher than the atmospheric pressure, the negative pressure is introduced from the intake passage 3 upstream of the compressor 5b of the turbocharger 5. Since the pressure is introduced, it is possible to introduce a negative pressure into the evaporation purge system even when the turbocharger 5 is supercharging. Therefore, the opportunity for introducing the negative pressure is increased, and the tank internal pressure Pt is compared. The target negative pressure Pm can be reduced in a short time. In addition, since the dead zone is set, the opening and closing of the first purge valve 14 and the second purge valve 15 are not frequently switched in a short time, and the negative pressure can be introduced satisfactorily.

  In addition, a check valve 27 is provided in the first purge passage 12, and the first purge valve 14 is normally opened in normal evaporation purge control, and is opened and closed only at the time of failure diagnosis. Further, it is not necessary to perform opening / closing control of the first purge passage 12, and evaporation purge control is facilitated.

  Further, a mechanically driven valve is employed as the second purge valve 15, and a diagnostic switching valve 24 is interposed in the pressure introduction passage 15 a, and the second purge valve 15 is switched by opening / closing control of the diagnostic switching valve 24. Therefore, the present invention can be easily applied to the existing second purge valve 15 that employs a mechanically driven valve, and high versatility can be obtained.

  On the other hand, when the suction pipe pressure Pa decreases to the target negative pressure Pm (Pa ≦ Pm), the process proceeds from step S73 to step S74. In steps S74 and S75, the negative pressure holding mode is executed as in the first embodiment. That is, in step S74, the first purge valve 14 is closed. When the first purge valve 14 is closed, negative pressure is sealed in the pressure introduction passage 15a, so that the second purge valve 15 is maintained in the closed state. As a result, the internal pressure of the evaporation purge system is maintained, and the internal pressure rises with time due to evaporation of the fuel stored in the fuel tank 7.

  Next, the process proceeds to step S75, and the elapsed time is measured. When the elapsed time reaches the set time, the process proceeds to step S76, and the negative pressure change amount measurement mode is executed in steps S76 to S78. Steps S76 to S78 correspond to steps S16 to S18 of the first form.

  That is, in step S76, a negative pressure change amount of the evaporation purge system that is a change amount of the tank internal pressure Pt in a predetermined time is measured, and in step S77, the change amount is compared with a preset failure determination change amount. If the measured change amount is larger than the failure determination change amount, it is determined that there is an abnormality, and the process proceeds to step S78 where warning means such as a warning lamp is driven to display an abnormality and a trouble code indicating the failure content is stored. Then, the process proceeds to step S79. On the other hand, if the measured change amount is smaller than the failure determination change amount, it is determined as normal and the process proceeds to step S79.

  When the process proceeds to step S79, a diagnosis end process such as storing the current diagnosis history is performed, then the routine is exited, and the normal control is started.

Schematic configuration diagram of an evaporative fuel purge system provided in an engine with a supercharger according to the first embodiment Flowchart showing the failure diagnosis routine (No. 1) Flowchart showing the failure diagnosis routine (part 2) Same as above, time chart showing fluctuations in tank internal pressure and suction pipe pressure at the time of failure diagnosis, and valve control states of first purge valve, second purge valve and CCV Schematic configuration diagram of an evaporative fuel purge system provided in an engine with a supercharger according to a second embodiment Flowchart showing the failure diagnosis routine (No. 1) Flowchart showing the failure diagnosis routine (part 2) Same as above, time chart showing fluctuations in tank internal pressure and suction pipe pressure at the time of failure diagnosis, and valve control states of the first purge valve, diagnosis switching valve and CCV Schematic configuration diagram of an evaporative fuel purge system provided in an engine with a supercharger according to a third embodiment Flowchart showing the failure diagnosis routine (No. 1) Flowchart showing the failure diagnosis routine (part 2) Same as above, time chart showing fluctuations in tank internal pressure and suction pipe pressure at the time of failure diagnosis and valve control states of purge switching valve, evaporation purge valve and CCV Schematic configuration diagram of an evaporative fuel purge system provided in an engine with a supercharger according to a fourth embodiment Flowchart showing the failure diagnosis routine (No. 1) Flowchart showing the failure diagnosis routine (part 2) Same as above, time chart showing fluctuations in tank internal pressure and suction pipe pressure during failure diagnosis, and valve control states of first purge valve and CCV

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Intake system, 2 ... Air chamber, 3 ... Intake passage, 4 ... Throttle valve, 5 ... Turbocharger, 5b ... Compressor, 7 ... Fuel tank, 8 ... Internal pressure sensor, 9 ... Evaporation passage, 10 ... Canister, DESCRIPTION OF SYMBOLS 10a ... Fresh air introduction port, 11 ... Upstream purge passage, 12 ... First purge passage, 13 ... Second purge passage, 14 ... First purge valve, 15 ... Purge valve, 15a ... Pressure introduction passage, 16 ... CCV, 21 ... ECU, 23 ... suction pipe pressure sensor, 24 ... diagnostic switching valve, 25 ... purge switching valve, 26 ... evaporation purge valve, 27 ... check valve, P1, P2, Po ... set pressure, Pa ... suction pipe pressure, Pat ... large Atmospheric pressure, Pm ... Target negative pressure, Pt ... Tank internal pressure

Agent Patent Attorney Susumu Ito

Claims (6)

An intake passage that interposes the supercharger, a purge passage having first and second purge passages that communicate with the downstream intake passage and the upstream intake passage of the supercharger, and an upstream side of the purge passage A canister, an evaporation passage communicating the canister and the fuel tank, a purge valve interposed in the purge passage, an air release valve disposed in a fresh air inlet provided in the canister, and the fuel An internal pressure detecting means for detecting the internal pressure of the evaporation purge system from the tank to the purge valve, an intake pipe pressure detecting means for detecting the intake pipe pressure in the downstream intake passage, and a control means for controlling the open / close state of each valve. In an evaporative fuel purge system for a turbocharged engine comprising:
The control means includes
A negative pressure introduction means for closing the purge valve and the air release valve when the diagnosis condition is satisfied and maintaining the internal pressure of the evaporation purge system, and then introducing a negative pressure into the evaporation purge system;
Diagnostic means for holding the internal pressure of the evaporation purge system after introduction of negative pressure and diagnosing the presence or absence of a failure by detecting an increase in internal pressure of the evaporation purge system due to evaporated fuel generated in the fuel tank by the internal pressure detection means ,
The negative pressure introducing means operates the purge valve based on the suction pipe pressure detected by the suction pipe pressure detecting means. When the suction pipe pressure is negative, the first purge passage is opened and the second purge is A supercharged engine characterized by closing a passage and closing the first purge passage and opening the second purge passage when the suction pipe pressure is positive to introduce a negative pressure into the evaporation purge system. Evaporative fuel purge system. 2. The negative pressure introducing means according to claim 1, wherein when the suction pipe pressure is in a dead zone between a negative pressure and a positive pressure, the purge valve is closed to maintain the internal pressure of the evaporation purge system. An evaporative fuel purge system for a turbocharged engine as described. The purge valve has a first purge valve interposed in the first purge passage, and a second purge valve interposed in the second purge passage,
The negative pressure introduction means opens the first purge valve and closes the second purge valve when the suction pipe pressure is negative, and closes the first purge valve when the suction pipe pressure is positive. 3. The evaporative fuel purge system for an engine with a supercharger according to claim 1, wherein the second purge valve is opened and a negative pressure is introduced into the evaporation purge system. The second purge valve is a mechanically driven valve that opens when the suction pipe pressure is higher than the atmospheric pressure due to a differential pressure between the suction pipe pressure and the atmospheric pressure in the downstream intake passage,
The operating chamber of the second purge valve communicates with the downstream intake passage through a pressure introduction passage,
A diagnostic switching valve is interposed in the pressure introduction passage,
The negative pressure introducing means opens both the first purge valve and the diagnosis switching valve when the suction pipe pressure is negative, and closes the first purge valve when the suction pipe pressure is positive. 4. The evaporative fuel purge system for an engine with a supercharger according to claim 3, wherein the valve is opened and the diagnosis switching valve is opened to introduce a negative pressure into the evaporation purge system. The purge valve has a purge switching valve interposed at a branch portion between the first purge passage and the second purge passage, and an evaporation purge valve interposed in the purge passage on the upstream side of the purge switching valve. And
In the negative pressure introducing means, after the evaporation purge valve is closed and the internal pressure of the evaporation purge system is maintained, the evaporation purge valve is maintained in an open state, and the purge switching valve is set to a state where the suction pipe pressure is negative. 3. The valve according to claim 1, wherein the valve opens to the first purge passage side and opens to the second purge passage side when the suction pipe pressure is positive to introduce a negative pressure into the evaporation purge system. Evaporative fuel purge system for turbocharged engines. The second purge valve is a mechanically driven valve that opens when the suction pipe pressure is higher than the atmospheric pressure due to a differential pressure between the suction pipe pressure and the atmospheric pressure in the downstream intake passage,
The operating chamber of the second purge valve communicates with the first purge passage upstream of the first purge valve,
A pressure introduction passage for introducing the suction pipe pressure is communicated with the first purge passage upstream of the first purge valve;
A check valve for preventing a flow when the internal pressure on the downstream side is higher than the internal pressure on the upstream side is interposed on the upstream side of the portion where the pressure introduction passage of the first purge passage is communicated,
The negative pressure introducing means opens the first purge valve when the suction pipe pressure is negative, and closes the first purge valve when the suction pipe pressure is positive to apply a negative pressure to the evaporation purge system. The evaporative fuel purge system for a supercharged engine according to claim 3, wherein the evaporative fuel purge system is used.

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