JP2006152822A - Leak detection device for evaporated fuel treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leak detection device for an evaporated fuel treatment system which can purge evaporated fuel to an intake system of an internal combustion engine during detection while materializing accurate detection of leak without influence of evaporated fuel. <P>SOLUTION: A leak detection device for an evaporated fuel treatment system adjusts an opening of a purge control valve and reduces pressure in the evaporated fuel treatment system to a first target pressure so as to compute a purge flow rate (average reduced pressure flow rate 1 or QGEN 1) at that time (S18-S28), and to a second target pressure so as to compute a purge flow rate (average reduced pressure flow rate 2 or QGEN 2) at that time (S34-S40), and further compares the difference between the purge flow rates with a prescribed value #DQGEN (S44) and makes the judgment that there is a leakage in the evaporated fuel treatment system when the difference exceeds the prescribed value (S48). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leak detection apparatus for an evaporated fuel processing system.

Evaporative fuel processing that connects the fuel tank and the canister to charge the evaporated fuel evaporated from the fuel tank and adsorb it to the canister, and purges the evaporated fuel desorbed from the canister in a predetermined operating state to the intake system of the internal combustion engine In the system, it is desired to detect a leak (leakage) due to a crack or the like, and an example thereof is the technique described in Patent Document 1.
JP-A-8-128362

  In the technique described in Patent Document 1, after the engine is started, the drain cut valve is opened, the residual pressure of the canister is released, and when the failure diagnosis execution condition is satisfied, the drain cut valve is closed, When the internal pressure of the fuel tank drops to the specified pressure, the purge control valve is closed and the tank internal pressure is read.Then, the internal pressure of the tank after a predetermined time is read, and it is determined whether or not the differential pressure is less than or equal to the judgment value. I have a diagnosis.

  The pressure in the evaporative fuel treatment system is affected by the evaporative fuel (fuel vapor) from the fuel tank. However, in the technique described in Patent Document 1, from the pressure when the pressure is reduced after the evaporative fuel treatment system is closed. Since the detection is limited to the leak, there is a disadvantage that the detection accuracy is not sufficiently satisfied, and the vaporized fuel cannot be purged to the intake system of the internal combustion engine during the detection.

  Accordingly, the object of the present invention is to solve the above-described problems, and to detect leaks accurately without being affected by the evaporated fuel, and also to allow the evaporated fuel to be purged into the intake system of the internal combustion engine during the detection. An object of the present invention is to provide a leak detection apparatus for an evaporated fuel processing system.

  In order to solve the above-mentioned object, according to claim 1, a canister for storing an adsorbent, and a fuel tank and the canister connected to each other, the evaporated fuel evaporated from the fuel tank is adsorbed in the canister. A charge passage to be adsorbed by the fuel, a purge passage for connecting the canister and an intake system of an internal combustion engine to purge the fuel vapor desorbed from the adsorbent into the intake system, and the purge passage inserted in the purge passage. In a leak detection apparatus for an evaporative fuel processing system comprising at least a purge control valve for opening and closing a passage, the pressure detection means for detecting the pressure in the evaporative fuel processing system and the detection by adjusting the opening of the purge control valve Pressure reduction control means for reducing the pressure in the evaporated fuel processing system to the first target pressure, and when the pressure in the evaporated fuel processing system is reduced to the first target pressure. A purge flow rate calculating means for calculating a chromatography di flow was composed as and a leakage judging means for judging leakage of the evaporated fuel processing system based on the calculated purge flow rate.

  The leak detection apparatus for an evaporated fuel processing system according to claim 2 further adjusts the opening of the purge control valve to reduce the detected pressure in the evaporated fuel processing system to a second target pressure. And a second purge flow rate calculation means for calculating a purge flow rate when the pressure in the evaporated fuel processing system is reduced to the second target pressure, and the leak determination The means is configured to determine a leak of the evaporated fuel processing system based on a purge flow rate when the pressure is reduced to the first target pressure and a purge flow rate when the pressure is reduced to the second target pressure.

  According to claim 1, the pressure in the evaporated fuel processing system detected by adjusting the opening of the purge control valve is reduced to the first target pressure, and when the pressure is reduced to the first target pressure. The purge flow rate is calculated, and the leak is determined based on the calculated purge flow rate. That is, it is assumed that the purge flow rate when the pressure is reduced to the first target pressure is the purge flow rate necessary for maintaining the first target pressure, in other words, there is no leak and the amount of evaporated fuel generated does not change suddenly. The value means a certain amount corresponding to the amount of evaporated fuel generated. Therefore, for example, a plurality of purge flow rates when the pressure is reduced to the first target pressure are calculated, and dispersion or standard deviation is obtained for the calculated plurality of purge flow rates and compared with a reference value set as appropriate. Whether the first target pressure is maintained (the amount of evaporated fuel generated is constant) or the first target pressure is not maintained (that is, a crack is generated in the charge passage or the like to cause a leak) Can be determined).

  As a result, it is possible to accurately detect leaks caused by cracks or the like generated in the charge passage of the evaporated fuel processing system without being influenced by whether or not the evaporated fuel is generated or not, and also during the detection It is possible to purge the intake system of the engine, thereby promoting the desorption of the evaporated fuel.

  Further, the purge flow rate when the pressure in the fuel vapor processing system is reduced to the second target pressure is calculated, and the purge flow rate when the pressure is reduced to the first target pressure The leak is determined based on the purge flow rate when the pressure is reduced to the second target pressure. As described above, the purge flow rate when the pressure is reduced to the target pressure means the purge flow rate necessary to maintain the pressure, in other words, if there is no leak, it means a certain amount corresponding to the amount of evaporated fuel generated. Therefore, the purge flow rate when the pressure is reduced to the first and second target pressures should be almost the same value.

  As far as the inventors have found, the difference between the purge flow rate when the pressure is reduced to the first target pressure and the purge flow rate when the pressure is reduced to the second target pressure increases as the leak is larger (the cracks are larger). If there is no leak, the difference in purge flow rate when the pressure is reduced to the first and second target pressures is the difference in the amount of evaporated fuel, but as described above, the amount of evaporated fuel changes rapidly in a short time. Assuming nothing was done, the value was negligibly small.

  Therefore, on the basis of the purge flow rate when the pressure is reduced to the first and second target pressures (preferably the average value thereof from the improvement in accuracy), specifically, a predetermined value appropriately set by obtaining the difference between them. It is possible to determine whether the first and second target pressures are maintained or whether a leak has occurred.

  This makes it possible to detect leaks caused by cracks or the like generated in the charge passage of the evaporated fuel processing system with higher accuracy without being influenced by the presence or absence of evaporated fuel, and also during the detection. Can be purged into the intake system of the internal combustion engine, and therefore, the desorption of the evaporated fuel can be promoted.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out a fuel vapor processing system leak detection apparatus according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view showing a leak detection apparatus for a fuel vapor processing system according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes a canister. The canister 10 is made of a resin material or a metal material, and stores therein an adsorbent 10a made of pelleted activated carbon. Reference numeral 12 denotes a fuel tank, and gasoline fuel 14 is stored in the fuel tank 12. The fuel tank 12 is also manufactured from a resin material or a metal material, and is also airtight and liquidtight. The opening formed at the tip of the filler neck 12a of the fuel tank 12 is closed with a filler cap 12b.

  The canister 10 and the upper liquid level space 12 c of the fuel tank 12 are connected by the charge passage 16, and the gasoline fuel (fuel vapor) 14 evaporated in the fuel tank 12 flows (charges) through the charge passage 16 to the canister 10. The The evaporated fuel that has flowed into the canister 10, particularly the hydrocarbon (HC) component therein, is adsorbed by the adsorbent 10 a stored inside the canister 10.

  Reference numeral 20 denotes an internal combustion engine (hereinafter referred to as “engine”). The engine 20 is a four-cycle four-cylinder engine, and air drawn from an air cleaner (not shown) flows through the intake pipe 22 and is adjusted by the throttle valve 24 through the intake manifold 26 to the intake port of each cylinder. It reaches. The gasoline fuel 14 stored in the fuel tank 12 is supplied to an injector 30 through a fuel supply pipe (not shown), and is injected there and mixed with inflow air to form an air-fuel mixture. The air-fuel mixture flows into the combustion chamber 34 (only one is shown) of each cylinder when the intake valve 32 is opened.

  The inflowing air-fuel mixture is ignited by the spark plug 36 and burned, and the piston 40 is driven. When the exhaust valve 42 is opened, the gas generated by the combustion flows through the exhaust manifold 44 and is released to the atmosphere (outside the engine) through the exhaust pipe 46.

  The canister 10 is connected by a purge passage 50 to the intake system of the engine 20, more specifically, to a downstream position of the throttle valve 24. A purge control valve 50 a is inserted in the purge passage 50. The purge control valve 50a is composed of an electromagnetic solenoid valve, and opens and closes the purge passage 50 with an opening degree corresponding to the energization amount to the solenoid. When the purge passage 50 is opened, the evaporated fuel adsorbed on the adsorbent 10a is desorbed by the negative pressure of the intake system of the engine 20, and then the intake air of the engine 20 is flowed at a flow rate corresponding to the opening of the purge passage 50. The system is aspirated and purged.

  The energization amount to the solenoid of the purge control valve 50a is given as a duty value in PWM. The purge flow rate of the desorbed evaporated fuel increases as the duty value increases, and increases as the intake pipe pressure PBA becomes negative.

  The canister 10 is connected (opened) to the atmosphere via the atmosphere passage 52. Similarly, an atmospheric release valve 52a composed of an electromagnetic solenoid valve is inserted in the atmospheric passage 52. When the atmosphere release valve 52a is driven to the fully open position, the evaporated fuel processing system including the canister 10 is opened to the atmosphere, and the internal pressure becomes atmospheric pressure. On the other hand, when the atmospheric release valve 52a is driven to the fully closed position, the evaporated fuel processing system becomes a closed circuit.

  The canister 10 is provided with a pressure sensor (pressure detection means) 56 in the vicinity of the position where the charge passage 16 is connected, and outputs a signal corresponding to the pressure P in the evaporated fuel processing system including the canister 10 and the like.

  Further, a crank angle sensor 60 is disposed in the vicinity of the crankshaft or camshaft (both not shown) of the engine 20, and a cylinder discrimination signal, a TDC signal of each piston, and a signal indicating a crank angle obtained by subdividing it. Output. In the intake pipe 22, an absolute pressure sensor 62 is arranged downstream of the arrangement position of the throttle valve 24, and outputs a signal corresponding to the intake pipe internal pressure PBA (indicating the engine load).

  In addition, an outside air temperature sensor 64 is disposed at a position facing the inside of the intake pipe 22 of the engine 20 and outputs a signal corresponding to the temperature TA of the air (outside air) sucked into the engine 20.

  In addition, a water temperature sensor 66 is disposed near the cooling water passage (not shown) to output a signal corresponding to the engine water temperature TW, and an air-fuel ratio sensor (not shown) is arranged in the exhaust pipe 46. A signal corresponding to the oxygen concentration in the exhaust gas is output.

  The output of the sensor group described above is sent to an ECU (electronic control unit) 70. The ECU 70 is composed of a microcomputer comprising a CPU, ROM, RAM, etc., and the sensor output is waveform-shaped or converted into a digital value via an A / D conversion circuit (not shown) and stored in the RAM. The output of the crank angle sensor 60 is counted by a counter (not shown), and the engine speed NE is detected.

  FIG. 2 is a flowchart showing the operation of the leak detection apparatus for the evaporated fuel processing system shown in FIG.

  The illustrated program shows the operation of the ECU 70 described above, and is executed at predetermined time intervals, for example, at intervals of 80 msec.

  More specifically, when the engine 20 is in an operation state in which canister purge (evaporated fuel processing) for purging the evaporated fuel desorbed from the adsorbent 10a of the canister 10 to the intake system of the engine 20 is permitted, the engine 20 starts every 80 msec. Is done.

  The CPU in the ECU 70 executes the program shown in the figure while determining the operating state in which the canister purge is permitted based on the parameters indicating the operating state of the engine 20 such as the detected engine speed NE and the intake pipe pressure PBA. To do.

  In the following, it is determined in S10 whether or not the bit of the flag MONIEND is set to 1. As will be described later, when the bit of this flag is set to 1, it means that the leak determination has been completed, and thus the processing here means to determine whether or not the above-described leak determination has been completed.

  In this specification, the leakage of the evaporative fuel processing system refers to a leak (leakage) caused by a crack occurring in the canister 10, the charge passage 16, the purge passage 50, or a connecting portion thereof constituting the evaporative fuel processing system. This means a state in which atmospheric air enters from the outside, but in addition, it is used to include a case where the filler cap 12b of the fuel tank 12 is not properly closed (so-called loose cap).

  When the result in S10 is affirmative, the subsequent processing is unnecessary and is skipped. That is, in this embodiment, the engine 20 is configured to be executed only once after the engine 20 is started.

  On the other hand, when the result in S10 is negative, the program proceeds to S12, in which it is determined whether or not the bit of the flag GEN2END is 1. When the flag bit is set to 1, as described later, the purge flow rate when the pressure is reduced to the second target pressure, specifically the average value thereof, more specifically, the average reduced pressure flow rate 2 is calculated. Means that has ended.

  In the first program loop, this determination is of course denied and the process proceeds to S14 to determine whether or not the monitor condition (leak determination condition) is satisfied. The monitoring condition is that the detected engine water temperature TW is in a predetermined range (for example, 4 degrees or more and less than 35 degrees), and the detected outside air temperature TA is in a predetermined range (for example, 4 degrees or more and less than 35 degrees), And it means that the detected outside air temperature TA is not less than the detected value −10 degrees at the start of the engine 20.

  That is, the monitoring condition is when the temperature of the engine 20 or the surrounding temperature is within a predetermined range and the decrease in outside air is not large. One of the monitoring conditions when the outside air is not greatly reduced is, for example, a garage soak, that is, when the engine 20 is started and running while being kept at room temperature, there is a risk of false detection. It is. As described above, it is necessary to be in an operation state in which canister purge is permitted as a precondition for establishment of the monitoring condition.

  When the result in S14 is negative, the subsequent processing is skipped. When the result is affirmative, the process proceeds to S16 to determine whether or not the bit of the flag GEN1END is 1. When the flag bit is set to 1, as described later, the purge flow rate when the pressure is reduced to the first target pressure, specifically the average value thereof, more specifically, the average reduced pressure flow rate 1 is calculated. Means that has ended.

  Similarly, in the first program loop, this determination is of course denied and the process proceeds to S18, where the pressure is reduced to the first target pressure. That is, the opening degree of the purge control valve 50a is adjusted to reduce the pressure in the evaporated fuel processing system detected via the pressure sensor 56 to a first target pressure, for example, −5 mmHg.

  This process is performed in another routine (not shown) by operating the duty ratio when the purge control valve 50a is energized using a PID control law or the like so that the detected pressure is reduced to the first target pressure. Is adjusted to control the amount of negative pressure introduced from the intake system of the engine 20.

  During this time, the evaporated fuel is purged into the intake system of the engine 20 according to the opening degree of the purge control valve 50. Although not shown, prior to the processing of the flow chart of FIG. 2, the atmosphere release valve 52a of the canister 10 is closed, and the evaporated fuel processing system is closed to form a closed circuit.

  Next, the process proceeds to S20, in which it is determined whether or not the first target pressure has been reached, that is, whether the detected pressure has been reduced to the first target pressure. If the determination is negative, the process proceeds to S22 and the timer TGENATSU (down counter) is set to a predetermined value. A value #TMGENATSU (for example, 5 sec) is set, and time measurement is started. The process of S22 is repeated as long as the result of S20 is negative, and the timer is reset every time.

  If the result of the next program loop is affirmative in S20, the process proceeds to S24, where it is determined whether or not the value of the timer has reached zero. If the result is negative, the process proceeds to S26, and the above-described average reduced pressure flow rate 1 is calculated. When the result is affirmative, the process proceeds to S28, where the calculated average reduced pressure flow 1 is set to the value QGEN1 (purge flow when the pressure is reduced to the first target pressure), the process proceeds to S30, and the bit of the flag GEN1END is set to 1 To do.

  The process of S26 will be described. FIG. 3 is a graph showing the characteristics of the purge flow rate QPGC (l / min) with respect to the intake pipe pressure and the (energization) duty ratio (l: liter). Since the intake pipe pressure is indicated by a negative pressure, it is indicated as PBG. In the illustrated example, only three types of duty ratios of 97%, 50%, and 20% are shown. As shown in the figure, the purge flow rate QPGC increases as the intake pipe pressure (negative pressure) PBG increases in the negative pressure direction, and increases as the duty ratio increases.

  In the process of S26, the intake pipe pressure PBA detected through the absolute pressure sensor 62 is converted into a negative pressure PBG, and the duty ratio commanded (energized) to the purge control valve 50a at that time is detected. 3 is searched to calculate the purge flow rate QPGC. When the duty ratio is not in the characteristic shown in FIG. 3, the purge flow rate QPGC is calculated by appropriately interpolating the characteristic shown in FIG. The timer TMGENATSU is set to 5 seconds, and the flow chart of FIG. 2 is looped every 80 msec, so the process of S26 is repeated about 62 times.

  In the first program loop, the calculated value is stored as it is. In the second program loop, the sum obtained by adding the newly calculated value to the stored value is divided by 2, and an average value is obtained. In the program, the newly calculated value is added to the sum and divided by 3 to obtain an average value. Thereafter, the same process is repeated to calculate the average reduced pressure flow rate 1.

  When the processing of S30 is completed, the determination of S16 is affirmed in the next and subsequent program loops, and the processing proceeds to S32, in which the opening of the purge control valve 50a is adjusted and detected in the evaporated fuel processing system through the pressure sensor 56. The pressure is further reduced to a second target pressure, for example -20 mmHg.

  This process is also performed in another routine (not shown) by operating the duty value of the purge control valve 50a using a PID control law or the like so that the detected pressure is reduced to the second target pressure and adjusting the opening degree. This is executed by controlling the amount of negative pressure introduced from the intake system of the engine 20.

  Next, the process proceeds to S34, where it is determined whether or not the second target pressure has been reached, that is, whether the detected pressure has been reduced to the second target pressure, and whenever the result is negative, the process proceeds to S22, and similarly, the timer TGENATSU has a predetermined value #. Set TMGENATSU and start time measurement.

  In the next and subsequent program loops, if the result in S34 is affirmative, the process proceeds to S36, where it is determined whether or not the timer value has reached zero. If the result is negative, the process proceeds to S38, and the same method as described in S26. The average reduced pressure flow 2 is calculated, and if the result is affirmative, the process proceeds to S40, and the calculated average reduced pressure flow 2 is set to the value QGEN2 (purge flow when the pressure is reduced to the second target pressure), and the process proceeds to S42. The bit of the flag GEN2END is set to 1.

  As a result, the determination of S12 is affirmed in the next program loop and the process proceeds to S44, where it is determined whether the difference obtained by subtracting the value QGE1 from the value QGE2 exceeds the predetermined value #DQGEN. Proceeding to S46, it is determined that there is no leak in the evaporated fuel processing system, and if affirmative, the process proceeds to S48 and it is determined that there is leak in the evaporated fuel processing system. Next, in S50, the bit of the above-mentioned flag MONIEND is set to 1 and the program is terminated.

  FIG. 4 is a time chart for explaining the operation of the apparatus shown in the flow chart of FIG.

  After the atmosphere release valve 52a is closed, the purge control valve 50a is opened and the negative pressure is introduced from the engine 20, so that the pressure of the evaporated fuel processing system decreases, and the first target pressure (−5 mmHg) at time t1. The pressure is reduced to The pressure is then further reduced and reduced to the second target pressure (−20 mmHg) at time t2. In the figure, the purge flow rates QGEN1 and QGEN2 are indicated by solid lines when there is no leak, and are indicated by alternate long and short dash lines when there is a leak (for convenience of understanding, QGEN1 and 2 are indicated as values before being averaged).

  As described above, the amount of evaporated fuel generated does not change suddenly in a short time, and assuming that there is no leak, the purge flow rate when the pressure is reduced to the first and second target pressures, in other words, the pressure is maintained. The purge flow rates QGEN1 and QGEN2 required for the above are constant amounts corresponding to the amount of evaporated fuel generated, and should be substantially the same value.

  In fact, as far as the inventors have found, for example, if the amount of evaporated fuel is 5 (l / min), the purge flow rate becomes the value or a value in the vicinity thereof, and the difference is small enough to be ignored.

  Further, as far as the inventors have found, the difference between the purge flow rate when the pressure is reduced to the first target pressure and the purge flow rate when the pressure is reduced to the second target pressure increases as the leak (cracking, etc.) increases. Specifically, when the crack diameter is 0.09 inch and the amount of evaporated fuel is zero, the average purge flow rate is 6.88 (l / min) for QGEN1 and 13.9 (l / min) for QGEN2. Met. Further, when the crack diameter is 0.09 inch and the amount of evaporated fuel is 5 (l / min), the average purge flow rate is 12.05 (l / min) for QGEN1 and 19.2 (l / min) for QGEN2. Met.

  The present invention has been made on the basis of the above knowledge, and calculates the purge flow rates QGEN1, 2 when the pressure in the evaporated fuel processing system is reduced to the first and second target pressures, and the first Leakage is determined based on the purge flow rate QGEN1 when the pressure is reduced to the target pressure and the purge flow rate QGEN2 when the pressure is reduced to the second target pressure. Specifically, the leak is reduced to the first and second target pressures. More specifically, based on the average value of the purge flow rate (average reduced pressure flow rate 1 or 2 or QGEN 1 or 2), the difference is obtained and compared with a predetermined value DQGEN set as appropriate. In addition, it is determined whether the second target pressure is maintained, in other words, whether a leak has occurred or whether a leak has occurred.

  The leak detection apparatus for the evaporated fuel processing system according to this embodiment is configured as described above, so that it occurs in the charge passage 16 of the evaporated fuel processing system without being affected by the presence or absence of evaporated fuel. In addition to accurately detecting a leak caused by a crack or the like, it is possible to purge the evaporated fuel into the intake system of the engine 20 during the detection, thereby promoting the desorption of the evaporated fuel.

  FIG. 5 is a flow chart similar to FIG. 2, showing a second embodiment of the leak detection apparatus for an evaporated fuel processing system according to the present invention.

  In the second embodiment, the leak is detected only from the purge flow rate when the pressure is reduced to the first target pressure.

  Explained below, after the same processing as the processing of the flow chart of FIG. 2 of the first embodiment is performed from S100 to S110, the process proceeds to S114, and the variance value Vx of the average reduced pressure flow rate 1 is calculated according to Equation 1. As shown in Equation 1, the dispersion Vx indicates the degree of dispersion from X1 (average vacuum flow rate 1).

  Next, in S116, the calculated variance value Vx is replaced with VXQ, and in S118, the bit of the flag GEN1END is set to 1. As a result, in the next and subsequent program loops, the determination in S102 is affirmed and the process proceeds to S120, where it is determined whether or not the replaced value VXQ exceeds the reference value VXREF. When the determination is positive, the process proceeds to S124 and it is determined that there is a leak.

  To explain this, as described above, the purge flow rate QGEN1 when the pressure is reduced to the first target pressure is the purge flow rate necessary to maintain the pressure, in other words, there is no leakage, and the amount of evaporated fuel generated changes suddenly. If not, the value means a certain amount corresponding to the amount of evaporated fuel generated. Therefore, for example, a plurality of purge flow rates when the pressure is reduced to the first target pressure are calculated, and dispersion (dispersion from the average value) is calculated for the calculated plurality of purge flow rates, and a reference value appropriately set If the first target pressure is maintained (whether the amount of evaporated fuel is constant) or whether the first target pressure is not maintained (that is, in the charge passage or the like). It is possible to determine whether a crack has occurred and a leak has occurred. That is, the large dispersion value of the purge flow rate QGEN indicates that the purge flow rate necessary for maintaining the target pressure varies, in other words, leak has occurred and atmospheric pressure has entered.

  Therefore, in the second embodiment, the purge flow rate when the pressure is reduced to the first target pressure is calculated, and a leak is determined based on the calculated purge flow rate. More specifically, the pressure is reduced to the first target pressure. A plurality of (60) purge flow rates (average reduced pressure flow rate 1 or QGEN1) are calculated, and a dispersion value (dispersion value from the average value) Vx is calculated and appropriately set for the calculated purge flow rates. Whether or not a leak has occurred is determined by comparing with the reference value VXREF.

  Thereby, also in the second embodiment, it is possible to accurately detect a leak caused by a crack or the like generated in the charge passage 16 of the evaporative fuel processing system without being influenced by the presence or absence of evaporative fuel or the amount thereof. During the detection, the evaporated fuel can be purged into the intake system of the engine 20, and thus the evaporation of the evaporated fuel can be promoted.

  As described above, in the second embodiment of the present invention, the evaporated fuel (gasoline fuel 14) evaporated from the fuel tank by connecting the canister 10 storing the adsorbent 10a, the fuel tank 12 and the canister. Is connected to the adsorbent in the canister and the canister and the intake system (intake pipe 22) of the internal combustion engine (engine) 20 to connect the evaporated fuel released from the adsorbent to the intake system. In the leak detection device for an evaporated fuel processing system, the pressure P in the evaporated fuel processing system is set to at least a purge passage 50 that is purged at a time and a purge control valve 50a that is inserted in the purge passage and opens and closes the purge path. Pressure detecting means (pressure sensor 56) for detecting, and adjusting the opening degree of the purge control valve to adjust the detected pressure in the evaporated fuel processing system to a first target Depressurization control means (ECU 70, S106 (S18)) for depressurizing to the force, and a purge flow rate when the pressure in the evaporated fuel processing system is reduced to the first target pressure (average depressurization flow rate 1, more specifically, Is a purge flow rate calculation means (ECU 70, S108 to S116 (S20 to S28)) for calculating the dispersion value of the average reduced pressure flow rate 1 and a leak for determining a leak of the evaporated fuel processing system based on the calculated purge flow rate Judgment means (ECU 70, S120 to S124 (S44 to S48)) is provided.

  Furthermore, in the fuel vapor processing system leak detection apparatus according to the first embodiment, the opening of the purge control valve is adjusted so that the detected pressure in the fuel vapor processing system becomes the second target pressure. Second decompression control means (ECU 70, S32) for decompressing and a purge flow rate (average reduced pressure flow rate 2 or QGEN2) when the pressure in the evaporated fuel processing system is reduced to the second target pressure. 2 purge flow rate calculation means (ECUs 70, S34 to S40), and the leak determination means includes a purge flow rate when the pressure is reduced to the first target pressure (average reduced pressure flow rate 1 or QGEN1) and the second Based on the purge flow rate when the pressure is reduced to the target pressure, the leakage of the evaporated fuel processing system is determined (ECU 70, S44 to S48).

  In the first embodiment described above, the average reduced pressure flow rate is calculated by a simple average, but may be calculated by a moving average or a weighted average. Furthermore, instead of using all of the 60 values, it may be calculated from an appropriate one or a plurality (for example, the maximum value of 60 or a value in the vicinity thereof).

  In the second embodiment described above, the dispersion value of the purge flow rate (average reduced pressure flow rate 1) is obtained, but a standard deviation may be used. Further, it is not always necessary to use all 60 values as in the case of the first embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the overall configuration of a fuel vapor processing system leak detection apparatus according to a first embodiment of the present invention; It is a flowchart which shows operation | movement of the apparatus shown in FIG. 2 is a graph showing the characteristics of the purge flow rate QPGC with respect to the intake pipe pressure and the duty ratio, which are used to calculate the purge flow rate (average reduced pressure flow rates 1 and 2) in the flow chart of FIG. 3 is a time chart for explaining the operation of the apparatus shown in the flow chart of FIG. FIG. 6 is a flow chart similar to FIG. 2 showing the operation of the evaporative fuel treatment system leak device according to the second embodiment of the present invention;

Explanation of symbols

10 canister 12 fuel tank 16 charge passage 20 engine (internal combustion engine)
22 Intake pipe (intake system)
50 Purge passage 50a Purge control valve 52 Air passage 52a Air release valve 56 Pressure sensor (pressure detection means)
70 ECU (Electronic Control Unit)

Claims (2)

  A canister for storing an adsorbent, a charge passage for connecting the fuel tank and the canister to adsorb evaporated fuel evaporated from the fuel tank to the adsorbent in the canister, and the canister and an intake system of the internal combustion engine Leakage in an evaporative fuel processing system comprising at least a purge passage connected to purge the fuel vapor desorbed from the adsorbent into the intake system and a purge control valve inserted in the purge passage to open and close the purge passage In the detection device, pressure detecting means for detecting the pressure in the evaporated fuel processing system, and adjusting the opening of the purge control valve to reduce the detected pressure in the evaporated fuel processing system to a first target pressure. A depressurization control means for performing, a purge flow rate calculating means for calculating a purge flow rate when the pressure in the evaporative fuel processing system is reduced to the first target pressure, and the performance Been evaporated fuel processing system of the leak detector being characterized in that a leakage determination means for determining a leakage of the evaporated fuel processing system based on the purge flow rate.   Further, a second pressure reduction control means for adjusting the opening of the purge control valve to reduce the detected pressure in the evaporated fuel processing system to a second target pressure, and a pressure in the evaporated fuel processing system. And a second purge flow rate calculating means for calculating a purge flow rate when the pressure is reduced to the second target pressure, and the leak determination means is configured to calculate a purge flow rate when the pressure is reduced to the first target pressure. 2. The evaporative fuel processing system leak detection apparatus according to claim 1, wherein the evaporative fuel processing system leak is determined based on a purge flow rate when the pressure is reduced to the second target pressure.

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