JP2006316702A - Leakage diagnostic system in purge device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage diagnostic system capable of diagnosing the existence of a leakage hole in a purge device in a shorter time than a conventional time. <P>SOLUTION: In this purge device 10 for purging fuel gas generated by evaporating fuel in a fuel tank 20 to an intake passage of an internal combustion engine, the leakage diagnostic system 100 diagnoses the existence of the leakage hole in the purge device 10 on the basis of pressure in the purge device 10 after a predetermined time by reducing the pressure in the purge device 10 for diagnosing whether or not the leakage hole of a predetermined diameter or more is generated, and includes a negative pressure pump 130 constituted so that capacity can be varied, a secondary driving control means for driving the negative pressure pump by predetermined capacity where the pressure in the purge device 10 becomes reference pressure when the leakage hole of the predetermined diameter is generated in the purge device 10, and a primary driving control means for driving the negative pressure pump 130 by capacity higher than the capacity in its secondary driving control means before its secondary driving control means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a leak diagnosis device for diagnosing whether or not a leak hole having a predetermined diameter or more exists in a purge device that purges fuel gas generated by evaporation of fuel in a fuel tank into an intake passage of an internal combustion engine. About.

  In order to prevent the fuel gas generated from the fuel tank from leaking into the atmosphere, the fuel gas generated from the fuel tank is adsorbed to the canister, and the purge passage that connects the canister and the intake path of the internal combustion engine communicates. 2. Description of the Related Art A purge device that purges fuel gas adsorbed by a canister to an intake passage by using a negative pressure in the intake passage by opening a purge control valve provided is known. In order to prevent the state in which the fuel gas leaks from the purge device into the atmosphere from being left for a long period of time, a leak hole is formed in the purge device from the pressure in the purge device when the pressure in the purge device is reduced or increased. There has been proposed a leak diagnosis apparatus for diagnosing whether or not there exists.

  For example, this is the device described in Patent Document 1. The apparatus of Patent Document 1 includes a negative pressure pump communicated with the inside of the purge apparatus, and the suction capability of the negative pressure pump is such that a hole having a predetermined diameter (for example, a diameter of 0.5 mm) is opened in the purge apparatus. In such a case, the purge device internal pressure is set to a constant value.

Therefore, if the negative pressure pump is driven for a predetermined time with the purge device as a closed system, the purge device internal pressure converges to a certain value. If the pressure is higher than that, it can be diagnosed that a larger hole is open, and if the internal pressure of the purge device falls below the predetermined value before the predetermined time elapses, the hole is not opened. Can be diagnosed.
JP 2004-293438 A

  By making the suction capacity of the pump a predetermined constant capacity as in Patent Document 1, it is possible to diagnose whether or not a hole having a predetermined diameter or more is opened in the purge device. If the capacity is fixed, if the remaining amount of fuel in the fuel tank is small, it will take more time to lower the pressure in the purge device than if the remaining amount of fuel is large. There is a problem that it takes time. In addition, this diagnosis is performed when the engine is stopped or idling because it is necessary to perform the diagnosis in a stable state of the vehicle in which a pressure change does not occur due to the fuel in the fuel tank shaking. Therefore, the longer the diagnosis takes, the higher the possibility that the diagnosis will be stopped because the vehicle is not in a stable state by starting the engine or restarting the vehicle.

  Here, in order to quickly reduce the pressure in the purge device even when the remaining amount of fuel in the fuel tank is small, it is conceivable to use a pump having a higher capacity. However, if a pump with a high capacity is used, the pressure in the purge device will continue to drop even if there is a leak hole of a predetermined diameter or more in the purge device, and the leak hole can be detected. It will disappear.

  The present invention has been made based on this situation, and an object of the present invention is to provide a leak diagnosis device capable of diagnosing the presence or absence of a leak hole in a purge device in a shorter time than before. It is in.

In order to achieve this object, the invention according to claim 1 is characterized in that a leak hole having a predetermined diameter or more is formed in a purge device that purges fuel gas generated by evaporation of fuel in a fuel tank into an intake path of an internal combustion engine. In order to diagnose whether or not there is a leak, the pressure in the purge device is transformed by a pump, and the presence or absence of a leak hole in the purge device is diagnosed based on the pressure in the purge device after transformation. And
As the pump, provided with a variable pump device configured to be variable in capacity,
A secondary drive control means for driving the variable pump device with a predetermined ability in which the pressure in the purge device becomes a reference pressure when a leak hole of the predetermined diameter is generated in the purge device;
Prior to the secondary drive control means, the variable pump includes primary drive control means for driving the variable pump with a capacity higher than that of the secondary drive control means.

  According to the first aspect of the present invention, the variable-capacity variable pump is provided as the pump, and when the leak hole having a predetermined diameter is generated in the purge device as in the conventional case, the pressure in the purge device is reduced. Prior to the execution of the secondary drive control means for driving the variable pump with a predetermined capacity as a reference pressure, the primary drive control means is executed, and the variable pump is driven with a higher capacity than that in the secondary drive control means. Therefore, the inside of the purge device is transformed in a shorter time than before. Therefore, the presence or absence of a leak hole in the purge apparatus can be diagnosed in a shorter time than in the past.

  The switching from the primary drive control means to the secondary drive control means can be performed based on the pressure in the purge device, for example, as described in claim 2. That is, according to a second aspect of the present invention, in the leak diagnostic apparatus according to the first aspect, the primary drive control is based on the fact that the internal pressure of the purge device becomes a predetermined switching pressure on the atmospheric pressure side with respect to the reference pressure. The means is terminated and the secondary drive control means is executed.

  According to the second aspect of the invention, since the primary drive control means is switched to the secondary drive control means when the purge device internal pressure reaches the predetermined switching pressure, the fuel remaining in the fuel tank can be changed. Therefore, the diagnosis time can be shortened as much as possible.

  The second aspect of the invention is an invention for switching from the primary drive control means to the secondary drive control means based on the pressure. If the remaining amount of fuel in the fuel tank is known, the gas in the closed system including the purge device is provided. The volume of the portion can be obtained, and the time until the pressure in the closed system becomes the switching pressure can be estimated from the volume of the gas portion in the closed system and the capacity of the variable pump device. Therefore, the execution time of the primary drive control means can be determined as in claim 3. That is, the invention according to claim 3 is the leakage diagnosis apparatus according to claim 1, further comprising a fuel level sensor for detecting a remaining amount of fuel in the fuel tank, wherein the primary drive control means is a fuel remaining amount in the fuel tank. The execution time is determined from the remaining fuel amount actually detected by the fuel level sensor using a pre-stored relationship between the amount and the execution time of the primary drive control means. And

  According to a fourth aspect of the present invention, in the leakage diagnosis apparatus according to any one of the first to third aspects, the voltage of the battery that supplies power to the variable pump device is lower than a predetermined primary controllable value. When the value is equal to or greater than a predetermined secondary controllable value, the secondary drive control means is directly executed without executing the primary drive control means.

  In this way, when the capacity of the battery is reduced, the primary drive control means having a large load on the battery is not executed, but the pressure in the purge device is transformed only by the secondary drive control means, and the battery Leakage diagnosis can be performed without causing a rise.

  According to a fifth aspect of the present invention, in the leakage diagnosis apparatus according to the first to fourth aspects, the variable pump device includes a variable pump having a variable capacity. In this way, the leak diagnosis apparatus becomes more compact than a plurality of pumps.

  Hereinafter, embodiments of a leakage diagnosis apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a purge apparatus 10 and a leak diagnosis apparatus 100 to which the present invention is applied. The purge device 10 includes a canister 30, a connection pipe 32, a valve pipe 33, and a purge valve 34. The connection pipe 32 connects the canister 30 and the fuel tank 20. The canister 30 is filled with an adsorbent 31 such as activated carbon, and when the fuel gas generated in the fuel tank 20 is introduced into the canister 30 via the connection pipe 32, it is adsorbed by the adsorbent 31. .

  The valve pipe 33 connects the canister 30 and an intake pipe 41 that supplies air to an engine (not shown), and the purge valve 34 is provided in the valve pipe 33. The purge valve 34 is an electromagnetic valve whose opening degree can be adjusted. When the purge valve 34 is opened, the canister 30 and the intake pipe 41 communicate with each other. Purge (release) into the intake pipe 41 by the negative pressure.

  The leak diagnosis apparatus 100 for diagnosing the presence or absence of a leak hole in the purge apparatus 10 configured as described above includes a leak check module 110, an electronic control unit (hereinafter referred to as ECU) 200, a battery 210, and a fuel level sensor 220. And.

  The leak check module 110 includes a switching valve 120, an electric negative pressure pump 130, a pressure sensor 140, and a reference orifice 150. The switching valve 120 is connected to the canister 30 via the connection pipe 35 and the canister communication path 122. Further, the switching valve 120 is connected to the negative pressure pump 130 by the negative pressure introduction path 124, and the atmospheric communication passage 126 is also connected to the switching valve 120. The atmosphere communication path 126 is connected to a connection pipe 128, and the other end of the connection pipe 128 communicates with the atmosphere via an air filter 160.

  The switching valve 120 has a state (atmospheric communication state) shown in FIG. 1 in which the canister communication path 122 and the atmospheric communication path 126 communicate with each other when the coil 121 provided in the switching valve 120 is controlled by the ECU 200. This is an electromagnetic valve that switches between a state where the canister communication path 122 and the negative pressure introduction path 124 communicate with each other (negative pressure introduction state). Note that the negative pressure introduction path 124 is provided with a check valve 170 that is closed while the negative pressure pump 130 is stopped to prevent the backflow of the atmosphere.

  The reference orifice 150 is provided in the middle of a bypass passage 172 that bypasses the switching valve 120 and connects the canister communication passage 122 and the negative pressure introduction passage 124. The hole diameter of the reference orifice 150 is determined based on the diameter of the leak hole that needs to be detected by the purge device 10, and is, for example, 0.5 mm or 0.45 mm in diameter. Note that the diameters of the bypass passage 172, the canister communication passage 122, the negative pressure introduction passage 124, and the atmosphere communication passage 126 are sufficiently larger than the hole diameter of the reference orifice 150.

  Further, the pressure sensor 140 is connected to the negative pressure introduction path 124 on the side of the negative pressure pump 130 from the portion where the bypass passage 172 is connected to the negative pressure introduction path 124.

  The negative pressure pump 130 has a known positive displacement pump structure and includes an electric motor 132, and the electric motor 132 is controlled by a drive control circuit 134. The drive control circuit 134 controls the rotation speed of the electric motor 132 by controlling the electric power supplied from the battery 210 according to the drive signal from the ECU 200 and supplying the electric power to the electric motor 132. In the present embodiment, the rotation speed of the electric motor 132 is controlled by changing the width of the pulse signal as a drive signal from the ECU 200, that is, by pulse width modulation, and the suction of the negative pressure pump 130 is thereby controlled. The amount can be controlled. Therefore, the negative pressure pump 130 is a variable pump device with variable suction amount, that is, capacity.

  When the purge valve 34 is closed and the switching valve 120 is in a negative pressure introduction state, the purge device 10 and the leak check module 110 are in a sealed state. When the negative pressure pump 130 is driven in this state, the sealing is performed. A negative pressure is generated in the system, and the negative pressure, that is, the pressure p in the purge device 10 is detected by the pressure sensor 140.

  On the other hand, when the purge valve 34 is closed and the switching valve 120 is in the atmosphere communication state and the negative pressure pump 130 is stopped, the inside of the purge device 10 and the leak check module 110 is large. The atmospheric pressure is detected by the pressure sensor 140. Further, when the purge valve 34 and the switching valve 120 are left as they are and the negative pressure pump 130 is driven, the canister communication path 122 is more than the reference orifice 150 among the atmosphere communication path 126, the canister communication path 122, and the bypass path 172. While the portion on the side becomes atmospheric pressure, the portion closer to the negative pressure introduction passage 124 than the negative pressure introduction passage 124 and the reference orifice 150 becomes negative pressure, and the negative pressure is detected by the pressure sensor 140.

  The conventional leak diagnosis apparatus has a suction capability of a negative pressure pump that allows the pressure detected by the pressure sensor 140 to converge to a certain value when the negative pressure pump is driven with the switching valve 120 in an atmospheric communication state (hereinafter, This suction ability is set to the reference suction ability b). On the other hand, the negative pressure pump 130 of the present embodiment is also used with the reference suction capability b, but also with a higher suction capability a.

  If the suction capacity of the negative pressure pump 130 is the reference suction capacity b, when the negative pressure pump 130 is driven in a state where the purge apparatus 10 is in a sealed system, the purge apparatus 10 has a leak of the same diameter as the reference orifice 150. If there is a hole, the value detected by the pressure sensor 140 converges to a constant value (hereinafter, this value is referred to as a judgment reference pressure β) after a predetermined time, and the purge device 10 leaks larger than the reference orifice 150. If there is a hole, the value detected by the pressure sensor 140 after a predetermined time becomes a value larger than the judgment reference pressure β, and there is no leak hole in the purge device 10 or it exists. However, if the leak hole is sufficiently smaller than the diameter of the reference orifice 150, the pressure p detected by the pressure sensor 140 is determined based on the judgment criterion before the predetermined time elapses. Pressure β or less. Therefore, the presence of a leak hole can be diagnosed.

  A signal indicating the voltage of the battery 210 is supplied to the ECU 200. Further, the fuel level sensor 220 is provided in the fuel tank 20, detects the remaining amount of gasoline as fuel, and supplies a signal representing the remaining amount of gasoline to the ECU 200.

  The ECU 200 is a so-called computer having a CPU, a ROM, a RAM, and the like (not shown), and a soak timer 230 is built in the ECU 200. The soak timer 230 starts a time measuring operation after an ignition switch (not shown) is turned off, that is, after the engine is stopped, and measures an elapsed time after the engine is stopped. The ECU 200 controls the negative pressure pump 130 and the switching valve 120 based on the signal supplied from the battery 210, the signal supplied from the fuel level sensor 220, and the like when diagnosing leakage in the purge apparatus 10.

  Next, the leak diagnosis control executed in the ECU 200 will be described. FIG. 2 is a main routine of the leakage diagnosis control of the ECU 200. This main routine is executed every short predetermined time.

  In FIG. 2, first, in step S300, it is determined whether or not the ignition switch (IG switch) is off, that is, whether or not the engine is stopped. If this determination is negative, this routine is temporarily terminated. On the other hand, when it is determined that the IG switch is off, in the subsequent step S310, the measurement time of the soak timer 230, that is, the elapsed time since it was determined that the IG switch was turned off in step S300 is set in advance. It is determined whether the set stabilization time has elapsed. This stabilization time is determined based on experiments as a time required for the internal pressure of the fuel tank 20 to stabilize, and is, for example, 3 to 5 hours.

  If the determination in step S310 is negative, the routine is temporarily terminated. If the determination is affirmative, a leakage diagnosis routine shown in detail in FIG. 3 is executed in subsequent step S320.

  In the leakage diagnosis routine of FIG. 3, first, in step S350, the reference pressure β (and switching pressure α) is determined. This step S350 executes steps S360 to 390 shown in FIG. In FIG. 4, the switching valve 120 is maintained in the atmospheric communication state in step S360, and the process proceeds to the next step S370. In step S370, by outputting a predetermined pulse signal to the drive control circuit 134, the negative pressure pump 130 is driven with a preset reference suction capability b. In subsequent step S375, the pressure p is measured. That is, in step S375, a signal from the pressure sensor 140 is read.

  In the subsequent step S380, in order to determine whether or not the pressure p has converged to a certain value, it is determined whether or not the rate of change of the pressure p that is sequentially measured in the step S375 has become slower than a predetermined speed. . If the determination in step S380 is negative, suction at the reference suction capability b is continued by repeatedly executing step S370 and subsequent steps.

  On the other hand, if the determination in step S380 is affirmed, the process proceeds to step S390, where the pressure p detected by the pressure sensor 140 is determined as the reference pressure β, and a value obtained by adding a predetermined value to the reference pressure β is determined. The switching pressure α is determined. The switching pressure α may be a value closer to the atmospheric pressure than the determination reference pressure β, but is preferably set to a value close to the reference pressure β between the reference pressure β and the atmospheric pressure.

  When step S390 is executed, step S400 and subsequent steps in FIG. 3 are executed. In step S400, the switching valve 120 is switched to the negative pressure introduction state. Since the purge valve 34 is fully closed when the IG switch is off, the purge device 10 and the leak check module 110 become a closed system by executing step S400.

  Subsequently, steps S410 to S450 corresponding to the primary drive control means are executed. First, in step S410, it is determined whether or not the number of pressure determinations in step S450 described later is equal to or greater than a preset reference number. This step S410 is provided in consideration of the case where the pressure p in the purge apparatus 10 does not decrease to the switching pressure α even if the suction with the high suction capability a by the negative pressure pump 130 is continued for a predetermined time. If the determination in S410 is affirmative, it is expected that a large leak hole has occurred in the purge device 10. If the determination in step S410 is affirmed, step S480 described later is directly executed.

  On the other hand, if the determination in step S410 is negative, the negative pressure pump 130 is driven with a predetermined high suction capability a by outputting a predetermined pulse signal to the drive control circuit 134 in the subsequent step S420. In addition, when execution of step S420 is the second time or later, since the negative pressure pump 130 is already driven, the state is maintained.

  In the subsequent step S430, whether or not the elapsed time since the negative pressure pump 130 was driven with the suction capability a or the elapsed time since the execution of the next step S440 last time has passed a predetermined pressure measurement cycle. Judging. In this pressure measurement cycle, when the inside of the purge device 10 is sucked with the suction capability a, the next step S440 is executed a plurality of times while the pressure p in the purge device 10 decreases from the atmospheric pressure to the switching pressure α. The period is set. Therefore, the next step S450 is executed only when the pressure p in the purge apparatus 10 is significantly lower than the switching pressure α, and the switching to the reference suction capacity b is not delayed.

  If the determination in step S430 is negative, the determination in step S430 is repeatedly executed until the pressure measurement cycle elapses. If step S430 is affirmed, the pressure p in the purge apparatus 10 is measured in the subsequent step S440. That is, in step S440, a signal from the pressure sensor 140 is read.

  In subsequent step S450, it is determined whether or not the pressure p measured in step S440 is equal to or lower than the switching pressure α determined in step S350. If the determination in step S450 is negative, the suction with the suction capability a is continued by repeatedly executing the above-described step S410 and subsequent steps. On the other hand, when the pressure p in the purge device 10 is equal to or lower than the switching pressure α and the determination in step S450 is affirmative, in the subsequent step S460, the rotation speed of the electric motor 132 is made slower than before and the negative pressure is set. A pulse signal for setting the suction capability of the pump 130 to the reference suction capability b is output to the drive control circuit 134.

  In the subsequent step S470, it is determined whether or not the elapsed time from the first execution of step S460 has passed the leak determination time T1 set in advance by experiment. Since the purge device 10 and the leak check module 110 are in a closed system, the gas volume in the closed system can be calculated in advance if the remaining amount of fuel in the fuel tank 20 is zero. When step S460 is first executed, the pressure in the purge device 10 is substantially the switching pressure α. Therefore, assuming that there is no leak hole in the purge device 10, suction is performed with the suction capability b. In this case, the time required for the internal pressure of the purge device 10 to decrease from the switching pressure α to the reference pressure β can be calculated in advance. A time obtained by adding a predetermined margin time to this time is preset as the leakage determination time T1.

  When the determination in step S470 is negative, by repeatedly executing step S460 and subsequent steps, the suction with the reference suction capability b is continued until the leakage determination time T1 elapses. In FIG. 3, steps S460 and 470 correspond to secondary drive control means.

  On the other hand, if the determination in step S470 is affirmative, leakage determination is executed in the subsequent step S480. That is, in step S480, a signal is read from the pressure sensor 140 to detect the pressure p in the purge apparatus 10, and if the detected pressure p is lower than the reference pressure β determined in step S350, a leak hole exists. If the detected pressure p is substantially equal to the reference pressure β, it is determined that a leak hole equivalent to the diameter of the reference orifice 150 has occurred, and the detected pressure p is higher than the reference pressure β. If it is higher, it is determined that a leak hole having a larger diameter than that of the reference orifice 150 has occurred.

  When the leak determination in step S480 is completed, the negative pressure pump 130 is stopped in the subsequent step S490. Then, in the following step S500, the switching valve 120 is brought into the atmosphere communication state, and this routine is finished.

  FIG. 5 is a time chart showing an example of a change with time of the pressure p when the leakage diagnosis routine of FIG. 3 is executed. Note that L1 has no leak hole, L2 has a leak hole corresponding to the hole diameter of the reference orifice 150, and L3 has an example of a leak hole larger than the hole diameter of the reference orifice 150. Show.

  When the suction at the reference suction capability b is started in step S370 in FIG. 3, the pressure p starts to decrease as shown at the time t1 in FIG. 5, and the time p2 at which the pressure p is stabilized at a constant value is step S380. Is determined to be the reference pressure β, and the switching pressure α is also determined based on the reference pressure β. When the switching valve 120 is brought into the negative pressure introduction state in step S400, the pressure sensor 140 communicates with the inside of the purge device 10 that was at atmospheric pressure without passing through the reference orifice 150, so that the pressure p is once near atmospheric pressure. However, since the suction with the suction capability a is started immediately, the pressure p starts decreasing again. In the case of L1, the determination in step S450 is affirmed at time t3 in the case of L2, and in time t4 in case of L2, and the suction is switched to the reference suction capacity b similar to the conventional case. In the case of L1, leakage is determined at time t5 when the leakage determination time T1 has elapsed from time t3. Since the pressure p at time t5 is lower than the reference pressure β, it is determined that no leak hole has occurred. . In the case of L2, the leak is determined at the time t6 when the leak determination time T1 has elapsed from the time t4, and the pressure p at the time t6 is substantially the reference pressure β. It is determined that it has occurred. In the case of L3, since the pressure p in the purge device 10 does not decrease to the switching pressure α, for example, the determination in step S410 is affirmed at time t6, and the leakage determination is performed.

  As described above, according to the present embodiment, the negative pressure pump 130 having a variable suction amount is provided as a pump, and when a leak hole having a predetermined diameter is generated in the purge device 10 as in the prior art, the purge is performed. Prior to the execution of steps S460 and 470 (secondary drive control means) for driving the negative pressure pump 130 with the reference suction capability b at which the pressure p in the apparatus 10 is constant, steps S410 to 450 (primary drive control means). Is executed, and the negative pressure pump 130 is driven with a suction capability a higher than the capability in steps S460 and 470 (secondary drive control means), so the pressure in the purge apparatus 10 is reduced in a shorter time than before. Therefore, the presence / absence of a leak hole in the purge apparatus 10 can be diagnosed in a shorter time than before. In addition, since the diagnosis can be performed in a short time, the risk that the diagnosis is interrupted due to the engine being restarted during the diagnosis is reduced, so that the number of diagnosis can be ensured.

  In addition, according to the present embodiment, the switching from the suction capability a to the reference suction capability b is performed based on the pressure p in the purge apparatus 10, so whether or not this predetermined switching has elapsed for a predetermined time. Compared with the case where it carries out based on this, the diagnosis time can be shortened as much as possible regardless of the fluctuation of the remaining amount of fuel in the fuel tank 20.

  Next, a second embodiment of the present invention will be described. In the following description, parts common to the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  The second embodiment is different from the first embodiment described above only in the control function of the ECU 200. More specifically, the second embodiment differs from the first embodiment in that a leak diagnosis routine shown in FIG. 6 is executed instead of the leak diagnosis routine of FIG. 3 described above.

  In FIG. 6, first, in step S600, it is determined whether or not the voltage V of the battery 210 is equal to or higher than the secondary controllable value V2. The secondary controllable value V2 is the minimum voltage at which the above-described secondary drive control, that is, the one-step pump control based only on the reference suction capability b as in the prior art, can be executed. Is set. If the determination in step S600 is negative, the leakage diagnosis cannot be performed, and thus this routine ends.

  On the other hand, if the determination in step S600 is affirmative, in subsequent step S610, it is further determined whether or not voltage V of battery 210 is equal to or higher than primary controllable value V1. The primary controllable value V1 is the minimum voltage that can execute the above-described secondary drive control and the primary drive control preceding that, that is, the above-described leakage diagnosis routine of FIG. 3, and is set based on experiments or the like in advance. ing. If the determination in step S610 is affirmative, that is, if there is sufficient battery capacity, step S350 and subsequent steps shown in FIG. 3 are executed.

  On the other hand, if the determination in step S610 is negative, leakage diagnosis is performed by executing step S620 and the subsequent steps. First, in step S620, the reference pressure β is determined. Step S620 is substantially the same as Steps S360 to S390 shown in FIG. 4, and the switching pressure α is determined in addition to the reference pressure β in Step S390, but it differs only in that the switching pressure α is not determined. .

  In subsequent step S630, the switching valve 120 is switched to the negative pressure introduction state in the same manner as in step S400. In the subsequent step S640, a predetermined pulse signal is output to the drive control circuit 134, and the negative pressure pump 130 is driven with the aforementioned reference suction capability b. In addition, when execution of step S640 is the second time or later, since the negative pressure pump 130 has already been driven, the state is maintained.

  In subsequent step S650, it is determined whether or not the pressure p detected by the pressure sensor 140 has become lower than the reference pressure β described above. If the determination in step S650 is negative, the determination in step S660 is further executed. In step S660, it is determined whether or not the elapsed time since the negative pressure pump 130 is driven with the reference suction capacity b, that is, the elapsed time after the first execution of step S640 has exceeded a predetermined leakage determination time T2. to decide. This leak determination time T2 is necessary for the inside of the closed system including the purge device 10 to be reduced from the atmospheric pressure to the reference pressure β by suction with the reference suction capability b when no leak hole is generated in the purge device 10. This is a time obtained by adding a predetermined margin time to the time, and is longer than the above-described leakage determination time T1. When this determination is also denied, the above-described step S640 and subsequent steps are repeatedly executed. Steps S640 to S660 correspond to secondary drive control means.

  Steps S640 to S660 are repeated, and if the pressure p detected by the pressure sensor 140 becomes lower than the reference pressure β before the leakage determination time T2 elapses, step S650 is affirmed and the above-described step S480 and subsequent steps are executed. Even when the leakage determination time T2 has elapsed, the pressure p does not decrease to the reference pressure β, and the processing in step S480 and subsequent steps is also executed when the determination in step S650 is affirmed. In this case, in step S480, it is determined that a leak hole having a hole diameter equal to or larger than the hole diameter of the reference orifice 150 is generated.

  As described above, according to the second embodiment described above, since the battery capacity is low, when the primary drive control means having a large load on the battery due to the high suction capacity is executed, the secondary drive is performed even when there is a concern about the battery running out. Since the pressure in the purge apparatus 10 is reduced only by the control means (steps S640 to S660), the leakage diagnosis can be performed without causing the battery to run out.

  Next, a third embodiment of the present invention will be described. Also in the third embodiment, only the control function of the ECU 200 is different from the above-described first embodiment. More specifically, the third embodiment differs from the first embodiment in that a leak diagnosis routine shown in FIG. 7 is executed instead of the leak diagnosis routine of FIG. 3 described above.

  In FIG. 7, first, the reference pressure β is determined by executing the same step S620 as in FIG. Subsequently, in step S700, the switching valve 120 is switched to the negative pressure introduction state. In the subsequent step S710, the remaining amount of gasoline in the fuel tank 20 is detected by reading a signal from the fuel level sensor 220.

  In subsequent step S720, it is determined whether or not the remaining amount of gasoline detected in step S710 is equal to or greater than a predetermined determination reference remaining amount R. The determination reference remaining amount R is set to a relatively large value (a value close to the internal volume of the fuel tank 20) such as 90% of the internal volume of the fuel tank 20, for example. If the determination in step S720 is affirmative, since the gas volume in the closed system including the purge device 10 is small because the gasoline remaining in the fuel tank 20 is large, the negative pressure pump 130 is connected to the suction capacity a described above. Even if it is driven by, it can not be expected to shorten the diagnosis time so much. Therefore, one-stage pump control based on only the reference suction capability b as in the prior art, that is, steps S630 to S660 shown in FIG. 6 are executed.

  On the other hand, if the determination in step S720 is negative, in step S730, the remaining amount of gasoline and the primary suction time T3 (corresponding to the execution time of the primary drive control means) stored in advance in a storage device (not shown). Using the relationship, the primary suction time T3 is determined from the gasoline remaining amount actually detected in step S710. The primary suction time T3 is a time required to reduce the inside of the closed system including the purge device 10 from the atmospheric pressure to the switching pressure α when the suction is performed with the above-described suction capability a. That is, in the first embodiment described above, it is determined whether or not the pressure p has been actually decreased by detecting the pressure p by the pressure sensor 140, but in this third embodiment, the gasoline remaining amount is determined. By determining whether or not the primary suction time T3 determined based on the amount has elapsed, it is determined whether or not the pressure has decreased to the switching pressure α. In this way, it is possible to determine whether or not the pressure has decreased to the switching pressure α based on the passage of time. If the remaining amount of gasoline is known, the gas volume in the closed system including the purge device 10 can be calculated. This is because the pressure at the start of suction, that is, the atmospheric pressure has a relatively narrow fluctuation range, and the pressure range to be reduced can be determined with relatively high accuracy. In the relation stored in advance, the primary suction time T3 is shortened as the remaining amount of gasoline increases.

  When step S730 is executed, in the subsequent step S740, a predetermined pulse signal is output to the drive control circuit 134 to drive the negative pressure pump 130 with a predetermined high suction capability a. In addition, when execution of step S740 is the second time or later, since the negative pressure pump 130 has already been driven, the state is maintained.

  In the subsequent step S750, it is determined whether or not the elapsed time after the negative pressure pump 130 is driven with the suction capability a has exceeded the primary suction time T3 determined in step S730. When this judgment is denied, the suction with the suction capability a is continued by executing step S740 and subsequent steps. On the other hand, if the result is affirmative, the same step S460 and subsequent steps as in FIG.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following embodiment is also contained in the technical scope of this invention, and also the summary other than the following is also included. Various modifications can be made without departing from the scope.

  For example, each of the above-described embodiments includes the negative pressure pump 130, and the inside of the purge device 10 is depressurized by the negative pressure pump 130, but instead of the negative pressure pump 130, the inside of the purge device 10 is added. A positive pressure pump that pressurizes may be used.

  In addition, the negative pressure pump 130 of the above-described embodiment is a positive displacement pump, and its capability is changed by changing the rotation speed of the electric motor 132 by pulse width modulation. Other known modulation methods such as frequency modulation may be used, and a centrifugal pump or the like may be used instead of the positive displacement type. Further, a variable pump device comprising a plurality of pumps may be provided, and the primary drive control means may use a larger number of pumps than the secondary drive control means.

  In the above-described embodiment, the execution condition of the leakage diagnosis (FIGS. 3, 6, and 7) is that the IG switch is turned off (step S300) and a predetermined stabilization time has elapsed (step S310). However, in addition to these conditions, other conditions such as the vehicle operation time continuing for a certain period of time or the outside air temperature being a predetermined temperature or higher may be added to the leakage diagnosis execution condition.

  In addition, the leak determination time T1 in the above-described step S470 is a predetermined constant time. However, the leak determination time T1 is shortened as the remaining amount of gasoline increases. The leakage determination time T1 may be determined from the gasoline remaining amount.

  In the above-described embodiment, the leak diagnosis is performed when the engine is stopped when the IG switch is turned off. However, the leak diagnosis may be performed during idling.

  Further, in the above-described leakage diagnosis apparatus 100, for example, a bypass passage on the canister 30 side with respect to the reference orifice 150, a negative pressure introduction path on the switching valve 120 side with respect to a portion to which the pressure sensor 140 is connected, or a negative pressure pump A mesh filter may be provided as appropriate in the atmosphere communication passage 126 near 130.

It is a schematic diagram which shows the structure of a purge apparatus and the leak diagnostic apparatus to which this invention was applied. FIG. 3 is a main routine for ECU leakage diagnosis control in FIG. 1; FIG. 3 is a leakage diagnosis routine showing details of control in step S320 of FIG. It is a flowchart which shows the control content of step S350 of FIG. 3 in detail. It is a time chart which shows an example of the time-dependent change of the pressure p at the time of performing the leak diagnosis routine of FIG. It is a leak diagnosis routine executed in the second embodiment of the present invention. It is a leak diagnosis routine executed in the third embodiment of the present invention.

Explanation of symbols

10: Purge device, 20: Fuel tank, 100: Leak diagnostic device, 110: Leak check module, 130: Negative pressure pump (variable pump device), 200: Electronic control unit (ECU), 210: Battery, 220: Fuel level Sensor

Claims (5)

In order to diagnose whether or not a leak hole of a predetermined diameter or more has occurred in the purge device that purges the fuel gas generated by evaporation of the fuel in the fuel tank into the intake path of the internal combustion engine,
A leakage diagnostic device that transforms the pressure in the purge device by a pump and diagnoses the presence or absence of a leak hole in the purge device based on the pressure in the purge device after the transformation,
As the pump, provided with a variable pump device configured to be variable in capacity,
A secondary drive control means for driving the variable pump device with a predetermined ability in which the pressure in the purge device becomes a reference pressure when a leak hole of the predetermined diameter is generated in the purge device;
Prior to the secondary drive control means, the leakage diagnosis apparatus comprises: primary drive control means for driving the variable pump with a higher capacity than that in the secondary drive control means.   The primary drive control means is terminated and the secondary drive control means is executed based on the fact that the internal pressure of the purge apparatus has become a predetermined switching pressure on the atmospheric pressure side with respect to the reference pressure. The leak diagnosis apparatus according to claim 1. A fuel level sensor for detecting the remaining amount of fuel in the fuel tank;
The primary drive control means uses a pre-stored relationship between the fuel remaining amount in the fuel tank and the execution time of the primary drive control means to determine from the fuel remaining amount actually detected by the fuel level sensor. The leak diagnosis apparatus according to claim 1, wherein an execution time is determined. When the voltage of the battery that supplies power to the variable pump device is lower than a predetermined primary controllable value, but not less than a predetermined secondary controllable value, without executing the primary drive control means, The leakage diagnosis apparatus according to any one of claims 1 to 3, wherein the secondary drive control means is directly executed.   The leak diagnosis apparatus according to claim 1, wherein the variable pump apparatus includes a variable pump having a variable capacity.

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