JP2016217359A - Abnormality detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly execute abnormality detection of an evaporated fuel processing system.SOLUTION: An ECU 40 is applied to an evaporated fuel processing system for allowing an evaporated fuel generating in a fuel tank 15 to be adsorbed by a canister 21, and for purging the adsorbed evaporated fuel to an intake passage 12 of an engine 11. The system includes: an atmosphere pipe 28 in which a pump 31 is provided; and a pressure sensor 33 provided further on the canister 21 side than the pump 31 in the atmosphere pipe 28. The ECU 40 includes: a control part for, in a state where a purge control valve 27 is closed, bringing an object space including the canister 21 and the fuel tank 15 into a negative pressure state, on the opposite side to an atmosphere opening port of the atmosphere pipe 28 by operating the pump 31; and an abnormality detection part for, after the operation start of the pump 31 by the control part, detecting that clogging abnormality is occurring in the evaporated fuel processing system, in the case where a descent rate of a pressure detection value of the pressure sensor 33 is larger than a clogging determination value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abnormality detection device applied to an evaporative fuel processing system that discharges evaporative fuel adsorbed by a canister to an intake passage of an internal combustion engine.

  2. Description of the Related Art Conventionally, there has been known an apparatus in which evaporated fuel generated in a fuel tank is adsorbed by a canister, and the evaporated fuel is discharged into an intake passage during operation of the engine and burned in the engine. According to such a technique, the evaporated fuel generated in the fuel tank is adsorbed by the canister and burned by the engine, so that release to the atmosphere is suppressed.

  Moreover, the technique described in patent document 1 is known as a technique regarding abnormality detection of an evaporative fuel processing system. In such a technique, a clogging abnormality in a path through which evaporated fuel passes is detected by using intake negative pressure. Specifically, during engine operation, the inside of the evaporation system including the fuel tank and the evaporated fuel path is made into a negative pressure state, and the clogging abnormality is detected based on the pressure behavior in the evaporation system under the negative pressure state. It is.

JP 2009-264207 A

  By the way, in the above technique, the inside of the evaporation system is made into a negative pressure state by using the intake negative pressure generated during engine operation. Therefore, the clogging abnormality is detected based on the pressure behavior in the evaporation system during engine operation. On the other hand, during engine operation, the fuel temperature varies depending on the operating conditions, and this variation in fuel temperature is considered to affect the generation of evaporated fuel in the fuel tank, and hence the pressure in the evaporation system. Therefore, in the above technique, there is a concern that the detection accuracy of the clogging abnormality is lowered depending on the operating conditions. In addition, in order to solve this problem, it is necessary to construct a complicated logic such as setting various conditions and giving conformity.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide an abnormality detection device capable of appropriately performing abnormality detection of the evaporated fuel processing system.

  In the present invention, evaporated fuel generated in the fuel tank (15) is adsorbed to the canister (21), and the adsorbed evaporated fuel is sucked into the intake passage of the internal combustion engine (11) by opening the purge control valve (27). (12) An abnormality detection device (40) applied to an evaporative fuel processing system of an internal combustion engine to be purged, wherein the evaporative fuel processing system has one end connected to the canister and the other end opened to the atmosphere, And an atmospheric pipe (28) provided with a pump (31), and a pressure sensor (33) provided on the canister side with respect to the pump in the atmospheric pipe, and closing the purge control valve In this state, by operating the pump, the target space including the canister and the fuel tank is placed in a negative pressure state on the side opposite to the atmosphere opening port of the atmosphere pipe. When the rate of decrease in the pressure detection value of the pressure sensor is greater than a predetermined clogging determination value after the start of the pump operation by the control unit, a clogging abnormality occurs in the evaporated fuel processing system. And an abnormality detection unit that detects that the image is detected.

  In the evaporative fuel processing system, the evaporative fuel path through which the evaporative fuel passes may be clogged with foreign matter or the like. In such a case, there is a possibility that trouble may occur in purging the evaporative fuel into the intake passage.

  In this regard, in the above configuration, an atmospheric pipe having one end connected to the canister and the other end opened to the atmosphere and provided with a pump, and a pressure sensor provided on the canister side of the pump in the atmospheric pipe, In the evaporative fuel processing system provided, the target space including the canister and the fuel tank is brought into a negative pressure state on the side opposite to the atmosphere opening port of the atmosphere piping by operating the pump with the purge control valve closed. Then, after the start of the pump operation, when the rate of decrease in the pressure detection value of the pressure sensor is greater than a predetermined clogging determination value, it is detected that a clogging abnormality has occurred in the evaporated fuel processing system.

  In this case, by operating the pump with the purge control valve closed, the pressure in the target space decreases. However, when a clogging abnormality occurs in the evaporated fuel processing system, the space that is actually depressurized by the pump. The volume of is smaller than that at normal time. Therefore, when the clogging is abnormal, it is considered that the descending speed of the detected pressure value is larger than that in the normal state because the volume of the space to be decompressed is smaller. In consideration of such circumstances, when the rate of decrease in the pressure detection value of the pressure sensor is greater than a predetermined clogging determination value, it is possible to detect clogging abnormality appropriately by determining clogging abnormality. In addition, since the target space is brought into a negative pressure state using a pump provided in the evaporated fuel processing system, the target space can be brought into a negative pressure state regardless of the operating state of the internal combustion engine. Thereby, for example, a clogging abnormality can be detected in a state where the operation of the internal combustion engine is stopped. In such a case, since it is not influenced by the pressure change of the target space depending on the operating condition of the internal combustion engine, the abnormality detection of the evaporated fuel processing system can be properly performed.

The block diagram of an evaporative fuel processing system. The flowchart which shows the process sequence of abnormality detection in an evaporative fuel processing system. The time chart explaining an abnormality detection process more concretely. (A) The figure for demonstrating the 2nd state of the switching valve 34, (b) The figure for demonstrating the 1st state of the switching valve 34. FIG.

  Hereinafter, embodiments will be described with reference to the drawings. This embodiment is embodied as an evaporative fuel processing system for an in-vehicle engine.

  As shown in FIG. 1, an intake passage 12 is connected to the engine 11, and a throttle valve 13 for adjusting the intake air amount is provided in the intake passage 12. A fuel injection valve 14 is provided at the intake port of the engine 11. Fuel is supplied to the fuel injection valve 14 from a fuel tank 15 via a fuel pipe (not shown), and fuel injection is performed when the fuel injection valve 14 is opened. In the engine 11, the air sucked from the intake passage 12 and the fuel injected from the fuel injection valve 14 are mixed, and the mixture is burned by ignition. The fuel tank 15 is provided with a fuel gauge 16 for measuring the remaining amount of fuel.

  In the evaporated fuel processing system, the evaporated fuel generated in the fuel tank 15 is discharged to the intake passage 12 of the engine 11. Specifically, the evaporative fuel treatment system includes a canister 21 filled with an adsorbent such as activated carbon, and the evaporative fuel adsorbed by the canister 21 is released to the intake passage 12.

  The canister 21 is provided with a fuel port 22, a purge port 23 and an atmospheric port 24. The fuel port 22 is connected to the fuel tank 15 via a fuel pipe 25. The purge port 23 is connected to the intake passage 12 via a purge pipe 26. The purge pipe 26 is provided with a purge control valve 27. The opening degree of the purge control valve 27 is adjusted according to the energization duty ratio.

  Although not shown, the fuel pipe 25 may be provided with a check valve that allows a gas flow from the fuel tank 15 to the canister 21 and blocks a gas flow from the canister 21 to the fuel tank 15. . Further, in the purge pipe 26, a check that allows a gas flow from the canister 21 to the intake passage 12 and blocks a gas flow from the intake passage 12 to the canister 21 between the purge control valve 27 and the intake passage 12. A valve may be provided.

  An atmospheric piping 28 communicating with the atmosphere is connected to the atmospheric port 24. An end of the atmospheric pipe 28 opposite to the atmospheric port 24 is an atmospheric opening 29. The air pipe 28 is provided with a pump 31 having an electric motor. By driving the pump 31, the gas in the atmospheric pipe 28 is discharged to the atmosphere opening port 29 side, and accordingly, the inside of the atmospheric pipe 28 is shifted to a negative pressure state.

  Further, in the atmospheric piping 28, the canister 21 side of the pump 31 is divided into two branch piping portions 28a and 28b, and one branch piping portion 28a has an orifice having a predetermined diameter (for example, a diameter of 0.5 mm). 32 and a pressure sensor 33 is provided on the pump 31 side of the orifice 32. The other branch piping portion 28b is provided with an electromagnetically driven switching valve 34.

  The switching valve 34 is a two-position switching valve that switches between a first state in which the branch pipe portion 28b of the two branch pipe portions 28a and 28b in the atmospheric pipe 28 is communicated and a second state in which the communication is blocked. In the present embodiment, when the switching valve 34 is in a non-energized state, the switching valve 34 enters a second state (the state shown in the figure) in which the communication of the branch pipe portion 28b is cut off, and the switching valve 34 is branched when the switching valve 34 is energized. It is assumed that the first state is established in which the pipe portion 28b is communicated.

  Here, in the first state of the switching valve 34, the first position P1 between the canister 21 and the orifice 32 in the atmospheric pipe 28 bypasses the orifice 32 and is connected to the second position P2 between the pump 31 and the orifice 32. Is done. Further, in the second state of the switching valve 34, the first position P1 and the second position P2 are not connected while bypassing the orifice 32. Incidentally, in the present embodiment, a bypass pipe 35 that bypasses the pump 31 is provided at the third position P3 on the atmosphere opening port 29 side of the pump 31 in the atmosphere pipe 28. In the second state of the switching valve 34, The first position P1 and the third position P3 are connected.

  As is well known, the ECU 40 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) composed of a CPU, ROM, RAM, etc., and executes various control programs stored in the ROM, thereby including the evaporated fuel including the engine 11. Implement various controls of the processing system. Specifically, the ECU 40 inputs various detection signals from the various sensors described above, and controls driving of the purge control valve 27, the pump 31, the switching valve 34, and the like based on the input various detection signals.

  Regarding the purge control, the ECU 40 calculates the purge control flow rate based on the engine rotation speed and the engine load (for example, intake negative pressure) under the engine operation state, and commands the purge control valve 27 based on the purge control flow rate. Calculate the opening. Based on the command opening, the opening of the purge control valve 27 is duty-controlled. In this case, the evaporated fuel adsorbed by the canister 21 is discharged into the intake passage 12 by the intake negative pressure of the engine 11.

  Further, the ECU 40 functions as an abnormality detection device that detects whether there is an abnormality in the evaporated fuel processing system. In this embodiment, a clogging abnormality is particularly targeted as an abnormality of the system. The clogging abnormality occurs when the evaporated fuel path (fuel piping 25 and purge piping 26) through which the evaporated fuel passes is clogged with foreign matter or the like, or the piping is crushed. When the clogging abnormality occurs, there is a problem in discharging the evaporated fuel in the fuel tank 15 to the intake passage 12.

  Here, the clogging abnormality process executed by the ECU 40 will be described. In the present embodiment, the clogging abnormality process is executed when a predetermined time has elapsed since the engine stopped. In this case, since the purge control has been completed, this processing is performed with the purge control valve 27 closed. The ECU 40 operates the pump 31 in a state where the switching valve 34 is in the first state (a state where the branch pipe portion 28b is connected). When the pump 31 is operated, the pressure in the inner space between the purge control valve 27 and the pump 31 is reduced, that is, on the opposite side to the atmosphere opening port 29 of the atmosphere pipe 28. As a result, the evaporative fuel path, the space including the canister 21 and the fuel tank 15 are in a negative pressure state. In the present embodiment, when the switching valve 34 is in the first state, the space including the evaporated fuel path, the canister 21, and the fuel tank 15 is a space that is subject to pressure reduction of the pump 31, and this space is the “target space”. It corresponds to.

  Here, for example, when a clogging abnormality occurs in the fuel pipe 25, the space in the fuel tank 15 is not depressurized due to the clogging, so the volume of the depressurized space is reduced. That is, when a clogging abnormality occurs in the evaporated fuel path, the volume of the space to be depressurized becomes smaller than that in the normal state. Therefore, in the present embodiment, after the operation of the pump 31 is started, if the rate of decrease in the pressure detection value of the pressure sensor 33 is greater than a predetermined clogging determination value, a clogging abnormality has occurred in the evaporated fuel processing system. It was made to detect. That is, the ECU 40 detects a clogging abnormality based on the increase in the pressure decrease rate of the space as the volume of the space to be decompressed by the pump 31 decreases. In the present embodiment, the ECU 40 corresponds to a “control unit” and an “abnormality detection unit”.

  The determination of the clogging abnormality will be described in more detail. The ECU 40 determines the clogging abnormality based on the time until the pressure detection value when the target space is decompressed by the pump 31 reaches the determination value PA. When the arrival time at the determination value PA is smaller than the determination value TA, the evaporative fuel processing system assumes that the pressure decrease rate of the target space is large, that is, the rate of decrease in the pressure detection value is larger than the clogging determination value. It is determined that a clogging abnormality has occurred.

  Further, the ECU 40 detects a leakage abnormality in addition to the clogging abnormality as the abnormality of the evaporated fuel processing system. Leakage abnormality occurs when a hole or the like is opened in the evaporated fuel path or the like. If leakage abnormality occurs, evaporated fuel may be released to the atmosphere.

  Hereinafter, the leakage abnormality process executed by the ECU 40 will be described. First, when a predetermined time has elapsed since the engine was stopped, the ECU 40 is in a state in which the purge control valve 27 is closed and the switching valve 34 is in the second state (a state in which the communication of the branch pipe portion 28b is shut off). Below, the pump 31 is operated. When the pump 31 is operated, the atmospheric piping 28 is opposite to the atmospheric opening 29, and in this case, the atmospheric piping 28 between the orifice 32 and the pump 31 is in a negative pressure state. Then, the leakage abnormality process is executed when the vicinity of the reference pressure (reference pressure REF) corresponding to the orifice 32 is stabilized.

  In the leakage abnormality process, the ECU 40 switches the switching valve 34 from the second state to the first state (a state in which the branch pipe portion 28b is communicated) while the pump 31 is operated. Then, a leakage abnormality is detected based on the pressure detection value of the pressure sensor 33 in the first state. Specifically, the ECU 40 detects that a leakage abnormality has occurred in the evaporated fuel processing system when the rate of decrease in the pressure detection value of the pressure sensor 33 is smaller than a predetermined leakage determination value. That is, the ECU 40 detects a leakage abnormality based on the fact that the rate of pressure decrease in the space decreases as air flows into the space to be decompressed.

  As described above, the clogging abnormality and the leakage abnormality are detected based on the decreasing rate of the pressure detection value of the pressure sensor 33 under the same state of the switching valve 34 and the like. Therefore, in this embodiment, the clogging abnormality detection and the leakage abnormality detection are performed at the same timing. That is, based on the pressure detection value in the first state after switching the switching valve 34 from the second state to the first state after the pressure is stabilized at the reference pressure REF under the state where the switching valve 34 is in the second state. Thus, it is configured to detect a clogging abnormality and a leakage abnormality.

  FIG. 2 is a flowchart showing a procedure for detecting an abnormality in the evaporated fuel processing system. This process is performed by the ECU 40 at a predetermined timing while the engine is stopped. For example, the ECU 40 performs this processing when the ignition switch of the vehicle is switched from on to off and a predetermined time (for example, 3 hours) has elapsed since the ignition was turned off.

  Note that when this process is performed, the purge control valve 27 is closed. In addition, at the beginning of this processing, the energization of the switching valve 34 is turned off, and the switching valve 34 is in the second state (the state where communication of the branch pipe portion 28b is blocked).

  In FIG. 2, in step S11, driving of the pump 31 is started. By this pump driving, the gas in the atmospheric piping 28 is discharged from the atmospheric opening 29, and the pressure in the atmospheric piping 28 between the orifice 32 and the pump 31 becomes a negative pressure.

  Thereafter, in step S12, the detection value of the pressure sensor 33 is acquired, and in the subsequent step S13, it is determined whether or not the pressure detection value is stabilized within a predetermined range. Then, the process proceeds to subsequent step S14 on condition that the pressure detection value is stable within a predetermined range. In step S13, the process may proceed to step S14 on the condition that the elapsed time from the start of driving the pump 31 has reached a predetermined time.

  In step S14, path switching by the switching valve 34 is performed. At this time, by starting energization of the switching valve 34, the switching valve 34 is switched from the second state to the first state. Step S14 corresponds to a “switching control unit”. Thereafter, in step S15, the elapsed time from the path switching by the switching valve 34 is measured.

  Thereafter, in step S16, it is determined whether or not the pressure detection value of the pressure sensor 33 has decreased below the determination value PA. The determination value PA is set as a determination value for determining clogging abnormality and leakage abnormality. The determination value PA may be a fixed value set in advance. Further, it may be a relative value based on the reference pressure REF (the detected pressure value that is stable in step S13). In this case, the determination value PA is set to the same value as the reference pressure REF or a value that is 2/3 of the reference pressure REF. . As other than the reference pressure REF, for example, the maximum value (peak value) of the pressure detection value when the switching valve 34 is switched from the second state to the first state may be used.

  And when step S16 is affirmed, it progresses to step S17, and it is determined whether the elapsed time from path switching is below the determination value TA. The determination value TA is set as a determination value for determining that a clogging abnormality has occurred. If the elapsed time is not less than the determination value TA, the process proceeds to step S18 to determine that the system is normal. On the other hand, if the elapsed time is equal to or less than the determination value TA, the process proceeds to step S19 to determine that a clogging abnormality has occurred in the system.

  When step S16 is denied, the process proceeds to step S20, and it is determined whether or not the elapsed time from the path switching is the determination value TB or more. The determination value TB is a determination value for determining that a leakage abnormality has occurred, and is set to a value larger than the determination value TA. If the elapsed time is not equal to or greater than the determination value TB, the process returns to step S15 and the elapsed time is measured again. On the other hand, if the elapsed time is equal to or greater than the determination value TB, the process proceeds to step S21, and it is determined that a leakage abnormality has occurred in the system.

  FIG. 3 is a time chart for explaining the above-described abnormality detection process more specifically. FIG. 3 shows the operation of the abnormality detection process after the ignition switch is turned off.

  In FIG. 3, the drive of the pump 31 is started at a timing t11 when the predetermined execution timing of the abnormality detection process is reached after the engine is stopped. As a result, the pressure in the atmospheric piping 28 decreases, and the pressure detection value of the pressure sensor 33 decreases to the reference pressure REF. At this time, the pump 31 is driven in the state shown in FIG. 4A, and the pressure in the internal space between the pump 31 and the orifice 32 in the atmospheric piping 28 is reduced to the reference pressure REF determined according to the orifice diameter. .

  Then, at the timing t12 when the stability of the pressure detection value is confirmed at the reference pressure REF, the energization of the switching valve 34 is turned on while the pump drive is continued. As a result, the pressure detection value increases from the reference pressure REF. At this time, as shown in FIG. 4B, when the switching valve 34 is switched from the second state to the first state, a space to be decompressed by driving the pump 31 is expanded, and the pressure detection value is increased accordingly. . That is, in the state of FIG. 4B, in addition to the atmospheric pipe 28, the canister 21 and the fuel tank 15 become spaces to be depressurized, and the pressure detection value temporarily increases immediately after the transition from the second state to the first state.

  Thereafter, the pump drive is continued in the first state, so that the pressure detection value decreases again. Here, the behavior of the pressure detection value changes depending on whether there is an abnormality in the evaporated fuel processing system. In FIG. 3, the behavior of the pressure detection value at the normal time is indicated by a solid line, the behavior of the pressure detection value at the time of leakage abnormality is indicated by a broken line, and the behavior of the pressure detection value at the time of clogging abnormality is indicated by a one-dot chain line.

  When a leakage abnormality occurs in this system, a hole or the like communicating with the atmosphere is opened in any of the parts to be decompressed, and the degree of pressure drop is reduced due to air inflow from there. That is, when the leak is abnormal, the rate of decrease in the pressure detection value is smaller than when the leak is normal. In this case, in the leakage abnormality determination in the ECU 40, it is determined that a leakage abnormality has occurred because the pressure detection value passes the determination value TB without reaching the determination value PA.

  In addition, when a clogging abnormality occurs in any of the parts to be decompressed in this system, the volume in the space to be decompressed is reduced, so that the pressure in the space is quickly reduced. In other words, when the clogging is abnormal, the rate of decrease in the pressure detection value is greater than when it is normal. In this case, in the clogging abnormality determination in the ECU 40, the clogging abnormality occurs because the time ΔT from when the switching valve 34 is switched until the pressure detection value reaches the determination value PA is smaller than the determination value TA. It is determined that

  2 and 3, the elapsed time from the path switching by the switching valve 34 is measured (step S15), and the clogging abnormality determination (step S17) and the leakage abnormality determination (step S17) are performed. Although step S20) has been performed, the timing at which the elapsed time starts may be changed. For example, the timing at which the pressure once rises by switching the path of the switching valve 34 and then the pressure starts to decrease (timing t13 in FIG. 3) may be used as the starting point. In this case, the elapsed time from the timing t13 is measured, and the clogging abnormality determination (step S17) and the leakage abnormality determination (step S20) are performed based on the elapsed time. Note that the determination values TA and TB are appropriately changed along with the change of the starting point of the elapsed time.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  In the above configuration, by operating the pump 31 with the purge control valve 27 closed, the target space including the canister 21 and the fuel tank 15 is brought into a negative pressure state on the side opposite to the atmosphere opening port 29 of the atmosphere pipe 28. . Then, after the operation of the pump 31 is started, when the rate of change in decrease in the pressure detection value of the pressure sensor 33 is greater than a predetermined clogging determination value, it is detected that a clogging abnormality has occurred in the evaporated fuel processing system. did. In this case, the pressure in the target space is reduced by operating the pump 31 with the purge control valve 27 closed, but when the clogging abnormality occurs in the evaporated fuel processing system, the pump 31 actually reduces the pressure. The volume of the space to be made is smaller than in normal times. Therefore, when the clogging is abnormal, it is considered that the descending speed of the detected pressure value is larger than that in the normal state because the volume of the space to be decompressed is smaller. In consideration of such circumstances, when the rate of change in the pressure detection value of the pressure sensor 33 is greater than a predetermined clogging determination value, it is possible to properly detect the clogging abnormality by determining that the clogging is abnormal.

  In addition, the clogging abnormality is detected when the operation of the engine 11 is stopped. In this case, when the operation of the engine 11 is stopped, the pump 31 reduces the pressure because the temperature change of the fuel in the fuel tank 15 is more stable than when the engine 11 is operating. It is thought that the pressure change in the space is stable. Therefore, according to the said structure, the pressure change at the time of abnormality can be determined appropriately.

  When the evaporative fuel processing system leaks abnormally, when the target space is brought into a negative pressure state, air flows in through the hole or the like, so that the rate of decrease in the pressure detection value is considered to be smaller than in the normal state. Considering this point, when the rate of decrease in the pressure detection value of the pressure sensor 33 is smaller than a predetermined leak determination value, it is possible to properly detect the leak abnormality by determining that the leak is abnormal.

  Further, the same pressure detection value decreasing rate is used for clogging abnormality detection and leakage abnormality detection, thereby detecting clogging abnormality and leakage abnormality at the same time. Thereby, simplification of the abnormality detection process of an evaporative fuel processing system can be achieved.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In the above embodiment, a preset value is used as the judgment value PA for judging abnormality detection of the evaporated fuel processing system. However, the invention is not limited to this, and the judgment value PA is variably set based on a predetermined condition. It may be a value.

  Here, when the switching valve 34 operates the pump 31 under the first state, the volume of the space that is actually decompressed by the pump 31 varies depending on the remaining amount of fuel in the fuel tank 15. That is, it is considered that as the remaining amount of fuel increases, the volume of the space to be depressurized decreases, and the rate of decrease in the pressure detection value increases accordingly. In consideration of this point, for example, the determination value PA may be variably set according to the remaining amount of fuel in the fuel tank 15. In this case, the ECU 40 acquires the remaining fuel amount in the fuel tank 15 and variably sets the determination value PA based on the remaining fuel amount. In view of the fact that the volume of the decompressed space decreases as the remaining fuel amount increases, in this configuration, the determination value PA may be set to a smaller value as the remaining fuel amount increases. According to the above configuration, it is possible to determine the pressure change at the time of the clogging abnormality without being influenced by the remaining amount of fuel, and to appropriately determine the clogging abnormality of the present system. In the ECU 40, the process of acquiring the fuel remaining amount in the fuel tank 15 corresponds to an “acquisition unit”, and the process of setting the determination value PA based on the fuel remaining amount corresponds to a “setting unit”.

  Further, the determination value TA for determining the clogging abnormality of the evaporated fuel processing system may be a value variably set based on a predetermined condition. In such a case, similarly to the determination value PA, for example, the determination value TA may be variably set according to the remaining amount of fuel in the fuel tank 15. In view of the fact that the volume of the space to be depressurized decreases as the remaining fuel amount increases, in this configuration, the determination value TA is set to a smaller value (that is, a shorter time) as the remaining fuel amount increases. Good. According to the above configuration, it is possible to determine the pressure change at the time of the clogging abnormality without being influenced by the remaining amount of fuel, and to appropriately determine the clogging abnormality of the present system.

  In the above embodiment, the determination value PA is provided as the pressure detection value determination value in the clogging abnormality determination, but a plurality of pressure detection value determination values may be provided. In this case, it is considered that by providing a plurality of determination values, it is possible to estimate which of, for example, the atmospheric piping 28, the fuel piping 25, and the purge piping 26 is clogged. In other words, since the volume of the space to be decompressed by the pump 31 correlates with the rate of pressure reduction, in this configuration, when a clogging abnormality occurs in the atmospheric piping 28, a clogging abnormality occurs in the fuel piping 25, When the clogging abnormality occurs in the purge pipe 26, the volume of the space to be depressurized is estimated, and a plurality of determination values of the pressure detection value are set based on each estimated volume. Then, the position of the clogging abnormality is estimated according to which determination value region the pressure detection value belongs to.

  In addition, when the fuel vapor path is clogged due to clogging abnormality, it is considered that the pressure behavior when the pressure decreases according to the degree of clogging is different. Considering this point, it is considered that the degree of clogging at the time of clogging abnormality can be estimated by setting a plurality of determination values.

  In the above-described embodiment, the configuration in which the abnormal clogging of the present system is determined based on the time until the pressure detection value reaches the determination value PA is not limited to this. For example, it is good also as a structure which determines based on the pressure detection value in the time of predetermined time passing, after switching the switching valve 34. FIG. In such a configuration, if the detected pressure value when a predetermined time has elapsed after switching the switching valve 34 is smaller than the predetermined value, it is determined that a clogging abnormality has occurred in the system.

  Moreover, it is good also as a structure which determines clogging abnormality of this system based on the pressure fall amount per unit time. In such a configuration, if the amount of pressure drop per unit time is greater than a predetermined value, it is determined that a clogging abnormality has occurred in the system.

  In the above embodiment, the abnormality detection of the evaporated fuel processing system is performed after the ignition switch is turned off. However, this may be changed. For example, an abnormality detection of the evaporated fuel processing system may be performed while the engine is operating (when the ignition switch is on). In addition, taking into account that the pressure changes depending on the operating conditions, the abnormality detection of the evaporated fuel processing system should be performed in a state where the combustion of the engine 11 is stable, such as a state where idling stop is being performed. Is preferred.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake passage, 15 ... Fuel tank, 21 ... Canister, 28 ... Atmospheric piping, 31 ... Pump, 32 ... Orifice, 33 ... Pressure sensor, 34 ... Switching valve, 40 ... ECU (control) Section, abnormality detection section, acquisition section, setting section, switching control section).

Claims (4)

The evaporated fuel generated in the fuel tank (15) is adsorbed to the canister (21), and the adsorbed evaporated fuel is opened to the intake passage (12) of the internal combustion engine (11) by opening the purge control valve (27). An abnormality detection device (40) applied to an evaporated fuel processing system of an internal combustion engine to be purged,
The evaporative fuel processing system includes an atmospheric pipe (28) having one end connected to the canister and the other end opened to the atmosphere, and provided with a pump (31).
A pressure sensor (33) provided closer to the canister than the pump in the atmospheric pipe,
A control unit that causes the target space including the canister and the fuel tank to be in a negative pressure state on the side opposite to the atmosphere opening port of the atmosphere piping by operating the pump with the purge control valve closed;
After the start of operation of the pump by the control unit, if the rate of decrease in the pressure detection value of the pressure sensor is greater than a predetermined clogging determination value, it is detected that a clogging abnormality has occurred in the evaporated fuel processing system. An anomaly detector to
An abnormality detection device comprising: An acquisition unit for acquiring the remaining amount of fuel in the fuel tank;
The abnormality detection device according to claim 1, further comprising a setting unit that variably sets the clogging determination value based on the fuel remaining amount. The control unit is configured to place the target space in a negative pressure state by operating the pump in a state where the operation of the internal combustion engine is stopped,
The abnormality detection device according to claim 1 or 2, wherein the abnormality detection unit detects that a clogging abnormality has occurred in the evaporated fuel processing system after the operation of the pump by the control unit is started. In the evaporative fuel processing system, the atmospheric piping is bifurcated between the pump and the canister, and one of the piping portions (28a) is provided with an orifice (32), and the other piping portion. (28b) is provided with a switching valve (34) capable of switching between a communication state and a cutoff state, and the pressure sensor is provided between the pump and the orifice,
The control unit closes the purge control valve and before the target space is set to a negative pressure state, operates the pump with the other piping unit shut off by the switching valve. The piping part of is in a negative pressure state,
On the condition that the pressure detection value of the pressure sensor has dropped to a reference pressure range corresponding to the diameter of the orifice when the one pipe part is in a negative pressure state, the switching valve is connected to the other pipe part. Provided with a switching control unit that switches from a blocked state to a connected state,
In the evaporated fuel processing system, when the change rate of decrease in the pressure detection value is smaller than a predetermined leak determination value after the switching control unit switches the switching valve to the communication state, the abnormality detection unit 2. It is detected that a leakage abnormality has occurred and detects that a clogging abnormality has occurred in the evaporated fuel processing system when the rate of decrease in the pressure detection value is greater than the clogging determination value. 4. The abnormality detection device according to any one of items 3 to 3.

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