JP3948002B2 - Abnormality diagnosis device for evaporative gas purge system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality diagnosis apparatus for an evaporative gas purge system for diagnosing the presence or absence of an abnormality in an evaporative gas purge system that purges (releases) evaporative gas (fuel evaporative gas) generated by evaporation of fuel in a fuel tank into an intake pipe of an internal combustion engine. It is about.
[0002]
[Prior art]
Conventionally, in an evaporative gas purge system, in order to prevent the evaporative gas generated from the fuel tank from leaking into the atmosphere, the evaporative gas is adsorbed in the canister through the evaporative gas passage in the fuel tank and is adsorbed in the canister. A purge control valve is provided in the purge passage for purging the evaporation gas to the intake pipe of the internal combustion engine, and the purge gas is purged from the canister to the intake pipe by controlling the opening and closing of the purge control valve according to the operating state of the internal combustion engine. The flow rate is controlled. In order to prevent the abnormality in which the evaporation gas leaks from the evaporation gas purge system into the atmosphere from being left for a long period of time, it is necessary to detect the leakage of the evaporation gas at an early stage.
[0003]
Therefore, as shown in Japanese Patent Application Laid-Open No. 5-125997, a pressure sensor is provided for detecting the pressure in the evaporation gas purge system from the fuel tank to the purge control valve, and the atmospheric pressure is introduced into the evaporation gas purge system. After detecting the pressure change amount ΔP1 from the atmospheric pressure in the evaporation gas purge system with the system sealed, the purge control valve is temporarily opened to introduce a negative pressure into the evaporation gas purge system. The pressure change amount ΔP2 from the negative pressure of the evaporative gas purge system is detected in a sealed state, and these two pressure change amounts ΔP1 and ΔP2 are compared to diagnose leakage of the evaporative gas purge system. is there.
[0004]
[Problems to be solved by the invention]
By the way, since the pressure change when the evaporation gas purge system is normal is caused by the evaporation of fuel, the pressure change amount decreases as the fuel evaporation amount (evaporation gas generation amount) decreases. Since the evaporation of fuel occurs because the partial pressure of the evaporated gas component is lower than the saturated vapor pressure, the amount of fuel evaporated decreases as the differential pressure between the evaporated gas component and the saturated vapor pressure decreases. When the amount of change decreases and the partial pressure of the vapor gas component increases to the saturated vapor pressure, the fuel no longer evaporates and the pressure of the vapor gas purge system does not change.
[0005]
The partial pressure of the evaporative gas component at the start of the pressure change measurement changes due to the influence of the fuel system state such as the fuel temperature, so the measured value of the pressure change changes depending on the fuel system state at the start of the measurement. . As a result, the abnormality diagnosis performed based on the amount of change in pressure is affected by the state of the fuel system, which causes a decrease in abnormality diagnosis accuracy.
[0006]
The present invention has been made in consideration of such circumstances, and the object of the present invention is to provide an evaporative gas purge system that can accurately diagnose the abnormalities of the evaporative gas purge system without being affected by the state of the fuel system. It is to provide an abnormality diagnosis device.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, according to the abnormality diagnosis apparatus for an evaporation gas purge system of claim 1 of the present invention, the abnormality diagnosis means comprises:When the partial pressure of the evaporative gas component in the fuel tank is estimated to be close to the saturated vapor pressure,Before measuring the pressure change of the evaporation gas purge system, an operation for releasing the evaporation gas in the fuel tank and reducing the evaporation gas concentration (hereinafter referred to as “evaporation gas concentration reduction operation”) is performed. This way,Even when the partial pressure of the vapor component in the fuel tank is close to the saturated vapor pressure,Before measuring the pressure change, the differential pressure between the vapor pressure component and the saturated vapor pressure in the evaporation gas purge system can be increased sufficiently, and the abnormality of the evaporation gas purge system can be diagnosed without being affected by the state of the fuel system. It can be performed with high accuracy.In addition, when it is estimated that the partial pressure of the evaporated gas component is sufficiently lower than the saturated vapor pressure (that is, the difference between the partial pressure of the evaporated gas component and the saturated vapor pressure is large), the operation for reducing the evaporated gas concentration is omitted. Thus, since the pressure change of the evaporation gas purge system can be measured, the time required for abnormality diagnosis of the evaporation gas purge system can be shortened, and rapid abnormality diagnosis can be performed.
[0008]
In this case, the pressure change of the evaporation gas purge system is measured by measuring both the pressure change from the state where the atmospheric pressure is introduced into the evaporation gas purge system and the pressure change from the state where the predetermined pressure is introduced. However, the measurement of the pressure change from the atmospheric pressure may be performed in comparison with the measurement of the pressure change from the predetermined pressure. Since the differential pressure from the pressure is small, it is easily affected by the state of the fuel system.
[0009]
Accordingly, when performing the operation for reducing the evaporation gas concentration as in claim 2, the pressure in the evaporation gas purge system is changed to a predetermined pressure to release the evaporation gas in the fuel tank, and then returned to the vicinity of the atmospheric pressure. It is sufficient to measure the pressure change from In this way, it is possible to accurately measure the pressure change from the atmospheric pressure without being affected by the state of the fuel system.
[0010]
Also, when measuring both the pressure change from atmospheric pressure and the pressure change from negative pressure, either may be performed first, but when measuring the pressure change from negative pressure first According to the third aspect of the present invention, the pressure change from the atmospheric pressure may be measured after the evaporative gas concentration reducing operation is performed after the elapse of a predetermined time after the pressure change from the negative pressure is measured. In other words, if the pressure change from negative pressure is measured and then returned to near atmospheric pressure, the evaporated gas component in the evaporated gas purge system suddenly becomes saturated, and the evaporated gas purge system becomes unstable for a while. Therefore, the evaporative gas concentration in the fuel tank is reliably reduced before the pressure change measurement by performing the evaporative gas concentration reduction operation after waiting for a predetermined time until the state in the evaporative gas purge system becomes stable. Is.
[0011]
Further, when the pressure in the evaporation gas purge system is returned to the vicinity of the atmospheric pressure at the end of the evaporation gas concentration reduction operation, the canister closing means is opened and the purge control valve is closed as in claim 4, or As in claim 5, both the canister closing means and the purge control valve may be opened. In either case, the atmospheric pressure can be introduced into the evaporation gas purge system by opening the canister closing means. At this time, in claim 4, the purge control valve is closed when the atmospheric pressure is introduced to prevent the evaporation gas in the evaporation gas purge system from being sucked into the intake pipe, while in claim 5, the atmospheric pressure is introduced. By opening the purge control valve, the evaporation gas adsorbed in the canister is prevented from returning into the fuel tank.
[0012]
By the way, if the partial pressure of the evaporation gas component in the evaporation gas purge system is sufficiently lower than the saturated vapor pressure, there is no need to perform the evaporation gas concentration reduction operation before measuring the pressure change.
[0013]
Therefore, as in claim 6, it may be determined whether to perform the evaporative gas concentration reduction operation or not based on at least one of the fuel temperature determined by the fuel temperature determination means and the amount of change. In other words, if it is estimated that the partial pressure of the evaporated gas component is sufficiently lower than the saturated vapor pressure based on the fuel temperature and the amount of change, the operation for reducing the evaporated gas concentration is omitted and the pressure change is measured. Do. Thereby, the time required for abnormality diagnosis of the evaporation gas purge system can be shortened.
[0014]
Further, as described in claim 7, before making an abnormality diagnosis, a preliminary measurement for adjusting the pressure in the evaporation gas purge system to near atmospheric pressure and measuring a pressure change is performed once or a plurality of times, and based on the measurement result. Thus, it may be determined whether to perform the evaporation gas concentration reduction operation or not. That is, if it is estimated by preliminary measurement that the partial pressure of the vapor component in the vapor purge system is sufficiently lower than the saturated vapor pressure, the vapor gas concentration reduction operation is omitted. As a result, the operation of reducing the evaporation gas concentration can be minimized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire system will be described with reference to FIG. An air cleaner 13 is provided on the upstream side of the intake pipe 12 of the engine 11, and air that has passed through the air cleaner 13 is sucked into each cylinder of the engine 11 through the throttle valve 14. The opening degree of the throttle valve 14 is adjusted by the depression amount of the accelerator pedal 15. The intake pipe 12 is provided with a fuel injection valve 16 for each cylinder. The fuel (gasoline) in the fuel tank 17 is sent to each fuel injection valve 16 through a fuel pipe 19 by a fuel pump 18. The fuel tank 17 is provided with a pressure sensor 20 such as a semiconductor pressure sensor for detecting the pressure in the fuel tank 17.
[0016]
Next, the configuration of the evaporation gas purge system 21 will be described. A canister 23 is connected to the fuel tank 17 via a communication pipe 22. In the canister 23, an adsorbent 24 such as activated carbon that adsorbs the evaporative gas is accommodated. Further, an atmospheric communication pipe 25 communicating with the atmosphere is provided on the bottom surface of the canister 23, and a canister closing valve 26 (canister closing means) is attached to the atmospheric communication pipe 25.
[0017]
The canister closing valve 26 is constituted by an electromagnetic valve, and is kept open by a spring (not shown) in the off state, and the atmosphere communication pipe 25 of the canister 23 is kept open to the atmosphere. When a predetermined voltage is applied to the canister closing valve 26, the canister closing valve 26 is switched to a closed state, and the atmosphere communication pipe 25 is closed.
[0018]
On the other hand, between the canister 23 and the intake pipe 12, purge passages 30a and 30b for purging (releasing) the evaporated gas adsorbed by the adsorbent 24 to the intake pipe 12 are provided, and the purge passages 30a and 30b are provided. A purge control valve 31 for adjusting the purge flow rate is provided therebetween. The purge control valve 31 is constituted by an electromagnetic valve.
[0019]
A voltage is applied to the solenoid coil (not shown) of the purge control valve 31 by a pulse signal, and by adjusting the ratio of the pulse width to the period of the pulse signal (duty ratio), the purge control valve 31 The purge gas purge flow rate from the canister 23 to the intake pipe 12 is controlled by adjusting the ratio of the valve opening time to the opening / closing cycle.
[0020]
A fuel cap 38 with a relief valve is attached to the fuel filler port 17a of the fuel tank 17, and when the internal pressure of the fuel tank exceeds -40 mmHg to 150 mmHg (relief pressure), the relief valve is opened and the pressure is increased. It comes to pull out. Therefore, the section from the fuel tank 17 to the canister 23 is always kept at a pressure within this relief pressure range.
[0021]
Next, the configuration of the control system will be described. The control circuit 39 is configured by connecting a CPU 40, a ROM 41, a RAM 42, an input / output circuit 43, and the like to each other via a common bus 44. The input / output circuit 43 is connected to various sensors for detecting the engine operating state, such as a throttle sensor 45, an idle switch 46, a vehicle speed sensor 47, an intake pipe pressure sensor 49, a cooling water temperature sensor 50, an intake air temperature sensor 51, and the like. Abnormal diagnosis of fuel injection control, ignition control, evaporation gas purge control, evaporation gas purge system 21 based on signals input from these various sensors via the input / output circuit 43 and programs and data stored in the ROM 41 and RAM 42 And a drive signal is output to the fuel injection valve 16, the spark plug 52, the canister closing valve 26, the purge control valve 31 and the like via the input / output circuit 43, and a warning is given when an abnormality of the evaporation gas purge system 21 is detected. The lamp 53 is turned on to inform the driver.
[0022]
Hereinafter, the abnormality diagnosis program of the evaporation gas purge system 21 executed by the control circuit 39 will be described with reference to the flowcharts of FIGS. This abnormality diagnosis program is repeatedly executed every predetermined time (for example, every 256 msec) when an ignition switch (not shown) is turned on, and serves as an abnormality diagnosis means in the claims. When the program is started, first, in steps 101 to 105 in FIG. 2, the process branches to various steps while determining whether or not the current process has progressed from the set state of the flags F1 to F5. The flags F1 to F5 are reset to “0” by the initialization process immediately after the ignition switch is turned on.
[0023]
When all the flags F1 to F5 are set to “0”, that is, when all the determinations at steps 101 to 105 are “No”, the process proceeds to step 106 in FIG. 3, and based on the fuel temperature and the fuel temperature change amount. It is determined whether or not an evaporation gas concentration reduction operation (steps 107 to 118) is to be executed. In this case, the fuel temperature may be detected by attaching a fuel temperature sensor (not shown) to the fuel tank 17 or the like, but the cooling water temperature, the intake air temperature (or the outside air temperature), the operation time from the start, the operation The fuel temperature may be estimated based on the state or the like.
[0024]
The execution conditions of the evaporation gas concentration reduction operation determined in step 106 are: (1) the fuel temperature is equal to or higher than the predetermined temperature α, and (2) the fuel temperature change amount is equal to or lower than the predetermined amount β. Since the partial pressure of the vapor gas component in the tank 17 is estimated to be close to the saturated vapor pressure, the vapor gas concentration reduction operation is executed as follows.
[0025]
First, in step 108, the canister closing valve 26 is fully closed, and in step 109, the purge control valve 31 is opened, and the negative pressure of the intake pipe 12 is introduced into the evaporation gas purge system from the fuel tank 17 to the purge control valve 31. Is introduced (time T1 to T2 in FIG. 5). As a result, the evaporation gas in the evaporation gas purge system is sucked into the intake pipe 12 to reduce the concentration (partial pressure) of the evaporation gas component in the evaporation gas purge system. Increase the differential pressure.
[0026]
In the next step 110, it is determined whether or not the internal pressure PT of the fuel tank detected by the pressure sensor 20 has decreased to a predetermined negative pressure (for example, −5 mmHg). If not yet decreased to −5 mmHg, the process proceeds to step 111. Then, the first flag F1 is set to “1” which means that negative pressure is being introduced, and this program is terminated. In this case, when the program is executed next time or later, it is determined as “Yes” in step 101, and the processing is repeated in the order of step 101 → step 110 → ……, so that the fuel tank internal pressure PT is −5 mmHg or less. The introduction of negative pressure (opening of the purge control valve 31) is continued until the pressure decreases.
[0027]
Accordingly, when the fuel tank internal pressure PT decreases to −5 mmHg at time T2 in FIG. 5, the determination in step 110 becomes “Yes”, the process proceeds to step 112, and the first flag F1 is reset to “0”. Thereafter, in step 113, the canister closing valve 26 is fully opened, and in step 114, the purge control valve 31 is fully closed to introduce atmospheric pressure into the evaporation gas purge system.
[0028]
In the next step 115, it is determined whether or not the internal pressure PT of the fuel tank has returned to the atmospheric pressure (0 mmHg). If not yet returned to the atmospheric pressure, the routine proceeds to step 116 where the second flag F2 is being introduced into the atmospheric pressure. Set to “1” which means that the program is finished. In this case, when this program is executed next time or later, “No” is determined in step 101 and “Yes” is determined in step 102, and processing is performed in the order of step 101 → step 102 → step 115 →. The atmospheric pressure introduction is continued until the fuel tank internal pressure PT returns to the atmospheric pressure repeatedly.
[0029]
Accordingly, when the fuel tank internal pressure PT returns to the atmospheric pressure, the determination in step 115 becomes “Yes”, the process proceeds to step 117, and the second flag F2 is reset to “0”. Thereafter, in step 118, the canister closing valve 26 is fully closed to seal the evaporation gas purge system, and the pressure change ΔP1 from the atmospheric pressure is measured by the processing in steps 122 to 127.
[0030]
On the other hand, if the fuel temperature <α and the fuel temperature change amount> β correspond to either of the fuel temperature <α and the fuel temperature change amount> β in step 106 described above, the differential pressure between the partial pressure of the evaporated gas component in the fuel tank 17 and the saturated vapor pressure is relatively Since it is estimated that it is large, it is not necessary to perform the above-described evaporative gas concentration reduction operation. Therefore, in this case, the operation for reducing the evaporation gas concentration is omitted, and the process proceeds to Steps 120 and 121. The purge control valve 31 and the canister closing valve 26 are both fully closed, and the evaporation gas purge system is sealed. By the process 127, the pressure change amount ΔP1 from the atmospheric pressure is measured.
[0031]
In step 122, the pressure change amount ΔP1 from the atmospheric pressure is measured. First, the internal pressure P1a of the fuel tank at time T3 in FIG. 5 is read, the timer T is reset and started, and then the process proceeds to step 123. For example, it is determined whether or not it has become 15 seconds or longer. If 15 seconds have elapsed, the process proceeds to step 124, where the third flag F3 is set to “1” which means that the pressure change is being measured, and this program is terminated.
[0032]
Thus, by setting the third flag F3 to “1”, it is determined that “No” is determined in steps 101 and 102 and “Yes” is determined in step 103 when the program is executed next time. The processing is repeated in the order of steps 101 to 103 → step 123 →. During this time, the fuel tank internal pressure PT rises from 0 mmHg in accordance with the amount of vapor generated from the fuel in the fuel tank 17 between time T3 and time T4 in FIG.
[0033]
Thereafter, when 15 seconds elapse from the time T3 (detection time of P1a), the process proceeds to step 125 in FIG. 4 to read the fuel tank internal pressure P1b detected by the pressure sensor 20, and in step 126, the pressure change amount ΔP1 for 15 seconds. After calculating (= P1b−P1a), in step 127, the third flag F3 is reset, and the measurement of the pressure change amount ΔP1 from the atmospheric pressure is ended.
[0034]
Thereafter, in step 128, the purge control valve 31 is opened, and at the same time, the timer T is reset and started. When the purge control valve 31 is opened, the intake pipe negative pressure is introduced into the previous evaporative gas purge system under atmospheric pressure (time T4 to T5 in FIG. 5). Therefore, if there is no leak in the evaporation gas purge system, the fuel tank internal pressure PT begins to decrease.
[0035]
In the next step 129, it is determined whether or not the fuel tank internal pressure PT detected by the pressure sensor 20 has decreased to a predetermined negative pressure (for example, −15 mmHg). If not yet decreased to −15 mmHg, the process proceeds to step 130. Then, it is determined whether or not a predetermined time (for example, 2 seconds) has elapsed since the negative pressure introduction start. If 2 seconds have elapsed, the process proceeds to step 133, the fourth flag F4 is set to “1” which means that negative pressure is being introduced, and the program is terminated.
[0036]
In this way, by setting the fourth flag F4 to “1”, it is determined that “No” in steps 101 to 103 and “Yes” in step 104 when the program is executed next time, The processing is repeated in the order of steps 101 to 104 → step 129 →.
[0037]
As a result of such processing, when the result of step 130 is “Yes” before step 129, that is, even if a predetermined time (for example, 2 seconds) elapses from the start of the introduction of the negative pressure, the fuel tank internal pressure PT is predetermined When the pressure does not drop to a negative pressure (for example, −15 mmHg), it means that the negative pressure cannot be introduced into the fuel tank 17. A possible cause of the inability to introduce negative pressure into the fuel tank 17 is that clogging has occurred somewhere in the evaporation gas purge system. In this case, the process proceeds to step 131, where the clogging flag Fclose is set to “1” which means that clogging has occurred, and in step 132, the warning lamp 53 is turned on to notify the abnormality, and the program ends.
[0038]
On the other hand, if the result of step 129 is “Yes” before step 130, that is, the fuel tank internal pressure PT is a predetermined negative pressure (for example, −15 mmHg) within a predetermined time (for example, 2 seconds) from the start of the negative pressure introduction. If it has decreased, the process proceeds to step 134, the fourth flag F4 is reset to “0”, and in the subsequent step 135, the purge control valve 31 is fully closed again, and the introduction of the negative pressure is terminated (FIG. 5). Time T5). Thereafter, the routine proceeds to step 136, and at the time T6 immediately after the evaporation gas purge system is brought into the negative pressure sealed state, the fuel tank internal pressure P2a detected by the pressure sensor 20 is read and stored, and the timer T is reset and started. Thereafter, the fuel tank internal pressure PT rises from −15 mmHg in accordance with the amount of vapor generated in the fuel tank 17 between time T6 and time T7 in FIG.
[0039]
Then, in the next step 137, it is determined whether or not 15 seconds have elapsed since the fuel tank internal pressure P2a was read. If 15 seconds have elapsed, the process proceeds to step 138, and the fifth flag F5 is being detected for pressure change. Is set to “1”, meaning that the program is terminated. As a result, at the next and subsequent executions of the program, “No” is determined in steps 101 to 104 and “Yes” is determined in step 105, and the processing is repeated in the order of steps 101 to 105 → step 137 →. .
[0040]
Thereafter, when 15 seconds have elapsed from the reading of the fuel tank internal pressure P2a, the routine proceeds to step 139, where the fuel tank internal pressure P2b detected by the pressure sensor 20 is read and stored at time T7, and the pressure change ΔP2 (= P2b-P2a) is calculated.
[0041]
Thereafter, in step 141, it is determined whether or not there is a leak based on a leak determination condition expressed by the following equation.
ΔP2> α ・ ΔP1 + β
[0042]
Here, α is a coefficient for correcting the difference in the amount of fuel evaporation due to the difference between atmospheric pressure and negative pressure, and β is a coefficient for correcting the detection accuracy of the pressure sensor 20, the pressure leak of the canister closing valve 26, and the like. If the above equation is satisfied, it is determined that there is a leak. That is, if there is a cause of leakage in the sealed section from the fuel tank 17 to the purge control valve 31, outflow from the sealed section to the atmosphere occurs under positive pressure, while air flows from the atmosphere to the sealed section under negative pressure. Happens. Therefore, “(pressure change amount ΔP2 under negative pressure) than“ (pressure change amount ΔP1 under atmospheric pressure) = (amount of evaporative gas generated from the fuel tank 17) − (amount of outflow from the sealed section to the atmosphere) ”. = (Amount of evaporated gas generated from the fuel tank 17) + (amount of inflow from the atmosphere to the sealed section) "is larger. From this relationship, the above-described leak determination condition is derived.
[0043]
If the leak judgment condition of the above equation is satisfied, that is, if it is judged that there is a leak in step 141, there is a part that causes a leak somewhere in the purge path from the fuel tank 17 to the intake pipe 12. In step 142, the leak flag Fleak is set to "1". In the subsequent step 143, the warning lamp 53 is turned on to notify the abnormality, and the program ends.
[0044]
On the other hand, if “NO” is determined in step 141, that is, if it is determined that there is no leak, the process proceeds to step 144, and the first to fifth flags F1 to F5 are reset to “0”. Exit this program.
[0045]
In the present embodiment (1) described above, the evaporation gas concentration in the fuel tank 17 is released to reduce the evaporation gas concentration before the pressure change amount ΔP1 from the atmospheric pressure is measured. Before the measurement, the differential pressure between the vapor pressure component and the saturated vapor pressure in the fuel tank 17 can be sufficiently increased, and the pressure from the atmospheric pressure is not affected by the fuel system state such as the fuel temperature. The change amount ΔP1 can be measured with high accuracy, and abnormality diagnosis of the evaporation gas purge system can be performed with high accuracy.
[0046]
Further, in the present embodiment (1), it is determined whether or not the execution condition of the evaporation gas concentration reduction operation is satisfied based on the fuel temperature and the fuel temperature change amount, and when the execution condition is not satisfied (that is, the evaporation gas component When the partial pressure is estimated to be sufficiently low compared to the saturated vapor pressure), the evaporative gas concentration reduction operation is omitted and the pressure change ΔP1 is measured. The required time can be shortened, and a rapid abnormality diagnosis can be performed.
[0047]
Note that the execution condition of the evaporation gas concentration reduction operation may be determined by only one of the fuel temperature and the fuel temperature change amount. Further, the process for determining the execution condition of the evaporation gas concentration reduction operation may be omitted, and the evaporation gas concentration reduction operation may be executed every time. Even in this case, the intended purpose of the present invention can be sufficiently achieved.
[0048]
[Embodiment (2)]
In the embodiment (1), the canister closing valve 25 is opened and the purge control valve 31 is closed when the fuel tank internal pressure PT is returned to atmospheric pressure (T2 to T3) at the end of the evaporation gas concentration reduction operation. However, in the embodiment (2) of the present invention shown in FIG. 6, when the fuel tank internal pressure PT is returned to the atmospheric pressure at the end of the evaporation gas concentration reduction operation (T2 to T3), the canister closing valve 25 and the purge control valve 31 are Open both. In this way, by opening the purge control valve 31 when the atmospheric pressure is introduced, the evaporation gas adsorbed in the canister 23 can be prevented from returning to the fuel tank 17, and the evaporation gas concentration in the fuel tank 17 is reliably reduced. it can.
[0049]
[Embodiment (3)]
In the above embodiments (1) and (2), after measuring the pressure change amount ΔP1 from the atmospheric pressure, the pressure change amount ΔP2 from the negative pressure is measured, but the embodiment of the present invention shown in FIG. In (3), after a predetermined time has elapsed since the pressure change ΔP2 from the negative pressure was measured and the fuel tank internal pressure PT was returned to the atmospheric pressure, the evaporation gas concentration reduction operation was performed, and the pressure change from the atmospheric pressure. ΔP1 is measured. Also in the present embodiment (3), the method for measuring the pressure change amounts ΔP2 and ΔP1 and the method for reducing the evaporation gas concentration are the same as those in the above-described embodiment (1) or (2).
[0050]
In this case, if the pressure change amount ΔP2 from the negative pressure is measured and then returned to the atmospheric pressure, the evaporated gas component in the fuel tank 17 suddenly becomes saturated, and the state in the fuel tank 17 remains unsatisfactory for a while. In order to become stable, the evaporative gas concentration in the fuel tank 17 is measured before the pressure change amount ΔP1 is measured by waiting for a predetermined time until the state in the fuel tank 17 becomes stable and performing the evaporative gas concentration reducing operation. Is reliably reduced.
[0051]
[Embodiment (4)]
In the embodiment (1), it is determined whether or not the evaporation gas concentration reduction operation is executed based on the fuel temperature and the fuel temperature change amount. However, in the embodiment (4) of the present invention shown in FIG. Before making an abnormality diagnosis of the evaporation gas purge system, a preliminary measurement is performed to measure the pressure change ΔP0 by adjusting the fuel tank internal pressure PT to the atmospheric pressure, and the pressure change ΔP0 is compared with a predetermined value to reduce the evaporation gas concentration. Determine whether to perform or omit the operation. That is, when the pressure change amount ΔP0 is less than the predetermined value, it is estimated that the partial pressure of the evaporated gas component in the fuel tank 17 is close to the saturated vapor pressure, and the evaporated gas concentration in the fuel tank 17 needs to be reduced. In the same manner as in the embodiment (1), the evaporation gas in the fuel tank 17 is released to reduce the evaporation gas concentration. On the other hand, when the pressure change amount ΔP0 is equal to or larger than the predetermined value, it is estimated that the partial pressure of the vapor gas component in the fuel tank 17 is sufficiently lower than the saturated vapor pressure, and the vapor gas concentration in the fuel tank 17 is reduced. Since there is no need, the operation of reducing the evaporation gas concentration is omitted and the pressure change ΔP1 from the atmospheric pressure is measured.
The number of times the pressure change amount ΔP0 is measured may be one time, but may be two or more times.
[0052]
[Embodiment (5)]
In each of the above embodiments (1) to (4), when returning the fuel tank internal pressure PT to atmospheric pressure, the canister closing valve 25 is opened to introduce atmospheric pressure into the evaporation gas purge system. In the embodiment (5) of the present invention shown in FIG. 9, the release valve 61 is provided in the purge path from the fuel tank 17 to the canister 23, and the release valve 61 is opened when the fuel tank internal pressure PT is returned to the atmospheric pressure. Introducing atmospheric pressure into the evaporation gas purge system.
[0053]
1 and 9, the pressure sensor 20 detects the internal pressure of the fuel tank 17. However, for example, the pressure in the communication pipe 22 that connects the fuel tank 17 and the canister 23 is detected. In short, the pressure at any point in the evaporation gas purge system from the fuel tank 17 to the purge control valve 31 may be detected.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire system showing an embodiment (1) of the present invention.
FIG. 2 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 1).
FIG. 3 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 2).
FIG. 4 is a flowchart showing a flow of processing of an abnormality diagnosis program (part 3).
FIG. 5 is a time chart for explaining the relationship between the opening / closing of the purge control valve and the canister closing valve and the change in the internal pressure of the fuel tank at the time of abnormality diagnosis in the embodiment (1) of the present invention.
FIG. 6 is a time chart for explaining the relationship between the opening / closing of the purge control valve and the canister closing valve and the change in the fuel tank internal pressure during abnormality diagnosis in the embodiment (2) of the present invention.
FIG. 7 is a time chart for explaining the relationship between the opening / closing of the purge control valve and the canister closing valve and the change in the fuel tank internal pressure during abnormality diagnosis in the embodiment (3) of the present invention.
FIG. 8 is a time chart for explaining the relationship between the opening / closing of the purge control valve and the canister closing valve and the change in the internal pressure of the fuel tank at the time of abnormality diagnosis in the embodiment (4) of the present invention.
FIG. 9 is a schematic configuration diagram of the entire system showing an embodiment (5) of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Throttle valve, 16 ... Fuel injection valve, 17 ... Fuel tank, 18 ... Fuel pump, 20 ... Pressure sensor, 21 ... Evaporative gas purge system, 22 ... Communication pipe, DESCRIPTION OF SYMBOLS 23 ... Canister, 24 ... Adsorber, 26 ... Canister block valve, 30a, 30b ... Purge passageway, 31 ... Purge control valve, 39 ... Control circuit (abnormality diagnostic means), 53 ... Warning lamp, 61 ... Open / close valve

Claims (7)

A canister that adsorbs the evaporation gas generated by evaporation of the fuel in the fuel tank in a passage communicating the fuel tank and the intake pipe of the internal combustion engine, and a purge control that controls the purge of the evaporation gas from the canister to the intake pipe In an evaporation gas purge system provided with a valve,
An abnormality diagnosing means for sealing the evaporation gas purge system including the fuel tank and the canister at the time of abnormality diagnosis, measuring a pressure change of the evaporation gas purge system, and diagnosing the presence or absence of abnormality of the evaporation gas purge system based on the measured value With
When the partial pressure of the vapor gas component in the fuel tank is estimated to be close to the saturated vapor pressure, the abnormality diagnosis unit releases the vapor gas in the fuel tank before measuring the pressure change in the vapor gas purge system. An abnormality diagnosis apparatus for an evaporation gas purge system, which performs an operation for reducing the evaporation gas concentration (hereinafter referred to as an “evaporation gas concentration reduction operation”).   The abnormality diagnosing means changes the pressure in the evaporation gas purge system to a predetermined pressure to release the evaporation gas in the fuel tank and then returns it to near atmospheric pressure when performing the operation for reducing the evaporation gas concentration. The abnormality diagnosis apparatus for an evaporation gas purge system according to claim 1.   The abnormality diagnosing means measures the first pressure change after adjusting the pressure in the evaporation gas purge system to a negative pressure, and then adjusts the pressure in the evaporation gas purge system to the vicinity of the atmospheric pressure and then the second pressure. By measuring the change and comparing both pressure changes, the evaporative gas purge system is diagnosed for the presence or absence of an abnormality, and the evaporative gas concentration reduction operation is performed after a predetermined time has elapsed since the end of the first pressure change measurement. 3. The apparatus for diagnosing abnormality of an evaporation gas purge system according to claim 2, wherein the second pressure change is measured after the measurement. A canister closing means for opening and closing an air communication hole provided in the canister;
The abnormality diagnosis means opens the canister closing means and closes the purge control valve when returning the pressure in the evaporation gas purge system to near atmospheric pressure at the end of the evaporation gas concentration reduction operation. The abnormality diagnosis apparatus for an evaporation gas purge system according to claim 2 or 3. A canister closing means for opening and closing an air communication hole provided in the canister;
The abnormality diagnosis means opens both the canister closing means and the purge control valve when returning the pressure in the evaporation gas purge system to near atmospheric pressure at the end of the evaporation gas concentration reduction operation. Item 4. An abnormality diagnosis apparatus for an evaporation gas purge system according to Item 2 or 3.   Fuel temperature determination means for determining the temperature of the fuel in the fuel tank is provided, and the abnormality diagnosis means performs the operation for reducing the evaporation gas concentration based on at least one of the fuel temperature determined by the fuel temperature determination means and the change amount thereof. 6. The abnormality diagnosis apparatus for an evaporation gas purge system according to claim 1, wherein it is determined whether to execute or omit.   The abnormality diagnosing means performs one or more preliminary measurements to measure a pressure change by adjusting the pressure in the evaporative gas purge system to near atmospheric pressure before performing abnormality diagnosis, and based on the measurement result, The abnormality diagnosis apparatus for an evaporation gas purge system according to any one of claims 1 to 6, wherein it is determined whether to execute or omit an evaporation gas concentration reduction operation.

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