JP2006257937A - Leakage diagnostic device of evaporation gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately diagnose the existence of leakage more than a conventional diagnosis, regardless of a kind of fuel stored in a fuel tank. <P>SOLUTION: An evaporation gas discharge device has a communicating passage 14, a canister 20 and an opening-closing valve 12. The leakage diagnostic device has a negative pressure pump 28 corresponding to a negative pressure introducing means, a pressure sensor 34, and an ECU 32 corresponding to a leakage diagnostic means. The leakage diagnostic means repeatedly performs a stroke of detecting measured pressure (pressure in the evaporation gas discharge device) by the pressure sensor 34 after generating negative pressure in the evaporation gas discharge device by the negative pressure pump 28. When detected measured pressure of respective times is lower than reference pressure, a leakage nonexistence frequency is increased, and when the measured pressure is higher than the reference pressure, a leakage existence frequency is increased. When any one frequency reaches a predetermined frequency, a corresponding discriminating result is determined as a diagnostic result of leakage. Since the diagnostic result is determined by performing detection of a plurality of times, leakage diagnostic accuracy is enhanced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for diagnosing the presence or absence of leakage of an evaporation gas, which is configured to discharge an evaporation gas (abbreviation of evaporation gas, meaning fuel evaporative gas) into an intake passage of an internal combustion engine. About.

  The evaporation gas release device has a canister provided in the middle of a passage connecting the intake passage and the fuel tank of the internal combustion engine, and an open / close valve provided between the canister and the intake passage. This evaporation gas releasing device functions to adsorb the evaporation gas evaporated from the fuel in the fuel tank into the canister and to release the evaporation gas adsorbed in the canister to the intake passage by using the negative pressure of the intake passage.

However, when the evaporation gas is released into the intake passage by the evaporation gas discharge device, the evaporation gas may leak to the outside (that is, in the atmosphere). This leakage (leak) is a cause of air pollution because the evaporation gas contains a large amount of hydrocarbons. On the other hand, the leakage itself also leads to fuel loss, so it is necessary to detect the leakage of the evaporation gas at an early stage. Conventionally, an example of a technique for diagnosing the presence or absence of a leak of evaporation gas after introducing not only a negative pressure generated by a negative pressure pump but also a negative pressure of an intake passage into the evaporation gas discharge device has been disclosed (for example, Patent Documents) 1).
Japanese Patent Laying-Open No. 2004-301027 (page 5-6, FIG. 5)

However, according to the technique disclosed in Patent Document 1 described above, regardless of the type of fuel in the fuel tank, the evaporative gas is released after a predetermined time (for example, 2 minutes) has elapsed since the start of simply introducing the negative pressure. The pressure of the device (specifically, the passage) is measured, and the presence or absence of a leak is merely diagnosed based on whether the pressure is higher or lower than a reference value. If highly volatile fuel is contained in the fuel tank, the fuel vaporization rate is faster than that of low volatile fuel, so the pressure when measured after a predetermined time has passed May be high. In this case, although there is no leak, it is mistakenly diagnosed that there is a leak.
The present invention has been made in view of the above points, and provides an evaporative gas leak diagnosis apparatus capable of diagnosing the presence or absence of a leak more accurately than before regardless of the type of fuel contained in the fuel tank. Objective.

(1) Means for solving the problem (hereinafter simply referred to as “solution means”) 1 is as described in claim 1. This leak diagnosis apparatus has a negative pressure introduction means, a pressure sensor, a leak diagnosis means, etc., and the leak diagnosis means diagnoses the presence or absence of a leak of the evaporation gas according to a certain procedure.
In this procedure, after a negative pressure is generated in the evaporation gas discharge device by the negative pressure introducing means, the pressure in the evaporation gas discharge device is detected by a pressure sensor. For each detected pressure, if the pressure is lower than the predetermined pressure, the number of leaks is increased, and if the pressure is higher than the predetermined pressure, the number of leaks is increased. The pressure detection and determination are repeated for each time until either one reaches the determination end count (for example, 3 times or 5 times). The determination result that has reached the determination end count is determined as the leakage diagnosis result (presence or absence of evaporation gas leakage).
Even if highly volatile fuel is contained in the fuel tank, the pressure is detected a plurality of times and the greater discrimination result is determined as the diagnosis result, so that the accuracy of the leak diagnosis is improved. Therefore, regardless of the type of fuel contained in the fuel tank, it is possible to diagnose the presence or absence of leakage more accurately than in the past.

(2) Solution 2 is as described in claim 2. Since it takes time to detect the pressure a plurality of times, the pressure that should serve as a reference may change with a change in the diagnostic environment (for example, a change in temperature or pressure). Therefore, when one of the number of times without leakage and the number of times with leakage reaches the determination end number, the reference pressure is detected by the pressure sensor after switching the switch to the negative pressure introduction passage, and the number of determination end times The average pressure is obtained by averaging the pressures. The leakage diagnosis result is determined only when the average value thus obtained and the reference pressure have a certain relationship. Even if the diagnostic environment changes, the presence or absence of leakage is diagnosed based on the reference pressure, so that the diagnostic accuracy can be improved.

(3) The solving means 3 is as described in claim 3. As described above, the reference pressure may change as the diagnostic environment changes. Therefore, after either one of the number of times without leak and the number of times with leak reaches the determination end number, the reference pressure is detected in a state where the evaporation gas release device is opened to the atmosphere. When the difference value between the reference pressure and the predetermined pressure is outside the allowable range, re-diagnosis is performed. Accordingly, since the leak diagnosis result is determined under a stable diagnosis environment, the accuracy of the leak diagnosis can be further increased.

(4) The solving means 4 is as described in claim 4. The negative pressure introduction period is a period from when the negative pressure is started to be introduced into the evaporation gas discharge device until the pressure is detected. In relation to the diagnostic environment (atmospheric pressure, temperature), if the negative pressure introduction period is too long or too short, the determination result of the presence or absence of leakage may be inappropriate. For example, if the negative pressure introduction period is long when the temperature is high, the pressure increases due to the influence of the temperature, and therefore it may be determined that there is a leak where it should be determined that there is no leak. Therefore, the first data table prescribes the relationship between one or both of atmospheric pressure and temperature and the negative pressure introduction period, determines the negative pressure introduction period based on the input of atmospheric pressure and temperature, Perform detection. Thus, since the appropriate length of the negative pressure introduction period is set, the accuracy of leak diagnosis can be further increased.

(5) Solution 5 is as described in claim 5. The determination end count is the number of times pressure detection and determination are repeated. In relation to the capacity of the fuel tank, if the number of determination end times is too large or too small, the determination result of the presence or absence of leakage may be inappropriate. For example, if the number of end of determination is small when the fuel tank has a large capacity, the volume of evaporation gas generated by the vaporization of the fuel also increases, so that it may be determined that there is a leak where it should be determined that there is no leak. Accordingly, the relationship between the capacity of the fuel tank and the number of determination completions is defined in the second data table, and the pressure is detected after determining the number of determination completions based on the input of the capacity of the fuel tank. In this way, since an appropriate number of determination end times is set, the accuracy of leak diagnosis can be further increased.

  According to the present invention, it is possible to diagnose the presence or absence of leakage more accurately than in the past, regardless of the type of fuel contained in the fuel tank.

  The best mode for carrying out the present invention will be described with reference to the drawings. “Communicating” means a state in which the two passages can mutually flow.

First, a configuration example for realizing leak diagnosis will be described with reference to FIGS. 1 and 2. In FIG. 1, the evaporative gas discharge device has a communication passage 14, a canister 20, an on-off valve 12, and the like. The communication passage 14 is a passage that connects the intake passage 10 of the internal combustion engine and the fuel tank 16. The canister 20 is provided in the middle of the communication passage 14, adsorbs the evaporated vapor of fuel in the fuel tank 16, and discharges the evaporated gas to the intake passage 10 using negative pressure.
The on-off valve 12 is configured to operate in accordance with a signal transmitted from an electronic control unit (Electro Control Unit; hereinafter simply referred to as “ECU”) 32.

  The diagnostic module 30 includes a plurality of passages (that is, the common passage 22, the atmosphere opening passage 27, the negative pressure introduction passage 40, etc.), the switch 24, a plurality of sensors (that is, the pressure sensor 34, the temperature sensor 36), and the negative pressure pump 28. Etc.

  The common path 22 connected to the canister 20 is communicated with one of the atmosphere release path 27 and the negative pressure introduction path 40 by the switch 24. The atmosphere opening passage 27 is a passage that opens to the atmosphere, but a filter (for example, activated carbon or the like) for preventing evaporation of the evaporated gas to the atmosphere may be interposed. The negative pressure introduction passage 40 is a bypass passage branched from the common passage 22 and is a passage through which negative pressure is introduced by the negative pressure pump 28. The negative pressure pump 28 corresponds to negative pressure introducing means. In the configuration of this example, when the switch 24 switches to the negative pressure introduction passage 40 side, the negative pressure introduction passage 40 has a loop shape (see FIG. 2).

  In the negative pressure introduction passage 40, an orifice hole 38 is provided midway from the branch point with the common path 22 to the installation position of the negative pressure pump 28. The inner diameter of the orifice hole 38 is significantly narrower than the inner diameter of the negative pressure introducing passage 40, and is formed so as to have a reference leak hole diameter (for example, a diameter of 0.42 [mm]). By providing the orifice hole 38 in this manner, even when the switch 24 is switched to the atmosphere release passage 27 side, a part of the negative pressure introduction passage 40 (that is, a passage portion extending from the orifice hole 38 to the negative pressure pump 28). Can reduce the fluctuation range of pressure.

The switch 24 switches to either one of the negative pressure introduction passage 40 and the atmosphere release passage 27 and communicates with the common passage 22. Both the pressure sensor 34 and the temperature sensor 36 are provided in the middle of the negative pressure introduction passage 40. However, since the negative pressure introduction passage 40 is connected to the canister 20 through the common passage 22, the pressure sensor 34 and the temperature sensor 36 are equivalent to measuring the pressure and temperature in the evaporation gas discharge device as a result. The negative pressure pump 28 is provided in the negative pressure introduction passage 40, and introduces a negative pressure to the evaporation gas discharge device through the common path 22.
The result measured by the pressure sensor 34 or the temperature sensor 36 is configured to be input to the ECU 32 as a signal or information. Further, the switch 24 and the negative pressure pump 28 are configured to operate according to a signal transmitted from the ECU 32.

In addition to the above-described evaporation gas release device and the diagnostic module 30, the ECU 32, the temperature sensors 26 and 42, and the like are included. The ECU 32 is mainly configured by a CPU, and includes a ROM, a RAM, an input / output circuit, a timer, an input device, and the like. A storage medium such as a ROM or a RAM corresponds to a storage device. The ROM stores a program for realizing a leak determination process described later, and predetermined data (for example, a first temperature and a second temperature described later). The timer may be configured by hardware, and the timer function may be realized by software. The input device is a device capable of inputting data such as temperature, pressure, and fuel tank 16 capacity.
The temperature sensor 42 detects the temperature of a fluid (for example, air, including evaporation gas, and so on) flowing through the intake passage 10 as indicated by an arrow D2. The temperature sensor 26 detects the temperature of the cooling water flowing through the cooling passage 25 provided in the cylinder block, the radiator, or the like. The temperatures measured by the temperature sensors 26 and 42 are each input to the ECU 32 as signals or information.

  With respect to an example of a procedure for diagnosing the presence or absence of a leak with the apparatus configured as described above, the time chart shown in FIG. 5 and FIG. This will be described with reference to the negative pressure state shown in FIG. Since this leak determination process is executed by the ECU 32, the ECU 32 corresponds to a leak diagnosis means. 3 and 4 are connected by connectors A, B, C, and D, and the processing continues between these connectors. In FIG. 5, switching to the atmosphere opening passage 27 side is denoted as “atmosphere side”, and switching to the negative pressure introduction passage 40 side is denoted as “negative pressure side”. Further, it is assumed that the switch 24 is switched to the atmosphere release passage 27 side prior to executing the leak determination process.

  First, a timer that performs period management such as a negative pressure introduction period and a standby period is started [Step S10], and waits until a temperature at which leakage can be determined is reached [Step S12]. In step S12, for example, the temperature of the cooling water detected by the temperature sensor 26 is equal to or lower than the first temperature (eg, 50 [° C.]), and the temperature of the fluid detected by the temperature sensor 42 is the second temperature (eg, 50 [° C.). ]) Wait until: For the first temperature and the second temperature, appropriate values are set according to the type of fuel 18 (that is, whether or not the volatility is high), the capacity of the fuel tank 16, and the like.

  When the temperature reaches a temperature at which the presence / absence of leakage can be determined (YES in step S12), a negative pressure introduction period, the number of determination completion times, and the like are set [step S14]. An arbitrary value may be set for the negative pressure introduction period and the number of determination end times, but the negative pressure introduction period may be set to the number of seconds determined based on the temperature and the atmospheric pressure as shown in Table 1 described later. As for the number of determination end times, the number determined based on the capacity of the fuel tank 16 may be set as shown in Table 2 described later.

  Table 1 described above corresponds to the first data table, and Table 2 corresponds to the second data table. These tables 1 and 2 are stored in a ROM, a RAM or the like in the ECU 32. Here, the temperature detected by the temperature sensor 36 before driving the negative pressure pump 28 is substantially equal to the air temperature, and the pressure detected by the pressure sensor 34 is substantially equal to the atmospheric pressure. Therefore, for example, if the temperature detected by the temperature sensor 36 is 15 [° C.] and the atmospheric pressure detected by the pressure sensor 34 is 690 [hPa], 100 [seconds] is set as the negative pressure introduction period according to Table 1. . If the capacity of the fuel tank 16 is 40 [liters], three times are set as the number of determination end times according to Table 2.

  After setting the negative pressure introduction period, the number of times of determination completion, etc., the switch 24 transmits a signal to the negative pressure pump 28 and starts driving it while switching to the atmosphere release passage 27 side [step S16]. The negative pressure pump 28 continues to be driven until it is stopped at step S58, except that it is temporarily stopped at step S38 to be described later. In the example of FIG. 5, the driving is continued from time t12 when the negative pressure pump 28 starts to be driven until time t38 at which it finally stops (except for the period from time t30 to time t32). Therefore, during this time, a negative pressure is introduced into the evaporation gas discharge device by the negative pressure pump 28.

In this state, a standby period (for example, 30 seconds or 50 seconds) is waited (step S18), and the reference pressure is detected by the pressure sensor 34 (step S20). The length of the standby period in step S18 is appropriately set in consideration of the type of cooling water, the temperature, the atmospheric pressure, and the like. The reference pressure in step S20 corresponds to “predetermined pressure”.
In the example of FIG. 5, the pressure P10 was at time t10 immediately before the start of processing, but the pressure dropped to pressure P16 at time t14 after waiting for the waiting period Tb. In this example, the pressure P16 becomes the reference pressure. The pressure state at this time is a negative pressure state in the portion indicated by the hatched area in FIG. 6 (particularly, the evaporation gas discharge device such as the communication passage 14 and the canister 20).

  Returning to FIG. 3, if the reference pressure detected in step S20 is outside the proper range (NO in step S22), it is assumed that an abnormality has occurred in the negative pressure pump 28. After transmitting a signal for stopping the negative pressure pump 28 [step S58], the leak determination process is finished. The appropriate range is set according to the capability of the negative pressure pump 28, and for example, a range of -1.0 to -4.5 [KPa] is applicable.

  Returning to FIG. 3, if the reference pressure obtained in step S20 is within the appropriate range (YES in step S22), it is assumed that the negative pressure pump 28 is operating normally. Then, the detection of the actually measured pressure is repeated until the termination condition is satisfied. That is, after switching the switch 24 to the negative pressure introduction passage 40 side and closing the on-off valve 12 [Step S26], the switch 24 is set to the atmosphere immediately before the negative pressure introduction period started from the execution of Step S26. While switching to the open passage 27 side, the on-off valve 12 is opened [step S28].

  When the switch 24 is switched to the negative pressure introduction passage 40 in step S26, negative pressure is introduced from the evaporative gas discharge device such as the communication passage 14 and the canister 20 through the switch 24 (in other words, not through the orifice hole 38). Since the fluid flows into a portion of the passage 40 provided with the pressure sensor 34, the pressure detected by the pressure sensor 34 changes greatly. Thereafter, as the negative pressure is introduced by the negative pressure pump 28, the pressure detected by the pressure sensor 34 decreases. When step S26 is executed in this way, the portion indicated by the hatched area in FIG. 6 is in a negative pressure state. In the example of FIG. 5, the switch 24 is switched to the negative pressure introduction passage 40 side at each time point of time t16, t20, t24, t28, and suddenly increases to the pressure P12 (or a pressure in the vicinity thereof) with this switching. You can see that

  Further, when the switch 24 is switched to the atmosphere release passage 27 side in step S28, the fluid flowing into the portion having the pressure sensor 34 in the negative pressure introduction passage 40 always passes through the orifice hole 38, and the negative pressure. Since the introduction of the negative pressure by the pump 28 continues, the pressure detected by the pressure sensor 34 does not change much. Therefore, when step S28 is executed, a portion indicated by hatching in FIG. 7 (that is, only the negative pressure introduction passage 40) is in a negative pressure state. In the example of FIG. 5, the period of switching to the atmosphere release passage 27 side corresponds to each period from time t18 to time t20, from time t22 to time t24, from time t26 to time t28, and from time t30 to time t32. .

4, the measured pressure is detected by the pressure sensor 34 when the negative pressure introduction period starting from the execution of step S26 has elapsed (step S30), and if the obtained measured pressure is lower than the reference pressure (step S32). YES), the number of “no leak” is increased [step S34]. The actually measured pressure in step S30 corresponds to “pressure in the evaporation gas discharge device”.
On the other hand, if the actually measured pressure obtained is higher than the reference pressure (NO in step S32), the number of “leak” is increased [step S50]. Steps S26 to S34 and S50 described above are repeated until either one of the number of “no leak” and the number of “leak” reaches the determination end number [step S36].

  In the example of FIG. 5, the negative pressure introduction period Ta (from time t16 to time t20) is waited, and the actually measured pressure is detected at time t20. The actually measured pressure detected is the pressure P22, which is lower than the reference pressure P16, so that it is determined that there is no leak in the first detection. Since this is the first time of “no leak”, “None (1)” is shown in FIG.

  The above-described processing from time t16 to time t20 is similarly repeated from time t20 to time t24, from time t24 to time t28, and from time t28 to time t32. The obtained measured pressures are pressure P14 (> P16), pressure P24 (<P16), and pressure P18 (<P16) in order. For this reason, the determination results are also the first “with leak”, the second with “no leak”, and the third with “no leak”. FIG. 5 shows “Yes (1)”, “No (2)”, It is expressed as “Nothing (3)”. Since the number of “no leak” has reached the number of determination end times (three times) at time t32, the processing of steps S26 to S34 and S50 (hereinafter simply referred to as “repetition processing”) is completed.

  Returning to FIG. 4, when one determination result reaches a predetermined result in step S <b> 36 (YES), the switch 24 is switched to the atmosphere release passage 27 side in order to temporarily return the pressure in the evaporative gas discharge device to almost atmospheric pressure. The negative pressure pump 28 is temporarily stopped and then driven again [step S38]. The length of the period during which the negative pressure pump 28 is stopped (from the time t32 to the time t34 in the example of FIG. 5) can be arbitrarily set, but corresponds to, for example, 30 seconds.

  After returning the pressure in the evaporation gas discharge device to almost atmospheric pressure, the pressure sensor 34 detects the reference pressure [step S40]. However, the detection of the reference pressure is performed after the negative pressure to be introduced is stabilized as in step S20. In the example of FIG. 5, the pressure returns to the pressure P10 from the time t32 to the time t34, but decreases to the pressure P20 at the time t36 after waiting for the standby period Tc (for example, 20 seconds or 50 seconds). In this example, the pressure P20 becomes the reference pressure. Note that the length of the waiting period Tc is set appropriately in consideration of the temperature, atmospheric pressure, and the like. The same length as the waiting period Tb described above may be set, or a different length may be set.

After detecting the reference pressure, a difference value between the reference pressure and the reference pressure detected in step S20 is obtained. If the difference value thus obtained is out of the allowable range (NO in step S42), it is affected by fluctuations in atmospheric pressure. In this case, since the determination result already made may be inappropriate, the negative pressure pump 28 is stopped, and after waiting for a standby period (for example, 2 hours) to perform re-diagnosis [step S44]. The process is executed again from step S16.
An appropriate value is set in the allowable range according to the type of the fuel 18, the capacity of the fuel tank 16, the temperature, the atmospheric pressure, and the like. For example, 1 [KPa] and 2 [KPa] are applicable. When executing again from step S16, both the number of “no leak” and the number of “leak” are initialized (that is, set to zero).

On the other hand, if the difference value is within the allowable range in step S42 (YES), the average value of the actually measured pressures for the determination result that has reached the determination end count is obtained in step S36 [step S52]. In the example of FIG. 5, since the number of “no leak” has reached the number of determination end times (three times), the average value Pav is based on the actually measured pressures (P22, P24, P18) when the “no leak” is determined. Ask for. In this example, it is obtained by Pav = (P22 + P24 + P18) / 3.
When the number of “leak” has reached the determination end number, the average value Pav is obtained based on the actually measured pressure for the number of determination end times determined to be “leak”.

  Based on the average value thus obtained, it is determined whether or not the end condition of the determination process is satisfied [step S54]. The end condition is a condition for determining whether or not the actually measured pressure acquired by the repetitive processing is appropriate. For example, when the number of “no leak” reaches the determination end number, the condition is that the average value Pav is lower than the reference pressure detected in step S40. When the number of “leak” reaches the determination end number The condition is that the average value Pav is higher than the reference pressure detected in step S40.

  If the termination condition is not satisfied (NO in step S54), it can be said that the actually measured pressure obtained by the repetitive processing is inappropriate. Therefore, the negative pressure pump 28 is stopped and a standby period is waited for rediagnosis. Then, [Step S44] is executed again from Step S16.

  On the other hand, when the end condition is satisfied in step S54 (YES), it can be said that the actually measured pressure acquired by the repetitive processing is appropriate. Therefore, the determination result that has reached the number of determination end times in step S36 is the leak diagnosis result. [Step S56]. Then, the negative pressure pump 28 that has been driven so far is stopped [step S58], and the leak determination process is ended. In step S58, the on-off valve 12 is opened as necessary to release the evaporated gas into the intake passage 10. In the example of FIG. 5, since the average value is lower than the reference pressure (Pav <P20), “no leak” is determined as a diagnosis result at time t36. Further, the opening / closing valve 12 is opened from time t38 to time t40, and the evaporated gas is discharged into the intake passage 10.

According to the embodiment described above, the following effects can be obtained.
(1) The leak diagnosis apparatus includes a negative pressure pump 28 corresponding to the negative pressure introducing means, a pressure sensor 34, and an ECU 32 corresponding to the leak diagnosis means (see FIGS. 1 to 4). The leak diagnosing means repeatedly performed the process of detecting the actually measured pressure (that is, the pressure in the evaporation gas discharge device) by the pressure sensor 34 after generating the negative pressure in the evaporation gas discharge device by the negative pressure pump 28 (FIG. 3). Step S26 to Step S36 in FIG. If the detected pressure at each time is lower than the reference pressure, the number of leaks is increased (step S34 in FIG. 4), and if it is higher than the reference pressure, the number of leaks is increased (step S50 in FIG. 4). When any one of the counts reaches the determination end count, the corresponding determination result is determined as a leak diagnosis result (step S56 in FIG. 4). Even if highly volatile fuel is contained in the fuel tank, detection is performed a plurality of times (four times in the example of FIG. 5), and the greater discrimination result is determined as the diagnosis result. Rise. Therefore, regardless of the type of fuel contained in the fuel tank, the presence or absence of leakage can be diagnosed more accurately than before.

(2) The leak diagnosis means (ECU 32) switches to the negative pressure introduction passage 40 when either one of the number of times without leak and the number of times with leak reaches the determination end number (step S36 in FIG. 4). While detecting a pressure (step S38, S40 of FIG. 4), the average value was calculated | required by averaging the measured pressure for the frequency | count of determination completion (step S52 of FIG. 4). Only when the average value and the reference pressure have a certain relationship (YES in step S54 in FIG. 4), the leakage diagnosis result is determined (step S56 in FIG. 4). Even if the diagnostic environment changes, the presence or absence of leakage is diagnosed based on the reference pressure after repeated processing, so that the diagnostic accuracy can be improved.

(3) The leak diagnosis means (ECU 32) introduces a negative pressure into the evaporation gas discharge device after either one of the number of times without leak and the number of times with leak has reached the determination end number (step S36 in FIG. 4). In this state, the reference pressure was detected (step S40 in FIG. 4). When the difference value between the reference pressure and the reference pressure (predetermined pressure) is outside the allowable range (NO in step S42 in FIG. 4), re-diagnosis is performed. Accordingly, since the leak diagnosis result is determined under a stable diagnosis environment, the accuracy of the leak diagnosis can be further increased.

(4) The leak diagnosis means (ECU 32) stores in the storage device a first data table (Table 1) that defines the relationship between both the pressure and temperature and the negative pressure introduction period, and inputs the pressure and temperature. Based on the determination of the negative pressure introduction period (step S14 in FIG. 3), the actually measured pressure was detected (step S30 in FIG. 4). Thus, since the appropriate length of the negative pressure introduction period is set, the accuracy of leak diagnosis can be further increased.

(5) The leak diagnosis means (ECU 32) stores in the storage device a second data table (Table 2) that defines the relationship between the capacity of the fuel tank 16 and the number of determination completion times, and inputs the capacity of the fuel tank 16 After determining the number of times of determination based on (step S14 in FIG. 3), the measured pressure was detected (step S30 in FIG. 4). In this way, since an appropriate number of determination end times is set, the accuracy of leak diagnosis can be further increased.

[Other Embodiments]
As mentioned above, although the best form for implementing this invention was demonstrated, this invention is not limited to the said form at all. In other words, the present invention can be implemented in various forms without departing from the gist of the present invention. For example, the following forms may be realized.

(1) In the above-described embodiment, the relationship between both the atmospheric pressure and the temperature and the negative pressure introduction period is defined (see Table 1). Instead of this form, only the relationship between the atmospheric pressure and the negative pressure introduction period may be defined, or only the relationship between the temperature and the negative pressure introduction period may be defined. In the example of Table 1, for example, the former corresponds to a one-column portion where the atmospheric pressure is 620 to [hPa], and the latter corresponds to a one-row portion where the temperature is 25 to [° C.], for example. The same applies to the other one column portion and the other one row portion. Even in these cases, an appropriate negative pressure introduction period can be set even if any one of the atmospheric pressure and the air temperature changes, so that it is possible to further improve the accuracy of the leak diagnosis.

(2) In the above-described embodiment, the leakage diagnosis is performed by executing a program stored in the ROM (storage device) of the ECU 32 (see FIGS. 3 and 4). Instead of this form, a leak diagnosis may be performed by an external device other than the ECU 32. The external device can receive signals and information measured by the pressure sensor 34, the temperature sensors 26, 36, 42, etc., and can operate the switch 24, the negative pressure pump 28, etc. by transmitting the signals. It is only necessary to be able to execute the procedure of the leak determination process shown in FIGS. In addition, the leak determination process may be configured so that equivalent processing can be performed by hardware regardless of the configuration in which the CPU executes the program. In any of these cases, it is possible to diagnose the presence or absence of a leak in a vehicle or device that is not equipped with the ECU 32 described in the embodiment.

(3) In the above-described embodiment, the negative pressure introduction period is set before the negative pressure pump 28 is driven in order to detect the reference pressure (see step S14 in FIG. 3). Instead of (or in addition to) this form, the negative pressure introduction period may be set each time the actually measured pressure is detected in the repeated process as indicated by a two-dot chain line in FIG. 3 (step S24 in FIG. 3). ). This negative pressure introduction period has a length set according to Table 1 based on the temperature and the atmospheric pressure as in step S14. Even if there is a change in temperature or pressure during the diagnosis, it is possible to more accurately detect the actually measured pressure at each time. Therefore, it is possible to further improve the accuracy of leak diagnosis.

(4) In the above-described embodiment, when the difference value between the reference pressure and the reference pressure is out of the allowable range regardless of the number of times the repetitive process is executed (NO in step S42 in FIG. 4), within the allowable range Even if the end condition is not satisfied (NO in step S54 in FIG. 4), the process is repeated after waiting for the standby period (see steps S42 and S44 in FIG. 4). ). Instead of this form, an upper limit may be set for the number of executions of the repetitive processing. In this case, when the number of executions of the repetitive process reaches the upper limit value, the diagnosis result may be determined and the process may be ended, or the diagnosis result may not be determined and the process may be ended. When the diagnosis result is determined and the process is terminated, the result of reaching one determination result in step S36 is the result of the continuous result a plurality of times (for example, twice or three times), or the result of one determination in step S36. As a result of the larger number of times reaching the upper limit, the leakage diagnosis result is determined according to the larger number of “no leak” and “leak” times obtained until the upper limit is reached (FIG. 4). Step S56). In any case, since the diagnosis result of the leak is determined after determining a large number of times, the accuracy of the leak diagnosis can be improved as compared with the conventional case.

(5) In the above-described embodiment, the reference pressure detected when the standby period elapses after the negative pressure pump 28 starts to introduce the negative pressure into the evaporation gas discharge device is used as the “predetermined pressure” (FIG. 3). (See Steps S16 to S20). Instead of this form, a constant pressure value (for example, 700 [hPa]) or a reference pressure detected before the previous time may be used as the “predetermined pressure”. Even when these pressures are used as “predetermined pressures”, the determination of “no leak” or “leak” can be performed appropriately, so that the accuracy of leak diagnosis is increased.

It is a figure which represents typically the structural example which implement | achieves this invention. It is a figure which represents typically the structural example which implement | achieves this invention. It is a flowchart showing the example of a procedure of a leak determination process. It is a flowchart showing the example of a procedure following FIG. It is a time chart showing the time-dependent change in the determination process. It is a figure explaining the state at the time of negative pressure introduction. It is a figure explaining the state at the time of air release.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intake passage 12 On-off valve 14 Connection passage 16 Fuel tank 18 Fuel 20 Canister 22 Common passage 24 Switch 25 Cooling passage 26 Temperature sensor 27 Atmospheric release passage 28 Negative pressure pump (negative pressure introduction means)
30 diagnostic module 32 electronic control unit (ECU; leak diagnostic means)
34 Pressure sensor 36 Temperature sensor 38 Orifice hole 40 Negative pressure introduction passage 42 Temperature sensor Ta Negative pressure introduction period Tb, Tc Standby period

Claims (5)

An evaporative gas discharge apparatus configured to discharge an evaporative gas vaporized by fuel in a fuel tank to an intake passage of an internal combustion engine, wherein the evaporative gas leak diagnosis apparatus diagnoses the presence or absence of the evaporative gas leak,
A negative pressure introducing means for generating a negative pressure in the evaporation gas releasing device;
A pressure sensor for detecting the pressure in the evaporation gas release device;
Leak diagnostic means for diagnosing the presence or absence of the leak of the evaporative gas,
The leak diagnosis means includes
(1) After generating a negative pressure in the evaporation gas discharge device by the negative pressure introducing means, the pressure in the evaporation gas discharge device is detected by the pressure sensor,
(2) If the pressure detected in (1) is lower than the predetermined pressure, increase the number of leaks, if higher, increase the number of leaks,
(3) The process of (1) and (2) is repeated until either one of the number of times without leak and the number of times with leak reaches the determination end number consisting of two or more natural numbers,
(4) When one of the number of times without leak and the number with leak reaches the determination end number, the leak diagnosis apparatus for evaporative gas determines the determination result that has reached the determination end number as the leak diagnosis result . The apparatus for diagnosing evaporative gas leakage according to claim 1,
The leak diagnostic means detects the reference pressure by a pressure sensor when either one of the number of times without leak or the number of leaks reaches the number of determination completion, and an average obtained by averaging the pressures for the number of determination completion A leak diagnosis apparatus for evaporative gas that determines a diagnosis result of leak based on a value and the reference pressure. The apparatus for diagnosing evaporative gas leakage according to claim 1 or 2,
The leak diagnosis means detects a reference pressure by a pressure sensor when either one of the number of times of no leak and the number of leaks reaches the determination end number, and a difference value between the reference pressure and the predetermined pressure is out of an allowable range. In this case, an evaporative gas leak diagnosis apparatus that performs (1) to (4) again. The evaporative leak diagnostic apparatus according to any one of claims 1 to 3,
A storage device that stores a first data table that defines a relationship between one or both of atmospheric pressure and temperature and a negative pressure introduction period;
The leak diagnosis unit is an evaporative gas leak diagnosis apparatus that determines a negative pressure introduction period based on the first data table when one or both of atmospheric pressure and temperature is input. The evaporative leak diagnosis apparatus according to any one of claims 1 to 4,
A storage device for storing a second data table defining the relationship between the capacity of the fuel tank and the number of times of determination completion;
The leak diagnosis unit is an evaporative gas leak diagnosis apparatus that determines the number of times of determination end based on the second data table when the capacity of the fuel tank is input.

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