JP2001193579A - Fault diagnostic device for fuel vapor purge system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fault diagnostic device for fuel vapor purge system capable of avoiding favorably misdiagnosis originating from a change in tank internal pressure due to a running state of vehicle and outside temperature to secure high diagnosis accuracy. SOLUTION: This fault diagnostic device for fuel vapor purge system introduces a negative pressure of an intake passage 3 into a purge path for sealing it to diagnose whether there is a leak abnormality in the path or not on the basis of a changing state of internal pressure in the path after sealing. At that time, the fault diagnosis system prohibits at least a part of the fault diagnosis if the running state of vehicle switches from climbing/descending running to flat running.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis system for a fuel vapor purge system for purging and processing fuel vapor generated in a fuel tank into an intake system of an internal combustion engine.

[0002]

2. Description of the Related Art As is well known, in a fuel vapor purge system mounted on a vehicle, fuel vapor generated in a fuel tank is introduced into a canister through a fuel vapor introduction passage.
While being collected by the canister, the collected fuel vapor is discharged (purged) from the canister to the intake passage through a purge passage as appropriate while introducing air into the canister.

In addition, the failure of such a fuel vapor purge system, that is, the presence or absence of leakage due to a hole in a purge passage (including a fuel tank, a fuel vapor introduction passage, a canister, and a purge passage) is determined. Devices for diagnosing are also well known. In many of the apparatuses, for example, a negative pressure in an intake passage during operation of an internal combustion engine is introduced into a purge passage through a purge passage, and then the air passage is closed once. When the value is larger than the value, it is diagnosed that the failure has occurred.

[0004]

Incidentally, the temperature of the fuel in the fuel tank tends to fluctuate based on the running state and the environmental state of the vehicle.

[0005] That is, in a vehicle, the fuel tank is often located at a position distant from the engine and below the fuel tank so that the exhaust system of the internal combustion engine passes therethrough.
Therefore, the fuel tank is heated by heat of the exhaust system or the atmosphere, or radiant heat from the road surface, and the temperature of the fuel in the fuel tank changes. When the fuel temperature changes under the influence of the exhaust gas temperature and the outside air temperature, the pressure in the fuel tank (tank pressure) also changes in accordance with the temperature change. Such a change in the temperature of the exhaust system increases when the running state of the vehicle is switched from uphill running to flat running. Further, when the traveling environment of the vehicle switches between the sun and the shade, the outside air temperature and the radiant heat from the road surface also change greatly. Therefore, when the running state of the vehicle is switched from uphill running to flat running, or when the running environment is switched between sunny and shaded, the temperature change of the fuel in the fuel tank and the change of the tank internal pressure are also increased.

If such a change in the tank internal pressure occurs during the above-described failure diagnosis, the pressure in the purge path fluctuates irrespective of the presence or absence of leakage in the same path, resulting in deterioration of the diagnosis accuracy. Become.

As a failure diagnosis device for a fuel vapor purge system, a technique for detecting the amount of fuel vapor in a fuel tank by a pressure detection sensor and prohibiting failure determination when it is determined that the amount of fuel vapor is large. (Japanese Patent No. 2635270) and a technique in which a temperature rise in a fuel tank is detected based on the number of times the internal pressure of the fuel tank fluctuates above a predetermined pressure, and failure diagnosis is prohibited when the count value exceeds a predetermined value. (JP-A-10-238420) has been proposed.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to appropriately avoid erroneous diagnosis caused by a change in tank internal pressure caused by a running state or an environmental state of a vehicle. It is an object of the present invention to provide a failure diagnosis device for a fuel vapor purge system that can ensure high diagnostic accuracy.

[0009]

The means for achieving the above object and the effects thereof will be described below. According to the first aspect of the present invention, an internal combustion engine is mounted on a vehicle and collects fuel vapor generated in a fuel tank in a canister, and the collected fuel vapor passes through a purge path including the fuel tank. A fuel vapor purge system configured to purge the air into the intake passage, and providing a differential pressure between the internal pressure and the external pressure of the purge passage to close the purge passage and to detect a leak in the purge passage based on a change in the internal pressure measured. A failure diagnosis device for a fuel vapor purge system comprising: a diagnosis unit that diagnoses whether there is an abnormality; and calculating a predetermined temperature change of the fuel in the fuel tank based on a change in a running state of the vehicle or a change in an outside air temperature. A temperature change calculation unit; and a diagnosis prohibition unit that prohibits at least a part of the diagnosis by the diagnosis unit when a predetermined temperature change is calculated by the temperature change calculation unit. The gist of the door.

According to the above configuration, the temperature of the fuel in the fuel tank changes with a change in the running state of the vehicle or a change in the outside air temperature. Since at least a part of the diagnosis can be prohibited, erroneous diagnosis due to a pressure change in the purge path can be suitably avoided, and high diagnostic accuracy can be secured.

According to a second aspect of the present invention, in the failure diagnosis device for a fuel vapor purge system according to the first aspect, the temperature change calculating means switches the running state of the vehicle from uphill running to flat running. The point is to calculate a predetermined temperature change of the fuel based on

According to the above configuration, at least a part of the failure diagnosis is prohibited when the traveling state of the vehicle is switched from uphill traveling to flat traveling and when the traveling state of the vehicle is switched from downhill traveling to flat traveling. So that
Even when the exhaust gas temperature changes based on the change in the running state and the change in the pressure in the purge path changes, erroneous diagnosis caused by the change in the pressure in the purge path is preferably avoided, and high diagnosis accuracy is secured. Will be able to

According to a third aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to the second aspect, the temperature change calculating means is configured to detect a temperature of the vehicle based on a predetermined change in the exhaust gas temperature of the internal combustion engine. The gist of the present invention is to determine that the traveling state has been switched from uphill traveling to flat traveling.

According to the above configuration, when a predetermined temperature change occurs in the exhaust gas temperature while the vehicle is running, a predetermined temperature change of the fuel in the fuel tank occurs, and the pressure in the purge passage changes due to the change. In this case, at least a part of the failure diagnosis is prohibited.

According to a fourth aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to the second aspect, the temperature change calculating means determines that a difference between a running resistance of the vehicle and a running resistance in flat steady running is obtained. The gist of the present invention is to determine that the vehicle has traveled uphill or downhill based on whether or not the value is equal to or more than a predetermined value.

According to the above configuration, when the difference between the running resistance of the vehicle and the running resistance in flat steady running is equal to or more than the predetermined value, the predetermined temperature change of the exhaust gas temperature occurs, and the fuel in the fuel tank is changed. When a predetermined temperature change occurs and the change causes a change in the pressure in the purge path, at least a part of the failure diagnosis is prohibited.

According to a fifth aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to any one of the second to fourth aspects, the diagnosis prohibiting means includes: The point is that at least a part of the failure diagnosis is prohibited until a predetermined time elapses after the switching to.

According to the above configuration, since the tank internal pressure changes after a change in the exhaust gas temperature based on a change in the running state of the vehicle, the failure diagnosis is performed until a predetermined time elapses after switching from uphill running to flat running. Prohibition stabilizes the tank internal pressure. For this reason, erroneous diagnosis due to a change in pressure in the purge path can be more appropriately avoided, and higher diagnostic accuracy can be secured.

According to a sixth aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to the first aspect, the diagnosis prohibiting means is provided until a predetermined time elapses after a predetermined temperature change of the outside air temperature. States that at least part of the failure diagnosis is prohibited.

According to the above configuration, since the tank internal pressure changes after a change in the outside air temperature, the failure diagnosis is prohibited until a predetermined time elapses from the occurrence of the predetermined temperature change in the outside air temperature. Becomes stable. For this reason, erroneous diagnosis due to a change in pressure in the purge path can be more appropriately avoided, and higher diagnostic accuracy can be secured.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A fuel vapor purge system according to a first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the overall configuration of a fuel vapor purge system according to this embodiment. The fuel vapor purge system is mounted on a gasoline engine mounted on a vehicle. The fuel vapor purge system is roughly divided into a canister 2 for collecting fuel vapor generated in a fuel tank 1, and the collected fuel vapor is supplied to an engine 4. A purge passage 11 for purging the passage 3, an air introduction passage 17 for introducing air into the canister 2 when performing the purge, and the like are provided.

Inside the canister 2, there are a main chamber 22 and a sub chamber 23 separated by a partition plate 21.
There is formed a diffusion chamber 24 that communicates with the diffusion chambers 2 and 23. Further, the inside of the main chamber 22 and the sub chamber 23 is filled with an adsorbent (for example, activated carbon) for adsorbing fuel vapor.

A purge passage 11 communicating with the intake passage 3 is connected to a portion of the canister 2 on the main chamber 22 side. The purge passage 11 is provided with a purge control valve 11a for adjusting the cross-sectional area of the passage 11. The opening of the purge control valve 11a is set based on the operating state of the engine. Therefore, the intake passage 3
The amount of purged fuel vapor (purge flow rate) is also controlled in accordance with the operating state.

One end of a fuel vapor introduction passage 13 is connected to a portion of the canister 2 on the main chamber 22 side via a throttle 12. The other end of the fuel vapor introduction passage 13 is connected to the fuel tank 1 via a float valve 13 a for preventing liquid fuel from flowing into the passage 13.

Further, another float valve 1 is provided in the fuel tank 1.
A differential pressure valve 14b is mounted via 4a, and this valve 14b is connected to the canister 2 via a breather passage 14. The differential pressure valve 14b opens only when the internal pressure of the fuel tank 1 becomes higher than the internal pressure of the canister 2 by a predetermined pressure or more during refueling. By opening the differential pressure valve 14b, the fuel vapor in the fuel tank 1 is introduced into the main chamber 22 through the breather passage 14.

An air valve 16 is attached to a portion of the canister 2 on the side of the sub-chamber 23 via a pressure shut-off valve 15. The air valve 16 is attached to the air cleaner 3 of the intake passage 3.
The air introduction passage 17 leading to a and the air discharge passage 18 having one end open to the atmosphere are connected to each other.

The atmosphere valve 16 is composed of two diaphragm valves 16a and 16b having different functions. When performing the purge, the first diaphragm valve 16a opens when the pressure in the purge passage 11 becomes lower than the atmospheric pressure by a predetermined pressure or more. Hereinafter, in this specification, a pressure lower than the atmospheric pressure is referred to as negative pressure, and a pressure higher than the atmospheric pressure is referred to as positive pressure. With the opening of the first diaphragm valve 16a, the atmosphere is introduced into the sub chamber 23 through the atmosphere introduction passage 17. On the other hand, the second diaphragm valve 16b opens when the internal pressure of the sub chamber 23 becomes a positive pressure equal to or higher than a predetermined pressure. By opening the second diaphragm valve 16b, the atmosphere discharge passage 18 is opened.
The air in the sub-chamber 23 is discharged to the atmosphere.

The pressure shut-off valve 15 is normally kept open, while being closed during a failure diagnosis, which will be described later, to shut off the communication between the sub-chamber 23 and the outside (atmosphere).

In the fuel vapor purge system thus configured, when fuel vapor is generated in the fuel tank 1, the fuel vapor in the fuel tank 1 is introduced into the canister 2 through the fuel vapor introduction passage 13 and the throttle 12. . Further, at the time of refueling, the differential pressure valve 14b is also opened, so that the fuel vapor in the fuel tank 1 is introduced into the canister 2 not only through the fuel vapor introduction passage 13 but also through the breather passage 14. Then, the fuel vapor thus introduced into the canister 2 is once adsorbed by the adsorbent in the main chamber 22 or the sub chamber 23.

On the other hand, during operation of the engine, the purge control valve 1
When the valve 1a is opened, a negative pressure of the intake passage 3 is introduced into the purge passage 11, and the first diaphragm valve 16a is opened with the introduction of the negative pressure. Is supplied. Then, the fuel vapor in each of the chambers 22 and 23 is released from the adsorbent by this atmosphere, and is purged into the intake passage 3 through the purge passage 11. Further, the fuel vapor is mixed with the intake air in the intake passage 3 and supplied to a cylinder (not shown).
In the cylinder, the fuel is burned together with the fuel injected from the fuel injection valve 52.

The failure diagnosis apparatus for the fuel vapor purge system includes the purge control valve 11a, the pressure shutoff valve 15
A pressure sensor 31 provided at an upper portion of the fuel tank 1 for detecting its internal pressure (tank internal pressure); a detection signal of the pressure sensor 31 is appropriately taken in at the time of failure diagnosis; And an electronic control unit (ECU) 40 for controlling the ECU. In the present embodiment, a pressure sensor that detects a relative pressure based on the atmospheric pressure is used. In addition, the failure diagnosis apparatus includes a vehicle speed sensor 32 for detecting a traveling speed (vehicle speed) of the vehicle, an engine 4 and an engine 4 in addition to the pressure sensor 31.
An exhaust gas temperature sensor 6 for detecting the temperature of the exhaust gas is provided. The vehicle speed sensor 32 is provided near an axle (not shown), and outputs a signal corresponding to the rotation speed of the axle. The ECU 40 receives this signal and calculates the vehicle speed based on the signal. The exhaust gas temperature sensor 6 is disposed immediately after a catalyst (not shown) provided in the exhaust passage 5 of the engine 4 and outputs a signal corresponding to the exhaust gas temperature.

In this failure diagnosis apparatus, a path (hereinafter, referred to as a “portion”) constituted by a part into which the fuel vapor is introduced, such as the inside of the fuel tank 1, the fuel vapor introduction passage 13, the breather passage 14, the inside of the canister 2, and the purge passage 11. These are collectively referred to as a “purge path”), and the presence or absence of a leak abnormality due to a hole in the pipe, a detached pipe, or the like is determined as a diagnosis target. Specifically, as a diagnosis method, the presence or absence of a leakage abnormality in the purge path is diagnosed based on the pressure behavior in the purge path after the inside of the purge path is sealed under a predetermined negative pressure.

Hereinafter, a procedure for performing a fault diagnosis by such a fault diagnosis apparatus will be described with reference to a timing chart shown in FIG. This failure diagnosis is based on the conditions that the tank internal pressure is stable, that the predetermined time has not elapsed since the start of the engine, that there is no abnormality in the pressure sensor 31, and that the purging process is being performed. That is, it is executed when all the preconditions such as that the purge control valve 11a is opened at a predetermined opening degree based on the operation state are satisfied.

When these preconditions are satisfied, first, the pressure blocking valve 15 is driven to close by the ECU 40 (time t10), and the negative pressure in the intake passage 3 is introduced into the purge passage. As a result, the pressure in the purge path (= tank internal pressure) gradually decreases (time t10 to t2).
0).

Next, when the tank internal pressure reaches the target negative pressure PA (time t20), the purge control valve 11 is controlled by the ECU 40.
a is forcibly closed. As a result, the inside of the purge path is closed. If the tank internal pressure does not decrease to the target negative pressure PA even after a predetermined time has elapsed after the introduction of the negative pressure, it is diagnosed that a relatively large leak has occurred in the purge path. You.

As described above, the pressure in the purge path is low (negative pressure).
When the tank is closed in a state where it is placed below, the tank internal pressure temporarily decreases to the predetermined pressure PA or lower, but the fuel in the same path (for example, the fuel in the fuel tank 1 or the adsorbent of the canister 2 is adsorbed by the fuel). The fuel which starts to rise gradually starts to evaporate (after time t21). The failure diagnosis, that is, the determination of the presence or absence of a leak abnormality in the purge path is performed based on the increasing speed of the tank internal pressure at this time.

That is, [normal judgment] When the increasing speed of the tank internal pressure is less than a predetermined value (normal judgment value), the tank internal pressure is increased only by the evaporation of the fuel in the purge passage, and the tank leaks to the same passage. It is determined that there is no abnormality. [Abnormality determination] When the rising speed of the tank internal pressure is equal to or higher than a predetermined value (abnormality determination value), the tank internal pressure rises due to the rise of fuel in the same route and the inflow of air into the same route. Therefore, it is determined that there is a leak abnormality in the same route. [Determination suspension] When the rising speed of the tank internal pressure is equal to or higher than the normal determination value and lower than the abnormality determination value, it is difficult to reliably determine whether or not there is a leak abnormality. You. Is determined.

Incidentally, in order to perform such a failure diagnosis with high accuracy, a negative pressure is introduced to seal the purge path,
Until the failure diagnosis based on the increasing speed of the tank internal pressure is completed, the temperature in the fuel tank 1, that is, the saturated vapor pressure determined by the temperature needs to be kept substantially constant. However, as described above, when the running state of the vehicle is switched from uphill running to flat running, the fuel temperature in the fuel tank 1 changes due to the effect of the exhaust (catalyst) temperature. When the fuel temperature fluctuates in this manner, the tank internal pressure also fluctuates. As a result, the rate of increase in the tank internal pressure does not accurately reflect the presence / absence of a leak abnormality in the purge path, leading to erroneous diagnosis. There is a risk.

Hereinafter, the change in the running state of the vehicle, the change in the fuel temperature and the change in the tank internal pressure will be described with reference to FIG. In the figure, (a) shows a change in altitude of the traveling road, (b) shows a change in exhaust (catalyst) temperature,
(C) shows the transition of the fuel temperature in the fuel tank 1, and (d) in the figure shows the transition of the tank internal pressure.

As shown in the figure, for example, when the running state of the vehicle is switched from flat running on lowland to uphill running,
Since the engine load increases and the fuel injection amount increases, and the exhaust temperature of the engine increases accordingly, the amount of heat applied to the fuel tank 1 increases due to the increase in the exhaust temperature. As a result, the balance between the amount of heat absorption and the amount of heat radiation in the fuel tank 1 is temporarily lost, and the fuel tank 1
The temperature rises later than the exhaust temperature due to heat from the exhaust system (including the exhaust itself) of the engine and the road surface. Then, the fuel temperature gradually rises with the temperature rise, and the saturated vapor pressure of the fuel in the fuel tank 1 rises, so that the tank internal pressure likewise rises (after time t32).

Next, when the running state of the vehicle is switched from uphill running at high altitude to flat running, the fuel injection amount decreases and the exhaust temperature rises, and thereafter the exhaust temperature drops to almost the same value as during flat running. And stabilize. The increase in the tank internal pressure will continue for a while because the fuel temperature will continue to rise even after the running state of the vehicle has been switched from uphill running to flat running. Then, the temperature rise of the fuel tank 1 is reduced, and the fuel tank 1 is stabilized at the same value as that during the flat running. Therefore, the fuel temperature converges to substantially the same value as during flat running, and the tank internal pressure converges to a substantially constant value (time t33 to t35). In this period, since the altitude of the traveling road is high, the magnitude of the atmospheric pressure itself decreases, and the tank internal pressure has an apparently increased value with respect to the tank internal pressure at lowland.

Further, when the running state of the vehicle is switched from flat running at high altitude to downhill running, the engine load is reduced, the fuel injection amount is greatly reduced, and the exhaust temperature of the engine is lowered accordingly. As the exhaust gas temperature decreases, the amount of heat applied to the fuel tank 1 decreases. As a result, the balance between the amount of heat absorption and the amount of heat radiation in the fuel tank 1 is temporarily lost, and the temperature of the fuel tank 1 falls later than the fall of the exhaust gas temperature. Then, the fuel temperature gradually decreases with this temperature decrease, and the saturated vapor pressure of the fuel in the fuel tank 1 decreases, so that the tank internal pressure also decreases (time t).
36 onwards).

Next, when the running state of the vehicle is switched from downhill running to flat running at low altitude, the fuel injection amount increases and the exhaust gas temperature falls, and after that, the exhaust temperature becomes almost the same value as during flat running. Ascends and stabilizes. The decrease in the tank internal pressure continues for a while because the fuel temperature continues to decrease even after the traveling state of the vehicle is switched from downhill traveling to flat traveling. Then, the temperature of the fuel tank 1 decreases, and the fuel tank 1 rises to almost the same value as that during flat running and stabilizes. Therefore, the fuel temperature converges to substantially the same value as during flat running, and the tank internal pressure converges to a substantially constant value (time t37 to t39). In this period, since the altitude of the traveling road is low, the magnitude of the atmospheric pressure itself increases, and the tank internal pressure has an apparently reduced value with respect to the tank internal pressure at high altitude.

Next, a description will be given of the influence on the diagnosis accuracy when the above-mentioned failure diagnosis is performed when the tank internal pressure changes due to such a change in the vehicle speed. First, when the diagnosis is performed when the traveling state of the vehicle is flat traveling on a lowland, the fuel temperature in the fuel tank 1 has a substantially constant value. Therefore, the fuel temperature does not affect the tank internal pressure, and the atmospheric pressure becomes a normal value at lowland, and therefore,
There is no risk of erroneous diagnosis.

On the other hand, when the running state of the vehicle is switched from the uphill running to the flat running at high altitude during the execution of the failure diagnosis processing, as shown by a broken line in the period from time t34 to t35 in FIG. The tank internal pressure rises more than when the running state is flat running on lowland (the change in tank internal pressure in this case is indicated by a solid line in FIG. 4D). This is because an increase in the fuel temperature and a decrease in the value of the atmospheric pressure affect the tank internal pressure.

As a result, despite the fact that there is no leakage abnormality in the purge path, there is a possibility that the abnormality is erroneously diagnosed as having the abnormality because the tank internal pressure rises at a high rate. On the other hand, when the traveling state of the vehicle is switched from downhill traveling to flat traveling on lowland during the execution of the failure diagnosis process, the tank is changed from the time t37 to the time t39 in FIG. The rising speed of the internal pressure is lower than when the traveling state is flat traveling at high altitude (the change in the tank internal pressure in this case is indicated by a solid line in FIG. 4D). This is because a decrease in the fuel temperature and an increase in the value of the atmospheric pressure affect the tank internal pressure.

As a result, despite the fact that there is a leak abnormality in the purge path, there is a possibility that the abnormality is erroneously diagnosed as having no such abnormality because the rising speed of the tank internal pressure is low. Therefore, in the failure diagnosis processing by the diagnostic device of the present embodiment, in order to prevent erroneous diagnosis, as shown in FIG. 3, during the period TB during which the exhaust gas temperature change per time | ΔTemp1 | <B ° C. (B> 0) is satisfied. The failure diagnosis is executed, and the failure diagnosis is prohibited during a period TA where the exhaust gas temperature change per time | ΔTemp1 |> A ° C. (A> B).

Hereinafter, the details of the failure diagnosis processing will be described. FIG. 4 is a flowchart showing an execution procedure of the failure diagnosis processing. A series of processing shown in this flowchart is executed by the ECU 40 as an interruption processing every predetermined time (for example, every 65 ms).

In this process, first, at step 10
In 2, it is determined whether or not the diagnosis of the leak abnormality is not completed based on whether or not the diagnosis completion flag is 0. Here, through this processing, when it is determined that there is a leakage abnormality (abnormality determination) or when it is determined that there is no such abnormality (normality determination), it is determined that the diagnosis has been completed. If it is determined in step 102 that the diagnosis completion flag is 0, that is, the diagnosis is not completed, the process proceeds to step 104. If it is determined in step 102 that the diagnosis completion flag is 1, that is, the diagnosis has been completed, the routine exits from this routine and proceeds to normal purge control.

In step 104, it is determined whether or not the introduction of the negative pressure to the purge path has been completed based on whether or not the negative pressure introduction flag is 1. This step 10
If it is determined in step 4 that the introduction of the negative pressure has not been completed, the process proceeds to step 112. If it is determined that the introduction of the negative pressure has been completed, the process proceeds to step 106.

In step 112, it is determined whether or not the aforementioned negative pressure introduction precondition other than the exhaust gas temperature change is satisfied. If a negative determination is made in step 112, the process exits this routine and proceeds to normal purge control. If an affirmative determination is made in step 112, the process proceeds to step 114.

In step 114, change in exhaust gas temperature |
It is determined whether ΔTemp1 | is lower than predetermined temperature B ° C. The predetermined temperature B is for determining whether or not the introduction of the negative pressure may be performed, and is set to a value that hardly affects the increase and decrease of the tank internal pressure. If it is determined in step 114 that the exhaust gas temperature change | ΔTemp1 | is equal to or higher than B ° C., it is determined that there is a risk of erroneous diagnosis, and the process exits this routine and proceeds to normal purge control. If it is determined in step 114 that the exhaust gas temperature change | ΔTemp1 | is less than B ° C., it is determined that there is no risk of erroneous diagnosis, and the process proceeds to step 116.

At step 116, a negative pressure is introduced into the purge path. At the next step 118, a negative pressure introduction flag indicating completion of the negative pressure introduction is set to 1, and the routine exits from this routine. In step 106, the exhaust gas temperature change | Δ
It is determined whether Temp1 | is lower than predetermined temperature A ° C.
The predetermined temperature A is for determining whether or not there is a risk of erroneous diagnosis even if the determination of the presence or absence of a leak abnormality is performed. In this step 106, the exhaust gas temperature change | ΔTemp1
Is less than A ° C., it is determined that there is no risk of erroneous diagnosis, and the routine proceeds to step 108, where the exhaust gas temperature change | ΔTe
If it is determined that mp1 | is equal to or higher than A ° C., it is determined that there is a risk of erroneous diagnosis, and the routine proceeds to step 120.

In step 108, it is determined whether or not the determination of the presence or absence of a leak abnormality has been completed. When it is determined that the determination has been completed, the diagnosis completion flag is set to 1 in the next step 110.

Further, in step 120, the determination of the presence / absence of a leak abnormality is interrupted. Then, in the next step 122, the negative pressure introduction flag is set to 0 and the negative pressure introduction is not completed, and the process exits this routine and proceeds to the normal purge control.

According to the failure diagnosis apparatus of the present embodiment in which the execution of the failure diagnosis is prohibited in the manner described above, the following effects can be obtained. (1) When the traveling state of the vehicle is switched from uphill traveling to flat traveling, and when the traveling state of the vehicle is switched from downhill traveling to flat traveling, at least a part of the failure diagnosis is prohibited. Even if the exhaust gas temperature changes based on a change in the state and the pressure in the purge path changes due to this change, erroneous diagnosis due to the pressure change in the purge path is preferably avoided to ensure high diagnosis accuracy. Will be able to

(2) In particular, when the exhaust temperature change | ΔTemp1 | becomes equal to or higher than the predetermined temperature A ° C. based on the change in the running state of the vehicle, the leak determination after the introduction of the negative pressure into the purge passage is performed. However, when the exhaust temperature rises from the exhaust temperature during flat running, the rise in fuel temperature and the decrease in atmospheric pressure increase the rate of increase in the tank internal pressure, leading to erroneous diagnosis of a leak abnormality or negative pressure on the purge path. In the middle of the leak determination after pressure introduction, when the exhaust temperature drops from the exhaust temperature during flat running, the decrease in fuel temperature and the increase in the atmospheric pressure decrease the rate of increase in the tank internal pressure, and there is no leakage abnormality. It may lead to misdiagnosis. In the present embodiment, the diagnosis is prohibited in such a case, so that the erroneous diagnosis can be more appropriately avoided.

(Second Embodiment) Next, a second embodiment of the failure diagnosis apparatus for a fuel vapor purge system according to the present invention will be described, focusing on differences from the first embodiment. Note that the failure diagnosis device according to the second embodiment includes:
Since it is assumed that the configuration has the same configuration as that described in the first embodiment, the description of the configuration will be omitted.

As described above, when the running state of the vehicle is switched from the uphill running to the flat running during the execution of the failure diagnosis processing, as shown in FIG. 3, the exhaust gas temperature rapidly rises during the uphill running (period TA). The exhaust gas temperature increases, slightly increases or decreases immediately before the end of the uphill traveling (period TB), rapidly decreases in the period TA, and transitions to a period TB in which the exhaust gas temperature during flat traveling on lowland is stabilized to substantially the same value as the exhaust temperature. . At this time,
The tank internal pressure changes similarly after a change in the exhaust gas temperature, and the tank internal pressure converges to a substantially constant value. However, at the end of the period TA during which the exhaust gas temperature rapidly decreases, the tank internal pressure has not yet converged. Absent. Therefore, if the failure diagnosis is prohibited during this period TA and the failure diagnosis is permitted immediately after this period TA, there is a risk of erroneous diagnosis.

When the running state of the vehicle is switched from downhill running to flat running during the failure diagnosis processing, as shown in FIG. 3, the exhaust gas temperature rapidly decreases during downhill running (period TA). A period T which slightly increases or decreases immediately before the end of the downhill traveling (period TB), further increases rapidly during period TA, and stabilizes at the exhaust temperature during flat traveling on lowland.
It changes to B. At this time, the tank internal pressure changes similarly with a delay of the change in the exhaust gas temperature, and the tank internal pressure converges to a substantially constant value.
At the end of A, the tank internal pressure has not yet converged. Therefore, if the failure diagnosis is prohibited during this period TA and the failure diagnosis is permitted immediately after this period TA, there is a risk of erroneous diagnosis.

Therefore, in the second embodiment, a predetermined time C or D sufficient to stabilize the tank internal pressure is set from the point in time when the rise or fall of the exhaust temperature has ceased. The failure diagnosis is prohibited and the predetermined time C
Alternatively, the failure diagnosis is permitted after D.

Hereinafter, the details of the failure diagnosis processing will be described with reference to the flowchart shown in FIG. The processing in FIG. 5 is different from the processing in FIG. 4 in that the processing in step 130 is added between the processing in step 114 and the processing in step 116 in FIG. Therefore, the detailed description is omitted.

That is, in step 114, it is determined whether or not the exhaust gas temperature change | ΔTemp1 | is less than the predetermined temperature B ° C. If it is determined that the exhaust gas temperature change | ΔTemp1 | If so, the process exits this routine and proceeds to the normal purge control. If it is determined in step 114 that the exhaust gas temperature change | ΔTemp1 | is less than B ° C., the process proceeds to step 130.

In step 130, change in exhaust gas temperature |
After ΔTemp1 | falls below the predetermined temperature B ° C., it is determined whether a predetermined time C or D has elapsed. Here, if it is determined that the predetermined time C or D has not elapsed, it is determined that there is a risk of erroneous diagnosis, and the routine is temporarily exited. If it is determined in step 130 that the predetermined time C or D has elapsed, the process proceeds to step 116, and the processing after step 116 is executed.

According to the apparatus of the present embodiment in which the execution of the failure diagnosis is prohibited in the manner described above, in addition to the effects (1) and (2) of the diagnostic apparatus of the first embodiment, (3) ) Failure diagnosis is prohibited during a predetermined time C or D during which the tank internal pressure stabilizes from the point in time when the rise or fall of the exhaust temperature based on the change in the running state of the vehicle is stopped. Diagnosis is allowed. Therefore, even when the exhaust gas temperature changes based on the change in the traveling state and the pressure in the purge path changes due to this change, erroneous diagnosis caused by the pressure change in the purge path is more appropriately avoided, and Diagnostic accuracy can be ensured.

(Third Embodiment) Next, a third embodiment of the failure diagnosis apparatus for a fuel vapor purge system according to the present invention will be described, focusing on differences from the first embodiment. Note that the failure diagnosis device according to the third embodiment includes:
Since it is assumed that the exhaust gas temperature sensor 6 is omitted in the failure diagnosis device described in the first embodiment, the description of the configuration is omitted.

In the first embodiment, the exhaust gas temperature of the vehicle is detected by the exhaust gas temperature sensor 6 and the change of the exhaust gas temperature between the uphill running and the flat running is detected. In the embodiment, the switching between the uphill running and the flat running of the vehicle is detected on the basis of the running resistance in the flat steady running and the running resistance in the uphill running. That is, as shown by the solid line in FIG. 6, the flat running resistance of the vehicle can be obtained from the vehicle speed and the intake air amount Ga per cycle. Also,
The area indicated by the diagonal lines above the flat running resistance is the area of uphill running, and the area indicated by the diagonal lines below the flat running resistance is the area of downhill running. Therefore, the difference between the intake air amount at the current vehicle speed of the vehicle and the intake air amount Ga for the vehicle speed at the flat running resistance, that is, the intake air amount change ΔGa
, It is possible to detect whether the current traveling state is uphill traveling, downhill traveling, or flat traveling.

In the diagnostic device according to the third embodiment, the switch between the uphill running and the flat running is detected based on the vehicle speed, the intake air amount, and the flat running resistance, and based on the intake air amount change ΔGa. Thus, the execution of the failure diagnosis is permitted and prohibited.

FIG. 7 shows a change in the running state of the vehicle, a change in the fuel temperature and a change in the tank internal pressure accompanying the change, and the exhaust (catalyst) temperature in FIG. 3B is replaced by the intake air amount. is there. The amount of intake air in FIG. 7B is the same as that in FIG.
Of the exhaust (catalyst) temperature. FIG.
In the intake air amount of (b), the period TB is a period in which the intake air amount change | ΔGa | <b (b> 0), and the period TB
A is a period in which the intake air amount change | ΔGa |> a (a> b).

In this embodiment, since the running state of the vehicle can be detected in real time based on the vehicle speed and the intake air amount, as shown in FIG.
a is switched to a negative value, that is, a predetermined time E or F sufficient to stabilize the tank internal pressure is set from the point in time when the traveling state of the vehicle is switched from uphill traveling to flat traveling, and the predetermined time E or F is set. During the period, the failure diagnosis is prohibited, and the failure diagnosis is permitted after the predetermined time E or F.

Hereinafter, details of the failure diagnosis processing will be described with reference to a flowchart shown in FIG. In the processing in FIG. 8, the detailed description of the same processing as in FIG. 5 is partially omitted. A series of processing shown in this flowchart is performed at predetermined time intervals (for example, 65
This is executed by the ECU 40 as an interrupt process (every ms).

In this process, if it is determined in step 102 that the diagnosis completion flag is 0, that is, the diagnosis is not completed, it is determined in step 104 whether the introduction of the negative pressure to the purge path is completed. . This step 1
If it is determined in 04 that the introduction of the negative pressure has not been completed, the process proceeds to step 142. If it is determined that the introduction of the negative pressure has been completed, the process proceeds to step 140.

In step 142, it is determined whether or not the above-described negative pressure introduction precondition other than the steady steady running is satisfied. If a negative determination is made in step 142, the process exits this routine and proceeds to normal purge control. If an affirmative determination is made in step 142, the process proceeds to step 144.

In step 144, it is determined whether or not the change in intake air amount | ΔGa | is less than a predetermined value b. The predetermined value b is for determining whether the introduction of the negative pressure may be performed, and is set to a value that hardly affects the increase and decrease of the tank internal pressure. If it is determined in this step 144 that the change in intake air amount | ΔGa | is equal to or greater than the predetermined value b, it is determined that there is a risk of erroneous diagnosis, and this routine is exited.
Proceed to normal purge control. If it is determined in step 144 that the change in intake air amount | ΔGa | is less than the predetermined value b, it is determined that there is no risk of erroneous diagnosis, and the process proceeds to step 146.

In step 146, it is determined whether a predetermined time E or F has elapsed after the intake air amount change | ΔGa | has become less than the predetermined value b. Here, if it is determined that the predetermined time E or F has not elapsed, it is determined that there is a possibility of erroneous diagnosis, and the routine is temporarily exited. If it is determined in step 146 that the predetermined time E or F has elapsed, the process proceeds to step 116, and the subsequent processing is executed.

In step 140, it is determined whether or not the intake air amount change | ΔGa | is less than a predetermined value a. The predetermined value a is for determining whether or not there is a risk of erroneous diagnosis even if the determination of the presence or absence of a leak abnormality is performed. If it is determined in step 140 that the change in intake air amount | ΔGa | is less than the predetermined value a, it is determined that there is no risk of erroneous diagnosis, and the process proceeds to step 108, and the processes after step 108 are executed.

Therefore, according to the apparatus of the present embodiment, the first
In addition to the functions and effects (1) and (2) of the apparatus according to the embodiment, (4) switching between uphill running and flat running of the vehicle is performed by:
The prohibition time of the failure diagnosis can be set based on the vehicle speed and the intake air amount Ga per cycle, and based on the switching point, the exhaust temperature sensor 6 for detecting the exhaust gas temperature can be omitted. Can be simplified, and an increase in cost can be suppressed.

(5) In the period of the predetermined time E or F when the tank internal pressure is stabilized from the time when the change ΔGa in the intake air amount is switched to a negative value, that is, when the running state of the vehicle is switched from the uphill running to the flat running. The failure diagnosis is prohibited, and the failure diagnosis is permitted after the predetermined time E or F. Therefore, even when the exhaust gas temperature changes based on the change in the intake air amount and the pressure in the purge path changes due to this change, erroneous diagnosis caused by the pressure change in the purge path can be more appropriately avoided, and High diagnostic accuracy can be ensured.

(Fourth Embodiment) Next, a fourth embodiment of a failure diagnosis apparatus for a fuel vapor purge system according to the present invention will be described, focusing on differences from the first embodiment. Note that the failure diagnosis device according to the fourth embodiment includes:
In the failure diagnosis device described in the first embodiment, it is assumed that the exhaust gas temperature sensor 6 is omitted and an external air temperature sensor for detecting an external air temperature is provided, so that the description of the configuration is omitted.

As described above, when the running environment of the vehicle is switched between the sun and the shade, the outside air temperature and the radiant heat from the road surface also change, and the heat changes the fuel temperature in the fuel tank. The internal pressure will also change.

Therefore, in the diagnostic device of the fourth embodiment, the failure diagnosis is prohibited during a period in which the fuel temperature changes based on the change in the outside air temperature and the tank internal pressure is unstable.

The change in the running state of the vehicle and the change in the fuel temperature and the change in the tank internal pressure are shown in FIG.
Is replaced with the outside air temperature. In this case, the outside air temperature changes without directly relating to the change in the running state of the vehicle.

FIG. 9 shows the details of the failure diagnosis processing performed by the diagnosis apparatus of this embodiment. It should be noted that in the processing in FIG.
Since the processing of steps 112, 114, and 130 is different from the processing of FIG. 5, the detailed description of other similar processing is partially omitted. A series of processes shown in this flowchart is executed by the ECU 40 as an interrupt process at predetermined time intervals (for example, at every 65 ms).

In this process, if it is determined in step 102 that the diagnosis has not been completed, it is determined in step 104 whether the introduction of the negative pressure into the purge path has been completed. If it is determined in step 104 that the introduction of the negative pressure has not been completed, the process proceeds to step 152,
If it is determined that the introduction of the negative pressure has been completed, the process proceeds to step 150.

In step 152, it is determined whether or not the above-described negative pressure introduction precondition other than the outside air temperature change is satisfied. If a negative determination is made in step 152, the process exits this routine and proceeds to normal purge control. If an affirmative determination is made in step 152, the process proceeds to step 154.

In step 154, the outside air temperature change |
It is determined whether ΔTemp2 | is lower than predetermined temperature B ° C. The predetermined temperature B ° C. is for determining whether or not a negative pressure may be introduced, and is set to a value that hardly affects the increase and decrease of the tank internal pressure. If it is determined in step 154 that the change in outside air temperature | ΔTemp2 | is equal to or higher than B ° C., it is determined that there is a risk of erroneous diagnosis, and the process exits this routine and proceeds to normal purge control. If it is determined in step 154 that the change in outside air temperature | ΔTemp2 | is less than B ° C., it is determined that there is no risk of erroneous diagnosis, and the process proceeds to step 156.

In step 156, the outside air temperature change |
After ΔTemp2 | becomes less than B ° C., it is determined whether a predetermined time C or D has elapsed. Here, if it is determined that the predetermined time C or D has not elapsed, it is determined that there is a risk of erroneous diagnosis, and the routine is temporarily exited. If it is determined in step 156 that the predetermined time C or D has elapsed, the process proceeds to step 116, and the subsequent processing is executed.

In step 150, it is determined whether or not the change in outside air temperature | ΔTemp2 | is lower than a predetermined temperature A ° C. The predetermined temperature A ° C is for determining whether or not there is a risk of erroneous diagnosis even if the determination of the presence / absence of a leak abnormality is performed. At this step 150, the outside air temperature change | ΔTe
If it is determined that mp2 | is less than A ° C., it is determined that there is no possibility of erroneous diagnosis, and the process proceeds to step 108, and step 108 is performed.
The following processing is executed.

According to the failure diagnosis apparatus of this embodiment in which the execution of the failure diagnosis is prohibited in the manner described above, the fuel temperature changes based on the change in the outside air temperature, and the change in the pressure in the purge passage changes. In this case, the same effect as in the second embodiment can be obtained.

Each of the above embodiments can be implemented by changing its configuration as follows. In the first embodiment, the exhaust gas temperature is detected by the exhaust gas temperature sensor 6 provided in the exhaust passage 5 of the engine 4. However, the estimated value of the catalyst bed temperature used for detecting the catalyst deterioration may be used. Good.

In the fourth embodiment, the outside air temperature is detected by the outside air temperature sensor. However, the outside air temperature is detected based on the detection result of the intake air temperature sensor provided in the normal intake passage of the engine. You may. In this case, it is not necessary to separately provide an outside air temperature sensor.

In the third embodiment, the switching between the uphill running and the flat running of the vehicle is detected based on the running resistance of the vehicle in the steady steady running and the running resistance in the uphill running. The switching between the uphill and downhill traveling and the flat traveling may be detected based on the exhaust gas temperature during the steady traveling of the vehicle and the exhaust temperature during the uphill traveling. That is, after the completion of the warm-up of the engine, the change in the exhaust gas temperature is almost the same as the change in the intake air amount per cycle, and the exhaust gas temperature during flat running changes as shown by the solid line in FIG. Accordingly, the difference between the exhaust gas temperature at the current vehicle speed of the vehicle and the exhaust gas temperature for the vehicle speed during flat running, that is, the exhaust gas temperature change Δ
By obtaining Te, the current traveling state is uphill traveling,
It is possible to detect whether the vehicle is traveling downhill or traveling flat.

In the above embodiments, the diagnosis prohibition periods (predetermined times C, D, E, and F) are fixed values. However, these values may be set in the fuel tank 1 such as the outside air temperature and the engine cooling water temperature. The setting may be variably set based on a parameter that affects the changing speed of the fuel temperature.

In the above-described embodiment, the fuel vapor purge system is embodied as a type in which the fuel tank 1 and the canister 2 are always in communication, but instead the tank internal pressure control is provided between the fuel tank and the canister. A fuel vapor purge system may be embodied in which a valve is provided, and a bypass passage is provided for communicating the fuel tank with the canister at the time of introducing a negative pressure into the purge path and after the introduction of the negative pressure.

In the first and second embodiments, the failure diagnosis is prohibited at a time when there is a possibility of erroneous diagnosis. However, during the leak determination after introducing the negative pressure into the purge path, However, when the exhaust temperature rises from the exhaust temperature during flat running, only the diagnosis of a leak abnormality is prohibited, and when the exhaust temperature falls from the exhaust temperature during flat running, only the diagnosis of no leak abnormality is prohibited. Good.

Next, other technical ideas that can be grasped from the above embodiments will be described below. In the failure diagnosis device for a fuel vapor purge system according to any one of claims 2 to 5, the diagnosis prohibition unit includes:
A failure diagnosis device for a fuel vapor purge system, wherein only a diagnosis of a leak abnormality is prohibited when the traveling state of the vehicle shifts from uphill traveling to flat traveling.

[0098] In the failure diagnosis device for a fuel vapor purge system according to any one of claims 2 to 5, the diagnosis prohibiting means is configured to detect a leakage abnormality when the traveling state of the vehicle shifts from downhill traveling to flat traveling. A failure diagnosis device for a fuel vapor purge system that prohibits only the diagnosis of no fuel vapor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel vapor purge system and a failure diagnosis device thereof according to a first embodiment.

FIG. 2 is a timing chart for explaining a procedure of failure diagnosis by the failure diagnosis device.

FIG. 3 is a timing chart showing a pressure fluctuation mode in a purge path due to a fluctuation in a running state of a vehicle.

FIG. 4 is a flowchart illustrating a procedure of a failure diagnosis process according to the first embodiment;

FIG. 5 is a flowchart illustrating a processing procedure of a failure diagnosis process according to the second embodiment.

FIG. 6 is a graph showing a relationship between a vehicle speed and an intake air amount.

FIG. 7 is a timing chart showing a mode of a pressure change in a purge path due to a change in a running state of a vehicle.

FIG. 8 is a flowchart illustrating a procedure of a failure diagnosis process according to the third embodiment.

FIG. 9 is a flowchart illustrating a procedure of a failure diagnosis process according to a fourth embodiment.

FIG. 10 is a graph showing the relationship between vehicle speed and exhaust temperature.

[Explanation of symbols]

1: fuel tank, 2: canister, 6: exhaust temperature sensor,
11: purge passage, 13: fuel vapor introduction passage, 31: pressure sensor, 40: ECU.

Continuing from the front page (72) Inventor ▲ Mr. Oka Mamoru 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kenichiro Kawase 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation ( 72) Inventor Masahiro Tominaga 2-1-1 Toyota-cho, Kariya-shi, Aichi Pref. In Toyota Industries Corporation (72) Inventor Jin Tanaka 2-1-1 Toyota-machi, Kariya-shi, Aichi Pref. 72) Inventor Takataka Taga 1-1-1, Kyowa-cho, Obu City, Aichi Prefecture Inside Aisan Industry Co., Ltd.

Claims (6)

[Claims] A fuel vapor mounted in a vehicle and generated in a fuel tank is collected in a canister, and the collected fuel vapor is supplied to an intake passage of an internal combustion engine through a purge path including the fuel tank. A fuel vapor purge system configured to purge, and a differential pressure between the internal pressure and the external pressure of the purge path is provided to seal the purge path and to determine whether there is a leak abnormality in the purge path based on a change state of the internal pressure measured. A failure diagnosis device for a fuel vapor purge system, comprising: a diagnosis unit for performing a diagnosis; a temperature change calculation unit configured to calculate a predetermined temperature change of the fuel in the fuel tank based on a change in a running state of the vehicle or a change in an outside air temperature. And a diagnosis prohibition unit for prohibiting at least a part of the diagnosis by the diagnosis unit when a predetermined temperature change is calculated by the temperature change calculation unit. Failure diagnosis apparatus of the local system. 2. A failure diagnosis apparatus for a fuel vapor purge system according to claim 1, wherein said temperature change calculating means determines a predetermined amount of said fuel based on a change of a running state of the vehicle from uphill running to flat running. Diagnosis device for fuel vapor purge system that calculates temperature change of fuel. 3. The failure diagnosis apparatus for a fuel vapor purge system according to claim 2, wherein the temperature change calculating means changes the running state of the vehicle from uphill running based on a predetermined temperature change of the exhaust temperature of the internal combustion engine. Failure diagnosis device for the fuel vapor purge system that determines that the vehicle has switched to flat running. 4. A failure diagnosis apparatus for a fuel vapor purge system according to claim 2, wherein said temperature change calculating means determines whether a difference between a running resistance of the vehicle and a running resistance in flat steady running is equal to or greater than a predetermined value. A failure diagnosis device for a fuel vapor purge system that determines that a vehicle has traveled uphill or downhill based on a vehicle. 5. A failure diagnosis apparatus for a fuel vapor purge system according to claim 2, wherein said diagnosis prohibiting means elapses a predetermined time after a running state of the vehicle is switched from uphill running to flat running. A failure diagnosis device for a fuel vapor purge system that prohibits at least a part of the failure diagnosis until the failure diagnosis is performed. 6. The failure diagnosis device for a fuel vapor purge system according to claim 1, wherein said diagnosis prohibition means is configured to perform at least a part of the failure diagnosis until a predetermined time elapses after a predetermined temperature change of the outside air temperature. Prohibit fuel vapor purge system failure diagnosis device.