JPH0412157A - Trouble shooting device for evaporation fuel supply system of engine - Google Patents

Abstract

PURPOSE:To restrain deterioration in driving performance by carrying out a purge of an evaporation fuel in a predetermined control zone and by prohibiting the purge of the evaporation fuel for failure judgment when a generation amount of the evaporation fuel is large in judging occurrence of the failure in an evaporation fuel supply system through according to change in a fuel state at that time. CONSTITUTION:A control means 40 for controlling a purge adjusting means 24 is provided so that a purge of an evaporation fuel is carried out in a specific driving area where an influence of the purge of the evaporation fuel on driving performance is small, and the purge of the evaporation fuel is forcedly carried out in an air fuel ratio feedback control zone in the driving area other than that. In carrying out the forced purge of the evaporation fuel in the air fuel ratio feedback control zone, failure in an evaporation fuel supply system is judged by a failure judging means 42 based on the combustion state detected by a combustion state detecting means 41. At this time, an output of an evaporation amount detecting means 44 for detecting a signal relating to a generation amount of the evaporation fuel is received, and when the generation amount of the evaporation amount is larger than a predetermined value, the forced purge of the evaporation fuel for failure judgement is prohibited by a limiting means 43.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a failure diagnosis device for determining a failure in an evaporative fuel supply system of an engine.

(Prior Art) Conventionally, as a technology in which evaporated fuel evaporated in the fuel tank of an engine is introduced into the intake system and combusted in the engine, for example, there is a technology disclosed in Japanese Patent Laid-Open No. 85249/1983. , the evaporated fuel is purged in the air-fuel ratio feedback control range, and if the feedback correction amount exceeds the predetermined control range, the evaporated fuel is purged until the feedback correction amount falls within the above control range. There are known methods that correct weight loss.

(Problem to be solved by the invention) By the way, in an evaporated fuel supply system in which evaporated fuel generated in a fuel tank is adsorbed in a canister, and the adsorbed evaporated fuel is sucked out into an intake passage and supplied to an engine,
For example, if some kind of failure occurs, such as a blockage in the supply passage, evaporated fuel will not be supplied to the engine, but will increase in the fuel tank and evaporative fuel supply system, and the canister will not be able to absorb the evaporated fuel completely. This may cause problems such as overflow and evaporated fuel being released into the atmosphere. Therefore, it is desirable to be able to know as soon as possible whether or not a failure has occurred in this evaporative fuel supply system.

Therefore, we focused on the fact that when evaporated fuel is purged into the engine, the air-fuel ratio shifts to the rich side and the combustion state changes due to the evaporated fuel. It is conceivable that by executing a fuel purge, the presence or absence of a failure in the vaporized fuel supply system may be determined by observing changes in the combustion state.

At that time, we want to have as many opportunities as possible to make a failure determination as quickly as possible, so instead of making a failure determination in a limited specific driving range where the effect on drivability due to purge of evaporated fuel is small, we If the fuel vapor is forcibly purged in a high air-fuel ratio feedback control range (for example, the idling range) to determine a failure, there will be more opportunities for failure determination, and the determination can be made more quickly. . However, in this case, the evaporated fuel is forcibly purged in an operating range where evaporative fuel purge is not normally performed, so if a large amount of evaporated fuel is purged at this time, the air-fuel ratio becomes too rich and the feedback control is There is a concern that drivability may deteriorate due to exceeding the control range.

The present invention has been made in view of the above points, and its purpose is to determine whether or not there is a failure in the evaporative fuel supply system that supplies evaporative fuel to the engine as quickly as possible while suppressing deterioration of drivability. It's about doing.

(Means for Solving the Problems) In order to achieve the above object, the present invention purges evaporated fuel in an air-fuel ratio feedback control range other than a specific operating range, and monitors changes in the combustion state at that time. Basically, it is determined whether or not a failure has occurred in the evaporative fuel supply system by looking at the evaporative fuel supply system. However, when a large amount of evaporated fuel is generated, purging of the evaporated fuel for the above failure determination is prohibited.

Specifically, the solution taken by the present invention targets an engine in which the air-fuel ratio of the supplied air-fuel mixture is feedback-controlled to a predetermined air-fuel ratio, and as shown in FIG. A purge passage 20 for introducing the evaporated fuel generated in step 19 into the intake passage 7, a canister 23 interposed in this purge passage 20 and adsorbing the evaporated fuel, and a canister 23 for introducing the evaporated fuel adsorbed into the canister 23 together with outside air. Purge adjustment means 24 that adjusts the purge air flow rate to the intake passage
It is assumed that the system is equipped with the following.

Then, the purge of vaporized fuel is executed in a specific driving range where purging of vaporized fuel has little effect on drivability, and the purge of vaporized fuel is forcibly executed in the air-fuel ratio feedback control area in other operating ranges. a control means 40 for controlling the purge adjustment means 24; a combustion state detection means 41 for detecting a signal related to the combustion state; A failure determination means 42 that determines a failure of the evaporated fuel supply system consisting of the purge passage 20, the canister 23, and the purge adjustment means 24 based on the combustion state detected by the combustion state detection means 41;
and an evaporation amount detection means 44 that detects a signal related to the amount of evaporated fuel generated; upon receiving the output of this evaporation amount detection means 44, if the amount of evaporated fuel generated is greater than a predetermined value, a failure is detected by the control means 40. This configuration includes a restriction means 43 that prohibits forced purging of evaporated fuel for determination.

(Function) With the above configuration, in the present invention, the control means 40:
Purging of evaporated fuel is forcibly executed in an air-fuel ratio feedback control region in which the air-fuel ratio is maintained stably in other operating regions than in a limited specific operating region, and at that time, the combustion state detection means 41 detects the The failure determining means 42 determines whether the evaporative fuel is being supplied to the engine without any abnormality from the evaporative fuel supply system consisting of the purge passage 20, the canister 23, and the purge adjusting means 24, and the air-fuel ratio has shifted to the rich side. A failure determination is made by determining the In this case, since the air-fuel ratio feedback control region in which the above-mentioned forced purge of vaporized fuel is executed is an operating region with high frequency of operation (for example, an idling operating region), there are many opportunities for failure determination, and failure determination can be made at an early stage. It will be done. At this time, when the amount of evaporated fuel generated is detected by the evaporation amount detection means 44 to be larger than a predetermined value, the restriction means 43 prohibits purging of the evaporated fuel for failure determination. In the operating range where no purge is performed, bar share containing a large amount of evaporated fuel is supplied to the engine, thereby preventing deterioration of drivability due to the air-fuel ratio becoming too rich.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of an embodiment of the present invention. In the figure, 1 is an engine, and this engine 1 has a cylinder block 3 having a cylinder 2, a cylinder head 4 joined to the upper surface of the cylinder block 3, and a piston 5 that reciprocates within the cylinder 2. A combustion chamber 6 defined by the lower surface of the cylinder head 4 and the top surface of the piston 5 is formed within the cylinder 2 . 7 is an intake passage that supplies intake air into the combustion chamber 6, and 9 is an intake valve that opens and closes a downstream end opening of the intake passage 7. 10 is an exhaust passage for discharging the exhaust gas in the combustion chamber 6; 11 is an exhaust valve that opens and closes the upstream end opening of the exhaust passage 10; and 12 is an exhaust purification device disposed midway through the exhaust passage 10.

In order from the upstream side, the intake passage 7 is supplied with an air flow meter 13 for detecting the amount of intake air Q, a throttle valve 14 for controlling the amount of intake air, a surge tank 15 for absorbing intake pulsation, etc., and fuel injected. An injector 16 is provided, and an upstream end of the intake passage 7 is connected to an air cleaner 17.

8 is a bypass passage that bypasses the throttle valve 14 and supplies air to the combustion chamber 6;
An idle speed control valve 18, which is a proportional solenoid valve, is provided to control the amount of air flowing through the bypass passage 8 and adjust the engine speed (idle speed) when the engine is idling.

Reference numeral 19 denotes a fuel tank connected to the injector 16 via a fuel supply passage (not shown), and an upper portion of the fuel tank 19 supplies evaporative fuel (fuel evaporative gas) in the fuel tank 19 to the engine 1. Purge passage 2 for
The upstream end of the purge passage 20 is open, and the downstream end of the purge passage 20 is open to the intake passage 7 at the surge tank 15. In the middle of the purge passage 20, from the upstream side (fuel tank 19 side), there are a separator 21 for separating liquid fuel from evaporated fuel, a two-way valve 22a, and a three-way valve 2.
2b, a canister 23 that adsorbs evaporated fuel, and a purge valve 24 as a purge adjustment means consisting of a solenoid valve that opens and closes the purge passage 20 to adjust the supply (purge) of evaporated fuel to the intake passage 7. The separator 21 is connected to the fuel tank 19 via a fuel return passage 25 for returning the separated liquid fuel.

These purge passage 20, separator 21, 2-way valve 22a, 3-way valve 22b, canister 23, and purge valve 24 constitute an evaporative fuel supply system.

The operation of the injector 16, idle speed control valve 18, and purge valve 24 is controlled by a control unit 30 containing a CPU. This control unit 30 includes the air flow meter 1
3 detection signal and the intake passage 7 immediately downstream of the air cleaner 17.
The crank angle of the engine 1 is detected based on the detection signal of the intake air temperature sensor 31 that detects the intake air temperature, the detection signal of the throttle sensor 32 that detects the opening degree of the throttle valve 14, and the rotation angle of the camshaft 26 in the cylinder head 4. the detection signal of the crank angle sensor 33, the rotation signal of the distributor 34, the detection signal of the 02 sensor 35 disposed in the exhaust passage 10 upstream of the exhaust purification device 12, and the cooling water inside the water jacket 3a in the cylinder block 3. A detection signal from a water temperature sensor 36 that detects temperature is input. Although not shown, the throttle sensor 32 is provided with an idle switch that outputs an ON signal when the throttle valve 14 is fully open and the throttle opening becomes zero.

Next, a signal processing procedure for determining a failure of the vaporized fuel supply system by controlling the operation of the purge valve 24 in the control unit 30 will be explained based on the flowchart of FIG. 3. In the figure, after the ignition switch is turned on to start, various signals are initialized in step S1, and various signals are read in step S2.

Then, in step S3, it is determined whether or not the engine operating region is a purge zone, which is a specific operating region in which purging can be performed without adversely affecting engine drivability even if purge of vaporized fuel is performed.

If the answer is YES in the purge zone, the purge valve 24 is controlled to an opening degree according to the operating state of the engine in step s4 to purge the vaporized fuel, and the process returns to step S2. If it is not a barge zone, the process proceeds to step s5, and it is determined whether or not the failure determination has been completed using a completion flag (set to "1" when the failure determination is completed), which will be described later. If the answer is YES, the process proceeds to step S6, where the purge valve 24 is closed, the purge is cut, and the process returns to step s2. On the other hand, if the failure determination is not completed (No), the process advances to step S7 and it is determined whether the engine is in idle operation. During this idle operation, the engine rotation speed Ne is the target rotation speed NO.
Idle speed control valve 18 so that
Feedback control is performed to control the amount of air flowing through the bypass passage 8 depending on the opening degree of the bypass passage 8. If the answer in step S7 is NO that the engine is not in idle operation, the process proceeds to step S6, closes the purge valve 24, cuts the purge, and returns to step S2. On the other hand, if the answer is YES, which means that the engine is in idle operation, the process proceeds to step S8, and it is determined whether or not the engine was in idle operation in the previous determination.

If the answer is No because it was not during idling operation last time, the timer is set to the set time T1 in step s9, and the process proceeds to step s3.
: Go to l. On the other hand, YES was displayed during idling last time.
If so, the process directly proceeds to step S31]. Step S
At step 30, it is determined whether the feedback correction amount GFB, which performs feedback control of the idle speed by the idle speed control valve 18, is less than a predetermined value. This is to check whether there is room to increase the amount of air in the filled pack control by the idle speed control valve 18. Here, when the feedback correction amount GFB is larger than the predetermined value (NO), the process proceeds to step s6, the purge valve 24 is closed, the purge is cut, and the process returns to step s2. On the other hand, the feed pack correction j is less than the predetermined value of YES.
If there is room in lGFB, the process advances to step SIO. Then, in step SIO, the purge valve 24 is opened to a predetermined value (for example, a duty value of 30%) to purge the evaporated fuel, and the process proceeds to step S1+. Step S11
Then, it is determined whether the set time T1 set in step S9 has elapsed. If No, the set time T1 has not yet elapsed, the process proceeds to step 512, where the count value of the timer is decremented by "1", and the process returns to step S2, where the time T1 set at step S9 is
Wait for the period to pass. In this case, if the determination in step S30 is No, the process proceeds to step S6, but this is because when the vaporized fuel is purged in step SIO and the vaporized fuel is supplied and the air-fuel ratio becomes rich, the combustion state changes. As a result, the feedback correction amount GFB by the idle speed control valve 18 changes, but especially when a large amount of vaporized fuel is generated and a large amount of vaporized fuel is supplied, the feedback correction amount GFB changes greatly. This is to prevent deterioration of drivability due to the fact that since the predetermined value is exceeded, there is no margin for the control range or the control range is exceeded, and further correction is no longer possible. Also, when a large amount of air is required due to the external load condition, such as when the air conditioner is turned on, the feedback correction amount GFB will greatly deviate toward the side where the amount of air increases. If evaporated fuel is purged even if it is not generated, the feedback correction amount GFB will exceed the predetermined value, and this is also to prevent deterioration of drivability as described above.

That is, in this step S3), it is determined whether or not the condition is such that the above-described deterioration of drivability is caused by the feedback correction amount GFB of the idle rotation speed.
If No here, it is considered that it is not possible to purge the evaporated fuel from the viewpoint of drivability, and the process proceeds to step S6 to stop the purge. It is assumed that the situation is such that the deterioration in performance can be suppressed, and the process proceeds to the following steps to determine the failure. Then, after the set time T1 has elapsed, Y becomes T1-0.
When it is ES, the process proceeds to step S+3, where the feedback correction tc that performs feedback control of the air-fuel ratio is performed.
It is determined whether the amount of variation in CF B has shifted to the lean side from a predetermined value. This is to check whether the air-fuel ratio has shifted to the rich side due to vaporized fuel being supplied by executing the vaporized fuel purge in step SIO.If YES, the vaporized fuel will be evaporated as usual by executing the vaporized fuel purge in step SIO. Since fuel has been supplied, the fail flag for failure determination is set to "0" indicating that there is no failure in step S14, and the completion flag for failure determination is set to "1-" indicating completion in step SI5. Then, the process returns to step S2. On the other hand, if No in step S13, that is, the air-fuel ratio feedback correction amount CFB does not shift to the lean side because vaporized fuel is not supplied and the air-fuel ratio does not shift to the rich side even though the vaporized fuel purge is executed. If this occurs, it is considered that there is a failure in the evaporative fuel supply system or that the canister 23 is in an empty state with no evaporated fuel adsorbed, and in this case, the process advances to step S16. In step S+6, the timer is set to the set time T2, and in step S+7, the opening degree of the purge valve 24 is set to step 5.
It opens to a value larger than the predetermined value opened at 1G (for example, a duty value of 60%) and purges the evaporated fuel. This means that by increasing the opening degree of the purge valve 24, intake negative pressure is applied to the inside of the fuel tank 19, so that the evaporated fuel in the fuel tank 19 is forcibly sucked in and introduced into the intake passage. Here, one experimental data that serves as the basis for applying negative intake pressure in the fuel tank by increasing the opening degree of the purge valve 24 is shown below.

Idle boost (negative pressure) 530 Dragon Hg Barge valve duty value (opening degree) 60% 2-way valve opening pressure 450 layer 11Ag (-33 layer yaHg) 3-way valve opening pressure 800-1000-■Ag ('= ;59 ~74w+
Evening Hg) Canister atmospheric release diameter 81
When a condition equal to or higher than Il is satisfied, the internal pressure of the fuel tank becomes 130 gHz, and evaporated fuel is introduced from the tank.

Then, in step S18, it is determined whether the set time T2 set in step S16 has elapsed. If the answer is No, the set time T2 has not yet elapsed, proceed to step SI.
9, the count value of the timer is decremented by 1 degree, and the process proceeds to step S~.Then, in step S2s, it is determined whether or not idling operation continues, and if YES is determined to be idling operation. If so, the process returns to step S+y and waits until the set time T2 has elapsed.

On the other hand, if No, it is not during idling operation, step S6
Return to , close the purge valve 24, and perform a purge cut. At step SI8, the set time T2 has elapsed and T2-0
If YES, the process advances to step S21. In this step S21, the determination made in the previous step 513 is executed once again. That is, it is determined whether the air-fuel ratio has shifted to the rich side and the variation amount of the air-fuel ratio feedback correction amount CFB has shifted to the lean side from a predetermined value. Here, if the variation amount of the air-fuel ratio feedback correction ff1CFB is deviated to the lean side from the predetermined value (YES), it is assumed that the NO determination in step S13 is because the canister is empty, and the process proceeds to step S22. Then, the fail flag for failure determination is set to "0" which indicates no failure, and the process advances to step S24. On the other hand, in step 52+, as in step 513, if the variation amount of the air-fuel ratio feedback correction JICFB does not deviate to the lean side from the predetermined value (No), it is determined that there is a failure in the evaporative fuel supply system, and the process proceeds to step S23. Then, the fail flag for failure determination is set to "1", which is the time of failure, and a signal is output to turn on a failure detection lamp to notify the driver of the failure, and the process advances to step S24.

In step S2J, the failure determination completion flag is set to "1°" indicating completion, and the process returns to step S2.

In the above flow, all the steps from step 82 onwards purge the evaporated fuel in a specific driving range where the purge of the evaporated fuel has little effect on drivability, and perform the purge in the air-fuel ratio feedback control range in other driving ranges. Control means 4 that controls the purge valve 24 (purge adjustment means) to forcibly purge the evaporated fuel
Configure 0. Then, step SI3 and step S
21 constitutes a combustion state detection means 41 that detects a signal related to the combustion state, and the steps from step 87 onwards detect the combustion state when the control means 40 executes forced purge of vaporized fuel in the air-fuel ratio feedback control region. Based on the combustion state detected by the state detection means, the purge passage 20, separator 21, 2-way valve 22a,
A failure determination means 42 is configured to determine that the vaporized fuel supply system consisting of the three-way valve 22b1, the canister 23, and the purge valve 24 has failed. Further, in step S3), an evaporation amount detection means 44 for detecting a signal related to the amount of evaporated fuel generated is configured, and step S30 and step S
6 receives the output of the evaporation amount detection means 44, and when the amount of evaporated fuel generated is greater than a predetermined value, the control means 40
This constitutes a restricting means 43 that prohibits forced purging of evaporated fuel for failure determination.

Therefore, in the above embodiment, the failure determination of the evaporative fuel supply system is performed during idle operation, which is a high frequency of operation, so there are many opportunities for determination, and since the engine normally starts idle operation and then shifts to load operation, this Since failure can be determined during idling operation immediately after startup, failure can be determined early.

In addition, when making this failure determination, it is determined whether or not the evaporative fuel purge is to be executed for failure determination, or whether the condition is causing deterioration of drivability, based on the feedback correction amount GFB of the idle rotation speed by the idle speed control valve 18. When a large amount of evaporated fuel is supplied,
Alternatively, purge of evaporated fuel is prohibited when the operating state of the external load is such that purging of evaporated fuel is not suitable, so a large amount of evaporated fuel is It is possible to prevent drivability from deteriorating due to the fuel vapor being supplied or purging of the vapor fuel being executed when the vapor fuel purge is not suitable.

Furthermore, this failure determination is performed in two stages, so that when the first failure determination indicates that a failure has occurred, the failure determination is not immediately determined, but the second stage of failure determination is subsequently performed. By doing so, the determination result that a failure has occurred when the inside of the canister 23 is empty in the first failure determination is canceled and it is determined that there is no abnormality.
Misjudgment when the canister 23 is empty can be prevented.

In addition, as a modification of the above embodiment, the determination in step S3:l may be made to determine whether the intake air temperature detected by the intake air temperature sensor 31 is below a predetermined temperature (for example, 80° C.). This is because a high intake air temperature means a high atmospheric temperature in the engine compartment, and in this case, the outside temperature is generally high and the fuel tank 19 is also high.
It is predicted that a large amount of evaporated fuel will be generated as it is likely that evaporated fuel will be generated within the area. That is, the amount of evaporated fuel generated is indirectly determined based on the intake air temperature. For this reason, when the intake air temperature is higher than the predetermined temperature in the above judgment, if the evaporative fuel purge is executed for failure judgment, a large amount of evaporative fuel will be supplied and the drivability will deteriorate, so in such a case, This arrangement is such that purging of evaporated fuel is stopped in advance, and the same effect as in the above embodiment can be obtained.

(Effects of the Invention) As explained above, according to the failure diagnosis device for the evaporated fuel supply system of the engine of the present invention, the evaporated fuel is By executing this purge, a failure determination of the evaporative fuel supply system is made. At that time, when the amount of evaporated fuel generated is large, purging of evaporative fuel for the above failure determination is prohibited, so that the operation Failure can be determined in frequently occurring operating regions, which increases the number of opportunities for failure determination and enables earlier failure determination.In addition, in operating regions where evaporated fuel is not normally purged, a large amount of evaporated fuel is contained. It is possible to prevent drivability from deteriorating due to the air-fuel ratio becoming too rich due to the purge air being supplied to the engine.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the structure of the present invention. 2 and 3 show an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the overall configuration thereof, and FIG. 3 is a flowchart showing a signal processing procedure for failure determination in the control unit. 7... Intake passage 8... Bypass passage 13... Air flow meter 16... Injector 18... Idle speed control valve 19.
... Fuel tank (fuel evaporation source) 20 ... Purge passage 23 ... Canister 24 ... Purge valve (purge adjustment means) 35 ...
02 sensor 40...Control means 41...Combustion state detection means 42...Failure determination means 43...Restriction means 44...Evaporation amount detection means

Claims (2)

[Claims] (1) In an engine in which the air-fuel ratio of the supplied air-fuel mixture is feedback-controlled to a predetermined air-fuel ratio, there is provided a purge passage for introducing evaporated fuel generated at a fuel evaporation source into the intake passage; an interposed canister that adsorbs the evaporated fuel; a purge adjustment means that adjusts a purge air flow rate that purges the evaporated fuel adsorbed by the canister into the intake passage together with outside air; a control means for controlling the purge adjustment means to purge the evaporated fuel in a specific operating range and forcibly purge the evaporated fuel in an air-fuel ratio feedback control range in other operating ranges; and a combustion state. a combustion state detection means for detecting a signal related to the air-fuel ratio feedback control region; ,
a failure determination means for determining a failure of the evaporated fuel supply system consisting of a canister and a purge adjustment means; an evaporation amount detection means for detecting a signal related to the amount of evaporated fuel generated; 1. A failure diagnosis device for an evaporative fuel supply system of an engine, comprising: a restriction means for prohibiting the control means from forcibly purging the evaporated fuel for fault determination when the amount of fuel generated is greater than a predetermined value. (2) The air-fuel ratio feedback control region in the control means is an idle operation region, and the evaporation amount detection means is means for detecting a control amount for performing feedback control so that the idle rotation speed becomes the target rotation speed during idle operation, Claim (1), wherein the limiting means prohibits the forced purge of the evaporated fuel when a control amount for performing feedback control so that the idle rotation speed becomes the target rotation speed during idling operation becomes larger than a predetermined value. A failure diagnosis device for the evaporative fuel supply system of the engine.