Fuel vapor treatment apparatus for internal combustion engine

Abstract

A fuel vapor treatment apparatus includes a first determiner that determines a concentration of purged fuel based on an amount of deviation from a target air-fuel ratio of an air-fuel ratio detected by a sensor provided in an exhaust pipe. A second determiner that determines the concentration of purged fuel in a state in which a purge control valve is closed. Air-fuel ratio controller controls a fuel injection quantity to bring an air-fuel ratio to the target air-fuel ratio on the basis of the concentration of the purged fuel. The air-fuel ratio controller uses the concentration of fuel determined by the second determiner when purge is started or restarted, and uses the concentration of fuel determined by the first determiner thereafter in the course of performing purge. It is possible to increase a purge ratio when purge is started or restarted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a construction diagram to show the construction of a fuel vapor treatment apparatus according to an embodiment of the present invention;

FIG. 2 is a flowchart of an air-fuel ratio control routine;

FIG. 3 is a flowchart to show a fuel concentration determination routine for determining a fuel vapor concentration in purge gas purged from a canister;

FIG. 4 is a flowchart to show a concentration detection routine for detecting a fuel concentration on the basis of pressure measurement;

FIG. 5 is a flowchart of a purge ratio control routine;

FIG. 6 is a flowchart of a normal purge ratio control processing executed in the purge ratio control routine;

FIG. 7 is a flowchart of a purge ratio initial value determination routine;

FIG. 8 is a graph to show one example of a base flow rate;

FIG. 9 is a graph to show the relationship between a fuel concentration C and a ratio (Qc/Q100) of predicted flow rate Qc to a base flow rate Q100;

FIG. 10 is a graph to show the region of an air-fuel ratio correction factor FAF;

FIG. 11 is a flowchart of processing of computing a purge ratio to be corrected at the time of restarting purge which is executed in the purge ratio control routine;

FIG. 12 is a flowchart of a purge valve driving routine;

FIG. 13 shows an example of a set map for determining a fully open purge ratio;

FIG. 14 is a flowchart of a fuel concentration learning routine for computing a fuel concentration FGPG;

FIG. 15 is a flowchart of an injector control routine;

FIG. 16 is a timing chart in which purge timing is compared between this embodiment and a related art;

FIG. 17 is a flowchart to show an abnormality diagnosis control for diagnosing a leak and an abnormality in a fuel concentration detection system of a fuel vapor treatment apparatus;

FIG. 18 is a flowchart to show an abnormality diagnosis routine;

FIG. 19 is a diagram to show a state in which gas flows at the time of executing step in FIG. 18;

FIG. 20 is a diagram to show a state in which gas flows at the time of executing step in FIG. 18; and

FIG. 21 is a flowchart to show a fuel concentration determination routine for determining a fuel vapor concentration in purge gas purged from the canister.

Claims

1. A fuel vapor treatment apparatus for an internal combustion engine, comprising: a canister that temporarily adsorbs fuel vapor developed in a fuel tank;a purge pipe that introduces the fuel vapor purged from the canister into an intake pipe of the internal combustion engine;a purge control valve that is arranged in the purge pipe and controls a purge flow rate from the purge pipe to the intake pipe; an air-fuel ratio sensor that is provided in an exhaust pipe of the internal combustion engine and measures an air-fuel ratio;a first fuel state determination means that determines a state of fuel of an air-fuel mixture containing the fuel vapor purged from the canister on the basis of an amount of deviation from a target air-fuel ratio of an air-fuel ratio detected by the air-fuel ratio sensor when the purge control valve is opened; andan air-fuel ratio control means that controls a fuel injection quantity to the internal combustion engine so as to bring an air-fuel ratio to the target air-fuel ratio on the basis of the state of fuel of the air-fuel mixture purged from the canister; anda second fuel state determination means that determines the state of fuel of the air-fuel mixture purged from the canister when the purge control valve is closed, whereinthe air-fuel ratio control means switches a state of fuel for controlling the fuel injection quantity between the state of fuel determined by the first fuel state determination means and the state of fuel determined by the second fuel state determination means on the basis of an operating state of a vehicle.

2. The fuel vapor treatment apparatus according to claim 1, wherein when the vehicle is in an operating state in which it is before a purge is started, the air-fuel ratio control means determines a fuel injection quantity when the purge is started based on the state of fuel determined by the second fuel state determination means.

3. The fuel vapor treatment apparatus according to claim 1, wherein when the vehicle is in an operating state in which a purge is started and is continued, the air-fuel ratio control means controls the fuel injection quantity based on the state of fuel determined by the first fuel state determination means.

4. The fuel vapor treatment apparatus according to claim 1, wherein when the vehicle is in an operating state in which a purge is interrupted, the air-fuel ratio control means determines a fuel injection quantity when purge is started again based on the state of fuel determined by the second fuel state determination means.

5. The fuel vapor treatment apparatus according to claim 4, wherein when the vehicle is in an operating state in which the purge is interrupted, and when a determination of a state of fuel by the second fuel concentration determination means is uncompleted, the air-fuel ratio control means determines the fuel injection quantity when purge is started again based on a fuel state concentration determined by the first fuel state determination means immediately before the purge is interrupted.

6. The fuel vapor treatment apparatus according to claim 1, further comprising: a measurement passage that has a restrictor;a gas flow producing means that produces a gas flow passing through the restrictor;a pressure measurement means that measures a drop in pressure caused by the restrictor when the gas flow producing means produces the gas flow; anda measurement passage switching means that switches the measurement passage between a first state of measurement in which the measurement passage is opened to the atmosphere and in which gas flowing through the measurement passage is air and a second state of measurement in which the measurement passage is made to communicate with the canister to change gas flowing through the measurement passage to an air-fuel mixture containing the fuel vapor from the canister,wherein the second fuel state determination means determines the state of fuel on the basis of a first pressure measured by the pressure measurement means in the first state of measurement and a second pressure measured by the pressure measurement means in the second state of measurement.

7. The fuel vapor treatment apparatus according to claim 1, wherein the first fuel state determination means determines a relative state of fuel vapor of an air-fuel mixture with respect to the target air-fuel ratio, and further comprising:a state conversion means that converts the state of fuel determined by the second fuel state means determination means to a relative state of fuel vapor of an air-fuel mixture with respect to the target air-fuel ratio, whereinthe air-fuel ratio control means uses a state of fuel after conversion by the state conversion means as the state of fuel determined by the second fuel state determination means.

8. A fuel vapor treatment apparatus for an internal combustion engine, comprising: a canister that temporarily adsorbs fuel vapor developed in a fuel tank;a purge pipe that introduces the fuel vapor purged from the canister into an intake pipe of the internal combustion engine;a purge control valve that is arranged in the purge pipe and controls a purge flow rate from the purge pipe to the intake pipe;an air-fuel ratio sensor that is provided in an exhaust pipe of the internal combustion engine and measures an air-fuel ratio;a first fuel state determination means that determines a state of fuel of an air-fuel mixture containing the fuel vapor purged from the canister on the basis of an amount of deviation from a target air-fuel ratio of an air-fuel ratio detected by the air-fuel ratio sensor when the purge control valve is opened; andair-fuel ratio control means that controls a fuel injection quantity to the internal combustion engine to bring an air-fuel ratio to the target air-fuel ratio on the basis of the state of fuel of the air-fuel mixture purged from the canister;a second fuel state determination means that determines the state of fuel of the air-fuel mixture by purging the air-fuel mixture containing the fuel vapor from the canister in a state in which the purge control valve is closed; andan abnormality detection means that detects an abnormality in the second fuel state determination means, whereinwhen no abnormality is detected by the abnormality detection means, the air-fuel ratio control means switches a state of fuel for controlling the fuel injection quantity between the state of fuel determined by the first fuel state determination means and the state of fuel determined by the second fuel state determination means on the basis of an operating state of a vehicle, andwhen an abnormality is detected by the abnormality detection means, the air-fuel ratio control means uses the state of fuel determined by the first fuel state determination means as the state of fuel for controlling the fuel injection quantity irrespective of the operating state of the vehicle.

9. The fuel vapor treatment apparatus according to claim 8, wherein the second fuel state determination means includes: a measurement passage that has a restrictor;a pump that produces a gas flow passing through the restrictor;a pressure measurement means that measures a drop in pressure caused by the restrictor when the pump produces the gas flow; anda measurement passage switching means that switches the measurement passage between a first state of measurement in which the measurement passage is opened to the atmosphere and in which gas flowing through the measurement passage is air and a second state of measurement in which the measurement passage is made to communicate with the canister in a state in which the purge control valve is closed to change gas flowing through the measurement passage to an air-fuel mixture containing the fuel vapor from the canister,the second fuel state determination means determines the state of fuel on the basis of a first pressure measured by the pressure measurement means in the first state of measurement and a second state of measurement measured by the pressure measurement means in the second state of measurement, andthe abnormality detection means detects an abnormality in at least one of the measurement passage, the pump, the pressure measurement means, and the measurement passage switching means.

10. The fuel vapor treatment apparatus according to claim 9, further comprising: a closed space forming valve that brings at least a part of a fuel state detection system including the measurement passage, the pump, the pressure measurement means, and the measurement passage switching means to a closed space;a leak inspection passage that has one end opened to the atmosphere and has a base restrictor arranged;a pressurizing means that pressurizes or depressurizes the closed space and the leak inspection passage;a pressure measurement means that measures pressure in the closed space and the leak inspection passage which are pressurized or depressurized by the pressure application means; anda pressurizing region switching means that switches a pressurized region pressurized or depressurized by the pressurizing means so as to include at least one of the closed space and the leak inspection passage and to switch between two kinds of states of leak measurement that are different from each other in the pressurizing region, whereinthe abnormality detection means detects an abnormality in the fuel state detection system on the basis of comparison of two pressures measured by the pressure measurement means in the two kinds of states of leak measurement.

11. The fuel vapor treatment apparatus according to claim 10, wherein the leak inspection passage is the measurement passage.

12. The fuel vapor treatment apparatus according to claim 11, wherein the pressurizing region switching means is the measurement passage switching means.

13. The fuel vapor treatment apparatus according to claim 10, wherein the pressurizing means is a pump that produces a gas flow in the measurement passage.

14. The fuel vapor treatment apparatus according to claim 8, wherein when an abnormality is not detected by the abnormality detection means and the vehicle is in an operating state before starting purge, the air-fuel ratio control means uses the state of fuel determined by the second fuel state determination means.

15. The fuel vapor treatment apparatus according to claim 8, wherein when the vehicle is in an operating state in which a purge is started and is continued, the air-fuel ratio control means uses the state of fuel determined by the first fuel state determination means.

16. The fuel vapor treatment apparatus according to claim 8, wherein when no abnormality is detected by the abnormality detection means and the vehicle is in an operating state in which purge is interrupted, the air-fuel ratio control means uses the state of fuel determined by the second fuel state determination means.

17. The fuel vapor treatment apparatus of an internal combustion engine according to claim 16, wherein when the vehicle is in an operating state in which purge is interrupted, and when a determination of the state of fuel by the second fuel concentration determination means is uncompleted, the air-fuel ratio control means uses the state of fuel determined by the first fuel state determination means immediately before purge is interrupted.

18. A fuel vapor treatment apparatus for an internal combustion engine, comprising: a canister that temporarily adsorbs fuel vapor developed in a fuel tank;a purge pipe that introduces the fuel vapor purged from the canister into an intake pipe of the internal combustion engine;a purge control valve that is arranged in the purge pipe and controls a purge flow rate from the purge pipe to the intake pipe; an air-fuel ratio sensor that is provided in an exhaust pipe of the internal combustion engine and measures an air-fuel ratio;a first fuel state determiner that determines a state of fuel of an air-fuel mixture containing the fuel vapor purged from the canister on the basis of an amount of deviation from a target air-fuel ratio of an air-fuel ratio detected by the air-fuel ratio sensor when the purge control valve is opened; andan air-fuel ratio controller that controls a fuel injection quantity to the internal combustion engine so as to bring an air-fuel ratio to the target air-fuel ratio on the basis of the state of fuel of the air-fuel mixture purged from the canister; anda second fuel state determiner that determines the state of fuel of the air-fuel mixture purged from the canister when the purge control valve is closed, whereinthe air-fuel ratio controller switches a state of fuel for controlling the fuel injection quantity between the state of fuel determined by the first fuel state determination means and the state of fuel determined by the second fuel state determination means on the basis of an operating state of a vehicle.

19. A fuel vapor treatment apparatus for an internal combustion engine, comprising: a canister that temporarily adsorbs fuel vapor developed in a fuel tank;a purge pipe that introduces the fuel vapor purged from the canister into an intake pipe of the internal combustion engine;a purge control valve that is arranged in the purge pipe and controls a purge flow rate from the purge pipe to the intake pipe;an air-fuel ratio sensor that is provided in an exhaust pipe of the internal combustion engine and measures an air-fuel ratio;a first fuel state determiner that determines a state of fuel of an air-fuel mixture containing the fuel vapor purged from the canister on the basis of an amount of deviation from a target air-fuel ratio of an air-fuel ratio detected by the air-fuel ratio sensor when the purge control valve is opened; andair-fuel ratio controller that controls a fuel injection quantity to the internal combustion engine to bring an air-fuel ratio to the target air-fuel ratio on the basis of the state of fuel of the air-fuel mixture purged from the canister;a second fuel state determiner that determines the state of fuel of the air-fuel mixture by purging the air-fuel mixture containing the fuel vapor from the canister in a state in which the purge control valve is closed; andan abnormality detector that detects an abnormality in the second fuel state determination means, whereinwhen no abnormality is detected by the abnormality detector, the air-fuel ratio controller switches a state of fuel for controlling the fuel injection quantity between the state of fuel determined by the first fuel state determiner and the state of fuel determined by the second fuel state determiner on the basis of an operating state of a vehicle, andwhen an abnormality is detected by the abnormality detector, the air-fuel ratio controller uses the state of fuel determined by the first fuel state determiner as the state of fuel for controlling the fuel injection quantity irrespective of the operating state of the vehicle.