Diagnosis apparatus and method for an evapo-purge system

• US 5,780,728 A
• Filed: 04/25/1995
• Issued: 07/14/1998
• Est. Priority Date: 04/27/1994
• Status: Expired due to Fees

• Current Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Takamori, Katsuhito
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US08/429,245
• Time in Patent Office: 1,176 Days
• Field of Search: 123/520, 123/516, 123/518, 73/40, 73/46, 73/47, 73/49.7, 73/116, 73/117.2, 73/117.3
• US Class Current: 73/114.39
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

In the general mode, the pressure sensor is communicated with an intake pipe through the first diverged tube by the directional valve so that the sensor can measure the pressure in the intake pipe. Also, in the evapo-purge mode, the pressure sensor is communicated with the purge line through the second diverged tube by the directional valve so that the sensor can measure pressures in the purge line produced when the purge control valve is closed and open. That is, the pressure sensor for measuring a pressure in the purge line is also adapted for measuring the pressure in the intake pipe of the engine. Also, a predetermined range of the difference between the pressures can be settled depending on the load of the engine, such as an engine speed, an intake pipe negative pressure, a throttle opening, and a fundamental injection pulse duration.

Claims

1. A diagnosis apparatus for an evapo-purge system having a canister for storing an evaporated fuel generated from a fuel tank, an intake pipe connected to an engine for inducing air thereof, and a purge line connected to said canister, comprising:

a purge control valve installed in the purge line for controlling purge flow rate;

a directional valve connected between the intake pipe and the purge line via a first tube diverged from the intake pipe and a second tube diverged from the purge line;

a pressure sensor, in a general mode, communicated with the intake pipe through the first diverged tube by switching the directional valve and measuring a pressure in the intake pipe and, in a evapo-purge mode, communicated with the purge line through the second diverged tube by switching the directional valve and measuring pressures in the purge line when the purge control valve is closed and open; and

discriminating means for discriminating the state of the evapo-purge system;

wherein when the evapo-purge system is concluded to be normal, the measured value of pressure in the purge line produced when the purge control valve is closed can be regarded as equivalent to atmospheric pressure so that the measured value is adapted for some other control of the engine, and is concluded to be abnormal when the measured values are of a difference falling outside a predetermined range between pressure in the purge line produced when the purge control valve is closed and pressure in the purge line produced when the purge control valve is open.

2. The diagnosis apparatus for an evapo-purge system according to claim 1, wherein

the predetermined range is settled depending on load of the engine.

3. A diagnosis method for an evapo-purge system having a canister for storing an evaporated fuel generated from a fuel tank, an intake pipe connected to an engine for inducing air thereof, and a purge line connected to said canister, comprising steps of:

installing a control valve for controlling purge flow rate in the purge line;

installing a directional valve connected between the intake pipe and the purge line by a first tube diverged from the intake pipe and a second tube diverged from the purge line;

connecting a pressure sensor, in a general mode to the intake pipe through the first diverged tube by switching the directional valve and measuring a pressure in the intake pipe and, in a evapo-purge mode, connecting the pressure sensor to the purge line through the second diverged tube by switching the directional valve and measuring pressures in the purge line produced when the purge control valve is closed and open, so wherein when engine operating conditions satisfy examining conditions, said pressure sensor measures the pressures in the purge line produced when the purge control valve is closed and open;

connecting an electronic controller to the directional valve for controlling the switching of the direction of the directional valve; and

discriminating the evapo-purge system to be abnormal in case a difference between a measured value of pressure in the purge line produced when the purge control valve is closed and the measured value of pressure in the purge line produced when the purge control valve is open is outside a predetermined range.

4. A diagnosis method for an evapo-purge system having a canister for storing an evaporated fuel generated from a fuel tank, an intake pipe connected to an engine for inducing air thereof, and a purge line connected to said canister, comprising steps of:

installing a control valve for controlling purge flow rate in the purge line;

installing a directional valve connected between the intake pipe and the purge line by a first tube diverged from the intake pipe and a second tube diverged from the purge line;

connecting a pressure sensor, in a general mode, to the intake pipe through the first diverged tube by switching the directional valve and measuring a pressure in the intake pipe and, in a evapo-purge mode, connecting the pressure sensor to the purge line through the second diverged tube by switching the directional valve and measuring pressures in the purge line produced when the purge control valve is closed and open, so wherein when engine operating conditions satisfy examining conditions, said pressure sensor measures the pressures in the purge line produced when the purge control valve is closed and open; and

discriminating the evapo-purge system where when the evapo-purge system is concluded to be normal, the measured value of pressure in the purge line produced when the purge control valve is closed can be regarded as equivalent to atmospheric pressure so that the measured value is adapted for some other control of the engine, and where the evapo-purge system is determined to be abnormal in case the measured pressure between the measured value of the pressure in the purge line produced when the purge control valve is closed and the measured value of the pressure in the purge line produced when the purge control valve is open is outside a predetermined range.

5. A diagnosis method during engine operation for an evapo-purge system having a canister for storing an evaporated fuel generated from a fuel tank, an intake pipe connected to an engine for inducing air thereof, and a purge line connected to said canister, comprising steps of:

providing a control valve for controlling purge flow rate in the purge line;

providing a directional valve connected between the intake pipe and the purge line by a first tube diverged from the intake pipe and a second tube diverged from the purge line;

providing a pressure sensor connected, in a general mode, to the intake pipe through the first diverged tube by switching the directional valve and measuring a pressure in the intake pipe and, in a evapo-purge mode, providing the pressure sensor connected to the purge line through the second diverged tube by switching the directional valve and measuring pressures in the purge line produced when the purge control valve is closed and open, wherein when engine operating conditions satisfy examining conditions, said pressure sensor measures the pressures in the purge line produced when the purge control valve is closed and open; and

discriminating the evapo-purge system to achieve a diagnosis where the evapo-purge system is determined to be abnormal when subtraction of the measured value of the pressure in the purge line produced when the purge control valve is closed and the measured value of the pressure in the purge line produced when the purge control valve is open yields a difference outside a predetermined range and disregarding the diagnosis when conditions during engine operation at the start and end thereof exceed a set value.

6. A diagnosis method during engine operation for an evapo-purge system having a canister for storing an evaporated fuel generated from a fuel tank, an intake pipe connected to an engine for inducing air thereof, and a purge line connected to said canister, comprising steps of:

providing a control valve for controlling purge flow rate in the purge line;

providing a directional valve connected between the intake pipe and the purge line a first tube diverged from the intake pipe and a second tube diverged from the purge line;

providing a pressure sensor connected, in a general mode, to the intake pipe through the first diverged tube by switching the directional valve and measuring a pressure in the intake pipe and, in a evapo-purge mode, providing the pressure sensor connected to the purge line through the second diverged tube by switching the directional valve and measuring pressures in the purge line produced when the purge control valve is closed and open;

wherein when engine operating conditions satisfy examining conditions, said pressure sensor measures the pressures in the purge line produced when the purge control valve is closed and open; and

discriminating the evapo-purge system to achieve a diagnosis where the evapo-purge system is determined to be abnormal when subtraction of the measured value of the pressure in the purge line produced when the purge control valve is closed and the measured value of the pressure in the purge line produced when the purge control valve is open yields a difference outside a predetermined range wherein an atmospheric pressure value measured by the pressure sensor is fixed to a predetermined value when the evapo-purge system is concluded to be abnormal.

7. A diagnosis apparatus for an evapo-purge system of an automotive vehicle having, an engine for driving the vehicle, a fuel tank mounted on the vehicle for containing a fuel, an intake pipe connected to the engine for inducing air thereof, a purge line connected between the fuel tank and the intake pipe for purging an evaporated fuel vapor to the intake pipe, and a canister inserted in the purge line for storing the evaporated fuel vapor generated from the fuel tank, comprising:

a purge control valve inserted in the purge line for controlling an amount of the evaporated fuel vapor in dependency on driving conditions of the engine;

a first line connected to the intake pipe at an approximately downstream position from a connecting point of the purge line with the intake pipe;

a second line connected to the purge line at an approximately intermediate position between the canister and the intake pipe;

for detecting a first inside pressure of the purge line and a second inside pressure of the purge line when the purge control valve is turned off and for generating a first signal when a first inside pressure is detected and a second signal when a second inside pressure is detected;

a directional valve connected with the pressure sensor and communicated with the first and second lines for changing a communication of the first line or the second line to the pressure sensor; and

judging means responsive to the first and second signals for deriving a difference between the first and second inside pressures and for deciding the evapo-purge system as a malfunction if the difference is smaller than a first predetermined value or larger than a second predetermined value that is larger than the first predetermined value.

8. The diagnosis apparatus according to claim 7, wherein the pressure sensor detects the inside pressures when the purge control valve continues a repetition of closing and opening operations for purging while the engine is operated in a steady state.

9. The diagnosis apparatus according to claim 7, wherein the first signal is used for other controls of the engine as a value representing an atmospheric pressure when the purge control valve is closed and when the evapo-purge system is judged normal.

10. The diagnosis apparatus according to claim 7, wherein the first and second predetermined values vary in accordance with a load to the engine.

11. The diagnosis apparatus according to claim 7, wherein the first and second predetermined values are stored in a table.

12. The diagnosis apparatus according to claim 7, wherein the first and second predetermined values are determined in accordance with engine operating conditions when the engine is in steady state.

13. The diagnosis apparatus according to claim 7, wherein the first and second predetermined values are decided in accordance with one of or a combination of parameters indicative of load, vehicle environmental conditions, and engine operating conditions.

14. A diagnosis method for an evapo-purge system of an automotive vehicle having, an engine for driving the vehicle, a fuel tank mounted on the vehicle for containing a fuel, an intake pipe connected to the engine for inducing air thereof, a purge line connected between the fuel tank and the intake pipe for purging evaporated fuel vapor to the intake pipe, and a canister inserted in the purge line for storing evaporated fuel vapor generated from the fuel tank, comprising the steps of:

purging the evaporated fuel vapor from the fuel tank to the intake pipe via the purge line;

controlling an amount of the evaporated fuel vapor in dependency on driving conditions of the engine;

providing a line connected between an upstream position of a purge control valve and the intake pipe;

inserting a directional valve in the line therebetween;

changing a communication of the purge line and the intake pipe by the directional valve;

sensing inside pressures of the purge line and the intake pipe;

comparing the inside pressure of the purge line with that of the intake pipe;

calculating a difference between the inside pressures of the purge line and the intake pipe based on the comparison result; and

deciding the evapo-purge system as a malfunction when the difference is smaller than a first predetermined value or larger than a second predetermined value that is larger than the first predetermined value.

15. The diagnosis method according to claim 14, wherein the sensing step is executed when the purge control valve continues closing and opening operations for purging while the engine is operated in a steady state.

16. The diagnosis method according to claim 14, further comprising the step of using the detected inside pressure of the purge line for other controls of the engine as a value representing an atmospheric pressure when the purge control is closed and when the evapo-purge system is judged normal.

17. The diagnosis method according to claim 14, further comprising the step of varying the first and second predetermined values in accordance with a load to the engine.

18. The diagnosis method according to claim 14, wherein the sensing step is interrupted when the engine operating condition is changed beyond a set range of diagnosis conditions.

19. The diagnosis method according to claim 18, wherein the calculated difference is abandoned when a difference between the engine operating conditions at a starting time of the diagnosis and at an ending time of the diagnosis exceeds the set range.

20. The diagnosis method according to claim 14, wherein the diagnosis is suspended when the pressure is judged as said malfunction.

21. The diagnosis method according to claim 14, further comprising the step of fixing the sensed inside pressure of the purge line at a predetermined value when the evapo-purge system is determined as being in an abnormal condition.

22. A diagnosis apparatus for an evapo-purge system of an automotive vehicle having, an engine for driving the vehicle, a fuel tank mounted on the vehicle for containing a fuel, an intake pipe connected to the engine for inducing air thereof, a purge line connected between the fuel tank and the intake pipe for purging evaporated fuel vapor to the intake pipe, and canister inserted in the purge line for storing the evaporated fuel vapor generated from the fuel tank, comprising:

a purge control valve inserted in the purge line for controlling an amount of the evaporated fuel vapor in dependency on driving conditions of the engine;

a line connected to the purge line at an approximately intermediate distance position between the canister and the intake pipe;

a pressure sensor connected to the line for detecting a first inside pressure of the purge line when the purge control valve is closed and a second inside pressure of the purge line when the purge control valve is opened and for generating a signal for each of the first and second inside pressures of the purge line; and

judging means responsive to the signal for deriving a difference between the first and second inside pressures and for deciding the evapo-purge system as a malfunction if the difference is smaller than first predetermined value or larger than a second predetermined value that is larger than the first predetermined value.

23. A diagnosis method for an evapo-purge system of an automotive vehicle having, an engine for driving the vehicle, a fuel tank mounted on the vehicle for containing a fuel, an intake pipe connected to the engine for inducing air thereof, a purge line connected between the fuel tank and the intake pipe for purging an evaporated fuel vapor to the intake pipe, and a canister inserted in the purge line for storing the evaporated fuel vapor generated from the fuel tank, comprising the steps of:

purging the evaporated fuel vapor from the fuel tank to the intake pipe via the purge line;

controlling an amount of the evaporated fuel vapor in dependency on driving conditions of the engine;

providing a line connected to the purge line;

sensing a first inside pressure of the purge line when the purging is executed and a second inside pressure of the purge line when the purging is stopped;

comparing the first and second inside pressures with each other;

calculating a difference between the inside pressures based on the comparison result; and

deciding the evapo-purge system as a malfunction when the difference is smaller than a first predetermined value or larger than a second predetermined value that is larger than the first predetermined value.