Tank venting system and method for diagnosing same

• US 9,551,304 B2
• Filed: 09/19/2012
• Issued: 01/24/2017
• Est. Priority Date: 10/13/2011
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Haefele, Matthias
• Primary Examiner(s): Nguyen, Hung Q
• Assistant Examiner(s): MO, XIAO EN
• Application Number:
  US14/351,474
• Publication Number:
  US 20140345574A1
• Time in Patent Office: 1,588 Days
• Field of Search: 123518-521
• US Class Current: 1/1
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F02M 25/0836 Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold

Abstract

A tank venting system of an internal combustion engine having an intake manifold, a fuel tank, and an activated carbon filter includes: a tank vent valve; at least one check valve; and a pressure sensor situated between the tank vent valve and the check valve. For diagnosing this tank venting system, a negative pressure which is lower than the ambient pressure outside the engine system is stored between the tank vent valve and the check valve. The stored pressure is changed by controlling the tank vent valve, and the change in the pressure is measured via the pressure sensor. The functioning of the tank venting line, of the check valve, and of the tank vent valve is deduced from the correlation of the opening state of the tank vent valve with the change in pressure.

Claims

1. A method for diagnosing a tank vent valve in a tank venting system for an internal combustion engine having an intake manifold, a fuel tank, and an activated carbon filter, the tank venting system including a tank valve situated in a line connecting the activated carbon filter to the intake manifold, at least one check valve situated in the line between the tank vent valve and the intake manifold, and a pressure sensor situated in the line between the tank vent valve and the check valve, the method comprising:

while the internal combustion engine is switched off, opening the tank vent valve

measuring, via the pressure sensor, a first pressure between the tank vent valve and the check valve;

subsequently closing the tank valve vent when the first pressure is not equal to ambient pressure; and

(i) after the tank vent valve is closed, measuring, via the pressure sensor, the first pressure between the tank vent valve and the check valve, and determining an upward sensor drift if the first pressure is greater than the sum of the ambient pressure and a predefined error threshold;

(ii) after the tank vent valve is closed and the first pressure is measured, if the first pressure is less than a setpoint pressure which is ascertained over the engine switched-off period on the basis of the difference between the first pressure at the immediately preceding time the internal combustion engine was switched off and the ambient pressure, measuring a curve of the first pressure when the internal combustion engine is started, and detecting a downward sensor drift if at least one of (a) at any point in time during the starting operation, the first pressure is less than a second pressure in the intake manifold of the internal combustion engine by a predefined error threshold, and (b) at the end of the starting operation, the first pressure is less than a minimum achieved pressure; and

(iii) at the end of a starting operation, opening the tank vent valve if the second pressure is less than the ambient pressure and determining a jamming of the tank vent valve if one of no change in the first pressure is measured, or the first pressure remains equal to the minimum achieved pressure since the starting of the engine.

2. The method as recited in claim 1, wherein when the first pressure is not equal to the second pressure in the intake manifold of the internal combustion engine during starting, the following conditions are determined:

a) if the first pressure is equal to the ambient pressure, the line between the pressure sensor and an inlet point of the tank venting line into the intake manifold is determined as being interrupted, and

b) if the first pressure is less than the ambient pressure and greater than the second pressure in the intake manifold, and the first pressure during continued operation of the internal combustion engine is equal to the second pressure plus the predefined error threshold, a lower limiting pressure is defined as the first pressure which is measured at the pressure sensor when the tank vent valve is open and the line between the tank vent valve and the check valve is intact, and an upper limiting pressure is defined as the first pressure which is measured at the pressure sensor when the tank vent valve and the check valve are intact but the line between the tank vent valve and the check valve has fallen off, and

b1) if the first pressure is no greater than the upper limiting pressure and greater than the lower limiting pressure, the pressure line between the pressure sensor and the tank vent valve is recognized as being defective;

b2) if the first pressure is no greater than the lower limiting pressure and greater than the second pressure in the intake manifold, the tank vent valve is recognized as being open;

b3) if the first pressure is greater than the second pressure in the intake manifold and less than the ambient pressure, in an engine system which has two tank venting inlet points and which includes a full load inlet point, (i) the check valve of the line between the tank vent valve and the full load inlet point is recognized as being defective if a change in pressure occurs when the tank vent valve is energized, and (ii) the pressure line between the pressure sensor and the tank vent valve is recognized as being defective when no pressure jump occurs when the tank vent valve is energized.

3. A method for diagnosing a tank vent valve in a tank venting system for an internal combustion engine having an intake manifold, a fuel tank, and an activated carbon filter, the tank venting system including a tank valve situated in a line connecting the activated carbon filter to the intake manifold, at least one check valve situated in the line between the tank vent valve and the intake manifold, and a pressure sensor situated in the line between the tank vent valve and the check valve, the method comprising:

measuring, via the pressure sensor, a first pressure between the tank vent valve and the check valve during operation of the internal combustion engine;

opening and closing the tank vent valve during the operation of the internal combustion engine, wherein during the operation of the internal combustion engine, if the first pressure does not vary when the tank vent valve is opened and closed, a lower limiting pressure is defined as the first pressure which is measured at the pressure sensor when the tank vent valve is open and the line between the tank vent valve and the check valve is intact, and an upper limiting pressure is defined as the first pressure which is measured at the pressure sensor when the tank vent valve and the check valve are intact but the line between the tank vent valve and the check valve has fallen off, and if a second pressure in the intake manifold is less than the ambient pressure, and

(i) if the tank vent valve has been recognized as defective, the tank vent valve is recognized as being jammed open if the first pressure is no greater than the lower limiting pressure and greater than the second pressure in the intake manifold,

(ii) if a diagnosis of the tank vent valve is not possible, a line defect is recognized if the first pressure is greater than the lower limiting pressure and less than the ambient pressure,

(iii) if the first pressure is no greater than the second pressure in the intake manifold and remains at the minimum achieved value, the tank vent valve is recognized as being jammed shut, or

(iv) if the first pressure is consistently equal to the second pressure in the intake manifold, the check valve is recognized as being defective, if the second pressure in the intake manifold is greater than the ambient pressure, and

(v) if the first pressure drops with increasing of the second pressure in an engine system which has two tank venting inlet points and which includes a full load inlet point, the tank vent valve is recognized as being jammed open if the first pressure is not greater than the lower limiting pressure and greater than the pressure at the full load inlet point, and the tank vent valve is recognized as being jammed shut if the first pressure is equal to the pressure at the full load inlet point,

(vi) if the first pressure is equal to the ambient pressure when the tank vent valve is open, the line between the pressure sensor and the full load inlet point is recognized as being defective,

(vii) if the first pressure is greater than the ambient pressure, and the first pressure is correlated with the second pressure, the check valve is recognized as being defective, and

(viii) if the first pressure is greater than the lower limiting pressure and no greater than the upper limiting pressure, the line between the tank vent valve and the pressure sensor is recognized as being defective.

4. The method as recited in claim 3, wherein during operation of the internal combustion engine,

when the tank vent valve is closed, the first pressure is no greater than the second pressure in the intake manifold, and the second pressure is less than the ambient pressure,

(i) a falling off of the line is recognized if the first pressure is equal to the ambient pressure,

(ii) a downward sensor drift is recognized if the first pressure is continuously less than the second pressure by an offset, and

(iii) the check valve is recognized as being jammed open if the first pressure is equal to the second pressure with increasing of the second pressure,

when the tank vent valve is open, a lower limiting pressure is defined as the first pressure which is measured at the pressure sensor when the tank vent valve and the line between the tank vent valve and the check valve is intact, and an upper limiting pressure is defined as the first pressure which is measured at the pressure sensor when the tank vent valve and the check valve are intact but the line between the tank vent valve and the check valve has fallen off, and

(i) the line between the tank vent valve and the pressure sensor is recognized as having fallen off if the first pressure is greater than the lower limiting pressure and no greater than the upper limiting pressure, and

(ii) the line between the pressure sensor and a tank venting inlet point is recognized as having fallen off if the first pressure is equal to the ambient pressure.

5. The method as recited in claim 3, wherein during operation of the internal combustion engine, during the transition of the second pressure in the intake manifold from a value less than the ambient pressure to a value greater than the ambient pressure, the tank vent valve is opened until the first pressure corresponds to the ambient pressure, and a defect in the line between the tank vent valve and a full load inlet point is recognized if the first pressure does not fall below the ambient pressure after the tank vent valve is closed.

6. The method as recited in claim 3, wherein prior to switching off the internal combustion engine, the tank vent valve is closed in order to store the second pressure in the intake manifold as the first pressure between the tank vent valve and the check valve, and after closing of the tank vent valve, an increase in the first pressure is measured and the tank vent valve and the lines have been assessed as defect-free,

(i) the check valve of an inlet point into the intake manifold is recognized as being defective if the first pressure is consistently equal to the first pressure and the second pressure is less than the ambient pressure,

(ii) the check valve of the full load inlet point is recognized as being defective if the first pressure is always greater than the second pressure by an offset and the second pressure is less than the ambient pressure, and when the second pressure is greater than the ambient pressure, the first pressure remains constant when the second pressure drops.