Leak detection method and associated valve and fuel system

• US 7,908,099 B2
• Filed: 02/05/2007
• Issued: 03/15/2011
• Est. Priority Date: 02/07/2006
• Status: Expired due to Fees

• Current Assignee: Plastic Omnium Advanced Innovation and Research
• Original Assignee: Inergy Automotive Systems Research (Societe Anonyme) (Solvac SA)
• Inventors: Garabedian, Scott, McCleary, Ryan, Hill, David, Dirkson, Dave, Behar, Ron, Slusser, Kevin, Grant, Eric, Mehta, Saurin
• Primary Examiner(s): Dunn; Drew A
• Assistant Examiner(s): Cherry; Stephen J
• Application Number:
  US12/162,439
• Publication Number:
  US 20090099795A1
• Time in Patent Office: 1,499 Days
• Field of Search: 702/51, 731/143.9, 731/144.1, 73/497
• US Class Current: 702/51
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• 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

Method of detecting a leak in a fuel system comprising a fuel tank and an orifice with a controlled section between the tank and the atmosphere, according to which

• a) the controlled section is set to a value A_l at a time T₁ and a pressure differential Δp₁ between the inside of the tank and the atmosphere is measured at least after an interval of time ΔT from T₁, for a constant fuel flow out of the tank;
• b) the controlled section is set to a value A₂ at a time T₂ and a pressure differential Δp₂ between the inside of the tank and the atmosphere is measured at least after the same interval of time ΔT from T₂, for the same constant fuel flow;
• c) a ratio of the pressure differentials Δp₁ and Δp₂ is computed and is compared to a reference pressure differential ratio Δp_L obtained with the same fuel system but comprising a calibrated leak.

Claims

1. A method of detecting a leak in a fuel system comprising a fuel tank and an orifice with a controlled section between the tank and the atmosphere, according to which:

a) the controlled section is set to a value A₁ at a time T₁ and a pressure differential Δ

p₁ between the inside of said fuel tank and the atmosphere is measured at least after an interval of time Δ

T from T₁, for a constant fuel flow out of said fuel tank;

b) the controlled section is set to a value A₂ at a time T₂ and a pressure differential Δ

p₂ between the inside of said fuel tank and the atmosphere is measured at least after the same interval of time Δ

T from T₂, for the same constant fuel flow;

c) a ratio of said pressure differentials Δ

p₁ and Δ

p₂ is computed and is compared to a reference pressure differential ratio Δ

p_L obtained with the same fuel system but comprising a calibrated leak; and

d) a leak bigger than said calibrated leak is detected if said ratio computed at stage c) is smaller than said reference ratio Δ

p_L.

2. The method according to claim 1, wherein the fuel system comprises an evaporative emission control system comprising a canister and an electronically controlled electromechanical valve, wherein the orifice of controlled section is between the fuel tank and the canister, and wherein said controlled section is controlled by the electromechanical valve.

3. The method according to claim 2, wherein said valve comprises a stationary outer housing comprising at least three bores, and a translating inner section which translates along the primary axis of the outer housing and which comprises adequate bores defining with the bores of the housing at least three ports of the valve.

4. The method according to claim 1, wherein the orifice of controlled section is in between the vent port of a canister, and the atmosphere and is controlled by a vent valve allowing to vent the tank during normal service and during refueling.

5. The method according to claim 1, wherein the fuel system comprises a fuel system control unit (FSCU), and wherein steps a) to d) are performed by the FSCU.

6. The method according to claim 5, wherein said fuel system comprises a fuel pump, and wherein said fuel flow is controlled by said fuel pump which is controlled by said FSCU.

7. The method according to claim 6, wherein said fuel pump is controlled through a variable speed/variable pressure control program.

8. The method according to claim 1, wherein said pressure differentials Δ

p₁ and Δ

p₂ are measured only once after the interval of time Δ

T from respectively T₁, and T₂.

9. The method according to claim 1, wherein

a) said pressure differential Δ

p₁ is measured after successive intervals of time Δ

T starting from T₁ in such a manner as to obtain one sequence of N measurements where N is a constant;

b) said pressure differentials Δ

p₂ is measured after successive intervals of time Δ

T starting from T₂ in such a manner as to obtain one sequence of N measurements; and

c) a sequence of N ratios of said pressure differentials Δ

p₁ and Δ

p₂ is computed from sequences of measurements obtained at stages a) and b), a numerical filter is applied to this sequence of N ratios in such a manner as to obtain a sequence of N filtered ratios, and said sequence of filtered ratios is compared to a sequence of N reference pressure differential ratios Δ

p_L, obtained with the same fuel system but comprising a calibrated leak.

10. The method according to claim 1, wherein said method is included in an on-board diagnostic (OBD) test.

11. A fuel system equipped with leak detection means, said fuel system comprising:

a) a fuel tank;

b) an orifice with a controlled section between the tank and the atmosphere;

c) means for varying said controlled section between at least two values;

d) means for measuring a pressure differential between the inside of the tank and the atmosphere at said at least two values of said controlled section; and

e) means for computing a ratio between two pressure differentials measured by the means for measuring a pressure differential at stage d) and for comparing said ratio with a reference pressure differential ratio obtained with the same fuel system but with a calibrated leak and the atmosphere.

12. The fuel system according to claim 11, wherein the means for varying the controlled section are included into a valve which is located between a canister and the atmosphere and which is a vent valve allowing to vent the tank during normal service and during refueling.