Method for detecting leaks in a motor vehicle tank ventilation system

• US 5,490,414 A
• Filed: 09/22/1994
• Issued: 02/13/1996
• Est. Priority Date: 08/21/1992
• Status: Expired due to Fees

• Current Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Original Assignee: Mercedes-Benz AG (Mercedes-Benz Group AG)
• Inventors: Durschmidt, Ferry, Strauss, Wolfgang
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/310,425
• Time in Patent Office: 509 Days
• Field of Search: 73/40, 73/49.2, 73/49.3, 73/49.7, 73/117.3, 73/118.1, 73/40.5, 73/46, 73/49.8, 73/40.7, 123/520
• US Class Current: 73/49.2
• CPC Class Codes: B60K 15/03504 adapted to avoid loss of fuel or fuel vapour, e.g. with vapour recovery systems
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

In a method for detecting leaks in a motor vehicle tank ventilation system which includes an adsorption filter connected to the tank, via a ventilation conduit, to the induction pipe of an internal combustion engine via a discharge conduit and to the atmosphere via an air supply conduit, a shut-off valve arranged in the air supply conduit is closed to isolate the system from the atmosphere, a regeneration valve arranged in the discharge conduit is then opened so as to generate in the system a predetermined vacuum up to a point of time at which a stable equilibrium state of the air/fuel ratio in the system is achieved, the regeneration valve is then closed to isolate the system also from the induction pipe, and the vacuum in the system is subsequently maintained over a predetermined period and the existence of a leak in the tank ventilation system is indicated if the vacuum in the system falls below a predetermined threshold value during the predetermined monitoring period.

Claims

1. A method for detecting leaks in a motor vehicle tank ventilation system including a fuel tank, an adsorption filter in communication with said fuel tank via a ventilation conduit, a differential pressure sensor arranged in the ventilation conduit, an air supply conduit connecting said adsorption filter with the atmosphere and having a shut-off valve arranged therein, a discharge conduit connecting said adsorption filter to an induction pipe of an internal combustion engine and including a controllable regeneration valve, and a control unit for controlling the valves, said differential pressure sensor being connected to said control unit for relating thereto the pressure sensed in said ventilation conduit, said method comprising the steps of:

closing said shut-off valve so as to isolate said system from the atmosphere, opening and controlling said regeneration valve so as to generate in said system a reduction of the pressure while the air/fuel vapor ratio changes until a predetermined vacuum is generated and to maintain said predetermined vacuum up to a point of time at which a stable equilibrium state of the air/fuel vapor ratio in the system is achieved, then closing said regeneration valve to isolate said system also from said induction pipe, monitoring the vacuum in said system over a predetermined period and indicating the existence of a leak in the tank ventilation system if the vacuum in said system falls below a predetermined threshold value during said predetermined period.

2. A method according to claim 1, wherein the existence of a major leak is indicated if said predetermined vacuum cannot be generated.

3. A method for detecting leaks in a motor vehicle tank ventilation system including a fuel tank, an adsorption filter in communication with said fuel tank via a ventilation conduit, a differential pressure sensor arranged in the ventilation conduit, an air supply conduit connecting said adsorption filter with the atmosphere and having a shut-off valve arranged therein, a discharge conduit connecting said adsorption filter to an induction pipe of an internal combustion engine and including a controllable regeneration valve, and a control unit for controlling the valves, said differential pressure sensor being connected to said control unit for relating thereto the pressure sensed in said ventilation conduit, said method comprising the steps of:

closing said shut-off valve so as to isolate said system from the atmosphere, opening said regeneration valve to provide for communication between said engine induction pipe in which a vacuum is maintained during engine operation, and said adsorption filter and controlling said regeneration valve to reduce the pressure in the tank ventilation system so as to generate in said system a predetermined vacuum, maintaining said predetermined vacuum for a predetermined control period after which a stable equilibrium state of the air/fuel vapor ratio in the system is achieved, then closing said regeneration valve to isolate said system also from said induction pipe, monitoring the vacuum in said system over a predetermined period and indicating the existence of a leak in the tank ventilation system if the vacuum in said system falls below a predetermined threshold value during said predetermined period.

4. A method according to claim 3, wherein the existence of a major leak is indicated if said predetermined vacuum cannot be generated.

5. A method for detecting leaks in a motor vehicle tank ventilation system including a fuel tank, an adsorption filter in communication with said fuel tank via a ventilation conduit, a differential pressure sensor arranged in the ventilation conduit, an air supply conduit connecting said adsorption filter with the atmosphere and having a shut-off valve arranged therein, a discharge conduit connecting said adsorption filter to an induction pipe of an internal combustion engine and including a controllable regeneration valve, and a control unit for controlling the valves, said differential pressure sensor being connected to said control unit for relating thereto the pressure sensed in said ventilation conduit, said method comprising the steps of:

closing said shut-off valve so as to isolate said system from the atmosphere, opening said regeneration valve while the air/fuel vapor ratio changes so as to provide in said system a reduction of pressure to achieve a vacuum that is greater than a predetermined vacuum, and controlling said regeneration valve over a predetermined control period, after which a stable equilibrium state of the air/fuel vapor ratio in the system is achieved, so as to maintain the pressure in said system, such that the vacuum is reduced from the initial value to the predetermined vacuum within said predetermined control period, then closing said regeneration valve to isolate said system also from said induction pipe, monitoring the vacuum in said system over a predetermined period and indicating the existence of a leak in the tank ventilation system if the vacuum in said system falls below a predetermined threshold value during said predetermined period.

6. A method according to claim 5, wherein the existence of a major leak is indicated if said predetermined vacuum cannot be generated.