INTEGRATED PRESSURE MANAGEMENT SYSTEM FOR A FUEL SYSTEM

Abstract: An integrated pressure management system (20) manages pressure and detects leaks in a fuel system. The integrated pressure management system also performs a leak diagnostic for the head space in a fuel tank (12), a canister (18) that collects volatile fuel vapors from the head space, a purge valve (16), and all associated.

Description: INTEGRATED PRESSURE MANAGEMENT SYSTEM FOR A FUEL SYSTEM Field of Invention The present invention relates to an integrated pressure management system that manages pressure and detects leaks in a fuel system. The present invention also relates to an integrated pressure management system that performs a leak diagnostic for the head space in a fuel tank, a canister that collects volatile fuel vapors from the head space, a purge valve, and all associated hoses. Background of Invention In a conventional pressure management system for a vehicle, fuel vapor that escapes from a fuel tank is stored in a canister. If there is a leak in the fuel tank, canister or any other component of the vapor handling system, some fuel vapor could exit through the leak to escape into the atmosphere instead of being stored in the canister. Thus, it is desirable to detect leaks. In such conventional pressure management systems, excess fuel vapor accumulates immediately after engine shut-down, thereby creating a positive pressure in the fuel vapor management system. Thus, it is desirable to vent, or Ablow-off,≡ this excess fuel vapor and to facilitate vacuum generation in the fuel vapor management system. Similarly, it is desirable to relieve positive pressure during tank refueling by allowing air to exit the tank at high flow rates. This is commonly referred to as onboard refueling vapor recovery (ORVR). Summary of the Invention According to the present invention, a sensor or switch signals that a predetermined pressure exists. In particular, the sensor/switch signals that a predetermined vacuum exists. As it is used herein, Apressure * ≡ is measured relative to the ambient atmospheric pressure. Thus, positive pressure refers to pressure greater than the ambient atmospheric pressure and negative pressure, or Avacuum,≤ refers to pressure less than the ambient atmospheric pressure. A valve can provide relief for positive pressure above a first predetermined pressure value, and can provide relief for vacuum below a second predetermined pressure value. A solenoid can displace the valve to an open configuration for vacuum monitoring during natural cooling, e.g., after an engine is turned off, and thereby perform a leak detection diagnostic. The solenoid can also be actuated while the engine is on to confirm purge flow and switch/sensor function. Additionally, vacuum relief by the valve can provide fail-safe operation of the purge flow system in the event that the solenoid fails with the valve in a closed configuration. The sensor/switch, the valve, and the solenoid can be integrally packaged in a single unit to improve system integrity since there are fewer leak points, i.e., possible openings in the system, and fewer electrical connectors as compared to conventional systems. Brief Description of the Drawings The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the present invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention. Like reference numerals are used to identify similar features. Figure 1 is a schematic illustration showing the operation of an apparatus according to the present invention. Figure 2 is a cross-sectional view of a first embodiment of the apparatus according to the present invention Figure 3 is a cross-sectional view of a second embodiment of the apparatus according to the present invention. Detailed Description of the Preferred Embodiment Referring to Figure 1, a fuel system 10, e.g., for an engine (not shown), includes a fuel tank 12, a vacuum source 14 such as an intake manifold of the engine, a purge valve 16, a charcoal canister 18, and an integrated pressure management system (IPMA) 20. The IPMA 20 performs a plurality of functions including signaling 22 that a first predetermined pressure (vacuum) level exists, relieving pressure 24 at a value below the first predetermined pressure level, relieving pressure 26 above a second pressure level, and controllably connecting 28 the charcoal canister 18 to the ambient atmospheric pressure A. In the course of cooling that is experienced by the fuel system 10, e.g., after the engine is turned off, a vacuum is created in the charcoal canister 18. The existence of a vacuum at the first predetermined pressure level indicates that the integrity of the fuel system 10 is satisfactory. Thus, signaling 22 is used for detecting leaks. Subsequently relieving pressure 24 at a value below the first predetermined pressure level protects the integrity of the fuel tank 12. Immediately after the engine is turned off, relieving pressure 26 allows excess fuel vapor to Ablow off, thereby facilitating the desired vacuum generation that occurs during cooling. Similarly, in the course of refueling the fuel tank 12, relieving pressure 26 allows air to exit the fuel tank 12 at high flow. While the engine is turned on, controllably connecting 28 the canister 18 to the ambient air A allows confirmation of the purge flow and allows confirmation of the signaling 22 performance. While the engine is turned off, controllably connecting 28 allows a computer for the engine to monitor the vacuum generated during cooling. Figure 2, shows a first embodiment of the IPMA 20 mounted on the charcoal canister 18. The IPMA 20 includes a housing 30 that can be mounted to the body of the charcoal canister 18 by a Abayonet≡ style attachment 32. A seal 34 is interposed between the charcoal canister 18 and the IPMA 20. This attachment 32, in combination with a snap finger 36, allows the IPMA 20 to be readily serviced in the field. As will be described in greater detail below, the housing 30 can be assembled from three housing pieces 30a,30b,30c. Signaling 22 occurs when vacuum at the first predetermined pressure level is present in the charcoal canister 18. A pressure operable device 36 separates an interior chamber in the housing 30. The pressure operable device 36, which includes a diaphragm 38 that is operatively interconnected to a valve 40, separates the interior chamber of the housing 30 into an upper portion 42 and a lower portion 44. The upper portion 42 is in fluid communication with the ambient atmospheric pressure through a first port 46. The lower portion 44 is in fluid communication with a second port 48 between housing 30 the charcoal canister 18. The lower portion 44 is also in fluid communicating with a separate portion 44a via first and second signal passageways 50,52. The present inventors have discovered that orienting the opening of the first signal passageway toward the charcoal canister 18 yields unexpected advantages in providing fluid communication between the portions 44,44a. Sealing between the housing pieces 30a,30b for the second signal passageway 52 can be provided by a protrusion 38a of the diaphragm 38 that is penetrated by the second signal passageway 52. A branch 52a provides fluid communication, over the seal bead of the diaphragm 38, with the separate portion 44a. A rubber plug 30a is installed after the housing portion 30a is molded. The force created as a result of vacuum in the separate portion 44a causes the diaphragm 38 to be displaced toward the housing part 30b. This displacement is opposed by a resilient element 54, e.g, a leaf spring. The bias of the resilient element 54 can be adjusted by a calibrating screw 56 such that a desired level of vacuum, e.g., one inch of water, will depress a switch 58 that can be mounted on a printed circuit board 60. In turn, the printed circuit board is electrically connected via an intermediate lead frame 62 to an outlet terminal 64 supported by the housing part 30c. The intermediate lead frame 62 can also penetrate a protrusion 38b of the diaphragm 38 similar to the penetration of protrusion 38a by the second signal passageway 52. The housing part 30c is sealed with respect to the housing parts 30a,30b by an O-ring 66. As vacuum is released, i.e., the pressure in the portions 44,44a rises, the resilient element 54 pushes the diaphragm 38 away from the switch 58, whereby the switch 58 resets. Pressure relieving 24 occurs as vacuum in the portions 44,44a increases, i.e., the pressure decreases below the calibration level for actuating the switch 58. Vacuum in the charcoal canister 18 and the lower portion 44 will continually act on the valve 40 inasmuch as the upper portion 42 is always at or near the ambient atmospheric pressure A. At some value of vacuum below the first predetermined level, e.g., six inches of water, this vacuum will overcome the opposing force of a second resilient element 68 and displace the valve 40 away from a lip seal 70. This displacement will open the valve 40 from its closed configuration, thus allowing air to be drawn from the upper portion 42 into the lower the portion 44. That is to say, in an open configuration of the valve 40, the first and second ports 46,48. In this way, vacuum in the fuel system 10 can be regulated. Controllably connecting 28 to similarly displace the valve 40 from its closed configuration to its open configuration can be provided by a solenoid 72. At rest, the second resilient element 68 displaces the valve 40 to its closed configuration. A ferrous armature 74, which can be fixed to the valve 40, can have a tapered tip that creates higher flux densities and therefore higher pull-in forces. A coil 76 surrounds a solid ferrous core 78 that is isolated from the charcoal canister 18 by an O-ring 80. The flux path is completed by a ferrous strap 82 that serves to focus the flux back towards the armature 74. When the coil 76 is energized, the resultant flux pulls the valve 40 toward the core 78. The armature 74 can be prevented from touching the core 78 by a tube 84 that sits inside the second resilient element 68, thereby preventing magnetic lock-up. Since very little electrical power is required for the solenoid 72 to maintain the valve 40 in its open configuration, the power can be reduced to as little as 10% of the original power by pulse- width modulation. When electrical power is removed from the coil 76, the second resilient element 68 pushes the armature 74 and the valve 40 to the normally closed configuration of the valve 40. Relieving pressure 26 is provided when there is a positive pressure in the lower portion 44, e.g., when the tank 12 is being refueled. Specifically, the valve 40 is displaced to its open configuration to provide a very low restriction path for escaping vapors from the tank 12. When the charcoal canister 18, and hence the lower portions 44, experience positive pressure above ambient atmospheric pressure, the first and second signal passageways 50,52 communicate this positive pressure to the separate portion 44a. In turn, this positive pressure displaces the diaphragm 38 downward toward the valve 40. A diaphragm pin 39 transfers the displacement of the diaphragm 38 to the valve 40, thereby displacing the valve 40 to its open configuration with respect to the lip seal 70. Thus, the refueling pressure is allowed to escape from the charcoal canister 18, through the lower portion 44, past the lip seal 70, through the upper portion 42, and through the second port 58. Relieving pressure 26 is also useful for regulating the pressure in fuel tank 12 during any situation in which the engine is turned off. By limiting the amount of positive pressure in the fuel tank 12, the cool-down vacuum effect will take place sooner. Figure 3 shows a second embodiment of the present invention that is substantially similar to the first embodiment shown in Figure 2, except that the first and second signal passageways 50,52 have been eliminated. Instead, the signal from the lower portion 44 is communicated to the separate portion 44a via a path that extends through spaces between the solenoid 72 and the housing 30, and through spaces between the intermediate lead frame 62 and the housing 30. While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and their equivalents thereof. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.

Claims: What we claim is: 1. An integrated pressure management apparatus comprising: a housing including an interior chamber, a first port, and a second port; a pressure operable device separating the chamber into a first portion and a second portion, the first portion communicating with the first port, the second port communicating with the second port, the device permitting communication between the first and second ports in one configuration and inhibiting communication between the first and second ports in a second configuration; and a switch signaling displacement of the device in response to vacuum in the first portion. 2. The integrated pressure management apparatus according to claim 1, wherein the switch is disposed in the housing. 3. The integrated pressure management apparatus according to claim 2, wherein the switch is disposed in the first portion. 4. The integrated pressure management apparatus according to claim 1 , further comprising: a solenoid displacing the device from the first configuration to the second configuration. 5. The integrated pressure management apparatus according to claim 4, wherein the solenoid includes an elongated ferrous core extending transversely with respect to a displacement direction of the device between the first and second configurations. 6. The integrated pressure management apparatus according to claim 1, further comprising: a first resilient element opposing the displacement of the device in response to vacuum in the first portion. 7. The integrated pressure management apparatus according to claim 6, further comprising: an adjuster calibrating a biasing force of the first resilient element. 8. The integrated pressure management apparatus according to claim 1, further comprising: a second resilient element opposing displacement of the device from the first configuration to the second configuration. 9. The integrated pressure management apparatus according to claim 8, wherein a biasing force of the second resilient element is greater than a biasing force of the vacuum in the first portion displacing the device. 10. The leak detection apparatus according to claim 7, wherein the first portion communicates with the first port via a passage defined at least in part by a space between the housing and the solenoid. 11. The leak detection apparatus according to claim 1, wherein the first portion communicates with the first port via a passage defined at least in part by a space between the housing and electrical connections to the switch. 12. The leak detection apparatus according to claim 1, wherein the first portion communicates with the first port via a passage defined by the housing. 13. The integrated pressure management apparatus according to claim 8, further comprising: a solenoid displacing the valve from the first configuration to the second configuration. 14. The leak detection apparatus according to claim 13, wherein the solenoid includes an elongated ferrous core extending transversely with respect to a displacement direction of the valve between the first and second configurations. 15. The integrated pressure management apparatus according to claim 14, further comprising: a ferrous armature secured to the valve, the ferrous armature being displaced in the displacement direction by the ferrous core. 16. A method of using fluid volume variations for leak detection, the method comprising: an actuator displacing the device. 17. The leak detection apparatus according to claim 2, wherein the actuator includes a solenoid. 18. The leak detection apparatus according to claim 3, wherein the detector includes a ferrous armature being disposed on the housing and signals] in response to displacement of the device in the chamber.

Inventors: COOK JOHN EDWARD, PERRY PAUL DOUGLAS, COOK, JOHN, EDWARD, PERRY, PAUL, DOUGLAS
Applicants: SIEMENS CANADA LTD, SIEMENS CANADA LIMITED
Application year: 2000
Main classification: F02M25
IPC codes: F02M25