Abstract:
Apparatus and method for detecting a fuel leak from a component includes providing a fuel leak enclosure about the component being monitored.

Description:
TECHNICAL FIELD 
     The present invention relates to fuel leak detection for fuel containing devices. In one particularly advantageous embodiment, the invention relates to an apparatus and method for detecting a fuel leak in a fuel pump of the fuel system of a vehicle. 
     BACKGROUND OF THE INVENTION 
     Fuel systems for driving machinery or engines include various components such as a fuel tank, fuel lines for delivering the fuel to the engine, fuel pumps for pumping the fuel from the tank through the fuel lines to the engine, and fuel injectors for injecting fuel into a respective cylinder, for example. Fuel leaks (both liquid and vapor) may occur in any part of the fuel system and it is desirable to be alerted to such leaks at the earliest possible moment. Furthermore, due to environmental concerns and engine operating efficiency, it is desirable to prevent passage of leaked fuel into the atmosphere or into or onto surrounding components. 
     For example, one potential source of a fuel leak is at the mechanical rotary or reciprocating pump seal of a high pressure fuel pump in a vehicle fuel system. Direct injected gasoline engines require fuel pressures as high as 20 MPa to operate. The fuel pressure is normally generated by a mechanical engine-driven fuel pump. This high pressure fuel pump can be either directly mounted to the engine and driven from a dedicated cam lobe on the camshaft or a coupling driven from the end of the crankshaft, or remotely mounted and driven by the engine serpentine or a dedicated belt coming off the engine. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above need by providing a unique fuel leak detection system. In a broad aspect of the invention, a fuel leak enclosure is provided adjacent the component that is being monitored for a fuel leak. The component being monitored may be any component that comes into contact with fuel. In a vehicle, such components may include the fuel tank, fuel lines, fuel rails, fuel pumps and fuel injectors, for example. 
     The fuel leak enclosure is operable to capture the leaked fuel and substantially prevent the fuel from releasing to the atmosphere or surrounding components. In one embodiment of the invention, an outlet port is provided in the enclosure which directs any fuel leaked into the enclosure to a fuel monitoring system which is operable to detect the leaked fuel. If fuel is detected from the enclosure, further fuel control measures may be taken as desired such as an adjustment to the fuel delivery rate. In yet a further embodiment, the fuel diagnostic system may be used to identify the source of the leaked fuel. In yet another alternate embodiment of the invention, a fuel detector is positioned in proximity to the fuel leak enclosure and provides a signal if fuel is detected in the enclosure so that remedial measures may be taken. 
     In one exemplary application of the invention, the system detects fuel leaking from the piston or crank bearing seal of the fuel chamber of a fuel pump for a direct injection engine. In a preferred embodiment, a leak detection enclosure is provided externally of the pump&#39;s fuel chamber drive seal. The leak detection enclosure includes an outlet port that connects to a manifold vacuum source or the intake side of the PVC. Should the pump fuel chamber drive seal begin to fail, fuel will leak past the seal from the fuel chamber and into the leak detection enclosure, pass through the outlet port and enter the engine manifold. The air/fuel diagnostic system would detect an unexpectedly higher level of fuel and could be programmed to generate a diagnostic check or warning signal to the driver. For example, if an unexpected fuel level is detected, the diagnostic system can trigger a check engine or service engine code so that remedial measures may be initiated as soon as possible and preferably prior to complete seal failure. 
     In an alternate embodiment, fuel leak detection is provided by a hydrocarbon detector positioned in proximity to the leak detection chamber. Different fuel detectors may be used to detect the type of fuel being used in a particular application. For example, an alcohol detector may be used to detect an ethanol leak, and a hydrogen detector may be used to detect a hydrogen leak. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a cross sectional schematic of an embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is seen a schematic representation of an exemplary embodiment of the invention incorporated into a fuel pump  10  having a pump body  11 , a low pressure fuel inlet  12  and a high pressure fuel outlet  14  for connecting to a fuel rail having fuel injectors for delivering fuel under pressure to the engine (fuel rail, injectors and engine are not shown). Fuel pump body  11  defines a fuel pump chamber  16  into which fuel is delivered from the fuel tank via inlet  12 . A reciprocating piston  18  compresses the fuel during the advance stroke to deliver fuel under high pressure to the fuel rail via fuel outlet  14 . Piston rod  20  may be driven by lobe  22  of cam shaft  24  although other mounting locations and drive means for operating fuel pump  10  may be used as dictated by the particular engine design being employed (e.g., a rotary driven pump or remotely mounted cambox system). It is therefore understood that this embodiment of the invention is not limited to the reciprocating pump design illustrated in  FIG. 1 . 
     As known in the art, fuel pump  10  is fit with a “wet” seal ring  25  to prevent fuel from leaking out of fuel pump chamber  16  between the interfacing surfaces of piston  18  (including rod  20 ) and pump body  11 . According to a preferred embodiment of the invention, a fuel leak enclosure  26  is provided on the side of piston  18  opposite fuel chamber  16 . A second “dry” seal ring  28  is provided adjacent the base  11   a  of pump body  11  such that leak detection enclosure  26  is defined by first seal ring  25 , pump body  11 , rod  20  and second seal ring  28 . It will be appreciated that as rod  20  reciprocates, both first seal ring  25  and second seal ring  28  remain stationary with respect to the pump body  11 . An outlet port  30  extends from leak detection  26  through pump body  11  for connecting to a line  32  ultimately leading to the engine induction system. Should fuel leak from pump chamber  16  into leak detection enclosure  26 , the leaked fuel will be drawn into the engine by the manifold vacuum. Thus, the leaked fuel combines with the air/fuel mixture entering the engine. This of course increases the amount of fuel in the air/fuel mixture and this is detected by the vehicle&#39;s fuel monitoring system. 
     Present day vehicle closed loop fuel systems monitor the fuel delivery rate and can make real time adjustments to the rate of fuel delivery to maintain proper fuel control and emissions. As is well known to those skilled in the art, such closed loop fuel systems measure the oxygen level at the exhaust manifold to determine if the rate of fuel delivery is producing a combustion exhaust that is rich or lean. Based on the detected oxygen level and engine operating condition, the rate of fuel delivery may be increased or decreased to achieve the optimum air/fuel ratio input. A block learn multiplier (“BLM”) may also be employed to calculate correction factors and make necessary adjustments to the fuel delivery rate to help keep the air/fuel ratio at the most efficient operating level. 
     Thus, with line  32  leading to the closed loop fuel system, any leaked fuel traveling through line  32  is sensed as an unexpectedly high fuel level by the fuel monitoring system which responds with the proper fuel delivery adjustment. 
     In a further, optional embodiment of the invention, a diagnostic component such as a solenoid  33 , for example, may be positioned along line  32  to indicate whether or not the pump  10  is the source of the unexpected high fuel level. If the fuel monitoring system detects a higher than normal fuel level, the solenoid  33  may be activated to close line  32 . If the fuel level drops back to expected ranges, then a leaking pump  10  is identified as the source of the unexpectedly high fuel level. If no change in fuel level is detected by the monitoring system when the solenoid is activated, the pump  10  may be ruled out as the source of the high fuel level and other sources may then be investigated. 
     In an alternate embodiment, a hydrocarbon or other fuel detector  36  is positioned inside or in close proximity to fuel leak enclosure  26 . In this embodiment, an outlet port  30  and line  32  are not required. Hydrocarbon detector  36  may connect to the fuel monitoring system to provide a signal when a predetermined threshold of hydrocarbons (or other fuel molecules or atoms) are detected in enclosure  26 . 
     It will thus be appreciated that the present inventive fuel leak detection system allows for detection of a fuel leak at the earliest possible moment. Since the leaked fuel is captured in the leak detection enclosure  26 , leaked fuel is not released to the atmosphere or surrounding components. Early alert of the leak allows for quick remedial measures to be taken and thereby hopefully avoiding a total seal and pump failure. 
     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.