Patent Application
20140326534
Embodiments of the invention relate to a noise attenuation device for a natural vacuum leak detection valve.
A known fuel system for vehicles with internal combustion engines includes a canister that accumulates fuel vapor from a headspace of a fuel tank. If there is a leak in the fuel tank, the canister, or any other component of the fuel system, fuel vapor could escape through the leak and be released into the atmosphere instead of being accumulated in the canister. Various government regulatory agencies, e.g., the U.S. Environmental Protection Agency and the Air Resources Board of the California Environmental Protection Agency, have promulgated standards related to limiting fuel vapor releases into the atmosphere. Thus, it is believed that there is a need to avoid releasing fuel vapors into the atmosphere, and to provide an apparatus and a method for performing a leak diagnostic, so as to comply with these standards.
An automotive leak detection on-board diagnostic (OBD) determines if there is a leak in the vapor management system of an automobile. The vapor management system includes the fuel tank headspace, the canister that collects volatile fuel vapors from the headspace, a purge valve and all associated hoses. A pressure/vacuum sensor or switch allows the engine computer to monitor the vacuum that is caused by the system cooling after the engine has been turned off and thereby performs the leak detection diagnostic. A vacuum relief function provides fail-safe operation of the purge flow system and guarantees that vacuum levels in the fuel tank do not endanger the integrity of the tank both with the engine on and off.
A pressure relief function is desired in order to “blow off” any excessive fuel vapor immediately after engine shutdown and to facilitate the desired vacuum generation. Another benefit of the pressure relief function is to allow air to exit the tank at high flow rates during tank refueling. This function is commonly known as Onboard Refueling Vapor Recovery (ORVR).
The pressure relief function is typically achieved through the use of a Natural Vacuum Leak Detector (NLVD), which includes a pressure relief valve having a poppet mounted on the end of a shaft, and a diaphragm. The NLVD functions to relieve excessive negative pressure (vacuum). It is possible for the NLVD to resonate, and make noise, because of the air flow through the NLVD. The air flow is turbulent during normal operating conditions, and at times, there may be pulsating air flow which causes vibration in the NLVD, generating noise, which is considered undesirable.
Accordingly, there exists a need for a device which reduces or eliminates noise generated by turbulent or pulsating air in an NLVD.
In one embodiment, the present invention is a noise attenuation device for reducing resonance in a natural vacuum leak detector. The device includes a housing, a first connector connected to the housing, and a first fitting connected to the first connector. Also included is a second connector which is connected to the housing on an opposite end of the housing in relation to the first connector, and a second fitting connected to the second connector. A plurality of tubes is disposed within the housing between the first connector and the second connector such that air flows through the first fitting, the first connector, the plurality of tubes, through the second connector and the second fitting. A plurality of flow paths is created by the plurality of tubes, and the plurality of flow paths change the air flow through the housing.
More particularly, the plurality of flow paths reduces the turbulence and the pulsation of air flow through the housing, reducing or eliminating resonance in the natural vacuum leak detector.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
A noise attenuation device for reducing noise resulting from turbulent and pulsating air flow is shown in the Figures generally at 10. The device 10 includes a first fitting 12 and a second fitting 14, where the fittings 12,14 are used for connecting the device 10 to a tube disposed in the flow path of a natural vacuum leak detector (NLVD). The first fitting 12 includes a first connector 16 which is used for connecting the fitting 12 to a housing 18, and the second fitting 14 includes a second connector 20 which is also connected to the housing 18.
The housing 18 is substantially cylindrical in shape, and disposed within the housing 18, is a plurality of tubes, shown generally at 22. The tubes 22 are substantially parallel to each other, and extend from the first connector 16 to the second connector 20 within the housing 18. When air flows through the device 10, a portion of the air flows through the tubes 22, and a portion of the air flows around the tubes 22. The area through the tubes 22 and around the tubes 22 provides a plurality of flow paths, shown generally at 24, which reduces the turbulence or pulsation in the air flow. The smoother air flow exiting the second fitting 14 reduces or eliminates the resonance generated by the poppet in the NLVD.
In alternate embodiments of the invention, the length and diameter of the device 10 are varied to accommodate and change different air flow rates and air flow volumes. Additionally, changing the length and diameter of the device 10 also changes the amount and size of tubes 22 that may be placed in the housing 18, which also affects the turbulence levels and pulsation of the air flow through the device 10.
In the embodiment shown in
An example of the improvement in air flow because of the device 10 is shown in a chart 32 in
The reduction in pulsation of the air flowing through the device 10 is affected by the length 26 of the housing 26, and therefore the length of the tubes 22 and flow paths 24. The diameter 28 of the housing 26 (which allows for a greater or lesser amount of tubes 22 to be placed in the housing 26) and the diameter 30 of each tube 22 also has an effect on the reduction in pulsation of the air. More specifically, as the length 26 of the housing 26 and tubes 22 is increased, the length of the flows paths 24 is also increased, the more the pulsation and turbulence of the air is reduced. Furthermore, the turbulence and pulsation of the air is further reduced by having a greater number of flow paths 24 which are smaller, rather than a smaller number of flow paths which are larger.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
