Abstract:
A housing and a method of using a liquid for controlling vapor flow through a valve apparatus between a canister and atmospheric conditions. The housing includes a container and a first partition that projects from the housing into the liquid and divides the vapor chamber into first and second vapor sub-chambers. A second partition projects from the container into the first vapor sub-chamber. And a third partition projects from the container into the second vapor sub-chamber. The housing contains the liquid in an upright arrangement of the valve apparatus, and prevents the liquid from flowing out of the container in a non-upright arrangement of the valve apparatus.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/817,521, filed Apr. 5, 2004 now abandoned, entitled “Valve Apparatus,” the contents of which is incorporated by reference herein in its entirety, and is a continuation-in-part of U.S. patent application Ser. No. 10/817,522, filed Apr. 5, 2004, entitled “System and Method of Managing Pressure in a Fuel System,” now U.S. Pat. No. 6,889,669, issued May 10, 2005, the contents of which is incorporated by reference herein in its entirety. 
   A related co-pending application filed concurrently herewith is identified as “Liquid for a Valve Apparatus” U.S. application Ser. No. 10/821,178), and is incorporated by reference herein in its entirety. 

   FIELD OF THE INVENTION 
   A fuel vapor pressure management apparatus that manages pressure and detects leaks in a fuel system. In particular, a fuel vapor pressure management apparatus using a liquid seal valve that vents positive pressure, vents excess negative pressure, and uses evaporative natural vacuum to perform a leak diagnostic. 
   BACKGROUND OF THE INVENTION 
   A known fuel system for vehicles with internal combustion engines can include 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. 
   In such known fuel systems, excess fuel vapor can accumulate immediately after engine shutdown, thereby creating a positive pressure in the fuel vapor pressure management system. Thereafter, a vacuum in the fuel vapor pressure management system can result from natural system cooling after the engine has been turned off. Excess negative or positive pressure in closed fuel systems can occur under some atmospheric and operating conditions, thereby causing stress on components of these fuel systems. 
   An automotive on-board diagnostic (OBDII) can perform a leak detection test to determine if there is a leak in the fuel vapor pressure management system, which includes the fuel tank head space, the canister that collects volatile fuel vapors from the head-space, a purge valve and any associated hoses. A vacuum sensing function can perform the leak detection diagnostic. For example, a pressure/vacuum sensor or switch will allow the engine computer to monitor the vacuum that is caused by natural system cooling after the engine has been turned off, and thereby perform the leak detection diagnostic. 
   A vacuum relief function can provide fail-safe operation of the purge flow system, when the engine is ON, and guarantee that vacuum levels in the fuel tank do not endanger the integrity of the tank, when the engine is OFF. In general, the vacuum relief function should only allow flow at a pressure level below the vacuum sensor level. 
   A pressure relief function is desirable in order to “blow-off” the positive pressure due to excessive fuel vapor in the fuel vapor pressure management system immediately after engine shutdown. This can facilitate, e.g., expedite, the creation of the vacuum that is caused by the natural system cooling. 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). In general, the pressure relief function should be at a very low-pressure level in order to minimize the backpressure during refueling, and to limit excess pressure in a hot system. 
   SUMMARY OF THE INVENTION 
   The present invention provides a housing for a valve apparatus, which includes a liquid that controls vapor flow between a canister and atmospheric conditions. The housing includes a container and first, second and third partitions. The container defines a vapor chamber portion and a vapor flow control portion. The vapor flow control portion holds the liquid, and the vapor chamber portion is positioned above the vapor flow control portion in an upright arrangement of the valve apparatus. The first partition projects from the container into the liquid in the vapor flow control portion of the container, and divides the vapor chamber into first and second vapor sub-chambers. The first vapor sub-chamber is in vapor communication with the canister, and the second vapor sub-chamber is in vapor communication with the atmospheric conditions. The second partition projects from the container into the first vapor sub-chamber. And the third partition projects from the container into the second vapor sub-chamber. 
   The present invention also provides a method of using a liquid for controlling vapor flow through a valve apparatus between a canister and atmospheric conditions. The method includes defining a vapor flow path through a housing containing the liquid. The vapor flow path extends between first and second ports in the housing and passes through the liquid. The housing contains the liquid in a first reservoir in an upright arrangement of the valve apparatus. And the method includes preventing the liquid from flowing out of the first and second ports in a non-upright arrangement of the valve apparatus. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention. 
       FIG. 1  is a schematic illustration of a fuel system that includes a fuel vapor pressure management apparatus in accordance with the detailed description of certain preferred embodiments. 
       FIG. 2A  is a top view of a model illustrating the operating principles of a vapor pressure management apparatus according to the present invention. 
       FIG. 2B  is an elevation view showing the resting state of the model shown in  FIG. 2A . 
       FIG. 3  is an elevation view showing a first operating state of the model shown in  FIG. 2A . 
       FIG. 4  is an elevation view showing a second operating state of the model shown in  FIG. 2A . 
       FIG. 5  is an elevation view showing a third operating state of the model shown in  FIG. 2A . 
       FIG. 6  is a schematic illustration of a vapor pressure management apparatus according to the present invention. 
       FIG. 7  is a cross-section of a first embodiment of a vapor pressure management apparatus according to the present invention. 
       FIG. 8  is a cross-section of a second embodiment of a vapor pressure management apparatus according to the present invention. 
       FIGS. 9A ,  9 B and  9 C are plan views of a third embodiment of a vapor pressure management apparatus according to the present invention. 
       FIG. 9D  is an isometric view of the third embodiment of a vapor pressure management apparatus shown in  FIGS. 9A ,  9 B and  9 C. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As it is used in this description, “atmosphere” generally refers to the gaseous envelope surrounding the Earth, and “atmospheric” generally refers to a characteristic of this envelope. 
   As it is used in this description, “pressure” is measured relative to the ambient atmospheric pressure. Thus, positive pressure refers to pressure greater than the ambient atmospheric pressure and negative pressure, or “vacuum,” refers to pressure less than the ambient atmospheric pressure. 
   Also, as it is used in this description, “headspace” refers to the variable volume within an enclosure, e.g. a fuel tank, that is above the surface of a liquid, e.g., fuel, in the enclosure. In the case of a fuel tank for volatile fuels, e.g., gasoline, vapors from the volatile fuel may be present in the headspace of the fuel tank. 
   Referring to  FIG. 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 fuel vapor collection canister  18  (e.g., a charcoal canister), and a fuel vapor pressure management apparatus  20 . 
   The fuel vapor pressure management apparatus  20  performs a plurality of functions including signaling  22  that a first predetermined pressure (vacuum) level exists, “vacuum relief” or relieving negative pressure  24  at a value below the first predetermined pressure level, and “pressure blow-off” or relieving positive pressure  26  above a second pressure level. 
   Other functions are also possible. For example, the fuel vapor pressure management apparatus  20  can be used as a vacuum regulator, and in connection with the operation of the purge valve  16  and an algorithm, can perform large leak detection on the fuel system  10 . Such large leak detection could be used to evaluate situations such as when a refueling cap  12   a  is not replaced on the fuel tank  12 . The fuel pressure management apparatus  20  and purge valve  16  communicate with an automotive on-board diagnostic (OBDII) engine computer  82 . 
   It is understood that volatile liquid fuels, e.g., gasoline, can evaporate under certain conditions, e.g., rising ambient temperature, thereby generating fuel vapor. In the course of cooling that is experienced by the fuel system  10 , e.g., after the engine is turned off, a vacuum is naturally created by cooling the fuel vapor and air, such as in the headspace of the fuel tank  12  and in the fuel vapor collection canister  18 . According to the present description, 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 to indicate the integrity of the fuel system  10 , i.e., that there are no appreciable leaks. Subsequently, the vacuum relief  24  at a pressure level below the first predetermined pressure level can protect the fuel tank  12 , e.g., can prevent structural distortion as a result of stress caused by excess vacuum in the fuel system  10 . 
   After the engine is turned off, the pressure blow-off  26  allows excess pressure due to fuel evaporation to be vented, and thereby expedite the onset of vacuum generation that subsequently occurs during cooling. The pressure blow-off  26  allows air within the fuel system  10  to be released while fuel vapor is retained. Similarly, in the course of refueling the fuel tank  12 , the pressure blow-off  26  allows air to exit the fuel tank  12  at a high rate of flow. 
   At least two advantages are achieved in accordance with a system including the fuel vapor pressure management apparatus  20 . First, a leak detection diagnostic can be performed on fuel tanks of all sizes, including large volume fuel tanks, e.g., 100 gallons or more. Second, the fuel vapor pressure management apparatus  20  is compatible with a number of different types of the purge valves, including digital and proportional purge valves. 
   Referring to  FIGS. 2A and 2B , a model  100  of the fuel vapor pressure management apparatus  20  will now be described. The model relies on the principal of a standing column of liquid. Consider a cylindrical vessel  110  consisting of a container  112  with a freestanding cylindrical tube  114 . The vessel  110  is partially filled with liquid  120  that separates the vessel  110  into a first chamber  122  and a second chamber  124 . The first chamber is defined within the cylindrical tube  114 , and the second chamber  124  is defined between the wall of the container  112  and the cylindrical tube  114 . As shown in  FIG. 2A , the first chamber  122  is circular and the second chamber  124  is annular. The shapes of the chambers  122 ,  124  in the model  100  may alternatively be defined by irregular or regular shapes other than circles, and may or may not share a common central axis A. The operation of this model will now be described. 
     FIG. 2B  shows a resting state of the model  100 . In the resting state, the liquid  120  is at a level L, with respect to the bottom of the vessel  110 , that is the same in both the first and second chambers  122 ,  124 . According to the model  100  shown in  FIGS. 2A and 2B , the cylindrical tube  114  has an inside diameter d 1  and the container  112  has an inside diameter d 2 . The vessel  110  is filled with the liquid  120  so that the cylindrical tube  114  is immersed to a depth of h1. The volume of liquid below the cylindrical tube  114  is irrelevant. In the resting state, the model  100  will not allow vapor, e.g., air, to pass between the first and second chambers  122 ,  124 . In effect, the liquid  120  contiguously engaging the bottom end  114   a  of the cylindrical tube  114  creates a perfect seal. Flow will only occur through the model  100 , i.e., between the first and second chambers  122 ,  124 , when a pressure or vacuum threshold is achieved as explained below. 
   Referring now to  FIG. 3 , the pressure relief mode of the model  100  is enabled, when a positive pressure differential exists in the first chamber  122  relative to the second chamber  124 . If a system to which the model  100  is connected, e.g., the fuel system  10 , applies pressure to the first chamber  122 , the column of liquid  120  within the cylindrical tube  114  is displaced until vapor escapes under the bottom end  114   a  into the second chamber  124 . As positive pressure increases, the liquid  120  will be displaced from the cylindrical tube  114  into the annular volume of between the container  112  and the cylindrical tube  114 . The start to flow pressure is governed by the head, h 2 . The volume of the liquid  120  inside the cylindrical tube  114  in the resting state can be calculated as:
 
h 1 ×π(d 1 /2) 2  or h 1 ×A 1  
 
where A 1  is the cross-sectional area inside the cylindrical tube  114 . When the positive pressure differential reaches a level where the entire volume of the liquid  120  inside the cylindrical tube  114  has been displaced, vapor in the form of bubbles, as depicted in  FIG. 3 , will be begin to escape from the first chamber  122 . The level at which this pressure relief flow will begin to occur can be calculated by:
 
 h   2   =h   1 +(( h   1   ×A   1 )/ A   2 )
 
   The pressure differential h 2  at which pressure relief occurs is dependent on the specific gravity of the liquid. As can be seen by this formula, the pressure relief point h 2  can be made significantly lower by increasing the difference in area between A 1  and A 2 . 
   Vacuum sensing is depicted in  FIG. 4 . An appropriate liquid level sensor  140  has been placed approximate halfway up the cylindrical tube  114 . The level sensor  140  is active when the vehicle engine is OFF. If the system to which the model  100  is connected, e.g., the fuel system  10 , applies vacuum to the first chamber  122 , the column of liquid  120  within the cylindrical tube  114  is raised. The column of the liquid  120  can be detected by a number of methods (float, thermistor, capacitive, optical, conductive, etc.) when the liquid head reaches the detection threshold, h 3 . The sensor  140  will signal a passing diagnostic when a negative pressure differential that exists in the first chamber  122  relative to the second chamber  124  draws the liquid  120  up to the point of touching or triggering the level sensor  140 . The vacuum sensing level or calibration is related to head differential between the first and second chambers  122 ,  124 , and to the specific gravity of the liquid  120 . For example, at a given position of the level sensor  140 , the vacuum sense calibration will increase with increasing specific gravity. 
   Vacuum relief is depicted in  FIG. 5 . As vacuum continues to raise the column of the liquid  120  in the first chamber  120  to a higher level than in  FIG. 4 , the liquid  120  will be displaced from the second chamber  124 , under the bottom end  114   a  of the cylindrical tube  114 , and into the first chamber  122 . When the negative pressure differential reaches a level where the entire volume of the liquid  120  outside the cylindrical tube  114  has been displaced, i.e., to the bottom  114   a  of the cylindrical tube  114 , vapor in the form of bubbles, as depicted in  FIG. 5 , will begin to escape from the second chamber  124 , under the bottom end  114   a  of the cylindrical tube  114 , and into the first chamber  122 . The level at which this vacuum relief flow will begin to occur can be calculate by:
 
 h   4   =h   1 +(( h   1   ×A   2 )/ A   1 )
 
     FIG. 6  schematically illustrates a vapor pressure management apparatus  200  according to the present invention. Features having characteristics and functions that are similar to those of the model  100  are indicated with reference numerals that are incremented by one-hundred. Thus, for example, sensor  240  of the vapor pressure management apparatus  200  has characteristics and functions that are similar to sensor  140  of the model  100 .  FIG. 6  also illustrates several additional features that will now be described. 
   The vessel  210  encloses the liquid  220  so as to contain the liquid  220  regardless of the orientation of the vapor pressure management apparatus  200 . The liquid provides a means for controlling the direction of vapor flow, without a resilient element and without an electric element. Containment of the liquid  220  is in large part achieved by an inner partition  216  and an outer partition  218 . The inner partition  216  establishes fluid communication path between a vapor port  226  and the first chamber  222 , and the outer partition  218  establishes a fluid communication path between a vent port  228  and the second chamber  224 . A first reservoir  232  is partially defined by the inner partition and the container  212 , and a second reservoir  234  is partially defined by the outer partition  218  and the container  212 . The first and second reservoirs  232 ,  234  provide holding volumes for any of the liquid  220  that may be displaced as a consequence of tipping or turning over the vessel  210 . And at such time as the vessel is returned to its upright condition, the liquid  210  that was held in the first and second reservoirs  232 ,  234  is returned to the first and second chambers  222 ,  224  without being permitted to flow out either the vapor port  226  or the vent port  228 . In this way, the liquid  220  that is placed inside the vessel  210  is contained in the vessel  210  regardless of changes in orientation of the vapor pressure management apparatus  200 . 
   Referring now to  FIG. 7 , there is shown a fuel vapor pressure management apparatus  300  according to a first preferred embodiment. Again, features having characteristics and functions that are similar to those of the model  100  or the schematic illustration of the vapor pressure management apparatus  200  are indicated with reference numerals that are incremented by two-hundred and one-hundred, respectively. Thus, for example, sensor  340  of the fuel vapor pressure management apparatus  300  has characteristics and functions that are similar to sensor  140  of the model  100 , and to sensor  240  of the vapor pressure management apparatus  200 .  FIG. 7  also illustrates several additional features that will now be described. 
   Vapor port  326  includes a fitting that is particularly suited to being mounted on the fuel vapor collection canister  18  of the fuel system  10  ( FIG. 1 ). The fuel vapor pressure management apparatus  300  includes a container  312  that can be mounted directly to the fuel vapor collection canister  18  by a “bayonet” style attachment  302 . A seal (not shown) can be interposed between the fuel vapor collection canister  18  and the fuel vapor pressure management apparatus  300  so as to provide a fluid tight connection. The bayonet style attachment  302 , in combination with a snap finger  304 , allows the fuel vapor pressure management apparatus  300  to be readily serviced in the field. Of course, different styles of attachments between the fuel vapor pressure management apparatus  300  and the fuel vapor collection canister  18  can be substituted for the illustrated bayonet attachment  302 . Examples of different attachments include a threaded attachment, and an interlocking telescopic attachment. Alternatively, the fuel vapor collection canister  18  and the container  312  can be bonded together (e.g., using an adhesive). 
   A semi-spherical portion  306  of container  312  contains the liquid  320  in the resting state of the fuel vapor pressure management apparatus  300 . The inventors of the present invention have discovered that the semi-spherical shaped portion  306  reduces the impact of tilting from the vertical on the calibration of the fuel vapor pressure management apparatus  300 . 
     FIG. 8  shows an in-line style of connecting the fuel vapor pressure management apparatus  400  with the fuel vapor collection canister  18 . Again, features having characteristics and functions that are similar to those of the model  100 , the schematic illustration of the vapor pressure management apparatus  200 , and the fuel vapor pressure management apparatus  300  are indicated with reference numerals that are incremented by three-hundred, two-hundred and one-hundred, respectively. The in-line style of connection includes a nipple  426  that can be interconnected with the fuel vapor collection canister  18  via an intermediate member such as a rigid pipe or a flexible hose (not shown). 
     FIGS. 9A-9D  show a fuel vapor pressure management apparatus  500  according to a third preferred embodiment of the present invention. Again, features having characteristics and functions that are similar to those of the model  100 , the schematic illustration of the vapor pressure management apparatus  200 , and the fuel vapor pressure management apparatuses  300  and  400  are indicated with reference numerals that are incremented by four-hundred, three-hundred, two-hundred and one-hundred, respectively. The fuel vapor pressure management apparatus  500  includes a bayonet-style attachment  506  for coupling to the fuel vapor collection canister  18 . Notably, the fuel vapor pressure management apparatus  500  uses non-circular walls to separate and partition the first and second chambers  522 ,  524 , and uses fewer components so that the cost of manufacturing is reduced. 
   With regard to the liquid  120 ,  220 ,  320 ,  420 ,  520 , increasing the specific gravity of the liquid will reduce the physical size of the device. For example, increasing the specific gravity of the liquid reduces the displacement (i.e., h 4  in the case of vacuum relief) of the liquid column necessary to achieve the same vacuum level at the point of relief. 
   Preferably, the viscosity of the liquid  120 ,  220 ,  320 ,  420 ,  520  is heavy enough that the bursting bubbles to not spray liquid into the air stream to be carried away. Liquid traps may be used to capture and retain the liquid so as not to drain out of the container  112 ,  212 ,  312 ,  412 ,  512  if the vessel  110 ,  210 ,  310 ,  410 ,  510  is tilted or overturned. A liquid trap can include partitions, baffles, etc. that direct the flow of the liquid way from the ports. A, tortuous path can also be implemented to keep the liquid inside the vapor pressure management apparatus. Preferably, the viscosity remains fluid enough to enable the apparatus to operate at extreme low temperatures. 
   For the device to be viable over the life of a vehicle, the liquid needs have a very low evaporation rate and must not freeze into a solid until at least −40° Celsius. According to the present invention, a preferable liquid should possess the following properties:
         Excellent oxidative and thermal stability   Low volatility and vapor pressure   Non-flammable and chemically inert   Excellent plastic and elastomer compatibility   Resistant to aggressive chemicals and solvents
 
Low evaporation is required so that that apparatus function can be maintained over a 15-year and 150,000-mile life of a vehicle. In addition, a low evaporation rate ensures that the liquid itself will not create stray airborne hydrocarbon molecules that could fail an evaporative emissions test. A preferable liquid will have a kinematic viscosity range of 75-600 centistokes throughout a temperature range of −40 to +100 degrees Celsius, and will have a near zero vapor pressure (˜5×10 −9  torr at 100 degrees Celsius).
       

   A synthetic oil, such as Fluorinated Polyether, is an example of an acceptable liquid. Preferably, the liquid may be Perfluoropolyether (PFPE), which has an acceptable viscosity and may be used in extreme temperature environments or in applications that require chemical, fuel, or solvent resistance. 
   The liquid may also include suspended carbon particles to act as an electrical conductor, or the liquid may include glass micro-spheres to thicken the liquid and prevent splashing and liquid carry-over. The liquid may also be a gel. 
   With regard to the sensor  140 ,  24 ,  340 ,  44 ,  540 , the vacuum sensing  22  can be accomplished with a positive or negative temperature coefficient thermistor, a capacitive sensor, a float and a contact switch, a magnet and a reed switch, resistive/conductive oil, and many others. These devices can be used to sense the liquid level of the column in the first chamber. For example, the presence or absence of the liquid at a level can be sensed using a heated thermistor that dissipates more heat in liquid than in air, or with a capacitive sensor inasmuch as oil and air have very different dielectric constants. Further, sensors that measure that directly measure the pressure differential that causes liquid displacement can also be used in conjunction with the vacuum relief and pressure blow-off the pressure differentials between the first and second chambers. 
   Numerous advantages are achieved in accordance with the vapor pressure management apparatus according to the present invention. These advantages include providing a leak detection diagnostic using vacuum monitoring during natural cooling, e.g., after the engine is turned off, providing relief for vacuum below the first predetermined pressure level, and providing relief for positive pressure above the second predetermined pressure level. Additionally, the vacuum relief  24  provides fail-safe purging of the canister  18 , and the relieving pressure  26  regulates the pressure in the fuel tank  12  during any situation in which the engine is turned off, thereby limiting the amount of positive pressure in the fuel tank  12  and allowing the cool-down vacuum effect to occur sooner. 
   According to the present invention, the liquid has the ability to wet-out on the walls and effectively lower the volume that has to be displaced, and to lower the back-pressure because the liquid clings to the walls and out of the path of airflow. The liquid also acts as a wet filter to remove debris from the incoming air stream. 
   The present invention advantageously includes a semi-spherical shaped lower housing that reduces the impact of tilt angle on calibration. A spill-proof housing uses tortuous paths and reservoirs to contain liquid in the event that the part is inverted, and then the liquid returns to its original location when part is set upright. Further, a reservoir of unused liquid can be provided to top up the liquid level if there is a liquid loss due to evaporation or liquid carry-over. And if liquid becomes contaminated or destroyed, a service procedure could be created to rejuvenate the part by extracting the used liquid and inject a replacement amount of new liquid. 
   It is also possible according to the present invention to take advantage of the meniscus effect on the cylindrical tube end. This will tend to create a higher than expected level of pressure or vacuum relief. Also, the meniscus effect can be used to make the device smaller than expected. 
   According to the present invention, installation options include in-line and canister mounted variations. The vapor pressure management apparatuses according to the present invention also inherently provide zero vacuum leakage, allow positive and negative pressure relief values to be designed by geometry, presents no mechanical moving parts and thus there is no wear, no filtration is required, reduced durability testing, no calibration is required, and a very low parts count to ease assembly and reduced manufacturing costs. 
   While the present 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 present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.