Abstract:
The present invention provides a valve assembly for relieving fluid pressure having a pump housing with a low pressure inlet chamber and a high pressure discharge chamber, a relief aperture positioned between the low pressure inlet chamber and the high pressure discharge chamber, a valve seat along the perimeter of the relief aperture, and a valve body located in the high pressure discharge chamber. The valve body has a first end capable of engaging the valve seat in a closed position and is also capable of axial travel opposite the fluid discharge at a predetermined pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 60/799,192, entitled “Inverted Pressure Regulating Valve for an Engine Oil Pump” filed on May 10, 2006, which is hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to fluid pumps, and more particularly, to an inverted pressure-regulating valve for an engine oil pump. 
     BACKGROUND OF THE INVENTION 
     There are numerous uses for fluid pumps across a wide range of industries. The automotive industry is one such industry that requires fluid pumps. In particular, a combustion engine vehicle includes an engine lubrication system designed to deliver clean oil at the correct temperature and pressure to the engine. The heart of the system is the oil pump, which pumps oil from the oil reservoir through a simple wire screen to strain out debris and then feeds the oil through a filter to further clean the oil. The oil is then pumped to different parts of the engine to assist in cooling and lubrication and then falls to the bottom of the engine crankcase, or oil reservoir, to continue the process. 
     One particular type of oil pump mechanism typically used in a vehicle engine is the gerotor pump. Gerotor pumps are positive displacement pumps using nested hypocycloid gear elements as their pumping elements. The inner rotor, called a pinion gear, meshes with and is located inside of the outer rotor, called a ring gear. These elements are supported on a pump housing for rotation about parallel, laterally separated centerlines. In a gerotor pump, the motor drives either the inner or the outer element, that element then driving the other element. These gear elements rotate relative to each other so as to create a pumping action. 
     Since the outer gear element has one tooth more than the inner gear element and both elements are mounted on fixed centers eccentric to each other, a one-tooth volume is opened and closed across each rotation. As the toothed elements turn, the chamber between the teeth of the inner and outer gear elements gradually increases in size through approximately 180° of each revolution until it reaches its maximum size, which is equivalent to the full volume of the “missing tooth”. During this initial half of the cycle, the gradually enlarging chamber is exposed to the low pressure inlet port of the pump housing, creating a partial vacuum into which the oil flows. During the subsequent 180° of the revolution, the chamber gradually decreases in size as the teeth mesh and the liquid is forced out through the high pressure discharge port of the pump housing. Therefore, 360° rotation of the pumping elements creates a pumping action. 
     Oil pumps are designed to deliver oil in greater quantities and pressures than the engine actually requires. For example, when the inner gear element drives the gerotor pump, that inner drive element is coupled to the driveshaft so that the oil pump runs continuously while the engine is running. The gerotor will deliver a known, predetermined quantity of fluid in proportion to the speed of the input power. Such a continuously running oil pump provides consistently greater quantities of oil and oil pressure to the engine than are actually required. Constant oil pressure is maintained, and the additional oil pressure not required is vented off. 
     Automotive engine oil pumps typically employ a pressure relief valve to prevent overpressure. Typically, pressure relief valves are located on the low pressure inlet side. The front end of a valve body engages a valve seat, also on the low pressure side, along the perimeter of a relief aperture. Such configurations generally result in a cavity or depression on the high pressure side. Accordingly, when the pressure must be relieved, the fluid pressure acts on the front end of the valve body so that the valve body travels downward in the direction of the vented fluid flow to relieve the pressure to the low pressure inlet side. 
     During operation of the pump, however, debris may settle in the depression on the high pressure side. Therefore, as pressure is relieved, the debris flows through the gap generated between the front end and the valve seat and along the valve body toward the valve housing. As the pressure decreases, the front end reengages the valve seat to close the relief aperture. At any point in this operation, debris may become trapped between the valve seat and the front end and/or the sliding valve body and the valve housing, resulting in relief valve failure. As relief valve assemblies are manufactured with close tolerances, only a small amount of debris may result in relief valve failure. Further, it is difficult to prevent the introduction of debris, such as bits of wire, etc. into the oil system, even when a wire screen and filter is employed. 
     Such configurations may result in a variety of relief valve failures that may cause oil pressure problems. For example, when the relief valve is stuck in the closed position, pressure builds and may rupture the oil filter. When the relief valve is stuck in the open position, the resulting low oil pressure may cause bearing failure. If the relief valve is sticking, erratic pressure results. Therefore, there is a need in the art to vent off additional pressure without exposing the relief valve to debris that may result in relief valve failure. The present invention overcomes the deficiencies of the prior art by inverting the pressure relief valve and the valve seat to the high-pressure side. Therefore, as the valve opens the debris immediately “blows out” to the low-pressure side in a manner that prevents debris from wedging between the valve body and the valve seat. 
     Additional information will be set forth in the description that follows, which will be obvious in part from the description or may be learned by practice of the invention. 
     SUMMARY OF THE INVENTION 
     The valve assembly for relieving fluid pressure is provided. The valve assembly comprises a pump housing with a low pressure inlet chamber and a high pressure discharge chamber, a relief aperture positioned between the low pressure inlet chamber and the high pressure discharge chamber, a valve seat along the perimeter of the relief aperture, and a valve body located in the high pressure discharge chamber. The valve body has a first end capable of engaging the valve seat in a closed position, and is also capable of axial travel opposite the fluid discharge at a predetermined pressure. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein: 
         FIG. 1A  is a sectional view of an embodiment of a valve assembly according to the present invention. 
         FIG. 1B  is a sectional view of an embodiment of a valve assembly according to the present invention. 
         FIG. 2  is a perspective view of a pump housing of an oil pump provided with an embodiment of a valve assembly according to the present invention. 
         FIG. 3  is a perspective view of a gerotor pump. 
         FIG. 4  is a perspective view similar to  FIG. 2  showing another operational mode of the valve assembly. 
         FIG. 5A  is a sectional view of an embodiment of a valve assembly according to the present invention. 
         FIG. 5B  is a sectional view of an embodiment of a valve assembly according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     While the present invention is described with reference to the embodiments described herein, it should be clear that the present invention should not be limited to such embodiments. Therefore, the description of the embodiments herein is illustrative of the present invention and should not limit the scope of the invention as claimed. 
     Reference will now be made in detail to the embodiments of the invention as illustrated in the accompanying figures. Embodiments of a pressure relief valve assembly  10  are shown in  FIGS. 1 through 5 . As shown in  FIGS. 1A and 1B , the pressure relief valve assembly  10  generally has a relief valve  20 , a valve housing  30 , and a relief aperture  40 . As shown in  FIG. 2 , the relief valve assembly  10  may be installed in an engine oil pump housing  70 . 
     The housing  70  is generally directly secured to an engine block or integrally mounted to an engine front cover. The housing  70  may be made from any suitable material, such as aluminum, and has a substantially circular cavity  80  for rotatably accommodating a pump. As shown in  FIG. 3 , the pump may be a gerotor pump  60  with an inner rotor  155  with external teeth  160  and an outer rotor  165  with internal teeth  170  whose number of teeth is larger by one than that of inner rotor  155 . In the meshed state, the two rotors  155 / 165  cooperate with each other to define a plurality of fluid chambers  175 . Inner rotor  155  may be coupled with an engine crankshaft (not shown) which acts as a driving shaft for inner rotor  155 . Outer rotor  165  is driven by rotation of inner rotor  155  to circumferentially move fluid chambers  175  for variation in volume of each fluid chamber  175  to create a pumping action. 
     As best shown in  FIG. 2 , the housing  70  has a low-pressure suction chamber  90  and a higher-pressure discharge chamber  95 . Fluid chambers  175  communicate with suction chamber  90 , where the volume of each fluid chamber  175  increases, and discharge chamber  95  where the volume decreases. The suction chamber  90  and discharge chamber  95  may also be arranged in an inner wall of the cover (not shown) in the same way to correspond to those of the main body. Such an arrangement allows oil to enter suction chamber  90  via a suction port  100  and exit from discharge chamber  95  through a channel  97  and out a discharge port  105 . 
     Referring to  FIGS. 1A-B , a valve body  20  is slidingly disposed in the valve housing  30 . Similar to the housing  70 , the valve body  20  and valve housing  30  may be made from any suitable material, such as aluminum. The main function of the valve body  20  is to regulate oil pressure within the engine by keeping a substantially constant flow of oil to the engine. The valve body  20  is generally cylindrically shaped and has a front end  110  capable of engaging the valve seat  150  surrounding relief aperture  40 . As shown, the front end  110  may be tapered to facilitate engagement with a valve seat  150  surrounding relief aperture  40 . The valve body  20  is biased in the direction of the valve seat  150  by a pressure relief spring  120  disposed between inner wall  130  and valve housing end cap  140 . It is understood that end cap  140  may be removable to allow replacement of the spring  120  and/or the valve body  20 . 
     Accordingly, when oil pressure throughout discharge chamber  95  is below a predetermined level, the front end  110  remains engaged with valve seat  150  so that relief aperture  40  remains closed. As shown in  FIGS. 1B and 4 , when the oil pressure reaches the predetermined level, the pressure exerted on the surface of the valve body  20 , such as a shoulder  180 , slides the valve body  20  toward end cap  140  away from relief aperture  40 . This allows the oil to vent through relief aperture  40  and channel  98  to the low-pressure suction chamber  90 . 
     In some embodiments, as shown in  FIGS. 5A and 5B  (spring  120  not shown), spring chamber  170  may be internally vented by either an orifice  190  extending through the front end  110  and/or by an orifice  130  in end cap  140 , if the oil pump design permits. This provides a low-pressure area in the spring chamber  170  that allows valve body  20  to move toward the end cap  140  when the external high pressure overcomes the opposing spring force. 
     Turning to the valve assembly  10 , an example of how to use the valve assembly  10  as illustrated in  FIGS. 1-5  is set forth below. As shown in  FIG. 2 , the valve body  20  is slidingly disposed in valve housing  30  and is capable moving toward and away from relief aperture  40  as the pressure changes. During normal pump operation, the biasing force of the spring  120  causes front end  110  to be engaged with valve seat  150 , thereby closing relief aperture  40 . As the gerotor pump  60  operates, oil is drawn through inlet  100  into suction chamber  90  and is pumped into discharge chamber  95 . The oil flows around valve body  20  through channel  97 , exiting via the outlet  105 . During operation, debris may settle around the front end  110  and the relief aperture  40 . 
     When a predetermined oil pressure has been achieved, the oil must be vented. To do so, as shown in  FIGS. 1B and 4 , the oil pressure exerted on shoulder  180  slides valve body  20  toward end cap  140  and away from relief aperture  40 . Accordingly, the oil from the discharge chamber  95  is vented through relief aperture  40  and channel  98 , connecting discharge chamber  95  to the low-pressure suction chamber  90 . The assembly serves as a bypass to allow the oil to recirculate in the pump assembly from the high pressure discharge chamber  95  to the low pressure suction chamber  90 , thereby preventing overpressure in the discharge chamber  95 . 
     Unlike typical relief valve assemblies, the valve body  20  and valve seat  150  are located in the high-pressure discharge chamber  95 . In addition, the valve body  20  moves counter to the direction of the oil flow when relieving pressure. By inverting the valve body  20  and providing a surface area (shoulder  180 ) for the pressure to act on the valve body  20 , there is no cavity or depression for debris to collect in on the high-pressure discharge side. If any debris does accumulate near the valve seat  150 , it will “blow free” and away from the valve body  20  and valve housing  30  when the valve body  20  slides toward end cap  140 . Therefore, unlike the prior art configurations, the valve body  20  and valve housing  30  are not exposed to the fluid flow that could wedge debris therebetween. In addition, the assembly  10  eliminates the bottleneck of the prior art, in which the debris could easily lodge between the valve body and the valve seat. Therefore, any debris present is quickly removed away from the valve body  20 , valve housing  30 , and valve seat  150 , resulting in fewer failures and increased operational reliability. 
     In addition, as shown in  FIGS. 5A and 5B , low pressure in the spring chamber  170  can be achieved by venting the otherwise trapped volume to the low pressure suction chamber  90  via orifice  190 . Venting may also be achieved by simply venting end cap  140  via orifice  130  to the environment of the oil crankcase, if the design allows. This allows a low-pressure area in the location of the spring, which further allows the valve body  20  to move toward the end cap  140  when the external high pressure overcomes the opposing spring force. If the spring chamber  170  were not vented to low pressure at that point, it might become hydraulically locked, and thus inoperative. 
     The invention has been described above and, obviously, modifications and alternations will occur to others upon the reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar, as they come within the scope of the claims or the equivalent thereof.