Patent Grant
6840270
This invention relates generally to a low deviation pressure relief valve for a fuel pump. The dead head pressure variation for newer higher flow applications in vehicles are met by this invention.
In this invention, a smaller ball in the valve creates less low flow restriction. Less flow restriction causes reduced pressure variation as the fuel flows past the ball. In the present relief valve, the various parts add up to less buckling in the spring so as to achieve less force variation. With less force variation comes less cracking pressure variation. This creates a more uniform dead head pressure. The pre-coining process is used to create a retainer seat for the ball. The ball is smaller than the retainer seat in diameter to ensure an edge seal with the ball. With an edge seal condition comes a more consistent seal and therefore a more consistent cracking pressure. This creates a more uniform dead head pressure.
Guide ribs are provided on the inside of the bore to prevent undue buckling of the spring. The ribs also prevent the ball from deviating too much from the seat centerline. This ensures more consistent sealing time and prevents the ball from becoming stuck off the seat. The star-shaped bore provides flow area for the fuel so that the fuel doesn't have to pass through the spring's coil. This reduces the flow restriction and therefore reduces the dead head pressure variation. The star-shaped bore also prevents the ball from “corking” in the event of a miss-build, whereby the pump was built without a spring.
In summary, in this invention a smaller ball provides for less flow restriction. With less flow restriction comes reduced pressure variation as the fuel flows passed the ball. Less buckling of the spring that seats the ball creates less force variation. With less force variation comes less cracking pressure variation. This combination creates a more uniform dead head pressure.
By using a smaller sealing ball than the seat coining diameter, an edge seal condition can be ensured. With an edge seal condition comes more consistent sealing diameter and therefore a more consistent cracking pressure. This further creates a more uniform dead head pressure.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiment and the appended claims taken in conjunction with the accompanying drawings.
The low deviation pressure relief valve of this invention is shown generally at 10 in FIG. 1. The valve 10 comprises a housing 12 having a bore 14 defining a continuous wall 16. The bore 14 further defines a central axis 18 and the wall 16 is interrupted with passages 19 and 21 that respectively terminate in shoulders 20 and 22. The shoulders 20 and 22 are spaced apart along the axis 18 and, as shown in
A ball 24 is located on the axis 18, the ball 24 being significantly less in diameter than the bore 14. A ball retainer 26 is press-fit or otherwise mounted in the bore 14 and supported on the housing 10. The retainer 26 in its form shown in
A spring 28 coaxial with the axis 18 is located downstream from the ball 24 and supported on the shoulders 22. The ball 24 is therefore located between the spring 28 and the ball seat 25 so as to achieve low flow restriction and produce reduced pressure variation as fluid flows passed the ball 24 and to lessen the probability of buckling of the spring 28.
In use of the pressure relief valve 10, fuel flows through the bore 14 in the direction of the arrow 31 with enough pressure to move the ball 24 off the seat 25 with less flow restriction. With less flow restriction comes reduced pressure variation as the fuel flows passed the ball 24. The spring 28 being supported on the shoulders 22 is provided with a shorter free length that reduces buckling tendencies. This creates a more uniform dead head pressure. The seat 25 is defined by a reverse bend portion of the ball retainer 26 by the coining process with a sphere diameter larger than the diameter of the ball 24, and as such creates an edge seat condition that in turn creates a more consistent sealing diameter and therefore a more consistent cracking pressure for the valve 10. This creates a more uniform dead head pressure.
The guide ribs 30 prevent the spring 28 from buckling. The ribs also prevent the ball 24 from deviating from the centerline of the seat 25. This ensures more consistent sealing and prevents the ball 24 from becoming stuck off the seat. If the rib 30 is too long it will limit the axial movement of the ball 24 at higher open pressures. If the rib 32 is too short, then the ball 24 may move to the space between the retainer 26 and the rib 32 in the opening process and will not reseat itself.
The star-shaped bore 14 provides flow area for the fuel so that the fuel does not have to pass through the springs coils 28. This reduces the flow restriction and therefore reduces the dead head pressure variation. The star-shaped bore 14 also prevents the ball from “corking” in the event of a miss-build where the pump was built without a spring 28.
In an actual low deviation pressure relief valve described as set forth above, follows the design details. The flow resistance coefficient R=D (ball diameter)/C^3 (C=(Dbore−Dball)/2). The spring stiffness coefficient S=free length/pitch diameter.
The Pressure Relief Valve used in the fuel pump and/or fuel system consists of the following: 1) The flow existence coefficient R is in the range from 0.5 to 5, preferably 2.8; 2) A spring with spring stiffness coefficient S preferably in the range from 0.5 to 3.5, preferably 2.85; 3) The retainer has a larger coined diameter than the ball diameter; 4) Guide ribs are of a thickness, length, and profile in the PRV bore to centralize the ball and spring; 5) An outlet housing with a feature to allow fuel flow to bypass the spring to reduce flow restriction.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiment and the appended claims taken in conjunction with the accompanying drawings. The foregoing discussion discloses and describes preferred embodiments of the invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that changes and modifications can be made to the invention without parting from the true spirit and fair scope of the invention as defined in the following claims. The invention has been described in an illustrative manner and it is to be understood that the terminology that has been used is intended to be in the nature of words and description rather than of limitation.
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| Number | Date | Country | |
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| 20040069351 A1 | Apr 2004 | US |
