Patent Application
20130266457
The following description relates to a metering rod, and in particular, a metering rod in a pressure sensitive droop flow pump.
A pressure sensitive droop flow pump may be used in hydraulic power steering pump applications and include a pressure sensitive droop flow control device, such as a metering rod. The pressure sensitive droop flow control device operates according to power steering system pressure. At low engine speeds, and when a pressure increase is detected, the metering rod moves to a position allowing power steering flow to increase, thereby allowing reduced effort to perform steering operations. At higher speeds, the metering rod moves to a position where flow drops, or “droops,” to provide fuel economy savings.
With reference to
Typically, the transition section 13 extends at a smooth transition angle a between the large diameter section and small diameter. That is, the transition section 13 typically extends along a length of the metering rod 10 between the small diameter section 11 and larger diameter section 12, and increases in diameter along the length from the small diameter section 11 to the large diameter section 12, thereby forming a generally conical transition section 13. The transition angle a, formed between the small diameter section 11 and the transition section 13, is typically greater than 135°, but may vary slightly to provide a gradual transition between the small diameter section 11 and large diameter section 12 that has a length dimension “L” along the length of the metering rod 10.
However, the conical transition section 13 has limitations with regard to fuel economy. For example, when the metering rod 10 moves from the position where the small diameter section 11 is positioned in the opening 14, i.e., the increased flow condition, corresponding to a low angular velocity (RPM) of the engine and pump, to the position where the large diameter section 12, i.e., the drooped flow condition, corresponding to a higher RPM of the engine and pump, flow is not drooped until the large diameter section 12 is positioned in the opening 14. That is, increased flow may still occur during the time the conical transition section 13 is passing through the opening 14. Thus, increased flow may occur for a period of time while the angular velocity of the pump and engine increase when the drooped flow condition is desired. As a result, excess fuel may be used during the time when the conical transition section 14 passes through the opening 14, resulting in inefficient use of fuel.
Accordingly, it is desirable to provide a metering rod in a pressure sensitive droop flow pump that may transition between a higher flow to a drooped flow in a reduced range of angular velocity (RPM) of the pump and engine to improve fuel economy.
According to an exemplary embodiment of the present invention, there is provided a pressure sensitive droop flow pump having a fluid conduit having a partition with an aperture formed therein and a metering rod. The metering rod includes a first section having a first diameter and a second section having a section diameter, the second diameter larger than the first diameter. A shoulder is formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.
According to another exemplary embodiment of the present invention, there is provided a metering rod assembly for a pressure sensitive droop flow pump. The assembly includes a metering rod having a first section with a first diameter and a second section with a section diameter, the second diameter larger than the first diameter, and a shoulder formed at a junction of the first section and second section, the shoulder extending radially perpendicular to the first section.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limiting same,
Referring to
The metering rod 22 includes a first section 26 and second section 28. In an exemplary embodiment, the first section 26 has a first diameter D1 and the second section 28 includes a second diameter D2. The second diameter D2 is greater than the first diameter D1. In addition, the first section 26 is positioned proximate to the housing 24, while the second section 28 extends from the first section 26 at a distal portion of the metering rod 22.
Still referring to
In an exemplary embodiment, the first section 26 and second section 28 are formed as generally cylindrical sections. It is understood however, that variations in the shape of these sections are envisioned. For example, the first and second sections 26, 28 may respectively include beveled or chamfered sections 32, 34 at end portions, away from the shoulder 30. The metering rod 22 may also include a stop flange 36, positioned between the first section 26 and the housing 24. The stop flange 36 may act as a stop to define a travel distance of the metering rod 22 along the axis ‘A’ by abutting adjacent elements.
In the exemplary embodiments above, the shoulder 30 extends perpendicularly from the first section 26 and/or axis ‘A’. However, it is understood that slight variations in the angle θ are also envisioned, for example, for manufacturing purposes. Further, and with reference to
The pump 38 includes a fluid conduit 40 having a first chamber 42, a second chamber 44 and a partition 46 with an aperture 48. Fluid communicates between the first and second chambers 42, 44 through the aperture 48. That is, a flow path for a fluid in the pump 38 is defined in the fluid conduit 40 in the first chamber 42, aperture 48 and second chamber 44. In an exemplary embodiment, the aperture 48 is generally circular in shape and has a third diameter D3. The third diameter D3 is greater than the second diameter D2.
The metering rod 22 is configured for reciprocal movement along the axis ‘A’ between a first position and a second position within the fluid conduit 40 and through the aperture 48 to control flow of the fluid through the fluid conduit 40. For example, in a high flow rate condition, in the first position, when an engine and the pump 38 are operating at a low angular velocity (RPM), the first section 26 of the metering rod 22 is positioned in the aperture 48. In the high flow/low RPM condition, reduced effort is needed to perform steering operations.
In a low flow condition, the metering rod 22 moves linearly along the axis ‘A’ to the second position so that the second section 28 is positioned within the aperture 48. Due the larger second diameter D2 within the aperture 48, flow of the fluid within the pump 38 is restricted, such that the flow rate is reduced or “drooped”.
Compared to a metering rod in a typical pressure sensitive droop flow pump, for example, as shown in
In one example of an implementation of the exemplary embodiment described above, high flow scenario may generally refer to a first fluid flow rate through pump 38, for example, approximately 14 lpm. The drooped flow scenario may generally refer to a scenario where flow is reduced or drooped to a second flow rate, for example, less than 10 lpm. When the metering rod 22 with the shoulder 30 moves from the first position to the second position where the second section 28 is positioned in the aperture 48, fluid flow through the pump 38 may be reduced to the second flow rate over an increase of angular velocity, for example, of 1200 RPM in the pump 38, thereby transitioning from the high flow scenario to the drooped flow scenario. That is, the flow rate may be sufficiently drooped over an increase from a first angular velocity to a second angular velocity of, for example, 1200 RPM in an exemplary embodiment of the present invention.
It is understood that the present invention is not limited to the example above. Similar results and advantages may be realized using the metering rod 22 with the square shoulder 30 in environments having different ranges of angular velocities and flow rates. In addition, the metering rod 22 may be tuned to specific applications by altering relative dimensions and positions of the different components while maintaining the square shoulder 30. That is, the metering rod 22 of the present invention may be used under different operating parameters than those described in the example above to droop flow to a suitable level within a suitable angular velocity range across different applications, while still realizing benefits of doing so described herein.
In contrast, with the typical metering rod 10 having the conical transition section 13, an increase in angular velocity of the pump of about 5000 RPM is required to reduce fluid flow through the pump from around 14 lpm to less than 10 lpm. As described above, according to an exemplary embodiment of the present invention flow may be sufficiently drooped over a range of about 1200 RPM. Due the reduced angular velocity range using the square shoulder metering rod 22 of the present invention, fuel efficiency may be improved.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.
This patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/621,798, filed Apr. 9, 2012, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61621798 | Apr 2012 | US |
