Patent Application
20070277763
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.
A brief overview of a typical environment in which the invention operates shall be described to help in understanding the invention. Turning to the drawings, and particularly to
As is well known in the art, to convert the rotational motion to a linear motion, the pump includes a rotatable camshaft having a lobe that extends radially outward from the camshaft. The lobe has an eccentric radial profile. In other words, each lobe has a non-circular or non-concentric cross-section. The linear output of the camshaft is characterized by the radial variation of the lobe. Thus, the difference between the minimum radius establishing the lobe's periphery and the maximum radius establishing the lobe's periphery determines the amount of linear motion that the camshaft provides.
The cam roller 34 of the tappet assembly 10 rides on the outer surface of the lobe as the camshaft rotates, and the lobe imparts at least a radial load on the cam roller 34 causing the cam roller 34 to move away from the camshaft, providing an input for the fluid pumping action of the tappet assembly 10. During operation, a plunger 60 actuated by the tappet assembly 10 moves “up and down” relative to and within a pumping chamber 52 with the cam roller 34 as the cam roller 34 moves “up and down” in response to the rotation of the lobe, thereby drawing fluid into the pumping chamber 52 on a “downward” motion, and pressurizing and pumping the fluid out of the pumping chamber 52 on an “upward” motion.
A coil spring 76 provides means for actuating the plunger 60 vertically downward during the downward stroke during which the plunger 60 draws fluid into the pumping chamber 52.
As will be appreciated, the plunger 60, coil spring carrier 80, and tappet 92 are in fixed vertical relation to one another such that all the components move vertically upward and downward, during the cyclical motion of the tappet assembly 10, substantially in unison.
The housing of the pump slidingly receives the tappet 92. To reduce friction, the outer surface 93 of the tappet 92 includes an annular lubrication groove 94 to provide lubrication between the tappet 92 and the pump housing, when inserted therein. The tappet 92 also includes an anti-rotation slot 95 in a side wall to prevent the tappet 92 from rotating relative to the pump housing.
With further reference to
Referring to
Referring to
The roller pin 110 includes a lubrication supply port 142 that extends substantially radially inward towards the central axis 97 of the roller pin 110 as well as cants relative to the central axis 97 such that the lubrication supply port 142 extends axially towards a second end 144, opposite the first end 140, of the roller pin 110 when moving in a radially inward direction (from the surface 130 to the central axis 97). The lubrication supply port 142 intersects and fluidly communicates with the lubrication ports 136 and 138 at intersection 141. The lubrication supply port 142 fluidly communicates with a port 146 in the tappet 92, illustrated in
To further promote lubrication of the interface 135 between the roller pin 110 and the cam roller 34, the outer surface 130 of the roller pin 110 includes first and second axially spaced apart annular channels 148 and 150. These channels 148 and 150 are spaced apart substantially the axial width, indicated as w1 in
As shown in
The roller pin of the present invention reduces and/or eliminates the high localized contact pressure at the edges of the cam roller, which, in previous tappet assemblies, caused the inner surface of the cam roller at the localized area of high contact pressure and corresponding outer surface of the roller pin to wear at a higher rate than the axially inner portion of the interface of the cam roller and roller pin.
Turning now to
In the embodiment shown in
With reference to
As best illustrated in the embodiment shown in
In an embodiment, the maximum depth of the grooves 174, 176, i.e. the value of R2 minus the minimum value for R3, is significantly deeper than the depth of the annular lubrication grooves 148 and 150. In an embodiment the depth of the grooves 174, 176 is between about 15 to 20 percent of the diameter of the roller pin 110 at its deepest. Furthermore, the grooves 174, 176 do not function to facilitate lubrication between the cam roller 34 and the roller pin 110. The width, w2, of the grooves 174, 176 may vary as a function of angular position from the first groove end 178 to the second groove end 180. The width w2 of the grooves 174 and 176 may also vary as a function of radial position from the outer surface 130 of the roller pin 110 to the bottom 182 of the grooves 174, 176.
The grooves 174, 176 eliminate the end loading of the cam roller inner diameter to the roller pin outer diameter. Additionally, elimination of the end loading and moving of the peak contact pressure inboard and away from the roller ends allows for higher load carrying capacity for the cam roller. As a result, the roller pin 110 may be made from steel material and the like instead of brass material, thereby increasing the durability of tappet assembly. Additionally, the grooves 174, 176 reduce, and in some instances, eliminate the need for the pump run-in operation previously described.
One benefit of the grooves is that unlike a worn-in roller pin, the grooves flex in proportion to the applied load, thereby providing proper contact pressure at the ends of the roller pin for all operating loads. A worn-in roller pin, on the other hand, only provides proper end loading only at a single operating load with the end loads going lower or higher as the roller loads are lower or higher, respectively.
Another benefit of the grooves is that the resulting proper contact pressure across the full width of the roller pin helps prevent the roller pin from becoming unstable and chattering in a manner that can cause axial thrust loads and increased wear rates.
The moving of the peak contact pressure inward and away from the roller ends results in the load being supported where a proper EHD (elastrohydrodynamic) bearing fluid film can be generated. Additionally, the grooves provide increased EHD fluid film thickness at each end of the roller pin to prevent seizure of the cam roller to the roller pin.
Furthermore, the grooves 174, 176 add local compliance to the roller pin outer diameter in the area of the end contact loading such that the bending curvature of the cam roller and the roller pin match when the roller bending curvature is reduced at each end of the roller.
While the grooves 174, 176 have been illustrated and described above as being disposed axially inward from the ends of the roller pin 110, in an alternative embodiment, the grooves 174, 176 are formed at and intersect the ends of the roller pin such that the grooves form a stepped profile in the roller pin.
All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
