This Invention relates to controlling mechanical lash and preventing rotation between two reciprocating members and, more particularly, to valve train components used in internal combustion engines having an elongated outer housing with a bore therein and a cylindrical inner housing where the inner housing moves in the bore in a reciprocating manner with respect to the outer housing.
Valve train components, such as switchable hydraulic pivot elements, switchable roller lifters and valve lifters, typically comprise an outer housing with a bore therein that houses an inner cylindrical body which moves reciprocally in the bore. The bore and the inner housing are concentric and the surface of the bore and the outer surface of the inner housing have opposing cylindrical surfaces which are coaxial to one another.
In order to prevent rotational movement between the two opposing cylindrical surfaces, anti-rotational mechanisms, such as a channel and a pin, are often used. The channel is cut or formed axially in one of the opposing cylindrical surfaces and a pin is radially fixed in the other opposing cylindrical surface. The pin extends radially into the channel and, thereby, prevents rotational movement between the two cylindrical surfaces. The channel can be closed at one or both ends such that the closed end of the channel acts as a stop to control lash between the outer and inner housings.
It can be difficult to form the channel-pin arrangement in the opposing cylindrical surfaces. The groove has to be cut in one of the opposing cylindrical surfaces, a hole has to be drilled in the other of the opposing cylindrical surfaces, and the pin inserted in the hole. Depending on the size of the two cylindrical members, this can be a rather complicated process.
In switchable valve train components, mechanical lash is generally defined as the axial play or clearance between the locking mechanism of the inner housing and an engageable feature on the outer housing during the locked mode. Control of mechanical lash is achieved by altering the axial height of the locking mechanism contained within the inner housing with respect to the engageable locking surface of the outer housing.
It is important to control mechanical lash to a specified range and avoid excessive play or movement between the inner and outer housings. The camshaft that actuates a switchable component is designed to accommodate the prescribed mechanical lash. If the mechanical lash falls outside of the design parameters of the camshaft, the potential for accelerated locking mechanism wear is increased. In this state, the dynamic performance of the valve train may be compromised. A controlled mechanical lash between the housings provides for a more durable switchable valve train component as well as the other components of the valve train.
It is the object of this Invention to provide an inexpensive and simple mechanism for controlling lash and for preventing rotation between two opposing cylindrical surfaces of reciprocating members.
These and other objects and advantages of the Invention become clearer from the following description.
The Invention achieves the above objects by using a radial U-shaped groove in the outer surface of the outer housing, a radial cut in at least one of the legs of the U-shaped groove wherein the cut extends from the groove into the bore of the outer housing, a stop and/or axial indentation on the outer surface of the inner cylindrical housing and a U-shaped clip adapted to fit the U-shaped groove, wherein the clip has a ledge on one leg that extends through the cut and into the bore.
To control mechanical lash, the thickness of the U-shape clip is categorized to control the axial position of the inner housing assembly stop or stops. The number of inner housing assembly stops may be one or two depending on the number of axial indentations, as shown in
Using two axially spaced stops, one stop is referred to as an assembly stop and the other stop is referred to as a mis-switch stop. It is the interaction between the assembly stop and the U-shaped clip that controls the lash. The appropriate thickness of the U-shaped clip is selected to achieve a mechanical lash within the specification of the given component.
To prevent rotation of the inner housing in the bore, the axial indentation has a flat axial surface and the ledge has a flat axial surface that matches the flat axial surface of the indentation so as to prevent rotation of the inner housing.
This arrangement of the cut, stop, ledge and indentation can be provided on more than one side of the housings, preferably, this arrangement is on two sides such that they mirror each other.
Broadly, the lash control mechanism device of the present Invention can be defined as comprising:
Preferably, there is a second radial cut in the second leg of said U-shaped groove, said second cut extending from said groove into said bore; a second ledge on the second leg of said U-shaped clip, said second ledge extending through said second cut and into said bore; and a second stop on said outer surface of said inner cylindrical body which abuts said second ledge such that the first stop and second stop and first ledge and second ledge interact to control mechanical lash.
Preferably, there is a third stop positioned axially apart from said first stop on the outer surface of said inner housing and the first ledge of said U-shaped clip is positioned axially between the first and third stop. The third stop acts as a mis-switch stop to prevent excessive telescoping of the inner housing within the outer housing.
More preferably, there is a fourth stop positioned axially apart from said second stop on the outer surface of the inner housing and the second ledge of said U-shaped clip is positioned axially between the second and the fourth stop. The fourth stop acts as a mis-switch stop to prevent excessive telescoping of the inner housing within the outer housing.
In order to prevent rotational movement between the bore and the inner housing the mechanism of the present Invention can be defined as comprising:
Preferably, there is a second radial cut in the second leg of said U-shaped groove, said second cut extending from said groove into said bore; a second ledge on the second leg of said U-shaped clip, said second ledge extending through said second cut and into said bore, the second ledge has a flat axial surface; and a second axial indentation on said outer surface of said inner housing, said second indentation having a flat axial surface that matches said flat axial surface of said second ledge such that the first indentation and the second indentation and first ledge and second ledge interact to prevent rotation of the inner housing in the bore.
Preferably, the antirotational mechanism and the lash control mechanism are combined. In such a combination, the first axial indentation extends axially from the first stop. More preferably, said second axial indentation extends axially from the second stop and forms a parallel flat surface to the surface of said first axial indentation. Even more preferably, the first and third stops are positioned at either axial end of the first indentation and the second and fourth stops are positioned at either axial end of the second indentation so as to provide lash control and prevent rotation of the inner housing in the bore.
The Invention will now be described more closely with reference to the following drawings, wherein:
Valve lifter 10 comprises outer cam follower 20 which is an elongated outer housing having a cylindrical bore 21 therein. Slidably positioned within bore 21 of outer cam follower 20 are upper inner housing assembly 22 and lower inner cam follower 24. Upper locking means 26 is provided in upper inner housing assembly 22 and lower locking means 28 is provided in lower inner cam follower 24. Lost motion spring 30 is positioned between upper, inner housing assembly 22 and lower inner cam follower 24. Hydraulic oil is provided through engine block 12 to the locking means 26 and 28 to lock and unlock the inner cam followers 22 and 24 so as to allow for reciprocating movement between the outer cam follower 20 and inner housing assembly 22 and the inner cam followers 24. Antirotational lash control mechanism 40 is provided in lifter 10. Inner housing assembly 22 and inner cam follower 24 move reciprocally in bore 21.
As can be seen in more detail in
U-shaped clip 48 has first leg 49 with first ledge 50 and second leg 51 with second ledge 52. First ledge 50 has top surface 54, bottom surface 56 and flat axial surface 58. Second ledge 52 has top surface 60, bottom surface 62 and flat axial surface 64.
Inner cam follower 24 has first axial indentation 66 and second axial indentation 68. First axial indentation 66 has a top stop 70, a bottom stop 72 and a flat axial surface 74 which matches the flat axial surface 58.
Second axial indentation 68 has top stop 76, bottom stop 78 and flat axial surface 80 that matches flat axial surface 64.
Top surfaces 54 and 60 abut stops 70 and 76, respectively, to stop downward movement while bottom surfaces 56 and 62 abut bottom stops 72 and 78, respectively, to stop upward movement. In
Flat axial surfaces 58 and 64 match flat axial surfaces 74 and 80 to prevent rotational movement of inner cam follower 24 inside bore 21.
As will be appreciated, the ease of assembly and disassembly of the present Invention is self apparent. This is due to the exposed U-shaped clip that is easily removed from the U-shaped groove offering a simple means of disassembling the inner housing from the outer housing.
Furthermore, the present Invention provides superior packaging space because no additional component length is necessary in the present Invention.
Furthermore, forming the groove and making the cuts in the outer housing are simple compared to forming a groove inside the bore of the outer housing.
The U-shaped clip is made from sheet metal and has natural resistancy to maintain its U-shaped configuration thereby holding itself in the U-shaped groove.
Furthermore, the thickness t of the clip, as shown in
Where two clips are used, one clip is necessary to hold the entire assembly together while a mechanical lash measurement is made. This measurement will determine the thickness of the clip necessary to achieve the required mechanical lash specification for the particular switchable component. After this measurement, the appropriate clip size is chosen and placed in the assembly.
This application is a 371 of PCT/EP2008/057893 filed Jun. 20, 2008, which in turn claims the priority of U.S. 60/948,630 filed Jul. 9, 2007, the priority of both applications is hereby claimed and both applications are incorporated by reference herein.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/057893 | 6/20/2008 | WO | 00 | 1/8/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/007225 | 1/15/2009 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3108580 | Crane, Jr. | Oct 1963 | A |
3886808 | Weber | Jun 1975 | A |
4089234 | Henson et al. | May 1978 | A |
5022356 | Morel et al. | Jun 1991 | A |
Number | Date | Country |
---|---|---|
43 24 756 | Feb 1995 | DE |
103 32 981 | Feb 2005 | DE |
03008771 | Jan 2003 | WO |
03067038 | Aug 2003 | WO |
Number | Date | Country | |
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20100175643 A1 | Jul 2010 | US |
Number | Date | Country | |
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60948630 | Jul 2007 | US |