US20090308339A1

US20090308339A1 - Switchable valve train device having a single locking pin

Info

Publication number: US20090308339A1
Application number: US12/157,990
Authority: US
Inventors: Nick J. Hendriksma
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 2008-06-16
Filing date: 2008-06-16
Publication date: 2009-12-17

Abstract

A switchable valve train device including a pin housing slidably disposed in a body and having a transverse bore. A stepped plug in the transverse bore extends beyond the pin housing to engage a slot in the body to prevent rotation of the pin housing. The upper end of the slot limits travel of the pin housing. The plug is a seat for a compression spring. A locking pin is disposed in the transverse bore against the spring to selectively engage a locking port in the body, the locking pin and the locking port have mating flats to distribute the load. Mechanical lash is set by use of a gage tool during assembly, allowing selection of a locking pin of appropriate thickness. The device may be, for example, a switchable hydraulic lash adjuster or a switchable valve lifter.

Description

TECHNICAL FIELD

The present invention relates to switchable valve train members for internal combustion engines for supporting a roller finger follower or a pushrod in a combustion valve train; more particularly, to a switchable hydraulic lash adjuster or a switchable valve lifter that is switchable between a first mode wherein valve actuation is permitted and a second mode wherein valve actuation is prevented; and most particularly, to a sub-assembly for a switchable member wherein a latchable pin housing is selectively latched to a sub-assembly body by a single transverse locking pin, and wherein the pin housing is prevented from rotation within the adjuster body, and wherein axial mechanical lash in the sub-assembly is easily set during assembly thereof without requiring repeated assembly and disassembly of the sub-assembly.

BACKGROUND OF THE INVENTION

Switchable valve train devices are well known in the engine arts for selectively permitting or preventing the opening of an associated engine combustion valve. See, for example, U.S. Pat. No. 7,263,956 B1 (“the '956 patent”) wherein a pin housing of a switchable valve lifter (SVL) is slidably disposed within an outer body bore. Opposing dual, flatted locking pins having a compression spring therebetween are disposed in a transverse bore in the pin housing for extending radially to engage an annular locking shelf in the body bore. Pressurized oil is applied selectively to the outer ends of the pins to retract the pins into the pin housing, allowing the pin housing to slide in the body bore in lost motion. The dual locking pin concept, as disclosed in the '956 patent, offers several benefits over the prior art single locking pin concept. For example, the valve train load that is transferred through the switchable device during valve lift is supported by two locking pins instead of one and the overall diameter of the device may be reduced since load bearing lengths may be shared by both sides of the body and pin housing. This dual flatted locking pin construction disclosed in the '956 patent has been adapted to other valve train members such as switchable hydraulic lash adjusters (SHLA).
An additional known problem in prior art SHLAs having dual locking pins is that side-loading of the pin housing with respect to the body is significantly greater than in prior art SVLs wherein forces are nearly parallel to the axis of the SVL. This is because a hydraulic lash adjuster supports and is a pivot point for a roller finger follower (RFF), and force vectors imposed on the RFF by an associated cam lobe during opening and closing of such a valve are not entirely parallel to the axis of the SHLA. Because the pin housing of a prior art SHLA is not constrained from rotation within the SHLA body, there are orientations of the pin housing with respect to the sideloading wherein the entire axial load is carried by a single locking pin during certain periods during the valve lift event.
A separate issue in prior art SHLAs is the need for a precise setting of the internal axial lash (mechanical lash) between the pin housing and adjuster body with the pin in locked position. It is important that the locking pin be given sufficient clearance to engage reliably and securely; however, if too much clearance is permitted, the SHLA will be noisy and will experience excessive wear. Also, too much clearance will adversely effect the opening timing of the associated valve since, in the valve opening direction, the pin housing must first traverse the mechanical lash before the switchable valve train can even begin to open the associated valve. Because the stack-up of manufacturing tolerances of the individual lash adjuster components cannot provide a consistent, as-built mechanical lash, a means for adjusting the mechanical lash of each SHLA must be provided. Typically, in the prior art, each SHLA is at least partially assembled and the gross axial lash is measured. The required clearance is then subtracted from the gross axial lash and a graded shim of the resulting thickness is inserted into the SHLA, typically after first disassembling the partially-assembled device.
What is needed in the art is an improved SHLA wherein the axial load is reliably carried by a single locking pin and wherein the gross mechanical lash may be easily measured and a desired mechanical lash may be set without disassembly of the device.
It is a principal object of the present invention to provide a reliable single-pin SHLA or SVL.
It is a further object of the invention to reduce the manufacturing complexity and cost of a SHLA or SVL.

SUMMARY OF THE INVENTION

Briefly described, a sub-assembly for a switchable valve train device, which may be either a SHLA or a SVL, includes a pin housing slidably disposed in a body and having a transverse bore. A stepped plug has a major diameter portion that is full-fitting in the transverse bore and a minor diameter portion extending beyond the surface of the pin housing to engage a longitudinal slot in a wall of the body to prevent rotation of the pin housing within the body. The upper end of the slot limits axial travel of the pin housing and thus participates in setting mechanical lash in the device.
The plug also acts as a seat for a compression spring. A locking pin is disposed in the transverse bore against the spring for extension beyond the pin housing to engage a locking port formed in a wall of the body opposite the longitudinal slot. Because the pin housing is prevented from rotation within the body, the orientation of the locking pin to the locking port is maintained.
The locking pin and the locking port are provided with mating flats to distribute the locked load. The locking pin is prevented from rotation within the cross-bore by action of an anti-rotation cross pin to maintain the rotational orientation of the locking pin flat to the locking port flat.
Mechanical lash is readily set by use of a gage tool during assembly via selection of a locking pin having an appropriate thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an elevational cross-sectional view of a first prior art single locking pin SVL substantially as disclosed in U.S. Pat. No. 6,196,175 B1;

FIG. 2 is an elevational cross-sectional view of a second prior art single locking pin SVL substantially as shown in U.S. Pat. No. 6,606,972 B2;

FIG. 3 is an elevational cross-sectional view of a sub-assembly of a single locking pin SHLA in accordance with the present invention;

FIG. 4 is an elevational view of a first side of the SHLA sub-assembly shown in FIG. 3;

FIG. 5 is an elevational view of a second and opposite side of the SHLA sub-assembly shown in FIGS. 3 and 4; and

FIGS. 6 through 12 are elevational cross-sectional views showing progressive steps in the assembling and lash-setting of the sub-assembly shown in FIG. 3.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As noted above, the construction and functionality of SVLs and SHLAs are very similar. Although the following presentation is directed to an improved single-pin SHLA, the disclosed principles of construction are equally applicable to an improved single-pin SVL. Prior art is found in two single-pin SVL disclosures.
Referring to FIG. 1, a first prior art single-pin SVL 10 is shown substantially as disclosed in U.S. Pat. No. 6,196,175 B1 (“the '175 patent”). SVL 10 is shown disposed in a bore 11 in engine 12 for selectively converting the eccentric motion of cam lobe 14 into linear motion of pushrod 16. SVL 10 comprises a body 18 having a stepped bore 20 for receiving an annular spacer 22 and a stepped pin housing 24 slidably disposed in bore 20. Pin housing 24 contains a conventional hydraulic lash-adjusting apparatus 26 for eliminating lash in a valve train. A lost motion spring 25 is disposed in an annular space 27 between body 18 and pin housing 24. A transverse stepped bore 28 in pin housing 24 receives a press-fit plug 30 extending from pin housing 24 through a first longitudinal slot 32 in body 18 and into a second longitudinal slot 34 formed in bore 11 for preventing rotation of pin housing 24 in body 18 and rotation of body 18 in bore 11. Plug 30 is axially slidable in slots 32 and 34. The upper end 35 of slot 32 defines a stop for the axial travel of plug 30 and therefore the axial travel of pin housing 24 within body 18. A single locking pin 36 having a circular cross-section is also disposed in stepped bore 28 for selective locking and unlocking with a circular locking port 38 formed through the wall of body 18. When pressurized oil (not shown) is supplied to end 40 of pin 36, return spring 42, disposed in compression between plug 30 and pin 36, is overcome and pin 36 is forced from locking port 38. During engine operation, when the SVL is in unlocked mode, pin housing 24 is held motionless by pushrod 16 and body 18 is free to oscillate within bore 11 in lost motion of cam lobe 14. When oil pressure is removed from pin end 40, spring 42 returns pin 36 into locking engagement with locking port 38. In locked mode, SVL 10 functions as a conventional valve lifter.
The disclosed SVL 10 has at least the shortcomings that would exist if the locking arrangement were used in a single-pin SHLA.
First, operating experience has shown that a round pin disposed in a round port suffers from undesirably rapid wear to the pin and/or port because of the relatively short bearing length of the mating bore and because the pin and port have essentially line contact as a result of a deliberate difference in diameters that allows the pin to enter the port reliably. The result is that, as the wear occurs, the internal mechanical lash between the pin housing and the body increases undesirably. The increased lash results in objectionably noisier operation of the engine, but more importantly, results in a later valve opening point and a progressively lower valve lift.
Second, there is no apparent method for conveniently setting internal mechanical lash during assembly of SVL 10 as shown in the '175 patent.
Third, the axial positions of upper end 35 of slot 32 and locking port 38 define the amount of internal mechanical lash and are subject to variation in manufacturing tolerances of pin housing 24, plug 30, and body 18, making the amount of lash in any given unit, and hence the precise point of opening and lift of an associated valve, unreliable.
Referring to FIG. 2, a second prior art single-pin SVL 10′ is shown substantially as disclosed in U.S. Pat. No. 6,606,972 B2 (“the '972 patent”). It is seen that the basic construction is very similar to that of first prior art SVL 10 except that return spring 25′ is disposed below pin housing 24′ rather than surrounding it.
While a means has been provided in SVL 10′ for setting mechanical lash, SVL 10′ has the other shortcomings as SVL 10 recited above, especially since it utilizes a cylindrical locking pin 36′ having a circular cross-section that locks into a round locking port 38′ formed in bore 20′ of body 18′. As noted above, this shortcomings would also exist if the locking arrangement were used in a single-pin SHLA.
As an improvement over a single locking pin design, switchable valve train members in the prior art employ dual opposing locking pins, as disclosed in the '956 patent, which arrangement provides greater locking stability and reliability than a single-pin arrangement. Experience has shown, however, that a dual-pin arrangement can have a drawback in certain applications. As noted above, because the pin housing is free to rotate within the body of a prior art SHLA having dual locking pins for engagement with an annular locking shelf, there are orientations of the pin housing with respect to an associated RFF wherein the entire axial load is carried by only one of the two locking pins during periods of the valve lift event, the force balance within the SHLA prevents contact of the opposite pin with the locking shelf due to the component of force applied to the pin housing that is transverse to the axis of the body. Further, as the diameter of the pin housing is reduced for packaging purposes, the transverse length of the bore in the pin housing also becomes smaller, leading to shorter pins having a reduced length/diameter ratio, resulting in increased potential for cocking and wear of the pins, thereby reducing the stiffness of the locking mechanism.
Referring now to FIGS. 3 through 5, a sub-assembly portion 100 of an improved single-pin SHLA or SVL 110 is shown. Sub-assembly 100 comprises body 118; pin housing 124 slidably disposed in body 118; and a stepped plug 130, spring 142, and locking pin 136 disposed in a transverse bore 128 in pin housing 124. Stepped plug 130 extends into a slot 134 formed in body 118 for preventing rotation of the pin housing within the body as in the prior art. Also, as in the prior art, plug stop 135 limits the axial travel of pin housing 124 within body 118. The shapes and relationships of these components is the subject of the present invention.
In one aspect of the present invention, a locking port 138 formed in a wall of body 118 is provided with a locking ledge 150 for receiving a mating flat 152 on locking pin 136. The use of a broad planar contact area between the pin and the body overcomes the prior art wear problem wherein a locking pin having a circular cross-section engages a circular bore of a slightly larger diameter as noted above. This arrangement requires that locking pin 136 be prevented from rotation about its own axis, which is readily accomplished in many ways by providing an additional flat (not visible) on the side of pin 136 and a mating flat-ended cross-pin (not visible) disposed in pin housing 124, substantially as disclosed in U.S. Pat. No. 6,513,470 (“the '470 patent”) directed to a SVL, the relevant disclosure of which is herein incorporated by reference. Note that if the rotational orientation of the body of a SHLA or SVL relative to the receiving bore in the engine is critical, such as, for example, for maintaining roller alignment with a cam lobe in the case of a roller SVL or for oil port alignment in either a SHLA or SVL, a means for locating the body in the receiving bore, as known in the art, may be provided.
Further, locking port 138 is provided with an additional notch 154 to allow locking pin 136 to be installed through port 138 after pin housing 124 is inserted into body 118, the benefits of which are described below.
Referring now to FIGS. 6 through 12, a method will be described for assembling and setting the desired internal mechanical lash in a SHLA or SVL sub-assembly in accordance with the present invention. First, a flat-ended cross-pin (not visible) is mounted into a bore in pin housing 124, as shown in the incorporated '470 patent, and stepped plug 130 is inserted into transverse bore 128 (slidable therein). Then, after the lost motion springs such as shown in FIG. 2 (numeral 25′) is installed in chamber 160, the pin housing is installed into bore 120 in body 118, as shown in FIG. 6, until transverse bore 128 is aligned with locking port 138, as shown in FIGS. 6 and 7.
Next, a gage tool 156 is inserted (FIG. 7) through locking port 138 until a flat 158 on the gage tool is directly adjacent locking ledge 150 (FIG. 8). The thickness 157 of gauge tool 156 at flat 158 is known and preferably is the nominal thickness of a locking pin 136 at pin flat 152. Pin housing 124 is lowered into body 118 against the force of the lost motion springs until flat 158 makes contact with locking ledge 150, defined as a first position A (FIG. 9). Simultaneously, gage tool 156 is advanced to urge the minor diameter portion of plug 130 into slot 134. Pin housing 124 is then released, and lost motion springs (not shown) in chamber 160 urge pin housing 124 upward until plug 130 is stopped by the upper end 135 of slot 134, defined as a second position B. Thus, the measured lash 162 between position A and position B is the mechanical lash in subassembly 100 inherent when a locking pin of thickness 157 is used. The desired lash is then subtracted from the measured lash 162 to yield a lash correction which, when added to the gage tool of known thickness, yields a desired thickness for the actual locking pin 136 to be used. A locking pin 136 of the desired thickness is selected from the sorted family of locking pins having a suitable range of sizes.
Plug 130 is then urged back into transverse bore 128 and pin housing 124 is raised a small distance, without disassembly, to permit gage tool 156 to be withdrawn (FIG. 10). Then, return spring 142 and the selected locking pin 136 are inserted into transverse bore 128 (FIG. 11). Pin housing 124 is again depressed within body 118 until stopped by pin flat 152 against locking ledge 150. Simultaneously, pin 136 is urged by the locking pin spring further into transverse bore 128, re-seating the minor portion of plug 130 into slot 134. Pin housing 124 and locking pin 135 are released, again allowing the lost motion springs to urge pin housing 124 upwards until slot end 136 is engaged. A stopper such as a wire clip (not shown) may be installed in transverse bore 128 before plug 131 is inserted in the bore to prevent end face 131 of plug 130 (FIG. 3) from rubbing against the inside bore of body 118 when locking pin 136 is retracted from locking port 138 and pin housing 124 is cycle in lost motion.
Sub-assembly 100 is now fully assembled with the correct internal mechanical lash and is ready for subsequent insertion of a prior art lash adjusting mechanism 26 (FIG. 1) to complete the assembly in accordance with the present invention.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Claims

1. A switchable valve train device for selective switching of a valve train in an internal combustion engine, the device comprising:

a) a body having a locking port formed in a first body wall and a longitudinal slot formed in a second and opposite body wall, wherein said locking port includes a locking ledge;

b) a pin housing slidingly disposed in said body and having a transverse bore;

c) a plug slidably disposed in said transverse bore and having a plug portion extending into said longitudinal slot for preventing rotation of said pin housing within said sub-assembly body; and

d) a locking pin slidably disposed in said transverse bore and having a locking flat for selectively engaging said locking ledge.

2. A switchable valve train device in accordance with claim 1 further comprising a return spring disposed in said transverse bore between said plug and said locking pin for urging said locking pin into said locking port.

3. A switchable valve train device in accordance with claim 1

wherein said pin housing assumes a first axial position when said locking pin flat is engaged with said locking ledge, and

wherein said pin housing assumes a second axial position when said portion of said plug extending into said slot is engaged with an end of said slot, and

wherein the difference between said first and second axial positions defines the internal mechanical lash within said device.

4. A switchable valve train device in accordance with claim 3 wherein said locking pin has a thickness at said locking flat such that said internal mechanical lash is set at a predetermined value.

5. A switchable valve train device in accordance with claim 1 wherein said device is a switchable hydraulic lash adjuster.

6. A switchable valve train device in accordance with claim 1 wherein said device is a switchable hydraulic valve lifter.

7. A switchable hydraulic lash adjuster for selective deactivation of a valve train in an internal combustion engine, comprising:

b) a pin housing slidingly disposed in said body and having a transverse bore;

c) a plug slidably disposed in said transverse bore and having a plug portion extending into said longitudinal slot for preventing rotation of said pin housing within said body; and

8. A switchable hydraulic lash adjuster in accordance with claim 7 comprising a return spring disposed in said transverse bore between said plug and said locking pin for urging said locking pin into said locking port.

9. An internal combustion engine, comprising a switchable hydraulic lash adjuster for selective deactivation of a valve train in an internal combustion engine, wherein said deactivating hydraulic lash adjuster includes:

a sub-assembly body disposable in a bore in said engine for receiving said deactivating hydraulic lash adjuster and having a locking port formed in a first body wall and a longitudinal slot formed in a second and opposite body wall, wherein said locking port includes a locking ledge,

a pin housing slidingly disposed in said body and having a transverse bore and having an axial bore containing a hydraulic lash adjustment mechanism,

a plug slidably disposed in said transverse bore and having a plug portion extending into said longitudinal slot for preventing rotation of said pin housing within said sub-assembly body,

a locking pin slidably disposed in said transverse bore and having a flat for selectively engaging said locking ledge, and

a return spring disposed in said transverse bore between said plug and said locking pin for urging said locking pin into said locking port.

10. A method for setting internal mechanical lash of a switchable valve train device to a desired value wherein the device includes a body having a locking port and a longitudinal slot, wherein said locking port includes a locking ledge; a pin housing slidingly disposed in said body and having a transverse bore; a plug disposed in said transverse bore and having a plug portion extending into said longitudinal slot; and a locking pin slidably disposed in said transverse bore and having a locking flat for engaging said locking ledge, the method comprising the steps of:

a) inserting said plug into said transverse bore in said pin housing;

b) inserting said pin housing and said plug into said body until said transverse bore is adjacent said locking port;

c) inserting a gage tool through said locking port into said transverse bore to seat a portion of said plug into said longitudinal slot;

d) moving said pin housing axially within said body until a flat on said gage tool engages said locking ledge in said locking port, defining a first axial position of said pin housing;

e) moving said pin housing axially in said body until said plug portion in said longitudinal slot engages an end of said slot, defining a second axial position of said pin housing;

f) observing the axial distance between said first position and said second position;

g) removing said gage tool from said transverse bore and said locking port;

h) providing a selected locking pin having a thickness at said locking pin flat such that the difference between said thickness and said observed axial distance is equal to said desired value of internal mechanical lash; and

i) inserting said selected locking pin into said transverse bore through said locking port.

11. The method in accordance with claim 10 further including the steps of:

a) inserting a return spring into said transverse bore through said locking port before step i) and;

b) displacing said locking pin in said transverse bore to reseat said plug portion in said longitudinal slot.

12. The method in accordance with claim 10 further including the step, prior to the removing step, of moving the gage tool away from the locking ledge by raising the pin housing, without disassembling the pin housing from the body, to permit the gage tool to be removed from the transverse bore.