WO2008079833A1

WO2008079833A1 - High-low lift and deactivating roller lifter

Info

Publication number: WO2008079833A1
Application number: PCT/US2007/088024
Authority: WO
Inventors: Matt Evans; Florin Bugescu
Original assignee: Schaeffler Kg
Priority date: 2006-12-20
Filing date: 2007-12-19
Publication date: 2008-07-03

Abstract

The three mode valve lifter has three cam followers, an outer cam follower, an upper, inner cam follower, and a lower, inner cam follower. The upper, inner cam follower has an upper locking means for coupling the upper, inner cam follower and the outer cam follower. The lower, inner cam follower has a lower locking means for coupling the lower, inner cam follower to the outer cam follower. A lost motion spring is provided between the upper, inner cam follower and the lower, inner cam follower. By coupling and uncoupling the cam followers, the valve lifter is able to actuate a low lift mode, a high lift mode and a deactivated mode.

Description

HIGH-LOW LIFT AND DEACTIVATING ROLLER LIFTER

FIELD OF THE INVENTION

This Invention relates to valve lifters for internal combustion engines and, more particularly, to cam activated variable hydraulic valve lifters especially designed for lifting a push rod in an overhead valve engine or other engines with overhead cam configurations.

BACKGROUND OF THE INVENTION

Variable valve lifters having more than one mode are known and, for example, are taught in U.S. Patent Nos . 5,361,733 and 6,427,652.

In U.S. '733, the valve lifter has a pair of cam followers, one for high lift valve actuation and another for low lift valve actuation. The cam followers are concentric, one being housed inside the bore of the other, and the inner cam follower acts as a seat for the push rod and contains a conventional hydraulic lash adjuster at the base of the push rod. A locking mechanism is used to selectively connect the cam followers. The locking mechanism uses a hydraulic fluid delivery system to couple the two cam followers . The valve lifter operates in two modes or steps, a high lift mode, when the two cam followers are coupled, and a low lift mode, when the cam followers are uncoupled.

In U.S. '652, Lho valve lifter comprises a housinq with an inner element that is slidably mounted in a bore of the housing. The housing acts as a cam follower while the inner element acts as a push rod seat. The inner element also contains a conventional hydraulic lash adjuster. The valve lifter has a hydraulic fluid delivery system to provide hydraulic fluid for uncoupling the inner element from the housinq. The valve lifter of U.S. '652 has two modes of operation, the coupled mode and a deactivated mode.

OBJECT OF THE INVENTION

It is an object of the Invention to achieve a valve lifter that has three modes of operation, a high lift mode, a low lift mode and a deactivated mode.

These and other objects and advantages of the Invention will become obvious from the following detailed description. SUMMARY OF THE INVENTION

The Invention achieves the above objects with a valve lifter comprising three cam followers and two locking mechanisms which allow for the coupling and uncoupling of the three cam followers. The valve lifter of the Invention has a high lift mode, a low lift mode and a deactivation mode that allows for optimization of engine performance due to the ability to achieve different lift modes.

Broadly, the Invention can be defined as a three mode valve lifter comprising:

an outer cam follower having a cylindrical body and a bore therein;

an upper, inner cam follower slidably mounted in said bore of said outer cam follower;

an upper locking means on the outer and upper, inner cam followers and engageable for selectively locking the outer and the upper, inner cam followers together for coincident reciprocating motion;

a lower, inner cam follower slidably mounted in said bore of said outer cam follower, below said upper, inner cam follower;

a lower locking means on the outer and lower, inner cam followers and engageable for selectively locking the outer and the lower cam followers together for coincident reciprocal motion;

a lost motion spring positioned in said bore of said outer cam follower between said upper and lower inner cam followers; and

a hydraulic fluid delivery means for separately delivering hydraulic fluid to both said upper and lower locking means so as to activate a low lift mode, a high lift mode, and a deactivated mode.

A hydraulic lash adjuster can be mounted in the upper, inner cam follower in conjunction with a seat for a push rod. In such a situation, conventional passageways are provided to supply hydraulic fluid to the hydraulic lash adjuster. The other end of the push rod is suitably attached to a rocker arm. The push rod can be hollow so as to provide hydraulic fluid to the hydraulic lash adjuster. Alternatively, a side feed arrangement can be employed to provide hydraulic fluid to the hydraulic lash adjuster.

Alternatively, the hydraulic lash adjuster can be mounted on the end of the push rod that is in contact with the rocker arm and the top of the upper, inner cam follower can provide the seat for the push rod.

The upper locking means is suitably mounted in a radial bore of the upper, inner cam follower and comprises at least one locking pin which is biased by a coil spring to extend outward from the upper, inner cam follower and to mate with an upper port in the outer cam follower. The upper port in the outer cam follower is in fluid communication with an oil gallery which is connected to the hydraulic fluid delivery means. By providing hydraulic fluid to the upper port, the pin of the upper locking means can be retracted and the upper, inner cam follower uncoupled from the outer cam follower.

The lower locking means is mounted in a radial bore in the lower inner cam follower and comprises at least one locking pin which is spring biased into the lower cam follower. The lower locking means has an oil reservoir that is in fluid communication with the hydraulic fluid delivery means. The outer cam follower has a lower port which accommodates the pin of the lower locking means when the reservoir of the lower locking means is filled with hydraulic fluid, thereby coupling the lower inner cam follower and the outer cam follower. When the hydraulic fluid is drained from the reservoir, the spring bias forces the pin into the lower cam follower and uncouples the lower cam follower from the outer cam follower.

The hydraulic fluid delivery means is in fluid communication with the upper port so as to actuate movement of the upper locking means and is in fluid communication with the fluid passageway in the lower cam follower so as to provide hydraulic fluid to the reservoir in the lower locking means.

BRIEF DESCRIPTION OF THE DRAWINGS

The Invention will now be described more closely with reference to the following drawings, wherein:

FIG. 1 is a cross sectional view of a valve lifter of the present Invention; FIG. 2 is a cross sectional view of a valve lifter of

FIG. 1 taken along lines H-II of FIG. 1. FIG. 3 is an exploded view of the valve lifter; and FIG. 4 is a view of the valve lifter. DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates valve lifter 10 slidably mounted in engine block 12. One end of valve lifter 10 is associated with push rod 14 while the other end of valve lifter 10 is associated with low lift cam 16 and high lift cams 1.8 which are each connected to a conventional cam shaft, not shown.

Valve lifter 10 comprises outer cam follower 20 which is a cylindrical body having a cylindrical bore therein. Slidably positioned within the bore of outer cam follower 20 is upper, inner cam follower 22 and lower inner cam follower 24. Upper locking means 26 is provided in upper, inner cam follower 22 and lower locking means 28 is provided in lower inner cam follower 24. Lost motion spring 30 is positioned between upper, inner cam follower 22 and lower inner cam follower 24.

Hydraulic fluid delivery means comprises an oil gallery 32 which is in fluid communication with upper port 34. Hydraulic fluid delivery means also comprises oil passageway 36 which is in fluid communication with lower oil port 38 and lower oil passageway 40. Hydraulic fluid delivery means is controlled in a conventional manner so as to independently provide hydraulic fluid to either the upper locking means or the lower locking means so as to cause coupling or uncoupling of the upper or lower, inner cam follower from the outer cam follower. Outer cam follower 20 has slide pads 42 which are in contact with lower lift cams 16.

Upper, inner cam follower 22 comprises cylindrical body 44 which slidably moves within the bore of outer cam follower 20. Upper, inner cam follower 22 has push rod seat 46 to accommodate push rod 14. Hydraulic lash adjuster 48 is mounted in the upper part of upper, inner cam follower 22. Push rod 14 can be a hollow push rod so as to provide oil to hydraulic lash adjuster 48 in a conventional manner. Hydraulic lash adjuster 48 can also be mounted at the other end of push rod 14.

Upper, inner cam follower 22 has radial bore 50 in which upper locking means 26 is positioned.

Upper locking means 26 is shown as comprising locking pins 52 and spring 54 which biases locking pins 52 in an outward direction into upper port 34.

Upper locking means 26 can also be designed in the same manner as the locking means illustrated in U.S. '733 Patent wherein the locking pin and the biasing spring is positioned in the outer cam follower and upper port 34 is positioned in upper, inner cam follower 22. Additionally, the upper section of the valve lifter can also be designed in a conventional manner where a lost motion spring for the upper assembly is situated on top of the Lifter for space conserving purposes, and a lost motion spring for the lower assembly, of reduced height, is positioned between upper and lower inner cam followers.

Lower, inner cam follower 24 comprises body 56 with a radial bore 58 therein. Radial bore 58 accommodates lower locking means 28. Roller 60 is mounted on lower, inner cam follower 24 and is in contact with high lift cam 18. U-shaped pin 62 is mounted in outer cam follower and penetrates to lower, inner cam follower 24 to set mechanical lash and prevent rotation of the assembly.

Lower locking means 28 comprises locking pins 64 and springs 66. Springs 66 bias locking pins 64 inwardly towards the center of lower, inner cam follower 24. Lower locking means 28 are housed in bore 58. Oil reservoir 68 is positioned behind pins 64 and is in fluid communication with oil inlet 70. Oil inlet 70 is in fluid communication with lower oil passageway 40 and lower oil port 38 and oil passageway 36. Hydraulic fluid delivery means provides oil to reservoir 68 and allow for coupling of lower, inner cam follower 24 and outer cam follower 20. Locking pins 64 mate with lower port 72 when oil is provided to oil reservoir 68 so as to couple lower inner cam follower 24 to outer cam follower 20.

The three modes of the valve lifter of the present Invention will now be described with reference to Figure 1.

In low lift mode, no hydraulic fluid is provided to either locking means 26 or 28. Locking pins 52 engage upper port 34 and couple upper, inner cam follower 22 with outer cam follower 20. This coupling can be considered a pressureless locking because the locking force for pins 52 is provided by spring 54. Locking pins 64 are disengaged from outer cam follower 20 because of springs 66. Therefore, pins 64 do not engage lower port 72. This allows lower cam follower to slidably move inside the bore of outer cam follower 20 when high lift cam 18 makes contact with roller 60. Because of lost motion spring 30, high lift cam 18 does not transfer its motion to rocker arm 14. Low lift cams 16, however, transfer their motion to slide pads 42 which, in turn, cause outer cam follower 20 to move in conjunction with lower lift cams 16. Because upper, inner cam follower 22 is coupled with outer cam follower 20, the lower lift cam motion is transferred to rocker arm 14. In high lift mode, hydraulic fluid delivery means provides oil to reservoir 68 so as to force pins 64 into lower port 72. This couples lower, inner cam follower 24 to outer cam follower 20. The coupling between upper, inner cam follower 22 and outer cam follower 20 is maintained and, thus, the motion of high lift cam 18 is transferred to rocker arm 14 because of the coupling of both lower, inner cam follower 24 and upper, inner cam follower 22 to outer cam follower 20. In the high lift mode, there is no lost motion stroke.

In the deactivating mode, locking pins 64 are retracted out of lower port 72 by releasing oil from oil reservoir 68. Locking pins 52 are disengaged from upper port 34 in a conventional manner using hydraulic fluid from the hydraulic fluid delivery means provided by oil gallery 32 through port 34. In the deactivation mode, neither the high lifb cam 18 nor the low lift cam 16 act on push rod 14 because of the uncoupling of both inner cam followers 22 and 24 from outer cam follower 20.

Because outer cam follower is cylindrical in shape, it will allow for a simple manufacturing process and thereby reduce manufacturing costs. The valve lifter of the present Invention provides for wear and mechanical lash increase improvements because roller 60 is provided to an inner cam follower. The slide pad area 42 of outer cam follower 20 can have increased hardness and thereby provide a more robust valve lift design.

The use of U-shaped pins 62 both sets the proper mechanical lash and prevents rotation of the lower, inner cam follower since the U-shaped pins mate with flat surface of lower, inner cam follower.

REFERENCE CHARACTERS

10 Valve lifter 52. Locking pin

12. Engine block 54. Spring

14. Push rod 56. Body

16. Low lift cam 58. Radial bore

18. High lift cam 60. Roller

20. Outer cam follower 62. U-shaped pins

22. Upper, inner cam follower 63. Flats

24. Lower, inner cam follower 64. Locking pins

26. Upper locking means 66. Spring

28. Lower locking means 68. Oil Reservoir

30. Lost motion spring 70. Oil Inlet

32. Oil gallery 72. Lower port

34. Upper port

36. Oil passageway

38. Lower oil port

40. Lower oil passageway

42. Slide pads

44. Body cylinder

46. Push rod seat

48. Hydraulic lash adjuster

50. Radial bore

Claims

WHAT WE CLAIM IS :

1. A three-mode valve lifter comprising: an outer cam follower having a cylindrical body and a bore therein; an upper, inner cam follower slidably mounted in said bore of said outer cam follower; an upper locking means on the outer and upper, inner cam followers and engageable for selectively locking the outer and upper, inner cam followers together for coincident reciprocal motion; a lower, inner cam follower slidably mounted in said bore of said inner cam follower, below said upper, inner cam follower; a lower locking means on the outer and lower inner cam followers and engageable for selectively locking the outer and lower cam followers together for coincidental reciprocal motion; a lost motion spring positioned in said bore of said outer cam follower between said upper and lower, inner cam followers; a hydraulic fluid delivery means for separately delivering hydraulic fluid to both said upper and lower locking means so as to activate a low lift mode, a high lift mode and a deactivated mode.

2. A valve lifter of Claim 1 further comprising a hydraulic lash adjuster mounted in the upper, inner cam follower.

3. The valve lifter of Claim 2 wherein one end of a push rod is in contact with said hydraulic lash adjuster and the other end of said push rod is in contact with a rocker arm.

4. The valve lifter of Claim 1 wherein one end of a push rod is in contact with an upper surface of said upper, inner cam follower and the other end of the push rod is in contact with a hydraulic lash adjuster.

5. The valve lifter of Claim 1 wherein the upper, inner cam follower has a radial bore, the upper locking means is mounted in said radial bore, and the outer cam follower has an upper port which mates with a locking pin of said upper locking means to couple the upper, inner cam follower with the outer cam follower.

6. The valve lifter of Claim 1 wherein the lower, inner cam follower has a radial bore therein, the lower locking means is mounted in said bore; and said outer cam follower has a lower port which mates with a locking pin of said lower locking means to couple the lower, inner cam follower to the outer cam follower.

7. The valve lifter of Claim 4 wherein the upper locking means comprises the locking pin radially mounted in said bore and a spring which biases said pin outward into said upper port .

8. The valve lifter of Claim 6 wherein the lower locking means comprises the locking pin radially mounted in said bore of said lower inner cam follower, a spring biasing said pin into said lower, inner cam follower and an oil reservoir positioned behind said pin and in fluid communication with said hydraulic fluid delivery means.

9. The valve lifter of Claim 1 wherein said hydraulic fluid delivery means comprises an oil gallery for delivering hydraulic fluid to said upper locking means and a oil passageway through said lower, inner cam follower to deliver hydraulic fluid to said a reservoir in said lower locking means.