U.S. patent number 3,742,921 [Application Number 05/165,642] was granted by the patent office on 1973-07-03 for variable lift hydraulic valve lifter.
Invention is credited to Michael J. Rendine.
United States Patent |
3,742,921 |
Rendine |
July 3, 1973 |
VARIABLE LIFT HYDRAULIC VALVE LIFTER
Abstract
A hydraulic valve lifter which has its effective length varied
by application of the varying hydraulic pressures of the engine
lubricating oil so that the effective length of the lifter is the
least at low speed and the greatest at high speeds. The effective
length of the hydraulic lifter varies the lift and consequently the
duration of lift of the valves so that at high speeds the valves
open wider and stay open for a greater percentage of each cycle of
the engine. The hydraulic lifter has a cylindrical central bore in
which are positioned free pistons arranged to receive lubricating
oil under pressure therebetween. The higher the pressure the
greater the distance the pistons will be separated until a maximum
separation is attained. One of the pistons engages the bottom of
the bore in the lifter while the other engages the lower end of the
push rod. The two pistons are freely movable in the bore and also
provide a cushioning connection between the lifter and push rod. In
a modified form of the invention, the upper piston is ported to
provide lubricating oil to the push rod and the valve stem.
Inventors: |
Rendine; Michael J. (Dayton,
OH) |
Family
ID: |
22599809 |
Appl.
No.: |
05/165,642 |
Filed: |
July 23, 1971 |
Current U.S.
Class: |
123/90.16;
123/90.55 |
Current CPC
Class: |
F01L
13/0031 (20130101); F01L 1/245 (20130101) |
Current International
Class: |
F01L
1/20 (20060101); F01L 13/00 (20060101); F01L
1/245 (20060101); F01l 001/24 () |
Field of
Search: |
;123/90.55,90.57,90.16 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Koczo, Jr.; Michael
Claims
What is claimed is:
1. In an engine of the type including exhaust and intake valves
operated by a push rod, and a cam shaft having cam lobes, a
variable lift hydraulic lifter in combination therewith comprising
a cylindrical lifter body mounted for reciprocation in said engine
having its lower end in engagement with said cam lobe of said cam
shaft, a port in said engine communicating engine oil under engine
induced pressure to said body, an annular groove in the outer
cylindrical surface of said body intermediate the opposite ends
thereof adapted to communicate with said port when said body is in
its lowermost position only, an axial bore in said body opening
through the upper end thereof, a bore communicating said axial bore
with said annular groove, first and second spaced apart pistons
mounted for sliding movement in said axial bore in said body
respectively above and below said port, the first of said pistons
positioned adjacent the open end of said axial bore and adapted to
engage said push rod and a stop mounted in said axial bore adjacent
the open end thereof, the second of said pistons positioned
adjacent the closed inner end of said axial bore and normally
spring biased toward said first piston, whereby on operation of
said engine on slow speeds oil is pumped between the pistons at a
low pressure insufficient to overcome the spring bias of said
second piston and rotation of said cam lobe moves said body to move
said annular groove out of registry with said port to lock the oil
in the axial bore in said body between said pistons to fix the
effective length of said lifter, on operation of said engine at a
medium speed the oil pressure is higher and a portion of the spring
bias is overcome to lengthen the effective length of said lifter
and on operation of said engine at a high speed the oil pressure is
higher and all of the spring bias is overcome to further lengthen
the effective length of said lifter.
2. A device as claimed in claim 1, wherein means are provided for
normally maintaining said pistons in spaced apart relation.
3. A device as claimed in claim 2, wherein said means for
maintaining said pistons in spaced apart relation comprises a coil
spring positioned between said pistons in engagement at each end
with said pistons.
4. A device as claimed in claim 2, wherein a shoulder is formed in
said bore to limit the inward movement of one of said pistons to
provide the means for maintaining said pistons in spaced apart
relation.
5. A device as claimed in claim 8 , wherein said spring biasing of
said second piston includes a coil spring seated in a bore formed
in said body at the base of said first-named bore to normally urge
the second of said pistons toward the first of said pistons.
6. A device as claimed in claim 1, wherein means are provided in
one of said pistons for supplying lubricating oil under pressure to
the push rod of an engine used therewith.
Description
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a variable lift hydraulic valve
lifter for internal combustion engines.
SUMMARY OF THE INVENTION
A hydraulic valve lifter includes a generally cylindrical body
having a cylindrical axial bore extending therein. A pair of
pistons are slidably mounted in the bore and are secured therein by
a removable retaining ring. A spring is positioned between the
pistons to normally urge them apart. The cylindrical lifter is
mounted in a bore in the engine and has a port aligned with a port
in the engine to receive lubricating oil therefrom under pressure.
The lubricating oil flows to the bore in the lifter between the two
pistons so as to separate the pistons by hydraulic pressure. The
greater the hydraulic pressure the greater the separation of the
pistons until the limit of separation is reached. Reciprocation of
the lifter due to the action of the cam shaft causes a similar
reciprocation of the pistons therein, with the upper piston
engaging the push rod to transmit the motion thereto. Under low
speed pressure conditions, the pistons are substantially less than
their maximum spaced apart condition and lift the push rod a
relatively short amount. With the engine moving at medium speeds,
the pistons are further apart and the lift of the push rod is
greater. With the engine operating at maximum speeds with maximum
pressure on the lubricating oil, the pistons are further apart and
provide the greatest lift for the push rod.
In a modified form of the invention, the upper piston is ported to
feed lubricating oil to the push rod and thence to the valve
stem.
The primary object of the invention is to provide a hydraulic valve
lifter with a variable lift controlled by the pressure on the
lubricating oil of the engine so that the lift of the valve and the
duration thereof is increased as the pressure on the lubricating
oil increases at higher speeds.
Other objects and advantages will become apparent from the
following specification when considered in the light of the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view taken through invention
illustrating the starting position of the hydraulic lifter when
operating at low engine speeds;
FIG. 2 is a view similar to FIG. 1 of the hydraulic lifter in
lifted position when operating at medium engine speeds;
FIG. 3 is a view similar to FIG. 1 of the lifter in beginning
position at high speed engine operation;
FIG. 4 is a fragmentary sectional view of a modified form of the
invention;
FIG. 5 is a sectional view of another modified form of the
invention;
FIGS. 6, 7 and 8 are sectional views illustrating the position of
the lifter and its associated pistons at three cam positions during
low speed operation of the engine;
FIGS. 9, 10 and 11 and similar to FIGS. 6, 7 and 8 at medium speed
operation of the engine; and
FIGS. 12, 13 and 14 are similar to FIGS. 6, 7 and 8 at high speed
operations of the engine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings in detail wherein like reference
characters indicate like parts throughout the several figures, the
reference numeral 20 indicates generally a variable lift hydraulic
valve lifter constructed in accordance with the invention.
The lifter 20 is adapated for use with an internal combustion
engine fragmentarily shown at 21. The engine 21 is conventional and
has a bore 22 extending therein in aligned relation with a cam lobe
23 on a cam shaft 24. A lubricating oil port 25 opens into the bore
22 intermediate its upper and lower ends.
A generally cylindrical hydraulic lifter 26 is mounted for
reciprocation in the bore 22 with its lower end 27 in contact with
the cam lobe 23 of the cam shaft 24. The hydraulic lifter 26 has an
annular groove 28 formed therein intermediate its upper and lower
ends and communicating with a bore 29 which opens into a
cylindrical bore 30 formed axially in the lifter 26. The groove 28
is positioned so as to communicate with the port 25 when the lifter
26 is in its lowermost position.
A bore 31 extends axially from the inner end of the bore 30 and
terminates at a point spaced well above the lower end 27 of the
lifter 26. A port 32 opens from the bore 31 through the lower end
27 of the lifter 26 for reasons to be assigned.
A piston 33 is slidably mounted in the bore 30 and has a
cylindrical extension 34 on its lower end slidably mounted in the
bore 31. A relatively short spring retainer extension 35 is
integrally formed on the lower end of the extension 34 to engage in
the upper end of a compression coil spring 36 seated in the bore
31. The coil spring 36 normally urges the piston 33 upwardly in the
bore 30. A second piston 37 is mounted for sliding movement in the
bore 30 above the piston 33. A lock ring 38 engages in an annular
groove 39 in the upper end of the bore 30 to secure the pistons 37,
33 therein.
A compression coil spring 40 is positioned in the bore 30 between
the pistons 33 and 37 to normally urge them apart. A conventional
push rod 41 forming part of the engine 21 extends into the bore 30
and contacts the upper face of the piston 37.
While I have described the port 25 as communicating with the
lubricating oil under normal engine pressure, it should be
understood that an oil pressure control device may be installed in
the engine to control the pressure of the lubricating oil reaching
the valve lifter 26 so as to more closely control the operation of
the valve lifter 26.
In the use and operation of the invention with the engine 21
operating at low speed, oil pressure flows through the port 25 into
the groove 28 and through the port 29 into the bore 30 between the
piston 33 and the piston 37. The piston 37, under these conditions,
will normally be engaged against the stop ring 38 and the piston 33
will be spaced well above the lower end 27 of the lifter 26. The
spring 36 will maintain the piston 33 in its raised position, as
illustrated in FIG. 1, and the spring 40, engaging between the
pistons 33, 37, will maintain the piston 37 in engagement with the
lock ring 38. The pressure of the oil in the bore 30 at low speed
operation of the engine is not sufficient to overcome the pressure
of the spring 36 and hence the piston 33 and the piston 37 remain
in their raised positions, as illustrated in FIG. 1. As the cam
shaft 24 rotates the cam lobe 23 raises the valve lifter 26 in the
bore 22 and the groove 28 moves upwardly out of communication with
the bore 25, sealing the oil under pressure in the bore 30 between
the pistons 33 - 37. As the lifter 26 is raised further by the cam
lobe 23, the pressure of the push rod 41 against the piston 37
exceeds the pressure of the spring 36 so that the valve lifter 26
moves upwardly in the bore 22 with the pistons 37, 33 remaining for
a time at the same height. As the valve lifter 26 continues to move
upwardly, the shoulder 42 formed at the juncture of the bores 30,
31 engages the lower face of the piston 33 and raises the piston 33
therewith. The oil, being locked in the bore 30, then exerts a
pressure on the piston 37 sufficient to overcome the resistance of
the push rod 41 and thus moves the push rod 41 upwardly.
The bore 32 through the bottom of the valve lifter 26 vents the
bore 31 and permits the escape of any oil which might seep by the
piston 33.
In FIGS. 6, 7 and 8 a low position, medium position and high
position of the valve lifter 26 is illustrated with the engine
operating at low speeds. It should be noted that the distance
between the piston 34 and the piston 37 remains constant during the
rotation of the cam lobe 23 with the valve lifter 26 moving to
follow the cam lobe 23. To the left of FIG. 8, a pair of lines
between opposed arrows indicate the total lift given to the push
rod 41 at the highest point of the lobe 23.
In FIGS. 9, 10 and 11 a medium speed operation of the engine is
illustrated with three positions of lift of the cam lobe 23. The
pressure through the port 25 into the bore 30 during medium speed
operation of the engine is sufficient to partially overcome the
compression of the spring 36 to thus move the piston 37 and the
piston 34 apart a distance slightly greater than the distance
illustrated in FIGS. 6 through 8 for low speed operation. With the
piston 37 and the piston 34 locked slightly further apart, the
piston 37 remains higher with respect to the valve lifter 26 and
hence the total lift is greater, as indicated to the left of FIG.
11 by the lines between opposed arrows.
In FIGS. 12 through 14, the highest speed is illustrated with the
highest oil pressure. The oil pressure through the port 25 at high
engine speeds is sufficient to completely overcome the compression
of the spring 36, thus forcing the piston 34 down against the
shoulder 42 while the piston 37 is engaged with the lock ring 38.
Now, as the cam lobe 23 starts lifting the lifter 26, the piston 37
remains against the lock ring 38 and the total lift to the push rod
41 is greater due to the higher position of the piston 37 in the
lifter 26. The total lift of the lifter 26 at high speed engine
operation is illustrated to the left of FIG. 14 by the pair of
lines between the opposed arrows.
It should be noted that if separate controls are provided for the
oil pressure reaching the bore 30, it would be possible to reduce
the oil pressure on deceleration of the engine so as to limit the
intake valves to a minimum lift to thus enhance fuel economy and
reduce blow by exhaust emission, normally encountered.
In FIG. 4 the engine 121 has a port 143 communicating with the
lubricating oil under pressure of the engine. The hydraulic valve
lifter 126 has a port 144 communicating with the port 143 when the
lifter 126 is in its lowermost position. The upper piston 137 has
an annular groove 145 communicating with one end of a radial bore
146 extending into the piston 137. An axial bore 147 communicates
with the upper end of the piston 137 and with the inner end of the
bore 146. A valve lifter 141 has an axial bore 148 extending
therethrough and communicating with the bore 147.
The function of the modification illustrated in FIG. 4 is to
lubricate the push rod, valve stem and other valve elements
requiring lubrication.
In FIG. 5, another modified form of the invention is illustrated
generally at 220 and includes a valve lifter 226 having a bore 230
extending axially therein. A piston 233 is mounted for
reciprocation in the bore 230 and has an extension 234 on its lower
end. The extension 234 engages in a bore 231 which extends axially
of the bore 230 and supports a compression spring 236. A bore 230A,
slightly larger than the bore 230, extends inwardly from the upper
end of a lifter 226 and has a piston 237 mounted for reciprocation
therein. A shoulder 249 between the bore 230 and the bore 230A
limits the inward movement of the piston 237 and a lock ring 238
engaged in a groove 239 in the bore 230A limits the outward
movement of the piston 237. The annular groove 228 in the valve
lifter 226 communicates with a port 229 extending into the bore 230
between the pistons 237 and 233. The limit of the inward movement
of the piston 237 by the shoulder 249 eliminates the need for a
spring 40 such as is disclosed in the preferred form of the
invention. The use and operation of the valve lifter 220 is
identical in every respect to the valve lifter 20 with the
exception that the spring 40 and its function have been
eliminated.
Having thus described the preferred embodiments of the invention,
it should be understood that numerous structural modifications and
adaptations may be resorted to without departing from the spirit of
the invention.
* * * * *