U.S. patent application number 16/291938 was filed with the patent office on 2019-07-11 for a cylinder head with valve deactivators.
This patent application is currently assigned to Ford Global Technologies, LLC. The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Theodore Beyer, Jeff D. Fluharty, John Christopher Riegger.
Application Number | 20190211716 16/291938 |
Document ID | / |
Family ID | 61564032 |
Filed Date | 2019-07-11 |
United States Patent
Application |
20190211716 |
Kind Code |
A1 |
Riegger; John Christopher ;
et al. |
July 11, 2019 |
A Cylinder Head With Valve Deactivators
Abstract
To improve fuel efficiency, some gasoline engines are equipped
with valve deactivators in some of the cylinders so that at low
torque conditions only a subset of the total number of cylinders
are active. In prior art engines, particularly when they have four
valves per cylinder, space is tight. It is known to provide a cam
carrier in the head between the cylinder head and the camshaft. The
cylinder head bolts pass through the head under the cam carrier.
According to the present disclosure, the cam carrier, and its
associated disadvantages, is obviated by widening the bearings for
the camshafts, using smaller diameter head bolts, and putting the
orifices tor the head bolts directly through the bearings.
Inventors: |
Riegger; John Christopher;
(Ann Arbor, MI) ; Beyer; Theodore; (Canton,
MI) ; Fluharty; Jeff D.; (Woodhaven, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies,
LLC
Dearborn
MI
|
Family ID: |
61564032 |
Appl. No.: |
16/291938 |
Filed: |
March 4, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15278258 |
Sep 28, 2016 |
10267259 |
|
|
16291938 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 2250/04 20130101;
F02D 13/06 20130101; F02B 75/22 20130101; F01L 2810/02 20130101;
Y02T 10/18 20130101; F01L 2810/04 20130101; F02B 2275/02 20130101;
Y02T 10/12 20130101; F02F 1/4214 20130101; F01L 2303/00 20200501;
F01L 1/185 20130101; F01L 2001/186 20130101; F01L 2305/00 20200501;
F01L 2001/0537 20130101; F02B 1/04 20130101; F01L 2001/0476
20130101; F01L 2800/08 20130101; F01L 1/26 20130101; F02D 17/02
20130101; F01L 1/053 20130101; F01L 2013/001 20130101; F01L 1/047
20130101; F02B 2075/1832 20130101 |
International
Class: |
F01L 1/047 20060101
F01L001/047; F01L 1/26 20060101 F01L001/26; F02F 1/42 20060101
F02F001/42 |
Claims
1-12. (canceled)
13. A method to assemble an engine, comprising: casting a cylinder
head that comprises combustion chamber tops and a plurality of cam
towers, the cam towers having bearing surfaces each having an
orifice defined in the bearing surfaces; bolting the cylinder head
to an engine block with bolts passing through the orifices in the
bearing surfaces of the cam towers; and installing followers in the
cylinder head, at least one-quarter of the followers being
deactivatable followers.
14. The method of claim 13, further comprising: installing two
intake poppet valves and two exhaust poppet valves into ports
formed in each of the combustion chamber tops in the cylinder
head.
15. The method of claim 13, further comprising: installing a
plurality of non-deactivatable followers in the cylinder head.
16. The method of claim 13 wherein: the cylinder head has four
combustion chamber tops; each combustion chamber top has two intake
valves and two exhaust valves disposed therein; half of the intake
valves and half of the exhaust valves are provided with the
deactivatable followers.
17. The method of claim 13, further comprising: placing camshafts
in the cam towers; and installing cam caps onto cam towers of the
cylinder head to thereby capture the camshafts.
18. The method of claim 13 wherein the cam towers are unitary with
the cylinder head.
19. The method of claim 13 wherein the bearing surfaces have a
first land on a first side of the orifice and a second land on a
second side of the orifice.
20. The method of claim 13 wherein: the cylinder head has two
deactivatable cylinders and two non-deactivatable cylinders, the
method further comprising: installing deactivatable followers in
valves associated with the two deactivatable cylinders; and
installing non-deactivatable followers in valves associated with
the two non-deactivatable cylinders.
21. The method of claim 13 wherein: the cylinder head has four
combustion chamber tops; each combustion chamber top has two intake
valves and two exhaust valves disposed therein; half of the intake
valves are provided with the deactivatable followers.
22. A method to assemble an engine, comprising: casting a cylinder
head that comprises combustion chamber tops and a plurality of cam
towers integrally cast, the cam towers having bearing surfaces each
having an orifice defined in the bearing surfaces; bolting the
cylinder head to an engine block with bolts passing through the
orifices in the bearing surfaces of the cam towers; and installing
a plurality of deactivatable intake followers in the cylinder
head.
23. The method of claim 22, further comprising: installing a
plurality of non-deactivatable exhaust followers in the cylinder
head.
24. The method of claim 22, further comprising: installing two
intake poppet valves and two exhaust poppet valves into ports
formed in each of the combustion chamber tops in the cylinder
head.
25. The method of claim 22 wherein: the cylinder head has four
combustion chamber tops; and half of the intake valves are provided
with the deactivatable followers.
26. The method of claim 25 wherein: half of the exhaust valves are
provided with the deactivatable followers.
27. The method of claim 22 wherein the bearing surfaces in the cam
towers have a first land on a first side of the orifice and a
second land on a second side of the orifice.
28. The method of claim 22, further comprising: placing camshafts
in the cam towers; and installing cam caps onto cam towers of the
cylinder head to thereby capture the camshafts.
29. The method of claim 22 wherein the bolts used to bolt the
cylinder head to the engine block are internal drive bolts.
Description
FIELD
[0001] The present disclosure relates to cylinder heads for
internal combustion engines, in particular those with valve
deactivators.
BACKGROUND
[0002] It is well-known that efficiency of a spark-ignition engine
suffers when torque demand is low. In engines provided with
cylinder deactivation, efficiency at such low-torque operation
conditions can be improved by deactivating some cylinders, which
causes activated cylinders to operate at a higher torque operating
condition than they would be otherwise if all the cylinders were
activated. When cylinder deactivation mode is scheduled, the
exhaust and intake valves are decoupled from the cam lobe motion by
means of a switchable or deactivatable roller finger follower. The
cam motion is absorbed as lost motion within the follower. Thus,
the valves remain closed and their respective cylinders are
inactive. Typically, a portion of the cylinders, often half, are
equipped with deactivators, the packaging of which complicates the
cylinder head layout because the deactivatable finger follower is
bulkier. Such an engine is referred to as Variable Displacement
Engine (VDE), Displacement on Demand, Cylinder Deactivation, Active
Fuel Management, etc.
[0003] An illustration of a front end of an internal combustion
engine 10 is shown in FIG. 1. Engine 10 has a block 12 to which an
oil pan 14 is coupled. Engine 10 is a vee engine having two
cylinder heads 16. A crankshaft (not shown) is coupled to a pulley
20. Camshafts (not shown) are coupled to pulleys 22. A belt 24 is
driven by crankshaft pulley 20 to drive camshaft pulleys 22.
[0004] An underside of a cylinder head 30 is show in FIG. 2. The
heads of two intake poppet valves 34 and the heads of two exhaust
poppet valves 36 are contained within the upper portion of the
combustion chamber 32. The combustion chamber is defined by the
piston top (not shown), the cylinder wall (not shown), and the
upper portion of the combustion chamber 32, called combustion
chamber top herein. Orifice 38 is provided for a spark plug. A
combustion chamber in a typical, internal-combustion engine is
defined by a cylinder wall, a top of a piston that reciprocates
within the cylinder wall, and a portion of a cylinder head that
includes the intake and exhaust valves. Herein, the portion of the
combustion chamber in the cylinder head is called a combustion
chamber top.
[0005] A prior art cylinder head 50 having cylinder deactivation is
shown in FIG. 3. Cylinder head 50 covers four cylinders with two
intakes and two exhaust valves per cylinder, thus, 16 valves (not
shown). A flange 52 is provided for a valve cover (not shown) to be
affixed to the valve train side of cylinder head 50. In the
embodiment shown in FIG. 3, valves associated with the outer
cylinders are deactivatable and valves associated with the inner
cylinders are fixed. Eight deactivatable roller finger followers
54, four exhausts on the left side of FIG. 3 and four intakes on
the right side, have the ability to become lost motion devices
based on hydraulic pressure provided to followers 54. Any other
suitable mechanism or system to actuate may be substituted.
Deactivatable followers 54 are wider than fixed roller finger
follower 56 provided for the inside cylinders. Inner cylinders are
provided with fixed roller finger followers 56: four for exhaust
valves on the left hand side and four for intake valves on the
right hand side. The deactivatable followers 54 complicate an
already crowded cylinder head because they are wider than fixed
followers 56. In addition to having four valves and the associated
valvetrain hardware to actuate the valves, a spark plug and a
direct injector, in some cases, must access the inside of the
cylinder head.
[0006] The poppet valves are not visible in FIG. 3 due to the
followers occluding the valve tip and valve springs occluding the
valve stems. Numerals for only one each of sixteen valve springs 60
and sixteen retainers 62 are provided in FIG. 3 in the interest of
clarity for other elements that will be discussed in more detail.
FIG. 3 is a view of the valvetrain without at least the cam
carrier, the camshafts, the cam towers, the cam caps, and the cam
cover affixed. Head bolts 58 affix cylinder head 50 to the engine
block (not shown in FIG. 3). Orifices 64 are provided for affixing
the cam carrier (not shown in this view).
[0007] At the front of cylinder head 50 (bottom edge of FIG. 3) an
exhaust camshaft pulley 42 and an intake camshaft pulley 44 are
visible.
[0008] A cam carrier 180 is shown in FIG. 4. Cam carrier 180 has
semicircular bearings 186 and 188. The left hand bearings support
journals of an exhaust camshaft (not shown); the right hand
bearings support journals of an intake camshaft (not shown).
Orifices 164 and 165 provided through cam carrier 180 are used to
secure cam caps (not shown) to secure the camshafts within bearings
186 and 188. Other orifices 167 are provided as bolt through holes
to secure cam carrier 180 to the cylinder head.
[0009] In FIG. 5, cylinder head 50 is shown with cam carrier 80
installed via bolts 67. Cam carrier 80 has an outer wall 84 to
provide structure for cam carrier 80. Bearings 88, that are
essentially hemispherical, are provided to cradle camshafts (not
shown). During operation, pressurized oil is provided to bearings
88 to lubricate the rotating camshaft (not shown) moving with
respect to bearings 88. Bearings 88 of cam carrier 80 are mounted
over head bolts 58 (shown in FIG. 3) with only a small portion of
some of the head bolts visible beyond bearings 88. The width of
bearings 88 are shown by dimension 90.
[0010] In FIG. 6, an exhaust camshaft 100 and an intake camshaft
102 are shown installed in cylinder head 50 with cam caps 104 and
108 capturing exhaust camshaft 100 and cam caps 106 and 109
capturing intake camshaft 102. Cam caps 104, 106, 108, and 109 are
secured to the cylinder head via bolts 120 that extend through cam
carrier 80 and into cylinder head 50. Bolts 120 assist in affixing
cam carrier 80 to cylinder had 50. Cam caps 104, 106, 108, and 109
are secured on the inner side by bolts 122 that affix to cam
carrier 80. Cam carrier is secured to cylinder head 50 via bolts
67. Intake and exhaust camshafts 102 and 100 are provided with
lobes 112 and 110, respectively, that press on followers (not
visible) to actuate intake and exhaust valves, respectively.
[0011] It would be desirable to obviate the cam carrier in such a
cylinder head to simplify assembly, reduce weight, reduce cost, and
reduce part count.
SUMMARY
[0012] A cylinder head assembly for an internal combustion engine
that overcomes problems in the prior art includes: a cylinder head
that has a plurality of combustion chambers tops each having two
intake and two exhaust valves, cam towers unitarily formed with the
cylinder head, and an intake camshaft having multiple cam lobes
that act upon the intake valves via intake followers disposed in
the cylinder head wherein at least a portion of the followers are
deactivatable.
[0013] The cylinder head assembly also includes: an exhaust
camshaft having multiple cam lobes that act upon the exhaust valves
via exhaust followers disposed in the cylinder head and a bearing
surface disposed between each pair of cam towers. The intake
camshaft is cradled in a first plurality of the bearing surfaces.
The exhaust camshaft is cradled in a second plurality of the
bearing surfaces.
[0014] The bearing surfaces have orifices defined therein to
accommodate head bolts.
[0015] The bearing surfaces have first lands on a first side of the
orifice associated with the bearing surface and second lands on a
second side of the orifice.
[0016] The cylinder head has four cylinders, all of the valves
associated with the inner cylinders having deactivatable followers
and all of the valves associated with the outer cylinders having
fixed followers. In other embodiments, the cylinder has more or
fewer cylinders.
[0017] The bearing surfaces are unitary with the cylinder head.
[0018] Also disclosed is an engine having: a cylinder block and a
cylinder head. The cylinder head has: cam towers unitarily formed
with the cylinder head, semicircular bearings located between pairs
of cam towers with orifices defined within the bearings, cylinder
head bolts inserted in the orifices that engage with the cylinder
block, a camshaft cradled in a plurality of the bearings and having
a plurality of cam lobes that act upon valves, and an intake
camshaft having multiple cam lobes that act valves disposed in the
cylinder head via intake followers wherein at least a portion of
the followers are deactivatable.
[0019] The engine further includes cam caps placed over the
camshaft and bolts installed into orifices in the cam caps engaging
with threads in the cam towers.
[0020] The engine has an intake camshaft that actuates intake
valves and an exhaust camshaft that actuates exhaust valves. The
intake camshaft is cradled in a first plurality of the bearings and
the exhaust camshaft is cradled in a second plurality of the
bearings.
[0021] In some embodiments, the engine has an engine bank having
four cylinders. Valves in a first and a second of the four
cylinders are provided with deactivatable followers. Valves in a
third and a fourth of the four cylinders are provided with fixed
followers.
[0022] The bearings are unitary with the cylinder head.
[0023] The bearing surface has first and second lands on first and
second sides of the orifice.
[0024] Also disclosed is a method to assemble an engine that
includes: casting a cylinder head that comprises combustion tops
and a plurality of cam towers, the cam towers having bearing
surfaces each having an orifice defined in the bearing surfaces,
bolting the cylinder head to an engine block with bolts passing
through the orifices in the bearing surfaces of the cam towers; and
installing followers in the cylinder head, at least half of the
followers being deactivatable followers.
[0025] The method includes: installing two intake poppet valves and
two exhaust poppet valves into ports formed in each of the
combustion tops in the cylinder head.
[0026] The method includes: installing a plurality of
non-deactivatable followers in the cylinder head.
[0027] The cylinder head has four combustion chamber tops. Each
combustion chamber top has two intake valves and two exhaust valves
disposed in each combustion chamber top. Half of the intake valves
and half of the exhaust valves are provided with the deactivatable
followers.
[0028] The method also includes: placing camshafts in the cam
towers and
[0029] installing cam caps onto cam towers of the cylinder head to
thereby capture the camshafts.
[0030] The cam towers are unitary with the cylinder head.
[0031] The bearing surfaces have a first land on a first side of
the orifice and a second land on a second side of the orifice.
[0032] The cylinder head has two deactivatable cylinders and two
non-deactivatable cylinders. The method includes installing
deactivatable followers in valves associated with the two
deactivatable cylinders and installing non-deactivatable followers
in valves associated with the two non-deactivatable cylinders.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is an illustration of an internal-combustion
engine;
[0034] FIG. 2 is an illustration of an underside of a cylinder
head;
[0035] FIGS. 3, 5, and 6 are illustrations of a prior art cylinder
head in several stages of assembly;
[0036] FIG. 4 is an illustration of a prior art cam carrier;
[0037] FIG. 7 is a graph of forces exerted by a camshaft on bearing
surfaces associated with a bearing and cam cap;
[0038] FIG. 8 shows a head bolt with a small overall diameter;
[0039] FIGS. 9 and 10 show a cylinder head according to embodiments
of the present disclosure;
[0040] FIG. 11 is a cylinder head according to an embodiment of the
present disclosure;
[0041] FIG. 12 shows processes by which a prior-art engine is
assembled; and
[0042] FIG. 13 shows processes by which an engine is assembled
according to embodiments of the present disclosure.
DETAILED DESCRIPTION
[0043] As those of ordinary skill in the art will understand,
various features of the embodiments illustrated and described with
reference to any one of the Figures may be combined with features
illustrated in one or more other Figures to produce alternative
embodiments that are not explicitly illustrated or described. The
combinations of features illustrated provide representative
embodiments for typical applications. However, various combinations
and modifications of the features consistent with the teachings of
the present disclosure may be desired for particular applications
or implementations. Those of ordinary skill in the art may
recognize similar applications or implementations whether or not
explicitly described or illustrated.
[0044] Many advantages accrue to the engine manufacturer if the cam
carrier is integrated into the cylinder head, i.e., the separate
part obviated. Bolts that are used to couple the cam carrier to the
cylinder head and the concomitant thicker part of the cam carrier
to provide threads and sufficient stiffening can be eliminated. The
advantages include at least: cost savings, reduced part count,
weight savings, and simplified assembly.
[0045] Inaccuracy in the tolerances lead to valvetrain noise and
durability concerns. By obviating the cam carrier, i.e., fewer
parts, there is less variation due to stackup, i.e., improved
dimensional accuracy. According to embodiments in the disclosure,
accuracy is improved to avoid valvetrain noise and reduced
durability.
[0046] In FIG. 7, a graph of the forces on the bearing is shown
over the course of two revolutions. Because there is a valve spring
associated with each of the valves that pushes upward, the forces
are overwhelmingly in the positive y direction. There is rarely
downward force on bearing 88 of FIG. 5, and even when downward, the
force is of a trivial magnitude. Thus, the surface area on bearing
88, i.e., the width, is greater than needed in the part of the
bearing 88 shown in FIG. 5. Cam caps 104 and 106 (FIG. 6) are
affixed to the cam towers on either side of bearing 88. The
positive y force shown in FIG. 7 is against the bearing caps. This
bearing surface area in cam caps cannot be reduced. In some prior
art cylinder heads, the width of the cam cap is wider in
recognition that the forces against the cam cap are greater than
against the bearing opposite the cam cap.
[0047] According to embodiments of the disclosure, the width of the
bearing is increased and the orifices for the head bolts are
machined directly through the bearing, i.e. the part of the bearing
surface that has low forces. The hole for the head bolt is centered
on the bearing so that there is a land on either side of the bolt
hole to maintain an oil film.
[0048] Another feature that facilitates putting the head bolt
through the bearing is a smaller-outer diameter head bolt. A head
bolt 58 that has an internal drive 59 is shown in FIG. 8. Internal
drive 59 facilitates the smaller overall diameter.
[0049] A cylinder head 200 in which head bolts are inserted through
bearings is shown in FIG. 9. Head bolts 202 are internal drive
bolts that are smaller in diameter than bolts 58 in FIG. 3. Head
bolts 202 are centered on bearing 224. On either side of bearing
224 are cam towers 220 and 222 that have orifices 204 into which
bolts are inserted to attach a cam cap. Bearings 224 and cam towers
220 and 224 are formed out of the parent material of cylinder head
200. This is in contrast to the cylinder head in FIGS. 5 and 6 in
which bearings 88 and the cam towers on either side of 88, which
are not separately called out, are formed in a separate component,
i.e., cam carrier 80. Referring again to FIG. 9, at the front of
the engine proximate pulleys 42 and 44, bearings 234 have a groove
190. A thrust bearing (not shown) engages with groove 190. The
graph in FIG. 7 generally applies to bearings 220. However,
bearings 234 proximate pulleys 42 and 44 have mostly upward forces.
To allow head bolts to traverse through bearings 234 while
continuing to provide sufficient bearing surface, the width is
markedly wider than the other bearings. Furthermore, only one
groove 190 is provided. Grooves 92 that are shown in prior art cam
carrier of FIG. 4 are provided in the bearing cap of the disclosed
cylinder head (not shown in FIG. 9).
[0050] In FIG. 10, cylinder had 200 is shown with cam caps 240 and
242 installed to secure exhaust camshaft 103 and intake camshaft
104. Cam caps 240 are secured via bolts 240 that engage with the
cam towers that are integral with cylinder head 200. Cam caps 242
are secured via bolt 244 that engage with cam towers integral with
cylinder head 200.
[0051] The cam towers are cast with cylinder head 200. Casting
processes do not provide the dimensional accuracy for many
purposes. The cam towers are machined to provide bearing surfaces
for the camshaft, as an example. In that situation, both the
dimensional accuracy and surface finish are provided via the
machining. The outside surfaces of the cam towers can encroach upon
the space needed for the deactivatable followers, which are wider
than the standard followers that do not allow deactivation. The
cylinder head is machined to ensure that there is sufficient space
for the deactivatable followers. Some of the material of the cam
towers proximate the deactivatable followers or the valve springs
may be removed to accommodate the deactivatable followers or other
elements in the cylinder head. An example of material from cam
towers is shown as 238 in FIG. 10. According to an embodiment of
the disclosure, the normal wider tolerances between the cam towers
and the components proximate the cam towers, e.g., valve springs or
roller finger followers, is made narrower so that the components
can be packaged. Where there are inaccuracies in the casting that
yields overlap of the cam tower with one of these components, the
cam tower is separately machined to provide the desired clearance
between components.
[0052] Another view of a portion of a cylinder head 250 in FIG. 11
shows cam towers 252 that are integrally formed with cylinder head
250. A bearing 254 is provided between cam towers 252 and supports
a journal of a camshaft (not shown). Bearing 254 has an orifice 256
into which a cylinder head bolt (not visible) is inserted to couple
cylinder head 250 with a block (not shown). Bearing 254 has lands
258 on either side of orifice 256 that are sufficient to limit oil
leakage to provide a proper oil film thickness so that the journal
of the camshaft is properly lubricated. After head bolts secure
cylinder head 250 to the block, cam caps 260 are secured to cam
towers 252 via bolts 262. In practice, the camshaft is placed onto
bearing 254 prior to installing cam caps 260. However, orifice 256
would be occluded by the camshaft. Thus, the camshaft is not
included in FIG. 11 for illustrative purposes.
[0053] Referring to FIG. 12, processes by which a cylinder head
with valve deactivators and a cam carrier is shown in brief. A
cylinder head is cast and machined in block 750. A cam carrier is
cast and machined in block 752. There are many machining processes
for preparing the cylinder head and the cam carrier for assembly.
However,
[0054] The poppet valves and their associated springs and other
hardware are installed in ports of the cylinder head in block 756.
In block 758, the cylinder head is bolted to the engine block. The
followers are installed and the camshafts are placed in the bearing
surfaces of the cam carrier, in block 760. At least some of the
followers are deactivatable to thereby deactivate the valves with
which they are associated upon a command from an engine control
unit. In block 762, the cam carrier is bolted to the cylinder head.
At least some of the followers are deactivatable to thereby
deactivate the valves with which they are associated upon a command
from the engine control unit. In block 764, camshafts are placed
into the bearings formed in the cam carrier. In block 766, cam caps
are installed onto the cam towers of the cam carrier. The cam caps
retain the camshafts in the bearing surfaces of the cam carrier.
The process in FIG. 12 is for the prior-art configuration that
employs a cam carrier.
[0055] A process for assembling a cylinder head with deactivatable
followers is shown in FIG. 13. In block 800 a cylinder head is cast
that has integral cam towers. The cylinder head is machined to
include: orifices through which head bolts are provided (the head
bolts pass through bearing surfaces in the cam towers); the cam
towers are qualified to accommodate followers with deactivators,
and bearing surfaces for the camshaft. In block 806, the poppet
valves and associated hardware are installed into the ports in the
cylinder head. In block 808, the cylinder head is bolted to the
engine block with the head bolts passing through the bearings. In
block 810, the followers are installed, some of which are
deactivatable. In block 812, the camshafts, intake and exhaust, are
placed in the bearings between the cam towers. In block 814, the
cam caps are coupled to the cam towers of the cylinder head to
capture the camshafts.
[0056] The cam towers are cast with the cylinder head. Casting
processes do not provide the dimensional accuracy for many
purposes. The cam towers are machined to provide bearing surfaces
for the camshaft, as an example. In that situation, both the
dimensional accuracy and surface finish are provided via the
machining. The outside surfaces of the cam towers can encroach upon
the space needed for the deactivatable followers, which are wider
than the standard followers that do not allow deactivation. The
cylinder head is machined to ensure that there is sufficient space
for the deactivatable followers. Some of the material of the cam
towers proximate the deactivatable followers may be removed to
accommodate the deactivatable followers or other elements in the
cylinder head.
[0057] While the best mode has been described in detail with
respect to particular embodiments, those familiar with the art will
recognize various alternative designs and embodiments within the
scope of the following claims. While various embodiments may have
been described as providing advantages or being preferred over
other embodiments with respect to one or more desired
characteristics, as one skilled in the art is aware, one or more
characteristics may be compromised to achieve desired system
attributes, which depend on the specific application and
implementation. These attributes include, but are not limited to:
cost, strength, durability, life cycle cost, marketability,
appearance, packaging, size, serviceability, weight,
manufacturability, ease of assembly, etc. The embodiments described
herein that are characterized as less desirable than other
embodiments or prior art implementations with respect to one or
more characteristics are not outside the scope of the disclosure
and may be desirable for particular applications.
* * * * *