Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AXIAL VANE ROTARY ENGINE WITH CONTINUOUS FUEL INJECTION
BACKGROIJND OF THE INVENTION
Field of the Invention
This invention relates to rotary engines of the axial vane type, particularly the class of
devices where volume change occurs between relatively close vames and cam surfaces on
each side of the rotor and where tll~ vanes translate axially relative to the rotational axis of
10 therotor.
Description of Related Art
Many different types of rotary engines have been suggested in the past and have been
15 covered by a large number of patents. Only a relatively small number of these have been
thoroughly tested. Many rotary engines are appealing on paper, but practical difficulties
arise when prototypes are constructed.
The best known rotary engine is the Wanlcel engine which is in volume production in Mazda
20 ~ m--hilP~ Even this engine has had considerable difficulties with proper sealing of tlle
rotors, although such problems have been largely overcome. Elowever, the engine is not
I~ly efficient and high fuel consumption is a . I.,..,~ IP, ;~ of vehicles using this
technology.
25 Another type of rotary engine is referred to herein as the "axial vane type". This type of
engine has a cylindrical rotor located within a cylindrical chamber in a stator. A plurality
of blade-like vanes extend slidably through the rotor, parallel to the axis of rotation. There
are undulating cam surfaces on each side of the rotor. High portions of the cam surface on
one side align with low portions of the cam surface on the other side such that the vanes are
30 caused to reciprocate back and forth in the axial direction as the rotor rotates.
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One such engine is found, for example, in United States Patent No. 4,401,070 by James
Lawrence McCann. This type of engine compresses gases forwardly of each vane in tlle
di}ection of rotation as the rotor rotates. The compression occurs as the vane moves from
a low cam surface, relatively dist~nt from the rotor, to a hign cam surfæe relahvely close the
5 rotor. After the gases are compressed, tl1ey must be transferred to the rearward side of ~ach
vane prior to ~mh~ \n so tna~ the ignited gases will propel the rotor forwards.
The need for ~"~ rc";l,~ the l,ULUlJlCi~ ,d gases is removed in a variation of this type of
rotary engine such as found in Polish Patent No. 38112 to Czyzewslii. In this case, the gases
10 are compressed between adjæent vanes which are angularly spaced-apart much closer than
in the McCann engine. The gases are ~u~ c~i~cd as each pair of adjacent vanes moves
towards a high cam area. Expansion of the ignited gases is permitted, and the propulsion
force created, as the vanes continue to move past the high cam area to a relatively low cam
area after ignition.
This type of rotary engine offers many potential advantages including high efficiency, simple
~ulL~L ucLiull and light weight. However, while the theoretical possibility of such an engine
has been suggested in the past, many practical difficulties have inhibited Icvcluplllcllt of
such en~ines beyond the stage of a worl~ing prototype. For example, considerable time and
20 effort have been expended trying to develop practical sealing systems between the vanes, the
rotor and the stator of such an engine.
Fu, llc~ u~;; the rotational speed of such engines has been limited in some instances by fuel
injectors which can only pulse on and off at a flnite rate.
Rotary engines of the axial vane type typically operate on a four stroke cycle. However the
entire four stroke cycle is repeated by each vane upon each complete rotation of the rotor.
In other words, the engine uses only 360 of rotation to do what a ~ U~.Lil,~ engine does
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in 720. In short, each degree of rotation of such an engine is equivalent to t~vo degrees of
rotation of a ~ U-,aLill~ engine.
Applying this lûgic, a compression ignition rotary engine of the type would optimally start
S fuel irljection ât lO~BTDC with an injection duration of 15 because a typical l~ i,ulu~,aLillg
diesel engine starts injection at 20BTDC and ends fuel injection at 10ATDC for a total
injection duration of 30. The total injection duration of an equivalent rotary engine wûuld
therefore be 15.
10 Prâctical experience with rotary engines however shows that such engines optimize with
longer fuel injection durations which tal~e about 30 of their shaft rotations. In other words,
these engines typically take a larger percentage of their cycle to inject the fuel. This is
because such engines typically operate with hotter combustion chamber walls and have
shorter ignition delays and faster burning rates. The shape of the volume versus crankshaft
15 angle curve allows more time at minimal volumes for the ~r~nnh~ ion to take plæe.
Some previous rotary engines of the type have been provided with eight vanes and are
designed for an injection duration of 30. This meant that each chamber was in position
under the injection nozzle for 45 shaft degrees. The injection took place up to two thirds of
20 this time. This means cycling the injectors offand on at a rate equal to the number of vanes
times the rotational speed of the engine.
It is an object of the invention to provide an improved axial vane rotary device which
overcomes the d;~alva~ associated with earlier engines of the type.
It is another object of the invention to provide an axial vane rotary device which has a
simplified ~ " ,. .l ;. " . without complex sealing systems between the vanes, rotor and stator.
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It is a further object of the invention to provide an improved axial vane rotary device with
a simplified fuel injection system which does not limit the rotations speed of the engine.
It is a still further object of the invention to provide an improved axial vane rotary device
5 ~hich is practical to produce, relatively low in cost and durable.
SUMMARY OF THE INVENTION
In accordance with these objects, tllere is provided an axial vane rotary engine which
10 includes a stator having a cylindrical internal chamber defined by an annular outer wall and
two side walls of the stator. Each side ~vali has an annular cam surface. There is a rotor
rotatably mounted within the chamber having an annular outer wall and a plurality of
angularly spaced-apart, axial slots extending Lh~ U.1VU~II. There is a vane slidably received
in each slot. Each vane has an outer edge, am inner edge and side edges. The side edges
15 slidably engage the cam surfaces. There is means for al~ ld~iv~ly expanding and
co~ g spaces between adjacent said vanes and the cam surfaces as the cam rotates.
This means includes alternating first portions and second portions on the cam surfaces Tlle
second portions are further from the rotor than the second portions. The first portions of one
cam surface are aligned with the second portions of another said cam surface. There is
20 means for ~ .."l; ", .... ,~ly injecting fuel into the chamber during each complete revolution of
the rotor. The means for injecting is at a position to inject fuel between each pair of vanes
as tlley rotate past the fuel injecting means.
In one example of the invention, there are t~velve vanes spaced-apart about the rotor at 30
25 intervals. Alternatively there may be sixteen vanes which are 22.5 apart.
Sigmficarlt advantages are achievable by utilizing continuous injection. The injectors do not
have to turn offand on at all. This simplifies the nature of the injectors amd means that the
rotational speed of the engine is no longer limited by the response time of the mjectors to
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turning on and off. With a twelve vane engine, locating the fuel injection nozzles at TDC
results in an effective beginning of injection timing of 15BTDC and an effective injection
duration of 30. Control of engine power output may be d~,coll~ cd by controlling the
pressure applied by to the nozles with power mcreased by simply raising the fuel pressure.
s
Alternatively, a sixteen vane engine will shorten the effective injection duration to 22.5
which may result in an even better combustion efficiency. The twelve and sixteen vane
a~nfigllr~ti--nc result in zero thrust loads on the bearings.
10 In addition, constant volume combustion is obtained by using the twelve or sixteen vane
engine geometry with appropriate dwells on the cans. By this method the time (shdft angle)
which it talses for the engine volume to increase from minimum to d~ lcly 5% of
maximum volume can be doubled. This gives more time for combustion at any given speed
which effectively makes the combustion cycle operate as if the engine speed were actually
15 lower than it is.
Th~ rnmhin~til~n of continuous injection and constant volume r~lmhl l~tir)n has the effect of
increasing peak heat flux. The engine can be designed without seals on the vanes, so there
is no surface in the combustion chamber which requires lubrication. Therefore it is possible
20 to apply thermal barrier coatings to all surfaces of the ~omh~lcti-.n chamber to reduce the
pealc heat flux and the overall heat transfer. These coatings can be applied to the face of the
rotor, to the cam surface and to the inner and outer housings. The usually problem of
applying thermal barlier coatings to diesel engines is avoided by eliminating its effect on
lubrication and by isolating the various E)ortions of the cycle by geometry. The hot area is
25 always hot and the cold area is al~vay cold. The avoids volumetric efficiency ~P~r~ tion
due to the hot walls of the ~,mh~l~ti~-n area being exposed to the intake portion of the cycle.
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This ~onf ~llrPtion of rotary engine, utilizing continuous injection and constant volume
combustion is ideal for incorporation of the Miller Cycle and/or the K-Miller Cycle. There
is no sig[uficant siæ penalty imposed by the Miller Cycle because of the very high specific
volume of tbis type of rotary engine. Furthermore it is easy to incorporate the K-Miller
S Cycle by using multiple intake ports ~vith a simple on/off valve to vary the intake portion
closing angle. This feature leads to si~nificant efficiency illl~llOY~lll.,llis including the use
of internal . .,,.,l...,l",li.,~ The inherent low heat rejection of the high speed continuous
injection engine, along with the additional heat due to the thermal barrier coatings, raises the
exhaust energy recovery potential of tlle engine. The æro overlap .~ i. of the ports
10 enables the intake pressure to be significantly higher than the exhaust pressure.
In general, rotary engines according to the invention cam be significantly reduced in
complexity and costs compared to some earlier designs. Reliability is increased compared
with ;, .f., . I I Irl 1~ t,Ype diesel fuel injection systems. The output power of the engine can be
15 effectively doubled by doubling the speed of tbe engine because there is no upward limit
placed by the response rate of the fuel injectors. The maximum rotational speed can now be
increased to well over 2~00 rpm.
Other advantages are as follows:
1. Lower cost of urltimed fuel system offsets cost of more vanes.
2. More vames results in lower pumping work losses.
3. There are lower exhaust emissions. Poor combustion from poor
quality (low pressure) A~(lmirRtion at the beginning and end of
injection are eliminated. This reduces the ll~dl~ lJull and
particulate emissions.
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4. The higher frequency c~-mhll~tion resulting from more vanes and
higher speeds reduces oYerall noise levels. Likewise the rlimin~til)n
of the conventional fuel injection nozzles eliminates a major source
of structural borne noise caused by the opening and closing of the
injector valves.
5. The untimed fuel injection system weighs less than a diesel fuel
injection system. Controls are simplified and also weigh less.
6. The engine, particularly in multi-rotor form, is smaller because of the
single untimed continuous flow fuel pump instead of two separate
pumps for each rotor. The result is a significant length reduction for
the engine.
7. There is a significant reduction in the number of critical parts and
accordingly this eliminates potential failure from many critical
c~ L~. This is pal Li~,ulafly important for aircraft applications.
Examples are potential failures due to sticking or leaking fuel
injection nozzles, seized pumping elements and the like. It is also
~0 easy to incorporate redundant systems with two pressure pumps
isolated from each otner by check valves.
8. The elimination of the diesel fuel injection pumps and nozzles and
their associated high accuracy cam drive malies a significant
iUl~JlVr~ in engine durability. The increase in number of vanes
to twelve or sixteen results in lower bearing loads and therefore
longer bearing life.
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BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. I is a simplified isometric view of an axial vane rotary device according to an
bodilll~llL of the invention vvith the stator thereof partly broken away;
Fig. 2 an unfolded geometrically developed view of a fragment of the stator, rotor
and four ofthe vanes thereof, showing the position upon ~ iull of the mixture;
Fig. 3 is a view similar to Fig. 2 showing the position upon combustion;
Fig. 4 is ~ ,., . "" ,~ side elevation of the device,
Fig. 5 is an unfolded geometrically developed view of the vanes as they traverse one
complete revolution within the stator;
Fig. 6 is a sectional view taken along line 6-6 of Fig. 5;
Fig. 7 is a ~à~ Laly top elevation of one of the vanes and portions of the rotor and
stator;
Fig. 8 is a Jîa~ll~ll~y side elevation of the vane of Fig. 7 and portions of the rotor
and stator;
Fig. 9 is a graph showing volume bet~veen pairs of vanes plotted against sha~t angle
for a 12 vane engine and 8 vane engine; and
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Fig. 10 is a (li ~ """ ,~ les.,~ ion of the control system for the secondary
intake port for a variation of tlle engine operating on the K-Miller cycle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to Fig. 1, this shows an axial vane rotary device which in this example is
configured as an engine 14. The engine 14 has a stator 16 which includes a barrel-shaped
housin~ 18. Various materials could be used including cast iron, but aluminum is preferred
for wei~ht and improved cooling. The housing includes a pair of annular members æ and
24 in this example. Each member has an annular outer wall 26 and an inner wall 28 rotatably
supporting a shaft 30 by means of a bearing 32 on each side, one only being shown only in
Fig. 1. There is a cylindrical internal charnber 34 within the stator defined by side walls 36
and 38 and annular outer wall 40.
Tllesidewalls36and38haveradiallyoutwardportionsthereofcomprisingcamsurfaces42
and 44 respectively. The cam surfaces in this embodiment form the irlner surface of separate
annular cam members 46 and 47.
The cam surfaces 42 and 44 preferably are coated with a slurry type ceramic or cermei
20 coating to prevent wear and reduce friction. The cam members 46 and 47, require precise
angular location between the two sides of the engine and the outer housing 18. Dowel pins
or other devices are preferably used to give this alignment. This permits the cam surfaces
to be separately positioned relative to the sides of the rotor to provide precise control of the
gap between tlle side edges of tlle vanes and the cam surfaces 40 and 42.
Clearance can be provided between the cam surfaces and the housing 18. This clearance can
be sealed with a pair of metallic circular seals and used to permit local thermal expansion of
the cam surfaces. The cam surfaces can be ground machined using a tapered grinding wheel
which is tapered so that the point of the taper would be at the center axis of the engine.
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A rotor 54, which is generally cylindrical in shape, is installed within chamber 34 and is
rotatably supported by the shaft 30. The rotor in this example is a hollow casting that is cast
using twelve pie shaped cores for a twelve vane engine or sixteen cores for a sixteen vane
engine to make the rotor hollow in the areas between the vanes and are supported by holes
S in the side of the rotor.
Referring back to Fig. 1, a vane 68 is slidably received within each of the slots 64. The
vanes are caused to reciprocate axially, in the direction parallel to shaft 30, as the rotor
rotates. The vanes reciprocate back and forth and slidably engage undulating cam surfaces
42 and 44 as the rotor rotates. In this way, the engine is similar to previous engines of the
type.
Tlle vanes have outer edges 74 which slidingly engage outer wall 40 of the stator. This
occurs because the slots 64 extend all the way out to the outer wall 66 of the rotor. The outer
edge 74 of each vane is machined in this ~Illbodil.l~llL to match the outer wall 40 of the
stator. In other words, the outer edge is slightly convex. This reduces crevice volume effects
between the vane and outer housing. A separate wear insert piece can be installed over the
entire end of the outer edge of each vane to reduce friction and wear. The insert can be
simply pressed into a slot in the vane.
As seen in Fig. 1, the engine 1~ has provision for the intake of air at opening 76. Exhaust
gases leave the engine tbrough opening 78. Opening 80 admits cooling fluid into the engine,
while opening 82 is for the discharge of coolant from the engine. There are ~ ~w~y~ 83
in the stator which carry the coolant in order to cool the engine. The engine also has fuel
injectors 84 and 84.1, the latter shown only in Fig. 5, which extend through the stator into
the chamber 34. There is one fuel injector on each side of this engine.
2lsalss
As described above, the fuel injectors 84 and 84.1 inject fuel f ~ IY into the chamber
34. The space between adjæent vanes dc~vldill~;ly is filled with aeomized fuel as each pair
of vanes passes the fuel injector.
There are combustion chambers 1 04 and 1 04.1 on the rotor between each pair of vanes as
shown best in Fig. I and 6. In this exarnple the r~mh--cti-~n chambers are arcuate recesses
spaced-apart a small dist~nce inwardly from the outer wall 66 of the rotor. The fuel injectors
are positioned to sp}ay the fuel into these ~,U~ Liull chambers as seen best in Fig. 6.
Alternatively these combustion chambers can be rounded pockets or the like formed in the
wall of the rotor or dlL~ aLi~,'y in the wall of the stator adjacent the rotor.
It should be noted that the engine 14 does not have the complex seals found on the vanes and
rotors of some earlier engines of this type. This considerably simplifies the structure of the
engine. Such seals do not appear on the engines in some earlier patents, but this is because
such engines were actually not reduced to practice and had not been reflned to the point
where seals had been designed. However in the present instance seals are not critical. The
twelve or sixteen vane engine with continuous fuel injection obviates the need for seals. Any
leakage of compression simply goes into an adjacent chamber and does not have a
significant, detrimental effect upon the efficiency or operation of the engine.
The operation of the engine is best understood with reference to Fig. 5. As may be seen, this
particular engine has twelve vanes identified as 68.1 - 68.12 ~ .,ly. Each side of the
engine operates essentially i".l. l~ ,,.l. ..tlY of the other side. Therefore, for ~l,l,.,.,"i,...
2~i purposes, only the left half of the engine, from the point of view of Fig. 5, will be described.
Rotor 54 rotates downwards from the point of view of the drawing. Each side of the engine
has a primary intake port 86 through tlle stator which ~l""",.";. - ~ ~ with the opening 76
shown in Fig. 1. Tllere is also a secondary intake port 87 separated from the primary intal~e
pûrt by a portion 89 of the stator. Exhaust port 88 ~ .-",.".1.,; ,.IPC with opening 78. The
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engme is described with reference to degrees of rotation about cam surface 42 starting with
O at the top of the drawing. Vane 68.1 is located at 0 while vane 68.4 is a~lu~ aL~ly
90, just prior to intake port 86. As this vane continues to move forward, air received
thrûugh primary intake port 86 is trapped between vanes 68.4 and 68.5. More air is taken
S in between these vanes as they pass by secondary intake port 87. Tllere is then a period of
dwell when the vanes move over the low pûrtion 90 of the cam surface shown between vanes
68.6 and 68.7. Vane 68.7 is shown at 180 at the beginning of the compression stroke. The
air between vane 68.7 and vane 68.8 is ~,u~ ,d due to the decreasing volume between
the vanes as vane 68.7 moves from low cam portion 90 to high cam portion 92. The low cam
portions are further from rotor 52 than the high cam portions.
Il1 a variation of the engine adapted to operate on the Miller cycle the secûndary intake port
87 may be closed by for example, valve 150 shown s~hPm~ti~lly in Fig. 10. The intake
process ends when the primary port closes which is before maximum volume is achieved
This is early intalse closure timing. This effectively reduces the compression ratio of the
engine without affecting the expansion ratio. Miller cycle engines are built with abnormally
large expansion ratios which result in significant efficiency illl~lluvc~ La. Normally the
UU~ ;Ull ratio equals the expansion ratio which means that excessive compressionpressures and hence excessive peak pressures occur. The Miller cycle limits these peak
pressures by early cessation of the intalse cycle and reducing the amount of air trapped in the
chamber.
The K-Miller cycle is a variant which allows the timing to be varied such that the higher
l,U~ iUII iS allowed during starting and light load operation. The valve 150 closing the
secondary port 87 can be controlied by a simple aneroid bellows 152 fed by the outlet
pressure of LUIIJOGIIal~t;l UUIII~ UI 154 to allow the port to be open when ~,UIII,UI~ 01
pressure is low and closed when the pressure is high. A conduit 156 connects the compressor
to the bellows. A link arm 158, connects the billows to a pivot pin 159 connected to the
valve which opens or closes by pivoting about pin 160.
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The air between two vanes is further compressed as vane 68.8 moves to the position of vane
68.9 and is fully compressed when they achieve the positions of vanes 68.9 and 68.10 where
tl1e two vanes are located over the high cam portion 92. Vane 68.9 is at a 240, while vane
68.4 is at 270. Ignition occurs when the vanes are just past the positions shown and vane
68.9 is at a 255. Fuel is injected by injector 84 of this engine which is configured as a
compression ignition engine.
Expansion of the ignited mixture is permitted as the vane 68.10 moves forwardly to the
position of vane 68.11. This is the expansion stroke of the engine. The exhaust strolie
begins at the position of vane 68.1 at 0. At this point the exhaust gases are located between
vane 68.1 and vane 68.2. The exhaust gases are forced out through exhaust port 88 as vane
68.1 moves forwardly, which is downwards from the point of view of the drawing.
The other side of the engine operates in a similar manner, but the positions of the various
strokes are stag~ered and follow the sequence of compression stroke, expansion stroke,
exhaust stroke and intake stroke from lef~ to right from the point of view of Fig. 5.
Constant volume ~nnnhllcti~n results from the . . ."1~", ..~;. .., shown in Fig. 5. As stated, top
dead center occurs at the position of fuel injector 84 which is at the center of high cam
20 portion 92. There is a period of 30 of dwell as each vane passes over this high cam portion.
Likewise, the fuel injection duration is also 30. The power stroke occurs for each vane as
each vane moves from the position of vane 68.10 to the position of vane 68.12, giving a
power stroke of 60. Tllere is an exhaust stroke of 60 as each vane moves from the position
ofvame68.1,pasttheexhaustport88tothepositionofvane68.3. Thereisthenaperiodof
25 dwell as each vane moves the next 30 over high cam portion 92 between the positions of
vanes 68.3 and 68.4 when they are located as shown in Fig. 5. This stroke is shortened, as
discussed above, for Miller cycle and K-Miller cycle variations. The intake stroke also
occupies 60 of the cycle as the vanes move past primary intake port 86 and secondary intalie
port 87 between the positions occupied by vanes 68.4 and 68.6 in Fig. 5. Tllere is then a 30
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period of dwell as the vanes move over the low cam portion positioned between vanes 68.6
and 68.7 in Fig. 5. The compression stroke occurs in the next 60 of }otation of the rotor
bet~veen the positions of vanes 68.7 and 68.9 in Fig. 5.
5 As may be seen in Fig. 5, high cam portions 92 on one side of tne engine are located opposite
low cam portions 90 on the other side of ti~e engine such tnat the vanes reciprocate while the
distance between the cam surfaces remains relatively constant at the width of each vane.
Engine 14 does not rely upon the cam surfæes to reciprocate the vanes. Instead, as seen in
Fig. 1, 5 and 8, tne engine has means for lc~ ,a~ , the vames in~,lldcll~ly of the cam
10 surfaces in tne form of an umdulating cam groove 96 extending about the outer wall 40 of
chamber 34. The cam groove 96, also referred to as a guide cam, extends about the stator
in an undulating pattern between the cam surfaces 42 and 44 as shown in Fig. 5. In this
particular example, tbe groove is generally midway between the cam surfaces although this
is not essential.
Each ~ane has a cam follower in the form of a pin 98. The pin 98 of each vane is slightly
smaller in diameter than the width of cam groove 96 so tnat the pins slidably follow along
tlle groove as the rotor rotates. This may be appreciated from the different positions of the
vanes shown in Fig. 5. The pins 98 cause the vanes to reciprocate axially as the rotor rotates.
The provision of a guide cam and follower, in tne form of cam groove 96 and pins 98, means
that the force to move the vanes is removed from the carn surfæes 42 and 44. Thus the
strength of materials on tne cam surfaces may be reduced so that lighter materials such as
aluminum can be employed. In addition, liquid lubrication can be applied to the cam
25 grooves and pins to reduce friction and wear. A lubricant can be introduced into the cam
groove, located on housing 18 of the stator, eitner tnrough the rotor and drained out tlle
through the outer housing or through the outer housing and drained out through other
openings in the outer housing or back through the rotor. The cam groove can be machined
directly into the outer housing, as in the illustrated ~mhn~imrnt of Fig. I, or can be mach~ned
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into an insert which is cast or otherwise attached to the inside of the outer housmg. The cam
groove may be coated with a wear resistant material if desired.
The pins 98 may be provided with a follower member rotatably located thereon. The
S follower member may be generally elliptical with trlmcated ends. The follower member
increases the hydrodynamic load carrying capacity of each pin.
Alternatively, separate loose members can be attached to each pin 98. These are loose parts
used to guide the lubricant towards the sides of groove 96 to enhance the hydrodynamic load
10 carrying capacity of the pins. The follo~ver member may be pointed.
The illustrated pins 98 are cylindrical. However, other shapes are possible such as a
truncated oval or other non-circular cross-sections adopted to optimize load carrying
capacity
The engine described above is a compression ignition engine. The compression ratio is
between 14:1 and 22:1 and designed so the engine operates as a true direct injected diesel
engine. Altematively tlle compression ratio could be reduced and spark plugs added for a
spark ignition engine.
It will be understood by someone skilled in the art that many of the details provided above
are by way of example only and are not intended to limit the scope of the invention which
is to be deteimined with reference to the followin~ claims.
