V-type engine has intake and exhaust valves for each cylinder, the intake valve being inclined at an angle relative to a center line of each cylinder bore larger than an angle relative to the center line at which the exhaust valve is inclined, and having a length between an intake valve face and an intake cam longer than a length between an exhaust valve face and an exhaust cam of the exhaust valve.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates to a V-type internal combustion engine which has a 
plurality of cylinders formed in two cylinder banks arranged in a V 
formation. 
Description of the Related Art 
Typically, automobile engines have intake and exhaust valves, provided for 
each of cylinders, which are mechanically opened and closed by intake and 
exhaust camshafts, respectively, of a valve drive mechanism. Such an 
automobile engine is known from, for instance, Japanese Unexamined Utility 
Model Publication No. 59-90003. Because of a long overall length of an 
in-line multiple cylinder internal combustion engine, a V-type 
configuration is advantageously provided in which a number of cylinders 
are divided into two groups, each group of cylinders being arranged in one 
and the same of a pair of banks arranged in a V-formation. 
In such a V-type engine in which intake and exhaust camshafts are displaced 
above the cylinder head of each cylinder bank, the intake valve for each 
cylinder of one cylinder bank is located close to the other cylinder bank, 
and the exhaust valve for the same cylinders is located far from the other 
cylinder bank. In addition, the inclination of the intake valve is offset 
to a greater degree relative to the vertical center line of the cylinder 
bore than the inclination of the exhaust valve. Such a configuration of 
V-type engine allows an intake port of each cylinder to be formed so as to 
force air mixture to flow into the cylinder along the center of the 
cylinder bore, thereby increasing an air charging efficiency and providing 
a measurable increase in engine output. Such a configuration of V-type 
engine is described in, for instance, Japanese Unexamined Patent 
Publication No. 63-150404. 
Notwithstanding the advantages of the prior art V-type engines, in which an 
improvement of air charging efficiency is realized by offsetting the 
inclination of the intake valve relative to the center line of cylinder 
bore toward a greater degree than the inclination of the exhaust valve, an 
increase in horizontal inclination angle of the exhaust valve causes a 
lateral outward offset of the cylinder head from the V-type engine, thus 
unavoidably providing an increase in the overall width of the V-type 
engine. In addition, even if the V-type engine is configured with an 
accompanying improvement in fuel combustion efficiency and engine output, 
the efficiency of a fuel mixture in a combustion chamber is still less 
improved, so that it is less expected to provide a measurable improvement 
in combustion efficiency and exhaust performance. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a V-type engine which 
provides a measurable improvement in fuel combustion efficiency and 
exhaust performance, while enabling a reduction in the overall transverse 
width of the V-type engine. 
The foregoing object of the present invention is achieved by providing a 
V-type multiple cylinder internal combustion engine for an automobile, 
which has two cylinder banks arranged in a V-formation at an appropriate 
angle so as to form a V-shaped space between the cylinder banks. Each 
cylinder bank is divided into a number of cylinders. An intake valve 
provided for each cylinder is displaced in one cylinder bank closer to the 
other cylinder bank than an exhaust valve for the cylinder is displaced in 
the one cylinder bank, and is inclined at an angle relative to the center 
line of the cylinder bore larger than an angle relative to the center line 
at which the exhaust valve is inclined. Further, the intake valve is 
configured to have a length between its intake valve face and an intake 
cam longer than a length between an exhaust valve face of the exhaust 
valve and an exhaust cam. 
The intake and exhaust camshafts are operationally coupled to each other by 
means of gears directly or indirectly attached to the intake and exhaust 
camshafts, respectively. In addition, a variable valve timing mechanism 
cooperates with either one of the intake and exhaust camshafts, for 
instance the intake camshaft, so as to regulate a timing of valve opening 
and closing. The other camshaft, for instance the exhaust camshaft, is 
operationally coupled to a crankshaft via an interim shaft by means of a 
chain belt so as to enable the V-shaped space to be freed up, thereby 
allowing a supplemental equipment, such as a supercharger, to be placed in 
the V-shaped space. 
According to the V-type, multiple cylinder internal combustion engine of 
the present invention, by offsetting the angle of inclination of the 
exhaust valve relative to the center line of the cylinder bore to a lesser 
degree than the angle of inclination of the intake valve, this results in 
the angle of the exhaust valve with respect to the horizontal plane being 
large therefore, there is a lesser need to provide a lateral offset of the 
cylinder head on the side of the exhaust valves from the V-type engine, so 
as to make it certain to decrease the overall width of the V-type engine. 
Moreover, since the angle of inclination of the intake valve, and hence of 
the intake port, with respect to the center line of cylinder bore is 
relatively large, a tumble of air flowing into the fuel combustion chamber 
from the intake port is caused, which promotes a better mixture of the 
fuel mixture within the combustion chamber with an accompanying 
improvement in fuel combustion efficiency and exhaust performance. 
In addition, since the length of the stem of the intake valve is longer 
than that of the exhaust valve, the intake camshaft is offset outward from 
the transverse center of cylinder bank, which provides an affordable space 
between the cylinder banks in which supplementary equipments can be 
displaced and the placement of fuel injectors can be made in close 
proximity to the intake port. Furthermore, since the torque of the 
crankshaft is transmitted to the exhaust camshaft in one cylinder bank, 
which is displaced far from the other cylinder bank with respect to the 
intake camshaft in the one cylinder bank, via the torque transmission 
gear, so that the sprocket which drives the torque transmission gear does 
not impose upon the space between the cylinder banks, thereby enabling the 
supercharger to be displaced between the cylinder banks without any 
difficulty.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings in detail and, in particular, to FIGS. 1 and 2, a 
V-type engine 1, such as a V-type, six cylinder engine, in accordance with 
a preferred embodiment of the present invention is shown, The V-type 
engine is provided with two cylinder banks A and B arranged in a 
V-formation so as to form a V-shaped space V therebetween. A number of 
cylinders are divided into two groups, each of which are assigned to 
either one and the same cylinder bank A or B. The V-type engine E is 
equipped with a crankshaft 1 to which a crankshaft pulley 2 is attached. 
The V-type engine E is further accompanied by an oil pump (not shown) to 
which a pulley 3 is attached, a supercharger 4 having a pulley 5, an 
automatic tensioner 6. These pulleys 3 and 5 are operationally coupled to 
the pulley 2 of crankshaft 1 by means of a belt 8 so as to drive those 
engine related devices, namely the oil pump and supercharger 4. This belt 
8 is applied with tension by means of an automatic tensioner 6 and an 
idler roller 7. The V-type engine E is also equipped with an air 
conditioning compressor 9 to which a pulley 10 is attached, a water pump 
11 to which a pulley 12 is attached, a power steering pump (not shown) to 
which a pulley 13 is attached, and an alternator 14 to which a pulley 15 
is attached. These pulleys 10,12, 13 and 15 are operationally coupled to 
the pulley 2 of crankshaft 1 by means of a belt 18 so as to drive those 
engine related devices, namely, the air conditioning compressor, water 
pump 11, power steering pump and alternator 14. This belt 18 is applied 
with tension by means of idler rollers 16 and 17. 
Intake and exhaust camshafts 20 and 21 integrally formed with intake and 
exhaust cams 20a and 21a, respectively, which open and close the intake 
and exhaust valves, respectively, are displaced over the top of the 
cylinder heads 19. The supercharger 4 is displaced in the V-shaped space V 
between twin cylinder banks A and B. 
An intake manifold 22, connected to each of cylinder banks A and B is 
displaced above supercharger 4 as shown in FIG. 1. Cylinder intake ports 
25 are formed within each of the cylinder heads 24, attached to the top of 
cylinder block 23. Intake valves 27 and exhaust valves 28, which open and 
close the intake ports 25 and exhaust ports 26, respectively, are arranged 
in a V formation relative to a spatial plane including the center lines 0 
of the cylinder bores. Further, each of intake valves 27 in one of 
cylinder banks A and B is positioned in close proximity to the transverse 
center of V-type engine and closer to the other of cylinder banks A and B 
than the exhaust valve 28. On the other hand, each of exhaust valves 28 in 
one of cylinder banks A and B is positioned far away from the other of 
cylinder banks A and B. Intake manifold 22 is connected to intake port 25 
communicating with a fuel combustion chamber 29. Similarly, exhaust port 
26 communicates an exhaust manifold (not shown) with fuel combustion 
chamber 29. 
The angle of inclination .THETA.2 of exhaust valve 28 relative to the 
center line 0 of cylinder bore is offset to a lesser degree than the angle 
of inclination .THETA.1 of intake valve 27 relative to the center line of 
cylinder bore. Furthermore, the length L1 between its intake valve face 
and the intake cam 20a of intake valve 27 is longer than the length L2 
between its exhaust valve face and the exhaust cam 21a of exhaust valve 
28. In this instance, the angle of inclination .THETA.1 of intake valve 27 
is less than half the angle at which the cylinder banks A and B are 
arranged in a V-formation. 
Intake camshaft 20 is displaced on each of cylinder banks A and B above 
intake valves 27 on each cylinder head 24. Similarly, the exhaust camshaft 
21 is disposed on each of cylinder banks A and B above exhaust valves 28 
on each cylinder head 24. Tappets 30 and 31 of intake valves 27 and 
exhaust valves 28 are disposed between cams 20a and 21a, and intake and 
exhaust valves 27 and 28 and are pressed against cams 20a and 21a by means 
of springs 32. In accompaniment with the rotation of camshafts 20 and 21, 
the intake valves 27 and exhaust valves 28 are reciprocally slid up and 
down by means of cams 20a and 21a, thereby opening and closing intake 
ports 25 and exhaust ports 26, respectively. 
Referring to FIG. 3, a variable timing mechanism 33, which has a housing 35 
with a camshaft gear 34 fixedly attached externally thereto, is provided 
at to the external shaft end of either one of, for instance in this 
embodiment intake camshaft 20. The external shaft end of intake camshaft 
20 extends within housing 35. An external helical gear is formed on 
camshaft 20, and an internal helical gear is formed on housing 35. An 
hydraulic piston (not shown), which is disposed between the housing 35 and 
intake camshaft 20, is enmeshed with both helical gears of the housing 35 
and intake camshaft 20. By means of a hydraulic control mechanism 
operative in accordance with engine operating conditions (i.e. speeds of 
the vehicle), the hydraulic piston is forced along the axis of intake 
camshaft 20, so as to cause a relative rotation or angular displacement 
between the camshaft gear 34 fixed to the housing 35 and the camshaft 20, 
thereby regulating the timing of opening of the intake valves 27. On the 
other hand, at the end shaft of exhaust camshaft 21 is fixedly attached a 
camshaft gear 36 which is enmeshed with camshaft gear 34 related to intake 
camshaft 20 so as to synchronize intake camshaft 20 and exhaust camshaft 
21 in rotation. 
Cylinder head 24 is further provided with an interim shaft 37. Although 
this interim shaft 37 is shown in FIG. 3 as if it is adjacent to exhaust 
camshaft 21 in the same plane, it is actually located below the exhaust 
camshaft 21 and between exhaust camshaft 21 and crankshaft 1. A sleeve 39, 
integrally formed, or otherwise fixedly provided, with a torque 
transmission gear 38, is press-fitted onto interim shaft 37. The torque 
transmission gear 38 is in engagement with the camshaft gear 36 of exhaust 
camshaft 21. Sleeve 39 is further provided with a sprocket 40 fixedly 
attached thereto. This sprocket 40 is operationally coupled by means of a 
chain 42 to a sprocket 41 fixedly attached to crankshaft 1 so as to drive 
the torque transmission gear 38 by the crankshaft 1. 
Referring to FIG. 4, the torque transmission mechanism T1, including the 
sprockets 40 and 41 and the chain 42, is accompanied by a tension means T2 
rotatable about a pivot shaft 43. The tension means T2 includes a tension 
lever 45 pivoted on the pivot shaft 43 and a stationary guide 46. The 
tension lever 45 is linked to an actuator 44 so as to press chain 42. 
Referring again to FIG. 1, there are shown both torque transmission 
mechanisms T1 related to the left and right cylinder banks A and B 
arranged on the same side of V-type engine E, which is for the sake of 
convenience of providing an easy understanding. Practically, in order to 
balance the weight distribution of V-type engine E, the torque 
transmission mechanisms T1 are separately located on opposite sides of 
V-type engine E. As is apparent from FIG. 1, the torque transmission 
mechanism T1 for one of right and left cylinder banks A and B, which 
includes the variable timing mechanism 35, camshaft gears 34 and 36, 
torque transmission gear 38, sleeve 39, sprockets 40 and 41, chain 42, 
tension means T2, etc., is reversed 180 degrees in position relative to 
that for the other. In addition, the torque transmission mechanism T1 may 
also be utilized with a V-type engine mounted in a lengthwise direction in 
the V-type engine compartment. 
Camshaft gear 36 on the exhaust camshaft 21 is provided with front and rear 
friction gears 47 and 48 disposed on opposite sides thereof. These 
friction gears 47 and 48 are pressed and held in place by resilient 
conical springs 49, respectively. In order to apply a specified amount of 
friction between the friction gears 47 and 48 and the camshaft gear 36, a 
nut 52 is fastened to the external threaded shaft 51 until a boss 36a of 
camshaft gear 36 abuts against a flange 50 formed on exhaust camshaft 21. 
These friction gears 47 and 48 are resiliently coupled to camshaft gear 36 
by means of resilient conical springs 49. One of friction gears 47 and 48, 
for instance in this embodiment the friction gear 47, located on the side 
of the end shaft 51 of exhaust camshaft 21, is engaged with torque 
transmission gear 38, and the other, i.e. the friction gear 48, located 
far from the end shaft 51 of exhaust camshaft 21, is engaged with camshaft 
gear 34, forming part of variable timing mechanism 33 on the intake 
camshaft 20. In this instance, the number of teeth of friction gear 47, in 
engagement with the torque transmission gear 38, exceeds the number of 
teeth of camshaft gear 34 by one. Conversely, there is one less tooth in 
the number of teeth of friction gear 48 than camshaft gear 34. 
In V-type engine E configured as described above, the torque of crankshaft 
1 originating in V-type engine E is transmitted to sleeve 39 through 
sprockets 40 and 41 and chain 42. The rotation of torque transmission gear 
38 causes camshaft gear 36 of the exhaust camshaft 21 to rotate, thereby 
rotating exhaust camshaft 21. This causes inter-linked camshaft gear 34 
and camshaft 20 to also rotate, thereby opening and closing the intake 
valves 27 and exhaust valves 28 of the respective cylinders. With V-type 
engine E, since the angle of inclination .THETA.2 relative to the center 
line 0 of cylinder bore of exhaust valve 28 is offset toward a smaller 
degree than the angle of inclination el of the intake valve 27, there is a 
lesser need to provide a lateral offset of the cylinder head on the side 
of exhaust valves 28 from V-type engine E, making it possible to decrease 
the overall width of the V-type engine E. On the other hand, since the 
angle of inclination .THETA.1 of intake valve 27 is greater, then, the 
angle of the intake port 25 relative to the center line 0 of cylinder bore 
becomes greater with respect to the fuel combustion chamber 29. This 
causes a tumble of air flowing into the fuel combustion chamber 29 from 
the intake port 25, promoting a better mixture of the fuel mixture within 
the combustion chamber 29, with an accompanying improvement in fuel 
combustion efficiency and exhaust performance. 
In addition, since the length L1 between its intake valve face and the 
intake cam 20a of intake valve 27 is longer than that L2 of exhaust valve 
28, the intake camshaft 20 is effected to offset outwardly far from the 
center of cylinder bank, so as to create an affordable space between the 
cylinder banks A and B. This results in being able to locate on place the 
supplemental equipments between the cylinder banks A and B. Specifically, 
as shown in FIG. 2, the fuel injection valve 53 is placed close to the 
intake port 25, and the supercharger 4 is easily placed between the 
cylinder banks A and B. In addition, since the linkage of the intake 
camshaft 20 with the exhaust camshaft 21 is accomplished by means of the 
camshaft gears 34 and 36, the close placement of the camshafts 20 and 21 
is realized, and helps to facilitate a reduction in the overall size of 
V-type engine E. If the camshafts 20 and 21 are linked by means of a 
timing belt or chain, the camshafts 20 and 21 have to be placed far away 
from each other so as to avoid obstruction between the pulleys and/or 
sprockets attached to them, thereby requiring an increase in the width of 
cylinder heads 24. However, the camshaft gear linkage arrangement of this 
embodiment eliminates such a disadvantage, and with the combined effect of 
appropriately setting the angles of inclination of intake and exhaust 
valves 27 and 28 and the lengths of intake and exhaust valves 27 and 28 in 
the manner described above, an overall reduction in the size of V-type 
engine E is achieved. 
Variable timing mechanism 33, attached to the intake camshaft 20 of V-type 
engine E, serves in part to determine the diameters of camshaft gears 34 
and 36. In this instance, from the effect of offsetting the angles of 
inclination and the lengths of intake and exhaust valves 27 and 28, the 
overall size of V-type engine E is reduced within the limitation of the 
diameters of camshaft gears 34 and 36. Furthermore, the torque of 
crankshaft 1 is transmitted to the camshaft gear 36 on the exhaust 
camshaft 21. If it is to be transmitted to the camshaft gear 34 on the 
intake camshaft 20, the sprocket 40 and torque transmission gear 38 have 
to be transversely shifted toward the center of V-type engine E, causing 
the sprocket 40 to be in the V-space between the cylinder banks A and B, 
thereby preventing or making difficult the placement of the supercharger 4 
between the cylinder banks A and B. This problem is avoided by 
transmitting the torque of crankshaft 1 through the camshaft gear 36 on 
the exhaust camshaft 21 which is on the far side of one cylinder bank from 
the other cylinder bank. Furthermore, if the torque transmission is made 
directly to the exhaust valve camshaft 21 from the crankshaft 1, the 
attachment of a large diameter of sprocket to the camshaft 21 is essential 
to reduce and transmit the torque of crankshaft 1. Such a large diameter 
sprocket extends out of the cylinder head and increases the overall height 
of V-type engine E, consequently. However, with the V-type engine E of the 
present invention, the torque of crankshaft 1 is once transmitted to the 
transmission gear 38 and then, it is input to the camshaft gear 36 of 
exhaust camshaft 21 from the transmission gear 38. Accordingly, as shown 
in FIGS. 3 and 4, since the transmission gear 38, which is linked to the 
sprocket 40, is made smaller in diameter than the camshaft gear 36, the 
torque of camshaft 1 is transmitted at a reduced rate to the camshaft gear 
36. This eliminates the provision of a large diameter of sprocket for the 
sprocket 40, avoiding an increase in the overall height of V-type engine 
E. 
When torque is transmitted from the transmission gear 38 to the exhaust 
camshaft gear 36, and from the exhaust camshaft gear 36 to the intake 
camshaft gear 34, backlash possibly produced by changes in engine speed 
and/or by changes in torque of camshafts 20 and 21 is controlled or 
eliminated and hence, no noise is caused due to backlash. This is 
accomplished through the engagement of friction gear 47 with both of the 
transmission gear 38 and camshaft gear 36, and the similar engagement of 
friction gear 48 with both of the camshaft gears 34 and 36. 
When transmitting torque from the crankshaft 1 to the camshafts 20 and 21 
by means of chain 42, tension is appropriately applied to the chain 42 by 
means of a tension lever 45 as shown in FIG. 4, and the chain 42 must 
cooperate with and be guided by the chain guide 46. However, with some 
engines, such as V-type, six cylinder engines, the engagement of chain 42 
with the sprockets 40 and 41 is tight, making noise between the chain 42 
and sprockets 40 and 41 on the side of stretching, which possibly leads to 
wear of chain 42 and sprockets 40 and 41. 
Spraying of a lubrication oil to the chain 42 and sprockets 40 and 41 
serves as an effective counter measure for treating wear and noise. 
Referring to FIG. 5, a lubrication oil is supplied into an hollow pivot 
shaft 43 of tension lever 45. The pivot shaft 43 and a metal bearing 54 
are formed with holes forming an oil passage 55, through which the 
lubricating oil introduced into the hollow pivot shaft 43 is sprayed onto 
the sprocket 40 in engagement with the chain 42 on the side of stretching. 
The lubrication oil serves to control noise and suppress wear the sprocket 
40 and/or chain 42. The chain guide 56 is formed with an oil passage 57 
extending along the whole length of chain guide 56 and an inlet hole 58 
through which a lubrication oil is introduced into the oil passage 57 from 
the cylinder block 23. This oil passage 57 enables spraying of lubrication 
oil to sprockets 40 and 41. 
Referring to FIGS. 6 and 7, a guide member 59 is provided in the area where 
a chain 42 engages with the sprocket 40 on the side of stretching so as to 
cross over the chain 42. This guide member 59 is formed with an oil 
passage 61 in communication with an oil passage formed in a cylinder block 
23. An oil is applied to the chain 42 through the oil passage 61 from the 
cylinder block 23 via the oil passage 60. 
It is to be understood that although the present invention has been 
described in detail with respect to a preferred embodiment thereof, 
various other embodiments and variations, which fall within the scope and 
spirit of the invention, may occur to those skilled in the art. Such other 
embodiments and variations are intended to be covered by the following 
claims.