Variable valve timing apparatus

An apparatus for controlling a valve timing in an internal combustion engine. A timing piston 7 is in splined engagement with both a camshaft sleeve connected to the camshaft 1 and a pulley sleeve connected to the timing pulley. The timing piston 7 is connected, via a ball bearing unit 8, to a screw nut 9 of a ball screw mechanism. The bearing unit 8 is connected to the nut 9, with a clearance C. A disk spring 20, via a spacer 21, urges the inner race 8a of the bearing 8 so that it abuts against a washer 23 an a snap ring 22 on the screw shaft 9. As a result, the screw shaft 9 is connected to the timing piston 7 so that the axial movement from the shaft 9 is transmitted to the piston 7, while the piston 7 is rotating on the shaft 9, and a slight radial relative movement is allowed between the screw shaft 9 and the piston 7 without generating any play in the axial movement. An oil passageway is formed for lubricating the ball nut mechanism.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates an apparatus for controlling a valve timing 
in an internal combustion engine, wherein the opening or closing timing of 
an intake or exhaust valve is suitably controlled in accordance with 
engine operating conditions. 
2. Description of Related Art 
Japanese Unexamined Patent Publication No. 60-243308 discloses a mechanism 
for controlling a rotating phase difference between a camshaft and a 
crankshaft in an internal combustion engine, the mechanism being provided 
with a first helical splined shaft fixed to the camshaft and defining on 
an outer surface thereof a helical spline, a second helical splined shaft 
fixed to a timing pulley of the camshaft and connected by a belt to a 
timing pulley fixed to a crankshaft and defining on an outer surface 
thereof a helical spline, and a timing piston having a spline which is in 
mesh with the helical splines of the first and second helical splined 
shafts. The timing piston is connected to a mechanism for obtaining a 
movement of the timing shaft in parallel to the direction of the axis of 
the camshaft, to thereby cause the first and second helical splined shafts 
to be relatively rotated, and thus allow a rotational phase difference to 
be obtained between the timing pulley, connected to the crankshaft via a 
belt-pulley mechanism, and the camshaft. The mechanism for obtaining the 
movement of the timing piston is constructed by an electric motor for 
obtaining a rotational movement, and a mechanism, such as a ball nut, for 
transforming the rotational movement from the motor to a linear movement 
in parallel to the direction of the camshaft. The mechanism for 
transforming the rotational movement into a linear movement comprises a 
worm member on an output shaft of the electric motor, a pinion in mesh 
with the worm, a first slider sleeve defining at an outer surface thereof 
a gear portion in mesh with the pinion, a second slider sleeve in screw 
engagement with the first slider, a pin for preventing a rotation of the 
second slider sleeve about its own axis, and a ball bearing for connecting 
the second slider with the timing piston while allowing the timing piston 
to be rotatable with respect to the second slider sleeve. The rotation of 
the output shaft of the motor causes the pinion to be rotated via the 
worm, and the rotation of the pinion causes the first slider to be rotated 
about its own axis, which causes the second slider to be moved axially 
along the direction of the axis of the camshaft, because the second slider 
is screw-engaged with the first slider and a rotation of the second shaft 
is prevented by the pin. The axial movement of the second slider in 
parallel to the axis of the camshaft is transmitted to the camshaft, and 
thus a relative angular displacement between the crankshaft and the 
camshaft is controlled. 
The camshaft is provided with cams for obtaining a lifting movement of the 
respective intake valves and exhaust valves, which causes a rotating 
torque as a reaction force to be generated in the cam shaft. The direction 
of the reaction force is such that the rotation of the camshaft is 
relatively delayed with respect to the crankshaft. Namely, even when the 
valve timing control device is operated such that the camshaft is rotated 
in a direction that is advanced with respect to the crankshaft, a reaction 
force will be generated in the crankshaft in a direction in which the 
rotation of the camshaft is delayed with respect to the crankshaft. To 
maintain the camshaft at an angular position that is advanced with respect 
to the crankshaft, a means of preventing the camshaft from being returned 
in the direction in which the rotation of the camshaft is delayed with 
respect to the crankshaft must be provided. The worm gear arranged between 
the rotating drive motor and the slider in the prior art allows only one 
directional transmission of the movement from the electric motor to the 
slider. Namely, any transmission of the movement in the reverse direction, 
i.e., the direction from the slider to the motor, is prevented, and this 
allows the obtained relative rotational angle relationship between the 
crankshaft and the camshaft to be maintained unchanged even if no 
provision is made therefore. 
In the prior art, the slider moves the timing piston in the direction 
parallel to the axis of the camshaft, to obtain a relative rotating 
movement of the first and second helical splines in spline engagement with 
the first and second helical splines. In this construction, the timing 
piston is connected to the slider via a ball bearing assembly, which 
allows the timing piston to rotate about the slider while the axial 
movement of the slider along the axis of the camshaft is transmitted to 
the timing piston. In the prior art, however, a rigid connection is 
obtained between the slider and the timing piston. Namely, the ball 
bearing assembly is provided with an inner race press fitted to the timing 
piston and an outer race press-fitted to the slider. Such a rigid 
connection between the slider and the timing piston in the prior art makes 
it difficult to obtain a smooth movement between the slider and the timing 
piston, when there is a misalignment of the axis of the slider and the 
axis of the camshaft in a tolerance range, and as a result, a smooth 
control of a mutual positioning of the slider and the camshaft cannot be 
obtained. 
Furthermore, the prior art construction is disadvantageous in that a 
desired amount of lubricating oil cannot be supplied to the worm gear 
mechanism and the ball nut mechanism, each having parts which are mutually 
engaging, so that a smooth movement between these parts is sometimes lost. 
Still further, the prior art construction is disadvantageous in that the 
lubrication oil for the worm gear mechanism and the ball nut mechanism is 
often accumulated therein when the engine is stopped. The viscosity of the 
oil is increased during low temperature condition, and the high viscosity 
of the oil thus accumulated during a stoppage of the engine at a low 
temperature can make it difficult to ensure that the worm gear and/or the 
ball nut mechanism are moved smoothly, and thus a desired control of the 
mutual position of the camshaft with respect to the crankshaft cannot be 
obtained, and accordingly, the cold engine cannot be easily started. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a valve timing control 
apparatus capable of overcoming the above mentioned drawbacks. 
Another object of the present invention is to provide a valve timing 
control apparatus capable of obtaining a smooth control of the valve 
timing, regardless of any misalignment of the axis of the member connected 
to the camshaft and the member connected to a feed mechanism. 
Still another object of the present invention is to provide a valve timing 
control apparatus capable of obtaining a desired lubrication of parts 
wherein a relative sliding movement occurs. 
A further object of the present invention is to provide a valve timing 
control apparatus capable of obtaining a desired operation when a cold 
engine is to be started. 
According to one aspect of the present invention, an apparatus is provided 
for controlling a valve timing in an internal combustion engine, having an 
engine block, a crankshaft mounted to the engine block, a camshaft mounted 
to the engine block, and a power receiving member rotatably mounted on the 
camshaft for receiving a rotational movement from the crankshaft, said 
apparatus comprising: 
a housing connected to the engine block; 
a first sleeve member fixedly connected to one end of the camshaft, the 
first sleeve member defining, at a cylindrical surface thereof, a helical 
spline; 
a second sleeve member fixedly connected to the power receiving member; 
a timing piston movable along the axis of the camshaft, the timing piston 
having a first helical spline portion engaging with the first sleeve 
member and a second spline portion engaging with the second sleeve in such 
a manner that the axial movement of the timing piston causes a mutual 
angular position between the camshaft and the power receiving member to be 
obtained; 
rotary drive means for generating a rotating movement; 
a feed mechanism having a rotating part rotatable with respect to the 
housing and connected to said rotary drive means and a linearly moving 
part moved with respect to the housing along the axis of the camshaft upon 
the rotation of the rotating part, and; 
means for connecting the linearly moving part with the timing piston so 
that the axial movement from the feed mechanism is transmitted to the 
rotating timing piston, while a limited radial, relative movement is 
allowed between the linearly moving part and the timing piston. 
This invention allows the feed mechanism and the timing piston to be 
connected and be radially movable within a limited range, so that a smooth 
transmission of the axial movement from the feed mechanism to the timing 
piston is obtained regardless of an inevitable misalignment of the axis of 
the feed mechanism and the axis of the timing piston. 
According to another aspect of the invention, an apparatus is provided for 
controlling a valve timing in an internal combustion engine, having an 
engine block, a crankshaft mounted to the engine block, a camshaft mounted 
to the engine block, and a power receiving member rotatably mounted on the 
camshaft for receiving a rotational movement from the crankshaft, said 
engine including an oil supply passageway in the engine block for a 
lubrication of various parts therein, said apparatus comprising: 
a housing connected to the engine block; 
a first sleeve member fixedly connected to one end of the camshaft, the 
first sleeve member defining, at a cylindrical surface thereof, a helical 
spline; 
a second sleeve member fixedly connected to the power receiving member; 
a timing piston movable along the axis of the camshaft, the timing piston 
having a first helical spline portion engaging with the first sleeve 
member and a second spline portion engaging with the second sleeve in such 
a manner that the axial movement of the timing piston causes a mutual 
angular position between the camshaft and the power receiving member to be 
obtained; 
rotary drive means for generating a rotating movement; 
a feed mechanism having a rotating part rotatable with respect to the 
housing and connected to said rotary drive means and a linearly moving 
part moved with respect to the housing along the axis of the camshaft upon 
the rotation of the rotating part; 
means for connecting the linearly moving part with the timing piston for 
transmission of the axial movement from the feed mechanism to the timing 
piston; 
said oil supply passageway being opened to a space formed between the 
housing and the engine block for lubricating the parts therein, including 
the feed mechanism, and; 
means for defining an oil returning passageway constructed such that the 
oil supplied to the feed mechanism is exhausted and does not remain 
therein when the engine is stopped. 
This invention allows the feed mechanism to be properly lubricated, and the 
oil to be smoothly evacuated via the return passageway when the engine is 
stopped, which prevents the oil from being accumulated in the feed 
mechanism, and thus a smooth operation of the feed mechanism is obtained 
even when the viscosity of the oil is high because the engine is cold.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows an internal combustion engine of V-type wherein an engine 
block 102 has first and second banks 100 and 100', each provided therein 
with a plurality of cylinders. Each of the banks 100 and 100' has a 
camshaft 1 for intake valves (not shown) and a camshaft 104 for exhaust 
valves (not shown). Each of the camshafts 1 for the intake valves of the 
respective banks has a timing pulley 2 mounted thereon, and each of the 
camshafts 104 for the exhaust valves has a timing pulley 106 mounted 
thereon. The engine block 102 is provided with a crankshaft 108 on which a 
timing pulley 110 is mounted, and looped around the timing pulleys 2, 104 
and 110 is a timing belt 112 for transmitting the rotational movement of 
the crankshaft 108 to the camshafts 1 and 104. Reference numerals 114 are 
idler pulleys. Reference numerals 118 and 118' illustrate valve timing 
control devices, respectively, according to the present invention, for 
controlling the intake valve timing for the intake valves of the banks 100 
and 102, respectively. As will be easily seen, the valve timing control 
devices 118 and 118' are provided with electric rotating motors 16 and 
16', respectively, as actuators for obtaining a desired valve timing, as 
will be fully explained later. 
FIG. 2 is a axial cross-sectional view taken along a line II--II in FIG. 1. 
As shown in FIG. 2, a housing 17 is connected, via an O ring 122, to a 
stay 18, which is an integral part of an engine block 102, whereby a space 
51 is created between the housing 17 and the stay 18 for housing therein 
parts of the variable valve timing apparatus to be lubricated, as will be 
described later. The center boss portion 2-1 of the timing pulley 2 has a 
bore 2a that receives one end of the camshaft 1, and a bolt 4 is 
screw-engaged to the camshaft 1 via a camshaft sleeve 3 at a closed end 
3-1 thereof. The camshaft sleeve 3 has a sleeve portions 3-2 which is 
slidably and rotatably inserted to the boss portion 2-1 of the timing 
pulley 2, which is itself slidably and rotatably inserted to the camshaft 
1. A pin 3a is inserted to aligned bores formed axially along the camshaft 
1 and the sleeve 3, by which the rotational movement of the camshaft 1 and 
the sleeve 3 are integrated about the axis of the camshaft 1, and the 
timing pulley 2 is slidable and rotatable with respect to both the 
camshaft 1 and the camshaft sleeve 3. 
A pulley sleeve 25 is arranged coaxially with respect to the camshaft 1, 
via a seal unit 26, and has an outer flange 25-1 fixedly connected to the 
hub portion of the timing pulley 2 by bolts 25a. The camshaft sleeve 3 and 
the pulley sleeve 25 form, respectively, opposite outer and inner 
cylindrical surfaces on which helical splines 6 and 5, respectively, are 
formed, and which extend along opposite directions at the same angle with 
respect to the axis of the camshaft 1. A timing piston 7 is arranged 
between the camshaft sleeve 3 and the pulley sleeve 25, and has a sleeve 
shape defining inner and outer cylindrical surfaces on which helical 
splines 7-1 and 7-2 are respectively formed. The inner helical spline 7-1 
of the timing piston 7 is engaged with the outer helical spline 6 of the 
camshaft sleeve 2, and the outer helical spline 7-2 of the timing piston 7 
is engaged with the inner helical spline 5 of the pulley sleeve 25. Due to 
the spline engagement of the timing piston 7 with respect to the camshaft 
sleeve 3 integrally rotated with the camshaft 1 and the pulley sleeve 25 
integrally rotated with the timing pulley 2, the rotational movement of 
the timing pulley 2 transmitted from the crankshaft 108 via the timing 
pulley 112 is transmitted to the camshaft 1. Further, upon an axial 
movement of the timing piston 7, positions of the engagement of the inner 
spline 7-1 of the timing pulley 7 with the outer spline 6 of the camshaft 
sleeve 3, as well as positions of the engagement of the outer spline 7-2 
of the timing piston 7 with the inner spline 5 of the pulley sleeve 25, 
are correspondingly changed. The movement of the positions of the 
engagement between the helical splines 7-1 and 6, and between 7-2 and 5 
cause the camshaft sleeve 3 and the pulley sleeve 25 to be rotated with 
each other in opposite directions, because the engaged splines 7-1 and 6 
and the engaged splines 7-2 and 5 are oppositely inclined with respect to 
the axis of the camshaft 1. As a result, a mutual angular displacement of 
the timing pulley 2 with respect to the camshaft 1 can be controlled in 
accordance with the axial position of the timing piston 7 when the engine 
is operating. 
A ball-screw mechanism is provided for obtaining an axial movement of the 
timing piston 7, and is constructed by a ball screw 12 and a sleeve-shaped 
nut 9 which are in a screw engagement via balls (not shown) housed in a 
closed passageway (not shown) in the nut 9, as well known to those skilled 
in this art. The ball screw 12 has a first end connected rotatably to the 
housing 17 via a ball bearing unit 14, and a second end located adjacent 
to the camshaft sleeve 3 and having a screw thread. The nut 9 has a screw 
thread 9' which engages with the ball screw 12, and has a first end 
axially slidably supported by a sleeve-shaped oil-less metal bearing 10 
connected to the housing 17, and a second end connected to the timing 
piston 7 via a means for connecting the nut 9 to the timing piston 7 while 
allowing a rotation of the timing piston 7 with respect to the nut 9 and 
allowing a slight mutual movement between the nut 9 and the timing piston 
7 without allowing a rattle, as will be fully described later. The nut 9 
has, axially, on the outer wall thereof, a key-way 9-1 with which a key 11 
is engaged at an end thereof. The key 11 is fixedly connected to the 
housing and extended radially inward therefrom. The key-way key 9-1 and 
the key 11 can prevent a rotation of the nut about its own axis so that 
the rotational movement of the ball shaft 12 is transformed into the axial 
slidable movement of the nut 9. The oil-less metal bearing member 10 is 
axially slidable with respect to the nut 9, to thereby obtain a smooth and 
frictionless linear movement of the nut 9. 
A gear wheel 13, with which a worm shaft 15 is engaged, is fixed on the 
ball screw shaft 12. The worm shaft 15 is extended from the electric motor 
16 as an output shaft, and a rotational movement of the worm shaft 15 
causes the ball screw shaft 12 to be rotated via the gear 13. The 
rotational movement of the screw shaft 12 causes the nut 9 to axially 
slide on the oilless metal bearing, because the key connection between the 
key-way on nut 9 and the key 11 of the housing prevents a rotation of the 
nut 9 about its own axis. The axial movement of the nut 9 is transmitted, 
via the ball bearing assembly 8, to the timing piston 7, to obtain a 
mutual rotational movement of the timing pulley 2 connected to the 
crankshaft 108 and the camshaft 1. A control of a rotation number of the 
electric motor obtains a desired degree of a mutual rotation angle between 
the timing pulley 2 and the camshaft 1, to thus obtain a desired valve 
timing. 
It should be noted that the motor 16 is connected to the housing 17, which 
is separate from the engine body 102, and fixedly connected to a stay 18 
by bolts 19. The stay 18 is connected to the engine block 102 by a 
suitable fixing means. 
FIG. 3 illustrates, in detail, a means for a transmission of the axial 
linear movement of the nut 9 to the timing piston 7 during the rotation of 
the piston 7, and a slight radial movement between the nut and the timing 
piston 7 is allowed without generating any rattle therebetween. Namely, 
the nut 9 has a reduced diameter end portion forming a shoulder 9a. A 
Belleville spring (disk spring) 20 and a spacer member 21 having an 
L-cross-section are closely fitted to the reduced diameter portion of the 
nut 9, so that the spring 20 abuts against the shoulder portion 9a. The 
annular member 21 forms a flange portion 21a extended radially to be 
located between the spring 20 and an inner racing of the bearing assembly 
8. An annular washer 23 is also closely fitted to the reduced diameter end 
of the nut 9 so that the washer 23 abuts against the end of the inner race 
8a of the bearing assembly remote from the spacer member 21. Furthermore, 
the nut 9 has an annular groove in which a snap ring (as a stopper) 22 is 
fitted so that it abuts against the washer 23 at an axial end thereof 
remote from the inner race of the bearing unit 8. As a result, the spring 
20 generates a spring force causing the inner race 8a of the bearing unit 
8 to be held between the flange portion 21a of the spacer 21 and the 
washer 23. Furthermore, the inner race 8a of the bearing unit 8 has an 
inner diameter larger than the outer diameter of the end of the nut 9, and 
thus an annular clearance S is formed between the bearing unit 8 and the 
nut 9. Contrary to this, the outer race 8b of the bearing unit 8 is 
press-fitted to an annular recess 7-1 of the timing piston 7. As a result, 
the bearing unit 8 can rotatably support the timing piston 7 with respect 
to the nut 9, and the axial movement from the nut 9 is transmitted to the 
piston 7 without any play because the bearing unit 8 is resiliently fixed 
to the nut 9 by the force of the spring 20. In addition, the clearance S 
between the bearing unit 8 and the nut 9 allows the timing piston 7 and 
the nut 9 to be radially moved by a limited degree where there is some 
misalignment of the axis of the timing piston 7 and the axis of the nut 9, 
which is usually inevitable even within a range of tolerance. As a result, 
a smooth transmission of movement can be obtained between the nut 9 and 
timing piston 7. 
In the first embodiment as described above, an oil supply passageway is 
provided for a lubrication of the engaged portion created between the worm 
15 and worm wheel 13, and portions between which any sliding movement 
occurs, and as a result, a low friction movement along these portions is 
realized, resulting in an increased service life of the device. As shown 
in FIG. 2, the camshaft 1 has a central bore 30 for receiving a flow of 
the lubricant from a lubrication oil pump (not shown), and a pair of 
lubricant oil holes A have first ends thereof connected to the central 
bore 30 for receiving the flow of oil therefrom, and second ends thereof 
opened to an annular groove formed at the outer periphery of the camshaft 
1, and as a result, the lubrication oil is supplied to sliding portions 
between the camshaft 1, the timing pulley 2, and the camshaft sleeve 3. 
Furthermore, an end of the camshaft sleeve 3 has axial openings B for an 
introduction of the oil for lubricating the bearing unit 8, as well as the 
helical splines 7-1 and 6 between the camshaft sleeve 3 and the timing 
piston 7. The timing piston 7 has angularly spaced holes C formed 
therethrough for introducing oil for lubricating the helical splines 7-2 
and 5 between the timing piston 7 and the pulley sleeve 25. Furthermore, 
the pulley sleeve has angularly spaced lubrication holes D for receiving 
the flow of the oil directed outward. The seal unit 26 prevents the oil 
from leaking into the timing pulley 2. The timing piston 7 has, at an end 
thereof remote from the timing pulley 2, an angularly spaced axially 
extending groove I for receiving the flow of oil from the openings C, and 
for directing the oil to the nut 9 and the ball screw 12, which are 
engaged with each other, for a lubrication therefore. The housing 17 has 
an axially extending groove E on the inner cylindrical surface thereof 
facing the metal bearing 10 for directing the oil flow from the groove I 
into the portion at which the worm 15 is engaged with the wheel 13, for a 
lubrication thereof. The housing 17 has, at a location below the ball 
screw, a downwardly-inclined oil passageway F having an upper end opened 
toward an inside of the housing 17 at a location facing the worm member 15 
and a lower end opened to an oil reservoir recess H formed inside the 
housing 17 at a location adjacent to the pulley sleeve 25 and at the 
bottom thereof. An oil return pipe G has an upper end connected to the oil 
reservoir recess and a lower end (not shown) connected to an oil pan (not 
shown), for removing the oil after a lubrication of the various parts in 
the valve timing control device as shown in FIG. 1. 
It should be noted that, in addition to the oil seal 26 between the pulley 
sleeve 25 and an engine body portion 18 on one side of the pulley 2, a 
second oil seal 35 is arranged between the portion 2-1 of the timing 
pulley 2 and the portion of the engine body. As a result, the oil for 
lubricating the camshaft 1 and the valve timing control devise is 
prevented from being leaked into the timing pulley 2 with which the timing 
belt 112 made of a rubber material is engaged, which would otherwise cause 
the timing belt 112 to be damaged. 
An oil pump (not shown) is provided as in a conventional technique, so that 
a forced flow of the lubrication oil from the not shown oil pump is 
created, which flow is introduced into the passageway 30 as shown by an 
arrow f. The oil is then directed into the passageway B for lubricating 
the sliding parts between the portion 2-1 of the timing pulley 2 and the 
camshaft 1. Then part of the oil is passed through the openings B and is 
introduced into the ball bearing 8 and the ball screw 12, to lubricate 
same. The remaining part of the oil is directed to the engaged helical 
spline 6 of the camshaft sleeve 3 and the helical spline 7-1 of the timing 
piston 7, and a part thereof is directed to the engaged helical spline 5 
of the pulley sleeve 25 and the helical spline 7-2 of the timing piston 7, 
to lubricate same. Most of the remaining lubricating oil is passed through 
the radial oil holes C under the effect of centrifugal force, and then 
flows along the inner periphery of the pulley sleeve 25 toward the free 
end thereof via the axially extending grooves I thereon. The flow of the 
oil along the grooves I is subjected to the centrifugal force, at the free 
end thereof and thus is directed to the inner surface of the housing 17, 
and mainly directed to a space 51 for lubricating the screw shaft 12 and 
the nut 9, which are engaged with each other, and part thereof is 
introduced into the axial grooves E so that the oil is supplied to the 
engaged worm gear 15 and the worm wheel 13, for lubricating same. The oil 
after lubricating the engaged portions is received by the return 
passageway F. 
The oil after lubricating the various parts of the device as described 
above flows downward along the return passageway F and the inner wall of 
the housing 17, and is introduced into the reservoir portion H and 
returned, via the return pipe G, to the oil pan (not shown). 
It should be noted that a plurality of the lubrication passageways C and E 
are arranged to be spaced circumferentially, so that a smooth axial 
movement of the timing piston 7 can be obtained without being blocked by 
the lubricating oil, which will be otherwise locally filled therein. 
Furthermore, the oil introduced into an annular portion adjacent to the 
seal member 26 via the radial passageways D can be exhausted into the 
reservoir portion H by way of a small gap created between the pulley 
sleeve 25 and the housing 17. 
When the internal combustion engine is stopped, the lubrication oil in the 
ignition timing control apparatus is returned back to the oil pan via the 
oil passageways as above mentioned, and thus the oil in the apparatus does 
not remain therein. Otherwise, the oil in the apparatus will increase a 
resistance force to the starting of the engine when it is cold, because 
the viscosity of the oil is high. 
According to the first embodiment, the engaged portions of the worm gear 15 
and the worm wheel 13, and of the helical splines 6 and 7-1, and 5 and 7-2 
are always supplied by a flow of lubrication oil, which effectively 
prevents a rapid wear of these parts even when a high relative speed is 
generated between parts engaged with each other, and thus an increased 
durability and service life thereof can be realized. 
Furthermore, various loads are applied to parts in the apparatus, such as 
the helical splines 6 and 7-1, and 5 and 7-2, the ball bearing 8, the ball 
screw 12 and the nut 9, due to the engine vibration and a variation of the 
rotating torque of the camshaft 1, which causes a rapid wear of these 
parts and a sticking thereof. The lubrication means in the first 
embodiment prevents the occurrence of these problems. 
FIG. 4 shows a second embodiment of the present invention wherein, in place 
of the separate pipe G in the first embodiment (FIG. 2), the stay 18 has 
bores 300 and 302 formed therein, which bores are outwardly closed by 
plugs 304 and 306 for constructing a return passageway G' in communication 
with a passageway 308 in the engine block 102, which passageway 308 is 
connected to the oil pan (not shown). This embodiment is advantageous in 
that the number of parts is reduced, and thus the construction can be 
simplified. Similar to the first embodiment, the second embodiment is also 
provided with connecting means, constructed by a ball bearing 8 (having an 
inner race connected to the nut 9 with a clearance), a Belleville spring 
20, a spacer 21, a washer 23 and a snap ring 22, for connecting the nut 9 
and the timing piston 7 for a transmission of an axial movement during the 
rotational movement of the timing piston 7 with respect to the nut 9, and 
allowing a slight radial movement between the timing piston 7 and the nut 
9. 
FIG. 5 shows a third embodiment wherein, in place of the timing pulley 2, a 
timing gear 40 is rotatably mounted on a camshaft 1. The timing gear 40 is 
in mesh with a gear (not shown) for transmitting the rotational movement 
from the camshaft (not shown in FIG. 5). A timing piston 7 is arranged 
between a camshaft sleeve 3 fixed to the camshaft 1 by a bolt 4, and a 
sleeve 40A, which is integral with the hub portion of the timing gear 40. 
The timing piston 7 has, at outer and inner cylindrical surfaces thereof, 
helical splines 7-1 and 7-2 in engagement with corresponding helical 
splines 6 and 5 on the camshaft sleeve 3 and the gear sleeve 40A, and as a 
result, a mutual rotational movement is obtained between the camshaft 1 
and the gear 40 due to the axial movement of the timing piston 7, to 
thereby control the valve timing. 
Similar to the first and second embodiments, the third embodiment is also 
provided with a connecting means constructed by a ball bearing 8, a 
Belleville spring 20, a spacer 21, a washer 23 and a snap ring 22, for 
connecting the nut 9 and the timing piston 7 for a transmission of the 
axial movement, and allowing a rotating movement of the timing piston 7 
with respect to the nut 9, and further allowing a slight radial movement 
between the timing piston 7 and the nut 9. 
Unlike the first and second embodiments, wherein the timing pulley 2 
connected to a timing belt is used, and thus the sealing members 26 and 25 
are essential for preventing damage to the belt, the gear engagement in 
the third embodiment uses the oil to lubricate the gear 40, as the latter 
is housed in a chamber 400 in the engine block 102 to which the 
lubrication oil from the oil pump (not shown) is circulated. Therefore, in 
the third embodiment, the separate passageway G in FIG. 2 or G' in FIG. 4 
can be eliminated, and the oil after having lubricated various parts of 
the apparatus is directly introduced from the space 51 and through the 
passageway F into the chamber 400. 
The employment of the lubrication oil from the oil pan in the above 
embodiments allows the worm gear mechanism to smoothly rotate the ball 
screw to thereby obtain a mutual rotational movement of the camshaft and 
the timing pulley or timing gear. The employment of the worm gear 
mechanism provides a very high reduction ratio, and thus only a rotational 
motor having a very low rotating torque is needed for obtaining a force 
necessary to obtain a desired axial movement of the timing piston, for 
obtaining a desired mutual position of the camshaft to the timing pulley 2 
or timing gear 40. Such a low torque motor 16 reduces the size of the 
apparatus, and thus is advantageous when mounting same in a limited space 
in an engine room. The employment of the worm gear mechanism prevents the 
transmission of a reaction torque from the ball screw 12 to the motor 16, 
and accordingly, the a rotation of the ball screw 12 by the reaction force 
is prevented even when the electric motor 16 is deenergized after a 
desired mutual position between the camshaft 1 and the timing pulley 2 is 
obtained. Therefore, a consumption of electric energy is lowered, and this 
is advantageous for the service life of the batteries. 
Furthermore, the low output torque of the electric motor 16 with a high 
rotational speed increases a response time, because a quick initial 
increase in the speed can be obtained. 
FIG. 6 shows a fourth embodiment of the present invention. This embodiment 
is based on the use of the low torque motor due to the employment of the 
worm mechanism. Namely, a flexible wire 45 is provided for connecting the 
electric motor 16 with the worm wheel 15 engaged with the worm wheel 13 
for transmitting the rotational movement from the motor 16 to the ball 
screw 12. This embodiment increases the freedom of the arrangement of the 
motor 16. Namely, the motor 16 in this embodiment is arranged below the 
housing 17, and is directly connected to the stay 18, and as a result, a 
weight overhanging the device can be reduced, resulting in a reduction in 
a vibration thereof. 
It should be noted that the device in FIG. 6 is also provided with an oil 
return passageway for returning the oil to the engine after lubricating 
various portions of the valve timing control device, as in the previous 
embodiments, although this is not shown, for the sake of simplicity. 
Furthermore, the upper half portion of the nut 9 is shown at the most 
forwardly moved position thereof where the timing piston 7 is moved so 
that the piston 7 abuts against the hub portion of the timing pulley 2, 
and the lower half position thereof is, shown when it is at the most 
rearwardly moved position where the timing piston 7 is located adjacent to 
the housing 17. 
Similar to the previous embodiments, the embodiment in FIG. 6 is also 
provided with a connection means constructed by a ball bearing 8, spring 
20, spacer 21, washer 23, and snap ring 22. 
As explained with reference to FIG. 1, for a V-type internal combustion 
engine, separate motors 16 and 16', which are controlled by the control 
circuits 43 and 43', respectively, are provided, and these electric motors 
16 and 16' are connected to respective valve timing control devices for 
controlling relative angular positions of the camshafts 1 and the timing 
pulleys 2 of the banks 118 and 118', respectively. 
In another modification, as shown in FIG. 7, only a single electric motor 
16 is provided, which is connected, via respective flexible wires 45 and 
45', to the respective valve timing control devices for controlling 
relative angular positions of the camshafts 1 and the timing pulleys 2 of 
the banks 100 and 100', respectively. In this case, the single electric 
motor 16 is connected to a single control circuit 43 for controlling the 
operation of the motor 16 to thus adjust the valve timing. 
FIG. 8 is a flowchart illustrating the operation of the control circuit 43 
or 43' when controlling the valve timing. At step S1, a target value of a 
valve timing ANG0, which is a relative angular position of the camshaft 1 
with respect to the crankshaft 108, is calculated. The target valve timing 
is determined in accordance with engine operating conditions, such as an 
engine rotational speed and intake pressure. In a well known manner, a map 
of the values of the valve timings is provided for various combinations of 
values of the engine speed and intake pressure, and a map interpolation 
calculation is carried out to obtain a target value of ANG0 corresponding 
to a combination of a detected engine speed and intake air pressure. In 
this case, it is determined that the larger the value of the relative 
angle ANG0, the more advanced the valve timing. 
At step S2, an actual relative angle ANG1 of the camshaft 1 with respect to 
the crankshaft 108, which is detected by the cam angle sensor 41 or 41', 
is obtained, and at step S3, it is determined if the value of the target 
value of the cam angle ANG0 is larger than the actual value of the cam 
angle ANG1, i.e., the valve timing is controlled in a direction for 
advancing same. When it is determined that ANG0&gt;ANG1, the routine goes to 
step S4 and the motor 16 or 16' is controlled so that a rotation thereof 
is obtained in the direction for advancing the valve timing. When it is 
not determined that ANG0&lt;ANG1 at step S3, the routine goes to step S5 and 
it is determined if the value of the target value of the cam angle ANG0 is 
smaller than the actual value of the cam angle ANG1, i.e., the valve 
timing is controlled in a direction for delaying same. When it is 
determined that ANG0&lt;ANG1, the routine goes to step S6 and the motor 16 or 
16' is controlled so that a rotation thereof is obtained in the direction 
for delaying the valve timing. When it is not determined that ANG0&gt;ANG1 at 
step S6, i.e, ANG0=ANG1, steps S4 and S6 are bypassed because it is 
considered that the detected valve timing ANG1 is equal to the target 
valve timing ANG0. 
FIG. 9 shows another embodiment of the connection means for connecting the 
axial movement of the timing piston 7 rotatably to the nut 9, while 
permitting the nut 9 to be slightly radially movable with respect to the 
timing piston 7. The radially adjustable connection of the inner race 8a 
of the ball bearing 8 to the ball screw 9 in the first embodiment in FIG. 
3 is changed to a radially adjustable connection of the outer race 8b to 
the timing piston 7 in FIG. 9. Namely, the inner race 8a of the bearing 
unit 8 is press-fitted to the nut 9, and the outer race 8b of the bearing 
unit 8 is inserted to the timing piston 7 so that an annular space S' is 
created between the facing cylindrical surfaces of the bearing 8 and the 
timing piston 7. The outer race is contact at one end thereof with a snap 
ring 25, as a stopper fitted to an annular groove 7b on the inner 
cylindrical surface of the timing piston 7, and in contact at the other 
end thereof with a waved washer 24 having an annular shape and inserted to 
the screw shaft 9 at one side thereof. The wave-shaped washer 24 is in 
contact, at the other side thereof, with an annular shoulder 7a formed on 
the inner cylindrical surface of the timing piston 7. The wave washer 24 
generates an axial elastic force urging the outer race 8b into firm 
contact with the stopper 25, to thereby axially fix the bearing unit 8 on 
the screw shaft 9. This construction shown in FIG. 9 allows the axial 
movement of the nut 9 to be transmitted to the timing piston 7, while 
allowing the timing piston 7 to be rotatable with respect to the screw 
shaft 9. Furthermore, the space S' allows a relatively limited radial 
movement between the bearing unit 8 and the timing piston 7, so that a 
smooth transmission of power is always obtained from the screw 9 to the 
timing piston 7, regardless of any inevitable small amount of misalignment 
of the axis of the screw shaft 9 and the axis of the timing piston 7 
within a tolerance. 
FIG. 10 illustrates a construction of another embodiment, and further, 
illustrates how the apparatus is assembled. The construction of this 
embodiment is similar to that of FIG. 2, but is different therefrom in 
that the angular position of the motor 16 with respect to the housing 17 
is rotated by an angle of 90 degree with regard to the construction of 
FIG. 2. The apparatus is constructed from two sub-assemblies 600 and 602. 
The first sub-assembly 600 includes parts held by the stay 18, i.e., a 
pulley 2 with a pulley sleeve 25 is connected to the camshaft 1 by a bolt 
4 via a camshaft sleeve 3, and a seal stay 18 connected to the engine 
block 102. The second sub-assembly 602 is constructed by parts supported 
by the housing 17, i.e., a nut 9, a screw shaft 12, a timing piston 7, a 
bearing unit 8 together with the connection means constructed by the 
spring 20, the spacer 21, stopper 23 and a snap ring 23, and the motor 50. 
The obtained second sub-assembly 602 is connected to the stay 18 in the 
first sub-assembly by the bolts 19. 
It should be noted that a similar sub-assembly structure based on the 
housing 17, which is conveniently connected to the stay 18, can be also 
employed in embodiments other than that of FIG. 10, in a similar way. 
Although embodiments of the present invention are described with reference 
to the attached drawing, many modifications and changes can be made by 
those skilled in this art without departing from the scope and spirit of 
the present invention.