Variable valve timing apparatus

Details Variable valve timing apparatus Variable valve timing apparatus

1999-01-27

2001-01-09

Lo, Wellun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090170

Reexamination Certificate

active

06170448

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to variable valve timing apparatuses that are employed in engines. More particularly, the present invention relates to a variable timing apparatus that includes a phase adjustor and a lift adjustor for controlling valve timing with a three-dimensional cam.
Engine variable valve timing apparatuses control the valve timing of intake valves and exhaust valves in accordance with the operating state of the engine. A variable valve timing apparatus generally includes a timing pulley and a sprocket, which synchronously rotates a camshaft with a crankshaft.
Japanese Unexamined Patent Publication No. 9-60508 describes a typical variable timing apparatus. As shown in
FIGS. 10
,
11
, and
12
, the variable valve timing apparatus includes a phase adjustor arranged on one end of a camshaft
202
.
FIG. 10
is a cross-sectional view taken along line
10
—
10
in
FIG. 11
, while
FIG. 11
is a cross-sectional view taken along line
11
—
11
in FIG.
10
.
FIG. 12
is a cross-sectional view taken along line
12
—
12
in FIG.
11
.
A sprocket
204
, which is driven by a crankshaft (not shown), is coupled with a housing
206
and supported to rotate integrally with the housing
206
. A vane rotor
208
is arranged in the center of the housing
206
and secured to the end of the camshaft
202
to rotate integrally with the camshaft
202
.
Vanes
210
project outward from the hub of the vane rotor
208
to contact the inner wall of the housing
206
. Partititions
212
project inward from the housing
206
to contact the hub surface of the vane rotor
208
. Cavities
214
are defined between the partitions
212
. A first pressure chamber
216
and a second pressure chamber
218
are defined in each cavity
214
between each vane
210
and the partitions
212
.
Hydraulic pressure is communicated to the first and second pressure chambers
216
,
218
to rotate the vane rotor
208
relative to the housing
206
. As a result, the rotational phase of the vane rotor
208
relative to the housing
206
is adjusted. This, in turn, adjusts the rotational phase of the camshaft
202
relative to the crankshaft.
The camshaft
202
has a journal
224
, which is supported by a bearing
222
formed in a cylinder head of the engine. A first oil channel, which is connected with a hydraulic unit
220
, extends through the cylinder head and connects to an oil groove
226
extending along the peripheral surface of the journal
224
. The oil groove
226
is connected to oil conduits
227
,
228
, which extend through the camshaft
202
. The oil conduit
228
is further connected to oil conduits
230
,
232
, which extend through the vane rotor
208
and lead into the first pressure chambers
216
. Accordingly, hydraulic pressure is communicated between the hydraulic unit
220
and the first pressure chambers
216
through the first oil channel, the oil groove
226
and the oil conduits
227
,
228
,
230
,
232
.
A second oil channel, which is connected with the hydraulic unit
220
, extends through the cylinder head and connects to an oil groove
236
extending along peripheral surface of the journal
224
. The oil groove
236
is connected to an oil conduit
238
, which extends through the camshaft
202
. The oil conduit
238
is further connected to oil conduits
240
,
242
,
244
, which extend through the vane rotor
208
and lead into the second pressure chambers
218
. Accordingly, hydraulic pressure is communicated between the hydraulic unit
220
and the second pressure chambers
218
through the second oil channel, the oil groove
236
, and the oil conduits
238
,
240
,
242
,
244
.
In addition to the phase adjustor, a lift adjustor employed in a variable valve timing apparatus to change the lift amount of intake or exhaust valves with a three-dimensional cam and to control the valve timing is also known in the prior art. Japanese Unexamined Patent Publication No. 9-32519 describes such a lift adjustor. As shown in
FIG. 13
, three-dimensional cams
302
are arranged on a camshaft
304
. A timing pulley
306
is arranged on one end of the camshaft
304
. The timing pulley
306
is supported such that it slides axially along and rotates integrally with the camshaft
304
. A cylinder
308
is arranged on one side of the timing pulley
306
. A piston
310
secured to the end of the camshaft
304
is fitted into the cylinder
308
. A pressure chamber
312
is defined between one side of the piston
310
and the inner wall of the cylinder
308
. A spring
314
is arranged between the other side of the piston
310
and the timing pulley
306
in a compressed state. When the pressure in the pressure chamber
312
is high, the piston
310
urges the camshaft
304
against the force of the spring
314
toward the right (as viewed in FIG.
13
). When the pressure in the pressure chamber
312
is low, the spring
314
pushes the piston
310
and forces the camshaft
304
toward the left.
Hydraulic pressure is communicated between the pressure chamber
312
and an oil control valve
318
through oil conduits
322
,
324
, which extend through a bearing
320
, oil conduits
326
,
328
, which extend through the camshaft
304
, and an oil conduit
332
, which extends through a bolt
330
. The bolt
330
fastens the piston
310
to the camshaft
304
. A microcomputer
316
controls the oil control valve
318
to adjust the hydraulic pressure communicated to the pressure chamber
312
and change the axial position of the camshaft if
304
.
Accordingly, the position of contact between each cam
302
and the associated valve lift mechanism is adjusted to alter the opening duration of a corresponding intake valve or exhaust valve in accordance with the profile of the cam
302
. This varies the valve timing.
When varying the valve timing with the phase adjustor illustrated in
FIGS. 10
to
12
, the opening and closing timing of the valves are both varied in the same manner. That is, if the opening timing is advanced, the closing timing is advanced accordingly, and if the opening timing is retarded, the closing timing is retarded accordingly. On the other hand, when varying the valve timing with the lift adjustor illustrated in
FIG. 13
, the opening and closing timing of the valves are inversely varied. That is, if the opening timing is retarded, the closing timing is advanced, and if the opening timing is advanced, the closing timing is retarded. Therefore, the opening and closing timing of the valves cannot be independently varied. This limits the control of the valve timing.
To solve this problem, the phase adjustor of
FIGS. 10
to
12
and the lift adjustor of
FIG. 13
can be arranged together on a camshaft to adjust both the rotational phase of a camshaft relative to a crankshaft and the lift amount of the valves. This would reduce the limitations on the opening and closing timing control.
For example, the phase adjustor of
FIGS. 10
to
12
incorporating a timing pulley and a sprocket may be arranged on one end of a camshaft, and the lift adjustor of
FIG. 13
may be arranged on the other end of the camshaft. In this case, the cylinder
308
of the apparatus illustrated in
FIG. 13
is supported at a fixed position on a cylinder head or the like.
When employing the phase adjustor of
FIGS. 10
to
12
together with the lift adjustor of
FIG. 13
, the phase adjustor must be unaffected by the camshaft axial movement that is caused by the lift adjustor of
FIG. 13. A
spline mechanism
406
such as that shown in
FIG. 14
is thus required between a camshaft
402
and a vane rotor
404
. The spline mechanism
406
includes splines
408
, which extend along the inner surface of the vane rotor
404
and splines
414
extending along an inner gear
412
, which is coupled to the camshaft
402
. The vane rotor splines
408
and the inner gear splines
414
mesh with one another and are supported such that the gear splines
414
slide axially with respect to the vane rotor splines
408
.
In this structure, the communication of hydraulic pressure may be performed i

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