Valve timing control device

Details Valve timing control device Valve timing control device

2001-12-14

2002-10-08

Lo, Wellun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

Reexamination Certificate

active

06460496

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve timing control device altering timing for the closing and opening of an exhaust valve or intake valve of an internal-combustion engine (hereafter, referred as an engine) with reference to any operating conditions.
2. Description of the Prior Art
Conventional valve timing control devices shown in
FIG. 1
to
FIG. 5
for example are known.
FIG. 1
is a lateral cross sectional view of an internal construction of a conventional vane-equipped valve timing control device.
FIG. 2
is a longitudinal cross sectional view taken along lines A—A of FIG.
1
.
FIG. 3
is a longitudinal cross sectional view of a conventional locking/unlocking mechanism shown in FIG.
2
.
FIG. 4
is an enlarged perspective view of an important part of a locking/unlocking mechanism of the conventional valve timing control device shown in FIG.
1
.
FIG. 5
is a graph of a relationship between an operational stroke of a locking member of the conventional locking mechanism shown in FIG.
2
and
FIG. 3 and a
hydraulic pressure exerted on the locking member. Moreover, in
FIG. 2
, right side is defined as forward and left side is defined as backward. In FIG.
3
and
FIG. 4
, lower side is defined as forward and upper side is defined as backward.
In the drawings, a reference numeral
1
denotes a first rotor, which is coupled to a crankshaft (not shown) as an output shaft of the engine by way of chains (not shown), belts (not shown) and so on and is rotatable in synchronization with the crankshaft (not shown). The first rotor
1
, a sprocket
2
, a case
3
and a cover
4
are fixed integrally using a threaded member
5
such as bolts. The sprocket
2
is rotated integrally with the crankshaft (not shown). The case
3
has a plurality of shoes
3
a
projected inwardly from an inner periphery of the case
3
to constitute a plurality of hydraulic chambers. The hydraulic chambers are covered with the cover
4
.
A rotor (second rotor)
6
is rotated relative to the first rotor
1
and is disposed in the case
3
. The rotor
6
is integrally fixed on a camshaft
7
, which relates to timing for the closing and opening of intake or exhaust valve, using a threaded member
8
such as bolts. The rotor
6
has a plurality of vanes
6
a
each partitioning the hydraulic chambers, which are constituted by the shoes
3
a
of the case
3
, into an advance side hydraulic chamber
9
and a retardation side hydraulic chamber
10
. A first oil path (hydraulic chamber supply path)
11
and a second oil path (hydraulic chamber supply path)
12
are arranged in the camshaft
7
. The first oil path
11
supplies a hydraulic pressure to the advance side hydraulic chamber
9
and discharges the hydraulic pressure therefrom. The second oil path
12
supplies a hydraulic pressure to the retardation side hydraulic chamber
10
and discharges the hydraulic pressure therefrom.
Seal means
13
are disposed at front ends of the shoes
3
a
of the case
3
and at front ends of the vanes
6
a
of the rotor, respectively. Each of the seal means
13
prevents an oil leak from a boundary between the advance side hydraulic chamber
9
and the retardation side hydraulic chamber
10
. The seal means
13
includes a seal member
13
a
sliding over an inner wall of the advance side hydraulic chamber
9
or the retardation side hydraulic chamber
10
and a leaf spring
13
b
pressing the seal member
13
a
against the inner wall thereof.
An accommodation hole
14
accommodating a locking pin described later is arranged at one of the vanes
6
a
of the rotor
6
as the second rotor. The locking pin (locking member, lockingmechanism)
15
, which controls relative rotation of the first rotor
1
and the second rotor and is defined as a straight pin having a cylindrical shape, is disposed in the accommodation hole
14
. The locking pin
15
prevents the occurrence of beat noise (abnormal noise). The second rotor
6
vibrates in rotational directions due to loads of cams (not shown) integrally fixed to the camshaft
7
when the engine is started in a state of hydraulic pressure-free in the valve timing control device. The rotor
6
attaches repeatedly to or detaches from the first rotor
1
due to the vibration. Therefore, the beat noise occurs due to the repetition. the locking pin
15
is pressed against the first rotor
1
at all times using a biasing means (locking mechanism)
16
such as coil springs disposed between a rear wall of the accommodation hole
14
and the locking pin
15
and engages in an engagement hole described later. A discharge hole (unlocking mechanism)
17
, which discharges a backward pressure exerted on the back section of the locking pin
15
to outside of the device, is formed in the accommodation hole
14
.
On the other hand, an engagement hole
18
is formed at a position of the sprocket
2
defined as the first rotor
1
. The position of the sprocket
2
allows the fit of the locking pin
15
into the engagement hole
18
when the rotor
6
defined as the second rotor locates at the most retarded position with respect to the first rotor
1
.
A check valve (unlocking mechanism)
19
is arranged at the vane
6
a
having the accommodation hole
14
. The check valve
19
selects the higher pressure of the two different pressures in the advance and retardation side hydraulic chambers
9
and
10
, and supplies the selected pressure to the engagement hole
18
engaged with the locking pin
15
to unlock the engagement (hereafter, referred as locking relation). The check valve
19
communicates to the engagement hole
18
by way of a first unlocking hydraulic pressure supply path (unlocking mechanism)
20
formed in the vane
6
a
of the rotor
6
, a second unlocking hydraulic pressure supply path (unlocking mechanism)
21
formed in the sprocket
2
. The check valve
19
communicates to the advance side hydraulic chamber (unlocking mechanism)
9
by way of an advance side partitioned pressure path (unlocking mechanism)
22
. The check valve communicates to the retardation side hydraulic pressure chamber
10
by way of a retardation side partitioned pressure path (unlocking mechanism)
23
.
An unlocking operation will be explained hereafter.
On unlocking the locking relation, a hydraulic pressure derived from an oil pump (not shown) passes through the advance side hydraulic chamber
9
or the retardation side hydraulic chamber
10
. The hydraulic pressure is then supplied to the engagement hole
18
through the check valve
19
, the first and second unlocking partitioned pressure paths
20
and
21
. In the engagement hole
18
, an unlocking hydraulic pressure is supplied to a boundary between the inner wall of the engagement hole
18
and an outer wall of the locking pin
15
and presses the locking pin
15
against a biasing force of the biasing means
16
. In this way, the locking pin
15
is moved back the deep of the accommodation hole
14
and is released from the engagement hole
18
. At this time, the backward pressure of the locking pin
15
is discharged from the accommodation hole
14
through the discharge hole
17
to outside of the valve timing control device. When a front end of the locking pin
15
is released from the engagement hole
18
and the whole is come back to the accommodation hole
14
, it is possible to unlock the locking relation to allow a free rotation of the first and second rotors.
Moreover, since a pressure-exerted area, on which a hydraulic pressure is exerted, of the locking pin
15
is constant over a period of time during the switching from a locked state due to the locking pin
15
to an unlocked state, a discharge speed of the backward pressure becomes constant. The operational stroke of the locking pin
15
is determined depending on the biasing force of the biasing means
16
and the hydraulic pressure to establish the one-on-one relationship between the operational stroke of the locking pin
15
and an applied hydraulic pressure as illustrated in
FIG. 5. A
nun locking hydraulic pressure is t

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