Valve timing control device

Details Valve timing control device Valve timing control device

2001-06-18

2002-05-07

Lo, Weilun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

Reexamination Certificate

active

06382156

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve timing control device,for modifying the-opening and closing timing of the intake and exhaust valves in an internal-combustion engine (hereafter, ref erred as an engine) according to any operating condition.
2. Description of the Prior Art
Conventional valve timing control devices of various structures,are proposed as disclosed in JP-A-1998/159519, JP-A1998/159520 and JP-A-1999/294120, for example.
FIG. 1
is a lateral cross sectional view of an internal construction of the) conventional vane-type valve timing control device.
FIG. 2
is a longitudinal cross sectional view taken along lines A-A of FIG.
1
. FIG.
3
A and
FIG. 3B
are enlarged cross sectional views of a lock member in the valve timing control device of
FIG. 2
,
FIG. 3A
showing a locked state, and
FIG. 3B
showing a released state. In the drawings, reference numeral
1
denotes a pulley which connects with, a crankshaft (not shown) of the engine through chains (not shown) to rotate in synchronization with the crankshaft (not shown).
2
denotes a housing fitted to the pulley
1
and having a bearing part
2
a
with respect to an intake or exhaust camshaft (hereafter, referred as a camshaft)
3
.
4
denotes a case having a plurality of shoes
4
a
, the respective shoes
4
a
projecting from an inside of the case
4
to constitute a plurality of hydraulic pressure chambers defined between the shoes
4
a
.
5
denotes a cover of covering the hydraulic pressure chambers of the case
4
. The housing
2
, the case
4
and the cover
5
are connected, integrally to each other by a threaded member
6
such as a bolt and soon. Here, the pulley
1
, the housing
2
, the case
4
and the Cover
5
constitute a first, rotor.
A rotor (second rotor)
9
is fixed integrally to an one end
3
a
of the camshaft
3
by a threaded member
8
such as a bolt and so on through a washer
9
. The rotor
7
is arranged rotatably in the first rotor. A plurality of vanes
7
a
are arranged at an outer circumferential portion of the rotor
7
, dividing the hydraulic pressure chambers into an advance side hydraulic pressure chamber
10
and a retardation side hydraulic pressure chamber
11
. A first oil passage
12
and a second oil passage
13
are arranged in the camshaft
3
. The first oil passage
12
supplies hydraulic pressure to and discharges hydraulic pressure from the advance side hydraulic pressure chamber
10
, and the second oil passage
13
supplies hydraulic pressure to and discharges hydraulic pressure from the retardation side hydraulic pressure chamber
11
. Moreover, seal means
14
are arranged on both of front ends of the shoes
4
a
of the case
4
and the vanes
7
a
of the rotor
7
, respectively. The respective seal means
14
prevent leakage of oil between the both of the hydraulic pressure chamber
10
and
11
. The seal means
14
includes a seal member
14
a
of sliding on an inner wall face of the hydraulic pressure chamber
10
or
11
and a plate spring
14
b
of biasing the seal member
14
a
toward the inner wall face.
A lock pin
15
having a cylindrical shape is arranged at the housing
2
constituting the first rotor above and restricts relative rotation of the first rotor and the second rotor. Since hydraulic pressure in the valve timing control device is reduced on starting the engine, the rotor
7
acting as the second rotor vibrates in the rotational direction by a cam load applied to a cam (not shown) integrated with the camshaft
3
. In this way, since the first and second rotors undergo repetitive contact and separation as a result of the vibration, beat noise (abnormal noise) necessarily results. The lock pin
15
prevents the occurrence of beat noise (abnormal noise). Therefore, the lock pin
15
is biased by a biasing member
17
such as a coil spring toward the second rotor and thus allows the engagement with an engagement hole will be explained hereafter. The biasing member
17
is arranged between a rear wall of a backward pressure chamber
16
and the lock pin
15
. A discharge hole
18
, which discharges a backward pressure of the lock pin
15
, is formed in the backward pressure chamber
16
.
On the other hand, an engagement hole
19
, which allows insertion of the lock pin
15
, is formed at the vane
7
a
of the rotor
7
acting as the second rotor The engagement hole
19
communicates with a valve
21
through a hydraulic pressure supply passage
20
of supplying a release hydraulic pressure for releasing engagement (hereafter, referred as lock) of the lock pin
15
. The valve
21
communicates with both the advance side hydraulic pressure chamber
10
and the retardation side hydraulic pressure chamber
11
, and is a member for selecting the higher hydraulic pressure from the above chambers in order to supply the selected pressure to the hydraulic pressure supply passage
20
.
Next, a release operation will be explain.
In a release operation, hydraulic pressure is supplied from an oil pump (not shown) to the engagement hole
19
through the advance side hydraulic pressure chamber
10
or the retardation side hydraulic pressure chamber
11
, the valve
21
and the hydraulic pressure supply passage
20
. In this way, the hydraulic pressure presses the lock pin
15
against the biasing force of the biasing member
17
to move the lock pin
15
back in the backward pressure chamber
16
. Here, backward pressure of the lock pin
15
is discharged from the discharge hole
18
to the outside of the valve timing control device. Since an area (an area determined by a diameter D of the lock pin
15
as shown in
FIG. 3A
) subjected to hydraulic pressure is constant from a locked state of the lock pin
15
to the end of a released state, discharge of the backward pressure is also constant. When a front end of the lock pin
15
is released from the engagement hole
19
and is accommodated in the backward pressure chamber
16
, the lock of the lock pin
15
is released to allow free rotation between the first and second rotors.
It is noted that when the engine is stopped, oil in the advance side hydraulic pressure chamber
10
and the retardation side hydraulic pressure chamber
11
moves downwardly to an oil-pan (not shown) through the first and second oil passages
12
and
13
and so on. Therefore, air accumulates in pipe arrangement such as the respective hydraulic pressure chambers and the respective oil passages. In this state, when the engine is restarted, a hydraulic pressure rises by the oil pump (not shown) and simultaneously air accumulated in the pipe arrangement is discharged at once. Thus, the air-mixing oil is applied in the valve timing control device to release instantly the lock pin
15
from the engagement hole
19
.
However, the following problems result from the above structure for a conventional valve timing control device.
When the air-mixing oil releases the lock on starting the engine, the hydraulic pressure in the advance side hydraulic pressure chamber
10
and the retardation side hydraulic pressure chamber
11
cannot absorb the cam load described above because of air mixing oil. Since the first and second rotors repeat contact and separation therebetween, beat noise (abnormal noise) necessarily results.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a valve timing control device, which prevents the occurrence of beat noise (abnormal noise) in a release operation resulting from the air-mixing oil on starting the engine.
In order to achieve the object of the present invention, a valve timing control device comprises a first rotor rotating in synchronization with a crankshaft of an internal combustion engine; a second rotor fixed on an end of an intake camshaft or an exhaust camshaft of the internal combustion engine and rotatably arranged in the first rotor; a lock member locking the first and second rotors at a required angle which any one of the rotors forms with the other; a backward pressure chamber arranged at any one of th

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