Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-08-16
2001-11-06
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C074S56800M, C464S002000
Reexamination Certificate
active
06311656
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a valve timing control apparatus for varying opening and closing timings of intake and exhaust valves of an internal combustion engine in accordance with engine operating conditions.
A published Japanese patent application Publication (Kokai) No. 09(1997)-280018 shows a conventional valve timing control apparatus of a vane type.
The outline is described with reference to
FIGS. 4 and 5
. This valve timing control apparatus includes a timing sprocket
50
having a tooth portion
50
a
on the outer periphery, a tubular housing
51
fixed to the main body of the timing sprocket
50
by bolts
63
. A rotor member
54
is fixed to one end of a cam shaft
52
by a bolt
64
, and received rotatably in the tubular housing
51
. The housing
51
has four of projections having a generally trapezoidal section projecting radially inwardly. On the other hand, the rotor member
54
includes four of vanes or blades
54
a,
54
b,
54
c
and
54
d
each separating an advance side hydraulic chamber
55
and a retard side hydraulic chamber
56
between two adjacent projections. Each of the vanes
54
a
~
54
d
has a seal member for sealing between the advance and retard hydraulic chambers
55
and
56
, by sliding on the inner circumferential surface of the housing
51
.
The rotating member
54
is rotated in the forward and reverse directions by supplying and draining hydraulic pressure to and from the advance and retard hydraulic chamber
55
and
56
in accordance with engine operating conditions, to change the relative rotation phase of the timing sprocket
50
and the cam shaft
52
and thereby to change the opening and closing timing of an intake valve.
Between the vane
54
a
and the timing sprocket
50
, there is provided a locking mechanism
57
for preventing or allowing relative rotation between the timing sprocket
50
and the rotating member
54
.
This locking member
57
includes a pin sliding hole
58
formed in the van
54
a
along the axial direction of the cam shaft
52
, a lock pin
59
slidable in this pin sliding hole
58
in a manner immune from the influence of the centrifugal force generated by rotation, and a latching bore
60
formed in the inner end surface of the timing sprocket
50
. Moreover, the lock pin
59
is urged toward the latching bore
60
by the spring force of a coil spring
61
. The lock pin
59
can disengage from the latching bore
60
by the aid of hydraulic pressure of an oil pump supplied to a pressure receiving chamber at the rear end of the pin sliding hole
58
.
When the pressure of the oil pump is still low as in a starting operation of the engine, the lock pin
59
urged into the latching bore
60
by the coil spring
61
can prevent collision and tapping noise between the housing
51
and the rotating member
54
due to forward and reverse torque fluctuation of the cam shaft.
When the hydraulic pressure from the oil pump rises with increase in the engine rotational speed, the lock pin
59
moves out of the latching bore
60
by the increased pressure in the pressure receiving chamber, and thereby allows the rotating member
54
to rotate freely.
SUMMARY OF THE INVENTION
By repeated sliding movement of the lock pin
59
along the pin sliding hole
58
into and out of the latching bore
60
, sliding portions between the lock pin
59
and the pin sliding hole
58
and engaging portions between the edge of the latching bore
60
and the tip of the lock pin
59
become worn with time, producing abrasion metal powder. Since the abrasion metal powder has a higher specific gravity than the hydraulic fluid in the hydraulic chambers
55
and
56
, it is liable to drift toward the inner circumferential surface of the housing
51
by the centrifugal force by rotation of the housing
51
and the rotating member
54
. Consequently, this abrasion metal powder infiltrates between the outer surface of each seal member and the inner circumferential surface of housing
51
, and thereby damages the outer surface of the seal member and the inner surface of the housing
51
, so that the sealing performance between the housing
51
and the seal members and the durability of the seal members may decline.
It is therefore an object of the present invention to provide a valve timing control apparatus effective in performance and durability of sealing.
According to the present invention, a valve timing control apparatus for an internal combustion engine, comprises:
a rotating body receiving rotation from a crankshaft of the engine;
a cam shaft rotatable relative to the rotating body;
a housing stationary relative to one of the rotating body and the cam shaft, the housing including a hydraulic chamber, and an engaging recess;
a rotor member stationary relative to the other of the rotating body and the cam shaft, the rotor member including a vane extending radially and dividing the hydraulic chamber of the housing into an advance chamber and a retard chamber, and a pin sliding hole extending along an axial direction of the cam shaft;
a seal member provided at an outer end of the vane, for sealing between an inner circumferential surface of the housing and the outer end of the vane;
a hydraulic circuit selectively supplying and draining hydraulic fluid to and from the advance and retard chambers and thereby rotating the vane in one of a forward direction and a reverse direction;
a lock pin received slidably in the pin sliding hole of the rotor member, to prevent relative rotation between the housing and the rotor member by engaging with the engaging recess of the housing, and to allow relative rotation between the housing and the rotor member by disengaging from the engaging recess; and
an oil reservoir being located radially between the pin sliding hole and the inner circumferential surface of the housing, and communicating with one of the advance chamber and retard chamber.
REFERENCES:
patent: 5836276 (1998-11-01), Iwasaki et al.
patent: 5947067 (1999-09-01), Kawaharaguchi et al.
patent: 6129063 (2000-10-01), Niethammer et al.
patent: 6173686 (2001-01-01), Nakayoshi et al.
patent: 9-280018 (1997-10-01), None
patent: 11-62522 (1999-03-01), None
Foley & Lardner
Lo Weilun
Unisia Jecs Corporation
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