Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Tension adjuster or shifter driven by electrical or fluid motor
Reexamination Certificate
2000-06-27
2002-06-04
Marmor, Charles A (Department: 3681)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Tension adjuster or shifter driven by electrical or fluid motor
Reexamination Certificate
active
06398682
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hydraulic tensioner with a relief valve for use to apply an appropriate tension to a timing belt, a timing chain or a like member of an engine for a vehicle.
2. Description of the Related Art
As a hydraulic tensioner for use to apply an appropriate tension to a timing belt, a timing chain or a like member of an engine for a vehicle, a hydraulic tensioner with a relief valve or with an orifice is frequently used in order to eliminate an excessive tension when it acts upon the timing belt, timing chain or like member.
A hydraulic tensioner with a relief valve is disclosed in Japanese Utility Model Laid-Open Publication No. HEI-3-12995.
FIG. 5
is a schematic sectional view showing the hydraulic tensioner with a relief valve disclosed in the Japanese Publication just mentioned. Referring to
FIG. 5
, the hydraulic tensioner
60
with a relief valve shown includes a housing
61
, a cylindrical plunger
62
mounted for sliding movement in the housing
61
and having an opening at one end thereof, and a spring
63
fitted in the inside of the plunger
62
and extending between the housing
61
and the plunger
62
for biasing the plunger
62
in a direction in which the plunger
62
projects from the housing
61
so that an outer end face
64
of the plunger
62
is resiliently pressed against a tensioner lever
65
to apply a tension to a chain
66
through the tensioner lever
65
.
The housing
61
has an oil path
68
formed therein for supplying oil from a hydraulic pressure source such as an oil pump not shown into an oil chamber
67
in the inside of the plunger
62
. Also a ball seat
69
has an oil path
70
formed therein for communicating the oil path
68
of the housing
61
and the oil chamber
67
with each other. A check ball
71
is biased toward the ball seat
69
by a coil spring
73
having one end contacting with a retainer
72
. The ball seat
69
, check ball
71
, retainer
72
and coil spring
73
cooperatively form a check valve. The check valve permits oil from flowing from the oil path
70
into the oil chamber
67
but prevents the oil from flowing out from the oil chamber
67
to the oil path
70
.
The plunger
62
has an oil path
74
which communicates with the oil chamber
67
, and a sub oil chamber
76
which communicates with the oil chamber
67
through the oil path
74
and is formed from a plug
75
which closes up the other end of the plunger
62
. A sleeve
77
is fitted for sliding movement in contact with an inner face of the sub oil chamber
76
. Also a spring
78
is fitted in the sub oil chamber
76
between the sleeve
77
and the plug
75
for biasing the sleeve
77
so that the sleeve
77
may be pushed into the sub oil chamber
76
. The plunger
62
further has an outlet port
79
formed radially therein. The outlet port
79
is communicated with the sub oil chamber
76
when the sleeve
77
is pushed back in a direction against the biasing force of the spring
78
by a hydraulic load applied in the oil chamber
67
. Thus, the elements mentioned form a relief valve.
In the conventional hydraulic tensioner
60
with a relief valve, if slackening of the chain
66
occurs while the engine is operating, then the plunger
62
is allowed to be projected by the biasing force of the spring
63
. Thereupon, the check ball
71
is simultaneously spaced away from the ball seat
69
to allow oil to be supplied into the oil chamber
67
through the oil path
68
of the housing
61
and the oil path
70
of the ball seat
69
. Consequently, the tension of the chain
66
is maintained by the oil thus supplied to the oil chamber
67
.
On the other hand, if an excessively high tension is applied to the chain
66
by an increase of the distance between the axes of sprocket wheels S
1
and S
2
or the like which arises from heat of the engine, then the plunger
62
is acted upon by a pressing load in the direction opposite to the biasing direction to the plunger
62
from the tensioner lever
65
. Thereupon, the check valve acts to prevent the oil in the oil chamber
67
from flowing out. Consequently, the oil in the oil chamber
67
, which is non-compressible fluid, prevents backward movement of the plunger
62
. However, the sleeve
77
of the sub oil chamber
76
is acted upon by a hydraulic pressure generated in the oil chamber
67
so that it is slidably moved in the direction opposite to the biasing direction of the spring
78
to allow the oil from the oil chamber
67
into the sub oil chamber
76
to allow the plunger
62
to move back a little thereby to absorb the excessive tension acting upon the chain
66
. If the pressing load to the plunger
62
further increases to retract the sleeve
77
, then the sub oil chamber
76
and the outlet port
79
are communicated with each other thereby to open the check valve to allow the oil of the oil chamber
67
and the sub oil chamber
76
to be discharged through the outlet port
79
to allow the plunger
62
to move back a comparatively great amount thereby to eliminate the excessive tension of the chain
66
. As the hydraulic pressure drops as a result of the discharge of the oil, the sleeve
77
is moved by the biasing force of the spring
78
until it closes up the outlet port
79
so that the oil chamber
67
may thereafter be kept in a fixed pressure condition. However, if the hydraulic pressure drops excessively, then the check valve operates to allow the oil to flow into the oil chamber
67
from the hydraulic source thereby to return the hydraulic pressure in the oil chamber
67
to its ordinary level.
Meanwhile, another conventional hydraulic tensioner with a orifice is disclosed in Japanese Utility Model Laid-Open Publication No. HEI-3-12043.
FIG. 6
is a schematic sectional view showing the hydraulic tensioner with an orifice disclosed in the Japanese Publication just mentioned. Referring to
FIG. 6
, the hydraulic tensioner with an orifice is generally denoted at
80
and includes a housing
81
, and a cylindrical plunger
82
mounted for sliding movement in the housing
81
and having an opening formed at one end thereof. An oil chamber
83
is defined by and between the housing
81
and the plunger
82
.
The housing
81
has an oil path
84
formed therein for supplying oil from a hydraulic source such as an oil pump not shown to the oil chamber
83
. A spring
85
is fitted in the plunger
82
and extends between the housing
81
and the plunger
82
. The plunger
82
is acted upon by a projecting force provided by a hydraulic pressure from the hydraulic source and a biasing force of the spring
85
, and applies a tension to a chain
86
under the projecting force mentioned.
A check valve
87
is interposed between the oil path
84
and the oil chamber
83
for permitting oil to flow from the oil path
84
into the oil chamber
83
but preventing the oil to flow backwardly from the oil chamber
83
to the oil path
84
. Accordingly, oil having entered the oil chamber
83
cannot flow out from the oil chamber
83
thereby to prevent backward or retraction movement of the plunger
82
. An orifice
88
is provided to permit such slow backward or retraction movement of the plunger
82
and exhibits its effect when the tension of the chain
86
becomes excessively high.
The orifice
88
is provided in the plunger
82
. In particular, a plug
90
is mounted in a hole
89
perforated at an end of the plunger
82
, and the orifice
88
is provided in the plug
90
. A check valve
92
is formed at an outward opening
91
of the plug
90
for permitting oil from flowing out through the orifice
88
but preventing admission of air into the orifice
88
from the outside. The check valve
92
includes a check ball
93
positioned in the outward opening
91
, a retainer
94
, and a spring
95
for biasing the check ball
93
into the outward opening
91
. An oil path
97
is formed in a tensioner lever
96
, and oil discharged through the orifice
88
flows out from the oil path
97
.
In the conventional hydraulic tens
Fujimoto Nobuyuki
Suzuki Tadasu
Dann Dorfman Herrell and Skillman
Marmor Charles A
Parekh Ankur
Skillman Henry H.
Tsubakimoto Chain Co.
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