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
2002-05-01
2004-05-04
Hannon, Thomas R. (Department: 3682)
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
06729986
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydraulic type tensioner with a relief valve, which is used for applying proper tension to a timing chain or the like in a vehicle engine.
BACKGROUND OF THE INVENTION
Hydraulic type tensioners, which are used for applying proper tension to a timing chain or the like in a vehicle engine, include, as shown by a timing transmission in
FIG. 4
, a hydraulic type tensioner with a relief valve
50
. The relief valve adjusts chain tension through a tensioner lever TL for relieving excess tension when the excess tension is generated in a timing chain TC, which is stretched and transmitted between a drive shaft side sprocket S
1
and a driven shaft side sprocket S
2
.
FIG. 5
is a front cross-sectional view showing one example of a conventional hydraulic type tensioner with a relief valve. The conventional hydraulic type tensioner with a relief valve
50
shown in
FIG. 5
comprises a housing
51
, a plunger
52
slidably fit into a plunger-accommodating hole
51
a
with a bottom formed in the housing
51
, a spring
53
, which biases in a direction where the plunger
52
is projected, a high pressure oil chamber
54
formed between the housing
51
and the plunger
52
, a check valve mechanism
55
provided on a bottom portion of the plunger-accommodating hole
51
a
formed in the housing
51
, and a relief valve
56
provided in the housing
51
outside the check valve mechanism
55
in the radial direction thereof.
The check valve mechanism
55
comprises a ball seat
55
b
having an oil path
55
a
press-fit into a hole
51
b
formed at a bottom portion of the plunger-accommodating hole
51
a
, a check ball
55
c
, which can be abutted on this ball seat
55
b
, a retainer
55
d
, which holds this check ball
55
c
, and a spring
55
e
, which biases the check ball
55
c
toward the ball seat
55
b
. The hole
51
b
formed in the housing
51
has an oil supply port (not shown) for supplying oil from an oil pressure generating source such as an oil pump or the like to a high pressure oil chamber
54
and a supply oil path, which flows through this oil supply port. This check valve mechanism
55
has the dual functions of permitting the flowing of oil into the high pressure oil chamber
54
and on the contrary blocking the flowing of oil out of the high pressure oil chamber
54
.
The relief valve
56
comprises a valve body fitting hole
56
a
formed in the housing
51
, a communicating hole
56
b
, which communicates between the high pressure oil chamber
54
and the valve body fitting hole
56
a
, a valve body
56
c
slidably fit into the valve body fitting hole
56
a
, a spring
56
d
, which biases the valve body
56
c
, a relief hole
56
e
, which communicates between the valve body fitting hole
56
a
formed in the housing
51
and the outside thereof, and a plug
56
f
press-fit into the valve body fitting hole
56
a
from the outside. The relief valve
56
has the function that when the oil pressure in the high pressure oil chamber
54
exceeds a predetermined pressure, the valve body
56
c
is moved backward against a bias force of the spring
56
d
and the communicating hole
56
b
communicates with the relief hole
56
e
thereby to reduce the oil pressure in the high pressure chamber
54
.
In this hydraulic type tensioner with the relief valve
50
, in a state where an engine is in a predetermined usual drive, when slackening of the timing chain occurs, the plunger
52
is projected by the bias force of the spring
53
and at the same time the check ball
55
c
is separated from the ball seat
55
b
so that oil is supplied from an oil pressure generating source such as an oil pump (not shown) or the like formed in the housing
51
through the supply hole
51
b
into the high pressure oil chamber
54
, and through the oil path
55
a
in the ball seat
55
b
thereby to maintain the tension of the timing chain.
Further, in this hydraulic type tensioner with the relief valve
50
, when excessive tension is generated in the chain, the plunger
52
receives a thrust load from a tensioner lever TL in a direction opposite to the bias direction. Then the check valve mechanism
55
acts so as to prevent the backflow of oil in the high pressure oil chamber
54
, and oil in the high pressure oil chamber
54
, which is non-compressible fluid, prevents the return of the plunger
52
. However, the valve body
56
c
of the relief valve
56
receives an oil pressure generated in the high pressure oil chamber
54
and is slid against the bias force of the spring
56
d
to be slightly moved backward, whereby excessive tension generated in the timing chain is absorbed.
Further, when the thrust load to the plunger
52
is increased and the valve body
56
c
of the relief valve
56
is further backed, the communicating hole
56
b
communicates with the relief hole
56
e
, so that a discharge of oil in the high pressure oil chamber
54
to the outside of the tensioner
50
is permitted. Thus, the oil pressure in the high pressure oil chamber
54
is decreased and excessive tension of the timing chain is absorbed.
Then, if the oil pressure in the high pressure oil chamber
54
is decreased with the discharge of oil outside the tensioner, the valve body
56
c
receives the bias force of the spring
56
d
and closes the relief hole
56
e
to maintain the oil pressure in the high pressure oil chamber
54
to a preset value. In this case, if the oil pressure in the high pressure oil chamber
54
is excessively decreased, the check valve mechanism
55
acts so that oil flows into the high pressure oil chamber
54
to return the oil pressure in the high pressure oil chamber
54
to a normal level.
However, in the above-mentioned conventional hydraulic type tensioner with the relief valve
50
shown in
FIG. 5
, when excessive tension has been generated in the timing chain, oil in the high pressure oil chamber
54
is discharged outside the tensioner through the relief valve
56
in a larger amount than is necessary so that the oil pressure in the high pressure oil chamber
54
is excessively decreased further than a preset value. Therefore, it has been found that proper tension cannot be applied to the timing chain till the valve mechanism
55
acts to cause oil to flow into the high pressure oil chamber
54
, thereby to return the oil pressure therein to a preset value.
Further, in such a conventional hydraulic type tensioner with a relief valve
50
, when the oil supplied from an oil pressure generating source such as an oil pump or the like has reached excessively high pressure or when the resonance phenomenon due to high frequency vibration of the whole apparatus, the oil supplied from the oil pressure generating source such as an oil pump or the like is one-sidedly supplied under pressure to the high pressure oil chamber
54
through the check valve mechanism
55
and the pressure of the supplied oil in the high pressure oil chamber
54
aids the bias force of the spring
56
d
so that the spring
56
d
further tensions the timing chain more than is necessary. Accordingly, there are problems that the vibration noise during traveling of chain is increased and the timing chain is broken in an early stage.
Further, in the conventional hydraulic type tensioner with a relief valve
50
, oil is supplied from an oil pressure generating source such as an oil pump or the like by the activation of an engine. Thus, when smooth supply of oil from the oil pressure generating source such as an oil pump or the like is not obtained at the starting of an engine or the like and the supplied oil pressure is low, the oil pressure in the high pressure oil chamber
54
does not reach a preset pressure, whereby the bias force due to the oil pressure in the high pressure oil chamber
54
is insufficient. As a result, tension must be applied to a traveling timing chain at the starting of transmission by the movement of the plunger
52
according to only the bias force of the spring
56
d
and there is a problem that proper tension of a chain cannot be obtained.
SUMMA
Kawamura Kazuaki
Kurohata Junya
Tomioka Hisashi
Dann Dorfman Herrell and Skillman
Hannon Thomas R.
Skillman Henry H.
Tsubakimoto Chain Co.
LandOfFree
Hydraulic type tensioner with relief valve does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic type tensioner with relief valve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic type tensioner with relief valve will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3253855