DESC:Field of Invention
The present invention relates with the field of tensioner and more
particularly, it relates to a hydraulic tensioner for uniform load distribution which
induces a smooth and silent drive system (transmission mechanism) in internal
5 combustion engine of automotive vehicles.
Background of Invention
A tensioner is a mechanical device that applies a force to create or generate
a tension. The force is generated by a spring, in both mechanical tensioners and
10 hydraulic tensioners. In hydraulic tensioners, oil is additionally used to avoid
retraction of plunger during operation. A tensioner plays an important role in
maintaining a certain degree of tension in a timing chain in engine of vehicles, to
prevent noise. Further, application of proper tension on a chain guide allows proper
functioning of a cam shaft.
15
Hydraulic tensioner is a key focus to maintain an accurately correct tension
of the timing chain in high capacity internal combustion (IC) of automotive
vehicles. Since last few decades, a gradual evolution is being carrying out in an
automobile industry to develop an improved hydraulic tensioner than that of the
20 existing one to achieve a smooth and silent mechanical transmission in vehicles’
engines.
In internal combustion engines, a timing chain is a key element for
transmitting rotary motion of the crankshaft to the camshaft and auxiliaries to
25 synchronize the motion of engine pistons with the cams that govern an air intake
and exhaust emission. However, the length of the timing chain is caused to be
elongated due to thermal expansion and vibrations in IC engines. Therefore, the
timing chain will inevitably be slacked which causes wear and tear thereof.
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3
Conventionally, hydraulic tensioners are widely used to suppress backlash
and vibration due to changes in tension in timing belts and timing chains which
transmit rotation from the crankshaft to one or more camshafts in a vehicle engine.
A typical hydraulic tensioner comprises a plunger slidable in and protruding from,
a housing. The plunger and housing cooperate 5 to provide a pressurized oil chamber
into which oil is introduced through a ball-type check valve for blocking backflow
of oil from the pressurized oil chamber. Although the check valve unit, in
conventional hydraulic tensioner, can block backflow of oil from the pressurized
oil chamber, air can become mixed with the oil in the pressurized oil chamber. The
10 compressibility of the air allows backlash and vibration of the traveling
transmission medium, especially upon engine start-up.
One such conventional hydraulic tensioner has been disclosed in US patent
no. US 5833220, which includes a plunger being slidably fitted in cylinder and a
15 spring urging the plunger upwardly. However, the problem associated with said
conventional hydraulic tensioner is having non-uniform load distribution due to
conventional spring effect, which cannot uniformly apply an accurately correct
tension to the timing belt or timing chain of vehicle’s engine, which results in
increased level of noise and reduced lifespan of the mechanical transmission system
20 of vehicles’ engines.
One more such hydraulic tensioner is disclosed in US patent no.6383103
which includes a relief valve mechanism assembled in a plunger which is slidably
inserted in a housing; the relief valve mechanism is having an orifice formed in an
25 outer circumferential surface thereof, and a spring urging the sleeve toward the
high-pressure chamber. Said hydraulic tensioner of US6383103 encounters with the
problem of increased noise of engine due to non-uniform load (tension) onto the
timing chain. Further, said hydraulic tensioner of US6383103 is not able to
effectually reduce the noise of mechanical transmission system of the vehicles’ IC
30 engines.
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4
Therefore, a need yet exists to provide a smooth drive system of internal
combustion (IC) engine for improved lifespan of timing chain and better
performance of IC engines by achieving uniform load or tension distribution of the
hydraulic tensioner. Although, the conventional hydraulic tensioners are proved to
be suitable for certain applications, 5 there is still scope to provide an
improved hydraulic tensioners having an effectually improved functionality; which
can almost eliminate the noise of camshaft drive and auxiliaries drive systems of
internal combustion engines to increase the lifecycle of the timing chain and
improve the performance of internal combustion (IC) engines.
10
Hence, it is desperately required to provide and develop a hydraulic
tensioner which can overcome the aforesaid drawbacks and shortcomings of the
conventional hydraulic tensioners.
15 Object of Invention
The main object of the present invention is to provide a hydraulic tensioner.
Another object of the present invention is to provide a hydraulic tensioner which
eliminates the slippage and unmeshing of the toothed timing chain.
20
Still another object of the present invention is to provide a hydraulic tensioner
which induces uniform load or tension onto the timing chain of the drive system in
IC engine.
25 Yet another object of the present invention is to provide a hydraulic tensioner which
substantially ameliorate the lifecycle and functionality of the drive system in IC
engine.
5
5
Yet another object of the present invention is to provide a hydraulic tensioner which
is configured to induce a smooth and silent drive system in IC engine.
Yet another object of the present invention is to provide a hydraulic tensioner which
5 enables an easy installation while assembling.
Yet another object of the present invention is to provide a hydraulic tensioner which
is having a spring of maximum stiffness and least buckling.
10 Yet another object of the present invention is to provide a hydraulic tensioner which
overcomes drawbacks and shortcomings of prior art hydraulic tensioners.
Summary of Invention
15 This summary is provided to introduce aspects related to a hydraulic
tensioner, and the aspects are further described below in the detailed description.
This summary is not intended to identify essential features of the claimed subject
matter nor is it intended for use in determining or limiting the scope of the claimed
subject matter.
20
A hydraulic tensioner according to present invention comprises a hollow
cylindrical housing having an open top and a closed bottom wall; a plunger, having
a tip portion and a closed bottom wall, longitudinally slidably fitted into the hollow
cylindrical housing and configured to define a pressurized oil chamber; a barrel
25 spring, facing closed bottom wall of the hollow cylindrical housing, compressibly
coaxially disposed into the hollow cylindrical housing to define a spring-loaded
pressure chamber; and a check valve assembly removably mounted between the
barrel spring and the bottom wall of the plunger, and fixed with the plunger. Further,
barrel spring has least buckling and high stiffness, and provides uniform load
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6
distribution for having a parabolic spring rate. Therefore, with usage of the barrel
spring, a smooth and silent drive system is provided. Such smooth and silent
operation substantially ameliorates lifecycle and functionality of the drive system
in IC engine.
5
In one embodiment, a hydraulic tensioner comprises a hollow cylindrical
housing having an open top and a closed bottom wall. Further, a plunger having a
tip portion and a closed bottom wall may be longitudinally slidably fitted into the
hollow cylindrical housing. A barrel spring facing the closed bottom wall of the
10 hollow cylindrical housing may be used in the hydraulic tensioner. The barrel spring
has least buckling and high stiffness. The barrel spring provides uniform load
distribution for having a parabolic spring rate. The barrel spring may be
compressibly coaxially disposed into the hollow cylindrical housing to define a
spring-loaded pressure chamber. A check valve assembly may be removably
15 mounted between the barrel spring and the bottom wall of the plunger, and fixed
with the plunger. The hydraulic tensioner maintains tension onto a timing chain by
extending the hollow cylindrical housing towards the timing chain, using resilience
energy of the barrel spring, when the timing chain tends to slack. The cylindrical
housing may be extendible, around the plunger, upto a released length of the barrel
20 spring, to compensate slackness of the timing chain.
In one embodiment, the bottom wall may comprise an aperture to define a
pressurized oil chamber. The check valve assembly may comprise a valve cap
mountably facing the barrel spring. The valve cap may comprise openings to allow
25 flow of the oil from the pressurized oil chamber to the spring-loaded pressure
chamber. A valve ball may be movably fixed into the valve cap. Further, a valve
spring may be compressibly disposed between the valve ball and the valve cap.
In one embodiment, the check valve assembly may be a press-fit check
30 valve assembly or an integrated check valve assembly, which is rigidly fixed to the
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7
bottom wall of the plunger, in such manner that the valve cap is supportably sited
onto the barrel spring. Alternatively, the check valve assembly may be a floating
type assembly, which is removably fixed through a valve seat to the bottom wall of
the plunger, in such manner that the valve cap is supportably sited onto the barrel
5 spring.
Upon elongation of the plunger towards the exterior of the hollow
cylindrical housing, a volume may be created into the spring-loaded pressure
chamber which leads to decrease in pressure therein, to cause oil to flow from the
10 pressurized oil chamber into the spring-loaded pressure chamber, through the
aperture present on the bottom wall of the plunger. Furthermore, upon elongation
of the plunger to compensate slackness of the chain, the plunger is prevented from
moving towards the bottom wall of the cylindrical housing, due to incompressible
property of the oil.
15
Brief description of drawings
Various other objects, features and many of the attendant advantages of the
present invention will be understood by reference to the following detailed
description of the preferred embodiment of the present invention when considered
20 in connection with the accompanying drawings, in which:
Fig.1 illustrates a cross sectional view of the hydraulic tensioner, according to an
embodiment of present invention;
Fig. 2 illustrates a cross-sectional view of hydraulic tensioner, according to another
25 embodiment of the present invention;
Fig. 3 illustrates a perspective view of a convex/ barrel spring, being utilized in
hydraulic tensioner, according to an embodiment of the present invention;
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8
Fig. 4a illustrates spring load distribution characteristics of the barrel spring,
according to an embodiment of the present invention; and
Fig. 4b illustrates a performance curve of the barrel spring, according to an
5 embodiment of the present invention.
Detailed description of Invention
The nature of the invention and the manner in which it works is clearly
described in the provisional specification. The invention has various embodiments
10 and they are clearly described in the following pages of the provisional
specification. Before explaining the present invention, it is to be understood that the
phraseology and terminology employed herein is for the purpose of description and
not of limitation.
15 Before explaining the present invention, it is to be understood that a
hydraulic tensioner is normally installed in a compressed state (condition) of a
spring which gradually elongates and extends, as a timing chain tends to slack or
loose due to thermal expansion and vibration in an IC engine, to maintain a required
tension onto the timing chain.
20
Now referring to Figs. 1-2 collectively, a hydraulic tensioner (1) according
to the present invention comprises a hollow cylindrical housing (2) having an open
top (2a) and a closed bottom wall (2b); a plunger (3) having a tip portion (3a) and
a closed bottom wall (3b), longitudinally slidably fitted into the hollow cylindrical
25 housing (2); a barrel spring (5) facing the closed bottom wall (2b) of the hollow
cylindrical housing (2), compressibly coaxially disposed into the hollow cylindrical
housing (2) to define a spring-loaded pressure chamber (6); and a check valve
assembly (7) removably mounted between the barrel spring (5) and the bottom wall
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9
(3b) of the plunger (3). Further, the check valve assembly (7) may be fixed with the
plunger (3).
The term “plunger”, herein described, refers to a hollow cylindrical body,
having a bore open at the tip portion (3a) and 5 closed with the bottom wall (3b)
having an aperture (not shown in figure) to define a pressurized oil chamber (4).
Further referring to Figs. 1-2 collectively, said plunger (3) is configured to be
slidably guided within the hollow cylindrical housing (2), and being urged by the
barrel spring (5) that causes hollow cylindrical housing (2) to be projected and
10 extended towards the chain due to a resilience energy of the barrel spring (5), when
the timing chain tends to slack or loose.
Before explaining the detailed invention, it is to be noted that the hydraulic
tensioner (1) works on principal of incompressible property of oil, in which the
15 check valve assembly (7) permits an oil to flow into the spring-loaded pressure
chamber (6) through an aperture (not shown in figure) of the plunger (3) [at
predefined pressure of the hydraulic tensioner] from the pressurized oil chamber (4)
while preventing the oil from flowing out of the spring-loaded pressure chamber
(6). Said plunger (3) is configured to be prevented to move in reverse direction
20 [towards the bottom wall (2b) of the cylindrical housing (2)] due to incompressible
property of oil.
Further referring to Figs.1-2 collectively, the check valve assembly (7)
includes a valve cap (8) of cup-shaped mountably facing the barrel spring (5) and
25 having openings to allow the oil to flow from the pressurized oil chamber (4) to the
spring-loaded pressure chamber (6); a valve ball (9) movably fixed into the cupshaped
valve cap (8); and a valve spring (10) compressibly disposed between the
valve ball (9) and the valve cap (8).
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10
The term “released length”, hereinafter described, refers to a length of the
barrel spring (5) at which the plunger (3) is effectually and operatively fully
extended through the open top (2a) of the cylindrical housing (2) in working
condition of the hydraulic tensioner (1).
5
According to first embodiment of the present invention, the check valve
assembly (7), as depicted in Fig.1, is rigidly fixed to the bottom wall (3b) of the
plunger (3), in such manner that the cup-shaped valve cap (8) is supportably sited
onto the barrel spring (5). Said check valve assembly (7), as depicted in Fig. 1, is
10 referred to as a press-fit or integrated check valve assembly.
According to another embodiment of the present invention, the check valve
assembly (7), as depicted in Fig. 2, is removably fixed through a valve seat (11) to
the bottom wall (3b) of the plunger (3), in such manner that the valve cap (8) is
15 supportably sited onto the barrel spring (5). Said check valve assembly (7), as
depicted in Fig. 2, is referred to as a floating type assembly.
Now referring to Fig. 3 of the present invention, shape and properties of the
barrel spring (5) are explained. The barrel spring (5) has a highest diameter at
20 middle section, and the diameter keeps decreasing towards both ends of the barrel
spring (5). Because the diameter of the barrel spring (5) is highest at the middle
section, compared to diameter at ends, chances of buckling are very low. Therefore,
the barrel spring (5) has least buckling and high stiffness (spring-rate).
25 Fig. 4a illustrates spring load distribution characteristics of the barrel spring
(5), according to an embodiment of the present invention. As illustrated in Fig. 4a,
the barrel spring (5) provides a parabolic spring rate i.e. spring load increases as the
barrel spring (5) goes into a relaxed condition. Such property of the barrel spring
(5) is very different from regular compression springs, because in regular
30 compression springs, spring load decreases when the regular compression spring
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11
goes into a relaxed condition. Therefore, because of its parabolic spring rate, the
barrel spring (5) provides uniform load distribution with respect to stroke.
Fig. 4b illustrates a performance curve of the barrel spring, according to an
embodiment of the present invention. As illustrated 5 in Fig. 4b, performance curve
of the barrel spring (5) is almost linear. Thus, the barrel spring (5) could suitably
bear variable loads, resulting in a silent operation of drive systems in IC engines.
The term “installed length”, hereinafter disclosed, refers to a length of the
10 barrel spring (5) at which the hydraulic tensioner (1) is initially installed as per
predefined load of the timing chain.
In operational characteristics of the present invention, initially the hydraulic
tensioner (1) is installed in wound condition, having an installed length of the barrel
15 spring (5) to sustain the tension of timing chain according to predefined load of the
timing chain. Now, when the timing chain tends to slack/loose due to thermal
expansion and vibration, the plunger (3) of the hydraulic tensioner (1) is configured
to be elongated and extended towards an exterior of the hollow cylindrical housing
(2) through the open top (2a) due to resilience of the barrel spring (5) to maintain
20 the required tension onto the timing chain. After elongation or extension of the
plunger (3) towards an exterior of the hollow cylindrical housing (2), a volume is
created into the spring-loaded pressure chamber (6) which leads to decrease in
pressure therein to cause the oil flow from the pressurized oil chamber (4) into the
spring-loaded pressure chamber (6).
25
Now, when the plunger (3) is extended to a specific distance to compensate
slackness of the timing chain, the plunger (3) is now prevented to move in a reverse
direction [i.e. towards the bottom wall (2b) of the cylindrical housing (2)] due to an
incompressible property of oil. Further, the cylindrical housing (2) is allowed to be
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12
extended, around the plunger (3), upto a released length of the barrel spring (5), to
compensate slackness of the timing chain.
The hydraulic tensioner of the present invention induces a smooth and silent
drive system by reducing the rattling 5 noise and substantially ameliorates the
lifecycle and functionality of the drive system in IC engine. Further, said hydraulic
tensioner also eliminates the unmeshing of the timing chain and induces uniform
load or tension onto the timing chain of the drive system in IC engine. Said
hydraulic tensioner enables an easy installation while assembling in assembly unit.
10
The present invention has been described with reference to the specific
embodiment, which is merely illustrative and not intended to limit the scope of the
present invention as defined in the specification.
15 ,CLAIMS:We Claim:
1. A hydraulic tensioner (1) comprising:
a hollow cylindrical housing (2) having an open top (2a) and a closed bottom
wall (2b);
a plunger (3) having a tip 5 portion (3a) and a closed bottom wall (3b),
longitudinally slidably fitted into the hollow cylindrical housing (2);
a barrel spring (5) facing the closed bottom wall (2b) of the hollow
cylindrical housing (2), wherein the barrel spring (5) is compressibly coaxially
disposed into the hollow cylindrical housing (2) to define a spring-loaded pressure
10 chamber (6); and
a check valve assembly (7) removably mounted between the barrel spring
(5) and the bottom wall (3b) of the plunger (3), and fixed with the plunger (3),
wherein the hydraulic tensioner (1) maintains tension onto a timing chain
by extending the hollow cylindrical housing (2) towards the timing chain, using
15 resilience energy of the barrel spring (5), when the timing chain tends to slack.
2. The hydraulic tensioner (1) as claimed in claim 1, wherein the barrel spring
(5) has least buckling and high stiffness.
20 3. The hydraulic tensioner (1) as claimed in claim 1, wherein the barrel spring
(5) provides uniform load distribution for having a parabolic spring rate.
4. The hydraulic tensioner (1) as claimed in claim 1, wherein the bottom wall
(3b) comprises an aperture to define a pressurized oil chamber (4).
25
5. The hydraulic tensioner (1) as claimed in claim 4, wherein the check valve
assembly (7) comprises:
a valve cap (8) mountably facing the barrel spring (5), wherein the valve
cap (8) comprises openings to allow flow of the oil from the pressurized oil
30 chamber (4) to the spring-loaded pressure chamber (6);
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14
a valve ball (9) movably fixed into the valve cap (8); and
a valve spring (10) compressibly disposed between the valve ball (9) and
the valve cap (8).
6. The hydraulic tensioner (1) as claimed 5 in claim 5, wherein the check valve
assembly (7) is a press-fit check valve assembly or an integrated check valve
assembly, which is rigidly fixed to the bottom wall (3b) of the plunger (3), in such
manner that the valve cap (8) is supportably sited onto the barrel spring (5).
10 7. The hydraulic tensioner (1) as claimed in claim 5, wherein the check valve
assembly (7) is a floating type assembly, which is removably fixed through a valve
seat (11) to the bottom wall (3b) of the plunger (3), in such manner that the valve
cap (8) is supportably sited onto the barrel spring (5).
15 8. The hydraulic tensioner (1) as claimed in claim 4, wherein upon elongation
of the plunger (3) towards the exterior of the hollow cylindrical housing (2), a
volume is created into the spring-loaded pressure chamber (6) which leads to
decrease in pressure therein, to cause oil to flow from the pressurized oil chamber
(4) into the spring-loaded pressure chamber (6), through the aperture present on the
20 bottom wall (3b) of the plunger (3).
9. The hydraulic tensioner (1) as claimed in claim 8, wherein upon elongation
of the plunger (3) to compensate slackness of the chain, the plunger (3) is prevented
from moving towards the bottom wall (2b) of the cylindrical housing (2), due to
25 incompressible property of the oil.
10. The hydraulic tensioner (1) as claimed in claim 1, wherein the cylindrical
housing (2) is extendible, around the plunger (3), upto a released length of the barrel
spring (5), to compensate slackness of the chain.